Diester compounds, lubricants, and magnetic recording media

Abstract

To provide a lubricant capable of improving the durability of a magnetic recording medium, and to provide a magnetic recording medium to which such a lubricant is applied and which has excellent durability. [Solution] A diester compound represented by formula (1) or formula (2), and a lubricant containing the diester compound. TIFF2026144056000032.tif30153 TIFF2026144056000033.tif33153 (wherein n is an integer of 0 or more, R 1 , R 2 is a hydrocarbon group or an alkyleneoxy group, R 1 , R 2 at least one of has 6 or more carbon atoms, R 1 and R 2 the number of carbon-carbon double bonds among the carbon-carbon bonds contained in is 0 or 1.)

Description

[Technical Field]

[0001] This invention relates to diester compounds, lubricants, and magnetic recording media. [Background technology]

[0002] Magnetic recording media such as magnetic tapes are treated with lubricants to reduce friction between the recording media and the magnetic head. It is known that fatty acid esters are used as lubricants for magnetic recording media. For example, Patent Document 1 (Japanese Patent Application Publication No. 2-24825) discloses the use of a lubricant containing an ester of a fatty acid and a branched alcohol having 8 to 15 carbon atoms. Patent Document 1 discloses fatty acid monoesters in which stearic acid and oleic acid are used as the fatty acid.

[0003] Patent Document 2 (Japanese Patent Publication No. 2-105321) discloses fatty acid ester compounds with a molecular weight of 430 or more and having unsaturated bonds or branching in the acid residue or alcohol residue, particularly those having methyl branching in the alcohol residue, as lubricants for use in magnetic disks. In the examples of Patent Document 2, fatty acid monoester compounds such as oleyl stearate and isocetyl stearate are used.

[0004] Patent Document 3 (Japanese Patent Publication No. 2022-45294) discloses the use of a diester compound having two hydrocarbon groups as an alcohol residue as one component of a lubricant additive used in engine oil and the like. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2-24825 [Patent Document 2] Japanese Patent Application Publication No. 2-105321 [Patent Document 3] Japanese Patent Publication No. 2022-45294 Summary of the Invention Problem to be Solved by the Invention

[0006] In recent years, in magnetic recording media for data recording, thinning of magnetic layers and smoothing of tape surfaces have progressed, increasing friction between a magnetic head and a magnetic tape. Accordingly, there is a demand for a lubricant that can further improve the friction coefficient between a magnetic head and a magnetic recording medium and enhance the durability of the magnetic recording medium. One object of the present invention is to provide a lubricant capable of improving the friction characteristics of a magnetic recording medium, and to provide a magnetic recording medium excellent in durability to which such a lubricant is applied. Means for Solving the Problem

[0007] The present disclosure relates to a diester compound represented by the following formula (1) or the following formula (2). Chemical Formula Chemical Formula (In formula (1) and formula (2), n is an integer of 0 or more, and R 1 and R 2 each independently represent a hydrocarbon group or a structure represented by the following formula (3), and R 1 and R 2 have at least one of 6 or more carbon atoms, and the number of carbon-carbon double bonds among the carbon-carbon bonds contained in R 1 and R 2 is 0 or 1.) Chemical Formula (In formula (3), m is an integer of 1 to 8, R 3 is a hydrocarbon group, and R 4 and R 5 each independently represent an alkylene group having 1 to 6 carbon atoms.) A composition according to this disclosure comprises a diester compound represented by formula (1) or formula (2) above and an organic acid or organic salt compound. [Effects of the Invention]

[0008] The diester compounds and lubricants containing such diester compounds provided in this disclosure offer lubricants capable of improving the frictional properties of magnetic recording media. Furthermore, magnetic recording media with excellent durability are provided when such lubricants are applied. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium according to this disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium according to this disclosure. [Modes for carrying out the invention]

[0010] [Summary of the Embodiment] First, embodiments relating to this disclosure will be listed and described. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or greater and B or less". Embodiments combining different technical means are also included in the technical scope of the present invention.

[0011] This disclosure relates to diester compounds represented by the following formula (1) or formula (2). [ka] [ka] (In equations (1) and (2), n is a non-negative integer, R 1 and R 2 Each of these is independently a hydrocarbon group or a structure represented by the following formula (3), R 1 and R 2At least one of them has 6 or more carbon atoms, R 1 and R 2 The number of carbon-carbon double bonds in the carbon-carbon bond structure is either 0 or 1. [ka] (In equation (3), m is an integer from 1 to 8, R 3 R is a hydrocarbon group. 4 and R 5 Each of these independently represents an alkylene group with 1 to 6 carbon atoms.

[0012] Conventionally, fatty acid monoesters have been known to be used as lubricants for magnetic recording media. On the other hand, with the thinning of the magnetic layer and the smoothing of the tape surface, friction between the magnetic head and the magnetic tape tends to increase. For this reason, conventional fatty acid monoesters have insufficient lubrication performance, and magnetic tapes coated with these lubricants sometimes exhibit inadequate practical characteristics, such as a decrease in playback output during tape running tests. In contrast, the compound according to this disclosure has a diester structure and contains two carbonyl groups and hydrocarbon chains at both ends of the molecule. Although not particularly bound by theory, it is believed that with the compound according to this disclosure, by having two carbonyl groups and one or fewer carbon-carbon double bonds, the hydrocarbon chains at both ends can freely exist on the surface of the magnetic recording media, resulting in a high friction reduction effect.

