JP2004075498A - Oxide-based glass and its manufacturing method - Google Patents
Oxide-based glass and its manufacturing method Download PDFInfo
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- JP2004075498A JP2004075498A JP2002241531A JP2002241531A JP2004075498A JP 2004075498 A JP2004075498 A JP 2004075498A JP 2002241531 A JP2002241531 A JP 2002241531A JP 2002241531 A JP2002241531 A JP 2002241531A JP 2004075498 A JP2004075498 A JP 2004075498A
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- oxide
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
- C03C1/004—Refining agents
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
- C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
- C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
- C03C3/093—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium
Abstract
Description
【0001】
【発明の属する技術分野】
本発明は、酸化物系ガラス及びその製造方法に関し、特にディスプレイ用途に主として使用される無アルカリの酸化物系ガラス(無アルカリガラス)とその製造方法に関するものである。
【0002】
【従来の技術】
液晶ディスプレイ等の透明ガラス基板として、無アルカリガラスが使用されている。この種の無アルカリガラスには、耐熱性、耐薬品性等の特性の他に、表示欠陥となる泡を含まないことが要求される。
【0003】
【発明が解決しようとする課題】
無アルカリガラスは、ガラス融液の粘度が高いため、アルカリ金属成分を含有するガラスに比べてより高温で溶融が行われる。無アルカリガラスの溶融では、通常1200〜1300℃でガラス化反応が起こり、1400℃以上の高温で脱泡、均質化が行われる。このため少なくとも脱泡、均質化が行われる高温域で清澄ガスを放出することができる清澄剤を使用する必要がある。このような事情から、従来、無アルカリガラスでは、幅広い温度域で清澄ガスを発生させることができるAs酸化物が清澄剤として広く用いられている。
【0004】
ところがAs酸化物は有害物質であり、その削減或いは全廃が望まれている。そこで近年では、As酸化物の代替清澄剤として、高温で清澄ガスを放出可能なSn酸化物が注目されている。
【0005】
本発明の目的は、Sn酸化物を清澄剤として効果的に機能させることにより、泡品位に優れた酸化物系ガラスを得ることにある。
【0006】
【課題を解決するための手段】
本発明者は種々の実験を行った結果、最終的に得られるガラス中のSn2+/全Snの割合が0.13以上となるような条件で製造すれば、Sn酸化物が清澄剤として効果的に機能することを見いだし、本発明として提案するものである。
【0007】
即ち、本発明の酸化物系ガラスは、Sn成分を含む酸化物系ガラスにおいて、Sn2+/全Snの割合が0.13以上であることを特徴とする。
【0008】
また本発明の酸化物系ガラスの製造方法は、清澄剤としてSn酸化物を添加したガラス原料調合物を溶融した後、成形する酸化物系ガラスの製造方法において、Sn2+/全Snの割合が0.13以上となる条件で溶融することを特徴とする。
【0009】
【発明の実施の形態】
本発明においては、清澄剤としてSn酸化物を使用する。Sn酸化物は、ガラス中で、Sn4+やSn2+の形で存在し、1400℃以上の高温で高価数種であるSn4+から低価数種であるSn2+へと価数変化する。この価数変化に伴って、清澄ガス(酸素ガス)が放出される。そして一定割合以上のSn4+がSn2+へ価数変化すると、十分なガスが放出されるため、効果的な清澄が可能となる。本発明者の実験によれば、最終的に得られたガラスのSn2+/全Snの割合が0.13以上、好ましくは0.15以上、より好ましくは0.2以上となるような条件で溶融すれば、効果的な清澄を行うのに必要な量の清澄ガスをSnの価数変化により提供できることがわかった。
【0010】
ガラスのSn2+/全Snの割合を大きくするには、例えば溶融温度を高くする、溶融時間を長くする等、の方法を採用すればよい。なお連続溶融炉を使用した工業的規模の生産においては、得られたガラスのSn2+/全Snの割合を求め、その値に応じてSn2+/全Snの割合が適正値となるように繰炉条件を変更すればよい。
【0011】
次に本発明の酸化物系ガラスを製造する方法を述べる。
【0012】
