JPS6066316A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent dispersibility of magnetic powder, excellent durability, etc. by providing a magnetic layer dispersed with metallic magnetic powder having specific pH or below together with carboxylate of a specific diamine in a binder. CONSTITUTION:A magnetic layer dispersed with the fatty acid salt of the diamine which is the diamine expressed by the formula I (R is >=C3 satd. or unsatd. alkyl group, n is 2-8), for example, the fatty acid salt of diamine having the stable coordination with Fe as shown in the formula II, for example, caproic acid, oleate and metallic magnetic powder such as Fe, Ni, Co, etc. having <=7pH when measured by a specific method together with a necessary dispersant, carbon black powder, etc. is formed on a base. The magnetic recording medium which has good dispersibility of the magnetic powder, good wear resistance, good adhesion to the base, is free from dislodging of the powder and prevents drop-out, noise, etc. is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium, and more specifically, in a magnetic tape or a magnetic sheet having a coated magnetic layer on a support, the magnetic layer is coated with a metal reinforcement. This invention relates to improved dispersibility in a binder when magnetic powder is used.

BACKGROUND OF THE INVENTION Magnetic recording media such as magnetic tapes and magnetic sheets are widely used in the audio field for recording sound and the video field for recording images. Magnetic recording media used in these various fields include magnetic recording media (45), a coated type in which a magnetic layer is formed on the support by coating a magnetic coating mainly consisting of a binder resin and a solvent on a support and drying it. are widely used. In such magnetic recording media, the magnetic layer comes into intense contact with the magnetic head during recording and reproduction, making it easy for wear and magnetic powder to come off. When these things happen, the reproduction output decreases, output fluctuation,
Since dropouts, increased noise, etc. occur, the magnetic layer is required to have mechanical properties that can withstand friction with the head.

In particular, in recent years, technology related to magnetic recording has changed, for example, in audio tapes, there has been a shift from the use of compact cassettes to the use of micro-force centrifuges.
In addition, in the field of video, the current 0VIIS and β formats are transitioning to 8mm video and electronic cameras, all of which are aimed at becoming smaller and more dense. The mechanical properties have become more complex, and there are many opportunities for contact with guide balls, guide rollers, etc., resulting in frequent rubbing, and further improvement of the above mechanical properties is desired.

In addition, especially in recording media for 8 mm video systems and electronic cameras, it is necessary to improve the recording density, and to make short wavelength recording possible, the surface of the magnetic layer must be smooth and the S.
/N ratio is expected to be high, and in order to achieve this, Fe, Fe-Co, which has a higher saturation magnetization than oxide magnetic materials, is used.
, Fe-Co:Ni and other ferromagnetic metals or alloy powders have been used, and efforts have been made to improve the dispersibility of this ferromagnetic powder in binders. However, these ferromagnetic metal or alloy powders are difficult to disperse in a binder, and even if they are forced to disperse, the dispersion stability is poor and agglomeration tends to occur during storage. Generally, the smaller the particle size of the magnetic powder, the worse the dispersibility becomes. For example, in the case of iron alloys, when the specific surface area BET value exceeds 40rd/g, the dispersibility decreases rapidly. Satisfactory dispersion is difficult to achieve using known dispersion methods.

In order to improve this dispersibility, dispersants are sometimes used, but in this case, if excess dispersant is used next to the magnetic layer, this will act on the magnetic layer and plasticize the coating film. become This deteriorates the mechanical properties such as the surface being easily scratched when the tape is rubbed against the head, and also reduces the Young's modulus of the magnetic layer, making the tape weak, especially for long periods of time. This is a fatal flaw for thin recording tapes. In addition, excess dispersant migrates to the tape surface, increasing the friction between the tape and the magnetic S, yF, resulting in an increase in running tension, sticking to the head, and magnetic powder particles. This results in increased fall. Therefore, attempts have been made to use various additives that are effective in relatively small amounts to the magnetic powder in order to improve the dispersibility of the magnetic powder and improve the wear resistance. For example, Special Publication No. 41-18064, No. 42-2234
No. 5, No. 43-186, No. 43-669, No. 47-
No. 15624, No. 50-40103, Japanese Unexamined Patent Publication No. 1983-5
No. 3402, No. 49-58804, No. 49-8440
No. 5, No. 51-40904, and No. 52-7 oau, a magnetic paint containing magnetic powder and a binder contains higher fatty acids, fatty acid amides, fatty acid esters, higher alcohols, metal soaps, Sulfate esters of higher alcohols, polyethylene oxide, lecithin,
A magnetic layer is formed by coating a support with a magnetic paint containing N-alkyl 1-rimethylenediamine fatty acid salt or the like. However, none of these dispersants can sufficiently disperse ferromagnetic metal or alloy magnetic powder. On the other hand, the neutralized product of tallow diamine and oleic acid disclosed in JP-A-58-14321 is an effective dispersant.

However, the average particle size disclosed in the same publication is 0.8μ, Il
When ferromagnetic powder with c = 12000e and σS = 150 emu/g was dispersed in a binder using a neutralization product of several types of tallow diamine and oleic acid (Duomin TDO), it was found that the dispersion effect of this dispersant alone was not sufficient. It has not been possible to uniformly obtain the high dispersion that meets the above-mentioned recent trends for any metal magnetic material. In order to improve the recording density and achieve short wavelength recording by making the surface of the magnetic layer flat tFk and obtaining the desired electromagnetic properties, it is necessary to use hard-to-disperse metal magnetic powder in the form of fine particles in a binder. However, in order to satisfy the requirement for a high degree of dispersion of the magnetic layer 5, it is not sufficient to simply add tallow diamine carboxylate. Therefore, a method is needed to effectively disperse ferromagnetic powder in the form of fine particles in a binder with a relatively small amount of dispersant, and it is necessary to develop a magnetic recording medium having a magnetic layer in which such magnetic powder is highly dispersed. development was desired.

OBJECT OF THE INVENTION The object of the present invention is to provide a magnetic powder with dispersibility that is non-adhesive to a magnetic head, has wear resistance and durability, has excellent surface smoothness, and has good electromagnetic properties. An object of the present invention is to provide a magnetic recording medium having an excellent magnetic layer.

