Glass substrate, solar panel including same, and architectural window including same

Abstract

A glass substrate including: a composition including, in mol% and on an oxide basis: (i) SiO2, within a range of from 50 to 70; (ii) Al2O3, within a range of from 0.5 to 1.5; (iii) B2O3, within a range of from 9.5 to 14.75; (iv) CaO, within a range of from 10.0 to 15.0; and (v) Na2O, within a range of from 8.0 to 13.0. The glass substrate exhibits a Young's Modulus within a range of from 79 GPa to 85 GPa. The glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C. A solar panel including the glass substrate over an array of photovoltaic cells. An architectural window including the glass substrate as part of a pane.

Description

GLASS SUBSTRATE, SOLAR PANEL INCLUDING SAME, AND ARCHITECTURAL WINDOW INCLUDING SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 612,550 filed December 20, 2023, the content of which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure pertains to glass substrates including B2O3 and presenting improved Young’s modulus and thermal tempering capability at relatively thin thicknesses.BACKGROUND

[0003] Glass substrates have been used to separate interior spaces in buildings and photovoltaic modules in solar panels from the external environment. Desirable wavelength ranges of electromagnetic radiation, such as those in the visible spectrum, transmit through the glass substrate into the interior spaces and to photovoltaic cells. Nevertheless, the glass substrate physically protects the interior spaces and the photovoltaic cells from otherwise damaging events that originate from the external environment. The glass substrate is often thermally tempered, to increase the damage resistance of the glass substrate.

[0004] There are commercial, environmental, and governmental incentives to reduce the thickness of glass substrates used for architectural and solar panel applications. Reducing the thickness of the glass substrate reduces the weight of the glass substrate, which reduces transportation costs, and reduces the amount of raw ingredients required to form the glass substrate, which reduces cost and generates less environmental impact. Similar incentives exist to reduce the temperature at which the glass substrate is formed, because the lower the melting temperature of the glass substrate is, the less energy and expense is required.

[0005] However, there is a problem in that it becomes increasingly more difficult to thermally temper a glass substrate as the thickness of the glass substrate decreases.SUMMARY

[0006] The present disclosure addresses that problem with a glass substrate with a composition including B2O3, AI2O3, CaO, and Na2O in particular mole percentage ranges. The glass substrate, due to the composition, exhibits (i) Young’s modulus values and (ii) coefficients of thermal expansion at high temperatures that are higher than those that soda lime glass substrates typically used for architectural and solar panel applications exhibit. The relatively high Young’s modulus value permits the glass substrate to have a thickness that is reduced and yet still exhibit flexural rigidity that is comparable to thicker soda lime glass substrates. Therelatively high high temperature coefficient of thermal expansion causes thermal tempering of the glass substrate to induce higher levels of compressive stress. In addition, less energy may be required to thermally temper the glass substrate of the present disclosure at any given thickness and to achieve a predetermined degree of compressive stress compared to thermal tempering of soda lime glass substrates.

[0007] According to a first aspect of the present disclosure, a glass substrate comprises: a composition comprising, in mol% and on an oxide basis: (i) SiCh, within a range of from 50 to 70; (ii) AI2O3, within a range of from 0.5 to 1.5; (iii) B2O3, within a range of from 9.5 to 14.75; (iv) CaO, within a range of from 10 to 15; and (v) Na2O, within a range of from 8.0 to 13.0.

[0008] According to a second aspect of the present disclosure, the glass substrate of the first aspect is presented, wherein the SiCh of the composition is within a range of from 57 to 70.

[0009] According to a third aspect of the present disclosure, the glass substrate of any one of the first through second aspects is presented, wherein the AI2O3 of the composition is within a range of from 0.95 to 1.5.

[0010] According to a fourth aspect of the present disclosure, the glass substrate of any one of the first through third aspects is presented, wherein the B2O3 of the composition is within a range of from 9.90 to 14.75.

[0011] According to a fifth aspect of the present disclosure, the glass substrate of any one of the first through fourth aspects is presented, wherein the CaO of the composition is within a range of from 10.0 to 14.4.

[0012] According to a sixth aspect of the present disclosure, the glass substrate of any one of the first through fifth aspects is presented, wherein the Na2O of the composition is within a range of from 8.9 to 13.

[0013] According to a seventh aspect of the present disclosure, the glass substrate of any one of the first through sixth aspects is presented, wherein (i) CaO - Na2O of the composition is less than or equal to 2.3, (ii) B2O3 - CaO of the composition is within a range of from -0.4 to 0.7, and (iii) CaO / Na2O of the composition is greater than 1.

[0014] According to an eighth aspect of the present disclosure, the glass substrate of any one of the first through seventh aspects is presented, wherein the composition further comprises, in mole percentage and on an oxide basis, MgO within a range of from 0.05 to 0.15.

[0015] According to a ninth aspect of the present disclosure, the glass substrate of any one of the first through eighth aspects is presented, wherein the composition is substantially free of

[0016] According to a tenth aspect of the present disclosure, the glass substrate of any one of the first through ninth aspects is presented, wherein the composition consists essentially of SiCh, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2O3, SnCh, and SO3.

[0017] According to an eleventh aspect of the present disclosure, the glass substrate of any one of the first through tenth aspects further comprises: a first primary surface, a second primary surface facing away from the first primary surface, and a thickness between the first primary surface, wherein, the thickness is less than or equal to 4.5 mm.

[0018] According to a twelfth aspect of the present disclosure, the glass substrate the eleventh aspect is presented, wherein the thickness is less than or equal to 3.1 mm.

[0019] According to a thirteenth aspect of the present disclosure, the glass substrate of any one of the first through twelfth aspects is presented, wherein the glass substrate exhibits a Young’s Modulus within a range of from 79 GPa to 85 GPa.

[0020] According to a fourteenth aspect of the present disclosure, the glass substrate of any one of the first through thirteenth aspects is presented, wherein (i) the glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C and (ii) a difference between the high temperature coefficient and a low temperature coefficient that the glass substrate exhibits is greater than 25 ppm / °C.

[0021] According to a fifteenth aspect of the present disclosure, the glass substrate of any one of the first through fourteenth aspects is presented, wherein the glass substrate exhibits a shear modulus that is within a range of from 32.5 GPa to 34.5 GPa.

[0022] According to a sixteenth aspect of the present disclosure, the glass substrate of any one of the first through fifteenth aspects further comprises: (i) a first region of compressive stress; (ii) a second region of compressive stress; and (iii) a region of central tension disposed between the first region of compressive stress and the second region of compressive stress.

[0023] According to a seventeenth aspect of the present disclosure, the glass substrate of any one of the first through sixteenth aspects is presented, wherein the glass substrate exhibits a liquidus temperature that is less than 1400 °C.

