Patent Application
20120277085
The disclosure relates generally to glass articles having enhanced strength and durability properties, and to methods of making and using the glass articles.
The disclosure provides a glass article having enhanced strength and durability properties, and to methods of making and using the glass article. The methods of making can include, for example, contacting the glass with steam or hot water immersion at atmospheric pressure.
In embodiments of the disclosure:
a shows FTIR results of Beta-OH content as measured through 1.3 mm thick Glass D (non-IOX) steam treated glass showing a 10 to 20% increase in bulk BOH.
b shows an FTIR Beta-OH profile of a cross-section of the steam treated 1.3 mm thick—Glass D (non-IOX) glass of
Various embodiments of the disclosure will be described in detail with reference to drawings, if any. Reference to various embodiments does not limit the scope of the invention, which is limited only by the scope of the claims. Additionally, any examples set forth in this specification are not limiting and merely set forth some of the many possible embodiments of the claimed invention.
“Standardized,” “standard,” or like terms refer to actual or simulated handling defects or surface flaws. In embodiments, standardized glass can be obtained by, for example, contacting the glass article with an abrasive, such as by sandblasting, or like abrading treatments, to simulate handling defects or surface flaws. In embodiments, standardized glass can be obtained by, for example, selecting glass articles that have been handled during typical post-manufacture unit operations that can be performed manually or autonomously, such as etching, polishing, washing, cleaning, picking, placing, conveying, stacking, wrapping, packing, testing, and like handling or processing operations.
“Low-alkali,” “alkali-free,” or like terms refer to, for example, an alkali content of less than about 0.5 wt %.
“Sharp contact” or like terms refer to, for example, a contact force that can permanently deform the surface of the glass article, such as simulated in a Vickers indentation analysis and like contact forces.
“IOX” refers to ion-exchanged glass.
“Non-IOX” refers to non-ion-exchanged glass.
“Include,” “includes,” or like terms means encompassing but not limited to, that is, inclusive and not exclusive.
“About” modifying, for example, the quantity of an ingredient in a composition, concentrations, volumes, process temperature, process time, yields, flow rates, pressures, and like values, and ranges thereof, employed in describing the embodiments of the disclosure, refers to variation in the numerical quantity that can occur, for example: through typical measuring and handling procedures used for making compounds, compositions, composites, concentrates or use formulations; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of starting materials or ingredients used to carry out the methods; and like considerations. The term “about” also encompasses amounts that differ due to aging of a composition or formulation with a particular initial concentration or mixture, and amounts that differ due to mixing or processing a composition or formulation with a particular initial concentration or mixture. The claims appended hereto include equivalents of these “about” quantities.
“Consisting essentially of” in embodiments refers, for example: to a glass article having enhanced strength and durability properties resulting from contacting the glass article for a sufficient time with steam, hot water immersion, or a combination thereof, compared to an uncontacted glass article; to a glass surface having enhanced strength and durability properties resulting from the same contacting; to a method of making an enhanced strength and durability glass article; devices incorporating the article, or any apparatus of the disclosure, and can include the components or steps listed in the claim, plus other components or steps that do not materially affect the basic and novel properties of the compositions, articles, apparatus, or methods of making and use of the disclosure, such as particular reactants, particular additives or ingredients, a particular agent, a particular surface modifier or condition, or like structure, material, or process variable selected. Items that may materially affect the basic properties of the components or steps of the disclosure or that may impart undesirable characteristics to the present disclosure include, for example, a surface having low Vickers indentation crack resistance, that are beyond the values, including intermediate values and ranges, defined and specified herein.
The indefinite article “a” or “an” and its corresponding definite article “the” as used herein means at least one, or one or more, unless specified otherwise.
Abbreviations, which are well known to one of ordinary skill in the art, may be used (e.g., “h” or “hr” for hour or hours, “g” or “gm” for gram(s), “mL” for milliliters, and “rt” for room temperature, “nm” for nanometers, and like abbreviations).
Specific and preferred values disclosed for components, ingredients, additives, and like aspects, and ranges thereof, are for illustration only; they do not exclude other defined values or other values within defined ranges. The composition, device, apparatus, and methods of the disclosure can include any value or any combination of the values, specific values, more specific values, and preferred values described herein, including intermediate values and ranges.
