Alkali-containing, fusion formable glasses for high UV transmission

Abstract

An alkali-containing, fusion formable glass with high UV transmission may include on an oxide basis: ≥ 65.00 mol% to ≤ 72.50 mol% SiO2; ≥ 2.50 mol% to ≤ 13.75 mol% Al2O3; ≥ 0.00 mol% to ≤ 18.00 mol% B2O3; ≥ 0.00 mol% to ≤ 6.00 mol% MgO; ≥ 0.00 mol% to ≤ 15.00 mol% Na2O; ≥ 3.10 mol% to ≤ 7.50 mol% K2O; ≤ 1.00 mol% of each of Li2O and ZnO; ≤ 0.04 mol% SnO2; ≤ 0.10 mol% of each of TiO2, Fe2O3, and Ce2O3; and ≤ 2 mol% F-. A sum of Al2O3 + B2O3 – R2O – CaO – SrO – BaO is ≥ -0.75 mol% and ≤ 40.00 mol%, where R2O is the sum of Na2O + K2O + Li2O. A sum of Na2O + K2O is ≥ 3.10 mol% and ≤ 15.50 mol%. A sum of As2O3 + Sb2O3 + PbO is ≤ 0.01 mol%.

Description

SP24-184 ALKALI-CONTAINING, FUSION FORMABLE GLASSES FOR HIGH UVTRANSMISSION Cross Reference to Related Application

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S.Provisional Application Serial No. 63 / 672830, filed on July 18, 2024, the content of which is relied upon and incorporated herein by reference in its entirety. Field

[0002] The present specification generally relates to glasses with relatively high UVtransmission and, more particularly, alkali-containing glasses with high UV transmission that are fusion formable. Technical Background

[0003] Optical properties of glasses dictate their usefulness for many applications, such asphotolithographic steps for microchip fabrication in which ultraviolet (UV) light may be transmitted through a glass substrate. Other characteristics of glasses influence their manufacturability and cost. For example, while fused silica is highly transparent to UV, fused silica is expensive and it is difficult to form wide sheets of fused silica. Fusion forming processes, for example, enable large-scale manufacturing of wide sheets of glass. However, typical glasses formed by fusion forming have poor UV transmission characteristics.

[0004] Accordingly, a need exists for alternative glasses with relatively high UVtransmission that are also fusion formable. SUMMARY

[0005] Provided herein are alkali-containing glasses, alkali-containing glass articles, andsheets of alkali-containing glasses having a high deep UV transmission, such as greater than 50% or even greater than 60% at wavelengths of 248 nm. The glasses also have liquidus viscosities such that the glasses are compatible fusion forming processes.SP24-184

[0006] According to a first aspect A1, A glass comprises, on an oxide basis: greater than orequal to 65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 18.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 3.10 mol% to less than or equal to 7.50 mol% K2O; less than or equal to 1.00 mol% of each of Li2O and ZnO; less than or equal to 0.04 mol% SnO2; less than or equal to 0.10 mol% of each of TiO2, Fe2O3, and Ce2O3; and less than or equal to 2 mol% F-, wherein: the glass comprises a β-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a 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%, where R2O is the sum of Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 3.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

[0007] A second aspect A2 includes the glass of aspect A1, comprising greater than or equalto 12.00 mol% to less than or equal to 18.00 mol% B2O3.

[0008] A third aspect A3 includes the glass of any preceding aspect, comprising greater thanor equal to 2.00 mol% to less than or equal to 10.00 mol% Na2O.

[0009] A fourth aspect A4 includes the glass of any preceding aspect, comprising greaterthan or equal to 3.10 mol% to less than or equal to 7.00 mol% K2O.

[0010] A fifth aspect A5 includes the glass of any preceding aspect, comprising greater thanor equal to 1.00 mol% to less than or equal to 6.00 mol% MgO.

[0011] A sixth aspect A6 includes the glass of any preceding aspect, comprising greater thanor equal to 0.20 mol% to less than or equal to 6.00 mol% CaO.

[0012] A seventh aspect A7 includes the glass of any preceding aspect, comprising greaterthan or equal to 0.10 mol% to less than or equal to 1.50 mol% SrO.

[0013] An eighth aspect A8 includes the glass of any preceding aspect, wherein R2O – Al2O3is less than or equal to 9.00 mol%.SP24-184

[0014] A ninth aspect A9 includes the glass of aspect A8, wherein R2O – Al2O3 is less thanor equal to 0.00 mol% and greater than or equal to –6.50.

[0015] A tenth aspect A10 includes the glass of aspect A8, wherein R2O – Al2O3 is greaterthan 0.00 mol%.

[0016] An eleventh aspect A11 includes the glass of any preceding aspect, wherein RxO –Al2O3is greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, where RxO is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO.

[0017] A twelfth aspect A12 includes the glass of any preceding aspect, wherein a ratio of(RO + R2O):(Al2O3+ B2O3) is less than 1.5, where RO is the sum of MgO + CaO + BaO + SrO.

[0018] A thirteenth aspect A13 includes the glass of any preceding aspect, wherein the glasscomprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm in as-formed condition.

[0019] A fourteenth aspect A14 includes the glass of aspect A13, wherein the transmittanceis greater than or equal to 70%.

[0020] A fifteenth aspect A15 includes the glass of aspect A13, wherein the transmittance isgreater than or equal to 80%.

[0021] A sixteenth aspect A16 includes the glass of any preceding aspect, wherein the glasscomprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm after exposure to 3000 pulses of UV light at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with a pulse repetition rate of 10 Hz.

[0022] A seventeenth aspect A17 includes the glass of aspect A16, wherein the transmittanceis greater than or equal to 60%.

[0023] An eighteenth aspect A18 includes the glass of aspect A16, wherein the transmittanceis greater than or equal to 70%.SP24-184

[0024] A nineteenth aspect A19 includes the glass of any preceding aspect, wherein the glasscomprises an average coefficient of thermal expansion of greater than or equal to 50x10-7 / °C and less than or equal to 75x10-7 / °C from 0°C to 300°C.

[0025] A twentieth aspect A20 includes the glass of any preceding aspect, wherein the glasscomprises a liquidus viscosity of greater than or equal to 10,000 pascal*seconds.

[0026] A twenty-first aspect A21 includes a glass comprising, on an oxide basis: greater thanor equal to 65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 17.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 2.10 mol% to less than or equal to 8.50 mol% K2O; less than or equal to 1.50 mol% of each of Li2O and ZnO; less than or equal to 0.01 mol% of SnO2, less than or equal to 0.10 mol% of each of TiO2 and Fe2O3; 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 comprises a β-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a 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%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3+ Sb2O3+ PbO is less than or equal to 0.01 mol%.

[0027] A twenty-second aspect A22 includes the glass of aspect A21, comprising greaterthan or equal to 12.00 mol% to less than or equal to 17.00 mol% B2O3.

[0028] A twenty-third aspect A23 includes the glass of any of aspects A21-A22, comprisinggreater than or equal to 2.00 mol% to less than or equal to 10.00 mol% Na2O.

[0029] A twenty-fourth aspect A24 includes the glass of any of aspects A21-A23,comprising greater than or equal to 3.10 mol% to less than or equal to 7.00 mol% K2O.

[0030] A twenty-fifth aspect A25 includes the glass of any of aspects A21-A24, comprisinggreater than or equal to 1.00 mol% to less than or equal to 6.00 mol% MgO.

[0031] A twenty-sixth aspect A26 includes the glass of any of aspects A21-A25, comprisinggreater than or equal to 0.20 mol% to less than or equal to 6.00 mol% CaO.SP24-184

[0032] A twenty-seventh aspect A27 includes the glass of any of aspects A21-A26, whereinR2O – Al2O3 is less than or equal to 9.00 mol%.

[0033] A twenty-eighth aspect A28 includes the glass of any of aspects A21-A27, whereinR2O – Al2O3 is less than or equal to 0.00 mol% and greater than or equal to -6.50.

[0034] A twenty-ninth aspect A29 includes the glass of aspect A27, wherein R2O – Al2O3 isgreater than 0.00 mol%.

[0035] A thirtieth aspect A30 includes the glass of any of aspects A21-A29, wherein RxO –Al2O3is greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, where RxO is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO.

[0036] A thirty-first aspect A31 includes the glass of any of aspects A21-A30, wherein aratio of (RO + R2O):(Al2O3 + B2O3) is less than 1.5, where RO is the sum of MgO + CaO + BaO + SrO.

[0037] A thirty-second aspect A32 includes the glass of any of aspects A21-A31, whereinthe glass comprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm in as-formed condition.

[0038] A thirty-third aspect A33 includes the glass of any of aspects A21-A32, wherein theglass comprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm after exposure to 3000 pulses of UV light at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with a pulse repetition rate of 10 Hz.

[0039] A thirty-fourth aspect A34 includes the glass of any of aspects A21-A33, wherein theglass comprises an average coefficient of thermal expansion of greater than or equal to 50x10-7 / °C and less than or equal to 75x10-7 / °C from 0°C to 300°C.

[0040] A thirty-fifth aspect A35 includes the glass of any of aspects A21-A34, wherein theglass comprises a liquidus viscosity of greater than or equal to 10,000 pascal*seconds.

[0041] A thirty-sixth aspect A36 includes a glass comprising, on an oxide basis: greater thanor equal to 65.50 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 3.00 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to lessSP24-184 than or equal to 20.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.10 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 2.00 mol% to less than or equal to 8.50 mol% K2O; less than or equal to 1.25 mol% Li2O; less than or equal to 0.05 mol% SnO2; less than or equal to 0.20 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; less than or equal to 0.5 mol% ZrO2; less than or equal to 5 mol% ZnO; and less than or equal to 0.75 mol% BaO, wherein: the glass comprises a β-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a sum of Al2O3+ B2O3– R2O – CaO – SrO – BaO is greater than or equal to -1.50 mol% and less than or equal to 40.00 mol%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

[0042] A thirty-seventh aspect A37 includes the glass of aspect A36, wherein R2O – Al2O3is less than or equal to 9.00 mol%.

