JPH08102039A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To provide a satisfactory magnetic recording medium having high electromagnetic transducing characteristics and high mechanical strength. CONSTITUTION: Iron nitride powder having 160-210emu/g saturation magnetization σs, 1,500-2,000Oe coercive force Hc, an acicularity ratio of 5-15 and 0.05-0.15μm major axis size is used as magnetic powder and one to four kinds of binders selected from among a vinyl chloride copolymer, a vinyl chloride-vinyl acetate copolymer, polyester resin and urethane resin are used. These binders contain amino, methylol, carboxyl, acid amido, isocyanato, metallic sulfonate, phosphate, quat. ammonium salt, sulfobetaine and epoxy groups as functional groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium, and more particularly to a magnetic recording medium which has high electromagnetic conversion characteristics and good reliability.

[0002]

2. Description of the Related Art In order to increase the recording density of a magnetic recording medium, the magnetic characteristics are being improved. Therefore, it is well known that it is effective to use magnetic powder having high magnetic properties in order to improve the magnetic properties of the coating film of the medium.

However, magnetic powders having high magnetic properties, especially those having a high saturation magnetization σ _s , have a strong magnetic attraction between the magnetic powders and the dispersibility of the magnetic powders during the preparation of the magnetic coating is poor. Good dispersibility contributes to improved magnetic properties, improved reproduction output, and reduced noise level. In addition, resin is more adsorbed on the magnetic powder surface during the manufacturing process, increasing mechanical strength and increasing reliability. Will be improved. From the above, improving the dispersibility of magnetic powder having high magnetic characteristics improves both electromagnetic conversion characteristics and reliability, but it is not yet sufficient.

[0004]

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a good magnetic recording medium having high electromagnetic conversion characteristics and mechanical strength. Therefore, in a magnetic recording medium in which a magnetic layer is coated on a film-shaped support, the magnetic powder used for the magnetic layer is iron nitride-based and the saturation magnetization σ _s is 160 to 210 emu / g. , Holding power Hc is 1500
~ 2000 Oe, needle ratio 5 ~ 15, major axis length 0.05
To 0.15 μm, 1 to 4 kinds of vinyl chloride copolymer, vinyl chloride vinyl acetate copolymer, polyester resin and urethane resin are used as binders, and these binders have amino groups, methylol groups as functional groups, By containing a carboxyl group, an acid amide group, an isocyanate group, a sulfonate metal base, a phosphate group, a quaternary ammonium base, a sulfobetaine group, and an epoxy group, high electromagnetic conversion characteristics, storability, magnetic coating stability, Provided is a magnetic recording medium having a good magnetic layer surface property.

[0005]

EXAMPLES Examples of the magnetic recording medium according to the present invention will be described in detail below. In the magnetic recording medium of the present invention, iron nitride magnetic powder shown below is used for the magnetic layer.

[0006]

Embedded image

As the binder, vinyl chloride copolymer, vinyl chloride vinyl acetate copolymer, polyester resin and urethane resin are used, and these binders have functional groups such as amino group, methylol group, carboxyl group and acid amide group. By containing an isocyanate group, a metal sulfonate group, a phosphate group, a quaternary ammonium salt group, a sulfobetaine group, and an epoxy group, high electromagnetic conversion characteristics and good reliability are realized. In order to achieve high electromagnetic conversion characteristics, it is effective to use fine magnetic powder having high magnetic characteristics and to sufficiently disperse the magnetic particles, which results in good reliability of the medium.

The present invention proposes to use the above-mentioned iron nitride-based magnetic powder as the magnetic powder having high magnetic characteristics, but this shows a higher saturation magnetization amount than the widely used metal magnetic powder. And was effective in achieving good magnetic properties. For the composition of magnetic powder,

[0009]

[Chemical 1]

By adopting the above, high magnetic properties and good chemical stability are provided. Saturation magnetization of magnetic powder σ
_{When s} was 160 emu / g or less, the saturation magnetic flux density Bm of the magnetic layer after the medium was formed was not sufficient, and the electromagnetic conversion characteristics could not be satisfied. If the chemical stability of the magnetic powder is good, the saturation magnetization σ _s is 210 emu / g.
The above magnetic powder could not be produced.

If the acicular ratio of the magnetic powder is less than 5 μm, the orientation will be poor, the squareness ratio after mediumization will be low, and good electromagnetic conversion characteristics cannot be realized, and the acicular ratio will exceed 15. And the magnetic characteristics and electromagnetic conversion characteristics after being made into a medium were low. It is presumed that the cause of this is that it is difficult to disperse the magnetic powder in terms of shape and that the magnetic powder is destroyed.

