KR100813772B1 - Glasses for flat panel displays - Google Patents

Abstract

The present invention relates to glass used to manufacture substrates for flat panel display devices. The glass is composed of 65 to 75 mol% SiO ₂ , 7 to 13 mol% Al ₂ O ₃ , 5 to 15 mol% B ₂ O ₃ , 0 to 3 mol% MgO, 5 to 15 mol% CaO and 0 on an oxide basis. Consisting essentially of a composition containing ˜5 mol% SrO and essentially free of BaO, exhibiting a density of less than about 2.45 g / cm ³ and a liquid viscosity greater than about 200,000 poise.

Flat Panel Displays, Glass, Substrates, Aluminosilicates, Density, Liquid Viscosity

Description

Glass for flat panel displays {Glasses for flat panel displays}

The present invention relates to alkali-free, aluminosilicate glass exhibiting desirable physical and chemical properties in substrates for flat panel display devices.

Displays will largely be classified into one of two forms: radial (e.g., CRT and plasma display panels (PDPs)) or non-emissive. The latter includes liquid crystal displays (LCDs) and rely on an external light source with a display provided only as a light modulator. In the case of a liquid crystal display, this external light source may be either ambient light (used in the reflective display) or dedicated light source (as found in a direct view display).

Liquid crystal displays rely on three original properties of liquid crystal (LC) materials to modulate light. First is the LC's ability to cause optical rotation of the polarized light. Second is the LC's ability to set the rotation by the mechanical direction of the liquid crystal. A third characteristic is the ability of the liquid crystal to withstand the mechanical direction by the application of an external electromagnetic field.

In the construction of a simple, twisted nematic liquid crystal display, two substrates are wrapped in a layer of liquid crystal material. In the form of a display known as Normally White, a 90 [deg.] Spiral of the liquid crystal director is created by applying an alignment layer on the inner surface of the substrates. This means that the polarization of linearly polarized light entering one side of the liquid crystal cell will be rotated 90 ° by the liquid crystal material. Polarization films, each directed at 90 ° to each other, are placed on the outer surface of the substrates.

When entering the first polarizing membrane, light is linearly polarized. When passing through the liquid crystal cell, the polarization of light is rotated by 90 ° and exits through the second polarization membrane. Application of an electromagnetic field across the liquid crystal layer aligns liquid crystal directors with the electromagnetic field, hindering the liquid crystal's ability to rotate light. Linearly polarized light passing through the cell has no rotated polarization and is therefore blocked by a second polarization membrane. Thus, in the simplest sense, the liquid crystal material becomes a light valve, and the ability to allow or block the transmission of light is controlled by the application of an electromagnetic field.

The foregoing description relates to the manipulation of a single pixel in a liquid crystal display. Display in the form of high information requires the assembly of millions of such pixels, which are called sub pixels in matrix form. While maximizing addressing speed and minimizing cross-talk, several attempts are made to address all of these subpixels or to apply an electromagnetic field to them. One preferred method for addressing subpixels is to adjust the electromagnetic field with thin film transistors located in each subpixel, which form the basis of active matrix liquid crystal display devices (AMLCDs).

The production of such displays is very complex and the nature of the substrate glass is of paramount importance. Initially, the glass substrates used in the manufacture of AMLCD devices require precisely adjusted physical values. As described in US Pat. No. 3,338,696 (Dockerty) and US Pat. No. 3,682,609 (Dockerty), downdraw sheets or fusion processes are expensive, such as lapping and polishing. It is one of the few things that can be transported without requiring post forming finishing. Unfortunately, the melting process is subject to rather stringent limitations on glass properties when it requires a relatively high liquid viscosity, preferably greater than 200,000 poises.

Typically, two substrates containing the display are manufactured separately. One color filter plate has a series of red, blue, green and black organic dyes stacked thereon. Each of these primary colors must precisely correspond to the pixel electrode area of the tuning active plate. In order to eliminate the influence of the difference between the surrounding thermal conditions encountered in the manufacture of the two plates, it is preferable to use a glass (ie glass having a low coefficient of thermal expansion) whose size is independent of the thermal conditions. However, this property needs to be balanced due to stress generation between the laminated film and the substrates, which rises due to expansion mismatch. The optimum coefficient of thermal expansion is estimated to be in the range of 28-33 × 10 ⁻⁷ / ° C.

Because of the inclusion of active thin film transistors, active plates called so-called active plates are manufactured using conventional semiconductor form processes. Such methods include sputtering, CVD, photolithography, and etching. Most preferred are glasses that do not change during these processes. Thus, the glass needs to exhibit both thermal and chemical stability.

Thermal stability (or known as thermal compression or shrinkage) depends both on the intrinsic viscosity of the precision glass composition (represented by the strain point) and the thermal history of the glass sheet as determined by the production process. U.S. Pat. No. 5,374,595 discloses that glass having a strain point exceeding 650 ° C. and a thermal history of the melting process is acceptable thermal stability in active plates based on both a-Si thin film transistors (TFTs) and super low temperature p-Si TFTs. It is described that it will have. Higher temperature processes (as required by low temperature p-Si TFTs) will require the addition of an annealing step to the glass substrate to measure thermal stability.

Chemical stability refers to the resistance to corrosion of the various caustic solutions used in the production process. Of particular interest is resistance to corrosion from the dry etching conditions used to etch the silicon layer. In order to benchmark the dry etching conditions, the substrate sample is exposed to a corrosion solution known as 110 BHF. This test consists of immersing the sample for 5 minutes in a solution of 50% by weight of HF and 10% by weight of NH ₄ F 10 parts by weight. The sample is separated into weight loss and shape.

In addition to these requirements, AMLCD producers recognize that both the demand for larger display sizes and the economies of scale enable them to handle larger size glass plates. The current industry standards are Gen III (550 nm x 650 nm) and Gen III.5 (600 nm x 720 nm), but in the future they will be scaled to Gen IV (1 m x 1 m), potentially larger. This raises some interest. The first is simply the weight of the glass. The 50 +% increase in the weight of glass from Gen III.5 to Gen IV has significant implications for robotic handlers used to transfer glass through and towards the process station. . In addition, the elastic sag, which depends on the glass density and Young's Modulus, has a greater influence on the ability to load, retrieve and position the glass in a cassette used to transfer the glass between process areas. The size of the sheet matters.

Accordingly, it is desirable to provide glass compositions having a low density, preferably less than 2.45 g / cm ³ and a liquid viscosity greater than about 200,000 poise, in order to reduce the difficulties associated with larger sheet sizes for display devices. In addition, the glass is preferred having about 28~35 × 10 ^-7 / ℃, preferably the thermal expansion of 28~33 × 10 ^-7 / ℃ over a temperature range of 0~300 ℃. Moreover, glass having a strain point higher than 650 ° C. and having corrosion resistance to the corrosion solution is preferred.

Summary of the Invention

The present invention has a density of less than 2.45 g / cm ³ and greater than about 200,000 poise, preferably greater than about 400,000 poise, more preferably greater than about 600,000 poise, most preferably greater than about 800,000 poise It was based on the discovery of glass exhibiting liquid viscosity (defined as the viscosity of glass at liquid temperature). In addition, the glass of the present invention exhibits a linear thermal expansion coefficient of 28 to 35 × 10 ⁻⁷ / ° C., preferably 28 to 33 × 10 ⁻⁷ / ° C., in a temperature range of 0 to 300 ° C., and exceeds about 650 ° C. The strain point is shown. The glass of the present invention has a melting temperature of less than about 1700 ° C. In addition, the glass was immersed in a solution of 50 parts by weight of HF 1 part and 40 parts by weight of NH ₄ F 10 parts at 30 ° C. for 5 minutes, and exhibited a weight loss of less than 0.5 mg / cm ₂ .

The glass of the present invention comprises 65 to 75 mol% SiO ₂ , 7 to 13 mol% Al ₂ O ₃ , 5 to 15 mol% B ₂ O ₃ , 0 to 3 mol% MgO, 5 to 15 mol% CaO on an oxide basis. And a composition consisting essentially of a composition containing 0-5 mol% SrO and essentially free of BaO. More preferably, the glass of the present invention is 67-73 mol% SiO ₂ , 8-11.5 mol% Al ₂ O ₃ , 8-12 mol% B ₂ O ₃ , 0-1 mol% MgO, 5.5-11 mol% It has a composition consisting essentially of CaO and 0-5 mol% SrO.

The inventors have found that, in glasses having physical properties and the above-mentioned compositions, particularly preferred compositions and glasses having desirable properties, the liquid viscosity of the glass is based on the mole percent of alumina, alkaline earth, RO (R = Mg, Ca, Sr). It was found to be strongly influenced by the ratio of the sum, or RO / Al ₂ O ₃ = (MgO + CaO + SrO) / Al ₂ O ₃ . The ratio is referred to as RO / Al ₂ O ₃ and lies in the range of 0.9 to 1.2. The most preferred range for obtaining the highest liquid viscosity is 0.92 <RO / Al ₂ O ₃ <0.96.

The glass of the present invention is essentially free of BaO, which means that the glass preferably contains less than about 0.1 mole percent BaO. In addition, the glasses of the present invention are essentially free of alkali metal oxides, which means that they preferably contain less than about 0.1 mol% of alkali metal oxides in total. In addition, these glasses will contain a fining agent (such as arsenic, antimony, cerium, tin, and / or halides, chlorine / fluorine).

In another aspect of the invention, the glass has a melting temperature of less than about 1700 ° C. In addition, the glass of the present invention shows a weight loss of less than 0.5 mg / cm ₂ after being immersed in a solution of 50 parts by weight of HF 1 part and 40 parts by weight of NH ₄ F 10 parts at 30 ° C. for 5 minutes. Glass is useful as a substrate for flat panel displays. Substrates made of glass of the present invention have an average surface roughness of less than about 0.5 nm measured by atomic force microscopy and less than about 150 psi measured by optical retardation. It has an average internal stress.

The present invention relates to an improved glass for use as a flat panel display substrate. In particular, glass meets the various property requirements of the substrate.

Preferred glasses according to the invention exhibit a density of less than 2.45 g / cm ³ , preferably less than 2.40 g / cm ³ , and 28 to 35 × 10 ⁻⁷ / ° C., preferably 28, in the temperature range of 0 to 300 ° C. The linear thermal expansion coefficient of -33x10 <^-7> / degreeC is shown, and the strain point which exceeds about 650 degreeC, Preferably it exceeds 660 degreeC is shown. High strain points are desirable to help prevent panel distortion due to compression / shrinkage during subsequent thermal processes.

For further demanding production conditions, such as the melting process, described in US Pat. Nos. 3,338,696 (Dockerty) and 3,682,609 (Dockerty), glass with high liquid viscosity is required. Thus, in a preferred embodiment of the invention, the glass exhibits a density of less than 2.45 g / cm ³ , exceeding about 200,000 poises, preferably exceeding about 400,000 poises, more preferably exceeding about 600,000 poises. Most preferably a liquid viscosity in excess of about 800,000 poise. Although the substrate made of the glass of the present invention is produced using another production process such as a flotation process, the melting process is preferred for several reasons. First, glass substrates produced by the melting process do not require polishing. Polishing of current glass substrates can produce glass substrates with an average surface roughness of more than 0.5 nm (Ra) as measured by nuclear microscopy. Glass substrates produced using the melting process according to the present invention have an average surface roughness of less than 0.5 nm as measured by nuclear microscopy.

Chemical stability refers to the resistance to corrosion of various caustic solutions used in the production process. Of particular interest is resistance to corrosion from the dry etching conditions used to etch the silicon layer. One benchmark of dry etching conditions is exposed to a caustic solution known as 110 BHF. This test consists of immersing the sample for 5 minutes in a solution of 50 parts by weight of HF and 10 parts by weight of NH ₄ F 10 parts by weight. Chemical resistance is determined by measuring weight loss in units of mg / cm ² . This property is described in Table 1 as "110 BHF".

The glass of the present invention contains 65 to 75 mol%, preferably 67 to 73 mol% SiO ₂ as the main glass former. Increasing silica improves liquid viscosity and reduces glass density and CTE, but excess silica is not beneficial to the melting temperature. At least 8 mole percent is required to have the most desirable strain point, but 11.5 mole percent may be below the desired liquid temperature.

The glass further comprises 5 to 15 mol%, preferably 8 to 12 mol% boron oxide. Boron oxide lowers the liquid temperature and density and is preferably present at least 8 mole percent, but above 12 mole percent negatively affects the glass strain point.

MgO is present in the glass of the invention in an amount of 0 to 3 mol%, preferably 0 to 1 mol%. As the MgO increases, the liquid viscosity decreases, so less than 3 mole% MgO is present in the glass. However, the smaller the amount of MgO, the more advantageous it is to lower the density.

CaO is useful for lowering both the melting and liquid temperatures of the glass, but above 11 mole% results in below the desired strain point and even higher than the desired coefficient of thermal expansion. Thus, the glass of the present invention may comprise 5-15 mol% CaO, more preferably 5.5-11 mol% CaO.

The RO / Al ₂ O ₃ ratio is in the range of 0.9 to 1.2. Within this range a local minimum at liquid temperature corresponding to cotectics and / or eutectics can be found in the base CaO-Al ₂ O ₃ -SiO ₂ . The viscosity curves of the glass in this order do not change at all, and therefore, the change in these liquid temperatures is a major factor for the increase in liquid viscosity.

Because of negative effects on thin film transistor (TFT) performance, alkalis such as lithium oxide, soda or potash have been excluded from the glass compositions of the present invention. Similarly, heavy alkaline earth metals (SrO and BaO) will be minimized or eliminated due to negative effects on glass density. Therefore, the glass of this invention contains 0-5 mol% SrO. However, the glass of the present invention is essentially free of BaO. As used herein, essentially free of BaO means containing less than 0.1 mole percent BaO in the composition.

In addition, a fining agent such as As ₂ O ₃ , Sb ₂ O ₃ , CeO ₂ , SnO ₂ , Cl, F, SO _2, etc. will assist in the removal of seeds from the glass. The glass will also contain contaminants as commonly found in commercially available glass. In addition, oxides such as TiO ₂ , ZnO, ZrO ₂ , Y ₂ O ₃ , La ₂ O ₃ may be added to an extent not exceeding 1 mol% without pushing properties outside the above-mentioned range. Table 1 below shows an example of the glass according to the invention in mole% together with their physical properties. A comparative example in Table 1 below is Corning Incorporated's 1737 glass.

The invention is further illustrated by the following examples, which do not limit the scope of the invention as claimed for illustration only. Table 1 shows the preferred glass compositions in mol%, which is calculated on an oxide basis from the glass batch. The glass of this example was prepared by fusing 1,000 to 25,000 gram batches of each glass composition at a temperature and time resulting in a relatively homogeneous glass composition, for example at about 1625 ° C. for about 4-16 hours in a platinum crucible. In addition, related glass properties are described for each glass composition in which glass is determined according to a conventional technique in glass technology. Accordingly, the linear coefficient of thermal expansion (CTE) in the temperature range of 0 to 300 ° C. is expressed as × 10 ⁻⁷ / ° C. and the softening point (Soft pt.) And the annealing point (Ann. Pt.) And the strain point (Str. Pt.) Is expressed in degrees Celsius. These are determined from fiber tensile techniques (ASTM references E228-85, C338, and C336, respectively). Density (Den.) of g / cm ³ is measured by the Archmed method (ASTM C693).

The 200 poise temperature (melting temperature, ° C.) (defined as the temperature at which the glass melt exhibits a viscosity of 200 poise [20 Pa.s]) is the Puller equation according to the high temperature viscosity data (rotating cylinder viscometer, ASTM C965-81). Calculated using The liquid temperature (Liq. Temp.) Of the glass was measured using standard liquid methods. The method comprises the steps of placing the ground glass particles in a platinum boat, placing the boat in a furnace with a temperature gradient, heating the boat at an appropriate temperature for 24 hours, and Involved by microscopic experiments determining the highest temperature at which the crystal exhibits the decorativeness of the glass. The liquid viscosity (poise) is determined from the coefficients of this temperature and the pooler equation.

Table 1 below lists many glass compositions, expressed in parts by oxide reference moles, and shows the variables in terms of composition of the present invention. Since the sum of each component is approximately approximately 100, the values reported for all practical purposes will mean mole%. Actual batch drugs include any of oxides or other compositions, and when melted with other batch compositions, it will be converted to the desired oxide in the proper proportion. For example, SrCO ₃ and CaCO ₃ can provide a source of SrO and CaO, respectively.

Glasses having the compositions and properties shown in Examples 14 and 19 are now considered to be the optimum mode according to the invention, ie the best combination of properties for the purposes of the invention.

Although the present invention has been described in detail for purposes of illustration, it is to be understood that this description is for illustrative purposes only and may be modified by those skilled in the art without departing from the scope of the invention as defined in the following claims. .

One 2 3 4 5 6 7 8 Match composition (mol%) SiO ₂ 69.75 69.78 69.75 69.8 70.7 70.57 69.1 70.85 Al ₂ O ₃ 10.2 10.2 10.3 10.3 10 9.77 10.35 9.5 B ₂ O ₃ 9.7 9.7 9.5 9.5 10 9.95 10.25 10.1 MgO 0.8 0.8 0.8 0.8 0.12 0.15 1.25 CaO 7 7 8.5 8.5 9 9.17 9.8 6.7 SrO 2.2 2.2 0.8 0.8 1.3 BaO As ₂ O ₃ 0.3 0.3 0.4 0.33 Sb ₂ O ₃ 0.3 0.3 0.3 0.1 CeO ₂ 0.2 Y ₂ O ₃ SnO ₂ 0.05 0.02 0.05 0.05 0.02 0.02 Cl 0.2 0 0.2 0.2 0.2 RO / Al ₂ O ₃ 0.98 0.98 0.98 0.98 0.90 0.95 0.96 0.98 CTE (0-300 ° C, × 10 ^-7 / ° C) 32.7 31.2 31.9 30.8 30.5 30.2 31.5 31.4 Density (g / cm ³ ) 2.416 2.404 2.394 2.38 2.37 2.355 2.375 2.367 Strain point (℃) 672 674 673 679 671 666 673 664 Annealing Point (℃) 727 731 729 734 728 729 729 720 Softening point (℃) 984 991 991 995 1001 1001 976 992 110 BHF (mg / cm ² ) 0.15 0.14 0.145 0.135 0.14 0.15 0.18 0.27 Liquid temperature (℃) 1125 1120 1120 1125 1150 1135 1115 1140 Liquid viscosity (p) 5.04E + 05 7.06E + 05 6.34E + 05 6.30E + 05 3.66E + 05 5.95E + 05 5.30E + 05 4.77E + 05 Melting temperature (℃) 1659 1668 1650 1659 1668 1680 1635 1686
9 10 11 12 13 14 15 16 17 Match composition (mol%) SiO ₂ 69.1 69.65 69.75 69.1 68.8 69.33 69.65 70.05 69.33 Al ₂ O ₃ 10.35 10.1 10.55 10.2 10.35 10.55 10.2 9.9 10.55 B ₂ O ₃ 10.25 10.25 10.25 10.55 10.55 9.97 10.25 10.25 9.97 MgO 0.15 0.15 0.15 0.15 0.15 0.18 0.15 1.15 0.18 CaO 9.3 9.45 9.9 9.65 9.8 9.08 8.85 9.25 9.58 SrO 0.5 0.5 0.5 BaO As ₂ O ₃ 0.33 0.4 0.4 0.33 0.33 0.37 0.4 0.4 0.37 Sb ₂ O ₃ CeO ₂ Y ₂ O ₃ SnO ₂ 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Cl RO / Al ₂ O ₃ 0.96 0.95 0.95 0.96 0.96 0.93 0.93 0.95 0.93 CTE (0-300 ° C, × 10 ^-7 / ° C) 32.2 31.4 31.8 32 31.8 31.5 30.9 30.8 31.4 Density (g / cm ³ ) 2.377 2.366 2.371 2.364 2.366 2.376 2.369 2.357 2.366 Strain point (℃) 671 669 674 666 667 676 671 668 674 Annealing Point (℃) 727 725 729 722 723 731 728 726 730 Softening point (℃) 983 985 986 980 980 985 987 992 987 110 BHF (mg / cm ² ) 0.15 0.12 0.12 Liquid temperature (℃) 1095 1090 1100 1090 1115 1095 1100 1100 1120 Liquid viscosity (p) 1.05E +06 1.23E +06 9.19E +05 1.07E + 06 5.74E +05 1.19E +06 1.04E +06 1.12E +06 6.23E +05 Melting temperature (℃) 1649 1654 1650 1642 1650 1651 1657 1674 1654