[0043] A thirty-eighth aspect A38 includes the glass of any of aspects A36-A37, whereinR2O – Al2O3 is less than or equal to 0.00 mol% and greater than or equal to -6.50.

[0044] A thirty-ninth aspect A39 includes the glass of any of aspects A36-A38, wherein R2O– Al2O3is greater than 0.00 mol%.

[0045] A fortieth aspect A40 includes the glass of any of aspects A36-A39, wherein RxO –Al2O3is greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, where RxO is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO.

[0046] A forty-first aspect A41 includes the glass of any of aspects A36-A40, wherein a ratioof (RO + R2O):(Al2O3 + B2O3) is less than 1.5, where RO is the sum of MgO + CaO + BaO + SrO.

[0047] A forty-second aspect A42 includes the glass of any of aspects A36-A41, whereinthe glass comprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm in as-formed condition.

[0048] A forty-third aspect A43 includes the glass of any of aspects A36-A42, wherein theglass comprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm after exposure to 3000 pulses of UV light at a wavelength of 248 nm from an excimerSP24-184 laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with a pulse repetition rate of 10 Hz.

[0049] A forty-fourth aspect A44 includes the glass of any of aspects A36-A43, wherein theglass comprises an average coefficient of thermal expansion of greater than or equal to 50x10-7 / °C and less than or equal to 75x10-7 / °C from 0°C to 300°C.

[0050] A forty-fifth aspect A45 includes the glass of any of aspects A36-A44, wherein theglass comprises a liquidus viscosity of greater than or equal to 10,000 pascal*seconds.

[0051] Additional features and advantages of the alkali-containing, fusion formable glasseswith relatively high UV transmission described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0052] It is to be understood that both the foregoing general description and the followingdetailed 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 the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] FIG. 1 graphically depicts the UV transmittance (y-axis) as a function of wavelength(x-axis) upon initial UV exposure for example glasses according to embodiments described herein;

[0054] FIG. 2 graphically depicts the UV transmittance (y-axis) as a function of wavelength(x-axis) after initial UV exposure for example glasses according to embodiments described herein; and

[0055] FIG. 3 graphically depicts the UV transmittance (y-axis) as a function of wavelength(x-axis) for a conventional fusion-formable glass substrate.SP24-184 DETAILEDDESCRIPTION

[0056] Reference will now be made in detail to embodiments of the alkali-containing, fusionformable glasses with relatively high UV transmission described herein. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. In embodiments, an alkali-containing, fusion formable glass with relatively high UV transmission includes on an oxide basis: greater than or equal to 65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 18.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 3.10 mol% to less than or equal to 7.50 mol% K2O; less than or equal to 1.00 mol% or each of Li2O and ZnO; less than or equal to 0.04 mol% SnO2; less than or equal to 0.10 mol% of each of TiO2, Fe2O3, and Ce2O3; and less than or equal to 2 mol% F-. The glass comprises a β-OH value from greater than or equal to 0 / mm to less than or equal to 0.7 / mm. A sum of Al2O3+ B2O3 – R2O – CaO – SrO – BaO in the glass may be greater than or equal to -0.75 mol% and less than or equal to 40.00 mol%, where R2O is the sum of Na2O + K2O + Li2O. A sum of Na2O + K2O in the glass may be greater than or equal to 3.10 mol% and less than or equal to 15.50 mol%. A sum of As2O3+ Sb2O3+ PbO in the glass may be less than or equal to 0.01 mol%. Various embodiments of alkali-containing, fusion formable glasses with relatively high UV transmission will be further described herein with specific reference to the appended drawings.

[0057] UV transmission (also referred to herein as “transmittance”) is measured at 248 nmon optically polished samples with plane parallel faces using a Perkin Elmer Lambda 650 spectrophotometer. The transmission is measured on the glass article itself without any coatings or other applications. UV transmission was also measured over the wavelength range from 200 nm to 300 nm using the same instrument.

[0058] The liquidus temperature of a glass is the temperature (in °C) above which nocrystalline phases can coexist in equilibrium with the glass. The liquidus temperature is measured according to ASTM C829-81 (2022).

[0059] The liquidus viscosity of a glass is the viscosity of the glass at the liquidustemperature. The liquidus viscosity is measured according to ASTM C965-23 (2023).SP24-184

[0060] Density is measured in accordance with ASTM C693-93 (2019).

[0061] The term “softening point,” as used herein, refers to the temperature at which theviscosity of the glass is 1x107.6poise. The softening point is determined using the parallel plate viscosity method of ASTM C1351M-96 (2012).

[0062] The term “annealing point” as used herein, refers to the temperature at which theviscosity of the glass is 1x1013poise. The annealing point is determined using the beam bending viscosity method of ASTM C598-93 (2013).

[0063] The term “strain point” and “Tstrain” as used herein, refer to the temperature at whichthe viscosity of the glass is 1x1014.68poise. The strain point is determined using the beam bending viscosity method of ASTM C598-93 (2013).

[0064] The linear coefficient of thermal expansion (CTE) of the glass over the temperaturerange 0 °C to 300 °C is expressed as the average CTE over the range in terms “x10-7 / °C” and was determined using a push-rod dilatometer in accordance with ASTM E228-11 (2016).

[0065] The OH concentration (in ppm by weight) for the glasses described herein can bederived from the measurement of infrared transmittance of the glass. The wavelength range of interest is 2-5 µm (wave number range 5000 cm-1to 2000 cm-1). A conventional infrared spectrophotometer, either an FT-IR (Fourier transform infrared) spectrometer or a dispersive infrared spectrophotometer, may be employed. For high spatial resolution measurements, such as for variation of OH concentration, additional equipment may be used as is known in the art. The OH group has characteristic absorption bands near 2.72 µm (3676 cm-1), 2.21 µm (4525 cm-1) and 1.38 µm (7246 cm-1) in fused silica. The parameter β-OH is defined as the relative linear absorption coefficient of hydroxyl (OH) in a glass matrix, or the absorption per unit path length (mm-1). It is calculated using the following equation:where: T ref = Transmittance of sample at reference position, a non-absorbing wavelength suchas 4000 cm-1; T OH = Transmittance of sample at OH absorption peak (∼3676 cm-1 for silica);SP24-184and t = Thickness of sample (mm). This β-OH value is linearly proportional tothe hydroxyl concentration.

[0066] The OH concentration, c, in mol·liter-1, is derived from the Beers-Lambert Law:where the absorbance A = log(T ref / T OH), ε is the molar absorptivity in liter·mol-1·cm-1, c isconcentration in mol·liter-1, and b is the path length (sample thickness) in Concentration of OH in ppm by weight can thus be calculated from c in mol·liter-1using the density of the glass and molecular weight of OH (∼17 g / mol). The constant ε for high purity silica glass at a particular wavelength is available known in the art.

[0067] The terms “free” and “substantially free,” when used to describe the concentrationand / or absence of a particular constituent component in a glass, means that the constituent component is not intentionally added to the glass. However, the glass may contain traces of the constituent component as a contaminant or tramp in amounts of less than 0.05 mol% unless specified otherwise herein.

[0068] Ranges can be expressed herein as from “about” one particular value, and / or to“about” another particular value. When such a range is 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 the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0069] 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.

[0070] Unless otherwise expressly stated, it is in no way intended that any method set forthherein be construed as requiring that its steps be performed in a specific order, nor that withSP24-184 any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0071] As used herein, the singular forms “a,” “an” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0072] Some microchip fabrication processes on silicon substrates include photolithographicsteps which involve the use of UV light, such as in a photoresist step which utilizes deep UV (~250 nm) optical transmission for the exposure. As such, any materials, such as glass substrates, between the UV exposure beam and the silicon substrate should be highly transparent in the UV portion of the spectrum. Most commonly available glasses are not sufficiently transparent at these UV wavelengths (e.g., from 245-270 nm). The UV transparency of the glass dictates the exposure time, with lower transparency translating to longer exposure times being required. Conversely, shorter exposure time allows for faster manufacturing throughput, which is desired for production costs. Other applications and methods may also be improved by glasses with high UV transmission.

[0073] 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. Further, fused silica is generally incompatible with down draw processes, such as fusion forming processes, due to the viscosity characteristics of fused silica and, as such, fused silica cannot be readily formed into large glass sheets using such processes.

[0074] Moreover, it has been observed that compositional components added to silica todecrease manufacturing costs and improve the formability of the fused glass also have the effect of reducing the UV transmission of the glass. As an example, compositional componentsSP24-184 commonly added to glass to enhance the properties of the glass (e.g., the formability of the glass and / or the coefficient of thermal expansion of the glass), such as alkali metal ions and alkaline earth ions, significantly decrease the UV transmission of the glass. In that regard, conventional glasses compatible with large format, sheet-producing manufacturing techniques (such as fusion forming) generally have poor UV transmission and thus are not suitable for use in applications where high UV transmission is required. Indeed, some of these glasses may actually darken following an initial UV exposure, further degrading the UV transmission of the glass.

[0075] In particular, glass manufacturing techniques that include melting batch materials,such as fusion forming techniques, introduce constraints on the physical and optical properties of the glasses due to the composition of the glasses required to facilitate compatibility with the manufacturing technique. As one example particular to the UV transmission of glasses, most commercial glasses contain alkali metal ions, such as Li+, Na+, and K+, and alkaline earth metal ions, such as Ca2+, Sr2+, Mg2+, and Ba2+. Such constituents may be introduced in the glass batch to aid in melting and forming, for example, as well as to enhance other properties of the glass. When these constituents are included in the glass in excess of Al2O3 and B2O3, non- bridging oxygens (NBOs) or oxygen dangling bonds are produced in the glass. These NBOs decrease the UV transmission of the glass. In particular, such glasses include energy states within the nominal silica bonding structure. The introduction of energy states, and particularly the NBO energy state, within the SiO2optical gap reduces the UV transmission of the resulting glass.

