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

Abstract

This fluorine-containing ether compound is characterized by being represented by formula (1). Formula (1): R1-CH2-R2-CH2-R3 (In formula (1), R2 is a perfluoropolyether chain represented by formula (2); R1 is a terminal group bonded to R2 via CH2, and is represented by formula (3); and R3 is a terminal group bonded to R2 via CH2, having one or more hydroxyl groups, and may be the same as or different from R1.) Formula (2): -(CF2)p-1-O-((CF2)pO)q-(CF2)p-1- (In formula (2), p is an integer of 2 to 3, and q is the average polymerization degree and is 1 to 20.) Formula (3): -O(CH2-CH(OH)-CH2-O)2-CH2-(CH2)n-OH (In formula (3), n is an integer of 1 to 8.)

Description

[Technical field]

[0001] The present invention relates to a fluorine-containing ether compound suitable for use as a lubricant for magnetic recording media, a lubricant for magnetic recording media containing the same, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2019-202285, filed on November 7, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] In order to improve the recording density of magnetic recording and reproducing devices, development of magnetic recording media suitable for high recording density is underway. Conventionally, magnetic recording media include those 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 also improves the sliding properties of the magnetic head. However, the durability of the magnetic recording medium cannot be sufficiently obtained by simply providing a protective layer on the recording layer. For this reason, a lubricant is generally applied to the surface of the protective layer to form a lubricating layer.

[0003] As lubricants used in forming a lubricating layer of a magnetic recording medium, for example, lubricants containing a compound having a polar group such as a hydroxyl group at the end of a fluorine-based polymer having a repeating structure containing CF2 have been proposed (see, for example, Patent Documents 1 and 2). Specifically, Patent Document 1 discloses a compound having multiple hydroxyl groups at both terminal portions. Furthermore, Patent Document 2 discloses a compound having a perfluoropolyether main chain, and an end group of the molecule containing two or more polar groups, each polar group being bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded being bonded to each other via a linking group containing a carbon atom to which no polar group is bonded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4632144 [Patent Document 2] JP 2018-24614 A Summary of the Invention [Problem to be solved by the invention]

[0005] In magnetic recording and reproducing devices, there is a demand for higher reliability as well as improved recording density. For example, improved chemical resistance and pick-up suppression are required. Chemical resistance refers to resistance to contamination of magnetic recording media by environmental substances, and pick-up suppression refers to the ability to suppress the adhesion of fluorine-containing ether compounds in the lubricating layer to the magnetic head as foreign matter (smear).

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a fluorine-containing ether compound that can be suitably used as a material for a lubricant for a magnetic recording medium, which has good adhesion to a protective layer, can suppress pick-up, and can form a lubricating layer that has excellent chemical resistance. Another object of the present invention is to provide a lubricant for magnetic recording media, which contains the fluorine-containing ether compound of the present invention. Another object of the present invention is to provide a magnetic recording medium having excellent reliability and durability, which has a lubricating layer containing the fluorinated ether compound of the present invention. [Means for solving the problem]

[0007] The present inventors have conducted extensive research in order to solve the above problems. As a result, the present inventors discovered that a fluorine-containing ether compound having multiple hydroxyl groups of a specific structure arranged at at least one end of a rigid perfluoropolyether (hereinafter sometimes referred to as "PFPE") chain would be sufficient, and thus arrived at the present invention. That is, the present invention relates to the following.

[0008] [1] A fluorinated ether compound represented by the following formula (1): R1 -CH2-R 2 -CH2-R 3 (1) (In formula (1), R 2 R is a perfluoropolyether chain represented by the following formula (2). 1 is connected via CH2 to R 2 R is a terminal group bonded to 3 is connected via CH2 to R 2 is a terminal group having one or more hydroxyl groups and bonded to R 1 may be the same as or different from.) -(CF2) p-1 -O-((CF2) p O) q -(CF2) p-1 - (2) (In formula (2), p represents an integer of 2 to 3, and q represents the average degree of polymerization, which is 1 to 20.)

[0009] [ka] (In formula (3), n is an integer of 1 to 8.)

[0010] [2] R in the above formula (1) 3 wherein R is a terminal group represented by the formula (3). [3] The fluorine-containing ether compound according to [2], wherein the compound represented by formula (1) is any of compounds represented by the following formulae (D) to (G):

[0011] [ka] (In formula (D), xd is the average degree of polymerization and represents 1 to 14.) (In formula (E), xe is the average degree of polymerization and represents 1 to 14.) (In formula (F), xf is the average degree of polymerization and represents 1 to 14.) (In formula (G), xg is the average degree of polymerization and represents 1 to 14.)

[0012] [4] The fluorine-containing ether compound according to [2], wherein the ether compound represented by the formula (1) is any of the compounds represented by the following formulae (N) to (Q):

[0013] [ka] (In formula (N), yn is the average degree of polymerization and represents 1 to 20.) (In formula (O), yo is the average degree of polymerization and represents 1 to 20.) (In formula (P), yp is the average degree of polymerization and represents 1 to 20.) (In formula (Q), yq is the average degree of polymerization and represents 1 to 20.)

[0014] [5] R in the above formula (1) 3 is a hydroxyl group or a terminal group represented by any one of the following formulas (4-1) and (4-2): -O-CH2-CH(OH)-CH2-OH (4-1) -O-CH2-CH(OH)-CH2-O-(CH2) k -OH (4-2) (In formula (4-2), k represents an integer of 1 to 5.)

[0015] [6] R in the above formula (1) 3 is a terminal group represented by the formula (4-2).

[0016] [7] The fluorine-containing ether compound according to [5], wherein the ether compound represented by the formula (1) is any one of compounds represented by the following formulas (C) and (H):

[0017] [ka] (In formula (C), xc is the average degree of polymerization and represents 1 to 14.) (In formula (H), xh is the average degree of polymerization and represents 1 to 14.)

[0018] [8] The fluorine-containing ether compound according to [5], wherein the ether compound represented by the formula (1) is any one of compounds represented by the following formulas (M) and (R):

[0019] [ka] (In formula (M), ym is the average degree of polymerization and represents 1 to 20.) (In formula (R), yr is the average degree of polymerization and represents 1 to 20.)

[0020] [9] The fluorinated ether compound according to any one of [1] to [8], which has a number average molecular weight in the range of 400 to 3,000.

[0021]

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

[11] A magnetic recording medium comprising at least a magnetic layer, a protective layer, and a lubricating layer provided in that order on a substrate, the lubricating layer comprising the fluorine-containing ether compound according to any one of [1] to [8].

[12] The magnetic recording medium according to

[11] , wherein the lubricating layer has an average thickness of 0.5 nm to 1.5 nm. Effect of the Invention

[0022] The fluorine-containing ether compound of the present invention is suitable as a material for a lubricant for a magnetic recording medium. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore has good adhesion to the protective layer, can suppress pick-up, and can form a lubricating layer with excellent chemical resistance. The magnetic recording medium of the present invention has excellent reliability and durability because it has good adhesion to the protective layer, can suppress pick-up, and is provided with a lubricating layer that has excellent resistance to chemicals. [Brief description of the drawings]

[0023] [Figure 1]1 is a schematic cross-sectional view showing one embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The fluorine-containing ether compound, the lubricant for magnetic recording media (hereinafter sometimes abbreviated as "lubricant"), and the magnetic recording media of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments.

[0025] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2 -CH2-R 3 (1) (In formula (1), R 2 R is a perfluoropolyether chain represented by the following formula (2). 1 is connected via CH2 to R 2 R is a terminal group bonded to 3 is connected via CH2 to R 2 is a terminal group having one or more hydroxyl groups and bonded to R 1 may be the same as or different from.) -(CF2) p-1 -O-((CF2) p O) q -(CF2) p-1 - (2) (In formula (2), p represents an integer of 2 to 3, and q represents the average degree of polymerization, which is 1 to 20.)

[0026] [ka] (In formula (3), n is an integer of 1 to 8.)

[0027] In formula (2), p is an integer of 2 to 3, and q is an average degree of polymerization of 1 to 20. When p is within the above range, it is suitable for forming a thin film having a thickness of 10 Å or less. When p is less than 2, the perfluoropolyether chain is insufficiently rigid, and the fluorine-containing ether compound is likely to aggregate on the protective layer. When p is more than 3, the perfluoropolyether chain is too rigid, and it is difficult to obtain adhesion to the protective layer.

[0028] In this embodiment, the number average molecular weight of the fluorinated ether compound falls within a preferred range, since p in formula (2) is an integer of 2 to 3 and q, which is the average degree of polymerization, is 1 to 20. Furthermore, since p in formula (2) is an integer of 2 to 3 and q, which is the average degree of polymerization, is 1 to 20, the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the PFPE chain becomes appropriate, resulting in a fluorinated ether compound having appropriate rigidity. In addition, since p in formula (2) is an integer of 2 to 3, and q, which is the average degree of polymerization, is 1 to 20, the direction of the polar group in the fluorine-containing ether compound applied on the protective layer is easily maintained by the rigidity of the PFPE chain, and the fluorine-containing ether compound is less likely to aggregate on the protective layer. As a result, with the fluorine-containing ether compound of this embodiment, a thin lubricating layer can be formed on the protective layer with a sufficient coverage, and the PFPE chain can form a loop structure on the protective layer. When p in formula (2) is 3, the average degree of polymerization q is preferably 1 to 14, more preferably 4 to 10. When p in formula (2) is 2, the average degree of polymerization q is preferably 5 to 16, more preferably 6 to 12.

[0029] The terminal group R represented by formula (3) in formula (1) 1 is an organic terminal group having 8 to 15 carbon atoms which contains three hydroxyl groups, each of which is bonded to a different carbon atom, and in which the carbon atoms to which the hydroxyl groups are bonded are bonded via a linking group which contains a carbon atom to which no hydroxyl group is bonded. The value of n in formula (3) is an integer of 1 to 8. The value of n is preferably 1 to 4, more preferably 2 to 4, and even more preferably 2 or 3. When the value of n is within this range, adhesion to the protective layer is good, and the fluorinated ether compound can be prevented from adhering to the magnetic head as foreign matter (smear).

[0030] R in formula (1) 3 is a terminal group represented by formula (3), R 1 and R 3 The value of n in R may be the same or different. The fluorine-containing ether compound represented by formula (1) is easily formed with a loop structure due to the PFPE chain on the protective layer, and can be produced with a small number of production steps. 3 is a terminal group represented by formula (3), R 1 and R 3 It is more preferable that the values ​​of n in and are the same.

[0031] The terminal group R in formula (1) 3 R 1 If the end group is different from R 3 The number of hydroxyl groups contained in the terminal group represented by the following formula is preferably 1 to 2, and more preferably 2. R 3 The number of carbon atoms contained in the terminal group represented by R is preferably 10 or less, and more preferably 8 or less. 3 The terminal group represented by the formula (I) may not contain a fluorine atom. In particular, R 3 When the terminal group represented by the formula: has 10 or less carbon atoms and 1 to 2 hydroxyl groups, R 1 This provides a good balance with the terminal group represented by the formula (I), making it easier to form a loop structure due to the PFPE chain on the protective layer, and further improving the adhesion to the protective layer. R 3 It is preferable that the terminal group represented by R does not have a double bond or a triple bond. 3 In the chain structure of the terminal group represented by R 2In this case, hydroxyl groups are arranged at the extreme ends of both of the fluorinated ether compounds represented by formula (1), which allows stronger adhesion to the protective layer. R 3 It is preferable that the polar group contained in the terminal group represented by R is only a hydroxyl group. 3 If all the polar groups in the terminal group represented by R 1 This provides a good balance with the terminal group represented by the formula:

[0032] R 3 is preferably a hydroxyl group or a terminal group represented by any one of the following formulas (4-1) and (4-2). -O-CH2-CH(OH)-CH2-OH (4-1) -O-CH2-CH(OH)-CH2-O-(CH2) k -OH (4-2) (In formula (4-2), k represents an integer of 1 to 5.)

[0033] Among these, R 3 is more preferably formula (4-1) or formula (4-2), and most preferably formula (4-2). The terminal groups represented by formula (4-1) and formula (4-2) each contain two hydroxyl groups. R 3 is a terminal group represented by formula (4-1) or formula (4-2), R 3 The two hydroxyl groups in R 1 The hydroxyl groups contained in R allow the PFPE chain to adhere to the protective layer at both ends. 3 is the formula (4-2), the two hydroxyl groups are bonded to different carbon atoms, and the carbon atoms to which the hydroxyl groups are bonded are bonded via a linking group that includes a carbon atom to which no hydroxyl groups are bonded. In addition, an ether bond is included between the carbon atoms to which the hydroxyl groups are bonded. For this reason, R 3 When is formula (4-2), the adhesion to and coverage of the protective layer will be further improved. The value of k in formula (4-2) is an integer of 1 to 5. When the value of k is within this range, adhesion to the protective layer is good. The value of k is preferably an integer of 2 to 4, and more preferably 2 or 3. When the value of k is 2 or 3, the distance between the carbon atoms to which the hydroxyl groups are bonded becomes appropriate, and adhesion and coverage to the protective layer are further improved.

[0034] R in the fluorine-containing ether compound represented by formula (1) 1 has three hydroxyl groups. R in the fluorine-containing ether compound represented by formula (1) 3 has one or more hydroxyl groups, and preferably has one or two hydroxyl groups. In the fluorine-containing ether compound represented by formula (1), R 3 R 1 In the case where R is a terminal group represented by the same formula (3), the total number of hydroxyl groups in formula (1) is 6. 3 R 1 When the terminal group is different from the above, the total number of hydroxyl groups in formula (1) is 4 or more, preferably 4 to 5, and more preferably 5. In the fluorine-containing ether compound represented by formula (1), when the total number of hydroxyl groups is within the above range, the compound has good adhesion and can prevent the compound from adhering to the magnetic head as foreign matter (smear). In particular, when the total number of hydroxyl groups is 5 or 6, the compound has good adhesion and improves the pick-up suppression effect. R in formula (1) 1 and R 3 can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0035] Here, the fluorine-containing ether compound of the present embodiment is R 2 and a PFPE chain represented by R 2 The terminal group R linked to 1 This section explains why, when a lubricant containing this is used to form a lubricating layer on a protective layer of a magnetic recording medium, the result is a lubricating layer that has good adhesion to the protective layer, can suppress pick-up, and has excellent resistance to chemical substances. The fluorine-containing ether compound of the present embodiment is represented by the formula (1), 2 R 2 In the lubricating layer containing the fluorine-containing ether compound of this embodiment, the PFPE chain represented by formula (2) covers the surface of the protective layer and imparts lubricity to the lubricating layer to reduce the friction between the magnetic head and the protective layer. Furthermore, in the lubricating layer containing the fluorine-containing ether compound of this embodiment, the PFPE chain represented by formula (2) having a repeating unit having rigidity composed of a linear fluorinated alkyl ether group is adhered (adsorbed) to the protective layer by the hydroxyl groups of the terminal groups arranged at both ends. Therefore, the PFPE chain can form a loop structure on the protective layer. As a result, the lubricating layer has good adhesion to the protective layer.

[0036] In addition, R in formula (1) 1 is connected to R via CH2. 2 is an end group bonded to the R 1 In R, the carbon atoms to which hydroxyl groups are bonded are bonded via a linking group containing a carbon atom to which no hydroxyl groups are bonded. Therefore, when the protective layer to which the lubricant is applied is formed of carbon or carbon containing nitrogen, the following two effects are achieved. First, R 1 The hydroxyl groups of R are easily spread on the protective layer without agglomeration, and the coating property is easily improved. 1 The three hydroxyl groups of the compound tend to face in the same direction relative to the surface of the protective layer, resulting in a three-dimensional arrangement that allows the hydroxyl groups to easily adhere to the surface of the protective layer. Therefore, it is presumed that the lubricating layer containing the fluorine-containing ether compound of this embodiment has even better adhesion to the protective layer, particularly when the protective layer is formed of carbon or nitrogen-containing carbon, and can suppress pick-up, resulting in a lubricating layer with excellent chemical resistance.

[0037] Specifically, the fluorine-containing ether compound of the present embodiment is preferably any one of the compounds represented by the following formulas (A) to (V). In the following formulae (A) to (J) and (U), xa to xj and xu correspond to q in formula (2). In the following formulae (K) to (T) and (V), yk to yt and yv correspond to q in formula (2). The repeat numbers represented by xa to xj, xu, yk to yt and yv in formulae (A) to (V) are values ​​indicating the average degree of polymerization, and therefore are not necessarily integers.

[0038] The compounds represented by the following formulas (A) to (C), (H) to (M), (R) to (T), (U), and (V) are all compounds represented by formula (1), 3 R 1 In addition, the compounds represented by the following formulas (D) to (G) and (N) to (Q) are all compounds in which R 3 R 1 It is a compound having the same terminal group as The compounds represented by the following formulas (A) to (C), (H) to (M), and (R) to (T) are all R 1 is represented by formula (3), and n in formula (3) is 1. The compounds represented by the following formulas (U) and (V) are both R 1 is represented by formula (3), and n in formula (3) is 2. In addition, the compounds represented by formulas (A) and (K) are both R 3 is a hydroxyl group. The compounds represented by formulas (B) and (L) are both R 3 The compounds represented by the formulas (C), (H) to (J), (M), (R) to (T), (U), and (V) are all R 3 is equation (4-2). The compounds represented by the following formulas (A) to (C), (H) to (J), and (U) are all R 2 In the formulae (K) to (M), (R) to (T), and (V), p is 3. 2 In this case, p is 2. The compounds represented by the following formulas (D) and (N) are both R 1 and R 3 Both of these compounds are represented by formula (3), and n in formula (3) is 1. The compounds represented by the following formulas (E) and (O) are both represented by R 1 and R 3Both of the compounds represented by the following formulas (F) and (P) are represented by the formula (3), and n in the formula (3) is 2. 1 and R 3 Both of these compounds are represented by formula (3), and n in formula (3) is 3. The compounds represented by the following formulas (G) and (Q) are both represented by R 1 and R 3 and are both represented by formula (3), where n is 4. The compounds represented by the following formulas (D) to (G) are all R 2 In the formula (N) to (Q), p is 3. 2 In this case, p is 2.

[0039] [ka] (In formula (A), xa is the average degree of polymerization and represents 1 to 14.) (In formula (B), xb is the average degree of polymerization and represents 1 to 14.) (In formula (C), xc is the average degree of polymerization and represents 1 to 14.)

[0040] [ka] (In formula (D), xd is the average degree of polymerization and represents 1 to 14.) (In formula (E), xe is the average degree of polymerization and represents 1 to 14.) (In formula (F), xf is the average degree of polymerization and represents 1 to 14.) (In formula (G), xg is the average degree of polymerization and represents 1 to 14.)

[0041] [ka] (In formula (H), xh is the average degree of polymerization and represents 1 to 14.) (In formula (I), xi is the average degree of polymerization and represents 1 to 14.) (In formula (J), xj is the average degree of polymerization and represents 1 to 14.) (In formula (U), xu is the average degree of polymerization and represents 1 to 14.)

[0042] [ka] (In formula (K), yk is the average degree of polymerization and represents 1 to 20.) (In formula (L), yl is the average degree of polymerization and represents 1 to 20.) (In formula (M), ym is the average degree of polymerization and represents 1 to 20.)

[0043] [ka] (In formula (N), yn is the average degree of polymerization and represents 1 to 20.) (In formula (O), yo is the average degree of polymerization and represents 1 to 20.) (In formula (P), yp is the average degree of polymerization and represents 1 to 20.) (In formula (Q), yq is the average degree of polymerization and represents 1 to 20.)

[0044] [ka] (In formula (R), yr is the average degree of polymerization and represents 1 to 20.) (In formula (S), ys is the average degree of polymerization and represents 1 to 20.) (In formula (T), yt is the average degree of polymerization and represents 1 to 20.) (In formula (V), yv is the average degree of polymerization and represents 1 to 20.)

[0045] When the fluorine-containing ether compound represented by formula (1) is any of the compounds represented by formulas (A) to (V), it is preferable because a lubricating layer having better adhesion to the protective layer, which can suppress pick-up, and excellent chemical resistance can be obtained. Among the fluorine-containing ether compounds represented by formulas (A) to (V), the fluorine-containing ether compounds represented by formulas (C), (D), (E), (M), (N) and (O) are particularly preferred because they are capable of forming a lubricating layer having good adhesion to the protective layer.

[0046] The number average molecular weight of the fluorine-containing ether compound of this embodiment is preferably within the range of 400 to 3000. When the number average molecular weight is 400 or more, the lubricant containing the fluorine-containing ether compound of this embodiment is less likely to evaporate, and the lubricant can be prevented from evaporating and transferring to the magnetic head. The number average molecular weight of the fluorine-containing ether compound is more preferably 800 or more. In addition, when the number average molecular weight is 3000 or less, the viscosity of the fluorine-containing ether compound becomes appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing this. The number average molecular weight of the fluorine-containing ether compound is more preferably 2500 or less.

[0047] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 This is a value measured by F-NMR. Specifically, 19 The number of repeating units of the PFPE chain was calculated from the integral value measured by F-NMR to obtain the number average molecular weight. Note that the number of repeating units may be expressed as a decimal number to indicate the average value. In the measurement of NMR (nuclear magnetic resonance), the sample was diluted in a hexafluorobenzene / d-acetone (4 / 1 v / v) solvent and used for the measurement. 19 The reference for F-NMR chemical shifts was the hexafluorobenzene peak at −164.7 ppm, and the reference for 1H-NMR chemical shifts was the acetone peak at 2.2 ppm.

