JPH0289220A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the generation of an output fluctuation and drop-out by specifying the surface roughness of a magnetic coated film and the average grain size of the alumina to be incorporated into a magnetic layer. CONSTITUTION:The high-recording density magnetic recording medium which has <=0.015mum surface roughness of the magnetic coated film and is specified in the average grain size of the solid additive to be added into this magnetic coated film to <=50 times the surface roughness is used. The reason thereof lies in that the parts of the solid additive projecting from the surface of the coated film increase if the average grain size of the solid additive increases. The increases in the amt. at which the magnetic head or cleaning sheet in sliding contact with the magnetic recording medium is chipped away is then caused. The generation of the output fluctuation ad the drop-out is prevented in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to magnetic HC recording media, and more particularly to improvements in solid additives added to magnetic layers.

[Conventional technology]

Conventionally, magnetic recording media have been developed for the purpose of improving durability.
Morse lil! J! solid additive agent such as alumina with high degree of 1! -Ratio of concentration contained in it. However, this solid additive with a high Mohs hardness acts as an abrasive for the magnetic head, cleaning sheet, etc. that come into sliding contact with the media, and after being scraped off, the shavings from the magnetic head, cleaning sheet, etc. adhere to the magnetic coating. It has become clear that dropouts cause output fluctuations. Especially for short wavelength magnetic recording media.

Since the surface smoothness of the magnetic surface is good, even small particles can cause output fluctuations and dropouts.

[Problems that the invention attempts to solve] This invention solves the following problem: 1) The occurrence of output fluctuations and dropouts during one period of use in a short-wavelength magnetic recording medium with good surface smoothness.
It is an object of the present invention to solve the disadvantage of adding high density data and to provide a highly reliable magnetic recording medium for high-density recording.

[Means to solve the problem]

In view of this situation, the inventors of the present invention conducted extensive studies and found that the magnetic property was 31! It was discovered that if the average particle size of the Mohs f1 solid additive contained in the film is 50 times or less than the surface roughness of the tm-based coating, the increase in output fluctuation during use will be reduced.1 The present invention was developed. I arrived at the eggplant. This is because as the average particle size of the solid additive increases, the portion of the solid additive that protrudes from the coating surface increases9, which increases the amount of the magnetic head and cleaning sheet that are in sliding contact with the magnetic recording medium that are scraped off. Presumed.

In particular, when magnetic powder suitable for high-density recording, such as metal magnetic powder, is used, the surface roughness of the magnetic layer surface is reduced in order to better exhibit its performance. In this case, even if minute foreign matter adheres to the surface of the magnetic 11, it will cause output fluctuations or dropouts, so it is necessary to prevent the generation of minute dust as much as possible. Therefore, the medium is stored in the cartridge case. However, during use, it is constantly in sliding contact with a cleaning sheet to remove dust from the surface of the medium. For this reason, it is necessary to prevent the magnetic head cleaning sheet from being scraped as much as possible. For such high-density recording media, selection of solid additives with high Mohs hardness has a very large effect.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

<Preparation of magnetic disk> Metal magnetic powder (coercive force, 16500@, 8mxr,
55rl/11) 161 parts chloride, vinyl acetate, vinyl alcohol copolymer CUCC,
VAGH) 19.8fls
Polyurethane resin (manufactured by Mitsubishi Chemical Industries, Ltd., ME664)
11.8 parts trifunctional low molecular weight incyanate compound (Japan Polyurethane Co., Ltd. IA, Coronate L) 7.8 parts α-AhOs (average particle size XIJ) 32.2 parts oleyl oleate
16.2 Part 7 Clohexanone
240 parts toluene
240 parts The average particle diameter Xμ+@ of α-AJmOs in the above composition was determined as shown in Table 381 according to each Example and Comparative Example.

This composition was dispersed at 96 hours in a ball mill to form a magnetic a
Prepare m ingredients and use this? On both sides of a polyethylene terephthalate film with a near 5μ corner thickness,
After coating, drying, and calendering to form a .mu.-diameter, a magnetic disk was punched out into a disk shape with an outer diameter of 860 mm. -The surface smoothness of the air disk was controlled by changing the conditions of calendering process. this magnetic disk.

A cleaning sheet was placed inside and subjected to ultrasonic waves. The product was made into a product by storing it in a cartridge case made of hard melon synthetic resin.

Are the surfaces of the magnetic disks obtained in the above Examples and Comparative Examples flat? The average particle size of W Note and α-kl*Os was measured, and for the 1M product, its output level, initial output fluctuation,
The output fluctuation t-meter was measured after aging for 96 hours at 45° C. and 45% RHo environment.

Using a stylus type surface roughness needle with surface smoothness = R of 2 μm, stylus speed 0.03 mm/sea, cutoff 0.08
Determine the surface rM roughness of the magnetic m capture under the following conditions.

Average particle size of a-Alton: cross-sectional photograph of coating film 1ft50
The diameters of 1,000 α-A4sQ particles were measured, and the diameters of 1,000 α-A4sQ particles were calculated and integrated starting from the smallest particle size. The particle size at which 50% of the total number of particles was directly placed was defined as the average particle size.

Output level: Using the Meshari KVjHl floppy disk characteristics test @ (uses Sendust magnetic head),
Output level t request for 35kfci*.

Output variation 2 outputs and bell t-3 with the same test machine that was measured
00 rPm, 500 kt (z The average absolute value over all tracks is taken as the output fluctuation.

The results of each measurement are shown in Table 1.

Margin below From the above results, the output level of the magnetic disk with one surface flatness of 0.015μ or more (Comparative Example 1) is low,
Also, the output fluctuation after the initial run is large. Furthermore, even if the surface smoothness is 0.015 μm or less, the average particle diameter of the round-shaped gsjJLI agent is larger than the surface smoothness (1) For magnetic disks (Comparative Examples 2 and 3), the output level and the initial It is recognized that although the output fluctuation is small, the output return after driving is large and the reliability is poor.

〔Effect of the invention〕

As explained above, the surface roughness of the magnetic layer is 0.01
The high density magnetic recording system in which the average particle diameter of the hexagonal additive in the Mi-based coating is less than 5 OtV1, which is the surface roughness, has a high output level.

It is clear that this is a recording medium with a high axial power of 1, which has a small increase in output fluctuation during use.

Applicant: Hitachi Maxell, Ltd. Representative - Atsushi Mizu

Claims (3)

[Claims] (1) A magnetic recording medium characterized in that the surface roughness of the magnetic coating is 0.015 μm or less, and the average particle size of alumina contained in the magnetic layer is 50 times or less the surface roughness. (2) The magnetic recording medium according to claim (1), wherein the magnetic powder contained in the magnetic coating film is metal magnetic powder. (3) A floppy disk characterized in that the magnetic recording medium according to claim (1) is housed in a disk shape in a cartridge case comprising a pair of front and back shells and a cleaning sheet supported on the inner surface of the shell. disk.