[0076] Therefore, there is a need for glasses that have high UV transmission while also beingcompatible with large scale manufacturing techniques such as down draw processes, including fusion forming.

[0077] The glasses disclosed herein mitigate the foregoing problems of conventional glassesby providing glasses that have both high UV transmission and compatibility with fusion forming processes. In particular, the glasses disclosed herein may be generally described as alkali-containing silicate glasses comprising SiO2, alkali metal oxide(s), and Al2O3. In embodiments, the alkali metal oxide includes at least K2O. In embodiments, the glasses may further comprise B2O3. In embodiments, the glasses may further comprise alkaline earth oxides. The amounts of Al2O3, alkali oxides, B2O3(when included), and alkaline earth oxidesSP24-184 (when included) may be balanced to achieve glasses having relatively high UV transmission in combination with liquidus viscosities compatible with fusion forming techniques.

[0078] In the embodiments described herein, the glasses comprise SiO2. SiO2 is the primaryglass former and functions to stabilize the network structure of the glass and improve the chemical durability of the glass. The amount of SiO2 may be limited to control the melting temperature of the glass, as the melting temperature of pure SiO2or high-SiO2glasses is undesirably high.

[0079] In embodiments, the glasses comprise greater than or equal to 65.00 mol% and lessthan or equal to 75.00 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 74.50 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 74.00 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 73.50 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 73.00 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 72.50 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 72.00 mol% SiO2, greater than or equal to 65.00 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 65.50 mol% and less than or equal to 72.50 mol% SiO2, greater than or equal to 65.50 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 66.00 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 66.50 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 67.00 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 67.50 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 68.00 mol% and less than or equal to 75.00 mol% SiO2, greater than or equal to 68.00 mol% and less than or equal to 74.50 mol% SiO2, greater than or equal to 68.00 mol% and less than or equal to 74.00 mol% SiO2, greater than or equal to 68.00 mol% and less than or equal to 73.50 mol% SiO2, greater than or equal to 68.00 mol% and less than or equal to 73.00 mol% SiO2, or even greater than or equal to 68.00 mol% and less than or equal to 72.50 mol% SiO2. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0080] Embodiments of the glasses described herein further include Al2O3. Al2O3 maystabilize the glass network and improves the mechanical properties and chemical durability of the resulting glasses. The amount of Al2O3 can be tailored to control the viscosity of the glasses during melting and forming. If the amount of Al2O3is too high, the viscosity of the melt is alsoSP24-184 generally increased. Additions of Al2O3 also aid in reducing the amount of NBOs in the glass, thereby improving the UV transmission of the glass.

[0081] In embodiments, the glasses described herein comprise greater than or equal to 2.50mol% and less than or equal to 22.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 21.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 20.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 19.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 18.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 17.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 16.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 15.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 14.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 13.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 12.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 11.50 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 11.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 10.50 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 10.00 mol% Al2O3, 2.50 mol% and less than or equal to 9.50 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 9.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 8.50 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 8.00 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 7.50 mol% Al2O3, greater than or equal to 2.50 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 3.00 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 3.50 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 4.00 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 4.50 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 5.00 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 5.50 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 6.00 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 6.50 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 7.00 mol% and less than or equal to 13.75 mol% Al2O3, greater than or equal to 3.00 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 3.50 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 4.00 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 4.50 mol% and less than or equal to 13.50 mol%SP24-184 Al2O3, greater than or equal to 5.00 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 5.50 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 6.00 mol% and less than or equal to 13.50 mol% Al2O3, greater than or equal to 6.50 mol% and less than or equal to 13.50 mol% Al2O3, or even greater than or equal to 7.00 mol% and less than or equal to 13.50 mol% Al2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0082] In embodiments, the glasses may further include B2O3. Without wishing to be boundby theory, it is believed that additions of B2O3(when included) may lower the liquidus viscosity of the glasses, thereby improving the formability of the glasses as well as improving the compatibility of the glasses with fusion forming processes. Additions of B2O3 (when included) may also aid in reducing the amount of NBOs in the glass, thereby improving the UV transmission of the glasses.

[0083] Embodiments of the glasses described herein may comprise greater than or equal to0.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 0.00 mol% and less than or equal to 20.00 mol% B2O3, greater than or equal to 0.00 mol% and less than or equal to 19.00 mol% B2O3, greater than or equal to 0.00 mol% and less than or equal to 18.00 mol% B2O3, or even greater than or equal to 0.00 mol% and less than or equal to 17.00 mol% B2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0084] In embodiments, the glasses may comprise greater than or equal to 0.50 mol% andless than or equal to 21.00 mol% B2O3, greater than or equal to 1.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 1.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 2.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 3.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 3.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 4.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 4.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 5.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 5.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 6.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equalSP24-184 to 6.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 7.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 7.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 8.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 8.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 9.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 9.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 10.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 10.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 11.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 11.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 12.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 12.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 13.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 13.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 14.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 14.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 15.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 15.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 16.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 16.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 17.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 17.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 18.00 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 18.50 mol% and less than or equal to 21.00 mol% B2O3, greater than or equal to 19.00 mol% and less than or equal to 21.00 mol% B2O3, or even greater than or equal to 19.50 mol% and less than or equal to 21.00 mol% B2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0085] In embodiments, the glasses described herein may comprise greater than or equal to2.50 mol% and less than or equal to 20.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 19.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 16.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 15.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 14.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 13.00 mol% B2O3, greater than or equal to 2.50 mol% and lessSP24-184 than or equal to 12.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 11.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 10.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 9.50 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 9.00 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 8.50 mol% B2O3, greater than or equal to 2.50 mol% and less than or equal to 8.00 mol% B2O3, or even greater than or equal to 2.50 mol% and less than or equal to 7.50 mol% B2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0086] In embodiments, the glasses may comprise greater than or equal to 5.00 mol% andless than or equal to 18.00 mol% B2O3, greater than or equal to 5.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 6.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 6.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 7.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 7.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 8.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 8.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 9.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 9.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 10.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 10.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 11.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 11.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 12.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 12.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 13.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 13.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 14.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 14.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 15.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 15.50 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 16.00 mol% and less than or equal to 18.00 mol% B2O3, greater than or equal to 16.50 mol% and less than or equal to 18.00 mol% B2O3, or even greater than or equal to 17.00 mol% and less than or equal to 18.00 mol% B2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.SP24-184

[0087] In embodiments, the glasses may comprise greater than or equal to 5.00 mol% andless than or equal to 17.00 mol% B2O3, greater than or equal to 5.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 6.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 6.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 7.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 7.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 8.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 8.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 9.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 9.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 10.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 10.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 11.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 11.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 12.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 12.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 13.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 13.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 14.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 14.50 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 15.00 mol% and less than or equal to 17.00 mol% B2O3, greater than or equal to 15.50 mol% and less than or equal to 17.00 mol% B2O3, or even greater than or equal to 16.00 mol% and less than or equal to 17.00 mol% B2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0088] In embodiments, the glasses do not include B2O3. In embodiments, the glasses aresubstantially free of B2O3.

[0089] Embodiments of the glasses described herein may comprise Na2O. Additions ofNa2O (when included) improve the meltability and formability of the glass. Additions of Na2O may also enhance the coefficient of thermal expansion of the glass, specifically increasing the coefficient of thermal expansion of the glass, which may be desirable for certain end-user applications. Additions of Na2O may also facilitate strengthening the glass, such as by ion exchange strengthening.SP24-184

[0090] In embodiments, the glasses may comprise greater than or equal to 0.00 mol% andless than or equal to 15.00 mol% Na2O, greater than or equal to 0.10 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 0.50 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 1.00 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 2.50 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 3.00 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 3.50 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 4.00 mol% and less than or equal to 15.00 mol% Na2O, greater than or equal to 4.50 mol% and less than or equal to 15.00 mol% Na2O, or even greater than or equal to 5.00 mol% and less than or equal to 15.00 mol% Na2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0091] In embodiments, the glasses may comprise greater than or equal to 1.50 mol% andless than or equal to 10.00 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 9.50 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 9.00 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 8.50 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 9.00 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 8.50 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 8.00 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 7.50 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 7.00 mol% Na2O, greater than or equal to 1.50 mol% and less than or equal to 6.50 mol% Na2O, or even greater than or equal to 1.50 mol% and less than or equal to 6.00 mol% Na2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0092] In embodiments, the glasses may comprise greater than or equal to 2.00 mol% andless than or equal to 10.00 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 9.50 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 9.00 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 8.50 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 8.00 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 7.50 mol% Na2O, greater than or equal to 2.00 mol% and less than or equal to 7.00 mol% Na2O, greater than or equal to 2.00 mol% and lessSP24-184 than or equal to 6.50 mol% Na2O, or even greater than or equal to 2.00 mol% and less than or equal to 6.00 mol% Na2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0093] In embodiments, the glasses do not contain Na2O. In embodiments, the glasses aresubstantially free of Na2O.

[0094] Embodiments of the glasses described herein further comprise K2O. Like Na2O,additions of K2O, improve the meltability and formability of the glass. Additions of K2O may also enhance the coefficient of thermal expansion of the glass, specifically increasing the coefficient of thermal expansion of the glass, which may be desirable for certain end-user applications. Additions of K2O may also facilitate strengthening the glass, such as by ion exchange strengthening.

