Alkali-containing, melt-moldable high uv transmittance glasses

Abstract

Alkali-containing, melt-moldable glass having high UV transmittance can include, in terms of oxides: > = 65.00 mol% to < = 72.50 mol% SiO2; al2O3 of > = 2.50 mol% to < = 13.75 mol%; b2O3 of > = 0.00 mol% to < = 18.00 mol%; mgO of > = 0.00 mol% to < = 6.00 mol%; from > = 0.00 mol% to < = 15.00 mol% of Na2O; k2O of > = 3.10 mol% to < = 7.50 mol%; < = 1.00 mol% of each of Li2O and ZnO; less than or equal to 0.04 mol% of SnO2; less than or equal to 0.10 mol% of each of TiO2, Fe2O3 and Ce2O3; and < = 2 mol% F-. The sum of Al2O3 + B2O3-R2O-CaO-SrO-BaO is greater than or equal to-0.75 mol% and less than or equal to 40.00 mol%, wherein R2O is the sum of Na2O + K2O + Li2O. The sum of Na2O + K2O is > = 3.10 mol% and < = 15.50 mol%. And the sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 672830, filed July 18, 2024, pursuant to 35 U.S. SC §119, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] This specification generally relates to glass with relatively high UV transmittance, and more specifically, to alkali-containing glass with high UV transmittance that can be melt-formed. Background Technology

[0004] The optical properties of glass determine its usefulness in many applications, such as the photolithography step in microchip manufacturing, where ultraviolet (UV) light can pass through the glass substrate. Other properties of glass affect its manufacturability and cost. For example, while fused silica is highly transparent to UV, it is expensive and difficult to form wide sheets. Melt-forming processes, for instance, enable the mass production of wide glass sheets. However, typical glass formed by melt-forming has poor UV transmission characteristics.

[0005] Therefore, there is a need for alternative glass with relatively high UV transmittance, which is also melt-formable. Summary of the Invention

[0006] This article provides alkali-containing glass, alkali-containing glass articles, and alkali-containing glass sheets, which have high deep UV transmittance, for example, greater than 50% or even greater than 60% at a wavelength of 248 nm. The glass also has a liquidus viscosity, making it compatible with melt-forming processes.

[0007] According to the first aspect A1, a glass, based on oxides, comprises: 65.00 mol% to 72.50 mol% of SiO2; 2.50 mol% to 13.75 mol% of Al2O3; 0.00 mol% to 18.00 mol% of B2O3; 0.00 mol% to 6.00 mol% of MgO; 0.00 mol% to 15.00 mol% of Na2O; 3.10 mol% to 7.50 mol% of K2O; 1.00 mol% each of Li2O and ZnO; 0.04 mol% of SnO2; 0.10 mol% each of TiO2, Fe2O3, and Ce2O3; and 2 mol% of F -wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of AI2O3 + B2O3 - R2O - CaO - SrO - BaO is greater than or equal to -0.75 mole% and less than or equal to 40.00 mole%, where R2O is the sum of Na2O + K2O + Li2O; the sum of Na2O + K2O is greater than or equal to 3.10 mole% and less than or equal to 15.50 mole%; and the sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mole%.

[0008] A second aspect, A2, includes the glass of aspect Al, comprising B2O3 greater than or equal to 12.00 mole% to less than or equal to 18.00 mole%.

[0009] A third aspect, A3, includes the glass of any of the preceding aspects, comprising Na2O greater than or equal to 2.00 mole% to less than or equal to 10.00 mole%.

[0010] A fourth aspect, A4, includes the glass of any of the preceding aspects, comprising K2O greater than or equal to 3.10 mole% to less than or equal to 7.00 mole%.

[0011] A fifth aspect, A5, includes the glass of any of the preceding aspects, comprising MgO greater than or equal to 1.00 mole% to less than or equal to 6.00 mole%.

[0012] A sixth aspect, A6, includes the glass of any of the preceding aspects, comprising CaO greater than or equal to 0.20 mole% to less than or equal to 6.00 mole%.

[0013] A seventh aspect, A7, includes the glass of any of the preceding aspects, comprising SrO greater than or equal to 0.10 mole% to less than or equal to 1.50 mole%.

[0014] An eighth aspect, A8, includes the glass of any of the preceding aspects, wherein R2O - AI2O3 is less than or equal to 9.00 mole%.

[0015] A ninth aspect, A9, includes the glass of aspect A8, wherein R2O - AI2O3 is less than or equal to 0.00 mole% and greater than or equal to -6.50.

[0016] A tenth aspect, A10, includes the glass of aspect A8, wherein R2O - AI2O3 is greater than 0.00 mole%.

[0017] An eleventh aspect, Al l, includes the glass of any of the preceding aspects, wherein R x O - AI2O3 is greater than or equal to 2.00 mole% and less than or equal to 10.00 mole%, where R xO is the sum of R20 and RO, where RO is the sum of MgO + CaO + BaO + SrO.

[0018] A twelfth aspect, A12, includes the glass of any of the preceding aspects, wherein the ratio of (RO + R20):(Al203 + B203) is less than 1.5, where RO is the sum of MgO + CaO + BaO + SrO.

[0019] A thirteenth aspect, A13, includes the glass of any of the preceding aspects, wherein the glass has a transmittance greater than 50% at a wavelength of 248 nm and a thickness of 1 mm in an as-formed condition.

[0020] A fourteenth aspect, A14, includes the glass of aspect A13, wherein the transmittance is greater than or equal to 70%.

[0021] A fifteenth aspect, A15, includes the glass of aspect A13, wherein the transmittance is greater than or equal to 80%.

[0022] A sixteenth aspect, A16, includes the glass of any of the preceding aspects, wherein the glass has a transmittance greater than 50% at a wavelength of 248 nm and a thickness of 1 mm after exposure to 3000 UV light pulses from an excimer laser at a wavelength of 248 nm, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse at a pulse repetition rate of 10 Hz.

[0023] A seventeenth aspect, A17, includes the glass of aspect A16, wherein the transmittance is greater than or equal to 60%.

[0024] An eighteenth aspect, A18, includes the glass of aspect A16, wherein the transmittance is greater than or equal to 70%.

[0025] A nineteenth aspect, A19, includes the glass of any of the preceding aspects, wherein the glass has an average coefficient of thermal expansion from 0 °C to 300 °C greater than or equal to 50 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C.

[0026] A twentieth aspect, A20, includes the glass of any of the preceding aspects, wherein the glass has a liquidus viscosity greater than or equal to 10,000 pascal*seconds.

[0027] A twenty-first aspect, A21, includes a glass, in mole percent on an oxide basis, comprising: greater than or equal to 65.00 to less than or equal to 72.50 Si02; greater than or equal to 2.50 to less than or equal to 13.75 AI2O3; greater than or equal to 0.00 to less than or equal to 17.00 B203; greater than or equal to 0.00 to less than or equal to 6.00 MgO; greater than or equal to 0.00 to less than or equal to 15.00 Na20; greater than or equal to 2.10 to less than or equal to 8.50 K20; each less than or equal to 1.50 Li20 and ZnO; less than or equal to 0.01 Sn02; each less than or equal to 0.10 Ti02and Fe203; less than or equal to 0.40 BaO; less than or equal to 4.00 BeO; and less than or equal to 2 F - wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of AI2O3 + B203 - R2O - CaO - SrO - BaO is greater than or equal to -0.75 mole percent and less than or equal to 40.00 mole percent, where R2O is Na20 + K20 + Li20; the sum of Na20 + K20 is greater than or equal to 2.10 mole percent and less than or equal to 15.50 mole percent; and the sum of As203 + Sb203 + PbO is less than or equal to 0.01 mole percent.

[0028] A twenty-second aspect, A22, includes the glass of aspect A21, comprising greater than or equal to 12.00 to less than or equal to 17.00 B203.

[0029] A twenty-third aspect, A23, includes the glass of any one of aspects A21 to A22, comprising greater than or equal to 2.00 to less than or equal to 10.00 Na20.

[0030] A twenty-fourth aspect, A24, includes the glass of any one of aspects A21 to A23, comprising greater than or equal to 3.10 to less than or equal to 7.00 K20.

[0031] A twenty-fifth aspect, A25, includes the glass of any one of aspects A21 to A24, comprising greater than or equal to 1.00 to less than or equal to 6.00 MgO.

[0032] A twenty-sixth aspect, A26, includes the glass of any one of aspects A21 to A25, comprising greater than or equal to 0.20 to less than or equal to 6.00 CaO.

[0033] A twenty-seventh aspect, A27, includes the glass of any one of aspects A21 to A26, wherein R2O-Al2O3is less than or equal to 9.00 mol%.

[0034] A twenty-eighth aspect, A28, includes the glass of any one of aspects A21 to A27, wherein R2O-Al2O3is less than or equal to 0.00 mol% and greater than or equal to -6.50.

[0035] A twenty-ninth aspect, A29, includes the glass of aspect A27, wherein R2O-Al2O3is greater than 0.00 mol%.

[0036] A thirtieth aspect, A30, includes the glass of any one of aspects A21 to A29, wherein R x O-Al2O3is greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, wherein R x O is the sum of R2O and RO, wherein RO is the sum of MgO + CaO + BaO + SrO.

[0037] A thirty-first aspect, A31, includes the glass of any one of aspects A21 to A30, wherein the ratio of (RO+R2O):(Al2O3+B2O3) is less than 1.5, wherein RO is the sum of MgO + CaO + BaO + SrO.

[0038] A thirty-second aspect, A32, includes the glass of any one of aspects A21 to A31, wherein the glass has a transmittance greater than 50% at a 248 nm wavelength and 1 mm thickness in an as-formed state.

[0039] A thirty-third aspect, A33, includes the glass of any one of aspects A21 to A32, wherein the glass has a transmittance greater than 50% at a 248 nm wavelength and 1 mm thickness after exposure to 3000 UV light pulses from an excimer laser at a wavelength of 248 nm, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse at a pulse repetition rate of 10 Hz.

[0040] A thirty-fourth aspect, A34, includes the glass of any one of aspects A21 to A33, wherein the glass has an average coefficient of thermal expansion from 0 °C to 300 °C greater than or equal to 50 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C.

[0041] A thirty-fifth aspect, A35, includes the glass of any one of aspects A21 to A34, wherein the glass has a liquidus viscosity greater than or equal to 10,000 Pascal*seconds.

[0042] A thirty-sixth aspect A36 includes a glass comprising, in mole percent on an oxide basis: greater than or equal to 65.50 to less than or equal to 72.50 Si02; greater than or equal to 3.00 to less than or equal to 13.75 AI2O3; greater than or equal to 0.00 to less than or equal to 20.00 B203; greater than or equal to 0.00 to less than or equal to 6.00 MgO; greater than or equal to 0.10 to less than or equal to 15.00 Na20; greater than or equal to 2.00 to less than or equal to 8.50 K20; less than or equal to 1.25 Li20; less than or equal to 0.05 Sn02; less than or equal to 0.20 Ti02; less than or equal to 0.10 Fe203; less than or equal to 0.5 Zr02; less than or equal to 5 ZnO; and less than or equal to 0.75 BaO, wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of AI2O3 + B203 - R2O - CaO - SrO - BaO is greater than or equal to -1.50 mole percent and less than or equal to 40.00 mole percent, where R2O is Na20 + K20 + Li20; the sum of Na20 + K20 is greater than or equal to 2.10 mole percent and less than or equal to 15.50 mole percent; and the sum of As203 + Sb203 + PbO is less than or equal to 0.01 mole percent.

[0043] A thirty-seventh aspect A37 includes the glass of aspect A36, wherein R2O - AI2O3 is less than or equal to 9.00 mole percent.

[0044] A thirty-eighth aspect A38 includes the glass of any of aspects A36 to A37, wherein R2O - AI2O3 is less than or equal to 0.00 mole percent and greater than or equal to -6.50.

[0045] A thirty-ninth aspect A39 includes the glass of any of aspects A36 to A38, wherein R2O - AI2O3 is greater than 0.00 mole percent.

[0046] A fortieth aspect A40 includes the glass of any of aspects A36 to A39, wherein R2O - AI2O3 is greater than or equal to 2.00 mole percent and less than or equal to 10.00 mole percent, wherein R2O is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO. x x A fortieth aspect A40 includes the glass of any of aspects A36 to A39, wherein R2O - AI2O3 is greater than or equal to 2.00 mole percent and less than or equal to 10.00 mole percent, wherein R2O is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO.

[0047] ​Forty-first aspect A41 includes the glass of any of aspects A36 to A40, wherein the ratio of (RO + R2O):(Al203 + B203) is less than 1.5, where RO is the sum of MgO + CaO + BaO + SrO.

[0048] Forty-second aspect A42 includes the glass of any of aspects A36 to A41, wherein the glass has a transmittance at a 248 nm wavelength and 1 mm thickness of greater than 50% in an as-formed state.

[0049] Forty-third aspect A43 includes the glass of any of aspects A36 to A42, wherein the glass has a transmittance at a 248 nm wavelength and 1 mm thickness of greater than 50% after exposure to 3000 UV light pulses from an excimer laser at a wavelength of 248 nm, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse, and a pulse repetition rate of 10 Hz.

[0050] Forty-fourth aspect A44 includes the glass of any of aspects A36 to A43, wherein the glass has an average coefficient of thermal expansion from 0 °C to 300 °C of greater than or equal to 50 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C.

