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

Abstract

Provided is a fluorine-containing ether compound which has excellent chemical resistance and abrasion resistance, can form a lubricating layer with a high corrosion inhibition effect for a magnetic recording medium, and can be suitably used as a material for a lubricant for a magnetic recording medium. 【Solution means】The fluorine-containing ether compound is represented by the following formula. R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3’ n -CH2-R 5 -R 6 (n is 1 or 2; R 3 and R 3’ are perfluoropolyether chains; R 4 is a divalent linking group having one polar group; R 2 and R 5 are divalent linking groups having one or more polar groups; R 2 The terminal on the side where R 1 is bonded, the terminal on the side where R 5 is bonded is an oxygen atom; R 6 The terminal on the side where R 1 and R 6 are R 2 or R 5 Terminal groups bonded to the terminal oxygen atoms; R 1 and R 6 are organic groups having 1 to 50 carbon atoms, and at least one of them is a group in which a carbonyl carbon atom or a nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms. )​

Description

Technical Field

[0001] The present invention relates to a fluorinated ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2021-143417 filed in Japan on September 2, 2021, and incorporates the content herein by reference.

Background Art

[0002] In order to improve the recording density of a magnetic recording and reproducing apparatus, the development of a magnetic recording medium suitable for high recording density has been underway. Conventionally, as a magnetic recording medium, there is one in which a recording layer is formed on a substrate and a protective layer such as carbon is formed on the recording layer. The protective layer protects the information recorded in the recording layer and enhances the sliding property of the magnetic head. However, simply providing a protective layer on the recording layer does not sufficiently provide the durability of the magnetic recording medium. For this reason, generally, a lubricant is applied to the surface of the protective layer to form a lubricating layer.

[0003] As a lubricant used when forming the lubricating layer of a magnetic recording medium, for example, a compound having a polar group such as a hydroxyl group or an amino group at the end of a fluorine-based polymer having a repeating structure containing -CF2- has been proposed. For example, Patent Documents 1 and 2 disclose a fluoropolyether compound in which perfluoropolyethers are respectively bonded to both sides of an aliphatic hydrocarbon chain having a hydroxyl group present in the central part of the molecule. In addition, Patent Document 3 discloses a fluoropolyether compound in which a plurality of perfluoropolyether groups are linked by an aliphatic hydrocarbon group having a hydroxyl group.

[0004] In addition, Patent Document 4 discloses a fluorinated ether compound in which a divalent linking group having a polar group is linked to both ends of a perfluoropolyether chain, and a terminal group in which one or more hydrogens of a chain-like organic group having 1 to 8 carbon atoms are substituted with a group having an amide bond is bonded to at least one of them.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a magnetic recording and reproducing apparatus, it is further required to reduce the flying height of the magnetic head. For this reason, it is required to make the thickness of the lubricating layer on the magnetic recording medium thinner. However, generally, when the thickness of the lubricating layer is reduced, the chemical resistance and wear resistance of the magnetic recording medium tend to decrease. Also, when the thickness of the lubricating layer is reduced, the corrosion resistance of the magnetic recording medium may become insufficient. Therefore, there is a demand for a lubricating layer having excellent chemical resistance and wear resistance and a high corrosion suppression effect for the magnetic recording medium.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a fluorine-containing ether compound that can form a lubricating layer having excellent chemical resistance and wear resistance and a high corrosion suppression effect for the magnetic recording medium and can be suitably used as a material for a lubricant for the magnetic recording medium. Another object of the present invention is to provide a lubricant for a magnetic recording medium that contains the fluorine-containing ether compound of the present invention, can form a lubricating layer having good chemical resistance and wear resistance and excellent corrosion resistance. Another object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorine-containing ether compound of the present invention, which has good chemical resistance, wear resistance, and excellent corrosion resistance.

Means for Solving the Problems

[0008] The present invention includes the following aspects. The first aspect of the present invention provides the following fluorine-containing ether compound.

[0009] [1] A fluorine-containing ether compound characterized by being represented by the following formula (1). R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3’ n -CH2-R 5 -R 6 (1) (In formula (1), n is 1 or 2; R 3 and R 3’ are perfluoropolyether chains; R 3 and one or two R 3’ may be partly or entirely the same or different from each other; R 4 is a divalent linking group having one polar group; when n is 2, the two R 4 may be the same or different; R 2 and R 5 are divalent linking groups having one or more polar groups and may be the same or different; R 2 is such that the terminal on the side bonded to R 1 is an oxygen atom; R 5 is such that the terminal on the side bonded to R 6 is an oxygen atom; R 1 and R 6 are terminal groups bonded to the terminal oxygen atoms of R 2 or R 5 and may be the same or different; R 1 and R 6This refers to an organic group having 1 to 50 carbon atoms, where at least one of the atoms is a carbonyl carbon atom or nitrogen atom constituting an amide bond, attached to a carbon atom of an organic group having 1 to 8 carbon atoms.

[0010] The fluorine-containing ether compound of the first embodiment of the present invention preferably has the characteristics described in [2] to

[11] below. It is also preferable to combine two or more of the characteristics described in [2] to

[11] below. [2] R in equation (1) above 1 and R 6 The fluorine-containing ether compound according to [1], wherein at least one of the members is a group in which a carbonyl carbon atom or nitrogen atom constituting an amide bond is bonded to a carbon atom of a phenyl group or an alkyl group having 1 to 6 carbon atoms. [3] R in equation (1) above 2 , R 4 and R 5 The fluorine-containing ether compound according to [1] or [2], wherein all of its polar groups are hydroxyl groups. [4] R in equation (1) above 2 The hydroxyl group that R 5 The fluorine-containing ether compound according to [3], wherein the total number of hydroxyl groups it possesses is 2 to 6. [5] R in equation (1) above 1 and R 6 However, the fluorine-containing ether compound according to any one of [1] to [4] is a group in which a carbonyl carbon atom or nitrogen atom constituting an amide bond is bonded to a carbon atom of a phenyl group or an alkyl group having 1 to 6 carbon atoms.

[0011] [6] R in equation (1) above 2 However, the linking group is represented by the following formula (2-1) or (2-2), R in equation (1) above 5 However, the linking group is represented by the following formula (2-3) or (2-4), and is a fluorine-containing ether compound as described in any of [1] to [5].

[0012] [Chemical formula] (In formula (2-1), p1 represents an integer from 1 to 3.) (In formula (2-2), q1 represents an integer from 2 to 4.) (In formula (2-3), p2 represents an integer from 1 to 3.) (In formula (2-4), q2 represents an integer from 2 to 4.)

[0013] [7] R in the above formula (1) 3 and one or two Rs 3’ are all the same, and R 1 -R 2 - and R 6 -R 5 - are the same, the fluorine-containing ether compound according to any one of [1] to [6].

[0014] [8] R in the above formula (1) 4 is a linking group represented by any one of the following formulas (3-1) to (3-3), the fluorine-containing ether compound according to any one of [1] to [7].

[0015] [Chemical formula] (In formula (3-2), r is an integer from 2 to 4.) (In formula (3-3), s is an integer from 2 to 4.)

[0016] [9] R in the above formula (1) 3 and one or two Rs 3’ are each independently a perfluoropolyether chain represented by the following formula (4), the fluorine-containing ether compound according to any one of [1] to [8]. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In equation (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20; however, w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are average values ​​representing the number of CF2 units, each independently representing 1 to 3; there are no particular restrictions on the order of the repeating units in equation (4).)

[0017]

[10] R in equation (1) above 3 and one or two R 3’ However, each of the perfluoropolyether chains represented independently by the following formulas (4-1) to (4-4) is one of the fluorine-containing ether compounds described in any of [1] to [9]. -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In equation (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In equation (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In equation (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 are average values ​​representing the number of CF2s, each independently representing 1 to 2.)

[0018]

[11] A fluorine-containing ether compound according to any of [1] to

[10] , wherein the number average molecular weight is in the range of 500 to 10000. A second aspect of the present invention provides the following lubricant for magnetic recording media.

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

[11] . A third aspect of the present invention provides the following magnetic recording medium.

[0019]

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

[11] . A magnetic recording medium according to a third aspect of the present invention preferably has the features described in

[14] below.

[14] The magnetic recording medium according to

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

[0020] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is suitable as a material for a lubricant for magnetic recording media. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore has good chemical resistance and wear resistance, and can form a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0021] The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention. Therefore, the magnetic recording medium of the present invention has good chemical resistance and wear resistance, excellent corrosion resistance, and superior reliability and durability. Furthermore, because the lubricating layer of the magnetic recording medium of the present invention has good chemical resistance and wear resistance and has a high corrosion suppression effect on the magnetic recording medium, its thickness can be reduced. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic cross-sectional view showing a preferred embodiment of the magnetic recording medium of the present invention. [Modes for carrying out the invention]

[0023] To solve the above problems, the inventors of this invention have diligently conducted research as described below. Conventionally, fluorine-containing ether compounds having polar groups such as hydroxyl groups at the ends of their chain-like structures have been preferably used as materials for lubricants for magnetic recording media applied to the surface of protective layers (hereinafter sometimes abbreviated as "lubricant"). The polar groups in the fluorine-containing ether compounds bind to active sites on the protective layer, improving the adhesion of the lubricant layer to the protective layer. For this reason, fluorine-containing ether compounds having polar groups not only at the ends of the chain-like structure but also within the chain-like structure are particularly preferred as materials for lubricants.

[0024] However, when a thin lubricating layer is formed on a protective layer using conventional lubricants, it has been difficult to achieve a lubricating layer with good chemical resistance, wear resistance, and excellent corrosion resistance, as shown below. In other words, if the lubricant does not adhere well to the protective layer, the lubricant applied to the protective layer will be bulky. This makes it easy for the lubricant layer to have an uneven coating over the protective layer. If the lubricant layer has an uneven coating, the chemical resistance and corrosion resistance of the lubricant layer will be insufficient. Therefore, if the adhesion of the lubricant layer is insufficient, sufficient chemical resistance and corrosion resistance cannot be obtained unless the film thickness is increased to make the lubricant layer's coating over the protective layer uniform.

[0025] One possible method for improving the adhesion of the lubricant to the protective layer is to use a fluorine-containing ether compound as the lubricant material, in which polar groups are bonded to the terminal carbon atoms at both ends of the chain structure, to the carbon atoms bonded to the terminal carbon atoms, and to the other carbon atoms in the chain structure. However, in lubricating layers formed using such fluorine-containing ether compounds, the adhesion with the protective layer was too strong, which sometimes impaired lubricity and resulted in insufficient wear resistance. Furthermore, in lubricating layers formed using such fluorine-containing ether compounds, the high hydrophilicity of the lubricant facilitated water penetration, sometimes leading to corrosion of the magnetic recording medium.

[0026] The adhesion of the lubricant to the protective layer can be adjusted, for example, by changing the heat treatment temperature during a heat treatment performed as needed after applying a lubricant containing a fluorine-containing ether compound to the protective layer. Specifically, the adhesion of the lubricant to the protective layer becomes stronger when the heat treatment temperature is increased and weaker when the heat treatment temperature is decreased. Therefore, if the adhesion of the lubricant to the protective layer is too strong, the adhesion between the lubricant layer and the protective layer can be weakened by methods such as lowering the heat treatment temperature, thereby improving the wear resistance of the lubricant layer to an appropriate strength.

[0027] However, in a lubricating layer formed using a fluorine-containing ether compound in which polar groups are bonded to the terminal carbon atoms at both ends of the chain structure, to the carbon atoms bonded to the terminal carbon atoms, and to the other carbon atoms in the chain structure, weakening the adhesion to the protective layer using the above method deteriorates the chemical resistance and corrosion resistance of the lubricating layer. This is presumed to be because the proportion of polar groups in the fluorine-containing ether compound that do not participate in bonding with active sites on the protective layer increases. In other words, it is presumed that the polar groups in the fluorine-containing ether compound that do not participate in bonding with active sites on the protective layer attract environmental substances that generate pollutants and water that causes corrosion of magnetic recording media to the lubricating layer, thereby worsening the chemical resistance of the lubricating layer and the corrosion resistance of the magnetic recording media.

[0028] Therefore, the inventors focused on the bonding between polar groups contained in fluorine-containing ether compounds and active sites on the protective layer. They then diligently conducted research to realize a fluorine-containing ether compound that would not generate polar groups that do not participate in bonding with active sites on the protective layer, would have a uniform coating state on the protective layer with excellent adhesion, would have good chemical resistance and wear resistance, and would form a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0029] As a result, we found that the resulting compound should have a skeleton in which multiple perfluoropolyether chains are linked together via a linking group having one polar group, and on both sides, a divalent linking group having a polar group via a methylene group (-CH2-) and a terminal group which is an organic group having 1 to 50 carbon atoms are bonded in that order, and at least one of the terminal groups is a fluorine-containing ether compound in which a carbonyl carbon atom or nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms.

[0030] In such fluorine-containing ether compounds, polar groups that do not bond with the numerous functional groups (active sites) present on the protective layer are less likely to form for the reasons described below. Moreover, in such fluorine-containing ether compounds, for the reasons described below, the amide contained in at least one terminal group and the polar groups of the divalent linking group each independently exhibit good interaction with the protective layer and can independently bond with the numerous functional groups (active sites) present on the protective layer. From these points, it is presumed that the above-mentioned fluorine-containing ether compounds can form a lubricating layer with good adhesion to the protective layer, exhibiting good chemical resistance and wear resistance, and forming a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0031] In other words, in the fluorine-containing ether compounds described above, at least one terminal group contains an amide bond. The bonds of carbon atoms adjacent to the carbonyl carbon or nitrogen atom constituting the amide bond of the terminal group are difficult to rotate freely. Therefore, interaction between the amide contained in at least one terminal group and the polar group of the divalent linking group in the fluorine-containing ether compound is difficult. Consequently, the ability of the amide contained in at least one terminal group and the polar group of the divalent linking group in the fluorine-containing ether compound to inhibit interaction with each other's protective layers is extremely small.

[0032] Furthermore, in the fluorine-containing ether compounds described above, perfluoropolyether chains are positioned between the divalent linking groups within the fluorine-containing ether compound. Therefore, the distance between the polar groups of adjacent divalent linking groups is appropriate. Moreover, at least one terminal group is an organic group with an amide bond that is difficult to rotate freely. For these reasons, the polar groups of the divalent linking groups in the fluorine-containing ether compounds are less likely to have their binding to the active site on the protective layer inhibited by the amide contained in at least one terminal group or the polar groups of adjacent divalent linking groups.

[0033] Therefore, in the above-mentioned fluorine-containing ether compounds, the polar groups of the amide and divalent linking group contained in at least one terminal group are designed to readily participate in bonding with the active sites on the protective layer without inhibiting each other's bonding. As a result, it is difficult for polar groups that do not bond with the active sites on the protective layer to be generated, and the number of polar groups that do not participate in bonding with the active sites on the protective layer is suppressed. Moreover, in the above-mentioned fluorine-containing ether compounds, the polar groups of the amide and divalent linking group contained in at least one terminal group do not readily inhibit each other's bonding with the active sites on the protective layer, and therefore each independently exhibits good interaction with the protective layer. As a result, the polar groups of the amide and divalent linking group contained in at least one terminal group can independently bond with the numerous functional groups (active sites) present on the protective layer.

