JPH01192013A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder and to improve electromagnetic conversion characteristics as well as the durability of a coated film by incorporating a specific compd. into a magnetic layer. CONSTITUTION:A resin having a basic polar group in the molecule is used for the binder of the magnetic layer 2 of this magnetic recording medium. The compd. having >=1 groups having salt formability and >=1 groups having salt formability or coordination performance is incorporated into the magnetic layer 2. Such multifunctional low-molecular compd. intervenes between a binder resin and the magnetic powder or nonmagnetic powder and binds well thereto and, therefore, the dispersibility of the powder is greatly improved. The deterioration in the electromagnetic conversion characteristics is thereby prevented and the durability of the coated film is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and particularly relates to the dispersibility of magnetic powder and non-magnetic powder mixed in a magnetic layer or back coat layer. It is related to the improvement of

[Summary of the invention]

The present invention uses a resin having a basic polar group in its molecule as the binder for the magnetic layer or back coat layer constituting the magnetic recording medium, and furthermore, contains a group having salt-forming ability in the magnetic layer or back coat layer. By containing a compound having the above and one or more groups having salt-forming ability or coordination ability, it is possible to improve the dispersibility of magnetic powder and non-magnetic powder, reduce dropout, and improve deterioration of electromagnetic conversion characteristics. At the same time, the aim is to improve the durability of the coating film.

[Conventional technology Magnetic recording media are moving toward higher density recording year by year. Under these circumstances, in the magnetic layer, magnetic powder with an extremely fine particle size is highly dispersed in the binder resin, making the surface of the magnetic layer mirror-finished, improving the electromagnetic conversion characteristics, and at the same time improving the magnetic properties. There is a need to improve the durability of paint films.

In addition, in the back coat layer formed on the surface opposite to the magnetic layer forming surface of the magnetic recording medium, non-magnetic powder such as carbon having a fine particle size is highly dispersed, and the surface of the back surface is roughened. It is possible to improve the winding characteristics of a magnetic recording medium by controlling the degree of winding, improve the durability of the back surface to reduce dropouts and reduce the coefficient of friction, and furthermore, to prevent the non-magnetic support from being charged. There are demands to prevent the adhesion of dust due to charging, to improve running stability, and to reduce migration of lubricant in the magnetic layer.

In other words, in the above magnetic recording medium, it is important to know how well the powder such as magnetic powder or non-magnetic powder contained in the magnetic layer or back coat layer is dispersed in the paint. A very important issue is how to properly bind the body with the binder.

It is.

Conventionally, as a method to satisfy the above requirements, a so-called dispersant (for example, a surfactant) is added to the magnetic paint or back coat layer paint, and the hydrophilic groups of the surfactant and the hydrophilic groups of the powder are bonded. Furthermore, by bonding the lipophilic group of the surfactant with the lipophilic group in the binder, the powder and binder are bonded, improving durability and dispersibility of the powder. It is proposed to aim for. However, in this method, the lipophilic group of the dispersant has no polarity, so the bonding force with the binder is very weak, and the interfacial reinforcing function cannot be fully exerted.Also, in order to exert the interfacial reinforcing function, an excessive amount of the dispersing agent is used. When added, the binder becomes plasticized and the dispersant precipitates on the surface of the coating film, resulting in a significant lack of durability of the coating film.

In response to this, in recent years, a method of introducing a polar group into a binder has been proposed, and a technique has been proposed in which the binder has both the functions of a polymer, a dispersant, and an interface reinforcing agent. However, when attempting to introduce a polar group into the binder as described above and thereby reinforcing the interface with the powder, the hydrophilic group of the polar group causes steric hindrance due to the function of the binder as a polymer. In addition, various lubricants such as compounds with long-chain alkyl groups and fatty acids that are added to the paint for the purpose of improving durability may not be able to sufficiently adsorb to the hydrophilic groups on the powder surface, resulting in deterioration of dispersibility. If agents, dispersants, etc. are present, they will be preferentially adsorbed to the powder, which will hinder the adsorption of the binder that has a dispersion function, leading to problems such as deterioration of the dispersibility of the powder.

[Problem to be solved by the invention]

As mentioned above, in the field of magnetic recording media, there are various practical characteristics due to insufficient capacity of the binder used and the polar group added to it, and the relationship between the polar group and the surface characteristics of the powder. remains dissatisfied with.

Therefore, the present invention has been proposed in view of the above-mentioned conventional situation, and aims to improve the dispersibility of magnetic powder and non-magnetic powder and reduce the falling off, and to improve magnetic recording with excellent electromagnetic characteristics and durability. The purpose is to provide a medium.

[Means to solve the problem]

As a result of intensive research in order to achieve the above-mentioned object, the present inventor has discovered that powders such as magnetic powders or non-magnetic powders do not interact directly with binders having basic polar groups, but rather have salt-forming ability. One or more groups and one group having salt-forming ability or coordination ability
It has been found that the affinity between the powder and the binder is significantly improved by bonding via the compound having the above, and the dispersibility of the powder is dramatically improved.

The present invention has been made based on the above findings, and as shown in FIG. In the recording medium, the binder is a resin having a basic polar group in its molecule, and the magnetic layer (2) contains one or more groups having salt-forming ability and one or more groups having salt-forming ability or coordination ability. It is characterized by containing one or more compounds.

The present invention also provides a non-magnetic support (1
In a magnetic recording medium comprising a magnetic layer (12) on one surface of 1) and a back coat layer (13) mainly composed of non-magnetic powder and a binder on the other surface, the binder is a molecule. It is a resin having a basic polar group therein, and the back coat layer (13) contains a compound having one or more groups having salt-forming ability and one or more groups having salt-forming ability or coordination ability. It is characterized by this.

That is, in the present invention, a resin having a basic polar group is used as a binder for either the magnetic layer or the back coat layer, and one or more groups having salt-forming ability and a group having salt-forming ability or coordination ability are used. It is made by blending a compound having one or more of the following (hereinafter referred to as a polyfunctional low-molecular compound). Of course, in the case of a coating-type magnetic recording medium, both the magnetic layer and the back coat layer may have the above structure.

Here, the resin having a basic polar group constituting the magnetic layer paint or back coat layer paint of the magnetic recording medium is a resin that is usually used as a binder for this type of magnetic recording medium, and is as follows. Any material can be used as long as it has a basic polar group introduced therein. Furthermore, for example, a resin into which a basic polar group has been introduced may be used alone, a resin into which a basic polar group has been introduced and a resin without a polar group, or a resin into which a basic polar group has been introduced. Any combination of different resins can be used. In addition, in the combination of a resin into which a basic polar group has been introduced and a resin into which no polar group has been introduced,
It is necessary that a small amount of the resin into which the basic polar group has been introduced is combined (at a ratio of 10% or more).

Examples of such resins include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, Nil-
Acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane resin, polyfluoride vinyl chloride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative.

Bonding side resins include styrene-butadiene copolymers, polyester resins, phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, or mixtures thereof.

The basic polar groups introduced into these resins include (b)
Examples include primary amines (-NHl), secondary amines (;NH), and tertiary amines (N) introduced in the form of -NHClbCHt-;
It may also be introduced in the form of an ammonium salt.

Alternatively, it may be introduced in the form of a heterocycle such as the following.

Furthermore, it may be introduced in the form of a Schiff base (>C=N-) as shown in the following, or it may be introduced in the form of a diazo group (-N, N-). .

Any conventionally known method can be used to introduce the above-mentioned basic polar group. For example, a typical basic polar group such as tertiary amine or quaternary ammonium may be introduced into a condensation resin (for example, polyurethane). To introduce, (1) a method using a basic polar group-containing polyol, polyisocyanate, etc. as part of the chain extender, (ii) active hydrogen, etc. (e.g., hydroxyl group) remaining in the side chain or terminal of the condensation resin. For example, a method may be used in which a compound is modified using a compound having both a group capable of reacting with active hydrogen and a basic polar group in the molecule.

