JP2007137696A - Manufacturing method of glass sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of glass sheet excellent in bubble quality while minimizing the usage of arsenic oxide. <P>SOLUTION: The glass sheet is manufactured by preparing a glass raw material batch containing as a clarificant an arsenic oxide at least a part of which is diarsenic pentaoxide (As<SB>2</SB>O<SB>5</SB>) and at least one kind selected from an antimony oxide, a tin oxide and a cerium oxide, melting this glass raw material batch and forming it to glass sheet. The clarificant can contain for example 0.01-0.5 pt.mass of an arsenic oxide, 0-3 pts.mass of an antimony oxide, 0-2 pts.mass of a tin oxide and 0-1 pt.mass of a cerium oxide against 100 pts.mass of the residue that is removed the clarificant from the glass raw material batch. In the clarificant, even if the total of the pts.mass of the antimony oxide, the tin oxide and the cerium oxide is larger than the pts.mass of the arsenic oxide, glass sheet having a good bubble quality can be manufactured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a glass plate characterized by a clarification method, and more particularly to a method for producing a glass plate useful for producing alkali-free glass.

  When melting the glass raw material, a so-called clarifier is added. This fining agent usually has an effect of growing bubbles by the generation of gas by its own decomposition at the initial stage of the melting process of the raw material, and promoting the detachment of the bubbles contained therein from the molten glass. Further, in the latter half of the melting step, the fining agent has an effect of absorbing the gas in the remaining fine bubbles and promoting the disappearance thereof.

Alkali glass has recently been in increasing demand as a liquid crystal display substrate and the like, but since the melting point is high, clarification is important for maintaining quality. In the case of alkali-free glass, arsenous acid (As ₂ O ₃ ) has been conventionally used as a fining agent. In addition to arsenous acid, an oxidant typified by nitrate has been added to promote clarification.

On the other hand, antimony trioxide (Sb ₂ O ₃ ) is known to show the same effect as As ₂ O _3, and is described in “Glass Engineering Handbook (Masayuki Yamane et al., P292, Asakura Shoten, 1999)”. Are described in part in place of As ₂ O ₃ .

In recent years, the burden on the environment due to raw materials tends to be emphasized in various fields. In the field of alkali-free glass, which is mainly used for TFT liquid crystal substrates, it has been proposed to convert As ₂ O ₃ that has been used as a fining agent into Sb ₂ O ₃ and SnO _2, which have less environmental burden. ing. For example, see Japanese Patent Application Laid-Open Nos. 10-59741 and 10-114538.

JP-A-10-59741 discloses a method for producing an alkali-free glass characterized by “adding 0.05 to ₂ % by weight of SnO ₂ as a fining agent” and not using As ₂ O ₃ as a fining agent. Has been.

Japanese Patent Application Laid-Open No. 10-114538 is characterized by “adding 0.05 to ₂ % by weight of SnO ₂ and 0.05 to 3% by weight of Sb ₂ O ₃ as clarifying agents”. A method for producing alkali-free glass that does not use As ₂ O ₃ is disclosed.

A clarification method using SnO ₂ , Sb ₂ O ₃ and As ₂ O ₃ in combination has also been proposed.

For example, Japanese Patent Application Laid-Open No. 10-130034 discloses that “as a fining agent, 0.05 to ₂ % by weight of As ₂ O ₃ and 0.05 to ₂ % by weight of SnO ₂ are added to a glass raw material preparation. A method for producing alkali-free glass ”is disclosed.

Japanese Patent Application Laid-Open No. 2001-151534 discloses “As ₂ O ₃ 0-0.5%, SnO ₂ 0.05-1%, Sb ₂ O ₃ 0.05-5” as a clarifier in mass%. % "Is disclosed.

As described above, arsenic oxide added to the raw material as a fining agent is usually arsenous acid (As ₂ O ₃ ), which is a trivalent arsenic oxide, but as arsenic oxide, pentavalent arsenic oxidation is performed. Also known is arsenic pentoxide (As ₂ O ₅ ; hereinafter referred to as arsenic pentoxide), which is a product.

