JPH0316018A - Magnetic disk - Google Patents

Abstract

PURPOSE:To reduce friction of a medium without losing electromagnetic conversion characteristics and to improve durability of the medium by incorporating carbon black into a magnetic layer in a manner that the quantity of carbon black is larger in the nonrecording layer side than in the recording surface side. CONSTITUTION:The magnetic disk is produced by applying a coating material for the magnetic recording layer on the one side of 33mum thick polyethylene terephthalate film, applying another coating material for nonrecording layer on the other side of the film, drying so as to obtain each 4.0mum thick layer after dried, then calendering and punching into a 47mm-diameter disk. Carbon black is incorporated as a solid additive into the magnetic layer in a manner that the quantity of carbon black is larger in the nonrecording layer side of the magnetic layer than in the recording surface side. Thereby, frictional property of the disk is improved, and the disk has excellent electromagnetic conversion characteristics and durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic disks, and more particularly to improving running performance.

[Conventional technology]

In recent years, magnetic disk drives have become smaller and smaller.
Along with this, the motors used are also becoming smaller and more power efficient. For this reason, magnetic recording media are also required to reduce the load torque.

Conventionally, carbon black has been incorporated into the magnetic layer as one means for reducing the coefficient of friction of a-air recording media. However, in order to reduce the friction coefficient to the target [1] by adding carpon crack, the amount added is large, and the residual magnetic flux density of the magnetic layer becomes small. Subasing loss between the magnetic coating film and the magnetic head in sliding contact deteriorates the electromagnetic conversion characteristics of the magnetic recording medium.

In addition, when it comes to durability, when sliding contact with the magnetic head,
The amount of carbon plaque particles falling off from the surface of the magnetic layer increases, which causes a decrease in the durability of the magnetic recording medium.

[Problem that the invention seeks to solve]

This invention solves the drawback of conventional products, which involve adding a large amount of carbon black to the magnetic layer.
! The purpose of the present invention is to provide a magnetic disk with a low coefficient of friction and excellent electromagnetic conversion characteristics and durability.

[Means to solve the problem]

Normally, magnetic disks are required to have good contact with the magnetic head, so it is necessary to reduce the resistance of the magnetic layer. Therefore, it is common practice to coat both the front and back surfaces of a non-magnetic support with a paint having the same composition κ. In a magnetic disk having such a recording magnetic layer and a non-recording magnetic layer, its frictional performance is improved by adding carbon black, which has the effect of reducing the coefficient of friction, to the non-recording magnetic layer in an amount that sufficiently reduces the coefficient of friction. On the other hand, in the recording magnetic layer that comes into sliding contact with the magnetic head, by adding an amount that does not reduce the electromagnetic conversion characteristics and durability, a magnetic material with a low b1 friction coefficient and excellent electromagnetic conversion characteristics and durability is added. I got Dinuk.

On the other hand, it is desirable to add 2.0 to 50.0% by weight.

If the amount added is less than 2.0%, the friction coefficient of the surface of the non-recording magnetic layer cannot be sufficiently lowered, and if it is more than 50.0%, the adhesive force of the magnetic layer decreases, causing the carpon crack to fall off. It increases rapidly, stains the pad surface, and eventually causes dropout.

On the other hand, the amount of carbon blank in the recording magnetic layer does not need to be added if the friction coefficient of the non-recording magnetic layer surface is sufficiently reduced. Chirui is 2.0% by weight compared to ferromagnetic fine particles! Depending on the amount added, the friction performance can be sufficiently improved, and the electromagnetic conversion characteristics and durability can also be excellent.

〔Example〕

EXAMPLES The present invention will be explained in detail with reference to Examples below.

Example (Paint for recording magnetic layer) Metallic iron powder (SBET: 50trf/9, He:
1530 0eS's: 125 emu/9)
100 parts polyurethane resin 6
．． 6 parts trifunctional isocyanate compound 4.4 parts alumina 15 parts isoamyl stearate 1.10 parts cyclohexanone 155 parts toluene
155 parts of the above composition was placed in a ball mill and kneaded for 72 hours to uniformly disperse it to prepare a coating material for the magnetic layer.

<Materials for non-recording magnetic layer> Graphdate carbon black (
Mitsubishi Kasei #4010, particle size: 80mμ, SRE
T: 25 m'/l) 8 parts of the composition was used as a non-recording layer paint in the same manner as the recording layer paint.

A recording layer paint was applied to one side of a polyethylene terephthalate film with a thickness of 33 capes, and a non-recording layer paint was applied to the other side to a dry thickness of 4.0 cm. After drying, calendering was performed. was applied. Next, a disk-shaped magnetic disk having a diameter of 471 liters was punched out.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that one case of the recording layer paint was used as the non-recording layer paint.

Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1, except that both the recording layer paint and the non-recording layer paint were coolants to which 1 part of goufite carbon plaque was added.

Comparative Example 3 A magnetic disk was produced in the same manner as in Example 1 except that a magnetic layer coating material in which 4 parts of graphitized carbon black was added to the recording layer coating material was used.

3600 magnetic disks obtained in each of the above Examples and Comparative Examples
The friction coefficient at that time, the ratio of the output level and the nozzle level (C/Nl) are
was measured.

The durability of the housing is 1 to 5 in an environment of 55℃ and 30%RH.
The time until the eyelid membrane peeled off 111 when the vehicle was running on a 0 track seek was measured.

〔Effect of the invention〕

As explained above, in a magnetic disk in which magnetic layers are formed on both the front and back sides of a non-magnetic support, the amount of carbon brass contained in the non-recording layer side is greater than the content in the recording layer side. It has become clear that by increasing the amount, low friction performance can be achieved without deteriorating the electromagnetic conversion characteristics, and durability performance can also be significantly improved.

Claims (2)

[Claims] (1) In a magnetic disk in which magnetic layers in which ferromagnetic fine particles are dispersed in a non-magnetic binder are formed on the front and back surfaces of a non-magnetic support, addition of carbon black contained as a solid additive in the magnetic layer A magnetic disk characterized in that a larger amount is contained in the magnetic layer on the non-recording surface side than on the recording surface side. (2) The amount of carbon black added in the magnetic layer on the non-recording side is 2.0 to 50.0 W relative to the ferromagnetic fine particles in the magnetic layer.
The magnetic disk according to claim 1, wherein the magnetic disk is t%.