In addition, in order to introduce these polar groups into a copolymer resin such as a vinyl chloride resin, (iii) both a vinyl monomer such as vinyl chloride and a basic polar group having a copolymerizable double bond are added to the molecule. (1v) A method of introducing active hydrogen in advance and modifying it with a compound having both a group capable of reacting with active hydrogen and a basic polar group in the molecule, etc. It's fine.

In addition, the content of basic polar groups contained in the binder is 0.001 mmol to 1.0+mmol nog.
It is preferable that it is within the range of .

Further, as the powder used in the magnetic recording medium, magnetic powder is used for the magnetic layer, and non-magnetic powder is used for the back coat layer.

Here, examples of the magnetic powder used in the magnetic layer include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed as general FeOx, that is, magnetite (r-Fe103).

X-1,50), magnetite (Fes04.
= 1.33) and their solid solutions (FeOx, 1.3
3 < There are two types.

The above-mentioned ferromagnetic chromium dioxide may include CrO or RurS n *T for the purpose of improving coercive force.
It is possible to use a material to which at least one of O, Sb, Fe, Ti, V, Mn, etc. is added.

Examples of the ferromagnetic alloy powder include Fe, 'Co, and NL.

Fe-Co, Fe-Ni, Fe-Co-Ni, C.

-Ni, Fe-Go-B, Fe-Co-Cr-
B.

Mn-B1. Mn-Aj! , Fe-Co-V, etc. can be used, and AI, S
Metal components such as i, Ti, Cr, Mn, Cu, and Zn may be added.

On the other hand, non-magnetic powders added to the back coat layer include all kinds of carbon blacks such as contact black, channel black, roll black, disk black, furnace black, thermal black, lamp black, CaC0 powder, BaSO4 powder,
ZnO powder, α-Fe, 02 powder, T i O2 powder,
Am! ! No O, powder, Cr, O, powder, etc. 41! Examples include pigments. The particle size of the non-magnetic powder contained in the back coat layer is preferably about 0,000 μm to 1 μm, and the surface of the non-magnetic powder has been modified by oxidation treatment or the like. It may be.

In the magnetic recording medium of the present invention, the magnetic layer may be formed, for example, by dispersing the above-mentioned ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent, and applying a magnetic paint to the surface of the non-magnetic support. On the other hand, for the back coat layer, the non-magnetic powder described above is similarly dispersed in the basic polar group-containing binder, and this is dissolved in an organic solvent to prepare a back coat layer paint. It can be formed by coating on the opposite side. In the case of providing a back coat layer as described above, the magnetic layer may be formed by applying a magnetic paint as described above, or a ferromagnetic material may be non-deposited by means such as vacuum evaporation, ion blasting, sputtering, plating, etc. A magnetic layer may be formed by depositing it on a magnetic support.

Examples of organic solvents used in coating and forming the magnetic layer and Basokuko-1-FJ include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate. Ester types such as monoethyl ether, glycol ether types such as glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.
Aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as hexane and heptane, methylene chloride, ethylene chloride, and carbon tetrachloride.

Examples include chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene.

In the present invention, the above-mentioned binder having a basic polar group is interposed between the binder and powder such as magnetic powder or non-magnetic powder to increase the affinity between the binder and the powder. A polyfunctional low-molecular compound is blended into the magnetic layer or back coat layer as an additive to improve the dispersibility of the powder and strengthen the bond between the binder and the powder.

Here, the group having salt-forming ability constituting the polyfunctional low-molecular compound is a proton-donating acidic crater, and -CO
OH, -OH, -3R, -3O3H, -POJ□, -
Noll.

-CHo and the like. On the other hand, the group having coordination ability is a proton-accepting basic crater, and is -NHj.

-NH, -kure-1g-9-Koichi, etc. are mentioned.

