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

Abstract

This fluorine-containing ether compound is represented by R1-R2-Y-(CH2)z-O-CH2-R3[-CH2-R4-CH2-R3]x-CH2-O-(CH2)z-Y-R5-R6 (x is 0-1; z is an integer of 2-10; Y is any of O, NH, or S; R3 is a perfluoropolyether chain; R4 is a divalent linking group having 1-3 hydroxyl groups and having oxygen atoms at both ends; R2 is formula (2-1) or (2-2); R5 is formula (2-3) or (2-4); and R1 and R6 are end groups.).

Description

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

[0001] The present invention relates to a fluorine-containing ether compound, a coating material, a lubricant for magnetic recording media, and a magnetic recording medium. This application claims priority to Japanese Patent Application No. 2024-066210, filed April 16, 2024, the contents of which are incorporated herein by reference.

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

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

[0004] For example, Patent Documents 1, 3 and 4 disclose perfluoropolyether chains each having an ether bond (—O—) and a methylene group (—CH ２ Patent Document 2 discloses a fluorine-containing ether compound having a linking group combining a methylene group (-CH(OH)-) in which one hydrogen atom is substituted with a hydroxyl group and a methylene group (-CH(OH)-) in which one hydrogen atom is substituted with a hydroxyl group.

[0005] International Publication No. 2021 / 251318 Japanese Patent No. 5334064 International Publication No. 2019 / 054148 International Publication No. 2021 / 090940

[0006] In magnetic recording and reproducing devices, there is a demand for ever smaller flying heights of magnetic heads. To this end, there is a demand for thinner lubricating layers in magnetic recording media. However, reducing the thickness of a lubricating layer generally tends to reduce its wear resistance. A reduction in the wear resistance of the lubricating layer can lead to damage to the magnetic recording medium (head crash) due to contact with the magnetic head.

[0007] One way to maintain sufficient wear resistance while thinning the lubricating layer is to use a lubricant made of a compound with a low number-average molecular weight. However, lubricating layers formed using compounds with a low number-average molecular weight are prone to spin-off. Spin-off is a phenomenon in which the lubricant scatters or evaporates due to centrifugal force and heat generated by the rotation of a magnetic recording medium. In recent years, the rotation speed of magnetic recording media has increased along with the rapid improvement in recording density of magnetic recording media. This makes spin-off more likely to occur. When spin-off occurs, the thickness of the lubricating layer decreases, reducing the wear resistance of the lubricating layer and the durability of the magnetic recording medium.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that can form a lubricating layer that has excellent wear resistance even when thin and is resistant to film thickness reduction due to spin-off, and that can be suitably used as a material for a lubricant for a magnetic recording medium.

[0009] Another object of the present invention is to provide a coating material and a lubricant for magnetic recording media that contain the fluorinated ether compound of the present invention and that are capable of forming a lubricating layer that has excellent wear resistance even when thin and is resistant to film thickness reduction due to spin-off.Another object of the present invention is to provide a magnetic recording medium that has a lubricating layer containing the fluorinated ether compound of the present invention and has excellent reliability and durability.

[0010] The present invention relates to the following:

[0011] [1] A fluorinated ether compound represented by the following formula (1): R １ -R ２ -Y-(CH ２) ｚ -O-CH ２ -R ３ [-CH ２ -R ４ -CH ２ -R ３ ] ｘ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ (1) (In formula (1), x is 0 to 2; each z is independently an integer from 2 to 10; each Y is independently O, NH, or S; R ３ is a perfluoropolyether chain. (x+1) R ３ may be the same in part or in whole, or may be different from each other; R ４ is a divalent linking group having 1 to 3 hydroxyl groups and oxygen atoms at both ends; when x is 2, two R ４ may be the same or different; R ２ is a linking group represented by the following formula (2-1) or (2-2); R ５ is a linking group represented by the following formula (2-3) or (2-4); R １ and R ６ is R ２ or R ５ are terminal groups bonded to the terminal oxygen atoms of R １ and R ６ are each independently a terminal group selected from the group consisting of a hydrogen atom, an alkyl group which may have a substituent, and an organic group which has a double bond or a triple bond and which may have a substituent.

[0012] (In formula (2-1), f1 represents an integer of 1 to 3. The oxygen atom at the left end of formula (2-1) is R １ (In formula (2-2), g1 represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-2) is bonded to R １ (In formula (2-3), f2 represents an integer of 1 to 3. The oxygen atom at the right end of formula (2-3) is bonded to R ６(In formula (2-4), g2 represents an integer of 2 to 6. The oxygen atom at the right end of formula (2-4) is bonded to R ６ )

[0013] [2] The fluorinated ether compound according to [1], wherein each z in formula (1) is independently an integer of 2 to 6. [3] The fluorinated ether compound according to [2], wherein each z in formula (1) is independently an integer of 2 to 4.

[0014] [4] The fluorine-containing ether compound according to any one of [1] to [3], wherein each Y in the formula (1) is independently O or NH. [5] The fluorine-containing ether compound according to [4], wherein all Y in the formula (1) are O.

[0015] [6] R １ and R ６ [7] The fluorine-containing ether compound according to any one of [1] to [5], wherein the alkyl groups which may have a substituent are each independently an alkyl group having 1 to 8 carbon atoms which may have a substituent. １ and R ６ The fluorine-containing ether compound according to any one of [1] to [6], wherein the organic groups having a double bond or a triple bond and which may have a substituent are each independently at least one selected from the group consisting of aromatic hydrocarbon groups, unsaturated heterocyclic groups, alkenyl groups, and alkynyl groups, which may have a substituent.

[0016] [8] x R in the formula (1) ４ are each independently a divalent linking group represented by any one of the following formulas (2-5) to (2-8):

[0017] (In formula (2-5), r represents an integer of 1 to 3.) (In formula (2-6), s represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-6) is R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２In formula (2-7), t represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-7) is bonded to R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ In formula (2-8), u represents an integer of 1 to 6, and v represents an integer of 1 to 6. u and v cannot be 1 at the same time. The oxygen atom at the left end of formula (2-8) is bonded to R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ - and bond.)

[0018] [9] (x+1) R in the formula (1) ３ are each independently represented by the following formula (Rf): -(CF ２ ) ｐ１ -O-(CF ２ O) ｐ２ -(CF ２ CF ２ O) ｐ３ -(CF ２ CF ２ CF ２ O) ｐ４ -(CF ２ CF ２ CF ２ CF ２ O) ｐ５ -(CF ２ ) ｐ６ - (Rf) (In formula (Rf), p2, p3, p4, and p5 represent an average degree of polymerization, each independently representing 0 to 20. However, p2, p3, p4, and p5 cannot all be 0 at the same time. p1 and p6 are -CF ２ - is an average value representing the number of -, each independently representing 1 to 3. ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２There are no particular restrictions on the arrangement order of O).

[0019]

[10] (x+1) R in the formula (1) ３ are each independently represented by the following formulas (3-1) to (3-4): ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (3-1) (In formula (3-1), 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 - (3-2) (In formula (3-2), 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 - (3-3) (In formula (3-3), 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 - (3-4) (In formula (3-4), 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

[0020]

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

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

[12] A coated material comprising the fluorinated ether compound according to any one of [1] to

[11] .

[13] A lubricant for magnetic recording media, comprising the coated material according to

[12] .

[0021]

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

[11] .

[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.

[0022] The fluorine-containing ether compound according to an embodiment of the present invention is a compound represented by the above formula (1), and is suitable as a material for a lubricant for a magnetic recording medium. The coating material and the lubricant for a magnetic recording medium according to an embodiment of the present invention contain the fluorine-containing ether compound according to an embodiment of the present invention, and therefore can form a lubricating layer that has excellent wear resistance even when thin and is resistant to film thickness reduction due to spin-off. The magnetic recording medium according to an embodiment of the present invention has excellent reliability and durability because it is provided with a lubricating layer that contains the fluorine-containing ether compound according to an embodiment of the present invention and has excellent wear resistance and spin-off resistance.

[0023] 1 is a schematic cross-sectional view showing an example of an embodiment of a magnetic recording medium of the present invention.

[0024] In order to solve the above problems, the present inventors have conducted extensive research as described below. Conventionally, fluorine-containing ether compounds having a terminal structure containing a polar group such as a hydroxyl group at one or both ends of a perfluoropolyether chain have been preferably used as materials for lubricants for magnetic recording media (hereinafter sometimes abbreviated as "lubricants") that are applied to the surface of a protective layer.

[0025] The polar group contained in the fluorine-containing ether compound bonds with the active site on the protective layer, improving the adhesion of the lubricating layer to the protective layer. Among the polar groups, the hydroxyl group in particular has a high positive charge of the hydrogen atom and has a high adsorption property to the protective layer. Therefore, as a method for improving the wear resistance of the lubricating layer, it is considered to arrange a plurality of hydroxyl groups in the terminal structure of the fluorine-containing ether compound to improve the adhesion to the protective layer.

[0026] However, as a result of investigations by the present inventors, it was found that, among the hydroxyl groups contained in the terminal structure of the fluorinated ether compound, the hydroxyl group closest to the perfluoropolyether chain (hereinafter referred to as the primary hydroxyl group) has low adsorption to the protective layer. This is presumably because the perfluoropolyether chain exhibits strong electron-withdrawing properties and has large steric hindrance, making it difficult for the primary hydroxyl group to interact with the active site on the protective layer.

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

[0028] As a result, they discovered that in a fluorine-containing ether compound having a terminal structure containing hydroxyl groups at both ends of the perfluoropolyether chain, by introducing an alkylene chain between the perfluoropolyether chain, which exhibits strong electron-withdrawing properties and has large steric hindrance, and the primary hydroxyl group, and by maintaining an appropriate distance between the two, the electron density of the primary hydroxyl group can be increased and the steric hindrance around the primary hydroxyl group can be alleviated.

[0029] In such a fluorine-containing ether compound, the primary hydroxyl group can interact with the active site on the protective layer with sufficient strength, so the adhesion between the primary hydroxyl group and the protective layer is good.Therefore, it is estimated that the lubricating layer containing the above-mentioned fluorine-containing ether compound is unlikely to have adsorption sites that are not involved in the interaction with the protective layer, has good adhesion with the protective layer, and has excellent wear resistance and spin-off resistance even if it is thin.

[0030] Furthermore, the present inventors have confirmed that by forming a lubricating layer on the protective layer of a magnetic recording medium using a lubricant containing the above-mentioned fluorine-containing ether compound, a lubricating layer having excellent wear resistance and spin-off resistance can be formed even if it is thin, and have conceived the present invention.

[0031] The fluorine-containing ether compound, coating material, lubricant for magnetic recording media, and magnetic recording media of the present invention are described in detail below. The present invention is not limited to the following embodiments. The number, amount, ratio, composition, type, position, material, configuration, and the like of the present invention can be added, omitted, substituted, or modified within the scope of the spirit (technical requirements) of the present invention. The term "polar group" used in this specification does not include halogeno groups (such as -F, -Cl, -Br, etc.) and ether bonds (-O-).

[0032] [Fluorine-containing ether compound] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1): １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ [-CH ２ -R ４ -CH ２ -R ３ ] ｘ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ (1) (In formula (1), x is 0 to 2; each z is independently an integer from 2 to 10; each Y is independently O, NH, or S; R ３ is a perfluoropolyether chain. (x+1) R ３ may be the same in part or in whole, or may be different from each other; R ４ is a divalent linking group having 1 to 3 hydroxyl groups and oxygen atoms at both ends; when x is 2, two R ４ may be the same or different; R ２ is a linking group represented by the following formula (2-1) or (2-2); R ５is a linking group represented by the following formula (2-3) or (2-4); R １ and R ６ is R ２ or R ５ are terminal groups bonded to the terminal oxygen atoms of R １ and R ６ are each independently a terminal group selected from the group consisting of a hydrogen atom, an alkyl group which may have a substituent, and an organic group which has a double bond or a triple bond and which may have a substituent.

