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

Abstract

This fluorine-containing ether compound is represented by formula: R1-CH2-R2-CH2-OCH2CH(OH)CH2O-CH2-R3-CH2-R4 (in the formula, R2 and R3 each represent a perfluoropolyether chain, and R1 and R4 each represent a terminal group including two or three polar groups which are bound to different carbon atoms, and in which the carbon atoms bound to the polar groups are bound to one another via linkage groups including carbon atoms not bound to the polar groups).

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2020-101574, filed on June 11, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] In order to increase the recording density in magnetic recording and reproducing devices, development of magnetic recording media suitable for high recording densities is underway. Conventional magnetic recording media include those in which a recording layer is formed on a substrate and a protective layer made of carbon or the like is formed on the recording layer. The protective layer protects the information recorded on the recording layer and improves the sliding properties of the magnetic head. The protective layer also covers the recording layer to prevent the metal contained in the recording layer from being corroded by environmental substances.

[0003] However, the durability of a magnetic recording medium cannot be sufficiently achieved by simply providing a protective layer on the recording layer. Therefore, a lubricant is applied to the surface of the protective layer to form a lubricating layer with a thickness of approximately 0.5 to 3 nm. The lubricating layer improves the durability and protective power of the protective layer and prevents contaminants from penetrating into the magnetic recording medium. After forming the lubricating layer on the surface of the protective layer, a burnishing process may be carried out to remove protrusions and particles present on the surface of the magnetic recording medium and to improve the smoothness of the surface.

[0004] Lubricants used in forming the lubricating layer of a magnetic recording medium include, for example, those containing a fluorine-based polymer having a repeating structure containing -CF2- and having polar groups such as hydroxyl groups at the terminals. For example, Patent Document 1 discloses a magnetic disk including a lubricating layer containing a perfluoropolyether having hydroxyl groups at both ends, while Patent Documents 2 and 3 disclose compounds in which a perfluoropolyether is bonded to both ends of an aliphatic hydrocarbon chain containing a hydroxyl group. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5786047 [Patent Document 2] U.S. Patent No. 9,805,755 [Patent Document 3] US Patent Application Publication No. 2020 / 0002640 [Patent Document 4] International Publication No. 2019 / 054148 Summary of the Invention [Problem to be solved by the invention]

[0006] In magnetic recording and reproducing devices, there is a demand for ever smaller flying heights of magnetic heads, which in turn requires thinner protective layers and lubricating layers in magnetic recording media. However, when the thickness of the protective layer and / or lubricating layer is reduced, the corrosion resistance of the magnetic recording medium may become insufficient. In particular, when a tape burnish is applied to the surface of the magnetic recording medium after the lubricating layer is formed, the corrosion resistance of the magnetic recording medium tends to become insufficient. For this reason, a lubricating layer that is highly effective in suppressing corrosion of the magnetic recording medium is required.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that can be used as a material for a lubricant for a magnetic recording medium, which can provide a lubricating layer having a high corrosion-inhibiting effect on the magnetic recording medium. Another object of the present invention is to provide a lubricant for magnetic recording media, which contains the fluorine-containing ether compound of the present invention. Another object of the present invention is to provide a magnetic recording medium having excellent corrosion resistance and a lubricating layer containing the fluorine-containing ether compound of the present invention. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems. As a result, the present inventors discovered that a fluorine-containing ether compound can be obtained by placing a glycerin structure (-OCH2CH(OH)CHO-) at the center of a chain structure, and bonding to both sides of the glycerin structure via methylene groups (-CH2-) in this order: a perfluoropolyether chain, a methylene group, and a specific terminal group having two or three polar groups, and thus arrived at the present invention. That is, the present invention relates to the following: The present invention includes the following first aspect.

[0009] [1] A fluorine-containing ether compound represented by the following formula (1): R 1 -CH2-R 2 -CH2-OCH2CH(OH)CH2O-CH2-R 3 -CH2-R 4 (1) (In formula (1), R 2 and R 3 is a perfluoropolyether chain; R 1 and R 4 is a terminal group containing two or three polar groups, each of which is bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded are bonded via a linking group containing a carbon atom to which no polar group is bonded.

[0010] The compound according to the first aspect of the present invention preferably includes the features described in the following items [2] to [8]. It is also preferable to combine two or more of these features. [2] In the formula (1), R 1 and R 4 The fluorine-containing ether compound according to [1], wherein all of the polar groups are hydroxyl groups.

[0011] [3] In the formula (1), -CH2-R 1 and -CH2-R 4 The fluorine-containing ether compound according to [1] or [2], wherein the compound is represented by the following formula (2): -CH2-[A]-[B]-OZ (2) (In formula (2), [A] is represented by the following formula (3), [B] is represented by the following formula (4), and Z is H or a group represented by the following formula (5); in formula (2), [A] and [B] may be interchanged, and when [A] is directly bonded to -OZ, Z is a group represented by the following formula (5).)

[0012] [ka] (In formula (3), X is an integer of 0 to 2; in formula (4), Y is an integer of 0 to 1, and a is an integer of 1 to 4; the sum of X in formula (3) and Y in formula (4) is 1 or 2; and in formula (5), b is an integer of 2 to 4.)

[0013] [4] R in the formula (1) 2 and R 3 is any one of the following formulae (6) to (8):

[0022] (1) a fluorine-containing ether compound according to any one of [1] to [3]; -CF2O-(CF2CF2O) c -(CF2O) d -CF2- (6) (In formula (6), c and d each represent an average degree of polymerization and represent 0 to 20; provided that c or d is 0.1 or more.) -CF2CF2O-(CF2CF2CF2O) e -CF2CF2- (7) (In formula (7), e represents the average degree of polymerization and represents 0.1 to 20.) -CF2CF2CF2O-(CF2CF2CF2CF2O) f -CF2CF2CF2- (8) (In formula (8), f represents the average degree of polymerization and represents 0.1 to 10.)

[0014] [5] In the formula (1), R 1 and R 4 The fluorine-containing ether compound according to any one of [1] to [4], wherein each of the groups contains two polar groups. [6] In the formula (1), R 1 and R 4 The fluorine-containing ether compound according to any one of [1] to [5], wherein [7] In the formula (1), R 2 and R 3 The fluorine-containing ether compound according to any one of [1] to [6], wherein [8] The fluorinated ether compound according to any one of [1] to [7], which has a number average molecular weight in the range of 500 to 10,000.

[0015] A second aspect of the present invention is the following lubricant. [9] A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of [1] to [8]. A third aspect of the present invention is the following magnetic recording medium.

[10] A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, A magnetic recording medium, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of [1] to [8].

[11] The magnetic recording medium according to

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

[0016] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and therefore can be used as a material for a lubricant for magnetic recording media, which provides a lubricating layer with a high corrosion-inhibiting effect on the magnetic recording media. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore can form a lubricating layer that has a high corrosion-inhibiting effect on magnetic recording media. The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention, and therefore has excellent corrosion resistance. Therefore, the magnetic recording medium of the present invention has excellent reliability and durability. Furthermore, since the magnetic recording medium of the present invention has a lubricating layer with a high corrosion-inhibiting effect, the thickness of the protective layer and / or lubricating layer can be reduced. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view showing a preferred embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred examples of the fluorine-containing ether compound, lubricant for magnetic recording media (hereinafter sometimes abbreviated as "lubricant"), and magnetic recording media of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments. For example, the present invention is not limited to the following examples, and additions, omissions, substitutions, or changes can be made to the number, amount, ratio, composition, type, position, material, configuration, etc., within the scope of the present invention.

[0019] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2 -CH2-OCH2CH(OH)CH2O-CH2-R 3 -CH2-R 4 (1) (In formula (1), R 2 and R 3 is a perfluoropolyether chain; R 1 and R 4 is a terminal group containing two or three polar groups, each of which is bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded are bonded via a linking group containing a carbon atom to which no polar group is bonded.

[0020] In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 are each independently a terminal group containing two or three polar groups. In the fluorine-containing ether compound represented by formula (1), R 1 and R 4Since the compound has a polar group, when a lubricating layer is formed on a protective layer using a lubricant containing the compound, a favorable interaction occurs between the lubricating layer and the protective layer.

[0021] In the fluorine-containing ether compound represented by formula (1), R 1 and the polar groups contained in R 4 The total number of polar groups contained in is 4 to 6. Since the total number is 4 or more, the lubricating layer containing the fluorine-containing ether compound has high adhesion (tight adhesion) to the protective layer. Furthermore, since the total number is 6 or less, in a magnetic recording medium having a lubricating layer containing a fluorine-containing ether compound, it is possible to prevent pickup of the fluorine-containing ether compound, which is too high in polarity and adheres to the magnetic head as foreign matter (smear).

[0022] R 1 and the number of polar groups in R 4 The number of polar groups contained in R is preferably the same. 1 and R 4 each containing two polar groups, or R 1 and R 4 Each of R preferably contains three polar groups. In this case, the lubricant containing the fluorine-containing ether compound adheres to the protective layer in a well-balanced manner, making it easier to obtain a lubricating layer with a high coverage. In particular, R 1 and R 4 When each of R contains two polar groups, the polar groups contained in the fluorine-containing ether compound do not interact with each other too much, and the polar groups are not distributed unevenly, so intramolecular aggregation is unlikely to occur. 1 and R 4 When each of R contains two polar groups, the hydrophilicity of the molecule is not too high, resulting in a fluorine-containing ether compound with moderate hydrophobicity. 1 and R 4 A lubricating layer containing a fluorine-containing ether compound, each of which contains two polar groups, is more preferred because it has excellent adhesion to the protective layer and is highly effective in inhibiting corrosion of the magnetic recording medium.

[0023] R 1and R 4 The polar group contained in R can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound. 1 and R 4 Examples of polar groups contained in R include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), an aldehyde group (-COH), a carbonyl group (-CO-), and a sulfo group (-SO3H). 1 and R 4 The polar group contained in R is preferably a hydroxyl group. The hydroxyl group has a strong interaction with the protective layer, especially the protective layer formed of a carbon-based material. Therefore, R 1 and / or R 4 When the polar group of R is a hydroxyl group, the lubricating layer containing the fluorine-containing ether compound has high adhesion (adhesion) to the protective layer. 1 and R 4 It is more preferable that the two or three polar groups are all hydroxyl groups.

[0024] R 1 and R 4 Each polar group in R is bonded to a different carbon atom. 1 and R 4 In the formula (1), the carbon atoms bonded to polar groups are bonded together via a linking group containing a carbon atom that is not bonded to a polar group.Therefore, the fluorine-containing ether compound represented by formula (1) has better hydrophobicity than, for example, the case where the carbon atoms bonded to polar groups are bonded together.As a result, it is estimated that the lubricating layer containing the fluorine-containing ether compound represented by formula (1) can prevent water from penetrating and effectively suppress the corrosion of magnetic recording media.

