KR101476076B1 - Alkali-free Glass for Flat Panel Display and Melting Process Thereof - Google Patents

Abstract

The present invention discloses an alkali free aluminoborosilicate glass for a flat panel display and its melting process. Wherein the glass contains 54 to 68% of SiO ₂ , 10.8 to 17.1% of Al ₂ O ₃ , 7.6 to 12.5% of B ₂ O ₃ , 0 to 1.8% of MgO, 4.2 to 15% of CaO, 0.6 to 7.1% SrO, 0.1 to 5% of BaO, 0.2 to 1% of ZnO, 0.01 to 1.54% of ZrO ₂ and 0.1 to 1.3% of SnO ₂ + SnO ₂ . The aluminoborosilicate glass of the present invention does not contain arsenic and antimony which may cause serious pollution to the environment, and the content of gas inclusion in the glass is reduced by a predetermined process to improve glass quality.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an alkali-free glass for a flat panel display,

The present invention belongs to the technical field of glass and relates to an alkali-free glass for a flat panel display and its melting process, and more particularly to an aluminoborosilicate glass for a flat panel display.

A liquid crystal display (LCD) is formed by interposing a liquid crystal between two glass substrates, and applies a voltage to realize a display. The glass substrate has two functions: first, maintaining the liquid crystal at a specified thickness; Secondly, it contains transparent electrodes and switch elements necessary for driving. There is a space between the two glass substrates, which has a strict dimension of 5 to 10 μm.

In response to the development of LCD technology, various glass substrates having different composition and physical properties and prepared by different methods are provided. LCDs have very high requirements for glass substrate properties and LCD flat panels. The requirements for LCD glass substrates are as follows.

First, there is a requirement for precise dimensions: the manufacturing process of high performance displays involves repeated precision photolithography, and the machining accuracy of the outer dimensions of the substrate is required to reach 1/10 mm. Most importantly, the requirements for surface flatness and thickness are very stringent. If accuracy is not guaranteed on the two substrates of the active matrix LCD, the full space (the space between the two substrates) will have a local error, which will have a direct effect on the electric field and the pixels, resulting in uneven grayscale and hue. Substrates with low flatness also cause problems in the photolithography process, for example, light may not be concentrated on the entire surface and defects may occur in the electrical circuit. When using proximity printing, the warped substrate can damage the photomask. The deviation of the flatness of the substrate includes simple warpage, corrugation pattern of the entire substrate, and roughness of the unit of the nanometer.

Second, there is a requirement for thermal resistance: Thermal resistance is mainly related to thermal properties and thermal shrinkage, and there is an internal connection between them. In a process of manufacturing a thin film transistor (TFT), a substrate is subjected to repeated heat treatment. The p-Si TFT type LCD can be heated up to 625 DEG C during preparation, and the substrate is required to maintain rigidity at this temperature without viscous flow. If not, glass is distorted during cooling, resulting in dimensional changes as well as thermal stresses. Glass has this property only below the strain temperature T _st . Therefore, the T _st of such a glass substrate must exceed 625 ° C, and if it is added to 25 ° C, the T _st of such a glass substrate should be at least 650 ° C. It has been found that the substrate still exhibits dimensional changes even under T _{st due to} structural relaxation.

The display repeatedly and rapidly undergoes several times of temperature rise and drop during the manufacturing process, which inevitably leads to structural relaxation and dimensional change of the glass substrate, leading to variations in the electronic circuitry for manufacturing photolithographic flat plates. Therefore, the shrinking dimension of the entire substrate component is required to be a small fraction of the width of the thinnest line in the circuit, i.e., several microns. The amount of shrinkage allowed for displays with dimensions of hundreds of millimeters is only a few millionths of a day. The width of the lines in the circuit is getting thinner for better resolution, but the dimensions of the display are getting bigger and bigger. Automatic compensation techniques can compensate for deviations due to thermal shrinkage during the photolithography process, but a low heat shrinkage is still required.

Third, there is a requirement for chemical stability: the substrate glass must be able to withstand various chemical treatments within the display manufacturing process. For example, an a-Si active matrix LCD has seven or more layers of thin film circuitry, thus requiring a number of corrosion steps corresponding to the number of layers. Caustic and cleaning agents, there are there things from the strong acid in the strong alkali, for example, such as 10% excess of NaOH, a 10% excess of H ₂ SO _4, and concentrated HNO _3, 10% of HF-HNO _3, and concentrated H ₃ PO _4. The chemical stability requirements for substrates are one of the most stringent requirements for all types of glassware.

