JP5616450B2 - Manufacturing method of glass plate - Google Patents

Manufacturing method of glass plate Download PDF

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JP5616450B2
JP5616450B2 JP2012525556A JP2012525556A JP5616450B2 JP 5616450 B2 JP5616450 B2 JP 5616450B2 JP 2012525556 A JP2012525556 A JP 2012525556A JP 2012525556 A JP2012525556 A JP 2012525556A JP 5616450 B2 JP5616450 B2 JP 5616450B2
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molten glass
glass
tube
glass substrate
manufacturing
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JPWO2012132472A1 (en
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次伸 村上
次伸 村上
宣之 日沖
宣之 日沖
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Avanstrate Inc
Avanstrate Asia Pte Ltd
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/225—Refining
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/04—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in tank furnaces
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/18—Stirring devices; Homogenisation
    • C03B5/182—Stirring devices; Homogenisation by moving the molten glass along fixed elements, e.g. deflectors, weirs, baffle plates
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/18—Stirring devices; Homogenisation
    • C03B5/187—Stirring devices; Homogenisation with moving elements
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/42—Details of construction of furnace walls, e.g. to prevent corrosion; Use of materials for furnace walls
    • C03B5/43—Use of materials for furnace walls, e.g. fire-bricks

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Glass Compositions (AREA)

Description

本発明は、ガラス板を製造するガラス板の製造方法に関する。   The present invention relates to a glass plate manufacturing method for manufacturing a glass plate.

液晶ディスプレイやプラズマディスプレイなどのフラットパネルディスプレイ（以下ＦＰＤという）に用いるガラス基板は、例えば、厚さが０．５〜０．７ｍｍで、サイズが３００×４００ｍｍ〜２８５０〜×３０５０ｍｍのものが主流である。   For example, glass substrates used for flat panel displays (hereinafter referred to as FPD) such as liquid crystal displays and plasma displays are mainly 0.5 to 0.7 mm in thickness and 300 to 400 mm to 2850 to 3050 mm in size. is there.

ＦＰＤ用ガラス基板の製造方法として、オーバーフローダウンドロー法が知られている。オーバーフローダウンドロー法は、成形炉において、熔融ガラスの成形体の上部から溢れさせることにより板状ガラスに成形し、成形された板状ガラスを徐冷し、切断する。その後、切断された板状ガラスは、さらに、顧客の仕様に合わせて所定のサイズに切断され、洗浄、端面研磨などが行われ、出荷される。   An overflow down draw method is known as a method for manufacturing a glass substrate for FPD. In the overflow down draw method, the glass sheet is formed into a glass sheet by overflowing from the upper part of the molten glass molded body in a molding furnace, and the formed glass sheet is gradually cooled and cut. Thereafter, the cut sheet glass is further cut into a predetermined size in accordance with the customer's specifications, cleaned, end-polished, etc., and shipped.

ＦＰＤ用ガラス基板のうち、特に液晶表示装置用ガラス基板は、その表面に半導体素子が形成されるため、アルカリ金属成分を全く含有しないか、または、含まれていても半導体素子等に影響を及ぼさない程度の微量であることが好ましい。
また、ガラス基板中に泡が存在すると表示欠点の原因となるため、泡が存在するガラス基板は、ＦＰＤ用ガラス基板として用いることはできない。このため、泡がガラス基板に残存しないことが求められている。ガラス基板の製造において、熔融ガラスの泡を取り除くことを清澄といい、この清澄では、Ａｓ2Ｏ3などの清澄剤の酸化還元反応により、泡が取り除かれる。より具体的には、粗熔解した熔融ガラスの温度をさらに上げて、清澄剤を機能させ泡を浮上脱泡させ、その後、温度を下げることにより、脱泡しきれず残った小泡をガラス内に溶解吸収させる。清澄剤としては、Ａｓ2Ｏ3の他、近年の環境負荷の観点から、Ａｓ2Ｏ3に代わって、ＳｎＯ2やＦｅ2Ｏ3などが用いられている。上述したように、アルカリ金属成分を全く含有しないか、微量であるガラス基板の場合、ソーダライムガラスなどのアルカリ金属を多量に含有したガラス基板に比べて、高温粘性が高く、製造中の熔融ガラスから泡が抜けにくいため、より高い清澄効果が必要となる。Among the glass substrates for FPD, in particular, the glass substrate for liquid crystal display devices has a semiconductor element formed on the surface thereof, and therefore does not contain an alkali metal component at all or even if it is contained, the semiconductor element is affected. It is preferable that the amount is as small as possible.
In addition, if bubbles are present in the glass substrate, it causes a display defect. Therefore, a glass substrate in which bubbles are present cannot be used as a glass substrate for FPD. For this reason, it is calculated | required that a bubble does not remain | survive in a glass substrate. In the production of a glass substrate, removing bubbles from the molten glass is called clarification. In this clarification, the bubbles are removed by an oxidation-reduction reaction of a clarifier such as As 2 O 3 . More specifically, the temperature of the melted molten glass is further increased, the fining agent is caused to function by causing the fining agent to function, and then the temperature is lowered to reduce the remaining small bubbles in the glass. Dissolve and absorb. As the fining agent, SnO 2 or Fe 2 O 3 is used in place of As 2 O 3 in addition to As 2 O 3 from the viewpoint of environmental load in recent years. As described above, in the case of a glass substrate that does not contain an alkali metal component at all or is in a very small amount, the high-temperature viscosity is higher than that of a glass substrate that contains a large amount of alkali metal such as soda lime glass. Since bubbles are difficult to escape from, a higher clarification effect is required.

一方、白金または白金合金で構成される管の清澄槽に電流を流すことにより清澄槽を加熱し（通電加熱）、この加熱された清澄槽に熔融ガラスを流通させることにより、熔融ガラスの温度を上昇させ、清澄を行う技術が知られている。（特許文献１）。   On the other hand, the temperature of the molten glass is controlled by heating the clarification tank by passing an electric current through a clarification tank of a tube made of platinum or a platinum alloy (conduction heating), and circulating the molten glass in the heated clarification tank. Techniques for raising and clarifying are known. (Patent Document 1).

特表２０１１−５０２９３４号公報Special table 2011-502934 gazette

白金または白金合金の管で構成された清澄槽を加熱して熔融ガラスの温度を上げるとき、溶融ガラスの温度が均一に加熱されない場合がある。例えば、図５に示すように、管を通過する熔融ガラスのうち、管路の中心付近を流れる熔融ガラスの流速は、壁面抵抗が大きい管の壁面近傍を流れる熔融ガラスの流速に比べて速いので、さらには、加熱する管の壁面から遠いので、管路の中心付近を流れる溶融ガラスは、管の壁面近傍を流れる熔融ガラスの温度に比べて低くなり、清澄に必要な温度まで上がりきらず、清澄が不十分となってしまうという問題がある。この問題は、白金または白金合金の管で構成された清澄槽に電流を流す場合に発生する問題でもある。
また、管の中心付近の温度を上げるために、白金あるいは白金合金からなる清澄槽の加熱量を増やすと、白金あるいは白金合金の揮発を促進してしまい、清澄槽の寿命を短くするという問題がある。特に、近年、環境負荷の観点から、Ａｓ2Ｏ3に代わって、ＳｎＯ2が清澄剤として用いられる場合、Ａｓ2Ｏ3よりも熔融ガラスを高温にするため、ますます白金あるいは白金合金の揮発が問題となっている。このため、白金あるいは白金合金で構成される管に対して過剰な加熱をすることは好ましくい状況にある。When the temperature of the molten glass is raised by heating a clarification tank composed of platinum or a platinum alloy tube, the temperature of the molten glass may not be heated uniformly. For example, as shown in FIG. 5, among the molten glass that passes through the tube, the flow rate of the molten glass that flows near the center of the pipe line is faster than the flow rate of the molten glass that flows near the wall surface of the tube having a large wall resistance. Furthermore, since it is far from the wall surface of the tube to be heated, the molten glass that flows near the center of the pipe line is lower than the temperature of the molten glass that flows near the wall surface of the tube. Has the problem of becoming insufficient. This problem is also a problem that occurs when an electric current is passed through a clarification tank composed of a platinum or platinum alloy tube.
In addition, increasing the heating amount of a clarification tank made of platinum or a platinum alloy in order to increase the temperature near the center of the tube promotes volatilization of the platinum or platinum alloy and shortens the life of the clarification tank. is there. In particular, in recent years, from the viewpoint of environmental impact, when SnO 2 is used as a refining agent instead of As 2 O 3 , the volatility of platinum or platinum alloys is increasingly increased in order to make molten glass higher than As 2 O 3. Is a problem. For this reason, it is preferable to excessively heat a tube made of platinum or a platinum alloy.

また、清澄槽では、泡が浮上しやすい粘度とすることにより脱泡が促進されるが、例えば液晶表示装置用ガラス基板などで好適に用いられる無アルカリガラスでは、高温粘性が高く、熔融ガラスの温度をアルカリガラスに比べて高温にする必要があるため、ますます白金あるいは白金合金の揮発が問題となる。このため、白金あるいは白金合金で構成される管に対して過剰な加熱をすることは好ましくない状況にある。   Further, in the clarification tank, defoaming is promoted by setting the viscosity at which bubbles are likely to rise. For example, non-alkali glass suitably used in a glass substrate for a liquid crystal display device, etc. Since the temperature needs to be higher than that of alkali glass, volatilization of platinum or platinum alloys becomes a problem. For this reason, it is in a situation where it is not preferable to heat excessively with respect to a pipe constituted of platinum or a platinum alloy.

そこで、本発明は、熔融ガラスの清澄において、従来に比べて、清澄槽の管を構成する白金あるいは白金合金の揮発を防止しつつ、熔融ガラスの清澄効果を高めることができるガラス基板の製造方法を提供することを目的とする。   Therefore, the present invention provides a method for producing a glass substrate capable of enhancing the clarification effect of molten glass while preventing the volatilization of platinum or platinum alloy constituting the tube of the clarification tank in the clarification of molten glass, as compared with the prior art. The purpose is to provide.