Therefore, the polyfunctional low-molecular compound used in the present invention is a compound having two or more groups having salt-forming ability, or a compound having one or more groups having salt-forming ability and one group having coordination ability.
Compounds having the above-mentioned properties are listed. The most suitable one may be selected depending on the properties of the magnetic powder and non-magnetic powder; for example, the former is preferable when the surface of the powder is basic, and the latter is preferable when the surface of the powder is acidic. However, when the powder is, for example, a metal magnetic powder, the present invention is not limited to this, and good results can be obtained with any compound.

Specific examples of such polyfunctional low molecular weight compounds will be illustrated below.

First, oxyacids, which are compounds having one or more of each of one or more -coon and -OH, which are groups having salt-forming ability, are mentioned. The above-mentioned oxyacids include monobasic aliphatic oxyacids, dibasic aliphatic oxyacids, lactones of aliphatic oxyacids, and others. Specifically, monobasic acids of aliphatic oxyacids include glycolic acid, glyceric acid, lactic acid, 3-hydroxypropionic acid, α-hydroxyisobutyric acid, β-hydroxy-n-butyric acid, α-hydroxy- Iso-caproic acid, α-hydroxy-n-caprylic acid, α-hydroxy-butyric acid, 2,2-bis-hydroxymethylpropionic acid, oxyvaleric acid, oxylauric acid, oxymyristic acid, oxypalmitic acid, oxystearic acid , oxybehenic acid, etc., and examples of dibasic acids of aliphatic oxyacids include tartaric acid, malic acid, tartronic acid, dioxymyristic acid, dioxypalmitic acid, dioxystearic acid, trioxypalmitic acid, etc. Examples of the lactone include L-ascorbic acid. In addition, other oxyacids include gallic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid,
0-Hydroxybenzoic acid, parasorbic acid, ricinoleic acid, salicylic acid, oxyphenylacetic acid, protocatechuic acid, gentisic acid, α-resorcylic acid, β-resorcylic acid, T-resorcylic acid, orceric acid, caffeic acid, lamberic acid, 3 -Oxyphthalic acid and the like.

Next, polyhydric carboxylic acids, which are compounds having two or more monoCOOH, which is a group having salt-forming ability, in the molecule, can be mentioned.
Specific examples of the above-mentioned polyhydric carboxylic acids include -coon
Examples include dicarboxylic acid having two molecules of -Coon, tricarboxylic acid having three -Coon molecules, and tetracarboxylic acid having four -COOH molecules. Examples of the dicarboxylic acids include aliphatic saturated dicarboxylic acids such as Scheric acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, superric acid, azelaic acid, and sebacic acid;
Examples include aliphatic unsaturated dicarboxylic acids such as maleic acid and fumaric acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. Examples of the tricarboxylic acid include benzenetricarboxylic acid, and examples of the tetracarboxylic acid include benzenetetracarboxylic acid.

Furthermore, examples include aminocarboxylic acids, which are compounds each having one or more -000) groups having salt-forming ability and one or more amine groups having coordination ability in their molecules. Specific examples of the above aminocarboxylic acids include iminoniacetic acid (IDA),
Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NT^), uramyldiacetic acid (ODA), diethylenetriaminepentaacetic acid (DTPA), ethylene glycol bis(2-aminoethyl)etherdiaminetetraacetic acid (GEDT)
A) , triethylenetetraminehexaacetic acid (TTIIA)
, 1.2 cyclohexanediamine-N, N'-tetraacetic acid (CYDTA), β-aminoethylsulfonic acid-N,
N'-dual acid, β-aminoethylphosphonic acid-N,
In addition to N'-double acids, aliphatic aminocarboxylic acids include glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, cystine, methionine, aspartic acid, glutamic acid, lysine, arginine, and aromatic nuclei. Examples of aminocarboxylic acids include phenylalanine and tyrosine; examples of aminocarboxylic acids with heterocycles include histidine, tryptophan, proline, and oxyproline; furthermore, β-aminopropionic acid,
Examples include T-aminobutyric acid, anthranilic acid, --aminobenzoic acid, p-aminobenzoic acid, and the like.

