WO2022138478A1

WO2022138478A1 - Fluorine-containing ether compound, lubricant for magnetic recording medium, and magnetic recording medium

Info

Publication number: WO2022138478A1
Application number: PCT/JP2021/046691
Authority: WO
Inventors: 晋毅南口
Original assignee: 昭和電工株式会社
Priority date: 2020-12-25
Filing date: 2021-12-17
Publication date: 2022-06-30

Abstract

Provided is a fluorine-containing ether compound represented by the following formula. R¹-R²-CH₂-R³-CH₂-R⁴-R⁵ (R¹ and R⁵ each represent a terminal group represented by formula (2) and including an oxime group, R² and R⁴ each represent a divalent linkage group having a polar group, and R³ represents a perfluoropolyether chain.)

Description

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

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. 2020-216497 filed in Japan on December 25, 2020, the contents of which are incorporated herein by reference.

In order to improve the recording density of the magnetic recording / playback device, the development of a magnetic recording medium suitable for a high recording density is underway.
Conventionally, as a magnetic recording medium, there is a magnetic recording medium in which a recording layer is formed on a substrate and a protective layer such as carbon is formed on the recording layer. The protective layer protects the information recorded on the recording layer and enhances the slidability of the magnetic head. However, the durability of the magnetic recording medium cannot be sufficiently obtained only by providing the protective layer on the recording layer. Therefore, in general, a lubricant is applied to the surface of the protective layer to form the lubricating layer.

Examples of the lubricant used when forming the lubricating layer of the magnetic recording medium include polar groups such as a hydroxyl group, an amino group, an imino group, and an isocyanate group at the end of a fluorine-based polymer having a repeating structure containing CF ₂ . Those containing a compound having the above have been proposed.
For example, Patent Document 1 discloses a fluorine-containing ester compound having a terminal group containing an oxime group at the molecular terminal.

Patent Document 2 describes that an activation-treated layer is formed on the surface of a protective film layer made of a fluorine-based organic compound, and a lubricating layer made of a compound having a cumulative double bond is provided on the activation-treated layer. .. Patent Document 2 describes that an activation-treated layer is formed by introducing at least one group selected from a hydroxyl group, an amino group, and an imino group. Further, Patent Document 2 describes isocyanate as a compound having a cumulative double bond, which is an active moiety that causes a double addition reaction with the above-mentioned introduction group.

Further, in Patent Document 3, an ether bond (-O-), a methylene group ( _-CH2- ) and one hydrogen atom are substituted with hydroxyl groups between the perfluoropolyether chain and both terminal groups, respectively. A fluorine-containing ether compound in which a linking group in combination with a methylene group (-CH (OH)-) is arranged is disclosed.

Japanese Unexamined Patent Publication No. 2005-263746 Special Fair 7-99576 Gazette International Publication No. 2019/054148

In the magnetic recording / reproducing device, it is required to further reduce the floating amount of the magnetic head. Therefore, it is required to make the thickness of the lubricating layer in the magnetic recording medium thinner.
However, when the thickness of the lubricating layer is reduced, the number of molecules of the compound constituting the lubricating layer is reduced, and the adhesion of the lubricating layer to the magnetic recording medium tends to be lowered.

Further, in the magnetic recording / playback device, the rotation speed of the magnetic recording medium is increasing in order to increase the capacity of the magnetic recording medium. Along with this, spin-off of the lubricating layer is likely to occur. Spin-off is a phenomenon in which the lubricant scatters or evaporates due to centrifugal force and heat generated by the rotation of the magnetic recording medium. If the adhesion of the lubricating layer to the magnetic recording medium is insufficient, spin-off is likely to occur.

As a method for improving the adhesion of the lubricating layer to the magnetic recording medium, it is conceivable to use a fluorine-containing ether compound containing many polar groups in the molecule as the compound contained in the lubricating layer. However, if the number of polar groups contained in the fluorine-containing ether compound is increased, the fluorine-containing ether compound in the lubricating layer containing the polar groups tends to be picked up as foreign matter (smear) attached to the magnetic head.

The present invention has been made in view of the above circumstances, has excellent adhesion even if the thickness is thin, can form a lubricating layer in which pickup and spin-off are unlikely to occur, and is suitable as a material for a lubricant for a magnetic recording medium. It is an object of the present invention to provide a fluorine-containing ether compound that can be used in the above.
Another object of the present invention is to provide a lubricant for a magnetic recording medium containing the fluorine-containing ether compound of the present invention.
Another object of the present invention is to provide a magnetic recording medium having an excellent reliability and durability having a lubricating layer containing the fluorine-containing ether compound of the present invention.

The present inventor has conducted extensive research to solve the above problems.
As a result, they found that a fluorine-containing ether compound in which a specific terminal group including an oxime group is bonded via a divalent linking group having a polar group at both ends of the perfluoropolyether chain may be used. I came up with the present invention.
That is, the present invention relates to the following matters.
The first aspect of the present invention provides the following fluorine-containing ether compounds.

[1] A fluorine-containing ether compound represented by the following formula (1).
R ¹ -R ² -CH ₂ -R ³ -CH ₂ -R ⁴ -R ⁵ (1)
(In formula (1), R ¹ and R ⁵ are terminal groups represented by the following formula (2) containing an oxime group, respectively; R ² and R ⁴ are divalent linking groups having polar groups, respectively. R ³ is a perfluoropolyether chain.)

(In the formula (2), X and Y are either a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have a substituent, and an organic group having a double bond or a triple bond, respectively.)

The fluorine-containing ether compound according to the first aspect of the present invention preferably has the characteristics described in the following [2] to [10]. It is also preferable to arbitrarily combine two or more of the features described in the following [2] to [10].
[2] The fluorine-containing ether compound according to [1], wherein the number of hydroxyl groups contained in the molecule is 8 or less.
[3] The fluorine-containing ether compound according to [1], wherein the number of hydroxyl groups contained in the molecule is 6 or less.

[4] The fluorine-containing ether compound according to any one of [1] to [3], wherein the polar group contained in R ² and R ⁴ is a hydroxyl group.

[5] The inclusion of any of [1] to [4], wherein the R ³ -CH ₂ -R ^2- and the R ³ -CH ₂ -R ^4- are represented by the following formula (3). Fluorine ether compound.
R ³ -CH _2- [A]-[B]-[C]-(3)
(In the formula (3), [A] is represented by the following formula (4), [B] is represented by the following formula (5), and [C] is represented by the following formula (6); ), The order of [A], [B], and [C] may be changed; the ether bond side in the formulas (4) to (6) is the CH ₂ side in the formula (3).)

(In equation (4), a is an integer of 0 to 3; in equation (5), b is an integer of 0 to 3 and c is an integer of 1 to 4; in equation (6), d. Is an integer of 0 to 3 and e is an integer of 1 to 4; however, at least one of a, b, and d is 1 or more.)

[6] The inclusion according to any one of [1] to [5], wherein X and / or Y in the formula (2) in at least one of R ¹ and R ⁵ is an alkyl group having a hydroxyl group. Fluorine ether compound.

[7] The fluorine-containing ether compound according to any one of [1] to [6], wherein R ³ is represented by any of the following formulas (7) to (11).
-CF ₂ O- (CF ₂ CF ₂ O) _m- (CF ₂ O) _n -CF _2- (7)
(M and n in the formula (7) indicate the average degree of polymerization, and each represents 0.1 to 30.)
-CF ₂ O- (CF ₂ CF ₂ O) _w -CF _2- (8)
(W in the formula (8) indicates the average degree of polymerization and represents 0.1 to 30.)
-CF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ O) _x -CF ₂ CF _2- (9)
(X in the formula (9) indicates the average degree of polymerization and represents 0.1 to 30).
-CF ₂ CF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ CF ₂ O) _y -CF ₂ CF ₂ CF _2- (10)
(Y in the formula (10) indicates the average degree of polymerization and represents 0.1 to 30).
-CF (CF ₃ )-(OCF (CF ₃ ) CF ₂ ) _z -OCF (CF ₃ )-(11)
(Z in the formula (11) indicates the average degree of polymerization and represents 0.1 to 30.)

[8] The fluorine-containing ether compound according to any one of [1] to [7], wherein R ¹ and R ⁵ are the same.
[9] The fluorine-containing ether compound according to any one of [1] to [8], wherein R ² and R ⁴ are the same.
[10] The fluorine-containing ether compound according to any one of [1] to [9], wherein the number average molecular weight is in the range of 500 to 10000.

A second aspect of the present invention provides the following lubricants for magnetic recording media.
[11] A lubricant for a magnetic recording medium, which comprises the fluorine-containing ether compound according to any one of [1] to [10].
A third aspect of the present invention provides the following magnetic recording medium.
[12] A magnetic recording medium in which at least a magnetic layer, a protective layer, and a lubricating layer are 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 [10].
The magnetic recording medium of the third aspect of the present invention preferably has the characteristics described in the following [13].
[13] The magnetic recording medium according to [12], wherein the lubricating layer has an average film thickness of 0.5 nm to 2.0 nm.

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.
Since the lubricant for a magnetic recording medium of the present invention contains the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer having excellent adhesion even if the thickness is thin.
Since the magnetic recording medium of the present invention is provided with a lubricating layer having excellent adhesion, it has excellent reliability and durability.

It is the schematic sectional drawing which showed the preferable embodiment of the magnetic recording medium of this invention.

Hereinafter, the fluorine-containing ether compound of the present invention, the lubricant for a magnetic recording medium (hereinafter, may be abbreviated as “lubricant”), and the magnetic recording medium will be described in detail. The present invention is not limited to the embodiments shown below. The present invention can be added, omitted, replaced, or changed in terms of number, quantity, ratio, material, composition, etc., without departing from the spirit of the present invention.

[Fluorine-containing ether compound]
The fluorine-containing ether compound of this embodiment is represented by the following formula (1).
R ¹ -R ² -CH ₂ -R ³ -CH ₂ -R ⁴ -R ⁵ (1)
(In formula (1), R ¹ and R ⁵ are terminal groups represented by the following formula (2) containing an oxime group, respectively; R ² and R ⁴ are divalent linking groups having polar groups, respectively. R ³ is a perfluoropolyether chain.)

Here, the reason why excellent adhesion can be obtained even if the thickness is thin when the lubricating layer is formed on the protective layer of the magnetic recording medium by using the lubricant containing the fluorine-containing ether compound of the present embodiment. explain.

As shown in the formula (1), the fluorine-containing ether compound of the present embodiment has a perfluoropolyether chain represented by R3 ⁽ hereinafter, may be abbreviated as “PFPE chain”). In the lubricating layer containing the fluorine-containing ether compound of the present embodiment, the PFPE chain covers the surface of the protective layer and imparts lubricity to the lubricating layer to reduce the frictional force between the magnetic head and the protective layer.

Further, R ¹ and R ⁵ in the formula (1) are terminal groups represented by the formula (2) containing an oxime group, respectively. The nitrogen and oxygen atoms forming the oxime group have polarity, and have an interaction (affinity) with the protective layer and an intramolecular interaction.
The nitrogen atom forming the oxime group has a strong interaction with the protective layer and is equivalent to a hydroxyl group. Therefore, the oxime groups contained in R ¹ and R ⁵ promote the adsorption of the fluorine-containing ether compound to the protective layer.

Moreover, the intramolecular interaction of the nitrogen atom forming the oxime group is weaker than that of the hydroxyl group. Therefore, in the nitrogen atom of the fluorine-containing ether compound represented by the formula (1), the interaction with the surface of the protective layer has priority over the intramolecular interaction. Therefore, the fluorine-containing ether compound represented by the formula (1) is compared with the fluorine-containing ether compound in which the two oxime groups (-C = NO-) are each replaced with a divalent linking group having a hydroxyl group. Therefore, it does not easily aggregate on the protective layer. Further, the oxime groups contained in R ¹ and R ⁵ have a rigid C = N bond. The rigid C = N bond is a polar group possessed by the fluoroether compound (the polar group possessed by R ² or R ⁴ , and the polar group thereof when X and / or Y in the formula (2) has a polar group. ) Is moderately restricted, and the aggregation of the fluorine-containing ether compound represented by the formula (1) on the protective layer is suppressed.

As described above, R ¹ and R ⁵ promote the adsorption of the fluorine-containing ether compound to the protective layer, suppress the aggregation of the fluorine-containing ether compound on the protective layer, and spread in the plane direction on the protective layer. Make it easy to arrange in a uniformly extended state. As a result, the lubricating layer containing the fluorine-containing ether compound represented by the formula (1) can be formed with a sufficient coverage even if the thickness is thin, and the adhesion to the protective layer is good.

Further, R ² and R ⁴ in the formula (1) are divalent linking groups having polar groups, respectively. The polar group of R ² or R ⁴ has an interaction (affinity) with the protective layer and promotes the adsorption of the fluorine-containing ether compound to the protective layer. Therefore, in the lubricating layer containing the fluorine-containing ether compound represented by the formula (1), the interaction between the oxime group contained in R ¹ and R ⁵ and the protective layer, and the polar group and protection of R ² and R ⁴ are protected. The synergistic effect of the interaction with the layer provides good adhesion to the protective layer.

(R ¹ and R ⁵ )
In the fluorine-containing ether compound of the present embodiment represented by the formula (1), R ¹ is a terminal group bonded to R ² and R ⁵ is a terminal group bonded to R ⁴ . R ¹ and R ⁵ may be the same or different.
In the fluorine-containing ether compound represented by the formula (1), since R ¹ and R ⁵ each contain an oxime group, the fluorine-containing ether compound and the protective layer adhere to each other in the lubricating layer containing the fluorine-containing ether compound. The sex becomes good.