[0013] The diester compound is a diester compound represented by formula (1) or (2), where R 1 and R 2 They may be different from each other. 1 and R 2 When the molecules have different asymmetrical molecular structures, their solubility in the solvent 2-butanone (methyl ethyl ketone) improves, allowing for the successful manufacture of magnetic recording media.

[0014] The diester compound is a diester compound represented by formula (1) or (2), where R1 and R 2 The hydrocarbon group may be a hydrocarbon group having 6 to 22 carbon atoms. Also, in formulas (1) and (2), n may be between 1 and 3. When n is within this range, the effects of this disclosure are clearer.

[0015] The compositions relating to this disclosure include a diester compound represented by the following formula (1) or formula (2) and an organic acid or organic acid salt compound. [ka] [ka] (In equations (1) and (2), n is a non-negative integer, R 1 and R 2 Each of these is independently a hydrocarbon group or a structure represented by the following formula (3), R 1 and R 2 At least one of them has 6 or more carbon atoms, R 1 and R 2 The number of carbon-carbon double bonds in the carbon-carbon bond structure is either 0 or 1. [ka] (In equation (3), m is an integer from 1 to 8, R 3 R is a hydrocarbon group. 4 and R 5 Each of these independently represents an alkylene group with 1 to 6 carbon atoms.

[0016] The lubricant according to this disclosure comprises the diester compound and at least one of the compositions.

[0017] The magnetic recording medium according to this disclosure comprises a non-magnetic support and a magnetic layer laminated on the non-magnetic support, and includes the lubricant.

[0018] The magnetic recording medium may contain the lubricant in its magnetic layer. The magnetic recording medium comprises a lubricant layer laminated on the magnetic layer, and the lubricant layer may contain the lubricant.

[0019] [Specific examples of embodiments] The compounds, lubricants, and magnetic recording media related to this disclosure will be described in more detail below. [Diester compounds] The diester compound represented by formula (1) is a compound having a dicarboxylic acid residue and two alcohol residues. The diester compound represented by formula (2) is a compound having a dialcohol residue and two carboxylic acid residues. [ka] [ka] (In equations (1) and (2), n is a non-negative integer, R 1 and R 2 Each of these is independently a hydrocarbon group or a structure represented by formula (3), and R 1 and R 2 At least one of them has 6 or more carbon atoms, R 1 and R 2 The number of carbon-carbon double bonds among the carbon-carbon bonds contained is 0 or 1. [ka] (In equation (3), m is an integer from 1 to 8, R 3 R is a hydrocarbon group. 4 and R 5 Each of these independently represents an alkylene group with 1 to 6 carbon atoms.

[0020] In formulas (1) and (2), n may be 0 or an integer greater than or equal to 1. When n is 0, it is a single bond where the carbon atoms of the carbonyl group are bonded together. n may be 1 to 8, preferably 1 to 3, and more preferably 1 to 2. Specifically, it is preferable that the carbonyl groups are bonded together via a divalent hydrocarbon group having 1 to 8 carbon atoms. The divalent hydrocarbon group having 1 to 8 carbon atoms is an alkylene group consisting of a carbon atom and a hydrogen atom, and is preferably linear. Specific examples of alkylene groups include methylene, ethylene, propylene, butylene, pentylene, and hexylene groups, and among these, methylene, ethylene, and propylene groups are preferred. When n is between 1 and 3, affinity with the solvent and friction reduction effects are easily obtained.

[0021] R 1 and R 2 R is a hydrocarbon group that may be the same or different from each other, and is preferably a hydrocarbon group having 6 to 22 carbon atoms. The hydrocarbon group is a functional group consisting of a carbon atom and a hydrogen atom, and is selected from, for example, alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups and aralkyl groups, and may be linear, branched, or cyclic. That is, R 1 and R 2 R may be a saturated hydrocarbon group or an unsaturated hydrocarbon group having a carbon-carbon double bond. 1 and R 2 When the hydrocarbon group has 6 to 22 carbon atoms, a friction reduction effect can be obtained.

[0022] R 1 and R 2Preferably, the alkyl or alkenyl groups have 6 to 22 carbon atoms, and more preferably, linear or branched alkyl groups have 8 to 22 carbon atoms, or alkenyl groups have 12 to 22 carbon atoms. Examples of linear or branched alkyl groups have 8 to 22 carbon atoms include octyl group, 2-ethylhexyl group, 3,5,5-trimethylhexyl group, decyl group, isotridecyl group, palmityl group, stearyl group, isostearyl group, and 2-octyldecyl group. Examples of alkenyl groups have 12 to 23 carbon atoms include hexadecenyl group, octadecenyl group, eicocenyl group, and dococenyl group, but those with 16 to 18 carbon atoms are preferred, and oleyl group and linoleyl group are more preferred. 1 and R 2 R is preferably a linear alkyl group or alkenyl group. 1 and R 2 Preferably, one of the groups is an alkyl group and the other is an alkenyl group.

[0023] R 1 and R 2 R may be a structure represented by equation (3). That is, R in equations (1) and (2) 1 and R 2 R may be a structure containing a repeating oxyalkylene group structure (polyoxyalkylene structure). In formula (3), 3 R is a hydrocarbon group, preferably an alkyl group having 1 to 3 carbon atoms. 3 Specifically, examples include methyl groups, ethyl groups, propyl groups, isopropyl groups, etc., with methyl or ethyl groups being preferred. 4 R is an alkylene group having 1 to 3 carbon atoms, preferably at least one of a methylene group, an ethylene group, or a propylene group. m is 1 to 8, preferably 4 to 6. m R 4 All of them may be identical, or two or more may be included. 5 R is an alkylene group having 1 to 8 carbon atoms, preferably 1 to 3 carbon atoms. 5Examples of such groups include methylene groups, ethylene groups, propylene groups, butylene groups, pentylene groups, and hexylene groups, with methylene groups, ethylene groups, and propylene groups being preferred.

[0024] R 1 and R 2 If the structure represented by equation (3) is included, R 1 and R 2 Both may be structures shown in equation (3), but R 1 and R 2 It is more preferable that one of them has the structure shown in formula (3) and the other has a hydrocarbon group.

[0025] The diester compounds relating to this disclosure are R in formula (1) or formula (2). 1 and R 2 Of these, at least one has the characteristic of having 6 or more carbon atoms. That is, R 1 and R 2 At least one of them may have 5 or fewer carbon atoms. 1 and R 2 One of them may have 5 or fewer carbon atoms, and the other may have 6 or more carbon atoms, R 1 and R 2 Both may have 6 or more carbon atoms.

[0026] Also, R 1 and R 2 Of these, the carbon-carbon double bond is either 0 or 1. In other words, R 1 and R 2 The total number of carbon-carbon double bonds in the carbon-carbon bonds contained in R is either 0 or 1. 1 and R 2 It is preferable that it has one carbon-carbon double bond. The number of carbon-carbon double bonds is 0, which means R 1 and R 2 This means that both are saturated hydrocarbon groups or structures represented by formula (3). Also, the number of double bonds being 1 means that R 1 and R 2one of which is a hydrocarbon group containing a double bond, and the other is a saturated hydrocarbon group or a structure represented by formula (3). A diester compound having 1 or less carbon-carbon double bonds can provide a favorable friction reducing effect in magnetic recording media.

[0027] R 1 and R 2 are not particularly limited as long as they fall within the above ranges, but R 1 and R 2 as a preferred combination, R 1 and R 2 preferably have structures different from each other. That is, the diester compound according to the present disclosure preferably has an asymmetric structure. R 1 and R 2 preferred combinations include, for example, R 1 is an alkyl group having 6 to 22 carbon atoms and R 2 is an alkenyl group having 6 to 22 carbon atoms; R 1 is a structure represented by formula (3) and R 2 is an alkyl group having 6 to 22 carbon atoms; R 1 is a structure represented by formula (3) and R 2 is an alkenyl group having 6 to 22 carbon atoms; and R 1 and R 2 both are alkyl groups having 12 to 18 carbon atoms.

[0028] [Method for Producing Diester Compound] The method for producing the diester compounds according to this disclosure is not particularly limited. For example, the diester compound represented by formula (1) can be produced by heating and stirring a dicarboxylic acid anhydride with 0.9 to 1.1 molar equivalents of an aliphatic monoalcohol or polyalkylene glycol monoalkyl ether in the presence of a solvent. Subsequently, 1.0 to 1.1 molar equivalents of an aliphatic monoalcohol or polyalkylene glycol monoalkyl ether is added and the mixture is heated and stirred. After that, the desired diester compound can be obtained by washing and filtering as needed to remove the solvent. The heating and stirring conditions are not particularly limited as long as the reaction proceeds, but for example, stirring can be carried out at 110 to 240°C for 1 to 20 hours. The use of a catalyst is not particularly limited, and for example, an acid catalyst such as sulfuric acid or p-toluenesulfonic acid may be used, or the reaction may be carried out without a catalyst. For example, the diester compound represented by formula (2) can be produced by heating and stirring a dialcohol with 0.9 to 1.1 molar equivalents of an aliphatic monocarboxylic acid or R 3 (R 4 O) m R 5 -COOH (however, R 3 , R 4 , m, R 5 The same as in formula (3). Heat and stir the mixture, then add 1.0 to 1.1 molar equivalents of aliphatic monocarboxylic acid or R 3 (R 4 O) m R 5 -COOH (however, R 3 , R 4 , m, R 5 The same as in formula (3). It is obtained by adding () and heating and stirring. The manufacturing method and purification method may be the same as the method for producing the compound represented by formula (1).

[0029] The obtained compounds can be identified, for example, by nuclear magnetic resonance spectroscopy (NMR) or Fourier transform infrared spectroscopy (FTIR) measurements. When identifying compounds by NMR measurements, the methyl group of tetramethylsilane (TMS) is used as a standard. 1 The target compound can be identified by 1H-NMR measurement.

