JPS6154035A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve the uniform dispersibility of magnetic powder and to obtain an excellent magnetic recording medium by coating the magnetic powder with a water-soluble high-polymer surface active agent then dispersing the same into an org. solvent contg. polyalkylene oxide alkyl phosphate and binder to prepare a magnetic paint and using such paint. CONSTITUTION:The magnetic powder is immersed into the aq. water soluble high-polymer surface active agent soln. of carboxymethyl cellulose, sulfonated polystyrene, etc. and is then dried, by which the magnetic powder coated with the surface active agent is obtd. Such magnetic powder is dispersed into the org. solvent contg. polyalkylene oxide alkyl phosphate and a binder resin as well as a necessary lubricating agent, antistatic agent, etc. to obtain the magnetic paint. Such paint is coated on a substrate and is dried and the dried surface is subjected to a surface treatment by a calender, by which the magnetic recording medium having the good surface smoothness and the uniform dispersibility of the magnetic powder, the good bonding property with the binder resin and excellent magnetic characteristic is thus obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a magnetic recording medium which has an excellent surface smoothness of a magnetic layer, and has a high filling property and orientation of magnetic powder, and a good property of <61°C, and a method for manufacturing the same. It is related to.

[Conventional technology]

Generally, the magnetic powder used for the magnetic layer of a magnetic recording medium has a strong surface hydrophilicity, so it is dispersed in a binder containing a binder component and a magnetic coating material that is the forming material of the magnetic layer. Various surfactants have conventionally been used as dispersants when preparing . These surfactants usually have a molecular chain composed of a hydrophilic group and a hydrophobic group, and the above-mentioned method uses these to hydrophobize the surface of the magnetic powder to increase its affinity for organic solvents. (This is an attempt to improve the dispersibility of a silica powder (document unknown).

However, in the conventional method described above, the presence of a surfactant conversely reduces the adsorption ability of the binder component to the surface of the magnetic powder, resulting in poor dispersion stability and poor surface smoothness of the tape. be.

This is thought to be because the surfactants conventionally used have low molecular weights and are too strong in making the surface of the magnetic powder hydrophobic.

Therefore, in order to eliminate the above-mentioned drawbacks, the present inventors coated the surface of the magnetic powder with a specific surfactant, that is, a water-soluble and high-molecular surfactant such as an acrylic acid salt type or a styrene-maleic acid copolymer type. It was previously proposed to cover with
JP-A-58-161133, JP-A-58-161
No. 134 Koyori). The surface of the magnetic powder coated with a water-soluble polymeric surfactant has good affinity for organic solvents and also has excellent adsorption ability for binder components, thus improving the dispersion stability of the magnetic powder in the magnetic paint. is significantly improved, and the water-soluble polymeric surfactant has the advantage that it does not adversely affect surface smoothness.

However, subsequent research conducted by the inventors revealed that the proposed method still leaves room for improvement in the filling properties and orientation of the magnetic powder.

[Problem that the invention seeks to solve]

This invention solves the problem of insufficient dispersion stability and adverse effects on surface smoothness due to a decrease in the adsorption ability of binder components and magnetic powder caused by surfactants conventionally used as dispersants for magnetic powder. In addition to solving this problem by using a surfactant, we also improve the filling and orientation properties of magnetic powder, which are limited by the use of a water-soluble polymer surfactant alone, by using a specific combination of ingredients, thereby reducing the residual magnetic flux density and The object of the present invention is to provide a magnetic recording medium that has excellent magnetic properties such as squareness ratio and good surface smoothness.

[Means for solving problems]

The inventors have conducted intensive studies to obtain a magnetic recording medium with even higher performance using the magnetic powder in the proposed method whose surface is coated with a water-soluble polymeric surfactant. When preparing an RJFI paint by dispersing magnetic powder in an organic solvent containing a binder component, if polyalkylene oxide alkyl phosphate is added, the magnetic paint formed by applying this magnetic paint to a substrate and drying it It has been found that the magnetic properties of the layer are better.

The reason for this is not clear, but the water-soluble polymer surfactant coated on the surface of the magnetic powder increases the adsorption ability for the binder component and contributes to improving the dispersion stability of the magnetic powder. On the other hand, polyalkylene oxide alkyl phosphate esters are used at adsorption points (adsorption points) on the surface of magnetic powder where binder components should be adsorbed when they are not added. By partially adsorbing the binder component (site), the adsorption amount of the binder component can be controlled and the affinity with the organic solvent used as the dispersion medium can also be improved. It is presumed that magnetic properties such as residual magnetic flux density and squareness ratio are improved when used as a magnetic recording medium, and good results are obtained in terms of surface smoothness.

That is, the gist of the present invention is to provide a magnetic recording medium in which a water-soluble polymer surfactant and a polyalkylene oxide alkyl phosphate are contained in a magnetic layer provided on a substrate, and a magnetic recording medium in which a magnetic powder is dissolved in water. The magnetic powder coated with the above-mentioned surfactant is dispersed in an organic solvent containing a polyalkylene oxide alkyl phosphate ester and a binder component. A magnetic layer containing a water-soluble polymeric surfactant and a polyalkylene oxide alkyl phosphate is formed by preparing a 6-color paint, coating it on a substrate, and drying it. A method of manufacturing a magnetic recording medium is provided.

[Structure and operation of the invention]

The water-soluble polymer surfactant used in this invention is
It usually has a molecular weight in the range of 1,000 to 10,000, and specific examples include polyvinyl alcohol, carboxymethyl cellulose, sulfonated polystyrene, sulfonated styrene-maleic anhydride copolymer, and methyl vinyl ether-maleic anhydride copolymer. , methylcellulose, sodium polyacrylate, polyethylene oxide, and derivatives thereof. Among these, sodium polyacrylate and the sodium salt of a sulfonated styrene-maleic anhydride copolymer are preferred.

A preferred means of coating the surface of the magnetic powder with such a water-soluble polymeric surfactant is, for example, 0.05 to 0.
．． A common method is to add about 10 parts by weight of magnetic powder to 100 parts by weight of an aqueous solution of a water-soluble surfactant with a concentration of 5% by weight, stir thoroughly, and then take out the magnetic powder and dry it.

The polyalkylene oxide alkyl phosphate ester used in this invention has a general formula in which the alkylene oxide is ethylene oxide;
monoester (m=1), diester (m=2) or triester (m-3), or a mixture of two or more of these, represented by (m is an integer of 1 to 3) are preferably used. be done. Other phosphoric acid esters similar to those of the above general formula, in which the alkylene oxide is propylene oxide or a mixture of propylene oxide and ethylene oxide, can also be used.

The amount of polyalkylene oxide alkyl phosphate used is preferably in the range of 0.5 to 5 parts by weight based on 100 parts by weight of the magnetic powder whose surface is coated with a water-soluble polymeric surfactant.

On the other hand, the magnetic powder used in this invention is
For example, r-Fe20:l, Fe3O4, Co-containing T
Oxide-based magnetic powders such as Fe, 03, Crux, and barium ferrite are suitable, and these are used alone or as a mixture of two or more.

In this invention, as described above, magnetic powder whose surface is coated with a water-soluble polymeric surfactant is dispersed in an organic solvent containing a polyalkylene oxide alkyl phosphate and a binder component to prepare magnetic = :FJF. As the binder component, θ is conventionally used as a binder component of magnetic powder, such as vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose resin, polyurethane resin, isocyanate compound, and epoxy resin. Both can be used. Furthermore, conventionally known additive components such as colorants, lubricants, antistatic agents, abrasives, etc. may be appropriately incorporated into the magnetic coating material as required.

The magnetic paint prepared as described above is coated on a substrate such as a polyester film and dried to form a magnetic layer containing a water-soluble polymer surfactant and a polyalkylene oxide alkyl phosphate ester. A magnetic recording medium is obtained.

〔Effect of the invention〕

The magnetic recording medium according to the present invention contains a water-soluble polymer surfactant and a polyalkylene oxide alkyl phosphate in the magnetic layer, and exhibits excellent dispersibility of magnetic powder as well as high filling property and orientation. It has good surface smoothness and magnetic properties such as residual magnetic flux density and squareness ratio.

In addition, these effects are produced by the synergistic action of the water-soluble polymer surfactant and the polyalkylene oxide alkyl phosphate ester, and the above properties are improved compared to when either one is omitted. Is recognized.

〔Example〕

Next, the present invention will be specifically explained based on examples. In the following, parts refer to parts by weight.

Example 1 10 parts of Co-containing -F103 powder was added to an aqueous solution in which 0.2 parts of sodium polyacrylate having an average molecular weight of about 5,000 was dissolved in 100 parts of water, and the mixture was thoroughly stirred at room temperature. Thereafter, it was dehydrated and dried to obtain a magnetic powder whose surface was coated with a water-soluble polymeric surfactant.

For 100 parts of this magnetic powder,
3-410C As the main component, R in the general formula has 1 carbon number
Monoster with 3 alkyl groups and n=6 (m=1)
Polyalkylene oxide alkyl phosphate ester containing diester (m = 2) with a dielectric-like structure] 1
18 parts of VAGH (vinyl chloride-vinyl acetate-vinyl alcohol copolymer) manufactured by UCC, USA, 12 parts of polyurethane elastomer, desmodular trifunctional polyisocyanate compound manufactured by Nippon Polyurethane Co., Ltd.) A magnetic paint was prepared by dispersing a mixture of 3 parts of lauric acid, 2 parts of lauric acid, and 160 parts of a cyclohexanone-toluene (weight ratio 1:1) mixture in a sand mill.

This magnetic paint was applied onto a polyester film having a thickness of 12 μm to a dry film thickness of about 4 μm, dried, and subjected to surface treatment using a calendar, and then cut to a predetermined width to produce a magnetic tape.

Example 2 Instead of sodium polyacrylate in Example 1, sodium salt of sulfonated styrene-maleic acid copolymer with molecules is and ooo was used with the same composition.
A magnetic tape was produced in the same manner as in Example 1.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that R5-410 in Example 1 was not used.

Comparative Example 2 A 6-2 air tape was produced in the same manner as in Example 1, except that Go-containing -Fe203 was not subjected to the surface coating treatment with I-lium polyacrylate in Example 1.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 1, except that the surface coating treatment with sodium polyacrylate in Example 1 was not performed and R3-110 was not used.

Regarding the magnetic tapes obtained in the above Examples and Comparative Examples, the magnetic properties include coercive force (Hc), residual magnetic flux density (
Br) and squareness ratio (Br/Bs) were measured, and the surface smoothness was tested.

The results are shown in the table below. Incidentally, the surface smoothness was expressed as the center line average (CLA) when measured at Cut off 0.08 +n using a stylus type surface roughness meter.

From the results in the above table, it can be seen that the magnetic tape according to the present invention (Example 1
~2) is a magnetic tape (Comparative Example 3) produced without surface coating treatment with a water-soluble polymeric surfactant and without using polyalkylene oxide alkyl phosphate ester.
Of course, the magnetic properties of residual magnetic flux density (Br) and squareness ratio (Br/Bs) and magnetic tapes produced by omitting either one of the above (Comparative Examples 1 and 2) It is clear that the surface smoothness is excellent.

Therefore, it can be seen that according to the present invention, a synergistic effect is exhibited by the combination of the water-soluble polymer surfactant and the polyalkylene oxide alkyl phosphate ester.

Claims (2)

[Claims] (1) A magnetic recording medium comprising a water-soluble polymer surfactant and a polyalkylene oxide alkyl phosphate ester in a magnetic layer provided on a substrate. (2) Magnetic powder is immersed in an aqueous solution of a water-soluble polymeric surfactant and then dried. A magnetic layer containing a water-soluble polymer surfactant and a polyalkylene oxide alkyl phosphate is formed by dispersing it in an organic solvent to prepare a magnetic paint, applying it onto a substrate, and drying it. A method of manufacturing a magnetic recording medium, characterized in that: