JPS58159231A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium with small noise and high output by using metallic magnetic powder bundled by arranging >=2 needlelike particles having a specified specific surface area in a row in the same direction. CONSTITUTION:Metallic magnetic powder is applied to a substrate together with a binder resin to obtain a magnetic recording medium. At this time, metallic magnetic powder bundled by arranging >=2 needlelike particles having >=20m<2>/g specific surface area according to the BET method in a row in the same direction is used as the magnetic metallic powder. Thus, a magnetic recording medium with small noise, a high output level and superior electromagnetic conversion characteristics is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium using gold Ji11 magnetic powder as the magnetic powder, and its purpose is to provide an all-in-one recording medium with low noise and high output level electromagnetic conversion characteristics. Our goal is to provide the following.

Magnetic recording media are usually made by coating magnetic powder together with a binder resin on a substrate such as BoJ ester film to form a magnetic layer. There is peace of mind in selecting one that has excellent properties and can provide various excellent electromagnetic conversion characteristics such as high sensitivity and high S/N ratio to the magnetic recording medium.

For this reason, metal magnetic powders that have a much higher coercive force than oxide-based magnetic powders are used, or two types of magnetic powders with different characteristics are mixed and this mixed magnetic powder is used. Efforts have been made to improve the electromagnetic conversion characteristics, but satisfactorily results have not yet been obtained.

In view of the current situation, the present inventors conducted a seed blue study and found that a metal magnetic powder made by arranging two or more acicular particles having a specific surface area of 20 m''/1 or more in the same direction and forming a bundle according to the BET method. The present inventors have discovered that when used, a magnetic recording medium with sufficiently improved electromagnetic characteristics, low noise, and high output can be obtained, leading to the present invention.

The metal magnetic powder used in this invention is preferably a bundle of two or more acicular particles with a specific surface area of 20 m"71 or more as determined by the BET method, arranged in parallel in the same direction. If it is less than ``/I, the noise of the magnetic recording medium obtained using it will not be sufficiently reduced, so it is not preferable.

Furthermore, even if the specific surface area of the acicular particles is 20 wL"/1 or more, if the acicular particles are not bundled but individually separated, the coercive force will be about 1250 Oersted, and the squareness ratio (
σr/, , ) is about 0.51 to 0.53, and the magnetic recording medium obtained using this has a squareness ratio (''/Bin) of about 0.78, which reduces noise but reduces output. The level is not very large, and in the case where the acicular particles are condensed to the east, the coercive force is about 1250 The squareness ratio (Br/8m) of the magnetic recording medium obtained using this is
) is about 0.70, and the magnetic properties deteriorate. On the other hand, when two or more acicular particles with a specific surface area of 20 m"/F or more are bundled in parallel without condensation, the coercive force is about 1250L x 7F and the squareness ratio (σr, 'ys) is about 0.46 to 0.51, and the squareness ratio (Br/B[n) of the magnetic recording medium obtained using this is about 0.80, which reduces noise and outputs is roaring.

As described above, the metal magnetic powder used in this invention has a particle size of 1 m@ if it is a bundle of two or more acicular particles with a specific surface area of 20 s2/f or more according to the BET method, arranged in parallel in the same direction. Not particularly limited, for example, Fe powder, C
In addition to O powder, N1 powder, various alloy powders thereof, and metal magnetic powders made of iron containing elements such as AiCrxMnsSisZn, etc., various conventionally known Dankin W4 magnetic powders are widely included.

The magnetic recording medium of the present invention may be manufactured according to a conventional method. For example, the specific surface area according to the BET method is 20
A magnetic paint is prepared by mixing and dispersing metal magnetic powder in which two or more acicular particles of a”/f or more are arranged in parallel in the same direction and bundled together with a binder resin, an organic solvent, etc., and this magnetic paint is It may be applied onto an M body such as a polyester film by any means such as spraying or roll coating and dried.

As the binder resin used here, conventionally widely used binder resins such as vinyl chloride-vinyl acetate thread copolymer, polyvinyl butyral resin, fiber bulk resin, polyurethane resin, and insine compound are widely used. used.

Examples of organic solvents include ketone thread solvents such as methyl isobutylnaton, methyl ethyl ketone, and cyclohexanone; ester thread solvents such as ethyl acetate and butyl acetate; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; , tetrahydro-7, dimethylformamide, dimethyl sulfoxide, etc. may be used alone or in combination.

