JPS60219628A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder in a magnetic paint and to improve the magnetic characteristic thereof by using a copolymer derived from acrylate and maleic anhydride as at least part of a binder resin. CONSTITUTION:The copolymer derived from the acrylate (CH2=CHCOOR, R is an alkyl group of 1-8C) and maleic anhydride has about 1,000-10,000mol.wt. and is used together with a binder resin of an acrylic resin-or phenolic resin base consisting essentially of an epoxy resin. The compsn. consisting of about 50-120pts.wt. the entire binder by 100pts.wt. the magnetic powder is kneaded for 24hr by a ball mill to prepare the magnetic paint. Said magnetic paint is coated on an aluminum alloy substrate and is cured by baking and thereafter the surface thereof is subjected to a polishing treatment, by which a magnetic disk is obtd. The dispersibility is thus improved, the decrease in the coercive force and squareness ratio owing to the damage of the magnetic powder is prevented and the wear resistance is semipermanently improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media such as Katsuki tapes, floppy disks, and hard disks, and particularly to magnetic recording media used in magnetic disk devices such as computers.

[Prior art and its problems]

Conventionally, magnetic recording media used in information recording devices such as magnetic disk drives have been produced by dispersing magnetic powder in a solvent containing a binder such as epoxy resin, phenol resin, melamine resin, urea resin, acrylic resin, or butyral resin. The magnetic paint is coated on a non-magnetic substrate and cured by baking.

As the performance of information recording devices increases, the magnetic recording medium described above is required to have higher density.In order to meet such demands, it is necessary to make the magnetic recording layer thinner.
In order to improve the surface properties of the magnetic powder, it is necessary to uniformly disperse the magnetic powder in the recording layer. It has been proposed to use

However, simply making the magnetic recording layer thinner will reduce the amount of magnetic powder, so instead of reducing the amount of magnetic powder, it is important to reduce the amount of other components, such as the binder, but this will reduce the binder effect. Durability becomes a big problem.

In addition, magnetic powders with high coercive force generally have small particles and a large acicular ratio, as well as a large specific surface area, making them difficult to ablate compared to conventional γ-Fe20s magnetic powders. Therefore, in order to improve the dispersibility of magnetic powder, it is necessary to mix and disperse magnetic paint for a long time.
If such long-term mixing and dispersion is performed, there is a problem that the magnetic powder is broken and the magnetic properties are deteriorated, such as a decrease in coercive force.

[Disclosure of the invention]

The present inventor uses a copolymer derived from acrylic ester and maleic anhydride as at least a portion of the binder resin in a magnetic recording medium in which magnetic powder is dispersed in a binder resin and cured by baking. This allows the magnetic powder to be dispersed well in the magnetic coating material without long-term cross-talk, so the magnetic properties do not deteriorate, and even if the magnetic recording layer is made thinner, it has excellent mechanical strength. I found out that there is.

This improved dispersibility not only has the effect of preventing a decrease in coercive force and squareness due to breakage of the magnetic powder, but also
It is possible to drastically shorten the time required to mix the magnetic paint, and if the surface properties are the same as those of conventional magnetic recording media, the crosstalk time will be less than half that of the conventional magnetic recording medium, and therefore the manufacturing time will be reduced. It is possible to shorten the width 5 and reduce the manufacturing cost significantly, and if the magnetic paint is kneaded for a relatively long time to the extent that the magnetic powder does not break, the surface properties will be significantly improved without any decrease in coercive force etc. It will improve.

Moreover, the above-mentioned superiority of mechanical strength is due to the adhesion of the magnetic recording layer,
It has excellent abrasion resistance and solvent resistance. For example, in the case of magnetic disks, abrasion resistance is evaluated by the number of contact start and stop (CSS), and IS
Although there is a standard for TC97/5C1ON228 of O, it can be used more than 10,000 times, but the magnetic disk according to the present invention far exceeds this standard value, and there is extremely little chance of magnetic powder falling off, and furthermore, it can be used for surface cleaning of magnetic disks. It has strong resistance to solvents such as alcohol, and the magnetic recording layer is extremely durable against denaturation.

The copolymer derived from the above acrylic ester and maleic anhydride has a molecular weight of about 500 to 50,000.
In terms of compatibility, the proportion of maleic anhydride in the above copolymer is preferably in the range of about 5 to 10,000, more preferably about 1,000 to 10,000. 80%, more preferably about 20-50%
It is preferable from the viewpoint of dispersibility in the magnetic powder.

Moreover, rather than using only the copolymer derived from the above-mentioned queacrylic acid ester and maleic anhydride as the inder resin, a copolymer derived from the above-mentioned queacrylic acid ester and maleic anhydride, for example, an epoxy resin, a phenol resin, a melamine resin, a urea resin, etc. It is preferable to use acrylic resin, butyral resin, and other resins having a binder effect in combination.In other words, among all the binder resins added when preparing the magnetic paint, copolymer derived from acrylic ester and maleic anhydride is preferable. From the viewpoint of surface properties, etc., it is desirable that the proportion of coalescence be within the range of about 1 to 50% by weight.

In particular, a copolymer derived from an acrylic acid ester ζ maleic anhydride is mixed with an epoxy resin, more preferably an epoxy resin and an acrylic resin system, an epoxy resin and a phenol resin system, or an epoxy resin, an acrylic resin, and a phenol resin system (both of which are It is preferable to use it together with a binder resin (mainly epoxy resin).

Further, the total amount of the binder such as a copolymer derived from an acrylic ester and maleic anhydride is in the range of about 30 to 200 parts by weight, more preferably about 50 to 120 parts by weight, based on 100 parts by weight of the magnetic powder. It is preferable that it be within.

In addition, in the acrylic acid ester CH2=CHCOOR used for copolymerization with maleic anhydride, R has 1 to 18 carbon atoms.
, more preferably an alkyl group having 1 to 8 carbon atoms. The acrylic ester used in the copolymerization with maleic anhydride is not limited to one type, but two or more types of acrylic ester may be used at the same time.

[Example 1] Co coated type γ-1? 100 parts by weight of e203 magnetic powder, α
- 10 parts by weight of kt20s powder, 45 parts by weight of epoxy resin (Epicoat 1007 manufactured by Shell Kajigakusha), 2 parts by weight of phenolic resin (Sumilac PC-25 manufactured by Sumitomo Bakelite Co., Ltd.)
0M parts, acrylic ester-maleic anhydride copolymer (alternating copolymer, acrylic ester is butyl acrylate, butyl acrylate/maleic anhydride-50/5
0, Mw=500000 parts by weight, mixed solvent 620
Parts by weight of the composition are placed in a ball mill and kneaded for 24 hours to prepare a magnetic coating material.

Then, the magnetic paint is applied onto an aluminum alloy substrate, baked and hardened at 200° C. for 1 hour, and then polished to produce a magnetic disk.

[Example 2] In Example 1, the crosstalk time in the ball mill was halved.
The magnetic disk was produced in the same manner except for 2 hours.

[Example 3] 100 parts by weight of Co-coated 7-Fe2O3 magnetic powder, a
10 parts by weight of A403 powder, 35 parts by weight of epoxy resin (Epicor 1001, manufactured by Shell Chemical Co., Ltd.), acrylic resin (
25 parts by weight of Dianaru 5E-5437 (manufactured by Mitsubishi Rayon Co., Ltd.), 25 parts by weight of acrylic ester-maleic anhydride copolymer (
Maleic anhydride is a random copolymer with no bonds, acrylic ester is ethyl acrylate, ethyl acrylate/maleic anhydride = 60/40, Mw = 20
00) A magnetic disk is manufactured in the same manner as in Example 1 using a composition containing 15 parts by weight of the mixed solvent and 620 parts by weight of the mixed solvent.

[Comparative example]

Co-coated type 7 Fe20s magnetic powder 100 parts by weight, a-
At*Os powder 10 parts by weight, Epicor) 100750
Parts by weight, Sumilac PC-2525 parts by weight, mixed solvent 6
A magnetic disk is manufactured in the same manner as in Example 1 using 20 parts by weight.

[Characteristics test]

The magnetic properties (coercive force, squareness ratio), surface defects, and wear resistance of the magnetic disks manufactured in Examples 1 to 3 and Comparative Example were examined as shown in Table 1. 71 In other words, the product of the present invention has less damage to the magnetic powder when the magnetic paint is crossed, less deterioration of magnetic properties, and has a larger coercive force than the comparative example, and a larger squareness ratio. It can be seen that it is a recording medium with good magnetic properties due to its good dispersibility.

In addition, the number of surface defects is also reduced compared to dog rJi, and
In terms of abrasion resistance, it is so excellent that it can be said to be semi-permanent in practical terms.

Furthermore, an excellent recording medium was obtained even when the crosstalk time of the magnetic paint was reduced to half of the conventional one.In other words, when comparing Example 2 and the comparative example, Example 2 was far superior. In fact, if it were sufficient to simply meet the current standards, the kneading time could be significantly shortened.
The manufacturing cost is also low, and the restrictions on magnetic powder etc. can be relaxed, and the range of selection is extremely wide.

Patent applicant: Victor Japan Co., Ltd. Representative Uko Katsu l(b');, :>,,,.

Claims (1)

[Claims] An R6 recording medium characterized in that the magnetic layer contains a copolymer of acrylic acid ester and maleic anhydride.