JPS60143430A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium which is suitable for high- density recording and vertical magnetic recording and having improved dispersion of magnetic particles by providing a magnetic layer contg. magnetic particles which are of a flat plate shape and of which the axis of easy magnetization is approximately perpendicular to the flat plate plane, a binder resin and a magnetic layer contg. a polymer (more particularly oligomer) having a polar functional group. CONSTITUTION:Magnetic particles are of a flat plate shape and have an axis of easy magnetization in a perpendicular direction and therefore said particles are made stable by a vertical orientation treatment and exhibit high-density recording performance of a high output; at the same time, the dispersibility (further stability, magnetic orientation) of said magnetic particles in the binder of a magnetic layer 13 is remarkably improved by the polymer of an oligomer having a polar functional group. The magnetic particles that can be used are enumerated by, for example, hexagonal ferrite 1. The hexagonal ferrite magnetic particle consists of barrium ferrite, strontium ferrite, etc. and may be the magnetic particle in which part of the iron element is substd. by other element (for example, Ti, Co, Zn, In, Mn, Ge, Hb, etc.).

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a magnetic recording medium, particularly a magnetic recording medium suitable for high-density recording.

2. Conventional technology In the conventional recording method using residual magnetization in the in-plane longitudinal direction,
As recording density increases, the demagnetizing field within the magnetic recording medium increases, deteriorating the recording characteristics in the short wavelength region. In order to improve this, the retention power (He) of the recording medium can be increased,
Alternatively, the layer is made thinner. Additionally, measures have been taken to smooth the surface of the magnetic layer to reduce spacing loss, but these are still not sufficient.

Therefore, recently, a perpendicular magnetic recording method using residual magnetization in a direction perpendicular to the surface of a magnetic recording medium has been proposed. This method is suitable for high-density recording because the demagnetizing field in the recording medium decreases as the recording density increases.

Perpendicular magnetic recording media include those formed by sputtering or vapor depositing a Co-Cr alloy layer on a high magnetic permeability layer,
It is known that magnetic powder is kneaded with a binder and applied. However, perpendicular magnetic recording media with metal thin films formed by sputtering or vapor deposition are suitable for high-density recording, but they are still not practical due to insufficient chemical stability, friction against magnetic heads, and durability. has not been standardized.

On the other hand, media in which a magnetic material is kneaded together with a binder and coated on a support, and an orienting magnetic field is applied in a direction perpendicular to the surface to form a perpendicular magnetic recording layer, is a medium that is formed by dispersion of magnetic powder, which has been established in the past. This is considered the most promising method since the technology can be used as is.

Such magnetic recording media include (1), JP-A-58-
No. 80136, No. 58-56232, No. 58-12138
A method of vertically aligning a flat magnetic material as described in each publication. (2) As shown in Japanese Patent Publication No. 57-501053, a method in which magnetic powder with a minor axis ratio is applied without orientation and a perpendicular magnetization component is formed on the surface of the magnetic layer using a narrow gap head. (3), Special Public Interest Publication Showa 49-15203
There is a method of utilizing oblique or perpendicular magnetization components that are not parallel to the magnetic layer using K1 acicular magnetic powder, as disclosed in US Pat. No. 3,185,775 and US Pat.

However, the above method (2) inevitably has problems with the stability of the magnetic recording medium itself, and the above method (3) has the drawbacks of high noise level and low output.

However, these drawbacks are minimal in the method (11) above, and method (1) is the best as a coated perpendicular recording medium. However, in method (1), the magnetic material is flat and easy to magnetize. Since the axis is perpendicular to the plate surface, it is difficult to disperse and agglomeration is likely to occur. In each publication of No. 57-56329, a phosphoric acid ester is used as a dispersant for a flat magnetic material,
JP-A-57-177074 uses lecithin and a cationic surfactant as a dispersant for a flat magnetic material, and JP-A-57-56904 improves dispersibility by coating the surface of a flat magnetic material with silica. In Japanese Patent Application Laid-Open No. 57-186302, a flat magnetic material is treated with a silane coupling agent having an epoxy group. However, the dispersion effect obtained by these known techniques is insufficient and is not yet satisfactory.

3. OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that is suitable for high-density recording and has improved dispersion of magnetic particles.

4. Structure of the invention and its effects In other words, the present invention comprises flat magnetic particles whose axis of easy magnetization is substantially perpendicular to the flat surface, a binder resin, and a polymer (especially an oligomer) having a polar functional group. The present invention relates to a magnetic recording medium characterized by comprising a magnetic layer containing the above.

