WO2006080444A1

WO2006080444A1 - Process for producing glass

Info

Publication number: WO2006080444A1
Application number: PCT/JP2006/301331
Authority: WO
Inventors: Yutaka Senshu; Junji Kurachi; Akihiro Koyama; Hiromitsu Seto; Kazuhiro Yamamoto; Daisuke Miyabe
Original assignee: Nippon Sheet Glass Company, Limited
Priority date: 2005-01-31
Filing date: 2006-01-27
Publication date: 2006-08-03
Also published as: JP2008105860A

Abstract

A process for producing a glass containing substantially no alkali metal oxide and substantially no clarifier which is As2O3 or Sb2O3. It has a high clarifying effect. A molten glass containing water is formed by at least one means selected among selecting ingredients for a raw glass material batch, adding water to a raw glass material batch, introducing water into a melting atmosphere for molten-glass formation, and introducing water into a molten glass so as to yield a glass having a β-OH in the range of 0.2-0.35 mm-1. The molten glass formed is clarified in a reduced-pressure atmosphere which has a lower partial water vapor pressure than the melting atmosphere.

Description

Specification

Glass manufacturing method

Technical field

The present invention relates to a glass manufacturing method, and more specifically to a glass manufacturing method suitable for manufacturing an alkali-free glass used for a display substrate or the like.

Background art

[0002] As a glass used for substrates of various displays such as a liquid crystal display, a glass composition substantially free of an alkali component, particularly sodium is suitable. The melting temperature of a glass composition substantially free from alkali components (non-alkali glass) is higher than that of a general glass composition such as soda lime glass. For this reason, as a fining agent used in the production of alkali-free glass, an arsenic compound such as Aso, which has a good fining action even in a high temperature range, has been representative. However, from the viewpoint of reducing the environmental load

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Therefore, it is desirable to use a clarifier that does not contain arsenic.

[0003] For example, in the international publication WO98 / 03442 pamphlet (Japanese Patent Publication No. 2001-500098: reference 1), the glass production process is such that j8-OH in the obtained glass is less than about 0.5. By keeping the water content in the molten glass low, antimony compounds such as Sb 2 O, which are usually not as efficient at high melting temperatures, can be used as fining agents instead of As O.

2 3 2 3

It has been shown that good fining can be performed. According to the production method of Document 1, alkali-free glass that contains substantially no arsenic (concentration of less than 0.02 mol%) can be produced. The use of Sb 2 O as the agent is preferred

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The preferred content of the obtained glass is in the range of 0.2 to 0.5 mol%. In order to further reduce the burden on the environment, it is desirable to use a clarifier that does not contain antimony as well as arsenic, but the method described in Document 1 is difficult. Reference 1 shows that a halide is reduced to a glass raw material batch as a desiccant to reduce the amount of water in the glass!

[0004] In addition to Reference 1, glass manufacturing methods using moisture in molten glass are disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-128549 (Reference 2), Japanese Patent Application Laid-Open No. 10-114529 (Reference 3), Kaihei 11-797 No. 55 (Reference 4) and Japanese Unexamined Patent Application Publication No. 2002-293547 (Reference 5).

[0005] In Document 2, the glass raw material is melted by heat obtained by the combustion of fuel and oxygen gas to obtain a molten glass having a higher content of water and carbon dioxide than before. It has been shown that it can be clarified under reduced pressure better while reducing the degree of reduced pressure. However, the method of Document 2 is predicated on the use of oxygen gas and requires a high cost.

[0006] References 3 and 4 include Na SO, As O and Sb O in the glass manufacturing process.

It has been shown that the amount of fining agent can be reduced by using a conventional fining agent such as 2 4 2 3 2 3 and dissolved water in combination. Reference 5 shows that by defining the relationship between the water content in molten glass and the pressure during clarification under reduced pressure, bubbles and ash defects in the obtained glass can be reduced. Documents 3 to 5 are methods for producing glass containing a large amount of alkali components. In the production of such an alkali-containing glass, a sulfate raw material is generally used as a fining agent. For example, in Examples 3 to 5, a sulfate raw material is used as a fining agent. However, in a glass composition having a low basicity such as an alkali-free glass, the solubility of SO in the glass composition is low, and SO tends to remain as bubbles.

3 2

It is not preferable to use a sulfate raw material as a fining agent. For this reason, it is difficult to apply the methods of References 3 to 5 to the production of alkali-free glass as they are.

[0007] In addition, in References 2 to 4, there is no disclosure or suggestion of a method for performing clarification well without using antimony compound and β-OH in the obtained glass. Disclosure of the invention

[0008] The present invention provides an arsenic compound such as As O and an antimony compound such as Sb 2 O as a clarifying agent.

2 3 2 3

It is an object of the present invention to provide a method for producing a glass that can provide a high clarification effect without using a copper compound.

[0009] The method for producing a glass of the present invention comprises an alkali metal oxide, AsO and a fining agent.

2 3 Glass with virtually no Sb O, i.e. As O and Sb O as fining agents

This is a method for producing alkali-free glass substantially free of 2 3 2 3 2 3. In the production method of the present invention, selection of components in the glass raw material batch, addition of water to the glass raw material batch, so that j8-OH in the obtained glass is in the range of 0.2 to 0.35 mm- ¹ . Introduction of water into the melting atmosphere that forms the molten glass and introduction of water into the molten glass At least one of them forms a molten glass containing water, and the formed molten glass is clarified in a reduced pressure atmosphere having a water vapor partial pressure lower than that of the molten atmosphere.

[0010] Here, j8-OH reflects the content of hydroxyl groups (hydroxyl groups) in the glass and is a value measured by infrared spectroscopy (IR spectroscopy). The amount of moisture in the glass can be estimated from the value of β OH, and the larger the value, the greater the amount of moisture.

[0011] β OH may be obtained as follows.

(1) Measure the infrared absorption spectrum of the obtained glass in the wavelength range of 2700-2900 nm, and let T be the minimum transmittance in the spectrum.

1

(2) Separately from the above (1), measure the infrared transmittance of the obtained glass at a wavelength of 2500 nm, and let the transmittance be T. The wavelength of 2500 nm is derived from the hydroxyl group in the glass

0

It is located in the wavelength region where there is no absorption, and is the reference wavelength for determining β OH.

(3) Let d (mm) be the thickness of the glass sample used for the measurements in (1) and (2) above, and β according to the formula: β— Ο H = (1 / d) Find OH.

10 0 1

[0012] According to the production method of the present invention, a glass with a reduced number of bubbles can be obtained by a high clarification effect without using an arsenic compound and an antimony compound as a clarifier.

Brief Description of Drawings

FIG. 1 is a diagram showing the relationship between j8-OH and the number of bubbles in a glass sample produced in the example.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, the present invention will be described in detail.

[0015] In the melting step in the production method of the present invention, the amount of water contained is increased compared to the conventional method! A molten glass is formed. That is, the proportion of water (H 2 O) in the gas components dissolved in the molten glass is substantially equal to the alkali metal oxide formed in the conventional melting process.

2

It is larger than a molten glass having a composition (non-alkali composition).

[0016] Here, as long as 13-OH in the obtained glass is in the range of 0.2 to 0.35mm- ¹ , the amount of water contained in the molten glass formed in the melting step is larger. High clarification effect can be obtained. The reason for this is not clear, but for example, consider the following reasons: available.

[0017] In the melting step, an equilibrium is established between a gas component dissolved in the molten glass and a gas corresponding to the gas component in the melting atmosphere, for example, water vapor when the gas component is water. Yes. For this reason, the water vapor partial pressure in the molten atmosphere can be increased by increasing the amount of water contained in the molten glass. On the contrary, when the partial pressure is increased, the partial pressures of nitrogen and carbon dioxide in the molten atmosphere are decreased, and thus the partial pressures of these gases in the bubbles contained in the molten glass are also decreased. Since nitrogen and carbon dioxide have a low diffusion rate in the molten glass and a low solubility in the molten glass, bubbles whose nitrogen or carbon dioxide partial pressure has been reduced are absorbed into the glass as the molten glass solidifies. Cheap. For this reason, it is considered that the clarification effect can be enhanced as the partial pressures of nitrogen and carbon dioxide in the molten atmosphere are reduced.

[0018] In the clarification step in the production method of the present invention, β-OH in the obtained glass is 0.

The molten glass formed in the melting step is clarified in a reduced pressure atmosphere (clarified atmosphere) with a partial pressure of water vapor lower than that of the molten atmosphere so as to be in the range of 2 to 0.35 mm ¹ .

[0019] In the clarification step, by using the clarification atmosphere, the amount of water contained in the molten glass can be reduced and clarification can be promoted. A clarification effect can be obtained.

That is, from the viewpoint of the amount of moisture contained in the molten glass, in the production method of the present invention, a molten glass having a large amount of moisture is formed in the melting step, and the amount of moisture is reduced in the refining step. It can be said that there is. In other words, in the production method of the present invention, the melting process is performed in a melting atmosphere having a relatively high water vapor partial pressure so that j8-OH in the obtained glass is in the range of 0.2 to 0.35 mm- ¹ . It can be said that the clarification process is performed in a clarification atmosphere with a relatively low water vapor partial pressure. As described above, the production method of the present invention is different from the production method disclosed in Document 1 in which the moisture content in the molten glass in the glass production process is kept low.

[0021] Further, the amount of moisture in the molten glass can be effectively reduced by setting the clarification atmosphere. For example, after the clarification step, the glass is homogeneously mixed by stirring for the purpose of reducing striae. In this case, the generation of bubbles in the steps after the clarification step can be suppressed, for example, the generation of bubbles due to the cavity can be suppressed.

[0022] In the production method of the present invention, the molten glass is formed by the melting step so that 13 OH in the obtained glass is 0.3 mm ¹ or less, and the formed molten glass is clarified by the clarification step. It is preferable. In the production method of the present invention, the molten glass is formed by the melting step so that j8-OH in the obtained glass is 0.24 mm ¹ or more, and the formed molten glass is clarified by the clarification step. It is preferable to do. In these cases, a higher clarification effect can be realized, and a glass with a reduced number of bubbles can be obtained. The above melting and clarification steps may be performed so that j8—OH in the obtained glass is in the range of 0.24-0.3 mm- ¹ .ヽ.

[0023] A method for forming a molten glass containing water over the melting step is as follows.

(A) selection of ingredients in glass raw material batch,

(B) adding water to the glass raw material batch,

(C) introduction of water into the melting atmosphere, and

(D) introduction of water into the molten glass,

It is sufficient that at least one force is selected. For example, also in the method (C), since equilibrium is established between water vapor in the molten atmosphere and water in the molten glass, a molten glass containing water can be formed. The melting step in the production method of the present invention is general except that the molten glass containing water is formed by at least one of the above methods so that j8-OH of the obtained glass falls within a predetermined range. Apply the melting process in the alkali-free glass manufacturing method.

[0024] The selection method of (A) is not particularly limited. For example, if the glass raw material containing water as the component and at least one glass raw material selected to generate water during melting are selected. Good.

[0025] As a glass raw material that generates water at the time of melting, for example, a hydrate having hydrated water (crystal water), a hydroxide or the like may be used.

[0026] The addition method of (B) is not particularly limited. For example, after spraying water onto a glass raw material batch, the batch may be melted. [0027] The method for introducing (C) is not particularly limited. For example, (C 1) supply of water to the melting atmosphere, and (C 2) generation of water in the melting atmosphere, and at least one selected by force are performed. Just do it.

[0028] The method of (C-1) is not particularly limited. For example, water or separately formed water vapor is melted into a melting atmosphere via a pipe or the like, more specifically, to a melting tank for melting a glass raw material batch. , Supply. When supplying water, for example, water may be sprayed into the melting atmosphere (to the inside of the melting tank). In addition, for the formation of water vapor to be supplied, waste heat from a melting tank or a clarification tank for clarification of molten glass may be used.

[0029] The method (C-2) is not particularly limited. For example, a gas containing hydrogen gas may be burned in a melting atmosphere. The heat generated by the combustion of the gas can be used as a heat source for melting the glass raw material batch. However, in terms of manufacturing cost, the combustion power must not be the main heat source for melting the glass raw material batch. Favored ,.

[0030] The method for introducing (D) is not particularly limited. For example, water vapor may be published into the molten glass.

[0031] Among the above methods (A), (B), (C) and (D), the water content in the molten glass is relatively easy to control. It is preferable to form a molten glass containing. Among them, it is preferable to introduce water into the melting atmosphere by the method (C1) because of its low cost and easy control of the amount of water introduced into the melting atmosphere.

[0032] In the clarification step, the method for obtaining a clarified atmosphere having a reduced partial pressure of water vapor and a reduced pressure as compared with the melting atmosphere is not particularly limited.

[0033] In order to obtain a higher clarification effect, it is preferable to increase the degree of decompression, but excessive decompression causes an increase in production cost and makes it difficult to configure the production equipment. Specifically, for example, it is preferable to set the clarified atmosphere to about 51 kPa (0.5 atm) or less and to less than about lOkPa (0.1 atm).

[0034] The temperature of the molten glass at the time of clarification is usually in the range of about 1400 to 1600 ° C, more preferably in the range of about 1450 to 1550 ° C.

[0035] When heating of the molten glass is necessary in the clarification step, it is preferable to perform the heating by a method that does not generate water vapor. In this case, compared to the water vapor partial pressure of the molten atmosphere. Thus, the water vapor partial pressure in the clear atmosphere can be kept lower. Examples of such heating methods include heater heating, heating by direct energization of glass, induction using electromagnetic waves and dielectric heating, and combustion of fuels that do not contain hydrogen, such as carbon monoxide and carbon. The method used is mentioned.

[0036] The clarification step in the production method of the present invention is a general production of alkali-free glass except that the molten glass is clarified in the clarification atmosphere so that the β-OH of the obtained glass falls within a predetermined range. The clarification process in the method may be applied.

[0037] The production method of the present invention may include an optional step such as a homogenization step in addition to the melting step and the clarification step.

[0038] In the production method of the present invention, except for arsenic compounds and antimony compounds, a refining agent usually used in the production of alkali-free glass may be used. For example, chlorine may be used as a refining agent. Chlorine forms hydrogen chloride in the molten glass by reaction with water, and the formed salt hydrogen can remove the molten glass force relatively easily. Chlorine also has the effect of reducing the surface tension of the molten glass. For these reasons, clarification of the molten glass in the clarification process can be promoted by using chlorine as a clarifier.

[0039] In order to use chlorine as a fining agent, for example, a glass raw material batch may contain salty soup. When a glass raw material batch contains chloride, the chloride content in the batch is usually in the range of about 0.02 to 5% by weight in terms of C1 and an external number relative to the total of components other than chloride. The range of 0.02 to 1% by weight is preferable, and the range of 0.02% to less than 0.5% by weight is more preferable.

[0040] As the chloride, it is preferable to use MgCl and Z or CaCl! /.

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[0041] When the glass raw material batch contains a chloride, the C1 content in the obtained glass becomes smaller than the C1 content in the glass raw material batch due to the desorption of C1 in the clarification step. The content of C1 in the obtained glass is not particularly limited, but is, for example, in the range of 0.01 to 2.5% by weight, preferably in the range of 0.01 to 2% by weight. A range of 5% by weight is more preferred.

[0042] In the production method of the present invention, fluorine may be used together with chlorine as a fining agent. Although fluorine is less effective in reducing the surface tension of molten glass than chlorine, It has the effect of reducing the viscosity of the gas and increasing the rising speed of the bubbles. For this reason, the clarification of the molten glass in the clarification process can be further promoted by using fluorine together with chlorine as a clarifier.

[0043] In order to use fluorine as a fining agent, for example, a glass raw material batch may further contain fluoride. When a glass raw material batch contains fluoride, the content of food salt in the batch is an F number and an external number relative to the total of components other than chloride and fluoride, and usually contains chloride in the batch. It may be less than the rate. More specifically, for example, the range up to about 3% by weight is preferred, the range up to about 1% by weight is preferred, and the range up to 0.5% by weight is more preferred.

[0044] Since the effect of clarification promotion by fluorine is based on the effect of reducing the surface tension of molten glass by chlorine, the effect of promoting clarification even if the fluorine content is excessively increased beyond the chlorine content. Is thought to improve little.

[0045] As fluorides, MgF and

2 Use Z or CaF! /.

2

[0046] When the glass raw material batch contains fluoride, the F content in the obtained glass is smaller than the F content in the glass raw material batch, as in the case of C1. The content of F in the obtained glass is not particularly limited, but is, for example, in the range of 0 to 1.5% by weight, preferably in the range of 0 to 0.5% by weight. 0 to 0.3% by weight % Range is more preferred.

[0047] The production method of the present invention can be widely applied regardless of its glass composition as long as it is non-alkali glass, and in particular, can be suitably applied to the production of aluminoborosilicate glass. Here, alkali-free means substantially an alkali metal oxide, specifically Na 0, K Ο and Li O.

2 2 2 means not included. The glass obtained by the production method of the present invention contains As O and Sb.

2 3 2

In the present specification, “substantially free”, including the fact that it does not substantially contain O.

Three

Unless stated in the above, impurities inevitably mixed from industrial glass raw materials are intended to allow trace components of less than 0.1% by weight.

[0048] Although the specific composition of the aluminoborosilicate glass is not particularly limited, the production method of the present invention may be used for the production of glass (glass composition) having the following composition.

[0049] Expressed by weight percent,

SiO 45-75% AI O 5-25%

B O 2-20%

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MgO 0-10%

CaO 0-15%

SrO 0-15%

BaO 0-25%

MgO + CaO + SrO + BaO

ZnO 0-10%

CI 0.01-2.5%

F 0 ~ 1.5%

including.

[0050] Further, the production method of the present invention,

SiO 45-75%

2

AI O 5-25%

twenty three

B O 2-20%

twenty three

MgO 0-10%

CaO 0-15%

SrO 0-15%

BaO 0-25%

MgO 4-CaO + SrO + BaO

ZnO 0-10%

CI 0.01-2.5%

F 0 ~ 1.5%

It can be used to make powerful glass.

[0051] Preferred ranges of the content of each of the above components in the glass obtained by the production method of the present invention are as follows. In addition, the display of “%” in the description of each component means “heavy transition%”.

[0052] (SiO 2) SiO is an essential component that forms a glass network, and its content is less than 45%.

2

The chemical durability of the glass will decrease, and if it exceeds 75%, the meltability of the glass will deteriorate.

[0053] The content of SiO is preferably in the range of 58 to 65%, more preferably in the range of 59 to 64.5%.

2

Yes.

[0054] (Al O)

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Al O is an essential component that suppresses devitrification of glass and improves its heat resistance.

twenty three

The When the Al O content is less than 5%, the heat resistance of the glass decreases.

twenty three

As the acid resistance of the steel decreases, the meltability deteriorates.

[0055] The Al O content is preferably in the range of 10 to 20%, more preferably in the range of 10% or more and less than 17%.

twenty three

preferable.

[0056] (B O)

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B O

23 3 is an essential component that lowers the viscosity of the molten glass and facilitates melting of the glass by acting as a flux. When the content of B 2 O is less than 2%, it is difficult to melt and clarify the glass.

twenty three

When it exceeds 20%, the strain point of the obtained glass is lowered.

[0057] The content of B 2 O is preferably in the range of 5 to 17%, more preferably in the range of 8 to 16%.

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[0058] Further, the lower limit of the content of B 2 O is preferably 8% by weight or more, more preferably 10% by weight or more.

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That's right.

[0059] (MgO)

MgO is an optional component that improves the meltability of the glass without lowering the strain point of the resulting glass. If the MgO content exceeds 10%, the devitrification temperature of the glass increases.

[0060] The content of MgO is preferably in the range of 0 to 5%, more preferably in the range of 1 to 2.5%.

[0061] (CaO)

CaO is an optional component that reduces the high temperature viscosity of the glass. If the CaO content exceeds 15%, the devitrification temperature of the glass increases.

[0062] The CaO content is preferably in the range of 3 to 10%, more preferably in the range of 5 to 9%.

[0063] (SrO)

SrO is an optional component that improves its meltability without reducing the devitrification resistance of the glass. is there. If the SrO content exceeds 15%, the thermal expansion coefficient of the glass becomes too large.

[0064] The SrO content is preferably in the range of 0 to 3%, more preferably in the range of 0 to 2.5%.

[0065] (BaO)

BaO is an optional component that suppresses devitrification of the glass. If the BaO content exceeds 25%, the thermal expansion coefficient of the glass becomes too large.

[0066] The content of BaO is preferably in the range of 0 to 2%, and more preferably in the range of 0 to 0.5%.

[0067] (MgO + CaO + SrO + BaO)

If the total content of MgO, CaO, SrO and BaO is less than 5%, the meltability of the glass decreases, and if it exceeds 35%, the thermal expansion coefficient becomes too large. The total is preferably in the range of 5-20%, more preferably in the range of 7-13%.

[0068] (C1)

A range of 0.01 to 2% is preferred. A range of 0.01 to 0. 5% is more preferred.

[0069] (F)

A range of 0 to 0.5% is preferred. A range of 0 to 0.3% is more preferred.

[0070] The glass obtained by the production method of the present invention may contain components other than the above-described components as necessary. These components include, for example, NiO, CoO, CrO, etc.

2 3 color components are included, and the content thereof is usually less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.2% by weight and less than 0.1% by weight.

[0071] The glass obtained by the production method of the present invention may be substantially free of SO.

Three

Yes.

Example

[0072] Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

[0073] (Example 1)

(Preparation of glass raw material batch)

First, in terms of oxide, SiO: 60%, Al 2 O: 14%, B 2 O: 15%, MgO: 2%,

2 2 3 2 3

CaO: 8%, SrO: and such that 1% of the composition (all weight ^_0/0), mixed with glass material. Next, with respect to 100 parts by weight of the obtained mixture, CaCl and CaF as clarifying agents, 0.24 parts by weight and 0.1 part by weight were further added to obtain a glass raw material batch. As the glass raw material, use the hydroxide for A1 and B (boron), and use MgO hydrate for Mg. The water content in the glass raw material batch is 7.7% by weight. I made it.

[0074] (Melting process)

The glass raw material batch thus prepared was put into a platinum crucible housed in a furnace maintained at atmospheric pressure and melted at 1600 ° C. for 2 hours using the furnace. At this time, the water vapor partial pressure in the melting atmosphere was adjusted by continuously supplying a certain amount of water into the furnace from the start to the end of the melting.

[0075] Water was supplied to the inside of the furnace through the nove by passing a platinum pipe from the outside through the center of the bottom of the furnace. At this time, a base for the crucible is assembled in the furnace using refractory bricks so that the stable water supply is achieved and the supplied water does not directly contact the platinum crucible for melting the glass raw material batch. The crucible was housed away from the bottom of the furnace. During melting, the opening of the furnace was covered so that the water vapor generated in the furnace was confined by supplying water. A tubing pump was used to control the amount of water supplied.

[0076] (Clarification process)

Next, the water supply was stopped and the furnace temperature was set to 1500 ° C, and the furnace pressure was reduced to about 10 kPa (0.1 atm) by applying the pressure in the furnace for 20 minutes. Subsequently, after maintaining this pressure and temperature for 30 minutes, while maintaining the temperature, the pressure in the furnace was increased for 20 minutes to return to atmospheric pressure, whereby the molten glass was clarified under reduced pressure. Thereafter, the crucible was taken out from the furnace and rapidly cooled to room temperature, and the obtained glass lump was gradually cooled to obtain a glass sample for evaluation.

[0077] (Evaluation of the number of bubbles)

In the glass sample obtained in this way, a section of 3 cm X 3 cm was set in the part where the foam layer was not seen in the surface layer part, and the number of bubbles existing up to a depth of 10 mm was also counted in the surface layer force in the section. . The number of bubbles was counted by irradiating light from the lower side of each sample and projecting the light transmitted through the sample on the screen (magnification factor 10 times). The bubbles to be counted were taken to have a length in the major axis direction of 50 m or more at the original size, and the number of counted bubbles was converted to the number per lg of glass. [0078] (| 8—OH rating)

J8-OH in the glass sample obtained as described above was determined by the method described above.