Furthermore, as other polyfunctional low molecular weight compounds, ■-CO
A compound that has OH and -CIO in its molecule. For example, glyoxylic acid, formyl acetic acid, β-formylpropionic acid, β
Formyl acrylic acid, phthalic aldehyde, etc.

(2) Compounds having -〇〇 and -CHO in the molecule 0 For example, aldol, glycolaldehyde, salicylaldehyde, aldehyde-D-glucose, 4,6-dihyde, etc.

(2) Compounds containing -COOH and -5llhl (in the molecule. For example, β-aminoethylsulfonic acid, NN-diacetic acid, etc.).

(2) Compounds containing -Cool (and -PO3H!) in the molecule. For example, β-aminoethylphosphonic acid NN diacetic acid.

(2) Compounds containing two or more -NOH molecules in the molecule, e.g.

(2) Compounds having -NOH and -OH in the molecule 0 For example, salicyl atomoxime, 2.5 dihydroxyterephthalaldehyde oxime, etc.

Compound 0 having two ■-〇H in the molecule, e.g. ■-3H
A compound that has 1 and 10 in its molecule. For example, 2.3 dimercapto-1-propatur.

(2) A compound having -COOH and -SR in the molecule. For example, mercaptosuccinic acid, mercaptoacetic acid, β-mercaptopropionic acid, etc.

[Phase] Compound 0 having two -SH molecules in the molecule, such as dithioxalic acid.

etc.

In the polyfunctional low-molecular compound described above, if the nonpolar moiety such as an alkyl group is too large, the bonding force with the binder will decrease;
In addition, since the polyfunctional low-molecular compound itself does not function as a dispersant or lubricant, it is preferable that the number of carbon atoms is 9 or less. However, especially in the case of aromatic compounds, this There is no limit.

These polyfunctional low molecular compounds can be interposed between the powder and the binder by adding them when producing magnetic paint or back coat layer paint, or by adding magnetic powder or non-magnetic powder to the polyfunctional low molecular compound in advance. There is a method of surface treatment with a compound, and a method of forming a magnetic layer and then coating it from above. In the case of a magnetic layer, the amount of the polyfunctional low-molecular compound added is within the range of 0.05 to 5 parts by weight (expressed as 0.05 to 5 PHP, hereinafter the same) per 100 parts by weight of magnetic powder. It is preferably in the range of 0.3 to 3 PHP, more preferably in the range of 0.3 to 3 PHP, and in the case of a back coat layer, it is preferably in the range of 0.05 to 10 PHP with respect to the non-magnetic powder. More preferably, it is within the range of .3 to 5 PHP.

If the amount added is less than the above range, the effect of adding a polyfunctional low-molecular compound cannot be expected, and if the amount added is increased, the coating film becomes acidic and the corrosion resistance of the magnetic recording medium deteriorates. I will invite you.

In addition to the above-mentioned binder and various powders, the above-mentioned magnetic layer and back coat layer contain dispersants, lubricants, abrasives, antistatic agents, rust preventives, etc., which are usually used as additives for magnetic recording media. may be added. When adding these things, it is preferable to add them within a range that does not inhibit the effect of adding the polyfunctional low-molecular compound.

The material for the non-magnetic support forming the magnetic layer and back coat layer as described above may be any material that is normally used in this type of magnetic recording medium, such as polyethylene terephthalate. polyesters,
Polyolefins such as polyethylene and polypropylene,
Cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, polyamide, and polyamideimide, paper, aluminum,
Examples include metals such as copper, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon.The form of this non-magnetic support may be film, tape, sheet, disk, card, drum, etc. But it's okay.

[Effect]

The polyfunctional low-molecular-weight compound used in the present invention has at least one group having a salt-forming ability (proton-donating acidic crater) or a group having a coordination ability as a basic active site on the surface of the magnetic powder or non-magnetic powder.

In addition to bonding with acidic active sites, the other group with salt-forming ability coordinates with the basic polar group (especially proton-accepting nitrogen) of the binder resin. It has a remarkable effect on the dispersibility and interface reinforcement of magnetic powder or non-magnetic powder.

In addition, polyfunctional low-molecular compounds are adsorbed to the basic active sites on the surface of magnetic powder or non-magnetic powder, and the surface of the magnetic powder or non-magnetic powder is covered with proton-donating acidic craters. It prevents the adsorption of various additives containing oxygen-donating atomic groups to the powder, and as a result, the coating film is completed without losing dispersion stability or interfacial reinforcement, has high magnetic properties, and has a high surface gloss. A coating film with excellent durability is completed.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

First, an example of a magnetic layer will be shown.

Co-deposited r-FexOs on the blood spot 12 parts by weight (
Basic 1 surface area 30 m”/g) Binder (tertiary amine group 0.30 m mol/g 3
Polyurethane resin containing parts by weight) Solvent (methyl ethyl ketone) 26.7 parts by weight Lactic acid, which is a polyfunctional low-molecular compound, was added to the magnetic paint having the above composition, mixed in a ball mill for 24 hours, and then taken out through a filter. This magnetic paint was applied onto a polyethylene terephthalate film having a thickness of 12 μm so that the thickness after drying would be 5 μm, and after magnetic field orientation, the film was wound up. After calendaring this 1/
A sample tape was prepared by cutting into a 2-inch width.

2-59 In Example 1, the polyfunctional low-molecular-weight compound and the amount added thereof were replaced with those shown in Tables 1, 2, 3, and 4, and then samples were prepared in the same manner as in Example 1. A tape was made.

Comparison (2) Sample tapes were prepared in the same manner as in the examples except for the basic composition shown in Example 1, in which no polyfunctional low-molecular compound was added.

(Left below) Table 1 Table 2 Table 3 Table 4 For each sample tape produced as described above, gloss, powder removal, magnetic flux density Bes squareness Rs, coercive force H
e was measured. The above gloss uses a glossy needle with an incident angle of 75
The reflectance at a reflection angle of 75° was measured. In addition, powder falls off the head drum after running the shuttle 100 times for 60 minutes.
The amount of powder falling onto the guide pin etc. was visually observed, and a score of 0 was given for almost no powder falling, and a score of 15 was given for a large amount of falling powder. Furthermore, the magnetic properties were measured in a magnetic field of 2500 Gauss. The results are shown in Tables 5 to 8.

Table 5 Table 6 Table 7 Table 8 As is clear from Tables 5 to 8 above, by adding a polyfunctional low molecular weight compound to the magnetic layer, powder drop-off is greatly reduced, and magnetic recording The durability of the medium is improved, the magnetic properties and gloss are improved, and the electromagnetic conversion characteristics of the magnetic recording medium are improved.

Among oxyacids, tartaric acid, citric acid, glyceric acid, malic acid, glycolic acid, L-ascorbic acid, gallic acid, lin-hydroxybenzoic acid, tartronic acid, etc. are particularly effective in improving Carboxylic acids include maleic acid, isophthalic acid, benzenetricarboxylic acid, malonic acid, terephthalic acid, fumaric acid, succinic acid, benzenetetracarboxylic acid, etc.Aminocarboxylic 61 types include NTA, UOA, 5IDA, and EDT.
ASCYDTA, ? Examples include spartic acid.

Next, an example of a back coat layer will be shown.

Implementation ■ Average carbon (particle size 23 m μ, pH 2.5) 5 parts by weight activating agent (urethane containing 3.3 parts by weight of 0.3 mol of tertiary amine) Solvent (methyl ethyl ketone) 24.9 parts by weight polyfunctional low molecular compound ( Citric acid) 0.1 parts by weight The above composition was mixed in a ball mill for 24 hours, taken out through a filter, and this back coat layer paint was applied to the back side of a 12 μm thick polyethylene terephthalate film on which a magnetic layer had been formed in advance. The film was coated to a thickness of 2 μm, oriented in a magnetic field, and then wound up. This was calendered and cut into 1/2 inch width to produce sample tapes.

