JP3911321B2

JP3911321B2 - Method for producing highly homogeneous glass

Info

Publication number: JP3911321B2
Application number: JP14532097A
Authority: JP
Inventors: 哲也青木; 龍也妹尾; 敬一吉田; 弘康遠藤
Original assignee: Ohara Inc
Current assignee: Ohara Inc
Priority date: 1997-06-03
Filing date: 1997-06-03
Publication date: 2007-05-09
Anticipated expiration: 2017-06-03
Also published as: JPH10338528A

Description

【０００１】
【発明の属する技術分野】
この発明は、例えば、半導体製造用ステッパーの光学系に用いられるような高均質ガラスの製造方法に関する。
【０００２】
【従来の技術】
光学ガラスの製造方法として、例えば、ガラス原料を溶融する溶融工程、溶融ガラスの清澄を行う清澄工程、溶融ガラスを攪拌する攪拌工程を連続的に行った後、型成形等によりガラスの成形を行う製造方法が一般的に知られている。清澄工程では、例えば気泡やガス等の除去を行い、攪拌工程では、溶融ガラスの局所的ならびに大域的な屈折率の均一化を行う。
【０００３】
ところで、例えば、半導体製造用ステッパーの光学系などに用いられる光学ガラス（高均質ガラス）では、ガラス製品の一端から一端における屈折率変動幅が１０^-7オーダーの範囲内であることが求められつつある。
【０００４】
このような高均質ガラスを製造すべく、従来、攪拌工程や清澄工程に関する多くの提案がなされている。例えば、特開昭５６−１４００３０号には、攪拌工程における提案として、溶融窯のネック部に特定のバリヤーを設け、このバリヤーにより溶融ガラス流を攪拌して均質化を行う方法が開示されている。特開平５−２０８８３０号には、清澄工程における提案として、減圧状態で溶融ガラスを攪拌して脱泡と均質化を行う方法が開示されている。特開昭５８−８８１２６号や特開昭６１−２１９２２号や特開平２−４８４２２号には、攪拌工程に関する提案として攪拌翼の考案がなされている。
しかしながら、上記の攪拌工程や清澄工程に関する提案だけでは、上記屈折率変動幅が１０^-7オーダーの許容誤差におさまる高均質ガラスの製造は達成できなかった。
【０００５】
更に、上記の攪拌工程や清澄工程に関する多数の提案は、溶融ガラスの局所的な均一化、或いは、比較的小さな攪拌槽内での均一化を計るものであり、均質化される範囲はさほど大きなものでなかった。つまり、清澄工程、攪拌工程を経て型に流し込まれる溶融ガラスを、時間的変化でみた場合、屈折率の時間的変化は比較的大きなものであった。
そのため、複数のガラス製品（同一種のガラス製品）を連続して製造したり、ガラス製品をロット生産で製造する場合、各製品間でみた屈折率の変化や、ロット間での屈折率の変化は比較的大きくなるという問題があった。
【０００６】
この問題に関し、溶融ガラスの屈折率の時間的変化を小さくするために、例えば、図５に示す特公昭３１−１６８１号公報の技術が提案されている。
この技術は、溶融されたガラスを移送流路Ｐ２を介して混合槽（循環混合槽）Ｐ３に送り、混合槽Ｐ３で大域的な攪拌を行った後、攪拌流路Ｐ８で局所的な攪拌を行い、その後、溶融ガラスを送給口Ｐ１２から型等へ送給するものである。
【０００７】
上記混合槽Ｐ３での大域的な攪拌は、還流機構（推進翼Ｐ４、循環混合筒としての還流管Ｐ５）により、溶融ガラスを上下に還流することで行われている。そして、混合槽Ｐ３から攪拌流路Ｐ８に流入させる量より大量の溶融ガラスを、混合槽Ｐ３内で還流させることにより、攪拌流路Ｐ８に流入する溶融ガラス、延いては、送給口Ｐ１２から送給される溶融ガラスの屈折率の時間的変化を小さくしようとするものである。
