Perfluoropolyether compound, lubricant and magnetic disk using same

Abstract

Provided is a perfluoropolyether compound that is highly soluble in fluorinated solvents, has high heat resistance and shows a strong interaction with magnetic disks. A perfluoropolyether compound that has a structure represented by formula (1). Formula (1): R1-CH2-Rf-(L-Rf)P-CH2-R2 In formula (1): Rf represents a perfluoropolyether group; R1 and / or R2 represent a group having a structure represented by formula (2); and an OH group is further present between Rf and a molecular end.

Description

[Technical Field]

[0001] The present invention relates to a perfluoropolyether compound, and a lubricant and a magnetic disk using the same. [Background technology]

[0002] The mainstream configuration for magnetic disks is one in which a protective layer is formed on a recording layer formed on a substrate to protect the information recorded on the recording layer, and a lubricant layer is further provided on the protective layer. In recent years, lubricants for magnetic disks have been decreasing in molecular weight to improve performance. This decrease in molecular weight of lubricants makes them more susceptible to scattering and volatilization when the magnetic disk rotates at high speeds. To prevent this, lubricants that exhibit strong interaction with the magnetic disk are required.

[0003] The present inventors have previously developed lubricants with excellent durability or heat resistance in order to accommodate the increasing speed of disk rotation and the decreasing clearance of magnetic heads (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2009 / 066784 [Patent Document 2] International Publication No. WO2021 / 002178 Summary of the Invention [Problem to be solved by the invention]

[0005] However, all of the above-mentioned techniques have room for further improvement in terms of heat resistance and interaction with magnetic disks. Furthermore, the lubricant described in Prior Art Document 2 has room for improvement in terms of solubility in fluorine-based solvents. The object of the present invention is to provide a perfluoropolyether compound that has excellent heat resistance, exhibits strong interaction with magnetic disks, and is highly soluble in fluorine-based solvents. [Means for solving the problem]

[0006] As a result of intensive research to solve the above problems, the present inventors have discovered that the above problems can be solved by introducing a specific number of OH groups into specific positions of a perfluoropolyether compound, and have thus completed the present invention.

[0007] One aspect of the present invention comprises the following configuration.

[0008] A perfluoropolyether compound having a structure represented by formula (1):

[0009] [ka] In formula (1), Rf is a perfluoropolyether group, L is a C3-C 20 wherein at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom, and p is 0 or 1; R 1 is a group having a structure represented by formula (2),

[0010] [ka] In formula (2), R 4 has an OH group, C3 to C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; R 3is a hydrogen atom or a C1-C2 hydrocarbon group, and R 3 is a hydrogen atom, q is an integer from 2 to 10, and R 3 is a C1-C2 hydrocarbon group, q is an integer of 1 to 10, R 2 is a group having a structure represented by formula (2) or a group having a structure represented by formula (3),

[0011] [ka] In formula (3), R 5 has an OH group, C3 to C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to provide a perfluoropolyether compound that has excellent heat resistance, exhibits strong interaction with a magnetic disk, and is highly soluble in a fluorine-based solvent. [Brief explanation of the drawings]

[0013] [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

[0014] 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."

[0015] [1. Perfluoropolyether compounds] A perfluoropolyether compound according to one embodiment of the present invention has a structure represented by the following formula (1).

[0016] [ka] In formula (1), Rf is a perfluoropolyether group, and L is a C3-C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; p is 0 or 1; R 1 is a group having a structure represented by formula (2),

[0017] [ka] In formula (2), R 4 has an OH group, C3 to C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; R 3 is a hydrogen atom or a C1-C2 hydrocarbon group, and R 3 is a hydrogen atom, q is an integer from 2 to 10, and R 3 is a C1-C2 hydrocarbon group, q is an integer of 1-10.

[0018] R 2 is a group having a structure represented by formula (2) or a group having a structure represented by formula (3).

[0019] [ka] In formula (3), R 5 has an OH group, C3 to C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom.

[0020] The perfluoropolyether compound according to one embodiment of the present invention has the above structure, which has two primary OH groups at one end of the perfluoropolyether compound and one or two primary OH groups at the other end (i.e., a total of three or four primary OH groups at the ends), and also has an OH group located closer to the interior of the molecule than the primary OH groups at both ends, in other words, between the perfluoropolyether group and the primary OH group at the molecular end. By using such a structure, the perfluoropolyether compound can be realized as a perfluoropolyether compound that has excellent heat resistance, exhibits strong interaction with magnetic disks, and is also excellent in solubility in fluorine-based solvents. Note that the interaction with the magnetic disk here refers to the interaction between the perfluoropolyether compound and the surface of the magnetic disk that comes into contact with the lubricant. Therefore, when a lubricant layer is formed on a protective layer to protect information recorded on the recording layer, interaction with the protective layer is intended.

[0021] It is believed that the presence of OH groups further inward in the molecule than the primary OH groups at both ends can further strengthen the interaction with the magnetic disk.

[0022] Rf in formula (1) is not particularly limited as long as it is a perfluoropolyether group, but a preferred example is a perfluoropolyether group represented by formula (4).

[0023] [ka] In formula (4), x is a real number from 0 to 3, y is a real number from 0 to 1, and z, l, m, n, and o are each a real number from 0 to 30, more preferably a real number from 0 to 15. However, any one of x and y is a real number of 1 or greater, and any one of z, l, m, n, and o is a real number of 1 or greater.

[0024] Examples of the Rf include a demnum skeleton (C3 skeleton): -(CFCFCFO) m-, Fomblin skeleton (C1C2 skeleton): -(CF2O) z (CF2CF2O) l -, C2 skeleton: -(CF2CF2O) l -, C4 skeleton: -(CF2CF2CF2CF2O) n -, Krytox skeleton: -(CF(CF3)CF2O) o -containing groups.

[0025] More preferred examples of Rf include groups in which, in formula (4), x is a real number of 0 to 3, y is a real number of 0 to 1, provided that either one of x and y is a real number of 1 or more, and z, l, m, n, and o are any of the following (i) to (v):

[0026] (i) m = a real number between 1 and 30, and z, l, n, and o = 0 (ii) z = l = real number between 1 and 30, and m, n, and o = 0 (iii) l = a real number between 1 and 30, and z, m, n, and o = 0 (iv) n = a real number between 1 and 30, and z, l, m, and o = 0 (v) o = real number between 1 and 30, and z, l, m, and n = 0 In addition, in the Fomblin skeleton, CFO and CFO may be repeated randomly. Among them, a more preferred example of Rf is a group in which, in formula (4), x is a real number of 0 to 3, y is a real number of 0 to 1, provided that either one of x and y is a real number of 1 or more, and z, l, m, n, and o are (i) or (ii). From the viewpoint of heat resistance, a particularly preferred example of Rf is a group (i) (Demnum skeleton).

[0027] In formula (1), R 1 is a group having a structure represented by formula (2), in which R 4 has an OH group, C3 to C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom.

[0028] Said C3~C 10 The hydrocarbon group may be a linear hydrocarbon group or a branched hydrocarbon group. The hydrocarbon group may be saturated or unsaturated, but is more preferably a saturated hydrocarbon group. The lower limit of the number of carbon atoms in the hydrocarbon group may be 3, more preferably 4, and even more preferably 5. The upper limit of the number of carbon atoms in the hydrocarbon group may be 10, more preferably 7, and even more preferably 6. Note that the number of carbon atoms in the hydrocarbon group includes carbon atoms substituted with oxygen atoms.

[0029] R in equation (2) 4 has an OH group. 4 However, the presence of an OH group is preferable because it can further strengthen the interaction between the perfluoropolyether compound and the magnetic disk. 4 The number of OH groups contained in R is preferably 1 to 5. 4 The upper limit of the number of OH groups contained in R is more preferably 3, and even more preferably 2. 4 If the number of OH groups contained therein is 5 or less, it is preferable because the solubility in fluorine-based solvents is good.

[0030] R 4 The OH group contained in R may be any of a primary OH group, a secondary OH group, and a tertiary OH group, or may be a combination of two or more of these. From the viewpoint of high yield and easy production, it is more preferable that the compound contains a secondary OH group. From the viewpoint of strengthening the interaction between the perfluoropolyether compound and the magnetic disk, it is preferable that the compound contains a secondary OH group. 4 The OH group contained in preferably contains a primary OH group.

[0031] The secondary OH group is R 4 or may be bonded to a carbon atom of the main chain of the hydrocarbon group constituting R 4 When R has a side chain, it may be bonded to the side chain. The secondary OH group is preferably R 4It is more preferable that the carbon atom is bonded to a carbon atom in the main chain of the hydrocarbon group constituting the formula (I).

[0032] When the OH group is a primary OH group, the primary OH group may be contained in the form of an OH group in a hydroxyalkyl group bonded to a carbon atom in the main chain or side chain of the hydrocarbon group. Examples of such hydroxyalkyl groups include, but are not limited to, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

[0033] At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom. The number of oxygen atoms substituting the carbon atoms in the main chain, i.e., the number of ether groups contained in the main chain, is 1 to 5, and more preferably 1 to 3.

[0034] R in equation (2) 4 Although it is sufficient for the group to have the above-described structure, a more preferred example is a group represented by the following formula (5-1): -(CH2) r -, at least one hydrogen atom of which has been substituted with an OH group. The terminal oxygen atom in the following formula (5-1) is bonded to a methylene group bonded to the perfluoropolyether group in the formula (1).

[0035] [ka] In formula (5-1), r is 1 to 7, and s is 0 to 2. In formula (5-1), r is more preferably 1 to 6, and s is more preferably 0 to 1. In formula (5-1), -(CH2) r It is sufficient that at least one hydrogen atom of - is substituted with an OH group, but it is more preferable that one hydrogen atom bonded to each of 1 to 3 carbon atoms is substituted with an OH group.

[0036] R in equation (2) 4 A more preferred example of the group is a group represented by formula (5-2).

[0037] [ka] In formula (5-2), t is preferably 0 or 1.

[0038] R in equation (2) 3 is a hydrogen atom or a C1 to C2 hydrocarbon group. The hydrocarbon group is not particularly limited, but is more preferably an alkyl group, such as a methyl group or an ethyl group.

[0039] q in equation (2) is R 3 When q is a hydrogen atom, it may be an integer of 2 to 10, more preferably 2 to 8. 3 When R is a C1-C2 hydrocarbon group, it may be an integer of 1 to 10, and more preferably 1 to 4. 3 is preferably a hydrocarbon group from the viewpoint of material availability and material cost.

[0040] In formula (1), R 2 is a group having a structure represented by formula (2) or a group having a structure represented by formula (3). The group having a structure represented by formula (2) is as described above, and therefore further explanation will be omitted.

[0041] R in equation (3) 5 has an OH group, C3 to C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom.

[0042] Said C3~C 10 The hydrocarbon group may be a linear hydrocarbon group or a branched hydrocarbon group. The hydrocarbon group may be saturated or unsaturated, but is more preferably a saturated hydrocarbon group. The lower limit of the number of carbon atoms in the hydrocarbon group may be 3, but is more preferably 4. The upper limit of the number of carbon atoms in the hydrocarbon group may be 10, but is more preferably 9, and even more preferably 8.

[0043] R in equation (3)5 has an OH group. 5 However, the presence of an OH group is preferable because it can further strengthen the interaction between the perfluoropolyether compound and the magnetic disk. 5 The number of OH groups contained in R is preferably 1 to 5. 5 The upper limit of the number of OH groups contained in R is more preferably 4, and even more preferably 2. 5 If the number of OH groups contained therein is 5 or less, it is preferable because the solubility in fluorine-based solvents is good.

