JPS59172149A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the surface smoothness of a magnetic layer and to improve a short wavelength recording characteristics in particular by incorporating the magnetic powder which is subjected to a surface treatment with copolymerized polyester resin having a specific compd. in one molecule into the magnetic layer. CONSTITUTION:Magnetic powder which is subjected to surface treatment with a copolymerized polyester resin having metallic salt comp. of sulfonic acid and nitrogen element-contg. compd. in one molecule is coated together with a binder resin on a base body. The copolymerized polyester resin having the metallic salt comp. of sulfonic acid and nitrogen element-contg. compd. in one molecular has an anionic metallic salt comp. of sulfonic acid and cationic nitrogen element-contg. compd. in one molecule and therefore even if the surface of the magnetic powder is alkaline or acidic, said resin sticks satisfactorily on the particle surface of the magnetic powder and forms a film without receiving adverse influence, by which the dispersibility and filling property of the magnetic powder are improved and the surface smoothness of the magnetic layer is improved. The short wavelength recording characteristic in particular is improved. Such copolymerized polyester resin is preferably used at 0.1-15wt% to the magnetic powder.

Description

Detailed Description of the Invention The present invention relates to a magnetic recording medium, and its objects are to provide excellent dispersibility and filling properties of magnetic powder, good surface smoothness of the magnetic layer, and particularly improved short wavelength recording characteristics. The objective is to provide a magnetic recording medium that is

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
The magnetic layer is required to have good surface smoothness, excellent electrical properties, and excellent durability.

Therefore, the magnetic powder used has excellent dispersibility, and the surface smoothness of the magnetic layer is good, making it possible to provide magnetic recording media with high sensitivity and high S.
It is desirable to have excellent electrical properties such as N ratio, as well as improved durability, but because conventional magnetic powders have a hydrophilic surface, it is difficult to disperse them well in hydrophobic binder components. However, the dispersibility of the magnetic powder is not sufficiently good and tends to aggregate easily.

Therefore, in order to improve the dispersibility of magnetic powder, methods such as treating magnetic powder with a dispersant such as lecithin have been carried out to improve the dispersibility of magnetic powder, but this is still insufficient. It is not satisfactory, and furthermore, there are problems such as a decrease in abrasion resistance when this type of dispersant is used.

The inventors conducted various studies in view of the current situation, and as a result, they surface-treated magnetic powder with a copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule. The inventors have discovered that when incorporated into the magnetic layer, the dispersibility and filling properties of the magnetic powder are sufficiently improved, the surface flat magnetic properties of the magnetic layer are further improved, and the short wavelength recording characteristics in particular are improved, and this invention has been achieved. reached.

The copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule used in this invention contains 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-
Sulfonic acid metal salt compounds such as sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, 2-sodium sulfo-1,4-butanediol, 2-potassium sulfo-L4-butanediol, and hexamethylene diamine, trimethylene Diamine, 6-amino-n-caproic acid, 2-amino-4so-caproic acid, ω-aminocaprylic acid, 4-amino-n-butyric acid, 2-hydroxyethyl-p-)luidine, p-aminohendiylhydrazide , 0-aminobenzyl alcohol, ethanolamine, 1110-diaminodecane, etc., and these are copolymerized singly or in combination of two or more.

To produce this resin, for example, acid components such as adipic acid, isophthalic acid, and terephthalic acid; glycol components such as ethylene glycol and neopentyl glycol;
Add a predetermined amount of a sulfonic acid metal salt compound such as 5-sodium sulfoisophthalic acid, a nitrogen element-containing compound such as hexamethylene diamine, etc. together with other necessary components, and perform an esterification reaction and a polycondensation reaction under reduced pressure. The esterification reaction and the polycondensation reaction may be carried out separately by charging them all at once or in any order.

