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

Abstract

Provided is a fluorine-containing ether compound represented by the following formula. Formula: R1-CH2-R2-CH2-R3-CH2-R4-CH2-R5 (wherein: R3 represents a divalent organic group containing an alicyclic structure having 3-13 carbon atoms and at least one polar group and containing no perfluoropolyether chain; R2 and R4 represent a perfluoropolyether chain; and R1 and R5 represent a terminal group which contains two or three polar groups and in which the individual polar groups are bonded to different carbon atoms and the carbon atoms, to which the polar groups are bonded, are bonded to one another via a linkage group including a carbon atom to which no polar group is bonded).

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2020-197545, filed on November 27, 2020, the contents of which are incorporated herein by reference. [Background technology]

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

[0003] However, simply providing a protective layer on the recording layer does not provide sufficient durability for the magnetic recording medium. Therefore, a lubricant is applied to the surface of the protective layer to form a lubricating layer with a thickness of approximately 0.5 to 3 nm. The lubricating layer improves the durability and protective power of the protective layer and prevents contaminants from penetrating into the magnetic recording medium. Lubricants used in forming the lubricating layer of magnetic recording media include fluoropolymers with a repeating structure containing -CF2-. Proposed fluoropolymers are compounds with polar groups, such as hydroxyl groups, at the terminals linked together via saturated alicyclic structures.

[0004] For example, Patent Document 1 discloses a fluorine-containing ether compound in which three fluorine-containing ether groups having polar groups at their terminals are connected to a trivalent atom or a trivalent atomic group. Patent Document 2 discloses a fluorine-containing ether compound having an alicyclic hydrocarbon near the center and a polar group at the end. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 159232 [Patent Document 2] International Publication No. 2013 / 054393 Summary of the Invention [Problem to be solved by the invention]

[0006] In magnetic recording and reproducing devices, there is a demand for an even smaller flying height of the magnetic head, which in turn requires a thinner lubricating layer in the magnetic recording medium. However, when the thickness of the lubricating layer is reduced, the coverage of the lubricating layer tends to decrease, and the chemical resistance of the magnetic recording medium and the wear resistance of the lubricating layer tend to decrease.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluorine-containing ether compound suitable as a material for a lubricant for a magnetic recording medium, which can form a lubricating layer that has excellent chemical resistance and abrasion resistance even when the layer is thin. Another object of the present invention is to provide a lubricant for magnetic recording media, which contains the fluorine-containing ether compound of the present invention. Another object of the present invention is to provide a magnetic recording medium having excellent reliability and durability, which has a lubricating layer containing the fluorine-containing ether compound of the present invention. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems. As a result, the present inventors have found that a fluorine-containing ether compound can be obtained by placing an organic group containing an alicyclic structure having 3 to 13 carbon atoms and at least one polar group at the center of the molecule, and on both sides of the organic group, a perfluoropolyether chain, a methylene group, and an end group having a specific structure containing two or three polar groups, bonded in this order via methylene groups, and have arrived at the present invention. That is, the present invention relates to the following items.

[0009] A first aspect of the present invention provides the following fluorine-containing ether compound: [1] A fluorine-containing ether compound represented by the following formula (1): R 1 -CH2-R 2 -CH2-R 3 -CH2-R 4 -CH2-R 5 (1) (In formula (1), R 3 is a divalent organic group containing an alicyclic structure having 3 to 13 carbon atoms and at least one polar group, and does not contain a perfluoropolyether chain; R 2 and R 4 is a perfluoropolyether chain; R 1 and R 5 is a terminal group containing two or three polar groups, each bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded are connected via a linking group containing a carbon atom to which no polar groups are bonded.

[0010] The compound according to the first aspect of the present invention preferably has the characteristics described in the following items [2] to

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

[11] . [2] R 3 is represented by any one of the following formulas (2-1) to (2-4):

[0011] [ka] (In formula (2-1), X represents an alicyclic structure having 3 to 13 carbon atoms; and Y represents —O—, —NH—, or —CH—.) (In formula (2-2), X' is an alicyclic structure having 3 to 13 carbon atoms and has at least one substituent containing a polar group; Y represents -O-, -NH-, or -CH2-.) (In formula (2-3), X represents an alicyclic structure having 3 to 13 carbon atoms; and Y represents —O—, —NH—, or —CH—.) (In formula (2-4), X represents an alicyclic structure having 3 to 13 carbon atoms; Y represents —O—, —NH—, or —CH—.)

[0012] [3] The fluorine-containing ether compound according to [2], wherein Y in the formulae (2-1) to (2-4) is —O—. [4] R 3 The fluorine-containing ether compound according to any one of [1] to [3], wherein the alicyclic structure contained in the above is a saturated alicyclic structure.

[0013] [5] R 3 The fluorine-containing ether compound according to any one of [1] to [4], wherein the alicyclic structure contained in is one selected from the group consisting of cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, and adamantane. [6] R 3 The fluorine-containing ether compound according to any one of [1] to [5], wherein at least one polar group contained in is a group containing a polar group selected from the group consisting of a hydroxyl group, an alkoxy group, an amide group, an amino group, a carbonyl group, a carboxy group, a nitro group, a cyano group, and a sulfo group.

[0014] [7] R 2 and the R 4 is any one of the following formulae (4) to (6):

[0022] (1) a fluorine-containing ether compound according to any one of [1] to [6], -CF2O-(CF2CF2O) b -(CF2O) c -CF2- (4) (In formula (4), b and c represent the average degree of polymerization, each independently representing 0 to 30; however, b and c cannot simultaneously be 0.) -CF(CF3)-(OCF(CF3)CF2) d -OCF(CF3)- (5) (In formula (5), d represents the average degree of polymerization and is 0.1 to 30.) -CF2CF2O-(CF2CF2CF2O) e -CF2CF2- (6) (In formula (6), e represents the average degree of polymerization and is 0.1 to 30.)

[0015] [8] R 1 and the R 5 The fluorine-containing ether compound according to any one of [1] to [7], wherein the two or three polar groups contained in each of the above are all hydroxyl groups.

[0016] [9] R 1 and the R 5 is a terminal group of any one of the following formulae (7) to (10):

[0023] (1) A fluorine-containing ether compound according to any one of [1] to [8].

[0017] [ka] (In formula (7), f represents an integer of 1 to 2, and g represents an integer of 1 to 5.) (In formula (8), h represents an integer of 1 to 5.) (In formula (9), i represents an integer of 1 to 5.) (In formula (10), j represents an integer of 1 or 2, and k represents an integer of 1 or 2.)

[0018]

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

[0019]

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

[10] , wherein the compound represented by formula (1) is any one of the compounds represented by the following formulae (A) to (P):

[0020] [ka] (In formula (A), ba1, ca1, ba2, and ca2 represent average degrees of polymerization, ba1 and ba2 represent 0 to 30, and ca1 and ca2 represent 0 to 30; however, ba1 and ca1 cannot be 0 at the same time, and ba2 and ca2 cannot be 0 at the same time.) (In formula (B), bb1, cb1, bb2, and cb2 represent average degrees of polymerization, bb1 and bb2 represent 0 to 30, and cb1 and cb2 represent 0 to 30; however, bb1 and cb1 cannot be 0 at the same time, and bb2 and cb2 cannot be 0 at the same time.) (In formula (C), bc1, cc1, bc2, and cc2 represent average degrees of polymerization, bc1 and bc2 represent 0 to 30, and cc1 and cc2 represent 0 to 30; however, bc1 and cc1 cannot be 0 at the same time, and bc2 and cc2 cannot be 0 at the same time.)

[0021] [ka] (In formula (D), bd1, cd1, bd2, and cd2 represent average degrees of polymerization, bd1 and bd2 represent 0 to 30, and cd1 and cd2 represent 0 to 30; however, bd1 and cd1 cannot be 0 at the same time, and bd2 and cd2 cannot be 0 at the same time.) (In formula (E), be1, ce1, be2, and ce2 represent average degrees of polymerization, be1 and be2 represent 0 to 30, and ce1 and ce2 represent 0 to 30; however, be1 and ce1 cannot be 0 at the same time, and be2 and ce2 cannot be 0 at the same time.) (In formula (F), bf1, cf1, bf2, and cf2 represent average degrees of polymerization, bf1 and bf2 represent 0 to 30, and cf1 and cf2 represent 0 to 30; however, bf1 and cf1 cannot be 0 at the same time, and bf2 and cf2 cannot be 0 at the same time.)

[0022] [ka] (In formula (G), bg1, cg1, bg2, and cg2 represent average degrees of polymerization, bg1 and bg2 represent 0 to 30, and cg1 and cg2 represent 0 to 30; however, bg1 and cg1 cannot be 0 at the same time, and bg2 and cg2 cannot be 0 at the same time.) (In formula (H), bh1, ch1, bh2, and ch2 represent average degrees of polymerization, bh1 and bh2 represent 0 to 30, and ch1 and ch2 represent 0 to 30; however, bh1 and ch1 cannot be 0 at the same time, and bh2 and ch2 cannot be 0 at the same time.) (In formula (I), bi1 and bi2 represent average degrees of polymerization, and bi1 and bi2 represent 0.1 to 30.) (In formula (J), ej1 and ej2 represent the average degree of polymerization, and ej1 and ej2 represent 0.1 to 30.)

[0023] [ka] (In formula (K), bk1, ck1, bk2, and ck2 represent average degrees of polymerization, bk1 and bk2 represent 0 to 30, and ck1 and ck2 represent 0 to 30; however, bk1 and ck1 cannot be 0 at the same time, and bk2 and ck2 cannot be 0 at the same time.) (In formula (L), bl1, cl1, bl2, and cl2 represent average degrees of polymerization, bl1 and bl2 represent 0 to 30, and cl1 and cl2 represent 0 to 30; however, bl1 and cl1 cannot be 0 at the same time, and bl2 and cl2 cannot be 0 at the same time.)

[0024] [ka] (In formula (M), bm1, cm1, bm2, and cm2 represent average degrees of polymerization, bm1 and bm2 represent 0 to 30, and cm1 and cm2 represent 0 to 30; however, bm1 and cm1 cannot be 0 at the same time, and bm2 and cm2 cannot be 0 at the same time.) (In formula (N), bn1, cn1, bn2, and cn2 represent average degrees of polymerization, bn1 and bn2 represent 0 to 30, and cn1 and cn2 represent 0 to 30; however, bn1 and cn1 cannot be 0 at the same time, and bn2 and cn2 cannot be 0 at the same time.) (In formula (O), bo1, co1, bo2, and co2 represent average degrees of polymerization, bo1 and bo2 represent 0 to 30, and co1 and co2 represent 0 to 30; however, bo1 and co1 cannot be 0 at the same time, and bo2 and co2 cannot be 0 at the same time.) (In formula (P), bp1, cp1, bp2, and cp2 represent average degrees of polymerization, bp1 and bp2 represent 0 to 30, and cp1 and cp2 represent 0 to 30; however, bp1 and cp1 cannot be 0 at the same time, and bp2 and cp2 cannot be 0 at the same time.)

[0025] A second aspect of the present invention provides the following lubricant for a magnetic recording medium.

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

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

[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, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of [1] to

[11] . The third aspect of the present invention preferably has the following features.

[14] The magnetic recording medium according to

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

[0026] 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 a magnetic recording medium. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore can form a lubricating layer that has excellent chemical resistance and abrasion resistance even if it is thin. The magnetic recording medium of the present invention has excellent reliability and durability because it is provided with a lubricating layer that has excellent chemical resistance and wear resistance. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic cross-sectional view showing an example of a preferred embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The fluorine-containing ether compound, the lubricant for magnetic recording media (hereinafter sometimes abbreviated as "lubricant"), and the magnetic recording media of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments. For example, the present invention is not limited to the following examples, and additions, omissions, substitutions, and changes can be made to the number, amount, ratio, composition, type, position, material, configuration, and the like, without departing from the spirit of the present invention.

[0029] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2 -CH2-R 3 -CH2-R 4 -CH2-R 5 (1) (In formula (1), R 3 is a divalent organic group containing an alicyclic structure having 3 to 13 carbon atoms and at least one polar group, and does not contain a perfluoropolyether chain; R 2 and R 4 is a perfluoropolyether chain; R 1 and R 5 is a terminal group containing two or three polar groups, each bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded are connected via a linking group containing a carbon atom to which no polar groups are bonded.

[0030] Here, we will explain why, when a lubricating layer is formed on the protective layer of a magnetic recording medium using a lubricant containing the fluorine-containing ether compound of this embodiment, a lubricating layer having excellent chemical resistance and wear resistance can be formed even if it is thin.

[0031] The fluorine-containing ether compound of the present embodiment is a compound represented by the formula (1), 2 and R 4 The PFPE chains have a perfluoropolyether chain (hereinafter sometimes abbreviated as "PFPE chains") represented by the formula: When a lubricant containing a fluorine-containing ether compound is applied to a protective layer to form a lubricating layer, the PFPE chains coat the surface of the protective layer and impart lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer.