[0044] R 5 The OH group contained in R may be any of a primary OH group, a secondary OH group, and a tertiary OH group, or may be a combination of two or more of these. From the viewpoint of high yield and easy production, it is more preferable that the compound contains a secondary OH group. From the viewpoint of strengthening the interaction between the perfluoropolyether compound and the magnetic disk, it is preferable that the compound contains a secondary OH group. 5 The OH group contained in R preferably contains a primary OH group. 5 The OH groups contained in R may be only secondary OH groups, or may be a combination of secondary OH groups and at least one of primary OH groups and tertiary OH groups. 5 The number of secondary OH groups contained in R is preferably 1 to 5. 5 The upper limit of the number of secondary OH groups contained in R is more preferably 4, and even more preferably 2. 5 If the number of secondary OH groups contained therein is 5 or less, it is preferable because the solubility in fluorine-based solvents is good.

[0045] The secondary OH group is R 5 or may be bonded to a carbon atom of the main chain of the hydrocarbon group constituting R 5 When R has a side chain, it may be bonded to the side chain. The secondary OH group is preferably R 5 It is more preferable that the carbon atom is bonded to a carbon atom in the main chain of the hydrocarbon group constituting the formula (I).

[0046] When the OH group is a primary OH group, the primary OH group may be contained in the form of an OH group in a hydroxyalkyl group bonded to a carbon atom in the main chain or side chain of the hydrocarbon group. Examples of such hydroxyalkyl groups include, but are not limited to, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

[0047] At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom. The number of oxygen atoms substituting the carbon atoms in the main chain, i.e., the number of ether groups contained in the main chain, is 1 to 5, and more preferably 1 to 3.

[0048] R in equation (3) 5 Although it is sufficient for the group to have the above-described structure, a more preferred example is a group having a structure represented by formula (6).

[0049] [ka] In formula (6), u is preferably 1 to 2, and more preferably 2. In formula (6), the hydrocarbon group that forms the main chain is not substituted, but may be substituted with an alkyl group having 1 to 10 carbon atoms.

[0050] R in equation (3) 5 A more specific example of the alkyl group is -OCH2CH(OH)CH2- or -OCH2CH(OH)CH2OCH2CH(OH)CH2-.

[0051] In formula (1), p is 0 or 1. That is, the perfluoropolyether compound according to one aspect of the present invention may be a perfluoropolyether compound having one perfluoropolyether group in the molecule, or may be a perfluoropolyether compound having two perfluoropolyether groups in the molecule.

[0052] L in formula (1) is a C3 to C 20At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom. 20 The hydrocarbon group may be a linear hydrocarbon group or a branched hydrocarbon group. The hydrocarbon group may be saturated or unsaturated, but is more preferably a saturated hydrocarbon group. The lower limit of the number of carbon atoms in the hydrocarbon group may be 3, more preferably 5, and even more preferably 7. The upper limit of the number of carbon atoms in the hydrocarbon group may be 20, but is more preferably 18, and even more preferably 16.

[0053] L in formula (1) has an OH group. It is preferable that L in formula (1) has an OH group, since this further strengthens the interaction between the perfluoropolyether compound and the magnetic disk. The number of OH groups contained in L is preferably 1 to 5. The upper limit of the number of OH groups contained in L is more preferably 4, and even more preferably 3. It is preferable that the number of OH groups contained in L is 5 or less, since this provides good solubility in fluorine-based solvents.

[0054] The OH group contained in L may be any of a primary OH group, a secondary OH group, and a tertiary OH group, or a combination of two or more of these. From the viewpoint of high yield and simple production, it is more preferable that it contains a secondary OH group. From the viewpoint of strengthening the interaction between the perfluoropolyether compound and the magnetic disk, it is more preferable that the OH group contained in L contains a primary OH group. The OH group contained in L may be only a secondary OH group, or may be a combination of a secondary OH group and at least one of a primary OH group and a tertiary OH group. The number of secondary OH groups contained in L is preferably 1 to 5. The upper limit of the number of secondary OH groups contained in L is more preferably 4, and even more preferably 2. It is preferable that the number of secondary OH groups contained in L is 3 or less because this provides good solubility in fluorine-based solvents.

[0055] The secondary OH group may be bonded to a carbon atom in the main chain of the hydrocarbon group constituting L, or when L has a side chain, to the side chain. From the viewpoint of efficient and simple production, the secondary OH group is more preferably bonded to a carbon atom in the main chain of the hydrocarbon group constituting L.

[0056] When the OH group is a primary OH group, the primary OH group may be contained in the form of an OH group in a hydroxyalkyl group bonded to a carbon atom in the main chain or side chain of the hydrocarbon group. Examples of such hydroxyalkyl groups include, but are not limited to, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

[0057] At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom. The number of oxygen atoms substituting the carbon atoms in the main chain, i.e., the number of ether groups contained in the main chain, is 1 to 10, and more preferably 2 to 4.

[0058] L in formula (1) may have the above-described structure, but a more preferred example is a linking group represented by formula (7).

[0059] [ka] In formula (7), g is preferably 1 to 5, more preferably 1 to 3, and even more preferably 3. In formula (7), some of the OH groups may be substituted with at least one group selected from a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, etc. In addition, in formula (7), the hydrocarbon group that forms the main chain is not substituted, but may be substituted with an alkyl group having 1 to 10 carbon atoms.

[0060] In the perfluoropolyether compound according to one embodiment of the present invention, the number average molecular weight of each of the perfluoropolyether groups is preferably 200 to 5000, more preferably 800 to 1500. Here, the number average molecular weight is measured using JNM-ECX400 manufactured by JEOL Ltd. 19 This is a value measured by F-NMR. In NMR measurements, the sample is not diluted and is used as is. The chemical shift reference is a known peak that is part of the fluoropolyether backbone structure.

