JP2015040244A - Lubricant and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant having excellent heat resistance and lubricity and a magnetic recording medium having excellent practical characteristics.SOLUTION: There is used a lubricant containing an ionic liquid formed from a sulfonic acid having a perfluoropolyether skeleton and an aliphatic amine having a linear hydrocarbon group having 10 or more carbon atoms. A lubricant layer 15 is formed using the lubricant, thereby enabling to provide excellent lubrication properties and improve practical characteristics such as travelling performance, abrasion resistance and durability.

Description

  The present invention relates to a lubricant containing an ionic liquid composed of a Bronsted acid and a Bronsted base, and a magnetic recording medium using the lubricant.

  In recent years, with the development of an advanced information society, it is required to communicate, process and store a large amount of information. The amount of data generated every year worldwide is said to be 1 zettabyte (1 billion times 1 terabyte), and magnetic disk devices are attracting attention as storage media for storing them. Since the magnetic disk device can store a large amount of data and record / reproduce at high speed as compared with other optical disks and magnetic tapes, further improvement in performance is expected.

  In order to improve the recording capacity and processing speed of a magnetic disk, it is necessary to convert a recording / reproducing magnetic field into an electric signal with high efficiency. For this purpose, it is necessary to reduce the flying height of the magnetic head, which is the gap between the head and the disk. On the other hand, when the magnetic head is lowered, the frictional force between the magnetic head and the disk increases and wears away from each other, so that the reliability of the magnetic disk decreases. In order to achieve high reliability of the magnetic disk device, it is important to design a lubricating film that can maintain excellent lubricity even when repeatedly sliding.

  In recent years, HAMR (Heat Assisted Magnetic Recording) has been developed as a method for improving the recording capacity of a magnetic disk. 3 and 4 show an outline of the HAMR method. This HAMR system is locally heated by near-field light, and records and reproduces a magnetic field while applying a thermal offset, so even weak signals are not affected by the surrounding thermal noise and can maintain reliability. it can.

  However, since this HAMR system is heated by near-field light, further heat resistance and repeated durability are required for the lubricant. For example, Non-Patent Document 1 describes a simulation result that locally rises to near 200 ° C. as shown in FIG. Therefore, considering long-term durability, the lubricant is required to have a heat resistance of 250 ° C. or higher.

  As a current lubricant, a perfluoropolyether (PFPE) having a molecular weight of 2000 to 6000 as a main skeleton, a fomblin lubricant having a polar group and a hydroxyl group at the end in order to increase the adsorption power with a carbon protective film (for example, And Fomblin Z-DOL, manufactured by Solvay Solexis, Inc.). Patent Document 1 describes a structure having a perfluoropolyether and a polar group (hydroxyl group). The lubricating film is formed by a so-called dipping method in which a magnetic disk is dipped in a lubricant solution and pulled up, and the lubricating film thickness is generally 1 to 3 nm.

Attempts have been made to improve the heat resistance of Fomblin lubricants. In Non-Patent Document 2, as a problem related to heat resistance of fomblin lubricants, a repeating unit of — (CF ₂ CF ₂ O) _m — (CF ₂ O) _n — is used as AlCl ₃ acting as a Lewis acid. It is described that the polymer chain is cut by the reaction. As a solution to this problem, Patent Document 2 describes that chemical stability is improved by introducing phosphazene at the terminal.

  Further, Patent Document 3 shows a structure modified by reaction with an epoxy having an aromatic group at the terminal of the hydroxyl group, and the terminal modified structure prevents thermal oxidation and prevents scattering during high-speed rotation by adsorption. It is stated that both are effective. Patent Document 4 describes that, in a magnetic tape, high repetition durability can be obtained by using an amine salt having a carboxyl group at the end of perfluoropolyether.

However, the above-mentioned Fomblin lubricant cannot provide sufficient heat resistance and lubricity in the next-generation recording technology such as the HAMR method. The lubricating agent using perfluoroalkane sulfonic acid is primarily CF ₂ in the framework is equipped with a hydrocarbon directly sulfonic acid without going through the (CH _2), reached by acid to get the hydrocarbon (CH ₂₎ Although it has high heat resistance, perfluoroalkanesulfonic acid is highly accumulative to the human body and cannot be commercialized because it falls under PFOS (perfluorooctanesulfonic acid) regulations with 8 or more carbon atoms. .

JP 2010-168512 A JP 2006-307123 A JP 2010-143855 A JP-A-5-93059

Fuji Electric Technical Report 2012 Vol.85 No.4 P.329-332 Macromolecules 1992, 25, 6791-6799

  The present invention has been proposed in view of such conventional circumstances, and provides a lubricant having excellent heat resistance and lubricity, and a magnetic recording medium having excellent practical characteristics.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by an ionic liquid having a sulfonic acid having a perfluoropolyether skeleton as a Bronsted acid and an aliphatic amine as a Bronsted base. The invention has been completed.

  That is, the lubricant according to the present invention contains an ionic liquid formed by Bronsted acid (HX) and Bronsted base (B) represented by the following general formula (1). It is a sulfonic acid having a fluoropolyether skeleton.

一般式（１）中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４のうち少なくとも１つは水素原子であり、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４のうち少なくとも１つは炭素数が１０以上の直鎖状の炭化水素基である。

In general formula (1), at least one of R ₁ , R ₂ , R ₃ , and R ₄ is a hydrogen atom, and at least one of R ₁ , R ₂ , R ₃ , and R ₄ has 10 carbon atoms. These are the above linear hydrocarbon groups.