R ¹ and R ⁵ are terminal groups represented by the formula (2) containing an oxime group, respectively. In formula (2), X and Y are each a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have a substituent, and an organic group having a double bond or a triple bond, respectively. In the present embodiment, since X and Y in the formula (2) provide a function of exhibiting a better interaction with the protective layer of the magnetic recording medium, a fluorine-containing lubricating layer capable of forming a lubricating layer having excellent adhesion can be formed. It becomes an ether compound.
The alkyl group having 1 to 12 carbon atoms which may have a substituent as X and / or Y in the formula (2) and the organic group having a double bond or a triple bond are oxygen atom, sulfur atom and nitrogen. It may contain any of the atoms. X and Y may be the same or different.

(Alkyl group which may have a substituent)
The alkyl group in the alkyl group having 1 to 12 carbon atoms which may have a substituent (hereinafter, may be referred to as "alkyl group which may have a substituent") is an alkyl having 1 to 8 carbon atoms. It is preferably a group, and more preferably an alkyl group having 1 to 6 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group and an octyl group. The alkyl group may be linear or may have a branch.
When both X and Y in the formula (2) are alkyl groups which may have a substituent, the total number of carbon atoms contained in X and Y is preferably 2 to 8, preferably 2 to 6. Is more preferable.

Examples of the substituent in the alkyl group which may have a substituent include a halogeno group, an alkoxy group, a hydroxyl group and a cyano group. When the alkyl group which may have a substituent has these substituents, it becomes a fluorine-containing ether compound capable of forming a lubricating layer having better adhesion.

The alkyl group having a halogeno group as a substituent is preferably an alkyl group having at least one fluoro group. Examples of the alkyl group having a fluoro group include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, an octafluoropentyl group, and a tridecafluorooctyl group. Group etc. can be mentioned.

Examples of the alkyl group having a hydroxyl group as a substituent include an alkyl group represented by the following formula (14). In the fluorine-containing ether compound represented by the formula (1), it is preferable that X and / or Y in the formula (2) in at least one of R ¹ and R ⁵ is an alkyl group having a hydroxyl group, and the formula (14). ) Is more preferable. When X and / or Y in the formula (2) in at least one of R ¹ and R ⁵ is an alkyl group represented by the formula (14), the affinity between the lubricating layer containing the fluorine-containing ether compound and the protective layer. The property becomes even better, which is preferable.

(In formula (14), R ⁶ is an alkyl group which may have a hydrogen atom or a hydroxyl group; d represents an integer of 1 to 6; when d is 2 or more, R ⁶ is the same. It may or may not be different.)

In formula (14), R ⁶ is an alkyl group which may have a hydrogen atom or a hydroxyl group. R ⁶ is preferably an alkyl group or a hydrogen atom having 1 to 6 carbon atoms, more preferably an alkyl group or a hydrogen atom having 1 to 4 carbon atoms, and an alkyl group or a hydrogen atom having 1 to 2 carbon atoms. Is particularly preferable. In the group represented by the formula (14), the dotted line on the left side in the formula (14) is bonded to the carbon atom forming the double bond of the oxime group contained in the formula (2).

In the formula (14), d represents an integer of 1 to 6, preferably an integer of 1 to 4, and more preferably 2 or 3. When d is an integer of 1 to 6, the distance between the rigid C = N bond of the oxime group and the hydroxyl group in the formula (14) becomes appropriate, and the C = N bond makes the hydroxyl group in the formula (14) appropriate. Motility is moderately restricted and preferred.
The number of carbon atoms in the formula (14) (the total number of carbon atoms contained in R ⁶ and the number of d) is 1 to 12, preferably 1 to 8, and more preferably 1 to 6. It is preferable, and it is more preferably 1 to 4. When the number of carbon atoms in the formula (14) is 1 to 8, the surface free energy of the entire molecule does not decrease due to the low proportion of fluorine atoms in the fluorine-containing ether compound molecule, which is preferable.

When X and / or Y in the formula (2) is an alkyl group represented by the formula (14), R ¹ and R ⁵ are specifically represented by the following formulas (12-1) to (12-6). ), Whichever structure is represented by the formulas (13-1) to (13-4) is preferable.

(Organic group with double or triple bond)
When X and / or Y in the formula (2) is an organic group having a double bond or a triple bond, the organic group has at least one double bond or a triple bond, and is, for example, aromatic. Examples thereof include a group containing a group hydrocarbon, a group containing an aromatic heterocycle, a group containing an alkenyl group, and a group containing an alkynyl group. The double bond or triple bond is preferably a carbon-carbon double bond or a carbon-carbon triple bond.

Specifically, examples of the organic group having a double bond or a triple bond include a phenyl group, a methoxyphenyl group, a phenyl fluoride group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a phenethyl fluoride group, a benzyl group and a methoxybenzyl group. Group, naphthylmethyl group, methoxynaphthyl group, pyrrolyl group, pyrazolyl group, methylpyrazolylmethyl group, imidazolyl group, frill group, flufuryl group, oxazolyl group, isooxazolyl group, thienyl group, thienylethyl group, thiazolyl group, methylthiazolyl Ethyl group, isothiazolyl group, pyridyl group, pyrimidinyl group, pyridazinyl group, pyrazinyl group, indolinyl group, benzofuranyl group, benzothienyl group, benzoimidazolyl group, benzoxazolyl group, benzothiazolyl group, benzopyrazolyl group, benzoisoxazolyl group , Benzoisothiazolyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, cinnolinyl group, vinyl group, allyl group, butenyl group, 1-propynyl group, propargyl group (2-propynyl group), butynyl group. , Methylbutynyl group, pentynyl group, methylpentinyl group, hexynyl group and the like.

Examples of the organic group having a double bond or a triple bond include a phenyl group, a methoxyphenyl group, a thienylethyl group, a butenyl group, an allyl group, a propargyl group, a phenethyl group, a methoxyphenethyl group and a fluorinated phenethyl group. Any of them is preferable, and any of a phenyl group, a methoxyphenyl group, an allyl group, a butenyl group, and a propargyl group is more preferable.
When the organic group having a double bond or a triple bond is any one of a phenyl group, a methoxyphenyl group, an allyl group, a butenyl group, and a propargyl group, a fluorine-containing ether compound capable of forming a lubricating layer having better adhesion can be formed. Will be.

The above-mentioned organic group having a double bond or a triple bond may have a substituent such as an alkyl group, an alkoxy group, a hydroxyl group, a mercapto group, a carboxy group, a carbonyl group, an amino group or a cyano group.

The alkyl group, which may have a substituent as X and / or Y, and the organic group, which has a double bond or a triple bond, are carbons forming a double bond of the oxime group contained in the formula (2). A linking group consisting of an ether bond and a methylene chain may be bonded to the atom. In particular, the above-mentioned organic group having a double bond or a triple bond has one ether bond and one methylene chain between the carbon atom forming the double bond of the oxime group contained in the formula (2). It is preferable that the linking group consisting of is bonded. In this case, the distance between the double or triple bond and the rigid C = N bond of the oxime group is appropriate, and the C = N bond moderately limits the motility of the double or triple bond, resulting in more aggregation. It is a fluorine-containing ether compound that is difficult to form and can form a lubricating layer having excellent adhesion.

Examples of the linking group bonded to the carbon atom forming the double bond of the oxime group contained in the formula (2) include an oxyethyl group (-O-CH ₂ -CH _2- ) and an oxypropyl group (-). Examples thereof include O-CH ₂ -CH ₂ -CH _2- ) and an oxybutyl group (-O-CH ₂ -CH ₂ -CH ₂ -CH _2- ). The number of carbon atoms of the methylene chain contained in the linking group is preferably 1 to 6, and more preferably 1 to 4. When the number of carbon atoms in the methylene chain is 1 to 6, the surface free energy of the entire molecule does not decrease due to the low proportion of fluorine atoms in the fluorine-containing ether compound molecule, which is preferable.

When an organic group having an alkyl group, a double bond or a triple bond, which may have a substituent, has a linking group consisting of an ether bond and a methylene chain with an oxime group, for the following reasons, It is preferable that the carbon atom forming the double bond of the oxime group is bonded to the methylene chain of the linking group. That is, the rigid C = N bond of the oxime group has the function of appropriately limiting the motility of the alkyl group which may have a substituent or the motility of the organic group which has a double bond or a triple bond. This is because it is unlikely to be hindered by the ether bond contained in the linking group. As a result, the adsorption of the fluorine-containing ether compound to the protective layer is promoted, and better adhesion to the protective layer can be obtained.

(R ² and R ⁴ )
R ² and R ⁴ in the formula (1) are divalent linking groups having polar groups, respectively. R ² and R ⁴ may be the same or different.
Since R ² and R ⁴ have polar groups, when a lubricating layer is formed on the protective layer by using the lubricant containing the fluorine-containing ether compound of the present embodiment, it is suitable between the lubricating layer and the protective layer. Interaction occurs. The divalent linking group having a polar group forming R ² and R ⁴ can be appropriately selected depending on the performance required for the lubricant containing the fluorine-containing ether compound and the like.

The polar groups contained in R ² and R ⁴ cause a suitable interaction between the lubricant and the protective layer when a lubricating layer made of a lubricant containing a fluorine-containing ether compound is formed on the protective layer. It is preferable that the lubricant is used. Examples of such a polar group include a hydroxyl group (-OH), an amino group (-NH ₂ ), a carboxy group (-COOH), an aldehyde group (-CHO), a carbonyl group (-CO-), and a sulfonic acid group (-CO-). -SO ₃ H) and the like. Of these, hydroxyl groups are particularly preferred. The hydroxyl group is a polar group having a strong interaction with a protective layer, particularly a carbon-based protective layer. Therefore, when the polar group contained in R ² and R ⁴ is a hydroxyl group, it becomes a fluorine-containing ether compound having excellent adhesion to the surface of the protective layer.

When R ² and R ⁴ are divalent linking groups having a hydroxyl group as a polar group, the total of the number of hydroxyl groups contained in R ² and the number of hydroxyl groups contained in R ⁴ is 2 or more, and 3 or more. May be. When R ² and R ⁴ each contain one or more hydroxyl groups, the adhesion between the fluorine-containing ether compound and the protective layer becomes better in the lubricating layer containing the fluorine-containing ether compound, which is preferable.
The total number of hydroxyl groups contained in R ² and the number of hydroxyl groups contained in R ⁴ is preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less. If the total number of hydroxyl groups contained in R ² and the number of hydroxyl groups contained in R ⁴ is 8 or less, the polarity of the fluorine-containing ether compound becomes too high, and the pickup adheres to the magnetic head as a foreign substance (smear). Can be prevented from occurring, which is preferable.

It is preferable that a methylene group (-CH _2- ) is arranged at the end of R ² on the R ¹ side and / or the end of R ⁴ on the R ⁵ side. When a methylene group is arranged at the end of R ² on the R ¹ side, the methylene group of R ² and the oxygen atom of the oxime group (—C = NO—) contained in R ¹ are bonded. When a methylene group is arranged at the end of R ⁴ on the R ⁵ side, the methylene group of R ⁴ and the oxygen atom of the oxime group (-C = NO-) contained in R ⁵ are bonded. To. This allows the rigid C = N bond of the oxime group in R ¹ or R ⁵ to moderately limit the motility of the polar group of R ² or R ⁴ . As a result, the effect of suppressing the aggregation of the fluorine-containing ether compound on the protective layer becomes remarkable. On the other hand, for example, when a carbonyl group (-C (= O)-) is arranged at the end of R ² on the R ¹ side and / or the end of R ⁴ on the R ⁵ side, it is caused by an intramolecular interaction. It is not preferable because the aggregation of the fluorine-containing ether compound on the protective layer is promoted and the stability against light and heat is lowered.

When R ² and R ⁴ are divalent linking groups having a hydroxyl group as a polar group, R ³ -CH ₂ -R ^2- and R ³ -CH ₂ -R ^4- are respectively represented by the following formula (3). It is preferably represented.
R ³ -CH _2- [A]-[B]-[C]-(3)
(In the formula (3), [A] is represented by the following formula (4), [B] is represented by the following formula (5), and [C] is represented by the following formula (6). ), The order of [A], [B], and [C] may be changed. The ether bond (—O—) side in the formulas (4) to (6) is the CH ₂ side in the formula (3). be.)

A in the formula (4), b in the formula (5), and d in the formula (6) are integers of 0 to 3, respectively. The a in the formula (4), the b in the formula (5) and the d in the formula (6) further improve the adhesion between the fluorine-containing ether compound and the protective layer in the lubricating layer containing the fluorine-containing ether compound. Therefore, at least one is one or more. That is, the formula (3) includes at least one of [A], [B], and [C].

The total of a in the formula (4), b in the formula (5) and d in the formula (6) is preferably 4 or less, and more preferably 2 or less. If the total of a in the formula (4), b in the formula (5), and d in the formula (6) is 4 or less, the polarity of the fluorine-containing ether compound becomes too high, and as a foreign substance (smear). It is possible to effectively prevent the generation of pickups adhering to the magnetic head.

C in the formula (5) and e in the formula (6) are integers of 1 to 4, respectively. c and e are preferably integers of 1 to 3, respectively, and most preferably 2. When c in the formula (5) is an integer of 1 to 4, the distance between the hydroxyl group in the formula (5) and R ¹ or R ⁵ becomes appropriate. Further, when c in the formula (5) is an integer of 1 to 4, the distance between the hydroxyl groups in the formula (5) becomes appropriate when b is 2 or 3, which is preferable. When e in the formula (6) is an integer of 1 to 4, the distance between the hydroxyl groups in the formula (6) becomes appropriate when d is 2 or 3, which is preferable.

(R ³ )
In the fluorine-containing ether compound of the present embodiment represented by the above formula ( ¹ ), R3 is a perfluoropolyether chain (PFPE chain). R3 is not particularly limited ^, and can be appropriately selected depending on the performance required for the lubricant containing the fluorine-containing ether compound and the like. Examples of the PFPE chain include a perfluoromethylene oxide polymer, a perfluoroethylene oxide polymer, a perfluoro-n-propylene oxide polymer, a perfluoroisopropylene oxide polymer, and a copolymer thereof. ..

The PFPE chain may have, for example, a structure represented by the following formula (Rf) derived from a polymer or copolymer of perfluoroalkylene oxide.
-(CF ₂ ) _p1 O (CF ₂ O) _p2 (CF ₂ CF ₂ O) _p3 (CF ₂ CF ₂ CF ₂ O) _p4 (CF ₂ CF ₂ CF ₂ CF ₂ O) _p5 (CF ₂ ) _p6- ( Rf)
(In the formula (Rf), p2, p3, p4, p5 indicate the average degree of polymerization and each independently represents 0 to 30; however, all of p2, p3, p4 and p5 cannot be 0 at the same time; p1 and p6 are average values indicating the number of -CF _2- , and each represents 1 to 3 independently; the arrangement order of the repeating units in the formula (Rf) is not particularly limited.)
In the formula (Rf), p2, p3, p4, and p5 indicate the average degree of polymerization, each of which independently represents 0 to 30, preferably 0 to 20, and more preferably 0 to 15.
In the formula (Rf), p1 and p6 are average values indicating the number of _−CF2 −, and each independently represents 1 to 3. p1 and p6 are determined according to the structure of the repeating unit arranged at the end of the chain structure in the polymer represented by the formula (Rf).
(CF ₂ O), (CF ₂ CF ₂ O), (CF ₂ CF ₂ CF ₂ O), and (CF ₂ CF ₂ CF ₂ CF ₂ O) in the formula (Rf) are repeating units. The arrangement order of the repeating units in the formula (Rf) is not particularly limited. Further, the number of types of repeating units in the equation (Rf) is not particularly limited.

It is preferable that R ³ in the formula (1) is, for example, a PFPE chain represented by the following formula (Rf-1).
-(CF ₂ ) _p7 O- (CF ₂ CF ₂ O) _p8- (CF ₂ CF ₂ CF ₂ O) _p9- (CF ₂ ) _p10- (Rf-1)
(In the formula (Rf-1), p8 and p9 indicate the average degree of polymerization and independently represent 0.1 to 30; p7 and p10 are average values indicating the number of _−CF2 − and are independent of each other. Represents 1-2.)
The sequence order of the repeating units (CF ₂ CF ₂ O) and (CF ₂ CF ₂ CF ₂ O) in the formula (Rf-1) is not particularly limited. The formula (Rf-1) includes any of a random copolymer composed of a monomer unit (CF ₂ CF ₂ O) and (CF ₂ CF ₂ CF ₂ O), a block copolymer, and an alternate copolymer. It may be a thing. In the formula (Rf-1), p8 and p9 indicating the average degree of polymerization independently represent 0.1 to 30, preferably 0.1 to 20, and more preferably 1 to 15. P7 and p10 in the formula (Rf-1) are average values indicating the number of _−CF2 −, and each independently represents 1 to 2. p7 and p10 are determined according to the structure of the repeating unit arranged at the end of the chain structure in the polymer represented by the formula (Rf-1).

It is also preferable that R ³ in the formula (1) is any of the following formulas (7) to (11). The order of arrangement of (CF ₂ CF ₂ O) and (CF ₂ O), which are repeating units in the formula (7), is not particularly limited. The formula (7) includes any of a random copolymer composed of a monomer unit (CF2 _- CF2 _- O) and (CF2 _- O), a block copolymer, and an alternate copolymer. You may.

-CF ₂ O- (CF ₂ CF ₂ O) _m- (CF ₂ O) _n -CF _2- (7)
(M and n in the formula (7) indicate the average degree of polymerization, and each represents 0.1 to 30.)
-CF ₂ O- (CF ₂ CF ₂ O) _w -CF _2- (8)
(W in the formula (8) indicates the average degree of polymerization and represents 0.1 to 30.)
-CF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ O) _x -CF ₂ CF _2- (9)
(X in the formula (9) indicates the average degree of polymerization and represents 0.1 to 30).
-CF ₂ CF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ CF ₂ O) _y -CF ₂ CF ₂ CF _2- (10)
(Y in the formula (10) indicates the average degree of polymerization and represents 0.1 to 30).
-CF (CF ₃ )-(OCF (CF ₃ ) CF ₂ ) _z -OCF (CF ₃ )-(11)
(Z in the formula (11) indicates the average degree of polymerization and represents 0.1 to 30.)

When m, n, w, x, y, and z in the formulas (7) to (11) are 0.1 to 30, respectively, a lubricant containing them is easy to apply and has good adhesion. Will be obtained. The m, n, w, x, y, and z in the formulas (7) to (11) are preferably 30 or less, and more preferably 20 or less, respectively. For example, m, n, w, x, y, and z may be 0.1 to 20, 1 to 15, 1 to 10, 2 to 8, 2 to 5, and the like, respectively.

When R ³ in the formula (1) is any of the formulas (7) to (11), it is preferable because the synthesis of the fluorine-containing ether compound is easy. When R ³ is of the formula (7), it is more preferable because the raw material can be easily obtained.
When R ³ is any of the formulas (7) to (11), 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 , Will be appropriate. Therefore, it becomes a fluorine-containing ether compound having an appropriate hardness. Therefore, the fluorine-containing ether compound applied on the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage. Further, when R ³ is any of the formulas (7) to (11), it is a fluorine-containing ether compound that can obtain a lubricating layer having good adhesion.

In the fluorine-containing ether compound represented by the formula (1), R ¹ and R ⁵ may be the same or different. When R ¹ and R ⁵ are the same, the fluorine-containing ether compound represented by the formula (1) can be easily produced, which is preferable.
Further, in the fluorine-containing ether compound represented by the formula (1), R ² and R ⁴ may be the same or different. When R ² and R ⁴ are the same, the fluorine-containing ether compound represented by the formula (1) can be easily produced, which is preferable.
Therefore, it is preferable that R ¹ and R ⁵ of the fluorine-containing ether compound represented by the formula (1) are the same, and R ² and R ⁴ are the same, because it can be produced more easily.

In the fluorine-containing ether compound represented by the formula (1), the total number of hydroxyl groups contained in the molecule is preferably 8 or less, more preferably 6 or less, still more preferably 5 or less. It is particularly preferable that it is 4 or less. When the total number of hydroxyl groups contained in the molecule is 8 or less, aggregation of the fluorine-containing ether compound on the protective layer due to the intramolecular interaction of the hydroxyl groups is unlikely to occur. Therefore, a thin lubricating layer can be formed with a better coverage, and better adhesion can be obtained. Further, in the lubricating layer containing this, the fluorine-containing ether compound aggregates and is less likely to be picked up as foreign matter (smear) attached to the magnetic head.

In the fluorine-containing ether compound represented by the formula (1), the total number of hydroxyl groups contained in the molecule is preferably 2 or more, and more preferably 3 or more. When the total number of hydroxyl groups contained in the molecule is 2 or more, the synergistic effect of the interaction between the fluorine-containing ether compound and the protective layer due to the inclusion of hydroxyl groups together with the oxime group can be sufficiently obtained. Therefore, a lubricating layer having even better adhesion can be obtained.

Specifically, the fluorine-containing ether compound represented by the formula (1) is preferably any compound represented by the following formulas (A) to (Z) and (AA) to (AI). The repetition numbers ma to mz, mA to mE, na to nz, nA to nE, w, x, y, and z in the formulas (A) to (Z) and (AA) to (AI) are average values. Since it is a value shown, it is not necessarily an integer.

In the compound represented by the formula (A), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxymethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compounds represented by the formula (A) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (B), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compounds represented by the formula (B) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (C), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxypropyl group. R ² is [A], a in the formula (4) is 1, and R ³ is the formula (7). The compounds represented by the formula (C) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (D), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,2-dihydroxyethyl group. R ² is [A], a in the formula (4) is 1, and R ³ is the formula (7). The compounds represented by the formula (D) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

The compound represented by the formula (E) is a 1,3-dihydroxypropyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compounds represented by the formula (E) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

The compound represented by the formula (F) is a 1,3-dihydroxypropyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 1-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compounds represented by the formula (F) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (G), R ¹ is represented by the formula (2), and X and Y are hydroxymethyl groups. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compound represented by the formula (G) has the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (H), R ¹ is represented by the formula (2), and X and Y are hydroxyethyl groups. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compounds represented by the formula (H) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (I), R ¹ is represented by the formula (2), X is a hydroxymethyl group, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compounds represented by the formula (I) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (J), R ¹ is represented by the formula (2), X is a hydroxymethyl group, and Y is a hydroxypropyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). The compound represented by the formula (J) has the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (K), R ¹ is represented by the formula (2), X is a hydrogen atom, Y is a hydroxyethyl group, and R ² is [B] in the formula (5). B is 1 and c is 1. R ³ is the equation (7). The compound represented by the formula (K) has the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (L), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [B], b in the equation (5) is 1, and c is 2. R ³ is the equation (7). The compounds represented by the formula (L) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (M), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 2. R ³ is the equation (7). The compounds represented by the formula (M) have the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (N), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. -CH ₂ -R ² -R ¹ is -CH _2- [B]-[C] -R ¹ , b in equation (5) is 1, c is 1, and equation (6). In d is 1, and e is 1. R ³ is the equation (7). -CH ₂ -R ⁴ -R ⁵ is -CH _2- [B]-[C] -R ⁵ , b in equation (5) is 1, c is 1, and equation (6). In d is 1, and e is 1. The compound represented by the formula (N) has the ^same ^R1 and R5, and the same ^R2 and ^R4 .

In the compound represented by the formula (O), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 2. R ³ is the equation (7). -CH ₂ -R ⁴ -R ⁵ is -CH _2- [B]-[C] -R ⁵ , b in equation (5) is 1, c is 2, and equation (6). In d is 1, and e is 2. The compound represented by the formula (O) has the ^same ^R1 and R5.

In the compound represented by the formula (P), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxymethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. The compound represented by the formula (P) has the same ^R2 and ^R4 .

In the compound represented by the formula (Q), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxypropyl group. The compound represented by the formula (Q) has the same ^R2 and ^R4 .

In the compound represented by the formula (R), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,2-dihydroxyethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,3-dihydroxypropyl group bonded at the 2-position. The compound represented by the formula (R) has the same ^R2 and ^R4 .

The compound represented by the formula (S) is a 1,3-dihydroxypropyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 1-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydroxymethyl group, and Y is a hydroxyethyl group. The compound represented by the formula (S) has the same ^R2 and ^R4 .

The compound represented by the formula (T) is a 1,4-dihydroxybutyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), and X and Y are hydroxymethyl groups. The compound represented by the formula (T) has the same ^R2 and ^R4 .

The compound represented by the formula (U) is a 1,4-dihydroxybutyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. The compound represented by the formula (U) has the same ^R2 and ^R4 .

In the compound represented by the formula (V), R ¹ is represented by the formula (2), X is a hydrogen atom, Y is a hydroxyethyl group, and R ² is [B] in the formula (5). B is 1 and c is 1. R ³ is the equation (7). R ⁴ is [A] and a in the formula (4) is 1. R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxypropyl group.

In the compound represented by the formula (W), R ¹ is represented by the formula (2), X is a hydrogen atom, Y is a hydroxymethyl group, and R ² is [B] in the formula (5). B is 1 and c is 1. R ³ is the equation (7). R ⁴ is [B], b in the equation (5) is 1, and c is 2. R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,4-dihydroxybutyl group bonded at the 2-position.

In the compound represented by the formula (X), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [B], b in the equation (5) is 1, and c is 1. R ³ is the equation (7). R ⁴ is [A] and a in the formula (4) is 1. R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,4-dihydroxybutyl group bonded at the 2-position.

In the compound represented by the formula (Y), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 2. R ³ is the equation (7). R ⁴ is [A] and a in the formula (4) is 1. The compound represented by the formula (Y) has the ^same ^R1 and R5.

In the compound represented by the formula (Z), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. -CH ₂ -R ² -R ¹ is -CH _2- [B]-[C] -R ¹ , b in equation (5) is 1, c is 1, and equation (6). In d is 1, and e is 1. R ³ is the equation (7). R ⁴ is [A] and a in the formula (4) is 2. The compound represented by the formula (Z) has the ^same ^R1 and R5.

In the compound represented by the formula (AA), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydroxymethyl group, and Y is a hydroxyethyl group. The compound represented by the formula (AA) has the same ^R2 and ^R4 .

In the compound represented by the formula (AB), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a 2- (3-butenyloxy) ethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,4-dihydroxybutyl group bonded at the 2-position. The compound represented by the formula (AB) has the same ^R2 and ^R4 .

In the compound represented by the formula (AC), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a 2-butoxyethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,4-dihydroxybutyl group bonded at the 2-position. The compound represented by the formula (AC) has the same ^R2 and ^R4 .

In the compound represented by the formula (AD), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a 2- (2-propynyloxy) ethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,4-dihydroxybutyl group bonded at the 2-position. The compound represented by the formula (AD) has the same ^R2 and ^R4 .

In the compound represented by the formula (AE), R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is a 2- (4-methoxyphenoxy) ethyl group. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (7). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a 1,4-dihydroxybutyl group bonded at the 2-position. The compound represented by the formula (AE) has the same ^R2 and ^R4 .

