CN105916821B

CN105916821B - Method for producing silicate glass, and silica raw material for silicate glass

Info

Publication number: CN105916821B
Application number: CN201580004471.2A
Authority: CN
Inventors: 成田利治; 小森宏师; 高谷辰弥
Original assignee: Nippon Electric Glass Co Ltd
Current assignee: Nippon Electric Glass Co Ltd
Priority date: 2014-02-28
Filing date: 2015-02-16
Publication date: 2020-07-10
Anticipated expiration: 2035-02-16
Also published as: TW201542481A; TWI647188B; KR20160125350A; JP2015178440A; JP6562240B2; KR102344757B1; WO2015129495A1; CN105916821A

Abstract

A method for producing a silicate glass, which comprises melting and shaping a glass batch to obtain a silicate glass, wherein a silica raw material containing an alkaline earth metal component in an amount of 0.01 to 2 mass% in terms of oxide is introduced into the glass batch.

Description

Method for producing silicate glass, and silica raw material for silicate glass

Technical Field

The present invention relates to a method for producing silicate glass, and a silica raw material for silicate glass, and more particularly, to a method for producing silicate glass suitable for substrates of liquid crystal displays, organic E L displays, and the like, and to the silicate glass and the silica raw material for silicate glass.

Background

The silicate glass is produced as follows: various glass raw materials are blended to obtain a glass batch, and the glass batch is melted and formed to produce a glass product. As is well known, silicate glasses are SiO₂Glass as a main component. Thus, the silica raw material accounts for a greater proportion of the glass batch than the other glass raw materials.

In order to improve the quality of silicate glass when used for display applications, the silica raw material needs to be of high purity. That is, a silica raw material having a small amount of impurities has been used so far.

Alkali-free glass (silicate glass having an alkali metal oxide content of less than 0.5 mass% in the glass composition) is being used as silicate glass used for liquid crystal displays and the like. Alkali-free glass is infusible, and therefore has a characteristic of being difficult to melt as compared with glass containing alkali. Under such circumstances, it is considered to adjust the particle size of the silica raw material to a predetermined range to improve the meltability of the glass batch material.

For example, patent document 1 discloses: use of Cr as a refractory impurity₂O₃The content of the silica raw material is low, so as to reduce the chromite foreign matter in the silicate glass. Patent document 2 discloses: by using the average particle diameter D₅₀Is a silica raw material of 30 to 60 μm to improve the homogeneity of silicate glass. Patent document 3 discloses: by using the average particle diameter D₅₀Is a silica raw material with a particle size of 70 to 200 μm to improve the bubble quality of the silicate glass.

Documents of the prior art

Patent document

Patent document 1 Japanese patent laid-open No. 2012-201524

Patent document 2 Japanese laid-open patent publication No. 2004-067408

Patent document 3 Japanese patent laid-open publication No. 2013-107801

Disclosure of Invention

Problems to be solved by the invention

In addition, in order to improve the bubble quality of silicate glass, a fining agent that generates a fining gas is used during melting. A hardly soluble silicate glass, for example, an alkali-free glass undergoes a vitrification reaction at a temperature of, for example, 1200 to 1300 ℃, and is defoamed and homogenized at a high temperature of 1400 ℃ or higher. Therefore, As which generates a fining gas at about 1200 to 1600 ℃ is used As a fining agent for a sparingly soluble silicate glass₂O₃And generates clear gas at about 1200-1300 DEG CSb₂O₃. However, As₂O₃、Sb₂O₃Are substances that affect the environment, and thus their use is gradually limited.

In place of As₂O₃、Sb₂O₃The most promising fining agent of (b) SnO₂。SnO₂Has the following properties: at temperatures above 1400 ℃ clear gases are released when the valence changes to 2.