  According to the present invention, in the magnetic recording medium having at least a magnetic layer on a nonmagnetic support, the magnetic layer contains the lubricant described above.

  In the ionic liquid formed from Bronsted acid (HX) and Bronsted base (B) represented by the following general formula (1), the Bronsted acid has a perfluoropolyether skeleton. It is a sulfonic acid.

一般式（１）中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４のうち少なくとも１つは水素原子であり、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４のうち少なくとも１つは炭素数が１０以上の直鎖状の炭化水素基である。

In general formula (1), at least one of R ₁ , R ₂ , R ₃ , and R ₄ is a hydrogen atom, and at least one of R ₁ , R ₂ , R ₃ , and R ₄ has 10 carbon atoms. These are the above linear hydrocarbon groups.

  According to the present invention, thermal stability such as evaporation and thermal decomposition of a lubricant can be improved, and excellent lubrication characteristics can be maintained over a long period of time. Further, when a lubricant is used for a magnetic recording medium, it is excellent in lubrication characteristics and can improve practical characteristics such as runnability, wear resistance and durability.

It is sectional drawing which shows an example of the hard disk which concerns on one embodiment of this invention. It is sectional drawing which shows an example of the magnetic tape which concerns on one embodiment of this invention. It is the schematic which shows a HAMR system. It is a graph which shows the outline of the recording method of a HAMR system. It is a graph which shows the simulation result of the surface temperature of a magnetic recording medium.

Hereinafter, embodiments of the present invention will be described in detail in the following order with reference to the drawings.
1. 1. Lubricant 2. Magnetic recording medium Example

<1. Lubricant>
The lubricant shown as one embodiment of the present invention contains an ionic liquid formed from Bronsted acid (HX) and Bronsted base (B) represented by the following general formula (1).

一般式（１）中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４のうち少なくとも１つは水素原子であり、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４のうち少なくとも１つは炭素数が１０以上の直鎖状の炭化水素基である。炭素数が１０以上の直鎖状の炭化水素以外のＲは、分岐炭化水素、芳香環、脂環、不飽和結合を有する炭化水素、又は水素のいずれかであることが好ましい。また、複素環化合物であっても良く、ハロゲンが置換されていても良い。

In general formula (1), at least one of R ₁ , R ₂ , R ₃ , and R ₄ is a hydrogen atom, and at least one of R ₁ , R ₂ , R ₃ , and R ₄ has 10 carbon atoms. These are the above linear hydrocarbon groups. R other than the straight-chain hydrocarbon having 10 or more carbon atoms is preferably any of a branched hydrocarbon, an aromatic ring, an alicyclic ring, a hydrocarbon having an unsaturated bond, or hydrogen. Further, it may be a heterocyclic compound and may be substituted with halogen.

Bronsted acid is a sulfonic acid having a perfluoropolyether skeleton. Examples of the perfluoropolyether skeleton include the following structural formulas (2) to (5).
_{(2): -CF 2 - (} OCF 2 CF 2) m - (OCF 2) n -OCF 2 -
_{(3): - (CF 2} O) j - (CF 2 CF 2 O) k - (CF 2 O) l -CF 2 -
_{(4): - (CF 2} CF 2 CF 2 O) o -CF 2 CF 2 -
_{(5): - (CF 2} CF (CF 3) O) p -CF 2 -
In the structural formulas (2) to (5), m, n, j, k, l, o, and p are each independently an integer of 1 or more.

The sulfonic acid having a perfluoropolyether skeleton has, for example, a sulfonic acid group (—SO ₂ —OH) at the end of the compound having a skeleton of the above structural formulas (2) to (5), preferably perfluoropolyester. A compound having an ether skeleton has sulfonic acid groups at both ends. By having a sulfonic acid group at both ends of the compound having a perfluoropolyether skeleton, excellent heat resistance can be obtained.

The sulfonic acid having a perfluoropolyether skeleton preferably has a skeleton of the structural formula (2) among the skeletons of the structural formulas (2) to (5). Structural formula (2) is made by Solvay Solexis Fomblin Z-DOL _{(formula: HO-CH 2 -CF 2 -} (OCF 2 CF 2) m- (OCF 2) n-OCF 2 -CH 2 -OH) Fomblin Z-DIAC (Structural Formula: HOOC-CF _2- (OCF ₂ CF ₂ ) _m- (OCF ₂ ) _n -OCF ₂ -COOH) and the main skeleton and the like manufactured by Solvay Solexis Therefore, excellent lubricity can be obtained. Moreover, since Fomblin Z-DOL, Fomblin Z-DIAC, etc. by Solvay Solexis can be used as a raw material, it can manufacture at low cost.

Specific sulfonic acids having a skeleton of the structural formula (2) include HO—SO ₂ —CH ₂ CH ₂ CH ₂ —O—CH ₂ —CF ₂ — (OCF ₂ CF ₂ ) _m — (OCF ₂ ) _{n. -OCF 2 -CH 2 -O-CH 2} CH 2 CH 2 -SO 2 -OH, CF 2 CF 2 CF 2 CF 2 -O-CF 2 -CF 2 -OCF 2 CF 2 -OCF 2 -CH 2 -O _{-CH 2 CH 2 CH 2 -SO 2} -OH , and the like.