Structure of the Invention In order to achieve the above object, the present inventors conducted intensive research and found that the above-mentioned beef tallow diamine and neutralized salt of oleic acid exert a remarkable dispersion effect on certain magnetic powders. We found that there is a synergistic effect between these. It was also found that this constant characteristic of the magnetic powder is due to the fact that the circle I value of the magnetic powder is 7 or less.

From this, the magnetic recording medium of the present invention is a magnetic recording medium having a support and a magnetic layer, in which the magnetic layer is made of at least one metal-based magnetic powder having a pH value of 7 or less and is represented by the following general formula. It is characterized by being dispersed and contained in the binder together with the carboxylate of the compound.

General formula % Formula % (In the formula, R represents a saturated or unsaturated alkyl group having 3 or more carbon atoms, and n represents a real number from 2 to 8.) Hereinafter, the present invention will be explained in more detail.

In the present invention, metal-based magnetic powder having an I'll value of 7 or less is used. 11 II of this metallic magnetic powder
To find out the value, there are, for example, a method from the titration curve and a method from the zeta potential. For example, as shown in Figure 1, the titration curve can be determined by adding a portion of metallic magnetic wax to a KOJ+ aqueous solution at a constant concentration, and titrating it with a standard hydrochloric acid solution at a constant concentration in a nitrogen atmosphere. Look at the curve a that shows the change in the circle I value, and then 01 for not containing magnetic powder.
The same titration curve was calculated for the aqueous solution of 1, and the intersection point was found from these curves a and b, and this intersection point was taken as the point of zero charge, and the circle value of the magnetic powder was determined. In addition, as shown in Figure 2, the method of determining the zeta potential is to determine the zeta potential of a metal magnetic powder (for example, 0.01 to O, Ig) in an electrolyte solution having an appropriate circle 1 value (for example, 100 m i'). The value of circle 1 is measured while changing the value of circle 1, and the value of circle 2 when the zeta potential becomes zero (isoelectric point) on this Zeke potential-circle 1 value curve is taken as the circle 1 value of the metal magnetic powder. .
The surface chemical properties of the metal magnetic powder used in magnetic recording media vary depending on the manufacturing process, and the circle 1 value is generally determined by the amount of the mixture (additive). The metal-based magnetic powder used in the present invention has a coercive force of 1000 Oersted or more, preferably 1200 to 2000 Oersted. Further, from the viewpoint of electromagnetic properties, metal-based magnetic powder containing 70 atomic weight % or more of Fe is preferable.

Examples of the metal-based magnetic powder used in the present invention include F
e, Ni,, C0% Fe-Ni alloy, Fe-Co alloy, Fe-Nj-P alloy, Fe-'N1-Go alloy, F
e-Mn-Zn alloy, Fe-Nj-Zn alloy, Fe-C
o-Ni-Cr alloy, Fe-Go-Ni-P alloy, CQ
-Ni alloys, Go-P alloys, etc. whose main components are Fe, Ni, and Go. Additives for these include Si, Cu, Zn, Aj! ,P,,Mn
Elements such as sCr or compounds thereof may be included.

In the present invention, a carboxylate salt of the compound represented by the above general formula is used. n in the above general formula is a real number of 2 or more and 8 or less. In this range, the number of methylene groups is 2 or more and 8 or less, and when the amine groups on both sides coordinate with a constituent element of the metal magnetic powder, for example, Fe, it can take a form that facilitates coordination. Any diamine compound having such a methylene group can be used, but among these, preferably one in which n is 2.3.4.

As shown below, these are considered to have stable coordination with, for example, Fe.

R.

I ClI2-C112 O In the above general formula, R is preferably an alkyl group in order to facilitate coordination between the compound of this general formula and the metal magnetic powder, and this alkyl group may be saturated or unsaturated. It's okay. Such an alkyl group, for example, has a Fe
This is because the ability to coordinate with metals such as metals is less likely to be impaired. For the same reason, in the case of an unsaturated alkyl group, for example, it is preferable that the double bond is not adjacent to a nitrogen atom.

For example, 1do-C1l = CI+-(:+12-N11
- (C1j2)n-Nil2, where R' is a saturated or unsaturated alkyl group having 2 or more carbon atoms. Further, the alkyl group may have a substituent as long as it does not interfere with the coordination ability of the secondary amino group of the compound represented by the above general formula.

Examples include the following:

Regarding the function of R in the above general formula, for example, the above n = 2
As exemplified in compounds 4 to 4, it is considered to be a hydrophobic portion, and since it is easily compatible with the normally hydrophobic binder described below, it is thought to act as an intermediary between the hydrophilic metal magnetic powder and the binder. The compound of the above general formula is 2 from the viewpoint of the ratio of the metal magnetic powder to the binder: 11 &
More than one species may be included, which may be preferable depending on the case. This is thought to be because by mixing two or more of these compounds, the dispersibility of these compounds in the binder is improved, and various metal-based magnetic powders can be well dispersed in the binder. . The average molecular weight of the compound of this general formula is 200 or more, more preferably 300 or more. R preferably has 30 or less carbon atoms. If the number of carbon atoms in R is larger than this, the electromagnetic properties of the metal-based magnetic powder may be impaired.

The compound represented by the above general formula is used as a carboxylate salt. Examples of this carboxylic acid salt include, but are not limited to, those of Hagi.

(1) C(, H13NII (C112)5Nll
Caproate of 2 (2) C81117NII (CI
I2) Elaidate of 3Nl12 (3) Cl011
21 Nil (CH2)2N112 laurate (
4) Cl41129 Nil (C112)4 NH
Caprate of 2 (5) Cl81135 Nll (
C1l 2 >3 Nil 2 oleate (6)
C81117NII (CH2)3Nll 2 oleate (7) (2) H41NH (CI+ 2 )4 N
Caprylate of H2 (8) Cl81155 NH(C
1l 2 ) 4 Nil 2 myristate (9)
Q81157 Behenate of Nil (C1l 2 )4N112 (10) C2D1141NII (C11
2) 2-Methylvalerate of GNII2 The compounds shown in the above specific examples are usually commercially available under the name "Duomeen TDO" (Lion Akzo Co., Ltd.), such as (5) and (6), and are easily obtained. Some can be synthesized by known methods.

