JPS61133023A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve sufficiently the dispersibility of magnetic powder in a binder resin and to improve the electromagnetic transducing characteristic of the titled medium by incorporating isohydrosorbic acid into a magnetic layer along with magnetic powder. CONSTITUTION:Isohydrosorbic acid shown by the chemical formula CH3CH2CH2 CH=CHCOOH is directly added when a magnetic paint is prepared, or the acid is dissolved in an appropriate solvent such as alcohol and ether and the sol. obtained by the dissolution is added when the magnetic paint is prepared. Or magnetic powder is immersed into the soln. The magnetic powder is previously surface-treated, and used for preparing the magnetic paint. The paint is coated on a base body, and dried to incorporate the acid into the magnetic layer. The content of the isohydrosorbic acid in the magnetic layer isopreferably regulated to 0.1-10wt%, based on the magnetic powder. Various kinds of magnetic powder such as gamma-Fe2O3 powder, Fe3O4 powder, and Fe4N powder are used as the magnetic powder to be used.

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 electrical properties.

[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 electrical characteristics is required.

Therefore, it is desirable that the magnetic powder used has excellent dispersibility and can impart excellent electrical properties to the magnetic recording medium. However, since the surface of magnetic powder is usually hydrophilic, if it is used as it is, it will not be able to absorb the lipophilic binder resin. Difficult to disperse well in

Therefore, in order to improve the dispersibility of magnetic powder, it has been proposed to mix saturated or unsaturated fatty acids, which have a hydrophilic group at one end of the molecule and a lipophilic group at the other end, into the magnetic paint as a dispersant. (Special Publication No. 44-18221,
(Special Publication No. 58-9488).

[Problems that the invention attempts to solve]

However, with the method of mixing these saturated or unsaturated fatty acids into magnetic paint as a dispersant, the bonding force with the magnetic powder is still weak (and the dispersibility of the magnetic powder in the binder resin has not yet been sufficiently improved). I couldn't.

[Means for solving problems]

The present invention aims to find something more effective for dispersing magnetic powder in a binder resin. It was discovered that isohydrosorbate has particularly excellent dispersion ability, and by incorporating isohydrosorbate in the magnetic layer together with the magnetic powder, the dispersibility of the magnetic powder in the binder resin can be improved. This has been sufficiently improved and the electromagnetic conversion characteristics have been sufficiently improved.

It has not yet been clearly elucidated why isohydrosorbate has such remarkable dispersion ability, but considering its unique chemical structure, , Electron density is localized within the molecule, increasing polarizability, which increases functionality; and ■ Isohydrosorbate has 6 carbon atoms, so it has a moderate melting point and a good property. It is presumed that it is easy to mix into the binder resin in order to impart fluidity to the paint.

The isohydrosorbic acid used in this invention is
It is a compound represented by the chemical formula CH3CH2CH2CH=CHC00H, has a double bond, has a relatively small molecular weight, adheres well to the surface of magnetic powder, and is compatible with binder resin. Therefore, when this isohydrosorbate is contained in the magnetic layer, the dispersibility of the magnetic powder in the binder resin is sufficiently improved, and a magnetic recording medium with excellent electrical properties can be obtained.

Such isohydrosorbic acid can be added directly when preparing magnetic paint, or dissolved in a suitable solvent such as alcohol or ether, and the solution obtained by this dissolution can be added when preparing magnetic paint, or this Surface treatment of the magnetic powder is carried out in advance by immersing the magnetic powder in a solution, a magnetic paint is prepared using this magnetic powder, and it is incorporated into the magnetic layer by applying it onto a substrate and drying it. be done.

The content of such isohydrosorbic acid 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, and if it is too small, the desired effect may not be achieved. is not obtained, and if there is too much, there is a risk of bleed-out.

In addition to such isohydrosorbate, isohydrosorbate derivatives and isohydrosorbate metal salts may also be used to obtain the same effect. Further, the isohydrosorbate contained in the magnetic layer as described above may be used in combination with isohydrosorbate derivatives, isohydrosorbate metal salts, etc., and other dispersants such as saturated fatty acids, It may be used in combination with unsaturated fatty acids, fatty acid esters, phosphoric acid esters, lecithin, metal soaps, alcohols, etc.

