Patent ID: 9347148
Filing Date: 2016-05-24
CPC Classification: C30B,Y10T

Claim Text:
1. A vitreous silica crucible comprising a substantially cylindrical straight body portion, a curved bottom portion, and a corner portion smoothly connecting the straight body portion and the bottom portion, wherein a wall of the vitreous silica crucible includes, from an inner surface side, a transparent layer and a bubble-containing layer, and a ratio of a thickness of the bubble-containing layer with respect to a thickness of the transparent layer at an intermediate position between an upper end and a lower end of the straight body portion is 0.7 to 1.4; wherein the transparent layer is made of at least one of synthetic vitreous silica and natural vitreous silica, and the bubble-containing layer is made of natural vitreous silica; wherein a ratio of a thickness of the transparent layer to a thickness of the bubble-containing layer at the corner portion is from 2.25 to 10; wherein the thickness of the transparent layer is larger than that of the bubble-containing layer at the corner portion; wherein the thickness of the transparent layer is 2 mm or more and 5 mm or less, and the thickness of the bubble-containing layer is 7 mm or more and 8.5 mm or less at the border between the bottom portion and the corner portion; wherein the bubble-containing layer consists of two or more bubble-containing layers having different bubbles content rates from each other, without any other intervening layer, wherein the bubble content rate of each bubble-containing layer is 0.2% or more and 1% or less; and wherein the bubble content rate of the transparent layer in the center of the bottom portion (B