Process for producing glass bar
In a heating drawing, a base material glass plate is heated and softened in a heating furnace, and drawn to a desired thickness to form a glass strip. In the heating drawing, the base material glass plate is heated so that the base material glass plate has a U-shaped temperature distribution in a width direction. Such process can be realized through heating by a heating element which has a non-heating portion at a position opposite to a central portion of the base material glass plate in the width direction and a heating portion on both sides of the non-heating portion. Thus provided is a method of manufacturing a glass strip, the method includes heating and softening the base material glass plate, and drawing the base material glass plate to a desirable thickness to form a glass strip, and is capable of manufacturing a thin, rod-like glass strip with an excellent flatness.
1. A method of manufacturing a glass strip comprising:
heating and softening a base material glass plate in a heating furnace; and
drawing the base material glass plate to a desirable thickness to form a glass strip,
wherein the heating furnace includes a rectangular core tube through which the base material glass plate passes, the core tube having a plurality of side surfaces,
wherein at least one of the plurality of side surfaces of the core tube includes a plurality of heaters positioned along the outside of the side surface, the plurality of heaters being arranged along a width direction of the base material glass plate,
wherein the base material glass plate is heated by adjusting temperatures of the plurality of heaters so that the base material glass plate has a U-shaped temperature distribution in a width direction in a meniscus portion from a position where melting starts to a position of the inflection point formed at the time of drawing on the contour of the base material glass plate,
wherein the base material glass plate is heated so that a viscosity ratio of a central portion to a side portion in a highest temperature portion of the base material glass plate in the width direction is larger than one and not larger than 20,
wherein the base material glass plate is drawn while an aspect ratio in cross section of the base material glass plate is substantially maintained, and so that the glass strip has a flatness of not more than 10 μm against a width of 20 mm of the glass strip,
wherein the glass strip has an aspect ratio in cross section equal to or higher than 50, and
wherein the plurality of heaters are arranged in parallel with only a width direction of the base material glass plate.
2. The method of manufacturing a glass strip according to claim 1 , wherein a viscosity ratio of the central portion to the side portion of the base material glass plate in the width direction is equal to or larger than 3.4.