本発明の一態様は、ガラス基板の製造方法であって、
白金または白金合金からなる外周壁が加熱される管に、熔融ガラスを流しながら清澄する清澄工程を含む。
前記清澄工程は、前記熔融ガラス中の気泡を熔融ガラスの液面から前記管内の気相に向けて放出させる脱泡工程を含む。
前記脱泡工程では、前記熔融ガラスを攪拌することにより、前記管の流路断面の中央領域にある熔融ガラスの流れを抑制し、前記熔融ガラスの前記管の径方向に沿った温度分布を均一化させる、ことを特徴とするガラス基板の製造方法。 One aspect of the present invention is a method of manufacturing a glass substrate,
It includes a clarification step of clarification while flowing molten glass in a tube whose outer peripheral wall made of platinum or a platinum alloy is heated.
The clarification step includes a defoaming step of discharging bubbles in the molten glass from the liquid surface of the molten glass toward the gas phase in the tube.
In the defoaming step, by stirring the molten glass, the flow of the molten glass in the central region of the flow path cross section of the tube is suppressed, and the temperature distribution along the radial direction of the tube of the molten glass is uniform. The manufacturing method of the glass substrate characterized by the above-mentioned.

上記形態のガラス基板の製造方法では、熔融ガラスの清澄において白金あるいは白金合金の揮発を防止しつつ、熔融ガラスの清澄効果を高めることができる。   In the manufacturing method of the glass substrate of the said form, the clarification effect of molten glass can be heightened, preventing volatilization of platinum or a platinum alloy in the clarification of molten glass.

本実施形態のガラス基板の製造方法の工程図である。It is process drawing of the manufacturing method of the glass substrate of this embodiment. 図１に示す熔解工程〜切断工程を行う装置を模式的に示す図である。It is a figure which shows typically the apparatus which performs the melting process-cutting process shown in FIG. （ａ）は、図１に示す清澄工程を行う清澄槽を主に示す図であり、（ｂ）は、清澄槽の外周壁の温度を示す図である。(A) is a figure which mainly shows the clarification tank which performs the clarification process shown in FIG. 1, (b) is a figure which shows the temperature of the outer peripheral wall of a clarification tank. （ａ）〜（ｃ）は、清澄槽に用いる板材を説明する図である。(A)-(c) is a figure explaining the board | plate material used for a clarification tank. 従来の清澄槽における熔融ガラスの流速と温度を説明する図である。It is a figure explaining the flow velocity and temperature of the molten glass in the conventional clarification tank. （ａ）〜（ｃ）は、図４（ａ）〜（ｃ）に示す板材と異なる形態の板材の例を示す図である。(A)-(c) is a figure which shows the example of the board | plate material of a form different from the board | plate material shown to FIG. 4 (a)-(c). 図４（ａ）〜（ｃ）に示す板材で構成された攪拌手段と異なる形態の攪拌手段の例を示す図である。It is a figure which shows the example of the stirring means of a form different from the stirring means comprised with the board | plate material shown to Fig.4 (a)-(c).

以下、本実施形態のガラス板の製造方法について説明する。   Hereinafter, the manufacturing method of the glass plate of this embodiment is demonstrated.

（ガラス基板の製造方法の全体概要）
図１は、本実施形態のガラス基板の製造方法の工程図である。
ガラス板の製造方法は、熔解工程（ＳＴ１）と、清澄工程（ＳＴ２）と、均質化工程（ＳＴ３）と、供給工程（ＳＴ４）と、成形工程（ＳＴ５）と、徐冷工程（ＳＴ６）と、切断工程（ＳＴ７）と、を主に有する。この他に、研削工程、研磨工程、洗浄工程、検査工程、梱包工程等を有し、梱包工程で積層された複数のガラス基板は、納入先の業者に搬送される。(Overall overview of glass substrate manufacturing method)
FIG. 1 is a process diagram of a method for producing a glass substrate according to the present embodiment.
The glass plate manufacturing method includes a melting step (ST1), a refining step (ST2), a homogenizing step (ST3), a supplying step (ST4), a forming step (ST5), and a slow cooling step (ST6). And a cutting step (ST7). In addition, a plurality of glass substrates that have a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like and are stacked in the packing process are transported to a supplier.

図２は、熔解工程（ＳＴ１）〜切断工程（ＳＴ７）を行う装置を模式的に示す図である。当該装置は、図２に示すように、主に熔解装置２００と、成形装置３００と、切断装置４００と、を有する。熔解装置２００は、熔解槽２０１と、清澄槽２０２と、攪拌槽２０３と、ガラス供給管２０４，２０５，２０６と、を主に有する。なお、熔解槽２０１以降、成形装置３００までの各槽間を接続するガラス供給管２０４，２０５，２０６および清澄槽２０２と攪拌槽２０３は、白金あるいは白金ロジウム合金等の白金合金による金属管により構成されている。   FIG. 2 is a diagram schematically showing an apparatus for performing the melting step (ST1) to the cutting step (ST7). As shown in FIG. 2, the apparatus mainly includes a melting apparatus 200, a forming apparatus 300, and a cutting apparatus 400. The melting apparatus 200 mainly has a melting tank 201, a clarification tank 202, a stirring tank 203, and glass supply pipes 204, 205, and 206. In addition, the glass supply pipes 204, 205, and 206, the clarification tank 202, and the stirring tank 203 that connect the respective tanks from the melting tank 201 to the molding apparatus 300 are made of a metal pipe made of platinum or a platinum alloy such as a platinum rhodium alloy. Has been.

熔解工程（ＳＴ１）では、例えばＳｎＯ2等の清澄剤が添加されて熔解槽２０１内に供給されたガラス原料を、図示されない火焔および電気ヒータで加熱して熔解することで溶融ガラスを得る。具体的には、図示されない原料投入装置を用いてガラス原料Ｍは溶融ガラスＧの液面に供給される。ガラス原料は、火炎で高温となった気相により加熱されて徐々に熔解し、溶融ガラスＭＧ中に溶ける。溶融ガラスＭＧは、電気ヒータによる通電加熱で昇温される。
清澄工程（ＳＴ２）は、少なくともガラス供給管２０４、清澄槽２０２およびガラス供給管２０５において行われる。清澄工程では、清澄槽２０２内の溶融ガラスＭＧが昇温されることにより、溶融ガラスＭＧ中に含まれるＯ2、ＣＯ2あるいはＳＯ2を含んだ泡が、例えばＳｎＯ2等の清澄剤の還元反応により生じたＯ2を吸収して成長し、溶融ガラスＭＧの液面に浮上して放出される（脱泡工程）。また、清澄工程では、脱泡後、溶融ガラスＭＧの温度を低下させることにより、例えばＳｎＯ2等の清澄剤の還元反応により得られたＳｎＯ等の清澄剤が酸化反応をすることにより、溶融ガラスＭＧに残存する泡中のＯ2等のガス成分が溶融ガラスＭＧ中に吸収されて、泡が消滅する（吸収工程）。清澄剤による酸化反応及び還元反応は、溶融ガラスＭＧの温度を制御することにより行われる。溶融ガラスＭＧの温度は、ガラス供給管２０４に設けられた図示されないヒータ電極と、清澄槽２０２に設けられた後述するヒータ電極２０２ａ（図３参照）との間で電流を流し、さらに、ヒータ電極２０２ａと、ヒータ電極２０２ａに比べて溶融ガラスＭＧの下流側の清澄槽２０２に設けられたヒータ電極２０２ｂ（図３（ａ）参照）との間に電流を流すことにより、清澄槽２０２を加熱して溶融ガラスＭＧが昇温される。さらに、ヒータ電極２０２ｂと、ヒータ電極２０２ｂに比べて溶融ガラスＭＧの下流側の清澄槽２０２に設けられたヒータ電極２０２ｃ（図３参照）との間に電流を流すことにより、清澄槽２０２を加熱しながら溶融ガラスＭＧが降温される。この通電加熱は３つの領域の通電加熱による温度制御に限定されず、１つまたは２つの領域の通電加熱を行って、溶融ガラスＭＧの温度制御を行うこともできる。清澄槽２０２における清澄工程についての詳細は後述する。In the melting step (ST1), for example, a glass raw material to which a fining agent such as SnO 2 is added and supplied into the melting tank 201 is heated and melted by a flame and an electric heater (not shown) to obtain a molten glass. Specifically, the glass raw material M is supplied to the liquid surface of the molten glass G using a raw material charging apparatus (not shown). The glass raw material is heated and melted gradually by the gas phase heated to a high temperature by the flame, and melted in the molten glass MG. Molten glass MG is heated by energization heating with an electric heater.
The clarification step (ST2) is performed at least in the glass supply pipe 204, the clarification tank 202, and the glass supply pipe 205. In the clarification step, when the molten glass MG in the clarification tank 202 is heated, the bubbles containing O 2 , CO 2, or SO 2 contained in the molten glass MG are reduced with a clarifier such as SnO 2. It grows by absorbing O 2 generated by the reaction, floats on the liquid surface of the molten glass MG, and is released (defoaming step). In the clarification step, after defoaming, the temperature of the molten glass MG is lowered, and for example, a clarifier such as SnO obtained by a reduction reaction of a clarifier such as SnO 2 undergoes an oxidation reaction, thereby Gas components such as O 2 in the foam remaining in the MG are absorbed into the molten glass MG, and the foam disappears (absorption process). The oxidation reaction and reduction reaction by the fining agent are performed by controlling the temperature of the molten glass MG. As for the temperature of the molten glass MG, an electric current is passed between a heater electrode (not shown) provided in the glass supply pipe 204 and a heater electrode 202a (see FIG. 3) provided in the clarification tank 202, which will be described later. The clarification tank 202 is heated by flowing an electric current between 202a and the heater electrode 202b (see FIG. 3A) provided in the clarification tank 202 on the downstream side of the molten glass MG as compared with the heater electrode 202a. The molten glass MG is heated. Furthermore, the clarification tank 202 is heated by passing an electric current between the heater electrode 202b and the heater electrode 202c (see FIG. 3) provided in the clarification tank 202 on the downstream side of the molten glass MG as compared with the heater electrode 202b. Meanwhile, the temperature of the molten glass MG is lowered. This energization heating is not limited to the temperature control by the energization heating in the three regions, and the temperature control of the molten glass MG can be performed by performing the energization heating in one or two regions. The detail about the clarification process in the clarification tank 202 is mentioned later.