[0025] R 1 and R 4In the formula (I), the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded may contain a carbon atom to which no polar group is bonded, and may or may not contain an oxygen atom. In other words, the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded may or may not contain an ether bond (-O-).

[0026] R 1 and R 4 In the above, when the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded contains an oxygen atom, the linking group preferably has a linear structure of 3 to 9 atoms, including a carbon atom to which no polar group is bonded, and more preferably a linear structure of 3 to 5 atoms. Even when the linking group contains an oxygen atom, if it has a linear structure of three or more atoms, including a carbon atom to which no polar group is bonded, the fluorine-containing ether compound will have good hydrophobicity. Furthermore, if the linking group has a linear structure of 9 or fewer atoms, the hydrophobicity of the linking group will not be too high and will not hinder adhesion to the protective layer. As a result, a lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure with the above number of atoms will have excellent adhesion to the protective layer, will be able to prevent water penetration, and will have a high corrosion inhibitory effect on magnetic recording media.

[0027] R 1 and R 4In the above, when the linking group between the carbon atom to which the terminal polar group is bonded and the carbon atom to which the polar group adjacent to the terminal polar group is bonded does not contain an oxygen atom, the linking group preferably has a linear structure consisting of 1 to 4 atoms, including a carbon atom to which no polar group is bonded. When the linking group does not contain an oxygen atom and has a linear structure consisting of one or more atoms, including a carbon atom to which no polar group is bonded, the fluorine-containing ether compound has good hydrophobicity. Furthermore, when the linking group has a linear structure consisting of four or less atoms, the hydrophobicity of the linking group is not too high, which does not hinder adhesion to the protective layer. As a result, a lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure consisting of the above number of atoms has excellent adhesion to the protective layer, can prevent water penetration, and has a high corrosion suppression effect on the magnetic recording medium.

[0028] R 1 and R 4 may be the same or different. R 1 and R 4 When R is the same, the fluorine-containing ether compound is likely to wet and spread evenly on the protective layer, and to easily obtain a lubricating layer with a uniform thickness. As a result, the lubricating layer containing this fluorine-containing ether compound is likely to have a good coverage, which is preferable. 1 and R 4 If the same, R 1 and R 4 In comparison with the case where the thickness is different, the manufacturing process can be performed efficiently with fewer manufacturing steps.

[0029] In the fluorine-containing ether compound represented by formula (1), -CH2-R 1 and -CH2-R 4 is preferably represented by the following formula (2). -CH2-[A]-[B]-OZ (2) (In formula (2), [A] is represented by the following formula (3), [B] is represented by the following formula (4), and Z is H or a group represented by the following formula (5); in formula (2), [A] and [B] may be interchanged, and when [A] is directly bonded to -OZ, Z is a group represented by the following formula (5).)

[0030] [ka] (In formula (3), X is an integer of 0 to 2; in formula (4), Y is an integer of 0 to 1, and a is an integer of 1 to 4; the sum of X in formula (3) and Y in formula (4) is 1 or 2; and in formula (5), b is an integer of 2 to 4.)

[0031] -CH2-R represented by formula (2) 1 and -CH2-R 4 may each have, for example, one [A] represented by formula (3) and one [B] represented by formula (4), or may have one or two [A]s only, or may have only one [B]. When both [A] and [B] are present, either [A] or [B] may be located on the perfluoropolyether chain side. Furthermore, when [A] is directly bonded to -OZ, Z is a group represented by formula (5).

[0032] -CH2-R 1 and -CH2-R 4 Since is expressed by equation (2), R 1 and / or R 4 When R contains two or three hydroxyl groups, the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded has a linear structure consisting of the appropriate number of atoms. 1 and / or R 4 When there are three hydroxyl groups in the -CH2-R, the linking group between the carbon atom to which the hydroxyl group located on the perfluoropolyether chain is bonded and the carbon atom to which the hydroxyl group adjacent to that hydroxyl group is bonded also has a linear structure consisting of the appropriate number of atoms. 1 and -CH2-R 4 is represented by formula (2), the resulting fluorine-containing ether compound has appropriate hydrophobicity.

[0033] In formula (2), when [A] is directly bonded to -OZ, Z is a group represented by formula (5), and Z cannot be H. For example, when [A] is directly bonded to -OZ, if Z is H, the carbon atom to which the hydroxyl group in [A] is bonded and the carbon atom to which the hydroxyl group in -OZ where Z is H are bonded form a directly bonded terminal group. This increases the hydrophilicity of the fluorine-containing ether compound. As a result, the hydrophobicity of the lubricating layer containing the fluorine-containing ether compound is insufficient, and the corrosion resistance of the magnetic recording medium provided with the lubricating layer is insufficient.

[0034] In addition, in formula (2), X in formula (3) is an integer of 0 to 2, Y in formula (4) is an integer of 0 to 1, and the sum of X in formula (3) and Y in formula (4) is 1 or 2. Therefore, -CH2-R 1 and / or -CH2-R 4 Therefore, the proportion of R in the molecule does not become too high. 2 and R 3 The compound contains a sufficient amount of perfluoropolyether chains represented by the formula (I) and becomes a fluorine-containing ether compound having better hydrophobicity.

[0035] In formula (2), when Y in formula (4) is 1 and a is an integer of 1 to 4, the resulting fluorinated ether compound has appropriate hydrophobicity, which is preferred. In formula (4), a is preferably an integer of 2 to 4, since this results in a fluorinated ether compound with more appropriate hydrophobicity.

[0036] In formula (2), when Z is formula (5) and b is an integer of 2 to 4, the resulting fluorine-containing ether compound has appropriate hydrophobicity, which is preferred. When Z is formula (5) and b is 2 or greater, the oxygen atom of the ether bond (—O—) bonded to Z and the hydroxyl group in formula (5) are terminal groups bonded to different carbon atoms. This prevents the hydroxyl group in formula (5) from aggregating in close proximity to the hydroxyl groups in [A] and / or [B] due to the flexibility of the ether bond, or from becoming too hydrophilic in the fluorine-containing ether compound. Furthermore, when b is 4 or less, the hydrophobicity of the linking group is so high that it does not impair adhesion to the protective layer. In formula (5), b is preferably an integer of 3 to 4, which results in a fluorine-containing ether compound with more appropriate hydrophobicity.

[0037] In the fluorine-containing ether compound represented by the above formula (1), R 2 and R 3 is a perfluoropolyether chain (PFPE chain). 2 and R 3 When a lubricant containing the fluorine-containing ether compound of this embodiment is applied to a protective layer to form a lubricating layer, the PFPE chains shown in Figure 1 coat the surface of the protective layer and impart lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. Furthermore, the PFPE chains, due to their low surface energy, impart water resistance to the lubricating layer containing the fluorine-containing ether compound of this embodiment, thereby improving the corrosion resistance of a magnetic recording medium provided with a lubricating layer.

[0038] R 2 and R 3 is a PFPE chain and can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound, etc. Examples of the PFPE chain include perfluoromethylene oxide polymer, perfluoroethylene oxide polymer, perfluoro-n-propylene oxide polymer, perfluoroisopropylene oxide polymer, and copolymers thereof.

[0039] Specifically, R in formula (1)2 and R 3 is preferably any one of the following formulas (6) to (8). The arrangement order of the repeating units (CF2CF2O) and (CF2O) in formula (6) is not particularly limited. Formula (6) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CF2-CF2-O) and (CF2-O).

[0040] -CF2O-(CF2CF2O) c -(CF2O) d -CF2- (6) (In formula (6), c and d each represent an average degree of polymerization and represent 0 to 20; provided that c or d is 0.1 or more.) -CF2CF2O-(CF2CF2CF2O) e -CF2CF2- (7) (In formula (7), e represents the average degree of polymerization and represents 0.1 to 20.) -CF2CF2CF2O-(CF2CF2CF2CF2O) f -CF2CF2CF2- (8) (In formula (8), f represents the average degree of polymerization and represents 0.1 to 10.)

[0041] In formula (6), c and d, which represent the average degree of polymerization, are each 0 to 20 (provided that c or d is 0.1 or greater). In formula (7), e, which represents the average degree of polymerization, is 0.1 to 20. In formula (8), f, which represents the average degree of polymerization, is 0.1 to 10. When c, d, e, and f are 0.1 or greater, the resulting fluorine-containing ether compound provides a lubricating layer that has good wear resistance and can further inhibit corrosion of magnetic recording media. Furthermore, when c, d, and e are each 20 or less and f is 10 or less, the viscosity of the fluorine-containing ether compound is not too high, making it easier to apply a lubricant containing the fluorine-containing ether compound. The average degrees of polymerization c, d, e, and f are each preferably 2 to 10, more preferably 3 to 8, because the resulting fluorine-containing ether compound easily spreads on the protective layer and provides a lubricating layer with a uniform thickness. c, d, and e may each be 0.5 to 18, 1 to 16, 3 to 14, 4 to 7, or 5 to 6, as needed. f may each be 1 to 10, 2 to 9, 3 to 8, 3 to 6, 4 to 7, or 5 to 6, as needed.

[0042] R in Equation (1) 2 and R 3 is any one of formulas (6) to (8), the synthesis of the fluorine-containing ether compound is easy, which is preferable. 2 and R 3 is formula (6) or formula (7), it is more preferable because raw materials are easily available. Also, R 2 and R 3 When is any one of formulas (6) to (8), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the perfluoropolyether chain is appropriate. This results in a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage.

[0043] In the fluorine-containing ether compound represented by formula (1), R 2 and R 3The PFPE chains represented by R may be the same or different. 2 and R 3 When these are the same, the synthesis of the fluorine-containing ether compound is easy, which is preferable. Furthermore, R 2 and R 3 and R 1 and R 4 The fluorine-containing ether compound, which is the same as R, has a symmetrical structure with the glycerin structure at the center, and therefore is more likely to wet and spread evenly on the protective layer, making it easier to obtain a lubricating layer with a uniform thickness, which is more preferable. 2 and R 3 and R 1 and R 4 The fluorine-containing ether compound can be easily and efficiently produced with a small number of production steps.

[0044] In the fluorine-containing ether compound represented by formula (1), the hydroxyl group (-OH) of the glycerin structure (-OCH2CH(OH)CHO-) located at the center of the chain structure improves the adhesion of the lubricating layer containing the fluorine-containing ether compound to the protective layer. Furthermore, the oxygen atoms at both ends of the glycerin structure bond with the methylene groups (-CH2-) on both sides to form ether bonds (-O-). These two ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increase the affinity between the hydroxyl groups of the glycerin structure and the protective layer.