[0048] "Manufacturing method" The method for producing the fluorine-containing ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorine-containing ether compound of the present embodiment can be produced, for example, by the production method shown below. First, R in Equation (1) 2A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to the formula (1) is prepared. Next, the hydroxyl groups of the hydroxymethyl groups at both ends (or one end) of the fluorine-based compound are converted to R 1 The compound is substituted with an organic end group consisting of:

[0049] As the fluorine-containing ether compound, R 3 In the case of producing a fluorine-containing ether compound represented by formula (1) in which R is a hydroxyl group, 1 The compound having an organic terminal group consisting of R is used in an amount of about 0.5 to 1 equivalent based on the perfluoropolyether chain. 3 R 1 In the case of producing a fluorine-containing ether compound represented by formula (1) having the same terminal group as R 1 The compound having an organic terminal group consisting of the following is used in an amount of about 2 equivalents based on the perfluoropolyether chain. In the fluorine-containing ether compound represented by formula (1), R 3 R 1 In the case where the terminal group is the same as that of the above, production can be easily performed, which is preferable.

[0050] As the fluorine-containing ether compound, R 3 R 1 In the case of producing a fluorine-containing ether compound represented by formula (1) having a terminal group different from 1 The above substitution reaction is carried out using about 0.5 to 1 equivalent of a compound having an organic terminal group consisting of the following perfluoropolyether chain, and then the fluorine-based compound R 1 The hydroxyl group of the hydroxymethyl group located at the end that is not substituted with an organic terminal group consisting of R 3 The compound having a terminal group consisting of R 3 R 1 The fluorine-containing ether compound represented by formula (1) having a terminal group different from R 1 and R 3 is a terminal group represented by formula (3), R 1and R 3 This also includes cases where the number of n in and is different. In formula (1), R 3 R 1 When producing a fluorine-containing ether compound having a terminal group different from that of R, the hydroxymethyl group of the perfluoropolyether chain and 1 and substitution reactions with organic end groups consisting of R 3 The substitution reaction with the terminal group consisting of may be carried out in either order. These substitution reactions can be carried out by conventional methods. 1 and R 3 The amount of the ion exchange can be appropriately determined depending on the type of the ion exchange.

[0051] The fluorine-containing ether compound of the present embodiment is a compound represented by the above formula (1). Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing this compound, R 2 The surface of the protective layer is covered with the PFPE chain represented by the formula (I) and the frictional force between the magnetic head and the protective layer is reduced. In addition, in the lubricating layer formed using the lubricant containing the fluorine-containing ether compound of this embodiment, the PFPE chain represented by the formula (I) is represented by the formula (I). 2 R placed at one end of 1 and R placed at the other end 3 The terminal group having four or more hydroxyl groups represented by the formula (I) allows the fluorine-containing ether compound to adhere strongly to the protective layer, thereby providing excellent pick-up suppression and excellent resistance to chemical substances.

[0052] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by formula (1). The lubricant of the present embodiment can be used by mixing, as necessary, known materials used as lubricant materials, so long as the properties resulting from the inclusion of the fluorinated ether compound represented by formula (1) are not impaired.

[0053] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of the present embodiment preferably has a number average molecular weight of about 400 to 3,000.

[0054] When the lubricant of the present embodiment contains a material other than the fluorinated ether compound represented by formula (1), the content of the fluorinated ether compound represented by formula (1) in the lubricant of the present embodiment is preferably 50 mass% or more, and more preferably 70 mass% or more.

[0055] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1), so even if the lubricant is thin, it can cover the surface of the protective layer with a high coverage rate, and can form a lubricant layer with excellent adhesion to the protective layer.In addition, since the lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1), the fluorine-containing ether compound in the lubricant layer that does not adhere (adsorb) to the protective layer is unlikely to aggregate.Therefore, it is possible to prevent the fluorine-containing ether compound from aggregating and adhering to the magnetic head as a foreign matter (smear).

[0056] [Magnetic recording media] FIG. 1 is a schematic cross-sectional view showing one embodiment of a magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0057] "substrate" For example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy can be used as the substrate 11. Alternatively, a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin can be used as the substrate 11, or a non-magnetic substrate in which a film of NiP or a NiP alloy is formed on a base made of such a non-metallic material can be used.

[0058] "Adhesion layer" When the adhesive layer 12 is disposed in contact with the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12, the adhesive layer 12 prevents the progress of corrosion of the substrate 11. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0059] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC)-coupled by sandwiching the intermediate layer made of a Ru film between two soft magnetic films. When the soft magnetic layer 13 has an AFC-coupled structure, it is possible to increase resistance to an external magnetic field and resistance to the WATER (Wide Area Track Erasure) phenomenon, which is a problem specific to perpendicular magnetic recording.

[0060] The first and second soft magnetic films are preferably films made of a CoFe alloy. When the first and second soft magnetic films are films made of a CoFe alloy, a high saturation magnetic flux density Bs (1.4 (T) or more) can be realized. Moreover, it is preferable to add any one of Zr, Ta, and Nb to the CoFe alloy used for the first and second soft magnetic films, which promotes the amorphization of the first and second soft magnetic films, improves the orientation of the first underlayer (seed layer), and reduces the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0061] "First base layer" The first underlayer 14 is a layer for controlling the orientation and crystal size of the second underlayer 15 and the magnetic layer 16 provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, or a CrMo, CoW, CrW, CrV, or CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0062] "Second base layer" The second underlayer 15 is a layer that controls good orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a layer consisting of one layer, or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0063] "Magnetic layer" The magnetic layer 16 is a magnetic film with an easy axis of magnetization oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt, and may be a layer containing an oxide, Cr, B, Cu, Ta, Zr, etc. to further improve the SNR characteristics. The oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, TiO2, and the like.

[0064] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, a first magnetic layer, a second magnetic layer, and a third magnetic layer, stacked in order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. As the oxide contained in the first magnetic layer, for example, oxides such as Cr, Si, Ta, Al, Ti, Mg, and Co are preferably used. Among them, TiO2, Cr2O3, SiO2, and the like can be particularly preferably used. In addition, the first magnetic layer is preferably made of a composite oxide to which two or more kinds of oxides are added. Among them, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, and the like can be particularly preferably used.

[0065] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re, in addition to Co, Cr, Pt, and oxides. The second magnetic layer may be made of the same material as the first 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 that contains Co, Cr, and Pt and does not contain oxides. In addition to Co, Cr, and Pt, the third magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0066] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a nonmagnetic layer between adjacent magnetic layers. When the magnetic layer 16 is formed of three layers, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a nonmagnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0067] The non-magnetic layer provided between adjacent magnetic layers in the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0068] For the non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16, it is preferable to use an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, TiO2, etc. can be used as the oxide. For example, AlN, Si3N4, TaN, CrN, etc. can be used as the metal nitride. For example, TaC, BC, SiC, etc. can be used as the metal carbide. The nonmagnetic layer can be formed by, for example, a sputtering method.