[0051] Forty-fifth aspect A45 includes the glass of any of aspects A36 to A44, wherein the glass has a liquidus viscosity of greater than or equal to 10,000 Pascal-seconds.

[0052] Other features and advantages of the alkali-containing, melt-formable glasses having relatively high UV transmittance described herein will be set forth in the detailed description that follows, and in part will be apparent from the description or can be learned by practice of the embodiments described herein, including the detailed description that follows, the claims, and the appended drawings.

[0053] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments described herein and, together with the description, serve to explain the principles and operations of the claimed subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 illustrates UV transmittance (y-axis) as a function of wavelength (x-axis) for an exemplary glass according to embodiments described herein after initial UV exposure;

[0055] Figure 2 FIG. 3 illustrates UV transmittance (y-axis) as a function of wavelength (x-axis) for an exemplary glass according to embodiments described herein after initial UV exposure; and

[0056] Figure 3 FIG. 4 illustrates UV transmittance (y-axis) as a function of wavelength (x-axis) for a conventional melt-formable glass substrate. DETAILED DESCRIPTION

[0057] Reference will now be made in detail to embodiments of alkali-containing, melt-formable glasses having relatively high UV transmittance described herein. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In embodiments, the alkali-containing, melt-formable glasses having relatively high UV transmittance comprise, in mole percent on an oxide basis: greater than or equal to 65.00 to less than or equal to 72.50 Si02; greater than or equal to 2.50 to less than or equal to 13.75 Al203; greater than or equal to 0.00 to less than or equal to 18.00 B203; greater than or equal to 0.00 to less than or equal to 6.00 MgO; greater than or equal to 0.00 to less than or equal to 15.00 Na20; greater than or equal to 3.10 to less than or equal to 7.50 K20; each less than or equal to 1.00 Li20 and ZnO; less than or equal to 0.04 Sn02; each less than or equal to 0.10 Ti02, Fe203, and Ce203; and less than or equal to 2 F - The glasses have a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm. The sum of Al203+B203-R20-CaO-SrO-BaO in the glasses can be greater than or equal to -0.75 mole percent and less than or equal to 40.00 mole percent, where R20 is the sum of Na20+K20+Li20. The sum of Na20+K20 in the glasses can be greater than or equal to 3.10 mole percent and less than or equal to 15.50 mole percent. The sum of As203+Sb203+PbO in the glasses can be less than or equal to 0.01 mole percent. Various embodiments of alkali-containing, melt-formable glasses having relatively high UV transmittance will be further described herein with specific reference to the figures.

[0058] UV transmittance (also referred to herein as “transmittance”) is measured using a Perkin Elmer Lambda 650 spectrophotometer at 248 nm on an optically polished sample with plane-parallel faces. Transmittance is measured on the glass article itself, without any coating or other application. UV transmittance is also measured using the same instrument over a wavelength range of 200 nm to 300 nm.

[0059] The liquidus temperature of a glass is the temperature in °C above which no crystalline phase can exist in equilibrium with the glass. The liquidus temperature is measured according to ASTM C829-81 (2022).

[0060] The liquidus viscosity of a glass is the viscosity of the glass at the liquidus temperature. The liquidus viscosity is measured according to ASTM C965-23 (2023).

[0061] Density is measured according to ASTM C693-93 (2019).

[0062] As used herein, the term “softening point” refers to the temperature at which the viscosity of the glass is 1 x 10 7.6 poise. The softening point is determined using the parallel plate viscosity method of ASTM C1351M-96 (2012).

[0063] As used herein, the term “annealing point” refers to the temperature at which the viscosity of the glass is 1 x 10 13 poise. The annealing point is determined using the beam bending viscosity method of ASTM C598-93 (2013).

[0064] As used herein, the terms “strain point” and “T 应变 ” refer to the temperature at which the viscosity of the glass is 1 x 10 14.68 poise. The strain point is determined using the beam bending viscosity method of ASTM C598-93 (2013).

[0065] The coefficient of linear thermal expansion (CTE) of a glass over a temperature range of 0 °C to 300 °C is expressed as the average CTE over the range expressed in “x 10 -7 / °C” and is determined using a push-rod dilatometer according to ASTM E228-11 (2016).

[0066] The OH concentration (in ppm by weight) of the glasses described herein can be derived from measurements of the infrared transmittance of the glass. The wavelength range of interest is 2-5 pm (wavenumber range of 5000 cm -1 to 2000 cm -1Conventional infrared spectrophotometers, i.e., FT-IR (Fourier Transform Infrared) spectrometers or dispersive infrared spectrophotometers, can be used. For high spatial resolution measurements, such as for changes in OH concentration, additional equipment known in the art can be used. In molten silica, OH groups are located at 2.72 μm (3676 cm⁻¹). -1 ), 2.21μm (4525cm) -1 ) and 1.38μm (7246cm) -1 The vicinity exhibits a characteristic absorption band. The parameter β-OH is defined as the relative linear absorption coefficient of hydroxyl (OH) groups in the glass matrix, or the absorption per unit path length (mm). -1 It uses the following equation for calculation:

[0067]

[0068] Wherein: T ref = Transmittance of the sample at a reference position, where the reference position is the non-absorption wavelength, for example, 4000 cm⁻¹ -1 ;T OH =The sample shows an OH absorption peak (approximately 3676 cm⁻¹ for silica). -1 The transmittance at ) is given by t, where t = sample thickness (mm). This β-OH value is linearly proportional to the hydroxyl concentration.

[0069] The OH concentration c, expressed in moles per liter, is derived from the Beers-Lambert Law:

[0070] A=∈·c·b

[0071] Where absorbance A = log(T) ref / T OH ), ε is in liters·molars -1 ·centimeter -1 The value is expressed as molar absorbance, c is the concentration in moles per liter, and b is the path length (sample thickness).

[0072] c(moles·liters) -1 Therefore, the concentration of OH (in ppm by weight) can be calculated from c (in moles·liters) using the density of the glass and the molecular weight of OH (approximately 17 g / mol). The constant ε of high-purity silica glass at a specific wavelength is known in the art.

[0073] When used to describe the concentration and / or absence of a particular constituent component in glass, the terms "free of" and "substantially free of" mean that the constituent component was not intentionally added to the glass. However, unless otherwise stated herein, glass may contain trace amounts of the constituent component as contaminants or impurities, in amounts less than 0.05 mol%.

[0074] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such ranges are expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that each end point of every range is encompassed.

[0075] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0076] Unless specifically stated otherwise, and as apparent from the previous discussion, it is not intended that any method or process recited herein be construed as requiring its steps to be performed in a particular order. Accordingly, unless specifically stated otherwise, it is not intended that any device, system or structures recited herein be limited in construction or operation to the particular order or hierarchy of components described herein or illustrated in the drawings. It is not intended that the described embodiments be construed as having any relationship to the order or hierarchy of steps or components illustrated and / or described herein. The methods and processes recited herein can be carried out in the order of presentation, in reverse order or in any appropriate order deemed suitable by those having average skill in the art, including simultaneous completion of some steps or processes. Any process, method or steps recited herein can be carried out in any suitable order or sequence, or concurrently, unless the context clearly indicates otherwise. This applies even if the process, method or steps recited are described or illustrated as being dependent on other processes, methods or steps.

[0077] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” or “the” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0078] Some microchip fabrication processes on silicon substrates include photolithography steps involving the use of UV light, for example in photoresist steps that utilize deep UV (about 250 nm) light transmission for exposure. Therefore, any material between the UV exposure beam and the silicon substrate (e.g. a glass substrate) should be highly transparent in the UV portion of the spectrum. The most commonly used glasses are not sufficiently transparent at these UV wavelengths (e.g. 245-270 nm). The UV transparency of the glass determines the exposure time, with lower transparency translating to the need for longer exposure times. Conversely, shorter exposure times can improve manufacturing throughput, which is desirable to reduce production costs. Other applications and methods can also be improved by glasses having high UV transmission.

[0079] Generally, UV transparent glass substrates are formed from fused silica. However, the manufacturing cost of fused silica substrates is prohibitively high, particularly for larger substrate sizes. Moreover, due to the viscosity characteristics of fused silica, fused silica is generally incompatible with down-draw processes (e.g., fusion forming processes), and thus, fused silica cannot be readily formed into large glass sheets using such processes.

[0080] Further, it has been observed that constituent components added to silica to reduce manufacturing costs and improve formability of the molten glass also have the effect of reducing the UV transmittance of the glass. For example, constituent components (e.g., alkali and alkaline earth ions) that are typically added to glass to enhance glass properties (e.g., formability of the glass and / or coefficient of thermal expansion of the glass) significantly reduce the UV transmittance of the glass. In this regard, conventional glasses that are compatible with large format panel production manufacturing techniques (e.g., fusion forming) are generally poor in UV transmittance and thus are not suitable for applications requiring high UV transmittance. In fact, some of these glasses can actually darken upon initial UV exposure, further reducing the UV transmittance of the glass.

[0081] In particular, glass manufacturing techniques that include melting a batch (e.g., fusion forming techniques) place restrictions on the physical and optical properties of the glass due to the composition of the glass required to promote compatibility with the manufacturing technique. As one example specific to the UV transmittance of the glass, most commercial glasses contain alkali ions (e.g., Li + , Na + , and K + ) and alkaline earth ions (e.g., Ca 2+ , Sr 2+ , Mg 2+ , and Ba 2+ ). Such constituents can be introduced into the glass batch to aid, for example, melting and forming, as well as to enhance other properties of the glass. When these constituents are included in the glass in excess of Al2O3and B2O3, non-bridging oxygen (NBO) or oxygen dangling bonds are created in the glass. These NBOs reduce the UV transmittance of the glass. In particular, such glasses include energy states within the nominal silica bonding structure. The introduction of energy states, particularly NBO energy states, within the SiO2optical gap reduces the UV transmittance of the resulting glass.

[0082] Accordingly, there is a need for a glass that has high UV transmittance while also being compatible with large scale manufacturing techniques (e.g., down-draw processes, including fusion forming).

[0083] The glasses disclosed herein alleviate the aforementioned problems of conventional glasses by providing glasses having high UV transmittance and compatibility with fusion forming processes. Specifically, the glasses disclosed herein can generally be described as alkali-containing silicate glasses that include Si02, an alkali metal oxide, and AI2O3. In embodiments, the alkali metal oxide includes at least K2O. In embodiments, the glasses can also include B2O3. In embodiments, the glasses can also include an alkaline earth oxide. The amounts of AI2O3, alkali metal oxide, B2O3 (when included), and alkaline earth oxide (when included) can be balanced to obtain a glass having a relatively high UV transmittance and a liquidus viscosity that is compatible with fusion forming techniques.

[0084] In embodiments described herein, the glass includes Si02. Si02 is a primary glass former that functions to stabilize the network structure of the glass and improve the chemical durability of the glass. The amount of Si02 can be limited to control the melting temperature of the glass, as pure Si02 or high Si02 glasses have undesirably high melting temperatures.

[0085] In embodiments, the glass comprises greater than or equal to 65.00 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 74.50 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 74.00 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 73.50 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 73.00 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 72.50 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 72.00 mol.% Si02, greater than or equal to 65.00 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 65.50 mol.% and less than or equal to 72.50 mol.% Si02, greater than or equal to 65.50 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 66.00 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 66.50 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 67.00 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 67.50 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 68.00 mol.% and less than or equal to 75.00 mol.% Si02, greater than or equal to 68.00 mol.% and less than or equal to 74.50 mol.% Si02, greater than or equal to 68.00 mol.% and less than or equal to 74.00 mol.% Si02, greater than or equal to 68.00 mol.% and less than or equal to 73.50 mol.% Si02, greater than or equal to 68.00 mol.% and less than or equal to 73.00 mol.% Si02, or even greater than or equal to 68.00 mol.% and less than or equal to 72.50 mol.% Si02. The above ranges include all sub-ranges between the expressly disclosed ranges and ranges formed by any combination of the endpoints of the ranges.

[0086] Embodiments of the glasses described herein also include AI2O3. AI2O3 can stabilize the glass network and improve the mechanical properties and chemical durability of the resulting glass. The amount of AI2O3 can be adjusted to control the viscosity of the glass during melting and forming. If the amount of AI2O3 is too high, the viscosity of the melt will generally also increase. Adding AI2O3 also helps to reduce the amount of NBOs in the glass, thereby improving the UV transmittance of the glass.

[0087] In embodiments, the glasses described herein comprise greater than or equal to 2.50 mole% and less than or equal to 22.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 21.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 20.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 19.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 18.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 17.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 16.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 15.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 14.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 13.50 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 13.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 12.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 11.50 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 11.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 10.50 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 10.00 mole% AI2O3, 2.50 mole% and less than or equal to 9.50 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 9.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 8.50 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 8.00 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 7.50 mole% AI2O3, greater than or equal to 2.50 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 3.00 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 3.50 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 4.00 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 4.50 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 5.00 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 5.50 mole% and less than or equal to 13.75 mole% AI2O3, greater than or equal to 6.00 mole% and less than or equal to 13.75 mol.% to 21.00 mol.% B203, greater than or equal to 0.00 mol.% to less than or equal to 20.00 mol.% B203, greater than or equal to 0.00 mol.% to less than or equal to 19.00 mol.% B203, greater than or equal to 0.00 mol.% to less than or equal to 18.00 mol.% B203, or even greater than or equal to 0.00 mol.% to less than or equal to 17.00 mol.% B203. The above ranges include all subranges contained therein, as well as ranges created by combining any of the endpoints of the ranges.

