Dimensionally stable glass

Abstract

To provide a glass capable of manufacturing a smaller and faster transistor, thereby finally providing a glass for a brighter and faster display.SOLUTION: A glass that is substantially free of alkali and has a high annealing point and therefore good dimensional stability (e.g., low compaction) for use as a TFT backplane substrate in amorphous silicon, oxide, and low temperature polysilicon TFT processes.SELECTED DRAWING: Figure 3

Description

Description of Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Patent Application No. 62 / 736,070, filed September 25, 2018, the contents of which are relied upon and incorporated herein by reference in their entirety. This application is also a divisional application of Japanese Patent Application No. 2024-032819, which is a divisional application of Japanese Patent Application No. 2021-516922. [Technical Field]

[0002] Embodiments of the present disclosure utilize an unexpected combination of viscosity curve and high liquidus viscosity that allows glasses meeting specific thresholds of customer-facing attributes to be produced at better cost and quality than any previously disclosed glass composition. [Background technology]

[0003] The manufacture of liquid crystal displays, such as active matrix liquid crystal display (AMLCD) devices, is highly complex, and the properties of the substrate glass are critical. First and foremost, the glass substrates used in the manufacture of AMLCD devices must have tightly controlled physical dimensions. Downdraw sheet stretching, and particularly the fusion process, described in U.S. Patent Nos. 5,629,997 and 5,729,222, both to Dockerty, can produce glass sheets that can be used as substrates without the need for costly post-forming finishing operations such as lapping and polishing. Unfortunately, the fusion process imposes fairly severe limitations on the glass 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 due to their ability to transport electrons more efficiently. Polycrystalline silicon transistors (p-Si) are characterized as having higher mobility than those based on amorphous silicon transistors (a-Si). This allows for the production of smaller, faster transistors, which ultimately leads to brighter, faster displays. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 3,338,696 [Patent Document 2] U.S. Patent No. 3,682,609 Summary of the Invention

[0006] One or more embodiments of the present disclosure provide a substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 66-70.5 SiO, 11.2-13.3 AlO, 2.5-6 BO, 2.5-6.3 MgO, 2.7-8.3 CaO, 1-5.8 SrO, and 0-3 BaO, where SiO, AlO, BO, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components. Further embodiments include an RO / AlO ratio of 0.98≦(MgO+CaO+SrO+BaO) / AlO≦1.38 or an MgO / RO ratio of 0.18≦MgO / (MgO+CaO+SrO+BaO)≦0.45. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. Some embodiments may have an anneal point greater than 750°C, greater than 765°C, or greater than 770°C. Some embodiments may have a liquidus viscosity greater than 100,000 poise, greater than 150,000 poise, or greater than 180,000 poise. Some embodiments may have a Young's modulus greater than 80 GPa, greater than 81 GPa, or greater than 81.5 GPa. Some embodiments may have a density less than 2.55 g / cc, less than 2.54 g / cc, or less than 2.53 g / cc. Some embodiments may have a T200P less than 1665°C, less than 1650°C, or less than 1640°C. Some embodiments may have a T35kP less than 1280°C, less than 1270°C, or less than 1266°C. Some embodiments may have a T200P-T(ann) less than 890°C, less than 880°C, less than 870°C, or less than 865°C. Some embodiments may have a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.Some embodiments may have a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise. Some embodiments may have a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise. In some embodiments, As2O3 and Sb2O3 comprise less than about 0.005 mol%. In some embodiments, Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials comprise between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary objects made from these glasses can be manufactured by downdraw sheet manufacturing or the fusion process or variations thereof.

[0007] Some embodiments provide a substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 68-79.5 SiO2, 12.2-13 Al2O3, 3.5-4.8 B2O3, 3.7-5.3 MgO, 4.7-7.3 CaO, 1.5-4.4 SrO, and 0-2 BaO, where SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components. Further embodiments include an RO / Al2O3 ratio of 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2 or an MgO / RO ratio of 0.24≦MgO / (MgO+CaO+SrO+BaO)≦0.36. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. Some embodiments may have a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise. Some embodiments may have a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise. Some embodiments may have a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise. In some embodiments, As2O3 and Sb2O3 comprise less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary bodies made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes, or variations thereof.

[0008] Some embodiments provide a substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 68.3-69.5 SiO2, 12.4-13 Al2O3, 3.7-4.5 B2O3, 4-4.9 MgO, 5.2-6.8 CaO, 2.5-4.2 SrO, and 0-1 BaO, where SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components. Further embodiments include an RO / Al2O3 ratio of 1.09≦(MgO+CaO+SrO+BaO) / Al2O3≦1.16 or an MgO / RO ratio of 0.25≦MgO / (MgO+CaO+SrO+BaO)≦0.35. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. Some embodiments may have a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise. Some embodiments may have a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise. Some embodiments may have a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise. In some embodiments, As2O3 and Sb2O3 comprise less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary bodies made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes, or variations thereof.

[0009] Some embodiments are based on the relationship: 70 GPa≦549.899-4.811 * SiO2-4.023 * Al2O3-5.651 * B2O3-4.004 * MgO-4.453 * CaO-4.753 * SrO-5.041 * Glasses are provided having a Young's modulus in the range defined by BaO≦90 GPa, where SiO2, Al2O3, BO3, MgO, CaO, SrO, and BaO represent the mole percent of oxide components. Further embodiments include an RO / Al2O3 ratio of 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. In some embodiments, As2O3 and Sb2O3 account for less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary objects made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes or variations thereof.

[0010] Some embodiments may be based on the relationship: 720°C≦1464.862−6.339 * SiO2-1.286 * Al2O3-17.284 * B2O3-12.216 * MgO-11.448 * CaO-11.367 * SrO-12.832 *Glasses are provided having annealing points in the range defined by BaO≦810°C, where SiO2, Al2O3, BO3, MgO, CaO, SrO, and BaO represent the mole percent of oxide components. Further embodiments include an RO / Al2O3 ratio of 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. In some embodiments, As2O3 and Sb2O3 account for less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary objects made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes or variations thereof.

[0011] Additional embodiments of the present disclosure relate to objects made from glass produced by the downdraw sheet manufacturing process. Further embodiments relate to glass produced by the fusion process or variations thereof.

[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments described below. [Brief explanation of the drawings]

[0013] [Figure 1] Schematic of a forming mandrel used to produce precision sheet in the fusion draw process [Figure 2] A cross-sectional view of the forming mandrel of Figure 1 taken along location 6 [Figure 3] Convex Hull Graph for Some Embodiments of the Present Disclosure [Figure 4]Convex hull graphs for other embodiments of the present disclosure [Figure 5] Convex Hull Graphs for Additional Embodiments of the Disclosure [Figure 6] Convex Hull Graphs for Further Embodiments of the Disclosure [Figure 7] Graphical representation of equation (1) for several randomly selected embodiments inside the convex hull of FIG. [Figure 8] Graphical representation of equation (2) for several randomly selected embodiments inside the convex hull of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] One problem with p-Si-based transistors is that their fabrication requires higher process temperatures than those used to fabricate a-Si transistors. These temperatures range from 450°C to 600°C, compared to the peak temperature of 350°C used in a-Si transistor fabrication. At these temperatures, most AMLCD glass substrates undergo a process known as consolidation. Consolidation, also known as thermal stability or dimensional change, is an irreversible dimensional change (shrinkage) in the glass substrate due to a change in the fictive temperature of the glass. "Fictive temperature" is a concept used to describe the structural state of glass. Glass that is rapidly cooled from a high temperature is said to have a higher fictive temperature due to the "frozen in" higher temperature structure. Glass that is cooled more slowly, or annealed by being held near the anneal point for a period of time, is said to have a lower fictive temperature.

[0015] The amount of compaction depends on both the process for making the glass and the viscoelastic properties of the glass. In the float process for producing sheet products from glass, the glass sheet cools relatively slowly from the melt and therefore "freezes" into a relatively low-temperature structure. In contrast, in the fusion process, the glass sheet cools very rapidly from the melt and freezes into a relatively high-temperature structure. As a result, glass produced by the float process will experience less compaction than glass produced by the fusion process, since the driving force for compaction is the difference between the fictive temperature and the process temperature experienced by the glass during compaction. Therefore, it would be desirable to minimize the level of compaction in glass substrates produced by the downdraw process.

[0016] There are two approaches to minimize compaction in the glass. The first approach is to thermally pretreat the glass to create a fictive temperature similar to that experienced by the glass during p-Si TFT fabrication. This approach has several drawbacks. First, the multiple heating steps utilized during p-Si TFT fabrication create slightly different fictive temperatures in the glass that the pretreatment cannot fully compensate for. Second, the thermal stability of the glass becomes closely tied to the details of its p-Si TFT fabrication, which could mean different pretreatments for different end users. Finally, pretreatments add cost and complexity to the process.

[0017] Another approach is to slow the strain rate at the process temperature by increasing the viscosity of the glass. This can be achieved by increasing the viscosity of the glass. The anneal point represents the temperature corresponding to the fixed viscosity of the glass, so increasing the anneal point is the same as increasing the viscosity at the fixed temperature. However, the challenge with this approach is cost-effectively producing high-anneal point glasses. The primary factors affecting cost are defects and asset life. Four types of defects are commonly encountered in conventional melters coupled to fusion draw systems: (1) gaseous inclusions (bubbles or blisters), (2) solid inclusions due to the inability to properly melt the refractory or batch, (3) metallic defects consisting primarily of platinum, and (4) devitrification products resulting from low liquidus viscosity or excessive devitrification at both ends of the isopipe. Glass composition has a disproportionate effect on the melting rate and, therefore, the tendency of the glass to form gaseous or solid defects, and the oxidation state of the glass affects its tendency to contain platinum defects. Devitrification of the glass on the forming mandrel, or isopipe, is best controlled by selecting a composition with a high liquidus viscosity.