均質化工程（ＳＴ３）では、ガラス供給管２０５を通って供給された攪拌槽２０３内の溶融ガラスＭＧを、スターラ２０３ａを用いて攪拌することにより、ガラス成分の均質化を行う。攪拌槽２０３は、１つのスターラ２０３ａを用いて溶融ガラスＭＧを攪拌するが、２つ以上のスターラ２０３ａを用いて溶融ガラスＭＧを攪拌することもできる。
供給工程（ＳＴ４）では、ガラス供給管２０６を通して溶融ガラスＭＧが成形装置３００に供給される。In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass MG in the stirring tank 203 supplied through the glass supply pipe 205 using the stirrer 203a. The stirring tank 203 stirs the molten glass MG using one stirrer 203a, but can also stir the molten glass MG using two or more stirrers 203a.
In the supply step (ST4), the molten glass MG is supplied to the molding apparatus 300 through the glass supply pipe 206.

成形装置３００では、成形工程（ＳＴ５）及び徐冷工程（ＳＴ６）が行われる。
成形工程（ＳＴ５）では、溶融ガラスＭＧをシート状ガラスＧに成形し、シート状ガラスＧの流れを作る。本実施形態は、後述する成形体３１０を用いたオーバーフローダウンドロー法を用いる。徐冷工程（ＳＴ６）では、成形されて流れるシート状ガラスＧが所望の厚さになり、内部歪が生じないように冷却される。
切断工程（ＳＴ７）では、切断装置４００において、成形装置３００から供給されたシート状ガラスＧを所定の長さに切断することで、板状のガラス基板を得る。切断されたガラス基板はさらに、所定のサイズに切断され、目標サイズのガラス基板が作製される。この後、ガラス基板の端面の研削、研磨およびガラス基板の洗浄が行われ、さらに、泡や脈理等の欠点の有無が検査された後、検査合格品のガラス基板が最終製品として梱包される。In the molding apparatus 300, a molding process (ST5) and a slow cooling process (ST6) are performed.
In the forming step (ST5), the molten glass MG is formed into a sheet glass G, and a flow of the sheet glass G is created. In the present embodiment, an overflow down draw method using a molded body 310 described later is used. In the slow cooling step (ST6), the sheet-like glass G that is formed and flows is cooled to have a desired thickness and no internal distortion occurs.
In a cutting process (ST7), in the cutting device 400, the sheet-like glass G supplied from the shaping | molding apparatus 300 is cut | disconnected to predetermined length, and a plate-shaped glass substrate is obtained. The cut glass substrate is further cut into a predetermined size to produce a glass substrate of a target size. After this, the end face of the glass substrate is ground, polished and the glass substrate is cleaned. Further, after checking for defects such as bubbles and striae, the glass substrate that has passed the inspection is packed as a final product. .

（清澄工程）
上述したように、清澄工程（ＳＴ２）の脱泡工程および吸収工程は、少なくともガラス供給管２０４、清澄槽２０２およびガラス供給管２０５において行われる。脱泡工程は、主に、供給管２０４および清澄槽２０２の前半で行われる。また、吸収工程は、主に清澄槽２０２の後半で行われる。なお、脱泡工程は、清澄槽２０２の後半で行われることもある。この場合吸収工程は、清澄槽２０２の後半あるいはそれ以降の供給管２０５で行われる。(Clarification process)
As described above, the defoaming step and the absorption step of the clarification step (ST2) are performed at least in the glass supply pipe 204, the clarification tank 202, and the glass supply pipe 205. The defoaming step is mainly performed in the first half of the supply pipe 204 and the clarification tank 202. The absorption process is mainly performed in the latter half of the clarification tank 202. The defoaming step may be performed in the latter half of the clarification tank 202. In this case, the absorption step is performed in the supply pipe 205 in the latter half of the clarification tank 202 or later.

以降、清澄工程を、脱泡工程から説明する。
熔解槽２０１からガラス供給管２０４に供給される熔融ガラスＭＧは、ガラス供給管２０４および清澄槽２０２の前半では、ＳｎＯ2等の清澄剤の酸素の放出反応が促進されるように、かつ、清澄槽２０２の前半において泡が浮上しやすい粘度（好ましくは、１２０［ｐｏｉｓｅ］〜４００［ｐｏｉｓｅ］：１ｐｏｉｓｅ＝０．１Ｐａ・秒）となるように、清澄槽２０２に供給される前に加熱される。例えば、無アルカリガラスやアルカリを微量しか含まないアルカリ微量含有ガラス（高温粘性ガラス）、例えば１０2.5［ｐｏｉｓｅ］の粘度に相当する温度が１５００℃以上であるガラスの場合、例えば１５８０℃〜１６２０℃、より好ましくは１，６００℃〜１６２０℃でガラス供給管２０４に供給され、清澄槽２０２の入り口で例えば１６１０℃〜１６５０℃、より好ましくは１６３０℃〜１６５０℃となるように加熱される。さらに、清澄槽２０２において、後述するヒータ電極２０２ａと、ヒータ電極２０２ｂとの間に電流を流すことにより、清澄槽２０２を加熱して溶融ガラスＭＧが例えば１６７０℃〜１７１０℃、好ましくは１６９０℃〜１７１０℃まで昇温される。つまり、清澄槽２０２の温度を、清澄槽２０２を構成する金属管の白金あるいは白金合金の耐熱温度近傍まで上げる必要がある。
つまり、脱泡工程では、熔融ガラスＭＧを加熱するために、一定以上の長さの管が必要となる。また、清澄槽２０２の内径は、ガラス供給管２０４の内径よりも大きく、熔融ガラスＭＧの液面と管との間に気相空間を有するように構成される。このような構成にすることにより、ガラス供給管２０４で開始された脱泡が、清澄槽２０２で泡が浮上しやすい粘度となったときに急激に放出することができ、効果的な清澄効果を促進することができる。ここで、清澄槽２０２の管は、上述したように内径が大きいため、管の径方向の温度分布が不均一になり易い。なお、この問題は、内径が比較的小さなガラス供給管２０４では生じ難い。Hereinafter, the clarification process will be described from the defoaming process.
The molten glass MG supplied from the melting tank 201 to the glass supply pipe 204 is clarified in the first half of the glass supply pipe 204 and the clarification tank 202 so that the oxygen release reaction of a clarifier such as SnO 2 is promoted. It is heated before being supplied to the clarification tank 202 so that the viscosity of the bubbles easily rises in the first half of the tank 202 (preferably 120 [poise] to 400 [poise]: 1 poise = 0.1 Pa · sec). . For example, in the case of glass having a temperature corresponding to a viscosity of 10 2.5 [poise] of 1500 ° C. or more, for example, 1580 ° C. to 1620 ° C. More preferably, it is supplied to the glass supply tube 204 at 1,600 ° C. to 1620 ° C., and is heated at, for example, 1610 ° C. to 1650 ° C., more preferably 1630 ° C. to 1650 ° C. at the entrance of the clarification tank 202. Further, in the clarification tank 202, by passing an electric current between a heater electrode 202a and a heater electrode 202b described later, the clarification tank 202 is heated and the molten glass MG is, for example, 1670 ° C. to 1710 ° C., preferably 1690 ° C. The temperature is raised to 1710 ° C. That is, it is necessary to raise the temperature of the clarification tank 202 to the vicinity of the heat resistance temperature of platinum or a platinum alloy of the metal tube constituting the clarification tank 202.
That is, in the defoaming step, a tube having a certain length or more is required to heat the molten glass MG. Moreover, the inner diameter of the clarification tank 202 is larger than the inner diameter of the glass supply pipe 204 and is configured to have a gas phase space between the liquid surface of the molten glass MG and the pipe. With such a configuration, defoaming started in the glass supply pipe 204 can be rapidly released when the viscosity of the foam is likely to rise in the clarification tank 202, and an effective clarification effect can be obtained. Can be promoted. Here, since the pipe of the clarification tank 202 has a large inner diameter as described above, the temperature distribution in the radial direction of the pipe tends to be uneven. This problem hardly occurs in the glass supply tube 204 having a relatively small inner diameter.

次に、吸収工程を説明する。
吸収工程では、ヒータ電極２０２ｂと、ヒータ電極２０２ｃ（図３参照）との間に電流を流すことにより、清澄槽２０２を加熱しながら溶融ガラスＭＧが降温され、清澄剤としてＳｎＯ2を用いた場合、ＳｎＯ2の還元反応により得られたＳｎＯが酸化反応をすることにより、溶融ガラスＭＧに残存する泡中のＯ2等のガス成分が溶融ガラスＭＧ中に吸収されて、泡が消滅する。Next, the absorption process will be described.
In the absorption process, when flowing current between the heater electrode 202b and the heater electrode 202c (see FIG. 3), the temperature of the molten glass MG is lowered while heating the clarification tank 202, and SnO 2 is used as a clarifier. When SnO obtained by the reduction reaction of SnO 2 undergoes an oxidation reaction, gas components such as O 2 in bubbles remaining in the molten glass MG are absorbed in the molten glass MG, and the bubbles disappear.

（清澄槽）
図３（ａ）は、上述した清澄工程を主に行う清澄槽２０２の構成を具体的に示す図である。清澄槽２０２は、具体的には、ヒータ電極２０２ａ，２０２ｂ，２０２ｃと、金属管２０２ｄと、を有する。金属管２０２ｄは、白金または白金合金製の管となっている。金属管２０２ｄの管路を流路として、熔融ガラスＭＧは金属管２０２ｄの内部を流れる。ヒータ電極２０２ａ，２０２ｂ，２０２ｃは、金属管２０２ｄの外周壁面から金属管２０２ｄに電流を流し、金属管２０２ｄの抵抗によって生じるジュール熱を用いて金属管２０２ｄを加熱して熔融ガラスＭＧの温度を所定の温度に上げて熔融ガラスＭＧ中の清澄剤を用いて熔融ガラスＭＧの脱泡を行う。すなわち、金属管２０２ｄは、白金または白金合金の外周壁からなり、この外周壁が加熱される。(Clarification tank)
FIG. 3A is a diagram specifically illustrating the configuration of the clarification tank 202 that mainly performs the above-described clarification step. Specifically, the clarification tank 202 includes heater electrodes 202a, 202b, and 202c, and a metal tube 202d. The metal tube 202d is a tube made of platinum or a platinum alloy. The molten glass MG flows through the inside of the metal tube 202d using the pipe line of the metal tube 202d as a flow path. The heater electrodes 202a, 202b, and 202c cause a current to flow from the outer peripheral wall surface of the metal tube 202d to the metal tube 202d and heat the metal tube 202d using Joule heat generated by the resistance of the metal tube 202d to set the temperature of the molten glass MG to a predetermined value. The molten glass MG is defoamed using a fining agent in the molten glass MG. That is, the metal tube 202d is made of an outer peripheral wall of platinum or a platinum alloy, and the outer peripheral wall is heated.

