Fluoropolyether compound, lubricant, and magnetic disk

Abstract

To provide a lubricant having further improved heat resistance and adhesion to a magnetic disk, an oligomerized fluoropolyether compound for achieving the lubricant, and a magnetic disk using the lubricant and the oligomerized fluoropolyether compound.SOLUTION: The problem is solved by linking two perfluoropolyether group-containing groups with a linking group having the following structure. -R5-CH (OH) CH2 (CF2) iCH2CH (OH) - R6 - In the formula, I is an integer of 1 to 10, and R5 and R6 are each independently a hydrocarbyl group having 1 to 10 carbons, and may contain ether bonds in which at least one carbon atom is substituted with oxygen atoms, and / or polar groups.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fluoropolyether compound, a lubricant, and a magnetic disk. [Background technology]

[0002] In a magnetic disk using a thermally assisted magnetic recording (HAMR) method, the magnetic disk is heated, so the lubricant applied to the magnetic disk is also required to have high heat resistance.

[0003] As a technique for improving the heat resistance and adhesion of a lubricant to a magnetic disk surface, a technique using a fluoropolyether compound in which multiple perfluoropolyether groups are bonded via an aliphatic hydrocarbon ether group, i.e., a polymerized fluoropolyether compound, is known (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 084781 [Patent Document 2] Patent Publication No. 2024-52300 [Patent Document 3] International Publication No. 2024 / 071399 [Patent Document 4] U.S. Patent Application Publication No. 2015 / 0235664 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to improve the long-term stability of magnetic disks, it is desirable to develop lubricants that have improved heat resistance and adhesion to magnetic disks compared to the prior art techniques described above.

[0006] One aspect of the present invention aims to provide a lubricant having improved heat resistance and adhesion to a magnetic disk, a polymerized fluoropolyether compound to achieve this, and a magnetic disk using the same. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention includes the following aspects.

[0008] [1] A fluoropolyether compound represented by the following formula (1): R 1 -CH2-Rf 1 -CH2O-R 2 -OCH2-Rf 2 -CH2-R 3 (1) In formula (1), Rf 1 and Rf 2 are each independently a perfluoropolyether group represented by the following formula (2): -(CF2) a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a - (2) In formula (2), c, d, e, f, and g each independently represent a real number of 0 to 30, and a and b each independently represent an integer of 0 to 3. R 1 and R 3 are each independently an optionally substituted hydrocarbon group having one or more OH groups, which may contain an ether bond, or an OH group; R 2 is a group represented by the following formula (3): -R 5 -CH(OH)CH2(CF2) i CH2CH(OH)-R 6- (3) In formula (3), i is an integer from 1 to 10, and R 5 and R 6 are each independently a hydrocarbon group having 1 to 10 carbon atoms, and may contain an ether bond in which at least one carbon atom is substituted with an oxygen atom, and / or a polar group.

[0009] [2]R 1 and R 3 are each independently -OH, -OCH2CH(OH)CH2OH, -OCH2CH(OH)CH2OCH2CH(OH)CH2OH, -O(CH2) h OH, and OCH2CH(OH)CH2-OC6H4-R 4 (where h is an integer from 2 to 8, and R 4 is a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, an amino group, an alkylamino group, an amido group, or a phenoxy group.

[0010] [3]R 5 and R 6 The fluoropolyether compound according to [1] or [2], wherein the polar group is an OH group, an amino group, an alkylamino group, a carboxy group, a carbonyl group, a sulfo group, an amido group, or a phenoxy group.

[0011] [4] A lubricant comprising the fluoropolyether compound according to any one of [1] to [3].

[0012] [5] A magnetic disk having a lubricating layer containing the lubricant according to [4]. [Effects of the Invention]

[0013] According to one aspect of the present invention, it is possible to provide a lubricant having improved heat resistance and adhesion to a magnetic disk, a polymerized fluoropolyether compound to achieve this, and a magnetic disk using the same. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing the configuration of a magnetic disk according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing the configuration of a magnetic disk according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to these, and various modifications are possible within the scope of the description. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0016] [1. Fluoropolyether Compounds] The increased molecular weight of a polymerized fluoropolyether compound makes it less likely to evaporate when heated, and the increased amount of functional groups that interact with the magnetic disk surface allows it to adhere more strongly to the magnetic disk. This improves the heat resistance and adhesion to the magnetic disk of a lubricant containing such a fluoropolyether compound. In an effort to further improve the heat resistance and adhesion to the magnetic disk of a lubricant using a fluoropolyether compound, the inventors connected two perfluoropolyether group-containing groups with a linking group having a specific structure, and surprisingly found that the heat resistance and adhesion to the magnetic disk of the lubricant were significantly improved, leading to the completion of the present invention. In this specification, "adsorption" refers to adsorption caused by interactions due to chemical bonds, hydrogen bonds, and intermolecular forces.

[0017] That is, a fluoropolyether compound according to one embodiment of the present invention is a fluoropolyether compound represented by the following formula (1): R 1 -CH2-Rf 1 -CH2O-R 2 -OCH2-Rf 2-CH2-R 3 (1) In formula (1), Rf 1 and Rf 2 are each independently a perfluoropolyether group represented by the following formula (2): -(CF2) a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a - (2) In formula (2), c, d, e, f, and g each independently represent a real number of 0 to 30, and a and b each independently represent an integer of 0 to 3. R 1 and R 3 are each independently an optionally substituted hydrocarbon group having one or more OH groups, which may contain an ether bond, or an OH group; R 2 is a group represented by the following formula (3): -R 5 -CH(OH)CH2(CF2) i CH2CH(OH)-R 6 - (3) In formula (3), i is an integer from 1 to 10, and R 5 and R 6 are each independently a hydrocarbon group having 1 to 10 carbon atoms, and may contain an ether bond in which at least one carbon atom is substituted with an oxygen atom, and / or a polar group.