Note that various combinations of the above-exemplified diamine compounds and carboxylic acids are possible, and of course other diamine compounds and carboxylic acids may be used. As described above, it is important to form a carboxylate of a diamine compound; diamine alone cannot provide the desired effect.

It is preferable that the salt of the compound of the above general formula is sparingly soluble in water from the viewpoint of improving the dispersibility of the metal magnetic powder in the magnetic layer.

This is because it is generally compatible with hydrophobic binders.

The proportion of the salt of the compound represented by the above general formula used in the present invention is usually 0 parts by weight per 100 parts by weight of the metal magnetic powder.
．． The amount is from 5 parts by weight to 10 parts by weight, preferably from 1 part by weight to 5 parts by weight. If it is less than 0.5 parts by weight, a good dispersion effect of the magnetic powder cannot be obtained, and if it is more than 10 parts by weight, it may cause a blooming phenomenon in the coated film or plasticize the coated film, making it difficult to prevent friction with magnetic heads, for example. This is undesirable as it reduces the strength of the target.

The binder resin used in the present invention includes the commonly known resins described below, and the amount used is 5 to 400 parts by weight, preferably 5 to 50 parts by weight, per 100 parts by weight of the metal magnetic powder. This is desirable in terms of the recording density and mechanical strength of the magnetic layer containing it.

A paint is used to form the magnetic layer of the magnetic recording medium according to the present invention. To prepare this paint, a carboxylic acid salt of the compound of the formula and a suitable solvent for general paints are kneaded in a kneader or the like for a predetermined period of time. Then, remove excess solution that is not adsorbed by the magnetic powder by filtration or centrifugation. After drying, the metal magnetic powder treated in this manner can be pulverized to a desired particle size and classified.

Then, this treated metal magnetic powder is mixed with a binder resin and an organic solvent using, for example, a ball mill or a sand mill.
Disperse and make paint. In addition, the metal magnetic powder treated with the salt of the compound of the above general formula is prepared by adding the salt of this compound to toluene,
Dissolve in a solvent such as methyl ethyl ketone, ethyl cellosolve, acetone, cyclohexane, tetrahydrofuran, methanol, etc., and add the above circle I value of 7 to the solution in a prescribed proportion.
After immersing the following metal magnetic powder and stirring and mixing, filtration,
It can also be produced by centrifugation or evaporation of the solvent, followed by further drying if necessary.

(2) Salt of the compound represented by the above general formula, the above P117
The following metallic magnetic powder and binder resin solution are mixed in a suitable solvent and dispersed in a ball mill or sand mill to form a paint.

Among these, method (1) is more efficient because the excess of the salt of the compound of the above general formula that is not adsorbed by the metal-based magnetic powder is removed, and there are fewer other components that are adsorbed by the metal-based magnetic powder. As a result, the dispersion efficiency in the binder is also improved, so when used as a magnetic layer, the squareness ratio, output,
Electromagnetic properties such as s/N Jt are good (and desirable).

In order to produce the magnetic recording medium of the present invention, coating is applied to a support described later by a conventional method described later. The magnetic layer coated on such a support is subjected to a treatment to orient the magnetic powder in the layer, if necessary, and then dried. Further, if necessary, the magnetic recording medium of the present invention is prepared by subjecting it to surface smoothing or cutting it into a desired shape.

In this way, the magnetic recording medium of the present invention is completed.
When the specific surface area of the metal magnetic material 15) to be treated is 30 nf/g or more, the surface treatment effect by the salt of the compound of the above general formula is exhibited well, and the dispersion in the binder is improved. That is, the specific surface area is 30rr
If the particle size exceeds r/g, the particle size becomes small, and although the magnetic properties generally improve to some extent in terms of high-density recording, the dispersibility of metal-based magnetic powder tends to deteriorate. The effect of the salt of the compound of the general formula is remarkable. In this way, the dispersibility of the metal-based magnetic powder with a small particle size is improved, so that a magnetic layer using a metal magnetic powder with a specific surface area of 30 m / g or more can be used in a similar manner to a magnetic layer using an untreated metal magnetic powder. The characteristics are dramatically improved compared to the magnetic layer. This shows that not only can the decrease in the dispersibility of the metal magnetic powder be effectively prevented by, for example, surface treatment with a salt of the compound having the above general formula, but also the dispersibility can be significantly improved. Note that if the specific surface area of the magnetic powder used is increased more than necessary, poor dispersion will occur, so it is preferable to set the upper limit to 100 rd/g. In the above, “
"Specific surface area" refers to the surface area per unit weight, and is a physical quantity that is completely different from the average particle size.For example, even if the average particle size is the same, some particles have a larger specific surface area and others have a smaller specific surface area. . The specific surface area is generally measured using B, E,
A method for measuring the specific surface area called the T method is used, and details are given in J. Ame.

Chem, Soc, 60, 309 (1938).

The magnetic layer of the magnetic recording medium of the present invention further has a specific surface area (BET value) Bl of 40rd/g<B+<200.
rd/g carbon black (hereinafter referred to as CB).

) and the specific surface area (BIET value) B2 is 200 rd/g ≦B 2 <500 of/g T
: It is preferable to contain Alkaho 7 Black (hereinafter sometimes referred to as CB2). This is because magnetic recording media are generally rubbed during use, and static electricity accumulates, and when this is discharged between the magnetic head and the magnetic head, it generates noise.
In addition, since dust may come into contact with the magnetic field or throat while remaining attached, and cause dropouts, the surface electrical resistance of the magnetic layer should be set to 109Ω or less to improve conductivity and prevent static electricity from occurring. This is to prevent dirt from sticking to it. In addition, for devices that adjust the running of the tape by detecting the difference in light transmittance between the tape part with the magnetic layer and the leader tape part, such as some types of video magnetic recording media, the part with the magnetic layer is It is necessary to make the light transmittance of 0.05% or less, and this is also useful for this purpose.