[0018] The useful life of an asset is primarily determined by 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 isopipe refractories offer the potential to significantly extend the useful operating life of conventional melting equipment coupled to fusion draw equipment. As a result, the life-limiting components of conventional fusion draw melting and forming platforms are the electrodes used to heat the glass. Tin oxide electrodes corrode slowly over time, and the corrosion rate is a strong function of both temperature and glass composition. To maximize the useful life of an asset, it is desirable to identify compositions that reduce the corrosion rate of the electrodes while maintaining the defect-limiting attributes described above.

[0019] Described herein are alkali-free glasses with high annealing points and therefore good dimensional stability (i.e., low compaction), and methods for their manufacture. In addition, the exemplary compositions have very high liquidus viscosities, thus reducing or eliminating the possibility of devitrification on forming mandrels. As a result of the specific details of their compositions, the exemplary glasses melt to good quality with very low levels of gaseous inclusions and minimal corrosion to precious metals, refractories, and tin oxide electrode materials.

[0020] The embodiments described herein improve manufacturability and cost over the existing Lotus™ glass family while maintaining excellent total pitch velocity (TPV). This is achieved through a unique combination of high liquidus viscosity and viscosity curve while maintaining density and CTE within the range traditionally desired for display applications. Previous glasses with moderate anneal points may have exhibited some of these attributes, but not all at the same time, which results in a unique and unexpected composition range.

[0021] Disclosed herein are substantially alkali-free glasses with high annealing points and therefore good dimensional stability (i.e., low compaction) for use as TFT backplane substrates in amorphous silicon, oxide, and low-temperature polysilicon TFT processes. The exemplary glasses described herein also find suitable use for high-performance displays using a-Si and oxide-TFT technologies. Glasses with high annealing points can prevent panel distortion due to compaction / shrinkage or stress relaxation during thermal processing after glass fabrication. The disclosed glasses have the additional feature of relatively low melting and fining temperatures due to their viscosity curves. For glasses with such viscosity curves, the exemplary glasses also have unusually high liquidus viscosities and therefore significantly reduced risk of devitrification in the cold zones of molding equipment. While low alkali concentrations are generally desirable, it should be understood that in practice, it may be difficult or impossible to economically produce glasses that are completely alkali-free. The alkalis of concern arise as contaminants in raw materials, trace components in refractories, etc., and can be very difficult to completely eliminate. Thus, an exemplary glass is considered to be substantially alkali-free when the total concentration of the alkali elements Li2O, Na2O, and K2O is less than about 0.1 mole percent (mol %).

[0022] In one embodiment, the substantially alkali-free glasses have anneal points greater than about 750°C, greater than 765°C, or greater than 770°C. Such high anneal points provide low relaxation rates (due to either compaction, stress relaxation, or both) and therefore small amounts of dimensional change, to enable use of the exemplary glasses as backplane substrates or carriers. In another embodiment, at a viscosity of 35,000 poise, the exemplary glasses have corresponding temperatures (T35kP) less than about 1280°C, less than 1270°C, or less than 1266°C. The liquidus temperature (T liq) is the highest temperature above which crystalline phases cannot coexist in equilibrium with the glass. In another embodiment, the viscosity corresponding to the liquidus temperature of the glass is greater than about 100,000 poise, greater than about 150,000 poise, or greater than about 180,000 poise. In another embodiment, at a viscosity of 200 poise, exemplary glasses have a corresponding temperature (T200P) less than about 1665°C, less than 1650°C, or less than 1640°C. In another embodiment, exemplary glasses have a temperature difference between T200P and the annealing point (T(ann)) less than 890°C, less than 880°C, less than 870°C, or less than 865°C.

[0023] In one or more embodiments, the substantially alkali-free glass comprises, expressed in mole percent on an oxide basis, 66-70.5 SiO, 11.2-13.3 AlO, 2.5-6 BO, 2.5-6.3 MgO, 2.7-8.3 CaO, 1-5.8 SrO, and 0-3 BaO, wherein 0.98≦(MgO+CaO+SrO+BaO) / AlO≦1.38, and 0.18≦MgO / (MgO+CaO+SrO+BaO)≦0.45, where AlO, MgO, CaO, SrO, and BaO represent the mole percent of the respective oxide components.

[0024] In a further embodiment, the substantially alkali-free glass comprises, expressed in mole percent on an oxide basis, 68-69.5 SiO, 12.2-13 AlO, 3.5-4.8 BO, 3.7-5.3 MgO, 4.7-7.3 CaO, 1.5-4.4 SrO, and 0-2 BaO, wherein 1.07≦(MgO+CaO+SrO+BaO) / AlO≦1.2, and 0.24≦MgO / (MgO+CaO+SrO+BaO)≦0.36, where AlO, MgO, CaO, SrO, and BaO represent the mole percent of the respective oxide components.

[0025] In a further embodiment, the substantially alkali-free glass comprises, expressed in mole percent on an oxide basis, 68.3-69.5 SiO, 12.4-13 AlO, 3.7-4.5 BO, 4-4.9 MgO, 5.2-6.8 CaO, 2.5-4.2 SrO, and 0-1 BaO, wherein 1.09≦(MgO+CaO+SrO+BaO) / AlO≦1.16, and 0.25≦MgO / (MgO+CaO+SrO+BaO)≦0.35, where AlO, MgO, CaO, SrO, and BaO represent the mole percent of the respective oxide components.

[0026] In one embodiment, the exemplary glass includes chemical fining agents. Such fining agents include, but are not limited to, SnO2, As2O3, Sb2O3, F, Cl, and Br, and the concentration of the chemical fining agents is maintained at a level of 0.5 mol% or less. Chemical fining agents may also include other oxides of transition metals, such as CeO2, Fe2O3, and MnO2. These oxides may impart color to the glass due to visible absorption in the final valence state in the glass, and therefore, their concentration may be maintained at a level of 0.2 mol% or less.

[0027] In one embodiment, the exemplary glass is manufactured into sheets by a fusion process. This fusion draw process results in a pristine, fire-polished glass surface that reduces surface-mediated distortion for high-resolution TFT backplanes and color filters. Figure 1 is a schematic diagram of the fusion draw process at the forming mandrel, or isopipe, so named because its sloped flute design results in the flow being the same (hence "iso") at all points along the length of the isopipe (from left to right). Figure 2 is a schematic cross-sectional view of the isopipe near location 6 in Figure 1. Glass is introduced at inlet 1 and flows along the bottom 4 of the flute formed by weir walls 9 to the compression end 2. The glass overflows the weir walls 9 on both sides of the isopipe (see Figure 2), and the two streams of glass join or fuse at the base 10. Edge directors 3 at each end of the isopipe serve to cool the glass and create thicker pieces, called beads, at the edges. The bead is pulled down by a pulling roll, thus allowing the sheet to be formed at high viscosity. By controlling the speed at which the sheet is drawn from the isopipe, the fusion draw process can be used to produce a wide range of thicknesses at a constant melt rate.

[0028] Downdraw sheet stretching methods, and in particular the fusion process described in U.S. Patent Nos. 5,629,999 and 5,729,999 (both to Dockerty), both of which are incorporated herein by reference, can be used herein. Compared to other forming processes, such as the float process, the fusion process is preferred for several reasons. First, glass substrates produced by the fusion process do not require polishing. Current glass substrate polishing can produce glass substrates with an average surface roughness (Ra) of greater than about 0.5 nm, as measured by atomic force microscopy. Glass substrates produced by the fusion process have an average surface roughness, as measured by atomic force microscopy, of less than 0.5 nm. The substrates also have an average internal stress, as measured by optical retardation, of 150 psi (about 1.03 MPa) or less.

[0029] In one embodiment, the exemplary glasses are manufactured into sheet form using a fusion process. While the exemplary glasses are compatible with the fusion process, they may also be manufactured into sheets or other commercial products by less demanding manufacturing processes, including slot draw, float, rolling, and other sheet forming processes known to those skilled in the art. As such, the embodiments described herein are equally applicable to other forming processes, such as, but not limited to, float forming, and the claims appended hereto should not be limited to the fusion process.

[0030] In contrast to these alternative methods of forming glass sheets, the fusion process, as described above, can produce very thin, very flat, highly uniform sheets with pristine surfaces. While the slot draw process can produce pristine surfaces, the dimensional uniformity and surface quality of glass produced by the slot draw process are generally inferior to glass produced by the fusion draw process due to changes in orifice shape over time, the accumulation of volatile debris at the orifice-glass interface, and the challenges of creating orifices that deliver truly flat glass. The float process can deliver very large, uniform sheets, but their surfaces are substantially damaged by contact with the float bath on one side and exposure to condensation products from the float bath on the other side. This means that float glass must be polished for use in high-performance display applications.

[0031] Unlike the float process, the fusion process results in a rapid cooling of the glass from a high temperature, which results in a high fictive temperature Tf. This fictive temperature can be considered to represent the difference between the structural state of the glass and the state it would have if it were fully relaxed at the temperature of interest. Here, consider the result of the process of reheating a glass with a glass transition temperature Tg to a process temperature Tp such that Tp < Tg ≤ Tf. Since Tp < Tf, the structural state of the glass is out of equilibrium at Tp, and the glass spontaneously relaxes to an equilibrium structural state at Tp. This relaxation rate is inversely proportional to the effective viscosity of the glass at Tp, and thus, a high viscosity results in a slow relaxation rate and a low viscosity results in a fast relaxation rate. The effective viscosity varies inversely with the fictive temperature of the glass, and thus, a low fictive temperature results in a high viscosity and a high fictive temperature results in a relatively low viscosity. Therefore, the relaxation rate at Tp is directly related to the fictive temperature of the glass. The process of introducing a high fictive temperature results in a relatively high relaxation rate when the glass is reheated at Tp.

