JPS60209925A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having an excellent magnetic characteristic and excellent wear resistance and durability by using a mixture composed of urethane-modified nitrocellulose, urethane resin and polyisocyanate as a binder for the magnetic recording medium and adding a prescribed amt. of chromium oxide into a magnetic coated film. CONSTITUTION:A mixture composed of urethane-modified nitrocellulose, polyurethane resin and polyisocyanate compd. is used as a binder in the magnetic recording medium formed with the magnetic coated film and chromium oxide powder is added into the magnetic coated film at 0.3-10wt% by the weight of the magnetic powder. Oxides such as for example, plate-like Ba-ferrite powder, gamma-Fe2O3 powder, Fe3O4 powder, Co-contg. gamma-Fe2O3 and metallic powder such as Fe-Ni powder are usable for the magnetic powder. Even if the urethane-modified nitrocellulose which is the constituting component for the binder is excessively added, bleeding or the like does not arise and therefore there are no troubles in practicable characteristics such as wear resistance, durability, etc.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in magnetic recording media.

[Technical background of the invention and its problems]

In order to improve the abrasion resistance of magnetic recording media, various studies have been conducted regarding the type of binder used in the magnetic coating film. For example, resins such as preurethane resins, epoxy resins, and vinyl chloride-vinyl acetate copolymer resins have been used as binders. However, these binders do not have sufficient dispersibility of magnetic powder, and the abrasion resistance, durability, runnability, etc. of the coating film are not necessarily satisfactory.

[Purpose of the invention]

The present invention aims to provide a magnetic recording medium that has good dispersibility of magnetic powder in a magnetic coating film, excellent magnetic properties, and excellent wear resistance and durability.

[Summary of the invention]

As a result of intensive research to solve the problems of conventional magnetic recording media, the present inventors used a mixture of urethane-modified nitrocellumose, urethane resin, and polyisocyanate as a binder, and oxidized the magnetic coating film. By adding a certain amount of chromium, it is possible to improve the dispersibility of magnetic powder without using any dispersant and improve electromagnetic conversion characteristics such as output and S, and it is also possible to create a magnetic powder with excellent wear resistance and durability. I found a recording medium.

Examples of the magnetic powder include plate-like Ba-ferrite powder, r-Fe2O powder, re, O4 powder, C
o-containing-Fe 20. Oxide such as powder or Fe-Ni
Metal powder such as powder and other conventionally known magnetic powder can be used.

Even if urethane-modified nitrocellulose, which is one of the constituent components of the binder, is added in excess, no lead or the like is generated, so there is no problem with practical properties such as abrasion resistance and durability. In addition, urethane resin, which is another component of the binder, generally has a large coefficient of dynamic friction and is considered to have problems with runnability, but with sufficient curing treatment and selection of lubricant, this problem is rarely a problem. .

The reason for limiting the amount of chromium oxide added is that if the amount is less than 0.5% by weight based on the magnetic powder, the wear resistance of the magnetic coating cannot be sufficiently improved; This is because if the amount exceeds 10% by weight, the head during reproduction and recording will be damaged.

[Embodiments of the invention]

The present invention will be explained in detail below.

Example 1 A mixture with the following composition? - After thorough mixing with Lumil, 4 parts by weight of a polyisocyanate compound was added and passed through the mouth to prepare a magnetic paint.

<Composition of the mixture> Platy Ha-7 elite magnetic powder 100 parts by weight chromium oxide powder 5 Urethane modified nitrocellulose 5' Urethane resin (
Average molecular weight: approx. 5 minutes) 151 Lubricant 1 1 Methyl ethyl ketone/toluene/silica 190 N chlorohexanone = t : i : t mixed solvent Next, the above magnetic paint was applied onto a 21 μm thick polyester film to a dry thickness of 4 μm. After coating and drying to form a magnetic coating film, the back surface was treated and cut into 1/2 inch width to prepare magnetic recording medium samples.

Examples 2 to 9 Magnetic paints were prepared in the same manner as in Example 1, except that the magnetic powder shown in the table below was used and the amount of chromium oxide powder added was changed, and these were further coated on a polyester film, dried, etc. Eight types of samples were prepared.

Therefore, the dynamic friction coefficient, steel durability, and S/N of the samples of Examples 1 to 9 were investigated.

The results are also listed in the same table.

As is clear from the above table, the magnetic recording medium of the present invention is superior in various properties such as the coefficient of dynamic friction.

Example 10 A plurality of magnetic recording medium samples were prepared in the same manner as in Example 1, except that the amount of chromium oxide added was varied.

When a wear resistance test was performed on each of the obtained samples, the characteristic diagram shown in the figure was obtained. In the abrasion resistance test, a magnetic recording tape of unit length is made into a loop and slid against a magnetic head for a unit time at a speed of 40 w'tIee, and the change in weight of the magnetic recording tape is measured, and the amount of wear of the magnetic coating is measured. Calculated. Similarly, the reduction in surface thickness (wear amount) of the magnetic head due to sliding of the magnetic recording tape with the magnetic head was measured and is also shown in the same figure. Note that A in the figure is a characteristic line showing the relationship between the amount of chromium oxide added and the amount of wear of the magnetic coating film of the magnetic recording tape.
B is a characteristic line showing the relationship between the amount of chromium oxide added and the amount of wear of the magnetic head.

As is clear from the figure, zero chromium oxide powder was added to the magnetic coating film.
．． By adding more than 3% by weight, the amount of abrasion of the magnetic coating film is reduced, and the maximum effect is obtained at about 12% by weight, and there is no change even if more than 12% by weight is added. On the other hand, as the amount of oxide powder increases, the amount of wear on the magnetic head increases.
When it exceeds % by weight, it tends to increase rapidly.

Further, when the amount of chromium oxide powder added is increased, the electromagnetic conversion characteristics are adversely affected, but when the amount added is up to 10% by weight, there is almost no adverse effect.

Therefore, the amount of chromium oxide powder added is 0 to the magnetic powder.
, 3 to lO weight -.

〔Effect of the invention〕

As detailed above, according to the magnetic recording medium of the present invention, it is possible to improve the dispersibility of the magnetic powder in the magnetic coating film, improve the electromagnetic conversion characteristics, and have remarkable effects such as improved abrasion resistance and durability. has.

[Brief explanation of drawings]

The figure is a characteristic diagram showing the relationship between the amount of chromium oxide powder added and the amount of wear of the magnetic coating film of a magnetic recording tape. Applicant's agent Patent attorney Suzue Takehiko Late Ishikrom #
East addition amount (tl-mu)

Claims (1)

[Claims] A magnetic recording medium in which a magnetic powder is dispersed in a binder and applied onto a substrate to form a magnetic coating film, in which a mixture of urethane-modified nitrocellulose, a polyurethane resin, and an I-lysocyanate compound is used as the binder, and 0.3 to 10% of the magnetic powder in the magnetic coating film.
A magnetic recording medium characterized in that a weight of chromium oxide powder is added.