[0079] (Evaluation of remaining ratio of fining agent)

The residual ratio of the fining agents (C1 and F) in the glass samples obtained as described above was determined by semi-quantitative analysis using fluorescent X-rays. In addition, the calculated | required residual rate is a value as a content rate in a glass composition.

[0080] In Example 1, with respect to Example Samples 1 to 2 in which the amount of water supplied was changed in the melting process, and Comparative Sample A with no water supplied, the number of bubbles, β-ΟΗ, And the clarifier residual rate was evaluated.

[0081] Table 1 below shows the evaluation results together with the amount of water supplied in each sample.

[0082] [Table 1]

[0083] As shown in Table 1, the value of j8-OH in the obtained glass sample was 0.2 to 0 compared to Comparative Sample A in which the value of j8-OH was less than 0.2 mm ^1. In Example Samples 1 and 2 that were in the range of 35 mm— ¹ , the number of bubbles could be reduced.

[0084] (Example 2)

In terms of oxide, SiO: 63%, A1 0: 16%, B 2 O: 11%, MgO: 2%, CaO: 6

2 2 3 2 3

%, SrO: After mixing the glass raw materials so as to have a composition of 2% (all by weight%), CaCl and CaF were added as fining agents to 100 parts by weight of the obtained mixture, respectively.

twenty two

A glass raw material batch was prepared by further adding parts by weight and 0.1 part by weight. In the same manner as in Example 1, the water content in the glass raw material batch was adjusted to 11.5% by weight.

[0085] Next, a glass sample was obtained in the same manner as in Example 1 except that the glass raw material batch was used. I got it.

[0086] Next, the number of bubbles, j8-OH, and the clarifying agent remaining rate in the glass sample thus obtained were determined in the same manner as in Example 1.

[0087] In Example 2, with respect to Example Samples 3 to 5 in which the amount of water supplied was changed in the melting step, and Comparative Sample B with no water supplied, the number of bubbles, β-ΟΗ, And the clarifier residual rate was evaluated.

[0088] The evaluation results are shown in Table 2 below together with the amount of water supplied in each sample.

[0089] [Table 2]

[0090] As shown in Table 2, the value of j8-OH was 0.2 to 0. 0 compared to Comparative Sample B in which the 13-OH value in the obtained glass sample was less than 0.2 mm. In Example Samples 3 to 5 which were in the range of 35 mm- ¹ , good fining could be realized and the number of bubbles could be reduced.

[0091] The results of Examples 1 and 2 are collectively shown in Fig. 1 by a graph in which the horizontal axis is set to β OH and the vertical axis is set to the number of bubbles.

[0092] As shown in FIG. 1, a high clarification effect is obtained when the value of j8-OH in the obtained glass sample is 0.2 mm ¹ or more, and the higher the β OH value, the higher the value. It was found that a clear clarification effect was obtained. The range of j8-OH, 0. 2~0. 35mm "1 force S preferably, 0. 24~0. 35mm" \ 0. 2~0. 3mm- preferably from ¹ force S, 0. 24~0. 3 mm "1 gave even more favorable results.

[0093] The lower limit of β-OH may be determined according to the desired quality with respect to the number of bubbles in the obtained glass. According to the results of the above example, when the value of β OH is at least about 0.24 mm ¹ , the number of bubbles was reduced particularly, that is, the number of bubbles. A glass having a particularly good quality is obtained.

[0094] On the other hand, the upper limit of βOH is considered to be determined by the amount of water contained in the molten glass and the partial pressure of water vapor in the clarified atmosphere.

Here, even if an attempt is made to increase the amount of water contained in the molten glass, for example, from the following points:

There is a limit to the increase in the amount of moisture.

(1) The types of compounds that can be used as a glass raw material are limited. For example, there are not many choices of hydrates and hydroxides that can supply moisture.

(2) If excessive water is added to the raw material batch, defects will occur when the batch is charged, and the homogeneity of the glass will be impaired. Further, extra energy is required to melt the glass, and the economic efficiency is impaired.

