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

Abstract

The present invention provides a fluorine-containing ether compound represented by formula (1). In the formula (1), X is a formula (2-1) to a formula (2-5), and A is a formula (3-1) or a formula (3-2). And B is a perfluoropolyether chain. D has 2-4 polar groups, has an oxygen atom bonded to a methylene group adjacent to D, and has 1-15 carbon atoms, and the number of carbon atoms in the shortest distance between the carbon atoms bonded to the adjacent polar groups in D is 0-9. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium.

[0002] This application claims priority based on Japanese Patent Application No. 2022-210111 filed in Japan on December 27, 2022, and the contents of which are incorporated herein by reference. Background Art

[0003] In recent years, the amount of information processed through the Internet has increased dramatically. Along with this, the development of recording media for storing information has attracted attention. In particular, magnetic recording media, which is a type of recording medium, can store large amounts of information at low cost, and is therefore expected to become a container for the growing amount of information.

[0004] Generally speaking, in order to ensure the durability and reliability of magnetic recording media, a protective layer and a lubricating layer are provided on the magnetic layer (magnetic recording layer) of the magnetic recording medium. The lubricating layer disposed on the outermost surface of the magnetic recording medium is required to have various properties such as long-term stability, chemical resistance (preventing contamination by siloxane, etc.), wear resistance, and heat resistance.

[0005] Examples of lubricants used when forming the lubricating layer of the magnetic recording medium include lubricants containing a compound having a fluorine-based polymer having a repeating structure of -CF2- and having a polar group such as a hydroxyl group or an amino group at the terminal.

[0006] For example, Patent Document 1 discloses an ether composition having a skeleton in which a perfluoropolyether chain is bonded to a perfluorinated divalent or higher saturated hydrocarbon group, and an end group as an organic group containing a polar group is bonded to the end of the skeleton via a methylene group (-CH2-).

[0007] Patent Documents 2 and 3 disclose a fluorine-containing ether compound having a skeleton in which three perfluoropolyether chains are bonded to a trivalent atomic group via a polar group-containing linking group, and a substituent as an organic group containing a polar group is bonded to the terminal via a methylene group.

[0008] Patent Document 4 discloses a fluorine-containing ether compound having a skeleton in which two perfluoropolyether chains are bonded to a divalent organic group containing an alicyclic structure and at least one polar group, and a terminal group as an organic group containing a polar group is bonded to the terminal through a methylene group.

[0009] Patent Document 5 discloses a structure having a perfluoropolyether chain bonded to a cyclic group via a polar group-containing linking group, and having a C n F 2n+1 A lubricant composition of the group.

[0010] Patent Document 6 discloses a compound having a skeleton in which a perfluoropolyether chain is bonded to a benzene ring via a methylene-containing linking group, and having a hydroxyl group at the terminal.

[0011] Patent Document 7 discloses a lubricant for a magnetic disk having a skeleton in which two perfluoropolyether chains are bonded to an aliphatic hydrocarbon chain located near the center of the molecule and having a hydroxyl group at the terminal.

[0012] Patent Documents 8 and 9 disclose fluorine-containing ether compounds having a skeleton in which three perfluoropolyether chains are connected in series via a hydroxyl-containing linking group and having a hydroxyl group at the terminal.

[0013] Prior art literature

[0014] Patent Literature

[0015] Patent Document 1: International Publication No. 2011 / 007782

[0016] Patent Document 2: International Publication No. 2018 / 159232

[0017] Patent Document 3: International Publication No. 2021 / 065380

[0018] Patent Document 4: International Publication No. 2022 / 113854

[0019] Patent Document 5: Japanese Patent Application Publication No. 2012-184339

[0020] Patent Document 6: International Publication No. 2015 / 093237

[0021] Patent Document 7: Japanese Patent No. 5743438

[0022] Patent Document 8: U.S. Patent No. 10262685

[0023] Patent Document 9: International Publication No. 2018 / 116742 Summary of the invention

[0024] Problems to be solved by the invention

[0025] In recent years, due to the diversification of the uses of magnetic recording media, the environmental resistance required of magnetic recording media has become very strict. In conjunction with this, the lubricating layer, which has a significant impact on the reliability and durability of magnetic recording media, needs to have further improved long-term stability.

[0026] As indicators of the long-term stability of the lubricating layer, chemical resistance and spinoff resistance are known. Spinoff is a phenomenon in which the lubricant is scattered or evaporated due to the centrifugal force and heat associated with the rotation of the magnetic recording medium. If spinoff occurs, the film thickness of the lubricating layer is reduced, so the chemical resistance and wear resistance of the lubricating layer are deteriorated. As one of the methods to suppress spinoff, it is to consider improving the adhesion of the lubricating layer to the protective layer. The polar groups possessed by the compounds contained in the lubricant help to improve the adhesion between the lubricant and the protective layer. However, if the number of polar groups possessed by the compounds contained in the lubricant is too large, chemical pollutants are attracted to the lubricating layer formed using the lubricant, and the chemical resistance of the lubricating layer is deteriorated.

[0027] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluorine-containing ether compound which can form a lubricating layer having excellent chemical resistance and capable of suppressing spin-off and can be suitably used as a material for a lubricant for a magnetic recording medium.

[0028] An object of the present invention is to provide a lubricant for a magnetic recording medium, which comprises the fluorine-containing ether compound of the present invention and can form a lubricating layer having excellent chemical resistance and a good spin-off suppressing effect.

[0029] An object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorinated ether compound of the present invention and having excellent chemical resistance and a good spin-off suppressing effect.

[0030] Means used to solve problems

[0031] The present invention includes the following aspects.

[0032] [1] A fluorine-containing ether compound characterized by being represented by the following general formula (1).

[0033]

[0034] In the general formula (1), X is a trivalent atomic group represented by any one of the following formulas (2-1) to (2-5). A is a connecting group represented by the following formula (3-1) or (3-2). The three A's may be partially or entirely the same, or they may be different. B is a perfluoropolyether chain. The three B's may be partially or entirely the same, or they may be different. D is an end group having 2 to 4 polar groups, an ether oxygen atom bonded to a methylene group adjacent to D, 1 to 15 carbon atoms, and 0 to 9 carbon atoms in the shortest distance between carbon atoms to which adjacent polar groups in D are bonded. The three D's may be partially or entirely the same, or they may be different.

[0035]

[0036] In the formula (2-4), a represents an integer of 0-5.

[0037] In the formula (2-5), b represents an integer of 0-5.

[0038]

[0039] In the formula (3-1), n ​​represents an integer of 0 to 6.

[0040] In the formula (3-2), m represents an integer of 1 to 2.

[0041] [2] The fluorine-containing ether compound according to [1], wherein a in the formula (2-4) is 0, and b in the formula (2-5) is an integer from 0 to 2.

[0042] [3] The fluorine-containing ether compound according to [1] or [2], wherein the polar group is at least one polar group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group.

[0043] [4] The fluorine-containing ether compound according to any one of [1] to [3], wherein the polar group contains at least one hydroxyl group.

[0044] [5] The fluorinated ether compound according to any one of [1] to [4], wherein D in the general formula (1) is independently a terminal group represented by any one of the following formulas (4-1) to (4-3).

[0045]

[0046] In formula (4-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5.

[0047] In the formula (4-2), s represents an integer of 0-2, and t represents an integer of 0-5.

[0048] In formula (4-3), u represents an integer of 2 to 4, and Y represents a linear alkylene group which may have an ether oxygen atom, or a single bond. When Y is the above alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5.

[0049] [6] The fluorinated ether compound according to any one of [1] to [5], wherein the three Ds in the general formula (1) are all the same.

[0050] [7] The fluorinated ether compound according to any one of [1] to [6], wherein at least one of the three A's in the general formula (1) is the formula (3-1).

[0051] [8] The fluorinated ether compound according to any one of [1] to [7], wherein the three Bs in the general formula (1) are each independently a perfluoropolyether chain represented by the following formula (5).

[0052] -(CF2) v1 -O-(CF2O) v2 -(CF2CF2O) v3 -(CF2CF2CF2O) v4 -(CF2CF2CF2CF2O) v5 -(CF2) v6 -(5)

[0053] In formula (5), v2, v3, v4, and v5 represent average polymerization degrees, and each independently represents 0 to 20. However, v2, v3, v4, and v5 are not all 0 at the same time. v1 and v6 represent average values ​​of CF2 numbers, and each independently represents 1 to 3. The arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (5) is not particularly limited.

[0054] [9] The fluorinated ether compound according to any one of [1] to [8], wherein the three Bs in the general formula (1) are each independently selected from any one of the perfluoropolyether chains represented by the following formulas (5-1) to (5-4).

[0055] -CF2-(OCF2CF2) h -(OCF2) i -OCF2-(5-1)

[0056] In the formula (5-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.

[0057] -CF2CF2-(OCF2CF2CF2) j -OCF2CF2-(5-2)

[0058] In the formula (5-2), j represents an average degree of polymerization and is 1 to 15.

[0059] -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2-(5-3)

[0060] In the formula (5-3), k represents an average degree of polymerization and is 1 to 10.

[0061] -(CF2) v7 -O-(CF2CF2CF2O) v8 -(CF2CF2O) v9 -(CF2) v10 -(5-4)

[0062] In formula (5-4), v8 and v9 represent average polymerization degrees, and each independently represents 1 to 20. v7 and v10 represent average values ​​of CF2 numbers, and each independently represents 1 to 2.

[0063]

[10] The fluorinated ether compound according to any one of [1] to [9], which has a number average molecular weight in the range of 500 to 10,000.

[0064]

[11] A lubricant for a magnetic recording medium, comprising the fluorine-containing ether compound according to any one of [1] to

[10] .

[0065]

[12] A magnetic recording medium comprising at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate, wherein the lubricating layer comprises the fluorine-containing ether compound according to any one of [1] to

[10] .

[0066]

[13] The magnetic recording medium according to

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

[0067] Effects of the Invention

[0068] The fluorine-containing ether compound of the present invention is a compound represented by the above-mentioned general formula (1), and is suitable as a material for a lubricant for magnetic recording media.

[0069] Since the lubricant for a magnetic recording medium of the present invention contains the fluorine-containing ether compound of the present invention, a lubricating layer having excellent chemical resistance and a high spin-off suppressing effect can be formed.

[0070] The magnetic recording medium of the present invention has a lubricating layer comprising a fluorinated ether compound of the present invention. Therefore, the magnetic recording medium of the present invention has good chemical resistance, good spin-off suppression effect, and excellent reliability and durability. In addition, since the magnetic recording medium of the present invention has a lubricating layer that has good chemical resistance and can suppress spin-off, the floating amount of the magnetic head can be further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention.

[0072] Figure 2 It is a diagram for explaining an environment in which continuous LUL operations are repeatedly performed. DETAILED DESCRIPTION

[0073] The present inventors have conducted intensive studies to solve the above-mentioned problems as follows.

[0074] In the past, as the material of the lubricant for magnetic recording media (hereinafter, sometimes referred to as "lubricant") coated on the surface of the protective layer, it is preferred to use a fluorine-containing ether compound having a chain structure containing multiple perfluoropolyether chains, and an adsorption site having a polar group is arranged at the end of the chain structure and between the perfluoropolyether chains. The adsorption site in the fluorine-containing ether compound combines with the active point on the protective layer to improve the adhesion of the lubricating layer to the protective layer.

[0075] However, when a thin lubricating layer is formed on a protective layer using a conventional lubricant, it is difficult to realize a lubricating layer that has good chemical resistance and is less likely to spin off, as described below.

[0076] That is, if a fluorinated ether compound having a plurality of hydroxyl groups in the lubricant molecule is used to improve the adhesion of the lubricating layer to the protective layer, the spin-off can sometimes be suppressed. However, the proportion of polar groups in the fluorinated ether compound that do not interact with the active points on the protective layer increases, and environmental substances that generate pollutants are attracted to the lubricating layer, resulting in a decrease in the chemical resistance of the lubricating layer.

[0077] Therefore, the present inventors focused on the adsorption sites possessed by the fluorinated ether compound contained in the lubricating layer that can interact with the active sites on the protective layer, and repeatedly conducted in-depth studies as shown below in order to realize a fluorinated ether compound that is less likely to produce adsorption sites that do not participate in the interaction with the active sites on the protective layer in the lubricating layer.

[0078] The inventors first studied a fluorine-containing ether compound in which three perfluoropolyether chains B are bonded to a trivalent atomic group X disposed in the center via a linking group A having a plurality of hydroxyl groups, and terminal groups D having polar groups are disposed at the ends of the three perfluoropolyether chains B. In the fluorine-containing ether compound, the trivalent atomic group X is in close contact with the protective layer via the three linking groups A as adsorption sites disposed near the trivalent atomic group X. In addition, the perfluoropolyether chains B extending in three directions from the trivalent atomic group X are in close contact with the protective layer via the linking groups A disposed at both ends of each perfluoropolyether chain B and the terminal groups D as adsorption sites.

[0079] Furthermore, in order to prevent the generation of adsorption sites that do not participate in the interaction with the active sites on the protective layer in such fluorine-containing ether compounds, the strength of the interaction between each adsorption site and the active sites on the protective layer was studied.

[0080] From the results, it can be seen that it is necessary to prepare a fluorinated ether compound in which the strength of the interaction between the end group D and the active point on the protective layer and the strength of the interaction between the linking group A and the active point on the protective layer are appropriately balanced, and the end group D and the linking group A can interact with the active point on the protective layer with sufficient strength.

[0081] That is, in the interaction between the end group D and the active point on the protective layer and the interaction between the linking group A and the active point on the protective layer, if the interaction on the linking group A side tends to be stronger, an adsorption group (polar group) that does not participate in the interaction with the active point on the protective layer is generated in the end group D. As a result, the adsorption group that does not participate in the interaction attracts chemical pollutants to the lubricating layer, and the chemical resistance is reduced. In addition, in the interaction between the end group D and the active point on the protective layer and the interaction between the linking group A and the active point on the protective layer, if the interaction is too weak, spin-off will occur, and the film thickness of the lubricating layer will be reduced.

[0082] Therefore, the present inventors have repeatedly studied the structures of the trivalent atomic group X, the terminal group D and the linking group A in the above-mentioned fluorine-containing ether compound.

[0083] As a result, it was found that any fluorine-containing ether compound having a skeleton in which three perfluoropolyether chains B are bonded to the trivalent atomic group X represented by the above formula (2-1) to (2-5) via the divalent linking group A represented by the above formula (3-1) or (3-2), and a specific terminal group D is bonded to the end of each perfluoropolyether chain B via a methylene group. The terminal group D has 2 to 4 polar groups, an ether oxygen atom bonded to a methylene group adjacent to D, and has 1 to 15 carbon atoms, and the shortest distance between carbon atoms to which adjacent polar groups in D are bonded is 0 to 9 carbon atoms.