This type of copolymerized polyester resin, which has a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule, has very good affinity with magnetic powder. Because it has a compound in one molecule, it adheres well to the particle surface of the magnetic powder to form a film without being adversely affected even if the surface of the magnetic powder is alkaline or acidic. The dispersibility and filling properties of the powder are sufficiently improved, the surface smoothness of the magnetic layer is also improved, and the short wavelength recording characteristics are particularly improved. As such copolymerized polyester resin,
Those with a relatively low molecular weight of 5,000 to 10,000 are preferably used; if the molecular weight is greater than 10,000, the adsorption ability for magnetic powder decreases as the viscosity increases, and the dispersibility and filling properties of the magnetic powder are not sufficiently improved. .

The surface treatment of magnetic powder with such a copolymerized polyester resin is performed by treating the copolymerized polyester resin containing the above-mentioned sulfonic acid metal salt compound and nitrogen element-containing compound in one molecule with an organic compound such as methyl isobutyl ketone, methyl ethyl ketone, benzene, or toluene. The magnetic powder is dissolved in a solvent, dispersed in the solution using an appropriate means such as a kneader, and then dried. The amount used is within the range of 0.1 to 15% by weight based on the magnetic powder,
It is preferable to use it within the range of 1 to 5% by weight; if it is too small, the desired effect cannot be obtained, and if it is too large, the surface smoothness of the magnetic layer will deteriorate.

Examples of the magnetic powder used in this invention include yF
e203 powder, Fe3O4 powder, CO containing r-Fe20
3 powder, Co-containing Fe3O4 powder, CrO2 powder, cobalt ferrite powder, barium ferrite powder, Fe powder, Co powder, Fe-Ni powder, Co-N1-P powder,
Co-Ni-Fe powder, Co-Ni-F e-B powder, Fe-Ni-Zn powder, Fe-Mn-Zn powder, F
Various conventionally known magnetic powders such as e-Co-N1-P powder and Ni-Co powder are widely included.

In addition, as the binder resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose resin,
Any conventionally widely used binder resin such as polyurethane resin or isocyanate compound can be used.

Examples of organic solvents include ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone, ethyl solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and sulfoxide solvents such as dimethyl sulfoxide. Yong? Solvents suitable for dissolving the binder resin used, such as ether solvents such as J, tetrahydrofuran, and dioxane, may be used alone or in combination of two or more without particular restriction.

In addition, various additives commonly used in magnetic paints,
For example, a dispersant, an A'lJ+ holding agent, an abrasive, an antistatic agent, etc. may be added as appropriate.

Next, embodiments of the invention will be described.

Example 1 0.4 mol of terephthalic acid and 0.4 mol of isophthalic acid were placed in a reaction vessel equipped with a thermometer, stirrer, compressor, and partial reflux condenser.
4 mol, adipine MO, 19 mol, ethylene glycol 0.49 mol, neopentyl glycol 0.49 mol,
0.01 mol of 5-sodium sulfoisophthalic acid and 0.02 mol of hexamethylene diamine were added, and further 0.01 mol of zinc acetate, 0.005 mol of sodium acetate and 0.01 mol of antimony trioxide were added to give a solution of 140-22
React at 0°C, then at 210-250°C, 1ml 11g
A polycondensation reaction was carried out under the following reduced pressure to produce a copolymerized polyester resin having a sodium sulfonate group and an amino group. The molecular weight of this copolymerized polyester resin material was 4,000. Using this copolymerized polyester resin, epitaxial type cobalt containing 600 parts by weight r
-Fe203 magnetic powder A copolymerized polyester resin having a sodium sulfonate group and a 12-amino group methyl isobutyl ketone 108 was mixed and dispersed in a Ni-Goo to perform surface treatment on the magnetic powder.