The compound represented by the formula (AF) is a 1,4-dihydroxybutyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (8). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. The compound represented by the formula (AF) has the same ^R2 and ^R4 .

The compound represented by the formula (AG) is a 1,4-dihydroxybutyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (9). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. The compound represented by the formula (AG) has the same ^R2 and ^R4 .

The compound represented by the formula (AH) is a 1,4-dihydroxybutyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (10). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. The compound represented by the formula (AH) has the same ^R2 and ^R4 .

The compound represented by the formula (AI) is a 1,4-dihydroxybutyl group in which R ¹ is represented by the formula (2), X is a hydrogen atom, and Y is bonded at the 2-position. R ² is [A] and a in the formula (4) is 1. R ³ is the equation (11). R ⁵ is represented by the formula (2), X is a hydrogen atom, and Y is a hydroxyethyl group. The compound represented by the formula (AI) has the same ^R2 and ^R4 .

(In the formula (A), ma and na represent the average degree of polymerization, ma represents 1 to 30, and na represents 0.1 to 30.)
(In the formula (B), mb and nb indicate the average degree of polymerization, mb represents 1 to 30, and nb represents 0.1 to 30.)
(In the formula (C), mc and nc represent the average degree of polymerization, mc represents 1 to 30, and nc represents 0.1 to 30.)
(In the formula (D), md and nd indicate the average degree of polymerization, md represents 1 to 30, and nd represents 0.1 to 30.)

(In the formula (E), me and ne indicate the average degree of polymerization, me represents 1 to 30, and ne represents 0.1 to 30.)
(In the formula (F), mf and nf indicate the average degree of polymerization, mf represents 1 to 30, and nf represents 0.1 to 30).
(In the formula (G), mg and ng indicate the average degree of polymerization, mg represents 1 to 30, and ng represents 0.1 to 30.)
(In the formula (H), mh and nh indicate the average degree of polymerization, mh represents 1 to 30, and nh represents 0.1 to 30).

(In the formula (I), mi and ni indicate the average degree of polymerization, mi represents 1 to 30, and ni represents 0.1 to 30.)
(In the formula (J), mj and nj indicate the average degree of polymerization, mj represents 1 to 30, and nj represents 0.1 to 30.)
(In the formula (K), mk and nk represent the average degree of polymerization, mk represents 1 to 30, and nk represents 0.1 to 30.)
(In the formula (L), ml and nl indicate the average degree of polymerization, ml represents 1 to 30, and nl represents 0.1 to 30.)

(In the formula (M), mm and nm indicate the average degree of polymerization, mm represents 1 to 30, and nm represents 0.1 to 30.)
(In the formula (N), mn and nn indicate the average degree of polymerization, mn represents 1 to 30, and nn represents 0.1 to 30.)
(In the formula (O), mo and no indicate the average degree of polymerization, mo represents 1 to 30, and no represents 0.1 to 30.)
(In the formula (P), mp and np indicate the average degree of polymerization, mp represents 1 to 30, and np represents 0.1 to 30.)

(In the formula (Q), mq and nq indicate the average degree of polymerization, mq represents 1 to 30, and nq represents 0.1 to 30).
(In the formula (R), mr and nr indicate the average degree of polymerization, mr represents 1 to 30, and nr represents 0.1 to 30.)
(In the formula (S), ms and ns represent the average degree of polymerization, ms represents 1 to 30, and ns represents 0.1 to 30.)
(In the formula (T), mt and nt indicate the average degree of polymerization, mt represents 1 to 30, and nt represents 0.1 to 30.)

(In the formula (U), mu and nu indicate the average degree of polymerization, mu represents 1 to 30, and nu represents 0.1 to 30.)
(In the formula (V), mv and nv indicate the average degree of polymerization, mv represents 1 to 30, and nv represents 0.1 to 30.)
(In the formula (W), mw and nw indicate the average degree of polymerization, mw represents 1 to 30, and nw represents 0.1 to 30).
(In the formula (X), mx and nx indicate the average degree of polymerization, mx represents 1 to 30, and nx represents 0.1 to 30.)

(In the formula (Y), my and ny indicate the average degree of polymerization, my represents 1 to 30, and ny represents 0.1 to 30.)
(In the formula (Z), mz and nz indicate the average degree of polymerization, mz represents 1 to 30, and nz represents 0.1 to 30.)
(In the formula (AA), mA and nA indicate the average degree of polymerization, mA represents 1 to 30, and nA represents 0.1 to 30.)
(In the formula (AB), mB and nB indicate the average degree of polymerization, mB represents 1 to 30, and nB represents 0.1 to 30.)

(In the formula (AC), mC and nC indicate the average degree of polymerization, mC represents 1 to 30, and nC represents 0.1 to 30.)
(In the formula (AD), mD and nD indicate the average degree of polymerization, mD represents 1 to 30, and nD represents 0.1 to 30.)
(In the formula (AE), mE and nE indicate the average degree of polymerization, mE represents 1 to 30, and nE represents 0.1 to 30.)
(In the formula (AF), w indicates the average degree of polymerization, and w represents 0.1 to 30.)

(In the formula (AG), x indicates the average degree of polymerization, and x represents 0.1 to 30.)
(In the formula (AH), y indicates the average degree of polymerization, and y represents 0.1 to 30.)
(In the formula (AI), z indicates the average degree of polymerization, and z represents 0.1 to 30.)

When the compound represented by the formula (1) is any of the compounds represented by the above formulas (A) to (Z) and (AA) to (AI), the raw material is easily available and the thickness is thin. However, it is preferable because a lubricating layer capable of obtaining excellent adhesion can be formed.

The fluorine-containing ether compound of the present embodiment preferably has a number average molecular weight (Mn) in the range of 500 to 10,000. When the number average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of the present embodiment is difficult to evaporate. Therefore, it is possible to prevent the lubricant from evaporating and transferring to the magnetic head, and it is possible to form a lubricating layer in which pickup and spin-off are unlikely to occur. The number average molecular weight of the fluorine-containing ether compound is more preferably 1000 or more. Further, when the number average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound becomes appropriate, and by applying a lubricant containing this, a thin lubricating layer can be easily formed. The number average molecular weight of the fluorine-containing ether compound is more preferably 3000 or less because it has a viscosity that is easy to handle when applied to a lubricant. The molecular weight may be 500 to 9000, 650 to 7000, 800 to 5000, 900 to 4000, 1000 to 3000, 1100 to 2500, depending on the need. It may be 1200 to 2000 or 1200 to 1800.

The number average molecular weight (Mn) of the fluorine-containing ether compound is a value measured by ¹ H-NMR and ¹⁹ F-NMR by AVANCE III400 manufactured by Bruker Biospin. In NMR (nuclear magnetic resonance) measurements, the sample was diluted with a single or mixed solvent such as hexafluorobenzene, d-acetone, d-tetrahydrogen and used for the measurement. The standard for ¹⁹ F-NMR chemical shift was -164.7 ppm for the peak of hexafluorobenzene, and the standard for ¹ H-NMR chemical shift was 2.2 ppm for the peak of acetone.

"Production method"
The method for producing the fluorine-containing ether compound of the present embodiment is not particularly limited, and can be produced by using a conventionally known production method. The fluorine-containing ether compound of the present embodiment can be produced, for example, by using the production method shown below.
First, a fluorine-based compound in which a hydroxymethyl group (-CH ₂ OH) is arranged at both ends of the perfluoropolyether chain corresponding to R ³ in the formula (1) is prepared.

Next, the hydroxyl group of the hydroxymethyl group arranged at one end of the fluorine-based compound is replaced with the group consisting of R1 ^- R2- in the formula ( ¹ ) (first reaction). Then, the hydroxyl group of the hydroxymethyl group arranged at the other end is replaced with the terminal group consisting of ^—R4 ^−R5 in the formula (1) (second reaction).
The first reaction and the second reaction can be carried out by using conventionally known methods, and can be appropriately determined according to the types of R ¹ , R ² , R ⁴ , R ⁵ and the like in the formula (1). Further, either of the first reaction and the second reaction may be performed first. When R ¹ and R ⁵ are the same and R ² and R ⁴ are the same, the first reaction and the second reaction may be performed at the same time.
By the above method, the compound represented by the formula (1) can be obtained.

In the present embodiment, it is preferable to use an epoxy compound in order to produce the fluorine-containing ether compound represented by the above formula (1). This epoxy compound may be purchased commercially or may be synthesized. When synthesizing an epoxy compound, an oxime compound having a structure corresponding to a terminal group represented by R ¹ or R ⁵ of the fluorine-containing ether compound to be produced, epichlorohydrin, epibromohydrin, 2- (2- (2-) It can be synthesized using any of bromoethyl) oxylans. Epoxy compounds may be synthesized by a method of oxidizing unsaturated bonds.

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 the protective layer using a lubricant containing this, the surface of the protective layer is covered with the PFPE chain represented by R3 in the formula ( ¹ ), and the magnetic head and the protective layer are covered. The frictional force with and is reduced.

Further, in the lubricating layer containing the fluorine-containing ether compound of the present embodiment, the nitrogen atom of the oxime group in R ¹ and R ⁵ and one or more polar groups contained in each of R ² and R ⁴ linked to the PFPE chain are contained. The PFPE chain is brought into close contact with the protective layer by the interaction with the protective layer. Therefore, by using the lubricant containing the fluorine-containing ether compound of the present embodiment, the lubricating layer and the protective layer are firmly bonded to each other, and a lubricating layer having excellent adhesion can be obtained.

[Lubricant for magnetic recording medium]
The lubricant for a magnetic recording medium of the present embodiment contains a fluorine-containing ether compound represented by the formula (1).
The lubricant of the present embodiment needs a known material used as a material of the lubricant as long as it does not impair the characteristics due to the inclusion of the fluorine-containing ether compound represented by the formula (1). Depending on the situation, they can be mixed and used.

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), and the like. The known material used in combination with the lubricant of the present embodiment preferably has a number average molecular weight of 1000 to 10000.

When the lubricant of the present embodiment contains another material of the fluorine-containing ether compound represented by the formula (1), the inclusion of the fluorine-containing ether compound represented by the formula (1) in the lubricant of the present embodiment. The amount is preferably 50% by mass or more, and more preferably 70% by mass or more. The upper limit can be arbitrarily selected, and for example, it may be 99% by mass or less, 95% by mass or less, 90% by mass or less, or 85% by mass or less. ..

Since the lubricant of the present embodiment contains the fluorine-containing ether compound represented by the formula (1), the surface of the protective layer can be coated with a high coverage even if the thickness is reduced, and the adhesion with the protective layer is improved. An excellent lubricating layer can be formed.
More specifically, since the lubricant of the present embodiment contains a fluorine-containing ether compound represented by the formula (1), the oxime groups in R ¹ and R ⁵ in the formula (1), and R ² and R ⁴ By the interaction between the polar groups contained in one or more of each and the protective layer, a lubricating layer having excellent adhesion can be formed.
Further, since the lubricant of the present embodiment contains the fluorine-containing ether compound represented by the formula (1), the fluorine-containing ether compound in the lubricant that exists without adhering (adsorbing) to the protective layer can be used. Hard to aggregate. Therefore, in the lubricating layer formed by using the lubricant of the present embodiment, it is possible to prevent the fluorine-containing ether compound from aggregating and adhering to the magnetic head as a foreign substance (smear), and the pickup is suppressed.

[Magnetic recording medium]
In the magnetic recording medium of the present embodiment, at least a magnetic layer, a protective layer, and a lubricating layer are sequentially provided on a substrate.
In the magnetic recording medium of the present embodiment, one layer or two or more base layers can be provided between the substrate and the magnetic layer, if necessary. Further, an adhesive layer and / or a soft magnetic layer may be provided between the base layer and the substrate.

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

"substrate"
The substrate 11 can be arbitrarily selected. As the substrate 11, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a substrate made of a metal such as Al or an alloy material such as an Al alloy can be preferably used.
As the substrate 11, a non-magnetic substrate made of a non-metal material such as glass, ceramics, silicon, silicon carbide, carbon, or resin may be used, or a NiP or NiP alloy is further placed on the substrate made of these non-metal materials. A non-magnetic substrate having a film made of the same material may be used.

"Adhesion layer"
The adhesive layer 12 prevents the progress of corrosion of the substrate 11 that occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are arranged in contact with each other.
The material of the adhesion layer 12 can be arbitrarily selected, and for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy and the like can be appropriately selected. The adhesive layer 12 can be formed by, for example, a sputtering method.

"Soft magnetic layer"
The soft magnetic layer 13 can be arbitrarily selected, and 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. The soft magnetic layer 13 has a structure in which the upper and lower soft magnetic films of the intermediate layer are bonded by anti-ferro coupling (AFC) by sandwiching an intermediate layer made of a Ru film between the two soft magnetic films. It is preferable to do.

Examples of the material of the first soft magnetic film and the second soft magnetic film include CoZrTa alloy and CoFe alloy.
It is preferable to add any of Zr, Ta, and Nb to the CoFe alloy used for the first soft magnetic film and the second soft magnetic film. As a result, the amorphization of the first soft magnetic film and the second soft magnetic film is promoted, the orientation of the first base layer (seed layer) can be improved, and the floating amount of the magnetic head can be increased. It is possible to reduce it.
The soft magnetic layer 13 can be formed by, for example, a sputtering method.

"First base layer"
The first base layer 14 controls the orientation and crystal size of the second base layer 15 and the magnetic layer 16 provided on the first base layer 14.
Examples of the first base layer 14 include a Cr layer, a Ta layer, a Ru layer, a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, and a CrTi alloy layer. The first base layer 14 can be formed by, for example, a sputtering method.

