JPH01253824A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of ferromagnetic powder by incorporating a specific compd. into a magnetic layer. CONSTITUTION:The keto acid amide expressed by the formula is incorporated into the magnetic layer which is provided on a nonmagnetic base and is formed by dispersing the ferromagnetic powder into a binder. In the formula, R, R' are a satd. or unsatd. hydrocarbon of 4-22C. The amt. of the keto acid amide to be used is 0.2-20pts.wt., more preferably 0.5-3pts.wt. per 100pts.wt. magnetic powder. The surface treatment of the ferromagnetic powder by the keto acid amide in place of incorporating the keto acid amid into a coating compd. of magnetic powder is more preferable. A silane coupling agent, titanium coupling agent and phosphate compd. may be used in combination as a surface treating agent in this case. The ratio of the binder to be compounded in the magnetic layer is 15-60pts.wt. per 100pts.wt. magnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having excellent magnetic powder dispersibility, surface smoothness, and electromagnetic conversion characteristics.

[Prior Art and Problems to be Solved by the Invention] Magnetic powder in magnetic recording media such as magnetic tapes and magnetic disks is required to have a high degree of dispersibility.

Magnetic recording media are generally manufactured by kneading magnetic powder, a binder, various additives, and solvents, and then uniformly coating a magnetic paint on a plastic film or sheet substrate and drying it. Then, a magnetic layer is applied. However, unless the magnetic powder in the magnetic paint is sufficiently dispersed and peptized to remove agglomerated particles, it is not possible to create a uniform and smooth magnetic layer with a high packing density.

Non-uniformity of the magnetic layer due to agglomerated particles of magnetic powder has a serious adverse effect on the electromagnetic conversion characteristics and magnetic properties of the magnetic tape. That is, it causes a decrease in output, an increase in noise, dropouts, etc. Additionally, if the adhesive force between the magnetic powder and the binder is weak, the magnetic powder may peel off from the magnetic coating layer (so-called "powder shedding") when the magnetic recording medium and the recording head or reproduction head slide. This easily occurs, and the coating surface becomes rough, impairing the durability of the magnetic recording medium.

In recent years, particularly advanced electrical properties have been required, and as a result, magnetic paints are required to have better dispersibility of ferromagnetic powder than ever before.

In addition, in order to improve the performance of magnetic recording media, iron powder with a smaller particle size (hereinafter referred to as metal powder) is being used in addition to the conventionally used iron oxide-based ferromagnetic powder. The smaller the particle size, the more difficult it becomes to disperse the particles uniformly in the magnetic layer, and the current situation is that a dispersant, a magnetic powder surface treatment agent, a dispersion technique, etc. are required for this purpose.

[Means to solve the problem]

The present inventors have arrived at the present invention as a result of intensive research into dispersion of ferromagnetic powder.

That is, the present invention provides a magnetic recording medium in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support. The present invention provides a magnetic recording medium characterized by containing a keto acid amide.

R' (n, p' represent a saturated or unsaturated hydrocarbon group having 4 to 22 carbon atoms.) The keto acid amide of the present invention can be obtained by, for example, reacting 1 mole of alkyl (or alkenyl) ketene dimer with 1 mole of jetanolamine. It can be obtained by

The amount of the keto acid amide used in the present invention is suitably 0.2 to 20 parts by weight, preferably 0.5 to 8 parts by weight, per 100 parts by weight of the ferromagnetic powder.

In order to incorporate these keto acid amides into the magnetic layer of a magnetic recording medium, they may be added as a component of the paint during the preparation of the magnetic paint, but it is necessary to treat the surface of the ferromagnetic powder with these keto acid amides in advance. , this processed ferromagnetic powder is used as a paint ~
It is preferable to prepare a paint by adding it as a component. To treat the surface, the above keto acid amide may be dissolved in a solvent and mixed and stirred with the ferromagnetic powder at room temperature or under heat.

The above-mentioned keto acid amide according to the present invention is thought to serve as a dispersing agent or a surface treatment agent for strongly n-poly powder, but silane coupling agents and titanium coupling agents that are usually used as such agents may also be used. Agents, phosphate ester compounds, etc. may be used in combination.