[0024] According to an eighteenth aspect of the present disclosure, a solar panel comprises: (1) an array of photovoltaic cells; and (2) a glass substrate separating the photovoltaic cell from an external environment, the glass substrate (a) exhibiting an average transmittance through the glass substrate of greater than or equal to 80% for a wavelength of electromagnetic radiation within a range of from 500 nm to 950 nm, (b) comprising a first primary surface facing the external environment, a second primary surface facing the photovoltaic cell, and a thicknessbetween the first primary surface and the second primary surface that is less than or equal to 4.5 mm, and (c) comprising a composition comprising, in mol% and on an oxide basis: (i) SiCh, within a range of from 50 to 70; (ii) AI2O3, within a range of from 0.5 to 1.5; (iii) B2O3, within a range of from 9.5 to 14.75; (iv) CaO, within a range of from 10 to 15; and (v) Na2O, within a range of from 8.0 to 13.0.

[0025] According to a nineteenth aspect of the present disclosure, the solar panel of the eighteenth aspect is presented, wherein (i) the SiCh of the composition is within a range of from 57 to 70; (ii) the AI2O3 of the composition is within a range of from 0.95 to 1.5; (iii) the B2O3 of the composition is within a range of from 9.90 to 14.75; (iv) the CaO of the composition is within a range of from 10.0 to 14.4; and (v) the Na2O of the composition is within a range of from 8.9 to 13.

[0026] According to a twentieth aspect of the present disclosure, the solar panel of any one of the eighteenth through nineteenth aspects is presented, wherein (i) the composition further comprises, in mole percentage and on an oxide basis, MgO within a range of from 0.05 to 0.15; (ii) the composition of the glass substrate is substantially free of K2O; (iii) CaO - Na2O of the composition of the glass substrate is less than or equal to 2.3; (iv) B2O3 - CaO of the composition of the glass substrate is within a range of from -0.4 to 0.7; and (v) CaO / Na2O of the composition is greater than 1.

[0027] According to a twenty-first aspect of the present disclosure, the solar panel of any one of the eighteenth through twentieth aspects is presented, wherein the composition of the glass substrate consists essentially of SiCh, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2O3, SnO2, and SO3.

[0028] According to a twenty-second aspect of the present disclosure, the solar panel of any one of the eighteenth through twenty-first aspects is presented, wherein the thickness of the glass substrate is less than or equal to 3.1 mm.

[0029] According to a twenty-third aspect of the present disclosure, the solar panel of any one of the eighteenth through twenty-second aspects is presented, wherein (i) the glass substrate exhibits a Young’s Modulus within a range of from 79 GPa to 85 GPa; (ii) the glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C; (iii) a difference between the high temperature coefficient and a low temperature coefficient that the glass substrate exhibits is greater than 25 ppm / °C; and (iv) the glass substrate exhibits a liquidus temperature that is less than 1400 °C.

[0030] According to a twenty -fourth aspect of the present disclosure, an architectural window comprises: (1) a first pane comprising a glass substrate, the glass substrate (a) exhibiting anaverage transmittance through the glass substrate of greater than or equal to 80% for a wavelength of electromagnetic radiation within a range of from 500 nm to 950 nm, (b) comprising a first primary surface facing an external environment, a second primary surface facing away from the external environment, and a thickness between the first primary surface and the second primary surface that is less than or equal to 4.5 mm, and (c) comprising a composition comprising, in mol% and on an oxide basis: (i) SiCh, within a range of from 50 to 70; (ii) AI2O3, within a range of from 0.5 to 1.5; (iii) B2O3, within a range of from 9.5 to 14.75;(iv) CaO, within a range of from 10.0 to 15.0; and (v) Na2O, within a range of from 8.0 to 13.0; and (2) a second pane separated from the first pane by a space, the second pane comprising the glass substrate or another glass substrate.

[0031] According to a twenty-fifth aspect of the present disclosure, the architectural window of the twenty-fourth aspect further comprises: a frame surrounding perimeters of, and supporting, both the first pane and the second pane.

[0032] According to a twenty-sixth aspect of the present disclosure, the architectural window of any one of the twenty-fourth through twenty-fifth aspects is presented, wherein (i) the SiCh of the composition is within a range of from 57 to 70; (ii) the AI2O3 of the composition is within a range of from 0.95 to 1.5; (iii) the B2O3 of the composition is within a range of from 9.90 to 14.75; (iv) the CaO of the composition is within a range of from 10.0 to 14.4; and (v) the Na2O of the composition is within a range of from 8.9 to 13.0.

[0033] According to a twenty-seventh aspect of the present disclosure, the architectural window of any one of the twenty-fourth through twenty-sixth aspects is presented, wherein (i) the composition further comprises, in mole percentage and on an oxide basis, MgO within a range of from 0.05 to 0.15; (ii) the composition of the glass substrate is substantially free of K2O; (iii) CaO - Na2O of the composition of the glass substrate is less than or equal to 2.3; (iv) B2O3 - CaO of the composition of the glass substrate is within a range of from -0.4 to 0.7; and(v) CaO / Na2O is greater than 1.

[0034] According to a twenty-eighth aspect of the present disclosure, the architectural window of any one of the twenty-fourth through twenty-seventh aspects is presented, wherein the composition of the glass substrate consists essentially of SiCh, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2O3, SnO2, and SO3.

[0035] According to a twenty-ninth aspect of the present disclosure, the architectural window of any one of the twenty-fourth through twenty-eighth aspects is presented, wherein the thickness of the glass substrate is less than or equal to 3.1 mm.

[0036] According to a thirtieth aspect of the present disclosure, the architectural window of any one of the twenty-fourth through twenty-ninth aspects is presented, wherein (i) the glass substrate exhibits a Young’s Modulus within a range of from 79 GPa to 85 GPa; (ii) the glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C; (iii) a difference between the high temperature coefficient and a low temperature coefficient that the glass substrate exhibits is greater than 25 ppm / °C; and (iv) the glass substrate exhibits a liquidus temperature that is less than 1400 °C.

[0037] Additional features and advantages will be set forth in the detailed description which follows, and will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0038] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the disclosure and the appended claims.