On the other hand, SnO₂Has a property of releasing little clear gas at the initial melting temperature (for example, 1000 to 1400 ℃). Thus, SnO₂It is difficult to reduce the amount of dissolved gas in the glass, and reboiling is likely to occur thereafter. In particular to reduce As As fining agent₂O₃、Sb₂O₃This tendency is more remarkable. Therefore, reboiling refers to a phenomenon in which re-foaming occurs in glass due to reheating treatment of the glass composition or the like.

As a method for increasing the fining power at the temperature in the initial stage of melting, it is also conceivable to adjust the particle size of the glass raw material. However, the silica raw materials described in patent documents 1 to 3 have an effect of improving the meltability of the glass batch, but lack an effect of enhancing the refining power, and hardly contribute to improvement of the reboiling property.

The present invention has been made in view of the above circumstances, and has a technical object to develop a method for reducing As As a clarifying agent₂O₃、Sb₂O₃In this case, the foam quality of the hardly soluble silicate glass, particularly the alkali-free glass, can be improved by using the silica raw material whose refining power is increased at the initial melting temperature.

Means for solving the problems

As a result of intensive studies, the present inventors have found that when a silica raw material containing a small amount of an alkaline earth metal component is introduced into a glass batch, CO is generated at an initial melting temperature₂Gas (carbon dioxide gas), the CO₂The gas has improved clarity and reduced dissolved gas, and can contribute to improvement of reboiling property, and the present invention has been proposed. Namely, production of the silicate glass of the present inventionThe method for producing a silicate glass is a method for producing a silicate glass by melting and shaping a glass batch, and is characterized in that a silica raw material containing an alkaline earth metal component in an amount of 0.01 to 2 mass% in terms of oxide is introduced into the glass batch. Wherein "silica raw material" means SiO₂The content of (b) is 95 mass% or more. The above CO is₂The gas also has the effect of stirring the molten glass at the initial melting temperature to improve the homogeneity of the silicate glass.

It is known that the decomposition of the carbonate raw material is completed at a low temperature, and therefore CO is not generated at the initial melting temperature₂A gas. According to the investigation of the present inventors, it has been unexpectedly found that when a silica raw material containing a small amount of an alkaline earth metal component is used, CO is generated even at a temperature of 1200 ℃ or higher₂A gas.

Second, the method for producing a silicate glass of the present invention preferably includes: a silica raw material containing 0.01 to 0.3 mass% of Mg component in terms of MgO is introduced into a glass batch. This enables gas to be reliably generated at the initial melting temperature.

Third, the method for producing a silicate glass of the present invention preferably includes: a silica raw material containing 0.01 to 0.5 mass% of Ca component in terms of CaO is introduced into a glass batch. This enables gas to be reliably generated at the initial melting temperature.

Fourth, the method for producing a silicate glass of the present invention preferably includes: introducing Fe into the glass batch₂O₃A silica raw material containing 0.001 to 0.008 mass% of Fe in terms of the total mass. This can suppress the coloring of the silicate glass while controlling the cost of the silica raw material.

Fifth, the method for producing a silicate glass of the present invention preferably includes: introducing CO in the glass batch in a temperature range of 1000 to 1400 DEG C₂A gaseous silica source. This can reliably enhance the refining power at the initial melting temperature.

Sixth, the method for producing a silicate glass of the present invention preferably includes: is introduced into the glass batch at 10CO is generated in a temperature range of 00-1400 DEG C₂Gas and H₂Silica raw material of O gas (water vapor).

It is known that the hydroxide raw material is decomposed at a low temperature, and therefore H is not generated at the initial melting temperature₂And (4) O gas. According to the investigation of the present inventors, it has been unexpectedly found that when a silica raw material containing a small amount of an alkaline earth metal component is used, a large amount of H is generated even at a temperature of 1200 ℃ or higher₂And (4) O gas. And H generated in the high temperature region₂The O gas can contribute to the improvement of the clarification, the reduction of dissolved gas, and the improvement of the reboiling property. Further, the H₂The O gas also has an effect of stirring the molten glass at the initial melting temperature to improve the homogeneity of the silicate glass.

