Fluorine-containing ether compounds, lubricants for magnetic recording media, and magnetic recording media

Abstract

By using the lubricant for a magnetic recording medium containing the fluorine-containing ether compound of the present invention, a lubricating layer with good corrosion resistance and capable of suppressing spin-off can be formed even if it is thin. 【Solution means】A fluorine-containing ether compound represented by formula (1). R 1 -CH2-R 2 -CH2-R 3 (1). R 2 is a perfluoropolyether chain. R 1 and R 3 are terminal groups having 1 to 4 polar groups and 1 to 50 carbon atoms. R 1 and R 3 At least one of them is a terminal group represented by formula (2). -O-X-CH(OH)-CH2OH (2). X is a divalent organic group having 2 to 30 carbon atoms which may contain at least one of 1 to 2 polar groups and 1 to 3 ether oxygen atoms. X contains at least one carbon atom not bonded to either the polar group or the ether oxygen atom.

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for magnetic recording media, and a magnetic recording media. This application claims priority based on Japanese Patent Application No. 2023-074981, filed in Japan on April 28, 2023, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] To improve the recording density of magnetic recording and playback devices, development of magnetic recording media suitable for high recording densities is underway. Conventionally, magnetic recording media have been formed by creating a recording layer on a substrate and then forming a protective layer, such as carbon, on top of the recording layer. The protective layer protects the information recorded on the recording layer and also improves the sliding properties of the magnetic head. However, simply providing a protective layer on top of the recording layer does not provide sufficient durability for the magnetic recording media. For this reason, a lubricant is generally applied to the surface of the protective layer to form a lubricating layer.

[0003] As a lubricant used to form the lubricating layer of a magnetic recording medium, for example, a compound containing a polar group such as a hydroxyl group or an amino group at the end of a fluorine-based polymer having a repeating structure including -CF2- has been proposed.

[0004] For example, Patent Documents 1 and 2 disclose fluorine-containing ether compounds in which a glycerin linking group (-O-CH2-CH(OH)-CH2-O-) and a terminal group which is an organic group having a polar group are bonded to both ends of a perfluoropolyether chain via a methylene group (-CH2-) in that order.

[0005] Patent Document 3 describes a structure in which glycerin linking groups are extended at both ends of a perfluoropolyether chain via methylene groups (-CH2-) (-O-CH2-CH(OH)-CH2-(CH2)). n A fluorine-containing ether compound is disclosed in which a linking group containing -O-) and a terminal group are bonded in this order.

[0006] Patent Document 4 discloses a fluorine-containing ether compound in which one or more glycerol structures are bonded to both ends of a perfluoropolyether chain via a methylene group (-CH2-). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2021 / 090940(A) [Patent Document 2] Japanese Patent No. 6804893(B) [Patent Document 3] International Publication No. 2019 / 054148(A) [Patent Document 4] International Publication No. 2009 / 013785(A) [Overview of the project] [Problems that the invention aims to solve]

[0008] In recent years, in order to increase the capacity of magnetic recording media, there has been an increasing demand for further reduction in magnetic spacing (the distance between the magnetic head and the magnetic layer of the magnetic recording media). Therefore, there is a need to make the lubrication layer in magnetic recording media thinner.

[0009] However, generally, reducing the thickness of the lubricating layer tends to decrease the corrosion resistance of the magnetic recording medium. Furthermore, when the lubricating layer thickness is reduced, spin-off (a phenomenon where the lubricant is scattered or evaporated due to centrifugal force and heat generated during the rotation of the magnetic recording medium) can occur, making it impossible to maintain a sufficient film thickness to fulfill the function of the lubricating layer. Therefore, there is a need for a lubricating layer that possesses excellent corrosion resistance and can suppress spin-off, even when the lubricating layer thickness is reduced.

[0010] The present invention has been made in view of the above circumstances, and provides a fluorine-containing ether compound that has excellent corrosion resistance, can form a lubricating layer capable of suppressing spin-off, and can be suitably used as a material for a lubricant for a magnetic recording medium.

[0011] The present invention aims to provide a lubricant for a magnetic recording medium that contains the fluorine-containing ether compound of the present invention, has good corrosion resistance, and can form a lubricating layer capable of suppressing spin-off.

[0012] The present invention aims to provide a magnetic recording medium that has a lubricating layer containing the fluorine-containing ether compound of the present invention, has good corrosion resistance, and can suppress spin-off.

Means for Solving the Problems

[0013] The present invention includes the following aspects.

[0014] [1] A fluorine-containing ether compound characterized by being represented by the following formula (1). R 1 -CH2-R 2 -CH2-R 3 (1) (In formula (1), R 2 is a perfluoropolyether chain. R 1 and R 3 are end groups having 1 to 4 polar groups and having 1 to 50 carbon atoms. R 1 and R 3 may be the same or different from each other. At least one of R 1 and R 3 is an end group represented by the following formula (2).) -O-X-CH(OH)-CH2OH (2) (In formula (2), X is a divalent organic group having 2 to 30 carbon atoms that may contain at least one of 1 to 2 polar groups and 1 to 3 ether oxygen atoms. X contains at least one carbon atom that is not bonded to either a polar group or an ether oxygen atom.)

[0015] [2] The fluorine-containing ether compound according to [1], wherein the terminal group represented by formula (2) is one of the following formulas (2-1) to (2-7).

[0016] [ka] (In equation (2-1), a represents an integer from 1 to 8, and b represents an integer from 1 to 7.) (In equation (2-2), c represents an integer from 1 to 7.) (In equation (2-3), d represents an integer from 1 to 6.) (In equation (2-4), e represents an integer from 1 to 6. e R a and R b (Each of these independently represents either a hydrogen atom or a methyl group.) (In equation (2-5), f represents an integer from 1 to 6.) (In equation (2-6), g represents an integer from 1 to 6.) (In equation (2-7), g2 represents an integer from 1 to 6.)

[0017] [3] R in equation (1) above 1 and R 3 The fluorine-containing ether compound according to [1] or [2], wherein each of the terminal groups is independently represented by formula (2).

[0018] [4] R in equation (1) above 1 and R 3 The fluorine-containing ether compound is the same as any of the compounds described in [1] to [3].

[0019] [5] R in equation (1) above 1 and R 3 The fluorine-containing ether compound described in [1] or [2], wherein one of the groups is a terminal group represented by formula (2) above, and the other is a terminal group represented by the following formula (3) that does not correspond to formula (2).

[0020] [ka] (In formula (3), l represents an integer between 1 and 3. Each of the l m independently represents an integer between 1 and 6. Each of the l n independently represents an integer between 1 and 6. In one repeating unit, at least one of m and n is 1. B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond, or a hydrogen atom.)

[0021] [6] R in equation (1) above 1 and R 3 A fluorine-containing ether compound according to [1], [2], or [5], wherein one of the members is a terminal group represented by formula (2) above, and the other is a terminal group represented by any of the following formulas (3-1) to (3-3).

[0022] [ka] (In formula (3-1), p represents an integer between 0 and 3. q represents an integer between 0 and 2. r represents an integer between 0 and 5. The sum of p and r is between 1 and 5. D represents a polar group, a vinyl group, an ethynyl group, or an optionally substituted aryl group.) (In equation (3-2), s represents an integer between 0 and 2, and t represents an integer between 1 and 5.) (In formula (3-3), u represents an integer from 1 to 3. Each of the five E's independently represents a polar group, an alkoxy group with 1 to 8 carbon atoms, a halogeno group, or a hydrogen atom. However, if one of the five E's is a polar group, the number of polar groups among the five E's is 1.)

[0023] [7] R in equation (1) above 1 and R 3 The total number of polar groups present is 4 to 6, as described in any of [1] to [6].

[0024] [8] R in equation (1) above 2 The fluorine-containing ether compound is a perfluoropolyether chain represented by the following formula (4), as described in any of [1] to [7]. -(CF2) w1 -O-(CF2O) w2-(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In equation (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are average values ​​representing the number of CF2 molecules, each independently representing 1 to 3. There are no particular restrictions on the order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in equation (4).)

[0025] [9] R in equation (1) above 2 The fluorine-containing ether compound is one of the perfluoropolyether chains represented by the following formulas (4-1) to (4-4), as described in any of [1] to [8]. -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In equation (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In equation (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In equation (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization, each independently representing a value between 1 and 20. w7 and w10 are average values ​​representing the number of CF2 molecules, each independently representing a value between 1 and 2.)

[0026]

[10] A fluorine-containing ether compound as described in any of [1] to [9], wherein the number average molecular weight is in the range of 500 to 10000.

[0027] A lubricant for magnetic recording media, characterized by containing a fluorine-containing ether compound as described in any of [1] to

[10] .

[0028]

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

[10] .

[0029]

[13] The magnetic recording medium according to

[12] , wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm. [Effects of the Invention]

[0030] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is therefore suitable as a material for a lubricant for magnetic recording media.

[0031] The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore has good corrosion resistance and can form a lubricating layer that can suppress spin-off.

[0032] The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention. Therefore, the magnetic recording medium of the present invention has good corrosion resistance, can suppress spin-off, and has excellent reliability and durability. Therefore, because the thickness of the lubricating layer of the magnetic recording medium of the present invention can be reduced, it can contribute to reducing magnetic spacing and further reduce the amount of magnetic head levitation. [Brief explanation of the drawing]

[0033] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. [Modes for carrying out the invention]

[0034] To solve the above problems, the inventors of this invention conducted diligent research as described below. Conventionally, fluorine-containing ether compounds having terminal groups containing polar groups such as hydroxyl groups have been preferred as materials for lubricants for magnetic recording media applied to the surface of protective layers (hereinafter sometimes abbreviated as "lubricant").

[0035] However, when a thin lubricating layer was formed on a protective layer using conventional fluorine-containing ether compounds having terminal groups containing polar groups, it was difficult to achieve a lubricating layer with good corrosion resistance and the ability to suppress spin-off, as shown below. In other words, the polar groups in the fluorine-containing ether compound bind to active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer. If the adhesion of the lubricating layer to the protective layer is insufficient, the lubricating layer will not adequately cover the protective layer, making it easier for water, which causes corrosion, to be incorporated into the protective layer, and thus insufficient corrosion resistance cannot be obtained.

[0036] Furthermore, polar groups in fluorinated ether compounds not only bind to active sites on the protective layer and participate in interactions with the protective layer, but also participate in intramolecular and intermolecular interactions. If there is a deficiency of polar groups involved in intermolecular interactions between fluorinated ether compounds, the fluorinated ether compounds in the lubricating layer will easily scatter as the magnetic recording medium rotates, making spin-off more likely.

[0037] Therefore, fluorine-containing ether compounds need to contain a sufficient number of polar groups involved in interaction with the protective layer and polar groups involved in intermolecular interactions in order to form a lubricating layer with good corrosion resistance and suppressed spin-off. However, increasing the number of polar groups in the fluorine-containing ether compound reduces the hydrophobicity of the lubricating layer containing it, making it impossible to obtain sufficient corrosion resistance.

[0038] Therefore, the inventors diligently studied the strength of polar groups contained in fluorine-containing ether compounds and the interactions of polar groups. As a result, they concluded that at least a portion of the polar groups in the fluorine-containing ether compound should be hydroxyl groups of a 1,2-diol structure located at the end of the perfluoropolyether chain. In this case, as shown below, it is possible to ensure hydroxyl groups that can interact with the protective layer and hydroxyl groups that can participate in intermolecular interactions, while suppressing the decrease in hydrophobicity caused by the hydroxyl groups contained in the 1,2-diol structure.

[0039] In the 1,2-diol structure (-CH(OH)-CH2OH), the carbon atoms to which the hydroxyl groups are bonded are close together, leading to steric and electrostatic repulsion between the hydroxyl groups. As a result, the two hydroxyl groups in the 1,2-diol structure are in opposite conformations relative to the carbon atoms to which the 1,2-diol structure is bonded. Therefore, the dipole moments generated by the two hydroxyl groups in the 1,2-diol structure cancel each other out, suppressing an increase in the overall polarity of the fluorine-containing ether compound molecule.

[0040] Furthermore, the distance between active sites on the protective layer is sufficiently large compared to the distance between hydroxyl groups in the 1,2-diol structure. Moreover, the two hydroxyl groups in the 1,2-diol structure are in opposite conformations with respect to the carbon atom to which the 1,2-diol structure is bonded. Therefore, the two hydroxyl groups in the 1,2-diol structure cannot simultaneously be oriented toward the protective layer, and only one of the two hydroxyl groups can interact with the active sites on the protective layer. Consequently, the other hydroxyl group can participate in intermolecular interactions between fluorine-containing ether compounds.

[0041] Conventionally, the structure of fluorine-containing ether compounds used as lubricants has been designed to improve adhesion to the protective layer by ensuring that as many polar groups as possible in the compound are arranged to easily interact with active sites on the protective layer. For this reason, structures in which the orientation of adjacent hydroxyl groups is reversed on the protective layer due to bonding between carbon atoms to which hydroxyl groups are attached tended to be avoided. However, the inventors deliberately made some of the polar groups in the fluorine-containing ether compound hydroxyl groups with a 1,2-diol structure, thereby securing polar groups that can participate in intermolecular interactions between fluorine-containing ether compounds. Furthermore, they reasoned that the number of polar groups that can interact with the active sites on the protective layer could be adjusted as needed.

[0042] Furthermore, the inventors have conducted extensive research to improve the corrosion resistance of lubricating layers containing fluorine-containing ether compounds in which a 1,2-diol structure is arranged at one or both ends of a perfluoropolyether chain, and to suppress spin-off. As a result, we discovered that a fluorine-containing ether compound can be formed in which end groups having 1 to 50 carbon atoms and each containing 1 to 4 polar groups are arranged at both ends of a perfluoropolyether chain, and at least one of the two end groups contains at least one carbon atom that is not bonded to either a polar group or an ether oxygen atom, and has a 1,2-diol structure represented by formula (2). This led to the invention of the present invention.

[0043] In such fluorine-containing ether compounds, the number of polar groups is appropriate, and some of the polar groups are hydroxyl groups of a 1,2-diol structure located at the ends of the perfluoropolyether chain. Therefore, while suppressing the decrease in hydrophobicity caused by the polar groups, it is possible to ensure sufficient hydroxyl groups that can interact with the protective layer and hydroxyl groups that can participate in intermolecular interactions. Moreover, the terminal group represented by formula (2) located at at least one end contains at least one carbon atom that is not bonded to either a polar group or an ether oxygen atom. Because this carbon atom has an extremely low affinity for water, it strongly inhibits the interaction between the fluorine-containing ether compound molecule and water. Therefore, sufficient hydrophobicity can be obtained even if the fluorine-containing ether compound contains multiple polar groups. Furthermore, because the motion of the above carbon atom is suppressed, it brings appropriate rigidity to the fluorine-containing ether compound molecule, suppressing intramolecular interactions between polar groups and making it easier for the polar groups to participate in intermolecular interactions between fluorine-containing ether compounds.