[0039] The accompanying drawings are included to provide a further understanding of principles of the disclosure, and are incorporated in, and constitute a part of, this specification. The drawings illustrate one or more embodiment(s) and, together with the description, serve to explain, by way of example, principles and operation of the disclosure. It is to be understood that various features of the disclosure disclosed in this specification and in the drawings can be used in any and all combinations. By way of non-limiting examples, the various features of the disclosure may be combined with one another according to the following embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The following is a description of the figures in the accompanying drawings. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

[0041] In the Drawings:

[0042] FIG. l is a perspective view of a glass substrate of the present disclosure, illustrating a first primary surface, a second primary surface facing away from the first primary surface, and a thickness between the first primary surface and the second primary surface;

[0043] FIG. 2 is a perspective view of a solar panel including the glass substrate of FIG. 1, illustrating the first primary surface of the glass substrate facing the Sun and an array of photovoltaic cells disposed under the glass substrate;

[0044] FIG. 3 is a plan view of the solar panel of FIG. 2;

[0045] FIG. 4 is an elevational view of a cross-section of the solar panel of FIG. 2 taken through line IV-IV of FIG. 3, illustrating the glass substrate, the array of photovoltaic cells, and a backsheet arranged as a package and supported by a frame;

[0046] FIG. 5 is a magnified view of area V of FIG. 4;

[0047] FIG. 6 is a plan view of an architectural window including the glass substrate of FIG. 1; and

[0048] FIG. 7 is an elevational view of a cross-section of the architectural window of FIG. 6 taken through line VII- VII of FIG. 6, illustrating the architectural window including the glass substrate of FIG. 1 as part of a first pane, a second pane, and a spacer separating the first pane from the second pane.DETAILED DESCRIPTION

[0049] Additional features and advantages will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description, or recognized by practicing the embodiments as described in the following description, together with the claims and appended drawings.

[0050] Referring now to FIG. 1, a glass substrate 10 is herein described. The glass substrate 10 includes a composition. The composition includes, in mole percentage (“mol%”) and on an oxide basis: (i) SiCh, within a range of from 50 to 70; (ii) AI2O3, within a range of from 0.5 to 1.5; (iii) B2O3, within a range of from 9.5 to 14.75; (iv) CaO, within a range of from 10.0 to 15.0; and (v) Na2O, within a range of from 8.0 to 13.0.

[0051] In the composition, the SiCh is the largest, by mole percentage, constituent. Similarly, the SiC>2 is the primary constituent of the glass network that the composition forms. However, raising the mole percentage of SiCh to lower the coefficient of thermal expansion of the glass substrate 10 can also increase the liquidus temperature, which can exacerbate the problem described in Background. For purposes of the glass substrate 10 of the present disclosure, the competing concerns are balanced with the mole percentage of SiCh being within the stated range of from 50 to 70. In embodiments, the mole percentage of SiCh in the composition is 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, or 70, or within any range bound by any two of those values (e.g., from 54 to 65, from 57 to 70, and so on).

[0052] Like SiC>2, AI2O3 can form part of the glass network of the glass substrate 10. The presence of AI2O3 can reduce the liquidus temperature of the composition. However, too much AI2O3 can increase the viscosity of the composition of melted, and thus hinder formability of the glass substrate 10. For purposes of the glass substrate 10 of the present disclosure, the competing concerns are balanced with the mole percentage of AI2O3 being within the stagedrange of from 0.5 to 1.5 In embodiments, the mole percentage of AI2O3 in the composition is 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, or within any range bound by any two of those values (e.g., from 0.6 to 1.4, from 0.95 to 1.5, and so on).

[0053] Like SiCh and AI2O3, B2O3 can form part of the glass network of the glass substrate 10. Without being bound by theory, it is believed that the addition of B2O3 to the composition increases the Young’s modulus and high temperature coefficient of thermal expansion of the glass substrate 10. Boron oxide, B2O3, helps scavenge non-bridging oxygen atoms (NBOs), which are created when the amount or concentration of modifiers, as here, exceeds that of AI2O3. Boron oxide converts the NBOs to bridging oxygen atoms through the formation of BO4 tetrahedra, which increases the rigidity of the glass by increasing the interconnectedness of the glass structure. Too little B2O3 would not increase the Young’s modulus and high temperature coefficient of thermal expansion sufficiently. However, too much B2O3 increases the cost of the composition so as to outweigh the benefits of the property improvements. For purposes of the glass substrate 10 of the present disclosure, the competing concerns are balanced with the mole percentage of B2O3 being within the stated range of from 9.5 to 14.75. In embodiments, the mole percentage of B2O3 in the composition is 9.5, 9.75, 9.90, 10.0, 10.25, 10.50, 10.75, 11.0, 11.25, 11.50, 11.75, 12.0, 12.25, 12.50, 12.75, 13.0, 13.25, 13.50, 13.75, 14.0, 14.25, 14.50, or 14.75, or within any range bound by any two of those values (e.g., from 9.90 to 14.75, from 11.0 to 13.50, and so on).

[0054] The presence of CaO in the composition is thought to help convert B2O3 from trigonal planar to tetrahedral coordination, which increases the Young’s modulus. Further, CaO is more effective at converting B2O3 from trigonal planar to tetrahedral than MgO. It is non-intuitive to have a glass with CaO that has a higher Young's modulus than one with MgO because MgO has a higher field strength. However, too much CaO relative to Na2O increases the liquidus temperature and density of the glass, which makes it more difficult and expensive to manufacture, and which also counters efforts to reduce weight of the glass substrate 10. For purposes of the glass substrate 10 of the present disclosure, the competing concerns are balanced with the mole percentage of CaO being within the stated range of from 10.0 to 15.0. In embodiments, the mole percentage of CaO is 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.4, 14.5, or 15.0, or within any range bound by any two of those values (e.g., from 10.0 to 14.4, from 12.5 to 15.0, and so on).

[0055] The presence of Na2O in the composition helps increase the coefficient of thermal expansion of the glass substrate 10, decrease the liquidus temperature, and lower the cost of the composition. However, in general, too much Na2O would lower the Young’s modulus ofthe glass substrate 10. For purposes of the glass substrate 10 of the present disclosure, the competing concerns are balanced with the mole percentage of Na?O being within the stated range of from 8.0 to 13.0. In embodiments, the mole percentage of Na?O is 8.0, 8.5, 8.9, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, or 13.0, or within any range bound by any two of those values (e.g., from 8.9 to 13, from 10.0 to 12.5, and so on).

[0056] In embodiments, a ratio of the mole percentage of CaO to the mole percentage of Na?O is greater than 1. However, in embodiments, the mole percentage of CaO minus the mole percentage of Na?O is less than or equal to 2.3 mol%. With that ratio, it is theorized that the CaO helps force B2O3 into tetrahedral coordination that increases the Young’s modulus of the glass substrate 10. Yet, the latter caveat is thought to help prevent phase separation of the glass substrate 10, as too much more CaO than Na?O could cause phase separation even in the presence of AI2O3.

[0057] Further, in embodiments, the mole percentage of B2O3 minus the mole percentage of CaO is within a range of from -0.4 to 0.7. In embodiments, the mole percentage of B2O3 minus the mole percentage of CaO is -0.4, -0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7, or within any range bound by any two of those values (e.g., from -0.3 to 0, from -0.2 to 0.5, and so on).

