JPH02132640A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To adequately combine orienting and drying and to form a good coated film by incorporating specific resins into a magnetic coating compd., drying the magnetic coating compd.-coated layer in the orienting part of the final position in a manner as to attain a specific ratio of the magnetic powder and solvent in the coated layer and completing the drying in the last position in the orienting part of the final position. CONSTITUTION:One or more kinds of the resins selected from the group consisting of polyurethane in which the negative functional group forms an intramolecular salt, polyurethane contg. the alkaline metal salt of a sulfo group and polyurethane contg. the alkaline metal salt of an oxysulfino group are incorporated into the magnetic coating compd. 8. The magnetic coating compd. 8 is so dried that the ratio of the magnetic powder and solvent therein attains 1/1.1 to 1/2.3 by weight in the position of a rear orienting magnet 9. The performances, more particularly squareness ratio (SQ) of the magnetic recording medium are significantly affected in this way and can be thereby improved. The good coated film is thus formed by adequately combining the orienting and drying.

Description

[Detailed description of the invention] a. INDUSTRIAL APPLICATION FIELD The present invention relates to a method and apparatus for manufacturing magnetic recording media such as magnetic tapes and magnetic sheets.

mouth. BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it.

In recent years, there has been an increasing demand for higher performance through higher density and higher filling of magnetic recording. In particular, it has been known that improving the residual magnetic flux density of the magnetic layer and improving the ratio of the residual magnetic flux density to the saturation magnetic flux density (squareness ratio) in the magnetic hysteresis curve are effective in improving output.

In manufacturing such magnetic recording media, after applying the magnetic paint, the coated layer is subjected to orientation treatment in a magnetic field and drying treatment, but conventional methods do not control these two treatments in a correlated manner. In some cases, the coating film dries before the magnetic particles are sufficiently oriented, or the coating film may not be properly oriented during the drying process. As a result, the squareness ratio (SQ) is low and good electromagnetic conversion performance cannot be obtained.

Furthermore, it has been well known that magnetic field orientation is performed during the drying process, but in the actual manufacturing process, it is difficult to perform orientation without maintaining constant drying conditions, such as controlling the film thickness and controlling the coating liquid. Due to fluctuations in various conditions such as viscosity control, air volume, and temperature control, variations were large and the range of suitable orientation points was narrow.

In addition, the fine structure of the surface contributes to the sliding noise, which is a particular problem with ferrite heads that are commonly used in current magnetic recording and playback. cannot be controlled.

C. Object of the Invention The object of the present invention is to form a good coating film by skillfully combining orientation and drying, and to have a suitable surface roughness, good running durability, and good Hesid sliding noise level. The present invention provides a manufacturing method that can be formed and has a wide range of suitable points for orientation and drying.

two. Structure of the Invention and Its Effects The present invention provides a method for producing a magnetic recording medium in which a magnetic paint is applied onto a support, and the magnetic paint coating layer is subjected to an orientation treatment using a magnetic field and a drying treatment. The ratio of the magnetic powder to the solvent in the magnetic paint coating layer in the rearmost alignment region, which is contained in the magnetic paint containing an alkali metal salt of a polyurethane and a sulfo group, in which groups form an inner salt in the molecule; Magnetic powder/melting agent) weight ratio is 1/1.1 to 1/
2.3, and the drying is completed after the rearmost alignment portion.

FIG. 1 shows an apparatus for carrying out a method for manufacturing a 77'';1j&$l'FIIf magnetic recording medium.

That is, a long, strip-shaped non-magnetic support 1 is fed from a feed roll 4 and wound up by a winding roll 6. During this time, a magnetic paint 8 is first applied to the surface of the support 1 in a coating section 2.

A smoother 3, a first-stage orientation magnet 7, a drying zone 5, and a second-stage orientation magnet 9 are provided in this order from the application section 2 toward the downstream side in the support transport direction. The drying zone 5 may be of a known type that directs hot air from a nozzle, but these are omitted for simplicity of illustration.

The non-magnetic support 1 is smoothed by a smoother 3 while the magnetic coating film 8 remains undried, and the viscosity of the non-magnetic support 1 is reduced by the properties of the magnetic coating 8, and then oriented in a desired direction by a pre-stage orientation magnet 7. As this front-stage oriented magnet, a unipolar permanent magnet, a same-polar facing permanent magnet, an electromagnet, or the like is used.

This pre-stage oriented magnet 7 has an average magnetic flux density of 1 to 6 times (especially 1 to 3 times) the coercive force of the magnetic powder used in the magnetic paint 8, and an average magnetic flux density of 300.
~5000 Gauss is preferably used.

Next, the non-magnetic support 1 is sent to a drying zone 5 that supplies drying air to the surface of the non-magnetic support 1. In this drying zone 5, the non-magnetic support is conveyed from an inlet A to an outlet B. In the meantime, the solvent content of the coating 8 at the inlet A can be continuously reduced. This decreasing curve corresponds to dry zone 5
It can be controlled arbitrarily by changing the temperature distribution and air volume distribution. Also, in the drying zone, there is a rear orientation magnet 9.
is installed, and this orientation magnet can change its position within the drying tunnel 5 from closer to A to closer to B.

At the outlet B of the drying zone 5, it is preferable to dry up to 99% or more of the amount of solvent in the coating liquid supplied to the coating section 2. The magnetic field strength of the rear orientation magnet 9 is preferably 1.2 to 6 times the coercive force of the magnetic powder.

What should be noted here is that the ratio of magnetic powder to solvent in the magnetic coating film (magnetic powder/solvent: hereinafter abbreviated as M/S) is 1/1 in weight ratio at the position of the rear orientation magnet 9. It should be dry to a ratio of .1 to 1/2.3. That is, M/S =
The second stage orientation magnet 9 is installed at a position where the angle is 1/1.1 to 1/2.3.

This range or position was discovered for the first time from repeated experimental results by the present inventors, which will be described later, and it is believed that this range or position greatly influences the performance of the magnetic recording medium, especially the squareness ratio (SQ), and can significantly improve this. It became clear.

