Abstract: Of disk-shaped or tape-shaped magnetic recording media composed of non-magnetic supports and magnetic layers which, formed on the supports, contain a magnetic powder and a binder for it, the magnetic recording medium having superior electro-magnetic conversion characteristics, high durability, and high reliability has been obtained as a result of improving the abrasion resistance of the magnetic layer without impairing the surface smoothness thereof, by incorporating a non-magnetic inorganic powder of at least 5 Mohs hardness which has a dendrite or chain structure.

Abstract: A magnetic recording medium which comprises a support and a magnetic layer formed on opposite sides of the support and comprised of a ferromagnetic fine powder and an non-magnetic powder of an abrasive both dispersed in a resin binder. The non-magnetic powder consists essentially of a first non-magnetic inorganic powder having an average particle size of from 0.01 to 1.0 .mu.m and a second non-magnetic inorganic powder having an arborescent or chain-like structure and an average particle size of from 0.03 to 2.0 .mu.m. The first and second powders is present at a mixing ratio by weight of 8:2 to 2:8.

Abstract: A method of manufacturing capacitance video discs comprising thermoplastic resins and conductive carbon black, wherein said conductive carbon black having an average primary particle size of 25 millimicrons or less is washed by water or an inorganic acid, heated at temperatures of 400.degree. to 1,200.degree. C. in a non-oxidizing atmosphere and wherein the coarse particles having a grain size of 0.05 mm or more are substantially eliminated. This method can provide video discs having reduced surface defects and stability after a moisture-proof test.

Abstract: This invention provides a method for preparing a photoconductive powder comprising firing a combined starting mixture of CdSe, ZnS, ZnO, a Cu or Ag salt, and a Cd or Zn chloride or bromide as a flux, and preferably a Mn salt also, at a temperature higher than the melting point of the flux, cooling the fired product, and re-firing the cooled product in a sulfur vapor containing atmosphere. The photoconductive powder obtained by this method has high photosensitivity, high threshold voltage and fine particle size.

Abstract: A photoconductive layer having superior characteristics is made by steps of suspending uniformly photoconductive particles in a viscous solution by stirring, pouring the stirred mixture of the photoconductive particles, binder and solvent on a substrate which is put horizontally at a bottom of a container, precipitating the photoconductive particles on the surface of the substrate so as to form a wet photoconductive layer, removing the clear solution on the wet photoconductive layer, drying the wet photoconductive layer and baking the dried photoconductive layer.