[0030] [Composition] A composition comprising the compounds according to this disclosure comprises at least one diester compound represented by formula (1) or formula (2), and may further contain components other than the diester compounds represented by formula (1) or formula (2). The composition may consist only of compounds of the same type, or it may contain a mixture of multiple types of compounds represented by formula (1) or formula (2). A composition comprising the diester compounds according to this disclosure is a composition comprising one or more types represented by formula (1) or formula (2). The composition according to this disclosure preferably contains 30 wt% or more of the diester compounds represented by formula (1) or formula (2) above, more preferably 40 wt% or more, and may consist substantially only of the diester compounds represented by formula (1) or formula (2) above. The composition according to this disclosure is solid or liquid at room temperature and may be provided as a powder or granular or liquid composition, or dissolved in a solvent and provided as a solution.

[0031] Furthermore, the compositions relating to this disclosure may also include organic acids or organic acid salt compounds as components other than the diester compound represented by formula (1) or formula (2). Preferably, the organic acid or organic acid salt compound has a function as a lubricant. Examples of organic acids or organic acid salt compounds included in the compositions according to this disclosure include organic acids, organic acid monoesters, and organic acid salts. Examples of organic acids include stearic acid, oleic acid, and myristic acid. An example of an organic acid monoester is butyl stearate. Examples of organic acid salts include ammonium fatty acid salts, ammonium phosphonate salts, and ammonium sulfonate salts. The ammonium fatty acid salt is preferably a compound represented by formula (4). [ka] (In formula (4), R 6 R is a hydrocarbon group with 9 or more carbon atoms. 7 , R 8 and R 9(Each of these represents a saturated hydrocarbon group with 1 to 25 carbon atoms.)

[0032] In particular, a composition combining the diester compound according to this disclosure with at least one of a fatty acid having 5 to 50 carbon atoms and a tertiary ammonium salt of a fatty acid can be preferably used as the composition according to this disclosure. When the diester compound is combined with a fatty acid having 5 to 50 carbon atoms and a tertiary ammonium salt of a fatty acid, it is easy to obtain lubrication performance equivalent to or even better than when used alone. The content of the diester compound according to this disclosure is preferably 10 to 70 wt%, and more preferably 10 to 50 wt%, relative to the total of the diester compound, the fatty acid and the tertiary ammonium salt of the fatty acid.

[0033] [Lubricant] The lubricant according to this disclosure comprises the diester compound or the composition described above. The lubricant according to this disclosure may contain at least one of the diester compounds described above, and may further contain other components. When the lubricant contains the diester compound and other components described above, the proportion of the diester compound according to this disclosure to the total lubricant is not limited as long as the effects described in this disclosure are obtained, but may be 50 wt% or more, preferably 60 wt% or more, and may consist substantially of the diester compound according to this disclosure. The lubricant may also use the diester compound or the composition described above as an additive to the lubricant. In that case, the diester compound may be 1 wt% or more and less than 50 wt% relative to the lubricant. The lubricant according to this disclosure has a structure having aliphatic alcohol residues or polyalkylene glycol structures at both ends, which is thought to provide a high degree of freedom in orientation on the surface of the magnetic recording medium, and thus be able to obtain lubricating performance even in small amounts.

[0034] The lubricant of the present invention may contain diester compounds other than those represented by formulas (1) and (2) as by-products in the synthesis of diester compounds, insofar as the effects described herein are obtained. Examples of diester compounds other than those represented by formulas (1) and (2) include those that, when applied to formulas (1) and (2), result in R 1 and R 2 Examples include diester compounds in which there are two or more carbon-carbon double bonds among the carbon-carbon bonds contained. Typically, diester compounds with two or more carbon-carbon double bonds can be included in the lubricant as a byproduct during the synthesis of the compound of the present invention. Diester compounds with two or more carbon-carbon double bonds may be included in the lubricant in amounts of 25 wt% or less, preferably 10 wt% or less, and it is more preferable that they are substantially absent.

[0035] The diester compounds according to this disclosure are solid or liquid compounds at room temperature and may be provided as powders, granules, or liquid lubricants. In this case, when applied to a magnetic recording medium (coated or added to a magnetic layer), it is preferable that they be dissolved in a solvent as needed and used as a solution. Examples of solvents include hydrocarbon solvents such as diisopropyl ether, n-hexane, 2-butanone (methyl ethyl ketone), toluene, and cyclohexanone, and mixed solvents thereof. When used as a solution, the content of the diester compound according to this disclosure in the lubricant containing the solvent is not particularly limited as long as it does not impair the performance of the lubricant, but it is preferably 0.001 to 40 g / L, and more preferably 0.05 to 20 g / L. Furthermore, by combining the diester compounds according to this disclosure with fatty acids having 5 to 50 carbon atoms and tertiary ammonium salts of fatty acids, the diester compounds become more soluble in the solvent, making it easier to prepare high-concentration solutions.