[0032] Furthermore, as shown in equation (1), R 2 and R 4 The end (first end) of the PFPE chain represented by 3 and a divalent organic group containing at least one polar group are arranged via a methylene group (—CH2—). 3 The alicyclic structure having 3 to 13 carbon atoms contained in R is suitably bulky, and therefore imparts a suitable fluidity to the molecular structure of the fluorine-containing ether compound represented by formula (1). As a result, in the lubricating layer containing the fluorine-containing ether compound of this embodiment, R 3 A part of the alicyclic structure contained in the protective layer can rise from the protective layer. As a result, the lubricating layer collides with the magnetic head before the magnetic head collides with the protective layer, protecting the protective layer. 3 The alicyclic structure contained in improves the wear resistance of the lubricating layer containing the fluorine-containing ether compound of this embodiment.

[0033] In addition, R shown in equation (1) 3 R is a divalent organic group containing at least one polar group. 3 The polar group contained in R has a pinning effect that prevents the bulky alicyclic structure having 3 to 13 carbon atoms from excessively floating up from the protective layer. 3The polar group contained in contributes to the adhesion between the protective layer to which the lubricant containing the fluorine-containing ether compound of this embodiment is applied and the lubricating layer formed by applying the lubricant.

[0034] Furthermore, as shown in equation (1), R 2 and R 4 R of the PFPE chain represented by 3 The opposite end (second end) contains R 1 and R 5 The terminal group represented by R is arranged via a methylene group (-CH2-). 1 and R 5 The terminal group represented by R contributes to the adhesion between the protective layer to which the lubricant containing the fluorine-containing ether compound of this embodiment is applied and the lubricating layer formed by applying the lubricant. 1 and R 5 The two or three polar groups contained in the terminal group represented by the formula (I) bond the fluorine-containing ether compound and the protective layer together in the lubricating layer containing the fluorine-containing ether compound of this embodiment, thereby exhibiting excellent chemical resistance.

[0035] Also, R 1 and R 5 The two or three polar groups contained in the terminal group represented by the formula (I) are bonded to different carbon atoms, and the carbon atoms to which the polar groups are bonded are bonded via a linking group containing a carbon atom to which no polar group is bonded. 1 and R 5 The two or three polar groups contained in it have an appropriate distance between the polar groups. As a result, R 1 and R 5 The fluorine-containing ether compound having a terminal group represented by the formula: 1 and R 5 In addition, the fluorine-containing ether compound represented by formula (1) is less likely to aggregate than a fluorine-containing ether compound in which at least some of the carbon atoms bonded to polar groups contained in the terminal groups represented by formula (1) are directly bonded to each other. 3 does not contain a perfluoropolyether chain. Therefore, for example, R 3However, it is less likely to aggregate than when it contains perfluoropolyether chains.

[0036] Thus, the fluorine-containing ether compound of this embodiment is difficult to aggregate with other fluorine-containing ether compounds, so it is easy to be arranged in a state of spreading uniformly in the surface direction on the protective layer.Therefore, even if the lubricant containing the fluorine-containing ether compound of this embodiment is thin, it can cover the surface of the protective layer with a high coverage rate, and can form a lubricating layer with excellent chemical resistance.Therefore, the lubricant containing the fluorine-containing ether compound of this embodiment contributes to thinning the lubricating layer (reducing magnetic spacing).

[0037] From the above, it is presumed that the lubricant containing the fluorine-containing ether compound of this embodiment can cover the surface of the protective layer at a high coverage rate even when it is thin, and can form a lubricating layer that has excellent chemical resistance and wear resistance.

[0038] (R 3 (organic group represented by In the fluorinated ether compound of the present embodiment represented by formula (1), R 3 The organic group represented by the formula (I) has an alicyclic structure having 3 to 13 carbon atoms. The number of carbon atoms can be selected arbitrarily within the above range, and may be, for example, 3 to 6, 7 to 9, or 10 to 13. The alicyclic structure having 3 to 13 carbon atoms is preferably a saturated alicyclic structure, since this results in a fluorine-containing ether compound that can provide a lubricating layer with even better wear resistance. The saturated alicyclic structure may be a bridged saturated alicyclic structure. R 3 The saturated alicyclic structure of the fluorine-containing ether compound gives the molecular structure of the fluorine-containing ether compound represented by formula (1) superior fluidity. Therefore, the saturated alicyclic structure portion of the lubricating layer containing the fluorine-containing ether compound is more likely to lift up from the protective layer, and the lifted lubricating layer can effectively protect the protective layer.

[0039] Specifically, the saturated alicyclic structure having 3 to 13 carbon atoms is preferably any one selected from cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, and adamantane. 3 As the alicyclic structure having 3 to 13 carbon atoms in the organic group represented by the formula (I), a saturated alicyclic structure having 4 to 8 carbon atoms is particularly preferred among the above, since it results in a fluorine-containing ether compound that can provide a lubricating layer with even better wear resistance.

[0040] R 3 The number of alicyclic structures having 3 to 13 carbon atoms in the organic group represented by the formula (R) may be one or more. For example, when the number of alicyclic structures is more than one, the number may be 2 to 6, 3 to 5, etc., but is not limited to these examples. 1 When the organic group represented by the formula (R) has a plurality of alicyclic structures having 3 to 13 carbon atoms, some or all of the alicyclic structures may be the same or different from each other. 3 The number of alicyclic structures having 3 to 13 carbon atoms in the organic group represented by the formula (I) is preferably small, and most preferably only one, so that the fluorine-containing ether compounds are less likely to aggregate together.

[0041] R 3 The alicyclic structure having 3 to 13 carbon atoms in the organic group represented by the formula may have one or more substituents. When the alicyclic structure has two or more substituents, some or all of the two or more substituents may be the same, or may be different from each other. When the alicyclic structure having 3 to 13 carbon atoms has a substituent, the number of the substituents can be appropriately determined depending on the type of the alicyclic structure having 3 to 13 carbon atoms, and is not particularly limited. The number of carbon atoms in the substituents is not included in the number of carbon atoms in the alicyclic structure.

[0042] When the alicyclic structure having 3 to 13 carbon atoms has a substituent, the substituent is preferably a substituent having 0 to 10 carbon atoms. When the substituent has 0 to 10 carbon atoms, the substituent of the alicyclic structure does not become a steric hindrance due to the substituent having too many carbon atoms. Therefore, the substituent of the alicyclic structure does not suppress the adsorption force of the lubricating layer to the protective layer, and a lubricating layer with good coating properties can be obtained. The number of carbon atoms in the substituent may be 1 to 8 or may be 2 to 6. The number of carbon atoms in the substituent is more preferably 0 to 5, and even more preferably 0 to 3.

[0043] When the alicyclic structure having 3 to 13 carbon atoms has a substituent, the substituent is preferably a substituent containing a polar group. Specific examples include functional groups selected from the group consisting of hydroxyl groups, alkoxy groups, amide groups, amino groups, carbonyl groups, carboxy groups, nitro groups, cyano groups, and sulfo groups, and alkyl groups having at least one selected from the above functional groups. In the alkyl groups having the above functional groups, the number of carbon atoms in the alkyl group is preferably 1 to 3, and more preferably 2 or 3.

[0044] Among these substituents, a substituent selected from a hydroxyl group, an amide group, an amino group, a cyano group, or an alkyl group or an alkoxy group having any one of these functional groups is more preferred.Specific examples of the substituent include -OH, -CH2OH, -CH2CH2OH, -CH2CH2CH2OH; -OCH3, -OCH2CH3, -OCH2CH2CH3; -OCH2OH, -OCH2CH2OH, -OCH2CH2CH2OH; -CONH2, -CH2CONH2, -CH2CH2CONH2; -NH2, -CH2NH2, -CH2CH2NH2, -CH2CH2CH2NH2; -CN, -CH2CN, -CH2CH2CN, etc.

[0045] Among these substituents, those selected from hydroxyl, amino, and amide groups, and alkyl or alkoxy groups having any one of these polar groups are particularly preferred, since they are polar groups capable of forming hydrogen bonds. When the alicyclic structure having 3 to 13 carbon atoms has one or more substituents selected from these, the interaction between the substituent and the protective layer disposed in contact with the lubricating layer containing the fluorine-containing ether compound further increases the adsorption force of the lubricating layer to the protective layer. As a result, the lubricant containing the fluorine-containing ether compound has even better chemical resistance and wear resistance, which is preferable.

[0046] In particular, when an alicyclic structure having 3 to 13 carbon atoms has a substituent, the substituent is preferably a substituent in which a carbon atom to which a polar group in the substituent is bonded is bonded to the alicyclic structure via a linking group containing an ether bond and a carbon atom. Examples of such a substituent include an alkoxy group having a polar group at the terminal, and specific examples include -OCH2CH2OH and -OCH2CH2CH2OH. When a carbon atom to which a polar group in the substituent is bonded is bonded to the alicyclic structure via a linking group containing an ether bond and a carbon atom, R 3 In this case, the distance between the alicyclic structure and the polar group in the substituent is sufficiently ensured by the linking group having appropriate flexibility, resulting in an appropriate pinning effect of the alicyclic structure by the polar group in the substituent, resulting in a fluorine-containing ether compound capable of forming a lubricating layer with even more excellent wear resistance.

[0047] In the fluorine-containing ether compound represented by formula (1), R 3 The organic group represented by R contains at least one polar group. 3 The polar group contained in R 2 and R 4 It may be bonded to a linking group that connects the -CH2- (methylene group) bonded to the perfluoropolyether chain represented by the formula (I) to the alicyclic structure, or it may be a substituent possessed by the alicyclic structure. 3 is R 2 and R 4It is preferable that the alicyclic structure has both a polar group bonded to a linking group that bonds the —CH 2 — bonded to the —CH 2 — to the alicyclic structure, and a polar group as a substituent on the alicyclic structure.

[0048] R 3 At least one polar group contained in R is preferably a group containing a polar group selected from the group consisting of a hydroxyl group, an alkoxy group, an amide group, an amino group, a carbonyl group, a carboxy group, a nitro group, a cyano group, and a sulfo group. 3 Among the above, R 3 At least one polar group contained in is preferably a group containing a hydroxyl group or an amino group, and more preferably a group containing a hydroxyl group.

[0049] R 3 The number of polar groups contained in R is preferably 1 to 3, and more preferably 2 to 3. When the number of polar groups is 3 or less, R 3 The fluidity of the entire molecule due to the inclusion of an alicyclic structure is 3 The pinning effect of the polar group contained in R is not too strong and is therefore not weakened more than necessary. In other words, the pinning effect is not too strong. 3 When contains two or more polar groups, the polar groups may be of different types or may all be the same, and it is preferable that all are hydroxyl groups.

[0050] In formula (1), R 3 The organic group represented by formula (1) does not contain a perfluoropolyether chain. 3 As a result, the fluorine-containing ether compound represented by formula (1) is less likely to aggregate than the fluorine-containing ether compound represented by formula (1) 3 Compared with fluorine-containing ether compounds containing perfluoropolyether chains, these are preferred because they tend to be arranged in a state where they spread uniformly in the surface direction on the protective layer, and therefore have excellent chemical resistance and abrasion resistance.

[0051] In the fluorine-containing ether compound represented by formula (1), R 3 The organic group represented by is connected to R via -CH2- (methylene group). 2 and R 4 From the viewpoint of ease of synthesis, R 2 and R 4 The methylene group bonded to R 3 Preferably, the carbon atom, oxygen atom, or nitrogen atom contained in R 3 It is more preferable that the bond is made to an oxygen atom or a nitrogen atom contained in R 2 and R 4 The methylene group bonded to R 3 It is preferable that the fluorine-containing ether compound represented by formula (1) is bonded to an oxygen atom contained in the compound. In this case, the molecular structure of the fluorine-containing ether compound represented by formula (1) has appropriate flexibility. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has even better adhesion to the protective layer.

[0052] R shown in equation (1) 3 is preferably represented by any one of the following formulas (2-1) to (2-4): In this case, the lubricating layer containing the fluorine-containing ether compound will have even more excellent chemical resistance and wear resistance.

[0053] [ka] (In formula (2-1), X represents an alicyclic structure having 3 to 13 carbon atoms; and Y represents —O—, —NH—, or —CH—.) (In formula (2-2), X' is an alicyclic structure having 3 to 13 carbon atoms and has at least one substituent containing a polar group; Y represents -O-, -NH-, or -CH2-.) (In formula (2-3), X represents an alicyclic structure having 3 to 13 carbon atoms; and Y represents —O—, —NH—, or —CH—.) (In formula (2-4), X represents an alicyclic structure having 3 to 13 carbon atoms; Y represents —O—, —NH—, or —CH—.)

[0054] In the above formulas (2-1) to (2-4), Y represents -O-, -NH-, or -CH2-. Y is preferably -O- (ether bond) because it is easy to procure raw materials for the fluorinated ether compound and the molecular structure of the fluorinated ether compound has appropriate fluidity. In the above formulas (2-1) to (2-4), X and X' contain the above-mentioned alicyclic structure having 3 to 13 carbon atoms. That is, X and X' in these formulas may have the above-mentioned alicyclic structure having 3 to 13 carbon atoms and can have the characteristics thereof. The bonding position of Y in the alicyclic structures X and X' in the formulae (2-1) to (2-4) is not particularly limited, and Y may be bonded to any carbon atom constituting the alicyclic structures X and X'.