Manufacturers of mobile phones, laptops, and other electronic devices are selecting glass, especially strengthened ion-exchanged glass, as the material of choice for the top cover piece on their flat panel display devices. Certain strengthened ion-exchanged glass can be further strengthened and its durability enhanced against damage according to the methods of making of the disclosure.
In embodiments, the disclosure provides a method of making a strengthened and durable glass article by contacting with steam or water immersion.
In embodiments, the disclosure provides a method for strengthening an alkali-containing glass article comprising, for example:
contacting a standardized glass article and aqueous vapor at about 80 to 500° C. for 0.5 to 400 hours at atmospheric pressure, such as 1 atmosphere.
The aqueous vapor can be, for example, at about 200 to about 300° C. for 0.5 to 100 hours. The contacting can be accomplished, for example, at a temperature at least below the anneal point of the bulk glass, for example, from 5 to 200° C. below the anneal point, and from 10 to 200° C. below the anneal point, from 100 to 200° C. below the anneal point. The water fraction in the aqueous vapor can be, for example, about 20 to 100% by volume, about 50 to 100% by volume, and like volume % values, including intermediate values and ranges.
In embodiments, the method can further comprise, for example, contacting the standardized glass article with an ion-exchange medium to strengthen the standardized glass article prior to contacting the standardized glass article and aqueous vapor.
In embodiments, the beta-OH content of the contacted glass surface can be, for example, at least 1.5 times greater than the beta-OH content of the center of the glass article, at least 2 times greater than the beta-OH content of the center of the glass article, at least 3 times greater than the beta-OH content of the center of the glass article, and like glass surface beta-OH contents. The beta-OH surface can be, for example, at least 1 micron and the glass article thickness can be, for example, at least 50 microns. The beta-OH surface can be, for example, at least 10 microns and the glass article thickness can be, for example, at least 100 microns. The beta-OH surface can be, for example, at least 50 microns and the glass article thickness can be, for example, at least 250 microns.
The beta-OH surface can have, for example, a decreasing gradient profile approaching the bulk glass.
In embodiments, the disclosure provides a method for strengthening an ion-exchanged alkali-containing glass article comprising, for example:
immersing a standardized glass article in liquid water at about 100 to 500° C. for 0.5 to 400 hours.
In embodiments, the disclosure provides a method for making a damage resistant, low-alkali, glass article comprising, for example:
contacting a standardized glass article and aqueous vapor at about 100 to 600° C. for about 0.5 to about 200 hours at atmospheric pressure.
The contacting can improve the indentation crack resistance of the contacted glass article by, for example, from about 5 to about 10% relative to an un-contacted glass article. The contacting can also heal or reduce the severity of existing handling flaws on the glass article by from about 10 to about 60% relative to an uncontacted glass article.
The contacting can also increase the resistance of the glass article to subsequent handling flaw formation from sharp contact.
In embodiments, the aqueous vapor can be, for example, at 300 to 500° C. for about 50 to about 120 hours at one atmosphere of pressure.
In embodiments, the standardized, low-alkali, glass can be obtained, for example, from abrasive treatment comprising contacting with 90 grit SiC, and like abrasive treatment methods.
In embodiments, the disclosure provides a glass article prepared by any of the disclosed methods, or method combinations thereof.
In embodiments, the disclosure provides methods for strengthening glass articles, such as glass sheets. In embodiments, the method can comprise, for example, steam or aqueous immersion treatment that can be applied to alkali-containing glasses including alkali-alumino silicates. Although not bound by theory, the method is believed to impregnate the contacted glass surface with H2O molecules at atmospheric pressure.
In embodiments, the disclosure provides a method for strengthening, for example, alkali-containing glasses by steam or aqueous immersion treatment at temperatures less than the anneal point of the glass. Glass compositions that readily ion-exchange Na+ (glass) for K+ (KNO3 salt), such as sodium alumino silicates (without prior ion-exchange), will also strengthen when exposed to steam. The disclosed steam or aqueous immersion treatment methods can be an alternative to traditional ion-exchange methods that enhance damage resistance. In addition, the disclosed post-ion-exchange (IOX) steam or aqueous immersion treatment can be used in place of other treatments such as HF etching used for surface strengthening or conditioning for surface properties, such as anti-glare and anti-reflection.
