JP2004299947A - Alkali-free glass and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alkali-free glass using no As<SB>2</SB>O<SB>3</SB>as a clarifier, and including no foam causing display fault in using as a glass substrate for a display. <P>SOLUTION: This alkali-free glass is manufactured to contain 40-70% SiO<SB>2</SB>, 6-25% Al<SB>2</SB>O<SB>3</SB>, 5-20% B<SB>2</SB>O<SB>3</SB>, 0-10% MgO, 0-15% CaO, 0-30% BaO, 0-10% SrO, 0-10% ZnO, 0.0001-0.03% SO<SB>3</SB>, and 0.05-2% SnO<SB>2</SB>in mass%, and to contain essentially no alkali metal oxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３６】
表中の各試料ガラスは、次のようにして作製した。
【００３７】
まず表１のＳｉＯ_２、Ａｌ_２Ｏ_３、Ｂ_２Ｏ_３、ＣａＯ、ＳｒＯ、ＢａＯ、ＺｎＯの合計１００質量％となるようにガラス原料を調製し、清澄剤（ＳＯ_３、ＳｎＯ_２、Ａｓ_２Ｏ_３）は、これに添加（外挿）する形で加え混合した後、電気炉で溶融した。ガラス化反応過程での清澄性を評価するために、１６００℃で４時間と、１６００℃で８時間溶融し、また清澄過程での清澄性を評価するために１６００℃で４時間溶融した後、さらに１６５０℃で４時間溶融した。尚、ＳＯ_３は溶融時に分解するため、試料ｃ、ｅ、ｆのガラス中のＳＯ_３の残存量は、いずれの溶融条件でも０．００１質量％であった。
【００３８】
次いで溶融ガラスをカーボン板上に流し出し、徐冷した。流し出した板状ガラスの大きさは、長さ１０ｃｍ、幅６ｃｍ、高さ１ｃｍ程度であり、このガラスの流し始め１．５〜７ｃｍの部分について、ガラス中の泡数を顕微鏡を用いて目視で観察し、表に示した。この泡数は、最大径が２０μｍ以上の大きさの泡を求めたものであり、ガラス１００ｇ中の泡が１００００個を超える場合は×、１００１〜１００００個の場合は△、１０１〜１０００個の場合は○、１００個以下の場合は◎で示した。
【００３９】
また表中の歪点はＡＳＴＭ Ｃ３３６−７１の方法に基づいて測定した。粘度１０^２．５ｄＰａ・ｓの温度は、白金球引き上げ法で測定した高温粘度から、Ｆｕｌｃｈｅｒの式を用いて計算した。耐塩酸性は、各試料ガラスを８０℃に保持された１０質量％塩酸水溶液に２４時間浸漬した後、ガラスの表面状態を観察した。耐バッファードフッ酸性は、各試料ガラスを２０℃に保持された３８．７質量％フッ化アンモニウムと１．６％質量％フッ酸からなるバッファードフッ酸に３０分間浸漬した後、ガラスの表面状態を観察した。耐塩酸性と耐バッファードフッ酸性は、外観変化が無かったものを◎、外観変化が起きたものを×として示した。
【００４０】
表から明らかなように、Ａｓ_２Ｏ_３を添加した試料ａのガラスは、良好な清澄性を有していたが、清澄剤を添加しない試料ｂのガラスは清澄性が著しく悪かった。また硫酸塩（ＳＯ_３）のみを添加した試料ｃのガラスは、ガラス化過程で多量の清澄ガスが発生したものの、清澄過程では十分な清澄ガスが発生せず、結果として清澄性が悪かった。さらにＳｎＯ_２のみを添加した試料ｄのガラスは、清澄過程で多量のガスが発生したものの、ガラス化過程で十分な清澄ガスが発生せず、結果として清澄性が悪かった。
【００４１】
一方、硫酸塩とＳｎＯ_２を添加した試料ｅ、ｆのガラスは、Ａｓ_２Ｏ_３を添加した試料ａのガラスと略同等の良好な清澄性を有していた。また試料ｅ、ｆのガラスは、いずれも歪点が６６５℃であるため耐熱性に優れ、塩酸やバッファードフッ酸処理しても外観変化が認められず、耐薬品性にも優れていた。
【００４２】
【発明の効果】
以上のように、本発明の方法によれば、清澄剤として所定量の硫酸塩とＳｎＯ_２を添加するため、Ａｓ_２Ｏ_３を使用することなく、清澄性に優れ、泡の少ない無アルカリガラスを製造することが可能である。
【００４３】
また本発明の無アルカリガラスは、清澄性に優れ、泡が少なく、優れた耐熱性、耐薬品性を有しているため、特にディスプレイ用ガラス基板として好適である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an alkali-free glass, particularly to an alkali-free glass used as a transparent glass substrate for a display or the like, and a method for producing the same.