[0055] R 3 is any one of formulas (2-1), (2-3) and (2-4), R 3 Alicyclic structure X and R 3 The carbon atom to which the hydroxyl group in R is bonded is bonded via a linking group containing Y and a carbon atom. 3 The distance between the alicyclic structure X and the hydroxyl group in R is sufficiently secured by the linking group having appropriate flexibility. 3 The pinning effect of the alicyclic structure X due to the hydroxyl groups in the fluorine-containing ether compound is sufficiently obtained, and the compound is capable of forming a lubricating layer with even greater wear resistance.

[0056] R 3 When R is the formula (2-2), X' is the above-mentioned alicyclic structure having 3 to 13 carbon atoms and has at least one substituent containing a polar group. 3 When R is the formula (2-2), the alicyclic structure X′ contains at least one substituent containing a polar group, and may further contain a substituent not containing a polar group. 3 is the formula (2-2), the number of substituents containing polar groups in the alicyclic structure X′ is3 is the number of polar groups contained in R 3 When the formula is (2-2), the number of substituents containing a polar group in the alicyclic structure X′ is at least one, preferably 1 to 3, and more preferably 1 or 2.

[0057] The polar group-containing substituent of the alicyclic structure X' in formula (2-2) is preferably a hydroxyl group-containing substituent, specifically, preferably any one selected from -OH, -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -OCH2OH, -OCH2CH2OH, and -OCH2CH2CH2OH. When the polar group-containing substituent of the alicyclic structure X' in formula (2-2) is any one selected from these, a pinning effect that prevents the bulky alicyclic structure X' contained in the lubricating layer containing a fluorine-containing ether compound from completely lifting off from the protective layer can be more effectively obtained.

[0058] (R 2 and R 4 (perfluoropolyether chain represented by In the fluorine-containing ether compound represented by formula (1), R 2 and R 4 is a perfluoropolyether chain (PFPE chain). In the fluorine-containing ether compound represented by formula (1), the PFPE chain contained in the molecule is R 2 and R 4 That is, it is preferable that R in formula (1) 1 and R 5 It is preferable that the fluorine-containing ether compound does not contain a PFPE chain. When the molecule contains only two PFPE chains, the fluorine-containing ether compounds are less likely to aggregate with each other. Therefore, in a lubricating layer containing the fluorine-containing ether compound represented by formula (1), the fluorine-containing ether compound is more likely to be arranged in a state where it spreads uniformly in the surface direction on the protective layer, which is preferable.

[0059] R 2 and R 4The PFPE chain represented by the following formula is not particularly limited and can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound. R 2 and R 4 may be the same or different. 2 and R 4 is the same perfluoropolyether chain, it is preferable because the synthesis of the fluorine-containing ether compound is easy.

[0060] The PFPE chain may be, for example, a structure represented by the following formula (Rf) derived from a polymer or copolymer of perfluoroalkylene oxide. -(CF2) w1 O(CF2O) w2 (CF2CF2O) w3 (CF2CF2CF2O) w4 (CF2CF2CF2CF2O) w5 (CF2) w6 - (Rf) (In formula (Rf), w2, w3, w4, and w5 represent an average degree of polymerization and each independently represent 0 to 30; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 represent an average value indicating the number of -CF2- and each independently represent 1 to 3; there are no particular limitations on the arrangement order of repeating units in formula (Rf).) In formula (Rf), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 30, preferably 0 to 20, and more preferably 0 to 15. In formula (Rf), w1 and w6 are average values ​​indicating the number of -CF2- groups, and each independently represents 1 to 3. w1 and w6 are determined depending on the structure of the repeating units located at the ends of the chain structure in the polymer represented by formula (Rf), etc. In formula (Rf), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular restrictions on the arrangement order of the repeating units in formula (Rf). There are also no particular restrictions on the number of types of repeating units in formula (Rf).

[0061] The PFPE chain preferably has a structure represented by the following formula (Rf-1), for example. -(CF2) w7 O-(CF2CF2O) w8 -(CF2CF2CF2O) w9 -(CF2) w10 - (Rf-1) (In formula (Rf-1), w8 and w9 represent the average degree of polymerization, each independently representing 0.1 to 30; w7 and w10 represent the average value representing the number of -CF2-, each independently representing 1 to 2.) The sequence of the repeating units (CFCFO) and (CFCFCFO) in formula (Rf-1) is not particularly limited. Formula (Rf-1) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CFCFO) and (CFCFCFO). In formula (Rf-1), w8 and w9, which represent the average degree of polymerization, each independently represent 0.1 to 30, preferably 0.1 to 20, and more preferably 1 to 15. In formula (Rf-1), w7 and w10 represent the average number of -CF- groups and each independently represent 1 to 2. w7 and w10 are determined depending on the structure of the repeating units located at the ends of the chain structure in the polymer represented by formula (Rf-1).

[0062] R 2 and R 4 It is also preferable that R is any one of the following formulas (4) to (6): 2 and R 4 When the formula (4) is any one of the formulas (4) to (6), the synthesis of the fluorine-containing ether compound is easy, which is preferable. Also, R 2 and R 4When R is any one of formulas (4) to (6), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the perfluoropolyether chain is appropriate. This results in a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage. In addition, R 2 and R 4 When is any one of the formulas (4) to (6), the resulting fluorine-containing ether compound provides a lubricating layer having good chemical resistance.

[0063] -CF2O-(CF2CF2O) b -(CF2O) c -CF2- (4) (In formula (4), b and c represent the average degree of polymerization, each independently representing 0 to 30; however, b and c cannot simultaneously be 0.)

[0064] In formula (4), there is no particular restriction on the arrangement order of the repeating units (CF2-CF2-O) and (CF2-O). In formula (4), the number b of (CF2-CF2-O) and the number c of (CF2-O) may be the same or different. However, b and c cannot be 0 at the same time. Formula (4) may contain any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CF2-CF2-O) and (CF2-O).

[0065] R in Equation (1) 2 and / or R 4 When R is represented by formula (4), b, which indicates the average degree of polymerization, is 0 to 30, preferably 1 to 20, and more preferably 1 to 15. b may be 1 to 10, or 1 to 5. In formula (1), R 2 and / or R 4When formula (4) is given, c, which indicates the average degree of polymerization, is 0 to 30, preferably 0 to 20, and more preferably 0 to 15. c may be 1 to 10, or 1 to 5. When c is 0, b is preferably 1 to 17.

[0066] -CF(CF3)-(OCF(CF3)CF2) d -OCF(CF3)- (5) (In formula (5), d represents the average degree of polymerization and is 0.1 to 30.) In formula (5), when d, which represents the average degree of polymerization, is 0.1 to 30, the number average molecular weight of the fluorinated ether compound of the present embodiment tends to fall within a preferred range. d is preferably 1 to 30, more preferably 2 to 20, and even more preferably 3 to 10.

[0067] -CF2CF2O-(CF2CF2CF2O) e -CF2CF2- (6) (In formula (6), e represents the average degree of polymerization and is 0.1 to 30.) In formula (6), when e, which represents the average degree of polymerization, is 0.1 to 30, the number average molecular weight of the fluorinated ether compound of this embodiment tends to fall within a preferred range. e is preferably 1 to 20, more preferably 2 to 15, and even more preferably 2 to 8.

[0068] (R 1 and R 5 (end group represented by In the fluorine-containing ether compound represented by formula (1), R 1 and R 5 are terminal groups each containing two or three polar groups, each polar group bonded to a different carbon atom, and the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom not bonded to a polar group. 1 and R 5 It is preferable that the terminal group represented by the formula (I) does not contain a perfluoropolyether chain (PFPE chain).

[0069] The fluorine-containing ether compound represented by formula (1) is R 1 and R 5 Since the number of polar groups contained in each of R is two or three, it is possible to form a lubricating layer with excellent adhesion to the protective layer and a high coverage rate. 1 and R 5 The number of polar groups contained in each of R is preferably two, since this results in a fluorine-containing ether compound that can provide a lubricating layer with even better chemical resistance. 1 and R 5 If the number of polar groups contained in R is too large, the polarity of the fluorine-containing ether compound becomes too high, resulting in low fluidity and a tendency for the wear resistance of the lubricating layer containing the fluorine-containing ether compound to decrease. 1 and R 5 Since the number of polar groups contained in each of the formulas is 2 or 3, it is possible to suppress a decrease in abrasion resistance caused by the fluorine-containing ether compound having too high a polarity.

[0070] R 1 and R 5 Examples of the two or three polar groups in the terminal group represented by the formula (I) include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), and a mercapto group (-SH). The ether bond (-O-) is represented by the formula (I) 1 and R 5 Among the above polar groups, the polar group is preferably a hydroxyl group. 1 The two or three polar groups contained in the terminal group represented by R may be different from each other or may all be the same. 5 The two or three polar groups contained in the terminal group represented by R may be different from each other or may all be the same. 1 and R 5 It is preferred that all of the two or three polar groups in the terminal group represented by the formula: are hydroxyl groups.

[0071] Hydroxyl groups have a strong interaction with the protective layer of the magnetic recording medium, especially with the protective layer made of a carbon-based material. 1and R 5 When some or all of the two or three polar groups in the terminal group represented by the formula (I) are hydroxyl groups, the lubricating layer containing the fluorine-containing ether compound has an even stronger adhesive force to the protective layer, which is preferable.

[0072] R 1 and R 5 Preferably, the terminal group represented by R contains an ether bond. 1 and R 5 In the terminal group represented by the formula (I), two or three polar groups are bonded to different carbon atoms, and the carbon atoms bonded to the polar groups are bonded to a carbon atom not bonded to a polar group via a linking group containing an oxygen atom (-O- (ether bond)). The linking group containing an ether bond is preferably represented by the formula (I), 1 and R 5 When carbon atoms bonded to polar groups are bonded to a carbon atom not bonded to a polar group via a linking group containing an ether bond, a lubricating layer containing this compound is more likely to be adsorbed to a protective layer, and the adhesion between the lubricating layer and the protective layer is excellent, compared to a fluorine-containing ether compound in which, for example, two polar groups contained in the terminal group are bonded to different carbon atoms and the carbon atoms bonded to the polar groups are directly bonded to each other.

[0073] R in Equation (1) 1 and R 5 The terminal group represented by the formula (I) can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound. R 1 and R 5 may be the same or different. 1 The number of polar groups contained in the terminal group represented by R 5 The number of polar groups contained in the terminal groups represented by R may be the same or different. 1 and R 5 are the same terminal groups, which is preferable since the synthesis of the fluorine-containing ether compound is easy.

[0074] R in Equation (1) 1 and R 5 is preferably a terminal group of any one of the following formulas (7) to (10): 1 and R 5 is an end group of any one of the formulae (7) to (10), the adhesion and coverage between the protective layer to which the lubricant containing the fluorinated ether compound of this embodiment is applied and the lubricating layer formed by applying the lubricant are improved.

[0075] [ka] (In formula (7), f represents an integer of 1 to 2, and g represents an integer of 1 to 5.) (In formula (8), h represents an integer of 1 to 5.) (In formula (9), i represents an integer of 1 to 5.) (In formula (10), j represents an integer of 1 or 2, and k represents an integer of 1 or 2.)

[0076] In formula (7), f represents an integer of 1 to 2. From the viewpoint of adhesion between the lubricating layer and the protective layer, f is preferably 2. In formula (7), g represents an integer of 1 to 5. When g is an integer of 1 to 5, the distance between hydroxyl groups in the terminal group represented by formula (7) becomes appropriate, resulting in a fluorine-containing ether compound that has excellent adhesion to the protective layer and can form a lubricating layer with a high coverage. From the viewpoint of adhesion between the lubricating layer and the protective layer, g is preferably 1 or 2, and most preferably 1.

[0077] In formula (8), h represents an integer of 1 to 5. When h is an integer of 1 to 5, R 2 or R 4The distance between the side hydroxyl group and the terminal hydroxyl group is appropriate, resulting in a fluorine-containing ether compound that can form a lubricating layer with excellent adhesion to the protective layer and high coverage. From the viewpoint of adhesion between the lubricating layer and the protective layer, h is preferably 1 to 3, and most preferably 1. The terminal group represented by formula (8) contains -CF2-, and thus confers lubricity to a lubricating layer containing the fluorine-containing ether compound. Therefore, a fluorine-containing ether compound having a terminal group represented by formula (8) can form a lubricating layer with even more excellent wear resistance.

[0078] In formula (9), i represents an integer of 1 to 5. When i is an integer of 1 to 5, R 2 or R 4 The distance between the side hydroxyl group and the terminal hydroxyl group is appropriate, resulting in a fluorine-containing ether compound that can form a lubricating layer that has excellent adhesion to the protective layer and a high coverage. From the viewpoint of adhesion between the lubricating layer and the protective layer, i is preferably 1 or 2, and most preferably 1.

[0079] In formula (10), j represents an integer of 1 to 2. From the viewpoint of adhesion between the lubricating layer and the protective layer, j is preferably 2. In formula (10), k represents an integer of 1 to 2. When k is an integer of 1 to 2, the distance between hydroxyl groups in the terminal group represented by formula (10) becomes appropriate, resulting in a fluorine-containing ether compound that has excellent adhesion to the protective layer and can form a lubricating layer with a high coverage. From the viewpoint of adhesion between the lubricating layer and the protective layer, k is preferably 1. Furthermore, from the viewpoint of wear resistance, k is preferably 2.