[0084] In the lubricating layer comprising such fluorinated ether compound, the end group D and the linking group A in the fluorinated ether compound can interact with the active point on the protective layer with sufficient strength, and the strength of the interaction between the end group D and the active point on the protective layer and the strength of the interaction between the linking group A and the active point on the protective layer are moderately balanced, so it is not easy to produce an adsorption site that does not participate in the interaction with the active point on the protective layer. As a result, a lubricating layer with excellent adhesion to the protective layer and not easy to spin off can be formed. In addition, since there are few polar groups that do not participate in the interaction with the active point on the protective layer in the fluorinated ether compound, chemical pollutants can be suppressed from being attracted to the lubricating layer, and a lubricating layer with excellent chemical resistance can be formed. Moreover, the fluorinated ether compound has 3 perfluoropolyether chains B, and the carbon number of the end group D is not too much. Therefore, the surface free energy of the lubricating layer comprising it is low, it is difficult to produce a point with high surface free energy locally, and it is not easy to produce pollution caused by chemical pollutants.

[0085] Furthermore, the present inventors have confirmed that a lubricating layer having excellent chemical resistance and a high spin-off suppressing effect can be formed by using a lubricant containing the above-mentioned fluorinated ether compound, and thus have conceived the present invention.

[0086] The fluorine-containing ether compound, the lubricant for a magnetic recording medium, and the magnetic recording medium of the present invention are described in detail below. It should be noted that the present invention is not limited to the embodiments described below.

[0087] [Fluorinated ether compounds]

[0088] The fluorine-containing ether compound of the present embodiment is represented by the following general formula (1).

[0089]

[0090] In the general formula (1), X is a trivalent atomic group represented by any one of the following formulas (2-1) to (2-5). A is a connecting group represented by the following formula (3-1) or (3-2). The three A's may be partially or entirely the same, or they may be different. B is a perfluoropolyether chain. The three B's may be partially or entirely the same, or they may be different. D is an end group having 2 to 4 polar groups, an ether oxygen atom bonded to a methylene group adjacent to D, 1 to 15 carbon atoms, and 0 to 9 carbon atoms in the shortest distance between carbon atoms to which adjacent polar groups in D are bonded. The three D's may be partially or entirely the same, or they may be different.

[0091]

[0092] In the formula (2-4), a represents an integer of 0-5.

[0093] In the formula (2-5), b represents an integer of 0-5.

[0094]

[0095] In the formula (3-1), n ​​represents an integer of 0 to 6.

[0096] In the formula (3-2), m represents an integer of 1 to 2.

[0097] (X represents a trivalent atomic group)

[0098] X is a trivalent atomic group represented by the above formulae (2-1) to (2-5). Therefore, the three perfluoropolyether chains B bonded to the above trivalent atomic group X via the divalent linking group A are arranged to extend in three directions from the trivalent atomic group X. As a result, a lubricating layer having excellent adhesion to the protective layer can be formed.

[0099] In the case where the trivalent atomic group X is of formula (2-1) to (2-3), the three connection sites with the divalent linking group A in formula (2-1) to (2-3) are the same number of carbon atoms away from each other. In addition, in the case where the trivalent atomic group X is of formula (2-4), the tertiary or quaternary carbon atom arranged in the center of formula (2-4) and the two carbon atoms adjacent thereto are the three connection sites with the divalent linking group A. In addition, in the case where the trivalent atomic group X is of formula (2-5), the three carbon atoms adjacent to the tertiary or quaternary carbon atom arranged in the center of formula (2-5) are the three connection sites connected to the divalent linking group A. Therefore, it can be considered that the three perfluoropolyether chains B bonded to the trivalent atomic groups represented by formulas (2-1) to (2-5) by means of the divalent linking group A can be extended at approximately equal intervals in three directions relative to these trivalent atomic groups X, showing better coating properties for the protective layer.

[0100] The trivalent atomic groups X represented by formulas (2-1) to (2-5) all have a moderate volume in the stereo. Specifically, the trivalent atomic groups represented by formulas (2-1) to (2-3) have a large ring structure in the center. Since the trivalent atomic groups represented by formulas (2-4) to (2-5) have a tertiary or quaternary carbon atom in the center, they are large in volume. Thus, the trivalent atomic group X moderately suppresses the interaction between the hydroxyl group possessed by the linking group A and the active point on the protective layer.

[0101] Here, for example, when a divalent or trivalent atomic group having less steric hindrance than the linking group A is arranged instead of the trivalent atomic group X represented by formulas (2-1) to (2-5), the interaction between the linking group A and the active point on the protective layer becomes too strong. Therefore, the balance between the strength of the interaction between the linking group A and the active point on the protective layer and the strength of the interaction between the terminal group D and the active point on the protective layer is disrupted, and the chemical resistance of the lubricating layer containing the fluorinated ether compound is reduced.

[0102] In addition, for example, when a divalent atomic group having a large steric hindrance relative to the linking group A is arranged instead of the trivalent atomic group X represented by formulas (2-1) to (2-5), although the interaction between the hydroxyl group possessed by the linking group A and the active point on the protective layer can be suppressed by the divalent atomic group, there are only two perfluoropolyether chains B bonded to the divalent atomic group. Therefore, compared with the lubricating layer of the fluorine-containing ether compound represented by formula (1) in which three perfluoropolyether chains B are arranged extending in three directions, the coating property with the protective layer is insufficient, and sufficient chemical resistance cannot be obtained.

[0103] In formula (2-4), a represents an integer of 0 to 5. Since a is 5 or less, -(CH2) aThe substituent represented by -H is not too large, and the trivalent atomic group represented by formula (2-4) forms a structure having a suitable volume in terms of steric volume. From the viewpoint of the availability of raw materials, a is preferably an integer of 0 to 1, and a is more preferably 0.

[0104] In formula (2-5), b represents an integer of 0 to 5. Since b is 5 or less, -(CH2) b The substituent represented by -H is not too large, and the trivalent atomic group represented by formula (2-5) forms a structure having a suitable volume in terms of steric volume. From the viewpoint of the availability of raw materials, b is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0105] (Connection group represented by A)

[0106] A is a divalent linking group represented by formula (3-1) or formula (3-2). The linking group A can interact with the active points on the protective layer with sufficient strength through the synergistic effect of the functions of (A-1) to (A-3) shown below. Moreover, through the synergistic effect of the functions of (A-4) and (A-5) shown below, the strength of the interaction between the linking group A and the active points on the protective layer and the balance of the strength of the interaction between the end group D and the active points on the protective layer become appropriate. That is, it is possible to suppress the interaction between the linking group A and the active points on the protective layer from becoming excessively stronger than the interaction between the end group D and the active points on the protective layer. As a result, it is possible to suppress the lack of active points on the protective layer that can interact with the end group D, thereby generating polar groups that do not participate in the interaction with the active points on the protective layer. Therefore, it is possible to prevent the polar groups that do not participate in the interaction with the active points on the protective layer from attracting chemical contaminants to the lubricating layer, thereby deteriorating the chemical resistance of the lubricating layer.

[0107] (A-1) linking group A has 2 or 3 hydroxyls. Specifically, the divalent linking group represented by formula (3-1) has 2 hydroxyls. The divalent linking group represented by formula (3-2) has 2 or 3 hydroxyls. Since the above-mentioned linking group A has more than 2 hydroxyls, even if the adsorption of a part of the hydroxyls possessed by the linking group A to the protective layer is hindered due to the large volume of the adjacent trivalent atomic group X and the perfluoropolyether chain B, the hydroxyls other than this can also be adsorbed on the protective layer. Therefore, the adhesion of the lubricating layer comprising the above-mentioned fluorinated ether compound is good, and spin-off is suppressed.

[0108] Here, for example, when a divalent connecting group having only one hydroxyl group is arranged instead of the connecting group A, the adsorption of the hydroxyl group of the divalent connecting group to the protective layer is hindered by the trivalent atomic group X and the perfluoropolyether chain B, and sometimes cannot participate in the interaction with the active site on the protective layer.

[0109] (A-2) The linking group A has an ether oxygen atom bonded to the methylene group bonded to the perfluoropolyether chain B. Therefore, the linking group A has moderate flexibility and can move freely independently without being linked to the perfluoropolyether chain B. As a result, the linking group A is unlikely to be detached from the protective layer due to the linked movement of the linking group A and the molecular movement of the perfluoropolyether chain B, and the hydroxyl group of the linking group A is likely to participate in the interaction with the active point on the protective layer.

[0110] (A-3) The linking group A has a chain structure with more than 6 atoms. Specifically, the number of atoms forming the chain structure in the divalent linking group represented by formula (3-1) is 6 to 12. The divalent linking group represented by formula (3-2), when m in formula (3-2) is 1, the number of atoms forming the chain structure is 9, and when m is 2, the number of atoms forming the chain structure is 13. Therefore, in the fluorine-containing ether compound represented by general formula (1), the distance between the adjacent trivalent atomic group X and the perfluoropolyether chain B can be fully ensured by the linking group A. Moreover, since the linking group A is provided with ether oxygen atoms at both ends of the chain structure, it has moderate flexibility. As a result, the volume of the trivalent atomic group X and the perfluoropolyether chain B does not affect the adsorption force of the hydroxyl group of the linking group A on the protective layer too much. Therefore, the hydroxyl group of the linking group A can interact with the active point on the protective layer with sufficient strength. That is, the adsorption force of the hydroxyl group of the linking group A on the protective layer can maintain appropriate strength.

[0111] (A-4) The linking group A is disposed between the trivalent atomic group X and the perfluoropolyether chain B. Therefore, the interaction between the hydroxyl group of the linking group A and the active point on the protective layer is buffered by the trivalent atomic group X and the perfluoropolyether chain B having a large steric bulk skeleton disposed on both sides of the linking group A, and the interaction between the hydroxyl group of the linking group A and the active point on the protective layer is appropriately suppressed.

[0112] (A-5) The number of hydroxyl groups in the linking group A is 3 or less, so that the interaction between the linking group A and the active point on the protective layer can be suppressed from becoming too strong. In order to make the balance of the interaction strength between the linking group A and the end group D and the active point on the protective layer more appropriate, the number of hydroxyl groups possessed by the linking group A is preferably 2.

[0113] In the divalent linking group represented by formula (3-1), the carbon atoms to which the two hydroxyl groups in formula (3-1) are respectively bonded have 0 to 6 carbon atoms, so the distance between the two hydroxyl groups is appropriate. Since the number of carbon atoms between the two carbon atoms to which the hydroxyl groups are bonded is 6 or less, the distance between the hydroxyl groups will not be too far, and a synergistic effect of the interaction between the two hydroxyl groups and the protective layer can be obtained. Therefore, a lubricating layer having sufficient adhesion to the protective layer and inhibiting spin-off can be formed. n in formula (3-1) is preferably 0 to 4, more preferably 0 to 2, because the synergistic effect of the interaction between the two hydroxyl groups in formula (3-1) supporting each other and the protective layer becomes more significant.

[0114] The divalent connecting group represented by formula (3-2) includes a structure formed by connecting 2 to 3 glycerol structures (-O-CH2-CH(OH)-CH2-). The glycerol structure is soft, so the structure represented by formula (3-2) formed by connecting 2 to 3 glycerol structures is extremely flexible, and the hydroxyl group can move flexibly. Therefore, even when the perfluoropolyether chain B arranged on the terminal side of the connecting group A undergoes molecular motion, the 2 to 3 hydroxyl groups in the divalent connecting group represented by formula (3-2) can move freely and independently, and it is easy to maintain the interaction between the hydroxyl groups in the divalent connecting group and the protective layer.

[0115] In formula (3-2), m represents an integer of 1 to 2. When m is 1, the number of hydroxyl groups in the divalent linking group represented by formula (3-2) is 2. Therefore, when the three linking groups A in the general formula (1) are all represented by formula (3-2) and m is 1, the total number of hydroxyl groups in the linking group A of the fluorinated ether compound represented by general formula (1) is 6. When m is 2, the number of hydroxyl groups in the divalent linking group represented by formula (3-2) is 3. Therefore, when the three linking groups A in the general formula (1) are all represented by formula (3-2) and m is 2, the total number of hydroxyl groups in the linking group A of the fluorinated ether compound represented by general formula (1) is 9. Therefore, when m is 1 or 2, the number of interaction points with the protective layer becomes appropriate, a lubricating layer with sufficient adhesion can be formed, and the deterioration of spin separation can be suppressed.

[0116] The 3 linking groups A in the general formula (1) can be partly or entirely identical, or they can be different from each other. Therefore, the hydroxyl numbers of the 3 linking groups A can be identical, or they can be different from each other. In order to make the coating state of the protective layer of the fluorine-containing ether compound more uniform, a lubricating layer with better adhesion can be formed, and the hydroxyl numbers of the 3 linking groups A are preferably all identical. And then, if the structures of the 3 linking groups A are all identical, the fluorine-containing ether compound is easily synthesized, which is more preferred.

[0117] Preferably, at least one of the three linking groups A in the general formula (1) is a formula (3-1). Since the linking group A represented by the formula (3-1) does not have an ether oxygen atom between adjacent hydroxyl groups, it has excellent rigidity compared to the linking group represented by the formula (3-2) having an ether oxygen atom between adjacent hydroxyl groups. Therefore, when the perfluoropolyether chain B is configured with the help of the linking group A represented by the formula (3-1), each perfluoropolyether chain B can easily be configured to extend in three directions on the protective layer relative to the trivalent atomic group X. As a result, even if the thickness of the lubricating layer is thin, excellent adhesion and coating properties to the protective layer can be obtained.

[0118] (D represents the terminal group)

[0119] In the fluorinated ether compound represented by the general formula (1), D is an end group having 2 to 4 polar groups, an ether oxygen atom bonded to a methylene group adjacent to D, 1 to 15 carbon atoms, and 0 to 9 carbon atoms in the shortest distance between carbon atoms bonded to adjacent polar groups in D. The end group D can interact with the active points on the protective layer with sufficient strength through the synergistic effect of the functions (D-1) to (D-3) shown below. Moreover, through the function (D-4) shown below, the balance between the interaction strength between the end group D and the active points on the protective layer and the interaction strength between the linking group A and the active points on the protective layer becomes appropriate.

[0120] (D-1) Since the number of polar groups of the terminal group D is 2 or more, when a lubricating layer is formed on the protective layer using a lubricant containing a fluorinated ether compound, a suitable interaction occurs between the lubricating layer and the protective layer. As a result, a lubricating layer having excellent adhesion to the protective layer and a good spin-off suppression effect is formed.

[0121] (D-2) The terminal group D has an ether oxygen atom at the end of the side bonded to the methylene group adjacent to the terminal group D. The ether oxygen atom disposed at the end of the terminal group D forms an ether bond (-O-) with the adjacent methylene group. The ether bond imparts moderate softness to the fluorinated ether compound represented by the general formula (1), thereby increasing the affinity of the polar group possessed by the terminal group D with the protective layer. Therefore, the fluorinated ether compound represented by the general formula (1) is not likely to produce polar groups that do not participate in the interaction with the active points on the protective layer, and can evenly cover the entire surface of the protective layer, thereby forming a lubricating layer with excellent adhesion to the protective layer.

[0122] (D-3) For the end group D, the number of carbon atoms in the shortest distance between the carbon atoms to which the adjacent polar groups in the end group D are bonded is less than 9, and the distance between the adjacent polar groups is not too far. Therefore, while the end group D has sufficient flexibility, when each polar group contained in the end group D interacts with the active point on the protective layer, a synergistic effect of supporting the interaction between other adjacent polar groups and the active point on the protective layer can be obtained. As a result, the polar group contained in the end group D is not easy to detach from the protective layer, and it is not easy to become a polar group that does not participate in the interaction with the active point on the protective layer. Therefore, the fluorine-containing ether compound represented by the general formula (1) has excellent adhesion to the protective layer and can form a lubricating layer with good spin-off inhibition effect. The number of carbon atoms in the shortest distance between the carbon atoms to which the adjacent polar groups are bonded is preferably 0 to 6, and more preferably 0 to 4.

[0123] (D-4) Since the number of polar groups in the end group D is 4 or less, in the lubricating layer containing the fluorinated ether compound, the balance of the strength of the interaction between the linking group A and the end group D and the active points on the protective layer becomes appropriate, and it is not easy to produce polar groups that do not interact with the active points on the protective layer. Therefore, it is possible to suppress the attraction of chemical pollutants to the lubricating layer, and it is possible to suppress the reduction in the chemical resistance of the lubricating layer. In order to form a fluorinated ether compound that is not easy to produce polar groups that do not interact with the active points on the protective layer, and has a good balance of spin resistance and chemical resistance, the number of polar groups contained in the end group D is preferably 2 to 3, and most preferably 2. If the number of polar groups contained in the three end groups D is 2, respectively, in the magnetic recording medium having a lubricating layer containing the fluorinated ether compound, the balance of the interaction between the linking group A and the active points on the protective layer, and the interaction between the end group D and the active points on the protective layer becomes better.

[0124] Furthermore, the number of carbon atoms contained in the end group D is 15 or less. If there is a portion in the lubricating layer containing the fluorine-containing ether compound in which the number of carbon atoms is greater than the number of fluorine atoms, a point with high surface free energy will be locally generated, and sometimes it will be contaminated by chemical pollutants. In contrast, the lubricating layer containing the fluorine-containing ether compound represented by the general formula (1) has a low surface free energy and is not easily contaminated by chemical pollutants because the number of carbon atoms contained in the end group D is 15 or less. The number of carbon atoms contained in the end group D is preferably 10 or less.

[0125] The 3 end groups D in the general formula (1) can be partly or entirely identical, or they can be different from each other. Therefore, the quantity of the polar groups possessed by the 3 end groups D can be identical, or they can be different from each other. In order to make the coated state of the fluorinated ether compound to the protective layer more uniform, a lubricating layer with better adhesion can be formed, and the quantity of the polar groups possessed by the 3 end groups D is preferably all identical. And then, if the structures of the 3 end groups D are all identical, the fluorinated ether compound is easily synthesized, thereby being more preferred.

[0126] The total number of polar groups possessed by the three end groups D in the general formula (1) is 6 to 12, preferably 6 to 9, more preferably 6 to 7, and most preferably 6. Since the total number of the above polar groups is 6 or more, the interaction between the polar groups possessed by the end groups D in the fluorinated ether compound and the protective layer becomes strong. As a result, the spin-off of the end groups D of the fluorinated ether compound from the protective layer, thereby reducing the film thickness of the lubricating layer, can be suppressed. Therefore, a fluorinated ether compound with a high spin-off suppression effect can be obtained. If the total number of the above polar groups is 9 or less, it becomes more difficult to produce polar groups that do not participate in the binding of the lubricating layer with the active points on the protective layer. Therefore, the polar groups that do not participate in the binding of the lubricating layer with the active points on the protective layer can be further suppressed from attracting chemical contaminants to the lubricating layer. Therefore, a lubricating layer with better chemical resistance can be formed, which is preferred.

[0127] The polar group possessed by the terminal group D is preferably a polar group selected from the group consisting of a hydroxyl group (-OH), an amino group (-NH2), a carboxyl group (-COOH), a carbonyl group (-CO-), and a sulfonic group (-SO3H). The 2 to 4 polar groups possessed by each terminal group D may be partially or completely the same, or may be different from each other. Among the above groups, the polar group possessed by the terminal group D is preferably at least one polar group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group. In the case where the protective layer coated with the lubricant is formed by carbon containing nitrogen, the hydroxyl group, the amino group, and the carboxyl group can form hydrogen bonds with the nitrogen atom, thereby increasing the affinity with the protective layer.

[0128] It is more preferred that the terminal group D contains at least one hydroxyl group as a polar group. If at least one of the 2 to 4 polar groups contained in the terminal group D is a hydroxyl group, then when the protective layer coated with the lubricant is formed of carbon containing nitrogen, the adhesion between the protective layer and the lubricating layer containing the fluorine-containing ether compound is further improved. In order to form a lubricating layer with better adhesion to the protective layer, it is further preferred that all the polar groups contained in the terminal group D are hydroxyl groups.

[0129] In the fluorine-containing ether compound represented by the general formula (1), each terminal group D is preferably independently a terminal group represented by any one of the formulae (4-1) to (4-3).

[0130]

[0131] In formula (4-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5.

[0132] In the formula (4-2), s represents an integer of 0-2, and t represents an integer of 0-5.

[0133] In formula (4-3), u represents an integer of 2 to 4, Y represents a linear alkylene group optionally having an ether oxygen atom, or a single bond, and when Y is the alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5.

[0134] In the terminal group represented by formula (4-1), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded contains an ether oxygen atom. In formula (4-1), p represents an integer of 0 to 3, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5. Therefore, the above-mentioned linking group has a linear structure composed of 3 to 7 atoms including carbon atoms to which the hydroxyl group is not bonded.

[0135] In the end group represented by formula (4-1), the above-mentioned linking group is a linear structure comprising ether oxygen atoms and composed of more than 3 atoms of carbon atoms comprising unbonded hydroxyl groups, so the distance between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group is appropriate. Therefore, it is possible to suppress the interaction between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group in the molecule, and the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group can be closely fitted to the protective layer. In addition, since the above-mentioned linking group is a linear structure consisting of more than 3 atoms, the mobility of the molecule is appropriate and intramolecular cohesion is not easy to occur.

[0136] The linking group is a linear structure containing an ether oxygen atom and composed of 7 or less atoms including carbon atoms to which a hydroxyl group is not bonded, so the hydrophobicity of the linking group is not too high to hinder the adhesion with the protective layer. Thus, the lubricating layer containing the fluorinated ether compound having the terminal group represented by formula (4-1) has excellent adhesion with the protective layer, can obtain excellent chemical resistance, and has a good spin-off inhibition effect.

[0137] In formula (4-1), the total value of p and r is 1 to 5, preferably 1 to 3. In the terminal group D, the carbon atoms contained in the connecting group arranged between the carbon atoms bonded with the hydroxyl group prevent the intramolecular interaction between the adjacent hydroxyl groups from occurring in priority to the interaction between the hydroxyl group and the protective layer, thereby improving the adhesion between the hydroxyl group in the terminal group D and the protective layer. On the other hand, if the number of carbon atoms contained in the above-mentioned connecting group is too large, the flexibility of the terminal group D is reduced, and it is sometimes difficult to evenly cover the protective layer. In the terminal group represented by formula (4-1), the total value of p and r is 5 or less, so the alkylene chain of the main chain part of the terminal group D will not be too long. Therefore, the flexibility of the terminal part is reduced by the rigid alkylene chain length, which can prevent the terminal part from floating due to the weakening of the interaction with the protective layer. In addition, since the alkylene chain of the main chain part of the terminal group D is not too long, it is not easy to produce a point with high surface free energy formed by a part with a larger number of carbon atoms relative to the number of fluorine atoms in the lubricating layer containing a fluorine-containing ether compound. Therefore, a lubricating layer that is not easily contaminated by chemical contaminants can be formed. p is preferably 0 or 1, and more preferably 0. r is preferably 1 or 2, and more preferably 1.

[0138] In formula (4-1), q represents an integer of 0 to 2. The number of hydroxyl groups in formula (4-1) is q+2, and as described above, the number of hydroxyl groups contained in D is preferably 2 to 3, and most preferably 2. Therefore, q in formula (4-1) is preferably 0 or 1, and more preferably 0.

[0139] When q in formula (4-1) is 0 and the total value of p and r is 2 or more, p is preferably 1 or more. This is because the ether oxygen atom is arranged near the primary hydroxyl group in formula (4-1), the flexibility of the primary hydroxyl group to move becomes good, and the interaction between the primary hydroxyl group and the protective layer becomes stronger.

[0140] In the terminal group D represented by formula (4-2), the connecting group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an ether oxygen atom. T in formula (4-2) represents an integer of 0 to 5. Therefore, the above-mentioned connecting group is a single bond (the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded are directly bonded), or has a straight-chain structure consisting of 1 to 5 atoms of carbon atoms containing unbonded hydroxyl groups. Therefore, the distance between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group becomes appropriate, supporting each other's hydroxyl groups to interact with the protective layer respectively, and excellent adhesion to the protective layer.

[0141] In the terminal group D represented by formula (4-2), t is 5 or less, so the alkylene chain of the main chain part of D will not be too long. Therefore, the rigid alkylene chain length can prevent the flexibility of the terminal part from decreasing and the interaction with the protective layer from weakening, thereby preventing the terminal part from floating up, and the protective layer can be evenly coated. Furthermore, since t is 5 or less, in the lubricating layer containing the fluorine-containing ether compound, it is not easy to generate points with high surface free energy formed by the part with a larger number of carbon atoms relative to the number of fluorine atoms. Therefore, the state of low surface free energy of the lubricating layer can prevent contamination caused by chemical pollutants. t is preferably 0 to 4, more preferably 0 to 2, and even more preferably 0 to 1.

[0142] In the terminal group D represented by formula (4-2), the connecting group is a single bond or a linear structure containing 1 to 5 carbon atoms without an ether oxygen atom and containing an unbonded hydroxyl group. Therefore, the hydrophobicity of the connecting group is not too high to hinder the adhesion with the protective layer.

[0143] Thus, the lubricating layer containing the fluorine-containing ether compound having a terminal group represented by the formula (4-2) has excellent adhesion to the protective layer, can obtain excellent chemical resistance, and has a high spin-off suppressing effect.

[0144] In formula (4-2), s represents an integer of 0 to 2. The number of polar groups in formula (4-2) is s+2, and as described above, the number of polar groups contained in the terminal group D is preferably 2 to 3, and most preferably 2. Therefore, s in formula (4-2) is preferably 0 or 1, and more preferably 0.

[0145] The end group D represented by formula (4-3) does not have a secondary hydroxyl group, but has two terminal primary hydroxyl groups. When the hydroxyl group contained in the end group D is a primary hydroxyl group, the hydroxyl group is more likely to participate in the interaction with the active point on the protective layer than when it is a secondary hydroxyl group. The end group represented by formula (4-3) does not have a secondary hydroxyl group, but has only two primary hydroxyl groups that are more likely to interact with the active point on the protective layer. Therefore, when the end group D is the end group represented by formula (4-3), it becomes a fluorine-containing ether compound that can form a lubricating layer with good adhesion to the protective layer.

[0146] In the terminal group represented by formula (4-3), the connecting group between the carbon atoms to which the two primary hydroxyl groups are respectively bonded contains carbon atoms to which the hydroxyl groups are not bonded and ether oxygen atoms. u in formula (4-3) represents an integer of 2 to 4. Y represents a straight-chain alkylene group which may have an ether oxygen atom, or a single bond. When Y is the above-mentioned alkylene group, the total number of carbon atoms and oxygen atoms possessed by Y is 1 to 5. Therefore, the above-mentioned connecting group has a structure consisting of 3 to 10 atoms including carbon atoms to which the hydroxyl groups are not bonded and ether oxygen atoms.

[0147] In the end group represented by formula (4-3), the above-mentioned linking group is a structure containing an ether oxygen atom and composed of three or more atoms of carbon atoms containing unbonded hydroxyl groups, so the distance between the two primary hydroxyl groups is appropriate. Therefore, the hydroxyl groups that can support each other interact with the protective layer respectively. Therefore, it becomes a fluorine-containing ether compound that can form a lubricating layer with good adhesion to the protective layer.

[0148] In the terminal group represented by formula (4-3), the above-mentioned connecting group is a structure containing ether oxygen atoms and composed of 10 or less atoms of carbon atoms containing unbonded hydroxyl groups, so the hydrophobicity of the connecting group is not too high to hinder the adhesion with the protective layer. Furthermore, in the lubricating layer containing the fluorine-containing ether compound, it is not easy to produce points with high surface free energy formed by the part with more carbon atoms relative to the number of fluorine atoms, forming a state of low surface free energy of the lubricating layer. Therefore, the lubricating layer containing the fluorine-containing ether compound having the terminal group represented by formula (4-3) has excellent adhesion with the protective layer, can obtain excellent chemical resistance, and has a good spin-off inhibition effect.

[0149] Since u in formula (4-3) is 2 or more, -O-(CH2) in formula (4-3) u The distance between the primary hydroxyl group contained in -OH (hereinafter sometimes referred to as "side chain part") and the PFPE chain represented by B bonded to the terminal group D via a methylene group, the tertiary carbon atom bonded to the side chain part of formula (4-3) and other bulky parts becomes sufficiently far. Therefore, the primary hydroxyl group contained in the side chain part of formula (4-3) can easily move freely. In addition, since u is less than 4, the flexibility of the side chain part in formula (4-3) can be maintained. In addition, in the lubricating layer containing fluorine-containing ether compounds, it is not easy to produce points with high surface free energy formed by the part with a large number of carbon atoms relative to the number of fluorine atoms, forming a state of low surface free energy of the lubricating layer. Therefore, it becomes a fluorine-containing ether compound that can form a lubricating layer with excellent adhesion to the protective layer, excellent chemical resistance, and good effect of inhibiting spin-off. u is preferably 2 or 3, and more preferably 2.

[0150] In formula (4-3), the primary hydroxyl group contained in -Y-CH2-OH is bonded to the carbon atom bonded to the side chain portion of formula (4-3) via -Y-CH2-. Therefore, the primary hydroxyl group contained in -Y-CH2-OH is easy to move freely and is easy to participate in the interaction with the active point on the protective layer.

[0151] In order to make the primary hydroxyl group contained in -Y-CH2-OH in formula (4-3) more easily participate in the interaction with the active point on the protective layer, Y in formula (4-3) is preferably not a single bond, but a straight-chain alkylene group that may have an ether oxygen atom. In this case, the distance between the primary hydroxyl group contained in -Y-CH2-OH and the PFPE chain represented by B bonded to the terminal group D via the methylene group and the tertiary carbon atom bonded to the side chain part of formula (4-3) becomes farther, because the primary hydroxyl group contained in -Y-CH2-OH is more likely to move freely.

[0152] In formula (4-3), when Y is a straight-chain alkylene group optionally having an ether oxygen atom, the total number of carbon atoms and oxygen atoms possessed by Y is 1 to 5. In the terminal group represented by formula (4-3), the total number of carbon atoms and oxygen atoms possessed by Y is 5 or less, so the alkylene chain of the main chain portion in formula (4-3) will not be too long. Therefore, the flexibility of the terminal portion is reduced by the rigid alkylene chain length, and the interaction with the protective layer is prevented from being weakened and causing the terminal portion to float. Furthermore, in the lubricating layer containing a fluorine-containing ether compound, it is not easy to generate a point with high surface free energy formed by a portion with a large number of carbon atoms relative to the number of fluorine atoms, forming a state of low surface free energy of the lubricating layer. The total number of carbon atoms and oxygen atoms possessed by Y is preferably 1 to 4, and more preferably 1 to 3. The number of carbon atoms possessed by Y is preferably 1 to 3, and more preferably 1 to 2.

[0153] When Y in formula (4-3) is a straight-chain alkylene group which may have an ether oxygen atom, specific examples thereof include -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2OCH2-, -CH2OCH2CH2-, -CH2OCH2CH2CH2-, -CH2CH2OCH2- and the like.

[0154] (PFPE chain represented by B)

[0155] In the fluorinated ether compound represented by the general formula (1), B is a perfluoropolyether chain. When a lubricant containing the fluorinated ether compound of the present embodiment is applied to a protective layer to form a lubricating layer, the PFPE chain represented by B coats the surface of the protective layer and imparts lubricity to the lubricating layer to reduce the friction between the magnetic head and the protective layer. The PFPE chain represented by B can be appropriately selected according to the performance required by the lubricant containing the fluorinated ether compound.

[0156] The three Bs may be partially or entirely the same, or may be different. Preferably, all three Bs are the same. This is because the coating state of the protective layer with the fluorinated ether compound becomes more uniform, and a lubricating layer with better adhesion is obtained. Two or more of the three Bs are the same, which means that the three Bs have the same structure of repeating units containing two or more PFPE chains. The same B also includes Bs having the same repeating unit structure but different average polymerization degrees.

[0157] Examples of the PFPE chain represented by B include PFPE chains composed of polymers or copolymers of perfluoroalkylene oxides. Examples of the perfluoroalkylene oxides include perfluoromethylene oxide, perfluoroethylene oxide, perfluoropropylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0158] The three Bs in the general formula (1) are preferably each independently a PFPE chain represented by the following formula (5) derived from a polymer or copolymer of a perfluoroalkylene oxide, for example.

[0159] -(CF2) v1 -O-(CF2O) v2 -(CF2CF2O) v3 -(CF2CF2CF2O) v4 -(CF2CF2CF2CF2O) v5 -(CF2) v6 -(5)

[0160] In formula (5), v2, v3, v4, and v5 represent average polymerization degrees, and each independently represents 0 to 20. However, v2, v3, v4, and v5 are not 0 at the same time. v1 and v6 represent average values ​​of the number of CF2, and each independently represents 1 to 3. The arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (5) is not particularly limited.

[0161] In formula (5), v2, v3, v4, and v5 represent average polymerization degrees, and each independently represents 0 to 20, preferably 0 to 15, and more preferably 0 to 10.

[0162] In formula (5), v1 and v6 represent the average value of the number of CF2, and each independently represents 1 to 3. v1 and v6 are determined based on the structure of the repeating unit arranged at the end of the chain structure in the PFPE chain represented by formula (5).

[0163] In formula (5), (CF2O), (CF2CF2CF2O), (CF2CF2CF2O), (CF2CF2CF2CF2O) are repeating units. The arrangement order of the repeating units in formula (5) is not particularly limited. In addition, the number of types of repeating units in formula (5) is not particularly limited.

[0164] The three Bs in the general formula (1) are each independently selected from any one of the PFPE chains represented by the following formulas (5-1) to (5-4). If the three Bs are selected from any one of the PFPE chains represented by the formulas (5-1) to (5-4), a fluorine-containing ether compound is obtained that can provide a lubricating layer with good lubricity. In addition, when the three Bs are selected from any one of the PFPE chains represented by the formulas (5-1) to (5-4), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) in the PFPE chain to the number of carbon atoms is appropriate. Therefore, a fluorine-containing ether compound with appropriate hardness is obtained. Therefore, the fluorine-containing ether compound coated on the protective layer is not easy to aggregate on the protective layer, and a thinner lubricating layer can be formed with sufficient coverage. In addition, by making the fluorine-containing ether compound have moderate softness, a lubricating layer with better chemical resistance can be formed.

[0165] -CF2-(OCF2CF2) h -(OCF2) i -OCF2-(5-1)

[0166] In the formula (5-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.

[0167] -CF2CF2-(OCF2CF2CF2) j -OCF2CF2-(5-2)

[0168] In the formula (5-2), j represents an average degree of polymerization and is 1 to 15.

[0169] -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2-(5-3)

[0170] In the formula (5-3), k represents an average degree of polymerization and is 1 to 10.

[0171] -(CF2) v7 -O-(CF2CF2CF2O) v8 -(CF2CF2O) v9 -(CF2) v10 -(5-4)

[0172] In formula (5-4), v8 and v9 represent average polymerization degrees, and each independently represents 1 to 20. v7 and v10 represent average values ​​of the number of CF2, and each independently represents 1 to 2.

[0173] In formula (5-1), the arrangement order of (OCF2CF2) and (OCF2) as repeating units is not particularly limited. In formula (5-1), the number h of (OCF2CF2) and the number i of (OCF2) may be the same or different. The PFPE chain represented by formula (5-1) may be a polymer of (OCF2CF2). In addition, the PFPE chain represented by formula (5-1) may be any one of a random copolymer, a block copolymer, and an alternating copolymer composed of (OCF2CF2) and (OCF2).

[0174] In formulas (5-1) to (5-3), since h, which represents the average degree of polymerization, is 1 to 20, i is 0 to 20, j is 1 to 15, and k is 1 to 10, a fluorine-containing ether compound can obtain a lubricating layer having good lubricity. In addition, in formulas (5-1) to (5-3), since h and i, which represent the average degree of polymerization, are 20 or less, j is 15 or less, and k is 10 or less, the viscosity of the fluorine-containing ether compound does not become too high, and a lubricant containing it is easy to apply, which is preferred. In order to obtain a fluorine-containing ether compound that is easy to wet and spread on the protective layer and easy to obtain a lubricating layer with a uniform film thickness, h, i, j, and k, which represent the average degree of polymerization, are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7.

[0175] Furthermore, it is particularly preferred that h, which represents the average degree of polymerization, is 4 to 5 and i is 4 to 5 in formula (5-1). If h and i are 4 or more, the anti-spin-off property becomes further improved. In addition, if h and i are 5 or less, the coating property of the lubricating layer using them on the protective layer becomes good, and the chemical resistance becomes better.

[0176] In addition, in formula (5-1), when i representing the average degree of polymerization is 0, if h representing the average degree of polymerization is 6 to 8, a lubricating layer with good chemical resistance and spin-off resistance can be obtained, which is preferred. In addition, in formula (5-2), when j representing the average degree of polymerization is 3.5 to 5.0, a lubricating layer with good chemical resistance and spin-off resistance can be obtained, which is preferred.

[0177] In formula (5-4), the arrangement order of (CF2CF2CF2O) and (CF2CF2O) as repeating units is not particularly limited. In formula (5-4), the number v8 of (CF2CF2CF2O) and the number v9 of (CF2CF2O) may be the same or different. Formula (5-4) may be any one of a random copolymer, a block copolymer, and an alternating copolymer composed of monomer units (CF2CF2CF2O) and (CF2CF2O).

[0178] In formula (5-4), v8 and v9 representing the average degree of polymerization are each independently 1-20, preferably 1-15, and more preferably 1-10.

[0179] v7 and v10 in formula (5-4) are average values ​​of the number of CF2, and each independently represents 1 to 2. v7 and v10 are determined based on the structure of the repeating unit disposed at the end of the chain structure in the PFPE chain represented by formula (5-4).

[0180] In the fluorine-containing ether compound represented by the general formula (1), it is preferred that the three A's, the three B's, and the three D's in the general formula (1) are the same. That is, it is preferred that the three -A-CH2-B-CH2-D's in the general formula (1) are the same. This is to make the fluorine-containing ether compound easily and efficiently produced.

[0181] The fluorine-containing ether compound represented by the general formula (1) is preferably any one of the compounds represented by the following formulas (AA) to (AU) and (BA) to (BD). When the compound represented by the general formula (1) is any one of the compounds represented by the following formulas (AA) to (AU) and (BA) to (BD), the raw material is easy to obtain, and even if the thickness is thin, the chemical resistance is better, and a lubricating layer with a good spin-off suppression effect of the magnetic recording medium can be formed.

[0182] The compounds represented by the following formulas (AA) to (AH), (AJ) to (AU), and (BA) to (BD) are all the same as the three -A-CH2-B-CH2-D in the general formula (1). In the compounds represented by the following formulas (AA) to (AU), (BA) to (BD), Rf1, Rf2, and Rf3 representing the PFPE chain are the following structures. That is, in the compounds represented by the following formulas (AA) to (AQ), (AT), (AU), and (BA) to (BD), Rf1 is the PFPE chain represented by the above formula (5-1). In the compound represented by the following formula (AR), Rf2 is the PFPE chain represented by the above formula (5-2). In the compound represented by the following formula (AS), Rf3 is the PFPE chain represented by the above formula (5-3). In addition, h and i in Rf1, j in Rf2, and k in Rf3 representing PFPE chains in formulas (AA) to (AU) and (BA) to (BD) are values ​​indicating average polymerization degrees and are not necessarily integers.

[0183]

[0184] In the compounds represented by the following formulas (AA) to (AU), (BA) to (BD), X is a linking group represented by the above formulas (2-1) to (2-5). In the compounds represented by the following formulas (AA) to (AU), (BA) to (BD), A is a linking group represented by the above formula (3-1) or (3-2). In the compounds represented by the following formulas (AA) to (AU), (BA) to (BD), D is a terminal group represented by any one of the above formulas (4-1) to (4-3).

[0185]

[0186] In the three Rf1 in the formula (AA), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0187] In the three Rf1 in the formula (AB), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0188] In the three Rf1 in the formula (AC), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0189] In the three Rf1 in the formula (AD), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0190]

[0191] In the three Rf1 in the formula (AE), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0192] In the three Rf1 in the formula (AF), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0193] In the three Rf1 in the formula (AG), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0194] In the three Rf1 in the formula (AH), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0195]

[0196] In the three Rf1 in the formula (AI), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0197] In the three Rf1 in the formula (AJ), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0198] In the three Rf1 in the formula (AK), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0199] In the three Rf1 in the formula (AL), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0200]

[0201] In the three Rf1 in the formula (AM), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0202] In the three Rf1 in the formula (AN), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0203] In the three Rf1 in the formula (AO), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0204] In the three Rf1 in the formula (AP), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0205]

[0206] In the three Rf1 in the formula (AQ), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0207] In the three Rf2 in the formula (AR), j represents an average degree of polymerization and is 1 to 15. The j in the three Rf2 may be different from each other or may be partially or entirely the same.

[0208] In the three Rf3 in the formula (AS), k represents an average degree of polymerization and is 1 to 10. The k in the three Rf3 may be different from each other or may be partially or entirely the same.

[0209] In the three Rf1 in the formula (AT), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0210] In the three Rf1 in the formula (AU), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0211]

[0212] In the three Rf1 in the formula (BA), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0213] In the three Rf1 in the formula (BB), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0214] In the three Rf1 in the formula (BC), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0215] In the three Rf1 in the formula (BD), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. h and i in the three Rf1 may be different from each other, or may be partially or entirely the same.

[0216] The number average molecular weight (Mn) of the fluorinated ether compound of the present embodiment is preferably in the range of 500 to 10,000, more preferably in the range of 1,000 to 5,000, further preferably in the range of 2,000 to 4,800, and particularly preferably in the range of 3,000 to 4,600. If the number average molecular weight is 500 or more, the lubricating layer formed by the lubricant containing the fluorinated ether compound of the present embodiment has excellent heat resistance. The number average molecular weight of the fluorinated ether compound is more preferably 1,000 or more. In addition, if the number average molecular weight is 10,000 or less, the viscosity of the fluorinated ether compound becomes appropriate, and a lubricating layer with a thin film thickness can be easily formed by applying a lubricant containing it. In order to form a viscosity that is easy to handle when applied to a lubricant, the number average molecular weight of the fluorinated ether compound is preferably 5,000 or less.

[0217] The number average molecular weight (Mn) of the fluorinated ether compound was determined using AVANCE III 400 manufactured by Bruker BioSpin. 1 H-NMR determination and 19 The value obtained by F-NMR measurement. 19 The number of repeating units of the PFPE chain was calculated from the integrated value of the F-NMR measurement to determine the number average molecular weight. In the NMR (nuclear magnetic resonance) measurement, the sample was diluted in a hexafluorobenzene / d-acetone (4 / 1 v / v) solvent for measurement. 19 The standard for F-NMR chemical shifts was the peak of hexafluorobenzene assigned to -164.7 ppm. 1 The standard for H-NMR chemical shifts was the peak of acetone assigned to 2.2 ppm.

[0218] The fluorine-containing ether compound of the present embodiment is preferably subjected to molecular weight fractionation by an appropriate method so that the molecular weight distribution (ratio of weight average molecular weight (Mw) / number average molecular weight (Mn)) is 1.3 or less.

[0219] In the present embodiment, the method of molecular weight fractionation is not particularly limited, and for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or the like, molecular weight fractionation by supercritical extraction, or the like can be used.

[0220] [Preparation method]

[0221] The method for preparing the fluorine-containing ether compound of the present embodiment is not particularly limited, and the fluorine-containing ether compound can be prepared by a conventionally known method. The fluorine-containing ether compound of the present embodiment can be prepared by, for example, the following method.

[0222] [First Production Method]

[0223] (When D is a terminal group represented by formula (4-1) or (4-2))

[0224] A fluorine-based compound having hydroxymethyl groups (—CH 2 OH) disposed at both ends of a perfluoropolyether chain corresponding to B in the general formula (1) is prepared.

[0225] Next, the hydroxyl group of the hydroxymethyl group at one end of the fluorine compound is reacted with an epoxy compound having a group corresponding to D in the general formula (1) (first reaction). Thus, an intermediate compound 1-1 having a group corresponding to D at one end of the perfluoropolyether chain corresponding to B is obtained.

[0226] As the epoxy compound having a group corresponding to D in the general formula (1), for example, compounds represented by the following formulas (6-1) to (6-11) can be used. THP in the following formulas (6-1) to (6-11) represents a tetrahydropyranyl group. The compounds represented by the following formulas (6-1) to (6-11) can be prepared by a known method.