[0045] In addition, in the fluorine-containing ether compound represented by formula (1), the glycerin structure located at the center of the chain structure and R 1 and R 4 and a perfluoropolyether chain (R 2 and R 3 ) are arranged. Therefore, the hydroxyl group (-OH) of the glycerin structure and R 1 and R 4 Therefore, the distance between the hydroxyl group of the glycerin structure and the polar group of the terminal group represented by R 1 and R4 The polar group of the terminal group represented by R is also unlikely to be inhibited from bonding with the active site on the protective layer by the adjacent polar group. 1 and R 4 The polar groups of the terminal groups represented by the formula (I) are all likely to be involved in bonding with the active sites on the protective layer. In other words, the polar groups of the fluorine-containing ether compound are unlikely to become polar groups that are not involved in bonding with the active sites on the protective layer. Therefore, the fluorine-containing ether compound can reduce the number of polar groups that are not involved in bonding with the active sites on the protective layer. As a result, the lubricating layer containing the fluorine-containing ether compound has a high coverage rate, and environmental substances that generate contaminants are less likely to penetrate through gaps, so corrosion of the magnetic recording medium can be suppressed.

[0046] In addition, in the above-mentioned fluorine-containing ether compound, the hydroxyl group of the glycerin structure and the R 1 and R 4 Since the distance between the polar group of the terminal group represented by R 1 and R 4 Moreover, both ends of each perfluoropolyether chain are bonded to the hydroxyl group of the glycerin structure and the polar group of the terminal group represented by R 1 and R 4 The fluorine-containing ether compound adheres to the protective layer through the polar group of the terminal group represented by the formula (I). Therefore, the fluorine-containing ether compound applied to the protective layer is unlikely to be bulky. Therefore, the fluorine-containing ether compound is likely to wet and spread on the protective layer, and a lubricating layer having a uniform coating state is likely to be obtained. As a result, the above-mentioned fluorine-containing ether compound can form a lubricating layer that has good wear resistance and can suppress corrosion of the magnetic recording medium.

[0047] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any of the compounds represented by the following formulae (1A) to (1M), (2A) to (2L), (3A) to (3L), and (4A). Note that ma1 to mm1, ma2 to mm2, na1 to nm1, and na2 to nm2 in formulae (1A) to (1M), m′a1 to m′l1 and m′a2 to m′l2 in formulae (2A) to (2L), pa1 to p11 and pa2 to p12 in formulae (3A) to (3L), and qa1 and qa2 in formula (4A) are values ​​indicating the average degree of polymerization and are not necessarily integers.

[0048] The compounds represented by the following formulas (1A) to (1L) are all R 1 and R 4 The compounds represented by the following formulas (1A) to (1M) are all R 2 and R 3 is the same, and R 2 and R 3 is the PFPE chain represented by the above formula (6). -CH2-R in the following formulas (1A) to (1K) and (1M): 1 are all represented by formula (2), and the bond order in formula (2) is represented by -CH2-[A]-[B]-OZ.

[0049] In the compound represented by the following formula (1A), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). In formula (5), b is 2. In the compound represented by the following formula (1B), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (1C), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5).

[0050] In the compound represented by the following formula (1D), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (1E), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (1F), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5).

[0051] In the compound represented by the following formula (1G), X in formula (3) is 0, Y in formula (4) is 1, a is 1, and Z is a hydrogen atom. In the compound represented by the following formula (1H), X in formula (3) is 0, Y in formula (4) is 1, a is 2, and Z is a hydrogen atom. In the compound represented by the following formula (1I), X in formula (3) is 0, Y in formula (4) is 1, a is 4, and Z is a hydrogen atom.

[0052] In the compound represented by the following formula (1J), X in formula (3) is 1, Y in formula (4) is 1, a is 1, and Z is a hydrogen atom. In the compound represented by the following formula (1K), X in formula (3) is 0, Y in formula (4) is 1, a is 1, and Z is formula (5). The compound represented by the following formula (1L) is -CH2-R 1 is a group represented by formula (2), and the bonding order in formula (2) is represented by -CH2-[B]-[A]-OZ. X in formula (3) is 1, Y in formula (4) is 1, a is 2, and Z is formula (5). b in formula (5) is 2. The compound represented by the following formula (1M) is -CH2-R 1 is a group represented by formula (2), X in formula (3) is 1, Y in formula (4) is 0, Z is formula (5), and b in formula (5) is 2. 4 is a group represented by formula (2), X in formula (3) is 0, Y in formula (4) is 1, a is 2, and Z is H.

[0053] The compounds represented by the following formulas (2A) to (2L) are all R 1 and R 4 The compounds represented by the following formulas (2A) to (2L) are all R 2 and R 3 is the same, and R 2 and R 3is the above formula (6), and d in the above formula (6) is a PFPE chain represented by 0. -CH2-R in the following formulas (2A) to (2K) 1 are all represented by formula (2), and the bond order in formula (2) is represented by -CH2-[A]-[B]-OZ.

[0054] In the compound represented by the following formula (2A), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (2B), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (2C), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5).

[0055] In the compound represented by the following formula (2D), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (2E), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (2F), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5).

[0056] In the compound represented by the following formula (2G), X in formula (3) is 0, Y in formula (4) is 1, a is 1, and Z is a hydrogen atom. In the compound represented by the following formula (2H), X in formula (3) is 0, Y in formula (4) is 1, a is 2, and Z is a hydrogen atom. In the compound represented by the following formula (2I), X in formula (3) is 0, Y in formula (4) is 1, a is 4, and Z is a hydrogen atom.

[0057] In the compound represented by the following formula (2J), X in formula (3) is 1, Y in formula (4) is 1, a is 1, and Z is a hydrogen atom. In the compound represented by the following formula (2K), X in formula (3) is 0, Y in formula (4) is 1, a is 1, and Z is formula (5). The compound represented by the following formula (2L) is -CH2-R 1 is a group represented by formula (2), and the bonding order in formula (2) is represented by -CH2-[B]-[A]-OZ. X in formula (3) is 1, Y in formula (4) is 1, a is 2, and Z is formula (5). b in formula (5) is 2.

[0058] The compounds represented by the following formulas (3A) to (3L) are all R 1 and R 4 The compounds represented by the following formulae (3A) to (3L) are all R 2 and R 3 is the same, and R 2 and R 3 is the PFPE chain represented by the above formula (7). -CH2-R in the following formulas (3A) to (3K) 1 are all represented by formula (2), and the bond order in formula (2) is represented by -CH2-[A]-[B]-OZ.

[0059] In the compound represented by the following formula (3A), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (3B), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (3C), X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5).

[0060] In the compound represented by the following formula (3D), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (3E), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5). In the compound represented by the following formula (3F), X in formula (3) is 2, Y in formula (4) is 0, and Z is formula (5).

[0061] In the compound represented by the following formula (3G), X in formula (3) is 0, and Y in formula (4) is 1, a is 1, and Z is a hydrogen atom. In the compound represented by the following formula (3H), X in formula (3) is 0, Y in formula (4) is 1, a is 2, and Z is a hydrogen atom. In the compound represented by the following formula (3I), X in formula (3) is 0, Y in formula (4) is 1, a is 4, and Z is a hydrogen atom.

[0062] In the compound represented by the following formula (3J), X in formula (3) is 1, Y in formula (4) is 1, a is 1, and Z is a hydrogen atom. In the compound represented by the following formula (3K), X in formula (3) is 0, Y in formula (4) is 1, a is 1, and Z is formula (5). The compound represented by the following formula (3L) is -CH2-R 1 is a group represented by formula (2), and the bonding order in formula (2) is represented by -CH2-[B]-[A]-OZ. X in formula (3) is 1, Y in formula (4) is 1, a is 2, and Z is formula (5). b in formula (5) is 2.

[0063] The compound represented by the following formula (4A) is R 1 and R 4 is the same, and R 2 and R 3 is the same, and R 2 and R 3 is the PFPE chain represented by the above formula (8). The compound represented by the following formula (4A) is -CH2-R 1 is a group represented by formula (2), and the bonding order in formula (2) is represented by -CH2-[A]-[B]-OZ. X in formula (3) is 1, Y in formula (4) is 0, and Z is formula (5). b in formula (5) is 2.

[0064] [ka] (In formula (1A), ma1, ma2, na1, and na2 represent average degrees of polymerization, ma1 and ma2 represent 0.1 to 20, and na1 and na2 represent 0.1 to 20.) (In formula (1B), mb1, mb2, nb1, and nb2 represent average degrees of polymerization, mb1 and mb2 represent 0.1 to 20, and nb1 and nb2 represent 0.1 to 20.) (In formula (1C), mc1, mc2, nc1, and nc2 represent average degrees of polymerization, mc1 and mc2 represent 0.1 to 20, and nc1 and nc2 represent 0.1 to 20.)

[0065] [ka] (In formula (1D), md1, md2, nd1, and nd2 represent average degrees of polymerization, md1 and md2 represent 0.1 to 20, and nd1 and nd2 represent 0.1 to 20.) (In formula (1E), me1, me2, ne1, and ne2 represent average degrees of polymerization, me1 and me2 represent 0.1 to 20, and ne1 and ne2 represent 0.1 to 20.) (In formula (1F), mf1, mf2, nf1, and nf2 represent average degrees of polymerization, mf1 and mf2 represent 0.1 to 20, and nf1 and nf2 represent 0.1 to 20.)

[0066] [ka] (In formula (1G), mg1, mg2, ng1, and ng2 represent average degrees of polymerization, mg1 and mg2 represent 0.1 to 20, and ng1 and ng2 represent 0.1 to 20.) (In formula (1H), mh1, mh2, nh1, and nh2 represent average degrees of polymerization, mh1 and mh2 represent 0.1 to 20, and nh1 and nh2 represent 0.1 to 20.) (In formula (1I), mi1, mi2, ni1, and ni2 represent average degrees of polymerization, mi1 and mi2 represent 0.1 to 20, and ni1 and ni2 represent 0.1 to 20.)

[0067] [ka] (In formula (1J), mj1, mj2, nj1, and nj2 represent average degrees of polymerization, mj1 and mj2 represent 0.1 to 20, and nj1 and nj2 represent 0.1 to 20.) (In formula (1K), mk1, mk2, nk1, and nk2 represent average degrees of polymerization, mk1 and mk2 represent 0.1 to 20, and nk1 and nk2 represent 0.1 to 20.) (In formula (1L), ml1, ml2, nl1, and nl2 represent the average degree of polymerization, ml1 and ml2 represent 0.1 to 20, and nl1 and nl2 represent 0.1 to 20.) (In formula (1M), mm1, mm2, nm1, and nm2 represent the average degree of polymerization, mm1 and mm2 represent 0.1 to 20, and nm1 and nm2 represent 0.1 to 20.)

