Fluorine-containing ether compound and method for producing the same, lubricant for magnetic recording medium and magnetic recording medium

Abstract

Provided is a fluorine-containing ether compound represented by the following formula. R1-CH2-R2a-CH2-R3a-CH2-R2b-CH2-R3b-CH2-R2c-CH2-R3c-CH2-R2d-CH2-R4 (R2a, R2b, R2c,and R2d are perfluoropolyether chains. R3a, R3b, and R3c are divalent linking groups having at least one polar group. At least one among R3a, R3b, and R3c is represented by -OCH2CH(OH)CH2O-. R1 and R4 are C1-C50 terminal groups having at least one polar group, and may be the same as or different from each other.)

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound and a method for producing the same, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2022-137937, filed on August 31, 2022, the contents of which are incorporated herein by reference. [Background technology]

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

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

[0004] For example, Patent Document 1 discloses a fluorine-containing ether compound having a skeleton in which two perfluoropolyether chains are bonded to both ends of a glycerin structure (-OCH2CH(OH)CHO-) via methylene groups (-CH2-), and in which terminal groups having polar groups are bonded to both ends of the skeleton via methylene groups.

[0005] Furthermore, Patent Documents 2 and 3 disclose fluorine-containing ether compounds having a skeleton in which three perfluoropolyether chains are bonded via a linking group having one polar group, and in which terminal groups having polar groups are bonded to both sides of the skeleton via methylene groups (-CH-). Patent Document 4 discloses a fluorine-containing ether compound having a skeleton in which three perfluoropolyether chains are bonded via a linking group having one or more polar groups, and in which terminal groups having polar groups are bonded to both sides of the skeleton via a methylene group (-CH2-).

[0006] Furthermore, Patent Document 5 discloses a fluorine-containing polymer in which a plurality of perfluoropolyether chains are linked by an aliphatic hydrocarbon chain having a polar group. Furthermore, Patent Document 6 discloses a fluoropolyether compound in which a plurality of perfluoropolyether groups are linked via a linking group consisting of a hydrocarbon group having at least one hydroxyl group, and in which terminal groups having at least one hydroxyl group are arranged at both ends. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2021 / 251335 [Patent Document 2] International Publication No. 2018 / 116742 [Patent Document 3] International Publication No. 2017 / 145995 [Patent Document 4] US Patent Application Publication No. 2016 / 0260452 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-231056 [Patent Document 6] Patent No. 6763980 Summary of the Invention [Problem to be solved by the invention]

[0008] In magnetic recording and reproducing devices, there is a demand for an even smaller flying height of the magnetic head, which in turn requires a thinner lubricating layer in the magnetic recording medium. However, reducing the thickness of the lubricating layer generally tends to reduce the corrosion resistance of the magnetic recording medium, and reducing the thickness of the lubricating layer can also result in insufficient flying stability of the magnetic head.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that has good floating stability for a magnetic head, can form a lubricating layer that has a high corrosion-inhibiting effect on a magnetic recording medium, and can be suitably used as a material for a lubricant for a magnetic recording medium, and a method for producing the same. Another object of the present invention is to provide a lubricant for magnetic recording media, which contains the fluorinated ether compound of the present invention and is capable of forming a lubricating layer that has good flying stability for a magnetic head and a high corrosion-inhibiting effect on the magnetic recording medium. Another object of the present invention is to provide a magnetic recording medium which has a lubricating layer containing the fluorine-containing ether compound of the present invention, and which has good flying stability for a magnetic head and excellent corrosion resistance. [Means for solving the problem]

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

[0011] [1] A fluorine-containing ether compound represented by the following formula (1): R 1 -CH2-R 2a -CH2-R 3a -CH2-R 2b -CH2-R 3b -CH2-R 2c -CH2-R 3c -CH2-R 2d -CH2-R 4 (1) (In formula (1), R 2a , R 2b , R 2c and R 2d is a perfluoropolyether chain; R 2a , R 2b , R 2c and R2d may be the same in part or in whole, or may be different from each other; R 3a , R 3b and R 3c is a divalent linking group having one or more polar groups; R 3a , R 3b and R 3c may be the same in part or in whole, or may be different from each other; R 3a , R 3b and R 3c At least one of these is represented by formula (3); R 1 and R 4 are terminal groups having 1 to 50 carbon atoms and one or more polar groups, and may be the same or different.) -OCH2CH(OH)CH2O- (3)

[0012] The fluorine-containing ether compound of the first aspect of the present invention preferably has the characteristics described in the following [2] to

[12] . It is also preferable to arbitrarily combine two or more of the characteristics described in the following [2] to

[12] . [2] R in the formula (1) 1 and R 4 at least one of which is an end group of any one of the following formulae (2-1) to (2-4):

[0013] [ka] (In formula (2-1), p represents an integer of 1 to 3, and q represents an integer of 1 to 3.) (In formula (2-2), r represents an integer of 0 to 2, and s represents an integer of 1 to 3.) (In formula (2-3), t represents an integer of 1 to 3, u represents an integer of 0 to 2, and v represents an integer of 1 to 3.) (In formula (2-4), l represents an integer of 1 to 3, l m's each independently represent an integer of 1 to 4, and l n's each independently represent an integer of 1 to 4; X represents an organic group containing a double bond or a triple bond.)

[0014] [3] R in the formula (1) 3a , R 3b and R 3c The fluorine-containing ether compound according to [1] or [2], wherein all of the polar groups are hydroxyl groups. [4] R in the formula (1) 1 and the hydroxyl group of R 4 The fluorine-containing ether compound according to any one of [1] to [3], wherein the total number of hydroxyl groups contained in the above and the hydroxyl groups contained in the above is 2 to 6.

[0015] [5] R in the formula (1) 3a , R 3b and R 3c The fluorine-containing ether compound according to any one of [1] to [4], wherein all of the above are represented by formula (3).

[0016] [6] R in the formula (1) 3a , R 3b and R 3c The fluorine-containing ether compound according to any one of [1] to [4], wherein one or two of the above are divalent linking groups other than those represented by formula (3), and the divalent linking groups other than those represented by formula (3) are each independently divalent linking groups having 4 to 9 carbon atoms and 1 to 3 hydroxyl groups. [7] The fluorine-containing ether compound according to [6], wherein the divalent linking groups other than those represented by the formula (3) are each independently a linking group represented by any one of the following formulas (3-1) to (3-4):

[0017] [ka] (In formula (3-1), d represents 2 or 3.) (In formula (3-2), e represents an integer of 2 to 4; in formula (3-2), the oxygen atom on the left side is R 1 The oxygen atom on the right is bonded to the methylene group on the left side, and the oxygen atom on the right side is bonded to the R 4 It bonds to the methylene group on the side.) (In formula (3-3), f represents an integer of 2 to 4; the oxygen atom on the left side in formula (3-3) is R 1The oxygen atom on the right is bonded to the methylene group on the left side, and the oxygen atom on the right side is bonded to the R 4 It bonds to the methylene group on the side.) (In formula (3-4), g represents an integer of 0 to 4.)

[0018] [8] R in the formula (1) 2a and R 2d and are the same, and R 2b and R 2c and are the same, and R 3a Atoms contained in and R 3c The atoms contained in R 3b are arranged symmetrically with respect to R 1 and R 4 The fluorine-containing ether compound according to any one of [1] to [7], wherein [9] R in the formula (1) 2a , R 2b , R 2c , and R 2d are all the same and R 3a , R 3b , and R 3c are all expressed by equation (3), and R 1 and R 4 The fluorine-containing ether compound according to [5], wherein

[0019]

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

[0020]

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

[0021]

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

[11] , which has a number average molecular weight in the range of 500 to 10,000. A second aspect of the present invention provides the following lubricant for a magnetic recording medium.

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

[12] .

[0022] A third aspect of the present invention provides the following magnetic recording medium.

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

[12] . The magnetic recording medium according to the third aspect of the present invention preferably has the characteristics described in

[15] below.

[15] The magnetic recording medium according to

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

[0023] A fourth aspect of the present invention provides the following method for producing a fluorinated ether compound.

[16] A method for producing the fluorinated ether compound according to [1], R in the formula (1) 1 -CH2-R 2a an intermediate compound 1a having a group corresponding to —CH— and —CH—R in formula (1) 2d -CH2-R 4 an end preparation step of preparing an intermediate compound 1b having a group corresponding to -R in the formula (1) 3a -CH2-R 2b -CH2-R 3b -CH2-R 2c -CH2-R 3c a linking structure preparation step for preparing an intermediate compound 3 having a group corresponding to R of the intermediate compound 3 3a R reacting the side end with the intermediate compound 1a 1 Side reaction step and R of the intermediate compound 33c R reacts the side end with the intermediate compound 1b 4 a compound structure producing step including a side reaction step, The step of producing the linked structure is 3a -CH2-R 2b an intermediate compound 2a having a group corresponding to —CH— and —CH—R in formula (1) 2c -CH2-R 3c a linking end preparation step for preparing an intermediate compound 2b having a group corresponding to -; R in the formula (1) 3b R of a compound having a group corresponding to 2b R reacts the side end with the intermediate compound 2a 2b a side reaction step; R 3b R of a compound having a group corresponding to 2c R reacts the side end with the intermediate compound 2b 2c a side reaction step.

[0024] The method for producing a fluorinated ether compound according to the fourth aspect of the present invention preferably has the characteristics described in

[17] below.

[17] R in the formula (1) 2a and R 2d and are the same, and R 2b and R 2c and are the same, and R 3a Atoms contained in and R 3c The atoms contained in R 3b are arranged symmetrically with respect to R 1 and R 4 and In the end portion production step, the intermediate compound 1a and the intermediate compound 1b are simultaneously produced, In the step of producing the linking end portion, the intermediate compound 2a and the intermediate compound 2b are simultaneously produced, and the R 2b Side reaction step and the R 2c and a side reaction step are carried out simultaneously, In the compound structure production process, 1 Side reaction step and the R 4 The method for producing a fluorinated ether compound according to

[16] , characterized in that a side reaction step is carried out simultaneously. [Effects of the Invention]

[0025] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is suitable as a material for a lubricant for a magnetic recording medium. According to the process for producing a fluorinated ether compound of the present invention, the compound represented by the above formula (1) can be produced. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore can be uniformly applied in a thin thickness to form a thin lubricating layer that provides good flying stability for the magnetic head and has a high corrosion-inhibiting effect on the magnetic recording medium.

[0026] The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention. The lubricating layer of the magnetic recording medium of the present invention can obtain good magnetic head flying stability even when it is thin, and can effectively suppress corrosion of the magnetic recording medium. Therefore, in the magnetic recording medium of the present invention, the thickness of the lubricating layer can be reduced to reduce the flying height of the magnetic head. Furthermore, the magnetic recording medium of the present invention has good magnetic head flying stability and a lubricating layer that has a high corrosion suppression effect on the magnetic recording medium, so it is excellent in reliability and durability. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a flowchart illustrating an example of the method for producing a fluorinated ether compound of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing an embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to solve the above problems, the present inventors have conducted extensive research as described below. Conventionally, fluorine-containing ether compounds having polar groups such as hydroxyl groups at the ends of their chain structures have been preferably used as materials for lubricants for magnetic recording media (hereinafter sometimes abbreviated as "lubricants") to be applied to the surface of protective layers. The polar groups in the fluorine-containing ether compounds bond with active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer. For this reason, fluorine-containing ether compounds having polar groups not only at the ends of the chain structures but also in the center of the chain structures have been particularly preferably used as materials for lubricants.

[0029] However, when a thin lubricating layer is formed on a protective layer using a conventional lubricant, it is difficult to achieve a lubricating layer that provides good magnetic head flying stability and a high corrosion suppression effect on the magnetic recording medium, as will be described below.

[0030] That is, when a lubricant is applied to a protective layer to form a thin lubricating layer, if the adhesion of the lubricant to the protective layer is insufficient, the lubricant applied to the protective layer becomes bulky, making it difficult to uniformly apply the lubricant to the protective layer.For this reason, if the thickness of the lubricating layer is thin, protrusions and the like are likely to be formed on the lubricating layer, resulting in insufficient flying stability of the lubricating layer.In addition, if the covering state of the lubricating layer on the protective layer is uneven, the corrosion suppression effect of the lubricating layer cannot be sufficiently obtained.Therefore, if the adhesion of the lubricant to the protective layer is insufficient, sufficient flying stability and corrosion resistance cannot be obtained unless the film thickness is increased to make the covering state of the lubricating layer on the protective layer uniform.

[0031] Therefore, the present inventors have focused on the bond between the polar group contained in the fluorine-containing ether compound and the active site on the protective layer, and have conducted extensive research to realize a fluorine-containing ether compound that is unlikely to produce polar groups that are not involved in the bond with the active site on the protective layer, has good adhesion to the protective layer, and can uniformly cover the protective layer even when the thickness is reduced, and can form a lubricating layer that ensures the flying stability of the magnetic head and has a high corrosion suppression effect on the magnetic recording medium.

[0032] As a result, they found that a fluorine-containing ether compound having a skeleton in which four perfluoropolyether chains are linked via a divalent linking group having one or more polar groups sandwiched between two methylene groups (-CH2-), at least one of the three linking groups contained in the skeleton is a glycerin structure (-OCH2CH(OH)CHO-), and terminal groups having 1 to 50 carbon atoms and having one or more polar groups are linked to both sides of the skeleton via methylene groups (-CH2-).

[0033] For the reasons described below, such fluorine-containing ether compounds are less likely to produce polar groups that do not bond with the numerous functional groups (active sites) present on the protective layer, and have good adhesion to the protective layer. For this reason, it is presumed that the fluorine-containing ether compounds can form a lubricating layer with a uniform coating state even when the thickness is thin.

[0034] That is, in the above-mentioned fluorine-containing ether compound, perfluoropolyether chains are arranged between the three divalent linking groups in the fluorine-containing ether compound and between the divalent linking group and the two terminal groups. Therefore, the distance between the polar groups of adjacent divalent linking groups and the distance between the polar group of the terminal group and the polar group of the divalent linking group adjacent to the terminal group are appropriate. Furthermore, at least one of the three divalent linking groups is a glycerin structure (-OCH2CH(OH)CHO-) with excellent flexibility. The oxygen atoms located at both ends of the glycerin structure form ether bonds (-O-) with the methylene groups (-CH2-) located on both sides. These two ether bonds impart appropriate flexibility to the above-mentioned fluorine-containing ether compound and increase the affinity between one hydroxyl group of the glycerin structure and the protective layer.

[0035] Thus, in the above-mentioned fluorine-containing ether compound, the distance between the polar groups of the two terminal groups and the three divalent linking groups is appropriate, so the polar groups of the two terminal groups and the three divalent linking groups are less likely to aggregate, and polar groups that do not bond to active sites on the protective layer are less likely to be generated. Moreover, both ends of the four perfluoropolyether chains are adhered to the protective layer by the polar groups of the terminal groups and / or divalent linking groups. Furthermore, one hydroxyl group (-OH) in the glycerin structure (-OCH2CH(OH)CHO-) contained in at least one of the above-mentioned fluorine-containing ether compounds adheres the fluorine-containing ether compound to the protective layer. For these reasons, the fluorine-containing ether compound applied to the protective layer is less likely to be bulky, and the fluorine-containing ether compound easily spreads over the protective layer. As a result, it is presumed that the above-mentioned fluorine-containing ether compound can form a lubricating layer with a uniform coating even when the thickness is reduced.