[0032] One means of reducing the relaxation rate at Tp is to increase the viscosity of the glass at that temperature. The annealing point of the glass represents the temperature at which the glass has a viscosity of 10 13.2 poises. As the temperature drops below the annealing point, the viscosity of the supercooled melt increases. At a fixed temperature below Tg, the glass with the higher annealing point has a higher viscosity than the glass with the lower annealing point. Therefore, one might choose to increase the annealing point of the substrate glass in order to increase its viscosity at Tp. Unfortunately, in general, the compositional changes necessary to increase the annealing point also increase the viscosity at all other temperatures. Specifically, the fictive temperature of glass produced by the fusion process is about 10 11 ~10 12Increasing the anneal point of a glass, which corresponds to a viscosity in poises and is therefore compatible with the fusion process, generally increases its fictive temperature as well. For a given glass, the higher the fictive temperature, the lower the viscosity at temperatures below Tg; therefore, increasing the fictive temperature counters the increase in viscosity that would otherwise be obtained by increasing the anneal point. A relatively large change in anneal point is generally necessary to see a substantial change in the relaxation rate at Tp. Exemplary glass embodiments are those in which the glass has an anneal point greater than about 750°C, greater than 765°C, or greater than 770°C. While not bound by any particular theory of operation, it is believed that such a high anneal point results in an acceptably slow rate of thermal relaxation during low-temperature TFT processing, e.g., typical low-temperature polysilicon rapid thermal annealing cycles or compatible cycles in oxide TFT processing.

[0033] Increasing the anneal point, in addition to its effect on the fictive temperature, also increases the temperature of the entire melting and forming system, particularly the temperature above the isopipe. For example, Eagle XG and Lotus (Corning Incorporated, Corning, New York) have anneal points that differ by approximately 50°C, and the temperatures at which they are delivered to the isopipe also differ by approximately 50°C. Zircon refractories exhibit thermal creep when held at high temperatures for extended periods, which can be accelerated by the mass of the glass above the isopipe in addition to the mass of the isopipe itself. A second exemplary glass embodiment has an anneal point greater than 750°C while having a delivery temperature below 1280°C. Such a delivery temperature allows for long production campaigns without isopipe replacement, and the high anneal point allows the glass to be used in the manufacture of high-performance displays, such as those based on oxide TFT or LTPS processes.

[0034] In addition to this criterion, the fusion process typically involves glasses with high liquidus viscosities. This is necessary to avoid devitrification products at the interface with the glass and minimize visible devitrification products in the final glass. For a given glass suitable for fusion of a particular sheet size and thickness, adjusting the process to produce wider or thicker sheets generally results in lower temperatures at both ends of the isopipe (the forming mandrel for the fusion process). Therefore, exemplary glasses with higher liquidus viscosities allow for greater manufacturing versatility via the fusion process.

[0035] To be formed by a fusion process, the exemplary glass compositions desirably have liquidus viscosities of 130,000 poise or greater, 150,000 poise or greater, or 200,000 poise or greater. A surprising result is that throughout the range of the exemplary glasses, it is possible to obtain sufficiently low liquidus temperatures and sufficiently high viscosities such that the liquidus viscosities of the glasses are unusually high compared to compositions outside the exemplary range.

[0036] In the glass compositions described herein, SiO serves as a base glass former. In certain embodiments, the SiO concentration can be 66 mole percent or greater to provide the glass with density and chemical durability suitable for flat panel display glasses (e.g., AMLCD glasses) and a liquidus temperature (or liquidus viscosity) that allows the glass to be formed by downdraw processes (e.g., fusion processes). Regarding the upper limit, the SiO concentration can generally be about 70.5 mole percent or less to allow batch materials to be melted using conventional bulk melting techniques, e.g., Joule melting in a refractory melter. As the SiO concentration increases, the 200 poise temperature (melting temperature) generally increases. In various applications, the SiO concentration is adjusted so that the glass composition has a melting temperature of 1665°C or less. In one embodiment, the SiO concentration is between 66 and 70.5 mole percent.

[0037] Al2O3 is another glass former used to produce the glasses described herein. Concentrations of Al2O3 of 11.2 mole percent or greater impart a low liquidus temperature and high viscosity to the glass, resulting in a high liquidus viscosity. Using at least 12 mole percent Al2O3 also improves the annealing point and Young's modulus of the glass. It is desirable to maintain the concentration of Al2O3 below about 13.3 mole percent so that the ratio (MgO + CaO + SrO + BaO) / Al2O3 is 0.98 or greater. In one embodiment, the concentration of Al2O3 is between about 11.2 mole percent and 13.3 mole percent; in other embodiments, this range is maintained while maintaining the ratio of (MgO + CaO + SrO + BaO) / Al2O3 at 0.98 or greater.

[0038] B2O3 is both a glass former and a fluxing agent that promotes melting and lowers the melting temperature. Its effect on liquidus temperature is at least as great as its effect on viscosity, so increasing B2O3 can be used to increase the liquidus viscosity of the glass. To maximize the liquidus viscosity of these glasses, the glass compositions described herein have a B2O3 concentration of 2.5 mole percent or greater. As noted above with respect to SiO2, glass durability is critical for LCD applications. Durability can be controlled to some extent by increased concentrations of alkaline earth oxides, but can be significantly reduced by increased B2O3 content. Annealing points, like Young's modulus, decrease with increasing B2O3, so it is desirable to keep the B2O3 content low relative to concentrations typical in amorphous silicon substrates. Therefore, in one embodiment, the glasses described herein have a B2O3 concentration between 2.5 and 6 mole percent.

[0039] The concentrations of Al2O3 and B2O3 can be selected as a pair to increase the anneal point, increase the modulus, improve durability, lower density, and decrease the coefficient of thermal expansion (CTE) while maintaining the melting and forming properties of the glass.

[0040] For example, increasing B2O3 and correspondingly decreasing Al2O3 can help maintain lower density and CTE, while increasing Al2O3 and correspondingly decreasing B2O3 can help increase the annealing point, modulus, and durability, provided that the Al2O3 increase does not reduce the (MgO + CaO + SrO + BaO) / Al2O3 ratio below about 1.0. For (MgO + CaO + SrO + BaO) / Al2O3 ratios less than about 1.0, it may be difficult or impossible to remove gaseous inclusions from the glass due to late melting of the silica raw materials. Furthermore, when (MgO + CaO + SrO + BaO) / Al2O3 ≦1.05, mullite, an aluminosilicate crystal, may appear as a liquid phase. Once mullite is present as a liquid phase, the compositional sensitivity of the liquidus increases significantly, and mullite devitrification products grow very rapidly and are very difficult to remove once formed. Thus, in one embodiment, the glasses described herein have (MgO+CaO+SrO+BaO) / Al2O3 ≥ 1.05. Additional exemplary glasses for use in AMLCD applications have a 28-42 x 10 -7 / ℃, 30-40×10 -7 / ℃, or 32-38×10 -7 / °C range (22 to 300°C).

[0041] The glasses described herein contain alkaline earth oxides in addition to the glass formers (SiO, AlO, and BO). In one embodiment, at least three alkaline earth oxides, e.g., MgO, CaO, and BaO, and optionally SrO, are part of the glass composition. In another embodiment, SrO is used in place of BaO. In another embodiment, all four of MgO, CaO, SrO, and BaO are present. The alkaline earth oxides impart various properties to the glass that are important for melting, fining, forming, and end-use applications. Therefore, to improve the glass's performance in these respects, in one embodiment, the ratio (MgO + CaO + SrO + BaO) / AlO is 1.05 or greater. As this ratio increases, the viscosity tends to decrease more strongly than the liquidus temperature, and therefore, it becomes increasingly difficult to obtain suitably high values ​​of liquidus viscosity. Therefore, in another embodiment, the ratio (MgO+CaO+SrO+BaO) / Al2O3 is less than or equal to 1.38.

[0042] For certain embodiments, alkaline earth oxides may be treated as if they were a single compositional component, since their effects on viscoelastic properties, liquidus temperatures, and liquidus relations are qualitatively more similar to each other than to the glass-forming oxides SiO, AlO, and BO. However, while the alkaline earth oxides CaO, SrO, and BaO can form solid solutions with feldspar minerals, particularly anorthite (CaAlSiO) and celsian (BaAlSiO), and the same strontium, MgO does not participate significantly in these crystals. Thus, if the feldspar crystals are already in the liquid phase, the over-addition of MgO will serve to stabilize the liquid relative to the crystals and thus lower the liquidus temperature. At the same time, the viscosity curve generally becomes steeper, lowering the melting temperature with little or no effect on the low-temperature viscosity. In this sense, the addition of small amounts of MgO favors forming by lowering the liquidus temperature and increasing the liquidus viscosity, while maintaining a high anneal point and therefore low compaction, and favors melting by lowering the melting temperature. Thus, in various embodiments, the glass composition includes MgO in an amount ranging from about 2.5 mole percent to about 6.3 mole percent.

[0043] A surprising result of investigating the liquidus trends in high annealing point glasses is that for glasses with adequately high liquidus viscosity, the ratio of MgO to other alkaline earth oxides, MgO / (MgO + CaO + SrO + BaO), falls within a relatively narrow range. As noted earlier, adding MgO can destabilize feldspar minerals, thus stabilizing the liquid and lowering the liquidus temperature. However, once MgO reaches a certain level, mullite Al6SiO 13will be stabilized, thus increasing the liquidus temperature and decreasing the liquidus viscosity. Furthermore, higher concentrations of MgO tend to decrease the viscosity of the liquid, and therefore, even if the liquidus viscosity remains unchanged with the addition of MgO, the liquidus viscosity will decrease over time. Therefore, in another embodiment, 0.18≦MgO / (MgO+CaO+SrO+BaO)≦0.45. MgO may be varied relative to the glass formers and other alkaline earth oxides within this range to maximize the liquidus viscosity value, consistent with obtaining other desired properties.