"Second base layer"
The second base layer 15 is controlled so that the orientation of the magnetic layer 16 is good. The second base layer 15 can be arbitrarily selected, and is preferably a layer made of Ru or a Ru alloy.
The second base layer 15 may be a layer composed of one layer or may be composed of a plurality of layers. When the second base layer 15 is composed of a plurality of layers, all the layers may be made of the same material, or at least one layer may be made of a different material.
The second base layer 15 can be formed by, for example, a sputtering method.

"Magnetic layer"
The magnetic layer 16 is made of a magnetic film whose axis for easy magnetization is perpendicular or horizontal to the substrate surface. The magnetic layer 16 can be arbitrarily selected, and is preferably a layer containing Co and Pt. The magnetic layer 16 may be a layer containing an oxide, Cr, B, Cu, Ta, Zr, etc. in order to further improve the SNR (Signal to Noise Ratio) property.
Examples of the oxide contained in the magnetic layer 16 include SiO ₂ , SiO, Cr ₂ O ₃ , CoO, Ta ₂ O ₃ , TIO ₂ and the like.

The magnetic layer 16 may be composed of one layer or may be composed of a plurality of magnetic layers made of materials having different compositions.
For example, when the magnetic layer 16 is composed of three layers of a first magnetic layer, a second magnetic layer, and a third magnetic layer laminated in order from the bottom, the first magnetic layer contains Co, Cr, and Pt, and is further oxidized. It is preferable to have a granular structure made of a material containing an object. As the oxide contained in the first magnetic layer, for example, it is preferable to use an oxide such as Cr, Si, Ta, Al, Ti, Mg, Co. Among them, in particular, TiO ₂ , Cr ₂ O ₃ , SiO ₂ , and the like can be preferably used. The first magnetic layer is preferably made of a composite oxide to which two or more kinds of oxides are added. Among them, in particular, Cr ₂ O ₃ -SiO ₂ , Cr ₂ O ₃ -TiO ₂ , SiO ₂ -TiO ₂ , and the like can be preferably used.

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

The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr and Pt and not containing oxides. In addition to Co, Cr, and Pt, the third magnetic layer contains one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn. be able to.

When the magnetic layer 16 is formed of a plurality of magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 is composed of three layers of a first magnetic layer, a second magnetic layer, and a third magnetic layer, between the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer. It is preferable to provide a non-magnetic layer between the two.

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

It is preferable to use an alloy material containing an oxide, a metal nitride, or a metal carbide for the non-magnetic layer provided between the adjacent magnetic layers of the magnetic layer 16. Specifically, as the oxide, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , TIO ₂ and the like can be used. As the metal nitride, for example, AlN, Si _{3N 4} _, TaN, CrN and the like can be used. As the metal carbide, for example, TaC, BC, SiC and the like can be used.
The non-magnetic layer can be formed by, for example, a sputtering method.

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 in order to realize a higher recording density. The magnetic layer 16 may be a magnetic layer for in-plane magnetic recording.
The magnetic layer 16 may be formed by any conventionally known method such as a vapor deposition method, an ion beam sputtering method, a magnetron sputtering method, or the like. The magnetic layer 16 is usually formed by a sputtering method.

"Protective layer"
The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or may be composed of a plurality of layers. Examples of the material of the protective layer 17 include carbon, carbon containing nitrogen, silicon carbide and the like.
As the protective layer 17, a carbon-based protective layer can be preferably used, and an amorphous carbon protective layer is particularly preferable. When the protective layer 17 is a carbon-based protective layer, the interaction with the polar groups (particularly hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

The adhesive force between the carbon-based protective layer and the lubricating layer 18 is determined by adjusting the hydrogen content and / or nitrogen content in the carbon-based protective layer by using the carbon-based protective layer as carbon hydride and / or carbon dioxide. It is controllable. The hydrogen content in the carbon-based protective layer is preferably 3 to 20 atomic% as measured by the hydrogen forward scattering method (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 to 15 atomic% when measured by X-ray photoelectron spectroscopy (XPS).

Hydrogen and / or nitrogen contained in the carbon-based protective layer need not be uniformly contained in the entire carbon-based protective layer. The carbon-based protective layer is preferably, for example, a composition gradient layer in which nitrogen is contained on the lubricating layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesive force between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved.

The film thickness of the protective layer 17 is preferably 1 nm to 7 nm. When the film thickness of the protective layer 17 is 1 nm or more, the performance as the protective layer 17 can be sufficiently obtained. When the film thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of thinning the protective layer 17.

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

"Lubrication layer"
The lubricating layer 18 prevents contamination of the magnetic recording medium 10. Further, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording / reproducing device sliding on the magnetic recording medium 10 to improve the durability of the magnetic recording medium 10.
As shown in FIG. 1, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 contains the above-mentioned fluorine-containing ether compound.

The lubricating layer 18 is bonded to the protective layer 17 with a high bonding force, especially when the protective layer 17 arranged under the lubricating layer 18 is a carbon-based protective layer. As a result, even if the thickness of the lubricating layer 18 is thin, it is easy to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and it is possible to effectively prevent contamination of the surface of the magnetic recording medium 10.

The average film thickness of the lubricating layer 18 can be arbitrarily selected, preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and preferably 0.5 nm (5 Å) to 1.0 nm (10 Å). More preferred. When the average film thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform film thickness without forming an island shape or a mesh shape. Therefore, the surface of the protective layer 17 can be covered with a high coverage by the lubricating layer 18. Further, by setting the average film thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be sufficiently thinned, and the floating amount of the magnetic head can be sufficiently reduced.

When the surface of the protective layer 17 is not covered with a sufficiently high coverage by the lubricating layer 18, the environmental substances adsorbed on the surface of the magnetic recording medium 10 pass through the gaps of the lubricating layer 18 and become the lower layer of the lubricating layer 18. invade. Environmental substances that have entered the lower layer of the lubricating layer 18 are adsorbed and bonded to the protective layer 17 to generate contaminants. Then, during magnetic recording / reproduction, this contaminant (aggregate component) adheres (transfers) to the magnetic head as a smear, damaging the magnetic head or deteriorating the magnetic recording / reproducing characteristics of the magnetic recording / reproducing device. ..

Examples of environmental substances that generate contaminants include siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, hydrocarbons with relatively high molecular weight such as octacosan, and plasticizers such as dioctyl phthalate. Examples of the metal ion contained in the ionic impurities include sodium ion and potassium ion. Examples of the inorganic ions contained in the ionic impurities include chloride ions, bromine ions, nitrate ions, sulfate ions, and ammonium ions. Examples of the organic ion contained in the ionic impurities include oxalate ion and formic acid ion.

"Method of forming a lubricating layer"
As a method for forming the lubricating layer 18, for example, a magnetic recording medium in the middle of manufacturing in which each layer up to the protective layer 17 is formed on the substrate 11 is prepared, and a solution for forming the lubricating layer is applied on the protective layer 17. Examples include a method of drying.

The lubricating layer forming solution is obtained by dissolving and dissolving the lubricant for the magnetic recording medium of the above-described embodiment in a solvent, if necessary, to obtain a viscosity and concentration suitable for the coating method.
Examples of the solvent used for the solution for forming the lubricating layer include fluorine-based solvents such as Bertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.).

The method for applying the solution for forming the lubricating layer is not particularly limited, and examples thereof include a spin coating method, a spray method, a paper coating method, and a dip method.
When the dip method is used, for example, the method shown below can be used. First, the substrate 11 on which each layer up to the protective layer 17 is formed is immersed in the lubricating layer forming solution contained in the dipping tank of the dip coating device. Next, the substrate 11 is pulled up from the immersion tank at a predetermined speed. As a result, the lubricating layer forming solution is applied to the surface of the substrate 11 on the protective layer 17.
By using the dip method, the solution for forming the lubricating layer can be uniformly applied to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform film thickness.

In the present embodiment, it is preferable to heat-treat the substrate 11 on which the lubricating layer 18 is formed. By applying 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 improved.
The heat treatment temperature is preferably 100 to 180 ° C. When 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. Further, 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.

In the magnetic recording medium 10 of the present embodiment, at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11. In the magnetic recording medium 10 of the present embodiment, the lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed in contact with the protective layer 17. The lubricating layer 18 has good adhesion to the protective layer 17, and can cover the surface of the protective layer 17 with a high coverage even if the thickness is thin. Therefore, the magnetic recording medium 10 of the present embodiment has a lubricating layer 18 in which spin-off is unlikely to occur.

Further, in the magnetic recording medium 10 of the present embodiment, the surface of the protective layer 17 is covered with a high coverage by the lubricating layer 18 having good adhesion to the protective layer 17. Therefore, environmental substances that generate contaminants such as ionic impurities are prevented from entering through the gaps in the lubricating layer 18. Therefore, the magnetic recording medium 10 of the present embodiment has a small amount of contaminants present on the surface. Further, the lubricating layer 18 in the magnetic recording medium 10 of the present embodiment is less likely to generate foreign matter (smear) and can suppress pickup.
From the above, the magnetic recording medium 10 of the present embodiment has excellent reliability and durability.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

"Manufacturing of lubricant"
(Example 1)
The compound represented by the above formula (A) was produced by the method shown below.
First, the compound represented by the following formula (15) and epibromohydrin were reacted in dichloromethane to synthesize the compound represented by the following formula (16).

The compound represented by the following formula (15) was synthesized by the method shown below. The hydroxy group on one side of ethylene glycol was protected with dihydropyran and oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. Then, the obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

Next, in a 200 mL eggplant flask under a nitrogen atmosphere, HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (in the formula, m indicating the average degree of polymerization is 4. 20 g of a fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by 5 and n indicating an average degree of polymerization is 4.5, and compound 9 represented by the formula (16). .47 g (molecular weight 215.12, 44 mmol) and 20 mL of t-butanol were added and stirred at room temperature until uniform.

To this uniform liquid, 0.90 g of potassium tert-butoxide (molecular weight 112.21, 8 mmol) was added, and the mixture was stirred and reacted at 70 ° C. for 14 hours. The reaction solution obtained after the reaction was returned to room temperature, 33 g of a 10% hydrogen chloride / methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added, and the mixture was stirred at room temperature for 2 hours. The reaction solution was gradually transferred to a separating funnel containing 100 mL of saline solution, and extracted three times using 200 mL of ethyl acetate. The organic layer was washed in the order of 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering out the drying agent (anhydrous sodium sulfate), the filtrate is concentrated, and the residue is purified by silica gel column chromatography. The compound represented by the formula (A) (ma showing the average degree of polymerization in the formula (A)) Is 4.5, and na indicating the average degree of polymerization is 4.5.) Was obtained in an amount of 12.6 g.

¹ H-NMR measurement of the obtained compound (A) was carried out, and the structure was identified by the following results.
Compound (A); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 3.4 to 3.9 (22H), 7.4 (2H)

(Example 2)
The same operation as in Example 1 was carried out except that 10.1 g of the compound represented by the following formula (18) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (B) was used. (In the formula (B), mb indicating the average degree of polymerization is 4.5, and nb indicating the average degree of polymerization is 4.5) was obtained in an amount of 12.9 g.

The compound represented by the formula (18) was synthesized by reacting the compound represented by the formula (17) with epibromohydrin in dichloromethane.
The compound represented by the formula (17) was synthesized by the method shown below. The hydroxy group on one side of 1,3-propanediol was protected with dihydropyran and oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. Then, the obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (B) was carried out, and the structure was identified by the following results.
Compound (B); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (4H), 3.4-3.9 (22H), 7.4 (2H)

(Example 3)
The same operation as in Example 1 was carried out except that 10.7 g of the compound represented by the following formula (20) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (C) was used. (In the formula (C), mc indicating the average degree of polymerization is 4.5, and nc indicating the average degree of polymerization is 4.5) was obtained in 13.2 g.

The compound represented by the formula (20) was synthesized by reacting the compound represented by the formula (19) with epibromohydrin in dichloromethane.
The compound represented by the formula (19) was synthesized by the method shown below. The hydroxy group on one side of 1,4-butanediol was protected with dihydropyran and oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. Then, the obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (C) was carried out, and the structure was identified by the following results.
Compound (C); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.8 (4H), 2.5 (4H), 3.4-3.9 (22H), 7.4 (2H)

(Example 4)
The same operation as in Example 1 was carried out except that 8.9 g of the compound represented by the following formula (22) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (D) was used. (In the formula (D), md indicating the average degree of polymerization is 4.5, and nd indicating the average degree of polymerization is 4.5) was obtained in 13.2 g.

The compound represented by the formula (22) was synthesized by reacting the compound represented by the formula (21) with epibromohydrin in dichloromethane.
The compound represented by the formula (21) is synthesized by reacting a compound obtained by oxidizing Solketal with dess-Martin peryodinan in dichloromethane in a 50% aqueous ethanol solution with hydroxylamine and potassium carbonate. did.

¹ H-NMR measurement of the obtained compound (D) was carried out, and the structure was identified by the following results.
Compound (D); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 3.4 to 3.9 (26H), 7.4 (2H)

(Example 5)
The same operation as in Example 1 was carried out except that 9.5 g of the compound represented by the following formula (24) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (E) was used. (In the formula (E), me indicating the average degree of polymerization is 4.5, and ne indicating the average degree of polymerization is 4.5) was obtained in an amount of 13.5 g.