[0036] Furthermore, the present inventors have confirmed that by using a lubricant containing the above-mentioned fluorine-containing ether compound, it is possible to form a lubricating layer that has good flying stability for a magnetic head and a high corrosion-inhibiting effect on a magnetic recording medium, even if the lubricating layer is thin, and have thus arrived at the present invention.

[0037] Preferred examples of the fluorine-containing ether compound and its manufacturing method, the lubricant for magnetic recording media, and the magnetic recording media of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments. The present invention allows addition, omission, substitution, and modification of the number, amount, position, ratio, material, configuration, type, order, etc., within the scope of the present invention.

[0038] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2a -CH2-R 3a -CH2-R 2b -CH2-R 3b -CH2-R 2c -CH2-R 3c-CH2-R 2d -CH2-R 4 (1) (In formula (1), R 2a , R 2b , R 2c and R 2d is a perfluoropolyether chain; R 2a , R 2b , R 2c and R 2d may be the same in part or in whole, or may be different from each other; R 3a , R 3b and R 3c is a divalent linking group having one or more polar groups; R 3a , R 3b and R 3c may be the same in part or in whole, or may be different from each other; R 3a , R 3b and R 3c At least one of these is represented by formula (3); R 1 and R 4 are terminal groups having 1 to 50 carbon atoms and one or more polar groups, and may be the same or different.) -OCH2CH(OH)CH2O- (3)

[0039] The fluorine-containing ether compound of the present embodiment is, as represented by formula (1), 3a , R 3b and R 3c (Hereafter, these will be collectively referred to as "R 3 ") and has three divalent linking groups each having one or more polar groups represented by R 2a , R 2b , R 2c and R 2d (Hereafter, these will be collectively referred to as "R 2 As shown in formula (1), the compound has four perfluoropolyether chains (hereinafter sometimes referred to as "PFPE chains") represented by the formula (1), and a divalent linking group R 3 Through four perfluoropolyether chains R 2 On both sides of the skeleton formed by bonding, there are methylene groups and R1 or R 4 and the terminal groups represented by the formula (I) are bonded in this order.

[0040] The fluorine-containing ether compound of the present embodiment is a compound having a divalent linking group R 3b The PFPE chains (R 2b , R 2c ), a divalent linking group (R 3a , R 3c ), PFPE chain (R 2a , R 2d ) are arranged in this order, and there are terminal groups (R 1 or R 4 ) are arranged in a single layer. Therefore, the fluorine-containing ether compound of the present embodiment has good adhesion to the protective layer, easily wets and spreads uniformly on the protective layer, and even when the thickness is reduced, a lubricating layer having a uniform thickness is easily obtained.

[0041] In contrast, for example, a compound having two PFPE chains, which has a skeleton in which a PFPE chain is arranged on each side of a divalent linking group having one or more polar groups, and a compound having three PFPE chains, which has a skeleton with a PFPE chain at the center and a divalent linking group having one or more polar groups and a PFPE chain arranged in this order, have a small number of linking groups in the skeleton, resulting in insufficient adhesion to the protective layer. As a result, the fluorine-containing ether compound is less likely to spread on the protective layer, and the coating state of the fluorine-containing ether compound on the protective layer is likely to be uneven. Furthermore, in a compound having a skeleton in which PFPE chains and divalent linking groups having one or more polar groups are alternately arranged, and which has a skeleton consisting of five or more PFPE chains and four or more divalent linking groups, the entire molecule becomes larger and its mobility decreases, making it less likely to spread on the protective layer. Therefore, a compound having a skeleton consisting of five or more PFPE chains and four or more divalent linking groups is also likely to result in uneven coating of the fluorine-containing ether compound on the protective layer.

[0042] (R 3 (R 3a , R 3b and R3c ) a divalent linking group represented by In the fluorine-containing ether compound represented by formula (1), three R 3 are divalent linking groups each having one or more polar groups. 3 At least one of R is represented by formula (3). In this specification, the linking group represented by formula (3) may be referred to as a "glycerin structure". 3 The four R's 2 This allows the R 3 The fluorine-containing ether compound adheres closely to the protective layer, forming a thin lubricating layer with a sufficient coverage.

[0043] In equation (1), three R 3 The three Rs may be partly or entirely the same, or may be different from one another. 3 At least one of the formulas is (3), and the three R 3 Preferably, two of the three R 3 It is more preferable that all of them are formula (3). 3 When two of the three R are formula (3), the adhesion between the fluorine-containing ether compound and the protective layer is further improved. 3 If two of the formulas are (3), then R 3a and R 3c is preferably the formula (3). This is because the state of coverage of the fluorine-containing ether compound on the protective layer becomes more uniform. 3 (R 3a , R 3b and R 3c When all of the above are formula (3), the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer can be formed that has a higher flying stability for the magnetic head and a higher corrosion-inhibiting effect on the magnetic recording medium.

[0044] R 3 The divalent linking group represented by the formula (I) is preferably a group having oxygen atoms at both ends thereof. The oxygen atoms at both ends of the linking group are preferably R 3The methylene groups (-CH2-) on both sides of R form an ether bond (-O-). These two ether bonds provide the fluorine-containing ether compound represented by formula (1) with adequate flexibility. 3 This increases the affinity between the polar group of the divalent linking group represented by the formula (I) and the protective layer.

[0045] R 3 The divalent linking group represented by the formula (I) is preferably an alkylene group having 3 to 9 carbon atoms, which may contain an oxygen atom between the carbon atoms, in which a polar group is bonded to at least one carbon atom of the alkylene group, and both ends of the alkylene group are oxygen atoms. The alkylene group having 3 to 9 carbon atoms is preferably an alkylene group having 3 to 6 carbon atoms, and more preferably an alkylene group having 3 to 4 carbon atoms. The alkylene group having 3 to 9 carbon atoms preferably has a linear structure. R 3 In particular, it is preferable that a polar group be bonded to a carbon atom of a linear alkylene group having 3 to 9 carbon atoms that is not adjacent to an oxygen atom. This is because the fluorine-containing ether compound can be more uniformly coated on the protective layer, resulting in a lubricating layer with better adhesion.

[0046] R 3 Examples of polar groups that R have include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SO3H), a cyano group (-CN), and a group having an amide bond (e.g., -CONH2 or -NHCOCH3). 3 Each of the R preferably contains a hydroxyl group as a polar group. The hydroxyl group has a strong interaction with the protective layer, especially the protective layer formed of a carbon-based material. 3 When each of R contains a hydroxyl group as a polar group, the lubricating layer containing the fluorine-containing ether compound has even higher adhesion to the protective layer. In this embodiment, the fluorine-containing ether compound has even higher adhesion to the protective layer, so that the three R 3 (R 3a , R 3b and R 3cIt is more preferable that all of the polar groups of the hydroxyl group are hydroxyl groups.

[0047] The Three Rs 3 The number of polar groups each of R has is preferably 1 to 3, and more preferably 1 or 2. 3 When has two or more polar groups, some or all of the polar groups may be the same type, or may be different types.

[0048] R in Equation (1) 3a , R 3b and R 3c When one or two of the groups are divalent linking groups other than those of formula (3), it is preferable that the divalent linking groups other than those of formula (3) are each independently divalent linking groups having 1 to 3 hydroxyl groups and 4 to 9 carbon atoms. It is more preferable that the divalent linking group other than those of formula (3) is a divalent linking group formed by a combination of an oxygen atom (-O-), a methylene group (-CH-), and a methylene group bonded to a hydroxyl group (-CH(OH)-).

[0049] The divalent linking groups other than those of formula (3) are preferably each independently any one of the following formulae (3-1) to (3-4): In formulae (3-1) to (3-4), the leftmost oxygen atom is R 1 The rightmost oxygen atom is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side. When the divalent linking groups other than the formula (3) are each independently any one of the formulae (3-1) to (3-4), the synthesis of the fluorine-containing ether compound represented by the formula (1) is easy, which is preferable.

[0050] [ka] (In formula (3-1), d represents 2 or 3.) (In formula (3-2), e represents an integer of 2 to 4; in formula (3-2), the oxygen atom on the left side is R 1The oxygen atom on the right is bonded to the methylene group on the left side, and the oxygen atom on the right side is bonded to the R 4 It bonds to the methylene group on the side.) (In formula (3-3), f represents an integer of 2 to 4; the oxygen atom on the left side in formula (3-3) is R 1 The oxygen atom on the right is bonded to the methylene group on the left side, and the oxygen atom on the right side is bonded to the R 4 It bonds to the methylene group on the side.) (In formula (3-4), g represents an integer of 0 to 4.)

[0051] In formula (3-1), d is 2 or 3, and preferably 2. When d in formula (3-1) is 2, R 3 The hydrophilicity of the divalent linking group represented by the formula (I) does not become too high, and the lubricating layer can be prevented from attracting water, which causes corrosion, and a lubricating layer with better corrosion resistance can be obtained. In formula (3-2), e is an integer of 2 to 4, preferably 2 or 3, and more preferably 2. This is because the fluorine-containing ether compound is more uniformly coated on the protective layer, resulting in a lubricating layer with better adhesion. In formula (3-3), f is an integer of 2 to 4, preferably 2 or 3, and more preferably 2. This is because the fluorine-containing ether compound is more uniformly coated on the protective layer, resulting in a lubricating layer with better adhesion. In formula (3-4), g is an integer of 0 to 4, preferably an integer of 0 to 2, and more preferably 0. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion.

[0052] The linking groups represented by formulas (3-2) and (3-3) have a structure in which one to three methylene groups are extended from the formula (3) (glycerin structure). 3 The lubricating layer containing the fluorine-containing ether compound, at least one of which is represented by formula (3-2) or (3-3), has three R 3are all represented by formula (3) (glycerin structure), the lubricating layer has better hydrophobicity. As a result, the lubricating layer can effectively prevent the intrusion of water, which causes corrosion of magnetic recording media, and has a high corrosion-inhibiting effect on magnetic recording media.

[0053] In formula (1), R 3a Atoms contained in and R 3c The atoms contained in R 3b It is preferable that they are arranged symmetrically with respect to R. 3a and R 3c is a compound represented by formula (3); R 3a and R 3c are represented by formula (3-1), and the value of d in formula (3-1) is the same; R 3a and R 3c a compound in which one of the groups is represented by formula (3-2) and the other is represented by formula (3-3), and e in formula (3-2) and f in formula (3-3) have the same value; R 3a and R 3c is represented by formula (3-4), and the value of g in formula (3-4) is the same. 3a and R 3c If one of the equations is expressed by formula (3-2) and the other is expressed by formula (3-3), and e in formula (3-2) and f in formula (3-3) have the same value, then R 3a is expressed by equation (3-3), and R 3c is preferably represented by formula (3-2).

[0054] (R 2 (R 2a , R 2b , R 2c and R 2d ) PFPE chains indicated by In the fluorine-containing ether compound represented by formula (1), R 2 is a perfluoropolyether chain. 2 When a lubricating layer is formed by applying a lubricant containing the fluorine-containing ether compound of this embodiment onto a protective layer, the PFPE chain represented by R not only covers the surface of the protective layer but also imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. 2The PFPE chain represented by the formula (I) is appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0055] The fluorine-containing ether compound represented by formula (1) is R 2a , R 2b , R 2c , and R 2d The fluorine-containing ether compound represented by formula (1) contains four PFPE chains, and therefore has a terminal group (R 1 , R 4 ) and the linking group contained in the skeleton (R 3a , R 3b and R 3c ) are unlikely to aggregate with each other. Therefore, the fluorine-containing ether compound represented by formula (1) is prevented from having poor adhesion to the protective layer due to aggregation of polar groups in the molecule, and from having reduced floating stability and corrosion resistance.

[0056] The Four Rs 2 The four R's may be partly or entirely the same, or may be different from one another. 2 Among them, R 2a and R 2d is the same and R 2b and R 2c are preferably the same, and the four R 2 It is more preferable that all of the above be the same. This is because the fluorine-containing ether compound will be more uniformly coated on the protective layer, resulting in a lubricating layer with better adhesion. The Four Rs 2 Two or more of the R 2 are the same, the four R 2 Among them, R 2 It means that two or more of the same R are included. 2 The term also includes those having the same repeating unit structure but different average degrees of polymerization.

[0057] R 2 Examples of the PFPE chain represented by the formula (1) include those made of a polymer or copolymer of perfluoroalkylene oxide. Examples of perfluoroalkylene oxide include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0058] R in Equation (1) 2 are each preferably independently a PFPE chain represented by the following formula (4) derived from a polymer or copolymer of perfluoroalkylene oxide. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In formula (4), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represent 0 to 20; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 represent the average value representing the number of CF2 and each independently represent 1 to 3; there are no particular limitations on the arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (4).)

[0059] In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In formula (4), w1 and w6 are average values ​​indicating the number of CF2, and each independently represents 1 to 3. w1 and w6 are determined depending on the structure of the repeating unit arranged at the end of the chain structure in the PFPE chain represented by formula (4), etc. In formula (4), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular limitations on the arrangement order of the repeating units in formula (4). There are also no particular limitations on the number of types of repeating units in formula (4).

[0060] R 2 Specifically, the PFPE chains represented by the following formulae (4-1) to (4-4) are preferably each independently any one selected from the PFPE chains represented by the following formulae (4-1) to (4-4). The Four Rs 2 are each one selected from the PFPE chains represented by formulas (4-1) to (4-4), a fluorine-containing ether compound can be obtained that provides a lubricating layer with good lubricity. 2 is any one selected from the PFPE chains represented by formulas (4-1) to (4-4), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the PFPE chain is appropriate. This results in a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, allowing for the formation of a thinner lubricating layer with sufficient coverage. Furthermore, the fluorine-containing ether compound has appropriate flexibility, allowing for the formation of a lubricating layer with better flying stability.

[0061] -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In formula (4-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 represent the average number of CF2, each independently representing 1 to 2.)

[0062] In formula (4-1), the arrangement order of the repeating units (OCF2CF2) and (OCF2) is not particularly limited. In formula (4-1), the number h of (OCF2CF2) and the number i of (OCF2) may be the same or different. The PFPE chain represented by formula (4-1) may be a polymer of (OCF2CF2). In addition, the PFPE chain represented by formula (4-1) may be any of a random copolymer, a block copolymer, and an alternating copolymer composed of (OCF2CF2) and (OCF2).

[0063] In formulas (4-1) to (4-3), h, which indicates the average degree of polymerization, is 1 to 20, i, which is 0 to 20, j, which is 1 to 15, and k, which is 1 to 10, and therefore the fluorine-containing ether compound provides a lubricating layer with good lubricity. Furthermore, in formulas (4-1) to (4-3), h and i, which indicate the average degree of polymerization, are 20 or less, j is 15 or less, and k is 10 or less, and therefore the viscosity of the fluorine-containing ether compound does not become too high, and lubricants containing the fluorine-containing ether compound are easily applied, which is preferable. h, i, j, and k, which indicate the average degree of polymerization, are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7, and therefore the fluorine-containing ether compound easily wets and spreads on the protective layer, and a lubricating layer with a uniform thickness is easily obtained.

