JPH1036867A - Lubricant and magnetic recording medium produced by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a novel lubricant which exhibits excellent lubricating characteristics under all running conditions whatever and provides a lubricating effect persistent for a long time or period and stable running properties, abrasion resistance, durability, etc., and to obtain a magnetic recording medium produced by using the same. SOLUTION: This lubricant has a molecular structure represented by formula I: Rf -COOR1 NR2 R3 or formula II: R2 R3 NR1 OCO-Rf -COOR1 NR2 R3 wherein one kind of polar group selected from among amino, alkylamino, and dialkylamino group is bonded to one end or to both ends of a perfluoropolyether group. In the formulas, Rf is a perfluoropolyether group; R1 is an alkylene group or an alkylene group having an arom. ring; and R2 and R3 are each independently H or a hydrocarbon group. This magnetic recording medium may be of a coating type or a thin film type.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant and a magnetic recording medium using the same, and more particularly, to a method in which a polar group such as an amino group, an alkylamino group or a dialkylamino group forms a perfluoropolyether group through an ester bond. The present invention relates to a novel lubricant having a structure bonded to a terminal, and a magnetic recording medium using the same, which is excellent in running property, durability and the like.

[0002]

2. Description of the Related Art Thin film type and coating type magnetic recording media are mainly used as magnetic recording media used in audio recording devices, video recording devices, magnetic recording devices attached to computer devices and the like. The thin film type is obtained by depositing a ferromagnetic metal thin film such as Co on a nonmagnetic support by a thin film forming technique such as sputtering, vapor deposition or plating. The coating type is a magnetic paint prepared by dispersing and kneading a magnetic powder, an organic binder and various additives in an organic solvent,
It uses a magnetic recording layer formed by coating, drying and curing on a non-magnetic support.

In these various magnetic recording devices, in recent years, miniaturization and lightening, high image quality, long time, digital recording, and the like have progressed, and there has been a strong demand for high-density recording of magnetic recording media. It has become so. To meet this demand, recent magnetic recording media tend to have their surfaces smoothed to a state close to a mirror surface, narrow the gap between the magnetic head and the magnetic layer, and reduce spacing loss as much as possible. For this reason, the effective contact area between the sliding member such as the magnetic head, the magnetic drum or the guide pin and the magnetic layer increases, and both the friction coefficient and the frictional force increase. Therefore, the phenomenon of adhesion of the magnetic recording medium to the sliding member, that is, so-called sticking, is likely to occur, and there is a problem to be solved in running properties and durability.

As an example, in the case of an 8 mm video tape recorder, a magnetic tape is wound around a magnetic drum through ten or more fixed guide pins made of stainless steel, and the tape tension is about 20 g by a pinch roller, a capstan and a reel motor. , Running speed is 0.5cm / sec
And both are kept constant. In the running system of the magnetic tape recorder, when the frictional force between the sliding member and the magnetic layer increases, the magnetic tape causes a tape squeal due to self-excited vibration called a stick-slip, thereby causing distortion of a reproduced screen. The relative speed between the magnetic tape and the magnetic head is 3.8.
m / sec, and particularly in the still reproduction mode, the same portion of the magnetic tape is continuously contacted at high speed, so that the magnetic layer is worn and the reproduction output is reduced. This problem is further exacerbated in thin-film magnetic tapes because the magnetic layer is thin.

In the case of a hard disk drive, when stopped, the magnetic head is in contact with the surface of the magnetic disk, and when the magnetic disk rotates at a high speed, the magnetic head slightly floats due to the airflow generated by CSS (Contact Start and Storage).
This is a driving mode called p). For this reason, at the time of starting and stopping, the magnetic head runs by rubbing the surface of the magnetic disk, so that a wide range of frictional state from static friction to dynamic friction becomes a problem, which is an extremely severe running condition. In order to guarantee the reliability and durability of an actual product, it is required that the friction coefficient after performing the CSS operation 20,000 times is 0.5 or less, for example. A solution to a head crash that is broken when the magnetic head comes into contact with the surface of the magnetic disk rotating at high speed is also one of the problems required on the magnetic disk side.

In order to solve these problems, the use of various lubricants has been studied. One example is an attempt to reduce the coefficient of friction by internally adding or topcoating a higher fatty acid or an ester thereof to the magnetic layer.

[0007] Lubricants used in recent high-density magnetic recording media are required to have extremely strict characteristics for the purpose of use, and the fact is that conventional lubricants cannot sufficiently cope with such circumstances. The following are representative of such required characteristics. (1) To be excellent in low-temperature characteristics so as to ensure a predetermined lubricating effect when used in a cold environment. (2) It must be extremely thin, for example, several nanometers, and can be uniformly applied on a single-molecule level, or a thin coating film can be formed uniformly so that there is no problem in spacing loss with the magnetic head. Even in such a case, sufficient lubrication characteristics should be exhibited. (3) To withstand long-term use or long-term use, for example, 10 years, and to maintain a lubricating effect.

In order to satisfy these required characteristics and obtain strong adhesion to the surface of the magnetic recording medium, it is necessary to first study the molecular design of the lubricant. It has been clarified that the lubricating properties and adhesion largely depend on the molecular structure of the lubricant. Lubricants developed for magnetic recording media are broadly classified into silicone-based, hydrocarbon-based, and fluorocarbon-based lubricants.

[0009] Silicone-based lubricants are one of the lubricants often used in coating type magnetic recording media because of their excellent thermal stability and low vapor pressure. However, in a thin-film magnetic recording medium having improved surface smoothness, it is becoming difficult to satisfy lubrication characteristics required in a wear-acceleration test by a pin-on-disk method or a CSS test.

[0010] Hydrocarbon lubricants are still the mainstream lubricants in coating type magnetic recording media. However, in general, the vapor pressure is large, and the thermal and chemical stability is often inferior to silicone or fluorocarbon lubricants. In addition, a reaction product called frictional polymer generated by frictional heat or the like adheres to the sliding surface, deteriorating lubrication characteristics, and in some cases, may be a fatal defect. Even a thin film type magnetic recording medium shows excellent initial lubrication characteristics, but it is difficult to replenish a missing lubrication layer due to a high vapor pressure, and there is a problem in long-term durability.

[0011] Fluorocarbon lubricants are currently the most frequently used lubricants in thin-film magnetic recording media. Among them, perfluoropolyethers having a plurality of ether bonds are widely used because of their excellent lubricating properties and surface protection. This is presumably because the CF ₂ —O—CF ₂ bond is flexible, so that the viscosity is smaller than other fluorocarbon compounds having the same molecular weight, and the change in viscosity is small over a wide temperature range. In addition, they are generally chemically inert, have low vapor pressure, have excellent thermal and chemical stability, have low surface energy, have good boundary lubrication properties, and have good water repellency. Characteristics.

The properties of perfluoropolyether are strongly dependent on its molecular structure. Several types of perfluoropolyethers are already commercially available and differ in molecular weight, main chain repeat units, end groups, and the like. For example,
Fomblin-Y type -CF (CF ₃₎ CF ₂ O
-And -CF ₂ O-, in which the main chain repeating unit has a side chain, whereas Fomblin-Z
The type is a random copolymer of —CF ₂ CF ₂ O— and —CF ₂ O—, and the main chain repeating unit has a linear structure. The demnum type and the Krytox type are homopolymers of hexafluoropropylene oxide and hexafluoroisopropylene oxide, respectively. Due to their chemical inertness, perfluoropolyethers generally lack adsorption capacity on the surface of the magnetic layer. Therefore, to improve the adsorption capacity, that is, the adhesion, Fomblin-Z-DOL, which is a perfluoropolyether having a hydroxyl group as a polar group at both ends, and Fomblin-AM2001, which has a piperonyl group as a polar group, have been developed. It is said that Fomblin-AM 2001 has a strong fixing effect particularly on a metal surface or a carbon surface, and that when used for a magnetic disk, the service life is improved to some extent. As described above, various improvements have been made to lubricants for magnetic recording media, including molecular design, but there is still no lubricant that satisfies all required characteristics. Note that F
Omblin, Demnum and Krytox are all trade names.

By the way, in a magnetic recording apparatus in which the relative speed between the magnetic head and the magnetic recording medium is about several m / sec or more, the frictional heat generated at the contact portion causes the surface temperature to suddenly increase instantaneously. Although there is no method for accurately measuring the temperature at the contact point between the two in real time, it is estimated from simulation results that the temperature locally exceeds several hundred degrees Celsius. In particular, under such boundary conditions, a surface having high reactivity is exposed, so that the decomposition reaction of the lubricant molecules is promoted at the contact point where the temperature becomes high. Perfluoropolyether is generally stable in air at a high temperature of 350 ° C. or higher, but it is not limited to metals and alloys such as iron and titanium, or AlCl.
_3. Decomposition is likely in the presence of a Lewis acid or Lewis base such as FeCl ₃ or Al ₂ O ₃ . Decomposition of such lubricants
Naturally, this has an adverse effect on the lubrication properties, which results in a loss of the reliability of the entire magnetic recording device. Therefore, it is also desired to develop a lubricant that has less decomposition in addition to the lubricating properties.

As a more recent tendency, an increase in the relative speed between the magnetic head and the magnetic recording medium causes an altered layer called brown stain to be generated on the sliding surface of the magnetic head. The output may be significantly deteriorated. Although the mechanism of brown stain generation is not clear, it is thought to be due to the formation of an oxide layer such as iron oxide. The lubricant on the surface of the magnetic layer is also expected to have an effect of preventing the formation of the oxide layer, and therefore, development of a new lubricant is required.

[0015]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned circumstances, and provides excellent lubricating properties under all driving conditions, while maintaining a stable lubricating effect for a long time or a long time. It is an object of the present invention to provide a novel lubricant capable of obtaining running properties, abrasion resistance or durability, and a magnetic recording medium using the same.

[0016]

SUMMARY OF THE INVENTION The lubricant of the present invention is proposed to solve the above-mentioned problems, and comprises an amino group, an alkylamino group and a dialkylamino group represented by the following general formula (1). Wherein any one of the polar groups has a molecular structure in which the polar group is bonded to an end of a perfluoropolyether group by an ester bond. R _f -COOR ₁ NR ₂ R ₃ (1) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring, and R ₂ and R ₃ are Each independently represents one of hydrogen and a hydrocarbon group.)

Further, another lubricant according to the present invention is characterized in that any one of polar groups selected from an amino group, an alkylamino group and a dialkylamino group represented by the following general formula (2) is a perfluoro group formed by an ester bond. It has a molecular structure bonded to both ends of a polyether group. R ₂ R ₃ NR ₁ OCO-R _f —COOR ₁ NR ₂ R ₃ (2) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring) And R ₂ and R ₃ each independently represent any one of hydrogen and a hydrocarbon group.)

The magnetic recording medium of the present invention is characterized in that the lubricant represented by the general formula (1) or (2) is applied to the surface of a magnetic layer formed on a non-magnetic support. I do. In this case, the magnetic layer is desirably a thin film type magnetic recording medium made of a ferromagnetic metal thin film or a coating type magnetic recording medium in which magnetic powder is dispersed in an organic binder.

Another magnetic recording medium according to the present invention is characterized in that the lubricant represented by the general formula (1) or (2) is internally added to a magnetic layer formed on a non-magnetic support. Features. In this case, the magnetic layer is preferably a coating type magnetic recording medium in which magnetic powder is dispersed in an organic binder. Regardless of the magnetic recording medium, the general formula (1)
Alternatively, the lubricant represented by (2) may be used in combination.

The molecular structure of the perfluoropolyether group _Rf in the lubricant of the present invention is not particularly limited, but one example is shown below. As a repeating unit of a monofunctional perfluoropolyether group, a copolymer of a perfluorooxyisoprene group and a perfluorooxymethylene group represented by the following general formula (3) CF ₃ [OCF (CF ₃ ) CF ₂ ] _j (OCF ₂ ) _k- (3) or a homopolymer of a perfluorooxyisoprene group represented by the following general formula (4) F [CF (CF ₃ ) CF ₂ O] _l- (4) Examples of the perfluorooxypropylene group homopolymer F (CF ₂ CF ₂ CF ₂ O) _m − (5) represented by 5), etc. Further, as the repeating unit of the polyfunctional perfluoropolyether group, Examples are shown by the following general formula (6):-(OC ₂ F ₄ ) _p (OCF ₂ ) _q- (6) However, j, k, l in the general formulas (3) to (6). , M, p and q are Deviation even preferably 0.5 to 2.0 independently values of .p / q representing a natural number of 1 or more, 700-10000 about any molecular weight, 700 to 4,000
The degree is more preferred.

The hydrocarbon groups R ₂ and R ₃ introduced into the amino group are selected irrespective of the molecular weight, the number of carbon atoms, the branched structure, the presence or absence of an unsaturated bond, the presence or absence of an aromatic ring or an alicyclic structure, and the isomer structure. can do. It may be hydrogen. However, from the viewpoint of solubility in general-purpose solvents such as hydrocarbons other than fluorocarbon (CF) solvents or chlorofluorocarbon (CFC) solvents, one of R ₂ and R ₃ has a carbon number of, for example, Desirably, it is a long-chain hydrocarbon group of 6 or more. From the viewpoint of durability, there is no particular limitation.

R ₁ between the amino group and the ester bond is
Linear or branched hydrocarbons having 2 or more carbon atoms and having an aromatic ring in the structure are preferred from the viewpoint of reducing the friction coefficient. Also in this case, as in R ₂ and R ₃ , the greater the number of carbon atoms in R ₁ , the better the solubility in general-purpose solvents.

As the magnetic layer of the magnetic recording medium of the present invention,
It can be applied to both thin film type and coating type. Among them, the thin film type magnetic layer is formed by forming a ferromagnetic metal on a nonmagnetic support by a thin film forming technique such as vapor deposition, sputtering or plating. When used as a hard disk, a diamond-like carbon film, amorphous carbon film, chromium oxide film,
A hard protective film such as a silicon oxide film or a zirconium oxide film may be formed extremely thin. As the material of the ferromagnetic metal, a simple ferromagnetic metal such as Co, Fe, or Ni, a Co—Ni-based alloy, a Co—Ni—Pt-based alloy,
-Cr alloy, Co-Cr-Ta alloy, Co-Cr-Pt
Alloys such as alloys, Fe-Co-Ni alloys, Fe-N
i-B alloy, Fe-Co-B alloy, Fe-Co-Ni-
Examples thereof include Fe-based alloys such as B alloys, and alloys having a structure in which oxides, nitrides, carbides, and the like are precipitated in these ferromagnetic materials and at grain boundaries. In particular, in a thin-film magnetic recording medium using an in-plane magnetization mode, a magnetic layer is formed on the surface of a nonmagnetic support by oblique vapor deposition or the like, and the axis of easy magnetization is oriented substantially in the plane of the magnetic layer. Bi, Sb, Pb, Sn, on a non-magnetic support
A non-magnetic underlayer such as Ga, In, Ge, Si or Ti may be formed, and a ferromagnetic metal may be deposited or sputtered from a vertical ring on the surface of the non-magnetic support. By interposing such a non-magnetic underlayer, it is possible to diffuse a non-magnetic metal into the magnetic layer, control the morphology of the magnetic layer to impart in-plane isotropic magnetization, and improve coercive force. .

The lubricant of the present invention can be applied by coating, ie, top-coating, on such a thin-film type magnetic layer or a hard protective film. The coating amount of the lubricant, it is preferably a 0.5 to 100 mg / m ^2, and still more desirably 1 to 20 mg / m ^2.
Below this range, the effects of lubricity and durability are small, and even if the amount is larger than this range, the effects of lubricity and durability are saturated.

In order to maintain the lubrication effect of the thin film type magnetic recording medium under severe running conditions, an extreme pressure agent may be used in addition to the lubricant of the present invention. The mixing ratio of the lubricant and the extreme pressure agent is preferably in the range of about 30:70 to 70:30.
The extreme pressure agent reacts with the exposed metal surface when the metal contact occurs partially in the boundary lubrication area and generates frictional heat, and forms a reaction product film, thereby causing friction and wear. It is an additive that has a protective effect. There are phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogenated extreme pressure agents, organometallic extreme pressure agents, composite extreme pressure agents, and the like, all of which can be used in combination with the lubricant of the present invention. It is possible.

In the case of a thin film type magnetic recording medium or a coating type magnetic recording medium of a metal magnetic powder type, a rust preventive may be applied in the form of a coating or internally added in order to prevent oxidation of the ferromagnetic metal. . As rust inhibitors, for example, phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom,
Any of a heterocyclic compound containing an oxygen atom and a heterocyclic compound containing a sulfur atom can be used.