[0095] In embodiments, the glasses may comprise greater than or equal to 2.00 mol% andless 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0096] In embodiments, the glasses may comprise greater than or equal to 2.10 mol% andless 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,SP24-184 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0097] In embodiments, the glasses may comprise greater than or equal to 3.10 mol% andless 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0098] In embodiments, the total concentration Na2O + K2O (i.e., the sum of Na2O (mol%)+ K2O (mol%)) in the glasses may 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% of Na2O + K2O, greater than or equal to 2.50 mol% and less than or equal to 15.50 mol% of Na2O + K2O, greater than or equal to 3.00 mol% and less than or equal to 15.50 mol% of Na2O + K2O, greater than or equal to 3.50 mol% and less than or equal to 15.50 mol% of Na2O + K2O, greater than or equal to 4.00 mol% and less than or equal to 15.50 mol% of Na2O + K2O, greater than or equal to 4.50 mol% and less than or equal to 15.50 mol% of Na2O + K2O, or even greater than or equal to 5.00 mol% and less than or equal to 15.50 mol% of Na2O + K2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0099] In embodiments, the glasses may comprise greater than or equal to 2.00 mol% andless than or equal to 11.00 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 10.00 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 9.50 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than orSP24-184 equal to 9.00 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 8.50 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 9.00 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 8.50 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 8.00 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 7.50 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 7.00 mol% of Na2O + K2O, greater than or equal to 2.00 mol% and less than or equal to 6.50 mol% of Na2O + K2O, or even greater than or equal to 2.00 mol% and less than or equal to 6.00 mol% of Na2O + K2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0100] In embodiments, the glasses may comprise greater than or equal to 2.10 mol% andless than or equal to 15.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 14.50 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 14.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 13.50 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 13.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 12.50 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 12.0 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 11.5 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 11.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 10.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 9.50 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 9.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 8.50 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 8.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 7.50 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 7.00 mol% of Na2O + K2O, greater than or equal to 2.10 mol% and less than or equal to 6.50 mol% of Na2O + K2O, or even greater than or equal to 2.10 mol% and less than or equal to 6.00 mol% of Na2O + K2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0101] In embodiments, the glasses may comprise greater than or equal to 3.10 mol% andless than or equal to 15.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and lessSP24-184 than or equal to 15.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 14.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 14.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 13.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 13.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 12.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 12.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 11.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 11.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 10.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 10.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 9.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 9.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 8.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 8.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 7.50 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 7.00 mol% of Na2O + K2O, greater than or equal to 3.10 mol% and less than or equal to 6.50 mol% of Na2O + K2O, or even greater than or equal to 3.10 mol% and less than or equal to 6.00 mol% of Na2O + K2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0102] Embodiments of the glasses described herein may comprise Li2O. Like Na2O andK2O, additions of Li2O (when included) improve the meltability and formability of the glass. Additions of Li2O may also facilitate strengthening the glass, such as by ion exchange strengthening. However, Li+ions in the glass may be highly mobile and, as such, have a propensity to migrate from the glass. When the glasses described herein are used in semiconductor processing, the migration of Li+ions from the glass may damage semiconductor materials deposited on the glass. As such, the amount of Li2O present in the glasses should be minimized.

[0103] In embodiments, the glasses may comprise greater than or equal to 0.00 mol% to lessthan or equal to 1.50 mol% Li2O, greater than or equal to 0.00 mol% to less than or equal to 1.25 mol% Li2O, greater than or equal to 0.00 mol% to less than or equal to 1.00 mol% Li2O, greater than or equal to 0.00 mol% to less than or equal to 0.75 mol% Li2O, greater than orSP24-184 equal to 0.00 mol% to less than or equal to 0.50 mol% Li2O, greater than or equal to 0.00 mol% to less than or equal to 0.25 mol% Li2O, or even greater than or equal to 0.00 mol% to less than or equal to 0.10 mol% Li2O. In embodiments, the glasses do not contain Li2O. In embodiments, the glasses are substantially free of Li2O. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0104] Embodiments of the glasses described herein may contain Na2F2. Na2F2 may beincluded in the glasses as a fining agent (i.e., to aid in the removal and / or prevention of entrained gas bubbles from the glass melt). Additions of Na2F2may also improve the UV transmission of the glass.

[0105] In embodiments, the glasses may comprise greater than or equal to 0.00 mol% andless 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 glasses may 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 glasses do not contain Na2F2. In embodiments, the glasses are substantially free of Na2F2. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0106] Embodiments of the glasses described herein may contain K2F2. K2F2 may beincluded in the glasses as a fining agent (i.e., to aid in the removal and / or prevention of entrained gas bubbles in the glass melt). Additions of K2F2 may also improve the UV transmission of the glass.SP24-184

[0107] In embodiments, the glasses may comprise greater than or equal to 0.00 mol% andless 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 glasses may 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 glasses do not contain K2F2. In embodiments, the glasses are substantially free of K2F2. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0108] Embodiments of the glasses described herein may contain MgO. Additions of MgO(when included) may improve the meltability of the glass. Additions of MgO may also enhance the coefficient of thermal expansion of the glass, specifically increasing the coefficient of thermal expansion of the glass, which may be desirable for certain end-user applications.

[0109] In embodiments, the glasses may comprise greater than or equal to 0.00 mol% andless than or equal to 8.00 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 7.50 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 7.00 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 6.50 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 6.00 mol% MgO, or even greater than or equal to 0.00 mol% and less than or equal to 5.50 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 5.00 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 4.50 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 4.00 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 3.50 mol% MgO, greater than or equal to 0.00 mol% and less than or equal to 3.00 mol% MgO, or even greater than or equal to 0.00 mol% and less than or equal to 2.50 mol% MgO. In embodiments, the glasses may comprise greater than or equal to 1.00 mol% and less than or equal to 8.00 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 7.50 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 7.00 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 6.50 mol% MgO, greater than or equal to 1.00 mol% andSP24-184 less than or equal to 6.00 mol% MgO, or even greater than or equal to 1.00 mol% and less than or equal to 5.50 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 5.00 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 4.50 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 4.00 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 3.50 mol% MgO, greater than or equal to 1.00 mol% and less than or equal to 3.00 mol% MgO, or even greater than or equal to 1.00 mol% and less than or equal to 2.50 mol% MgO. In embodiments, the glasses do not contain MgO. In embodiments, the glasses are substantially free of MgO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0110] Embodiments of the glasses described herein may contain CaO. Additions of CaO(when included) may improve the meltability of the glass. Additions of CaO may also enhance the coefficient of thermal expansion of the glass, specifically increasing the coefficient of thermal expansion of the glass, which may be desirable for certain end-user applications.

[0111] In embodiments, the glasses may comprise greater than or equal to 0.00 mol% andless 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 glasses may 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 orSP24-184 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 glasses do not contain CaO. In embodiments, the glasses are substantially free of CaO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0112] In embodiments, the glasses may contain CaF2. CaF2 may be included in the glassesas a fining agent (i.e., to aid in the removal and / or prevention of entrained gas bubbles in the glass melt). Additions of CaF2 may also improve the UV transmission of the glass. In embodiments, the glasses may comprise 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 glasses may comprise 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 glasses do not contain CaF2. In embodiments, the glasses are substantially free of CaF2. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0113] In embodiments, the sum of MgO and CaO (i.e., MgO (mol%) + CaO (mol%) maybe 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 may be present in the glass and the UV transmission of the glass may be correspondingly diminished. In embodiments, the glasses may comprise greater than or equal to 0.00 mol% and less than or equal to 9.50 mol% of 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% of MgO + CaO, greater than or equal to 0.00 mol% and less than or equal to 8.00 mol% of MgO + CaO, greater than or equal to 0.00 mol% and less than or equal to 7.50 mol% MgO + CaO, or even greater than or equal to 0.00 mol% and less than or equal to 7.00 mol% MgO + CaO. In embodiments, the glasses may comprise greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%,SP24-184 greater than or equal to 2.00 mol% and less than or equal to 9.50 mol% of 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% of 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% MgO + CaO, or even greater than or equal to 2.00 mol% and less than or equal to 7.00 mol% MgO + CaO. In embodiments, the glasses may comprise greater than or equal to 4.00 mol% and less than or equal to 10.00 mol%, greater than or equal to 4.00 mol% and less than or equal to 9.50 mol% of 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% of 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% MgO + CaO, or even greater than or equal to 4.00 mol% and less than or equal to 7.00 mol% MgO + CaO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0114] Embodiments of the glasses described herein may contain SrO. SrO may be addedto the glasses to modify the liquidus viscosity. However, SrO may undesirably increase the density of the glasses. Accordingly, the amount of SrO in the glasses should be minimized. In embodiments, the glasses may comprise greater than or equal to 0.00 mol% and less than or equal to 2.00 mol% SrO, greater than or equal to 0.00 mol% and less than or equal to 1.50 mol% SrO, greater than or equal to 0.00 mol% and less than or equal to 1.00 mol% SrO, or even greater than or equal to 0.00 mol% and less than or equal to 0.50 mol% SrO. In embodiments, the glasses may comprise greater than or equal to 0.10 mol% and less than or equal to 2.00 mol% SrO, greater than or equal to 0.10 mol% and less than or equal to 1.50 mol% SrO, greater than or equal to 0.10 mol% and less than or equal to 1.00 mol% SrO, or even greater than or equal to 0.10 mol% and less than or equal to 0.50 mol% SrO. In embodiments, the glasses do not contain SrO. In embodiments, the glasses are substantially free of SrO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0115] Embodiments of the glasses described herein may contain BaO. BaO may be addedto the glasses to modify the liquidus viscosity. However, BaO may undesirably increase the density of the glasses. Accordingly, the amount of BaO in the glasses should be minimized.SP24-184 In embodiments, the glasses may comprise greater than or equal to 0.00 mol% and less than or equal to 2.00 mol% BaO, greater than or equal to 0.00 mol% and less than or equal to 1.50 mol% BaO, greater than or equal to 0.00 mol% and less than or equal to 1.00 mol% BaO, greater than or equal to 0.00 mol% and less than or equal to 0.75 mol% BaO, greater than or equal to 0.00 mol% and less than or equal to 0.50 mol% BaO, or even greater than or equal to 0.00 mol% and less than or equal to 0.40 mol% BaO. In embodiments, the glasses may comprise greater than or equal to 0.10 mol% and less than or equal to 2.00 mol% BaO, greater than or equal to 0.10 mol% and less than or equal to 1.50 mol% BaO, greater than or equal to 0.10 mol% and less than or equal to 1.00 mol% BaO, greater than or equal to 0.10 mol% and less than or equal to 0.75 mol% BaO, greater than or equal to 0.10 mol% and less than or equal to 0.50 mol% BaO, or even greater than or equal to 0.10 mol% and less than or equal to 0.40 mol% BaO. In embodiments, the glasses do not contain BaO. In embodiments, the glasses are substantially free of BaO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0116] As noted herein, the amounts of Al2O3, B2O3, alkali oxides, and alkaline earth oxidesmay be balanced to achieve glasses having relatively high UV transmission in combination with liquidus viscosities compatible with fusion forming techniques. In particular, it has been found that minimizing the amount of K2O, Na2O, CaO, SrO, and BaO in the glasses in excess of the amount of Al2O3and B2O3results in glasses that have relatively high UV transmittance and liquidus viscosities compatible with fusion forming processes. In particular, it has been found that when Al2O3(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 glasses have relatively high UV transmittance and liquidus viscosities compatible with fusion forming processes. While not wishing to be bound by theory, it is believed that the amount of NBOs is significantly reduced in glasses satisfying this relationship, thereby increasing the UV transmittance of the glass.