That is, when M/S is larger than 1/1.1, drying progresses too much and it becomes difficult to perform magnetic field orientation by the rear orientation magnet 9.
If M/S is smaller than 1/2.3, the drying rate is small, and the particles oriented by the magnet 9 tend to flow afterwards, resulting in disordered orientation. Therefore, M/S is 1/1.1~
It is essential that the ratio be 1/2.3, and it is further desirable that this range be 1/1.3 to 1/2.1.

The position of the second-stage orientation magnet 9 is preferably such that 7% to 35% of the amount of solvent in the coating solution supplied to the coating section 2 is dried.

In addition, the magnetic field strength is also important in determining the orientation state,
It is preferable that the magnetic field strength of the rear-stage orientation magnet 9 is equal to or stronger than that of the front-stage orientation magnet 7.

That is, the first-stage orientation magnet 7 is used to orient the magnetic powder particles while the coating liquid has a low viscosity to the extent that they do not agglomerate. However, when the coating liquid is then dried and the viscosity becomes high, the flow of the particles is suppressed and almost no rotation occurs. This is because when movement occurs, the stronger rear-stage orientation magnet 9 allows orientation without causing aggregation.

FIGS. 2 and 3 show cross-sectional views of two examples of magnetic recording media manufactured by the above method. 18 in the figure is a magnetic layer formed by drying and hardening the magnetic paint 8, 13 is a back coat layer (BC layer) provided as necessary after forming the magnetic layer, and 14 is before forming the magnetic layer. This is an undercoat layer provided on the .

The magnetic powder, particularly the ferromagnetic powder, used in the magnetic layer 18 is 7-Fe20,, Co-containing 1-Fe. O. ,F e
30a, Co-containing Fe20+, 1-FeOx,
Co-containing 7-FeO x (X = 1.3
3-1.50). CrOz, Co'-Ni-P alloy,
Co-Ni-FeB alloy, Fe-Ni-Zn alloy, Ni
-Co alloy, Co-Ni-Fe alloy, and other known ferromagnetic fine powders can be used.
No. 0, Special Publication No. 18372, Special Publication No. 47-2
No. 2062, Japanese Patent Publication No. 47-3389014, etc. The particle size of these ferromagnetic fine powders is approximately o. With a length of oi ~ 1 micron, the ratio of axial length/axial width is 1
It is about /1 to 50/1. Further, the specific surface area of these ferromagnetic fine powders is about lrd/g to 60 m/g. The surface of these ferromagnetic fine powders may be impregnated with a dispersant, a lubricant, an antistatic agent, etc., which will be described later, in a solvent prior to dispersion for each purpose, and then adsorbed thereon.

Further, as the ferromagnetic fine powder used in the present invention, plate-shaped hexagonal barium ferrite can also be used.

The particle size of barium ferrite is about 0.001 to 1 micron in diameter, and the thickness is 1/2 to 1/2 of the diameter.

Barium ferrite has a specific gravity of 4 to 6 g/cc and a specific surface area of 1%/g to 60 rT'r/g. The surface of these ferromagnetic fine powders may be impregnated with a dispersant, a lubricant, an antistatic agent, etc., which will be described later, in a solvent prior to dispersion and adsorbed thereto for each purpose.

In particular, as an example of a ferromagnetic alloy powder, the metal content in the ferromagnetic alloy powder is 75% by weight or more, and 80% by weight or more of the metal content is at least one ferromagnetic metal or alloy (e.g., Fe, Co, etc.). , Ni, FeCo, Fe-Ni, Fe
-Aj2, Fe-Af-Ni, Fe-Zn, Fe-Aj
! Zn, CoNi, Co-Ni-Fe), and other components (e.g. Af
, St, S, Sc, Ti, V, Cr, Mn, Cu, Zn
, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, B
a, Ta, W, Re, Au, Hg, Pb, Bi, La,
Mention may be made of alloys which may contain Ce, Pr, Nd, B, P). In addition, if the above ferromagnetic metal is mixed with a small amount of water,
It may contain a hydroxide or an oxide. Methods for producing these ferromagnetic metal powders are already known, and ferromagnetic alloy powder, which is a typical example of the ferromagnetic powder used in the present invention, can also be produced according to these known methods.

That is, examples of the method for producing ferromagnetic alloy powder include the following method.

(a) A method of reducing complex organic acid salts (mainly oxalates) with a reducing gas such as hydrogen: (b) A method of reducing iron oxide with a reducing gas such as hydrogen to produce F
Method for obtaining e or Fe-Co particles: (C)
Method for thermally decomposing carbonyl compounds: (d) Method for reducing an aqueous solution of a ferromagnetic metal by adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine: (e) Using a mercury cathode Method for electrolytically depositing ferromagnetic metal powder and then separating it from mercury: (f) Method for obtaining fine powder by evaporating the metal in a low-pressure inert gas: When using ferromagnetic alloy powder, its shape Although there are no particular limitations, needle-shaped, granular, dice-shaped, rice-grain-shaped, and plate-shaped ones are usually used.

The specific surface area (S B.ET) of this ferromagnetic alloy powder is 4
It is preferable that it is 0 rrr/g or more, and it is particularly preferable to use one that is 45 i/g or more.

As the binder for the magnetic layer 18, one with a negative functional group is used.

Similar to the usual polyurethane synthesis method, polyurethane is used to synthesize high molecular weight polyols (molecular weight 500-3000) such as polycarbonate polyols, polyester polyols, borilactone polyols, polyether polyols, etc. Synthesized by reacting polyfunctional aromatic and aliphatic isocyanates. As a result, polyester polyurethane, polyether polyurethane, and polycarbonate polyurethane carbonated with phosgene or diphenyl carbonate are synthesized.

These polyurethanes are primarily produced by the reaction of polyisocyanates with polyols and optionally other copolymers, and may also be in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups; It may also be in the form of a urethane elastomer, which does not contain any reactive end groups. As the isocyanate component, various diisocyanate compounds such as hexamethylene diisocyanate (HMDI), diphenylmethane diisocyanate (
MDI), hydrogenated MDT (H.■MDI), toluene diisocyanate (TDI), 1.5-naphthalene diisocyanate (NDI), tolidine diisocyanate (
TODI), lysine diisocyanate methyl ester (
．． LDI), inphorone diisocyanate} (
IPDI) etc. can be used.

In addition, 1,4-butanediol, 1,6-
A low-molecular polyfunctional alcohol such as hexanediol or 1,3-butanediol is used to adjust the molecular weight, resin physical properties, etc.