[0044] Thus, the above-mentioned fluorine-containing ether compounds maintain low polarity while ensuring a sufficient number of polar groups involved in interaction with the protective layer, and possess sufficient hydrophobicity. For this reason, lubricants containing these compounds are less likely to absorb water, which causes corrosion, and have excellent corrosion resistance. Moreover, the above-mentioned fluorine-containing ether compounds readily generate polar groups that do not participate in interaction with the protective layer or intramolecular interactions, and these polar groups readily form intermolecular interactions. For this reason, scattering of the fluorine-containing ether compounds due to the rotation of the magnetic recording medium is less likely, and a lubricating layer with excellent spin-off resistance can be formed.

[0045] In contrast, if a fluorine-containing ether compound is too flexible, for example, the polar groups contained within the fluorine-containing ether compound are more likely to form intramolecular interactions, thus making it less likely for the polar groups to participate in intermolecular interactions. Furthermore, if all of the polar groups in a fluorine-containing ether compound are positioned with sufficient distance between adjacent polar groups, all polar groups will be more likely to interact with the protective layer, and sufficient interaction between the fluorine-containing ether compounds due to the polar groups will not be achieved.

[0046] Furthermore, the inventors of the present invention have confirmed that by using a lubricant containing the above-mentioned fluorine-containing ether compound, it is possible to form a lubricating layer that has good corrosion resistance and can suppress spin-off even when the thickness is reduced, and thus conceived the present invention.

[0047] The fluorine-containing ether compound, lubricant for magnetic recording media, and magnetic recording media of the present invention will be described in detail below. However, the present invention is not limited to the embodiments shown below.

[0048] [Fluorine-containing ether compounds] The fluorine-containing ether compound of this embodiment is represented by the following formula (1). R 1 -CH2-R 2 -CH2-R 3 (1) (In formula (1), R 2 This is a perfluoropolyether chain. 1 and R 3 R is a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. 1 and R 3 They may be the same, or they may be different. 1 and R 3 At least one of them is a terminal group represented by the following formula (2). -OX-CH(OH)-CH2OH (2) (In formula (2), X is a divalent organic group having 2 to 30 carbon atoms, which may contain at least one of one or two polar groups and one to three ether oxygen atoms. X contains at least one carbon atom that is not bonded to either a polar group or an ether oxygen atom.)

[0049] The fluorine-containing ether compound of this embodiment is as shown in formula (1), R 2 In relation to the perfluoropolyether chain represented by (hereinafter sometimes referred to as a PFPE chain), one end of the skeleton has a methylene group connected to it, R 1 The terminal group indicated by is attached, and at the other end of the skeleton, via a methylene group, R 3The terminal group indicated by is attached.

[0050] (R 1 and R 3 (Terminal group indicated by) R 1 and R 3 R is a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. 1 and R 3 At least one of these is a terminal group represented by formula (2) above.

[0051] R 1 and R 3 If one of them is a terminal group that does not correspond to formula (2), then R 1 and R 3 The number of polar groups in the terminal groups that do not correspond to formula (2) is one or more. Also, the number of polar groups in the terminal groups represented by formula (2) is two or more. Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing a fluorine-containing ether compound, a suitable interaction occurs between the lubricating layer and the protective layer. 1 and R 3 The number of polar groups contained in each is preferably two or more. 1 and R 3 When the compound contains two or more polar groups, it exhibits excellent adhesion to the protective layer, and favorable intermolecular interactions between the polar groups are formed, resulting in a fluorine-containing ether compound that can form a lubricating layer that suppresses spin-off.

[0052] R 1 and R 3 The number of polar groups contained in each is four or less. Therefore, in a lubricating layer containing a fluorine-containing ether compound, it is possible to suppress the aggregation and formation of clumps of the fluorine-containing ether compound due to excessive polarity, which would otherwise lead to a loss of smoothness in the lubricating layer. 1 and R 3 The number of polar groups contained in each is preferably 3 or less. 1 and R 3If the number of polar groups contained in each compound is three or less, the hydrophilicity of the fluorine-containing ether compound becomes too high, preventing water, which causes corrosion, from being incorporated into the magnetic recording medium, thus forming a fluorine-containing ether compound that can form a highly corrosion-resistant lubricating layer.

[0053] R in equation (1) 1 and R 3 The total number of polar groups is preferably 3 to 6, and more preferably 4 to 6. If the total number of polar groups is 3 or more, R 1 and R 3 The interaction between the polar groups and the protective layer is effectively achieved. As a result, a fluorine-containing ether compound is formed that can create a lubricating layer with high adhesion to the protective layer. Therefore, a lubricating layer with superior spin-off resistance can be obtained. Furthermore, if the total number of the above polar groups is 6 or less, it is possible to prevent the fluorine-containing ether compound from becoming too polar and attracting water, which can cause corrosion. Thus, a lubricating layer with superior corrosion resistance can be formed.

[0054] R 1 and R 3 The polar groups that each possess may be some or all the same, or they may be different. Also, R 1 The number of polar groups it possesses, and R 3 The number of polar groups in each may be the same or different. 1 The number of polar groups it possesses, and R 3 The number of polar groups present is preferably the same, as this results in a more uniform coating state on the protective layer of the fluorine-containing ether compound, and allows for the formation of a lubricating layer with better adhesion.

[0055] R 1 and R 3 The polar groups contained are hydroxyl group (-OH), carboxyl group (-COOH), formyl group (-(C=O)H), and carbonyl group (-(C=O)R). 7 ;R 7 These are organic groups: a sulfo group (-SO3H), a cyano group (-CN), and a group having an amide bond (-NR).8 COR 9 or -CONR 10 R 11 ; R 8 , R 9 , R 10 and R 11 are each independently a hydrogen atom or an organic group.), an amino group (-NR 12 R 13 ; R 12 and R 13 are each independently a hydrogen atom or an organic group.). It is preferably at least one polar group selected from the group consisting of. As the group having an amide bond, as shown in the above formula, the group bonded to the carbon atom constituting the amide bond (for example, carboxamide group (-C(=O)NH2)) and the group bonded to the nitrogen atom constituting the amide bond (for example, acetamide group (-NHC(=O)CH3)) are both included. In the group having an amide bond, the said R 8 and R 9 may be bonded to each other to form a ring, and the said R 10 and R 11 may be bonded to each other to form a ring. The said R 8 , R 9 , R 10 and R 11 in the group having an amide bond are each independently preferably selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group. The "polar group" in this specification does not include a halogeno group (-F, -Cl, -Br, etc.) or an ether bond (-O-).

[0056] R 1 and R 3 each independently preferably contain at least one polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond. The hydroxyl group, the cyano group, and the group having an amide bond are chemically stable, and the lubricating layer containing the fluorine-containing ether compound having these polar groups does not deteriorate over a long period of time. Also, the hydroxyl group, the cyano group, and the group having an amide bond do not have too high acidity and are less likely to corrode the substrate.

[0057] R in equation (1) 1 and R 3 The polar groups of each preferably contain at least one hydroxyl group. 1 and R 3 It is more preferable that all of the polar groups present are hydroxyl groups. 1 and R 3 This is because if all of the polar groups present are hydroxyl groups, the coating of the protective layer of the fluorine-containing ether compound becomes more uniform.

[0058] R 1 and R 3 The number of carbon atoms in the terminal group represented by R is 1 to 50, preferably 3 to 20, and more preferably 4 to 15. 1 and R 3 If the number of carbon atoms in the terminal group represented by is 1 or more, the hydrophobicity of the terminal group can be ensured, which prevents water that causes corrosion from being attracted to the lubricating layer, resulting in a lubricating layer with good corrosion resistance. 1 and R 3 When the number of carbon atoms in the terminal group represented by is 50 or less, the terminal group has a flexible structure, resulting in good adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer. As a result, a lubricating layer that can suppress spin-off is obtained.

[0059] R 1 and R 3 At least one of them is a terminal group represented by formula (2) above. The terminal group represented by formula (2) is R 2 It has an oxygen atom (ether oxygen atom) bonded to the methylene group (-CH2-) that is bonded to it. The oxygen atom located at the end of the terminal group represented by formula (2) forms an ether bond (-O-) with the atoms bonded on both sides of it. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the terminal group represented by formula (2) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with excellent adhesion to the protective layer.

[0060] The terminal group represented by formula (2) has a 1,2-diol structure (-CH(OH)-CH2OH) at its end. Therefore, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) has good corrosion resistance and can suppress spin-off.

[0061] The terminal group represented by formula (2) has a divalent organic group represented by X, having 2 to 30 carbon atoms. Since the organic group represented by X has 2 or more carbon atoms, it is moderately rigid, which suppresses intramolecular interactions while providing sufficient hydrophobicity. Also, since the number of carbon atoms is 30 or less, it is possible to prevent the terminal group represented by formula (2) from becoming too bulky, which would hinder the movement of polar groups and inhibit interaction with the protective layer. The number of carbon atoms in the organic group represented by X is preferably 2 to 15, and more preferably 3 to 10.

[0062] The organic group represented by X contains at least one carbon atom that is not bonded to either a polar group or an ether oxygen atom. Examples of carbon atoms that are not bonded to either a polar group or an ether oxygen atom include carbon atoms of a methylene group, a methine group, or a fluorinated version thereof that is not bonded to either a polar group or an ether oxygen atom. As mentioned above, fluoro groups are not included in the polar groups. If the organic group represented by X has a polar group containing carbon atoms (for example, a carboxyl group, a formyl group, a carbonyl group, a cyano group, or a group having an amide bond), the carbon atoms included in the polar group shall not be included in the "carbon atoms that are not bonded to either the polar group or the ether oxygen atom."

[0063] The number of carbon atoms not bonded to either the polar group or the ether oxygen atom can be one or more, for example, 1 to 6, or 1 to 4. When the number of carbon atoms not bonded to either the polar group or the ether oxygen atom is one or more, the hydrophobicity of the lubricating layer containing the fluorine-containing ether compound is good. Furthermore, when the number of carbon atoms not bonded to either the polar group or the ether oxygen atom is 6 or less, the ratio of carbon atoms to the number of polar groups becomes appropriate, resulting in appropriate molecular polarity, and the ratio of carbon atoms to the number of ether oxygen atoms also becomes appropriate, resulting in a fluorine-containing ether compound with appropriate molecular flexibility. In addition, when there are multiple carbon atoms not bonded to either the polar group or the ether oxygen atom, these carbon atoms not bonded to either the polar group or the ether oxygen atom may be bonded to each other. In this case, the fluorine-containing ether compound molecule becomes more rigid, intramolecular interactions between polar groups are suppressed, and the polar groups become more involved in intermolecular interactions between fluorine-containing ether compounds.

[0064] The organic group represented by X may contain one or two polar groups. In this case, the adhesion to the protective layer of the fluorine-containing ether compound represented by formula (1) is improved, making it easier to form a lubricating layer that provides sufficient coverage even with a thin thickness. When the organic group represented by X contains polar groups, it is preferable that there is one polar group. In this case, the high hydrophilicity of the fluorine-containing ether compound represented by formula (1) can be more effectively suppressed, as it can induce water that causes corrosion.

[0065] If the organic group represented by X includes a polar group, then the polar group is R. 1 and R 3 Examples of polar groups included are those listed above, and it is more preferable that the polar group be selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond.

[0066] In formula (2), the organic group represented by X may contain 1 to 3 ether oxygen atoms. In this case, the ether oxygen atoms impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increase the affinity between the polar group and the protective layer. When the organic group represented by X contains ether oxygen atoms, it is preferable that there be 1 or 2 ether oxygen atoms. In this case, it is possible to further suppress the occurrence of intramolecular interactions due to the fluorine-containing ether compound represented by formula (1) becoming too flexible.

[0067] In formula (2), the organic group represented by X may be partially fluorinated. In this case, the hydrophilicity of the organic group represented by X in formula (2) is reduced compared to the case where the organic group is not fluorinated. As a result, the induction of water, which causes corrosion, can be suppressed, and a fluorine-containing ether compound that can form a lubricating layer with good corrosion resistance can be obtained.

[0068] In formula (2), the organic group represented by X is preferably an acyclic organic group. When the organic group represented by X is acyclic, compared to when X has a cyclic structure, it is possible to suppress the problem of the group becoming too bulky, which would hinder the movement of the polar group and inhibit its interaction with the protective layer. The acyclic organic group may be linear or branched.

[0069] In formula (2), the organic group represented by X preferably does not contain an unsaturated carbon-carbon bond. When the organic group represented by X does not contain an unsaturated carbon-carbon bond, the orientation of the molecule is restricted, the movement of the polar group is hindered, and the inhibition of interaction with the protective layer can be suppressed, compared to when X contains an unsaturated carbon-carbon bond.

[0070] The terminal group represented by formula (2) is preferably one of the following formulas (2-1) to (2-7).

[0071] [ka] (In equation (2-1), a represents an integer from 1 to 8, and b represents an integer from 1 to 7.) (In equation (2-2), c represents an integer from 1 to 7.) (In equation (2-3), d represents an integer from 1 to 6.) (In equation (2-4), e represents an integer from 1 to 6. e R a and R b (Each of these independently represents either a hydrogen atom or a methyl group.) (In equation (2-5), f represents an integer from 1 to 6.) (In equation (2-6), g represents an integer from 1 to 6.) (In equation (2-7), g2 represents an integer from 1 to 6.)

[0072] The terminal group represented by formula (2-1) is the organic group represented by X in formula (2) -CH2-CH(OH)-(CH2) a -O-(CH2) b This is -CH2-. a represents an integer from 1 to 8. b represents an integer from 1 to 7.

[0073] The terminal group represented by formula (2-1) has a structure in which a glycerin structure (-O-CH2-CH(OH)-CH2OH) is extended by b methylene groups at the terminal portion. Because the structure with extended glycerin structures has appropriate rigidity, it can suppress the formation of intramolecular interactions of the terminal group represented by formula (2-1). In addition, the ether bond of the structure with extended glycerin structures imparts appropriate mobility to the terminal group represented by formula (2-1), so that when one of the two hydroxyl groups at the terminal portion interacts with the protective layer, the other hydroxyl group becomes more likely to participate in intermolecular interactions between fluorine-containing ether compounds. Therefore, polar groups in the fluorine-containing ether compound represented by formula (1) can form intermolecular interactions more easily. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less prone to scattering of the fluorine-containing ether compound due to the rotation of the magnetic recording medium, and has even better spin-off resistance.

[0074] Since a in formula (2-1) is 1 or greater, the terminal group represented by formula (2-1) has sufficient hydrophobicity. Also, since a is 8 or less, the terminal group represented by formula (2-1) does not become too bulky due to an excessively large number of a, and the movement of the hydroxyl group in the terminal group represented by formula (2-1) is not hindered, which inhibits interaction with the protective layer. a is preferably 1 to 6, and more preferably 1 to 4.

[0075] Since b in formula (2-1) is 1 or greater, the terminal group represented by formula (2-1) has sufficient hydrophobicity. Also, since b is 7 or less, the terminal group represented by formula (2-1) does not become too bulky due to an excessively large number of b, and the movement of the hydroxyl group in the terminal group represented by formula (2-1) is not hindered, which inhibits interaction with the protective layer. b is preferably 1 to 5, and more preferably 1 to 3.

[0076] The sum of a and b in formula (2-1) is preferably 9 or less. In this case, the terminal group represented by formula (2-1) does not become too bulky, and the movement of the hydroxyl group in the terminal group represented by formula (2-1) is not hindered, which further suppresses the inhibition of interaction with the protective layer. The sum of a and b is more preferably 6 or less, and even more preferably 4 or less.

[0077] The terminal group represented by formula (2-2) is the organic group represented by X in formula (2) -CH2-CH(OH)-CH2-(CH2) c The expression is -O-CH2-, where c represents an integer between 1 and 7.

[0078] The terminal group represented by formula (2-2) has a glycerol structure (-O-CH2-CH(OH)-CH2OH) at its terminal portion. Because the glycerol structure has high mobility, when one of the two hydroxyl groups at the terminal portion interacts with the protective layer, the other hydroxyl group is more likely to interact intermolecularly with polar groups in other fluorine-containing ether compounds. Therefore, polar groups in the fluorine-containing ether compound represented by formula (1) can more easily form intermolecular interactions. As a result, lubricants containing the fluorine-containing ether compound represented by formula (1) are less likely to scatter the fluorine-containing ether compound when the magnetic recording medium rotates, and exhibit even greater spin-off resistance.

[0079] Since c in formula (2-2) is 1 or greater, the terminal group represented by formula (2-2) has sufficient hydrophobicity. Also, since c is 7 or less, the terminal group represented by formula (2-2) does not become too bulky due to an excessively large number of c, and the movement of the hydroxyl group in the terminal group represented by formula (2-2) is not hindered, which inhibits interaction with the protective layer. c is preferably 1 to 5, and more preferably 1 to 3.

[0080] The terminal group represented by formula (2-3) is the organic group represented by X in formula (2) -CH2-CH(OH)-(CH2) d - is the case. d represents an integer from 1 to 6.

[0081] The terminal group represented by formula (2-3) does not contain the hydrophilic ether oxygen atom in X. Therefore, the terminal group represented by formula (2-3) has low affinity for water. Consequently, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to absorb water, which causes corrosion, resulting in better corrosion resistance.

[0082] The terminal groups represented by formula (2-3) do not contain an ether oxygen atom in X in formula (2), and since d is 1 or greater, they are moderately rigid. As a result, intramolecular interactions between polar groups are more effectively suppressed, intermolecular interactions are formed more easily, and a lubricating layer with even greater spin-off resistance can be formed. Furthermore, since d is 6 or less, the terminal groups represented by formula (2-3) do not become too bulky due to an excessively large number of d, and the movement of hydroxyl groups in the terminal groups represented by formula (2-3) is not hindered, which inhibits interaction with the protective layer. d is preferably 1 to 4, and more preferably 2 to 4.

[0083] The terminal group represented by formula (2-4) is the organic group represented by X in formula (2) -CH2-CH(OH)-CH2-O-CH2-(CR a R b ) e -CH2-O-CH2-. e represents an integer from 1 to 6. e R a and R b Each of these independently represents either a hydrogen atom or a methyl group.

[0084] e-CR groups at the terminal group represented by formula (2-4) a R b - can be any of -CH2-, -CH(CH3)-, or -C(CH3)2-, respectively.

[0085] In the terminal groups represented by formulas (2-4), the organic group represented by X in formula (2) has a linear structure, i.e., R a and R bWhen X is a hydrogen atom, the terminal group does not become excessively bulky compared to when X has branching. This suppresses the obstruction of hydroxyl group movement and the resulting inhibition of interaction with the protective layer. As a result, when one of the two hydroxyl groups forming the terminal 1,2-diol structure interacts with the protective layer, the other hydroxyl group can more easily form intermolecular interactions with polar groups in other fluorine-containing ether compounds. Consequently, lubricants containing the fluorine-containing ether compound represented by formula (1) are less prone to scattering of the fluorine-containing ether compound during rotation of magnetic recording media and exhibit even greater spin-off resistance.

[0086] In terminal groups represented by formulas (2-4), if the organic group represented by X in formula (2) has a branched structure, i.e., contains -CH(CH3)- and / or -C(CH3)2-, X becomes moderately rigid, effectively suppressing intramolecular interactions between the hydroxyl groups of the terminal group. As a result, polar groups in the fluorine-containing ether compound represented by formula (1) can more easily form intermolecular interactions. Consequently, lubricants containing the fluorine-containing ether compound represented by formula (1) are less prone to scattering of the fluorine-containing ether compound during rotation of magnetic recording media, and exhibit even greater spin-off resistance.

[0087] Since e in formula (2-4) is 1 or greater, the terminal group represented by formula (2-4) has sufficient hydrophobicity. Also, since e is 6 or less, the terminal group represented by formula (2-4) does not become too bulky, which can prevent the movement of the hydroxyl group from being hindered and inhibiting its interaction with the protective layer. e is preferably 1 to 4, and more preferably 1 to 2.

[0088] The terminal group represented by formula (2-5) is the organic group represented by X in formula (2) -CH2-CH(OH)-CH2-O-CH2-(CF2) f The expression is -CH2-O-CH2-, where f represents an integer from 1 to 6.

[0089] The terminal group represented by formula (2-5) includes a straight perfluoroalkylene chain with 1 to 6 carbon atoms that reduces affinity for water. When the terminal group represented by formula (2-5) is present, the saturated hydrocarbon group containing the perfluoroalkylene chain (-CH2-(CF2) in formula (2-5)) f The -CH2- group reduces the overall polarity of the molecule and improves its hydrophobicity. This reduces the affinity between the fluorine-containing ether compound and water, which causes corrosion. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to absorb water, which causes corrosion, and exhibits even better corrosion resistance.

[0090] Since f in formula (2-5) is 1 or greater, the terminal group represented by formula (2-5) becomes moderately rigid, suppressing intramolecular interactions. Also, since f is 6 or less, the terminal group represented by formula (2-5) does not become too bulky, preventing the movement of the hydroxyl group from being hindered and inhibiting interaction with the protective layer. Preferably, f in formula (2-5) is 1 to 4, and more preferably 2 to 4.

[0091] The terminal group represented by formula (2-6) is the organic group represented by X in formula (2) -(CH2) g This is -CH2-, where g represents an integer from 1 to 6.

[0092] The terminal groups represented by formula (2-6) do not contain hydrophilic polar groups or ether oxygen atoms in X. Therefore, the terminal groups represented by formula (2-6) have low affinity for water. Consequently, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to absorb water, which causes corrosion, resulting in better corrosion resistance.

[0093] Since g in formula (2-6) is 1 or greater, formula (2-6) becomes moderately rigid, making it difficult for the hydroxyl groups of the 1,2-diol structure to form intramolecular interactions. Also, since g in formula (2-6) is 6 or less, the terminal group represented by formula (2-6) does not become too bulky, which can suppress the obstruction of the movement of the hydroxyl groups and the inhibition of interaction with the protective layer. g is preferably 1 to 5, and more preferably 1 to 3.

[0094] The terminal group represented by formula (2-7) is the organic group represented by X in formula (2) -(CH2) g2 The expression is -CH2-CH(OH)-CH2-O-CH2-. g2 represents an integer from 1 to 6. The terminal group represented by formula (2-7) has a glycerol structure (-O-CH2-CH(OH)-CH2OH) at its terminal portion. Because the glycerol structure has high mobility, when one of the two hydroxyl groups at the terminal portion interacts with the protective layer, the other hydroxyl group is more likely to interact intermolecularly with polar groups in other fluorine-containing ether compounds. Therefore, polar groups in the fluorine-containing ether compound represented by formula (1) can more easily form intermolecular interactions. As a result, lubricants containing the fluorine-containing ether compound represented by formula (1) are less likely to scatter the fluorine-containing ether compound when the magnetic recording medium rotates, and exhibit even greater spin-off resistance.

[0095] Since g2 in formula (2-7) is 1 or greater, formula (2-7) becomes moderately rigid, making it difficult for the hydroxyl groups of the 1,2-diol structure to form intramolecular interactions. Also, since g2 in formula (2-7) is 6 or less, the terminal group represented by formula (2-7) does not become too bulky, which suppresses the obstruction of the movement of the hydroxyl groups and inhibits interaction with the protective layer. g2 is preferably 1 to 5, and more preferably 1 to 3.

[0096] Of the terminal groups represented by formulas (2-1) to (2-7), the terminal groups represented by formulas (2-3), (2-5), and (2-6) exhibit better corrosion resistance.

[0097] Of the terminal groups represented by formulas (2-1) to (2-7), the terminal groups represented by formulas (2-1), (2-2), (2-4), and (2-7) exhibit superior spin-off resistance when the sum of a and b in formula (2-1) is 4 or less, c in formula (2-2) is 3 or less, e in formula (2-4) is 2 or less, and g2 in formula (2-7) is 3 or less, respectively.

[0098] In the fluorine-containing ether compound represented by formula (1), R 1 and R 3 These can be the same or different. 1 and R 3 It is preferable that the same. In this case, fluorine-containing ether compounds can be easily and efficiently produced. Note that "R 1 and R 3 "The same as R" means 1 Atoms and R contained in 3 The atoms contained in -CH2-R 2 This means that the configuration is symmetrical with respect to -CH2-.

[0099] In the fluorine-containing ether compound represented by formula (1), R 1 and R 3 If they are different, R 1 and R 3 These may each be terminal groups represented independently by formula (2), and R 1 and R 3 One of the terminal groups may be represented by formula (2), and the other may be a terminal group that does not correspond to formula (2). The terminal group that does not correspond to formula (2) may be any terminal group that has 1 to 4 polar groups and has 1 to 50 carbon atoms, as described above.

[0100] R 1 and R 3 If one of the terminal groups is represented by formula (2) and the other is a terminal group that does not correspond to formula (2), it is preferable that the terminal group that does not correspond to formula (2) is represented by the following formula (3).

[0101] [ka] (In formula (3), l represents an integer between 1 and 3. Each of the l m independently represents an integer between 1 and 6. Each of the l n independently represents an integer between 1 and 6. In one repeating unit, at least one of m and n is 1. B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond, or a hydrogen atom.)

[0102] The terminal group represented by formula (3) is R 2 It has an oxygen atom (ether oxygen atom) bonded to the methylene group (-CH2-) that is bonded to it. The oxygen atom located at the end of the terminal group represented by formula (3) forms an ether bond (-O-) with the atoms bonded on both sides of it. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the terminal group represented by formula (3) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with excellent adhesion to the protective layer.

[0103] In formula (3), l is an integer between 1 and 3, preferably between 1 and 2, and more preferably 1. When l in formula (3) is 3 or less, it is possible to prevent water, which causes corrosion, from being attracted to the lubricating layer due to an excess of hydroxyl groups in the terminal group represented by formula (3), and a lubricating layer with good corrosion resistance can be obtained.

[0104] If l in equation (3) is 2 or 3, then 2 or 3 repeating units (-(CH2) m -CH(OH)-(CH2) n The combinations of m and n in -O-) may be different, or some or all of them may be the same.

[0105] In equation (3), each of the l m represents an independent integer from 1 to 6. Each of the l n represents an independent integer from 1 to 6. One repeating unit in equation (3) (-(CH2) m -CH(OH)-(CH2) nIn -O-), at least one of m and n is 1. In this case, it is possible to suppress the decrease in the mobility of the hydroxyl group in the repeating unit due to having too many carbon atoms in the alkylene group between the carbon atom to which the hydroxyl group is bonded and the ether oxygen atom.

[0106] In formula (3), B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond, or a hydrogen atom.

[0107] When B in formula (3) is an alkyl group that does not have a polar group, examples of B include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and the like.

[0108] If B in formula (3) is an alkyl group having a polar group, then the polar group is R 1 and R 3 It is preferable that the polar group included is one of the examples listed above. Among the polar groups mentioned above, it is more preferable that the polar group is selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond.

[0109] When B in formula (3) is an alkyl group having a polar group, examples of B include 2-hydroxyethyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 5-hydroxypentyl group, 6-hydroxyhexyl group, 2-aminoethyl group, 3-aminopropyl group, 1-carboxymethyl group, 2-carboxyethyl group, 3-carboxypropyl group, 1-carbonylmethyl group, 2-carbonylethyl group, 3-carbonylpropyl group, 1-acetylmethyl group, 2-acetylethyl group, 3-acetylpropyl group, 2-sulfoethyl group, 3-sulfopropyl group, 1-cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, 2-acetamidoethyl group, 3-acetamidopropyl group, 4-acetamidobutyl group, 1-carboxamidemethyl group, 2-carboxamideethyl group, 3-carboxamidepropyl group, and 4-carboxamidebutyl group.

[0110] Among the alkyl groups having polar groups as described above, it is preferable that the alkyl group is any of the following: 2-hydroxyethyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 5-hydroxypentyl group, 6-hydroxyhexyl group, 1-cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 2-acetamidoethyl group, 1-carboxamidemethyl group, 2-carboxamideethyl group, or 3-carboxamidepropyl group, and more preferably that it is any of the following: 2-hydroxyethyl group, 3-hydroxypropyl group, 2-cyanoethyl group, 3-cyanopropyl group, 2-acetamidoethyl group, or 1-carboxamidemethyl group.

[0111] In formula (3), if B is an organic group containing a carbon-carbon unsaturated bond, examples of B include organic groups containing at least one selected from aromatic hydrocarbons, unsaturated heterocycles, alkenyl groups, and alkynyl groups.

[0112] If B in formula (3) is an organic group containing a carbon-carbon unsaturated bond, then B may be a phenyl group, methoxyphenyl group, phenyl fluoride group, acetamidophenyl group, carboxamidephenyl group, cyanophenyl group, naphthyl group, phenethyl group, methoxyphenethyl group, phenethyl fluoride group, benzyl group, methoxybenzyl group, naphthylmethyl group, methoxynaphthyl group, pyrrolyl group, pyrazolyl group, methylpyrazolylmethyl group, imidazolyl group, furyl group, furfuryl group, oxazolyl group, isoxazolyl group, thienyl group, thienylethyl group, thiazolyl group, methylthiazolyl Examples include the tyl group, isothiazolyl group, pyridyl group, pyrimidinyl group, pyridadinyl group, pyrazinyl group, indolinyl group, benzofuranyl group, benzothienyl group, benzimidazolyl group, benzoxazolyl group, benzothiazolyl group, benzopyrazolyl group, benzoisoxazolyl group, benzoisothiazolyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, synnolinyl group, vinyl group, allyl group, butenyl group, propynyl group, propargyl group, butynyl group, methylbutynyl group, pentynyl group, methylpentynyl group, and hexynyl group.

[0113] Among the organic groups containing the carbon-carbon unsaturated bond described above, any one of a phenyl group, a methoxyphenyl group, an acetamidophenyl group, a carboxamidophenyl group, a cyanophenyl group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a thienylethyl group, an allyl group, a butenyl group, and a propargyl group is preferable, and particularly, any one of a phenyl group, a methoxyphenyl group, a carboxamidophenyl group, an allyl group, and a butenyl group is more preferable. In this case, the terminal group represented by the formula (3) has sufficient hydrophobicity and does not become too bulky, and it is possible to suppress the movement of the hydroxyl group in the formula (3) from being hindered and the interaction with the protective layer from being inhibited.

[0114] When B in the formula (3) is a hydrogen atom, B forms a hydroxyl group together with the oxygen atom in the formula (3).

[0115] The terminal group represented by the formula (3) is more preferably represented by any one of the following formulas (3-1) to (3-3).

[0116]

Chemical formula

[0117] In the end groups represented by formulas (3-1) to (3-3), each polar group contained in the end group is bonded to a different carbon atom. Further, the carbon atoms to which the polar groups are bonded are bonded to each other via a linking group containing a carbon atom to which no polar group is bonded. Therefore, the end groups represented by formulas (3-1) to (3-3) can be oriented such that both the terminal polar group and the hydroxyl group adjacent to the terminal polar group can adhere to the protective layer by the linking group containing a carbon atom to which no polar group is bonded. Accordingly, a lubricating layer capable of obtaining a strong interaction with the protective layer can be formed.

[0118] Compared with the end groups in which the carbon atoms to which the polar groups are bonded are directly bonded, the polar groups in the end groups represented by formulas (3-1) to (3-3) are less likely to aggregate with each other, and an interaction with the protective layer is likely to occur. For this reason, in the end groups represented by formulas (3-1) to (3-3), the terminal portion in the fluorine-containing ether compound is less likely to float, and the adhesion to the protective layer is less likely to decrease.

[0119] In the end group represented by formula (3-1), the linking group between the carbon atom to which D is bonded and the carbon atom to which the hydroxyl group adjacent to D arranged at the terminal is bonded contains an ether oxygen atom. The linking group has a linear structure composed of 2 to 7 atoms including a carbon atom to which no polar group is bonded.

[0120] The end group represented by formula (3-1) has a linear structure composed of 2 or more atoms including a carbon atom to which no polar group is bonded. For this reason, the distance between D and the hydroxyl group adjacent to D is appropriate. Therefore, since the interaction between D and the hydroxyl group adjacent to D in the molecule can be suppressed, the polar group can adhere to the protective layer efficiently. Further, since the end group represented by formula (3-1) has the above structure, a fluorine-containing ether compound having good hydrophobicity can be obtained even if it contains an ether oxygen atom. Also, the molecular mobility is appropriate, intramolecular aggregation is unlikely to occur, and it has excellent adhesion to the protective layer.

[0121] The terminal group represented by formula (3-1) is a linear structure consisting of seven or fewer atoms, including a carbon atom that is not bonded to a polar group, and the linking group contains an ether oxygen atom. Therefore, the high hydrophobicity of the linking group does not impede the adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer.

[0122] These findings suggest that fluorine-containing ether compounds having terminal groups represented by formula (3-1) exhibit excellent adhesion to protective layers, high corrosion resistance, and can form a lubricating layer that suppresses spin-off.

[0123] In the terminal group represented by formula (3-1), the sum of p and r is between 1 and 5, preferably between 1 and 3. The terminal group represented by formula (3-1) has a linking group between the carbon atom to which D is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal D is bonded. The carbon atoms included in the linking group prevent intramolecular interactions between adjacent polar groups from taking precedence over interactions between the polar group and the protective layer. As a result, the carbon atoms included in the linking group improve the adhesion between the polar group in formula (3-1) and the protective layer.

[0124] If there are too many carbon atoms in the linking group described above, the flexibility of the terminal group represented by formula (3-1) decreases, making it difficult to uniformly coat the entire surface of the protective layer. In the terminal group represented by formula (3-1), the sum of p and r is 5 or less, so the alkylene chain in the main chain portion of formula (3-1) is not too long. Therefore, a long, rigid alkylene chain reduces the flexibility of the terminal portion, weakens the interaction with the protective layer, and prevents the terminal portion from lifting. p is an integer from 0 to 3, preferably 0 or 1, and more preferably 0. r is an integer from 0 to 5, preferably 1 or 2, and more preferably 1.

[0125] In formula (3-1), D represents a polar group, a vinyl group, an ethynyl group, or an optionally substituted aryl group. If D is a polar group, then D is R 1 and R 3It is preferable that the polar group included is one of the examples listed above. Among the above polar groups, it is more preferable that it is a polar group selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond. If D is an aryl group which may have substituents, then an aryl group which may have substituents can be used, which is included in the organic group that can be used when B in formula (3) above is an organic group containing a carbon-carbon unsaturated bond.

[0126] In equation (3-1), q represents an integer between 0 and 2. The number of polar groups in equation (3-1) is q+2 if D is a polar group, and q+1 if D is a vinyl group or an ethynyl group. As mentioned above, R 1 and R 3 The number of polar groups contained in each is preferably two or three. Therefore, in formula (3-1), q is preferably 0 or 1 when D is a polar group, and preferably 1 or 2 when D is a vinyl group or an ethynyl group. When D is an aryl group which may have substituents, it is preferable to select q such that the number of polar groups in formula (3-1) is two or three.

[0127] In the terminal group represented by formula (3-2), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the adjacent hydroxyl group is bonded does not contain an oxygen atom. Therefore, intramolecular interactions are small, and intramolecular aggregation is less likely to occur, resulting in excellent adhesion to the protective layer.

[0128] The terminal group represented by formula (3-2) is a linear structure consisting of 1 to 5 atoms, including a carbon atom that is not bonded to a hydroxyl group. Because the above-mentioned terminal group is a linear structure consisting of one or more atoms, including a carbon atom that is not bonded to a hydroxyl group, the distance between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group is appropriate. Therefore, intramolecular aggregation is unlikely to occur, and a fluorine-containing ether compound with good hydrophobicity can be obtained.

[0129] The terminal group represented by formula (3-2) is a linear structure consisting of five or fewer atoms, including carbon atoms that do not contain oxygen atoms and to which hydroxyl groups are not bonded. Therefore, the hydrophobicity of the linking group is not too high, which would hinder adhesion to the protective layer, and the linking group does not become too bulky, which would have a small effect in hindering the movement of the hydroxyl group.

[0130] In the terminal group represented by formula (3-2), t is an integer from 1 to 5. In the terminal group represented by formula (3-2), as with the terminal group represented by formula (3-1), if there are too many carbon atoms in the linking group positioned between carbon atoms to which the polar group is bonded, the flexibility of the terminal group represented by formula (3-2) decreases, making it difficult to uniformly coat the entire surface of the protective layer. In the terminal group represented by formula (3-2), since t is 5 or less, the alkylene chain in the main chain portion of formula (3-2) is not too long. Therefore, it is possible to prevent a decrease in the flexibility of the terminal portion and a decrease in the interaction between the terminal hydroxyl group and the protective layer due to a long, rigid alkylene chain. t is preferably 1 or 2, and more preferably 1.

[0131] From these findings, the fluorine-containing ether compound having a terminal group represented by formula (3-2) has a linear structure in which the linking group in formula (3-2) does not contain an oxygen atom and contains 1 to 5 atoms including carbon atoms that are not bonded to a hydroxyl group. Therefore, it can form a lubricating layer that has excellent adhesion to the protective layer, high corrosion resistance, and can suppress spin-off.

[0132] In equation (3-2), s represents an integer from 0 to 2. The number of polar groups in equation (3-2) is s+2, and as mentioned above, R 1 and R 3 The number of polar groups contained in each is preferably two or three. Therefore, the value of s in formula (3-2) is preferably 0 or 1.

[0133] In the terminal group represented by formula (3-3), each of the five E atoms independently represents a polar group, an alkoxy group with 1 to 8 carbon atoms, a halogen group, or a hydrogen atom. If the five E atoms include a polar group, the number of polar groups among the five E atoms is 1.

[0134] In the terminal group represented by formula (3-3), if five E atoms contain polar groups, the linking group between the carbon atom to which the polar group represented by E is bonded and the carbon atom to which the adjacent hydroxyl group is bonded contains an oxygen atom forming an ether bond. The above linking group has a structure consisting of 3 to 5 atoms, including carbon atoms that are not bonded to the polar group. The number of atoms in the above linking group refers to the number of atoms in the shortest distance between the carbon atom to which the polar group contained in E is bonded and the carbon atom to which the adjacent hydroxyl group contained in E is bonded.

[0135] In the terminal group represented by formula (3-3), if the five E atoms include polar groups, the linking group has a structure consisting of three or more atoms, including an oxygen atom that forms an ether bond and a carbon atom that is not bonded to a polar group. Therefore, the distance between the polar group represented by E and the hydroxyl group adjacent to the polar group represented by E is appropriate. Furthermore, because the benzene ring is rigid, free rotation is difficult. Thus, interaction between the polar group represented by E, which is a substituent bonded to the benzene ring, and the hydroxyl group adjacent to the polar group represented by E can be suppressed.

[0136] In equation (3-3), u represents an integer from 1 to 3. If u in equation (3-3) is 2 or 3, then -(CH2CH(OH)CH2O) u The linking groups between carbon atoms bonded to multiple adjacent hydroxyl groups in this molecule have a linear structure consisting of three atoms, including an oxygen atom forming an ether bond and a carbon atom not bonded to a hydroxyl group. Because the above linking groups have a linear structure consisting of three atoms including a carbon atom not bonded to a hydroxyl group, the distance between adjacent hydroxyl groups is appropriate. Therefore, it is possible to suppress interactions between hydroxyl groups within the molecule.

[0137] From these facts, in the fluorine-containing ether compound having the terminal group represented by formula (3-3), the interaction between polar groups within the molecule can be suppressed. Therefore, the lubricating layer containing the fluorine-containing ether compound having the terminal group represented by formula (3-3) has excellent adhesion to the protective layer and a high spin-off suppression effect.

[0138] In the terminal group represented by formula (3-3), when none of the five Es contain a polar group, the hydrophobicity of the molecule becomes higher compared to the case where one of the five Es is a polar group. Therefore, the lubricating layer containing the fluorine-containing ether compound having the terminal group represented by formula (3-3) can further suppress the induction of water that causes corrosion and becomes more corrosion-resistant.

[0139] In the terminal group represented by formula (3-3), when E is a polar group, E is preferably one of the preferred examples of the polar groups contained in R 1 and R 3 Among the above polar groups, E is more preferably a polar group selected from the group consisting of a cyano group and a group having an amide bond, and further preferably a cyano group, an acetamide group (-NHC(=O)CH3) or a carboxamide group (-C(=O)NH2). This is because when the polar group is a cyano group, an acetamide group or a carboxamide group, it becomes a fluorine-containing ether compound that can form a lubricating layer with a stronger interaction with the protective layer. Also, the cyano group, acetamide group or carboxamide group has a low acidity, so there is almost no effect of the fluorine-containing ether compound having these groups on corroding the substrate. When E is not a polar group, it is preferably independently a methoxy group, a fluoro group or a hydrogen atom.

[0140] The number of polar groups in formula (3-3) is u + 1 when the five Es contain a polar group, and u when the five Es do not contain a polar group. As described above, R 1 [[ID=!8]]and R 3The number of polar groups contained in each is preferably two or three. Therefore, in formula (3-3), u is preferably 1 or 2 if the five E contain polar groups, and preferably 2 or 3 if the five E do not contain polar groups.

[0141] If the five E atoms in formula (3-3) include polar groups, the other four E atoms may be partially or entirely the same, or they may each be different. If the five E atoms include polar groups, it is preferable that the other four E atoms are all the same. If the five E atoms do not include polar groups, the five E atoms may be partially or entirely the same, or they may each be different.

[0142] If the five E atoms in formula (3-3) contain polar groups, the polar groups may be located at any of the five E atoms.

[0143] (R 2 (PFPE chain shown by) In the fluorine-containing ether compound represented by formula (1), R 2 This is a perfluoropolyether chain. 2 The PFPE chain shown in this embodiment, when a lubricant containing the fluorine-containing ether compound of this embodiment is applied to the protective layer to form a lubricating layer, covers the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. 2 The PFPE chain shown is appropriately selected according to the performance requirements of the lubricant containing the fluorine-containing ether compound.

[0144] R 2 Examples of PFPE chains represented by include those consisting of polymers or copolymers of perfluoroalkylene oxides. Examples of perfluoroalkylene oxides include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0145] R in equation (1) 2 Preferably, this is a PFPE chain represented by the following formula (4), derived from a polymer or copolymer of perfluoroalkylene oxides. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In equation (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are average values ​​representing the number of CF2 molecules, each independently representing 1 to 3. There are no particular restrictions on the order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in equation (4).)

[0146] In formula (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing a range of 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In equation (4), w1 and w6 are average values ​​indicating the number of CF2 units, each independently representing 1 to 3. w1 and w6 are determined according to the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by equation (4). In equation (4), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular restrictions on the order in which the repeating units are arranged in equation (4). There are also no particular restrictions on the number of different types of repeating units in equation (4).

[0147] R in equation (1) 2 It is preferable that this is one of the PFPE chains selected from the following formulas (4-1) to (4-4). -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In equation (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In equation (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In equation (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization, each independently representing a value between 1 and 20. w7 and w10 are average values ​​representing the number of CF2 molecules, each independently representing a value between 1 and 2.)

[0148] R 2 If R is one of the PFPE chains represented by formulas (4-1) to (4-4), it becomes a fluorine-containing ether compound that yields a lubricating layer with good lubricity. 2 When is one of the PFPE chains represented by formulas (4-1) to (4-4), the ratio of oxygen atoms (ether bond (-O-) number) to carbon atoms in the PFPE chain is appropriate. Therefore, a fluorine-containing ether compound with appropriate hardness is formed. Thus, the fluorine-containing ether compound applied on the protective layer is less likely to aggregate on the protective layer, and an even thinner lubricating layer can be formed with sufficient coverage. Also, R 2 A lubricating layer containing a fluorine-containing ether compound, where is one of the PFPE chains represented by formulas (4-1) to (4-4), is preferable because it becomes denser and can further suppress spin-off.

[0149] In formula (4-1), there are no particular restrictions on the sequence order of the repeating units, (OCF2CF2) and (OCF2). In formula (4-1), the number of (OCF2CF2) units h and the number of (OCF2) units i may be the same or different. The PFPE chain represented by formula (4-1) may be a polymer of (OCF2CF2). Furthermore, the PFPE chain represented by formula (4-1) may be a random copolymer, block copolymer, or alternating copolymer composed of (OCF2CF2) and (OCF2).

[0150] In formulas (4-1) to (4-3), the average degree of polymerization is 1 to 20 for h, 0 to 20 for i, 1 to 15 for j, and 1 to 10 for k, resulting in a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Furthermore, in formulas (4-1) to (4-3), the average degrees of polymerization are 20 or less for h and i, 15 or less for j, and 10 or less for k, so the viscosity of the fluorine-containing ether compound does not become too high, making it easy to apply lubricants containing it, which is preferable. The average degrees of polymerization of h, i, j, and k are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7, as this results in a fluorine-containing ether compound that spreads easily on the protective layer and yields a lubricating layer with a uniform film thickness.

[0151] In formula (4-4), there are no particular restrictions on the order of the repeating units (CF2CF2CF2O) and (CF2CF2O). In formula (4-4), the number of (CF2CF2CF2O) units w8 and the number of (CF2CF2O) units w9, which indicate the average degree of polymerization, may be the same or different. Formula (4-4) may include any of the monomer units (CF2CF2CF2O) and (CF2CF2O), such as a random copolymer, a block copolymer, or an alternating copolymer.

[0152] In formula (4-4), w8 and w9, which represent the average degree of polymerization, are each independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. In equation (4-4), w7 and w10 are average values ​​indicating the number of CF2 units, and each independently represents 1 to 2. w7 and w10 are determined according to the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by equation (4-4).

[0153] The fluorine-containing ether compound represented by formula (1) is preferably one of the compounds represented by the following formulas (AA) to (AS), (BA) to (BH), or (CA) to (CK). When the compound represented by formula (1) is one of the compounds represented by the following formulas (AA) to (AS), (BA) to (BH), or (CA) to (CK), the raw materials are readily available, and even with a thin thickness, a lubricating layer with even better corrosion resistance and spin-off suppression can be formed.

[0154] In the compounds represented by the following formulas (AA)~(AS), (BA)~(BH), and (CA)~(CK), Rf1, Rf2, and Rf3, which represent the PFPE chain, have the following structures. That is, in the compounds represented by the following formulas (AA)~(AS), (BA)~(BF), (CA), (CB), and (CE), Rf1 is the PFPE chain represented by formula (4-1) above. In the compounds represented by the following formulas (BG), (CC), and (CF)~(CK), Rf2 is the PFPE chain represented by formula (4-2) above. In the compounds represented by the following formulas (BH) and (CD), Rf3 is the PFPE chain represented by formula (4-3) above. Note that in equations (AA)~(AS), (BA)~(BH), and (CA)~(CK), h and i in Rf1, j in Rf2, and k in Rf3, which represent the PFPE chain, are values ​​that indicate the average degree of polymerization and are therefore not necessarily integers.

[0155] [ka]

[0156] The compounds represented by the following formulas (AA) to (AS) are R in formula (1). 1 and R 3R is a terminal group represented by any of the above formulas (2-1) to (2-6). 2 This is the PFPE chain represented by the above formula (4-1).

[0157] The compounds represented by the following formulas (BA) to (BE) are R in formula (1). 1 and R 3 One of them is a terminal group represented by formula (2-1) above, and the other is a terminal group represented by either formula (3-1) or (3-2) above. 2 This is the PFPE chain represented by the above formula (4-1).

[0158] The compound represented by the following formula (BF) is R in formula (1). 1 and R 3 One of them is the terminal group represented by formula (2-1) above, and the other is the terminal group represented by formula (3). 2 This is the PFPE chain represented by formula (4-1) above. The terminal group represented by formula (3) does not correspond to any of the above formulas (3-1) to (3-3).

[0159] The compounds represented by the following formulas (BG) and (BH) are R in formula (1). 1 and R 3 This is the terminal group represented by the above formula (2-1). 2 This is the PFPE chain represented by the above formula (4-2) or (4-3).

[0160] [ka] (In formula (AA), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AB), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AC), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AD), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0161] [ka] (In formula (AE), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AF), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AG), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AH), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0162] [ka] (In formula (AI), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AJ), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AK), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AL), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0163] [ka] (In formula (AM), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AN), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AO), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AP), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0164] [ka] (In formula (AQ), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AR), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (AS), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0165] [ka] (In formula (BA), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (BB), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (BC), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (BD), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0166] [ka] (In formula (BE), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (BF), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (BG), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (BH), in Rf3, k represents the average degree of polymerization and is expressed as 1 to 10.)

[0167] The compounds represented by the following formulas (CA) to (CK) are R in formula (1). 1 and R 3R is a terminal group represented by any of the above formulas (2-1) to (2-7). 2 This is a PFPE chain represented by any of the above formulas (4-1) to (4-3).

[0168] [ka] (In formula (CA), in Rf1, h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0.) (In formula (CB), in Rf1, h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0.) (In formula (CC), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (CD), in Rf3, k represents the average degree of polymerization and is expressed as 1 to 10.) (In formula (CE), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (CF), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (CG), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (CH), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (CI), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (CJ), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (CK), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.)

[0169] The fluorine-containing ether compound in this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10000, and particularly preferably in the range of 1000 to 5000. If the number-average molecular weight is 500 or more, the lubricating layer made of the lubricant containing the fluorine-containing ether compound in this embodiment will have excellent heat resistance. The number-average molecular weight of the fluorine-containing ether compound is more preferably 1000 or more. Furthermore, if the number-average molecular weight is 10000 or less, the viscosity of the fluorine-containing ether compound will be appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing it. The number-average molecular weight of the fluorine-containing ether compound is preferably 5000 or less, as this results in a viscosity that is easy to handle when applied to a lubricant.

[0170] The number-average molecular weight (Mn) of fluorine-containing ether compounds was determined using a Bruker BioSpin AVANCE III 400. 1 H-NMR and 19 These values ​​were measured by F-NMR. Specifically, 19 The number of repeating units in the PFPE chain is calculated from the integrated value measured by 1F-NMR, and the number-average molecular weight is determined. For NMR (nuclear magnetic resonance) measurements, the sample is diluted in hexafluorobenzene / d-acetone (4 / 1v / v) solvent before measurement. 19 The reference point for the F-NMR chemical shift is the hexafluorobenzene peak at -164.7 ppm. 1 The standard for the 1H-NMR chemical shift is to set the acetone peak at 2.2 ppm.

[0171] In this embodiment, it is preferable to fractionate the fluorine-containing ether compound by a suitable molecular weight method to achieve a molecular weight dispersion (weight-average molecular weight (Mw) / number-average molecular weight (Mn) ratio) of 1.3 or less. In this embodiment, there are no particular limitations on the molecular weight fractionation method, but for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or molecular weight fractionation by supercritical fluid extraction can be used.

[0172] "Manufacturing method" The method for producing the fluorine-containing ether compound of this embodiment is not particularly limited and can be produced using conventionally known production methods. The fluorine-containing ether compound of this embodiment can be produced, for example, using the production method shown below.

[0173] (R 1 and R 3 (If they are the same) In equation (1), R 1 and R 3 To produce a compound that is the same as R in formula (1), first, 2 Prepare a fluorine-based compound in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain.

[0174] Next, the hydroxyl groups of the hydroxymethyl groups located at both ends of the fluorinated compound, and R in formula (1) 1 The base (=R) 3 The epoxy group of an epoxy compound having a group that becomes R is reacted with this. 2 R at both ends of the corresponding perfluoropolyether chain 1 The corresponding base (=R 3 A compound having the corresponding group is obtained.

[0175] R in equation (1) 1 The base (=R) 3 Examples of epoxy compounds having a group that becomes (5-1) include compounds represented by the following formulas (5-1) to (5-16) and (5-24). In the above reaction, instead of the epoxy compound, R in formula (1) is used. 1 The base (=R) 3 Compounds having a leaving group (hereinafter sometimes simply referred to as "compounds having a leaving group") may also be used. As compounds having a leaving group, compounds represented by the following formulas (5-25) to (5-27) can be used. In formulas (5-25) and (5-26), MOM represents a methoxymethyl group. In formulas (5-25) to (5-27), Ts represents a tosyl group.

[0176] [ka]

[0177] [ka]

[0178] When reacting a fluorinated compound with an epoxy compound (or a compound having a leaving group), the hydroxyl group of the epoxy compound (or compound having a leaving group) may be protected with an appropriate protecting group before reacting it with the fluorinated compound.

[0179] Epoxy compounds (for example, epoxy compounds represented by formula (5-1)) can be produced by reacting an alcohol compound, which may be appropriately protected, with a halogen compound having an epoxy group, for example, as shown in formula (6-1) below.

[0180] [ka]

[0181] Epoxy compounds (for example, epoxy compounds represented by formula (5-5)) may be produced by reacting an alcohol compound having a vinyl group with a halogen compound having an alcohol that may be appropriately protected, as shown in formula (6-2) below, and then oxidizing the resulting compound by treating it with m-chloroperbenzoic acid (mCPBA).

[0182] [ka]

[0183] Epoxy compounds (for example, epoxy compounds represented by formula (5-10)) may be produced by sequentially reacting a halogen compound having an alcohol that may be appropriately protected with a diol compound, and a halogen compound having an epoxy group, as shown in formula (6-3) below.

[0184] [ka]

[0185] Epoxy compounds (or compounds with leaving groups) may be purchased commercially and used.

[0186] By performing the above steps, R in equation (1) 1 and R 3 A compound identical to the one described is obtained.

[0187] In equation (1), R 1 and R 3 To produce a compound that is the same as [the other compound], the following methods may be used.

[0188] First, in equation (1), R 2 A fluorine-based compound is prepared in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain. The hydroxyl groups of the hydroxymethyl groups positioned at both ends of the fluorine-based compound are reacted with a halogen compound having a vinyl group at its end. This yields a compound having vinyl groups at both ends of a chain structure containing a perfluoropolyether chain.

[0189] Next, the vinyl groups at both ends of the obtained compound are oxidized to obtain a compound having epoxy groups at both ends of a chain structure containing a perfluoropolyether chain. The ring-opening reaction of the epoxy groups at both ends converts them to a 1,2-diol. By performing the above steps, R in formula (1) is obtained. 1 and R 3 A compound identical to the one described is obtained.

[0190] (R 1 and R 3 (If they are different) In equation (1), R 1 and R 3 To produce a compound that is different from the one in formula (1), first, R in formula (1) 2 Prepare a fluorine-based compound in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain.

[0191] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine compound, and R in formula (1) 1 The epoxy group of an epoxy compound having a group that becomes R is reacted with this. 2 R at one end of the corresponding perfluoropolyether chain 1 Intermediate compound 1 having the corresponding group is obtained (first reaction).

[0192] Next, the above intermediate compound 1 and R in formula (1) 3 The epoxy compound having the resulting group is reacted with the epoxy compound (second reaction). In the first and / or second reaction, a compound having a leaving group may be used instead of the epoxy compound.

[0193] R 1 and R 3 If the two are different, and one is a terminal group represented by formula (2) while the other is a terminal group that does not correspond to formula (2), then, for example, epoxy compounds represented by the following formulas (5-17) to (5-23) can be used as the epoxy compound corresponding to the terminal group that does not correspond to formula (2). In formulas (5-17), (5-18), (5-21) to (5-23), THP represents a tetrahydropyranyl group.

[0194] [ka]

[0195] By performing the above steps, R in equation (1)1 and R 3 Different compounds are obtained.

[0196] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of this embodiment can be mixed with known materials used as lubricants, as necessary, as long as the properties are not impaired by the inclusion of the fluorine-containing ether compound represented by formula (1) above.

[0197] Specific examples of known materials include, for example, FOMBLIN® ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), and Moresco A20H (manufactured by Moresco). The known materials used in combination with the lubricant of this embodiment preferably have a number average molecular weight of 1,000 to 10,000.

[0198] If the lubricant of this embodiment contains other materials of the fluorine-containing ether compound represented by formula (1) above, it is preferable that the content of the fluorine-containing ether compound represented by formula (1) in the lubricant of this embodiment be 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0199] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1) above, and therefore has excellent corrosion resistance and can form a lubricating layer that can suppress spin-off.

[0200] [Magnetic recording medium] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers can be provided between the substrate and the magnetic layer, as needed. Furthermore, at least one of an adhesive layer and a soft magnetic layer can be provided between the underlayer and the substrate.

[0201] Figure 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 adhesion 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.

[0202] "substrate" As the substrate 11, for example, a non-magnetic substrate can be used, which has a film made of NiP or NiP alloy formed on a base made of a metal or alloy material such as Al or an Al alloy. Furthermore, the substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a non-magnetic substrate in which a film of NiP or NiP alloy is formed on a substrate made of one of these non-metallic materials.

[0203] "Adhesion layer" The adhesive layer 12 prevents the progression 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 placed in contact with each other. The material of the adhesion layer 12 can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed, for example, by sputtering.

[0204] "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 sequentially laminated. That is, the soft magnetic layer 13 preferably has a structure in which the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC) coupled by sandwiching an intermediate layer made of a Ru film between the two soft magnetic films.

[0205] Examples of materials for the first and second soft magnetic films include CoZrTa alloy and CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it becomes possible to improve the orientation of the first underlayer (seed layer) and reduce the amount of levitation of the magnetic head. The soft magnetic layer 13 can be formed, for example, by a sputtering method.

[0206] "First base layer" The first sublayer 14 is a layer that controls the orientation and crystal size of the second sublayer 15 and the magnetic layer 16 which are placed on top of it. Examples of the first subsoil layer 14 include a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, a CrTi alloy layer, and so on. The first subsoil layer 14 can be formed, for example, by a sputtering method.

[0207] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16 to a good degree. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second sublayer 15 may consist of one layer or multiple layers. If the second sublayer 15 consists of multiple layers, all layers may be made of the same material, or at least one layer may be made of a different material. The second subsoil layer 15 can be formed, for example, by sputtering.

[0208] "Magnetic layer" The magnetic layer 16 consists of a magnetic film whose easy magnetization axis is oriented perpendicular or horizontal to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. The magnetic layer 16 may also contain oxides, Cr, B, Cu, Ta, Zr, etc., to improve the SNR characteristics. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0209] The magnetic layer 16 may consist of a single layer, or it may consist of multiple magnetic layers made of materials with different compositions. For example, if the magnetic layer 16 consists of three layers stacked from bottom to top—a first magnetic layer, a second magnetic layer, and a third magnetic layer—the first magnetic layer is preferably a granular structure made of a material containing Co, Cr, Pt, and an oxide. As the oxide contained in the first magnetic layer, it is preferable to use oxides such as Cr, Si, Ta, Al, Ti, Mg, and Co. Among these, TiO2, Cr2O3, and SiO2 are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide with two or more oxides added. Among these, Cr2O3-SiO2, Cr2O3-TiO2, and SiO2-TiO2 are particularly suitable. In addition to Co, Cr, Pt, and oxides, the first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re.

[0210] The second magnetic layer can be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure. The third magnetic layer is preferably a non-granular structure made of a material containing Co, Cr, and Pt, but free of oxides. In addition to Co, Cr, and Pt, the third magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0211] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 consists of three layers, 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.

[0212] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can preferably be made of, for example, Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (where 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, B).

[0213] For the non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16, it is preferable to use an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, as oxides, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, TiO2, etc. can be used. As metal nitrides, for example, AlN, Si3N4, TaN, CrN, etc. can be used. As metal carbides, for example, TaC, BC, SiC, etc. can be used. The non-magnetic layer can be formed, for example, by sputtering.

[0214] To achieve a higher recording density, the magnetic layer 16 is preferably a perpendicular magnetic recording layer in which the easy magnetization axis is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be an in-plane magnetic recording layer. The magnetic layer 16 may be formed by any conventionally known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0215] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may consist of one layer or multiple layers. A carbon-based protective layer is preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. A carbon-based protective layer is preferable because it further enhances the interaction with polar groups (especially hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18.

[0216] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrated 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 atoms when measured by hydrogen forward scattering (HFS). Furthermore, the nitrogen content in the carbon-based protective layer is preferably 4 to 15 atoms when measured by X-ray photoelectron spectroscopy (XPS).

[0217] The hydrogen and / or nitrogen contained in the carbon-based protective layer do not need to be uniformly distributed throughout the entire layer. Preferably, the carbon-based protective layer is a compositionally graded layer, for example, in which nitrogen is contained on the lubrication layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubrication layer 18 and the carbon-based protective layer is further improved.

[0218] 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 a 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 thinning the protective layer 17.

[0219] As a method for forming the protective layer 17, sputtering using a carbon-containing target material, CVD (chemical vapor deposition) using hydrocarbon raw materials such as ethylene and toluene, and IBD (ion beam deposition) can be used. When forming a carbon-based protective layer as the protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when forming a carbon-based protective layer as the protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface and low roughness.

[0220] "Lubricant layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. Furthermore, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording / reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in Figure 1, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 is formed by applying the lubricant for magnetic recording media of the above-described embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-described fluorine-containing ether compound.

[0221] The lubricating layer 18 is bonded with a particularly strong bond to the protective layer 17, especially when the protective layer 17 located beneath the lubricating layer 18 is a carbon-based protective layer. As a result, even with a thin lubricating layer 18, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high degree of coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0222] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.2 nm (12 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming island-like or mesh-like structures. Therefore, the surface of the protective layer 17 can be covered with a high coverage rate by the lubricating layer 18. Furthermore, by making the average thickness of the lubricating layer 18 2.0 nm or less, the lubricating layer 18 can be sufficiently thinned, and the amount of levitation of the magnetic head can be sufficiently reduced.

[0223] "Method for forming a lubricating layer" One method for forming the lubricating layer 18 is to prepare a magnetic recording medium in the process of being manufactured, in which each layer up to the protective layer 17 has been formed on the substrate 11, apply a lubricating layer forming solution to the protective layer 17, and dry it.

[0224] The lubricating layer-forming solution is obtained by dispersing and dissolving the lubricant for magnetic recording media of the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to be suitable for the coating method. Examples of solvents used in lubrication layer forming solutions include fluorine-based solvents such as Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals) and Asahi Clean® AE-3000 (trade name, manufactured by AGC).

[0225] The method for applying the lubricating layer-forming solution is not particularly limited, but examples include the spin coating method, spray method, paper coating method, and dip method. When using the dip 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 lubricating layer forming solution placed in the immersion tank of the dip coating apparatus. Next, the substrate 11 is withdrawn from the immersion tank at a predetermined speed. This coats the surface of the protective layer 17 of the substrate 11 with the lubricating layer forming solution. By using the dipping method, the lubrication layer-forming solution can be uniformly applied to the surface of the protective layer 17, and a lubrication layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0226] In this embodiment, it is preferable to heat-treat the substrate 11 on which the lubricating layer 18 is formed. By heat-treating, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesion force between the lubricating layer 18 and the protective layer 17 is improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. A heat treatment temperature of 100°C or higher provides sufficient improvement in adhesion between the lubricating layer 18 and the protective layer 17. Furthermore, a heat treatment temperature of 180°C or lower prevents thermal decomposition of the lubricating layer 18 due to heat treatment. The heat treatment time can be appropriately adjusted according to the heat treatment temperature, and is preferably 10 to 120 minutes.

[0227] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) light before or after heat treatment.

[0228] 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 provided on a substrate 11. In the magnetic recording medium 10 of this embodiment, the lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed in contact with the protective layer 17. Even with a thin film thickness, this lubricating layer 18 has good corrosion resistance and can suppress spin-off. Therefore, the magnetic recording medium 10 of this embodiment is excellent in reliability, particularly corrosion resistance, spin-off suppression, and durability. As a result, the magnetic recording medium 10 of this embodiment can contribute to reducing magnetic spacing, allowing for a low magnetic head levitation amount (for example, 10 nm or less), and can operate stably over a long period of time even in harsh environments associated with the diversification of applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk mounted in a LUL (Load Unload) type magnetic disk drive. [Examples]

[0229] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0230] [Example 1] The compound represented by the above formula (AA) was obtained by the method described below. HOCH2CF2O(CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i 5 g of the compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5) (number average molecular weight 1000, molecular weight distribution 1.1), 2.70 g of the compound represented by the above formula (5-1), and 5 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 0.30 g of potassium tert-butoxide was added to this mixture and the mixture was stirred at 70°C for 16 hours to allow it to react.

[0231] The compound represented by formula (5-1) was synthesized by protecting the 1,2-diol moiety of 1,2,4-butanetriol with acetone, and then reacting the hydroxyl group at position 4 with epibromohydrin.

[0232] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 10 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 25 mL of saturated sodium bicarbonate solution and extracted twice with 50 mL of ethyl acetate. The organic layer was washed in the following order: 25 mL of saline solution, 25 mL of saturated sodium bicarbonate solution, and 25 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.71 g of compound (AA) (in formula (AA), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5).

[0233] The obtained compound (AA) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0234] [Example 2] The compound represented by formula (AB) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-2) was used instead of the compound represented by formula (5-1), and 3.85 g of compound (AB) (wherein Rf1 in formula (AB) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0235] The compound represented by formula (5-2) was synthesized by protecting the 1,2-diol moiety of 1,2,6-hexanetriol with acetone, and then reacting the hydroxyl group at position 6 with epibromohydrin.

[0236] The obtained compound (AB) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0237] [Example 3] The compound represented by the above formula (AC) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-3) was used instead of the compound represented by formula (5-1), and 3.85 g of compound (AC) (wherein Rf1 in formula (AC) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0238] The compound represented by formula (5-3) was synthesized by protecting the 1,2-diol moiety of 1,2,8-octantriol with acetone, and then reacting the hydroxyl group at position 8 with epibromohydrin.

[0239] The obtained compound (AC) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(20H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0240] [Example 4] The compound represented by the above formula (AD) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-4) was used instead of the compound represented by formula (5-1), and 3.91 g of compound (AD) (wherein Rf1 in formula (AD) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0241] The compound represented by formula (5-4) was synthesized by the following method: The 1,2-diol moiety of 1,2,4-butanetriol was protected with acetone, the hydroxyl group at position 4 was brominated, and the compound was reacted with 3-buten-1-ol to obtain the compound. The vinyl group of the obtained compound was then oxidized with m-chloroperbenzoic acid (mCPBA) to synthesize the compound.

[0242] The obtained compound (AD) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0243] [Example 5] The compound represented by the above formula (AE) was obtained by the method described below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), and 3.26 g of compound (AE) (wherein Rf1 in formula (AE) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0244] The compound represented by formula (5-5) was synthesized by reacting a compound in which the hydroxyl group of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) was brominated with 3-buten-1-ol, and then oxidizing the vinyl group of the resulting compound with m-chloroperbenzoic acid (mCPBA).

[0245] The obtained compound (AE) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0246] [Example 6] The compound represented by the above formula (AF) was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-6) was used instead of the compound represented by formula (5-1), and 3.43 g of compound (AF) (wherein Rf1 in formula (AF) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0247] The compound represented by formula (5-6) was synthesized by reacting a compound in which the hydroxyl group of solketal has been brominated with 5-hexen-1-ol, and then oxidizing the vinyl group of the resulting compound with m-chloroperbenzoic acid (mCPBA).

[0248] The obtained compound (AF) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0249] [Example 7] The compound represented by the above formula (AG) was obtained by the method described below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (5-7) was used instead of the compound represented by formula (5-1), and 3.56 g of compound (AG) (wherein Rf1 in formula (AG) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0250] The compounds represented by formula (5-7) were synthesized by reacting a compound in which the hydroxyl group of solketal was brominated with 7-octen-1-ol, and then oxidizing the vinyl group of the resulting compound with m-chloroperbenzoic acid (mCPBA).

[0251] The obtained compound (AG) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(20H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0252] [Example 8] The compound represented by the above formula (AH) was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-8) was used instead of the compound represented by formula (5-1), and 3.40 g of compound (AH) (wherein Rf1 in formula (AH) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0253] The compound represented by formula (5-8) was synthesized by the following method: The epoxy group of 1,2-epoxy-5-hexene was opened using dilute sulfuric acid. The 1,2-diol moiety resulting from the ring opening was protected with acetone, and the vinyl group of the resulting compound was oxidized with m-chloroperbenzoic acid (mCPBA) to synthesize the compound.

[0254] The resulting compound (AH) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(18H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0255] [Example 9] The compound represented by the above formula (AI) was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-9) was used instead of the compound represented by formula (5-1), and 3.45 g of compound (AI) (wherein Rf1 in formula (AI) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0256] The compound represented by formula (5-9) was synthesized by the following method: One vinyl group of 1,7-octadiene was oxidized with m-chloroperbenzoic acid (mCPBA). The epoxy group resulting from the oxidation was opened using dilute sulfuric acid. The 1,2-diol moiety resulting from the ring opening was protected with acetone, and the vinyl group of the resulting compound was oxidized with mCPBA to synthesize the compound.

[0257] The obtained compound (AI) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(18H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0258] [Example 10] The compound represented by the above formula (AJ) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-10) was used instead of the compound represented by formula (5-1), and 3.68 g of compound (AJ) (wherein Rf1 in formula (AJ) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0259] The compound represented by formula (5-10) was synthesized by reacting one hydroxyl group of 1,3-propanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0260] The obtained compound (AJ) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0261] [Example 11] The compound represented by the above formula (AK) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1), and 3.76 g of compound (AK) (wherein Rf1 in formula (AK) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0262] The compound represented by formula (5-11) was synthesized by reacting one hydroxyl group of 2,2-dimethyl-1,3-propanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0263] The obtained compound (AK) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.20-1.25(12H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0264] [Example 12] The compound represented by the above formula (AL) was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-12) was used instead of the compound represented by formula (5-1), and 3.78 g of compound (AL) (wherein Rf1 in formula (AL) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0265] The compound represented by formula (5-12) was synthesized by reacting one hydroxyl group of 1,4-butanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0266] The obtained compound (AL) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0267] [Example 13] The compound represented by the above formula (AM) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-13) was used instead of the compound represented by formula (5-1), and 3.85 g of compound (AM) (wherein Rf1 in formula (AM) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0268] The compound represented by formula (5-13) was synthesized by reacting one hydroxyl group of 2,3-dimethyl-1,4-butanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0269] The obtained compound (AM) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.25(12H), 1.65-1.85(4H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0270] [Example 14] The compound represented by the above formula (AN) was obtained by the method described below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (5-14) was used instead of the compound represented by formula (5-1), and 3.81 g of compound (AN) (wherein Rf1 in formula (AN) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0271] The compound represented by formula (5-14) was synthesized by reacting one hydroxyl group of 1,8-octanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0272] The obtained compound (AN) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(24H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0273] [Example 15] The compound represented by the above formula (AO) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-15) was used instead of the compound represented by formula (5-1), and 4.02 g of compound (AO) (wherein Rf1 in formula (AO) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0274] The compound represented by formula (5-15) was synthesized by reacting one hydroxyl group of 2,2,3,3-tetrafluoro-1,4-butanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0275] The obtained compound (AO) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=3.40-3.85(26H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F), -128.5~130.0(8F)

[0276] [Example 16] The compound represented by the above formula (AP) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-16) was used instead of the compound represented by formula (5-1), and 4.31 g of compound (AP) (wherein Rf1 in formula (AP) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0277] The compound represented by formula (5-16) was synthesized by reacting one hydroxyl group of 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-octanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin.

[0278] The obtained compound (AP) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(26H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F), -122.5~-124.5(16F), -128.5~130.0(8F)

[0279] [Example 17] The compound represented by the above formula (AQ) was obtained by the method described below. HOCH2CF2O(CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i 5 g of a compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5) (number average molecular weight 1000, molecular weight distribution 1.1), 4.50 g of 1-bromo-4-pentene, and 10 mL of N,N-dimethylformamide were charged together and stirred at room temperature until homogeneous to form a mixture. 1.20 g of sodium hydride (60% purity, containing mineral oil) was added to this mixture and the mixture was stirred at 70°C for 16 hours to allow it to react.

[0280] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 50 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.76 g of the compound shown in formula (7-1) below as an intermediate compound.

[0281] [ka] (In formula (7-1), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0282] Next, under a nitrogen gas atmosphere, 4.76 g of the intermediate compound shown in formula (7-1), obtained above, 20 mL of methylene chloride, and 3.15 g of m-chloroperbenzoic acid (mCPBA (73% purity, hydrated)) were charged into a 100 mL round-bottom flask and reacted by stirring at room temperature for 16 hours.

[0283] To the reaction solution obtained after the reaction, 50 mL of an aqueous solution of 3.18 g of sodium sulfite was added to deactivate the excess mCPBA. After filtering off the resulting solid, it was transferred to a separatory funnel and extracted three times with 100 mL of methylene chloride. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.21 g of the compound shown in formula (7-2) below as an intermediate compound.

[0284] [ka] (In formula (7-2), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0285] Next, under a nitrogen gas atmosphere, 4.21 g of the intermediate compound shown in formula (7-2), obtained above, along with 20 mL of acetone and 20 mL of 10% dilute sulfuric acid, were charged into a 100 mL round-bottom flask and reacted by stirring at room temperature for 16 hours.

[0286] After the reaction, 20 mL of saturated sodium bicarbonate solution was added to the reaction mixture to neutralize it, and the resulting solid was filtered off. Then, it was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.32 g of compound (AQ) (wherein Rf1 in formula (AQ) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5).

[0287] The obtained compound (AQ) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(14H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0288] [Example 18] The compound represented by the above formula (AR) was obtained by the method described below. The procedure was the same as in Example 17, except that 1-bromo-7-octene was used instead of 1-bromo-4-pentene, and 3.35 g of compound (AR) (wherein Rf1 in formula (AR) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0289] The obtained compound (AR) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(20H), 3.40-3.85(14H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0290] [Example 19] The compound represented by the above formula (AS) was obtained by the method described below.

[0291] (First reaction) HOCH2CF2O(CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i12.5 g of the compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5) (number average molecular weight 1000, molecular weight distribution 1.1), 2.70 g of the compound represented by the above formula (5-1), and 12 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 1.10 g of potassium tert-butoxide was added to this mixture and the mixture was reacted by stirring at 70°C for 16 hours.