[0227]

[0228] An epoxy compound having a group corresponding to D in the general formula (1) can be prepared, for example, using the method shown below. That is, as represented by the following formula (7-1), an alcohol having a structure corresponding to a part of the terminal group represented by D in the general formula (1) (R in the formula (7-1)) can be prepared by reacting a halogen compound such as a bromine compound, a chlorine compound, etc. having an epoxy group (the formula (7-1) is the case where the halogen compound is a bromine compound). Before reacting the alcohol with the halogen compound having an epoxy group, the hydroxyl group contained in R of the alcohol represented by R-OH can be protected by a known method. The number of methylene groups contained in the halogen compound having an epoxy group (a1 in the formula (7-1)) is 1 to 4, and can be appropriately determined according to the structure of the terminal group of the synthesized compound.

[0229]

[0230] In the formula (7-1), R represents a structure corresponding to a part of the terminal group represented by D in the general formula (1), and a1 represents an integer of 1-4.

[0231] The above-mentioned epoxy compound can be prepared using the method shown below. That is, as shown in the following formula (7-2), an alcohol having a structure (R in formula (7-2)) corresponding to a part of the terminal group represented by D in the general formula (1) is reacted with a halogen compound such as a bromine compound or a chlorine compound having an alkenyl group (the formula (7-2) is the case where the halogen compound is a bromine compound). Then, it is prepared by a method in which meta-chloroperbenzoic acid (mCPBA) is allowed to act on the obtained compound to oxidize it. Before reacting the alcohol with the halogen compound having an alkenyl group, the hydroxyl group contained in R of the alcohol represented by R-OH can be protected by a known method. The number of methylene groups contained in the halogen compound having an alkenyl group (a2 in formula (7-2)) is 1 to 4, which can be appropriately determined according to the structure of the terminal group of the synthesized compound.

[0232]

[0233] In the formula (7-2), R represents a structure corresponding to a part of the terminal group represented by D in the general formula (1), and a2 represents an integer of 1-4.

[0234] The above-mentioned epoxy compound can be prepared using the method shown below. That is, as shown in the following formula (7-3), an alcohol having a structure (R in formula (7-3)) corresponding to a part of the terminal group represented by D in general formula (1) is subjected to an addition reaction with a compound having an alkenyl group and an epoxy group. Then, meta-chloroperbenzoic acid (mCPBA) is allowed to act on the compound obtained by the addition reaction to oxidize it. Before meta-chloroperbenzoic acid (mCPBA) is allowed to act on the compound obtained by the addition reaction to oxidize it, the hydroxyl group generated by the addition reaction can be protected by a known method. The number of methylene groups contained in the compound having an alkenyl group and an epoxy group (a3 in formula (7-3)) is 1 to 4, which can be appropriately determined according to the structure of the terminal group of the synthesized compound.

[0235]

[0236] In the formula (7-3), R represents a structure corresponding to a part of the terminal group represented by D in the general formula (1), and a3 represents an integer of 1-4.

[0237] Then, the terminal hydroxyl group of the intermediate compound 1-1 produced in the first reaction is subjected to an addition reaction with a compound having two epoxy groups corresponding to A in the general formula (1), thereby obtaining the intermediate compound 1-2 (second reaction).

[0238] As the compound having two epoxy groups corresponding to A in the general formula (1), for example, compounds represented by the following formulas (8-1) to (8-5) can be used. THP in the following formula (8-5) represents a tetrahydropyranyl group.

[0239]

[0240] The compound having two epoxy groups corresponding to A in the general formula (1) can be prepared using the method shown below. For example, for the compound represented by formula (8-4), as shown in the following formula (9-1), it can be prepared by allowing meta-chloroperbenzoic acid (mCPBA) to act on the alkenyl group of a compound having an alkenyl group and an epoxy group (allyl glycidyl ether) to oxidize it.

[0241]

[0242] The compound represented by formula (8-5) can be prepared using the method shown in the following formula (9-2). A halogen compound such as a bromine compound or a chlorine compound having an epoxy group (formula (9-2) is the case where the halogen compound is a bromine compound) is reacted with an alcohol (allyl alcohol) having an alkenyl group. Then, the secondary hydroxyl group of the compound generated after the reaction is protected with dihydropyran, and meta-chloroperbenzoic acid (mCPBA) is allowed to act to oxidize the alkenyl group. THP in formula (9-2) represents tetrahydropyranyl.

[0243]

[0244] As the compound having two epoxy groups corresponding to A in the general formula (1), a commercially available product can be used.

[0245] A protective group such as a tetrahydropyranyl group is introduced into the secondary hydroxyl group of the intermediate compound 1-2 having an epoxy group and a secondary hydroxyl group produced in the second reaction, and then a triol corresponding to X in the general formula (1) is reacted (third reaction).

[0246] Examples of the triol corresponding to X in the general formula (1) include 1,3,5-cyclohexanetriol, 1,3,5-benzenetriol, 1,3,5-cyclohexanedimethanol, glycerol, 2-methyl-1,2,3-propanetriol, trimethylolmethane, trimethylolethane, and trimethylolpropane.

[0247] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the general formula (1) in which three perfluoropolyether chains B are bonded to the trivalent atomic group X represented by formula (2-1) to (2-5) via a connecting group A represented by formula (3-1) or (3-2), and the end group D is an end group represented by formula (4-1) or (4-2).

[0248] [Second production method]

[0249] (When D is a terminal group represented by formula (4-3))

[0250] The intermediate compound 1-1 generated in the first reaction of the first preparation method has a terminal hydroxyl group at one end of the perfluoropolyether chain and a secondary hydroxyl group at the other end. After introducing a protective group such as a tert-butyldimethylsilyl group into the terminal hydroxyl group, the terminal group represented by formula (4-3) is u The hydroxyl group in the -OH group is reacted with a protected halogen compound and a secondary hydroxyl group, and then the protecting group of the terminal hydroxyl group is deprotected by a known method to obtain an intermediate compound 2-1 (first reaction).

[0251] -(CH2) as the terminal group represented by formula (4-3) u Examples of the halogen compound in which the hydroxyl group in -OH is protected include compounds represented by the following formulae (10-1) to (10-3). THP in the formulae (10-1) to (10-3) represents a tetrahydropyranyl group.

[0252]

[0253] The intermediate compound 2-1 obtained is subjected to an addition reaction with a compound having two epoxy groups corresponding to A in the general formula (1) by the same method as the second reaction of the first production method (second reaction). The compound obtained is subjected to an addition reaction with a triol corresponding to X in the general formula (1) by the same method as the third reaction of the first production method (third reaction).

[0254] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the general formula (1) in which three perfluoropolyether chains B are bonded to the trivalent atomic group X represented by formula (2-1) to (2-5) via a connecting group A represented by formula (3-1) or (3-2), and the end group D is an end group represented by formula (4-3).

[0255] [Third Production Method]

[0256] (When at least one of the three -A-CH2-B-CH2-D bonded to X in the general formula (1) is different)

[0257] By the same method as the first reaction and the second reaction of the first preparation method or the second preparation method, two or three intermediate compounds corresponding to -A-CH2-B-CH2-D are synthesized. Then, the triol corresponding to X in the general formula (1) and the two or three intermediate compounds corresponding to gA-CH2-B-CH2-D are reacted in sequence.

[0258] After the above steps, a deprotection reaction is carried out using a known method, thereby preparing a compound in which at least one of the three -A-CH2-B-CH2-D bonded to X in the general formula (1) is different.

[0259] [Lubricant for magnetic recording media]

[0260] The lubricant for magnetic recording media according to the present embodiment contains the fluorine-containing ether compound represented by the above general formula (1).

[0261] The lubricant of the present embodiment may be mixed with a known material used as a lubricant material as needed within a range not impairing the properties of the fluorine-containing ether compound represented by the above general formula (1).

[0262] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), and Moresco A20H (manufactured by Moresco). The number average molecular weight of the known material used in combination with the lubricant of the present embodiment is preferably 1,000 to 10,000.

[0263] When the lubricant of this embodiment contains a material other than the fluorinated ether compound represented by the general formula (1), the content of the fluorinated ether compound represented by the general formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more.

[0264] Since the lubricant of the present embodiment contains the fluorine-containing ether compound represented by the above general formula (1), it is possible to form a lubricating layer having excellent chemical resistance and a high spin-off suppressing effect.

[0265] [Magnetic recording media]

[0266] The magnetic recording medium of the present embodiment includes at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate.

[0267] In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer as required. In addition, at least one of an adhesion layer and a soft magnetic layer may be provided between the underlayer and the substrate.

[0268] Figure 1 It is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention.

[0269] The magnetic recording medium 10 of the present 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 .

[0270] "Substrate"

[0271] As the substrate 11 , for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy can be used.

[0272] In addition, as the substrate 11, a non-magnetic substrate made of non-metallic materials such as glass, ceramics, silicon, silicon carbide, carbon, and resin can be used, and a non-magnetic substrate in which a film of NiP or NiP alloy is formed on a base made of these non-metallic materials can also be used.

[0273] "Attachment Layer"

[0274] The adhesive layer 12 prevents corrosion of the substrate 11 when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are arranged in contact with each other.

[0275] 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 by, for example, sputtering.

[0276] "Soft magnetic layer"

[0277] The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer composed 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 antiferromagnetically coupled (AFC) by sandwiching an intermediate layer composed of a Ru film between two soft magnetic films.

[0278] Examples of the material of the first soft magnetic film and the second soft magnetic film include CoZrTa alloy and CoFe alloy.

[0279] In the CoFe alloy used in the first soft magnetic film and the second soft magnetic film, it is preferred to add any one of Zr, Ta, and Nb. This can promote the amorphization of the first soft magnetic film and the second soft magnetic film. As a result, the orientation of the first base layer (seed layer) can be improved, and the floating amount of the magnetic head can be reduced.

[0280] The soft magnetic layer 13 can be formed by, for example, sputtering.

[0281] "First Base Layer"

[0282] The first base layer 14 is a layer that controls the orientation and crystal size of the second base layer 15 and the magnetic layer 16 provided thereon.

[0283] Examples of the first base layer 14 include a Cr layer, a Ta layer, a Ru layer, a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, a CrTi alloy layer, and the like.

[0284] The first base layer 14 can be formed by, for example, sputtering.

[0285] "Second base layer"

[0286] The second underlayer 15 is a layer that controls and improves the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer composed of Ru or a Ru alloy.

[0287] The second base layer 15 may be composed of a single layer or a plurality of layers. When the second base layer 15 is composed of a plurality of layers, all the layers may be composed of the same material, or at least one layer may be composed of a different material.

[0288] The second base layer 15 can be formed by, for example, sputtering.

[0289] "Magnetic layer"

[0290] The magnetic layer 16 is composed of a magnetic film whose easy magnetization axis is oriented in a vertical or horizontal direction relative to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. In order to improve the SNR characteristics, the magnetic layer 16 may also be a layer containing oxide, Cr, B, Cu, Ta, Zr, etc.

[0291] Examples of the oxide contained in the magnetic layer 16 include SiO 2 , SiO, Cr 2 O 3 , CoO, Ta 2 O 3 , and TiO 2 .

[0292] The magnetic layer 16 may be composed of a single layer or a plurality of magnetic layers including materials having different compositions.

[0293] For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, which are stacked in order from the bottom, the first magnetic layer is preferably a granular structure composed of a material containing Co, Cr, Pt, and further containing an oxide. As the oxide contained in the first magnetic layer, for example, oxides of Cr, Si, Ta, Al, Ti, Mg, Co, etc. are preferably used. Among them, TiO2, Cr2O3, SiO2, etc. are particularly preferred. In addition, the first magnetic layer is preferably composed of a composite oxide to which two or more oxides are added. Among them, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, etc. are particularly preferred.

[0294] The first magnetic layer may contain, in addition to Co, Cr, Pt, and oxides, one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re.

[0295] 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.

[0296] The third magnetic layer is preferably a non-granular structure formed of a material containing Co, Cr, Pt and no oxide. 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 in addition to Co, Cr, and Pt.

[0297] When the magnetic layer 16 is formed of a plurality of magnetic layers, a non-magnetic layer is preferably provided between adjacent magnetic layers. When the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, a non-magnetic layer is preferably provided between the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer.

[0298] The non-magnetic layer arranged between adjacent magnetic layers of the magnetic layer 16 can preferably use Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, B), etc.

[0299] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing oxides, metal nitrides or metal carbides. 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.

[0300] The non-magnetic layer can be formed by, for example, sputtering.

[0301] In order to achieve a higher recording density, the magnetic layer 16 is preferably a perpendicular magnetic recording magnetic layer with its easy magnetization axis oriented perpendicularly to the substrate surface. The magnetic layer 16 may also be an in-plane magnetic recording magnetic layer.

[0302] The magnetic layer 16 can be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0303] "Protective layer"

[0304] The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or multiple layers. As the protective layer 17, a carbon protective layer may be preferably used, and an amorphous carbon protective layer is particularly preferred. If the protective layer 17 is a carbon protective layer, the interaction with the polar groups (especially hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18 is further improved, so it is preferred.

[0305] The adhesion between the carbon protective layer and the lubricating layer 18 can be controlled by making the carbon protective layer hydrogenated carbon and / or carbon nitride and adjusting the hydrogen content and / or nitrogen content in the carbon protective layer. When measured by hydrogen forward scattering (HFS), the hydrogen content in the carbon protective layer is preferably 3 atomic % to 20 atomic %. In addition, the nitrogen content in the carbon protective layer is preferably 4 atomic % to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0306] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained in the entire carbon-based protective layer. For example, it is suitable to set a composition gradient layer containing nitrogen on the lubricating layer 18 side of the protective layer 17 and hydrogen on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved.

[0307] The protective layer 17 preferably has a thickness of 1 nm to 7 nm. When the protective layer 17 has a thickness of 1 nm or more, sufficient performance as the protective layer 17 can be obtained. When the protective layer 17 has a thickness of 7 nm or less, it is preferred from the perspective of reducing the thickness of the protective layer 17.

[0308] As a film-forming method of the protective layer 17, a sputtering method using a carbon-containing target, a CVD (chemical vapor deposition) method using a hydrocarbon raw material such as ethylene and toluene, an IBD (ion beam deposition) method, or the like can be used.

[0309] When a carbon-based protective layer is formed as the protective layer 17, for example, the film can be formed by a DC magnetron sputtering method. In particular, when a carbon-based protective layer is formed as the protective layer 17, it is preferred to form an amorphous carbon protective layer by a plasma CVD method. The surface of the amorphous carbon protective layer formed by the plasma CVD method is uniform and has little roughness.

[0310] "Lubricating layer"

[0311] The lubricating layer 18 prevents contamination of the magnetic recording medium 10. In addition, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording and reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10.