[0068] [ka] (In formula (2A), m′a1 and m′a2 represent average degrees of polymerization, and m′a1 and m′a2 represent 0.1 to 20.) (In formula (2B), m′b1 and m′b2 represent average degrees of polymerization, and m′b1 and m′b2 represent 0.1 to 20.) (In formula (2C), m′c1 and m′c2 represent the average degree of polymerization, and m′c1 and m′c2 represent 0.1 to 20.)

[0069] [ka] (In formula (2D), m′d1 and m′d2 represent average degrees of polymerization, and m′d1 and m′d2 represent 0.1 to 20.) (In formula (2E), m'e1 and m'e2 represent the average degree of polymerization, and m'e1 and m'e2 represent 0.1 to 20.) (In formula (2F), m′f1 and m′f2 represent the average degree of polymerization, and m′f1 and m′f2 represent 0.1 to 20.)

[0070] [ka] (In formula (2G), m′g1 and m′g2 represent the average degree of polymerization, and m′g1 and m′g2 represent 0.1 to 20.) (In formula (2H), m′h1 and m′h2 represent the average degree of polymerization, and m′h1 and m′h2 represent 0.1 to 20.) (In formula (2I), m′i1 and m′i2 represent the average degree of polymerization, and m′i1 and m′i2 represent 0.1 to 20.)

[0071] [ka] (In formula (2J), m′j1 and m′j2 represent the average degree of polymerization, and m′j1 and m′j2 represent 0.1 to 20.) (In formula (2K), m′k1 and m′k2 represent the average degree of polymerization, and m′k1 and m′k2 represent 0.1 to 20.) (In formula (2L), m′l1 and m′l2 represent the average degree of polymerization, and m′l1 and m′l2 represent 0.1 to 20.)

[0072] [ka] (In formula (3A), pa1 and pa2 represent the average degree of polymerization, and pa1 and pa2 represent 0.1 to 20.) (In formula (3B), pb1 and pb2 represent the average degree of polymerization, and pb1 and pb2 represent 0.1 to 20.) (In formula (3C), pc1 and pc2 represent the average degree of polymerization, and pc1 and pc2 represent 0.1 to 20.)

[0073] [ka] (In formula (3D), pd1 and pd2 represent the average degree of polymerization, and pd1 and pd2 represent 0.1 to 20.) (In formula (3E), pe1 and pe2 represent the average degree of polymerization, and pe1 and pe2 represent 0.1 to 20.) (In formula (3F), pf1 and pf2 represent the average degree of polymerization, and pf1 and pf2 represent 0.1 to 20.)

[0074] [ka] (In formula (3G), pg1 and pg2 represent the average degree of polymerization, and pg1 and pg2 represent 0.1 to 20.) (In formula (3H), ph1 and ph2 represent the average degree of polymerization, and ph1 and ph2 represent 0.1 to 20.) (In formula (3I), pi1 and pi2 represent the average degree of polymerization, and pi1 and pi2 represent 0.1 to 20.)

[0075] [ka] (In formula (3J), pj1 and pj2 represent the average degree of polymerization, and pj1 and pj2 represent 0.1 to 20.) (In formula (3K), pk1 and pk2 represent the average degree of polymerization, and pk1 and pk2 represent 0.1 to 20.) (In formula (3L), p11 and p12 represent the average degree of polymerization, and p11 and p12 represent 0.1 to 20.) (In formula (4A), qa1 and qa2 represent the average degree of polymerization, and qa1 and qa2 represent 0.1 to 10.)

[0076] When the compound represented by formula (1) is any of the compounds represented by the above formulas (1A) to (1M), (2A) to (2L), (3A) to (3L), and (4A), the raw materials are easily available, and a lubricating layer that can suppress corrosion of the magnetic recording medium can be formed even if it is thin, which is preferable.

[0077] The fluorine-containing ether compound of this embodiment can be selected arbitrarily, but preferably has a number-average molecular weight (Mn) in the range of 500 to 10,000, more preferably in the range of 700 to 7,000, and particularly preferably in the range of 1,000 to 5,000. When the number-average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of this embodiment is less likely to evaporate, preventing the lubricant from evaporating and transferring to the magnetic head. Furthermore, when the number-average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound is appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing this compound. A number-average molecular weight of 5,000 or less is more preferred because it results in a viscosity that is easy to handle when applied to a lubricant. The number average molecular weight may be, for example, in the range of 1000 to 4500, 1200 to 4000, 1400 to 3500, 1600 to 3000, 1800 to 2800, 2000 to 2600, or 2100 to 2500.

[0078] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 This is a value measured by F-NMR. In NMR (nuclear magnetic resonance) measurements, samples were diluted in a single or mixed solvent such as hexafluorobenzene, d-acetone, or d-tetrahydrofuran and used for the measurements. 19 The reference for F-NMR chemical shifts was set to −164.7 ppm for the hexafluorobenzene peak. 1 The reference for H-NMR chemical shifts was the acetone peak at 2.2 ppm.

[0079] "Manufacturing method" The method for producing the fluorinated ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorinated ether compound of the present embodiment can be produced, for example, by the production method shown below.

[0080] R 1 and R 4 and R2 and R 3 In order to prepare a compound in which two PFPE chains represented by the formula (1) are the same, first, 2 (=R 3 A fluorine-based compound is prepared in which a hydroxymethyl group (-CHOH) is arranged at each end of a perfluoropolyether chain corresponding to the -R 1 (=-R 4 ) (first reaction). 2 (=R 3 ) at one end of the perfluoropolyether chain corresponding to -R 1 (=-R 4 ) is obtained. -R 1 (=-R 4 The epoxy compound having a group consisting of (a) may be reacted with the above fluorine-based compound after protecting the hydroxyl group with an appropriate protecting group.

[0081] Thereafter, the hydroxyl group of the hydroxymethyl group located at the terminal of the intermediate compound is reacted with epibromohydrin to obtain an epoxy compound, and the terminal hydroxyl group of another molecule of the intermediate compound is then reacted with this epoxy compound (second reaction). By carrying out the above steps, a polymer having a glycerin structure at the center of a chain structure and represented by the formula (1) R 1 and R 4 and R 2 and R 3 Two PFPE chains shown below can produce the same compound.

[0082] R 1 and R 4 , R 2 and R 3 When one or more of the two PFPE chains represented by the formula (1) are different, R 1 and R 4 and R 2 and R 3In the same manner as in the case of preparing a compound in which two PFPE chains represented by 2 -R at one end of the perfluoropolyether chain corresponding to 1 A first intermediate compound is prepared having a group corresponding to:

[0083] Next, add -R to one end 1 In the same manner as the first intermediate compound having a group corresponding to 3 -R at one end of the perfluoropolyether chain corresponding to 4 A second intermediate compound is prepared having a group corresponding to: Thereafter, the first intermediate compound is reacted with epibromohydrin to produce an epoxy compound, which is then reacted with a second intermediate compound. By carrying out the above steps, a polymer having a glycerin structure at the center of a chain structure and represented by the formula (1) R 1 and R 4 , R 2 and R 3 Compounds can be prepared in which one or more of the two PFPE chains shown in By the above method, the compound represented by formula (1) can be obtained.

[0084] The epoxy compound used in producing the fluorinated ether compound of the present embodiment may be, for example, an epoxy compound having -R 1 (or -R 4 ) with a compound having an epoxy group selected from epichlorohydrin, epibromohydrin, 2-bromoethyloxirane, and allyl glycidyl ether. Such epoxy compounds may be synthesized by oxidizing an unsaturated bond, or may be purchased commercially.

[0085] Here, the function of the lubricating layer formed on the protective layer using the lubricant containing the fluorine-containing ether compound of this embodiment will be described. One cause of corrosion of magnetic recording media is ionic contaminants present on the surface of the magnetic recording medium. Most ionic contaminants are externally attached during the manufacturing process of the magnetic recording medium. Ionic contaminants can also be generated when environmental substances that enter a hard disk drive (magnetic recording / reproducing device) adhere to the magnetic recording medium. Specifically, for example, when a magnetic recording medium and / or a hard disk drive are maintained under high temperature and humidity conditions, water containing environmental substances such as ions can adhere to the surface of the magnetic recording medium. When water containing environmental substances such as ions passes through the lubricating layer formed on the surface of the magnetic recording medium, it condenses minute ionic components present below the lubricating layer, generating ionic contaminants.

[0086] The fluorine-containing ether compound of this embodiment is a compound represented by formula (1), and therefore a lubricating layer containing this compound has a high corrosion-inhibiting effect on magnetic recording media. The corrosion-inhibiting effect on magnetic recording media is based on the synergistic effect of the fact that a lubricating layer formed on a protective layer using a lubricant containing the fluorine-containing ether compound of this embodiment has excellent adhesion to the protective layer, excellent water resistance, appropriate hydrophobicity, and is easily formed on the protective layer in a uniform coating state.

[0087] More specifically, the lubricating layer formed on the protective layer is a fluorine-containing ether compound represented by formula (1) having a hydroxyl group (-OH) of a glycerin structure (-OCH2CH(OH)CHO-) located at the center of the chain structure, and a hydroxyl group (-OH) of R 1 and R 4 The lubricating layer adheres to the protective layer through the polar groups contained in each of the two or three groups. As a result, the lubricating layer prevents contaminants from penetrating the magnetic recording medium, thereby suppressing corrosion of the magnetic recording medium.

[0088] In the fluorine-containing ether compound represented by formula (1), the hydroxyl group of the glycerin structure located at the center of the chain structure and the R 1 and R 4 Between the terminal group represented by R 2 and R 3 Therefore, the hydroxyl group of the glycerin structure and the PFPE chain represented by R1 and R 4 As a result, the distance between the hydroxyl group of the glycerin structure and the polar group of the terminal group represented by R 1 and R 4 The fluorine-containing ether compound represented by formula (1) is unlikely to aggregate with the polar group of the terminal group represented by formula (1), and adheres to the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) easily spreads on the protective layer, and a lubricating layer containing the compound is likely to be formed in a uniform coating state. The lubricating layer formed in a uniform coating state has a high coverage rate, is less susceptible to the penetration of environmental substances that generate contaminants through gaps, and suppresses corrosion of the magnetic recording medium.

[0089] The fluorine-containing ether compound represented by formula (1) is R 2 and R 3 The lubricating layer contains a PFPE chain represented by the formula: 2 and R 3 The PFPE chains represented by formula (1) coat the surface of the protective layer and, due to their low surface energy, impart water resistance to the lubricating layer. Therefore, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) is impervious to water and can prevent water from penetrating into the magnetic recording medium, thereby improving the corrosion resistance of the magnetic recording medium.

[0090] Furthermore, in the fluorine-containing ether compound represented by formula (1), R 1 and R 4 Each polar group contained in is bonded to a different carbon atom, and the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom not bonded to a polar group. Under high temperature and humidity conditions, fluorine-containing ether compounds undergo thermal molecular motion, and water is thought to penetrate through the gaps between the molecules. For this reason, the R group located at the end of the molecule 1 and R 4 Each of the compounds has two or three polar groups, and the hydrophobicity of the carbon atoms to which the polar groups are bonded and the carbon atoms contained in the linking group determines the hydrophobicity of the lubricating layer containing the fluorine-containing ether compound represented by formula (1). As a result, the lubricating layer prevents water from penetrating into the magnetic recording medium, thereby suppressing corrosion of the magnetic recording medium.

[0091] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by formula (1). The lubricant of the present embodiment can be used by mixing, as needed, known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorinated ether compound represented by formula (1) are not impaired.

[0092] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of the present embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0093] When the lubricant of this embodiment contains a material other than the fluorinated ether compound represented by formula (1), the content of the fluorinated ether compound represented by formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more. The content of the fluorinated ether compound represented by formula (1) may be 80% by mass or more, or 90% by mass or more. However, it is not limited to these examples.

[0094] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1), and therefore can form a lubricating layer that is highly effective in inhibiting corrosion of magnetic recording media. The lubricating layer made of the lubricant of this embodiment has a high corrosion-inhibiting effect on magnetic recording media, and therefore can be made thin.

[0095] [Magnetic recording media] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer, if necessary. An adhesive layer and / or a soft magnetic layer may also be provided between the underlayer and the substrate.

[0096] FIG. 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0097] "substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. The substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or may be a non-magnetic substrate having a NiP or NiP alloy film formed on a base made of any of these non-metallic materials.

[0098] "Adhesion layer" The adhesive layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are disposed in contact with each other. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0099] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are antiferro-coupling (AFC).

[0100] The first and second soft magnetic films may be made of a material such as a CoZrTa alloy or a CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films, which promotes the amorphization of the first and second soft magnetic films, improves the orientation of the first underlayer (seed layer), and reduces the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0101] "First base layer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, or a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0102] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a single layer or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all of the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0103] "Magnetic layer" The magnetic layer 16 is a magnetic film with an easy axis of magnetization oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 contains Co and Pt, and may also contain oxides, Cr, B, Cu, Ta, Zr, or the like to further improve the SNR characteristics. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0104] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. The oxide contained in the first magnetic layer is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among these, TiO2, Cr2O3, SiO2, and the like are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide containing two or more types of oxides. Among these, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, and the like are particularly suitable.

[0105] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re, in addition to Co, Cr, Pt, and oxides. The second magnetic layer may be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure.

[0106] The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0107] When magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0108] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0109] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, oxides that can be used include, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, and TiO2. Metal nitrides that can be used include, for example, AlN, Si3N4, TaN, and CrN. Metal carbides that can be used include, for example, TaC, BC, and SiC. The non-magnetic layer can be formed by, for example, a sputtering method.

[0110] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for longitudinal magnetic recording. The magnetic layer 16 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0111] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be made of a single layer or multiple layers. Examples of materials for the protective layer 17 include carbon, carbon containing nitrogen, and silicon carbide. A carbon-based protective layer, particularly an amorphous carbon protective layer, can be preferably used as the protective layer 17. When the protective layer 17 is a carbon-based protective layer, the interaction with the hydroxyl group contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0112] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0113] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of protective layer 17 and hydrogen is contained on the magnetic layer 16 side of protective layer 17. In this case, the adhesion between the magnetic layer 16 and lubricating layer 18 and the carbon-based protective layer is further improved.

[0114] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0115] The protective layer 17 can be formed by sputtering using a target material containing carbon, CVD (chemical vapor deposition) using a hydrocarbon raw material such as ethylene or toluene, or IBD (ion beam deposition). When a carbon-based protective layer is formed as protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed as protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface with little roughness.

[0116] "Lubricant layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. The lubricating layer 18 also reduces the frictional force of the magnetic head of the magnetic recording / reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 1, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 contains the above-mentioned fluorine-containing ether compound.

[0117] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 bonds with the protective layer 17 with particularly high bonding strength. As a result, even if the thickness of the lubricating layer 18 is thin, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0118] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.0 nm (10 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. This allows the lubricating layer 18 to cover the surface of the protective layer 17 with a high coverage. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0119] If the surface of the protective layer 17 is not covered with the lubricating layer 18 at a sufficiently high coverage rate, environmental substances adsorbed to the surface of the magnetic recording medium 10 will pass through the gaps in the lubricating layer 18 and penetrate underneath the lubricating layer 18. The environmental substances that penetrate underneath the lubricating layer 18 will adsorb and bond to the protective layer 17, generating contaminants. The generated contaminants (aggregated components) will adhere (transfer) to the magnetic head as smear during magnetic recording and playback, damaging the magnetic head or degrading the magnetic recording and playback characteristics of the magnetic recording and playback device.

[0120] Environmental substances that generate contaminants include, for example, siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, hydrocarbons with relatively high molecular weights such as octacosane, and plasticizers such as dioctyl phthalate. Examples of metal ions contained in ionic impurities include sodium ions and potassium ions. Examples of inorganic ions contained in ionic impurities include chloride ions, bromide ions, nitrate ions, sulfate ions, and ammonium ions. Examples of organic ions contained in ionic impurities include oxalate ions and formate ions.

[0121] "Method for forming lubricating layer" A method for forming the lubricating layer 18 includes, for example, preparing a magnetic recording medium in the middle of manufacturing in which all layers up to the protective layer 17 are formed on the substrate 11, applying a solution for forming a lubricating layer onto the protective layer 17, and drying the solution.

[0122] The lubricant layer forming solution can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium according to the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.).

[0123] The method for applying the lubricating layer-forming solution is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in a lubricant layer-forming solution placed in an immersion tank of a dip coating device. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricating layer forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0124] In this embodiment, a burnishing (precision polishing) step is preferably performed after forming the lubricating layer 18 on the surface of the substrate 11. By performing the burnishing step, protruding defects and particles present on the surface of the substrate 11 on which the lubricating layer 18 has been formed can be removed, resulting in a magnetic recording medium 10 with a smooth surface. A smooth surface of the magnetic recording medium 10 is preferable because it reduces spacing loss with the magnetic head and improves signal characteristics.

[0125] The burnishing step can be, for example, a step of scanning a burnishing tape over the surface of the substrate 11 on which the lubricating layer 18 has been formed. The burnishing tape can be, for example, a resin film holding abrasive grains. The grain size of the abrasive grains can be, for example, #6000 to #20000.

[0126] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100 to 180° C. If the heat treatment temperature is 100° C. or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180° C. or lower, thermal decomposition of the lubricating layer 18 can be prevented. The heat treatment time is preferably 10 to 120 minutes.

[0127] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed on and in contact with the protective layer 17. This lubricating layer 18 is highly effective in suppressing corrosion of the magnetic recording medium 10. As a result, the magnetic recording medium 10 of this embodiment has few contaminants present on its surface, excellent corrosion resistance, and good reliability and durability. Furthermore, because the magnetic recording medium 10 of this embodiment has a lubricating layer 18 with a high corrosion suppression effect, the thickness of the protective layer 17 and / or the lubricating layer 18 can be reduced. Furthermore, the lubricating layer 18 in the magnetic recording medium 10 of this embodiment is less likely to produce foreign matter (smear), thereby suppressing pickup. [Example]

[0128] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0129] [Example 1] The compound represented by the above formula (1A) was produced by the method shown below. Under a nitrogen gas atmosphere, place HOCH2CF2O (CF2CF2O) in a 200 mL recovery flask. m (CF2O) n 20 g of a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where m, representing the average degree of polymerization, is 4.5, and n, representing the average degree of polymerization, is 4.5), 2.4 g of a compound (molecular weight 202.3, 12 mmol) represented by the following formula (9), and 19 mL of t-butanol were charged and stirred at room temperature until homogeneous. 0.67 g of potassium tert-butoxide (molecular weight 112.21, 6 mmol) was further added to this homogeneous solution, and the mixture was reacted at 70°C for 16 hours with stirring.

[0130] The compound represented by formula (9) was synthesized by oxidizing a compound in which ethylene glycol monoallyl ether was protected with dihydropyran. The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 9.6 g (molecular weight 1202.3, 8.0 mmol) of the compound represented by the following formula (10) as an intermediate.

[0131] [ka] (In formula (9), THP represents a tetrahydropyranyl group.) (In formula (10), m, which represents the average degree of polymerization, is 4.5, and n, which represents the average degree of polymerization, is 4.5. In formula (10), THP represents a tetrahydropyranyl group.)

[0132] Under a nitrogen gas atmosphere, 9.6 g (molecular weight 1202.3, 8.0 mmol) of the intermediate compound represented by formula (10), 5.6 mL of t-butanol, and 0.539 g (molecular weight 112.21, 4.8 mmol) of potassium tert-butoxide were placed in a 200 mL recovery flask and stirred at room temperature until homogeneous. To this homogeneous solution, 0.27 mL (molecular weight 137, 3.3 mmol) of epibromohydrin was added and the mixture was stirred at 70°C for 24 hours to react.

[0133] After the reaction, the resulting reaction mixture was returned to room temperature, and 31 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 2 hours. The reaction mixture was gradually transferred to a separatory funnel containing 100 mL of brine and extracted three times with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated sodium bicarbonate solution, and 100 mL of brine, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography. Through these steps, 4.1 g (molecular weight 2292, 1.8 mmol) of compound (1A) was obtained. (In formula (1A), ma1, ma2, na1, and na2, which represent the average degree of polymerization, are 4.5.)

[0134] The obtained compound (1A) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.24(36H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0135] [Example 2] The same procedure as in Example 1 was carried out, except that 2.6 g of a compound represented by the following formula (11) was used instead of the compound represented by formula (9), to obtain 4.2 g of a compound represented by the above formula (1B) (in formula (1B), mb1, mb2, nb1, and nb2, which represent the average degree of polymerization, are 4.5). The compound represented by formula (11) was synthesized by protecting one hydroxyl group of 1,3-propanediol with a THP (tetrahydropyranyl) group and reacting the other hydroxyl group with epibromohydrin.

[0136] [ka] (In formula (11), THP represents a tetrahydropyranyl group.)

[0137] The obtained compound (1B) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.57~1.81(4H), 3.38~4.25(36H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0138] [Example 3] The same procedure as in Example 1 was carried out, except that 2.8 g of a compound represented by the following formula (12) was used instead of the compound represented by formula (9), to obtain 4.2 g of a compound represented by the above formula (1C) (in formula (1C), mc1, mc2, nc1, and nc2, which represent the average degree of polymerization, are 4.5). The compound represented by formula (12) was synthesized by protecting one hydroxyl group of 1,4-butanediol with a THP group and reacting the other hydroxyl group with epibromohydrin.