【０００８】
補助管Ｐ１０は、バッチ処理など、溶融ガラスの混合槽Ｐ３への投入をまとめて間欠的に行う際に、攪拌流路Ｐ８に残った残ガラスを還流させるものであって、溶融ガラスを連続的に処理する際には使用されないものである。連続的な処理の際には補助管Ｐ１０中の溶融ガラスを固化させて補助管Ｐ１０を塞ぐとしている。
【０００９】
【発明が解決しようとする課題】
上記の技術について、本発明者らが調査確認したところ、次にあげるような様々な不具合が生じて、溶融ガラスの屈折率の時間的変化を所望のレベルまで十分に小さくすることが出来ないという結論に達した。
【００１０】
即ち、上記の混合槽Ｐ３内で溶融ガラスを還流させる方法では、撹拌装置Ｐ１に入るガラス流と混合槽Ｐ３内のガラスの温度をほぼ同じにしなければならず、それらの温度がずれると、温度差に起因する比重差によって、例えば、流入する溶融ガラスの温度が低ければ、撹拌されずに混合槽Ｐ３の壁を伝わって、撹拌されないまま攪拌流路Ｐ８に入ってしまうガラスが多くなってしまい、逆に流入するガラスの温度が高ければ、混合槽Ｐ３の上面に滞留し、混合槽Ｐ３の上面の外周部分にあるガラスが撹拌されないまま攪拌流路Ｐ８に入ってしまうという不具合を生じさせる。
【００１１】
また、流入する溶融ガラスと混合槽Ｐ３の溶融ガラスの温度を同一にしても、推進翼Ｐ４によって、混合槽Ｐ３内の溶融ガラスに回転方向の流れが生じ、流入した溶融ガラスの一部はその遠心力により混合槽Ｐ３上面の壁の周りに滞留し、次いで、攪拌流路Ｐ８の上面付近へ達した混合されていない溶融ガラスが、そのまま攪拌流路Ｐ８に引き込まれていくという現象を生じて、溶融ガラスの均質度を低下させるという不具合が生じる。
【００１２】
また、この混合槽Ｐ３内で溶融ガラスを還流させる方法では、溶融ガラスの還流量の制御が任意に行い難いという欠点を有するため、この方法を、連続的にガラスを溶融・流出・成形していく処理に用いようとすると、次のような不具合が生じる。即ち、溶融ガラスの流出量を大きくしようとすると、流出量に対する還流量の比率が低減して、還流による屈折率変動の低減が難しくなるが、これを回避すべく、推進翼Ｐ４を高回転にさせると、還流機構（推進翼Ｐ４、還流管Ｐ５）に高負荷がかかり、還流機構の破損等の危険を生じたり、またこれを設備的に回避しても、混合槽Ｐ３内の推進翼Ｐ４上にボルテックスが生じ、そこから気泡を巻き込んでしまうため、結局、高回転にして還流量を確保しようとする方法を採ることができない。また推進翼Ｐ４の回転を逆にして循環の方向を逆にして、推進翼Ｐ４上のボルテックスだけでも防止しようとすると、高速に回転している攪拌手段Ｐ７による溶融ガラスの流れと還流による溶融ガラスの循環の方向が同一になり、混合槽Ｐ３に流入してきた溶融ガラスが還流を経ないままショートパスして攪拌流路Ｐ８に流入する様になり、逆に屈折率の変動を増進してしまうことになる。
【００１３】
つまり、上記の技術によれば、還流機構（推進翼Ｐ４、還流管Ｐ５）で溶融ガラスを還流させることで屈折率の時間的な平均化が行われるものの、上述のような不具合が生じるため総合的には屈折率変動幅を低くすることが出来ず、屈折率変動幅が１０^-7オーダーの高均質ガラスの製造には適用できない。
【００１４】
この発明は、上記実状に鑑みてなされたもので、屈折率変動幅の許容誤差が１０^-7オーダーの高均質ガラスの製造に利用でき、且つ、複数の製品間や製造ロット間でも屈折率の変化を小さくすべく、型に流し込まれる溶融ガラスの屈折率の時間的変化を十分に小さくすることが可能な高均質ガラスの製造方法を提供することを目的としている。
【００１５】
【課題を解決するための手段】
上記課題を解決するため、
請求項１記載の発明は、溶融ガラスを均質化する循環混合工程を含んだ高均質ガラスの製造方法であって、
