Patent ID: 8277559

Claim:
A quartz glass crucible for pulling up a silicon single crystal, comprising: a quartz glass crucible body having a hollow cylindrical top portion forming an opening into the quartz glass crucible, a bottom portion forming a circular depression with a centrally-located bottom dead center point and a bent portion interconnecting the top portion and the bottom portion to form an inside surface of the quartz glass crucible body, the quartz glass crucible body having an opaque outer layer formed by melting natural silica powder and a transparent layer structure formed on the inside thereof, characterized in that the transparent layer structure includes a transparent layer made of natural quartz glass with a thickness of 0.4 to 5.0 mm covering the entirety of the inside of the opaque outer layer, and a transparent layer made of a synthetic quartz glass having a lower transparent layer portion and an upper transparent layer portion, the lower transparent layer portion formed on and covering a lower portion of the transparent layer made of the natural quartz glass of the inside of the crucible and having: a thickness extending in a range from 0.15 to 0.55 L selected from a thickness range of 0.2 to 1.5 mm, the upper transparent layer portion having a thickness of 0.1 mm or less and formed on and covering an upper portion of the transparent layer made of the natural quartz glass of the inside of the crucible in a range from 0.6 to 1.0 L, wherein L is a distance extending along the inside surface of the quartz glass crucible body, as viewed in cross-section, from the bottom dead center point to the opening into the quartz glass crucible body and wherein the range of 0.15 to 0.55 L is inclusive of the bottom portion and the bent portion and is exclusive of the top portion.