[0069] In order to achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for in-plane magnetic recording. The magnetic layer 16 may be formed by any known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0070] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be made of a single layer or multiple layers. Examples of materials for the protective layer 17 include carbon, carbon containing nitrogen, and silicon carbide. A carbon-based protective layer, particularly an amorphous carbon protective layer, can be preferably used as the protective layer 17. When the protective layer 17 is a carbon-based protective layer, the interaction with the polar group (particularly a hydroxyl group) contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0071] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by making the carbon-based protective layer from hydrogenated carbon and / or nitrogenated carbon and adjusting the hydrogen content and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS). The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer in which, for example, 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 adhesion between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved.

[0072] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0073] The protective layer 17 can be formed by 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 deposition) method, or the like. When a carbon-based protective layer is formed as the protective layer 17, it can be deposited 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 deposit an amorphous carbon protective layer by a plasma CVD method. The amorphous carbon protective layer deposited by the plasma CVD method has a uniform surface with small roughness.

[0074] "Lubricating layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. In addition, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording and reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 1, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 contains the fluorine-containing ether compound of this embodiment.

[0075] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 is bonded with a high bonding strength to the protective layer 17. 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 rate, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0076] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 1.5 nm (15 Å), and more preferably 0.6 nm (6 Å) to 1.1 nm (11 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without being island-shaped or mesh-shaped. Therefore, the surface of the protective layer 17 can be covered with the lubricating layer 18 with a high coverage. In addition, by setting the average thickness of the lubricating layer 18 to 1.5 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0077] If the surface of the protective layer 17 is not covered with the lubricating layer 18 at a sufficiently high coverage rate, environmental substances adsorbed to the surface of the magnetic recording medium 10 will pass through the gaps in the lubricating layer 18 and penetrate underneath the lubricating layer 18. The environmental substances that penetrate underneath the lubricating layer 18 will be adsorbed and bonded to the protective layer 17 to generate contaminants. Then, during magnetic recording and reproduction, these contaminants (aggregated components) will adhere (transfer) to the magnetic head as smear, damaging the magnetic head or degrading the magnetic recording and reproduction characteristics of the magnetic recording and reproduction device. Examples of environmental substances that generate pollutants include siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, hydrocarbons with relatively high molecular weights such as octacosane, and plasticizers such as dioctyl phthalate. Examples of metal ions contained in ionic impurities include sodium ions and potassium ions. Examples of inorganic ions contained in ionic impurities include chloride ions, bromide ions, nitrate ions, sulfate ions, and ammonium ions. Examples of organic ions contained in ionic impurities include oxalate ions and formate ions.

[0078] "Method of forming lubricating layer" One method for forming the lubricating layer 18 is to prepare a magnetic recording medium in the middle of manufacture in which all layers up to the protective layer 17 are formed on the substrate 11, and then apply a solution for forming a lubricating layer onto the protective layer 17 and dry it.

[0079] The lubricant layer forming solution can be obtained by dispersing and dissolving the lubricant for magnetic recording media of the above-mentioned embodiment in a solvent as necessary, and adjusting the viscosity and concentration to be suitable for the coating method. Examples of the solvent used in the lubricant layer forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (product name, manufactured by Mitsui DuPont Fluorochemicals).

[0080] The method for applying the solution for forming the lubricating layer is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in the lubricant layer forming solution placed in the immersion tank of a dip coater. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricant layer forming solution can be applied uniformly onto the surface of the protective layer 17, and the lubricant layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0081] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is improved. The heat treatment temperature is preferably 90 to 180° C. If the heat treatment temperature is 90° C. or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180° C. or lower, thermal decomposition of the lubricating layer 18 can be prevented. The heat treatment time is preferably 10 to 120 minutes.

[0082] The magnetic recording medium 10 of this embodiment is a medium in which 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 this embodiment, a lubricating layer 18 containing the fluorine-containing ether compound of this embodiment is formed on the protective layer 17. Even if the lubricating layer 18 is thin, it covers the surface of the protective layer 17 with a high coverage. Therefore, in the magnetic recording medium 10 of this embodiment, environmental substances that generate contaminants such as ionic impurities are prevented from penetrating through the gaps in the lubricating layer 18. Therefore, the magnetic recording medium 10 of this embodiment has a small amount of contaminants present on its surface. In addition, the lubricating layer 18 in the magnetic recording medium 10 of this embodiment is less likely to generate foreign matter (smear), and can suppress pick-up. Therefore, the magnetic recording medium 10 of this embodiment has excellent reliability and durability. EXAMPLES

[0083] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0084] Example 1 A compound represented by the following formula (A) was produced by the method shown below. Under a nitrogen gas atmosphere, HOCH2CF2CF2O (CF2CF2CF2O) was added to a 100 mL eggplant flask. x22.2 g (20 mmol) of a compound represented by CF2CF2CH2OH (where x is 5.0) (number average molecular weight 1108, molecular weight distribution 1.1), 3.84 g (12 mmol) of a compound represented by the following formula (7), and 18 mL of t-butanol were charged and stirred at room temperature until homogenized. 0.674 g (6.0 mmol) of potassium tert-butoxide was further added to this homogenous liquid, and the mixture was reacted by stirring at 70°C for 10 hours, and then allowed to cool to room temperature. 40 mL of a 10% hydrogen chloride-methanol solution (trade name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the reaction liquid, and the mixture was stirred at room temperature for 2 hours to deprotect the methoxymethyl (MOM) group and tetrahydropyranyl (THP) group, which are the protecting groups derived from the compound represented by formula (7). 5% sodium bicarbonate water was added to the obtained reaction solution until the pH of the reaction solution became alkaline, and 20 mL of water was further added. This reaction solution was extracted twice with 100 mL of ethyl acetate. The organic phase obtained by extraction was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 10.42 g of compound (A) represented by the following formula (A).

[0085] The compound represented by formula (7) was synthesized by the method shown below. The primary hydroxyl group of commercially available 3-allyloxy-1,2-propanediol was protected with a tert-butyldimethylsilyl (TBS) group, and then the secondary hydroxyl group was protected with a methoxymethyl group. The TBS group was then removed from the compound, and the resulting primary hydroxyl group was reacted with 2-(2-bromoethoxy)tetrahydro-2H-pyran and then oxidized. The compound represented by formula (7) was obtained by the above steps.

[0086] [ka] (In formula (A), xa is 5.0.)

[0087] The obtained compound (A) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (A); 1H-NMR(CD3COCD3); δ[ppm]3.4~4.2(22H)

[0088] Example 2 After carrying out the same reaction as in Example 1, 50 mL of water was added to the obtained reaction solution without adding 10% hydrogen chloride-methanol solution (product name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was extracted twice with 100 mL of ethyl acetate. The organic phase obtained by extraction was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 11.45 g of the compound represented by the following formula (21).

[0089] [ka] (In formula (21), x is 5.0.)