溶融ガラスを均質化するための循環混合槽と、
該循環混合槽内に収容され両端側に開口部を有する循環混合筒と、
該循環混合筒内に配置され、循環混合筒内の溶融ガラスに推進力を与える推進手段と、
前記循環混合槽外から前記循環混合筒の側壁部に直結された筒直結管と、
前記循環混合槽外から前記循環混合槽に接続された槽接続管と
を有する循環混合装置を使用し、
前記循環混合工程において、
前工程の溶融ガラスを前記筒直結管に通して前記循環混合筒に流入させ、
前記循環混合筒内で溶融ガラスを推進して該溶融ガラスを前記循環混合筒の内側と外側に沿った還流経路で還流させ、
前記循環混合筒外の溶融ガラスを前記槽接続管を通して次工程に流出させる処理を含んでいる方法とした。
【００１６】
この高均質ガラスの製造方法によれば、上記の循環混合筒の内側と外側に沿って回る溶融ガラスの還流によって、溶融ガラスの屈折率の時間的な平均化が行われることに加え、溶融ガラスの流入が上記筒直結管を介して循環混合筒内に直接行われ、且つ、溶融ガラスの流出が上記槽接続管を介して循環混合筒の外から行われるので、従来の技術（循環混合槽内の循環混合筒で還流を行う形式の技術）にあった次のような不具合を解消して、攪拌性能を向上させることが出来る。
【００１７】
即ち、従来のものでは、流入した溶融ガラスの一部が循環混合槽の壁伝いに移動して循環混合筒に入らないまま流出してしまうという不具合があったのに対して、この発明では、溶融ガラスの流入は循環混合筒内に、流出は循環混合筒外で行われるので、従来のように溶融ガラスが壁伝いにショートパスして流出することがない。
【００１８】
また、従来のものでは、上記のようなショートパスが発生しやすいことから推進方向を上向きに出来ず、それによりボルテックスが生じやすく推進力をあまり大きく出来ないという不具合があったのに対して、この発明では、ショートパスの回避作用が溶融ガラスの推進方向を逆向きにしても同様に及ぼされるので、推進方向を上向きにしてボルテックスの発生を防止すると共に、推進力を大きくして溶融ガラスの還流量を多くすることが出来る。つまり、溶融ガラスの還流方向や還流速度が任意に選択できることとなり、攪拌作用が飛躍的に向上する。
【００１９】
また、従来のものでは、流入した溶融ガラスの温度が槽内の溶融ガラスより高温である場合に、流入した溶融ガラスが上層で滞留して悪影響を及ぼすことがあったのに対して、この発明では、流入する溶融ガラスの温度変化があった場合でも、流入した溶融ガラスは循環混合筒で強制的に推進される（推進手段が攪拌作用も有していれば強制的に攪拌も行われる）ので、上記の滞留現象を回避することが出来る。また、上述したように溶融ガラスの還流速度を大きくすることが出来ることから、上記の滞留現象を回避することが出来る。
以上のように、この発明の高均質ガラスの製造方法によれば、攪拌性が良く、屈折率の時間的な平均化が確実に行われて、溶融ガラスの均一化の向上を計ることが出来る。従って、屈折率の許容誤差が１０^-7オーダーの高均質ガラスの製造に利用可能で、且つ、複数の製品間や製造ロット間でも屈折率の変化を小さくすることが出来る。
【００２０】
また、請求項２記載の高均質ガラスの製造方法のように、前記循環混合工程の前工程の溶融ガラスを前記槽接続管を通して前記循環混合筒外に流入させ、前記循環混合筒内で溶融ガラスを推進し溶融ガラスを前記循環混合筒の内側と外側に沿って回る還流経路で還流させ、前記循環混合筒内の溶融ガラスを前記筒直結管に通して次工程に流出させるようにしても良く、この製造方法により請求項１記載の発明と同様の効果が得られる。
【００２１】
なお、推進手段には、推進機能と共に攪拌機能も付加することが好ましく、そうすることで、還流する溶融ガラスの局所的な攪拌も行われ、還流による屈折率の平均化も確実となる。また、循環混合槽において攪拌処理を行っても良く、更に、その攪拌処理は様々な公知技術を適用することが可能であり、また、攪拌処理を行う箇所も循環混合筒の内側や外側、並びに、筒直結管内や槽接続管内など適宜選択可能である。