[0036] The lubricant according to this disclosure is suitably used as a lubricant for magnetic recording media, particularly as a lubricant for magnetic tapes. By using the lubricant according to this disclosure on a magnetic recording media, excellent lubrication is maintained even during low-speed operation. Furthermore, it is believed that the lubricant is less likely to precipitate on the surface of the magnetic recording media, and the lubricating effect will be sustained even after long-term use. This provides excellent running performance and durability. While the lubricant according to this disclosure is suitable as a lubricant for magnetic recording media, it can also be applied as a lubricant for polymer films and other materials that do not contain a magnetic layer.

[0037] [Magnetic recording medium] The magnetic recording medium according to this disclosure comprises a non-magnetic support and a magnetic layer laminated on the non-magnetic support, and contains the above-mentioned lubricant. The magnetic layer may also contain the above-mentioned lubricant. The magnetic layer containing the lubricant means that the lubricant is internally added to the magnetic layer. When the lubricant is internally added, it seeps out onto the surface of the magnetic recording medium and exhibits lubricity. Furthermore, the magnetic recording medium according to this disclosure comprises a non-magnetic support and a magnetic layer laminated on the non-magnetic support, with a lubricant layer formed on the magnetic layer, and the lubricant layer may contain the above-mentioned lubricant. The non-magnetic support may also contain the above-mentioned lubricant. The lubricant in the non-magnetic layer plays a role in supplying lubricant to the magnetic layer. The lubricant may be contained in either the non-magnetic support or the magnetic layer, or in both.

[0038] Examples of magnetic recording media include magnetic tapes and magnetic disks. From the viewpoint of reducing the coefficient of friction and improving durability, magnetic tapes or magnetic disks are preferred as magnetic recording media.

[0039] Figure 1 is a schematic cross-sectional view showing the configuration of a magnetic tape according to this disclosure. Referring to Figure 1, the magnetic tape 1 is formed by laminating and integrating a magnetic layer 11, a non-magnetic layer 21, a base film 31, and a back coat layer 41 in this order. The non-magnetic layer and the base film constitute a non-magnetic support. In the magnetic tape of Figure 1, a lubricant is added to the magnetic layer 11. The lubricant may also be added to the magnetic layer 11, the non-magnetic layer 21, and / or the back coat layer. The magnetic layer 11 may be in the form of pigment and magnetic powder dispersed in an organic layer containing a binder and lubricant. The lubricant seeps from the inside of the magnetic layer 11 to the surface, thereby continuously maintaining a low coefficient of friction of the magnetic tape. The non-magnetic layer 21 may be in the form of pigment and / or non-magnetic powder dispersed in an organic layer containing a binder and lubricant. In addition, the magnetic layer 11 and the non-magnetic layer 21 may contain other additives. Examples of additives include dispersants, dispersing aids, fungicides, antistatic agents, and antioxidants.

[0040] The pigment contained in the magnetic layer 11 is not particularly limited as long as it is a component found in known magnetic tapes, and examples include abrasives such as alumina and carbon black powder. The magnetic powder contained in the magnetic layer 11 is not particularly limited as long as it is a component found in known magnetic tapes, and examples include ferromagnetic iron oxide particles such as γ-Fe2O3 and cobalt-coated γ-Fe2O3, ferromagnetic chromium dioxide particles, ferromagnetic metal particles made of metals such as Fe, Co, and Ni, and alloys containing these, and hexagonal plate-shaped hexagonal ferrite fine particles. Examples include hexagonal ferrite, epsilon-type iron oxide (ε-iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, and cobalt-coated iron oxide. The crystal structure of hexagonal ferrite is composed of at least iron atoms, divalent metal atoms, and oxygen atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples include strontium atoms, barium atoms, alkaline earth metal atoms such as calcium atoms, and lead atoms. Examples of hexagonal ferrites include hexagonal strontium ferrite and hexagonal barium ferrite.

[0041] Examples of binders included in the organic layers constituting the magnetic layer 11 and the non-magnetic layer 21 include polymers such as vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylic acid esters, methacrylic acid esters, styrene, butadiene, and acrylonitrile, or copolymers combining two or more of these, polyurethane resins, polyester resins, epoxy resins, etc. Hydrophilic polar groups such as sulfonic acid groups, carboxyl groups, and phosphate groups may be introduced into the binder to improve the dispersibility of the magnetic powder. The binder is not particularly limited as long as it is generally used in magnetic tapes, and examples include crosslinked polyurethane resins or vinyl chloride resins, thermosetting resins, or reactive resins.

[0042] The base film 31 is a layer that functions as a support for the magnetic tape. Examples of materials for the base film 31 include polyester, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polycyclohexylene dimethylene terephthalate (PCT), polyethylene-p-oxybenzoate (PEB), aramid (aromatic polyamide), polyethylene bisphenoxycarboxylate, etc., and one or more of these may be used in combination.

[0043] The back coat layer 41 is a layer for improving the running performance of the magnetic tape. The back coat layer 41 may contain a lubricant. Examples of materials for the back coat layer 41 include polyurethane resins containing carbon and calcium carbonate, nitrocellulose resins, polyester resins, etc.