[0002]
[Prior art]
Conventionally, non-alkali glass has been used as a transparent glass substrate for a liquid crystal display or the like. Alkali-free glass for display applications is required to have no bubbles that cause display defects in addition to properties such as heat resistance and chemical resistance.
[0003]
Various glasses have been conventionally proposed as such non-alkali glass. For example, Patent Literature 1 discloses a non-alkali glass based on SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —CaO—SrO—BaO. Is disclosed.
[0004]
[Patent Document 1]
JP-A-6-263473
[Problems to be solved by the invention]
By the way, in order to obtain a bubble-free glass, a fining agent that generates a fining gas in a vitrification reaction process by a solid-phase reaction, a solid-liquid phase reaction, and a fining process in which defoaming of a glass melt is selected. This is very important. This is because the gas generated when the raw material undergoes the vitrification reaction is expelled from the glass melt by the fining gas, and the remaining fine bubbles are enlarged and removed by the fining gas generated again in the fining process. is there.
[0006]
Alkali-free glass such as that used for a glass substrate for a liquid crystal display has a high viscosity of a glass melt, and is melted at a higher temperature than glass containing an alkali component. In this type 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. Such As ₂ O ₃ are known as a fining agent capable of generating a fining gas in a vitrification reaction process and refining process under high temperature conditions, even Patent Literature 1, the As ₂ O ₃ as a fining agent It is disclosed for use.
[0007]
However, As ₂ O ₃ is a very toxic substance, and may pollute the environment during the glass manufacturing process, the processing of waste glass, and the like. In recent years, its use has been restricted.
[0008]
The present invention has been made in view of the above circumstances, and does not use As ₂ O ₃ as a fining agent and, even when used as a glass substrate for a display, has no alkali-free glass that causes display defects. The purpose is to provide.
[0009]
[Means for Solving the Problems]
As a result of repeating various experiments, the present inventor has found that the above object can be achieved by using a sulfate and tin oxide in place of As ₂ O ₃ as a fining agent for alkali-free glass, and proposed as the present invention. Is what you do.
[0010]
That is, the alkali-free glass of the present invention is, by mass%, 40 to 70% of SiO ₂ , 6 to 25% of Al ₂ O ₃ , 5 to 20% of B ₂ O ₃ , 0 to 10% of MgO, 0 to 15% of CaO, BaO 0-30%, SrO 0-10%, ZnO 0-10%, SO ₃ 0.0001-0.03%, SnO ₂ 0.05-2%, essentially containing alkali metal oxides It is characterized by not having.
[0011]
The process for producing an alkali-free glass of the present invention, in _{mass%, SiO 2 40~70%, Al} 2 O 3 6~25%, B 2 O 3 5~20%, 0~10% MgO, CaO 0~ After fusing a glass raw material formulation containing 15%, BaO 0-30%, SrO 0-10%, and ZnO 0-10% and blended so as to be essentially free of alkali metal oxides, The method for producing an alkali-free glass to be molded is characterized in that a sulfate is added to the glass raw material mixture as a fining agent in an amount of 0.005 to 1% in terms of SO ₃ and SnO ₂ in an amount of 0.05 to ₂ %.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The sulfate used in the present invention is decomposed in a temperature range of about 1200 to 1500 ° C., and generates a large amount of fining gas (sulfur dioxide and oxygen gas) by decomposition. Since SO ₃ is decomposed even at a high temperature of 1400 ° C., it is most suitable for glass whose vitrification reaction process is at a high temperature such as non-alkali glass. That SO ₃ when the temperature corresponding to a viscosity of ¹⁰ 2.5 dPa · s to melt the 1500 ° C. or more glass, effectively acts as a fining agent. However, since the solubility of SO ₃ in glass generally decreases as the alkali content decreases, the solubility of SO ₃ is very low in the case of non-alkali glass. That is, SO ₃ releases a large amount of gas in the vitrification reaction process, but in the fining process after vitrification, the fining effect is reduced due to the small amount of remaining SO ₃ .