The coating type magnetic layer is formed by dispersing and kneading a magnetic powder, a dispersant, an abrasive, a matting agent, an antistatic agent and the like together with an organic binder in an organic solvent, using a non-magnetic support. It is formed through steps such as coating, magnetic orientation, drying and curing. The lubricant of the present invention may be added to the magnetic paint in advance, or may be separately applied on the formed magnetic layer. Among these, the material of the magnetic powder is not particularly limited, and metal magnetic powder,
Either oxide magnetic powder or other compound magnetic powder is used. Fe, Co,
Metals such as Ni and their alloys, or Al, Si, Ti, Cr, V, Mn, Cu, Zn,
Any one of elements such as Mg, Bi, rare earth, P, B, N, and C, or a plurality of elements added thereto may be used. Among them, Fe or Fe—Co alloy is preferably used in terms of saturation magnetization. Further, the surface layer of these metal magnetic powders may contain a sintering preventing element or a shape maintaining element such as Al, Si, P or B. As iron oxide-based magnetic powders, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , γ-Fe
Belt compound which is an intermediate between ₂ O ₃ and Fe ₃ O ₄ , Co-containing γ-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , C
various spinel-type iron oxides such as a beltride compound which is an intermediate between o-containing γ-Fe ₂ O ₃ and Co-containing Fe ₃ O ₄ ,
Various barium ferrites such as M type, W type, Y type, Z type,
In order to improve the coercive force of calcium ferrite, lead ferrite, and these various magnetoplumbite iron oxides,
Magnetoplumbite-type iron oxide to which Co, Ti, Zn, Nb, Cu or Ni is added is exemplified. Examples of the iron compound include iron oxide, iron nitride, iron carbide, and iron boride. As the oxide-based material, CrO ₂ or a material obtained by adding a small amount of Te, Sb, Fe, B, or the like thereto may be used. These magnetic powders can be used alone or in combination of two or more.

As the shape of the magnetic powder used in the present invention, the major axis length is, for example, about 0.05 μm to 0.5 μm, and the axial ratio (aspect ratio) is about 3 to 30, preferably 5 to 1.
It is preferably about 5 and has a needle-like, column-like, spindle-like or rod-like outer shape. If the major axis length is less than 0.05 μm, it is difficult to disperse the magnetic paint, and the major axis length is not more than 0.1 μm.
If it exceeds 5 μm, the noise characteristics may deteriorate, which is not preferable. If the axial ratio is less than 3, the magnetic field orientation of the individual magnetic particles deteriorates, the squareness ratio and the residual magnetic flux decrease, and as a result, the output decreases. On the other hand, if the axial ratio exceeds 30, the short-wavelength signal may be reduced, which is not preferable. In the case of magnetoplumbite-type iron oxide, a fine hexagonal plate is used. This has a plate diameter of 0.01 to 0.5 μm and a plate thickness of 0.1 μm.
It is preferably about 001 to 0.2 μm. The major axis length, the axial ratio, the plate diameter, the plate thickness, and the like can be determined from the average value of particles of 100 or more samples randomly extracted from a transmission electron micrograph. The specific surface area of these magnetic powders is 30 m ²
/ G to 80 m ² / g, especially 40 m ² / g to 70 m ²
/ G is preferable. By selecting the specific surface area within this range, it is possible to obtain a high-density recording accompanying finer magnetic powder and a magnetic recording medium excellent in noise characteristics.

As the organic binder used for the coating type magnetic layer, any of thermoplastic resins, thermosetting resins, and reactive resins conventionally used as binders for magnetic recording media can be used. . It is desirable that the thermoplastic resin be used in combination with a thermosetting resin, a reactive resin, or the like. The molecular weight of the resin is preferably from 5,000 to 200,000, more preferably from 10,000 to 100,000. As the thermoplastic resin, for example, vinyl chloride resin, vinyl acetate resin, vinyl fluoride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, Vinyl chloride-acrylonitrile copolymer, vinylidene chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacryl Acid ester-vinylidene chloride copolymer, methacrylate-ethylene copolymer,
Acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, polyurethane resin, polyester polyurethane resin, polycarbonate polyurethane resin,
Polyamide resin, polyvinyl butyral resin, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer, polyester resin, amino resin,
Various types of synthetic rubbers can be used. Examples of thermosetting resins and reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea formaldehyde resins, melamine resins, alkyd resins, silicone resins, polyamine resins, high molecular weight polyester resins and isocyanate prepolymers. Examples thereof include a mixture, a mixture of a polyester polyol and a polyisocyanate, a mixture of a low molecular weight glycol, a high molecular weight diol, and an isocyanate, and a mixture of these resins. These resins are
In order to improve the dispersibility of the magnetic powder, -SO ₃ M, -OS
It may contain a polar functional group such as O ₃ M, —COOM, or —PO (OM ′) ₂ (where M is H or an alkali metal such as Li, Ka, Na, and M ′ is H or Li , Ka, Na, etc. or an alkyl group). In addition to the polar functional group, -NR
₁ R ₂ , -NR ₁ R ₂ R ₃ ⁺ X ⁻ side chain type having a terminal group, and> NR ₁ R ₂ ⁺ X ⁻ main chain type (here, R ₁ , R ₂ , R ₃ is a hydrogen atom or a hydrocarbon group, X ^- represents fluorine, chlorine, bromine, halogen ion or an inorganic iodine, the organic ions). In addition, a polar functional group such as —OH, —SH, —CN, or an epoxy group may be used. The content of these polar functional groups is 10 ^-1
-10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6
mol / g. These organic binders can be used alone or in combination of two or more. The amount of these organic binders in the magnetic recording layer is 1 to 200 parts by weight based on 100 parts by weight of the magnetic powder.
Preferably it is 10 to 50 parts by weight.