Examples of the magnetic powder used in this invention include r-
Fe203 powder, Fe3O4 powder, intermediate compound powder of γ-Fe203 powder and Fe3O4 powder, CO-containing r-Fe
203 powder, CO-containing Fe3O4 powder, CrO2 powder, cx-p'e powder, co powder, Fe-Ni powder, F
A wide variety of conventionally known magnetic powders such as metal powders such as e4N powder are included.

In addition, conventional binder resins include vinyl chloride-vinyl acetate copolymers, cellulose resins, butyral resins, polyurethane resins, polyester resins, epoxy resins, polyether resins, and isocyanate compounds. Any of the binder resins listed above 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, dioxane, etc.
The solvent used to dissolve the binder resin is not particularly limited and may be used alone or in combination of two or more.

In addition, various additives commonly used in magnetic paints,
For example, a lubricant, an abrasive, an antistatic agent, etc. may be added as appropriate.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 7-Fe2O3 powder 800 parts by weight VAGH
(Manufactured by U, C, C, USA, salt 120 vinylide-vinyl acetate vinyl alcohol copolymer) Isohydrosorbate 16 Methyl isobutyl ketone 410 Toluene
410 After mixing and dispersing this composition in a ball mill for 72 hours, Takelac E-551T (Bu 1) 65μ manufactured by Yakuhin Kogyo Co., Ltd., polyurethane resin) Coronate L (manufactured by Nippon Polyurethane Co., Ltd.
A trifunctional low molecular weight isocyanate compound) was added to make a magnetic paint, and this was applied onto a polyester film with a thickness of 11 μm to a dry thickness of approximately 6 μm.
After drying and calendering, it was cut to a predetermined width and magnetic tape was attached.

Example 2 r-Fe203 powder 800g isohydrosorbic acid 20g ethanol
After dispersing 500 ml of the above ingredients in a homomixer for 5 hours, the powder particles were dried to coat 16 mg/g of isohydrosorbic acid on the surface of the powder particles.
-Fe2O3 powder was obtained, and this γ-Fe203 powder was used in the same amount in place of the r-Fe203 powder used in Example 1, and further, in the composition of the magnetic paint in Example 1,
A magnetic tape was prepared in the same manner as in Example 1 except that isohydrosorbic acid was omitted.

Example 3 A magnetic tape was produced in the same manner as in Example 1 except that the amount of isohydrosorbic acid used in the composition of the magnetic coating material in Example 1 was changed from 16 parts by weight to 4 parts by weight.

Example 4 A magnetic tape was produced in the same manner as in Example 1 except that the amount of isohydrosorbic acid used in the composition of the magnetic coating material in Example 1 was changed from 16 parts by weight to 40 parts by weight.

Example 5 Example 1 except that the composition of the magnetic paint in Example 1 was changed from 16 parts by weight to 8 parts by weight of isohydrosorbic acid and 8 parts by weight of lauric acid was added.
I made magnetic tape in the same way.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that isohydrosorbic acid was omitted from the composition of the magnetic paint in Example 1.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1 except that the same amount of lauric acid was used in place of isohydrosorbic acid in the composition of the magnetic paint in Example 1.

For each magnetic tape obtained in each example and each comparative example, the coercive force, residual magnetic flux density, maximum magnetic flux density, squareness, and degree of orientation were measured as magnetic properties, and the sensitivity (333 Hz, 7KHz, 12.5KH
), maximum undistorted output (333Hz -M, 0.L)
, and the S/N ratio were measured. However, regarding the sensitivity and maximum undistorted output in the table, due to the relationship with the recording and playback equalizer due to the difference in coercive force, Comparative Example 1 was taken as a reference in OdB and expressed as the difference.

The table below shows the results.

As is clear from the table above, the magnetic tapes obtained by the present invention (Examples 1 to 5) have a higher square shape and degree of orientation than conventional magnetic tapes (Comparative Examples 1 and 2), and have improved sensitivity and The maximum strain-free output was good, and this shows that the magnetic recording medium obtained by the present invention has good dispersibility of magnetic powder and excellent magnetic properties and electromagnetic conversion properties.

Claims (1)

[Claims] 1. Magnetic recording medium having a magnetic layer containing magnetic powder and isohydrosorbate