[0033] <-Y-(CH ２ ) ｚ In formula (1), two z's each independently represent an integer of 2 to 10. ２ ) ｚ - is R ２ and R ５ Among the hydroxyl groups contained in R ３ and a primary hydroxyl group which is the hydroxyl group closest to the perfluoropolyether chain represented by R ３ The distance between the primary hydroxyl group and R ３ In order to make the distance between the first and second electrodes more appropriate, the value is preferably an integer of 2 to 6, more preferably an integer of 2 to 4, and even more preferably 2.

[0034] Since z in formula (1) is 2 or more, R ２ and R ５ The primary hydroxyl group in the formula (1) exhibits strong electron-withdrawing properties, is less susceptible to the influence of the perfluoropolyether chain, which has large steric hindrance, and is more likely to interact with the active site on the protective layer. Therefore, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to have adsorption sites that are not involved in the interaction with the protective layer, has good adhesion to the protective layer, and has excellent wear resistance and spin-off resistance even when it is thin.

[0035] In addition, since z in formula (1) is 10 or less, R ２ and the primary hydroxyl group in R ５Therefore, the number of carbon atoms not bonded to a hydroxyl group between the primary hydroxyl group in the lubricating layer and the fluorine-containing ether compound is not too large. ２ ) ｚ -O-CH ２ -R ３ [-CH ２ -R ４ -CH ２ -R ３ ] ｘ -CH ２ -O-(CH ２ ) ｚ Therefore, when a force is applied in a direction away from the protective layer around the arch-shaped curved skeleton, R ２ The primary hydroxyl group in R ５ and the primary hydroxyl group in the skeleton (i.e., R when x is 1 or 2). ４ Therefore, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer having excellent wear resistance and spin-off resistance.

[0036] Y in formula (1) is R ２ or R ５ and -(CH ２ ) ｚ - is a divalent group bonded to. The two Y's in formula (1) are each independently O, S, or NH. When Y is any of these, the unpaired electron of the heteroatom interacts with the substrate, resulting in a fluorine-containing ether compound that exhibits good adhesion to the protective layer. Among these, Y in formula (1) is preferably O or NH, and particularly preferably O, in order to provide a fluorine-containing ether compound that exhibits good affinity with the protective layer of a magnetic recording medium.

[0037] <R ２ and R ５ > R in the above formula (1) ２ is a linking group represented by the following formula (2-1) or (2-2): ５is a linking group represented by the following formula (2-3) or (2-4).

[0038] (In formula (2-1), f1 represents an integer of 1 to 3. The oxygen atom at the left end of formula (2-1) is R １ (In formula (2-2), g1 represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-2) is bonded to R １ (In formula (2-3), f2 represents an integer of 1 to 3. The oxygen atom at the right end of formula (2-3) is bonded to R ６ (In formula (2-4), g2 represents an integer of 2 to 6. The oxygen atom at the right end of formula (2-4) is bonded to R ６ )

[0039] R ２ and R ５ is a divalent linking group having a hydroxyl group, as represented by formulas (2-1) to (2-4). f1 in formula (2-1) and f2 in formula (2-3) are each integers of 1 to 3. Therefore, formulas (2-1) and (2-3) have one to three hydroxyl groups. Furthermore, formulas (2-2) and (2-4) have one hydroxyl group regardless of the numerical values ​​of g1 and g2.

[0040] As represented by formulas (2-1) to (2-4), R ２ and R ５ is -CH ２ -, -O-, and -CH(OH)-, and R in formula (1) １ Side or R ６ -O- is located at the end of the R ３ -CH at the end of the side ２ - is placed, and R １ Side or R ６ One or more —CH ２ - is a divalent linking group having a chain structure in which R ２ and R ５ is -CH ２ Since it is a divalent linking group having a chain structure composed of -, -O-, and -CH(OH)-, it has a hydroxyl group that contributes to improving adhesion to the protective layer and also has appropriate flexibility. ２ and R５ is R １ Side or R ６ between —O— and —CH(OH)— located at the terminal on the side, and between —Y— and —CH(OH)— in formula (1); ２ - is placed, so R ２ Middle and R ５ In addition to the interaction between the hydroxyl groups in the １ Side or R ６ The interaction between the unpaired electrons of -O- located at the terminal of the R side and -Y- in formula (1) and the protective layer is obtained. ２ and R ５ improves the affinity between the lubricating layer containing the fluorinated ether compound of this embodiment and the protective layer, and therefore the fluorinated ether compound of this embodiment can form a lubricating layer having excellent wear resistance and spin-off resistance.

[0041] f1 in the above formula (2-1) and f2 in the formula (2-3) are integers of 1 to 3, preferably 2. Furthermore, f1 and f2 preferably have the same integer value. Since f1 is an integer of 1 or more, R ２ is a linking group represented by formula (2-1), R ２ has one or more hydroxyl groups. ２ is a linking group represented by formula (2-1), an interaction between the hydroxyl groups in formula (2-1) and the protective layer can be obtained by forming a lubricating layer on the protective layer using a lubricant containing the fluorinated ether compound of this embodiment. When f1 is an integer of 2 or more, formula (2-1) has two or more hydroxyl groups. Therefore, the interaction between the hydroxyl groups in formula (2-1) and the protective layer becomes more pronounced.

[0042] In addition, since f2 is an integer of 1 or more, R ５ is a linking group represented by formula (2-3), R ５ has one or more hydroxyl groups. ５is a linking group represented by formula (2-3), an interaction between the hydroxyl groups in formula (2-3) and the protective layer can be obtained by forming a lubricating layer on the protective layer using a lubricant containing the fluorinated ether compound of this embodiment. When f2 is an integer of 2 or more, formula (2-3) has two or more hydroxyl groups. Therefore, the interaction between the hydroxyl groups in formula (2-3) and the protective layer becomes more pronounced.

[0043] Since f1 and f2 are each an integer of 3 or less, the number of hydroxyl groups in formulas (2-1) and (2-3) is 3 or less. Therefore, the polarity of the fluorine-containing ether compound does not become too high due to the presence of too many hydroxyl groups in formulas (2-1) and / or (2-3). Therefore, the occurrence of pickup in which the fluorine-containing ether compound adheres to the magnetic head as foreign matter (smear) can be suppressed.

[0044] Formula (2-2) has one hydroxyl group, so R ２ is a linking group represented by formula (2-2), R ２ has one hydroxyl group. ２ By forming a lubricating layer on a protective layer using a lubricant containing a fluorine-containing ether compound in which R is a linking group represented by formula (2-2), a favorable interaction occurs between the hydroxyl group of formula (2-2) and the protective layer. ５ is a linking group represented by formula (2-4), R ５ has one hydroxyl group. ５ By forming a lubricating layer on a protective layer using a lubricant containing a fluorine-containing ether compound in which R is a linking group represented by formula (2-4), a favorable interaction occurs between the hydroxyl group in formula (2-4) and the protective layer. ２ is a linking group represented by formula (2-2), and / or R ５ When is a linking group represented by formula (2-4), a lubricating layer having excellent wear resistance can be obtained.

[0045] Furthermore, g1 in formula (2-2) and g2 in formula (2-4) are each an integer of 2 to 6. Since g1 in formula (2-2) and g2 in formula (2-4) are 2 or more, the hydroxyl groups in formula (2-2) and formula (2-4) and R １ or R ６ The distance between the oxygen atom bonded to the fluorine-containing ether compound and the hydroxyl group in formula (2-2) and formula (2-4) is more appropriate. Therefore, the intramolecular interaction caused by the hydroxyl group in formula (2-2) and formula (2-4) does not become too strong, and the interaction between the fluorine-containing ether compound and the protective layer becomes stronger. In addition, since g1 and g2 are 6 or less, the number of methylene groups (-CH ２ Therefore, it is possible to prevent the fluorine-containing ether compound from bending into a bow shape with g1 or g2 methylene groups (-CH ２ When the fluorine-containing ether compound is curved in an arch shape around the group (-), the interaction between the hydroxyl groups of formula (2-2) and formula (2-4) and the protective layer is not reduced, and the hydroxyl groups of formula (2-2) and formula (2-4) can contribute to improving the adhesion to the protective layer. g1 and g2 are preferably 4 or less.

[0046] <R １ and R ６ In the fluorine-containing ether compound represented by formula (1), １ is R ２ is a terminal group bonded to the terminal oxygen atom of R ６ is R ５ is a terminal group bonded to the terminal oxygen atom of R １ and R ６ may be the same or different. １ and R ６ are each independently a terminal group selected from the group consisting of a hydrogen atom, an alkyl group which may have a substituent, and an organic group which has a double bond or a triple bond and which may have a substituent.

[0047] (hydrogen atom) R １ is a hydrogen atom, R ２ forms a hydroxyl group together with the oxygen atom at the end of R ６is a hydrogen atom, R ５ forms a hydroxyl group together with the terminal oxygen atom.

[0048] (Alkyl group which may have a substituent) R １ and / or R ６ The alkyl group which may have a substituent as the alkyl group is preferably an alkyl group having 1 to 8 carbon atoms which may have a substituent, and more preferably an alkyl group having 1 to 6 carbon atoms which may have a substituent. Specific examples of the alkyl group in the alkyl group which may have a substituent include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. The alkyl group may be linear or branched.

[0049] When the alkyl group has a substituent, examples of the substituent include a halogeno group, an alkoxy group, a hydroxyl group, a cyano group, and a mercapto group. When the alkyl group has a substituent selected from these, the fluorine-containing ether compound can form a lubricating layer with better wear resistance. The alkyl group that may have a substituent is preferably an alkyl group having a hydroxyl group and / or a mercapto group, since it can form a lubricating layer with better adhesion to the protective layer. When the alkyl group has two or more substituents, the types of the substituents may be the same or different.

[0050] The alkyl group having a halogeno group as a substituent is preferably an alkyl group having at least one fluoro group, such as a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, an octafluoropentyl group, or a tridecafluorooctyl group.

[0051] The alkyl group having a hydroxyl group as a substituent is preferably an alkyl group having at least one primary hydroxyl group. The hydroxyl group is a polar group that can obtain a strong interaction with the protective layer. Moreover, the primary hydroxyl group located at the end of the fluorine-containing ether compound has high mobility, so that it is likely to interact with the protective layer. For this reason, R １ and / or R ６ When the alkyl group having at least one primary hydroxyl group is an alkyl group having at least one primary hydroxyl group, a lubricating layer having even better adhesion to the protective layer can be formed. The alkyl group having at least one primary hydroxyl group preferably has 2 to 5 carbon atoms, and specifically, -CH ２ CH ２ OH, -CH ２ CH ２ CH ２ OH, -CH ２ CH ２ CH ２ CH ２ OH, -CH ２ CH ２ CH ２ CH ２ CH ２ OH, -CH ２ CH (CH ２ OH) ２ Among these, -CH ２ CH ２ OH or -CH ２ CH ２ CH ２ OH is preferred.

[0052] (organic group having a double bond or a triple bond and optionally having a substituent) R １ and / or R ６ The organic group having a double bond or a triple bond as the group (hereinafter simply referred to as an "organic group having a double bond or a triple bond"), which may have a substituent, is an organic group having at least one double bond or a triple bond, and is preferably an organic group having 2 to 12 carbon atoms, and more preferably an organic group having 2 to 8 carbon atoms.

[0053] The double bond contained in the organic group having a double bond or a triple bond may be either an ethylenic double bond or an aromatic double bond. The carbon-carbon unsaturated bond site contained in the organic group having a double bond or a triple bond has a delocalized charge, and therefore exhibits adsorption ability by interacting with a site on the protective layer where the charge distribution is widespread. Examples of the organic group having a double bond or a triple bond include a group containing an aromatic hydrocarbon (aromatic hydrocarbon group), a group containing an unsaturated heterocycle (unsaturated heterocyclic group), an alkenyl group, and an alkynyl group.