[0034] Furthermore, in the above-mentioned fluorine-containing ether compounds, the distance between the polar groups of the divalent linking groups is appropriate, making it difficult for the polar groups of the divalent linking groups to aggregate. Moreover, both ends of each perfluoropolyether chain are tightly adhered to the protective layer by the polar groups of the divalent linking groups. As a result, the fluorine-containing ether compound applied to the protective layer does not tend to be bulky, the fluorine-containing ether compound spreads easily over the protective layer, and a lubricating layer with a uniform coating state is easily obtained. From these points, it is presumed that the above-mentioned fluorine-containing ether compounds can form a lubricating layer with good chemical resistance and wear resistance, and a high corrosion suppression effect on magnetic recording media.

[0035] Furthermore, the inventors of the present invention conceived of this invention after confirming that by using a lubricant containing the above-mentioned fluorine-containing ether compound, it is possible to form a lubricating layer that exhibits good chemical resistance, wear resistance, and excellent corrosion resistance.

[0036] The following describes in detail examples of the fluorine-containing ether compounds, lubricants for magnetic recording media, and magnetic recording media of the present invention. However, the present invention is not limited to the embodiments shown below. Within the scope of the present invention, additions, omissions, substitutions, and modifications are possible regarding the number, quantity, ratio, materials, composition, etc.

[0037] [Fluorine-containing ether compounds] A fluorine-containing ether compound characterized by being represented by the following formula (1). R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3’ ] n -CH2-R 5 -R 6 (1) (In equation (1), n ​​is either 1 or 2; R 3 and R 3’ R is a perfluoropolyether chain; 3 and one or two R 3’ They may be partially or entirely the same, or they may be different; R 4 is a divalent linking group having one polar group; if n is 2, then two R 4 They may be the same or different; R 2 and R 5 R is a divalent linking group having one or more polar groups, and may be the same or different; 2 R 1 The end that bonds with it is an oxygen atom; R 5 R 6 The end that bonds with it is an oxygen atom; R 1 and R 6 R 2Or R 5 is a terminal group bonded to the oxygen atom at the end of 5 , which may be the same or different; R 1 and R 6 are organic groups having 1 to 50 carbon atoms, and at least one of them is a group in which a carbonyl carbon atom or a nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms.)

[0038] As shown in formula (1), the fluorine-containing ether compound of this embodiment has a linking structure in which a methylene group, a divalent linking group having one polar group represented by R 4 , and a methylene group are bonded in this order, and a plurality of perfluoropolyether chains (hereinafter sometimes referred to as "PFPE chains") represented by R 3 and R 3’ are linked. On both sides of the skeleton, a methylene group, a divalent linking group having one or more polar groups represented by R 2 and R 5 , and terminal groups represented by R 1 and R 6 are bonded in this order, respectively. And at least one of the terminal groups of R 1 and R 6 is a group (hereinafter sometimes referred to as "terminal group having an amide bond") in which a carbonyl carbon atom or a nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms.)

[0039] The fluorine-containing ether compound of this embodiment has the number n of the repeating unit [-CH2-R 4 -CH2-R 3’ in formula (1) being 1 or 2. When n is 1, it has a skeleton in which two PFPE chains of R 4 and R 3 and R 3’ are arranged on both sides thereof via methylene groups around a divalent linking group having one polar group represented by R 4 . Therefore, it becomes a fluorine-containing ether compound that is likely to spread uniformly and wet on the protective layer, and it is easy to obtain a lubricating layer having a uniform film thickness, which is preferable. When n is 2, R 3’With R at the center, on both sides 4 The linking group shown and the PFPE chain (R 3 or R 3’ This results in a structure in which the ) and are arranged respectively. Therefore, it is preferable to have a fluorine-containing ether compound that spreads uniformly on the protective layer and easily yields a lubricating layer with a uniform film thickness. n can be appropriately determined depending on the application of the fluorine-containing ether compound.

[0040] (R 4 (The divalent linking group shown by) In the fluorine-containing ether compound represented by formula (1), R 4 R is a divalent linking group having one polar group. 4 R 3 and one or two R 3’ They are positioned between the PFPE chains shown by . 4 This involves adhering the fluorine-containing ether compound to the protective layer, forming a thin lubricating layer with sufficient coverage.

[0041] The repeating unit in equation (1) is [-CH2-R 4 -CH2-R 3’ If the number n of ] is 2, then the two R 4 They can be the same or different. Two R's 4 When these factors are the same, the coating state of the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed. In this specification, "two R's 4 "They are the same" means that the two R's of the fluorine-containing ether compound 3’ Among them, R is located in the center of the fluorine-containing ether compound represented by formula (1). 3’ For the two R 4 This means that the atoms contained within are arranged symmetrically.

[0042] R 4 The divalent linking group shown is preferably one in which oxygen atoms are located at both ends. The oxygen atoms located at both ends of the linking group are R 4The methylene groups (-CH2-) located on both sides form an ether bond (-O-). These two ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), R 4 This increases the affinity between the polar group of the divalent linking group shown and the protective layer.

[0043] R 4 The divalent linking group shown is preferably a group in which one polar group is bonded to a carbon atom of an alkylene group having 3 to 6 carbon atoms, with oxygen atoms at both ends. The alkylene group having 3 to 6 carbon atoms is preferably an alkylene group having 3 to 4 carbon atoms. The alkylene group having 3 to 6 carbon atoms preferably has a linear structure. 4 Preferably, the polar group is bonded to a carbon atom located near the center of a linear alkylene group having 3 to 6 carbon atoms. This is because it results in a more uniform coating state on the protective layer of the fluorine-containing ether compound, leading to a lubricating layer with better adhesion.

[0044] R 4 Examples of polar groups include hydroxyl groups (-OH), amino groups (-NH2), carboxyl groups (-COOH), aldehyde groups (-COH), carbonyl groups (-CO-), and sulfonic acid groups (-SO3H). Among these, it is particularly preferable that the polar group be a hydroxyl group. Hydroxyl groups have a strong interaction with the protective layer, especially the protective layer formed from carbon-based materials. Therefore, R 4 If the polar group it possesses is a hydroxyl group, the lubricating layer containing the fluorine-containing ether compound will have even greater adhesion to the protective layer. When n is 2, two R 4 It is preferable that at least one of the polar groups that each of them possesses is a hydroxyl group, and it is more preferable that both are hydroxyl groups.

[0045] In the fluorine-containing ether compound represented by formula (1), R 4 Since it is a divalent linking group having one polar group, for example, R 4Compared to fluorine-containing ether compounds having divalent linking groups with two or more polar groups, a lubricating layer containing this compound provides sufficient corrosion suppression for magnetic recording media. This is because the hydrophilicity of the fluorine-containing ether compound is not excessively high, thus preventing the lubricating layer containing it from allowing water to penetrate and cause corrosion of the magnetic recording media.

[0046] R 4 Specifically, it is preferable that it be one of the following formulas (3-1) to (3-3). In formulas (3-1) to (3-3), the oxygen atom on the left is R 4 Of the two methylene groups bonded to it, R 2 The oxygen atom on the right side is bonded to the methylene group on the left, and R 5 It binds to the methylene group on the side. R 4 However, if it is any of formulas (3-1) to (3-3), the synthesis of the fluorine-containing ether compound represented by formula (1) is easy and therefore preferable. In particular, R 4 If the formula is (3-1), the synthesis of the fluorine-containing ether compound represented by formula (1) is easier and therefore preferable.

[0047] [ka] (In equation (3-2), r is an integer between 2 and 4.) (In equation (3-3), s is an integer between 2 and 4.)

[0048] In formula (3-2), r is an integer between 2 and 4, preferably between 2 and 3, and more preferably 2. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion. In formula (3-3), s is an integer between 2 and 4, preferably between 2 and 3, and more preferably 2. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion.

[0049] The linking group represented by formula (3-2) or (3-3) has a structure in which 1 to 3 methylene groups are added to the glycerol skeleton (-OCH2CH(OH)CH2O-). Therefore, R 4 A lubricating layer containing a fluorine-containing ether compound, such as (3-2) or (3-3), exhibits good hydrophobicity. As a result, it effectively prevents water from penetrating, which causes corrosion of magnetic recording media, resulting in a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0050] (R 3 and R 3’ (PFPE chain shown by) In the fluorine-containing ether compound represented by formula (1), R 3 and R 3’ This is a perfluoropolyether chain. 3 and R 3’ The PFPE chain shown in this embodiment, when a lubricant containing the fluorine-containing ether compound of this embodiment is applied to the protective layer to form a lubricating layer, covers the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. 3 and R 3’ The PFPE chain shown is appropriately selected according to the performance requirements of the lubricant containing the fluorine-containing ether compound.

[0051] R 3 and one or two R 3’ They may be partially or entirely the same, or they may be different. 3 and one or two R 3’ It is preferable that all of them be the same. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion. 3 and one or two R 3’ Being the same includes cases where the structure of the repeating units of the PFPE chain is the same, but the average degree of polymerization is different.

[0052] R 3 and R 3’Examples of PFPE chains represented by include those consisting of polymers or copolymers of perfluoroalkylene oxides. Examples of perfluoroalkylene oxides include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, and perfluorobutylene oxide.

[0053] R in equation (1) 3 and one or two R 3’ Preferably, this is a PFPE chain represented by the following formula (4), derived from a polymer or copolymer of perfluoroalkylene oxides. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In equation (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20; however, w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are average values ​​representing the number of CF2 units, each independently representing 1 to 3; there are no particular restrictions on the order of the repeating units in equation (4).)

[0054] In formula (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing a range from 0 to 20, preferably from 0 to 15, and more preferably from 0 to 10. For example, w2, w3, w4, and w5 may each independently represent a range of 1 to 18, 2 to 13, 3 to 8, 4 to 6, and so on. In equation (4), w1 and w6 are average values ​​indicating the number of CF2 units, each independently representing 1 to 3. w1 and w6 are determined according to the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by equation (4). In equation (4), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular restrictions on the order in which the repeating units are arranged in equation (4). There are also no particular restrictions on the number of different types of repeating units in equation (4).

[0055] R 3 and R 3’ The PFPE chain represented by is preferably one of the PFPE chains independently selected from the following formulas (4-1) to (4-4). R 3 and R 3’ If each of these is selected from the PFPE chains represented by formulas (4-1) to (4-4), then a fluorine-containing ether compound is obtained that yields a lubricating layer with good lubricity. 3 and R 3’ When each of the PFPE chains represented by formulas (4-1) to (4-4) is selected, the ratio of oxygen atoms (ether bond (-O-) number) to carbon atoms in the PFPE chain is appropriate. As a result, a fluorine-containing ether compound with appropriate hardness is formed. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with sufficient coverage. Furthermore, because the fluorine-containing ether compound has appropriate flexibility, a lubricating layer with better chemical resistance and wear resistance can be formed.

[0056] -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In equation (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In equation (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In equation (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 are average values ​​representing the number of CF2s, each independently representing 1 to 2.)

[0057] In formula (4-1), there are no particular restrictions on the sequence order of the repeating units, (OCF2CF2) and (OCF2). In formula (4-1), the number of (OCF2CF2) units h and the number of (OCF2) units i may be the same or different. The PFPE chain represented by formula (4-1) may be a polymer of (OCF2CF2). Furthermore, the PFPE chain represented by formula (4-1) may be a random copolymer, block copolymer, or alternating copolymer composed of (OCF2CF2) and (OCF2).

[0058] In formulas (4-1) to (4-3), the average degree of polymerization is 1 to 20 for h, 0 to 20 for i, 1 to 15 for j, and 1 to 10 for k, resulting in a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Furthermore, in formulas (4-1) to (4-3), the average degrees of polymerization are 20 or less for h and i, 15 or less for j, and 10 or less for k, so the viscosity of the fluorine-containing ether compound does not become too high, making it easy to apply lubricants containing it, which is preferable. The average degrees of polymerization of h, i, j, and k are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7, as this results in a fluorine-containing ether compound that spreads easily on the protective layer and yields a lubricating layer with a uniform film thickness.

[0059] In formula (4-4), there are no particular restrictions on the order of the repeating units (CF2CF2CF2O) and (CF2CF2O). In formula (4-4), the number of (CF2CF2CF2O) units w8 and the number of (CF2CF2O) units w9, which indicate the average degree of polymerization, may be the same or different. Formula (4-4) may include any of the monomer units (CF2CF2CF2O) and (CF2CF2O), such as a random copolymer, a block copolymer, or an alternating copolymer.

[0060] In formula (4-4), w8 and w9, which represent the average degree of polymerization, are independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. In equation (4-4), w7 and w10 are average values ​​indicating the number of CF2 units, and each independently represents 1 to 2. w7 and w10 are determined according to the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by equation (4-4).

[0061] (R 2 and R 5 (A divalent linking group having a polar group as shown) In the fluorine-containing ether compound represented by formula (1), R 2 and R 5 R is a divalent linking group having one or more polar groups. 2 R 1 The terminal that bonds to the other end has an oxygen atom, and R is bonded by an ether bond. 1 It combines with R. 5 R 6 The terminal that bonds to the other end has an oxygen atom, and R is bonded by an ether bond. 6 It bonds with. In the fluorine-containing ether compound represented by formula (1), R 2 and R 5 Since each of these has one or more polar groups, when a lubricating layer is formed on a protective layer using a lubricant containing these, a suitable interaction occurs between the lubricating layer and the protective layer. 2 and R 5 These can be appropriately selected depending on the performance requirements for the lubricant containing fluorine-containing ether compounds.

[0062] R 2 and R 5 They can be the same or different. 2 and R 5 When these factors are the same, the coating state of the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed. In this specification, "R 2 and R 5 "They are the same" means that the central skeleton (-R) of the fluorine-containing ether compound represented by formula (1) is the same. 3 [-CH2-R 4 -CH2-R 3’ ] n -) vs R 2 Atoms and R contained in 5 This means that the atoms contained within are arranged symmetrically.

[0063] R 2 and R 5 Examples of polar groups include hydroxyl groups (-OH), amino groups (-NH2), carboxyl groups (-COOH), aldehyde groups (-COH), carbonyl groups (-CO-), and sulfonic acid groups (-SO3H). Among these, it is particularly preferable that the polar group be a hydroxyl group. Hydroxyl groups have a strong interaction with the protective layer, especially the protective layer formed from carbon-based materials. Therefore, R 2 and / or R 5 If at least a portion of the polar groups of are hydroxyl groups, the lubricating layer containing the fluorine-containing ether compound will have even greater adhesion to the protective layer. In this embodiment, R 2 and R 5 It is more preferable that all of the polar groups present are hydroxyl groups. R 2 and R 5 The number of polar groups in each is preferably 1 to 3, and more preferably 1 to 2. 2 and / or R 5 If the number of polar groups in is two or more, the types of polar groups may be some or all the same, or they may be different.

