JPS6173240A - Magnetic disk - Google Patents

Abstract

PURPOSE:To prevent the deterioration in wear resistance during preservation at a high temp. by providing a magnetic layer contg. magnetic metallic powder and binder on a base and incorporating unsatd. fatty ester and polishing agent particles having specific hardness or above into the magnetic layer. CONSTITUTION:The ester of unsatd. fatty acid of 14-20C and alcohol of 4-20C is used for the unsatd. fatty ester. The polishing agent particles to be used in combination are the component to impact such strength at which the magnetic layer in sliding contact powerfully with a magnetic head and pad withstands the sliding contact pressure. The polishing agent having >=7 Mohs hardness in particular is selectively used. As the embodiment thereof, alpha-Al2O3 powder, Cr2O3 powder and SiC powder are used. The magnetic disk is formed by preparing a magnetic paint consisting of the magnetic metallic powder and suitable binder kneaded with a wear resistance imparting component, coating such paint on one or both surfaces of the base consisting of a polyester film and drying the coating to form the magnetic layer, then subjecting the base to a calender treatment and blanking treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a magnetic disk such as a floppy disk, which has a magnetic layer containing metal magnetic powder and a binder provided on a base.

[Prior Art 1] This type of magnetic disk differs from other magnetic recording media such as magnetic tape in that it has a magnetic layer and a magnetic head.

Because the magnetic layer slides into contact with an object such as a pad at a very high speed, the magnetic layer is likely to wear out. In particular, those using metal magnetic powder as the magnetic powder have the disadvantage that they are softer than oxide-based magnetic powders, and therefore tend to cause abrasion of the magnetic layer.

Therefore, an attempt has been made to add a lubricant such as a known saturated fatty acid ester and abrasive particles with a Mohs hardness of 6 or more to the magnetic layer of a magnetic disk as a component that imparts wear resistance to the magnetic layer of a magnetic tape. (Reference unknown). However, since magnetic disks undergo particularly severe wear, it is difficult to obtain a sufficient wear resistance improvement effect with the general wear resistance imparting ingredients such as those mentioned above. In other words, the type of abrasive particles In some cases, there was a problem in that almost no improvement effect was observed, and in many cases, the abrasion resistance was extremely reduced after being stored at high temperatures for a long period of time.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problem that conventional magnetic disks do not have a sufficiently satisfactory wear-resistance improvement effect, and provides a novel wear-resistance improvement effect. The purpose of the present invention is to significantly improve the wear resistance of the magnetic layer by using a properties-imparting component, thereby significantly improving the durability of the magnetic disk.

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the inventors used unsaturated fatty acid ester as a lubricant component, and used abrasive particles with a particularly high Mohs hardness. 7 or more, and when these are included together in the magnetic layer of the magnetic disk as wear resistance imparting components, the wear resistance of the magnetic layer using metal magnetic powder as the magnetic powder can be greatly improved. At the same time, they discovered that it is possible to prevent a decrease in wear resistance under high-temperature storage, leading to the completion of this invention.

That is, the present invention provides a magnetic disk in which a magnetic layer containing metal magnetic powder and a binder is provided on a base,
The present invention relates to a magnetic disk characterized in that the magnetic layer contains an unsaturated fatty acid ester and abrasive particles having a Mohs hardness of 7 or more.

[Structure and operation of the invention] The unsaturated fatty acid ester used in this invention differs from conventionally known saturated fatty acid esters in that it contains carbon-carbon in the molecule.
It has a carbon double bond and is generally characterized by low volatility. The reason why this ester greatly contributes to improving the wear resistance of the magnetic layer is not necessarily clear. It is speculated that this ester has good affinity and adsorption with the metal magnetic powder that has a polar group on the particle surface, and that it itself is difficult to scatter from the magnetic layer.
It functions effectively as a lubricant component for magnetic disks that are subject to severe wear, and is thought to bring about very good results in improving the wear resistance of the magnetic layer not only initially but also after long-term storage at high temperatures.

Such unsaturated fatty acid esters have a carbon number of 14
Esters of ~20 unsaturated fatty acids and alcohols having 4 to 20 carbon atoms are preferred. The unsaturated fatty acids mentioned above may contain one carbon-carbon double bond in the molecule or two.
It may contain more than one. Further, the alcohol may contain a carbon-carbon double bond or an ether bond in its molecule. Some representative examples of such esters include 2-ethylhexyl oleate, phthyl oleate, oleino oleate, 2-ethylhexyl elaidate, butyl elaidate, oleyl elaidate, butyl cellosolve oleate, and 2-ethylhexyl elaidate. - Examples include ethylhexyl cellosolve.

In this invention, the abrasive particles used in combination with the unsaturated fatty acid ester are components that impart strength to the magnetic layer that makes strong sliding contact with magnetic heads, pads, etc. to withstand the sliding contact pressure. A hardness on the Mohs scale of 7 or higher must be selected. Less than the above Mohs hardness,
For example, α-Fe20, which is used in magnetic tape, etc.
If powder No. 3 is used, the effect of highly improving wear resistance, which is the objective of this invention, cannot be obtained.

Specific examples of abrasive particles with a Mohs hardness of 7 or higher include α-
Examples include A1203 powder, Cr2O3 powder, and SiC powder. The average particle diameter of these particles is generally 01 to 2.
It is preferable that it be about 0 P.