According to the present invention, the magnetic grains are flat and have an axis of easy magnetization in the direction perpendicular to the flat plate.The vertical alignment process achieves stable, high-output, high-density recording performance due to the stability and magnetic field orientation. performance) has been significantly improved. In other words, polymers such as the above oligomers bind sufficiently to the surface of magnetic particles (particularly hydrophilic surfaces) due to the presence of their polar functional groups, and on the other hand, they have the property of being compatible with the binder, so that they are magnetic. It has an excellent effect as a dispersant for particles.

Furthermore, it is thought that the polymers such as oligomers also have the function of effectively preventing the alignment of magnetic particles from being disturbed by the demagnetizing field after the magnetic particles have been oriented in the magnetic field.

Examples of the above-mentioned magnetic particles that can be used in the present invention include
As shown in the figure, hexagonal ferrite 1 is mentioned. This hexagonal ferrite has a flat plate shape (diameter d is, for example, 0.1μ
m1 thickness t is, for example, 0.03 μm), and the axis of easy magnetization is perpendicular to the plate surface (i.e., the C-axis direction), so it can be easily oriented in the vertical direction by a magnetic field or mechanical orientation. A recording medium suitable for magnetic recording can be obtained. This round-hole square ferrite magnetic material is made of barium ferrite, strontium ferrite, etc., and some of the iron elements are other elements (for example, Ti, Co, Zn,
In.

MnXGe1Hb, etc.).

Regarding this ferrite magnetic material, IEEE Tran
s.

on Mag, MAG-1816 (1982).

The method for vertically aligning the above-mentioned plate-shaped magnetic powder is disclosed in Japanese Patent Application Laid-Open No. 58-80
No. 136, No. 58-12138, No. 58-1213,
58-12136, 58-12135, 55-14
242, No. 55-16363363633, there is a method of applying a vertical magnetic field to an undried coating film, and a method of rolling a high viscosity coating liquid between rolls to arrange plate-shaped particles in a horizontal direction. Either method can be used.

Polymers such as the above oligomers that can be used in the present invention include styrene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer and its salts and semi-amide derivatives thereof, acrylic acid-butyl acrylate, carboxyl group-containing acrylonitrile-butadiene copolymer, olico ester acrylate, polyvinylphenol, polyvinyl alcohol, acrylic acid-N-octylacrylamide copolymer, maleic anhydride-propylene copolymer, methacrylic acid-methylmethacrylate copolymer ,
Examples include 2-hydroxyethyl acryloylhofusl ether lauryl acrylate copolymer. Among these, salts of diisobutylene-maleic anhydride copolymer (e.g. ammonium salt, sodium salt,
Potassium salt), polystyrene sulfonic acid, etc. are preferred. Specifically, these compounds include Demol LP (manufactured by Kao Soap Co., Ltd.), Orotane 165 (Roam & No.
It is commercially available under trade names such as

In the present invention, the magnetic particles may be pretreated with the above polar functional group-containing polymer and then added to the magnetic paint, or the above polymer may be added at the time of mixing the magnetic paint. It is a new and useful finding discovered for the first time by the present inventors that the addition or inclusion of such a polymer significantly improves the dispersion of the tabular magnetic particles in the magnetic paint. In this case, the polar functional groups include hydroxyl group, sulfo group,
Examples include carboxyl groups, carbonyl groups, amide groups, phosphoric acid groups, and salts thereof. Among these, when a salt of a negative organic group such as a carboxyl group is contained, the solubility in water is appropriate and it is easy to treat magnetic particles with a polymer sometimes in an aqueous medium.

Furthermore, it was found that when magnetic particles were pretreated with the above polymer, the vertical orientation ratio of the flat magnetic powder was significantly improved. The reason for this is not yet clear, but it is said that even if flat magnetic powder is vertically oriented, if the orientation field is removed, the orientation tends to be disturbed again due to the demagnetizing field that remains in the coating film. However, the degree of polymerization of the above polymer is preferably 10 to 100, more preferably 10 to 50, which is thought to be because the treatment of the present invention prevents disorder after orientation. That is, if the degree of polymerization is less than 10, the plasticizing effect of the binder will be large in addition to the dispersion effect, and the physical properties and abrasion resistance of the medium will tend to deteriorate, and if the degree of polymerization exceeds 100, the surfactant effect will decrease. Easy to do.