[0064] R 2 and / or R 5 If the polar group of contains a hydroxyl group, then R in formula (1) 2 The hydroxyl group and R contained in 5 The total number of hydroxyl groups contained in is preferably 2 to 6, more preferably 2 to 4, and most preferably 2. When the total number of hydroxyl groups is 2 or more, R 2 and / or R 5 The interaction between the hydroxyl groups and the protective layer is effectively achieved. As a result, a fluorine-containing ether compound is formed that can create a lubricating layer with high adhesion to the protective layer. Furthermore, when the total number of hydroxyl groups is 6 or less, there are fewer polar groups that are not involved in the bonding between the lubricating layer and the active sites on the protective layer. Therefore, it is possible to prevent polar groups that are not involved in the bonding between the lubricating layer and the active sites on the protective layer from attracting environmental substances that generate contaminants and water that causes corrosion of magnetic recording media to the lubricating layer. Thus, a lubricating layer that can more effectively suppress contamination and corrosion of magnetic recording media can be formed. In addition, when the total number of hydroxyl groups is 4 or less, the fluidity of the lubricating layer containing the fluorine-containing ether compound becomes sufficiently high. Therefore, even if a part of the lubricating layer containing the fluorine-containing ether compound is deformed due to wear and the fluorine-containing ether compound in the lubricating layer moves to another location, it has a high restorative power to return to its original position, resulting in superior wear resistance.

[0065] R 2 The divalent linking group shown is R 1 The end that bonds has an oxygen atom, and the other end (R 2 It is also preferable that oxygen atoms are placed at the end (bonding to the adjacent CH2). 5 The divalent linking group shown is R 6 The end that bonds has an oxygen atom, and the other end (R 5 It is preferable that oxygen atoms are also placed at the end (bonding to the adjacent CH2). 2 and R 5The oxygen atoms positioned at both ends of the divalent linking group shown form ether bonds (-O-) with the atoms bonded to either side. These ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), and R 2 and R 5 This increases the affinity between the polar group of the divalent linking group shown and the protective layer.

[0066] R 2 and R 5 The divalent linking group shown is preferably a group in which one or more polar groups are bonded to carbon atoms of an alkylene group having 3 to 8 carbon atoms, with oxygen atoms at both ends. The alkylene group may contain ether bonds between carbon atoms. The alkylene group having 3 to 8 carbon atoms is preferably an alkylene group having 3 to 5 carbon atoms. The alkylene group having 3 to 8 carbon atoms is preferably linear in structure. This is because the coating state of the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed.

[0067] R in equation (1) 2 It is preferable that the linking group is represented by the following formula (2-1) or (2-2). In formulas (2-1) and (2-2), the oxygen atom on the left is R 1 Bonded to the right oxygen atom, R 2 It binds to the adjacent CH2. R 2 However, if the linking group is represented by the following formula (2-1) or (2-2), then R 2 and R 1 and are ether-bonded, and R 2 And, R 2 An ether bond is formed between the adjacent CH2. As a result, a fluorine-containing ether compound with moderate flexibility is formed, enabling the creation of a lubricating layer with better chemical resistance and wear resistance. 2 If the formula is (2-1), the synthesis of the fluorine-containing ether compound represented by formula (1) is easy and therefore preferable.

[0068] [ka] (In equation (2-1), p1 represents an integer between 1 and 3.) (In equation (2-2), q1 represents an integer between 2 and 4.)

[0069] The linking group shown in formula (2-2) has a structure in which 1 to 3 methylene groups are added to the glycerol skeleton (-OCH2CH(OH)CH2O-). Therefore, R 2 A lubricating layer containing a fluorine-containing ether compound, as shown in formula (2-2), exhibits good hydrophobicity. As a result, it effectively prevents water from penetrating, which is a cause of corrosion of magnetic recording media, resulting in a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0070] R in equation (1) 5 It is preferable that the linking group is represented by the following formula (2-3) or (2-4). In formulas (2-3) and (2-4), the oxygen atom on the left is R 5 Bonded to the adjacent CH2, the oxygen atom on the right is R 6 Combine. R 5 However, if the linking group is represented by the following formula (2-3) or (2-4), then R 5 and R 6 and are ether-bonded, and R 5 And, R 5 An ether bond is formed between the adjacent CH2. As a result, a fluorine-containing ether compound with moderate flexibility is formed, enabling the creation of a lubricating layer with better chemical resistance and wear resistance. 5 If the formula is (2-3), the synthesis of the fluorine-containing ether compound represented by formula (1) is easy and therefore preferable.

[0071] [ka] (In equation (2-3), p2 represents an integer between 1 and 3.) (In equation (2-4), q2 represents an integer between 2 and 4.)

[0072] The linking group shown in formula (2-4) has a structure in which 1 to 3 methylene groups are added to the glycerol skeleton (-OCH2CH(OH)CH2O-). Therefore, R 5 A lubricating layer containing a fluorine-containing ether compound represented by formula (2-4) exhibits good hydrophobicity. As a result, it effectively prevents water from penetrating, which is a cause of corrosion of magnetic recording media, resulting in a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0073] In equation (1), R 2 is a linking group represented by formula (2-1) or (2-2), and R 5 It is more preferable that the linking group is represented by formula (2-3) or (2-4). The linking groups represented by formulas (2-1) to (2-4) all have a hydroxyl group, which is a polar group that has a particularly strong interaction with the protective layer among polar groups. In addition, in the linking groups represented by formulas (2-1) to (2-4), methylene groups (-CH2-) are positioned on both sides of the carbon atom to which the hydroxyl group is bonded. Therefore, R 2 is a linking group represented by formula (2-1) or (2-2), and R 5 When the linking group is represented by formula (2-3) or (2-4), it becomes a fluorine-containing ether compound that can form a lubricating layer with even greater adhesion to the protective layer for the following reasons.

[0074] That is, in the linking group represented by formulas (2-1) to (2-4), the carbon atom to which the hydroxyl group is bonded and R 1 or R 6 Between them are a methylene group and R 2 or R 5 At least one oxygen atom (-O-) of is positioned. Therefore, the hydroxyl group contained in the linking group represented by formulas (2-1) to (2-4) and R 1 and / or R 6 The distance to the amide bond is appropriate. Also, R 1 and R 2 , and / or, R 5 and R 6The ether bond, which is the connecting part, slightly suppresses the free rotation of the terminal group. Therefore, R 1 and / or R 6 The amide possessed by and the hydroxyl group possessed by the linking group represented by formulas (2-1) to (2-4) do not readily interact with each other. Therefore, the hydroxyl group possessed by the linking group represented by formulas (2-1) to (2-4) and R 1 and / or R 6 The terminal groups indicated by the symbol each independently exhibit good interaction with the protective layer and each independently readily binds to the numerous functional groups (active sites) present on the protective layer.

[0075] In the linking group represented by equation (2-1), p1 is an integer from 1 to 3. Since p1 in the linking group shown in equation (2-1) is 1 or greater, R 2 When the linking group is represented by formula (2-1), it contains one or more hydroxyl groups, which have a particularly strong interaction with the protective layer, as polar groups. As a result, a fluorine-containing ether compound is obtained that provides a lubricating layer with even better adhesion to the protective layer. Furthermore, since the p1 in formula (2-1) is 3 or less for the linking group represented by formula (2-1), it is possible to prevent the polarity of the fluorine-containing ether compound from becoming too high due to a large number of hydroxyl groups in the linking group represented by formula (2-1), thereby preventing contamination or corrosion of magnetic recording media equipped with a lubricating layer containing it.

[0076] Furthermore, in the linking group represented by formula (2-1), when p1 in formula (2-1) is 2 or 3, the distance between the hydroxyl groups contained in the linking group represented by formula (2-1) becomes appropriate. As a result, R 2 Even if there are multiple hydroxyl groups in R 2 The hydroxyl groups contained within each component are likely to be involved in binding to active sites on the protective layer. In the linking group represented by formula (2-1), p1 is preferably 1 or 2. In the linking group represented by formula (2-1), when p1 is 1, it is more preferable because it results in a fluorine-containing ether compound that is easy to synthesize.

[0077] In the linking group represented by formula (2-2), q1 is an integer between 2 and 4, preferably between 2 and 3, and more preferably 2. When q1 in formula (2-2) is between 2 and 4, the methylene group included in formula (2-2) improves the hydrophobicity of the fluorine-containing ether compound, resulting in an even higher corrosion inhibition effect.

[0078] In the linking group represented by equation (2-3), p2 is an integer between 1 and 3. Since p2 in the linking group shown by equation (2-3) is 1 or greater, R 5 When the linking group is represented by formula (2-3), it contains one or more hydroxyl groups, which have a particularly strong interaction with the protective layer, as polar groups. As a result, a fluorine-containing ether compound is obtained in which a lubricating layer with even better adhesion to the protective layer is obtained. Furthermore, since the p2 in formula (2-3) is 3 or less for the linking group represented by formula (2-3), it is possible to prevent the polarity of the fluorine-containing ether compound from becoming too high due to a large number of hydroxyl groups in the linking group represented by formula (2-3), thereby preventing contamination or corrosion of magnetic recording media equipped with a lubricating layer containing it.

[0079] Furthermore, in the linking group represented by formula (2-3), when p2 in formula (2-3) is 2 or 3, the distance between the hydroxyl groups contained in the linking group represented by formula (2-3) becomes appropriate. As a result, R 5 Even if there are multiple hydroxyl groups in R 5 The hydroxyl groups contained within each component are likely to be involved in binding to active sites on the protective layer. In the linking group represented by formula (2-3), p2 is preferably 1 or 2. In the linking group represented by formula (2-3), when p2 is 1, it is more preferable because it results in a fluorine-containing ether compound that is easy to synthesize.

[0080] In the linking group represented by formula (2-4), q2 is an integer between 2 and 4, preferably between 2 and 3, and more preferably 2. When q2 in formula (2-4) is between 2 and 4, the methylene group included in formula (2-4) improves the hydrophobicity of the fluorine-containing ether compound, resulting in an even higher corrosion inhibition effect.

[0081] In the fluorine-containing ether compound represented by formula (1), R 2 is a linking group represented by formula (2-1) or (2-2), and R 5 If is a linking group represented by formula (2-3) or (2-4), then R 2 and R 5 It is preferable that they are the same. Specifically, "R 2 Equation (2-1), R 5 "Equation (2-3) is the same as p1 in equation (2-1) and p2 in equation (2-3)" or "R 2 Equation (2-2), R 5 It is preferable that the equation is (2-4), and that q1 in equation (2-2) and q2 in equation (2-4) are the same.

[0082] (R 1 and R 6 (Terminal group indicated by) In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 The terminal groups indicated by are organic groups having 1 to 50 carbon atoms, and at least one of them is a group in which a carbonyl carbon atom or nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms (a terminal group having an amide bond).

[0083] In the fluorine-containing ether compound represented by formula (1), the amide contained in the terminal group having an amide bond exhibits appropriate interaction with the protective layer. Therefore, the terminal group having an amide bond has the function of improving the adhesion between the lubricating layer and the protective layer, forming a lubricating layer with good chemical resistance and wear resistance. In the fluorine-containing ether compound represented by formula (1), the type of terminal group having an amide bond can be appropriately selected according to the performance required for the lubricant containing the fluorine-containing ether compound.

[0084] The number of amide bonds in a terminal group having an amide bond is not particularly limited and may be one or two or more. Preferably, the number of amide bonds in a terminal group having an amide bond is one, as this results in a fluorine-containing ether compound that is relatively easy to produce.

[0085] An amide-bonded terminal group is a group in which a carbonyl carbon atom or nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms. In the fluorine-containing ether compound represented by formula (1), since the organic group has 1 to 8 carbon atoms, the amide-bonded terminal group does not cause steric hindrance, resulting in a fluorine-containing ether compound with good affinity between the amide and the protective layer.

[0086] Examples of organic groups in terminal groups having an amide bond include phenyl groups or alkyl groups having 1 to 8 carbon atoms having a linear or branched structure, with phenyl groups or alkyl groups having 1 to 6 carbon atoms being preferred. When the organic group in terminal groups having an amide bond is a phenyl group or an alkyl group having 1 to 6 carbon atoms, R 1 and / or R 6 The amide possessed by and the adjacent linking group (R 2 or R 5 The interaction with the polar groups of the amide is more effectively suppressed, resulting in a fluorine-containing ether compound with high affinity between the amide and the protective layer.

[0087] Specifically, examples of groups that bond to carbon atoms in organic groups having 1 to 8 carbon atoms include the groups shown in the following formulas (5-1) or (5-2). The dotted lines in equations (5-1) and (5-2) represent R 1 or R 6 This is a bond that is attached to the organic group inside. When the terminal group having an amide bond has the group shown in formula (5-1), the terminal group having an amide bond is R 1 or R 6The carbon atom of the organic group inside is bonded to the carbonyl carbon atom that constitutes the amide bond. When the terminal group having an amide bond has the group shown in formula (5-2), the terminal group having an amide bond is R 1 or R 6 The group is formed when a nitrogen atom, which constitutes an amide bond, is bonded to a carbon atom of the organic group inside.

[0088] [ka] (In equations (5-1) and (5-2), X 1 , X 2 , X 3 , X 4 Each of these independently consists of a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, an octafluoropentyl group, a tridecafluorooctyl group, a phenyl group, a methoxyphenyl group, a phenyl fluoride group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a phenethyl fluoride group, a benzyl group, a methoxybenzyl group, a naphthylmethyl group, a methoxynaphthyl group, a pyrrolyl group, a pyrazolyl group, a methylpyrazolylmethyl group, an imidazolyl group, a furyl group, a furfuryl group, an oxazolyl group, and an isoxazolyl group. (The group is one of the following selected groups: thienyl group, thienylethyl group, thiazolyl group, methylthiazolylethyl group, isothiazolyl group, pyridyl group, pyrimidinyl group, pyridadinyl group, pyrazinyl group, indolinyl group, benzofuranyl group, benzothienyl group, benzimidazolyl group, benzoxazolyl group, benzothiazolyl group, benzopyrazolyl group, benzoisoxazolyl group, benzoisothiazolyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, synnolinyl group, vinyl group, allyl group, butenyl group, propynyl group, propargyl group, butynyl group, methylbutynyl group, pentynyl group, methylpentynyl group, hexynyl group, or cyanoethyl group.)

[0089] In equation (5-1), X 1 , X 2 Preferably, each of these groups is independently selected from a hydrogen atom, a methyl group, an ethyl group, a phenyl group, a methoxyphenyl group, a trifluoromethyl group, and an allyl group. In equation (5-2), X 3 It is preferable that the group is selected from a methyl group, an ethyl group, a phenyl group, a methoxyphenyl group, a naphthyl group, a trifluoromethyl group, and an allyl group. 4 Preferably, the group is selected from a hydrogen atom, a methyl group, an ethyl group, a phenyl group, a methoxyphenyl group, a trifluoromethyl group, or an allyl group.

[0090] X in equation (5-1) 1 and X 2 These may be bonded to each other to form a ring structure. In this case, X in equation (5-1) 1 -X 2 X in formula (5-1) can be a structure consisting of a combination of one or more groups selected from the group consisting of a methylene group (-CH2-), an ether bond (-O-), and an amine structure (-NH-). 1 and X 2 The cyclic structure formed by the bonding of these elements is preferably a 5- to 7-membered ring containing nitrogen atoms that constitute the amide bond.

