JPS59172128A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent durability and heat resistance by adding cobalt stearate into a magnetic coating contg. an isocyanate compd. and applying the coating on a magnetic body thereby forming a magnetic layer. CONSTITUTION:A magnetic coating contg. cobalt stearate, isocyante compd. and magnetic powder is coated on a base body. When the cobalt stearate is added into the magnetic coating contg. the isocyanate compd., the crosslinking reaction between the isocyanate compd. and a binder resin such as a vinyl chloride resin, polyester resin or the like having active hydrogen is much accelerated and the network cross-linking and bonding are quickly effected, by which the strength of the magnetic layer is improved and the wear resistance and heat resistance thereof are imprved. A trifunctional low mol.wt. isocyanate compd. or the like is preferable as the isocyanate compd., and if the other binder resin having active hydrogen is used in combination with isocyanate compd., the strength of the magnetic layer is improved by cross-linking and bonding. If the cobalt stearate is used in combination in this stage, the cross-linking reaction is much accelerated and therefore the strength of the magnetic layer is improved and the wear resistance of the magnetic layer and heat resistance is much improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium with excellent durability and heat resistance.

In general, magnetic recording media, which are made by coating a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components on a substrate such as a polyester film, come into violent sliding contact with magnetic heads, etc. during recording and playback. The magnetic layer is easily abraded (excellent durability with little abrasion is required).

In order to meet these demands, various improvements have been made to binder components. For example, a curing accelerator such as zinc stearate is added to a magnetic paint containing an isocyanate compound, and this curing accelerator is The wear resistance of the magnetic layer is improved by strengthening the strength of the magnetic layer.

However, by adding zinc stearate to the magnetic paint, the crosslinking reaction between the isocyanate compound and other binder components containing active hydrogen is promoted and the strength of the magnetic layer is improved, but it is still not sufficient. Moreover, since this zinc stearate does not have good oxidation stability, it cannot exhibit a sustained effect of promoting crosslinking reaction, and cannot sufficiently improve wear resistance and heat resistance.

The inventors conducted various studies in view of the current situation, and found that when cobalt stearate is added to a magnetic paint containing an isocyanate compound and coated on a substrate to form a magnetic layer, cobalt stearate The curing accelerating effect is superior to that of conventional zinc stearate, and this curing accelerating effect is sustained, so the crosslinking reaction of the isocyanate compound is quickly and sufficiently promoted, and the strength of the magnetic layer is sufficiently strengthened. The inventors have discovered that the abrasion resistance and heat resistance of the magnetic layer can be sufficiently improved, leading to the present invention.

The cobalt stearate used in this invention has a much better effect of promoting the crosslinking reaction between isocyanate compounds and other binder components containing active hydrogen than conventional zinc stearate, and therefore, this type of stearate When acid cobalt is added to a magnetic paint containing an isocyanate compound, the isocyanate compound and a binder containing active hydrogen such as vinyl chloride resin, polyester resin, polyurethane resin, polyvinyl acecool resin, cellulose resin, etc. The crosslinking reaction with the resin is further promoted, and these are quickly crosslinked into a network, thereby strengthening the strength of the magnetic layer and improving its abrasion resistance and heat resistance. In addition, this type of cobalt stearate has good compatibility with commonly used binder resins and has a sustained effect of promoting the crosslinking reaction, so it is well mixed into magnetic paints and is used to promote the crosslinking reaction. The promoting effect of is fully and sustainably exhibited, and the abrasion resistance and heat resistance of the magnetic layer are further improved. Such an effect is exhibited by adding 0.1% by weight or more of cobalt stearate to the total amount of the binder components, and the effect becomes more pronounced as the amount added increases, but it is less than 10% by weight.
If the amount is too large, it may bleed out onto the surface of the magnetic layer and deteriorate the electromagnetic characteristics, so the amount of cobalt stearate used is preferably within the range of 0.1 to 10% by weight based on the total amount of binder components. .