【００２６】
また、請求項３記載の発明のように、
前記循環混合筒の中央軸に垂直な平面視で、前記循環混合槽の内径をＤ、前記循環混合筒の内径をｄとして、ｄ／Ｄが０．２〜０．８である循環混合装置を用いると好ましく、更に好ましくは、ｄ／Ｄが０．４〜０．６のものを用いると良い。
【００２７】
循環混合槽の内径Ｄに対して循環混合筒の内径ｄを小さくすると、循環混合筒の内側の還流速度に対して外側の還流速度が低くなって、攪拌効率が低下する。一方、循環混合槽の内径Ｄに対して循環混合筒の内径ｄを大きくすると、推進手段の負荷が増して還流効率が低下する。
両者の効率を総合的な指標に表すと、ｄ／Ｄ＝０．２〜０．８の範囲、更にはｄ／Ｄ＝０．４〜０．６の範囲にピークを有し、この範囲内に設定するのが好ましい。
【００２８】
また、請求項４記載のように、
前記循環混合筒は両端部を上下に配置され、
前記循環混合工程中に前記循環混合槽中に満たされる溶融ガラスの溶液面高さをＨ、
前記循環混合筒の上部開口部の下端から前記溶融ガラスの溶液面高さまでの距離をｈ１、
前記循環混合筒の下部開口部の上端から前記循環混合槽底面までの距離をｈ２として、
ｈ１／Ｈを０〜０．５、
ｈ２／Ｈを０．０２〜０．５に設定すると好ましく、
更に好ましくは、
ｈ１／Ｈを０．０５〜０．４、
ｈ２／Ｈを０．０５〜０．４に設定すると良い。
【００２９】
溶液面高さＨに対して、溶液面から循環混合筒の上部開口部の下端までの距離ｈ１を大きくすると循環混合筒より上方の還流速度が低くなって、溶融ガラスの滞留現象が生じやすくなる。また、溶液面高さＨに対して、循環混合槽の底から循環混合筒の下部開口部の上端までの距離ｈ２を大きくすると循環混合筒より下方の還流速度が低くなって、溶融ガラスの滞留現象が生じやすくなる。一方、上記の距離ｈ２を小さくすると溶液ガラスが流れにくくなる。
上記の作用を総合的な指標に表すと、ｈ１／Ｈ＝０〜０．５、更にはｈ１／Ｈ＝０．０５〜０．４の範囲にピークを有し、この範囲に設定するのが効果的である。また、ｈ２／Ｈ＝０．０２〜０．５、更にはｈ２／Ｈ＝０．０５〜０．４の範囲にピークを有し、この範囲に設定するのが効果的である。
【００３０】
また、請求項５記載の高均質ガラスの製造方法のように、前記筒直結管あるいは槽接続管を介して流出する溶融ガラスの流量に対して、前記循環混合筒を通過する溶融ガラスの流量を２．０倍以上にするのが好ましく、更に好ましくは３．０〜８０．０倍、更に好ましくは４．０〜６０．０倍にするのが良い。
【００３１】
循環混合筒の内側と外側に沿って回る還流により溶融ガラスの屈折率の時間的な平均化を行うには、上記の還流流量が循環混合槽から流出する溶融ガラスの流量の２．０倍以上必要であり、それより多ければ多い程、屈折率の時間的な平均化を確実にできる。一方、還流流量が多すぎると生産効率の低下を招く。
両者の効率を考慮すれば、還流流量と循環混合槽からの流出流量とを上記の範囲に設定するのが妥当である。好ましくは３．０〜８０．０倍、更に好ましくは４．０〜６０．０倍である。
【００３２】
【発明の実施の形態】
以下、この発明の実施の形態について、図１〜図４の図面を参照しながら説明する。
［第１の実施の形態］
図１は、本発明の第１の実施の形態の高均質ガラスの製造装置を示す概要図である。
【００３３】
この実施の形態の高均質ガラスの製造装置１００は、本発明に係る高均質ガラスの製造方法を実施するもので、溶解槽２、清澄槽３、循環混合装置１０、攪拌槽４を連通管５，６，７を介して接続して構成される。また、図示しないが、ガラス原料を所定量ずつ溶解槽２に投入していく原料投入装置や、各槽（溶解槽２、清澄槽３、循環混合槽１０Ａ、攪拌槽４）の温度を制御する温度制御装置、並びに、成形型を有し攪拌槽４から排出される溶融ガラスを成形する成形装置などを備えている。
【００３４】
溶解槽２と清澄槽３は、投入されるガラス原料を溶解する機能、並びに、溶融ガラスから例えば気泡やガス等を除去して清澄する機能を有する一般的なもので、様々な従来技術が適用可能である。
攪拌槽４は、溶融ガラスの小さな脈理を解消するためのもので、例えば、攪拌手段８により溶融ガラスを局所的に攪拌する形式など、様々な従来技術が適用可能である。この攪拌槽４の下流側に排出口９が設けられている。
【００３５】
循環混合装置１０は、本発明に係るもので、図２（ａ）にその拡大図を示すが、循環混合槽１０Ａ、循環混合筒１２、槽接続管１４、筒直結管１５、および、推進・攪拌手段１８等から構成される。
【００３６】
循環混合槽１０Ａは、中心軸が鉛直に向いた略円筒形状のもので、底部１０Ｂを有している。なお、循環混合槽は円筒形状に限られるものではなく適宜変更可能である。
循環混合筒１２は、中心軸が鉛直に向いた略円筒形状のもので、その内径ｄが循環混合槽１０Ａの内径Ｄに対してｄ／Ｄ＝０．４〜０．６の範囲のものを用いている。循環混合筒１２は、循環混合槽１０Ａの略中央に配置され、その上端と下端は開口した状態になっている。また、循環混合筒１２の側面下部には複数の開口部１２ａ，１２ａ…が設けられている。
【００３７】
循環混合筒１２の開口部の上下端の位置は、上部開口部の下端と溶融ガラスの溶液面との距離をｈ１、下部開口部の上端と循環混合槽１０Ａの底部１０Ｂとの距離をｈ２、底部１０Ｂから溶融ガラスの溶液面の高さをＨとして、ｈ１／Ｈ＝０．０５〜０．４、並びに、ｈ２／Ｈ＝０．０５〜０．４になるように配置されている。
【００３８】
槽接続管１４は、循環混合装置１０から溶融ガラスを排出するための管で、一端側が循環混合槽１０Ａの壁部に接続され、他端側が連通管７を介して攪拌槽４に接続されている。
筒直結管１５は、循環混合装置１０に溶融ガラスを流入するための管で、一端側が連通管６を介して清澄槽３に接続され、他端側が循環混合筒１２の側壁部に接続されている。
【００３９】
これら槽接続管１４と筒直結管１５は、例えば、水平方向にみて反対側の位置で、且つ、上下方向で中段より上方位置に接続されている。即ち、循環混合筒１２の内側と外側に沿って回る還流経路において経路長が長くなる配置となっている。この配置によって、循環混合装置１０の流入口から流出口への溶融ガラスのショートパスが確実に回避されるようになっている。
なお、推進・攪拌手段１８による推進方向を逆転する場合には、槽接続管１４および筒直結管１５を上下方向で中段より下方位置に接続することで、還流経路において、循環混合装置１０の流入口から流出口までの経路長を長くすることが出来る。
【００４０】
推進・攪拌手段１８は、例えば、推進翼１８ａ，１８ａや攪拌棒１８ｂ，１８ｂ、並びに、これらを回転させるモーター１８ｃなどから構成され、推進翼１８ａ，１８ａの回転により循環混合筒１２内の溶融ガラスに推進力を与えると共に、攪拌棒１８ｂ，１８ｂ（或いは推進翼１８ａ，１８ａも含む）の回転により循環混合筒１２内の溶融ガラスを攪拌して、溶融ガラスの局所的な屈折率の均一化、例えば、水平方向の屈折率の均一化を及ぼすようになっている。
【００４１】
これら推進翼１８ａ，１８ａや攪拌棒１８ｂ，１８ｂの回転径は、循環混合筒１２の内側面に近接する長さに設けられ、それにより、循環混合筒１２を通過する溶融ガラスが攪拌翼１８ａ，１８ａや攪拌棒１８ｂ，１８ｂの回転径範囲の外側を通って攪拌されないまま還流するのを防止している。
【００４２】
本発明に係る高均質ガラスの製造方法は、上記のような構成の製造装置１００を用いて次のように実施される。
【００４３】
すなわち、原料投入装置により溶解槽２に溶融ガラスの流出量と等量となるガラス原料を連続的に投入していき、溶解槽２でのガラス原料の溶解工程、清澄槽３での溶融ガラスの清澄工程、循環混合槽１０Ａでの溶融ガラスの循環混合工程、攪拌槽４での溶融ガラスの攪拌工程を順次連続して行い、均質化された溶融ガラスを連続的に排出口９から排出していく。