[0058] In embodiments, the composition further includes MgO. The mole percentage of MgO in the composition can be within a range of from 0.05 to 0.15. In embodiments, the mole percentage of MgO in the composition is 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, or 0.15, or within any range bound by any two of those values (e.g., from 0.06 to 0.12, from 0.10 to 0.14, and so on).

[0059] In embodiments, the composition is substantially free of, or free of, MgO. In embodiments, the composition is substantially free of, or free of, K2O. “Substantially free” here means that MgO or K2O, as the case may be, is not intentionally added to the composition but may be present unintentionally in trace (e.g., 0.001 mol% or less) amounts due to manufacturing imprecision. In embodiments, the composition consists of, or consists essentially of, SiO2, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2O3, SnO2, and SO3.

[0060] Referring again to FIG. 1, in embodiments, the glass substrate 10 further includes a first primary surface 12 and a second primary surface 14. The second primary surface 14 faces away from the first primary surface 12. The first primary surface 12 and the second primary surface 14 can face in directions 16, 18 that are opposite of each other. The glass substrate 10 further includes a thickness 20, which in those embodiments is the straight-line distancebetween the first primary surface 12 and the second primary surface 14. In embodiments, the thickness 20 is within a range of from 0.5 mm to 4.5 mm. The thickness 20 can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, or 4.5 mm, or within any range bound by any two of those values (e.g., from 0.5 mm to 3.1 mm, from 1.8 mm to 2.5 mm, and so on). The thickness 20 can be less than or equal to 3.1 mm. Thicknesses 20 of less than 0.5 mm are envisioned.

[0061] Due to the composition as described herein, the glass substrate 10 exhibits characteristic properties. For example, in embodiments, the glass substrate 10 exhibits a Young’s modulus within a range of from 79 GPa to 85 GPa. In embodiments, the Young’s modulus that the glass substrate 10 exhibits is 79 GPa, 80 GPa, 81 GPa, 82 GPa, 83 GPa, 84 GPa, or 85 GPa, or within any range bound by any two of those values (E.g., from 80 GPa to 84 GPa, from 82 GPa to 85 GPa, and so on). Unless specified otherwise, the Young's modulus values disclosed in this disclosure refer to a value as measured by a resonant ultrasonic spectroscopy technique of the general type set forth in ASTM C623-21 titled “Standard Test Method for Young’s Modulus, Shear Modulus, and Poisson’s Ratio for Glass and Glass-Ceramics by Resonance.”

[0062] As further set forth below, it is believed that the glass substrate 10, to be used for solar panel and architectural window applications (both of which are introduced below), should resist bending or deformation in response to impact events (e.g., hail strikes). It is further believed that resistance to bending and deformation is addressed by the concept of flexural rigidity. In turn, flexural rigidity is a function of the Young’s modulus, according to the following equation:Flexural > Rigidly = Z) = (E *3) / 12(1 - L>2) where “E” is the Young’s modulus, “Z” is the thickness 20, and “v” is the Poisson’s ratio. Thus, it is believed that increasing the Young’s modulus can compensate for decreasing thickness 20 of the glass substrate 10 and still provide sufficient flexural rigidity to resist impact events.

[0063] In embodiments, the glass substrate 10 exhibits a high temperature coefficient of thermal expansion (CTE) that is within a range of from 30 ppm / °C to 70 ppm / °C. High temperature CTE refers to the coefficient of thermal expansion of the glass composition above the glass transition temperature of the glass composition. The high temperature CTE is determined by plotting the instantaneous CTE (y-axis) as a function of the temperature (x-axis).The high temperature CTE is the value of the CTE where the slope of the CTE v. temperature curve is approximately zero following a pronounced increase (e.g., where the CTE v. temperature curve “plateaus”). The value of the high temperature CTE can be a measure of the volume change of the glass during cooling from high temperatures, such as during a thermal tempering process. In embodiments, the high temperature CTE is 30 ppm / °C, 35 ppm / °C, 40 ppm / °C, 45 ppm / °C, 50 ppm / °C, 55 ppm / °C, 60 ppm / °C, 65 ppm / °C, or 70 ppm / °C, or within any range bound by any two of those values (e.g., from 35 ppm / °C to 65 ppm / °C, from 45 ppm / °C to 55 ppm / °C, and so on).

[0064] In embodiments, the glass substrate 10 exhibits a low temperature coefficient of thermal expansion (CTE) that is within a range of from 6.0 ppm / °C to 12 ppm / °C. Low temperature CTE refers to the coefficient of thermal expansion of the glass composition below 300 °C (e.g., from 250 °C to 300 °C). In embodiments, the low temperature CTE is 6.0 ppm / °C, 6.5 ppm / °C, 7.0 ppm / °C, 7.5 ppm / °C, 8.0 ppm / °C, 8.5 ppm / °C, 9.0 ppm / °C, 9.5 ppm / °C, 10.0 ppm / °C, 10.5 ppm / °C, 11.0 ppm / °C, 11.5 ppm / °C, or 12.0 ppm / °C, or within any range bound by any two of those values (e.g., from 6.5 ppm / °C to 8.5 ppm / °C, from 11.0 ppm / °C to 11.5 ppm / °C, and so on).

[0065] The high temperature CTE that the glass substrate 10 of the present disclosure exhibits, which may be attributable to increased mole percentages of B2O3, is much higher than the high temperature CTE that a typical soda lime glass exhibits. The relatively high high temperature CTE of the glass substrate 10 of the present disclosure increases the effectiveness of thermal tempering the glass substrate 10 when the thickness 20 of the glass substrate 10 is relatively thin (e.g., less than 2.0 mm) in imparting compressive stress to the first primary surface 12 and the second primary surface 14 of the glass substrate 10. When the thickness 20 is relatively thin, the distance between the mid-plane of the glass substrate 10 and the first primary surface 12 becomes sufficiently small that it is very difficult to impart a thermal gradient that can be sustained long enough to develop the final tempering stresses. The high high temperature CTE of the glass substrate 10 helps to overcome that difficulty.