[0061] The perfluoropolyether groups are compounds having a molecular weight distribution, and the molecular weight distribution (PD) expressed as weight average molecular weight / number average molecular weight is usually 1.0 to 1.5, more preferably 1.0 to 1.3, and even more preferably 1.0 to 1.1. The molecular weight distribution was measured using a Tosoh HPLC-8220GPC, a Polymer Laboratory column (PLgel Mixed E), an HCFC-based alternative chlorofluorocarbon as the eluent, and a non-functional perfluoropolyether as the reference substance.

[0062] The perfluoropolyether compound according to one embodiment of the present invention is 1 , R 2 , L, p, and Rf represented by the above formula (4) may be included in any combination.

[0063] A more specific example of the perfluoropolyether compound according to one embodiment of the present invention is a compound represented by the following formula: [ka] In Compound 1, n is a real number from 1 to 30. [ka] In Compound 2, n is a real number of 1 to 30. Compound 2 is a compound represented by R 3is a hydrogen atom, and q is an integer of 1. However, as will be described later, compounds having a Demnam skeleton have high heat resistance, and therefore Compound 2, in which the perfluoropolyether group of Rf has a Demnam skeleton, also has high heat resistance. Therefore, Compound 2 is also included in the perfluoropolyether compounds that have excellent heat resistance, exhibit strong interaction with magnetic disks, and solve the problem of high solubility in fluorine-based solvents. [ka] In Compound 3, n is a real number from 1 to 30. [ka] In Compound 4, n is a real number from 1 to 30. [ka] In Compound 5, n is a real number of 1 to 30. [ka] In Compound 6, n is a real number from 1 to 30. [ka] In Compound 7, n is a real number from 1 to 30.

[0064] The molecular weight of the perfluoropolyether compound is preferably 2,000, and more preferably 1,500.

[0065] 2. Method for producing perfluoropolyether compounds The method for producing a perfluoropolyether compound according to one embodiment of the present invention is not particularly limited as long as it can produce a perfluoropolyether compound having the structure represented by the above-mentioned formula (1). For example, compound 1 can be produced by reacting a perfluoropolyether and a compound obtained by epoxidizing trimethylolpropane in a solvent such as t-butyl alcohol in the presence of a reaction accelerator such as potassium t-butoxide. Here, the compound obtained by epoxidizing trimethylolpropane can be produced, for example, by using a compound containing two or more primary OH groups and three or more OH groups (e.g., trimethylolpropane, 2-hydroxymethyl-1,3-propanediol, etc.) as a raw material, reacting it with epichlorohydrin or epibromohydrin in the presence of a base, and then purifying it by column chromatography.

[0066] R in the above formula (1) 1 and R 2 Depending on the compound, trimethylolpropane may be replaced with an epoxidized compound, 1 and R 2 A compound having an epoxide structure at the terminal of the compound may be used.

[0067] Furthermore, when p in the above formula (1) is 1, two primary OH groups and one secondary OH group are introduced to one end of the perfluoropolyether by reacting it with a compound obtained by epoxidizing trimethylolpropane.Then, the OH group at the other end is reacted with a compound containing two reactive sites for OH groups, such as a diepoxy compound or epihalohydrin, under basic conditions, and the resulting product can be produced by purifying it by column chromatography.

[0068] Perfluoropolyether and R 1 and R 2 The temperature at which the compound having an epoxide structure at its terminal is reacted is preferably 50 to 120° C., more preferably 60 to 90° C. The reaction time is preferably 1 to 96 hours, more preferably 15 to 25 hours.

[0069] The raw material perfluoropolyether and R 1 and R 2 After reacting the resulting product with a compound having an epoxide structure at the end thereof, the resulting product is washed with water, dehydrated, and purified by silica gel column chromatography or the like to obtain a perfluoropolyether compound according to one embodiment of the present invention.

[0070] [3. Lubricants] The lubricant according to one embodiment of the present invention contains the perfluoropolyether compound according to one embodiment of the present invention. The perfluoropolyether compound can be used alone as a lubricant, or the perfluoropolyether compound can be mixed with other components in any ratio within a range that does not impair the performance of the lubricant.

[0071] 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.), and Krytox (registered trademark) (manufactured by Dupont), as well as MORESCO PHOSFAROL A20H (manufactured by MORESCO) and MORESCO PHOSFAROL D-4OH (manufactured by MORESCO).

[0072] The lubricant can be used as a lubricant for recording media to improve the sliding characteristics of magnetic disks. The lubricant 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, the lubricant can be used not only in recording devices, but also in devices that have sliding parts.

[0073] [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.

[0074] 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.

[0075] 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 the individual 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.

[0076] 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.

[0077] The method for forming a lubricating layer by laminating the lubricant on the exposed surface of the protective layer of a laminate formed by laminating a recording layer and a protective layer is not particularly limited. A preferred method for laminating a lubricant on the exposed surface of the protective layer is to dilute the lubricant in a solvent and then laminate it. Examples of solvents include PF-5060, PF-5080, HFE-7100, and HFE-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. If the concentration of the lubricant after dilution with the solvent is 0.005% by weight to 0.1% by weight, the interaction between lubricant molecules can be weakened, making it easier to form a uniform lubricating film.

[0078] 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.

[0079] By performing ultraviolet irradiation or heat treatment, stronger bonds are formed between the lubricating layer and 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] [6. Summary] The present invention includes the following aspects. <1> A perfluoropolyether compound having a structure represented by formula (1):

[0081] [ka] In formula (1), Rf is a perfluoropolyether group, L is a C3-C 20wherein at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom, and p is 0 or 1; R 1 is a group having a structure represented by formula (2),

[0082] [ka] In formula (2), R 4 has an OH group, C3 to C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; R 3 is a hydrogen atom or a C1-C2 hydrocarbon group, and R 3 is a hydrogen atom, q is an integer from 2 to 10, and R 3 is a C1-C2 hydrocarbon group, q is an integer of 1 to 10, R 2 is a group having a structure represented by formula (2) or a group having a structure represented by formula (3),

[0083] [ka] In formula (3), R 5 has an OH group, C3 to C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom. <2> In formula (2), R 4 has a structure represented by formula (5-2): <1> The perfluoropolyether compounds according to

[0084] [ka] In formula (5-2), t is 0 or 1. <3> In formula (3), R 5 is -OCH2CH(OH)CH2- or -OCH2CH(OH)CH2OCH2CH(OH)CH2-, <1> or <2> The perfluoropolyether compound according to claim 1. <4> In formula (1), L has a structure represented by formula (7): <1> ~ <3> 1. The perfluoropolyether compound according to any one of claims 1 to 9.