In embodiments, the disclosure provides a method comprising high temperature steam treatment to improve the strength of a display glass article that has had some strength limiting damage introduced by, for example, handling or mis-handling. The disclosure also provides a method to enhance the damage resistance of the glass.
In embodiments, steam treatment of the as-drawn or as-molded glass can be sufficient to increase damage resistance. Replacement of ion-exchange salt baths with a steam or water process can lead to considerable reduction in manufacturing costs. In ion-exchange processes the salt becomes contaminated with the smaller exchanged alkali ions from the glass substrate and has to be changed frequently. Deionized water is less expensive than KNO3 salt and can be used fresh in every instance to provide the benefit of having a consistent compressive stress profile. In existing ion-exchange processes the compressive stress profile can change as the KNO3 salt becomes contaminated with Na+ until the Na+ levels are unacceptable requiring production shut down and bath change-out.
In embodiments, when the glass is water-treated after being ion-exchanged, the surface layer gains compressive stress strength that improves mechanical test results, such as ring-on-ring strength on as-received glass. In embodiments, the disclosure provides a method for enhancing glass, such as display glass, strength and durability, that is, enhanced damage resistance. In embodiments, one of the disclosed methods comprises steam treatment that can be applied to, for example, non-alkali glasses including alkaline earth alumino silicates such as Glasses A and E in Table 1. The method comprises contacting glass with steam at atmospheric pressure as defined herein.
Particularly significant aspects of the disclosure of contacting a glass article with steam or hot water immersion include, for example: either treatment method improves the mechanical strength of glasses by reducing the severity of handling flaws. The steam treatment method also increases the resistance of the glass surface to the formation of new flaws. In embodiments, the method can provide one or more advantages or benefits, including for example: improved mechanical strength as measured by, for example, edge and ball drop methods; resistance to crack formation as measured by, for example, Vickers Hardness (indentation; see for example, www.instron.us and ASTM E384); and avoiding concentrated acid etch processing, such as HF, used for surface strengthening. These and other aspects of the disclosure are illustrated and demonstrated herein.
In embodiments, a significant and preferred condition for the disclosed method is that the contacting or treatment temperature remain relatively low, for example, below the anneal point of the glass, preferably at least 100 degrees below the anneal point of the as-initially formed glass, and more preferably at least 200 degrees below the anneal point of the glass, to achieve the disclosed enhanced mechanical attributes.
In embodiments, the article comprises, consists essentially of, or consists of one of a soda lime silicate glass, an alkaline earth aluminosilicate glass, an alkali aluminosilicate glass, an alkali borosilicate glass, and combinations thereof. Examples of such glasses are described herein. For additional definitions, descriptions, and methods of silica materials and related metal oxide materials, see for example, R. K. Iler, The Chemistry of Silica, Wiley-Interscience, 1979.
In embodiments, the glass article can be a transparent or semi-transparent glass sheet, such as those used as cover plates and windows for display and touch screen applications, for example, portable communication and entertainment devices such as telephones, music players, video players, or like devices; and as display screens for information-related terminal (IT) (e.g., portable or laptop computers) devices; and like applications. The glass article or substrate can have a thickness of up to about 3 millimeters (mm). In embodiments, the thickness can be from about 0.2 to about 3 mm.
In embodiments, the glass article can have at least one surface that is unpolished.
In embodiments, contacting the surface of the glass article or substrate can include additional optional preparative, pretreatment, or post-treatment procedures, for example, for removing oil, foreign matter, or other surface debris that may inhibit H2O absorption, penetration, or imbibation, from at least one surface of the glass article using known methods, including, for example, washing with soaps or detergents, ultrasonic cleaning, treatment with surfactants, and like methods. Other optional preparative procedures can include, for example, etching at least one surface of the glass article using known methods.
In embodiments, a glass article is provided. The glass article can be, for example, a sheet that can be ion-exchanged or ion-exchangeable, and can have two smooth surfaces or at least one roughened surface. The roughened surface can have a distinctness-of-reflected image (DOI) of less than 90 when measured at an incidence angle of 20°. A pixelated display system that includes the glass article treated in accord with the present disclosure is also provided. The glass article can be, for example, a planar sheet or panel having two major surfaces joined on the periphery by at least one edge, although the glass article can be formed into other shapes such as, for example, a three-dimensional shape. At least one of the surfaces can be a roughened surface including, for example, topological or morphological features, such as, projections, protrusions, depressions, pits, closed or open cell structures, particles, and like structures or geometries, or combinations thereof.
In embodiments, the disclosure provides an aluminosilicate glass article. The aluminosilicate glass article can comprise at least 2 mol % Al2O3, can be ion-exchangeable, and has at least one roughened surface. The aluminosilicate glass article can have at least one roughened surface comprising a plurality of topographical features. The plurality of topographical features can have an average characteristic largest feature size (ALF) of from about 1 micrometer to about 50 micrometers.
In embodiments, the disclosure provides a display system. The display system can include at least one aluminosilicate glass panel and a pixelated image-display panel adjacent to the aluminosilicate glass panel. The image-display panel has a minimum native pixel pitch dimension. The average characteristic largest feature size of the glass panel can be less than the minimum native pixel pitch dimension of the display panel. The pixelated image display panel can be, for example, one of an LCD display, an OLED display, or like display devices. The display system can also include touch-sensitive elements or surfaces. The aluminosilicate glass can be ion-exchanged and has at least one roughened surface comprising a plurality of features having an average largest feature size, or ALF, and the image-displaying panel can have a minimum native pixel pitch. The minimum native pixel pitch can be, for example, greater than the ALF of the roughened surface of the aluminosilicate glass panel.
In embodiments, the alkali aluminosilicate glass can comprise, consist essentially of, or consist of, for example: 60-70 mol % SiO2; 6-14 mol % Al2O3; 0-15 mol % B2O3; 0-15 mol % Li2O; 0-20 mol % Na2O; 0-10 mol % K2O; 0-8 mol % MgO; 0-10 mol % CaO; 0-5 mol % ZrO2; 0-1 mol % SnO2; 0-1 mol % CeO2; less than 50 ppm As2O3; and less than 50 ppm Sb2O3; wherein 12 mol % Li2O+Na2O+K2O≦20 mol % and 0 mol % MgO+CaO≦10 mol %. In embodiments, the alkali aluminosilicate glass can comprise, consist essentially of, or consist of, for example: 60-72 mol % SiO2; 9-16 mol % Al2O3; 5-12 mol % B2O3; 8-16 mol % Na2O; and 0-4 mol % K2O. In embodiments, the alkali aluminosilicate glass can comprise, consist essentially of, or consist of 61-75 mol % SiO2; 7-15 mol % Al2O3; 0-12 mol % B2O3; 9-21 mol % Na2O; 0-4 mol % K2O; 0-7 mol % MgO; and 0-3 mol % CaO. In embodiments, the glass can be batched with 0 to 2 mol % of at least one fining agent, such as Na2SO4, NaCl, NaF, NaBr, K2SO4, KCl, KF, KBr, SnO2, or combinations thereof. The aluminosilicate glass, in embodiments, can be substantially free of lithium. In embodiments, the aluminosilicate glass can be substantially free of at least one of arsenic, antimony, barium, or combinations thereof.
In embodiments, the selected glass can be, for example, down drawable, i.e., formable by methods such as slot draw or fusion draw processes that are known in the art. In these instances, the glass can have a liquidus viscosity of at least 130 kpoise. Examples of alkali aluminosilicate glasses are described in commonly owned and assigned U.S. patent application Ser. No. 11/888,213, to Ellison, et al., entitled “Down-Drawable, Chemically Strengthened Glass for Cover Plate,” filed Jul. 31, 2007, having priority to U.S. Provisional Appln 60/930,808, filed May 22, 2007; U.S. patent application Ser. No. 12/277,573, to Dejneka, et al., entitled “Glasses Having Improved Toughness and Scratch Resistance,” filed Nov. 25, 2008, which claims priority from U.S. Provisional Appln 61/004,677, filed Nov. 29, 2007; U.S. patent application Ser. No. 12/392,577, to Dejneka, et al., entitled “Fining Agents for Silicate Glasses,” filed Feb. 25, 2009, which claims priority from U.S. Provisional Appln No. 61/067,130, filed Feb. 26, 2008; U.S. patent application Ser. No. 12/393,241, to Dejneka, et al., entitled “Ion-Exchanged, Fast Cooled Glasses,” filed Feb. 26, 2009, which claims priority to U.S. Provisional Appln No. 61/067,732, filed Feb. 29, 2008; U.S. patent application Ser. No. 12/537,393, to Barefoot, et al., entitled “Strengthened Glass Articles and Methods of Making,” filed Aug. 7, 2009, having priority to U.S. Provisional Appln No. 61/087,324, entitled “Chemically Tempered Cover Glass,” filed Aug. 8, 2008; U.S. Provisional Patent Appln No. 61/235,767, to Barefoot, et al., entitled “Crack and Scratch Resistant Glass and Enclosures Made Therefrom,” filed Aug. 21, 2009; and U.S. Provisional Patent Appln No. 61/235,762, to Dejneka, et al., entitled “Zircon Compatible Glasses for Down Draw,” filed Aug. 21, 2009.
In embodiments, a particularly useful and popular glass composition for use in the disclosed process is Code 2318 glass, commercially available from Corning, Inc. (i.e., Corning® Gorilla® glass; see for example, U.S. Provisional Patent Application 61/235,762, supra.). The Code 2318 glass can have a composition specified within the following combined ranges, for example: 61 mol %≦SiO2≦75 mol %; 7 mol %≦Al2O3≦15 mol %; 0 mol %≦B2O3≦12 mol %; 9 mol %≦Na2O≦21 mol %; 0 mol %≦K2O≦4 mol %; 0 mol %<MgO≦7 mol %; and 0 mol %≦CaO≦3 mol %. In embodiments, other suitable glass compositions for use in the disclosed methods can include, for example, low-alkali and alkali-containing glasses, such as those compositions listed in Table 1.
The following examples serve to more fully describe the manner of using the above-described disclosure, and to further set forth the best modes contemplated for carrying out various aspects of the disclosure. It is understood that these examples do not limit the scope of this disclosure, but rather are presented for illustrative purposes. The working examples further describe the methods of how to prepare the glass articles of the disclosure.
FTIR beta-OH Content Characterization.
The beta-OH content of the steam treated samples was measured by FTIR. IR analysis of hydrated glass was performed as follows. Measurements were conducted using a Nicolet 8700 bench (Thermo Fisher Scientific, Waltham, Mass.) with a DTGS detector and XT-KBr beam splitter. 128 scans were taken at 16 cm−1 resolution with a gain of 1. Each glass spectrum is relative to an open beam through the same 5 mm aperture in the nitrogen purged sample compartment.
The β-OH content (also known as BOH or beta-OH) was calculated from the spectral transmittance at two frequencies (or wavelengths): at a reference frequency, 3900 cm−1 (2.56 microns); and at the frequency of minimum transmittance of the hydroxyl band near 3550 cm−1 (2.8 microns), with the latter frequency being composition dependent and can be from about 2.6 to 2.9 microns.
The β-OH content can be calculated by:
β-OH content=(1/x)·log10(TRef/TOH)
where TRef=Transmittance at reference frequency, 3900 cm−1, TOH=Transmittance at OH minimum about 3550 cm−1), and x=thickness of sample (mm).
Glass Etch Conditions.
Glass samples were chemically etched at room temperature (about 23° C.) using an aqueous solution of 1.5 M HF/0.9 M H2SO4 for the stated period of time then triple rinsed in DI water at room temperature. An FTIR measurement followed each acid treatment. After each acid etching step a thickness measurement was taken over about ten equally spaced areas of the glass using a digital micrometer, recorded, and averaged to determine the average etching rate for each sequence. The acid bath was replaced prior to each etching sequence.
In embodiment, alkali alumino silicates (glasses B to D in Table 1, without prior ion-exchange) all had Vickers indentation crack resistance exceeding 2 kgf (kilograms force) following treatment in 100% steam atmosphere at atmospheric pressure. As an alternative to steam treatment, the alkali-containing glass samples were immersed in liquid water at elevated temperatures and achieved a high surface compression layer.