The functional group forming the inner salt may be introduced into the isocyanate component, but it can also be introduced into the polyol component, and further into the above-mentioned low-molecular polyfunctional alcohol.

Polyester polyols whose negative functional groups form an inner salt can be made of various dicarboxylic acid components, polyhydric alcohol components, and dicarboxylic acid components and/or negative functional groups whose negative functional groups form an inner salt. It can be synthesized by polycondensing polyhydric alcohol components that form an inner salt.

Examples of dicarboxylic acid components include terephthalic acid, isophthalic acid, sebacic acid, adipic acid, dimerized linoleic acid, and maleic acid. Polyhydric alcohol components include glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; polyhydric alcohols such as trimethylolpropane, hexanetriol, glycerin, trimethylolpropane, trimethylolethane, and penquerythritol; Examples include two or more arbitrary types selected from glycols and polyhydric alcohols.

Polycarbonate polyols in which the negative functional group forms an inner salt are generally synthesized by a transesterification method between a polyhydric alcohol and a dialkyl carbonate or diallyl carbonate, or obtained by condensation of a polyhydric alcohol and phosgene. be able to.

In producing the above polyester polyol and polycarbonate polyol (including polycarbonate polyester polyol), the following aromatic polyhydric alcohols can be used. Moreover, when reacting the above-mentioned polyester polyol or polycarbonate polyol with polyisocyanate, the following aromatic polyhydric alcohol can be used.

Aromatic polyhydric alcohol: [n represents an integer of 1 to 10. ] [n represents 1 or 2. ] [n=1, 2] [n represents 1 or 2. ] [R is - (CHz) t-, -CH(CHi)-C
Indicates Hz-CIIz-.

X is -so2-, -co-, -C(CH3)! -,
-C(CL) z-Call4-C(CH*) 2- is shown. ] [n represents 1 or 2. ] [n represents l or 2. ] N [R represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R' represents a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, or an aryl group. ] [n represents 1 or 2.

] In the polyurethane having these aromatic polyhydric alcohol components in the main chain, the content of these components is preferably 1% or more based on the IOmo of the entire polyhydric alcohol component.

In order to produce a lactone-based polyester polyol in which the negative functional group forms an inner salt, S-caplactam,
The above-mentioned functional group may be introduced into lactams such as α-methyl-1-cabuchiolactam, S-methyl-S-cabuchiulactam, and T-butinolactam.

In order to produce a polyether polyol in which a negative functional group forms an inner salt, the above functional group may be introduced into ethylene oxide, propylene oxide, butylene oxide, or the like.

As the functional group forming the inner salt, a betaine group mentioned below can be exemplified.

A general method for synthesizing polyester is carried out by a condensation reaction between an acid component having an aliphatic or aromatic polyfunctional acid or a derivative thereof and an aliphatic or aromatic polyfunctional alcohol component. Intramolecular amphoteric base of the present invention (betaine group, etc.)
may be contained in either the acid component or the alcohol component, or a method of introducing a betaine group or the like into the polymer as a polymer reaction may be used. However, in consideration of unreacted components and introduction rate, it is easier to control if the polymer monomer has the functional group.

Examples of the betaine group include a sulfobetaine group, a phosphobetaine group, and a carboxybetaine group. The general formula of these betaine type functional groups is expressed as follows.

Na ? : Contained in urethane chains.

x:-so. -o-so3 -cooe -O-PO,H -OPO3 10PO■H2.

A: Hydrogen or an alkyl group having 1 to 60 carbon atoms (eg, methyl group, ethyl group, etc.).

m: an integer from 1 to 10.

(II) Company R − B −{−C H 2 +−r−tJ−+c
H2→]1XchiB: 1Coo or CONH. R: an alkyl group, alkenyl group, or aryl group having 1 to 12 carbon atoms.

n, m: integer from 1 to IO.

Examples of usable betaine group-containing monomers include the compounds listed below, but it goes without saying that the polyurethane resin used in the present invention is not limited to those using these monomers.

The monomer in which the negative functional group forms an inner salt is available as a commercially available drug, but it can be easily obtained by the method described below.

1) Synthesis method using monochloroacetic acid R-N (CHz-COOH)2 +Cf-CH2 -
COOHR = Alkyl group such as methyl, ethyl, etc. 2) Synthesis method using monochlorosuccinic acid (below, blank) CH. =COOH 3) Synthesis method using propane sultone C Hz A compound having a COOH group, etc. is synthesized, and this is reacted with a polyfunctional isocyanate such as diisocyanate in equimolar amounts, and one NCOi of the diisocyanate and the hydroxyl group in the above compound are reacted. A reaction product is obtained. Then, by reacting the OH groups of the polyurethane with the unreacted NGO groups, a polyurethane into which betaine groups and the like are introduced can be obtained.

Examples of the above-mentioned compounds having a hydroxyl group and a betaine group include, but are not limited to, the following compounds.

Furthermore, as a polymer reaction, a reaction for introducing betaine groups and the like into a polymer will be described. In this method, a compound having a betaine group or the like is reacted with an OH group present at the end or side chain of a polyurethane whose chain has been extended to a predetermined molecular weight by a polymerization reaction. In this case, first, the amount of betaine groups etc. introduced into the polyurethane resin of the present invention is preferably 0.01 to 1.0 mmoE/g, more preferably 0.1 to 0.5 mm.
It is in the range of ol/g. The amount of the above polar group introduced is 0
．． If it is less than 0.01 mmoE/g, it will be difficult to see a sufficient effect on the dispersibility of the ferromagnetic powder. Furthermore, if the amount of the polar group introduced exceeds 1.0 mmol/g, intermolecular or intramolecular aggregation tends to occur, which not only adversely affects dispersibility but also causes selectivity to the solvent, making it difficult for ordinary general-purpose solvents to There is also a risk that it will become unusable.

Further, the number average molecular weight of the polyurethane resin according to the present invention is 5
000-100000, more preferably 10000-s
The range is preferably oooo. If the number average molecular weight is less than 5,000, the coating film-forming ability of the resin is likely to be insufficient, and if the number average molecular weight exceeds 100,000, problems may occur in paint manufacturing processes such as mixing, transport, and coating. There is.