【００４４】
上記一連の過程中、清澄槽３で清澄処理された後に溶融ガラスが連通管６に進入して循環混合装置１０に圧送されると、該溶融ガラスは先ず筒直結管１５を通って循環混合筒１２内に流入し、推進・攪拌手段１８により例えば水平方向の攪拌を受けながら下方に推進される。
この推進された溶融ガラスは、循環混合筒１２の下端に達した後、水平方向に分散して循環混合筒１２の外側に回り、その後、循環混合筒１２の外側を上昇して溶液面近傍まで達し、再び、循環混合筒１２の内側に流入して下方に推進される。そして、このような循環混合筒１２の内側と外側に沿って回る経路で何度も還流を行う。
【００４５】
ここで、推進・攪拌手段１８の回転数は、溶融ガラスの還流量が溶融ガラスの流出量の４．０倍〜６０．０倍になるように制御されている。
溶融ガラスの還流中、還流している溶融ガラスの一部は槽接続管１４を介して循環混合槽１０Ａから流出する一方、その流出量と同量の溶融ガラスが循環混合筒１２内に流入され攪拌されていく。つまり、循環混合装置１０に流入した溶融ガラスは、上記の還流によって攪拌されながら除々に流出されるので、溶融ガラスの屈折率が時間的に平均化される。
【００４６】
その後、更に、攪拌槽４で局所的な攪拌が行われて小さな脈理が除去された後、均質化された溶融ガラスが排出口９から排出される。排出された溶融ガラスは、例えば、成形型で受け、所定量排出した段階で切断して冷却し、後に加工・アニール等の工程を経てガラス製品が製造される。
【００４７】
以上のように、この実施の形態の高均質ガラスの製造方法によれば、循環混合筒１２の内側と外側に沿って回る還流によって、溶融ガラスの屈折率が時間的に平均化されるので、複数の製品間や製造ロット間でも屈折率の変動を小さくすることが出来る。
【００４８】
更に、循環混合装置１０において、溶融ガラスは筒直結管１５を介して循環混合筒１２に直接流入される一方、流出する溶融ガラスは循環混合槽１０Ａの壁部から流出されるので、従来の技術（循環混合槽内の循環混合筒で還流を行う形式の技術）にあった、流入した溶融ガラスが壁伝いに移動して還流せずに流出されるといった不具合を回避することが可能で攪拌性能を向上させることが出来る。
【００４９】
また、推進・攪拌手段１８の回転方向を逆転させて推進方向を上向きにしても従来の技術にあったショートパスが生じないことから、推進方向を上向きにして、ボルテックスを発生させずに推進力を大きくすることが可能である。即ち、還流方向や還流速度が任意に選択可能となり攪拌性能を飛躍的に向上させる。
また、循環混合装置１０において、溶融ガラスが循環混合筒１２に直接流入して強制的に推進・攪拌されること、並びに、溶融ガラスの還流方向や還流速度が任意に選択できることから、流入する溶融ガラスに温度変化があった場合でも、従来の技術にあった滞留現象などの不具合が回避され、攪拌性能が向上する。
【００５０】
従って、この発明の高均質ガラスの製造方法によれば、攪拌性が良く、屈折率の時間的な平均化が確実に行われて、溶融ガラスの均一化の向上を計ることができ、屈折率の許容誤差が１０^-7オーダーの高均質ガラスの製造に利用できると共に、複数の製品間や製造ロット間でも屈折率の変化を小さくすることが出来る。
【００５１】
なお、本発明は、この実施の形態の高均質ガラスの製造方法に限られるものでなく、例えば、循環混合工程以外で行われる処理は、溶解工程、清澄工程、攪拌工程などの他、様々な従来技術が適用可能であるし、また、それら工程の順序も適宜変更可能である。また、循環混合装置１０内での攪拌処理は、循環混合筒１２内で推進処理と共に行われる処理に限られず、例えば、循環混合筒１２の外側や槽接続管１４や筒直結管１５などで行われても良く、また、その攪拌処理の形式も、攪拌棒１８ｂ，１８ｂでの攪拌の他、様々な従来技術が応用可能である。その他、具体的に示した細部構造および方法は、発明の主旨を逸脱しない範囲で適宜変更可能である。
