JP4624860B2 - Magnetic recording medium - Google Patents

Description

  The present invention relates to a magnetic recording medium for high density recording in which a magnetic layer contains a ferromagnetic powder.

  Due to demands for high-density recording and high electromagnetic conversion characteristics, the surface roughness of magnetic recording media has been required to be small. In accordance with this, the true contact area between the magnetic recording medium and the VTR head, guide poles and other members becomes larger and the friction coefficient becomes very high. As the friction coefficient increases, the tape tension increases, and serious problems such as tape scratches, shavings and poor running occur frequently. Conventionally, higher fatty acids, fatty acid esters, fatty acid amides and the like have been used as lubricants in the magnetic layer in order to lower the friction coefficient. Among these, stearic acid, myristic acid, stearamide, and the like have a large effect of reducing the friction coefficient and have been widely used in magnetic recording media.

  However, for example, VHS, S-VHS, 8mm video, Hi8 video, high-density digital video, and high-definition television magnetic recording media have a very smooth magnetic layer surface. The friction coefficient of such an extremely smooth magnetic layer cannot be lowered sufficiently, and if the amount added is increased, blooming tends to occur over time, and it will precipitate as white powder on the surface of the magnetic recording medium, causing head contamination. .

  In order to solve the above problem, Patent Document 1 describes a magnetic recording medium containing a compound having an aliphatic carboxylic acid and an alkylene oxide segment between a hydrocarbon chain and a carboxyl group as a lubricant. Patent Document 2 describes a magnetic recording medium including a monocyclic liquid crystal molecule in a magnetic layer. However, both Patent Documents 1 and 2 have insufficient lubrication performance, particularly durability in a computer tape.

Japanese Patent Laid-Open No. 9-7164 JP-A-11-39643

  An object of the present invention is to provide a magnetic recording medium having excellent running properties and excellent durability.

In order to achieve the above object, the present invention has the following <1> or <2> configuration.
<1> A magnetic recording medium in which at least one magnetic layer in which a ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support, wherein the magnetic layer is at least selected from compounds represented by formula (I) A magnetic recording medium comprising one compound;

（式（Ｉ）中、Ｒ₁〜Ｒ₃はそれぞれ独立に−ＮＲ₄Ｒ₅、−ＳＲ₆、−ＯＲ₇、−ＣＯＮＲ₈Ｒ₉、−Ｒ₁₀よりなる群から選ばれる基を表し、Ｒ₁〜Ｒ₃はそれぞれ同一であっても異なっていてもよく、Ｒ₄〜Ｒ₁₀は水素原子又は−（Ｒ₁₁−Ｌ）_n−Ｒ₁₂を表し、Ｒ₁₁は二価の炭化水素基を表し、Ｒ₁₂は一価の炭化水素基を表し、Ｌは二価の連結基を表し、ｎは０〜２０の整数を表し、また、それぞれＲ₁₁とＬは同一であっても異なっていてもよい。ただし、Ｒ₁〜Ｒ₃のうち少なくとも１つは炭素数６以上の炭化水素鎖を有する基である。）
＜２＞ 非磁性支持体上に非磁性粉末を結合剤中に分散した非磁性層を介して、強磁性粉末を結合剤中に分散した磁性層を設けた磁気記録媒体であって、該非磁性層及び／又は該磁性層に前記式（Ｉ）で表される化合物から選ばれる少なくとも１種の化合物を含むことを特徴とする磁気記録媒体。

(In the formula (I), R _{1 to} R ₃ each independently represents a group selected from the group consisting of —NR ₄ R ₅ , —SR ₆ , —OR ₇ , —CONR ₈ R ₉ , —R ₁₀ ; _{1 to} R ₃ may be the same or different, R _{4 to} R _{10 each} represents a hydrogen atom or — (R ₁₁ -L) _n —R ₁₂ , and R ₁₁ represents a divalent hydrocarbon group. R ₁₂ represents a monovalent hydrocarbon group, L represents a divalent linking group, n represents an integer of 0 to 20, and R ₁₁ and L may be the same or different. However, at least one of R _{1 to} R ₃ is a group having a hydrocarbon chain having 6 or more carbon atoms.)
<2> A magnetic recording medium in which a magnetic layer in which a ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support via a nonmagnetic layer in which the nonmagnetic powder is dispersed in the binder. A magnetic recording medium comprising at least one compound selected from the compounds represented by the formula (I) in the layer and / or the magnetic layer.

  According to the present invention, it is possible to provide a magnetic recording medium that has improved running performance and that has improved durability by suppressing scraping of the folded portion during repeated running.

  One embodiment of the present invention is a magnetic recording medium in which at least one magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support, and the magnetic layer is represented by the formula (I). A magnetic recording medium comprising at least one compound selected from compounds.

（式（Ｉ）中、Ｒ₁〜Ｒ₃はそれぞれ独立に−ＮＲ₄Ｒ₅、−ＳＲ₆、−ＯＲ₇、−ＣＯＮＲ₈Ｒ₉、−Ｒ₁₀よりなる群から選ばれる基を表し、Ｒ₁〜Ｒ₃はそれぞれ同一であっても異なっていてもよく、Ｒ₄〜Ｒ₁₀は水素原子又は−（Ｒ₁₁−Ｌ）_n−Ｒ₁₂を表し、Ｒ₁₁は二価の炭化水素基を表し、Ｒ₁₂は一価の炭化水素基を表し、Ｌは二価の連結基を表し、ｎは０〜２０の整数を表し、また、それぞれＲ₁₁とＬは同一であっても異なっていてもよい。ただし、Ｒ₁〜Ｒ₃のうち少なくとも１つは炭素数６以上の炭化水素鎖を有する基である。）

(In the formula (I), R _{1 to} R ₃ each independently represents a group selected from the group consisting of —NR ₄ R ₅ , —SR ₆ , —OR ₇ , —CONR ₈ R ₉ , —R ₁₀ ; _{1 to} R ₃ may be the same or different, R _{4 to} R _{10 each} represents a hydrogen atom or — (R ₁₁ -L) _n —R ₁₂ , and R ₁₁ represents a divalent hydrocarbon group. R ₁₂ represents a monovalent hydrocarbon group, L represents a divalent linking group, n represents an integer of 0 to 20, and R ₁₁ and L may be the same or different. However, at least one of R _{1 to} R ₃ is a group having a hydrocarbon chain having 6 or more carbon atoms.)

  In another embodiment of the present invention, a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support via a nonmagnetic layer in which nonmagnetic powder is dispersed in the binder. A magnetic recording medium, wherein the nonmagnetic layer and / or the magnetic layer contains at least one compound selected from the compounds represented by the formula (I).

  The magnetic recording medium of the present invention achieves a balance between extremely high running performance and durability as compared with the prior art. Among running durability, it is possible to reduce friction during low-speed sliding and reduce the abrasion of the surface layer of the magnetic layer. Specifically, when running repeatedly with a computer backup tape, the friction between the recording / reproducing head and the magnetic layer at the start of running or when the running direction is reversed is reduced, and the stick-slip phenomenon is less likely to occur and stable tape running. Phenomena such as scraping can be suppressed.

I. Compound Represented by Formula (I) The magnetic recording medium of the present invention contains at least one compound represented by the formula (I) in the magnetic layer and / or the nonmagnetic layer. When the magnetic recording medium of the present invention is provided with both a magnetic layer and a nonmagnetic layer, the compound represented by the formula (I) may be contained only in either the magnetic layer or the nonmagnetic layer. Although it is good, it is preferably contained in both the magnetic layer and the nonmagnetic layer.
The compound represented by the above formula (I) of the present invention has a structure having a side chain on a triazine ring, and a triazine ring having a highly polar and tabular structure is arranged on the surface of the magnetic layer of the magnetic recording medium, and the outside thereof. It is presumed that the structure is such that the side chain is facing.
For this reason, when sliding with a head member or the like at low speed and high pressure, the compound represented by the formula (I) is stably present on the surface of the magnetic layer at the start of traveling or when the traveling direction is reversed, and the surface energy Small side chains are considered to reduce friction with the head member.
In order for the compound represented by formula (I) to exist stably in the magnetic layer, there is a nonmagnetic layer that is added to the magnetic layer, coated on the surface of the magnetic layer, or in contact with the magnetic layer. In this case, it can be added to the nonmagnetic layer and diffused on the surface of the magnetic layer.
In particular, a smooth magnetic layer has a high coefficient of friction and the surface of the magnetic layer is easily scraped. However, the magnetic recording medium of the present invention has a small increase in friction, and the surface is hardly scratched.
Further, the compound represented by the formula (I) of the present invention is preferable because the effect of running durability is further improved when the binder of the magnetic layer described later contains a polyurethane resin derived from aromatic diisocyanate. This is presumably because the affinity between the triazine ring of the compound represented by the formula (I) and the aromatic diisocyanate segment of the polyurethane is good.

R _{1 to} R ₃ in the formula (I) each independently represent a group selected from the group consisting of —NR ₄ R ₅ , —SR ₆ , —OR ₇ , —CONR ₈ R ₉ , and —R ₁₀ . R _{1 to} R ₃ may be the same or different. In addition, at least one of R _{1 to} R ₃ is a group having a hydrocarbon chain having 6 or more carbon atoms.
The hydrocarbon chain may be a monovalent or divalent hydrocarbon group, and is preferably an alkyl group or an alkylene group. The hydrocarbon chain may have a substituent. As carbon number of a hydrocarbon chain, carbon number of a main chain should just be 6 or more, it is preferable that it is 6-30, and it is more preferable that it is 6-22.

R ₄ to R ₁₀ is a hydrogen atom or represents - _{(R 11 -L) n -R 12} .
R ₁₁ represents a divalent hydrocarbon group which may have a substituent, R ₁₂ represents a monovalent hydrocarbon group which may have a substituent, and L represents a divalent linking group. N represents an integer of 0-20. when n is 0, it indicates a -R _12, also when n is 2 or more, may be different even in plural R ₁₁ and L are respectively the same.

Examples of the divalent hydrocarbon group include an alkylene group having 1 to 30 carbon atoms, an alkenylene group having 2 to 30 carbon atoms, an alkynylene group having 2 to 30 carbon atoms, an arylene group having 6 to 30 carbon atoms, or And groups composed of these combinations.
The monovalent hydrocarbon group includes an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or And groups composed of these combinations.
Examples of the divalent linking group include a linking group comprising an oxygen atom, a sulfur atom, a nitrogen atom, a silicon atom, a carbonyl group, or a combination thereof, such as -O-, -S-, -NH-, -NR-, -SiRR'-, -CO-, -COO-, -OCO-, -CONH-, -NHCO-, -CONR-, -NRCO-, -O-SiRR'-O- and the like. R and R ′ each independently represent a substituent described later. Among them, the divalent linking group is more preferably —O—, —COO—, or —OCO—.
n represents an integer of 0 to 20, preferably 0 to 10, and more preferably 0 to 3.

  Examples of the substituent that the monovalent and divalent hydrocarbon groups may have include a halogen atom, an alkyl group (including linear, branched, and cyclic alkyl groups), and an alkenyl group (linear, branched, ring). Including alkenyl groups of structures), alkynyl groups, aryl groups, heterocyclic groups, cyano groups, hydroxyl groups, nitro groups, carboxyl groups, alkoxy groups, aryloxy groups, silyloxy groups, heterocyclic oxy groups, acyloxy groups, carbamoyloxy Group, alkoxycarbonyloxy group, aryloxycarbonyloxy, amino group (including anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl and arylsulfonyl Amino group, mercapto group, alkylthio group, Thiol group, heterocyclic thio group, sulfamoyl group, sulfo group, alkyl and arylsulfinyl group, alkyl and arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, carbamoyl group, aryl and heterocyclic azo group, imide group Phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, silyl group and the like. These substituents may be further substituted with the above substituents.

  More specifically, the above substituents are halogen atoms (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyl groups [representing linear, branched, cyclic substituted or unsubstituted alkyl groups. An alkyl group (preferably an alkyl group having 1 to 30 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, 2-chloroethyl, 2-cyanoethyl, 2-ethylhexyl), cycloalkyl A group (preferably a substituted or unsubstituted cycloalkyl group having 3 to 30 carbon atoms, such as cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl), a bicycloalkyl group (preferably a substituted or unsubstituted group having 5 to 30 carbon atoms). A substituted bicycloalkyl group, that is, a monovalent group obtained by removing one hydrogen atom from a C 5-30 bicycloalkane, for example, bicyclo [1,2,2] heptan-2-yl, bicyclo [2, 2,2] octane-3-yl), and tricyclo structures having more ring structures. An alkyl group (for example, an alkyl group of an alkylthio group) in the substituents described below also represents such an alkyl group. ], An alkenyl group [represents a linear, branched or cyclic substituted or unsubstituted alkenyl group. An alkenyl group (preferably a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, such as vinyl, allyl, prenyl, geranyl, oleyl), a cycloalkenyl group (preferably a substituted or unsubstituted group having 3 to 30 carbon atoms) A cycloalkenyl group, that is, a monovalent group obtained by removing one hydrogen atom of a cycloalkene having 3 to 30 carbon atoms (for example, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl), bicycloalkenyl group (Substituted or unsubstituted bicycloalkenyl group, preferably a substituted or unsubstituted bicycloalkenyl group having 5 to 30 carbon atoms, that is, a monovalent group in which one hydrogen atom of a bicycloalkene having one double bond is removed. For example, bicyclo [2,2,1] hept-2-en-1-yl, bicyclo [2,2,2] octyl 2-en-4-yl)], an alkynyl group (preferably a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, e.g., ethynyl, propargyl, trimethylsilylethynyl group),

  An aryl group (preferably a substituted or unsubstituted aryl group having 6 to 30 carbon atoms such as phenyl, p-tolyl, naphthyl, m-chlorophenyl, o-hexadecanoylaminophenyl), a heterocyclic group (preferably 5 or 6 A monovalent group obtained by removing one hydrogen atom from a substituted or unsubstituted aromatic or non-aromatic heterocyclic compound, more preferably a 5- or 6-membered aromatic having 3 to 30 carbon atoms For example, 2-furyl, 2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl),

  A cyano group, a hydroxyl group, a nitro group, a carboxyl group, an alkoxy group (preferably a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms such as methoxy, ethoxy, isopropoxy, t-butoxy, n-octyloxy, 2-methoxyethoxy), an aryloxy group (preferably a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, such as phenoxy, 2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy, 2 -Tetradecanoylaminophenoxy), a silyloxy group (preferably a silyloxy group having 3 to 20 carbon atoms, such as trimethylsilyloxy, t-butyldimethylsilyloxy), a heterocyclic oxy group (preferably having 2 to 30 carbon atoms) Substituted or unsubstituted heterocyclic oxy group, 1-phenyl Trazol-5-oxy, 2-tetrahydropyranyloxy), acyloxy group (preferably formyloxy group, substituted or unsubstituted alkylcarbonyloxy group having 2 to 30 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms) A carbonyloxy group such as formyloxy, acetyloxy, pivaloyloxy, stearoyloxy, benzoyloxy, p-methoxyphenylcarbonyloxy), a carbamoyloxy group (preferably a substituted or unsubstituted carbamoyloxy group having 1 to 30 carbon atoms, For example, N, N-dimethylcarbamoyloxy, N, N-diethylcarbamoyloxy, morpholinocarbonyloxy, N, N-di-n-octylaminocarbonyloxy, Nn-octylcarbamoyloxy), alkoxyca A bonyloxy group (preferably a substituted or unsubstituted alkoxycarbonyloxy group having 2 to 30 carbon atoms, such as methoxycarbonyloxy, ethoxycarbonyloxy, t-butoxycarbonyloxy, n-octylcarbonyloxy), aryloxycarbonyloxy group (preferably Is a substituted or unsubstituted aryloxycarbonyloxy group having 7 to 30 carbon atoms, such as phenoxycarbonyloxy, p-methoxyphenoxycarbonyloxy, pn-hexadecyloxyphenoxycarbonyloxy),

  An amino group (preferably an amino group, a substituted or unsubstituted alkylamino group having 1 to 30 carbon atoms, a substituted or unsubstituted anilino group having 6 to 30 carbon atoms, such as amino, methylamino, dimethylamino, anilino, N-methyl-anilino, diphenylamino), acylamino group (preferably formylamino group, substituted or unsubstituted alkylcarbonylamino group having 1 to 30 carbon atoms, substituted or unsubstituted arylcarbonylamino group having 6 to 30 carbon atoms Groups such as formylamino, acetylamino, pivaloylamino, lauroylamino, benzoylamino, 3,4,5-tri-n-octyloxyphenylcarbonylamino), aminocarbonylamino groups (preferably substituted with 1 to 30 carbon atoms) Or unsubstituted aminocarbonylamino, such as Carbamoylamino, N, N-dimethylaminocarbonylamino, N, N-diethylaminocarbonylamino, morpholinocarbonylamino), alkoxycarbonylamino group (preferably a substituted or unsubstituted alkoxycarbonylamino group having 2 to 30 carbon atoms, such as methoxy Carbonylamino, ethoxycarbonylamino, t-butoxycarbonylamino, n-octadecyloxycarbonylamino, N-methyl-methoxycarbonylamino), aryloxycarbonylamino group (preferably substituted or unsubstituted aryl having 7 to 30 carbon atoms) Oxycarbonylamino groups such as phenoxycarbonylamino, p-chlorophenoxycarbonylamino, mn-octyloxyphenoxycarbonylamino), sulfamoylamino A group (preferably a substituted or unsubstituted sulfamoylamino group having 0 to 30 carbon atoms such as sulfamoylamino, N, N-dimethylaminosulfonylamino, Nn-octylaminosulfonylamino), alkyl and Arylsulfonylamino group (preferably substituted or unsubstituted alkylsulfonylamino having 1 to 30 carbon atoms, substituted or unsubstituted arylsulfonylamino having 6 to 30 carbon atoms, such as methylsulfonylamino, butylsulfonylamino, phenylsulfonylamino 2,3,5-trichlorophenylsulfonylamino, p-methylphenylsulfonylamino),

  A mercapto group, an alkylthio group (preferably a substituted or unsubstituted alkylthio group having 1 to 30 carbon atoms, such as methylthio, ethylthio, n-hexadecylthio), an arylthio group (preferably a substituted or unsubstituted arylthio group having 6 to 30 carbon atoms) , For example, phenylthio, p-chlorophenylthio, m-methoxyphenylthio), a heterocyclic thio group (preferably a substituted or unsubstituted heterocyclic thio group having 2 to 30 carbon atoms, such as 2-benzothiazolylthio, 1 -Phenyltetrazol-5-ylthio),

  Sulfamoyl group (preferably a substituted or unsubstituted sulfamoyl group having 0 to 30 carbon atoms such as N-ethylsulfamoyl, N- (3-dodecyloxypropyl) sulfamoyl, N, N-dimethylsulfamoyl, N- Acetylsulfamoyl, N-benzoylsulfamoyl, N- (N-phenylcarbamoyl) sulfamoyl), sulfo group, alkyl and arylsulfinyl group (preferably a substituted or unsubstituted alkylsulfinyl group having 1 to 30 carbon atoms, 6-30 substituted or unsubstituted arylsulfinyl groups such as methylsulfinyl, ethylsulfinyl, phenylsulfinyl, p-methylphenylsulfinyl), alkyl and arylsulfonyl groups (preferably substituted or unsubstituted having 1 to 30 carbon atoms) No al Rusuruhoniru group, 6 to 30 substituted or unsubstituted arylsulfonyl group, e.g., methylsulfonyl, ethylsulfonyl, phenylsulfonyl, p- methylphenyl sulfonyl),

  An acyl group (preferably a formyl group, a substituted or unsubstituted alkylcarbonyl group having 2 to 30 carbon atoms, a substituted or unsubstituted arylcarbonyl group having 7 to 30 carbon atoms, such as acetyl, pivaloyl, 2-chloroacetyl, stearoyl; , Benzoyl, pn-octyloxyphenylcarbonyl), an aryloxycarbonyl group (preferably a substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms such as phenoxycarbonyl, o-chlorophenoxycarbonyl, m- Nitrophenoxycarbonyl, pt-butylphenoxycarbonyl), alkoxycarbonyl group (preferably a substituted or unsubstituted alkoxycarbonyl group having 2 to 30 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, t-butoxycarbonyl n-octadecyloxycarbonyl), a carbamoyl group (preferably a substituted or unsubstituted carbamoyl having 1 to 30 carbon atoms, such as carbamoyl, N-methylcarbamoyl, N, N-dimethylcarbamoyl, N, N-di-n- Octylcarbamoyl, N- (methylsulfonyl) carbamoyl),

  Aryl and heterocyclic azo groups (preferably substituted or unsubstituted arylazo groups having 6 to 30 carbon atoms, substituted or unsubstituted heterocyclic azo groups having 3 to 30 carbon atoms such as phenylazo, p-chlorophenylazo, 5- Ethylthio-1,3,4-thiadiazol-2-ylazo), an imide group (preferably N-succinimide, N-phthalimide), a phosphino group (preferably a substituted or unsubstituted phosphino group having 2 to 30 carbon atoms, For example, dimethylphosphino, diphenylphosphino, methylphenoxyphosphino), phosphinyl group (preferably a substituted or unsubstituted phosphinyl group having 2 to 30 carbon atoms, such as phosphinyl, dioctyloxyphosphinyl, diethoxyphosphini ), Phosphinyloxy group (preferably carbon number) -30 substituted or unsubstituted phosphinyloxy groups, such as diphenoxyphosphinyloxy, dioctyloxyphosphinyloxy, phosphinylamino groups (preferably substituted or unsubstituted having 2 to 30 carbon atoms) A phosphinylamino group such as dimethoxyphosphinylamino, dimethylaminophosphinylamino, a silyl group (preferably a substituted or unsubstituted silyl group having 3 to 30 carbon atoms such as trimethylsilyl, t-butyl Dimethylsilyl, phenyldimethylsilyl).