[0088] In embodiments, the glass can further comprise B203. Without wishing to be bound by theory, it is believed that the addition of B203, when included, can lower the liquidus viscosity of the glass, thereby improving the formability of the glass as well as improving the compatibility of the glass with fusion forming processes. The addition of B203, when included, can also help to reduce the amount of NBOs in the glass, thereby improving the UV transmittance of the glass.

[0089] Embodiments of the glasses described herein can comprise greater than or equal to 0.00 mol.% to less than or equal to 21.00 mol.% B203, greater than or equal to 0.00 mol.% to less than or equal to 20.00 mol.% B203, greater than or equal to 0.00 mol.% to less than or equal to 19.00 mol.% B203, greater than or equal to 0.00 mol.% to less than or equal to 18.00 mol.% B203, or even greater than or equal to 0.00 mol.% to less than or equal to 17.00 mol.% B203. The above ranges include all subranges contained therein, as well as ranges created by combining any of the endpoints of the ranges.

[0090] In embodiments, the glass can comprise greater than or equal to 0.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 1.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 1.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 2.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 2.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 3.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 3.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 4.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 4.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 5.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 5.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 6.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 6.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 7.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 7.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 8.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 8.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 9.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 9.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 10.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 10.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 11.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 11.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 12.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 12.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 13.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 13.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 14.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 14.50 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 15.00 mol.% and less than or equal to 21.00 mol.% B203, greater than or equal to 15.50 mole percent or less than or equal to 21.00 mole percent B203, greater than or equal to 16.00 mole percent and less than or equal to 21.00 mole percent B203, greater than or equal to 16.50 mole percent and less than or equal to 21.00 mole percent B203, greater than or equal to 17.00 mole percent and less than or equal to 21.00 mole percent B203, greater than or equal to 17.50 mole percent and less than or equal to 21.00 mole percent B203, greater than or equal to 18.00 mole percent and less than or equal to 21.00 mole percent B203, greater than or equal to 18.50 mole percent and less than or equal to 21.00 mole percent B203, greater than or equal to 19.00 mole percent and less than or equal to 21.00 mole percent B203, or even greater than or equal to 19.50 mole percent and less than or equal to 21.00 mole percent B203. The above ranges include all subranges within the expressly disclosed ranges as well as ranges created by any combination of the endpoints from the ranges.

[0091] In embodiments, the glasses described herein can comprise greater than or equal to 2.50 mole percent and less than or equal to 20.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 19.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 18.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 17.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 16.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 15.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 14.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 13.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 12.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 11.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 10.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 9.50 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 9.00 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 8.50 mole percent B203, greater than or equal to 2.50 mole percent and less than or equal to 8.00 mole percent B203, or even greater than or equal to 2.50 mole percent and less than or equal to 7.50 mole percent B203. The above ranges include all subranges within the expressly disclosed ranges as well as ranges created by any combination of the endpoints from the ranges.

[0092] In embodiments, the glass can comprise greater than or equal to 5.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 5.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 6.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 6.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 7.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 7.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 8.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 8.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 9.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 9.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 10.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 10.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 11.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 11.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 12.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 12.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 13.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 13.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 14.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 14.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 15.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 15.50 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 16.00 mol.% and less than or equal to 18.00 mol.% B203, greater than or equal to 16.50 mol.% and less than or equal to 18.00 mol.% B203, or even greater than or equal to 17.00 mol.% and less than or equal to 18.00 mol.% B203. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0093] In embodiments, the glass can comprise greater than or equal to 5.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 5.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 6.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 6.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 7.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 7.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 8.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 8.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 9.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 9.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 10.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 10.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 11.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 11.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 12.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 12.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 13.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 13.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 14.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 14.50 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 15.00 mol.% and less than or equal to 17.00 mol.% B203, greater than or equal to 15.50 mol.% and less than or equal to 17.00 mol.% B203, or even greater than or equal to 16.00 mol.% and less than or equal to 17.00 mol.% B203. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0094] In embodiments, the glass does not comprise B203. In embodiments, the glass is essentially free of B203.

[0095] Embodiments of the glasses described herein can include Na2O. The addition of Na2O, when included, improves the meltability and formability of the glass. The addition of Na2O can also enhance the coefficient of thermal expansion of the glass, particularly increasing the coefficient of thermal expansion of the glass, which can be desirable for certain end user applications. The addition of Na2O can also facilitate strengthening of the glass, for example by ion exchange strengthening.

[0096] In embodiments, the glass can include greater than or equal to 0.00 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 0.10 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 0.50 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 1.00 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 1.50 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 2.00 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 2.50 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 3.00 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 3.50 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 4.00 mole % and less than or equal to 15.00 mole % Na2O, greater than or equal to 4.50 mole % and less than or equal to 15.00 mole % Na2O, or even greater than or equal to 5.00 mole % and less than or equal to 15.00 mole % Na2O. The above ranges include all subranges between the expressly disclosed ranges and ranges formed by any combination of the endpoints of the ranges.

[0097] In embodiments, the glass can comprise greater than or equal to 1.50 mol.% and less than or equal to 10.00 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 9.50 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 9.00 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 8.50 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 9.00 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 8.50 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 8.00 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 7.50 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 7.00 mol.% Na20, greater than or equal to 1.50 mol.% and less than or equal to 6.50 mol.% Na20, or even greater than or equal to 1.50 mol.% and less than or equal to 6.00 mol.% Na20. The above ranges include all sub-ranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0098] In embodiments, the glass can comprise greater than or equal to 2.00 mol.% and less than or equal to 10.00 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 9.50 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 9.00 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 8.50 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 8.00 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 7.50 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 7.00 mol.% Na20, greater than or equal to 2.00 mol.% and less than or equal to 6.50 mol.% Na20, or even greater than or equal to 2.00 mol.% and less than or equal to 6.00 mol.% Na20. The above ranges include all sub-ranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0099] In embodiments, the glass is free of Na20. In embodiments, the glass is substantially free of Na20.

[0100] Embodiments of the glasses described herein also comprise K20. As with Na20, the addition of K20 improves the meltability and formability of the glass. The addition of K20 can also enhance the coefficient of thermal expansion of the glass, particularly increasing the coefficient of thermal expansion of the glass, which can be desirable for certain end user applications. The addition of K20 can also facilitate strengthening of the glass, for example by ion exchange strengthening.

[0101] In embodiments, the glass can comprise greater than or equal to 2.00 mol.% and less than or equal to 8.50 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 8.00 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 7.50 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 7.00 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 6.50 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 6.00 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 5.50 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 5.00 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 4.50 mol.% K2O, greater than or equal to 2.00 mol.% and less than or equal to 4.00 mol.% K2O, or even greater than or equal to 2.00 mol.% and less than or equal to 3.50 mol.% K2O. The above ranges include all sub-ranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0102] In embodiments, the glass can comprise greater than or equal to 2.10 mol.% and less than or equal to 8.50 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 8.00 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 7.50 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 7.00 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 6.50 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 6.00 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 5.50 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 5.00 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 4.50 mol.% K2O, greater than or equal to 2.10 mol.% and less than or equal to 4.00 mol.% K2O, or even greater than or equal to 2.10 mol.% and less than or equal to 3.50 mol.% K2O. The above ranges include all sub-ranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0103] In embodiments, the glass can include greater than or equal to 3.10 mol.% and less than or equal to 8.50 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 8.00 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 7.50 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 7.00 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 6.50 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 6.00 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 5.50 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 5.00 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 4.50 mol.% K2O, greater than or equal to 3.10 mol.% and less than or equal to 4.00 mol.% K2O, or even greater than or equal to 3.10 mol.% and less than or equal to 3.50 mol.% K2O. The above ranges include all sub-ranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0104] In embodiments, the total concentration of Na2O + K2O in the glass (i.e., the sum of Na2O (mol.%) + K2O (mol.%)) can be greater than or equal to 2.00 mol.% and less than or equal to 15.50 mol.%, greater than or equal to 2.10 mol.% and less than or equal to 15.50 mol.% Na2O + K2O, greater than or equal to 2.50 mol.% and less than or equal to 15.50 mol.% Na2O + K2O, greater than or equal to 3.00 mol.% and less than or equal to 15.50 mol.% Na2O + K2O, greater than or equal to 3.50 mol.% and less than or equal to 15.50 mol.% Na2O + K2O, greater than or equal to 4.00 mol.% and less than or equal to 15.50 mol.% Na2O + K2O, greater than or equal to 4.50 mol.% and less than or equal to 15.50 mol.% Na2O + K2O, or even greater than or equal to 5.00 mol.% and less than or equal to 15.50 mol.% Na2O + K2O. The above ranges include all sub-ranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0105] In embodiments, the glass can comprise greater than or equal to 2.00 mol.% and less than or equal to 11.00 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 10.00 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 9.50 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 9.00 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 8.50 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 9.00 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 8.50 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 8.00 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 7.50 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 7.00 mol.% Na2O + K2O, greater than or equal to 2.00 mol.% and less than or equal to 6.50 mol.% Na2O + K2O, or even greater than or equal to 2.00 mol.% and less than or equal to 6.00 mol.% Na2O + K2O. The above ranges include all subranges within the expressly disclosed ranges as well as ranges formed by any combination of the endpoints from the ranges.

[0106] In embodiments, the glass can comprise greater than or equal to 2.10 mol.% and less than or equal to 15.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 14.50 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 14.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 13.50 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 13.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 12.50 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 12.0 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 11.5 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 11.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 10.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 9.50 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 9.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 8.50 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 8.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 7.50 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 7.00 mol.% Na2O + K2O, greater than or equal to 2.10 mol.% and less than or equal to 6.50 mol.% Na2O + K2O, or even greater than or equal to 2.10 mol.% and less than or equal to 6.00 mol.% Na2O + K2O. The above ranges include all sub-ranges between the expressly disclosed ranges as well as ranges formed by any combination of the endpoints of the ranges.

[0107] In embodiments, the glass can comprise greater than or equal to 3.10 mole% and less than or equal to 15.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 15.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 14.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 14.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 13.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 13.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 12.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 12.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 11.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 11.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 10.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 10.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 9.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 9.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 8.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 8.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 7.50 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 7.00 mole% Na2O + K2O, greater than or equal to 3.10 mole% and less than or equal to 6.50 mole% Na2O + K2O, or even greater than or equal to 3.10 mole% and less than or equal to 6.00 mole% Na2O + K2O. The above ranges include all sub-ranges between the expressly disclosed ranges and ranges formed by any combination of the endpoints of the ranges.

[0108] Embodiments of the glasses described herein can comprise Li2O. As with Na2O and K2O, the addition of Li2O, when included, improves the fusibility and formability of the glass. The addition of Li2O can also facilitate strengthening of the glass, for example, by ion exchange strengthening. However, Li2O in the glass can be highly mobile and, as a result, have a tendency to migrate from the glass. When the glasses described herein are used in semiconductor processing, Li + Ions can be highly mobile and, as a result, have a tendency to migrate from the glass. When the glasses described herein are used in semiconductor processing, Li +Ion migration from the glass can damage semiconductor materials deposited on the glass. Therefore, the amount of Li20 present in the glass should be minimized.

[0109] In embodiments, the glass can comprise greater than or equal to 0.00 mol.% to less than or equal to 1.50 mol.% Li20, greater than or equal to 0.00 mol.% to less than or equal to 1.25 mol.% Li20, greater than or equal to 0.00 mol.% to less than or equal to 1.00 mol.% Li20, greater than or equal to 0.00 mol.% to less than or equal to 0.75 mol.% Li20, greater than or equal to 0.00 mol.% to less than or equal to 0.50 mol.% Li20, greater than or equal to 0.00 mol.% to less than or equal to 0.25 mol.% Li20, or even greater than or equal to 0.00 mol.% to less than or equal to 0.10 mol.% Li20. In embodiments, the glass is free of Li20. In embodiments, the glass is substantially free of Li20. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0110] Embodiments of the glasses described herein can contain Na2F2. Na2F2may be included in the glass as a fining agent (i.e., to help remove and / or prevent gas bubbles from being entrained in the glass melt). The addition of Na2F2may also improve the UV transmittance of the glass.

[0111] In embodiments, the glass can comprise greater than or equal to 0.00 mol.% and less than or equal to 5.00 mol.% Na2F2, greater than or equal to 0.00 mol.% and less than or equal to 4.50 mol.% Na2F2, greater than or equal to 0.00 mol.% and less than or equal to 4.00 mol.% Na2F2, greater than or equal to 0.00 mol.% and less than or equal to 3.50 mol.% Na2F2, greater than or equal to 0.00 mol.% and less than or equal to 3.00 mol.% Na2F2, greater than or equal to 0.00 mol.% and less than or equal to 2.50 mol.% Na2F2, or even greater than or equal to 0.00 mol.% and less than or equal to 2.00 mol.% Na2F2. In embodiments, the glass can comprise greater than or equal to 0.10 mol.% and less than or equal to 5.00 mol.% Na2F2, greater than or equal to 0.10 mol.% and less than or equal to 4.50 mol.% Na2F2, greater than or equal to 0.10 mol.% and less than or equal to 4.00 mol.% Na2F2, greater than or equal to 0.10 mol.% and less than or equal to 3.50 mol.% Na2F2, greater than or equal to 0.10 mol.% and less than or equal to 3.00 mol.% Na2F2, greater than or equal to 0.10 mol.% and less than or equal to 2.50 mol.% Na2F2, or even greater than or equal to 0.10 mol.% and less than or equal to 2.00 mol.% Na2F2. In embodiments, the glass is free of Na2F2. In embodiments, the glass is substantially free of Na2F2. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0112] Embodiments of the glasses described herein can contain K2F2. K2F2may be included in the glass as a fining agent (i.e., helps to remove and / or prevent bubbles entrained in the glass melt). The addition of K2F2may also improve the UV transmittance of the glass.

[0113] In embodiments, the glass can comprise greater than or equal to 0.00 mol.% and less than or equal to 3.00 mol.% K2F2, greater than or equal to 0.00 mol.% and less than or equal to 2.50 mol.% K2F2, or even greater than or equal to 0.00 mol.% and less than or equal to 2.00 mol.% K2F2. In embodiments, the glass can comprise greater than or equal to 0.10 mol.% and less than or equal to 5.00 mol.% K2F2, greater than or equal to 0.10 mol.% and less than or equal to 4.50 mol.% K2F2, greater than or equal to 0.10 mol.% and less than or equal to 4.00 mol.% K2F2, greater than or equal to 0.10 mol.% and less than or equal to 3.50 mol.% K2F2, greater than or equal to 0.10 mol.% and less than or equal to 3.00 mol.% K2F2, greater than or equal to 0.10 mol.% and less than or equal to 2.50 mol.% K2F2, or even greater than or equal to 0.10 mol.% and less than or equal to 2.00 mol.% K2F2. In embodiments, the glass is free of K2F2. In embodiments, the glass is substantially free of K2F2. The above ranges include all subranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0114] Embodiments of the glasses described herein can contain MgO. The addition of MgO, when included, can improve the fusibility of the glass. The addition of MgO can also enhance the coefficient of thermal expansion of the glass, particularly increasing the coefficient of thermal expansion of the glass, which can be desirable for certain end user applications.

[0115] In embodiments, the glass can comprise greater than or equal to 0.00 mole % and less than or equal to 8.00 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 7.50 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 7.00 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 6.50 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 6.00 mole % MgO, or even greater than or equal to 0.00 mole % and less than or equal to 5.50 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 5.00 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 4.50 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 4.00 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 3.50 mole % MgO, greater than or equal to 0.00 mole % and less than or equal to 3.00 mole % MgO, or even greater than or equal to 0.00 mole % and less than or equal to 2.50 mole % MgO. In embodiments, the glass can comprise greater than or equal to 1.00 mole % and less than or equal to 8.00 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 7.50 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 7.00 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 6.50 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 6.00 mole % MgO, or even greater than or equal to 1.00 mole % and less than or equal to 5.50 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 5.00 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 4.50 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 4.00 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 3.50 mole % MgO, greater than or equal to 1.00 mole % and less than or equal to 3.00 mole % MgO, or even greater than or equal to 1.00 mole % and less than or equal to 2.50 mole % MgO. In embodiments, the glass is free of MgO. In embodiments, the glass is substantially free of MgO. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0116] Embodiments of the glasses described herein can contain CaO. The addition of CaO, when included, can improve the meltability of the glass. The addition of CaO can also enhance the coefficient of thermal expansion of the glass, particularly increasing the coefficient of thermal expansion of the glass, which can be desirable for certain end user applications.

[0117] In embodiments, the glass can comprise greater than or equal to 0.00 mol.% and less than or equal to 8.00 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 7.50 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 7.00 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 6.50 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 6.00 mol.% CaO, or even greater than or equal to 0.00 mol.% and less than or equal to 5.50 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 5.00 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 4.50 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 4.00 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 3.50 mol.% CaO, greater than or equal to 0.00 mol.% and less than or equal to 3.00 mol.% CaO, or even greater than or equal to 0.00 mol.% and less than or equal to 2.50 mol.% CaO. In embodiments, the glass can comprise greater than or equal to 0.20 mol.% and less than or equal to 8.00 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 7.50 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 7.00 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 6.50 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 6.00 mol.% CaO, or even greater than or equal to 0.20 mol.% and less than or equal to 5.50 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 5.00 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 4.50 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 4.00 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 3.50 mol.% CaO, greater than or equal to 0.20 mol.% and less than or equal to 3.00 mol.% CaO, or even greater than or equal to 0.20 mol.% and less than or equal to 2.50 mol.% CaO. In embodiments, the glass is free of CaO. In embodiments, the glass is substantially free of CaO. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0118] In embodiments, the glass can contain CaF2. CaF2may be included in the glass as a fining agent (i.e., helps to remove and / or prevent air bubbles entrained in the glass melt). The addition of CaF2may also improve the UV transmittance of the glass. In embodiments, the glass can include greater than or equal to 0.00 mol.% and less than or equal to 1.00 mol.% CaF2, greater than or equal to 0.00 mol.% and less than or equal to 0.75 mol.% CaF2, greater than or equal to 0.00 mol.% and less than or equal to 0.50 mol.% CaF2, or even greater than or equal to 0.00 mol.% and less than or equal to 0.25 mol.% CaF2. In embodiments, the glass can include greater than or equal to 0.10 mol.% and less than or equal to 1.00 mol.% CaF2, greater than or equal to 0.10 mol.% and less than or equal to 0.75 mol.% CaF2, greater than or equal to 0.10 mol.% and less than or equal to 0.50 mol.% CaF2, or even greater than or equal to 0.10 mol.% and less than or equal to 0.25 mol.% CaF2. In embodiments, the glass is free of CaF2. In embodiments, the glass is substantially free of CaF2. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0119] In embodiments, the sum of MgO and CaO (i.e., MgO (mol%) + CaO (mol%) can be greater than or equal to 0.00 mol% and less than or equal to 10.00 mol%. When the sum of MgO and CaO exceeds 10.00 mol%, NBOs can be present in the glass, and the UV transmittance of the glass can be correspondingly reduced. In embodiments, the glass can comprise MgO + CaO greater than or equal to 0.00 mol% and less than or equal to 9.50 mol%, MgO + CaO greater than or equal to 0.00 mol% and less than or equal to 9.00 mol%, MgO + CaO greater than or equal to 0.00 mol% and less than or equal to 8.50 mol%, MgO + CaO greater than or equal to 0.00 mol% and less than or equal to 8.00 mol%, MgO + CaO greater than or equal to 0.00 mol% and less than or equal to 7.50 mol%, or even MgO + CaO greater than or equal to 0.00 mol% and less than or equal to 7.00 mol%. In embodiments, the glass can comprise MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 9.50 mol%, MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 9.00 mol%, MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 8.50 mol%, MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 8.00 mol%, MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 7.50 mol%, or even MgO + CaO greater than or equal to 2.00 mol% and less than or equal to 7.00 mol%. In embodiments, the glass can comprise MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 10.00 mol%, MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 9.50 mol%, MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 9.00 mol%, MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 8.50 mol%, MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 8.00 mol%, MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 7.50 mol%, or even MgO + CaO greater than or equal to 4.00 mol% and less than or equal to 7.00 mol%. The above ranges include all sub-ranges within the expressly disclosed ranges as well as ranges formed by any combination of the endpoints from the disclosed ranges.

[0120] Embodiments of the glasses described herein can contain SrO. SrO can be added to the glass to change the liquidus viscosity. However, SrO can undesirably increase the density of the glass. Therefore, the amount of SrO in the glass should be minimized. In embodiments, the glass can comprise greater than or equal to 0.00 mole % and less than or equal to 2.00 mole % SrO, greater than or equal to 0.00 mole % and less than or equal to 1.50 mole % SrO, greater than or equal to 0.00 mole % and less than or equal to 1.00 mole % SrO, or even greater than or equal to 0.00 mole % and less than or equal to 0.50 mole % SrO. In embodiments, the glass can comprise greater than or equal to 0.10 mole % and less than or equal to 2.00 mole % SrO, greater than or equal to 0.10 mole % and less than or equal to 1.50 mole % SrO, greater than or equal to 0.10 mole % and less than or equal to 1.00 mole % SrO, or even greater than or equal to 0.10 mole % and less than or equal to 0.50 mole % SrO. In embodiments, the glass is free of SrO. In embodiments, the glass is substantially free of SrO. The above ranges include all subranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0121] Embodiments of the glasses described herein can contain BaO. BaO can be added to the glass to change the liquidus viscosity. However, BaO can undesirably increase the density of the glass. Therefore, the amount of BaO in the glass should be minimized. In embodiments, the glass can comprise greater than or equal to 0.00 mole % and less than or equal to 2.00 mole % BaO, greater than or equal to 0.00 mole % and less than or equal to 1.50 mole % BaO, greater than or equal to 0.00 mole % and less than or equal to 1.00 mole % BaO, greater than or equal to 0.00 mole % and less than or equal to 0.75 mole % BaO, greater than or equal to 0.00 mole % and less than or equal to 0.50 mole % BaO, or even greater than or equal to 0.00 mole % and less than or equal to 0.40 mole % BaO. In embodiments, the glass can comprise greater than or equal to 0.10 mole % and less than or equal to 2.00 mole % BaO, greater than or equal to 0.10 mole % and less than or equal to 1.50 mole % BaO, greater than or equal to 0.10 mole % and less than or equal to 1.00 mole % BaO, greater than or equal to 0.10 mole % and less than or equal to 0.75 mole % BaO, greater than or equal to 0.10 mole % and less than or equal to 0.50 mole % BaO, or even greater than or equal to 0.10 mole % and less than or equal to 0.40 mole % BaO. In embodiments, the glass is free of BaO. In embodiments, the glass is substantially free of BaO. The above ranges include all subranges between the explicit endpoints and ranges formed by any combination of the endpoints.

[0122] As described herein, the amounts of AI2O3, B2O3, alkali metal oxides, and alkaline earth metal oxides can be balanced to obtain a glass having a relatively high UV transmittance and a liquidus viscosity compatible with a fusion forming technique. In particular, it has been found that minimizing the amounts of K2O, Na2O, CaO, SrO, and BaO in the glass and exceeding the amounts of AI2O3 and B2O3 results in a glass having a relatively high UV transmittance and a liquidus viscosity compatible with a fusion forming process. In particular, it has been found that when AI2O3(mol%) + B2O3(mol%) - R2O(mol%) - CaO(mol%) - SrO(mol%) - BaO(mol%) is greater than or equal to -1.5 mol% and less than or equal to 40 mol% (where R2O is the sum of K2O(mol%) and Na2O(mol%)), the glass has a relatively high UV transmittance and a liquidus viscosity compatible with a fusion forming process. While not wishing to be bound by theory, it is believed that the amount of NBOs in the glass is significantly reduced when this relationship is satisfied, thereby increasing the UV transmittance of the glass.

[0123] In embodiments, AI2O3(mol%) + B2O3(mol%) - R2O(mol%) - CaO(mol%) - SrO(mol%) - BaO(mol%) is greater than or equal to -0.95 mol% and less than or equal to 40 mol%, greater than or equal to -0.75 mol% and less than or equal to 40 mol%, greater than or equal to -0.50 mol% and less than or equal to 40 mol%, greater than or equal to -0.25 mol% and less than or equal to 40 mol%, greater than or equal to 0.00 mol% and less than or equal to 40 mol%, greater than or equal to 0.50 mol% and less than or equal to 40 mol%, greater than or equal to 0.75 mol% and less than or equal to 40 mol%, greater than or equal to 1.00 mol% and less than or equal to 40 mol%, or even greater than or equal to 1.50 mol% and less than or equal to 40 mol%.

[0124] In embodiments, Al2O3(mol%) + B2O3(mol%) - R2O(mol%) - CaO(mol%) - SrO(mol%) - BaO(mol%) is greater than or equal to -1.5 mol%, greater than or equal to -0.95 mol%, greater than or equal to -0.75 mol%, greater than or equal to -0.50 mol%, greater than or equal to -0.25 mol%, greater than or equal to 0 mol%, greater than or equal to 0.50 mol%, greater than or equal to 0.75 mol%, greater than or equal to 1.00 mol%, or even greater than or equal to 1.50 mol%, and less than or equal to 35 mol%, less than or equal to 30 mol%, less than or equal to 25 mol%, less than or equal to 20 mol%, less than or equal to 15 mol%, less than or equal to 10 mol%, or even less than or equal to 5 mol%. The above ranges include all sub-ranges within the expressly disclosed ranges as well as ranges formed by any combination of the endpoints from the disclosed ranges.

[0125] It has also been discovered that when the ratio of (RO(mol%) + R2O(mol%)) to (Al2O3(mol%) + B2O3(mol%)) (i.e., (RO(mol%) + R2O(mol%)) : (Al2O3(mol%) + B2O3(mol%))) is less than 1.5, where RO is the sum of MgO(mol%), CaO(mol%), BaO(mol%), and SrO(mol%) in the glass, and R2O is the sum of K2O(mol%), Na2O(mol%), and Li2O(mol%) in the glass, glasses having relatively high UV transmittance and liquidus viscosities compatible with a fusion forming process can be obtained. In embodiments, the ratio of (RO(mol%) + R2O(mol%)) : (Al2O3(mol%) + B2O3(mol%)) in the glass is less than or equal to 1.25, less than or equal to 1.00, less than or equal to 0.75, less than or equal to 0.60, less than or equal to 0.50, or even less than or equal to 0.40.