CBi is mainly used for this light shielding, and its specific surface area 161 is calculated as 4orrt7B < B 1 < 200r
It is extremely important that the range is limited, such as d/g. With a specific surface area within this range, the light shielding properties of the magnetic layer can be sufficiently exhibited, and the dispersibility of CB1 in the magnetic layer can be improved. Outside this range, when the cniO specific surface area is less than 4 On (/g), the particle size becomes too large and the light shielding properties tend to deteriorate, and therefore the amount added must be greater than a. .Also, CB10
If the specific surface area is 200 rl/g or more, the particle size will be too small and the dispersibility in the magnetic layer will likely be poor. On the other hand, in order to improve the conductivity of the magnetic layer, CB2 is
TM IA) 6. together with B1, but it is important that the specific surface area of CB2 is limited as described above. If the specific surface area of CB2 is less than 200 rd/g, the particle size will be too large and the improvement of conductivity will be insufficient; if it is over 500 tl/g J:d, the particle size will be too small and the dispersibility will be insufficient. It will be enough. For these reasons, CB for light shielding
By limiting the specific surface areas of 1 and conductive CB2 to the above ranges, the surface electrical resistance and optical transparency of the magnetic layer can be sufficiently reduced, and the dispersibility of the carbon blank in the magnetic layer can be improved. can improve its surface smoothness. By selectively using light-shielding and conductive carbon blanks like Manokoko, it is possible to reduce the amount used and obtain the desired effect. Mechanical strength, that is, durability can be improved. From these facts, the specific surface area of CBI is 100≦B H<200,
It is preferable that CB2 is 200≦82<300, and in terms of particle size, CBI is 20 mμ or less, C
It is desirable that B2 is 40 to 50 mμ.

The amount of carbon blank added is determined within a range that can maintain the mechanical strength of the magnetic layer, but when applying electricity, the amount of carbon blank added to the binder is 5 to 35% by weight (preferably 10 to 35% by weight).
25% by weight). Within this additive amount range, the mechanical properties of the magnetic layer, such as suppression of magnetic powder dust, can be maintained well, and the surface electrical resistance is, for example, 109C:1 J/m or less and the light transmittance is 0.05% or less. can be obtained. The reason why the desired effect can be obtained without increasing the amount of carbon blank added is due to the selective use of carbon blanks having the above-mentioned specific surface area. The effect of adding this carbon blank to one having the above-mentioned specific surface area also appears in the coating film condition and electromagnetic conversion characteristics. In other words, carbon black with a small particle size (large surface area) is advantageous because it improves the surface resistivity and light transmittance of the coating film compared to a magnetic layer containing other carbon blanks of the same weight. Dispersion in the membrane becomes difficult,
Surface roughness due to poor dispersion, occurrence of pinballs, etc. will actually increase surface resistivity and light transmittance, and will also cause deterioration of electromagnetic conversion characteristics. In the case of shaped magnetic materials, they tend to break when being dispersed, and in particular, if they are overdispersed, many of them break, resulting in a significant problem.If you try to prevent this,
The dispersion operation should be stopped when the magnetic material is fully dispersed without breaking, but in this case, if the particle size of carbon black is too small and the dispersibility is poor, carbon black may be present in the paint. This not only causes separation of the blank particles, but also causes problems such as surface roughening of the coating film described above.

As mentioned above, it is preferable to use conductive CB2 in order to reduce the surface ratio of the magnetic layer to a sufficient range, but such carbon black is made up of particles arranged in a cluster of grapes. It is preferable to use a material that is porous and has a large specific surface area, that is, a material with a high so-called stracture level. An example of such a carbon blank is Conductex (Cond
ucLex) 975 (specific surface area 270 nr/g,
Particle size: 46 mμ), Palcan manufactured by Cabot Co., Ltd.
Vulcan) XC-72 (specific surface area 257 rr
r/g, particle size 18 mμ), etc. can be used. Although these carbon blanks have a large specific surface area, when used in a magnetic layer, they can be sufficiently dispersed in the amount of magnetic powder before completion. Therefore, there is no problem of bending of the magnetic layer due to overdispersion of the carbon blank as described in item 1 (and there are no defects in the coating film due to non-dispersion of the carbon blank.Also, to reduce the light transmittance of the magnetic layer, it is necessary to CB1 with good properties and excellent dispersibility is
By adding a small amount of CB2 to B2, the light transmittance can be sufficiently reduced due to a synergistic effect compared to using CB2 alone.

This makes it possible to significantly reduce the amount of conductive carbon black added, thereby reducing the overall amount of carbon blank added and improving the mechanical properties and surface smoothness of the magnetic layer as described above. CDI used for light shielding as described above has a small particle size, a relatively low structure, and a relatively low specific surface area.
For example, Columbia Carbon's Raven
) 2000 (specific surface area 180 i/g, particle size 19
mμ), 2100.1170.1000, Mitsubishi Chemical (1
1) #100, #75, #44, #40, #35,
#30 etc. can be used.

There is a certain preferable range for the mixing ratio (weight ratio) of each carbon blank described above, and CB 2 /CB 1 = 9
0/10~50150 is good<, 80/20~60/4
0 is even better. If this mixing ratio is greater than 90/10, the proportion of CB2 in the conductive carbon blank will increase, resulting in insufficient light-shielding properties, and if it is less than 50150, the surface resistivity will increase due to the small amount of CB2 in the conductive carbon black. I end up.

The above binder is a thermoplastic resin! :1 curable resin, reactive resin, electron beam curable resin, and mixtures thereof with others are used.

The thermoplastic resin used as the binder has a softening temperature of 150°C or less and an average molecular weight of 10,000 to 200°C.
OO1 polymerization degree is about 200 to 2,000, such as acrylic ester-acrylonyl 1-lyl copolymer, acrylic ester-vinylidene chloride copolymer (combination), acrylic ester-styrene copolymer, methacryl Acid ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer,
Acrylic nitrile-cyclodiene copolymer, polyamide resin, polyvinyl)tyral, styrene-butadiconine copolymer, polyester resin, chlorovinyl ether-acrylic acid ester copolymer, amino resin, various synthetic rubber-based Thermoplastic resins, mixtures thereof, etc. 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. 40-20907, 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
- No. 17947, No. 44-18232, No. 45-14
No. 020, No. 45-14500, No. 47-18573
No. 47-22063, No. 47-22064, No. 47-22068, No. 47-22069, No. 47-
22070, U.S. Patent No. 48-27886, U.S. Patent No. 3,144,352, U.S. Pat.
It is listed in the number specification.

The thermosetting resin or reactive resin used is one that has a molecular weight of 200,000 or less in the state of a coating solution and becomes insolubilized by a reaction such as condensation or addition after coating and drying. Among these 4M fats, those that do not soften or melt before the 46 fat is thermally decomposed are preferred. in particular,
For example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin,
Silicone resins, acrylic reactive resins, vinyl chloride-vinyl acetate resins, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of high molecular weight polyester resins and isocyanate prepolymers, urea formaldehyde resins, polynisol polyols and incyanates mixture, polyamide 4AJ resin, low molecular weight glycol,
These include mixtures of high molecular weight diols and l-liphenylmectun triisocyanate, and mixtures thereof.

These resins are disclosed in Japanese Patent Publications Nos. 39-8103 and 40-97.
79 No. 41-7192, No. 41-8016, No. 4
No. 1-14275, No. 42-18179, No. 43-1
No. 2081, No. 44-28023, No. 45-1450
No. 1, No. 45-24902, No. 46-13103,
No. 47-22067, No. 47-22072, No. 47
-22073, 47-28045, 47-28
No. 048, U.S. Patent No. 47-28922, U.S. Pat.
It is described in the specifications of the same No. 3,78L210 and the same No. 3,781,211.

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., or as a polyfunctional monomer, ether acrylic type, urethane acrylic type, phosphate ester acrylic type, etc. -ru type, hydrocarbon type, etc.

Phenoxy resins, epoxy resins and polyurethane resins are preferred for use with these diaphragm powders. The reason why phenoxy resin is suitable as a dispersion medium for metal-based magnetic powder is that, for example, high-molecular-weight polyhydroxyether made from bisphenol and epichlorohydrin as a raw material is chemically stable and is suitable for use as a dispersion medium for metal-based magnetic powder. It is not easily decomposed by Furthermore, since it has a high concentration of hydroxyl groups along the main chain, it has excellent dispersibility of magnetic powder and excellent crosslinking properties. In addition, when it is included as a binder in a magnetic layer, it can provide appropriate softness, and the liquid phase does not change suddenly to a solid phase even with a slight temperature change, so the mechanical properties of the surface do not change. It is possible to provide a magnetic layer with excellent surface properties. It is particularly preferable to use phenoxy resin in combination with polyurethane.

The following phenoxy resins can be used, and these are desirable in terms of storage stability and abrasion resistance.

5TX-04 (manufactured by Tobu Kasei Co., Ltd.: hydrogenated type) STX-05 (
(manufactured by Tobu Kasei Co., Ltd.: co-bonded type) PKIIH (manufactured by LICC Co., Ltd.) Also, examples of epoxy resins include the following.

Araldite 6084 (Ciba Geigy M: bisphenol type, average molecular weight 1740-2050) Araldite 6099' (Ciba Geigy M: bisphenol type, average molecular weight [4800-8000) ECN-127
3 (Ciba Geigy Ni Novolac type average molecular weight 108
0) Epicote 834 (manufactured by Shell: bisphenol crystal type,
(average molecular weight: 470) Epicoat 1004 (Shell Co., Ltd.: bisphenol crystal type, average molecular weight: ff11600) Epicoat 1007 (Shell Co., Ltd. IM: bisphenol Δ type, average molecular weight: 2900) BP-4080 (Asahi Denka Co., Ltd.: hydrogenated bisphenol A type) RPV -6 (manufactured by Asahi Denka Co., Ltd.: urethane modified) The phenoxy resin and epoxy resin of this invention may be used alone or in combination.

The following polyurethane resins can be used.

Acretan (Niacryl urethane manufactured by Fujikura Kasei Co., Ltd.) PS-
706 (Nihard type, manufactured by Mitsui Nisso Urethane Co., Ltd.) PS-815 (Nihard type, manufactured by Mitsui Nisso Urethane Co., Ltd.) MAD-2010 (Manufactured by Dainichiseika Co., Ltd.) N-3022 (Manufactured by Nippon Polyurethane Co., Ltd.) DN-398
5 (manufactured by Nippon Polyurethane Co., Ltd.) NISTAN 5701 (manufactured by Goodlynch Co., Ltd.) PANDEX 78-8 (manufactured by Dainippon Ink Co., Ltd.) Furthermore, in order to improve the durability of the magnetic recording medium according to the present invention, various curing agents are added to the magnetic layer etc. For example, isocyanate may be contained.

Aromatic isocyanes that can be used include, for example, l-lylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XD), meta-xylylene diisocyanate (MXDI), and these isocyanates.
The average molecular weight is preferably in the range of 100 to 3,000.

Specifically, Sumidur T80, Sumidur 44S, Sumidur PF, Desmodur T65, Desmodur 15, R1 RF, IL, and SL manufactured by Sumitomo Bayer Urethane 01 Co., Ltd.
iProduct name: Takenate 300S, Takenate 50, manufactured by Takeda Pharmaceutical Co., Ltd.
0; Product name 1'-NDI J, manufactured by Mitsui Nisso Urethane Co., Ltd.
TODIJ iB Manufactured by Honpolyurethane Co., Ltd. Product name: Desmodur T100. Millionate MR, Same MT, Coronae 1
-L.

Product name PAPI-135 manufactured by Kasei Upshun Co., Ltd.: TD
165, 80, 100, Isonate 125M, 1
Examples include products such as 431.

