JPH07196955A - Magnetic coating composition and magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a coating compsn. containing a copolymer resin binder and used in the production of a magnetic recording medium.

CONSTITUTION: A copolymer resin binder is a copolymer obtained by copolymerizing comonomers including (a) vinyl chloride, (b) a monoethylenically unsaturated monomer like vinyl acetate, (c) a monoethylenically unsaturated monomer having a phosphorus-containing group represented by the formula -(O)_mPO₃X₂ (wherein (m) is 0 or 1; X is same or different and is a hydrogen atom, alkali metal atom, protonated amine or a substd. or unsubstd. hydrocarbon residue and, optionally, (d) at least one monoethylenically unsaturated monomer different from other comonomers in a specific ratio.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating composition used for forming a magnetic layer on a magnetic recording medium. More particularly, the present invention relates to a resin that can uniformly disperse particles of a ferromagnetic material and that is suitable for binding the particles and that is used as a binder component in a coating composition.

[0002]

BACKGROUND OF THE INVENTION For many years, magnetic recording has been a vital part of a myriad of industries. Therefore, magnetic tape is used for audio, video, computer, metrology and other recording purposes. Magnetic recording media are used in various forms including, for example, magnetic cards, magnetic discs, reels, video tapes, high-performance audio tapes, computer tapes, floppy discs, and the like.

Although there are several different types of magnetic recording media, most types are magnetic coated on a plastic, paper or metal substrate, sometimes referred to as a pigment. It consists of a layer of particles.
The information to be recorded is stored in the magnetic pigment applied to the substrate as a series of small areas magnetized by the recording head. The coating layer of magnetic pigments includes a binder system that creates a cohesive matrix between the magnetic pigment particles and adheres the particles to the substrate.

The magnetic coating is applied to the substrate by a coating device, such as a gravure roll coater, and the coated substrate is then typically immediately advanced to a magnetic orientation process in which the orientation of pigment particles is undried. Done on layers. In this step, the long axis of the pigment particles (typically needle crystals) is aligned with the magnetization direction.

In order to achieve good recording performance, the magnetic paint must have various characteristics. Pigment particles, preferably of relatively uniform size, should form as much of the paint layer as possible. Furthermore, the dispersity of pigment particles in paints, which is often evaluated as gloss, should be as high as possible. Moreover, the highly dispersed pigment particles must be able to be properly oriented as described above (the degree of orientation is measured as the layer "squareness").

Furthermore, the adhesion and abrasion resistance of the magnetic paint or magnetic film should be high. Also, the coefficient of friction of the magnetic surface should be low for the head material and yet have a reasonable value for the driving means such as pitch rollers and capstan rollers.

Satisfying these and various other criteria indicates that a fundamentally delicate balance of opposite or contradictory properties is required. Much effort has been directed over the years to improve various properties of magnetic recording media.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a binder system for a particular substance, such as a magnetic recording medium, which is capable of providing desirable dispersion and magnetic properties and also has excellent rheological properties, and vinyl chloride. A monoethylenically unsaturated monomer such as vinyl acetate or ethyl acrylate,
Wherein _{:-( O) m PO 3 X 2} ( wherein, m is a value of 0 or 1, X is identical or different, a hydrogen atom, an alkali metal atom, protonated amine or substituted, Or a monoethylenically unsaturated monomer having a phosphorus-containing group represented by an unsubstituted hydrocarbon residue) and optionally one or more monoethylenically unsaturated monomers different from other copolymers. It is based on the finding that it can be obtained by using a copolymer with a saturated monomer.

The present invention is as follows, when dissolved or dispersed in an organic solvent:

(A) Copolymer resin containing the following monomer moieties:

(A) a first monomer moiety which is a vinyl chloride represented by the formula: --CH ₂ CHCl--, preferably 65 to 95% by weight;

(B) Monoethylenically unsaturated monomer different from components (a), (c) and (d), preferably of the formula: --CH ₂ --CH (O--CO--CH ₃ ). A second monomer portion which is vinyl acetate represented by-, preferably 3 to 30% by weight;

(C) Formula:-(O) _m PO ₃ X ₂ (wherein
m has a value of 0 or 1, and X is the same or different and is a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue)
A third monomer portion which is a monoethylenically unsaturated monomer having a phosphorus-containing group represented by, preferably 0.1 to 5% by weight; and

(D) optionally a fourth monomer moiety which is one or more monoethylenically unsaturated monomer different from components (a), (b) and (c), preferably Is 0 to 20% by weight; and

(B) particles of a ferromagnetic material dispersed in the copolymer resin as a vehicle,

A magnetic coating composition for a magnetic recording medium, which comprises

[0017]

DETAILED DESCRIPTION The present invention provides an economical polymeric resin suitable for uniformly dispersing and firmly binding fine particles of a ferromagnetic material in a magnetic coating composition. The present invention also provides a coating composition for forming a magnetic layer on the surface of a base film by using the above resin as a binder for ferromagnetic particles.

The polymeric resin provided by the present invention as a binder for ferromagnetic particles in coating compositions for magnetic recording media includes (1) vinyl chloride, (2) vinyl acetate or monoethylene such as ethyl acrylate. sex unsaturated monomer (3) :-( O) _m PO ₃ X ₂ (wherein, m is a value of 0 or 1, or X is the same or different,
A hydrogen atom, an alkali metal atom, a protonated amine, a phosphorus-containing group represented by a substituted or unsubstituted hydrocarbon residue), and (4) optionally And a copolymer resin of a monomer mixture containing one or more kinds of monoethylenically unsaturated monomers different from other copolymer components.

The copolymer resin has the formula (a): --CH _2-
The first monomer portion of a vinyl chloride represented by CHCl-, (b) a monoethylenically unsaturated monomer, preferably of the _{formula: -CH 2 -CH (O-CO} -CH 3)
- second monomer portion of the vinyl acetate represented by in formula (c) _{:-( O) m PO 3 X 2} ( wherein, m is a value of 0 or 1, or X is the same , Or, differently, a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue), which is a monoethylenically unsaturated monomer having a phosphorus-containing group. And (d) optionally a fourth monomer which is one or more monoethylenically unsaturated monomers different from components (a), (b) and (c). It is composed of a monomer part including a body part. The weight fraction of these monomer moieties is preferably 6 relative to (a).
5 to 95%, 3 to 30% relative to (b),
0.1 to 5% for (c) and 0 to 20% for (d). Further, the copolymer preferably has an average degree of polymerization in the range of 200 to 800.

This polymeric resin is very useful as a matrix for magnetic paint layers due to the high dispersibility of the ferromagnetic particles in the resin and the high loadability of the ferromagnetic powder. In addition to that, the polymer resin is sufficiently compatible with a polyurethane resin or the like conventionally used as a matrix resin of a magnetic coating layer,
Therefore, the coating composition of the present invention is produced not only by using the above-defined polymer resin alone, but also by using another conventional resin in combination with the above-mentioned polymer resin for the purpose of improving the properties of the conventional resin. can do. Furthermore, the coating composition of the present invention can provide a magnetic coating layer having excellent characteristics in both magnetic properties and usefulness regarding durability during use and thermal stability over time.