[0091] Also, X in equation (5-2) 3 and X 4 These may be bonded to each other to form a ring structure. In this case, X in equation (5-2) 3 -X 4 X in formula (5-2) can be a structure consisting of a combination of one or more groups selected from the group consisting of a methylene group (-CH2-), an ether bond (-O-), and an amine structure (-NH-). 3 and X 4 The cyclic structure formed by the bonding of these elements is preferably a 5- to 7-membered ring containing carbonyl carbon atoms and nitrogen atoms that constitute the amide bond.

[0092] Examples of terminal groups having an amide bond include any of the organic groups shown in the following formulas (6-1) to (6-12). The dotted lines in formulas (6-1) to (6-12) represent the R in formula (1). 2 or R 5 It is a bonding hand that connects to [something]. The terminal groups having amide bonds in the fluorine-containing ether compounds of this embodiment are not limited to the organic groups represented by formulas (6-1) to (6-12).

[0093] [ka] (In equation (6-1), t represents an integer between 0 and 7.) (In equation (6-2), u represents an integer between 0 and 7.)

[0094] As terminal groups having an amide bond, it is preferable to use terminal groups represented by formulas (6-1) to (6-4) among the terminal groups represented by formulas (6-1) to (6-12). This is because they result in fluorine-containing ether compounds that are relatively easy to manufacture. The terminal groups represented by formulas (6-1) or (6-2) have linear aliphatic amides and have higher fluidity compared to the terminal groups represented by formulas (6-3) to (6-12). Therefore, even if a portion of the lubricating layer containing the fluorine-containing ether compound is deformed due to wear and the fluorine-containing ether compound in the lubricating layer moves to another location, it has a high restorative ability to return to its original position. As a result, fluorine-containing ether compounds having terminal groups represented by formulas (6-1) or (6-2) can form a lubricating layer with superior wear resistance.

[0095] In equation (6-1), t is an integer between 0 and 7, and preferably an integer between 0 and 5. 1 and / or R 6 The amide possessed by and the adjacent linking group (R 2 or R 5 This is because the interaction with the polar groups of ) is more effectively suppressed. In equation (6-2), u is an integer between 0 and 7, and preferably an integer between 0 and 5.1 and / or R 6 The amide possessed by and the adjacent linking group (R 2 or R 5 This is because the interaction with the polar groups of ) is more effectively suppressed.

[0096] Furthermore, the terminal groups represented by formula (6-3) or (6-4) have relatively rigid aromatic amides, thus restricting molecular motion to some extent. For this reason, fluorine-containing ether compounds having terminal groups represented by formula (6-3) or (6-4) have a lower R content compared to fluorine-containing ether compounds having terminal groups represented by formula (6-1) or (6-2). 1 and R 6 The amide that it possesses, and R 2 and R 5 The polar groups present have little ability to inhibit the interaction between each other and their respective protective layers.

[0097] Furthermore, aromatic amides having terminal groups represented by formula (6-3) or (6-4) are sp 2 These compounds widely possess a planar structure consisting of carbon, oxygen, and nitrogen with hybrid orbitals, ranging from aromatic rings to amide skeletons. Therefore, the interaction between the aromatic amides of terminal groups represented by formula (6-3) or (6-4) and the protective layer is presumed to be stronger than the interaction between the aliphatic amides of terminal groups represented by formula (6-1) or (6-2) and the protective layer.

[0098] Furthermore, aromatic amides with terminal groups represented by formulas (6-3) or (6-4) have a phenyl group as the organic group at the terminal group. Therefore, the lubricating layer containing the fluorine-containing ether compound has good hydrophobicity and can effectively prevent water from penetrating, which can cause corrosion of magnetic recording media. These findings suggest that fluorine-containing ether compounds having terminal groups represented by formulas (6-3) or (6-4) possess superior chemical resistance and can form a lubricating layer that provides even greater corrosion suppression for magnetic recording media.

[0099] In terminal groups having an amide bond as shown in formula (6-3), the carbonyl carbon atoms constituting the amide bond may be bonded to any position of the organic phenyl group: ortho, meta, or para. 1 and / or R 6 The amide possessed by and the adjacent linking group (R 2 or R 5 It is preferable that the carbonyl carbon atom constituting the amide bond is bonded to the para position of the phenyl group, in order to more effectively suppress the interaction with the polar group of the phenyl group. In terminal groups having an amide bond as shown in formula (6-4), the nitrogen atom constituting the amide bond may be bonded to any position of the organic phenyl group: ortho, meta, or para. 1 and / or R 6 The amide possessed by and the adjacent linking group (R 2 or R 5 It is preferable that the nitrogen atom constituting the amide bond is bonded to the para position of the phenyl group, in order to more effectively suppress the interaction with the polar group of the phenyl group.

[0100] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 If both terminal groups indicated by are terminal groups having an amide bond, then R 1 and R 6 These can be the same or different. 1 and R 6 When these factors are the same, the coating state of the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed. In this specification, "R 1 and R 6 "They are the same" means that the central skeleton (-R) of the fluorine-containing ether compound represented by formula (1) is the same. 3 [-CH2-R 4 -CH2-R 3’ ] n -) and the methylene group and R 2 or R 5 via R 1 Atoms and R contained in6 This means that the atoms contained within are arranged symmetrically.

[0101] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 One of the terminal groups shown (for example, R 1 If only R is a terminal group having an amide bond, then the other terminal group that does not have an amide bond (for example, R 6 The terminal group can be any organic group having 1 to 50 carbon atoms, and is not particularly limited. The other terminal group is preferably an organic group having 1 to 30 carbon atoms, and more preferably an organic group having 1 to 15 carbon atoms.

[0102] The other terminal group is preferably an organic group having at least one double or triple bond, such as a group containing an aromatic ring, a group containing an unsaturated heterocycle, a group containing an alkenyl group, or a group containing an alkynyl group. The organic group having at least one double or triple bond may be, for example, a group containing a cyano group. That is, the double and triple bonds may be carbon-carbon bonds, or bonds between a carbon atom and a heteroatom (for example, a carbon-nitrogen bond). The other terminal group may be an alkyl group having 1 to 8 carbon atoms, which may have substituents. Examples of substituents include alkoxy groups, hydroxyl groups, mercapto groups, carboxyl groups, carbonyl groups, amino groups, and fluoro groups. The alkyl group is more preferably having 1 to 6 carbon atoms, and even more preferably having 1 to 4 carbon atoms. Among alkyl groups having 1 to 8 carbon atoms, which may have substituents, alkyl groups having 1 to 8 carbon atoms and a hydroxyl group are preferred.

[0103] If the other terminal group mentioned above is an organic group having at least one double or triple bond, specifically, this includes phenyl group, methoxyphenyl group, phenyl fluoride group, naphthyl group, phenethyl group, methoxyphenethyl group, phenethyl fluoride group, benzyl group, methoxybenzyl group, naphthylmethyl group, methoxynaphthyl group, pyrrolyl group, pyrazolyl group, methylpyrazolylmethyl group, imidazolyl group, furyl group, furfuryl group, oxazolyl group, isoxazolyl group, thienyl group, thienylethyl group, thiazolyl group, methylthiazolylethyl group, isothiazolyl group, pyridyl Examples include the yl group, pyrimidinyl group, pyridadinyl group, pyrazinyl group, indolinyl group, benzofuranyl group, benzothienyl group, benzimimidazolyl group, benzooxazolyl group, benzothiazolyl group, benzopyrazolyl group, benzoisooxazolyl group, benzoisothiazolyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, synnolinyl group, vinyl group, allyl group, butenyl group, propynyl group, propargyl group, butynyl group, methylbutynyl group, pentynyl group, methylpentynyl group, hexynyl group, and cyanoethyl group.

[0104] When the other terminal group is an alkyl group having 1 to 8 carbon atoms that may have substituents, specific examples include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, trifluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, octafluoropentyl group, tridecafluorooctyl group, hydroxymethyl group (-CH2OH), hydroxyethyl group (-CH2CH2OH), hydroxypropyl group (-CH2CH2CH2OH), and hydroxybutyl group (-CH2CH2CH2CH2OH).

[0105] The other terminal group is preferably one of the following: phenyl group, methoxyphenyl group, thienylethyl group, naphthyl group, butenyl group, allyl group, propargyl group, phenethyl group, methoxyphenethyl group, fluorinated phenethyl group, hydroxyethyl group, or hydroxypropyl group. In particular, it is preferably one of the following: phenyl group, naphthyl group, thienylethyl group, allyl group, butenyl group, or hydroxyethyl group. In this case, a fluorine-containing ether compound is formed that can create a lubricating layer with superior wear resistance.

[0106] In the fluorine-containing ether compound represented by formula (1), R in formula (1) 3 and one or two R 3’ They are all the same, R 1 -R 2 -and R 6 -R 5 - Preferably the same as . This is because it results in a fluorine-containing ether compound that can be easily and efficiently manufactured. Furthermore, R 4 When the linking group is represented by formula (3-1) and is a fluorine-containing ether compound, it can be produced more easily and efficiently, and is therefore more preferable.

[0107] The fluorine-containing ether compound represented by formula (1) is preferably one of the compounds represented by the following formulas (A) to (Y). When the compound represented by formula (1) is one of the compounds represented by formulas (A) to (Y) below, the raw materials are readily available, and a lubricating layer can be formed that has excellent adhesion even with a thin thickness, even better chemical resistance and wear resistance, and a high corrosion suppression effect on magnetic recording media.

[0108] The compounds represented by the following formulas (A) to (Y) all contain R in formula (1). 3 and one or two R 3’The PFPE chains shown are all the same. In the compounds represented by the following formulas (A) to (Y), Rf1, Rf2, and Rf3, which represent the PFPE chains, have the following structures. That is, in the compounds represented by the following formulas (A) to (M) and (P) to (X), Rf1 is the PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulas (N) and (Y), Rf2 is the PFPE chain represented by the above formula (4-2). In the compound represented by the following formula (O), Rf3 is the PFPE chain represented by the above formula (4-3). Note that h and i in Rf1, j in Rf2, and k in Rf3, which represent the PFPE chains in formulas (A) to (Y), are values ​​that indicate the average degree of polymerization and are therefore not necessarily integers.

[0109] [ka]

[0110] The compounds represented by the following formulas (A) to (Y) are all R 2 is a linking group represented by the above formula (2-1) or (2-2), and R 5 This is the linking group represented by the above formula (2-3) or (2-4). The compounds represented by the following formulas (A) to (Y) are all R 4 This is the linking group represented by the above formulas (3-1) to (3-3). The compounds represented by the following formulas (A) to (Y) are all R 1 and / or R 6 It has a group represented by formula (5-1) or (5-2).

[0111] The compound represented by the following formula (A) is one in which n in formula (1) is 1. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). 3 and R3’ This is the PFPE chain represented by the above formula (4-1).

[0112] The compounds represented by the following formulas (B) to (D) all have n = 1 in formula (1). 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (B) is R 1 and R 6 The terminal group represented by the above formula (6-2) is u = 1. The compound represented by the following formula (C) is R 1 and R 6 The terminal group represented by the above formula (6-2) is u = 3. The compound represented by the following formula (D) is R 1 and R 6 This is the terminal group represented by the above formula (6-2) where u is 5.

[0113] The compound represented by the following formula (E) is one in which n in formula (1) is 1. 1 and R 6 This is the terminal group represented by the above formula (6-3), and the carbonyl carbon atom constituting the amide bond is bonded to the para position of the phenyl group. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0114] The compound represented by the following formula (F) is one in which n in formula (1) is 1. 1 and R 6 This is the terminal group represented by the above formula (6-4), and the nitrogen atom constituting the amide bond is bonded to the para position of the phenyl group.2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0115] The compound represented by the following formula (G) is one in which n in formula (1) is 1. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 The linking group is represented by the above formula (2-1) and has two p1s. 5 The linking group is represented by the above formula (2-3) and p2 is 2. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0116] The compound represented by the following formula (H) is one in which n in formula (1). 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 2. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0117] The compound represented by the following formula (I) is one in which n in formula (1). 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 The linking group is represented by the above formula (2-2) and q1 is 2. 5 The linking group is represented by the above formula (2-4) and q2 is 2. 4 This is the linking group represented by the above formula (3-1).3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0118] The compound represented by the following formula (J) is one in which n in formula (1) is 1. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 R is a linking group represented by the above formula (3-3) where s is 2. 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0119] The compound represented by the following formula (K) is one in which n in formula (1) is 1. 1 R is the terminal group represented by the above formula (6-1) and t is 1. 6 The terminal group is a hydroxyethyl group (-CH2CH2OH) that does not have an amide bond. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0120] The compound represented by the following formula (L) is one in which n in formula (1) is 1. 1 R is the terminal group represented by the above formula (6-1) and t is 1. 6 R is an allyl group, which is a terminal group that does not have an amide bond. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 2. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0121] The compound represented by the following formula (M) is one in which n in formula (1) is 1. 1 R is the terminal group represented by the above formula (6-1) and t is 1. 6 R is a phenyl group, which is a terminal group that does not have an amide bond. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). 3 and R 3’ This is the PFPE chain represented by the above formula (4-1).

[0122] The compounds represented by the following formulas (N) and (O) both have n = 1 in formula (1). 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. 4 This is the linking group represented by the above formula (3-1). The compound represented by the following formula (N) is R 3 and R 3’ This is the PFPE chain represented by the above formula (4-2). The compound represented by the following formula (O) is R 3 and R 3’ This is the PFPE chain represented by the above formula (4-3).

[0123] The compound represented by the following formula (P) is one in which n in formula (1) is 2. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’This is the PFPE chain represented by the above formula (4-1).

[0124] The compounds represented by the following formulas (Q) and (R) both have n = 2 in formula (1). 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’ This is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (Q) is R 1 and R 6 The terminal group represented by the above formula (6-2) is u = 1. The compound represented by the following formula (R) is R 1 and R 6 This is the terminal group represented by the above formula (6-2) where u is 3.

[0125] The compound represented by the following formula (S) is one in which n in formula (1) is 2. 1 and R 6 This is the terminal group represented by the above formula (6-3), and the carbonyl carbon atom constituting the amide bond is bonded to the para position of the phenyl group. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’ This is the PFPE chain represented by the above formula (4-1).

[0126] The compound represented by the following formula (T) is one in which n in formula (1) is 2. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. Two R 4These are the linking group represented by formula (3-2) and the linking group represented by formula (3-3) above. 3 and two R 3’ This is the PFPE chain represented by the above formula (4-1).

[0127] The compound represented by the following formula (U) is one in which n in formula (1) is 2. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 The linking group is represented by the above formula (2-1) and p1 is 2. 5 The linking group is represented by the above formula (2-3) and p2 is 2. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’ This is the PFPE chain represented by the above formula (4-1).

[0128] The compound represented by the following formula (V) is one in which n in formula (1) is 2. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 The linking group is represented by the above formula (2-2) and q1 is 2. 5 The linking group is represented by the above formula (2-4) and q2 is 2. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’ This is the PFPE chain represented by the above formula (4-1).

[0129] The compound represented by the following formula (W) is one in which n in formula (1) is 2. 1 R is the terminal group represented by the above formula (6-1) and t is 1. 6 The terminal group is a hydroxyethyl group (-CH2CH2OH) that does not have an amide bond. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R3’ This is the PFPE chain represented by the above formula (4-1).