Implementation ■ Hunger The citric acid used as an additive in Example 60 was
A sample tape was prepared in the same manner as in Example 60, except that TA (trilotriacetic acid) was used.

A sample tape was prepared in the same manner as in Example 60 except that citric acid used as an additive in Example 60 was replaced with phthalic acid.

More than five implementation The carbon used in Example 60 had a particle size of 23 mμ.

A sample tape was prepared in the same manner as in Example 60 except that the pH was 6.0.

Daifune Madaramochi The carbon used in Example 61 had a particle size of 23 mμ.

A sample tape was prepared in the same manner as in Example 61 except that the pH was 6.0.

Actual situation ■ Casting The carbon used in Example 62 had a particle size of 23 mμ.

A sample tape was prepared in the same manner as in Example 62, except that the pH was 6.0.

1 Comparison ■1 The binder used in Example 63 was 0.05 m
s.

A sample tape was prepared in the same manner as in Example 63, except that urethane containing 1/g was used.

The binder used in Main Example 64 was
+wn.

A sample tape was prepared in the same manner as in Example 64, except that urethane containing 1/g was used.

The binder used in Example 65 was 13O, Na group 0.05
s ts.

A sample tape was prepared in the same manner as in Example 65, except that urethane containing 1/g was used.

Sample tape was prepared in the same manner as in Example 60, except that a blank composition containing no additives was used in Example 60.

Sample tape was prepared in the same manner as in Example 63, except that a blank composition without additives was used in Example 63.

Five Comparison Group 1 A sample tape was prepared in the same manner as in Example 2 except for using the blank composition to which no additives were added.

Gloss and powder falling were measured for each sample tape produced as described above. The reflectance of the above gloss was measured using a glossy needle at an incident angle of 45° and a reflection angle of 45°, and at an incident angle of 75° and a reflection angle of 759°.

In addition, for powder falling off, visually observe the amount of powder falling on the head drum, guide pins, etc. after running the shuttle 100 times for 60 minutes, and score 0 if there is almost no powder falling off, and 15 points if there is a large amount of falling powder. It was evaluated as

The results are shown in Table 9.

(Left below) Table 9 As is clear from the results in Table 9, adding a polyfunctional low-molecular compound to the back coat layer greatly reduces powder falling off and improves the durability of the magnetic recording medium. .

[Effects of the Invention] As is clear from the above explanation, the polyfunctional low-molecular compound interposes between the binder resin and the magnetic powder or non-magnetic powder and bonds well with them. It is possible to prevent adsorption of various additives such as additives to the powder, and to complete a coating film with high surface gloss and excellent strength without losing dispersion stability and interfacial reinforcing properties.

Therefore, by using this as the magnetic layer and back coat layer of a magnetic recording medium, a magnetic recording medium with excellent electromagnetic conversion characteristics and coating film durability can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a magnetic recording medium to which the present invention is applied. FIG. 2 is a schematic cross-sectional view showing another example of the configuration of a magnetic recording medium to which the present invention is applied. 1.11...Nonmagnetic support 2.12...Magnetic layer 13...Back coat layer Patent applicant Sony Corporation representative Patent attorney Kodo Kobo, Sakae Tamura - Masaru Sato Figure 2 Procedures ( Hoshosho (spontaneous) June 21, 1986

Claims (2)

[Claims] (1) In a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder on a non-magnetic support, the binder is a resin having a basic polar group in the molecule, and the binder is a resin having a basic polar group in the molecule, and A magnetic recording medium comprising a compound having one or more groups having salt-forming ability and one or more groups having salt-forming ability or coordination ability. (2) In a magnetic recording medium comprising a magnetic layer on one side of a non-magnetic support and a back coat layer mainly composed of non-magnetic powder and a binder on the other side, the binder is present in the molecule. The resin is a resin having a basic polar group, and is characterized in that the back coat layer contains a compound having one or more groups having a salt-forming ability and one or more groups having a salt-forming ability or a coordination ability. magnetic recording media.