Specific examples of preferred structures of R _{1 to} R ₃ include the following groups.
As —NR ₄ R ₅ ,
_{-NHCH 2 (CH 2) 4 CH} 3,
_{-NHCH 2 (CH 2) 5 CH} 3,
_{-NHCH 2 (CH 2) 6 CH} 3,
_{-NHCH 2 (CH 2) 7 CH} 3,
_{-NHCH 2 (CH 2) 8 CH} 3,
_{-NHCH 2 (CH 2) 10 CH} 3,
_{-NHCH 2 (CH 2) 12 CH} 3,
_{-NHCH 2 (CH 2) 14 CH} 3,
_{-NHCH 2 (CH 2) 16 CH} 3,
_{-NHCH 2 (CH 2) 18 CH} 3,
_{-NHCH 2 (CH 2) 20 CH} 3,
_{-NHCH 2 CH (C 2 H 5} ) (CH 2) 3 CH 3,
_{-NHCH 2 (CH 2) 5 OC} 2 H 4 OC 2 H 4 O (CH 2) 5 CH 3,
_{-NHCH 2 (CH 2) 9 COOC} 2 H 4 O (CH 2) 5 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 4 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 5 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 6 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 8 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 10 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 12 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 14 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 16 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 18 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 20 CH 3,
_{-N (CH 3) CH 2 CH} (C 2 H 5) (CH 2) 3 CH 3,

等が好ましく挙げられる。

Etc. are preferable.

-As SR ₆ ,
_{-SCH 2 (CH 2) 4 CH} 3,
_{-SCH 2 (CH 2) 5 CH} 3,
_{-SCH 2 (CH 2) 6 CH} 3,
_{-SCH 2 (CH 2) 7 CH} 3,
_{-SCH 2 (CH 2) 9 CH} 3,
_{-SCH 2 (CH 2) 10 CH} 3,
_{-SCH 2 (CH 2) 14 CH} 3,
_{-SCH 2 (CH 2) 16 CH} 3,
_{-SCH 2 (CH 2) 18 CH} 3,
_{-SCH 2 (CH 2) 20 CH} 3,
_{-SCH 2 CH (C 2 H 5} ) (CH 2) 3 CH 3 and the like preferably.

As -OR ₇ ,
_{-OCH 2 (CH 2) 4 CH} 3,
_{-OCH 2 (CH 2) 5 CH} 3,
_{-OCH 2 (CH 2) 6 CH} 3,
_{-OCH 2 (CH 2) 7 CH} 3,
_{-OCH 2 (CH 2) 9 CH} 3,
_{-OCH 2 (CH 2) 10 CH} 3,
_{-OCH 2 (CH 2) 14 CH} 3,
_{-OCH 2 (CH 2) 16 CH} 3,
_{-OCH 2 (CH 2) 18 CH} 3,
_{-OCH 2 (CH 2) 20 CH} 3,
_{-OCH 2 CH (C 2 H 5} ) (CH 2) 3 CH 3,
_{-OC 2 H 4 OC 2 H 4} O (CH 2) 5 CH 3 , and the like preferably.

As -CONR ₈ R ₉ ,
_{-CONHCH 2 (CH 2) 4 CH} 3,
_{-CONHCH 2 (CH 2) 5 CH} 3,
_{-CONHCH 2 (CH 2) 6 CH} 3,
_{-CONHCH 2 (CH 2) 7 CH} 3,
_{-CONHCH 2 (CH 2) 9 CH} 3,
_{-CONHCH 2 (CH 2) 10 CH} 3,
_{-CONHCH 2 (CH 2) 14 CH} 3,
_{-CONHCH 2 (CH 2) 16 CH} 3,
_{-CONHCH 2 (CH 2) 18 CH} 3,
_{-CONHCH 2 (CH 2) 20 CH} 3,
_{-CONHCH 2 CH (C 2 H 5} ) (CH 2) 3 CH 3 and the like preferably.

The -R _{10,
-CH 2 (CH 2) 4 CH} 3,
_{-CH 2 (CH 2) 5 CH} 3,
_{-CH 2 (CH 2) 6 CH} 3,
_{-CH 2 (CH 2) 7 CH} 3,
_{-CH 2 (CH 2) 9 CH} 3,
_{-CH 2 (CH 2) 10 CH} 3,
_{-CH 2 (CH 2) 12 CH} 3,
_{-CH 2 (CH 2) 14 CH} 3,
_{-CH 2 (CH 2) 16 CH} 3,
_{-CH 2 (CH 2) 18 CH} 3,
_{-CH 2 (CH 2) 20 CH} 3,
_{-CH 2 CH (C 2 H 5} ) (CH 2) 3 CH 3,
_{-CH 2 (CH 2) 3 C} (= O) (CH 2) 5 CH 3,
_{-CH 2 (CH 2) 5 S} (CH 2) 5 CH 3,
_{-CH 2 (CH 2) 5 Si} (CH 3) 3,
_{-CH 2 (CH 2) 5 OSi} (CH 3) 2 OSi (CH 3) 3 and the like are preferably mentioned.

Among the above structures, as a more preferable structure,
_{-NHCH 2 (CH 2) 10 CH} 3,
_{-NHCH 2 (CH 2) 12 CH} 3,
_{-NHCH 2 (CH 2) 14 CH} 3,
_{-NHCH 2 (CH 2) 16 CH} 3,
_{-N (CH 3) CH 2 (} CH 2) 10 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 12 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 14 CH 3,
_{-N (CH 3) CH 2 (} CH 2) 16 CH 3,
_{-SCH 2 (CH 2) 10 CH} 3,
_{-SCH 2 (CH 2) 14 CH} 3,
_{-SCH 2 (CH 2) 16 CH} 3,
_{-SCH 2 CH (C 2 H 5} ) (CH 2) 3 CH 3,
_{-OCH 2 (CH 2) 10 CH} 3,
_{-OCH 2 (CH 2) 14 CH} 3,
_{-OCH 2 (CH 2) 16 CH} 3,
_{-CONHCH 2 (CH 2) 10 CH} 3,
_{-CH 2 (CH 2) 10 CH} 3,
_{-CH 2 (CH 2) 12 CH} 3,
_{-CH 2 (CH 2) 14 CH} 3,
_{-CH 2 (CH 2) 16 CH} 3,

等が挙げられる。

Etc.

Of R _{1 to} R ₃ in formula (I), at least two preferably have the same structure, and more preferably R _{1 to} R ₃ all have the same structure.

The compound represented by the formula (I) may be added to the coating solution for the magnetic layer and applied, or when the magnetic layer is applied via the nonmagnetic layer, it is added to the coating solution for the nonmagnetic layer and applied. Even so, it can exist on the surface of the magnetic layer by diffusion and movement between layers. Alternatively, a coating solution obtained by dissolving the compound represented by formula (I) in a suitable solvent may be applied to the surface of the magnetic layer after coating.
A method of adding to the magnetic layer coating solution and / or the nonmagnetic layer coating solution is preferred.

The amount of the compound represented by formula (I) in the magnetic layer of the present invention is preferably 0.01 to 15 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. Parts by weight.
Moreover, the preferable addition amount of the compound represented by the formula (I) in the nonmagnetic layer of the present invention is preferably 0.01 to 15 parts by weight, more preferably 0 with respect to 100 parts by weight of the nonmagnetic powder. .1 to 5 parts by weight.

II. Magnetic layer The magnetic layer in the present invention is a magnetic layer in which ferromagnetic powder is dispersed in a binder, and the magnetic recording medium of the present invention has at least one magnetic layer provided on a nonmagnetic support. .

<Binder>
Binders used in the magnetic layer include polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins copolymerized with styrene, acrylonitrile, methyl methacrylate, cellulose resins such as nitrocellulose, and epoxy resins. In addition, polyvinyl alkyl resins such as phenoxy resin, polyvinyl acetal, and polyvinyl butyral can be used alone or in combination. Among these, a polyurethane resin, a vinyl chloride resin, and an acrylic resin are preferable, and a polyurethane resin is more preferable because of its high affinity with the compound represented by the formula (I), which is derived from an aromatic diisocyanate compound. Use of a polyurethane resin is more preferable because running durability is particularly excellent.

The binder preferably has a functional group (polar group) adsorbed on the surface of the powder in order to improve the dispersibility of the magnetic material and nonmagnetic powder. Preferred functional groups include —SO ₃ M, —SO ₄ M, —PO (OM) ₂ , —OPO (OM) ₂ , —COOM, R ¹ R ² NSO ₃ M, R ¹ R ² NRSO ₃ M, and —NR. ¹ R ^2, and the like ^{-N + R 1 R 2 R 3} X. Here, M represents a hydrogen atom or an alkali metal such as Na or K, R represents an alkylene group, R ¹ , R ² , R ³ represent an alkyl group, a hydroxyalkyl group or a hydrogen atom, and R ¹ and R ² are bonded to each other. A ring may be formed. X is a halogen atom such as Cl or Br. The amount of the functional group in the binder is preferably 10 μeq / g to 200 μeq / g, and more preferably 30 μeq / g to 120 μeq / g. Within this range, the dispersibility is good.

  In addition to the adsorptive functional group, the binder reacts with an isocyanate curing agent to form a crosslinked structure, and a functional group having an active hydrogen such as an —OH group is preferably imparted to improve the coating film strength, Moreover, the thing into which the epoxy group was introduce | transduced is preferable. When a functional group such as an —OH group or an epoxy group is introduced, the compound represented by the formula (I) and the —OH group have a high affinity or may be bonded. A preferred amount is from 0.1 meq / g to 2 meq / g. The molecular weight of the binder is preferably 10,000 to 200,000 in terms of weight average molecular weight, more preferably 20,000 to 100,000. When the weight average molecular weight is 10,000 or more, the coating film strength is high and the durability is good. Moreover, if it is 200,000 or less, a dispersibility is favorable.

  As the polyurethane resin which is a preferable binder, polyester urethane, polyether urethane, polycarbonate urethane, polyether ester urethane, acrylic polyurethane, or the like can be used. Polyurethane resins that can be used in the present invention are described in detail in, for example, “Polyurethane Resin Handbook” (edited by Keiji Iwata, 1986, Nikkan Kogyo Shimbun), and are usually long-chain diols and short-chain diols (with chain extenders and And may be obtained by addition polymerization of a diisocyanate compound. As the long-chain diol, polyester diol, polyether diol, polyether ester diol, polycarbonate diol, polyolefin diol and the like having a molecular weight of 500 to 5,000 can be used. Depending on the type of this long-chain polyol, it is called polyester urethane, polyether urethane, polyether ester urethane, polycarbonate urethane or the like.

  The polyester diol can be obtained by condensation polymerization of an aliphatic dibasic acid such as adipic acid, sebacic acid or azelaic acid, an aromatic dibasic acid such as isophthalic acid, orthophthalic acid, terephthalic acid or naphthalenedicarboxylic acid and glycol. . Examples of the glycol component include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6- Hexanediol, 2,2-dimethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and the like can be used. In addition, polycaprolactone diol and polyvalerolactone diol obtained by ring-opening polymerization of lactone such as ε-caprolactone and γ-valerolactone can also be used as the polyester diol. The polyester diol is preferably one having a branched side chain, one obtained from an aromatic or alicyclic raw material from the viewpoint of hydrolysis resistance.

  Polyether diols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, aromatic glycols such as bisphenol A, bisphenol S, bisphenol P, hydrogenated bisphenol A, and alicyclic diols, and alkylenes such as ethylene oxide and propylene oxide. Those obtained by addition polymerization of oxide can be used.

  These long-chain diols can be used in combination of a plurality of types. The short-chain diol can be selected from the same group of compounds as exemplified for the glycol component of the polyester diol. In addition, when a small amount of trifunctional or higher polyhydric alcohols such as trimethylolethane, trimethylolpropane, pentaerythritol, etc. are used in combination, a branched polyurethane resin can be obtained, reducing the viscosity of the solution or increasing the OH group at the end of the polyurethane. With this, the curability with the isocyanate curing agent can be increased.

As the diisocyanate compound, MDI (diphenylmethane diisocyanate), 2,4-TDI (tolylene diisocyanate), 2,6-TDI, 1,5-NDI (naphthalene diisocyanate), TODI (tolidine diisocyanate), p-phenylene diisocyanate, o -Aromatic diisocyanates such as phenylene diisocyanate, m-phenylene diisocyanate, XDI (xylylene diisocyanate), transcyclohexane-1,4-diisocyanate, HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), H ₆ XDI (hydrogenated xylylene) Aliphatic and alicyclic diisocyanates such as diisocyanate) and H ₁₂ MDI (hydrogenated diphenylmethane diisocyanate) be able to. Among them, aromatic diisocyanate is preferably used, and TDI (tolylene diisocyanate), MDI (diphenylmethane diisocyanate), p-phenylene diisocyanate, o-phenylene diisocyanate, m-phenylene diisocyanate, XDI (xylylene diisocyanate) and the like. More preferred.

The preferred composition of the long chain diol / short chain diol / diisocyanate in the polyurethane resin is (80 to 15% by weight) / (5 to 40% by weight) / (15 to 50% by weight). The urethane group concentration of the polyurethane resin is preferably 1 to 5 meq / g. Furthermore, it is preferable that it is 1.5-4.5 meq / g. If the urethane group concentration is 1 meq / g or more, the mechanical strength is high, and if it is 5 meq / g or less, the solution viscosity is low and the dispersibility is good. The glass transition temperature of the polyurethane resin is preferably −50 to 200 ° C., more preferably 30 to 150 ° C. If it is −50 ° C. or higher, the durability is high, and if it is 200 ° C. or lower, the calendar moldability is good, and the smoothness and electromagnetic conversion characteristics are improved.
As a method for introducing the above-mentioned adsorptive functional group (polar group) into the polyurethane resin, a method using a functional group as a part of a monomer of a long-chain diol, a method using a part of a short-chain diol, or after polymerizing polyurethane, There is a method of introducing a polar group by a polymer reaction.

As the vinyl chloride resin, a vinyl chloride monomer copolymerized with various monomers can be used. Examples of copolymer monomers include fatty acid vinyl esters such as vinyl acetate and vinyl propionate, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and benzyl (meth) acrylate. Alkyl allyl ethers such as acrylates, methacrylates, allyl methyl ether, allyl ethyl ether, allyl propyl ether, allyl butyl ether, other styrene, α-methyl styrene, vinylidene chloride, acrylonitrile, ethylene, butadiene, acrylamide, etc. can be used. .
Further, as the vinyl chloride resin, a vinyl chloride monomer may be copolymerized with a monomer having a functional group such as hydroxyl group or epoxy group or the polar group, and the copolymer monomer having a functional group or polar group may be vinyl. Alcohol, 2-hydroxyethyl (meth) acrylate, polyethylene glycol (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polypropylene glycol (meth) acrylate, 2-hydroxyethyl allyl ether, 2-hydroxypropyl allyl ether, 3-hydroxypropyl allyl ether, p-vinylphenol, maleic acid, maleic anhydride, acrylic acid, methacrylic acid, glycidyl (meth) acrylate, allyl glycidyl ether , Phosphoethyl (meth) acrylate, sulfoethyl (meth) acrylate, p- styrenesulfonic acid, and the like can be used as Na salts, K salts.
In addition, (meth) acrylate means what contains at least any one of an acrylate and a methacrylate.

  The composition of the vinyl chloride monomer in the vinyl chloride resin is preferably 60 to 95% by weight. If it is 60% by weight or more, the mechanical strength is high, and if it is 95% by weight or less, the solvent solubility is high, the solution viscosity is low, and the dispersibility is good. The preferred amount of the functional group for enhancing the curability with the adsorption functional group (polar group) and the polyisocyanate curing agent is as described above. These functional groups may be introduced by copolymerizing the above functional group-containing monomers, or by copolymerizing a vinyl chloride resin and then introducing a functional group by a polymer reaction. The polymerization degree is preferably 200 to 600, more preferably 240 to 450. If the degree of polymerization is 200 or more, the mechanical strength is high, and if it is 600 or less, the solution viscosity is low and the dispersibility is good.

In the present invention, a curing agent can be used to crosslink and cure the binder to increase the mechanical strength and heat resistance of the coating film. As a hardening | curing agent, it is preferable that a polyisocyanate compound and an epoxy compound are contained, and a polyisocyanate compound is more preferable.
As the polyisocyanate compound, known compounds can be used, and among these, a polyisocyanate having 3 or more functional groups is preferable. Specifically, a compound obtained by adding 3 moles of TDI (tolylene diisocyanate) to trimethylolpropane (TMP), a compound obtained by adding 3 moles of HDI (hexamethylene diisocyanate) to TMP, and 3 moles of IPDI (isophorone diisocyanate) to TMP Compounds, adduct-type polyisocyanate compounds such as compounds obtained by adding 3 moles of XDI (xylylene diisocyanate) to TMP, TDI condensed isocyanurate type trimer, TDI condensed isocyanurate pentamer, TDI condensed isocyanurate 7 amount And mixtures thereof, isocyanurate type condensates of HDI, isocyanurate type condensates of IPDI, and crude MDI. Among these, preferred are a compound obtained by adding 3 mol of TDI to TMP, an isocyanurate type trimer of TDI, and the like.

  In addition to the isocyanate curing agent, a radiation curing type curing agent such as an electron beam or an ultraviolet ray may be used. In this case, a curing agent having two or more, preferably three or more acryloyl groups or methacryloyl groups in the molecule as a radiation curing functional group can be used. Examples thereof include TMP (trimethylolpropane) triacrylate, pentaerythritol tetraacrylate, urethane acrylate oligomer, and the like. In this case, it is preferable to introduce a (meth) acryloyl group into the binder in addition to the curing agent. In the case of ultraviolet curing, a photosensitizer is used in combination. It is preferable to add 0 to 80 parts by weight of the curing agent with respect to 100 parts by weight of the binder. Within the above range, the dispersibility is good and preferable.

  The amount of the binder used in the magnetic layer is preferably 5 to 25 parts by weight with respect to 100 parts by weight of the ferromagnetic powder including the curing agent.

<Ferromagnetic powder>
As the ferromagnetic powder contained in the magnetic layer in the present invention, any of the following acicular and flat ferromagnetic powders can be used. Ferromagnetic metal powder is preferably used as the acicular ferromagnetic powder, and ferromagnetic hexagonal ferrite powder is preferably used as the flat ferromagnetic powder.

The ferromagnetic metal powder that can be used in the magnetic recording medium of the present invention is acicular, cobalt-containing ferromagnetic iron oxide or ferromagnetic alloy powder, and preferably has a S _BET specific surface area of 40 to 80 m ² / g, more preferably. 50-70 m ² / g. The crystallite size is 5 to 25 nm, preferably 8 to 20 nm, particularly preferably 10 to 15 nm. The major axis length is 20 to 200 nm, preferably 25 to 60 nm.
Examples of the ferromagnetic metal powder include yttrium-containing Fe, Fe—Co, Fe—Ni, and Co—Ni—Fe. The yttrium content in the ferromagnetic metal powder is a ratio of yttrium atoms to iron atoms, Y / Fe is preferably 0.5 atomic% to 20 atomic%, and more preferably 5 to 10 atomic%. Within the above range, the ferromagnetic metal powder is increased in σs, and good magnetic characteristics and electromagnetic conversion characteristics can be obtained. Further, since the iron content is appropriate, it is preferable because good magnetic characteristics and electromagnetic conversion characteristics can be obtained.

  Furthermore, within a range of 20 atomic% or less with respect to 100 atomic% of iron, aluminum, silicon, sulfur, scandium, titanium, vanadium, chromium, manganese, copper, zinc, molybdenum, rhodium, palladium, tin, antimony, boron, Barium, tantalum, tungsten, rhenium, gold, lead, phosphorus, lanthanum, cerium, praseodymium, neodymium, tellurium, bismuth, and the like can be included. Further, the ferromagnetic metal powder may contain a small amount of water, hydroxide or oxide.

The pH of the ferromagnetic metal powder is preferably optimized depending on the combination with the binder used. The range is preferably pH 4-12, more preferably pH 7-10. The ferromagnetic powder may be surface-treated with Al, Si, P, or an oxide thereof as required. The amount thereof is 0.1 to 10% with respect to the ferromagnetic powder. When the surface treatment is performed, the adsorption of a lubricant such as a fatty acid is preferably 100 mg / m ² or less.
The ferromagnetic metal powder may contain soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr. However, if it is 200 ppm or less, the properties are not particularly affected. Further, the ferromagnetic metal powder used in the magnetic layer in the present invention preferably has fewer vacancies, and its value is 20% by volume or less, more preferably 5% by volume or less. In addition, the shape may be acicular, granular, rice granular, or plate-like as long as it satisfies the above-mentioned characteristics regarding the particle size, but in particular, acicular ferromagnetic powder should be used. Is preferred. In the case of acicular ferromagnetic metal powder, the acicular ratio is preferably 4 to 12, and more preferably 5 to 12.

The coercive force Hc of the ferromagnetic metal powder is preferably 159 to 239 kA / m (2,000 to 3,000 Oe), and preferably 167 to 231 kA / m (2,100 to 2,900 Oe). Further preferred. The saturation magnetic flux density is preferably 150 to 300 mT (1,500 to 3,000 G), and more preferably 160 to 290 mT (1,600 to 2,900 G). Saturation magnetization σs is preferably ^{100~170A · m 2 / kg (emu} / g), 100~160A · m 2 / kg (emu / g) is more preferable.
The SFD (switching field distribution) of the magnetic material itself is preferably small and is preferably 0.8 or less. When the SFD is 0.8 or less, the electromagnetic conversion characteristics are good, the output is high, the magnetization reversal is sharp, the peak shift is small, and it is suitable for high-density digital magnetic recording. In order to reduce the Hc distribution, there are methods such as improving the particle size distribution of goethite in the ferromagnetic metal powder, using monodispersed α-Fe ₂ O ₃ , and preventing sintering between particles.

An example of a method for producing a ferromagnetic metal powder introduced with cobalt and yttrium that can be used in the present invention will be described.
An example in which iron oxyhydroxide obtained by blowing an oxidizing gas into an aqueous suspension in which a ferrous salt and an alkali are mixed is used as a starting material can be given.
As the type of this iron oxyhydroxide, α-FeOOH is preferable, and as its production method, ferrous salt is neutralized with an alkali hydroxide to form an aqueous suspension of Fe (OH) _2. There is a first production method in which an oxidizing gas is blown into a needle-like α-FeOOH. On the other hand, there is a second production method in which ferrous salt is neutralized with alkali carbonate to form an aqueous suspension of FeCO ₃ , and oxidizing gas is blown into this suspension to form spindle-shaped α-FeOOH. Such an iron oxyhydroxide is obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution to obtain an aqueous solution containing ferrous hydroxide and oxidizing it by air oxidation or the like. Is preferred. In this case, Ni salt, alkaline earth element salt such as Ca salt, Ba salt, Sr salt, Cr salt, Zn salt, etc. may coexist in the ferrous salt aqueous solution, and such salt is appropriately selected. Thus, the particle shape (axial ratio) and the like can be prepared.

