Abstract: An aqueous solution of a metal salt to an alkaline aqueous solution to forma hydroxide or a hydrate of a metal, and the hydroxide or hydrate of the metal is heated at a temperature of 110 to 300° C. in the presence of water. Then, the hydroxide or hydrate of the metal is filtered and dried and then further heated at a temperature of 300 to 1200° C. in an air to form oxide particles such as the particles of cerium oxide, zirconium oxide, aluminum oxide silicon oxide, iron oxide, etc. Thereby the particles of cerium oxide, zirconium oxide, aluminum oxide silicon oxide, iron oxide, etc. having a plate-form shape and a particle size of from 10 nm to 100 nm in the plate direction of the particle are obtained. The non-magnetic particles, in particular, plate-form oxide particles of the present invention have a uniform particle size distribution, are less sintered or agglomerated, and have good crystallinity.

Abstract: A first information recording medium according to the present invention includes a substrate and an ink receiving layer disposed on one main face of the substrate. The water contact angle of the surface of the ink receiving layer is at least 85° and at most 110°. The surface of the ink receiving layer is provided with protrusions with a height of at least 4 ?m. The number of the protrusions is at least 20 pcs/mm2 and at most 100 pcs/mm2. Furthermore, in a second information recording medium according to the present invention, the ink receiving layer contains particles with a particle size of at least 20 ?m. The particles include particles that are exposed partially on the surface of the ink receiving layer. The number of these particles is at least 75 pcs/mm2 and at most 250 pcs/mm2.

Abstract: Non-magnetic particles, in particular, of an oxide such as cerium oxide, zirconium oxide, aluminum oxide, silicon oxide or iron oxide which have the shape of a plate and have an average particle diameter in the direction of the plate surface in a range of 10 to 100 nm; and a method for producing the above non-magnetic particles of the oxide which comprises adding a salt of the above element to an aqueous alkaline solution to provide a hydroxide or hydrate thereof, heating the hydroxide or hydrate in the presence of water at a temperature in the range of 110 to 300° C., followed by filtration and drying, and further heating the resultant product in air at a temperature in the range of 300 to 1200° C., to thereby produce particles of the oxide. The above non-magnetic particles, in particular, of on oxide has a narrow distribution of particle diameter, is extremely reduced in sintering or coagulation, and exhibits good crystallinity.

Abstract: The object of the present invention is to provide a magnetic recording medium, particularly, a tape for data backup, which is less in wear of head, small in output deterioration and high in recording density. According to the present invention, there is provided a magnetic recording medium comprising a non-magnetic support having on one side at least one non-magnetic undercoat layer and a magnetic layer in succession and on another side a back coat layer, in which the magnetic layer is an ultra-thin magnetic layer having a thickness of not more than 0.20 &mgr;m provided by adjusting a standard deviation of histogram obtained by measuring the surface roughness of the magnetic layer by a light interference surface roughness meter to not more than 0.56 nm.

Abstract: The object of the present invention is to provide a magnetic recording medium, particularly, a tape for data backup, which is less in wear of head, small in output deterioration and high in recording density. According to the present invention, there is provided a magnetic recording medium comprising a non-magnetic support having on one side at least one non-magnetic undercoat layer and a magnetic layer in succession and on another side a back coat layer, in which the magnetic layer is an ultra-thin magnetic layer having a thickness of not more than 0.20 &mgr;m provided by adjusting a standard deviation of histogram obtained by measuring the surface roughness of the magnetic layer by a light interference surface roughness meter to not more than 0.56 nm.

Abstract: The object of the present invention is to provide a magnetic recording medium, particularly, a tape for data backup, which is less in wear of head, small in output deterioration and high in recording density. According to the present invention, there is provided a magnetic recording medium comprising a non-magnetic support having on one side at least one non-magnetic undercoat layer and a magnetic layer in succession and on another side a back coat layer, in which the magnetic layer is an ultra-thin magnetic layer having a thickness of not more than 0.20 &mgr;m provided by adjusting a standard deviation of histogram obtained by measuring the surface roughness of the magnetic layer by a light interference surface roughness meter to not more than 1.0×10−5 m.

Abstract: A magnetic recording medium comprising a non-magnetic support, an intermediate layer which is formed on the non-magnetic support containing carbon black and non-magnetic particles other than carbon black, a particle size ratio between the carbon black and non-magnetic particles being from 1.0 to 4.0 in terms of a ratio of a diameter or a short axis size of the non-magnetic particles to a particle size of carbon black, and a magnetic layer which is formed on the intermediate layer and has a thickness of 0.2 to 1.0 .mu.m, in which magnetic layer a difference of an intensity at 102 mm.sup.-1 and that at 205 mm.sup.-1, in a frequency analysis of non-contact surface roughness is from 9 dB to 15 dB, in which a total thickness of the non-magnetic support, the intermediate layer and the magnetic layer is not greater than 13 .mu.m, which recording medium is excellent in electromagnetic conversion characteristics and durability.

Abstract: A magnetic recording medium which comprises a substrate and a magnetic layer formed thereon comprising a magnetic metal powder, an abrasive and, as the binder resin, a polyurethane resin having cyclohexyl rings in its molecular chain and a vinyl chloride base resin containing hydroxyl groups, which has improved durability.

Abstract: A magnetic recording tape comprising a non-magnetic substrate, a magnetic layer which comprises magnetic powder and a binder resin coated on one surface of the substrate and a back coating layer which comprises non-magnetic powder and a binder resin coated on the other surface of the substrate, wherein an amount of compounds having a molecular weight of 1000 to 5000, as converted to polystyrene molecular weight, extracted with tetrahydrofuran and converted to a polystyrene extraction amount, per 3 .mu.m thickness from the magnetic layer (W.sub.M) and per 1 .mu.m thickness of from the back coating layer (W.sub.B), are both less than 200 mg/m.sup.2, which tape has improved traveling stability and durability.