On the other hand, examples of aliphatic isocyanates include hexamethylene diisocyanate (l(MDI)), lysine isocyanate, trimethylhexamethylene diisocyanate (T
MDI) and adducts of these isocyanates and active hydrogen compounds. Among these aliphatic isocyanates and adducts of these isocyanates and active hydrogen compounds, those having a molecular weight in the range of 100 to a.ooo are preferred.

Among the aliphatic isocyanates, non-alicyclic isocyanates 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., Duranate 50M, 24A-100, and 24 manufactured by Asahi Kasei Co., Ltd.
There are products such as A-90CX, Coronate Old 5 manufactured by Nippon Polyurethane Co., Ltd., and TMDI manufactured by Huls.

Furthermore, examples of alicyclic isocyanates among aliphatic isocyanates include methylcyclohexane-2,4-
Diisocyanate (Structural Formula) (Structural Formula) Examples include isophorone diisocyanate and its adduct of an active hydrogen compound.

Specifically, product names IPDI and PDI manufactured by Huls Chemical Co., Ltd.
There are products such as -71890, ll-2921, and ll-131065.

Examples of the adduct of the above-mentioned isocyanate and an active hydrogen compound include an adduct of a diisocyanate and a trivalent polyol. Polyisocyanates can also be used as curing agents, including, for example, a pentagonal diisocyanate, a decarboxylation compound of 3 moles of diisocyanate and water, and the like. 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, and 3 moles of tolylene diisocyanate. There is a pentamer consisting of 2 moles of hexamethylene diisocyanate, etc., which can be easily obtained industrially.

For these isocyanane-1, it is preferable to use, for example, an aromatic isocyanate and an aliphatic isocyanate in combination in view of the film properties of the magnetic layer.

In order to create the magnetic recording medium of the present invention using these isocyanes-1, a magnetic paint is prepared by mixing and dispersing the binder resin exemplified above and various additives described below as necessary in an organic solvent. This is coated with the above-mentioned isocyanate (preferably aromatic isocyanate and aliphatic isocyanate) on a support such as a polyester film, and dried if necessary. In this case, the amount of isocyanate added is 5 to 1 to the binder.
5% by weight is preferred. If it is less than 5% by weight, the coating film tends to be insufficiently cured, and if it is more than 15% by weight, the coating film becomes too hard, which is not preferable.

The above-mentioned magnetic paint may contain additives other than those mentioned above, such as a dispersant, a lubricant, an abrasive, and an antistatic agent other than the above-mentioned carbon black, if necessary.

For example, other dispersants that may be used in combination include lecithin;
caprylic acid, capric acid, lauric acid, myristic acid,
Fats rIJ having 8 to 18 carbon atoms such as palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, etc. (R represented by R-COO11 is a saturated or unsaturated alkyl group); metal soaps made of the alkali metals (Li, Na, K, etc.) of the above-mentioned fatty acids and alkaline earth metals (W, Mg, Ca, Ba, etc.); In addition, higher alcohols having 12 or more carbon atoms, sulfuric esters, and the like 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. In addition, as lubricants, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, carbon atoms 12 to 16
Fatty acid esters (waxes) having 21 to 23 carbon atoms made of a monobasic fatty acid and a monohydric alcohol can also be used. These lubricants are 0 parts per 100 parts by weight of magnetic powder.
．． It is added in an amount of 2 to 20 parts by weight.

In addition, commonly used abrasives include fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main ingredients are corundum and magnetite), titanium dioxide, etc. . These abrasives have an average particle size of 0.05~
A size of 5μ is used, particularly preferably 0.1
~1μ. These abrasives are magnetic (100)
It is added in an amount of 1 to 20 parts by weight. In addition, antistatic agents include conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium oxide-stinous oxide-antimony oxide compounds; natural surfactants such as saponin; alkylene oxite-based, glycerin-based, Nonionic surfactants such as glycidol; cationic surfactants such as higher alkyl amines, quaternary ammonium salts, pyridine and other heterocycles, phosphonium or sulfonium; carboxylic acids, sulfonic acids, phosphoric acids, sulfuric esters anionic surfactants containing acidic groups such as groups, phosphoric acid ester groups; amphoteric surfactants such as amino@s, aminosulfonic acids j'n, sulfuric acid or phosphoric acid esters of amino alcohols, and the like.

The solvents to be added to the above magnetic paint or the diluting solvent when applying this paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol monomers. Esters such as acetate; ethers such as ethylene glycol dimethyl ether, diethylene glycol monoethyl ether, dioxane, and tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, dichlorobenzene and other halogenated hydrocarbons can be used.

In addition, as a support, polyethylene terephthalate,
Polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polyamide and polycarbonate, metals such as A11Zn, glass, BN-Si carbide, porcelain, Ceramics such as pottery are used.

The thickness of these supports is approximately 3 to 100 μm, preferably 5 to 50 μm in the case of a film or sheet, approximately 30 μm = 10 mm in the case of a disk or card, and cylindrical in the case of a drum. The type is determined depending on the recorder used.

The surface of the support opposite to the side on which the magnetic layer is provided for the purpose of preventing static electricity, preventing transfer, etc. is coated with a so-called back coat.
kcoat).゛Coating methods for forming a magnetic layer by coating the magnetic paint on the support include air 1-lid coating, blade coating, air knife coating, squeeze coating, impregnation coating, and reverse coating.
Examples of coating materials that can be used include, but are not limited to, ``ru coat'', transfer roll coat, gravure coat, kiss coat, cast coat, and swab rainy note.

Effects of the Invention As described above, the present invention provides a method for dispersing a metal-based magnetic material with a pH value of 7 or less in a binder using a carboxylic acid salt of a compound represented by the above general formula. Therefore, metal-based magnetic powder, which is difficult to disperse due to both its type and size, can be effectively made into fine particles. In this way, the synergistic effect of the metal-based magnetic powder and the salt of the compound of the above general formula significantly improves the dispersibility, so there is no need to use a large amount of dispersant as in the past. At the same time, the coating film of the magnetic layer is not excessively plasticized and maintains a suitable strength, improving its abrasion resistance and preventing powder falling. Not only are the mechanical properties improved in this way, but the finely dispersed magnetic powder improves the squareness ratio and surface flatness! 1 degree, and characteristics such as high frequency output, S/N, and dropout are further improved.