The polymer resin of the present invention can be obtained by copolymerizing the above-mentioned monomer mixture into a copolymer having an average degree of polymerization of 200 to 800. The polymeric resin is:

(A) a first monomer portion which is a vinyl chloride represented by the formula: --CH ₂ CHCl--, 65 to 95% by weight;

(B) Monoethylenically unsaturated monomer different from the components (a), (c) and (d), preferably of the formula: --CH ₂ --CH (O--CO--CH ₃ ). A second monomer portion which is vinyl acetate represented by-, 3 to 30% by weight;

(C) Formula:-(O) _m PO ₃ X ₂ (wherein
m has a value of 0 or 1, and X is the same or different and is a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue)
A third monomer portion which is a monoethylenically unsaturated monomer having a phosphorus-containing group represented by 0.1 to 5% by weight;
as well as

(D) One or more monomeric moieties, ie one or more monoethylenically unsaturated monomers different from components (a), (b) and (c). Four monomer moieties, 0 to 20% by weight;

It is composed of a monomer portion including

Generally, the first monomeric moiety, ie, the moiety derived from vinyl chloride, has a reasonable mechanical properties necessary to properly function as a binder resin in magnetic recording media and its analogs. It is the main ingredient that determines sex. Therefore, it is necessary to use a sufficient amount of vinyl chloride to impart the requisite properties to the resin. The above essential properties can be appropriately determined by referring to the Tg of the resin.

It is generally desirable to use a suitable amount of vinyl chloride to provide a resin of the present invention having a Tg of at least 40 ° C, preferably at least about 50 ° C, more preferably at least about 70 ° C. Therefore, it may be necessary to use a resin having at least about 65% by weight vinyl chloride. More preferably about 8
It is desirable to use from 0 to about 90% by weight vinyl chloride. Amounts above about 95% by weight may have inadequate solubility in conventional solvents. If the weight fraction of this monomeric portion is too small, the paint layer formed from the paint composition will have some poor mechanical properties. If the weight fraction is too large, difficulties will be encountered in preparing the coating composition due to the reduced solubility of the polymeric resin in organic solvents.

Suitable monoethylenically unsaturated monomers which are the second monomeric moieties are, for example, vinyl esters of carboxylic acids such as vinyl acetate and vinyl propionate; methyl vinyl ether, isobutyl vinyl ether and cetyl vinyl ether. Vinyl ethers such as;
Vinylidene halides such as vinylidene chloride and vinylidene fluoride; acrylic acid, methacrylic acid,
Unsaturated carboxylic acids such as maleic acid and itaconic acid; unsaturated carboxylic acids such as maleic anhydride;
Esters of unsaturated carboxylic acids such as diethyl maleate, butyl benzyl maleate, dimethyl itaconate, methyl (meth) acrylate, ethyl (meth) acrylate and lauryl (meth) acrylate; (meth)
Unsaturated nitriles such as acrylonitrile; and aromatic vinyl compounds such as styrene, α-methylstyrene and p-methylstyrene. The weight fraction of the second monomer portion should be in the range of 3 to 30%. If the weight fraction of the monoethylenically unsaturated monomer is too large, the mechanical strength and thermal stability of the coating layer formed from the coating composition will decrease, and the magnetic recording produced from the coating layer will occur. Affects the durability of the medium.

The third monomer moiety has the formula:-(O) _m PO ₃
X ₂ (wherein, m is a value of 0 or 1, X is the same or different, and is a hydrogen atom, an alkali metal atom, a protonated amine, or a substituted or unsubstituted hydrocarbon residue. Is a monoethylenically unsaturated monomer having a phosphorus-containing group. Suitable monoethylenically unsaturated monomers include, for example, acrylates, methacrylates, vinylphosphonates and the like. This monomer portion acts to increase the dispersion of the ferromagnetic particles in the coating composition. In this regard,
The weight fraction of the monomeric part should be at least 0.1%, but an excess weight fraction above 5% has no particular beneficial effect. This type of monomer moiety is introduced into the polymeric resin by copolymerization of a monomer having an ethylenically unsaturated polymerizable group and a phosphorus-containing group. Following structural formula Examples of suitable _{monomers: CH 2 = CH-CO-} C 4 H 8 - (O) m PO 3 X 2; CH 2 = C (CH 3) -CO-O-C 2 H ₄ - (O) _m P
O ₃ X ₂ ; CH ₂ ═CH—P (O) (OX) ₂ (in the above formula, m and X are as defined above), and analogs thereof.