[0044] The presence of calcium oxide in the glass composition can result in a low liquidus temperature (high liquidus viscosity), a high anneal point and Young's modulus, and a CTE in the range most desirable for flat panel applications, particularly AMLCD applications. Its presence also favorably contributes to chemical durability, and compared to other alkaline earth oxides, it is relatively inexpensive as a batch material. However, at high concentrations, CaO increases density and CTE. Furthermore, at sufficiently low SiO concentrations, CaO can stabilize anorthite and therefore reduce liquidus viscosity. Thus, in one embodiment, the concentration of CaO can be 4 mole percent or greater. In another embodiment, the concentration of CaO in the glass composition is between about 2.7 mole percent and 8.3 mole percent.

[0045] Both SrO and BaO can contribute to a low liquidus temperature (high liquidus viscosity); therefore, the glasses described herein typically contain at least both 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 anneal point. The relative proportions of SrO and BaO can be balanced to obtain the appropriate combination of physical properties and liquidus viscosity so that the glass can be formed by downdraw processes, with their total concentration being between 1 mol% and 9 mol%. In some embodiments, the glass contains SrO in the range of about 1 mol% to about 5.8 mol%. In one or more embodiments, the glass contains BaO in the range of about 0 mol% to about 3 mol%.

[0046] To summarize the effects / roles of the core components of the glass of the present disclosure, SiO is the base glass former. AlO and BO are also glass formers and can be selected as pairs. For example, increasing BO and correspondingly decreasing AlO can be used to obtain lower density and CTE, while increasing AlO and correspondingly decreasing BO can be used to increase the annealing point, Young's modulus, and durability, provided that the ratio of RO / AlO is not reduced below about 1 (RO = (MgO + CaO + SrO + BaO)). If this ratio becomes too low, meltability may be impaired, i.e., the melting temperature may become too high. BO can be used to lower the melting temperature, but high levels of BO impair the annealing point.

[0047] In addition to meltability and annealing point considerations, for AMLCD applications, the CTE of the glass should match that of silicon. To achieve such a CTE value, exemplary glasses 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, glasses with suitable CTEs can be produced when the RO / Al2O3 ratio is less than about 1.38.

[0048] In addition to these considerations, the glasses may be formable by downdraw processes, e.g., fusion processes. This means that the liquidus viscosity of the glass must be relatively high. Individual alkaline earths play an important role in this regard, as they can destabilize crystalline phases that would otherwise form. BaO and SrO are particularly effective in controlling liquidus viscosity and are included in exemplary glasses at least for this purpose. As shown in the examples presented below, various combinations of alkaline earths produce glasses with high liquidus viscosity, whose total alkaline earth content satisfies the constraints of a low melting temperature, a high anneal point, and the R0 / Al2O3 ratio required to achieve an adequate CTE.

[0049] In addition to the above components, the glass compositions described herein may contain 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, ZrO2, Ta2O5, WO3, YO3, La2O3, and CeO2. In one embodiment, the amount of each of these oxides may be 2.0 mole percent or less, and their total concentration may be 4.0 mole percent or less. The glass compositions described herein may also contain various contaminants, particularly Fe2O3 and ZrO2, associated with batch 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 as a result of Joule melting using tin oxide electrodes and / or through batch incorporation of tin-containing materials such as SnO2, SnO, SnCO3, SnC2O2, and the like.

[0050] The glass compositions are generally alkali-free; however, the glass may contain some alkali contaminants. For AMLCD applications, it is desirable to maintain alkali levels below 0.1 mole percent to avoid adverse effects on thin film transistor (TFT) performance due to diffusion of alkali ions from the glass into the silicon of the TFT. As used herein, an "alkali-free glass" is a glass having a total alkali concentration of 0.1 mole percent or less, where the total alkali concentration is the sum of the concentrations of Na2O, KO, and Li2O. In one embodiment, the total alkali concentration is 0.1 mole percent or less.

[0051] As previously mentioned, a (MgO + CaO + SrO + BaO) / Al2O3 ratio of 1 or greater improves fining, i.e., the removal of gaseous inclusions from molten batch materials. This improvement allows for the use of more environmentally friendly fining packages. For example, on an oxide basis, the glass compositions described herein can have one or more or all of the following compositional characteristics: (i) an As2O3 concentration of at most 0.05 mole percent, (ii) an Sb2O3 concentration of at most 0.05 mole percent, and (iii) an SnO2 concentration of at most 0.25 mole percent.

[0052] As2O3 is an effective high-temperature fining agent for AMLCD glasses, and in some embodiments described herein, As2O3 is used in fining due to its excellent fining properties. However, As2O3 is hazardous and requires special handling during the glassmaking process. Therefore, in certain embodiments, fining is performed without the use of significant amounts of As2O3, i.e., the finished glass contains at most 0.05 mole percent As2O3. In one embodiment, As2O3 is not intentionally used in fining the glass. In such cases, the finished glass typically has at most 0.005 mole percent As2O3 as a result of contaminants present in the batch materials and / or the equipment used to melt the batch materials.

[0053] Although less toxic than As2O3, Sb2O3 is also hazardous and requires special handling. Furthermore, Sb2O3 increases density, increases CTE, and decreases annealing point compared to glasses using As2O3 or SnO2 as a fining agent. Therefore, in certain embodiments, fining is performed without significant amounts of Sb2O3, i.e., the finished glass has at most 0.05 mole percent Sb2O3. In other embodiments, no Sb2O3 is intentionally used in fining the glass. In such cases, the finished glass typically has at most 0.005 mole percent Sb2O3 as a result of contaminants present in the batch materials and / or the equipment used to melt the batch materials.

[0054] Compared to As2O3 and Sb2O3 fining, tin fining (i.e., SnO2 fining) is generally less effective, but SnO2 is a ubiquitous material with no known detrimental properties. Also, for many years, SnO2 has been a component of AMLCD glasses due to the use of tin oxide electrodes in the Joule melting of batch materials for such glasses. The presence of SnO2 in AMLCD glasses has not caused any known adverse effects on the use of these glasses in the manufacture of liquid crystal displays. However, high concentrations of SnO2 are undesirable because they can cause the formation of crystalline defects in AMLCD glasses. In one embodiment, the concentration of SnO2 in the finished glass is 0.25 mole percent or less.

[0055] 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, sulfate, sulfide, cerium oxide, mechanical frothing, and / or vacuum fining in addition to tin fining. It is believed that these other fining techniques can be used alone. In certain embodiments, maintaining the (MgO + CaO + SrO + BaO) / Al2O3 ratio and the individual alkaline earth concentrations within the ranges previously described makes the fining process easier and more effective.

[0056] The glasses described herein can be manufactured using various techniques known in the art. In one embodiment, the glasses are manufactured using a downdraw process, such as a fusion downdraw process. In one embodiment, an alkali-free glass sheet is produced, comprising SiO, Al, O, B, MgO, CaO, and BaO, the glass comprising the sheet comprising the batch materials being selected, melted, and refined to have, on an oxide basis: (i) a (MgO + CaO + SrO + BaO) / AlO ratio of 1 or greater; (ii) an MgO content of 2.5 mole percent or greater; (iii) a CaO content of 2.7 mole percent or greater; and (iv) a (SrO + BaO) content of 1 mole percent or greater.

[0003] A method is described for producing alkali-free glass sheets by a downdraw process, wherein (a) the fining step is carried out without the use of significant amounts of arsenic (and, optionally, without the use of significant amounts of antimony), and (b) a population of 50 consecutive glass sheets produced by the downdraw process from the fused and fined batch material has an average gaseous inclusion level of less than 0.10 gaseous inclusions per cubic centimeter, and each sheet in the population has a volume of at least 500 cubic centimeters.

[0057] U.S. Patent Nos. 5,785,726 (Dorfeld et al.), 6,128,924 (Bange et al.), 5,824,127 (Bange et al.), and co-pending patent application Ser. No. 11 / 116,669 disclose processes for producing arsenic-free glass. U.S. Patent No. 7,696,113 (Ellison) discloses a process for producing arsenic- and antimony-free glass using iron and tin to minimize gaseous inclusions. Each of U.S. Patent Nos. 5,785,726, 6,128,924, 5,824,127, co-pending patent application Ser. No. 11 / 116,669, and U.S. Patent No. 7,696,113 is incorporated herein by reference in its entirety.

[0058] In one embodiment, a population of 50 consecutive glass sheets produced by a downdraw process from molten and refined batch material has an average gaseous inclusion count of less than 0.05 gaseous inclusions per cubic centimeter, and each sheet in the population has a volume of at least 500 cubic centimeters.

[0059] In some embodiments, exemplary glasses have viscosity curves and high liquidus viscosities that meet certain thresholds of customer-facing attributes, and have the composition ranges in Table 1 below, where Al2O3, MgO, CaO, SrO, and BaO represent the mole percent of each oxide component.

[0060] [Table 1]

[0061] In some embodiments, exemplary glasses have viscosity curves and high liquidus viscosities that meet certain thresholds of customer-facing attributes, and have the composition ranges in Table 2 below, where Al2O3, MgO, CaO, SrO, and BaO represent the mole percent of each oxide component.

[0062] [Table 2]

[0063] In some embodiments, exemplary glasses have viscosity curves and high liquidus viscosities that meet certain thresholds of customer-facing attributes, and have the composition ranges in Table 3 below, where Al2O3, MgO, CaO, SrO, and BaO represent the mole percent of each oxide component.