[0130] The compound represented by the following formula (X) is one in which n in formula (1) is 2. 1 R is the terminal group represented by the above formula (6-1) and t is 1. 6 R is an allyl group, which is a terminal group that does not have an amide bond. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 2. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’ This is the PFPE chain represented by the above formula (4-1).

[0131] The compound represented by the following formula (Y) is one in which n in formula (1) is 2. 1 and R 6 R is the terminal group represented by the above formula (6-1) and t is 1. 2 R is a linking group represented by the above formula (2-1) where p1 is 1. 5 The linking group is represented by the above formula (2-3) and p2 is 1. Two R 4 This is the linking group represented by the above formula (3-1). 3 and two R 3’ This is the PFPE chain represented by the above formula (4-2).

[0132] [ka] (In the two Rf1 in equation (A), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (B), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (C), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.)

[0133] [ka] (In the two Rf1 in equation (D), h and i represent the average degree of polymerization, where h is between 1 and 20 and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (E), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (F), h and i represent the average degree of polymerization, where h is between 1 and 20 and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.)

[0134] [ka] (In the two Rf1 in equation (G), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (H), h and i represent the average degree of polymerization, where h is between 1 and 20 and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (I), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.)

[0135] [ka] (In the two Rf1 in equation (J), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (K), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (L), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.)

[0136] [ka] (In the two Rf1 in equation (M), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In equation (N), in the two Rf2s, j represents the average degree of polymerization and is between 1 and 15; the average degrees of polymerization in the two Rf2s may be the same or different.) (In the two Rf3 values ​​in equation (O), k represents the average degree of polymerization and is between 1 and 10; the average degrees of polymerization may be the same or different for the two Rf3 values.)

[0137] [ka] (In equation (P), h and i represent the average degree of polymerization in the three Rf1 values, where h is between 1 and 20 and i is between 0 and 20; the average degrees of polymerization in the three Rf1 values ​​may be different, or the average degrees of polymerization in two or three Rf1 values ​​may be the same.) (In equation (Q), h and i represent the average degree of polymerization in the three Rf1 values, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1 values ​​may be different, or the average degrees of polymerization in two or three Rf1 values ​​may be the same.) (In equation (R), in the three Rf1 terms, h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1 terms may be different, or the average degrees of polymerization in two or three Rf1 terms may be the same.)

[0138] [ka] (In equation (S), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization of the three Rf1s may be different, or the average degrees of polymerization of two or three Rf1s may be the same.) (In equation (T), h and i represent the average degree of polymerization in the three Rf1 values, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1 values ​​may be different, or the average degrees of polymerization in two or three Rf1 values ​​may be the same.) (In equation (U), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization of the three Rf1s may be different, or the average degrees of polymerization of two or three Rf1s may be the same.)

[0139] [ka] (In equation (V), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization of the three Rf1s may be different, or the average degrees of polymerization of two or three Rf1s may be the same.) (In equation (W), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization of the three Rf1s may be different, or the average degrees of polymerization of two or three Rf1s may be the same.)

[0140] [ka] (In equation (X), h and i represent the average degree of polymerization in the three Rf1 values, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1 values ​​may be different, or the average degrees of polymerization in two or three Rf1 values ​​may be the same.) (In equation (Y), in the three Rf2s, j represents the average degree of polymerization and is between 1 and 15; the average degrees of polymerization of the three Rf2s may be different, or the average degrees of polymerization of two or three Rf2s may be the same.)

[0141] The fluorine-containing ether compound in this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10000, and particularly preferably in the range of 1000 to 5000. If the number-average molecular weight is 500 or more, the lubricating layer made of the lubricant containing the fluorine-containing ether compound in this embodiment will have excellent heat resistance. The number-average molecular weight of the fluorine-containing ether compound is more preferably 1000 or more. Furthermore, if the number-average molecular weight is 10000 or less, the viscosity of the fluorine-containing ether compound will be appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing it. The number-average molecular weight of the fluorine-containing ether compound is preferably 5000 or less, as this results in a viscosity that is easy to handle when applied to a lubricant.

[0142] The number-average molecular weight (Mn) of fluorine-containing ether compounds was determined using a Bruker BioSpin AVANCE III 400. 1 H-NMR and 19 These values ​​were measured by F-NMR. Specifically, 19The number of repeating units in the PFPE chain is calculated from the integrated value measured by 1F-NMR, and the number-average molecular weight is determined. For NMR (nuclear magnetic resonance) measurements, the sample is diluted in hexafluorobenzene / d-acetone (4 / 1v / v) solvent before measurement. 19 The reference point for the F-NMR chemical shift is the hexafluorobenzene peak at -164.7 ppm. 1 The standard for the 1H-NMR chemical shift is to set the acetone peak at 2.2 ppm.

[0143] In this embodiment, it is preferable to fractionate the fluorine-containing ether compound by an appropriate molecular weight method to achieve a molecular weight dispersion (weight-average molecular weight (Mw) / number-average molecular weight (Mn) ratio) of 1.3 or less. In this embodiment, the method for molecular weight fractionation is not particularly limited, but for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or molecular weight fractionation by supercritical fluid extraction can be used.

[0144] "Manufacturing method" The method for producing the fluorine-containing ether compound of this embodiment is not particularly limited and can be produced using conventionally known production methods. The fluorine-containing ether compound of this embodiment can be produced, for example, using the production method shown below.

[0145] (1st manufacturing method) In equation (1), n ​​is 1, and R 3 and R 3’ The two PFPE chains shown are the same, and R 1 -R 2 -and R 6 -R 5 When producing a compound that is the same as -, the following production method can be used. First, in equation (1), R 3 and R 3’ Prepare a fluorine-based compound in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain.

[0146] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine compound, and R in formula (1) 1 -R 2 -The base (=R) 6 -R 5 The epoxy group of an epoxy compound having a - group is reacted with this. 3 (=R 3’ At one end of the perfluoropolyether chain corresponding to ), R 1 -R 2 -(=R 6 -R 5 A first intermediate compound having a group corresponding to -) is obtained.

[0147] R in equation (1) 1 -R 2 -The base (=R) 6 -R 5 Examples of epoxy compounds having a group that becomes - include compounds represented by the following formulas (7-1a) to (7-1c), (7-2a) to (7-2c), (7-3), and (7-4). When synthesizing the first intermediate compound by reacting the above fluorine-based compound with the above epoxy compound, the hydroxyl groups of the epoxy compound may be protected with an appropriate protecting group before reacting with the fluorine-based compound.

[0148] [ka]

[0149] R in equation (1) 1 -R 2 -The base (=R) 6 -R 5 An epoxy compound having a group that becomes - is, for example, R 2 The linking group is represented by the above formula (2-1) and p1 is 1 (=R 5 If the linking group is represented by the above formula (2-3) and p2 is 1, it can be manufactured using the method shown below. That is, as shown in formula (8) below, R in formula (1) 1 or R6 An alcohol having a structure corresponding to the terminal group represented by (R in formula (8)), and R 2 or R 5 It can be produced by reacting it with a halogen compound having an epoxy group corresponding to it.

[0150] [ka] (In equation (8), R is the same as R in equation (1)) 1 or R 6 (This shows the structure corresponding to the terminal group represented by .)

[0151] Furthermore, the epoxy compound mentioned above is, for example, R 2 The linking group is represented by the above formula (2-1) and p1 is 2 (=R 5 If the linking group is represented by the above formula (2-3) and p2 is 2, it can be manufactured using the method shown below. That is, as shown in formula (9) below, R in formula (1) 1 or R 6 An alcohol having a structure corresponding to the terminal group represented by (R in formula (9)) is subjected to an addition reaction with an allyl glycidyl ether. Subsequently, the compound obtained by the addition reaction can be produced by oxidation with m-chloroperbenzoic acid (mCPBA).

[0152] [ka] (In equation (9), R is the same as R in equation (1)) 1 or R 6 (This shows the structure corresponding to the terminal group represented by .)

[0153] Furthermore, the epoxy compound mentioned above is, for example, R 2 The linking group is represented by the above formula (2-2) and q1 is 2 (=R 5 If the linking group is represented by the above formula (2-4) and q2 is 2, it can be manufactured using the method shown below. That is, as shown in formula (10) below, R in formula (1)1 or R 6 An alcohol having a structure corresponding to the terminal group represented by (R in formula (10)), and R 2 or R 5 The compound can be produced by reacting it with a halogen compound having the corresponding alkenyl group, and then oxidizing the resulting compound with m-chloroperbenzoic acid (mCPBA).

[0154] [ka] (In equation (10), R is the same as R in equation (1)) 1 or R 6 (This shows the structure corresponding to the terminal group represented by .)

[0155] The epoxy compound mentioned above may be purchased commercially and used. Next, R 3 (=R 3’ At one end of the perfluoropolyether chain corresponding to ), R 1 -R 2 - Corresponding base (=R 6 -R 5 A first intermediate compound having a group corresponding to - and R 4 The halogen compound having the corresponding epoxy group or the dihalogen compound having a protected hydroxyl group is reacted with it.

[0156] In the first manufacturing method, the following steps may be performed instead of the above steps. That is, R 3 (=R 3’ At one end of the perfluoropolyether chain corresponding to ), R 1 -R 2 - Corresponding base (=R 6 -R 5 A first intermediate compound having a group corresponding to - and R 4A second intermediate compound is produced by reacting it with a halogen compound having the corresponding alkenyl group. Subsequently, the obtained second intermediate compound may be oxidized to an epoxy compound and then reacted with the first intermediate compound described above.

[0157] By performing the above steps, n in equation (1) is 1, and R 3 and R 3’ The two PFPE chains shown are the same, and R 1 -R 2 -and R 6 -R 5 - A compound that is the same as - is obtained.

[0158] (Second manufacturing method) In equation (1), n ​​is 1, and R 1 and R 6 , R 2 and R 5 , R 3 and R 3’ When producing a compound in which one or more of the two PFPE chains shown are different, the following production method can be used. In this case as well, R is produced in the same manner as in the first manufacturing method. 3 At one end of the corresponding perfluoropolyether chain, R 1 -R 2 A first intermediate compound having the corresponding group is produced.

[0159] Next, R 3 At one end of the corresponding perfluoropolyether chain, R 1 -R 2 - A first intermediate compound having a group corresponding to R 4 The halogen compound having the corresponding epoxy group, or the dihalogen compound having a protected hydroxyl group, is reacted with this. 3 R at one end of the corresponding perfluoropolyether chain 1 -R 2 - has a corresponding group, and the other end has R 4 A third intermediate compound having an epoxy group or halogen group corresponding to the present is produced.

[0160] Next, in the same manner as the first intermediate compound, R 3’ At one end of the corresponding perfluoropolyether chain, R 6 -R 5 A fourth intermediate compound having the corresponding group is produced. Subsequently, the third intermediate compound and the fourth intermediate compound are reacted. By performing the above steps, n in equation (1) is 1, and R 1 and R 6 , R 2 and R 5 , R 3 and R 3’ Compounds can be produced in which one or more of the two PFPE chains shown are different.

[0161] (Third manufacturing method) In equation (1), n ​​is 2, and R 3 and two R 3’ The three PFPE chains shown are the same, R 4 The two linking groups shown are the same, R 1 -R 2 -and R 6 -R 5 When producing a compound that is the same as -, the following production method can be used.

[0162] First, the R in the center of the molecule in equation (1) 3’ A fluorine-based compound is prepared in which a hydroxymethyl group (-CH2OH) is positioned at both ends of the perfluoropolyether chain corresponding to R. Next, the hydroxyl groups of the hydroxymethyl groups positioned at both ends of the fluorine-based compound and R 4 The R in the center of the molecule in formula (1) is reacted with a halogen compound having an epoxy group corresponding to it (first reaction). 3’ An intermediate compound 1 is obtained, having epoxy groups at both ends of the corresponding perfluoropolyether chain.

[0163] Next, R in equation (1) 3 (=R 6R on the side 3’ A fluorine-based compound is prepared in which a hydroxymethyl group (-CH2OH) is positioned at both ends of the perfluoropolyether chain corresponding to ). Next, the hydroxyl group of the hydroxymethyl group positioned at one end of the fluorine-based compound and the R in formula (1) are taken together. 1 -R 2 -The base (=R) 6 -R 5 The epoxy compound having a group that becomes - is reacted (second reaction). As a result, R 3 (=R 6 R on the side 3’ At one end of the perfluoropolyether chain corresponding to ), R 1 -R 2 - Corresponding base (=R 6 -R 5 An intermediate compound 2 having the corresponding group (-) is obtained.

[0164] R in equation (1) 1 -R 2 -The base (=R) 6 -R 5 As epoxy compounds having a group that becomes -, for example, compounds represented by the above formulas (7-1a) to (7-1c), (7-2a) to (7-2c), (7-3), and (7-4) can be used, as in the first manufacturing method. When synthesizing intermediate compound 2 by reacting the above-mentioned fluorine-based compound with the above-mentioned epoxy compound, the hydroxyl groups of the epoxy compound may be protected with an appropriate protecting group before reacting with the above-mentioned fluorine-based compound.

[0165] Subsequently, the hydroxyl group of the hydroxymethyl group located at one end of intermediate compound 2 is reacted with the epoxy groups located at both ends of intermediate compound 1 (third reaction). By performing the above steps, n in equation (1) is 2, and R 3 and two R 3’ The three PFPE chains shown are the same, R 4 The two linking groups shown are the same, R 1 -R 2 -and R6 -R 5 -It is possible to produce compounds that are the same as -. In this embodiment, the second reaction was carried out after the first reaction, but the first reaction may be carried out after the second reaction.

[0166] (4th manufacturing method) In equation (1), n ​​is 2, and R 4 The two linking groups shown are the same, R 1 and R 6 , R 2 and R 5 , R 3 and R 6 R on the side 3’ When producing a compound in which one or more of the PFPE chains shown are different, the following production method can be used. First, the first reaction is carried out in the same manner as in the third manufacturing method to produce intermediate compound 1.

[0167] Next, in the second reaction, R 3 R at one end of the corresponding perfluoropolyether chain 1 -R 2 - Synthesize intermediate compound 2a having the corresponding group. Furthermore, in the second reaction, R 6 R on the side 3’ R at one end of the corresponding perfluoropolyether chain 6 -R 5 Synthesize intermediate compound 2b having the corresponding group.

[0168] Then, in the third reaction, intermediate compound 2a and intermediate compound 2b are sequentially reacted with the epoxy groups located at each end of intermediate compound 1. By performing the above steps, n in equation (1) is 2, and R 4 The two linking groups shown are the same, R 1 and R 6 , R 2 and R 5 , R 3 and R 6 R on the side 3’It is possible to produce compounds in which one or more of the PFPE chains shown are different.

[0169] (Fifth manufacturing method) In equation (1), n ​​is 2, and R 3 and two R 3’ The three PFPE chains shown are the same, R 4 The two linking groups shown are different, R 1 -R 2 -and R 6 -R 5 When producing a compound that is the same as -, the following production method can be used.