  The Bronsted base is an aliphatic amine having a linear hydrocarbon group having 10 or more carbon atoms. The hydrocarbon group may be linear, and may be a saturated hydrocarbon group, an unsaturated hydrocarbon group partially having a double bond, or an unsaturated branched hydrocarbon group partially having a branch. . Among these, an alkyl group which is a saturated hydrocarbon group is preferable from the viewpoint of wear resistance.

Specific Bronsted base, stearylamine _{(CH 3 (CH 2) 17} NH 2), oleylamine _{(C 18 H 35 NH 2)} , N, N- dimethyl-octadecylamine _{(C 18 H 37 N (CH} 3) _2), decylamine _{(C 10 H 21 NH 2)} , tetradecyl amine _{(C 14 H 29 NH 2)} , eicosyl amine _{(C 20 H 41 NH 2)} , 2- heptyl undecyl amine _(CH 3 _(CH 2) Aliphatic amines such as nCH (C ₇ H ₁₅ ) NH ₂ ) are preferably used. In addition, the structure of amine is not restricted to these, For example, the hydrocarbon chain may be introduce | transduced into the heterocyclic compound, the alicyclic compound, and the aromatic compound.

  Thus, by using a salt of a sulfonic acid having a main skeleton of perfluoropolyether (PFPE) and an aliphatic amine having a linear hydrocarbon group having 10 or more carbon atoms, a conventional carboxylic acid and Compared to the case of using a salt with an aliphatic amine, it is possible to maintain a frictional characteristic equivalent to or higher than that of the conventional one, and to improve the thermal decomposition temperature due to high ionic bondability.

  Further, the thermal decomposition temperature of the ionic liquid is preferably 250 ° C. or higher, and more preferably 300 ° C. or higher. When the thermal decomposition temperature of the ionic liquid is 250 ° C. or higher, for example, the lubricity can be maintained even during heating during recording in the HAMR method. Moreover, it is preferable that melting | fusing point of an ionic liquid is 100 degrees C or less. When the melting point of the ionic liquid is 100 ° C. or less, for example, the storage characteristics of HAMR recording can be maintained. The difference between the thermal decomposition temperature and melting point of the ionic liquid is preferably 150 ° C. or higher. When the difference between the thermal decomposition temperature and the melting point of the ionic liquid is 150 ° C. or more, for example, it is possible to obtain a difference in coercive force Hc between HAMR recording and storage.

  As the lubricant in the present embodiment, the ionic liquid described above may be used alone, or may be used in combination with a conventionally known lubricant. For example, it can be used in combination with long chain carboxylic acid, long chain carboxylic acid ester, perfluoroalkyl carboxylic acid ester, carboxylic acid perfluoroalkyl ester, perfluoroalkyl carboxylic acid perfluoroalkyl ester, perfluoropolyether derivative, etc. Is possible.

  In order to maintain the lubrication effect under severe conditions, an extreme pressure agent may be used in combination at a weight ratio of about 30:70 to 70:30. The extreme pressure agent acts to prevent friction and wear by forming a reaction product film by reacting with the metal surface due to frictional heat when metal contact occurs partially in the boundary lubrication region. It is. As the extreme pressure agent, any of a phosphorus extreme pressure agent, a sulfur extreme pressure agent, a halogen extreme pressure agent, an organometallic extreme pressure agent, a composite extreme pressure agent, and the like can be used.

  Moreover, you may use a rust preventive agent together as needed. As the rust preventive agent, any rust preventive agent that can be used as a rust preventive agent for this type of magnetic recording medium is acceptable. Examples include phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, and oxygen atoms. Heterocyclic compounds, heterocyclic compounds containing a sulfur atom, and the like can be mentioned. In addition, the rust preventive may be used as a lubricant, but a magnetic layer is formed on the non-magnetic support, and after applying the rust preventive layer on top of the magnetic layer, the lubricant layer is applied. Thus, it may be deposited in two or more layers.

  Moreover, as a solvent of a lubricant, it can be used alone or in combination from alcohol solvents such as isopropyl alcohol (IPA) and ethanol. For example, it can be used even if a hydrocarbon solvent such as normal hexane or a fluorine solvent is mixed.

  Next, a method for synthesizing an ionic liquid according to the present embodiment will be described. The ionic liquid is synthesized from a Bronsted acid and a Bronsted base. Specifically, it can be obtained by neutralizing a sulfonic acid having a perfluoropolyether as a main skeleton and an aliphatic amine having a linear hydrocarbon group having 10 or more carbon atoms.

A sulfonic acid having a perfluoropolyether as a main skeleton is Fomblin Z-DOL (structural formula: HO—CH ₂ —CF ₂ — (OCF ₂ CF ₂ ) m— (OCF ₂ ) n, manufactured by Solvay Solexis, Inc. -OCF ₂ -CH _{2 -OH),} are synthesized using _{CF 2 CF 2 CF 2 CF 2} -O-CF 2 -CF 2 -OCF 2 -CF 2 -OCF 2 -CH 2 -O-H or the like.