[0064] In formula (4-4), the arrangement order of the repeating units (CFCFCFO) and (CFCFO) is not particularly limited. In formula (4-4), the number w8 of (CFCFCFO) and the number w9 of (CFCFO), which indicate the average degree of polymerization, may be the same or different. Formula (4-4) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CFCFCFO) and (CFCFO).

[0065] In formula (4-4), w8 and w9, which represent the average degree of polymerization, are each independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. In formula (4-4), w7 and w10 are average values ​​indicating the number of CF2, and each independently represents 1 to 2. w7 and w10 are determined depending on the structure of the repeating unit located at the end of the chain structure in the PFPE chain represented by formula (4-4), etc.

[0066] (R 1 and R 4 (end group indicated by In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 is a terminal group having 1 to 50 carbon atoms and one or more polar groups. In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 Each of these has one or more polar groups, so when a lubricating layer is formed on a protective layer using a lubricant containing these, a favorable interaction occurs between the lubricating layer and the protective layer. 1 and R 4 can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0067] R 1 and R 4 may be the same or different. 1 and R 4When the values ​​are the same, the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer having better adhesion can be formed.

[0068] R 1 and R 4 Examples of polar groups include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SOH), a cyano group (-CN), and a group having an amide bond (e.g., -CONH or -NHCOCH).

[0069] R 1 and R 4 The number of polar groups contained in each of the above is 1 or more, preferably 1 to 3, and more preferably 2 to 3. This is because the resulting fluorine-containing ether compound has high adhesion to the protective layer and can form a lubricating layer with excellent flying stability and corrosion-inhibiting effect. R 1 and / or R 4 If the number of polar groups contained in is 2 or more, R containing 2 or more polar groups 1 and / or R 4 The polar group may be of one type or two or more types.

[0070] R 1 and R 4 Preferably, R contains one or more hydroxyl groups as polar groups. 1 and / or R 4 When the polar group of the compound has a hydroxyl group, R 1 The hydroxyl group contained in R 4 The total number of hydroxyl groups contained in R is preferably 2 to 6, more preferably 3 to 5, and most preferably 3 or 4. When the total number of hydroxyl groups is 2 or more, R 1 and R 4The interaction between the hydroxyl groups and the protective layer is more effectively achieved. As a result, the fluorine-containing ether compound can form a lubricating layer with high adhesion to the protective layer. Furthermore, when the total number of hydroxyl groups is 6 or less, the number of hydroxyl groups not involved in the bonding between the lubricating layer and the active sites on the protective layer is reduced. This prevents the hydroxyl groups not involved in the bonding between the lubricating layer and the active sites on the protective layer from aggregating and forming protrusions that collide with the magnetic head. This allows the formation of a lubricating layer with better flying stability. Furthermore, when the total number of hydroxyl groups is 4 or less, the hydrophobicity of the lubricating layer containing the fluorine-containing ether compound is sufficiently high. This prevents the lubricating layer from attracting water, which causes corrosion of magnetic recording media. This allows the formation of a lubricating layer that can more effectively suppress contamination and corrosion of magnetic recording media.

[0071] R 1 and / or R 4 has only hydroxyl groups as polar groups, R 1 and / or R 4 The number of hydroxyl groups contained in each of R is preferably 2 to 3, and more preferably 2. 1 and / or R 4 When the number of hydroxyl groups contained in each of R is 2 or more, the lubricating layer containing the fluorine-containing ether compound has high adhesion (tight adhesion) to the protective layer, improving the flying stability of the magnetic recording medium. 1 and / or R 4 When the number of hydroxyl groups contained in each of R is 3 or less, in a magnetic recording medium having a lubricating layer containing a fluorine-containing ether compound, the polarity of the fluorine-containing ether compound is too high, and the lubricating layer can prevent water, which causes corrosion, from being induced to the surface of the protective layer. 1 and / or R 4 When the number of hydroxyl groups contained in each of the above is 2 or less, aggregation of the hydroxyl groups contained in the terminal groups of the fluorine-containing ether compound can be prevented in the lubricating layer containing the fluorine-containing ether compound.

[0072] R 1 and R 4 Each of the terminal groups represented by R has 1 to 50 carbon atoms, preferably 3 to 20 carbon atoms, and more preferably 4 to 15 carbon atoms. 1 and R 4 Since the number of carbon atoms in the terminal group represented by is 1 or more, the hydrophobicity of the terminal group portion can be ensured. This prevents water, which causes corrosion, from being attracted to the lubricating layer, resulting in a lubricating layer with good corrosion resistance. 1 and R 4 Since the number of carbon atoms in the terminal group represented by the formula (I) is 50 or less, the terminal group portion has a flexible structure. As a result, a thin lubricating layer can be formed with sufficient coverage, resulting in a lubricating layer with good flying stability.

[0073] R 1 The terminal group represented by R 2a It is preferable that R has an oxygen atom at the end of the bonded side to CH2 adjacent to R. 4 The terminal group represented by R 2d It is preferable that R has an oxygen atom at the end of the bonded side to CH2 adjacent to R. 1 and R 4 The oxygen atom located at the end of the terminal group represented by R forms an ether bond (-O-) with the atoms bonded to both sides of it. These ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), and 1 and R 4 This increases the affinity between the polar group of the terminal group represented by the formula (I) and the protective layer.

[0074] The fluorine-containing ether compound represented by formula (1) is R 1 and R 4 At least one of the groups represented by the formulas (2-1) to (2-4) is preferably an end group of any one of the groups represented by the formulas (2-1) to (2-4), and R 1 and R 4 and each independently represent a terminal group of any one of the following formulae (2-1) to (2-4):

[0075] [ka] (In formula (2-1), p represents an integer of 1 to 3, and q represents an integer of 1 to 3.) (In formula (2-2), r represents an integer of 0 to 2, and s represents an integer of 1 to 3.) (In formula (2-3), t represents an integer of 1 to 3, u represents an integer of 0 to 2, and v represents an integer of 1 to 3.) (In formula (2-4), l represents an integer of 1 to 3, l m's each independently represent an integer of 1 to 4, and l n's each independently represent an integer of 1 to 4; X represents an organic group containing a double bond or a triple bond.)

[0076] Each hydroxyl group contained in formulas (2-1) to (2-3) is bonded to a different carbon atom. In formulas (2-1) to (2-3), the carbon atoms bonded to the hydroxyl groups are bonded to each other via a linking group containing a carbon atom not bonded to a hydroxyl group. Therefore, R 1 and R 4 When at least one of R is formula (2-1) to (2-3), the fluorine-containing ether compound represented by formula (1) has good hydrophobicity compared to, for example, a case where the fluorine-containing ether compound has an end group in which carbon atoms bonded to hydroxyl groups are bonded to each other. 1 and R 4 When at least one of the formulas (2-1) to (2-3) is a formula, it is presumed that a lubricating layer containing a fluorine-containing ether compound represented by formula (1) can prevent water penetration and effectively suppress corrosion of magnetic recording media. Furthermore, when carbon atoms bonded to hydroxyl groups are bonded to each other via a linking group containing a carbon atom not bonded to a hydroxyl group, the linking group containing a carbon atom not bonded to a hydroxyl group can orient both the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group so that they can adhere to the protective layer. Therefore, it is presumed that excellent flying stability can be obtained. From the above, R 1 and R 4 It is preferable that at least one of the formulas (2-1) to (2-3) is any one of the formulas (2-1) to (2-3).

[0077] Furthermore, in the terminal groups represented by formulas (2-1) and (2-3), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded contains an oxygen atom. The linking group has a linear structure consisting of 3 to 8 atoms, including a carbon atom to which no hydroxyl group is bonded. Even when the linking group contains an oxygen atom, if it has a linear structure consisting of three or more atoms, including a carbon atom to which no hydroxyl group is bonded, the fluorine-containing ether compound will have good hydrophobicity. Furthermore, if the linking group has a linear structure consisting of three or more atoms, the molecular mobility is appropriate, intramolecular aggregation is unlikely to occur, and excellent adhesion to the protective layer can be obtained. Furthermore, if the linking group has a linear structure consisting of eight or fewer atoms, the linking group will not be so hydrophobic that it will impair adhesion to the protective layer. For these reasons, a lubricating layer containing a fluorine-containing ether compound in which the linking group contains an oxygen atom and has a linear structure consisting of the above number of atoms has excellent adhesion to the protective layer, exhibits high floating stability, can prevent water penetration, and has a high corrosion inhibition effect on magnetic recording media.

[0078] Furthermore, in the terminal group represented by formula (2-2), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an oxygen atom. Therefore, intramolecular interactions are small, intramolecular aggregation is unlikely to occur, and excellent adhesion to the protective layer is achieved. Furthermore, the linking group has a linear structure consisting of 1 to 3 atoms, including a carbon atom to which no hydroxyl group is bonded. When the linking group does not contain an oxygen atom and has a linear structure consisting of one or more atoms including a carbon atom to which no hydroxyl group is bonded, the fluorine-containing ether compound exhibits good hydrophobicity. Furthermore, when the linking group has a linear structure consisting of three or fewer atoms, the hydrophobicity of the linking group is not too high, thereby preventing interference with the protective layer. For these reasons, a lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure consisting of the above number of atoms and does not contain an oxygen atom exhibits excellent adhesion to the protective layer, exhibits high flying stability, can prevent water penetration, and has a high corrosion inhibition effect on magnetic recording media.

[0079] In the terminal groups represented by formulae (2-1) to (2-3), the carbon atoms contained in the linking group located between the carbon atoms bonded to the hydroxyl groups play a role in improving the hydrophobicity of the fluorine-containing ether compound. On the other hand, if the number of carbon atoms contained in the linking group is too large, the terminal group (R 1 and R 4 ) may become less flexible, making it difficult to uniformly coat the entire surface of the protective layer. Therefore, in formula (2-1), q is preferably 1 or 2, and more preferably 1. Furthermore, in formula (2-2), s is preferably 1 or 2, and more preferably 1. Similarly, in formula (2-3), t is preferably 1 or 2, and more preferably 1. v is preferably 1 or 2, and more preferably 1.

[0080] The terminal groups represented by formulas (2-1) to (2-3) all have only a hydroxyl group as a polar group. 1 and / or R 4 has only hydroxyl groups as polar groups, R 1 and / or R 4 The number of hydroxyl groups contained in each of the above is preferably 2 to 3, and more preferably 2. In formula (2-1), the number of hydroxyl groups is p+1, so p is preferably 1 or 2, and more preferably 1. In formula (2-2), the number of hydroxyl groups is r+2, so r is preferably 0 or 1, and more preferably 0. In formula (2-3), the number of hydroxyl groups is u+2, so u is preferably 0 or 1, and more preferably 0.

[0081] In the organic group containing a double bond or a triple bond represented by X in formula (2-4), the double bond may be any of a carbon-carbon bond, a carbon-oxygen bond, and a carbon-nitrogen bond, and the triple bond may be any of a carbon-carbon bond and a carbon-nitrogen bond. Specific examples of the organic group containing a double bond or a triple bond represented by X include organic groups containing at least one selected from aromatic hydrocarbons, unsaturated heterocycles, alkenyl groups, alkynyl groups, cyano groups, and groups having an amide bond. The organic group represented by X may contain a polar group. The number of carbon atoms contained in the organic group represented by X is preferably 2 to 15, and more preferably 2 to 10.

[0082] Here, we will explain the bond between the terminal group represented by formula (2-4) and the active site on the protective layer. The numerous functional groups (active sites) present on the protective layer have both locally charged sites and sites with widely distributed charges. The hydroxyl group contained in formula (2-4) exhibits adsorption ability by interacting with locally charged sites on the protective layer through hydrogen bonds between its hydrogen atoms. On the other hand, aromatic hydrocarbons, unsaturated heterocycles, alkenyl groups, and alkynyl groups possess delocalized charges. Therefore, when the organic group represented by X in formula (2-4) contains at least one selected from aromatic hydrocarbons, unsaturated heterocycles, alkenyl groups, and alkynyl groups, the organic group represented by X exhibits adsorption ability by interacting with sites with widely distributed charges on the protective layer. Furthermore, cyano groups and groups containing amide bonds possess widely polarized charges while also possessing delocalized charges. Therefore, when the organic group represented by X in formula (2-4) contains at least one selected from a cyano group and a group having an amide bond, the organic group represented by X can interact with both locally charged sites and sites on the protective layer where the charge distribution is widespread.

[0083] Therefore, the hydroxyl group contained in formula (2-4) and the organic group containing a double or triple bond can be adsorbed to different sites on the protective layer. Therefore, the hydroxyl group contained in formula (2-4) and the organic group containing a double or triple bond can each independently interact with the functional group (active site) on the protective layer. As a result, R 1 and R 4 A lubricating layer containing a fluorine-containing ether compound in which at least one of the above is represented by formula (2-4) has excellent adhesion to the protective layer, exhibits high flying stability, can prevent water penetration, and has a high corrosion-inhibiting effect on the magnetic recording medium. From the above, R 1 and R 4 It is preferable that at least one of the following is formula (2-4).

[0084] In formula (2-4), l is an integer of 1 to 3, preferably an integer of 1 to 2, and most preferably 1. The number of l in formula (2-4) is determined by R 1 or R 4 When l (the number of hydroxyl groups) in formula (2-4) is 3 or less, the number of hydroxyl groups in the terminal groups represented by formula (2-4) is too large, which prevents water, which causes corrosion, from being attracted to the lubricating layer, and a lubricating layer with good corrosion resistance can be obtained. When l in formula (2-4) is 2 or 3, 2 or 3 repeating units (-(CH2) m -CH(OH)-(CH2) n The combinations of m and n in —O—) may be different from one another, or some or all of them may be the same.

[0085] In formula (2-4), l m's each independently represent an integer of 1 to 4, and l n's each independently represent an integer of 1 to 4. One repeating unit (-(CH2) m -CH(OH)-(CH2) nIn the -O-), m+n is preferably 2 to 4, and more preferably 2 to 3. This is because the repeating unit structure does not become rigid due to the alkylene group having too many carbon atoms. Therefore, the terminal group portion has a flexible structure, and a thinner lubricating layer can be formed with a sufficient coverage, resulting in a lubricating layer with good flying stability.

[0086] One repeating unit (-(CH2) m -CH(OH)-(CH2) n At least one of m and n in —O—) is preferably 1. This is because the mobility of the hydroxyl group is not reduced due to the excessive number of carbon atoms in the alkylene group between the carbon atom to which the hydroxyl group is bonded and the ether oxygen atom.

[0087] When X in formula (2-4) contains an aromatic hydrocarbon or an unsaturated heterocycle, X is -(CH2) z1 -R 5 (wherein z1 represents an integer of 0 to 3; R 5 represents an aromatic hydrocarbon or an unsaturated heterocycle. ) is preferred. The aromatic hydrocarbon and the unsaturated heterocycle may have a substituent on the ring structure. Examples of the substituent include a methyl group, an ethyl group, a methoxy group, an ethoxy group, a halogeno group, a cyano group, an acetamide group (-NH(C=O)CH3), and a carboxamide group (-(C=O)NH2).