[0090] 11.43 g (8.0 mmol) of the compound represented by formula (21), 1.27 g (8.0 mmol) of the compound represented by formula (8) below, and 22 mL of t-butanol were charged and stirred at room temperature until the mixture became homogeneous. 0.135 g (1.2 mmol) of potassium tert-butoxide was further added to this homogeneous liquid, and the mixture was reacted by stirring at 70°C for 120 hours, and then allowed to cool to room temperature. 20 mL of 10% hydrogen chloride-methanol solution (trade name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the reaction liquid, and the mixture was stirred at room temperature for 2 hours to deprotect the methoxymethyl (MOM) group and tetrahydropyranyl (THP) group, which are the protecting groups derived from the compound represented by formula (7). 5% sodium bicarbonate water was added to the obtained reaction liquid until the pH of the reaction liquid became alkaline, and 16 mL of water was further added. This reaction liquid was extracted twice with 100 mL of ethyl acetate. The organic phase obtained by extraction was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated and the residue was purified by silica gel column chromatography to obtain 10.42 g of compound (B) represented by the following formula (B). The compound represented by formula (8) was obtained by oxidation of commercially available 2-allyloxytetrahydropyran.

[0091] [ka] (In formula (B), xb is 5.0.)

[0092] The obtained compound (B) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (B); 1 H-NMR(CD3COCD3); δ[ppm]3.4~4.2(28H)

[0093] Example 3 The same procedure as in Example 2 was carried out except that 1.62 g of a compound represented by the following formula (9) was used instead of the compound represented by the formula (8), to obtain 7.94 g of a compound (C) represented by the following formula (C). The compound represented by formula (9) was synthesized by protecting the hydroxy group of commercially available ethylene glycol monoallyl ether with dihydropyran and then oxidizing the double bond.

[0094] [ka] (In formula (C), xc is 5.0.)

[0095] The obtained compound (C) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (C); 1 H-NMR(CD3COCD3); δ[ppm]3.4~4.2(32H)

[0096] Example 4 Under a nitrogen gas atmosphere, HOCH2CF2CF2O (CF2CF2CF2O) was added to a 100 mL eggplant flask. x11.1g (10mmol) of the compound represented by CF2CF2CH2OH (x in the formula is 5.0) (number average molecular weight 1108, molecular weight distribution 1.1), 6.41g (20mmol) of the compound represented by formula (7), and 30mL of t-butanol were charged and stirred at room temperature until homogenized. 0.168g (1.5mmol) of potassium tert-butoxide was further added to this homogenous liquid, and the mixture was reacted by stirring at 70℃ for 20 hours, and then cooled to room temperature. 40mL of 10% hydrogen chloride-methanol solution (trade name: X0041, hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the reaction liquid, and the mixture was stirred at room temperature for 2 hours to deprotect the methoxymethyl (MOM) group and tetrahydropyranyl (THP) group, which are the protecting groups derived from the compound represented by formula (7). 5% sodium bicarbonate water was added to the obtained reaction solution until the pH of the reaction solution became alkaline, and 20 mL of water was further added. This was extracted twice with 100 mL of ethyl acetate. The organic phase obtained by extraction was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 10.45 g of compound (D) represented by the following formula (D).

[0097] [ka] (In formula (D), xd is 5.0.)

[0098] The obtained compound (D) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (D); 1 H-NMR(CD3COCD3): δ[ppm]3.4~4.2(38H)

[0099] Example 5 The same procedure as in Example 4 was carried out, except that 6.69 g of a compound represented by the following formula (10) was used instead of the compound represented by formula (7), to obtain 10.64 g of a compound (E) represented by the following formula (E). The compound represented by the following formula (10) was synthesized using 2-(3-bromopropoxy)tetrahydro-2H-pyran, in the same manner as the compound represented by the formula (7).

[0100] [ka] (In formula (E), xe is 5.0.)

[0101] The obtained compound (E) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (E); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(4H), 3.4~4.2(38H)

[0102] Example 6 The same procedure as in Example 4 was carried out, except that 6.97 g of a compound represented by the following formula (11) was used instead of the compound represented by formula (7), to obtain 10.07 g of a compound (F) represented by the following formula (F). The compound represented by the following formula (11) was synthesized using 2-(4-chlorobutoxy)tetrahydropyran, in the same manner as the compound represented by the formula (7).

[0103] [ka] (In formula (F), xf is 5.0.)

[0104] The obtained compound (F) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (F); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(8H), 3.4~4.2(38H)

[0105] Example 7 The same procedure as in Example 4 was carried out, except that 7.20 g of a compound represented by the following formula (12) was used instead of the compound represented by formula (7), to obtain 9.46 g of a compound (G) represented by the following formula (G). The compound represented by the following formula (12) was synthesized using 2-(5-bromopentyloxy)tetrahydro-2H-pyran derived from 5-bromo-1-pentanol, similarly to the compound represented by the formula (7).

[0106] [ka] (In formula (G), xg is 5.0.)

[0107] The obtained compound (G) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (G); 1 H-NMR(CD3COCD3): δ[ppm]1.4~1.8(12H), 3.4~4.2(38H)

[0108] Example 8 The same procedure as in Example 3 was carried out, except that 1.73 g of a compound represented by the following formula (13) was used instead of the compound represented by formula (9), to obtain 7.68 g of a compound (H) represented by the following formula (H). The compound represented by formula (13) was synthesized from a compound in which one of the hydroxyl groups of 1,3-propanediol was protected with THP and epichlorohydrin.

[0109] [ka] (In formula (H), xh is 5.0.)

[0110] The obtained compound (H) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (H); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(2H), 3.4~4.2(32H)

[0111] Example 9 The same procedure as in Example 3 was carried out, except that 1.84 g of a compound represented by the following formula (14) was used instead of the compound represented by formula (9), to obtain 8.58 g of compound (I) represented by the following formula (I). The compound represented by the following formula (14) was synthesized from a compound in which one of the hydroxyl groups of 1,4-butanediol was protected with THP and epichlorohydrin.

[0112] [ka] (In formula (I), xi is 5.0.)

[0113] The obtained compound (I) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (I); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(4H), 3.4~4.2(32H)

[0114] Example 10 The same procedure as in Example 3 was carried out, except that 1.96 g of a compound represented by the following formula (15) was used instead of the compound represented by formula (9), to obtain 8.88 g of a compound (J) represented by the following formula (J). The compound represented by the following formula (15) was synthesized from a compound in which one of the hydroxyl groups of 1,5-pentanediol was protected with a tetrahydropyranyl (THP) group, and epichlorohydrin.

[0115] [ka] (In formula (J), xj is 5.0.)

[0116] The obtained compound (J) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (J); 1 H-NMR(CD3COCD3): δ[ppm]1.4~1.8(6H), 3.4~4.2(32H)

[0117] Example 11 HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 1 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 9.92 g of a compound (K) represented by the formula (K).

[0118] [ka] (In formula (K), yk is 8.0.)

[0119] The obtained compound (K) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (K); 1 H-NMR(CD3COCD3): δ[ppm]3.4~4.2(22H)

[0120] Example 12 HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 2 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 7.94 g of compound (L) represented by the following formula (L).

[0121] [ka] (In formula (L), yl is 8.0.)

[0122] The obtained compound (L)1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (L); 1 H-NMR(CD3COCD3): δ[ppm]3.4~4.2(28H)

[0123] (Example 13) HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 3 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 8.17 g of a compound (M) represented by the following formula (M).

[0124] [ka] (In formula (M), ym is 8.0.)

[0125] The obtained compound (M) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (M); 1 H-NMR(CD3COCD3): δ[ppm]3.4~4.2(32H)

[0126] Example 14 HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 4 was carried out except that 11.06 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 8.89 g of compound (N) represented by the following formula (N).