In the present invention, as described above, since the magnetic material is flat and has an axis of easy magnetization in the direction perpendicular to the flat plate surface, magnetic poles are generated above and below the plate surface, and for this reason, plate surfaces with different magnetic poles are They tend to attract each other and cause aggregation, and once agglomerated, it is very difficult to disperse. In this case, if a strong shearing force is applied to disperse the powder, the magnetic powder will be destroyed, causing undesirable problems such as variations in coercive force and deterioration of the S/N ratio. Also, when a large amount of dispersant is used, the excess dispersant plasticizes the coating film and significantly impairs the physical properties of the medium. However, when a flat magnetic material is treated with the polymer of the present invention,
It is thought that a large number of polar groups in the polymer are adsorbed on the surface of the magnetic material, creating a so-called train-loop adsorption in which the lipophilic portions of the polymer protrude outward. Therefore,
Since the surface of the magnetic powder is made lipophilic, it is believed that when the magnetic powder is kneaded with an organic solvent and a binder, it is compatible with the binder and the dispersibility is improved.

Further, the above-mentioned polymer of the present invention can be called a polymeric surfactant, and has a large number of functional groups in one molecule that can be strongly adsorbed to the surface of the magnetic powder. Therefore, low-molecular surfactants with only one to several functional groups in one molecule (e.g. lecithin, phosphoric acid ester, alkyl quaternary ammonium salt, etc.)
There is less detachment from the surface of the magnetic powder in the magnetic coating material than in the magnetic paint, and therefore it has excellent dispersion stability. Since the magnetic material surface-treated with the polymer of the present invention exhibits excellent dispersibility, dispersants such as lecithin, phosphate ester, etc.
Although it is not necessary to add fatty acids, alkylated quaternary ammonium salts, etc., a small amount may be added to improve milling and coating properties. Since the amount of low molecular weight dispersant used can be significantly reduced, the mechanical properties of the recording medium can be significantly improved.

In order to incorporate the above-mentioned polymer according to the present invention into the magnetic layer, at least 1f4) of the above-mentioned polymers may be used:
Either the magnetic powder is dissolved in a solvent such as methanol or water, immersed in the solution at a predetermined ratio, stirred and mixed, and then filtered or evaporated and subjected to a drying process, or at least one of the above polymers is added to the magnetic powder. It may be added directly or dissolved in an appropriate solvent during dispersion.

The above polymer according to the present invention is normally used in an amount of 0.5 parts to 15 parts by weight, preferably 0.5 parts to 10 parts by weight, based on 100 parts by weight of the magnetic powder.
When the amount of this polymer is less than 0.5 parts by weight, the effect is not significant, and when it exceeds 15 parts by weight, blooming phenomenon and plasticization of the coating film may occur, giving undesirable results.

The magnetic paint used to create the medium of the present invention has magnetic powder, a binder, the above polymer, and a coating solvent as main components,
In addition, other additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be contained as necessary. This magnetic coating material is prepared by dissolving and dispersing the composition described above in an organic solvent, and is coated on a non-magnetic support to form a magnetic recording layer.

The magnetic paint used in the present invention includes Japanese Patent Publications No. 35-15, No. 39-26794, No. 43-186, and No. 47-28.
No. 043, No. 47-28045, No. 47-28046
No. 47-28048, No. 47-31445, No. 48-11162, No. 48-21331, No. 48-
It may be created in the same manner as the methods described in publications such as No. 33683 and Soviet Patent Specification No. 308033.

As the binder used in the present invention, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins can be used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200 to 2,000, such as acrylic acid ester-acrylonitrile copolymer, acrylic Acid ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer,
Polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, styrene-butadiene copolymer, polyester resin, chlorovinyl ether-acrylic ester copolymer, amino resin, various Synthetic rubber-based thermoplastic resins and mixtures thereof are used.