The compound represented by the formula (24) was synthesized by reacting the compound represented by the formula (23) with epibromohydrin in dichloromethane.
The compound represented by the formula (23) is a compound obtained by oxidizing (2,2-dimethyl-1,3-dioxane-5-yl) methanol in dichloromethane using Dess-Martin peryodinane. It was synthesized by reacting hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (E) was performed, and the structure was identified by the following results.
Compound (E); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (2H), 3.4-3.9 (28H), 7.4 (2H)

(Example 6)
The same operation as in Example 1 was carried out except that 9.5 g of the compound represented by the following formula (26) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (F) was used. (In the formula (F), mf indicating the average degree of polymerization is 4.5, and nf indicating the average degree of polymerization is 4.5) was obtained in an amount of 13.5 g.

The compound represented by the formula (26) was synthesized by reacting the compound represented by the formula (25) with epibromohydrin in dichloromethane.
The compound represented by the formula (25) is a compound obtained by oxidizing (2,2-dimethyl-1,3-dioxane-4-yl) methanol in dichloromethane using Dess-Martin peryodinane. It was synthesized by reacting hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (F) was carried out, and the structure was identified by the following results.
Compound (F); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (2H), 3.4-3.9 (28H), 7.4 (2H)

(Example 7)
The same operation as in Example 1 was carried out except that 14.5 g of the compound represented by the following formula (28) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (G) was used. (In the formula (G), mg indicating the average degree of polymerization is 4.5, and ng indicating the average degree of polymerization is 4.5) was obtained in 13.2 g.

The compound represented by the formula (28) was synthesized by reacting the compound represented by the formula (27) with epibromohydrin in dichloromethane.
The compound represented by the formula (27) was synthesized by protecting the hydroxy group of 1,3-dihydroxyacetone with dihydropyran and reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (G) was carried out, and the structure was identified by the following results.
Compound (G); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 3.4 to 3.9 (28H)

(Example 8)
The same operation as in Example 1 was carried out except that 15.7 g of the compound represented by the following formula (30) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (H) was used. (In the formula (H), mh indicating the average degree of polymerization is 4.5, and nh indicating the average degree of polymerization is 4.5) was obtained in an amount of 13.8 g.

The compound represented by the formula (30) was synthesized by reacting the compound represented by the formula (29) with epibromohydrin in dichloromethane.
The compound represented by the formula (29) was synthesized by protecting the hydroxy group of 1,5-dihydroxy-3-pentanone with dihydropyran and reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (H) was performed, and the structure was identified by the following results.
Compound (H); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (8H), 3.4-3.9 (28H)

(Example 9)
The same operation as in Example 1 was carried out except that 15.1 g of the compound represented by the following formula (32) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (I) was used. (In the formula (I), mi indicating the average degree of polymerization is 4.5, and ni indicating the average degree of polymerization is 4.5) was obtained in an amount of 13.5 g.

The compound represented by the formula (32) was synthesized by reacting the compound represented by the formula (31) with epibromohydrin in dichloromethane.
The compound represented by the formula (31) was synthesized by protecting the hydroxy group of 1,4-dihydroxy-2-butanone with dihydropyran and reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (I) was carried out, and the structure was identified by the following results.
Compound (I); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (4H), 3.4-3.9 (28H)

(Example 10)
The same operation as in Example 1 was carried out except that 15.7 g of the compound represented by the following formula (34) was used instead of the compound represented by the formula (16), and the compound represented by the above formula (J) was used. (In the formula (J), mj indicating the average degree of polymerization is 4.5, and nj indicating the average degree of polymerization is 4.5) was obtained in an amount of 13.8 g.

The compound represented by the formula (34) was synthesized by reacting the compound represented by the formula (33) with epibromohydrin in dichloromethane.
The compound represented by the formula (33) was synthesized by protecting the hydroxy group of 1,5-dihydroxy-2-pentanone with dihydropyran and reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

¹ H-NMR measurement of the obtained compound (J) was performed, and the structure was identified by the following results.
Compound (J); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.8 (4H), 2.5 (4H), 3.4-3.9 (28H)

(Example 11)
The same procedure as in Example 2 was carried out except that 2- (2-bromoethyl) oxylane was used instead of epibromohydrin, and the compound represented by the above formula (K) (mean among the formulas (K)) was averaged. The mk indicating the degree of polymerization was 4.5, and the nk indicating the average degree of polymerization was 4.5).) Was obtained in an amount of 13.2 g.

¹ H-NMR measurement of the obtained compound (K) was carried out, and the structure was identified by the following results.
Compound (K); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (2H), 2.2 to 2.4 (2H), 2.5 (4H), 3.4 to 3.9 (22H), 7.4 (2H)

(Example 12)
The same procedure as in Example 2 was carried out except that 2- (3-bromopropyl) oxylane was used instead of epibromohydrin, and the compound represented by the above formula (L) (in the formula (L)), The ml indicating the average degree of polymerization was 4.5, and the nl indicating the average degree of polymerization was 4.5.) Was obtained in an amount of 13.5 g.

¹ H-NMR measurement of the obtained compound (L) was performed, and the structure was identified by the following results.
Compound (L); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (2H), 2.2 to 2.4 (6H), 2.5 (4H), 3.4 to 3.9 (22H), 7.4 (2H)

(Example 13)
The same operation as in Example 2 was carried out except that the compound represented by the formula (35) was used instead of the epibromohydrin, and the compound represented by the above formula (M) (mean in the formula (M)). The mm indicating the degree of polymerization was 4.5, and the nm indicating the average degree of polymerization was 4.5.) Was obtained in an amount of 15.0 g.
The compound represented by the formula (35) was synthesized by oxidizing the double bond of allyl ether.

¹ H-NMR measurement of the obtained compound (M) was performed, and the structure was identified by the following results.
Compound (M); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (4H), 3.4-3.9 (34H), 7.4 (2H)

(Example 14)
The same operation as in Example 2 was carried out except that the compound represented by the formula (36) was used instead of the epibromohydrin, and the compound represented by the above formula (N) (mean in the formula (N)). The mn indicating the degree of polymerization was 4.5, and the nn indicating the average degree of polymerization was 4.5).) Was obtained in an amount of 15.6 g.
The compound represented by the formula (36) was synthesized by oxidizing the double bond of 3-butenyl ether.

¹ H-NMR measurement of the obtained compound (N) was performed, and the structure was identified by the following results.
Compound (N); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (4H), 2.2 to 2.4 (4H), 2.5 (4H), 3.4 to 3.9 (34H), 7.4 (2H)

(Example 15)
The compound represented by the above formula (O) was produced by the method shown below.
In a nitrogen gas atmosphere, in a 100 mL eggplant flask, HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (in the formula, m indicating the average degree of polymerization is 4.5. 20.0 g of a fluoropolyether (number average molecular weight 1000, molecular weight distribution 1.1) represented by (n is 4.5) indicating an average degree of polymerization and 3.65 g of a compound represented by the following formula (37). And 12 mL of t-butanol were charged and stirred at room temperature until uniform. Further, 0.674 g of potassium tert-butoxide was added to this uniform liquid, and the mixture was stirred and reacted at 70 ° C. for 8 hours to obtain a reaction product.

The obtained reaction product was cooled to 25 ° C., transferred to a separating funnel containing 100 mL of water, and extracted three times using 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 10.4 g of the compound represented by the following formula (38) as an intermediate.

The compound represented by the formula (37) was synthesized by reacting the compound represented by the formula (17) with the compound represented by the formula (35).

(In the formula (38), mo indicating the average degree of polymerization is 4.5, and no indicating the average degree of polymerization is 4.5.)

The double bond of 4-pentenyl ether was oxidized to synthesize the compound represented by the following formula (39).
Further, the compound represented by the formula (17) was reacted with the compound represented by the formula (39) to synthesize the compound represented by the following formula (40).

In a nitrogen gas atmosphere, 6.52 g of the compound represented by the above formula (38), 2.16 g of the compound represented by the formula (40) and 50 mL of t-butanol are charged in a 200 mL eggplant flask and become uniform at room temperature. Stirred to. To this uniform solution, 0.168 g of potassium tert-butoxide was added, and the mixture was stirred at 70 ° C. for 16 hours to react to obtain a reaction product.

The obtained reaction product was cooled to 25 ° C., 33 g of a 10% hydrogen chloride / methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added, and the mixture was stirred at room temperature for 2 hours. .. The reaction solution was gradually transferred to a separating funnel containing 100 mL of saline solution, and extracted three times using 200 mL of ethyl acetate. The organic layer was washed in the order of 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering out the drying agent (anhydrous sodium sulfate), the filtrate is concentrated, and the residue is purified by silica gel column chromatography to show the average degree of polymerization in the compound represented by the above formula (O) (formula (O)). The mo was 4.5, and the no indicating the average degree of polymerization was 4.5.) Was obtained in an amount of 5.24 g.

¹ H-NMR measurement of the obtained compound (O) was carried out, and the structure was identified by the following results.
Compound (O); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (6H), 2.2 to 2.4 (2H) 2.5 (4H), 3.4 to 3.9 (34H), 7.4 (2H)

(Example 16)
The same operation as in Example 15 was carried out except that the compound represented by the formula (16) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (41) as an intermediate. rice field.
Then, as an intermediate, the compound represented by the formula (41) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (18). The same operation as in Example 15 was carried out except that the above compound was used, and the compound represented by the above formula (P) (in the formula (P), the mp showing the average degree of polymerization was 4.5, and the average polymerization was performed. The np indicating the degree is 4.5.) Was obtained in an amount of 4.47 g.

(In the formula (41), mp indicating the average degree of polymerization is 4.5, and np indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (P) was carried out, and the structure was identified by the following results.
Compound (P); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (2H), 3.4-3.9 (22H), 7.4 (2H)

(Example 17)
The same operation as in Example 15 was carried out except that the compound represented by the formula (18) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (42) as an intermediate. rice field.
Then, as an intermediate, the compound represented by the formula (42) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (20). The same operation as in Example 15 was carried out except that the above compound was used, and the mq indicating the average degree of polymerization was 4.5 in the compound represented by the above formula (Q) (in the formula (Q)), the average polymerization was carried out. The nq indicating the degree is 4.5.) Was obtained in an amount of 4.57 g.

(In the formula (42), mq indicating the average degree of polymerization is 4.5, and nq indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (Q) was carried out, and the structure was identified by the following results.
Compound (Q); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.8 (2H), 2.5 (4H), 3.4-3.9 (22H), 7.4 (2H)

(Example 18)
The same operation as in Example 15 was carried out except that the compound represented by the formula (22) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (43) as an intermediate. rice field.
Then, as an intermediate, the compound represented by the formula (43) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (24). The same operation as in Example 15 was carried out except that the above compound was used, and the compound represented by the above formula (R) (in the formula (R), mr indicating the average degree of polymerization was 4.5, and the average polymerization was performed. The nr indicating the degree is 4.5.) Was obtained in an amount of 4.68 g.

(In the formula (43), mr indicating the average degree of polymerization is 4.5, and nr indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (R) was performed, and the structure was identified by the following results.
Compound (R); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.8 (1H), 3.4-3.9 (27H), 7.4 (2H)

(Example 19)
The same operation as in Example 15 was carried out except that the compound represented by the formula (26) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (44) as an intermediate. rice field.
Then, as an intermediate, the compound represented by the formula (44) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (32). The same operation as in Example 15 was carried out except that the compound represented by the above compound (S) was used. In the compound represented by the above formula (S), ms indicating the average degree of polymerization was 4.5, and the average polymerization was performed. The ns indicating the degree is 4.5.) Was obtained in an amount of 4.68 g.

(In the formula (44), ms indicating the average degree of polymerization is 4.5, and ns indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (S) was carried out, and the structure was identified by the following results.
Compound (S); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (1H), 2.2 to 2.4 (1H), 2.5 (2H), 3.4 to 3.9 (27H), 7.4 (1H)

(Example 20)
The same operation as in Example 15 was carried out except that the compound represented by the following formula (47) was used instead of the compound represented by the formula (37), and the compound represented by the formula (45) was used as an intermediate. Obtained.

The compound represented by the formula (47) was synthesized by the method shown below. The compound represented by the formula (46) was synthesized by reacting 1,3-dioxepan-5-carbaldehyde with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution. Then, the compound represented by the formula (46) was reacted with epibromohydrin to synthesize the compound represented by the formula (47).

Then, as an intermediate, the compound represented by the formula (45) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (28). The same operation as in Example 15 was carried out except that the above compound was used, and the compound represented by the above formula (T) (in the formula (T), the mt showing the average degree of polymerization was 4.5, and the average degree of polymerization was set to 4.5. The indicated nt is 4.5.) Was obtained in an amount of 4.78 g.

(In the formula (45), the mt indicating the average degree of polymerization is 4.5, and the nt indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (T) was performed, and the structure was identified by the following results.
Compound (T); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.8 (2H), 2.5 (1H), 3.4-3.9 (30H), 7.4 (1H)

(Example 21)
The same operation as in Example 20 was carried out to obtain a compound represented by the following formula (48), which is the same as the compound represented by the formula (45) as an intermediate.
Then, the same operation as in Example 20 except that the compound represented by the formula (48) was used as an intermediate and the compound represented by the formula (18) was used instead of the compound represented by the formula (28). Was carried out to obtain 4.68 g of the compound represented by the above formula (U) (in the formula (U), mu indicating the average degree of polymerization is 4.5 and nu indicating the average degree of polymerization is 4.5). ..

(In the formula (48), mu indicating the average degree of polymerization is 4.5, and nu indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (U) was performed, and the structure was identified by the following results.
Compound (U); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.8 (2H), 2.5 (3H), 3.4-3.9 (25H), 7.4 (2H)

(Example 22)
The same operation as in Example 15 was carried out except that the compound represented by the following formula (50) was used instead of the compound represented by the formula (37), and the compound represented by the formula (49) was used as an intermediate. Obtained.
The compound represented by the formula (50) was synthesized by reacting the compound represented by the formula (17) with 2- (2-bromoethyl) oxylane.