Fourth, there are requirements for surface defects and internal defects: substrates must have high surface quality and internal quality, and the edges and surfaces of the manufactured circuit should be free of scratches or stains. The defects will have to be less than a few microns to prevent circuit damage. The internal bubbles and inclusions are permitted for small portions of the pixel size, for example, a display with a 100 micron pixel dimension may contain inclusions of 50 micron dimensions, and the maximum allowable limit of the defective area is 25 % to be.

Fifth, there is a requirement for alkali limitation: the temperature of the heat treatment in the manufacturing process of the intrinsic matrix LCD is less than 350 ° C, and a soda lime glass substrate can be used. A method of plating a strike layer of SiO _{2 on} the surface to prevent Na ⁺ from moving into the circuit is widely used. However, when the temperature of the heat treatment approaches T _st , the stratum layer hardly prevents Na ⁺ migration. In a non-intrinsic matrix LCD (active matrix LCD), the heat treatment temperature is very high due to the production of? -Si or p-Si devices on the substrate. Especially in p-Si devices having a higher heat treatment temperature than? Do. The heat treatment temperature mainly depends on the process of manufacturing the TFT device. Since plating of the gate dielectric material SiNx requires a high temperature above 600 ° C and Na ⁺ from the substrate can then pass through the smoothening layer, the LCD substrate in this manner is as low as possible, It should have the content.

U.S. Patent Nos. 5811361, 5851939, 6329310, etc. mention that the substrate glass for TFT-LCD should have the following basic physical properties:

1. In order to reduce the damage caused by the expansion and contraction due to cooling by the heat depending on the production temperature of the substrate in the glass substrate for TFT-LCD, and the thermal expansion coefficient of the glass be sufficiently low, in general, 40 × 10 ^-7 / Lt; / RTI >

2. In a glass substrate for a TFT-LCD, the strain point of the glass must exceed at least 650 DEG C in order to reduce the volume shrinkage and dimensional instability which are caused by repetitive heating depending on the production temperature of the substrate.

3. In order to meet the growing demand for lighter weight of large flat panel displays, the density of the glass should be less than 2.6 g / cm ³ , and the lighter the better.

In addition, TFT-LCD liquid crystal glass substrates need to have better performance as LCDs develop toward large-sized LCDs, high image quality, and high brightness in order to meet market demand.

The LCD provides a display using a "back transparent" illumination mode. Since the utilization rate of light of the backlight is not high, the luminous intensity is inferior to that of CRT, PDP and OLED. Increasing brightness has always been the direction of LCD development. Therefore, an increase in the light transmittance of the glass substrate can lead to a better function. At present, the light transmittance of major glass substrates reaches 90%.

As the dimension of the LCD increases, the area of the glass substrate is also increased in order to reduce the production cost. Substrates having a thickness of less than 1 mm and an area of more than 1 m ² can be easily implemented, and some manufacturers even implement substrates larger than 6 m ² . Such a thin glass substrate is easily broken during use and transportation, and gravity causes sagging on the glass. The problem of deflection of a thin and wide substrate results in difficulty in manufacturing the substrate. Therefore, in order to prevent little or no distortion of the glass substrate due to external forces or self-gravity, it is desirable to increase the bending strength of the glass substrate in order to reduce damage to the glass substrate, It is advantageous.

Currently, overflow molding methods are among the most widely used mature methods for producing LCD glass substrates. This is because the glass substrate produced by this method does not require surface polishing in the post-treatment. However, this method requires a high level of control of the production process. The flow rate, temperature, and tension of the stretching machine must be precisely controlled at the same time, and even slight changes can cause excessive tension on the stretching machine, resulting in breakage of the glass substrate. When the glass substrate is broken, it takes a long time to carry out the work such as re-transfer of the substrate, which reduces the production efficiency and yield of good products. Therefore, a high flexural strength is also required for the LCD glass substrate to prevent breakage of the substrate during the overflow molding process.

In recent years, the TFT type of the active matrix LCD is required to be lightweight and the substrate tends to be thin, depending on the tendency of the LCD to become larger and larger, and it is required to increase the strength of the substrate and reduce its own weight in order to achieve lighter weight.

In general, 40 × 10 ^-7 / ℃ transformation point of the thermal expansion coefficient of less than, greater than 650 ℃, and an alkali-free glass is to achieve the physical properties required in the LCD glass substrate, a selection, such as density of less than 2.6g / cm ³ typically _{RO-Al 2 O 3 -B 2} O 3 -SiO ₂ glass belongs to the series.

As requirements for environmental protection become increasingly stringent, the use of refining agents such as As ₂ O ₃ , Sb ₂ O ₃ and the like is progressively limited. Currently, EU countries prohibit products containing arsenic from entering the European Union market. The present invention therefore focuses on the realization of products that do not contain As and Sb.

According to Stokes' law, the velocity of the bubbles rising from the molten glass to the surface is inversely proportional to the viscosity of the molten glass. That ^{is, V = 2r 2 g (ρ} -ρ ') as / 9η, V denotes a rising rate of air bubbles, r denotes the radius of the bubble, g denotes the acceleration of gravity, ρ denotes the density of the glass, ρ 'Represents the density of gas in the bubbles, and η represents the viscosity of the molten glass. In order to ensure smooth release of the bubble inclusions, it is desirable that the viscosity of the molten glass is as low as possible, especially at high temperatures.

The inclusion of gas (bubbles) is a major defect in glass, which comes from a fairly complex source, some of which are air in space during batch melting, some of which are gases produced by the decomposition of various compounds, Is a gas released from a material (e.g., refractory material). Conventionally, these gas inclusions are removed by using arsenic or antimony as a refining agent, but they are harmful to the environment and human body. Therefore, the present invention focuses on the production of glass having a very low content of arsenic and antimony, preferably glass containing no arsenic and antimony. The following quantitative indicators of the effect of gas inclusions on the quality of the product: The content of gas inclusions in commercially produced glass (glass substrates) should be less than or equal to one gas inclusion per kilogram of glass Excess gas inclusions are considered defects). For glass weighing greater than 1 kg, the indicator is preferably 0.5 gaseous inclusions per kilogram of glass. With respect to glass having a weight of 2 kg or more, it is needless to say that the index is preferably 0.3 gaseous inclusions per kilogram of glass, but less.

It is an object of the present invention to provide an alkali-free (Al ₂ O ₃ ) free glass having a low density, a low thermal expansion coefficient, a high strain point, a high chemical stability, a high bending strength and a high light transmittance without containing harmful substances As ₂ O ₃ and Sb ₂ O ₃ ) Glass.

In order to achieve the above object, the present invention provides an alkali-free glass for a flat panel display which comprises 54 to 68% SiO ₂ , 10.8 to 17.1% Al ₂ O ₃ , 7.6 to 12.5% B ₂ O ₃ , 0.2 to 1.8% of MgO, 4.2 - 8% of CaO, 0.6 ~ 7.1% of SrO, 0.1 ~ 5% of BaO, 0.2 ~ 1% of ZnO, 0.01 ~ 1.54% of ZrO ₂ and 0.1 ~ 1.3% of SnO + SnO _{2. &} Lt; / RTI > The alkali-free glass according to the present invention overcomes the defects according to the above-mentioned prior art.

The weight ratio of MgO + SrO + BaO in the glass is 0.7 to 12%.

The light transmittance of the glass is 93 to 97%.

The strain point of the glass is 650 ~ 685 ℃.

The coefficient of thermal expansion of the glass is 30 × 10 ^-7 / ° C. to 40 × 10 ^-7 / ° C. in the range of 0 to 300 ° C.

The liquid temperature of the glass is 1110 ~ 1210 ℃.

The density of the glass is 2.300 to 2.550 g / cm < ^{3 &} gt ;.

The process for preparing the alkali-free aluminoborosilicate glass is as follows:

(1) A glass composition comprising 54 to 67% SiO ₂ , 13 to 18% Al ₂ O ₃ , 7 to 12% B ₂ O ₃ , 0 to 1.8% MgO, 3 to 10% CaO , 0.2 to 8% of SrO, 0.1 to 7% of BaO, 0.001 to 1.5% of ZnO, 0.001 to 1.0% of ZrO ₂ and 0.01 to 1.0% of a refining agent are prepared;

(2) reacting the raw material according to the step (1) in a temperature range of 1500 to 1620 캜 for 4 hours to obtain a glass solution in the first vessel of the non-metallic refractory material and introducing the glass solution into the second vessel;

(3) keeping the glass solution in the second vessel at 1640 占 폚 for 40 to 75 minutes and at 1600 占 폚 for 40 to 120 minutes;

(4) The solution obtained in the above step (3) is introduced into a metal mold, cooled to form a flat plate, and then annealed to have a thermal expansion coefficient of 28 to 39 × 10 ^-7 / , An alkali free glass having a density of 2.5 g / cm ³ or less and an elastic modulus of 70 GPa or more is obtained.

The alkali-free glass according to the present invention has a light transmittance of more than 93% in a wavelength range of 500 to 650 nm, a flexural strength of more than 110 MPa, a strain point of more than 650 캜, a thermal expansion coefficient of 28 to 39 × 10 ^-7 / ° C., the liquidus temperature is less than 1250 ° C., the density is from 2.35 to 2.55 g / cm ³ , the modulus of elasticity is greater than 70 GPa, and the viscosity exceeds 15000 poise at the liquidus temperature.

In the present invention, by controlling the content of SrO + BaO + MgO and the ratio of CaO / (SrO + BaO + MgO), the glass has a flexural strength of more than 110 MPa, preferably more than 118 MPa, more preferably more than 130 MPa So that the effect of reducing the distortion in the manufacturing process of the large glass substrate is provided.

The alkali-free glass according to the present invention has a network structure formed of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ , SiO ₂ + Al ₂ O ₃ + B ₂ O ₃ ≥80 wt%, ΣRO , Ca, Sr, Ba and Zn) / Al ₂ O ₃ is 0.9 to 1.2 (weight ratio). Here, Si is the main component of the glass network, Al ³⁺ may be introduced into the glass network in the form of a tetrahedron [AlO _4] in the presence of free oxygen supplied by the RO. Since Si ⁴⁺ is tetravalent and Al ³⁺ is trivalent, if the Si ⁴⁺ is substituted with Al ³⁺ , the electrons are imbalanced and thus the metal ions are attracted to the glass network, Which increases both the viscosity and the softening point of the glass.

When free oxygen is lacking, intermediate ions are generally introduced into the network in the following order: [BeO ₄ ] → [AlO ₄ ] → [GaO ₄ ] → [BO ₄ ] → [TiO ₄ ] → [ZnO ₄ ]. Therefore, ΣRO (R is Mg, Ca, Sr, Ba, Be, and Zn) / Al ₂ O ₃ when the 0.9 to 1.2 (weight ratio), and the condition that the Al ³⁺ tetrahedron meets First, B is [BO3 ] Triangles are formed to perform regulatory actions and prevent excessively high melting temperatures. In a preferred case, ΣRO / Al ₂ O ₃ is 0.9 to 1 (weight ratio), and more preferably 0.96 to 1 (weight ratio).

In the present invention, the SiO ₂ content is 54-67 wt%. The increase in the SiO ₂ content will be advantageous for light weight glass, low thermal expansion coefficient and chemical resistance improvement, but will increase the high temperature viscosity, which is disadvantageous in terms of production. Therefore, the SiO ₂ content is determined to be 54 to 68 wt%.

The Al ₂ O ₃ content is 13 to 18 wt%, preferably 15 to 18 wt%. The high Al ₂ O ₃ content is advantageous for improving the strain point and the bending strength of the glass, but the excessive Al ₂ O ₃ content will easily cause crystallization of the glass.

B ₂ O ₃ plays a special role, allowing the individual formation of glass. Under the conditions of high temperature melting, B ₂ O ₃ is difficult to form [BO ₄ ], and consequently the high temperature viscosity is reduced. At low temperatures, B tends to trap free oxygen to form [BO ₄ ] and prevent crystallization. Excess B ₂ O _3, however, reduces the strain point of the glass. Therefore, the B ₂ O ₃ content is preferably in the range of 7 to 12 wt%, and more preferably in the range of 8 to 12 wt%.

MgO forms the outside of the network, and Mg is introduced into the network only in the form of [MgO ₄ ] only when oxides such as Al ₂ O ₃ and B ₂ O ₃ do not exist. Excess MgO can result in coarse structure and reduced density and hardness. MgO can also reduce the crystallization tendency and crystallization rate and increase the chemical stability and mechanical strength of the glass. However, the excessive content should not be included, in which case the glass tends to crystallize and the thermal expansion coefficient becomes excessively high. Another important role of the introduction of MgO is to compensate for changes in material properties (viscosity-temperature characteristics) due to an increase in the CaO content in the examples of the present invention. The MgO content is 0 to 1.8 wt%, preferably 0 to 1 wt%.

CaO plays a role similar to MgO, and Ca has the effect of forming a denser glass structure. CaO can control and reduce the high temperature viscosity and can significantly improve the melt property without reducing the strain point of the glass. Excessive CaO can reduce the chemical resistance of glass. Here, the content of CaO is selected in the range of 3 to 10 wt%, preferably 4 to 9 wt%.

In the RO-SiO ₂ -B ₂ O ₃ -Al ₂ O ₃ series glasses, the additional effect of CaO is reflected in the effect of the change in CaO / (SrO + BaO + MgO) ratio on the glass bending strength. Ca, Mg, Sr and Ba jointly become a component of the glass as the oxidizing agent RO, and ΣRO / Al ₂ O ₃ is determined within a predetermined range. As the CaO content decreases, SrO and BaO should be added to the glass to compensate for the reduced CaO. As the ratio of CaO / (SrO + BaO + MgO) changes, an extreme value of the glass bending strength appears. According to the experiment, the weight ratio of CaO / (SrO + BaO + MgO) is preferably in the range of 0.3 to 6, more preferably in the range of 0.3 to 2, and most preferably in the range of 0.3 to 0.8. As a result, the bending strength of the glass can be increased to more than 110 MPa, more preferably more than 118 MPa, and most preferably more than 130 MPa.

Both SrO and BaO have the effect of improving chemical stability and resistance to crystallization, but excessive SrO and BaO can cause an increase in glass density and thermal expansion coefficient. Both SrO and BaO are components with physical properties that enhance chemical resistance in particular, and the total content of both components should exceed 0.2%. With respect to the improvement of the chemical resistance, it is preferable that the content of SrO and BaO is as high as possible, but it is preferable that the content of SrO and BaO is as low as possible with respect to the density and the thermal expansion coefficient of the glass. Therefore, the content of SrO and BaO should be controlled to fall within a predetermined range. More specifically, the SrO content is set to 0.2 to 8 wt%, the BaO content is set to 0.1 to 7 wt%, the content of SrO + BaO is set to a range of 1 to 10 wt%, preferably 2 to 9 wt% And more preferably 2 to 6 wt%.

ZnO can reduce the high temperature viscosity of glass, improve chemical resistance, and reduce the thermal expansion coefficient. Excess ZnO content, however, may reduce the strain point of the glass.

ZrO ₂ can effectively improve the chemical stability of the glass, decrease the coefficient of thermal expansion, and significantly improve the modulus of elasticity. However, ZrO ₂ has a low solubility in the glass, which can increase the high temperature viscosity and liquid temperature of the glass and increase the crystallization tendency of the glass. ZrO ₂ is also advantageous in improving the properties of glass such as acid resistance, elasticity, flexural strength and thermal expansion.

The content of Fe ³⁺ , Cl ^- and S ^2- in the composition of the glass substrate for the LCD should be as low as possible. In the present ^{invention, Fe 3+ <0.3wt%, Cl} - <10ppm, S 2- <0.3wt% , preferably from ^{Fe 3+ <0.1wt%, Cl -} <10ppm, S 2- <0.1wt% , and , More preferably Fe < ^{3 +} < 0.05 wt%, Cl ^- < 10 ppm, and S ^2- &lt; 0.05 wt%.

Hereinafter, the present invention will be further described with reference to examples. It is to be understood that the embodiments are used by way of illustration and description of the invention only, and are not intended to limit the invention in any way.