[0127] [ka] (In formula (N), yn is 8.0.)

[0128] The obtained compound (N) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (N); 1 H-NMR(CD3COCD3): δ[ppm]3.4~4.2(38H)

[0129] Example 15 HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 5 was carried out except that 11.06 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 8.99 g of compound (O) represented by the following formula (O).

[0130] [ka] (In formula (O), yo is 8.0.)

[0131] The obtained compound (O) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (O); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(4H), 3.4~4.2(38H)

[0132] (Example 16) HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 6 was carried out except that 11.06 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 9.78 g of a compound (P) represented by the following formula (P).

[0133] [ka] (In formula (P), yp is 8.0.)

[0134] The obtained compound (P) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (P); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(8H), 3.4~4.2(38H)

[0135] (Example 17) HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 7 was carried out except that 11.06 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 9.87 g of compound (Q) represented by the following formula (Q).

[0136] [ka] (In formula (Q), yq is 8.0.)

[0137] The obtained compound (Q) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (Q); 1 H-NMR(CD3COCD3): δ[ppm]1.4~1.8(12H), 3.4~4.2(38H)

[0138] (Example 18) HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 8 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 8.24 g of a compound (R) represented by the following formula (R).

[0139] [ka] (In formula (R), yr is 8.0.)

[0140] The obtained compound (R) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (R); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(2H), 3.4~4.2(32H)

[0141] (Example 19) HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 9 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 8.24 g of compound (S) represented by the following formula (S).

[0142] [ka] (In formula (S), ys is 8.0.)

[0143] The obtained compound (S) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (S); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(4H), 3.4~4.2(32H)

[0144] (Example 20) HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). yThe same procedure as in Example 10 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 8.24 g of a compound (T) represented by the following formula (T).

[0145] [ka] (In formula (T), yt is 8.0.)

[0146] The obtained compound (T) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (T); 1 H-NMR(CD3COCD3): δ[ppm]1.4~1.8(6H), 3.4~4.2(32H)

[0147] Example 21 In the same reaction as in Example 1 shown in Example 2, 4.18 g of the compound represented by formula (10) was used instead of the compound represented by formula (7), and 11.40 g of the compound represented by the following formula (16) was obtained instead of the compound represented by formula (21) as an intermediate by the method shown in Example 2. Then, the same operation as in Example 2 was performed except that the compound represented by formula (13) was used instead of the compound represented by formula (8), and 7.59 g of the compound (U) represented by the following formula (U) was obtained.

[0148] [ka] (In formula (16), x is 5.0.) (In formula (U), xu is 5.0.)

[0149] The obtained compound (U) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (U); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(4H), 3.4~4.2(32H)

[0150] Example 22 In a reaction similar to that in Example 1 shown in Example 21, HOCH2CF2CF2O(CF2CF2CF2O) x HOCH2CF2O(CF2CF2O) instead of CF2CF2CH2OH (where x is 5.0). y The same procedure as in Example 21 was carried out except that 22.12 g of CF2CH2OH (wherein y is 8.0) was used, to obtain 10.02 g of compound (V) represented by formula (V).

[0151] [ka] (In formula (V), yv is 8.0.)

[0152] The obtained compound (V) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (V); 1 H-NMR(CD3COCD3): δ[ppm]1.6~1.8(4H), 3.4~4.2(32H)

[0153] Comparative Example 1 Compound (X) represented by the following formula (X) was synthesized by the method described in Patent Document 1.

[0154] [ka] (In formula (X), a is 5.0 and b is 5.0.)

[0155] The obtained compound (X) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (X); 1 H-NMR(CD3COCD3); δ[ppm]3.4~4.2(26H)

[0156] Comparative Example 2 Compound (Y) represented by the following formula (Y) was synthesized in the same manner as in Example 4, except that a compound represented by formula (8) was used instead of the compound represented by formula (7).

[0157] [ka] (In formula (Y), c is 5.0.)

[0158] The obtained compound (Y) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (Y); 1 H-NMR(CD3COCD3); δ[ppm]3.4~4.2(18H)

[0159] Comparative Example 3 Compound (Z) represented by the following formula (Z) was synthesized by the method described in Patent Document 2.

[0160] [ka] (In formula (Z), d is 5.0.)

[0161] The obtained compound (Z) 1 H-NMR measurement was performed, and the structure was identified from the following results. Compound (Z); 1 H-NMR(CD3COCD3); δ[ppm]3.4~4.2(26H)

[0162] The compounds of Examples 1 to 22 and Comparative Examples 1 to 3 thus obtained are represented by the formula (1) 1 ~R 3 The structures of the compounds are shown in Tables 1 and 2. The number average molecular weights (Mn) of the compounds of Examples 1 to 22 and Comparative Examples 1 to 3 are shown in Tables 1 to 2. 1 H-NMR and 19 The results were obtained by F-NMR measurement. The results are shown in Tables 1 and 2.

[0163] [Table 1]

[0164] [Table 2]

[0165] Next, a solution for forming a lubricant layer was prepared by the method described below using the compounds obtained in Examples 1 to 22 and Comparative Examples 1 to 3. Then, the obtained solution for forming a lubricant layer was used to form a lubricant layer for a magnetic recording medium by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 22 and Comparative Examples 1 to 3.

[0166] "Lubricant layer forming solution" The compounds obtained in Examples 1 to 22 and Comparative Examples 1 to 3 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (product name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the film thickness when applied onto the protective layer would be 9 Å to 10 Å, to prepare solutions for forming the lubricating layer of Examples 1 to 22 and Comparative Examples 1 to 3.

[0167] "Magnetic recording media" A magnetic recording medium was prepared by sequentially providing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate having a diameter of 65 mm. The protective layer was made of carbon. On the protective layer of the magnetic recording medium on which each layer up to the protective layer had been formed, the lubricant layer forming solutions of Examples 1 to 22 and Comparative Examples 1 to 3 were applied by dipping. The dipping was performed under the conditions of an immersion speed of 10 mm / sec, an immersion time of 30 sec, and a pull-up speed of 1.2 mm / sec. The magnetic recording medium coated with the lubricant layer-forming solution was then placed in a thermostatic chamber at 120°C and heated for 10 minutes to remove the solvent in the lubricant layer-forming solution, thereby forming a lubricant layer on the protective layer and obtaining the magnetic recording media of Examples 1 to 22 and Comparative Examples 1 to 3.

[0168] The thickness of the lubricating layer of each of the magnetic recording media thus obtained in Examples 1 to 22 and Comparative Examples 1 to 3 was measured using an FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific Co., Ltd.) The results are shown in Table 4.

[0169] Next, the magnetic recording media of Examples 1 to 22 and Comparative Examples 1 to 3 were subjected to the following adhesion (bond ratio) measurement, pick-up suppression test, and chemical resistance test.

[0170] (Measurement of adhesion (bond ratio) between lubricating layer and protective layer) The magnetic recording medium on which the lubricating layer was formed was immersed in a solvent, Vertrel XF, for 10 minutes and then pulled up for cleaning. The magnetic recording medium was immersed in the solvent at a speed of 10 mm / sec and pulled up at a speed of 1.2 mm / sec. The thickness of the lubricating layer was then measured using the same method as that used to measure the thickness of the lubricating layer before cleaning. The thickness of the lubricant layer before cleaning was designated A, and the thickness of the lubricant layer after cleaning (solvent immersion) was designated B. The bond ratio of the lubricant was calculated from the ratio of A to B ((B / A) x 100(%)). Using the calculated bond ratio, the adhesion between the lubricant layer and the protective layer was evaluated according to the following criteria. The results are shown in Table 4.