ヒータ電極２０２ａ，２０２ｂ，２０２ｃは、金属管２０２ｄの長手方向であるＸ方向の上流側から順番にヒータ電極２０２ａ、ヒータ電極２０２ｂ、ヒータ電極２０２ｃが順番に設けられ、ヒータ電極２０２ａ及びヒータ電極２０２ｃは、金属管２０２ｄの両端に位置する。ヒータ電極２０２ｂは、ヒータ電極２０２ａとヒータ電極２０２ｃとの間の略中間に位置する。すなわち、ヒータ電極２０２ａとヒータ電極２０２ｂとの間の領域が第１の加熱領域となり、ヒータ電極２０２ｂとヒータ電極２０２ｃとの間の領域が第２の加熱領域となる。
本実施形態では、３つのヒータ電極２０２ａ〜２０２ｃが設けられるが、２つのヒータ電極であってもよい。すなわち、金属管２０２ｄを加熱する領域は１つであってもよい。The heater electrodes 202a, 202b, and 202c are sequentially provided with the heater electrode 202a, the heater electrode 202b, and the heater electrode 202c in order from the upstream side in the X direction, which is the longitudinal direction of the metal tube 202d, and the heater electrode 202a and the heater electrode 202c are , Located at both ends of the metal tube 202d. The heater electrode 202b is located approximately in the middle between the heater electrode 202a and the heater electrode 202c. That is, a region between the heater electrode 202a and the heater electrode 202b is a first heating region, and a region between the heater electrode 202b and the heater electrode 202c is a second heating region.
In the present embodiment, three heater electrodes 202a to 202c are provided, but two heater electrodes may be provided. That is, the number of regions for heating the metal tube 202d may be one.

さらに、金属管２０２ｄの内部では、熔融ガラスＭＧが金属管２０２ｄの流路断面全体を流れるわけでなく、上方に気相の空間が設けられる。熔融ガラスＭＧの脱泡すべき泡を、熔融ガラスＭＧの液表面で破泡させて泡中のガス成分を大気に放出させるために、金属管２０２ｄの上部には、金属管２０２ｄの気相からガス成分を大気に放出するための図示されないガス排気孔が設けられている。   Further, inside the metal tube 202d, the molten glass MG does not flow through the entire flow path section of the metal tube 202d, but a gas phase space is provided above. In order to cause bubbles to be defoamed in the molten glass MG to break up on the liquid surface of the molten glass MG and to release gas components in the bubbles to the atmosphere, the upper part of the metal tube 202d is from the gas phase of the metal tube 202d. A gas exhaust hole (not shown) for releasing a gas component to the atmosphere is provided.

金属管２０２ｄは、円筒状の形状であることが好ましい。金属管２０２ｄの厚さは、例えば１ｍｍ〜１．５ｍｍであることが好ましい。金属管２０２ｄの内径は、ガラス供給管２０４，２０５の内径よりも大きく、ガラス供給管２０４，２０５の内径の３０％以上大きいことが好ましく、４０％以上大きいことがより好ましい。金属管２０２ｄの内径は、例えば３００ｍｍ以上である。金属管２０２ｄの内径を例えば３００ｍｍ以上の内径とすることにより、金属管２０２ｄ内を流れる熔融ガラスＭＧの流速が低下して熔融ガラスＭＧが金属管２０２ｄを滞在する時間を長くすることができ、熔融ガラスＭＧの清澄を効率よく行うことができる。   The metal tube 202d preferably has a cylindrical shape. The thickness of the metal tube 202d is preferably 1 mm to 1.5 mm, for example. The inner diameter of the metal tube 202d is larger than the inner diameter of the glass supply tubes 204 and 205, preferably 30% or more larger than the inner diameter of the glass supply tubes 204 and 205, and more preferably 40% or more. The inner diameter of the metal tube 202d is, for example, 300 mm or more. By setting the inner diameter of the metal tube 202d to an inner diameter of 300 mm or more, for example, the flow rate of the molten glass MG flowing in the metal tube 202d can be reduced, and the time for the molten glass MG to stay in the metal tube 202d can be increased. The glass MG can be clarified efficiently.

清澄槽２０２では、ヒータ電極２０２ａ，２０２ｂ，２０２ｃに電流を流すことにより、熔融ガラスＭＧの温度を図３（ｂ）に示すようなＸ方向に沿った分布にする。熔解槽２０１から送られる熔融ガラスＭＧは、ガラス供給管２０４で加熱されて徐々に昇温され、さらに、ヒータ電極２０２ａとヒータ電極２０２ｂとの間では、熔融ガラスＭＧの温度が最大となるように熔融ガラスＭＧは加熱され、ヒータ電極２０２ｂとヒータ電極２０２ｃとの間では、熔融ガラスＭＧの温度が徐々に低下するように熔融ガラスＭＧは加熱される。すなわち、ヒータ電極２０２ａとヒータ電極２０２ｂとの間の領域では、熔融ガラスＭＧに含まれる清澄剤、例えばＳｎＯ2（酸化錫）の還元作用により、例えばＳｎＯ2が酸素を放出するように、熔融ガラスＭＧは昇温される。一方、ヒータ電極２０２ｂとヒータ電極２０２ｃとの間の領域では、熔融ガラスＭＧに含まれる清澄剤、例えばＳｎＯ（ＳｎＯ2が還元された清澄剤）の酸化作用によりＳｎＯが酸素を吸収するように、熔融ガラスＭＧは降温される。さらに、熔融ガラスＭＧは、ガラス供給管２０５において、徐々に降温される。In the clarification tank 202, the temperature of the molten glass MG is distributed along the X direction as shown in FIG. 3B by passing a current through the heater electrodes 202a, 202b, and 202c. The molten glass MG sent from the melting tank 201 is heated by the glass supply pipe 204 and gradually heated, and further, the temperature of the molten glass MG is maximized between the heater electrode 202a and the heater electrode 202b. The molten glass MG is heated, and the molten glass MG is heated between the heater electrode 202b and the heater electrode 202c so that the temperature of the molten glass MG gradually decreases. That is, in the region between the heater electrode 202a and the heater electrode 202b, the molten glass is released so that, for example, SnO 2 releases oxygen by the reducing action of the fining agent contained in the molten glass MG, for example, SnO 2 (tin oxide). MG is heated. On the other hand, in the region between the heater electrode 202b and the heater electrode 202c, so that SnO absorbs oxygen by the oxidizing action of a fining agent contained in the molten glass MG, for example, SnO (a fining agent obtained by reducing SnO 2 ). Molten glass MG is cooled. Furthermore, the temperature of the molten glass MG is gradually lowered in the glass supply pipe 205.

図４（ａ）は、清澄槽２０２の金属管２０２ｄをＸ方向に切断した断面図である。金属管２０２ｄは、熔融ガラスＭＧの流路となる金属管２０２ｄの内壁面に、Ｘ方向に直交する壁となる板材２０２ｅ，２０２ｆが交互に複数設けられている。板材２０２ｅ，２０２ｆは、金属管２０２ｄ内に、金属管２０２ｄに固定された白金又は白金合金等の材質からなる部材によって構成された静的攪拌手段である。すなわち、板材２０２ｅ，２０２ｆは金属管２０２ｄ内を流れる熔融ガラスＭＧを攪拌することにより、熔融ガラスＭＧの管の径方向に沿った温度分布を均一化させる。ここで、熔融ガラスＭＧの径方向に沿った温度の均一化とは、温度分布における温度差が２０℃以内、より好ましくは１０℃以内であることを言い、さらに好ましくは、５℃以内であることをいう。   FIG. 4A is a cross-sectional view of the metal tube 202d of the clarification tank 202 cut in the X direction. In the metal tube 202d, a plurality of plate materials 202e and 202f that are walls orthogonal to the X direction are alternately provided on the inner wall surface of the metal tube 202d that is a flow path of the molten glass MG. The plate members 202e and 202f are static stirring means constituted by a member made of a material such as platinum or a platinum alloy fixed to the metal tube 202d in the metal tube 202d. That is, the plate materials 202e and 202f agitate the molten glass MG flowing in the metal tube 202d, thereby uniformizing the temperature distribution along the radial direction of the tube of the molten glass MG. Here, the homogenization of the temperature along the radial direction of the molten glass MG means that the temperature difference in the temperature distribution is within 20 ° C, more preferably within 10 ° C, and more preferably within 5 ° C. That means.