In embodiment, the disclosed strengthening method includes steam treatment or water immersion for achieving enhanced damage resistance of glasses containing ion-exchangeable alkalis. Traditionally, ion-exchange glass strengthening is performed by treatment of glasses containing smaller alkalis, e.g., Na+, in a salt containing larger alkalis, e.g., K+. Non-ion-exchanged samples of alkali alumino silicates (glasses B to D in Table 1), showed enhanced Vickers crack resistance following steam treatment at 250° C. for 3 days. Non-ion-exchanged glass B had a Vickers crack initiation load of 300 to 500 gf (grams force). Following steam treatment the Vickers crack initiation load of glass B was increased to greater than 2000 gf. Non-ion-exchanged glass C had Vickers crack initiation load of 200 to 300 gf. Following steam treatment the Vickers crack initiation load was increased to 1000 to 2000 gf. Non-ion-exchanged Glass D had Vickers crack initiation load of 1000 to 2000 gf. Following steam treatment the Vickers crack initiation load was increased to greater than 2000 gf. The results of steam treating non-ion-exchanged glasses showed strength increases of about 2 to about 10 fold compared to the same glass sample without the steam or water immersion treatment.
The etching and measurement sequence was continued until loss of glass resulted in no change to BOH indicating the complete loss of the enriched hydroxyl layer. The data is plotted in
Samples of 1.3 mm thick Glass D (an alkali-containing glass) were exposed to a 100% steam containing atmosphere at 1 atm. pressure, for temperatures selected from 250 to 500° C., and for times selected from 72 to 144 hours. The results show an increase in BOH of 10 to 21% when averaged across the entire thickness of the samples (see
Table 2 shows that an increase of BOH can be controlled by exposing samples to different temperatures, times, and partial pressures of steam in the atmosphere, where “NA” refers to not tested, and “steam” refers to 1 atmosphere pressure of 100% steam.
Steam or water immersion treatment of glass can also be used post-ion-exchange to enhance the compression layer near the surface. Immersion in water at 95° C. for 240 hrs showed a significant increase in the ring-on-ring load-at-failure of ion-exchanged glass D samples when compared to those samples that were ion-exchanged, but not water immersion treated. There was an improvement in strength at all failure loads. The largest improvement in ring-on-ring load-at-failure occurred at the high end of the strength distribution; this is where the smallest flaws (i.e., about 1 micron or less) were present. The post-ion-exchange steam or water immersion treatment is sufficiently effective to replace or supplement other surface strengthening treatments, such as HF etching, used for surface strengthening.
Following standard ion-exchange treatments for alkali alumino silicates (glasses B to D in Table 1), in which Na+ is exchanged for K+, the glass can be treated in water or steam at low to moderate (up to several hundred degrees C.) temperatures to achieve additional surface strengthening. Ion-exchanged samples of glass D were water-immersion treated by holding the samples in distilled water at 95° C. for 240 hrs and then tested by ring-on-ring. The average ring-on-ring load-at-failure for the 1.3 mm thick ion-exchanged parts without water immersion treatment was 408 kgf. The average ring-on-ring load at failure for the 1.3 mm thick ion-exchanged parts then water treated was 503 kgf (i.e., a 23% increase). The strength distribution for ring-on-ring testing shows that the advantage gained from water treatment was at the high end of the strength distribution for specimens that failed from small flaws.
Non-ion-exchanged test glass samples B to D were tested under various steam treatment conditions. Following steam treatment the Vickers indentation thresholds were measured for the treated glasses. When the glasses were treated in 100% steam atmosphere (at 1 atm. pressure) and at a lower temperature of, for example, 250° C. for 3 days, the Vickers indentation threshold was enhanced in each glass as shown in Table 3.
As mentioned above, FTIR was used to characterize the beta-OH profile of 1.3 mm thick glass D (non-IOX) glass samples that were steam treated under varying conditions. The results showed a 10 to 20% increase in bulk OH (
The Vickers crack initiation load of Glass B went from 300 to 500 gf in the untreated glass to greater than 2000 gf after steam treatment. The Vickers crack initiation load of Glass C went from 200 to 300 gf in the untreated glass to 1000 to 2000 gf after steam treatment. The Vickers crack initiation load of Glass D went from 1000 to 2000 gf in the untreated glass to greater than 2000 gf after steam treatment.
Samples of ion-exchanged 1.3 mm thick Glass D (compressive stress=772 MPa, depth of layer of 49 microns) were treated post-ion-exchange (i.e., after being ion-exchanged) by water immersion in distilled water at 95° C. for 240 hr. The results of ring-on-ring mechanical testing as shown in
Although not bound by theory,
The disclosed process that provides beta-OH profiles having improved strength and durability properties for treated glass samples are expected to be applicable to other glasses including, for example, Corning code 7740 (e.g., Pyrex®), and (non-alkali) alkaline earth alumino silicates such as Glasses A and E in Table 1.