[0170] First, in the first reaction, the R in the center of the molecule in equation (1) 3’ A fluorine-based compound is prepared in which a hydroxymethyl group (-CH2OH) is positioned at both ends of the corresponding perfluoropolyether chain. Next, the hydroxyl group of the hydroxymethyl group positioned at one end of the fluorine-based compound and R 4 A halogen compound having an epoxy group corresponding to one of the two linking groups shown is reacted with the hydroxyl group of the hydroxymethyl group located at the other end of the fluorine compound, and R 4 The halogen compound having an epoxy group corresponding to the other of the two linking groups shown is reacted with (first reaction). This causes the R in the center of the molecule in formula (1) to 3’ At both ends of the corresponding perfluoropolyether chain, R 4 An intermediate compound 1a is obtained having epoxy groups corresponding to the two linking groups shown.

[0171] Next, the second reaction is carried out in the same manner as the third manufacturing method to produce intermediate compound 2. Subsequently, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 2 is reacted with the epoxy groups located at both ends of the intermediate compound 1a (third reaction). By performing the above steps, n in equation (1) is 2, and R 3 and two R 3’The three PFPE chains shown are the same, R 4 The two linking groups shown are different, R 1 -R 2 -and R 6 -R 5 -It is possible to produce compounds that are the same as -.

[0172] The fluorine-containing ether compound of this embodiment is a compound represented by formula (1), comprising a methylene group and a divalent linking group (R) having one polar group. 4 ) and a methylene group are bonded in this order to a linkage structure through which multiple perfluoropolyether chains (R 3 and R 3’ ) has a skeleton in which these are linked, and on both sides of the skeleton are a methylene group and a divalent linking group (R) having one or more polar groups. 2 and R 5 ) and terminal group (R 1 and R 6 ) are joined in this order. And R 1 and R 6 At least one of the terminal groups is a group in which a carbonyl carbon atom or nitrogen atom constituting an amide bond is bonded to a carbon atom of an organic group having 1 to 8 carbon atoms. For this reason, the lubricating layer formed on the protective layer using the lubricant containing the fluorine-containing ether compound of this embodiment has good chemical resistance and wear resistance, and has a high corrosion suppression effect on magnetic recording media.

[0173] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of this embodiment can be mixed with known materials used as lubricants, as necessary, as long as the properties are not impaired by the inclusion of the fluorine-containing ether compound represented by formula (1) above.

[0174] Specific examples of known materials include, for example, FOMBLIN® ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), and Moresco A20H (manufactured by Moresco). The known materials used in combination with the lubricant of this embodiment preferably have a number average molecular weight of 1,000 to 10,000.

[0175] If the lubricant of this embodiment contains other materials of the fluorine-containing ether compound represented by formula (1) above, it is preferable that the content of the fluorine-containing ether compound represented by formula (1) in the lubricant of this embodiment be 50% by mass or more, and more preferably 70% by mass or more.

[0176] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1) above, and therefore has excellent chemical resistance and wear resistance, and can form a lubricating layer with a high corrosion suppression effect on magnetic recording media.

[0177] [Magnetic recording medium] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers can be provided between the substrate and the magnetic layer, as needed. Furthermore, at least one of an adhesive layer and a soft magnetic layer can be provided between the underlayer and the substrate.

[0178] Figure 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesion layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0179] "substrate" As the substrate 11, for example, a non-magnetic substrate can be used, which has a film made of NiP or NiP alloy formed on a base made of a metal or alloy material such as Al or an Al alloy. Furthermore, the substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a non-magnetic substrate in which a film of NiP or NiP alloy is formed on a substrate made of one of these non-metallic materials.

[0180] "Adhesion layer" The adhesive layer 12 prevents the progression of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are placed in contact with each other. The material of the adhesion layer 12 can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed, for example, by sputtering.

[0181] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are sequentially laminated. That is, the soft magnetic layer 13 preferably has a structure in which the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC) coupled by sandwiching an intermediate layer made of a Ru film between the two soft magnetic films.

[0182] Examples of materials for the first and second soft magnetic films include CoZrTa alloy and CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it becomes possible to improve the orientation of the first underlayer (seed layer) and reduce the amount of levitation of the magnetic head. The soft magnetic layer 13 can be formed, for example, by a sputtering method.

[0183] "First base layer" The first sublayer 14 is a layer that controls the orientation and crystal size of the second sublayer 15 and the magnetic layer 16 which are placed on top of it. Examples of the first subsoil layer 14 include a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, a CrTi alloy layer, and so on. The first subsoil layer 14 can be formed, for example, by a sputtering method.

[0184] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16 to a good degree. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second sublayer 15 may consist of one layer or multiple layers. If the second sublayer 15 consists of multiple layers, all layers may be made of the same material, or at least one layer may be made of a different material. The second subsoil layer 15 can be formed, for example, by sputtering.

[0185] "Magnetic layer" The magnetic layer 16 consists of a magnetic film whose easy magnetization axis is oriented perpendicular or horizontal to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. The magnetic layer 16 may also contain oxides, Cr, B, Cu, Ta, Zr, etc., to improve the SNR characteristics. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0186] The magnetic layer 16 may consist of a single layer, or it may consist of multiple magnetic layers made of materials with different compositions. For example, if the magnetic layer 16 consists of three layers stacked from bottom to top—a first magnetic layer, a second magnetic layer, and a third magnetic layer—the first magnetic layer is preferably a granular structure made of a material containing Co, Cr, Pt, and an oxide. As the oxide contained in the first magnetic layer, it is preferable to use oxides such as Cr, Si, Ta, Al, Ti, Mg, and Co. Among these, TiO2, Cr2O3, and SiO2 are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide with two or more oxides added. Among these, Cr2O3-SiO2, Cr2O3-TiO2, and SiO2-TiO2 are particularly suitable.

[0187] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re, in addition to Co, Cr, Pt, and oxides. The second magnetic layer can be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure.

[0188] The third magnetic layer is preferably a non-granular structure made of a material containing Co, Cr, and Pt, but free of oxides. In addition to Co, Cr, and Pt, the third magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0189] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 consists of three layers, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer.

[0190] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can preferably be made of, for example, Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (where X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, B).

[0191] For the non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16, it is preferable to use an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, as oxides, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, TiO2, etc. can be used. As metal nitrides, for example, AlN, Si3N4, TaN, CrN, etc. can be used. As metal carbides, for example, TaC, BC, SiC, etc. can be used. The non-magnetic layer can be formed, for example, by sputtering.

[0192] To achieve a higher recording density, the magnetic layer 16 is preferably a perpendicular magnetic recording layer in which the easy magnetization axis is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be an in-plane magnetic recording layer. The magnetic layer 16 may be formed by any conventionally known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0193] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may consist of one layer or multiple layers. A carbon-based protective layer is preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. A carbon-based protective layer is preferable because it further enhances the interaction with polar groups (especially hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18.

[0194] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 to 20 atoms when measured by hydrogen forward scattering (HFS). Furthermore, the nitrogen content in the carbon-based protective layer is preferably 4 to 15 atoms when measured by X-ray photoelectron spectroscopy (XPS).

[0195] The hydrogen and / or nitrogen contained in the carbon-based protective layer do not need to be uniformly distributed throughout the entire layer. Preferably, the carbon-based protective layer is a compositionally graded layer, for example, in which nitrogen is contained on the lubrication layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubrication layer 18 and the carbon-based protective layer is further improved.

[0196] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as a protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of thinning the protective layer 17.

[0197] As a method for forming the protective layer 17, sputtering using a carbon-containing target material, CVD (chemical vapor deposition) using hydrocarbon raw materials such as ethylene and toluene, and IBD (ion beam deposition) can be used. When forming a carbon-based protective layer as the protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when forming a carbon-based protective layer as the protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface and low roughness.

[0198] "Lubricating layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. Furthermore, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording / reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in Figure 1, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 is formed by applying the lubricant for magnetic recording media of the above-described embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-described fluorine-containing ether compound.

[0199] The lubricating layer 18 is bonded with a particularly strong bond to the protective layer 17, especially when the protective layer 17 located beneath the lubricating layer 18 is a carbon-based protective layer. As a result, even with a thin lubricating layer 18, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high degree of coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0200] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.2 nm (12 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming islands or a mesh-like structure. Therefore, the surface of the protective layer 17 can be covered by the lubricating layer 18 with a high coverage rate. Furthermore, by making the average thickness of the lubricating layer 18 2.0 nm or less, the lubricating layer 18 can be sufficiently thinned, and the amount of levitation of the magnetic head can be sufficiently reduced.

[0201] "Method for forming a lubricating layer" To form the lubricating layer 18, for example, one method is to prepare a magnetic recording medium in the process of being manufactured, in which each layer up to the protective layer 17 has been formed on the substrate 11, and then apply a lubricating layer forming solution onto the protective layer 17.

[0202] The lubricating layer forming solution is obtained by dispersing and dissolving the lubricant for magnetic recording media of the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to be suitable for the coating method. Examples of solvents used in lubrication layer-forming solutions include fluorine-based solvents such as Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals).

[0203] The method for applying the lubricating layer-forming solution is not particularly limited, but examples include the spin coating method, spray method, paper coating method, and dip method. When using the dip method, for example, the following method can be used. First, the substrate 11, on which each layer up to the protective layer 17 has been formed, is immersed in a lubricating layer forming solution placed in the immersion tank of the dip coating apparatus. Next, the substrate 11 is withdrawn from the immersion tank at a predetermined speed. This coats the surface of the protective layer 17 of the substrate 11 with the lubricating layer forming solution. By using the dipping method, the lubrication layer-forming solution can be uniformly applied to the surface of the protective layer 17, and a lubrication layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0204] In this embodiment, it is preferable to heat-treat the substrate 11 on which the lubricating layer 18 is formed. By heat-treating, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesion force between the lubricating layer 18 and the protective layer 17 is improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. A heat treatment temperature of 100°C or higher provides sufficient improvement in adhesion between the lubricating layer 18 and the protective layer 17. Furthermore, a heat treatment temperature of 180°C or lower prevents thermal decomposition of the lubricating layer 18 due to heat treatment. The heat treatment time can be appropriately adjusted according to the heat treatment temperature, and is preferably 10 to 120 minutes.

[0205] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) light before or after heat treatment.

[0206] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially provided on a substrate 11. In the magnetic recording medium 10 of this embodiment, the lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed in contact with the protective layer 17. Even with a thin film thickness, this lubricating layer 18 has excellent adhesion, good chemical resistance and wear resistance, and a high corrosion suppression effect on the magnetic recording medium. Therefore, the magnetic recording medium 10 of this embodiment is excellent in reliability, in particular in suppressing silicon contamination and durability. As a result, the magnetic recording medium 10 of this embodiment can achieve a low magnetic head levitation amount (for example, 10 nm or less), and operates stably over a long period of time even in harsh environments associated with the diversification of applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk mounted in a LUL (Load Unload) type magnetic disk drive. [Examples]

[0207] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0208] [Example 1] The compound represented by formula (A) above was obtained by the method described below. HOCH2CF2O(CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i 20 g of the compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 3.2, and i, representing the average degree of polymerization, is 3.2) (number average molecular weight 700, molecular weight distribution 1.1), 4.15 g of the compound represented by the above formula (7-1a), and 20 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 1.60 g of potassium tert-butoxide was added to this mixture and the mixture was reacted by stirring at 70°C for 16 hours. The compound represented by formula (7-1a) was synthesized by reacting 3-hydroxypropanamide with epibromohydrin.

[0209] The reaction product obtained after the reaction was allowed to return to room temperature, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 8.69 g of the compound shown in formula (15) below as an intermediate.

[0210] [ka] (In formula (15), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0211] Next, under a nitrogen gas atmosphere, 8.69 g of the compound represented by formula (15), which was the intermediate obtained above, 0.845 g of epibromohydrin, and 10 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.92 g of potassium tert-butoxide was added to this homogeneous solution and the mixture was reacted by stirring at 70°C for 23 hours.

[0212] The reaction solution obtained after the reaction was allowed to return to room temperature, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 5.74 g of compound (A) (wherein Rf1 in formula (A) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, represents 3.2).

[0213] The obtained compound (A) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(22H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0214] [Example 2] The compound represented by formula (B) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-2a) was used instead of the compound represented by formula (7-1a) in Example 1, to obtain 5.89 g of compound (B) (wherein Rf1 in formula (B) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2). The compound represented by formula (7-2a) was synthesized by reacting N-(2-hydroxyethyl)acetamide with epibromohydrin.

[0215] The obtained compound (B) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(6H), 3.40-4.00(26H), 4.10-4.20(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0216] [Example 3] The compound represented by formula (C) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-2b) was used instead of the compound represented by formula (7-1a) in Example 1, and 6.08 g of compound (C) (wherein Rf1 in formula (C) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained. The compound represented by formula (7-2b) was synthesized by reacting an intermediate obtained by reacting 4-aminobutanol with acetyl chloride with epibromohydrin.

[0217] The obtained compound (C) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(8H), 3.40-4.00(26H), 4.10-4.20(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0218] [Example 4] The compound represented by formula (D) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-2c) was used instead of the compound represented by formula (7-1a) in Example 1, and 6.28 g of compound (D) (wherein Rf1 in formula (D) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained. The compound represented by formula (7-2c) was synthesized by reacting an intermediate obtained by reacting 6-aminohexanol with acetyl chloride with epibromohydrin.

[0219] The obtained compound (D) 1 H-NMR and19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(16H), 3.40-4.00(26H), 4.10-4.20(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0220] [Example 5] The compound represented by formula (E) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1a) in Example 1, and 6.14 g of compound (E) (wherein Rf1 in formula (E) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained. The compound represented by formula (7-3) was synthesized by reacting 4-hydroxybenzamide with epibromohydrin.

[0221] The obtained compound (E) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-4.00(18H), 4.10-4.20(8H), 6.30-6.70(4H), 7.30-7.80(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0222] [Example 6] The compound represented by formula (F) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-4) was used instead of the compound represented by formula (7-1a) in Example 1, and 6.09 g of compound (F) (wherein Rf1 in formula (F) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained. The compound represented by formula (7-4) was synthesized by reacting N-(4-hydroxyphenyl)acetamide with epibromohydrin.

[0223] The obtained compound (F) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(6H), 3.40-4.00(18H), 4.10-4.20(8H), 6.30-6.50(2H), 7.30-7.80(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0224] [Example 7] The compound represented by formula (G) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-1b) was used instead of the compound represented by formula (7-1a) in Example 1, to obtain 5.95 g of compound (G) (wherein Rf1 in formula (G) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2).

[0225] The compound represented by formula (7-1b) was synthesized by reacting 3-hydroxypropanamide with allyl glycidyl ether to obtain an intermediate, and then reacting that intermediate with m-chloroperbenzoic acid.

[0226] The obtained compound (G) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(34H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0227] [Example 8] The compound represented by the above formula (H) was obtained by the method shown below. By reacting the compound represented by formula (15) above, which is an intermediate of Example 1, with epibromohydrin, a compound represented by formula (16) below was obtained as an intermediate.

[0228] [ka] (In formula (16), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0229] Next, under a nitrogen gas atmosphere, 4.23 g of the compound represented by formula (16), which is the intermediate obtained above, 4.15 g of the compound represented by formula (17), which is the intermediate of Example 7, and 10 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.92 g of potassium tert-butoxide was added to this homogeneous solution and the mixture was stirred at 70°C for 23 hours to allow the reaction to proceed.