【００５２】
［その他の実施の形態］
本発明の高均質ガラスの製造方法は、循環混合装置における筒直結管および槽接続管の配置や作用、並びに、循環混合筒内での溶融ガラスの推進方向について、様々なバリエーションが有り得る。以下、これらのバリエーションについて説明する。なお、循環混合装置以外の構成および循環混合工程以外の処理については、第１の実施の形態と同様のものであり説明を省略する。また、循環混合装置についても、第１の実施の形態と同様の構成は同符号をふって説明を省略する。
【００５３】
図２（ｂ）は、第２の実施の形態の循環混合装置２０を示す概要図である。
この第２の実施の形態の循環混合装置２０は、槽接続管２４および筒直結管２５の接続先が第１の実施の形態のものと異なっている。
【００５４】
槽接続管２４は、循環混合装置２０に溶融ガラスを流入するための管で、一端側が連通管６を介して清澄槽３に接続され、他端側が循環混合槽２０Ａの側壁部に接続されている。
筒直結管２５は、循環混合装置２０から溶融ガラスを流出するための管で、一端側が循環混合筒１２の壁部に接続され、他端側が連通管７を介して攪拌槽４に接続されている。
【００５５】
このような循環混合装置２０を使用した循環混合工程では、清澄槽３から圧送された溶融ガラスが、先ず、循環混合筒１２の外側に流入し、その後、循環混合筒１２の外側と内側を回って還流しながら攪拌されて、循環混合筒１２の内側から除々に流出していく。そして、この還流により溶融ガラスの屈折率が時間的に平均化される。
【００５６】
図３（ａ）は、第３の実施の形態の循環混合装置３０を示す概要図である。
この第３の実施の形態の循環混合装置３０は、槽接続管３４および筒直結管３５の配置が第１の実施の形態のものと異なっている。
【００５７】
槽接続管３４は、循環混合装置３０に溶融ガラスを流入するための管で、一端側が連通管６を介して清澄槽３に接続され、他端側が循環混合槽３０Ａの側壁部の下端部に接続されている。
筒直結管３５は、循環混合装置３０から溶融ガラスを流出するための管で、一端側が循環混合筒１２の壁部の下端部に接続され、他端側が連通管７を介して攪拌槽４に接続されている。
【００５８】
つまり、これら槽接続管３４と筒直結管３５の配置は、例えば、水平方向にみて反対側の位置で、且つ、循環混合筒１２の内側と外側に沿って回る還流経路において経路長が最も長くなる配置となっている。この配置によって、循環混合装置３０の流入口から流出口への溶融ガラスのショートパスが確実に回避されるようになっている。
【００５９】
図３（ｂ）は、第４の実施の形態の循環混合装置４０を示す概要図である。
この第４の実施の形態の循環混合装置４０は、槽接続管４４および筒直結管４５の配置、並びに、推進・攪拌手段１８による推進方向が第１の実施の形態のものと異なっている。
【００６０】
槽接続管４４は、循環混合装置４０に溶融ガラスを流入するための管で、一端側が連通管６を介して清澄槽３に接続され、他端側が循環混合槽４０Ａの側壁部において溶液面Ｓの近傍位置に接続されている。
筒直結管４５は、循環混合装置４０から溶融ガラスを流出するための管で、一端側が循環混合筒１２の壁部の上端部に接続され、他端側が連通管７を介して攪拌槽４に接続されている。
【００６１】
つまり、これら槽接続管４４と筒直結管４５の配置は、推進・攪拌手段１８による推進方向が上昇方向の場合に、循環混合筒１２の内側と外側に沿って回る還流経路において経路長が最も長くなる配置となっている。この配置によって、循環混合装置４０の流入口から流出口への溶融ガラスのショートパスが確実に回避されるようになっている。
【００６２】
図４（ａ）は、第５の実施の形態の循環混合装置５０を示す概略図である。
