JPS59154646A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a magnetic layer with superior surface smoothness and wear resistance by incorporating nonmagnetic oxide powder surface-coated with an isocyanate compound into a magnetic layer. CONSTITUTION:The surface of at least one kind of nonmagnetic oxide powder selected among aluminum oxide powder, chromium oxide powder and titanium oxide powder is coated with a compound having one isocyanate group in the molecule, and the surface-coated powder is incorporated into a magnetic layer consisting of dispersed magnetic powder and a binder. Said isocyanate compound is represented by one of chemical structural formulae (a)-(e) (where R is alkyl, preferably 12-18C alkyl). The amount of the isocyanate compound used is 0.2- 2pts.wt. per 100pts.wt. nonmagnetic oxide powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic tapes and other magnetic recording media, and an object of the present invention is to provide a recording medium whose magnetic layer has excellent wear resistance and surface smoothness.

In order to improve the wear resistance of the magnetic layer of magnetic tapes, etc., it is common practice to include hard non-magnetic oxide powder such as aluminum oxide or chromium oxide as a filler in the magnetic layer. There is.

This type of magnetic layer is formed by adding and mixing the above-mentioned oxide powder to a predetermined magnetic paint and applying the mixture onto a substrate. However, the above-mentioned oxide powder causes a microscopic reaction with the binder in the paint due to its strong surface activity, and the city magnetic conversion value is said to be careful not to deteriorate the surface condition of the formed magnetic layer and generate noise 4. There was also the issue of having undesirable effects on the subject. Furthermore, depending on the type of binder, it may gel during paint preparation, making it impossible to apply it onto the base, making it difficult to even manufacture magnetic recording media.

In order to solve the above problem, the inventors made extensive studies and found that the non-magnetic oxide powder used as the filler was treated in advance with a compound having one isocyanate group in the molecule, and then It was discovered that by mixing it with a paint and applying it on the base, good results could be obtained in preventing gelation of the paint and improving the abrasion resistance and surface properties of the magnetic layer formed, which led to the creation of this invention. It is something that

That is, the present invention provides aluminum oxide (Al
2O3) powder, chromium oxide (Cr2O3) powder, and titanium oxide (TiO2) powder. According to this, it is possible to obtain a direct recording medium in which the magnetic layer has excellent surface smoothness and wear resistance, and it is also possible to avoid problems such as gelation during the preparation of the magnetic paint.

The total amount of one or more of the aluminum oxide powder, chromium oxide powder and titanium oxide powder used in this invention is usually 01 to 20 parts by weight, preferably 01 to 20 parts by weight, based on 100 parts by weight of the magnetic powder. When added in an amount of 0.5 to 2 parts by weight, it can greatly improve the wear resistance of the magnetic layer, and its average particle size is generally 0.5 to 2 parts by weight.
It is about ~20μ. In addition, these oxide powders have remarkable surface activity if left untreated, and binders such as nitrocellulose will gel the magnetic paint, while binders that do not gel, such as vinyl chloride and butyral diameter Even when various binders are selected, the surface properties of the magnetic layer deteriorate, but when the surface of the oxide powder is coated with a compound having one isocyanate group in the molecule according to the present invention, the wear resistance is improved. All of the above-mentioned problems can be avoided without substantially impairing the improvement effect of .

Representative examples of the above isocyanate compounds include those having the following chemical structural formula.

In each of the above formulas, R is an alkyl group, preferably an alkyl group having 12 to 18 carbon atoms. If the number of carbon atoms is too small, it becomes volatile, which is unfavorable from a safety and health standpoint.If the number of carbon atoms becomes too large, the solubility in organic solvents will deteriorate, impairing the workability of coating the surface of non-magnetic oxide powder. .

In order to coat the surface of the non-magnetic oxide powder with this kind of isocyanate compound, the isocyanate compound is generally dissolved in a suitable volatile organic solvent, the oxide powder is added to this solution, and the mixture is heated using a homomixer or the like. It may be dried after stirring. Through the above stirring treatment, the hydroxyl groups, carboxyl groups, etc. on the surface of the non-magnetic oxide react with the isocyanate groups to form chemical bonds, thereby forming a strong surface coating layer of the isocyanate compound on the surface of the oxide. Ru. The specific amount may be generally 0.2 parts by weight or more and up to 2 parts by weight per 100 parts by weight of the non-magnetic oxide powder.