[0085] [ka] In formula (7), g is an integer of 1 to 5, the OH group may be substituted with at least one group selected from a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group, and the hydrogen atom bonded to the carbon may be substituted with an alkyl group having 1 to 10 carbon atoms. <5> A perfluoropolyether compound having a structure represented by the following formula:

[0086] [ka] In the formula, n is a real number from 1 to 30. <6> <1> ~ <5> A lubricant comprising the perfluoropolyether compound according to any one of the above items. <7> A magnetic disk having a recording layer, a protective layer, and a lubricating layer laminated in this order, wherein the lubricating layer is <6> A magnetic disk comprising the lubricant described in claim 1. [Example]

[0087] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0088] [Evaluation method] (Heat resistance) The heat resistance of the lubricants was evaluated using a thermogravimetric analyzer (Seiko Instruments, EXSTAR6000). 5 mg of each of the perfluoropolyether compounds obtained in the examples and comparative examples was placed in a platinum container and heated to 550°C at a rate of 2°C / min under a nitrogen atmosphere. The temperature at which a 50% weight loss occurred (T50) was measured to evaluate the heat resistance.

[0089] (Solubility in fluorinated solvents) 0.03 g of each perfluoropolyether compound obtained in the Examples and Comparative Examples was weighed out, and Vertrel-XF (Mitsui Chemours Fluoroproducts) was added to bring the total weight to 30 g. After vigorous stirring, the solubility in fluorine-based solvents was evaluated. The solution was visually inspected; a clear solution was marked with a 'good', and a cloudy solution was marked with an 'x'.

[0090] (bond rate) The perfluoropolyether compounds obtained in the examples and comparative examples were each dissolved in Vertrel-XF and applied to a magnetic disk by dipping to a lubricant film thickness of α Å. The lubricant film thickness was measured using an FT-IR (Bruker, VERTEX70). After leaving the disk stationary for two weeks, the disk was again immersed in Vertrel-XF to wash away the lubricant, which had weak interactions with the magnetic disk. The film thickness of the lubricant remaining on the magnetic disk after washing with Vertrel-XF was measured using FT-IR, and the film thickness at this time was defined as β Å. To quantify the interaction with the disk, the bond ratio was calculated as β / α × 100 (%).

[0091] Example 1 Compound 1 was synthesized as follows, and the obtained compound 1 was used as a lubricant in Example 1.

[0092] A mixture of t-butyl alcohol (65 g), perfluoropolyether (100 g) represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (1.2 g), and a compound obtained by epoxidizing trimethylolpropane (51 g) was stirred under an argon atmosphere at 70°C for 20 hours. The resulting reaction product was then washed with water, dehydrated, and further purified by silica gel column chromatography to obtain 62 g of a perfluoropolyether compound (Compound 1).

[0093] The identification results of Compound 1 using NMR are shown below. 19 F-NMR (solvent: none, reference material: -OCF2C in the product) FSet 2CF2O- to -129.7 ppm.) δ = -129.7 ppm [8F, -OCF2C F 2CF2O-] δ = -84.1 ppm [15F, -OC F 2CF2C F 2O-] δ = -124.0 ppm [4F, -OCF2C F 2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH] δ = -86.4 ppm [4F, -OC F 2CF2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH] 1 H-NMR (solvent: none, reference substance: D2O) δ = 0.7 ppm [6H, HOCH2C(CH2OH)(CH2C H 3)CH2OCH2CH(OH)CH2OCH2CF2CF2O(CF2CF2CF2O)mCF2CF2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH] δ = 1.2 ppm [4H, HOCH2C(CH2OH)(C H 2CH3)CH2OCH2CH(OH)CH2OCH(OH)CH2OCH2CF2CF2O(CF2CF2CF2O)mCF2CF2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH] δ = 3.2~4.0 ppm [32H, H OC H 2C(C H 2O H )(CH2CH3)C H 2OC H 2C H (O H )C H 2OC H 2CF2CF2O(CF2CF2CF2O)mCF2CF2C H 2OC H 2C H (O H )C H 2OC H 2C(CH2CH3)(C H 2OH )C H 2O H ] 19 F-NMR and 1 The results of H-NMR showed that Compound 1 was a compound in which n=4.

[0094] Example 2 Compound 2 was synthesized as follows, and the obtained compound 2 was used as a lubricant in Example 2.

[0095] A mixture of t-butyl alcohol, perfluoropolyether represented by HOCHCFCFO(CFCFCFO)CFCFCHOH, potassium t-butoxide, and a compound of epoxidized 2-hydroxymethyl-1,3-propanediol is stirred under an argon atmosphere at 70°C for 20 hours. The mixture is then washed with water, dehydrated, and purified by silica gel column chromatography to obtain a perfluoropolyether compound (Compound 2).

[0096] Example 3 Compound 3 was synthesized as follows, and the obtained compound 3 was used as a lubricant in Example 3.

[0097] A mixture of t-butyl alcohol (65 g), perfluoropolyether (100 g) represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (1.2 g), and a compound obtained by epoxidizing 1,2,6-hexanetriol (51 g) was stirred at 70°C under an argon atmosphere for 20 hours. The mixture was then washed with water, dehydrated, and purified by silica gel column chromatography to obtain 60 g of a perfluoropolyether compound (compound 3).

