In the magnetic tapes for the audio, video or computer purpose, in general, there is recently an increasing demand for high-density recording, so that the particle size of the conventional Co-containing magnetic iron oxides becomes finer.
Attention is also paid to the ferromagnetic metal thin-film type magnetic recording media, which rely upon ferromagnetic alloy powders, or are formed by the vapor deposition techniques such as vacuum deposition, sputtering and ion plating, and such media have been put to practical use.
In such audio, video or computer magnetic tapes, the magnetic layers are finished to a certain smoothness to improve the sensitivity (especially output in a high-frequency range). In some cases, however, improvements in sensitivity could not be introduced even with the magnetic layers having a smoothly finished surface, since the irregularity of the backing layers is transferred thereto.
In recent years, the total thickness of magnetic tapes tends to be reduced as much as possible, and is in most cases no higher than about 20 microns.
This is accompanied by a reduction in the thickness of the associated backing layers, and often causes that they are coated in a thickness of no higher than 2 microns. For that reason, wear of the backing layers is likely to occur.
Thus, the reduction in the total thickness of the magnet tapes is accompanied by a drop in the strength thereof, and have adverse influences upon running characteristics, running durability, taking-up characteristic, output variations, etc.