Synthesis Example (a) 1 mole of N-methyldiethanolamine and 1 mole of propanesultone were reacted at a temperature of 120°C for 3 hours to obtain a sulfobetaine type polyfunctional monomer.

Next, 1.5 mol of adipic acid, 1.7 mol of 1,4-butanediol, and 0.06 mol of the above-mentioned sulfobetaine type acid-base polyfunctional monomer were charged, and the mixture was heated at 150 to 200°C for about 3 mol.
The temperature was raised over time, and the reaction was further carried out at 200°C for 4 hours.
Unreacted raw materials were removed at ~5 mmHg, and the reaction continued until the acid value reached 2 or less. The molecular weight of the obtained copolymerized polyester is Mw
It was 2500. 165 g of copolymerized polyester was dissolved in 300 parts of methyl ethyl ketone, 80 parts of diphenylmethane diisocyanate was added, and the mixture was reacted for 2 hours at 80"C. 20 parts of 1,4-butanediol was added and the mixture was reacted for another 2 hours. 4 parts of butanediol was added and reacted for 1 hour.The molecular weight of the obtained polyurethane was M w =
35,000, and M n =22,000.

Is it polyurethane that uses sulfo gold? The resin is a modified resin having SO:IM and OSO■M as polar groups.

However, M represents a metal, preferably an alkali metal, and more preferably lithium, sodium, or potassium.

Various methods can be applied to modify polyurethane with the above polar groups.

(-303 M,'-OSO.M) (hereinafter sometimes referred to as the above-mentioned metal base), the polyurethane containing the above-mentioned metal base is a starting material of the polyester polyol containing the above-mentioned metal base. It can be obtained by a condensation reaction and an addition reaction using three types of compounds: an acid, a dicarboxylic acid containing no metal base, and a diol, and a diisocyanate.

Furthermore, a urethane resin can be synthesized by introducing the metal base into a diol.

Furthermore, the above polar groups can also be introduced into polyurethane by polymer reaction.

That is, these resins and, for example, CI CHz CHz SO:+ M, Cl-CH2
This is a method in which the metal base and a compound containing chlorine are condensed and introduced into a molecule such as CH20S02M2 (wherein M has the same meaning as above) through a dehydrochloric acid reaction.

The carboxylic acid component used to obtain the polyurethane resin includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid; P-oxybenzoic acid, P-(hydroxyethoxy) Aromatic oxycarboxylic acids such as benzoic acid; aliphatic dicarboxylic acids such as succinic acid, adivic acid, azelaic acid, sehasic acid, dodecanedicarboxylic acid; tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid, etc. can be mentioned.

Among these, preferred are terephthalic acid, isophthalic acid, adipic acid, and sebacic acid.

Examples of the dicarboxylic acid component containing the sulfonic acid metal base include 5-sodium sulfoisophthalic acid, 5-sodium sulfoisophthalic acid,
-Potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, and the like.

Examples of the diol component include ethylene glycol, propylene glycol, 1,3-propanediol,
1.4-butanediol, 1.5-pentanediol,
1,6-hexanediol, neopentyl glycol,
diethylene glycol, dipropylene glycol, 2,
2.4-trimethyl-1. Examples include 3-opentanediol, 1,4-cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Further, tri- and/or tetraols such as trimethylolethane, trimethylolpropane, glycerin, and bentaerythritol can also be used in combination.

Examples of the isocyanate component used to obtain the polyurethane resin include 2.4-tolylene diisocyanate, 2.6-}lylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, and hexamethylene diisocyanate. , tetramethylene diisocyanate, 3.3'-dimethoxy-4,4'-biphenylene diisocyanate, 4.4'-diisocyanate diphenyl ether, 1,3-naphthalene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1.3 -diisocyanate methyl hexane, 1,4-diisocyanate methyl hexane, 4,4 diisocyanate dihexane, 4,
Examples include 4' diisocyanate dihexylmethane and isophorone diisocyanate.

As SO3Na-containing polyurethane, rUR-830
0 J, rUR-8600J (manufactured by Toyobo Co., Ltd.)
etc. The amount of the metal base introduced into the polyurethane is 0.01 to 1.0 IIlflo! ! ．． /g is preferred.

"One or more resins selected from polyurethanes containing an inner salt of negative groups, polyurethanes containing metal salts of sulfo groups, and polyurethanes containing metal salts of oxysulfino groups" are magnetic in the magnetic layer. It is preferable to use 0.5 to 25 parts by weight per 100 parts by weight of flour.

As the binder for the magnetic layer and the BC (back coat) layer, known thermoplastic resins, thermosetting resins, reactive resins, ultraviolet curable resins, electron beam curable resins, and mixtures thereof can be used.

As a thermoplastic resin, the softening temperature is 150"C or less, the average molecular weight is toooo~300,000, and the degree of polymerization is about 50~
For example, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer, acrylic ester vinylidene chloride copolymer, acrylic ester styrene copolymer,
Methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer,
Nylon-silicon resin, nitrocellulose-polyamide resin, polyfluorinated vinyl, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose) triacetate, cellulose propionate, nitrocellulose, etc.), styrene-ptadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubber-based thermoplastic resins, and mixtures thereof. be done.

-SO3M group, -COOM group, -0M group, -0 in the molecule
Also preferred are SO, M groups, nyl-based copolymers, and polyester resins.

Hydrophilic groups are particularly preferred.

Here, M is hydrogen or an alkali metal (Li, Na,
K, etc.), M' represents hydrogen, an alkali metal (Li, Na, K, etc.) or a hydrocarbon group.

A vinyl chloride copolymer containing an epoxy group in addition to the above-mentioned functional groups can also be used (Japanese Patent Application No. 60-288935).
.

A preferred combination of binders is a vinyl chloride copolymer having the above functional group and the polyurethane of the present invention.
A combination is preferred.

A specific example of the hydrophilic group-containing binder is 1000H group-containing polyurethane (rTIM-3005 manufactured by Sanyo Chemical Co., Ltd.) -C
OOH group-containing vinyl chloride vinyl acetate copolymer (manufactured by Niki Zeon Co., Ltd. 400X110A), S Oz Na-containing polyester (manufactured by Toyobo Co., Ltd. [Vylon 530J) -S
o, Na-containing vinyl chloride pgyniy copolymer (rMR-110J manufactured by Nippon Zeon Co., Ltd.). The hydrophilic group content is preferably in the range of 1 to 10,000 equivalents/106 g. Further, the molecular weight is preferably 3,000 to 200,000.