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

Next, the actual INN of this invention will be explained.

Example Corner M where two or more acicular particles are arranged in a bundle in the same direction
Various types of a-
Using Fe magnetic powder, α-Fe magnetic powder 80 parts by weight VAG
H (Kaikuni UC, Company C, chloride 14 1 vinyl-vinyl acetate-vinyl alcohol joint stock) Takelac E551T (trial chemical 5 parts by weight plus urethane pre-remer manufactured by the company) Coronate Nippon Polyurethane 11 ml Each magnetic coating material was prepared by mixing and dispersing a mixture of 60 liters of toluene and 60 liters of 1-methyl isobutyl ketone for 72 hours in a ball mill. Apply each of these magnetic paints to a thickness of 1
A large number of magnetic tapes were made by coating a 2μ polyester film to a dry thickness of 4 tones, drying, surface treatment, and cutting to a predetermined width.

Comparative Example 1 In the composition of the magnetic paint in the practical example, in place of the α-Fe magnetic powder used in the practical example, needle-shaped particles were scattered one by one and each square shape (σr/,,) was 051 or more. A large number of magnetic tapes were made in the same manner as in the example except that the same amount of various α-Fe magnetic powders having different specific surface areas measured by the BET method of acicular particles were used for each.

The noise level and angle II (Br/8m) of a large number of magnetic tapes obtained in Examples and Comparative Example 1 were measured, and the relationship between these and the specific surface area of α-Fe magnetic powder determined by the BET method was investigated. Figure #I1 is a graph showing the relationship between noise level and specific surface area. Both the magnetic tape obtained in Example and the magnetic tape obtained in Comparative Example 1 are shown by the same straight line A. It can be seen that it is preferable to use a material having a specific surface area of 20 V1 or more as determined by the BET method in order to make the value sufficiently small. In addition, Figure 12 is a graph showing the relationship between the square shape (Br/8m) and the specific surface area, where graph B shows Jiyusu and graph C shows Comparative Example 1.
shows. As is clear from these graphs B and C, the square type using α-Fe magnetic powder in which acicular particles are bundled (graph B) has a specific surface area of 20% compared to the conventional type (graph C). The value is higher at V1 or above, which indicates that the magnetic recording medium obtained by the present invention has excellent magnetic properties.

Comparative Example 2 In the composition of the magnetic paint in the example, instead of the α-Fe magnetic powder used in the example, each acicular particle was one by one, and the specific surface area by the BET method was 26 th"/f.
A magnetic tape was produced in the same manner as in the example except that the same amount of tt-Fe magnetic powder having an N-gonal shape (''/*s) of 0.52 was used.

In the actual example 1lIi, the specific surface area by BET method is 30 m
”/9 magnetic tape obtained using α-Fe magnetic powder, the specific surface area by BET method in Comparative Example 1 was 30f.
For the magnetic tape obtained using t%2/l of tt-Fe magnetic powder and the magnetic tape obtained with comparative fiI42, the maximum output level at 315 Hz (
M, 0. L), the saturated power level (S,L) and AC noise at 10 KHz were measured.

The maximum output level, saturated output level, and AC noise are expressed as comparative values based on those obtained in Comparative Example 2.

The to table is the result (′).

As is clear from the above table, the magnetic tape obtained by this invention (Example) is different from the conventional magnetic tape (Comparative Examples 1 and 2).
Compared to the AC noise, the AC noise is small and the output level is low. Therefore, according to the present invention, the noise is small and the output level is low! It is advantageous to be able to obtain a Mi magnetic recording medium with excellent magnetic conversion characteristics.

44. Brief description of the drawings Figure 1 shows the noise level of a magnetic tape obtained using the metal magnetic powder of this invention and the BE of the gold-magnetic powder used.
A diagram showing the relationship between the specific surface area and the specific surface area determined by the T method, and FIG. 2 is a w4 scale diagram of the isogonal shape and the specific surface area determined by the BET method of the metal magnetic powder used.

Claims (1)

[Claims] 1. In a recording medium in which a metal magnetic powder is coated on a substrate together with a binder resin, two or more acicular particles having a specific surface area of 20 s2/I or more by the BET method are arranged in the same direction as the metal magnetic powder. A magnetic recording medium characterized by using metal magnetic powder bundled in parallel.