JPS59172119A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the surface smoothness, heat resistance, solvent resistance and durability of a magnetic layer and to improve a short wavelength recording characteristic by using a copolymerized polyester resin having a specific compd. in one molecule and an isocyanate compd. in combination as a binder component. CONSTITUTION:A copolymerized polyester resin contg. a metallic salt of sulfonic acid and nitrogen element contg. compd. in one molecule and a vinyl chloride resin are incorporated as a binder component in a magnetic layer. The copolymerized polyester resin having the metallic salt of sulfonic acid and nitrogen element contg. compd. in one molecule has an anionic metallic salt of sulfonic acid and a cationic nitrogen element contg. compd. in one molecule and therefore the dispersibility and packability of magnetic powder are improved and the surface smoothness of the magnetic layer is improved, by which the short wavelength recording characteristic in particular is improved. If a trifunctional low-mol.wt. isocyanate compd. is further incorporated in the magnetic layer, said compd. generates cross-linking and bonding by reacting with the amino group in the copolymerized polyester resin and the OH group, etc. that the vinyl chloride resin has, thus contributing to an improvement in the resistance of the magnetic layer to wear, heat and solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and its purpose is to provide excellent dispersibility and filling properties of magnetic powder, and to improve surface smoothness, heat resistance, solvent resistance, and durability of the magnetic layer. in good condition,
In particular, it is an object of the present invention to provide a magnetic recording medium with improved short wavelength recording characteristics.

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 binder component used in this case has excellent dispersibility and filling properties of the magnetic powder, improves the smoothness of the surface of the magnetic layer, and provides the magnetic recording medium with excellent electrical properties such as a high S/N ratio. It is necessary to select a material that has excellent heat resistance, solvent resistance, and durability.In particular, it is necessary to select a material that has excellent heat resistance, solvent resistance, and durability.In particular, as in video tapes, the electrical properties of which depend greatly on the smoothness of the magnetic layer surface, and if the surface smoothness of the magnetic layer is poor, In magnetic recording media where the video signal-to-noise ratio is degraded, it is desirable to use a binder component that can improve the smoothness of the magnetic layer surface as much as possible.

For this reason, various research and developments have been conducted on binder resins.
For example, a copolyester resin containing a sulfonic acid metal base has been proposed as a material with excellent dispersibility and filling properties of magnetic powder.For example, Kakutani et al., Kobunshi Ronshu, Volume 2, 139 (1981) , Japanese Patent Publication No. 54-28
No. 603, JP-A-56-74830, etc.

However, copolymerized polyester resin containing this type of sulfonic acid metal base has a strong interaction with magnetic powder, so a large amount of adsorption occurs, and when used as a binder component in magnetic paint, the viscosity becomes extremely high. In addition, if the surface of the magnetic powder is alkaline, since this type of copolyester resin has an anionic sulfonate metal base,
Not only does the viscosity of the magnetic paint become even higher and the fluidity deteriorates, causing various problems when coating it on a substrate, but the dispersibility and filling properties of the magnetic powder are still insufficient, and the surface smoothness of the magnetic layer is affected. The properties of hardness, heat resistance, solvent resistance and durability are also not very good.

The inventors conducted various studies in view of the current situation and found that a copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule and a vinyl chloride resin were used in combination as binder components of the magnetic layer. Then, since the copolymerized polyester resin used contains an anionic sulfonic acid metal salt compound and a cationic nitrogen element-containing compound in one molecule, it is difficult to determine whether the surface of the magnetic powder used is alkaline or acidic. The fluidity of the magnetic paint is improved without increasing the viscosity of the magnetic paint, and the interaction with the magnetic powder is not too strong. The surface smoothness is also improved, and since the vinyl chloride resin used in combination has excellent dispersibility of the magnetic powder, the dispersibility of the magnetic powder is further improved. , because this trifunctional low molecular weight isocyanate compound crosslinks with the above-mentioned copolyester resin, vinyl chloride resin, etc.
Heat resistance, solvent resistance and abrasion resistance are further improved,
It was discovered that a magnetic recording medium having excellent heat resistance, solvent resistance, and durability as well as particularly excellent short wavelength recording characteristics can be obtained, and the present invention was completed.

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 sulfol-1,4-butanediol, 2-potassium sulfo-1,4-butanediol, and hexamethylene diamine, Trimethylenediamine, 6-amino-n-caproic acid, 2-amino-1so-caproic acid, ω-aminocaprylic acid, 4-amino-n-butyric acid, 2-hydroxyethyl-p-)luidine, p-aminobenzoyl It is obtained by copolymerizing compounds such as hydrazide, 0-aminobenzyl alcohol, ethanolamine, and 1,10-diaminodecane, 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 copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule differs from the conventional copolymerized polyester resin containing a sulfonic acid metal base, because it contains an anionic sulfonic acid metal salt compound. Because it contains a cationic nitrogen element-containing compound in one molecule, the magnetic paint will not become highly viscous and will not interact with the magnetic powder even if the surface of the magnetic powder is alkaline or acidic. Since the adsorption is moderate and not too strong, the dispersibility and filling properties of the magnetic powder are sufficiently improved, the surface smoothness of the magnetic layer is also improved, and short wavelength recording characteristics in particular are improved.