[0312] like Figure 1As shown, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 is formed by applying the lubricant for a magnetic recording medium of the above-mentioned embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-mentioned fluorine-containing ether compound.

[0313] When the protective layer 17 disposed under the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 is particularly strongly bonded to the protective layer 17. As a result, even if the lubricating layer 18 is thin, it is easy to obtain a magnetic recording medium 10 having a surface covered with the protective layer 17 at a high coverage rate, and the surface contamination of the magnetic recording medium 10 can be effectively prevented.

[0314] The average film thickness of the lubricating layer 18 is preferably More preferably If the average film thickness of the lubricating layer 18 is more than 0.5nm, the lubricating layer 18 will not become an island or a mesh shape but will be formed with a uniform film thickness. Therefore, the surface of the protective layer 17 can be coated with a high coverage rate by the lubricating layer 18. In addition, by setting the average film thickness of the lubricating layer 18 to less than 2.0nm, the lubricating layer 18 can be fully filmized, and the floating amount of the magnetic head can be fully reduced.

[0315] "Method for forming a lubricating layer"

[0316] Examples of a method for forming the lubricating layer 18 include a method of preparing a magnetic recording medium in the manufacturing process in which each layer up to the protective layer 17 is formed on the substrate 11 , applying a lubricating layer forming solution on the protective layer 17 , and drying the solution.

[0317] The lubricating layer-forming solution can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium of the above-described embodiment in a solvent as necessary to obtain a solution having a viscosity and a concentration suitable for a coating method.

[0318] Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Batler (registered trademark) XF (trade name, manufactured by DuPont Mitsui Fluorochemicals) and Asahicrine (registered trademark) AE-3000 (trade name, manufactured by AGC Corporation).

[0319] The coating method of the lubricating layer forming solution is not particularly limited, and examples thereof include spin coating, spray coating, paper coating, and dipping.

[0320] When the dipping method is used, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 is formed is dipped in the lubricating layer forming solution placed in the dipping tank of the dipping device. Then, the substrate 11 is pulled out of the dipping tank at a predetermined speed. Thus, the lubricating layer forming solution is applied to the surface of the substrate 11 on the protective layer 17.

[0321] By using the dipping method, the lubricating layer-forming solution can be uniformly applied to the surface of the protective layer 17 , and the lubricating layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0322] In this embodiment, it is preferable to perform heat treatment on the substrate 11 formed with the lubricating layer 18. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesion between the lubricating layer 18 and the protective layer 17 is improved.

[0323] The heat treatment temperature is preferably set to 100° C. to 180° C., and more preferably set to 100° C. to 160° C. If the heat treatment temperature is 100° C. or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be fully obtained. In addition, by setting the heat treatment temperature to 180° C. or lower, thermal decomposition of the lubricating layer 18 caused by the heat treatment can be prevented. The heat treatment time can be appropriately adjusted according to the heat treatment temperature, and is preferably set to 10 minutes to 120 minutes.

[0324] 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 light (UV) before or after the heat treatment.

[0325] As the magnetic recording medium 10 of the present embodiment, at least a magnetic layer 16, a protective layer 17 and a lubricating layer 18 are sequentially arranged on a substrate 11. In the magnetic recording medium 10 of the present embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed in contact with the protective layer 17. The lubricating layer 18 has good chemical resistance and a good effect of suppressing spin-off. Therefore, the magnetic recording medium 10 of the present embodiment has excellent reliability and durability. Therefore, the magnetic recording medium 10 of the present embodiment can reduce the floating amount of the magnetic head (for example, less than 10nm), and can work stably for a long time even in a harsh environment accompanied by diversified uses. Therefore, the magnetic recording medium 10 of the present embodiment is particularly suitable as a magnetic disk mounted on a magnetic disk device of the LUL (Load Unload) method.

[0326] Example

[0327] The present invention will be described in more detail below by way of examples and comparative examples. It should be noted that the present invention is not limited to the following examples.

[0328] [Example 1]

[0329] The compound (AA-1) represented by the above formula (AA) is obtained by the method shown below.

[0330] (First reaction)

[0331] Under nitrogen atmosphere, add HOCH2CF2O (CF2CF2O) into a 100 mL eggplant flask. h (CF2O) i 20 g of a compound represented by CF2CH2OH (wherein 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), 4.05 g of a compound represented by the above formula (6-1), and 20 mL of tert-butanol were stirred at room temperature until uniform to form a mixture. 1.12 g of potassium tert-butoxide was added to the mixture, and the mixture was stirred at 70°C for 16 hours to react.

[0332] The compound represented by the formula (6-1) is synthesized by protecting the hydroxyl group of ethylene glycol monoallyl ether with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0333] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel with 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 the desiccant was filtered and separated, the filtrate was concentrated and the residue was purified by silica gel column chromatography to obtain 9.6 g of a compound represented by the following formula (11) as an intermediate compound 1-1.

[0334]

[0335] (Rf1 in formula (11) is the PFPE chain represented by the above formula (5-1). Rf1 represents the average degree of polymerization, h represents 4.5, and i represents the average degree of polymerization, and THP represents tetrahydropyranyl.

[0336] (Second reaction)

[0337] Next, 9.0 g of the compound represented by formula (11) as the intermediate compound 1-1 obtained above, 0.64 g of 1,2,3,4-diepoxybutane represented by the above formula (8-1), and 20 mL of tert-butanol were added to a 100 mL eggplant-shaped flask under a nitrogen atmosphere, and stirred at room temperature until uniform to form a mixture. 0.40 g of potassium tert-butoxide was added to the mixture, and the mixture was stirred at 70° C. for 16 hours to react.

[0338] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel with 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 the desiccant was filtered and separated, the filtrate was concentrated and the residue was purified by silica gel column chromatography to obtain 7.1 g of a compound represented by the following formula (12) as an intermediate compound 1-2.

[0339]

[0340] Rf1 in formula (12) is the PFPE chain represented by the above formula (5-1). h representing the average degree of polymerization in Rf1 represents 4.5, and i representing the average degree of polymerization represents 4.5. THP represents tetrahydropyranyl.

[0341] (Third reaction)

[0342] Next, the compound represented by formula (12) as the intermediate compound 1-2 obtained above was protected with dihydropyran to obtain a compound represented by the following formula (13). Then, 7.0 g of the compound represented by formula (13) was added to a 100 mL eggplant-shaped flask under a nitrogen atmosphere, and 0.23 g of 1,3,5-cyclohexanetriol and 20 mL of tert-butanol were added, and stirred at room temperature until it became uniform to form a mixture. 0.40 g of potassium tert-butoxide was added to the mixture, and stirred at 70°C for 48 hours to react.

[0343]

[0344] Rf1 in formula (13) is the PFPE chain represented by the above formula (5-1). h representing the average degree of polymerization in Rf1 represents 4.5, and i representing the average degree of polymerization represents 4.5. THP represents tetrahydropyranyl.

[0345] The reaction solution obtained after the reaction was returned to room temperature, 50 g of 10% hydrogen chloride·methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and stirred at room temperature for 4 hours. Then, the reaction solution was transferred little by little to a separatory funnel added with 100 mL of saturated sodium bicarbonate aqueous solution, and extracted twice with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated sodium bicarbonate water, and 100 mL of brine in sequence, and dehydrated with anhydrous sodium sulfate. After filtering and separating the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.2 g of compound (AA-1) (Rf1 in formula (AA) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0346] The obtained compound (AA-1) was subjected to1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0347] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0348] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0349] [Example 2]

[0350] The compound (AA-2) represented by the above formula (AA) is obtained by the method shown below.

[0351] Using HOCH2CF2O (CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (wherein h representing the average degree of polymerization is 3.5, and i representing the average degree of polymerization is 3.5) (number average molecular weight 815, molecular weight distribution 1.1) is substituted for HOCH2CF2O (CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (wherein h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5) was prepared by the same operation as in Example 1, to obtain 4.5 g of compound (AA-2) (Rf1 in formula (AA) is the PFPE chain represented by the above formula (5-1). Among the three Rf1s, h representing the average degree of polymerization is 3.5, and i representing the average degree of polymerization is 3.5).

[0352] The obtained compound (AA-2) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0353] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0354] 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(21F), -78.5(6F), -80.5(6F), -91.0~-88.5(42F)

[0355] [Example 3]

[0356] The compound (AA-3) represented by the above formula (AA) is obtained by the method shown below.

[0357] Using HOCH2CF2O (CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (wherein h representing the average degree of polymerization is 5.5, and i representing the average degree of polymerization is 5.5) (number average molecular weight 1180, molecular weight distribution 1.1) is substituted for HOCH2CF2O (CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (wherein h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5) was prepared by the same operation as in Example 1, to obtain 3.5 g of compound (AA-3) (Rf1 in formula (AA) is the PFPE chain represented by the above formula (5-1). Among the three Rf1s, h representing the average degree of polymerization is 5.5, and i representing the average degree of polymerization is 5.5).

[0358] The obtained compound (AA-3) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0359] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0360] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(33F), -78.5(6F), -80.5(6F), -91.0~-88.5(66F)

[0361] [Example 4]

[0362] The compound represented by the above formula (AB) is obtained by the method shown below.

[0363] Except for using the compound represented by formula (6-2) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 4.4 g of compound (AB) (Rf1 in formula (AB) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0364] The compound represented by formula (6-2) is synthesized by protecting one hydroxyl group of 1,3-propanediol with dihydropyran and then reacting the protected group with epibromohydrin.

[0365] The obtained compound (AB) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0366] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(6H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0367] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0368] [Example 5]

[0369] The compound represented by the above formula (AC) is obtained by the method shown below.

[0370] Except for using the compound represented by formula (6-3) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 4.2 g of compound (AC) (Rf1 in formula (AC) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0371] The compound represented by the formula (6-3) is synthesized by protecting the hydroxyl group of glycidol using dihydropyran.

[0372] The obtained compound (AC) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0373] 1H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(36H), 3.85~4.10(12H)

[0374] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0375] [Example 6]

[0376] The compound represented by the above formula (AD) is obtained by the method shown below.

[0377] Except for using the compound represented by formula (6-4) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 4.3 g of compound (AD) (Rf1 in formula (AD) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0378] The compound represented by the formula (6-4) is synthesized by protecting the hydroxyl group of 3-butene-1-ol with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0379] The obtained compound (AD) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0380] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(6H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(36H), 3.85~4.10(12H)

[0381] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0382] [Example 7]

[0383] The compound (AE) represented by the above formula (AE) is obtained by the method shown below.

[0384] Except for using the compound represented by formula (6-5) instead of the compound represented by formula (6-1), the same operations as in Example 1 were carried out to obtain 4.3 g of compound (AE) (Rf1 in formula (AE) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0385] The compound represented by formula (6-5) is synthesized by allowing 2-(2-bromoethoxy)tetrahydro-2H-pyran to act on the hydroxyl group of 3-butene-1-ol, followed by oxidation with m-chloroperbenzoic acid.

[0386] The obtained compound (AE) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0387] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(6H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0388] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0389] [Example 8]

[0390] The compound represented by the above formula (AF) is obtained by the method shown below.

[0391] Except for using the compound represented by formula (6-6) instead of the compound represented by formula (6-1), the same operations as in Example 1 were carried out to obtain 3.7 g of compound (AF) (Rf1 in formula (AF) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0392] The compound represented by the formula (6-6) is synthesized by subjecting the compound represented by the formula (6-1) to an addition reaction with allyl alcohol, protecting the hydroxyl group of the obtained compound with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0393] The obtained compound (AF) was subjected to 1 H-NMR determination and 19The structure was identified based on the following results from F-NMR measurement.

[0394] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(15H), 2.50(3H), 3.35~3.85(63H), 3.85~4.10(12H)

[0395] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0396] [Example 9]

[0397] The compound represented by the above formula (AG) is obtained by the method shown below.

[0398] Except for using the compound represented by formula (6-7) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 3.8 g of compound (AG) (Rf1 in formula (AG) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0399] The compound represented by the formula (6-7) is synthesized by subjecting the compound represented by the formula (6-4) to an addition reaction with allyl alcohol, protecting the hydroxyl group of the obtained compound with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0400] The obtained compound (AG) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0401] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(6H), 1.95~2.10(15H), 2.50(3H), 3.35~3.85(51H), 3.85~4.10(12H)

[0402] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0403] [Example 10]

[0404] The compound represented by the above formula (AH) is obtained by the method shown below.

[0405] Except for using the compound represented by formula (6-8) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 3.7 g of compound (AH) (Rf1 in formula (AH) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0406] The compound represented by formula (6-8) is synthesized by subjecting the compound represented by formula (6-1) to an addition reaction with 3-butene-1-ol, protecting the hydroxyl group of the obtained compound with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0407] The obtained compound (AH) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0408] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(6H), 1.95~2.10(15H), 2.50(3H), 3.35~3.85(63H), 3.85~4.10(12H)

[0409] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0410] [Example 11]

[0411] The compound represented by the above formula (AI) is obtained by the method shown below.

[0412] The addition reaction was carried out in the same manner as in Example 1 except that the amount of the compound represented by the formula (13) used in the third reaction of Example 1 was reduced to 2 / 3 and the reaction was carried out with 1,3,5-cyclohexanetriol.

[0413] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel added with 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 and separating the desiccant, the filtrate was concentrated and the residue was purified by silica gel column chromatography to obtain 4.6 g of a compound represented by the following formula (14) as an intermediate compound.

[0414]

[0415] In the two Rf1 in the formula (14), h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5. THP represents a tetrahydropyranyl group.

[0416] Then, 4.0 g of the compound represented by formula (14), 2.0 g of the compound represented by formula (15) as the intermediate compound of Example 8 and 20 mL of tert-butanol were added to a 100 mL eggplant-shaped flask under a nitrogen atmosphere, and stirred at room temperature until uniform to form a mixture. 0.4 g of potassium tert-butoxide was added to the mixture, and stirred at 70° C. for 24 hours to react.

[0417]

[0418] In Rf1 in the formula (15), h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5. THP represents a tetrahydropyranyl group.

[0419] The reaction solution obtained after the reaction was returned to room temperature, 50 g of 10% hydrogen chloride·methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and stirred at room temperature for 4 hours. Then, the reaction solution was transferred little by little to a separatory funnel added with 100 mL of saturated sodium bicarbonate aqueous solution, and extracted twice with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated sodium bicarbonate water, and 100 mL of brine in sequence, and dehydrated with anhydrous sodium sulfate. After filtering and separating the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 2.5 g of compound (AI) (Rf1 in formula (AI) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0420] The obtained compound (AI) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0421] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(13H), 2.50(3H), 3.35~3.85(53H), 3.85~4.10(12H)

[0422] 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0423] [Example 12]

[0424] The compound represented by the above formula (AJ) is obtained by the method shown below.

[0425] Except for using the compound represented by formula (6-9) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 4.6 g of compound (AJ) (Rf1 in formula (AJ) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0426] The compound represented by formula (6-9) is synthesized by protecting one hydroxyl group of 1,6-hexanediol with dihydropyran and then reacting the resulting mixture with epibromohydrin.