Then, as an intermediate, the compound represented by the formula (49) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (20). The same operation as in Example 15 was carried out except that the above compound was used, and the mv indicating the average degree of polymerization was 4.5 in the compound represented by the above formula (V) (in the formula (V)), the average polymerization was carried out. The nv indicating the degree is 4.5.) Was obtained in an amount of 4.62 g.

(In the formula (49), the mv indicating the average degree of polymerization is 4.5, and the nv indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (V) was performed, and the structure was identified by the following results.
Compound (V); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (3H), 2.2 to 2.4 (1H), 2.5 (2H), 3.4 to 3.9 (24H), 7.4 (2H)

(Example 23)
The same operation as in Example 15 was carried out except that the compound represented by the following formula (52) was used instead of the compound represented by the formula (37), and the compound represented by the formula (51) was used as an intermediate. Obtained.
The compound represented by the formula (52) was synthesized by reacting the compound represented by the formula (15) with 2- (2-bromoethyl) oxylane.

Then, as an intermediate, the compound represented by the formula (51) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was replaced by the following formula (53). The same operation as in Example 15 was carried out except that the indicated compound was used, and the compound represented by the above formula (W) (in the formula (W), mw indicating the average degree of polymerization was 4.5, which was an average. The nw indicating the degree of polymerization is 4.5.) Was obtained in an amount of 4.77 g.
The compound represented by the formula (53) was synthesized by reacting the compound represented by the formula (46) with 2- (3-bromopropyl) oxylane.

(In the formula (51), mw indicating the average degree of polymerization is 4.5, and nw indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (W) was performed, and the structure was identified by the following results.
Compound (W); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (6H), 2.2 to 2.4 (2H), 2.5 (3H), 3.4 to 3.9 (23H), 7.4 (2H)

(Example 24)
The same operation as in Example 15 was carried out except that the compound represented by the formula (50) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (54) as an intermediate. rice field.
Then, as an intermediate, the compound represented by the formula (54) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (47). The same operation as in Example 15 was carried out except that the above compound was used, and the compound represented by the above formula (X) (in the formula (X), mx indicating the average degree of polymerization was 4.5, and the average degree of polymerization was set to 4.5. The indicated nx is 4.5.) Was obtained in an amount of 4.73 g.

(In the formula (54), mx indicating the average degree of polymerization is 4.5, and nx indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (X) was carried out, and the structure was identified by the following results.
Compound (X); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (3H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3.9 (25H), 7.4 (2H)

(Example 25)
The same operation as in Example 15 was carried out to obtain a compound represented by the formula (55), which is the same as the compound represented by the formula (38) as an intermediate.
Then, the same operation as in Example 15 was performed except that the compound represented by the formula (18) was used instead of the compound represented by the formula (40), and the compound represented by the above formula (Y) (formula). In (Y), my indicating the average degree of polymerization was 4.5, and ny indicating the average degree of polymerization was 4.5).) Was obtained in an amount of 4.78 g.

(In the formula (55), my indicating the average degree of polymerization is 4.5, and ny indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (Y) was carried out, and the structure was identified by the following results.
Compound (Y); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (4H), 3.4-3.9 (28H), 7.4 (2H)

(Example 26)
The same operation as in Example 15 was carried out except that the compound represented by the formula (57) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (56) as an intermediate. rice field.
The compound represented by the formula (57) was synthesized by reacting the compound represented by the formula (36) with the compound represented by the formula (17).

Then, as an intermediate, the compound represented by the formula (56) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (37). The same operation as in Example 15 was carried out except that the above compound was used, and the mz indicating the average degree of polymerization was 4.5 in the compound represented by the above formula (Z) (in the formula (Z)), the average polymerization was carried out. The nz indicating the degree is 4.5.) Was obtained in an amount of 5.09 g.

(In the formula (56), mz indicating the average degree of polymerization is 4.5, and nz indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (Z) was performed, and the structure was identified by the following results.
Compound (Z); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (2H), 2.2 to 2.4 (2H), 2.5 (4H), 3.4 to 3.9 (32H), 7.4 (2H)

(Example 27)
The same operation as in Example 15 was carried out except that the compound represented by the formula (18) was used instead of the compound represented by the formula (37) to obtain the compound represented by the formula (58) as an intermediate. rice field.
Then, as an intermediate, the compound represented by the formula (58) was used instead of the compound represented by the formula (38), and the compound represented by the formula (40) was represented by the formula (32). The same operation as in Example 15 was carried out except that the above compound was used, and the compound represented by the above formula (AA) (in the formula (AA), mA showing the average degree of polymerization was 4.5, and the average polymerization was performed. The nA indicating the degree is 4.5.) Was obtained in an amount of 5.09 g.

(In the formula (58), mA indicating the average degree of polymerization is 4.5, and nA indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AA) was performed, and the structure was identified by the following results.
Compound (AA); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (4H), 3.4-3.9 (38H), 7.4 (2H)

(Example 28)
The same operation as in Example 24 was carried out except that the compound represented by the following formula (60) was used instead of the compound represented by the formula (50), and the compound represented by the formula (59) was used as an intermediate. Obtained.

The compound represented by the formula (60) was synthesized by reacting the compound represented by the following formula (61) with epibromohydrin in dichloromethane.
The compound represented by the formula (61) was synthesized by the method shown below. 3- (3-Butene-1-iroxy) -1-propanol was oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. The obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

Then, the same operation as in Example 24 was performed except that the compound represented by the formula (59) was used instead of the compound represented by the formula (54) as the intermediate, and the compound represented by the above formula (AB) was used. 4.89 g of the compound (in the formula (AB), mB indicating the average degree of polymerization is 4.5 and nB indicating the average degree of polymerization is 4.5) was obtained.

(In the formula (59), mB indicating the average degree of polymerization is 4.5, and nB indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AB) was performed, and the structure was identified by the following results.
Compound (AB); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (1H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3.9 (32H), 5.0 to 5. 1 (1H), 5.1 to 5.2 (1H), 5.8 to 6.0 (1H), 7.4 (2H)

(Example 29)
The same operation as in Example 24 was carried out except that the compound represented by the following formula (63) was used instead of the compound represented by the formula (50), and the compound represented by the formula (62) was used as an intermediate. Obtained.

The compound represented by the formula (63) was synthesized by reacting the compound represented by the formula (64) with epibromohydrin in dichloromethane.
The compound represented by the formula (64) was synthesized by the method shown below. 3-Butoxypropanol was oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. The obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

Then, the same operation as in Example 24 was performed except that the compound represented by the formula (62) was used instead of the compound represented by the formula (54) as the intermediate, and the compound represented by the above formula (AC) was used. 4.87 g of the compound (mC indicating the average degree of polymerization is 4.5 and nC indicating the average degree of polymerization is 4.5 in the formula (AC)) was obtained.

(In the formula (62), mC indicating the average degree of polymerization is 4.5, and nC indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AC) was performed, and the structure was identified by the following results.
Compound (AC); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 0.9 to 1.1 (5H), 1.6 to 2.0 (1H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3. 9 (45H), 7.4 (2H)

(Example 30)
The same operation as in Example 24 was carried out except that the compound represented by the following formula (66) was used instead of the compound represented by the formula (50), and the compound represented by the formula (65) was used as an intermediate. Obtained.

The compound represented by the formula (66) was synthesized by reacting the compound represented by the following formula (67) with epibromohydrin in dichloromethane.
The compound represented by the formula (67) was synthesized by the method shown below. 3- (2-Propinyloxy) propanol was oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. The obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

Then, the same operation as in Example 24 was performed except that the compound represented by the formula (65) was used instead of the compound represented by the formula (54) as the intermediate, and the compound represented by the above formula (AD) was used. 4.80 g of the compound (mD indicating the average degree of polymerization is 4.5 and nD indicating the average degree of polymerization is 4.5 in the formula (AD)) was obtained.

(In the formula (65), the mD indicating the average degree of polymerization is 4.5, and the nD indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AD) was performed, and the structure was identified by the following results.
Compound (AD); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (3H), 2.7 (1H), 3.4-3.9 (32H), 7.4 (2H)

(Example 31)
The same operation as in Example 24 was carried out except that the compound represented by the following formula (69) was used instead of the compound represented by the formula (50), and the compound represented by the formula (68) was used as an intermediate. Obtained.

The compound represented by the formula (69) was synthesized by reacting the compound represented by the following formula (70) with epibromohydrin in dichloromethane.
The compound represented by the formula (70) was synthesized by the method shown below. 3- (4-Methoxyphenoxy) propanol was oxidized in dichloromethane with Dess-Martin peryodinane to give the compound. The obtained compound was synthesized by reacting with hydroxylamine and potassium carbonate in a 50% aqueous ethanol solution.

Then, the same operation as in Example 24 was performed except that the compound represented by the formula (68) was used instead of the compound represented by the formula (54) as the intermediate, and the compound represented by the above formula (AE) was used. In the formula (AE), mE indicating the average degree of polymerization was 4.5, and nE indicating the average degree of polymerization was 4.5).

(In the formula (68), mE indicating the average degree of polymerization is 4.5, and nE indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AE) was performed, and the structure was identified by the following results.
Compound (AE); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 2.5 (3H), 3.4-3.9 (31H), 6.8 (4H), 7.4 (2H)

(Example 32)
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (In the formula, m indicating the average degree of polymerization is 4.5, and n indicating the average degree of polymerization is 4. HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _w CF ₂ CH ₂ OH (in the formula, w indicating the average degree of polymerization is 7.0) instead of the fluoropolyether represented by 5). The same operation as in Example 21 was carried out except that the fluoropolyether represented by the above formula (AF) was used, and the compound represented by the above formula (AF) was passed through the compound represented by the formula (71) as an intermediate. In the formula (AF), w indicating the average degree of polymerization is 7.0) was obtained in an amount of 4.59 g.

(In formula (71), w indicating the average degree of polymerization is 7.0.)

¹ H-NMR measurement of the obtained compound (AF) was performed, and the structure was identified by the following results.
Compound (AF); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (3H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3.9 (25H), 7.4 (2H)

(Example 33)
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (In the formula, m indicating the average degree of polymerization is 4.5, and n indicating the average degree of polymerization is 4. HOCH ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ O) _x CF ₂ CF ₂ CH ₂ OH (in the formula, x indicating the average degree of polymerization) instead of the fluoropolyether represented by (5). Is 4.5.), Except for the fact that the fluoropolyether represented by the above formula (AG) was used, the same operation as in Example 21 was carried out, and the compound represented by the formula (72) was passed as an intermediate, and then the above formula (AG) was used. ) (X in the formula (AG), which indicates the average degree of polymerization is 4.5) was obtained in an amount of 4.70 g.

(In formula (72), x indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AG) was performed, and the structure was identified by the following results.
Compound (AG); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (3H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3.9 (25H), 7.4 (2H)

(Example 34)
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (In the formula, m indicating the average degree of polymerization is 4.5, and n indicating the average degree of polymerization is 4. HOCH ₂ CF ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ CF ₂ O) _y CF ₂ CF ₂ CF ₂ CH ₂ OH (in the formula, The same operation as in Example 21 was carried out except that the fluoropolyether represented by (3), which indicates the average degree of polymerization, was used, and the compound represented by the formula (73) was used as an intermediate. Then, 4.71 g of the compound represented by the above formula (AH) (in the formula (AH), y showing the average degree of polymerization is 3.0) was obtained.

(In formula (73), y indicating the average degree of polymerization is 3.0.)

¹ H-NMR measurement of the obtained compound (AH) was performed, and the structure was identified by the following results.
Compound (AH); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (3H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3.9 (25H), 7.4 (2H)

(Example 35)
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (In the formula, m indicating the average degree of polymerization is 4.5, and n indicating the average degree of polymerization is 4. HOCH ₂ CF (CF ₃ ) (OCF (CF ₃ ) CF ₂ ) _z OCF (CF ₃ ) CH ₂ OH (in the formula, the average degree of polymerization is shown) instead of the fluoropolyether represented by 5). The same operation as in Example 21 was carried out except that the fluoropolyether represented by (z) was 4.5, and the compound represented by the formula (74) was passed as an intermediate to the above formula (z). 4.71 g of the compound represented by AI) (in the formula (AI), z indicating the average degree of polymerization is 4.5) was obtained.

(In formula (74), z indicating the average degree of polymerization is 4.5.)

¹ H-NMR measurement of the obtained compound (AI) was performed, and the structure was identified by the following results.
Compound (AI); ^{1 1} H-NMR (CD ₃ COCD ₃ );
δ [ppm] 1.6 to 2.0 (3H), 2.2 to 2.4 (1H), 2.5 (3H), 3.4 to 3.9 (25H), 7.4 (2H)

Table ¹ shows the structure of R1 (X, Y in the formula (2)) when the compounds of Examples 1 to 35 thus obtained are applied to the formula (1). Further, the structure of R ² when applied to the formula (1) (a in [A] in the formula (3), b, c in [B], d, e in [C]), the structure of R ³ The structure of ^R4 (a in [A], b, c in [B], d, e in [C]) in the formula (3) is shown in Table 2. Table 3 shows the total number of the structures of R5 ⁽ X, Y in the formula (2)) and the hydroxyl groups [-OH] contained in the molecule when applied to the formula (1).

"Comparative Example 1"
The compound represented by the following formula (AJ) was synthesized by the method described in Patent Document 1.

(In the formula (AJ), jA indicating the average degree of polymerization is 4.5, and kA indicating the average degree of polymerization is 4.5.)