For example, the synthesis method using H—O—CH ₂ —CF ₂ — (OCF ₂ CF ₂ ) _m — (OCF ₂ ) _n —OCF ₂ —CH ₂ —O—H as a raw material is as follows. It is. tert-Butoxypotassium and tert-butyl alcohol are mixed, stirred and completely dissolved, and then the raw materials are added little by little using a dropping funnel and stirred at room temperature. 1,3-propane sultone is added thereto and stirred at a temperature of about 60 ° C. Then, by removing the solvent with an evaporator, a potassium salt of sulfonic acid having a perfluoropolyether as a main skeleton can be obtained. Distilled water and concentrated hydrochloric acid are added to this potassium salt, and the mixture is stirred at room temperature. Then, the aqueous hydrochloric acid is removed by an evaporator, extracted with methyl isobutyl ketone, and the extract is evaporated to obtain perfluoropolyether. A sulfonic acid having a main skeleton is obtained.

The aliphatic amine having a linear hydrocarbon group having 10 or more carbon atoms is not particularly limited as described above, but stearylamine (CH ₃ (CH ₂ ) ₁₇ NH ₂ ), oleylamine (C Aliphatic amines such as ₁₈ H ₃₅ NH ₂ ) and N, N-dimethyloctadecylamine (C ₁₈ H ₃₇ N (CH ₃ ) ₂ ) are preferably used.

<2. Magnetic recording media>
Next, a magnetic recording medium using the above-described lubricant will be described. A magnetic recording medium shown as an embodiment of the present invention has at least a magnetic layer on a nonmagnetic support, and the magnetic layer contains the above-mentioned lubricant.

  The lubricant in the present embodiment can be applied to a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed on the surface of a nonmagnetic support by a technique such as vapor deposition or sputtering. The present invention can also be applied to a magnetic recording medium having a configuration in which an underlayer is interposed between a nonmagnetic support and a magnetic layer. Examples of such a magnetic recording medium include a magnetic disk and a magnetic tape.

  FIG. 1 is a cross-sectional view showing an example of a hard disk. This hard disk has a structure in which a substrate 11, an underlayer 12, a magnetic layer 13, a carbon protective layer 14, and a lubricant layer 15 are sequentially laminated.

  FIG. 2 is a cross-sectional view showing an example of a magnetic tape. This magnetic tape has a structure in which a backcoat layer 25, a substrate 21, a magnetic layer 22, a carbon protective layer 23, and a lubricant layer 24 are sequentially laminated.

  In the magnetic disk shown in FIG. 1, the nonmagnetic support corresponds to the substrate 11 and the underlayer 12, and in the magnetic tape shown in FIG. 2, the nonmagnetic support corresponds to the substrate 21. When a rigid substrate such as an Al alloy plate or glass plate is used as the non-magnetic support, an oxide film such as anodized or Ni-P film may be formed on the substrate surface to harden the surface. good.

  The magnetic layers 13 and 22 are formed as a continuous film by a technique such as plating, sputtering, vacuum deposition, or plasma CVD. As the magnetic layers 13 and 22, metals such as Fe, Co, Ni, Co—Ni alloys, Co—Pt alloys, Co—Ni—Pt alloys, Fe—Co alloys, Fe—Ni alloys, In-plane magnetization recording metal magnetic film made of Fe-Co-Ni alloy, Fe-Ni-B alloy, Fe-Co-B alloy, Fe-Co-Ni-B alloy, etc., Co-Cr alloy Examples thereof include perpendicular magnetic recording metal magnetic thin films such as thin films and Co—O thin films.

  In particular, when an in-plane magnetization recording metal magnetic thin film is formed, a nonmagnetic material such as Bi, Sb, Pb, Sn, Ga, In, Ge, Si, or Tl is previously formed on the nonmagnetic support as the underlayer 12. In addition, metal magnetic materials are vapor-deposited or sputtered from the vertical direction, and these non-magnetic materials are diffused in the magnetic metal thin film to eliminate orientation and ensure in-plane isotropy and improve coercive force. You may do it.

Further, hard protective layers 14 and 23 such as a carbon film, diamond-like carbon film, chromium oxide film, and SiO ₂ film may be formed on the surfaces of the magnetic layers 13 and 22.

As a method for retaining such a lubricant in such a metal thin film type magnetic recording medium, as shown in FIGS. 1 and 2, the top of the surface of the magnetic layers 13 and 22 or the surface of the protective layers 14 and 23 is used. The method of coating is mentioned. The coating amount of the lubricant is preferably 0.1-100 mg / ^{m 2,} more preferably 0.5-20 / ^{m 2.}

  Further, as shown in FIG. 2, in the metal thin film type magnetic tape, in addition to the metal magnetic thin film that is the magnetic layer 22, a back coat layer 25 may be formed as necessary.

  The back coat layer 25 is formed by adding a carbon fine powder for imparting conductivity to the resin binder and an inorganic pigment for controlling the surface roughness. In the present embodiment, the above-described lubricant may be contained in the back coat layer 25 by internal addition or top coat. Further, the above-described lubricant may be added to both the magnetic layer 22 and the back coat layer 25 by internal addition or top coat.

  As another embodiment, the lubricant can be applied to a so-called coating type magnetic recording medium in which a magnetic coating film is formed as a magnetic layer by applying a magnetic paint to the surface of a nonmagnetic support. is there. In the coating-type magnetic recording medium, any conventionally known magnetic powder, resin binder and the like constituting the nonmagnetic support, the magnetic coating film, and the like can be used.