These resins are disclosed in Japanese Patent Publications Nos. 37-6877 and 39-1.
No. 2528, No. 39-19282, No. 40-5349
No. 4゜-20907, No. 41-9463, No. 4
No. 1-14059, No. 41 16985, No. 42-6
No. 428, No. 42-11621, No. 43-4623, No. 43-15206, No. 44-2889, No. 44
-17947, 44-18232, 45-14
No. 020, No. 45-14500, No. 47-18573
No. 47-22063, No. 47-22064, No. 47-22068, No. 47-2206Q Tatami, No. 47-
9. ')n7n compromise rMA-91-91-Ki Publication, U.S. Patent No. 3,144,352, U.S. Patent No. 3,419,42
No. 0, No. 3.499.789, No. 3.71.3.
It is described in the specification of No. 887.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, mixtures of methacrylate copolymers and diisocyanate prepolymers, urea formaldehyde resins, polyamine resins, and A mixture of these, etc.

These resins are disclosed in Japanese Patent Publications Nos. 39-8103 and 40-97.
No. 79, No. 41-7192, No. 41-8016, No. 41-14275, No. 42-18179, No. 43-
No. 12081, No. 44-28023, No. 45-145
No. 01, No. 45-24902, No. 46-13103, No. 47-22067 tatami, lff1,17-'>9 (1
No. 79, No. 47-22073, No. 47-28045, No. 47-28048, No. 47-28922,
U.S. Pat. No. 33,144.353, U.S. Pat. No. 3.320.
No. 090, No. 3,437,510, No. 3,597
, No. 273, No. 3,781,210, No. 3.78
No. 1,211.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
For example, maleic anhydride type, urethane acrylic type, polyester acrylic type, polyether acrylic type, polyurethane acrylic type, polyamide acrylic type, etc. Also, as polyfunctional monomers, ether acrylic type, urethane acrylic type, phosphate ester acrylic type, etc. Examples include aryl type and hydrocarbon type.

Further, when polycarbonate polyurethane described below is used, a magnetic layer with excellent durability can be obtained. This polyurethane is synthesized, for example, by a urethanization reaction with a polycarbonate polyol [H(O-R-0--R'-NCO) based on the following formula.

It is. 1 is 5 to reduce Tg and prevent stickiness.
It is preferably 0 or less, and preferably 1 to 30.

m is preferably 5 to 500, preferably 10 to 300, in order to maintain film-forming ability and improve solvent solubility. L and m
is selected so that the average molecular weight of this polycarbonate polyol polyurethane is desirably 50,000 to 200,000. ) The polycarbonate polyol that can be used here is formed by linking polyols with carbonate bonds, and is obtained, for example, by condensation of a conventionally known polyhydric alcohol with phosgene, chloroformic acid ester, dialkyl carbonate, diallyl carbonate, etc. .

Examples of the polyhydric alcohol include 1,10-decanediol, 1,6-hexanediol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, 1,5-bentanediol, and the like. The number of carbon atoms in this polyhydric alcohol, such as diol, is important and is preferably set to 4 to 12.
This is because problems (after running twice) are likely to occur. Correspondingly, the molecular weight of polycarbonate polyol is approximately 70, based on the properties of dust removal after 100 runs: 60°C and storage for one week.
It is preferable to set it to 0 to 3000.

In the above-described urethanization reaction, it is important that active hydrogen (due to -〇H) exists in the polycarbonate, but in addition to the polyhydric alcohols listed above as compounds that supply similar active hydrogen, Ethylene glycol, diethylene glycol, propylene glycol, 1. 4-phthylene gellicol, bisphenol A1
Glycerin, 1.3.6-hexanediol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, diethylene glycol, methyljetanolamine, ethylbiynepropanolamine, triethanolamine, ethylenediamine, hexamethylenediamine, bis(p-amino cyclohexane), tolylenediamine, diphenylmethanediamine, methylenebis(2-chloroaniline), and/or these compounds, combined with one or more of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide, etc. (Hereinafter simply referred to as alkylene oxide.) Examples include polyether polyols obtained by addition.

Next, although the active hydrogen-containing polycarbonate such as the above-mentioned polycarbonate polyol can be used alone, other polyhydric alcohols may be used in combination with the above-mentioned urethanization, and other known chain extenders may be used in combination.

In addition, in the present invention, if a cellulose resin and a vinyl chloride copolymer are also contained as a binder together with the above-mentioned polyurethane, the dispersibility of the magnetic powder will be further improved when applied to the magnetic layer, and its mechanical properties will be improved. Strength increases. However, if the cellulose resin and vinyl chloride copolymer are used alone, the layer will not be too hard, but this can be prevented by containing polyurethane.