まず、清澄剤としてSn酸化物を添加したガラス原料調合物を用意する。Sn酸化物の添加量は、SnO2に換算して0.02〜2質量%が好適である。Sn酸化物の添加量が少ないと、十分な清澄効果を得ることができず、逆に多すぎるとガラスが失透する等の不都合が生じやすい。またSn酸化物としてはSnO及びSnO2の2種が存在するが、単に分解することにより清澄ガスである酸素を放出することができるSnO2を使用することが好ましい。なおSn酸化物以外の清澄剤、例えばSb酸化物、Ce酸化物、硫酸塩、塩化物等を併用することも可能である。ただしAs酸化物の添加は極力避けるべきである。
【0013】
また液晶ディスプレイ用途等に用いる場合には、ガラス原料調合物中に、実質的にアルカリ金属成分が含まれないようにすることが重要である。さらにこの用途の場合、目標組成として、質量百分率でSiO2 40〜70%、Al2 O3 6〜25%、B2 O3 5〜20%、MgO 0〜10%、CaO 0〜15%、BaO 0〜30%、SrO 0〜10%、ZnO 0〜10%、Sn酸化物 0.02〜2%、特にSiO2 55〜70%、Al2 O3 5〜20%、B2 O3 9〜20%、MgO 0〜5%、CaO 2〜15%、BaO 0〜8%、SrO 0〜8%、ZnO 0〜1%、Sn酸化物 0.02〜2%の組成を有するようにガラス原料を調合することが望ましい。上記範囲内であれば、耐熱性、耐薬品性等、液晶用途に求められる種々の特性を満足する無アルカリガラスを製造することが可能になる。
【0014】
次に、ガラス原料調合物を溶融する。このとき、最終的に得られるガラスのSn2+/全Snの割合が0.13以上、好ましくは0.15以上、より好ましくは0.2以上となるような条件で溶融することが重要である。
【0015】
その後、溶融ガラスを所定の形状に成形することにより、Sn2+/全Snの割合が0.13以上であり、泡品位に優れた酸化物系ガラスを得ることができる。なお成形方法は、用途に応じて適宜選択して使用すれば良く、例えば液晶ディスプレイの透明ガラス基板として用いる場合、フュージョンダウンドロー法、スロットダウン法等が好適に使用できる。
【0016】
【実施例】
以下、実施例に基づいて本発明を説明する。
【0017】
表1は、種々の溶融条件で溶融して作製したガラス試料を示している。実験には、質量百分率でSiO2 60%、Al2 O3 15%、B2 O3 10.5%、CaO 6%、SrO 6.5%、BaO 2%からなる基本組成を有し、さらに清澄剤としてSn酸化物(SnO2)を1%添加したガラスを使用した。
【0018】
【表1】
【0019】
各試料は次のようにして調製した。まず上記組成となるようにガラス原料を調合して、ガラス原料調合物を用意した。次いで、白金製の円錐形坩堝に充填して電気炉に入れ、表に示す条件で溶融した。その後に電気炉から取り出し、ガラスが固化したのを見計らってから、坩堝からガラス塊を取り外し、徐冷した。続いてガラス塊を、中央縦方向に10mmの厚さで切り出して評価用試料とした。
【0020】
次に、試料中央下部の2cm3(20×10×10mm厚)に残存する泡の個数を実体顕微鏡(50倍)にて計数し、5個以下のものを◎、6〜25個のものを○、26〜100個のものを●、100個をこえるものを×として清澄性を評価した。またガラス塊の一部を化学分析に供し、存在する全Sn及びSn2+を定量した。定量はガラスを酸溶液中にて分解し、機器分析および酸化還元滴定により行った。Sn2+量に関しては、分解溶液中でSn2+により還元されて生成したFe2+の量を硫酸セリウム溶液で滴定することにより間接的に求めた。具体的には、全Snは、ガラス粉末を硫酸および弗化水素酸で加熱分解し、塩酸に溶解した後にICP−AES装置を用いて定量した。Sn2+は、まず不活性ガス雰囲気中で、ガラス粉末に0.1%Fe3+溶液を2ml、さらに硫酸および弗化水素酸を添加して10分間加温(ウォーターバス中)分解させた。この加温分解中にFe3+がSn2+で還元されてFe2+が生成する。続いて硼酸を加え、過剰の弗化水素酸を中和させた後に不活性ガスの導入を中止した。その後、0.015MのOsO4溶液1mlを本反応の触媒として加え,O−フェナントロリン指示薬1.0mlを添加後にN/200硫酸セリウム溶液でオレンジ色から淡青色に変わるまで滴定する間接滴定法により、Sn2+を分析定量した。
【0021】
表から明らかなように、Sn2+/全Snの割合が0.13以上であれば良好な清澄性を示すことが確認された。
【0022】
【発明の効果】
以上説明したように、本発明によれば、Sn酸化物を清澄剤として効果的に機能させることが可能となるため、泡品位に優れた酸化物系ガラスを得ることができる。従って、無アルカリガラスのような高温溶融を必要とするガラスにおいて、As酸化物の削減或いは全廃が容易になる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an oxide-based glass and a method for producing the same, and particularly to an alkali-free oxide-based glass (alkali-free glass) mainly used for display applications and a method for producing the same.