"Comparative Example 2"
A commercially available compound represented by the following formula (AK) was used.

(In the formula (AK), jB indicating the average degree of polymerization is 4.5, and kB indicating the average degree of polymerization is 4.5.)

"Comparative Example 3"
The compound represented by the following formula (AL) was synthesized by the method described in Patent Document 3.

(In the formula (AL), jC indicating the average degree of polymerization is 4.5, and kC indicating the average degree of polymerization is 4.5.)

"Comparative Example 4"
The compound represented by the following formula (AM) was synthesized by the method described in Patent Document 3. That is, the compound represented by the formula (33) described in Patent Document 3 is HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF ₂ CH ₂ OH (in the formula, the average degree of polymerization is determined. The indicated m is 4.5, and the n indicating the average degree of polymerization is 4.5).

(In the formula (AM), jD indicating the average degree of polymerization is 4.5, and kD indicating the average degree of polymerization is 4.5.)

Table 4 shows the number average molecular weights (Mn) of the compounds of Examples 1 to 35 and Comparative Examples 1 to 4 thus obtained.

Next, a solution for forming a lubricating layer was prepared using the compounds obtained in Examples 1 to 35 and Comparative Examples 1 to 4 by the methods shown below. Then, using the obtained lubricating layer forming solution, the lubricating layer of the magnetic recording medium was formed by the method shown below, and the magnetic recording media of Examples 1 to 35 and Comparative Examples 1 to 4 were obtained.

"Solution for forming a lubricating layer"
The compounds obtained in Examples 1 to 35 and Comparative Examples 1 to 4 were each dissolved in Bertrel (registered trademark) XF, and the film thickness when applied onto the protective layer was 9 Å. It was diluted with XF to prepare a solution for forming a lubricating layer.

"Magnetic recording medium"
A magnetic recording medium in which an adhesive layer, a soft magnetic layer, a first base layer, a second base layer, a magnetic layer, and a protective layer are sequentially provided on a substrate having a diameter of 65 mm was prepared. The protective layer was made of carbon.
The solutions for forming a lubricating layer of Examples 1 to 35 and Comparative Examples 1 to 4 were applied onto the protective layer of the magnetic recording medium on which each layer up to the protective layer was formed by a dip method. The dipping method was performed under the conditions of a dipping speed of 10 mm / sec, a dipping time of 30 sec, and a pulling speed of 1.2 mm / sec.
After that, the magnetic recording medium coated with the solution for forming the lubricating layer is placed in a constant temperature bath at 120 ° C. and heated for 10 minutes to remove the solvent in the solution for forming the lubricating layer to form the lubricating layer on the protective layer. Then, a magnetic recording medium was obtained.

The film thickness of the lubricating layer of the magnetic recording media of Examples 1 to 35 and Comparative Examples 1 to 4 thus obtained was measured by using FT-IR (trade name: Nicolet iS50, Thermo Fisher Scientific). It was measured. The results are shown in Table 4.

Next, the following tests were performed on the magnetic recording media of Examples 1 to 35 and Comparative Examples 1 to 4, and the bond ratio, pickup characteristics, and spin-off characteristics were evaluated. The results are shown in Table 4.

(Measurement of adhesion (bond ratio) between lubricating layer and protective layer)
The magnetic recording medium on which the lubricating layer was formed was washed by immersing it in the solvent Bartrel XF for 10 minutes and pulling it up. The speed at which the magnetic recording medium was immersed in the solvent was 10 mm / sec, and the speed at which the magnetic recording medium was pulled up was 1.2 mm / sec. After that, the film thickness of the lubricating layer was measured by the same method as the film thickness measurement of the lubricating layer performed before cleaning.

The thickness of the lubricating layer before cleaning is α, the thickness of the lubricating layer after cleaning (after immersion in the solvent) is β, and the ratio of α to β ((β / α) × 100 (%)). The bond rate (bond rate) of the lubricant was calculated. Using the calculated bond ratio, the adhesion between the lubricating layer and the protective layer was evaluated according to the following evaluation criteria.
The bond ratio can be used as an index showing the bonding force between the lubricating layer and the protective layer. If the adhesion between the lubricating layer and the protective layer is poor, a part of the fluorine-containing ether compound contained in the lubricating layer is dissolved into Bertrel XF and washed away. Therefore, the film thickness of the lubricating layer after cleaning becomes small, and the bond ratio decreases.

"Evaluation criteria for adhesion (bond rate)"
◎ (excellent): Bond rate 75% or more 〇 (Good): Bond rate 70% -74%
△ (possible): Bond rate 50% to 69%
× (impossible): Bond rate 49% or less

(Pickup characteristic test)
A magnetic recording medium and a magnetic head were attached to the spin stand, rotated under normal temperature and reduced pressure (about 250 torr), and the magnetic head was levitated at a fixed point for 10 minutes. Then, the surface of the magnetic head facing the magnetic recording medium was analyzed using an ESCA (Electron Spectroscopy for Chemical Analysis) analyzer. The intensity of the fluorine-derived peak (signal intensity (a.u.)) obtained by ESCA analysis indicates the amount of the lubricant attached to the magnetic head. Using the obtained signal strength, the pickup characteristics were evaluated according to the evaluation criteria shown below.

"Evaluation criteria for pickup characteristics"
◎ (excellent): Signal strength 160 or less (adhesion amount is very small)
〇 (Good): Signal strength 161 to 300 (small amount of adhesion)
△ (possible): Signal strength 301 to 1000 (large amount of adhesion)
× (impossible): Signal strength 1001 or more (adhesion amount is very large)

(Spin-off characteristic test)
A magnetic recording medium was attached to the spin stand and rotated at a rotation speed of 10000 rpm for 72 hours in an environment of 80 ° C. Before and after this operation, the film thickness of the lubricating layer at a position with a radius of 20 mm from the center of the magnetic recording medium was measured by FT-IR, and the film thickness reduction rate of the lubricating layer before and after the test ({1- (film thickness after test). / Pre-test film thickness)} × 100 (%)) was calculated. Using the calculated film thickness reduction rate, the spin-off characteristics were evaluated according to the evaluation criteria shown below.

"Evaluation criteria for spin-off characteristics"
◎ (excellent): film thickness reduction rate 2% or less 〇 (good): film thickness reduction rate greater than 2% and 3% or less △ (possible): film thickness reduction rate greater than 3% and 9% or less × (impossible): film Thickness reduction rate greater than 9%

Based on these results, a comprehensive evaluation was performed according to the evaluation criteria shown below.
"Comprehensive evaluation"
◎ (excellent): The evaluation of bond rate, pickup characteristics, and spin-off characteristics are all ◎.
〇 (Good): The evaluation of bond rate, pickup characteristics, and spin-off characteristics is ◎ or 〇, and one or more of them is 〇.
Δ (possible): One or more of the evaluations of the bond rate, the pickup characteristic, and the spin-off characteristic is Δ, and there is no ×.
× (impossible): One or more of the evaluations of the bond rate, the pickup characteristic, and the spin-off characteristic is ×.

As shown in Table 4, the magnetic recording media of Examples 1 to 35 have a higher bond ratio and better adhesion between the lubricating layer and the protective layer than the magnetic recording media of Comparative Examples 1 to 4. rice field.
Further, as shown in Table 4, the magnetic recording media of Examples 1 to 35 have a smaller signal intensity derived from fluorine obtained by ESCA analysis than the magnetic recording media of Comparative Examples 1 to 4, and the pickup can be used. It became clear that it was suppressed.
Further, as shown in Table 4, it is clear that the magnetic recording media of Examples 1 to 35 have a smaller film thickness reduction rate and suppress spin-off as compared with the magnetic recording media of Comparative Examples 1 to 4. Became.

These results show that in the magnetic recording media of Examples 1 to 35, the fluorine-containing ether compound represented by the formula (1) contained in the lubricating layer is represented by the formula (2) containing an oxime group at both ends. It is presumed that this is because it has a terminal group and a linking group containing a polar group (hydroxyl group) is arranged between both terminal groups and the perfluoropolyether chain.
In particular, among the magnetic recording media of Examples 1 to 35, the compounds (A) to (C), (K), (L), (L), in which the total number of hydroxyl groups [-OH] contained in the molecule is 5 or less. Magnetic recording media of Examples 1 to 3, 11, 12, 16, 17, 21 to 25, 27 to 35 using P), (Q), (U) to (Y), (AA) to (AI). The overall evaluation was ◎ (excellent), which was a good result.

In Examples 1 to 3, 11, 12 (Compounds (A) to (C), (K), (L)) and Comparative Example 3 (Compound (AL)), the total number of hydroxyl groups contained in the compound molecule. The numbers are the same. Further, in Examples 4 to 10 and 13 to 15 (Compounds (D) to (J), (M) to (O)) and Comparative Example 4 (Compound (AM)), the hydroxyl groups contained in the compound molecule. The total number of is the same. From this, it is presumed that the bond rate, pickup characteristics and spin-off characteristics were improved by arranging terminal groups containing an oxime group (-C = NO-) at both ends of the perfluoropolyether chain. Will be done. These results show that oxime groups (-C = NO-), which have the same interaction with the protective layer as the hydroxyl group and have a small intramolecular interaction with the hydroxyl group, are introduced into both ends of the molecule and contain fluorine. It is presumed that the use of the ether compound improved the adhesion of the lubricating layer to the protective layer.

By using the lubricant for a magnetic recording medium containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer having excellent adhesion even if the thickness is thin.
That is, according to the present invention, there is provided a fluorine-containing ether compound that has excellent adhesion even if it is thin, can form a lubricating layer in which pickup and spin-off are unlikely to occur, and is suitable as a material for a lubricant for a magnetic recording medium. can.

10 ... Magnetic recording medium, 11 ... Substrate, 12 ... Adhesive layer, 13 ... Soft magnetic layer, 14 ... First base layer, 15 ... Second base layer, 16 ... -Magnetic layer, 17 ... protective layer, 18 ... lubricating layer.

Claims

A fluorine-containing ether compound represented by the following formula (1).
R 1 -R 2 -CH 2 -R 3 -CH 2 -R 4 -R 5 (1)
(In formula (1), R 1 and R 5 are terminal groups represented by the following formula (2) containing an oxime group, respectively; R 2 and R 4 are divalent linking groups having polar groups, respectively. R 3 is a perfluoropolyether chain.)

(In the formula (2), X and Y are either a hydrogen atom, an alkyl group having 1 to 12 carbon atoms which may have a substituent, and an organic group having a double bond or a triple bond, respectively.)
The fluorine-containing ether compound according to claim 1, wherein the number of hydroxyl groups contained in the molecule is 8 or less.
The fluorine-containing ether compound according to claim 1, wherein the number of hydroxyl groups contained in the molecule is 6 or less.
The fluorine-containing ether compound according to any one of claims 1 to 3, wherein the polar group contained in R 2 and R 4 is a hydroxyl group.
The fluorine-containing product according to any one of claims 1 to 4, wherein the R 3 -CH 2 -R 2- and the R 3 -CH 2 -R 4- are represented by the following formula (3). Ether compound.
R 3 -CH 2- [A]-[B]-[C]-(3)
(In the formula (3), [A] is represented by the following formula (4), [B] is represented by the following formula (5), and [C] is represented by the following formula (6); ), The order of [A], [B], and [C] may be changed; the ether bond side in the formulas (4) to (6) is the CH 2 side in the formula (3).)

(In equation (4), a is an integer of 0 to 3; in equation (5), b is an integer of 0 to 3 and c is an integer of 1 to 4; in equation (6), d. Is an integer of 0 to 3 and e is an integer of 1 to 4; however, at least one of a, b, and d is 1 or more.)
The fluorine-containing product according to any one of claims 1 to 5, wherein X and / or Y in the formula (2) in at least one of R 1 and R 5 is an alkyl group having a hydroxyl group. Ether compound.
The fluorine-containing ether compound according to any one of claims 1 to 6 , wherein R3 is represented by any of the following formulas (7) to (11).
-CF 2 O- (CF 2 CF 2 O) m- (CF 2 O) n -CF 2- (7)
(M and n in the formula (7) indicate the average degree of polymerization, and each represents 0.1 to 30.)
-CF 2 O- (CF 2 CF 2 O) w -CF 2- (8)
(W in the formula (8) indicates the average degree of polymerization and represents 0.1 to 30.)
-CF 2 CF 2 O- (CF 2 CF 2 CF 2 O) x -CF 2 CF 2- (9)
(X in the formula (9) indicates the average degree of polymerization and represents 0.1 to 30).
-CF 2 CF 2 CF 2 O- (CF 2 CF 2 CF 2 CF 2 O) y -CF 2 CF 2 CF 2- (10)
(Y in the formula (10) indicates the average degree of polymerization and represents 0.1 to 30).
-CF (CF 3 )-(OCF (CF 3 ) CF 2 ) z -OCF (CF 3 )-(11)
(Z in the formula (11) indicates the average degree of polymerization and represents 0.1 to 30.)
The fluorine-containing ether compound according to any one of claims 1 to 7, wherein R 1 and R 5 are the same.
The fluorine-containing ether compound according to any one of claims 1 to 8, wherein R 2 and R 4 are the same.
The fluorine-containing ether compound according to any one of claims 1 to 9, wherein the number average molecular weight is in the range of 500 to 10000.
A lubricant for a magnetic recording medium, which comprises the fluorine-containing ether compound according to any one of claims 1 to 10.
A magnetic recording medium in which at least a magnetic layer, a protective layer, and a lubricating layer are sequentially provided on a substrate.
A magnetic recording medium, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of claims 1 to 10.
The magnetic recording medium according to claim 12, wherein the average film thickness of the lubricating layer is 0.5 nm to 2.0 nm.