Japanese Patent Application Laid-Open No. 2001-261365 describes the production of glass for a magnetic disk that allows an alkali component, but “SO ₃ , As ₂ O ₅ , Sb ₂ O _5, etc. to promote glass clarification. May be contained ".

Incidentally, in JP-A-63-225552, alkali-free borosilicate glass composition for fiber, fining As ₂ O _5, more fining As ₂ O ₅ + CeO _2, is disclosed. In addition, this glass composition contains 16-25 weight% of CaO as an essential component.
Glass Engineering Handbook (Masayuki Yamane et al., P292, Asakura Shoten, 1999) Japanese Patent Laid-Open No. 10-59741 JP-A-10-114538 Japanese Patent Laid-Open No. 10-130034 JP 2001-151534 A JP 2001-261365 A JP-A-63-225552

  An object of this invention is to provide the manufacturing method of the glass plate excellent in foam quality, reducing the usage-amount of an arsenic oxide as much as possible.

  The present invention prepares a glass raw material batch containing arsenic oxide, at least a part of which is arsenic pentoxide, and at least one selected from antimony oxide, tin oxide and cerium oxide as a fining agent, and melts the glass raw material batch And the manufacturing method of the glass plate which shape | molds and obtains a glass plate is provided.

According to the study of the present inventor, at least a part of arsenic oxide is arsenic pentoxide (As ₂ O ₅ ) and is used as a clarifier with at least one selected from antimony oxide, tin oxide and cerium oxide together with arsenic oxide. Thus, it becomes possible to produce a glass plate excellent in foam quality while reducing the amount of arsenic oxide added.

  Hereinafter, all the% indications indicating the component content are mass%.

Details of the reason why glass with excellent foam quality can be produced while reducing the amount of arsenic oxide added by using at least a part of arsenic oxide as arsenic pentoxide (As ₂ O ₅ ) with other fining agents. Although it is not clear, I think as follows.

Usually, arsenic acid used as arsenic oxide (arsenic trioxide: As ₂ O ₃ ) is deprived of oxygen released from nitrate used in combination with arsenic at 1000 to 1200 ° C., and becomes As ₂ O ₅ . When it returns to As ₂ O ₃ again at a higher temperature of 1300 ° C. or higher, oxygen is released. The glass is clarified by the stirring effect of oxygen.

Here, when arsenic pentoxide (As ₂ O ₅ ) is used as arsenic oxide, for example, it is not necessary to deprive oxygen released from nitrate, and oxygen can be released more efficiently. Therefore, it is considered that clarification is performed well.

  In addition, clarification is performed in a wide temperature range by using other clarifiers having different decomposition temperatures in combination. For example, antimony oxide releases oxygen at a much lower temperature than arsenic oxide. Cerium oxide decomposes at 1400 ° C. and releases oxygen. This is also considered to be performed well.

In the production method of the present invention, it is sufficient that at least a part of arsenic oxide is arsenic pentoxide, and arsenic acid (arsenic trioxide: As ₂ O ₃ ) may be included as arsenic oxide.

In a preferred embodiment of the present invention, the glass raw material batch contains at least one selected from antimony oxide and tin oxide, particularly at least antimony oxide, as a fining agent. Specifically, the antimony oxide may be at least one selected from antimony pentoxide (Sb ₂ O ₅ ) and antimony trioxide (Sb ₂ O ₃ ). In another preferred embodiment of the present invention from another aspect, the glass raw material batch comprises at least a) antimony oxide at least partly of antimony pentoxide, and b) at least one selected from tin oxide and cerium oxide. Contains as a fining agent. In this embodiment, the glass raw material batch may contain at least tin oxide as a fining agent. In this case, the glass raw material batch contains antimony pentoxide and tin oxide as a fining agent together with arsenic oxide.