[0044] Referring to Figure 2, in another embodiment of the present disclosure, the magnetic tape 2 has a lubricant layer 52, a magnetic layer 12, a non-magnetic layer 21, a base film 31, and a back coat layer 41 laminated in this order and integrated. In the magnetic tape 2 of Figure 2, the lubricant layer 52 is held on the surface of the magnetic layer 12, thereby reducing the coefficient of friction and maintaining the durability of the magnetic tape 2. The magnetic layer 12 may or may not contain a lubricant.

[0045] The specific dimensions of the magnetic tape are not particularly limited, but the thickness of the magnetic tape may be, for example, about 3 to 80 μm, and more specifically, about 3 to 10 μm. Generally, among the layers constituting the magnetic tape, the base film 31 has the greatest thickness. The thickness of the base film may be, for example, 3 to 80 μm, preferably 3 to 20 μm, and more preferably 3 to 10 μm.

[0046] The thickness of the magnetic layer 11 can be optimized according to the corresponding recording device and the bandwidth of the recording signal, and is not particularly limited, but from the viewpoint of high-density recording, it may be 10 nm to 150 nm, preferably 20 nm to 120 nm, and more preferably 30 nm to 100 nm. In a magnetic tape, at least one magnetic layer is sufficient, but two or more magnetic layers with different magnetic properties may be provided. If the magnetic layer includes multiple layers, the sum of the thicknesses of the multiple magnetic layers may be within the aforementioned range.

[0047] The thickness of the non-magnetic layer 21 is not particularly limited, but may be, for example, 10 nm to 500 nm, and preferably 50 nm to 300 nm. The thickness of the back coat layer 41 is not particularly limited, but may be, for example, 0.9 μm or less, and preferably 0.1 to 0.7 μm.

[0048] When a lubricant layer 52 is provided on the outermost surface of a magnetic tape, as shown in Figure 2 (magnetic tape 2), the thickness of the lubricant layer 52 may be, for example, about 0.1 to 10 nm, and preferably about 0.5 to 5 nm. Within this range, lubrication performance can be obtained while maintaining surface uniformity.

[0049] The thickness of each layer constituting a magnetic tape can be measured by known film thickness measurement methods. For example, the cross-section in the thickness direction of the magnetic tape can be exposed using known methods such as an ion beam or microtome, and then the exposed cross-section can be observed with a scanning electron microscope to determine the layer thickness from the obtained microscope image. Alternatively, the thickness of each layer can be determined as the design thickness calculated from the manufacturing conditions.

[0050] When the lubricant according to this disclosure is added to a magnetic layer, the content ratio of the lubricant in the magnetic layer is not limited as long as the effects according to this disclosure are obtained, but may be, for example, about 0.1 to 5.0 wt%, and preferably about 0.3 to 3.0 wt%. Within this range, lubrication performance can be obtained while maintaining surface uniformity.

[0051] When the lubricant according to this disclosure is applied as a lubricant layer to the surface of a magnetic tape, the amount of lubricant applied to the magnetic tape is not limited as long as the effects according to this disclosure are obtained, but for example, 0.1 to 5.0 mg / m² 2 It can be around 0.5-3 mg / m². 2 It is preferable that the range be within this range. Within this range, lubrication performance can be obtained while maintaining surface uniformity.

[0052] [Examples] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

[0053] [Synthesis of Compounds] The compounds of Examples 1-6 and Comparative Example 1 were obtained by following the procedure below. (1) Identification of the compound Each compound was analyzed using the JEOL JNM-ECX400. 1 The structure was identified by 1H-NMR measurement. Chloroform-d was used as the solvent and TMS as the reference material. (2) Purity check Product purity was determined by gas chromatography area percentage. An Agilent Technologies 7820A GC system was used. An Agilent Technologies HP-5 column (length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm) was used as the GC column. The temperature program involved raising the temperature from 80°C to 290°C at 40°C / min, holding at 290°C for 25 minutes, for a total run time of 30 minutes.

[0054] <Example 1> 35.02 g of succinic anhydride and 93.02 g of oleyl alcohol were reacted at 130°C for 5 hours while dissolving. Then, 113.60 g of stearyl alcohol, 2.40 g of p-toluenesulfonic acid monohydrate, and 600 g of toluene were added, and the mixture was stirred for 7 hours. After stirring, the mixture was filtered through silica using cyclohexane as the solvent. The solvent was removed from the filtrate using a rotary evaporator to obtain 117.37 g of product. The product contained compound 1 and distearyl succinate. The purity of compound 1 in the product was 61%, and the content of the compound corresponding to the diester compound of formula (1) in Example 1 was 90 wt%. ·Compound 1 [ka] 1 H-NMR:δ[ppm]=0.83-0.94(6H), 1.18-1.48(52H), 1.51-1.70(4H), 1.91-2.08(4H), 2.57-2.65(4H), 4.03-4.14(4H), 5.30-5.38(2H)

