JPS58161133A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance dispersibility and surface smoothness, by incorporating a maleate type high mol.wt. surfactant into a magnetic layer. CONSTITUTION:A vinyl compound-maleate copolymer with 1,000-100,000mol.wt. represented by the formula (where R1 is a vinyl compound, R2 is Na or K, and n is an integer of 2-400) is incorporated into a magnetic layer consisting essentially of magnetic powder and a binder such as resin. The surfactant is incorporated into the magnetic layer by dissolving the surfactant in water, adding the magnetic powder to the soln., and carrying out surface treatment.

Description

Detailed Description of the Invention The present invention relates to a magnetic recording medium, and its object is to have a magnetic layer having excellent dispersibility and dispersion stability of magnetic powder, good surface smoothness, and excellent electrical properties. The purpose of this invention is to provide a magnetic recording medium.

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.

The reason for this is that the magnetic powder used has excellent dispersibility, and the surface smoothness of the magnetic layer is good, giving the magnetic recording medium excellent electrical properties such as a high I/R ratio and a high signal-to-noise ratio, as well as durability. However, conventional magnetic powders do not have sufficiently good dispersibility and tend to aggregate easily.

As a result of various studies conducted in view of the current situation, the present inventors and their colleagues found that the dispersibility and dispersion stability of the magnetic powder were sufficiently improved by incorporating a maleic #cyclic high molecular weight surfactant into the magnetic layer. It has been discovered that the surface smoothness of the material is further improved and the electrical characteristics are further improved, leading to the present invention.

Maleate-based polymer used in this invention
#The surfactant has the general formula (where R1 is a vinyl compound, R is Na or
has 11 losses between 2 and 400. ) and the vinyl compound represented by! Rhein # salt copolymers having a molecular weight of 1,000 to 100,000 are preferably used, and specific examples include Demol P, Demol ST, and Demol EP manufactured by Kao Soap Co., Ltd., which are represented by the following structural formulas.

Demol P (vinyl acetate-sodium maleate copolymer) Demol ST (styrene-sodium maleate copolymer) HC-C-CHs CH.

Demol EP (vinyl derivative-sodium maleate copolymer) This type of maleate-based high molecular weight surfactant is water-soluble and adheres well to the particle surface when it comes into contact with magnetic powder dispersed in an aqueous solution. The magnetic powder is then coated to form a film, and the dispersibility and dispersion stability of the magnetic powder are sufficiently improved, the surface smoothness of the magnetic layer is improved, and the electrical properties are further improved.

In order to incorporate such maleate-based high molecular weight surfactants into the magnetic layer, they can be dissolved in water, and dried magnetic powder can be added to this aqueous solution to perform surface treatment on the magnetic powder. Alternatively, an aqueous dispersion of magnetic powder that has been shaped and treated by mixing an aqueous solution of iron or other metal salts with an aqueous alkaline solution is used as it is, and in this aqueous dispersion, maleate thread polymer wrinkles are formed. The surface treatment of the magnetic powder is carried out by adding an activator, and after drying, the magnetic powder is used to prepare a magnetic paint. The amount used is preferably within the range of 0.1 to 10 times the magnetic powder. If it is too small, the desired effect will not 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 r-F
e, O1 powder, Fe 304 powder, Co-containing -Fe
203 powder, Co-containing Fe, 0. In addition to powder, Fe powder,
Various conventionally known magnetic powders such as metal powders such as Co powder and Fe-Ni powder are widely included.

In addition, as the binder resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, fiber double type 4!1
Any conventional binder resin such as resin, polyurethane resin, or isocyanate compound can be used. - Examples of +1 solvents include ketone thread solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl naton;
Ester solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as benzene, toluene and xylene sodium,
Solvents suitable for dissolving the binder resin used are particularly suitable, such as alcoholic solvents such as isopropyl alcohol, acid amide yarn solvents such as dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, and ethereal solvents such as tetrahydrofuran and dioxane. They may be used alone or in combination of two or more without any restriction.

In addition, various additives commonly used in magnetic paints,
For example, dispersants, lubricants, abrasives, antistatic agents, etc. may be added as appropriate.