[0088] When X in formula (2-4) contains an alkenyl group or an alkynyl group, X is preferably an alkenyl group having 2 to 8 carbon atoms or an alkynyl group having 3 to 8 carbon atoms. When X in formula (2-4) contains a cyano group or a group having an amide bond, X is -(CH2) z2 -R 6 (wherein z2 represents an integer of 1 to 5; R 6represents -CN, -NH(C=O)CH3, or -(C=O)NH2.) As described above, X may also be an organic group containing an aromatic hydrocarbon or an unsaturated heterocycle, which has a cyano group, an acetamide group, or a carboxamide group as a substituent.

[0089] Specific examples of the organic group containing a double bond or a triple bond represented by X in formula (2-4) include a phenyl group, a methoxyphenyl group, a fluorinated phenyl group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a benzyl group, a methoxybenzyl group, a naphthylmethyl group, a methoxynaphthyl group, a pyrrolyl group, a pyrazolyl group, a methylpyrazolylmethyl group, an imidazolyl group, a furyl group, a furfuryl group, an oxazolyl group, an isoxazolyl group, a thienyl group, a thienylethyl group, a thiazolyl group, a methylthiazolylethyl group, an isothiazolyl group, a pyridyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, an indolinyl group, a benzofuranyl group, a benzothienyl group, a benzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzyl group, a benzomethyl group, a benzophenone ... Examples of the alkyl group include a benzopyrazolyl group, a benzisoxazolyl group, a benzisothiazolyl group, a quinolyl group, an isoquinolyl group, a quinazolinyl group, a quinoxalinyl group, a phthalazinyl group, a cinnolinyl group, a vinyl group, an allyl group, a butenyl group, a propynyl group, a propargyl group, a butynyl group, a methylbutynyl group, a pentynyl group, a methylpentynyl group, a hexynyl group, a cyanoethyl group, a cyanopropyl group, a cyanophenyl group, an acetamidoethyl group (-CH2CH2NH(C=O)CH3), an acetamidopropyl group (-CH2CH2CH2NH(C=O)CH3), an acetamidophenyl group, a carboxamidoethyl group (-CH2CH2(C=O)NH2), a carboxamidopropyl group (-CH2CH2CH2(C=O)NH2), and a carboxamidophenyl group.

[0090] The organic group represented by X in formula (2-4) is preferably any one selected from the group consisting of a phenyl group, a methoxyphenyl group, a thienylethyl group, a naphthyl group, a butenyl group, an allyl group, a propargyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a cyanoethyl group, a cyanopropyl group, an acetamidoethyl group, and an acetamidopropyl group, and more preferably any one selected from the group consisting of a phenyl group, a methoxyphenyl group, an allyl group, a butenyl group, a thienylethyl group, a cyanoethyl group, a cyanopropyl group, an acetamidoethyl group, and an acetamidopropyl group.

[0091] In particular, when the organic group represented by X in formula (2-4) is either a cyanoethyl group or an acetamidoethyl group, the polarity of the organic group represented by X is high, which enables the formation of a lubricating layer with even better adhesion to the protective layer and better flying stability. Also, when the organic group represented by X is either an allyl group, a methoxyphenyl group, or a thienylethyl group, the hydrophobicity of the organic group represented by X is high, which enables the formation of a lubricating layer with even better corrosion resistance.

[0092] R 1 and R 4 When one of the terminal groups is an end group of any of the above formulas (2-1) to (2-4) and the other is an end group other than the end groups represented by the above formulas (2-1) to (2-4), the other end group may be an end group having 1 to 50 carbon atoms and one or more polar groups. In this case, the other end group may be, for example, an end group having a hydroxyl group other than the end groups represented by the above formulas (2-1) to (2-4).Specific examples of the other end group include -OCH2CH2OH, -OCH2CH2CH2OH, -OCH2CH(OH)CH2OH, -OCH2CH(OH)CH2OCH2CH(OH)CH2OH, etc.

[0093] In the fluorine-containing ether compound represented by formula (1), R 2a and R 2d and are the same, and R 2b and R2c and are the same, and R 3a Atoms contained in and R 3c The atoms contained in R 3b are arranged symmetrically with respect to R 1 and R 4 This is because the resulting fluorine-containing ether compound can be produced easily and efficiently. Furthermore, in the fluorine-containing ether compound represented by formula (1), the four R 2 are all the same, and R 3a Atoms contained in and R 3c The atoms contained in R 3b are arranged symmetrically with respect to R 1 and R 4 It is more preferable that the three R 3 is a fluorine-containing ether compound represented by formula (3), which can be produced more easily and efficiently, and is therefore more preferred.

[0094] In the fluorine-containing ether compound represented by formula (1), the total number of hydroxyl groups contained in the molecule is preferably 5 to 9, and more preferably 5 to 8. When the total number of hydroxyl groups contained in the molecule is 5 or more, the adsorptive power of the entire molecule to the protective layer can be ensured, and a thinner lubricating layer can be formed with sufficient coverage. As a result, a lubricating layer with better flying stability can be formed. Furthermore, when the total number of hydroxyl groups contained in the molecule is 9 or less, the hydrophilicity of the entire molecule is not too high, and the attraction of water, which causes corrosion, to the lubricating layer can be prevented, and a lubricating layer with better corrosion resistance can be formed.

[0095] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any one of the compounds represented by the following formulae (A) to (Z). When the compound represented by formula (1) is any of the compounds represented by the following formulae (A) to (Z), the raw materials are easily available, and a lubricating layer can be formed that has excellent adhesion even when thin, has even better flying stability, and is highly effective in inhibiting corrosion of magnetic recording media.

[0096] In the compounds represented by the following formulas (A) to (Z), Rf1, Rf2, and Rf3, which represent PFPE chains, each have the following structure. That is, in the compounds represented by the following formulas (A) to (W) and (Z), Rf1 is a PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulas (X) and (Z), Rf2 is a PFPE chain represented by the above formula (4-2). In the compound represented by the following formula (Y), Rf3 is a PFPE chain represented by the above formula (4-3). Note that h and i in Rf1, j in Rf2, and k in Rf3, which represent PFPE chains in the formulas (A) to (Z), are values ​​indicating the average degree of polymerization, and are not necessarily integers.

[0097] [ka]

[0098] The compounds represented by the following formulae (A) to (R) and (X) to (Z) each have three R 3 is a linking group represented by formula (3). The compounds represented by the following formulas (A) to (Z) are all R 1 and R 4 At least one of the groups is a terminal group represented by any one of formulas (2-1) to (2-4).

[0099] The compound represented by the following formula (A) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-1), p is 1, and q is 1. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (B) is a compound represented by the formula (1) 1 and R 4is the terminal group represented by the above formula (2-1), p is 1, and q is 2. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (C) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-2), r is 0, and s is 1. 2 is the PFPE chain represented by the above formula (4-1).

[0100] The compound represented by the following formula (D) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-3), where t is 1, u is 0, and v is 1. Four R 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (E) is a compound represented by the formula (1) 1 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 4 is -OCH2CH(OH)CH2OH. Four R 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (F) is a compound represented by the formula (1) 1 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 4 is -OCH2CH(OH)CH2OCH2CH(OH)CH2OH. Four R 2 is the PFPE chain represented by the above formula (4-1).

[0101] The compound represented by the following formula (G) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-1), p is 2, and q is 1. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (H) is a compound represented by the formula (1) 1 is a terminal group represented by the above formula (2-1), p is 1, q is 1, and R 4 is the terminal group represented by the above formula (2-1), p is 2, and q is 1. 2is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (I) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-2), r is 1, and s is 1. 2 is the PFPE chain represented by the above formula (4-1).

[0102] The compound represented by the following formula (J) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-3), where t is 1, u is 1, and v is 1. Four R 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (K) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-4), l is 2, m is 1, n is 1, and X is an allyl group. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (L) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is a p-methoxyphenyl group. 2 is the PFPE chain represented by the above formula (4-1).

[0103] The compound represented by the following formula (M) is a compound represented by the formula (1) 1 is a terminal group represented by the above formula (2-1), p is 1, q is 1, and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is a p-methoxyphenyl group. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (N) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is a thienylethyl group. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (O) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is a cyanoethyl group. 2 is the PFPE chain represented by the above formula (4-1).

[0104] The compound represented by the following formula (P) is a compound represented by the formula (1) 1 is a terminal group represented by the above formula (2-1), p is 1, q is 1, and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is a cyanoethyl group. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (Q) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is an acetamidoethyl group. 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (R) is R in formula (1). 1 is a terminal group represented by the above formula (2-1), p is 1, q is 1, and R 4 is the terminal group represented by the above formula (2-4), l is 1, m is 1, n is 1, and X is an acetamidoethyl group. 2 is the PFPE chain represented by the above formula (4-1).

[0105] The compound represented by the following formula (S) is a compound represented by the formula (1) 1 and R 4 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 3a is a linking group represented by the above formula (3-3), f is 2, and R 3b is a linking group represented by the above formula (3), and R 3c is a linking group represented by the above formula (3-2), and e is 2. Four R 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (T) is a compound represented by the formula (1) 1and R 4 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 3a and R 3c is a linking group represented by the above formula (3), and R 3b is a linking group represented by the above formula (3-3), and f is 2. Four R 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (U) is a compound represented by the formula (1) 1 and R 4 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 3a and R 3c is a linking group represented by the above formula (3), and R 3b is a linking group represented by the above formula (3-1), and d is 2. Four R 2 is the PFPE chain represented by the above formula (4-1).

[0106] The compound represented by the following formula (V) is a compound represented by the formula (1) 1 and R 4 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 3a and R 3c is a linking group represented by the above formula (3), and R 3b is a linking group represented by the above formula (3-4), and g is 0. Four R 2 is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (W) is a compound represented by the formula (1) 1 and R 4 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 3a and R 3c is a linking group represented by the above formula (3), and R 3b is a linking group represented by the above formula (3-4), and g is 4. Four R 2 is the PFPE chain represented by the above formula (4-1).

[0107] The compound represented by the following formula (X) is a compound represented by the formula (1) 1 and R 4is the terminal group represented by the above formula (2-1), p is 1, and q is 1. 2 is the PFPE chain represented by the above formula (4-2). The compound represented by the following formula (Y) is a compound represented by the formula (1) 1 and R 4 is the terminal group represented by the above formula (2-1), p is 1, and q is 1. 2 is the PFPE chain represented by the above formula (4-3). The compound represented by the following formula (Z) is a compound represented by the formula (1) 1 and R 4 is a terminal group represented by the above formula (2-1), where p is 1 and q is 1. 2a and R 2d is a PFPE chain represented by the above formula (4-2), and R 2b and R 2c is the PFPE chain represented by the above formula (4-1).

[0108] [ka] (In the four Rf1s in formula (A), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (B), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (C), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0109] [ka] (In the four Rf1s in formula (D), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (E), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (F), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0110] [ka] (In the four Rf1s in formula (G), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (H), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (I), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0111] [ka] (In the four Rf1s in formula (J), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (K), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (L), h and i represent an average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; h and i in the four Rf1s may be different from each other or may be the same in part or in whole; Me represents a methyl group.)

[0112] [ka] (In the four Rf1s in formula (M), h and i represent an average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; h and i in the four Rf1s may be different from each other or may be the same in part or in whole; Me represents a methyl group.) (In the four Rf1s in formula (N), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (O), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0113] [ka] (In the four Rf1s in formula (P), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (Q), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (R), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0114] [ka] (In the four Rf1s in formula (S), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (T), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (U), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0115] [ka] (In the four Rf1s in formula (V), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.) (In the four Rf1s in formula (W), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the four Rf1s may be different from each other, or some or all of them may be the same.)

[0116] [ka] (In the four Rf2 in formula (X), j represents the average degree of polymerization and represents 1 to 15; j in the four Rf2 may be different from each other, or some or all of them may be the same.) (In the four Rf3s in formula (Y), k represents the average degree of polymerization and represents 1 to 10; k in the four Rf3s may be different from each other, or some or all of them may be the same.) (In the two Rf2's in formula (Z), j represents an average degree of polymerization and is 1 to 15; in the two Rf2's, j may be the same or different; in the two Rf1's in formula (Z), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; in the two Rf1's, h and i may be the same or different.)

[0117] The fluorine-containing ether compound of this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10,000, more preferably in the range of 1,000 to 8,000, even more preferably in the range of 1,500 to 7,000, and particularly preferably in the range of 2,000 to 6,000. When the number-average molecular weight is 500 or more, a lubricating layer formed from a lubricant containing the fluorine-containing ether compound of this embodiment will have excellent heat resistance. The number-average molecular weight of the fluorine-containing ether compound is more preferably 1,000 or more. Furthermore, when the number-average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound is appropriate, and by applying a lubricant containing this, a thin lubricating layer can be easily formed. The number-average molecular weight of the fluorine-containing ether compound is more preferably 8,000 or less, in order to achieve a manageable viscosity when applied to a lubricant.

[0118] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 These are values ​​measured by F-NMR. Specifically, 19The number of repeating units of the PFPE chain is calculated from the integrated value measured by F-NMR to determine the number average molecular weight. For NMR (nuclear magnetic resonance) measurements, the sample is diluted in a hexafluorobenzene / d-acetone (4 / 1 v / v) solvent and measured. 19 The reference for F-NMR chemical shifts is the hexafluorobenzene peak at -164.7 ppm. 1 The reference for H-NMR chemical shifts is the acetone peak at 2.2 ppm.

[0119] The fluorine-containing ether compound of this embodiment is preferably subjected to molecular weight fractionation by an appropriate method to make the molecular weight dispersity (ratio of weight average molecular weight (Mw) / number average molecular weight (Mn)) 1.3 or less. In this embodiment, the method for molecular weight fractionation is not particularly limited, but for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or the like, molecular weight fractionation by supercritical extraction, or the like can be used.

[0120] "Manufacturing method" The method for producing the fluorinated ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorinated ether compound of the present embodiment can be produced, for example, by the production method shown below.

[0121] Fig. 1 is a flow chart illustrating an example of the method for producing a fluorinated ether compound of the present invention. (a) shown in Fig. 1 is a flow chart showing all steps in the method for producing a fluorinated ether compound. (b) shown in Fig. 1 is a flow chart showing the step of producing a linked structure in (a) shown in Fig. 1. (c) shown in Fig. 1 is a flow chart showing the step of producing a compound structure in (a) shown in Fig. 1.

[0122] As shown in FIG. 1(a), the method for producing a fluorinated ether compound of this embodiment includes an end portion producing step S1, a linking structure producing step S2, and a compound structure producing step S3. [Edge manufacturing process S1] In the end manufacturing process S1, R in Equation (1) 1 -CH2-R 2a Intermediate compound 1a having a group corresponding to —CH— and —CH—R in formula (1) 2d -CH2-R 4 Either intermediate compound 1a or intermediate compound 1b may be produced first.

[0123] In the production method of this embodiment, the fluorine-containing ether compound is a compound represented by the formula (1) 2a and R 2d is the same as R 1 and R 4 When a compound in which R is the same as R in formula (1) is produced, intermediate compound 1a and intermediate compound 1b can be produced simultaneously in the end part production step S1. 2a and R 2d is the same as R 1 and R 4 Compounds in which the formula is the same as the formula can be produced efficiently and easily.