As the curing agent, epoxybolyamide, epoxypolycarboxylic acid, polyimine, and polyisocyanate are used.

Particularly preferred is polyisocyanate with one N=C= in the molecule.
These include di-, tri-, and tetra-isocyanates selected from aliphatic, aromatic, or alicyclic compounds having two or more O groups.

These isocyanates include ethane diisocyanate, butane diisocyanate, hexane diisocyanate, 2,2-dimethylpencune diisocyanate, 2.
, 2.4-1-limethylpentai diisocyanate, decane diisocyanate, ω. ω′-diisocyanate-
1.3-dimethylhendul, ω. ω′-diisocyanate-1,2-dimethylcyclohexane, ω. ω′ diisocyanate-1,4-diethylbenzole, ω. ω-
diisocyane}-1,5-dimethylnaphthalene, ω,
ω′-diisocyanate-n-probylbiphenyl, 1
, 3-phenylene diisocyanate, 1-methylbenzole-2.4-diisocyanate, 1.3-dimethylbenzole-2.6 diisocyanate, naphthalene-1,
4-diisocyanate, 1,1'-dinaphthyl-2,2
'diisocyanate, biphenyl 2,4'-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, diphenylmethane-44'-diisocyanate, 2,2'-dimethyldiphenylmethane-4,
4'-diisocyanate, 3,3'-dimethoxydiphenylmethane-4,4'-diisocyanate, 4,4'-jethoxydiphenylmethane-4,4'-diisocyanate, amethylbenzole-2.4.6-}lisocyanate, 1 , 3.5-trimethylbenzole-2.4.
6-triisocyanate, diphenylmethane 2,4.4
'-triisocyanate, triphenylmethane-4.4
',4''-} diisocyanate, tolylene diisocyanate, 1,5-naphthylene diisocyanate, etc.; dimer or trimer of these isocyanates, or addition of these isocyanates with divalent or trivalent polyalcohols These are, for example, addition products of trimethylprobane with tolylene diisocyanate or hexamethylene diisocyanate.

These curing agents are used in an amount of 10 to 100 parts by weight of the binder.
It is used in an amount within the range of 60 parts by weight.

Commercially available trade names of these polyisocyanates include Coronate, Coronate H, and Coronate 2.
030, Coronate 2031, Millionate MR, Millionate MTL (manufactured by Japan Polyurethane Side 3), Takenate D-102, Takenate D-110N, Takenate D
-200, Takenate D-202 (manufactured by Takeda Pharmaceutical ■)
, Desmodule L1 Desmodule IL, Desmodule N1 Desmodule HL (manufactured by Sumitomo Bayer), etc., and these can be used alone or in combination of two or more by taking advantage of the difference in curing reactivity. .

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred.

Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy bolyamide resin, nitrocellulose melamine resin,
Mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates mixtures of polyamine resins, polyamine resins, and mixtures thereof.

These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the ferromagnetic fine powder and the binder is preferably in the range of 5 to 300 parts by weight per 100 parts by weight of the ferromagnetic fine powder.

The mixing ratio of powder and binder in the back layer is powder: 10 by weight.
The binder is used in an amount of 30 to 300 parts by weight based on 0 parts by weight. These thermoplastic resins, thermosetting resins, and reactive resins have carboxylic acid, sulfinic acid, etc. as functional groups in addition to the main functional groups. Sulfonic acid, phosphoric acid, sulfuric acid ester groups. Acidic groups such as phosphoric acid ester groups, amino acids; aminosulfonic acids. Sulfuric acid or phosphoric acid esters of amino alcohols. Amphoteric groups such as alkyl betaine type, amino groups, imino groups,
Imide groups, amide groups, etc., hydroxyl groups, alkosyl groups. Thiol group. It usually contains one or more types of halogen groups, silyl groups, and siloxane groups, and each functional group contains I/g of resin.
XIO-6eq to I XIO-"eq may be included.

An abrasive may be contained in the magnetic layer and the back coat layer.

Commonly used abrasive materials include fused alumina, α-alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron monoxide, garnet, and emery (main component: corundum). and magnetite), garnet, silica, and silicon nitride. boron nitride,
Molybdenum carbide. Boron carbide, tungsten carbide, titanium carbide, tripoli, diatomaceous earth, dolomite, etc.
Preferably, one to four materials having a Mohs hardness of 6 or more are used in combination. These abrasives have an average particle size of 0.01 to 5 microns,
Particularly preferred is 0.05 to 5 microns.

These abrasives contain 0.00 parts by weight per 100 parts by weight of the binder.
It is added in an amount of 1 to 20 parts by weight.

A lubricant may also be used in the magnetic layer and back coat layer, such as silicone oil. Graphite, molybdenum sulfide, boron nitride, and solid graphite. Fluorine alcohol, polyolefin (polyethylene wax, etc.). Polyglycol (polyethylene oxide wax, etc.), alkyl phosphate ester, polyphenyl ether, tungsten disulfide, monobasic fatty acid with 10 to 20 carbon atoms, monohydric alcohol or dihydric alcohol with 3 to 12 carbon atoms, trihydric alcohol Fatty acid esters consisting of one or more of alcohols, tetravalent alcohols, and hexavalent alcohols, monobasic fatty acids with 10 or more carbon atoms, and carbon totals of the total number of carbon atoms in the fatty acids. Fatty acid ethesuls consisting of monohydric to hexahydric alcohols having 11 to 28 alcohols can be used. Furthermore, fatty acids, fatty acid amides, and fatty acid alcohols having 8 to 22 carbon atoms can also be used. Specific examples of these organic compound lubricants include butyl caprylate,
Octyl caprylate, ethyl laurate, butyl laurate, octyl laurate. Ethyl myristate, butyl myristate. Octyl myristate. Ethyl palmitate, butyl valmitate, octyl palmitate,
Ethyl stearate. Butyl stearate, octyl stearate, amyl stearate. Anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate. Oleyl alcohol, lauryl alcohol. These include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid. In addition, so-called lubricating oil additives can also be used alone as the lubricant used in the present invention, such as antioxidants (alkylphenols, etc.), rust inhibitors (naphthenic acid, alkenylsuccinic acid, dilauryl phosphate, etc.), oil-based agents (rapeseed oil, lauryl alcohol, etc.), extreme pressure agents (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.), cleaning and dispersing agents, viscosity index improvers. There are pour point depressants, anti-foaming agents, etc. These lubricants are used in an amount of 0.05 to 20 parts by weight per 100 parts by weight of binder.
It can be added within a range of parts by weight.