[0139] [ka] (In formula (12), THP represents a tetrahydropyranyl group.)

[0140] The obtained compound (1C) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.55~1.83(8H), 3.40~4.25(36H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0141] [Example 4] The same procedure as in Example 1 was carried out, except that 3.8 g of a compound represented by the following formula (13) was used instead of the compound represented by formula (9), to obtain 4.4 g of a compound represented by the above formula (1D) (in formula (1D), md1, md2, nd1, and nd2, which represent the average degree of polymerization, are 4.5).

[0142] [ka] (In formula (13), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0143] The compound represented by formula (13) was synthesized by the following method. A tert-butyldimethylsilyl (TBS) group was introduced as a protecting group to the primary hydroxyl group of 3-allyloxy-1,2-propanediol, and a methoxymethyl (MOM) group was introduced as a protecting group to the secondary hydroxyl group of the resulting compound. The TBS group was then removed from the compound, and the resulting primary hydroxyl group was reacted with 2-bromoethoxytetrahydropyran. The double bond of the resulting compound was then oxidized. The compound represented by formula (13) was obtained through these steps.

[0144] The obtained compound (1D) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.37~4.32(48H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0145] [Example 5] The same procedure as in Example 1 was carried out, except that 4.0 g of a compound represented by the following formula (14) was used instead of the compound represented by formula (9), to obtain 4.4 g of a compound represented by the above formula (1E) (in formula (1E), me1, me2, ne1, and ne2, which represent the average degree of polymerization, are 4.5).

[0146] [ka] (In formula (14), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0147] The compound represented by formula (14) was synthesized by the following method. A TBS group was introduced into the primary hydroxyl group of 3-allyloxy-1,2-propanediol, and a MOM group was introduced into the secondary hydroxyl group of the resulting compound. After removing the TBS group from the resulting compound, the resulting primary hydroxyl group was reacted with 2-(chloropropoxy)tetrahydro-2H-pyran. The double bond of the resulting compound was oxidized. Through these steps, a compound represented by formula (14) was obtained.

[0148] The obtained compound (1E) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.50~1.80(4H), 3.40~4.25(48H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0149] [Example 6] The same procedure as in Example 1 was carried out, except that 4.2 g of a compound represented by the following formula (15) was used instead of the compound represented by formula (9), to obtain 4.5 g of a compound represented by the above formula (1F) (in formula (1F), mf1, mf2, nf1, and nf2, which represent the average degree of polymerization, are 4.5).

[0150] [ka] (In formula (15), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0151] The compound represented by formula (15) was synthesized by the following method. A TBS group was introduced into the primary hydroxyl group of 3-allyloxy-1,2-propanediol, and a MOM group was introduced into the secondary hydroxyl group of the resulting compound. After removing the TBS group from the resulting compound, the resulting primary hydroxyl group was reacted with 2-(bromobutoxy)tetrahydro-2H-pyran. The double bond of the resulting compound was oxidized. Through these steps, a compound represented by formula (15) was obtained.

[0152] The obtained compound (1F) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.52~1.81(8H), 3.44~4.26(48H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0153] [Example 7] The same procedure as in Example 1 was carried out, except that 2.1 g of a compound represented by the following formula (16) was used instead of the compound represented by formula (9), to obtain 4.0 g of a compound represented by the above formula (1G) (in formula (1G), mg1, mg2, ng1, and ng2, which represent the average degree of polymerization, are 4.5). The compound represented by formula (16) was synthesized by introducing a THP group into the primary hydroxyl group of 3-buten-1-ol and oxidizing the double bond of the resulting compound.

[0154] [ka] (In formula (16), THP represents a tetrahydropyranyl group.)

[0155] The obtained compound (1G) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.50~4.32(32H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0156] [Example 8] The same procedure as in Example 1 was carried out, except that 2.2 g of a compound represented by the following formula (17) was used instead of the compound represented by formula (9), to obtain 4.1 g of a compound represented by the above formula (1H) (in formula (1H), mh1, mh2, nh1, and nh2, which represent the average degree of polymerization, are 4.5). The compound represented by formula (17) was synthesized by introducing a THP group into the primary hydroxyl group of 4-penten-1-ol and oxidizing the double bond of the resulting compound.

[0157] [ka] (In formula (17), THP represents a tetrahydropyranyl group.)

[0158] The obtained compound (1H) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.38~1.75(4H), 3.37~4.31(32H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0159] [Example 9] The same procedure as in Example 1 was carried out, except that 2.6 g of a compound represented by the following formula (18) was used instead of the compound represented by formula (9), to obtain 4.2 g of a compound represented by the above formula (1I) (in formula (1I), mi1, mi2, ni1, and ni2, which represent the average degree of polymerization, are 4.5). The compound represented by formula (18) was synthesized by introducing a THP group into the primary hydroxyl group of 6-hepten-1-ol and oxidizing the double bond of the resulting compound.

[0160] [ka] (In formula (18), THP represents a tetrahydropyranyl group.)

[0161] The obtained compound (1I) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.39~1.84(12H), 3.35~4.35(32H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0162] [Example 10] The same procedure as in Example 1 was carried out, except that 3.0 g of a compound represented by the following formula (19) was used instead of the compound represented by formula (9), to obtain 4.3 g of a compound represented by the above formula (1J) (in formula (1J), mj1, mj2, nj1, and nj2, which represent the average degree of polymerization, are 4.5).

[0163] [ka] (In formula (19), Ph represents a phenyl group.)

[0164] The compound represented by formula (19) was synthesized by the following method. 1,2,4-butanetriol was reacted with benzaldehyde dimethyl acetal to synthesize a compound in which the hydroxyl groups bonded to the 2- and 4-carbon positions of 1,2,4-butanetriol were protected. This compound was reacted with epibromohydrin to synthesize the compound represented by formula (19).

[0165] The obtained compound (1J) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.38~4.36(44H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0166] [Example 11] The same procedure as in Example 1 was carried out, except that 2.8 g of a compound represented by the following formula (20) was used instead of the compound represented by formula (9), to obtain 4.2 g of a compound represented by the above formula (1K) (in formula (1K), mk1, mk2, nk1, and nk2, which represent the average degree of polymerization, are 4.5).

[0167] [ka] (In formula (20), THP represents a tetrahydropyranyl group.)

[0168] The compound represented by formula (20) was synthesized by the following method. It was synthesized by the reaction of 3-buten-1-ol with 2-(3-bromopropoxy)tetrahydro-2H-pyran, followed by oxidation of the double bond of the compound obtained.

[0169] The obtained compound (1K) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.79(4H), 3.36~4.32(40H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0170] [Example 12] The same procedure as in Example 1 was carried out, except that 4.7 g of a compound represented by the following formula (21) was used instead of the compound represented by formula (9), to obtain 4.5 g of a compound represented by the above formula (1L) (in formula (1L), ml1, ml2, nl1, and nl2, which represent the average degree of polymerization, are 4.5).

[0171] [ka] (In formula (21), THP represents a tetrahydropyranyl group.)

[0172] The compound represented by formula (21) was synthesized by reacting the compound represented by formula (9) with the hydroxyl group of 4-penten-1-ol, protecting the secondary hydroxyl group with a THP group, and oxidizing the double bond of the resulting compound.

[0173] The obtained compound (1L) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.55~1.78(4H), 3.36~4.25(52H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0174] [Example 13] The intermediate of Example 13 (molecular weight 1186.2, 4.0 mmol) was obtained in the same manner as the intermediate of Example 1, except that the compound represented by the formula (17) above was used instead of the compound represented by the formula (9).

[0175] Under a nitrogen gas atmosphere, 4.8 g (molecular weight 1202.3, 4.0 mmol) of the compound represented by formula (10), which is the intermediate of Example 1, 5.6 mL of t-butanol, and 0.45 g (molecular weight 112.21, 4.0 mmol) of potassium tert-butoxide were placed in a 200 mL recovery flask and stirred at room temperature until homogeneous. To this homogeneous solution, 0.33 mL (molecular weight 137, 4.0 mmol) of epibromohydrin was added, and the mixture was stirred at 70°C for 24 hours to react.

[0176] To the resulting reaction solution, 4.75 g of the intermediate of Example 13 was added and stirred until homogenous. To this homogenous solution, 0.45 g (molecular weight 112.21, 4.0 mmol) of potassium tert-butoxide was added and reacted with stirring at 70°C for 24 hours.

[0177] After the reaction, the resulting reaction mixture was returned to room temperature, and 33 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 2 hours. The reaction mixture was gradually transferred to a separatory funnel containing 100 mL of brine and extracted three times with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated sodium bicarbonate solution, and 100 mL of brine, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography. Through these steps, 4.1 g (molecular weight 2276.4, 1.8 mmol) of compound (1M) was obtained. (In formula (1M), mm1, mm2, nm1, and nm2, which represent the average degree of polymerization, are 4.5.)

[0178] The obtained compound (1M) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.38~1.75(2H), 3.37~4.31(34H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0179] [Example 14] The compound represented by the above formula (2A) was produced by the method shown below. HOCHCFO(CFCFO) of Example 1 m (CF2O) n Instead of the compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where m, which indicates the average degree of polymerization, is 4.5, and n, which indicates the average degree of polymerization, is 4.5), HOCH2CF2O(CF2CF2O) m′ (CF2O) n′ The same procedure as in Example 1 was carried out except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (in the formula, m', which indicates the average degree of polymerization, is 7.1, and n', which indicates the average degree of polymerization, is 0) was used, to obtain 4.0 g of compound (2A) (in formula (2A), m'a1 and m'a2, which indicate the average degree of polymerization, are 7.1).

[0180] The obtained compound (2A) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.24(36H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0181] [Example 15] The compound represented by the above formula (2B) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the above formula (11) was used instead of the compound represented by the above formula (9), to obtain 4.2 g of compound (2B) (in formula (2B), m'b1 and m'b2, which represent the average degree of polymerization, are 7.1).

[0182] The obtained compound (2B) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1H-NMR(CD3COCD3):δ[ppm]=1.57~1.81(4H), 3.38~4.25(36H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0183] [Example 16] The compound represented by the above formula (2C) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the above formula (12) was used instead of the compound represented by the above formula (9), to obtain 4.2 g of compound (2C) (in formula (2C), m'c1 and m'c2, which indicate the average degree of polymerization, are 7.1).

[0184] The obtained compound (2C) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.55~1.83(8H), 3.40~4.25(36H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0185] [Example 17] The compound represented by the above formula (2D) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (13) was used instead of the compound represented by the formula (9), to obtain 4.4 g of compound (2D) (in formula (2D), m'd1 and m'd2, which represent the average degrees of polymerization, are 7.1).

[0186] The obtained compound (2D) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.37~4.32(48H) 19F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0187] [Example 18] The compound represented by the above formula (2E) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the above formula (14) was used instead of the compound represented by the above formula (9), to obtain 4.4 g of compound (2E) (in formula (2E), m'e1 and m'e2, which indicate the average degree of polymerization, are 7.1).

[0188] The obtained compound (2E) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.50~1.80(4H), 3.40~4.25(48H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0189] [Example 19] The compound represented by the above formula (2F) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (15) was used instead of the compound represented by the formula (9), to obtain 4.5 g of compound (2F) (in formula (2F), m'f1 and m'f2, which represent the average degree of polymerization, are 7.1).

[0190] The obtained compound (2F) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.52~1.81(8H), 3.44~4.26(48H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0191] [Example 20] The compound represented by the above formula (2G) was produced by the method shown below. The same procedure as in Example 14 was carried out except that the compound represented by the formula (16) was used instead of the compound represented by the formula (9), to obtain 4.0 g of compound (2G) (in formula (2G), m'g1 and m'g2, which represent the average degrees of polymerization, are 7.1).

[0192] The obtained compound (2G) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.50~4.32(32H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0193] [Example 21] The compound represented by the above formula (2H) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (17) was used instead of the compound represented by the formula (9), to obtain 4.1 g of compound (2H) (in formula (2H), m'h1 and m'h2, which represent the average degree of polymerization, are 7.1).

[0194] The obtained compound (2H) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.38~1.75(4H), 3.37~4.31(32H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0195] [Example 22] The compound represented by the above formula (2I) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (18) was used instead of the compound represented by the formula (9), to obtain 4.1 g of compound (2I) (in formula (2I), m'i1 and m'i2, which represent the average degree of polymerization, are 7.1).

[0196] The obtained compound (2I) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.39~1.84(12H), 3.35~4.35(32H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0197] [Example 23] The compound represented by the above formula (2J) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (19) was used instead of the compound represented by the formula (9), to obtain 4.3 g of compound (2J) (in formula (2J), m'j1 and m'j2, which represent the average degree of polymerization, are 7.1).

[0198] The obtained compound (2J) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.38~4.36(44H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0199] [Example 24] The compound represented by the above formula (2K) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (20) was used instead of the compound represented by the formula (9), to obtain 4.2 g of compound (2K) (in formula (2K), m'k1 and m'k2, which represent the average degree of polymerization, are 7.1).

[0200] The obtained compound (2K) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.79(4H), 3.36~4.32(40H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0201] [Example 25] The compound represented by the above formula (2L) was produced by the method shown below. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (21) was used instead of the compound represented by the formula (9), to obtain 4.1 g of compound (2L) (in formula (2L), m'l1 and m'l2, which represent the average degree of polymerization, are 7.1).

[0202] The obtained compound (2L) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.55~1.78(4H), 3.36~4.25(52H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0203] [Example 26] The compound represented by the above formula (3A) was produced by the method shown below. HOCHCFO(CFCFO) of Example 1 m (CF2O) nInstead of the compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where m, which indicates the average degree of polymerization, is 4.5, and n, which indicates the average degree of polymerization, is 4.5), HOCH2CF2CF2O(CF2CF2CF2O) p The same procedure as in Example 1 was carried out, except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where p, indicating the average degree of polymerization, is 4.4) was used, to obtain 4.0 g of compound (3A) (where pa1 and pa2, indicating the average degree of polymerization, are 4.4).

[0204] The obtained compound (3A) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.24(36H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0205] [Example 27] The compound represented by the above formula (3B) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (11) was used instead of the compound represented by the formula (9), to obtain 4.2 g of compound (3B) (in formula (3B), pb1 and pb2, which represent the average degree of polymerization, are 4.4).

[0206] The obtained compound (3B) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.57~1.81(4H), 3.38~4.25(36H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0207] [Example 28] The compound represented by the above formula (3C) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the above formula (12) was used instead of the compound represented by the above formula (9), to obtain 4.2 g of compound (3C) (in formula (3C), pc1 and pc2, which indicate the average degree of polymerization, are 4.4).

[0208] The obtained compound (3C) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.55~1.83(8H), 3.40~4.25(36H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0209] [Example 29] The compound represented by the above formula (3D) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (13) was used instead of the compound represented by the formula (9), to obtain 4.4 g of compound (3D) (in formula (3D), pd1 and pd2, which represent the average degrees of polymerization, are 4.4).

[0210] The obtained compound (3D) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.37~4.32(48H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0211] [Example 30] The compound represented by the above formula (3E) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the above formula (14) was used instead of the compound represented by the above formula (9), to obtain 4.4 g of compound (3E) (in formula (3E), pe1 and pe2, which represent the average degree of polymerization, are 4.4).

[0212] The obtained compound (3E) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.50~1.80(4H), 3.40~4.25(48H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0213] [Example 31] The compound represented by the above formula (3F) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (15) was used instead of the compound represented by the formula (9), to obtain 4.5 g of compound (3F) (in formula (3F), pf1 and pf2, which indicate the average degree of polymerization, are 4.4).

[0214] The obtained compound (3F) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.52~1.81(8H), 3.44~4.26(48H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0215] [Example 32] The compound represented by the above formula (3G) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the above formula (16) was used instead of the compound represented by the above formula (9), to obtain 4.0 g of compound (3G) (in formula (3G), pg1 and pg2, which represent the average degrees of polymerization, are 4.4).

[0216] The obtained compound (3G) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.50~4.32(32H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0217] [Example 33] The compound represented by the above formula (3H) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (17) was used instead of the compound represented by the formula (9), to obtain 4.1 g of compound (3H) (in formula (3H), ph1 and ph2, which indicate the average degree of polymerization, are 4.4).

[0218] The obtained compound (3H) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.38~1.75(4H), 3.37~4.31(32H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0219] [Example 34] The compound represented by the above formula (3I) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (18) was used instead of the compound represented by the formula (9), to obtain 4.1 g of compound (3I) (in formula (3I), pi1 and pi2, which indicate the average degree of polymerization, are 4.4).

[0220] The obtained compound (3I) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.39~1.84(12H), 3.35~4.35(32H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0221] [Example 35] The compound represented by the above formula (3J) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (19) was used instead of the compound represented by the formula (9), to obtain 4.3 g of compound (3J) (in formula (3J), pj1 and pj2, which represent the average degree of polymerization, are 4.4).

[0222] The obtained compound (3J) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.38~4.36(44H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0223] [Example 36] The compound represented by the above formula (3K) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (20) was used instead of the compound represented by the formula (9), to obtain 4.2 g of compound (3K) (in formula (3K), pk1 and pk2, which indicate the average degree of polymerization, are 4.4).

[0224] The obtained compound (3K) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.34~1.79(4H), 3.36~4.32(40H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0225] [Example 37] The compound represented by the above formula (3L) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the above formula (21) was used instead of the compound represented by the above formula (9), to obtain 4.2 g of compound (3L) (in formula (3L), p1 and p12, which represent the average degree of polymerization, are 4.4).

[0226] The obtained compound (3L) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.55~1.78(4H), 3.36~4.25(52H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0227] [Example 38] The compound represented by the above formula (4A) was produced by the method shown below. HOCHCFO(CFCFO) of Example 1m (CF2O) n CF2CH2OH (where m, which indicates the average degree of polymerization, is 4.5, and n, which indicates the average degree of polymerization, is 4.5) instead of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by HOCH2CF2CF2CF2O (CF2CF2CF2CF2O) q The same procedure as in Example 1 was carried out, except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CF2CH2OH (where q, which indicates the average degree of polymerization, is 3.0) was used, to obtain 4.3 g of compound (4A) (where qa1 and qa2, which indicate the average degree of polymerization, are 3.0).

[0228] The obtained compound (4A) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.46~4.24(36H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(32F), -122.5(8F), -126.0(24F), -129.0~-128.0(8F)

[0229] [Comparative Example 1] The compound represented by the following formula (1X) was synthesized by the method described in Patent Document 2.

[0230] [ka] (In formula (1X), mx1, mx2, nx1, and nx2, which represent the average degree of polymerization, are 4.5.)

[0231] The obtained compound (1X) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.42~4.29(28H) 19F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0232] Comparative Example 2 The compound represented by the following formula (2X) was synthesized by the method described in Patent Document 2.

[0233] [ka] (In formula (2X), m'x1 and m'x2, which represent the average degree of polymerization, are 7.1.)

[0234] The obtained compound (2X) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.41~4.30(28H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0235] Comparative Example 3 The compound represented by the following formula (3X) was synthesized by the method described in Patent Document 2.

[0236] [ka] (In formula (3X), px1 and px2, which represent the average degree of polymerization, are 4.4.)

[0237] The obtained compound (3X) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.40~4.32(28H) 19F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0238] Comparative Example 4 The compound represented by the following formula (1Y) was synthesized by the following method. The same procedure as in Example 1 was carried out, except that 3.8 g of a compound represented by the following formula (22) was used instead of the compound represented by formula (9), to obtain 4.2 g of a compound represented by the above formula (1Y) (in formula (1Y), my1, my2, ny1, and ny2, which represent the average degree of polymerization, are 4.5).

[0239] [ka] (In formula (1Y), my1, my2, ny1, and ny2, which represent the average degree of polymerization, are 4.5.)

[0240] [ka] (In formula (22), THP represents a tetrahydropyranyl group.)

[0241] The compound represented by formula (22) was synthesized by the following method. The primary and secondary hydroxyl groups of 3-allyloxy-1,2-propanediol were protected by THP groups, and the double bond of the resulting compound was oxidized. Through these steps, a compound represented by formula (22) was obtained.

[0242] The obtained compound (1Y) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.32~4.23(40H) 19F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0243] Comparative Example 5 The compound represented by the following formula (2Y) was synthesized by the following method. The same procedure as in Example 14 was carried out, except that the compound represented by the formula (22) was used instead of the compound represented by the formula (9), to obtain 4.2 g of compound (2Y) (in formula (2Y), m'y1 and m'y2, which represent the average degree of polymerization, are 7.1).

[0244] [ka] (In formula (2Y), m'y1 and m'y2, which represent the average degree of polymerization, are 7.1.)

[0245] The obtained compound (2Y) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.32~4.22(40H) 19 F-NMR (acetone-D6): δ[ppm]=-78.6(4F), -81.3(4F), -90.0~-88.5(56F)

[0246] Comparative Example 6 A compound represented by the following formula (3Y) was produced by the method shown below. The same procedure as in Example 26 was carried out, except that the compound represented by the formula (22) was used instead of the compound represented by the formula (9), to obtain 4.2 g of compound (3Y) (in formula (3Y), py1 and py2, which represent the average degree of polymerization, are 4.4).