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18 19 20 21 22 23 24 25 26 Match composition (mol%) SiO ₂ 69.45 69.33 68.3 70.45 70 70.4 70.1 70 68.3 Al ₂ O ₃ 11 10.55 10.9 9.85 10.35 10.05 10 10.23 10.9 B ₂ O ₃ 9 9.97 10.4 9.55 9.5 9.69 10.15 9.75 10.4 MgO 0.18 1.1 0.8 0.82 0.81 0.8 CaO 10 9.08 9.1 5.75 8.5 7.14 7.11 7 9.1 SrO 0.5 One 2.9 0.85 1.89 1.88 2.22 1.0 BaO As ₂ O ₃ 0.4 0.3 Sb ₂ O ₃ 0.3 0.37 0.3 CeO ₂ 0.2 0.2 0.2 0.2 Y ₂ O ₃ SnO ₂ 0.05 0.02 0.05 0.05 Cl 0.2 0.2 RO / Al ₂ O ₃ 0.91 0.93 0.93 0.99 0.98 0.98 0.98 0.98 0.93 CTE (0-300 ° C, × 10 ^-7 / ° C) 32 31.9 34.8 33.4 32.8 33.5 32.9 33.4 34.5 Density (g / cm ³ ) 2.386 2.383 2.403 2.405 2.378 2.378 2.374 2.391 2.392 Strain point (℃) 681 675 669 670 672 670 664 671 677 Annealing Point (℃) 737 730 725 727 728 727 720 727 732 Softening point (℃) 993 984 978 996 988 989 984 989 979 110 BHF (mg / cm ² ) 0.16 0.3 0.39 0.18 0.17 0.19 0.19 Liquid temperature (℃) 1050 1100 1140 1165 1160 1140 1150 1150 1150 Liquid viscosity (p) 2.90E +05 1.06E +06 2.40E +05 2.88E + 05 2.49E +05 4.29E +05 2.80E +05 3.11E +05 2.14E +05 Melting temperature (℃) 1642 1655 1617 1682 1656 1668 1653 1656 1620

27 28 29 30 31 32 comp. Ex Match composition (mol%) SiO ₂ 68 70 70.4 69.8 71 72 67.6 Al ₂ O ₃ 10.5 10 10.2 10.6 9.9 9.33 11.4 B ₂ O ₃ 11 10 9.1 9 10 10 8.5 MgO 1.3 CaO 10.5 9 5.68 7.14 9.1 8.66 5.2 SrO 4.55 3.42 1.3 BaO 4.3 As ₂ O ₃ 0.4 Sb ₂ O ₃ 0.3 0.3 0.3 0.3 0.3 CeO ₂ Y ₂ O ₃ SnO ₂ Cl RO / Al ₂ O ₃ 1.00 0.90 1.00 1.00 0.92 0.93 1.03 CTE (0-300 ° C, × 10 ^-7 / ° C) 34.9 32.0 34.4 34.4 32.1 31.2 37.8 Density (g / cm ³ ) 2.378 2.355 2.420 2.406 2.353 2.342 2.54 Strain point (℃) 659 673 669 672 669 672 666 Annealing Point (℃) 713 731 727 729 726 730 721 Softening point (℃) 967 999 987 984 998 1012 975 110 BHF (mg / cm ² ) 0.23 0.18 0.2 Liquid temperature (℃) 1120 1130 1130 1135 1120 1125 1050 Liquid viscosity (p) 3.07E + 05 5.99E + 05 5.67E + 05 4.38E + 05 8.46E + 05 8.79E + 05 2.97E + 06 Melting temperature (℃) 1611 1670 1671 1657 1685 1703 1636