As a curing agent for crosslinking and curing the above-mentioned organic binder, for example, polyisocyanate or the like can be added. Examples of the polyisocyanate include toluene diisocyanate and its adduct, alkylene diisocyanate and its adduct, and the like. Tetraglycidyl metaxylene diamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidylaminodiphenylmethane, triglycidyl-p
-Polyglycidylamine compounds such as aminophenol,
Polythiol compounds such as 2-dibutylamino-4,6-dimercapto-substituted triazine, epoxy compounds such as triglycidyl isocyanurate, mixtures of epoxy compounds and isocyanate compounds, mixtures of epoxy compounds and oxazoline compounds, mixtures of imidazole compounds and isocyanate compounds Any of those conventionally known, such as, methylnadic anhydride and the like can be used. The mixing ratio of these curing agents to the organic binder is 5 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the organic binder.

To disperse the magnetic powder well, it is preferable to use a dispersant. Specific examples of these dispersants include, but are not particularly limited to, fatty acids having 10 to 20 carbon atoms, salts of these fatty acids with alkali metals, alkaline earth metals or transition metals, phosphates and sulfates of these fatty acids, and silicon. Examples include surfactants such as various types of coupling agents based on titanium, titanium or aluminum. The addition amount of these dispersants is preferably 1 to 5 parts by weight based on 100 parts by weight of the magnetic powder. If the amount is less than 1 part by weight, the function as a dispersant cannot be sufficiently exhibited. If the amount exceeds 5 parts by weight, a large number of functional groups unreacted with the magnetic powder will be present in the magnetic recording layer, and the interaction of these excess functional groups will lower the dispersibility. In addition, these unreacted functional groups quickly react with a curing agent such as polyisocyanate, and in this case, the dispersibility may be reduced.

The abrasive also serves as a reinforcing agent for the magnetic recording layer, and has a Mohs hardness of 4 or more, preferably 5 or more, and a specific gravity of 2 or more.
~ 6, preferably 3 ~ 5. Specifically, various aluminas such as fused alumina, α, β, γ-alumina, silicon carbide, chromium oxide, titanium oxide (rutile and anatase) corundum, artificial corundum, artificial diamond, garnet, emery, silica, etc. Any known one can be used. These abrasives are
Average particle diameter 0.05-5 μm, preferably 0.1-2 μm
m is used, and is usually added in the range of 1 to 20 parts by weight based on 100 parts by weight of the organic binder.

As the matting agent, an organic powder, an inorganic powder or a mixture thereof is used. Acrylic styrene resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, and polyfluoroethylene resin powder can be used as the organic powder.
Examples of the inorganic powder include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, chromium oxide, silicon carbide, iron oxide, talc,
Kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide and the like are exemplified.

Examples of the antistatic agent include natural surfactants such as carbon black, graphite, tin oxide-antimony oxide composite oxide, titanium oxide-tin oxide-antimony oxide composite oxide, saponin, alkylene oxides, glycerin and the like. , Glycidol and other nonionic surfactants, higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, cationic surfactants such as phosphonium and sulfonium, carboxylic acids, sulfonic acids, phosphoric acids, sulfates And the like. Anionic surfactants containing an acidic group such as, for example, amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric acid esters of amino alcohol are exemplified.

As an organic solvent for preparing a magnetic paint for forming a magnetic recording layer or a diluting solvent used for applying the magnetic paint on a non-magnetic support, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone Ketones; alcohols such as methanol, ethanol, propanol, butanol, etc .; esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl lactate, ethylene glycol monoacetate, diethylene glycol dimethyl ether, glycol monoethyl ether, dioxane , Ethers such as tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform and dichlorobenzene Etc. is used. The mixing ratio of these organic binders, organic solvents and dispersants, lubricants, various additives such as abrasives and the like used in the coating type magnetic recording medium of the present invention may be the same as that of a normal coating type magnetic recording medium. .

The preparation of the magnetic paint is carried out through the steps of mixing, dispersing and kneading these magnetic powder, organic binder, various additives and organic solvent. For dispersion and kneading, a kneader, an agitator, a ball mill, a sand mill, a roll mill, an extruder, a homogenizer, an ultrasonic disperser, and the like are used.

The coating method for forming the coating type magnetic recording layer on the nonmagnetic support is not particularly limited, and may be air doctor coat, blade coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat. Conventional methods such as gravure coating, kiss coating, cast coating, extrusion coating, and spin coating can be employed. When forming a multi-layer coating layer including a magnetic recording layer on a non-magnetic support by these coating methods, a method in which coating and drying steps are stacked one by one may be performed, and a continuous coating is performed on an undried coating film. Alternatively, it may be formed by a wet-on-wet method in which coating is repeated at the same time.

The magnetic recording layer formed on the non-magnetic support is subjected to a magnetic field orientation treatment in an undried state, if necessary, and then dried with heated air or the like to remove the organic solvent. The orientation magnetic field is DC or AC, for example, 0.05T or more.
About 0.5T, the drying temperature is about 50-120 ° C,
The drying time is preferably about 0.1 to 10 minutes. After drying the magnetic recording layer, this is further applied with a lubricant if necessary, a surface smoothing process such as a calendar process, a winding process on a winding roll, a curing process, a cutting process into a desired shape. Through these steps, the magnetic recording medium is completed. The curing step may be performed before or after the calendaring. The lubricant application step may be performed after the surface smoothing step or the curing step.

