# US 9,751,802 B2 · Heat treatment for strengthening glasses > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,751,802 B2 - Document ID: US9751802B2 - Status: Granted - Kind: B2 - Application number: 13/992,925 - Filed: 2011-12-09 - Published: 2013-10-03 - Granted: 2017-09-05 - Earliest claimed: 2010-12-14 - Assignees: Corning Incorporated - Applicants: Douglas Clippinger Allan; Adam James Ellison; John Christopher Mauro - Inventors: Douglas Clippinger Allan; Adam James Ellison; John Christopher Mauro - Web page: https://patentgrep.com/patent/US9751802B2 ## CPC - C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)} - C03B 32/00: Thermal after-treatment of glass products not provided for in groups {C03B19/00} , C03B25/00 - C03B31/00 {or C03B37/00}, e.g. crystallisation, eliminating gas inclusions or other impurities; {Hot-pressing vitrified, non-porous, shaped glass products} - C03C 3/087: containing calcium oxide, e.g. common sheet or container glass - C03C 3/091: containing aluminium - C03C 3/097: containing phosphorus, niobium or tantalum - C03C 23/007: {by thermal treatment} - Y10T 428/315: Surface modified glass [e.g., tempered, strengthened, etc.] - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS - C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A method of making a strengthened glass article. The method includes altering the glass structure and subsequently creating a compressive layer extending from the surface of the glass to a depth of layer. In some embodiments, the structure is altered by heat treating the glass at a temperature that is less than the annealing point of the glass, and the compressive layer is formed by ion exchange. A strengthened glass article made by the method is also provided. ## Claims ### Claim 1 A method of making a glass article, the glass article having a surface that is under a compressive stress and comprising an alkali aluminosilicate glass or an alkali aluminoborosilicate glass, wherein the alkali aluminosilicate glass or the alkali aluminoborosilicate glass comprises at least one of Na2O and K2O, and from about 2 mol % to about 12 mol % P2O5, the method comprising: a. heating the glass article at a first temperature for a time period of less than 4 hours and greater than or equal to 0.5 hours, wherein the glass article has an annealing point and a fictive temperature that is greater than the annealing point, and wherein the first temperature is less than the annealing point; and b. ion exchanging the heated glass article in a molten salt bath comprising at least about 90 wt % KNO3 and from about 0.2 wt % to about 10 wt % NaNO3 at a second temperature to achieve a compressive stress layer extending from the surface to a depth of layer and a compressive stress maximum at the surface, wherein the first temperature is greater than the second temperature. ### Claim 2 (depends on 1) The method of claim 1, wherein the first temperature is in a range from about 25° C. to about 100° C. below the annealing point of the glass article. ### Claim 3 (depends on 1) The method of claim 1, wherein the first temperature is between the annealing point and the 1017 poise temperature of the glass article. ### Claim 4 (depends on 1) The method of claim 1, wherein the compressive stress is at least 800 MPa. ### Claim 5 (depends on 4) The method of claim 4, wherein the step of ion exchanging the glass article comprises ion exchanging the glass article at a temperature that is greater than about 410° C. ### Claim 6 (depends on 1) The method of claim 1, further comprising down-drawing the glass article. ### Claim 7 A method of strengthening an alkali aluminosilicate glass or an alkali aluminoborosilicate glass, wherein the alkali aluminosilicate glass or the alkali aluminoborosilicate glass comprises at least one of Na2O and K2O, and from about 2 mol % to about 12 mol % P2O5, and wherein the alkali aluminosilicate glass or the alkali aluminoborosilicate glass has an annealing point and a fictive temperature that is greater than the annealing point, the method comprising: a. heating the alkali aluminosilicate glass or the alkali aluminoborosilicate glass at a first temperature that is less than the annealing point for a time period of less than 4 hours and greater than or equal to 0.5 hours to at least partially restructure a surface of the alkali aluminosilicate glass or the alkali aluminoborosilicate glass; and b. creating a compressive stress layer extending from the surface to a depth of layer and a compressive stress maximum at the surface after restructuring the surface, wherein the step of creating the compressive stress comprises ion exchanging the alkali aluminosilicate glass or the alkali aluminoborosilicate glass in a molten salt bath comprising at least about 90 wt % KNO3 and from about 0.2 wt % to about 10 wt % NaNO3 at a second temperature to a depth of layer extending from a surface of the alkali aluminosilicate glass or the alkali aluminoborosilicate glass. ### Claim 8 (depends on 7) The method of claim 7, wherein the first temperature is in a range from about 25° C. to about 100° C. below the annealing point. ### Claim 9 (depends on 7) The method of claim 7, wherein the second temperature is less than the first temperature. ### Claim 10 (depends on 9) The method of claim 9, wherein the second temperature is greater than about 410° C. and less than the first temperature. ### Claim 11 (depends on 7) The method of claim 7, wherein the first temperature is between the annealing point and 1017 poise temperature of the glass. ### Claim 12 (depends on 7) The method of claim 7, wherein the compressive stress is at least 800 MPa. ### Claim 13 (depends on 7) The method of claim 7, wherein the glass is down-drawn.