The magnetic recording medium of the present invention comprises adding and mixing non-magnetic oxide powder whose surface is coated with the isocyanate compound into a magnetic paint made by dispersing various magnetic powders in various binders, and
It can be obtained by applying this onto a base and drying it. As the above-mentioned magnetic powder and binder, any conventionally known ones can be used, and there are no particular limitations.

Examples of this invention will be described below. In the following, parts shall mean parts by weight.

Example 1 The isocyanate compound represented by the above chemical structural formula C (R=C16H31) was dissolved in cyclohexanone, alumina powder with a particle size of 1.0μ was added thereto, and the mixture was reacted at 60°C for 10 hours with stirring. After that, it was filtered and washed, and further dried at 80°C until the solvent was completely volatilized.

A magnetic paint was prepared using the alumina powder whose surface was coated with the isocyanate compound obtained in this manner according to the following formulation. The amount of isocyanate compound attached to the above alumina powder is 0.5 parts per 100 parts of alumina powder.
It was hot at the club.

80 parts of CO-containing γ-Fe2O3 powder 8 parts of nitrocellulose 10 parts of polyurethane Coronae L (polyfunctional low molecular weight isocyanate compound manufactured by Nippon Polyurethane Co., Ltd.) Surface coating 2 parts of alumina powder 125 parts of cyclohexanone 125 parts of toluene The magnetic tape of the present invention was prepared by applying the magnetic tape to a thickness of 4 μm on a polyester base film and cutting it to a predetermined width.

Comparative Example 1 A magnetic paint was prepared in the same manner as in Example 1, except that the surface of the alumina powder was not coated with an isocyanate compound. I couldn't.

Example 2 A magnetic paint was prepared using the surface-coated alumina powder obtained in Example 1 according to the following formulation.

80 parts of CO-containing γ-Fc2O3 powder 12 parts of hydroxyl group-containing vinyl chloride-vinyl acetate copolymer 1 part toluene 125 parts A magnetic tape of the present invention was prepared in the same manner as in Example 1 using the above magnetic paint.

Comparative Example 2 A magnetic paint was prepared with the same composition as in Example 2, except that untreated alumina powder whose surface was not coated with an isocyanate compound was used, and a magnetic tape was made from it.

Example 3 Chromium oxide powder whose surface was coated with an isocyanate compound was obtained in the same manner as in Example 1. The isocyanate compound used was the same as in Example 1, and the coating amount was 0.5 parts per 100 parts of chromium oxide powder. A magnetic paint was prepared in the same manner as in Example 2, except that this surface-coated chromium oxide powder was used in place of the surface-coated alumina powder of Example 2, and a magnetic tape was also made from it.

Comparative Example 3 A magnetic paint was prepared with the same composition as in Example 3, except that untreated chromium oxide powder whose surface was not coated with an isocyanate compound was used, and a magnetic tape was made from this.

Example 4 Titanium oxide powder whose surface was coated with an isocyanate compound was obtained in the same manner as in Example 1. The isocyanate compound used was the same as in Example 1, and the coating amount was 0.5 parts per 100 parts of titanium oxide powder. A magnetic paint was prepared in the same manner as in Example 2, except that surface-coated titanium oxide powder was used in place of the surface-coated alumina powder of Example 2, and a magnetic tape was also made from it.

Comparative Example 4 A magnetic paint was prepared with the same composition as in Example 4, except that untreated titanium oxide powder whose surface was not coated with an isocyanate compound was used, and a magnetic tape was made from this.

For each of the magnetic tapes of Examples 1 to 4 and Comparative Examples 2 to 4, the surface roughness of the magnetic layer (Talysurf stylus surface roughness meter: 0.08 mm cutoff), video C/N ratio (4MH
z) and durability (room-temperature steel regeneration time), the results were as shown in the following table.

As is clear from the above results, it can be seen that the magnetic recording medium of the present invention has excellent wear resistance and surface smoothness of the magnetic layer.

Claims (1)

[Claims] (1) Selected from aluminum oxide powder, chromium oxide powder, and titanium oxide powder whose surface is coated with a compound having one isocyanate group in the molecule in a magnetic layer made by dispersing and bonding magnetic powder with a binder. A magnetic recording medium comprising at least one non-magnetic oxide powder.