As the non-magnetic support applied to the magnetic recording medium of the present invention, any of those used for ordinary coating type and thin film type magnetic recording media can be used, and polyethylene terephthalate, polyethylene-2,6 -Polyesters such as naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, vinylidene resins such as polyvinylidene chloride, polycarbonate, polyamide imide and polyimide And other organic polymers. A base material layer for improving adhesion may be provided on the surface of these nonmagnetic supports. A back coat layer for antistatic purposes may be provided on the surface of the non-magnetic support opposite to the magnetic recording layer.
Such a back coat layer is prepared by coating a carbon powder for imparting conductivity or an inorganic pigment for controlling surface roughness in an organic binder, and applying and drying this on the back surface of the non-magnetic support. Formed. In the magnetic recording medium of the present invention, the lubricant of the present invention may be applied or internally added to the back coat layer. In addition to this as a non-magnetic support,
A rigid substrate made of a metal or alloy such as an Al-based metal, a Ti-based metal, a Cu-based metal, or a Zn-based metal, ceramics such as alumina, quartz, or boron nitride, glass, or the like may be used.
An anodic oxide film, a Ni-P-based plating film, or the like may be formed as a base layer on the surface of the rigid substrate. The thickness of the non-magnetic support is 3 to 100 μm, preferably 5 to 50 μm in the case of a film or sheet, and about 30 μm to 10 mm in the case of a card or disk. In the case of a magnetic drum, it is used in a cylindrical shape, and the shape is determined according to the magnetic recording device used.

In both the thin film type and the coating type magnetic layers, other lubricants may be used in combination with the lubricant of the present invention. Examples of other lubricants include general fluorine-based lubricants, silicone oil, graphite, carbon black graphite polymer, molybdenum disulfide, tungsten disulfide, or lauric acid, myristic acid, or the like having about 10 to 22 carbon atoms. Any conventionally known fatty acid ester, terpene-based compound, or oligomer thereof composed of a fatty acid and a monohydric alcohol having 21 to 23 carbon atoms in total with the number of carbon atoms of the fatty acid can be used. . In the case of a coating type magnetic layer, these lubricants are usually added in an amount of 0.2 to 100 parts by weight of the organic binder.
It is added in the range of ２０20 parts by weight.

Next, the operation will be described. The present inventors have paid attention to the excellent lubricity of perfluoropolyether, and have continued a series of molecular designs for applying this to a lubricant for a high-density magnetic recording medium exposed to severe running conditions. In the process, an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol was disclosed in JP-A-5-194971. Also,
A perfluoropolyether compound having an amino group or an alkylamino group at a terminal is disclosed in JP-A-7-32025.
No. 5 discloses this. The present invention is also dedicated to responding to demands for higher density and digitalization of magnetic recording devices, measures for reducing reproduction level due to generation of brown stain, improvement of solubility in general-purpose solvents, and further reduction of friction coefficient. The research was advanced to complete the present invention.

The lubricant of the present invention has both a carbonyl group in an ester bond and an amino group as polar groups closely related to the adsorption ability of the magnetic layer surface. Therefore, the effect of immobilization on the surface of the magnetic layer is strong, and the lubricating effect of the perfluoropolyether portion is maintained for a long time or for a long time. In particular, this effect is not impaired even under low-temperature use conditions and high-humidity use conditions. Further, by specifying the number of carbon atoms of R ₁ , R ₂ and R ₃ , the solubility in general-purpose solvents other than a fluorocarbon solvent or a chlorofluorocarbon solvent is improved. Therefore, the magnetic recording medium using the lubricant of the present invention can obtain stable running property, durability, or abrasion resistance under all use conditions.

[0043]

EXAMPLES Hereinafter, specific examples of the present invention will be described with reference to comparative examples as appropriate. It should be noted that the following embodiments are merely examples of preferred embodiments of the present invention, and the present invention is not limited to these embodiments.

Synthesis Example 1 First, an outline of a synthesis example of the lubricant of the present invention will be described. The lubricant of the present invention represented by the general formula (1) or (2) is obtained by esterifying a perfluoropolyether having a carboxyl group at one or both terminals with an alcohol having an amino group, an alkylamino group or a dialkylamino group. It can be synthesized by a chemical reaction. Examples of the esterification method include a method of dehydration in a solvent such as toluene, and a method of chloride-forming perfluoropolyether having a carboxyl group at a terminal, followed by esterification using a base as a catalyst. Here, as an example, dimethylaminohexanol and perfluoropolyether of a random copolymer having a carboxyl group at both terminals are dehydrated in anhydrous toluene, the solvent is removed, extracted with ethyl acetate, and further subjected to silica gel chromatography. Purification was performed to obtain the desired ester compound. The compound (1) according to this synthesis example is represented by R ₁ in the general formula (2).
Is — (CH ₂ ) ₆ —, and R ₂ and R ₃ are both —CH
_It is equivalent to ₃ . FIG. 1 shows an IR (infrared) absorption spectrum of the compound (1). As seen in the figure, C-H stretching vibration in the vicinity of 2900 cm ^-1, around ^-1 absorption of a carbonyl group 1790 cm, and since the C-F stretching vibration appearing respectively around 1100～1300Cm ^-1, This compound is identified.

Synthetic Examples 2 to 10 By the same method as in Synthetic Example 1, various modifications of the molecular structure of the perfluoropolyether and the molecular structure of the alcohol having an amino group, an alkylamino group or a dialkylamino group were respectively esterified. As a result, compounds (2) to (10) were obtained. The ten compounds obtained as described above are summarized in [Table 1].