[0124] Specifically, the intermediate compounds 1a and 1b can be produced, for example, by the following method. <R 2a and R 2d , R 1 and R 4 When at least one of the following is different (when intermediate compound 1a and intermediate compound 1b are different)> First, R in Equation (1) 2a A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to the formula (1) is prepared, and the hydroxyl group of the hydroxymethyl group at one end is connected to the R 1 The resulting epoxy compound is reacted with an epoxy compound having a group corresponding to R 2a At one end of the perfluoropolyether chain corresponding to 1 The intermediate compound 1a is obtained, which has a group corresponding to

[0125] Next, R in Equation (1) 2d A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to the formula (1) is prepared, and the hydroxyl group of the hydroxymethyl group at one end is connected to the R 4 The resulting epoxy compound is reacted with an epoxy compound having a group corresponding to R 2d At one end of the perfluoropolyether chain corresponding to 4 The intermediate compound 1b is obtained, which has a group corresponding to

[0126] <R 2a and R 2d is the same, and R 1 and R 4 are the same (when intermediate compound 1a and intermediate compound 1b are the same) First, R in Equation (1) 2a (=R 2d A fluorine-based compound is prepared in which a hydroxymethyl group (-CHOH) is arranged at each end of a perfluoropolyether chain corresponding to R in formula (1). Next, the hydroxyl group of the hydroxymethyl group arranged at one end of the fluorine-based compound is reacted with the hydroxyl group of the hydroxymethyl group arranged at one end of the fluorine-based compound. 1 The group corresponding to (=R 4 The resulting epoxy compound is reacted with an epoxy compound having a group corresponding to R 2a (=R 2d ) at one end of the perfluoropolyether chain corresponding to 1 The group corresponding to (=R 4 The intermediate compound 1a (=intermediate compound 1b) having a group corresponding to

[0127] R in Equation (1) 1 The group (or R 4 Examples of epoxy compounds having a group corresponding to the formula (5-1) include compounds represented by the following formulas (5-1) to (5-14). THP in the following formulas (5-1) to (5-10) represents a tetrahydropyranyl group. Me in the following formula (5-11) represents a methyl group. When the fluorine-based compound and the epoxy compound are reacted to synthesize the intermediate compound 1a (or intermediate compound 1b), the hydroxyl group of the epoxy compound may be protected with an appropriate protecting group before the reaction with the fluorine-based compound.

[0128] [ka]

[0129] R in Equation (1) 1 The group (or R 4 An epoxy compound having a group corresponding to R in formula (1) can be produced, for example, by the method shown below. 1 (or R 4 The copolymer can be produced by reacting an alcohol having a structure corresponding to a part of the terminal group represented by the formula (I) with a halogen compound having an epoxy group.

[0130] [ka] (In formula (6-1), R is R in formula (1) 1 or R 4 a1 represents an integer of 1 or more.)

[0131] The epoxy compound can also be produced by the following method: That is, as shown in the following formula (6-2), R 1 (or R 4 ) is reacted with a halogen compound having an alkenyl group. The resulting compound is then oxidized with m-chloroperbenzoic acid (mCPBA).

[0132] [ka] (In formula (6-2), R is R in formula (1) 1or R 4 a2 represents an integer of 1 or more.)

[0133] The epoxy compound can also be produced by the following method: That is, as shown in the following formula (6-3), R in formula (1) 1 (or R 4 ) is subjected to an addition reaction with a compound having an alkenyl group and an epoxy group. The compound obtained by the addition reaction is then oxidized with m-chloroperbenzoic acid (mCPBA). The hydroxyl group generated by the addition reaction may be appropriately protected and then oxidized using mCPBA.

[0134] [ka] (In formula (6-3), R is R in formula (1) 1 or R 4 a3 and a4 each represent an integer of 0 or greater; and Y represents O or CH2.)

[0135] [Connected structure manufacturing process S2] In the connection structure manufacturing process S2, -R in formula (1) 3a -CH2-R 2b -CH2-R 3b -CH2-R 2c -CH2-R 3c The intermediate compound 3 is prepared by carrying a group corresponding to The connection structure manufacturing step S2 may be performed after the end portion manufacturing step S1 or may be performed before the end portion manufacturing step S1.

[0136] As shown in FIG. 1(b), the connection structure manufacturing process S2 includes a connection end manufacturing process S21 and a R 2b Side reaction step S22 and R 2c and a side reaction step S23. In the connecting end manufacturing process S21, -R in formula (1) 3a -CH2-R2b an intermediate compound 2a having a group corresponding to —CH— and —CH—R in formula (1) 2c -CH2-R 3c An intermediate compound 2b having a group corresponding to - is produced. Either the intermediate compound 2a or the intermediate compound 2b may be produced first.

[0137] R 2b In the side reaction step S22, R in formula (1) 3b R of a compound having a group corresponding to 2b The side end is reacted with intermediate compound 2a. 2c In the side reaction step S23, R in formula (1) 3b R of a compound having a group corresponding to 2c The side end is reacted with intermediate compound 2b. 2c The side reaction step S23 is R 2b It may be carried out after the side reaction step S22, or R 2b This may be carried out before the side reaction step S22.

[0138] In the production method of this embodiment, the fluorine-containing ether compound is a compound represented by the formula (1) 2b and R 2c is the same as R 3a Atoms contained in and R 3c The atoms contained in R 3b When producing a compound symmetrically arranged with respect to R in formula (1), intermediate compound 2a and intermediate compound 2b can be produced simultaneously in the linking structure production step S2. 2b and R 2c is the same as R 3a Atoms contained in and R 3c The atoms contained in R 3b Compounds that are symmetrically arranged with respect to R can be produced efficiently and easily. Furthermore, when intermediate compound 2a and intermediate compound 2b are produced simultaneously, intermediate compound 2a and intermediate compound 2b are the same. Therefore, R 2b Side reaction process S22 and R 2c The side reaction step S23 can be carried out simultaneously. 2b and R 2cis the same as R 3a Atoms contained in and R 3c The atoms contained in R 3b Compounds that are symmetrically arranged with respect to the compound are excellent in productivity.

[0139] Specifically, the intermediate compounds 2a and 2b can be produced by the following methods, for example. <R 2b and R 2c are different, and / or R 3a Atoms contained in and R 3c The atoms contained in R 3b When the intermediate compound 2a and the intermediate compound 2b are not symmetrically arranged relative to each other (when the intermediate compound 2a and the intermediate compound 2b are different) First, R in Equation (1) 2b A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of the perfluoropolyether chain corresponding to R 3a The resulting compound is reacted with a halogen compound or an epoxy compound having an alkenyl group corresponding to R 2b At one end of the perfluoropolyether chain corresponding to 3a An intermediate compound 2a having an alkenyl group corresponding to

[0140] Next, R in Equation (1) 2c A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of the perfluoropolyether chain corresponding to R 3c The resulting compound is reacted with a halogen compound or an epoxy compound having an alkenyl group corresponding to R 2c At one end of the perfluoropolyether chain corresponding to 3c The intermediate compound 2b is obtained, which has a group corresponding to

[0141] <R 2b and R 2c is the same, and R 3aAtoms contained in and R 3c The atoms contained in R 3b When the intermediate compounds 2a and 2b are symmetrically arranged relative to each other (when the intermediate compounds 2a and 2b are the same) R in Equation (1) 2b (=R 2c A fluorine-based compound is prepared in which a hydroxymethyl group (-CHOH) is arranged at each end of a perfluoropolyether chain corresponding to R. Next, the hydroxyl group of the hydroxymethyl group arranged at one end of the fluorine-based compound and the hydroxyl group of the hydroxymethyl group arranged at the other end of the fluorine-based compound are mixed. 3a (=R 3c ) is reacted with a halogen compound or an epoxy compound having an alkenyl group corresponding to R in formula (1). 2b (=R 2c ) at one end of the perfluoropolyether chain corresponding to 3a (=R 3c ) to give intermediate compound 2a (=intermediate compound 2b) having an alkenyl group corresponding to

[0142] R in Equation (1) 3a (or R 3c As the halogen compound or epoxy compound having an alkenyl group corresponding to (7-1), for example, compounds represented by the following formulas (7-1) to (7-5) can be used.

[0143] [ka]

[0144] R 2b Side reaction steps S22 and R 2c Specifically, the side reaction step S23 can be carried out by, for example, the following method. <R 2b and R 2c are different, and / or R 3a Atoms contained in and R 3c The atoms contained in R 3b When the intermediate compound 2a and the intermediate compound 2b are not symmetrically arranged relative to each other (when the intermediate compound 2a and the intermediate compound 2b are different) One molecule of intermediate compound 2a and R 3b was reacted with a halogen compound or diepoxy compound having an epoxy group corresponding to (R 2b After the side reaction step S22), the resulting compound is reacted with one molecule of intermediate compound 2b (R 2c Side reaction step S23). Alternatively, one molecule of intermediate compound 2b and R 3b was reacted with a halogen compound or diepoxy compound having an epoxy group corresponding to (R 2c After the side reaction step S23), the resulting compound is reacted with one molecule of intermediate compound 2a (R 2b Side reaction step S22). This results in R in Equation (1) 2b and R 2c The perfluoropolyether chain corresponding to R 3b and R 3a and the corresponding alkenyl group R 3c and an alkenyl group corresponding to

[0145] <R 2b and R 2c is the same, and R 3a Atoms contained in and R 3c The atoms contained in R 3b When the intermediate compounds 2a and 2b are symmetrically arranged relative to each other (when the intermediate compounds 2a and 2b are the same) Two molecules of intermediate compound 2a (= intermediate compound 2b) and R 3b The compound is reacted with a halogen compound or a diepoxy compound having an epoxy group corresponding to R in formula (1). 2b (=R 2c ) is a perfluoropolyether chain corresponding to R 3b and a methylene group is bonded to the linking group corresponding to 3a (=R 3c ) to give intermediate compound 3 having an alkenyl group corresponding to

[0146] R in Equation (1)3b As the halogen compound or diepoxy compound having an epoxy group corresponding to the above, for example, compounds represented by the following formulae (8-1) to (8-5) can be used.

[0147] [ka]

[0148] [Compound structure manufacturing process S3] The compound structure production step S3 is as shown in FIG. 1(c), 1 Side reaction step S31 and R 4 A side reaction step S32 is included. 1 In the side reaction step S31, R 3a The side end is reacted with intermediate compound 1a. 4 In the side reaction step S32, R of intermediate compound 3 (or intermediate compound 3-1 described later) 3c The side end is reacted with the intermediate compound 1b. 4 The side reaction step S32 is R 1 It may be carried out after the side reaction step S31, or R 1 It may be carried out before the side reaction step S31.

[0149] In the production method of this embodiment, the fluorine-containing ether compound is a compound represented by the formula (1) 2a and R 2d is the same as R 1 and R 4 When a compound having the same R 1 -CH2-R 2a The group corresponding to —CH— and —CH—R of intermediate compound 1b 2d -CH2-R 4 Since the groups corresponding to are the same, R 1 Side reaction process S31 and R 4 The side reaction step S32 can be carried out simultaneously. 2a and R 2d is the same as R 1 and R4 Compounds in which the formula is the same as the formula can be produced efficiently and easily.

[0150] In particular, in the production method of this embodiment, the fluorine-containing ether compound is a compound represented by the formula (1) 2a and R 2d and are the same, and R 2b and R 2c and are the same, and R 3a Atoms contained in and R 3c The atoms contained in R 3b are arranged symmetrically with respect to R 1 and R 4 In the case of producing a compound in which R is the same as R, intermediate compound 1a and intermediate compound 1b are simultaneously produced in end part production step S1, intermediate compound 2a and intermediate compound 2b are simultaneously produced in linking structure production step S2, and R 2b Side reaction process S22 and R 2c The side reaction step S23 is carried out simultaneously, and in the compound structure production step S3, R 1 Side reaction process S31 and R 4 A method of simultaneously carrying out the side reaction step S32 and the side reaction step S33 can be used, which allows for more efficient and easier production.

[0151] R 1 Side reaction steps S31 and R 4 Specifically, the side reaction step S32 can be carried out by, for example, the following method. The intermediate compound 3 used in the compound structure production step S3 is represented by the formula (1) -R 3a -CH2-R 2b -CH2-R 3b -CH2-R 2c -CH2-R 3c Specifically, when compound structure producing step S3 is performed, intermediate compound 3 produced in linking structure producing step S2 of the present embodiment may be used as is, or intermediate compound 3 produced in linking structure producing step S2 may be used after being treated by oxidizing the carbon-carbon double bonds present at both terminals to form epoxy groups, and this can be determined appropriately depending on the types of intermediate compound 1a and intermediate compound 1b.

[0152] In this embodiment, an intermediate compound (hereinafter referred to as "intermediate compound 3-1") is used as the intermediate compound 3, which is produced in the linking structure production step S2, and in which the carbon-carbon double bonds at both ends are oxidized to form epoxy groups. Intermediate compound 3-1 is a compound represented by the formula (1) R 2b The perfluoropolyether chain corresponding to R 2c and the perfluoropolyether chain corresponding to R 3b and the corresponding linking groups are bonded via methylene groups, and the R 2b R at the end of the side 3a and R 2c R at the end of the side 3c has an epoxy group corresponding to The reaction of oxidizing the carbon-carbon double bonds present at both ends of intermediate compound 3 to produce intermediate compound 3-1 may be carried out after the hydroxyl groups of intermediate compound 3 are appropriately protected.

[0153] <R 2a and R 2d , R 1 and R 4 When at least one of the following is different (when intermediate compound 1a and intermediate compound 1b are different)> R of one molecule of intermediate compound 1a and intermediate compound 3-1 2b The epoxy group at the end of the hydroxyl group reacted with the hydroxyl group (R 1 After the side reaction step S31), the resulting compound is reacted with one molecule of intermediate compound 1b (R 4 Side reaction step S32). Alternatively, one molecule of intermediate compound 1b and R of intermediate compound 3-1 2c The epoxy group at the end of the hydroxyl group reacted with the hydroxyl group (R 4 After the side reaction step S32), the resulting compound is reacted with one molecule of intermediate compound 1a (R 1 Side reaction step S31).

[0154] <R 2a and R 2d is the same, and R1 and R 4 are the same (when intermediate compound 1a and intermediate compound 1b are the same)> Two molecules of intermediate compound 1a (=intermediate compound 1b) are subjected to an addition reaction with the epoxy groups present at both ends of intermediate compound 3-1.

[0155] In this way, R 1 Side reaction steps S31 and R 4 After the side reaction step S32, the protecting group of the reaction product is deprotected using an appropriate reactant. By carrying out the above steps, the compound represented by formula (1) can be produced.

[0156] The fluorine-containing ether compound of the present embodiment is a compound represented by formula (1), which contains a divalent linking group (R 3a , R 3b , and R 3c ) through four perfluoropolyether chains (R 2a , R 2b , R 2c , and R 2d ) bonded to each other, at least one of the three linking groups forming the skeleton is represented by formula (3), and both sides of the skeleton are connected to terminal groups (R 1 and R 4 ) are bonded to the lubricating layer. Therefore, a lubricating layer formed on a protective layer using a lubricant containing the fluorinated ether compound of this embodiment has good floating stability for a magnetic head and a high corrosion-inhibiting effect on a magnetic recording medium.