[0054] When the organic group having a double bond or a triple bond has a substituent, the substituent can be, for example, an alkyl group, an alkoxy group, a hydroxyl group, a mercapto group, a carboxyl group, a carbonyl group, an amino group, a cyano group, a halogeno group, etc. Among these substituents, it is preferable that the substituent is a hydroxyl group and / or a mercapto group, since this can form a lubricating layer with better adhesion to the protective layer.When the organic group having a double bond or a triple bond has two or more substituents, the types of the substituents can be the same or different.

[0055] Specifically, examples of organic groups having a double bond or a triple bond 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, and a pyrimidinyl group. , pyridazinyl group, pyrazinyl group, indolinyl group, benzofuranyl group, benzothienyl group, benzimidazolyl group, benzoxazolyl group, benzothiazolyl group, benzopyrazolyl group, benzisoxazolyl group, benzisothiazolyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, cinnolinyl group, vinyl group, allyl group, butenyl group, 1-propynyl group, propargyl group (2-propynyl group), butynyl group, methylbutynyl group, pentynyl group, methylpentynyl group, and hexynyl group.

[0056] As the organic group having a double bond or a triple bond, among the above, particularly, a phenyl group, a methoxyphenyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a thienylethyl group, an allyl group, a butenyl group, or a propargyl group is preferable, and a phenyl group, a thienylethyl group, an allyl group, a butenyl group, or a propargyl group is more preferable.When the organic group having a double bond or a triple bond is a phenyl group, a thienylethyl group, an allyl group, a butenyl group, or a propargyl group, the resulting fluorine-containing ether compound can form a lubricating layer having better wear resistance.

[0057] <R ３ The fluorine-containing ether compound represented by formula (1) is a perfluoropolyether chain represented by R ３In the lubricating layer containing the fluorine-containing ether compound of this embodiment, the PFPE chain coats the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer.

[0058] (x+1) R ３ may be the same in part or in whole, or may be different from each other. ３ It is preferable that all R are the same. This is because the state of coating of the fluorine-containing ether compound on the protective layer becomes more uniform, and a lubricating layer having better adhesion can be obtained. When x is 1 or 2, (x+1) R ３ Among them, two or more R ３ are the same, (x+1) R ３ Among them, R ３ It means that two or more of the same R are included. ３ also includes PFPE chains having the same structural unit structure but different average degrees of polymerization.

[0059] R in formula (1) ３ is not particularly limited and can be appropriately selected depending on the performance required of the lubricant containing a fluorine-containing ether compound, etc. Examples of the PFPE chain include perfluoromethylene oxide polymer, perfluoroethylene oxide polymer, perfluoro-n-propylene oxide polymer, perfluoroisopropylene oxide polymer, perfluorobutylene oxide polymer, and copolymers thereof.

[0060] R in formula (1) ３ is preferably a PFPE chain represented by the following formula (Rf) derived from a polymer or copolymer of perfluoroalkylene oxide: -(CF ２ ) ｐ１ -O-(CF ２ O) ｐ２ -(CF ２ CF ２ O) ｐ３ -(CF ２ CF２ CF ２ O) ｐ４ -(CF ２ CF ２ CF ２ CF ２ O) ｐ５ -(CF ２ ) ｐ６ - (Rf) (In formula (Rf), p2, p3, p4, and p5 represent an average degree of polymerization, each independently representing 0 to 20. However, p2, p3, p4, and p5 cannot all be 0 at the same time. p1 and p6 are -CF ２ - is an average value representing the number of -, each independently representing 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).

[0061] In formula (Rf), p2, p3, p4, and p5 represent an average degree of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In formula (Rf), p1 and p6 represent -CF ２ p1 and p6 are determined depending on the structure of the structural unit located at the end of the chain structure in the PFPE chain represented by formula (Rf). ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ O) is a structural unit. There is no particular limitation on the order of the structural units in formula (Rf). There is also no particular limitation on the number of types of structural units in formula (Rf).

[0062] R in formula (1) ３is more preferably any one of the following formulas (3-1) to (3-4): ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (3-1) (In formula (3-1), 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 - (3-2) (In formula (3-2), 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 - (3-3) (In formula (3-3), 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 - (3-4) (In formula (3-4), 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

[0063] The structural unit in formula (3-1) is (CF ２ CF ２ O) and (CF ２ In formula (3-1), there is no particular limitation on the arrangement order of (CF ２ CF２ O) and the number h (CF ２ The number i of monomer units (CF) may be the same or different. ２ CF ２ O) and (CF ２ O) may be any of a random copolymer, a block copolymer, and an alternating copolymer.

[0064] The structural unit in formula (3-4) is (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ In formula (3-4), there is no particular limitation on the arrangement order of (CF ２ CF ２ CF ２ O) number w8 and (CF ２ CF ２ The number w9 of monomer units (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ In formula (3-4), w7 and w10 may be any of a random copolymer, a block copolymer, and an alternating copolymer composed of —CF ２ is an average value showing the number of -, and each independently represents 1 to 2. w7 and w10 are determined depending on the structure of the structural unit located at the end of the chain structure in the PFPE chain represented by formula (3-4).

[0065] In formulas (3-1) to (3-4), when h, j, k, w8, and w9 are each 1 or greater and i is 0 or greater, a lubricating layer with good adhesion can be obtained. Furthermore, when h, i, w8, and w9 are each 20 or less, j is 15 or less, and k is 10 or less, the viscosity of the fluorine-containing ether compound is not too high, and a lubricant containing the compound can be easily applied. h, i, w8, and w9, which indicate the average degree of polymerization, are all preferably 1 to 15, more preferably 2 to 10, and even more preferably 3 to 8, so that the fluorine-containing ether compound easily wets and spreads on the protective layer and easily forms a lubricating layer with a uniform thickness. j, which indicates the average degree of polymerization, is preferably 2 to 10, and more preferably 3 to 8. k, which indicates the average degree of polymerization, is preferably 1 to 8, and more preferably 1 to 6.

[0066] R in formula (1) ３ is any one of formulas (3-1) to (3-4), the synthesis of the fluorine-containing ether compound is easy, which is preferable. ３ is formula (3-1), it is more preferable because raw materials are easily available.

[0067] Also, R ３ is any one of formulas (3-1) to (3-4), the ratio of the number of oxygen atoms (the number of ether bonds (—O—)) to the number of carbon atoms in the perfluoropolyether chain is appropriate. Therefore, the fluorine-containing ether compound has an appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage. As a result, R ３ When is any one of formulas (3-1) to (3-4), the fluorine-containing ether compound provides a lubricating layer having good wear resistance and spin-off resistance.

[0068] <R ４ In the fluorine-containing ether compound represented by formula (1), R ４ When x is 1 or 2, the adjacent R ３ x R ４are each independently a divalent linking group having 1 to 3 hydroxyl groups and both ends of which are oxygen atoms. In the fluorine-containing ether compound represented by formula (1), when x is 1 or 2, adjacent R ３ R placed between ４ has 1 to 3 hydroxyl groups, and when a lubricating layer is formed on a protective layer using a lubricant containing this, R ４ A favorable interaction occurs between the hydroxyl groups of the fluorine-containing ether compound and the protective layer, which prevents the fluorine-containing ether compound from bending into an arch shape around the skeleton, and allows the formation of a lubricating layer with excellent wear resistance and spin-off resistance.

[0069] When x is 2, two R ４ may be the same or different. ４ are preferably each independently a divalent linking group represented by any one of formulas (2-5) to (2-8). ４ has a moderate flexibility, and R ４ This is because the interaction between the hydroxyl groups of the compound and the protective layer can more effectively prevent the fluorine-containing ether compound from curving into a bow shape around the skeleton.

[0070] (In formula (2-5), r represents an integer of 1 to 3.) (In formula (2-6), s represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-6) is R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ In formula (2-7), t represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-7) is bonded to R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ In formula (2-8), u represents an integer of 1 to 6, and v represents an integer of 1 to 6. u and v cannot be 1 at the same time. The oxygen atom at the left end of formula (2-8) is bonded to R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２- and bond.)

[0071] R ４ is represented by formulas (2-5) to (2-8), R ４ is a divalent linking group having a chain structure with 1 to 3 secondary hydroxyl groups and -O- at both ends, and R １ -CH on the side ２ One or more —CH ２ - is placed, and R ６ -CH on the side ２ One or more —CH ２ - is a divalent linking group. ４ has a hydroxyl group that contributes to improving adhesion to the protective layer and has appropriate flexibility. １ -CH on the side ２ One or more —CH ２ - is placed, and R ６ -CH on the side ２ One or more —CH ２ - is placed, so R ４ The hydroxyl group contained in R ４ methylene group (-CH ２ -) has a moderate flexibility, which allows it to be easily attached to the highly sterically hindered R ３ For these reasons, the fluorine-containing ether compound of the present embodiment is less susceptible to the influence of R ３ If the adjacent R ３ R placed between ４ The interaction between the hydroxyl groups of the compound and the protective layer prevents the compound from curving into an arch shape around the skeleton, resulting in a fluorine-containing ether compound that can form a lubricating layer having excellent wear resistance and spin-off resistance.

[0072] The divalent linking groups represented by formulas (2-5) to (2-8) all have oxygen atoms at both ends of a chain structure, and are connected to R ４The divalent linking group represented by formula (2-5) has three carbon atoms between the oxygen atoms forming the ether bond in the chain structure. The divalent linking group represented by formula (2-6) and formula (2-7) has four to eight carbon atoms between the oxygen atoms forming the ether bond in the chain structure. The divalent linking group represented by formula (2-8) has three to eight carbon atoms between the adjacent oxygen atoms forming the ether bond in the chain structure. Therefore, the divalent linking groups represented by formulas (2-5) to (2-8) have an appropriate number of carbon atoms and are sufficiently flexible. Furthermore, the oxygen atoms contained in the chain structure of the divalent linking groups represented by formulas (2-5) to (2-8) form ether bonds to impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), thereby increasing the affinity between the hydroxyl groups of the divalent linking groups represented by formulas (2-5) to (2-8) and the protective layer. Furthermore, since the divalent linking groups represented by formulas (2-5) to (2-8) have sufficient flexibility, they can move freely and independently without interlocking with the perfluoropolyether chains, even if the perfluoropolyether chains located on both sides of them undergo molecular motion. Therefore, the divalent linking groups represented by formulas (2-5) to (2-8) are less susceptible to the molecular motion of the perfluoropolyether chains bonded to them via methylene groups, and are more likely to interact with the active sites on the protective layer.

[0073] In the fluorine-containing ether compound represented by formula (1), x is 0 to 2. Therefore, the fluorine-containing ether compound represented by formula (1) is ３ The compound has (x+1) PFPE chains represented by the formula: ３ A compound having one x (a compound having x=0) is represented by R ３ In comparison with compounds having two or more R, the fluorine-containing ether compound is easier to synthesize. ３ The compound having two or three x's (the compound having x's equal to 1 or 2) is represented by R ３ Unlike compounds with one R ３ and a divalent linking group R ４ Therefore, R ３In comparison with a compound having only one R, a lubricating layer having excellent adhesion to the protective layer can be easily obtained. ３ The compound having two or three R ３ Compared with compounds having one unit, such compounds tend to have a large number average molecular weight, and can form a lubricating layer that is less susceptible to film thickness reduction due to spin-off.

[0074] Furthermore, the fluorine-containing ether compound represented by formula (1) has molecules that are not too large and can move freely, compared with compounds having four or more PFPE chains. For this reason, the fluorine-containing ether compound represented by formula (1) is more likely to wet and spread on the protective layer, compared with compounds having four or more PFPE chains, and can form a thin, uniformly thick lubricating layer.

[0075] In the fluorine-containing ether compound represented by formula (1), R １ -R ２ -Y-(CH ２ ) ｚ - and - (CH ２ ) ｚ -Y-R ５ -R ６ may be the same or different, and are preferably the same, because this results in a fluorine-containing ether compound that is easy to synthesize. １ -R ２ -Y-(CH ２ ) ｚ - and - (CH ２ ) ｚ -Y-R ５ -R ６ are the same, the atoms contained in both are -R located at the center of the molecule ３ [-CH ２ -R ４ -CH ２ -R ３ ] ｘ - means that they are arranged symmetrically.