[0046]

[Table 1]

The following Examples 1 to 10 are examples in which the lubricant of the present invention is applied to a thin film type magnetic recording medium. Example 1 Metal Co was deposited on a PET (polyethylene terephthalate) film by oblique evaporation to form a magnetic layer composed of a ferromagnetic metal thin film. The thicknesses of the PET film and the magnetic layer are, for example, 10 μm and 200 nm, respectively.
And On this magnetic layer, a diluted solution in which the lubricant of the compound (1) obtained in Synthesis Example 1 was dissolved in ethyl acetate was applied so that the application amount of the lubricant per unit area was 5 mg / m ^2. After drying, this was cut into a width of 8 mm and
Was obtained.

Examples 2 to 10 Example 2 was repeated in the same manner as in Example 1 except that the compounds (2) to (10) obtained in Synthesis Examples 2 to 10 were used instead of the compound (1). To 10 magnetic recording media were obtained.

[0049] except for using a perfluoropolyether having Comparative Example 1 Commercially available terminal carboxyl group as a lubricant were the same as before in Example 1 to obtain a magnetic recording medium of Comparative Example 1.

[0050] except for using a perfluoropolyether having a hydroxyl group into a commercially available terminal Comparative Example 2 as a lubricant, were the same as before in Example 1 to obtain a magnetic recording medium of Comparative Example 2.

Examples 1 to 10 prepared as described above
Of the magnetic recording media of Comparative Examples 1 and 2, and the friction coefficients were measured. In addition, Still durability and Shuttle durability were measured using a measuring machine modified from a commercially available 8 mm video tape recorder. As measurement conditions, 25 ° C., 60% RH (normal environmental conditions), 40 ° C.
80% RH (hot and humid condition) and -5 ° C (cold condition)
The following three conditions were selected. [Table 2] and [Table 3]
Are shown together.

[0052]

[Table 2]

[0053]

[Table 3]

From the results shown in Tables 2 and 3, one of the polar groups selected from an amino group, an alkylamino group and a dialkylamino group was converted into a perfluoropolyether group terminal or both terminals by an ester bond. The lubricant of the present invention having a structure bonded to is lower under any measurement conditions as compared with a commercially available comparative lubricant having a structure in which a carboxyl group or a hydroxyl group is bonded to a perfluoropolyether terminal. It is clear that it has a coefficient of friction and excellent running durability.

The following Examples 11 to 20 are examples in which the lubricant of the present invention is applied to a coating type magnetic recording medium. Example 11 A magnetic paint was prepared based on the following composition. Coating is carried out according to a conventional method. A magnetic powder, an organic binder, various additives and an organic solvent are mixed, kneaded with a kneader or the like, and then mixed with a sand mill.
Time dispersed. Magnetic powder 100 parts by weight (Fe-based metal magnetic powder, coercive force 160 kA / m, saturation magnetization 135 Am ² / kg, specific surface area 51 m ² / g, major axis length 0.12 μm, needle ratio 8) vinyl chloride vinyl acetate Combined 10.5 parts by weight Polyurethane resin 10.5 parts by weight Carbon powder 5 parts by weight Methyl ethyl ketone 150 parts by weight Methyl isobutyl ketone 150 parts by weight

After filtering the obtained magnetic paint, 4 parts by weight of a polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added as a curing agent, applied on a PET film using a die coater, and subjected to a magnetic field orientation treatment by a solenoid coil. Dried. The thickness of the PET film and the thickness of the dried magnetic layer were, for example, 12 μm and 3.0 μm, respectively. After calendering this, a diluted solution of the compound (1) lubricant obtained in Synthesis Example 1 dissolved in ethyl acetate was applied so that the amount of the lubricant applied per unit area was 5 mg / m ^2.・ Dry and weigh 8mm
The magnetic recording medium of Example 11 was obtained by cutting to width.

Examples 12 to 20 Example 12 was repeated in the same manner as in Example 11 except that the compounds (2) to (10) obtained in Synthesis Examples 2 to 10 were used instead of the compound (1). To 20 magnetic recording media were obtained.

[0058] except for using a perfluoropolyether having the Comparative Example 3 Commercially available terminal carboxyl group as a lubricant were the same as before in Example 11 to obtain a coating type magnetic recording medium of Comparative Example 3.

[0059] except for using a perfluoropolyether having a hydroxyl group in Comparative Example 4 Commercially available terminal as lubricant were the same as before in Example 11 to obtain a coating type magnetic recording medium of Comparative Example 4.

Embodiments 11 and 2 prepared as described above
The coefficient of friction was measured for the magnetic recording media of No. 0 and the magnetic recording media of Comparative Examples 3 and 4. The stick slip and the number of dropouts were measured using a measuring machine modified from a commercially available 8 mm video tape recorder. As measurement conditions, aging was performed for a predetermined time under 40 ° C. and 80% RH (high temperature and high humidity conditions), and measurement was performed before and after the aging. For stick-slip, samples with a coefficient of static friction exceeding 0.6 shall have a tape squeal in actual running,
Those exceeding 0.6 were evaluated as x. The dropout is 3
For 3 minutes or more, the actual output for 10 minutes
The number of times that the output was reduced by more than dB was counted.

The measurement results are shown in Tables 4 and 5.

[0062]

[Table 4]

[0063]

[Table 5]

As is evident from the results of Tables 4 and 5, one of the polar groups selected from an amino group, an alkylamino group and a dialkylamino group is converted to a perfluoropolyether group by an ester bond. The lubricant of the present invention having a structure bonded to the terminal or both terminals,
Compared with a commercially available comparative lubricant having a structure in which a carboxyl group or a hydroxyl group is bonded to a perfluoropolyether terminal, a low coefficient of friction, excellent running stability, and a low dropout number before and after aging, both before and after aging. It can be seen that

Although the lubricant of the present invention and the magnetic recording medium using the same have been described in detail above, these are merely examples, and the present invention is not limited to these examples. For example, in the embodiments, the magnetic tape is exemplified as the magnetic recording medium, but the same effect can be obtained for a floppy disk, a hard disk, a magnetic card, or the like. In a coating type magnetic recording medium, the same effect can be obtained even if the lubricant of the present invention is internally added to a magnetic paint in advance. It is obvious that the material of the magnetic powder, the composition of the magnetic paint, the metal or alloy composition of the ferromagnetic metal thin film, and the manufacturing conditions of the magnetic recording medium can be appropriately changed.