In this way, it is possible to meet the recent demands for small-sized, high-density recording media in the audio and video fields.

EXAMPLES Next, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Particle size 0 in 150 mff of 0.01N Koji aqueous solution
．． 3μ, surface area 40r+ by BET method described below? /g
, 1Ic=1200, σs=150 emu/g
Add and disperse 2.5 g of iron-based metal magnetic powder, and add 0.0 g to this dispersion. Titration was carried out with a standard IN hydrochloric acid solution under a nitrogen atmosphere. Further, the above KO11 aqueous solution was titrated with the above standard hydrochloric acid solution.

The intersection point (zero charge point) was determined from these titration curves. The pH value of this zero charge point "C" was 6.0.

130 g of the same metal magnetic powder was mixed with 5 g of the salt (1) of the exemplified compound of the alkyldiamine derivative represented by the above general formula.
and 4g of phenoxy resin to cycloxanone 250g
6 g of alumina was added and mixed into the solution dissolved in the above solution, and the mixture was dispersed in a Sun 1' mill for 4 hours.

Next, 10 g of polyurethane, 0.0 g of butyl stearate.
A solution of 0.5 g of myristic acid and 0.1 g of myristic acid dissolved in a mixed solvent of 10 g of Cylcohexanone and 100 g of tetrahydrofuran was mixed with the above dispersion, and further dispersed in a sand mill for 1 hour. 3 g of Coronate L as a hardening agent was added to this dispersion L+1 and mixed with stirring to prepare a paint.

This paint was applied to a base film of ``poly] diethylene terephthalate'' under an orienting magnetic field, further dried, and the dried material was calendered, and 1/2
The test tape of this example was prepared by cutting it into an inch width.

Examples 2 to 10 In Example 1, a salt of a compound represented by the above general formula (
Salts (2) to (10) of compounds of this general formula in place of 1)
) Test tapes of Examples 2 to 10 were obtained in the same manner as in Example 1, except that each of the test tapes was used.

Examples 11 to 20 Implemented except that iron-based metal magnetic powder with a Pit value of 6.8, which was prepared in the same manner as in Example 1, was used instead of the magnetic powder with a circle value of 6.0 used in Example 1. The test tapes corresponding to Examples 11 to 20 were obtained by operating in the same manner as in Examples 1 to 1o and treating with eJ solution containing salts (1) to (10) of the compounds of the above general formulas, respectively.

Comparative Example 1-10 Salts (1) to ( Test tapes of Comparative Examples 1 to 1o, each treated with a dispersion containing 10), were obtained.

Comparative Examples 11 to 20 A circle prepared in the same manner as in Example 1 (for iron-based metal magnetic powder with a value of 9.0, the same operation as in Comparative Examples 1 to 10 was carried out, and the salt (1) of the compound of the above general formula was Test pieces of Comparative Examples 11 to 20 were obtained by treating with a dispersion containing each of (10) to (10).

The surface of the magnetic layer of the test pieces of these Examples and Comparative Examples was
Observe with a 0x optical microscope and see 5 levels of O! The degree of dispersion of the closest standard Ii & photograph compared with the standard dispersion photograph of χ is taken as the degree of dispersion of the magnetic layer of the test piece, and the measurement results are shown in Table 1 (5 is the best, 1 is the worst) graded). We also measured the magnetic properties of these specimens,
The squareness ratio was calculated and the results are shown in Table 2.

(Margins below this page) Table 1 (Margins below this page) Table 2 From these results, the degree of dispersion and squareness ratio are determined by the PH of the magnetic powder.
It can be seen that when 41 becomes 7 or less, the condition improves rapidly.

Example 21 Electrolyte (for example, 1Icj2 or Na0) in 100 mjl of water
ll) to prepare a solution with an appropriate pH value, add 0.02 g of iron-based metal magnetic powder to this, disperse it, measure the zeta potential using the above-mentioned normal method, and measure the zeta potential until the zeta potential becomes zero. When I calculated the 1 value of the equal weighted circle, it was 6.0. To 100 parts of the same iron-based magnetic powder (the following parts indicate parts by weight), exemplified compounds (5) and (6
) and a small amount of solvent were added and kneaded in a kneader for 2 hours. The kneaded material was transferred to a rotary vibration dryer to evaporate the solvent, and the magnetic powder was further loosened in a colloid mill and classified through a mensch sieve to obtain surface-treated magnetic powder with a BET value of 40 rrr/g. .

Then, the following composition was prepared using this treated magnetic powder.

Above treated iron-based metal magnetic powder 100 parts Nisoborane 23
04 (Polyurekne resin manufactured by Nippon Polyurethane Co., Ltd.) 1
4 parts PKII11 (Phenoxy resin manufactured by Union Carbide) 6 parts Conductenx 975 (BET value 270 rd/g
Particle size 4 Particle size 4 Ken Laben 2000 (BET value 180 rt/g, particle size 19 mμ) 2.5 parts Lecithin o, 5 t++- Myristic acid 2.0 parts Palmitic acid butyl ester 1. o part alumina
4.0 parts Methyl ethyl ketone 50 parts Cyclohexanone 100 parts This composition was dispersed in a sand mill. At this time, samples are taken at regular intervals and applied to a glass plate.
The degree of dispersion was compared with that of quasi-plate III under a 100x microscope to determine the end point of dispersion. Then, 5 g 1% of Coronate 1 (manufactured by Nippon Polyurekun θ1) as a polyfunctional isocyanate as a curing agent was mixed into this composition, and the mixture was filtered through a filter with an average pore size of 1 μm to obtain a magnetic paint. This magnetic paint was applied onto a 14 μm thick polyester film using a reverse roll coater in a magnetic field and subsequently dried. The dry film thickness of the obtained magnetic layer was 6
It was μm. After that, a surface treatment was carried out to make the magnetic layer flat with a super calendar roll to obtain a wide magnetic film.This film was cut into 1/2 inch width and used as a test magnetic tape for video. It was created.

