Lubricant for magnetic recording medium

Abstract

[Problem] To provide a lubricant for a magnetic recording medium, which is capable of maintaining wear resistance and chemical resistance of a lubricating layer even if the number of coated substrates increases in a lubricant coating step. [Solution] A lubricant for a magnetic recording medium, which contains a fluorine-containing ether compound represented by formula (1), and in which the proportion of molecules having the same molecular weight contained in the fluorine-containing ether compound is 90% or more in terms of the peak area ratio by high performance liquid chromatography. R1-R2-CH2-R3 [-CH2-R4-CH2-R3 '] n-CH2-R5-R6 (1) (In formula (1), n is an integer of any one of 0 to 2. And R3 and R3'are each independently a prescribed perfluoropolyether chain. And R4 represents a divalent linking group having 1-3 polar groups. R2 and R5 are divalent linking groups having one or more polar groups, and may be the same or different. And the tail end of one side of R2 bonded with R1 is an oxygen atom. And the tail end of the side, bonded with the R6, of the R5 is an oxygen atom. R1 and R6 are terminal groups bonded to oxygen atoms at the terminals of R2 or R5, and R1 and R6 are hydrogen atoms or organic groups having 1-50 carbon atoms).

Description

Technical Field

[0001] The present invention relates to a lubricant for a magnetic recording medium and a method for producing the same, a magnetic recording medium and a method for producing the same. Background Art

[0002] In recent years, low-cost and large-capacity magnetic recording media have been developed for data centers.

[0003] As a magnetic recording medium, there is known a magnetic recording medium obtained by laminating a magnetic layer (magnetic recording layer) on a substrate, forming a protective layer such as carbon on the magnetic layer, and further forming a lubricating layer on the protective layer. The protective layer protects the information recorded in the magnetic layer and improves the sliding property of the magnetic head of the magnetic recording and reproducing device. The lubricating layer prevents the magnetic head from directly contacting the protective layer, and significantly reduces the friction of the sliding magnetic head.

[0004] Furthermore, the lubricating layer disposed on the outermost surface of the magnetic recording medium is required to have various properties, such as resistance to chemical substances (prevention of contamination by silicone or the like), long-term stability, and heat resistance, in addition to wear resistance.

[0005] A lubricant for magnetic recording media (hereinafter sometimes referred to as "lubricant") is applied on the lubricating layer. In recent years, a fluorinated polymer containing a perfluoropolyether (hereinafter sometimes referred to as "PFPE") chain having a perfluorooxyalkylene group as a structural repeating unit and having a polar group such as a hydroxyl group at the end has been used as a lubricant.

[0006] In order to manufacture fluorinated polymers for lubricants, PFPE polymers having hydroxyl groups at the ends are used as raw materials. Specific examples of PFPE polymers include Krytox (registered trademark) manufactured by Kermaz, Fomblin (registered trademark) manufactured by SOLVAY SOLEXIS, and Demnum (registered trademark) manufactured by Daikin Industries. Krytox (registered trademark) has -[CF(CF 3 )CF 2 O]-repeating unit is produced through the ring-opening polymerization of hexafluoropropylene oxide. Fomblin (registered trademark) is -[CF(Z)CF 2 O]-(wherein Z represents a fluorine atom or CF 3 ) and -[CF 2 O]-These two repeating units are randomly arranged in a copolymer produced by photochemical oxidative polymerization of tetrafluoroethylene and hexafluoropropylene. Demnum (registered trademark) has -[CF 2 CF 2 CF 2O]-repeating unit is produced through the ring-opening polymerization process of 2,2,3,3-tetrafluorooxetane. In addition, as a specific example of other PFPE polymers, it is known that -[CF 2 CF 2 Fluorinated polyethylene glycol containing a repeating unit of [O]- can be synthesized by liquid phase fluorination of polyethylene glycol derivatives.

[0007] As described above, PFPE polymers are produced by polymerizing completely or partially fluorinated monomers (in order to completely replace some of the remaining protons with fluorine atoms, a liquid phase fluorination step is sometimes added after the polymerization), or by liquid phase fluorination of a non-fluorinated polymer obtained by the polymerization reaction. Therefore, the PFPE polymer obtained by such a process is a mixture composed of components with different repeating numbers and has a wide molecular weight distribution.

[0008] Fluorinated polymers for lubricants prepared using these PFPE polymers as raw materials are also mixtures of components with different repeating numbers and have a broad molecular weight distribution of about Mw / Mn = 1.1 to 1.5. As fluorinated polymers for lubricants, compounds described in Patent Documents 1 to 3 are known.

[0009] Patent Document 1 describes a fluorinated ether compound having one perfluoropolyether chain. As a raw material, a PFPE polymer having a molecular weight distribution of 1.2 is described, wherein the repeating unit is -(CF 2 CF 2 CF 2 O)- and a mixture of 1 to 7 repetition numbers.

[0010] Patent Document 2 describes a fluorinated ether compound having two perfluoropolyether chains. Patent Document 3 describes a fluorinated ether compound having three perfluoropolyether chains. As their raw materials, a PFPE polymer having a molecular weight distribution of 1.1 is described.

[0011] It is known that various properties required of a lubricating layer, such as wear resistance, chemical resistance, and long-term stability, vary greatly depending on the molecular weight of the fluorinated polymer used in the lubricant. Therefore, it is important to control the molecular weight distribution of the fluorinated polymer within a desired range.

[0012] As a method for applying a lubricant on the protective layer of a magnetic recording medium, an immersion method is generally used. In the case of the immersion method, for example, the method shown below can be used. First, the lubricant is dissolved in a fluorine-based solvent such as Batler (registered trademark) XF (trade name, manufactured by Mitsui & Co., Ltd.), and a lubricant layer forming solution is prepared in a manner to obtain a concentration suitable for coating. Then, a substrate having various layers formed thereon up to the protective layer is immersed in the lubricant layer forming solution loaded into a dipping tank of a dipping device. Next, the substrate is lifted from the dipping tank at a specified speed. In this way, the lubricant can be applied to the surface on the protective layer.

[0013] Prior art literature

[0014] Patent Literature

[0015] Patent Document 1: Japanese Patent Application Publication No. 2018-024614

[0016] Patent document 2: WO2021 / 020066

[0017] Patent document 3: WO2022 / 215726 Summary of the invention

[0018] Problems to be solved by the invention

[0019] In the above-mentioned coating process of the lubricant based on the dipping method, the lubricating layer forming solution loaded in the dipping tank is repeatedly used within a certain period of time to process thousands to hundreds of thousands of substrates. However, if the conventional fluorinated polymer with a wide molecular weight distribution is used as a lubricant, there is the following problem: as the number of coated substrates increases, the number average molecular weight of the fluorinated polymer contained in the lubricating layer gradually increases. The reason is that in the coating process, the fluorinated polymer with a small molecular weight is first consumed and adsorbed on the protective layer, so the molecular weight distribution of the fluorinated polymer in the lubricating layer forming solution is biased towards the side with a large molecular weight. Fluorinated polymers with a small molecular weight have a large proportion of polar groups such as hydroxyl groups relative to the overall size of the molecule, and the polarity of the molecule as a whole becomes higher. Therefore, the adsorption force of fluorinated polymers with a small molecular weight to the protective layer is strong, and they are adsorbed on the protective layer first compared to fluorinated polymers with a large molecular weight. Therefore, as the number of coated substrates in the coating process increases, the proportion of fluorinated polymers with a small molecular weight in the lubricating layer forming solution gradually decreases significantly.

[0020] It is known that if the number average molecular weight of the fluorinated polymer in the lubricating layer increases, the wear resistance and chemical resistance deteriorate. Therefore, the lubricating layer forming solution in the immersion tank needs to be frequently replaced, which becomes the cause of the deterioration of the productivity of the coating process. In addition, among the fluorinated polymer contained in the lubricating layer forming solution, only a part of the components are coated as the lubricating layer, and the remaining components are not used and are discarded together with the fluorine-based solvent. Therefore, it is not preferred from the viewpoint of production cost and environmental load.

[0021] An object of the present invention is to provide a lubricant for a magnetic recording medium in which the wear resistance and chemical resistance of the lubricant layer are maintained without deteriorating even when the number of substrates to be coated increases in the lubricant coating step.

[0022] Means for solving problems

[0023] The inventors of the present application have conducted intensive studies to solve the above-mentioned problems.

[0024] As a result, it was found that when only the molecular weight range and molecular weight distribution were defined, the influence on the wear resistance and chemical resistance of the lubricating layer could not be fully understood when the number of coated sheets of the substrate was large. Furthermore, it was confirmed that by defining the molecular weight characteristics of the fluorinated ether compound contained in the lubricant for magnetic recording media by the peak area ratio based on high performance liquid chromatography, the wear resistance and chemical resistance of the lubricating layer would not deteriorate and could be maintained even if the number of coated sheets of the substrate increased in the lubricant coating process, thereby completing the present invention.

[0025] The present invention is constructed as follows.

[0026] [1] A lubricant for magnetic recording media, characterized in that it is a lubricant for magnetic recording media containing a fluorine-containing ether compound represented by formula (1), wherein the ratio of molecules of the same molecular weight contained in the fluorine-containing ether compound is 90% or more in terms of peak area ratio based on high performance liquid chromatography.

[0027] R 1 -R 2 -CH 2 -R 3 [-CH 2 -R 4 -CH 2 -R 3 '] n -CH 2 -R 5 -R 6 (1)

[0028] (In formula (1), n ​​is an integer from 0 to 2. 3 and R 3' are each independently a perfluoropolyether chain represented by formula (1f). When n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partially or completely the same, or can be different. 4 is a divalent linking group having 1 to 3 polar groups. When n is 2, the two R 4 Can be the same or different. 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different. 2 R 1 The terminal of one side of the bond is an oxygen atom. 5 R 6 The terminal of one side of the bond is an oxygen atom. 1 and R 6 is with R 2 or R 5 The terminal groups to which the terminal oxygen atoms of R are bonded may be the same or different. 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms.

[0029] -Af 2 -O-(Af 1 -O) m -Af 3 -(1f)

[0030] (In formula (1f), Af 1 It represents a divalent perfluorocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (Af 1 -O) are all identical. 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right. 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms. m represents an average degree of polymerization and is a real number of 1 to 13.

[0031] [2] A lubricant for magnetic recording media, characterized in that it is a lubricant for magnetic recording media comprising a fluorinated ether compound represented by formula (1), wherein the lubricant for magnetic recording media comprises a fluorinated ether compound in which the ratio of molecules represented by formula (1s) relative to 100% of the fluorinated ether compound represented by formula (1) is 90% or more, measured by peak area ratio based on high performance liquid chromatography.

[0032] R 1 -R 2 -CH 2 -R 3 [-CH 2 -R 4 -CH 2 -R 3 '] n -CH 2 -R 5 -R 6 (1)

[0033] (In formula (1), n ​​is an integer from 0 to 2. 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f). When n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partially or completely the same, or can be different. 4 is a divalent linking group having 1 to 3 polar groups. When n is 2, the two R 4 Can be the same or different. 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different. 2 R 1 The terminal of one side of the bond is an oxygen atom. 5 R 6 The terminal of one side of the bond is an oxygen atom. 1 and R 6 is with R 2 or R 5 The terminal groups to which the terminal oxygen atoms of R are bonded may be the same or different. 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms.

[0034] -Af 2 -O-(Af 1 -O) m -Af 3 -(1f)

[0035] (In formula (1f), Af 1 It represents a divalent perfluorocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (Af 1 -O) are all identical. 1 In the case of a branched structure, a part (Af 1-O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right. 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms. m represents an average degree of polymerization and is a real number of 1 to 13.

[0036] R 1 -R 2 -CH 2 -R 3 s [-CH 2 -R 4 -CH 2 -R 3s '] n -CH 2 -R 5 -R 6 (1s)

[0037] (In formula (1s), the same symbols as those in formula (1) represent the same structures or values ​​as those in formula (1). 3s and R 3s 'Each independently represents a perfluoropolyether chain represented by formula (1f-1).

[0038] -Af 2 -O-(Af 1 -O) s -Af 3 -(1f-1)

[0039] (In formula (1f-1), the same symbols as those in formula (1f) represent the same structures as those in formula (1f). s represents the degree of polymerization and is an integer of 1 to 13.)

[0040] [3] The lubricant for a magnetic recording medium according to [1] or [2], wherein the fluorine-containing ether compound has a number average molecular weight of 500 to 10,000.

[0041] [4] A method for producing a lubricant for a magnetic recording medium, characterized in that it is a method for producing a lubricant for a magnetic recording medium containing a fluorine-containing ether compound represented by formula (1), wherein the ratio of molecules of the same molecular weight contained in the fluorine-containing ether compound is 90% or more in terms of peak area ratio based on high performance liquid chromatography,

[0042] The production method comprises the step of synthesizing the fluorine-containing ether compound using a fluorinated polyalkylene glycol represented by formula (1f') as a raw material,

[0043] The ratio of molecules having the same molecular weight contained in the fluorinated polyalkylene glycol is 90% or more in terms of a peak area ratio based on high performance liquid chromatography.

[0044] R 1 -R 2 -CH 2 -R 3 [-CH 2 -R 4 -CH 2 -R 3 '] n -CH 2 -R 5 -R 6 (1)

[0045] (In formula (1), n ​​is an integer from 0 to 2. 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f). When n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partially or completely the same, or can be different. 4 is a divalent linking group having 1 to 3 polar groups. When n is 2, the two R 4 Can be the same or different. 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different. 2 R 1 The terminal of one side of the bond is an oxygen atom. 5 R 6 The terminal of one side of the bond is an oxygen atom. 1 and R 6 is with R 2 or R 5 The terminal groups to which the terminal oxygen atoms of R are bonded may be the same or different. 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms.

[0046] -Af 2 -O-(Af 1 -O) m -Af 3 -(1f)

[0047] (In formula (1f), Af 1 It represents a divalent perfluorocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (Af 1 -O) are all identical. 1 In the case of a branched structure, a part (Af 1-O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right. 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms. m represents an average degree of polymerization and is a real number of 1 to 13.

[0048] HO-CH 2 -Af 2 -O-(Af 1 -O) m -Af 3 -CH 2 -OH(1f')

[0049] (In formula (1f'), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). In formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R 3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 'The corresponding fluorinated polyalkylene glycol. )

[0050] [5] The method for producing a lubricant for a magnetic recording medium of [4] comprises synthesizing the fluorinated polyalkylene glycol represented by formula (1f') by a method comprising the following steps (A) to (C):

[0051] Step (A), liquid phase fluorination of a polyalkylene glycol represented by formula (2) having both ends protected and having a molecular weight ratio of 90% or more in the peak area ratio based on high performance liquid chromatography;

[0052] Step (B), reacting the obtained fluorination product represented by formula (3) with an alcohol having 1 to 6 carbon atoms;

[0053] In step (C), the obtained double-terminal esterified product represented by formula (4) is subjected to a reduction reaction.

[0054] A 4 -O-(A 1 -O) x -A 5 (2)

[0055] (In formula (2), A 1 represents a divalent hydrocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (A 1 -O) are all identical. 1In the case of a branched structure, a part (A 1 -O) in each repeating unit represented by 1 The arrangement direction of A is alternating left and right. x represents the average degree of polymerization, which is a real number from 3 to 15. 4 and A 5 Each independently represents a protecting group for a hydroxyl group. )

[0056] F-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-F (3)

[0057] (In formula (3), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f).

[0058] A 6 O-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-OA 7 (4)

[0059] (In formula (4), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). 6 and A 7 Each independently represents an alkyl group having 1 to 6 carbon atoms. )

[0060] [6] The method for producing a lubricant for a magnetic recording medium according to [5], comprising the following polyether synthesis step: prior to the step (A), a nucleophilic substitution reaction is performed to react two or more compounds having a polyether chain or a monomer unit constituting a polyether chain, thereby synthesizing a lubricant having (A) 1 -O) represented by a repeating unit.

[0061] [7] A method for producing a lubricant for a magnetic recording medium, characterized in that it is a method for producing a lubricant for a magnetic recording medium containing a fluorine-containing ether compound, wherein the fluorine-containing ether compound is a fluorine-containing ether compound represented by formula (1), and the ratio of the molecule represented by formula (1s) to 100% of the fluorine-containing ether compound represented by formula (1) is 90% or more in terms of peak area ratio based on high performance liquid chromatography,

[0062] The production method comprises the step of synthesizing the fluorine-containing ether compound using a fluorinated polyalkylene glycol represented by formula (1f') as a raw material,

[0063] The ratio of the molecule represented by formula (1f'-1) to 100% of the fluorinated polyalkylene glycol represented by formula (1f') is 90% or more in terms of peak area ratio by high performance liquid chromatography.

[0064] R 1 -R 2 -CH 2 -R 3 [-CH 2 -R 4 -CH 2 -R 3 '] n -CH 2 -R 5 -R 6 (1)

[0065] (In formula (1), n ​​is an integer from 0 to 2. 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f). When n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partially or completely the same, or can be different. 4 is a divalent linking group having 1 to 3 polar groups. When n is 2, the two R 4 Can be the same or different. 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different. 2 R 1 The terminal of one side of the bond is an oxygen atom. 5 R 6 The terminal of one side of the bond is an oxygen atom. 1 and R 6 is with R 2 or R 5 The terminal groups to which the terminal oxygen atoms of R are bonded may be the same or different. 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms.

[0066] -Af 2 -O-(Af 1 -O) m -Af 3 -(1f)

[0067] (In formula (1f), Af 1 It represents a divalent perfluorocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1In the case of a linear chain structure, (Af 1 -O) are all identical. 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right. 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms. m represents an average degree of polymerization and is a real number of 1 to 13.

[0068] R 1 -R 2 -CH 2 -R 3 s [-CH 2 -R 4 -CH 2 -R 3s '] n -CH 2 -R 5 -R 6 (1s)

[0069] (In formula (1s), the same symbols as those in formula (1) represent the same structures or values ​​as those in formula (1). 3s and R 3s 'Each independently represents a perfluoropolyether chain represented by formula (1f-1).

[0070] -Af 2 -O-(Af 1 -O) s -Af 3 -(1f-1)

[0071] (In formula (1f-1), the same symbols as those in formula (1f) represent the same structures as those in formula (1f). s represents the degree of polymerization and is an integer of 1 to 13.)

[0072] HO-CH 2 -Af 2 -O-(Af 1 -O) m -Af 3 -CH 2 -OH(1f')

[0073] (In formula (1f'), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). In formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 'The corresponding fluorinated polyalkylene glycol. )

[0074] HO-CH 2 -Af 2 -O-(Af 1 -O) t -Af 3 -CH 2 -OH(1f'-1)

[0075] (In formula (1f'-1), the same symbols as those in formula (1f') represent the same structures as those in formula (1f'). t represents the degree of polymerization and is an integer of 1 to 13.)

[0076] [8] The method for producing a lubricant for a magnetic recording medium of [7] comprises synthesizing the fluorinated polyalkylene glycol represented by formula (1f') by a method comprising the following steps (A-1) to (C-1):

[0077] Step (A-1), liquid phase fluorination of a polyalkylene glycol having both terminal protections, wherein the polyalkylene glycol having both terminal protections is a polyalkylene glycol having both terminal protections represented by formula (2), and the proportion of molecules represented by formula (2-1) in the peak area ratio based on high performance liquid chromatography is 90% or more;

[0078] Step (B-1), reacting the obtained fluorination product represented by formula (3) with an alcohol having 1 to 6 carbon atoms;

[0079] In step (C-1), the obtained double-terminal esterified product represented by formula (4) is subjected to a reduction reaction.

[0080] A 4 -O-(A 1 -O) x -A 5 (2)

[0081] (In formula (2), A 1 represents a divalent hydrocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (A 1 -O) are all identical. 1 In the case of a branched structure, a part (A 1 -O) in each repeating unit represented by 1 The arrangement direction of A is alternating left and right. x represents the average degree of polymerization, which is a real number from 3 to 15. 4 and A 5Each independently represents a protecting group for a hydroxyl group. )

[0082] A 4 -O-(A 1 -O) u -A 5 (2-1)

[0083] (In formula (2-1), the same symbols as those in formula (2) represent the same structures as those in formula (2). u represents the degree of polymerization and is an integer of 3 to 15.)

[0084] F-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-F (3)

[0085] (In formula (3), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f).

[0086] A 6 O-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-OA 7 (4)

[0087] (In formula (4), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). 6 and A 7 Each independently represents an alkyl group having 1 to 6 carbon atoms. )

[0088] [9] [8] A method for producing a lubricant for a magnetic recording medium, comprising the following polyether synthesis step: before the step (A-1), a nucleophilic substitution reaction is performed to react two or more compounds having a polyether chain or a monomer unit constituting a polyether chain, thereby synthesizing a lubricant having (A-2). 1 -O) represented by a repeating unit.

[0089]

[10] The method for producing a lubricant for a magnetic recording medium according to [6] or [9], wherein the polyether synthesis step includes a step of reacting the following compounds:

[0090] A compound having a leaving group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end; and

[0091] A compound having a hydroxyl group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end.

