JPS62245518A - Composition for magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of a magnetic recording medium compsn. and the surface strength of a coated film by constituting said compsn. of a high-polymer binder consisting of at least one kind of prescribed acrylic resin and epoxy resin and ferromagnetic powder. CONSTITUTION:The magnetic recording medium compsn. is constituted of the high-polymer binder consisting of at least one kind of the acrylic resin expressed by the formula and the epoxy resin. A methyl methacrylate, ethyl acrylate and others are used for the acrylic resin and a copolymer of the methyl methacrylate and hydroxyethyl methacrylate is more preferable in terms of the dispersibility and the hardness of the coated film. The acrylic resin is compounded at preferably 3-50pts.wt. per 100pts.wt. ferromagnetic powder. Other binders, aluminum oxide coupling agent, silicone oil, surface active agent, etc., may be added thereto according to need.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic recording medium composition, particularly to a magnetic recording medium composition applied to a magnetic disk having excellent magnetic properties and coating strength.

(Prior art) Conventionally, magnetic disks and the like have been manufactured by applying magnetic paint, which is made by dispersing magnetic powder in a solvent containing a polymeric binder such as epoxy resin, phenol resin, melamine resin, acrylamide resin, or polyvinyl butyral resin, to the disk substrate. It was manufactured by coating and curing by baking. (Unexamined Japanese Patent Publication No. 54-89
Publication No. 707.

JP-A-58-62828, JP-A-60-1434
(See Publication No. 28, etc.) (Problems to be Solved by the Invention) In recent years, as the performance of information recording devices has improved, there has been a growing demand for higher recording densities of recording media. To this end, magnetic disks require metallic powder (corrosion-resistant Fe powder, etc.), Co-treated PezO3, barium ferrite (
It is necessary to uniformly disperse magnetic powder with high coercive force such as I(aFe+□08.), make the magnetic recording layer thinner, and improve the surface strength of the recording layer.

However, simply making the magnetic recording layer thinner reduces the absolute amount of magnetic powder, so the amount of binder must be reduced. On the other hand, magnetic powder with high coercive force generally has small particles and a large specific surface area, so it is difficult to disperse. If a recording medium is made of a magnetic paint with poor dispersibility, its signal characteristics will have many defects, and high density recording will not be achieved. or,
In order to improve the dispersion of magnetic powder, if a magnetic paint is kneaded for a long period of time, the problem arises that the magnetic powder is damaged and the coercive force is reduced.

(Means for Solving the Problems) The present invention attempts to solve the above-mentioned problems by the configuration described in the claims.

HR, HR3 1] 1 1 -(C-C), l -(C-C)m --) (COOR
2') I C00R4-0) (i.e., a magnetic recording medium composition with significantly improved dispersibility by using a polymer binder consisting of a unique acrylic resin and an epoxy resin represented by the above general formula) This is what you get.

In the present invention, ferromagnetic powders are used from those mentioned in the prior art, and C.
O-treated T-FezO is particularly preferred.

As for the acrylic resin represented by the above general formula, the composition on the left side of the general formula is methyl methacrylate.

Examples include ethyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, etc., and compositions on the right side of the general formula include hydroxyethyl acrylate, hydroxyethyl methacrylate, etc., and copolymerization by one-to-one or multiple combinations of them. It can be obtained by Among them, methyl methacrylate and hydroxyethyl methacrylate are a particularly suitable combination because they provide sufficient dispersibility and coating hardness, and they may be difficult to clean after forming the coating, resulting in poor durability. They also tend to be inferior in gender. Furthermore, if n/m exceeds 15, the amount of hydroxyl groups will be relatively reduced and the dispersibility of the ferromagnetic powder may become insufficient.

The acrylic resin preferably has a weight average molecular weight of 10,000 to 2,000,000. The selection of molecular weight is primarily a matter of viscosity in spin cord coating of magnetic paints. The acrylic resin is preferably blended in an amount of 3 to 50 parts by weight per 100 parts by weight of the ferromagnetic powder.

If it is less than 3 parts by weight, the ferromagnetic powder will not be sufficiently dispersed, and if it exceeds 50 parts by weight, the amount of ferromagnetic powder will be relatively reduced and the magnetic properties will not be satisfactory.

Another essential component of the polymer binder in this invention is an epoxy resin. The epoxy resin reacts with the hydroxyl groups of the acrylic resin to cure the coating film and form a network structure. Various epoxy resins can be used, and there are no particular limitations.