Cellulose resins that can be used include cellulose mite-chill,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. Cellulose ethers include methylcellulose, ethylcellulose, propylcellulose, isopropylcellulose, methylcellulose, methylethylcellulose, methylhydroxyethylcellulose, ethylhydroxyethylcellulose, carboxymethylcellulose, carboxymethylcellulose sodium salt, hydroxyethylcellulose, benzylcellulose, cyanethylcellulose, vinylcellulose, Nitrocarboxymethylcellulose, diethylaminoethylcellulose, aminoethylcellulose, etc. can be used.

As the cellulose inorganic acid ester, nitrocellulose, cellulose sulfate, cellulose phosphate, etc. can be used.

In addition, cellulose organic acid esters include acetylcellulose, glopionylcellulose, butyrylcellulose, methacryloylcellulose, chloroacetylcellulose, β-oxypropionylcellulose, benzoylcellulose, p-toluenesulfonate cellulose, acetylpropionylcellulose, acetylbutylcellulose, Riru cellulose etc. can be used. Among these cellulose resins, nitrocellulose is preferred. Specific examples of nitrocellulose include Seltsuba BTH1/2 and Nitrocellulose 5L-1 manufactured by Asahi Kasei Corporation, Nitrocellulose R81/2 and Cellline L-200 manufactured by Daicel Corporation. Viscosity of nitrocellulose (JIS, K-
6703 (1975)) is 2 to T.
A time of 4 seconds is preferable, and a time of 1 to T seconds is particularly excellent. If it is outside this range, the film adhesion and film strength of the magnetic layer will be insufficient.

Moreover, as the above-mentioned vinyl chloride copolymers that can be used, there are those represented by the following. In this case, the molar ratio derived from L and m is 95 to 50 molti for the former unit and 5 to 50 molti for the latter unit.

In addition, X represents a monomer residue copolymerizable with vinyl chloride, including vinyl acetate, vinyl alcohol, maleic anhydride,
At least 11 selected from the group consisting of maleic anhydride, maleic acid, maleic ester, vinylidene chloride, acrylonitrile, acrylic acid, acrylic ester, methacrylic acid, methacrylic ester, vinyl propionate, glycidyl methacrylate, and glycidyl acrylate. represents weight. The degree of polymerization expressed as (J, +m) is preferably 100 to 600; if the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and 6
If it exceeds 00, the dispersibility will deteriorate. The vinyl chloride copolymer described above may be partially hydrolyzed.
As the vinyl chloride copolymer, preferably vinyl chloride-
Examples include copolymers containing vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymers"). Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-maleic anhydride, vinyl chloride-vinyl acetate-vinyl alcohol-maleic anhydride, and vinyl chloride-vinyl acetate. Examples include copolymers of rubinyl alcohol, maleic anhydride and maleic acid, and among vinyl chloride and vinyl acetate copolymers, partially hydrolyzed copolymers are preferred.

Specific examples of the vinyl chloride-vinyl acetate copolymer include Union Carbide's mnor V AGHJ,
rVYHHJ, rVMCHJ, Seishui Kagaku (&) H(D
"S-LEC A", "S-LEC A-5", "S-LEC C", "S-LEC M", [Denkabinil 100OG J, [Denkabinil 100] of Denka Kagaku Kogyo Co., Ltd.
OW j etc. can be used.

The above-mentioned vinyl chloride copolymer and cellulose resin may be used in any mixing ratio, but the weight ratio of vinyl chloride resin to cellulose resin is 90/10 to 5/95. It has been confirmed that 80/20 to 10/90 is more desirable. Outside this range, if the amount of cellulose resin increases (the above weight ratio is less than 5/95), stickiness tends to occur, resulting in poor surface properties and dropouts. Furthermore, if the amount of the vinyl chloride copolymer increases (if the above weight ratio exceeds 90/10), poor dispersion tends to occur, for example, the squareness ratio tends to deteriorate.

However, regarding the entire binder composition, the ratio of polyurethane to other resins is 90/10 to 30/30 by weight.
It has been confirmed that 70 is desirable, and 85/15 to 30/70 is even more desirable. Outside this range, if there is too much polyurethane, poor dispersion tends to occur and the still properties tend to deteriorate, and if other resins increase too much, surface properties tend to deteriorate and the still properties tend to deteriorate.
In particular, if it exceeds 70% by weight, the physical properties of the coating film become less favorable overall.