  As the ferrous salt, ferrous chloride, ferrous sulfate and the like are preferable. As the alkali, sodium hydroxide, aqueous ammonia, ammonium carbonate, sodium carbonate and the like are preferable. Moreover, as a salt which can coexist, chlorides, such as nickel chloride, calcium chloride, barium chloride, strontium chloride, chromium chloride, zinc chloride, are preferable.

Next, when introducing cobalt into iron, before introducing yttrium, an aqueous solution of a cobalt compound such as cobalt sulfate or cobalt chloride is stirred and mixed into the iron oxyhydroxide slurry. After preparing a slurry of iron oxyhydroxide containing cobalt, an aqueous solution containing a compound of yttrium can be added to the slurry and mixed by stirring.
In addition to yttrium, neodymium, samarium, praseodymium, lanthanum, gadolinium, and the like can be introduced into the ferromagnetic metal powder of the present invention. These can be introduced using chlorides such as yttrium chloride, neodymium chloride, samarium chloride, praseodymium chloride, lanthanum chloride, nitrates such as neodymium nitrate and gadolinium nitrate, and these are used in combination of two or more. Also good.

(Ferromagnetic hexagonal ferrite powder)
As the tabular ferromagnetic powder that can be used in the present invention, it is preferable to use a ferromagnetic hexagonal ferrite powder.
Examples of the ferromagnetic hexagonal ferrite powder include barium ferrite, strontium ferrite, lead ferrite, calcium ferrite substitutes, and Co substitutes. Specific examples include magnetoplumbite type barium ferrite and strontium ferrite, magnetoplumbite type ferrite whose particle surface is coated with spinel, and magnetoplumbite type barium ferrite and strontium ferrite partially containing spinel phase. In addition to predetermined atoms, Al, Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Hg , Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, B, Ge, Nb, and Zr may be included. In general, a material to which an element such as Co—Ti, Co—Ti—Zr, Co—Ti—Zn, Ni—Ti—Zn, Nb—Zn—Co, Sb—Zn—Co, or Nb—Zn is added is used. Can do. Some raw materials and manufacturing methods contain specific impurities.

The plate diameter of the tabular ferromagnetic powder is preferably 10 to 50 nm, and more preferably 20 to 40 nm. The particle size is preferably 10 to 50 nm as a hexagonal plate diameter, and more preferably 20 to 40 nm.
When reproducing with a magnetoresistive head, it is necessary to reduce the noise, and the plate diameter is preferably 40 nm or less. Within the above range, stable magnetization can be expected without being affected by thermal fluctuations, and noise is low, which is preferable and preferable for high-density magnetic recording.
The plate ratio (plate diameter / plate thickness) is preferably 1-15. Preferably it is 2-7. It is preferable that the plate ratio is in the above range because the filling property in the magnetic layer is high and sufficient orientation is obtained. Furthermore, it is preferable because noise due to stacking between particles is reduced.
S _BET (specific surface area by BET method) in this particle size range is 10 to ²⁰⁰ m ² / g. The specific surface area is generally signified as an arithmetic calculation value from the particle plate diameter and plate thickness. The crystallite size is 5 to 45 nm, preferably 10 to 35 nm.
The distribution of the particle plate diameter and plate thickness is generally preferably as narrow as possible. Although numerical conversion is difficult, it can be compared by randomly measuring 500 particles from a particle TEM photograph. In many cases, the distribution is not a normal distribution, but when calculated and expressed as a standard deviation with respect to the average size, σ / average size = 0.1 to 2.0. In order to sharpen the particle size distribution, the particle generation reaction system is made as uniform as possible, and the generated particles are subjected to a distribution improvement process. For example, a method of selectively dissolving ultrafine particles in an acid solution is also known.

The coercive force Hc measured with the ferromagnetic hexagonal ferrite powder can be made up to about 39.8 to 398 kA / m (500 to 5,000 Oe). A higher Hc is advantageous for high-density recording, but is limited by the capacity of the recording head. Usually, it is about 63.7 to 318 kA / m (800 to 4,000 Oe), but preferably 119 to 279 kA / m (1,500 to 3,500 Oe). When the saturation magnetization of the head exceeds 1.4 Tesler, it is preferable to set it to 159 kA / m (2,000 Oe) or more. Hc can be controlled by the particle size (plate diameter / plate thickness), the type and amount of contained elements, the substitution site of the elements, the particle generation reaction conditions, and the like. The saturation magnetization σs is preferably 40 to 80 A · m ² / kg (emu / g). σs is preferably higher, but tends to be smaller as the particles become finer. In order to improve σs, it is well known to combine spinel ferrite with magnetoplumbite ferrite and to select the type and amount of elements contained. It is also possible to use W-type hexagonal ferrite.

  When dispersing the ferromagnetic hexagonal ferrite powder, the surface of the ferromagnetic hexagonal ferrite powder particle is also treated with a substance suitable for the dispersion medium and polymer. As the surface treatment material, an inorganic compound or an organic compound is used. Typical examples of the main compound include oxides or hydroxides such as Si, Al, and P, various silane coupling agents, and various titanium coupling agents. The amount used is 0.1 to 10% with respect to the ferromagnetic hexagonal ferrite powder. The pH of the ferromagnetic hexagonal ferrite powder is also important for dispersion. Usually, about 4 to 12 has optimum values depending on the dispersion medium and polymer, but about 6 to 10 is selected from the chemical stability and storage stability of the medium. Water contained in the magnetic material also affects the dispersion. Although there are optimum values depending on the dispersion medium and polymer, it is usually preferably 0.01 to 2.0%.

  As a method for producing ferromagnetic hexagonal ferrite powder, (1) a metal oxide replacing barium oxide / iron oxide / iron and boron oxide as a glass-forming substance are mixed so as to have a desired ferrite composition and then melted; A glass crystallization method in which a barium ferrite crystal powder is obtained by rapid cooling to an amorphous body and then reheating treatment, followed by washing and pulverization. (2) A barium ferrite composition metal salt solution is neutralized with an alkali. After removing the product, liquid phase heating at 100 ° C. or higher, followed by washing, drying and pulverization to obtain a barium ferrite crystal powder, (3) neutralizing the barium ferrite composition metal salt solution with alkali, There is a coprecipitation method in which by-products are removed and then dried, treated at 1,100 ° C. or less, and pulverized to obtain barium ferrite crystal powder. However, the present invention does not select a production method.

Additives can be added to the magnetic layer in the present invention as necessary. Examples of the additive include an abrasive, a lubricant, a dispersant / dispersion aid, an antifungal agent, an antistatic agent, an antioxidant, a solvent, and carbon black. Further, other lubricants may be used in combination with the compound represented by the formula (I).
Examples of these additives include molybdenum disulfide, tungsten disulfide, graphite, boron nitride, graphite fluoride, silicone oil, silicone having a polar group, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, Polyolefin, polyglycol, polyphenyl ether, phenylphosphonic acid, benzylphosphonic acid group, phenethylphosphonic acid, α-methylbenzylphosphonic acid, 1-methyl-1-phenethylphosphonic acid, diphenylmethylphosphonic acid, biphenylphosphonic acid, benzylphenylphosphon Acid, α-cumylphosphonic acid, toluylphosphonic acid, xylylphosphonic acid, ethylphenylphosphonic acid, cumenylphosphonic acid, propylphenylphosphonic acid, butylphenylphosphonic acid, heptyl Aromatic ring-containing organic phosphonic acids such as phenylphosphonic acid, octylphenylphosphonic acid, nonylphenylphosphonic acid and alkali metal salts thereof, octylphosphonic acid, 2-ethylhexylphosphonic acid, isooctylphosphonic acid, isononylphosphonic acid, isodecyl Alkylphosphonic acids such as phosphonic acid, isoundecylphosphonic acid, isododecylphosphonic acid, isohexadecylphosphonic acid, isooctadecylphosphonic acid, isoeicosylphosphonic acid and alkali metal salts thereof, phenyl phosphate, benzyl phosphate, phosphorus Phenethyl phosphate, α-methylbenzyl phosphate, 1-methyl-1-phenethyl phosphate, diphenylmethyl phosphate, biphenyl phosphate, benzylphenyl phosphate, α-cumyl phosphate, toluyl phosphate, xylyl phosphate, phosphate Ethylpheny , Phenyl ester phosphate, propylphenyl phosphate, butylphenyl phosphate, heptylphenyl phosphate, octylphenyl phosphate, nonylphenyl phosphate, and alkali metal salts thereof, octyl phosphate, phosphate 2 -Ethylhexyl, isooctyl phosphate, isononyl phosphate, isodecyl phosphate, isoundecyl phosphate, isododecyl phosphate, isohexadecyl phosphate, isooctadecyl phosphate, isoeicosyl phosphate, and alkali metal salts thereof, alkyl Sulfonic acid esters and alkali metal salts thereof, fluorine-containing alkyl sulfates and alkali metal salts thereof, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, butyl stearate, oleic acid, linoleic acid, linoleic acid Monobasic fatty acids which may contain or be branched, such as acids, elaidic acid, erucic acid and the like, and their metal salts, or butyl stearate, octyl stearate, amyl stearate, Contains 10 to 24 carbon unsaturated bonds such as isooctyl stearate, octyl myristate, butyl laurate, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate However, it may be branched even if it contains a monobasic fatty acid that may be branched, an unsaturated bond having 2 to 22 carbon atoms or a 1 to 6-valent alcohol that may be branched, or an unsaturated bond having 12 to 22 carbon atoms. Monoalkoxy of alkoxy alcohol or alkylene oxide polymer which may be Mono-fatty acid esters consisting of any one of ether, di-fatty acid esters or polyvalent fatty acid esters, fatty acid amides having 2 to 22 carbon atoms, and aliphatic amines having 8 to 22 carbon atoms can be used. In addition to the above hydrocarbon groups, alkyl groups, aryl groups, and aralkyl groups substituted with nitro groups and groups other than hydrocarbon groups such as halogen-containing hydrocarbons such as F, Cl, Br, CF ₃ , CCl ₃ , and CBr ₃ You may have something.

  In addition, nonionic surfactants such as alkylene oxide, glycerin, glycidol, and alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium or sulfoniums, etc. Amphoteric interfaces such as cationic surfactants, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, and sulfate ester groups, amino acids, aminosulfonic acids, sulfuric or phosphate esters of aminoalcohols, and alkylbetaines An activator or the like can also be used. These surfactants are described in detail in “Surfactant Handbook” (published by Sangyo Tosho Co., Ltd.).

The dispersant, lubricant, antistatic agent and the like are not necessarily pure, and may contain impurities such as isomers, unreacted materials, side reaction products, decomposed products, and oxides in addition to the main components. These impurities are preferably 30% by weight or less, more preferably 10% by weight or less.
Specific examples of these additives include, for example, manufactured by NOF Corporation: NAA-102, castor oil hardened fatty acid, NAA-42, cation SA, Naimine L-201, Nonion E-208, Anon BF, Anon LG, Takemoto Oil and fat: FAL-205, FAL-123, Shin Nippon Chemical Co., Ltd .: NJELB OL, Shin-Etsu Chemical: TA-3, Lion Armor: Armide P, Lion: Duomin TDO, Nisshin Oil : BA-41G, Sanyo Kasei Co., Ltd .: Profan 2012E, New Pole PE61, Ionette MS-400, and the like.