In embodiments, the disclosure also relates to surface strengthening of silicate display glasses by steam treatment. In embodiments, the disclosure provides a method to improve the strength of the glass comprising steam treating a glass article having an abraded surface. The method can be applied to, for example, (non-alkali) alkaline earth alumino silicates such as glasses A and E in Table 1 to blunt, heal, or both, surface flaws caused by handling damage. In embodiments, water and steam treatments have been applied to glasses to improve their strength. Abraded silica glass that was treated in 100% steam atmosphere (1 atm. pressure) at 250° C. for 4 days showed a greater than 200% increase in the strength of the specimens.
Steam treatment of (non-alkali) alkaline earth alumino silicates, such as Glasses A and E in Table 1, also shows an improvement in the indentation crack resistance.
Strength testing using ring-on-ring methods was used to determine the strengths of Glass A samples following abrasion and subsequent high temperature steam treatment. Abrasion was performed by blasting the surface of the glass with 1 cm3 of 90 grit SiC at 5 psi for 5 sec. A mask was used to contain the abrasion to a circle of 10 mm diameter in the center of the 50 mm×50 min square glass specimens. Ring-on-ring strength testing was performed at room temperature at 50% RH with a support ring of 25.4 mm and a loading ring of 12.7 mm. The loading rate was fixed at 1.2 mm/min. Table 4 list the data for 0.69 mm thick Glass A samples that were: abraded with 90 grit SiC then treated in 100% steam atmosphere at 400° C., 1 atm. pressure for 96 hours; abraded with 90 grit SiC then treated in N2 at 400° C. for 96 hours; and untreated after abrasion with 90 grit SiC (control, i.e., not treated with either steam or nitrogen).
Table 4 shows Glass A (0.69 mm thick) as-formed, non-abraded, and abraded with 90 grit SiC, then treated under different conditions, followed by ring-on-ring strength testing. Table 3 above also shows the data for non-abraded samples that were treated in 100% steam atmosphere at 400° C., 1 atm., for 96 hours, in N2 at 400° C. for 96 hours; and untreated samples (i.e., tested as-is).
Parts tested as-drawn, and then abraded, had an average abraded strength of 58 MPa. Parts that were heat-treated in N2 had an average abraded strength of 71 MPa (22% median strength increase). Parts that were steam treated had an average abraded strength of 83 MPa for about a 43% median strength increase for the steam treated samples compared to the samples that were heat-treated in N2. The Weibull plot comparing these three data sets is given in
These results indicate that the steam treatment was most effective in increasing the strength of Glass A samples. Heat treatment in N2 increased the strength when compared to the non-treated samples and was possibly due to the relief of residual stress at the tips of the flaws. Although not bound by the theory, the steam treatment in the disclosed experiments was more effective possibly because it promoted residual stress relaxation or it blunted or healed the flaws. The Weibull plot shown in
Table 4 shows the data for non-abraded samples that were treated in 100% steam atmosphere at 400° C., 1 atm. for 96 hours, in N2 at 400° C. for 96 hours; and untreated (control, i.e., tested as-is).
The non-abraded samples were tested under these various conditions to understand the effect of treatment on samples that undergo typical handling damage. Parts tested as-drawn had an average strength of 180 MPa. Parts that were heat-treated in N2 had an average strength of 224 MPa (24% median strength increase). Parts that were steam treated had an average strength of 331 MPa (about an 84% median strength increase). The Weibull plot comparing these three data sets is shown in
When comparing
FTIR Beta-OH as measured through 0.69 mm thick steam treated Glass A showed a 4 to 11% increase in OH (
Other glass samples which were steam treated showed an eight fold or greater increase in beta-OH on the surface vs. the bulk glass. Although not bound by theory, it is believed that a greater relative beta-OH content and deeper beta-OH layer (e.g., about 100 microns) can further improve the toughness of the treated glass articles.
The disclosure has been described with reference to various specific embodiments and techniques. However, it should be understood that many variations and modifications are possible while remaining within the scope of the disclosure.
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 61/480,027, filed on Apr. 28, 2011, the content of which is relied upon and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61480027 | Apr 2011 | US |
