JPS5928237A - Magnetic recording disk - Google Patents

Abstract

PURPOSE:To improve the durability, by incorporating aliphatic amide and graphite of 500mmu-2mum average grain size into the magnetic layer to improve the wear resistance of the magnetic layer itself. CONSTITUTION:The frictional force of aliphatic amide represented by a general formula RCONH2 (where R is 13-17C alkyl or alkenyl) is reduced in accordance with an increase in the molecular size of the amide, yet the frictional force is not reduced any more when the amide attains to a certain molecular size, so the number of Cs in the aliphatic amide is restricted. Myristic acid amide, palmitic acid amide or the like is used as the aliphatic amide. The amide is preferably added by <=20pts.wt. per 100pts.wt. magnetic powder. 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. Graphite of 500mmu-2mum size is preferably added by <=20pts.wt. per 100pts.wt. magnetic powder. Thus, the durability is considerably improved.

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 Structures and Problems In magnetic recording media, such as magnetic recording disks, in which a magnetic layer and a magnetic head slide at high speed during recording and reproduction, the coefficient of friction of the magnetic layer must be kept as small as possible. As a method for reducing the coefficient of friction, a method is known in which a lubricant such as a higher fatty acid and a fatty acid ester, a higher fatty acid and a fluorine oil, etc. is applied to the surface of the magnetic layer. However, with such external addition, not only does the lubricant disappear quickly, making it impossible to maintain long-term durability, but the lubricant also 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 eliminate the above-mentioned conventional drawbacks and provide a magnetic recording disk with excellent durability by improving the wear resistance of the magnetic layer itself.

Structure of the Invention The present invention was achieved as a result of intensive studies on lubricants to be added to the magnetic layer. That is, the present invention provides general formula RC
A magnetic recording disk having a magnetic layer in which an aliphatic amide represented by ONH2 (where R is an alkyl group or an alkenyl group having 13 to 17 carbon atoms) and graphite with an average particle size of 500 to 2 μm coexists has friction. This was based on the discovery that gelaphite particles have a low friction coefficient and excellent wear resistance, and this is because aliphatic amides are strongly adsorbed to gelaphite particles, which lowers the friction coefficient and improves wear resistance. ” is considered to be the same.

It has been found that in the aliphatic amide represented by the above general formula, the frictional force decreases as the molecular size of the aliphatic amide increases, but the frictional force does not decrease once it reaches a certain size. For this reason, the number of carbon atoms in the aliphatic amide is limited. A specific example of the aliphatic amide is myristic acid amide.

Examples include palmitic acid amide, stearic acid amide, and oleic acid amide. However, the amount of aliphatic amide added is preferably 20 parts by weight or less per 100 parts by weight of the magnetic powder; if the amount is too much, embossment will occur on the surface of the magnetic layer, resulting in staining of the magnetic head.

Still, the suitable average particle size of graphite is 500 mμ to 2 μm, and it is difficult to obtain graphite smaller than this, and if it is thicker than this, the surface properties of the magnetic layer will be poor.
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, γ-
Fe206. Fe604. γ-Fe205 and γ-Fe2
Mixed crystal with O3, cobalt-containing γ-Fe 206. Examples include metal magnetic powder with an oxide film provided on the surface of cobalt-containing γ-Fθ6042. Binders that can still be used in the magnetic layer include thermoplastic polyurethane resins, phenoxy resins,
Vinylidene chloride-acrylonitrile copolymer.

Butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-acrylic acid copolymer.

Styrene-butadiene copolymer, polyvinyl butyral+ho+) ester resin, nitrocellulose.

vinyl chloride-vinyl acetate-vinyl alcohol copolymer,
Examples include vinyl chloride-vinyl acetate-maleic acid combination, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, and the like. Higher fatty acids such as lecithin and oleic acid can be used as dispersants, and α-alumina and α-alpha can be used as abrasives.
-Fe,,03. Chromium oxide etc. are used. However, conductive carbon such as Kettin Black E, C, etc. can also be added as an antistatic agent.

Various types of crosstalk devices are used to disperse magnetic paint crosstalk. For example, three roll mill, ball mill, pebble mill, sand grinder, high speed impeller disperser, high speed stone mill, high speed impact mill, disperser, kneader-2 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 6,:, -:; α-alumina group 3 parts by weight Lecithin Old... 1-fjrU vinyl chloride-vinyl acetate-vinyl alcohol copolymer union
・Old...15 parts by weight polyester resin
...10 parts by weight oleic acid
・・・・・・ 1 part by weight graphite (average particle size 1μ
m)... 4 parts by weight Ketin Black E-C,
・・・・・・ 2 parts by weight stearic acid amide ・
Old... 4 parts by weight MEK-toluene-cyclohexanone...300 parts by weight A magnetic paint with the above composition was prepared in 24 hours using a ball mill, and Coronate L (Japan Polyurethane) was added as a crosslinking agent.
After adding 5 parts of Co., Ltd. (trade name), three parts were stirred and mixed using a disper. Next, this was filtered through a filter having an average pore size of 3 μm, and then coated on both sides of a 75 μm thick polyester film to a dry thickness of 1.6 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 form a magnetic recording disk.
It's a page.

(Example 2) A magnetic recording disk was produced in the same manner as in Example 1 except that 4 parts by weight of palmitic acid amide was added instead of stearic acid amide.

(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 stearamide was removed.

(Example 4) In Example 1, a magnetic recording disk was produced by using magnetic powder containing cobalt.

(Example 5) Metallic iron powder silicone oil with an oxide film on the surface 1 part by weight Polyurethane resin 10 parts by weight Nitrocellulose 10 parts by weight Oleic acid ... 2 parts by weight Graphite (average particle size 1 μm) 4 parts by weight Oleic acid amide 3 parts by weight MEK
-) Luene-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,
a) 1. The output voltage is 2 while making sliding contact at o2m/sec.
The time at which the temperature decreased by 0% was measured. The results are shown in the table below.

Page 9 Effects of the Invention As is clear from the table above, the magnetic recording disk of the present invention that uses graphite and aliphatic amide in combination has significantly improved durability compared to the magnetic recording disk of the comparative example that uses graphite and aliphatic amide alone. , its practical value is significant.

Name of agent: Patent attorney Toshio Nakao and 1 other person19

Claims (1)

[Claims] General formula: RCONH2 (where R is an alkyl group or alkenyl group having 13 to 1 carbon atoms) and a magnetic layer containing graphite with an average particle size of 500 mμ to 2 μm. recording disc.