[0080] In the fluorine-containing ether compound of the present embodiment, R 3 and one or more polar groups contained in R 1 and R 5The two or three polar groups arranged at an appropriate distance from each other are arranged in a well-balanced manner throughout the molecule.Therefore, the lubricating layer containing the fluorine-containing ether compound of this embodiment has excellent adhesion (tightness) to the protective layer, and can cover the surface of the protective layer with a high coverage.Therefore, the lubricating layer containing the fluorine-containing ether compound of this embodiment has good chemical resistance, can be made thinner, and can contribute to reducing the magnetic spacing in magnetic recording media.

[0081] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any one of the compounds represented by the following formulae (A) to (P). The repeating numbers indicated by ba1 to bh1, ba2 to bh2, and ca1 to ch1, and ca2 to ch2 in formulas (A) to (H), bi1 and bi2 in formula (I), ej1 and ej2 in formula (J), and bk1 to bp1, bk2 to bp2, and ck1 to cp1, and ck2 to cp2 in formulas (K) to (P) are all values ​​indicating the average degree of polymerization, and are therefore not necessarily integers.

[0082] [ka] (In formula (A), ba1, ca1, ba2, and ca2 represent average degrees of polymerization, ba1 and ba2 represent 0 to 30, and ca1 and ca2 represent 0 to 30; however, ba1 and ca1 cannot be 0 at the same time, and ba2 and ca2 cannot be 0 at the same time.) (In formula (B), bb1, cb1, bb2, and cb2 represent average degrees of polymerization, bb1 and bb2 represent 0 to 30, and cb1 and cb2 represent 0 to 30; however, bb1 and cb1 cannot be 0 at the same time, and bb2 and cb2 cannot be 0 at the same time.) (In formula (C), bc1, cc1, bc2, and cc2 represent average degrees of polymerization, bc1 and bc2 represent 0 to 30, and cc1 and cc2 represent 0 to 30; however, bc1 and cc1 cannot be 0 at the same time, and bc2 and cc2 cannot be 0 at the same time.)

[0083] [ka] (In formula (D), bd1, cd1, bd2, and cd2 represent average degrees of polymerization, bd1 and bd2 represent 0 to 30, and cd1 and cd2 represent 0 to 30; however, bd1 and cd1 cannot be 0 at the same time, and bd2 and cd2 cannot be 0 at the same time.) (In formula (E), be1, ce1, be2, and ce2 represent average degrees of polymerization, be1 and be2 represent 0 to 30, and ce1 and ce2 represent 0 to 30; however, be1 and ce1 cannot be 0 at the same time, and be2 and ce2 cannot be 0 at the same time.) (In formula (F), bf1, cf1, bf2, and cf2 represent average degrees of polymerization, bf1 and bf2 represent 0 to 30, and cf1 and cf2 represent 0 to 30; however, bf1 and cf1 cannot be 0 at the same time, and bf2 and cf2 cannot be 0 at the same time.)

[0084] [ka] (In formula (G), bg1, cg1, bg2, and cg2 represent average degrees of polymerization, bg1 and bg2 represent 0 to 30, and cg1 and cg2 represent 0 to 30; however, bg1 and cg1 cannot be 0 at the same time, and bg2 and cg2 cannot be 0 at the same time.) (In formula (H), bh1, ch1, bh2, and ch2 represent average degrees of polymerization, bh1 and bh2 represent 0 to 30, and ch1 and ch2 represent 0 to 30; however, bh1 and ch1 cannot be 0 at the same time, and bh2 and ch2 cannot be 0 at the same time.) (In formula (I), bi1 and bi2 represent average degrees of polymerization, and bi1 and bi2 represent 0.1 to 30.) (In formula (J), ej1 and ej2 represent the average degree of polymerization, and ej1 and ej2 represent 0.1 to 30.)

[0085] [ka] (In formula (K), bk1, ck1, bk2, and ck2 represent average degrees of polymerization, bk1 and bk2 represent 0 to 30, and ck1 and ck2 represent 0 to 30; however, bk1 and ck1 cannot be 0 at the same time, and bk2 and ck2 cannot be 0 at the same time.) (In formula (L), bl1, cl1, bl2, and cl2 represent average degrees of polymerization, bl1 and bl2 represent 0 to 30, and cl1 and cl2 represent 0 to 30; however, bl1 and cl1 cannot be 0 at the same time, and bl2 and cl2 cannot be 0 at the same time.)

[0086] [ka] (In formula (M), bm1, cm1, bm2, and cm2 represent average degrees of polymerization, bm1 and bm2 represent 0 to 30, and cm1 and cm2 represent 0 to 30; however, bm1 and cm1 cannot be 0 at the same time, and bm2 and cm2 cannot be 0 at the same time.) (In formula (N), bn1, cn1, bn2, and cn2 represent average degrees of polymerization, bn1 and bn2 represent 0 to 30, and cn1 and cn2 represent 0 to 30; however, bn1 and cn1 cannot be 0 at the same time, and bn2 and cn2 cannot be 0 at the same time.) (In formula (O), bo1, co1, bo2, and co2 represent average degrees of polymerization, bo1 and bo2 represent 0 to 30, and co1 and co2 represent 0 to 30; however, bo1 and co1 cannot be 0 at the same time, and bo2 and co2 cannot be 0 at the same time.) (In formula (P), bp1, cp1, bp2, and cp2 represent average degrees of polymerization, bp1 and bp2 represent 0 to 30, and cp1 and cp2 represent 0 to 30; however, bp1 and cp1 cannot be 0 at the same time, and bp2 and cp2 cannot be 0 at the same time.)

[0087] The compounds represented by formulas (A) to (E), (I) to (J), and (M) to (O) are all the same as R in formula (1). 3 The alicyclic structure of is cyclohexane. The compounds represented by formulas (F) to (H), (K) to (L), and (P) are all the same as R in formula (1).3 The alicyclic structure of is cyclopentane. The compounds represented by formulas (A) to (E), (I), (J), and (M) to (O) are all the same as R in formula (1). 3 The compounds represented by formulas (F) to (H) are represented by the formula (2-1). 3 is the formula (2-3). The compound represented by formula (K) is 3 The compounds represented by formula (L) and (P) are represented by formula (2-2). 3 is equation (2-4).

[0088] The compounds represented by formulas (A) to (H), (K) to (L), and (P) are all the same as R in formula (1). 1 and R 5 is represented by formula (10), in which j is 1 and k is 1. The compound represented by formula (I) is 1 and R 5 is represented by formula (10), where j is 1 and k is 2. The compound represented by formula (J) is 1 and R 5 is represented by formula (7), where f is 2 and g is 1. The compound represented by formula (M) is 1 and R 5 is represented by formula (10), in which j is 2 and k is 1. The compound represented by formula (N) is 1 and R 5 is represented by formula (9), and i in formula (9) is 1. The compound represented by formula (O) is 1 and R 5 is expressed by equation (8), where h is 1.

[0089] The compounds represented by formulas (A) to (I) and (K) to (P) are all the same as R in formula (1). 2 and R 4 The compound represented by formula (J) is a compound represented by formula (4) 2 and R 4 is equation (6). In formulas (A) to (H) and (K) to (P), ba1 to bh1, ba2 to bh2, bk1 to bp1, and bk2 to bp2 may be 0, 1 to 20, 1 to 10, or 1 to 5. In formulas (A) to (H) and (K) to (P), ca1 to ch1, ca2 to ch2, ck1 to cp1, and ck2 to cp2 may be 0, 1 to 20, 1 to 10, or 1 to 5. In formulas (I) and (J), bi1, bi2, ej1, and ej2 may be 1 to 20, 1 to 10, or 1 to 5.

[0090] It is preferable that the fluorine-containing ether compound represented by formula (1) is any of the compounds represented by the above formulae (A) to (P), since the raw materials are easily available and a lubricating layer having even better chemical resistance and wear resistance can be formed even if the thickness is thin.

[0091] The fluorine-containing ether compound of this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10,000, more preferably in the range of 700 to 7,000, and particularly preferably in the range of 1,000 to 3,000. When the number-average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of this embodiment is less likely to evaporate, preventing the lubricant from evaporating and transferring to the magnetic head. Furthermore, when the number-average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound is appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing the compound. A number-average molecular weight of 3,000 or less is more preferred because it results in a viscosity that is easy to handle when applied to a lubricant.

[0092] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 This is a value measured by F-NMR. For NMR (nuclear magnetic resonance) measurements, samples were diluted in a single or mixed solvent such as hexafluorobenzene, d-acetone, or d-tetrahydrofuran and used for the measurements. 19The reference for F-NMR chemical shifts is the hexafluorobenzene peak at -164.7 ppm. 1 The reference for H-NMR chemical shifts was the acetone peak at 2.2 ppm.

[0093] "Manufacturing method" The method for producing the fluorinated ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorinated ether compound of the present embodiment can be produced, for example, by the production method shown below.

[0094] First, R in Equation (1) 1 -CH2-R 2 Alcohols represented by the following formula (1-1) corresponding to —CH—, and —CH—R 4 -CH2-R 5 The alcohol represented by the following formula (1-2) is synthesized. R 1 -CH2-R 2 -CH2-OH (1-1) (In formula (1-1), R 1 and R 2 is the same as equation (1). HO-CH2-R 4 -CH2-R 5 (1-2) (In formula (1-2), R 4 and R 5 is the same as equation (1).

[0095] The alcohol represented by formula (1-1) is HO-CH2-R 2 For perfluoropolyether compounds represented by -CH2-OH, R 1 It can be synthesized by an addition reaction of an epoxide compound having a structure corresponding to the following: The alcohol represented by formula (1-2) is HO-CH2-R 4 For perfluoropolyether compounds represented by -CH2-OH, R 5 It can be synthesized by an addition reaction of an epoxide compound having a structure corresponding to the following:

[0096] R in Equation (1) 3 However, when producing a fluorine-containing ether compound of formula (2-1), an epoxide represented by the following formula (1-3) corresponding to X-{Y-CH2CH(OH)CH2O-}2 is synthesized. X-{Y-CH2-Ep}2(1-3) (In formula (1-3), Ep represents an epoxy group; X and Y are the same as those in formula (2-1).) Next, the epoxide of formula (1-3) is subjected to an addition reaction with the alcohols of formulas (1-1) and (1-2), thereby producing the compound of formula (1).

[0097] The epoxide represented by formula (1-3) can be obtained by, for example, 3 It can be produced by an addition reaction of epibromohydrin with an alcohol having an alicyclic structure corresponding to the formula: Specifically, for example, R in formula (1) 1 When the alicyclic structure corresponding to formula (1-3) is cyclohexane, an epoxide in which X is cyclohexane having one hydroxyl group as a substituent and Y is —O— can be produced by adding epibromohydrin to cyclohexanetriol.

[0098] R in Equation (1) 3 However, when producing a fluorine-containing ether compound of formula (2-2), an epoxide represented by the following formula (1-4) corresponding to X'-Y-CH2CH(O-)CH2O- is synthesized. X'-Y-CH2-Ep (1-4) (In formula (1-4), Ep represents an epoxy group; X' and Y are the same as those in formula (2-2).)

[0099] The epoxide represented by formula (1-4) can be obtained by, for example, 3 It can be produced by an addition reaction of epibromohydrin with an alcohol having an alicyclic structure corresponding to the formula: Specifically, for example, R in formula (1) 1When the alicyclic structure corresponding to formula (1-4) is cyclohexane, an epoxide in which X' is cyclohexane having one hydroxyl group as a substituent and Y is -O- can be produced by adding epibromohydrin to cyclohexanediol.

[0100] Next, the epoxide represented by (1-4) is subjected to an addition reaction with the alcohol represented by formula (1-1), thereby producing the compound represented by the following formula (1-5). X'-Y-CH2CH(OH)CH2O-CH2-R 2 -CH2-R 1 (1-5) (In formula (1-5), X' and Y are the same as those in formula (2-2); R 1 and R 2 is the same as equation (1). Next, the hydroxyl group of the compound represented by formula (1-5) is converted to a leaving group such as a bromo group or a methanesulfonate group, and the resulting compound is subjected to an addition reaction with the alcohol represented by formula (1-2), thereby producing the compound represented by formula (1).

[0101] R in Equation (1) 3 In the case of producing a fluorine-containing ether compound represented by formula (2-3), R 3 is formula (2-2), a compound represented by formula (1-5) (a compound in which X' in formula (1-5) is X) is produced. Next, epibromohydrin is added to the hydroxyl group of the compound represented by formula (1-5) (a compound in which X' is X in formula (1-5)) to synthesize the epoxide represented by formula (1-6). XY-CH2CH(OCH2Ep)CH2O-CH2-R 2 -CH2-R 1 (1-6) (In formula (1-6), Ep represents an epoxy group; X and Y are the same as those in formula (2-3); R 1 and R 2 is the same as equation (1). Next, the epoxide represented by formula (1-6) is subjected to an addition reaction with the alcohol represented by formula (1-2), thereby producing the compound represented by formula (1).

[0102] R in Equation (1) 3 However, when producing a fluorine-containing ether compound of formula (2-4), an epoxide represented by the following formula (1-7) corresponding to XY-CH2CH(OCH2CH(OH)CH2O-)CH2OCH2CH(OH)CH2O- is synthesized. XY-CH2CH(OCH2Ep)CH2OCH2Ep (1-7) (In formula (1-7), Ep represents an epoxy group; X and Y are the same as those in formula (2-4).) Next, the epoxide of formula (1-7) is subjected to an addition reaction with the alcohols of formulas (1-1) and (1-2), thereby producing the compound of formula (1).