[0230] [ka] (In formula (17), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0231] The reaction solution obtained after the reaction was allowed to return to room temperature, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.52 g of compound (H) (wherein Rf1 in formula (H) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2).

[0232] The obtained compound (H) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(28H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0233] [Example 9] The compound represented by formula (I) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-1c) was used instead of the compound represented by formula (7-1a) in Example 1, to obtain 6.02 g of compound (I) (wherein Rf1 in formula (I) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2). The compound represented by formula (7-1c) was synthesized by reacting 3-hydroxypropanamide with 4-bromo-1-butene to obtain an intermediate, and then reacting this intermediate with m-chloroperbenzoic acid.

[0234] The obtained compound (I) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(4H), 1.90-2.05(4H), 3.40-4.00(22H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0235] [Example 10] The compound represented by formula (J) above was obtained by the method described below. The compound represented by formula (15) above, which is an intermediate of Example 1, was reacted with 4-bromo-1-butene, and then m-chloroperbenzoic acid was added to obtain the compound represented by formula (18) below as an intermediate.

[0236] [ka] (In formula (18), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0237] The procedure was the same as in Example 8, except that the compound represented by formula (18) was used instead of the compound represented by formula (16) in Example 8, and the compound represented by formula (15) was used instead of the compound represented by formula (17), and 5.89 g of compound (J) (wherein Rf1 in formula (J) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, represents 3.2) was obtained.

[0238] The obtained compound (J) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(2H), 1.90-2.05(4H), 3.40-4.00(22H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0239] [Example 11] The compound represented by the above formula (K) was obtained by the method described below. HOCH2CF2O(CF2CF2O) in a 200 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i 14 g of the compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 3.2, and i, representing the average degree of polymerization, is 3.2) (number average molecular weight 700, molecular weight distribution 1.1), 2.4 g of the compound represented by the following formula (19), and 14 mL of t-butanol were charged together and stirred at room temperature until homogeneous. To this homogeneous solution, 0.45 g of potassium tert-butoxide was added and the mixture was reacted by stirring at 70°C for 16 hours.

[0240] [ka]

[0241] The compound represented by formula (19) was synthesized by oxidizing a compound protected with ethylene glycol monoallyl ether using dihydropyran. The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 6.62 g of the compound shown in formula (20) below as an intermediate.

[0242] [ka] (In equation (20), Rf1 is the PFPE chain represented by equation (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0243] Next, under a nitrogen gas atmosphere, 3.63 g of the compound represented by formula (20), which is the intermediate obtained above, 4.05 g of the compound represented by formula (16), which is the intermediate from Example 8, and 10 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.90 g of potassium tert-butoxide was added to this homogeneous solution and the mixture was stirred at 70°C for 23 hours to allow the reaction to proceed.

[0244] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 18 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 2 hours. The mixture was transferred to a separatory funnel containing 100 mL of water and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.03 g of compound (K) (Rf1 in formula (K) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2).

[0245] The obtained compound (K) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(2H), 3.40-4.00(25H), 4.10-4.20(8H), 6.30-6.70(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0246] [Example 12] The compound represented by the above formula (L) was obtained by the method shown below. The same procedure as in Example 8 was followed, except that the compound represented by formula (21) was used instead of the compound represented by formula (17), to obtain 5.40 g of compound (L) (wherein Rf1 in formula (L) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2). The compound represented by formula (21) was synthesized according to Patent Document 5.

[0247] [ka] (In formula (21), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0248] The obtained compound (L) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.90-2.05(2H), 2.40-2.60(2H), 3.40-4.00(22H), 4.10-4.20(8H), 5.40-6.10(3H), 6.30-6.70(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0249] [Example 13] The compound represented by the above formula (M) was obtained by the method shown below. The same procedure as in Example 8 was followed, except that the compound represented by formula (22) was used instead of the compound represented by formula (17) in Example 8, to obtain 5.40 g of compound (M) (wherein Rf1 in formula (M) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2). The compound represented by formula (22) was synthesized in accordance with Patent Document 5.

[0250] [ka] (In equation (22), Rf1 is the PFPE chain represented by equation (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0251] The obtained compound (M) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(2H), 3.40-4.00(22H), 4.10-50(9H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0252] [Example 14] The compound represented by the above formula (N) was obtained by the method described below. HOCH2CF2O(CF2CF2O) from Example 1 h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2(OCF2CF2CF2). j The same procedure as in Example 1 was followed, except that a compound represented by OCF2CF2CH2OH (where j, representing the average degree of polymerization, is 2.6) was used (number average molecular weight 700, molecular weight distribution 1.1), and 6.17 g of compound (N) (where Rf2 in formula (N) is the PFPE chain represented by formula (4-2) above. In the two Rf2s, j, representing the average degree of polymerization, is 2.6) was obtained.

[0253] The obtained compound (N) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(22H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(36F), -86.4(8F), -124.3(8F), -130.0~-129.0(18F)

[0254] [Example 15] The compound represented by formula (O) above was obtained by the method shown below. HOCH2CF2O(CF2CF2O) from Example 1 h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2CF2(OCF2CF2CF2CF2). kThe same procedure as in Example 1 was followed, except that a compound represented by OCF2CF2CF2CH2OH (where k, representing the average degree of polymerization, is 1.6) was used (number average molecular weight 700, molecular weight distribution 1.1), and 6.02 g of compound (O) (where Rf3 in formula (O) is the PFPE chain represented by formula (4-3) above. In the two Rf3s, k, representing the average degree of polymerization, is 1.6) was obtained.

[0255] The obtained compound (O) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(22H), 4.10-4.20(8H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(34F), -122.5(8F), -126.0(13F), -129.0~-128.0(8F)

[0256] [Example 16] The compound represented by the above formula (P) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 3.2, and i, representing the average degree of polymerization, is 3.2) (number average molecular weight 700, molecular weight distribution 1.1) was reacted with epibromohydrin to obtain an intermediate represented by formula (23).

[0257] [ka] (In formula (23), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0258] Next, the same procedure as in Example 1 was carried out, except that the compound represented by formula (23) was used instead of epibromohydrin in the reaction between the compound represented by formula (15) and epibromohydrin, and 4.75 g of compound (P) (wherein Rf1 in formula (P) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0259] The obtained compound (P) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(28H), 4.10-4.20(12H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0260] [Example 17] The compound represented by formula (Q) above was obtained by the method described below. In the process of synthesizing the compound represented by formula (15), the same procedure as in Example 16 was performed except that the compound represented by formula (7-2a) was used instead of the compound represented by formula (7-1a), and 4.81 g of compound (Q) (wherein Rf1 in formula (Q) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0261] The obtained compound (Q) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.90-2.05(6H), 3.40-4.00(32H), 4.10-4.20(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0262] [Example 18] The compound represented by the above formula (R) was obtained by the method shown below. In the process of synthesizing the compound represented by formula (15), the same procedure as in Example 16 was performed except that the compound represented by formula (7-2b) was used instead of the compound represented by formula (7-1a), and 4.89 g of compound (R) (wherein Rf1 in formula (R) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0263] The obtained compound (R) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(8H), 3.40-4.00(32H), 4.10-4.20(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0264] [Example 19] The compound represented by the above formula (S) was obtained by the method described below. In the process of synthesizing the compound represented by formula (15), the same procedure as in Example 16 was performed except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1a), and 4.99 g of compound (S) (wherein Rf1 in formula (S) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0265] The obtained compound (S) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-4.00(24H), 4.10-4.20(12H), 6.30-6.70(4H), 7.30-7.80(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0266] [Example 20] The compound represented by the above formula (T) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i A compound represented by CF2CH2OH (where h, representing the average degree of polymerization, is 3.2, and i, representing the average degree of polymerization, is 3.2) (number average molecular weight 700, molecular weight distribution 1.1) was reacted with 4-bromo-1-butene, and then m-chloroperbenzoic acid was added to obtain an intermediate represented by formula (24).

[0267] The same procedure as in Example 16 was followed, except that the compound represented by formula (24) was used instead of the compound represented by formula (23) in Example 16, to obtain 4.32 g of compound (T) (wherein Rf1 in formula (T) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2).

[0268] [ka] (In formula (24), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 3.2, and i, which also indicates the average degree of polymerization, represents 3.2.)

[0269] The obtained compound (T) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(4H), 1.90-2.05(4H), 3.40-4.00(28H), 4.10-4.20(12H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0270] [Example 21] The compound represented by formula (U) above was obtained by the method described below. In the process of synthesizing the compound represented by formula (15), the same procedure as in Example 16 was performed except that the compound represented by formula (7-1b) was used instead of the compound represented by formula (7-1a), and 4.65 g of compound (U) (wherein Rf1 in formula (U) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0271] The obtained compound (U) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(40H), 4.10-4.20(12H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0272] [Example 22] The compound represented by formula (V) above was obtained by the method shown below. In the process of synthesizing the compound represented by formula (15), the same procedure as in Example 16 was performed except that the compound represented by formula (7-1c) was used instead of the compound represented by formula (7-1a), and 4.41 g of compound (V) (wherein Rf1 in formula (V) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0273] The obtained compound (V) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.20-1.80(4H), 1.90-2.05(4H), 3.40-4.00(28H), 4.10-4.20(12H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0274] [Example 23] The compound represented by the above formula (W) was obtained by the method shown below. In the step of reacting the compound represented by formula (20) with the compound represented by formula (16), the same procedure as in Example 11 was performed, except that an intermediate obtained by reacting the compound represented by formula (15) with the compound represented by formula (23) was used instead of the compound represented by formula (16), and 4.11 g of compound (W) (wherein Rf1 in formula (W) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0275] The obtained compound (W) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(2H), 3.40-4.00(31H), 4.10-4.20(12H), 6.30-6.70(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0276] [Example 24] The compound represented by formula (X) above was obtained by the method shown below. The same procedure as in Example 23 was followed, except that the compound represented by formula (21) was used instead of the compound represented by formula (20), and 4.31 g of compound (X) (wherein Rf1 in formula (X) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 3.2, and i, which indicates the average degree of polymerization, also represents 3.2) was obtained.

[0277] The obtained compound (X) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.90-2.05(2H), 2.40-2.60(2H), 3.40-4.00(28H), 4.10-4.20(12H), 5.40-6.10(3H), 6.30-6.70(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(13F), -78.5(4F), -80.5(4F), -91.0~-88.5(26F)

[0278] [Example 25] The compound represented by formula (Y) above was obtained by the method described below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of CF2CH2OH, use HOCH2CF2CF2(OCF2CF2CF2). j The same procedure as in Example 16 was followed, except that a compound represented by OCF2CF2CH2OH (where j, representing the average degree of polymerization, is 2.6) was used (number average molecular weight 700, molecular weight distribution 1.1), and 4.89 g of compound (Y) (where Rf2 in formula (Y) is the PFPE chain represented by formula (4-2) above. In the three Rf2s, j, representing the average degree of polymerization, is 2.6) was obtained.

[0279] The obtained compound (Y) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(4H), 3.40-4.00(28H), 4.10-4.20(12H), 6.30-6.70(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(26F), -86.4(8F), -124.3(8F), -130.0~-129.0(13F)

[0280] When compounds (A) to (Y) of Examples 1 to 25 obtained in this way are applied to formula (1), the R is1 (amide group, organic group), R 2 , R 3 , R 3´ , R 4 , R 5 Structure, R 6 The (amide group, organic group) and the number of n are shown in Tables 1 and 2.

[0281] [Table 1]

[0282] [Table 2]

[0283] [Comparative Example 1] The compound represented by the following formula (AA) was synthesized by the method described in Patent Document 1.

[0284] [ka] (In formula (AA), Rf1 is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, is 7.0, and i is 0.)

[0285] [Comparative Example 2] The compound represented by the following formula (AB) was synthesized by the method described in Patent Document 2.

[0286] [ka] (In formula (AB), Rf2 is the PFPE chain represented by formula (4-2) above. For the two Rf2s, j, which indicates the average degree of polymerization, is 4.0.)

[0287] [Comparative Example 3] The compound represented by the following formula (AC) was synthesized by the method described in Patent Document 3.

[0288] [ka] (In formula (AC), Rf2 is the PFPE chain represented by formula (4-2) above. For the three Rf2s, j, which indicates the average degree of polymerization, is 4.0.)

[0289] [Comparative Example 4] The compound represented by the following formula (AD) was synthesized by the method described in Patent Document 4.

[0290] [ka] (In formula (AD), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, both h and i, which indicate the average degree of polymerization, are 4.5.)

[0291] The number-average molecular weight (Mn) of the compounds obtained in Examples 1-25 and Comparative Examples 1-4 was measured using the method described above. The results are shown in Table 3.

[0292] Next, lubricating layer-forming solutions were prepared using the compounds obtained in Examples 1-25 and Comparative Examples 1-4 by the method described below. Then, using the obtained lubricating layer-forming solutions, a lubricating layer was formed on the magnetic recording medium by the method described below, obtaining the magnetic recording media of Examples 1-25 and Comparative Examples 1-4.

[0293] "Lubricant layer forming solution" The compounds obtained in Examples 1-25 and Comparative Examples 1-4 were each dissolved in Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals), a fluorine-based solvent, and then diluted with Bartrell XF to a film thickness of 9.0 Å to 9.5 Å when applied to a protective layer, to prepare a lubricating layer forming solution.

[0294] "Magnetic recording medium" A magnetic recording medium was prepared by sequentially layering an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon. The lubricating layer-forming solutions of Examples 1-25 and Comparative Examples 1-4 were applied to the protective layer of the magnetic recording medium, which had each layer up to the protective layer formed, by the dipping method. The dipping method was performed under the following conditions: dipping speed of 10 mm / sec, dipping time of 30 sec, and withdrawal speed of 1.2 mm / sec. Subsequently, the magnetic recording medium coated with the lubricating layer-forming solution was placed in a constant temperature bath, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent from the lubricating layer-forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0295] (Film thickness measurement) The thickness of the lubricating layer in the magnetic recording media of Examples 1-25 and Comparative Examples 1-4 obtained in this manner was measured using FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Table 3.

[0296] Next, the magnetic recording media of Examples 1 to 25 and Comparative Examples 1 to 4 were subjected to the following abrasion resistance tests, chemical resistance tests, and corrosion resistance tests. (Abrasion resistance test) Using a pin-on-disk type friction and wear tester, a 2 mm diameter alumina ball was slid across the lubricating layer of a magnetic recording medium at a load of 40 gf and a sliding speed of 0.25 m / sec to measure the coefficient of friction on the surface of the lubricating layer. The sliding time until the coefficient of friction on the surface of the lubricating layer rapidly increased was then measured. The sliding time until the coefficient of friction rapidly increased was measured four times for each lubricating layer of the magnetic recording medium, and the average value (time) was used as an indicator of the wear resistance of the lubricant coating.