  For example, as the non-magnetic support, a polymer support formed of a polymer material represented by polyesters, polyolefins, cellulose derivatives, vinyl resins, polyimides, polyamides, polycarbonate, etc., aluminum Examples thereof include a metal substrate made of an alloy, a titanium alloy, etc., a ceramic substrate made of alumina glass, etc., a glass substrate, and the like. Moreover, the shape is not limited at all, and any shape such as a tape shape, a sheet shape, or a drum shape may be used. Further, the non-magnetic support may be subjected to a surface treatment so as to form fine irregularities in order to control the surface property.

Magnetic powder includes ferromagnetic iron oxide particles such as γ-Fe ₂ O ₃ and cobalt-coated γ-Fe ₂ O ₃ , ferromagnetic chromium dioxide particles, metals such as Fe, Co, Ni, and the like. Examples thereof include ferromagnetic metal particles made of an alloy, hexagonal plate-shaped hexagonal ferrite fine particles, and the like.

  Examples of the resin binder include vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylic acid ester, methacrylic acid ester, styrene, butadiene, acrylonitrile, and the like, or a combination of two or more of these, polyurethane resin And polyester resins and epoxy resins. In these binders, a hydrophilic polar group such as a carboxylic acid group, a carboxyl group or a phosphoric acid group may be introduced in order to improve the dispersibility of the magnetic powder.

  In addition to the magnetic powder and the resin binder, a dispersant, an abrasive, an antistatic agent, an antirust agent, and the like may be added to the magnetic coating film as an additive.

  Such a coating type magnetic recording medium can be provided with the above-mentioned lubricant by adding it internally to the magnetic layer constituting the magnetic coating film formed on the non-magnetic support, or on the surface of the magnetic layer. There is a method of top coating, or a combination of both. Moreover, when adding a lubricant internally in a magnetic coating film, it adds in 0.2-20 mass parts with respect to 100 mass parts of resin binders.

Further, in the case of top coat a lubricant on the surface of the magnetic layer, the coating amount is preferably from 0.1-100 mg / ^{m 2,} more preferably 0.5-20 / ^{m 2.} In addition, as a deposition method when the lubricant is top-coated, an ionic liquid is dissolved in a solvent, and the obtained solution is applied or sprayed, or a magnetic recording medium is immersed in this solution.

  In this embodiment, a salt of a sulfonic acid having a main skeleton of perfluoropolyether (PFPE) and an aliphatic amine having a linear hydrocarbon group having 10 or more carbon atoms is used as a lubricant. Compared with the case of using a conventional salt of a carboxylic acid and an aliphatic amine, it is possible to maintain the frictional characteristics equivalent to or higher than those of the conventional salt and to improve the thermal decomposition temperature due to high ionic bondability.

  Therefore, the magnetic recording medium to which the lubricant according to the present embodiment is applied can exhibit excellent running performance, wear resistance, durability, and the like due to the lubricating action, and can further improve the thermal stability.

<3. Example>
Hereinafter, specific examples of the present invention will be described. In this example, an ionic liquid was synthesized and the melting point and thermal decomposition temperature of the ionic liquid were measured. Also, a lubricant containing an ionic liquid was prepared and the coefficient of friction was measured. The present invention is not limited to these examples.

[Measurement of melting point]
The endothermic peak temperature was determined as the melting point by DSC (manufacturer name: Seiko Instruments, model number: EXSTAR6000). The measurement conditions were a heating rate of 10 ° C./min and an N ₂ flow rate of 200 mL / min.

[Measurement of thermal decomposition temperature]
The weight loss with respect to temperature was measured by TG-DTA (manufacturer name: Seiko Instruments, model number: EXSTAR6000), and the temperature at a weight loss of 5% was defined as the thermal decomposition temperature. The measurement conditions were a heating rate of 10 ° C./min and an Air flow rate of 200 mL / min.

[Measurement of friction coefficient]
A sample was prepared by dipping coating a lubricant using a slide glass as a base material. The lubricant was prepared as a 0.2 wt% solution of ionic liquid using hexane / ethanol (90/10) as a solvent. FomblinZ-DOL manufactured by Solvay Solexis was formulated into a 0.2 wt% solution using Novec7200 as a solvent. The dipping coating was performed by pulling up the slide glass from the lubricant tank at a speed of 50 mm / min.

  Using an automatic friction measuring device (manufacturer name: Kyowa Interface Chemistry, model number: Triboster TS-501), under the conditions of point contact (3 mm steel ball), weight 15 g, speed 1.7 mm / sec, distance 20 mm, and 12 repetitions. The coefficient of friction of the sample was measured.

[Example 1]
A cooling tube, a thermometer, and a dropping funnel were set in a 200 ml three-necked flask. To the three-necked flask, 2.7 g (24 mmol) of tert-butoxypotassium and 50 ml of tert-butyl alcohol were added and stirred until completely dissolved. Thereto, 20 g (about 10 mmol) of Fomblin Z-DOL (molecular weight: about 2000) manufactured by Solvay Solexis was added little by little into the aqueous alkaline solution and stirred at room temperature for 2 hours. Thereto was added 2.9 g (24 mmol) of 1,3-propane sultone, and the mixture was stirred at 60 ° C. for 8 hours. And the white powder of the potassium salt of the sulfonic acid which has a perfluoropolyether frame | skeleton was obtained by removing a solvent with an evaporator. To 10 g of this white powder, 30 g of distilled water and 20 g of concentrated hydrochloric acid were added and stirred at room temperature for 8 hours. Thereafter, the aqueous hydrochloric acid was removed by an evaporator, extracted with methyl isobutyl ketone, and the extract was evaporated to obtain 1.0 g of a liquid. It was confirmed by 1 H-NMR (Proton Nuclear Magnetic Resonance) that the sulfonic acid has a perfluoropolyether skeleton. H-NMR (CD3OD) δ: 3.9, 3.7, 2.9, 2.1 (α, γ, δ, ε with respect to the perfluoropolyether chain)