板材２０２ｅ，２００ｆは、金属管２０２ｄのＸ方向に垂直な断面積が金属管２０２ｄのＸ方向に垂直な断面積の３分の１以上３分の２以下になるように、すなわち、熔融ガラスＭＧの流れを規制するように設けられることが好ましい。熔融ガラスＭＧの流れを規制する板材２０２ｅ，２００ｆの断面積（遮断面積）が小さすぎると、攪拌効果が小さく、遮断面積が大きすぎると、熔融ガラスＭＧの流れを阻害する要素が大きくなりすぎる。好ましくは、上記遮断面積は金属管２０２ｄのＸ方向に垂直な断面積の２分の１程度である。板材２０２ｅは、図４（ｂ）に示すように、金属管２０２ｄの流路断面中心を含む中央領域を通り、金属管２０２ｄを水平方向（図４（ｂ）の左右方向）に横切るように設けられ、流路断面の上記中央領域にある熔融ガラスＭＧの流れを規制する一方、熔融ガラスＭＧが、流路の上部と下部を通過できるようになっている。一方、板材２０２ｆは、図４（ｃ）に示すように、板材２０２ｅの配置と異なり、金属管２０２ｄの流路断面中心を含む中央領域を挟んで、流路断面の上部と下部のそれぞれを水平方向（図４（ｃ）の左右方向）に横切るように設けられ、流路断面の上部と下部にある熔融ガラスＭＧの流れを規制する一方、熔融ガラスＭＧが、金属管２０２ｄの流路断面中心を含む中央領域を通過できるようになっている。すなわち、金属管２０２ｄの管路の熔融ガラスＭＧの流路断面を規制するように、管路の流路方向の異なる位置に設けられた複数の板材２０２ｅ，２０２ｆで構成される。隣接する板材２０２ｅ，２０２ｆの組において、流路断面の規制する部分がお互いに異なっている。なお、板材２０２ｆは、中央領域を挟んで、流路断面の上部と下部のそれぞれを水平方向（図４（ｃ）の左右方向）に横切るように設けられるが、板材２０２ｆを９０度、流路断面の面内で回転させた形状、すなわち、管路の流路断面中心を含む中央領域を挟んで、流路断面の左右の両側の部分のそれぞれを垂直方向（図４（ｃ）の上下方向）に横切るように設けられてもよい。この場合、板材２０２ｅとして図４（ｂ）に示す形状のものを用いることが好ましい。また、板材２０２ｆとして図４（ｃ）に示す形状のものを用いる一方、図４（ｂ）に示す板材２０２ｅを９０度、流路断面の面内で回転させた形状のものが設けられてもよい。   The plate members 202e and 200f are formed so that the cross-sectional area perpendicular to the X direction of the metal tube 202d is not less than one third and not more than two thirds of the cross-sectional area perpendicular to the X direction of the metal tube 202d. It is preferable to be provided so as to regulate the flow of If the cross-sectional areas (blocking areas) of the plate members 202e and 200f that regulate the flow of the molten glass MG are too small, the stirring effect is small, and if the blocking area is too large, the elements that inhibit the flow of the molten glass MG become too large. Preferably, the blocking area is about one half of the cross-sectional area perpendicular to the X direction of the metal tube 202d. As shown in FIG. 4B, the plate member 202e is provided so as to pass through the central region including the center of the cross section of the metal tube 202d and cross the metal tube 202d in the horizontal direction (left and right direction in FIG. 4B). In addition, while restricting the flow of the molten glass MG in the central region of the flow path cross section, the molten glass MG can pass through the upper part and the lower part of the flow path. On the other hand, as shown in FIG. 4C, the plate member 202f is different from the arrangement of the plate member 202e in that the upper and lower portions of the cross section of the flow path are horizontally arranged across the central region including the flow path cross section center of the metal tube 202d. Is provided so as to cross in the direction (left and right direction in FIG. 4C) and regulates the flow of the molten glass MG at the upper and lower portions of the flow path cross section, while the molten glass MG is the center of the flow path cross section of the metal tube 202d. Can pass through a central area including That is, it is composed of a plurality of plate members 202e, 202f provided at different positions in the flow path direction of the pipe so as to regulate the cross section of the molten glass MG in the pipe of the metal pipe 202d. In the set of adjacent plate members 202e and 202f, the portions where the flow path cross section is regulated are different from each other. The plate member 202f is provided so as to cross the upper and lower portions of the cross section of the channel in the horizontal direction (left and right direction in FIG. 4C) across the central region. The shape rotated in the plane of the cross section, that is, the left and right portions of the cross section of the flow path in the vertical direction (vertical direction in FIG. ) May be provided across. In this case, it is preferable to use the plate 202e having the shape shown in FIG. Further, the plate member 202f having the shape shown in FIG. 4C is used, while the plate member 202e shown in FIG. 4B is rotated by 90 degrees in the plane of the channel cross section. Good.

本実施形態では、板材２０２ｅ，２０２ｆの流路断面を規制する部分がお互いに異なっているが、流路断面を規制する部分が同じであってもよい。しかし、熔融ガラスＭＧを上流側から下流側に直線的に流れるのを防止し、熔融ガラスＭＧを上下方向に攪拌しながら流す点で、板材２０２ｅ，２０２ｆの流路断面を規制する部分がお互いに異なっていることが好ましい。また、本実施形態では、２つの板材２０２ｅ，２０２ｆを設けるが、１つの板材のみが設けられて、熔融ガラスＭＧの流路断面を規制するものであってもよい。   In this embodiment, although the part which controls the flow-path cross section of board | plate material 202e, 202f mutually differs, the part which controls a flow-path cross section may be the same. However, it is possible to prevent the molten glass MG from flowing linearly from the upstream side to the downstream side, and to flow the molten glass MG while stirring it in the vertical direction. Preferably they are different. In the present embodiment, two plate members 202e and 202f are provided, but only one plate member may be provided to restrict the flow path cross section of the molten glass MG.

清澄槽２０２では、ガラス供給管２０４から供給された熔融ガラスＭＧを、白金または白金合金からなる外周壁が通電加熱される金属管２０２に流しながら脱泡する。この場合、加熱される金属管２０２ｄの壁付近を流れている熔融ガラスＭＧは、金属管２０２ｄの通電加熱にしたがって昇温し易いが、熔融ガラスＭＧのうち流路断面中心の部分は、加熱された金属壁２０２ｄから離れているため、昇温され難い。すなわち、金属管２０２ｄの径方向に沿って熔融ガラスＭＧの温度分布が生じやすい。このため、板材２０２ｅ，２０２ｆが設けられない従来の清澄槽では、流れる熔融ガラスの管の径方向に沿った温度分布は均一ではなくなる他、金属管の壁から遠い流路断面中心の部分の熔融ガラスの流速は、金属管の壁付近を流れる熔融ガラスの流速に比べて速い。したがって、流路断面中心を流れる熔融ガラスＭＧは加熱されないまま清澄槽を通り抜け易い。金属管２０２ｄの径方向に沿って熔融ガラスＭＧの温度分布が上記理由から生じると、温度分布の中で温度が最も低い部分の温度が、清澄剤が還元作用を発揮して酸素を放出する脱泡に適し、かつ、熔融ガラスＭＧが泡が浮上しやすい粘度を有する温度になるように金属管２０２の加熱温度を高く設定しなければならない。しかし、このような加熱温度を設定すると、金属管２０２ｄを構成する白金や白金合金等の金属成分の揮発が激しくなり、金属管２０２ｄの消耗が激しくなる。このため、本実施形態では、熔融ガラスＭＧの金属管２０２ｄの径方向の温度分布を均一に近づけるために（均一化させるために）、金属管２０２ｄの流路に、熔融ガラスＭＧを攪拌させる手段である板材２０２ｅ，２０２ｆが設けられる。これにより、従来に比べて、金属管２０２ｄを構成する白金あるいは白金合金の揮発を防止しつつ、熔融ガラスＭＧの清澄効果を高めることができる。   In the clarification tank 202, the molten glass MG supplied from the glass supply pipe 204 is defoamed while flowing through the metal pipe 202 whose outer peripheral wall made of platinum or platinum alloy is energized and heated. In this case, the molten glass MG flowing near the wall of the metal tube 202d to be heated is likely to rise in temperature as the metal tube 202d is energized and heated, but the central portion of the flow path cross section of the molten glass MG is heated. It is difficult to raise the temperature because it is away from the metal wall 202d. That is, the temperature distribution of the molten glass MG tends to occur along the radial direction of the metal tube 202d. For this reason, in the conventional clarification tank in which the plate materials 202e and 202f are not provided, the temperature distribution along the radial direction of the flowing molten glass tube is not uniform, and the melting of the central portion of the flow path section far from the wall of the metal tube The flow rate of the glass is faster than the flow rate of the molten glass flowing near the wall of the metal tube. Therefore, the molten glass MG flowing through the center of the channel cross section is likely to pass through the clarification tank without being heated. If the temperature distribution of the molten glass MG occurs along the radial direction of the metal tube 202d for the above-mentioned reason, the temperature at the lowest temperature in the temperature distribution is the desorption that the fining agent exhibits a reducing action and releases oxygen. The heating temperature of the metal tube 202 must be set high so that the molten glass MG has a viscosity at which the molten glass MG can easily float. However, when such a heating temperature is set, the volatilization of metal components such as platinum and platinum alloy constituting the metal tube 202d becomes violent, and the metal tube 202d is consumed greatly. For this reason, in this embodiment, in order to make the temperature distribution in the radial direction of the metal tube 202d of the molten glass MG closer to uniform (in order to make it uniform), means for stirring the molten glass MG in the flow path of the metal tube 202d The plate materials 202e and 202f are provided. Thereby, compared with the past, the clarification effect of molten glass MG can be improved, preventing volatilization of the platinum or platinum alloy which comprises the metal pipe 202d.

本実施形態の板材２０２ｅ，２０２ｆを用いた熔融ガラスＭＧの攪拌が、清澄槽２０２の金属管２０２ｄ内の熔融ガラスＭＧの入り口から、熔融ガラスＭＧの加熱により形成される最高温度（図３（ｂ）参照）近傍までの区間の少なくとも一部分で行われる。上記区間において熔融ガラスＭＧの脱泡工程が行われるので、この脱泡工程で、熔融ガラスＭＧの金属管２０２ｄの径方向に沿った温度分布を均一化させることにより金属管２０２ｄの余分な加熱を抑制でき、金属管２０２ｄを構成する白金あるいは白金合金の揮発を防止しつつ、熔融ガラスＭＧの清澄効果を高めることができる。ここで「最高温度近傍」の「近傍」とは、最高温度に対して例えば１０℃以内の範囲をいい、好ましくは、５℃以内の範囲をいう。したがって、上記区間とは、金属管２０２ｄ内の熔融ガラスＭＧの入り口から、熔融ガラスＭＧの加熱により形成される最高温度の位置を越えて温度が１０℃低下した、上記「近傍」の端までの区間をいう。   Stirring of the molten glass MG using the plate materials 202e and 202f of the present embodiment is the highest temperature formed by heating the molten glass MG from the inlet of the molten glass MG in the metal tube 202d of the clarification tank 202 (FIG. 3 (b ) See) It is performed in at least a part of the section to the vicinity. Since the defoaming step of the molten glass MG is performed in the above section, in this defoaming step, the temperature distribution along the radial direction of the metal tube 202d of the molten glass MG is made uniform so that extra heating of the metal tube 202d is performed. It is possible to suppress the volatilization of platinum or the platinum alloy constituting the metal tube 202d and to enhance the clarification effect of the molten glass MG. Here, “near the highest temperature” means a range within 10 ° C., preferably within 5 ° C. with respect to the highest temperature. Therefore, the section is from the entrance of the molten glass MG in the metal tube 202d to the end of the “near” where the temperature has dropped by 10 ° C. beyond the position of the highest temperature formed by heating the molten glass MG. Refers to a section.