[0157] In the method for producing a fluorinated ether compound of the present embodiment, R 1 -CH2-R 2a intermediate compound 1a having a group corresponding to —CH— and —CH—R 2d -CH2-R 4 and intermediate compound 1b having a group corresponding to -R 3a -CH2-R 2bintermediate compound 2a having a group corresponding to —CH— and —CH—R 2c -CH2-R 3c and intermediate compound 2b having a group corresponding to R 3b R of a compound having a group corresponding to 2b The side end is reacted with intermediate compound 2a to form R 3b R of a compound having a group corresponding to 2c The side end is reacted with intermediate compound 2b to form -R 3a -CH2-R 2b -CH2-R 3b -CH2-R 2c -CH2-R 3c Then, the intermediate compound 3 having a group corresponding to R 3a The side end of the intermediate compound 3 is reacted with the intermediate compound 1a to form R 3c The side end and intermediate compound 1b are reacted. For this purpose, the divalent linking group (R 3a , R 3b , and R 3c ) through four perfluoropolyether chains (R 2a , R 2b , R 2c , and R 2d The fluorine-containing ether compound of the present embodiment, which is represented by formula (1) and has a skeleton to which 2-(2-methyl-2-phenyl)-2-methyl-2-propanol is bonded, can be selectively produced.

[0158] According to the method for producing a fluorinated ether compound of the present embodiment, a fluorinated ether compound represented by formula (1) can be produced with high purity. <1> A method of reacting a fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain with epichlorohydrin (for example, the method described in Patent Document 5), <2> There is a method (for example, the method described in Patent Document 6) in which a fluorine-based compound in which a hydroxymethyl group (-CHOH) is arranged at each end of a perfluoropolyether chain is reacted with glycidol to obtain a mixture, and the mixture is reacted with a diepoxy compound.

[0159] The above-mentioned conventionally known <1> and <2> In the method, a divalent linking group (R 3a , R 3b , and R 3c ) and the compound corresponding to the perfluoropolyether chain (R 2a , R 2b , R 2c , and R 2d ) react randomly with compounds corresponding to the above, producing a mixture of fluorine-containing ether compounds with different numbers of perfluoropolyether chains in the molecule. The target compound and by-products contained in the resulting mixture have similar polarities, making them difficult to separate by column chromatography, and also have similar boiling points, making them difficult to separate by distillation. Therefore, it is difficult to isolate the target compound from the resulting mixture. For this reason, <1> and <2> In the method, a divalent linking group (R 3a , R 3b , and R 3c ) through four perfluoropolyether chains (R 2a , R 2b , R 2c , and R 2d However, it is difficult to obtain a fluorine-containing ether compound having a desired skeleton to which the aryl group is bonded with high purity.

[0160] Also, the above <1> and <2> The mixture obtained by this method contains a large amount of by-products, such as compounds with three or fewer perfluoropolyether chains that have poor adhesion to the protective layer, and / or compounds with five or more perfluoropolyether chains that have poor molecular fluidity. In contrast, the method for producing a fluorinated ether compound of the present embodiment can suppress the production of such by-products, and can selectively produce a fluorinated ether compound of the present embodiment that is likely to form a lubricating layer that is uniformly coated on the protective layer and has excellent adhesion.

[0161] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of the present embodiment can be used by mixing, as needed, known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorinated ether compound represented by the above formula (1) are not impaired.

[0162] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), and the like. The known material to be mixed with the lubricant of this embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0163] When the lubricant of the present embodiment contains a material other than the fluorinated ether compound represented by the above formula (1), the content of the fluorinated ether compound represented by the above formula (1) in the lubricant of the present embodiment is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0164] The lubricant of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). Therefore, the lubricant of this embodiment can be applied uniformly in a thin thickness, and can form a thin lubricating layer that provides good flying stability for the magnetic head and has a high corrosion-inhibiting effect on the magnetic recording medium.

[0165] [Magnetic recording media] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer, as needed, and at least one of an adhesive layer and a soft magnetic layer may also be provided between the underlayer and the substrate.

[0166] FIG. 2 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0167] "substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. The substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or may be a non-magnetic substrate having a NiP or NiP alloy film formed on a base made of any of these non-metallic materials.

[0168] "Adhesion layer" The adhesive layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are disposed in contact with each other. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0169] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are antiferro-coupling (AFC).

[0170] The first and second soft magnetic films may be made of a material such as a CoZrTa alloy or a CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it is possible to improve the orientation of the first underlayer (seed layer) and reduce the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0171] "First base layer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, or a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0172] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a single layer or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all of the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0173] "Magnetic layer" The magnetic layer 16 is a magnetic film whose easy axis of magnetization is oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 contains Co and Pt. To improve the SNR characteristics, the magnetic layer 16 may contain oxides, Cr, B, Cu, Ta, Zr, or the like. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0174] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. The oxide contained in the first magnetic layer is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among these, TiO2, Cr2O3, SiO2, and the like are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide containing two or more types of oxides. Among these, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, and the like are particularly suitable.

[0175] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxides. The second magnetic layer can be made of the same material as the first magnetic layer, and preferably has a granular structure.

[0176] The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0177] When magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0178] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0179] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, oxides that can be used include, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, and TiO2. Metal nitrides that can be used include, for example, AlN, Si3N4, TaN, and CrN. Metal carbides that can be used include, for example, TaC, BC, and SiC. The non-magnetic layer can be formed by, for example, a sputtering method.

[0180] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for longitudinal magnetic recording. The magnetic layer 16 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0181] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or multiple layers. A carbon-based protective layer is preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. If the protective layer 17 is a carbon-based protective layer, the interaction with the polar groups (particularly hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0182] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 atomic % to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 atomic % to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0183] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of protective layer 17 and hydrogen is contained on the magnetic layer 16 side of protective layer 17. In this case, the adhesion between the magnetic layer 16 and lubricating layer 18 and the carbon-based protective layer is further improved.

[0184] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. When the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. When the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0185] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, or ion beam deposition (IBD). When a carbon-based protective layer is formed as the protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed 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 with little roughness.

[0186] "Lubricant layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. The lubricating layer 18 also reduces the frictional force of the magnetic head of the magnetic recording / reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 2, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 is formed by applying the magnetic recording medium lubricant of the above-described embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-described fluorine-containing ether compound.

[0187] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 bonds with the protective layer 17 with particularly high bonding strength. As a result, even if the thickness of the lubricating layer 18 is thin, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0188] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.2 nm (12 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. Therefore, the surface of the protective layer 17 can be covered with the lubricating layer 18 at a high coverage rate. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be made sufficiently small.

[0189] "Method for forming lubricating layer" A method for forming the lubricating layer 18 includes, for example, preparing a magnetic recording medium in the middle of manufacturing in which the layers up to the protective layer 17 are formed on the substrate 11, applying a solution for forming the lubricating layer onto the protective layer 17, and drying the solution.

[0190] The lubricant layer forming solution can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium according to the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.).

[0191] The method for applying the lubricating layer-forming solution is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in a lubricant layer-forming solution placed in an immersion tank of a dip coating device. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricating layer forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0192] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. When the heat treatment temperature is 100°C or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180°C or lower, thermal decomposition of the lubricating layer 18 due to the heat treatment can be prevented. The heat treatment time can be adjusted appropriately depending on the heat treatment temperature, and is preferably 10 minutes to 120 minutes.

[0193] In this embodiment, in order to further improve the adhesive strength of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) rays before or after the heat treatment.

[0194] The magnetic recording medium 10 of this embodiment includes at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18, which are sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-described fluorine-containing ether compound is formed on and in contact with the protective layer 17. Even with a thin film thickness, this lubricating layer 18 has excellent adhesion, favorable floating stability, and a high corrosion suppression effect for the magnetic recording medium. Therefore, the magnetic recording medium 10 of this embodiment has excellent reliability and durability. Therefore, the magnetic recording medium 10 of this embodiment can be configured with a low floating height of the magnetic head (e.g., 10 nm or less) and operates stably for a long period of time, even in harsh environments associated with diverse applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk to be mounted in a magnetic disk device using the LUL (Load Unload) method. [Example]

[0195] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0196] [ reference Example 1] The compound represented by the above formula (A) was obtained by the method shown below. (Edge manufacturing process S1) Place HOCH2CF2O (CF2CF2O) in a 100 mL recovery flask under a nitrogen gas atmosphere. h (CF2O) i 10 g of a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5), 2.06 g of a compound represented by the above formula (5-1), and 10 mL of t-butanol were charged and stirred at room temperature until homogeneous to form a mixture. 0.37 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0197] The compound represented by formula (5-1) was synthesized by protecting ethylene glycol monoallyl ether with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0198] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 5.23 g of the compound represented by the following formula (9) as intermediate compound 1a (= intermediate compound 1b).

[0199] [ka] (Rf1 in formula (9) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0200] (Connected structure manufacturing process S2) (Connection end manufacturing process S21) Place HOCH2CF2O (CF2CF2O) in a 200 mL recovery flask under a nitrogen gas atmosphere. h (CF2O) i 20 g of a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where h, indicating the average degree of polymerization, is 4.5, and i, indicating the average degree of polymerization, is 4.5), 0.88 g of sodium hydride, and 20 mL of N,N-dimethylformamide were charged and stirred in an ice bath until foaming subsided to form a mixture. 2.42 g of a compound (allyl bromide) represented by formula (7-1) was added to this mixture, and the mixture was allowed to react with stirring at room temperature for 4 hours.

[0201] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 10.51 g of a compound represented by the following formula (10) as intermediate compound 2a (= intermediate compound 2b).

[0202] [ka] (Rf1 in formula (10) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0203] (R 2b Side reaction steps S22 and R 2c Side reaction step S23) Under a nitrogen gas atmosphere, 10.51 g of the compound represented by formula (10), which is intermediate compound 2a (= intermediate compound 2b) obtained above, 0.76 g of the compound represented by formula (8-1) (epibromohydrin), and 20 mL of t-butanol were charged into a 100 mL recovery flask, and the mixture was stirred at room temperature until homogeneous. 0.52 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted with stirring at 70 °C for 16 hours.

[0204] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 7.74 g of the compound represented by the following formula (11), which was used as intermediate compound 3.

[0205] [ka] (Rf1 in formula (11) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0206] (Compound structure manufacturing process S3) Under a nitrogen gas atmosphere, 7.74 g of the compound represented by formula (11), which is intermediate compound 3 obtained above, 1.22 g of dihydropyran, 0.07 g of p-toluenesulfonic acid monohydrate, and 20 mL of methylene chloride were placed in a 100 mL recovery flask, and the mixture was stirred at room temperature for 3 hours to react. The reaction solution was treated with 0.07 g of triethylamine and concentrated. Subsequently, 2.50 g of m-chloroperbenzoic acid and 20 mL of methylene chloride were added to the resulting mixture, and the mixture was stirred at room temperature for 18 hours.

[0207] The reaction mixture obtained after the reaction was transferred little by little to a separatory funnel containing 100 mL of water and extracted three times with 100 mL of ethyl acetate. The organic layer was washed successively with 100 mL of brine, 100 mL of saturated sodium bicarbonate solution, and 100 mL of brine, and then dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.65 g of the compound represented by the following formula (12) as intermediate compound 3-1.

[0208] [ka] (Rf1 in formula (12) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0209] (R 1 Side reaction steps S31 and R 4 Side reaction step S32) Under a nitrogen gas atmosphere, 5.23 g of the compound represented by formula (9), which is intermediate compound 1a (= intermediate compound 1b) obtained above, 4.42 g of the compound represented by formula (12), which is intermediate compound 3-1, and 20 mL of t-butanol were charged into a 100 mL recovery flask and stirred at room temperature until a homogeneous mixture was obtained. 0.15 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0210] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.51 g of compound (A). Rf1 in formula (A) represents the PFPE chain represented by formula (4-1) above. For the four Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5.

[0211] The obtained compound (A) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(40H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0212] [ reference Example 2] The compound represented by the above formula (B) was obtained by the method shown below. Except that the compound represented by formula (5-2) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.72 g of compound (B) (Rf1 in formula (B) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0213] The compound represented by formula (5-2) was synthesized by protecting one of the hydroxyl groups of 1,3-propanediol with dihydropyran, followed by the reaction with epibromohydrin.

[0214] The obtained compound (B) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(40H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0215] [ reference Example 3] The compound represented by the above formula (C) was obtained by the method shown below. Except that the compound represented by formula (5-3) was used instead of the compound represented by formula (5-1). referenceThe same procedure as in Example 1 was carried out to obtain 3.25 g of compound (C) (Rf1 in formula (C) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0216] The compound represented by formula (5-3) was synthesized by protecting 3-buten-1-ol with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0217] The obtained compound (C) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(32H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0218] [ reference Example 4] The compound represented by the above formula (D) was obtained by the method shown below. Except that the compound represented by formula (5-4) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.67 g of compound (D) (Rf1 in formula (D) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0219] The compound represented by formula (5-4) was synthesized by reacting 3-buten-1-ol with 2-(2-bromoethoxy)tetrahydro-2H-pyran, followed by oxidation with m-chloroperbenzoic acid.

[0220] The obtained compound (D) 1H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(32H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0221] [ reference Example 5] The compound represented by the above formula (E) was obtained by the method shown below. (Edge manufacturing process S1) reference The same procedure as in Example 1 was carried out to obtain the compound represented by the above formula (9) as intermediate compound 1a. In addition, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), reference The same operation as in the edge production step S1 in Example 1 was carried out to obtain a compound represented by the following formula (13) as intermediate compound 1b. The compound represented by formula (5-5) was synthesized by protecting allyl alcohol with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0222] [ka] (Rf1 in formula (13) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0223] (Compound structure manufacturing process S3) reference Using intermediate compound 3 prepared by carrying out linked structure preparation step S2 in the same manner as in Example 1, referenceIn the same manner as in Example 1, a compound represented by formula (12) was obtained as intermediate compound 3-1. (R 1 Side reaction step S31) Under a nitrogen gas atmosphere, 2.65 g of intermediate compound 1a (compound represented by formula (9)), 4.84 g of intermediate compound 3-1 (compound represented by formula (12)), and 20 mL of t-butanol were placed in a 100 mL recovery flask and stirred at room temperature until a homogeneous mixture was obtained. 0.15 g of potassium tert-butoxide was added to the mixture, and the mixture was allowed to react with stirring at 70°C for 16 hours.

[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 over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.31 g of the intermediate compound represented by the following formula (14).

[0225] [ka] (Rf1 in formula (14) is a PFPE chain represented by the above formula (4-1); in the three Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0226] (R 4 Side reaction step S32) Next, in a 100 mL recovery flask under a nitrogen gas atmosphere, 2.32 g of the compound represented by formula (13), which is intermediate compound 1b, and R 1 3.31 g of the compound represented by formula (14), which is the intermediate compound produced in the side reaction step S31, and 20 mL of t-butanol were added and stirred at room temperature until a homogeneous mixture was obtained. 0.15 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0227] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 2.08 g of compound (E). (Rf1 in formula (E) is the PFPE chain represented by formula (4-1) above; for the four Rf1s, h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5.)