Next, 0.75 g of sulfonic acid having a perfluoropolyether skeleton, 0.2 g of stearylamine, and 20 g of a hexane / ethanol (1/1) mixed solvent were stirred at room temperature for 5 hours. Then, after concentrating with an evaporator, it was reprecipitated with n-octane and suction filtered to obtain 0.66 g of white powder (total yield 6%). The FT-IR (Fourier Transform infrared Spectroscopy ), the band is burned with a peak at 3330cm ^-1 due to N-H stretching stearylamine, band 2700-3000Cm ^-1 by fatty chains of amine is produced, the target salt It was confirmed that the following compound 1 was synthesized.

  The measurement result of the melting point of Compound 1 was 75 ° C., the measurement result of the thermal decomposition temperature was 300 ° C., and the difference between the thermal decomposition temperature and the melting point was 225 ° C. The friction coefficients of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 1 and not heat-treated were 0.08 and 0.07, respectively. .01 decrease. The friction coefficients of the first and twelfth repetitions of the heat-treated sample at 150 ° C. for 2 h were 0.16 and 0.15, respectively, and decreased by −0.01 after 12 repetitions. The friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.20 and 0.19, respectively, and decreased by −0.01 after 12 repetitions. These results are shown in Tables 1 and 2.

[Example 2]
In the same manner as in Example 1, a sulfonic acid having a perfluoropolyether skeleton was synthesized. Thereafter, 1.0 g of sulfonic acid having a perfluoropolyether skeleton, 0.25 g of oleylamine, and 20 g of a mixed solvent of n-octane / ethanol (3: 1) were stirred for 5 hours. Thereafter, it was washed with n-octane, and the supernatant was removed by decantation. This operation was repeated three times. After concentration by an evaporator, 0.15 g (total yield 3%) of a brown viscous liquid was obtained. It was confirmed by FT-IR that the following compound 2 as the target salt was synthesized.

  The measurement result of the melting point of Compound 2 was 22 ° C., the measurement result of the thermal decomposition temperature was 304 ° C., and the difference between the thermal decomposition temperature and the melting point was 282 ° C. Further, the friction coefficients of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 2 and not heat-treated were 0.07 and 0.08, respectively. 01 increased. In addition, the friction coefficients of the first and twelfth repetitions of the sample heat-treated at 150 ° C. for 2 h were 0.13 and 0.14, respectively, and increased by 0.01 after 12 repetitions. In addition, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.20 and 0.22, respectively, and increased by 0.02 after 12 repetitions. These results are shown in Tables 1 and 2.

[Example 3]
A cooling tube, a thermometer, and a dropping funnel were set in a 200 ml three-necked flask. To the three-necked flask, 2.7 g (24 mmol) of tert-butoxypotassium and 50 ml of tert-butyl alcohol were added and stirred until completely dissolved. Thereto, 11 g (20 mmol) of 1H, 1H-perfluoro-3,6,9-trioxatridecan-1-ol was added little by little into the alkaline aqueous solution using a dropping funnel and stirred at room temperature for 2 hours. Thereto was added 2.9 g (24 mmol) of 1,3-propane sultone, and the mixture was stirred at 60 ° C. for 8 hours. And the white powder of the potassium salt of the sulfonic acid which has a perfluoro triether frame | skeleton was obtained by removing a solvent with an evaporator. To 10 g of this white powder, 30 g of distilled water and 20 g of concentrated hydrochloric acid were added and stirred at room temperature for 8 hours. Thereafter, hydrochloric acid water was removed by an evaporator, extraction was performed with Novec 7200 (manufactured by Sumitomo 3M), and the extract was evaporated to obtain 8.2 g of a liquid. It was confirmed by ¹ H-NMR (Proton Nuclear Magnetic Resonance) that the sulfonic acid had a perfluoropolyether skeleton. ¹ H-NMR (CD3OD) δ: 3.9, 3.7, 2.9, 2.1 (α, γ, δ, ε with respect to the perfluoropolyether chain)

Next, 4.96 g (7 mmol) of sulfonic acid having a perfluorotriether skeleton, 2.1 g (7.7 mmol) of stearylamine, and 20 g of a mixed solvent of hexane / ethanol (1/1) were stirred at room temperature for 5 hours. Thereafter, the solvent was evaporated to obtain a solid powder. Residual stearylamine was removed by washing the solid powder with hexane. After drying, 3.28 g of white powder (total yield 48%) was obtained. The FT-IR (Fourier Transform infrared Spectroscopy ), the band is burned with a peak at 3330cm ^-1 due to N-H stretching stearylamine, band 2700-3000Cm ^-1 by fatty chains of amine is produced, the target salt It was confirmed that the following compound 3 was synthesized.