[0066] In embodiments, a difference between the high temperature CTE that the glass substrate 10 exhibits and the low temperature CTE that the glass substrate 10 exhibits is greater than 25 ppm / °C. For example, if the glass substrate 10 exhibits a high temperature CTE of 63 ppm / °C, then the low temperature CTE that the glass substrate 10 exhibits is (63-25=38) less than 38 ppm / °C. In embodiments, the difference between the high temperature CTE that the glass substrate 10 exhibits and the low temperature CTE that the glass substrate 10 exhibits is 25 ppm / °C, 26 ppm / °C, 27 ppm / °C, 28 ppm / °C, 29 ppm / °C, 30 ppm / °C, 31 ppm / °C, 32 ppm / °C,33 ppm / °C, 34 ppm / °C, 35 ppm / °C, 36 ppm / °C, 37 ppm / °C, 38 ppm / °C, 39 ppm / °C, or 40 ppm / °C or greater, or within any range bound by any two of those values (e.g., from 28 ppm / °C to 37 ppm / °C, from 31 ppm / °C, 39 ppm / °C, and so on). It is believed that the difference between the high temperature CTE and the low temperature CTE that the glass substrate 10 exhibits, as well as the high temperature CTE that the glass substrate 10 exhibits, affects the compressive stress that the glass substrate 10 exhibits upon thermal tempering - with increases the difference causing an increase in the compressive stress.

[0067] In embodiments, the glass substrate 10 exhibits a shear modulus that is within a range of from 32.5 GPa to 34.5 GPa. It is believed that the presence of B2O3 in the composition of the glass substrate 10 additionally increases the shear modulus of the glass substrate 10 compared to soda lime glass. For purposes of this disclosure, the shear modulus refers to a value as measured by a resonant ultrasonic spectroscopy technique of the general type set forth in ASTM C623, mentioned above. In embodiments, the shear modulus that the glass substrate 10 exhibits is 32.5 GPa, 32.6 GPa, 32.7 GPa, 32.8 GPa, 32.9 GPa, 33.0 GPa, 33.2 GPa, 33.3 GPa, 33.4 GPa, 33.5 GPa, 33.6 GPa, 33.7 GPa, 33.8 GPa, 33.9 GPa, 34.0 GPa, 34.1 GPa, 34.2 GPa, 34.3 GPa, 34.4 GPa, or 34.5 GPa, or within any range bound by any two of those values (e.g., from 32.8 GPa to 34.4 GPa, from 33.7 GPa to 34.0 GPa, and so on).

[0068] In embodiments, the glass substrate 10 exhibits a density that is within a range of from 2.470 g / cm3to 2.590 g / cm3. Density for purposes of this disclosure can be as measured by the buoyancy method of ASTM C693-93 (2013). In embodiments, the density that the glass substrate 10 exhibits is 2.470 g / cm3, 2.480 g / cm3, 2.490 g / cm3, 2.500 g / cm3, 2.510 g / cm3, 2.520 g / cm3, 2.530 g / cm3, 2.540 g / cm3, 2.550 g / cm3, 2.560 g / cm3, 2.570 g / cm3, 2.580 g / cm3, or 2.590 g / cm3, or within any range bound by any two of those values (e.g., from 2.490 g / cm3to 2.580 g / cm3, from 2.530 g / cm3to 2.550 g / cm3, and so on).

[0069] In embodiments, the glass substrate 10 exhibits a liquidus temperature that is less than 1400 °C, such as less than 1125 °C. The liquidus temperature of a glass is the temperature above which no crystalline phases can coexist in equilibrium with the glass. Stated another way, the liquidus temperature of a glass is defined as the highest temperature at which a crystalline phase would appear if a glass were held indefinitely at that temperature. For purposes of this disclosure, the liquidus temperature can be measured using the standard gradient boat liquidus method of ASTM C829-81. That method involves placing crushed glass particles in a platinum boat, placing the boat in a furnace having a region of gradient temperatures, heating the boat in an appropriate temperature region for 24 hours, and determining by means of microscopic examination the highest temperature at which crystalsappear in the interior of the glass. More particularly, the glass sample is removed from the Pt boat in one piece and examined using polarized light microscopy to identify the location and nature of crystals which have formed against the Pt and air interfaces, and in the interior of the sample. Because the gradient of the furnace is very well known, temperature as a function of location can be well estimated, within 5-10° C. The temperature at which crystals are observed in the internal portion of the sample is taken to represent the liquidus of the glass (for the corresponding test period). Testing is sometimes carried out at longer times (e.g. 72 hours), to observe slower growing phases. In embodiments, the liquidus temperature that the glass substrate 10 exhibits is within a range of from 900 °C to 1150 °C. In embodiments, the liquidus temperature that the glass substrate 10 exhibits is 900 °C, 925 °C, 950 °C, 975 °C, 1000 °C, 1025 °C, 1050 °C, 1075 °C, 1100 °C, 1125 °C, 1150 °C, 1175 °C, 1200 °C, 1225 °C, 1275 °C, 1300 °C, 1325 °C, 1350 °C, 1375 °C, or 1400 °C, or within any range bound by any two of those values (e.g., from 925 °C to 1075 °C, from 1025 °C to 1300 °C, and so on).

[0070] In embodiments, the glass substrate 10 has been thermally tempered and thus has a first region of compressive stress 22 contiguous with the first primary surface 12 and a second region of compressive stress 24 contiguous with the second primary surface 14. A region of central tension 26 is disposed between the first region of compressive stress 22 and the second region of compressive stress 24.

[0071] The thermal tempering can be performed via any process that heats and then quickly cools the glass substrate 10. For example, an overall process for thermal tempering the glass substrate 10 can include heating the glass substrate 10 in a hot zone and then cooling the glass substrate 10. In the hot zone, the glass substrate 10 is heated to a temperature, for example, where the viscosity is within a range of from 1012to 1013 3Poise. Optionally, the glass substrate 10 can be transitioned from the hot zone to a cool zone through a transition zone. The first primary surface 12 and the second primary surface 14 of the glass substrate 10 are positioned adjacent to heat sinks, one on either of the primary surfaces 12, 14 with a gap in between the primary surface 12, 14 and the heat sink. Gas is delivered into the gaps through multiple apertures in the heat sinks. The glass substrate 10 is cooled by conduction more than by convection and sufficiently to thermally induce the first region of compressive stress 22, the second region of compressive stress 24, and the central tension 26.

[0072] Referring additionally to FIGS. 2-5, a solar panel 100 includes the glass substrate 10 and an array of photovoltaic cells 102 disposed beneath the glass substrate 10. In particular, the array of photovoltaic cells 102 are disposed beneath the second primary surface 14 of the glass substrate 10. The glass substrate 10 separates the array of photovoltaic cells 102 from anexternal environment 104. The first primary surface 12 of the glass substrate 10 faces the external environment 104. The first primary surface 12 of the glass substrate 10 is intended to face the Sun 106 during daytime hours. The second primary surface 14 of the glass substrate 10 faces the array of photovoltaic cells 102. During use of the solar panel 100, photons 108 from the Sun 106 enter the solar panel 100 through the glass substrate 10 and impinge upon the array of photovoltaic cells 102. The type of photovoltaic cells 102 are not particularly limited, though in preferred embodiments, the photovoltaic cells 102 are monocrystalline silicon photovoltaic cells 102.

[0073] The glass substrate 10 exhibits an average transmittance through the glass substrate 10 of greater than or equal to 80% for a wavelength of electromagnetic radiation within a range of from 500 nm to 950 nm. In embodiments, the glass substrate 10 exhibits an average transmittance through the glass substrate 10 of greater than or equal to 80% for a wavelength of electromagnetic radiation across an entire wavelength range of from 600 nm to 850 nm. All transmittance values mentioned herein are two-surface average transmittance values reported at an angle of incidence of 0 degrees and with no coatings on the second primary surface 14 of the glass substrate 10. An uncoated second primary surface 14 of a substrate having a glass composition typically has a reflectance of about 4%. Consequently, the maximum possible two-surface average transmittance value for the glass substrate 10 with the second primary surface 14 uncoated is approximately 96%. The two-surface average transmittance is the average of the two-surface transmittance throughout the stated wavelength range.

[0074] In embodiments, the solar panel 100 further includes a backsheet 110. The array of photovoltaic cells 102 are disposed between the glass substrate 10 and the backsheet 110. The backsheet 110 can have a glass composition. The glass composition of the backsheet 110 can be the same as the composition of the glass substrate 10 but need not be. One glass substrate 10 of the present disclosure can be the glass substrate 10 of the solar panel 100 and another glass substrate 10 of the present disclosure can be the backsheet 110 of the solar panel 100.

[0075] Having the array of photovoltaic cells 102 sandwiched between the glass substrate 10 and the backsheet 110 having a glass composition allows the array of photovoltaic cells 102 to receive photons 108 transmitting through both the glass substrate 10 and the backsheet 110. That arrangement in theory should increase the electricity production of the solar panel 100 compared to if the array of photovoltaic cells 102 received photons 108 transmitting only through the glass substrate 10 but not the backsheet 110.

[0076] A first polymer layer 112 can be disposed between the glass substrate 10 and the array of photovoltaic cells 102. Similarly, a second polymer layer 114 can be disposed between thebacksheet 110 and the array of photovoltaic cells 102. The first and second polymer layers 112, 114 can reduce migration of ions (e.g., Na+) from the glass substrate 10 and the backsheet 110, respectively, to the photovoltaic cells 102 that could cause potential -induced degradation, which is degradation of the photovoltaic cells 102 that lowers efficiency thereof. The first and second polymer layers 112, 114 can be formed of a transparent polymer, such as ethylene-vinyl acetate (EVA). The first and send polymer layers 112, 114 can encapsulate the array of photovoltaic cells 102.

[0077] In embodiments, the solar panel 100 further includes a frame 116. When the solar panel 100 is oriented horizontally such that the first primary surface 12 of the glass substrate 10 is horizontal and facing upwards, the frame 116 defines a top 118 and a bottom 120 of the solar panel 100 where the top 118 is the most elevated portion of the solar panel 100 and the bottom 120 is the least elevated portion of the solar panel 100, excluding wiring that may extend from the solar panel 100. In a more detailed example, the frame 116 includes sidewall 122, a C- channel 124 that is contiguous with the sidewall 122, and a tab 126 that extends inward relative to the sidewall 122. The C-channel 124 is disposed at or near the top 118 of the frame 116, and the tab 126 is disposed at or near the bottom 120 of the frame 116. The tab 126 forms a plane 128 that is generally parallel to an outward primary surface 130 of the backsheet 110. The glass substrate 10, the array of photovoltaic cells 102, and the backsheet 110 are all coupled to each other as a package 132. The sidewall 122 extends around a perimeter 134 of the package 132 with the perimeter 134 of the package 132 secured within the C-channel 124 of the frame 116.

[0078] Referring now to FIGS. 6-7, an architectural window 200 includes at least a first pane 202 and a second pane 204. The first pane 202 includes the glass substrate 10. As when included with the solar panel 100, the glass substrate 10 when included with the architectural window 200 exhibits an average transmittance through the glass substrate 10 of greater than or equal to 80% for a wavelength of electromagnetic radiation within a range of from 500 nm to 950 nm. The first primary surface 12 of the glass substrate 10 faces the external environment 104. The second primary surface 14 of the glass substrate 10 faces away from the external environment 104.

[0079] The architectural window 200 may be integral with an opening between the external environment 104 and interior of an enclosure or building. Further, the architectural window 200 may be part of a door system on an enclosure or building. In embodiments, the architectural window 200 is movable with respect to an opening in a building. The architecturalwindow 200 may be a double pane (as illustrated) or a triple pane window. Of course, the architectural window 200 may include any number of glass panes greater than one pane.

[0080] The architectural window 200 may further include a spacer 206 between its panes, such as to define a space 208 separating the first pane 202 from the second pane 204. The spacer 206 may be an edge seal formed around respective edges of its glass panes (e.g., the first pane 202 and the second pane 204), a metallic pillar between the surfaces of its glass panes, a low thermal conduction material, or a glass bump attached to or formed integral with one or both glass panes (e.g., the first pane 202 and the second pane 204). The space 208 is further defined at least in part by a distance 210 between the first pane 202 and the second pane 204. The distance can be within a range of from 50 pm to about 50 mm, or within a range of from 5 mm to 25 mm. The space 208 may be sealed and include an insulating gas such as air, argon, krypton, xenon, and combinations thereof. Alternatively, the space 208 may be sealed and include a pressure less than atmospheric pressure.

[0081] In embodiments, the architectural window 200 further includes a frame 212 surrounding perimeters of, and supporting, both the first pane 202 and the second pane 204. In embodiments, the frame 212 is configured to mate or communicate with an opening in a building or enclosure such that architectural window 200 installed with either the first pane 202 or the second pane 204 adjacent the building interior and the other adjacent the building exterior. In embodiments, the frame 212 includes an overhanging edge portion configured to interfere with an edge of an opening in a building or enclosure and to prevent the architectural window 200 from being installed in the opening such that the one of the first pane 202 or the second pane 204 is adjacent the building interior. The architectural window 200 may also include a locking mechanism adjacent the one of the first pane 202 or the second pane 204 and internal to the building or enclosure. In embodiments, the locking mechanism is configured to be accessible only from the building interior so as to limit access through the architectural window 200. In embodiments, the locking mechanism is fixed directly or indirectly to frame 116 and communicates with a portion opening in the building or enclosure.

[0082] The glass substrate 10 addresses the problems set forth in the Background, in a variety of ways. The composition is less expensive in terms of raw materials than a typical soda lime glass. Further, the glass substrate 10 is formable via rolling processes, which are relatively inexpensive.