[0076] In formula (1), when x is 1 or 2, R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３- and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ may be the same or different, and are preferably the same, because this results in a fluorine-containing ether compound that is easy to synthesize. １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ are the same, the atoms contained in both are -CH ２ -R ４ -CH ２ - or -CH ２ -R ４ -CH ２ -R ３ -CH ２ -R ４ -CH ２ - means that they are arranged symmetrically.

[0077] In formula (1), when x is 2, two R ４ may be the same or different, and more preferably are the same. ４ When the two R are the same, the state of coating of the fluorine-containing ether compound on the protective layer becomes more uniform, and a lubricating layer having better adhesion can be formed. ４ are the same, the fluorine-containing ether compound can be easily produced, which is preferable. ４ are the same, the atoms contained in both are -CH ２ -R ３ -CH ２ - means that they are arranged symmetrically.

[0078] In the fluorine-containing ether compound represented by formula (1), R１ -R ２ The total number of polar groups contained in - and -R ５ -R ６ The total number of polar groups contained in each of the above is preferably 1 to 4, and more preferably 2 to 3. When the total number of polar groups is 1 or more, the resulting fluorine-containing ether compound has good adsorption to the protective layer and can form a lubricating layer that exhibits excellent abrasion resistance. When the total number of polar groups is 4 or less, the intramolecular interaction caused by the inclusion of polar groups does not become too strong, and the resulting fluorine-containing ether compound can form a lubricating layer that exhibits excellent abrasion resistance.

[0079] In the fluorine-containing ether compound represented by formula (1), when x is 0 (in other words, R ４ When x is 1 or 2 (in other words, when R ４ The number of polar groups contained in one molecule is preferably 6 to 12, and more preferably 6 to 10.

[0080] When x is 0, the number of polar groups contained in one molecule is 4 or more, or when x is 1 or 2, the number of polar groups contained in one molecule is 6 or more, the adsorption of the whole molecule to the protective layer is good.In addition, when x is 0, the number of polar groups contained in one molecule is 10 or less, or when x is 1 or 2, the number of polar groups contained in one molecule is 12 or less, the intramolecular interaction caused by containing polar groups is not too strong, so the fluorine-containing ether compound is not likely to aggregate on the protective layer.Therefore, the aggregation of the fluorine-containing ether compound on the protective layer can be prevented from reducing the spin-off resistance of the lubricating layer.

[0081] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any of the compounds represented by the following formulae (A) to (P): In the compounds represented by the following formulae (A) to (P), Rf representing a PFPE chain １, Rf ２ In other words, in the compounds represented by the following formulas (A) and (B), Rf １ is a PFPE chain represented by the following formula (3-1). In the compounds represented by the following formulas (C) to (P), Rf ２ is a PFPE chain represented by the following formula (3-2). １ h and i in Rf ２ Since j in the formula is a value indicating the average degree of polymerization, it is not necessarily an integer.

[0082]

[0083] In the compounds represented by formulas (A) to (D), x is 0, and R in formula (1) １ and R ６ is a hydrogen atom, and R ２ is represented by formula (2-1), f1 is 2, and R ５ is represented by formula (2-3), f2 is 2, and Y is O. The compounds represented by formula (A) and (B) are compounds represented by formula (1) where R ３ is formula (3-1), and z is 2. The compound represented by formula (C) is a compound represented by formula (1) where R ３ is formula (3-2), and z is 2. The compound represented by formula (D) is a compound represented by formula (1) where R ３ is the formula (3-2), and z is 3.

[0084] The compounds represented by formula (E) and formula (F) are compounds represented by formula (1) １ and R ６ is a hydrogen atom, and R ３ is the formula (3-2), Y is O, and z is 2. The compound represented by formula (E) is a compound represented by formula (1) where R ２ is represented by formula (2-1), f1 is 1, and R ５ is represented by formula (2-3), f2 is 2, and x is 0. The compound represented by formula (F) is a compound represented by formula (1) ２ is represented by formula (2-1), f1 is 1, and R ５is represented by formula (2-3), and f2 is 1. The compound represented by formula (F) is represented by formula (2-3), and x is 1, and R ４ is expressed by formula (2-8), where u is 1 and v is 4.

[0085] The compounds represented by formula (G) and (H) are both compounds represented by formula (1) in which x is 0 and R １ and R ６ is a hydrogen atom, Y is O, and R ３ is represented by formula (3-2), and z is 2. The compound represented by formula (G) is a compound represented by formula (1) ２ is represented by formula (2-1), f1 is 1, and R ５ is represented by formula (2-3), and f2 is 1. The compound represented by formula (H) is a compound represented by formula (1) ２ is represented by formula (2-2), g1 is 2, and R ５ is expressed by equation (2-4), and g2 is 2.

[0086] The compounds represented by formulas (I) to (K) are all compounds represented by formula (1) where R １ and R ６ is a hydrogen atom, and R ２ is represented by formula (2-1), f1 is 1, and R ５ is represented by formula (2-3), f2 is 1, Y is O, and R ３ is represented by formula (3-2), and z is 2. The compound represented by formula (I) is a compound represented by formula (1), in which x is 1 and R ４ is represented by formula (2-5), and r is 1. The compound represented by formula (J) is a compound represented by formula (1), wherein x is 1 and R ４ is represented by formula (2-5), and r is 3. The compound represented by formula (K) is a compound represented by formula (1), in which x is 2 and R ４ is expressed by equation (2-5), where r is 1.

[0087] The compounds represented by formulas (L) to (N) are all compounds represented by formula (1) in which x is 0 and R ２ is represented by formula (2-1), f1 is 1, and R ５ is represented by formula (2-3), f2 is 1, Y is O, and R ３is represented by formula (3-2), and z is 2. The compound represented by formula (L) is a compound represented by formula (1) １ and R ６ Ga-CH ２ -CH ２ The compound represented by formula (M) is a compound represented by formula (1) in which R １ and R ６ Ga-CH ２ -CH ２ -CH=CH ２ (3-butenyl group). The compound represented by formula (N) is a compound represented by formula (1) １ and R ６ is a phenyl group.

[0088] The compounds represented by formula (O) and (P) are both compounds represented by formula (1) in which x is 0 and R １ and R ６ is a hydrogen atom, and R ２ is represented by formula (2-1), f1 is 1, and R ５ is represented by formula (2-3), f2 is 1, and R ３ is represented by formula (3-2), and z is 2. The compound represented by formula (O) is a compound represented by formula (1), in which Y is NH. The compound represented by formula (P) is a compound represented by formula (1), in which Y is S.

[0089] (Rf in formula (A) １ In the formula (B), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 1 to 20. １ In the formula (C), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0. ２ In the formula (D), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula, j represents the average degree of polymerization, and j represents 1 to 15.

[0090] (Rf in formula (E) ２ In the formula (F), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula, j represents the average degree of polymerization, and j represents 1 to 15. ２The average degrees of polymerization may be the same or different.

[0091] (Rf in formula (G) ２ In the formula (H), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula, j represents the average degree of polymerization, and j represents 1 to 15.

[0092] (Rf in formula (I) ２ In the formula (J), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula (K), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula, j represents the average degree of polymerization, and j represents 1 to 15.

[0093] (Rf in formula (L) ２ In the formula (M), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula (N), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula, j represents the average degree of polymerization, and j represents 1 to 15.

[0094] (Rf in formula (O) ２ In the formula (P), j represents the average degree of polymerization, and j represents 1 to 15. ２ In the formula, j represents the average degree of polymerization, and j represents 1 to 15.

[0095] When the compound represented by formula (1) is any of the compounds represented by formulas (A) to (F) above, the raw materials are easily available, and a lubricating layer can be formed that has excellent wear resistance and spin-off resistance even when it is thin, which is preferable.

[0096] The number-average molecular weight (Mn) of the fluorine-containing ether compound of this embodiment is preferably in the range of 500 to 10,000, more preferably in the range of 700 to 5,000, even more preferably in the range of 900 to 3,000, and particularly preferably in the range of 1,000 to 2,500. When the number-average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of this embodiment is less likely to evaporate, making it possible to form a lubricating layer that is even less susceptible to film thickness reduction due to spin-off. Furthermore, when the number-average molecular weight is 500 or more, it is possible to prevent the lubricant from evaporating and transferring to the magnetic head. The number-average molecular weight of the fluorine-containing ether compound is more preferably 900 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 3,000 or less, because this results in a manageable viscosity when applied to a lubricant.

[0097] The number average molecular weight (Mn) of the fluorine-containing ether compound was measured by AVANCEIII400 manufactured by Bruker Biospin. １ H-NMR and １９ This is a value measured by F-NMR. 1 H-NMR measurement or 1９ The number average molecular weight is calculated from the integrated intensity of each peak determined by F-NMR measurement and the number of hydrogen atoms or fluorine atoms assigned to each peak. In NMR (nuclear magnetic resonance) measurement, the sample is diluted in a single or mixed solvent such as hexafluorobenzene, d-acetone, or d-tetrahydrofuran and used for the measurement. 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.

[0098] "Production Method" The production method of the fluorinated ether compound of this embodiment is not particularly limited, and the compound can be produced using a conventionally known production method. The fluorinated ether compound of this embodiment can be produced, for example, using the production method shown below.

[0099] [First Production Method (when x is 0)] First, R ３ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound in which a hydroxyl group (OH) is arranged is prepared.

[0100] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound is converted to R １ -R ２ -Y-(CH ２ ) ｚ - (first reaction). ３ At one end of the perfluoropolyether chain corresponding to １ -R ２ -Y-(CH ２ ) ｚ An intermediate compound 1-1 having a group corresponding to - is obtained.

[0101] In the first reaction, R ３ At one end of the perfluoropolyether chain corresponding to １ -R ２ -Y-(CH ２ ) ｚ As well as intermediate compound 1-1 having a group corresponding to R ３ At both ends of the perfluoropolyether chain corresponding to １ -R ２ -Y-(CH ２ ) ｚ In this embodiment, a compound having a group corresponding to R at both ends is also produced by adjusting the amounts of the solvent and raw materials used in the first reaction. １ -R ２ -Y-(CH ２ ) ｚBy controlling the amount of the compound having a group corresponding to - and the amount of intermediate compound 1-1 produced, the proportion of intermediate compound 1-1 produced can be increased. １ -R ２ -Y-(CH ２ ) ｚ The compound having a group corresponding to - and intermediate compound 1-1 have different polarities, and therefore, by separating the product of the first reaction using a method such as column chromatography, intermediate compound 1-1, which is produced by the reaction of only one end, can be efficiently obtained.

[0102] R in formula (1) １ -R ２ -Y-(CH ２ ) ｚ As the halogen compound or pseudohalogen compound having a group corresponding to -, for example, compounds represented by the following formulas (4-1) to (4-3) can be used, in which MOM represents a methoxymethyl group and Ts represents a p-toluenesulfonyl group.

[0103]

[0104] For example, R in formula (1) １ -R ２ -Y-(CH ２ ) ｚ When a compound represented by formula (5-1) (shown in formula (6-1) below) is used as a halogen compound or pseudohalogen compound having a group corresponding to -, it can be produced by the following method. First, as shown in formula (6-1) below, １ -R ２ An alcohol having a structure (R in formula (6-1)) corresponding to a part of the terminal group represented by - is prepared. Also, an alcohol having a primary hydroxyl group and an epoxy group protected by a tetrahydropyranyl (THP) group, and represented by -R in formula (1), is prepared. ２ -Y-(CH ２ ) ｚ A compound having a structure corresponding to a portion of - is prepared.

[0105] And the above R １ -R ２and an alcohol having a structure corresponding to a portion of the above-R ２ -Y-(CH ２ ) ｚ - is reacted with a compound having a structure corresponding to a portion of the -, and the secondary hydroxyl groups of the resulting compound are protected with chloromethyl methyl ether (MOMC1). Thereafter, the resulting compound is treated with an acid to selectively deprotect the THP group from the protected primary hydroxyl groups, and the primary hydroxyl groups are reacted with paratoluenesulfonyl chloride (TsCl). By performing the above steps, a compound represented by formula (5-1) is obtained.

[0106] In the compound having a primary hydroxyl group protected by a THP group and an epoxy group used as a raw material, the number of methylene groups in the primary hydroxyl group protected by a THP group is z in formula (1). Therefore, a1 in formula (6-1) is 1 to 9 (z-1 in formula (1)) and is determined depending on the value of z in formula (1) of the compound to be synthesized.

[0107] (In formula (6-1), R is R in formula (1) １ -R ２ a1 represents an integer of 1 to 9. In formula (6-1), THP represents a tetrahydropyranyl group, MOM represents a methoxymethyl group, and Ts represents a p-toluenesulfonyl group.

[0108] In addition, R in the above formula (1) １ -R ２ -Y-(CH ２ ) ｚ When a compound represented by formula (5-2) (shown in formula (6-2) below) is used as a halogen compound or pseudohalogen compound having a group corresponding to -, it can be produced by the following method. First, as shown in formula (6-2) below, １ -R ２ A compound having a structure (R in formula (6-2)) corresponding to a part of the terminal group represented by - and a leaving group (Ts) is prepared. ２ ) ｚA diol having a hydroxyl group bonded to each end of an alkylene chain having a structure corresponding to a portion of - is prepared.

[0109] And the above R １ -R ２ a compound having a structure corresponding to a portion of - and a leaving group, and the above -Y-(CH ２ ) ｚ - is reacted with a diol having a structure corresponding to a portion of the -, and the primary hydroxyl group of the resulting compound is reacted with paratoluenesulfonyl chloride (TsCl). By performing the above steps, a compound represented by formula (5-2) is obtained. In the diol used as a raw material, the number of methylene groups forming the alkylene chain is z in formula (1). Therefore, a2 in formula (6-2) is 1 to 9 (z-1 in formula (1)) and is determined depending on the value of z of the compound to be synthesized.

[0110] (In formula (6-2), R is R in formula (1) １ -R ２ a2 represents an integer of 1 to 9. Ts represents a p-toluenesulfonyl group.

[0111] Next, the hydroxyl group of the hydroxymethyl group located at the other end of the intermediate compound 1-1 obtained by the above-mentioned method is converted to -(CH ２ ) ｚ -Y-R ５ -R ６ (second reaction) with a halogen compound or pseudohalogen compound having a group corresponding to

[0112] -(CH ２ ) ｚ -Y-R ５ -R ６ As the halogen compound or pseudohalogen compound having a group corresponding to R １ -R ２ -Y-(CH ２ ) ｚThe same compounds as halogen compounds or pseudohalogen compounds having a group corresponding to - can be used. Therefore, the -(CH ２ ) ｚ -Y-R ５ -R ６ As the halogen compound or pseudohalogen compound having a group corresponding to the above, for example, compounds represented by the above formulas (4-1) to (4-3) can be used.

[0113] The first and second reactions can be carried out by a conventionally known method. １ -R ２ -Y-(CH ２ ) ｚ - and -(CH ２ ) ｚ -Y-R ５ -R ６ The reaction time can be determined appropriately depending on the type of R. In addition, either the first reaction or the second reaction may be carried out first. １ -R ２ -Y-(CH ２ ) ｚ - and - (CH ２ ) ｚ -Y-R ５ -R ６ After the above steps, a deprotection reaction is carried out using a known method to remove the protecting group such as a THP group, a MOM group, a benzyl group, or the like, and convert it to a hydroxyl group, thereby producing a compound of formula (1) in which x is 0.

[0114] [Second manufacturing method (when x is 1)] (R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ If different) First, R １ -R ２ -Y-(CH ２ )ｚ - side R ３ A fluorine-based compound having a hydroxymethyl group at each end of a perfluoropolyether chain corresponding to the formula (I) is prepared. Then, a hydroxyl group at one end of the fluorine-based compound and the above-mentioned R １ -R ２ -Y-(CH ２ ) ｚ The intermediate compound 1a is obtained by reacting the compound with a halogen compound or a pseudohalogen compound having a group corresponding to the group (first reaction).

[0115] Next, -(CH ２ ) ｚ -Y-R ５ -R ６ Side R ３ A fluorine-based compound having a hydroxymethyl group at each end of a perfluoropolyether chain corresponding to the formula (I) is prepared. Then, a hydroxyl group at one end of the fluorine-based compound and the above-mentioned -(CH ２ ) ｚ -Y-R ５ -R ６ The intermediate compound 1b is obtained by reacting a halogen compound or a pseudohalogen compound having a group corresponding to the following (second reaction).

[0116] Next, the hydroxyl group at one end of the intermediate compound 1a is reacted with the R ４ Then, the double bond of the resulting compound is oxidized to obtain intermediate compound 1-2 (third reaction).

[0117] R in formula (1) ４ As a compound having an epoxy group at one end of a chain structure corresponding to the above and an alkenyl group at the other end, for example, compounds represented by the following formulas (7-1) to (7-4) can be used.

[0118]

[0119] R ４When a compound represented by formula (7-1) or formula (7-2) is used as the compound corresponding to formula (7), it can be produced, for example, by the method shown below. That is, as shown in formula (8-1) or formula (8-2) below, a halogen compound such as a bromine compound having an alkenyl group or a chlorine compound having an alkenyl group (in formulas (8-1) and (8-2), the halogen compound is a bromine compound) is reacted with an alcohol having an alkenyl group to obtain a compound having alkenyl groups at both ends. Then, the compound having alkenyl groups at both ends is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize one of the alkenyl groups, thereby producing the compound.

[0120]

[0121] The compound represented by formula (7-3) may be a commercially available product (for example, trade name: allyl glycidyl ether, manufactured by Tokyo Chemical Industry Co., Ltd.). The compound represented by formula (7-4) may be a commercially available product (for example, trade name: 2-[(3-butene-1-yloxy)methyl]oxirane, manufactured by Aurora Fine Chemicals).

[0122] Next, the hydroxyl group at one end of intermediate compound 1b is reacted with the epoxy group of intermediate compound 1-2 obtained in the third reaction (fourth reaction). After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by formula (1) where x is 1 and R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ can be prepared.

[0123] [Third Production Method (when x is 1)] (R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ is the same) R in formula (1) ３ A fluorine-based compound having a hydroxymethyl group at each end of a perfluoropolyether chain corresponding to R is prepared. Then, the hydroxyl group of the hydroxymethyl group at one end of the fluorine-based compound and the hydroxyl group of the hydroxymethyl group at the other end of the perfluoropolyether chain corresponding to R １ -R ２ -Y-(CH ２ ) ｚ The group corresponding to - (=-(CH ２ ) ｚ -Y-R ５ -R ６ (first reaction) with a halogen compound or pseudohalogen compound having a group corresponding to R ３ At one end of the perfluoropolyether chain corresponding to １ -R ２ -Y-(CH ２ ) ｚ The group corresponding to - (=-(CH ２ ) ｚ -Y-R ５ -R ６ An intermediate compound 1-3 having a group corresponding to (first reaction) is obtained.

[0124] Next, the hydroxyl group at one end of the intermediate compound 1-3 is reacted with the R ４ (second reaction) with a compound having epoxy groups at both ends of a chain structure corresponding to R ４ Examples of compounds having epoxy groups at both ends of a chain structure corresponding to the above formula include compounds represented by the following formula (9-1) or (9-2).

[0125]

[0126] R in formula (1) ４When a compound represented by formula (9-1) is used as a compound having epoxy groups at both ends of a chain structure corresponding to formula (9-1), it can be produced, for example, by the method shown below. That is, as shown in the following reaction formula (10), a halogen compound such as a bromine compound having an alkenyl group or a chlorine compound having an alkenyl group (in reaction formula (10), the halogen compound is a bromine compound) is reacted with an alcohol having an alkenyl group to obtain a compound having alkenyl groups at both ends. Then, the compound having alkenyl groups at both ends is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize both alkenyl groups, thereby producing the compound.

[0127]

[0128] As the compound represented by formula (9-2), commercially available products (for example, trade name: 1,3-diglycidyl glyceryl ether, manufactured by Aurora Fine Chemicals) can be used.

[0129] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ can produce the same compound.

[0130] [Fourth Production Method (when x is 2)] (R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ First, in the same manner as in the second manufacturing method, R １ -R２ -Y-(CH ２ ) ｚ - side R ３ At one end of the perfluoropolyether chain corresponding to １ -R ２ -Y-(CH ２ ) ｚ An intermediate compound 1a having a group corresponding to - is prepared (first reaction).

[0131] In addition, in the same manner as in the second production method, -(CH ２ ) ｚ -Y-R ５ -R ６ Side R ３ At one end of the perfluoropolyether chain corresponding to ２ ) ｚ -Y-R ５ -R ６ An intermediate compound 1b having a group corresponding to the following is prepared (second reaction).

[0132] Next, R at the center of the molecule in formula (1) ３ At both ends of the perfluoropolyether chain corresponding to ２ Then, a fluorine-based compound having hydroxyl groups of hydroxymethyl groups arranged at both ends of the fluorine-based compound and R ４ The compound having an epoxy group at one end of a chain structure corresponding to R in formula (1) and an alkenyl group at the other end is reacted with the compound having an epoxy group at one end of a chain structure corresponding to R in formula (1) (third reaction). ４ As a compound having an epoxy group at one end of a chain structure corresponding to the above and an alkenyl group at the other end, for example, compounds represented by the above formulas (7-1) to (7-4) can be used.

[0133] Next, the compound produced by the third reaction is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize the alkenyl group (fourth reaction). ３ At both ends of the perfluoropolyether chain corresponding to R in formula (1), ４In the case where the compound produced after the third reaction has a hydroxyl group, the fourth reaction may be carried out after the hydroxyl group has been appropriately protected by a known method.

[0134] Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of intermediate compound 1a is reacted with the epoxy group located at one end of intermediate compound 2-1 to obtain intermediate compound 2-2 (fifth reaction). Next, the hydroxyl group of the hydroxymethyl group located at one end of intermediate compound 1b is reacted with the epoxy group of intermediate compound 2-2 obtained in the fifth reaction (sixth reaction).

[0135] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ can be prepared.

[0136] [Fifth Production Method (when x is 2)] (R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ First, in the same manner as in the third manufacturing method, R １ -R ２ -Y-(CH ２ ) ｚ - side R ３ (=-(CH ２ ) ｚ -Y-R ５ -R ６ Side R ３) at one end of the perfluoropolyether chain corresponding to １ -R ２ -Y-(CH ２ ) ｚ The group corresponding to - (=-(CH ２ ) ｚ -Y-R ５ -R ６ An intermediate compound 1-3 having a group corresponding to (a group corresponding to) is prepared (first reaction).

[0137] Next, in the same manner as in the fourth production method, R at the center of the molecule in formula (1) ３ At both ends of the perfluoropolyether chain corresponding to R in formula (1), ４ An intermediate compound 2-1 having an epoxy group corresponding to the formula (2nd reaction) is prepared.

[0138] Then, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1-3 is reacted with the epoxy groups located at both ends of the intermediate compound 2-1 (third reaction). After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and R １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ - and -R ３ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ can produce the same compound.

[0139] [Sixth Production Method (when x is 0)] First, R ３ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound in which a hydroxyl group (OH) is arranged is prepared.

[0140] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and the -R ２ -Y-(CH ２ ) ｚ- is reacted with a compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or pseudohalogen group at the other end (first reaction). ３ At one end of the perfluoropolyether chain corresponding to ２ -Y-(CH ２ ) ｚ The intermediate compound 3a is obtained, which has a group corresponding to -.

[0141] -R in formula (1) ２ -Y-(CH ２ ) ｚ As a compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or pseudohalogen group at the other end, for example, compounds represented by the following formulae (11-1) to (11-4) can be used. In the following formulae (11-2) to (11-4), MOM represents a methoxymethyl group, and Ts represents a p-toluenesulfonyl group.

[0142]

[0143] For example, -R in formula (1) ２ -Y-(CH ２ ) ｚ When a compound represented by formula (12-1) (shown in formula (13-1) below) is used as a compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or pseudohalogen group at the other end, the compound can be produced by the following method. First, as shown in formula (13-1) below, a compound having an alcohol having an unsaturated bond, a primary hydroxyl group and an epoxy group protected by a tetrahydropyranyl (THP) group, and -R in formula (1) ２ -Y-(CH ２ ) ｚ A compound having a structure corresponding to a portion of - is prepared.

[0144] The above-mentioned allyl alcohol and the above-mentioned -R ２ -Y-(CH ２ ) ｚThe compound (12-1) is reacted with a compound having a structure corresponding to a portion of the hydroxyl group, and the secondary hydroxyl groups of the resulting compound are protected with chloromethyl methyl ether (MOMC1). The resulting compound is then reacted with an acid to selectively deprotect the THP groups from the protected primary hydroxyl groups, and the primary hydroxyl groups are reacted with paratoluenesulfonyl chloride (TsCl). By performing these steps, a compound represented by formula (12-1) is obtained.

[0145] In the compound having a primary hydroxyl group protected by a THP group and an epoxy group used as a raw material, the number of methylene groups in the primary hydroxyl group protected by a THP group is z in formula (1). Therefore, a3 in formula (13-1) is 1 to 9 (z-1 in formula (1)) and is determined depending on the value of z in formula (1) of the compound to be synthesized.

[0146] (In formula (13-1), a3 represents an integer of 1 to 9, and a4 represents an integer of 1 to 4. In formula (13-1), THP represents a tetrahydropyranyl group, MOM represents a methoxymethyl group, and Ts represents a p-toluenesulfonyl group.)

[0147] As the compound represented by formula (11-1), a commercially available product (for example, trade name: 3-[(2-bromoethoxy)]-propene, manufactured by Aurora Fine Chemicals) can be used.

[0148] Next, the hydroxyl group of the hydroxymethyl group located at the other end of the intermediate compound 3a obtained by the above-mentioned method is converted to -(CH ２ ) ｚ -Y-R ５ - is reacted with a compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or pseudohalogen group at the other end (second reaction). ３ At one end of the perfluoropolyether chain corresponding to ２ -Y-(CH ２ ) ｚ - at the other end, ２ ) ｚ -Y-R ５The intermediate compound 3b is obtained, which has a group corresponding to -.

[0149] -(CH ２ ) ｚ -Y-R ５ As a compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or a pseudohalogen group at the other end, -R ２ -Y-(CH ２ ) ｚ A compound similar to the compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or pseudohalogen group at the other end can be used. Therefore, the -(CH ２ ) ｚ -Y-R ５ As a compound having an alkenyl group at one end of a chain structure corresponding to - and a halogen group or a pseudohalogen group at the other end, for example, compounds represented by the above formulas (11-1) to (11-4) can be used.

[0150] The first and second reactions can be carried out by a conventionally known method, and the -R ２ -Y-(CH ２ ) ｚ - and -(CH ２ ) ｚ -Y-R ５ The reaction time can be determined appropriately depending on the type of -. In addition, either the first reaction or the second reaction may be carried out first. ２ -Y-(CH ２ ) ｚ - and - (CH ２ ) ｚ -Y-R ５ When the first and second reactions are the same, the first and second reactions may be carried out simultaneously.

[0151] Next, the double bond of the intermediate compound 3b is oxidized, and then treated with an acid to form R １ and R ６After the above steps, a deprotection reaction is carried out using a known method to remove the protecting group such as a THP group, a MOM group, or a benzyl group, converting it to a hydroxyl group, and then hydrolyzing the epoxy group to convert it to a diol, thereby producing a compound of formula (1) where x is 0.

[0152] [Lubricant for magnetic recording media] The lubricant for magnetic recording media (coating material) of this embodiment contains a fluorine-containing ether compound represented by formula (1). The lubricant of this embodiment can be used by mixing, as needed, with known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorine-containing ether compound represented by formula (1) are not impaired.

[0153] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of this embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0154] When the lubricant of this embodiment contains materials other than the fluorinated ether compound represented by formula (1), the content of the fluorinated ether compound represented by formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The upper limit of the content of the fluorinated ether compound represented by formula (1) can be selected arbitrarily and may, for example, be 99% by mass or less, or may be 95% by mass or less.

[0155] The lubricant of this embodiment contains the fluorine-containing ether compound represented by the above formula (1), and therefore can form a lubricating layer that has excellent wear resistance and a high spin-off suppression effect. In this embodiment, the case where the coating material of the present invention is used as a lubricant for magnetic recording media has been described as an example, but the use of the coating material of the present invention is not limited to lubricants for magnetic recording media.

[0156] [Magnetic Recording Medium] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided on a substrate in this order from the substrate side. In the magnetic recording medium of this embodiment, one or more underlayers can be provided between the substrate and the magnetic layer as needed. In addition, an adhesive layer and / or a soft magnetic layer can be provided between the underlayer and the substrate.

[0157] 1 is a schematic cross-sectional view showing one embodiment of a magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are provided on a substrate 11 in this order from the substrate 11 side.

[0158] "Substrate" The substrate 11 can be selected arbitrarily. A preferred example of the substrate 11 is a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. Alternatively, the substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a non-magnetic substrate in which a film of NiP or a NiP alloy is further formed on a base made of such a non-metallic material.

[0159] "Adhesion Layer" The adhesion layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesion layer 12 are disposed in contact with each other. The material of the adhesion layer 12 can be selected arbitrarily, and can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed, for example, by a sputtering method.

[0160] "Soft Magnetic Layer" The soft magnetic layer 13 can be selected arbitrarily, but preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC).

[0161] Examples of materials for the first and second soft magnetic films include CoZrTa alloys and CoFe alloys. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used for the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it is possible to improve the orientation of the first underlayer (seed layer) and reduce the flying height of the magnetic head. The soft magnetic layer 13 can be formed, for example, by sputtering.

[0162] "First Underlayer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. Examples of the first underlayer 14 include a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, and a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0163] "Second Underlayer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16 so that it is favorable. The second underlayer 15 can be selected arbitrarily, but is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a layer consisting of a single layer, or may be made of multiple layers. When the second underlayer 15 consists of multiple layers, all of the layers may be made of the same material, or at least one layer may be made of a different material. The second underlayer 15 can be formed, for example, by a sputtering method.

[0164] "Magnetic Layer" The magnetic layer 16 is made of a magnetic film with the axis of easy magnetization oriented perpendicular or horizontal to the substrate surface. The magnetic layer 16 can be selected arbitrarily, but is preferably a layer containing Co and Pt. To improve the SNR characteristics, the magnetic layer 16 may be a layer containing oxides, Cr, B, Cu, Ta, Zr, etc. Examples of oxides contained in the magnetic layer 16 include SiO ２ , SiO, Cr ２ O ３ , CoO, Ta ２ O ３ , TiO２ etc.

[0165] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. As the oxide contained in the first magnetic layer, it is preferable to use an oxide of, for example, Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among them, TiO is particularly preferable. ２ , Cr ２ O ３ , SiO ２ The first magnetic layer is preferably made of a composite oxide containing two or more kinds of oxides. ２ O ３ -SiO ２ , Cr ２ O ３ -TiO ２ , SiO ２ -TiO ２ The first magnetic layer may contain 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 thereof.

[0166] The second magnetic layer can be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure. The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides. In addition to Co, Cr, and Pt, the third magnetic layer can contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0167] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0168] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can be suitably made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0169] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 is preferably made of an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, the oxide may be, for example, SiO ２ , Al ２ O ３ , Ta ２ O ５ , Cr ２ O ３ , MgO, Y ２ O ３ , TiO ２ Examples of metal nitrides that can be used include AlN and Si. ３ N ４ , TaN, CrN, etc. As the metal carbide, for example, TaC, BC, SiC, etc. can be used. The non-magnetic layer can be formed by, for example, sputtering.

[0170] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be a magnetic layer for in-plane magnetic recording. The magnetic layer 16 may be formed by any conventionally known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0171] "Protective Layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or multiple layers. Examples of materials for the protective layer 17 include carbon, nitrogen-containing carbon, and silicon carbide. A carbon-based protective layer is preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. 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.

[0172] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen contents in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 atomic % to 20 atomic % 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).

[0173] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved.

[0174] 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.

[0175] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, ion beam deposition (IBD), or the like. When a carbon-based protective layer is formed as the protective layer 17, it can be formed by DC magnetron sputtering, for example. In particular, when a carbon-based protective layer is formed as the protective layer 17, it is preferable to form an amorphous carbon protective layer by plasma CVD. An amorphous carbon protective layer formed by plasma CVD has a uniform surface with little roughness.

[0176] "Lubricant Layer" The lubricant layer 18 prevents contamination of the magnetic recording medium 10. The lubricant layer 18 also reduces the frictional force of the magnetic head of the magnetic recording and reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in FIG. 1 , the lubricant layer 18 is formed on and in contact with the protective layer 17. The lubricant layer 18 is formed by applying the magnetic recording medium lubricant of the above-mentioned embodiment onto the protective layer 17. Therefore, the lubricant layer 18 contains the above-mentioned fluorine-containing ether compound.

[0177] 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 is easy 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.

[0178] The average thickness of the lubricating layer 18 can be selected arbitrarily, but is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.0 nm (10 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. Therefore, the surface of the protective layer 17 is covered with the lubricating layer 18 at a high coverage rate, making it even less susceptible to film thickness reduction due to spin-off. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0179] "Method for forming lubricating layer" As a method for forming the lubricating layer 18, for example, a method is given in which a magnetic recording medium in the middle of manufacture in which each layer up to the protective layer 17 is formed on the substrate 11, and a solution for forming a lubricating layer is applied to the protective layer 17 and dried.

[0180] The lubricant layer-forming solution can be obtained by dissolving and dispersing the magnetic recording medium lubricant of the above-described embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricant layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.) and / or Asahiklin (registered trademark) AE-3000 (trade name, manufactured by AGC).

[0181] The method for applying the lubricant layer-forming solution is not particularly limited, and examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, the following method can be used, for example. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in the lubricant layer-forming solution placed in the immersion tank of a dip coating device. Next, the substrate 11 is pulled out of the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the protective layer 17 of the substrate 11. By using the dipping method, the lubricant layer-forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricant layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0182] In this embodiment, it is preferable to subject the substrate 11 on which the lubricating layer 18 is formed to a heat treatment. By subjecting the substrate 11 to a heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive strength between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. A heat treatment temperature of 100°C or higher sufficiently improves the adhesion between the lubricating layer 18 and the protective layer 17. Furthermore, by setting the heat treatment temperature to 180°C or lower, thermal decomposition of the lubricating layer 18 due to the heat treatment can be prevented. The heat treatment time can be adjusted appropriately depending on the heat treatment temperature, and is preferably 10 minutes to 120 minutes.

[0183] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) rays before or after the heat treatment.

[0184] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed on and in contact with the protective layer 17. This lubricating layer 18 covers the surface of the protective layer 17 with a high coverage, even though it is thin. Therefore, the lubricating layer 18 in the magnetic recording medium 10 of this embodiment has excellent wear resistance and spin-off resistance. As a result, the magnetic recording medium 10 of this embodiment has excellent reliability and durability.

[0185] 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.

[0186] [Example 1] The compound represented by the above formula (A) was obtained by the following method. HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ 10 g of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by formula (4-1), 9.41 g of the compound represented by formula (4-1), and 50 mL of dimethylformamide were charged and stirred at room temperature until homogeneous to obtain a mixture. 11.9 g of cesium carbonate was added to this mixture, and the mixture was reacted with stirring at 50°C for 16 hours.