Example 22 In Example 21, iron-based metal magnetic powder having a pH value of 6.5 at the iso-point was used, and instead of the salts represented by the above general formula (5) and 6), the salts of the salts ( A test magnetic tape for video tape having a magnetic layer having the same film thickness as that of this example was prepared by operating in the same manner as in this example except that 6) was used.

Comparative Example 21 In Example 21, CIBI+37NII (C112) NowNI was used instead of the salt of the compound represented by the above general formula.
Test I was performed in the same manner as in this example except that +2 was used.
- Created magnetic tape.

Comparative Example 22 A magnetic test was carried out in the same manner as in Example 21 except that the salt of the compound represented by the above general formula was not used and the magnetic powder was not surface-treated.Comparative Example 23 In Example 21 The same procedure as in this example was carried out, except that 3 g of salt (5) of the exemplary compound represented by the above general formula was added to 100 g of iron-based metal magnetic powder using a saw having a pH value of 9 at the iso-point. A test magnetic tape was obtained by operation.

Comparative Example 24 In Example 21, instead of the iron-based metal magnetism (1Ic = 1100), the yen 1 value was 8.0 and Ilc = 1000.
A test magnetic tape of this comparative example was obtained in the same manner as in this example except that lecithin was used in place of the iron-based metal magnetic powder and the exemplified compound carrier (5) represented by the above general formula.

Above Example 21.22, Comparative Example 21.22.23.24
The squareness ratio, gloss, and video characteristics of the magnetic tape were measured, and the results are shown in Table 3.

Table 3: If the degree of dispersion of the magnetic powder is high, the surface of the magnetic layer will be smooth and its gloss will increase, so by measuring this, the degree of dispersion of the magnetic powder can be determined.

From these tables, Examples 21.22 and Comparative Examples 21 to 24
It can be seen that the squareness ratio and gloss are superior to that of .

The specific surface area was measured by the BET method described below, and each test tape was prepared in the same manner as in Example 21 or Comparative Example 21, except that several types of total magnetic powders with different specific surface areas were used. The results of measuring the video S/N for these test tapes are shown in Figure 2. Figures in the figure are for the present example, and B is for the comparative example.

From Figure 2, it is clear that the specific surface area of the metal magnetic powder has a large effect on the video S/N, and the video S/N of the test tape based on the present invention is significantly improved compared to the test tape of the comparative example. ” I can see that it is.

The above measurement method is as follows.

Gloss: Measure the intensity of incident light and reflected light at an angle of 60° with a variable angle photometer manufactured by Murakami Color Research Institute, and calculate the ratio, Comparative Example 2
A value of 1 is displayed as 100%. The larger the value, the better the surface smoothness.

The reproduction output of Video Characteristics 74 Mllz was measured, and the measured value of Comparative Example 21 was set as 0, and relative values to this were displayed. The same applies to video S/N and color S/N.

BET method: First, heat the magnetic powder at around 250'C for 30~
After heat-sensitive treatment for 60 minutes, the powder was degassed to remove the adsorbed substances, and then introduced into a measuring device, and nitrogen was added to the liquid nitrogen temperature with an initial pressure of 0.5 kg/m. Measurement is performed by adsorption at (-195°C).

This specific surface area (BET value) measuring device uses a hot water bath battery (
(2) and jointly manufactured by Yuasa Ionics fi1.
Use a particle measuring device (Canterthorpe).

A general explanation of specific surface area and its measurement method can be found in “
Powder measurement J (J, Fl, DAI, I, A day LLE
, co-authored by CLYDIEORR Jr., translated by others, published by Sangyo Toshosha), and also in the ``Chemistry Handbook''.
(Application Edition, pages 1170-1171, Nippon Kagaku Complete Edition, Kuzen, published April 30, 1966).

In addition, in the above-mentioned "Chemical Handbook", specific surface area is simply referred to as surface area (rr
r/g), which is the same as the specific surface area explained above.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of finding circle 1 of magnetic powder from the titration curve, Figure 2
Figure 3 is an explanatory diagram of calculating circle 1 of magnetism from the measurement of zeta potential, and Figure 3 is a video of the specific surface area of metal-based magnetic powder.
It is a graph showing the effect on. Fig. 1 Fig. 2 Fig. 3 Specific surface area (IT+2/9) Proceedings (self-proposal) October 1981 150 Commissioner of the Patent Office Kazuo Wakasugi 1, Indication of the case 1988 Patent Wi No. 174131 No. 2, Name of the invention Magnetic recording medium 3, Person making the amendment Relationship to the case Patent applicant 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo (127) Konishiroku Photo Industry Co., Ltd. Representative Nobuhiko Kawamoto 4, Agent Person 5. Date of amendment order Voluntary 6. Number of inventions increased by amendment None. 7. Target of amendment: “Detailed explanation of the invention in the specification.” 1. In line 5 of page 17 of the specification, “Appears in It can be easily seen from, for example, FIG. 3 that "A" in FIG. is an example of using untreated metal-based magnetic powder.'' . 2, Mei, Book 111, page 30, lines 16 and 17, ``
The sentence "to isocyanate-1 and active hydrogen compound" should be corrected to "There is an addition of isocyanate-1 and active hydrogen compound." 3. Details of Table 2 on page 44 of the specification, line 2 and line 4 of Th1.
At the top of the 6th and 8th lines, correct the words ``degree of dispersion'' as ``squareness ratio''. 4. 2nd line from the top of specification No. 50, 4 fi from the top of the same page
Correct "Figure 2" to "Figure 3" for l=j. JP-A-Sho GO-66316 (15)

Claims (1)

[Claims] (1) In a magnetic recording medium having a support and a magnetic layer, the magnetic layer contains a metal-based magnetic powder with a pH value of 7 or less in a binder together with at least one carboxylate salt of a compound represented by the following general formula. A magnetic recording medium characterized by containing dispersed . General formula % Formula % (In the formula, R represents a saturated or unsaturated alkyl group having 3 or more carbon atoms, and n represents a real number from 2 to 8)