[0092]

[11] The method for producing a lubricant for a magnetic recording medium according to [6] or [9], wherein the polyether synthesis step includes a step of reacting the following compounds:

[0093] A compound having a leaving group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end; and

[0094] A compound having hydroxyl groups at both ends of a polyether chain or a monomer unit constituting a polyether chain.

[0095]

[12] The method for producing a lubricant for a magnetic recording medium according to [6] or [9], wherein the polyether synthesis step includes a step of reacting the following compounds:

[0096] A compound having a hydroxyl group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end; and

[0097] A compound having leaving groups at both ends of a polyether chain or a monomer unit constituting a polyether chain.

[0098]

[13] A magnetic recording medium characterized by at least a magnetic layer, a protective layer, and a lubricating layer being provided in this order on a substrate, wherein the lubricating layer contains the lubricant for a magnetic recording medium described in any one of [1] to [3].

[0099]

[14] A method for manufacturing a magnetic recording medium, comprising the step of applying the lubricant for a magnetic recording medium described in any one of [1] to [3] on the protective layer of a substrate having at least a magnetic layer and a protective layer formed thereon to form a lubricating layer.

[0100] Effects of the Invention

[0101] The lubricant for magnetic recording media of the present invention can maintain the wear resistance and chemical resistance of the lubricating layer formed therefrom even if the number of substrates coated with the lubricant increases during the lubricant coating process. The method for manufacturing the lubricant for magnetic recording media of the present invention can efficiently manufacture such a lubricant for magnetic recording media.

[0102] The magnetic recording medium of the present invention can maintain the wear resistance and chemical resistance of the lubricating layer at a high level during production, and therefore has excellent reliability and durability.

[0103] According to the method for producing a magnetic recording medium of the present invention, such a magnetic recording medium can be produced efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] [Figure 1 ] is a schematic cross-sectional view showing a preferred embodiment of the magnetic recording medium of the present invention.

[0105] [ Figure 2 ] is the 1,3-propylene glycol pentamer synthesized in Example 1 1 H-NMR spectrum.

[0106] [ Figure 3 ] is the two-terminal acetylated 1,3-propylene glycol pentamer synthesized in Example 1 1 H-NMR spectrum.

[0107] [ Figure 4 ] is the GPC chromatogram of the two-terminal acetylated 1,3-propanediol pentamer synthesized in Example 1.

[0108] [ Figure 5 ] is the fluorinated 1,3-propylene glycol pentamer synthesized in Example 1 19 F-NMR spectrum.

[0109] [ Figure 6 ] is the compound (A1) synthesized in Example 1 1 H-NMR spectrum.

[0110] [ Figure 7 ] is the compound (A1) synthesized in Example 1 19 F-NMR spectrum.

[0111] [ Figure 8 ] is the normal phase LC chromatogram of compound (A1) synthesized in Example 1.

[0112] [ Fig. 9 ] is the GPC chromatogram of the dual-terminal acetylated 1,3-propanediol polymer synthesized in Comparative Example 1.

[0113] [ Fig.10 ] is a GPC chromatogram of the 1,3-propanediol polymer with acetylation at both ends synthesized in Comparative Example 1 after molecular weight distribution adjustment.

[0114] [ Fig.11 ] is the GPC chromatogram of the fluorinated 1,3-propylene glycol polymer synthesized in Comparative Example 1.

[0115] [ Fig.12 ] is the compound (B1) synthesized in Comparative Example 1 1 H-NMR spectrum.

[0116] [ Fig.13 ] is the compound (B1) synthesized in Comparative Example 1 19 F-NMR spectrum.

[0117] [ Fig.14 ] is the normal phase LC chromatogram of compound (B1) synthesized in Comparative Example 1.

[0118] [ Fig.15 ] is a diagram obtained by comparing the normal phase LC chromatograms of compounds (A1) to (C1).

[0119] [ Fig.16 ] is a graph showing the results of abrasion resistance tests of compounds (A1) to (C1).

[0120] [ Fig.17 ] is a graph showing the results of chemical substance resistance tests of compounds (A1) to (C1). DETAILED DESCRIPTION

[0121] Hereinafter, the embodiment of the lubricant for magnetic recording medium of the present invention is described in detail. It should be noted that the present invention is not limited to the embodiment shown below. The present invention can be added, omitted, replaced, and changed in number, amount, ratio, material, composition, etc. within the scope of the main purpose of the present invention.

[0122] The lubricant of the present embodiment contains a specific fluorine-containing ether compound. First, the fluorine-containing ether compound will be described.

[0123] [Fluorinated ether compounds]

[0124] The fluorine-containing ether compound is represented by the following formula (1), and is substantially composed of the same components. If the ratio of molecules of the same molecular weight (molecules constituting the same components) is defined by the peak area ratio based on high performance liquid chromatography, it is 90% or more, preferably 93% or more, and more preferably 95% or more. It should be noted that the upper limit is 100%. The so-called peak area ratio based on high performance liquid chromatography is 90% or more, which means that in the compound to be measured, the constituent elements, the number of repetitions, the side chains and the terminal functional groups constituting the main chain are substantially the same. The closer the peak area ratio is to 100%, the smaller the deviation of the number of repetitions. If it is 100%, the number of repetitions is also the same. This definition also applies to the raw materials and intermediates when synthesizing fluorine-containing ether compounds. It should be noted that in the case where the compound to be measured contains isomers (for example, in the case where isomers are generated during the synthesis process of the compound), the molecules of the same molecular weight also include isomers.

[0125] R 1 -R 2 -CH 2 -R 3 [-CH 2 -R 4 -CH 2 -R 3 ']n -CH 2 -R 5 -R 6 (1)

[0126] (In formula (1), n ​​is an integer from 0 to 2. 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f). When n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partially or completely the same, or can be different. 4 is a divalent linking group having 1 to 3 polar groups. When n is 2, the two R 4 Can be the same or different. 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different. 2 R 1 The terminal of one side of the bond is an oxygen atom. 5 R 6 The terminal of one side of the bond is an oxygen atom. 1 and R 6 is with R 2 or R 5 The terminal groups to which the terminal oxygen atoms of R are bonded may be the same or different. 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms.

[0127] -Af 2 -O-(Af 1 -O) m -Af 3 -(1f)

[0128] (In formula (1f), Af 1 It represents a divalent perfluorocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (Af 1 -O) are all identical. 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right. 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms. m represents an average degree of polymerization and is a real number of 1 to 13.

[0129] R 3 and R 3 ' represents the PFPE chain

[0130] In the fluorine-containing ether compound of this embodiment represented by formula (1), R 3 and R 3 'Each independently represents a PFPE chain represented by formula (1f). When a lubricant containing a fluorinated ether compound is applied to the protective layer to form a lubricating layer, the PFPE chain covers the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the friction between the magnetic head and the protective layer.

[0131] R 3 and 1 or 2 R 3 ' can be partially or completely the same, or can be different. 3 and 1 or 2 R 3 'It is preferred that all of them are the same. This is because the coating state of the protective layer with the fluorinated ether compound becomes more uniform, forming a lubricating layer with better adhesion. 3 and 1 or 2 R 3 The term "same" also includes the case where the structures of the repeating units of the PFPE chains are the same but the average polymerization degrees are different.

[0132] In formula (1f), Af 1 Af represents a divalent perfluorocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 Specific examples include, for example, -CF 2 -CF 2 -、-CF 2 -CF 2 -CF 2 -、-CF 2 -CF(CF 3 )-、-CF(CF 3 )-CF 2 -、-CF 2 -CF 2 -CF 2 -CF 2 -、-CF(CF 3 )-CF 2 -CF 2 -、-CF 2 -CF(CF 3 )-CF 2 -、-CF 2 -CF 2 -CF(CF 3 )-、-CF 2 -CF 2 -CF 2 -CF 2 -CF 2 -、-CF(CF3 ) - CF 2 - CF 2 - CF 2 -,-CF 2 - CF(CF 3 ) - CF 2 - CF 2 -,-CF 2 - CF 2 - CF(CF 3 ) - CF 2 -,-CF 2 - CF 2 - CF 2 - CF(CF 3 ) -,-CF(CF 3 ) - CF 2 - CF(CF 3 ) -。Af 1 Preferably from - CF 2 - CF 2 -,-CF 2 - CF 2 - CF 2 -,-CF 2 - CF(CF 3 ) -,-CF(CF 3 ) - CF 2 -,-CF 2 - CF 2 - CF 2 - CF 2 -,-CF 2 - CF 2 - CF 2 - CF 2 - CF 2 -,-CF(CF 3 ) - CF 2 - CF(CF 3 ) - is selected. Further preferably - CF 2 - CF 2 -,-CF 2 - CF 2 - CF 2 -,-CF 2 - CF(CF 3 ) -,-CF(CF 3 ) - CF 2 -,-CF 2 - CF 2 - CF 2 - CF 2 - and most preferably - CF 2 - CF 2 -,-CF 2-CF 2 -CF 2 -.

[0133] In formula (1f), in Af 1 In the case of a linear chain structure, (Af 1 -O) in each repeating unit represented by Af 1 All the same, in Af 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right. 1 In the case of a branched chain structure, (Af 1 The bonding pattern between the repeating units represented by (-O) is not limited to head-to-tail bonding, but may include head-to-head bonding and tail-to-tail bonding.

[0134] In formula (1f), Af 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms. 2 and Af 3 According to (Af 1 -O) is determined by the structure of the repeating unit represented by

[0135] Specifically, R in formula (1) 3 and R 3 'Each independently is preferably any one of the following formulas (1f-a) to (1f-d).

[0136] -CF 2 O-(CF 2 CF 2 O) ma -CF 2 -(1f-a)

[0137] -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) mb -CF 2 CF 2 -(1f-b)

[0138] -CF 2 CF 2 CF 2 O-(CF 2 CF 2 CF 2 CF 2 O) mc-CF 2 CF 2 CF 2 -(1f-c)

[0139] -CF 2 CF 2 CF 2 CF 2 O-(CF 2 CF 2 CF 2 CF 2 CF 2 O) md -CF 2 CF 2 CF 2 CF 2 -(1f-d)

[0140] (In formulas (1f-a) to (1f-d), ma to md each represent an average degree of polymerization, and are real numbers of 1 to 13.)

[0141] In formula (1f-a), ma representing the average degree of polymerization is a real number representing 1 to 13. When ma is 1 to 13, the number average molecular weight of the fluorine-containing ether compound of the present embodiment tends to be within the preferred range.

[0142] In formula (1f-b), mb indicating the average degree of polymerization is a real number representing 1 to 13. When mb is 1 to 13, the number average molecular weight of the fluorine-containing ether compound of the present embodiment tends to be within the preferred range. mb is preferably 1 to 8, and more preferably 2 to 6.

[0143] In formula (1f-c), mc indicating the average degree of polymerization is a real number representing 1 to 13. When mc is 1 to 13, the number average molecular weight of the fluorine-containing ether compound of the present embodiment tends to be within the preferred range. mc is preferably 1 to 6, and more preferably 2 to 4.

[0144] In formula (1f-d), md indicating the average degree of polymerization is a real number representing 1 to 13. When md is 1 to 13, the number average molecular weight of the fluorine-containing ether compound of the present embodiment tends to be within the preferred range. md is preferably 1 to 5, more preferably 1 to 3.

[0145] If R in formula (1) 3 and R 3 ' is any one of the formulas (1f-a) to (1f-d), a fluorine-containing ether compound can be used to obtain a lubricating layer having good lubricity. 3 and R 3'When each is any one of the PFPE chains represented by formulas (1f-a) to (1f-d), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) in the PFPE chain to the number of carbon atoms is appropriate. Therefore, a fluorinated ether compound having a moderate hardness is obtained. Therefore, the fluorinated ether compound applied to the protective layer is not easily agglomerated on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage. In addition, by making the fluorinated ether compound have moderate softness, a lubricating layer having better chemical resistance and wear resistance can be formed.

[0146] R 4 The divalent linking group represented by

[0147] In the fluorinated ether compound represented by formula (1), R 4 is a divalent linking group having 1 to 3 polar groups. When n is 1 or 2, R 4 Each is configured in R 3 and 1 or 2 R 3 ' represents the PFPE chains. Thus, R 4 The fluorine-containing ether compound is brought into close contact with the protective layer, and a thin lubricating layer is formed with a sufficient coverage.

[0148] In formula (1), the repeating unit [-CH 2 -R 4 -CH 2 -R 3 '] When the number n is 2, 2 R 4 They can be the same or different. 4 If the coating state of the protective layer with the fluorinated ether compound is the same, the coating state of the protective layer with the fluorinated ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed.

[0149] In this specification, when n is 2, "2 R 4 "Same" means: relative to the two R 3 ' wherein R is arranged at the center of the fluorine-containing ether compound represented by formula (1) 3 ', 2 R 4 The atoms contained in it have the same composition and are arranged symmetrically.

[0150] R 4 The divalent linking group represented by is preferably provided with oxygen atoms at both ends. 4 The methylene groups (-CH 2 These two ether bonds impart appropriate flexibility to the fluorinated ether compound represented by formula (1), making R 4 The polar group of the divalent linking group represented by has an increased affinity with the protective layer.

[0151] R 4 The number of carbon atoms contained in is preferably 3-9, more preferably 3-6.

[0152] R 4 The number of polar groups is 1 to 3, preferably 1 or 2, and more preferably 1. 4 When the number of polar groups is 2 or more, the types of the polar groups may be partially or entirely the same or may be different.

[0153] As R 4 The polar groups possessed include, for example, hydroxyl (-OH), amino (-NH 2 ), carboxyl (-COOH), aldehyde (-COH), carbonyl (-CO-), sulfonic acid (-SO 3 H) etc. Among them, the polar group is particularly preferably a hydroxyl group. The interaction between the hydroxyl group and the protective layer, especially the protective layer formed by the carbon-based material, is large. Therefore, if R 4 When the polar group has a hydroxyl group, the adhesion between the lubricating layer containing the fluorinated ether compound and the protective layer becomes higher. 4 At least one of the polar groups possessed by each includes a hydroxyl group, and more preferably both include a hydroxyl group.

[0154] Specifically, R 4 The following formula (1-1) is preferred. In formula (1-1), the oxygen atom on the left side is bonded to R 4 R of the two bonded methylene groups 2 The methylene on the side and the oxygen atom on the right are bonded to R 5 If R 4 The formula (1-1) is preferred because the synthesis of the fluorine-containing ether compound represented by the formula (1) is easier.

[0155]

[0156] (In formula (1-1), z is an integer from 1 to 3.)

[0157] In formula (1-1), z is an integer of 1 to 3, preferably an integer of 1 to 2, and most preferably 1. If z is 1, the number of hydroxyl groups of the fluorinated ether compound will not be too large, and the compound will have good hydrophobicity. As a result, the water intrusion that may cause corrosion of the magnetic recording medium can be effectively suppressed, and a lubricating layer having a high corrosion suppression effect on the magnetic recording medium can be formed.

[0158] It should be noted that in the present specification, the dot-dash lines in the formulas represent bonding ends to other structures.

[0159] R 2 and R 5 The divalent linking group represented by

[0160] In the fluorine-containing ether compound represented by formula (1), R 2 and R 5 is a divalent linking group having one or more polar groups. 2 In the R 1 The end of the bonding side has an oxygen atom, and R 1 In the case of an organic group, it is bonded to R 1 Bonding. 5 In the R 6 The end of the bonding side has an oxygen atom, and R 6 In the case of an organic group, it is bonded to R 6 In the fluorine-containing ether compound represented by formula (1), R 2 and R 5 Each of the polar groups has one or more polar groups, and therefore, when a lubricating layer is formed on the protective layer using a lubricant containing the polar groups, a suitable interaction occurs between the lubricating layer and the protective layer. 2 and R 5 It can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0161] R 2 With R 5 They can be the same or different. 2 With R 5 If the coating state of the protective layer with the fluorinated ether compound is the same, the coating state of the protective layer with the fluorinated ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed.

[0162] In this manual, “R 2 With R 5 "same" means that the skeleton (-R 3 [-CH 2 -R 4 -CH 2 -R 3 '] n -), R 2 The atoms contained in R 5 The atoms contained in it have the same composition and are arranged symmetrically.

[0163] R 2 and R 5 The number of carbon atoms contained in each is preferably 3-9, more preferably 3-6.

[0164] R 2 and R 5The number of polar groups each has is 1 or more, preferably 1 to 3, and more preferably 1 or 2. 2 and / or R 5 When the number of polar groups is 2 or more, the types of the polar groups may be partially or entirely the same or may be different.

[0165] As R 2 and R 5 The polar groups possessed include, for example, hydroxyl (-OH), amino (-NH 2 ), carboxyl (-COOH), aldehyde (-COH), carbonyl (-CO-), sulfonic acid (-SO 3 H) etc. Among them, the polar group is particularly preferably a hydroxyl group. The interaction between the hydroxyl group and the protective layer, especially the protective layer formed by the carbon-based material, is large. Therefore, if R 2 and / or R 5 When at least a part of the polar groups possessed by the fluorinated ether compound is a hydroxyl group, the adhesion between the lubricating layer containing the fluorinated ether compound and the protective layer becomes higher. 2 and R 5 All polar groups are hydroxyl groups.

[0166] In R 2 and / or R 5 When the polar group has a hydroxyl group, R in formula (1) 2 The hydroxyl groups contained in R 5 The total number of hydroxyl groups contained in is preferably 2 to 6, more preferably 2 to 4, and most preferably 2. When the total number of hydroxyl groups is 2 or more, R 2 and R 5 The interaction between the hydroxyl groups and the protective layer. As a result, a fluorine-containing ether compound is formed that can form a lubricating layer with high adhesion to the protective layer. In addition, if the total number of the above-mentioned hydroxyl groups is less than 6, the polar groups that are not involved in the bonding between the lubricating layer and the active sites on the protective layer become fewer. Therefore, it is possible to prevent the polar groups that are not involved in the bonding between the lubricating layer and the active sites on the protective layer from attracting environmental substances that generate pollutants and water that becomes the cause of corrosion of the magnetic recording medium to the lubricating layer. Therefore, a lubricating layer that can more effectively inhibit the contamination and corrosion of the magnetic recording medium can be formed. In addition, if the total number of the above-mentioned hydroxyl groups is less than 4, the fluidity of the lubricating layer containing the fluorine-containing ether compound is sufficiently high. Therefore, even if a part of the lubricating layer containing the fluorine-containing ether compound is deformed due to wear, the fluorine-containing ether compound in the lubricating layer moves to other parts, and the repairing power to return to the original position again is also high, and more excellent wear resistance can be obtained.

[0167] R 2 The divalent connecting group represented by1 The terminal of one side of the bond has an oxygen atom, and the other terminal (bonded to R 2 Adjacent CH 2 The end of R 5 The divalent connecting group represented by 6 The terminal of one side of the bond has an oxygen atom, and the other terminal (bonded to R 5 Adjacent CH 2 The end of R 1 and R 6 In the case of an organic group, it is arranged on R 2 and R 5 The oxygen atoms at both ends of the divalent linking group represented by the formula form ether bonds (-O-) with the atoms bonded to both sides thereof. These ether bonds impart appropriate flexibility to the fluorinated ether compound represented by the formula (1), making R 2 and R 5 The polar group of the divalent linking group represented by has an increased affinity with the protective layer.

[0168] Among the fluorine-containing ether compounds represented by formula (1), -R 2 - represented by -[B]-[A]-O-, -R 5 - is represented by -O-[C]-[D]-. That is, the fluorine-containing ether compound of the present embodiment is preferably represented by the following formula (1').

[0169] R 1 -[B]-[A]-O-CH 2 -R 3 [-CH 2 -R 4 -CH 2 -R 3 '] n -CH 2 -O-[C]-[D]-R 6 (1')

[0170] (In formula (1'), n, R 1 , R 3 , R 3 '、R 4 and R 6Same as formula (1). In formula (1'), [A] is represented by the following formula (1-2). a in formula (1-2) is an integer of 0 to 3. In formula (1'), [B] is represented by the following formula (1-3). b in formula (1-3) is an integer of 0 to 3, and c is an integer of 2 to 5. The total of a in formula (1-2) and b in formula (1-3) is 1 to 3. In formula (1'), [A] and [B] can be replaced. In formula (1'), [C] is represented by the following formula (1-4). d in formula (1-4) is an integer of 0 to 3. In formula (1'), [D] is represented by the following formula (1-5). e in formula (1-5) is an integer of 0 to 3, and f is an integer of 2 to 5. The total of d in formula (1-4) and e in formula (1-5) is 1 to 3. In formula (1'), [C] and [D] can be replaced.)

[0171]

[0172] -[B]-[A]-O- represented linking group

[0173] In the fluorinated ether compound of the present embodiment represented by formula (1'), [A] is represented by the above formula (1-2), and [B] is represented by the above formula (1-3). [A] and [B] in formula (1') are divalent linking groups. In formula (1'), [A] and [B] can be replaced. a in formula (1-2) and b in formula (1-3) are integers of 0 to 3. The total value of a and b is 1 to 3.