清澄槽２０２では、熔融ガラスＭＧを昇温して脱泡を行った後、熔融ガラスＭＧの温度をヒータ電極２０２ｂ，２０２ｃとの間の金属管２０２ｄを通電加熱することにより、清澄槽２０２の前半における熔融ガラスＭＧの温度に比べて低い、吸収工程に適した温度に下げる。ここで、清澄槽２０２の前半における熔融ガラスＭＧの温度とは、清澄剤の酸素の放出反応が促進され、かつ、熔融ガラスＭＧ中の泡が浮上しやすい粘度（好ましくは、１２０［ｐｏｉｓｅ］〜４００［ｐｏｉｓｅ］）となる温度をいい、この温度は、例えば、無アルカリガラスやアルカリを微量しか含まないアルカリ微量含有ガラス（高温粘性ガラス）、例えば１０2.5［ｐｏｉｓｅ］に相当する温度が１５００℃以上であるガラスにおいてＳｎＯ2を清澄剤として用いた場合、例えば１６１０℃〜１７１０℃の範囲内にある。吸収工程に適した温度は、上記アルカリガラスやアルカリ微量含有ガラスにおいてＳｎＯ2を清澄剤として用いた場合、１２００℃〜１６５０℃の範囲内にある。この結果生じる清澄槽２０２内の熔融ガラスＭＧの最高温度は、１６７０℃〜１７１０℃、あるいは１６９０℃〜１７１０℃にある。また、この場合、図３（ｂ）に示す最高温度の上限は、例えば１７００度〜１７１０度である。
このように、熔融ガラスＭＧに含まれる清澄剤に酸化作用を発揮させて、清澄剤に、熔融ガラスＭＧ中に残存した泡に含まれる酸素を吸収させて清澄を行わせる。このとき、溶融ガラスＭＧの温度は管の壁面の温度と比較して高いため、清澄槽２０２で攪拌が行われない場合には、管路の中心付近を流れる溶融ガラスＭＧは、管の壁面近傍を流れる熔融ガラスの温度に比べて高くなる。すなわち、吸収工程に適した温度まで下がりきらず、清澄が不十分となってしまうという問題がある。このとき、清澄槽２０２は、板材２０２ｅ，２０２ｆを熔融ガラスＭＧの攪拌手段として用いて、熔融ガラスＭＧを攪拌することができる。泡の吸収の際、熔融ガラスＭＧに上述した温度分布が存在すると、上述した理由により効率よく熔融ガラスＭＧに残存する泡を吸収することが難しくなる。このため、本実施形態では、図４（ａ）に示すように、熔融ガラスＭＧの脱泡の際のみならず、泡の吸収の際にも、板材２０２ｅ，２０２ｆが熔融ガラスＭＧの攪拌手段として用いられる。熔融ガラスＭＧの脱泡の際に熔融ガラスを攪拌することにより、あるいは、熔融ガラスＭＧの脱泡の際に加えて泡の吸収の際に熔融ガラスを攪拌することにより、熔融ガラスを攪拌しない場合に比べて、管の壁面の温度を例え数℃〜１０数℃低くすることができる。すなわち、管の壁面の温度を例えば数℃〜１０数℃低くしても、熔融ガラスを攪拌しない場合の熔融ガラスの温度と同じ温度にすることができる。
本実施形態の清澄工程では、熔融ガラスＭＧの脱泡を行うときのみならず、泡の吸収を行うとき、板材２０２ｅ，２０２ｆが熔融ガラスＭＧの攪拌手段として用いられるが、少なくとも熔融ガラスＭＧを昇温させて脱泡を行う部分で、上記温度分布が均一化されるように熔融ガラスＭＧが攪拌されればよい。In the clarification tank 202, after the molten glass MG is heated and defoamed, the temperature of the molten glass MG is energized and heated in the metal tube 202d between the heater electrodes 202b and 202c, thereby the first half of the clarification tank 202. The temperature is lowered to a temperature suitable for the absorption process, which is lower than the temperature of the molten glass MG. Here, the temperature of the molten glass MG in the first half of the clarification tank 202 is a viscosity (preferably, 120 [poise] to 120 [poise] to which the oxygen release reaction of the clarifier is promoted and bubbles in the molten glass MG easily float. 400 [poise]). This temperature is, for example, a non-alkali glass or a glass containing only a trace amount of alkali (high-temperature viscous glass), for example, a temperature corresponding to 10 2.5 [poise] is 1500 ° C. When SnO 2 is used as a fining agent in the glass as described above, for example, it is in the range of 1610 ° C. to 1710 ° C. Temperature suitable for the absorption step, the case of using SnO 2 as a fining agent in the alkali glass or alkali-trace-containing glass is in the range of 1200 ° C. to 1650 ° C.. The maximum temperature of the molten glass MG in the clarification tank 202 resulting from this is 1670 ° C to 1710 ° C, or 1690 ° C to 1710 ° C. In this case, the upper limit of the maximum temperature shown in FIG. 3B is, for example, 1700 degrees to 1710 degrees.
In this way, the fining agent contained in the molten glass MG exhibits an oxidizing action, and the fining agent absorbs the oxygen contained in the bubbles remaining in the molten glass MG and performs fining. At this time, since the temperature of the molten glass MG is higher than the temperature of the wall surface of the tube, when stirring is not performed in the clarification tank 202, the molten glass MG flowing near the center of the tube is near the wall surface of the tube. Higher than the temperature of the molten glass flowing through That is, there is a problem that the temperature is not lowered to a temperature suitable for the absorption process and the clarification becomes insufficient. At this time, the clarification tank 202 can stir the molten glass MG using the plate materials 202e and 202f as stirring means for the molten glass MG. If the temperature distribution described above exists in the molten glass MG during the absorption of bubbles, it becomes difficult to efficiently absorb the bubbles remaining in the molten glass MG for the reasons described above. For this reason, in this embodiment, as shown to Fig.4 (a), not only at the time of defoaming of molten glass MG, but also at the time of absorption of foam, plate material 202e, 202f serves as a stirring means of molten glass MG. Used. When the molten glass is not agitated by stirring the molten glass at the time of defoaming the molten glass MG, or by stirring the molten glass at the time of absorbing bubbles in addition to the defoaming of the molten glass MG As compared with the above, the temperature of the wall surface of the tube can be lowered by several degrees C. to several ten degrees C., for example. That is, even if the temperature of the wall surface of the tube is lowered by, for example, several to 10 ° C., it can be set to the same temperature as the molten glass when the molten glass is not stirred.
In the refining process of this embodiment, not only when defoaming the molten glass MG but also when absorbing bubbles, the plate materials 202e and 202f are used as stirring means for the molten glass MG. It is only necessary that the molten glass MG is stirred so that the temperature distribution is made uniform in the portion where the degassing is performed by heating.

本実施形態の脱泡が行われる金属管２０２ｄは、ガラス供給管２０４に対して段階的に拡大した拡大管であるが、連続的に拡径した拡大管であってもよい。少なくとも金属管２０２ｄは、ガラス供給管２０４に対して拡大した管であるので、金属管２０２ｄ内で、熔融ガラスＭＧの上方に気相空間が存在し、熔融ガラスＭＧに液面を持たせることができ、しかも、流路が広がるので、熔融ガラスＭＧの流速は低下して金属管２０２ｄ内の滞在時間は長くなる他、熔融ガラスＭＧの液面の面積が広がるので、脱泡を効率よく行うことができる。   The metal tube 202d on which defoaming is performed according to the present embodiment is an expansion tube that is expanded stepwise with respect to the glass supply tube 204, but may be an expansion tube that is continuously expanded. Since at least the metal tube 202d is a tube expanded with respect to the glass supply tube 204, a gas phase space exists above the molten glass MG in the metal tube 202d, and the molten glass MG can have a liquid surface. In addition, since the flow path is widened, the flow rate of the molten glass MG is lowered and the residence time in the metal tube 202d is increased, and the area of the liquid surface of the molten glass MG is widened, so that defoaming is performed efficiently. Can do.

（ガラス組成）
本実施形態のガラス基板の製造方法により製造されるガラス基板は、フラットパネルディスプレイ用ガラス基板に好適に用いられる。例えば、Ｌｉ、Ｎａ、及びＫのいずれの成分も含有されていないか、あるいは、Ｌｉ、Ｎａ、及びＫのいずれか少なくとも１つの成分が含有されているとしても、Ｌｉ、Ｎａ、及びＫの内含有する成分の合計量が、０．５質量％以下であるガラス組成を有することが、本実施形態の効果を効率よく発揮する点で好ましい。ガラス組成は、以下に示すものが好適に例示される。(Glass composition)
The glass substrate manufactured by the manufacturing method of the glass substrate of this embodiment is used suitably for the glass substrate for flat panel displays. For example, any component of Li, Na, and K is not contained, or even if at least one component of Li, Na, and K is contained, It is preferable that the total amount of the components to be contained has a glass composition of 0.5% by mass or less from the viewpoint of efficiently exhibiting the effects of the present embodiment. The glass composition is preferably exemplified as follows.

ガラス基板のガラス組成は例えば以下のものを挙げることができる。
以下示す組成の含有率表示は、質量％である。
ＳｉＯ２：５０〜７０％、
Ｂ２Ｏ３：５〜１８％、
Ａｌ２Ｏ３：０〜２５％、
ＭｇＯ：０〜１０％、
ＣａＯ：０〜２０％、
ＳｒＯ：０〜２０％、
ＢａＯ：０〜１０％、
ＲＯ：５〜２０％（ただし、ＲはＭｇ、Ｃａ、Ｓｒ及びＢａから選ばれる少なくとも１種であり、ガラス板が含有するものである)、
を含有する無アルカリガラスであることが好ましい。The glass composition of a glass substrate can mention the following, for example.
The content rate display of the composition shown below is mass%.
SiO 2: 50~70%,
B 2 O 3: 5~18%,
Al 2 O 3: 0~25%,
MgO: 0 to 10%,
CaO: 0 to 20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5 to 20% (However, R is at least one selected from Mg, Ca, Sr and Ba, and the glass plate contains),
It is preferable that it is an alkali free glass containing.

また、ガラス基板のガラスは、以下のガラス組成を挙げることができる
ＳｉＯ２：５０〜７０％、
Ｂ２Ｏ３：１〜１０％、
Ａｌ２Ｏ３：０〜２５％、
ＭｇＯ：０〜１０％、
ＣａＯ：０〜２０％、
ＳｒＯ：０〜２０％、
ＢａＯ：０〜１０％、
ＲＯ：５〜３０％（ただし、ＲはＭｇ、Ｃａ、Ｓｒ及びＢａの合量)、
を含有する無アルカリガラスであることも、同様に好ましい。Further, SiO 2 glass of the glass substrate, may be mentioned glass composition of the following: 50% to 70%,
B 2 O 3 : 1 to 10%,
Al 2 O 3: 0~25%,
MgO: 0 to 10%,
CaO: 0 to 20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5 to 30% (where R is the total amount of Mg, Ca, Sr and Ba),
Similarly, it is also preferable that the glass be an alkali-free glass.

また、ガラス基板のガラスは、以下のガラス組成を挙げることができる
ＳｉＯ２：５０〜７０％、
Ｂ２Ｏ３：３〜１５％、
Ａｌ２Ｏ３：８〜２５％、
ＭｇＯ：０〜１０％、
ＣａＯ：０〜２０％、
ＳｒＯ：０〜２０％、
ＢａＯ：０〜１０％、
ＲＯ：５〜３０％（ただし、ＲはＭｇ、Ｃａ、Ｓｒ及びＢａの合量)、
を含有する無アルカリガラスであることも、同様に好ましい。Further, SiO 2 glass of the glass substrate, may be mentioned glass composition of the following: 50% to 70%,
B 2 O 3 : 3 to 15%,
Al 2 O 3: 8~25%,
MgO: 0 to 10%,
CaO: 0 to 20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5 to 30% (where R is the total amount of Mg, Ca, Sr and Ba),
Similarly, it is also preferable that the glass be an alkali-free glass.

なお、本実施形態では無アルカリガラスとしたが、ガラス基板はアルカリ金属を微量含む（アルカリ金像の合計含有率が０質量％より大きい）アルカリ微量含有ガラスであってもよい。アルカリ金属を含有させる場合、Ｒ’２Ｏの合計が０．１０質量％以上０．５質量％以下(ただし、Ｒ’はＬｉ、Ｎａ及びＫから選ばれる少なくとも１種であり、ガラス基板Ｇが含有するものである)含むことが好ましい。また、ガラスの熔解を容易にするために、比抵抗を低下させるという観点から、ガラス中の酸化鉄の含有量が、Ｆｅ２Ｏ３に換算して０．０１〜０．２質量％であることが好ましく、０．０１〜０．１５質量％であることがより好ましく、０．０１〜０．１０質量％であることがさらに好ましい。また、清澄剤としてＳｎＯ2が添加される場合、ＳｎＯ2の含有量が０．０１〜０．５質量％であることがさらに好ましい。また、本実施形態においては、ＳｎＯ2はガラスを失透しやすくする成分であるため、清澄性を高めつつ失透を起こさせないためには、その含有率が０．０１〜０．５質量％であることが好ましく、０．０５〜０．４質量％であることがより好ましく、０．１〜０．３質量％であることがさらに好ましい。また、Ａｓ2Ｏ3，Ｓｂ2Ｏ3，ＰｂＯを実質的に含まないことが好ましい。Although the alkali-free glass is used in this embodiment, the glass substrate may be a glass containing a trace amount of alkali metal (a total content of alkali gold images is greater than 0% by mass). When the alkali metal is contained, the total of R ′ 2 O is 0.10% by mass or more and 0.5% by mass or less (provided that R ′ is at least one selected from Li, Na and K, and the glass substrate G is It is preferable to contain. In order to facilitate melting of the glass, the content of iron oxide in the glass is 0.01 to 0.2% by mass in terms of Fe 2 O 3 from the viewpoint of reducing the specific resistance. It is preferably 0.01 to 0.15% by mass, more preferably 0.01 to 0.10% by mass. Also, if the SnO 2 is added as a refining agent, it is more preferable that the content of SnO 2 is 0.01 to 0.5 mass%. In the present embodiment, since SnO 2 is a component for devitrified glass, in order not to cause devitrification while improving the clarity, the content of 0.01 to 0.5 mass% It is preferable that it is 0.05-0.4 mass%, and it is further more preferable that it is 0.1-0.3 mass%. Further, it is preferable that As 2 O 3 , Sb 2 O 3 , and PbO are not substantially contained.

上述した成分に加え、本実施形態のガラス基板は、ガラスの様々な物理的、溶融、清澄、および成形の特性を調節するために、様々な他の酸化物を含有しても差し支えない。そのような他の酸化物の例としては、以下に限られないが、ＴｉＯ2、ＭｎＯ、ＺｎＯ、Ｎｂ2Ｏ5、ＭｏＯ3、Ｔａ2Ｏ5、ＷＯ3、Ｙ2Ｏ3、およびＬａ2Ｏ3が挙げられる。   In addition to the components described above, the glass substrate of this embodiment may contain various other oxides to adjust various physical, melting, fining, and forming properties of the glass. Examples of such other oxides include, but are not limited to, TiO2, MnO, ZnO, Nb2O5, MoO3, Ta2O5, WO3, Y2O3, and La2O3.

本実施形態の製造方法では、熔融ガラスＭＧを攪拌することにより、金属管２０２ｄの径方向に沿った熔融ガラスＭＧの温度分布を均一化させる。このため、ガラス組成によって熔解性が低く、熔融ガラスの粘性が高い熔融ガラスを用いる場合であっても、熔融ガラスの粘度を脱泡に適した程度に熔融ガラスを加熱するだけでよく、従来のように、金属管の中心近傍を流れる熔融ガラスの温度を高くするために熔融ガラスをより一層加熱する必要がない。したがって、白金あるいは白金合金で構成された金属管２０２ｄの揮発を抑制しつつ、清澄工程を効果的に行うことができる。
すなわち、１０２．５［ｐｏｉｓｅ］に対応する温度が１５００℃以上（例えば１５００℃以上１６５０℃以下）である粘性の高いガラスであっても、本実施形態の製造方法では、好適にガラス基板を構成するガラスとして用いることができ、白金あるいは白金合金で構成された金属管２０２ｄの揮発を抑制しつつ、清澄工程を効果的に行うことができる。
また、粘性の高いガラスでなくても、近年、環境負荷の観点から、Ａｓ2Ｏ3に代わって、ＳｎＯ2が清澄剤として用いられる場合、Ａｓ2Ｏ3が清澄剤として用いられる場合よりも熔融ガラスを高温にするため、ますます白金あるいは白金合金の揮発が問題となっている。しかし、本実施形態の製造方法では、従来のように、金属管の中心近傍を流れる熔融ガラスの温度を高くするために熔融ガラスをより一層加熱する必要がない。したがって、白金あるいは白金合金で構成された金属管２０２ｄの揮発を抑制しつつ、清澄工程を効果的に行うことができる。In the manufacturing method of this embodiment, the temperature distribution of the molten glass MG along the radial direction of the metal tube 202d is made uniform by stirring the molten glass MG. For this reason, even when a molten glass having a low melting property and a high viscosity of the molten glass is used, it is only necessary to heat the molten glass to a degree suitable for defoaming. Thus, there is no need to further heat the molten glass in order to increase the temperature of the molten glass flowing near the center of the metal tube. Therefore, the clarification step can be effectively performed while suppressing volatilization of the metal tube 202d made of platinum or a platinum alloy.
That is, even in the case of highly viscous glass having a temperature corresponding to 102.5 [poise] of 1500 ° C. or higher (for example, 1500 ° C. or higher and 1650 ° C. or lower), the manufacturing method according to the present embodiment preferably configures the glass substrate. It can be used as a glass to be used, and the clarification step can be effectively performed while suppressing the volatilization of the metal tube 202d made of platinum or a platinum alloy.
Even if the glass is not highly viscous, in recent years, from the viewpoint of environmental load, instead of As2O3, when SnO2 is used as a fining agent, the molten glass is made to have a higher temperature than when As2O3 is used as a fining agent. Increasingly, volatilization of platinum or platinum alloys is a problem. However, in the manufacturing method of this embodiment, it is not necessary to heat the molten glass further in order to increase the temperature of the molten glass flowing in the vicinity of the center of the metal tube, as in the prior art. Therefore, the clarification step can be effectively performed while suppressing volatilization of the metal tube 202d made of platinum or a platinum alloy.

