JPS5928236A - Magnetic recording disk - Google Patents

Abstract

PURPOSE:To provide a magnetic recording disk with superior durability, by incorporating dibasic acid ester and graphite of 500mmu-2mum average grain size into a magnetic layer to improve the wear resistance of the magnetic layer itself. CONSTITUTION:The frictional force of dibasic acid ester represented by general formula I [where R<1> is -(CH2-)n (n=2-6) or -(CH=CH-), and each of R<2> and R<3> is 10-26C alkyl or alkenyl] is reduced in accordance with an increase in the molecular size of the ester, yet the frictional force is not reduced any more when the ester attains to a certain molecular size, so the number of Cs in the dibasic acid ester is restricted. The ester is preferably added by <=20pts.wt. per 100pts.wt. magnetic powder. When the amount is >20pts.wt., the ester rises to the surface of a magnetic layer. The suitable average grain size of graphite is 500mmu-2mum. Graphite of <500mmu size is not easily available, and graphite of >2mum size deteriorates the surface properties of the magnetic layer and produces many noise components in the wave-form of output voltage. Graphite of 500mmu-2mum size is preferably added by <=20pts.wt. per 100pts.wt. magnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording disk that is effectively used as a floppy disk and has excellent durability.

Conventional Structure and Problems In a magnetic recording medium, such as a magnetic recording disk, in which two pages of the magnetic layer and a magnetic head slide at high speed during recording and reproduction, the coefficient of friction of the magnetic layer must be made as small as possible. A known method for reducing the coefficient of friction is to coat the surface of the magnetic layer with a lubricant, such as a higher fatty acid and a fatty acid ester, a higher fatty acid and a fluorinated oil, or the like. However, with such external addition, not only does the lubricant disappear quickly, making it impossible to maintain long-term durability, but there is also the problem that the lubricant adheres to the magnetic head, causing clogging. Furthermore, the lubricant transfers to the porous sheet such as non-woven fabric that is attached to the inner surface of the dirt prevention jacket on the surface of the magnetic layer of the magnetic recording disk, increasing the coefficient of friction of the magnetic layer, and there is a risk that it will not be able to maintain its wear resistance. Ta.

OBJECTS OF THE INVENTION The present invention aims to provide a magnetic recording disk with excellent durability by eliminating the above-mentioned conventional drawbacks and improving the wear resistance of the magnetic layer itself.

Structure 3 of the Invention The present invention was achieved as a result of intensive studies on lubricants to be added to one magnetic layer. That is, the present invention provides an alkyl group or an alkenyl group having a prime number of 10 to 26, R
1 is +CH2÷n (n=2-6) or 1,000CH=CH
Dibasic acid ester represented by
This was based on the discovery that a magnetic recording disk with a magnetic layer in which graphite of oOmμ to 2μm coexisted had a low coefficient of friction and excellent wear resistance. It is thought that the strong adsorption of the dibasic acid ester lowers the friction coefficient and improves wear resistance.

It has been found that in the dibasic acid ester represented by the above general formula, the frictional force decreases as the molecular size of the dibasic acid ester increases, but the frictional force does not decrease once it reaches a certain size. For this reason, the number of carbon atoms in the dibasic acid ester is limited. Specific examples of dibasic acid esters include didecyl succinate and didecyl succinate.

Ditetratecylsuccinate, dihexadecylsuccinate, dioctadecylsuccinate, dioleylsuccinate, diicosylsuccinate.

Examples include dieicosyl glutarate, ditetracosyl adishate, dihegizacosyl acephate, dipentatecyl pimelate, 7-octadecyl pimelate, dioctadecyl suberate, hexadecyl eicosyl suberate, and the like. Embossing occurs on the surface of the dibasic acid ester and magnetic layer.

In addition, the average particle size of graphite is suitably between 500 mμ and 2 μm, and graphite smaller than this is difficult to obtain.
If it is larger than this, the surface properties of the magnetic layer will deteriorate,
There are many noise components in the output voltage waveform. The amount of graphite added is preferably 20 parts by weight or less per 100 parts by weight of the magnetic powder; if it is too large, the surface properties of the magnetic layer will deteriorate.

In addition, as the ferromagnetic powder that can be used in the present invention, 7-
Fe20s, Fes04, 7-Fe2O3 and 7
-Mixed crystal with Fe30a, cobalt-containing γ-Fe20s,
Examples include cobalt-containing γ-Fe50+, metal magnetic powder with an oxide film on the surface, and the like. Examples of binders that can be used in the magnetic layer include thermoplastic polyurethane resins, phenoxy resins, vinylidene chloride-acrylonitrile copolymers, and butadiene-acrylonitrile copolymers.

acrylonitrile-butadiene-acrylic acid copolymer,
Styrene-butadiene copolymer, polyvinyl butyral, polyester resin, nitrocellulose, vinyl chloride
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-
Examples include vinyl acetate-maleic acid copolymer, acrylic ester-acrylonitrile copolymer, and acrylic ester-vinyl chloride=IJ-dene copolymer. Higher fatty acids such as lecithin and oleic acid can be used as the dispersant, and α-alumina, α-Fe20s, chromium oxide, etc. can be used as the abrasive.

Page 6 Various types of crosstalk machines are used to disperse crosstalk in magnetic paint. For example, three-roll mill, ball mill, pebble mill, sand grinder, high-speed impeller dispersion machine, high-speed stone mill, high-speed impact mill, disper, niegu, high-speed mixer.

A homogenizer, an ultrasonic disperser, etc. can be used alone or in combination.

Description of examples Hereinafter, the present invention will be specifically explained with reference to Examples.

(Example 1) 60 parts by weight α-alumina 3 parts by weight Lecithin
1 part by weight Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 20 parts by weight Polyurethane resin 5 parts by weight Palmitic acid 1 Part by weight graphite (average particle size 1 μm)
・ 6 parts by weight 74, S ・ Dioctadecyl succinate ・・・・・・・・・
2 parts by weight MKK-) luene-cyclohexanone 300 parts by weight A magnetic paint having the above composition was prepared using a ball mill for 24 hours, and a crosslinking agent of Coronae) L (Japan Polyurethane (
After adding 5 parts of (trade name) (trade name), the mixture was stirred and mixed using a disper for 30 minutes. Next, this was filtered through a filter with an average pore size of 3 μm, coated on both sides of a 75 μm thick polyester film to a dry thickness of 1.5 μm, and dried to form a magnetic layer.

After curing, a disk with a diameter of 3 inches was punched out, and the surface of the magnetic layer was polished with an abrasive tape to obtain a magnetic recording disk.

(Example 2) A magnetic recording disk was produced in the same manner as in Example 1 except that 4 parts by weight of hexadecyl eicosyl suberate was added instead of dioctadecyl succinate.

(Example 3) In Example 1, graphite was made with an average particle size of 500 mμ.
A magnetic recording disk was produced in the same manner except that the following was used.

(Comparative Example 1) A magnetic recording disk was produced in the same manner as in Example 1 except that graphite was removed.

(Comparative Example 2) A magnetic recording disk was produced in the same manner as in Example 1 except that dioctadecyl succinate was removed.

(Example 4) A magnetic recording disk was prepared in the same manner.

(Example 5) An oxide film was formed on the surface...40 parts by weight α-We213...
5 parts by weight silicone oil, knockout, 1 t
t part polyurethane resin ・River... 10
Parts by weight: 9 bases - Mini nitrocellulose 10
Heavy I part oleic acid ・・・・・・・・・
2 parts by weight graphite (average particle size 1 μm)...
... 4 parts by weight dioctadecyl malate ...
3 parts by weight MKK-toluene-cyclohexanone 300 parts by weight A magnetic paint having the above composition was produced, and a magnetic recording disk was produced in the same manner as in Example 1.

The magnetic recording disks obtained in the above Examples and Comparative Examples were loaded into a recording/reproducing apparatus while being inserted into the dirt prevention jacket described above, and a magnetic head (pad pressure of 120 g, 4 mm) was used to drive the magnetic recording disks at 1.02 m/sec. The output voltage is 20% while making sliding contact.
The time until the percentage decrease was measured. The results are shown in the table below.

(Monday, 2nd 4b) Page 10 Effects of the Invention As is clear from the table above, the magnetic recording disk of the present invention that uses graphite and a dibasic acid ester in combination is more durable than the magnetic recording disk of the comparative example that uses graphite and dibasic acid ester alone. Its properties have been greatly improved, and its practical value is of great value.

Claims (1)

[Claims] an alkyl group or alkenyl group having 1 to 26 carbon atoms,
R1 is ÷CH2÷n (n=2~6) or +OH
1. A magnetic recording disk characterized by having a magnetic layer containing a dibasic acid ester represented by the formula (=l+) and graphite having an average particle size of 5 ooomμ to 2)bm.