[0297] The results for magnetic recording media using the compounds of Examples 1 to 25 and Comparative Examples 1 to 4 are shown in Table 3. The evaluation of wear resistance by sliding time until the coefficient of friction rapidly increases was performed as follows. ◎(Excellent): 650sec or more ○ (Good): 550 seconds or more, less than 650 seconds △ (Acceptable): 450 seconds or more, less than 550 seconds × (Not allowed): Less than 450 seconds

[0298] Furthermore, the time it takes for the coefficient of friction to increase rapidly can be used as an indicator of the wear resistance of the lubricating layer for the following reason: The lubricating layer of a magnetic recording medium wears down as the recording medium is used, and when the lubricating layer is completely gone due to wear, the contacts and the protective layer come into direct contact, causing the coefficient of friction to increase rapidly. This time until the coefficient of friction increases rapidly is thought to correlate with the results of friction tests.

[0299] (Chemical resistance testing) The contamination of magnetic recording media by environmental substances that generate pollutants under high-temperature conditions was investigated using the method described below. Si ions were used as the environmental substance, and the amount of Si adsorbed was measured as the amount of pollutant generated by the environmental substance that contaminates the magnetic recording media.

[0300] Specifically, the magnetic recording media under evaluation were kept in a high-temperature environment of 85°C and 0% humidity for 240 hours in the presence of siloxane-based Si rubber. Next, the amount of Si adsorbed on the surface of the magnetic recording media was analyzed and measured using secondary ion mass spectrometry (SIMS), and the degree of contamination by Si ions was evaluated as the amount of Si adsorbed. The evaluation of the amount of Si adsorbed was based on the following evaluation criteria, using the result of Comparative Example 1 as a baseline of 1.00. The results are shown in Table 3.

[0301] "Evaluation Criteria" ◎(Excellent): Si adsorption amount is less than 0.70 ○ (Good): Si adsorption amount is 0.70 or more and less than 0.90 △ (Acceptable): Si adsorption amount is 0.90 or more and less than 1.10 × (Not allowed): Si adsorption amount is 1.10 or higher

[0302] (Corrosion resistance test) Magnetic recording media were exposed to conditions of 85°C and 90% relative humidity for 48 hours. Subsequently, the number of corroded areas on the magnetic recording media was counted using an optical surface analyzer (Candela 7140, KLA-Tencor Co., Ltd.) and evaluated based on the following criteria. The results are shown in Table 3. "Evaluation Criteria" ◎(Excellent): Less than 150 ○ (Good): 150 or higher, less than 250 △ (Acceptable): 250 or more, less than 1000 ×(Not allowed): 1000 or more

[0303] [Table 3]

[0304] As shown in Table 3, the magnetic recording media of Examples 1 to 25 received an evaluation of ◎ (Excellent) or ○ (Good) in all evaluation items. From this, it was confirmed that the lubricating layers of the magnetic recording media of Examples 1 to 25 have good wear resistance and chemical resistance, and have a high corrosion suppression effect on the magnetic recording media.

[0305] In particular, the lubricating layers of the magnetic recording media in Examples 1-4, 9, 10, 14-18, 20, 22, and 25, using compounds (A)-(D), (I), (J), (N)-(R), (T), (V), and (Y), exhibited good wear resistance. In the group of compounds used in the above examples, R 2 and R 5 If the number of hydroxyl groups contained in is equal and n is 1, then R 4 Centered at, and when n is 2, R in the center of the molecule 3’ It has a symmetrical structure centered on [a specific point]. As a result, it is easy to wet and spread uniformly on the protective layer, and the resulting good coverage is thought to have led to better abrasion resistance.

[0306] Furthermore, compounds (A) to (D), (I), (J), (N) to (R), (T), (V), and (Y) are all R 1 and R 6Since the compound is of formula (6-1) or formula (6-2) and contains a linear aliphatic amide, it has high fluidity. For this reason, the magnetic recording media of Examples 1-4, 9, 10, 14-18, 20, 22, and 25 have high restorative power, meaning that even if a part of the lubricating layer deforms due to wear and the fluorine-containing ether compound in the lubricating layer moves to another location, it will return to its original position. As a result, it is presumed that particularly excellent wear resistance was obtained.

[0307] Furthermore, the magnetic recording media of Examples 1-4, 9, 10, 14-18, 20, 22, and 25 are R 1 and R 6 Equation (6-1) is, R 2 and R 5 Compared to the magnetic recording media of Examples 7, 8, and 21, which used compounds (G), (H), and (U) whose total number of hydroxyl groups is 3 or more, the abrasion resistance was better. This is because compounds (A) to (D), (I), (J), (N) to (R), (T), (V), and (Y) are R 2 and R 5 Since the total number of hydroxyl groups contained in this compound is 2, compared to compounds with a total of 3 or more hydroxyl groups, there are fewer hydroxyl groups involved in the adsorption between the lubricating layer and the protective layer, and the molecular fluidity is higher, which is thought to be the reason why the aforementioned repair ability is higher.

[0308] Also, R 1 Equation (6-1) is, R 6 The magnetic recording media of Examples 12, 13, and 24, using compounds (L), (M), and (X) in which the group is an allyl group or a phenyl group, exhibited good wear resistance. This is because R 1 The linear aliphatic amide present in provides adequate adhesion to the protective layer, and R does not have amide bonds. 6 This is thought to be due to the imparting of fluidity to the fluorine-containing ether compound.

[0309] Also, R in equation (1) 1 and R 6The magnetic recording media of Examples 5, 6, and 19, using compounds (E), (F), and (S) whose compound is either formula (6-3) or formula (6-4), exhibited a Si adsorption amount of less than 0.70, good chemical resistance, and good corrosion resistance. This is presumed to be due to the following reasons.

[0310] Compounds (E), (F), and (S) are R 1 and R 6 Because it has a relatively rigid aromatic amide, the motion of the molecules is restricted to some extent. For this reason, a lubricating layer using compounds (E), (F), and (S) is, for example, R 1 and R 6 Compared to the case where the compound has an aliphatic amide, R 1 and R 6 The amide that it possesses, and R 2 and R 5 The hydroxyl groups present have an extremely small ability to inhibit the interaction between each other and the protective layer. Therefore, R 1 and R 6 The amide that it possesses, and R 2 and R 5 It is presumed that the hydroxyl groups present in each compound are likely to be involved in binding to active sites on the protective layer.

[0311] Also, the R of compounds (E), (F), and (S) 1 and R 6 is, sp 2 It broadly possesses a planar structure consisting of carbon, oxygen, and nitrogen with hybrid orbitals, ranging from aromatic rings to amide skeletons. Therefore, the R of compounds (E), (F), and (S) 1 and R 6 The interaction between the aromatic amide and the protective layer is R 1 and R 6 Compared to the interaction between the aliphatic amide and the protective layer, this is presumed to be more robust. Furthermore, compounds (E), (F), and (S) are R 2 and R 5 If the number of hydroxyl groups contained in is equal and n is 1, then R 4 Centered at, and when n is 2, R in the center of the molecule 3’It has a symmetrical structure centered on [a specific point]. Therefore, it is thought that it can be easily wetted and spread uniformly on the protective layer, resulting in good coverage.

[0312] Thus, in the magnetic recording media of Examples 5, 6, and 19, the number of polar groups not involved in the bonding between the lubricating layer and the active sites on the protective layer is small, and the interaction between the aromatic amide and the protective layer is moderately strong. Therefore, it is thought that the attraction of environmental substances that generate pollutants by polar groups not involved in the bonding between the lubricating layer and the active sites on the protective layer is suppressed, resulting in particularly good chemical resistance. Furthermore, in the magnetic recording media of Examples 5, 6, and 19, R 1 and R 6 The introduction of aromatic rings results in a lubricating layer containing fluorine-containing ether compounds that exhibits excellent hydrophobicity. Therefore, the intrusion of water, which causes corrosion of magnetic recording media, is effectively inhibited, resulting in particularly superior corrosion resistance.

[0313] R in equation (1) 2 Equation (2-2) is a structure in which one methylene group is added to the glycerol skeleton (-OCH2CH(OH)CH2O-), and R 5 In the magnetic recording media of Examples 9 and 22, which used compounds (I) and (V) of formula (2-4), which have a structure in which one methylene group is added to the glycerin skeleton, good corrosion resistance was observed. Also, the two R's in equation (1) 4 However, the magnetic recording medium of Example 20, which used compounds (T) of formulas (3-2) and (3-3), which have a structure in which one methylene group is added to the glycerin skeleton, exhibited good corrosion resistance.

[0314] Compounds (I), (T), and (V) are R 4 Or, R 2 and R 5This compound has a structure in which one methylene group is added to the glycerin backbone. As a result, the lubricating layer containing the fluorine-containing ether compound becomes highly hydrophobic, effectively preventing water from penetrating and causing corrosion of the magnetic recording medium. For this reason, it is believed that particularly excellent corrosion resistance was obtained in the magnetic recording media of Examples 9, 20, and 22.

[0315] In contrast, the magnetic recording medium in Comparative Example 1, which used a compound (AA) having a glycerin structure in the center of a chain-like structure, with a perfluoropolyether chain and a terminal group having two hydroxyl groups bonded to each side in that order, showed a "△ (acceptable)" rating in all tests for abrasion resistance, chemical resistance, and corrosion resistance. Furthermore, in Comparative Example 2, a magnetic recording medium using compound (AB) in which an 8-carbon alkyl chain with two hydroxyl groups was placed in the center of the chain structure, and a perfluoropolyether chain and terminal groups with two hydroxyl groups were bonded to each side in that order, the abrasion resistance test result was "△ (acceptable)", and the chemical resistance and corrosion resistance test results were "× (unacceptable)".

[0316] This is thought to be because, in the magnetic recording media of Comparative Examples 1 and 2, the strong interaction between the hydroxyl groups in compound (AA) or compound (AB) and the protective layer resulted in excessive adhesion between the lubricating layer and the protective layer, impairing the fluidity of the lubricating layer and leading to insufficient wear resistance. Furthermore, in the lubricating layers of the magnetic recording media of Comparative Examples 1 and 2, there are many hydroxyl groups in compound (AA) or compound (AB) that are not involved in bonding with the active sites on the protective layer. As a result, Si and / or water are more likely to be mixed between the lubricating layer and the protective layer, which is thought to have resulted in insufficient chemical resistance and corrosion resistance.

[0317] Furthermore, in Comparative Example 3, a magnetic recording medium using a compound (AC) having a skeleton consisting of three perfluoropolyether chains linked via an alkyl chain having two hydroxyl groups, with a divalent linking group having one hydroxyl group at each end and a methoxyphenyl group bonded in that order, the test results for abrasion resistance, chemical resistance, and corrosion resistance were all "△ (acceptable)".

[0318] In compound (AC), an 8-carbon alkyl chain, each having two hydroxyl groups, is positioned at both ends of a perfluoropolyether chain located in the center of the chain structure. Therefore, the lubricating layer in the magnetic recording medium of Comparative Example 3 is highly hydrophilic, making it susceptible to water contamination. This is thought to result in insufficient corrosion resistance. Furthermore, in compound (AC), methoxyphenyl groups with poor adsorption capacity are positioned at both ends of the molecule. As a result, in the magnetic recording medium of Comparative Example 3, the adhesion of the lubricating layer is insufficient, creating gaps between the protective layer and the lubricating layer into which Si can enter, or the protective layer may become exposed. Consequently, it is thought that the chemical resistance and wear resistance became insufficient.

[0319] Furthermore, in Comparative Example 4, a magnetic recording medium using a compound (AD) in which terminal groups having amide bonds are positioned at both ends of a perfluoropolyether chain located in the center of a chain-like structure, via linking groups having hydroxyl groups, the chemical resistance test result was "△ (acceptable)" and the corrosion resistance test result was "× (unacceptable)". Compound (AD) does not have a structure containing a polar group in the center of its chain-like structure. Therefore, in the lubricating layer of the magnetic recording medium in Comparative Example 4, only the ends of the compound (AD) molecule are in close contact with the protective layer, while the central part of the chain-like structure is separated from the protective layer. As a result, Si and / or water are easily mixed between the protective layer and the lubricating layer, which is presumed to be the reason why the chemical resistance and corrosion resistance are inferior to those of the examples. [Industrial applicability]

[0320] By using a lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has excellent adhesion, good chemical resistance and wear resistance, and a high corrosion suppression effect on magnetic recording media, even when it is thin. The fluorine-containing ether compound can be suitably used as a material for lubricants for magnetic recording media. [Explanation of Symbols]

[0321] 10...Magnetic recording medium, 11...Substrate, 12...Adhesion layer, 13...Soft magnetic layer, 14...First underlayer, 15...Second underlayer, 16...Magnetic layer, 17...Protective layer, 18...Lubricating layer.

Claims

1. A fluorine-containing ether compound characterized by being represented by the following formula (1). R １ -R ２ -CH ２ -R ３ [-CH ２ -R ４ -CH ２ -R ３’ ] ｎ -CH ２ -R ５ -R ６ (1) (In equation (1), n ​​is 2; R ３ and R ３’ R is one of the perfluoropolyether chains selected from those represented by the following formulas (4-1) to (4-4); R ３ and two R ３’ They may be partially or entirely the same, or they may be different; R ４ R is a linking group represented by one of the following formulas (3-1) to (3-3); two R ４ They may be the same or different; R ２ R is a linking group represented by the following formula (2-1) or (2-2); ５ R is a linking group represented by the following formula (2-3) or (2-4); １ and R ６ R ２ or R ５ A terminal group bonded to the terminal oxygen atom of the , which may be the same or different; R １ and R ６ (These are organic groups having 1 to 50 carbon atoms, and at least one of them is one of the organic groups represented by the following formulas (6-1) to (6-12).) -CF ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (4-1) (In formula (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｊ -OCF ２ CF ２ - (4-2) (In formula (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (4-3) (In formula (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20; w7 and w10 are CF ２ This represents the average number of units, each independently representing 1 to 2. 【Chemistry 1】 (In equation (2-1), p1 represents an integer between 1 and 3.) (In equation (2-2), q1 represents an integer between 2 and 4.) (In equation (2-3), p2 represents an integer between 1 and 3.) (In equation (2-4), q2 represents an integer between 2 and 4.) 【Chemistry 2】 (In equation (3-2), r is an integer between 2 and 4.) (In equation (3-3), s is an integer between 2 and 4.) 【Transformation 3】 (In equation (6-1), t represents an integer between 0 and 7.) (In equation (6-2), u represents an integer from 0 to 7.) (The dotted lines in equations (6-1) to (6-12) represent R in equation (1) ２ or R ５ (This is a bonding hand that connects to [another hand].)

2. R in formula (1) １ and R ６ The fluorine-containing ether compound according to claim 1, wherein the organic group is one of the organic groups represented by formulas (6-1) to (6-12).

3. R in formula (1) ３ and two R ３’ They are all the same, R １ -R ２ - and R ６ -R ５ - The fluorine-containing ether compound according to claim 1 or claim 2, wherein - is the same as -.

4. A fluorine-containing ether compound according to claim 1 or claim 2, wherein the number average molecular weight is in the range of 500 to 10,000.

5. A lubricant for magnetic recording media, characterized by containing the fluorine-containing ether compound described in claim 1 or claim 2.

6. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, A magnetic recording medium characterized in that the lubricating layer contains the fluorine-containing ether compound described in claim 1 or claim 2.

7. The magnetic recording medium according to claim 6, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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