[0103] The epoxide represented by formula (1-7) can be produced, for example, by the following method. 3 The epoxide is obtained by addition reaction of epibromohydrin with an alcohol having an alicyclic structure corresponding to the formula: Next, the obtained epoxide is subjected to addition reaction of allyl alcohol and allyl bromide, and the allyl group is oxidized with metachloroperbenzoic acid.

[0104] The produced fluorine-containing ether compound represented by formula (1) is preferably purified, for example, by a method using column chromatography. By the above method, the fluorine-containing ether compound represented by formula (1) can be obtained.

[0105] The fluorine-containing ether compound of this embodiment is a compound represented by the above formula (1). Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing this compound, R 2 and R 4The surface of the protective layer is covered with the PFPE chain represented by R 3 The alicyclic structure of the organic group represented by formula (I) contributes to the fluidity of the molecular structure of the fluorine-containing ether compound. Therefore, the alicyclic structural portion can partially float from the protective layer. Therefore, the lubricating layer collides with the magnetic head before the magnetic head directly collides with the protective layer, thereby protecting the protective layer. Due to this function, the lubricating layer formed using the lubricant containing the fluorine-containing ether compound of this embodiment has excellent wear resistance.

[0106] In addition, the lubricating layer containing the fluorine-containing ether compound of this embodiment is formed by the addition of R 3 and R 1 and R 5 The two or three polar groups contained in each of the terminal groups represented by the formula (I) bond with the protective layer, thereby allowing the polymer to adhere tightly to the protective layer.

[0107] Moreover, in the fluorine-containing ether compound of this embodiment, R 1 and R 5 The two or three polar groups contained in the terminal group represented by are each bonded to different carbon atoms, and the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom not bonded to a polar group.Therefore, the fluorine-containing ether compound of this embodiment is unlikely to aggregate on the protective layer.Therefore, the lubricating layer containing the fluorine-containing ether compound of this embodiment has sufficient coverage and is excellent in adhesion to the protective layer. From the above, the fluorine-containing ether compound of this embodiment firmly bonds the lubricating layer and the protective layer, and a lubricating layer having excellent chemical resistance and abrasion resistance can be obtained.

[0108] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by formula (1). The lubricant of the present embodiment can be used by mixing, as needed, known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorinated ether compound represented by formula (1) are not impaired.

[0109] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of the present embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0110] When the lubricant of this embodiment contains a material other than the fluorinated ether compound represented by formula (1), the content of the fluorinated ether compound represented by formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more. The content of the fluorinated ether compound represented by formula (1) may be 80% by mass or more, or may be 90% by mass or more. The upper limit of the content of the fluorinated ether compound represented by formula (1) can be selected arbitrarily, but may be, for example, 99% by mass or less, 95% by mass or less, or 90% by mass or less.

[0111] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1), and therefore can cover the surface of the protective layer with a high coverage even when the thickness is small, and can form a lubricating layer that has excellent adhesion to the protective layer. 3 The protective layer is protected by the alicyclic structural moiety contained in the compound (I) partially floating up from the protective layer. For these reasons, the lubricant of this embodiment can provide a lubricating layer that has excellent chemical resistance and wear resistance even when it is thin.

[0112] [Magnetic recording media] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer, if necessary. An adhesive layer and / or a soft magnetic layer may also be provided between the underlayer and the substrate.

[0113] FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0114] "substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. The substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or may be a non-magnetic substrate having a NiP or NiP alloy film formed on a base made of any of these non-metallic materials.

[0115] "Adhesion layer" The adhesive layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are disposed in contact with each other. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0116] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are antiferro-coupling (AFC).

[0117] The first and second soft magnetic films may be made of a material such as a CoZrTa alloy or a CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films, which promotes the amorphization of the first and second soft magnetic films, improves the orientation of the first underlayer (seed layer), and reduces the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0118] "First base layer" The first underlayer 14 is a layer for controlling the orientation and crystal size of the second underlayer 15 and magnetic layer 16 provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, or a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0119] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a single layer or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all of the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0120] "Magnetic layer" The magnetic layer 16 is a magnetic film with an easy axis of magnetization oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 contains Co and Pt, and may also contain oxides, Cr, B, Cu, Ta, Zr, etc. to further improve the SNR characteristics. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0121] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. The oxide contained in the first magnetic layer is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among these, TiO2, Cr2O3, SiO2, and the like are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide containing two or more types of oxides. Among these, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, and the like are particularly suitable.

[0122] 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, and preferably has a granular structure.

[0123] The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0124] When magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0125] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0126] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, oxides that can be used include, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, and TiO2. Metal nitrides that can be used include, for example, AlN, Si3N4, TaN, and CrN. Metal carbides that can be used include, for example, TaC, BC, and SiC. The non-magnetic layer can be formed by, for example, a sputtering method.

[0127] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for longitudinal magnetic recording. The magnetic layer 16 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0128] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be made of a single layer or multiple layers. Examples of materials for the protective layer 17 include carbon, carbon containing nitrogen, and silicon carbide. A carbon-based protective layer, particularly an amorphous carbon protective layer, can be preferably used as the protective layer 17. A carbon-based protective layer is preferred as the protective layer 17 because it further enhances the interaction with the polar groups (particularly hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18.

[0129] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0130] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of protective layer 17 and hydrogen is contained on the magnetic layer 16 side of protective layer 17. In this case, the adhesion between the magnetic layer 16 and lubricating layer 18 and the carbon-based protective layer is further improved.

[0131] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0132] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, or ion beam deposition (IBD). When a carbon-based protective layer is formed as protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed as protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface with little roughness.

[0133] "Lubricant layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. The lubricating layer 18 also reduces the frictional force of the magnetic head of the magnetic recording / reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 1, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 contains the above-mentioned fluorine-containing ether compound.

[0134] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 bonds with the protective layer 17 with particularly high bonding strength. As a result, even if the thickness of the lubricating layer 18 is thin, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0135] The average thickness of the lubricating layer 18 can be selected arbitrarily, but is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.0 nm (10 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. This allows the lubricating layer 18 to cover the surface of the protective layer 17 with a high coverage. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0136] If the surface of the protective layer 17 is not covered with the lubricating layer 18 at a sufficiently high coverage rate, environmental substances adsorbed to the surface of the magnetic recording medium 10 will pass through the gaps in the lubricating layer 18 and penetrate underneath the lubricating layer 18. The environmental substances that penetrate underneath the lubricating layer 18 will adsorb and bond with the protective layer 17, generating contaminants. During magnetic recording and reproduction, these contaminants (aggregated components) will then adhere (transfer) to the magnetic head as smear, damaging the magnetic head or degrading the magnetic recording and reproduction characteristics of the magnetic recording and reproduction device.

[0137] Environmental substances that generate contaminants include, for example, siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, hydrocarbons with relatively high molecular weights such as octacosane, and plasticizers such as dioctyl phthalate. Examples of metal ions contained in ionic impurities include sodium ions and potassium ions. Examples of inorganic ions contained in ionic impurities include chloride ions, bromide ions, nitrate ions, sulfate ions, and ammonium ions. Examples of organic ions contained in ionic impurities include oxalate ions and formate ions.

[0138] "Method for forming lubricating layer" A method for forming the lubricating layer 18 includes, for example, preparing a magnetic recording medium in the middle of manufacturing in which all layers up to the protective layer 17 are formed on the substrate 11, applying a solution for forming a lubricating layer onto the protective layer 17, and drying the solution.

[0139] The lubricant layer forming solution can be obtained, for example, by dispersing and dissolving the lubricant for a magnetic recording medium according to the above-described embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.).

[0140] The method for applying the lubricating layer-forming solution is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in a lubricant layer-forming solution placed in an immersion tank of a dip coating device. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricating layer forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0141] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100 to 180° C. If the heat treatment temperature is 100° C. or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180° C. or lower, thermal decomposition of the lubricating layer 18 can be prevented. The heat treatment time is preferably 10 to 120 minutes.

[0142] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 on the substrate 11 may be irradiated with ultraviolet (UV) rays before or after the heat treatment.

[0143] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed on and in contact with the protective layer 17. This lubricating layer 18 covers the surface of the protective layer 17 with a high coverage, even though it is thin. Therefore, the magnetic recording medium 10 of this embodiment prevents environmental substances that generate contaminants such as ionic impurities from penetrating through gaps in the lubricating layer 18. Furthermore, the lubricating layer 18 in the magnetic recording medium 10 of this embodiment has excellent wear resistance. As a result, the magnetic recording medium 10 of this embodiment has excellent reliability and durability. [Example]

[0144] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0145] [Example 1] The compound represented by the above formula (A) (in formula (A), ba1 and ba2, which represent the average degree of polymerization, are 4.5, and ca1 and ca2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,3,5-cyclohexanetriol was reacted with epibromohydrin to synthesize a compound represented by the following formula (40). Then, one of the hydroxyl groups of 1,3-propanediol was protected with tetrahydropyran, and then the compound was reacted with epibromohydrin to synthesize a compound represented by the following formula (11).

[0146] [ka]

[0147] In a 200 mL recovery flask, add HOCH2CF2O (CF2CF2O) s (CF2O) t CF2CH2OH (where s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5) fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) (40.0 g), the compound (6.10 g) represented by the above formula (11), and t-BuOH (tertiary butyl alcohol) (40.0 mL) were charged and stirred at room temperature until homogenous. Furthermore, t-BuOK (potassium tertiary butoxide) (1.35 g) was added to the above recovery flask, heated to 70 °C, and stirred for 18 hours to react.

[0148] The resulting reaction product was then cooled to 25°C, water was added, and then Vertrel (registered trademark) XF (hereinafter sometimes referred to as "Vertrel XF") manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd. was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the desiccant was filtered off, and the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain a compound (17.5 g) represented by the following formula (12).

[0149] [ka] (In formula (12), s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5.)

[0150] Under a nitrogen gas atmosphere, a 200 mL recovery flask was charged with 17.5 g of the compound represented by formula (12), 2.67 g of the compound represented by formula (40), and 65.0 mL of tertiary butyl alcohol (t-BuOH) and stirred at room temperature until homogenous. 0.470 g of potassium tertiary butoxide (t-BuOK) was added to the recovery flask, heated to 70°C, and stirred for 23 hours to react.

[0151] The resulting reaction product was then cooled to 25°C, and water (3.3 mL) and 5-10% hydrochloric acid / methanol (trade name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) (21.5 mL) were added, followed by stirring at room temperature for 3 hours. 5% aqueous sodium bicarbonate (100 mL) was added to the resulting residue, which was extracted with ethyl acetate, and the organic layer was washed with water. Anhydrous magnesium sulfate was then added to the organic layer for dehydration, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain 8.1 g of compound (A).

[0152] The obtained compound (A) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(46H) 19 F-NMR (acetone-d6): δ[ppm]=-51.99~-55.72(18F), -78.48(4F), -80.66(4F), -89.16~-91.14(36F)

[0153] [Example 2] A compound represented by the above formula (B) (in formula (B), bb1 and bb2 representing the average degree of polymerization are 4.5, and cb1 and cb2 representing the average degree of polymerization are 4.5) was obtained by the method shown below. First, 1,2,3-cyclohexanetriol was reacted with epibromohydrin to synthesize a compound represented by the following formula (13).

[0154] [ka]

[0155] Then, the same procedure as in Example 1 was carried out except that 6.10 g of the compound represented by formula (13) was used instead of the compound represented by formula (40), to obtain 9.5 g of compound (B). The obtained compound (B) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(46H)

[0156] [Example 3] The compound represented by the above formula (C) (in formula (C), bc1 and bc2, which represent the average degree of polymerization, are 4.5, and cc1 and cc2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,2,4-cyclohexanetriol was reacted with epibromohydrin to synthesize a compound represented by the following formula (14).

[0157] [ka]

[0158] Then, the same procedure as in Example 1 was carried out except that 5.10 g of the compound represented by formula (14) was used instead of the compound represented by formula (40), to obtain 10.9 g of compound (C). The obtained compound (C) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(46H)

[0159] [Example 4] A compound represented by the above formula (D) (in formula (D), bd1 and bd2, which represent the average degree of polymerization, are 4.5, and cd1 and cd2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,2,4-cyclohexanetriol, epibromohydrin, and 2-(bromopropoxy)tetrahydro-2H-pyran were reacted to synthesize a compound represented by the following formula (15).

[0160] [ka]

[0161] Then, the same procedure as in Example 1 was carried out except that 6.10 g of the compound represented by formula (15) was used instead of the compound represented by formula (40), to obtain 10.9 g of compound (D). The obtained compound (D) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(12H), 3.20~4.20(50H)

[0162] [Example 5] A compound represented by the above formula (E) (in formula (E), be1 and be2, which represent the average degree of polymerization, are 4.5, and ce1 and ce2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,2,4-cyclohexanetriol, epibromohydrin, and 2-(bromoethoxy)tetrahydro-2H-pyran were reacted to synthesize a compound represented by the following formula (16).