[0126] In embodiments, the difference between R2O (mol%) and AI2O3 (mol%) in the glass (i.e., R2O (mol%) - AI2O3 (mol%)) is less than or equal to 9.00 mol%, where R2O is the sum of K2O (mol%), Na2O (mol%), and Li2O (mol%). Keeping this difference less than or equal to 9.00 mol% helps to minimize the amount of NBOs in the glass, which in turn helps to maintain a relatively high UV transmittance in the glass. In embodiments, R2O (mol%) - AI2O3 (mol%) is greater than or equal to -6.50 mol% and less than or equal to 9.00 mol%. In embodiments, R2O (mol%) - AI2O3 (mol%) is greater than or equal to -6.50 mol% and less than or equal to 0 mol%, greater than or equal to -6.00 mol% and less than or equal to 0.00 mol%, greater than or equal to -5.50 mol% and less than or equal to 0.00 mol%, greater than or equal to -5.00 mol% and less than or equal to 0.00 mol%, greater than or equal to -4.50 mol% and less than or equal to 0.00 mol%, greater than or equal to -4.00 mol% and less than or equal to 0.00 mol%, greater than or equal to -3.50 mol% and less than or equal to 0.00 mol%, greater than or equal to -3.00 mol% and less than or equal to 0.00 mol%, or even greater than or equal to -2.50 mol% and less than or equal to 0.00 mol%. In embodiments, R2O (mol%) - AI2O3 (mol%) is greater than or equal to 0.00 mol% and less than or equal to 9.00 mol%, greater than or equal to 0.00 mol% and less than or equal to 8.50 mol%, greater than or equal to 0.00 mol% and less than or equal to 8.00 mol%, greater than or equal to 0.00 mol% and less than or equal to 7.50 mol%, greater than or equal to 0.00 mol% and less than or equal to 7.00 mol%, greater than or equal to 0.00 mol% and less than or equal to 6.50 mol%, greater than or equal to 0.00 mol% and less than or equal to 6.00 mol%, greater than or equal to 0.00 mol% and less than or equal to 5.50 mol%, greater than or equal to 0.00 mol% and less than or equal to 5.00 mol%, greater than or equal to 0.00 mol% and less than or equal to 4.50 mol%, or even greater than or equal to 0.00 mol% and less than or equal to 4.00 mol%. The above ranges include all sub-ranges between the expressly disclosed ranges as well as ranges formed by any combination of the endpoints of the ranges.

[0127] In embodiments, the difference between R x O (mol%) and AI2O3 (mol%) in the glass (i.e., R x O (mol%) - AI2O3 (mol%)) is greater than or equal to 2 mol% and less than or equal to 10.00 mol%, where R xO (mol%) is the sum of R2O (mol%) and RO (mol%), RO is the sum of MgO (mol%), CaO (mol%), BaO (mol%), and SrO (mol%) in the glass, and R2O is the sum of K2O (mol%), Na2O (mol%), and Li2O (mol%) in the glass. Maintaining this difference greater than or equal to 2 mol% and less than or equal to 10.00 mol% helps to minimize the amount of NBO in the glass, which in turn helps to maintain a relatively high UV transmittance in the glass. In embodiments, R x O (mol%) - AI2O3 (mol%) is greater than or equal to 2 mol% and less than or equal to 9.5 mol%, greater than or equal to 2 mol% and less than or equal to 9.0 mol%, greater than or equal to 2 mol% and less than or equal to 8.5 mol%, greater than or equal to 2 mol% and less than or equal to 8.0 mol%, greater than or equal to 2 mol% and less than or equal to 7.5 mol%, greater than or equal to 2 mol% and less than or equal to 7.0 mol%, greater than or equal to 2 mol% and less than or equal to 6.5 mol%, greater than or equal to 2 mol% and less than or equal to 6.0 mol%, greater than or equal to 2 mol% and less than or equal to 5.5 mol%, or even greater than or equal to 2 mol% and less than or equal to 5.0 mol%. The above ranges include all sub-ranges within the expressly disclosed ranges as well as ranges formed by any combination of the endpoints from the recited ranges.

[0128] Embodiments of the glasses described herein can contain ZnO. However, the amount of ZnO in the glass should be minimized to avoid reducing the UV transmittance of the glass. In embodiments, the glass can include greater than or equal to 0.00 mole% and less than or equal to 5.00 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 4.50 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 4.00 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 3.50 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 3.00 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 2.50 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 2.00 mole% ZnO, greater than or equal to 0.00 mole% and less than or equal to 1.50 mole% ZnO, or even greater than or equal to 0.00 mole% and less than or equal to 1.00 mole% ZnO. In embodiments, the glass can include greater than or equal to 0.10 mole% and less than or equal to 5.00 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 4.50 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 4.00 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 3.50 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 3.00 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 2.50 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 2.00 mole% ZnO, greater than or equal to 0.10 mole% and less than or equal to 1.50 mole% ZnO, or even greater than or equal to 0.10 mole% and less than or equal to 1.00 mole% ZnO. In embodiments, the glass is free of ZnO. In embodiments, the glass is substantially free of ZnO. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0129] Embodiments of the glasses described herein can contain Sn02. The addition of Sn02may act as a fining agent to improve the quality of the glass by reducing defects in the glass, such as those formed from gases trapped in the glass. However, Sn02may act as a UV absorber. The addition of Sn02to the glass can also fluoresce under UV exposure, further reducing the UV transmittance of the glass. Thus, the amount of Sn02in the glass should be minimized to avoid reducing the UV transmittance of the glass.

[0130] In embodiments, the glass comprises greater than or equal to 0 mol % and less than or equal to 0.10 mol % Sn02, greater than or equal to 0 mol % and less than or equal to 0.05 mol % Sn02, greater than or equal to 0 mol % and less than or equal to 0.04 mol % Sn02, greater than or equal to 0 mol % and less than or equal to 0.03 mol % Sn02, greater than or equal to 0 mol % and less than or equal to 0.02 mol % Sn02, or even greater than or equal to 0 mol % and less than or equal to 0.01 mol % Sn02. In embodiments, the glass is free of Sn02. In embodiments, the glass is substantially free of Sn02. The above ranges include all sub-ranges between the explicit endpoints and ranges created by any combination of the endpoints.

[0131] Embodiments of the glasses described herein can contain As203, Sb203, and / or PbO. For example, the addition of As203and / or Sb203may act as a fining agent to improve the quality of the glass by reducing defects in the glass, such as those formed from gases trapped in the glass. The addition of PbO can lower the viscosity of the glass. However, As203, Sb203, and / or PbO can also lower the UV transmittance of the glass. Thus, the amount of As203, Sb203, and / or PbO in the glass should be minimized. In embodiments, the glass comprises greater than or equal to 0 mol % and less than or equal to 0.10 mol % As203+ Sb203+ PbO, greater than or equal to 0 mol % and less than or equal to 0.05 mol % As203+ Sb203+ PbO, greater than or equal to 0 mol % and less than or equal to 0.04 mol % As203+ Sb203+ PbO, greater than or equal to 0 mol % and less than or equal to 0.03 mol % As203+ Sb203+ PbO, greater than or equal to 0 mol % and less than or equal to 0.02 mol % As203+ Sb203+ PbO, or even greater than or equal to 0 mol % and less than or equal to 0.01 mol % As203+ Sb203+ PbO. In embodiments, the glass is free of As203, Sb203, and / or PbO. In embodiments, the glass is substantially free of As203, Sb203, and / or PbO. The above ranges include all sub-ranges between the explicit endpoints and ranges created by any combination of the endpoints.

[0132] Embodiments of the glasses described herein can contain Ti02. Ti02may be added to the glass to stabilize the glass network and improve the mechanical properties of the glass. However, the amount of Ti02added to the glass should be limited to avoid nucleation of crystalline phases in the glass. The addition of Ti02may also reduce the UV transmittance of the glass. In embodiments, the glass comprises greater than or equal to 0 mol.% and less than or equal to 0.50 mol.% Ti02, greater than or equal to 0 mol.% and less than or equal to 0.40 mol.% Ti02, greater than or equal to 0 mol.% and less than or equal to 0.30 mol.% Ti02, greater than or equal to 0 mol.% and less than or equal to 0.20 mol.% Ti02, or even greater than or equal to 0 mol.% and less than or equal to 0.10 mol.% Ti02. In embodiments, the glass is free of Ti02. In embodiments, the glass is substantially free of Ti02. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0133] Embodiments of the glasses described herein can contain Ce203. Ce203may be added to the glass to help reduce the amount of NBOs in the glass and prevent photodarkening of the glass. However, 3 + and 4 + Cerium ions in the +3 oxidation state can act as UV absorbers. Thus, the amount of Ce203in the glass should be minimized. In embodiments, the glass comprises greater than or equal to 0 mol.% and less than or equal to 0.10 mol.% Ce203, greater than or equal to 0 mol.% and less than or equal to 0.05 mol.% Ce203, greater than or equal to 0 mol.% and less than or equal to 0.04 mol.% Ce203, greater than or equal to 0 mol.% and less than or equal to 0.03 mol.% Ce203, greater than or equal to 0 mol.% and less than or equal to 0.02 mol.% Ce203, or even greater than or equal to 0 mol.% and less than or equal to 0.01 mol.% Ce203. In embodiments, the glass is free of Ce203. In embodiments, the glass is substantially free of Ce203. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0134] Embodiments of the glasses described herein can contain Fe203. However, the amount of Fe203in the glass should be minimized to avoid reducing the UV transmittance of the glass. In embodiments, the glass comprises greater than or equal to 0 mol % and less than or equal to 0.10 mol % Fe203, greater than or equal to 0 mol % and less than or equal to 0.05 mol % Fe203, greater than or equal to 0 mol % and less than or equal to 0.04 mol % Fe203, greater than or equal to 0 mol % and less than or equal to 0.03 mol % Fe203, greater than or equal to 0 mol % and less than or equal to 0.02 mol % Fe203, or even greater than or equal to 0 mol % and less than or equal to 0.01 mol % Fe203. In embodiments, the glass is free of Fe203. In embodiments, the glass is substantially free of Fe203. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0135] Embodiments of the glasses described herein can contain F - . F - may be included in the glass as a fining agent (i.e., to help reduce or prevent air bubbles entrapped in the glass melt). The addition of F - may also improve the UV transmittance of the glass. In embodiments, the glass can comprise greater than or equal to 0.00 mol % and less than or equal to 8.00 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 7.50 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 7.00 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 6.50 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 6.00 mol % F - , or even greater than or equal to 0.00 mol % and less than or equal to 5.50 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 5.00 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 4.50 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 4.00 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 3.50 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 3.00 mol % F - , greater than or equal to 0.00 mol % and less than or equal to 2.50 mol % F - , or even greater than or equal to 0.00 mol % and less than or equal to 2.00 mol % F -In embodiments, the glass can comprise greater than or equal to 0.10 mol.% and less than or equal to 8.00 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 7.50 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 7.00 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 6.50 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 6.00 mol.% F - or even greater than or equal to 0.10 mol.% and less than or equal to 5.50 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 5.00 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 4.50 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 4.00 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 3.50 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 3.00 mol.% F - greater than or equal to 0.10 mol.% and less than or equal to 2.50 mol.% F - or even greater than or equal to 0.10 mol.% and less than or equal to 2.00 mol.% F - In embodiments, the glass is free of F - In embodiments, the glass is substantially free of F - In embodiments, the glass is free of halogens. In embodiments, the glass is substantially free of halogens. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0136] In embodiments of the glasses described herein, the amount of water (H2O) in the glass is minimized as water increases the amount of NBOs in the glass. In embodiments, the glass can comprise greater than or equal to 0.00 mol.% and less than or equal to 1.00 mol.% H2O, greater than or equal to 0.00 mol.% and less than or equal to 0.75 mol.% H2O, greater than or equal to 0.00 mol.% and less than or equal to 0.50 mol.% H2O, or even greater than or equal to 0.00 mol.% and less than or equal to 0.25 mol.% H2O. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0137] The amount of H2O in the glass is proportional to the amount of hydroxyl (OH) groups in the glass, which, as described herein, is linearly proportional to the beta-OH value of the glass. Thus, the beta-OH value can generally be indicative of the amount of H2O in the glass. In embodiments described herein, the beta-OH value of the glass is greater than or equal to 0 / mm to less than or equal to 0.7 / mm or even greater than or equal to 0 / mm to less than or equal to 0.5 / mm.

[0138] Embodiments of the glasses described herein can contain BeO. However, the amount of BeO in the glass should be minimized because BeO can be toxic. In embodiments, the glass can include greater than or equal to 0.00 mole% and less than or equal to 4.00 mole% BeO, greater than or equal to 0.00 mole% and less than or equal to 3.50 mole% BeO, greater than or equal to 0.00 mole% and less than or equal to 3.00 mole% BeO, greater than or equal to 0.00 mole% and less than or equal to 2.50 mole% BeO, greater than or equal to 0.00 mole% and less than or equal to 2.00 mole% BeO, greater than or equal to 0.00 mole% and less than or equal to 1.50 mole% BeO, or even greater than or equal to 0.00 mole% and less than or equal to 1.00 mole% BeO. In embodiments, the glass can include greater than or equal to 0.10 mole% and less than or equal to 4.00 mole% BeO, greater than or equal to 0.10 mole% and less than or equal to 3.50 mole% BeO, greater than or equal to 0.10 mole% and less than or equal to 3.00 mole% BeO, greater than or equal to 0.10 mole% and less than or equal to 2.50 mole% BeO, greater than or equal to 0.10 mole% and less than or equal to 2.00 mole% BeO, greater than or equal to 0.10 mole% and less than or equal to 1.50 mole% BeO, or even greater than or equal to 0.10 mole% and less than or equal to 1.00 mole% BeO. In embodiments, the glass is free of BeO. In embodiments, the glass is substantially free of BeO. The ranges described above include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0139] Embodiments of the glasses described herein can contain Y2O3. However, the amount of Y2O3 in the glass should be minimized because Y2O3 undesirably lowers the liquidus viscosity of the glass. In embodiments, the glass can include greater than or equal to 0.00 mole% and less than or equal to 2.00 mole% Y2O3, greater than or equal to 0.00 mole% and less than or equal to 1.50 mole% Y2O3, greater than or equal to 0.00 mole% and less than or equal to 1.00 mole% Y2O3, or even greater than or equal to 0.00 mole% and less than or equal to 0.50 mole% Y2O3. In embodiments, the glass can include greater than or equal to 0.10 mole% and less than or equal to 2.00 mole% Y2O3, greater than or equal to 0.10 mole% and less than or equal to 1.50 mole% Y2O3, greater than or equal to 0.10 mole% and less than or equal to 1.00 mole% Y2O3, or even greater than or equal to 0.10 mole% and less than or equal to 0.50 mole% Y2O3. In embodiments, the glass is free of Y2O3. In embodiments, the glass is substantially free of Y2O3. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0140] Embodiments of the glasses described herein can contain ZrO2. ZrO2 can be added to the glass to improve the chemical durability of the glass and to consume NBOs. However, the addition of ZrO2 can act as a nucleating agent, causing the glass to undesirably crystallize. Therefore, the amount of ZrO2 added to the glass should be limited. In embodiments, the glass includes greater than or equal to 0 mole% and less than or equal to 0.50 mole% ZrO2, greater than or equal to 0 mole% and less than or equal to 0.40 mole% ZrO2, greater than or equal to 0 mole% and less than or equal to 0.30 mole% ZrO2, greater than or equal to 0 mole% and less than or equal to 0.20 mole% ZrO2, or even greater than or equal to 0 mole% and less than or equal to 0.10 mole% ZrO2. In embodiments, the glass is free of ZrO2. In embodiments, the glass is substantially free of ZrO2. The above ranges include all sub-ranges between the endpoints and ranges formed by any combination of the endpoints.

[0141] In embodiments, the glasses described herein can comprise: greater than or equal to 65.00 to less than or equal to 72.50 mol.% Si02; greater than or equal to 2.50 to less than or equal to 13.75 mol.% AI2O3; greater than or equal to 0.00 to less than or equal to 18.00 mol.% B203; greater than or equal to 0.00 to less than or equal to 6.00 mol.% MgO; greater than or equal to 0.00 to less than or equal to 15.00 mol.% Na20; greater than or equal to 3.10 to less than or equal to 7.50 mol.% K20; less than or equal to 1.00 mol.% Li20; less than or equal to 0.04 mol.% Sn02; less than or equal to 0.10 mol.% Ti02; less than or equal to 0.10 mol.% Fe203; less than or equal to 0.10 mol.% Ce203; less than or equal to 1 mol.% ZnO; and less than or equal to 2 mol.% F - wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of AI2O3 + B2O3 - R2O - CaO - SrO - BaO is greater than or equal to -0.75 mol.% and less than or equal to 40.00 mol.% where R2O is Na20 + K20 + Li20; the sum of Na20 + K20 is greater than or equal to 3.10 mol.% and less than or equal to 15.50 mol.%; and the sum of As203 + Sb203 + PbO is less than or equal to 0.01 mol.%.

[0142] In embodiments, the glasses described herein can comprise: greater than or equal to 65.00 to less than or equal to 72.50 mol.% Si02; greater than or equal to 2.50 to less than or equal to 13.75 mol.% AI2O3; greater than or equal to 0.00 to less than or equal to 17.00 mol.% B203; greater than or equal to 0.00 to less than or equal to 6.00 mol.% MgO; greater than or equal to 0.00 to less than or equal to 15.00 mol.% Na20; greater than or equal to 2.10 to less than or equal to 8.50 mol.% K20; less than or equal to 1.50 mol.% Li20; less than or equal to 0.01 mol.% Sn02; less than or equal to 0.10 mol.% Ti02; less than or equal to 0.10 mol.% Fe203; less than or equal to 1.50 mol.% ZnO; less than or equal to 0.40 mol.% BaO; less than or equal to 4.00 mol.% BeO; and less than or equal to 2 mol.% F -wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of Al2O3 + B2O3 - R2O - CaO - SrO - BaO is greater than or equal to -0.75 mole% and less than or equal to 40.00 mole%, wherein R2O is Na2O + K2O + Li2O; the sum of Na2O + K2O is greater than or equal to 2.10 mole% and less than or equal to 15.50 mole%; and the sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mole%.

[0143] In embodiments, the glasses described herein can comprise: greater than or equal to 65.00 mole% to less than or equal to 72.50 mole% SiO2; greater than or equal to 2.50 mole% to less than or equal to 20.00 mole% Al2O3; greater than or equal to 5.50 mole% to less than or equal to 18.00 mole% B2O3; greater than or equal to 0.00 mole% to less than or equal to 6.00 mole% MgO; greater than or equal to 0.00 mole% to less than or equal to 15.00 mole% Na2O; greater than or equal to 3.10 mole% to less than or equal to 7.50 mole% K2O; less than or equal to 1.00 mole% Li2O; less than or equal to 0.04 mole% SnO2; less than or equal to 0.10 mole% Fe2O3; less than or equal to 0.10 mole% Ce2O3; less than or equal to 1.50 mole% ZnO; less than or equal to 2.00 mole% F - wherein: the sum of Al2O3 + B2O3 - R2O - CaO - SrO - BaO is greater than or equal to -0.95 mole% and less than or equal to 40.00 mole%, wherein R2O is Na2O + K2O + Li2O; the sum of Na2O + K2O is greater than or equal to 3.10 mole% and less than or equal to 15.50 mole%; and the sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mole%.

[0144] In embodiments, the glasses described herein can comprise: greater than or equal to 65.00 to less than or equal to 72.50 mol.% Si02; greater than or equal to 5.00 to less than or equal to 13.75 mol.% AI2O3; greater than or equal to 0.00 to less than or equal to 21.00 mol.% B203; greater than or equal to 0.00 to less than or equal to 6.00 mol.% MgO; greater than or equal to 0.10 to less than or equal to 15.00 mol.% Na20; greater than or equal to 3.10 to less than or equal to 8.50 mol.% K20; less than or equal to 1.00 mol.% Li20; less than or equal to 0.01 mol.% Sn02; less than or equal to 0.10 mol.% Ti02; less than or equal to 0.10 mol.% Fe203; less than or equal to 1.00 mol.% ZnO; and less than or equal to 2.00 mol.% F - wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of AI2O3 + B2O3 - R2O - CaO - SrO - BaO is greater than or equal to -0.75 mol.% and less than or equal to 40.00 mol.% where R2O is Na20 + K20 + Li20; the sum of Na20 + K20 is greater than or equal to 2.10 mol.% and less than or equal to 15.50 mol.%; and the sum of As203 + Sb203 + PbO is less than or equal to 0.01 mol.%.

[0145] In embodiments, the glasses described herein can comprise: greater than or equal to 65.00 to less than or equal to 74.00 mol.% Si02; greater than or equal to 2.50 to less than or equal to 22.00 mol.% AI2O3; greater than or equal to 0.00 to less than or equal to 18.00 mol.% B203; greater than or equal to 0.00 to less than or equal to 7.50 mol.% MgO; greater than or equal to 0.00 to less than or equal to 15.00 mol.% Na20; greater than or equal to 3.10 to less than or equal to 7.50 mol.% K20; less than or equal to 0.04 mol.% Sn02; less than or equal to 0.50 mol.% Ti02; less than or equal to 0.10 mol.% Fe203; less than or equal to 1.50 mol.% ZnO; and less than or equal to 2 mol.% F -wherein: the sum of Al203+ B203- R20 - CaO - SrO - BaO is greater than or equal to 1.5 mole% and less than or equal to 40.00 mole%, wherein R20 is Na20 + K20 + Li20; the sum of Na20 + K20 is greater than or equal to 3.10 mole% and less than or equal to 15.50 mole%; the sum of MgO + CaO is greater than or equal to 0.10 mole% and less than or equal to 10.00 mole%; and the sum of As203+ Sb203+ PbO is less than or equal to 0.01 mole%.

[0146] In embodiments, the glasses described herein can comprise: greater than or equal to 65.50 mole% to less than or equal to 72.50 mole% Si02; greater than or equal to 2.50 mole% to less than or equal to 13.75 mole% Al203; greater than or equal to 0.00 mole% to less than or equal to 17.00 mole% B203; greater than or equal to 0.00 mole% to less than or equal to 6.00 mole% MgO; greater than or equal to 0.10 mole% to less than or equal to 15.00 mole% Na20; greater than or equal to 2.10 mole% to less than or equal to 8.50 mole% K20; less than or equal to 1.50 mole% Li20; less than or equal to 0.01 mole% Sn02; less than or equal to 0.10 mole% Ti02; less than or equal to 0.10 mole% Fe203; less than or equal to 1.50 mole% ZnO; less than or equal to 0.40 mole% BaO; less than or equal to 4.00 mole% BeO; and less than or equal to 8 mole% F - wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of Al203+ B203- R20 - CaO - SrO - BaO is greater than or equal to -0.75 mole% and less than or equal to 40.00 mole%, wherein R20 is Na20 + K20 + Li20; the sum of Na20 + K20 is greater than or equal to 2.10 mole% and less than or equal to 15.50 mole%; and the sum of As203+ Sb203+ PbO is less than or equal to 0.01 mole%.

[0147] In embodiments, the glasses described herein can comprise: greater than or equal to 65.50 mole% to less than or equal to 72.50 mole% Si02; greater than or equal to 3.00 mole% to less than or equal to 13.75 mole% AI2O3; greater than or equal to 0.00 mole% to less than or equal to 20.00 mole% B2O3; greater than or equal to 0.00 mole% to less than or equal to 6.00 mole% MgO; greater than or equal to 0.10 mole% to less than or equal to 15.00 mole% Na20; greater than or equal to 2.00 mole% to less than or equal to 8.50 mole% K2O; less than or equal to 1.25 mole% Li20; less than or equal to 0.05 mole% Sn02; less than or equal to 0.20 mole% Ti02; less than or equal to 0.10 mole% Fe203; less than or equal to 0.5 mole% Zr02; less than or equal to 5 mole% ZnO; and less than or equal to 0.75 mole% BaO; wherein: the glass has a beta-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; the sum of AI2O3 + B2O3 - R2O - CaO - SrO - BaO is greater than or equal to -1.50 mole% and less than or equal to 40.00 mole%, where R2O is Na20 + K2O + Li20; the sum of Na20 + K2O is greater than or equal to 2.10 mole% and less than or equal to 15.50 mole%; and the sum of As203 + Sb203 + PbO is less than or equal to 0.01 mole%.

[0148] In embodiments described herein, the glass can be formed from a batch composition that includes a reducing agent in addition to the aforementioned constituent components. Specifically, when the batch composition (and thus the resulting glass) also includes Fe 3+ ions, a reducing agent can be included in the batch composition, which Fe 3+ ions are from intentionally added iron (e.g., Fe203) or iron present as an impurity contaminant in other constituent components. In this regard, Fe 3+ is the most common contaminant in glass batches and strongly absorbs UV light, thereby reducing the UV transmittance of the glass. However, Fe 2+ absorbs more strongly in the near infrared portion of the spectrum and thus does not have the same deleterious effect on UV transmittance as Fe 3+ . Accordingly, one or more reducing agents can be added to the batch composition to facilitate the reduction of Fe 3+ in the batch to Fe 2+ . The reducing agent reduces the partial pressure of oxygen in the melt and converts Fe 3+ in the batch to Fe 2+In embodiments, the reducing agent can include, for example and without limitation, sugar, petroleum products (e.g., motor oil), graphite, and / or starch, each of which can introduce a carbon component into the batch composition to achieve reduction of Fe 3+ to Fe 2+ The amount of carbon from the reducing agent in the batch can be, for example and without limitation, less than or equal to 0.10 mole %, less than or equal to 0.05 mole %, less than or equal to 0.04 mole %, less than or equal to 0.03 mole %, or even less than or equal to 0.02 mole %. In embodiments, the batch is substantially free of carbon, for example when no reducing agent is added to the batch composition. In embodiments, the batch composition does not include carbon.

[0149] While carbon can be present in the batch composition used to form the glasses described herein, the carbon is burned off or otherwise consumed during the glass manufacturing process, and thus is not present in the final glass article (i.e., carbon is not present in the glass, glass substrate, glass article, etc.).

