JPS6275930A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder and to obtain a magnetic recording medium having an excellent electromagnetic conversion characteristic by incorporating a fatty acid diglycidyl ester into a magnetic layer. CONSTITUTION:The fatty acid diglicidyl ester is incorporated into the magnetic layer of the magnetic recording medium. The fatty acid diglicidyl ester having an aliphat. hydrocarbon as the skeletal structure, glicidyl ester at the molecular terminal and <=1,000mol.wt. is preferably used as said ester. Said ester is preferably incorporated at 0.1-10wt% by the weight of the magnetic powder in the magnetic layer. One kind of such ester may be incorporated into the magnetic layer or >=2 kinds thereof may be used in combination or may be used in combination with other dispersants. The aliphat. hydrocarbon forming the skeleton of this kind of the glicidyl ester has lipophic property and has the good affinity to a binder resin (PVA, etc.) and improves the dispersibility of the magnetic powder in the binder resin. The magnetic recording medium having the excellent electromagnetic conversion characteristic is thus obtd.

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 in which magnetic powder has good dispersibility and excellent electromagnetic conversion characteristics.

[Conventional technology]

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
A material with excellent electromagnetic conversion characteristics and excellent durability is required.

Therefore, it is desirable that the magnetic powder used has excellent dispersibility and can provide excellent electromagnetic conversion characteristics for magnetic recording media, as well as improve durability. However, since the surface of magnetic powder is usually hydrophilic, it cannot be used as is. Difficult to disperse well in lipophilic binder components.

Therefore, in order to improve the dispersibility of magnetic powder, dispersants such as lecithin and sodium dioctyl succinate, which have a hydrophilic group at one end of the molecule and a lipophilic group at the other end, are used. (Unexamined Japanese Patent Publication No. 55-160332) [Problems to be Solved by the Invention] However, in the methods using these dispersants such as lecithin and dioctyl sodium succinate, the dispersibility of the magnetic powder is still insufficient. In particular, this type of dispersant has insufficient bonding force with the magnetic powder, so the dispersant easily separates from the magnetic powder, making it impossible to sufficiently improve the dispersibility of the magnetic powder.

[Means for solving problems]

This invention was made as a result of various studies to improve the drawbacks of the prior art, and by using fatty acid glycidyl ester as a separating agent, this kind of fatty acid glycidyl ester can be easily applied to the surface of magnetic powder. The dispersibility of the magnetic powder in the magnetic layer is sufficiently improved.

The fatty acid glycidyl ester used in this invention adheres well to the surface of the magnetic powder, and the aliphatic hydrocarbons constituting the skeleton of this type of fatty acid glycidyl ester are lipophilic and have no bond with the binder resin. Since the magnetic powder has a very good dispersibility in the binder resin, a magnetic recording medium with excellent electromagnetic characteristics can be obtained.

As such fatty acid glycidyl esters, fatty acid glycidyl esters having an aliphatic hydrocarbon skeleton structure and a glycidyl ester at the molecular end and a molecular weight of 1000 or less are preferably used. For example, fatty acid glycidyl esters represented by the following structural formula are preferably used. Esters are preferably used.

Glycidyl sorbate ester Glycidyl linoleate Glycidyl oleate As specific examples of commercially available fatty acid glycidyl esters, for example, Denacol EX manufactured by Nagase Kasei Co., Ltd.
-181 (glycidyl sorbate ester), Bunacol EX-1113 (mixture of glycidyl linoleate and glycidyl oleate), and the like.

Such fatty acid glycidyl esters can be added directly when preparing magnetic paints, or they can be dissolved in a suitable solvent such as alcohol, ketone, ether, etc., and magnetic powder can be immersed in the solution obtained by this dissolution. The surface of the magnetic powder is preliminarily treated, a magnetic paint is prepared using the magnetic powder, and the paint is coated onto a substrate and dried to be incorporated into the magnetic layer. The content in the magnetic layer is preferably within the range of 0.1 to 10% by weight based on the magnetic powder in the magnetic layer; if it is too small, the desired effect cannot be obtained, and if it is too large, It may bleed out and become sticky.

Any one of the fatty acid glycidyl esters thus contained in the magnetic layer may be used alone, but
Two or more types may be used in combination, and other dispersants such as saturated fatty acids, unsaturated fats V, fatty acid esters,
It may be used in combination with phosphoric acid esters, lecithin, metal soaps, alcohols, etc.

As the magnetic powder used in this invention, for example, 7
-Fe2O3 powder, Fe3O4 powder, intermediate compound powder between T-Fe203 powder and Ff330-4 powder, Co-containing r
-In addition to Fe203 powder, CO-containing Fe3O4 powder,
A wide variety of conventionally known magnetic powders are included, such as powder, CO powder, metal powder such as p6-Ni powder, and barium ferrite.

