High strain point and high young's modulus glasses

Abstract

This invention discloses a substantially alkali-free glass that can be used to produce substrates for flat panel display devices, such as active-matrix liquid crystal displays (AMLCDs). The glass has a high annealing temperature and Young's modulus. A method for producing the substantially alkali-free glass using a pull-down process (e.g., a fusion process) is also disclosed.

Description

Technical Field

[0001] This application claims priority under patent law to U.S. Provisional Application No. 62 / 686,850, filed on June 19, 2018, the contents of which are relied upon and are incorporated herein by reference in their entirety.

[0002] Embodiments of the present disclosure relate to display glass. More particularly, embodiments of the present disclosure relate to display glass for active matrix liquid crystal displays. Prior Art

[0003] Liquid crystal displays, such as active matrix liquid crystal display (AMLCD) devices, are complex to manufacture, and the properties of the substrate glass are crucial. First, the physical dimensions of the glass substrates used in AMLCD device production require strict control. The sheet drawing process, and specifically the fusion process, described in U.S. Patent Nos. 3,338,696 and 3,682,609, both to Dockery, produce glass sheets that can be used as substrates without requiring costly post-formation finishing operations such as grinding and polishing. Unfortunately, the fusion process imposes significant constraints on the glass's properties, requiring a relatively high liquidus viscosity.

[0004] In the field of liquid crystal displays, thin film transistors (TFTs) based on polycrystalline silicon are preferred because they can transport electrons more efficiently. Polycrystalline silicon (p-Si)-based transistors are characterized by higher mobility than amorphous silicon (a-Si)-based transistors. This allows for the production of smaller and faster transistors, ultimately resulting in brighter and faster displays.

[0005] One issue with p-Si-based transistors is that their manufacturing requires higher process temperatures than those used in a-Si transistor manufacturing. Compared to the peak temperature of 350°C used in a-Si transistor manufacturing, the process temperatures for p-Si-based transistors range from 450°C to 600°C. At these temperatures, most AMLCD glass substrates undergo a process known as compaction. Compaction, also known as thermal stability or dimensional change, is an irreversible dimensional change (shrinkage) of the glass substrate due to a change in the glass's virtual temperature. "Virtual temperature" is a term used to indicate the structural state of glass. Glass that is rapidly cooled from a high temperature is believed to have a higher virtual temperature due to "freezing" at a higher temperature. Glass that is cooled more slowly or annealed by holding near the annealing point for a period of time is believed to have a lower virtual temperature.

[0006] The extent of compaction depends on the glassmaking process and the viscoelastic properties of the glass. In the float process, used to produce sheet products from glass, the glass sheet cools relatively slowly from the melt, thus "freezing" into glass at a relatively low temperature. In contrast, the fusion process causes the glass sheet to quench very rapidly from the melt and freeze at a relatively high temperature. Consequently, glass produced via the float process can experience less compaction than glass produced via the fusion process, as the driving force for compaction is the difference between the virtual temperature and the process temperature experienced by the glass during compaction. Therefore, it is desirable to minimize the level of compaction in glass substrates produced via the fusion process, as well as other forming processes (e.g., float).

[0007] There are two approaches to minimizing compaction in glass. The first is to thermally pretreat the glass to create a virtual temperature similar to the one the glass will experience during p-Si TFT manufacturing. This approach presents several difficulties. First, the multiple heating steps employed during p-Si TFT manufacturing create slightly different virtual temperatures in the glass that cannot be fully compensated for by this pretreatment. Second, the thermal stability of the glass becomes closely tied to the details of p-Si TFT manufacturing, which may mean different pretreatments for different end users. Finally, pretreatment increases processing cost and complexity.

[0008] Another approach is to slow the strain rate at process temperatures by increasing the viscosity of the glass. This can be achieved by increasing the viscosity of the glass. The annealing point represents the temperature corresponding to the fixed viscosity of the glass, so an increase in the annealing point is equal to an increase in viscosity at a fixed temperature. However, the challenge with this approach is to produce high annealing point glasses cost-effectively. The main factors affecting cost are defects and asset life. In modern melters coupled to fusion draw machines, four types of defects are commonly encountered: (1) gaseous inclusions (bubbles or blistering); (2) solid inclusions from refractory materials or failure to properly melt the batch; (3) metallic defects composed primarily of platinum; and (4) devitrified products at either end of the tube caused by low liquidus viscosity or excessive devitrification. The glass composition has a non-proportional effect on the melting rate and therefore on the tendency of the glass to form gaseous or solid defects, and the oxidation state of the glass affects the tendency to form platinum defects. Devitrification of the glass on the forming mandrel or isotube can be best managed by selecting a composition with a high liquidus viscosity.

[0009] Asset life depends largely on the rate of wear or deformation of the various refractory and precious metal components of the melting and forming system. Recent advances in refractory materials, platinum system design, and other tubular refractory materials have offered the potential to significantly extend the useful operating life of melters coupled to fusion draw machines. Consequently, the life-limiting component of modern fusion draw melting and forming platforms is the electrode used to heat the glass. Tin oxide electrodes slowly corrode over time, with the corrosion rate being a strong function of temperature and glass composition. To maximize asset life, it is desirable to identify compositions that reduce electrode corrosion rates while maintaining the aforementioned defect-limiting properties.

[0010] As long as the compaction of the glass is below a threshold level, a significant attribute determining a glass's suitability as a substrate is the variability, or lack thereof, of the substrate's overall pitch during TFT fabrication. This can lead to misalignment of TFT components and result in defective pixels in the final display. This variability is most pronounced due to variations in the compaction of the glass, variations in the elastic deformation of the glass under stresses imposed by the films deposited during TFT fabrication, and variations in the relaxation of these same stresses during TFT fabrication. Glass with high dimensional stability will have reduced compaction variability and reduced stress relaxation, while glass with a high Young's modulus will help reduce deformation due to film stress. Therefore, glass with both high modulus and high dimensional stability will minimize overall pitch variability during TFT fabrication, making it a favorable substrate for these applications.

[0011] In addition, glass with a high strain point and a high Young's modulus can also be used as a carrier for flexible organic light-emitting diodes (OLEDs) and as a substrate for hard disks made using heat-assisted magnetic recording (HAMR) technology.

[0012] Therefore, there is a need in the art for glass compositions having high modulus and high dimensional stability while also possessing other advantageous properties and characteristics. Summary of the Invention

[0013] One or more embodiments of the present disclosure are directed to glasses including, in mole percentages based on oxides, each within the following ranges: SiO 2 65-75%, Al 2 O 3 12-14%, B 2 O 30-3%, MgO 4-8%, CaO 5-10%, SrO 0-5%, and other oxides including Y 2 O 3, ZrO 2, ZnO 0-2%. In some embodiments, the glass includes, on a molar percentage basis on oxides, glass containing 69-73% SiO, 12-14% AlO, 30-3% BO, 4-7% MgO, 5-6% CaO, 3-4% SrO, and 0-1% other oxides including YO, ZrO, and ZnO, and has a strain point greater than 760°C, a 200°F temperature less than 1650°C, a liquidus temperature less than 1300°C, a liquidus viscosity greater than 20,000°C, a Young's modulus greater than 85 GPa, and / or a specific modulus greater than 33 GPa / g / cm3.

[0014] An exemplary glass may be a MgO-CaO-SrO-Al2O3-SiO2 system with small amounts of Y2O3, ZrO2, and ZnO to provide a strain point of 780°C, a liquidus viscosity greater than 68,000 P, and a 200 P (or typical melting temperature) of 1650°C. This provides a higher strain point, energy savings during melting, and extended melting tank life, all of which contribute to significant cost savings. Other glasses may be a MgO-CaO-SrO-BaO-B2O3-Al2O3-SiO2 system, providing a strain point of 757°C or greater, a liquidus viscosity greater than 62,400 P, a specific modulus greater than 32.18, and a Young's modulus greater than 83.56 GPa.

[0015] One or more embodiments of the present disclosure are directed to glasses comprising, in molar percentages on an oxide basis, 69-74% SiO2, 11-14% Al2O3, 0-3% B2O3, 4-7% MgO, 5-7% CaO, 0-3% SrO, and 1-5% BaO within the following ranges. Additional embodiments of the present disclosure are directed to glasses comprising, on a molar percentage basis on the oxides, within the following ranges: 70-73% SiO2, 11-13% Al2O3, 0-1% B2O3, 4-7% MgO, 5-7% CaO, 0-3% SrO, and 1-5% BaO, and having a strain point greater than 752°C, a liquidus temperature below 1300°C, a liquidus viscosity greater than 20,000 P, a Young's modulus greater than 83.56 GPa, and / or a specific modulus greater than 32 GPa / g / cm3.

[0016] One or more embodiments of the present disclosure are directed to glasses comprising, in molar percentages on an oxide basis, 68.84-74.07% SiO, 10.41-14.87% AlO, 0-2% BO, 3.44-7.45% MgO, 4.19-8.23% CaO, 0-3.36% SrO, 0.91-5.59% BaO, and 0.09-0.2% SnO. Additional embodiments of the present disclosure are directed to glasses comprising, in molar percentages on an oxide basis, each within the following ranges: 69.86-72.13% SiO2, 11.58-13.01% Al2O3, 0-1% B2O3, 4.44-6.45% MgO, 5.53-7.23% CaO, 0.09-1.67% SrO, 2.92-4.57% BaO, and 0.09-0.1% SnO2.

[0017] Additional embodiments of the present disclosure relate to articles comprising glass produced by a down-draw manufacturing process. Other embodiments relate to glass produced by a fusion process or variations thereof. Simple diagram description

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments described below.

[0019] Figure 1 shows a schematic representation of a mandrel for making a precise sheet in a fusion drawing process;

[0020] Figure 2 shows a cross-sectional view of the mandrel formed in Figure 1 taken along position 6;

[0021] Figure 3 shows the spectra of black bodies at 1200°C and 1140°C and the transmission spectrum of a 0.7 mm thick Eagle XG® amorphous thin film transistor substrate;

[0022] Figure 4 is a diagram of the boundary of the convex hull of some embodiments;

[0023] FIG5 is a diagram of the convex hull of FIG4 having sets of exemplary components;

[0024] FIG6 is a graph of equation (2) for randomly selected components within the convex hull of FIG4;

[0025] FIG7 is a graph of equation (3) for randomly selected components within the convex hull of FIG4; and

[0026] Figure 8 is a diagram of the MgO-CaO-SiO 2-Al 2O 3 (20 wt% Al 2O 3) system. Implementation Method

[0027] Described herein are alkali-free glasses with high annealing and / or strain points and high Young's modulus, and methods for their production. These high annealing and / or strain points and high Young's modulus allow the glasses to have excellent dimensional stability (i.e., low compaction) during TFT manufacturing, thereby reducing variability during the TFT manufacturing process. Glasses with high annealing and / or strain points can help prevent panel deformation due to compaction / shrinkage during heat treatment after glass manufacturing. Additionally, some embodiments of the present disclosure have high liquidus viscosities, thereby reducing or eliminating the possibility of devitrification on relatively cold forming mandrels. Due to specific details of the glass composition, exemplary glasses melt to excellent quality with extremely low levels of gaseous inclusions and minimal corrosion of precious metals, refractory materials, and tin oxide electrode materials.

[0028] In one embodiment, the substantially alkali-free glass may have a high annealing point. In some embodiments, the annealing point is greater than approximately 790°C, 795°C, 800°C, or 805°C. Without being bound by any particular theory of operation, it is believed that such a high annealing point results in a low relaxation rate (and therefore a relatively low amount of compaction) for exemplary glasses to be used as backplane substrates in low-temperature polysilicon processes.

[0029] The liquidus temperature (T liq ) of a glass is the temperature above which a crystalline phase cannot coexist in equilibrium with the glass. In various embodiments, the glass article has a T liq ranging from about 1200°C to about 1350°C, or from about 1220°C to about 1325°C. In another embodiment, the viscosity of the glass at the liquidus temperature is greater than or equal to about 150,000 P. In some embodiments, the viscosity of the glass at the liquidus temperature is greater than or equal to about 175,000 P, 200,000 P, 225,000 P, or 250,000 P.

[0030] In another embodiment, the exemplary glass may provide T35k - Tliq > 0.25 T35k - 225° C. This ensures minimal tendency to devitrify on the forming mandrel during the fusion process.

[0031] In one embodiment, the glass includes a chemical fining agent. Such fining agents include, but are not limited to, SnO2, As2O3, Sb2O3, F, Cl, and Br, wherein the concentration of the chemical fining agent is maintained at a level of 0.5 mol% or less. In some embodiments, the chemical fining agent includes one or more of SnO2, As2O3, Sb2O3, F, Cl, or Br at a concentration of less than or equal to approximately 0.5 mol%, 0.45 mol%, 0.4 mol%, 0.35 mol%, 0.3 mol%, or 0.25 mol%. The chemical fining agent may also include CeO2, Fe2O3, and other oxides of transition metals, such as MnO2. These oxides can introduce color to the glass through visible light absorption in their final valence states in the glass, and therefore their concentration may be 0.2 mol% or less. In one or more embodiments, the glass composition includes one or more oxides of a transition metal at a concentration of less than or equal to approximately 0.2 mol%, 0.15 mol%, 0.1 mol%, or 0.05 mol%. In some embodiments, the glass composition includes any one or a combination of SnO2, As2O3, Sb2O3, F, Cl, and / or Br in a range of approximately 0.01 mol% to approximately 0.4 mol%. In specific embodiments, the glass composition includes any one or a combination of Fe2O3, CeO2, and / or MnO2 in a range of approximately 0.005 mol% to approximately 0.2 mol%. In some embodiments, As2O3 and Sb2O3 comprise less than or equal to approximately 0.005 mol% of the glass composition.

[0032] In one embodiment, an exemplary glass is formed into a sheet via a fusion process. The fusion draw process results in an initial flame-polished glass surface that reduces surface media deformation for high-resolution TFT backplanes and color filters. Figure 1 is a schematic diagram of forming a mandrel or isotube in a non-restricted fusion draw process. Figure 2 is a schematic cross-section of the isotube near position 6 in Figure 1. Glass is introduced from an inlet 1 and flows along the bottom of a flow channel 4 formed by weir walls 9 to a compression end 2. The glass overflows the weir walls 9 on either side of the isotube (see Figure 2), and the two streams of glass merge or fuse at a root 10. Edge guides 3 on either side of the isotube cool the glass and create a deep, narrow strip at the edge, called a bead. The bead is drawn down by rollers, enabling sheet formation at high viscosities. By adjusting the rate at which the sheet is drawn from the isotube, the fusion draw process can produce a wide range of thicknesses at a fixed melt rate.

[0033] The tab-drawing process, and specifically the fusion process, described in U.S. Patent Nos. 3,338,696 and 3,682,609 (both to Dockerty), incorporated herein by reference, can be used herein. Without being bound by any particular theory of operation, it is believed that the fusion process can produce glass substrates that do not require polishing. Current glass substrate polishing techniques are capable of producing glass substrates with an average surface roughness greater than approximately 0.5 nm (Ra), as measured by atomic force microscopy. Glass substrates produced by the fusion process have an average surface roughness of less than 0.5 nm, as measured by atomic force microscopy. The substrates also have an average internal stress of less than or equal to 150 psi, as measured by photoresistance. Of course, the appended claims should not be limited to the fusion process, as the embodiments described herein are equally applicable to other forming processes, such as, but not limited to, float forming processes.

[0034] In one embodiment, the exemplary glass is formed into sheets using a fusion process. While the exemplary glass is compatible with fusion processes, the glass can also be formed into sheets or other blanks using various manufacturing processes. Such processes include slot drawing, float forming, rolling, and other sheet forming processes known to those skilled in the art.

[0035] Compared to these alternative methods for creating glass sheets, the fusion process described above is capable of creating extremely thin, flat, and uniform sheets with pristine surfaces. Slotted draw can also result in pristine surfaces, but the dimensional uniformity and surface quality of slotted-drawn glass are generally inferior to fusion-drawn glass due to variations in orifice shape over time, the accumulation of volatile residues at the orifice-glass interface, and the challenges of creating an orifice to deliver perfectly flat glass. The float process can deliver extremely large, uniform sheets, but the surface is substantially compromised by contact with the float bath on one side and exposure to the condensed product from the float bath on the other. This means that float glass must be polished for use in high-performance display applications.

[0036] The fusion process can involve rapid cooling of the glass from a high temperature, resulting in a high virtual temperature Tf. The virtual temperature can be considered to represent the difference between the structural state of the glass and the state it would otherwise exhibit if fully relaxed at the temperature of interest. Reheating a glass with a glass transition temperature Tg to a process temperature Tp, such that Tp < Tg ≤ Tf, can be influenced by the viscosity of the glass. Since Tp < Tf, the structural state of the glass is not in equilibrium at Tp, and the glass will spontaneously relax toward the structural state at equilibrium at Tp. This relaxation rate is inversely proportional to the effective viscosity of the glass at Tp, such that high viscosity results in a slow relaxation rate and low viscosity results in a fast relaxation rate. The effective viscosity is inversely proportional to the virtual temperature of the glass, such that low virtual temperatures result in high viscosities and high virtual temperatures result in relatively low viscosities. Therefore, the relaxation rate at Tp is directly proportional to the virtual temperature of the glass. Processes that introduce high virtual temperatures result in relatively high relaxation rates when the glass is reheated at Tp.

[0037] One method for reducing the relaxation rate at Tp is to increase the glass's peak viscosity at that temperature. The annealing point of a glass represents the temperature at which the glass has a viscosity of 10 13.2 P. As the temperature decreases below the annealing point, the viscosity of the supercooled melt increases. At a fixed temperature below Tg, glass with a higher annealing point has a higher viscosity than glass with a lower annealing point. Therefore, increasing the annealing point may increase the viscosity of the substrate glass at Tp. Generally, the compositional changes necessary to increase the annealing point also increase the viscosity at all other temperatures. In a non-limiting example, the virtual temperature of glass produced by a fusion process corresponds to a viscosity of approximately 10 11-10 12 P. Therefore, for fusion-compatible glasses, increasing the annealing point generally also increases the virtual temperature. For a given glass, regardless of the forming process, a higher virtual temperature results in lower viscosity at temperatures below Tg. Therefore, increasing the virtual temperature negates the viscosity increase that could otherwise be achieved by increasing the annealing point. To achieve a substantial change in the relaxation rate at Tp, it is generally necessary to change the annealing point relatively significantly. Exemplary glasses have annealing points greater than or equal to approximately 790°C, 795°C, 800°C, or 805°C. Without being bound by any particular theory of operation, it is believed that such high annealing points result in acceptably low thermal relaxation rates during low-temperature TFT processing, such as a typical low-temperature polysilicon rapid thermal annealing cycle.

[0038] In addition to its impact on the virtual temperature, increasing the annealing point also increases the temperature of the entire melting and forming system, specifically the temperature on the isotube. For example, the annealing points of Eagle XG® glass and Lotus™ glass (Corning Incorporated, Corning, NY) differ by approximately 50°C, and the temperatures at which the glasses are delivered to the isotube also differ by approximately 50°C. When held above approximately 1310°C for extended periods of time, the zircon refractory material forming the isotube exhibits thermal creep, which can be accelerated by the weight of the isotube itself plus the weight of the glass on top of the isotube. A second aspect of the exemplary glass is that its delivery temperature is less than or equal to approximately 1350°C, or 1345°C, or 1340°C, or 1335°C, or 1330°C, or 1325°C, or 1320°C, or 1315°C, or 1310°C. Such delivery temperatures can allow for extended manufacturing activities without replacing the isotube or extend the time between tube replacements.

[0039] In manufacturing trials of glasses with high annealing points and delivery temperatures below 1350°C and below 1310°C, it was discovered that the glasses exhibited a greater tendency to devitrify at the base of the isotube, and particularly at the edge guides, relative to glasses with lower annealing points. Careful measurements of the temperature distribution along the isotube revealed that the edge guide temperature was significantly lower than expected relative to the central root temperature, believed to be due to radiative heat losses. The edge guides are typically maintained at a temperature below the central root temperature to ensure that the glass is sufficiently viscous upon exiting the root for placement between the edge guides under tension, thereby maintaining a flat shape. When the edge guides are located at either end of the isotube, they are difficult to heat, and the temperature difference between the center of the root and the edge guides can be 50°C or more.

[0040] While not wishing to be bound by theory, we believe that the increasing trend of devitrification during the fusion process can be understood from the radiative heat loss of the glass as a function of temperature. Fusion is essentially an isothermal process, so the glass leaves the inlet at a certain viscosity and leaves the outlet at a much higher viscosity. However, the actual value of the viscosity is not strongly dependent on the bulk or process temperature of the glass. Therefore, glasses with higher annealing points typically require much higher isotube temperatures than glasses with lower annealing points simply to match the delivery and exit viscosities. For example, Figure 3 shows blackbody spectra corresponding to 1140°C and 1200°C, which are approximately the temperatures at the outlet of the isotube (10 in Figure 2) for Eagle XG® glass and Lotus™ glass, respectively. The vertical line at approximately 2.5 μm corresponds approximately to the onset of the infrared cutoff; the region in the near-infrared where optical absorption occurs in borosilicate glass rises very sharply to a nearly constant value. At wavelengths shorter than the cutoff wavelength, glass exhibits significant transmission between 300 and 400 nm, resulting in UV cutoff. Between approximately 300 nm and approximately 2.5 μm, a 1200°C blackbody exhibits greater absolute energy and a greater proportion of total energy than a 1140°C blackbody. Because glass exhibits significant transmission within this wavelength range, radiative heat loss from glass at 1200°C is significantly greater than that at 1140°C.

[0041] Furthermore, without being bound by any particular theory of operation, it is believed that because radiative heat loss increases with temperature, and because high annealing point glass is typically formed at higher temperatures than lower annealing point glass, the temperature difference between the center root and the edge director generally increases with the annealing point of the glass. This can be directly related to the tendency of the glass to form devitrified products on the isotube or edge director.

[0042] The liquidus temperature of a glass is defined as the highest temperature at which a crystalline phase will appear if the glass is held at that temperature indefinitely. The liquidus viscosity is the viscosity of the glass at the liquidus temperature. To completely avoid devitrification on the isotube, it may be helpful to have a sufficiently high liquidus viscosity to ensure that the glass no longer settles on the isotube refractory or edge guide material at or near the liquidus temperature.

[0043] In practice, very few alkali-free glasses have liquidus viscosities within the desired range. Experience with substrate glasses suitable for amorphous silicon applications (e.g., Eagle XG® glass) indicates that edge directors can be sustainably held at temperatures up to 60°C below the liquidus temperature of some alkali-free glasses. However, it should be understood that glasses with higher annealing points will require higher forming temperatures, and the edge directors are expected to be very cool relative to the center root temperature. A useful metric for tracking this effect is the difference between the delivery temperature on the isotube and the liquidus temperature of the glass, T liq . During the fusion process, it is generally desirable to deliver glass at approximately 35,000°C (T 35K). While it may be useful to maximize T 35K - T liq for a particular delivery temperature, for amorphous silicon substrates such as Eagle XG® glass, it has been found that a T 35K - T liq of approximately 80°C or higher allows for extended manufacturing operations. As temperature increases, T35k-Tliq must also increase, so that for T35k approaching 1300° C., it may be helpful to have T35k-Tliq equal to or greater than about 100° C. The minimum useful value of T35k-Tliq varies approximately linearly with temperature from about 1200° C. to about 1320° C. and can be expressed according to equation (1). Minimum T 35k - T liq = 0.25 T 35k - 225 (1) wherein all temperatures are in ° C. Thus, one or more embodiments of the exemplary glasses have T 35k - T liq > 0.25 T 35k - 225 ° C.

[0044] Furthermore, the forming process may require the glass to have a high liquidus viscosity. This is necessary to avoid devitrification products at the interface with the glass and minimize visible devitrification products in the final glass. Therefore, for a given glass compatible with fusion for a particular sheet size and thickness, adjusting the process to produce wider or thicker sheets generally results in lower temperatures at either end of the tube. Some embodiments have a higher liquidus viscosity to provide greater flexibility in manufacturing via the fusion process. In some embodiments, the liquidus viscosity is greater than or equal to approximately 150 kP.

[0045] In testing the relationship between liquidus viscosity and subsequent devitrification tendency during the fusion process, the inventors surprisingly discovered that high delivery temperatures (such as those of the exemplary glasses) generally require higher liquidus viscosities for long-term production compared to typical AMLCD substrate compositions with lower annealing points. While not wishing to be bound by theory, this is believed to be due to the acceleration of crystal growth rates with increasing temperature. Fusion is a substantially isoviscous process, so at some fixed temperature, a higher viscosity glass can be formed by fusion at a higher temperature than a lower viscosity glass. While some degree of undercooling (cooling below the liquidus temperature) can be sustained in glasses at lower temperatures for extended periods, the crystal growth rate increases with temperature, so higher viscosity glasses can grow an unacceptably high amount of devitrified products in a shorter period of time compared to lower viscosity glasses. Depending on the location of formation, devitrified products can compromise formation stability and introduce visible defects into the final glass.

[0046] To be formed by a fusion process, one or more embodiments of the glass composition have a liquidus viscosity greater than or equal to approximately 150,000 P, or 175,000 P, or 200,000 P. A surprising result is that across the entire range of exemplary glasses, it is possible to achieve a liquidus temperature that is low enough and a viscosity that is high enough to result in a glass with an unusually high liquidus viscosity compared to other compositions.

[0047] In the glass compositions described herein, SiO₂ serves as a primary glass former. In certain embodiments, the SiO₂ concentration may be greater than 60 mol% to provide the glass with density and chemical durability suitable for flat panel display glass (e.g., AMLCD glass), as well as a liquidus temperature (liquidus viscosity) that allows the glass to be formed via a down-draw process (e.g., a fusion process). As an upper limit, the SiO₂ concentration may typically be less than or equal to approximately 80 mol% to allow bulk material to be melted using conventional high-volume melting techniques, such as Joule melting in a refractory melter. As the SiO₂ concentration increases, the 200°F temperature (melting temperature) generally increases. In various applications, the SiO₂ concentration is adjusted to provide a glass composition having a melting temperature of less than or equal to 1,750°C. In some embodiments, the SiO2 concentration is in a range of about 65 mol% to about 75 mol%, or in a range of about 69 mol% to about 73 mol%, or in a range of about 69 mol% to about 74 mol%, or in a range of about 70 mol% to 73 mol%, or in a range of about 68.84 to 74.07 mol%, or in a range of about 69.86 mol% to about 72.13 mol%.

[0048] Al2O3 is another glass former used to make the glasses described herein. Al2O3 concentrations greater than or equal to 10 mol% provide the glass with a low liquidus temperature and high viscosity, resulting in a high liquidus viscosity. The use of at least 10 mol% Al2O3 also improves the annealing point and modulus of the glass. To achieve a ratio (MgO+CaO+SrO+BaO) / Al2O3 greater than or equal to 1.0, the Al2O3 concentration can be about 15 mol% or less. In some embodiments, the Al2O3 concentration is in the range of about 12 to 14 mol%, or in the range of about 11 to about 14 mol%, or in the range of about 11 mol% to about 13 mol%, or in the range of about 10.41 mol% to about 14.07 mol%, or in the range of about 11.58 mol% to about 13.01 mol%. In some embodiments, the Al2O3 concentration is greater than or equal to approximately 10.0 mol%, 10.5 mol%, 11.0 mol%, 11.5 mol%, 12.0 mol%, 12.5 mol%, or 13.0 mol%, while the ratio of (MgO+CaO+SrO+BaO) / Al2O3 is maintained at greater than or equal to approximately 1.0.

[0049] Some embodiments of the present disclosure have a modulus greater than about 83 GPa, or 83.5 GPa, or 84 GPa, or 84.5 GPa, or 85 GPa.

[0050] Some embodiments of the aluminosilicate glass articles have a density of less than about 2.7 g / cc, or 2.65 g / cc, or 2.61 g / cc. In various embodiments, the density is in the range of about 2.48 g / cc to about 2.65 g / cc.

[0051] B₂O₃ is both a glass former and a flux, aiding melting and lowering the melting temperature. This affects both the liquidus temperature and viscosity. Increasing B₂O₃ can be used to increase the liquidus viscosity of the glass. To achieve this, the glass composition of one or more embodiments may have a B₂O₃ concentration equal to or greater than 0.01 mol%. As discussed above with respect to SiO₂, glass durability is critical for LCD applications. Durability can be controlled by slightly increasing the concentration of alkaline earth oxides and significantly reducing the B₂O₃ content. Increasing B₂O₃ lowers the annealing point, thus potentially helping to maintain the B₂O₃ content below its typical concentration in amorphous silicon substrates. Therefore, in some embodiments, the glass composition has a B₂O₃ concentration in the range of approximately 0.0 to 3 mol%, or greater than 0 to approximately 3 mol%, or approximately 0.0 to approximately 1 mol%, or approximately 0 to approximately 2 mol%.

[0052] Al 2 O 3 and B 2 O 3 concentrations can be selected as a pair to increase the annealing point, increase the modulus, improve durability, reduce density, and reduce the coefficient of thermal expansion (CTE) while maintaining the melting and forming properties of the glass.

[0053] For example, it is hypothesized that increasing B2O3 with a corresponding decrease in Al2O3 can contribute to lower density and CTE, while increasing Al2O3 with a corresponding decrease in B2O3 can contribute to improved annealing point, modulus, and durability, without reducing the (MgO+CaO+SrO+BaO) / Al2O3 ratio below approximately 1.0. For (MgO+CaO+SrO+BaO) / Al2O3 ratios below approximately 1.0, it may be difficult or impossible to remove gaseous inclusions from the glass due to late melting of the silica feedstock. Furthermore, when (MgO+CaO+SrO+BaO) / Al2O3 ≤ 1.05, mullite, aluminosilicate crystals, may exhibit a liquid phase. Once mullite is present as a liquid phase, the compositional sensitivity of the liquid phase increases significantly, and mullite devitrification products not only grow very rapidly but are also very difficult to remove once established. Therefore, in some embodiments, the glass composition has a ratio of (MgO+CaO+SrO+BaO) / Al2O3 ≥ 1.0 (or greater than or equal to approximately 1.0). In various embodiments, the glass has a ratio of (MgO+CaO+SrO+BaO) / Al2O3 ≥ 1.05 (or greater than or equal to approximately 1.05), or between approximately 1 and approximately 1.25.

[0054] In one or more embodiments, the glass for AMLCD applications has a coefficient of thermal expansion (CTE) (22-300° C.) in a range of about 3.0 ppm to about 4.0 ppm, or in a range of about 3.2 ppm to 3.9 ppm, or in a range of about 3.23 ppm to about 3.88 ppm.

[0055] In addition to the glass formers (SiO₂, Al₂O₃, and B₂O₃), the glasses described herein also include alkaline earth oxides. In one embodiment, at least three alkaline earth oxides are part of the glass composition, for example, MgO, CaO, and BaO, and optionally, SrO. Alkaline earth oxides provide the glass with various properties that are critical for melting, refining, forming, and end-use. Therefore, to improve glass performance in these aspects, in one embodiment, the ratio (MgO+CaO+SrO+BaO) / Al₂O₃ is greater than or equal to approximately 1.0. As this ratio increases, viscosity tends to increase more steadily than liquidus temperature, making it increasingly difficult to achieve a suitably high value of T₃⁻⁻ - T₁⁻. Therefore, in another embodiment, the ratio (MgO+CaO+SrO+BaO) / Al₂O₃ is less than or equal to approximately 2. In some embodiments, the (MgO+CaO+SrO+BaO) / Al2O3 ratio is in a range of about 1 to about 1.2, or in a range of about 1 to about 1.16, or in a range of about 1.1 to about 1.6. In detailed embodiments, the (MgO+CaO+SrO+BaO) / Al2O3 ratio is less than about 1.7, or 1.6, or 1.5.

[0056] For certain embodiments of the present disclosure, alkaline earth oxides can be considered as effectively individual components. This is because their effects on viscoelastic properties, liquidus temperature, and liquidus relationships are qualitatively more similar to each other than those of the glass-forming oxides SiO₂, Al₂O₃, and B₂O₃. However, alkaline earth oxides CaO, SrO, and BaO can form feldspar minerals, particularly anorthite (CaAl₂Si₂O₈) and celsium feldspar (BaAl₂Si₂O₈), and their strontium-bearing solid solutions, but MgO does not participate to a significant extent in these crystals. Therefore, when feldspar crystals are already in the liquidus phase, the addition of MgO can serve to stabilize the liquid relative to the crystals, thereby lowering the liquidus temperature. Simultaneously, the viscosity curve generally becomes steeper, thereby lowering the melting temperature while having little or no effect on low-temperature viscosity.

[0057] The inventors have discovered that adding a small amount of MgO can benefit melting by lowering the melting temperature and forming by lowering the liquidus temperature and increasing the liquidus viscosity, while maintaining a high annealing point and, therefore, low compaction. In various embodiments, the glass composition includes an amount of MgO in the range of about 4 mol% to about 8 mol%, or in the range of about 4 mol% to about 7 mol%, or in the range of about 3.44 mol% to about 7.45 mol%, or in the range of about 4.44 mol% to about 6.45 mol%.

[0058] The inventors have surprisingly discovered that for glasses with appropriately high values of T 35k - T liq , the ratio of MgO to other alkaline earth elements, MgO / (MgO + CaO + SrO + BaO), falls within a relatively narrow range. As described above, the addition of MgO can destabilize feldspar minerals, thereby stabilizing the liquidus and lowering the liquidus temperature. However, once MgO reaches a certain level, mullite and Al 6 Si 2 O 13 can be stabilized, thereby raising the liquidus temperature and reducing the liquidus viscosity. Furthermore, higher concentrations of MgO tend to reduce the viscosity of the liquidus, so even if the liquidus viscosity remains unchanged after MgO addition, the ultimate situation is that the liquidus viscosity will decrease. Thus, in another embodiment, 0.20 < MgO / (MgO + CaO + SrO + BaO) ≤ 0.40, or in some embodiments, 0.22 ≤ MgO / (MgO + CaO + SrO + BaO) ≤ 0.37. Within these ranges, MgO can be varied relative to the glass formers and other alkaline earth oxides to maximize the value of T 35k - T liq consistent with achieving other desired properties.

[0059] Without being bound by any particular theory of operation, it is believed that the presence of calcium oxide in the glass composition can produce a low liquidus temperature (high liquidus viscosity), a high annealing point and modulus, and a CTE within the most desirable ranges for flat panel applications, particularly AMLCD applications. This also advantageously contributes to chemical durability and is relatively inexpensive as a bulk material compared to other alkaline earth oxides. However, at high concentrations, CaO increases density and CTE. Furthermore, at sufficiently low SiO2 concentrations, CaO can stabilize anorthite, thereby reducing liquidus viscosity. Therefore, in one or more embodiments, the CaO concentration may be greater than or equal to 4.0 mol%. In various embodiments, the CaO concentration of the glass composition is in the range of approximately 5 mol% to approximately 10 mol%, or in the range of approximately 5 mol% to approximately 6 mol%, or in the range of approximately 5 mol% to approximately 7 mol%, or in the range of approximately 4.19 mol% to approximately 8.23 mol%, or in the range of approximately 5.53 mol% to approximately 7.23 mol%.

[0060] Both SrO and BaO contribute to a low liquidus temperature (high liquidus viscosity), so the glasses described herein will typically contain at least two of these oxides. However, the selection and concentration of these oxides are chosen to avoid increasing the CTE and density, and decreasing the modulus and annealing point. The relative proportions of SrO and BaO can be balanced to achieve an appropriate combination of physical properties and liquidus viscosity to enable the glass to be formed by a down-draw process. In various embodiments, the glass includes SrO in an amount ranging from about 0 to about 5 mol%, or from about 3 to about 4 mol%, or in a range from greater than 0 to about 3 mol%, or in a range from about 0 mol% to about 3.36 mol%, or in a range from about 0.09 mol% to about 1.67 mol%. In one or more embodiments, the glass includes BaO in an amount ranging from about 0 to about 5 mol%, or from 1 to about 5 mol%, or from about 0.91 to about 5.59 mol%, or from about 2.92 mol% to about 4.57 mol%.

[0061] To summarize the effects / results of the central components of this disclosure, SiO2 is a primary glass former. Al2O3 and B2O3 are also glass formers and can be selected as a pair, where, for example, increasing B2O3 and correspondingly decreasing Al2O3 is used to achieve lower density and CTE, while increasing Al2O3 and correspondingly decreasing B2O3 is used to improve annealing point, modulus, and durability, assuming that the increase in Al2O3 does not lower the RO / Al2O3 ratio below approximately 1.0, where RO = (MgO + CaO + SrO + BaO). If the ratio becomes too low, meltability is compromised, i.e., the melting temperature becomes too high. B2O3 can be used to lower the melting temperature, but high levels of B2O3 compromise the annealing point.

[0062] In addition to meltability and annealing point considerations, for AMLCD applications, the CTE of the glass should be compatible with that of silicon. To achieve such CTE values, exemplary glasses can control the RO content of the glass. For a given Al2O3 content, controlling the RO content corresponds to controlling the RO / Al2O3 ratio. In practice, a RO / Al2O3 ratio below approximately 1.6 produces a glass with an appropriate CTE.

[0063] In addition to these considerations, the glass is preferably formed by a downdraw process, such as a fusion process, which means that the liquidus viscosity of the glass needs to be relatively high. Individual alkaline earth elements play an important role in this aspect because they destabilize the crystalline phase that would otherwise form. BaO and SrO are particularly effective in controlling the liquidus viscosity and are included in the exemplary glasses for at least this purpose. As illustrated in the examples presented below, various combinations of alkaline earth elements will produce glasses with high liquidus viscosity, where all alkaline earth elements that meet the RO / Al2O3 ratio constraint need to achieve a low melting temperature, a high annealing point, and an appropriate CTE. In some embodiments, the liquidus viscosity is greater than or equal to approximately 150 kPa.

[0064] In addition to the amounts described, the glass compositions described herein may include various other oxides to adjust various physical, melting, fining, and forming properties of the glass. Examples of such other oxides include, but are not limited to, TiO2, MnO, Fe2O3, ZnO, Nb2O5, MoO3, Ta2O5, WO3, Y2O3, La2O3, and CeO2, as well as other rare earth oxides and phosphates. In one embodiment, the amount of each of these oxides may be less than or equal to 2.0 mol%, and the total combined concentration may be less than or equal to 5.0 mol%. In some embodiments, the glass compositions include ZnO, Y2O3, and / or ZrO2 in amounts ranging from about 0 to about 2 mol%, or from about 0 to about 1 mol%. The glass compositions described herein may also include various contaminants, particularly Fe2O2 and ZrO2, associated with bulk materials and / or introduced into the glass by the melting, fining, and / or forming equipment used to produce the glass. The glass may also contain SnO2 due to Joule melting using tin oxide electrodes and / or via the dosing of tin-containing materials such as SnO2, SnO, SnCO3, SnC2O2, etc.

[0065] Glass compositions are typically alkali-free; however, the glass may contain some alkali contaminants. In AMLCD applications, it is desirable to maintain alkali levels below 0.1 mol% to prevent adverse effects on thin film transistor (TFT) performance due to alkali ion diffusion from the glass into the silicon of the TFT. As used herein, "alkali-free glass" refers to glass with a total alkali concentration of less than or equal to 0.1 mol%, where the total alkali concentration is the sum of the concentrations of Na₂O, K₂O, and Li₂O. In one embodiment, the total alkali concentration is less than or equal to 0.1 mol%.

[0066] As discussed above, a (MgO+CaO+SrO+BaO) / Al2O3 ratio of 1.0 or greater improves refining, i.e., the removal of gaseous inclusions from the melted bulk material. This improvement allows for the use of environmentally friendly refining packages. For example, based on the oxides, the glass compositions described herein may have one, more, or all of the following compositional characteristics: (i) an As2O3 concentration of up to 0.05 mol%; (ii) a Sb2O3 concentration of up to 0.05 mol%; and (iii) a SnO2 concentration of up to 0.25 mol%.

[0067] As₂O₃ is an effective high-temperature fining agent for AMLCD glass, and in some embodiments described herein, As₂O₃ is used for fining due to its excellent fining properties. However, As₂O₃ is toxic and requires special handling during the glassmaking process. Therefore, in certain embodiments, fining is performed without using substantial amounts of As₂O₃, i.e., the finished glass has at most 0.05 mol% As₂O₃. In one embodiment, no As₂O₃ is specifically used for fining the glass. In such cases, the finished glass will typically have at most 0.005 mol% As₂O₃ due to contaminants present in the bulk material and / or the equipment used to melt the bulk material.

[0068] While less toxic than As₂O₃, Sb₂O₃ is also toxic and requires special handling. Furthermore, Sb₂O₃ increases density, raises the CTE, and lowers the annealing point compared to glasses using As₂O₃ or SnO₂ as fining agents. Therefore, in certain embodiments, fining is performed without using substantial amounts of Sb₂O₃, i.e., the finished glass has at most 0.05 mol% Sb₂O₃. In another embodiment, no Sb₂O₃ is intentionally used for fining the glass. In such cases, the finished glass will have at most 0.005 mol% Sb₂O₃ due to contaminants present in the bulk material and / or the equipment used to melt the bulk material.

[0069] While tin fining (i.e., SnO 2 fining) is less efficient than fining with As 2 O 3 and Sb 2 O 3, SnO 2 is a ubiquitous material with no known detrimental properties. Furthermore, SnO 2 has been a component of AMLCD glass for many years, using tin oxide electrodes in Joule melting of bulk materials for such glass. The presence of SnO 2 in AMLCD glass does not result in any known adverse effects associated with the use of such glass in the manufacture of liquid crystal displays. However, high concentrations of SnO 2 are not preferred because they can lead to the formation of crystal defects in the AMLCD glass. In one embodiment, the concentration of SnO 2 in the finished glass is less than or equal to 0.25 mol %.

[0070] In some embodiments, it has been unexpectedly discovered that the higher viscosity glasses described herein can tolerate higher concentrations of SnO₂ without any detrimental effects on the glass's performance. For example, one skilled in the art will inform us that glasses with high annealing points result in high melting temperatures. Such high melting temperatures can lead to poor inclusion quality in the respective glasses. To address such inclusion quality, fining agents can be added; however, due to the crystallization of SnO₂ in the glass, glasses with low viscosities typically do not tolerate the addition of SnO₂. However, the exemplary glasses described herein can possess higher viscosities, which lead to higher formation temperatures, thereby allowing for the addition of higher concentrations of fining agents to the glass, thereby resulting in fewer inclusions. In short, we have discovered that by altering the composition of the exemplary glasses to create higher processing temperatures, larger amounts of fining agents can be added to remove inclusions before crystallization occurs. Thus, an exemplary glass may include SnO2 at a concentration between 0.001 mol% and 0.5 mol% and a T35kP greater than or equal to approximately 1270° C., greater than or equal to approximately 1280° C., or greater than or equal to approximately 1290° C. Another exemplary glass may include SnO2 at a concentration between 0.001 mol% and 0.5 mol% and a T200P greater than or equal to approximately 1650° C., greater than or equal to approximately 1660° C., or greater than or equal to approximately 1670° C. Another exemplary glass may include SnO2 at a concentration between 0.001 mol% and 0.5 mol% and a T35kP greater than or equal to approximately 1270° C., greater than or equal to approximately 1280° C., or greater than or equal to approximately 1290° C. and a T200P greater than or equal to approximately 1650° C., greater than or equal to approximately 1660° C., or greater than or equal to approximately 1670° C. Yet another exemplary glass may include SnO2 at a concentration between 0.001 mol% and 0.5 mol% and a liquidus temperature greater than approximately 1150°C, greater than approximately 1165°C, or greater than approximately 1170°C. Such a glass may also have a T35kP and / or a T200P as discussed above. Of course, SnO2 can be provided to the glass due to Joule melting using a tin oxide electrode and / or via the addition of tin-containing materials such as SnO2, SnO, SnCO3, SnC2O2, etc.

[0071] Tin fining can be used alone or in combination with other fining techniques, if desired. For example, tin fining can be combined with halide fining (e.g., bromine fining). Other possible combinations include, but are not limited to, tin fining plus sulfate, sulfide, cerium oxide, mechanical bubbling, and / or vacuum fining. It is contemplated that these other fining techniques can be used alone. In certain embodiments, maintaining the (MgO+CaO+SrO+BaO) / Al2O3 ratio and individual alkaline earth concentrations within the ranges described above makes the fining process easier to perform and more efficient.

[0072] The glass described herein can be manufactured using various techniques known in the art. In one embodiment, the glass is produced using a down-draw process, such as a fusion down-draw process. In other embodiments, the glass is produced using a float process. In one embodiment, a method for producing an alkali-free glass sheet is described. The manufacturing process includes selecting, melting, and refining batch materials such that the glass comprising the sheet includes SiO₂, Al₂O₃, B₂O₃, MgO, CaO, and BaO, and includes, based on the oxides, a (MgO+CaO+SrO+BaO) / Al₂O₃ ratio greater than or equal to 1.0.

[0073] U.S. Patent Nos. 5,785,726 (Dorfeld et al.), 6,128,924 (Bange et al.), 5,824,127 (Bange et al.), and 7,628,038 and 7,628,039 (De Angelis et al.) disclose processes for producing arsenic-free glass. U.S. Patent No. 7,696,113 (Ellison) discloses a process for producing arsenic-free and antimony-free glass. Iron and tin are used to minimize gaseous inclusions.

[0074] Some embodiments relate to glasses comprising, in molar percentages based on oxides, 65-75% SiO, 12-14% AlO, 30-3% B2O, 4-8% MgO, 5-10% CaO, 0-5% SrO, and other oxides including Y2O3, ZrO2, and 0-2% ZnO. In some embodiments, the glasses comprise, in molar percentages based on oxides, 69-73% SiO, 12-14% Al2O, 30-3% B2O, 4-7% MgO, 5-6% CaO, 3-4% SrO, and other oxides including Y2O3, ZrO2, and 0-1% ZnO. In some embodiments, the glasses have a strain point greater than 760°C. In some embodiments, the glasses have a strain point of 200 poise at a temperature below 1650°C. In some embodiments, the glasses have a liquidus temperature below 1300°C. In some embodiments, the glass has a liquidus viscosity greater than 20,000 P. In some embodiments, the glass has a Young's modulus greater than 85 GPa. In some embodiments, the glass has a specific modulus greater than 33 GPa / g / cm 3.

[0075] Some embodiments relate to glasses comprising, in molar percentages based on oxides, 69-74% SiO, 11-14% AlO, 30-3% B2O, 4-7% MgO, 5-7% CaO, 0-3% SrO, and 1-5% BaO. In some embodiments, the glasses comprise, in molar percentages based on oxides, 70-73% SiO, 11-14% Al2O, 30-1% B2O, 4-7% MgO, 5-7% CaO, 0-3% SrO, and 1-5% BaO. In some embodiments, the glasses have a strain point greater than 752°C. In some embodiments, the glasses have a liquidus temperature less than 1300°C. In some embodiments, the glasses have a liquidus viscosity greater than 20,000 P. In some embodiments, the glasses have a Young's modulus greater than 83.56 GPa. In some embodiments, the glasses have a specific modulus greater than 32 GPa / g / cm3.

[0076] Some embodiments relate to glasses comprising, in molar percentages based on oxides, SiO 268.84-74.07, Al 2O 310.41-14.87, B 2O 30-2, MgO 3.44-7.45, CaO 4.19-8.23, SrO 0-3.36, BaO 0.91-5.59, and SnO 20.09-0.2%. In some embodiments, the glass comprises, in molar percentages based on oxides, the following: SiO 269.86-72.13, Al 2 O 311.58-13.01, B 2 O 30-1, MgO 4.44-6.45, CaO 5.53-7.23, SrO 0.09-1.67, BaO 2.92-4.57, and SnO 20.09-0.1%. In some embodiments, the glass has a strain point greater than 760°C. In some embodiments, the glass has a poise of 200 at a temperature below 1650°C. In some embodiments, the glass has a liquidus temperature below 1300°C. In some embodiments, the glass has a liquidus viscosity greater than 20,000 P. In some embodiments, the glass has a Young's modulus greater than 85 GPa. In some embodiments, the glass has a specific modulus greater than 33 GPa / g / cm 3.

[0077] Some embodiments relate to glasses comprising SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO, based on molar percentages of the oxides, and having a Young's modulus defined by the following relationship: 78 GPa ≤ 69.91973399947 + 0.803977834357368*Al2O3 - 0.906331789808018*B2O3 + 0.773177760652988*MgO + 0.358794596568283*CaO + 0.0167545708595792*SrO - 0.382565908440928*BaO ≤ 90 GPa. Some embodiments relate to glasses including SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO, measured on a molar basis as oxides, and having an annealing temperature defined by the following relationship: 750°C < 854.140323860904 + 4.46948220485465 * Al2O3- 14.4689626526177*B2O3- 5.91884532478309*MgO -5.94752853843398*CaO - 5.85611498931903*SrO - 6.03112833503798*BaO ≤ 860°C.

[0078] It should be understood that the various disclosed embodiments may involve specific features, elements, or steps described in conjunction with a particular embodiment. It should also be understood that although specific features, elements, or steps are described with respect to a particular embodiment, the specific features, elements, or steps may be interchanged or combined with alternative embodiments in various combinations or permutations not illustrated.

[0079] It should also be understood that as used herein, the terms "the," "a," or "an" mean "at least one" and should not be limited to "only one" unless expressly indicated to the contrary.

[0080] Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When expressing such ranges, examples include from one particular value and / or to another particular value. Similarly, when values are expressed as approximate using the antecedent "about," it should be understood that the particular value forms another aspect. It should be further understood that the endpoints of each range are meaningful both in relation to the other endpoint and independently of the other endpoint.

[0081] As used herein, the terms "substantially," "substantially," and variations thereof are intended to indicate that the described feature is equal to or approximately equal to a value or description. Additionally, "substantially similar" is intended to mean that two values are equal or approximately equal. In some embodiments, "substantially similar" can mean that the values are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0082] Unless otherwise expressly stated, it is not intended that any method described herein be construed as requiring that the steps be performed in a specific order. Therefore, if a method claim does not actually recite the order followed by its steps, or if the claims or description do not expressly state that the steps are limited to a specific order, it is not intended that any particular order be inferred.

[0083] Although various features, elements, or steps of a particular embodiment may be disclosed using the transition phrase "comprising," it should be understood that the implied alternatives include those features, elements, or steps that may be described using the transition phrases "consisting of" or "consisting essentially of." Thus, for example, implied alternatives to an apparatus comprising A+B+C include an embodiment in which the apparatus consists of A+B+C and an embodiment in which the apparatus consists essentially of A+B+C.

[0084] Those skilled in the art will appreciate that modifications and variations can be made to the present disclosure without departing from the spirit and scope of the present disclosure. Although modifications, combinations, sub-combinations, and variations of the disclosed embodiments that incorporate the spirit and substance of the present disclosure may occur to those skilled in the art, the present disclosure should be construed to include all content within the scope of the appended claims and their equivalents. Examples

[0085] The following examples are presented below to illustrate methods and results according to the disclosed subject matter. These examples are not intended to be comprehensive, but rather to illustrate representative methods and results. These examples are not intended to exclude equivalents and variations of the present disclosure that would be apparent to one skilled in the art.

[0086] Efforts have been made to ensure accuracy with respect to numerical values (e.g., amounts, temperatures, etc.), but some errors and deviations should be accounted for. Unless otherwise indicated, temperatures are in ° C. or at ambient temperature, and pressures are at or near atmospheric. Ingredients themselves are given as molar percentages based on the oxide and are normalized to 100%. Numerous variations and combinations of reaction conditions, such as component concentrations, temperatures, pressures, and other reaction ranges and conditions, exist that can be used to optimize the product purity and yield obtained from the described processes. Optimizing such process conditions will require only reasonable and routine experimentation.

[0087] The glass properties described in Table 1 were determined according to conventional techniques in the glass art. Thus, the linear coefficient of thermal expansion (CTE) over the temperature range of 25-300°C is expressed in ppm, and the annealing point is expressed in °C. The CTE and annealing point were determined according to the fiber elongation technique (ASTM References E228-85 and C336, respectively). Density in g / cm³ was measured using the Archimedes method (ASTM C693). The melting temperature in °C (defined as the temperature at which the glass melt exhibits a viscosity of 200°C) was calculated using the Fulciu equation fitted to high-temperature viscosity data measured using rotating cylinder viscometry (ASTM C965-81). The strain point and annealing point were measured using a beam bending viscometer (BBV), and the high-temperature viscosity (HTV) above the glass softening point (corresponding to a glass viscosity of 10 7.6 P) was measured by rotating cylinder viscometry according to ASTM C 965 (B).

[0088] The liquidus temperature of glass, expressed in degrees Celsius, is measured using the standard gradient boat liquidus method of ASTM C829-81. This method involves placing crushed glass articles in a platinum boat, placing the boat in a furnace with a gradient temperature zone, heating the boat in the appropriate temperature zone for 24 hours, and determining the highest temperature at which crystals appear within the glass by microscopic examination. More specifically, glass samples are removed individually from the platinum boat and examined using polarizing microscopy to identify the location and nature of crystals that have formed within the sample, resisting the platinum-air interface. Because the furnace gradient is well known, a temperature-to-position relationship within a range of 5-10°C provides a good estimate. The temperature at which crystals are observed within the interior portion of the sample is used to represent the liquidus of the glass (for the corresponding test period). Tests are sometimes run for longer periods (e.g., 72 hours) to observe slower growth periods. The liquidus viscosity, expressed in P, is determined based on the liquidus temperature and the coefficients of the Fulciu equation.

[0089] Young's modulus values in GPa were determined using resonant ultrasonic spectroscopy techniques of the general type set forth in ASTM E1875-00e1.

[0090] Exemplary glasses are shown in Table 1. As can be seen in Table 1, the exemplary glasses have density, annealing point, and Young's modulus values that make them suitable for display applications such as AMLCD substrates, and more specifically, for low-temperature polysilicon and oxide thin-film transistor applications. Although not shown in Table 1, the glasses exhibit durability in acidic and alkaline media similar to that obtained from commercial AMLCD substrates and are suitable for AMLCD applications. The exemplary glasses can be formed using down-draw techniques and, in particular, are compatible with fusion processes, as described above.

[0091] The exemplary glasses in Table 1 were prepared using commercially available sand as a source of silica, milled so that 90 wt% passed through a standard U.S. 100 mesh sieve. Alumina was the source of aluminum oxide, periclase was the source of MgO, limestone was the source of CaO, strontium carbonate, strontium nitrate, or a mixture thereof was the source of SrO, barium carbonate was the source of BaO, and tin(IV) oxide was the source of SnO₂. The raw materials were thoroughly mixed, loaded into a platinum container suspended in a furnace heated by a silicon carbide hot rod, melted at temperatures between 1600 and 1650°C, stirred for several hours to ensure homogeneity, and delivered through an orifice in the base of the platinum container. The resulting cake of glass was annealed at or near the annealing point and subjected to various experimental methods to determine physical, viscosity, and liquidus properties.

[0092] These methods are not exclusive, and the glasses of Table 1 can be prepared using standard methods known to those skilled in the art. Such methods include continuous melting processes, such as would be performed in a continuous melting process in which the melter used in the continuous melting process is heated by gas, by electricity, or a combination thereof.

[0093] Raw materials suitable for producing exemplary glasses include commercially available sand as a source of SiO2; aluminum oxide, aluminum hydroxide, hydrous forms of aluminum oxide, and various aluminosilicates, nitrates, and halides as sources of Al2O3; boric acid, anhydrous boric acid, and boric oxide as sources of B2O3; periclase, dolomite (also a source of CaO), magnesium oxide, magnesium carbonate, magnesium hydroxide, and various forms of magnesium silicates, aluminosilicates, nitrates, and halides as sources of MgO; limestone, aragonite, dolomite (also a source of MgO), wollastonite, and various forms of calcium silicates, aluminosilicates, nitrates, and halides as sources of CaO; and oxides, carbonates, nitrates, and halides of strontium and barium. If chemical fining is desired, tin may be added as SnO 2 , as a mixed oxide with another major glass component (e.g., CaSnO 3 ), or under oxidizing conditions as SnO, tin oxalate, tin halide, or other compounds of tin known to those skilled in the art.

[0094] The glasses in Table 1 contain SnO₂ as a fining agent, but other chemical fining agents can also be used to achieve glass of sufficient quality for TFT substrate applications. For example, the exemplary glasses may utilize any one or a combination of As₂O₃, Sb₂O₃, CeO₂, Fe₂O₃, and halides as prudent additions to promote fining, and any of these can be used in conjunction with the SnO₂ chemical fining agent shown in the examples. As₂O₃ and Sb₂O₃ are generally identified as hazardous materials and are subject to control in waste streams generated during processes such as glass manufacturing or TFT panel processing. Therefore, the concentrations of As₂O₃ and Sb₂O₃ need to be limited to no more than 0.005 mol%, either individually or in combination.

[0095] In addition to the elements deliberately incorporated into the exemplary glasses, nearly all stable elements in the periodic table are present in the glass at some level, either as low-level contaminants in the raw materials, through high-temperature corrosion of refractory materials and precious metals during the manufacturing process, or through deliberate introduction at low levels to fine-tune the properties of the final glass. For example, zirconium can be introduced as a contaminant through interaction with zirconium-rich refractory materials. As another example, platinum and rhodium can be introduced through interaction with precious metals. As another example, iron can be introduced as an admixture in the raw materials or deliberately added to enhance control over gaseous inclusions. As another example, manganese can be introduced to control color or enhance control over gaseous inclusions. As another example, alkali can be present as admixtures of Li₂O, Na₂O, and K₂O at a combined concentration of up to approximately 0.1 mol%.

[0096] Hydrogen inevitably exists in the form of hydroxyl anions (OH-), and this presence can be determined using standard infrared spectroscopy techniques. Dissolved hydroxyl ions significantly and nonlinearly affect the annealing point of the exemplary glass, so to achieve the desired annealing point, it may be necessary to adjust the concentration of the primary oxide component to compensate. The hydroxyl ion concentration can be controlled to some extent by selecting the raw materials or the melting system. For example, boric acid is a major source of hydroxyl groups, and replacing boric acid with boron oxide can be a useful way to control the hydroxyl concentration in the final glass. Similar reasoning applies to other potential raw materials that include hydroxyl ions, hydrates, or compounds containing physically or chemically adsorbed water molecules. If a burner is used in the melting process, hydroxyl ions can also be introduced via combustion products and associated hydrocarbons from burning natural gas, so it may be desirable to transfer energy used in the melting process from the burner to the electrodes to compensate. Alternatively, one can instead employ an iterative process to adjust the primary oxide component to compensate for the deleterious effects of dissolved hydroxyl ions.

[0097] Sulfur is commonly present in natural gas and is a component of many carbonate, nitrate, halide, and oxide feedstocks. In the form of SO₂, sulfur can be a problematic source of gaseous inclusions. The tendency to form SO₂-rich defects can be managed to a significant degree by controlling the sulfur level in the feedstock and by incorporating low levels of relatively reducing multivalent cations into the glass matrix. While not wishing to be bound by theory, it appears that SO₂-rich gaseous inclusions arise primarily through the reduction of sulfates (SO₄=) dissolved in the glass. The elevated barium concentration of the exemplary glass appears to increase sulfur retention in the glass early in the melting process, but as discussed above, barium is required to achieve a low liquidus temperature, and thus a high T₃⁻T⁶ and high liquidus viscosity. Carefully controlling the sulfur level in the feedstock to a low level is a useful method for reducing dissolved sulfur (presumably sulfates) in the glass. In particular, sulfur is preferably less than 200 ppm by weight in the bulk material, and more preferably less than 100 ppm by weight in the bulk material.

[0098] Reducing multivalent electrons can also be used to control the tendency of the exemplary glasses to form SO 2 bubbles. While not wishing to be bound by theory, these elements act as potential electron donors to suppress the electromotive force for sulfate reduction. Sulfate reduction can be written in terms of half reactions such as SO 4 =→ SO 2 + O 2 + 2e - Where e - represents electrons. The equilibrium constant for the half reaction is K eq= [SO 2][O 2][e -] 2 / [SO 4 =] The brackets indicate chemical activity. Ideally, we want to force the reaction to form sulfate from SO₂, O₂, and 2e⁻. Adding nitrates, peroxides, or other oxygen-rich raw materials can help, but they may also counteract sulfate reduction early in the melt, potentially negating the benefit of adding them in the first place. SO₂ has very low solubility in most glasses and is therefore impractical to add to the glass melting process. Electrons can be "added" by reducing multiple valence electrons. For example, the appropriate electron-removing half-reaction for divalent iron (Fe₂+) is expressed as: 2Fe 2+→ 2Fe 3++ 2e -.

[0099] This "activity" of the electrons can force the sulfate reduction reaction to the left, thereby stabilizing SO₄⁻ in the glass. Suitable reducing multivalent electrons include, but are not limited to, Fe₂+, Mn₂+, Sn₂+, Sb₃+, As₃+, V₃+, Ti₃+, and others familiar to those skilled in the art. In each case, it can be important to minimize the concentration of these components to avoid adversely affecting the color of the glass or, in the case of As and Sb, to avoid adding these components at sufficiently high levels to complicate waste management by the end user.

[0100] In addition to the primary oxide components of the exemplary glasses and the minor or admixture components mentioned above, halides may be present at various levels as contaminants introduced through raw material selection or as prudent amounts used to eliminate gaseous inclusions in the glass halides. As fining agents, halides may be incorporated at levels of approximately 0.4 mol% or less, although lower amounts are generally desirable (if possible) to avoid corrosion of exhaust gas handling equipment. In some embodiments, the concentration of individual halide elements is below approximately 200 ppm by weight for each halide, or below approximately 800 ppm by weight for all halide elements combined.

[0101] In addition to these major oxide components, minor and admixture components, multivalent electron and halide fining agents, it may be useful to incorporate low concentrations of other colorless oxide components to achieve desired physical, optical, or viscoelastic properties. Such oxides include, but are not limited to, TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, MoO3, WO3, ZnO, In2O3, Ga2O3, Bi2O3, GeO2, PbO, SeO3, TeO2, Y2O3, La2O3, Gd2O3, and others known to those skilled in the art. Through an iterative process of adjusting the relative proportions of the major oxide components of the exemplary glass, such colorless oxides can be added to a level of up to about 2 mol% without unacceptably affecting the annealing point, T35k-Tliq, or liquidus viscosity.

[0102] Table 1 shows examples of glasses according to some embodiments. Table 1 1 2 3 4 5 6 <h2 style=";text-align:left;direction:ltr">SiO2<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 72.41<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 72.03<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 71.67<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 72.26<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 70.86<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 70.37<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> Al 2O 3<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 12.53<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 12.48<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 12.35<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 13.09<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 12.29<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 12.23<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> MgO<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 4.68<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 4.63<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 6.13<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 5.67<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 6.98<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 7.05<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> CaO<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 5.85<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 5.85<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 9.73<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 8.87<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 5.77<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 5.80<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> SrO<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 3.96<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 3.94<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 3.95<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 3.94<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> ZrO2<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 0.00<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 0.48<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> Y 2 O 3<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 0.44<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 0.00<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> ZnO<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> 0.93<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> -<h2 style=";text-align:left;direction:ltr"> - - SnO 2 0.09 0.10 0.10 0.10 0.10 0.10 Strain point (℃) 778.1 766.3 771 775 758.7 764.8 Annealing point (℃) 826.3 814.9 819.5 825 808.8 811.6 200 PT (℃) 1683 1684 1658 1663 1658 1649 CTE (ppm) 3.72 3.53 3.57 3.23 3.79 3.80 Density (g / cc) 2.569 2.561 2.491 2.483 2.558 2.574 Young's modulus (GPa) 86.4 85.8 87.1 87.2 86.6 87.4 Specific modulus (GPa / g / cc) 33.6 33.5 35.0 34.8 33.9 34.0 Liquidus temperature (℃) 1290 1275 1320 1325 1270 1275 Liquid phase white silica white silica white silica white silica Strontium feldspar calcium feldspar Liquid viscosity (P) 53,000 60,000 17,000 21,000 49,000 43,000 7 8 9 10 11 12 SiO 2 70.20 71.63 70.23 72.64 72.02 72.16 Al 2O 3 12.15 12.44 13.14 12.63 12.48 13.11 MgO 6.93 4.65 5.99 4.71 4.65 5.68 CaO 5.76 5.83 5.93 5.87 5.85 5.94 SrO 3.89 3.93 3.56 4.01 3.95 2.96 Y2O3 - - - - - - ZrO 2 0.92 0.91 1.01 - 0.92 - ZnO 0.00 0.47 - - 0.00 - SnO 2 0.09 0.09 0.10 0.10 0.09 0.09 Strain point (℃) 764.2 772.6 766.3 774.6 777.1 774 Annealing point (℃) 812.6 819.6 815.9 824.8 826.6 825 200 PT (℃) 1614 1651 1620 1700 1657 1679 CTE (ppm) 3.88 3.64 3.82 3.61 3.68 3.26 Density (g / cc) 2.62 2.611 2.61 2.54 2.6 2.528 Young's modulus (GPa) 88.2 87.2 88.4 86.0 87.2 86.9 Specific modulus (GPa / g / cc) 33.7 33.4 33.9 33.9 33.6 34.4 Liquidus temperature (℃) 1255 1310 1265 1285 1290 1290 Liquid phase white silica white silica Strontium feldspar Strontium feldspar white silica white silica Liquid viscosity (P) 50,000 25,000 39,000 65,000 41,000 49,000 13 14 15 16 17 18 SiO 2 70.20 70.66 69.98 72.31 71.09 72.31 Al 2O 3 12.17 12.20 12.06 12.55 13.21 13.04 MgO 6.96 6.91 6.89 4.68 6.08 5.61 CaO 5.74 5.75 5.71 5.86 9.50 5.37 SrO 3.88 3.91 3.85 3.98 - 3.53 ZrO 2 0.49 0.00 - 0.48 - - Y2O3 0.44 0.44 0.91 - - - ZnO - - 0.46 - - - SnO 2 0.09 0.09 0.09 0.10 0.10 0.10 Strain point (℃) 763.9 765.8 757.3 780 774.6 774.3 Annealing point (℃) 812.6 814.1 804.9 830.1 821.6 824.8 200 PT (℃) 1633 1639 1611 1693 1635 1685 CTE (ppm) 3.81 3.77 3.84 3.58 3.36 3.6 Density (g / cc) 2.603 2.585 2.63 2.553 2.496 2.534 Young's modulus (GPa) 88.1 87.2 88.8 85.9 87.9 86.2 Specific modulus (GPa / g / cc) 33.8 33.7 33.8 33.7 35.2 34.0 Liquidus temperature (℃) 1260 1300 1265 1285 1295 1280 Liquid phase white silica white silica white silica white silica calcium feldspar Strontium feldspar Liquid viscosity (P) 49,000 24,000 31,000 68,000 20,000 59,000 19 20 twenty one twenty two SiO 2 70.13 70.65 71.13 72.20 AI 2O 3 12.17 13.03 13.17 12.43 MgO 6.96 5.97 6.02 4.61 CaO 5.76 5.84 5.94 5.81 SrO 3.90 3.48 3.60 3.92 ZrO 2 - 0.39 - 0.48 Y2O3 0.00 0.50 - 0.43 ZnO 0.94 - - - SnO 2 0.10 0.09 0.10 0.09 Strain point (℃) 753.4 768.8 771.8 779.9 Annealing point (℃) 802.5 817.9 820.5 827 200 PT (℃) 1642 1643 1681 1674 CTE (ppm) 3.55 3.66 3.67 3.64 Density (g / cc) 2.581 2.596 2.548 2.582 Young's modulus (GPa) 86.8 88.5 86.5 86.7 Specific modulus (GPa / g / cc) 33.6 34.1 34.0 33.6 Liquidus temperature (℃) 1260 1270 1280 1285 Liquid phase white silica Strontium feldspar Strontium feldspar white silica Liquid viscosity (P) 47,000 42,000 51,000 54,000

[0103] Referring to Table 1 above, Example 3 provides the eutectic point of mullite, tridymite, and anorthite in the MgO-CaO-SiO₂-Al₂O₃ (20 wt%) system (see, for example, Figure 8 ). This embodiment offers many desirable properties, such as a high strain point, high Young's modulus, low 200°C temperature, low CTE, and low density. However, the liquidus temperature of Example 3 is high (1320°C) and the liquidus viscosity is low (17,000°C), which poses some challenges for certain manufacturing processes. Example 17 provides an increase of approximately 1 mol% Al₂O₃ relative to Example 3, which increases the strain point, Young's modulus, further reduces the 200°C temperature, lowers the liquidus temperature, and increases the liquidus viscosity. Example 21 further improves the liquidus by replacing part of the CaO in Example 17 with SrO, successfully lowering the liquidus temperature and doubling the liquidus viscosity. The addition of Y2O3 and ZrO2 in Example 21 (Examples 9 and 20) further lowers the liquidus temperature while maintaining a high strain point and high Young's modulus. In some embodiments, the inclusion of Y2O3 and ZrO2 can be used to increase the Young's modulus. Example 10 is a variation of Example 12, in which the concentration of Al2O3 is reduced and the concentration of alkaline earth elements is increased to improve the liquidus viscosity. To lower the liquidus temperature in Example 10, small amounts of Y2O3, ZnO, and ZrO2 are added. Thus, with 1 mol% Y2O3 (Example 16) and 1 mol% Y2O3 + 0.5 mol% ZnO (Example 8), the melting temperature (200°C temperature) is reduced by approximately 50°C, but the liquidus temperature remains unchanged. Example 5 is also a variation of Example 10, in which SiO2 is reduced and alkaline earth elements are increased to improve the melting temperature, resulting in a 40°C reduction compared to Example 10. Small amounts of Y2O3, ZnO, and ZrO2 were added to Example 5 to improve other properties. The remaining examples in Table 1 also provided improved Young's modulus and reduced melting temperatures.

[0104] Table 2 shows other examples of glasses according to some embodiments. Table 2 twenty three twenty four 25 26 27 28 SiO 2 72.86 72.12 70.93 71.58 72.04 69.66 AI 2O 3 11.43 12.03 12.42 12.51 12.33 13.13 B2O3 0.00 0.00 0.21 0.51 0.00 0.00 MgO 5.50 5.61 6.12 5.18 5.57 5.90 CaO 5.32 5.80 6.16 5.56 5.55 5.98 SrO 1.21 2.36 0.78 0.89 1.01 1.03 BaO 3.57 1.91 3.23 3.61 3.38 4.11 SnO 2 0.10 0.12 0.10 0.10 0.11 0.12 Strain point (℃) 759.70 764.30 759.90 757.20 769.30 760.50 Annealing point (℃) 811.50 815.70 810.60 810.10 819.80 810.60 200 PT (℃) 1711.00 1694.00 1678.00 1695.00 1700.00 1719.00 CTE (ppm) 3.77 3.65 3.72 3.63 3.80 3.78 Density (g / cc) 2.60 2.57 2.59 2.59 2.59 2.64 Young's modulus (GPa) 83.56 84.67 84.46 84.10 83.91 85.49 Specific modulus (GPa / g / cc) 32.12 32.91 32.57 32.31 32.35 32.35 Liquidus temperature (℃) 1240.00 1245.00 1230.00 1250.00 1255.00 >1265 Liquid phase white silica white silica barium feldspar barium feldspar unknown white silica Liquid viscosity (P) 1.78E+05 1.39E+05 1.46E+05 1.21E+05 1.14E+05 1.10E+05 29 30 31 32 33 34 35 SiO 2 71.72 72.13 69.86 72.99 73.07 72.20 71.24 Al 2O 3 12.76 11.58 12.83 11.41 11.90 12.65 12.63 B2O3 0.00 0.00 0.00 0.00 0.00 0.62 0.00 MgO 6.10 5.63 5.61 5.66 4.98 5.85 5.26 CaO 5.46 5.93 6.33 5.44 5.19 5.53 5.96 SrO 1.61 0.20 1.67 1.01 1.51 0.09 0.15 BaO 2.24 4.30 3.40 3.38 3.23 2.92 4.59 SnO 2 0.11 0.09 0.10 0.10 0.10 0.10 0.10 Strain point (℃) 769.50 761.70 765.90 764.60 760.60 Annealing point (℃) 818.90 813.00 812.33 813.60 818.20 815.60 812.80 200 P T (℃) 1683.00 1700 1662 1717.00 1710.00 1703.00 1699.00 CTE (ppm) 3.63 3.64 3.59 3.48 3.79 Density (g / cc) 2.57 2.61 2.63 2.59 2.59 2.55 2.62 Young's modulus (GPa) 85.36 84.13 85.47 83.56 83.63 83.98 84.51 Specific modulus (GPa / g / cc) 33.17 32.02 32.35 32.24 32.24 32.92 32.09 Liquidus temperature (℃) 1270.00 1220 1275 1255.00 1240.00 1235.00 1220.00 Liquid phase unknown white silica calcium feldspar white silica white silica barium feldspar barium feldspar Liquid viscosity (P) 7.21E+04 5.45 4.69 1.23E+05 1.79E+05 1.89E+05 2.54E+05 36 37 38 39 40 41 42 SiO 2 72.11 69.64 71.86 70.14 71.82 71.74 72.04 Al 2O 3 12.34 13.08 11.58 11.99 12.35 13.01 12.36 B2O3 0.00 0.00 0.00 0.00 0.00 0.28 0.00 MgO 6.14 6.44 5.91 6.45 5.59 4.85 6.12 CaO 5.46 5.44 5.72 6.45 5.81 5.75 5.49 SrO 1.60 2.07 0.29 6.48 1.54 0.19 1.41 BaO 2.23 3.16 4.40 4.53 2.73 4.01 2.45 SnO 2 0.11 0.11 0.10 0.10 0.11 0.10 0.11 Strain point (℃) 768.80 759.90 768.00 767.20 766.20 Annealing point (℃) 819.70 810.40 811.17 804.79 818.90 817.00 817.40 200 PT (℃) 1693.00 1708.00 1709 1679 1690.00 1714.00 1692.00 CTE (ppm) 3.62 3.68 3.75 3.61 3.66 Density (g / cc) 2.57 2.63 2.62 2.64 2.59 2.59 2.57 Young's modulus (GPa) 85.22 85.49 84.22 85.14 84.25 84.38 85.29 Specific modulus (GPa / g / cc) 33.15 32.51 31.98 32.02 32.58 32.40 33.15 Liquidus temperature (℃) 1280.00 1265.00 1220 1230 1240.00 1245.00 1265.00 Liquid phase unknown Iolite white silica barium feldspar Iolite barium feldspar unknown Liquid viscosity (P) 6.24E+04 9.36E+04 5.38 5.11 1.44E+05 1.59E+05 8.69E+04 43 44 45 46 47 48 49 SiO 2 71.48 71.25 71.99 71.78 70.84 71.47 70.34 Al 2O 3 12.67 12.46 12.37 12.93 13.87 12.52 12.46 B2O3 0.00 0.00 0.00 0.00 0.33 0.51 1.00 MgO 5.80 4.44 6.06 5.48 5.15 5.19 5.18 CaO 5.47 7.23 5.55 5.62 5.50 5.95 6.43 SrO 2.01 0.13 1.01 1.48 1.00 0.19 1.18 BaO 2.40 4.19 2.91 2.56 3.14 4.02 3.21 SnO 2 0.12 0.10 0.11 0.12 0.15 0.10 0.09 Strain point (℃) 766.90 768.20 770.10 771.50 759.60 Annealing point (℃) 817.20 817.33 817.50 821.40 820.90 809.50 800.95 200 P T (℃) 1684.00 1699 1693.00 1724.00 1672.00 1691.00 1663 CTE (ppm) 3.70 3.66 3.49 3.53 3.66 Density (g / cc) 2.59 2.62 2.58 2.58 2.60 2.59 2.60 Young's modulus (GPa) 84.60 84.34 84.94 85.36 84.12 83.56 84.21 Specific modulus (GPa / g / cc) 32.70 32.05 32.95 33.08 32.36 32.26 32.19 Liquid phase T (℃) 1260.00 1260 >1270 >1285 >1260 1260.00 1235 Liquid phase Iolite calcium feldspar unknown white silica Mullite barium feldspar calcium feldspar Liquid viscosity (P) 9.10E+04 4.98 7.98E+04 9.41E+04 8.66E+04 1.03E+05 5.05

[0105] In some embodiments, an exemplary component may be described by a convex hull, which may be defined as the smallest convex boundary containing a set of points in space of a given size. For example, if we consider the space bounded by: 68.64 - 74.07 mol% SiO2, 10.41 - 14.87 mol% Al2O3, 0 - 2 mol% B2O3, 3.44 - 7.45 mol% MgO, 4.19 - 8.23 mol% CaO, 0 - 3.36 mol% SrO, 0.91 - 5.59 mol% BaO, and 0.09 - 0.2 mol% SnO2, we can group Al2O3 and B2O3 into a group designated Al2O3_B2O3, and the remainder into a group designated RO, which contains MgO, CaO, SrO, BaO, and SnO2 within their respective ranges. Subsequently, a new ternary space can be defined by a space whose boundaries are set by the following compositions in mol %, as shown in Table 3 and Figures 4 and 5. Table 3 SiO 2 Al 2O 3_B 2O 3 RO 70.20 10.63 19.17 70.97 10.63 18.39 73.13 10.66 16.20 73.18 11.11 15.71 73.21 12.12 14.67 73.20 14.10 12.71 73.19 14.26 12.55 73.14 14.78 12.08 73.10 15.15 11.76 72.82 16.52 10.66 71.70 16.79 11.51 69.36 16.78 13.86 68.95 16.76 14.29 68.67 16.71 14.61 68.58 16.32 15.10 68.55 15.55 15.90 68.57 10.95 20.48 68.99 10.75 20.26 69.10 10.71 20.19

[0106] The compositions within the convex hull bounded by the boundaries consisting of the compositions listed in Table 3 above have annealing points and Young's moduli given by Equations 2 and 3, respectively, where oxides are measured in mol %: 78 GPa ≤ 69.91973399947 + 0.803977834357368*Al2O3 - 0.906331789808018*B2O3 + 0.773177760652988*MgO + 0.358794596568283*CaO + 0.0167545708595792*SrO - 0.382565908440928*BaO ≤ 90 GPa (2) 750 oC ≤ 854.140323860904 + 4.46948220485465*Al2O3 - 14.4689626526177*B2O3 - 5.91884532478309*MgO -5.94752853843398*CaO - 5.85611498931903*SrO - 6.03112833503798*BaO ≤ 860 oC (3)

[0107] Figures 6 and 7 show the predicted Young's modulus and annealing point using equations (2) and (3), respectively, for the overall model, where the convex hull bounded by the compositional boundaries shown in Table 3 (Figures 4 and 5) is randomly selected for the maximum composition set of the sample composition set. These figures illustrate the agreement between a simple linear model based on the data within the convex hull and the overall model. Once a random extraction of 1000 data from the convex hull is performed by predicting the individual Young's modulus and annealing points, a linear model can be established. Equations (2) and (3) are effective representations of the Young's modulus and annealing point within the convex hull.

[0108] The compositions within the convex hull whose boundary is given by the compositions listed in Table 3 (these compositions are in mol %) have Young's modulus and annealing point given by Equation (2) and Equation (3), respectively.

[0109] 1: Entrance 2: Compression end 3:Edge guide 4: Flow channel 6: Location 9: Weir Wall 10: Root

[0110] Domestic storage information (please note the order of storage institution, date, and number) none

[0111] Overseas deposit information (please note the order of deposit country, institution, date, and number) none

Claims

1. A glass comprising, in mole percentages based on oxides: SiO2 69-74, Al2O3 11-14, B2O3 0-2, MgO 4-7, CaO 5-7, SrO 0-2.01, and BaO 1.91-5, wherein the glass has a strain point greater than 752°C and a Young's modulus greater than 83.56 GPa, wherein the glass comprises 0.005 mole percentage to 0.2 mole percentage of Fe2O3, and wherein (MgO+CaO+SrO+BaO) / Al2O3 is 1.1 to 1.

16.

2. The glass as claimed in claim 1, wherein the glass comprises the following in mole percentage based on oxides: SiO2 70-73, Al2O3 11-14, B2O3 0-1, MgO 4-7, CaO 5-7, SrO 0-2.01, and BaO 1.91-5.

3. The glass as claimed in claim 1, wherein the glass contains 2.92 to 4.57 moles of BaO.

4. The glass as claimed in claim 1, wherein the glass has an annealing temperature defined by the following relationship: 750℃≤854.140323860904+4.46948220485465*Al2O3-14.4689626526177*B2O3-5.91884532478309*MgO-5.94752853843398*CaO-5.85611498931903*SrO-6.03112833503798*BaO≤860℃.

5. The glass as claimed in claim 1, wherein the glass has a liquidus temperature below 1300°C, and wherein the glass has a density of 2.48 g / cc to 2.61 g / cc.

6. The glass as claimed in claim 1, wherein the glass has a liquid viscosity greater than 20,000 P.

7. The glass as claimed in claim 1, wherein the glass has a specific modulus greater than 32 GPa / g / cm3.

8. The glass as claimed in claim 1, wherein the glass has one of the Young's moduli defined by the following relationship: 78GPa≤69.91973399947+0.803977834357368*Al2O3-0.906331789808018*B2O3+0.773177760652988*MgO+0.358794596568283*CaO+0.0167545708595792*SrO-0.382565908440928*BaO≤90GPa.

9. A liquid crystal display substrate comprising the glass as described in claim 4 or claim 8.

10. A liquid crystal display substrate comprising the glass as described in claim 1.

11. A glass comprising, in molar percentages based on oxides: SiO2 68.84-74.07, Al2O3 10.41-14.87, B2O3 0-2, MgO 3.44-7.45, CaO 4.19-8.23, SrO 0-2.01, BaO 1.91-5.59, and SnO2 0.09-0.2, wherein the glass has a strain point greater than 752°C and a Young's modulus greater than 83.56 GPa, wherein Fe2O3 in the glass is 0.005 molar percentage to 0.2 molar percentage, and wherein (MgO+CaO+SrO+BaO) / Al2O3 is 1.1 to 1.

16.

12. The glass as claimed in claim 11, wherein the glass comprises the following in mole percentage based on oxides: SiO2 69.86-72.13, Al2O3 11.58-13.01, B2O3 0-1, MgO 4.44-6.45, CaO 5.53-7.23, SrO 0.09-1.67, BaO 2.92-4.57, and SnO2 0.09-0.

1.

13. The glass as claimed in claim 11, wherein the glass comprises the following in mole percentage based on oxides: SiO2 69-74, Al2O3 11-14, B2O3 0-2, MgO 4-7, CaO 5-7, SrO 0-2.01, BaO 1.91-5, and SnO2 0.09-0.

2.

14. The glass as claimed in claim 11, wherein the glass has a strain point greater than 760°C.

15. The glass as claimed in claim 11, wherein the glass has a temperature of 200°C below 1650°C.

16. The glass as claimed in claim 11, wherein the glass has a liquidus temperature below 1300°C, and wherein the glass has a density of 2.48 g / cc to 2.61 g / cc.

17. The glass as claimed in claim 11, wherein the glass has a liquid phase viscosity greater than 20,000 P.

18. The glass as claimed in claim 11, wherein the glass has a Young's modulus greater than 85 GPa.

19. The glass as claimed in claim 11, wherein the glass has a specific modulus greater than 33 GPa / g / cm3.

20. A liquid crystal display substrate comprising the glass as described in claim 11.

21. The glass as claimed in claim 11, wherein the glass has one of the Young's moduli defined by the following relationship: 78 GPa ≤ 69.91973399947 + 0.803977834357368 * Al2O3 - 0.906331789808018 * B2O3 + 0.773177760652988 * MgO + 0.358794596568283 * CaO + 0.0167545708595792 * SrO - 0.382565908440928 * BaO ≤ 90 GPa.

22. The glass as claimed in claim 11, wherein the glass has an annealing temperature defined by one of the following relationships: 750℃≤854.140323860904+4.46948220485465*Al2O3-14.4689626526177*B2O3-5.91884532478309*MgO-5.94752853843398*CaO-5.85611498931903*SrO-6.03112833503798*BaO≤860℃.

23. An article comprising glass as described in claim 11.

Images