JPS60211621A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve uniform dispersibility of magnetic powder and to obtain a magnetic recording medium having an excellent electromagnetic characteristic by providing a magnetic layer contg. magnetic powder and sorbic acid or sorbic acid deriv. CONSTITUTION:The sorbic acid expressed by the formula or the deriv. such as the methyl, ethyl and butyl ester, sorbic acid amide, sorbic acid anilide, etc. is incorporated into the magnetic powder in the magnetic layer at 0.1-10wt% by the weight of the magnetic powder by a method consisting in adding such sorbic acid or the deriv. thereof into a magnetic paint in the stage of preparing said paint or using the magnetic powder stuck preliminarily with said sorbic acid by dipping the magnetic powder in a sorbic acid (deriv.) soln. The sorbic acid (deriv.) improves the dispersibility of the magnetic powder and the magnetic recording medium having excellent coercive force, squareness ratio, orientation of the magnetic powder, sensitivity, etc. is obtd.

Description

[Detailed Description of the Invention] [Technical Field and Objective] The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium with good dispersibility of magnetic powder and excellent electrical characteristics. be.

[Background technology]

Magnetic recording media are generally made by applying a magnetic paint consisting of a magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film and drying it. things are 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). However, the bonding force with the magnetic powder was still weak, and the dispersibility of the magnetic powder in the binder resin could not be sufficiently improved.

[Summary of the invention]

Under these circumstances, the present inventors conducted various studies on a group of compounds having both lipophilic and hydrophilic groups in order to find something more effective for dispersing magnetic powder into binder resin. , surprisingly revealed that sorbic acid and sorbic acid derivatives have particularly good dispersion abilities. The reason why such sorbic acid and sorbic acid derivatives have such remarkable dispersion ability is still not clearly elucidated, but considering their unique chemical structure, By having a double bond, the electron density is localized within the molecule and the polarizability is increased, which increases functionality. Moreover, ■The double bond has a trans (I/lance-trans) structure. As a result, the functional group is located at the outermost end of the molecule, making it statistically and geometrically easier for the functional group to be unevenly distributed on the surface of the dispersant. The number of such derivatives is 12 or less in total, and therefore, it is presumed that they have an appropriate melting point and are easily mixed into the binder resin in order to impart good fluidity to the paint.

The sorbic acid used in this invention has the chemical formula CH
It is a compound represented by 3CH=CHCH=CHCOOH, has a relatively small molecular weight, both double bonds are trans, and adheres well to the surface of magnetic powder, and is also compatible with binder resin. Therefore, when this sorbic acid 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.

Further, as the sorbic acid derivative used in this invention, for example, methyl ester of sorbic acid C5
I, C00CI]3, ethyl ester C5H2OOOC
2Hs, propyl ester C5H, COOC31-1
,, butyl ester c5i-t, c○0C41-19,
Amide C5H7CONH2, -tolyl c51-I, CN
, anilide c5 H, C0NHC6 (5, phenylhydrazide C51-1, C0NI-INHC, Hs, etc.), and these sorbic acid derivatives also have two double Both bonds are trans, the molecular weight is relatively small, it adheres well to the surface of the magnetic powder, and is compatible with the binder resin.

Therefore, when these sorbic acid derivatives are included in the magnetic layer, the same effect as the above-mentioned sorbic acid is obtained, and the dispersibility of the magnetic powder in the binder resin is sufficiently improved. A magnetic recording medium with excellent electrical properties can be obtained.

Such sorbic acid or sorbic acid derivatives can be added directly during the preparation of magnetic paints, or dissolved in a suitable solvent such as alcohol or ether, and the solution obtained by this dissolution can be added during the preparation of magnetic paints. or by immersing the magnetic layer 5) in this solution.
The surface of the magnetic powder is treated in advance, a magnetic paint is prepared using the magnetic powder, and the coating is applied onto a substrate and dried to be incorporated into the magnetic paint. 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. There is a risk of bleat-out.

The sorbic acid and sorbic acid derivatives thus contained in the magnetic layer may be used alone, or two or more may be used in combination;
For example, it may be used in combination with saturated fatty acids, unsaturated fatty acids, fatty acid esters, phosphoric acid esters, lecithin, metal soaps, alcohols, and the like.

Examples of the magnetic powder used in this invention include r-
Fe203 powder, Fe3O4 powder, T-]? Intermediate compound powder between e203 powder and Fe3O4 powder, Co-containing T-F
e'203 powder, CO-containing Fe3O4 powder, CrChJ
In addition to 'fl powder, tx, -Fe powder, CO powder, Fe
-Ni powder, metal powder such as Fe4N1'5) powder, and various conventionally known magnetic powders are widely included.

In addition, examples of binder resins include vinyl chloride-vinyl acetate copolymers, cellulose resins, butyral resins, polyurethane resins, polyester resins, epoxy resins, polyether resins, Isonane-1 compounds, etc. Any of the binder resins conventionally used for ρ・L 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. , tetrahydrofuran, ether solvents such as dioxane, etc.
Solvents suitable for dissolving the binder resin used may be used alone or in a mixture of two or more without particular limitation.

In addition, various additives commonly used in magnetic paints,
For example, /IX! I/I powder, abrasives, antistatic agents, etc. may be added as appropriate.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 rFe203 powder 800 parts by weight VAGII (manufactured by U.C.C. in the United States, salt 120 vinylide-hinyl acetate-hinyl alcohol combination) sorbic acid 16 methyl isobutyl ketone 410 toluene 410 This composition After mixing and dispersing in a ball mill for 72 hours, it was coronated with Takelac E-5517 (Take 1) 65 ~ Yakuhin Kogyo Co., Ltd., polyurethane resin) (Japan Polyurethane Industry Co., Ltd., trifunctional low molecular weight isocyanate 1).・Compound) was added to make a magnetic paint, and this was applied onto a polyester film with a thickness of 11 μm so that the dry film thickness of 17 was approximately 6 μm. After drying and calendering, a predetermined “1”
I cut it into pieces and made magnetic tape.

Example 2 T Fe2031'z) powder 800g sorbic acid 2
0fX ethanol 500ml After dispersing the above ingredients in a homomixer for 5 hours,
An r-Fe203 powder with 16 mg/g of sorbic acid deposited on the surface of the powder particles was obtained by drying, and the same amount of the γ-Fe203 powder was used in place of the γ-176203 powder used in Example 1, Furthermore, a magnetic tape was produced in the same manner as in Example 1, except that sorbic acid was omitted from the composition of the magnetic paint in Example 1.

Example 3 A magnetic tape was produced in the same manner as in Example 1 except that the amount of sorbic 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 sorbic acid used was changed from 16 parts by weight to 40 parts by weight in the composition of the magnetic coating composition in Example 1.

Example 5 A magnetic tape was produced in the same manner as in Example 1 except that in the composition of the magnetic coating composition in Example 1, the same amount of n-phthyl sorbic acid was used in place of sorbic acid.

Example 6 The composition of the magnetic paint in Example 1 was the same as in Example 1, except that the amount of sorbic acid used was changed from 16 parts by weight to 8 M parts, and 8 parts by weight of lauric acid was newly added. I made magnetic tape.

Example 7 In the composition of the magnetic paint in Example 1, T-Fe2
A magnetic tape was produced in the same manner as in Example 1 except that the same amount of Fe3O4 powder was used in place of the 03 powder.

Example 8 In the composition of the magnetic paint in Example 1, T-Fe2
A magnetic tape was produced in the same manner as in Example 1 except that the same amount of CO-containing -Fe203 powder was used in place of the 03 powder.

Example 9 In the composition of the magnetic paint in Example 1, T-Fe2
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of α-Fe powder was used in place of the 03 powder, and the dry thickness of the magnetic layer was changed from about 6 μm to about 4 μm.

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

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 8 except that sorbic acid was omitted from the composition of the magnetic coating material in Example 8.

Comparative Example 4 A magnetic tape was produced in the same manner as in Example 9 except that sorbic acid was omitted from the composition of the magnetic coating material in Example 9.

For each magnetic tape obtained in each example and each comparative example, the coercive force, residual magnetic flux density, squareness, and degree of orientation were measured as magnetic properties, and the sensitivity (
33311z, 7KIIz, 12.5KIIz) The maximum undistorted output (33311z -M, 0.L) was measured, respectively. However, the sensitivity and M in the table are 0. Regarding L, in Examples 1 to 7 and Comparative Examples 1 and 2, due to the relationship with the recording and playback equalizer due to the difference in coercive force,
Comparative Example 1 was set as 0 dll, and the difference was expressed as a reference.

Further, Example 8 is based on Comparative Example 3, and Example 9 is based on Comparative Example 4.
were each set to 0clB and expressed as the difference.

The table below shows the results.

As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 to 9) are different from the conventional magnetic tapes (Ratio Examples 1 to 9).
4), it has a higher square shape and degree of orientation, and has better sensitivity and maximum distortion-free output. Therefore, the magnetic recording medium obtained by this invention has good dispersibility of magnetic powder, and has excellent magnetic properties and electromagnetic conversion. It can be seen that the characteristics are excellent.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer containing magnetic powder and a norbic acid or sorbic acid derivative