[0292] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 7.21 g of the compound shown in formula (8) below as intermediate compound 1.

[0293] [ka] (In equation (8), Rf1 is the PFPE chain represented by equation (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0294] (Second reaction) Next, under a nitrogen gas atmosphere, 7.21 g of the compound represented by formula (8), which is intermediate compound 1 obtained above, 2.70 g of the compound represented by formula (5-5), and 20 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous to form a mixture. 0.55 g of potassium tert-butoxide was added to this mixture and the mixture was reacted by stirring at 70°C for 16 hours.

[0295] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 50 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saturated sodium bicarbonate solution and extracted twice with 200 mL of ethyl acetate. The organic layer was washed in the following order: 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.44 g of compound (AS) (in formula (AS), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5).

[0296] The obtained compound (AS) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0297] [Example 20] The compound represented by the above formula (BA) was obtained by the method described below. The same procedure as in Example 19 was followed, except that the compound represented by formula (5-17) was used instead of the compound represented by formula (5-5), and 3.61 g of compound (BA) (wherein Rf1 in formula (BA) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0298] The compound represented by formula (5-17) was synthesized by protecting the hydroxyl group of ethylene glycol monoallyl ether with dihydropyran, and then oxidizing the vinyl group with m-chloroperbenzoic acid (mCPBA).

[0299] The obtained compound (BA) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(2H), 3.40-3.85(24H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0300] [Example 21] The compound represented by the above formula (BB) was obtained by the method described below. The same procedure as in Example 19 was followed, except that the compound represented by formula (5-18) was used instead of the compound represented by formula (5-5), and 3.61 g of compound (BB) (wherein Rf1 in formula (BB) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0301] The compound represented by formula (5-18) was synthesized by the following method: Epichlorohydrin was reacted with 2 molar amounts of 3-buten-1-ol. The hydroxyl group produced by the reaction was protected with dihydropyran. One of the vinyl groups of the compound obtained by the reaction was oxidized with m-chloroperbenzoic acid (mCPBA) to synthesize the compound.

[0302] The obtained compound (BB) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(27H), 3.85-4.10(4H), 5.20-5.80(3H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0303] [Example 22] The compound represented by the above formula (BC) was obtained by the method shown below. The same procedure as in Example 19 was followed, except that the compound represented by formula (5-19) was used instead of the compound represented by formula (5-5), and 3.53 g of compound (BC) (wherein Rf1 in formula (BC) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0304] The compound represented by formula (5-19) was synthesized by reacting the hydroxyl group of 2-acetamidoethanol with epibromohydrin.

[0305] The obtained compound (BC) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(2H), 1.90(3H), 3.40-3.85(23H), 3.85-4.10(4H), 6.70-6.80(1H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0306] [Example 23] The compound represented by the above formula (BD) was obtained by the method described below. The same procedure as in Example 19 was followed, except that the compound represented by formula (5-20) was used instead of the compound represented by formula (5-5), and 3.72 g of compound (BD) (wherein Rf1 in formula (BD) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0307] The compound represented by formula (5-20) was synthesized by reacting the hydroxyl group of 3-cyanopropanol with epibromohydrin.

[0308] The obtained compound (BD) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 1.90-2.00(2H), 3.40-3.85(21H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0309] [Example 24] The compound represented by the above formula (BE) was obtained by the method shown below. The same procedure as in Example 19 was followed, except that the compound represented by formula (5-21) was used instead of the compound represented by formula (5-5), and 3.72 g of compound (BE) (wherein Rf1 in formula (BE) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0310] The compound represented by formula (5-21) was synthesized by protecting the hydroxyl group of 3-buten-1-ol with dihydropyran, and then oxidizing the vinyl group with m-chloroperbenzoic acid (mCPBA).

[0311] The obtained compound (BE) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(20H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0312] [Example 25] The compound represented by the above formula (BF) was obtained by the method described below. The same procedure as in Example 19 was followed, except that the compound represented by formula (5-22) was used instead of the compound represented by formula (5-5), and 3.72 g of compound (BF) (wherein Rf1 in formula (BF) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0313] The compound represented by formula (5-22) was synthesized by protecting the two hydroxyl groups of 3-allyloxy-1,2-propanediol with dihydropyran, and then oxidizing the vinyl group with m-chloroperbenzoic acid (mCPBA).

[0314] The obtained compound (BF) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(2H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0315] [Example 26] The compound represented by the above formula (BG) was obtained by the method described below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2O(CF2CF2CF2O). j The same procedure as in Example 1 was followed, except that a compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) was used (number average molecular weight 1000, molecular weight distribution 1.1), and 3.48 g of compound (BG) (where Rf2 in formula (BG) is the PFPE chain represented by the above formula (4-2). In Rf2, j, representing the average degree of polymerization, represents 4.5) was obtained.

[0316] The obtained compound (BG) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0317] [Example 27] The compound represented by the above formula (BH) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2CF2O(CF2CF2CF2CF2O) kExcept for using a compound represented by CF2CF2CF2CH2OH (where k, representing the average degree of polymerization, is 3.0), the same procedure as in Example 1 was carried out to obtain 3.44 g of compound (BH) (where Rf3 in formula (BH) is the PFPE chain represented by formula (4-3) above. In Rf3, k, representing the average degree of polymerization, represents 3.0).

[0318] The obtained compound (BH) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(16F), -122.5(4F), -126.0(12F), -129.0~-128.0(4F)

[0319] [Example 28] The compound represented by the above formula (CA) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5), use HOCH2CF2O(CF2CF2O) h (CF2O) i The same procedure as in Example 1 was carried out, except that a compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 7.0, and i, representing the average degree of polymerization, is 0) was used, and 3.15 g of compound (CA) (where Rf1 in formula (CA) is the PFPE chain represented by formula (4-1) above. In Rf1, h, representing the average degree of polymerization, represents 7.0, and i, representing the average degree of polymerization, represents 0) was obtained. The obtained compound (CA) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-78.5(4F), -91.0~-88.5(28F)

[0320] [Example 29] The compound represented by the above formula (CB) was obtained by the method shown below. The same procedure as in Example 28 was followed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), and 3.08 g of compound (CB) (wherein Rf1 in formula (CB) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 7.0, and i, which indicates the average degree of polymerization, represents 0) was obtained. The obtained compound (CB) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-78.5(4F), -91.0~-88.5(28F)

[0321] [Example 30] The compound represented by the above formula (CC) was obtained by the method shown below. The same procedure as in Example 26 was followed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), and 3.24 g of compound (CC) (where Rf2 in formula (CC) is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5) was obtained. The obtained compound (CC) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0322] [Example 31] The compound represented by the above formula (CD) was obtained by the method described below. The same procedure as in Example 27 was followed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), and 2.95 g of compound (CD) (wherein Rf3 in formula (CD) is the PFPE chain represented by formula (4-3) above. In Rf3, k, which indicates the average degree of polymerization, represents 3.0) was obtained. The obtained compound (CD) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(16F), -122.5(4F), -126.0(12F), -129.0~-128.0(4F)

[0323] [Example 32] The compound represented by the above formula (CE) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (5-24) was used instead of the compound represented by formula (5-1), and 3.35 g of compound (CE) (wherein Rf1 in formula (CE) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (5-24) was synthesized by reacting one hydroxyl group of 2-methyl-1,3-propanediol with a compound in which the hydroxyl group of solketal has been brominated, and then reacting the other hydroxyl group with epibromohydrin. The obtained compound (CE) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.25(6H), 1.25-1.35(2H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0324] [Example 33] The compound represented by the above formula (CF) was obtained by the method described below. HOCH2CF2CF2O(CF2CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. j 5 g of the compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) (number average molecular weight 1000, molecular weight distribution 1.1), 4.83 g of the compound represented by the above formula (5-25), and 20 mL of N,N-dimethylformamide were charged together and stirred at room temperature until homogeneous to form a mixture. 7.14 g of cesium carbonate was added to this mixture and the mixture was stirred at 70°C for 16 hours to allow it to react. The compound represented by formula (5-25) was synthesized by the following method. First, the hydroxyl group of 3-buten-1-ol was protected with dihydropyran, and then the alkenyl group was oxidized with m-chloroperbenzoic acid. Subsequently, the resulting compound was reacted with solketal, and the secondary hydroxyl group of the resulting compound was protected with chloromethyl methyl ether. The resulting compound represented by formula (5-25A) was treated with an acid to selectively deprotect the THP group, and then the primary hydroxyl group was reacted with p-toluenesulfonyl chloride to obtain the compound represented by formula (5-25). Selective deprotection of the THP group was carried out by mixing 3.60 g (10.3 mmol) of the compound represented by formula (5-25A) with a mixed solvent consisting of 16 g of 2-propanol and 16 g of acetone, to which 0.52 g (2.07 mmol) of pyridinium p-toluenesulfonate, an acid catalyst, was added, and the mixture was stirred in an air atmosphere at a reaction temperature of 55°C for 7 hours.

[0325] [ka]

[0326] The reaction solution obtained after the reaction of the above fluorine-based compound with the compound represented by formula (5-25) was allowed to return to room temperature, and 10 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction solution was gradually transferred to a separatory funnel containing 25 mL of saturated sodium bicarbonate solution and extracted twice with 50 mL of ethyl acetate. The organic layer was washed in the following order: 25 mL of saline solution, 25 mL of saturated sodium bicarbonate solution, and 25 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 2.81 g of compound (CF) (Rf1 in formula (CF) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5). The obtained compound (CF) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0327] [Example 34] The compound represented by the above formula (CG) was obtained by the method shown below. The same procedure as in Example 33 was followed, except that the compound represented by formula (5-26) was used instead of the compound represented by formula (5-25), and 2.92 g of compound (CG) (where Rf2 in formula (CG) is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5) was obtained. The compound represented by formula (5-26) was synthesized by the following method. First, the hydroxyl group of 5-hexen-1-ol was protected with dihydropyran, and then the alkenyl group was oxidized with m-chloroperbenzoic acid. Subsequently, the resulting compound was reacted with solketal, and the secondary hydroxyl group of the resulting compound was protected with chloromethyl methyl ether. The resulting compound was treated with an acid to selectively deprotect the THP group, and then the primary hydroxyl group was reacted with p-toluenesulfonyl chloride to obtain the compound represented by formula (5-26). The obtained compound (CG) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(26H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0328] [Example 35] The compound represented by the above formula (CH) was obtained by the method shown below. HOCH2CF2CF2O(CF2CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. j12 g of the compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) (number average molecular weight 1000, molecular weight distribution 1.1), 1.81 g of the compound represented by the above formula (5-27), and 20 mL of N,N-dimethylformamide were charged together and stirred at room temperature until homogeneous to form a mixture. 5.51 g of cesium carbonate was added to this mixture and the mixture was stirred at 50°C for 16 hours to allow it to react. The compound represented by formula (5-27) was synthesized by protecting the 1,2-diol moiety of 1,2,6-hexanetriol with acetone, and then reacting the hydroxyl group at position 6 with p-toluenesulfonyl chloride. The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 5.96 g of the compound shown in formula (9) below as intermediate compound 1. [ka] (In formula (9), Rf2 is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5.) Next, under a nitrogen gas atmosphere, 5.96 g of the compound represented by formula (9), which is intermediate compound 1 obtained above, 2.76 g of the compound represented by formula (5-26), and 20 mL of N,N-dimethylformamide were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous to form a mixture. 3.65 g of cesium carbonate was added to this mixture and the mixture was reacted by stirring at 50°C for 16 hours. The reaction mixture obtained after the reaction was allowed to return to room temperature, and 50 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saturated sodium bicarbonate solution and extracted twice with 200 mL of ethyl acetate. The organic layer was washed in the following order: 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 2.41 g of compound (CH) (Rf2 in formula (CH) is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5). The resulting compound (CH) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(20H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0329] [Example 36] The compound represented by the above formula (CI) was obtained by the method shown below. The same procedure as in Example 26 was followed, except that the compound represented by formula (5-8) was used instead of the compound represented by formula (5-1), and 3.13 g of compound (CI) (where Rf2 in formula (CI) is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5) was obtained. The obtained compound (CI) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(18H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0330] [Example 37] The compound represented by the above formula (CJ) was obtained by the method described below. The same procedure as in Example 26 was followed, except that the compound represented by formula (5-10) was used instead of the compound represented by formula (5-1), and 3.52 g of compound (CJ) (where Rf2 in formula (CJ) is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5) was obtained. The obtained compound (CJ) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0331] [Example 38] The compound represented by the above formula (CK) was obtained by the method described below. The same procedure as in Example 26 was followed, except that the compound represented by formula (5-15) was used instead of the compound represented by formula (5-1), and 3.61 g of compound (CK) (wherein Rf2 in formula (CK) is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5) was obtained. The obtained compound (CK) 1 H-NMR and 19The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(26H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-128.5(17F)

[0332] When the compounds (AA) to (AS), (BA) to (BH), and (CA) to (CK) obtained in this way are substituted into formula (1), the R values ​​are as follows: 1 , R 2 , R 3 The structure is shown in Tables 1 and 2.

[0333] [Table 1]

[0334] [Table 2]

[0335] [Comparative Example 1] The compound represented by the following formula (ZA) was synthesized by the method described in Patent Document 1.

[0336] [ka] (In formula (ZA), Rf2 represents the PFPE chain shown in formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5.)

[0337] [Comparative Example 2] The compound represented by the following formula (ZB) was synthesized by the method described in Patent Document 2.

[0338] [ka] (In formula (ZB), Rf2 is the PFPE chain represented by formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5.)

[0339] [Comparative Example 3] The compound represented by the following formula (ZC) was synthesized by the method described in Patent Document 3.

[0340] [ka] (In formula (ZC), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0341] [Comparative Example 4] The compound represented by the following formula (ZD) was synthesized by the following method.

[0342] [ka] (In formula (ZD), Rf2 represents the PFPE chain shown in formula (4-2) above. In Rf2, j, which indicates the average degree of polymerization, represents 4.5.)

[0343] Instead of the compound represented by formula (5-1), the compound represented by formula (5-23) was used, HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2O(CF2CF2CF2O). j The same procedure as in Example 1 was followed, except that a compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) (number-average molecular weight 1000, molecular weight distribution 1.1) was used, and 2.81 g of compound (ZD) was obtained.

[0344] The obtained compound (ZD) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(14H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0345] [Comparative Example 5] The compound represented by the following formula (ZE) was synthesized by the method described in Patent Document 4.

[0346] [ka] (In formula (ZE), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0347] The number-average molecular weight (Mn) of the compounds obtained in Examples 1-38 and Comparative Examples 1-5 was measured using the method described above. The results are shown in Tables 3 and 4.