Carbon black may be contained in the magnetic layer or back layer as an antistatic agent.

As the carbon black used in the magnetic layer and back layer of the present invention, furnace black for rubber, thermal black for rubber, black for color, acetylene black, etc. can be used. Specific examples of carbon black abbreviations in the United States include SAF, ISAF, I ISA. F,T,HAF,S
PF, FF, FEF, HMF, GPF, APF, S
RF, MPF, ECF, SCF, CF, FT, MT, H
There are CC, HCF, MCF, LFF, RCF, etc., and those classified as D-1765-82a of the American ASTM standard can be used. The average particle size of these carbon blacks used in the present invention is 10 to 10
00 millimicrons (electron microscope), nitrogen adsorption method specific surface area is 1 to 800 M/g. pH is 6-11 (JIS standard K-6221-1982 method), DBP oil absorption is 10
~400mN/100g (JIS standard K-
6221-1982).

The size of carbon black used in the medium is 10 to 100 millimicrons carbon plank for the purpose of lowering the surface electrical resistance of the coating film, and carbon black of 50 to 1000 millimicrons to control the strength of the coating film. use In addition, in order to control the surface roughness of the coating film, finer carbon plaque (100 millimicrons or less) is added for smoothing to reduce spacing loss, and coarser carbon plaque is used to roughen the surface and lower the coefficient of friction. Use black (50 mm or more). In this way, the type and amount of carbon black to be added can be selected depending on the purpose required for the magnetic recording medium. In addition, these carbon blacks can be surface-treated with a dispersant as described below, or
It may also be used by grafting with a resin.

In addition, the temperature of the furnace when manufacturing carbon black was
It is also possible to use a material whose surface is partially graphitized by being treated at 000°C or higher. Hollow carbon plaques can also be used as special carbon black.

In the case of a magnetic layer, these carbon plaques are desirably used in an amount of 0.1 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder. For carbon black that can be used in the present invention, reference may be made to, for example, "Carpon Black Handbook", Carbon Black Association Vol. 1, published in 1971.

For magnetic recording media, conductive powders such as graphite carbon black graft polymers may be used instead of or in addition to the above-mentioned carbon black as antistatic agents; natural surfactants such as sabonin; alkylene oxide-based, glycerin-based, glycidol-based, polyhydric Nonionic surfactants such as alcohols, polyhydric alcohol esters, alkylphenol EO adducts; higher alkylamines, cyclic amines. Hydantoin derivatives. Amidamine. Esteramide, quaternary ammonium salts. Cationic surfactants such as pyridine and other heterocycles, phosphoniums or sulfoniums; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric ester groups, and phosphoric ester groups; amino acids; amino sulfones Acid neck. Amphoteric surfactants such as sulfuric acid or phosphoric acid esters of amino alcohols and alkyl betaine type surfactants may also be used.

These surfactants may be added alone or in combination. Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

When the nonmagnetic support used in the present invention is used as a tape, the thickness of the support is preferably about 2.5 to 100 microns, preferably about 3 to 70 microns. In the case of a disk or card shape, the thickness is about 0.5 to 10 mm, and in the case of a drum, it can also be used in a cylindrical shape. Materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and vinyl resins such as polyvinyl chloride. polycarbonate, polyamide,
Plastics such as polysulfone are used.

Prior to coating, these supports may be subjected to corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, dust removal treatment, metal vapor deposition treatment, and alkali treatment.

The magnetic recording medium of the present invention is obtained by dispersing and kneading the above components using an organic solvent, applying the mixture to a nonmagnetic support, orienting the mixture as necessary, and then drying it. After drying, flattening may be performed if necessary.

The organic solvents used in the dispersion, kneading, and coating of the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran, etc.; methanol, ethanol, 1-propanol, butanol, Alcohols such as isobutyl alcohol, isopropyl alcohol, and methylcyclohexanol; methyl acetate. Ester systems such as ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether; ether, glycol dimethyl ether. Glycol monoethyl ether. Glycol ethers such as dioxane; benzene, toluene, xylene. Tar-based (aromatic hydrocarbons) such as cresol, chlorobenzene, and styrene; methylene chloride, ethylene chloride, carbon tetrachloride, and chloroform. Chlorinated hydrocarbons such as ethylene chlorohydrin dichlorobenzene, N, N dimethyl formaldehyde, hexane, etc. can be used.

There is no particular restriction on the mixing method, and the order of addition of each component can be set as appropriate. For preparing magnetic paints, conventional kneading machines such as two-roll mills, three-roll mills, ball mills, and pebble mills are used. Thoron mill, sand grinder, Szegvart attritor, high speed impeller, disperser 1 high speed stone mill, high speed impact mill, disburr, kneader, high speed mixer
Ribbon blender. A co-kneader, intensive mixer, tumbler, blender, disperser, homogenizer, single screw extruder, twin screw extruder, ultrasonic disperser, etc. can be used.

Methods for coating the magnetic recording layer and back layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cass coating, soubray coating, etc., and other methods are also possible, and specific explanations of these are described in detail in "Coating Engineering", pages 253 to 277 (published March 20, 1970), published by Asakura Shoten.

By method 2, the magnetic layer coated on the support is treated, if necessary, to orient the magnetic powder in the layer while immediately drying, and then the formed magnetic layer is dried. The support and feeding speed at this time is usually 10 m/min to 800 m/min.
The drying temperature is 20°C to 120°C.
controlled by If necessary, apply surface smoothing processing,
The magnetic recording body of the present invention is manufactured by cutting it into a desired shape.

Ho. Examples Examples will be described below, but the examples below can be modified in various ways. In the following examples, all "parts" represent "parts by weight."