[0117] In embodiments, Al2O3 (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 40 mol%, greater than or equal to -0.75 mol% and less than or equal 40 mol%, greater than or equal to - 0.50 mol% and less than or equal 40 mol%, greater than or equal to -0.25 mol% and less than or equal 40 mol%, greater than or equal to 0.00 mol% and less than or equal 40 mol%, greater than or equal to 0.50 mol% and less than or equal 40 mol%, greater than or equal to 0.75 mol%SP24-184 and less than or equal 40 mol%, greater than or equal to 1.00 mol% and less than or equal 40 mol%, or even greater than or equal to 1.50 mol% and less than or equal 40 mol%.

[0118] 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0119] It has also been found that glasses having relatively high UV transmittance andliquidus viscosities compatible with fusion forming processes can be achieved 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. In embodiments, the ratio of (RO (mol%) + R2O (mol%)):(Al2O3(mol%) + B2O3(mol%)) in the glasses 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.

[0120] In embodiments, the difference between R2O (mol%) and Al2O3 (mol%) (i.e., R2O(mol%) – Al2O3 (mol%)) in the glasses is less than or equal to 9.00 mol%, where R2O is the sum of K2O (mol%), Na2O (mol%) and Li2O (mol%). Maintaining this difference to less than or equal to 9.00 mol% aids in minimizing the amount of NBOs in the glasses which, in turn, aids in maintaining relatively high UV transmission in the glasses. In embodiments, R2O (mol%) – Al2O3 (mol%) is greater than or equal to -6.50 mol% and less than or equal to 9.00 mol%. In embodiments, R2O (mol%) – Al2O3 (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 -4.50SP24-184 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%) – Al2O3 (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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0121] In embodiments, the difference between RxO (mol%) and Al2O3 (mol%) (i.e., RxO(mol%) – Al2O3 (mol%)) in the glasses is greater than or equal to 2 mol% and less than or equal to 10.00 mol%, where RxO (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 to greater than or equal to 2 mol% and less than or equal to 10.00 mol% aids in minimizing the amount of NBOs in the glasses which, in turn, aids in maintaining relatively high UV transmission in the glasses. In embodiments, RxO (mol%) – Al2O3 (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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.SP24-184

[0122] Embodiments of the glasses described herein may contain ZnO. However, theamount of ZnO in the glasses should be minimized to avoid decreasing the UV transmittance of the glasses. In embodiments, the glasses may comprise greater than or equal to 0.00 mol% and less than or equal to 5.00 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 4.50 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 4.00 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 3.50 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 3.00 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 2.50 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 2.00 mol% ZnO, greater than or equal to 0.00 mol% and less than or equal to 1.50 mol% ZnO, or even greater than or equal to 0.00 mol% and less than or equal to 1.00 mol% ZnO. In embodiments, the glasses may comprise greater than or equal to 0.10 mol% and less than or equal to 5.00 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 4.50 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 4.00 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 3.50 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 3.00 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 2.50 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 2.00 mol% ZnO, greater than or equal to 0.10 mol% and less than or equal to 1.50 mol% ZnO, or even greater than or equal to 0.10 mol% and less than or equal to 1.00 mol% ZnO. In embodiments, the glasses do not contain ZnO. In embodiments, the glasses are substantially free of ZnO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0123] Embodiments of the glasses described herein may contain SnO2. Additions of SnO2may act as a fining agent to improve the quality of the glasses by reducing defects in the glass, such as defects formed by gasses trapped in the glass. However, SnO2 may act as a UV absorber. Additions of SnO2 to the glass may also fluoresce under UV exposure, further diminishing the UV transmission of the glass. As such, the amount of SnO2 in the glasses should be minimized to avoid decreasing the UV transmittance of the glasses.

[0124] In embodiments, the glasses comprise greater than or equal to 0 mol% and less thanor equal to 0.10 mol% SnO2, greater than or equal to 0 mol% and less than or equal to 0.05 mol% SnO2, greater than or equal to 0 mol% and less than or equal to 0.04 mol% SnO2, greater than or equal to 0 mol% and less than or equal to 0.03 mol% SnO2, greater than or equal to 0SP24-184 mol% and less than or equal to 0.02 mol% SnO2, or even greater than or equal to 0 mol% and less than or equal to 0.01 mol% SnO2. In embodiments, the glasses do not contain SnO2. In embodiments, the glasses are substantially free of SnO2. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0125] Embodiments of the glasses described herein may contain As2O3, Sb2O3, and / or PbO.For example, additions of As2O3and / or Sb2O3may act as a fining agent to improve the quality of the glasses by reducing defects in the glass, such as defects formed by gasses trapped in the glass. Additions of PbO may reduce the viscosity of the glass. However, As2O3, Sb2O3, and / or PbO may also decrease the UV transmittance of the glasses. As such, the amount of As2O3, Sb2O3, and / or PbO in the glasses should be minimized. In embodiments, the glasses comprise greater than or equal to 0 mol% and less than or equal to 0.10 mol% As2O3 + Sb2O3 + PbO, greater than or equal to 0 mol% and less than or equal to 0.05 mol% As2O3 + Sb2O3 + PbO, greater than or equal to 0 mol% and less than or equal to 0.04 mol% As2O3 + Sb2O3 + PbO, greater than or equal to 0 mol% and less than or equal to 0.03 mol% As2O3 + Sb2O3 + PbO, greater than or equal to 0 mol% and less than or equal to 0.02 mol% As2O3 + Sb2O3 + PbO, or even greater than or equal to 0 mol% and less than or equal to 0.01 mol% As2O3 + Sb2O3 + PbO. In embodiments, the glasses do not contain As2O3, Sb2O3, and / or PbO. In embodiments, the glasses are substantially free of As2O3, Sb2O3, and / or PbO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0126] Embodiments of the glasses described herein may contain TiO2. TiO2 may be addedto the glass to stabilize the glass network and improve the mechanical properties of the glass. However, the amount of TiO2added to the glass should be limited to avoid the nucleation of crystalline phases in the glass. Additions of TiO2 may also diminish the UV transmission of the glass. In embodiments, the glasses comprise greater than or equal to 0 mol% and less than or equal to 0.50 mol% TiO2, greater than or equal to 0 mol% and less than or equal to 0.40 mol% TiO2, greater than or equal to 0 mol% and less than or equal to 0.30 mol% TiO2, greater than or equal to 0 mol% and less than or equal to 0.20 mol% TiO2, or even greater than or equal to 0 mol% and less than or equal to 0.10 mol% TiO2. In embodiments, the glasses do not contain TiO2. In embodiments, the glasses are substantially free of TiO2. The above rangesSP24-184 include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0127] Embodiments of the glasses described herein may contain Ce2O3. Ce2O3 may beadded to the glasses to aid in reducing the amount of NBOs in the glass and to prevent photodarkening of the glass. However, cerium ions in the 3+and 4+oxidation states may act as UV absorbers. Accordingly, the amount of Ce2O3in the glass should be minimized. In embodiments, the glasses comprise greater than or equal to 0 mol% and less than or equal to 0.10 mol% Ce2O3, greater than or equal to 0 mol% and less than or equal to 0.05 mol% Ce2O3, greater than or equal to 0 mol% and less than or equal to 0.04 mol% Ce2O3, greater than or equal to 0 mol% and less than or equal to 0.03 mol% Ce2O3, greater than or equal to 0 mol% and less than or equal to 0.02 mol% Ce2O3, or even greater than or equal to 0 mol% and less than or equal to 0.01 mol% Ce2O3. In embodiments, the glasses do not contain Ce2O3. In embodiments, the glasses are substantially free of Ce2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0128] Embodiments of the glasses described herein may contain Fe2O3. However, theamount of Fe2O3in the glasses should be minimized to avoid reducing the UV transmittance of the glasses. In embodiments, the glasses comprise greater than or equal to 0 mol% and less than or equal to 0.10 mol% Fe2O3, greater than or equal to 0 mol% and less than or equal to 0.05 mol% Fe2O3, greater than or equal to 0 mol% and less than or equal to 0.04 mol% Fe2O3, greater than or equal to 0 mol% and less than or equal to 0.03 mol% Fe2O3, greater than or equal to 0 mol% and less than or equal to 0.02 mol% Fe2O3, or even greater than or equal to 0 mol% and less than or equal to 0.01 mol% Fe2O3. In embodiments, the glasses do not contain Fe2O3. In embodiments, the glasses are substantially free of Fe2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0129] Embodiments of the glasses described herein may contain F-. F- may be included inthe glasses as a fining agent (i.e., to aid in reducing or preventing entrained gas bubbles in the glass melt). Additions of F- may also improve the UV transmittance of the glass. In embodiments, the glasses may 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%SP24-184 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 glasses may 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 glasses do not contain F-. In embodiments, the glasses are substantially free of F-. In embodiments, the glasses do not contain halogens. In embodiments, the glasses are substantially free of halogens. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0130] In the embodiments of the glasses described herein the amount of water (H2O) in theglasses is minimized as water increase the amount of NBOs in the glass. In embodiments, the glasses may 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.SP24-184

[0131] The amount of H2O in the glass is proportional to the amount of hydroxyl (OH) inthe glass which, as noted herein, is linearly proportional to the β-OH value of the glass. Accordingly, the β-OH value may be generally indicative of the amount of H2O in the glass. In embodiments described herein, the glasses have a β-OH value from 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.

[0132] Embodiments of the glasses described herein may contain BeO. However, theamount of BeO in the glasses should be minimized as BeO may be toxic. In embodiments, the glasses may comprise greater than or equal to 0.00 mol% and less than or equal to 4.00 mol% BeO, greater than or equal to 0.00 mol% and less than or equal to 3.50 mol% BeO, greater than or equal to 0.00 mol% and less than or equal to 3.00 mol% BeO, greater than or equal to 0.00 mol% and less than or equal to 2.50 mol% BeO, greater than or equal to 0.00 mol% and less than or equal to 2.00 mol% BeO, greater than or equal to 0.00 mol% and less than or equal to 1.50 mol% BeO, or even greater than or equal to 0.00 mol% and less than or equal to 1.00 mol% BeO. In embodiments, the glasses may comprise greater than or equal to 0.10 mol% and less than or equal to 4.00 mol% BeO, greater than or equal to 0.10 mol% and less than or equal to 3.50 mol% BeO, greater than or equal to 0.10 mol% and less than or equal to 3.00 mol% BeO, greater than or equal to 0.10 mol% and less than or equal to 2.50 mol% BeO, greater than or equal to 0.10 mol% and less than or equal to 2.00 mol% BeO, greater than or equal to 0.10 mol% and less than or equal to 1.50 mol% BeO, or even greater than or equal to 0.10 mol% and less than or equal to 1.00 mol% BeO. In embodiments, the glasses do not contain BeO. In embodiments, the glasses are substantially free of BeO. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0133] Embodiments of the glasses described herein may contain Y2O3. However, theamount of Y2O3 in the glasses should be minimized as Y2O3 undesirably decreases the liquidus viscosity of the glasses. In embodiments, the glasses may comprise greater than or equal to 0.00 mol% and less than or equal to 2.00 mol% Y2O3, greater than or equal to 0.00 mol% and less than or equal to 1.50 mol% Y2O3, greater than or equal to 0.00 mol% and less than or equal to 1.00 mol% Y2O3, or even greater than or equal to 0.00 mol% and less than or equal to 0.50 mol% Y2O3. In embodiments, the glasses may comprise greater than or equal to 0.10 mol% and less than or equal to 2.00 mol% Y2O3, greater than or equal to 0.10 mol% and less than orSP24-184 equal to 1.50 mol% Y2O3, greater than or equal to 0.10 mol% and less than or equal to 1.00 mol% Y2O3, or even greater than or equal to 0.10 mol% and less than or equal to 0.50 mol% Y2O3. In embodiments, the glasses do not contain Y2O3. In embodiments, the glasses are substantially free of Y2O3. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0134] Embodiments of the glasses described herein may contain ZrO2. ZrO2 may be addedto the glass to improve the chemical durability of the glass and to consume NBOs. However, additions of ZrO2may act as a nucleating agent undesirably crystallizing the glass. Accordingly, the amount of ZrO2added to the glass should be limited. In embodiments, the glasses comprise greater than or equal to 0 mol% and less than or equal to 0.50 mol% ZrO2, greater than or equal to 0 mol% and less than or equal to 0.40 mol% ZrO2, greater than or equal to 0 mol% and less than or equal to 0.30 mol% ZrO2, greater than or equal to 0 mol% and less than or equal to 0.20 mol% ZrO2, or even greater than or equal to 0 mol% and less than or equal to 0.10 mol% ZrO2. In embodiments, the glasses do not contain ZrO2. In embodiments, the glasses are substantially free of ZrO2. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0135] In embodiments, the glasses described herein may comprise: greater than or equal to65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 18.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 3.10 mol% to less than or equal to 7.50 mol% K2O; less than or equal to 1.00 mol% Li2O; less than or equal to 0.04 mol% SnO2; less than or equal to 0.10 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; less than or equal to 0.10 mol% Ce2O3; less than or equal to 1 mol% ZnO; and less than or equal to 2 mol% F-, wherein: the glass comprises a β-OH value from greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a 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%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 3.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.SP24-184

[0136] In embodiments, the glasses described herein may comprise: greater than or equal to65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 17.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 2.10 mol% to less than or equal to 8.50 mol% K2O; less than or equal to 1.50 mol% Li2O; less than or equal to 0.01 mol% SnO2; less than or equal to 0.10 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; 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 comprises a β-OH value from greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a 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%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

[0137] In embodiments, the glasses described herein may comprise: greater than or equal to65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 20.00 mol% Al2O3; greater than or equal to 5.50 mol% to less than or equal to 18.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 3.10 mol% to less than or equal to 7.50 mol% K2O; less than or equal to 1.00 mol% Li2O; less than or equal to 0.04 mol% SnO2; less than or equal to 0.10 mol% Fe2O3; less than or equal to 0.10 mol% Ce2O3; less than or equal to 1.50 mol% ZnO; less than or equal to 2.00 mol% F-, wherein: a sum of Al2O3 + B2O3 – R2O – CaO – SrO – BaO is greater than or equal to -0.95 mol% and less than or equal to 40.00 mol%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 3.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

[0138] In embodiments, the glasses described herein may comprise: greater than or equal to65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 5.00 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 21.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.10 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 3.10 mol% to less than or equal to 8.50 mol% K2O; less than or equalSP24-184 to 1.00 mol% Li2O; less than or equal to 0.01 mol% SnO2; less than or equal to 0.10 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; less than or equal to 1.00 mol% ZnO; and less than or equal to 2.00 mol% F-, wherein: the glass comprises a β-OH value from greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a 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%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3+ Sb2O3+ PbO is less than or equal to 0.01 mol%.

[0139] In embodiments, the glasses described herein may comprise: greater than or equal to65.00 mol% to less than or equal to 74.00 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 22.00 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 18.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 7.50 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 3.10 mol% to less than or equal to 7.50 mol% K2O; less than or equal to 0.04 mol% SnO2; less than or equal to 0.50 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; less than or equal to 1.50 mol% ZnO; and less than or equal to 2 mol% F-, wherein: a 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 Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 3.10 mol% and less than or equal to 15.50 mol%; a sum of MgO + CaO is greater than or equal to 0.10 mol% and less than or equal to 10.00 mol%; and a sum of As2O3+ Sb2O3+ PbO is less than or equal to 0.01 mol%.

[0140] In embodiments, the glasses described herein may comprise: greater than or equal to65.50 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 17.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.10 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 2.10 mol% to less than or equal to 8.50 mol% K2O; less than or equal to 1.50 mol% Li2O; less than or equal to 0.01 mol% SnO2; less than or equal to 0.10 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; 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 8 mol% F-, wherein: the glass comprises a β-OH value from greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a sum of Al2O3 + B2O3 – R2O – CaO – SrO – BaO is greater than orSP24-184 equal to -0.75 mol% and less than or equal to 40.00 mol%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

[0141] In embodiments, the glasses described herein may comprise: greater than or equal to65.50 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 3.00 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 20.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.10 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 2.00 mol% to less than or equal to 8.50 mol% K2O; less than or equal to 1.25 mol% Li2O; less than or equal to 0.05 mol% SnO2; less than or equal to 0.20 mol% TiO2; less than or equal to 0.10 mol% Fe2O3; less than or equal to 0.5 mol% ZrO2; less than or equal to 5 mol% ZnO; and less than or equal to 0.75 mol% BaO; wherein: the glass comprises a β-OH value from greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a sum of Al2O3 + B2O3 – R2O – CaO – SrO – BaO is greater than or equal to -1.50 mol% and less than or equal to 40.00 mol%, where R2O is Na2O + K2O + Li2O; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3 + Sb2O3 + PbO is less than or equal to 0.01 mol%.

[0142] In embodiments described herein, the glasses may be formed from a batchcomposition that includes a reducing agent in addition to the aforementioned constituent components. In particular, a reducing agent may be included in the batch composition when the batch composition (and therefore the resulting glasses) also include Fe3+ions, either from intentionally added iron (such as Fe2O3) or iron present as a tramp contaminant in other constituent components. In that regard, Fe3+is the most common contaminant in glass batch materials and strongly absorbs UV light, decreasing the UV transmission of the glass. However, Fe2+absorbs more strongly in the near infrared portion of the spectrum, and therefore does not have the same deleterious impact on UV transmission as Fe3+. Accordingly, one or more reducing agents may be added to the batch composition to facilitate reducing Fe3+in the batch to Fe2+. The reducing agents lower the partial pressure of oxygen in the melt and convert the Fe3+in the batch to Fe2+. In embodiments, the reducing agents may include, for example and without limitation, sugar, petroleum product (e.g., motor oil), graphite, and / or starch, each of which may introduce a carbon component into the batch composition to effect reducing Fe3+in the batch to Fe2+. The amount of carbon in the batch from the reducing agents may be, forSP24-184 example and without limitation, less than or equal to 0.10 mol%, less than or equal to 0.05 mol%, less than or equal to 0.04 mol%, less than or equal to 0.03 mol%, or even less than or equal to 0.02 mol%. In embodiments, the batch is substantially free of carbon such as when no reducing agents are added to the batch composition. In embodiments, the batch composition does not include carbon.