(3) If a large amount of water vapor is supplied to the molten atmosphere, the energy loss due to the endotherm of water will be large, the temperature in the furnace will decrease, and extra energy will be required, which will impair economic efficiency.

[0096] Therefore, there is a limit to the amount of water that can be contained in the molten glass, and as a result, the value of ι8-OH in the obtained glass is also limited. The upper limit of beta-OH, in consideration of the degree of quality improvement of on the number of bubbles, 0. 35 mm ¹ or less are preferred, 0. 3 mm ¹ or less is more preferable.

[0097] The present invention can be applied to other embodiments without departing from its intent and essential characteristics. The embodiments disclosed in this specification are illustrative in all respects and are not limited thereto. The scope of the present invention is shown not by the above description but by the appended claims, and all modifications that are equivalent in meaning and scope to the claims are included therein.

Industrial applicability

[0098] As described above, according to the present invention, a high clarification effect can be realized without using an arsenic compound and an antimony compound as a clarifier, and a glass with a reduced number of bubbles can be obtained. The glass obtained by the production method of the present invention is suitable for substrates for various displays such as a liquid crystal display substrate and a plasma display substrate.

Claims

The scope of the claims

[1] Substantially free of alkali metal oxides and As O and Sb O as fining agents

2 3 2 3

A method for producing glass,

Selection of components in the glass raw material batch, addition of water to the glass raw material batch, and melting atmosphere for forming molten glass so that j8-OH in the obtained glass is in the range of 0.2 to 0.35 mm- ¹ . Water-containing molten glass is formed by at least one selected from introduction of water into the glass and introduction of water into the molten glass,

A method for producing glass, wherein the formed molten glass is clarified in an atmosphere having a reduced partial pressure of water vapor and lower pressure than the molten atmosphere.

[2] The method for producing glass according to claim 1, wherein the molten glass is formed so that the β-OH is 0.3 mm ¹ or less, and the formed molten glass is clarified.

[3] The method for producing glass according to claim 1, wherein the molten glass is formed so that the β-OH is 0.24 mm ¹ or more, and the formed molten glass is clarified.

[4] The beta-OH such that the range of 0. 24-0. 3 mm ^1, wherein the forming the molten glass, fining the molten glass obtained by the forming method of the glass according to claim 1.

5. The method for producing glass according to claim 1, wherein the molten glass containing the water is formed by introducing water into the molten atmosphere.

6. The glass production method according to claim 1, wherein a glass raw material containing water and at least one glass raw material capable of generating water at the time of melting are also selected as the component.

[7] The introduction of water into the melting atmosphere is performed by at least one selected from supply of water to the melting atmosphere and generation and force of water in the melting atmosphere. Production method.

8. The method for producing glass according to claim 1, wherein the introduction of water into the molten glass is performed by supplying water vapor into the molten glass.

[9] The method for producing glass according to [1], wherein the glass raw material batch contains a chloride.

10. The method for producing glass according to claim 9, wherein the glass raw material batch further contains a fluoride.

[11] The method for producing glass according to [1], wherein the glass is an aluminoborosilicate glass.

[12] The glass is expressed by weight%,

SiO 45 75%

2

〇〇

Al O 5 '25%

twenty three

B O 2 20%

twenty three

O L

MgO 0 '10%

CaO 0 -15%

SrO 0 -15%

BaO 0- -25%

MgO— CaO- f SrO + BaO

ZnO 0 -10%

CI

F 0 -1.5%

The method for producing glass according to claim 1, comprising:

[13] The glass is substantially represented by weight percent.

SiO 45 75%

2

Al O 5 25%

twenty three

B O 2 20%

twenty three

MgO 0 L0%

CaO 0 15%

SrO 0 15%

BaO 0 25%

MgO—-CaO + SrO + BaO

ZnO 0 10%

CI

F 0 1.5%

The method for producing glass according to claim 12, comprising:

14. The gas according to claim 12, wherein the content of B 2 O in the glass is 10% by weight or more.

twenty three

A manufacturing method for laths.

15. The method for producing glass according to claim 1, wherein the glass does not substantially contain SO.