In addition, the vinyl chloride resin used in combination in this invention has good affinity with the magnetic powder and has excellent dispersibility of the magnetic powder. Therefore, when this vinyl chloride resin is used in combination, the dispersibility of the magnetic powder is further improved. The surface smoothness of the magnetic layer is also improved, and the short wavelength recording characteristics are further improved. Such vinyl chloride resins include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinyl propionate copolymer. Polymers, vinylidene chloride resins, etc. are preferably used,
As a specific example, for example, VY manufactured by U.C.C.
HH,VAGH1VMCH.

VYLF, S-LEC A, S-RESOC C, S-RESOC M1 S-RESOC CN, manufactured by Denki Kagaku Kogyo Co., Ltd., Ryuron QS-430, manufactured by Toyo Soda Co., Ltd.,
Examples include Luron QA-431 and Diofan 207D-C manufactured by Pardish.

The blending ratio of the copolyester resin containing the sulfonic acid metal salt compound and nitrogen element-containing compound in one molecule and the vinyl chloride resin varies depending on the type of vinyl chloride resin used, but the weight ratio The ratio of polyester resin to vinyl chloride resin is preferably within the range of 9:1 to 1:9, and even if the amount of the copolymerized polyester resin is too little or too much, the desired effect will not be obtained. do not have.

The trifunctional low molecular weight isocyanate compound used in combination with the above-mentioned copolyester resin and vinyl chloride resin is a compound having a trifunctional isocyanate group, which is usually obtained by reacting 1 mol of triol with 3 mol of diisocyanate. When these kinds of isocyanate compounds are used in combination, the isocyanate groups of these compounds can be used together with the amino groups and vinyl chloride in the copolyester resin containing the above-mentioned sulfonic acid metal salt compound and nitrogen element-containing compound in one molecule. Since it reacts with the OH groups of the resin to form strong crosslinking bonds, the abrasion resistance, heat resistance, and solvent resistance of the magnetic layer are further improved. The amount to be used varies depending on the type of vinyl chloride resin used, etc., but it is preferably used in the range of 1 to 40% by weight based on the total amount of the binder component.If the amount is less than 0.1% by weight, the wear resistance of the magnetic layer will be affected. However, the heat resistance and solvent resistance are not sufficiently improved, and if the amount exceeds 40% by weight, there will be too much crosslinking, making the magnetic layer hard and reducing the calendering effect in surface treatment. Specific examples of such trifunctional low molecular weight isocyanate compounds include Coronate L manufactured by Nippon Polyurethane Industries, Desmodur manufactured by Bayer, Takenate D manufactured by Narita Pharmaceutical Industries, Ltd.
102 and the like.

Examples of the magnetic powder used in this invention include 7-F
e2O3 powder, Fe3O4 powder, CO-containing -Fe20
3 powder, Fe3O4 powder with COO, CrO2 powder, Co
Ferrite powder, Ba ferrite powder, Fe powder, C
Various conventionally known magnetic powders such as metal powders such as O powder are widely included.

In addition, as the organic solvent, cyclohexanone, methyl ethyl ketone, tetrahydrofuran, dioxane, dimethylformamide, etc. may be used alone or in combination;
Alternatively, a mixed solvent of these solvents and methyl isobutyl ketone or toluene may be used.

The magnetic recording medium of the present invention may be manufactured according to a conventional method, for example, by forming a copolymer containing a magnetic powder, a sulfonic acid metal salt compound, and a nitrogen element-containing compound in one molecule on a substrate such as a polyester film. Spraying or roll coating with a magnetic paint containing a binder component made of polyester resin and vinyl chloride resin, or a binder component further added with a trifunctional low molecular weight isocyanate compound, an organic solvent, and other additives. It may be applied by any means and dried.