[0055] <Example 2> The same procedure as in Example 1 was used, except that tetradecanol (90.04 g) was used instead of stearyl alcohol, to obtain 87.17 g of product. The product contained compound 2 and ditetradecanyl succinate. The purity of compound 2 in the product was 60%, and the content of the compound corresponding to the diester compound of formula (1) in Example 2 was 80 wt%. ·Compound 2 [ka] 1 H-NMR: δ[ppm]=0.83-0.94(6H), 1.18-1.40(44H), 1.57-1.67(4H), 1.94-2.08(4H), 2.57-2.65(4H), 4.03-4.14(4H), 5.30-5.38(2H)

[0056] <Example 3> Except for replacing succinic anhydride with glutaric anhydride (39.94 g) and stearyl alcohol with tetradecanol (90.04 g), the same procedure as in Example 1 was used to obtain 81.05 g of the product. The product contained compound 3 and distearyl glutarate. The purity of compound 3 in the product was 48%, and the content of the compound corresponding to the diester compound of formula (1) in Example 3 was 70 wt%. ·Compound 3 [ka]

[0057] <Example 4> 10 g of succinic anhydride, 22.4 g of polyethylene glycol monomethyl ether 220, and 1.94 g of 4-dimethylaminopyridine were added and stirred in dichloromethane at room temperature for 20 hours. After stirring, the dichloromethane layer was concentrated by two liquid-liquid extractions using distilled water. After concentration, 10.11 g of hexanol was added, and under an Ar atmosphere, 20.90 g of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and 0.95 g of DMAP were added and stirred at room temperature for 20 hours. After stirring, liquid-liquid extractions were performed twice with distilled water, and the solvent was removed from the dichloromethane layer using a rotary evaporator to obtain 24.65 g of product. In the product, the purity of compound 4 was 54%, and the content of the diester compound of formula (1) was 95 wt%. ·Compound 4 [ka] 1 H-NMR: δ[ppm]=0.83-0.94(3H), 1.21-1.42(6H), 1.57-1.67(2H), 2.55-2. 75(4H), 3.35-3.40(3H), 3.47-3.78(16H), 3.98-4.15(2H), 4.17-4.31(2H)

[0058] <Example 5> Except for replacing hexanol with tetradecanol (21.13 g), the same procedure as in Example 4 was used to obtain 31 g of the product. In the product, the purity of compound 5 was 60%, and the content of the diester compound of formula (1) was 91 wt%. ·Compound 5 [ka] 1 H-NMR: δ[ppm]=0.83-0.94(3H), 1.21-1.42(22H), 1.57-1.67(4H), 2.55-2. 75(4H), 3.35-3.40(3H), 3.47-3.78(16H), 3.98-4.15(2H), 4.17-4.31(2H)

[0059] <Example 6> A mixture of 10 g of octadecanol and 1.85 g of succinic anhydride, to which dichloromethane was added dropwise, was a small amount of concentrated sulfuric acid. After the addition of sulfuric acid, the mixture was stirred at room temperature for 1 hour, and then heated under reflux for 15 hours. After heating under reflux, the dichloromethane solution was cooled to room temperature, washed with aqueous sodium bicarbonate solution and water, and then water was removed by adding anhydrous sodium bisulfate. After removing the solvent, the crude product crystals were obtained. The obtained crystals were recrystallized using n-hexane to obtain 7.85 g of the product. The purity of compound 6 was 77%. The content of the compound corresponding to the diester compound of formula (1) in Example 6 was 77 wt%. ·Compound 6 [ka] 1 H-NMR:δ[ppm]=0.83-0.94(6H), 1.21-1.42(60H), 1.57-1.67(4H), 2.55-2.75(4H), 4.03-4.14(4H)

[0060] <Example 7> Dimethyldodecylamine and an equivalent amount of stearic acid were dissolved in ethanol and heated under reflux for 1 hour. The solvent was then removed to obtain dimethyldodecylammonium stearate (compound 7), an organic acid salt. Compound 7 and compound 1 were mixed in a weight ratio of 3:7. The content of the compound corresponding to the diester compound of formula (1) in Example 7 was 27 wt%. Compound 7: 1 H NMR (500MHz, CDCl3) δ(ppm): 2.606 (m, 2H), 2.469(s, 6H), 2.245(t / J=7.5Hz, 2H), 1.594(m, 4H), 1.304-1.245(m, 46H), 0.873(t / J=6.8Hz, 6H)

[0061] <Example 8> Example 1 and compound 7 were mixed in a weight ratio of 5:5. The content of the compound corresponding to the diester compound of formula (1) in Example 8 was 45 wt%.

[0062] <Example 9> Example 1 and compound 7 were mixed in a weight ratio of 7:3. The content of the compound corresponding to the diester compound of formula (1) in Example 9 was 63 wt%.

[0063] <Example 10> Example 1 and stearic acid (manufactured by Nacalai Tex) were mixed in a weight ratio of 5:5. The content of the compound corresponding to the diester compound of formula (1) in Example 10 was 45 wt%.