In the present invention, other binders such as polyvinyl butyral, phenol resin, melamine resin, etc. may be used in combination as necessary, and aluminum oxide coupling agents,
Silicone oil, surfactants, etc. can be added.

(Function) In the present invention, the above-mentioned acrylic resin has polar groups in a well-balanced manner, prevents agglomeration of the ferromagnetic powder, and greatly contributes to dispersibility. In addition, the epoxy resin also bonds with the acrylic resin, improving the surface strength of the coating film to a satisfactory level.

(Example) Example 1 Co-treated 7-Fe2O2 ferromagnetic powder 100QjfN
Department.

10 parts by weight of an acrylic resin consisting of a copolymer of methyl methacrylate and hydroxyethyl methacrylate <n/-39 weight average molecular weight 200,000), 30 parts by weight of an epoxy resin (Epicor 11001 manufactured by Shell Chemical Co., Ltd.), and a phenol resin (Sumitomo Heaklite). Sumilac P (,-25
) 20 parts by weight.

10 parts by weight of αAIz03 powder and 620 parts by weight of the mixed solvent were placed in a ball mill and kneaded for 20 hours to obtain a magnetic paint. The average particle size of this magnetic paint is shown in the table.

The obtained magnetic paint was applied to an aluminum alloy substrate using a spin cord, and baked and hardened at 150°C for 3 hours.
The coating was then polished to produce a magnetic disk. The smoothness of the magnetic disk coating, magnetic properties, signal properties,
Abrasion resistance is shown in the table.

Everything was the same as in Example 1 except that the n/m value of the acrylic resin in Example 1 was set to 12.

All Example 1 except that the acrylic resin was a copolymer of cyclohexane acrylate and hydroxyethyl acrylate.
I did the same thing.

The same procedure as in Example 1 was carried out except that 35 parts by weight of the acrylic resin of Example 1 was used based on 100 parts by weight of the ferromagnetic powder.

As a known binder, polybutyral resin was used in place of the acrylic resin in Example 1, and the rest was the same as in Example 1.

The same procedure as in Example 1 was used except that an acrylic resin with an n/m value of 20 was used.

Average particle diameter: Measured by centrifugal sedimentation using 5A-CP3 manufactured by Shimazu Seisakusho.

Surface smoothness: A Talistestrometer was used.

Magnetic properties: Coercive force and squareness ratio were measured using a vibrating sample magnetometer manufactured by Riken Denshi.

Signal characteristics: RD008 manufactured by National Semiconductor
The signal defects were counted.

C8S resistance; National Computer Co., Ltd. NCT-5
100, ISO TC97/5C1ON228
Measured according to.

(Margin below) Measurement result Note 1) * indicates the kneading time of the ball mill.

2) As for the recording medium characteristics of the comparative example, those with a kneading time of 200 hours were used.

As shown in the table, in all of Examples 1 to 4 according to the present invention, the ferromagnetic powder was sufficiently dispersed within 20 hours of kneading time, and the recording medium properties such as magnetic properties and CSS resistance were also good. .

On the other hand, in all of the comparative examples, the dispersibility was inferior to that of the present invention, and even the magnetic paints for which 200 hours of kneading were required had recording medium characteristics inferior to those of the present invention.

In Comparative Example 2, even when kneading for 200 hours, the kneading time was 20
It's not much improved over time.

(Effects of the Invention) As explained above, the present invention has excellent dispersibility of ferromagnetic powder, makes it possible to realize high-density information recording, and has sufficient coating strength to resist C8S, etc. will also be improved.

Claims (1)

[Claims] 1. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ [R_1, R_3 are hydrogen or methyl group R_2 is methyl group, ethyl group, benzyl group, or cyclohexane group R_4 is methylene group, ethylene group 1.5≦n/m≦15] A magnetic recording medium composition comprising at least one acrylic resin represented by the following formula, a polymeric binder made of an epoxy resin, and ferromagnetic powder. 2.Acrylic resin is 3 parts by weight for 100 parts by weight of ferromagnetic powder.
2. The magnetic recording medium composition according to claim 1, wherein the magnetic recording medium composition contains 50 parts by weight. 3. The magnetic recording medium composition according to claim 1 or 2, wherein the acrylic resin is a copolymer of methyl methacrylate and hydroxyethyl methacrylate.