[0187] The compound represented by formula (4-1) was synthesized by the following method. First, the hydroxyl group of ethylene glycol monoallyl ether was protected using dihydropyran, and then the alkenyl group was oxidized with m-chloroperbenzoic acid to obtain a compound having a primary hydroxyl group protected by a tetrahydropyranyl (THP) group and an epoxy group. The obtained compound was then reacted with solketal, and the secondary hydroxyl group of the resulting compound was protected using chloromethyl methyl ether (MOMC1). Next, the resulting compound was treated with an acid to selectively deprotect the THP group, and the primary hydroxyl group was reacted with paratoluenesulfonyl chloride (TsCl) to obtain the compound represented by formula (4-1).

[0188] After the reaction, the reaction solution obtained was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at room temperature for 4 hours. Thereafter, the reaction solution was transferred little by little to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate, and extracted twice with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine in that order, and 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 compound (A) (Rf in formula (A) １ is the PFPE chain represented by the above formula (3-1). １ In the above formula, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0189] The obtained compound (A) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (34H), 4.13-4.30 (4H)

[0190] [Example 2] The compound represented by the above formula (B) was obtained by the following method. ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O)ｉ CF ２ CH ２ OH (wherein h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5), a compound (number average molecular weight 1000, molecular weight distribution 1.1) was used instead of HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (B) (Rf in formula (B)) except that 9.86 g of a compound (number average molecular weight: 986, molecular weight distribution: 1.1) represented by the formula OH (where h representing the average degree of polymerization is 8.5, and i representing the average degree of polymerization is 0) was used. １ is the PFPE chain represented by the above formula (3-1). １ In this example, h representing the average degree of polymerization is 8.5, and i representing the average degree of polymerization is 0.

[0191] The obtained compound (B) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (34H), 4.13-4.30 (4H)

[0192] [Example 3] The compound represented by the above formula (C) was obtained by the following method. ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ OH (wherein h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5), a compound (number average molecular weight 1000, molecular weight distribution 1.1) was used instead of HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O)ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out, except that 10 g of a compound (number average molecular weight: 1,000, molecular weight distribution: 1.1) represented by the formula (Rf in formula (C)) was used. ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0193] The obtained compound (C) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (34H), 4.13-4.30 (4H)

[0194] [Example 4] The compound represented by the above formula (D) was obtained by the following method. The same procedure as in Example 3 was carried out, except that 9.25 g of the compound represented by formula (4-2) was used instead of the compound represented by formula (4-1), to obtain compound (D) (Rf ２ is the PFPE chain represented by the above formula (4-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0195] The compound represented by formula (4-2) was synthesized by the following method. First, the hydroxyl group of allyloxypropanol was protected using dihydropyran, and then the alkenyl group was oxidized with m-chloroperbenzoic acid to obtain a compound having a primary hydroxyl group protected by a tetrahydropyranyl (THP) group and an epoxy group. The obtained compound was then reacted with solketal, and the secondary hydroxyl group of the resulting compound was protected using chloromethyl methyl ether (MOMC1). Next, the resulting compound was treated with an acid to selectively deprotect the THP group, and the primary hydroxyl group was reacted with paratoluenesulfonyl chloride (TsCl) to obtain the compound represented by formula (4-2).

[0196] The obtained compound (D) １H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.81-1.97 (4H), 3.44-3.91 (34H), 4.13-4.30 (4H)

[0197] [Example 5] The compound represented by the above formula (E) was obtained by the following method. (First reaction) HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ 10 g of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by formula (4-3), 1.66 g of the compound represented by formula (4-3), and 20 mL of dimethylformamide were charged and stirred at room temperature until homogeneous to obtain a mixture. 4.61 g of cesium carbonate was added to this mixture, and the mixture was reacted by stirring at 50°C for 16 hours.

[0198] The compound represented by formula (4-3) was synthesized by the following method. First, the primary hydroxyl group of solketal was reacted with paratoluenesulfonyl chloride (TsCl). Then, the obtained compound was reacted with ethylene glycol. Then, the primary hydroxyl group of the produced compound was reacted with paratoluenesulfonyl chloride (TsCl) to obtain the compound represented by formula (4-3).

[0199] The reaction product obtained after the first 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 2.81 g of a compound represented by the following formula (11) as intermediate compound 1-1.

[0200] (Rf in formula (11) ２is the PFPE chain represented by the above formula (3-2). ２ In this case, j, which indicates the average degree of polymerization, is 4.5.

[0201] (Second Reaction) In a nitrogen gas atmosphere, 2.81 g of the compound represented by formula (11), which is intermediate compound 1-1 obtained above, 1.35 g of the compound represented by formula (4-1) above, and 20 mL of dimethylformamide were charged into a 100 mL recovery flask, and the mixture was stirred at room temperature until it became homogeneous. 1.78 g of cesium carbonate was added to the mixture, and the mixture was reacted by stirring at 50°C for 16 hours.

[0202] After the reaction, the reaction solution obtained was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at room temperature for 4 hours. Thereafter, the reaction solution was transferred little by little to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate, and extracted twice with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine in that order, and 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 compound (E) (Rf in formula (E) ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0203] The obtained compound (E) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (28H), 4.13-4.30 (4H)

[0204] [Example 6] A compound represented by the above formula (F) was obtained by the method shown below. (First Reaction) In the same manner as in the first reaction of Example 5, a compound represented by formula (11) was obtained as intermediate compound 1-3.

[0205] (Second Reaction) Subsequently, under a nitrogen gas atmosphere, 8.70 g of the compound represented by formula (11) as intermediate compound 1-3 obtained above, 0.83 g of the compound represented by formula (9-1) above, 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. 0.23 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0206] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (F) (Rf in formula (F) ２ is a PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0207] The obtained compound (F) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.81-1.97 (6H), 3.44-3.91 (34H), 4.13-4.30 (8H)

[0208] [Example 7] The compound represented by the above formula (G) was obtained by the following method. (First reaction) HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２5 g of a compound (number average molecular weight: 1,000, molecular weight distribution: 1.1) represented by formula (11-1), 1.73 g of the compound represented by formula (11-1), and 20 mL of dimethylformamide were charged and stirred at room temperature until homogeneous to obtain a mixture. 2.30 g of cesium carbonate was added to this mixture, and the mixture was reacted by stirring at 50°C for 16 hours.

[0209] The reaction product obtained after the first 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 4.11 g of the compound represented by the following formula (16-1) as intermediate compound 3b.

[0210] (Rf in formula (16-1) ２ is the PFPE chain represented by the above formula (3-2). ２ In this case, j, which indicates the average degree of polymerization, is 4.5.

[0211] (Second Reaction) The double bond of the compound represented by formula (16-1) was oxidized with m-chloroperbenzoic acid (mCPBA). After the reaction, an aqueous sodium thiosulfate solution was added, and the resulting reaction product was transferred to a separatory funnel containing 100 mL of water at 25°C and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.65 g of the compound represented by the following formula (16-2) as intermediate compound 3c.

[0212]

[0213] (Third Reaction) Finally, 31 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the compound represented by formula (16-2), and the mixture was stirred at room temperature for 2 hours. The reaction solution was transferred little by little to a separatory funnel containing 100 mL of brine, and extracted three times with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated sodium bicarbonate water, and 100 mL of brine in that order, 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 compound (G) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0214] The obtained compound (G) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (14H), 4.13-4.30 (4H)

[0215] [Example 8] The compound represented by the above formula (H) was obtained by the method shown below. The same procedure as in Example 7 was carried out, except that 2.34 g of the compound represented by formula (15) was used instead of the compound represented by formula (11-1), to obtain the compound represented by formula (H) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0216] The compound represented by formula (15) was synthesized by the following method. First, the primary hydroxyl group of oxiraneethanol was protected with dihydropyran, and then 3-buten-1-ol was reacted with it. Next, the alkenyl group was oxidized with m-chloroperbenzoic acid to obtain a compound, which was then reacted with ethylene glycol. The primary hydroxyl group of the resulting compound was then reacted with paratoluenesulfonyl chloride (TsCl) to obtain the compound represented by formula (15).

[0217]

[0218] The obtained compound (H) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.81-1.97 (8H), 3.44-3.91 (34H), 4.13-4.30 (4H)

[0219] [Example 9] The compound represented by the above formula (I) was obtained by the method shown below. The same procedure as in Example 6 was carried out, except that 0.66 g of epibromohydrin was used instead of the compound represented by formula (9-1), to obtain the compound represented by formula (I) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0220] The obtained compound (I) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (29H), 4.13-4.30 (8H)

[0221] [Example 10] A compound represented by the above formula (J) was obtained by the method shown below. The same procedure as in Example 6 was carried out, except that 0.99 g of a compound represented by formula (9-2) was used instead of the compound represented by formula (9-1), to obtain compound (J) represented by formula (J) (where Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0222] The obtained compound (J) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (40H), 4.13-4.30 (8H)

[0223] [Example 11] A compound represented by the above formula (K) was obtained by the method shown below. The same procedure as in Example 6 was carried out, except that 5.38 g of a compound represented by formula (17) was used instead of the compound represented by formula (9-1), to obtain compound (K) represented by formula (K) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0224] The compound represented by formula (17) is HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ OH (where j, which indicates the average degree of polymerization, is 4.5) (number average molecular weight: 1000, molecular weight distribution: 1.1) was reacted with epibromohydrin to obtain this compound.

[0225]

[0226] The obtained compound (K) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (34H), 4.13-4.30 (12H)

[0227] [Example 12] The compound represented by the above formula (L) was obtained by the following method. The same procedure as in Example 3 was carried out, except that 10.1 g of the compound represented by formula (18) was used instead of the compound represented by formula (4-1), to obtain compound (L) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0228] The compound represented by formula (18) was synthesized by the following method. First, the hydroxyl group of 2-allyloxyethanol was protected using dihydropyran, and then the alkenyl group was oxidized with m-chloroperbenzoic acid to obtain a compound having a primary hydroxyl group and an epoxy group protected by a tetrahydropyranyl (THP) group. The obtained compound was then reacted with ethylene glycol, and the primary hydroxyl group of the resulting compound was reacted with paratoluenesulfonyl chloride (TsCl). Next, the secondary hydroxyl group of the resulting compound was protected using tetrahydropyranyl (THP) to obtain the compound represented by formula (18).

[0229]

[0230] The obtained compound (L) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (30H), 4.13-4.30 (4H)

[0231] [Example 13] The compound represented by the above formula (M) was obtained by the method shown below. The same procedure as in Example 3 was carried out, except that 8.31 g of the compound represented by formula (19) was used instead of the compound represented by formula (4-1), to obtain compound (M) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0232] The compound represented by formula (19) was synthesized by the following method. First, 3-butenyl glycidyl ether was reacted with ethylene glycol, and the primary hydroxyl group of the resulting compound was reacted with paratoluenesulfonyl chloride (TsCl). Next, the secondary hydroxyl group of the resulting compound was protected with tetrahydropyranyl (THP) to obtain the compound represented by formula (19).

[0233]

[0234] The obtained compound (M) １H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (28H), 4.13-4.30 (4H), 5.1-5.2 (1H), 5.2-5.3 (1H), 5.8-6.0 (1H)

[0235] [Example 14] The compound represented by the above formula (N) was obtained by the following method. The same procedure as in Example 3 was carried out, except that 9.01 g of the compound represented by formula (20) was used instead of the compound represented by formula (4-1), to obtain compound (N) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0236] The compound represented by formula (20) was synthesized by the following method. First, glycidyl phenyl ether was reacted with ethylene glycol, and the primary hydroxyl group of the resulting compound was reacted with paratoluenesulfonyl chloride (TsCl). Next, the secondary hydroxyl group of the resulting compound was protected with tetrahydropyranyl (THP) to obtain the compound represented by formula (20).