  Although there is no particular limitation on the glass composition to which the production method of the present invention is applied, the present invention is prepared so that the balance obtained by removing the clarifier from the raw material batch is a glass that does not substantially contain an alkali metal oxide. In particular, it is suitable for the case where it is prepared so as to be a glass having substantially the following composition.

SiO ₂ 45~70%,
Al ₂ O ₃ 7.5-25%,
B ₂ O ₃ 4-17.5%,
MgO 0-10%,
CaO 0-10%,
SrO 0-10%,
BaO 0-30%,
MgO + CaO + SrO + BaO 5-30%,
TiO ₂ 0-5%,
ZrO ₂ 0-5%,
ZnO 0-5%,
Cl ₂ 0-0.5%,
SO ₃ 0~0.5%.

The above composition, the ingredients other than the above typified by _{Fe 2 O 3, Na 2 O} , may be contained in an amount of less than 0.1%, respectively. In particular, in industrial production of glass, it may be difficult to avoid a small amount of impurities derived from industrial raw materials. In this specification, “substantially” means to allow the presence of a trace component in a range of less than 0.1%. Therefore, “a glass substantially free of alkali metal oxide” means a glass having an alkali metal oxide content of less than 0.1%.

In addition, the components listed above include components having a clarifying action such as Cl ₂ and SO ₃ , but here, all components except arsenic oxide, antimony oxide, tin oxide and cerium oxide are included. It will be included in the “remainder”. In the present specification, “the refining agent” is four components of arsenic oxide, antimony oxide, tin oxide and cerium oxide.

The present invention is suitable for producing glass having a high SiO ₂ content and a high melting point due to this high content. The present invention is particularly suitable when the “remainder” is prepared to be a glass containing 57 to 70% SiO ₂ .

In the production method of the present invention, the refining agent is defined as 100 parts by mass of the balance obtained by removing the refining agent from the glass raw material batch.
0.01 to 0.5 parts by mass of arsenic oxide,
0 to 3 parts by mass of antimony oxide,
0-2 parts by mass of tin oxide,
Cerium oxide 0 to 1 part by mass,
It is preferable to contain.

  According to the present invention, the foam quality of glass can be improved while limiting the amount of arsenic oxide contained in the fining agent. For example, the arsenic oxide contained in the fining agent may be 0.01 to 0.25 parts by mass, 0.01 to 0.15 parts by mass, and further 0.01 to 0.1 parts by mass. The refining agent may contain 0.01 to 3 parts by mass of antimony oxide, may contain 0.05 to 2 parts by mass of tin oxide, and 0.05 to 1 part by mass of cerium oxide. May be included.

  In the production method of the present invention, in the fining agent, the total mass of antimony oxide, tin oxide and cerium oxide may be larger than the mass part of arsenic oxide, and the mass of antimony oxide, tin oxide and cerium oxide. The total of the parts may be 3 times or more, more preferably 5 times or more of the mass part of arsenic oxide.

  In the production method of the present invention, it is preferable that half (50%) or more, 60% or more, more preferably 90% or more of arsenic oxide is arsenic pentoxide on a mass basis, and the total amount of arsenic oxide is arsenic pentoxide. There may be.

The present invention is suitable when the glass raw material batch is prepared so that the remainder has the composition exemplified above. Further, the glass raw material batch further has a strain point of 575 ° C., particularly 630 ° C. Higher, and suitable for a glass manufacturing method prepared so as to obtain a glass having a thermal expansion coefficient of 28 to 46 × 10 ⁻⁷ / ° C. Further, the glass raw material batch is further suitable for a glass manufacturing method prepared such that the temperature when the melt of the glass raw material batch is 10 ² dPa · sec is 1615 ° C. or higher.

  In the production method of the present invention, the remainder obtained by removing the fining agent from the glass raw material batch may contain an oxidizing agent. As the oxidizing agent, nitrates and / or sulfates, in particular, at least one selected from nitrates of group 2 elements represented by magnesium, calcium, strontium and barium and sulfates of group 2 elements are suitable.

  The oxidizing agent that is nitrate and / or sulfate may be added so as to be up to 10 parts by mass in the remaining 100 parts by mass of the glass raw material batch excluding the refining agent.

  When an oxidizing agent is used in the production method of the present invention, it is preferable to premix the clarifying agent and the oxidizing agent in order to enhance the fining action. That is, a mixture of arsenic oxide, at least one selected from antimony oxide, tin oxide and cerium oxide and an oxidizing agent is prepared, and then this mixture is mixed with the remainder of the glass raw material batch excluding the above mixture. Then, it is good to obtain a glass raw material batch.

  The melting of the glass raw material batch and the molding of the melted batch may be performed according to a known method. The glass raw material batch may be melted at a temperature according to its composition, for example, 1550 ° C. or higher.

  The molten glass raw material batch is formed into a predetermined shape and slowly cooled. The molten glass raw material batch is formed into a glass plate by, for example, a fusion method, a downdraw method, a float method, or various methods obtained by improving these.

  Hereinafter, the reason for limitation will be described for the glass compositions exemplified above for which the present invention is preferably applied. However, the following% display is a mass% display.

SiO ₂ is a component that forms a network of glass. If the content is too low, the chemical resistance of the glass is deteriorated, the strain point is lowered, and sufficient heat resistance cannot be obtained. On the other hand, if the content is too high, the viscosity in the high temperature range becomes high and melting becomes difficult. Accordingly, the lower limit of SiO ₂ is preferably 45%, more preferably 50%, particularly 57%. A preferable upper limit of SiO ₂ is 70%.

Al ₂ O ₃ is a component that suppresses the devitrification of glass and improves heat resistance. If the content is too low, devitrification tends to occur. On the other hand, if the content is too high, the acid resistance decreases and the meltability deteriorates. Therefore, the lower limit of Al ₂ O ₃ is preferably 7.5%, more preferably 10%. The upper limit of Al ₂ O ₃ is preferably 25%, more preferably 20%.

B ₂ O ₃ is a component that improves the meltability of glass, suppresses devitrification, and improves chemical resistance, particularly durability against buffered hydrofluoric acid. If the content is too low, the meltability of the glass deteriorates and the durability against buffered hydrofluoric acid is insufficient. On the other hand, if the content is too high, the strain point of the glass is lowered and the heat resistance becomes insufficient. Therefore, the lower limit of B ₂ O ₃ is preferably 4%, more preferably 7.5%. The upper limit of B ₂ O ₃ is preferably 17.5%, more preferably 15%.

  MgO, CaO, SrO and BaO contain at least one of them, and the total content is preferably 5 to 30%. If the total content is too low, melting of the glass becomes difficult. On the other hand, when the total content is too high, the expansion coefficient of the glass becomes too large. Therefore, a preferable lower limit of the total content is 5%, and a preferable upper limit of the total content is 30%, and further 17.5%.

  MgO is a component that can improve the meltability of glass without significantly lowering the strain point. When the content rate is too high, the devitrification temperature of glass will become high. Therefore, the upper limit of MgO is preferably 10%, more preferably 7.5%.

  CaO is a component having the same effect as MgO. When the content rate is too high, the devitrification temperature of glass will become high. Therefore, the preferable upper limit of CaO is 10%.

  SrO is a component that can improve the meltability without deteriorating the devitrification of the glass. If the content is too high, the expansion coefficient of the glass becomes too large. Therefore, the preferable upper limit of SrO is 10%.

  BaO is a component that can suppress the devitrification of the glass. If the content is too high, the expansion coefficient of the glass becomes too large. Therefore, the upper limit of BaO is preferably 30%, more preferably 15%.

For example, TiO ₂ can be contained up to about 5% within a range not impairing the function as a display substrate.

