Abstract: A large sized opaque quartz glass ingot having an excellent heat ray shielding property, an outstanding light blocking property, high mechanical strength and small roughness of a baked finished smooth surface. The shape of bubbles inside the quartz glass are almost complete spheres and the average particle size of the bubbles is 1 ?m or less, such that the strength of the opaque quartz glass ingot is increased as the stress concentration at the edges of the bubbles is eliminated and an increase of surface roughness caused by baking is alleviated.

Abstract: An abrasive molding consisting essentially of inorganic particles having an average particle diameter in the range of 0.005 &mgr;m to 0.3 &mgr;m, and having a relative density in the range of 45% to 90%, provided that pores having a diameter of at least 0.5 &mgr;m are excluded from the molding. The abrasive molding is used for polishing a material to be polished by using a polishing liquid, preferably water or an aqueous solution of an alkali metal hydroxide, which does not contain a loose abrasive grain.

Abstract: An optical recording medium able to reproduce address information during seeking in which an optical head moves between tracks, to increase seek speed, to improve recording/reproduction speed and to obtain a good header reproducing signal is achieved by that the concave portions or convex portions constituting a reproducing signal in seeking reproduced even during seek and/or constituting a timing signal for writing a header signal are connected to each other in a direction orthogonal to the tracks, when these concave portions and/or convex portions are placed in positions equivalent to each other in the adjacent tracks.

Abstract: An abrasive molding composed of a mass of inorganic particles, said mass having pores intervening among the inorganic particles, which molding has abrasive area to be placed in frictional contact with an article to be abraded, and non-abrasive area on a abrading surface of the abrasive molding. The abrasive area has exposed pores having a diameter of not larger than 1 &mgr;m, the total area of said exposed pores having a diameter of not larger than 1 &mgr;m occupying below 15% of the total area of abrasive area, and the non-abrasive area occupies 20% to 60% of the sum of the abrasive area and the non-abrasive area.

Abstract: An abrasive molding comprising at least 90% by weight, based on the abrasive molding, of an inorganic material having a stock hardness of 50-400 kg/mm2, and said abrasive molding having a relative density of 20-70% and an average particle diameter of 0.001-50 &mgr;m. The abrasive molding preferably has pores having a pore size distribution such that the integrated pore volume of pores having a diameter of 0.01-1 &mgr;m is at least 20% of the integrated total pore volume of the entire pores, and the integrated pore volume of pores having a diameter of 1-360 &mgr;m is in the range of 10% to 70% of the integrated total pore volume of the entire pores. The abrasive molding is suitable for polishing a material having a Vickers hardness not larger than 300 kg/mm2.

Abstract: An abrasive molding composed of a mass of inorganic particles, said mass having pores intervening among the inorganic particles, which molding has abrasive area to be placed in frictional contact with an article to be abraded, and non-abrasive area on a abrading surface of the abrasive molding. The abrasive area has exposed pores having a diameter of not larger than 1 &mgr;m, the total area of said exposed pores having a diameter of not larger than 1 &mgr;m occupying below 15% of the total area of abrasive area, and the non-abrasive area occupies 20% to 60% of the sum of the abrasive area and the non-abrasive area.

Abstract: An abrasive molding comprising at least 90% by weight, based on the abrasive molding, of an inorganic material having a stock hardness of 50-400 kg/mm2, and said abrasive molding having a relative density of 20-70% and an average particle diameter of 0.001-50 &mgr;m. The abrasive molding preferably has pores having a pore size distribution such that the integrated pore volume of pores having a diameter of 0.01-1 &mgr;m is at least 20% of the integrated total pore volume of the entire pores, and the integrated pore volume of pores having a diameter of 1-360 &mgr;m is in the range of 10% to 70% of the integrated total pore volume of the entire pores. The abrasive molding is suitable for polishing a material having a Vickers hardness not larger than 300 kg/mm2.

Abstract: An abrasive molding consisting essentially of inorganic particles having an average particle diameter in the range of 0.005 &mgr;m to 0.3 &mgr;m, and having a relative density in the range of 45% to 90%, provided that pores having a diameter of at least 0.5 &mgr;m are excluded from the molding. The abrasive molding is used for polishing a material to be polished by using a polishing liquid, preferably water or an aqueous solution of an alkali metal hydroxide, which does not contain a loose abrasive grain.

Abstract: A magneto-optical recording medium and process for production of the same are disclosed, the magneto-recording medium comprising a substrate having thereon a magneto-optical recording film and at least one coating film provided on a light incident side and/or an opposite side thereto, of said magneto-optical recording film for protection of said magneto-optical recording film and/or Kerr effect enhancement, wherein said coating film contains silicon, nitrogen, and hydrogen as constituent elements. The magneto-optical recording medium has excellent reliability, excellent read-out performance properties as well as excellent recording sensitivity while exhibiting high magneto-optical effects and freedom from corrosion.