The total amount of the binder used in the present invention is 5 to 400 parts by weight (preferably 10 to 400 parts by weight) per 100 parts by weight of magnetic powder.
50 parts by weight) is desirable from the viewpoint of recording density, strength, etc. If the amount of binder is too large, the recording density of the magnetic recording medium will be lowered, and if it is too small, undesirable situations such as poor strength of the magnetic recording layer, decreased durability, and debris will occur.

Generally, when static electricity is accumulated during use of a magnetic recording medium, discharge occurs between the medium and the magnetic head, which tends to generate noise, and dust and the like may be attracted, causing dropouts. For this purpose, carbon black particles are usually added to the magnetic layer.

The amount of carbon black to be added is determined within a range that maintains the mechanical strength of the magnetic layer, but it is usually 5 to 35% by weight of carbon black to the binder (preferably, there is no need to increase the amount of carbon black added; When the content is set in the range of ~35% by weight, the mechanical properties of the magnetic layer (for example, powder removal of the magnetic layer) can be maintained well, and the desired surface electrical resistance (1
09Ω・(7) or less). For example, Conductex (Condu) manufactured by Columbia Carbon Co., Ltd.
ctex) 975 (specific surface area 270m2/1r, particle size 461μ), Conductex 950 (specific surface area 24
5m2/fr1 particle size 46mμ), Cabot Vulcan XC-72 (specific surface area 25tm''/lr-, particle size 18mμ), etc. can be used.

FIG. 2 shows a magnetic recording medium, for example a magnetic tape, according to the present invention, in which a subbing layer 12 (this layer may not be provided if necessary) on a support 10, a magnetic layer 13 are laminated.

According to the present invention, the above-described treated magnetic powder or magnetic powder, polymer, and binder are contained in the magnetic layer 13.

Furthermore, in order to improve the durability of the magnetic recording medium according to the present invention, various hardening agents can be incorporated into the magnetic layer.
For example, isocyanates can be incorporated.

Aromatic incyanates that can be used are, for example, tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), #silylene diisocyanate (XDI), metaxylylene diisocyanate) ( M, XDI) and these isocyanates,
It may be combined with an active hydrogen compound, and preferably has an average molecular weight in the range of 100 to 3,000.

Specifically, the products manufactured by Sumitomo Bayer Urethane Co., Ltd., Sumigeel T80, Sumigeel 44S1 PF, Desmodille L1 Desmodille T65, Desmodille 15, R1 RF, and Sumigeel IL.

Same SL; Product manufactured by Takeda Pharmaceutical Co., Ltd.) 3008゜ Same 500; Product manufactured by Mitsui Nisso Urethane Co., Ltd. rNDIj, rTO
Desmodule T10 manufactured by Nippon Polyurethane Co., Ltd. for DI
0, Millionate MR, Same MT, Coronate L1 Kasei Up Jijin Co., Ltd. product PAP I-135, TDI65,
I can praise the 80, 100, Isonate 125M1, 143L, etc.

On the other hand, examples of aliphatic isocyanates include hexamethylene diisocyanate (HMDI), lysine isocyanate, and trimethylhexamethylene diisocyanate (TMD).
I) and adducts of these incyanates and active hydrogen compounds. Among these aliphatic incyanates and adducts of these incyanates and active hydrogen compounds, those with a molecular weight of 100 are preferable.
~3.000. On the other hand, among the aliphatic isocyanates, non-alicyclic incyanates and adducts of these compounds with active hydrogen compounds are preferred.

Specifically, for example, Sumidur N1 Desmodur Z4273 manufactured by Sumitomo Bayer Urethane Co., Ltd., Derane 50M, 24 A-100, 24 manufactured by Asahi Kasei Co., Ltd.
A-90CX, Nippon Boriurekun product Coronae)H
There are products such as L. and TMDI manufactured by Huls. Further, examples of the alicyclic incyanate among the aliphatic incyanates include methylcycloCO 4,4'-methylenebis(cyclohexylisocyaisophorone diisocyanate and its adduct of an active hydrogen compound).

Specifically, products rIPDIj, I manufactured by Heals Chemical Co., Ltd.
PDI-T 1890, PDI-H2921, PDI-B
1065 etc.

The magnetic recording medium of the present invention is prepared by preparing a magnetic coating material by mixing and dispersing, for example, magnetic powder, an inder, and various additives in an organic solvent, and then adding the above-mentioned aromatic incyanate and aliphatic incyanate. It is prepared by coating it on a support (for example, a polyester film) and drying it if necessary.

The amount of incyanate added is 1 to 10 to the binder.
Add 0% by weight. If the amount is less than 1ti6, the hardening of the magnetic layer will be insufficient; if it is more than 100%, the magnetic layer will become "sticky" even though it is hardened. In order to obtain a more preferable magnetic layer, the amount of incyanate added is preferably 5 to 30% by weight based on the binder.

As the polyisocyanate, an adduct of diisocyanate and trivalent polyol, or an adduct of diisocyanate
There are 3 moles of diisocyanate and a decarboxylating compound of water.

Examples of these include an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of trimethylolpropane, a pentamer of tolylene diisocyanate,
There are pentamers consisting of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate, decarboxylated products obtained by reacting 3 moles of hexamethylene diisocyanate and 1 mole of water, etc., and these are easily obtained industrially. .

The coating material used to form the magnetic layer may contain other additives such as dispersants, lubricants, abrasives, and other antistatic agents, if necessary.

Other dispersants that may be used include lecithin, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid,
Fatty acids with 8 to 18 carbon atoms such as linoleic acid, lylic acid (R-COOH, where R is 7 to 17 carbon atoms)
saturated or unsaturated alkyl groups); and metal soaps made of alkali metals (Li, NaXK, etc.) or alkaline earth metals (MgXCaXBa, etc.) of the above-mentioned fatty acids. In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. Moreover, commercially available general surfactants can also be used. These dispersants may be used alone or in combination of two or more.

Li#% lubricants include silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acids having 12 to 16 carbon atoms, and a total number of carbon atoms of 21 to 23 carbon atoms. Fatty acid esters made of monohydric alcohols can also be used. These lubricants are used in amounts of 0.2 to 20 parts by weight per 100 parts by weight of magnetic powder.
It is added in a range of parts by weight.

Abrasive materials that may be used include commonly used materials such as fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond,
Garnet, emery (main ingredients: corundum and magnetite), etc. are used. Tora's abrasive has an average particle size of 0.05
-5μ in size is used, particularly preferably 0
．． It is 1 to 2μ. These abrasives are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the magnetic powder.

Other antistatic agents that may be used include conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds; natural surfactants such as Sanipon; alkylene oxide compounds. , nonionic surfactants such as glycerin type and glycidol type; cationic surfactants such as higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, phosphoniums or sulfoniums; carboxylic acids,
Anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; examples include amphoteric surfactants such as amino acids, aminosulfonic acids, amino acids, sulfuric acid or phosphoric esters of W-ru, etc. 0 Solvents for magnetic paint or solvents used when applying magnetic paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, pronochloro, butanol; methyl acetate, acetic acid. Esters such as ethyl, butyl acetate, ethyl lactate, and ethylene glycol monoacetate; Ethers such as ethylene glycol dimethyl ether, diethylene glycol monoethyl ether, dioxane, and tetrahydrofuran; benzene, toluene,
Aromatic hydrocarbons such as xylene; non-loginated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, dichlorobenzene, etc. can be used.

Support materials include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polycarbonate, Ai, ZN, etc. metals, glass, BN1Si carbide, porcelain, ceramics such as earthenware, etc. are used.

The thickness of these supports is about 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 pm.
In the case of a disk or card shape, the diameter is about 30 μm to 10 μm, and in the case of a drum shape, the shape is cylindrical, and the shape is determined depending on the recorder used.

The surface of the support opposite to the side on which the magnetic layer is provided may be coated with a so-called backcoat, as shown by a dashed line 14 in FIG. 2, for the purpose of preventing static electricity, preventing transfer, and the like.

Coating methods for forming a magnetic layer by applying the magnetic paint onto a support include air doctor coating, blade coating, air knife coating, Swiss coat, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, and kiss coating. , cast coat,
A tin ray coat or the like can be used, and other methods are also possible.

The magnetic layer coated on the support by such a method is optionally subjected to a treatment for orienting the magnetic powder in the multilayer, and then the formed magnetic layer is dried.

Further, the magnetic recording medium of the present invention is manufactured by subjecting it to surface smoothing processing, if necessary, and cutting it into a desired shape.

Hereinafter, the present invention will be explained with reference to specific examples.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

In addition, in the following examples, all "parts" are "parts by weight".
represents.

Example 1 First, cobalt-substituted barium ferrite (particle size 0.
1/jm, thickness 0.03 μm 1 coercive force He = 720
0e.