[0018] (Rf 1 and Rf 2 ) In the formula (1), Rf 1 and Rf 2 are each independently a perfluoropolyether group represented by the formula (2). In the formula (2), c, d, e, f, and g (also referred to as c to g) are Rf 1 and Rf2 In these, each may be a real number between 0 and 30, and more preferably a real number between 0 and 25. However, at least one of c to g is a real number greater than or equal to 1. Here, c to g are measured using a JNM-ECX400 manufactured by JEOL Ltd. 19 The average values ​​were calculated by F-NMR measurement. In the NMR measurement, the sample itself was measured without using a solvent. The chemical shift reference was substituted with the known peak of the fluoropolyether skeleton structure.

[0019] Rf 1 and Rf 2 For example, the demnam skeleton: -(CF2CF2CF2O) e -, Fomblin skeleton: -(CF2O) c (CF2CF2O) d -, C2 skeleton: -(CF2CF2O) d -, C4 skeleton: -(CF2CF2CF2CF2O) f - and Krytox skeleton: -(CF2CF(CF3)O) g - is a perfluoropolyether group containing at least one selected from the group consisting of:

[0020] Rf 1 and Rf 2 A more preferred example of the group is a group in which c to g in formula (2) are any of the following (i) to (v): The following configuration is preferred because it makes the molecular chain flatter.

[0021] (i) c = 2 to 12, and d = 2 to 12, and e to g = 0 (ii) d = real number between 4 and 14, and c and e to g = 0 (iii) e = a real number between 2 and 12, and c, d, f, and g = 0 (iv) f = real number between 1 and 9, and c to e and g = 0 (v) g = real number between 2 and 12, and c~f = 0 In addition, CF2O and CF2CF2O can be repeated randomly in the Fomblin skeleton. From the viewpoint of heat resistance, c=0 is more preferable.

[0022] (R 1 and R 3 ) In the formula (1), R 1 and R 3 R are each independently an optionally substituted hydrocarbon group having one or more OH groups, which may contain an ether bond, or an OH group. 1 and R 3 However, each independently having one or more OH groups is preferable because it improves the adhesion of the fluoropolyether compound represented by formula (1) to a magnetic disk. Here, the "optionally substituted hydrocarbon group" is, in other words, a substituted or unsubstituted hydrocarbon group. Furthermore, "optionally substituted" means that, in addition to the OH group, the group may be further substituted with a substituent other than the OH group.

[0023] In the substituted or unsubstituted hydrocarbon group having one or more OH groups and optionally containing an ether bond (hereinafter sometimes referred to as an "OH group-containing hydrocarbon group"), the hydrocarbon group (when substituted with an ether bond and / or a substituent, the hydrocarbon group before substitution) has 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and even more preferably 2 to 20 carbon atoms. The hydrocarbon group may be linear or branched, and may contain a cyclic hydrocarbon group. The hydrocarbon group is preferably linear or branched, and more preferably linear. The hydrocarbon group may be saturated or unsaturated. The number of OH groups in the OH group-containing hydrocarbon group is not limited as long as it is one or more, but is, for example, 1 to 6, more preferably 1 to 5, and even more preferably 1 to 4. From the viewpoint of adhesion to magnetic disks, the OH group-containing hydrocarbon group preferably contains a primary OH group. The number of ether bonds (the number of carbon atoms substituted with oxygen atoms) contained in the OH group-containing hydrocarbon group is, for example, 0 to 5, more preferably 1 to 4, and even more preferably 1 to 3.

[0024] In one embodiment of the present invention, when the hydrocarbon group is a linear or branched hydrocarbon group, the hydrocarbon group has 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and even more preferably 2 to 20 carbon atoms. The hydrocarbon group may be saturated or unsaturated, but is preferably saturated. The number of OH groups and the number of ether bonds (the number of carbon atoms substituted with oxygen atoms) contained in the OH group-containing hydrocarbon group are as described above. The linear or branched OH group-containing hydrocarbon group may contain, in addition to OH groups, an alkoxy group, an amino group, an alkylamino group, an amide group, a phenoxy group, an epoxy group, a nitrile group, an optionally substituted phosphazene group, or the like. In this specification, the term "amide group" refers to a group having an amide bond and is not particularly limited, but is preferably an aliphatic amide group such as acetamide (-NHCOCH3) or propionamide (-NHCOC2H5).

[0025] Such an OH group-containing hydrocarbon group includes, for example, a group represented by the following formula (4): -O-((CH2) j -CH(OH)-CHO) k H (4) In formula (4), j is an integer of 0 to 5, and k is an integer of 1 to 3. More preferred examples of the group represented by formula (4) include -OCH2CH(OH)CH2OH, -OCH2CH(OH)CH2OCH2CH(OH)CH2OH, -OCH2CH2CH(OH)CH2OH, -OCH2CH2CH2CH(OH)CH2OH, and the like.

[0026] Another example of the OH group-containing hydrocarbon group is a group represented by the following formula (5). -O-(CH2) h -OH (5) In the formula (5), h is preferably an integer of 2 to 8, and more preferably an integer of 2 to 4.

[0027] In one embodiment of the present invention, when the hydrocarbon group is a hydrocarbon group containing a cyclic hydrocarbon group, the hydrocarbon group preferably has 3 to 40 carbon atoms, more preferably 4 to 30 carbon atoms, and even more preferably 4 to 20 carbon atoms. The OH group-containing hydrocarbon group preferably has one or more OH groups and one or more cyclic hydrocarbon groups, thereby improving the adhesion of the fluoropolyether compound represented by formula (1) to a magnetic disk. The number of cyclic hydrocarbon groups contained in the hydrocarbon group is not limited thereto, but is, for example, 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. The cyclic hydrocarbon group is, for example, a cyclic hydrocarbon group having 3 to 10 carbon atoms, more preferably 3 to 8 carbon atoms, and even more preferably 5 to 6 carbon atoms. Examples of the cyclic hydrocarbon group include alicyclic hydrocarbon groups such as cyclohexyl, cyclohexylene, cyclopentyl, and cyclopentylene; and aromatic hydrocarbon groups such as phenyl, phenylene, naphthyl, and naphthylene. The cyclic hydrocarbon group may be a monocyclic hydrocarbon group or a fused polycyclic hydrocarbon group. The hydrocarbon group containing a cyclic hydrocarbon group may be linear or branched except for the cyclic hydrocarbon group. The hydrocarbon group containing a cyclic hydrocarbon group may be a hydrocarbon group containing a cyclic hydrocarbon group in the main chain and / or at the end of a linear or branched hydrocarbon group. The linear or branched hydrocarbon group contained in the hydrocarbon group containing a cyclic hydrocarbon group is not limited thereto, but is preferably a linear or branched hydrocarbon group having 0 to 35 carbon atoms, more preferably 2 to 30 carbon atoms, and even more preferably 2 to 20 carbon atoms, and may be saturated or unsaturated, substituted or unsubstituted. When the hydrocarbon group contains a cyclic hydrocarbon group, the number of OH groups and the number of ether bonds (the number of carbon atoms substituted with oxygen atoms) contained in the OH group-containing hydrocarbon group are as described above.