[0098] The identification results of compound 3 using NMR are shown below. 19 F-NMR (solvent: none, reference material: -OCF2C in the product) F 2CF2O- is -129.7 ppm.) δ=-129.7 ppm [8F, -OCF2C F 2CF2O-] δ=-84.0 ppm [16F, -OC F 2CF2C F 2O-] δ=-123.9 ppm [4F, -OCF2C F 2CH2OCH2CH(OH)CH2OCH(CH2OH)CH2CH2CH2CH2OH] δ=-86.1 ppm [4F, -OC F 2CF2CH2OCH2CH(OH)CH2OCH(CH2OH)CH2CH2CH2CH2OH] 1 H-NMR (no solvent, reference material DO) δ=0.9~1.2ppm[12H,HOCH2C H 2C H 2C H 2CH(CH2OH)OCH2CH(OH)CH2OCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OCH2CH(OH)CH2OCH(CH2OH)C H 2C H 2C H 2CH2OH] δ=1.2 ppm [30H, H OC H 2CH2CH2CH2C H (C H 2O H )OC H 2C H (O H )C H 2OC H 2CF2CF2O(CF2CF2CF2O)nCF2CF2C H 2OC H 2C H (O H )C H 2OC H (C H 2O H )CH2CH2CH2C H 2O H ] 19 F-NMR and 1 The results of H-NMR showed that Compound 3 was a compound in which n=5.

[0099] Example 4 Compound 4 was synthesized as follows, and the obtained compound 4 was used as a lubricant in Example 4.

[0100] A mixture of t-butyl alcohol, perfluoropolyether represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide, and glycidol is stirred under an argon atmosphere at 70°C for 20 hours. The mixture is then washed with water, dehydrated, and purified by silica gel column chromatography to obtain a compound with one hydroxyl group at one end of the PFPE and three hydroxyl groups at the other end. The resulting compound is mixed with t-butyl alcohol, potassium t-butoxide, and a compound obtained by epoxidizing trimethylolpropane under an argon atmosphere and stirred at 70°C for 20 hours. The resulting mixture is then purified by column chromatography to obtain the perfluoropolyether compound (Compound 4).

[0101] Example 5 Compound 5 was synthesized as follows, and the obtained compound 5 was used as a lubricant in Example 5.

[0102] A mixture of t-butyl alcohol (65 g), perfluoropolyether (100 g) represented by HOCH2CF2O(CF2CF2O)n(CF2O)nCF2CH2OH, potassium t-butoxide (1.2 g), and an epoxidized trimethylolpropane compound (51 g) was stirred under an argon atmosphere at 70°C for 20 hours. The mixture was then washed with water, dehydrated, and purified by silica gel column chromatography to obtain 65 g of a perfluoropolyether compound (compound 5).

[0103] The identification results of compound 5 using NMR are shown below. 19 F-NMR (solvent: none, reference material: -OC in the product) F 2C F 2O- is -90.7 ppm.) δ = -90.7 ppm [16F, -OC F 2C F 2O-] δ = -52.1 ppm [10F, -OC F 2O-] δ = -79.8 ppm [4F, -OC F 2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH] 1 H-NMR (solvent-free, reference substance D2O) δ = 0.7 ppm [6H, HOCH2C(CH2OH)(CH2C H 3)CH2OCH2CH(OH)CH2OCH2CF2O(CF2CF2O)n(CF2O)nCF2CH2OCH2CH(OH)CH2OCH2C(CH2C H 3)(CH2OH)CH2OH] δ = 1.2 ppm [4H, HOCH2C(CH2OH)(C H 2CH3)CH2OCH2CH(OH)CH2OCH2CF2O(CF2CF2O)n(CF2O)nCF2CH2OCH2CH(OH)CH2OCH2C(C H 2CH3)(CH2OH)CH2OH] δ = 3.2~4.0 ppm [32H, H OC H 2C(C H [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The results of H-NMR showed that Compound 5 was a compound in which n=5.

[0104] Example 6 Compound 6 was synthesized as follows, and the obtained compound 6 was used as a lubricant in Example 6.

[0105] A mixture of t-butyl alcohol (65 g), perfluoropolyether (100 g) represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (0.6 g), and a compound of epoxidized trimethylolpropane (24 g) was stirred at 70°C under an argon atmosphere for 20 hours. The mixture was then washed with water, dehydrated, and purified by silica gel column chromatography to obtain 40 g of a compound having one hydroxyl group at one end of the PFPE and three hydroxyl groups at the other end. The resulting compound was then mixed with t-butyl alcohol (25 g), potassium t-butoxide (0.5 g), and a compound of diepoxidized trimethylolpropane (20 g) under an argon atmosphere and stirred at 70°C for 20 hours. The mixture was then purified by column chromatography to obtain 15 g of a perfluoropolyether compound (Compound 6).

[0106] The identification results of compound 6 using NMR are shown below. 19 F-NMR (solvent: none, reference material: -OCF2C in the product) F 2CF2O- is -129.7 ppm.) δ=-129.7 ppm [16F, -OCF2C F 2CF2O-] δ=-84.1 ppm [32F, -OC F 2CF2C F 2O-] δ=-124.0 ppm [8F, -OCF2C F 2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH, -OCF2C F2CH2OCH2CH(OH)CH2OCH2C(CH2OH)(CH2CH3)CH2OCH2CH(OH)CH2OCH2C F 2CF2-] δ=-86.4ppm[8F, -OC F 2CF2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH, -OC F 2CF2CH2OCH2CH(OH)CH2OCH2C(CH2OH)(CH2CH3)CH2OCH2CH(OH)CH2OCH2CF2C F 2-] 1 H-NMR(without solvent, reference substance D2O) δ=0.7ppm[9H, -OCF2CF2CH2OCH2CH(OH)CH2OCH2C(CH2C H 3)(CH2OH)CH2OH, -OCF2CF2CH2OCH2CH(OH)CH2OCH2C(CH2OH)(CH2C H 3)CH2OCH2CH(OH)CH2OCH2CF2CF2-] δ=1.2ppm[6H, -OCF2CF2CH2OCH2CH(OH)CH2OCH2C(C H 2CH3)(CH2OH)CH2OH, -OCF2CF2CH2OCH2CH(OH)CH2OCH2C(CH2OH)(C H 2CH3)CH2OCH2CH(OH)CH2OCH2CF2CF2-] δ=3.2~4.0ppm[55H, H OC H 2C(C H 2O H )(CH2CH3)C H 2OC H 2C H (O H )C H 2OC H 2CF2CF2O(CF2CF2CF2O)mCF2CF2C H 2OC H 2C H (O H )C H 2OC H 2C(C H 2O H )(CH2CH3)CH 2OC H 2C H (O H )C H 2OC H 2CF2CF2O(CF2CF2CF2O)mCF2CF2C H 2OC H 2C H (O H )C H 2OC H 2C(CH2CH3)(C H 2O H )C H 2O H ] 19 F-NMR and 1 The results of H-NMR showed that Compound 6 was a compound in which n=5.

[0107] Example 7 Compound 7 was synthesized as follows, and the obtained compound 7 was used as a lubricant in Example 7.

[0108] A mixture of t-butyl alcohol (65 g), perfluoropolyether (100 g) represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (0.6 g), and a compound of epoxidized trimethylolpropane (24 g) was stirred at 70°C under an argon atmosphere for 20 hours. The mixture was then washed with water, dehydrated, and purified by silica gel column chromatography to obtain 40 g of a compound with one hydroxyl group at one end of the PFPE and three hydroxyl groups at the other end. The resulting compound was then mixed with t-butyl alcohol (25 g), potassium t-butoxide (0.5 g), and epichlorohydrin (8 g) under an argon atmosphere and stirred at 70°C for 20 hours. The mixture was then purified by column chromatography to obtain 17 g of a perfluoropolyether compound (compound 7).

[0109] The identification results of compound 7 using NMR are shown below. 19 F-NMR (solvent: none, reference material: -OCF2C in the product)F Set 2CF2O− to -129.7 ppm.) δ = -129.7 ppm [16F, -OCF2C F 2CF2O−] δ = -84.1 ppm [32F, -OC F 2CF2C F 2O−] δ = -124.0 ppm [8F, -OCF2C F 2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH, -OCF2C F 2CH2OCH2CH(OH)CH2OCH2C F 2CF2−] δ = -86.4 ppm [8F, -OC F 2CF2CH2OCH2CH(OH)CH2OCH2C(CH2CH3)(CH2OH)CH2OH, -OC F 2CF2CH2OCH2CH(OH)CH2OCH2CF2C F 2−] 1 H-NMR (without solvent, reference substance D2O) δ = 0.7 ppm [6H, -OCF2CF2CH2OCH2CH(OH)CH2OCH2C(CH2C H 3)(CH2OH)CH2OH] δ = 1.2 ppm [4H, -OCF2CF2CH2OCH2CH(OH)CH2OCH2C(C H 2CH3)(CH2OH)CH2OH] δ = 3.2~4.0 ppm [42H, H OC H 2C(C H 2O H (CH2CH3)C H 2OC H 2C H (O H )C H 2OC H 2CF2CF2O(CF2CF2CF2O)mCF2CF2C H 2OC H 2C H (O H )C H 2OC H2CF2CF2O(CF2CF2CF2O)mCF2CF2C H 2OC H 2C H (O H )C H 2OC H 2C(CH2CH3)(C H 2O H )C H 2O H ] 19 F-NMR and 1 The results of H-NMR showed that Compound 7 was a compound in which n=5.

[0110] (Comparative Example 1) Comparative Compound 1 was synthesized as follows, and the obtained comparative compound 1 was used as a lubricant in Comparative Example 1.

[0111] [ka] A mixture of t-butyl alcohol (65 g), perfluoropolyether (150 g) represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (2 g), and glycidol (18 g) was stirred under an argon atmosphere at 70°C for 18 hours. The mixture was then washed with water, dehydrated, and purified by silica gel column chromatography to obtain 90 g of perfluoropolyether compound. The resulting compound was identified using NMR.

[0112] 19 F-NMR and 1 The results of 1 H-NMR showed that Comparative Compound 1 was a compound in which n=6.

[0113] (Comparative Example 2) Comparative Compound 2 was synthesized as follows, and the obtained Comparative Compound 2 was used as a lubricant in Comparative Example 2.

[0114] [ka] A mixture of t-butyl alcohol (65 g), perfluoropolyether (150 g) represented by HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (2 g), and glycidol (10 g) was stirred under an argon atmosphere at 70°C for 17 hours. The resulting reaction product was then washed with water, dehydrated, and purified using silica gel column chromatography to obtain 60 g of perfluoropolyether having one hydroxyl group at one end and two hydroxyl groups at the other end due to the reaction with glycidol.

[0115] 60 g of this perfluoropolyether compound was dissolved in t-butyl alcohol (30 g). Potassium t-butoxide (1 g) and 2,2-dimethyl-4-(2,3-epoxy)propoxymethyl-1,3-dioxolane (5 g) were then added to this solution, and the mixture was stirred at 70°C for 17 hours under an argon atmosphere. The resulting reaction product was then washed with water, dehydrated, and 100 g of methanol, 11 g of water, and 0.4 g of 60% aqueous nitric acid solution were added, followed by stirring for 39 hours. The resulting reaction product was then washed with water, dehydrated, and further purified by distillation to obtain 20 g of perfluoropolyether compound. The resulting compound was identified using NMR.

[0116] 19 F-NMR and 1 The results of 1 H-NMR showed that Comparative Compound 3 was a compound in which n=6.

