Abstract: The spin coating apparatus includes: a collet including a tubular portion disposed coaxially with a predetermined rotation axis, the tubular portion having a slit that extends from a top portion of the tubular portion in a direction of the rotation axis to a midway part in the direction of the rotation axis; and a diameter-expanding member for urging the tubular portion of the collet radially outwardly to expand the outer diameter of the tubular portion. With the spin coating apparatus, a plate-like workpiece having a center hole is held at the center hole by the tubular portion of the collet with both sides of the workpiece exposed, and a flowable material can be applied to both the sides of the workpiece.

Abstract: A fine feldspathic earthenware including a body and a glaze layer covering surfaces of the body. The body has water absorption percentage of not lower than 3% and lower than 15% and includes an annular bottom formed on a bottom portion of the body. The glaze layer is absent on a surface of the annular bottom, and the surface of the annular bottom is covered with an annular vitrified layer which has substantially no water absorbing property. The vitrified layer is formed by coating the surface of the annular bottom with a composition having lower refractoriness than the body, and biscuit-firing the composition together with the body.

Abstract: A fine feldspathic earthenware including a body and a glaze layer covering surfaces of the body. The body has water absorption percentage of not lower than 3% and lower than 15% and includes an annular bottom formed on a bottom portion of the body. The glaze layer is absent on a surface of the annular bottom, and the surface of the annular bottom is covered with an annular vitrified layer which has substantially no water absorbing property. The vitrified layer is formed by coating the surface of the annular bottom with a composition having lower refractoriness than the body, and biscuit-firing the composition together with the body.

Abstract: A fine feldspathic earthenware including a body and a glaze layer covering surfaces of the body. The body has water absorption percentage of not lower than 3% and lower than 15% and includes an annular bottom formed on a bottom portion of the body. The glaze layer is absent on a surface of the annular bottom, and the surface of the annular bottom is covered with an annular vitrified layer which has substantially no water absorbing property. The vitrified layer is formed by coating the surface of the annular bottom with a composition having lower refractoriness than the body, and biscuit-firing the composition together with the body.

Abstract: A magnetic recording medium, comprising a substrate, a ferromagnetic film layer formed on the surface of said substrate, and a back coating layer deposited on the other surface of said substrate and formed of a mixture produced by dispersing a powdered non-magnetic substance in a binder containing therein a thermosetting resin and at least one lubricant selected from the group consisting of fatty acids and fatty acid ester.

Abstract: A back coating resin composition for a magnetic recording medium comprising:(A) a plastic compound having a molecular weight of from 5,000 to 100,000 and containing at least two radiation-curable unsaturated double bonds;(B) a rubber-like compound having a molecular weight of from 3,000 to 100,000 and containing at least one radiation-curable unsaturated double bond or containing no such double bond; and(C) a compound having a molecular weight of from 200 to 3,000 and containing at least one radiation-curable unsaturated double bond.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer formed on the other side of the substrate, wherein the back coating layer contains an inorganic pigment having a Mohs hardness of at least 5 and carbon black, and the inorganic pigment is in an amount of at most 1/9 by weight relative to the carbon black.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer formed on the other side of the substrate, characterized in that the back coating layer is a radiation-cured coating layer containing a fine particulate pigment having an average particle size of the primary particles of at most 50 m.mu.m and a specific surface area of at least 35 m.sup.2 /g as measured by BET method.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer formed on the other side of the substrate, characterized in that the back coating layer is a coating layer comprising zinc sulfide and a resin binder.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer formed on the other side of the substrate, wherein said back coating layer contains graphitized carbon black having an average particle size of from 10 to 50 m.mu.m as measured by an electron microscope.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on the substrate, and a top coating layer formed on the magnetic recording layer, wherein the top coating layer contains a fine particulate pigment at its surface, and the surface roughness (R20) of the top coating layer is less than 400 .ANG..

Abstract: A magnetic recording medium comprising a plastic base film, a magnetic layer formed on one side of the base film and a backing layer formed on the other side of the base film, characterized in that said magnetic layer has a surface roughness of at most 0.08 .mu.m, and said backing layer is composed essentially of first particles of an inorganic pigment having an average particle size of from 0.04 to 0.5 .mu.m and a Mohs hardness of from 2 to 4 and second particles of an inorganic pigment having an average particles size of from 0.04 to 0.5 .mu.m and a Mohs hardness of from 5 to 7, dispersed in a thermoset or radiation-cured binder.

Abstract: In a magnetic recording medium comprising a non-magnetic substrate having opposed major surfaces, a non-magnetic undercoat on one major surface of the substrate, a magnetic layer on the undercoat, and a non-magnetic backcoat on the other major surface of the substrate, at least one of said undercoat and said backcoat is formed of a coating composition comprising a radiation curable base resin preferably having a radiation-sensitive double bond such as acrylic, maleic or allylic double bond, an optional thermoplastic resin, and an effective amount of an anti-static agent selected from known surface-active agents, the composition being cured through crosslinking by exposure to radiation. The magnetic recording medium is prepared by mixing the resins with the anti-static agent, coating the substrate with the composition, and exposing the coating to radiation.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer formed on the other side of the substrate, characterized in that the back coating layer contains carbon black having an ash content of at most 0.05%, a specific surface area of from 20 to 350 m.sup.2 /g, an oil absorption of at most 200 ml/100 g and an average particle size of from 13 to 60 m.mu.m.

Abstract: A magnetic recording medium which comprises a plastic base film, a thin magnetic metal layer formed on one side of the base film and a thermoset backing layer formed on the other side of the base film, wherein the backing layer is made of a thermosetting composition comprising a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a polyurethane prepolymer and a polyisocyanate and has a surface roughness of from 0.05 to 0.6 .mu.m.

Abstract: A magnetic recording medium comprising a magnetic recording layer formed on one major surface of a non-magnetic substrate and a topcoat layer formed on the magnetic layer is characterized in that the topcoat layer contains a submicron particulate pigment observable under an electron microscope to have a linear distribution density of 10 to 1,000 per linear 100 .mu.m and a particle size of less than 200 .ANG. whereby the topcoat layer has a surface roughness R20 of not more than 400 .ANG..

Abstract: A magnetic recording medium comprising a plastic base film, a thin magnetic metal layer formed on one side of the base film and a backing layer formed on the other side of the base film, characterized in that the backing layer is composed essentially of a thermoset or radiation-cured resin and carbon black and inorganic compound powder uniformly dispersed in the resin, and has a surface roughness of from 0.05 to 0.4 .mu.m, said carbon black having an average particle size of from 10 to 150 m.mu.m as measured by an electron microscope, said inorganic compound powder having a Mohs hardness of at most 6 and a particle size of from 10 to 500 m.mu.m, and the ratio of the carbon black to the inorganic compound powder being from 1:9 to 9:1.

Abstract: A magnetic recording medium which comprises a plastic base film and a magnetic layer formed on one side of the base film and composed of ferromagnetic alloy powder dispersed in a resin binder, characterized in that said ferromagnetic alloy powder has a surface area of at least 48 m.sup.2 /g as measured by BDT method, said magnetic layer has a coercive force of at least 1,000 Oe and a surface roughness of at most 0.08 .mu.m, and a thermoset backing layer having a surface roughness of from 0.05 to 0.6 .mu.m is formed on the other side of the base film, the backing layer being made of a thermosetting resin composition comprising a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a polyurethane resin and a polyisocyanate.

Abstract: A magnetic recording medium comprising a transparent plastic film substrate, a primer coating layer formed on the substrate and a magnetic layer for magnetic recording formed on the primer coating layer, wherein said primer coating layer is formed by dispersing carbon black in a radiation curable coating material composed essentially of at least one oligomer or polymer containing at least one radiation curable unsaturated double bond per molecule and curing the resulting dispersion by radiation.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer on the other side of the substrate, characterized in that the back coating layer is a coating composed essentially of carbon black, a resin binder and a lubricant, the weight ratio of the carbon black to the binder being from 1:1 to 1:4, and the carbon black having a particle size of from 10 to less than 100 m.mu.m.