If the major axis length of the magnetic powder is less than 0.05, it is difficult to improve the magnetic properties of the magnetic powder, and dispersion is also difficult, resulting in the magnetic layer after being made into a medium. The magnetic properties became low. The major axis length is 0.1
If it exceeds 5 μm, the reproduction output and C / N during recording / reproduction of a short wavelength signal are lowered.

The holding power Hc of the magnetic powder is 1500
If it is Oe or less, the reproduction output at the time of recording / reproduction of the short wavelength signal is low, and if it is 2000 Oe or more, the reproduction output at the time of recording / reproduction of the long wavelength signal is low, which further deteriorates the erasing rate.

When a magnetic coating material is prepared by using the above-mentioned magnetic powder to prepare a magnetic layer of a medium, a vinyl chloride copolymer, a vinyl chloride vinyl acetate copolymer, a polyester resin, a urethane resin is used as a binder. These binders contain amino groups, methylol groups, carboxyl groups, acid amide groups, isocyanate groups, sulfonate metal bases, phosphate groups, quaternary ammonium bases, sulfobetaine groups, and epoxy groups as functional groups. As a result, high electromagnetic conversion characteristics and good reliability were realized.

In the medium, the physical properties of the binder itself have a great influence on the physical properties of the medium itself, but the resin selected as the binder, the molecular weight, etc., are those which are suitable for the conditions of use of the medium. And is not particularly limited here.

The concentration of the functional group to be contained or which kind of functional group of one kind and how many kinds to be contained is determined by the medium manufacturing process,
It is determined depending on the conditions of using the medium and the chemical properties of other compositions.

Examples of the present invention will be specifically described below. The magnetic paint was produced with the following composition.

Magnetic powder 100 parts by weight Resin 1 A parts by weight Resin 2 B parts by weight Resin 3 C parts by weight Resin 4 D parts by weight α-alumina 2 parts by weight Carbon black 2 parts by weight Palmitic acid 2 parts by weight Isocyanate 3 parts by weight Cyclohexanone 100 parts by weight Part Methyl ethyl ketone 100 parts by weight

The above mixture was mixed and dispersed by a sand mill. The magnetic powder, the surfactant and the addition amount thereof are used in Table 1, Table 2, Table 3 and Table 4, respectively. In Table 2, a vinyl chloride / vinyl acetate copolymer is referred to as a vinyl chloride / vinyl acetate copolymer.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

The glossiness of the magnetic paints of Examples 1 to 16 and Comparative Examples 1 to 7 thus obtained during dispersion was measured, and the results are shown in Table 5.

[0025]

[Table 5]

Further, the dispersed coating material is applied on a polyester film having a thickness of 10 μm and slit to ½ inch to prepare a tape for D-3 format, which is D-3VT.
Input a 40MHz sine wave signal using R (Matsushita AJ-D350) and measure the playback output, and 20 ° C, 10%
The still resistance was measured under the following environment and the results are shown in Table 6.
Shown in

[0027]

[Table 6]

From the above evaluations, according to the examples of the magnetic recording medium according to the present invention, the gloss during dispersion is high, the reproduction output is high, and the still resistance is remarkably excellent. On the other hand, Comparative Examples 1 and 2 using the resin not containing the functional group of the present invention have low gloss during dispersion and low reproduction output. Further, the still resistance is remarkably inferior. Comparative Examples 3 to 7 use the metal magnetic powder, but the reproduction output is remarkably inferior.

From the above, according to the present invention, iron nitride type magnetic powder is used, and the resin containing the above functional group is used to greatly improve the dispersibility, and the reproduction output and the still resistance are good. A recording medium can be obtained.

[0030]

According to the magnetic recording medium of the present invention, it is possible to obtain a magnetic recording medium having high electromagnetic conversion characteristics, storability, stability of magnetic paint, and surface property of medium magnetic layer.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a film-shaped support coated with a magnetic layer, wherein the magnetic powder used in the magnetic layer is iron nitride and the saturation magnetization σ _s is 160-.
210 emu / g, holding power Hc 1500-2000 Oe,
The acicular ratio is 5 to 15, the major axis length is 0.05 to 0.15 μm, and the binder is 1 of vinyl chloride copolymer, vinyl chloride vinyl acetate copolymer, polyester resin and urethane resin.
.About.4 types, and these binders have functional groups such as amino groups, methylol groups, carboxyl groups, acid amide groups, isocyanate groups, metal sulfonate groups, phosphate groups, quaternary ammonium groups, sulfobetaine groups, and epoxy groups. A magnetic recording medium containing: