Magnetic disk

Details Magnetic disk Magnetic disk

2001-11-29

2003-06-10

Resan, Stevan A. (Department: 1773)

Stock material or miscellaneous articles

Circular sheet or circular blank

Recording medium or carrier

C428S141000, C428S216000, C428S323000, C428S690000, C428S690000, C428S690000

Reexamination Certificate

active

06576322

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a particulate magnetic disk (i.e., a magnetic disk having a magnetic layer where a magnetic powder is dispersed in a binder) having a high recording density. Particularly, the invention relates to a magnetic disk for high-density recording, having a magnetic layer and a substantially non-magnetic lower layer and the magnetic layer contains a ferromagnetic metal powder or a hexagonal ferrite powder.
2. Description of the Related Art
In the field of magnetic disks, an Mf-2HD floppy disk of 2MB using Co-modified iron oxide has been standard-mounted on a personal computer. However, at present, the data capacities to be handled have been rapidly increased, the capacity thereof has not become sufficient, and the increase of the capacity of a floppy disk has been desired.
Hitherto, as a magnetic recording medium, the magnetic recording medium obtained by coating on a non-magnetic support a magnetic layer containing an iron oxide powder, a Co-modified iron oxide powder, a CrO
2
powder, a ferromagnetic metal powder, or a hexagonal ferrite powder dispersed in a binder has been widely used. In these magnetic substances, it is known that the ferromagnetic metal powder and the hexagonal ferrite powder are excellent in the high-density recording characteristics.
In the case of magnetic disks, as a large capacity magnetic disk using the ferromagnetic metal powder excellent in the high-density recording characteristics, there are MF-2TD of 10MB and MF-2SD of 21MB and as a large capacity magnetic disk using the hexagonal ferrite powder, there are MF-2ED of 4MB and 21MB floptical disk, etc., but it cannot be say that they are sufficient in the capacity and the performance. Under these circumstances, various attempts have been made for improving the high-density recording characteristics. Examples thereof are shown below.
For improving the characteristics of disk-form magnetic recording medium, Japanese Patent Laid-Open No. 84418/1989 proposes that a vinyl chloride resin having an acidic group, an epoxy group, and a hydroxyl group, Japanese Patent Examined Publication No. 12374/1991 proposes that a metal powder having Hc of at least 79.6 kA/m (1000 Oe) and a specific area of from 25 to 70 m
2
/g is used, and Japanese Patent Examined Publication No. 28106/1994 proposes that the specific area and the magnetizing amount of a magnetic substance are determined and an abrasive is incorporated.
For improving the durability of a disk-form magnetic recording medium, Japanese Patent Examined Publication No. 85304/1995 proposed that an unsaturated fatty acid ester and a fatty acid ester having an ether bond are used, Japanese Patent Laid-Open No. 124716/1979 proposes that a non-magnetic powder having a Mohs' hardness of at least 6 and a higher fatty acid ester are incorporated, Japanese Patent Examined Publication No. 89407/1995 proposes that the volume and the specific area of pores containing abrasives are established to be from 0.005 to 0.25 &mgr;m, Japanese Patent Laid-Open No. 294637/1986 proposes that a fatty acid ester having a low melting point and a fatty acid ester having a high melting point are used, Japanese Patent Examined Publication No. 36216/1995 proposes that an abrasive having particle sizes of from ¼ to ¾ to the thickness of the magnetic layer and a fatty acid ester are used, and Japanese Patent Laid-Open No. 203018/1991 proposes that a metal magnetic substance containing Al and chromium oxide are used.
As the construction of a disk-form magnetic recording medium having a non-magnetic lower layer or an interlayer, Japanese Patent Laid-Open No. 120613/1991 proposes a construction having an electrically conductive layer and a magnetic layer containing a metal powder, Japanese Patent Laid-Open No. 290446/1994 proposes a construction having a magnetic layer having a not thicker than 1 &mgr;m and a non-magnetic layer, Japanese Patent Laid-Open No. 159337/1987 proposes a construction comprised of a carbon interlayer and a magnetic layer containing an abrasive, and Japanese Patent Laid-Open No. 290358 proposes a construction having a non-magnetic layer wherein a carbon size is regulated.
On the other hand, recently, a disk-form magnetic recording medium comprised of a thin-layer magnetic layer and a functional non-magnetic layer has been developed, and floppy disks of 100 MB class have been appeared. As the floppy disks showing these characteristics, Japanese Patent Laid-Open No. 109061/1993 proposes a construction having a magnetic layer having Hc of 111.4 kA/m (1400 Oe) and a thickness of not thicker than 0.5 &mgr;m and a non-magnetic layer containing electrically conducive particles, Japanese Patent Laid-Open No. 197946/1993 proposes a construction containing an abrasive larger than the thickness of the magnetic layer, Japanese Patent Laid-Open No. 290354/1993 proposes a construction in which the thickness of the magnetic layer is not thicker than 0.5 &mgr;m, the thickness fluctuation of the magnetic layer thickness is restrained within ±15%, and the surface electric resistance is regulated, and Japanese Patent Laid-Open No. 68453/1994 proposes a construction in which two kinds of abrasives each having a different particle size are contained and the amounts of the abrasives are regulated.
Also, in Japanese Patent Laid-Open No. 52541/1994, a magnetic recording medium containing at least one kind of alumina, chromium oxide, and diamond as an abrasive is shown and it is described that by adding the powder of a high hardness, the running stability of the magnetic recording material is improved.
It is known to thin the magnetic layer for preventing lowering the reproducing output caused by the thickness loss of the magnetic layer, and, for example, Japanese Patent Laid-Open No. 182178/1993 disclose a magnetic recording medium obtained by forming a lower non-magnetic layer containing an inorganic powder dispersed in a binder on a non-magnetic support and an upper magnetic layer containing a ferromagnetic powder dispersed in a binder and a thickness of not thicker than 1.0 &mgr;m formed on the non-magnetic layer while the non-magnetic layer is yet in a wet state.
However, with the rapid increases of the capacity and the recording density of a magnetic disk, even by the above-described techniques, it has become difficult to obtain satisfactory characteristics.
Particularly, since in the case of high-density recording, the influence of a spacing loss on the reproducing output and the half width becomes large, it is necessary to smooth the surface property of the medium surface. However, when the surface is smoothed, the friction between a head and the medium is increased, whereby the abrasion and the breakdown of the medium surface are liable to occur. Thereby, reading of data becomes impossible to cause an error. Also, the surface of the medium is smoothed, the inter-medium friction is increased and the slipping property is deteriorated, whereby there are problems that not only handling in the production process becomes difficult but also the medium sticks to each other.
SUMMARY OF THE INVENTION
An object of the present invention provides a magnetic disk for high-density recording, which has the improved electromagnetic characteristics, and particularly the greatly improved high-density recording characteristics, does not generate the data loss by breaking of the magnetic layer in head running, does not generates blocking, etc., and can be easily produced.
The present invention is attained by the following (1) to (6).
(1) A magnetic disk having formed on a support a lower layer, which is substantially non-magnetic, and formed thereon a magnetic layer containing a ferromagnetic metal powder or a hexagonal ferrite powder dispersed in a binder, wherein the thickness of the magnetic layer is from 0.02 to 0.5 &mgr;m the ten-point mean height Rz of the magnetic layer surface measured by a non-contact surface roughness profiler is at least 20 nm and not higher than 50 nm, and the number of pr

Affiliated with

Also associated with

Rating

Magnetic disk does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Magnetic disk, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic disk will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3103347