[0228] The obtained compound (E) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(36H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0229] [ reference Example 6] The compound represented by the above formula (F) was obtained by the method shown below. Except that the compound represented by formula (5-6) was used instead of the compound represented by formula (5-5). reference The same procedure as in Example 5 was carried out to obtain 2.11 g of compound (F) (Rf1 in formula (F) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0230] The compound represented by formula (5-6) was synthesized by reacting one molecule of 3-allyloxy-1,2-propanediol with two molecules of dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0231] The obtained compound (F) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(42H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0232] [ reference Example 7] The compound represented by the above formula (G) was obtained by the method shown below. Except that the compound represented by formula (5-7) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.83 g of compound (G) (Rf1 in formula (G) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0233] The compound represented by formula (5-7) was synthesized by subjecting the compound represented by formula (5-1) to an addition reaction with allyl alcohol, protecting the resulting product with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0234] The obtained compound (G) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(52H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0235] [ reference Example 8] The compound represented by the above formula (H) was obtained by the method shown below. Except that the compound represented by formula (5-7) was used instead of the compound represented by formula (5-5). reference The same procedure as in Example 5 was carried out to obtain 2.25 g of compound (H) (Rf1 in formula (H) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0236] The obtained compound (H) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(46H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0237] [ reference Example 9] The compound represented by the above formula (I) was obtained by the method shown below. Except that the compound represented by formula (5-8) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.53 g of compound (I) (Rf1 in formula (I) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0238] The compound represented by formula (5-8) was synthesized by subjecting the compound represented by formula (5-3) to an addition reaction with allyl alcohol, protecting the resulting product with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0239] The obtained compound (I) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(44H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0240] [ reference Example 10] The compound represented by the above formula (J) was obtained by the method shown below. Except that the compound represented by formula (5-9) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.24 g of compound (J) (Rf1 in formula (J) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0241] The compound represented by formula (5-9) was synthesized by subjecting the compound represented by formula (5-1) to an addition reaction with 3-buten-1-ol, protecting the resulting product with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0242] The obtained compound (J) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(52H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0243] [ reference Example 11] The compound represented by the above formula (K) was obtained by the method shown below. Except that the compound represented by formula (5-10) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.91 g of compound (K) (Rf1 in formula (K) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0244] The compound represented by formula (5-10) was synthesized by reacting one molecule of epibromohydrin with two molecules of allyl alcohol, protecting the resulting product with dihydropyran, and then oxidizing one of the carbon-carbon double bonds with m-chloroperbenzoic acid.

[0245] The obtained compound (K) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(46H), 3.85-4.10(16H), 5.40-6.10(3H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0246] [ reference Example 12] The compound represented by the above formula (L) was obtained by the method shown below. Except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 4.08 g of compound (L) (Rf1 in formula (L) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; Me represents a methyl group).

[0247] The compound represented by formula (5-11) was synthesized by reacting p-methoxyphenol with epibromohydrin.

[0248] The obtained compound (L) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(36H), 3.85-4.10(16H), 6.70-7.40(10H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0249] [ reference Example 13] The compound represented by the above formula (M) was obtained by the method shown below. Except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-5). reference The same procedure as in Example 5 was carried out to obtain 2.41 g of compound (M) (Rf1 in formula (M) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; Me represents a methyl group).

[0250] The obtained compound (M) 1 H-NMR and 19F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(38H), 3.85-4.10(16H), 6.70-7.40(5H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0251] [ reference Example 14] The compound represented by the above formula (N) was obtained by the method shown below. Except that the compound represented by formula (5-12) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.67 g of compound (N) (Rf1 in formula (N) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0252] The compound represented by formula (5-12) was synthesized by reacting 2-thiopheneethanol with epibromohydrin.

[0253] The obtained compound (N) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=2.20-2.30(4H), 3.65-3.85(34H), 3.85-4.10(16H), 6.30-7.60(6H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0254] [ reference Example 15] The compound represented by the above formula (O) was obtained by the method shown below. Except that the compound represented by formula (5-13) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.94 g of compound (O) (Rf1 in formula (O) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0255] The compound represented by formula (5-13) was synthesized by reacting 2-cyanoethanol with epibromohydrin.

[0256] The obtained compound (O) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=2.00-2.10(4H), 3.65-3.85(34H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0257] [ reference Example 16] The compound represented by the above formula (P) was obtained by the method shown below. Except that the compound represented by formula (5-13) was used instead of the compound represented by formula (5-5). reference The same procedure as in Example 5 was carried out to obtain 2.32 g of compound (P) (Rf1 in formula (P) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0258] The obtained compound (P) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=2.00-2.10(2H), 3.65-3.85(37H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0259] [ reference Example 17] The compound represented by the above formula (Q) was obtained by the method shown below. Except that the compound represented by formula (5-14) was used instead of the compound represented by formula (5-1). reference The same procedure as in Example 1 was carried out to obtain 3.61 g of compound (Q) (Rf1 in formula (Q) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0260] The compound represented by formula (5-14) was synthesized by reacting 2-acetamidoethanol with epibromohydrin.

[0261] The obtained compound (Q) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(6H), 3.65-3.85(38H), 3.85-4.10(16H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0262] [ reference Example 18] The compound represented by the above formula (R) was obtained by the method shown below. Except that the compound represented by formula (5-14) was used instead of the compound represented by formula (5-5). reference The same procedure as in Example 5 was carried out to obtain 2.14 g of compound (R) (Rf1 in formula (R) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0263] The obtained compound (R) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(3H), 3.65-3.85(39H), 3.85-4.10(16H), 6.30-6.50(1H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0264] [Example 19] The compound represented by the above formula (S) was obtained by the method shown below. Except that the compound represented by formula (7-2) was used instead of the compound represented by formula (7-1). reference The same procedure as in Example 1 was carried out to obtain 3.41 g of compound (S) (Rf1 in formula (S) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0265] The obtained compound (S) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(40H), 3.85-4.10(16H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0266] [Example 20] The compound represented by the above formula (T) was obtained by the method shown below. Except that the compound represented by formula (8-2) was used instead of the compound represented by formula (8-1). reference The same procedure as in Example 1 was carried out to obtain 3.75 g of compound (T) (Rf1 in formula (T) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0267] The obtained compound (T) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(2H), 3.65-3.85(40H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0268] [Example 21] The compound represented by the above formula (U) was obtained by the method shown below. Except that the compound represented by formula (8-3) was used instead of the compound represented by formula (8-1). reference The same procedure as in Example 1 was carried out to obtain 3.62 g of compound (U) (Rf1 in formula (U) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0269] The obtained compound (U) 1 H-NMR and 19F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(46H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0270] [Example 22] The compound represented by the above formula (V) was obtained by the method shown below. Except that the compound represented by formula (8-4) was used instead of the compound represented by formula (8-1). reference The same procedure as in Example 1 was carried out to obtain 3.24 g of compound (V) (Rf1 in formula (V) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0271] The obtained compound (V) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(42H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0272] [Example 23] The compound represented by the above formula (W) was obtained by the method shown below. Except that the compound represented by formula (8-5) was used instead of the compound represented by formula (8-1). referenceThe same procedure as in Example 1 was carried out to obtain 3.24 g of compound (W) (Rf1 in formula (W) is a PFPE chain represented by the above formula (4-1); in the four Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0273] The obtained compound (W) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.25-1.85(8H), 3.65-3.85(42H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(36F), -78.5(8F), -80.5(8F), -91.0~-88.5(72F)

[0274] [ reference Example 24] The compound represented by the above formula (X) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH (where h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5), HOCH2CF2CF2O(CF2CF2CF2O) j The compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by CF2CF2CH2OH (where j, which indicates the average degree of polymerization, is 4.5) was used. reference The same procedure as in Example 1 was carried out to obtain 3.92 g of compound (X) (Rf2 in formula (X) is a PFPE chain represented by the above formula (4-2); in the four Rf2s, j, which indicates the average degree of polymerization, is 4.5).

[0275] The obtained compound (X) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=3.65-3.85(40H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(72F), -86.4(16F), -124.3(16F), -130.0~-129.0(36F)

[0276] [ reference Example 25] The compound represented by the above formula (Y) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH (where h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5), HOCH2CF2CF2CF2O(CF2CF2CF2CF2O) k The compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by CF2CF2CF2CH2OH (where k, which indicates the average degree of polymerization, is 3.0) was used. reference The same procedure as in Example 1 was carried out to obtain 3.67 g of compound (Y) (Rf3 in formula (Y) is a PFPE chain represented by the above formula (4-3); in the four Rf3s, k, which indicates the average degree of polymerization, is 3.0).

[0277] The obtained compound (Y) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(40H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(64F), -122.5(16F), -126.0(48F), -129.0~-128.0(16F)

[0278] [ reference Example 26] The compound represented by the above formula (Z) was obtained by the method shown below. In the edge manufacturing process S1, HOCH2CF2O (CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH (where h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5), HOCH2CF2CF2O(CF2CF2CF2O) j The compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CFCFCHOH (where j, which indicates the average degree of polymerization, is 4.5) was used, and in the linked structure production step S2, HOCHCFO (CFCFO) h (CF2O) i The compound represented by HOCH2CF2O(CF2CF2O)2CF2CH2OH was used instead of the compound represented by CF2CH2OH (where h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5). reference The same procedure as in Example 1 was carried out to obtain 3.15 g of compound (Z) (Rf1 in formula (Z) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h, which indicates the average degree of polymerization, is 2.0, and i, which indicates the average degree of polymerization, is 0; Rf2 in formula (Z) is a PFPE chain represented by the above formula (4-2); in the two Rf2s, j, which indicates the average degree of polymerization, is 4.5).

[0279] The obtained compound (Z) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.65-3.85(40H), 3.85-4.10(16H) 19 F-NMR (acetone-D6): δ[ppm]=-80.5(8F), -91.0~-88.5(16F)-84.0~-83.0(36F), -86.4(8F), -124.3(8F), -130.0~-129.0(18F)

[0280] This is how it was obtained Reference Examples 1 to 18 and 24 to 26 and Examples 19 to 23 When compounds (A) to (Z) are applied to formula (1), R 1 , R 2 (R 2a , R 2b , R 2c , and R 2d ), R 3 (R 3a , R 3b and R 3c ), R 4 The structures of are shown in Tables 1 and 2.

[0281] [Table 1]

[0282] [Table 2]

[0283] [Comparative Example 1] The compound represented by the following formula (ZA) was synthesized by the method described in Patent Document 1.

[0284] [ka] (Rf1 in formula (ZA) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i is 4.5.)

[0285] Comparative Example 2 The compound represented by the following formula (ZB) was synthesized by the method described in Patent Document 2.

[0286] [ka] (Rf1 and Rf1' in formula (ZB) are PFPE chains represented by the above formula (4-1); in Rf1, h indicating the average degree of polymerization is 4.5, and i is 4.5; in the two Rf1's, h indicating the average degree of polymerization is 7.0, and i is 0.)

[0287] Comparative Example 3 The compound represented by the following formula (ZC) was synthesized by the method described in Patent Document 3.

[0288] [ka] (Rf1 in formula (ZC) is a PFPE chain represented by the above formula (4-1); in the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i is 4.5.)

[0289] Comparative Example 4 The compound represented by the following formula (ZD) was synthesized by the method described in Patent Document 4.

[0290] [ka] (Rf1 in formula (ZD) is a PFPE chain represented by the above formula (4-1); in the three Rf1s, h indicating the average degree of polymerization is 7.0, and i is 0.)

[0291] Comparative Example 5 A compound represented by the following formula (ZE) was obtained by the method shown below. In the edge manufacturing process S1, HOCH2CF2CF2O (CF2CF2CF2O) j The compound represented by formula (1) was used as intermediate compound 1a (=intermediate compound 1b), except that one of the hydroxyl groups of the compound represented by formula (1) was protected with dihydropyran. reference The same procedure as in Example 24 was carried out to obtain compound (ZE).

[0292] [ka] (Rf2 in formula (ZE) is a PFPE chain represented by the above formula (4-2); in the four Rf2s, j representing the average degree of polymerization is 4.5.)

[0293] Compound (ZE) corresponds to an extract of only compounds having four PFPE chains from the mixture described in the examples of Patent Document 5.

[0294] Comparative Example 6 A compound represented by the following formula (ZF) was obtained by the method shown below. The compounds represented by the formula (5-5) were used instead of the compound represented by the formula (5-1), the compounds represented by the formula (7-1) were used instead of the compound represented by the formula (7-5), and the compounds represented by the formula (8-1) were used instead of the compound represented by the formula (8-5). reference The same procedure as in Example 24 was carried out to obtain compound (ZF).

[0295] [ka] (Rf2 in formula (ZF) is a PFPE chain represented by the above formula (4-2); in the four Rf2s, j representing the average degree of polymerization is 4.5.)

[0296] The compound (ZF) corresponds to an extract of only the compounds having four PFPE chains from the mixture described in the examples of Patent Document 6.

[0297] The compound represented by formula (7-5) was obtained by oxidizing one carbon-carbon double bond of 1,7-octadiene using m-chloroperbenzoic acid.

[0298] This is how it was obtained Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and The number average molecular weights (Mn) of the compounds of Comparative Examples 1 to 6 were measured by the above method. The results are shown in Tables 3 and 4.

[0299] Next, by the method shown below, Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and Solutions for forming a lubricating layer were prepared using the compounds obtained in Comparative Examples 1 to 6. Then, using the obtained solutions for forming a lubricating layer, a lubricating layer of a magnetic recording medium was formed by the method described below. Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and Magnetic recording media of Comparative Examples 1 to 6 were obtained.

[0300] "Lubricant layer forming solution" Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and The compounds obtained in Comparative Examples 1 to 6 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the film thickness when applied to the protective layer would be 9.0 Å to 9.5 Å, to prepare a solution for forming a lubricating layer.

[0301] "Magnetic recording media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate having a diameter of 65 mm. The protective layer was made of carbon. On the protective layer of the magnetic recording medium on which each layer up to the protective layer has been formed, Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and The lubricating layer-forming solutions of Comparative Examples 1 to 6 were applied by dipping under the conditions of an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a pull-up speed of 1.2 mm / sec. The magnetic recording medium coated with the lubricating layer-forming solution was then placed in a thermostatic chamber, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent in the lubricating layer-forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0302] (film thickness measurement) This is how it was obtained Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and The thickness of the lubricating layer of the magnetic recording media of Comparative Examples 1 to 6 was measured using a Fourier transform infrared spectrophotometer (FT-IR, product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Tables 3 and 4.

[0303] next, Reference Examples 1 to 18 and 24 to 26, Examples 19 to 23, and The magnetic recording media of Comparative Examples 1 to 6 were subjected to the following flying stability test and corrosion resistance test.

[0304] (Floating stability test) The following glide tests and credence measurements were carried out, and the flying stability was evaluated based on the following evaluation criteria. The results are shown in Tables 3 and 4.

[0305] "Glide Test" The glide test checks for protrusions on the surface of magnetic recording media. That is, when using a magnetic head to record or reproduce data on a magnetic recording medium, if there are protrusions on the surface of the magnetic recording medium that are higher than the flying height (the distance between the magnetic recording medium and the magnetic head), the magnetic head may collide with the protrusions, causing damage to the magnetic head or defects in the magnetic recording medium. In the glide test, 50 magnetic recording media are inspected for the presence of protrusions on the surface that are higher than the flying height.

[0306] Specifically, the distance between the testing magnetic head and the magnetic recording medium was set to 0.25 microinches, and the testing magnetic head was moved over the magnetic recording medium. If the testing magnetic head output a signal due to a collision with a protrusion on the surface of the magnetic recording medium, the magnetic recording medium was judged to be defective, and all other magnetic recording media were judged to be pass. Then, the number of magnetic recording media judged to be pass out of the 50 magnetic recording media was used for evaluation.