[0064] <Comparative Example 1> 7.09 g of octadecanol and 1.32 g of succinic anhydride were heated at 130°C, and a small amount of p-toluenesulfonic acid was added and the mixture was reacted for 5 hours. After the reaction, the mixture was returned to room temperature and purified by silica gel chromatography (ethyl acetate / hexane = 1:99) to obtain 6.91 g of the product. The purity of compound 7 was 79%. ·Compound 7 [ka] 1 H-NMR:δ[ppm]=0.83-0.94(6H), 1.18-1.40(44H), 1.57-1.67(4H), 1.94-2.08(8H), 2.57-2.65(4H), 4.03-4.14(4H), 5.30-5.38(4H)

[0065] [Preparation of evaluation samples (magnetic recording media)] The compounds obtained in Examples 1-6 and Comparative Example 1 were dissolved in a solvent to a concentration of 0.1 wt%. Isopropyl alcohol (IPA) or diisopropyl ether (DIPE) was used as the solvent. The resulting solution was coated onto the surface of a magnetic tape (Fujifilm Corporation, LTO Ultrium9) to a wet thickness of 4 μm, and air-dried for 2 hours to prepare a magnetic recording medium for evaluation. As a blank, a sample was prepared by applying only the solvent to the surface of a magnetic tape and allowing it to air dry for 2 hours. Note that most of the solvent evaporated during the drying process.

[0066] [Evaluation of magnetic recording media] (1)Low speed friction characteristics Friction was measured using a friction and wear testing machine (Tribogear) TYPE 40 manufactured by Shinto Kagaku Co., Ltd. under the following test conditions. Test ball: SUJ2 (10mm diameter) Load capacity: 50gf Sliding speed: 1.0 mm / sec. Sliding distance: 5 mm, 5 reciprocating motions Tests were conducted at three different locations on the evaluation sample, and the arithmetic mean of the obtained friction coefficients was defined as the friction coefficient (u). The low-speed friction coefficient was defined as the value obtained by normalizing the friction coefficient (u) with respect to the blank friction coefficient (u0) (u std = u / u0).

[0067] Tables 1 to 4 show the compounds used in Examples 1 to 10 and Comparative Example 1, the solvents used, and the evaluation results. [Table 1] [Table 2] [Table 3] [Table 4]

[0068] As shown in Tables 1 to 4, the magnetic recording media treated with the compounds of Examples 1 to 10 all had a low-speed friction coefficient of less than 1, indicating a friction reduction effect. On the other hand, R 1 and R 2 Comparative Example 1, in which each compound contained 2 carbon-carbon double bonds, had a low-speed friction coefficient of 1.04, and no friction reduction effect was obtained. Examples 7 to 10, in which the diester compound according to this disclosure was mixed with an organic acid salt compound or an organic acid, also obtained a friction reduction effect equivalent to or even better than that obtained when the diester compound was used alone.

[0069] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the present invention is defined by the claims and is intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of symbols]

[0070] 1,2 Magnetic tape, 11,12 Magnetic layer, 21 Non-magnetic layer, 31 Base film, 41 Back coat layer, 51 Lubricant layer 3 friction measuring instrument, 31 fixed part, 32 weight, 33 rotating body.

Claims

1. A diester compound represented by the following formula (1) or formula (2). 【Chemistry 1】 【Chemistry 2】 (In equations (1) and (2), n is a non-negative integer, R １ and R ２ Each of these is independently a hydrocarbon group or a structure represented by formula (3), R １ and R ２ At least one of them has 6 or more carbon atoms, R １ and R ２ The number of carbon-carbon double bonds in the carbon-carbon bond structure is either 0 or 1. 【Transformation 3】 (In formula (3), m is an integer from 1 to 8, and R ３ is a hydrocarbon group, R ４ and R ５ each independently represent an alkylene group having 1 to 6 carbon atoms.)

2. A diester compound represented by formula (1) or (2), R １ and R ２ The diester compound according to claim 1, wherein the two are different from each other.

3. A diester compound represented by formula (1) or (2), R １ and R ２ The diester compound according to claim 1, wherein the hydrocarbon group is a hydrocarbon group having 6 to 22 carbon atoms.

4. A diester compound represented by formula (1) or (2) above, wherein n is 1 to 3. The diester compound according to any one of claims 1 to 3.

5. A composition comprising a diester compound represented by the following formula (1) or formula (2), and an organic acid or organic acid salt compound. 【Chemistry 4】 【Transformation 5】 (In equations (1) and (2), n is a non-negative integer, R １ and R ２ Each of these is independently a hydrocarbon group or a structure represented by formula (3), R １ and R ２ At least one of them has 6 or more carbon atoms, R １ and R ２ The number of carbon-carbon double bonds in the carbon-carbon bond structure is either 0 or 1. 【Transformation 6】 (In equation (3), m is an integer from 1 to 8, and R ３ is a hydrocarbon group, R ４ and R ５ Each of these independently represents an alkylene group with 1 to 6 carbon atoms.

6. A lubricant comprising at least one of the compounds described in claims 1 to 3 and the composition described in claim 5.

7. A magnetic recording medium comprising a non-magnetic support and a magnetic layer laminated on the non-magnetic support, and containing the lubricant described in claim 6.

8. The magnetic recording medium according to claim 7, wherein the magnetic layer includes the lubricant.

9. The magnetic recording medium according to claim 7, further comprising a lubricant layer laminated on the magnetic layer, wherein the lubricant layer contains the lubricant.

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