[0174] In formula (1-2) and formula (1-3), a combination in which a is 1 and b is 0, or a combination in which a is 0 and b is 1 is preferred from the viewpoint of availability of raw materials and ease of synthesis.

[0175] In addition, in formula (1-2) and formula (1-3), from the viewpoint of adhesion to the protective layer, a combination of 2 and b is 0, or a combination of 1 and b is 1 is preferred. In particular, when a is 2 and b is 0, the arrangement direction of the two hydroxyl groups in formula (1-2) becomes the same direction in stereo with respect to the extension direction of the PFPE chain in the fluorinated ether compound, and the two hydroxyl groups in formula (1-2) tend to be easily adsorbed to the protective layer. In addition, when a and b are 1 and the bonding order of [A] and [B] is from R 1 When the side is -[A]-[B]-O-, the distance between the hydroxyl groups contained in the -[A]-[B]- structure becomes greater. Therefore, the intramolecular hydrogen bond of the fluorinated ether compound represented by formula (1') can be reduced, thereby improving the adhesion to the protective layer.

[0176] In the formula (1-3), c is an integer of 2 to 5. When b is an integer of 1 to 3, c is preferably an integer of 2 to 4, and 2 is most preferred.

[0177] In formula (1'), [A] and R 1 In the case of direct bonding, R 1 Not a hydrogen atom (R 1 is an organic group having 1 to 50 carbon atoms). In this case, the carbon atom to which the hydroxyl group contained in -[B]-[A]-O- is bonded will not be directly bonded to the carbon atom to which the adjacent hydroxyl group is bonded. Therefore, the hydroxyl group contained in -[B]-[A]-O- is easily adsorbed to the protective layer.

[0178] -O-[C]-[D]- represented linking group

[0179] In the fluorinated ether compound of the present embodiment represented by formula (1'), [C] is represented by the above formula (1-4), and [D] is represented by the above formula (1-5). [C] and [D] in formula (1') are divalent linking groups. In formula (1'), [C] and [D] can be replaced. d in formula (1-4) and e in formula (1-5) are integers of 0 to 3. The total value of d and e is 1 to 3.

[0180] In formula (1-4) and formula (1-5), from the viewpoint of raw material availability and ease of synthesis, a combination in which d is 1 and e is 0, or a combination in which d is 0 and e is 1 is preferred.

[0181] In addition, in formula (1-4) and formula (1-5), from the viewpoint of adhesion to the protective layer, a combination in which d is 2 and e is 0, or a combination in which d is 1 and e is 1 is preferred. In particular, when d is 2 and e is 0, in the fluorinated ether compound, the arrangement direction of the two hydroxyl groups in formula (1-4) becomes the same direction in terms of the extension direction of the PFPE chain, and the two hydroxyl groups in formula (1-4) tend to be easily adsorbed to the protective layer. In addition, when d and e are 1 and the bonding order of [C] and [D] is from R 3 When the side is -O-[D]-[C]-, the distance between the hydroxyl groups contained in the -[D]-[C]- structure becomes greater. Therefore, the intramolecular hydrogen bond of the fluorine-containing ether compound represented by formula (1') can be reduced, thereby improving the adhesion to the protective layer.

[0182] In the formula (1-5), f is an integer of 2 to 5. When e is an integer of 1 to 3, f is preferably an integer of 2 to 4, and most preferably 2.

[0183] In formula (1'), [C] and R 6 In the case of direct bonding, R 6 Not a hydrogen atom (R 6is an organic group having 1 to 50 carbon atoms). In this case, the carbon atom to which the hydroxyl group contained in -O-[C]-[D]- is bonded will not be directly bonded to the carbon atom to which the adjacent hydroxyl group is bonded. Therefore, the hydroxyl group contained in -O-[C]-[D]- is easily adsorbed to the protective layer.

[0184] R 1 and R 6 The terminal group

[0185] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 The terminal groups represented by are each independently a hydrogen atom or an organic group having 1 to 50 carbon atoms. 1 With R 6 Can be the same or different. 1 and R 6 It can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0186] R 1 and R 6 The terminal groups represented by are each independently preferably any one of the following formulae (1-6), (1-7) and (1-8). 1 and R 6 Since the molecular weight is large, the ratio of fluorine atoms in the fluorine-containing ether compound molecule is reduced, and the increase in the surface free energy of the entire molecule can be suppressed.

[0187]

[0188] (In formula (1-6), g represents an integer of 2 to 6, and h represents 0 or 1. 7 is any one of a hydrogen atom, an alkyl group which may have a substituent not including a hydroxyl group, and an organic group having at least one double bond or triple bond. The alkyl group and the organic group may be straight chain or branched.

[0189] (In formula (1-7), i represents an integer of 1 to 6. R 8 and R 9 It is represented by formula (1-9). 8 With R 9 Can be the same or different.)

[0190] (In formula (1-8), j represents an integer of 0 to 6. k and L each independently represent an integer of 1 to 6. R 10 and R 11 is a hydrogen atom or is represented by the formula (1-9). 10 With R 11 Can be the same or different.)

[0191] (In formula (1-9), p represents an integer of 2 to 6, and q represents 1 or 2.)

[0192] The terminal group represented by formula (1-6)

[0193] In formula (1-6), g represents an integer of 2 to 6, and h represents 0 or 1. When h in formula (1-6) is 0, the proportion of fluorine atoms in the fluorine-containing ether compound molecule is reduced, which can more effectively suppress the increase in the surface free energy of the entire molecule. When h is 1, the ether bond contained in formula (1-6) imparts flexibility to the fluorine-containing ether compound represented by formula (1), thereby making it a compound that is more easily adsorbed to the protective layer. g is preferably an integer of 2 to 4, and more preferably 2 or 3. If g is 2 or 3, the proportion of fluorine atoms in the fluorine-containing ether compound molecule is reduced, which can suppress the increase in the surface free energy of the entire molecule.

[0194] R in formula (1-6) 7 is any one of a hydrogen atom, an alkyl group which may have a substituent not including a hydroxyl group, and an organic group having at least one double bond or triple bond. 7 In the case of a hydrogen atom, R 7 Together with the adjacent oxygen atom, it forms a hydroxyl group. In formula (1-6), h is 1 and R 7 When R represented by formula (1-6) is a hydrogen atom 1 and / or R 6 It is an alkyl group having a hydroxyl group at the terminal.

[0195] In R 7 When it is a hydrogen atom and h in the formula (1-6) is 1, R represented by the formula (1-6) 1 and / or R 6 Preferred specific examples include -CH 2 CH 2 -OH (g in formula (1-6) is 2), -CH 2 CH 2 CH 2 -OH (g in formula (1-6) is 3).

[0196] In R 7 In the case of an alkyl group which may have a substituent not including a hydroxyl group, it is preferably an alkyl group having 1 to 6 carbon atoms which does not have a substituent, or an alkyl group having 1 to 6 carbon atoms which has a substituent. The substituent possessed by the alkyl group having 1 to 6 carbon atoms which has a substituent is preferably a fluoro group, a cyano group, or a group having an amide bond, and does not contain a hydroxyl group. The alkyl group having 1 to 6 carbon atoms which has a substituent is a group in which one or more hydrogen atoms possessed by the alkyl group are replaced by a substituent, and may be a group in which all hydrogen atoms possessed by the alkyl group are replaced by substituents.

[0197] The alkyl group of the alkyl group having 1 to 6 carbon atoms and having no substituent and the alkyl group having 1 to 6 carbon atoms and having a substituent may be a straight chain or a branched chain. Specifically, examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl and its structural isomers, and n-hexyl and its structural isomers.

[0198] Examples of the alkyl group having 1 to 6 carbon atoms in which one or more hydrogen atoms are substituted by a fluorine group include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 2,2,2,2,2,2-hexafluoroisopropyl group, a 2,2,3,3,4,4,4-heptafluorobutyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, and a 2,2,3,3,4,4,5,5,6,6,6-undecafluorohexyl group.

[0199] The number of cyano groups in the alkyl group having 1 to 6 carbon atoms obtained by replacing one or more hydrogen atoms with a cyano group may be 1 or 2 or more. If the number of cyano groups is large, the polarity of the fluorine-containing ether compound becomes too high, so the number of cyano groups is preferably 2 or less, and most preferably 1.

[0200] Examples of the alkyl group having 1 to 6 carbon atoms in which one or more hydrogen atoms are substituted with a cyano group include 2-cyanoethyl, 3-cyanopropyl, 4-cyanobutyl, 5-cyanopentyl, 6-cyanohexyl, 2-cyano-1-methylethyl and 2,2'-dicyanoisopropyl.

[0201] The number of amide bonds in the alkyl group having 1 to 6 carbon atoms obtained by replacing one or more hydrogen atoms with a group having an amide bond may be 1 or 2 or more. If the number of amide bonds is large, the polarity of the fluorine-containing ether compound becomes too high, so the number of amide bonds is preferably 2 or less, and most preferably 1.

[0202] In an alkyl group having 1 to 6 carbon atoms obtained by replacing one or more hydrogen atoms with a group having an amide bond, the carbon atom of the alkyl group may be amide bonded to the amide bond (-NR 12 C(=O)-;R 12 The amide bond (-NR 12 C(=O)-;R 12 The connecting bond of the alkyl group (i.e., alkyl) is preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a trifluoromethyl group, etc., preferably a hydrogen atom or a methyl group. 12 In the case of an organic group, R 12, for example, methyl, ethyl, propyl, butyl and the like can be mentioned.

[0203] Specific examples of the alkyl group having 1 to 6 carbon atoms in which one or more hydrogen atoms are substituted with a group having an amide bond include -(CH 2 ) r NHC(=O)CH 3 and-(CH 2 ) r C(=O)NH 2 In the formula, r is an integer of 1 to 6.

[0204] The organic group having at least one double bond or triple bond is preferably any one of an organic group having 6 to 12 carbon atoms having an aromatic hydrocarbon, an organic group having 3 to 10 carbon atoms having an aromatic heterocycle, an alkenyl group having 2 to 8 carbon atoms, and an alkynyl group having 3 to 8 carbon atoms. The organic group having at least one double bond or triple bond may be linear or branched.

[0205] Examples of the organic group having 6 to 12 carbon atoms and having an aromatic hydrocarbon include phenyl, methoxyphenyl, dimethoxyphenyl, cyanophenyl, dicyanophenyl, fluorophenyl, naphthyl, methoxynaphthyl, benzyl, methoxybenzyl, phenethyl, methoxyphenethyl, fluorophenethyl, naphthylmethyl, and naphthylethyl. When the aromatic hydrocarbon has a substituent, the substituent may be bonded to any position.

[0206] Examples of the organic group having 3 to 10 carbon atoms and having an aromatic heterocyclic ring include pyrrolyl, pyrazolyl, methylpyrazolylmethyl, imidazolyl, furanyl, furfuryl, oxazolyl, isoxazolyl, thienyl, thienylmethyl, thienylethyl, thiazolyl, methylthiazolylethyl, isothiazolyl, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, indolyl, benzofuranyl, benzothienyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, benzopyrazolyl, benzisoxazolyl, benzisothiazolyl, quinolyl, isoquinolyl, quinazolinyl, quinoxalinyl, phthalazinyl and cinnolinyl.

[0207] Examples of the alkenyl group having 2 to 8 carbon atoms include vinyl, allyl, 1-propenyl, isopropenyl, 3-butenyl and structural isomers thereof, 4-pentenyl and structural isomers thereof, 5-hexenyl and structural isomers thereof, 6-heptenyl and structural isomers thereof, and 7-octenyl and structural isomers thereof.

[0208] Examples of the alkynyl group having 3 to 8 carbon atoms include 1-propynyl, propargyl, 3-butynyl and structural isomers thereof, 4-pentynyl and structural isomers thereof, 5-hexynyl and structural isomers thereof, 6-heptynyl and structural isomers thereof, and 7-octynyl and structural isomers thereof.

[0209] From the viewpoint of availability and / or ease of synthesis, R in formula (1-6) 7 It is preferably one group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 2,2,2,2,2,2-hexafluoroisopropyl group, a 2-cyanoethyl group, a 3-cyanopropyl group, a 4-cyanobutyl group, a phenyl group, a methoxyphenyl group, a cyanophenyl group, a phenethyl group, a thienylethyl group, an N-methylpyrazolylmethyl group, an allyl group, a 3-butenyl group, a 4-pentenyl group, a propargyl group, a 3-butynyl group, and a 4-pentynyl group. Among them, it is more preferably one group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 3-cyanopropyl group, a 4-cyanobutyl group, a methoxyphenyl group, a cyanophenyl group, an allyl group, and a 3-butenyl group.

[0210] The terminal groups represented by formula (1-7) and (1-8)

[0211] In formula (1-7), i represents an integer of 1 to 6. In order to easily ensure the ratio of fluorine atoms in the fluorine-containing ether compound molecule, i is preferably an integer of 1 to 4, and more preferably 1 or 2. 8 and R 9 It is represented by formula (1-9). 8 With R 9 Can be the same or different.

[0212] In formula (1-8), j represents an integer of 0 to 6. In order to easily ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule, j is preferably an integer of 0 to 4, and more preferably an integer of 0 to 2. k and L each independently represent an integer of 1 to 6. In order to easily ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule, k and L each independently represent an integer of 1 to 4, and more preferably 1 or 2. k and L may be the same or different. In order to easily produce the fluorine-containing ether compound, k and L are preferably the same. R 10 and R 11 is a hydrogen atom or is represented by the formula (1-9). 10 With R 11 Can be the same or different.

[0213] Partial structure represented by formula (1-9)

[0214] In formula (1-9), p represents an integer of 2 to 6. In order to easily ensure the ratio of fluorine atoms in the fluorine-containing ether compound molecule, p is preferably an integer of 2 to 4, and more preferably 2 or 3. q represents 1 or 2. When q is 2, each [-(CH 2 ) pIn the above formula (a), p may be the same as or different from p. In order to easily ensure the ratio of fluorine atoms in the fluorine-containing ether compound molecule, q is preferably 1.

[0215] In the fluorine-containing ether compound of this embodiment, R in the formula (1) 1 -R 2 -with-R 5 -R 6 In other words, the fluorine-containing ether compound represented by the formula (1) preferably has a symmetrical structure at both ends.

[0216] When n is 1, R 1 -R 2 -with-R 5 -R 6 For the same structure, and R 3 and R 3 ' represents the same PFPE chain. In addition, when n is 2, preferably R 1 -R 2 -with-R 5 -R 6 For the same structure, and R 3 and 2 R 3 ' indicates the same PFPE chain, 2 R 4 The divalent linking group represented by is the same. This is because such fluorine-containing ether compounds can be easily manufactured and the manufacturing cost is low. It should be noted that the so-called R 3 and 1 or 2 R 3 The term "same" also includes the case where the structures of the repeating units of the PFPE chains are the same but the average polymerization degrees are different.

[0217] The number average molecular weight (Mn) of the fluorine-containing ether compound of the present embodiment is preferably in the range of 500 to 10,000, more preferably in the range of 700 to 7,000, and still more preferably in the range of 800 to 4,000.

[0218] If the number average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of the present embodiment is not easy to evaporate. Therefore, if the number average molecular weight is 500 or more, it becomes a fluorine-containing ether compound that can form a lubricating layer that is not easy to stick and fall off. In addition, if the number average molecular weight is 10000 or less, the viscosity of the fluorine-containing ether compound will not become too high, and it becomes a viscosity suitable for use as a lubricant. In order to become a viscosity that is easy to handle when applied to a lubricant, the number average molecular weight of the fluorine-containing ether compound is more preferably 4000 or less.

[0219] The number average molecular weight of the fluorinated ether compound of the present embodiment is particularly preferably in the range of 1000 to 3000. The lubricating layer containing the fluorinated ether compound having a number average molecular weight in the range of 1000 to 3000 does not deteriorate in coverage even if the film thickness is thin, and becomes a lubricating layer with excellent chemical resistance and wear resistance. The fluorinated ether compound having a number average molecular weight in such a range has the best balance of performance from the viewpoint of suppressing adhesion and detachment in the lubricating layer containing it and thinning the lubricating layer.

[0220] The so-called "the proportion of molecules of the same molecular weight contained in the fluorinated ether compound is 90% or more, measured by the peak area ratio based on high performance liquid chromatography" can also be stated as follows: relative to 100% of the fluorinated ether compound represented by formula (1), the proportion of molecules represented by formula (1s) is 90% or more, measured by the peak area ratio based on high performance liquid chromatography.

[0221] R 1 -R 2 -CH 2 -R 3 s [-CH 2 -R 4 -CH 2 -R 3s '] n -CH 2 -R 5 -R 6 (1s)

[0222] (In formula (1s), the same symbols as those in formula (1) represent the same structures or values ​​as those in formula (1). 3s and R 3s 'Each independently represents a perfluoropolyether chain represented by formula (1f-1).

[0223] -Af 2 -O-(Af 1 -O) s -Af 3 -(1f-1)

[0224] (In formula (1f-1), the same symbols as those in formula (1f) represent the same structures as those in formula (1f). s represents the degree of polymerization and is an integer of 1 to 13.)

[0225] In formula (1s), the same symbols as those in formula (1) represent the same structure or value as those in formula (1), and the specific examples thereof are the same as those described for formula (1). In formula (1f-1), the same symbols as those in formula (1f) represent the same structure as those in formula (1f), and the specific examples thereof are the same as those described for formula (1f).

[0226] s in formula (1f-1) is an integer of 1 to 13. Therefore, the "ratio of molecules represented by formula (1s)" refers to the ratio of (Af 1 -O) represents the ratio of molecules with a single number of repetitions (degree of polymerization) of the repeating unit.

[0227] The higher the ratio, the more molecules with a single degree of polymerization there are, and the fewer molecules with different degrees of polymerization there are. Such molecules can be obtained by making the (Af 1 -O) is prepared by making the number of repetitions (polymerization degree) of the repeating unit represented by a single unit.

[0228] [Lubricant for magnetic recording media]

[0229] The lubricant for magnetic recording media according to the present embodiment contains the fluorine-containing ether compound represented by the above formula (1).

[0230] The fluorine-containing ether compound represented by formula (1) has R 3 and R 3 The perfluoropolyether chain is represented by '. The perfluoropolyether chain is as shown in formula (1f), having (Af 1 Therefore, even if the fluorine-containing ether compound represented by formula (1) has a single structure (in other words, even if R 1 , R 2 , R 3 , R 4 , R 3 '、R 5 , R 6 The structure and value of n are the same), according to the (Af 1 The number of repetitions (polymerization degree) of the repeating unit represented by the formula (-O) also causes variations in the molecular weight of the molecules contained in the fluorinated ether compound represented by the formula (1).

[0231] This is because the production of (Af 1 It is difficult to define a completely single compound until the number of repetitions of the repeating unit represented by (i)-(2-(0)). However, in the properties such as molecular weight distribution in the past, it is difficult to fully define the deviation of the molecular weight. Therefore, in the present invention, the fluorine-containing ether compound with less deviation of the molecular weight is defined based on the peak area ratio of high performance liquid chromatography.

[0232] In the present embodiment, in the fluorinated ether compound represented by formula (1), the ratio of molecules of the same molecular weight is 90% or more in terms of the peak area ratio based on high performance liquid chromatography. Therefore, (Af 1 The number of repetitions (polymerization degree) of the repeating unit represented by (-O) is approximately uniform, and the variation in molecular weight is very small.

[0233] In other words, the ratio of the molecule represented by formula (1s) to 100% of the fluorinated ether compound represented by formula (1) is 90% or more in terms of the peak area ratio based on high performance liquid chromatography. 1 The number of repetitions (polymerization degree) of the repeating unit represented by (-O) is approximately uniform, and the variation in molecular weight is very small.

[0234] The lubricant for magnetic recording media of this embodiment preferably does not substantially contain other materials used as lubricants (compounds other than the fluorinated ether compound represented by formula (1), and fluorinated ether compounds represented by formula (1) but having a structure different from the main component), and is further preferably composed of a fluorinated ether compound represented by formula (1).

[0235] The content of other materials in the lubricant is preferably below 5 mass %, more preferably below 3 mass %, and further preferably below 1 mass %. That is, the lubricant for magnetic recording media of the present embodiment, the content of the fluorinated ether compound represented by the formula (1) as the main component is preferably above 95 mass %, more preferably above 97 mass %.

[0236] [Method for producing lubricant for magnetic recording medium]

[0237] The method for producing a lubricant for a magnetic recording medium of the present embodiment preferably includes a step of synthesizing a fluorinated ether compound represented by formula (1) using a fluorinated polyalkylene glycol represented by the following formula (1f') as a raw material. The ratio of molecules of the same molecular weight contained in the fluorinated polyalkylene glycol represented by formula (1f') is 90% or more in terms of peak area ratio based on high performance liquid chromatography.