[0083] Still further, the composition of the glass substrate 10 is configured to ease thermal tempering of the glass substrate 10, even as the thickness 20 of the glass substrate 10 is relatively thin. Without being bound by theory, it is believed that because of the presence ofrelatively high mole percentages of B2O3 in the composition, the glass substrate 10 provides for a high temperature CTE that is higher than that provided by a typical soda lime glass and, thus, makes thermal tempering feasible at a thickness 20 that is relatively thin. The glass substrate 10 allows for thermal tempering at a thickness 20 that is relatively thin, while keeping manufacturing of the glass substrate 10 low in cost. More particularly, thermal tempering of relatively thin soda lime glass would require extremely energy-intensive air cooling to form the necessary temperature gradient, but the relatively high high temperature CTE of the glass substrate 10 of the present disclosure avoids a need to use air cooling.

[0084] Further, again potentially because of the presence of relatively high mole percentages of B2O3 in the composition, the glass substrate 10 exhibits better mechanical performance than a typical soda lime glass having the same thickness 20 - in particular a higher Young’s modulus. The glass substrate 10, allowing for reduced thickness 20, requires less raw materials. The less raw materials mean decreased cost and environmental impact.

[0085] In terms of the solar panel 100 and architectural window 200, the glass substrate 10 can be thinner than panes typically used. Typical top panels made from soda lime glass can have a thickness of about 2.0 mm. The glass substrate 10 of the present disclosure, due to the enhanced Young’s modulus and high temperature CTE, can be utilized as the cover pane for the solar panel 100 while having a thickness 20 less than 2.0 mm. Because of the enhanced Young’s modulus of the glass substrate 10, the thickness 20 of the glass substrate 10 can be less than 2.0 mm and still resist fracturing in response to impact events such as hail strikes.

[0086] EXAMPLES

[0087] Examples 1-3 and Comparative Example 1 - For Examples 1-3, glass substrates were formed by batching raw materials in different proportions for each different example, melting the batch, and down drawing the molten composition into the glass substrate. The glass substrate representing each of Examples 1-3 was then analyzed to determine composition. The compositions are set forth in Table 1 below. Comparative Example 1 is a typical soda lime glass. In addition, various properties were measured and recorded in the table below for each of Examples 1-3.

[0088]

[0089] “ SOC” in the above table means stress optical coefficient, which is related to the birefringence of the glass. Unless specified otherwise, SOC is measured according to Procedure C (Glass Disc Method) described in ASTM standard C770-16, entitled “Standard Test Method for Measurement of Glass Stress-Optical Coefficient,” the contents of which are incorporated herein by reference in their entirety. “E” as mentioned is Young’s modulus. “G” is shear modulus, which is discussed in greater detail above. Poisson’s ratio can be determined according to ASTM C624, mentioned above, and relates the transverse strain to the axial strain in a material when subjected to an external load. “Strain” refers to the temperature at which the viscosity of the glass composition is 1 x IO1468poise as measured in accordance with ASTM C598. The strain temperature is generally the temperature at which the glass transitions froma hard and rigid state to a more viscous or "soft" state. “Anneal” means refers to the temperature at which the viscosity of the glass composition is 1 * 1013 18poise as measured in accordance with ASTM C598. At that viscosity, stresses within the glass can be relieved effectively. “Softening” refers to the temperature at which the viscosity of the glass composition is 1 * IO76poise, and is measured according to the parallel plate viscosity method which measures the viscosity of inorganic glass from 107to 109poise as a function of temperature, similar to ASTM C 135 IM. The softening temperature is generally the temperature at which glass begins to soften and becomes pliable, making it easier to shape and form. “A CTE (ppm / °C)” refers to the difference between the high temperature CTE and the low temperature CTE. “Liquidus” refers to the temperature at which crystals first appear as a molten glass cools down from the melting temperature (or the temperature at which the very last crystals melt away as temperature is increased from room temperature), as determined with the gradient furnace method according to ASTM C829-81, titled “titled “Standard Practice for Measurement of Liquidus Temperature of Glass by the Gradient Furnace Method.” Stated another way, the liquidus temperature is the temperature at which the glass transitions from a solid state to a molten state.

[0090] As Table 1 reveals, Examples 1-3 with the composition for the glass substrate of the present disclosure exhibited higher Young’s modulus values (79.4 GPa, 79.4 GPa, and 83.7 GPa) than the Young’s modulus that the soda lime glass of Comparative Example 1 (72 GPa) exhibited. The increase in Young’s modulus means that the thickness of the glass substrate can be reduced relative to a soda lime glass to provide the same flexural rigidity.

[0091] In addition, the data of Table 1 reveals dramatic increases in high temperature CTE for the glass substrates of Examples 1-3 (41.1 ppm / °C, 51.9 ppm / °C, and 57.6 ppm / °C), compared to Comparative Example 1 (26.5 ppm / °C). The dramatic increase in high temperature CTE leads to less energy intensive thermal tempering at thin thicknesses and with higher compressive stresses resulting therefrom.

[0092] Further, the data of Table 1 reveals that the glass substrates of Examples 1-3 have a lower low temperature CTE (6.39 ppm / °C, 7.83 ppm / °C, and 8.77 ppm / °C) than the Comparative Example 1 (10 ppm / °C). The higher high temperature CTE and the lower low temperature CTE of the glass substrates of the present disclosure compared to soda lime glass results in a much larger difference (A CTE (ppm / °C)) between the low temperature CTE and the high temperature CTE. In that regard, the data of Table reveals the A CTE for Examples 1-3 were 34.7 ppm / °C, 44.1 ppm / °C, and 48.8 ppm / °C, respectively, compared to the 16.5 ppm / °C of Comparative Example 1. The larger difference between high temperature CTE andlow temperature CTE, it is believed, causes thermal tempering to more efficiently and more effectively generate compressive stress.

[0093] While exemplary embodiments and examples have been set forth for the purpose of illustration, the foregoing description is not intended in any way to limit the scope of disclosure and appended claims. Accordingly, variations and modifications may be made to the abovedescribed embodiments and examples without departing substantially from the spirit and various principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

Claims

CLAIM(S)What is claimed is:

1. A glass substrate comprising: a composition comprising, in mol% and on an oxide basis:SiCh, within a range of from 50 to 70;AI2O3, within a range of from 0.5 to 1.5;B2O3, within a range of from 9.5 to 14.75;CaO, within a range of from 10.0 to 15.0; and Na2O, within a range of from 8.0 to 13.0.

2. The glass substrate of claim 1, wherein the SiCh of the composition is within a range of from 57 to 70.

3. The glass substrate of any one of claims 1-2, wherein the AI2O3 of the composition is within a range of from 0.95 to 1.5.

4. The glass substrate of any one of claims 1-3, wherein the B2O3 of the composition is within a range of from 9.90 to 14.75.