ZrO ₂ increases the strain point of the glass and improves acid resistance and alkali resistance, so it is a desirable component to contain. However, if the content exceeds 5%, striae and devitrification are likely to occur, and the meltability is also deteriorated.

  ZnO is a component that can suppress the devitrification of the glass and improve the meltability. When the content exceeds 5%, the strain point of the glass is lowered.

Cl ₂ is a component that acts as a fining agent and may remain up to 1% in the glass.

SO ₃ is a component that may remain up to 0.5% in the glass as the remainder of the sulfate used as the oxidizing agent.

  In summary, the glass composition to which the present invention can be applied more preferably is as follows.

SiO ₂ 50~70%,
Al ₂ O ₃ 10-20%,
B ₂ O ₃ 7.5~15%,
MgO 0-7.5%,
CaO 0-10%,
SrO 0-10%,
BaO 0-15%,
MgO + CaO + SrO + BaO 5 to 17.5%,
TiO ₂ 0-5%,
ZrO ₂ 0-5%,
ZnO 0-5%,
Cl ₂ 0-0.5%,
SO ₃ 0~0.5%
It is the glass composition which consists of.

(Examples 1 to 10)
Basic glass raw materials were respectively prepared so as to have the basic glass composition shown in Table 1 in terms of oxide. The basic glass raw material is 100 parts by mass, and the clarifiers shown in Table 2 and Table 3 are added to the basic glass raw material at the indicated mass part ratios. did. Moreover, the mass part shown in Table 2 and Table 3 among 100 mass parts of basic glass raw materials was added as a sulfate or nitrate.

(Table 1)
――――――――――――――――――――――――――――――――――――――
Component SiO ₂ Al ₂ O ₃ B ₂ O ₃ MgO CaO SrO BaO
――――――――――――――――――――――――――――――――――――――
Mass% 60.5 15.0 7.5 1.5 5.5 4.0 6.0
――――――――――――――――――――――――――――――――――――――

As raw materials for each composition component, basically, SiO ₂ : silica powder, Al ₂ O ₃ : alumina, B ₂ O ₃ : boric acid, MgO: magnesium carbonate, CaO: calcium carbonate, SrO: strontium carbonate, BaO: Barium carbonate was used.

  However, when sulfate was used as the oxidizing agent, calcium sulfate was used as a part of the calcium raw material. When nitrate was used as the oxidizing agent, magnesium, strontium, and barium nitrate were used, and the amount of nitrate was adjusted by changing the ratio with carbonate.

In addition, as a raw material for the fining agent, an oxide having a valence as shown in the table was used. In other words, the arsenic trioxide as a raw material of e.g. As ₂ O _3, as the material of the As ₂ O ₅ was pentoxide arsenic.
Further, in Example 8, the clarifier (arsenic pentoxide, antimony pentoxide and tin oxide) and the oxidizing agent were mixed (preliminarily mixed) in advance before mixing with the basic glass raw material.

(Table 2)
――――――――――――――――――――――――――――――――――――――
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
――――――――――――――――――――――――――――――――――――――
As ₂ O ₃ 0.1 0.05 0.075 −−− −−− −−−
As ₂ O ₅ 0.1 0.1 0.025 0.1 0.1 0.1
Sb ₂ O ₃ 2.0 2.0 --- ---- -------
Sb ₂ O ₅ --- ---- 2.0 2.0 2.0 2.0
SnO ₂ −−− 0.4 −−− −−− −−− −−−
CeO ₂ --- ---- --- ---- ---- 0.5
――――――――――――――――――――――――――――――――――――――
Oxidizing agent Sulfate --- --- ---- --- 1.5 ----
Nitrate 9.4 9.4 9.4 ----------
――――――――――――――――――――――――――――――――――――――
Premixing------
――――――――――――――――――――――――――――――――――――――
Number of bubbles 25 75 160 160 140 120
(Pieces / 100g)
――――――――――――――――――――――――――――――――――――――
Arsenic oxide volatilization 0.6 0.4 0.3 0.3 0.3 0.3 0.3
(G / kg)
――――――――――――――――――――――――――――――――――――――
* In the table, the component is expressed by mass%.

(Table 3)
――――――――――――――――――――――――――――
Example 7 Example 8 Example 9 Example 10
――――――――――――――――――――――――――――
As ₂ O ₃ --- --- ---- ----
As ₂ O ₅ 0.1 0.1 0.1 0.1
Sb ₂ O ₃ --- --- ---- ----
Sb ₂ O ₅ 2.0 2.0 ---- 2.5
SnO ₂ 0.1 0.1 1.0 ----
CeO ₂ --- ---- ---- ----
――――――――――――――――――――――――――――
Oxidizing agent Sulfate --- --- ---- ----
Nitrate 9.4 9.4 9.4 9.4
――――――――――――――――――――――――――――
Premixing-Yes--
――――――――――――――――――――――――――――
Number of bubbles 60 40 55 40
(Pieces / 100g)
――――――――――――――――――――――――――――
Arsenic oxide volatilization 0.3 0.3 0.3 0.3
(G / kg)
――――――――――――――――――――――――――――
* In the table, the component is expressed by mass%.

  Each batch prepared in this way was melted in an electric furnace at 1600 ° C. for 4 hours using a platinum crucible, and then the melt was poured onto a stainless steel plate to form a plate, and then cooled to room temperature. The number of bubbles was measured using an optical microscope at 5 cm square at the center of each obtained glass, and converted to the number per 100 g. Each result was combined with Table 2 and Table 3, and was shown.

  In addition, the residual amount of arsenic oxide in the obtained glass was measured by a fluorescent X-ray quantitative method using a calibration curve. From the difference between the residual amount and the amount added to the raw material, arsenic oxide volatilized during melting The amount of was determined. The amount of volatilization was converted per kg of glass. Table 2 and Table 3 show the volatilization amount of arsenic oxide thus obtained.

(Comparative Examples 1-3)
Comparative Example 1 is an example in which arsenic oxide was not added.
Comparative Example 2 is an example in which the entire amount of arsenic oxide was added with arsenous acid (As ₂ O ₃ ).
Comparative Example 3 is a conventional reference example in which a large amount of arsenic oxide (arsenous acid) was added and antimony oxide was not added.

  About Comparative Examples 1-3, the basic glass raw material was each prepared similarly to the Example mentioned above. The basic glass raw material is 100 parts by mass, and the clarifier and the oxidant shown in Table 4 are added to the basic glass raw material in proportions shown in Table 4, respectively. Batch.

(Table 4)
――――――――――――――――――――――――――
Comparative Example 1 Comparative Example 2 Comparative Example 3
――――――――――――――――――――――――――
As ₂ O ₃ ---- 0.1 1.2
Sb ₂ O ₃ 2.0 -------
Sb ₂ O ₅ --- 2.0 ----
――――――――――――――――――――――――――
Oxidizing agent Nitrate 9.4 9.4 9.4
――――――――――――――――――――――――――
Number of bubbles 280 200 30
(Pieces / 100g)
――――――――――――――――――――――――――
Arsenic oxide volatilization amount --- 0.3 3.6
(G / kg)
――――――――――――――――――――――――――
* In the table, the component is expressed by mass%.

  These batches were melted in the same manner as in the examples to obtain glass. The number of bubbles was also measured in the same manner, and the results are shown in Table 4.

In the following, what has been found by comparing the examples and comparative examples will be described.
From the results of comparison between Examples 1 to 10 and Comparative Examples 1 and 2, the number of bubbles can be reduced by using arsenic pentoxide as a clarifier and using it together with other clarifiers and oxidants.

  In Examples 1-10, the example with the largest ratio of an arsenic oxide is Example 1, The ratio is 0.2 mass part with respect to 100 mass parts of basic glass compositions, Comprising: 0.25 mass part It is as follows. Furthermore, in Examples 3-10, it is 0.1 mass part.

  From the comparison between Examples 1 and 8 and Comparative Example 3, when arsenic pentoxide was used as a fining agent and antimony oxide or tin oxide was used in combination, the amount of arsenic oxide was 1/6 or 1/10, respectively. Even if it is less than the following, the number of bubbles is at a level that does not change much. Therefore, even if arsenic oxide is 0.25 parts by mass or less, further 0.1 parts by mass or less with respect to 100 parts by mass of the basic glass composition, the foam quality is good.

  From the comparison between Example 3 and Comparative Example 2, it can be seen that the number of bubbles decreases when at least part of arsenic oxide is arsenic pentoxide.

  Example 2 and Example 7 are compared with reference to Example 1 and Example 3. As a result, Example 7 shows that although the amount of arsenic oxide is small, the total amount of arsenic oxide is used as arsenic pentoxide, so the number of bubbles is reduced.

  From the comparison between Example 4 and Comparative Example 2, it can be seen that the number of bubbles increases unless arsenic oxide is used in the form of arsenic pentoxide.

  From the comparison between Example 5 and Example 6, it can be seen that the number of bubbles decreases when cerium oxide is used simultaneously as a fining agent in addition to arsenic pentoxide and antimony pentoxide.

  From the comparison between Example 4 and Example 7, it can be seen that the number of bubbles is reduced when tin oxide is used simultaneously as a fining agent in addition to arsenic pentoxide and antimony pentoxide.

  From the comparison between Example 7 and Example 8, it can be seen that the number of bubbles decreases even when the combination of clarifiers and their amounts are the same by premixing.

  From the results of Example 9, it can be seen that the number of bubbles decreases when arsenic pentoxide and tin oxide are used simultaneously as fining agents.

  From the comparison between Example 4 and Example 5, it is understood that the number of bubbles decreases when sulfate is used as the oxidizing agent.

  In the comparative example 1, it is a case where only antimony trioxide is used as a clarifier, and it turns out that there are many bubbles.

  In Comparative Example 3, it is understood that arsenic acid is used as a fining agent, so that the number of bubbles is small, but the volatilization amount of arsenic oxide is large.

The thermal expansion coefficient of the glass obtained from each Example was in the range of 28 to 46 × 10 ⁻⁷ / ° C., and the strain points were all 630 ° C. or higher. In addition, the temperature when the viscosity of the melt of the glass raw material batch of each example was 10 ² d · sec was 1615 ° C. or higher. The thermal expansion coefficient was measured according to JIS R 3102. The strain point was measured according to JIS R 3103. Viscosity was measured according to JIS R 3104.

  The present invention has a great utility value in the technical field of glass production, as it provides a method for producing glass with excellent foam quality while reducing the amount of arsenic oxide used as much as possible.

Claims (25)

Preparing a glass raw material batch containing arsenic oxide, at least a part of which is arsenic pentoxide, and at least one selected from antimony oxide, tin oxide and cerium oxide as a fining agent;
A method for producing a glass plate, wherein the glass raw material batch is melted and molded to obtain a glass plate.   The manufacturing method of the glass plate of Claim 1 in which the said glass raw material batch contains at least 1 sort (s) chosen from an antimony oxide and a tin oxide at least as a clarifier.   The manufacturing method of the glass plate of Claim 2 in which the said glass raw material batch contains an antimony oxide at least as a clarifier. The glass raw material batch is at least
a) antimony oxide, at least a portion of which is antimony pentoxide;
b) at least one selected from tin oxide and cerium oxide;
The manufacturing method of the glass plate of Claim 1 which contains as a clarifier.   The manufacturing method of the glass plate of Claim 4 in which the said glass raw material batch contains a tin oxide at least as a clarifier. The balance obtained by removing the refining agent from the glass raw material batch is expressed in mass%, and is prepared so as to be a glass having substantially the following composition. Manufacturing method of glass plate.
SiO ₂ 45~70%,
Al ₂ O ₃ 7.5-25%,
B ₂ O ₃ 4-17.5%,
MgO 0-10%,
CaO 0-10%,
SrO 0-10%,
BaO 0-30%,
MgO + CaO + SrO + BaO 5-30%,
TiO ₂ 0-5%,
ZrO ₂ 0-5%,
ZnO 0-5%,
Cl ₂ 0-0.5%,
SO ₃ 0~0.5% The remainder other than the glass raw batch the fining agent, were prepared with glass containing SiO ₂ of 57 to 70 mass%, manufacturing method for a glass plate according to claim 6. The balance of the glass raw material batch excluding the refining agent as 100 parts by mass, the refining agent,
0.01 to 0.5 parts by mass of arsenic oxide,
0 to 3 parts by mass of antimony oxide,
0-2 parts by mass of tin oxide,
Cerium oxide 0 to 1 part by mass,
The manufacturing method of the glass plate of any one of Claims 1-7 containing these.   The manufacturing method of the glass plate of Claim 8 in which the said clarifier contains 0.01-0.25 mass part arsenic oxide.   The manufacturing method of the glass plate of Claim 9 in which the said clarifier contains 0.01-0.15 mass part arsenic oxide.   The manufacturing method of the glass plate of Claim 10 in which the said clarifier contains 0.01-0.1 mass part arsenic oxide.   The manufacturing method of the glass plate of any one of Claims 8-11 in which the said clarifier contains 0.01-3 mass parts antimony oxide.   The manufacturing method of the glass plate of any one of Claims 8-12 in which the said clarifier contains 0.05-2 mass parts tin oxide.   The manufacturing method of the glass plate of any one of Claims 8-13 in which the said clarifier contains 0.05-1 mass part cerium oxide.   The manufacturing method of the glass plate of any one of Claims 8-14 in which the sum total of the mass part of the said antimony oxide, the said tin oxide, and the said cerium oxide is larger than the mass part of the said arsenic oxide in the said clarifier. .   The manufacturing method of the glass plate of Claim 15 whose sum total of the mass part of the said antimony oxide, the said tin oxide, and the said cerium oxide is 5 times or more of the mass part of the said arsenic oxide in the said clarifier.   The method for producing a glass plate according to any one of claims 1 to 16, wherein at least half of the arsenic oxide is arsenic pentoxide on a mass basis.   The manufacturing method of the glass plate of Claim 17 which adds the whole quantity of the said arsenic oxide as an arsenic pentoxide. The glass plate according to claim 6, wherein the glass raw material batch is prepared such that a glass having a strain point higher than 575 ° C. and a thermal expansion coefficient in a range of 28 to 46 × 10 ⁻⁷ / ° C. is obtained. Manufacturing method. The glass plate according to claim 6, wherein the glass raw material batch is prepared so that a glass having a strain point higher than 630 ° C. and a thermal expansion coefficient in a range of 28 to 46 × 10 ⁻⁷ / ° C. is obtained. Manufacturing method. The manufacturing method of the glass plate of Claim 6 prepared so that the temperature when the viscosity of the melt of the said glass raw material batch was 10 < ² > dPa * sec might become 1615 degreeC or more.   The manufacturing method of the glass plate of any one of Claims 1-21 in which the remainder except the said clarifier from the said glass raw material batch contains an oxidizing agent.   The method for producing a glass plate according to claim 22, wherein the oxidizing agent is at least one selected from a nitrate of a Group 2 element and a sulfate of a Group 2 element.   A mixture of the arsenic oxide, at least one selected from the antimony oxide, tin oxide and cerium oxide and the oxidizing agent is prepared, and the mixture is mixed with the remainder of the glass raw material batch to obtain the glass raw material batch. The manufacturing method of the glass plate of Claim 22 or 23 obtained.   The manufacturing method of the glass plate of any one of Claims 1-24 which melts the said glass raw material batch at 1550 degreeC or more.