  In the present invention, known organic solvents can be used in the magnetic layer. Organic solvents can be used in any ratio, such as ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, alcohols such as methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol, acetic acid Esters such as methyl, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate and glycol acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, and aromatic hydrocarbons such as benzene, toluene, xylene and cresol , Methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, chlorobenzene, dichlorobenzene, etc. Fluorinated hydrocarbons, N, can be used N- dimethylformamide, hexane, tetrahydrofuran or the like.

  These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, side reaction products, decomposition products, oxides, and moisture in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less. The organic solvent used in the present invention is preferably the same in the magnetic layer and the nonmagnetic layer. The amount added may be changed. Use a solvent with high surface tension (such as cyclohexanone or dioxane) in the nonmagnetic layer to increase the coating stability. Specifically, the arithmetic average value of the upper layer solvent composition may not fall below the arithmetic average value of the nonmagnetic layer solvent composition. It is essential. In order to improve dispersibility, it is preferable that the polarity is somewhat strong, and it is preferable that 50% or more of a solvent having a dielectric constant of 15 or more is included in the solvent composition. The solubility parameter is preferably 8-11.

  These dispersants, lubricants, and surfactants used in the magnetic layer in the present invention can be properly used in the magnetic layer and the nonmagnetic layer described later as needed. For example, of course, the dispersant is not limited to the example shown here, but the dispersant has a property of adsorbing or binding with a polar group, and in the magnetic layer, mainly on the surface of the ferromagnetic powder, as will be described later. In the nonmagnetic layer, it is presumed that the organophosphorus compound adsorbed or bonded to the surface of the nonmagnetic powder mainly by the polar group and once adsorbed is difficult to desorb from the surface of metal or metal compound. Accordingly, the surface of the ferromagnetic powder of the present invention or the nonmagnetic powder surface described later is in a state of being coated with an alkyl group, an aromatic group, etc., so the affinity of the ferromagnetic powder or nonmagnetic powder for the binder resin component And the dispersion stability of the ferromagnetic powder or non-magnetic powder is also improved. In addition, as the lubricant exists in a free state, the non-magnetic layer and the magnetic layer use fatty acids having different melting points to control the bleeding to the surface, and esters having different boiling points and polarities ooze to the surface. It is conceivable to improve the coating stability by controlling the amount of the surfactant, to improve the lubrication effect by increasing the additive amount of the lubricant in the nonmagnetic layer. All or part of the additives used in the present invention may be added in any step during the production of the coating solution for the magnetic layer or nonmagnetic layer. For example, when mixing with a ferromagnetic powder before the kneading step, when adding at a kneading step with a ferromagnetic powder, a binder and a solvent, when adding at a dispersing step, when adding after dispersing, when adding just before coating, etc. There is.

In addition, carbon black can be added to the magnetic layer in the present invention as necessary.
As the type of carbon black, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. The carbon black of the radiation-cured layer should be optimized for the following characteristics depending on the desired effect, and the effect may be obtained more when used in combination.

The specific surface area of the carbon black is preferably 100 to 500 m ² / g, more preferably 150 to 400 m ² / g, preferably DBP oil absorption 20 to 400 ml / 100 g, more preferably 30 to 200 ml / 100 g. The particle size of carbon black is preferably 5 to 80 nm, more preferably 10 to 50 nm, and still more preferably 10 to 40 nm. Carbon black preferably has a pH of 2 to 10, a water content of 0.1 to 10%, and a tap density of 0.1 to 1 g / ml.

  Specific examples of carbon black used in the present invention include BLACKPEARLS 2000, 1300, 1000, 900, 800, 880, 700, VULCAN XC-72, manufactured by Cabot Corporation, # 3050B, # 3150B, # 3250B manufactured by Mitsubishi Kasei Kogyo Co., Ltd. , # 3750B, # 3950B, # 950, # 650B, # 970B, # 850B, MA-600, MA-230, # 4000, # 4010, CONDUCTEX SC, Raven 8800, 8000, 7000, 5750, 5250, manufactured by Columbia Carbon Co., Ltd. , 3500, 2100, 2000, 1800, 1500, 1255, 1250, Ketjen Black EC manufactured by Akzo Corporation, and the like.

  Carbon black may be surface-treated with a dispersant or the like, or may be used after being grafted with a resin, or may be obtained by graphitizing a part of the surface. Moreover, before adding carbon black to a coating material, you may disperse | distribute with a binder beforehand. The carbon black that can be used in the present invention can be referred to, for example, “Carbon Black Handbook” (edited by Carbon Black Association).

  These carbon blacks can be used alone or in combination. When carbon black is used, it is preferably used in an amount of 0.1 to 30% by weight based on the weight of the ferromagnetic powder. Carbon black functions to prevent the magnetic layer from being charged, reduce the coefficient of friction, impart light-shielding properties, and improve the film strength. These differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention change the type, amount, and combination in the magnetic layer, and depending on the purpose based on the above-mentioned various characteristics such as particle size, oil absorption, conductivity, and pH. Of course, it is possible to use them properly, but they should be optimized in each layer.

III. Nonmagnetic Layer The magnetic recording medium of the present invention may have a nonmagnetic layer in which a nonmagnetic powder is dispersed in a binder on a nonmagnetic support. The nonmagnetic layer in the present invention preferably contains at least one compound represented by the formula (I), but when the compound represented by the formula (I) is not contained in the magnetic layer, The nonmagnetic layer must contain at least one compound represented by the formula (I). The nonmagnetic powder that can be used in the nonmagnetic layer may be an inorganic substance or an organic substance.
As the binder that can be used for the nonmagnetic layer, those mentioned for the magnetic layer can be preferably used. The amount of the binder used in the nonmagnetic layer is preferably 10 to 30 parts by weight with respect to 100 parts by weight of the nonmagnetic powder.

(Non-magnetic powder)
The nonmagnetic powder that can be used in the nonmagnetic layer may be an inorganic substance or an organic substance. Carbon black or the like can also be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides.

Specifically, titanium oxide such as titanium dioxide, cerium oxide, tin oxide, tungsten oxide, ZnO, ZrO ₂ , SiO ₂ , Cr ₂ O ₃ , α-alumina, β-alumina having an α conversion of 90 to 100%, γ-alumina, α-iron oxide, goethite, corundum, silicon nitride, titanium carbide, magnesium oxide, boron nitride, molybdenum disulfide, copper oxide, MgCO ₃ , CaCO ₃ , BaCO ₃ , SrCO ₃ , BaSO ₄ , silicon carbide Titanium carbide or the like is used alone or in combination of two or more. Among these, titanium dioxide, zinc oxide, α-iron oxide, and barium sulfate are preferable, and α-iron oxide and titanium dioxide are more preferable.

The shape of the nonmagnetic powder may be any of acicular, spherical, polyhedral and plate shapes.
The crystallite size of the nonmagnetic powder is preferably 4 nm to 1 μm, and more preferably 40 to 100 nm. A crystallite size in the range of 4 nm to 1 μm is preferred because it does not become difficult to disperse and has a suitable surface roughness.
The average particle size of these non-magnetic powders is preferably 5 nm to 2 μm. However, if necessary, non-magnetic powders having different average particle sizes may be combined, or even a single non-magnetic powder may have a wide particle size distribution. It can also have an effect. The average particle size of the particularly preferred nonmagnetic powder is 10 to 200 nm. The range of 5 nm to 2 μm is preferable because the dispersion is good and the surface roughness is suitable.

The specific surface area of the non-magnetic powder is preferably 1 to 100 m ² / g, more preferably 5 to 70 m ² / g, and still more preferably 10 to 65 m ² / g. A specific surface area in the range of 1 to 100 m ² / g is preferred because it has a suitable surface roughness and can be dispersed with a desired amount of binder.
The oil absorption using dibutyl phthalate (DBP) is preferably 5 to 100 ml / 100 g, more preferably 10 to 80 ml / 100 g, and still more preferably 20 to 60 ml / 100 g.
The specific gravity is preferably 1 to 12, more preferably 3 to 6. The tap density is preferably 0.05 to 2 g / ml, more preferably 0.2 to 1.5 g / ml. When the tap density is in the range of 0.05 to 2 g / ml, there are few particles to be scattered, the operation is easy, and there is a tendency that it is difficult to adhere to the apparatus.

The pH of the nonmagnetic powder is preferably 2 to 11, but the pH is particularly preferably between 6 and 9. When the pH is in the range of 2 to 11, the friction coefficient does not increase due to high temperature, high humidity, or liberation of fatty acids.
The water content of the nonmagnetic powder is preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, and still more preferably 0.3 to 1.5% by weight. A water content in the range of 0.1 to 5% by weight is preferable because the dispersion is good and the viscosity of the paint after dispersion is stable.
The ignition loss is preferably 20% by weight or less, and the ignition loss is preferably small.

When the nonmagnetic powder is an inorganic powder, the Mohs hardness is preferably 4-10. If the Mohs hardness is in the range of 4 to 10, durability can be ensured. The nonmagnetic powder has a stearic acid adsorption amount of 1 to 20 μmol / m ² , more preferably ² to 15 μmol / m ² .
The heat of wetting of the nonmagnetic powder into water at 25 ° C. is preferably in the range of ^{20 to} 60 μJ / cm ² (200 to 600 erg / cm ² ). Moreover, the solvent which exists in the range of this heat of wetting can be used.
The amount of water molecules on the surface at 100 to 400 ° C. is suitably 1 to 10 / 100Å. The pH of the isoelectric point in water is preferably between 3 and 9.

The surface of these nonmagnetic powders is preferably surface-treated with Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ and ZnO. Particularly preferred for dispersibility are Al ₂ O ₃ , SiO ₂ , TiO ₂ , and ZrO ₂ , but more preferred are Al ₂ O ₃ , SiO ₂ , and ZrO ₂ . These may be used in combination or may be used alone. Further, a surface-treated layer co-precipitated according to the purpose may be used, or a method of treating the surface layer with silica after first treating with alumina, or vice versa may be employed. The surface treatment layer may be a porous layer depending on the purpose, but it is generally preferable that the surface treatment layer is homogeneous and dense.

  Specific examples of the nonmagnetic powder used for the nonmagnetic layer in the present invention include, for example, Showa Denko Nanotite, Sumitomo Chemical HIT-100, ZA-G1, Toda Kogyo DPN-250, DPN-250BX, DPN-245, DPN-270BX, DPB-550BX, DPN-550RX Titanium oxide made by Ishihara Sangyo TTO-51B, TTO-55A, TTO-55B, TTO-55C, TTO-55S, TTO-55D, SN-100, MJ- 7, α-iron oxide E270, E271, E300, STT-4D, STT-30D, STT-30, STT-65C, manufactured by Titanium Industry, MT-100S, MT-100T, MT-150W, MT-500B, T -600B, T-100F, T-500HD, etc. are mentioned. FINEX-25, BF-1, BF-10, BF-20, ST-M, Dowa Mining DEFIC-Y, DEFIC-R, Nippon Aerosil AS2BM, TiO2P25, Ube Industries 100A, 500A, Titanium Industry Y-LOP manufactured and what baked it are mentioned.