[0064] [Table 3]

[0065] In some embodiments, exemplary glasses have viscosity curves and high liquidus viscosities that meet certain thresholds of customer-facing attributes, and have the composition ranges in Table 4 below, where Al2O3, MgO, CaO, SrO, and BaO represent the mole percent of each oxide component.

[0066] [Table 4]

[0067] In some embodiments, some exemplary glass embodiments can be described by a convex hull, which corresponds to the smallest convex boundary line that contains a set of points within a space of a given dimension. Considering the space created by any of the compositions included in Tables 1, 2, 3, and 4, one can consider SiO2 as one group, Al2O3 and B2O3 as a group named Al2O3_B2O3, and the remaining components as a group named RO, containing MgO, CaO, SrO, BaO, SnO2, and other oxides listed in their respective ranges, and define respective convex hulls for these compositions. For example, a ternary space can be defined by the space shown in Figure 3, with boundaries set by the compositions in Table 1 in mole percent. Table 5 below provides the compositions (in mole percent) that define the boundaries of the convex hull for the composition ranges defined in Table 1.

[0068] [Table 5]

[0069] In further embodiments, exemplary glasses can be described by a convex hull defined by the space created by Table 2 above, with the remaining components considered in the group named SiO, AlO_B, and RO, which includes MgO, CaO, SrO, BaO, SnO, and other oxides listed in their respective ranges. The ternary component space can then be bounded by the compositions in Table 2 in mole percent and defined by the space shown in Figure 4. Table 6 below provides the compositions (in mole percent) that define the boundaries of the convex hull for the ranges defined in Table 2.

[0070] [Table 6]

[0071] In additional embodiments, exemplary glasses can be described by a convex hull defined by the space created by Table 3 above, with the remaining components considered in the group named SiO, AlO_B, and RO, which includes MgO, CaO, SrO, BaO, SnO, and other oxides listed in their respective ranges. The ternary component space can then be bounded by the compositions in Table 3 in mole percent and defined by the space shown in Figure 5. Table 7 below provides the compositions (in mole percent) that define the boundaries of the convex hull for the ranges defined in Table 3.

[0072] [Table 7]

[0073] In some embodiments, exemplary glasses can be described by a convex hull defined by the space created by Table 4 above, with the remaining components considered in the group named SiO, AlO_B, and RO, which includes MgO, CaO, SrO, BaO, SnO, and other oxides listed in their respective ranges. The ternary component space can then be bounded by the compositions in Table 4 in mole percent and defined by the space shown in Figure 6. Table 8 below provides the compositions (in mole percent) that define the boundaries of the convex hull for the ranges defined in Table 4.

[0074] [Table 8]

[0075] Formulas can then be developed for such exemplary composition embodiments in terms of attributes. For example, Equation 1 below provides suitable ranges for exemplary glasses, expressed in mole percent, that have viscosity curves and high liquidus viscosities that meet certain thresholds of customer-facing attributes, such as, but not limited to, Young's modulus: 70GPa≦549.899-4.811 * SiO2-4.023 * Al2O3-5.651 * B2O3-4.004 * MgO-4.453 * CaO-4.753 * SrO-5.041 * BaO≦90GPa (1)

[0076] FIG. 7 is a graphical representation of equation (1) for 20,000 compositions randomly selected within the convex hull of FIG. 3 bounded by the compositional boundaries shown in Table 5.

[0077] By way of further non-limiting example, Equation 2 below provides suitable ranges for exemplary glasses, expressed in mole percent, that have viscosity curves and high liquidus viscosities that meet certain thresholds of customer-facing attributes, such as, but not limited to, anneal point: 720℃≦1464.862-6.339 * SiO2-1.286 * Al2O3-17.284 * B2O3-12.216 * MgO-11.448 * CaO-11.367 * SrO-12.832 * BaO≦810℃ (2)

[0078] FIG. 8 is a graphical representation of equation (2) for 20,000 compositions randomly selected within the convex hull of FIG. 3 bounded by the compositional boundaries shown in Table 5.

[0079] Of course, such examples should not limit the scope of the claims appended hereto, as one skilled in the art would define additional compositional components of the exemplary glasses as a function of additional customer-facing attributes.

[0080] Some embodiments provide a substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 66-70.5 SiO2, 11.2-13.3 Al2O3, 2.5-6 B2O3, 2.5-6.3 MgO, 2.7-8.3 CaO, 1-5.8 SrO, and 0-3 BaO, where SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components. Further embodiments include an RO / Al2O3 ratio of 0.98≦(MgO+CaO+SrO+BaO) / Al2O3≦1.38 or an MgO / RO ratio of 0.18≦MgO / (MgO+CaO+SrO+BaO)≦0.45. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. Some embodiments may have an anneal point greater than 750°C, greater than 765°C, or greater than 770°C. Some embodiments may have a liquidus viscosity greater than 100,000 poise, greater than 150,000 poise, or greater than 180,000 poise. Some embodiments may have a Young's modulus greater than 80 GPa, greater than 81 GPa, or greater than 81.5 GPa. Some embodiments may have a density less than 2.55 g / cc, less than 2.54 g / cc, or less than 2.53 g / cc. Some embodiments may have a T200P less than 1665°C, less than 1650°C, or less than 1640°C. Some embodiments may have a T35kP less than 1280°C, less than 1270°C, or less than 1266°C. Some embodiments may have a T200P-T(ann) less than 890°C, less than 880°C, less than 870°C, or less than 865°C. Some embodiments may have a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.Some embodiments may have a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise. Some embodiments may have a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise. In some embodiments, As2O3 and Sb2O3 comprise less than about 0.005 mol%. In some embodiments, Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials comprise between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary objects made from these glasses can be manufactured by downdraw sheet manufacturing or the fusion process or variations thereof.

[0081] Some embodiments provide a substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 68-79.5 SiO2, 12.2-13 Al2O3, 3.5-4.8 B2O3, 3.7-5.3 MgO, 4.7-7.3 CaO, 1.5-4.4 SrO, and 0-2 BaO, where SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components. Further embodiments include an RO / Al2O3 ratio of 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2 or an MgO / RO ratio of 0.24≦MgO / (MgO+CaO+SrO+BaO)≦0.36. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. Some embodiments may have a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise. Some embodiments may have a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise. Some embodiments may have a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise. In some embodiments, As2O3 and Sb2O3 comprise less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary bodies made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes, or variations thereof.

[0082] Some embodiments provide a substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 68.3-69.5 SiO2, 12.4-13 Al2O3, 3.7-4.5 B2O3, 4-4.9 MgO, 5.2-6.8 CaO, 2.5-4.2 SrO, and 0-1 BaO, where SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components. Further embodiments include an RO / Al2O3 ratio of 1.09≦(MgO+CaO+SrO+BaO) / Al2O3≦1.16 or an MgO / RO ratio of 0.25≦MgO / (MgO+CaO+SrO+BaO)≦0.35. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. Some embodiments may have a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise. Some embodiments may have a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise. Some embodiments may have a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise. In some embodiments, As2O3 and Sb2O3 comprise less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary bodies made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes, or variations thereof.

[0083] Some embodiments are based on the relationship: 70 GPa≦549.899-4.811 * SiO2-4.023 * Al2O3-5.651 * B2O3-4.004 * MgO-4.453 * CaO-4.753 * SrO-5.041 * Glasses are provided having a Young's modulus in the range defined by BaO≦90 GPa, where SiO2, Al2O3, BO3, MgO, CaO, SrO, and BaO represent the mole percent of oxide components. Further embodiments include an RO / Al2O3 ratio of 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. In some embodiments, As2O3 and Sb2O3 account for less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary objects made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes or variations thereof.

[0084] Some embodiments may be based on the relationship: 720°C≦1464.862−6.339 * SiO2-1.286 * Al2O3-17.284 * B2O3-12.216 * MgO-11.448 * CaO-11.367 * SrO-12.832 *Glasses are provided having annealing points in the range defined by BaO≦810°C, where SiO2, Al2O3, BO3, MgO, CaO, SrO, and BaO represent the mole percent of oxide components. Further embodiments include an RO / Al2O3 ratio of 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2. Some embodiments may also contain 0.01 to 0.4 mol% of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent. Some embodiments may also contain 0.005 to 0.2 mol% of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent. In some embodiments, As2O3 and Sb2O3 account for less than about 0.005 mol%. In some embodiments, Li2O, Na2O, KO, or combinations thereof comprise less than about 0.1 mol% of the glass. In some embodiments, the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized. Exemplary objects made from these glasses can be manufactured by downdraw sheet manufacturing or fusion processes or variations thereof.

[0085] It will be recognized that various disclosed embodiments may include the specific features, elements, or steps described with respect to that particular embodiment. It will also be recognized that certain features, elements, or steps, although described with respect to one particular embodiment, may be substituted or combined in alternative embodiments in various non-illustrated combinations or orders.

[0086] It will also be understood that as used herein, nouns refer to "at least one" object and should not be limited to "only one" object unless expressly indicated to the contrary.

[0087] Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When a range is so expressed, examples include from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of these ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0088] As used herein, the terms "substantially," "substantially," and variations thereof are intended to note that a stated property is equal to or approximately equal to a certain value or description.

[0089] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be considered to require that its steps be performed in a particular order. Thus, unless a method claim actually recites the order in which its steps should be followed, or unless the claim or description specifically states otherwise that the steps should be limited to a particular order, no particular order is intended to be implied.