[0013]
However, SnO ₂ releases a large amount of fining gas (oxygen gas) by a chemical reaction caused by a change in the valence of Sn ions occurring in a temperature range of 1400 ° C. or higher, particularly 1500 ° C. or higher. That is, SnO ₂ (tetravalent) changes to SnO (divalent) by increasing the temperature, and releases a large amount of fining gas at that time.
[0014]
Therefore, in addition to SO ₃ , a glass that occurs at a relatively low temperature by using SnO ₂ that generates a fining gas not by decomposition but by a change in valence, and the valence change occurs in a temperature range where the alkali-free glass is melted is used. A high fining effect can be obtained in a wide temperature range from the crystallization reaction process to the high-temperature fining process, and an alkali-free glass with few bubbles can be produced.
[0015]
Next, a method for producing an alkali-free glass of the present invention will be described.
[0016]
First, in terms of mass%, 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%, BaO 0 to 30%, SrO 0 A glass raw material preparation is prepared so as to be a glass containing a composition of 10% to 10% and ZnO of 0% to 10%.
[0017]
Next, sulfate and SnO ₂ are added to the glass raw material mixture. As the sulfate, BaSO ₄ , CaSO _{4 and the} like can be used. Amount of sulfate, glass batch formulation 100% by mass of a 0.005 mass% converted to SO _3, SO ₃ in the glass in this amount of addition and 0.0001 to 0.03% Become. If the amount of the sulfate is less than 0.005%, it is difficult to expel the gas generated in the vitrification process. If the amount of the sulfate is more than 1%, the foam tends to be re-foamed, and the bubbles easily remain in the glass. The preferred amount of sulfate, 0.01% to 1% converted to SO _3, more preferably from 0.05 to 1%. The preferable content of SO ₃ is 0.001 to 0.03%, more preferably 0.005 to 0.03%. The addition amount of SnO ₂ is 0.05 to ₂ % by mass based on 100% by mass of the glass raw material mixture. If SnO ₂ is less than 0.05%, it is difficult to remove bubbles remaining in the glass melt during the fining process, and if it is more than 2%, the glass tends to be devitrified. The preferred amount of SnO ₂ is 0.05 to 1%, preferably 0.1% to 0.5%.
[0018]
In the present invention, in addition to sulfate and SnO ₂ , as a fining agent, Sb ₂ O ₃ can be added up to 3%, and chloride (in terms of Cl ₂ ) can be added up to 1%. However, fluoride is not added as much as As ₂ O ₃ but is not added because of toxicity. In addition, Fe ₂ O _{3 is} also a component having a clarifying action. However, if it is contained in a large amount, the visible light transmittance of the glass is reduced, and the glass is not suitable for display applications. Therefore, the content should be suppressed to 800 ppm or less, preferably 500 ppm or less. Is preferred.
[0019]
Next, the prepared glass raw material preparation is melted. As the glass raw material is heated, a vitrification reaction occurs first. At this time, sulfur dioxide and oxygen gas are generated due to decomposition of sulfate, and the gas generated in the vitrification reaction process is expelled from the melt. Thereafter, when the temperature rises in the fining process, the valence of SnO ₂ changes, and oxygen gas is generated to remove fine bubbles remaining in the glass melt.
[0020]
Thereafter, the molten glass is formed into a desired shape. When used for display applications, it is formed into a thin plate using a method such as an overflow downdraw method, a slot downdraw method, a float method, or a rollout method. In particular, it is preferable that the glass sheet is formed by the overflow down draw method and the slot down draw method, since a glass sheet having very excellent surface quality can be obtained.
[0021]
Thus, in _{mass%, SiO 2 40~70%, Al} 2 O 3 6~25%, B 2 O 3 5~20%, 0~10% MgO, CaO 0~15%, BaO 0~30%, SrO _{0~10%, 0~10% ZnO, sO} 3 0.0001~0.03%, containing SnO 2 0.05 to 2%, an alkali-free glass is obtained which is essentially free of alkali metal oxides . Incidentally, essentially containing no alkali metal oxide means that no alkali metal oxide (Li ₂ O, Na ₂ O, K ₂ O) is added as a glass raw material, and 0.2% as an impurity. Even if it is contained in an amount of not more than mass%, the present invention is not hindered.
[0022]
The reasons for limiting the composition of the alkali-free glass in this way are as follows.
[0023]
SiO ₂ is a component serving as a glass network, and its content is 40 to 70%. If the content of SiO ₂ is less than 40%, the chemical resistance is deteriorated, and the strain point is lowered to deteriorate the heat resistance. If it is more than 70%, the high temperature viscosity increases, the meltability deteriorates, and the devitrified cristobalite tends to precipitate. The preferred content of SiO ₂ is 45 to 65%.
[0024]
Al ₂ O ₃ is a component that enhances the heat resistance and devitrification resistance of the glass, and its content is 6 to 25%. If the content of Al ₂ O ₃ is less than 6%, the devitrification temperature rises remarkably and devitrification tends to occur in the glass. If it is more than 25%, acid resistance, especially buffered hydrofluoric acid resistance, decreases, and the glass surface becomes cloudy. Tends to occur. The preferred content of Al ₂ O ₃ is 10 to 20%.
[0025]
B ₂ O ₃ is a component that functions as a flux, lowers the viscosity and facilitates melting, and has a content of 5 to 20%. If the content of B ₂ O ₃ is less than 5%, the effect as a flux will be insufficient, and if it is more than 20%, the hydrochloric acid resistance will be reduced, and the strain point will be lowered, thus deteriorating the heat resistance. The preferable content of B ₂ O ₃ is 7.5 to 15%, and the more preferable content is 8.5 to 15%.
[0026]
MgO is a component that lowers the high-temperature viscosity without lowering the strain point to facilitate melting of the glass, and its content is 0 to 10%. If the content of MgO is more than 10%, the buffered hydrofluoric acid resistance of the glass is significantly reduced. The preferred content of MgO is 0 to 3.5%, and the more preferred content is 0 to 3%.
[0027]
CaO is also a component having the same function as MgO, and its content is 0 to 15%. If the content of CaO is more than 15%, the resistance to buffered hydrofluoric acid is significantly reduced. A preferable content of CaO is 0 to 10%, and a more preferable content is 6 to 10%.
[0028]
BaO is a component that improves the chemical resistance of glass and also improves the devitrification, and its content is 0 to 30%. If the content of BaO is more than 30%, the strain point is lowered and the heat resistance is deteriorated. The preferable content of BaO is 0 to 20%.
[0029]
SrO is also a component having the same function as BaO, and its content is 0 to 10%. If the content of SrO is more than 10%, the devitrification will increase, which is not preferable. The preferred content of SrO is 0 to 7%.
[0030]
By the way, portable devices such as mobile phones and notebook computers are required to be lightweight for convenience in carrying, and the glass substrate used for them is also required to have a low density in order to reduce the weight. ing. In addition, since a glass substrate of this kind is warped when its coefficient of thermal expansion with a thin film transistor (TFT) material increases, it is close to the coefficient of thermal expansion of the TFT material (about 30 to 33 × 10 ⁻⁷ / ° C.). It is desirable to have such a low expansion, specifically a thermal expansion coefficient of 28 to 35 × 10 ⁻⁷ / ° C. BaO and SrO are components that also affect the density and the coefficient of thermal expansion of the glass. In order to obtain a glass having a low density and a low expansion, the total amount of these components is controlled to 6% or less, preferably 4% or less. Should.
[0031]
ZnO is a component that improves buffered hydrofluoric acid resistance and devitrification, and its content is 0 to 10%. However, when the content of ZnO is more than 10%, the glass is liable to be devitrified, and the strain point is lowered to deteriorate the heat resistance. The preferable content of ZnO is 0 to 7%.
[0032]
In the present invention, in addition to the above components, ZrO ₂ , TiO ₂ , Fe ₂ O ₃ , P ₂ O ₅ , Y ₂ O ₃ , Nb ₂ O ₃ , La ₂ O _{3 and the} like are contained up to 5% in total. can do.
[0033]
【Example】
Hereinafter, the present invention will be described based on examples.
[0034]
Table 1 shows the effects of SO ₃ and SnO _{2 on} the alkali-free glass. In the table, the glass of sample a was a conventional alkali-free glass to which As ₂ O ₃ was added as a fining agent, the glass of sample b was an alkali-free glass prepared by removing As ₂ O ₃ from sample a, and a glass of sample c. The glass was alkali-free glass to which only sulfate (BaSO ₄ ) was added, the glass of sample d was alkali-free glass to which only SnO ₂ was added, and the glass of samples e and f was non-alkali glass to which both sulfate and SnO ₂ were used. It is an alkali glass.
[0035]
[Table 1]

[0036]
Each sample glass in the table was produced as follows.
