TW200927686A - Method for production of non-alkali glass - Google Patents

Abstract

Disclosed is a method for producing a highly uniform and highly flat non-alkali glass which has few bubbles formed therein. Specifically disclosed is a method for producing a non-alkali glass, which comprises melting a glass raw material comprising a glass base composition raw material containing a silica sand and a boron source and also comprising a clarifying agent and molding the molten material, wherein particles of the silica sand having a D50 value of 15 to 60 [mu]m and a particle diameter of 100 [mu]m or more make up 2.5 vol% or less of the total volume of the particles of the silica sand, the boron source contains anhydrous boric acid in an amount of 10 to 100 mass% relative to 100 mass% of the total amount of the boron source, SnO2 is used as the clarifying agent, and the melting of the glass raw material is carried out by the following steps (a) and (b): (a) heating the glass raw material at a temperature at which the viscosity of the molten glass becomes more than 102.4 dPas, thereby producing a molten glass; and (b) heating the molten glass at a temperature at which the viscosity of the molten glass becomes 102.4 dPas or less and which is higher by 30 DEG C or more than the temperature employed in the step (a), thereby removing air bubbles from the molten glass.

Description

200927686 IX. Description of the Invention Technical Field of the Invention The present invention relates to a method for producing an alkali-free glass. [Prior Art] In the glass for a liquid crystal display substrate, since it is required to substantially contain no alkali metal, an alkali-free glass is used as the glass. Further, the alkali-free glass for a liquid crystal display substrate is required to have high chemical resistance, high durability, low foam in the glass, high homogeneity, and high flatness. Therefore, in order to impart chemical resistance and durability to the alkali-free glass, the glass raw material contains a boron source, and in order to reduce bubbles in the alkali-free glass, the bubbles contained in the molten glass are defoamed in the production of the alkali-free glass (hereinafter, , remember as clarification). Helium, as a source of boron, uses ortho-boric acid which is inexpensive and easily available. As a clarification method, a method of using a Sn02 as a clarifying agent to change a valence of Sn due to a temperature rise of molten glass to produce a clarified Q gas is known (Patent Document 1). However, the alkali-free glass for a liquid crystal display substrate has a melting temperature higher than 100 ° C or higher than that of an alkali glass containing a glass for a plasma display substrate, a glass for construction, or an automobile glass, and is a glass which is hard to melt. Therefore, when the glass raw material is melted at a high temperature, Sn 2 is consumed, and when a clear gas is generated due to the temperature rise of the molten glass, there is no problem that a sufficient amount of SnO remains. As an effective clarification method using Sn02, it is known that after the glass raw material is melted at a high temperature, the Sn02 is kept at a low temperature, and thereafter, the temperature is raised to a temperature higher than the melting temperature, and the clarified gas is made. Method of production (Patent Document 2). In the case of this method, although effective clarification can be expected, the steps are complicated, and since the energy loss is large, it is difficult to stably produce an alkali-free glass which is less foamed at a low cost. On the other hand, if it is intended to melt the glass raw material at a low temperature, the cerium sand which is a main component of the glass raw material is not easily melted, and there is a disadvantage that unmelted cerium oxide is generated in the molten glass, and a homogeneous glass may not be obtained. 0 In addition, in order to make the cerium sand easy to melt and use a shale with a small particle size, the cerium is likely to aggregate. If the sand is aggregated, the homogeneity and flatness of the alkali-free glass will decrease. [Patent Document 1] Japanese Laid-Open Patent Publication No. 2004-075498 (Patent Document 2) International Publication No. 2007/018910 (Draft of the Invention) [Problems to be Solved by the Invention] Q The present invention provides a bubble which can be obtained in a glass. And a method for producing an alkali-free glass having high homogeneity and flatness. [Means for Solving the Problem] The method for producing an alkali-free glass according to the present invention is an alkali-free glass obtained by melting a glass raw material to which a clarifying agent is added to a raw material of a glass base material containing cerium and a boron source. In the production method, the ratio of the particles having a median diameter of 15 to 60 μm and a particle diameter of ΙΟΟμηη or more is 2.5% by volume or less, and the boron source is used as the boron source with respect to 1% by mass of 200927686. In the boron source of B2〇3, the boronic acid anhydride (in terms of B2〇3) containing 10 to 100% by mass is used as the clarifying agent, and at least the following steps are used to melt the glass raw material using at least Sn02': (a) heating the glass raw material at a temperature at which the viscosity of the molten glass exceeds 1 〇 24 dPa · s to form a molten glass; (b) after the above step (a), the molten glass is used to make the molten glass The viscosity is a temperature of 10 Pa 2 4 dPa · s and is heated at a temperature higher than 30 ° C higher than the temperature 0 in the above step (a) to defoam the bubbles in the molten glass. In the method for producing an alkali-free glass of the present invention, it is preferred that the glass base material composition is a hydroxide containing aluminum or an alkaline earth metal. In the method for producing an alkali-free glass according to the present invention, the raw material of the glass base material is prepared into an alkali-free glass of the glass base material composition (1), as indicated by the mass percentage based on the oxide, with respect to the glass mother. It is preferable to add tin to the material composition material in an amount of 0.01 to 2% by mass in terms of Sn02. 〇 Si〇2: 50 to 66% by mass, Al2〇3: 10.5 to 22% by mass, B2〇3: 5 to 12 by mass. /. MgO: 0 to 8 mass%, CaO: 0 to 14.5 mass%, SrO: 〇~24 mass%, BaO: 0 to 13.5 mass%, 1^§0 + €&0 + 81*0 + BaO : 9~29·5 mass% · . · (1). In the method for producing an alkali-free glass of the present invention, a sulphate of 3% by mass or less in terms of C1 and a sulphate of 3% by mass or less in terms of S03 are added to the raw material of the glass base material. The total amount of one or more selected from the group consisting of fluorides of 3% by mass or less in terms of f is preferably ~1 to 5% by mass, and is preferably a glass raw material. 200927686 In the method for producing an alkali-free glass according to the present invention, glass frit 15 composed of nitrate and alkali-free glass in an amount of 0.01 to 10% by mass in terms of N〇3 is further added to the raw material of the glass base material. It is preferably 300% by mass as a glass raw material. [Effects of the Invention] According to the method for producing an alkali-free glass of the present invention, an alkali-free glass having a small amount of zero bubbles in the glass and having high homogeneity and flatness can be obtained. [Embodiment] [Best Mode for Carrying Out the Invention] <Production Method of Alkali-Free Glass> The production of an alkali-free glass is a glass in which a clarifying agent is added to a raw material of a glass base material containing a cerium and a boron source. The raw material is melted and molded. The alkali-free glass is produced, for example, by the procedure of the following procedure. 0 ( i ) A sand source and a boron source, or a hydroxide of an alkaline earth metal oxide (MgO, CaO, SrO, BaO) and/or an aluminum or alkaline earth metal according to the need to make the target alkali-free glass The glass base material composition ratio is mixed and prepared into a glass base material constituent raw material, and a clarifying agent or the like is added to the glass base material constituent raw material to form a glass raw material. (Π) The glass raw material and the glass flakes as needed are continuously introduced into the melting kiln from the glass raw material inlet of the melting kiln to be melted to form a molten glass. (iii) The molten glass is subjected to a molding step of a glass ribbon of a predetermined thickness by a known molding method such as a float method. (iv) A step of obtaining a plate-shaped alkali-free glass by slowly cooling the formed glass ribbon and cutting it into a specified size. The present invention is characterized in that the ratio of the particles having a median diameter of 15 to 60 μm and the particle diameter of ΙΟΟμηη or more is 2.5% by volume or less, and the boron source is used as the boron source in an amount of 1% by mass. In the case of the boronic anhydride of 10 to 1% by mass (calculated as Β203), φ is used as the clarifying agent, and at least Sn02 is used, and the above step (ii) is divided into at least the following two steps. (a) The step of heating the glass raw material at a temperature at which the viscosity of the molten glass is more than 102 4 dPa · s to form molten glass. (b) after the step (a), the molten glass is heated at a temperature at which the viscosity of the molten glass becomes l〇24 dPa·s or less and is higher than the temperature in the step (a) by 30 ° C or higher. a step of defoaming the bubbles in the molten glass. ❿ Step (i): (矽砂) The diameter of the sand, that is, the particle size distribution of the powder, the volume of the particles larger than a certain particle size is the particle diameter of 50% of the volume of the whole powder (below, It is referred to as D5〇), preferably 15 to 60 μm, preferably 20 to 50 μm, and 20 to 40 μm is preferably 20 to 30 μm. The D5Q of the enamel sand is preferably less than 30 μm, and further preferably 27 μm or less. By setting the D5Q of the strontium sand to 15 μm or more, the aggregation of the strontium sand can be suppressed, and the -9-200927686 which is less, and has no homogeneity and high flatness can be obtained. By setting the 矽 5 〇 to 60 μm or less, the cerium can be easily melted uniformly, and the alkali-free glass having a high degree of uniformity and flatness can be easily melted. The ratio of the particles having a particle diameter of 1 〇〇Μ·ηι or more in the particle size distribution of the chopped sand is 2.5 vol% or less, and more preferably 0 vol%. When the ratio of the particles having a particle diameter of 1 μm or more is 2.5% by volume or less, the cerium can be easily and uniformly melted by 0, and the alkali-free glass crucible having a low degree of homogeneity and flatness can be obtained. The particle size distribution of the sand can be determined by laser diffraction and scattering. (Boron source) Examples of the boron compound as a boron source include orthoboric acid (Η3Β〇3), metaboric acid (ηβο2), tetraboric acid (η2β4ο7), and boric anhydride (β203). In the production of a normal alkali-free glass, n-boric acid is used from the viewpoint of being inexpensive and easy to obtain. However, when a glass material containing orthoboric acid is used, the following problems may occur. (1) In the presence of orthoboric acid, the eucalyptus sand having a small particle size is easily aggregated, and the amount of the glass raw material to be supplied to the melting kiln is likely to become unstable. Therefore, the temperature of the molten glass in the melting kiln becomes unstable. In addition, the cycle and residence time of the molten glass becomes unstable. As a result, the melting of the glass raw material is uneven, and the composition of the molten glass becomes uneven. (2) When the glass raw material is an alkaline earth metal compound, ～-10-200927686 The orthoboric acid melted in the glass raw material input port of the dissolution kiln aggregates with the alkaline earth metal compound, and aggregates are likely to occur. Since the orthoboric acid and the alkaline earth metal compound are also components which promote the melting of the cerium, when the aggregate is generated, the melting of the glass raw material in the melting kiln becomes uneven, and the composition of the molten glass also changes. Not uniform. When the problem of (n or (2) occurs, the homogeneity of the molten glass is deteriorated, and the homogeneity and flatness of the formed alkali-free glass are lowered. Further, 0 is unstable due to the cycle and residence time, and the bubble is unstable. Before the clarifying agent is removed from the molten glass in the melting kiln, a part of the molten glass flows out of the melting kiln. Moreover, since the melting of the glass raw material is uneven, the effect of the clarifying agent is relatively low relative to the slower molten cerium sand. Insufficient, the bubble cannot be sufficiently removed from the molten glass. Regarding the problem of (1), the inventors have found that the aggregation of the sand is caused by the moisture contained in the glass raw material, and then, to suppress the sand As long as the water contained in the glass raw material is reduced, that is, the amount of ortho-boric acid containing a large amount of water molecules in the hazelnut is reduced, and the amount of boric anhydride is increased, and the problem of (2) is The inventors have found that one water molecule is lost in orthoboric acid after the glass raw material input port is heated, and it becomes metaboric acid. The metaboric acid which is liquefied at 150 ° C or higher is aggregated with the alkaline earth metal compound. The aggregation of the boric acid and the alkaline earth metal compound can be carried out by using a boron source containing a boric anhydride which is in a state of losing water molecules from the metaboric acid. Further, it is also expected to use a boron source containing a boric anhydride. The effect of -11 - 200927686 is as follows: (i) Since the amount of water in the glass raw material is suppressed, the heat of vaporization of the water when the glass raw material is melted is reduced. Therefore, the energy consumed in the melting kiln is reduced by the heat of vaporization. By reducing the amount of heat of vaporization, it is possible to save energy and improve productivity. (ii) When the amount of water (/3 - OH ) in the molten glass is reduced and C1 is contained in the clarifying agent, The reaction becomes HC1, and the oxime volatilization can be suppressed. Therefore, the amount of the clarifying agent can be reduced, and the burden of the exhaust treatment containing HC1 can be further reduced. OH' + CT - HC1 t + 〇2-. (iii) From orthoboric acid The metaboric acid formed by the loss of one water molecule is easy to volatilize, since the boric anhydride is not easily volatilized, the amount of the boron source can be reduced, and the burden of the exhaust treatment containing the metaboric acid can be further reduced. Therefore, in the present invention, as the boron source ,use In the source 1 〇〇 mass % (calculated as B2 〇 3), the boronic anhydride is contained in an amount of 10 to 100% by mass (calculated as 8203 for Q). By controlling the boric anhydride at 10% by mass or more, the glass raw material can be suppressed. The aggregation is carried out to reduce the effect of the foam, and the effect of improving the homogeneity and the flatness. The boric anhydride is preferably 20 to 100% by mass, more preferably 50 to 100% by mass, and particularly preferably 100% by mass. Boron compounds are preferred from the viewpoint of being cheap and easy to obtain. (Other raw materials) Other materials include ai2o3 and alkaline earth metal oxides (-12-200927686)

MgO, CaO, SrO, BaO), A1(0H)3, alkaline earth metal hydroxide (Mg(OH) 2, Ca(OH) 2, Ba(OH) 2, Sr(OH) 2 )° In the present invention The glass base material is composed of a hydroxide containing aluminum or an alkaline earth metal in the raw material, and the initial melting is promoted in the step of melting the glass raw material (step (a)), and the surface of the molten glass can be obtained at a lower temperature. . Further, in the present invention, the glass base material may be composed of a hydroxide composed of 0 aluminum and an alkaline earth metal. Further, as described above, in order to reduce the amount of water in the molten glass, if a part or all of the boron source in the glass raw material is used with boric anhydride, the amount of water in the molten glass is excessively lowered, in the vacuum degassing step. The bubble becomes smaller, the floating speed of the bubble is lowered, and the homogeneity and flatness of the alkali-free glass are deteriorated. In this case, it is preferable to add a hydroxide of aluminum or an alkaline earth metal in order to replenish the amount of water in the molten glass. As the hydroxide, it is preferable to use A1(OH)3 to promote the initial melting of 0. Further, as the hydroxide of the alkaline earth metal, at least one of Mg(OH) 2 or Ca(OH) 2 is preferably used, and particularly Mg (OH) 2 is preferably used. When the content of the alkali metal-based metal hydroxide is contained in the raw material of the glass base material, 100 mol% of the alkaline earth metal source (in terms of MO, only the alkaline earth metal element), 15~ The range of 100% by mole is preferably (in terms of ΜΟ conversion). By adding the amount of the hydroxide to 15 mol% or more, in the step (a), the amount of the unmelted component of the SiO 2 component contained in the strontium sand can be reduced. Therefore, when the bubble occurs in the glass melt, it is possible to prevent the unmelted Si〇2 from being entangled by the bubble and accumulating in the vicinity of the surface layer of the glass melt. Then, as a result, the composition ratio of SiO 2 differs between the surface layer of the glass solution and the portion other than the surface layer, and the homogeneity and flatness of the glass can be prevented from being lowered. Further, as the molar ratio of the hydroxide in the alkaline earth metal source increases, the amount of the unmelted Si 2 component at the time of melting the glass raw material decreases, so that the higher the molar ratio of the hydroxide is, the better. In the case of the above-mentioned alkaline earth metal hydroxide, the reason U is such that the glass base material composition contains Al(OH) 3 in the raw material, and the aluminum source is 100% by mole (in terms of A1203). It is preferably in the range of 15 to 100 mol% (calculated as Al2〇3). Further, as the molar ratio of the hydroxide in the aluminum source increases, the amount of the unmelted Si 2 component at the time of melting the glass raw material decreases, so that the higher the molar ratio of the hydroxide is, the better. (Glass base material composition raw material) Q Glass base material constituent raw material is a powdery mixture in which the above respective raw materials are mixed. The raw material of the glass base material is prepared into an alkali-free glass having a composition as a target glass base material. The composition of the raw material of the glass base material is preferably a composition of the alkali-free glass which is a glass base material composition (1) to be described later, and is a non-alkali which is a glass base material composition (2) or a glass base material composition (3) which will be described later. The composition of the glass is Tejia-14-200927686 (clarifying agent) The clarifying agent is a component for improving the clarification property and is added to the raw material of the glass base material. In the present invention, at least Sn02 is used as the clarifying agent.

The Sn oxide changes from Sn02 (Sn4+) to SnO(Sn2+) at a high temperature of 1400 °C or higher. A clarified gas (oxygen) is released along with the change in the valence. Then, a certain percentage or more of the Sn02 valence is changed to SnO, and since sufficient clarified gas is released, effective clarification becomes possible. The amount of tin added is preferably 0.01 to 2% by mass, more preferably 0.1 to 0.7% by mass, based on the weight of the glass base material. The clarification can be sufficiently carried out by adding the amount of tin to 〇.〇1% by mass or more. When the amount of tin added is 2% by mass or less, defects such as unmelted tin can be suppressed. As a further clarifying agent, it is possible to further add a sulphate selected from a chlorinated product of 3 mass% or less in terms of C1, a sulphate of 3 mass% or less in terms of S03, and a F to the glass base material. One or more types of fluorides in an amount of 3% by mass or less are converted into a total amount of 0.01 to 5% by mass.尙, because the processing of glass swarf requires a lot of manpower, in addition to the inevitable mixture, it is better to contain impurities such as PbO, As203, Sb203, etc. (glass swarf) Discharged glass -15- 200927686 Debris. As the glass cullet, it is preferred to contain the same composition as the glass base material of the target alkali-free glass. The amount of the glass swarf added is preferably 15 to 300% by mass based on the glass base material composition. When the amount of the glass cullet added is 15% by mass or more, the initial meltability can be ensured. By adding the amount of the glass swarf to 300% by mass or less, the clarifying effect by Sn02 can be exhibited. ❹ (Other additives) When using glass swarf, it is preferable to add nitrate at the same time. In the glass cullet, the Sn oxide used as the clarifying agent has a ratio of a large amount of SnO (Sn2+) in which the ability to generate a clarified gas is lowered. Therefore, by adding nitrate to the re-melting of the glass cullet, the SnO (Sn2+) can be oxidized to Sn02 (Sn4+) by the nitrate to effectively clarify without adding Sn02 to the glass cullet. The amount of the nitrate added is preferably 0.01 to 10% by mass based on the glass base material constituent raw material 'N〇3. When the amount of the nitrate added is 0.01% by mass or more, SnO in the glass cullet can be efficiently oxidized to Sn02. Even if the amount of the nitrate added is more than 1% by mass, the effect of the oxidation of Sn02 is saturated is small. Step (Π): (Step (a)) The step (a) is an initial melting step of the step of melting the glass raw material to uniformly vitrify it from -16 to 200927686. The temperature in the step (a) is such that the viscosity of the molten glass is more than 1 02 4 dPa·s, and the viscosity of the molten glass is preferably 1025 dPa·s or more, and the viscosity of the molten glass is 1 〇 2.6 to 1 02. The temperature of 9dPa·s is better. If the viscosity of the molten glass exceeds 1029 dPa · s, the initial melting becomes difficult to homogenize. Therefore, it is preferable to have a temperature of 1029 dPa·s or less. Further, in the step (a), the temperature is preferably 1400 ° C or higher, and the temperature in the step (a) is such that the viscosity of the molten glass exceeds the temperature of 1200 dPas. Vitrification. Therefore, the clarification can be effectively carried out in the step (b) of the latter stage, and the bubbles in the glass can be reduced. As described above, in the present invention, at least Sn02 is used as the clarifying agent, and it is necessary to heat the glass raw material at a relatively low temperature even if the viscosity of the molten glass is higher than 1024 dPa·s to obtain molten glass. © However, if only boronic acid is used as the boron source, unmelted cerium oxide is likely to be generated in the molten glass because the cerium is easily aggregated at this temperature. On the other hand, in the present invention, the raw material of the glass base material contains boronic anhydride as a boron source, and even at this temperature, the glass raw material can be uniformly melted, and the generation of unmelted cerium oxide is also suppressed. The time of step (a) is preferably divided into 1 to 900, and more preferably 150 to 500. (Step (b)) -17- 200927686 Step (b) is a clarification step of 'molding the molten glass at a relatively high temperature even if the viscosity of the molten glass is below 1 〇 2_4 dPa · s' and is more than the aforementioned step (a) Heating at a temperature higher than 30 ° C at a temperature higher than 'the valence of Sn causes the clarified gas to produce a step of defoaming the bubbles in the molten glass. The temperature in the step (b) is such that the viscosity of the molten glass is not more than 24 dPa · s, so that the viscosity of the molten glass is preferably 1 〇 2 3 dPa s or less, so that the viscosity of the molten glass is good. The temperature is preferably 1〇18~l〇22dPa·s. When the viscosity of the molten glass is less than iO^dPa · s, the furnace material is liable to be corroded and becomes liable to be defective. Therefore, it is preferable to use a temperature of 10 〇 18 dPa · s or more. Further, the temperature in the step (b) is a temperature higher than the temperature in the above step (a) by more than 30 °C, and is higher than the temperature in the above step (a) by 50. (The above temperature is preferably a temperature higher than the temperature in the above step (a) by 70 ° C or higher. Further, the temperature in the step (b) is 1 700 ° C or less. The temperature in b) is such that the viscosity of the molten glass is 1 〇 2 4 dPa · s or less, and the temperature is higher than the temperature in the above step (a) by more than 30 ° C, the clarified gas can be efficiently generated. Efficient clarification can reduce the bubbles in the glass. The time of step (b) is better divided into 60~800, and the ratio of 120~300 is better. The viscosity of molten glass is measured by high temperature rotary viscometer. 18- 200927686 Step (iii), Step (iv): In the steps (iii) and (iv), molding, slow cooling, and cutting are carried out in the same manner as in the known method for producing alkali-free glass. <Alkaloid-free glass> The alkali-free glass obtained by the production method of the present invention has a glass base material composition containing SiO2 derived from cerium and B2〇3 derived from a boron source. The alkali-free glass is substantially free of Na20. An alkali metal oxide such as K20. Here, substantially no alkali metal oxide is contained. It means that the alkali metal oxide is not contained in addition to the unavoidable impurities from the raw materials, etc., that is, 'meaning that the alkali metal oxide is not intentionally contained. Hereinafter, the ideal glass base material composition for the alkali-free glass will be described. 〇Glass base material composition (1): Q Alkali-free glass, which has characteristics (thermal expansion coefficient: 25χ10_7 to 60x10_7/°C), chemical resistance, durability, etc., as a glass for liquid crystal display substrates, and is suitable for molding into sheet glass. From the viewpoint of the mass percentage based on the oxide, the alkali-free glass of the following glass base material composition (1) is preferred. 81〇2: 50 to 66% by mass, 12〇3:10.5 to 22% by mass, 82〇3: 5 to 12% by mass, MgO: 0 to 8% by mass, CaO: 〇~14.5% by mass, SrO: 〇 ~24% by mass, BaO: 0 to 13.5% by mass, MgO + CaO + SrO + BaO: 9 to 29.5 Mass 〇/〇-19- 200927686 Glass base material composition (2): Alkali-free glass' strain point is 640 ° C or more, the coefficient of thermal expansion and density are small, and it is possible to suppress the white turbidity caused by the buffer-grade hydrofluoric acid (BHF) used for etching. It is also excellent in durability against chemicals such as hydrochloric acid, and it is easy to melt and form. From the viewpoint of the molding of the formula, it is more preferable that the alkali-free glass based on the oxide base is represented by the following glass base material (2).

Si02: 58 to 66% by mass, a1203: 15 to 22% by mass, B2〇3: 5 to 12% by mass, MgO: 〇~8 mass%, CaO: 0 to 9 mass%, and SrO: 3 to 12.5 mass. /. , BaO : 0 〜 2 mass %, MgO + CaO + SrO + BaO: 9~18 mass % . . · (2). Explain the composition of the composition. When the SiO 2 is 58% by mass or more, the strain point of the alkali-free glass rises, the chemical resistance is improved, and the thermal expansion coefficient is lowered. When the SiO 2 Q is 66% by mass or less, the meltability of the glass is improved, and the devitrification property is improved.

Al2〇3 is used to suppress the phase separation of the alkali-free glass, lower the coefficient of thermal expansion, and increase the strain point. The above effect can be found by making Al2〇3 15% by mass or more. When Al2〇3 is 22% by mass or less, the meltability of the glass is improved. B2〇3 suppresses the white turbidity of the alkali-free glass caused by BHF, does not increase the viscosity at high temperatures, and lowers the alkali-free glass. Thermal expansion coefficient and density. -20- 200927686 When B2〇3 is 5% by mass or more, the BHF resistance of the alkali-free glass is good. When B2〇3 is 12% by mass or less, the acid resistance of the alkali-free glass is improved, and the strain point is also increased.

MgO improves the meltability of the glass raw material by suppressing the increase in the thermal expansion coefficient and the density of the alkali-free glass. When MgO is 8% by mass or less, white turbidity caused by BHF can be suppressed, and phase separation of the alkali-free glass can be suppressed. 0 CaO is the melting property of the glass raw material. When CaO is 9% by mass or less, the thermal expansion coefficient of the alkali-free glass is lowered, and the devitrification property is improved.

SrO suppresses the phase separation of the alkali-free glass and suppresses the white turbidity of the alkali-free glass caused by BHF. The above effects can be found by making SrO 3 mass% or more. When the SrO is 12.5% by mass or less, the coefficient of thermal expansion of the alkali-free glass is lowered. BaO suppresses the phase separation of the alkali-free glass, improves the meltability, and improves the Q-transfer characteristics. By making BaO 2% by mass or less, the density of the alkali-free glass is lowered, and the coefficient of thermal expansion is lowered. However, it is preferable to consider that the burden on the environment is not substantially contained. When the MgO + CaO + SrO + BaO is 9% by mass or more, the solubility of the glass becomes good. When Mg 〇 + Ca0 + Sr0 + Ba0 is 18% by mass or less, the density of the alkali-free glass is lowered. Glass base material composition (3): -21 - 200927686 Alkali-free glass, which is excellent in properties as a glass for liquid crystal display substrates, and is resistant to reduction, homogeneity, suppression of bubbles, and suitable for molding by floating method. It is preferable that the alkali-free glass of the following glass base material composition (3) is represented by the mass percentage of the oxide base.

Si02: 50 to 61.5% by mass, Al2〇3: 10.5 to 18% by mass, 3203: 7 to 10% by mass, ]^^0: 2 to 5% by mass, €&0: 0 to 14.5% by mass, SrO: 0 to 24% by mass, BaO: 0 to 1 3.5% by mass, MgO + CaO + SrO + BaO : 1 6 to 2 9 · 5 % by mass · ( ). Explain the composition of the composition. When Si〇2 is 50% by mass or more, the acid resistance of the alkali-free glass is improved, the density is lowered, the strain point is increased, the coefficient of thermal expansion is lowered, and the Young's modulus is increased. When the SiO 2 is 61.5 mass% or less, the devitrification property of the alkali-free glass becomes good. M2〇3 is to suppress the phase separation of the alkali-free glass, increase the strain point, and increase the Young's modulus. The above effect can be found by setting Al2〇3 to 10.5% by mass or more. When Al2〇3 is 18% by mass or less, the devitrification resistance of the alkali-free glass, the acid resistance, and the BHF resistance are improved. B2〇3 reduces the density of the alkali-free glass, improves the BHF resistance, improves the meltability, and deteriorates the devitrification property, which lowers the coefficient of thermal expansion. The above effect can be found by making B2〇3 7 mass% or more. When B2〇3 is 1% by mass or less, the strain point of the alkali-free glass rises, and the Young's modulus increases, and the acid resistance becomes good.

MgO is such that the density of the alkali-free glass is lowered 'and the coefficient of thermal expansion is not increased -22-200927686, so that the strain point is not greatly lowered' and the meltability is improved. When the MgO is 2% by mass or more, the effect of the above-mentioned effect is obtained. When the Mg Ο is 5% by mass or less, the phase separation of the alkali-free glass is suppressed, and the devitrification property, the acid resistance, and the BHF resistance are improved. .

CaO does not increase the density of the alkali-free glass, does not increase the coefficient of thermal expansion, and does not reduce the strain point excessively to increase the meltability. When CaO is 14.5% by mass or less, the devitrification property of the alkali-free glass becomes good, and the coefficient of thermal expansion is lowered, and the density is lowered, and the acid resistance and alkali resistance are improved.

SrO does not increase the density of the alkali-free glass. 'The thermal expansion coefficient is not increased, and the strain point is not excessively lowered to improve the meltability. When SrO is 24% by mass or less, the devitrification property of the alkali-free glass is improved, the coefficient of thermal expansion is lowered, and the density is lowered, and the acid resistance and alkali resistance are improved. B aO suppresses the phase separation of the alkali-free glass, improves the devitrification property, and improves the Q-resistant drug property. When BaO is 13.5% by mass or less, the density of the alkali-free glass is lowered, the coefficient of thermal expansion is lowered, and the Young's modulus is improved, and the meltability is improved, and the BHF resistance is improved. However, if you consider the burden on the environment, it is better not to contain it. When the MgO + CaO + SrO + BaO is 16% by mass or more, the meltability of the glass is improved. When the MgO + CaO + SrO + BaO is 29.5% by mass or less, the density and thermal expansion coefficient of the alkali-free glass are lowered. According to the method for producing an alkali-free glass of the present invention as described above, -23-200927686 is the above-mentioned ceramsite, D5〇 is 15 to 60 l·1111', and the ratio of particles having a particle diameter of 100 or more is 2.5% by volume. In the following, as a boron source, a boron source is used in an amount of 1% by mass (calculated as b2〇3), and 1 to 1% by mass of boric anhydride (in terms of B2〇3) is used as a clarifying agent. Use of Sn 〇 2 ' Since the melting of the glass raw material is carried out in at least the above steps (a) and (b), the alkali-free glass having a low degree of homogeneity and high flatness in the glass can be obtained. [Embodiment] The present invention will be specifically described by the following examples, but it should be understood that the invention should not be construed as limited. Examples 1 and 2 are experimental examples showing low-temperature meltability, Examples 3 to 5, 7 and 8 are Examples, and Example 6 is a comparative example. [Example 1] Q is represented by the mass percentage of the oxide, and has Si 〇 2 : 60 mass %, a 12 0 3 : 17 mass%, B 2 0 3 : 8 mass%, and M g 0 : 3% by mass, CaO: 4% by mass, SrO: 8% by mass of an alkali-free glass composed of a glass base material, 矽砂^050:27411^Particle ratio of particles larger than ιμηη: 〇% by volume, 〇99 (Particle size distribution) The volumetric frequency in the medium accounts for 99% of the particle diameter)··················· As a boron source, boric anhydride (1% by mass) is used as the aluminum source to form a raw material of the glass base material, and other raw materials are used to form a raw material for the glass base material, and further as a clarifying agent, a raw material is formed with respect to the glass base material. 0.5% by mass of Sn02, 0.5% by mass of SrCl4, and -24 to 200927686 0.3% by mass of CaS04 · 2H20 were added to make a glass raw material. The vitrified glass material having a mass of 250 g was placed in a bottomed cylindrical platinum crucible having a height of 90 mm and an outer diameter of 70 mm. The crucible was placed in a heating furnace, and air having a dew point of 60 ° C was blown from the side of the heating furnace, and heated at 30 ° C at 1 525 ° C (the viscosity of the molten glass was 102 6 dPa·s). The glass material was melted by stirring in a crucible for 30 minutes by a stirrer. Thereafter, the stirring was stopped, and the mixture was allowed to stand for 60 minutes, and the molten glass in the crucible was discharged to the carbon plate and cooled in a slow cooling furnace. After cooling, the sample was taken out from the slow cooling furnace, irradiated with light from the edge of the sample, and the number of unmelted cerium oxide was counted by a solid microscope. The results are shown in Table 1. Further, the same evaluation was carried out by setting the melting temperature of the glass raw material to 1550 ° C (the viscosity of the molten glass was 10 d 25 dPa · s). The results are shown in Table 1. © [Example 2] In addition to the use of strontium sand 1 (D5G: 39μιη, the ratio of particles larger than ΙΟΟμηη: 4.2% by volume, D99: 丨53^1111), orthoboric acid was used as the boron source ( The same evaluation as in Example 1 was carried out except that 100% by mass. The results are shown in Table 1. -25- 200927686 [Table 1] Melting temperature rc) Viscosity of molten glass (dPa. s) Amount of unmelted sand dioxide (pcs/kg) Example 1 Example 2 Silicate sand 1 + boric anhydride strontium sand 2+ orthoboric acid 1525 1025 757 1230 1550 ίο2·5 1 188 1021 The composition of the present invention (D5o: a ratio of particles of 15 to 60 μm, a particle size of ΙΟΟμηι or more: 2.5% by volume or less) is combined with a group of boric anhydride, and the present invention When the composition of the samarium 2 and the orthoboric acid are different, the amount of the unmelted cerium oxide is found to be small, and the initial dissolution can be performed at a lower temperature. Further, since the amount of unmelted cerium oxide is small, the glass having high homogeneity is high. Further, it is possible to obtain a glass having a high flatness when the sheet glass is molded. [Example 3] The glass base material composition raw material similar to that of Example 1 was further used as a clarifying agent, and 〇·5 mass% of Sn〇2 was added to the glass base material constituent raw material to form a glass raw material. Step (a): A half amount of the glass raw material (corresponding to 125 g in terms of glass) is placed in a 300 cc platinum crucible, and allowed to stand in an electric furnace of 1500 1 (the viscosity of the molten glass is 1 02 7 dPa·s). minute. Temporarily take out the platinum crucible from the electric furnace, and add the remaining half (125 g equivalent in terms of glass), and again set it in an electric furnace at 1500 T: (the viscosity of the molten glass is 1027 dPa·s) for 30 minutes. The glass raw material is melted. -26- 200927686 Step (b) ·· Then, quickly transfer to an electric furnace at 1 590 °C (the viscosity of the molten glass becomes 1 02 3dPa · s) and let stand for 30 minutes. Thereafter, the furnace was transferred to an electric furnace at 730 ° C, and it took 2 hours to slowly cool the glass to 610 ° C. Further, it took about 1 hour to cool the glass to room temperature. Then, the glass in the center of the upper portion of the crucible is drilled through a cylindrical glass having a diameter of 38 mm and a height of 35 mm 0. As shown in FIG. 1, the glass containing the central axis 12 of the cylindrical glass 10 is 2 to 5 mm thick. The board 14 is cut out. The two sides of the cut surface were subjected to optical honing processing (mirror honing surface treatment) to prepare a sample for evaluation. For the portion corresponding to the area between 1 and 10 mm from the top of the glass of the crucible, the optically honed surface was observed with a stereoscopic microscope, and the number of bubbles of 5 Ομηη or more in the glass plate was measured, and the glass plate was removed. The volume is the number of residual bubbles. The results are shown in Table 2. The same evaluation as in Example 3 was carried out, except that the temperature in the step (a) was changed to 1550 1: (the viscosity of the molten glass was 102 5 dPa ♦ s). The results are shown in Table 2. [Example 5] The mass ratio of Si 02 : 60% by mass and a12 〇 3 : 17 mass were expressed as a percentage by mass based on the oxide. /. , B2〇3: 8 mass%, MgO: 5 mass%, Ca〇: 6 mass%, SrO: 4 mass% of glass base material composition -27-200927686 alkali-free glass, strontium sand 1, boric acid as boron source An anhydride (1% by mass), an aluminum source of Α1203, and other raw materials to be used as a raw material for the glass base material, and further, as a clarifying agent, 0.5% by mass of Sn 添加 is added to the raw material of the glass base material. 2, made into glass raw materials. Step (〇: The half of the glass raw material (125 g equivalent in terms of glass) was placed in a 0 300 cc uranium crucible, and allowed to stand in an electric furnace at 1500 ° C (the viscosity of the molten glass was 1025 dPa·s) for 30 minutes. Temporarily take out the platinum crucible from the electric furnace, add the remaining half amount (125 g in terms of glass), and place it again in an electric furnace of ISOOt: (the viscosity of the molten glass becomes 102 5 dPa · s) for 30 minutes. The glass raw material is melted. Step (b): Thereafter, the furnace is rapidly transferred to an electric furnace at 1590 ° C (the viscosity of the molten glass is ❹ 1 〇 21 hearts • s), and allowed to stand for 30 minutes. Thereafter, it is transferred to 730 ° C. In the electric furnace, the glass was slowly cooled to 610 ° C for 2 hours, and the glass was gradually cooled to room temperature for about 10 hours. Then, a sample for evaluation was prepared in the same manner as in Example 3, and the number of residual bubbles was determined. As shown in Table 2. [Example 6] The same glass raw material as in Example 2 was prepared. -28- 200927686 Step (a): A half amount of the glass raw material (125 g equivalent in terms of glass) was placed in a 300 cc uranium crucible At 1590 °c (viscosity of molten glass) The electric furnace was allowed to stand for 30 minutes in an electric furnace of 1 02 3 dPa·s. The platinum crucible was taken out from the electric furnace, and the remaining half amount (125 g in terms of glass) was added, and the temperature was again set at 1590 ° C ( After 30 minutes in an electric furnace in which the viscosity of the molten glass is 1023 dPa·s, it is dissolved. © Step (b): Thereafter, the furnace is rapidly transferred to 1590 ° C (the viscosity of the molten glass is 102 3 dPa·s). After standing for 3 minutes, it was transferred to an electric furnace at 73 ° C. It took 2 hours to slowly cool the glass to 610 ° C, and further took about 1 hour to cool the glass to room temperature. Then, with Example 3 In the same manner, a sample for evaluation was prepared, and the number of residual bubbles was determined. The results are shown in 袠2.

[Table 2] Step (8) Step (b) Brewing residual temperature viscosity Viscosity time (b)-(a) (pieces/cm3) (°C) (dPa · s) CC) (dPa · s) (minutes) ( °C) Example 3 1500 ίο2·7 1590 1〇2.3 30 90 '~ 60 Example 4 1550 1025 1590 1023 30 40 215 Example 5 1500 1〇2.5 1590 1021 15 90 160 Example 6 1590 1〇2.3 1590 1023 30 0 1235

-29- 200927686 In addition to the use of Al(OH) 3 as a source of the same, in the same manner as in the case of the example 1, the raw material of the glass base material was further used as a clarifying agent, and the raw material of the glass base material was added. 0.5% by mass of Sn〇2, 〇5 mass% of SrCl4, 0.3% by mass of CaS〇4·2H20, and 0.1% by mass of CaF2 are used as glass raw materials. In the same manner as in Example 3 except that the glass raw material obtained above was used, a sample for evaluation was prepared, and the number of residual bubbles was determined. The results are shown in Table 3 [Example 8] except that the temperature of the step (a) was changed to 1450. The same evaluation as in Example 7 was carried out except that 黏 (the viscosity of the molten glass was changed to a temperature of 102 + 8 dPa·s). The results are shown in Table 3. [Table 3] Step (8) Step (b) Temperature difference Residual bubble number Brewing viscosity Temperature viscosity time (b)-(a) (pieces/cm3) CC) (dPa · s) CC) (dPa · s) (minutes) °C) Example 7 1500 1〇2·7 1590 1023 30 90 50 Example 8 1475 1〇2.8 1590 1023 30 115 45 The viscosity of the glass raw material in the molten glass will be more than 1 02 4dPa in the step (a). Heating at a temperature, in the step (b), the molten glass is heated at a temperature of 102 4 dPa·s or less, and heated at a temperature higher than the temperature in the step (a) by 30 ° C or higher. 〜5, and in step (a), the glass raw material is also heated at a temperature of -30-200927686 degrees of molten glass to a temperature below l〇2 4dPa·s, and the molten glass of step (a) and step (b) In comparison with Example 6 in which the viscosity is not different, it is found that the number of residual bubbles is small, and the clarification effect is a big one. Further, in Examples 7 and 8 in which the glass base material composition contains A1(OH)3, it is known that, in particular, in Example 8, the glass raw material is dissolved at a low temperature in the step (a), even if the viscosity of the molten glass becomes high, Good melting characteristics are also obtained, and the number of residual bubbles in Examples 7 and 8 is small, and the clarifying effect is a big one. [Industrial Applicability] The alkali-free glass obtained by the production method of the present invention is in the glass. The bubbles are small, and the homogeneity and flatness are high. In addition, it contains B2〇3, which is excellent in chemical resistance and durability. This alkali-free glass is extremely useful as a glass for a liquid crystal display substrate. The entire contents of the specification are the entire contents of the specification, the patent application, the drawings and the abstract of the Japanese Patent Application No. 2007-277802, filed on Jan. It is disclosed that the description of the present invention is incorporated by reference. BRIEF DESCRIPTION OF THE DRAWINGS [Fig. 1] is a view showing a portion of a glass plate for cutting a sample from a cylindrical glass. [Description of main component symbols] -31 - 200927686 1 0 : Glass 1 2 : Center axis 1 4 : Glass plate

-32

Claims (1)

200927686 X. Patent application scope: · A method for producing an alkali-free glass, which is a method for producing an alkali-free glass obtained by melting a glass raw material containing a clarifying agent in a raw material of a glass base material containing cerium and a boron source It is characterized in that, as the ceramsite, a cerium having a median diameter of 15 to 60 μm and a particle diameter of 1 〇〇μηη or more is 2.5% by volume or less, and the boron source is 100% by mass or less. 0 in the β2ο3 conversion, the boron source is used in an amount of 10 to 100% by mass of boric anhydride (in terms of Β203). As the clarifying agent, at least Sn02 is used, and the glass raw material is melted at least in the following two steps: (a) The glass raw material is heated at a temperature at which the viscosity of the molten glass exceeds 12 4 dPa · s to form a molten glass; (b) after the above step (a), the molten glass is made so that the viscosity of the molten glass is l〇 2 4dPa · s or less and heated at a temperature 30 ° C or higher higher than the temperature 0 in the above step (a) to defoam the bubbles in the molten glass. The method for producing an alkali-free glass according to the first aspect of the invention, wherein the glass base material constituent material contains a hydroxide of aluminum or an alkaline earth metal. 3. The method for producing an alkali-free glass according to any one of claims 1 to 2, wherein the raw material of the glass base material is prepared into a glass base material as described below by mass percentage based on the oxide. The alkali-free glass of the composition (1) is added to the glass base material composition material in an amount of S.〇1 to 2% by mass in terms of Sn02 to form a glass raw material, -33-200927686 81〇2:50~66% by mass, eight 12〇3:10.5~22% by mass, 82〇3: 5~12% by mass, MgO: 0~8% by mass, CaO: 0~1 4.5% by mass, SrO: 0 to 24% by mass, BaO: 0~13.5 Mass%, 1^〇+ 〇3〇+ 31'〇+ BaO: 9~29·5 mass% · · · (1). 4. The method for producing an alkali-free glass according to any one of claims 1 to 3, wherein, in the mass percentage based on the oxide, the raw material of the glass base material is prepared into a glass base material as described below. The alkali-free glass of the composition (20) is added to the glass base material composition material in an amount of 0.01 to 2 mass% in terms of Sn02 to form a glass raw material, Si〇2: 5 8 to 66 mass%, AI2〇3: 1 5 ~22% by mass, B2〇3: 5 to 12% by mass, MgO: 0 to 8% by mass. , CaO: 〇~9 mass %, SrO: 3~12·5 mass. /. , BaO: 0~2 quality. /. , MgO + CaO + SrO + BaO : 9 ~ 18 mass % · · ( 2 ). 5. In the ia method of the alkali-free glass described in any one of claims 1 to 4, wherein the glass base material is represented by a mass percentage based on the oxide Q, the glass base material is prepared into a glass as described below. The alkali-free glass of the base material composition (3) is added to the glass base material composition material in an amount of 0.01 to 2 mass% in terms of Sn 〇 2 to form a glass raw material, 81 〇 2: 5 〇 to 61.5 mass%, eight 12 〇. 3:1〇5 to 18% by mass, 32〇3: 7 to 10% by mass, MgO: 2 to 5 mass%, Ca〇: 〇~14 5 mass%, SrO: 0 to 24% by mass, BaO: 0~ 13.5 mass%, MgO + CaO + SrO + BaO : 16 to 29.5 mass % · · (3). 6. The method for producing an alkali-free glass according to any one of the first to fifth aspects of the present invention, wherein the raw material of the glass base material is further added to the step of -34 to 200927686, and the mass is converted from 3 in terms of ci. The total amount of the above-mentioned chlorides, which are selected from the group consisting of sulphuric acid salts of 3% by mass or less and fluorarated materials of 3% by mass or less in terms of F, are selected as 〇.01 to 5 masses. % as a glass raw material. 7. The method for producing an alkali-free glass according to any one of claims 1 to 6, wherein the raw material of the glass base material is further advanced, and 15 to 300% by mass of N is added. (3) 换算1~1〇% by mass of the glass slag composed of nitrate and alkali-free glass as a glass material. -35-