[0237]

[0238] The obtained compound (N) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (28H), 4.13-4.30 (4H), 5.1-5.2 (1H), 5.2-5.3 (1H), 5.8-6.0 (1H)

[0239] [Example 15] The compound represented by the above formula (O) was obtained by the method shown below. The same procedure as in Example 3 was carried out, except that 9.01 g of the compound represented by formula (21) was used instead of the compound represented by formula (4-1), to obtain compound (O) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0240] The compound represented by formula (21) was synthesized by reacting (2,2-dimethyl-1,3-dioxolan-4-yl)methanamine with di-tert-butyl dicarbonate in methanol, reacting the resulting compound with 2-bromoethanol, and then reacting the resulting compound with p-toluenesulfonyl chloride (TsCl).

[0241]

[0242] The obtained compound (O) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (16H), 4.13-4.30 (4H)

[0243] [Example 16] The compound represented by the above formula (P) was obtained by the following method. The same procedure as in Example 3 was carried out, except that 9.01 g of the compound represented by formula (22) was used instead of the compound represented by formula (4-1), to obtain compound (P) (Rf ２ is the PFPE chain represented by the above formula (3-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.5.

[0244] The compound represented by formula (22) was synthesized by reacting (2,2-dimethyl-1,3-dioxolan-4-yl)methanethiol with 2-bromoethanol, and then reacting the resulting compound with paratoluenesulfonyl chloride (TsCl).

[0245]

[0246] The obtained compound (P) １ H-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.44-3.91 (14H), 4.13-4.30 (4H)

[0247] The compounds (A) to (F) of Examples 1 to 16 thus obtained were applied to the formula (1), and the value of x and R １ , R ２ , R ３ , R ４ , R ５ , R ６ The structure, the element of Y, and the value of z are shown in Table 1.

[0248]

[0249] Comparative Example 1 A compound represented by the following formula (AA) was synthesized by the method described in Patent Document 1.

[0250] (Rf in formula (AA) ２ In the formula, j represents the average degree of polymerization, and j represents 4.5.

[0251] Comparative Example 2 A compound represented by the following formula (AB) was synthesized by the method described in Patent Document 2.

[0252] (Rf in formula (AB) １ In the formula, h and i represent the average degree of polymerization, h represents 4.5, and i represents 4.5.

[0253] Comparative Example 3 A compound represented by the following formula (AC) was synthesized by the method described in Patent Document 3.

[0254] (Rf in formula (AC) １ In the formula, h and i represent the average degree of polymerization, h represents 4.5, and i represents 4.5.

[0255] Comparative Example 4 A compound represented by the following formula (AD) was synthesized by the method described in Patent Document 4.

[0256] (Rf in formula (AD) ２ In the formula, j represents the average degree of polymerization, and j represents 4.5.

[0257] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 16 and Comparative Examples 1 to 4. Then, using the obtained solutions for forming lubricating layers, lubricating layers for magnetic recording media were formed by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 16 and Comparative Examples 1 to 4.

[0258] "Lubricant Layer-Forming Solution" The compounds obtained in Examples 1 to 16 and Comparative Examples 1 to 4 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.), and diluted with Vertrel so that the film thickness when applied to the protective layer would be 0.8 nm (8 Å) to 0.9 nm (9 Å), to prepare a lubricant layer-forming solution.

[0259] "Magnetic Recording Medium" A magnetic recording medium was prepared by sequentially providing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon. Each of the lubricant layer-forming solutions of Examples 1 to 16 and Comparative Examples 1 to 4 was applied by dipping onto the protective layer of the magnetic recording medium, on which each of the layers up to the protective layer had been formed. The dipping was performed 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.

[0260] 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.

[0261] The thickness of the lubricating layer of each of the magnetic recording media thus obtained in Examples 1 to 16 and Comparative Examples 1 to 4 was measured using a Fourier transform infrared spectrophotometer (FT-IR, product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Table 2.

[0262] Next, the magnetic recording media of Examples 1 to 16 and Comparative Examples 1 to 4 were subjected to the following wear resistance test and spin-off characteristic test.

[0263] [Wear Resistance Test] Using a pin-on-disk friction and wear tester, a 2 mm diameter alumina ball was slid as a contact on the lubricating layer of a magnetic recording medium at a load of 40 gf and a sliding speed of 0.25 m / sec to measure the friction coefficient of the surface of the lubricating layer. The sliding time until the friction coefficient of the surface of the lubricating layer suddenly increased was then measured. The sliding time until the friction coefficient suddenly increased was measured four times for the lubricating layer of each magnetic recording medium, and the average value (time) was used as an index of the wear resistance of the lubricant coating. The results for the magnetic recording media using the compounds of Examples 1 to 16 and Comparative Examples 1 to 4 are shown in Table 2. The time until the friction coefficient increased was evaluated as follows:

[0264] A: 850 seconds or more B: 750 seconds or more, less than 850 seconds C: 650 seconds or more, less than 750 seconds D: Less than 650 seconds

[0265] The time until the coefficient of friction increases sharply can be used as an indicator of the wear resistance of the lubricating layer for the following reason: The lubricating layer of a magnetic recording medium wears out as the magnetic recording medium is used, and when the lubricating layer is worn away, the contact and protective layer come into direct contact, causing a sharp increase in the coefficient of friction. The time until the coefficient of friction increases sharply is thought to be correlated with friction testing.

[0266] [Spin-off property test] A magnetic recording medium was mounted on a spin stand and rotated at a rotation speed of 10,000 rpm in an environment of 80°C for 72 hours. Before and after this operation, the film thickness of the lubricating layer at a position 20 mm radius from the center of the magnetic recording medium was measured using FT-IR, and the film thickness reduction rate of the lubricating layer before and after the test was calculated. The calculated film thickness reduction rate was used to evaluate the spin-off property according to the evaluation criteria shown below. The results for the magnetic recording media using the compounds of Examples 1 to 16 and Comparative Examples 1 to 4 are shown in Table 2.

[0267] "Evaluation criteria for spin-off characteristics" A: Film thickness reduction rate of 2% or less B: Film thickness reduction rate of more than 2% and 3% or less C: Film thickness reduction rate of more than 3% and 9% or less D: Film thickness reduction rate of more than 9%

[0268] An overall evaluation was made based on the results of the abrasion resistance test and the spin-off characteristic test, according to the evaluation criteria shown below. "Overall Evaluation" A: The evaluations in the abrasion resistance test and the spin-off characteristic test were all A. B: The evaluations in the abrasion resistance test and the spin-off characteristic test were A or B, with at least one of them being B. C: At least one of the evaluations in the abrasion resistance test and the spin-off characteristic test was C, and no D was received. D: At least one of the evaluations in the abrasion resistance test and the spin-off characteristic test was D.

[0269]

[0270] As shown in Table 2, the magnetic recording media of Examples 1 to 16, in which the lubricating layer was formed using the fluorine-containing ether compound represented by formula (1), were all evaluated as A in the wear resistance test and spin-off characteristic test, and the overall evaluation was A. In contrast, the -(CH ２ ) ｚ The magnetic recording media of Comparative Examples 1 to 4, which did not have -, showed inferior results in the evaluations of the wear resistance test and the spin-off characteristics test, compared to the magnetic recording media of Examples 1 to 16.

[0271] The fluorine-containing ether compound of this embodiment is suitably used as a material for a lubricant for a magnetic recording medium.

[0272] 10: magnetic recording medium, 11: substrate, 12: adhesive layer, 13: soft magnetic layer, 14: first underlayer, 15: second underlayer, 16: magnetic layer, 17: protective layer, 18: lubricating layer.

Claims

1. A fluorine-containing ether compound represented by the following formula (1): １ -R ２ -Y-(CH ２ ) ｚ -O-CH ２ -R ３ [-CH ２ -R ４ -CH ２ -R ３ ] ｘ -CH ２ -O-(CH ２ ) ｚ -Y-R ５ -R ６ (1) (In formula (1), x is 0 to 2; each z is independently an integer from 2 to 10; each Y is independently O, NH, or S; R ３ is a perfluoropolyether chain. (x+1) R ３ may be the same in part or in whole, or may be different from each other; R ４ is a divalent linking group having 1 to 3 hydroxyl groups and oxygen atoms at both ends; when x is 2, two R ４ may be the same or different; R ２ is a linking group represented by the following formula (2-1) or (2-2); R ５ is a linking group represented by the following formula (2-3) or (2-4); R １ and R ６ is R ２ or R ５ are terminal groups bonded to the terminal oxygen atoms of R １ and R ６ are each independently a terminal group selected from the group consisting of a hydrogen atom, an alkyl group which may have a substituent, and an organic group which has a double bond or a triple bond and which may have a substituent. (In formula (2-1), f1 represents an integer of 1 to 3. The oxygen atom at the left end of formula (2-1) is R １ (In formula (2-2), g1 represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-2) is bonded to R １ (In formula (2-3), f2 represents an integer of 1 to 3. The oxygen atom at the right end of formula (2-3) is bonded to R ６ (In formula (2-4), g2 represents an integer of 2 to 6. The oxygen atom at the right end of formula (2-4) is bonded to R ６ ) 2. The fluorine-containing ether compound according to claim 1, wherein each z in formula (1) is independently an integer of 2 to 6.

3. The fluorine-containing ether compound according to claim 2, wherein each z in formula (1) is independently an integer of 2 to 4.

4. The fluorine-containing ether compound according to claim 1, wherein each Y in formula (1) is independently O or NH.

5. The fluorine-containing ether compound according to claim 4, wherein all of the Y's in formula (1) are O.

6. R １ and R ６ 2. The fluorine-containing ether compound according to claim 1, wherein the optionally substituted alkyl groups in the formula (I) are each independently an optionally substituted alkyl group having 1 to 8 carbon atoms.

7. R １ and R ６ 2. The fluorine-containing ether compound according to claim 1, wherein the organic groups having a double bond or a triple bond and which may have a substituent are each independently at least one selected from the group consisting of aromatic hydrocarbon groups, unsaturated heterocyclic groups, alkenyl groups, and alkynyl groups, which may have a substituent.

8. x R in the formula (1) ４ are each independently a divalent linking group represented by any one of the following formulas (2-5) to (2-8): (In formula (2-5), r represents an integer of 1 to 3.) (In formula (2-6), s represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-6) is R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ In formula (2-7), t represents an integer of 2 to 6. The oxygen atom at the left end of formula (2-7) is bonded to R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ In formula (2-8), u represents an integer of 1 to 6, and v represents an integer of 1 to 6. u and v cannot be 1 at the same time. The oxygen atom at the left end of formula (2-8) is bonded to R １ -CH on the side ２ -, and the oxygen atom at the right end is R ６ -CH on the side ２ - and bond.) 9. (x+1) R in the formula (1) ３ are each independently represented by the following formula (Rf): -(CF ２ ) ｐ１ -O-(CF ２ O) ｐ２ -(CF ２ CF ２ O) ｐ３ -(CF ２ CF ２ CF ２ O) ｐ４ -(CF ２ CF ２ CF ２ CF ２ O) ｐ５ -(CF ２ ) ｐ６ - (Rf) (In formula (Rf), p2, p3, p4, and p5 represent an average degree of polymerization, each independently representing 0 to 20. However, p2, p3, p4, and p5 cannot all be 0 at the same time. p1 and p6 are -CF ２ - is an average value representing the number of -, each independently representing 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).

10. (x+1) R in the formula (1) ３ are each independently represented by the following formulas (3-1) to (3-4): ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (3-1) (In formula (3-1), 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 - (3-2) (In formula (3-2), 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 - (3-3) (In formula (3-3), 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 - (3-4) (In formula (3-4), 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 11. The fluorine-containing ether compound according to claim 1, which has a number average molecular weight in the range of 500 to 10,000.

12. A coated article comprising the fluorine-containing ether compound according to any one of claims 1 to 11.

13. A lubricant for magnetic recording media, comprising the coating material according to claim 12.

14. A magnetic recording medium comprising a substrate and at least a magnetic layer, a protective layer, and a lubricating layer provided thereon, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of claims 1 to 11.

15. The magnetic recording medium according to claim 14, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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