The magnetic powder used in the magnetic recording medium of the present invention includes fine needle-shaped T Fe 20 : l l Fe
x O4+ Metal oxides such as Cr 02, also Co
Adherence -FezO: +, C.

T-F processed like doped γ-Fe203
e203, metal powder, platelet-like barium ferrite and some of its Fe atoms are T I + Col Zn
Magnetic powder substituted with one or more types of lv, Nb, etc., Co.

Examples include ultrafine powders of metals or alloys such as Fe-Co and Fe-Ni, and the citric acid derivative according to the present invention has a particularly large dispersion effect on metal powders (iron powders).

In addition, examples of the binder used in the magnetic recording medium of the present invention include polyurethane, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyl
Nod resin, polyamide, polyacrylic ester, polymethacrylic ester, polyvinyl acetate, polyvinyl butyral, vinylidene chloride, vinylidene chloride copolymer,
Examples include nitrified cotton, maleic acid-modified vinyl chloride/vinyl acetate copolymer, and ethyl cellulose. These may be used alone or in combination of two or more.

Further, in order to adjust the hardness of the resin, a plasticizer or a hardening agent may be added.

Further, the amount of the binder blended is generally 15 to 60 parts by weight per 100 parts by weight of the magnetic powder.

In addition to the above-mentioned components, additives such as lubricants, abrasives, and antistatic agents commonly used in this field can be added to the magnetic layer of the magnetic recording medium of the present invention.

In addition, non-magnetic supports used in manufacturing the magnetic recording medium of the present invention include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; Vinyl chloride; polyimide; plastics such as aromatic polyamide; metals such as Al and Cu; paper, etc. are used. The form may be a film, tape, sheet, disk, card, drum, etc. Further, the surface of the support may be treated with corona discharge, radiation, ultraviolet light, etc., or may be precoated with a suitable resin.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

Note that "parts" in the examples are "parts by weight."

Example 1 Metal powder (
Specific surface area 53i/g, Hc: 14600e)
100 parts, 300 parts of toluene, R of the above general 2 (I),
Add 5 parts of a keto acid amide in which R' is rhohexyl, and add 8
The mixture was stirred at 0°C for 1 hour. Next, toluene was removed under reduced pressure to obtain surface-treated magnetic powder.

Next, a mixture containing each component shown in Table 1 was prepared using the treated powder, and the mixture was kneaded using a sand mill at 1200 rpm+ for 3 hours to obtain a magnetic paint. Apply this paint to a thickness of 36I
! 407 on polyethylene terephthalate film of m
The magnetic tape was applied using a No. m applicator, oriented in a magnetic field, dried, mirror-finished by calendering, and then cut into a predetermined width to obtain a magnetic tape. Regarding the magnetic tape, the squareness ratio (Br/Bs), reflectance (Gloss)
) and center line average roughness (Ra) were measured. The results are in the table-
Shown in 2.

Examples 2 to 5 In place of the keto acid amide used in Example 1, a keto acid amide represented by the general formula (I) with R and R' shown in Table 2 was used, and the method of Example 1 was followed. A magnetic paint was prepared and a magnetic tape was obtained. The squareness ratio, reflectance, and center line average roughness of these magnetic tapes were measured in the same manner as in Example 1.

The results are shown in Table-2.

Comparative Examples 1 to 3 Magnetic paints were prepared according to the method of Example 1, using the processing agents shown in Table 2 instead of the keto acid amide used in Example 1, and magnetic tapes were obtained.

The squareness ratio, reflectance, and center line average roughness of these magnetic tapes were measured in the same manner as in Example 1.

The results are shown in Table-2.

Table-1

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support, in which the following general formula (I) is present. 1. A magnetic recording medium containing the keto acid amide shown below. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [R and R' represent saturated or unsaturated hydrocarbon groups having 4 to 22 carbon atoms. 2. The magnetic recording medium according to claim 1, wherein the ferromagnetic powder is surface-treated with a keto acid amide represented by the general formula (I).