[0028] When the cyclic hydrocarbon group has a substituent other than an OH group, the substituent may be mono-substituted, di-substituted, or poly-substituted. Examples of the OH group-containing hydrocarbon group that contains the cyclic hydrocarbon group include groups represented by the following formula (6): -O-(CH2) n -CH(OH)-(CH2) p -OAR 7 (6) In formula (6), n and p each independently represent an integer of 1 to 5, A represents the cyclic hydrocarbon group, and R 7 is a hydrogen atom, an OH group, a nitro group, an alkoxy group having 1 to 10 carbon atoms (e.g., methoxy, ethoxy, propoxy, or butoxy), a perfluoroalkyl group having 1 to 10 carbon atoms (e.g., -CF3), an amino group, an alkylamino group (e.g., methylamino, dimethylamino, ethylamino, or diethylamino), a carboxy group, a formyl group, a carbonyl group, a sulfo group, a cyano group, an amide group (e.g., acetamide (-NHCOCH3), or propionamide (-NHCOC2H5)), or a phenoxy group. Substitution of the cyclic hydrocarbon group with these groups is preferred because it further improves the adhesion of the fluoropolyether compound represented by formula (1) to magnetic disks. Specific examples of OH-containing hydrocarbon groups including the cyclic hydrocarbon group include -OCH2CH(OH)CH2OC6H5, -OCH2CH(OH)CH2OC 10 H7, -OCH2CH(OH)CH2O(C6H4)NO2, -CH2OCH2CH(OH)CH2O(C6H5)OH, -CH2OCH2CH(OH)CH2O(C6H 10 )OCH3, -OCH2CH(OH)CH2O(C6H4)NH2, -OCH2CH(OH)CH2O(C6H4)OC6H5. R 7 is more preferably hydrogen, an alkoxy group having 1 to 4 carbon atoms, an amino group, an amido group, or a phenoxy group. 7 may be substituted with.

[0029] Furthermore, the linear or branched hydrocarbon group contained in the hydrocarbon group containing the cyclic hydrocarbon group may also be substituted with, in addition to an OH group, an alkoxy group, an amino group, an alkylamino group, an amide group, a phenoxy group, an epoxy group, a nitrile group, an optionally substituted phosphazene group, or the like.

[0030] R1 and R 3 are any of the above-mentioned OH group-containing hydrocarbon groups, but are particularly preferably each independently -OH, -OCH2CH(OH)CH2OH, -OCH2CH(OH)CH2OCH2CH(OH)CH2OH, -O(CH2) h OH, and OCH2CH(OH)CH2-OC6H4-R 4 (where h is an integer from 2 to 8, and R 4 is a group selected from the group consisting of hydrogen, an alkoxy group having 1 to 4 carbon atoms, an amino group, an alkylamino group, an amido group, or a phenoxy group.

[0031] (R 2 ) In the formula (1), R 2 is a group represented by the following formula (3): -R 5 -CH(OH)CH2(CF2) i CH2CH(OH)-R 6 - (3) In formula (3), i is an integer from 1 to 10, and R 5 and R 6 are each independently a hydrocarbon group having 1 to 10 carbon atoms, which may contain an ether bond and a polar group. 2 is a linking group that links two perfluoropolyether group-containing groups.

[0032] The fluoropolyether compound according to one embodiment of the present invention is R 2 By having the above structure, the heat resistance and adhesion to a magnetic disk of a lubricant using the fluoropolyether compound can be significantly improved for the following reasons.

[0033] Suppose R 2 When the central portion is a hydrocarbon group, the hydrocarbon group has a low affinity with the perfluoropolyether groups bonded to both sides of the linking group, and the two groups repel each other.

[0034] However, as in the present invention, R 2 The center of (CF2) iIn the case of a perfluoroalkyl chain represented by the formula "R", the affinity between the perfluoroalkyl group and the perfluoropolyether groups bonded to both sides of the linking group is high, and the repulsion between them is reduced. 2 The OH groups of the linking groups and the hydroxyl groups of the linking groups are more likely to approach the magnetic disk surface and are more strongly adsorbed to the magnetic disk surface. This is thought to improve the heat resistance and adhesion of the lubricant to the magnetic disk.

[0035] Furthermore, the linking group (R 2 ) is "(CF2) i ", the chemical stability of the fluoropolyether compound can be improved, thermal decomposition can be suppressed, and heat resistance can be improved compared to when the linking group is a hydrocarbon group.

[0036] In addition, the OH groups present at the ends and center of the fluoropolyether compound allow it to adsorb uniformly to the magnetic disk, making it possible to coat the magnetic disk surface with a small number of molecules, resulting in a small monomolecular film thickness.

[0037] The lubricants described in Patent Documents 3 and 4 contain a linking group consisting of "-CH(OH)-" and "(CF2) i In this case, since a hydrocarbon group having two or more carbon atoms is present near the OH group, the hydrocarbon group and the linking group (R 2 ) and the affinity with the perfluoropolyether groups attached on both sides of the linking group decreases. This causes repulsion between the linking group and the perfluoropolyether group, preventing the OH groups from approaching the disk surface and preventing them from adsorbing to the disk sufficiently. Furthermore, the "-CH(OH)-" and "(CF2) i "There is also an ether bond between "-CH(OH)-" and "(CF2) i " increases the distance between them, and the affinity between them decreases.

[0038] In contrast, the compounds of the present invention are composed of "-CH(OH)-" and "(CF2)i Between the OH group and the (CF2) group, there is only a methylene group (-CH2-), and there is no hydrocarbon group with two or more carbon atoms or an ether bond. i The distance between the linking group and the perfluoropolyether group becomes smaller, and the affinity between the linking group and the perfluoropolyether group becomes higher. 2 It is believed that the OH groups of the hydroxyl groups are more strongly adsorbed to the surface of the magnetic disk, improving the heat resistance of the lubricant and its adhesion to the magnetic disk.

[0039] Furthermore, for example, the compound described in Patent Document 4 is a compound containing "-CH(OH)-" and "(CF2) i ", and the carbon atom adjacent to the carbon atom to which the OH group is bonded is replaced with a fluorine atom. In this case, the electronegativity of the fluorine atom reduces the electron density of the OH group in "-CH(OH)-", reducing adhesion to the disk.

[0040] On the other hand, R 2 are "-CH(OH)-" and "(CF2) i ", and the carbon atom adjacent to the carbon atom to which the OH group is bonded is not substituted with a fluorine atom having a high electronegativity. Therefore, the compound of the present invention has a linking group (R 2 The OH groups of the hydroxyl groups are more strongly adsorbed to the surface of the magnetic disk. This is thought to improve the heat resistance of the lubricant and its adhesion to the magnetic disk.

[0041] In formula (3), i may be an integer of 1 to 10, more preferably an integer of 2 to 8, and even more preferably an integer of 2 to 6. In formula (3), R 5 and R 6 are each independently a hydrocarbon group having 1 to 10 carbon atoms, which may contain an ether bond and a polar group. 5 and R 6are each independently a hydrocarbon group having preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, which may contain a polar group, and which may contain an ether bond in which at least one carbon atom of the hydrocarbon group is substituted with an oxygen atom. The hydrocarbon group may be linear or branched, with linear being preferred. The hydrocarbon group may be saturated or unsaturated. The R 5 and R 6 The number of ether bonds contained in is not limited, but is, for example, 0 to 4, and may be 0 to 3, but from the viewpoint of heat resistance, it is preferable that the number of ether bonds is 0.

[0042] Examples of the polar group include an OH group, a nitro group, an alkoxy group having 1 to 10 carbon atoms (e.g., a methoxy group, an ethoxy group, a propoxy group, or a butoxy group), a perfluoroalkyl group having 1 to 10 carbon atoms (e.g., —CF3), an amino group, an alkylamino group (e.g., a methylamino group, a dimethylamino group, an ethylamino group, or a diethylamino group), a carboxy group, a formyl group, a carbonyl group, a sulfo group, a cyano group, an amide group (e.g., acetamide (—NHCOCH3), or propionamide (—NHCOC2H5)), or a phenoxy group.

[0043] Among them, R 5 and R 6 are each independently a hydrocarbon group having 1 to 10 carbon atoms and may contain a polar group. From the viewpoint of adhesiveness, the polar group is preferably an OH group, an amino group, an alkylamino group (e.g., a methylamino group, a dimethylamino group, an ethylamino group, a diethylamino group), a carboxy group, a carbonyl group, a sulfo group, an amido group, or a phenoxy group (more preferably an OH group, an amino group, an alkylamino group (e.g., a methylamino group, a dimethylamino group, an ethylamino group, a diethylamino group) or a carboxy group), and more preferably does not contain an ether bond.

[0044] (Fluoropolyether compound according to one embodiment of the present invention) The fluoropolyether compound according to one embodiment of the present invention is not particularly limited as long as it is a fluoropolyether compound represented by the formula (1), but more specific examples include compounds 1 to 3 represented by the following formulas.

[0045] [ka]

[0046] In Compound 1, d is a real number of 0 to 30, and more preferably a real number of 0 to 25.

[0047] [ka]

[0048] In the compound 2, e is a real number of 0 to 30, and more preferably a real number of 0 to 25.

[0049] [ka]

[0050] In Compound 3, e is a real number of 0 to 30, and more preferably a real number of 0 to 25.

[0051] The fluoropolyether compound according to one embodiment of the present invention is preferably a liquid or solid under normal conditions, and preferably has a number average molecular weight of 600 to 10,000. From the viewpoint of the volatility of the lubricant, the number average molecular weight is more preferably 800 or more. The fluoropolyether compound according to one embodiment of the present invention is suitably used as a lubricant. In this specification, the number average molecular weight is determined by the above-mentioned method using JNM-ECX400 manufactured by JEOL Ltd. 1 H and 19 This is a value calculated by F-NMR measurement.

[0052] 2. Method for producing fluoropolyether compounds The method for producing the fluoropolyether compound according to one embodiment of the present invention is not particularly limited as long as it is a method that can produce the above-mentioned fluoropolyether compound.

[0053] The fluoropolyether compound according to one embodiment of the present invention is, for example, a compound represented by the formula (1) in which -R 2 -linked group R 1 -CH2-Rf 1 -CH2O- (or -OCH2-Rf 2 -CH2-R 3 a perfluoropolyether group-containing compound (compound X) having a hydroxyl group instead of the O at the terminal of the CHO- side of the formula (1); and 2 -CH2(CF2) i The fluoropolyether compound can be obtained by reacting a compound X with a compound Y having epoxy groups at both ends of CH2-. That is, a method for producing a fluoropolyether compound according to one embodiment of the present invention includes a step of reacting compound X with compound Y.

[0054] R 5 and R 6 is other than CH2, the fluoropolyether compound according to one embodiment of the present invention can be prepared in advance by adding -R 2 -linked group R 1 -CH2-Rf 1 -CH2O- (or -OCH2-Rf 2 -CH2-R 3 The compound (X) is obtained by modifying the terminal hydroxyl group of a perfluoropolyether group-containing compound (compound X) to have a hydroxyl group instead of the terminal O at the CHO- side of the compound (X), and then reacting the compound (X) with a compound (compound Y) having an epoxy group.