  The measurement result of the melting point of Compound 3 was 75 ° C., the measurement result of the thermal decomposition temperature was 278 ° C., and the difference between the thermal decomposition temperature and the melting point was 203 ° C. In addition, the friction coefficients of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 3 and not heat-treated were 0.10 and 0.12, respectively, and 0. 02 increased. The friction coefficients of the first and twelfth repetitions of the heat-treated sample at 150 ° C. for 2 h were 0.14 and 0.17, respectively, and increased by 0.03 after 12 repetitions. In addition, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 hours were 0.22 and 0.23, respectively, and increased by 0.01 after 12 repetitions. These results are shown in Tables 1 and 2.

[Example 4]
In the same manner as in Example 3, a sulfonic acid having a perfluorotriether skeleton was synthesized. Thereafter, 4.96 g (7 mmol) of sulfonic acid having a perfluorotriether skeleton, 2.1 g (7.7 mmol) of oleylamine, and 20 g of methanol were stirred at 50 ° C. for 3 hours. Thereafter, it was washed with acetone, and the supernatant was removed by decantation. This operation was repeated three times. After concentration by an evaporator, 6.15 g of colorless viscous liquid (total yield 90%) was obtained. It was confirmed by FT-IR that the following compound 4 as the target salt was synthesized.

  The measurement result of the melting point of Compound 4 was 42 ° C., the measurement result of the thermal decomposition temperature was 287 ° C., and the difference between the thermal decomposition temperature and the melting point was 245 ° C. In addition, the friction coefficients of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 4 and not heat-treated were 0.09 and 0.11, respectively, and were 0. 02 increased. Further, the friction coefficients of the first and twelfth repetitions of the sample heat-treated at 150 ° C. for 2 h were 0.12 and 0.12, respectively, and there was no change due to the 12th repetition. Moreover, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.23 and 0.22, respectively, and increased by −0.01 after 12 repetitions. These results are shown in Tables 1 and 2.

[Comparative Example 1]
In a 200 ml eggplant flask, 10 g (5 mmol) of Fomblin Z-DIAC (molecular weight of about 2000) manufactured by Solvay Solexis, 3.23 g (12 mmol) of stearylamine, and 50 g of n-octane were stirred at room temperature for 5 hours. As a reprecipitation operation, the solution after the reaction was concentrated by an evaporator, 100 g of acetone was added, and the mixture was placed in a refrigerator overnight to precipitate white crystals. White crystals were taken out by suction filtration and dried in a vacuum oven. The FT-IR, verify that C = band with a peak 1690 cm ^-1 due to the expansion and contraction of the O disappeared, generated by a band of 1780 cm ^-1 of the amine salts, the following compounds 5 is a salt of interest is synthesized did.

  The measurement result of the melting point of Compound 5 was 53 ° C., the measurement result of the thermal decomposition temperature was 202 ° C., and the difference between the thermal decomposition temperature and the melting point was 149 ° C. In addition, the coefficient of friction of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 5 and not heat-treated was 0.02 and 0.02, respectively. There wasn't. Moreover, the friction coefficients of the first and twelfth repetitions of the sample heat-treated at 150 ° C. for 2 h were 0.07 and 0.05, respectively, and decreased by −0.02 after 12 repetitions. Further, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.15 and 0.36, respectively, and increased by 0.21 after 12 repetitions. These results are shown in Tables 1 and 2.

[Comparative Example 2]
In the flask, perfluorooctanoic acid and stearylamine were mixed in n-hexane and stirred. Then, it recrystallized with n-hexane / ethanol mixed solvent. The FT-IR, and band with a peak at 3330cm ^-1 due to N-H stearylamine disappeared, and generates band of 2700-300Cm ^-1 by fatty chains of amines, salts of interest following compound 6 It was confirmed that was synthesized.

  The measurement result of the melting point of Compound 6 was 60 ° C., the measurement result of the thermal decomposition temperature was 204 ° C., and the difference between the thermal decomposition temperature and the melting point was 144 ° C. In addition, the friction coefficient of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 6 and not heat-treated is 0.11 and 0.11, respectively, and the change due to the 12th repetition is There wasn't. Moreover, the friction coefficients of the first and twelfth repetitions of the sample heat-treated at 150 ° C. for 2 h were 0.24 and 0.32, respectively, and increased by 0.08 after 12 repetitions. In addition, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.24 and 0.32, respectively, and increased by 0.08 after 12 repetitions. These results are shown in Tables 1 and 2.

[Comparative Example 3]
In a flask, 1H, 1H-pentafluoro-1-octanol and stearylamine were mixed in n-hexane and stirred. Then, it recrystallized with n-hexane / ethanol mixed solvent. By FT-IR, a band having a peak at 3330 cm −1 due to NH of stearylamine disappeared, and a band of 2700 to 300 cm −1 due to the fatty chain of the amine was formed, and the target compound 7 It was confirmed that was synthesized.

  The measurement result of the melting point of Compound 7 was 49 ° C., the measurement result of the thermal decomposition temperature was 59 ° C., and the difference between the thermal decomposition temperature and the melting point was 10 ° C. In addition, the friction coefficients of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 7 and not heat-treated were 0.10 and 0.10, respectively. There wasn't. Moreover, the friction coefficients of the first and twelfth repetitions of the sample heat-treated at 150 ° C. for 2 h were 0.26 and 0.40, respectively, and increased by 0.14 after 12 repetitions. Moreover, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.29 and 0.50, respectively, and increased by 0.21 after 12 repetitions. These results are shown in Tables 1 and 2.

[Comparative Example 4]
Fomblin Z-DOL (molecular weight of about 2000) manufactured by Solvay Solexis shown as the following compound 8 was used.