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 temperature needle, a stirrer, a compressor, and a partial reflux condenser.
4 mol, adipic acid 0.19 mol, ethylene glycol 0.49 mol, neopentyl glycol 0.49 mol,
0.02 mole of 5-sodium sulfoisophthalic acid and 0.02 mole of hexamethylene diamine were added, and 0.01 mole of zinc acetate, 0.005 mole of sodium acetate 11, and 0.01 mole of antimony trioxide were added to give a solution of 140 to 220 React at 210-2
A polycondensation reaction was carried out at 50° C. under a reduced pressure of ln+Hg or less to produce a copolymerized polyester resin having a sodium sulfonate group and an amino group. Using the copolymerized polyester resin obtained in this way, 600 parts by weight of epitaxial CO-containing oxidized iron magnetic powder (acicularity, long axis 0.2μ), a copolymer having a sodium sulfonate group and an 80% amino group were prepared. Polymerized polyester resin VAGH (United States, C, C, Co., Ltd., vinyl chloride-vinyl acetate-vinyl alcohol copolymer) Coronae) L (Nippon Polyurethane Co., Ltd., trifunctional low molecular weight isocyanate compound) Toluene A magnetic coating material was prepared by mixing and dispersing a mixture of the following composition in a ball mill for 78 hours. This magnetic paint was applied onto a polyester film with a thickness of 15 μm to a dry thickness of 5 μm, dried, surface treated, and then cut into a predetermined size to produce a magnetic tape.

Example 2 In the composition of the magnetic paint in Example 1, Coronae)
A magnetic tape was produced in the same manner as in Example 1 except that the amount of L used was changed from 10 parts by weight to 5 parts by weight.

Example 3 Example 1 except that in the composition of the magnetic paint in Example 1, Coronate L was omitted and the amount of the copolyester resin having a sodium sulfonate group and an amino group was changed from 80 parts by weight to 90 parts by weight. I made magnetic tape in the same way.

Comparative Example 1 A copolyester resin having only sodium sulfonate groups was produced in the same manner as in Example 1, except that 4 parts of hexamethylene diamine were omitted, and the same amount of this copolyester resin was used. A magnetic tape was made in the same manner as in Example 1.

In each of the Examples and Comparative Examples, the viscosity of the magnetic paint used in making the magnetic tape was measured. In addition, for the magnetic tapes obtained in each example and comparative example, the surface roughness of the magnetic layer was measured, and the heat resistance, solvent resistance, and durability were tested, and the output at each frequency was examined to investigate short wavelength recording characteristics. was measured. The viscosity of the magnetic paint was measured at 30° C. using an E-type viscosity needle manufactured by Tokyo Keiki Co., Ltd. The shear rate at this time is
The viscosity was determined in mPa-s at 38.4 sec''4.The surface roughness was measured using a stylus type surface roughness meter manufactured by Tokyo Seimitsu Co., Ltd., and the center line average roughness was measured at a cutoff of 0.080. did.

Furthermore, the heat resistance test was performed by cutting the obtained magnetic tape into a length of 1.5 m, applying a load of 1 kg, wrapping it around a glass tube with a diameter of 36 m1, and placing it in a constant temperature bath at 60°C and 80% R11 for 48 hours. After storing the tape for 24 hours at room temperature, the tape was unwound from the glass tube and the degree of adhesion between the tape layers was observed. If no adhesion was observed, the score was 0.
The case where some adhesion was observed was evaluated as (△), and the case where the adhesion could hardly be loosened was evaluated as (×). The solvent resistance test was conducted by rubbing the surface of the magnetic layer of each magnetic tape several times with tissue paper soaked in tetrahydrofuran and observing the state of the magnetic layer surface at that time. Goods were evaluated as (Δ) and bad as (×). Furthermore, a durability test was conducted on the obtained magnetic tape at 4.75cm/
The magnetic head was run 100 times at a running speed of 100 seconds while a Sendust head with a gap length of 0.3 μm was in sliding contact, and the state of clogging of the magnetic head was observed. In addition, the short wavelength recording characteristics are as follows: The running speed of the magnetic tape is 4.75 cm/sec.
The non-bias saturated recording and reproducing output at a recording frequency of 30 to 80KIIz was measured using a Sendust head with a gap length of 0.3μ.

The table below shows the results.

As is clear from the above table, the viscosity of the magnetic paints in Examples 1 to 3 is lower than that of the magnetic paint in Comparative Example 1, and the magnetic tapes obtained in Examples 1 to 3 are lower than those in Comparative Example 1. Compared to conventional magnetic tape, the surface roughness is small and the short wavelength recording/reproducing output is high.Furthermore, when an isocyanate compound is contained in the magnetic layer, it has good heat resistance, solvent resistance, and durability. The magnetic recording medium obtained has good fluidity of the magnetic paint, excellent dispersibility and filling properties of the magnetic powder, and good surface smoothness of the magnetic layer.As a result, short wavelength recording characteristics are particularly improved, and heat resistance is also improved. It can be seen that the solvent resistance and durability are also improved.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] 1. Magnetic recording medium having a magnetic layer containing a vinyl chloride resin and a copolymerized polyester resin having a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule as a binder component 2. Binder component The magnetic recording medium according to claim 1, further comprising a trifunctional low molecular weight isocyanate compound contained in the magnetic layer.