[0427] The obtained compound (AJ) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0428] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(24H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0429] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0430] [Example 13]

[0431] The compound represented by the above formula (AK) is obtained by the method shown below.

[0432] Except for using the compound represented by formula (6-10) instead of the compound represented by formula (6-1), the same operation as in Example 1 was carried out to obtain 4.2 g of compound (AK) (Rf1 in formula (AK) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0433] The compound represented by the formula (6-10) is synthesized by protecting the hydroxyl group of 7-octen-1-ol with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0434] The obtained compound (AK) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0435] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(30H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(36H), 3.85~4.10(12H)

[0436] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0437] [Example 14]

[0438] The compound represented by the above formula (AL) is obtained by the method shown below.

[0439] Except for using the compound represented by formula (6-11) instead of the compound represented by formula (6-1), the same operations as in Example 1 were carried out to obtain 4.3 g of compound (AL) (Rf1 in formula (AL) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0440] The compound represented by the formula (6-11) is synthesized by allowing 2-(2-bromoethoxy)tetrahydro-2H-pyran to act on the hydroxyl group of 5-hexen-1-ol, followed by oxidation with m-chloroperbenzoic acid.

[0441] The obtained compound (AL) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0442] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(18H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0443] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0444] [Example 15]

[0445] The compound represented by the above formula (AM) is obtained by the method shown below.

[0446] Except for using 1,2,7,8-diepoxyoctane represented by formula (8-2) instead of the compound represented by formula (8-1), the same operation as in Example 1 was carried out to obtain 4.8 g of compound (AM) (Rf1 in formula (AM) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0447] The obtained compound (AM) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0448] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(24H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0449] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0450] [Example 16]

[0451] The compound represented by the above formula (AN) is obtained by the method shown below.

[0452] Except for using the compound represented by formula (8-3) instead of the compound represented by formula (8-1), the same operations as in Example 1 were carried out to obtain 4.8 g of compound (AN) (Rf1 in formula (AN) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0453] The compound represented by formula (8-3) is synthesized by oxidizing 1,9-decadiene with m-chloroperbenzoic acid.

[0454] The obtained compound (AN) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0455] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.65~1.85(36H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0456] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0457] [Example 17]

[0458] The compound represented by the above formula (AO) is obtained by the method shown below.

[0459] Except for using the compound represented by formula (8-4) instead of the compound represented by formula (8-1), the same operation as in Example 1 was carried out to obtain 5.0 g of compound (AO) (Rf1 in formula (AO) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0460] The compound represented by the formula (8-4) is synthesized by oxidizing allyl glycidyl ether with m-chloroperbenzoic acid.

[0461] The obtained compound (AO) is subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0462] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(60H), 3.85~4.10(12H)

[0463] 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0464] [Example 18]

[0465] The compound represented by the above formula (AP) is obtained by the method shown below.

[0466] The same operations as in Example 1 were performed except that the compound represented by formula (6-6) was used instead of the compound represented by formula (6-1), and the compound represented by formula (8-4) was used instead of the compound represented by formula (8-1), to obtain 3.8 g of compound (AP) (Rf1 in formula (AP) is the PFPE chain represented by the above formula (5-1). Among the three Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0467] The obtained compound (AP) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0468] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(15H), 2.50(3H), 3.35~3.85(75H), 3.85~4.10(12H)

[0469] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0470] [Example 19]

[0471] The compound represented by the above formula (AQ) is obtained by the method shown below.

[0472] Except for using the compound represented by formula (8-5) instead of the compound represented by formula (8-1), the same operations as in Example 1 were carried out to obtain 3.5 g of compound (AQ) (Rf1 in formula (AQ) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0473] The compound represented by formula (8-5) is synthesized by reacting two molecules of allyl alcohol with one molecule of epibromohydrin, protecting the secondary hydroxyl group of the compound produced after the reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0474] The obtained compound (AQ) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0475] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(15H), 2.50(3H), 3.35~3.85(75H), 3.85~4.10(12H)

[0476] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0477] [Example 20]

[0478] The compound (AA-4) represented by the above formula (AA) is obtained by the method shown below.

[0479] Using HOCH2CF2O (CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (wherein h representing the average degree of polymerization is 7.0 and i representing the average degree of polymerization is 0) (number average molecular weight 990, molecular weight distribution 1.1) is substituted for HOCH2CF2O (CF2CF2O) h (CF2O) i The same operation as in Example 1 was performed except that a compound represented by CF2CH2OH (wherein h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5) was obtained to obtain 4.6 g of compound (AA-4) (Rf1 in formula (AA) is a PFPE chain represented by the above formula (5-1). Among the three Rf1s, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0).

[0480] The obtained compound (AA-4) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0481] 1H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0482] 19 F-NMR (acetone-D6): δ[ppm]=-78.5(6F), -81.0(6F), -91.0~-88.5(84F)

[0483] [Example 21]

[0484] The compound represented by the above formula (AR) is obtained by the method shown below.

[0485] Using HOCH2CF2CF2O (CF2CF2CF2O) j A compound represented by CF2CF2CH2OH (wherein j representing the average degree of polymerization is 4.5) (number average molecular weight 1020, molecular weight distribution 1.1) is substituted for HOCH2CF2O (CF2CF2O) h (CF2O) i The same operation as in Example 1 was performed except for the above to obtain 4.7 g of compound (AR) (Rf2 in formula (AR) is the PFPE chain represented by the above formula (5-2). j representing the average degree of polymerization among the three Rf2s is 4.5).

[0486] The obtained compound (AR) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results of F-NMR measurement.

[0487] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0488] 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(54F), -86.4(12F), -124.3(12F), -130.0~-129.0(27F)

[0489] [Example 22]

[0490] The compound represented by the above formula (AS) is obtained by the method shown below.

[0491] Use HOCH2CF2CF2CF2O (CF2CF2CF2CF2O) k A compound represented by CF2CF2CF2CH2OH (where k representing the average degree of polymerization is 3.0) (number average molecular weight 995, molecular weight distribution 1.1) is substituted for HOCH2CF2O (CF2CF2O) h (CF2O) i The same operation as in Example 1 was carried out except for the above to obtain 4.1 g of compound (AS) (Rf3 in formula (AS) is the PFPE chain represented by the above formula (5-3). k representing the average degree of polymerization among the three Rf3 is 3.0).

[0492] The obtained compound (AS) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0493] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0494] 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(48F), -122.5(12F), -126.0(36F), -129.0~-128.0(12F)

[0495] [Example 23]

[0496] The compound represented by the above formula (AT) is obtained by the method shown below.

[0497] (First reaction)

[0498] The primary hydroxyl group of the compound represented by the above formula (11) described in Example 1 was protected with tert-butyldimethylsilyl chloride to obtain a compound represented by the formula (16).

[0499]

[0500] Rf1 in formula (16) is the PFPE chain represented by the above formula (5-1). h representing the average degree of polymerization in Rf1 represents 4.5, and i representing the average degree of polymerization represents 4.5. THP represents tetrahydropyranyl, and TBS represents tert-butyldimethylsilyl.

[0501] Next, 7.0 g of the compound represented by the formula (16) obtained as the intermediate compound, 0.96 g of 2-(2-bromoethoxy)tetrahydro-2H-pyran represented by the formula (10-1), and 20 mL of tert-butyl alcohol were added to a 100 mL eggplant-shaped flask under a nitrogen atmosphere, and stirred at room temperature until the mixture became uniform to form a mixture. 0.50 g of potassium tert-butylate was added to the mixture, and the mixture was stirred at 70° C. for 8 hours to react.

[0502] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel added with 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 and separating the desiccant, the filtrate was concentrated and the residue was purified by silica gel column chromatography to obtain 5.5 g of a compound represented by the following formula (17) as an intermediate compound.

[0503]

[0504] Rf1 in formula (17) is the PFPE chain represented by the above formula (5-1). In Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5. THP represents tetrahydropyranyl, and TBS represents tert-butyldimethylsilyl.

[0505] The compound represented by the formula (17) obtained as the intermediate compound is subjected to deprotection of the tert-butyldimethylsilyl group using tetrabutylammonium fluoride to obtain a compound represented by the following formula (18).

[0506]

[0507] Rf1 in formula (18) is the PFPE chain represented by the above formula (5-1). h representing the average degree of polymerization in Rf1 represents 4.5, and i representing the average degree of polymerization represents 4.5. THP represents tetrahydropyranyl.

[0508] (Second and third reactions)

[0509] Except for using the compound represented by formula (18) instead of the compound represented by formula (11), the same operations as the second reaction and the third reaction of Example 1 were carried out to obtain 4.0 g of compound (AT) (Rf1 in formula (AT) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0510] The obtained compound (AT) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0511] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(60H), 3.85~4.10(12H)

[0512] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0513] [Example 24]

[0514] The compound represented by the above formula (AU) is obtained by the method shown below.

[0515] By the method described in Example 5, a compound represented by formula (19) was obtained as an intermediate compound of the first reaction.

[0516]

[0517] Rf1 in formula (19) is the PFPE chain represented by the above formula (5-1). h representing the average degree of polymerization in Rf1 represents 4.5, and i representing the average degree of polymerization represents 4.5. THP represents tetrahydropyranyl.

[0518] Except for using the compound represented by formula (19) instead of the compound represented by formula (11), the same operations as in Example 23 were carried out to obtain 4.3 g of compound (AU) (Rf1 in formula (AU) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0519] The obtained compound (AU) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0520] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(48H), 3.85~4.10(12H)

[0521] 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0522] [Example 25]

[0523] The compound represented by the above formula (BA) is obtained by the method shown below.

[0524] The same operation as in Example 1 was carried out except that 1,3,5-benzenetriol was used instead of 1,3,5-cyclohexanetriol to obtain 2.9 g of compound (BA) (Rf1 in formula (BA) is the PFPE chain represented by the above formula (5-1). Among the three Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0525] The obtained compound (BA) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0526] 1 H-NMR (acetone-D6): δ[ppm]=1.95~2.10(12H), 3.35~3.85(45H), 3.85~4.10(12H), 6.60~6.80(3H)

[0527] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0528] [Example 26]

[0529] The compound represented by the above formula (BB) is obtained by the method shown below.

[0530] Except for using 1,3,5-cyclohexanedimethanol instead of 1,3,5-cyclohexanetriol, the same operations as in Example 1 were carried out to obtain 5.1 g of compound (BB) (Rf1 in formula (BB) is the PFPE chain represented by the above formula (5-1). Among the three Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0531] The obtained compound (BB) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0532] 1 H-NMR (acetone-D6): δ[ppm]=1.19(3H), 1.95~2.10(12H), 2.50(3H), 3.35~3.85(54H), 3.85~4.10(12H)

[0533] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0534] [Example 27]

[0535] The compound represented by the above formula (BC) is obtained by the method shown below.

[0536] Except for using glycerol instead of 1,3,5-cyclohexanetriol, the same operation as in Example 1 was carried out to obtain 4.4 g of compound (BC) (Rf1 in formula (BC) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0537] The obtained compound (BC) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0538] 1 H-NMR (acetone-D6): δ[ppm]=1.95~2.10(12H), 3.35~3.85(50H), 3.85~4.10(12H)

[0539] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0540] [Example 28]

[0541] The compound represented by the above formula (BD) is obtained by the method shown below.

[0542] Except for using trimethylolpropane instead of 1,3,5-cyclohexanetriol, the same operation as in Example 1 was carried out to obtain 4.3 g of compound (BD) (Rf1 in formula (BD) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5).

[0543] The obtained compound (BD) was subjected to 1 H-NMR determination and 19 The structure was identified based on the following results from F-NMR measurement.

[0544] 1 H-NMR (acetone-D6): δ[ppm]=1.10(3H), 1.65~1.85(2H), 1.95~2.10(12H), 3.35~3.85(51H), 3.85~4.10(12H)

[0545] 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0546] The structures of X, A, B, and D when the compounds (AA) to (AU) and (BA) to (BD) of Examples 1 to 28 obtained in this way correspond to the general formula (1) are shown in Table 1. It should be noted that, except for compound (AI), the structures of the three A, three B, and three D in the general formula (1) are all the same. The three Ds of compound (AI) are marked as D1, D2, and D3 in Table 1, respectively.

[0547] Table 1

[0548]

[0549] [Comparative Example 1]

[0550] According to the method described in Patent Document 1, a compound represented by the following formula (ZA) was synthesized.

[0551]

[0552] In the formula (ZA), d representing the average degree of polymerization is 7.0.

[0553] [Comparative Example 2]

[0554] According to the method described in Patent Document 2, a compound represented by the following formula (ZB) was synthesized.

[0555]

[0556] Rf1 in the formula (ZB) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0557] [Comparative Example 3]

[0558] According to the method described in Patent Document 2, a compound represented by the following formula (ZC) was synthesized.

[0559]

[0560] Rf1 in the formula (ZC) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0561] [Comparative Example 4]

[0562] According to the method described in Patent Document 3, a compound represented by the following formula (ZD) was synthesized.

[0563]

[0564] Rf1 in the formula (ZD) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0565] [Comparative Example 5]

[0566] According to the method described in Patent Document 4, a compound represented by the following formula (ZE) was synthesized.

[0567]

[0568] Rf1 in the formula (ZE) is the PFPE chain represented by the above formula (5-1). In the two Rf1, h indicating the average degree of polymerization is 4.5, and i indicating the average degree of polymerization is 4.5.

[0569] [Comparative Example 6]

[0570] According to the method described in Patent Document 5, a compound represented by the following formula (ZF) was synthesized.

[0571]

[0572] [Comparative Example 7]

[0573] According to the method described in Patent Document 6, a compound represented by the following formula (ZG) was synthesized.

[0574]

[0575] Rf2 in the formula (ZG) is the PFPE chain represented by the above formula (5-2). j, which represents the average degree of polymerization among the three Rf2s, is 4.5.

[0576] [Comparative Example 8]

[0577] According to the method described in Patent Document 7, a compound represented by the following formula (ZH) was synthesized.

[0578]

[0579] Rf1 in the formula (ZH) is the PFPE chain represented by the above formula (5-1). In the two Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0580] [Comparative Example 9]

[0581] According to the method described in Patent Document 8, a compound represented by the following formula (ZI) was synthesized.

[0582]

[0583] Rf1 in the formula (ZI) is the PFPE chain represented by the above formula (5-1). Among the three Rf1, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0.

[0584] [Comparative Example 10]

[0585] According to the method described in Patent Document 9, a compound represented by the following formula (ZJ) was synthesized.

[0586]

[0587] Rf1 in the formula (ZJ) is the PFPE chain represented by the above formula (5-1). In the two Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0588] The number average molecular weight (Mn) of the compounds of Examples 1 to 28 and Comparative Examples 1 to 10 thus obtained was measured by the above-mentioned method.