Carbon black can be mixed in the nonmagnetic layer together with nonmagnetic powder to lower the surface electrical resistance, reduce the light transmittance, and obtain the desired μ Vickers hardness. The μ Vickers hardness of the nonmagnetic layer is preferably 25 to 60 kg / mm ² , more preferably 30 to 50 kg / mm ² in order to adjust the head contact, and a thin film hardness meter (NEC HMA-400) is used. By using a diamond triangular pyramid needle having a ridge angle of 80 degrees and a tip radius of 0.1 μm, the tip can be measured. It is standardized that the light transmittance is generally 3% or less for absorption of infrared rays having a wavelength of about 900 nm, for example, 0.8% or less for a VHS magnetic tape. For this purpose, rubber furnace, rubber thermal, color black, acetylene black and the like can be used. As carbon black that can be used for the nonmagnetic layer, those mentioned for the magnetic layer can be preferably used.

  These carbon blacks are preferably used in a range not exceeding 50% by weight relative to the nonmagnetic powder and not exceeding 40% of the total weight of the nonmagnetic layer. These carbon blacks can be used alone or in combination.

  In addition, an organic powder can be added to the nonmagnetic layer according to the purpose. Examples of such organic powder include acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment, but polyolefin resin powder, polyester resin powder, polyamide resin powder, and polyimide resin. Resin powder and polyfluorinated ethylene resin can also be used. As the production method, those described in JP-A Nos. 62-18564 and 60-255827 can be used.

  Moreover, an additive can be added to the nonmagnetic layer in the present invention as necessary. Examples of the additive include abrasives, lubricants, dispersants / dispersing aids, antifungal agents, antistatic agents, antioxidants, solvents, carbon black, and the like mentioned in the magnetic layer. Further, other lubricants may be used in combination with the compound represented by the formula (I).

IV. Nonmagnetic Supports Examples of the nonmagnetic support that can be used in the present invention include known ones such as biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferable.
These supports may be subjected in advance to corona discharge, plasma treatment, easy adhesion treatment, heat treatment and the like. The surface roughness of the nonmagnetic support that can be used in the present invention is preferably a center average roughness Ra of 3 to 10 nm at a cutoff value of 0.25 mm.

V. Backcoat layer Generally, magnetic tape for computer data recording is strongly required to have repeated running characteristics as compared with video tape and audio tape. In order to maintain such high storage stability, a backcoat layer can be provided on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is provided. The coating material for the back coat layer disperses a particle component such as an abrasive and an antistatic agent and a binder in an organic solvent. Various inorganic pigments and carbon black can be used as the particulate component. Moreover, as a binder, resin, such as a nitrocellulose, a phenoxy resin, a vinyl chloride resin, a polyurethane, can be used individually or in mixture, for example.

VI. Undercoat Layer The magnetic recording medium of the present invention may be provided with an undercoat layer. By providing the undercoat layer, the adhesive force between the nonmagnetic support and the magnetic layer or nonmagnetic layer can be improved. As the undercoat layer, a polyester resin soluble in a solvent is used. The undercoat layer has a thickness of 0.5 μm or less.

VII. Smoothing layer The magnetic recording medium of the present invention may be provided with a smoothing layer. The smoothing layer is a layer for embedding protrusions on the surface of the nonmagnetic support. In the case of a magnetic recording medium in which a magnetic layer is provided on the nonmagnetic support, the nonmagnetic support is provided between the nonmagnetic support and the magnetic layer. In the case of a magnetic recording medium in which a nonmagnetic layer and a magnetic layer are provided in this order on a support, it is provided between the nonmagnetic support and the nonmagnetic layer.
The smoothing layer can be formed by curing a radiation curable compound by radiation irradiation. The radiation curable compound refers to a compound having a property of being polymerized or cross-linked when irradiated with radiation such as ultraviolet rays or an electron beam, and polymerized and cured.

VIII. Layer Configuration In the configuration of the magnetic recording medium used in the present invention, the preferred thickness of the nonmagnetic support is 3 to 80 μm. The thickness of the back coat layer provided on the surface opposite to the surface provided with the magnetic layer of the nonmagnetic support is preferably 0.1 to 1.0 μm, more preferably 0.2 to 0.8 μm. It is. The thickness of the undercoat layer is preferably 0.1 to 1.0 μm, and more preferably 0.5 to 0.7 μm. Moreover, it is preferable that the thickness of a radiation hardening layer is 0.1-1.0 micrometer, and 0.3-0.7 micrometer is more preferable.

  The thickness of the magnetic layer is optimized according to the saturation magnetization amount, head gap length, and recording signal band of the magnetic head to be used, but is preferably 0.01 to 0.12 μm, more preferably 0.00. It is 02-0.10 micrometer. The thickness variation rate of the magnetic layer is preferably within ± 50%, more preferably within ± 40%. There may be at least one magnetic layer, and the magnetic layer may be separated into two or more layers having different magnetic characteristics, and a configuration related to a known multilayer magnetic layer can be applied.

  In the present invention, the thickness of the nonmagnetic layer is preferably 0.2 to 3.0 μm, more preferably 0.3 to 2.5 μm, and further preferably 0.4 to 2.0 μm. . The non-magnetic layer of the magnetic recording medium of the present invention exhibits its effect if it is substantially non-magnetic. For example, even if it contains a small amount of magnetic material as an impurity or intentionally, This shows the effect of the invention and can be regarded as substantially the same configuration as the magnetic recording medium of the invention. “Substantially the same” means that the residual magnetic flux density of the nonmagnetic layer is 10 mT (100 G) or less or the coercive force is 7.96 kA / m (100 Oe) or less, preferably the residual magnetic flux density and the coercive force. It means not having.

IX. Manufacturing Method The process of manufacturing the magnetic layer coating liquid for the magnetic recording medium used in the present invention comprises at least a kneading process, a dispersing process, and a mixing process provided before and after these processes as necessary. Each process may be divided into two or more stages. All raw materials such as ferromagnetic hexagonal ferrite powder or ferromagnetic metal powder, non-magnetic powder, binder, carbon black, abrasive, antistatic agent, lubricant, solvent used in the present invention are used at the beginning or middle of any process. It may be added. In addition, individual raw materials may be added in two or more steps. For example, polyurethane may be divided and added in a kneading step, a dispersing step, and a mixing step for adjusting the viscosity after dispersion. In order to achieve the object of the present invention, a conventional known manufacturing technique can be used as a partial process. In the kneading step, it is preferable to use a kneading force such as an open kneader, a continuous kneader, a pressure kneader, or an extruder. In the case of using a kneader, the magnetic powder or non-magnetic powder and all or part of the binder (however, 30% or more of the total binder is preferable) and the range of 15 to 500 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. Kneaded. Details of these kneading treatments are described in JP-A-1-106338 and JP-A-1-79274. Further, glass beads can be used to disperse the liquid for the magnetic layer and the liquid for the nonmagnetic layer. Such glass beads are preferably zirconia beads, titania beads, and steel beads, which are high specific gravity dispersion media. The particle diameter and filling rate of these dispersion media are optimized. A well-known thing can be used for a disperser.

In the method for producing a magnetic recording medium of the present invention, for example, a magnetic layer coating solution is applied onto a running support so that the thickness of the magnetic layer after drying becomes a predetermined thickness. Here, a plurality of magnetic layer coating solutions may be applied sequentially or simultaneously, and a nonmagnetic layer coating solution and a magnetic layer coating solution may be applied sequentially or simultaneously. The coating machine for applying the above magnetic coating solution or non-magnetic layer coating solution includes air doctor coat, blade coat, rod coat, extrusion coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure coat Kiss coat, cast coat, spray coat, spin coat, etc. can be used.
For these, for example, “Latest Coating Technology” (May 31, 1983) issued by the General Technology Center Co., Ltd. can be referred to.

When applied to a magnetic recording medium having a nonmagnetic layer or a magnetic layer, the following can be proposed as an example of a coating apparatus and method.
(1) First, a lower layer is applied by a coating apparatus such as a gravure, a roll, a blade, and an extrusion that are generally applied in the application of a magnetic layer coating solution, and the lower layer is in an undried state. The upper layer is applied by a support pressure type extrusion coating apparatus as disclosed in Japanese Patent Laid-Open No. 60-238179, Japanese Patent Laid-Open No. 2-265672, and the like.
(2) Upper and lower layers by one coating head having two coating liquid passage slits as disclosed in JP-A-63-88080, JP-A-2-17971, and JP-A-2-265672. Are applied almost simultaneously.
(3) The upper and lower layers are applied almost simultaneously by an extrusion coating apparatus with a backup roll as disclosed in JP-A-2-174965.

  A back coat layer may be provided on the surface of the nonmagnetic support used in the present invention on which the magnetic layer coating solution is not applied. The back coat layer is a non-magnetic support that is coated with a back coat layer forming paint in which particulate components such as abrasives and antistatic agents and a binder are dispersed in an organic solvent. It is a layer provided. In addition, the well-known undercoat layer may be provided in the application | coating surface of the backcoat layer forming coating material on a nonmagnetic support body.

  The coating layer of the magnetic layer coating solution is dried after subjecting the ferromagnetic powder contained in the coating layer of the magnetic layer coating solution to a magnetic field orientation treatment. After being dried in this manner, the coating layer can be subjected to a surface smoothing treatment. For the surface smoothing treatment, for example, a super calendar roll or the like can be used. By performing the surface smoothing treatment, voids generated by removing the solvent during drying disappear and the filling rate of the ferromagnetic powder in the magnetic layer is improved, so that a magnetic recording medium having high electromagnetic conversion characteristics can be obtained. it can. As the calendering roll, a heat resistant plastic roll such as epoxy, polyimide, polyamide, polyamideimide or the like can be used. Moreover, it can also process with a metal roll.

The surface property of the magnetic layer in the magnetic recording medium of the present invention is 5 to 1,000 microprojections / 100 (μm) ² having a height of 10 to 20 nm measured by an atomic force microscope (AFM). 5 to 300/100 (μm) ² is more preferable. Within the above range, it is preferable not only because the running performance is extremely excellent, but also because the strength of the magnetic layer is high and the number of protrusions due to surface abrasion is small and the running durability is excellent even when running repeatedly.
In the magnetic recording medium of the present invention, the center line average roughness of the surface is preferably 0.1 to 5 nm at a cutoff value of 0.25 mm, more preferably extremely excellent smoothness in the range of 1 to 4 nm. It is preferable for the magnetic recording medium for high-density recording to have a surface having a surface. As the method, for example, as described above, the calendering is performed on the magnetic layer formed by selecting a specific ferromagnetic powder and a binder.
As the calendering conditions, the temperature of the calender roll is in the range of 60 to 100 ° C., preferably in the range of 70 to 100 ° C., particularly preferably in the range of 80 to 100 ° C., and the pressure is 100 to 500 kg / cm (98 to 490 kN / m). ), Preferably 200 to 450 kg / cm (196 to 441 kN / m), particularly preferably 300 to 400 kg / cm (294 to 392 kN / m). . The obtained magnetic recording medium can be cut into a desired size using a cutting machine or the like.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to an Example.
In addition, the display of “parts” in the examples indicates “parts by weight”.