Fusho lacquer 8 Cor FezO3 100 parts Coercive force (llc) 800 Oersted specific surface area
50 Bo/g Vinyl chloride copolymer containing epoxy group and sulfonic acid metal salt residue 10 parts Thermoplastic polyurethane 7 parts (contains sulfobetaine group) cr-Al203 (average particle size 6.2 μm) 5
Part stearic acid 2 parts Butyl stearate 1 part Methyl ethyl ketone 70 parts Cyclohexanone 110 parts Toluene
A magnetic paint was prepared by sufficiently mixing and dispersing 70 parts of the above composition using a sand mill and further adding 2 parts of a polyfunctional isocyanate (Coronate, manufactured by Nippon Polyurethane Co., Ltd.). The magnetic powder of this magnetic paint/? 8 drug ratio (M
/S) was 1/2.5.

Shinseiou ffB Co 7 FezO3 100 parts Coercive force 800 Oersted specific surface area 50 ITf/g Salt-vinyl acetate copolymer 10 parts (VA
C; H: Union, Carbide Co.) Thermoplastic polyurethane 7 parts (contains sulfobetaine group) α-Aj2.03 5 parts stearic acid 2 parts butyl stearate 1 part methyl ethyl ketone 70 parts cyclohexanone
110 parts toluene
70 parts Friability 1 and 100 parts Coercive force (Hc) 8000e Specific surface area 50 rrr/g Vinyl chloride copolymer containing epoxy groups and sulfonic acid metal salt residues 10 parts Thermoplastic polyurethane 7 parts (sulfonic acid (contains metal salt residues) α-AlzOz 5 parts stearic acid 2 parts butyl stearate 1 part methyl ethyl ketone 70 parts cyclohexanone
110 parts toluene
70 parts Co 7 FezOz 100
Part coercive force 800 Oersted specific surface area 50 Bo/g Salt vinyl acetate copolymer (VAGH) 10 parts Thermoplastic polyurethane 7 parts (contains sulfonic acid metal salt residue) α-A1. C3 5 parts stearin 2 parts butyl stearate 1 part methyl ethyl ketone 70 parts cyclohexa,non
110 parts toluene
70 copies ■Sho-nuri Co-7-F ez o3 100
Part coercive force 800 Oersted specific surface area 50 po/g Salt vinyl acetate copolymer (VAGH) 10 parts Thermoplastic polyurethane 7 parts (contains oxysulfino group metal salt residue) α-A/2203
5 parts stearic acid
2 parts putyl stearate
1 part methyl ethyl ketone
70 parts cyclohexanone 110
70 parts toluene
Raw - S a 6 1Co-7
-Fe20+ 100 parts coercive force (H
c) 8000e Specific surface area 50bo/g Salt vinyl acetate copolymer (VAGH) 10 parts Thermoplastic polyurethane (Eskun 5701 F) 7 parts α
-AEzOx 5 parts stearic acid 2 parts butyl stearate 1 part methyl ethyl ketone 70 parts cyclohexanone
110 parts toluene
70 parts sulfobene polyurethane Synthesized as shown in Synthesis Example (a) above.

Number average molecule N22,000 Tg Polar group concentration 0.04 mmol/g-20°C (CH2)3 Polyurethane chain O=S=O & sulfo gold Polyurethane diethylene glycol diglycidyl ether 0.5 mol and acidic sodium sulfite 1 A sulfonic acid group-containing polyfunctional monomer was obtained by reacting 0.5 mol with water as a solvent at a temperature of 100°C for 6 hours. Next, 1.5 mol of adipic acid, 1.7 mol of 1,4-butanediol, and 0.06 mol of the above-mentioned sulfonic acid group polyfunctional monomer were charged.
Raise the temperature to 200'C for about 3 hours, then further increase to 200°C.
The mixture was reacted for 4 hours at 3 to 5 mmHg, unreacted raw materials were removed, and the reaction was continued until the acid value reached 2 or less. The molecular weight of the obtained copolymerized polyester was Mw2500. 165 g of copolymerized polyester was dissolved in 300 parts of methyl ethyl ketone,
Add 80 parts of diphenylmethane diisocyanate,
The mixture was reacted at 0°C for 2 hours, 20 parts of 1,4-butanediol was added, and the mixture was further reacted for 2 hours, and 4 parts of 1,3-butanediol was added, and the mixture was reacted for 1 hour. The molecular weight of the obtained polyurethane was Mw=65,000 and Mn=23,000.

OSOJa x,j! , m, A magnetic paint was prepared by adding the following. The magnetic powder/solvent ratio M/S of this magnetic paint was 1/2.5.

Then, this magnetic paint was applied onto the surface of a polyethylene terephthalate base (non-magnetic support 1) with a thickness of 15 μm in a precisely controlled manner so that the dry thickness was 4.0 μm. The coating thickness distribution in the longitudinal and width directions was ±0.2 μm or less. This was supercalendered to '72 inch.
Cut to width. In order to form the BC layer, a paint for the BC layer is applied to the surface of the magnetic material on the opposite side of the magnetic layer to a dry thickness of 1 μm.

Then, each tape having a magnetic paint coating layer coated with each of the above-mentioned magnetic paints A, B, C, D, E, and a was oriented and dried in the following manner.

That is, as the front-stage orientation magnet 7 shown in FIG.
Using Gauss's same-polarity opposing permanent magnets, the rear orientation magnet 9
2000 Gauss permanent magnets with the same polarity and opposite sides were used.

Then, each of the magnetic paints A, B, C, D, E, and a is oriented by the first stage orientation magnet 7, and then oriented by the second stage orientation magnet 9 in the dryer 5, and when oriented by the second stage orientation magnet 9. Drying conditions were set so that the magnetic powder/solvent ratio (M/S ratio) in the magnetic coating layer was as shown in Table 1 below. In this way, samples A-1 to B-6, B-
1, S1-6, D-1, E-1, a-(7) for comparison
~(12) was obtained.