[0090] Although various features, elements, or steps of particular embodiments may be disclosed using the transitional phrase "comprising," it should be understood that alternative embodiments are implied, including those that may be described using the transitional phrases "consisting of" or "consisting essentially of." Thus, for example, alternative embodiments implied for a device comprising A+B+C include embodiments in which the device consists of A+B+C, and embodiments in which the device consists essentially of A+B+C.

[0091] It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the present disclosure. Since modifications, combinations, subcombinations, and variations of the disclosed embodiments that incorporate the spirit and substance of the present disclosure will occur to those skilled in the art, the present disclosure should be construed as including all within the scope of the appended claims and equivalents thereof. [Example]

[0092] The following examples are set forth below to illustrate methods and results according to the disclosed subject matter. These examples are not intended to be inclusive of all embodiments of the procedures disclosed herein, 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.

[0093] Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperatures, etc.), but some errors and deviations should be accounted for. Unless otherwise noted, temperatures are in °C or are ambient, and pressures are at or near atmospheric. The compositions themselves are given in mole percent on an oxide basis and are normalized to 100%. There are numerous variations and combinations of reaction conditions, e.g., component concentrations, temperatures, pressures, and other reaction ranges and conditions, that can be used to optimize product purity and yields from the described processes. No more than reasonable and routine experimentation will be required to optimize such process conditions.

[0094] The glass properties listed in the tables herein were determined according to standard techniques in the glass art. Therefore, the coefficient of linear thermal expansion (CTE) over the temperature range 25-300°C is 10 -7 The viscosity is expressed in grams per cm² / °C and the annealing point is expressed in °C. These were determined by the fiber stretching technique (ASTM standards E228-85 and C336, respectively). 3Density, in °C, was measured by the Archimedes method (ASTM C693). Melting temperature, in °C (defined as the temperature at which the glass melt exhibits a viscosity of 200 poise), was calculated using a fit of the Fulcher equation to high-temperature viscosity data measured with a cylindrical rotational viscometer (ASTM C965-81).

[0095] The liquidus temperature of a glass, expressed in °C, was measured using the isothermal liquidus method. This method involves placing crushed glass particles in a small platinum crucible, placing the crucible in a furnace with tightly controlled temperature changes, and heating the crucible at the temperature of interest for 24 hours. After heating, the crucible is air-cooled, and microscopy is used to determine the crystalline phases present and the percentage of crystallinity within the glass. More specifically, the glass sample is removed from the Pt crucible in one piece and examined using polarized light microscopy to identify the location and nature of any crystals formed relative to the Pt / air interface and within the sample. The sample is subjected to this process at multiple temperatures intended to encompass the actual liquidus temperature of the glass. Once the crystalline phases and percentage of crystallinity are identified at various temperatures, these temperatures can be used to identify the zero-crystallization temperature, or liquidus temperature, of the composition of interest. Tests are sometimes run for longer times (e.g., 72 hours) to observe slower growth stages. The crystalline phases for the various glasses in Table 9 are described by the following abbreviations: anor--anorthite, a calcium aluminosilicate mineral; cris--cristobalite (SiO2); cels--mixed alkaline earth celsian; Sr / Alsil--strontium aluminosilicate phase; SrSi--strontium silicate phase. The liquidus viscosity, expressed in poises, was determined from the liquidus temperature and the coefficients of the Fulcher equation.

[0096] Young's modulus values, expressed in GPa, were determined using a resonant ultrasonic spectroscopy technique of the general type described in ASTM E1875-00e1.

[0097] Exemplary glasses are provided in Table 9. As can be seen from Table 9, the exemplary glasses can have density, CTE, anneal point, and Young's modulus values ​​that make them suitable for AMLCD substrate applications, more particularly for display applications such as low-temperature polysilicon and oxide thin film transistor applications. Although not shown in the tables herein, the glasses have durability in acidic and basic media similar to that obtained from commercially available AMLCD substrates, and are therefore suitable for AMLCD applications. The exemplary glasses can be formed using downdraw techniques and are specifically compatible with the fusion process by the criteria described above.

[0098] The exemplary glasses in the tables herein were prepared using commercially available sand as the silica source, ground to 90% by weight to pass a standard 100-mesh U.S. sieve. Alumina was the alumina source, periclase was the MgO source, limestone was the CaO source, strontium carbonate, strontium nitrate, or a mixture thereof was the SrO source, barium carbonate was the BaO source, and tin(IV) oxide was the SnO source. The raw materials were thoroughly mixed, loaded into a platinum vessel suspended in a furnace heated by a silicon carbide glow bar, melted and stirred at temperatures between 1600°C and 1650°C for several hours to ensure homogeneity, and delivered through an orifice in the bottom of the platinum vessel. The resulting glass patty was annealed at or near the anneal point and then subjected to various experimental methods to determine its physical, viscous, and liquidus properties.

[0099] The glasses tabulated herein can be prepared using standard methods known to those skilled in the art, including continuous melting processes, such as those performed in a continuous melting process where the melter used is heated by gas, electricity, or a combination thereof.

[0100] Suitable raw materials for making exemplary glasses include commercially available sand as a source of SiO; alumina, aluminum hydroxide, hydrated forms of alumina, and various aluminosilicates, nitrates, and halides as sources of AlO; boric acid, boric anhydride, and boron oxide as sources of BO; periclase, dolomite (also a source of CaO), magnesia, magnesium carbonate, magnesium hydroxide, and magnesium silicate, various forms of aluminosilicates, nitrates, and halides as sources of MgO; limestone, aragonite, dolomite (also a source of MgO), wollastonite, and various forms of calcium silicate, aluminosilicates, nitrates, and halides as sources of CaO; and strontium and barium oxides, carbonates, nitrates, and halides. If a chemical fining agent is desired, tin can be added as SnO, as a mixed oxide with another major glass component (e.g., CaSnO), or under oxidizing conditions as SnO, tin oxalate, tin halides, or other compounds of tin known to those skilled in the art.

[0101] While the glasses in the tables herein contain SnO as a fining agent, other chemical fining agents may also be used to obtain glass of sufficient quality for TFT substrate applications. For example, the illustrated glasses may use any one or combination of AsO, SbO, CeO, FeO, and halides as deliberate additions to promote fining, any of which may be used with the SnO chemical fining agent shown in the examples. Of these, AsO and SbO are generally recognized as hazardous materials and are subject to regulation of waste streams such as those generated during glass manufacturing or TFT panel processing. Therefore, it is desirable to limit the concentrations of AsO and SbO, individually or in combination, to 0.005 mole percent or less.

[0102] In addition to the elements deliberately included in the exemplary glasses, nearly every stable element in the periodic table is present in the glasses at some level, either through low-level contamination in raw materials, high-temperature corrosion of refractories and precious metals during manufacturing, or deliberate introduction at low levels to fine-tune the properties of the final glass. For example, zirconium may be introduced as a contaminant through interaction with zirconium-rich refractories. As a further example, platinum and rhodium may be introduced through interaction with precious metals. As a further example, iron may be introduced as a tramp in raw materials or deliberately added to improve gaseous inclusion control. As a further example, manganese may be introduced for color control or to improve gaseous inclusion control. As a further example, alkalis may be present as tramp components at levels up to about 0.1 mole percent of the total concentration of LiO, NaO, and KO.

[0103] Hydrogen forms the hydroxyl anion OH - hydroxyl ions are inevitably present in the form of hydroxyl ions, and their presence can be confirmed by standard infrared spectroscopy techniques. Dissolved hydroxyl ions significantly and nonlinearly affect the annealing point of the exemplary glass, and therefore, to obtain the desired annealing point, it may be necessary to adjust the concentration of the major oxide component to compensate. Hydroxyl ion concentration can be controlled to some extent by the choice of raw materials or the melting system. For example, boric acid is a major source of hydroxyl, and replacing boric acid with boric oxide may be a useful means to control the hydroxyl concentration in the final glass. The same rationale applies to other potential raw materials, including hydroxyl ions, hydrates, or compounds containing physisorbed or chemisorbed water molecules. If a burner is used in the melting process, hydroxyl ions may also be introduced by combustion products from the combustion of natural gas and related hydrocarbons; therefore, it may be desirable to shift the energy used in melting from the burner to the electrode to compensate. Alternatively, an iterative process of adjusting the major oxide component to compensate for the deleterious effects of dissolved hydroxyl ions may instead be utilized.

[0104] Sulfur is often present in natural gas, as well as being a tramp component in many carbonate, nitrate, halide, and oxide raw materials. Sulfur, in the form of SO2, can be a troublesome source of gaseous inclusions. The tendency to form SO2-rich defects can be managed to a significant extent by controlling the sulfur level in the raw materials and by including low levels of relatively reduced polyvalent cations in the glass matrix. Without intending to be bound by theory, it is believed that SO2-rich gaseous inclusions may be formed by the formation of sulfate radicals (SO4) dissolved in the glass. = The barium content appears to be primarily due to the reduction of sulfur. The elevated barium concentration of the exemplary glasses appears to increase the desulfurization effect in the glass during the early stages of melting, but as noted above, barium is required to obtain low liquidus temperatures and therefore high liquidus viscosities. Carefully controlling the sulfur level in the raw materials to low levels is a useful means of reducing dissolved sulfur (presumably as sulfate) in the glass. Specifically, sulfur can be less than 200 ppm by weight of the batch materials, or less than 100 ppm by weight of the batch materials.

[0105] Reduced polyvalent elements can be used to control the tendency of exemplary glasses to form SO2 blisters. Without intending to be bound by theory, these elements behave as potential electron donors that suppress the electromotive force for sulfate reduction. The reduction of sulfate groups is SO4 = →SO2+O2+2e - where e - indicates an electron. The "equilibrium constant" for this half-reaction is K eq =[SO2][O2][e - ] 2 / [SO4 = ] where the square brackets indicate chemical activity. Ideally, the reaction produces SO2, O2, and e -We want to create sulfate groups from SO2. Adding nitrates, peroxides, or other oxygen-rich raw materials would be helpful, but would work against the reduction of sulfate groups in the early stages of melting, which would negate the benefit of adding them in the first place. SO2 has very low solubility in most glasses, and therefore is impractical to add to the glass melting process. Electrons will be "donated" by reduced polyvalent elements, e.g., ferrous iron (Fe 2+ The appropriate electron-donating half-reaction for 2Fe 2+ →2Fe 3+ +2e - This "activity" of electrons forces the sulfate reduction reaction to the left, forming SO4 = Suitable reduced polyvalent elements include, but are not limited to, Fe 2+ , Mn 2+ , Sn 2+ , Sb 3+ , As 3+ , V 3+ , Ti 3+ , and others familiar to those skilled in the art. In each case, it may be important to minimize the concentration of such components to avoid deleterious effects on the color of the glass, or, in the case of As and Sb, to avoid adding such components at levels high enough to minimize waste management complications in the end-user's process.

[0106] In addition to the major oxide components of the exemplary glasses and the minor or tramp components mentioned above, halides may be present at various levels, either as contaminants introduced by raw material selection or as intentional components used to eliminate gaseous inclusions in the glass. Halides may be included as fining agents at levels of about 0.4 mole percent or less, although it is generally desirable to use smaller amounts where possible to avoid corrosion of exhaust gas handling equipment. In some embodiments, the concentration of individual halide elements is less than about 200 ppm by weight for each individual halide, or less than about 800 ppm by weight for all halide elements combined.

[0107] In addition to these major oxide components, minor and trace components, polyvalent element and halide fining agents, it may be useful to include small concentrations of other colorless oxide components to achieve desired physical, optical, or viscoelastic properties. Examples of such oxides include, but are not limited to, TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, MoO3, WO3, ZnO, In2O3, Ga2O3, Bi2O3, GeO2, PbO, SeO3, TeO2, YO3, La2O3, Gd2O3, and other compounds known to those skilled in the art. Through an iterative process of adjusting the relative proportions of the major oxide components of the exemplary glasses, such colorless oxides can be added at levels up to about 2 mole percent without unacceptably affecting the annealing point or liquidus viscosity.

[0108] Table 9 lists exemplary glasses according to some embodiments of the present disclosure.

[0109] [Table 9-1]

[0110] [Table 9-2]

[0111] Table 9-3

[0112] Table 9-4

[0113] Table 9-5

[0114] Table 9-6

[0115] Table 9-7

[0116] Table 9-8

[0117] Table 9-9

[0118] Table 9-10

[0119] Table 9-11

[0120] Table 9-12

[0121] Table 9-13

[0122] [Table 9-14]

[0123] [Table 9-15]

[0124] [Table 9-16]

[0125] [Table 9-17]

[0126] [Table 9-18]

[0127] [Table 9-19]

[0128] [Table 9-20]

[0129] Preferred embodiments of the present invention will be described below in detail.

[0130] Embodiment 1 A substantially alkali-free glass containing, expressed in mole percent on an oxide basis, 66-70.5 SiO2, 11.2-13.3 Al2O3, 2.5-6 B2O3, 2.5-6.3 MgO, 2.7-8.3 CaO, 1-5.8 SrO, and 0-3 BaO.

[0131] Embodiment 2 2. The glass of embodiment 1, wherein 0.98≦(MgO+CaO+SrO+BaO) / Al2O3≦1.38.

[0132] Embodiment 3 2. The glass of embodiment 1, wherein 0.18≦MgO / (MgO+CaO+SrO+BaO)≦0.45.

[0133] Embodiment 4 10. The glass of embodiment 1 containing 0.01 to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0134] Embodiment 5 10. The glass of claim 1, comprising 0.005 to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0135] Embodiment 6 2. The glass of claim 1, wherein the glass has an anneal point greater than 750°C.

[0136] Embodiment 7 2. The glass of claim 1, wherein the glass has an anneal point greater than 765°C.

[0137] Embodiment 8 2. The glass of claim 1, wherein the glass has an anneal point greater than 770°C.

[0138] Embodiment 9 10. The glass of claim 1, wherein the glass has a liquidus viscosity greater than 100,000 poise.

[0139] Embodiment 10 10. The glass of claim 1, wherein the glass has a liquidus viscosity greater than 150,000 poise.

[0140] Embodiment 11 10. The glass of claim 1, wherein the glass has a liquidus viscosity greater than 180,000 poise.

[0141] Embodiment 12 10. The glass of claim 1, wherein the glass has a Young's modulus greater than 80 GPa.

[0142] Embodiment 13 10. The glass of claim 1, wherein the glass has a Young's modulus greater than 81 GPa.

[0143] Embodiment 14 10. The glass of claim 1, wherein the glass has a Young's modulus greater than 81.5 GPa.

[0144] Embodiment 15 10. The glass of claim 1, wherein the glass has a density less than 2.55 g / cc.

[0145] Embodiment 16 10. The glass of claim 1, wherein the glass has a density less than 2.54 g / cc.

[0146] Embodiment 17 10. The glass of claim 1, wherein the glass has a density less than 2.53 g / cc.

[0147] Embodiment 18 10. The glass of claim 1, wherein the glass has a T200P of less than 1665°C.

[0148] Embodiment 19 10. The glass of claim 1, wherein the glass has a T200P of less than 1650°C.

[0149] Embodiment 20 2. The glass of claim 1, wherein the glass has a T200P of less than 1640°C.

[0150] Embodiment 21 2. The glass of claim 1, wherein the glass has a T35kP of less than 1280°C.

[0151] Embodiment 22 2. The glass of claim 1, wherein the glass has a T35kP of less than 1270°C.

[0152] Embodiment 23 2. The glass of claim 1, wherein the glass has a T35kP of less than 1266°C.

[0153] Embodiment 24 2. The glass of claim 1, wherein the glass has a T200P-T(ann) of less than 890°C.

[0154] Embodiment 25 2. The glass of claim 1, wherein the glass has a T200P-T(ann) of less than 880°C.

[0155] Embodiment 26 2. The glass of claim 1, wherein the glass has a T200P-T(ann) of less than 870°C.

[0156] Embodiment 27 2. The glass of claim 1, wherein the glass has a T200P-T(ann) of less than 865°C.

[0157] Embodiment 28 2. The glass of claim 1, wherein the glass has a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.

[0158] Embodiment 29 2. The glass of claim 1, wherein the glass has a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise.

[0159] Embodiment 30 2. The glass of claim 1, wherein the glass has a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise.

[0160] Embodiment 31 10. The glass of claim 1, wherein As2O3 and Sb2O3 comprise less than about 0.005 mol %.

[0161] Embodiment 32 10. The glass of claim 1, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0162] Embodiment 33 10. The method of making the glass of embodiment 1, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0163] Embodiment 34 10. An object made from the glass of embodiment 1, wherein the object is made by a downdraw sheet manufacturing process.

[0164] Embodiment 35 10. An object made from the glass of embodiment 1, produced by the fusion process or a variant thereof.

[0165] Embodiment 36 A liquid crystal display substrate made from the glass of embodiment 1.

[0166] Embodiment 37 A substantially alkali-free glass containing, expressed in mole percent on an oxide basis, 68-79.5 SiO2, 12.2-13 Al2O3, 3.5-4.8 B2O3, 3.7-5.3 MgO, 4.7-7.3 CaO, 1.5-4.4 SrO, and 0-2 BaO.

[0167] Embodiment 38 38. The glass of embodiment 37, wherein 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2.

[0168] Embodiment 39 38. The glass of embodiment 37, wherein 0.24≦MgO / (MgO+CaO+SrO+BaO)≦0.36.

[0169] Embodiment 40 38. The glass of embodiment 37, comprising 0.01 to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0170] Embodiment 41 38. The glass of embodiment 37, comprising 0.005 to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0171] Embodiment 42 38. The glass of claim 37, wherein the glass has a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.

[0172] Embodiment 43 38. The glass of claim 37, wherein the glass has a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise.

[0173] EMBODIMENT 44 38. The glass of claim 37, wherein the glass has a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise.

[0174] Embodiment 45 38. The glass of embodiment 37, wherein As2O3 and Sb2O3 comprise less than about 0.005 mol %.

[0175] Embodiment 46 38. The glass of embodiment 37, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0176] Embodiment 47 38. The method of making the glass of embodiment 37, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0177] Embodiment 48 38. An object made from the glass of embodiment 37, wherein the object is made by a downdraw sheet manufacturing process.

[0178] Embodiment 49 38. An object made from the glass of embodiment 37, produced by the fusion process or a variant thereof.

[0179] Embodiment 50 38. A liquid crystal display substrate made from the glass of embodiment 37.

[0180] Embodiment 51 A substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 68.3 to 69.5 SiO2, 12.4 to 13 Al2O3, 3.7 to 4.5 B2O3, 4 to 4.9 MgO, 5.2 to 6.8 CaO, 2.5 to 4.2 SrO, and 0 to 1 BaO, wherein SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percents of the oxide components.

[0181] Embodiment 52 52. The glass of embodiment 51, wherein 1.09≦(MgO+CaO+SrO+BaO) / Al2O3≦1.16.

[0182] Embodiment 53 52. The glass of embodiment 51, wherein 0.25≦MgO / (MgO+CaO+SrO+BaO)≦0.35.

[0183] EMBODIMENT 54 52. The glass of embodiment 51, containing 0.01 to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0184] Embodiment 55 52. The glass of embodiment 51, comprising 0.005 to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0185] Embodiment 56 52. The glass of claim 51, wherein the glass has a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.

[0186] Embodiment 57 52. The glass of claim 51, wherein the glass has a T200P-T(ann) less than 880°C, a T(ann)≧765°C, a Young's modulus greater than 81 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 150,000 poise.

[0187] Embodiment 58 52. The glass of claim 51, wherein the glass has a T200P-T(ann) less than 865°C, a T(ann)≧770°C, a Young's modulus greater than 81.5 GPa, a density less than 2.54 g / cc, and a liquidus viscosity greater than 180,000 poise.

[0188] Embodiment 59 52. The glass of embodiment 51, wherein As2O3 and Sb2O3 comprise less than about 0.005 mol %.

[0189] Embodiment 60 52. The glass of embodiment 51, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0190] Embodiment 61 52. The method for making the glass of embodiment 51, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0191] Embodiment 62 52. An object made from the glass of embodiment 51, wherein the object is made by a downdraw sheet manufacturing process.

[0192] Embodiment 63 52. An object made from the glass of embodiment 51, produced by the fusion process or a variant thereof.

[0193] EMBODIMENT 64 A liquid crystal display substrate made from the glass of embodiment 51.

[0194] Embodiment 65 Relational formula: 70GPa≦549.899-4.811 * SiO2-4.023 * Al2O3-5.651 * B2O3-4.004 * MgO-4.453 * CaO-4.753 * SrO-5.041 * BaO≦90GPa wherein SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide components of the glass.

[0195] Embodiment 66 66. The glass of embodiment 65, wherein 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2.

[0196] Embodiment 67 66. The glass of embodiment 65, comprising 0.01 to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0197] Embodiment 68 66. The glass of embodiment 65, comprising 0.005 to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0198] Embodiment 69 66. The glass of embodiment 65, wherein As2O3 and Sb2O3 account for less than about 0.005 mol %.

[0199] Embodiment 70 66. The glass of embodiment 65, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0200] Embodiment 71 66. The method for making the glass of embodiment 65, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0201] Embodiment 72 66. An object made from the glass of embodiment 65, wherein the object is made by a downdraw sheet manufacturing process.

[0202] Embodiment 73 66. An object made from the glass of embodiment 65, produced by the fusion process or a variant thereof.

[0203] EMBODIMENT 74 66. A liquid crystal display substrate made from the glass of embodiment 65.

[0204] Embodiment 75 Relational formula: 720℃≦1464.862-6.339 * SiO2-1.286 *Al2O3-17.284 * B2O3-12.216 * MgO-11.448 * CaO-11.367 * SrO-12.832 * BaO≦810℃ wherein SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percent of the oxide constituents of said glass.

[0205] Embodiment 76 76. The glass of embodiment 75, wherein 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2.

[0206] Embodiment 77 76. The glass of embodiment 75, comprising 0.01 to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0207] Embodiment 78 76. The glass of embodiment 75, comprising 0.005 to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0208] Embodiment 79 76. The glass of embodiment 75, wherein As2O3 and Sb2O3 comprise less than about 0.005 mol %.

[0209] Embodiment 80 76. The glass of embodiment 75, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0210] Embodiment 81 76. The method of making the glass of embodiment 75, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0211] Embodiment 82 76. An object made from the glass of embodiment 75, wherein the object is made by a downdraw sheet manufacturing process.

[0212] Embodiment 83 76. An object made from the glass of embodiment 75, produced by the fusion process or a variant thereof.

[0213] Embodiment 84 76. A liquid crystal display substrate made from the glass of embodiment 75.

[0214] Embodiment 85 A substantially alkali-free glass containing, expressed in mole percent on an oxide basis, 68-79.5 SiO2, 12.2-13 Al2O3, 3.5-4.8 B2O3, 3.7-5.3 MgO, 4.7-7.3 CaO, 1.5-4.4 SrO, and 0.04-2 BaO.

[0215] Embodiment 86 86. The glass of embodiment 85, wherein 1.07≦(MgO+CaO+SrO+BaO) / Al2O3≦1.2.

[0216] Embodiment 87 86. The glass of embodiment 85, wherein 0.24≦MgO / (MgO+CaO+SrO+BaO)≦0.36.

[0217] Embodiment 88 86. The glass of embodiment 85, comprising 0.01 to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0218] Embodiment 89 86. The glass of embodiment 85, comprising 0.005 to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0219] Embodiment 90 86. The glass of claim 85, wherein the glass has a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.

[0220] Embodiment 91 86. The glass of embodiment 85, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0221] Embodiment 92 86. The method of making the glass of embodiment 85, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0222] Embodiment 93 86. An object made from the glass of embodiment 85, wherein the object is made by a downdraw sheet manufacturing process.

[0223] Embodiment 94 86. An object made from the glass of embodiment 85, produced by the fusion process or a variant thereof.

[0224] Embodiment 95 A liquid crystal display substrate made from the glass of embodiment 85.

[0225] Embodiment 96 1. A substantially alkali-free glass comprising, expressed in mole percent on an oxide basis, 68.3 to 69.5 SiO2, 12.4 to 13 Al2O3, 3.7 to 4.5 B2O3, 4 to 4.9 MgO, 5.2 to 6.8 CaO, 2.5 to 4.2 SrO, and 0.04 to 1 BaO, wherein SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO represent the mole percents of the oxide components.

[0226] Embodiment 97 97. The glass of embodiment 96, wherein 1.09≦(MgO+CaO+SrO+BaO) / Al2O3≦1.16.

[0227] Embodiment 98 97. The glass of embodiment 96, wherein 0.25≦MgO / (MgO+CaO+SrO+BaO)≦0.35.

[0228] Embodiment 99 97. The glass of embodiment 96, comprising 0.01 mol % to 0.4 mol % of any one or combination of SnO2, As2O3, or Sb2O3, F, Cl, or Br as a chemical fining agent.

[0229] Embodiment 100 97. The glass of embodiment 96, comprising 0.005 mol % to 0.2 mol % of any one or combination of Fe2O3, CeO2, or MnO2 as a chemical fining agent.

[0230] Embodiment 101 97. The glass of claim 96, wherein the glass has a T200P-T(ann) less than 890°C, a T(ann)≧750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.

[0231] Embodiment 102 97. The glass of embodiment 96, wherein Li2O, Na2O, K2O, or combinations thereof comprise less than about 0.1 mol% of the glass.

[0232] Embodiment 103 97. The method of making the glass of embodiment 96, wherein the raw materials contain between 0 and 200 ppm sulfur by weight for each raw material utilized.

[0233] Embodiment 104 97. An object made from the glass of embodiment 96, wherein the object is made by a downdraw sheet manufacturing process.

[0234] Embodiment 105 97. An object made from the glass of embodiment 96, produced by the fusion process or a variant thereof.

[0235] Embodiment 106 A liquid crystal display substrate made from the glass of embodiment 96. [Explanation of symbols]

[0236] 1 entrance 2 Compression end 3 Edge Director 4 Bottom 9 Weir Wall 10 base

Claims

1. 65.93 to 70.96 mol % of SiO ２ , 11.04 to 13.92 Al ２ O ３ , 2.83 to 6.38 B ２ O ３ 2.75 to 6.02 MgO, 3.98 to 7.34 CaO, 1.97 to 5.06 SrO, 0 to 1.54 BaO, 1.07≦(MgO+CaO+SrO+BaO) / Al ２ O ３ ≦1.38, 0.24≦MgO / (MgO+CaO+SrO+BaO)≦0.36, Relation: 70GPa≦549.899-4.811*SiO ２ -4.023*Al ２ O ３ -5.651*B ２ O ３ -4.004*MgO-4.453*CaO-4.753*SrO-5.041*BaO≦90GPa or a Young's modulus in the range defined by Relation: 720℃≦1464.862-6.339*SiO ２ -1.286*Al ２ O ３ -17.284*B ２ O ３ -12.216*MgO-11.448*CaO-11.367*SrO-12.832*BaO≦810℃ A glass having an annealing point in the range defined by

2. 68.3 to 69.5 SiO, expressed in mole percent on an oxide basis ２ , 11.2 to 13.3 Al ２ O ３ , 3.5 to 4.8 B ２ O ３ , 4 to 4.9 MgO, 1.07≦(MgO+CaO+SrO+BaO) / Al ２ O ３ 2. The glass of claim 1 wherein the refractive index is ≦1.

16.

3. 2. The glass of claim 1, comprising, in mole percent on an oxide basis, 2.5 to 4.2 SrO, 0 to 1 BaO, and 0.25≦MgO / (MgO+CaO+SrO+BaO)≦0.

35.

4. Expressed in mole percent on an oxide basis, 1.09≦(MgO+CaO+SrO+BaO) / Al ２ O ３ 2. The glass of claim 1, wherein the refractive index is ≦1.

13.

5. 10. The glass of claim 1 having a T200P-T(ann) less than 890°C, T(ann) > 750°C, a Young's modulus greater than 80 GPa, a density less than 2.55 g / cc, and a liquidus viscosity greater than 100,000 poise.

6. 12.4 to 13% Al, expressed in mole percent on an oxide basis ２ O ３ The glass of any one of claims 1 to 5, comprising:

7. 6. The glass according to claim 1, wherein 0.30≦MgO / (MgO+CaO+SrO+BaO)≦0.

35.

8. As a chemical fining agent, SnO ２ , As ２ O ３ , Sb ２ O ３ The glass of any one of claims 1 to 5, further comprising 0.01 mol % to 0.4 mol % of any one or any combination of: F, Cl, or Br.

9. As a chemical fining agent, Fe ２ O ３ , CeO ２ , or MnO ２ The glass of any one of claims 1 to 5, further comprising from 0.005 mol % to 0.2 mol % of any one or any combination of:

10. A liquid crystal display substrate made from the glass of any one of claims 1 to 5.

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