5. The glass substrate of any one of claims 1-4, wherein the CaO of the composition is within a range of from 10.0 to 14.4.

6. The glass substrate of any one of claims 1-5, wherein the Na2O of the composition is within a range of from 8.9 to 13.0.

7. The glass substrate of any one of claims 1-6, whereinCaO - Na2O is less than or equal to 2.3;B2O3 - CaO is within a range of from -0.4 to 0.7; and CaO / Na2O is greater than 1.

8. The glass substrate of any one of claims 1-7, wherein the composition further comprises, in mole percentage and on an oxide basis, MgO within a range of from 0.05 to 0.15.

9. The glass substrate of any one of claims 1-7, wherein the composition is substantially free of K2O.

10. The glass substrate of any one of claims 1-9, wherein the composition consists essentially of SiCh, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2C>3, SnCh, and SO3.

11. The glass substrate of any one of claims 1-10 further comprising: a first primary surface, a second primary surface facing away from the first primary surface, and a thickness between the first primary surface, wherein, the thickness is less than or equal to 4.5 mm.

12. The glass substrate of claim 11, wherein the thickness is less than or equal to 3.1 mm.

13. The glass substrate of any one of claims 1-12, wherein the glass substrate exhibits a Young’s Modulus within a range of from 79 GPa to 85 GPa.

14. The glass substrate of any one of claims 1-13, wherein the glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C; and a difference between the high temperature coefficient and a low temperature coefficient that the glass substrate exhibits is greater than 25 ppm / °C.

15. The glass substrate of any one of claims 1-14, wherein the glass substrate exhibits a shear modulus that is within a range of from 32.5 GPa to 34.5 GPa.

16. The glass substrate of any one of claims 1-15 further comprising: a first region of compressive stress; a second region of compressive stress; and a region of central tension disposed between the first region of compressive stress and the second region of compressive stress.

17. The glass substrate of any one of claims 1-16, wherein the glass substrate exhibits a liquidus temperature that is less than 1400 °C.

18. A solar panel comprising: an array of photovoltaic cells; and a glass substrate separating the photovoltaic cell from an external environment, the glass substrate (a) exhibiting an average transmittance through the glass substrate of greater than or equal to 80% for a wavelength of electromagnetic radiation within a range of from 500 nm to 950 nm, (b) comprising a first primary surface facing the external environment, a second primary surface facing the photovoltaic cell, and a thickness between the first primary surface and the second primary surface that is less than or equal to 4.5 mm, and (c) comprising a composition comprising, in mol% and on an oxide basis:SiCh, within a range of from 50 to 70;AI2O3, within a range of from 0.5 to 1.5;B2O3, within a range of from 9.5 to 14.75;CaO, within a range of from 10.0 to 15.0; andNa2O, within a range of from 8.0 to 13.0.

19. The solar panel of claim 18, wherein the SiCh of the composition is within a range of from 57 to 70; the AI2O3 of the composition is within a range of from 0.95 to 1.5; the B2O3 of the composition is within a range of from 9.90 to 14.75; the CaO of the composition is within a range of from 10.0 to 14.4; and the Na2O of the composition is within a range of from 8.9 to 13.0.

20. The solar panel of any one of claims 18-19, wherein the composition further comprises, in mole percentage and on an oxide basis, MgO within a range of from 0.05 to 0.15; the composition of the glass substrate is substantially free of K2O;CaO - Na2O of the composition of the glass substrate is less than or equal to 2.3;B2O3 - CaO of the composition of the glass substrate is within a range of from -0.4 to 0.7; andCaO / Na2O is greater than 1.

21. The solar panel of any one of claims 18-20, wherein the composition of the glass substrate consists essentially of SiCh, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2O3, SnCh, and SO3.

22. The solar panel of any one of claims 18-21, wherein the thickness of the glass substrate is less than or equal to 3.1 mm.

23. The solar panel of any one of claims 18-22, wherein the glass substrate exhibits a Young’s Modulus within a range of from 79 GPa to 85 GPa; the glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C; and a difference between the high temperature coefficient and a low temperature coefficient that the glass substrate exhibits is greater than 25 ppm / °C; and the glass substrate exhibits a liquidus temperature that is less than 1400 °C.

24. An architectural window comprising: a first pane comprising a glass substrate, the glass substrate (a) exhibiting an average transmittance through the glass substrate of greater than or equal to 80% for a wavelength of electromagnetic radiation within a range of from 500 nm to 950 nm, (b) comprising a first primary surface facing an external environment, a second primary surface facing away from the external environment, and a thickness between the first primary surface and the second primary surface that is less than or equal to 4.5 mm, and (c) comprising a composition comprising, in mol% and on an oxide basis:SiCh, within a range of from 50 to 70;AI2O3, within a range of from 0.5 to 1.5;B2O3, within a range of from 9.5 to 14.75;CaO, within a range of from 10.0 to 15.0; andNa2O, within a range of from 8.0 to 13.0; and a second pane separated from the first pane by a space, the second pane comprising the glass substrate or another glass substrate.

25. The architectural window of claim 24 further comprising:a frame surrounding perimeters of, and supporting, both the first pane and the second pane.

26. The architectural window of any one of claims 24-25, wherein the SiCh of the composition is within a range of from 57 to 70; the AI2O3 of the composition is within a range of from 0.95 to 1.5; the B2O3 of the composition is within a range of from 9.90 to 14.75; the CaO of the composition is within a range of from 10 to 14.4; and the Na2O of the composition is within a range of from 8.9 to 13.0.

27. The architectural window of any one of claims 24-26, wherein the composition further comprises, in mole percentage and on an oxide basis, MgO within a range of from 0.05 to 0.15; the composition of the glass substrate is substantially free of K2O;CaO - Na2O of the composition of the glass substrate is less than or equal to 2.3;B2O3 - CaO of the composition of the glass substrate is within a range of from -0.4 to 0.7; andCaO / Na2O is greater than 1.

28. The architectural window of any one of claims 24-27, wherein the composition of the glass substrate consists essentially of SiO2, AI2O3, B2O3, CaO, MgO, Na2O, and a fining agent selected from a group consisting of AS2O3, Sb2O3, SnO2, and SO3.

29. The architectural window of any one of claims 24-28, wherein the thickness of the glass substrate is less than or equal to 3.1 mm.

30. The architectural window of any one of claims 24-29, wherein the glass substrate exhibits a Young’s Modulus within a range of from 79 GPa to 85 GPa; the glass substrate exhibits a high temperature coefficient of thermal expansion that is within a range of from 30 ppm / °C to 70 ppm / °C; a difference between the high temperature coefficient and a low temperature coefficient that the glass substrate exhibits is greater than 25 ppm / °C; and the glass substrate exhibits a liquidus temperature that is less than 1400 °C.

Images