Cobalt-containing γ-Fe obtained by surface treatment in this way
The amount of copolyester resin having sodium sulfonate groups and amino groups deposited on 203 magnetic powder is 2
It was 0■/g. Using the thus obtained cobalt-containing γ-Fe203 magnetic powder, CO-containing 7-Fe2O3 magnetic 720 parts by weight powder Esresoku BLS (Made by Miki Kagaku 60, manufactured by Kogyo Co., Ltd.,
Polyvinyl butyral resin) Takelac E-5'51T 42 (Manufactured by Narita Pharmaceutical Co., Ltd., polyurethane elastomer) Desmod Shikaku Bayer 18μ, trifunctional low molecular weight isocyanate compound) Methyl isobutyl ketone 300 Toluene
A magnetic coating material was prepared by mixing and dispersing a mixture having a composition of 400% in a ball mill for about 78 hours. This magnetic paint was applied onto a polyester film with a thickness of 15μ so that the dry thickness was approximately 5μ, and dried.
After surface treatment, it was cut to a predetermined width to make magnetic tape.

Example 2 A copolymerized polyester resin having a sodium sulfonate group and an amino group with a molecular weight of 7,000 in Example 1 was produced, and this copolyester resin was used in place of the copolymerized polyester resin with a molecular weight of 4,000 used in Example 1. The cobalt-containing γ-Fe203 magnetic powder was surface-treated in the same manner as in Example 1 except that the same amount was used.
In place of the cobalt-containing r-Fe203 magnetic powder used in , the same amount of cobalt-containing r-Fe203 magnetic powder coated with 20 g/g of a copolymerized polyester resin having a sodium sulfonate group and an amino group with a molecular weight of 7000 was used. A magnetic tape was produced in the same manner as in Example 1 except for this.

Comparative Example 1 In the surface treatment of the cobalt-containing γ-Fe203 magnetic powder in Example 1, the same amount of lecithin was used in place of the copolymerized polyester resin having sodium sulfonate groups and amino groups. The cobalt-containing γ-Fe203 magnetic powder was subjected to surface treatment, and instead of the cobalt-containing γ-Fe203 magnetic powder used in Example 1, the cobalt-containing γ-Fe2 was coated with 20 μ/g of 11 lecithin.
A magnetic tape was made in the same manner as in Example 1 except that the same amount of 03 magnetic powder was used.

Comparative Example 2 The surface treatment of the cobalt-containing γ-176203 magnetic powder in Example 1 was omitted, and this cobalt-containing γ-Fe203
Cobalt-containing γ-Fe2 magnetic powder used in Example 1
A magnetic tape was made in the same manner as in Example 1 except that the same amount was used in place of No. 03 magnetic powder.

For the magnetic tapes obtained in each example and each comparative example, the surface roughness of the rectangular shape and magnetic layer was measured, the durability was further tested, and the output at each frequency was measured in order to investigate short wavelength recording characteristics. . The square shape was measured using a vibrating sample magnetometer with an applied magnetic field of 10 kG using the usual method, and the surface roughness was measured using a Tokyo Seimitsu stylus type surface roughness meter with a cutoff of 0.08 m.
The centerline average roughness was measured at m. The durability test was conducted by repeatedly running the obtained magnetic tape 3 times at a running speed of 4.75 cm/sec while slidingly contacting a Sendust head with a gap length of 0.3 μ, and observing the state of clogging of the magnetic head. Ta. Furthermore, the short wavelength recording characteristics are as follows: the running speed of the magnetic tape is 4
．． The non-bias saturated recording/reproducing behavior at a recording frequency of 30 to 80 Kllz at 75 cm/sec was determined using a gap length of 0.
Measurements were made using a 3μ Sendust head.

The table below shows the results.

4 As is clear from the table above, the magnetic tapes obtained in Examples 1 and 2 have higher squareness, lower surface roughness, and are more durable than the magnetic tapes obtained in Comparative Examples 1 and 2. often,
Furthermore, the short wavelength recording and reproducing output is high, and therefore the magnetic recording medium obtained by the present invention has excellent dispersibility and filling properties of magnetic powder, and good surface smoothness of the magnetic layer, and as a result, it has particularly short wavelength recording characteristics. It can be seen that the properties are improved and the durability is also improved.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] 1. A magnetic recording medium in which magnetic powder surface-treated with a copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule is coated on a substrate together with a binder resin.