[0163] [ka]

[0164] Then, the same procedure as in Example 1 was carried out except that 6.78 g of the compound represented by formula (16) was used instead of the compound represented by formula (40), to obtain 11.3 g of compound (E). The obtained compound (E) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(50H)

[0165] [Example 6] The compound represented by the above formula (F) (in formula (F), bf1 and bf2, which represent the average degree of polymerization, are 4.5, and cf1 and cf2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,2-cyclopentanediol, epibromohydrin, and dihydropyran were reacted to synthesize a compound represented by the following formula (17).

[0166] [ka]

[0167] Under a nitrogen gas atmosphere, a 200 mL recovery flask was charged with 17.5 g of the compound represented by formula (12), 3.67 g of the compound represented by formula (17), and 65.0 mL of tertiary butyl alcohol (t-BuOH) and stirred at room temperature until the mixture was homogenous. 0.470 g of potassium tertiary butoxide (t-BuOK) was then added to the recovery flask, heated to 70°C, and stirred for 23 hours to react.

[0168] The resulting reaction product was then cooled to 25°C, water was added, and then Vertrel XF (manufactured by DuPont-Mitsui Fluorochemicals) was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the drying agent was filtered off, and the filtrate was concentrated. This residue (16.4 g) was cooled to 0° C., and N,N-dimethylformamide (30 mL) and sodium hydride (1.5 g) were added, followed by stirring for 1 hour at 0° C. Epibromohydrin (3 mL) was then added dropwise at 0° C. and the mixture was stirred until homogenous, then heated to 25° C. and stirred for 15 hours to allow the reaction to proceed.

[0169] Thereafter, water was added to the obtained reaction product, and further, Vertrel XF manufactured by Mitsui DuPont Fluorochemicals Co., Ltd. was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and after filtering off the desiccant, the filtrate was concentrated. To this residue (15.3 g), the compound represented by the above formula (12) (3.67 g) and t-BuOH (tertiary butyl alcohol) (65.0 mL) were added and stirred at room temperature until the mixture became homogeneous. Furthermore, t-BuOK (potassium tertiary butoxide) (0.270 g) was added to the above recovery flask, heated to 70°C, and stirred for 23 hours to react.

[0170] The resulting reaction product was then cooled to 25°C, and water (3.3 mL) and 5-10% hydrochloric acid / methanol (20.3 mL) were added, followed by stirring at room temperature for 4 hours. 5% aqueous sodium bicarbonate (100 mL) was added to the resulting residue, which was extracted with ethyl acetate and the organic layer was washed with water. Anhydrous magnesium sulfate was then added to the organic layer for dehydration, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain 4.1 g of compound (F).

[0171] The obtained compound (F) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(44H)

[0172] [Example 7] A compound represented by the above formula (G) (in formula (G), bg1 and bg2, which represent the average degree of polymerization, are 4.5, and cg1 and cg2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,3-cyclopentanediol, epibromohydrin, and dihydropyran were reacted to synthesize a compound represented by the following formula (18).

[0173] [ka]

[0174] Then, the same procedure as in Example 6 was carried out except that 4.01 g of the compound represented by formula (18) was used instead of the compound represented by formula (17), to obtain 5.2 g of compound (G). The obtained compound (G) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(44H)

[0175] [Example 8] The compound represented by the above formula (H) (in formula (H), bh1 and bh2, which represent the average degree of polymerization, are 4.5, and ch1 and ch2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, 1,3-cyclopentanediol, epibromohydrin, and 2-(bromoethoxy)tetrahydro-2H-pyran were reacted to synthesize a compound represented by the following formula (19).

[0176] [ka]

[0177] Then, the same procedure as in Example 6 was carried out, except that 2.89 g of the compound represented by formula (19) was used instead of the compound represented by formula (17), to obtain 3.3 g of compound (H). The obtained compound (H) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(48H)

[0178] [Example 9] The compound represented by the above formula (I) (in formula (I), bi1 and bi2, which represent the average degree of polymerization, are 6.5) was obtained by the method shown below. First, 1,3,5-cyclohexanetriol, epibromohydrin, and 2-(bromopropoxy)tetrahydro-2H-pyran were reacted to synthesize a compound represented by the following formula (20). Then, one of the hydroxyl groups of 1,4-butanediol was protected with tetrahydropyran, and then the compound was reacted with epibromohydrin to synthesize a compound represented by the following formula (21).

[0179] [ka]

[0180] In a 200 mL recovery flask, add HOCH2CF2O (CF2CF2O) u 40.0 g of fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where u, the average degree of polymerization, is 6.5), 6.10 g of the compound represented by the above formula (21), and 40.0 mL of tertiary butyl alcohol (t-BuOH) were charged and stirred at room temperature until homogenous. 1.35 g of potassium tertiary butoxide (t-BuOK) was added to the above flask, heated to 70°C, and stirred for 18 hours to react.

[0181] The resulting reaction product was then cooled to 25°C, water was added, and Vertrel XF was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain the compound (14.5 g) represented by the following formula (22).

[0182] [ka] (In formula (22), u, which indicates the average degree of polymerization, is 6.5.)

[0183] Under a nitrogen gas atmosphere, a 200 mL recovery flask was charged with 14.5 g of the compound represented by formula (22), 3.67 g of the compound represented by formula (20), and 65.0 mL of tertiary butyl alcohol (t-BuOH) and stirred at room temperature until homogeneous. 0.470 g of potassium tertiary butoxide (t-BuOK) was added to the recovery flask, heated to 70°C, and stirred for 47 hours to react.

[0184] The resulting reaction product was then cooled to 25°C, and water (3.5 mL) and 5-10% hydrochloric acid / methanol (trade name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) (22.5 mL) were added, followed by stirring at room temperature for 3 hours. 5% aqueous sodium bicarbonate (100 mL) was added to the resulting residue, which was extracted with ethyl acetate, and the organic layer was washed with water. Anhydrous magnesium sulfate was then added to the organic layer for dehydration, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain 7.1 g of compound (I).

[0185] The obtained compound (I) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(16H), 3.20~4.20(50H) 19 F-NMR (acetone-d6): δ[ppm]=-77.85~-79.00(8F), -88.50~-91.22(52F)

[0186] [Example 10] A compound represented by the above formula (J) (in formula (J), ej1 and ej2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, a compound represented by the following formula (23) was synthesized by oxidizing a product obtained by reacting 3-allyloxy-1,2-propanediol-2-methoxymethyl ether with 2-(bromoethoxy)tetrahydro-2H-pyran.

[0187] [ka]

[0188] In a 200 mL recovery flask, add HOCH2CF2CF2O (CF2CF2CF2O) under a nitrogen gas atmosphere. v 40.0 g of fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where v, indicating the average degree of polymerization, is 4.5), 6.10 g of the compound represented by the above formula (23), and 40.0 mL of tertiary butyl alcohol (t-BuOH) were charged and stirred at room temperature until homogenous. 1.35 g of potassium tertiary butoxide (t-BuOK) was then added to the recovery flask, heated to 70°C, and stirred for 19 hours to react.

[0189] The resulting reaction product was then cooled to 25°C, water was added, and then Vertrel XF was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain the compound (13.5 g) represented by the following formula (24).

[0190] [ka] (In formula (24), v, which indicates the average degree of polymerization, is 4.5.)

[0191] Under a nitrogen gas atmosphere, a 200 mL recovery flask was charged with 13.5 g of the compound represented by formula (24), 3.37 g of the compound represented by formula (40), and 65.0 mL of tertiary butyl alcohol (t-BuOH) and stirred at room temperature until the mixture was homogenous. 0.570 g of potassium tertiary butoxide (t-BuOK) was then added to the recovery flask, heated to 70°C, and stirred for 25 hours to allow the mixture to react.

[0192] The resulting reaction product was then cooled to 25°C, and water (3.5 mL) and 5-10% hydrochloric acid / methanol (trade name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) (22.5 mL) were added, followed by stirring at room temperature for 3 hours. 5% aqueous sodium bicarbonate (100 mL) was added to the resulting residue, which was extracted with ethyl acetate, and the organic layer was washed with water. Anhydrous magnesium sulfate was then added to the organic layer for dehydration, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain 6.5 g of compound (J).

[0193] The obtained compound (J) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(6H), 3.20~4.20(58H) 19 F-NMR (acetone-d6): δ[ppm]=-82.66~-84.00(40F), -85.16~-86.91(8F), -123.16~-124.91(8F), -128.47~-130.20(8F)

[0194] [Example 11] The compound represented by the above formula (K) (in formula (K), bk1 and bk2 representing the average degree of polymerization are 4.5, and ck1 and ck2 representing the average degree of polymerization are 4.5) was obtained by the method shown below.

[0195] Under a nitrogen gas atmosphere, a 200 mL recovery flask was charged with 17.5 g of the compound represented by formula (12), 3.67 g of the compound represented by formula (17), and 65.0 mL of tertiary butyl alcohol (t-BuOH) and stirred at room temperature until the mixture was homogenous. 0.470 g of potassium tertiary butoxide (t-BuOK) was then added to the recovery flask, heated to 70°C, and stirred for 23 hours to react.

[0196] The resulting reaction product was then cooled to 25°C, water was added, and then Vertrel XF (manufactured by DuPont-Mitsui Fluorochemicals) was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the drying agent was filtered off, and the filtrate was concentrated. To this residue (16.4 g), dichloromethane (200 mL) and 4-dimethylaminopyridine (1.0 g) were added and cooled to 0° C. Furthermore, triethylamine (10 mL) was added dropwise, and the mixture was stirred at 0° C. until it became homogeneous. Then, methanesulfonic acid chloride (3.0 mL) was added dropwise, and the mixture was heated to 25° C. and stirred for 6 hours to allow the reaction to proceed.

[0197] Thereafter, water was added to the obtained reaction product, and further, Vertrel XF manufactured by Mitsui DuPont Fluorochemicals Co., Ltd. was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and after filtering off the desiccant, the filtrate was concentrated. To this residue (15.3 g), the compound represented by the above formula (12) (3.67 g) and t-BuOH (tertiary butyl alcohol) (65.0 mL) were added and stirred at room temperature until the mixture became homogeneous. Furthermore, t-BuOK (potassium tertiary butoxide) (0.470 g) was added to the above recovery flask, heated to 70 °C, and stirred for 23 hours to react.

[0198] The resulting reaction product was then cooled to 25°C, and water (3.3 mL) and 5-10% hydrochloric acid / methanol (20.3 mL) were added, followed by stirring at room temperature for 4 hours. 5% aqueous sodium bicarbonate (100 mL) was added to the resulting residue, which was extracted with ethyl acetate and the organic layer was washed with water. Anhydrous magnesium sulfate was then added to the organic layer for dehydration, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain 4.1 g of compound (K).

[0199] The obtained compound (K) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(38H)

[0200] [Example 12] The compound represented by the above formula (L) (in formula (L), bl1 and bl2, which represent the average degree of polymerization, are 4.5, and cl1 and cl2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, the compound represented by the following formula (25) was synthesized by reacting the product obtained by reacting 1,3-cyclopentanediol, dihydropyran, and epibromohydrin with allyl bromide and allyl alcohol and oxidizing the product.

[0201] [ka]

[0202] Then, the same procedure as in Example 1 was carried out except that 2.64 g of the compound represented by formula (25) was used instead of the compound represented by formula (40), to obtain 10.9 g of compound (L). The obtained compound (L) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(50H)

[0203] [Example 13] A compound represented by the above formula (M) (in formula (M), bm1 and bm2, which represent the average degree of polymerization, are 4.5, and cm1 and cm2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, the compound represented by the following formula (26) was synthesized by oxidizing the product obtained by reacting 3-allyloxy-1,2-propanediol-2-methoxymethyl ether with 2-(bromopropoxy)tetrahydro-2H-pyran.

[0204] [ka]

[0205] Then, the same operations as in Example 1 for synthesizing the compound represented by formula (12) were carried out, except that 6.70 g of the compound represented by formula (26) was used instead of the compound represented by formula (11), to obtain a compound represented by formula (27) below.

[0206] [ka] (In formula (27), s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5.)

[0207] Thereafter, the same procedure as in Example 1 was carried out except that 15.2 g of the compound represented by formula (27) was used instead of the compound represented by formula (12), to obtain 7.3 g of compound (M). The obtained compound (M) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): 1.2~2.0 (10H), 3.20~4.20 (58H)

[0208] [Example 14] A compound represented by the above formula (N) (in formula (N), bn1 and bn2 representing the average degree of polymerization are 4.5, and cn1 and cn2 representing the average degree of polymerization are 4.5) was obtained by the method shown below. First, a compound represented by the following formula (28) was synthesized by oxidizing a product in which 3-buten-1-ol was protected with a tetrahydropyranyl (THP) group.

[0209] [ka]

[0210] Then, the same operations as in Example 1 for synthesizing the compound represented by formula (12) were carried out, except that 6.30 g of the compound represented by formula (28) was used instead of the compound represented by formula (11), to obtain a compound represented by formula (29) below.

[0211] [ka] (In formula (29), s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5.)