[0238] HO-CH 2 -Af 2 -O-(Af 1 -O) m -Af 3 -CH 2 -OH(1f')

[0239] (In formula (1f'), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). In formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R 3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 'The corresponding fluorinated polyalkylene glycol. )

[0240] The term "m" in formula (1f') "corresponds to formula (1f)" means that m in formula (1f') representing the average degree of polymerization is roughly the same as m in formula (1f) representing the average degree of polymerization, and is not limited to being identical in value. This is because deviations in the average degree of polymerization may occur before and after the step of synthesizing the fluorinated ether compound represented by formula (1). Similarly, in the following formulas, the term "corresponding" between the average degrees of polymerization in the two formulas means being roughly identical, and is not limited to being identical in value.

[0241] In the method for manufacturing a lubricant for magnetic recording media of this embodiment, a fluorinated polyalkylene glycol represented by formula (1f') in which the ratio of molecules with the same molecular weight is more than 90% is used as a raw material, thereby the fluorinated ether compound represented by formula (1) finally obtained also becomes a fluorinated ether compound in which the ratio of molecules with the same molecular weight is more than 90%.

[0242] In the past, in known lubricants, the proportion of molecules of the same molecular weight of fluorinated polymers contained was about 15-20% at most. This is because the PFPE polymer used as a raw material has a wide molecular weight distribution. As methods for adjusting the molecular weight distribution of fluorinated polymers, distillation, liquid separation extraction, column chromatography, supercritical extraction and other methods can be considered. However, the difference in physical properties of fluorinated polymers due to differences in the number of repetitions is small, and from the perspective of purification costs, it is difficult to increase the proportion of molecules of the same molecular weight to more than 90%.

[0243] The fluorinated polyalkylene glycol represented by the formula (1f') is preferably synthesized by a method including the following steps (A) to (C).

[0244] Step (A), liquid phase fluorination of a polyalkylene glycol represented by the following formula (2) having both ends protected and having a ratio of molecules of the same molecular weight of 90% or more in the peak area ratio based on high performance liquid chromatography;

[0245] Step (B), reacting the obtained fluorination reaction product represented by the following formula (3) with an alcohol having 1 to 6 carbon atoms,

[0246] In step (C), the obtained double-terminal esterified product represented by the following formula (4) is subjected to a reduction reaction.

[0247] A 4 -O-(A 1 -O) x -A 5 (2)

[0248] (In formula (2), A 1 represents a divalent hydrocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 In the case of a linear chain structure, (A 1 -O) are all identical.1 In the case of a branched structure, a part (A 1 -O) in each repeating unit represented by 1 The arrangement direction of A is alternating left and right. x represents the average degree of polymerization, which is a real number from 3 to 15. 4 and A 5 Each independently represents a protecting group for a hydroxyl group. )

[0249] F-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-F (3)

[0250] (In formula (3), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f).

[0251] A 6 O-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-OA 7 (4)

[0252] (In formula (4), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). 6 and A 7 Each independently represents an alkyl group having 1 to 6 carbon atoms. )

[0253] <Pre-process of process (A)>

[0254] The double-terminal protected polyalkylene glycol represented by formula (2) used in step (A) and having a ratio of molecules of the same molecular weight in the peak area ratio based on high performance liquid chromatography of 90% or more is not particularly limited, but is preferably a double-terminal protected polyalkylene glycol synthesized by, for example, the polyether synthesis step described later.

[0255] The polyalkylene glycol represented by formula (2) can be prepared by converting the hydroxyl groups at both ends of the polyalkylene glycol represented by formula (2') in which the ratio of molecules of the same molecular weight in the peak area ratio based on high performance liquid chromatography is 90% or more to A in formula (2). 4 and A 5 The polyalkylene glycol represented by the formula (2') is also preferably a polyalkylene glycol synthesized by the following polyether synthesis step.

[0256] HO-(A 1 -O) x -H(2')

[0257] (In formula (2'), A 1 and x corresponds to formula (2).

[0258] [Polyether synthesis process]

[0259] The method for producing a lubricant for a magnetic recording medium of the present embodiment preferably includes the following step: before step (A), performing a nucleophilic substitution reaction of reacting two or more compounds having a polyether chain or a monomer unit constituting a polyether chain to synthesize a lubricant having (A) 1 By such a synthesis step, a polyether compound having a molecular weight ratio of 90% or more (for example, a polyalkylene glycol having both ends protected represented by formula (2) or a polyalkylene glycol represented by formula (2')) can be obtained. Therefore, a compound having a molecular weight ratio of 90% or more among the fluorinated ether compounds represented by formula (1) can be obtained.

[0260] In the polyether synthesis step, specifically, by carrying out any one of the following "reaction 1", "reaction 2" and "reaction 3", or by combining a plurality of reactions from "reaction 1", "reaction 2" and "reaction 3", a polyether compound having a ratio of molecules of the same molecular weight of 90% or more in the peak area ratio based on high performance liquid chromatography can be synthesized.

[0261] The number of times the reaction selected from "Reaction 1", "Reaction 2" and "Reaction 3" is performed may be adjusted according to the structure of the polyether compound to be synthesized and the structure of the compound having a polyether chain (or a monomer unit constituting a polyether chain) used in the reaction. When a plurality of reactions selected from "Reaction 1", "Reaction 2" and "Reaction 3" are combined and performed, the order of the reactions is not particularly limited.

[0262] "Reaction 1"

[0263] In Reaction 1, a compound having a leaving group at one end of a polyether chain (or a monomer unit constituting a polyether chain) and a protected hydroxyl group at the other end (hereinafter, sometimes referred to as a "compound having a leaving group at one end") and a compound having a hydroxyl group at one end of a polyether chain (or a monomer unit constituting a polyether chain) and a protected hydroxyl group at the other end (hereinafter, sometimes referred to as a "protected diol compound") are reacted to extend the polyether chain.

[0264] The compound having a leaving group at one end and the protected diol compound can be reacted at a molar ratio of about 1:1 to extend the polyether chain at one end of the protected diol compound. Specifically, for example, a compound represented by formula (G) can be used as a compound having a leaving group at one end, and a compound represented by formula (H) can be used as a protected diol compound to extend the polyether chain to obtain a polyether compound represented by formula (G+H).

[0265] L 1 -(A 1g -O) g -A 8 (G)

[0266] (-(A 1g -O) g - is -O-(A 1 -O) x - indicates a part of the structure. 1 A represents a leaving group. 8 represents a protective group for a hydroxyl group. g is an integer greater than 1.)

[0267] HO-(A 1h -O) h -A 9 (H)

[0268] (-(A 1h -O) h - is -O-(A 1 -O) x - indicates a part of the structure. 9 represents a protective group for a hydroxyl group. h is an integer greater than 1.)

[0269] A 8 -(OA 1g ) g -O-(A 1h -O) h -A 9 (G+H)

[0270] (The definitions of symbols are the same as those in formula (G) and formula (H).)

[0271] As the leaving group in the compound having a leaving group at one end, for example, a halide group, a p-toluenesulfonyloxy (toluenesulfonyloxy) group, a methanesulfonyloxy (methylsulfonyloxy) group, a trifluoromethanesulfonyloxy (trifuranyloxy) group, a nonafluorobutanesulfonyloxy group, a fluorosulfonyloxy group, a chloromethanesulfonyloxy group, a bromobenzenesulfonyloxy group, etc. can be used.

[0272] As the protecting group for protecting the hydroxyl group in the diol compound, the following can be used as A in the formula (2): 4 and A 5 The protecting groups are exemplified.

[0273] The polyether compound obtained by "Reaction 1" has at each end a protected hydroxyl group from a terminal not participating in the reaction in a compound having a leaving group at one terminal, and a protected hydroxyl group from a terminal not participating in the reaction in a protected diol compound. The polyether compound obtained by "Reaction 1" can be used directly as a polyalkylene glycol with both ends protected as represented by formula (2), or a compound obtained by deprotecting one or both of the protected hydroxyl groups and then protecting the hydroxyl groups with other protecting groups can be used as a polyalkylene glycol with both ends protected as represented by formula (2). In addition, after deprotecting one or both of the protected hydroxyl groups in the polyether compound obtained by "Reaction 1", "Reaction 2" or "Reaction 3" can be continued to further extend the polyether chain.

[0274] "Reaction 2"

[0275] In reaction 2, a compound having a leaving group at one end of a polyether chain (or a monomer unit constituting a polyether chain) and a protected hydroxyl group at the other end (a compound having a leaving group at one end) and a compound having hydroxyl groups at both ends of a polyether chain (or a monomer unit constituting a polyether chain) (hereinafter sometimes referred to as a "diol compound") are reacted to extend the polyether chain.

[0276] The compound having a leaving group at one end can be reacted with the diol compound at a molar ratio of about 2:1 to extend the polyether chain at both ends of the diol compound. Specifically, for example, the compound represented by the above formula (G) can be used as the compound having a leaving group at one end, and the compound represented by the formula (I) can be used as the diol compound to extend the polyether chain to obtain a polyether compound represented by the formula (2G+I).

[0277] HO-(A 1i -O) i -H(I)

[0278] (-(A 1i -O) i - is -O-(A 1 -O) x - represents a part of the structure. i is an integer greater than 1. )

[0279] A 8 -(OA 1g ) g -O-(A 1i-O) i -(A 1g -O) g -A 8 (2G+I)

[0280] (The definitions of symbols are the same as those in formula (G) and formula (I).)

[0281] The polyether compound obtained by "Reaction 2" has protected hydroxyl groups at both ends which are derived from the terminal that does not participate in the reaction in the compound having a leaving group at one end. The polyether compound obtained by "Reaction 2" can be used directly as the polyalkylene glycol with both ends protected represented by formula (2), or a compound obtained by deprotecting one or both of the protected hydroxyl groups and then protecting the hydroxyl groups with other protecting groups can be used as the polyalkylene glycol with both ends protected represented by formula (2). In addition, after deprotecting one or both of the protected hydroxyl groups in the polyether compound obtained by "Reaction 2", "Reaction 1", "Reaction 2" or "Reaction 3" can be continued to further extend the polyether chain.

[0282] "Reaction 3"

[0283] In reaction 3, a compound having a hydroxyl group at one end of a polyether chain (or a monomer unit constituting a polyether chain) and a protected hydroxyl group at the other end (protected diol compound) and a compound having leaving groups at both ends of a polyether chain (or a monomer unit constituting a polyether chain) (hereinafter sometimes referred to as "a compound having leaving groups at both ends") are reacted to extend the polyether chain.

[0284] The protected diol compound and the compound having leaving groups at both ends can be reacted at a molar ratio of about 2:1 to extend the polyether chain at both ends of the compound having leaving groups at both ends. Specifically, for example, the compound represented by the above formula (H) can be used as the protected diol compound, and the compound represented by the formula (J) can be used as the compound having leaving groups at both ends to extend the polyether chain to obtain a polyether compound represented by the formula (2H+J).

[0285] L 2 -(A 1j -O) j -A 1j -L 3 (J)

[0286] (-(A 1j -O) j -A 1j - is -O-(A 1 -O) x - indicates a part of the structure. 2 and L3 Each independently represents a leaving group. j is an integer greater than 0. )

[0287] A 9 -(OA 1h ) h -O-(A 1j -O) j -A 1j -O-(A 1h -O) h -A 9 (2H+J)

[0288] (The definitions of symbols are the same as those in formula (H) and formula (J).)

[0289] As the leaving group in the compound having a leaving group at both terminals, the leaving groups exemplified as the leaving group in the compound having a leaving group at one terminal can be used.

[0290] The polyether compound obtained by "Reaction 3" has protected hydroxyl groups at both ends, which are derived from the ends of the protected diol compound that do not participate in the reaction. The polyether compound obtained by "Reaction 3" can be used directly as the polyalkylene glycol with both ends protected represented by formula (2), or a compound obtained by deprotecting one or both of the protected hydroxyl groups and then protecting the hydroxyl groups with other protecting groups can be used as the polyalkylene glycol with both ends protected represented by formula (2). In addition, after deprotecting one or both of the protected hydroxyl groups in the polyether compound obtained by "Reaction 3", "Reaction 1", "Reaction 2" or "Reaction 3" can be continued to further extend the polyether chain.

[0291] The polyether compound obtained by the polyether synthesis step may have hydroxyl groups at both ends, and the hydroxyl groups at one or both ends may be protected by a protecting group. The protecting group of the hydroxyl group may be the same protecting group as the two-end protected polyalkylene glycol represented by formula (2), or may be another protecting group. In the case where the two ends of the polyether compound obtained by the polyether synthesis step are the same protecting groups as the two-end protected polyalkylene glycol represented by formula (2), it can be used directly in step (A). In the case where the two ends of the polyether compound are hydroxyl groups, and the hydroxyl groups of the polyether compound are protected by a protecting group different from that of the two-end protected polyalkylene glycol represented by formula (2), it can be used in step (A) after a step of protecting the hydroxyl groups with the same protecting group as that of the two-end protected polyalkylene glycol represented by formula (2) is carried out.

[0292] <Step (A)>

[0293] In the method for producing a lubricant for magnetic recording media of the present embodiment, step (A) is a step of liquid phase fluorination of a polyalkylene glycol represented by formula (2) having both ends protected and having a ratio of molecules of the same molecular weight of 90% or more in the peak area ratio based on high performance liquid chromatography.

[0294] A 4 -O-(A 1 -O) x -A 5 (2)

[0295] In formula (2), A 1 represents a divalent hydrocarbon group having a linear or branched structure and having 2 to 5 carbon atoms. 1 According to the Af in the fluorinated polyalkylene glycol represented by the formula (1f') to be obtained 1 As A 1 Specific examples include, for example, -CH 2 -CH 2 -、-CH 2 -CH 2 -CH 2 -、-CH 2 -CH(CH 3 )-、-CH(CH 3 )-CH 2 -、-CH 2 -CH 2 -CH 2 -CH 2 -、-CH(CH 3 )-CH 2 -CH 2 -、-CH 2 -CH(CH 3 )-CH 2 -、-CH 2 -CH 2 -CH(CH 3 )-、-CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -、-CH(CH 3 )-CH 2 -CH 2 -CH 2 -、-CH 2 -CH(CH 3 )-CH 2 -CH 2 -、-CH 2 -CH 2 -CH(CH3 )-CH 2 -、-CH 2 -CH 2 -CH 2 -CH(CH 3 )-、-CH(CH 3 )-CH 2 -CH(CH 3 )-.

[0296] In formula (2), in A 1 In the case of a linear chain structure, (A 1 -O) in each repeating unit represented by 1 All the same, in A 1 In the case of a branched structure, a part (A 1 -O) in each repeating unit represented by 1 The arrangement direction of A is alternating left and right. 1 In the case of a branched chain structure, (A 1 The bonding pattern between the repeating units represented by (-O) is not limited to head-to-tail bonding, but may include head-to-head bonding and tail-to-tail bonding.

[0297] A 4 and A 5 Each independently represents a protective group for a hydroxyl group. Examples of the protective group for a hydroxyl group include an acyl group, an alkoxycarbonyl group, a silyl group, and an alkyl group which may have a substituent. 4 With A 5 They can be the same or different. 4 With A 5 The same is preferred because synthesis is easy.

[0298] The acyl group is preferably -(C=O)-R 13 (R in the formula 13 The hydrocarbon group more preferably has 1 to 3 carbon atoms.

[0299] In R 13 In the case of an alkyl group having 1 to 8 carbon atoms which may have a substituent, the alkyl group may be linear or branched. Examples of the substituent include an alkoxy group, a fluoro group, a chloro group, and a bromo group.

[0300] In R 13 In the case of an aryl group having 1 to 8 carbon atoms which may have a substituent, examples of the substituent include an alkoxy group, a fluoro group, a chloro group, a bromo group, an acetoxy group, and a nitro group.

[0301] Specific examples of the acyl group include formyl, acetyl, ethoxyacetyl, fluoroacetyl, difluoroacetyl, trifluoroacetyl, chloroacetyl, dichloroacetyl, trichloroacetyl, bromoacetyl, dibromoacetyl, tribromoacetyl, propionyl, 2-chloropropionyl, 3-chloropropionyl, pentafluoropropionyl, butyryl, 2-chlorobutyryl, 3-chlorobutyryl, 4-chlorobutyryl, 2-methylbutyryl, 2-ethylbutyryl, heptafluorobutyryl, valeryl, 2-methylvaleryl, 4-methylvaleryl, perfluorovaleryl, hexanoyl, perfluorohexanoyl, Acyl, heptanoyl, perfluoroheptanoyl, octanoyl, perfluorooctanoyl, nonanoyl, perfluorononanoyl, isobutyryl, isovaleryl, pivaloyl, benzoyl, o-chlorobenzoyl, m-chlorobenzoyl, p-chlorobenzoyl, o-acetoxybenzoyl, m-acetoxybenzoyl, p-acetoxybenzoyl, o-methoxybenzoyl, m-methoxybenzoyl, p-methoxybenzoyl, o-nitrobenzoyl, m-nitrobenzoyl, p-nitrobenzoyl, o-fluorobenzoyl, m-fluorobenzoyl, p-fluorobenzoyl, pentafluorobenzoyl, etc.

[0302] Specific examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a 2,2,2-trichloroethoxycarbonyl group, and an allyloxycarbonyl group.

[0303] Specific examples of the silyl group include a trimethylsilyl group, a triethylsilyl group, a tert-butyldimethylsilyl group, and a tert-butyldiphenylsilyl group.

[0304] Examples of the alkyl group which may have a substituent include an alkyl group having a substituent selected from an alkoxy group, an aryl group, and a halogenated acyl group, an alkyl group having no substituent, etc. The number of carbon atoms in the alkyl group is not particularly limited, and an alkyl group having 1 to 8 carbon atoms is usually used.

[0305] Specific examples of the alkyl group having an alkoxy group include methoxymethyl, methoxyethoxymethyl, 1-ethoxyethyl, etc. The alkyl group having an alkoxy group may be a cyclic ether that forms an acetal structure or a ketal structure together with the oxygen atom derived from the hydroxyl group in formula (2), and specific examples thereof include 2-tetrahydropyranyl, etc.

[0306] Specific examples of the alkyl group having an aryl group include a benzyl group, a trityl group, an o-methoxybenzyl group, a m-methoxybenzyl group, and a p-methoxybenzyl group.

[0307] Specific examples of the alkyl group having a halogenated acyl group include -CH 2 C(=O)F, -CH 2 C(=O)Cl, -CH 2 CH 2 C(=O)F, -CH 2 CH 2C(=O)Cl, -CH 2 CH 2 CH 2 C(=O)F, -CH 2 CH 2 CH 2 C(=O)Cl, etc.

[0308] Specific examples of the unsubstituted alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a tert-butyl group.

[0309] Among the above, A 4 and A 5 More preferred is an acyl group, further preferred is an acetyl group, a trifluoroacetyl group, a propionyl group, a pentafluoropropionyl group, a butyryl group, or a heptafluorobutyryl group, and particularly preferred is an acetyl group or a trifluoroacetyl group.

[0310] Using the polyalkylene glycol with both ends protected represented by the above formula (2) (hereinafter sometimes referred to as "raw material compound"), an inert gas, a fluorine gas and a solvent are introduced into a reactor to carry out liquid phase fluorination.

[0311] The equivalent of the fluorine gas introduced into the reactor is preferably 1.0 to 5.0 equivalents relative to the molar number of hydrogen atoms contained in the raw material compound, and more preferably 1.1 to 3.0 equivalents. If the equivalent of the fluorine gas is 1.0 equivalents or more relative to the molar number of hydrogen atoms contained in the raw material compound, it is easy to fully carry out the fluorination reaction. If the equivalent of the fluorine gas is 5.0 equivalents or less relative to the molar number of hydrogen atoms contained in the raw material compound, it is possible to prevent the unconsumed fluorine gas from becoming wasted.

[0312] The concentration of the fluorine gas circulated in the reactor is preferably 1 to 30 volume %, more preferably 10 to 20 volume %, based on the total amount of circulating gas (fluorine gas + inert gas). If the fluorine gas concentration is more than 1 volume %, it is possible to prevent the reaction rate from decreasing and the reaction time from becoming longer. If the fluorine gas concentration is less than 30 volume %, it is possible to prevent the runaway of the reaction and the occurrence of side reactions. The pressure in the reactor when fluorine gas is introduced is preferably 0.08 to 0.12 MPa, more preferably normal pressure (0.1 MPa) to 0.115 MPa. If the above-mentioned pressure is less than 0.12 MPa, it is possible to prevent the runaway of the reaction and the occurrence of side reactions.

[0313] The inert gas is circulated in the reactor in such a manner that the fluorine gas concentration is within the above range. The inert gas and the fluorine gas can be introduced using different systems, or a mixed gas obtained by diluting the fluorine gas with the inert gas in advance can be introduced into the reactor. As the inert gas, nitrogen, helium, argon, etc. are preferred from the perspective of ease of acquisition and operation.