[0117] (Comparative Example 3) Comparative Compound 3 was synthesized as follows, and the obtained Comparative Compound 3 was used as a lubricant in Comparative Example 3.

[0118] [ka] A mixture of t-butyl alcohol (65 g), perfluoropolyether (150 g) represented by the formula HOCH2CF2CF2O(CF2CF2CF2O)nCF2CF2CH2OH, potassium t-butoxide (1 g), and 2,2-dimethyl-4-(2,3-epoxy)propoxymethyl-1,3-dioxolane (23 g) was stirred at 70°C for 18 hours under an argon atmosphere. The mixture was then washed with water and dehydrated. 100 g of methanol, 11 g of water, and 0.4 g of 60% aqueous nitric acid solution were added and stirred for 39 hours. The resulting reaction product was then washed with water, dehydrated, and further purified by distillation to yield 60 g of perfluoropolyether compound. The resulting compound was identified using NMR.

[0119] 19 F-NMR and 1 The results of 1 H-NMR showed that Comparative Compound 3 was a compound in which n=6.

[0120] (Evaluation results) The lubricants obtained in the examples and comparative examples were evaluated for heat resistance, bond ratio, and solubility in fluorine-based solvents, and the results are shown in Table 1. The bond ratio is an index that indicates the strength of the interaction between the lubricant and the magnetic disk, with a higher bond ratio indicating a stronger interaction. Note that comparative compound 3 was not soluble in fluorine-based solvents and therefore could not be applied to the magnetic disk.

[0121] [Table 1] It is clear from Table 1 that the perfluoropolyether compounds obtained in Examples 1, 3, and 5 to 7 are superior in solubility, heat resistance, and strength of interaction with the disk compared to Comparative Compounds 1 to 3. That is, it was found that the perfluoropolyether compound according to one embodiment of the present invention has excellent adhesive strength as a lubricant for adhering the magnetic disk and the protective layer to each other.

[0122] R 1 and R 2It is suggested that compound 4, which has the structure represented by formula (2) in only one of R 1 and R 2 When compound 1, whose Rf perfluoropolyether group is a Demnum skeleton, is compared with compound 5, whose Rf perfluoropolyether group is a Fomblin skeleton, it was found that compound 1 (Demnum skeleton) has higher heat resistance. This result suggests that compound 2, which has a Demnum skeleton, has higher heat resistance than the compound with a Fomblin skeleton. [Industrial Applicability]

[0123] The perfluoropolyether compound according to one embodiment of the present invention has high solubility in fluorine-based solvents, high heat resistance, and exhibits strong interaction with disks, and therefore can be suitably used as a lubricant for magnetic disks. [Explanation of symbols]

[0124] 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 perfluoropolyether compound having a structure represented by formula (1): 【Chemistry 1】 In formula (1), Rf is a perfluoropolyether group, L has an OH group, C 3 ~C 20 wherein at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom, and p is 0; R １ is a group having a structure represented by formula (2), 【Chemistry 2】 In formula (2), R ４ has an OH group, C 3 ~C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; R ３ is C 1 ~C 2 and q is an integer of 1 to 10. R ２ is a group having a structure represented by formula (2) or a group having a structure represented by formula (3), 【Transformation 3】 In formula (3), R ５ has an OH group, C 3 ~C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom.

2. A perfluoropolyether compound having a structure represented by formula (1): 【Chemistry 4】 In formula (1), Rf is a perfluoropolyether group, L has an OH group, C 3 ~C 20 wherein at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom, and p is 1; R １ is a group having a structure represented by formula (2), 【Transformation 5】 In formula (2), R ４ has an OH group, C 3 ~C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; R ３ is a hydrogen atom or C 1 ~C 2 is a hydrocarbon group of the formula R ３ is a hydrogen atom, q is an integer of 2 to 10, and R ３ is C 1 ~C 2 When the hydrocarbon group is a hydrocarbon group represented by the formula (I), q is an integer of 1 to 10; R ２ is a group having a structure represented by formula (2) or a group having a structure represented by formula (3), 【Transformation 6】 In formula (3), R ５ has an OH group, C 3 ~C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom.

3. A perfluoropolyether compound having a structure represented by formula (1): 【Transformation 7】 In formula (1), Rf is a perfluoropolyether group, L has an OH group, C 3 ~C 20 wherein at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom, and p is 0; R １ is a group having a structure represented by formula (2), 【Transformation 8】 In formula (2), R ４ has an OH group, C 3 ~C 10 At least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom; R ３ is a hydrogen atom, and q is an integer of 7 to 10, R ２ is a group having a structure represented by formula (2) or a group having a structure represented by formula (3), 【Chemistry 9】 In formula (3), R ５ has an OH group, C 3 ~C 10 and at least one carbon atom in the main chain of the hydrocarbon group may be substituted with an oxygen atom.

4. In formula (2), R ４ The perfluoropolyether compound according to any one of claims 1 to 3, having a structure represented by formula (5-2): 【Chemistry 10】 In formula (5-2), t is 0 or 1.

5. In formula (3), R ５ is -OCH ２ CH(OH)CH ２ - or -OCH ２ CH(OH)CH ２ OCH ２ CH(OH)CH ２ The perfluoropolyether compound according to any one of claims 1 to 3, wherein

6. The perfluoropolyether compound according to claim 2, wherein L in formula (1) has a structure represented by formula (7): 【Chemistry 11】 In formula (7), g is an integer of 1 to 5, the OH group may be substituted with at least one group selected from a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group, and the hydrogen atom bonded to the carbon may be substituted with an alkyl group having 1 to 10 carbon atoms.

7. A lubricant comprising the perfluoropolyether compound according to any one of claims 1 to 3.

8. A magnetic disk having a recording layer, a protective layer, and a lubricating layer laminated in this order, The magnetic disk, wherein the lubricating layer comprises the lubricant according to claim 7 .

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