[0055] Here, the R 1 -CH2-Rf 1 -CH2O- or -OCH2-Rf 2 -CH2-R 3 , and R 2 is as explained in [1. Fluoropolyether compounds].

[0056] (Compound X) Compound X is, for example, —CH2—Rf 1 -CH2- (or -CH2-Rf 2 A linear fluoropolyether compound (x1) having hydroxyl groups at both ends of the hydroxyl group (-CH2-) reacts with the OH group to form R 1 -(or R 3 -) with a compound (x2) that forms a group represented by the formula (x1). The reaction temperature is 20 to 90°C, preferably 60 to 80°C. The reaction time is, for example, 5 to 20 hours, preferably 10 to 15 hours. The amount of compound (x2) used is preferably 0.5 to 1.5 equivalents relative to compound (x1). Compound X is then obtained by purification, for example, by column chromatography. The reaction can be carried out in a solvent. Examples of solvents that can be used include t-butyl alcohol, dimethylformaldehyde, 1,4-dioxane, dimethyl sulfoxide, and dimethylacetamide. A reaction accelerator can be used in the reaction. Examples of the reaction accelerator include basic compounds such as sodium, potassium t-butoxide, and sodium hydride. Therefore, the method for producing the fluoropolyether compound may include a step of preparing compound X. 1 -(or R 3 When the group represented by -) is -OH, the linear fluoropolyether compound (x1) can be used as the compound X as it is.

[0057] -CH2-Rf 1 -CH2- (or -CH2-Rf 2 As the linear fluoropolyether compound (x1) having hydroxyl groups at both ends of HO-CH2-Rf 1 -CH2-OH (or HO-CH2-Rf 2 The number average molecular weight of the compound (x1) is usually 300 to 4,000, more preferably 500 to 2,000, and even more preferably 600 to 1,500.

[0058] The compound (x1) has a molecular weight distribution. The molecular weight distribution (PD), expressed as weight average molecular weight / number average molecular weight of the compound (x1), is, for example, 1.0 to 1.5, preferably 1.0 to 1.3, and more preferably 1.0 to 1.1. The molecular weight distribution is a characteristic value obtained using a Tosoh HPLC-8220GPC, a Polymer Laboratory column (PLgel Mixed E), an HCFC-based alternative chlorofluorocarbon as an eluent, and a non-functional perfluoropolyether as a reference material.

[0059] reacts with the OH group to form R 1 -(or R 3 Examples of the compound (x2) that forms a group represented by Z(CH2) - include a compound having an epoxy group as a group that reacts with the OH group, Z(CH2) h Examples include haloalkyl alcohols represented by OH (where Z is a halogen atom and h is an integer of 2 to 8).

[0060] The compound having an epoxy group includes R 1 -(or R 3 When the hydrocarbon group of (-) is a straight-chain or branched hydrocarbon group, examples thereof include glycidol, propylene oxide, glycidyl methyl ether, isobutylene oxide, and the like.

[0061] Also, R 1 -(or R 3 When the hydrocarbon group of (-) is a hydrocarbon group containing a cyclic hydrocarbon group, the compound having an epoxy group can be, for example, a compound represented by the following formula (7):

[0062] [ka]

[0063] In formula (7), R 4 is the aforementioned R 1 and R 3 R in the explanation of 4 is the same as

[0064] Specific examples of the compound represented by formula (7) include glycidyl 4-methoxyphenyl ether, glycidyl 4-ethoxyphenyl ether, glycidyl 4-propoxyphenyl ether, glycidyl 4-butoxyphenyl ether, glycidyl 4-aminophenyl ether, glycidyl 4-methylaminophenyl ether, glycidyl 4-dimethylaminophenyl ether, glycidyl 4-ethylaminophenyl ether, glycidyl 4-diethylaminophenyl ether, glycidyl 4-acetamidophenyl ether, and glycidyl 4-propionic acid amidophenyl ether.

[0065] Z(CH2) h In the haloalkyl alcohol represented by OH, Z is a halogen atom such as chlorine, bromine, iodine, etc. Examples of the haloalkyl alcohol include 2-chloroethanol, 3-chloropropanol, 4-chlorobutanol, 5-chloropentanol, 6-chlorohexanol, 7-chloroheptanol, 8-chlorooctanol, 2-bromoethanol, 3-bromopropanol, 4-bromobutanol, 5-bromopentanol, 6-bromohexanol, 7-bromoheptanol, 8-bromooctanol, 2-iodoethanol, 3-iodopropanol, 4-iodobutanol, 5-iodopentanol, 6-iodohexanol, 7-iodoheptanol, and 8-iodooctanol.

[0066] For example, the compound (x1) may be HO—CH—(CF) a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) aWhen -CH2-OH is used and glycidol is used as the compound (x2), the reaction of the two gives HO-CH2-CH(OH)-CHO-CH2-(CF2) as the compound X. a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a -CH2-OH is produced.

[0067] The compound (x1) is HO-CH2-(CF2) a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a When —CH2—OH is used and 2-bromoethanol is used as the compound (x2), HO—CH2—CH2O—CH2—(CF2) is used as the compound X. a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a -CH2-OH is produced.

[0068] The compound (x1) may also be HO-CH2-(CF2) a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O)e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a When —CH2—OH is used and glycidyl 4-methoxyphenyl ether is used as the compound (x2), CHO—CHO—CH2—CH(OH)—CHO—CH2—(CF2) is used as the compound X. a (CF(CF3)) b -O-(CF2O) c (CF2CF2O) d (CF2CF2CF2O) e (CF2CF2CF2CF2O) f (CF2CF(CF3)O) g -(CF(CF3)) b (CF2) a -CH2-OH is produced.

[0069] (Compound Y) The compound Y may be, for example, R 2 -CH2(CF2) i Compounds having epoxy groups at both ends of CH2-, specifically 1,4-bis(2',3'-epoxypropyl)perfluoro-n-butane, 1,4-bis(2',3'-epoxypropyl)perfluoro-n-propane, 1,4-bis(2',3'-epoxypropyl)perfluoro-n-pentane, 1,4-bis(2',3'-epoxypropyl)perfluoro-n-hexane, etc. can be mentioned.

[0070] (Step of reacting compound X with compound Y) In this step, compound X and compound Y are reacted in the presence of a base. The reaction temperature is, for example, 20 to 90°C, preferably 60 to 80°C. The reaction time is, for example, 5 to 20 hours, preferably 10 to 15 hours. It is preferable to use 0.5 to 1.5 equivalents of compound Y and 0.5 to 2.0 equivalents of base relative to compound X. Examples of bases that can be used include sodium t-butoxide, potassium t-butoxide, sodium hydroxide, potassium hydroxide, and sodium hydride. The reaction can be carried out in a solvent. Examples of solvents that can be used include t-butanol, toluene, and xylene. The reaction is then followed by, for example, washing with water and dehydration. This gives the compound of the present invention.

[0071] [3. Lubricants] A lubricant according to one embodiment of the present invention contains the fluoropolyether compound according to one embodiment of the present invention. The fluoropolyether compound can be used alone as a lubricant, or the lubricant may contain the fluoropolyether compound and other components in any ratio as long as the lubricant's performance is not impaired. When the fluoropolyether compound is mixed with other components to form a lubricant, the content of the fluoropolyether compound according to one embodiment of the present invention relative to the total weight of the lubricant is preferably more than 50 wt%, more preferably 80 wt% or more, even more preferably 90 wt% or more, and particularly preferably 99 wt% or more.

[0072] Examples of the other components include known lubricants for magnetic disks, such as Fomblin (registered trademark) Zdol (manufactured by Solvay Solexis), Ztetraol (manufactured by Solvay Solexis), Demnum (registered trademark) (manufactured by Daikin Industries, Ltd.), Krytox (registered trademark) (manufactured by Chemours), MORESCO PHOSFAROL A20H (manufactured by MORESCO), and MORESCO PHOSFAROL D-4OH (manufactured by MORESCO).

[0073] The lubricant can be used as a lubricant for recording media to improve the sliding characteristics of magnetic disks. It can also be used as a lubricant for recording media other than magnetic disks, such as magnetic tapes, in other recording devices that involve sliding between the recording media and the head. Furthermore, it can be used as a lubricant for devices that have sliding parts, not limited to recording devices.

[0074] [4. Magnetic Disk] 1, a magnetic disk 1 according to one embodiment of the present invention includes a recording layer 4, a protective film layer (protective layer) 3, and a lubricating layer 2, which are arranged on a non-magnetic substrate 8. The lubricating layer 2 contains the above-mentioned lubricant.

[0075] 2, the magnetic disk may include an underlayer 5 disposed under the recording layer 4, one or more soft magnetic underlayers 6 disposed under the underlayer 5, and an adhesion layer 7 disposed under the one or more soft magnetic underlayers 6. All of these layers may be formed on a non-magnetic substrate 8 in one embodiment.

[0076] Each layer of the magnetic disk 1, except for the lubricating layer 2, may comprise a material known in the art to be suitable for a particular layer of a magnetic disk. For example, the recording layer 4 may be made of an alloy of ferromagnetic elements such as iron, cobalt, or nickel, plus chromium, platinum, or tantalum, or an oxide thereof. The protective layer 3 may be made of carbon, Si3N4, SiC, or SiO2. The non-magnetic substrate 8 may be made of an aluminum alloy, glass, or polycarbonate.

[0077] 5. Magnetic Disk Manufacturing Method A method for manufacturing a magnetic disk according to one aspect of the present invention includes a step of forming a lubricating layer by laminating a lubricant according to one embodiment of the present invention onto the exposed surface of a protective layer of a laminate formed by laminating a recording layer and a protective layer.

[0078] The method for forming a lubricating layer by laminating the lubricant on the exposed surface of the protective layer of a laminate comprising a recording layer and a protective layer is not particularly limited. A preferred method for laminating the lubricant on the exposed surface of the protective layer is to immerse the magnetic disk in a solution prepared by diluting the lubricant with a solvent, then remove the magnetic disk, evaporate the solvent, and dry the disk. Examples of solvents include PF-5060, PF-5080, Novec (registered trademark) 7100, and Novec (registered trademark) 7200 manufactured by 3M, and Vertrel-XF (registered trademark) manufactured by DuPont. The concentration of the lubricant after dilution with the solvent is preferably 0.001% by weight to 1% by weight, more preferably 0.005% by weight to 0.5% by weight, and even more preferably 0.005% by weight to 0.1% by weight. A lubricant concentration of 0.005% by weight to 0.1% by weight after dilution with the solvent can weaken the interaction between lubricant molecules, making it easier to form a uniform lubricating film.

[0079] The recording layer and the protective layer may be formed in this order, and the lubricant may be laminated on the exposed surface of the protective layer, followed by ultraviolet irradiation or heat treatment. By performing ultraviolet irradiation or heat treatment, a stronger bond is formed between the lubricant layer and the exposed surface of the protective layer, and evaporation of the lubricant due to heating can be prevented. When ultraviolet irradiation is performed, it is preferable to use ultraviolet light having a dominant wavelength of 185 nm or 254 nm. When performing heat treatment, the temperature is preferably 60 to 170°C, more preferably 80 to 170°C, and even more preferably 80 to 150°C.

[0080] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0081] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. 1 H-NMR was measured under the conditions of no solvent and D2O as the reference material.19 F-NMR was measured without a solvent, using a known peak that is part of the fluoropolyether backbone structure as the chemical shift reference.

[0082] Example 1: Synthesis of Compound 1 Under an argon atmosphere, 21 g of t-butyl alcohol, HO-CH2CF2O(CF2CF2O) d A mixture of 50 g of fluoropolyether (number average molecular weight 981, molecular weight distribution 1.45) represented by CF2CH2-OH, 0.6 g of potassium t-butoxide, and 3.5 g of glycidol was stirred at 70°C for 14 hours. The resulting product was then washed with water, dehydrated, and purified by silica gel column chromatography to obtain 45 g of a compound having one hydroxyl group at one end of the perfluoropolyether group and two hydroxyl groups at the other end. 45 g of this compound was dissolved in 19 g of t-butyl alcohol, and 0.4 g of sodium t-butoxide and 5.2 g of 1,4-bis(2',3'-epoxypropyl)perfluoro-n-butane were added and stirred at 70°C for 14 hours. The resulting product was then washed with water, dehydrated, and purified by distillation to obtain 12 g of Compound 1 (number average molecular weight 2460) represented by the following formula:

[0083] [ka]

[0084] Compound 1 is a pale yellow, transparent liquid with a density of 1.72 g / cm at 20°C. 3 The results of identification of Compound 1 using NMR are shown below.

[0085] 19 F-NMR (reference material: OC in the product) F 2CF2O is -89.1 ppm.) δ=-124.2ppm(4F), δ=-113.0ppm(4F), δ=-89.8ppm(56F), δ=-78.8ppm(8F) d=7.0.

[0086] 1 H-NMR δ=2.2ppm(4H),δ=3.0~5.0ppm(30H) Example 2: Synthesis of Compound 2 HO-CHCFO(CFCFO) used in Example 1 d HO-CH2CF2CF2O(CF2CF2CF2O) instead of CF2CH2-OH e The same procedure as in Example 1 was carried out except that CF2CF2CH2-OH (number average molecular weight 1081, molecular weight distribution 1.26) was used, to obtain 9 g of Compound 2 (number average molecular weight 2629) represented by the following formula.

[0087] [ka]

[0088] 19 F-NMR (reference material: OCF2C in the product) F 2CF2O is -129.7 ppm.) δ=-129.7ppm(19F), δ=-124.2ppm(12F), δ=-113.0ppm(4F), δ=-86.5ppm(8F), δ=-83.7(38F) e=4.8.

[0089] 1 H-NMR δ=2.2ppm(4H),δ=3.0~5.0ppm(30H) Example 3: Synthesis of Compound 3 HO-CHCFO(CFCFO) used in Example 1 d HO-CH2CF2CF2O(CF2CF2CF2O) instead of CF2CH2-OH eThe same procedure as in Example 1 was carried out except that CF2CF2CH2-OH (number average molecular weight 1219, molecular weight distribution 1.25) was used and 5.8 g of 4-methoxyphenyl glycidyl ether was used instead of glycidol, to obtain 24 g of a compound having one hydroxyl group at one end of the perfluoropolyether group and a methoxyphenyl group at the other end, and finally 8 g of compound 3 (number average molecular weight 3902) represented by the following formula was obtained.

[0090] [ka]

[0091] 19 F-NMR (reference material: OCF2C in the product) F 2CF2O is -129.7 ppm.) δ=-129.7ppm(32F), δ=-124.2ppm(12F), δ=-113.0ppm(4F), δ=-86.5ppm(8F), δ=-83.7(64F) e=8.0.

[0092] 1 H-NMR δ=2.2ppm(4H), δ=3.0~5.0ppm(34H), δ=6.7ppm(10H) Comparative Example 1 Comparative compound 1 (number average molecular weight 2208) represented by the following formula was synthesized by the same procedure as in Example 1, except that 1,7-octadiene diepoxide was used instead of 1,4-bis(2',3'-epoxypropyl)perfluoro-n-butane.

[0093] [ka]

[0094] Comparative Example 2 Comparative compound 2 (number average molecular weight 2846) represented by the following formula was synthesized by the method described in Example 3 of Patent Document 2 (JP-A No. 2024-52300).

[0095] [ka]

[0096] Comparative Example 3 Comparative compound 3 (number average molecular weight 2670) represented by the following formula was synthesized by the same procedure as in Example 2, except that 1,7-octadiene diepoxide was used instead of 1,4-bis(2',3'-epoxypropyl)perfluoro-n-butane.

[0097] [ka]

[0098] Comparative Example 4 Comparative compound 4 (number average molecular weight 2898) represented by the following formula was synthesized by the same procedure as in Example 3, except that 1,7-octadiene diepoxide was used instead of 1,4-bis(2',3'-epoxypropyl)perfluoro-n-butane.

[0099] [ka]

[0100] [Measurement of thermogravimetric loss temperature] The thermal weight loss temperatures of the fluoropolyether compounds obtained in the examples and comparative examples were measured using a thermogravimetric analyzer (STA200, manufactured by Hitachi High-Tech Science). Five mg of each fluoropolyether compound obtained in the Examples and Comparative Examples was weighed out and placed in a platinum container, which was then heated to 550°C at a heating rate of 2°C / min in an air atmosphere. The temperature at which the weight of the fluoropolyether compound had decreased by 10% in an air atmosphere (10% weight loss temperature) was measured. The results are shown in Table 1.

[0101] [Measurement of Monolayer Film Thickness] Each of the fluoropolyether compounds obtained in the examples and comparative examples was dissolved in Vertrel XF manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd. so that the concentration was within the range of 0.12 to 0.15 wt %.

[0102] A portion (approximately 1 / 4) of a 2.5-inch diameter magnetic disk was immersed in the resulting solution and then pulled up at a speed of 2 mm / s to produce a disk consisting of a portion coated with a lubricant (fluoropolyether compound) as a lubricating layer (coated portion) and a portion not coated with a lubricant (uncoated portion). The average thickness of the coated portion was 20 to 50 Å.

[0103] Immediately after fabrication, the disk was loaded into an ellipsometer, and the change in film thickness near the boundary between the coated and uncoated areas was measured at regular intervals at room temperature. The film thickness of the formed terraces was taken as the monolayer film thickness of the lubricant. The results are shown in Table 1.

[0104] [Bond ratio measurement] Each of the fluoropolyether compounds obtained in the examples and comparative examples was dissolved in Vertrel XF manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd. to concentrations of 0.01, 0.02, 0.03, and 0.04 wt %, respectively. A magnetic disk with a diameter of 2.5 inches was immersed in the resulting solution for 3 minutes and then pulled up at a speed of 2 mm / s. The average film thickness of the fluoropolyether compound on the disk was then measured using an ellipsometer. This average film thickness is designated as fÅ.

[0105] Next, the disk whose average film thickness had been measured was immersed in an ethanol solvent for 3 minutes, then pulled out at a speed of 2 mm / s and left to stand at room temperature to evaporate the solvent. After this, the average film thickness of the fluoropolyether compound remaining on the disk was measured using an ellipsometer. This average film thickness is designated as bÅ. The commonly used bond ratio was used as an index to indicate the strength of adhesion to the disk. The bond ratio is expressed by the following formula: Bond ratio (%) = 100 × b / f.

[0106] Table 1 shows the bond ratio measurement results for each concentration.

[0107] [Table 1]

[0108] The compounds of Examples 1 to 3 each have a linking group (R 2 ) is "(CF2) i The compounds of Comparative Examples 1, 3 and 4 have structures corresponding to the compounds of Examples 1 to 3, respectively, but the linking group is an aliphatic hydrocarbon ether group, and is represented by "(CF2) i " is a linking group that does not contain ". The compounds of Examples 1 to 3 were shown to have a higher 10% weight loss temperature than the compounds of Comparative Examples 1, 3, and 4. This is thought to be because in the examples, some of the hydrogen atoms of the aliphatic hydrocarbon ether group in the linking group are substituted with fluorine atoms, thereby improving chemical stability and making thermal decomposition less likely to occur. Furthermore, the compound of Example 1, in which a methylene group (-CH2) exists near the OH group in the linking group, was shown to have a higher 10% weight loss temperature than the compound of Comparative Example 2, in which a methylene group does not exist near the OH group but -CF2- exists. This is thought to be because when a methylene group (-CH2) exists near the OH group in the linking group, the electron donating ability of the OH group is higher than when -CF2- exists near the OH group in the linking group, so the intermolecular force of the fluoropolyether compound is maintained high and thermal decomposition is less likely to occur.

[0109] Furthermore, the compounds of Examples 1, 2, and 3 were shown to have significantly higher bonding ratios than the corresponding compounds of Comparative Examples 1, 3, and 4. This is thought to be because in the Examples, some of the hydrogen atoms of the aliphatic hydrocarbon ether groups in the linking group were substituted with fluorine atoms, thereby improving the affinity between the linking group and the perfluoropolyether groups on both sides bonded to the linking group, thereby suppressing the repulsion between the perfluoropolyether groups and the linking group and making it easier for the linking group to approach the disk surface.

[0110] Furthermore, the compounds of Examples 1, 2, and 3 were shown to have a smaller monolayer thickness than the corresponding compounds of Comparative Examples 1, 3, and 4. This is thought to be because the compounds of the Examples were able to efficiently cover the disk surface with fewer molecules.

[0111] Furthermore, the compound of Example 1 was shown to have a significantly higher bonding ratio and a smaller monolayer film thickness than the compound of Comparative Example 2. This is thought to be because the presence of a methylene group near the OH group in the linking group increases the electron donating ability of the OH group compared to when -CF2- is present, allowing the OH group to be more strongly adsorbed to the magnetic disk surface. [Industrial Applicability]

[0112] The fluoropolyether compound according to one aspect of the present invention can be suitably used as a lubricant for magnetic disks. [Explanation of symbols]

[0113] 1. Magnetic disk 2 Lubricating layer 3 Protective film layer (protective layer) 4 Recording Layer 5 Lower layer 6 Soft magnetic underlayer 7 Adhesive layer 8 Non-magnetic substrate

Claims

1. A fluoropolyether compound represented by the following formula (1): R １ -CH ２ -Rf １ -CH ２ O-R ２ -OCH ２ -Rf ２ -CH ２ -R ３ (1) In formula (1), Rf １ and Rf ２ are each independently a perfluoropolyether group represented by the following formula (2): -(CF ２ ) ａ (CF(CF ３ )) ｂ -O-(CF ２ O) ｃ (CF ２ CF ２ O) ｄ (CF ２ CF ２ CF ２ O) ｅ (CF ２ CF ２ CF ２ CF ２ O) ｆ (CF ２ CF(CF ３ )O) ｇ -(CF(CF ３ )) ｂ (CF ２ ) ａ - (2) In formula (2), c, d, e, f, and g each independently represent a real number of 0 to 30, and a and b each independently represent an integer of 0 to 3. R １ and R ３ each independently represents an optionally substituted hydrocarbon group having one or more OH groups, which may contain an ether bond, or an OH group; R ２ is a group represented by the following formula (3): -R ５ -CH(OH)CH ２ (CF ２ ) ｉ CH ２ CH(OH)-R ６ - (3) In formula (3), i is an integer from 1 to 10, and R ５ and R ６ are each independently a hydrocarbon group having 1 to 10 carbon atoms, and may contain an ether bond in which at least one carbon atom is substituted with an oxygen atom, and / or a polar group.

2. R １ and R ３ are each independently —OH, —OCH ２ CH(OH)CH ２ OH, -OCH ２ CH(OH)CH ２ OCH ２ CH(OH)CH ２ OH, —O(CH ２ ) ｈ OH, and OCH ２ CH(OH)CH ２ -OC ６ H ４ -R ４ (wherein h is an integer from 2 to 8, and R ４ is a group selected from the group consisting of hydrogen, an alkoxy group having 1 to 4 carbon atoms, an amino group, an alkylamino group, an amido group, and a phenoxy group.

3. R ５ and R ６ 2. The fluoropolyether compound according to claim 1, wherein the polar group is an OH group, an amino group, an alkylamino group, a carboxy group, a carbonyl group, a sulfo group, an amido group, or a phenoxy group.

4. A lubricant comprising the fluoropolyether compound according to any one of claims 1 to 3.

5. A magnetic disk having a lubricating layer containing the lubricant according to claim 4.

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