In this invention, the amount of the unsaturated fatty acid ester and abrasive particles used as the wear resistance imparting component is based on 100 parts by weight of the metal magnetic powder in the magnetic layer. 1 to 30 parts by weight, 1 to 2 parts by weight of abrasive particles
It is desirable that the amount is 0 parts by weight. If either of the same components is too small, a sufficient effect of improving wear resistance cannot be obtained. Also,
If the amount of unsaturated fatty acid ester is too large, it will bleed out to the surface of the magnetic layer, contaminating the magnetic head, and if the number of abrasive particles increases too much, the amount of metal magnetic powder packed will decrease and the residual magnetic flux density of the magnetic layer will decrease. Both of these causes a decrease in output.

The magnetic disk of the present invention is produced by preparing a magnetic paint made by kneading the above-mentioned wear-resistance-imparting component with, for example, metal magnetic powder and a suitable binder, and applying this to one or both sides of a base such as a polyester film to a dry thickness. Usually 05~ on one side
3. It can be obtained by coating and drying to form a magnetic layer so that it becomes O-, and then performing calendering, punching, etc. in a conventional manner. In addition, unsaturated fatty acid esters among the wear resistance imparting components are removed from the magnetic paint to form a magnetic layer as described above, and then impregnated by spraying or dipping the surface of this layer in the form of a solution. There is no harm in letting them do so.

Although the metal magnetic powder described above exhibits superior performance compared to oxide-based magnetic powder for high-density recording, as mentioned above, it tends to have problems with its wear resistance when used in magnetic disks. These problems can be reliably solved by using the abrasion resistance imparting component of the present invention. Therefore, in order to take advantage of the characteristics mentioned above for high-density recording, it is preferable that the particle size is as small as possible, and generally the specific surface area measured by the nitrogen adsorption method is 30 to 60 r.
! f/fi' is used.

Examples of the metal magnetic powder include magnetic metal powders or alloy powders such as Fe, Co, and Ni, and alloy powders in which these magnetic metals contain non-magnetic metals. Furthermore, as the binder used in combination with this metal magnetic powder, any conventionally known binder such as polyvinyl chloride resin, cellulose resin, polyester resin, polyurethane resin, polyacetal resin, polyincyanate compound, etc. can be used. It is.

In addition to the above-mentioned components, the magnetic paint may optionally contain various commonly used additives such as surfactants, antistatic agents, and pigments. In some cases, it is also possible to contain other lubricants or abrasive particles different from the wear resistance imparting component according to the present invention in an amount within a range that does not impair the effects of the present invention.

[Effects of the Invention] As described above, in this invention, unsaturated fatty acid ester and abrasive particles having a Mohs hardness of 7 or more are included in the magnetic layer of a magnetic disk using metal magnetic powder as the magnetic powder. As a result, it is possible to provide a magnetic disk having excellent durability, in which the wear resistance of the magnetic layer is greatly improved, and the above-mentioned wear resistance improvement effect does not decrease even when stored at high temperatures for a long period of time. can.

〔Example〕

EXAMPLES Below, examples of the present invention will be described in more detail. In addition, in the following, parts shall mean parts by weight.

Example 1 Metal Fe powder (coercive force 1,650 oersted, saturated
150 parts magnetization 120 emu/p, specific surface area 50 emu/p4)
Vinyl chloride-vinyl acetate-vinyl alcohol 2
0 parts polymer (trade name: VAGH manufactured by UCC, USA) Polyurethane resin (trade name, manufactured by Dainippon Ink Co., Ltd. 20 Part name T
5250) Trifunctional incyanate compound Hatamoto polyurethane 10 parts Product name Coronate L manufactured by Rethan Co.) Graphitized carbon black (Mitsubishi Kasei 12
Product name manufactured by the company: $4010) α-A1203 powder (average particle size 0.7) m)
9 parts 2-ethylhexyl oleate
15 parts cyclohexanone 220 parts toluene
220 parts The above components were mixed and dispersed in a ball mill for 96 hours to prepare a magnetic paint, and this paint was applied to both sides of a 751 IM thick polyester film so that the dry thickness of both sides was 2.5 tones. A magnetic layer was formed. Next, a magnetic disk was produced by performing a calendering process and a disk-shaped punching process.

Example 2 A magnetic disk was produced in the same manner as in Example 1, except that the same amount of Cr2O5 powder (average particle size 0.4 μ) was used instead of α-A1203 powder.

Example 3 Instead of α-A1203 powder, SiC powder (average particle size 0.
A magnetic disk was produced in the same manner as in Example 1, except that the same amount of 7 units) was used.

Example 4 A magnetic disk was produced in the same manner as in Example 1, except that 15 parts of oleyl oleate was used instead of 2-ethylhexyl oleate.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1, except that the same amount of α-Fe203 powder (average particle size 0.7 pn) was used instead of α-A1203 powder.

Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1, except that the same amount of loobyl stearate was used instead of 2-ethylhexyl oleate.

In order to examine the durability performance of each of the magnetic disks of Examples 1 to 4 and Comparative Examples 1 to 2, each magnetic disk was loaded into a recording/reproducing device and a magnetic head was attached to it with a pad pressure of 30 y/min.
The running time until the playback output reached 70% of the initial output was measured while making sliding contact with the CRD. The above test was conducted on magnetic disks that were left at room temperature for a short time after production (initial stage) and those that were left at 60°C for 4 weeks (after high-temperature storage). The results were as shown in the table below.

As is clear from the above table, the magnetic disk of this invention has
It can be seen that it exhibits excellent durability not only initially but also after long-term storage at high temperatures.

Claims (1)

[Claims] (1) In a magnetic disk comprising a magnetic layer containing metal magnetic powder and a binder on a base, the magnetic layer contains an unsaturated fatty acid ester and abrasive particles having a Mohs hardness of 7 or more. A magnetic disk featuring