[0150] In embodiments, the glasses disclosed herein have a relatively high liquidus viscosity, which facilitates forming the glasses into large glass sheets using a fusion forming process. For example, in embodiments, the glass has a liquidus viscosity greater than or equal to 10,000 Pascal*seconds (100 kilopoise (kP)), greater than or equal to 11,000 Pascal*seconds (110 kP), greater than or equal to 12,000 Pascal*seconds (120 kP), greater than or equal to 12,500 Pascal*seconds (125 kP), greater than or equal to 13,000 Pascal*seconds (130 kP), greater than or equal to 13,500 Pascal*seconds (135 kP), greater than or equal to 14,000 Pascal*seconds (140 kP), greater than or equal to 14,500 Pascal*seconds (145 kP), or even greater than or equal to 15,000 Pascal*seconds (150 kP). In embodiments, the glass has a liquidus viscosity greater than or equal to 10,000 Pascal*seconds (100 kP), greater than or equal to 11,000 Pascal*seconds (110 kP), greater than or equal to 12,000 Pascal*seconds (120 kP), greater than or equal to 12,500 Pascal*seconds (125 kP), greater than or equal to 13,000 Pascal*seconds (130 kP), greater than or equal to 13,500 Pascal*seconds (135 kP), greater than or equal to 14,000 Pascal*seconds (140 kP), greater than or equal to 14,500 Pascal*seconds (145 kP), greater than or equal to 15,000 Pascal*seconds (150 kP), greater than or equal to 16,000 Pascal*seconds (160 kP), greater than or equal to 17,000 Pascal*seconds (170 kP), greater than or equal to 18,000 Pascal*seconds (180 kP), greater than or equal to 19,000 Pascal*seconds (190 kP), or even greater than or equal to 20,000 Pascal*seconds (200 kP), and less than or equal to 50,000,000 Pascal*seconds (500000 kP), less than or equal to 20,000,000 Pascal*seconds (200000 kP), less than or equal to 10,000,000 Pascal*seconds (100000 kP), less than or equal to 5,000,000 Pascal*seconds (50000 kP), less than or equal to 2,000,000 Pascal*seconds (20000 kP), less than or equal to 1,000,000 Pascal*seconds (10000 kP), less than or equal to 500,000 Pascal*seconds (5000 kP), less than or equal to 200,000 Pascal*seconds (2000 kP), or even less than or equal to 100,000 Pascal*seconds (1000 kP). The above ranges include all sub-ranges within the explicitly disclosed ranges and ranges formed by any combination of the endpoints of the ranges.

[0151] In embodiments, the 35 kPa (3500 Pascals per second) temperature of the glass, as measured according to ASTM C965-96 (2017), can be greater than or equal to 900°C and less than or equal to 1500°C, making the glass compatible with melt-forming processes. In embodiments, the 35 kPa temperature can be greater than or equal to 950°C and less than or equal to 1400°C, greater than or equal to 1000°C and less than or equal to 1350°C, or even greater than or equal to 1050°C and less than or equal to 1300°C. The above ranges include all sub-ranges within the explicitly disclosed range and ranges formed by any combination of their endpoints.

[0152] In the embodiments, the annealing point of the glass described herein may be greater than or equal to 400°C or even greater than or equal to 500°C, making the glass suitable for high-temperature processes.

[0153] The glass described herein has a relatively high UV transmittance, characterized by its transmittance at a wavelength of 248 nm. In an embodiment, a glass sheet formed from the glass described herein and having a thickness of 1 mm has a transmittance greater than 50% at a wavelength of 248 nm in its original formed state. The phrase "original formed state" means that the transmittance of the glass is measured on a glass substrate of a specified thickness that has not previously been exposed to UV light (other than ambient UV light). In an embodiment, in its original formed state, the transmittance of the 1 mm thick glass at a wavelength of 248 nm is greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, or even greater than or equal to 85%.

[0154] Furthermore, the glass described herein did not exhibit significant darkening after initial UV exposure. That is, the UV transmittance of the glass remained relatively high after initial exposure to UV light at a wavelength of 248 nm. In fact, in some embodiments, the UV transmittance of the glass may actually increase after initial exposure to UV light at a wavelength of 248 nm. In an embodiment, a glass plate formed from the glass described herein and with a thickness of 1 mm exhibited a transmittance greater than 50% at a wavelength of 248 nm after initial UV exposure. The phrase "after initial UV exposure" indicates that the transmittance of the glass was measured on a glass substrate of the stated thickness, which had previously been exposed to 3000 UV light pulses at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy greater than or equal to 110 mJ / pulse and less than or equal to 120 mJ / pulse, with a pulse repetition rate of 10 Hz. In the embodiments, after initial UV exposure, the transmittance of a 1 mm thick glass at a wavelength of 248 nm is greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, or even greater than or equal to 85%.

[0155] In embodiments, the change in transmittance after the initial UV exposure is greater than or equal to -10% and less than or equal to 15%, such as greater than or equal to -10% and less than or equal to 12%, greater than or equal to -10% and less than or equal to 10%, greater than or equal to -8% and less than or equal to 8%, or even greater than or equal to -5% and less than or equal to 5%. The above ranges include all sub-ranges within the expressly disclosed ranges and ranges formed by any combination of the endpoints of the ranges.

[0156] The UV cut-off wavelength is the wavelength at which the transmittance of the glass decreases to less than 50%. In embodiments described herein, the UV cut-off wavelength of the glass is less than or equal to 240 nm or even less than or equal to 225 nm.

[0157] In embodiments, the UV cut-off wavelength after the initial UV exposure is less than or equal to 240 nm or even less than or equal to 225 nm.

[0158] In embodiments, the change in UV cut-off wavelength from the as-formed state to after the initial UV exposure is less than 10 nm and greater than or equal to -20 nm.

[0159] As described herein, certain constituent components can be added to the glass to increase the coefficient of thermal expansion (CTE). For example, when a glass substrate formed from the glasses described herein is used to facilitate photolithography on a silicon substrate during microchip manufacturing, it can be desirable to make the CTE of the glass substrate more closely match the CTE of the silicon substrate that is subjected to the photolithography process to improve the performance of the process.

[0160] The average CTE of the glasses described herein over a temperature range of 0°C to 300°C can be greater than or equal to 50 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C. In embodiments, the average CTE of the glasses described herein over a temperature range of 0°C to 300°C can be greater than or equal to 55 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C, greater than or equal to 60 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C, greater than or equal to 65 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C, or even greater than or equal to 70 x 10 -7 / °C and less than or equal to 75 x 10 -7 / °C. In embodiments, the average CTE of the glasses described herein over a temperature range of 0°C to 300°C can be greater than or equal to 50 x 10 -7 / °C and less than or equal to 70 x 10 -7greater than or equal to 50 x 10 -7 greater than or equal to 50 x 10 -7 greater than or equal to 50 x 10 -7 greater than or equal to 50 x 10 -7 greater than or equal to 50 x 10 -7 greater than or equal to 50 x 10 -7 greater than or equal to 50 x 10 The above ranges include all sub-ranges within the expressly disclosed ranges as well as ranges created from any combination of the endpoints of the ranges.

[0161] In embodiments, the glasses described herein can have chemical durability. In particular, glass substrates formed from the glasses described herein can be used in manufacturing processes, such as photolithography processes, in which the glass substrates can be reused. To facilitate reuse, the glass substrates are cleaned, such as washed, between each use to remove residues of deposited materials from the previous use. Thus, the glass substrates should have sufficient chemical durability to withstand multiple cycles of use and cleaning without physical and optical degradation. In particular, as used herein, the phrase "chemical durability" means that the glass substrate has minimal weight loss and minimal loss of UV transmission after a specified cleaning cycle in an acid solution. In embodiments, the glass substrates described herein are considered to have "chemical durability" if they exhibit a weight loss of less than 0.01 mg / cm 2 and a UV transmission of greater than 50% after being cleaned in a 37 wt% aqueous HC1 solution at a temperature of 50 °C for 15 minutes. In embodiments, the glass substrates described herein are considered to have "chemical durability" if they exhibit a weight loss of less than 0.005 mg / cm 2 and a UV transmission of greater than 50% after being cleaned in a 37 wt% aqueous HC1 solution at a temperature of 50 °C for 15 minutes.

[0162] The glasses described herein are formed by and / or can be formed by conventional down-draw processes, such as slot draw processes and fusion draw processes. However, if desired, the glass materials described herein can be prepared using any other method known in the art, such as by using a crucible melting method.

[0163] In embodiments, the glasses described herein can be formed by a down-draw process. Down-draw processes produce glass materials having a uniform thickness with relatively pristine surfaces. Because the average flexural strength of a glass material is at least partially controlled by the amount and size of surface flaws, the pristine surfaces, which have minimal contact with other objects (e.g., forming equipment or portions of forming equipment), have a higher initial strength. In addition, down-drawn glasses have very flat, smooth surfaces that can be used in the as-formed state without the need for additional (and costly) post-forming steps, such as grinding and polishing. If desired, however, additional grinding and / or polishing can be employed for certain applications.

[0164] A fusion forming process is an industrial technique that has been used to mass produce thin glass sheets. In comparison to other flat glass manufacturing techniques, such as the float or slot draw processes, the fusion draw process produces thin glass sheets having superior flatness and surface quality. As a result, the fusion forming process has become the primary manufacturing technique for making thin glass substrates for liquid crystal displays as well as cover glasses for personal electronic devices, such as notebook computers, entertainment devices, tablets, laptops, smart phones, and the like.

[0165] For example, the glasses described herein can be formed using a fusion forming process (i.e., the glasses are fusion formable). A conventional fusion forming process uses a draw container having a channel for receiving a molten glass feedstock. The channel has a weir that opens at the top along the length of the channel on both sides of the channel. When the channel is filled with molten material, the molten glass overflows the weir. Due to gravity, the molten glass flows down the outer surfaces of the draw container forming two layers of flowing glass films. These outer surfaces of the draw container extend downward and inward such that they join at an edge below the draw container. The two layers of flowing glass films join at this edge, fuse, and form a single layer of flowing glass material. The fusion forming process provides the advantage that neither outer surface of the resulting glass will come into contact with any portion of the equipment because the two layers of glass films flowing through the channel fuse together. As a result of the lack of contact, the outer surfaces of the fusion drawn glass material are generally considered to be smooth and flat and can often be used without additional post-forming processing, such as grinding or polishing.

[0166] In some aspects, the glasses described herein can be formed by a slot draw process. A slot draw process is different from a fusion draw method. In a slot draw process, a molten feedstock glass is provided to a draw tank. The bottom of the draw tank has an open slot with a nozzle extending along the length of the slot. The molten glass flows through the slot / nozzle and is drawn downward as a continuous glass material and into an annealing region.

[0167] The glasses or articles thereof can be characterized by their manner of forming. For example, the glasses or articles thereof can be characterized as floatable (i.e., formed by a float process), down-drawable, particularly melt-formable, or slot-drawable (i.e., formed by a down-draw process such as a melt forming process or a slot draw process). To be melt-formable, the glass should have a sufficiently high liquidus viscosity, as described herein.

[0168] In embodiments, the glasses described herein can be formed into glass substrates by a down-draw process, such as a melt forming process. The resulting glass substrates can have a planar dimension (i.e., the length and width of the glass substrate) that is greater than the thickness of the glass substrate. Glass substrates having a relatively high UV transmittance, as described herein, can be used in various applications, including but not limited to as carrier substrates used in conjunction with photolithographic applications.

[0169] Examples

[0170] The embodiments described herein will be further clarified by the following examples.

[0171] Examples A-EE

[0172] The compositions listed in Tables 1A, 2A, 3A, and 4A were melted and formed into glass substrates having a thickness of about 1 mm. The glasses were measured for liquidus viscosity, liquidus temperature, 35 kP temperature, strain point, anneal point, and softening point in accordance with the test procedures described herein. During the measurement, the liquidus temperature was measured at the interface between the glass and the platinum boat that housed the glass. The glasses were also measured for density, average coefficient of thermal expansion (CTE) over the temperature range of 0 °C to 300 °C, UV transmittance before initial UV exposure, UV transmittance after initial UV exposure, UV cutoff wavelength before initial UV exposure, and UV cutoff wavelength after initial UV exposure, as also described herein. Initial UV exposure, as described herein, included exposing the glass substrate to 3000 UV light pulses from an excimer laser at a wavelength of 248 nm, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse, and a pulse repetition rate of 10 Hz. The measured properties are reported in Tables 1B, 2B, 3B, and 4B. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.); however, some errors and deviations can have occurred. The compositions themselves are given by weight in mol % on an oxide basis. Any exemplary compositions that do not sum to 100 mol % should be normalized to 100 mol % following standard and accepted practices in the glass chemistry art.