[0066]

As is clear from the above description, according to the present invention, a strong fixing effect on the surface of the magnetic layer can be obtained, excellent lubricating properties can be obtained under all running conditions, and Alternatively, it is possible to provide a novel lubricant that maintains a lubricating effect for a long period of time and provides stable running properties, abrasion resistance or durability, and a magnetic recording medium using the same.

[Brief description of the drawings]

FIG. 1 is an IR absorption spectrum of the compound (1) obtained in Example 1.

Claims (15)

[Claims] 1. A polar group selected from an amino group, an alkylamino group and a dialkylamino group represented by the following general formula (1) is bonded to a perfluoropolyether group terminal by an ester bond. A lubricant characterized by having a molecular structure. R _f -COOR ₁ NR ₂ R ₃ (1) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring, and R ₂ and R ₃ are Each independently represents one of hydrogen and a hydrocarbon group.) 2. One of polar groups selected from an amino group, an alkylamino group and a dialkylamino group represented by the following general formula (2) is bonded to both ends of a perfluoropolyether group by an ester bond. A lubricant characterized by having a modified molecular structure. R ₂ R ₃ NR ₁ OCO-R _f —COOR ₁ NR ₂ R ₃ (2) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring) And R ₂ and R ₃ each independently represent any one of hydrogen and a hydrocarbon group.) 3. The method according to claim 1, wherein R ₁ is any one of an alkylene group having 2 or more carbon atoms and an alkylene group having 2 or more carbon atoms having an aromatic ring.
The described lubricant. 4. The lubricant according to claim 1, wherein at least one of R ₂ and R ₃ is a long-chain alkyl group having 6 or more carbon atoms. 5. A magnetic recording medium having a magnetic layer formed on a nonmagnetic support, wherein an amino group, an alkylamino group and a terminal represented by the following general formula (1) are provided on the surface of the magnetic layer. A magnetic recording medium, which is coated with a lubricant having a molecular structure in which any one polar group selected from dialkylamino groups is bonded to a perfluoropolyether group terminal by an ester bond. R _f -COOR ₁ NR ₂ R ₃ (1) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring, and R ₂ and R ₃ are Each independently represents one of hydrogen and a hydrocarbon group.) 6. A magnetic recording medium having a magnetic layer formed on a nonmagnetic support, wherein an amino group, an alkylamino group and a terminal represented by the following general formula (2) are provided on the surface of the magnetic layer. A magnetic recording medium comprising a lubricant having a molecular structure in which any one polar group selected from dialkylamino groups is bonded to both ends of a perfluoropolyether group by an ester bond. R ₂ R ₃ NR ₁ OCO-R _f —COOR ₁ NR ₂ R ₃ (2) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring) And R ₂ and R ₃ each independently represent any one of hydrogen and a hydrocarbon group.) 7. The magnetic recording medium according to claim 5, wherein the magnetic layer is made of a ferromagnetic metal thin film. 8. The magnetic layer according to claim 5, wherein at least a magnetic powder is dispersed in an organic binder.
Or a magnetic recording medium according to 6. 9. The method according to claim 5, wherein R ₁ is _one of an alkylene group having 2 or more carbon atoms and an alkylene group having 2 or more carbon atoms having an aromatic ring.
The magnetic recording medium according to the above. 10. The magnetic recording medium according to claim 5, wherein at least one of R ₂ and R ₃ is a long-chain alkyl group having 6 or more carbon atoms. 11. A magnetic recording medium having a magnetic layer formed on a nonmagnetic support, wherein the magnetic layer has an amino group, an alkylamino group and a dialkylamino represented by the following general formula (1). A magnetic recording medium characterized in that a lubricant having a molecular structure in which any one of the polar groups selected from the groups is bonded to the end of a perfluoropolyether group by an ester bond is internally added. R _f -COOR ₁ NR ₂ R ₃ (1) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring, and R ₂ and R ₃ are Each independently represents one of hydrogen and a hydrocarbon group.) 12. A magnetic recording medium having a magnetic layer formed on a non-magnetic support, wherein the magnetic layer comprises an amino group, an alkylamino group and a dialkylamino represented by the following general formula (2). A magnetic recording medium characterized in that a lubricant having a molecular structure in which any one of the polar groups selected from the groups is bonded to both ends of a perfluoropolyether group by an ester bond is internally added. R ₂ R ₃ NR ₁ OCO-R _f —COOR ₁ NR ₂ R ₃ (2) (where R _f is a perfluoropolyether group, R ₁ is any one of an alkylene group and an alkylene group having an aromatic ring) And R ₂ and R ₃ each independently represent any one of hydrogen and a hydrocarbon group.) 13. The magnetic recording medium according to claim 11, wherein the magnetic layer is formed by dispersing at least a magnetic powder in an organic binder. 14. The magnetic recording according to claim 11, wherein R ₁ is any one of an alkylene group having 2 or more carbon atoms and an alkylene group having 2 or more carbon atoms having an aromatic ring. Medium. 15. The magnetic recording medium according to claim 11, wherein at least one of R ₂ and R ₃ is a long-chain alkyl group having 6 or more carbon atoms.