GLASS MANUFACTURING SYSTEM AND METHOD FOR FORMING A HIGH QUALITY THIN GLASS SHEET
A glass manufacturing system ( 100, 100′, 100 ″) and method are described herein for forming a high quality thin glass sheet ( 110 ). In one embodiment, the glass manufacturing system and method use at least one of a compensated rolling roll ( 108 a ), a temperature controlled environment ( 120 ) and edge rolls ( 122, 124 ) to form a high quality thin glass sheet that has a thickness less than about 2 mm and more preferably less than about 100 μm.
1 . A glass manufacturing system ( 100 , 100 ′, 100 ″) comprising:
a delivery system ( 102 ) where molten glass ( 104 ) transitions from a guided flow to a free fall flow;
a rolling roll pair ( 106 ) having two rolling rolls ( 108 a , 108 b ) which receive the molten glass free falling from the delivery system and roll the molten glass to form a glass sheet ( 110 ); and
a temperature controlled environment ( 120 ) with a cross temperature gradient located below the rolling pair where two outer edges ( 118 a , 118 b ) of the glass sheet are exposed to a hotter temperature than a central portion ( 116 ) of the glass sheet, wherein the temperature controlled environment provides the cross temperature gradient to stretch the glass sheet such that the glass sheet has a substantially constant thickness.
2 . The glass manufacturing system of claim 1 , wherein the temperature controlled environment has another cross temperature gradient where the two outer edges of the glass sheet are exposed to a colder temperature than the central portion of the glass sheet.
3 . The glass manufacturing system of claim 1 , further comprising:
a first edge roll pair ( 122 ) and a second edge roll pair ( 124 ), the first edge roll pair and the second edge roll pair are located within the temperature controlled environment, wherein a first edge portion ( 126 a ) of the glass sheet is drawn between two edge rolls ( 128 a , 128 b ) associated with the first edge roll pair, and an opposing second edge portion ( 126 b ) of the glass sheet is drawn between two edge rolls ( 130 a , 130 b ) associated with the second edge roll pair, wherein the first edge roll pair and the second edge roll pair stretch the glass sheet while substantially maintaining a width of the glass sheet.
4 . The glass manufacturing system of claim 3 , further comprising multiple edge roll pairs ( 132 a , 132 b , 134 a , 134 b , 136 a , 136 b , 138 a , 138 b ), the multiple edge roll pairs are located within the temperature controlled environment, wherein the multiple edge roll pairs stretch the glass sheet while substantially maintaining the width of the glass sheet.
5 . The glass manufacturing system of claim 1 , wherein at least one of the rolling rolls is a compensated roll such that when the molten glass is drawn between the rolling rolls then the glass sheet formed has a center portion that is thicker relative to the two outer edges.
6 . The glass manufacturing system of claim 1 , further comprising another rolling roll pair ( 112 ) having two rolling rolls ( 114 a , 114 b ) which receive the glass sheet and further draw the glass sheet before the glass sheet enters the temperature controlled environment.
7 . The glass manufacturing system of claim 1 , further comprising at least one pair of pulling rolls ( 140 ) where each pair of pulling rolls has two pulling rolls ( 142 a , 142 b ) which receive and draw the glass sheet after the glass sheet has traveled through the temperature controlled environment.
8 . A method for manufacturing a glass sheet ( 110 ), said method comprising the steps of:
providing a molten glass ( 104 );
rolling the molten glass between two rolling rolls ( 108 a , 108 b ) to form the glass sheet; and
heating the glass sheet in a temperature controlled environment ( 120 ) which has a cross temperature gradient located below the two rolling rolls such that two outer edges ( 118 a , 118 b ) of the glass sheet are exposed to a hotter temperature than a central portion ( 116 ) of the glass sheet, wherein the temperature controlled environment provides the cross temperature gradient to stretch the glass sheet such that the glass sheet has a substantially constant thickness.
9 . The method of claim 8 , wherein the step of stretching the glass sheet comprises drawing a first edge portion ( 126 a ) of the glass sheet between two edge rolls ( 128 a , 128 h ) associated with a first edge roll pair ( 122 ), and drawing an opposing second edge portion ( 126 b ) of the glass sheet between two edge rolls ( 130 a , 130 b ) associated with a second edge roll pair ( 124 ), the first edge roll pair and the second edge roll pair are located within the temperature controlled environment, wherein the first edge roll pair and the second edge roll pair stretch the glass sheet while substantially maintaining a width of the glass sheet.
10 . The method of claim 8 , wherein at least one of the rolling rolls is a compensated roll such that when the molten glass is drawn between the rolling rolls then the glass sheet formed has a center portion that is thicker relative to the two outer edges.
11 . The method of claim 8 , further comprising another rolling step where another two rolling rolls ( 114 a , 114 b ) receive the glass sheet and further roll the glass sheet before the glass sheet enters the temperature controlled environment.
12 . The method of claim 8 , further comprising a step of pulling the glass sheet by using at least one pair of pulling rolls ( 140 ) where each pair of pulling rolls has two pulling rolls ( 142 a , 142 b ) which receive and draw the glass sheet after the glass sheet has traveled through the temperature controlled environment.
13 . The method of claim 8 , where the glass sheet has a thickness between about 2-5 mm and a roughness between about 1-4 nm Ra after being drawn by the two rolling rolls and before entering the temperature controlled environment.
14 . The method of claim 8 , where the glass sheet has a thickness less than about 100 μm and a roughness about 0.25 nm Ra after travelling through the temperature controlled environment.
15 . The method of claim 8 , wherein the glass sheet is a glass-ceramic sheet, a borosilicate glass sheet, a white crown glass sheet, or an alkali-free glass sheet.