Examples of binder resins include polyvinyl chloride resins, vinyl chloride-vinyl acetate copolymers, cellulose resins, butyral resins, polyurethane resins, polyester resins, epoxy resins, polyether resins, Any conventionally widely used binder resin such as isocyanate 1 compound can be used.

Examples of organic solvents include ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and sulfoxide solvents such as dimethyl sulfoxide. , ether solvents such as tetrahydrofuran, dioxin, etc.
Solvents suitable for dissolving the binder resin used may be used alone or in combination without particular limitation.

In addition, various additives commonly used in magnetic paints,
For example, hot water agents, abrasives, antistatic agents, etc. may be added as appropriate.

〔Example〕

Next, embodiments of the invention will be described.

Example I CO-containing r-F 13203 powder 800 parts by weight VA
GI+ (USA+1.c, manufactured by c company, salt 120 vinylide-vinyl acetate-vinyl alcohol copolymer) Deconal EX-181 (manufactured by Naga 16 Se Kasei Co., Ltd.,
sorbic acid glycidyl ester) Methyl isobutyl ketone 400 l toluene
After mixing and dispersing the composition of 400〃-1- for 72 hours in a ball mill, Vandesox T-5201 (large 65 parts by weight, manufactured by Nippon Ink Kagaku Kogyo Co., Ltd., polyurethane resin), Coro Hakuto ■, (Nippon Boliureta 15〃 Trifunctional low molecular weight isocyanate compound (manufactured by N Kogyo Co., Ltd.) Methyl isobutyl ketone 150〃Toluene
150ッ was added and mixed and dispersed to prepare a magnetic paint. This magnetic paint was applied onto a 12 μm thick polyester film to a dry thickness of about 6 μm, dried, calendered, and then cut to a predetermined width to produce a magnetic tape.

Example 2 Co-containing 7 Fe2O3 powder 800 parts by weight Deconal EX-18116 Toluene 4000 // After dispersing the above components in a homomixer for 3 hours, drying and coating Deconal EX-181 on the surface of the magnetic powder. I let it happen. The Co-containing r-Fe203 powder thus obtained was used in the same amount in place of the Co-containing -Fe203 powder used in Example 1 in the composition of the magnetic paint in Example 1, and Deconal EX-181 A magnetic tape was produced in the same manner as in Example 1 except that .

Example 3 In the composition of the magnetic paint in Example 1, Bunacol EX-1113 (
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of linoleic acid glycidyl ester and oleic acid glycidyl ester (manufactured by Nagase Kasei Co., Ltd., a mixture of glycidyl linoleate and glycidyl oleate) was used.

Example 4 A magnetic tape was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the amount of Bunacol EX-[8] used was changed from 16 parts by weight to 0.5 parts by weight. .

Example 5 A magnetic tape was prepared in the same manner as in Example 1 except that the amount of Bunacol EX-181 used in the composition of the magnetic paint in Example 1 was changed from 16 parts by weight to 0.8 parts by weight. .

Example 6 A magnetic tape was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the amount of Bunacol EX-181 used was changed from 16 parts by weight to 4 parts by weight.

Example 7 A magnetic tape was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the amount of Bunacol EX-181 used was changed from 16 parts by weight to 40 parts by weight.

Example 8 A magnetic tape was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the amount of Bunacol EX-181 used was changed from 16 parts by weight to 80 parts by weight.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1, except that the same amount of lecithin was used in place of Bunacol EX-181 in the composition of the magnetic paint in Example 1.

Comparative Example 2 Same as Example 1 except that in the composition of the magnetic paint in Example 1, the same amount of Prenol B-18 (manufactured by Yoshimura Yuka Co., Ltd., sodium dialkyl sulfosuccinate) was used instead of Bunacol EX-181. and made magnetic tape.

The coercive force, residual magnetic flux density, and squareness of each magnetic tape obtained in each Example and each Comparative Example were measured. In addition, as electromagnetic conversion characteristics, sensitivity (33311z,
12.5KIIz ) and maximum undistorted output (33311
One z, 0. L) was measured.

The table below shows the results.

As is clear from the table, the magnetic tapes prepared in Examples 1 to 7 have better coercive force, residual magnetic flux density, square shape, sensitivity, and maximum All of the non-distorted outputs were high, which indicates that the magnetic recording medium obtained by the present invention has good dispersibility of magnetic powder and excellent electromagnetic properties.

Patent applicant: Hitachi Maxell, Ltd. -1chi9-

Claims (1)

[Claims] 1. Magnetic recording medium having a magnetic layer containing fatty acid glycidyl ester