[0314] The solvent used in the fluorination reaction is not particularly limited, but is preferably a solvent with high solubility of the raw material compound and the fluorination reaction product as the product, more preferably a solvent that does not react with the raw material compound, the product and the fluorine gas. Specifically, it is preferably a solvent that is completely substituted by halogen and does not contain a carbon-carbon unsaturated bond. The solvent that is completely substituted by halogen and does not contain a carbon-carbon unsaturated bond does not contain a CH bond and a carbon-carbon unsaturated bond, therefore, there is no situation where the CH bond or carbon-carbon unsaturated bond in the solvent reacts with the fluorine gas, and the increase in the amount of fluorine gas used and the temperature rise caused by the heat of reaction can be prevented. In addition, the decomposition reaction of the raw material compound will not occur due to the hydrogen fluoride generated when the CH bond reacts with the fluorine gas, so it is preferred.

[0315] Examples of the solvent used in the fluorination reaction include perhalogenated alkanes, perhalogenated polyethers, perhalogenated carboxylic acids or anhydrides thereof, etc. The solvent may be used alone or in combination of two or more.

[0316] The perhalogenated alkane is preferably a perhalogenated alkane having 2 to 8 carbon atoms. From the viewpoint of solubility of the raw material compound, the perhalogenated alkane is more preferably a perhalogenated alkane containing fluorine atoms and chlorine atoms, and examples thereof include dichlorotetrafluoroethane, trichlorotrifluoroethane, dichlorohexafluoropropane, and tetrachlorohexafluorobutane.

[0317] Examples of commercially available perhalogenated polyethers include DEMNUM (registered trademark) manufactured by DYKIN INDUSTRY CO., LTD., FLUORINERT (registered trademark) manufactured by SLEEM, GALDEN (registered trademark) manufactured by Solbispace Polymers, and KRYTOX (registered trademark) manufactured by Kemmers.

[0318] Examples of the perhalogenated carboxylic acid or anhydride thereof include trifluoroacetic acid and trifluoroacetic anhydride.

[0319] The solvent used in the fluorination reaction is preferably introduced into the reactor before the raw material compound is introduced. In addition, before the raw material compound is introduced, it is preferred to flow an inert gas and fluorine gas into the reactor in advance to saturate the solvent with fluorine gas.

[0320] As the introduction method of the raw material compound, it is preferably the following method: prepare a raw material solution obtained by dissolving the raw material compound in a solvent, and supply the raw material solution to the reactor while circulating inert gas and fluorine gas in the reactor. As the solvent for dissolving the raw material compound, the solvent exemplified as the solvent used in the fluorination reaction can be used, preferably the same as the solvent used in the fluorination reaction.

[0321] The concentration of the raw material compound in the reactor can be adjusted according to the solubility in the solvent, but is preferably 0 to 3.0 mol / L, and more preferably 0 to 1.5 mol / L. The supply rate of the raw material solution to the reactor can be adjusted according to the concentration and flow rate of the circulating fluorine gas so that the equivalent of fluorine gas relative to the raw material compound is within the above range. It should be noted that the fluorination reaction can also be carried out in the gas phase without using a solvent. It should be noted that in the gas phase reaction, the cleavage of the CC single bond sometimes occurs in the fluorination reaction, producing a variety of by-products.

[0322] In the step (A), the temperature in the reactor during the introduction of the fluorine gas is preferably -30 to 60°C, more preferably -20 to 30°C.

[0323] In one embodiment, the temperature in the reactor when the fluorine gas is introduced is preferably 20 to 60°C, more preferably 20 to 30°C. In order to efficiently remove the hydrogen fluoride generated by the side reaction, the temperature in the reactor is preferably above the boiling point (20°C) of hydrogen fluoride. When the above temperature is above 20°C, hydrogen fluoride will not remain, and the decomposition reaction of the raw material is not likely to occur, so it is preferred. When the above temperature is below 60°C, it is possible to prevent the runaway of the reaction and the occurrence of side reactions, so it is preferred.

[0324] In other embodiments, the temperature in the reactor when the fluorine gas is introduced may be -30 to 20°C, or -20 to 0°C. In this case, in order to efficiently remove the hydrogen fluoride generated by the side reaction, it is preferred to increase the dilution ratio of nitrogen to fluorine gas, or use a hydrogen fluoride scavenger. Examples of the hydrogen fluoride scavenger include alkali metal fluorides such as sodium fluoride and potassium fluoride, and organic bases such as trialkylamines.

[0325] As the reactor in the fluorination reaction, a reactor with high pressure resistance is preferably used, and an autoclave is usually used. The material of the reactor is not particularly limited, but from the perspective of being less likely to react with fluorine gas, a metal container made of stainless steel or nickel, or a container coated with fluororesin is preferably used.

[0326] The fluorination reaction may be carried out in a flow-through manner or a batch-wise manner.

[0327] In the case of a flow-through method, the flow rate of the raw material solution supplied to the reactor is not particularly limited and can be adjusted according to the equivalent of fluorine gas to the raw material compound, the size of the reactor, the pressure in the reactor, etc. The flow rate of the raw material solution supplied to the reactor is preferably 0.5 to 100 mmol / min, more preferably 2 to 30 mmol / min, based on the molar number of hydrogen atoms contained in the raw material compound.

[0328] In the case of a batch type, only the amount of fluorine gas whose pressure is adjusted that is consumed by the reaction may be introduced from the inlet of the reactor.

[0329] Through step (A), a compound represented by formula (2f) is produced in which hydrogen atoms bonded to carbon atoms contained in the both-terminal-protected polyalkylene glycol represented by formula (2) are substituted with fluorine atoms.

[0330] A 4 -O-(Af 1 -O) x -Af 5 (2f)

[0331] (Af in formula (2f) 1 Same as formula (1f). 4 A in expression (2) 4 A group obtained by replacing all hydrogen atoms with fluorine atoms. 5 A in expression (2) 5 A group obtained by replacing all hydrogen atoms of with fluorine atoms. x corresponds to formula (2).

[0332] Af in formula (2f) 1 Equivalent to A in formula (2) 1 The structure obtained by replacing all hydrogen atoms with fluorine atoms is similar to Af in formula (1f). 1 same.

[0333] The compound represented by the formula (2f) rapidly becomes a fluorination reaction product represented by the following formula (3) in the reaction system.

[0334] F-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-F (3)

[0335] (In formula (3), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f).

[0336] In formula (3), -O-(Af 1 -O) m - represents the structure equivalent to -O-(Af 1 -O) x - is a structure obtained by removing the structural units arranged at both ends of the structure represented by -. Therefore, m in formula (3) is a number that is 2 smaller than x in formula (2) and formula (2f).

[0337] In formula (3), -(C=O)-Af 2 - and -Af 3The structures represented by -(C=O)- are respectively -O-(Af 1 -O) x - represents the structure of the structural unit arranged at each end. Therefore, Af in formula (3) 2 and Af 3 The structure of is determined by the structure of the structural unit arranged at the end in formula (2f), and is the same as Af in formula (1f). 2 and Af 3 The same perfluoroalkyl group. 2 and Af 3 The number of carbon atoms contained in each of the structural units arranged at the terminal in formula (2f) is 1 less than the number of carbon atoms contained in the structural units arranged at the terminal in formula (2f).

[0338] [Optional process]

[0339] In the production method of the present embodiment, an optional step of introducing a perhalogenated unsaturated hydrocarbon compound into the reactor while flowing an inert gas and a fluorine gas into the reactor may be performed after the step (A) and before the step (B).

[0340] In the later stage of the fluorination reaction of step (A), the reaction rate of the fluorination reaction is sometimes reduced. Therefore, after step (A), it is preferably included to introduce a process of a fully halogenated unsaturated hydrocarbon compound into a reactor while circulating an inert gas and fluorine gas. By introducing a fully halogenated unsaturated hydrocarbon compound, the unsaturated bonds in the fully halogenated unsaturated hydrocarbon compound react with the fluorine gas to produce fluorine free radicals. The produced fluorine free radicals react with the raw material compound to fluorinate, and therefore, by carrying out this process, the fluorination reaction can be promoted.

[0341] As the inert gas used in the step of introducing the fully halogenated unsaturated hydrocarbon compound, the inert gas exemplified in step (A) can be used. The flow rates of the inert gas and the fluorine gas are preferably adjusted so that the concentration of the fluorine gas flowing into the reactor is within the range exemplified in step (A).

[0342] Examples of the fully halogenated unsaturated hydrocarbon compound include hexafluorobenzene, hexachlorobenzene, chloropentafluorobenzene, trichlorotrifluorobenzene, decafluorobiphenyl, octafluoronaphthalene, tetrachloroethylene, trichlorofluoroethylene, dichlorodifluoroethylene, trichlorotrifluoropropylene, and dichlorotetrafluoropropylene. Among these, hexafluorobenzene is particularly preferred because it is easily available and can be handled.

[0343] By using a fully halogenated unsaturated hydrocarbon compound, fluorine gas is not consumed for fluorination of CH bonds in the unsaturated hydrocarbon compound, unlike when an unsaturated hydrocarbon compound having a CH bond such as benzene is used, and the amount of fluorine gas used does not increase, which is preferred.

[0344] As a method for introducing a perhalogenated unsaturated hydrocarbon compound, it is preferred that the perhalogenated unsaturated hydrocarbon compound is dissolved in a solvent, and a certain amount of circulation is introduced into the reactor. The circulation amount of the perhalogenated unsaturated hydrocarbon compound is converted according to the molar number of the unsaturated bonds in the perhalogenated unsaturated hydrocarbon compound, and relative to the fluorine gas circulation amount, it is preferably 1 / 50 to 1 / 5 molar times, and more preferably 1 / 30 to 1 / 10 molar times. If the circulation amount of the perhalogenated unsaturated hydrocarbon compound is more than 1 / 50 molar times, the progress of the fluorination reaction will not slow down, and the reaction time can be prevented from being prolonged. If the circulation amount of the perhalogenated unsaturated hydrocarbon compound is less than 1 / 5 molar times, it is possible to prevent the runaway of the reaction and the occurrence of side reactions.

[0345] The pressure in the reactor when the perhalogenated unsaturated hydrocarbon compound is introduced is preferably 0.08 to 0.12 MPa, more preferably normal pressure (0.1 MPa) to 0.115 MPa. The temperature in the reactor when the perhalogenated unsaturated hydrocarbon compound is introduced is preferably -30 to 60°C, more preferably -20 to 30°C.

[0346] As the solvent used in the step of introducing the perhalogenated unsaturated hydrocarbon compound, it is preferred to use the same solvent as in step (A). When a solvent different from that in step (A) is used, the solvents exemplified in step (A) can be used.

[0347] When a perhalogenated unsaturated hydrocarbon compound is dissolved in a solvent to prepare a solution and supplied to a reactor, the concentration of the perhalogenated unsaturated hydrocarbon compound in the supplied solution can be adjusted according to the solubility in the solvent, and is preferably 0.01 to 100 mol / L, more preferably 0.1 to 10 mol / L, based on the molar number of unsaturated bonds in the perhalogenated unsaturated hydrocarbon compound.

[0348] <Process (B)>

[0349] In the method for producing a lubricant for magnetic recording media according to the present embodiment, step (B) is a step of reacting the fluorination reaction product represented by formula (3) obtained in step (A) with an alcohol having 1 to 6 carbon atoms.

[0350] The fluorinated reaction product generated in step (A) may react easily with moisture in the atmosphere to form a carboxylic acid compound. Therefore, considering the ease of operation in the subsequent steps, it is preferred to carry out step (B). In particular, in the raw material compound represented by formula (2), 4 and A 5 In the case of an acyl group, it is preferred to carry out step (B).

[0351] Examples of the alcohol having 1 to 6 carbon atoms include methanol, ethanol, propanol, butanol, pentanol, hexanol, etc. Among them, methanol is preferred.

[0352] The reaction temperature in step (B) is preferably -30 to 60° C., more preferably -20 to 30° C. The reaction pressure is preferably 0.08 to 0.12 MPa, more preferably normal pressure (0.1 MPa) to 0.115 MPa.

[0353] The amount of alcohol introduced is preferably 2 to 10 equivalents, more preferably 3 to 5 equivalents, relative to the number of moles of the reactive terminals contained in the fluorination reaction product generated in step (A) (theoretical amount based on the number of moles of the raw material compound).

[0354] Regarding the raw material compound represented by formula (2), 1 -CH 2 -CH 2 - and A 4 and A 5 In the case of an acetyl group, the reaction from step (A) to step (B) is shown in formula (i). The following formula shows the reaction when methanol is used in step (B).

[0355] Formula (i)

[0356]

[0357] By carrying out the step (B), a double-terminal esterified product represented by the following formula (4) can be obtained from the fluorination reaction product represented by the formula (3).

[0358] A 6 O-(C=O)-Af 2 -O-(Af 1 -O)m-Af 3 -(C=O)-OA 7 (4)

[0359] (In formula (4), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). 6 and A 7 Each independently represents an alkyl group having 1 to 6 carbon atoms. )

[0360] In formula (4), A 6 O- and -OA 7 The structure shown is derived from the alcohol used in step (B).

[0361] [Optional process]

[0362] The product of step (A) or step (B) can be separated as the residue after the solvent is distilled off. Before the solvent is distilled off, in order to remove by-products such as hydrogen fluoride produced in the fluorination reaction, it is preferably washed with an alkaline aqueous solution. The alkaline aqueous solution is not particularly limited, but is preferably an aqueous sodium carbonate solution or an aqueous sodium bicarbonate solution from the perspective of ease of acquisition and operation. After washing with an alkaline aqueous solution, the solvent layer that has undergone double-layer separation is recovered, and in order to completely remove water and hydrogen fluoride, it is preferably added with a hydrogen fluoride capture agent and a desiccant and stirred.

[0363] Examples of the hydrogen fluoride scavenger include alkali metal fluorides such as sodium fluoride and potassium fluoride and organic bases such as trialkylamines. From the perspective of ease of separation, the hydrogen fluoride scavenger is preferably a solid alkali metal fluoride, particularly preferably sodium fluoride.

[0364] As the desiccant, sodium sulfate or magnesium sulfate is preferred.

[0365] By filtering out the solid and then distilling off the solvent, the product of step (A) or step (B) can be separated and the recovered solvent can be easily reused, thereby reducing the loss of expensive solvents such as compounds completely substituted with halogens.

[0366] <Process (C)>

[0367] In the method for producing a lubricant for magnetic recording media according to the present embodiment, step (C) is a step of performing a reduction reaction on the double-terminal esterified product represented by formula (4) obtained in step (B).

[0368] In step (C), a known method for reducing an ester can be used. For example, a method of mixing the double-terminal ester obtained in step (B) with a reducing agent in a solvent can be used.

[0369] The solvent used in step (C) is preferably an alcohol having 1 to 5 carbon atoms. In particular, ethanol is preferably used as the alcohol because the double-terminal esterified product obtained in step (B) has high solubility.

[0370] The reducing agent used in step (C) is preferably at least one selected from alkali metal salts of boron hydride compounds such as sodium borohydride and lithium borohydride; alkaline earth metal salts of boron hydride compounds such as magnesium borohydride and calcium borohydride; and aluminum hydride salts such as lithium aluminum hydride and sodium aluminum hydride. Among them, sodium borohydride is particularly preferred in view of the ease of availability and handling.

[0371] By carrying out the step (C), the fluorinated polyalkylene glycol represented by the formula (1f') can be produced.

[0372] HO-CH 2 -Af 2 -O-(Af1 -O) m -Af 3 -CH 2 -OH(1f')

[0373] (In formula (1f'), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f). In formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R 3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 'The corresponding fluorinated polyalkylene glycol. )

[0374] In step (A) of the method for producing a lubricant for a magnetic recording medium of the present embodiment, a polyalkylene glycol with two terminal protections represented by formula (2) having a ratio of molecules of the same molecular weight of 90% or more in the peak area ratio based on high performance liquid chromatography is used as a raw material compound. Therefore, the fluorinated polyalkylene glycol represented by formula (1f') obtained through steps (A) to (C) is also the same, and the ratio of molecules of the same molecular weight is also 90% or more in the peak area ratio based on high performance liquid chromatography.

[0375] When a fluorinated polyalkylene glycol represented by formula (1f') having a ratio of molecules of the same molecular weight of 90% or more in terms of peak area ratio based on high performance liquid chromatography is used as a raw material to synthesize a fluorinated ether compound represented by formula (1), a conventionally known method can be used. When n in formula (1) is 0, for example, a method described in Patent Document 1 can be used. When n in formula (1) is 1, for example, a method described in Patent Document 2 can be used. When n in formula (1) is 2, for example, a method described in Patent Document 3 can be used.

[0376] In formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R 3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 ' The corresponding fluorinated polyalkylene glycol. In the case where n is 1 or 2 in formula (1), if R 3 and R 3 ' are all the same, it is sufficient to use one fluorinated polyalkylene glycol represented by formula (1f') as a raw material, and the fluorinated ether compound represented by formula (1) is easy to synthesize and is therefore preferred.

[0377] As described above, the so-called "the proportion of molecules of the same molecular weight contained in the fluorinated ether compound is 90% or more, measured by the peak area ratio based on high performance liquid chromatography" can also be recorded as follows: the proportion of the molecules represented by formula (1s) relative to 100% of the fluorinated ether compound represented by formula (1) is 90% or more, measured by the peak area ratio based on high performance liquid chromatography.

[0378] Therefore, in the method for manufacturing a lubricant for a magnetic recording medium of the present embodiment, the so-called "the proportion of molecules of the same molecular weight contained in the fluorinated polyalkylene glycol represented by formula (1f') is 90% or more in terms of the peak area ratio based on high performance liquid chromatography" can also be recorded as follows: relative to 100% of the fluorinated polyalkylene glycol represented by formula (1f'), the proportion of molecules represented by formula (1f'-1) is 90% or more in terms of the peak area ratio based on high performance liquid chromatography.

[0379] HO-CH 2 -Af 2 -O-(Af 1 -O) t -Af 3 -CH 2 -OH(1f'-1)

[0380] (In formula (1f'-1), the same symbols as those in formula (1f') represent the same structures as those in formula (1f'). t represents the degree of polymerization and is an integer of 1 to 13.)

[0381] In formula (1f'-1), the same symbols as those in formula (1f') represent the same structures as those in formula (1f'), and specific examples thereof are the same as those described for formula (1f').

[0382] In the formula (1f'-1), t is an integer of 1 to 13. Therefore, the "ratio of molecules represented by the formula (1f'-1)" refers to the ratio of (Af 1 -O) represents the ratio of molecules with a single number of repetitions (degree of polymerization) of the repeating unit.

[0383] In addition, in step (A) of the method for manufacturing a lubricant for magnetic recording media of the present embodiment, the so-called "two-end protected polyalkylene glycol represented by formula (2) in which the proportion of molecules with the same molecular weight in the peak area ratio based on high performance liquid chromatography is 90% or more" can also be said to be a two-end protected polyalkylene glycol represented by formula (2) in which the proportion of molecules represented by formula (2-1) in the peak area ratio based on high performance liquid chromatography is 90% or more.

[0384] The process of liquid-phase fluorination of the two-terminal protected polyalkylene glycol represented by formula (2) in which the proportion of the molecule represented by formula (2-1) in the peak area ratio of high performance liquid chromatography is 90% or more may also be referred to as process (A-1). Furthermore, the process of reacting the obtained fluorinated reactant represented by formula (3) with an alcohol having 1 to 6 carbon atoms may also be referred to as process (B-1), and the process of further performing a reduction reaction of the two-terminal esterified body represented by formula (4) may also be referred to as process (C-1), and they may also be combined as a method for manufacturing a lubricant for a magnetic recording medium according to the present embodiment.

[0385] A 4 -O-(A 1 -O) u -A 5 (2-1)

[0386] (In formula (2-1), the same symbols as those in formula (2) represent the same structures as those in formula (2). u represents the degree of polymerization and is an integer of 3 to 15.)

[0387] In formula (2-1), the same symbols as those in formula (2) represent the same structures as those in formula (2), and specific examples thereof are the same as those described for formula (2).

[0388] u in formula (2-1) is an integer of 3 to 15. Therefore, the "ratio of molecules represented by formula (2-1)" means (A 1 -O) represents the ratio of molecules with a single number of repetitions (degree of polymerization) of the repeating unit.

[0389] In addition, in the preceding step of step (A) of the method for manufacturing a lubricant for magnetic recording media of the present embodiment, the so-called "polyalkylene glycol represented by formula (2') in which the proportion of molecules of the same molecular weight in the peak area ratio based on high performance liquid chromatography is 90% or more" can also be said to be a polyalkylene glycol represented by formula (2') in which the proportion of molecules represented by formula (2'-1) in the peak area ratio based on high performance liquid chromatography is 90% or more.

[0390] HO-(A 1 -O) v -H(2'-1)

[0391] (In formula (2'-1), the same symbols as those in formula (2') represent the same structures as those in formula (2'). v represents the degree of polymerization and is an integer of 3 to 15.)

[0392] In formula (2'-1), the same symbols as those in formula (2') represent the same structures as those in formula (2'), and specific examples thereof are the same as those described for formula (2').