Next, embodiments of the invention will be described.

Example 1 Acicular r-Fe, 0@magnetic powder 1800f sulfur cobal) (CO5O, 7H, O) 600 F
Sulfuric acid (FeS04.7H,O) 1800
F Caustic Soda 2128F Dispersion 181 containing the above components was reacted at 45° C. for 8 hours, then washed with water and treated. Then in the resulting slurry,
Demol P (maleate-based high molecular weight surfactant manufactured by Kao Soap Co., Ltd.)-10 (add 301 liters of an aqueous solution and
After time dispersion treatment, it is dried to form cobalt-containing r-Fel.
O1 magnetic powder was obtained. The obtained Kobalsi-containing r -Fe
, the amount of Demol P deposited on the 03 magnetic powder was 35 Mf.
/I was. Using the cobalt-containing r-Fe20.03 magnetic powder thus obtained, Co-containing r-Fe20. Magnetic powder 100 parts by weight (Demol P coating amount 35 Hf/f) VAGH (manufactured by U, C, C, USA, chloride 18 N
Vinyl-vinyl acetate-vinyl alcohol copolymer) Takelac E-5517 (Bu 1) 12 #Manufactured by Yakuhin Kogyo Co., Ltd., polyurethane elastomer) Desmodu A/L (manufactured by Pieera, 31 trifunctional low molecular weight incyanate compound) Lauric acid 2 〃Cyclohexanone 80 #Toluene
A magnetic paint was prepared by dispersing 80 g of the mixture in a ball mill for about 100 hours. Apply this magnetic paint on a 12μ thick polyester film &:
After coating and drying to a dry thickness of about 3 tones and surface treatment, the magnetic tape was cut to a predetermined width.

Example 2 Cobalt-containing r-Fe in Example 1, 0. In the surface treatment of the magnetic powder, cobalt-containing r-Fe , O, in powder was subjected to surface treatment, and instead of the cobalt-containing r -Fe, O, magnetic powder used in Example 1, a cobalt-containing r -Fe2O, magnetic powder coated with Demol ST at 35 Nf/f was used. A magnetic tape was produced in the same manner as in Example 1, except that the amount used was different.

Practical Example 3 In the surface treatment of the cobalt-containing r -Fe, 01 magnetic powder in Practical Example 1, Demol E was used instead of Demol P.
P (maleate-based polymer wrinkle surfactant manufactured by Kao Soap Co., Ltd.)
Cobalt-containing r-Fe, Os magnetic powder was surface-treated in the same manner as in Example 1 except that the same amount of cobal-F-containing γ-Fe20. A magnetic tape was produced in the same manner as in Example 1, except that the same amount of cobalt-containing r-Fe, 03 magnetic powder coated with Demol EP at 35 Mf/f was used in place of the magnetic powder.

Comparative Example Cobalt-containing γ-Fe, O, 'Ba powder was obtained in the same manner as in Example 1 except that the surface treatment of the cobalt-containing r -Fe2O, magnetic powder in Example 1 was omitted. A magnetic tape was prepared in the same manner as in Example 1, except that the same amount of cobalt-containing r -Fe2O magnetic powder was used in place of the cobalt-containing γ-Fe, 0° magnetic powder used in Example 1.

Regarding the magnetic tapes obtained in each example and comparative example,
The output at 15 KHz, DC noise, and surface roughness of the magnetic layer were measured. The surface roughness of the magnetic layer was measured using a stylus type surface roughness meter, and the numerical value of the surface roughness was expressed as a center line average (C, L, A').

The table below shows the results.

As is clear from the table above, the magnetic tapes obtained by the present invention (Examples 1 to 3) have higher output, lower DC noise, and lower surface roughness than conventional magnetic tapes (Comparative Examples). This indicates that the magnetic recording medium obtained by the present invention has excellent dispersibility of magnetic powder, good surface smoothness of the magnetic layer, and excellent electrical properties.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] i, magnetic recording tX body containing magnetic powder and maleate-based high molecular weight surfactant in the middle layer of the fiB layer;