Embodiments of the present invention are shown in Tables 1-3. The amount of each material is as listed in the table, and the total amount of material in each example is about 300 kg. The materials are uniformly mixed and introduced into vessel 1 of refractory material. The temperature of the vessel 1 is heated to 1,500 to 1,600 ° C by the Joule heat, but not to exceed 1620 ° C. After a reaction time of 4 hours, the materials are introduced into the container 2 heated to 1640 占 폚 by the electrode, kept warm for about 60 minutes, but not more than 75 minutes. Subsequently, the temperature of the vessel 2 is reduced to 1600 캜 and maintained for 60 minutes, but not exceeding 120 minutes. After keeping warm, the molten glass is rapidly poured into a metal mold and cooled to form a substrate (100 mm * 200 mm * 10 mm) and annealed. The bubble content of the glass sample is examined to obtain physical properties such as elastic modulus, weight loss, flexural strength, strain point temperature, liquid temperature, hardness and thermal expansion coefficient of each glass sample.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 SiO ₂ (wt%) 54.50 54.50 60.50 61.00 56.20 67.3 58.00 Al ₂ O ₃ (wt%) 17.10 17.00 12.10 11.90 16.00 10.9 14.00 B ₂ O ₃ (wt%) 11.00 11.10 10.00 9.58 11.80 8.5 12.50 MgO (wt%) 1.80 1.70 0.56 0.70 1.20 0.40 1.02 CaO (wt%) 7.90 7.40 6.70 6.50 6.80 4.6 5.20 SrO (wt%) 7.10 6.60 4.60 4.20 5.00 2.7 5.20 BaO (wt%) 0.10 1.30 4.00 4.40 2.09 2.8 2.98 ZnO (wt%) 0.20 0.00 0.40 0.45 0.32 0.60 0.36 ZrO ₂ (wt%) 0.10 0.15 0.54 0.62 0.24 1.30 0.30 SnO ₂ + SnO ₂ (wt%) 0.20 0.25 0.60 0.65 0.35 0.90 0.44 MgO + SrO + BaO (wt%) 9.20 9.60 9.16 9.30 8.30 5.90 9.22 CaO / (MgO + SrO + Ba) (weight ratio) 0.88 0.77 0.73 0.70 0.82 0.78 0.57 Light transmittance (%) (T550) 92 95 93 90 93 93 96 Deformation point (캜) 638 640 654 656 650 665 652 Thermal expansion coefficient (占 10 ^-7 / 占 폚) 39.10 39.15 36.21 36.32 38.80 37.60 38.70 Flexural strength (MPa) 116 117 120 119 116 116 123 Liquid temperature (℃) 1120 1125 1125 1128 1158 1152 1165 Density (g / cm ³⁾ 2.6450 2.6370 2.5520 2.5310 2.5970 2.3620 2.5740 Elastic modulus (GPa) 72 72 73 76 70 75 74 Bubbles per kg glass 0.20 0.50 0.30 0.70 0.20 0.80 0.20

Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 SiO ₂ (wt%) 58.30 67.5 67.8 55.00 55.60 61.60 61.00 Al ₂ O ₃ (wt%) 12.80 12.5 13.2 17.00 16.80 11.50 12.00 B ₂ O ₃ (wt%) 10.20 8.45 7.6 11.20 11.30 9.40 8.00 MgO (wt%) 0.46 0.88 0.20 1.40 1.30 0.76 0.80 CaO (wt%) 8.00 4.9 4.7 7.30 7.00 6.00 15.0 SrO (wt%) 6.00 1.6 0.6 5.70 5.30 4.10 2.65 BaO (wt%) 3.00 1.8 2.3 1.60 1.80 4.75 0.10 ZnO (wt%) 0.39 0.80 0.90 0.30 0.35 0.50 0.30 ZrO ₂ (wt%) 0.40 1.42 1.50 0.20 0.22 0.69 0.0 SnO ₂ + SnO ₂ (wt%) 0.45 0.15 1.20 0.30 0.33 0.70 0.15 MgO + SrO + BaO (wt%) 9.46 4.28 3.10 8.70 8.40 9.61 3.55 CaO / (MgO + SrO + Ba) (weight ratio) 0.85 1.14 1.52 0.84 0.83 0.62 4.2 Light transmittance (%) (T550) 91 93 93 92.5 93 94 93 Deformation point (캜) 648 667 667 645 649 657 646 Thermal expansion coefficient (占 10 ^-7 / 占 폚) 36.41 36.54 36.51 38.80 38.82 36.25 42.80 Flexural strength (MPa) 120 109 105 118 118 124 101 Liquid temperature (℃) 1140 1205 1170 1136 1160 1176 1179 Density (g / cm ³⁾ 2.5700 2.3830 2.3820 2.6140 2.6120 2.5200 2.4900 Elastic modulus (GPa) 76 73 75 75 76 77 76 Bubbles per kg glass 0.20 0.90 1.10 0.30 0.30 0.40 0.20

Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 Example 21 SiO ₂ (wt%) 67.0 58.50 67.2 67.4 57.40 59.20 68.0 Al ₂ O ₃ (wt%) 11.0 12.30 11.5 10.8 14.70 12.50 8.1 B ₂ O ₃ (wt%) 8.6 10.40 8.9 9.0 12.20 10.00 12.0 MgO (wt%) 0.45 0.48 0.34 0.35 1.09 0.52 0.16 CaO (wt%) 4.8 7.80 4.2 5.0 5.60 7.40 4.9 SrO (wt%) 3.0 5.60 2.6 1.9 5.40 5.20 2.9 BaO (wt%) 3.0 3.64 2.5 2.6 2.61 3.78 0.1 ZnO (wt%) 0.55 0.36 0.64 0.70 0.34 0.40 1.00 ZrO ₂ (wt%) 0.82 0.42 1.20 1.30 0.26 0.47 1.54 SnO ₂ + SnO ₂ (wt%) 0.78 0.50 0.92 0.95 0.40 0.53 1.30 MgO + SrO + BaO (wt%) 6.45 9.68 5.45 4.85 9.09 9.52 3.15 CaO / (MgO + SrO + Ba) (weight ratio) 0.74 0.81 0.77 1.04 0.62 0.77 1.56 Light transmittance (%) (T550) 95 95 92 93 93 94 93 Deformation point (캜) 665 649 666 665 650 652 668 Thermal expansion coefficient (占 10 ^-7 / 占 폚) 37.80 36.38 36.50 36.52 38.74 36.24 36.53 Flexural strength (MPa) 115 114 113 109 118 117 107 Liquid temperature (℃) 1210 1100 1185 1191 1162 1120 1200 Density (g / cm ³⁾ 2.4900 2.5690 2.3850 2.3830 2.5860 2.5620 2.3810 Elastic modulus (GPa) 75 78 76 78 71 75 74 Bubbles per kg glass 0.70 0.30 0.70 0.70 0.20 0.40 0.80

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood by those skilled in the art that various changes or modifications may be made without departing from the technical scope of the present invention and that such modifications or alterations are within the scope of the invention as defined by the appended claims.

Claims (8)

As an alkali-free glass for flat panel displays,
Wherein the glass contains 54 to 68% of SiO ₂ , 10.8 to 17.1% of Al ₂ O ₃ , 7.6 to 12.5% of B ₂ O ₃ , 0.2 to 1.8% of MgO, 4.2 to 8% of CaO, % Of SrO, 0.1 to 5% of BaO, 0.2 to 1% of ZnO, 0.01 to 1.54% of ZrO ₂ and 0.2 to 1.3% of SnO ₂ + SnO ₂ ,
Wherein the glass has a weight ratio of MgO + SrO + BaO of 0.9 to 12%.
The method according to claim 1,
Wherein the glass has a light transmittance of 93 to 97% in a light wavelength range of 500 to 650 nm.
The method according to claim 1,
Wherein the glass has a strain point of 650 to 685 占 폚.
The method according to claim 1,
Thermal expansion coefficient of the glass is alkali-free glass, characterized in that in the range of ^{0 ~ 300 ℃ 30 × 10 -7} / ℃ to 40 × 10 ^-7 / ℃.
3. The method of claim 2,
Wherein the glass has a liquidus temperature of 1110 to 1210 占 폚.
The method according to claim 1,
Wherein the density of the glass is 2.300 to 2.550 g / cm &lt; ³ &gt;.
A method for producing the alkali-free glass of claim 1,
(1) The raw material of the glass is composed of 54 to 67% of SiO ₂ , 13 to 18% of Al ₂ O ₃ , 7 to 12% of B ₂ O ₃ , 0 to 1.8% of MgO, % Of CaO, 0.2 to 8% of SrO, 0.1 to 7% of BaO, 0.001 to 1.5% of ZnO, 0.001 to 1.0% of ZrO ₂ and 0.01 to 1.0% of a refining agent, and the refining agent is SnO ₂ + SnO ₂ ;
(2) The raw material according to the above step (1) is fully reacted for 4 hours at a temperature range of 1500 to 1620 ° C to obtain a glass solution in the first vessel of the non-metallic refractory material, ;
(3) the glass solution in the second vessel is kept at 1640 占 폚 for 40 to 75 minutes, and at 1600 占 폚 for 40 to 120 minutes;
(4) The solution obtained in the step (3) is introduced into a metal mold, cooled, formed into a flat plate, and then annealed to obtain the alkali free glass. Way.
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