[0589] Next, a lubricant layer forming solution was prepared by the method described below using the compounds obtained in Examples 1 to 28 and Comparative Examples 1 to 10. Then, the lubricant layer of a magnetic recording medium was formed by the method described below using the obtained lubricant layer forming solution, thereby obtaining magnetic recording media of Examples 1 to 28 and Comparative Examples 1 to 10.

[0590] "Lubricating layer forming solution"

[0591] The compounds obtained in Examples 1 to 28 and Comparative Examples 1 to 10 were respectively dissolved in a fluorine-based solvent, Batler (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and the films were coated on the protective layer to a thickness of The mixture was diluted with Batler XF in a manner of 1:1 to prepare a lubricating layer forming solution.

[0592] "Magnetic recording media"

[0593] A magnetic recording medium was prepared in which an adhesion layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer were sequentially provided on a substrate having a diameter of 65 mm. The protective layer was made of carbon.

[0594] On the protective layer of the magnetic recording medium formed with each layer including the protective layer, the lubricating layer forming solutions of Examples 1 to 28 and Comparative Examples 1 to 10 were applied by dipping. The dipping method was performed at a dipping speed of 10 mm / sec, a dipping time of 30 sec, and a pulling speed of 1.2 mm / sec.

[0595] Then, the magnetic recording medium coated with the lubricating layer forming solution is placed in a constant temperature bath, and heat treatment is performed at 140°C for 10 minutes to remove the solvent in the lubricating layer forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer to obtain a magnetic recording medium.

[0596] (Film thickness measurement)

[0597] The film thickness of the lubricating layer of the magnetic recording media of Examples 1 to 28 and Comparative Examples 1 to 10 obtained in this manner was measured using a Fourier transform infrared spectrophotometer (FT-IR, trade name: Nicolet iS50, manufactured by Thermo Fisher Scientific).

[0598] Next, the magnetic recording media of Examples 1 to 28 and Comparative Examples 1 to 10 were subjected to the chemical resistance test and spin-off resistance test described below.

[0599] [Chemical resistance test]

[0600] The following chemical resistance test was performed, and the chemical resistance was evaluated based on the following evaluation criteria. The results are shown in Tables 2 and 3.

[0601] A hard disk drive of LUL (Load / Unload) mode is prepared, and a magnetic recording medium with a lubricating layer is installed. The magnetic head of the hard disk drive uses a perpendicular magnetic recording head. A commercially available silicone rubber gel sheet (1cm×1cm×0.5cm) is placed in the hard disk drive, and continuous LUL operation is repeated under the following environment until the drive current of the spindle motor exceeds the threshold. Figure 2As shown, the environment for continuous LUL operation is set to a 5-hour cycle operation (start and stop for 1 hour each) of 25°C → 60°C → 25°C in a dry environment (relative humidity below 10%). In addition, the time from the start of continuous LUL operation to the moment when the drive current of the spindle motor exceeds the threshold is designated as the endurance time. When the endurance time exceeds 150 hours, the SEM observation of the perpendicular magnetic recording head used in the test is performed, and the contamination area of ​​the head is evaluated based on the SEM image.

[0602] If the compound in the lubricating layer is uniformly arranged on the protective layer without gaps, the cyclic siloxane vaporized from the silicone rubber gel sheet can be prevented from adhering to the magnetic recording medium. Therefore, no load is applied to the spindle motor of the hard disk drive, and the durability time is prolonged. On the other hand, if the compound in the lubricating layer is condensed, gaps are formed in the lubricating layer, and the vaporized cyclic siloxane adheres to the magnetic recording medium. As a result, a load is applied to the spindle motor of the hard disk drive, and the durability time is shortened.

[0603] "Evaluation criteria for chemical resistance tests"

[0604] A+: Durability time is more than 150 hours and the head contamination area is 50μm 2 the following

[0605] A: The endurance time is more than 150 hours and the head contamination area is greater than 50μm 2 , 100μm 2 the following

[0606] B: Durability time is more than 150 hours and the head contamination area is greater than 100μm 2

[0607] C: Durability time is more than 100 hours and less than 150 hours

[0608] D: Durability less than 100 hours

[0609] [Spin-off resistance test]

[0610] The magnetic recording medium was mounted on a rotating frame and rotated at a rotation speed of 10000 rpm for 72 hours under a relative humidity of 60% and a temperature of 80°C. Before and after this operation, the film thickness of the lubricating layer at a position with a radius of 20 mm from the center of the magnetic recording medium was measured using FT-IR, and the film thickness reduction rate of the lubricating layer was calculated after 24 hours, 48 ​​hours, and 72 hours from the start of the test. The evaluation of the magnetic recording medium whose film thickness reduction rate exceeded 9% before reaching 72 hours was stopped midway. Using the evaluation time and the calculated film thickness reduction rate, the spin-off resistance was evaluated by the evaluation criteria shown below.

[0611] "Evaluation criteria for spin-off resistance test"

[0612] A+: Film thickness reduction after 72 hours is less than 2%

[0613] A: The film thickness reduction rate after 72 hours is greater than 2% and less than 3%

[0614] B: The film thickness reduction rate after 72 hours is greater than 3% and less than 9%

[0615] C: Film thickness reduction after 72 hours is greater than 9%

[0616] D: Film thickness reduction rate after 48 hours is greater than 9%

[0617] [Comprehensive evaluation]

[0618] Based on the results of the chemical resistance test and the spin-off resistance test, comprehensive evaluation was performed based on the following criteria.

[0619] “Comprehensive evaluation”

[0620] A: Both the chemical resistance test and the spin-off resistance test were rated A+ or A

[0621] B: One of the chemical resistance test and the spin-off resistance test is B, and the other is A+, A, or B

[0622] C: One of the chemical resistance test and the spin-off resistance test is C, and the other is A+, A, B, or C

[0623] D: At least one of the evaluation in the chemical resistance test and the evaluation in the spin-off resistance test is D

[0624] Table 2

[0625]

[0626] Table 3

[0627]

[0628] As shown in Table 2, the evaluation results of the chemical resistance test and the evaluation results of the spin resistance test were good in Examples 1 to 28. In contrast, as shown in Table 3, the results of the chemical resistance test and the spin resistance test were poor in Comparative Examples 1 to 10.

[0629] Example 2 is a compound in which the molecular weight of the perfluoropolyether chain B is lower than that of Example 1. Therefore, in Example 2, the coating property is good and the chemical resistance is more excellent. On the other hand, although a tendency of reduced spin-off resistance is observed in Example 2, a good result is shown. Example 3 is a compound in which the molecular weight of the perfluoropolyether chain B is higher than that of Example 1. Therefore, in Example 3, although a tendency of reduced chemical resistance is observed, a good result is shown, and a result of more excellent spin-off resistance is shown.

[0630] Examples 8 to 10 and 18 have structures in which all three terminal groups D have three hydroxyl groups. It is considered that these compounds have stronger interaction with the protective layer, and thus have excellent chemical resistance and show more excellent spin-off resistance.

[0631] Although Examples 12 and 13 have good results in chemical resistance, a decreasing trend can be seen compared to Example 1. It is believed that this is because Examples 12 and 13 have structures in which there is a portion with a larger number of carbon atoms than the number of fluorine atoms in the lubricating layer containing the fluorine-containing ether compound. In Examples 12 and 14, the positions of the ether bond introduced between the two hydroxyl groups possessed by D are different. More specifically, in Example 14, the ether bond is introduced at a position closer to the primary hydroxyl group than in Example 12. Therefore, it is believed that in Example 14, flexibility is imparted to the movement of the primary hydroxyl group, and the interaction with the protective layer becomes stronger. Therefore, it is believed that Example 14 shows better chemical resistance than Example 12.

[0632] Comparative Example 1 is a compound having no polar group between the trivalent atomic group and the perfluoropolyether chain and the terminal group represented by formula (4-2). In Comparative Example 1, the chemical resistance and spin-off resistance are poor. It is believed that this is because the only interaction with the protective layer caused by the polar group is the terminal group, and the adhesion is insufficient.

[0633] Comparative Example 2 is a compound in which the trivalent atomic group has the structure represented by formula (2-1), but the hydroxyl group contained in the linking group and the terminal group is one each. Therefore, the chemical resistance is good, but the spin-off resistance is poor.

[0634] Comparative Example 3 is a compound having a structure in which the trivalent atomic group is represented by Formula (2-1) and the terminal group is represented by Formula (4-2), but the number of hydroxyl groups contained in the connecting group is one. Therefore, compared with Comparative Example 2, the result is that the chemical resistance is reduced and the spin-off resistance is improved, but both aspects are generally poor.

[0635] Comparative Example 4 is a compound having a structure in which the trivalent atomic group is represented by Formula (2-2) and the terminal group is represented by Formula (4-1), but the number of hydroxyl groups contained in the connecting group is one. Therefore, the compound has good anti-spinning property but poor chemical resistance.

[0636] Comparative Example 5 is a compound having a central cyclic structure and a terminal group having a structure represented by formula (4-1), but having two perfluoropolyether chains bonded to the central cyclic structure via a linking group and one hydroxyl group contained in the linking group. Therefore, the chemical resistance and spin-off resistance are poor.

[0637] Comparative Example 6 is a compound in which the trivalent atomic group has the structure represented by formula (2-2), but the linking group contains only one hydroxyl group and the terminal group has no polar group. Therefore, the chemical resistance and anti-rotation properties are poor.

[0638] Comparative Example 7 is a compound in which the trivalent atomic group has the structure represented by formula (2-2), but the linking group has no polar group and the terminal group is a hydroxyl group. Therefore, the chemical resistance and anti-rotation properties are poor.

[0639] Comparative Example 8 is a compound in which two perfluoropolyether chains are connected via a connecting group represented by formula (3-1) and the terminal group is represented by formula (4-2). Therefore, the chemical resistance and spin-off resistance are poor.

[0640] Comparative Example 9 is a compound in which three perfluoropolyether chains are connected via a connecting group represented by formula (3-2) and the terminal group is represented by formula (4-2). Therefore, the chemical resistance and spin-off resistance are poor.

[0641] Comparative Example 10 is a compound in which three perfluoropolyether chains are connected via a linking group having one hydroxyl group and the terminal group is represented by Formula (4-1). Therefore, the chemical resistance and spin-off resistance are poor.

[0642] As described above, it can be seen that by forming a lubricating layer containing the compounds of Examples 1 to 28 on the protective layer of the magnetic recording medium, even if the thickness is as thin as A lubricating layer with excellent chemical resistance and spin-off suppression effect can also be obtained.

[0643] Industrial Applicability

[0644] By using the lubricant for a magnetic recording medium containing the fluorine-containing ether compound of the present invention, a lubricating layer having excellent chemical resistance and a high spin-off suppressing effect can be formed.

[0645] Explanation of symbols

[0646] 10···magnetic recording medium, 11···substrate, 12···adhesion layer, 13···soft magnetic layer, 14···first base layer, 15···second base layer, 16···magnetic layer, 17···protective layer, 18···lubricating layer.

Claims

1. A fluorine-containing ether compound, characterized in that It is represented by the following general formula (1): In the general formula (1), X is a trivalent atomic group represented by any one of the following formulas (2-1) to (2-5); A is a connecting group represented by the following formula (3-1) or (3-2); the three A's may be partially or entirely the same or may be different from each other; B is a perfluoropolyether chain; the three B's may be partially or entirely the same or may be different from each other; D is an end group having 2 to 4 polar groups, having an ether oxygen atom bonded to a methylene group adjacent to D, having 1 to 15 carbon atoms, and the shortest distance between carbon atoms bonded to adjacent polar groups in D is 0 to 9 carbon atoms; the three D's may be partially or entirely the same or may be different from each other; In formula (2-4), a represents an integer from 0 to 5; In formula (2-5), b represents an integer from 0 to 5; In formula (3-1), n ​​represents an integer from 0 to 6; In the formula (3-2), m represents an integer of 1 to 2. 2 . The fluorine-containing ether compound according to claim 1 , wherein a in the formula (2-4) is 0, and b in the formula (2-5) is an integer of 0 to 2. 3 . The fluorine-containing ether compound according to claim 1 , wherein the polar group is at least one polar group selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group. The fluorine-containing ether compound according to claim 1 , wherein the polar group comprises at least one hydroxyl group.

5. The fluorine-containing ether compound according to claim 1, wherein D in the general formula (1) is independently a terminal group represented by any one of the following formulas (4-1) to (4-3), In formula (4-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5; In formula (4-2), s represents an integer from 0 to 2, and t represents an integer from 0 to 5; In formula (4-3), u represents an integer of 2 to 4, and Y represents a linear alkylene group which may have an ether oxygen atom, or a single bond; when Y is the alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5. 6 . The fluorinated ether compound according to claim 1 , wherein all three D's in the general formula (1) are the same. 7 . The fluorine-containing ether compound according to claim 1 , wherein at least one of the three A's in the general formula (1) is the formula (3-1).

8. The fluorinated ether compound according to any one of claims 1 to 5, wherein the three Bs in the general formula (1) are each independently a perfluoropolyether chain represented by the following formula (5): -(CF2) v1 -O-(CF2O) v2 -(CF2CF2O) v3 -(CF2CF2CF2O) v4 -(CF2CF2CF2CF2O) v5 -(CF2) v6 -(5) In formula (5), v2, v3, v4, and v5 represent average polymerization degrees, and each independently represents 0 to 20; wherein, v2, v3, v4, and v5 are not all 0 at the same time; v1 and v6 are average values ​​of CF2 numbers, and each independently represents 1 to 3; the arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (5) is not particularly limited.

9. The fluorinated ether compound according to any one of claims 1 to 5, wherein the three Bs in the general formula (1) are each independently selected from any one of the perfluoropolyether chains represented by the following formulas (5-1) to (5-4), -CF2-(OCF2CF2) h -(OCF2) i -OCF2-(5-1) In formula (5-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; -CF2CF2-(OCF2CF2CF2) j -OCF2CF2-(5-2) In formula (5-2), j represents the average degree of polymerization and is 1 to 15; -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2-(5-3) In formula (5-3), k represents the average degree of polymerization and is 1 to 10; -(CF2) v7 -O-(CF2CF2CF2O) v8 -(CF2CF2O) v9 -(CF2) v10 -(5-4) In formula (5-4), v8 and v9 represent average polymerization degrees, and each independently represents 1 to 20; v7 and v10 represent average values ​​of CF2 numbers, and each independently represents 1 to 2. 10 . The fluorine-containing ether compound according to claim 1 , which has a number average molecular weight in the range of 500 to 10,000.

11. A lubricant for a magnetic recording medium, characterized in that: The fluorine-containing ether compound according to any one of claims 1 to 5.

12. A magnetic recording medium, comprising a substrate on which at least a magnetic layer, a protective layer and a lubricating layer are sequentially arranged, The lubricating layer comprises the fluorine-containing ether compound according to any one of claims 1 to 5. 13 . The magnetic recording medium according to claim 12 , wherein the lubricating layer has an average film thickness of 0.5 nm to 2.0 nm.

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