[0348] Next, lubricating layer-forming solutions were prepared using the compounds obtained in Examples 1-38 and Comparative Examples 1-5 by the method described below. Then, using the obtained lubricating layer-forming solutions, a lubricating layer was formed on the magnetic recording medium by the method described below, obtaining the magnetic recording media of Examples 1-38 and Comparative Examples 1-5.

[0349] "Lubricant layer forming solution" The compounds obtained in Examples 1-38 and Comparative Examples 1-5 were each dissolved in Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals), a fluorine-based solvent, and then diluted with Bartrell XF to a film thickness of 9.0 Å to 9.5 Å when applied to a protective layer, to prepare a lubricating layer forming solution.

[0350] "Magnetic recording medium" A magnetic recording medium was prepared by sequentially layering 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. The lubricating layer-forming solutions of Examples 1-38 and Comparative Examples 1-5 were applied to the protective layer of the magnetic recording medium, which had each layer up to the protective layer formed, by the dipping method. The dipping method was performed under the following conditions: dipping speed of 10 mm / sec, dipping time of 30 sec, and withdrawal speed of 1.2 mm / sec.

[0351] Subsequently, the magnetic recording medium coated with the lubricating layer-forming solution was placed in a constant temperature bath, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent from the lubricating layer-forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0352] [Film thickness measurement] The thickness of the lubricating layer in the magnetic recording media of Examples 1-38 and Comparative Examples 1-5 obtained in this manner was measured using a Fourier transform infrared spectrophotometer (FT-IR, trade name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Tables 3 and 4.

[0353] Next, the magnetic recording media of Examples 1-38 and Comparative Examples 1-5 were subjected to the following corrosion resistance tests and spin-off characteristic tests. The results are shown in Tables 3 and 4.

[0354] [Corrosion resistance test] Magnetic recording media were exposed to conditions of 85°C and 90% relative humidity for 48 hours. Subsequently, the number of corrosion spots with a diameter of 5 μm or more that formed on the surface of the magnetic recording media was counted using an optical surface analyzer (Candela 7140, manufactured by KLA-Tencor Co., Ltd.) and evaluated based on the following evaluation criteria.

[0355] "Criteria for evaluating corrosion resistance" A+: Fewer than 100 corrosion spots A: Corrosion spots: 100 or more, but less than 300 B: Corrosion spots: 300 or more, but less than 500 C: Corrosion spots: 500 or more, but less than 1000 D: Over 1000 corrosion spots

[0356] [Spin-off characteristics test] A magnetic recording medium was mounted on a spin stand and rotated at a rotation speed of 10,000 rpm for 72 hours in an environment of 80°C. Before and after this operation, the thickness of the lubricating layer at a radius of 20 mm from the center of the magnetic recording medium was measured using FT-IR, and the rate of reduction in the thickness of the lubricating layer before and after the test was calculated. Using the calculated rate of reduction in thickness, the spin-off characteristics were evaluated according to the evaluation criteria shown below.

[0357] "Evaluation Criteria for Spin-Off Characteristics" A+: Film thickness reduction rate less than 2% A: Film thickness reduction rate of 2% or more, less than 3% B: Film thickness reduction rate of 3% or more, less than 5% C: Film thickness reduction rate of 5% or more, less than 10% D: Film thickness reduction rate of 10% or more

[0358] [comprehensive evaluation] Based on the results of corrosion resistance tests and spin-off characteristic tests, a comprehensive evaluation was conducted based on the following criteria.

[0359] "Overall Evaluation Criteria" A: Both the corrosion resistance test evaluation and the spin-off characteristics test evaluation are A+ or A B: One of the evaluations for corrosion resistance testing and spin-off properties testing is B, and the other is A+, A, or B. C: Either the corrosion resistance test evaluation or the spin-off properties test evaluation is C, and the other is A+, A, B, or C. D: At least one of the evaluations of the corrosion resistance test and the spin-off characteristics test is D

[0360] [Table 3]

[0361] [Table 4]

[0362] As shown in Tables 3 and 4, R is located at the end of the perfluoropolyether chain. 1 and R 3 In all of the magnetic recording media of Examples 1 to 38, which used fluorine-containing ether compounds (AA)~(AS), (BA)~(BH), and (CA)~(CK) that satisfy formula (1), at least one of which is a terminal group represented by formula (2), all received an evaluation of A+, A, or B in the corrosion resistance test and spin-off characteristic test, and an overall evaluation of A or B. From this, it was confirmed that the lubricating layer of the magnetic recording media of Examples 1 to 38 has good corrosion resistance and can suppress spin-off.

[0363] R 1 and R 3 In Examples 8, 9, 15-18, 35, 36, and 38, which used compounds (AH), (AI), (AO)-(AR), (CH), (CI), and (CK) whose terminal groups are represented by formulas (2-3), (2-5), (2-6), and (2-7), the corrosion resistance test evaluation was A+, showing favorable results.

[0364] R 1 and R 3 Compounds (AA), (AB), (AD), (BG), (BH), (CA), R, where the terminal group is represented by formula (2-1) and the sum of a and b is 4 or less. 1 and R 3 Compounds (AE), (AF), (CB), (CC), (CD), R, where the terminal group is represented by formula (2-2) and c is 3 or less. 1 and R 3 Compounds (AJ) to (AM), (CE), (CJ), R, where the terminal group is represented by formula (2-4) and e is 2 or less. 1 and R 3Compound (AS), R 1 and R 2 In Examples 1, 2, 4-6, 10-13, 19, 26-34, and 37, which used compounds (CF) and (CG) whose terminal group is represented by formula (2-7) and g2 is 3 or less, the spin-off characteristic test evaluation was A+, indicating good performance.

[0365] In contrast, as shown in Tables 3 and 4, in Comparative Examples 1 to 5 using compounds (ZA) to (ZE), all evaluations in the corrosion resistance test and spin-off characteristic test were either B, C, or D, and the overall evaluation was either C or D.

[0366] The compound (ZA) used in Comparative Example 1 does not contain a terminal group with a 1,2-diol structure, nor a carbon atom that is not bonded to either a polar group or an ether oxygen atom.

[0367] The terminal groups of compound (ZA) do not contain a 1,2-diol structure, and all hydroxyl groups contribute significantly to increasing the overall polarity of the molecule. Furthermore, since the terminal groups of compound (ZA) do not contain carbon atoms that are not bonded to either polar groups or ether oxygen atoms, the molecule does not exhibit sufficient hydrophobicity. For these reasons, it is thought that in Comparative Example 1, the fluorine-containing ether compound readily absorbed water, which is a cause of corrosion, resulting in a D rating in the corrosion resistance test.

[0368] In compound (ZA), the distance between hydroxyl groups is greater than the distance between hydroxyl groups in the 1,2-diol structure, so all hydroxyl groups readily interact with the protective layer. As a result, the intermolecular interactions between hydroxyl groups are reduced, making the lubricant more likely to scatter as the magnetic recording medium rotates, which is thought to be the reason for the C rating in the spin-off characteristic test.

[0369] The compounds used in Comparative Example 2 (ZB) and Comparative Example 3 (ZC) contain carbon atoms whose terminal groups are not bonded to either polar groups or ether oxygen atoms, but do not contain a 1,2-diol structure.

[0370] Compounds (ZB) and (ZC) exhibit high molecular hydrophobicity because their terminal groups contain carbon atoms that are not bonded to either polar groups or ether oxygen atoms. Furthermore, the total number of hydroxyl groups in compounds (ZB) and (ZC) is 4. Therefore, the total number of hydroxyl groups in compounds (ZB) and (ZC) is less than the total number of hydroxyl groups (6) in compound (ZA) used in Comparative Example 1. As a result, compounds (ZB) and (ZC) are less likely to absorb water, which is a cause of corrosion in fluorine-containing ether compounds, and the corrosion resistance test results for Comparative Examples 2 and 3 were better than those for Comparative Example 1.

[0371] In compounds (ZB) and (ZC), the distance between hydroxyl groups is greater than the distance between hydroxyl groups in the 1,2-diol structure, so all hydroxyl groups readily interact with the protective layer. Furthermore, the total number of hydroxyl groups in compounds (ZB) and (ZC) is four, which is relatively small, so there are very few hydroxyl groups that can contribute to intermolecular interactions. As a result, the intermolecular interactions of the fluorine-containing ether compounds are small, and the lubricant is more likely to scatter as the magnetic recording medium rotates, which is thought to be the reason why the spin-off characteristic test evaluation for Comparative Examples 2 and 3 was D.

[0372] The compounds used in Comparative Example 4 (ZD) and Comparative Example 5 (ZE) contain terminal groups with a 1,2-diol structure, but do not contain carbon atoms that are not bonded to either a polar group or an ether oxygen atom.

[0373] Compounds (ZD) and (ZE) have low molecular hydrophobicity because their terminal groups do not contain carbon atoms that are not bonded to either polar groups or ether oxygen atoms. As a result, the fluorine-containing ether compounds became more adept at absorbing water, which is a cause of corrosion, leading to a corrosion resistance test result of C for Comparative Example 4 and a corrosion resistance test result of D for Comparative Example 5. The reason why Comparative Example 4 received a C and Comparative Example 5 received a D is thought to be because compound (ZD) has a total of 4 hydroxyl groups, while compound (ZE) has a total of 8 hydroxyl groups, making Comparative Example 5, with its larger total number of hydroxyl groups, more adept at absorbing water.

[0374] Compounds (ZD) and (ZE) do not contain carbon atoms at their terminal ends that are not bonded to either polar groups or ether oxygen atoms, making it difficult to impart appropriate rigidity to the molecules. As a result, the two hydroxyl groups constituting the 1,2-diol structure tend to interact intramolecularly. Consequently, the hydroxyl groups in the fluorine-containing ether compounds become less likely to interact intermolecularly, and the lubricant tends to scatter more easily as the magnetic recording medium rotates. This is thought to be the reason why the spin-off characteristic tests for Comparative Examples 4 and 5 were evaluated as C. [Industrial applicability]

[0375] By using the lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has good corrosion resistance and can suppress spin-off, even if it is thin. [Explanation of Symbols]

[0376] 10 Magnetic recording media 11 circuit boards 12 Adhesion layer 13 Soft magnetic layer 14 1st base layer 15 Second base layer 16 Magnetic layer 17 Protective layer 18 Lubricant layer

Claims

1. A fluorine-containing ether compound characterized by being represented by the following formula (1). R １ -CH ２ -R ２ -CH ２ -R ３ (1) (In formula (1), R ２ This is a perfluoropolyether chain. １ and R ３ (One of these is represented by one of the following formulas (2-1) to (2-7), and the other is a terminal group represented by the following formula (3).) 【Chemistry 1】 (In equation (2-1), a represents an integer from 1 to 8, and b represents an integer from 1 to 7.) (In equation (2-2), c represents an integer from 1 to 7.) (In equation (2-3), d represents an integer from 1 to 6.) (In formula (2-4), e represents an integer from 1 to 6. The e R ａ and R ｂ each independently represent a hydrogen atom or a methyl group.) (In equation (2-5), f represents an integer from 1 to 6.) (In equation (2-6), g represents an integer from 1 to 6.) (In equation (2-7), g2 represents an integer from 1 to 6.) 【Chemistry 2】 (In formula (3), l represents an integer from 1 to 3. Each of the l m independently represents an integer from 1 to 6. Each of the l n independently represents an integer from 1 to 6. In one repeating unit, at least one of m and n is 1. B represents an alkyl group, a group containing a carbon-carbon unsaturated bond, or a hydrogen atom, which may have only one polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond.)

2. In formula (3), B is a phenyl group, methoxyphenyl group, phenyl fluoride group, acetamidophenyl group, carboxamidephenyl group, cyanophenyl group, naphthyl group, phenethyl group, methoxyphenethyl group, phenethyl fluoride group, benzyl group, methoxybenzyl group, naphthylmethyl group, methoxynaphthyl group, pyrrolyl group, pyrazolyl group, methylpyrazolylmethyl group, imidazolyl group, furyl group, furfuryl group, oxazolyl group, isoxazolyl group, thienyl group, thienylethyl group, thiazolyl group, methylthiazolylethyl group, isothiazolyl group, pyridyl group, pyrimidi The fluorine-containing ether compound according to claim 1, which is any of the following groups: nyl group, pyridadinyl group, pyrazinyl group, indolinyl group, benzofuranyl group, benzothienyl group, benzimidazolyl group, benzoxazolyl group, benzothiazolyl group, benzopyrazolyl group, benzoisoxazolyl group, benzoisothiazolyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, synnolinyl group, vinyl group, allyl group, butenyl group, propynyl group, propargyl group, butynyl group, methylbutynyl group, pentynyl group, methylpentynyl group, or hexynyl group.

3. The fluorine-containing ether compound according to claim 2, wherein B in formula (3) is any of a phenyl group, a methoxyphenyl group, an acetamidophenyl group, a carboxamidephenyl group, a cyanophenyl group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a thienylethyl group, an allyl group, a butenyl group, or a propargyl group.

4. The fluorine-containing ether compound according to claim 3, wherein B in formula (3) is any of a phenyl group, a methoxyphenyl group, a carboxamidephenyl group, an allyl group, or a butenyl group.

5. The fluorine-containing ether compound according to claim 1, wherein formula (3) is a terminal group represented by any of the following formulas (3-1) to (3-3). 【Transformation 3】 (In formula (3-1), p represents an integer from 0 to 3. q represents an integer from 0 to 2. r represents an integer from 0 to 5. The sum of p and r is from 1 to 5. D represents a polar group selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond, a vinyl group, an ethynyl group, or an optionally substituted aryl group.) (In equation (3-2), s represents an integer from 0 to 2, and t represents an integer from 1 to 5.) (In formula (3-3), u represents an integer from 1 to 3. Each of the five E's independently represents a polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond, an alkoxy group having 1 to 8 carbon atoms, a halogeno group, or a hydrogen atom. However, if the five E's include the aforementioned polar groups, the number of such polar groups among the five E's is one.)

6. R in formula (1) ２ The fluorine-containing ether compound according to claim 1, wherein is a perfluoropolyether chain represented by the following formula (4). -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (4) (In equation (4), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represents a value from 0 to 20. However, it is not possible for all of w2, w3, w4, and w5 to be 0 at the same time. w1 and w6 are CF ２ It is an average value representing the number of such values, each independently representing 1 to 3. It is the repeating unit in equation (4) (CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the order of the elements in (O).

7. R in formula (1) ２ The fluorine-containing ether compound according to claim 1, wherein is one selected from the perfluoropolyether chains represented by the following formulas (4-1) to (4-4). -CF ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (4-1) (In formula (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｊ -OCF ２ CF ２ - (4-2) (In formula (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (4-3) (In formula (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20. w7 and w10 are CF ２ This represents the average number of units, each independently representing 1 to 2.

8. The fluorine-containing ether compound according to claim 1, wherein the number-average molecular weight is in the range of 500 to 10,000.

9. A lubricant for magnetic recording media, characterized by containing a fluorine-containing ether compound according to any one of claims 1 to 8.

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

11. The magnetic recording medium according to claim 10, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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