Example 1
<Adjustment of paint for magnetic layer>
Ferromagnetic alloy powder 100 parts (composition: Co 100 atm% Co 20 atm%, Al 9 atm%, Y 6 atm%, Hc: 175 kA / m (2,200 Oe), crystallite size: 11 nm, BET specific surface area: 70 m ² / g, major axis diameter: 45 nm, σs: 111 A · m ² / kg (emu / g))
Is pulverized with an open kneader for 10 minutes, and then a 30% cyclohexanone solution of vinyl chloride resin MR110 manufactured by Nippon Zeon Co., Ltd.
30 parts Polyurethane resin A 30 parts (polyester polyurethane, diisocyanate component: diphenylmethane diisocyanate, Tg = 70 ° C., weight average molecular weight: 65,000, SO ₃ Na group = 10 × 10 ⁻⁵ eq / g, methyl ethyl ketone (MEK) / (Toluene 30% solution)
And kneaded for 60 minutes. Next, abrasive (Al ₂ O ₃ , particle size 0.1 μm) 2 parts Carbon black (particle size 40 μm) 2 parts MEK 100 parts Toluene 100 parts were added and dispersed in a sand mill for 120 minutes. Polyisocyanate 15 parts (Japanese polyurethane coronate 3041, MEK 30% solution)
Compound (a) (see Table 2) 2 parts 2-ethylhexyl stearate 1 part isohexadecyl stearate 1 part stearic acid 1 part myristic acid 1 part MEK 50 parts are added and stirred for another 20 minutes, then 1 μm average It filtered using the filter which has a hole diameter, and prepared the coating material for magnetic layers.

<Preparation of coating material for nonmagnetic layer>
80 parts of acicular α-iron oxide (major axis length: 100 nm, surface treatment layer: alumina, BET specific surface area: 52 m ^{2 /} g, pH: 9.4)
Carbon black “Ketjen Black EC” (manufactured by Ketjen Black International) 20 parts was pulverized with an open kneader for 10 minutes, and then a 30% cyclohexanone solution of vinyl chloride resin MR110 manufactured by Nippon Zeon Co., Ltd.
30 parts Polyurethane resin B 30 parts (polyester polyurethane, diisocyanate component: diphenylmethane diisocyanate, Tg = 30 ° C., weight average molecular weight: 82,000, SO ₃ Na group = 5 × 10 ⁻⁵ eq / g contained, MEK / toluene 30% solution)
30 parts of MEK was added and kneaded for 60 minutes. Next, 200 parts of MEK was added and dispersed in a sand mill for 120 minutes. To this, polyisocyanate (Japanese polyurethane coronate 3041, 30% solution of MEK) 100 parts Compound (a) (see Table 2) 2 parts 2-ethylhexyl stearate 1 part isohexadecyl stearate 1 part stearic acid 1 part myristic acid 1 part MEK 100 parts Toluene 100 parts was added, and the mixture was further stirred and mixed for 20 minutes, followed by filtration using a filter having an average pore diameter of 1 μm to prepare a coating for a nonmagnetic layer.

  Polyethylene with a thickness of 6.0 μm so that the thickness after drying of the obtained coating for nonmagnetic layer is 1.2 μm, and immediately after that, the thickness after drying of the coating for magnetic layer is 0.1 μm. A simultaneous multilayer coating was applied to the surface of the naphthalate support. With the magnetic layer coating in an undried state, magnetic field orientation was performed with a 5,000 gauss Co magnet and a 4,000 gauss solenoid magnet, and the coated material was a metal roll-metal roll-metal roll-metal roll-metal roll- After performing a calendar process by a combination of a metal roll and a metal roll (speed 100 m / min, wire thickness 300 kg / cm, temperature 90 ° C.), heat treatment was performed at 50 ° C. for 7 days and slit into a 1/2 inch width.

(Examples 2 to 10)
A sample was prepared in the same manner as in Example 1 except that the compound (a) was replaced with the compounds shown in Tables 1 and 2.

(Example 11)
Polyurethane resin A of the magnetic layer is polyurethane resin C (polyester polyurethane, diisocyanate component: hydrogenated diphenylmethane diisocyanate, Tg = 65 ° C., weight average molecular weight: 73,000, SO ₃ Na group = 10 × 10 ⁻⁵ eq / g, A sample was prepared in the same manner as in Example 1 except that the MEK / toluene 30% solution was used.

(Example 12)
A sample was prepared in the same manner as in Example 1 except that the compound (a) was not added to the nonmagnetic layer coating material.

(Example 13)
A sample was prepared in the same manner as in Example 1 except that the compound (a) was not added to the magnetic layer coating material.

(Example 14)
The ferromagnetic powder of the coating material for the magnetic layer is a ferromagnetic hexagonal barium ferrite powder (composition: Ba / Fe / Co / Zn / Al = 1 / 9.1 / 0.2 / 0.8 / 0.8, average plate diameter). : 30 nm, average plate thickness: 8 nm, Hc: 216 kA / m (2,700 Oe), BET specific surface area: 72 m ² / g, σs: 54 A · m ² / kg (emu / g)) A sample was prepared in the same manner as in Example 1.

(Comparative Example 1)
A sample was prepared in the same manner as in Example 1 except that the compound (a) was not added.

(Comparative Example 2)
A sample was prepared in the same manner as in Example 1 except that the compound (a) in the coating material for the magnetic layer and the coating material for the nonmagnetic layer was changed to the following compound (k).

(Comparative Example 3)
A sample was prepared in the same manner as in Example 1 except that the compound (a) in the magnetic layer coating material and the nonmagnetic layer coating material was replaced with the following compound (L).

〔Measuring method〕
(1) Magnetic layer surface roughness Ra
The centerline average roughness Ra was measured by a light interference method using a digital optical profilometer (manufactured by WYKO) under the condition of a cutoff value of 0.25 mm.
(2) Magnetic layer surface protrusion
Using NanoscopeIII (AFM atomic force microscope) manufactured by Digital Instrument, the number of protrusions with a height of 10 to 20 nm in 10 μm square (100 (μm) ² ) was measured using a SiN short needle with a pyramid with a ridge angle of 70 °. did.
(3) Electromagnetic conversion characteristics (S / N ratio)
[Assembly of magnetic recording / reproducing system]
1) Thin-film magnetic head Recording head structure: an inductive head in which a two-turn thin-film coil is sandwiched between Co-based amorphous magnetic thin-film yokes.
Track width: 24 μm, gap length: 1.4 μm
Reproduction head structure: a double shielded shunt bias MR (magnetoresistance) head. The MR element is a Fe / Ni (permalloy) alloy thin film.
Track width: 10 μm, shield spacing: 1.4 μm
2) Assembling the magnetic recording / reproducing system The recording / reproducing head is mounted on a Fujitsu F613A drive (3480 type 1/2 inch cartridge magnetic tape recording / reproducing device) to produce a magnetic recording / reproducing system with a tape speed of 100 inches / second. did.
Servo control was performed at 21 ° C. and 50% RH, and one track (width 20 μm) was reproduced with a 90 m long tape, and the S / N ratio was measured.
(4) Durability A 90 m long tape was repeatedly reciprocated 10,000 times at a tape tension of 20 gf and a speed of 100 inches / second in the recording / reproducing system of (3) under an environment of 40 ° C. and 80%.
The damage on the tape surface at the tape running start portion was evaluated according to the following rank.
Excellent: No scratches or deposits are observed.
Good: Slight scratches are observed, but there are no deposits.
Defect: Both deposits and tape scratches are observed on the magnetic layer surface.

  Table 1 shows the compounds used in Examples 1 to 14 and Comparative Examples 1 to 3 and the evaluation results. Table 2 shows details of the compounds (a) to (j) represented by the formula (I).

Claims (5)

A magnetic recording medium comprising at least one magnetic layer in which a ferromagnetic powder is dispersed in a binder on a nonmagnetic support,
A magnetic recording medium comprising at least one compound selected from compounds represented by formula (I) in the magnetic layer.

(In the formula (I), R _{1 to} R ₃ each independently represents a group selected from the group consisting of —NR ₄ R ₅ , —SR ₆ , —OR ₇ , —CONR ₈ R ₉ , —R ₁₀ ; _{1 to} R ₃ all have the same structure , R ₄ represents a hydrogen atom or — (R ₁₁ -L) _n —R ₁₂ , and R _{5 to} R ₁₀ represent — (R ₁₁ -L) _n —R ₁₂ . , R ₁₁ represents a divalent hydrocarbon group, R ₁₂ represents a monovalent hydrocarbon group, L is a divalent linking group, n represents an integer of 0 to 20, also respectively R ₁₁ And L may be the same or different, provided that R _{1 to} R ₃ are groups having a hydrocarbon chain having 6 or more carbon atoms. A magnetic recording medium in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support via a nonmagnetic layer in which nonmagnetic powder is dispersed in the binder,
A magnetic recording medium comprising at least one compound selected from the compounds represented by formula (I) in the nonmagnetic layer and / or the magnetic layer.

(In the formula (I), R _{1 to} R ₃ each independently represents a group selected from the group consisting of —NR ₄ R ₅ , —SR ₆ , —OR ₇ , —CONR ₈ R ₉ , —R ₁₀ ; _{1 to} R ₃ all have the same structure, R ₄ represents a hydrogen atom or — (R ₁₁ -L) _n —R ₁₂ , and R _{5 to} R ₁₀ represent — (R ₁₁ -L) _n —R ₁₂ . , R ₁₁ represents a divalent hydrocarbon group, R ₁₂ represents a monovalent hydrocarbon group, L represents a divalent linking group, n represents an integer of 0 to 20, and each of R ₁₁ represents R ₁₁ And L may be the same or different, provided that R _{1 to} R ₃ are groups having a hydrocarbon chain having 6 or more carbon atoms. 3. The magnetic recording medium according to claim 1, wherein the number of microprotrusions on the surface of the magnetic layer having a height of 10 to 20 nm measured with an atomic force microscope (AFM) is 5 to 1,000 / 100 (μm) ² .   The magnetic recording medium according to claim 1, wherein the binder of the magnetic layer contains a polyurethane resin derived from an aromatic diisocyanate.   R ₁ ~ R _Three The magnetic recording medium according to claim 1, wherein is a group selected from the following groups.
-NHCH ₂ (CH ₂ ) _Ten CH _Three ,
-NHCH ₂ (CH ₂ ) ₁₂ CH _Three ,
-NHCH ₂ (CH ₂ ) ₁₄ CH _Three ,
-NHCH ₂ (CH ₂ ) ₁₆ CH _Three ,
-N (CH _Three ) CH ₂ (CH ₂ ) _Ten CH _Three ,
-N (CH _Three ) CH ₂ (CH ₂ ) ₁₂ CH _Three ,
-N (CH _Three ) CH ₂ (CH ₂ ) ₁₄ CH _Three ,
-N (CH _Three ) CH ₂ (CH ₂ ) ₁₆ CH _Three ,
-SCH ₂ (CH ₂ ) _Ten CH _Three ,
-SCH ₂ (CH ₂ ) ₁₄ CH _Three ,
-SCH ₂ (CH ₂ ) ₁₆ CH _Three ,
-SCH ₂ CH (C ₂ H _Five ) (CH ₂ ) _Three CH _Three ,
-OCH ₂ (CH ₂ ) _Ten CH _Three ,
-OCH ₂ (CH ₂ ) ₁₄ CH _Three ,
-OCH ₂ (CH ₂ ) ₁₆ CH _Three ,
-CH ₂ (CH ₂ ) _Ten CH _Three ,
-CH ₂ (CH ₂ ) ₁₂ CH _Three ,
-CH ₂ (CH ₂ ) ₁₄ CH _Three ,
-CH ₂ (CH ₂ ) ₁₆ CH _Three .