[0307] "Credence measurement" During the glide test, noise temporarily increases, and even at the same location on the magnetic recording medium, signals resulting from collisions with surface protrusions may or may not be detected during multiple measurements. This phenomenon is called creedence. Creedence is not detected as a protrusion in the glide test and is not used to determine whether the glide test passed or failed. However, a temporary increase in noise during the glide test generally indicates unevenness in the lubricant layer or the presence of relatively soft foreign matter. For this reason, the glide test was performed on magnetic recording media, and the average greedence value was calculated by dividing the total number of creedence events detected by the number of magnetic recording media (50) tested. This value was used as an index of the smoothness and cleanliness of the lubricant layer.

[0308] "Evaluation Criteria" A+: 45 or more glide test passes and average credence less than 0.5 A: Glide test pass count is 45 or more and credence average is 0.5 or more but less than 1.0 B: Glide test pass count is 45 or more and credence average is 1.0 or more but less than 5.0 C: 45 or more glide test passes and average credence of 5.0 or more D: Less than 45 sheets passed the glide test

[0309] (Corrosion resistance test) The magnetic recording media were exposed to conditions of 85°C and 90% relative humidity for 48 hours. After that, the number of corrosion spots with a diameter of 5 microns or more that appeared on the surface of the magnetic recording media was counted using an optical surface analyzer (Candela 7140, manufactured by KLA-Tencor Corporation) and evaluated based on the following criteria. The results are shown in Tables 3 and 4.

[0310] "Evaluation Criteria" A+: Less than 100 locations A: Over 100 locations, but less than 200 locations B: 200 or more, less than 300 C: 300 or more, less than 1,000 D: Over 1,000 locations

[0311] (comprehensive evaluation) Based on the results of the floating stability test and the corrosion resistance test, an overall evaluation was made based on the following criteria. "comprehensive evaluation" A: Both the floating stability test and corrosion resistance test were evaluated as A+ or A. B: Either the floating stability test rating or the corrosion resistance test rating is B, and the other rating is A+, A, or B C: Either the floating stability test rating or the corrosion resistance test rating is C, and the other is A+, A, B, or C. D: At least one of the evaluations of the floating stability test and the corrosion resistance test is D

[0312] [Table 3]

[0313] [Table 4]

[0314] As shown in Table 3, Reference Examples 1 to 18 and 24 to 26 and Examples 19 to 23 The magnetic recording media of the above received an evaluation result of A+, A, or B in all evaluation items, resulting in an overall evaluation of A or B. Reference Examples 1 to 18 and 24 to 26 and Examples 19 to 23 It was confirmed that the lubricating layer of the magnetic recording medium in this example provides good flying stability for the magnetic head and has a high corrosion suppression effect on the magnetic recording medium.

[0315] In particular, compounds (G) to (J), (Q), (U), and (V) were used. reference Examples 7-10, 17 and Examples The lubricating layers of the magnetic recording media Nos. 21 and 22 were evaluated as A+ for flying stability, which was good. Compounds (G) to (J) each have a total of 8 or more hydroxyl groups, and three R 3 are each represented by formula (3), and in both terminal groups, the carbon atoms to which hydroxyl groups are bonded are bonded via a linking group containing a carbon atom to which no hydroxyl group is bonded. reference It is believed that in Examples 7 to 10, the molecules as a whole had a high adsorptive power to the protective layer, and the adhesion to the protective layer was good, resulting in a lubricating layer with better flying stability.

[0316] In addition, compound (Q) has groups with highly polar amide bonds at both ends. reference It is believed that Example 17 had a high adhesive force to the protective layer, and thus a lubricating layer with better flying stability was obtained.

[0317] In addition, the compounds (U) and (V) have a total of 8 or more hydroxyl groups in the compound, and R 3b The number of hydroxyl groups contained in R is two, and in both terminal groups, the carbon atoms to which the hydroxyl groups are bonded are bonded via a linking group containing a carbon atom to which no hydroxyl group is bonded. 3bis represented by formula (3-1), d is 2, and in compound (V), R 3b is expressed by equation (3-4) and g is 0, so R 3b The structure between the carbon atoms to which the two hydroxyl groups in 3b The two hydroxyl groups in the compound (U) and (V) easily interact with the protective layer. For this reason, it is believed that in Examples 21 and 22, which used compounds (U) and (V), the molecules as a whole had a high adsorption force to the protective layer, good adhesion to the protective layer, and a lubricating layer with superior flying stability was obtained.

[0318] reference The compounds (L), (N), (O), and (Q) used in Examples 12, 14, 15, and 17 all have a total of five hydroxyl groups in the compound. reference In examples 15 and 17, reference The floating stability was better than in Examples 12 and 14. This is presumably because the cyano group in compound (O) and the group having an amide bond in compound (Q) have high polarity and can interact with both locally charged sites and sites with a widespread charge distribution on the protective layer.

[0319] In addition, compounds (B) to (D), (K), (L), (N), (S), and (T) were used. reference Examples 2-4, 11, 12, 14 and Example The lubricating layers of magnetic recording media Nos. 19 and 20 were rated A+ for corrosion resistance, which was particularly good. R of compounds (B) and (D) 1 and R 4 is R of compound (A). 1 and R 4 The structure has one methylene group extended from the compound (S) and (T). 3 are the three R of compound (A). 3 One or two R 3 In this way, compounds (B), (D), (S), and (T) have a structure in which one methylene group is extended, and therefore the hydrophobicity of the entire molecule is higher than that of compound (A). reference Examples 2 and 4 and Examples 19 and 20 are reference It is believed that the corrosion resistance was rated higher compared to Example 1.

[0320] R of compound (C) 1 and R 4 is R of compound (A). 1 and R 4 As a result, the compound (C) has a structure with fewer ether bonds than the compound (A). As a result, the compound (C) has a higher hydrophobicity as a whole molecule than the compound (A). reference Example 3 is: reference It is believed that the corrosion resistance was rated higher compared to Example 1. In addition, compounds (K), (L), and (N) have either a highly hydrophobic allyl group, a methoxyphenyl group, or a thienylethyl group at both ends. Therefore, compounds (K), (L), and (N) have a higher hydrophobicity as a whole molecule than compound (A). As a result, reference Examples 11, 12, and 14 are: reference It is believed that the corrosion resistance was rated higher compared to Example 1.

[0321] reference The compounds (G), (I), and (J) used in Examples 7, 9, and 10 were all R 1 and R 4 Both of these have three hydroxyl groups. reference In Examples 9 and 10, compound (G) was used. reference The corrosion resistance was better than that of Example 7. This is thought to be because the compounds (I) and (J) have higher hydrophobicity as a whole molecule than the compound (G). More specifically, R of compound (I) 1 and R 4 is the R of compound (G) 1 and R 4 In addition, the R 1 and R 4 is the R of compound (G) 1 and R 4The structure has one methylene group extended compared to compound (G). From these facts, it is estimated that compounds (I) and (J) have a higher hydrophobicity as a whole molecule compared to compound (G).

[0322] Furthermore, as shown in Table 4, in Comparative Example 1, which used compound (ZA) having a skeleton in which two perfluoropolyether chains are bonded via a glycerin structure (-OCH2CH(OH)CHO-), the evaluation of flying stability was C, and the overall evaluation was C. In Comparative Examples 2 to 4, which used compounds (ZB) to (ZD) having a skeleton in which three perfluoropolyether chains are bonded via two divalent linking groups, the evaluations of flying stability and corrosion resistance were both C or D. The results of Comparative Examples 1 to 4 are presumably due to the fact that the number of perfluoropolyether chains in the compounds (ZA) to (ZD) is small, and the number of divalent linking groups arranged between the perfluoropolyether chains is also small, which is thought to have caused the compounds (ZA) to (ZD) to have insufficient adhesion (adsorption force) to the protective layer.

[0323] In addition, in Comparative Example 5, the flying stability was evaluated as D and the corrosion resistance was evaluated as C. In Comparative Example 5, a compound (ZE) was used, which has a skeleton in which four perfluoropolyether chains are bonded via three glycerin structures (-OCH2CH(OH)CHO-), and hydroxyl groups are bonded to both sides of the skeleton via methylene groups. In Compound (ZE), the terminal hydroxyl group is bonded to a methylene group bonded to the perfluoropolyether chain. For this reason, the acidity of the terminal hydroxyl group is high, and the terminal portion of the fluorine-containing ether compound cannot be sufficiently adsorbed to the protective layer. For this reason, it is believed that the lubricating layer of Comparative Example 5 had poor adhesion to the protective layer, resulting in significantly inferior flying stability and corrosion resistance of the magnetic head.

[0324] Furthermore, in Comparative Example 6, the flying stability was evaluated as D, and the corrosion resistance was evaluated as C. In Comparative Example 6, a compound (ZF) was used, which had a skeleton in which four perfluoropolyether chains were bonded via three linking groups each having eight carbon atoms and two hydroxyl groups. In Compound (ZF), all three linking groups arranged between the four perfluoropolyether chains have a relatively rigid structure in which an alkylene group having four carbon atoms is attached between the carbon atoms to which the hydroxyl groups are attached, and the compound (ZF) does not have a glycerin structure (—OCHCH(OH)CHO—), which is highly flexible. Therefore, none of the three linking groups in Compound (ZF) can move flexibly, and the hydroxyl groups in each of the three linking groups cannot sufficiently adsorb to the protective layer. This is thought to be the reason why the lubricating layer in Comparative Example 6 had poor adhesion, resulting in significantly inferior flying stability and corrosion resistance of the magnetic head. [Industrial Applicability]

[0325] By using a lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has excellent adhesion even when it is thin, has good flying stability for the magnetic head, and has a high corrosion-inhibiting effect on the magnetic recording medium. [Explanation of symbols]

[0326] 10...magnetic recording medium, 11...substrate, 12...adhesion layer, 13...soft magnetic layer, 14...first underlayer, 15...second underlayer, 16...magnetic layer, 17...protective layer, 18...lubricating layer.

Claims

1. A fluorine-containing ether compound represented by the following formula (1) and having a number average molecular weight in the range of 500 to 10,000: R １ -CH ２ -R ２ａ -CH ２ -R ３ａ -CH ２ -R ２ｂ -CH ２ -R ３ｂ -CH ２ -R ２ｃ -CH ２ -R ３ｃ -CH ２ -R ２ｄ -CH ２ -R ４ (1) (In formula (1), R ２ａ , R ２ｂ , R ２ｃ and R ２ｄ is a perfluoropolyether chain; R ２ａ , R ２ｂ , R ２ｃ and R ２ｄ may be the same in part or in whole, or may be different from each other; R ３ａ , R ３ｂ and R ３ｃ is a divalent linking group having one or more polar groups and is a linking group represented by formula (3) or any one of formulas (3-1) to (3-4); R ３ａ , R ３ｂ and R ３ｃ may be the same in part or in whole, or may be different from each other; R ３ａ , R ３ｂ and R ３ｃ at least one of R 3a , R 3b and R 3c is a divalent linking group other than that of formula (3), and the divalent linking group other than that of formula (3) is each independently a linking group represented by any one of the following formulas (3-1) to (3-4); R １ and R ４ is an end group of any one of formulas (2-1) to (2-4), and may be the same or different. -OCH ２ CH(OH)CH ２ O- (3) 【Chemistry 1】 (In formula (2-1), p represents an integer of 1 to 3, and q represents an integer of 1 to 3.) (In formula (2-2), r represents an integer of 0 to 2, and s represents an integer of 1 to 3.) (In formula (2-3), t represents an integer of 1 to 3, u represents an integer of 0 to 2, and v represents an integer of 1 to 3.) (In formula (2-4), l represents an integer of 1 to 3, l m's each independently represent an integer of 1 to 4, and l n's each independently represent an integer of 1 to 4; X represents an organic group containing a double bond or a triple bond.) 【Chemistry 2】 (In formula (3-1), d represents 2 or 3.) (In formula (3-2), e represents an integer of 2 to 4; in formula (3-2), the oxygen atom on the left side is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom on the right side is bonded to the methylene group on the R 4 side in formula (1).) (In formula (3-3), f represents an integer of 2 to 4; in formula (3-3), the oxygen atom on the left side is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom on the right side is bonded to the methylene group on the R 4 side in formula (1).) (In formula (3-4), g represents an integer of 0 to 4.)

2. R in the formula (1) １ and a hydroxyl group of R ４ and the total number of hydroxyl groups contained in the above formula (1) is 2 to 6.

3. R in the formula (1) ２ａ and R ２ｄ and R ２ｂ and R ２ｃ and R ３ａ Atoms contained in and R ３ｃ and the atoms contained in R ３ｂ are arranged symmetrically with respect to R １ and R ４ The fluorine-containing ether compound according to claim 1 or 2, wherein

4. R in the formula (1) ２ａ , R ２ｂ , R ２ｃ , and R ２ｄ and each independently represent a perfluoropolyether chain represented by the following formula (4): -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (4) (In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are each independently a value of CF ２ is an average value representing the number of repeating units in formula (4), each of which independently represents 1 to 3; ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the arrangement order of O).

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

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

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

8. 8. The magnetic recording medium according to claim 7, wherein the lubricating layer has an average film thickness of 0.5 nm to 2.0 nm.

9. A method for producing the fluorinated ether compound according to claim 1, R in the formula (1) １ -CH ２ -R ２ａ -CH ２ and an intermediate compound 1a having a group corresponding to —CH in the formula (1). ２ -R ２ｄ -CH ２ -R ４ an end preparation step of preparing an intermediate compound 1b having a group corresponding to -R in the formula (1) ３ａ -CH ２ -R ２ｂ -CH ２ -R ３ｂ -CH ２ -R ２ｃ -CH ２ -R ３ｃ a linking structure preparation step for preparing an intermediate compound 3 having a group corresponding to R of the intermediate compound 3 ３ａ R reacting the side end with the intermediate compound 1a １ Side reaction step and R of the intermediate compound 3 ３ｃ R reacting the side end with the intermediate compound 1b ４ a compound structure producing step including a side reaction step, The step of producing the linked structure is carried out by adding -R ３ａ -CH ２ -R ２ｂ -CH ２ and an intermediate compound 2a having a group corresponding to —CH in the formula (1). ２ -R ２ｃ -CH ２ -R ３ｃ a linking end preparation step for preparing an intermediate compound 2b having a group corresponding to -; R in the formula (1) ３ｂ R of a compound having a group corresponding to ２ｂ R reacting the side end with the intermediate compound 2a ２ｂ a side reaction step; The R ３ｂ R of a compound having a group corresponding to ２ｃ R reacting the side end with the intermediate compound 2b ２ｃ a side reaction step.

10. R in the formula (1) ２ａ and R ２ｄ and R ２ｂ and R ２ｃ and R ３ａ Atoms contained in and R ３ｃ and the atoms contained in R ３ｂ are arranged symmetrically with respect to R １ and R ４ and In the end portion production step, the intermediate compound 1a and the intermediate compound 1b are simultaneously produced, In the step of producing the linking end portion, the intermediate compound 2a and the intermediate compound 2b are simultaneously produced, and the R ２ｂ Side reaction step and the R ２ｃ and a side reaction step are carried out simultaneously, In the compound structure production process, １ Side reaction step and the R ４ The method for producing a fluorinated ether compound according to claim 9, wherein a side reaction step is carried out simultaneously with the above step.

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