JPS6154034A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having good surface smoothness and excellent magnetic characteristic by coating magnetic powder with a water soluble high-polymer surface active agent then dispersing the powder into a solvent contg. sodium dioctyl sulfosuccinate and binder to prepare a magnetic paint and using such binder. CONSTITUTION:Preferably the oxide magnetic powder is dippsed in the water soluble high-polymer surface active agent soln. of PVA, sodium polyacrylate, etc. and is then dried, by which the surface is coated with the surface active agent. The magnetic paint contg. the coated magnetic powder together with the binder such as sodium dioctyl sulfosuccinate and vinyl chloride/vinyl acetate copolymer and necessary lubricating agent, antistatic agent, etc. is prepd. The paint is coated on a substrate and is dried and the dried surface is subjected to a calender surface treatment. The uniform dispersibility and surface smoothness of the magnetic powder are improved and the packing property and orientation of the magnetic powder are improved. The magnetic recording medium having the excellent magnetic characteristic is thus obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium which has a magnetic layer with excellent surface smoothness, high filling and orientation of magnetic powder, and uneven magnetic properties, and a method for manufacturing the same. It is something.

[Conventional technology]

-IIIQ Since the magnetic powder used for the magnetic layer of a magnetic recording medium has a strong surface hydrophilicity, it is dispersed in an organic solvent containing a binder component to form the 4'il material, which is the forming material of the magnetic layer. Various surfactants have conventionally been used as dispersants when preparing paints. 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 and increase its affinity for organic solvents. ,
This is an attempt to improve the dispersibility of magnetic 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
Publication No. 134). 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 by the inventors revealed that the proposed method still leaves room for improvement in the filling properties and orientation of the magnetic powder.

(Problems to be Solved by the Invention) This invention solves the problem of insufficient dispersion stability due to a decrease in the adsorption ability of the binder component and tH magnetic powder due to the surfactant conventionally used as a dispersant for magnetic powder, and the surface In addition to eliminating the negative effect on smoothness by using a water-soluble polymeric surfactant, we can improve the filling and orientation properties of magnetic powder, which are limited by the use of water-soluble polymeric surfactants alone, by using specific combination ingredients. This improves the residual ≦
The object of the present invention is to provide a magnetic recording medium that is excellent in magnetic properties such as single density and squareness ratio, and has 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 a magnetic paint by dispersing magnetic powder in a solvent containing a binder component, adding sodium dioctyl sulfosuccinate will improve the magnetic layer formed by applying this magnetic paint to a substrate and drying it. It has been found that the characteristics 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 capacity for the binder component and contributes to improving the dispersion stability of the 611 powder, but the adsorption capacity is too high. On the other hand, when sodium dioctyl sulfosuccinate is not added, the adsorption point (adsorption site) on the surface of the magnetic powder where the binder component should be adsorbed is prevented. By partially adsorbing the binder component, it is possible to control the adsorption amount of the binder component and improve the affinity with the organic solvent that is the dispersion medium, resulting in better dispersion and better filling and orientation. It is presumed that when used as a magnetic recording medium, magnetic properties such as residual magnetic flux density and squareness ratio are improved, 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 sodium dioctyl sulfosuccinate are contained in a magnetic layer provided on a substrate, and a magnetic recording medium in which a water-soluble polymer surfactant and sodium dioctyl sulfosuccinate are contained in a magnetic layer provided on a substrate. A magnetic paint is prepared by immersing the magnetic powder in an aqueous solution of a surfactant and then drying it, and dispersing the resulting magnetic powder coated with the surfactant in an organic solvent containing sodium dioctyl sulfosuccinate and a binder component. A method for manufacturing a θl magnetic recording medium is characterized in that a magnetic layer containing a water-soluble polymer surfactant and sodium dioctyl sulfosuccinate is formed by coating this on a substrate and drying it.

[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 natrilam salt of a sulfonated styrene-maleic anhydride copolymer are particularly suitable.

A preferable means for coating the surface of the magnetic powder with such a water-soluble polymeric surfactant is, for example, 0.05~
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 0.5% by weight, stir thoroughly, and then take out the magnetic powder and dry it. be.

The sodium dioctyl sulfosuccinate used in this invention is represented by Co HI 70 0 CCHt Co Hl 700 CCHS Os Na, and the amount used is as follows: 0.5 to parts by weight
A range of 5 parts by weight is preferred.