Saturation magnetization σs = s7emu/g) of diisobutylene
The surface was treated with ammonium salt of maleic anhydride copolymer. That is, 100 parts of the magnetic powder to be treated (above) (lium ferrite) is transferred to a dryer to evaporate the water content until the solid content is 2.5 parts, and the magnetic powder is further loosened in a colloid mill to form a mesh. The powder was classified using a sieve, to obtain treated magnetic powder.

The following composition was prepared using this treated magnetic powder.

Treated barium ferrite powder (above) 100 parts Polycarbonate polyurethane 14 parts Nitrocellulose (Seltsuba BTHI/2 manufactured by Mukasei Co., Ltd.) 5 parts Vinyl chloride-vinyl acetate copolymer (MTB-i0 manufactured by Denki Kagaku Kogyo Co., Ltd.) 1 part Contact Kusu 975 (BET value zrom"/yrz particle size 4 particle size 46ku μ5 parts Seapen 2000 (BET value tsom"/rr1 particle size 1
Particle size: 1 part Ramiristic acid 2 parts Palmitic acid butyl ester 1 part Alumina 4 parts Toluene 20 parts Methyl ethyl ketone 50 parts Cyclohexanone 100 parts This composition was thoroughly dispersed with a sand grinder. At this time, samples were taken at regular intervals and applied onto a glass plate, and the degree of dispersion was compared with a standard plate under a 100x microscope to determine the end point of dispersion. This composition was applied onto a polyester film having a polyfunctional isocyanate thickness using a reverse roll coater, oriented in a vertical magnetic field, and further dried. Thereafter, the surface of the magnetic layer was treated using a suit calender roll to obtain a wide magnetic film having a magnetic layer of a predetermined thickness. This film was cut into tape shapes.

Example 2 A magnetic tape was prepared in the same manner as in Example 1, except that the coating composition of Example 1 was treated with a copolymer of sodium acrylic acid and butyl acrylate as magnetic powder. .

Example 3 A magnetic tape was prepared in the same manner as in Example 1 except that 1 part of phosphoric acid ester (dispersant) (GAFACRE-610) was further added to the coating composition of Example 1.

Example 4 One part of lecithin was further added to the coating composition of Example 1, and a magnetic tape was prepared in the same manner.

Comparative Example 1 In Example 1, barium ferrite powder that was not pretreated with diisobutylene-maleic anhydride copolymer was used, and phosphoric ester (GAFAC RE) was used as a dispersant.
A magnetic tape was prepared in the same manner except that 3 parts of A-610) were added.

Comparative Example 2 A magnetic tape was prepared in the same manner as in Example 1, using barium ferrite powder that was not pretreated with diisobutylene-maleic anhydride copolymer, and adding 3 parts of lecithin as a dispersant. The vertical squareness ratio (after demagnetizing field correction), gloss, and video characteristics were measured for each of the magnetic tapes with a rating of 0 or more, and the results are shown in the table below. The method for measuring these was as follows.

Gloss (cloth): Measured at the aoJ angle using a gloss meter manufactured by Murakami Color Research Institute, and expressed with a standard plate of 100 yen (the larger the value, the better the surface smoothness).

Video characteristics: Displayed as a relative value with the value set to 0 for a head with a narrow gap of 0.2 μm. Video S/N was also measured in the same way.

(The following margins continue on the next page.) From these results, it can be seen that sample tapes using magnetic powder pretreated with oligomers based on the present invention (Runs 1 to 4) were more dispersed than tapes without pretreatment. It can be seen that it has excellent properties such as square shape, gloss, electromagnetic conversion characteristics, SZN ratio, and paint preservability.

[Brief explanation of the drawing]

The drawings illustrate the present invention; FIG. 1 is an enlarged perspective view of hexagonal ferrite particles, and FIG. 2 is an enlarged sectional view of a portion of a magnetic tape. In addition, in the symbols shown in the drawings, 1......Hexagonal ferrite particles 10...・・・
Non-magnetic support 12・・・・・・・・・・・・・・・・・・・・・
Subbing layer 13 is a magnetic layer.

Claims (1)

[Claims] 1. A magnetic layer comprising flat magnetic particles whose easy axis of magnetization is about 11 perpendicular to the flat surface, a binder resin, a polymer having a polar functional group, and gold. magnetic recording media. 2. The magnetic recording medium according to claim 1, wherein the magnetic particles are hexagonal ferrite.