[0393] v in formula (2'-1) is an integer of any one of 3 to 15. Therefore, the "ratio of molecules represented by formula (2'-1)" means (A 1 -O) represents the ratio of molecules with a single number of repetitions (degree of polymerization) of the repeating unit.

[0394] "Method for determining the ratio of molecules of the same molecular weight"

[0395] In the fluorinated ether compound represented by formula (1), the fluorinated polyalkylene glycol represented by formula (1f'), the polyalkylene glycol with both ends protected represented by formula (2), or the polyalkylene glycol represented by formula (2'), the ratio of molecules of the same molecular weight contained therein is a value calculated from the peak area ratio based on high performance liquid chromatography, and can be determined by the method described in the examples.

[0396] As HPLC conditions, appropriate conditions are adopted according to the structure of the compound of the measurement object. For example, when the measurement object is a fluorinated polyalkylene glycol represented by formula (1f'), a two-end protected polyalkylene glycol represented by formula (2), or a polyalkylene glycol represented by formula (2'), it is preferred to adopt "HPLC conditions (i)" recorded in the embodiment. On the other hand, when the measurement object is a fluorinated ether compound represented by formula (1), it is preferred to adopt "HPLC conditions (ii)" recorded in the embodiment. "HPLC conditions (i)" are conditions using a differential refractive index detector (RID) as a detector, and "HPLC conditions (ii)" are conditions using an evaporative light scattering detector (ELSD) as a detector.

[0397] When the measurement target is a fluorinated polyalkylene glycol represented by formula (1f'), a polyalkylene glycol with both ends protected represented by formula (2), or a polyalkylene glycol represented by formula (2'), low molecular weight components may not be detected by an evaporative light scattering detector (ELSD) or the peak intensity may become extremely weak.

[0398] When the measurement object is a fluorinated ether compound represented by formula (1), it is sometimes impossible to accurately measure the content ratio of various repeating numbers of the fluorinated ether compound using a differential refractive index detector (RID). This is because the positive and negative effects of the PFPE chain part and other non-fluorinated parts of the fluorinated ether compound are opposite and cancel each other out, and the difference in refractive index with respect to the mobile phase becomes very small, or no peak can be detected.

[0399] [Magnetic recording media]

[0400] The magnetic recording medium of the present embodiment is a medium in which at least a magnetic layer, a protective layer, and a lubricating layer are provided in this order on a substrate.

[0401] In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer as required. In addition, an adhesion layer and / or a soft magnetic layer may be provided between the underlayer and the substrate.

[0402] Figure 1 This is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention.

[0403] The magnetic recording medium 10 of the present embodiment has a structure in which an adhesion layer 12 , a soft magnetic layer 13 , a first underlayer 14 , a second underlayer 15 , a magnetic layer 16 , a protective layer 17 , and a lubricating layer 18 are sequentially provided on a substrate 11 .

[0404] "Substrate"

[0405] As the substrate 11 , for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy can be used.

[0406] In addition, as the substrate 11, a non-magnetic substrate made of non-metallic materials such as glass, ceramics, silicon, silicon carbide, carbon, and resin can be used, and a non-magnetic substrate obtained by forming a film of NiP or NiP alloy on a base made of these non-metallic materials can also be used.

[0407] The glass substrate has rigidity and excellent smoothness, and is therefore suitable for high recording density. Examples of the glass substrate include aluminosilicate glass substrates. As the glass substrate, chemically strengthened aluminosilicate glass substrates are particularly suitable.

[0408] The roughness of the main surface of the substrate 11 is preferably ultra-smooth with Rmax of 6 nm or less and Ra of 0.6 nm or less. The surface roughness Rmax and Ra are values ​​defined in accordance with JIS B0601.

[0409] "Attachment Layer"

[0410] The adhesive layer 12 prevents the substrate 11 from being corroded when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are arranged in contact with each other.

[0411] The material of the adhesion layer 12 can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed by, for example, sputtering.

[0412] "Soft magnetic layer"

[0413] The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer composed of a Ru film, and a second soft magnetic film are stacked in sequence. That is, the soft magnetic layer 13 preferably has a structure in which the upper and lower soft magnetic films of the intermediate layer are antiferromagnetically coupled (AFC) by sandwiching an intermediate layer composed of a Ru film between two soft magnetic films.

[0414] Examples of the material of the first soft magnetic film and the second soft magnetic film include CoZrTa alloy and CoFe alloy.

[0415] In the CoFe alloy used for the first soft magnetic film and the second soft magnetic film, it is preferred to add any one of Zr, Ta, and Nb. This promotes the amorphization of the first soft magnetic film and the second soft magnetic film. As a result, the orientation of the first base layer (seed layer) can be improved, and the floating amount of the magnetic head can be reduced.

[0416] The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0417] "1st base layer"

[0418] 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.

[0419] Examples of the first base layer 14 include a Cr layer, a Ta layer, a Ru layer, a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, a CrTi alloy layer, and the like.

[0420] The first underlayer 14 can be formed by, for example, sputtering.

[0421] "Second base layer"

[0422] The second underlayer 15 is a layer for controlling the orientation of the magnetic layer 16 to be favorable. The second underlayer 15 is preferably a layer composed of Ru or a Ru alloy.

[0423] The second base layer 15 may be composed of a single layer or a plurality of layers. When the second base layer 15 is composed of a plurality of layers, all the layers may be composed of the same material, or at least one layer may be composed of a different material.

[0424] The second underlayer 15 can be formed by, for example, sputtering.

[0425] "Magnetic layer"

[0426] The magnetic layer 16 is composed of a magnetic film whose easy magnetization axis is oriented in a vertical or horizontal direction relative to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. The magnetic layer 16 may also be a layer containing oxide, Cr, B, Cu, Ta, Zr, etc. in order to improve the SNR (Signal to Noise Ratio) characteristics.

[0427] 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 wait.

[0428] The magnetic layer 16 may be composed of a single layer or a plurality of magnetic layers including materials having different compositions.

[0429] For example, when the magnetic layer 16 is composed of three layers, namely, the first magnetic layer, the second magnetic layer, and the third magnetic layer, which are stacked in order from the bottom, the first magnetic layer is preferably a granular structure composed of a material containing Co, Cr, Pt and 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, TiO can be particularly preferably used. 2 Cr 2 O 3 、SiO 2 In addition, the first magnetic layer is preferably composed of a composite oxide to which two or more oxides are added. Among them, Cr can be particularly preferably used. 2 O 3 -SiO 2 Cr 2 O 3 -TiO 2 、SiO 2 -TiO 2 wait.

[0430] The first magnetic layer may contain one or more elements selected from the group consisting of B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxides.

[0431] The second magnetic layer can be made of the same material as that of the first magnetic layer. The second magnetic layer preferably has a granular structure.

[0432] The third magnetic layer is preferably a non-granular structure composed of a material containing Co, Cr, Pt and no oxide. The third magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0433] When the magnetic layer 16 is formed of a plurality of magnetic layers, a non-magnetic layer is preferably provided between adjacent magnetic layers. When the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, a non-magnetic layer is preferably provided between the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer.

[0434] The non-magnetic layer arranged between adjacent magnetic layers of the magnetic layer 16 can be appropriately made of, for example, Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0435] In the non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16, an alloy material containing oxide, metal nitride or metal carbide is preferably used. Specifically, as the oxide, for example, SiO 2 、Al 2 O 3 、 2 O 5 Cr 2 O 3 ,MgO,Y 2 O 3 、TiO 2 As metal nitrides, for example, AlN, Si 3 N 4 , TaN, CrN, etc. As the metal carbide, for example, TaC, BC, SiC, etc. can be used.

[0436] The nonmagnetic layer can be formed by, for example, a sputtering method.

[0437] In order to achieve a higher recording density, the magnetic layer 16 is preferably a perpendicular magnetic recording magnetic layer in which the easy magnetization axis is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be an in-plane magnetic recording magnetic layer.

[0438] The magnetic layer 16 can be formed by any conventionally known method such as a vapor deposition method, an ion beam sputtering method, a magnetron sputtering method or other sputtering method. The magnetic layer 16 is usually preferably formed by a sputtering method.

[0439] "Protective layer"

[0440] The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of a single layer or a plurality of layers. Examples of the material of the protective layer 17 include carbon, carbon containing nitrogen, silicon carbide, and the like.

[0441] A carbon protective layer, particularly an amorphous carbon protective layer, can be preferably used as the protective layer 17. A carbon protective layer is preferred because the interaction with the polar groups (especially hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced.

[0442] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by making the carbon-based protective layer hydrogenated carbon and / or carbon nitride 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 atomic % to 20 atomic % when measured by hydrogen forward scattering (HFS). In addition, the nitrogen content in the carbon-based protective layer is preferably 4 atomic % to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0443] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained in the entire carbon-based protective layer. The carbon-based protective layer is suitable for a composition gradient layer in which, for example, the lubricating layer 18 side of the protective layer 17 contains nitrogen and the magnetic layer 16 side of the protective layer 17 contains hydrogen. In this case, the adhesion between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved. This is because the nitrogen in the protective layer 17 acts as an active site and promotes the bonding with the lubricating layer 18. The hydrogen or nitrogen in the carbon-based protective layer has a function as an active site.

[0444] The protective layer 17 preferably has a thickness of 1 nm to 7 nm. When the protective layer 17 has a thickness of 1 nm or more, sufficient performance as the protective layer 17 can be obtained. When the protective layer 17 has a thickness of 7 nm or less, this is preferred from the viewpoint of reducing the thickness of the protective layer 17.

[0445] As a method for forming the protective layer 17 , a sputtering method using a target 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 can be used.

[0446] When a carbon-based protective layer is formed as the protective layer 17, the protective layer 17 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 surface of the amorphous carbon protective layer formed by the plasma CVD method is uniform and has little roughness.

[0447] "Lubricating layer"

[0448] The lubricating layer 18 prevents contamination of the magnetic recording medium 10. In addition, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording and reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10.

[0449] like Figure 1 As shown, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 contains the above-mentioned lubricant for the magnetic recording medium.

[0450] When the protective layer 17 disposed under the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 is bonded to the protective layer 17 with a particularly high bonding force. As a result, it is easy to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is coated with a high coating rate even if the lubricating layer 18 is thin, and the surface contamination of the magnetic recording medium 10 can be effectively prevented.

[0451] The average film thickness of the lubricating layer 18 is preferably More preferably If the average film thickness of the lubricating layer 18 is more than 0.5nm, the lubricating layer 18 will not become an island or a mesh shape but will be formed with a uniform film thickness. Therefore, the surface of the protective layer 17 can be coated with a high coverage rate by the lubricating layer 18. In addition, by making the average film thickness of the lubricating layer 18 below 2.0nm, the lubricating layer 18 can be fully filmized, and the floating amount of the magnetic head can be fully reduced.

[0452] When the surface of the protective layer 17 is not covered by the lubricating layer 18 at a sufficiently high coverage rate, the environmental substances adsorbed on the surface of the magnetic recording medium 10 pass through the gaps of the lubricating layer 18 and intrude under the lubricating layer 18. The environmental substances intruding into the lower layer of the lubricating layer 18 are adsorbed and combined with the protective layer 17 to generate pollutants. Moreover, during magnetic recording and reproducing, the pollutants (agglomerated components) are attached (transferred) to the magnetic head as stains, causing damage to the magnetic head or reducing the magnetic recording and reproducing characteristics of the magnetic recording and reproducing device.

[0453] Environmental substances that generate pollutants include, for example, siloxane compounds (cyclic siloxane, linear siloxane), ionic impurities, hydrocarbons with high molecular weight such as octacosane, plasticizers such as dioctyl phthalate, etc. Metal ions contained in ionic impurities include, for example, sodium ions, potassium ions, etc. Inorganic ions contained in ionic impurities include, for example, chloride ions, bromide ions, nitrate ions, sulfate ions, ammonium ions, etc. Organic ions contained in ionic impurities include, for example, oxalate ions, formate ions, etc.

[0454] "Method for forming a lubricating layer"

[0455] The lubricating layer 18 may be formed by preparing a magnetic recording medium in which each layer up to the protective layer 17 is formed on the substrate 11 , applying a lubricating layer forming solution on the protective layer 17 , and drying the solution.

[0456] The lubricant layer-forming solution can be obtained, for example, by dispersing and dissolving the lubricant for a magnetic recording medium of the above-described embodiment in a solvent as necessary to adjust the viscosity and concentration to be suitable for a coating method.

[0457] Examples of the solvent used in the lubricating layer forming solution include fluorine-based solvents such as Batler (registered trademark) XF (trade name, manufactured by Mitsui & Co., Ltd.) and Asahicrine (registered trademark) AE-3000 (trade name, manufactured by AGC).

[0458] Examples of a method for applying the lubricating layer-forming solution include spin coating, spraying, paper coating, and dipping. Among them, dipping is preferred.

[0459] When the dipping method is adopted, for example, the following method can be adopted. First, the substrate 11 on which each layer up to the protective layer 17 is formed is dipped in the lubricating layer forming solution loaded into the dipping tank of the dipping device. Then, the substrate 11 is pulled out of the dipping tank at a predetermined speed. Thus, the lubricating layer forming solution is applied to the surface of the substrate 11 on the protective layer 17.

[0460] By adopting the dipping method, the lubricating layer-forming solution can be uniformly applied to the surface of the protective layer 17 , and the lubricating layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0461] By using a lubricating layer forming solution containing the lubricant for magnetic recording media of the above-mentioned embodiment, even if the number of coated sheets of the substrate in the coating process increases, the phenomenon that the proportion of the fluorine-containing ether compound with a small molecular weight in the lubricating layer forming solution is significantly reduced can be prevented. Therefore, even if the number of coated sheets of the substrate increases, the wear resistance and chemical resistance of the lubricating layer of the magnetic recording medium can be prevented from deteriorating.

[0462] In addition, the need to frequently replace the lubricating layer forming solution in the immersion tank (in order to prevent the wear resistance and chemical resistance of the lubricating layer from deteriorating as the number of coated substrates increases) can be reduced. Therefore, the replacement frequency of the lubricating layer forming solution can be reduced, and the productivity of the coating process can be improved.

[0463] In the present embodiment, it is preferable to perform heat treatment on the substrate 11 formed with the lubricating layer 18. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesion between the lubricating layer 18 and the protective layer 17 is improved.

[0464] The heat treatment temperature is preferably set to 100° C. to 180° C. If the heat treatment temperature is 100° C. or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. In addition, by setting the heat treatment temperature to 180° C. or lower, thermal decomposition of the lubricating layer 18 caused by the heat treatment can be prevented. The heat treatment time is preferably set to 10 minutes to 120 minutes.

[0465] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17 , the lubricating layer 18 of the substrate 11 before or after the heat treatment may be irradiated with ultraviolet light (UV).

[0466] Example

[0467] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. It should be noted that the present invention is not limited to the following Examples.

[0468] [Nuclear magnetic resonance (NMR) measurement method]

[0469] The structures of the compounds synthesized in the following Examples and Comparative Examples were determined by using an NMR apparatus (AVANCE III-400) manufactured by Bruno Biospin. 1 H-NMR determination and 19 The results of F-NMR measurement were used for identification.

[0470] Each measurement sample for NMR was prepared by dissolving about 10 mg of each compound in about 0.5 mL of deuterated chloroform (containing tetramethylsilane (TMS) as a reference substance) or deuterated acetone (containing TMS and hexafluorobenzene as reference substances). The compounds before the liquid phase fluorination step were measured by NMR using deuterated chloroform, and the compounds after the liquid phase fluorination step were measured by deuterated acetone. 1 The standard for H-NMR chemical shift was that the peak of tetramethylsilane was 0.0 ppm. 19 The F-NMR chemical shift was based on the peak of hexafluorobenzene at -164.7 ppm.

[0471] The number average molecular weight (Mn) and average degree of polymerization of each compound are determined by 1 H-NMR measurement or 19 The integrated intensity of each peak determined by F-NMR measurement and the number of hydrogen atoms or fluorine atoms attributable to each peak are calculated as follows: When a plurality of average polymerization degree values ​​can be calculated from the same NMR spectrum, the average value is adopted as the average polymerization degree value of the compound.

[0472] HO-(CH 2 CH 2 CH2 O) x' -H

[0473] (x' represents the average degree of polymerization.)

[0474] 1 H-NMR (CDCl 3 ): δ[ppm]=3.7~3.9(4H), 3.4~3.7(4(x'-1)H), 2.0~3.0(2H), 1.7~1.9(2x'H)

[0475] CH 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) x" -(C=O)-CH 3

[0476] (x" represents the average degree of polymerization.)

[0477] 1 H-NMR (CDCl 3 ): δ[ppm]=4.0~4.3(4H), 3.4~3.6(4(x"-1)H), 2.0~2.1(6H), 1.7~2.0(2x"H)

[0478] CH 3 O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) m' -CF 2 CF 2 -(C=O)-OCH 3

[0479] (m' represents the average degree of polymerization.)

[0480] 1 H-NMR (acetone-D 6 ): δ[ppm]=4.0~4.1(6H)

[0481] 19 F-NMR (Acetone-D 6 ): δ[ppm]=-84.2~-84.5(4m'F), -86.4~-86.6(4F), -122.5~-122.7(4F), -130.0~-130.2(2m'F)

[0482] HO-CH 2 -CF2 CF 2 O-(CF 2 CF 2 CF 2 O) m" -CF 2 CF 2 -CH 2 -OH

[0483] (m" represents the average degree of polymerization.)

[0484] 1 H-NMR (acetone-D 6 ): δ[ppm]=5.1~5.2(2H), 4.0~4.2(4H)

[0485] 19 F-NMR (Acetone-D 6 ): δ[ppm]=-84.2~-84.8(4m"F), -86.4~-87.3(4F), -126.3~-126.7(4F), -129.8~-130.2(2m"F)

[0486] [High performance liquid chromatography (HPLC) determination method]

[0487] HPLC measurement of each compound synthesized in the following Examples and Comparative Examples was performed under any of the following HPLC conditions (i) or (ii). The content ratio of the constituent components was determined for each number of repetitions from the peak area ratio relative to the elapsed time by the area percentage method.

[0488] HPLC conditions (i): Gel permeation chromatography (GPC)

[0489] Device name: HPLC Prominence UFLC manufactured by Shimadzu Corporation

[0490] Column: Shodex (registered trademark) KF-402HQ (1 column) and KF-401HQ (3 columns) manufactured by Resonac Co., Ltd. were connected in series and used.

[0491] Column oven: 30°C

[0492] Detector: Differential Refractive Index Detector (RID)

[0493] Eluent: Tetrahydrofuran

[0494] Flow rate: 0.2mL / min

[0495] Injection volume: 1μL

[0496] Sample preparation method: Dissolve about 50 mg of sample in about 1 mL of tetrahydrofuran

[0497] Standard substance: "EasiVial PEG" manufactured by Agilent

[0498] Use standard substances to create calibration curves and obtain molecular weight distribution data

[0499] HPLC conditions (ii): normal phase chromatography

[0500] Device name: HPLC Prominence manufactured by Shimadzu Corporation

[0501] Column: Inertsil SIL-100A manufactured by Dielsions Co., Ltd. (length 75 mm×inner diameter 2.1 mm, silica particle diameter 5 μm, pore diameter 10 nm)

[0502] Column oven: 40°C

[0503] Detector: Evaporative Light Scattering Detector (ELSD)

[0504] Eluent: AGC Corporation ASHICLIN (registered trademark) AE-3000 / 2-propanol gradient

[0505] Total flow rate: 0.5mL / min

[0506] Injection volume: 10 μL

[0507] Sample preparation method: Dissolve about 5 mg of sample in about 1.5 mL of AE-3000

[0508] It should be noted that the values ​​of Mw / Mn (Mw represents weight average molecular weight, Mn represents number average molecular weight) in the examples and comparative examples are obtained from the above-mentioned GPC measurement results. In addition, when the peak area ratio is obtained based on the area percentage method, if the peak separation is incomplete, the peak area is obtained by vertically dividing the peak at the minimum point or inflection point.

[0509] [Example 1]

[0510] <Polyalkylene glycol synthesis step>

[0511] 1,3-Propanediol pentamer (HO-(CH 2 CH 2 CH 2 O) 5 -H).

[0512]

[0513] Initially, 3-(benzyloxy)propyl p-toluenesulfonate was synthesized by the following steps.

[0514] In a 3L three-necked flask equipped with a thermometer, a dropping funnel and a stirrer, 3-benzyloxy-1-propanol (molecular weight 166.22, 149.60g, 900mmol, 1.00eq.) and dichloromethane (900mL) were added, and the flask was cooled in an ice bath. After p-toluenesulfonyl chloride (molecular weight 190.64, 188.73g, 990mmol, 1.10eq.) was added at once, triethylamine (molecular weight 101.19, 109.29g, 1080mmol, 1.20eq.) was added dropwise over 30 minutes. Then, the ice bath was removed and stirred at room temperature for 36 hours. The flask was cooled in an ice bath and distilled water (1000mL) was added. It was separated into two layers, and the aqueous layer was extracted twice with dichloromethane (500mL). The organic layers were combined and dried with sodium sulfate. After filtering out the drying agent, the filtrate was concentrated under reduced pressure to obtain 298 g of a crude product as a yellow oil. The crude product was purified by silica gel column chromatography to obtain 3-(benzyloxy)propyl p-toluenesulfonate (molecular weight 320.41, 253.76 g, 792 mmol, yield 88%) as a light yellow oil.

[0515] Next, 1,3-propylene glycol trimer (HO-(CH 2 CH 2 CH 2 O) 3 -H).

[0516] In a 3L three-necked flask equipped with a thermometer, a reflux tube and a mechanical stirrer, 1,3-propanediol (molecular weight 76.10, 25.11 g, 330 mmol, 1.00 eq.), 3-(benzyloxy)propyl p-toluenesulfonate (molecular weight 320.41, 253.76 g, 792 mmol, 2.40 eq.) and toluene (1560 mL) were added and stirred. Then, tetrabutylammonium hydrogen sulfate (molecular weight 339.54, 112.05 g, 330 mmol, 1.00 eq.) and a 50% aqueous sodium hydroxide solution (1305 g, 16.31 mol, 49.43 eq.) were added, and the mixture was heated under reflux while being vigorously stirred. After heating for 24 hours, the reaction solution was poured into 5% hydrochloric acid (6 L) while being ice-cooled to stop the reaction. Transfer to a separatory funnel, separate into two layers, and extract the aqueous layer three times with ethyl acetate (2L). Combine the organic layers and dry with sodium sulfate. After filtering out the desiccant, the filtrate was concentrated under reduced pressure to obtain 98.5g of crude product in the form of a yellow oil. The crude product was purified by silica gel column chromatography to obtain 1,3-propylene glycol trimer dibenzyl protected body (molecular weight 372.51, 87.28g, 234mmol, yield 71%) in the form of a light yellow oil.

[0517] The synthesized 1,3-propylene glycol trimer dibenzyl protected body (molecular weight 372.51, 87.28 g, 234 mmol, 1.00 eq.) and methanol (1500 mL) were added to a 3L three-necked flask and stirred at room temperature to prepare a solution. 10% Pd / C (8.73 g) was added, and after replacing the flask with hydrogen, it was vigorously stirred at room temperature for 1.5 hours. The reaction solution was filtered with diatomaceous earth, and the residue was washed with methanol (200 mL). The filtrate was concentrated and vacuum dried, and as a result, 87.6 g of crude product was obtained in the form of a colorless oil. The crude product was purified by silica gel column chromatography, and as a result, 1,3-propylene glycol trimer (molecular weight 192.26, 41.83 g, 218 mmol, yield 93%) was obtained in the form of a colorless oil.

[0518] Next, the 1,3-propanediol trimer (HO-(CH 2 CH 2 CH 2 O) 3 -H), and 3-(benzyloxy)propyl p-toluenesulfonate as raw materials, and the same operation as that for the synthesis of 1,3-propylene glycol trimer was repeated to obtain 1,3-propylene glycol pentamer (molecular weight 308.42, 42.87 g, 139 mmol). The obtained 1,3-propylene glycol pentamer HO-(CH 2 CH2 CH 2 O) na -H (na represents the average degree of polymerization) 1 The average degree of polymerization na was determined by H-NMR measurement and found to be na=5.01. Figure 2 The 1,3-propanediol pentamer is shown in 1 H-NMR spectrum. The ratio of molecules of the same molecular weight contained in the 1,3-propanediol pentamer was determined by the method of HPLC condition (i). As a result, the component with a polymerization degree of 5 (HO-(CH 2 CH 2 CH 2 O) 5 -H) is the component with the largest peak area ratio, with an area ratio of 97.93%.

[0519] <Step of introducing protecting groups into the hydroxyl groups at both terminals>

[0520] The obtained 1,3-propanediol pentamer was reacted with acetyl chloride to acetylate the hydroxyl groups at both ends, thereby synthesizing CH 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) 5 -(C=O)-CH 3 Represents the compound.

[0521] By operating as described above, CH 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) nb -(C=O)-CH 3 (nb represents the average degree of polymerization. nb = 5.03, Mn 394, Mw / Mn = 1.00). Figure 3 The 1,3-propanediol pentamer with acetylated 1,3-propanediol at both ends is shown in 1 H-NMR spectrum. The component with a degree of polymerization of 5 (CH 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) 5 -(C=O)-CH 3 ) ratio is 99.75%. Figure 4 The GPC chromatogram measured by the method of HPLC condition (i) is shown in FIG.

[0522] <Step (A) of Liquid Phase Fluorination>

[0523] 3100 mL of HFTCB (tetrachlorohexafluorobutane) was introduced into a 5 L autoclave and sealed. Nitrogen was introduced into the autoclave until the internal pressure reached 0.3 MPa and then slowly released to normal pressure 10 times for purging. 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) nb -(C=O)-CH 3 (nb represents the average degree of polymerization. nb = 5.03, Mn 394, Mw / Mn = 1.00) 15 g was dissolved in 5.7 mL of HFTCB to prepare a raw material solution. Fluorine gas was circulated at 588 mL / min and nitrogen gas was circulated at 4600 mL / min, and the raw material solution was introduced at a flow rate of 0.22 g / min based on the mass of the solution while cooling to 25°C, and a fluorination reaction was carried out.

[0524] After the raw material solution is introduced, C 6 F 6 (Hexafluorobenzene) 1.87 g was dissolved in 73 mL of HFTCB and C 6 F 6 The temperature in the autoclave was adjusted to 25 to 30°C, and while fluorine gas was passed at 150 mL / min and nitrogen gas was passed at 1350 mL / min, C was introduced at a flow rate of 0.83 g / min based on the mass of the solution. 6 F 6 solution, promoting the fluorination reaction.

[0525] <Step (B) of reacting the fluorination reaction product with an alcohol>

[0526] In step (A), C 6 F 6 After the introduction was completed, the flow of fluorine gas and nitrogen gas was continued for 10 minutes, and then the flow of fluorine gas was stopped, and nitrogen gas was flowed at 1350 mL / min for 1 hour to purge the autoclave. While the nitrogen gas was flowing, 24 g of methanol was introduced.

[0527] The reaction solution recovered from the autoclave was washed with an aqueous sodium carbonate solution. After separation into two layers, the organic solvent layer was recovered, dried with sodium sulfate and sodium fluoride, and the solid was filtered out. The solvent was distilled off using an evaporator to obtain 31 g of the product (recovery rate 97% (relative to the recovery rate of the raw material compound in the fluorination reaction in step (A))). 19 The obtained product was analyzed by F-NMR and it was confirmed that it was CH 3O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nc -CF 2 CF 2 -(C=O)-OCH 3 (nc represents the average degree of polymerization. nc=3.04, Mn 839).

[0528] <Step (C) of Obtaining Fluorinated Polyalkylene Glycol by Reduction Reaction>

[0529] The CH obtained in step (B) was subjected to the following method 3 O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nc -CF 2 CF 2 -(C=O)-OCH 3 reduction reaction.

[0530] 119 g of ethanol was placed in an eggplant-shaped bottle, cooled to 0°C, and 1.82 g of sodium borohydride was added. CH 3 O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nc -CF 2 CF 2 -(C=O)-OCH 3 (nc represents the average degree of polymerization. nc=3.04, Mn 839) 31 g was washed thoroughly with 10 g of ethanol and the reaction was carried out for 4.5 hours while the eggplant-shaped flask was returned to room temperature.

[0531] After the reaction was completed, 12.6 mL of 4M hydrochloric acid was added dropwise. After confirming that the pH of the solution was 3, an aqueous sodium bicarbonate solution (6.4 g of sodium bicarbonate, 76 mL of water) was added, and the pH of the solution was confirmed to be 8. The ethanol was distilled off using an evaporator, and after adding 80 mL of water, the aqueous layer was extracted 3 times with 80 mL of AE-3000. The organic layers were combined, dried over magnesium sulfate, and the solids were filtered out. The filtrate was concentrated under reduced pressure using an evaporator, and as a result, 28.5 g of a crude product was obtained (98.5% recovery). The crude product was purified by silica gel column chromatography, and as a result, 23.5 g (30.6 mmol, 81% yield) of fluorinated 1,3-propanediol pentamer HO-CH was obtained in the form of a colorless oil. 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nd -CF 2 CF 2 -CH 2 -OH (nd represents the average degree of polymerization. nd=2.96, Mn 769). Figure 5 The fluorinated 1,3-propanediol pentamer is shown in 19 F-NMR spectrum. The component with a degree of polymerization of 3 (HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) 3 -CF 2 CF 2 -CH 2 -OH) is the component with the largest peak area ratio, which is 97.2%.

[0532] <Synthesis process of fluorine-containing ether compound>

[0533]

[0534] The compound (A1) represented by the above formula (A1) was obtained by the method shown below (in the formula (A1), nf indicating the average degree of polymerization was 3.06).

[0535] First, ethylene glycol monoallyl ether is reacted with 3,4-dihydro-2H-pyran, and the hydroxyl group is protected with tetrahydropyranyl, and then the double bond is oxidized with meta-chloroperbenzoic acid, thereby synthesizing a compound represented by the following formula (A2). In addition, a compound represented by the following formula (A4) is synthesized by the method shown below. The primary hydroxyl group of 3-allyloxy-1,2-propanediol is protected with tert-butyldimethylsilyl. Then, the secondary hydroxyl group is protected with methoxymethyl, and the tert-butyldimethylsilyl group is removed from the obtained compound, thereby synthesizing a compound represented by the following formula (A3). After reacting the obtained compound (A3) with 2-(2-chloroethoxy)tetrahydropyran, the double bond is oxidized with meta-chloroperbenzoic acid, thereby synthesizing a compound represented by the following formula (A4).

[0536]

[0537] Under nitrogen atmosphere, 1,3-propylene glycol pentamer (HO-CH) was added into a 200 mL eggplant-shaped bottle. 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nd -CF 2 CF 2 -CH 2 -OH (nd represents the average degree of polymerization. nd = 2.96, Mn 769) (23.5 g), the compound represented by the above formula (A2) (3.71 g) and t-BuOH (tert-butyl alcohol) (40.0 mL) were stirred at room temperature until uniform. t-BuOK (potassium tert-butylate) (1.03 g) was further added to the above eggplant-shaped flask, heated to 70°C, and stirred for 12 hours to react.

[0538] Then, the obtained reaction product was cooled to 25°C, water was added, and ethyl acetate was further added as a solvent to extract the organic layer, and washed with water. Anhydrous sodium sulfate was added to the organic layer for dehydration, and after filtering out the desiccant, the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain a compound represented by the following formula (A5) (11.9 g, yield 40%).

[0539]

[0540] (In formula (A5), ne, which represents the average degree of polymerization, is 3.06.)

[0541] In a nitrogen atmosphere, a compound represented by formula (A5) (11.9 g), a compound represented by formula (A4) (4.31 g) and t-BuOH (tert-butyl alcohol) (65.0 mL) were placed in a 200 mL eggplant-shaped flask and stirred at room temperature until the mixture became uniform. t-BuOK (potassium tert-butylate) (0.41 g) was further added to the above-mentioned eggplant-shaped flask, heated to 70° C., and stirred for 16 hours to react.

[0542] Then, the obtained reaction product was cooled to 25° C., and a 7% hydrogen chloride / methanol reagent (63.7 g) was added thereto, followed by stirring at room temperature for 3 hours to carry out a deprotection reaction.

[0543] The obtained reaction product was added to a 7% sodium bicarbonate aqueous solution (250 mL) and neutralized. Ethyl acetate was added to extract the organic layer and washed with water. Anhydrous sodium sulfate was added to the organic layer for dehydration. After filtering out the desiccant, the filtrate was concentrated. The residue was purified by silica gel column chromatography to obtain the compound represented by the above formula (A1) (9.24 g, yield 70%, nf = 3.06 indicating the average degree of polymerization, Mn 1096).

[0544] Figure 6 and Figure 7 The compounds (A1) are shown in 1 H-NMR and 19 F-NMR spectrum: The component having a degree of polymerization of 3 determined by the method under HPLC condition (ii) was the component with the largest peak area ratio, with an area ratio of 97.3%. Figure 8 The normal phase LC chromatogram measured by the method of HPLC condition (ii) is shown in FIG.

[0545] [Comparative Example 1]

[0546] <Step of introducing protecting groups into the hydroxyl groups at both terminals>

[0547] The HO-(CH 2 CH 2 CH 2 O) ng -H (ng represents the average degree of polymerization) was reacted with acetyl chloride to acetylate the hydroxyl groups at both ends. 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) ng -(C=O)-CH 3(ng represents the average degree of polymerization. ng = 5.39) was used as the compound to be adjusted in the following molecular weight distribution adjustment step. The component (CH 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) 6 -(C=O)-CH 3 ) is the component with the largest peak area ratio, with an area ratio of 11.26%. Fig. 9 The GPC chromatogram measured by the method of HPLC condition (i) is shown in FIG. The numerical values ​​in the curve graph represent the attribution of the degree of polymerization of each peak. However, a degree of polymerization of 11 or more cannot be attributed.

[0548] <Molecular weight distribution adjustment step>

[0549] 100 g of the compound to be adjusted was fractionated twice by preparative chromatography (500 g of silica, n-hexane / ethyl acetate = 90 / 10 to 0 / 100 (volume ratio)). Components with a degree of polymerization of 4 to 8 were prepared to obtain CH as a raw material compound for adjusting the molecular weight distribution. 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) nh -(C=O)-CH 3 (nh represents the average degree of polymerization. nh = 5.66, Mn 431, Mw / Mn = 1.05) (recovery rate (mass ratio) 51%). The component with a degree of polymerization of 6 (CH 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) 6 -(C=O)-CH 3 ) is the component with the largest peak area ratio, with an area ratio of 21.98%.

[0550] Fig.10 The GPC chromatogram measured by the method of HPLC condition (i) is shown in FIG. The numerical values ​​in the graph represent the attribution of the degree of polymerization of each peak.

[0551] <Step (A) of Liquid Phase Fluorination>

[0552] 3100 mL of HFTCB was introduced into a 5 L autoclave and sealed. Nitrogen was introduced into the autoclave until the internal pressure reached 0.3 MPa and then slowly released to normal pressure 10 times for purging. The CH 3-(C=O)-O-(CH 2 CH 2 CH 2 O) nh -(C=O)-CH 3 (nh represents the average degree of polymerization. nh = 5.66, Mn 431, Mw / Mn = 1.05) 49 g was dissolved in 18.8 mL of HFTCB to obtain a raw material solution. Fluorine gas was circulated at 588 mL / min and nitrogen gas was circulated at 4600 mL / min, and the raw material solution was introduced at a flow rate of 0.22 g / min based on the mass of the solution while cooling to 25°C. The fluorination reaction was carried out.

[0553] After the raw material solution is introduced, C 6 F 6 1.87 g was dissolved in 73 mL of HFTCB to prepare C 6 F 6 The temperature in the autoclave was adjusted to 25 to 30°C, and while fluorine gas was passed at 150 mL / min and nitrogen gas was passed at 1350 mL / min, C was introduced at a flow rate of 0.83 g / min based on the mass of the solution. 6 F 6 solution, promoting the fluorination reaction.

[0554] <Step (B) of reacting the fluorination reaction product with an alcohol>

[0555] In step (A), C 6 F 6 After the introduction was completed, the flow of fluorine gas and nitrogen gas was continued for 10 minutes, and then the flow of fluorine gas was stopped, and nitrogen gas was flowed at 1350 mL / min for 1 hour to purge the autoclave. While the flow of nitrogen gas was continued, 73 g of methanol was introduced.

[0556] The reaction solution recovered from the autoclave was washed with an aqueous sodium carbonate solution. After separation into two layers, the organic solvent layer was recovered, dried with sodium sulfate and sodium fluoride, and the solid was filtered out. The solvent was distilled off using an evaporator to obtain 106 g of the product (recovery rate 99% (relative to the recovery rate of the raw material compound in the fluorination reaction in step (A))). 19 The obtained product was analyzed by F-NMR and it was confirmed that it was CH 3 O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) ni -CF 2 CF2 -(C=O)-OCH 3 (ni represents the average degree of polymerization. ni=3.82, Mn 968).

[0557] <Step (C) of Obtaining Fluorinated Polyalkylene Glycol by Reduction Reaction>

[0558] The CH obtained in step (B) was subjected to the following method 3 O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) ni -CF 2 CF 2 -(C=O)-OCH 3 reduction reaction.

[0559] 312 g of ethanol was placed in an eggplant-shaped bottle, cooled to 0°C, and 5.28 g of sodium borohydride was added. CH 3 O-(C=O)-CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) ni -CF 2 CF 2 -(C=O)-OCH 3 (ni represents the average degree of polymerization. ni=3.82, Mn 968) 104 g was thoroughly washed with 35 g of ethanol. The reaction was carried out for 4.5 hours while the eggplant-shaped flask was allowed to return to room temperature.

[0560] After the reaction was completed, 37 mL of 4M hydrochloric acid was added dropwise. After confirming that the pH of the solution was 3, an aqueous sodium bicarbonate solution (19.1 g of sodium bicarbonate, 220 mL of water) was added, and the pH of the solution was confirmed to be 8. The ethanol was distilled off using an evaporator, and after adding 80 mL of water, the aqueous layer was extracted three times with 200 mL of AE-3000. The organic layers were combined, dried over magnesium sulfate, and the solids were filtered out. The filtrate was concentrated under reduced pressure using an evaporator, and as a result, 96.6 g of a crude product (98.4% recovery) was obtained. The crude product was purified by silica gel column chromatography, and as a result, 76.4 g (84.6 mmol, 78% yield) of fluorinated 1,3-propylene glycol polymer HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2CF 2 O) nj -CF 2 CF 2 -CH 2 -OH (nj represents the average degree of polymerization. nj = 3.77, Mn 904). The component with a degree of polymerization of 4 (HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) 4 -CF 2 CF 2 -CH 2 -OH) is the component with the largest peak area ratio, with an area ratio of 22.6%. Fig.11 The GPC chromatogram measured by the method of HPLC condition (i) is shown in FIG. The numerical values ​​in the graph represent the attribution of the degree of polymerization of each peak.

[0561] <Synthesis process of fluorine-containing ether compound>

[0562]

[0563] The compound (B1) represented by the above formula (B1) was obtained by the method shown below (in the formula (B1), nk indicating the average degree of polymerization was 3.66).

[0564] Instead of the fluorinated 1,3-propylene glycol pentamer HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nd -CF 2 CF 2 -CH 2 -OH (nd represents the average degree of polymerization. nd = 2.96, Mn 769) and fluorinated 1,3-propylene glycol polymer HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nj -CF 2 CF 2 -CH 2The same operation as in Example 1 was carried out except that -OH (nj represents the average degree of polymerization. nj=3.77, Mn 904) to obtain the compound represented by the above formula (B1) (nk representing the average degree of polymerization: 3.66, Mn 1196). Fig.12 and Fig.13 The compounds (B1) are shown in 1 H-NMR and 19 F-NMR spectrum: The component with a degree of polymerization of 4 determined by the method under HPLC condition (ii) was the component with the largest peak area ratio, with an area ratio of 29.8%. Fig.14 The normal phase LC chromatogram measured by the method of HPLC condition (ii) is shown in FIG. The numerical values ​​in the graph represent the attribution of the degree of polymerization of each peak.

[0565] [Comparative Example 2]

[0566] The HO-(CH 2 CH 2 CH 2 O) nl -H (nl represents the average degree of polymerization) reacted with acetyl chloride to acetylate the hydroxyl groups at both ends. 3 -(C=O)-O-(CH 2 CH 2 CH 2 O) nm -(C=O)-CH 3 (nm represents the average degree of polymerization. nm = 4.68, Mn 374, Mw / Mn = 1.44) 48 g was directly supplied to step (A) without adjusting the molecular weight distribution. The reaction was carried out in the same manner as steps (A) to (C) of Comparative Example 1 to obtain 36 g of a product of step (C). 19 The obtained product was analyzed by F-NMR, and it was confirmed that it was a fluorinated 1,3-propylene glycol polymer HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nn -CF 2 CF 2 -CH 2 -OH (nn represents the average degree of polymerization. nn=4.38, Mn1005).

[0567] <Synthesis process of fluorine-containing ether compound>

[0568]

[0569] The compound (C1) represented by the above formula (C1) was obtained by the method shown below (in the formula (C1), no indicating the average degree of polymerization was 4.35).

[0570] Instead of the fluorinated 1,3-propylene glycol pentamer HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nd -CF 2 CF 2 -CH 2 -OH (nd represents the average degree of polymerization. nd = 2.96, Mn 769) and fluorinated 1,3-propylene glycol polymer HO-CH 2 -CF 2 CF 2 O-(CF 2 CF 2 CF 2 O) nn -CF 2 CF 2 -CH 2 -OH (nn represents the average degree of polymerization. nn = 4.38, Mn 1005), except for this, the same operation as in Example 1 was carried out to obtain the compound represented by the above formula (C1) (no representing the average degree of polymerization = 4.35, Mn 1310). The component with a degree of polymerization of 3 determined by the method of HPLC condition (ii) was the component with the largest peak area ratio, with an area ratio of 22.1%.

