Abstract: A surface-treated metal material includes a metal sheet, a plating layer formed on the metal sheet and containing aluminum, magnesium, and zinc, and a composite coating formed on a surface of the plating layer, the composite coating including an organic silicon compound, one or two of a zirconium compound and a titanium compound, a phosphoric acid compound, a fluorine compound, and a vanadium compound, wherein, when a surface of the composite coating is analyzed at a spot size of ?30 ?m using micro-fluorescent X-rays, a maximum value of V/Zn, which is a mass ratio of a V content to a Zn content, is 0.010 to 0.100.

Abstract: A light guide member includes a reflective surface with a diffusion groove array. The diffusion groove array includes diffusion grooves arranged in the reflective surface in a length direction of the light guide member. The diffusion groove array includes, as the diffusion grooves, at least two inspection grooves and a non-inspection diffusion groove. The two inspection grooves are spaced in the length direction of the light guide member. The non-inspection diffusion groove is between the two inspection grooves. An intermediate part, in a length direction, of each of the two inspection grooves is divided by an ungrooved portion with no groove.

Abstract: A light guide member includes a reflective surface with a diffusion groove array. The diffusion groove array includes diffusion grooves arranged in the reflective surface in a length direction of the light guide member. The diffusion groove array includes, as the diffusion grooves, at least two inspection grooves and a non-inspection diffusion groove. The two inspection grooves are spaced in the length direction of the light guide member. The non-inspection diffusion groove is between the two inspection grooves. An intermediate part, in a length direction, of each of the two inspection grooves is divided by an ungrooved portion with no groove.

Abstract: A Co-Cr perpendicular magnetic recording medium includes a chromium oxide film formed on a Co-Cr perpendicular magnetization film, and a SiO.sub.2 protective film formed on the chromium oxide film. The chromium oxide film is formed by conducting a heating treatment to the surface of the Co-Cr perpendicular magnetization film in an oxygen atmosphere of about 10 .sup.-4 to 10.sup.-3 Torr, at a temperature of about 300.degree. C. to 400.degree. C. for about two hours. The chromium oxide film has a thickness of about 20 to 200 .ANG.. The SiO.sub.2 protective film has a thickness greater than 50 .ANG., but the total thickness of the chromium oxide film and the SiO.sub.2 protective film is selected between 70 and 300 .ANG..

Abstract: A Co-Cr perpendicular magnetic recording medium includes a chromium oxide film formed on a Co-Cr perpendicular magnetization film, and a SiO.sub.2 protective film formed on the chromium oxide film. The chromium oxide film is formed by conducting a heating treatment to the surface of the Co-Cr perpendicular magnetization film in an oxygen atmosphere of about 10.sup.-4 to 10.sup.-3 Torr, at a temperature of about 300.degree. C. to 400.degree. C. for about two hours. The chromium oxide film has a thickness of about 20 to 200 .ANG.. The SiO.sub.2 protective film has a thickness greater than 50 .ANG., but the total thickness of the chromium oxide film and the SiO.sub.2 protective film is selected between 70 and 300 .ANG..