Claims (68)

delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete 65 to 75 mole% SiO ₂ , 7 to 13 mole% Al ₂ O ₃ , 5 to 15 mole% B ₂ O ₃ , 0 to 3 mole% MgO, 5 to 15 mole% CaO And a composition containing 0-5 mol% SrO and substantially free of BaO, wherein: (a) the ratio RO / Al ₂ O ₃ is from 0.92 to 0.96, where R represents Mg, Ca, Sr and Ba; And (b) has a linear coefficient of thermal expansion (CTE) of 28 to 33 × 10 ⁻⁷ / ° C. over a temperature range of 0 to 300 ° C., Aluminosilicate glass characterized by a density of less than 2.45 g / cm 3 and a liquid viscosity of greater than 200,000 poise. delete 65 to 75 mole% SiO ₂ , 7 to 13 mole% Al ₂ O ₃ , 5 to 15 mole% B ₂ O ₃ , 0 to 3 mole% MgO, 5 to 15 mole% CaO , 0-5 mol% SrO, and less than 0.1 mol% BaO, and a linear thermal expansion coefficient of 28 × 10 ⁻⁷ / ° C. to 33 × 10 ⁻⁷ / ° C. over a temperature range of 0 ° C. to 300 ° C. Aluminosilicate glass having a density of less than 2.45 g / cm 3 and a liquid viscosity of more than 200,000 poises. 65 to 75 mol% SiO ₂ , 7 to 13 mol% Al ₂ O ₃ , and 5 to 15 mol% B ₂ O ₃ on an oxide basis, wherein: (a) the ratio RO / Al ₂ O ₃ is 0.9 to 1.2, wherein R represents Mg, Ca, Sr and Ba; (b) has a CaO concentration of 5 mol% to 15 mol% on an oxide basis; And (c) a linear thermal expansion coefficient of 28 × 10 ⁻⁷ / ° C. to 33 × 10 ⁻⁷ / ° C. over a temperature range from 0 ° C. to 300 ° C., with a density less than 2.45 g / cm 3, a liquid viscosity greater than 200,000 poises, and It has aluminosilicate glass characterized by the above-mentioned. 34. The glass of claim 30, 32 or 33, wherein the glass is based on an oxide basis of 67 to 73 mole percent SiO ₂ , 8 to 11.5 mole percent Al ₂ O ₃ , 8 to 12 mole percent B ₂ O. ₃ , 0-1 mol% MgO, 5.5-11 mol% CaO, and 0-5 mol% SrO, Comprising: The glass characterized by the above-mentioned. The glass according to claim 30, 32 or 33, wherein the glass contains 0 to 1 mol% MgO when the glass does not contain SrO. 34. The glass according to claim 30 or 32 or 33, wherein the content of alkali metal oxide in the glass is less than 0.1 mol%. 34. The glass of claim 33, wherein the glass contains less than 0.1 mole percent BaO. 33. The glass of claim 32, wherein the ratio RO / Al ₂ O ₃ is from 0.9 to 1.2, wherein R represents Mg, Ca, Sr, and Ba. 34. The glass of claim 32 or 33, wherein the ratio of RO / Al ₂ O ₃ is from 0.92 to 0.96, wherein R represents Mg, Ca, Sr and Ba. 34. The glass of claim 30, 32 or 33, wherein the glass has a strain point of greater than 650 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a strain point of greater than 660 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a melting temperature of less than 1700 ° C. The glass according to claim 30, 32 or 33, wherein the glass is immersed in a solution of 50 parts by weight of 1 part of HF and 10 parts of 40 parts by weight of NH 4 F for 5 minutes at 30 ° C., and then 0.5 mg / cm 2. A glass characterized by exhibiting less than a weight loss. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity in excess of 400,000 poises. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity in excess of 600,000 poises. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity in excess of 800,000 poises. 34. The glass of claim 30, 32 or 33, wherein the glass has a density of less than 2.40 g / cm 3. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 400,000 poise and a density of less than 2.40 g / cm 3. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 600,000 poises and a density of less than 2.40 g / cm 3. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 800,000 poise and a density of less than 2.40 g / cm 3. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity greater than 400,000 poise, a density less than 2.40 g / cm 3, and a strain point greater than 650 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 600,000 poises, a density of less than 2.40 g / cm 3, and a strain point of greater than 650 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity greater than 800,000 poise, a density less than 2.40 g / cm 3 and a strain point greater than 650 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity greater than 400,000 poise, a density less than 2.40 g / cm 3, and a strain point greater than 660 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity greater than 600,000 poise, a density less than 2.40 g / cm 3, and a strain point greater than 660 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity greater than 800,000 poise, a density less than 2.40 g / cm 3, and a strain point greater than 660 ° C. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 400,000 poises and a density of less than 2.40 g / cm 3, and a 50% by weight concentration of HF and a 40% by weight concentration. A glass, characterized in that a weight loss of less than 0.5 mg / ㎠ after immersing for 5 minutes at 30 ℃ in a solution of 10 parts NH4F. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 600,000 poises and a density of less than 2.40 g / cm 3, and a 50% by weight concentration of HF and a 40% by weight concentration. A glass, characterized in that a weight loss of less than 0.5 mg / ㎠ after immersing for 5 minutes at 30 ℃ in a solution of 10 parts NH4F. 34. The glass of claim 30, 32 or 33, wherein the glass has a liquid viscosity of greater than 800,000 poises and a density of less than 2.40 g / cm 3, and a 50% by weight concentration of HF and a 40% by weight concentration. A glass, characterized in that a weight loss of less than 0.5 mg / ㎠ after immersing for 5 minutes at 30 ℃ in a solution of 10 parts NH4F. A flat panel display device comprising a substrate comprising the aluminosilicate glass according to claim 30, 32 or 33. 61. The flat panel display device of claim 60, wherein the substrate has an average surface roughness of less than 0.5 nm. 62. The flat panel display device of claim 61, wherein the substrate has an average surface roughness of less than 0.5 nm without polishing. 61. The flat panel display device of claim 60, wherein the substrate has an average internal stress of less than 150 psi. 61. The flat panel display device of claim 60, wherein the substrate has an average surface roughness of less than 0.5 nm and an average internal stress of less than 150 psi. 65 to 75 mole% SiO ₂ , 7 to 13 mole% Al ₂ O ₃ , 5 to 15 mole% B ₂ O ₃ , 0 to 3 mole% MgO, 5 to 15 mole% CaO And a composition containing 0-5 mol% SrO and substantially free of BaO, wherein the ratio RO / Al ₂ O ₃ is 0.92-0.96, where R is Mg, Ca, Sr and Ba Flat, exhibiting a linear coefficient of thermal expansion (CTE) of 28 to 33 × 10 ⁻⁷ / ° C. over a temperature range of 0 to 300 ° C. and a density of less than 2.40 g / cm 3 and a liquid viscosity exceeding 400,000 poises. A substrate for a flat panel display device comprising transparent glass. 66. The substrate of claim 65, wherein the glass exhibits a strain point greater than 660 ° C. 66. The substrate of claim 65, wherein the substrate has an average surface roughness of less than 0.5 nm. 66. The substrate of claim 65, wherein the substrate has an average internal stress of less than 150 psi.