Apparatus and method for heat treating a glass substrate
An apparatus and method for heat treating a plurality of glass substrates. The glass substrates are supported on support platform and housed in a heat treating furnace. The substrates are supported in a substantially vertical orientation by restraining pins extending through walls of the furnace, and are separated from each other by frame-shaped spacing members. The spacing members reduce convection currents between the substrates and reduce or eliminate the post-heat treating distortion of each glass substrate to less than 100 μm over the entire surface of the substrate.
1. A method of heat treating a plurality of glass substrates in a furnace comprising:
positioning at least one spacing member between pairs of adjacent glass substrates of the plurality of glass substrates, the at least one spacing member comprising a closed outer frame portion bounding an open interior, and wherein a difference between a CTE of the one or more spacing members and a CTE of the plurality of glass substrates is less than 10×10 −7 /° C.;
supporting the plurality of glass substrates on a support platform in the furnace in a substantially vertical orientation, the supporting comprising;
contacting a first outermost most glass substrate of the plurality of glass substrates with a first plurality of restraining pins, each restraining pin of the first plurality of restraining pins being rigidly fixed;
contacting a second outermost glass substrate of the plurality of glass substrates with a second plurality of restraining pins, wherein each restraining pin of the second plurality of restraining pins being movable along a longitudinal axis thereof, and wherein each restraining pin of the second plurality of restraining pins applies a force to the second outermost glass substrate;
heating the plurality of glass substrates in the furnace;
cooling the plurality of glass substrates; and
wherein an out-of-plane distortion of the plurality of glass substrates after cooling does not exceed 100 μm.
2. The method according to claim 1 , wherein the at least one spacing member comprises a plurality of spacing members arranged in a vertical and/or horizontal array between each pair of adjacent glass substrates.
3. The method according to claim 2 , wherein adjacent spacing members of the plurality of spacing members contact each other at outside edge portions of each adjacent spacing member.
4. The method according to claim 1 , wherein during the heating step the plurality of glass substrates are heated to a temperature greater than an annealing point of the plurality of glass substrates and less than a softening temperature of the plurality of glass substrates.
5. The method according to claim 1 , wherein during the heating step the plurality of glass substrates are heated to a temperature greater than 700° C.
6. The method according to claim 1 , wherein the at least one spacing member is a glass or a glass ceramic material.
7. The method according to claim 6 , wherein the at least one spacing member is glass and the glass of the spacing member is the same glass composition as a glass composition of the plurality of glass substrates.
8. The method according to claim 1 , wherein the adjacent glass substrates and the at least one spacing member positioned therebetween form an enclosed space bounded by the adjacent glass substrates and the at least one spacing member.
9. The method according to claim 1 , wherein a major surface of each glass substrate of the plurality of glass substrates has a surface area of at least 5 m 2 .
10. The method according to claim 1 , wherein the first plurality of restraining pins extend through a first side of the furnace.
11. The method according to claim 1 , wherein the force is applied by a spring or a pneumatic piston.
12. The method according to claim 1 , wherein the spacing member is a single piece of glass.
13. The method according to claim 1 , further comprising contacting a glass substrate of the plurality of glass substrates with at least one guide member.
14. The method according to claim 1 , wherein the guide member is a cable.
15. The method according to claim 1 , further comprising maintaining each pin of the second plurality such that distal ends of each pin are in contact with the second outermost glass substrates and are coplanar.