Patent ID: 10640390

Abstract:
An alumina powder containing a hydroxycarboxylic acid and an alkaline component contains amorphous alumina, pseudoboehmite, or boehmite, and satisfies all of (1) to (4). (1) A colloidal dispersion A with 2.5% by mass of Al2O3 consisting of the alumina powder and distilled water is free from precipitate, and has a light transmittance of at least 80% measured at a wavelength of 500 nm and an optical path length of 10 mm. (2) A colloidal dispersion B with 15% by mass of Al2O3 consisting of the alumina powder and distilled water is free from precipitate. (3) The dispersions A and B have a pH in a range of 5 to 8. (4) A colloidal dispersion C with 2.5% by mass of Al2O3 consisting of the alumina powder and methanol is free from precipitate, and has a light transmittance of at least 80% measured under the above condition.