（変形例）
本実施形態では、図４（ａ）に示すように、金属管２０２ｄ内に設けられた板材２０２ｅ，２０２ｆを交互に複数配置するが、板材２０２ｅ，２０２ｆを１組配置してもよい。
また、図６（ａ）に示すように、金属管２０２ｄの壁から管路の内側に向かって延びるが、延びる高さが異なる板材２０２ｅ，２０２ｆを金属管２０２ｄに交互に設けてもよい。すなわち、隣接する板材２０２ｅ，２０２ｆの高さが異なるので、板材２０２ｅ，２０２ｆの組の、流路断面を規制する部分がお互いに異なっている。この場合、板材２０２ｅ，２０２ｆによる攪拌によって、熔融ガラスＭＧは、図中に示す破線のように波打って流れる。すなわち、図６（ａ）に示す板材２０２ｅ，２０２ｆは、熔融ガラスＭＧを攪拌させる攪拌手段として用いられる。
さらに、本実施形態の図４（ａ），（ｂ）に示す板材２０２ｅ，２０２ｆの代わりに、図６（ｂ）に示すように、円形状または半円形状の複数の孔が開いた板材２０２ｅと、この孔と配置が異なる孔を設けた板材２０２ｆを、金属管２０２ｄに交互に設けてもよい。
また、本実施形態の図４（ａ），（ｂ）に示す板材２０２ｅ，２０２ｆの代わりに、図６（ｃ）に示すように、一方向に複数のスリット孔が開いた板材２０２ｅと、このスリット孔の向きが異なるスリット孔を設けた板材２０２ｆとを、金属管２０２ｄに交互に設けてもよい。図６（ｂ）、（ｃ）の場合においても、板材２０２ｅ，２０２ｆの組の、流路断面を規制する部分がお互いに異なっている。このため、熔融ガラスＭＧは、板材２０２ｅ，２０２ｆによって効率よく攪拌される。(Modification)
In the present embodiment, as shown in FIG. 4A, a plurality of plate members 202e and 202f provided in the metal tube 202d are alternately arranged, but one set of plate members 202e and 202f may be arranged.
As shown in FIG. 6A, plate members 202e and 202f extending from the wall of the metal pipe 202d toward the inside of the pipe line but having different extending heights may be alternately provided in the metal pipe 202d. That is, since the heights of the adjacent plate members 202e and 202f are different, the portions of the set of the plate members 202e and 202f that restrict the flow path cross section are different from each other. In this case, the molten glass MG flows undulatingly as indicated by the broken line shown in the figure by stirring with the plate materials 202e and 202f. That is, the plate materials 202e and 202f shown in FIG. 6A are used as stirring means for stirring the molten glass MG.
Furthermore, instead of the plate members 202e and 202f shown in FIGS. 4A and 4B of the present embodiment, as shown in FIG. 6B, a plate member 202e having a plurality of circular or semicircular holes opened. And the plate material 202f provided with the hole which arrangement | positioning differs from this hole may be provided in the metal pipe 202d alternately.
Further, instead of the plate members 202e and 202f shown in FIGS. 4A and 4B of the present embodiment, as shown in FIG. 6C, a plate member 202e having a plurality of slit holes in one direction, The plate member 202f provided with slit holes having different slit hole directions may be alternately provided in the metal tube 202d. In the case of FIGS. 6B and 6C as well, the portions of the set of plate members 202e and 202f that restrict the cross section of the flow path are different from each other. For this reason, the molten glass MG is efficiently stirred by the plate materials 202e and 202f.

さらに、本実施形態のように板材２０２ｅ，２０２ｆを熔融ガラスＭＧの攪拌のための手段（静的攪拌手段）として用いる代わりに、図７に示すように、回転軸２０２ｇに羽根２０２ｈを設け、回転軸２０２ｇを回転させる攪拌機２０２ｉを動的攪拌手段として金属管２０２ｄに設けることにより、熔融ガラスＭＧを攪拌させてもよい。   Further, instead of using the plate materials 202e and 202f as a means for stirring the molten glass MG (static stirring means) as in the present embodiment, as shown in FIG. The molten glass MG may be stirred by providing the metal tube 202d with a stirrer 202i that rotates the shaft 202g as a dynamic stirring means.

以上、本発明のガラス基板の製造方法について詳細に説明したが、本発明は上記実施形態に限定されず、本発明の主旨を逸脱しない範囲において、種々の改良や変更をしてもよいのはもちろんである。   As mentioned above, although the manufacturing method of the glass substrate of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, you may make various improvement and a change. Of course.

２００ 熔解装置
２０１ 熔解槽
２０２ 清澄槽
２０２ａ，２０２ｂ，２０２ｃ ヒータ電極
２０２ｄ 金属管
２０２ｅ，２０２ｆ 板材
２０２ｇ 回転軸
２０２ｈ 羽根
２０２ｉ 攪拌機
２０３ 攪拌槽
２０３ａ スターラ
２０４，２０５，２０６ ガラス供給管
３００ 成形装置
３１０ 成形体
４００ 切断装置200 melting apparatus 201 melting tank 202 clarification tank 202a, 202b, 202c heater electrode 202d metal tube 202e, 202f plate material 202g rotating shaft 202h blade 202i stirrer 203 stirring tank 203a stirrer 204, 205, 206 glass supply pipe 300 molding apparatus 310 molded body 400 Cutting device

Claims (13)

ガラス基板の製造方法であって、
白金または白金合金からなる外周壁が加熱される管に、熔融ガラスを流しながら清澄する清澄工程を含み、
前記清澄工程は、前記熔融ガラス中の気泡を熔融ガラスの液面から前記管内の気相に向けて放出させる脱泡工程を含み、
前記脱泡工程では、前記熔融ガラスを攪拌することにより、前記管の流路断面の中央領域にある熔融ガラスの流れを抑制し、前記熔融ガラスの前記管の径方向に沿った温度分布を均一化させる、ことを特徴とするガラス基板の製造方法。 A method of manufacturing a glass substrate,
Including a clarification step of clarification while flowing molten glass in a tube whose outer peripheral wall made of platinum or a platinum alloy is heated,
The clarification step includes a defoaming step of releasing bubbles in the molten glass from a liquid surface of the molten glass toward a gas phase in the tube,
In the defoaming step, by stirring the molten glass, the flow of the molten glass in the central region of the flow path cross section of the tube is suppressed, and the temperature distribution along the radial direction of the tube of the molten glass is uniform. The manufacturing method of the glass substrate characterized by the above-mentioned. 前記管内の前記熔融ガラスの入り口から、前記熔融ガラスの加熱により形成される最高温度近傍までの区間の少なくとも一部分で、前記熔融ガラスを攪拌する、請求項１に記載のガラス基板の製造方法。   The manufacturing method of the glass substrate of Claim 1 which stirs the said molten glass in at least one part of the area from the entrance of the said molten glass in the said pipe | tube to the maximum temperature vicinity formed by the heating of the said molten glass. 前記管は、前記管より上流側に設けられる上流管より拡径した拡大管であり、
前記脱泡工程は、前記拡大管で行われる、請求項１または２に記載のガラス基板の製造方法。 The pipe is an enlarged pipe having a diameter larger than that of an upstream pipe provided on the upstream side of the pipe,
The said defoaming process is a manufacturing method of the glass substrate of Claim 1 or 2 performed with the said expansion tube. 前記熔融ガラスには、清澄剤として、ＳｎＯ2を含有する、請求項１〜３のいずれか１項に記載のガラス基板の製造方法。Wherein the molten glass, as refining agent, containing SnO 2, method of manufacturing a glass substrate according to any one of claims 1 to 3. 前記製造されるガラス基板は、１０２．５［ｐｏｉｓｅ］の粘度に対応する温度が１５００℃以上である、請求項１〜４のいずれか１項に記載のガラス基板の製造方法。Glass substrate prepared above are 10 2.5 temperature corresponding to the viscosity of [poise] is 1500 ° C. or more, a manufacturing method of a glass substrate according to any one of claims 1 to 4. 前記脱泡工程において攪拌される前記熔融ガラスの粘度は、１２０〜４００［ｐｏｉｓｅ］である、請求項１〜５のいずれか１項に記載のガラス基板の製造方法。   The manufacturing method of the glass substrate of any one of Claims 1-5 whose viscosity of the said molten glass stirred in the said defoaming process is 120-400 [poise]. 前記管内の上方に気相の空間を有する、請求項１〜６のいずれか１項に記載のガラス基板の製造方法。   The manufacturing method of the glass substrate of any one of Claims 1-6 which has a gaseous-phase space above the said pipe | tube. 製造される前記ガラス基板は、無アルカリガラスあるいはアルカリ微量含有ガラスで構成される、請求項１〜７のいずれか１項に記載のガラス基板の製造方法。   The said glass substrate manufactured is a manufacturing method of the glass substrate of any one of Claims 1-7 comprised with an alkali free glass or alkali trace amount glass. 前記熔融ガラスの攪拌は、前記管に固定された板部材によって構成された静的攪拌手段を用いて行われる、請求項１〜８のいずれか１項に記載のガラス基板の製造方法。   The method for manufacturing a glass substrate according to any one of claims 1 to 8, wherein the stirring of the molten glass is performed using a static stirring means constituted by a plate member fixed to the tube. 前記静的攪拌手段は、前記管内の熔融ガラスの流路断面を規制するように設けられた板部材である、請求項９に記載のガラス基板の製造方法。   The said static stirring means is a manufacturing method of the glass substrate of Claim 9 which is a board member provided so that the flow-path cross section of the molten glass in the said pipe | tube may be controlled. 前記静的攪拌手段は、前記管内の熔融ガラスの流路断面を規制するように、前記管内の流路方向の異なる位置に設けられた複数の板部材で構成され、隣接する板部材の組のうち少なくとも１つの組では、前記流路断面の規制する部分がお互いに異なっている、請求項１０に記載のガラス基板の製造方法。   The static stirring means is composed of a plurality of plate members provided at different positions in the flow channel direction in the tube so as to regulate the flow channel cross section of the molten glass in the tube, and the set of adjacent plate members. The method for producing a glass substrate according to claim 10, wherein in at least one of the groups, the portions to be regulated of the cross section of the flow path are different from each other. 前記熔融ガラスの攪拌は、動的攪拌手段を用いて行われる、請求項１〜８のいずれか１項に記載のガラス基板の製造方法。   The method for producing a glass substrate according to any one of claims 1 to 8, wherein the stirring of the molten glass is performed using a dynamic stirring means. 前記清澄工程は、さらに、前記脱泡工程後、熔融ガラス中の気泡を前記熔融ガラスに吸収させる吸収工程を含み、
前記吸収工程では、前記熔融ガラスが攪拌される、請求項１〜１２のいずれか１項に記載のガラス基板の製造方法。The clarification step further includes an absorption step of absorbing bubbles in the molten glass into the molten glass after the defoaming step,
The manufacturing method of the glass substrate of any one of Claims 1-12 with which the said molten glass is stirred at the said absorption process.
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