[0002]
[Prior art]
Alkali-free glass is used as a transparent glass substrate for a liquid crystal display or the like. This kind of non-alkali glass is required to be free from bubbles that cause display defects, in addition to properties such as heat resistance and chemical resistance.
[0003]
[Problems to be solved by the invention]
Since alkali-free glass has a high viscosity of the glass melt, it is melted at a higher temperature than glass containing an alkali metal component. In the melting of alkali-free glass, a vitrification reaction usually occurs at 1200 to 1300 ° C, and defoaming and homogenization are performed at a high temperature of 1400 ° C or higher. Therefore, it is necessary to use a fining agent that can release a fining gas at least in a high temperature region where defoaming and homogenization are performed. Under such circumstances, conventionally, in an alkali-free glass, an As oxide capable of generating a fining gas in a wide temperature range has been widely used as a fining agent.
[0004]
However, As oxide is a harmful substance, and its reduction or elimination is desired. Therefore, in recent years, a Sn oxide capable of releasing a fining gas at a high temperature has attracted attention as an alternative fining agent for the As oxide.
[0005]
An object of the present invention is to obtain an oxide-based glass having excellent foam quality by effectively making a Sn oxide function as a fining agent.
[0006]
[Means for Solving the Problems]
As a result of various experiments, the present inventor has found that Sn oxide is effective as a fining agent if the glass is manufactured under conditions such that the ratio of Sn 2+ / total Sn in the finally obtained glass is 0.13 or more. The present invention has been found to function in a specific way, and is proposed as the present invention.
[0007]
That is, the oxide-based glass of the present invention is characterized in that, in the oxide-based glass containing a Sn component, the ratio of Sn 2+ / total Sn is 0.13 or more.
[0008]
Further, in the method for producing an oxide glass of the present invention, in the method for producing an oxide glass to be molded after melting a glass raw material mixture to which Sn oxide is added as a fining agent, the ratio of Sn 2+ / total Sn is reduced. It is characterized by melting under conditions of 0.13 or more.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, Sn oxide is used as a fining agent. The Sn oxide is present in the glass in the form of Sn 4+ or Sn 2+ and changes its valence from Sn 4+ which is an expensive species to Sn 2+ which is a low valence at a high temperature of 1400 ° C. or higher. A fining gas (oxygen gas) is released with the change in valence. When the valence of Sn 4+ changes to Sn 2+ at a certain ratio or more, sufficient gas is released, so that effective fining becomes possible. According to the experiment of the present inventors, under the condition that the ratio of Sn 2+ / total Sn of the finally obtained glass is 0.13 or more, preferably 0.15 or more, more preferably 0.2 or more. It has been found that when melted, the amount of fining gas required for effective fining can be provided by the change in the valence of Sn.
[0010]
In order to increase the ratio of Sn 2+ / total Sn in the glass, a method of, for example, increasing the melting temperature or lengthening the melting time may be adopted. In an industrial scale production using a continuous melting furnace, the ratio of Sn 2+ / total Sn of the obtained glass is determined, and the ratio of Sn 2+ / total Sn is adjusted to an appropriate value according to the value. The furnace conditions may be changed.
[0011]
Next, a method for producing the oxide-based glass of the present invention will be described.
[0012]
First, a glass raw material mixture to which a Sn oxide is added as a fining agent is prepared. The addition amount of Sn oxide, 0.02 to 2% by weight in terms of SnO 2 is preferred. If the added amount of Sn oxide is small, a sufficient fining effect cannot be obtained, while if too large, disadvantages such as devitrification of the glass tend to occur. Although there are two types of Sn oxide, SnO and SnO 2 , it is preferable to use SnO 2 that can release oxygen as a fining gas simply by decomposing. A fining agent other than Sn oxide, for example, Sb oxide, Ce oxide, sulfate, chloride and the like can be used in combination. However, the addition of As oxide should be avoided as much as possible.
[0013]
In addition, when used for a liquid crystal display or the like, it is important that the alkali metal component is not substantially contained in the glass raw material mixture. Further, in the case of this application, as target compositions, SiO 2 40 to 70%, Al 2 O 3 6 to 25%, B 2 O 3 5 to 20%, MgO 0 to 10%, CaO 0 to 15% by mass percentage BaO 0-30%, SrO 0-10%, ZnO 0-10%, Sn oxide 0.02-2%, especially SiO 2 55-70%, Al 2 O 3 5-20%, B 2 O 3 9 Glass having a composition of 0-20%, MgO 0-5%, CaO 2-15%, BaO 0-8%, SrO 0-8%, ZnO 0-1%, Sn oxide 0.02-2%. It is desirable to mix the raw materials. Within the above range, it becomes possible to produce an alkali-free glass satisfying various characteristics required for liquid crystal applications, such as heat resistance and chemical resistance.
[0014]
Next, the glass raw material mixture is melted. At this time, it is important that the glass finally obtained is melted under such conditions that the ratio of Sn 2+ / total Sn becomes 0.13 or more, preferably 0.15 or more, more preferably 0.2 or more. .
[0015]
Thereafter, by molding the molten glass into a predetermined shape, the ratio of Sn 2+ / total Sn is 0.13 or more, and an oxide-based glass excellent in bubble quality can be obtained. The molding method may be appropriately selected and used according to the application. For example, when the molding method is used as a transparent glass substrate of a liquid crystal display, a fusion down draw method, a slot down method, or the like can be suitably used.
[0016]
【Example】
Hereinafter, the present invention will be described based on examples.
[0017]
Table 1 shows glass samples produced by melting under various melting conditions. The experiment had a basic composition of 60% SiO 2 , 15% Al 2 O 3 , 10.5% B 2 O 3 , 6% CaO, 6.5% SrO, 2% BaO by mass percentage, and Glass to which 1% of Sn oxide (SnO 2 ) was added as a fining agent was used.
[0018]
[Table 1]
[0019]
Each sample was prepared as follows. First, a glass raw material was prepared so as to have the above-described composition to prepare a glass raw material preparation. Next, the mixture was filled in a platinum conical crucible, placed in an electric furnace, and melted under the conditions shown in the table. Thereafter, the glass was taken out of the electric furnace, and after the solidification of the glass was observed, the glass lump was removed from the crucible and gradually cooled. Subsequently, the glass lump was cut out at a thickness of 10 mm in the central longitudinal direction to obtain a sample for evaluation.