One or more monoethylenically unsaturated monomers different from components (a), (b) and (c), which may optionally be used in the polymeric resin of the present invention. Possible fourth monomeric moieties are vinyl esters of carboxylic acids such as vinyl propionate; vinyl ethers such as methyl vinyl ether, isobutyl vinyl ether and cetyl vinyl ether; vinylidene halides such as vinylidene chloride and vinylidene fluoride. Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid; unsaturated carboxylic acid anhydrides such as maleic anhydride; diethyl maleate, butyl benzyl maleate, dimethyl itaconate, methyl (meth) acrylate , Ethyl (meth) acrylate and lauryl (meth) acrylate Esters of unsaturated carboxylic acids such as relations; (meth) unsaturated nitriles such as acrylonitrile; including styrene, aromatic vinyl compounds such as α- methylstyrene and p- methylstyrene. The weight fraction of these optional monomer moieties is 0.
Can be in the range of 20% to 20%.

The copolymer resin obtained by copolymerizing the above-mentioned comonomers preferably has an average degree of polymerization in the range of 200 to 800. If the average degree of polymerization of the copolymer resin is too low, it is not possible to impart sufficiently high mechanical strength and durability to a magnetic recording medium having a magnetic paint layer of a composition formulated with the copolymer. . If the average degree of polymerization of the copolymer resin is too high, the coating composition formulated with the copolymer at the desired concentration may have a high viscosity and adversely affect the processability of the coating composition. is there.

The copolymerization reaction of the comonomer can be carried out by any known method including suspension polymerization method, emulsion polymerization method, solution polymerization method, bulk polymerization method and the like. The vinyl acetate moieties in the copolymer can optionally be replaced with vinyl propionate or other vinyl esters of lower carboxylic acids.

To produce the binder resin of the present invention,
Conventional solution polymerization techniques can preferably be utilized, as discussed below. Similarly, other polymerization techniques such as conventional suspension or emulsion polymerization can also be used. Thus, the method employed to produce the resin of the present invention is not critical and such techniques are well known to those of ordinary skill in the art. Suitable manufacturing techniques are described, for example, in U.S. Pat. No. 3,755,271.

Generally and exemplarily, the resins of the present invention can be prepared by utilizing solution polymerization using the resulting resin as well as the solvent for the various components used. Suitable solvents include the customary ester solvents such as butyl acetate, ethyl acetate, isopropyl acetate and the like, as well as acetone, methyl ethylene ketone, methyl-n-butyl ketone, methyl isopropyl ketone and the like. Such ketone solvents are included.

The polymerization can be carried out either batchwise or continuously. Typically, the solvent / monomer ratio will vary from about 0.3 / 1 to about 4/1 depending on the desired molecular weight. The temperature selected can vary from about 35 ° C to about 80 ° C depending on the reaction rate and the desired molecular weight of the resin. Any oil soluble free radical catalyst can be used in an amount that varies from about 0.01 to about 3.0% based on the weight of the monomer. Suitable catalysts include, by way of example, dibenzoyl peroxide, dilauroyl peroxide, azobisbutyronitrile and diisopropyl peroxydicarbonate. Any pressure above the vapor pressure of the components of the system can be employed, with pressures of about 2.1 to 7.0 kg / cm ² (about 30 to 100 psi) being typical.

Any substrate or adherend can be used. The particular substrate that will be particularly suitable will be described in large part by the individual application. Polyethylene terephthalate film and polypropylene film are widely used as substrate materials for magnetic recording media. Polyimide membranes, polyamide membranes, polyarylether membranes or the like can be used where heat resistance is an important consideration.
Polyester films as thin substrates are often used after uniaxial or biaxial orientation. It is likewise well known that pretreatment of the membrane may be advantageous in promoting wetting and adhesion.

