JPS60219632A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder in a magentic paint without kneading for a long period and to improve the magnetic characteristic thereof by using a copolymer derived from vinyl chloride and maleic anhydride as at least part of a binder resin. CONSTITUTION:The copolymer derived from the vinyl chloride and maleic anhydride has about 1,000-10,000mol.wt. and is used together with the binder resin consisting essentially of an epoxy resin which is incorporated phenolic 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 magnetic 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. It is constructed by applying a magnetic coating material on a non-borous substrate and curing it 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, it is necessary to uniformly disperse the magnetic powder in the magnetic recording layer, and to use magnetic powder with high coercive force, such as Co improved type-Fe203 boron powder, Cr-0s boron powder, metal It has been proposed to use magnetic powder or the like.

However, simply making the magnetic recording layer thinner will reduce the amount of magnetic powder, so it is important to reduce the amount of other components, such as the amount of binder, rather than reducing the amount of magnetic powder. It becomes less effective and durability becomes a major problem.

In addition, magnetic powder with high coercive force generally has small particles;
Moreover, in addition to having a large acicular ratio, it also has a large specific surface area, which makes it difficult to disperse compared to conventional γ-PET03 magnetic powder. Therefore, in order to improve the dispersibility of the magnetic powder, it is necessary to mix and disperse the magnetic paint for a long time. However, if such a long time mixing and dispersion is carried out, the magnetic powder may break and magnetic problems such as a decrease in coercive force may occur. There is a problem of deterioration of characteristics □.

[Disclosure of the invention]

The present inventor has proposed a type of magnetic recording medium in which magnetic powder is dispersed in a binder resin and hardened by baking, using a copolymer derived from vinyl chloride and maleic anhydride as at least a part of the binder resin. This allows the magnetic powder to be dispersed well in the magnetic paint without long-term cross-talk, so the magnetic properties do not deteriorate, and the magnetic recording layer has excellent mechanical strength even if it is made thinner. I discovered that.

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 significantly shorten the mixing time of magnetic paint. For example, if the surface characteristics are equivalent to those of conventional magnetic recording media, the mixing time will be less than half of the conventional one, and therefore the manufacturing time will be greatly reduced. The width can be shortened and the manufacturing cost can be reduced significantly, and if the magnetic paint is mixed for a relatively long time to the extent that the magnetic powder does not break, the surface characteristics can be significantly improved without decreasing the coercive force etc. It turns out.

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 (C8S), 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 vinyl chloride and maleic anhydride has a molecular needle size of approximately 500 to 500 mm.

From the viewpoint of compatibility, etc., it is preferable that the number is within the range of , more preferably within the range of about 100 to 10,000.

Further, the proportion of maleic anhydride in the above copolymer is about 5 to 80% in molar ratio, more preferably about 20 to 50%.
It is preferable from the viewpoint of dispersibility in the magnetic powder.

Moreover, rather than using only the copolymer derived from vinyl chloride and maleic anhydride as the binder resin, this copolymer and, for example, epoxy resin, phenol resin, melamine resin, urea resin, acrylic resin, butyral resin, It is preferable to use the resin in combination with another resin having a binder effect. That is, the proportion of the copolymer derived from vinyl chloride and maleic anhydride out of all the binder resins added when preparing the magnetic paint is about 1 to 1. It is desirable to use a material within the range of 50% by weight from the viewpoint of surface characteristics and the like.

In particular, a copolymer derived from vinyl chloride and maleic anhydride may be used in an epoxy resin, more preferably an epoxy resin and a phenol resin system, an epoxy resin and an acrylic resin system, or an epoxy resin, an acrylic resin, and a phenol resin system (all of which are epoxy resins and phenolic resins). It is preferable to use it together with a binder resin (mainly consisting of resin).

The total amount of the binder such as a copolymer derived from vinyl chloride and maleic anhydride is 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 preferably within the range of parts by weight.

[Example 1] 100 parts by weight of Co-coated γ-Fe203 magnetic powder, α-
10 parts by weight of A L 203 powder, 45 parts by weight of epoxy resin (Epicor 1007, manufactured by Shell Chemical Co., Ltd.), 45 parts by weight of phenolic resin (Sumilac PC-2, manufactured by Sumitomo Bakelite Co., Ltd.)
5) 20 parts by weight, vinyl chloride-maleic anhydride copolymer (alternating copolymer, vinyl chloride/maleic anhydride = 50
/50, Mw=5000) A composition containing 10 parts by weight and 620 parts by weight of a mixed solvent was placed in a ball mill and mixed 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 kneading time in the ball mill was reduced to 1/2.
The magnetic disk was produced in the same manner except for 2 hours.

[Example 3] Co-coated type 7-Fe2O3 magnetic powder 100 parts by weight, -
10 parts by weight of At 203 powder, 35 parts by weight of epoxy resin (Epicor 1001, manufactured by Shell Chemical Co., Ltd.), acrylic resin (Dianal 5E-5437, manufactured by Mitsubishi Rayon Co., Ltd.)
) 25 parts by weight, vinyl chloride-maleic anhydride copolymer (
Random copolymer in which maleic anhydride is not bonded to each other, vinyl chloride/maleic anhydride-60/40,
A magnetic disk was manufactured in the same manner as in Example 1 using a composition containing 15 parts by weight of Mw=2000) and 620 parts by weight of a mixed solvent.

[Comparative example]

100 parts by weight of Co-coated γ-1i”e203 magnetic powder,
a'-A220g powder 10 parts by weight, Epicote 1007
A magnetic disk was manufactured in the same manner as in Example 1 using 50 parts by weight of SUMILAC PC-2525 and 620 parts by weight of the mixed solvent.

[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.

Table 1 In other words, in the case of the present invention, there is less damage to the magnetic powder when the magnetic paint is crossed, and there is less deterioration of the magnetic properties.In other words, the coercive force is larger than that of the comparative example, and the squareness ratio is large.
It can be seen that it is a recording medium with good magnetic properties because of its good dispersibility.

Furthermore, the number of surface defects is greatly reduced, and the wear resistance 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 is far superior; In particular, if it were sufficient to simply satisfy the current standards, crosstalk time could be significantly reduced.
The manufacturing cost is also low, and restrictions on magnetic powder etc. can be relaxed, and the range of selection is extremely wide.

Patent applicant: Victor Japan Co., Ltd.

Claims (1)

[Claims] A magnetic recording medium characterized in that a magnetic layer contains a copolymer of vinyl chloride and maleic anhydride.