Seventh, the method for producing a silicate glass of the present invention preferably includes: the content of S component in the glass composition of silicate glass is defined as SO₃The silicate glass is produced in an amount of less than 0.01% by mass in terms of the weight. This improves reboiling performance.

Eighth, the method for producing a silicate glass of the present invention preferably includes: as in the glass composition of the silicate glass₂O₃Content of (B) is less than 0.05 mass%, Sb₂O₃Less than 0.05 mass%, SnO₂The glass batch is prepared so that the content of (A) is 0.01 to 1% by mass. This makes it possible to easily improve the bubble quality of silicate glass while satisfying recent environmental requirements.

Ninth, in the method for producing a silicate glass of the present invention, it is preferable that the glass batch is prepared so that the content of the alkali metal oxide in the glass composition of the silicate glass is less than 0.5 mass%, whereby the silicate glass can be used for substrates of liquid crystal displays, organic E L displays, and the like.

Tenth, the method for producing a silicate glass of the present invention preferably includes: the silicate glass contains SiO in terms of glass composition in mass%₂50～80％、Al₂O₃5～25％、B₂O₃0 to 20%, MgO 0 to 15%, CaO 1 to 15%, SrO0 to 15%, and BaO 0 to 15%Glass batch was prepared. This makes it easy to satisfy the required properties such as resistance to devitrification, high strain point, low density, and acid resistance.

Eleventh, the method for producing a silicate glass of the present invention preferably includes: the sheet is formed into a flat shape by an overflow downdraw method or a float method. This makes it easy to increase the size and reduce the thickness of the silicate glass.

Twelfth, the silicate glass of the present invention is produced by the above-described method for producing a silicate glass.

Thirteenth, the silica raw material for silicate glass of the present invention is preferably: contains 0.01 mass% or more of an alkaline earth metal component in terms of oxide.

Fourteenth, the silica raw material for silicate glass of the present invention is preferably: contains 0.01 to 0.3 mass% of Mg component in terms of MgO.

Fifteenth, the silica raw material for silicate glass of the present invention is preferably: contains 0.01 to 0.5 mass% of Ca component in terms of CaO.

Sixthly, the silica raw material for silicate glass of the present invention is preferably: containing Fe₂O₃0.001 to 0.008 mass% in terms of Fe component.

Seventeenth, the silica raw material for silicate glass of the present invention is characterized in that CO is generated in a temperature range of 1000 to 1400 ℃₂A gas.

Eighteenth, the silica raw material for silicate glass of the present invention is characterized in that CO is generated in a temperature range of 1000 to 1400 ℃₂Gas and H₂And (4) O gas.

Nineteenth, natural quartz sand is preferable as the silica material for silicate glass of the present invention.

Drawings

FIG. 1 shows a pair [ example 1]CO when sample Nos. 1 and 2 (1) were heated at a temperature rise rate of 8 ℃/min in a temperature range of 200 to 1300 ℃₂Measurement data of the amount of released gas.

FIG. 2 shows a pair [ example 1]]Sample Nos. 1 and 2 of (1) are at 200 ℃ up to 8 ℃/minH when heated in the temperature range of 1300 DEG C₂Measurement data of the amount of released O gas.

Detailed Description

The method for producing the silicate glass of the present invention will be described in detail below.

First, glass raw materials as introduction sources of the respective components are blended and mixed so as to have a desired glass composition, thereby producing a glass batch. If necessary, glass cullet may be used as the glass raw material. The glass cullet refers to glass cullet discharged in a glass manufacturing process or the like.

Then, the obtained glass batch was put into a glass melting furnace, and melted and vitrified. The charging of the glass batch into the glass melting furnace is usually carried out continuously, but may be carried out batchwise. The melting temperature of the glass batch in the glass melting furnace is about 1500 to 1650 ℃ in the case of alkali-free glass. Thereby, the glass raw material is melted to form molten glass.

Then, the molten glass is refined and stirred, and then supplied to a forming apparatus, and the molten glass is formed into a flat plate shape so as to have a predetermined thickness and surface quality. As the molding method, an overflow down draw method, a float method, or the like can be used.

The silicate glass in a flat plate shape produced in this way is used as a substrate for a liquid crystal display or the like, for example.

Next, the silica raw material of the present invention will be explained.

The silica raw material of the present invention preferably contains the following minor components. The content of the alkaline earth metal component is 0.01 to 2 mass%, preferably 0.03 to 1 mass%, more preferably 0.05 to 0.5 mass% in terms of oxide. When the content of the alkaline earth metal component is too small, it is difficult to release gas at the initial melting temperature. On the other hand, when the content of the alkaline earth metal component is too large, the glass batch is excessively sprayed upward at the initial stage of melting, and the durability life of the glass melting furnace is liable to be reduced. The alkaline earth metal component is preferably contained in the form of a carbonate.

The content of the Mg component is preferably 0.01 to 0.3 mass%, 0.01 to 0.2 mass%, or 0.02 to 0.1 mass%, particularly preferably 0.02 to 0.05 mass%, in terms of MgO. When the content of the Mg component is too small, it is difficult to release gas at the initial melting temperature. On the other hand, when the content of the Mg component is too large, the glass batch is excessively sprayed upward at the initial stage of melting, and the durability life of the glass melting furnace is liable to be reduced.

The content of the Ca component is preferably 0.01 to 0.5 mass%, 0.01 to 0.3 mass%, 0.01 to 0.2 mass%, or 0.02 to 0.1 mass%, particularly preferably 0.02 to 0.05 mass%, in terms of CaO. When the content of the Ca component is too small, it is difficult to release gas at the initial melting temperature. On the other hand, if the content of the Ca component is too large, the glass batch is excessively sprayed upward at the initial stage of melting, and the durability life of the glass melting furnace is liable to be reduced.

The content of Fe component is Fe₂O₃The content is preferably 0.001 to 0.008 mass%, particularly preferably 0.002 to 0.004 mass%. When the content of Fe is too small, the raw material cost of the silica raw material tends to be high. On the other hand, if the content of the Fe component is too large, the silicate glass tends to be colored.

The content of Ti component being TiO₂The content is preferably 0.0005 to 0.008 mass%, particularly preferably 0.001 to 0.004 mass%. When the content of the Ti component is too small, the raw material cost of the silica raw material tends to be high. On the other hand, when the content of the Ti component is too large, the silicate glass is easily colored.

In the method for producing a silicate glass of the present invention, it is preferable that CO generated in a temperature range of 1000 to 1400 ℃ is introduced into a glass batch₂The silica raw material for gas is preferably introduced into a temperature range of 1200 to 1400 ℃ to generate CO₂A gaseous silica source. This can reliably enhance the refining power at the initial melting temperature.

In the method for producing a silicate glass of the present invention, it is preferable that CO generated in a temperature range of 1000 to 1400 ℃ is introduced into a glass batch₂Gas and H₂The silica raw material of O gas is preferably introduced into a temperature range of 1200 to 1400 ℃ to generate CO₂Gas and H₂A silica raw material of O gas. This can reliably enhance the refining power at the initial melting temperature.

As a method for introducing a small amount of alkaline earth metal component into the silica raw material, a chemical synthesis method can be used, and from the viewpoint of raw material cost, it is preferable to use a natural raw material containing a small amount of alkaline earth metal component. For example, a high-purity quartz sand layer formed by erosion of a dolomite deposit is preferably collected and used as a silica raw material.

In the method for producing a silicate glass of the present invention, it is preferable to use As in the glass composition of the silicate glass₂O₃Content of (B) is less than 0.05 mass%, Sb₂O₃Less than 0.05 mass%, SnO₂The glass batch is prepared so that the content of (A) is 0.01 to 1% by mass. This makes it possible to easily improve the bubble quality of silicate glass while satisfying recent environmental requirements.

SnO₂The component having a good clarifying action in a high temperature region, the component for increasing the strain point, and the component for reducing the high temperature viscosity. SnO₂The content of (B) is preferably 0.01 to 1% by mass, or 0.05 to 0.5% by mass, particularly preferably 0.1 to 0.3% by mass. SnO₂When the content of (A) is too large, SnO₂Devitrification crystal of (2) is easily precipitated and further easily promotes ZrO₂Precipitation of devitrified crystals. In addition, SnO₂When the content of (b) is less than 0.01% by mass, the above-mentioned effects are hardly enjoyed.

As a clarifying agent, As₂O₃、Sb₂O₃Is also effective. However, although the silicate glass of the present invention does not completely exclude the case where these components are contained, it is preferable not to use these components from the viewpoint of the environment. Further, the content of As is high₂O₃In the case, the negative sensitivity resistance tends to be lowered. As₂O₃The content of (B) is preferably less than 0.05 mass%, and Sb₂O₃The content of (b) is preferably less than 0.05 mass%.

In the method for producing a silicate glass of the present invention, it is preferable that the glass composition of the silicate glass isThe content of S component is SO₃The silicate glass is produced SO as to be less than 0.01 mass% (0.005 mass% in terms of desired effect), and preferably SO is contained in the glass composition of the silicate glass in accordance with the content of the S component₃The glass batch material is prepared in such a manner that the content is less than 0.01% by mass (desirably less than 0.005% by mass) in terms of mass. SO (SO)₃Although functioning as a clarifier, when the content is too large, SO is easily generated₂And (5) reboiling.

As other clarifying agents, a halide such as F, Cl, CeO, or the like may be introduced₂. When a halide such as F, Cl is introduced as a clarifying agent, H is generated from the silica raw material₂O is released in the form of HF gas or HCl gas.

Specifically, the content of the alkali metal oxide is preferably less than 0.5 mass%, or less than 0.3 mass%, particularly preferably 0.01 to 0.2 mass%, and L i is an example of the material for the glass batch prepared so that the content of the alkali metal oxide in the glass composition of the silicate glass is less than 0.5 mass%₂O、Na₂The content of O is preferably less than 0.3% by mass, particularly preferably less than 0.2% by mass, in each component. K₂The content of O is preferably less than 0.5 mass%, or less than 0.3 mass%, particularly preferably 0.01 to 0.2 mass%.

In the method for producing a silicate glass of the present invention, it is preferable that the silicate glass contains SiO in terms of glass composition of the silicate glass in mass%₂50～80％、Al₂O₃5～25％、B₂O₃0 to 20%, 0 to 15% MgO, 1 to 15% CaO, 0 to 15% SrO, and 0 to 15% BaO. The reason why the glass composition of the silicate glass is defined as described above is as follows. In the description of the content ranges of the respective components,% represents mass%.

SiO₂Is a component forming the skeleton of the glass. SiO 2₂The content of (b) is preferably 50 to 80%, 54 to 70%, or 56 to 66%, particularlyPreferably 58 to 64%. SiO 2₂When the content of (b) is too small, the density becomes too high and the acid resistance is liable to decrease. On the other hand, SiO₂When the content (b) is too large, the high-temperature viscosity increases, the meltability tends to decrease, devitrified crystals such as cristobalite tend to precipitate, and the liquid phase temperature tends to increase.

Al₂O₃The component forming the glass skeleton, the component increasing the strain point and Young's modulus, and the component suppressing phase separation. Al (Al)₂O₃The content of (b) is preferably 5 to 25%, 12 to 24%, or 15 to 22%, particularly preferably 16 to 21%. Al (Al)₂O₃When the content of (b) is too small, the strain point and Young's modulus are liable to decrease, and the phase separation of the glass is liable to occur. On the other hand, Al₂O₃When the content of (b) is too large, devitrified crystals such as mullite and anorthite are likely to be precipitated, and the liquid phase temperature is likely to rise.

B₂O₃Is a component for improving meltability and devitrification resistance. B is₂O₃The content of (B) is preferably 0 to 20%, 0 to 12%, 0 to 10%, or 0.5 to 8%, particularly preferably 1 to 7%. B is₂O₃When the content (b) is too small, the meltability and devitrification resistance are liable to be lowered, and the resistance to a hydrofluoric acid-based chemical solution is liable to be lowered. On the other hand, B₂O₃When the content of (b) is too large, the Young's modulus and strain point tend to be lowered.

MgO is a component that reduces high-temperature viscosity and improves meltability, and significantly improves young's modulus in alkaline earth metal oxides. The content of MgO is preferably 0 to 15%, 0 to 8%, 0 to 7%, 0 to 6%, or 0 to 3%, particularly preferably 0 to 2%. When the content of MgO is too small, the meltability and Young's modulus are liable to decrease. On the other hand, when the content of MgO is too large, devitrification resistance is liable to decrease and the strain point is liable to decrease.

CaO is a component that does not cause a decrease in strain point, lowers high-temperature viscosity, and significantly improves meltability. Further, since the raw material to be introduced is relatively inexpensive, the alkaline earth metal oxide is a component for reducing the raw material cost. The content of CaO is preferably 1 to 15%, 3 to 11%, or 4 to 10%, and particularly preferably 5 to 9%. When the content of CaO is too small, the above effects are hardly obtained. On the other hand, when the content of CaO is too large, the glass is easily devitrified and the thermal expansion coefficient is easily increased.

SrO is a component that suppresses phase separation and improves resistance to devitrification. Further, the component is a component that improves the melting property by reducing the high-temperature viscosity without lowering the strain point, and is a component that suppresses the increase in the liquid phase temperature. The SrO content is preferably 0 to 15%, or 0.1 to 9%, and particularly preferably 0.5 to 6%. When the SrO content is too small, the above-described effects are hardly obtained. On the other hand, when the SrO content is too large, strontium silicate-based devitrification crystals are likely to be precipitated, and thus devitrification resistance is likely to be lowered.

BaO is a component that significantly improves resistance to devitrification. The content of BaO is preferably 0 to 15%, 0 to 12%, or 0.1 to 9%, particularly preferably 1 to 7%. When the content of BaO is too small, it is difficult to obtain the above-described effects. On the other hand, when the content of BaO is too large, the density becomes too high and the meltability is liable to decrease. Further, devitrified crystals containing BaO are likely to precipitate, and the liquid phase temperature is likely to rise.

ZrO₂Has effects of increasing strain point and Young's modulus. However, ZrO₂When the content of (b) is too large, the devitrification resistance is remarkably reduced. In particular containing SnO₂When ZrO is strictly regulated, it is preferable₂The content of (a). ZrO (ZrO)₂The content of (b) is preferably 0.4% or less, or 0.3% or less, particularly preferably 0.01 to 0.2%.

In addition to the above components, for example, the following components may be added. From the viewpoint of reliably obtaining the effects of the present invention, the content of the other components than the above components is preferably 10% or less, and particularly preferably 5% or less, in total.

In the method for producing a silicate glass of the present invention, it is preferable that the silicate glass is 10^2.5The glass batch is prepared so that the temperature at dPa · s is preferably 1500 ℃ or higher, 1530 ℃ or higher, 1540 ℃ or higher, or 1550 ℃ or higher. 10^2.5The temperature at dpas corresponds to the melting temperature, and becomes more refractory as the temperature becomes higher. As described above, the more refractory the silicate glass is, the more necessary it is to enhance the refining power at the initial melting temperature, and the effect of the present invention becomes relatively large。

The silicate glass of the present invention is characterized by being produced by the above-described method for producing a silicate glass. The technical features of the silicate glass of the present invention have already been described in the description of the method for producing the silicate glass of the present invention. Therefore, the silicate glass of the present invention will not be described in detail.

The silica raw material for silicate glass is characterized by containing 0.01-2 mass% of alkaline earth metal component in terms of oxide. Further, the silica raw material for silicate glass of the present invention is characterized in that CO is generated in a temperature range of 1000 to 1400 ℃₂A gas. Furthermore, the silica raw material for silicate glass of the present invention preferably generates CO at a temperature of 1000 to 1400 ℃₂Gas and H₂And (4) O gas. The technical features of the silica raw material for silicate glass of the present invention are described in the description of the method for producing silicate glass of the present invention. Therefore, the silica raw material for silicate glass of the present invention will not be described in detail.

Example 1

The present invention is described below based on examples. The following examples are merely illustrative. The present invention is not limited in any way by the following examples.

Sample No.1, which is an example of the present invention, is a silica raw material (silica sand) collected from a high-purity silica sand layer formed by erosion of a dolomite deposit. Sample No.2 is a comparative example of the present invention, and is a conventional silica raw material (silica sand) which is generally used.

The contents of the minor constituents in samples No.1 and 2 are shown in Table 1.

[ Table 1]

(wt：ppm)	No.1	No.2
			Fe₂O₃	25	110
MgO	300	15
			CaO	700	25
TiO₂	20	180

Then, with respect to samples No.1 and 2, CO at the time of heating in the temperature range of 200 ℃ to 1300 ℃ at the temperature rise rate of 8 ℃/min was measured by a quadrupole mass spectrometer₂And (4) releasing the amount. The results are shown in FIG. 1. Further, H in samples No.1 and 2 was measured by a quadrupole mass spectrometer at a heating rate of 8 ℃/min in a temperature range of 200 ℃ to 1300 ℃₂And (4) releasing amount of O. The results are shown in FIG. 2. In the figure, (1) indicates data of sample No.1, and (2) indicates data of sample No. 2.

As can be seen from FIGS. 1 and 2, sample No.1 produced CO in a wide temperature range from 600 ℃ to 1200 ℃₂Gas and H₂And (4) O gas. On the other hand, sample No.2 hardly generates CO at the time of heating at high temperature₂Gas, H₂The amount of generated O gas is also small.

Decomposition of carbonate generally occurs at a temperature of about 800 ℃ and CO is also observed in sample No.1 at a temperature of about 800 ℃₂The generation of gas. Further, sample No.1, CO was also observed in a temperature range where decomposition of carbonate was completed, i.e., at a high temperature of 1000 ℃ or higher₂The generation of gas. This phenomenon is considered to be caused by the fact that it takes time for the carbonate of the alkaline earth metal present inside the silica particles to release CO from the surface of the silica particles₂Gases, as a result, release CO at high temperatures above 1000 ℃₂A gas. For the same reason, it is considered that H is also observed in sample No.1 in the temperature range where the hydroxide salt is completely decomposed, that is, at a high temperature of 1000 ℃ or higher₂Generation of O gas.

Example 2

After preparing glass batches using the silica raw materials of samples nos. 1 and 2 as silica supply sources, alkali-free glasses were produced according to a conventional method. Specifically, the silicate glass contains SiO in mass%₂60％、Al₂O₃19％、B₂O₃6.5％、MgO 2.3％、CaO 6％、SrO 0.5％、BaO 5.5％、SnO₂Preparing a glass batch by blending various glass raw materials in an amount of 0.2% as a glass composition, charging the obtained glass batch into a continuous melting furnace, melting at 1500-1600 ℃, clarifying and stirring the molten glass, supplying the molten glass to a forming apparatus, forming the molten glass into a flat plate shape having a thickness of 0.7mm by an overflow down-draw method, cutting the flat plate shape into a size of 1800mm × 1500mm, obtaining a glass plate, and measuring SO remaining in the obtained glass plate₃Amount of the compound (A). The glass plate sample of sample No.1 and the glass plate of sample No.2 were produced under the same conditions except for the silica raw material.

As a result, SO remained in the glass plate of sample No.2 was larger than that in the glass plate of sample No.1₃The amount was 1.3 times. Further, the glass plate of sample No.2 had 10 times the number of bubbles as compared with the glass plate of sample No. 1. This is considered to be because, when the silica raw material of sample No.1 is used, CO is generated at a temperature of about 1200 ℃ during melting₂Gas, and further H₂The amount of O gas generated is also large, the refining power at the initial stage of melting is enhanced, and the amount of dissolved gas in the molten glass is reduced.

It is considered that the phenomenon obtained in the above experiment also occurs in the case of the materials (samples nos. a to I) shown in table 2.

[ Table 2]

(wt％)	A	B	C	D	E	F	G	H	I
										SiO₂	62.5	62.2	60.0	62.3	62.5	62.5	59.5	61.3	61.2
Al₂O₃	19.0	17.0	16.5	18.4	18.5	20.0	17.5	19.6	16.5
										B₂O₃	6.0	10.3	10.0	4.6	2.4	7.2	8.2	2.5	11.2
MgO	0.8	1.4	0.5	2.4	2.1	0.2	2.5	5.1	1.8
										CaO	7.5	7.9	8.0	5.0	4.4	9.8	4.1	4.4	5.6
SrO	2.0	0.8	4.0	2.6	2.2	0.0	7.8	7.0	2.6
										BaO	2.0	0.0	0.7	4.5	7.7	0.0	0.2	0.1	0.7
ZrO₂	0.0	0.2	0.1	0.0	0.0	0.0	0.2	0.0	0.0
										K₂O	0.0	0.0	0.0	0.0	0.0	0.3	0.0	0.0	0.3
SnO₂	0.2	0.2	0.2	0.2	0.2	0.2	0.0	0.0	0.2

Claims

1. A method for producing a silicate glass, characterized in that a silicate glass is produced by melting and shaping a glass batch,

introducing a glass batch material containing 0.01 to 0.3 mass% of Mg component in terms of MgO and 0.01 to 0.3 mass% of Ca component in terms of CaO, and generating CO in a temperature range of 1000 to 1400 DEG C₂The silicon dioxide starting material of the gas is,

the Mg component and Ca component in the silica raw material are contained in the form of carbonate.

2. The method of claim 1, wherein Fe is introduced into the glass batch₂O₃A silica raw material containing 0.001 to 0.008 mass% of Fe in terms of weight.

3. A method for producing a silicate glass according to claim 1 or 2, characterized in that CO is generated in the glass batch at a temperature in the range of 1000 ℃ to 1400 ℃₂Gas and H₂A silica raw material of O gas.

4. The method for producing a silicate glass according to claim 1 or 2, wherein the content of the S component in the glass composition of the silicate glass is SO₃The silicate glass is produced in an amount of less than 0.01% by mass in terms of the weight.

5. A method for producing a silicate glass according to claim 1 or 2, wherein As is contained in the glass composition of the silicate glass₂O₃Content of (B) is less than 0.05 mass%, Sb₂O₃Less than 0.05 mass%, SnO₂The glass batch is prepared in such a manner that the content of (b) is 0.01 to 1 mass%.

6. The method of producing a silicate glass according to claim 1 or 2, wherein the glass batch is prepared in such a manner that the content of alkali metal oxide in the glass composition of the silicate glass is less than 0.5 mass%.

7. The method for producing a silicate glass according to claim 1 or 2, wherein the silicate glass contains SiO in terms of glass composition by mass%₂50％～80％、Al₂O₃5％～25％、B₂O₃0-20%, MgO 0-15%, CaO 1-15%, SrO 0-15%, and BaO 0-15%.

8. The method of producing a silicate glass according to claim 1 or 2, wherein the silicate glass is formed into a flat plate shape by an overflow down-draw method or a float method.

9. The method according to claim 1, wherein the silica raw material is natural quartz sand.

10. A silicate glass produced by the method for producing a silicate glass according to any one of claims 1 to 9.