[0247] [ka] (In formula (3Y), py1 and py2, which represent the average degree of polymerization, are 4.4.)

[0248] The obtained compound (3Y) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=3.30~4.22(40H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(35F), -86.4(8F), -124.3(8F), -130.0~-129.0(17F)

[0249] Comparative Example 7 The compound represented by the following formula (1Z) was synthesized by the method described in Patent Document 4.

[0250] [ka] (In formula (1Z), mz and nz, which represent the average degree of polymerization, are 4.5.)

[0251] The obtained compound (1Z) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR(CD3COCD3):δ[ppm]=1.60~1.79(4H), 3.61~4.23(22H) 19 F-NMR (CD3COCD3): δ[ppm]=-55.6~-50.6(9F), -77.7(2F), -80.3(2F), -91.0~-88.5(18F)

[0252] The compounds of Examples 1 to 38 and Comparative Examples 1 to 7 thus obtained were applied to the formula (1) to obtain R 1 and R 4 (a, b, X, Y, and Z in formulas (2) to (5)), R 2 and R 3 The structures of the compounds are shown in Tables 1 to 7. In Comparative Example 7, the structures of both terminal groups are R1 The PFPE chain is shown in the R column. 2 The column indicates the

[0253] [Table 1]

[0254] [Table 2]

[0255] [Table 3]

[0256] [Table 4]

[0257] [Table 5]

[0258] [Table 6]

[0259] [Table 7]

[0260] The number average molecular weights (Mn) of the compounds of Examples 1 to 38 and Comparative Examples 1 to 7 were calculated using the above method. 1 H-NMR and 19 The average molecular weights of the synthesized compounds were determined by F-NMR measurement. The results are shown in Tables 1 to 7. It is estimated that there is a variation of about 1 to 5 in the average molecular weight of the synthesized compounds due to the molecular weight distribution of the fluoropolyether used as the raw material for the compounds and differences in the operations used to synthesize the compounds.

[0261] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 38 and Comparative Examples 1 to 7. Then, using the obtained solutions for forming lubricating layers, lubricating layers for magnetic recording media were formed by the method described below, to obtain the magnetic recording media of Examples 1 to 38 and Comparative Examples 1 to 7.

[0262] "Lubricant layer forming solution" The compounds obtained in Examples 1 to 38 and Comparative Examples 1 to 7 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the thickness of the coating film when applied to the protective layer would be 9 Å to 10 Å, to prepare a solution for forming a lubricating layer.

[0263] "Magnetic recording media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon and had a thickness of 1 to 5 nm. On the protective layer of each magnetic recording medium on which the layers up to the protective layer had been formed, the lubricating layer-forming solutions of Examples 1 to 38 and Comparative Examples 1 to 7 were each applied by dipping under the conditions of an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a pull-up speed of 1.2 mm / sec.

[0264] Thereafter, a burnishing step was carried out in which a burnishing tape carrying abrasive grains of grain size #6000 was scanned over the surface of the magnetic recording medium on which the lubricating layer had been formed. The magnetic recording medium after the burnishing process was placed in a thermostatic chamber at 120° C. and subjected to a heat treatment in which it was heated for 10 minutes. By the above steps, magnetic recording media (with burnish) of Examples 1 to 38 and Comparative Examples 1 to 7 were obtained.

[0265] Furthermore, magnetic recording media (without burnishing) of Examples 1 to 38 and Comparative Examples 1 to 7 were obtained in the same manner as the magnetic recording media with burnishing, except that the burnishing step was not carried out.

[0266] (film thickness measurement) The thickness of the lubricating layer of the magnetic recording media (with and without burnishing) obtained in this manner in Examples 1 to 38 and Comparative Examples 1 to 7 was measured using an FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). There was no difference in the thickness of the lubricating layer between the magnetic recording media with and without burnishing in any of Examples 1 to 38 and Comparative Examples 1 to 7. The results are shown in Tables 8 to 11.

[0267] [Table 8]

[0268] [Table 9]

[0269] [Table 10]

[0270] [Table 11]

[0271] Next, the magnetic recording media of Examples 1 to 38 and Comparative Examples 1 to 7, both with and without burnishing, were subjected to the corrosion resistance test shown below. (Corrosion resistance test) The magnetic recording medium was exposed to conditions of 85°C and 90% relative humidity for 48 hours. After that, the number of corroded areas on the magnetic recording medium was counted using an optical surface analyzer and evaluated based on the following evaluation criteria. The results are shown in Tables 8 to 11.

[0272] "Evaluation Criteria" A: Less than 200 B: 200 or more, less than 400 C: 400 or more, less than 600 D: Over 600, under 800 E: 800 or more

[0273] As shown in Tables 8 to 10, the magnetic recording media of Examples 1 to 38, which had a lubricating layer containing a compound represented by formula (1), showed good corrosion resistance, with or without tape varnish, with results of A or B in the corrosion resistance test. In contrast, as shown in Table 11, the magnetic recording media of Comparative Examples 1 to 7, both with and without tape varnish, all showed results of E in the corrosion resistance test, and were inferior in corrosion resistance to the magnetic recording media of Examples 1 to 38.

[0274] More specifically, magnetic recording media having lubricating layers containing compounds in which the linking group between the carbon atom bonded to the terminal hydroxyl group and the carbon atom bonded to the adjacent hydroxyl group has zero carbon atoms exhibited superior corrosion resistance. (Examples 7-9 compared to Comparative Example 1, Examples 20-22 compared to Comparative Example 2, Examples 32-34 compared to Comparative Example 3, Example 10 compared to Comparative Example 4, Example 23 compared to Comparative Example 5, and Example 35 compared to Comparative Example 6) Magnetic recording media having lubricating layers containing compounds in which the linking group has a larger number of carbon atoms exhibited particularly good corrosion resistance. This is presumably because increasing the number of carbon atoms in the linking group increases the hydrophobicity of the lubricating layer, preventing water from penetrating beneath the lubricating layer.

[0275] Furthermore, magnetic recording media having a lubricating layer containing a compound in which the linking group between the carbon atom bonded to a terminal hydroxyl group and the carbon atom bonded to an adjacent hydroxyl group contains an oxygen atom also exhibited superior corrosion resistance compared to magnetic recording media having a lubricating layer containing a compound in which the carbon atom bonded to a terminal hydroxyl group is bonded to the carbon atom bonded to an adjacent hydroxyl group (Comparative Examples 1 to 6) (Examples 1 to 6, 11 to 19, 24 to 31, and 36 to 38). This is presumably because, even if the linking group contains an oxygen atom, the number of carbon atoms contained in the linking group is within an appropriate range, so that the lubricating layer exhibits appropriate hydrophobicity, and the lubricating layer can prevent water penetration.

[0276] Furthermore, R in formula (1) 1 and the hydroxyl group contained in R 4 The materials having a total of 4 hydroxyl groups (for example, Examples 2 to 3, Examples 8 to 9, etc.) had particularly good corrosion resistance. 1 and the hydroxyl group contained in R 4 When the total number of hydroxyl groups contained in is 4, the interactions between the hydroxyl groups are not too great compared to when the total number is 6, and intramolecular aggregation is less likely to occur, which makes it easier to adhere to the protective layer and results in a lubricating layer with an appropriate coating. 1 and the hydroxyl group contained in R 4 It is presumed that when the total number of hydroxyl groups contained in is 4, the hydrophilicity of the molecule is not too high compared to when the total number is 6, and a lubricating layer with appropriate hydrophobicity is obtained.

[0277] Furthermore, the magnetic recording media of Examples 1 to 38 exhibited superior corrosion resistance compared to the magnetic recording medium of Comparative Example 7. Water resistance is imparted to the lubricating layer by the low surface energy of the PFPE chain. In Examples 1 to 38, which used a compound having two PFPE chains, the proportion of PFPE chains in the compound molecule was higher than in Comparative Example 7, which used a compound with one PFPE chain. For this reason, it is presumed that the water resistance of the lubricating layer was better in the magnetic recording media of Examples 1 to 38 than in the magnetic recording medium of Comparative Example 7, and that the lubricating layer was able to prevent water penetration. [Industrial Applicability]

[0278] By using a lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, a lubricating layer having a high corrosion-inhibiting effect on magnetic recording media can be formed. [Explanation of symbols]

[0279] 10...magnetic recording medium, 11...substrate, 12...adhesion layer, 13...soft magnetic layer, 14...first underlayer, 15...second underlayer, 16...magnetic layer, 17...protective layer, 18...lubricating layer.

Claims

1. A fluorine-containing ether compound represented by the following formula (1): R １ -CH ２ -R ２ -CH ２ -OCH ２ CH(OH)CH ２ O-CH ２ -R ３ -CH ２ -R ４ (1) (In formula (1), R ２ and R ３ is a perfluoropolyether chain of any one of the following formulas (6) to (8); —CH ２ -R １ and -CH ２ -R ４ is a terminal group represented by the following formula (2): -CH 2 -[A]-[B]-OZ (2) (In formula (2), [A] is represented by the following formula (3), [B] is represented by the following formula (4), and Z is H or a group represented by the following formula (5); in formula (2), [A] and [B] may be interchanged, and when [A] is directly bonded to -OZ, Z is a group represented by the following formula (5).) 【Chemical 1】 (In formula (3), X is an integer of 0 to 2; in formula (4), Y is an integer of 0 to 1, and a is an integer of 1 to 4; the sum of X in formula (3) and Y in formula (4) is 1 or 2; and in formula (5), b is an integer of 2 to 4.) -CF ２ O-(CF ２ CF ２ O) ｃ -(CF ２ O) ｄ -CF ２ - (6) (In formula (6), c and d each represent an average degree of polymerization, and each represents 0 to 20; provided that c or d is 2 or more.) -CF ２ CF ２ O-(CF ２ CF ２ CF ２ O) ｅ -CF ２ CF ２ - (7) (In formula (7), e represents the average degree of polymerization and represents 2 to 20.) -CF ２ CF ２ CF ２ O-(CF ２ CF ２ CF ２ CF ２ O) ｆ -CF ２ CF ２ CF ２ - (8) (In formula (8), f represents the average degree of polymerization and represents 2 to 10.)

2. In the formula (1), R １ and R ４ The fluorine-containing ether compound according to claim 1 , wherein each of the groups contains two polar groups.

3. In the formula (1), R １ and R ４ 3. The fluorine-containing ether compound according to claim 1, wherein:

4. In the formula (1), R ２ and R ３ 4. The fluorine-containing ether compound according to claim 1, wherein:

5. 5. The fluorine-containing ether compound according to claim 1, which has a number average molecular weight in the range of 500 to 10,000.

6. A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of claims 1 to 5.

7. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, 6. A magnetic recording medium, wherein the lubricating layer comprises the fluorine-containing ether compound according to claim 1.

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

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