[0571] Fig.15 A comparison of normal phase LC chromatograms of compounds (A1) to (C1) measured by the method under HPLC condition (ii) is shown in FIG. The numerical values ​​in the graph indicate the attribution of the degree of polymerization of each peak.

[0572] Next, a lubricating layer forming solution was prepared by the method shown below using the compounds obtained in Example 1 and Comparative Examples 1 and 2. Then, the lubricating layer of the magnetic recording medium was formed by the method shown below using the obtained lubricating layer forming solution, thereby obtaining the magnetic recording medium of the Example and Comparative Example. It should be noted that the film thickness of the lubricating layer in this Example was measured by the method shown below.

[0573] <Lubricating layer thickness measurement>

[0574] The peak height of the CF vibration expansion and contraction of the lubricating layer was measured using a Fourier transform infrared spectrophotometer (FT-IR, trade name: Nicolet iS50, manufactured by Thermo Fisher Scientific Co., Ltd.) Then, the film thickness of the lubricating layer was calculated from the measured value of the peak height of the CF vibration expansion and contraction of the lubricating layer using a correlation formula obtained by the method described below.

[0575] <Calculation method of correlation formula>

[0576] A disk was prepared in which an adhesion layer, a soft magnetic layer, a first base layer, a second base layer, a magnetic layer and a protective layer were sequentially arranged on a substrate having a diameter of 65 mm. ( The film thickness of the interval) forms a lubricating layer respectively.

[0577] Then, for each disk formed with a lubricating layer, the film thickness increase compared to the disk surface without a lubricating layer was measured using an ellipsometer as the film thickness of the lubricating layer. In addition, for each disk formed with a lubricating layer, the peak height in CF vibration expansion was measured using FT-IR.

[0578] Then, a correlation expression between the peak height obtained by FT-IR and the film thickness of the lubricating layer obtained using an ellipsometer was obtained.

[0579] <Lubricating Layer Forming Solution>

[0580] The compounds obtained in Examples and Comparative Examples were dissolved in a fluorine-based solvent, Batler (registered trademark) XF (trade name, manufactured by Mitsui & Co., Ltd.), so that the film thickness when applied on the protective layer would be The solution was diluted with Batler XF in a manner of 0.001 mass % to 0.005 mass % to form a lubricating layer.

[0581] <Magnetic Recording Media>

[0582] An adhesion 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. The protective layer is a layer composed of carbon nitride.

[0583] On the protective layer of the substrate on which each layer up to the protective layer is formed, the lubricating layer forming solution of the embodiment and the comparative example is applied by dipping. Then, the magnetic recording medium coated with the lubricating layer forming solution is placed in a constant temperature bath at 120° C. and subjected to a heat treatment for 10 minutes. Thus, a lubricating layer is formed on the protective layer, and the magnetic recording medium of the embodiment and the comparative example is obtained.

[0584] The lubricating layer forming solution loaded into the dipping tank of the dipping coating device was continuously coated, and heat treated by the same operation, thereby obtaining 2500 magnetic recording media for each embodiment and comparative example. The dipping method was carried out under the conditions of a dipping speed of 10 mm / sec and a dipping time of 30 sec. During the continuous coating on the 2500 substrates, the lifting speed of the substrate from the dipping tank was adjusted, thereby keeping the film thickness of the lubricating layer constant at 10 mm / sec. controlled in this way.

[0585] For the magnetic recording media of the embodiments and comparative examples obtained as described above, abrasion resistance tests and chemical resistance tests were performed by the following methods at intervals of 100 sheets after coating the 1st, 100th, 200th, etc. The results are shown in Fig.16 and Fig.17 middle.

[0586] <Abrasion resistance test>

[0587] Using a pin-disc friction and wear tester, a ball of aluminum oxide with a diameter of 2 mm as a contact member was slid on the lubricating layer of the magnetic recording medium under the conditions of a load of 40 gf and a sliding speed of 0.25 m / sec, and the friction coefficient of the surface of the lubricating layer was measured. Then, the sliding time until the friction coefficient of the surface of the lubricating layer increased sharply was measured. The sliding time until the friction coefficient increased sharply was measured 4 times for each lubricating layer of each magnetic recording medium, and the average value was used. It should be noted that the evaluation results of wear resistance were compared using the relative value when the sliding time until the friction coefficient of the first sheet of coating increased sharply was set to 1.00.

[0588] It should be noted that the time until the friction coefficient increases sharply can be used as an indicator of the wear resistance of the lubricating layer for the reasons shown below. This is because the lubricating layer of the magnetic recording medium is worn away by the use of the magnetic recording medium. If the lubricating layer disappears due to wear, the contact member directly contacts the protective layer, and the friction coefficient increases sharply.

[0589] <Chemical substance resistance test>

[0590] The contamination of magnetic recording media caused by environmental substances that generate contaminants in a high temperature environment was investigated by the evaluation method shown below. It should be noted that in the evaluation method shown below, Si ions were used as environmental substances, and the amount of contaminants that contaminated the magnetic recording medium generated by the environmental substances was measured by the Si adsorption amount.

[0591] Specifically, the magnetic recording medium to be evaluated was maintained for 240 hours in the presence of a silicone-based Si rubber 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 caused by Si ions was evaluated in the form of Si adsorption. It should be noted that the evaluation results of the Si adsorption were compared using the relative value when the Si adsorption of the first coated sheet was set to 1.00.

[0592] like Fig.16 and Fig.17 As shown, the magnetic recording medium of Example 1 confirmed that even if the number of coated sheets of the substrate increases, the wear resistance and chemical resistance of the lubricating layer will not deteriorate and can be maintained. On the other hand, in Comparative Examples 1 and 2, it can be confirmed that as the number of coated sheets of the substrate increases, the wear resistance and chemical resistance gradually deteriorate. In addition, when Comparative Example 1 is compared with Comparative Example 2, it is confirmed that Comparative Example 1 including the molecular weight distribution adjustment step can significantly suppress the deterioration of wear resistance and chemical resistance compared with Comparative Example 2 in which the molecular weight distribution is not adjusted.

[0593] This is because, if a conventional fluorinated ether compound having a wide molecular weight distribution is used as a lubricant as in Comparative Example 2, the number average molecular weight of the fluorinated ether compound contained in the lubricating layer gradually increases as the number of coated substrates increases, which can be explained by a sharp deterioration in wear resistance and chemical resistance.

[0594] On the other hand, if a fluorinated ether compound having no molecular weight distribution but in which the proportion of molecules with the same molecular weight is 90% or more is used as a lubricant as in Example 1, the number average molecular weight of the fluorinated ether compound contained in the lubricating layer hardly changes, and therefore, the wear resistance and chemical resistance of the lubricating layer will not deteriorate and can be maintained.

[0595] Description of Reference Numerals

[0596] 10···Magnetic recording media

[0597] 11···Substrate

[0598] 12. Adhesion layer

[0599] 13···Soft magnetic layer

[0600] 14···1st basal layer

[0601] 15···Second basal layer

[0602] 16···Magnetic layer

[0603] 17···Protective layer

[0604] 18···Lubricating layer

Claims

1. A lubricant for a magnetic recording medium, characterized in that: A lubricant for a magnetic recording medium comprising a fluorine-containing ether compound represented by formula (1), wherein the ratio of molecules of the same molecular weight contained in the fluorine-containing ether compound is 90% or more in terms of peak area ratio based on high performance liquid chromatography, R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3 '] n -CH2-R 5 -R 6 (1) In formula (1), n ​​is any integer from 0 to 2; R 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f); when n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partly or completely the same, or they can be different; R 4 is a divalent linking group having 1 to 3 polar groups; when n is 2, the two R 4 Can be the same or different; R 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different; R 2 R 1 The end of the bonded side is an oxygen atom; R 5 R 6 The end of the bonded side is an oxygen atom; R 1 and R 6 is with R 2 or R 5 The terminal groups bonded to the terminal oxygen atoms of may be the same or different; R 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms; -Of 2 -O-(Of 1 -ISLAND) m -Of 3 -(1f) In formula (1f), Af 1 It represents a divalent perfluoroalkyl group having a linear or branched structure and having 2 to 5 carbon atoms; 1 In the case of a linear chain structure, (Af 1 -O) are all identical; in Af 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right; 2 and Af 3 Each independently represents a divalent straight-chain perfluorocarbon group having 1 to 4 carbon atoms; m represents an average degree of polymerization and is a real number of 1 to 13.

2. A lubricant for a magnetic recording medium, characterized in that: A lubricant for a magnetic recording medium comprising a fluorinated ether compound represented by formula (1), wherein the lubricant for a magnetic recording medium comprises a fluorinated ether compound in which the ratio of molecules represented by formula (1s) to 100% of the fluorinated ether compound represented by formula (1) is 90% or more in terms of peak area ratio based on high performance liquid chromatography, R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3 '] n -CH2-R 5 -R 6 (1) In formula (1), n ​​is any integer from 0 to 2; R 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f); when n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partly or completely the same, or they can be different; R 4 is a divalent linking group having 1 to 3 polar groups; when n is 2, the two R 4 Can be the same or different; R 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different; R 2 R 1 The end of the bonded side is an oxygen atom; R 5 R 6 The end of the bonded side is an oxygen atom; R 1 and R 6 is with R 2 or R 5 The terminal groups bonded to the terminal oxygen atoms of may be the same or different; R 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms; -Of 2 -O-(Of 1 -ISLAND) m -Of 3 -(1f) In formula (1f), Af 1 It represents a divalent perfluoroalkyl group having a linear or branched structure and having 2 to 5 carbon atoms; 1 In the case of a linear chain structure, (Af 1 -O) are all identical; in Af 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right; 2 and Af 3 Each independently represents a divalent straight-chain perfluoroalkyl group having 1 to 4 carbon atoms; m represents an average degree of polymerization, which is a real number of 1 to 13; R 1 -R 2 -CH2-R 3s [-CH2-R 4 -CH2-R 3s '] n -CH2-R 5 -R 6 (1s) In formula (1s), the same symbols as those in formula (1) represent the same structures or values ​​as those in formula (1); R 3s and R 3s 'Each independently is a perfluoropolyether chain represented by formula (1f-1); -Of 2 -O-(Of 1 -ISLAND) s -Of 3 -(1f-1) In formula (1f-1), the same symbols as those in formula (1f) represent the same structures as those in formula (1f); s represents the degree of polymerization and is an integer of 1 to 13. 3 . The lubricant for a magnetic recording medium according to claim 1 , wherein the number average molecular weight of the fluorine-containing ether compound is 500 to 10,000.

4. A method for producing a lubricant for a magnetic recording medium, characterized in that: A method for producing a lubricant for a magnetic recording medium comprising a fluorine-containing ether compound represented by formula (1), wherein the ratio of molecules of the same molecular weight contained in the fluorine-containing ether compound is 90% or more in terms of peak area ratio based on high performance liquid chromatography, The production method comprises the step of synthesizing the fluorine-containing ether compound using a fluorinated polyalkylene glycol represented by formula (1f') as a raw material, The ratio of molecules having the same molecular weight contained in the fluorinated polyalkylene glycol is 90% or more in terms of peak area ratio based on high performance liquid chromatography, R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3 '] n -CH2-R 5 -R 6 (1) In formula (1), n ​​is any integer from 0 to 2; R 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f); when n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partly or completely the same, or they can be different; R 4 is a divalent linking group having 1 to 3 polar groups; when n is 2, the two R 4 Can be the same or different; R 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different; R 2 R 1 The end of the bonded side is an oxygen atom; R 5 R 6 The end of the bonded side is an oxygen atom; R 1 and R 6 is with R 2 or R 5 The terminal groups bonded to the terminal oxygen atoms of may be the same or different; R 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms; -Of 2 -O-(Of 1 -ISLAND) m -Of 3 -(1f) In formula (1f), Af 1 It represents a divalent perfluoroalkyl group having a linear or branched structure and having 2 to 5 carbon atoms; 1 In the case of a linear chain structure, (Af 1 -O) are all identical; in Af 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right; 2 and Af 3 Each independently represents a divalent straight-chain perfluoroalkyl group having 1 to 4 carbon atoms; m represents an average degree of polymerization, which is a real number of 1 to 13; HO-CH2-Of 2 -O-(Of 1 -ISLAND) m -Of 3 -CH2-OH(1f') In formula (1f'), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f); in formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R 3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 'The corresponding fluorinated polyalkylene glycol.

5. The method for producing a lubricant for a magnetic recording medium according to claim 4, wherein the fluorinated polyalkylene glycol represented by formula (1f') is synthesized by a method comprising the following steps (A) to (C): Step (A), liquid phase fluorination of a polyalkylene glycol represented by formula (2) having both ends protected and having a molecular weight ratio of 90% or more in the peak area ratio based on high performance liquid chromatography; Step (B), reacting the obtained fluorination product represented by formula (3) with an alcohol having 1 to 6 carbon atoms; Step (C), performing a reduction reaction on the obtained double-terminal esterified product represented by formula (4); A 4 -O-(A1 -O) x -A 5 (2) In formula (2), A 1 represents a divalent hydrocarbon group having a straight or branched structure and having 2 to 5 carbon atoms; 1 In the case of a linear chain structure, (A 1 -O) are all identical; in A 1 In the case of a branched structure, a part (A 1 -O) in each repeating unit represented by 1 The arrangement direction of the two groups is alternating left and right; x represents the average degree of polymerization, which is a real number ranging from 3 to 15; A 4 and A 5 each independently represents a protecting group for a hydroxyl group; F-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-F (3) In formula (3), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f); A 6 O-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-OA 7 (4) In formula (4), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f); A 6 and A 7 Each independently represents an alkyl group having 1 to 6 carbon atoms.

6. The method for producing a lubricant for magnetic recording media according to claim 5, comprising the following polyether synthesis step: before the step (A), a nucleophilic substitution reaction is performed to react two or more compounds having a polyether chain or a monomer unit constituting a polyether chain, thereby synthesizing a polyether having (A) 1 -O) represented by a repeating unit.

7. A method for producing a lubricant for a magnetic recording medium, characterized in that: A method for producing a lubricant for a magnetic recording medium containing a fluorine-containing ether compound, wherein the fluorine-containing ether compound is a fluorine-containing ether compound represented by formula (1), and the ratio of the molecule represented by formula (1s) to 100% of the fluorine-containing ether compound represented by formula (1) is 90% or more in terms of peak area ratio based on high performance liquid chromatography, The production method comprises the step of synthesizing the fluorine-containing ether compound using a fluorinated polyalkylene glycol represented by formula (1f') as a raw material, The ratio of the molecule represented by formula (1f'-1) to 100% of the fluorinated polyalkylene glycol represented by formula (1f') is 90% or more in terms of peak area ratio by high performance liquid chromatography, R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3 '] n -CH2-R 5 -R 6 (1) In formula (1), n ​​is any integer from 0 to 2; R 3 and R 3 ' are each independently a perfluoropolyether chain represented by formula (1f); when n is 1 or 2, R 3 and 1 or 2 R 3 ' can be partly or completely the same, or they can be different; R 4 is a divalent linking group having 1 to 3 polar groups; when n is 2, the two R 4 Can be the same or different; R 2 and R 5 is a divalent linking group having one or more polar groups, which may be the same or different; R 2 R 1 The end of the bonded side is an oxygen atom; R 5 R 6 The end of the bonded side is an oxygen atom; R 1 and R 6 is with R 2 or R 5 The terminal groups bonded to the terminal oxygen atoms of may be the same or different; R 1 and R 6 A hydrogen atom or an organic group having 1 to 50 carbon atoms; -Of 2 -O-(Of 1 -ISLAND) m -Of 3 -(1f) In formula (1f), Af 1 It represents a divalent perfluoroalkyl group having a linear or branched structure and having 2 to 5 carbon atoms; 1 In the case of a linear chain structure, (Af 1 -O) are all identical; in Af 1 In the case of a branched structure, a part (Af 1 -O) in each repeating unit represented by Af 1 The arrangement direction of Af is alternating left and right; 2 and Af 3 Each independently represents a divalent straight-chain perfluoroalkyl group having 1 to 4 carbon atoms; m represents an average degree of polymerization, which is a real number of 1 to 13; R 1 -R 2 -CH2-R 3s [-CH2-R 4 -CH2-R 3s '] n -CH2-R 5 -R 6 (1s) In formula (1s), the same symbols as those in formula (1) represent the same structures or values ​​as those in formula (1); R 3s and R 3s 'Each independently is a perfluoropolyether chain represented by formula (1f-1); -Of 2 -O-(Of 1 -ISLAND) s -Of 3 -(1f-1) In formula (1f-1), the same symbol as that of formula (1f) represents the same structure as that of formula (1f); s represents the degree of polymerization, which is any integer from 1 to 13; HO-CH2-Of 2 -O-(Of 1 -ISLAND) m -Of 3 -CH2-OH(1f') In formula (1f'), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f); in formula (1), n ​​is 1 or 2 and R 3 and 1 or 2 R 3 ' are not all the same, formula (1f') represents the same as each R 3 and R 3 'The corresponding fluorinated polyalkylene glycol; HO-CH2-Of 2 -O-(Of 1 -ISLAND) t -Of 3 -CH2-OH(1f'-1) In formula (1f'-1), the same symbols as those in formula (1f') represent the same structures as those in formula (1f'); t represents the degree of polymerization and is an integer of 1 to 13.

8. The method for producing a lubricant for a magnetic recording medium according to claim 7, wherein the fluorinated polyalkylene glycol represented by formula (1f') is synthesized by a method comprising the following steps (A-1) to (C-1): Step (A-1), liquid phase fluorination of a polyalkylene glycol having both terminal protections, wherein the polyalkylene glycol having both terminal protections is a polyalkylene glycol having both terminal protections represented by formula (2), and the proportion of molecules represented by formula (2-1) in the peak area ratio based on high performance liquid chromatography is 90% or more; Step (B-1), reacting the obtained fluorination product represented by formula (3) with an alcohol having 1 to 6 carbon atoms; Step (C-1), performing a reduction reaction on the obtained double-terminal esterified product represented by formula (4); A 4 -O-(A 1 -O) x -A 5 (2) In formula (2), A 1 represents a divalent hydrocarbon group having a straight or branched structure and having 2 to 5 carbon atoms; 1 In the case of a linear chain structure, (A 1 -O) are all identical; in A 1 In the case of a branched structure, a part (A 1 -O) in each repeating unit represented by 1 The arrangement direction of the two groups is alternating left and right; x represents the average degree of polymerization, which is a real number ranging from 3 to 15; A 4 and A 5 each independently represents a protecting group for a hydroxyl group; A 4 -O-(A 1 -O) u -A5 (2-1) In formula (2-1), the same symbols as those in formula (2) represent the same structures as those in formula (2); u represents the degree of polymerization, which is an integer between 3 and 15; F-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-F (3) In formula (3), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f); A 6 O-(C=O)-Af 2 -O-(Af 1 -O) m -Af 3 -(C=O)-OA 7 (4) In formula (4), Af 1 , Af 2 , Af 3 and m corresponds to formula (1f); A 6 and A 7 Each independently represents an alkyl group having 1 to 6 carbon atoms.

9. The method for producing a lubricant for a magnetic recording medium according to claim 8, comprising the following polyether synthesis step: before the step (A-1), a nucleophilic substitution reaction is performed to react two or more compounds having a polyether chain or a monomer unit constituting a polyether chain, thereby synthesizing a polyether having (A-2). 1 -O) represented by a repeating unit.

10. The method for producing a lubricant for a magnetic recording medium according to claim 6 or 9, wherein the polyether synthesis step comprises a step of reacting the following compounds: A compound having a leaving group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end; and A compound having a hydroxyl group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end.

11. The method for producing a lubricant for a magnetic recording medium according to claim 6 or 9, wherein the polyether synthesis step comprises a step of reacting the following compounds: A compound having a leaving group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end; and A compound having hydroxyl groups at both ends of a polyether chain or a monomer unit constituting a polyether chain.

12. The method for producing a lubricant for a magnetic recording medium according to claim 6 or 9, wherein the polyether synthesis step comprises a step of reacting the following compounds: A compound having a hydroxyl group at one end of a polyether chain or a monomer unit constituting the polyether chain and having a protected hydroxyl group at the other end; and A compound having leaving groups at both ends of a polyether chain or a monomer unit constituting a polyether chain.

13. A magnetic recording medium, characterized in that: At least a magnetic layer, a protective layer, and a lubricating layer are sequentially provided on a substrate, and the lubricating layer contains the lubricant for a magnetic recording medium according to claim 1 or 2. 14 . A method for producing a magnetic recording medium, comprising the step of applying the lubricant for a magnetic recording medium according to claim 1 or 2 on the protective layer of a substrate having at least a magnetic layer and a protective layer formed thereon to form a lubricating layer.

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