High expansion glass-ceramic articles
First Claim
1. A chemically-machinable glass-ceramic exhibiting a coefficient of thermal expansion over the interval of 20°
- -400°
C. of about 120-160×
10-7 /°
C. consisting predominantly of lithium metasilicate, lithium disilicate, and quartz and/or cristobalite crystals dispersed in a residual glassy matrix, said glass-ceramic having a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 5.5-15% Li2 O, 2-25% Al2 O3, the weight ratio Al2 O3 ;
Li2 O being less than 1.7;
1, 60-85% SiO2, and at least one photosensitive metal in the indicated proportion selected from the group of 0.001-0.03% gold, computed as Au, 0.001-0.3% silver, computed as AgCl, and 0.001-1% copper, computed as Cu2 O, the sum of those components constituting at least 90% by weight of the total composition.
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Abstract
The present invention relates to the production of photothermally crystallizable, chemically-machinable glass-ceramic articles exhibiting coefficients of thermal expansion over the temperature interval of 20°-400° C. between 120-160×10-7 /° C. Base glass articles having compositions consisting essentially, in weight percent, of 5.5-15% Li2 O, 2-25% Al2 O3, the weight ratio Al2 O3 :Li2 O being less than 1.7:1, 60-85% SiO2, and at least one photosensitive metal in the indicated proportion selected from the group of 0.001-0.03% gold, computed as Au, 0.001-0.3% silver, computed as AgCl, and 0.001-1% copper, computed as Cu2 O, are first exposed to ultraviolet radiations to develop a latent image therein, then heated to a temperature between the annealing and softening points thereof to generate metallic nuclei therein and the growth of lithium metasilicate particles thereon, and, finally, heated to a temperature in excess of 700° C., but less than 800° C., to effect an essentially crystalline article, including the conversion of a portion of the lithium metasilicate crystals to lithium disilicate. Quartz and/or cristobalite will also be formed.
91 Citations
2 Claims
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1. A chemically-machinable glass-ceramic exhibiting a coefficient of thermal expansion over the interval of 20°
- -400°
C. of about 120-160×
10-7 /°
C. consisting predominantly of lithium metasilicate, lithium disilicate, and quartz and/or cristobalite crystals dispersed in a residual glassy matrix, said glass-ceramic having a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 5.5-15% Li2 O, 2-25% Al2 O3, the weight ratio Al2 O3 ;
Li2 O being less than 1.7;
1, 60-85% SiO2, and at least one photosensitive metal in the indicated proportion selected from the group of 0.001-0.03% gold, computed as Au, 0.001-0.3% silver, computed as AgCl, and 0.001-1% copper, computed as Cu2 O, the sum of those components constituting at least 90% by weight of the total composition. - View Dependent Claims (2)
- -400°
Specification
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- Resources
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Current AssigneeCorning Glass Works Inc. (Corning Incorporated)
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Original AssigneeCorning Glass Works Inc. (Corning Incorporated)
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InventorsMcAlinn, Patrick
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Primary Examiner(s)Bell, Mark
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Application NumberUS06/575,902Time in Patent Office272 DaysField of Search501/4, 501/5US Class Current501/4CPC Class CodesC03C 10/00 Devitrified glass ceramics,...C03C 4/04 for photosensitive glass