  The measurement result of the melting point of Compound 8 was less than 30 ° C., the measurement result of the thermal decomposition temperature was 176 ° C., and the difference between the thermal decomposition temperature and the melting point was 146 ° C. In addition, the friction coefficients of the first and twelfth repetitions of the sample coated with the lubricant containing Compound 8 and not heat-treated were 0.05 and 0.02, respectively. Reduced by 0.03. Moreover, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 150 ° C. for 2 h were 0.06 and 0.08, respectively, and increased by 0.02 after 12 repetitions. Moreover, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.21 and 0.33, respectively, and increased by 0.12 after 12 repetitions. These results are shown in Tables 1 and 2.

[Reference example]
As a reference example, the coefficient of friction of a sample not coated with a lubricant was measured. The coefficient of friction for the first and twelfth repetitions of the sample that was not coated with the lubricant and was not heat treated was 0.14 and 0.17, respectively, and increased by 0.03 after 12 repetitions. Moreover, the friction coefficients of the first and twelfth repetitions of the sample heat-treated at 150 ° C. for 2 h were 0.16 and 0.57, respectively, and increased by 0.41 after 12 repetitions. Moreover, the friction coefficients of the first and twelfth repetitions of the heat-treated sample at 250 ° C. for 2 h were 0.17 and 0.64, respectively, and increased by 0.47 after 12 repetitions. These results are shown in Table 2.

  As shown in Table 1, Examples 1 to 4 have a heat decomposable temperature of 250 ° C. or higher and have sufficient heat resistance. On the other hand, Comparative Examples 1-4 caused thermal decomposition at a temperature of 250 ° C.

  In addition, as shown in Table 2, Examples 1 to 4 not only obtain a low friction coefficient even without heating, but also obtain a low friction coefficient even when heat treatment at 150 ° C. for 2 hours and 250 ° C. for 2 hours. Furthermore, a low coefficient of friction was obtained even with repetition. On the other hand, in Comparative Examples 1 to 4, the friction coefficient increased due to heating, and the friction coefficient increased even with repetition.

  When heat treatment at 250 ° C. was applied as in this example, the molecular structures of the ionic liquids of Comparative Examples 1 to 4 were thermally decomposed and the function as a lubricant was lost, but the ionic liquids of Examples 1 to 4 Since the molecular structure of sulfonic acid has a strong polarity of sulfonic acid, it has a strong adsorptive power to the base material, and further, the thermal decomposition temperature can be improved by a strong ionic bond between the sulfonic acid and the aliphatic amine. Due to these effects, in Examples 1 to 4, it was possible to maintain a low coefficient of friction against repetition even with heat treatment at 250 ° C.

DESCRIPTION OF SYMBOLS 11 Substrate, 12 Underlayer, 13 Magnetic layer, 14 Carbon protective layer, 15 Lubricant layer, 21 Substrate, 22 Magnetic layer, 23 Carbon protective layer, 24 Lubricant layer, 25 Backcoat layer

Claims (9)

An ionic liquid formed from a Bronsted acid (HX) and a Bronsted base (B) represented by the following general formula (1):
A lubricant in which the Bronsted acid is a sulfonic acid having a perfluoropolyether skeleton.

In general formula (1), at least one of R ₁ , R ₂ , R ₃ , and R ₄ is a hydrogen atom, and at least one of R ₁ , R ₂ , R ₃ , and R ₄ has 10 carbon atoms. These are the above linear hydrocarbon groups.   The lubricant according to claim 1, wherein the Bronsted acid has a sulfonic acid group at both ends or one end of the compound having the perfluoropolyether skeleton.   The lubricant according to claim 1 or 2, wherein the thermal decomposition temperature of the ionic liquid is 250 ° C or higher.   The lubricant according to claim 1 or 2, wherein the thermal decomposition temperature of the ionic liquid is 300 ° C or higher.   The lubricant according to any one of claims 1 to 4, wherein a melting point of the ionic liquid is 100 ° C or lower.   The lubricant according to any one of claims 1 to 5, wherein a difference between a thermal decomposition temperature and a melting point of the ionic liquid is 150 ° C or higher. The Bronsted base is stearylamine _{(CH 3 (CH 2) 17} NH 2), oleylamine _{(C 18 H 35 NH 2)} , N, N- dimethyl-octadecylamine _{(C 18 H 37 N (CH} 3) 2), decylamine _{(C 10 H 21 NH 2)} , tetradecyl amine _{(C 14 H 29 NH 2)} , eicosyl amine _{(C 20 H 41 NH 2)} , 2- heptyl undecyl amine _{(CH 3 (CH 2) nCH} (C 7. The lubricant according to claim 1, which is any one aliphatic amine of ₇ H ₁₅ ) NH ₂ ). In a magnetic recording medium having at least a magnetic layer on a nonmagnetic support,
A magnetic recording medium having the lubricant according to any one of claims 1 to 7 in the magnetic layer. In the ionic liquid formed from Bronsted acid (HX) and Bronsted base (B) represented by the following general formula (1):
An ionic liquid in which the Bronsted acid is a sulfonic acid having a perfluoropolyether skeleton.

In general formula (1), at least one of R ₁ , R ₂ , R ₃ , and R ₄ is a hydrogen atom, and at least one of R ₁ , R ₂ , R ₃ , and R ₄ has 10 carbon atoms. These are the above linear hydrocarbon groups.

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