On the other hand, the magnetic powder used in this invention is
For example, oxide-based magnetic powders such as T-Fezowl, Fe30a, CO-containing rFeZOz, CrOz, and barium ferrite are suitable, and these are used alone or as a mixture of two or more.

In this invention, as described above, a magnetic powder whose surface is coated with a water-soluble polymeric surfactant is dispersed in an organic solvent containing sodium dioctyl sulfosuccinate and a binder component to prepare a coating material. As the binder component, it is possible to use any of the binder components conventionally used as binder components for magnetic powders, such as vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, cellulose resins, polyurethane resins, isocyanate compounds, and epoxy resins. be. 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 spread on a substrate such as a polyester film and dried to form the magnetic coating of the present invention in which the water-soluble polymeric surfactant and sodium dioctyl sulfosuccinate are included in the magnetic layer. A recording medium is obtained.

〔Effect of the invention〕

The magnetic recording medium according to the present invention contains a water-soluble polymeric surfactant and sodium dioctyl sulfosuccinate in the magnetic layer, exhibits excellent dispersibility of magnetic powder, high filling property and orientation, and has a smooth surface. It also has good magnetic properties such as residual magnetic flux density and squareness ratio.

Moreover, such effects are produced by the synergistic action of the water-soluble polymeric surfactant and sodium dioctyl sulfosuccinate, and improvements in each of the above properties are observed compared to when either one is omitted.

〔Example〕

Next, the present invention will be specifically explained based on examples. Note that in the following, parts mean parts by weight.

Example 1 10 parts of Co-containing -Fe2Q 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 dried with JB'A water to obtain a magnetic powder whose surface was coated with a water-soluble polymeric surfactant.

To 100 parts of this magnetic powder, add 1 part of sodium dioctyl sulfosuccinate to 1 part of sodium dioctyl sulfosuccinate, and add
vinyl chloride-vinyl acetate-vinyl alcohol copolymer)
From the composition: 18 parts of polyurethane elastomer, 12 parts of polyurethane elastomer, 3 parts of Desmodulative Trifunctional Polyisocyanate Compound manufactured by Nippon Boliutane Co., Ltd., 2 parts of lauric acid, and 160 parts of a mixture of cyclohexanone and toluene (weight ratio 1:1). A magnetic paint was prepared by dispersing the mixture in a sand mill. This magnetic material was applied onto a 12 μm thick polyester film to a dry film thickness of about 4 μm, dried, surface treated with a calendar, and then cut into a predetermined width to produce a magnetic tape.

Example 2 The same procedure as in Example 1 was carried out except that a sodium salt of a sulfonated styrene-maleic acid copolymer having a molecular weight of 15,000 was used in place of sodium polyacrylate 1 in Example 1. A magnetic tape was made.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that the sodium dioctyl sulfosuccinate in Example 1 was not used.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1, except that CO-containing -FezO3 without the surface coating treatment with sodium polyacrylate in Example 1 was used.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 1, except that the surface coating treatment with I.lium polyacrylate in Example 1 was not performed and sodium dioctyl sulfosuccinate 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. In addition, the surface smoothness is the center line average (CLA) when measured at Cut off 0.08 + am using a stylus type surface roughness meter.
Shown in

From the results in the above table, it can be seen that the magnetic tape according to the present invention (Example 1
~2) is of course applicable to the magnetic tape (Comparative Example 3) produced without surface coating treatment with a water-soluble polymeric surfactant and without using sodium dioctyl sulfosuccinate, and any one of the above Even for the magnetic tape produced by omitting the residual magnetic flux density (Br) (Comparative Example 1゜2),
It is clear that the magnetic properties and squareness ratio (Br/Bs) and surface smoothness are excellent. Therefore, it can be seen that according to the present invention, a synergistic effect is exhibited by the combination of the water-soluble polymeric surfactant and sodium dioctyl sulfosuccinate.

Claims (2)

[Claims] (1) A magnetic recording medium comprising a water-soluble polymer surfactant and sodium dioctyl sulfosuccinate 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, and the resulting magnetic powder coated with the above surfactant is coated with an organic material containing sodium dioctyl sulfosuccinate and a binder component. A magnetic layer containing a water-soluble polymer surfactant and sodium dioctyl sulfosuccinate is formed by preparing a magnetic paint by dispersing it in a solvent, applying it onto a substrate, and drying it. A method for manufacturing a magnetic recording medium.