[0143] While carbon may be present in the batch composition for forming the glassesdescribed herein, the carbon is burned off or otherwise consumed during the glass manufacturing process and is thus not present in the final glass article (i.e., carbon is not present in the glasses, glass substrates, glass articles, etc.).

[0144] In embodiments, the glasses disclosed herein have relatively high liquidus viscosities,which facilitate use of fusion forming processes to form the glass into large glass sheets. For example, in embodiments, the glasses comprise liquidus viscosities 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 glasses comprise liquidus viscosities 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 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 thanSP24-184 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0145] In embodiments, the glasses may comprise a 35 kP (3500 pascal*seconds)temperature of greater than or equal to 900°C and less than or equal to 1500°C, as measured according to ASTM C965-96 (2017), such that the glasses are compatible with fusion forming processes. In embodiments, the 35 kP temperature may 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0146] In embodiments, the glasses described herein may have an annealing point greaterthan or equal to 400℃ or even greater than or equal to 500℃ such that the glasses may be used in elevated temperature processes.

[0147] The glasses described herein have a relatively high UV transmission as characterizedby the transmittance of the glasses at a wavelength of 248 nm. In embodiments, glass sheets formed from the glasses described herein and having a thickness of 1 mm have a transmittance of greater than 50% at a wavelength of 248 nm in as-formed condition. The phrase “as-formed condition” indicates that the transmittance of the glass is measured on a glass substrate having the indicated thickness that has not been previously exposed to UV light (other than ambient UV light). In embodiments, the glasses comprise a transmittance of 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% at a wavelength of 248 nm for a thickness of 1 mm in as-formed condition.

[0148] Further, the glasses described herein do not exhibit significant photo darkening afterinitial UV exposure. That is, the UV transmittance of the glasses remains relatively high following an initial exposure to UV light at a wavelength of 248 nm. Indeed, in some embodiments, the UV transmittance of the glasses may actually increase following initial exposure to UV light at a wavelength of 248 nm. In embodiments, glass sheets formed from the glasses described herein and having a thickness of 1 mm have a transmittance of greater than 50% at a wavelength of 248 nm after initial UV exposure. The phrase “after initial UVSP24-184 exposure” indicates that the transmittance of the glass is measured on a glass substrate having the indicated thickness that has previously been exposed to 3000 pulses of UV light at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with a pulse repetition rate of 10 Hz. In embodiments, the glasses comprise a transmittance of 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% at a wavelength of 248 nm for a thickness of 1 mm after initial UV exposure.

[0149] In embodiments, the change in the transmittance following initial UV exposure isgreater 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 subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0150] The UV cutoff wavelength is the wavelength at which the transmittance of the glassdecreases to less than 50%. In the embodiments described herein, the glasses have a UV cutoff wavelength of less than or equal to 240 nm or even less than or equal to 225 nm.

[0151] In embodiments, the UV cutoff wavelength after initial UV exposure is less than orequal to 240 nm or even less than or equal to 225 nm.

[0152] In embodiments, the change in the UV cutoff wavelength from as-formed conditionto after initial UV exposure is less than 10 nm and greater than or equal to -20 nm.

[0153] As noted herein, certain constituent components may be added to the glasses toincrease the coefficient of thermal expansion (CTE). For example, when glass substrates formed from the glasses described herein are used to facilitate photolithography on silicon substrates during microchip fabrication, it may be desirable to have the CTE of the glass substrate more closely match the CTE of the silicon substrates subject to the photolithography process to improve the performance of the process.

[0154] The glasses described herein may have an average CTE of greater than or equal to50x10-7 / °C and less than or equal to 75x10-7 / °C over the temperature range from 0°C to 300°C. In embodiments, the glasses may have an average CTE of greater than or equal to 55x10-7 / °CSP24-184 and less than or equal to 75x10-7 / °C, greater than or equal to 60x10-7 / °C and less than or equal to 75x10-7 / °C, greater than or equal to 65x10-7 / °C and less than or equal to 75x10-7 / °C, or even greater than or equal to 70x10-7 / °C and less than or equal to 75x10-7 / °C over the temperature range from 0°C to 300°C. In embodiments, the glasses described herein may have an average CTE of greater than or equal to 50x10-7 / °C and less than or equal to 70x10-7 / °C, greater than or equal to 50x10-7 / °C and less than or equal to 65x10-7 / °C, greater than or equal to 50x10-7 / °C and less than or equal to 60x10-7 / °C, or even greater than or equal to 50x10-7 / °C and less than or equal to 55x10-7 / °C over the temperature range from 0°C to 300°C. The above ranges include all subranges within the explicitly disclosed ranges as well as ranges formed from any combination of the endpoints thereof.

[0155] In embodiments, the glasses described herein may be chemically durable. Inparticular, glass substrates formed from the glasses described herein may be used in manufacturing processes, such a photolithography processes, in which the glass substrates may be reused. To facilitate reuse, the glass substrates are cleaned, such as washed, between each use to remove remnants of deposited materials from a previous use. As such, the glass substrates should be sufficiently chemically durable to withstand multiple cycles of use and cleaning without physically and optically degrading. In particular, the phrase “chemically durable,” as used herein, means that the glass substrates have minimal weight loss and minimal UV transmission loss following a specified cleaning cycle in an acid solution. In embodiments, the glass substrates described herein are deemed to be “chemically durable” if they exhibit a weight loss of less than 0.01 mg / cm2and a UV transmittance of greater than 50 % following cleaning in a solution of 37 wt% HCl in water at a temperature of 50°C for 15 minutes. In embodiments, the glass substrates described herein are deemed to be “chemically durable” if they exhibit a weight loss of less than 0.005 mg / cm2and a UV transmittance of greater than 50 % following cleaning in a solution of 37 wt% HCl in water at a temperature of 50°C for 15 minutes.

[0156] The glasses described herein are formed and / or are formable by conventional down-draw processes, such as slot-draw and fusion-draw processes. However, if desired, any other method known in the art can be used to prepare the glass materials described herein, such as by using a crucible melt method.SP24-184

[0157] In embodiments, the glasses described herein may be formed by a down-drawprocess. Down-draw processes produce glass materials having a uniform thickness that possess relatively pristine surfaces. Because the average flexural strength of the glass material is controlled at least in part by the amount and size of surface flaws, a pristine surface that has had minimal contact with other objections (such as forming apparatuses or portions of forming apparatuses) has a higher initial strength. In addition, down drawn glasses have a very flat, smooth surface that can be used in as-formed condition, without the need for additional (and costly) post-forming steps such as grinding and polishing. However, if desired, additional grinding and / or polishing may be employed for certain applications.

[0158] The fusion forming process is an industrial technique that has been used for the large-scale manufacture of thin glass sheets. Compared to other flat glass manufacturing techniques, such as the float or slot draw processes, the fusion draw process yields thin glass sheets with superior flatness and surface quality. As a result, the fusion forming process has become the dominant manufacturing technique in the fabrication of thin glass substrates for liquid crystal displays, as well as for cover glasses for personal electronic devices such as notebooks, entertainment devices, tablets, laptops, smartphones, and the like.

[0159] For example, the glasses described herein may be formed using a fusion formingprocess (i.e., the glasses are fusion-formable). A conventional fusion forming process uses a drawing vessel that has a channel for accepting molten glass raw material. The channel has weirs that are open at the top along the length of the channel on both sides of the channel. When the channel fills with molten material, the molten glass overflows the weirs. Due to gravity, the molten glass flows down the outside surfaces of the drawing vessel as two flowing glass films. These outside surfaces of the drawing vessel extend down and inwardly so that they join at an edge below the drawing vessel. The two flowing glass films join at this edge to fuse and form a single flowing glass material. The fusion forming process offers the advantage that, because the two glass films flowing over the channel fuse together, neither of the outside surfaces of the resulting glass comes in contact with any part of the apparatus. Thus, due to the lack of contact, the outside 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.SP24-184

[0160] In some aspects, the glasses described herein may be formed by a slot draw process.The slot draw process is distinct from the fusion draw method. In slot draw processes, the molten raw material glass is provided to a drawing tank. The bottom of the drawing tank has an open slot with a nozzle that extends 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.

[0161] Glasses or articles thereof may be characterized by the manner in which they formed.For instance, glasses or articles thereof may be characterized as float-formable (i.e., formed by a float process), down-drawable and, in particular, fusion-formable or slot-drawable (i.e., formed by a down draw process such as a fusion forming process or a slot draw process). To be fusion formable, glasses should have a sufficiently high liquidus viscosity, as described herein.

[0162] In embodiments, the glasses described herein may be formed into glass substrates bydown draw processes such as a fusion forming processes. The resulting glass substrates may have planar dimensions (i.e., the length and the width of the glass substrate) greater than the thickness of the glass substrates. The glass substrates with relatively high UV transmission (as described herein) may be used in a variety of applications including, without limitation, as carrier substrates used in conjunction with photolithography applications. Examples

[0163] The embodiments described herein will be further clarified by the followingexamples. EXAMPLES A-EE

[0164] The compositions listed in Tables 1A, 2A, 3A, and 4A were melted and formed intoglass substrates with thicknesses of approximately 1 mm. The liquidus viscosity, liquidus temperature, 35 kP temperature, strain point, annealing point, and softening point of the glasses were measured according to the testing procedures described herein. The liquidus temperature was measured at the interface between the glass and the platinum boat containing the glass during the measurement process. The density of the glasses, the average coefficient of thermal expansion (CTE) over the temperature range from 0°C to 300°C, the UV transmittance prior to initial UV exposure, the UV transmittance after initial UV exposure, the UV cutoffSP24-184 wavelength prior to initial UV exposure, and the UV cutoff wavelength after initial UV exposure were also measured as described herein. As noted herein, the initial UV exposure comprised exposing the glass substrates to 3000 pulses of UV light at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with 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.) but some errors and deviations should be accounted for. The compositions themselves are given in mol% on an oxide basis. Any example composition that does not sum to a total of 100 mol% should be normalized to 100 mol% as is standard and accepted practice in the field of glass chemistry.

[0165] Table 1A*s = Al2O3 + B2O3 – R2O – CaO – SrO – BaO **t = (RO + R2O):(Al2O3 + B2O3)

[0166] Table 1BSP24-184

[0167] Table 2A*s = Al2O3 + B2O3 – R2O – CaO – SrO – BaO **t = (RO + R2O):(Al2O3 + B2O3)

[0168] Table 2BExample J K L M N O P QSP24-184

[0169] Table 3ASP24-184

[0170] Table 3B

[0171] Table 4ASP24-184*s = Al2O3 + B2O3 – R2O – CaO – SrO – BaO **t = (RO + R2O):(Al2O3 + B2O3)

[0172] Table 4B

[0173] As indicated in Tables 1B, 2B, 3B, and 4B, the glasses of Examples A-EE allexhibited UV transmittances of greater than 50% at a wavelength of 248 nm upon initial UV exposure, with some glasses exhibiting UV transmittances of greater than 80% at a wavelengthSP24-184 of 248 nm upon initial UV exposure (e.g., Examples Z and AA). In addition, the glasses of Examples A-EE all exhibited UV transmittances of greater than 50% at a wavelength of 248 nm after initial UV exposure, with some glasses exhibiting UV transmittances of greater than 80% at a wavelength of 248 nm after initial UV exposure (e.g., Examples Z and AA). As evidenced by the data in the tables, the UV transmittance of some Examples actually increased after initial UV exposure at a wavelength of 248 nm.

[0174] Referring now to FIGS. 1 and 2, the UV transmittance upon initial UV exposure(FIG. 1) is plotted as a function of wavelength and the UV transmittance after initial UV exposure (FIG.2) is plotted as a function of wavelength for Examples Z and AA. As indicated in FIGS. 1 and 2, each of Examples Z and AA exhibited a UV transmittance of greater than 80% at a wavelength of 248 nm both upon initial UV exposure and after initial UV exposure. FIGS. 1 and 2 also demonstrate that the UV transmittance at a wavelength of 248 nm of Example Z actually increased slightly after initial UV exposure.

[0175] Further, Tables 1B, 2B, 3B, and 4B evidence that glasses having UV transmittancesof greater than 50% both upon initial UV exposure at a wavelength 248 nm and after initial UV exposure at a wavelength of 248 nm may also have liquidus viscosities of greater than 10,000 pascal*seconds (100 kP) such that the glasses are compatible with fusion forming processes. For example, each of Examples Z and AA exhibited liquidus viscosities of greater than 10,000 pascal*seconds (100 kP) (e.g., 24,800 pascal*seconds (248 kP) and 15,300 pascal*seconds (153 kP), respectively) such that the glasses are compatible with fusion forming processes. COMPARATIVE EXAMPLE 1

[0176] FIG. 3 graphically depicts the UV transmittance (y-axis) as a function of wavelength(x-axis) for a conventional glass substrate having a liquidus viscosity compatible with fusion forming processes. The conventional glass substrate was formed from a 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 glass substrate had a thickness of 0.3 mm.

[0177] As shown in FIG. 3, the glass substrate had a UV transmittance of less than 50% forwavelengths of UV light from ~250 nm to 256 nm at a thickness of 0.3 mm. While not wishing to be bound by theory, it is believed that the UV transmittance would further decrease as theSP24-184 thickness of the substrate is increased to 1.0 mm. As such, while the glass substrate has a liquidus viscosity that enables forming by fusion forming processes, the UV transmittance may be too low for use in applications requiring relatively high UV transmission. CHEMICALDURABILITY

[0178] The chemical durability of glass substrates formed from the glass of Example AAwas assessed. In particular, glass substrates of the composition of Example AA were formed with the dimensions, surface area, and initial weight indicated in Table 5.

[0179] Table 5

[0180] The substrates were initially rinsed in 16 MΩ water for five minutes and placed in anultrasonic cleaner in a solution of 4 wt% Semiclean detergent and water at a temperature of 60- 65°C for 1 minute. Thereafter, the substrates were again rinsed in 16 MΩ water for five minutes followed by a final rinse in 18 MΩ water for five minutes. The substrates were then dried on stainless steel trays at 110°C for one hour and placed in a desiccator until tested.

[0181] The UV transmittance of the substrates at 250 nm was initially measured prior toexposure to the cleaning protocol. Thereafter, the substrates were placed in 500 ml of concentrated HCl (37 wt% HCl in water) and heated to approximately 50°C for 15 minutes. The glass substrates were then rinsed with 16 MΩ water, placed on stainless steel trays, and dried at 110°C for at least 30 minutes. The glass substrates were then re-weighed and the UV transmittance of the substrates at 250 nm was again measured. The results are reported in Table 6. Thereafter, the substrates were exposed to 3000 pulses of UV light at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with a pulse repetition rate of 10 Hz. The absolute change in UV transmittance (i.e., |Delta UV (%)|) of the substrates at 250 nm following exposure was determined to be less than 5%. Based on the weight loss per area and theSP24-184 transmittance following exposure to the cleaning protocol, the substrates were determined to be chemically durable.

[0182] Table 6

[0183] It will be apparent to those skilled in the art that various modifications and variationscan be made to 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 modification and variations come within the scope of the appended claims and their equivalents.

Claims

SP24-184 What is claimed is:

1. A glass comprising, on an oxide basis:greater than or equal to 65.00 mol% to less than or equal to 72.50 mol% SiO2; greater than or equal to 2.50 mol% to less than or equal to 13.75 mol% Al2O3; greater than or equal to 0.00 mol% to less than or equal to 18.00 mol% B2O3; greater than or equal to 0.00 mol% to less than or equal to 6.00 mol% MgO; greater than or equal to 0.00 mol% to less than or equal to 15.00 mol% Na2O; greater than or equal to 2.10 mol% to less than or equal to 8.50 mol% K2O; less than or equal to 1.50 mol% or each of Li2O and ZnO; less than or equal to 0.04 mol% SnO2; less than or equal to 0.10 mol% of each of TiO2, Fe2O3, and Ce2O3; and less than or equal to 2 mol% F-, wherein: the glass comprises a β-OH value of greater than or equal to 0 / mm to less than or equal to 0.7 / mm; a 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; a sum of Na2O + K2O is greater than or equal to 2.10 mol% and less than or equal to 15.50 mol%; and a sum of As2O3+ Sb2O3+ PbO is less than or equal to 0.01 mol%.

2. The glass of claim 1, comprising greater than or equal to 12.00 mol% to less than orequal to 18.00 mol% B2O3.

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

4. The glass of any one of claims 1-3, comprising greater than or equal to 2.00 mol% toless than or equal to 10.00 mol% Na2O.SP24-1845. The glass of any one of claims 1-4, comprising greater than or equal to 3.10 mol% toless than or equal to 7.00 mol% K2O.

6. The glass of any one of claims 1-4, comprising:greater than or equal to 3.10 mol% to less than or equal to 7.50 mol% K2O; less than or equal to 1.00 mol% or each of Li2O and ZnO; the sum of Na2O + K2O is from greater than or equal to 2.10 mol% to 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 of any one of claims 1-6, comprising greater than or equal to 1.00 mol% toless than or equal to 6.00 mol% MgO.

8. The glass of any one of claims 1-7, comprising greater than or equal to 0.20 mol% toless than or equal to 6.00 mol% CaO.

9. The glass of any one of claims 1-8, comprising greater than or equal to 0.10 mol% toless than or equal to 1.50 mol% SrO.

10. The glass of any one of claims 1-9, wherein R2O – Al2O3is less than or equal to 9.00 mol%.

11. The glass of claim 10, wherein R2O – Al2O3is less than or equal to 0.00 mol% and greater than or equal to –6.

50.

12. The glass of any one of claims 1-11, comprising: less than or equal to 0.5 mol% ZrO2; less than or equal to 5 mol% ZnO; and less than or equal to 0.75 mol% BaO.SP24-184 13. The glass of any one of claims 1-12, wherein RxO – Al2O3 is greater than or equal to 2.00 mol% and less than or equal to 10.00 mol%, where RxO is the sum of R2O and RO, where RO is the sum of MgO + CaO + BaO + SrO.

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

15. The glass of any one of claims 1-14, wherein the glass comprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm in 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 of any one of claims 1-17, wherein the glass comprises a transmittance of greater than 50% at a wavelength of 248 nm and a thickness of 1 mm after exposure to 3000 pulses of UV light at a wavelength of 248 nm from an excimer laser, each pulse having a pulse energy of greater than or equal to 110 mJ / pulse to less than or equal to 120 mJ / pulse with a pulse repetition rate of 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 of any one of claims 1-20, wherein the glass comprises an average coefficient of thermal expansion of greater than or equal to 50x10-7 / °C and less than or equal to 75x10-7 / °C from 0°C to 300°C.

22. The glass of any one of claims 1-21, wherein the glass comprises a liquidus viscosity of greater than or equal to 10,000 pascal*seconds.

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