The magnetic particles can be any known and useful in conventional magnetic recording media. Typical examples are needle-like or granular γ-Fe ₂ O ₃ , Fe ₃
O ₄ , Co-doped γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ -Fe ₃ O ₄ solid solution, Co-based compound adsorbed γ-Fe ₂ O ₃ , Co-based compound adsorbed γ-Fe ₃
O ₄ (including those oxidized to an intermediate state between itself and γ-Fe ₂ O ₃ ) and acicular CrO ₂ .
(As used herein, the term Co-based compound refers to cobalt oxide, cobalt hydroxide, cobalt ferrite, which allows magnetic particles to take advantage of the magnetic anisotropy of cobalt in improving the coercivity of the particles. (Cobalt ion adsorbates and their analogs.) The magnetic particles can also be hexagonal or acicular strontium ferrite or barium ferrite. The magnetic particles are Co,
It can be a ferromagnetic metal element or alloy such as Fe-Co, Fe-Co-Ni or the like. Such magnetic fine particles include wet reduction of a starting material using a reducing agent such as NaBH ₄ , iron oxide surface treatment using a Si compound, and subsequent dry reduction using hydrogen gas,
And a number of methods including vacuum evaporation in a low pressure argon gas stream. Fine particles of single crystal barium ferrite can be used as well. The magnetic fine powder is used in the form of acicular particles or granular particles depending on the application of the resulting magnetic recording medium.

It is generally desirable to use a relatively large amount of magnetic particles in the paint layer. That is, a typical composition of the paint layer is about 65 or 7 based on the total weight of the paint layer.
It contains 0% to about 85 or 90% magnetic particles. As is known, it is desirable to use pigment particles of relatively uniform size, typically particles having a long axis of about 0.4 microns or even shorter.

The balance of the paint layer comprises a curable resin, and typically a binder system including a rubbery polymer, optionally a dispersant, optionally a crosslinker and any optional auxiliaries. Depending on the resin of the invention used, the dispersant may be minimized or even eliminated.

Conceptually, however, in addition to the pigment particles, the only additional essential ingredient in the present invention is the cured resin itself. However, typical paint layers often contain additional components that are determined by the particular end use. The balance of the paint layer is generally present in about 10 or 15% to 30 or 35% by weight of the paint layer, as will be apparent from the amount of pigment particles used in a typical formulation.

In preparing a magnetic coating composition by using the above specified copolymer as a vehicle for the ferromagnetic particles, the copolymer resin is added in a small amount, eg 50% by weight or less. Can be used in combination with other polymer resins commonly used in the production of magnetic recording media. Examples of polymer resins suitable for such combination use include polyurethane resin, nitrocellulose, epoxy resin, polyamide resin and phenol resin, and acrylic acid ester, methacrylic acid ester, styrene, acrylonitrile, butadiene, ethylene, propylene, vinylidene chloride. , Acrylamide, vinyl ethers and the like polymers and copolymers of which polyurethane resins and nitrocellulose are particularly preferred.

In the preferred embodiment, it is generally desirable for the binder system to include a rubbery polymer in an amount sufficient to provide a coating layer having the desired resilience and the like. A wide variety of rubbery polymers suitable for this purpose are known and can be used. Polyester urethanes are often preferred for high performance applications. Suitable materials are commercially available. Generally, these materials can be described as reaction products of polyester polyols, short chain diols and isocyanates. These resins have excellent toughness and abrasion resistance properties.

A wide variety of polyisocyanate crosslinkers are known and can be used. High molecular weight polyisocyanates are typically used. One example is polymeric toluene diisocyanate (TDI)
It is expedient to use adducts. The amount of crosslinker used is typically from about 1 to about 25% by weight of the amount of vinyl chloride copolymer and polyurethane in the formulation.

Polyisocyanate crosslinkers are typically used in magnetic media formulations to improve properties such as hardness, tensile strength, glass transition temperature and the like. It is unexpected that a similar improvement is observed in formulations containing the polymers described in this invention. This is because these polymers do not have any groups that are considered reactive with isocyanates. Without wishing to be bound by any particular theory or mechanism, at least some of the isocyanates may react with water to form amines that react with other isocyanates to interpenetrating. ) It seems to form a network. Such an interpenetrating network may partially contribute to the improved properties exhibited by the magnetic recording media formulations of the present invention.

As is known, in some cases various auxiliaries are used in the magnetic coating layer. Such additives are known and can be used if desired for a particular application. For example, basically, a magnetic coating composition of the present invention, which is a uniform dispersion of ferromagnetic particles in a polymer resin as a vehicle, is used in a limited amount of a lubricant, a dispersion aid, an anticorrosive and an antistatic agent It can be further mixed with various known additives conventionally used in magnetic coating compositions, including agents, leveling agents, antiwear agents, film reinforcing agents and the like. The magnetic coating composition can be diluted with an organic solvent in order to impart an appropriate viscosity or softness suitable for a coating means. Examples of suitable organic solvents include methyl ethyl ketone, methyl isobutyl ketone, toluene and the like.

According to the present invention, the magnetic paint layer uses the resin of the present invention to obtain the necessary dispersion and orientation properties of the paint and also to act as a cured resin. It is not necessary to use another cured resin. However, if desired,
The resin of the present invention can be used with a compatible curable resin to obtain the desired magnetic coating layer.

The present invention provides improved dispersion and orientation properties through the use of the resins of the present invention. However, if desired, other conventional dispersants can be used.

Generally, recording media can be prepared by dissolving the binder system in a sufficiently volatile vehicle to obtain a coatable dispersion of magnetizable microparticles. The dispersion can then be applied to a substrate to provide a coating on the substrate. The magnetic recording medium is, for example, Process in O
rganic Coatings, 10 (1982), p.195-204, S. Tochihara, "Magnetic Coatings and Thei".
r Applications in Japan ”.

The original magnetic coating composition produced by the above method includes, without particular limitation, synthetic resins such as polyester, polyolefin, cellulose acetate, polycarbonate, non-magnetic metals such as aluminum, and ceramics. Film, tape of various materials,
It can be applied to the surface of a substrate in the form of a sheet, foil, plate or the like. The coating means using the original coating composition can be carried out by any known method conventionally used in the production of magnetic recording media, and then subjected to surface treatment such as calendering to give high performance magnetic recording media. Improves the required smoothness of the painted surface.

The use of the resin of the present invention results in highly useful properties in magnetic recording media, and although the present invention has been described for this application, the resin may be any that could desirably incorporate its properties. It should be appreciated that it can be similarly used as a dispersant and / or a cured resin in other applications. For example, conventional zinc rich paints are useful for many applications requiring corrosion resistance and the like. Such compositions typically contain high proportions of zinc particles (up to 85 to 90% by weight of the composition) of zinc and resin, as is known in the art, of antisettling agents, thickeners and water scavengers. Included with such optional ingredients. Both the zinc rich maintenance coatings and other clear coatings and pigmented coatings provide improved dispersibility and thus improved adhesion to substrates. Therefore, the resin of the present invention can be easily shared with the above-mentioned paint.

For the purposes of this invention, the term "hydrocarbon" includes all acceptable compounds having at least one hydrogen atom and one carbon atom. In a broad aspect, the acceptable hydrocarbons may be substituted or unsubstituted acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, and aromatic. And non-aromatic organic compounds.