[0212] Thereafter, the same procedure as in Example 1 was carried out except that 14.8 g of the compound represented by formula (29) was used instead of the compound represented by formula (12), to obtain 7.0 g of compound (N). The obtained compound (N) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): 1.2~2.0 (10H), 3.20~4.20 (38H)

[0213] [Example 15] The compound represented by the above formula (O) (in formula (O), bo1 and bo2, which represent the average degree of polymerization, are 4.5, and co1 and co2, which represent the average degree of polymerization, are 4.5) was obtained by the method shown below. First, a compound represented by the following formula (30) was synthesized by reacting a product in which one hydroxyl group of 2,2-difluoro-1,3-propanediol was protected with a THP group with epibromohydrin.

[0214] [ka]

[0215] Then, the same operations as in Example 1 for synthesizing the compound represented by formula (12) were carried out, except that 6.4 g of the compound represented by formula (30) was used instead of the compound represented by formula (11), to obtain a compound represented by formula (31) below.

[0216] [ka] (In formula (31), s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5.)

[0217] Thereafter, the same procedure as in Example 1 was carried out except that 15.6 g of the compound represented by formula (31) was used instead of the compound represented by formula (12), to obtain 7.5 g of compound (O).

[0218] The obtained compound (O) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): 1.2~2.0 (6H), 3.20~4.20 (46H) 19 F-NMR (acetone-d6): δ[ppm]=-51.99~-55.72(9F), -78.48(2F), -80.66(2F), -89.16~-91.14(18F), -144.28(4F)

[0219] [Example 16] The compound represented by the above formula (P) (in formula (P), bp1 and bp2, which indicate the average degree of polymerization, are 4.5, and cp1 and cp2, which indicate the average degree of polymerization, are 4.5) was obtained by the method shown below. First, the product obtained by reacting 3-amino-cyclopentan-1-ol with epibromohydrin was reacted with allyl bromide and allyl alcohol, and oxidized to synthesize a compound represented by the following formula (32).

[0220] [ka]

[0221] Then, the same procedure as in Example 1 was carried out except that 2.89 g of the compound represented by formula (32) was used instead of the compound represented by formula (40), to obtain 11.1 g of compound (P). The obtained compound (P) 1 H-NMR measurement was carried out, and the structure was identified from the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(51H)

[0222] [Comparative Example 1] The compound represented by the following formula (Q) was obtained by the method shown below.

[0223] [ka] (In formula (Q), bq1, bq2, and bq3, which represent the average degrees of polymerization, are 4.5, and cq1, cq2, and cq3, which represent the average degrees of polymerization, are 4.5.)

[0224] First, 1,3,5-cyclohexanetriol was reacted with epibromohydrin to synthesize a compound represented by the following formula (33).

[0225] [ka]

[0226] In a 200 mL recovery flask, add HOCH2CF2O (CF2CF2O) s (CF2O) t 40.0 g of fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where s, indicating the average degree of polymerization, is 4.5, and t, indicating the average degree of polymerization, is 4.5), 3.10 g of the compound represented by the above formula (33), and 40.0 mL of tertiary butyl alcohol (t-BuOH) were charged and stirred at room temperature until homogenous. 2.55 g of potassium tertiary butoxide (t-BuOK) was then added to the above-mentioned recovery flask, heated to 70°C, and stirred for 50 hours to react.

[0227] The resulting reaction product was then cooled to 25°C, water was added, and then Vertrel XF was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain the compound represented by the above formula (Q) (15.5 g).

[0228] The obtained compound (Q) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(6H), 3.20~4.20(33H) 19 F-NMR(acetone-d6):δ[ppm]=-90.57~-88.88(36F),-83.21~-81.20(6F),-80.64~-78.64(6F),-53.32~-51.94(18F)

[0229] Comparative Example 2 A compound represented by the following formula (R) was obtained by the method shown below.

[0230] [ka] (In formula (R), br1, br2, and br3, which represent the average degrees of polymerization, are 4.5, and cr1, cr2, and cr3, which represent the average degrees of polymerization, are 4.5.)

[0231] Under a nitrogen gas atmosphere, 36 mL of t-butanol and 4 g of the above compound (Q) were placed in a 50 mL recovery flask and stirred until homogeneous, obtaining a mixture. Next, 0.4 g of potassium tert-butoxide was added to the mixture, and 300 μL of glycidol was added while heating to 70°C, followed by stirring for 5 hours to allow the reaction to proceed. The reaction mixture was then cooled to 25°C and neutralized with hydrochloric acid. A fluorine-based solvent (trade name: Asahiklin AK-225, manufactured by Asahi Glass Co., Ltd.) was added, followed by washing with water. Anhydrous sodium sulfate was added to the organic layer of the reaction mixture after washing to dehydrate it. The desiccant was filtered off, and the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain the compound represented by the above formula (R) (2.0 g).

[0232] The obtained compound (R) 1 H-NMR measurement and 19 F-NMR measurements were carried out, and the structure was identified from the following results. 1 H-NMR(acetone-d6):δ[ppm]=1.211(3H),2.523(3H),3.452(3H),3.574(3H),3.625(3H),3.744(6H),3.797~3.901(12H),3.927~4.116(18H) 19 F-NMR(acetone-d6):δ[ppm]=-90.87~-89.19(36F),-81.43~-78.90(12F),-55.63~-52.29(18F)

[0233] Comparative Example 3 A compound represented by the following formula (S) was obtained by the method shown below.

[0234] [ka] (In formula (S), bs1, bs2, and bs3, which represent the average degrees of polymerization, are 6.5.)

[0235] HOCH2CF2O(CF2CF2O) used in Comparative Example 1 s (CF2O) t Instead of the fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (wherein s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5), HOCH2CF2O(CF2CF2O) u The same procedure as in Comparative Example 1 was carried out, except that 40.0 g of a fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (wherein u, representing the average degree of polymerization, is 6.5) was used, and 11.1 g of compound (S) was obtained.

[0236] The obtained compound (S) 1 H-NMR measurement and 19 F-NMR measurements were carried out, and the structure was identified from the following results. 1 H-NMR(acetone-d6):δ[ppm]=1.185(3H),2.499(3H),3.427(3H),3.554(3H),3.600(3H),3.709(6H),3.735~3.918(12H),4.029~4.078(18H) 19 F-NMR (acetone-d6): δ[ppm]=-89.07(60F), -81.37(6F), -78.85(6F)

[0237] Comparative Example 4 A compound represented by the following formula (T) was obtained by the method shown below.

[0238] [ka] (In formula (T), bt1, bt2, and bt3, which represent the average degrees of polymerization, are 6.5.)

[0239] The same procedure as in Comparative Example 2 was carried out, except that 4.0 g of the compound represented by formula (S) was used instead of the compound represented by formula (Q) used in Comparative Example 2, to obtain 1.8 g of compound (T).

[0240] The obtained compound (T) 1 H-NMR measurement and 19 F-NMR measurements were carried out, and the structure was identified from the following results. 1 H-NMR(acetone-d6):δ[ppm]=1.211(3H),2.523(3H),3.452(3H),3.574(3H),3.625(3H),3.744(6H),3.797~3.901(12H),3.927~4.116(18H) 19 F-NMR(acetone-d6):δ[ppm]=-88.67(60F), -78.43(12F)

[0241] Comparative Example 5 A compound represented by the following formula (U) was obtained by the method shown below.

[0242] [ka] (In formula (U), bu1 and bu2, which represent the average degrees of polymerization, are 4.5, and cu1 and cu2, which represent the average degrees of polymerization, are 4.5.)

[0243] First, glycidol was protected with a tetrahydropyranyl (THP) group to synthesize a compound represented by the following formula (34).

[0244] [ka]

[0245] In a 200 mL recovery flask, add HOCH2CF2O (CF2CF2O) s (CF2O) t40.0 g of fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where s, indicating the average degree of polymerization, is 4.5, and t, indicating the average degree of polymerization, is 4.5), 2.10 g of the compound represented by the above formula (34), and 40.0 mL of tertiary butyl alcohol (t-BuOH) were charged and stirred at room temperature until homogenous. 1.55 g of potassium tertiary butoxide (t-BuOK) was then added to the above flask, heated to 70°C, and stirred for 50 hours to react.

[0246] The resulting reaction product was then cooled to 25°C, water was added, and then Vertrel XF was added as a solvent to extract the organic layer, which was then washed with water. Anhydrous sodium sulfate was added to the organic layer to dehydrate it, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain the compound (20.3 g) represented by the following formula (35).

[0247] [ka] (In formula (35), s, which indicates the average degree of polymerization, is 4.5, and t, which indicates the average degree of polymerization, is 4.5.)

[0248] N,N-dimethylformamide (200 mL) and the compound (20.3 g) represented by the above formula (35) were charged, cooled to 0°C, and stirred, and then sodium hydride (1.0 g) was added. After further stirring at 0°C for 2 hours, 1,4-dichlorocyclohexane (5.0 g) was added, and the mixture was heated to 25°C and stirred for 6 hours to allow the reaction to proceed.

[0249] Water (3.3 mL) and 5-10% hydrochloric acid / methanol (20.3 mL) were then added to the resulting reaction product and stirred at room temperature for 2 hours. 5% aqueous sodium bicarbonate (100 mL) was added to the resulting residue, which was extracted with ethyl acetate and the organic layer was washed with water. Anhydrous magnesium sulfate was then added to the organic layer for dehydration, and the desiccant was filtered off, after which the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain 10.2 g of compound (U).

[0250] The obtained compound (U) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(8H), 3.20~4.20(24H) 19 F-NMR(acetone-d6):δ[ppm]=-90.87~-89.19(24F),-81.43~-78.90(8F),-55.63~-52.29(12F)

[0251] Comparative Example 6 The compound represented by the following formula (V) was produced by the method shown below.

[0252] [ka] (In formula (V), bv1 and bv2, which represent the average degrees of polymerization, are 4.5, and cv1 and cv2, which represent the average degrees of polymerization, are 4.5.)

[0253] The same procedure as in Example 1 was carried out except that 4.20 g of epibromohydrin was used instead of the compound represented by formula (40), to obtain 8.5 g of compound (V).

[0254] The obtained compound (V) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-d6): δ[ppm]=1.2~2.0(10H), 3.20~4.20(46H) 19 F-NMR (acetone-d6): δ[ppm]=-55.6~-50.6(18F), -77.7(4F), -80.3(4F), -91.0~-88.5(36F)

[0255] The compounds of Examples 1 to 16 thus obtained were applied to formula (1) to obtain R 1 , R 5 The structure of R 2 , R 4 The structure of R 3 The structures (alicyclic structures X or X', Y, X or X' in formulas (2-1) to (2-4)) are shown in Table 1.

[0256] [Table 1]

[0257] The number average molecular weights (Mn) of the compounds of Examples 1 to 16 and Comparative Examples 1 to 6 were determined by the method described above. 1 H-NMR and / or 19 The results were obtained by F-NMR measurement, and are shown in Table 2. It is estimated that the average molecular weight of the synthesized compounds varies by about 1 to 5 points depending on the molecular weight distribution of the fluoropolyether used as the raw material for the compounds and differences in the operations used to synthesize the compounds.

[0258] [Table 2]

[0259] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 16 and Comparative Examples 1 to 6. Then, using the obtained solutions for forming lubricating layers, lubricating layers for magnetic recording media were formed by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 16 and Comparative Examples 1 to 6.

[0260] "Lubricant layer forming solution" The compounds obtained in Examples 1 to 16 and Comparative Examples 1 to 6 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel so that the film thickness when applied to the protective layer would be 8 Å to 9 Å, to prepare a solution for forming a lubricating layer.

[0261] "Magnetic recording media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate having a diameter of 65 mm. The protective layer was made of carbon. On the protective layer of each magnetic recording medium on which the layers up to the protective layer had been formed, the lubricating layer-forming solutions of Examples 1 to 16 and Comparative Examples 1 to 6 were each applied by dipping under the conditions of an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a pull-up speed of 1.2 mm / sec. The magnetic recording medium coated with the lubricating layer-forming solution was then placed in a thermostatic chamber at 120°C and heated for 10 minutes to remove the solvent in the lubricating layer-forming solution, thereby forming a lubricating layer on the protective layer and obtaining the magnetic recording medium.

[0262] The thickness of the lubricating layer of each of the magnetic recording media thus obtained in Examples 1 to 16 and Comparative Examples 1 to 6 was measured using an FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Table 2.

[0263] (Chemical resistance test) The following evaluation method was used to investigate the contamination of magnetic recording media by environmental substances that generate contaminants in high-temperature environments. In the evaluation method described below, Si ions were used as the environmental substances, and the amount of Si adsorption was measured as the amount of contaminants that contaminate the magnetic recording media generated by the environmental substances.

[0264] Specifically, the magnetic recording medium to be evaluated was stored in a high-temperature environment of 85°C and 0% humidity in the presence of siloxane-based Si rubber for 240 hours. The amount of Si adsorption on the surface of the magnetic recording medium was then analyzed and measured using secondary ion mass spectrometry (SIMS), and the degree of contamination by Si ions was evaluated as the amount of Si adsorption. The amount of Si adsorption was evaluated using a numerical value with the result of Comparative Example 1 set to 1.00. The results are shown in Table 2.

[0265] Next, the magnetic recording media of Examples 1 to 16 and Comparative Examples 1 to 6 were subjected to the following wear resistance test.