The isocyanate compound is not particularly limited as long as it has an isocyanate group; for example, 2.4
- Diisocyanate compounds such as tolylene diisocyanate, m-phenylene diisocyanate, 5-naphthalene diisocyanate, and trifunctional low molecular weight usually obtained by reacting 1 mole of triol with 3 moles of diisocyanate. Isocyanate compounds are preferably used, and when these isocyanate compounds and other binder resins containing active hydrogen are used together, they are crosslinked to strengthen the strength of the magnetic layer. When cobalt stearate is used in combination, the crosslinking reaction is further promoted, so the strength of the magnetic layer is further strengthened and the abrasion resistance and heat resistance of the magnetic layer are further improved. Specific examples of trifunctional low molecular weight isocyanate compounds include:
For example, Coronatoshi manufactured by Nippon Polyurethane Industries, Takenate D102 manufactured by Shikinichi Yakuhin Kogyo, Desmodur manufactured by Bayer, Lisbon N manufactured by Dainippon Ink and Chemicals.
Examples include X.

As the binder resin used in combination with the isocyanate compound, those normally used in manufacturing magnetic recording media are suitably used, including vinyl chloride resin, cellulose resin, polyurethane resin, and polyvinyl acecool. Binder resins having active hydrogen, such as polyester-based resins and polyester-based resins, are preferably used.

Examples of magnetic powder include r-Fe203 powder, Fe3O4 powder, Co-containing -Fe203 powder, Co-containing Fe3O4
In addition to powder, Cr O2 powder, Fe powder, Co powder, Fe
Various conventionally known magnetic powders such as metal powders such as -Nf powders are widely used.

In addition, examples of organic solvents include methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, 11
1-ethyl, tetrahydrofuran, dimethylformamide, etc. may be used alone or in combination of two or more.

In addition, various additives commonly used in magnetic paints,
For example, dispersants, lubricants, abrasives, antistatic agents, and the like may be optionally added.

Next, embodiments of the invention will be described.

Example I CO-containing Fe203 powder 80 parts by weight VA
G H (vinyl chloride 10-vinyl acetate-vinyl alcohol copolymer manufactured by U, C, C, Co., Ltd.) Vandenx T-5201 (Urethane elastomer manufactured by Nippon Ink Co., Ltd.) Coronate L (Nippon Polyurethane Co., Ltd. 2) trifunctional low molecular weight isocyanate compound) Cobalt stearate 1.0〃Methyl isobutyl ketone 50〃Toluene
50 This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint.
It was coated on a 2μ polyester base film to a coating thickness of 5μ. Then, after calendaring,
Magnetic tape was made by cutting it to a specified width.

Examples 2 to 4 Magnetic tapes were produced in the same manner as in Example 1, except that the amount of cobalt stearate used in the composition of the magnetic paint in Example 1 was changed as shown in Table 1 below.

Table 1 Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1, except that the same amount of zinc stearate was used in place of cobalt stearate in the composition of the magnetic paint in Example 1.

Regarding the magnetic tapes obtained in each example and comparative example,
Tested for heat resistance and abrasion resistance. 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 mm, and placing it in a constant temperature bath at 60°C and 80% RH for 48 hours. After storing the tape for an additional 24 hours at room temperature, the tape was unwound from the glass tube and the degree of adhesion between the tape layers was observed. The score was rated as (○) if it could not be loosened, (△) if it was slightly loosened, and (×) if it could not be loosened at all.

The wear resistance test was conducted by loading each magnetic tape into a tape recorder and running it 600 times at a running speed of about 4.8 ω/sec, and then measuring the output fluctuation.

Table 2 below shows the results.

As is clear from the upper table of Table 2, the magnetic tapes obtained in Examples 1 to 4 all had better heat resistance and smaller output fluctuations than the magnetic tape obtained in Comparative Example 1. It can be seen from the above that the magnetic recording medium obtained by the present invention has excellent durability and heat resistance11.

Patent applicant: Hitachi Maxell, Ltd. 146-

Claims (1)

[Claims] 1. A magnetic recording medium obtained by coating a substrate with a magnetic paint containing cobalt stearate, an isocyanate compound, and magnetic powder.