[0171] "Adhesion (bond rate) evaluation" A: Bond rate is 80% or more b: Bond ratio is 70% or more and less than 80% c: Bond ratio is 50% or more and less than 70% d: Bond ratio is less than 50%

[0172] (Pickup suppression test) The magnetic recording medium and the magnetic head were mounted on a spin stand, and the magnetic head was floated at a fixed point for 10 minutes under reduced pressure (approximately 250 torr) at room temperature. After that, the surface of the magnetic head facing the magnetic recording medium (the surface of the lubricant layer) was analyzed using an ESCA (Electron Spectroscopy for Chemical Analysis) analyzer. Then, the amount of lubricant attached to the magnetic head was evaluated according to the criteria shown in Table 3 below, based on the intensity (signal intensity (au)) of the peak derived from fluorine measured by ESCA. The results are shown in Table 4.

[0173] [Table 3]

[0174] (Chemical Resistance Test) This evaluation method is for investigating the contamination of magnetic recording media by environmental substances that generate contaminants in a high-temperature environment. In the evaluation method described below, Si ions were used as the environmental substances, and the amount of Si adsorption was measured as the amount of contaminants that contaminate the magnetic recording media and are generated by the environmental substances. Specifically, the magnetic recording medium to be evaluated was kept in the presence of siloxane-based Si rubber for 240 hours in a high-temperature environment of 85°C and 0% humidity. Next, the amount of Si adsorption on the surface of the magnetic recording medium was analyzed and measured using secondary ion mass spectrometry (SIMS), and the degree of contamination by Si ions was evaluated as the amount of Si adsorption. The Si adsorption amount was evaluated as follows, using the Si adsorption amount of each Example and Comparative Example calculated relative to the Si adsorption amount of the magnetic recording medium obtained using Compound Z of Comparative Example 3, which was set to 1.00. The results are shown in Table 4.

[0175] "Chemical Resistance Assessment" a: Less than 0.85 b: 0.85 or more, less than 1.0 c: 1.0 or more, less than 1.2 d:1.2 or more

[0176] [Table 4]

[0177] As shown in Table 4, the magnetic recording media of Examples 1 to 22 were all rated b or a in terms of adhesion (bond ratio), pick-up suppression, and chemical resistance. This is because, in the magnetic recording media of Examples 1 to 22, R 2 R placed at one end of 1 and R placed at the other end 3 It is presumed that this was achieved because the hydroxyl groups of the protective layer were strongly adsorbed to the protective layer.

[0178] On the other hand, the fluorine-containing ether compounds of Comparative Examples 1 and 2 were rated d for pick-up inhibition and c for adhesion (bonding ratio) and chemical resistance. This is presumably because, in Comparative Example 1, the number of hydroxyl groups bonded to both ends of the perfluoropolyether chain is small, resulting in insufficient adhesion to the protective layer, and because the repeating unit of the perfluoropolyether chain contains (-CF2-O-), the perfluoropolyether chain lacks rigidity and is prone to aggregation on the protective layer. Also, in Comparative Example 2, the number of hydroxyl groups bonded to both ends of the perfluoropolyether chain is small, resulting in insufficient adhesion to the protective layer, and because the carbon atoms to which the hydroxyl groups are bonded are bonded to each other, resulting in insufficient coverage.

[0179] The fluorine-containing ether compound of Comparative Example 3 was rated a for pick-up inhibition and b for adhesion (bond ratio), but was rated c for chemical resistance. This is presumably because in Comparative Example 3, the number of hydroxyl groups bonded to both ends of the perfluoropolyether chain was small, resulting in insufficient wetting and spreading on the protective layer. [Industrial Applicability]

[0180] By using a lubricant for magnetic recording media containing the fluorinated ether compound of the present invention, it is possible to form a lubricating layer that has good adhesion to a protective layer, can suppress pick-up, and has excellent resistance to chemical substances. [Explanation of symbols]

[0181] 10 magnetic recording medium, 11 substrate, 12 adhesion layer, 13 soft magnetic layer, 14 first underlayer, 15 second underlayer, 16 magnetic layer, 17 protective layer, and 18 lubricating layer.

Claims

1. A fluorine-containing ether compound characterized by being any compound represented by the following formulas (A) to (V): 【Chemistry 1】 (In formula (A), xa is the average degree of polymerization and represents 1 to 14.) (In formula (B), xb is the average degree of polymerization and represents 1 to 14.) (In formula (C), xc is the average degree of polymerization and represents 1 to 14.) 【Chemistry 2】 (In formula (D), xd is the average degree of polymerization and represents 1 to 14.) (In formula (E), xe is the average degree of polymerization and represents 1 to 14.) (In formula (F), xf is the average degree of polymerization and represents 1 to 14.) (In formula (G), xg is the average degree of polymerization and represents 1 to 14.) 【Chemistry 3】 (In formula (H), xh is the average degree of polymerization and represents 1 to 14.) (In formula (I), xi is the average degree of polymerization and represents 1 to 14.) (In formula (J), xj is the average degree of polymerization and represents 1 to 14.) (In formula (U), xu is the average degree of polymerization and represents 1 to 14.) 【Chemistry 4】 (In formula (K), yk is the average degree of polymerization and represents 1 to 20.) (In formula (L), yl is the average degree of polymerization and represents 1 to 20.) (In formula (M), ym is the average degree of polymerization and represents 1 to 20.) 【Chemistry 5】 (In formula (N), yn is the average degree of polymerization and represents 1 to 20.) (In formula (O), yo is the average degree of polymerization and represents 1 to 20.) (In formula (P), yp is the average degree of polymerization and represents 1 to 20.) (In formula (Q), yq is the average degree of polymerization and represents 1 to 20.) 【Chemistry 6】 (In formula (R), yr is the average degree of polymerization and represents 1 to 20.) (In formula (S), ys is the average degree of polymerization and represents 1 to 20.) (In formula (T), yt is the average degree of polymerization and represents 1 to 20.) (In formula (V), yv is the average degree of polymerization and represents 1 to 20.)

2. The fluorine-containing ether compound according to claim 1, which is any one of the compounds represented by formulas (D) to (G).

3. The fluorine-containing ether compound according to claim 1, which is any one of the compounds represented by formulas (N) to (Q).

4. The fluorine-containing ether compound according to claim 1 , which is any one of the compounds represented by formulas (C) and (H).

5. The fluorine-containing ether compound according to claim 1 , which is any one of the compounds represented by formula (M) and (R).

6. The fluorine-containing ether compound according to any one of claims 1 to 5, having a number average molecular weight in the range of 400 to 3,000.

7. A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of claims 1 to 6.

8. A magnetic recording medium comprising at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate, the lubricating layer comprising the fluorine-containing ether compound according to any one of claims 1 to 6.

9. 9. The magnetic recording medium according to claim 8, wherein the lubricating layer has an average thickness of 0.5 nm to 1.5 nm.

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