[0037]
First, a glass raw material was prepared so that the total amount of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , CaO, SrO, BaO, and ZnO in Table 1 was 100% by mass, and a fining agent (SO ₃ , SnO ₂ , As ₂ O ₃ ) was added (extrapolated) to this, mixed, and then melted in an electric furnace. After melting at 1600 ° C. for 4 hours and at 1600 ° C. for 8 hours to evaluate clarity in the vitrification process, and after melting at 1600 ° C. for 4 hours to evaluate fining in the fining process, Further, it was melted at 1650 ° C. for 4 hours. Since SO ₃ is decomposed during melting, the residual amount of SO _{3 in} the glasses of Samples c, e, and f was 0.001% by mass under any melting conditions.
[0038]
Next, the molten glass was poured out onto a carbon plate and gradually cooled. The size of the poured sheet glass was about 10 cm in length, about 6 cm in width, and about 1 cm in height. The number of bubbles in the glass was visually observed using a microscope for a portion of 1.5 to 7 cm at which the glass started to flow. And were shown in the table. The number of bubbles is obtained by measuring bubbles having a maximum diameter of 20 μm or more. When the number of bubbles in glass 100 g exceeds 10,000, x; when the number of bubbles is 1001 to 10,000, Δ is 101 to 1000. The case was indicated by ○, and the case of 100 or less was indicated by ◎.
[0039]
The strain points in the table were measured based on the method of ASTM C336-71. Temperature viscosity of ¹⁰ 2.5 dPa · s, from the high temperature viscosity measured at platinum ball pulling method was calculated using the formula Fulcher. Hydrochloric acid resistance was determined by immersing each sample glass in a 10% by mass aqueous hydrochloric acid solution maintained at 80 ° C. for 24 hours, and then observing the surface state of the glass. The buffered hydrofluoric acid resistance is determined by immersing each sample glass in buffered hydrofluoric acid composed of 38.7% by mass of ammonium fluoride and 1.6% by mass of hydrofluoric acid maintained at 20 ° C. for 30 minutes, and then immersing the glass surface. The condition was observed. Regarding the hydrochloric acid resistance and the buffered hydrofluoric acid resistance, ◎ indicates that there was no change in appearance, and X indicates that the change in appearance occurred.
[0040]
As is clear from the table, the glass of Sample a to which As ₂ O ₃ was added had good clarity, but the glass of Sample b to which no fining agent was added had extremely poor clarity. In addition, in the glass of Sample c to which only sulfate (SO ₃ ) was added, although a large amount of fining gas was generated in the vitrification process, sufficient fining gas was not generated in the fining process, and as a result, fining was poor. Furthermore, although the glass of sample d to which only SnO ₂ was added generated a large amount of gas in the fining process, sufficient fining gas was not generated in the vitrification process, resulting in poor fining properties.
[0041]
On the other hand, the glasses of Samples e and f to which sulfate and SnO ₂ were added had almost the same good clarity as the glass of Sample a to which As ₂ O ₃ was added. Further, the glasses of Samples e and f each had a strain point of 665 ° C., and thus had excellent heat resistance, no change in appearance even when treated with hydrochloric acid or buffered hydrofluoric acid, and also had excellent chemical resistance.
[0042]
【The invention's effect】
As described above, according to the method of the present invention, a predetermined amount of sulfate and SnO ₂ are added as fining agents, so that alkali-free glass with excellent fining properties and little bubbles is used without using As ₂ O _3. Can be manufactured.
[0043]
Further, the alkali-free glass of the present invention is excellent in clarity, has few bubbles, and has excellent heat resistance and chemical resistance, and thus is particularly suitable as a glass substrate for displays.

Claims (2)

By _{mass%, SiO 2 40~70%, Al} 2 O 3 6~25%, B 2 O 3 5~20%, 0~10% MgO, CaO 0~15%, BaO 0~30%, SrO 0~ Alkali-free glass containing 10%, ZnO 0 to 10%, SO ₃ 0.0001 to 0.03%, and SnO ₂ 0.05 to ₂ %, and containing essentially no alkali metal oxide. . By _{mass%, SiO 2 40~70%, Al} 2 O 3 6~25%, B 2 O 3 5~20%, 0~10% MgO, CaO 0~15%, BaO 0~30%, SrO 0~ In a method for producing an alkali-free glass, a glass raw material mixture containing 10% and ZnO of 0 to 10% and containing essentially no alkali metal oxide is melted and then molded. A method for producing an alkali-free glass, comprising adding a sulfate as a fining agent to the composition in an amount of 0.005 to 1% in terms of SO ₃ and 0.05 to ₂ % of SnO ₂ .