[0020]
Next, the number of bubbles remaining in 2 cm 3 (20 × 10 × 10 mm thickness) at the lower center of the sample was counted with a stereoscopic microscope (50 ×). 、, clarity was evaluated as 26 to 100, and ● as more than 100. In addition, a part of the glass lump was subjected to chemical analysis to determine the total amount of Sn and Sn 2+ present. The quantification was performed by decomposing the glass in an acid solution, and performing instrumental analysis and redox titration. Regarding the amount of Sn 2+, the amount of Fe 2+ formed by reduction by Sn 2+ in the decomposition solution was indirectly determined by titration with a cerium sulfate solution. Specifically, total Sn was quantified using an ICP-AES apparatus after the glass powder was thermally decomposed with sulfuric acid and hydrofluoric acid and dissolved in hydrochloric acid. Sn 2+ was first decomposed by heating (in a water bath) for 10 minutes by adding 2 ml of a 0.1% Fe 3+ solution to glass powder and further adding sulfuric acid and hydrofluoric acid in an inert gas atmosphere. Fe 3+ During this warming degradation is reduced by Sn 2+ and Fe 2+ is produced. Subsequently, boric acid was added to neutralize the excess hydrofluoric acid, and then the introduction of the inert gas was stopped. Thereafter, 1 ml of a 0.015 M OsO 4 solution was added as a catalyst for this reaction, and 1.0 ml of an O-phenanthroline indicator was added, followed by titration with an N / 200 cerium sulfate solution until the color changed from orange to pale blue. Sn 2+ was analyzed and quantified.
[0021]
As is clear from the table, it was confirmed that when the ratio of Sn 2+ / total Sn was 0.13 or more, good clarity was exhibited.
[0022]
【The invention's effect】
As described above, according to the present invention, an Sn-based oxide can be effectively functioned as a fining agent, so that an oxide-based glass having excellent foam quality can be obtained. Therefore, in a glass that requires high-temperature melting, such as non-alkali glass, it is easy to reduce or eliminate As oxide.
Claims (11)
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007004683A1 (en) * | 2005-07-06 | 2007-01-11 | Asahi Glass Company, Limited | Process for production of non-alkaline glass and non-alkaline glass |
JP2008069021A (en) * | 2006-09-12 | 2008-03-27 | Nippon Electric Glass Co Ltd | Alkali-free glass and alkali-free glass substrate using the same |
WO2008149888A1 (en) * | 2007-06-08 | 2008-12-11 | Nippon Electric Glass Co., Ltd. | Alkali-free glass and alkali-free glass substrate |
JP2016069246A (en) * | 2014-09-30 | 2016-05-09 | AvanStrate株式会社 | Manufacturing method for glass substrate and manufacturing apparatus for glass substrate |
ITUB20152157A1 (en) * | 2015-07-14 | 2017-01-14 | Oximet S R L | MICRO-GRANULATE INCLUDING TIN DIOXIDE, PARTICULARLY FOR THE MANUFACTURE OF GLASS. |
Citations (1)
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JPH1059741A (en) * | 1996-08-21 | 1998-03-03 | Nippon Electric Glass Co Ltd | Non-alkali glass and its production |
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Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH1059741A (en) * | 1996-08-21 | 1998-03-03 | Nippon Electric Glass Co Ltd | Non-alkali glass and its production |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007004683A1 (en) * | 2005-07-06 | 2007-01-11 | Asahi Glass Company, Limited | Process for production of non-alkaline glass and non-alkaline glass |
KR100977699B1 (en) * | 2005-07-06 | 2010-08-24 | 아사히 가라스 가부시키가이샤 | Process for production of non-alkaline glass and non-alkaline glass |
JP2008069021A (en) * | 2006-09-12 | 2008-03-27 | Nippon Electric Glass Co Ltd | Alkali-free glass and alkali-free glass substrate using the same |
WO2008149888A1 (en) * | 2007-06-08 | 2008-12-11 | Nippon Electric Glass Co., Ltd. | Alkali-free glass and alkali-free glass substrate |
JP2009013049A (en) * | 2007-06-08 | 2009-01-22 | Nippon Electric Glass Co Ltd | Alkali-free glass and alkali-free glass substrate |
US8455378B2 (en) | 2007-06-08 | 2013-06-04 | Nippon Electric Glass Co., Ltd. | Alkali-free glass and alkali-free glass substrate |
JP2016069246A (en) * | 2014-09-30 | 2016-05-09 | AvanStrate株式会社 | Manufacturing method for glass substrate and manufacturing apparatus for glass substrate |
ITUB20152157A1 (en) * | 2015-07-14 | 2017-01-14 | Oximet S R L | MICRO-GRANULATE INCLUDING TIN DIOXIDE, PARTICULARLY FOR THE MANUFACTURE OF GLASS. |
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