The term "substituted," as used herein, unless otherwise indicated, includes all permissible substituents of organic compounds. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic organic compound substituents. Exemplary substituents are, for example, alkyl, alkyloxy, aryl, aryloxy, hydroxy, hydroxyalkyl, amino, aminoalkyl which can range from 1 to about 20 or more carbon atoms, preferably 1 to about 12. , Halogen and the like. The permissible substituents can be one or more suitable organic compounds, the same or different.
The present invention in no way is limited by the permissible substituents of organic compounds.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Charles, Bernard, Malone 08502, Bell Meade, Shelburne Plais 290 (72) Inventor Claudio, Fernando, Nicolini United States, New Jersey, USA 08540, Princeton, Linden Lane 171 (72) Inventor James, Richard, Harvey, NJ, USA 08540, Bridgewater, Stella Drive 53

Claims (10)

[Claims] 1. The following as dissolved or dispersed in an organic solvent: (A) the following monomer moieties: (a) vinyl chloride, (b) components (a), (c) and (d). different monoethylenically unsaturated monomer; in formula (c) _{:-( O) m PO 3 X 2} ( wherein, m is 0 or 1
And X are the same or different and have a phosphorus-containing group represented by a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue). A monoethylenically unsaturated monomer; and (d) optionally one or more monoethylenically unsaturated monomers different from components (a), (b) and (c);
And (B) particles of a ferromagnetic substance dispersed in the copolymer resin as a vehicle, a magnetic coating composition for a magnetic recording medium. 2. A substrate and a magnetic coating layer on the substrate comprising a cured binder system and magnetic particles,
A magnetic recording medium in which the binder system comprises the copolymer resin of claim 1 present therein in an amount sufficient to enhance the dispersion characteristics of the magnetic coating layer. 3. The magnetic coating composition according to claim 1, wherein the amount of the copolymer resin as the component (A) is in the range of 8 to 30 parts by weight per 100 parts by weight of the particles of the ferromagnetic substance as the component (B). object. 4. The magnetic coating composition according to claim 1, wherein the monoethylenically unsaturated monomer as the component (b) is vinyl acetate or ethyl acrylate. 5. The monoethylenically unsaturated monomer of component (c) has the formula: CH ₂ ═C (CH ₃ ) —CO—O—C ₂ H ₄ — (O) _m P.
O ₃ X ₂ (where m is a value of 0 or 1 and X are the same,
Or a acrylate moiety or methacrylate moiety represented by a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue, which is different or different). 6. The following as dissolved or dispersed in an organic solvent: (A) The following monomer moiety: (a) Formula: --CH ₂ --CHCl-- The first monomer which is vinyl chloride. 65 to 95% by weight of the body part; (b) 3 to 30% by weight of the second monomer part which is a monoethylenically unsaturated monomer different from the components (a), (c) and (d); c) formula _{:-( O) m PO 3 X 2} ( wherein, m is 0 or 1
And X is the same or different and is a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue). 0.1-5% by weight of the third monomer portion which is an ethylenically unsaturated monomer; and (d) one or more mono-components different from components (a), (b) and (c) A copolymer resin containing a fourth monomer portion of 0 to 20% by weight which is an ethylenically unsaturated monomer; and (B) a ferromagnetic material dispersed in the copolymer resin as a vehicle. A magnetic coating composition for a magnetic recording medium, which comprises particles. 7. A substrate and a magnetic paint layer on the substrate comprising a hardened binder system and magnetic particles, wherein the binder system enhances the dispersion properties of the magnetic paint layer. A magnetic recording medium comprising the copolymer resin of claim 6 present in said binder system in an amount sufficient to 8. The magnetic coating composition according to claim 6, wherein the amount of the copolymer resin as the component (A) is in the range of 8 to 30 parts by weight per 100 parts by weight of the particles of the ferromagnetic substance as the component (B). . 9. The magnetic coating composition according to claim 6, wherein the monoethylenically unsaturated monomer of component (b) is vinyl acetate or ethyl acrylate. 10. The monoethylenically unsaturated monomer of component (c) has the formula: CH ₂ ═C (CH ₃ ) —CO—O—C ₂ H ₄ — (O) _m P.
O ₃ X ₂ (where m is a value of 0 or 1 and X are the same,
Or a different and an acrylate or methacrylate moiety represented by a hydrogen atom, an alkali metal atom, a protonated amine or a substituted or unsubstituted hydrocarbon residue).