[0266] (Wear resistance test) Using a pin-on-disk friction and wear tester, a 2 mm diameter alumina ball serving as a contact was slid on the lubricating layer of the magnetic recording medium at a load of 40 gf and a sliding speed of 0.25 m / sec to measure the friction coefficient of the surface of the lubricating layer. The sliding time until the friction coefficient of the surface of the lubricating layer suddenly increased was then measured. The sliding time until the friction coefficient suddenly increased was measured four times for the lubricating layer of each magnetic recording medium, and the average value (time) was used as an index of the wear resistance of the lubricant coating. The results for the magnetic recording media of Examples 1 to 16 and Comparative Examples 1 to 6 are shown in Table 2. The evaluation of the time until the friction coefficient suddenly increased was as follows: The larger the value, the better the result.

[0267] ◎(Excellent): 880sec or more ○ (Good): 780 seconds or more, less than 880 seconds △ (Acceptable): 680 seconds or more, less than 780 seconds × (Not allowed): Less than 680 seconds

[0268] The time until the coefficient of friction increases sharply 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 out as the magnetic recording medium is used, and when the lubricating layer is worn away, the contact and protective layer come into direct contact, causing a sharp increase in the coefficient of friction. The time until the coefficient of friction increases sharply is thought to be correlated with friction testing.

[0269] (comprehensive evaluation) Based on the results of the chemical resistance test and the abrasion resistance test, an overall evaluation was made according to the following criteria. ◯ (Good): In the chemical resistance test, the amount of Si adsorption was 0.60 or less, and the abrasion resistance test was evaluated as ⊚ (Excellent) or ◯ (Good). × (unacceptable): Did not meet the criteria for ○ (good) above.

[0270] As shown in Table 2, the magnetic recording media of Examples 1 to 16 had lower Si adsorption and better chemical resistance than the magnetic recording media of Comparative Examples 1 to 6. Furthermore, the magnetic recording media of Examples 1 to 16 had a longer sliding time before the coefficient of friction increased sharply, and also had better wear resistance. Furthermore, all of Examples 1 to 16 received an overall rating of ○ (good).

[0271] In particular, R 1 , R 5 In Examples 10 and 13, which each had three hydroxyl groups, the Si adsorption amount was 0.35 or less, and the chemical resistance was good. This is presumably due to the following reasons. 1 , R 3 , R 5 The polar group in 3 The bulky alicyclic structure contained in R has a pinning effect that prevents the protective layer from completely lifting off. 1 , R 5 The pinning effect is more effective because each of the three hydroxyl groups in the lubricating layer and the protective layer has three. As a result, it is presumed that an appropriate distance is maintained between the lubricating layer and the protective layer, improving chemical resistance.

[0272] Also, R 3 In Examples 4, 5, 8, and 9, the alicyclic structure contained in R has a substituent consisting of an alkoxy group having a hydroxyl group at the terminal, and all of these examples had good abrasion resistance. 3 This is presumably because the distance between the alicyclic structure X and the carbon atom to which the hydroxyl group in the substituent is bonded is sufficiently ensured by the linking group having appropriate flexibility, which contains an ether bond and a carbon atom, and therefore the pinning effect of the alicyclic structure X by the hydroxyl group in the substituent is appropriate. Also, R 2 , R 4 In Example 10, R 1 , R 5 In Example 15, where is the formula (8), the abrasion resistance was also good.

[0273] In contrast, the overall evaluation of Comparative Examples 1 to 6 was x (unacceptable). More specifically, Comparative Example 1, which used compound (Q) having three perfluoropolyether chains in the molecule, Comparative Example 2, which used compound (R), Comparative Example 3, which used compound (S), and Comparative Example 4, which used compound (T), all showed inferior results in the chemical resistance test compared to Examples 1 to 16.

[0274] Furthermore, R in formula (1) 1 and R 5 In Comparative Example 2, which used compound (R) in which each end group corresponding to the formula (I) contains two hydroxyl groups, each hydroxyl group is bonded to a different carbon atom, and the carbon atoms to which the hydroxyl groups are bonded are bonded to each other, the results of the abrasion resistance test were inferior to those of Comparative Example 1, which used compound (Q) in which each end group has one hydroxyl group.

[0275] Furthermore, R in Equation (1) 1 and R 5 In Comparative Example 4, which used compound (T) in which each end group corresponding to the formula (I) contains two hydroxyl groups, each hydroxyl group is bonded to a different carbon atom, and the carbon atoms to which the hydroxyl groups are bonded are bonded to each other, the results of the abrasion resistance test were inferior to those of Comparative Example 3, which used compound (S) in which each end group has one hydroxyl group.

[0276] R in Equation (1) 3 In Comparative Example 5, which used a compound (U) in which the organic group corresponding to the following formula did not contain a polar group, the evaluation in the chemical resistance test was inferior to Examples 1 to 16, and the results in the abrasion resistance test were also inferior. Furthermore, R in formula (1) 3 In Comparative Example 6, in which a compound (V) was used in which the organic group corresponding to the compound (V) did not have an alicyclic structure having 3 to 13 carbon atoms, the results of the chemical resistance test and the abrasion resistance test were inferior to those of Examples 1 to 16.

[0277] From the above results, it was found that by forming a lubricating layer containing the compounds of Examples 1 to 16 on the protective layer of a magnetic recording medium, a lubricating layer with excellent chemical resistance and wear resistance can be obtained, even if the thickness is as thin as 8 Å to 9 Å. [Industrial Applicability]

[0278] The present invention provides a fluorine-containing ether compound capable of forming a lubricating layer having excellent chemical resistance and abrasion resistance even when the thickness is reduced. 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 chemical resistance and abrasion resistance even if it is thin. [Explanation of symbols]

[0279] 10. Magnetic recording media 11... Substrate 12. Adhesion layer 13...Soft magnetic layer 14...1st base layer 15...Second base layer 16...magnetic layer 17...protective layer 18...Lubricating layer

Claims

1. A fluorine-containing ether compound represented by the following formula (1): R １ -CH ２ -R ２ -CH ２ -R ３ -CH ２ -R ４ -CH ２ -R ５ (1) (In formula (1), R ３ is a divalent organic group represented by any one of the following formulas (2-1) to (2-4), and does not contain a perfluoropolyether chain; R ２ and R ４ is a perfluoropolyether chain represented by any one of the following formulas (4) to (6); R １ and R ５ is a terminal group of any one of the following formulas (7) to (10): -CF 2 O- (CF 2 CF 2 O) b - (CF 2 O) c -CF 2 - (4) (In formula (4), b and c represent the average degree of polymerization, each independently representing 0 to 30; however, b and c cannot simultaneously be 0.) -CF(CF 3 )-(OCF(CF 3 )CF 2 ) d -OCF(CF 3 )- (5) (In formula (5), d represents the average degree of polymerization and is 0.1 to 30.) -CF 2 CF 2 O- (CF 2 CF 2 CF 2 O) e -CF 2 CF 2 - (6) (In formula (6), e represents the average degree of polymerization and is 0.1 to 30.) 【Chemistry 1】 (In formula (2-1), X represents an alicyclic structure having 3 to 13 carbon atoms; Y represents —O—, —NH—, or —CH 2 —.) (In formula (2-2), X' is an alicyclic structure having 3 to 13 carbon atoms and has at least one substituent containing a polar group; Y represents -O-, -NH-, or -CH 2 -.) (In formula (2-3), X represents an alicyclic structure having 3 to 13 carbon atoms; Y represents —O—, —NH—, or —CH 2 —.) (In formula (2-4), X represents an alicyclic structure having 3 to 13 carbon atoms; Y represents —O—, —NH—, or —CH 2 —.) 【Chemistry 2】 (In formula (7), f represents an integer of 1 to 2, and g represents an integer of 1 to 5.) (In formula (8), h represents an integer of 1 to 5.) (In formula (9), i represents an integer of 1 to 5.) (In formula (10), j represents an integer of 1 or 2, and k represents an integer of 1 or 2.)

2. 2. The fluorine-containing ether compound according to claim 1, wherein Y in the formulae (2-1) to (2-4) is —O—.

3. The R ３ 3. The fluorine-containing ether compound according to claim 1, wherein the alicyclic structure contained in the formula (I) is a saturated alicyclic structure.

4. The R ３ 4. The fluorine-containing ether compound according to any one of claims 1 to 3, wherein the alicyclic structure contained in the formula (I) is one selected from the group consisting of cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, and adamantane.

5. The R ３ 5. The fluorine-containing ether compound according to any one of claims 1 to 4, wherein at least one polar group contained in is a group containing a polar group selected from the group consisting of a hydroxyl group, an alkoxy group, an amide group, an amino group, a carbonyl group, a carboxy group, a nitro group, a cyano group, and a sulfo group.

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

7. The fluorine-containing ether compound according to any one of claims 1 to 6, wherein the compound represented by formula (1) is any one of compounds represented by the following formulas (A) to (P): 【Transformation 3】 (In formula (A), ba1, ca1, ba2, and ca2 represent average degrees of polymerization, ba1 and ba2 represent 0 to 30, and ca1 and ca2 represent 0 to 30; however, ba1 and ca1 will not be 0 at the same time, and ba2 and ca2 will not be 0 at the same time.) (In formula (B), bb1, cb1, bb2, and cb2 represent average degrees of polymerization, bb1 and bb2 represent 0 to 30, and cb1 and cb2 represent 0 to 30; however, bb1 and cb1 cannot be 0 at the same time, and bb2 and cb2 cannot be 0 at the same time.) (In formula (C), bc1, cc1, bc2, and cc2 represent average degrees of polymerization, bc1 and bc2 represent 0 to 30, and cc1 and cc2 represent 0 to 30; however, bc1 and cc1 cannot be 0 at the same time, and bc2 and cc2 cannot be 0 at the same time.) 【Chemistry 4】 (In formula (D), bd1, cd1, bd2, and cd2 represent average degrees of polymerization, bd1 and bd2 represent 0 to 30, and cd1 and cd2 represent 0 to 30; however, bd1 and cd1 cannot be 0 at the same time, and bd2 and cd2 cannot be 0 at the same time.) (In formula (E), be1, ce1, be2, and ce2 represent average degrees of polymerization, be1 and be2 represent 0 to 30, and ce1 and ce2 represent 0 to 30; however, be1 and ce1 will not be 0 at the same time, and be2 and ce2 will not be 0 at the same time.) (In formula (F), bf1, cf1, bf2, and cf2 represent average degrees of polymerization, bf1 and bf2 represent 0 to 30, and cf1 and cf2 represent 0 to 30; however, bf1 and cf1 will not be 0 at the same time, and bf2 and cf2 will not be 0 at the same time.) 【Transformation 5】 (In formula (G), bg1, cg1, bg2, and cg2 represent average degrees of polymerization, bg1 and bg2 represent 0 to 30, and cg1 and cg2 represent 0 to 30; however, bg1 and cg1 cannot be 0 at the same time, and bg2 and cg2 cannot be 0 at the same time.) (In formula (H), bh1, ch1, bh2, and ch2 represent average degrees of polymerization, bh1 and bh2 represent 0 to 30, and ch1 and ch2 represent 0 to 30; however, bh1 and ch1 cannot be 0 at the same time, and bh2 and ch2 cannot be 0 at the same time.) (In formula (I), bi1 and bi2 represent average degrees of polymerization, and bi1 and bi2 represent 0.1 to 30.) (In formula (J), ej1 and ej2 represent average degrees of polymerization, and ej1 and ej2 represent 0.1 to 30.) 【Transformation 6】 (In formula (K), bk1, ck1, bk2, and ck2 represent average degrees of polymerization, bk1 and bk2 represent 0 to 30, and ck1 and ck2 represent 0 to 30; however, bk1 and ck1 will not be 0 at the same time, and bk2 and ck2 will not be 0 at the same time.) (In formula (L), bl1, cl1, bl2, and cl2 represent average degrees of polymerization, bl1 and bl2 represent 0 to 30, and cl1 and cl2 represent 0 to 30; however, bl1 and cl1 cannot be 0 at the same time, and bl2 and cl2 cannot be 0 at the same time.) 【Transformation 7】 (In formula (M), bm1, cm1, bm2, and cm2 represent average degrees of polymerization, bm1 and bm2 represent 0 to 30, and cm1 and cm2 represent 0 to 30; however, bm1 and cm1 cannot be 0 at the same time, and bm2 and cm2 cannot be 0 at the same time.) (In formula (N), bn1, cn1, bn2, and cn2 represent average degrees of polymerization, bn1 and bn2 represent 0 to 30, and cn1 and cn2 represent 0 to 30; however, bn1 and cn1 cannot be 0 at the same time, and bn2 and cn2 cannot be 0 at the same time.) (In formula (O), bo1, co1, bo2, and co2 represent average degrees of polymerization, bo1 and bo2 represent 0 to 30, and co1 and co2 represent 0 to 30; however, bo1 and co1 cannot be 0 at the same time, and bo2 and co2 cannot be 0 at the same time.) (In formula (P), bp1, cp1, bp2, and cp2 represent average degrees of polymerization, bp1 and bp2 represent 0 to 30, and cp1 and cp2 represent 0 to 30; however, bp1 and cp1 cannot be 0 at the same time, and bp2 and cp2 cannot be 0 at the same time.)

8. A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of claims 1 to 7.

9. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, 8. A magnetic recording medium, wherein the lubricating layer comprises the fluorine-containing ether compound according to claim 1.

10. 10. The magnetic recording medium according to claim 9, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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