In addition, in the above, the dry special orientation magnet was removed and orientation was performed using only the pre-stage orientation magnet. The drying conditions themselves were the same as above, and comparative samples A-(1) to (6) and B-(1
), C-(1) to (6), D-(1), E-(1
), a(1) to (6) were obtained. In addition, in Table 1 below, the value of the magnetic powder/solvent ratio expressed using a box, for example (1/2.4), is the M/S when the rear orientation magnet is placed at a predetermined position. This indicates that the dryer 5 is operated under drying conditions such that the ratio is 1 / 2.4, and the rear orientation magnet is removed while maintaining this drying condition (sample A-1), and the comparative sample (here So A-
(1) ).

In addition, for samples A-7 and a-03), the former orientation magnet was removed and orientation was performed using only the latter orientation magnet.

(Left below) Table A-(1) A-(2) A-(3) A-(4) A-(5) A-(6) A-I A-2 A-3 A-4 A-5 A-6 C-(1) C-(2) C-(3) C-(4) C-(5) C-(6) (1/2.4) (1/2.1) (1/ 1.9) (1/1.5) (1/1.3) (1/1.0) 1 /2.4 1/2.1 1 /1.9 1 /1.5 1 /1.3 1 /1.0 (1/2.4) (1/2.1) (1/1.9) (1/1.5) (1/1.3) (1/1.0) 0.78 0.81 0.82 0.80 0.80 0.71 0.84 0.88 0.88 0.88 0.87 0.76 0.75 0.81 0.82 0.78 0.71 0. 66 C-I C-2 (,-3 C-4 C-5 (,-6 a-(1) a-(2) a-(3) a-(4) a-(5) a-(6 ) a -(7) a -(8) a -(9) a -On) a -(II) a-02) B-(1) 1 /2.4 1/2.1 1 /1.9 1 /1.5 1 /1.3 1 /1.0 (1 /2.4) (1/2.1) (1/1.9) (1/1.5) (1/1.3) ( 1 /1.0) 1 /2.4 1/2.1 1 /1.9 1 /1.5 1 /1.3 1 /1.0 (1/1.9) 0.76 0.84 0 .86 0.79 0.72 0.66 0.72 0.76 0.78 0.75 0.70 0.66 0.71 0.74 0.74 0.71 0.68 0.65 0.82 B-1 (1/1.9) 0.85
1500/2000D-(1) ( 〃
) 0.77 〃/D- 1
〃0.79 〃/2000E-(1) (
〃') 〃/ 1E-1
〃/20001-7
〃0.85 -/2000a -03)
〃0.76 − /2000 Also, the above samples A-(3), A-3, C-(3), C-3,
a-(3), a-(9), B-(1), B-1, D[1
), D-1, E-(1), E-1 Nitsuite, S-V H
The RF output, S/N ratio, and sliding noise were measured by loading the sample into a S cassette case. The measurement results are shown in Table 2 below.

RF output: HRS 6 as a VTR deck for RF measurement
000 was used to measure the RF output of a 100% white signal.

Lumi S/N; Shibasoku 925 D
/l.

Sliding noise: A- (3) A-3 B-(1) B-I C-(3) (,-3 D-(1) D- I E-(1) E-1 Using HR-36000, our standard tape "
After running the Konica HG-RJ for 1 hour to stabilize the head, the sliding noise of each sample was measured using a spectrum analyzer TR4171 (manufactured by Takedariken). The average value of the noise level was calculated from the integrated values from 4 MHz to 8 MHz.

Table −2 +1.6 +1.5 +4.3 +4.2 +1.6 +1.5 +3.2 +3. 1 +1.6 +1.5 +2.5 +2.5 +0.6 +0.6 +1.4 +1.5 →0.6 +0.6 +1・4 + 1.5 2.6 -3.5 2.2 1 .6 -1.6 l. 0 1. 〇１１、〇１１、O a −(3) 0 0
0a one (9) +0.2
0 o Also, each data shown in Table 2 above was plotted in FIG. 4 and graphed. Further, each data shown in Table 2 above is expressed as a bar graph in FIG.

From these, we understand the following.

(1). Based on the present invention, M/
By setting the S ratio from 1/1.1 to 1/2.3, the squareness ratio in the longitudinal direction of the tape is significantly improved.

(2). When a polyurethane having a sulfobetaine type functional group is used, sliding noise is reduced and electromagnetic conversion characteristics are particularly significantly improved.

(3). The use of polyurethane containing a betaine type functional group not only improves the squareness ratio and performance, but also maintains the squareness ratio even if the M/S ratio of the subsequent stage is changed, resulting in high squareness. The ratio is obtained.

This means that even if the setting position of the rear-stage orientation magnet, the drying conditions of the dryer, and the coating conditions are variously changed, a product with a high squareness ratio can still be stably obtained.

In addition, in the above example, for any magnetic paint,
The weight ratio of magnetic powder/binder is 100/17. Here, experiments were conducted by changing the weight ratio of magnetic powder/binder to various values.

As a result, the magnetic powder/binder content ratio is 100/14.
It was found that setting it to ~100/19 was the best.

When the amount of binder was increased, the squareness ratio decreased rapidly. When less binder was used, dropouts increased rapidly.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a manufacturing process flow diagram of a magnetic recording medium, FIGS. 2 and 3 are partially enlarged sectional views of an example of a magnetic recording medium, and FIG. The figure is a graph showing the relationship between the weight ratio of magnetic powder/solvent and the squareness ratio, and Figure 5 is a graph showing the RF output and sliding noise characteristics of each sample. In addition, in the symbols shown in the drawings, 1...Nonmagnetic support 2...Coating section 3...Smoother 5...・・・・・・Drying zone 7・・・・・・Pre-stage orientation magnet 8・・・・・・Magnetic paint (coating film) 9・・・・・・
. . . Post-stage orientation magnet 18 . . . Magnetic layer.

Claims (1)

[Claims] 1. In a method for manufacturing a magnetic recording medium in which a magnetic paint is applied onto a support and the magnetic paint coating layer is subjected to an orientation treatment using a magnetic field and a drying treatment, negative functional groups form an inner salt. The magnetic paint contains one or more resins selected from the group consisting of a polyurethane containing a metal salt of a sulfo group, a polyurethane containing a metal salt of an oxysulfino group, and a rearmost orientation. The drying is carried out so that the ratio of magnetic powder to solvent in the magnetic paint coating layer (magnetic powder/solvent) is 1/1.1 to 1/2.3 by weight, and A method for manufacturing a magnetic recording medium, characterized in that the drying is completed after the orientation section.