[0173] Table 1A

[0174] Mol % A B C D E F G H I SiO2 71.8 71.8 71.8 71.8 71.8 71.8 67.8 71.8 71.8 Al2O3 3.48 3.48 3.48 3.48 3.48 3.48 4.48 3.48 3.48 B2O3 18 16 16 16 16 16 17 16 16 Na2F2 2.56 2.56 2.56 0 0 0 0 1.75 1.75 Na2O 0 0 2 4.56 4.56 4.56 5.56 2.81 2.81 [K2F2] 1.7 1.7 1.7 1.7 0 0 0 K2O 2 4 2 2 3.7 3.7 4.7 3.7 3.7 MgO CaF2 0.45 0.45 0.45 0 0 0 0 CaO 0 0 0 0.45 0.45 0.45 0.45 0.45 0.45 SrO [Y2O3] s* 10.48 15.48 15.48 12.47 10.77 10.77 10.77 12.52 12.52 t** 0.51 0.21 0.21 0.36 0.45 0.45 0.50 0.36 0.36 [R2O-Al2O3] 2.78 4.78 4.78 4.78 4.78 4.78 5.78 4.78 4.78 [R x O-Al2O3]]> 3.23 5.23 5.23 5.23 5.23 5.23 6.23 5.23 5.23

[0175] * s = AI2O3 + B2O3 - R2O - CaO - SrO - BaO

[0176] **t = (RO + R20) : (Al203 + B203) Table IB

[0177]

[0178] Table 2A

[0179] Mol % J K L M N O P Q SiO2 70.8 69.8 67.8 69.8 70.65 70.65 70.65 70.65 Al2O3 3.48 3.48 5.48 5.48 3.48 3.48 3.48 3.48 B2O3 15 14 14 12 14.85 14.85 14.85 14.85 Na2F2 1.75 1.75 1.75 1.75 1.75 1.75 1.75 0 Na2O 3.81 4.81 4.81 4.81 3.96 3.96 3.96 5.71 [K2F2] K2O 4.7 5.7 5.7 5.7 4.85 4.85 4.85 4.85 MgO CaF2 CaO 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 SrO [Y2O3] s* 9.52 6.52 8.52 6.52 9.07 9.07 9.07 7.32 t** 0.48 0.63 0.56 0.64 0.51 0.51 0.51 0.60 [R2O-Al2O3] 6.78 8.78 6.78 6.78 7.08 7.08 7.08 7.08 [R x O-Al2O3]]> 7.23 9.23 7.23 7.23 7.53 7.53 7.53 7.53

[0180] *s = Al203 + B203 - R20 - CaO - SrO - BaO **t = (RO + R20) : (Al203 + B203) Table 2B

[0181]

[0182] Table 3A

[0183] Mol % R S T U V W X Y Z SiO2 68.65 68.65 68.65 66.65 66.65 68.65 66.65 68.65 71.37 Al2O3 5.48 3.48 5.48 7.48 5.48 5.48 5.48 5.48 12.15 B2O3 14.85 16.85 14.85 14.85 16.85 14.85 14.85 14.85 0 Na2F2 0 0 Na2O 5.71 5.71 5.71 5.71 5.71 5.71 5.71 5.71 2.8 [K2F2] K2O 4.85 4.85 4.85 4.85 4.85 4.85 4.85 4.85 4.41 MgO 4.3 CaF2 CaO 0.45 0.45 0.45 0.45 0.45 0 0.45 0.45 4.97 SrO 0 0 0 0.45 0 0 [Y2O3] 0 0 0 0 2 0 9.32 9.32 10.56 10.56 10.56 10.56 10.56 10.56 7.21 s* 0.54 0.54 9.32 11.32 11.32 9.32 9.32 9.32 -0.03 t** 5.08 7.08 0.54 0.49 0.49 0.54 0.54 0.54 1.36 [R2O-Al2O3] 5.53 7.53 5.08 3.08 5.08 5.08 5.08 5.08 -4.94 [R x O-Al2O3]]> R S 5.53 3.53 5.53 5.53 5.53 5.53 4.33

[0184] *s = Al203 + B203 - R20 - CaO - SrO - BaO **t = (RO + R20) : (Al203 + B203) Table 3B

[0185]

[0186] Table 4A

[0187] Mol % AA BB CC DD EE SiO2 70.27 68.97 69.6 68.95 69.02 Al2O3 11.8 11.96 9.25 12 11.95 B2O3 3.18 2.54 6.03 4.54 4.54 Na2F2 Na2O 1.88 2.8 0 2.79 3.8 [K2F2] K2O 3.81 5.42 5.67 5.36 4.41 MgO 4.03 3.76 4.13 2.81 2.78 CaF2 CaO 5.04 4.51 5.27 3.5 3.46 SrO [Y2O3] 5.69 8.22 5.67 8.15 8.21 s* 4.25 1.77 4.34 4.89 4.82 t** 0.99 1.14 0.99 0.87 0.88 [R2O-Al2O3] -6.11 -3.74 -3.58 -3.85 -3.74 [R x O-Al2O3]]> 2.96 4.53 5.82 2.46 2.5

[0188] *s = Al203 + B203 - R20 - CaO - SrO - BaO **t = (RO + R20) : (Al203 + B203)

[0189] Table 4B

[0190]

[0191] As shown in Tables IB, 2B, 3B, and 4B, the glasses of Examples A-EE all exhibited UV transmittance at 248 nm wavelength of greater than 50% at initial UV exposure, with some of the glasses exhibiting UV transmittance at 248 nm wavelength of greater than 80% at initial UV exposure (e.g., Examples Z and AA). Further, the glasses of Examples A-EE all exhibited UV transmittance at 248 nm wavelength of greater than 50% after initial UV exposure, with some of the glasses exhibiting UV transmittance at 248 nm wavelength of greater than 80% after initial UV exposure (e.g., Examples Z and AA). As evidenced by the data in the tables, the UV transmittance at 248 nm wavelength of some of the examples actually increased after initial UV exposure.

[0192] Reference is now made toFigure 1 and 2 For examples Z and AA, the UV transmittance at initial UV exposure ( Figure 1 Plotting the UV transmittance as a function of wavelength and then plotting the UV transmittance after initial UV exposure ( Figure 2 Plot it as a function of wavelength. For example... Figure 1 and 2 As shown, Examples Z and AA each exhibited UV transmittance greater than 80% at 248 nm wavelength both during and after initial UV exposure. Figure 1 and 2 It also shows that the UV transmittance of Example Z at a wavelength of 248 nm actually increases slightly after initial UV exposure.

[0193] Furthermore, Tables 1B, 2B, 3B, and 4B demonstrate that glasses with UV transmittance greater than 50% can also have a liquidus viscosity greater than 10,000 Pascals per second (100 kP) both during and after initial UV exposure at 248 nm wavelength, making them compatible with melt-forming processes. For example, Examples Z and AA each exhibit liquidus viscosities greater than 10,000 Pascals per second (100 kP) (e.g., 24,800 Pascals per second (248 kP) and 15,300 Pascals per second (153 kP), respectively), making them compatible with melt-forming processes.

[0194] Comparative Example 1

[0195] Figure 3 The figure illustrates the UV transmittance (y-axis) versus wavelength (x-axis) of a conventional glass substrate with a liquidus viscosity compatible with melt-forming processes. The conventional glass substrate is formed from commercially available glass comprising 67.57 mol% SiO2, 11.03 mol% Al2O3, 9.69 mol% B2O3, 2.29 mol% MgO, 8.76 mol% CaO, 0.5 mol% SrO, 0.01 mol% BaO, and 0.08 mol% SnO2. The substrate thickness is 0.3 mm.

[0196] like Figure 3 As shown, for UV light wavelengths of approximately 250 nm to 256 nm, the UV transmittance of a 0.3 mm thick glass substrate is less than 50%. While it is undesirable to be bound by theory, it is believed that UV transmittance will further decrease as the substrate thickness increases to 1.0 mm. Therefore, although the glass substrate has a liquidus viscosity that can be formed by melt-forming processes, its UV transmittance may be too low for applications requiring relatively high UV transmittance.

[0197] Chemical durability

[0198] A glass substrate formed from the glass of Example AA was evaluated for chemical durability. Specifically, a glass substrate was formed from the composition of Example AA having the dimensions, surface area, and initial weight as shown in Table 5.

[0199] Table 5

[0200] Glass Thickness (cm) Width (cm) Length (cm) Surface area (cm 2 )]]> Initial Weight (g) Example AA-1 0.244 2.544 5.091 29.6 7.64395 Example AA-2 0.244 2.544 5.081 29.6 7.65601

[0201] The substrate was initially rinsed in 16 MΩ water for five minutes and placed in an ultrasonic cleaner in a 4 wt% Semiclean cleaner and water solution at a temperature of 60-65 °C for 1 minute. Thereafter, the substrate was again rinsed in 16 MΩ water for five minutes, followed by a final rinse in 18 MΩ water for five minutes. The substrate was then dried on a stainless steel tray at 110 °C for one hour and placed in a desiccator until testing.

[0202] Prior to exposure to the cleaning regimen, the UV transmittance of the substrate at 250 nm was first measured. Thereafter, the substrate was placed in 500 ml of concentrated HC1 (37 wt% HC1 aqueous solution) and heated to about 50 °C for 15 minutes. The glass substrate was then rinsed with 16 MΩ water, placed on a stainless steel tray, and dried at 110 °C for at least 30 minutes. The glass substrate was then re- weighed and the UV transmittance of the substrate at 250 nm was again measured. The results are reported in Table 6. Thereafter, the substrate was exposed to 3000 UV light pulses from an excimer laser at a wavelength of 248 nm, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse at a pulse repetition rate of 10 Hz. The absolute change in UV transmittance of the substrate at 250 nm after exposure (i.e., |ΔUV(%)|) was determined to be less than 5%. Based on the weight loss per unit area and the transmittance after exposure to the cleaning regimen, the substrate was determined to have chemical durability.

[0203] Table 6

[0204]

[0205] It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modifications and variations come within the scope of the appended claims and their equivalents.

Claims

1. A glass, based on oxides, comprising: SiO2 with a content greater than or equal to 65.00 mol% and less than or equal to 72.50 mol%; Al2O3 with a content greater than or equal to 2.50 mol% to less than or equal to 13.75 mol%; B2O3 with a content greater than or equal to 0.00 mol% and less than or equal to 18.00 mol%; MgO with a content greater than or equal to 0.00 mol% and less than or equal to 6.00 mol%; Greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% of Na2O; K₂O concentrations greater than or equal to 2.10 mol% and less than or equal to 8.50 mol%; Each less than or equal to 1.50 mol% of Li₂O and ZnO; SnO2 less than or equal to 0.04 mol%; Each of TiO2, Fe2O3, and Ce2O3 is less than or equal to 0.10 mol%; and Less than or equal to 2 mol% of F - ,in: The β-OH value of the glass is greater than or equal to 0 / mm and less than or equal to 0.7 / mm; The sum of Al2O3+B2O3-R2O-CaO-SrO-BaO is greater than or equal to -1.5 mol% and less than or equal to 40.00 mol%, where R2O is the sum of Na2O+K2O+Li2O; The total amount of Na₂O + K₂O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and The total amount of As₂O₃ + Sb₂O₃ + PbO is less than or equal to 0.01 mol%.

2. The glass according to claim 1, comprising 12.00 mol% to 18.00 mol% of B2O3.

3. The glass according to claim 1, comprising: B2O3 with a content greater than or equal to 0.00 mol% and less than or equal to 17.00 mol%; SnO2 less than or equal to 0.01 mol%; BaO less than or equal to 0.40 mol%; and Less than or equal to 4.00 mol% of BeO.

4. The glass according to any one of claims 1 to 3, comprising more than or equal to 2.00 mol% to less than or equal to 10.00 mol% of Na2O.

5. The glass according to any one of claims 1 to 4, comprising more than or equal to 3.10 mol% to less than or equal to 7.00 mol% of K2O.

6. The glass according to any one of claims 1 to 4, comprising: K₂O concentrations greater than or equal to 3.10 mol% and less than or equal to 7.50 mol%; Each less than or equal to 1.00 mol% of Li₂O and ZnO; The total concentration of Na₂O + K₂O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and The sum of Al2O3+B2O3-R2O-CaO-SrO-BaO is greater than or equal to -0.75 mol% and less than or equal to 40.00 mol%.

7. The glass according to any one of claims 1 to 6, comprising MgO at a concentration greater than or equal to 1.00 mol% to less than or equal to 6.00 mol%.

8. The glass according to any one of claims 1 to 7, comprising more than or equal to 0.20 mol% to less than or equal to 6.00 mol% of CaO.

9. The glass according to any one of claims 1 to 8, comprising more than or equal to 0.10 mol% to less than or equal to 1.50 mol% of SrO.

10. The glass according to any one of claims 1 to 9, wherein R2O-Al2O3 is less than or equal to 9.00 mol%.

11. The glass according to claim 10, wherein R2O-Al2O3 is less than or equal to 0.00 mol% and greater than or equal to -6.

50.

12. The glass according to any one of claims 1 to 11, comprising: Less than or equal to 0.5 mol% of ZrO2; Less than or equal to 5 mol% ZnO; and BaO less than or equal to 0.75 mol%.

13. The glass according to any one of claims 1 to 12, wherein R x O-Al2O3 is greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, where R x O is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO.

14. The glass according to any one of claims 1 to 13, wherein the ratio of (RO+R2O):(Al2O3+B2O3) is less than 1.5, wherein RO is the sum of MgO+CaO+BaO+SrO.

15. The glass according to any one of claims 1 to 14, wherein the glass has a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm in its as-formed condition.

16. The glass of claim 15, wherein the transmittance is greater than or equal to 70%.

17. The glass of claim 15, wherein the transmittance is greater than or equal to 80%.

18. The glass according to any one of claims 1 to 17, wherein the glass, after being exposed to 3000 UV light pulses of wavelength 248 nm from an excimer laser, has a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm, wherein the pulse energy of each pulse is greater than or equal to 110 mJ / pulse and less than or equal to 120 mJ / pulse, and the pulse repetition rate is 10 Hz.

19. The glass of claim 18, wherein the transmittance is greater than or equal to 60%.

20. The glass of claim 18, wherein the transmittance is greater than or equal to 70%.

21. The glass according to any one of claims 1 to 20, wherein the glass has an average coefficient of thermal expansion from 0°C to 300°C greater than or equal to 50 × 10⁻⁶. -7 / ℃ and less than or equal to 75×10 -7 / ℃.

22. The glass according to any one of claims 1 to 21, wherein the liquidus viscosity of the glass is greater than or equal to 10,000 Pascals per second.

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