この第５の実施の形態の循環混合装置５０は、循環混合筒５２の構造、推進・攪拌手段５８の構成、槽接続管５４と筒直結管５５の配置の点で、第１の実施の形態のものと異なる。
【００６３】
循環混合筒５２は、大きさや形状は第１の実施の形態のものと同様であるが、その中段部に複数の貫通口５２ａ…が設けられている。
推進・攪拌手段５８は、上段部と下段部とで異なる方向に推進力を及ぼすもので、例えば、中段から上段には回転により順方向に推進力を作用させる推進翼５８ａが、中段から下段には回転により逆方向に推進力を作用させる推進翼５８ｂが設けられている。これら推進翼５８ａ，５８ｂは中段部において重複部分を有しており、上下層間での溶融ガラスの対流も促進できるようになっている。
【００６４】
槽接続管５４は、循環混合装置５０に溶融ガラスを流入するための管で、一端側が連通管６を介して清澄槽３に接続され、他端側が循環混合槽５０Ａの側壁部の中段に接続されている。
筒直結管５５は、循環混合装置５０から溶融ガラスを流出するための管で、一端側が循環混合筒５２の壁部の中段部に接続され、他端側が連通管７を介して攪拌槽４に接続されている。
【００６５】
このような循環混合装置５０を使用した循環混合工程では、清澄槽３から圧送された溶融ガラスは、先ず、循環混合筒５２の外側中段部に流入した後、還流している溶融ガラスに従って上下に分かれる。そして、循環混合槽５０Ａの中段より上側では貫通口５２ａを通過して循環混合筒５２の内側と外側に沿って回る還流が行われ、循環混合槽５０Ａの中段より下側では貫通口５２ａを通過して循環混合筒５２の内側と外側に沿って回る還流が行われる。これらの還流中、循環混合筒５２の内側中段部において、上層の溶融ガラスと下層の溶融ガラスとの混合も行われる。そして、これらの還流中に溶融ガラスは循環混合筒５２の内側から除々に流出していく。
【００６６】
この第５の実施の形態の高均質ガラスの製造方法によれば、循環混合筒５２内での溶融ガラスの循環経路が短縮するので溶融ガラスの混合が促進され、また、循環混合槽５０Ａ内の上下層の溶融ガラスの混合も促進される。
【００６７】
図４（ｂ）は、第６の実施の形態の循環混合装置６０を示す概略図である。
この第６の実施の形態の循環混合装置６０は、推進・攪拌手段５８の回転方向および槽接続管６４と筒直結管６５の接続先の点で、第５の実施の形態のものと異なる。
推進・攪拌手段５８の回転方向は、第５の実施の形態の逆になっており、溶融ガラスを中段から上段と下段に推進するようになっている。
槽接続管６４は、循環混合装置６０から溶融ガラスを流出するための管で、一端側が循環混合槽６０Ａの壁部の中段部に接続され、他端側が連通管７を介して攪拌槽４に接続されている。
筒直結管６５は、循環混合装置６０に溶融ガラスを流入するための管で、一端側が連通管６を介して清澄槽３に接続され、他端側が循環混合筒５２の側壁部の中段に接続されている。
【００６８】
このような循環混合装置６０を使用した循環混合工程では、清澄槽３から圧送された溶融ガラスは、先ず、循環混合筒５２の内側中段部に流入した後、推進・攪拌手段５８の推進力により上下に分かれて、一方は上昇し他方は下降する。そして、循環混合槽６０Ａの中段より上側では貫通口５２ａを通過して循環混合筒５２の内側と外側に沿って回る還流が行われ、循環混合槽６０Ａの中段より下側では貫通口５２ａを通過して循環混合筒５２の内側と外側に沿って回る還流が行われる。これらの還流中、循環混合筒５２の外側中段部において、上層の溶融ガラスと下層の溶融ガラスとの混合も行われる。そして、これらの還流中に溶融ガラスは循環混合筒５２の外側から除々に流出していく。尚、前記推進・攪拌手段５８には、前記攪拌・推進手段１８と同様、各種攪拌手段を付加する事が均質化の上で好ましい。
【００６９】
【実施例】
原料投入手段、原料溶解槽、清澄槽、循環混合槽、攪拌槽、流出口、これら各槽をつなぐ連通管、各槽の温度制御装置、溶融ガラス切断手段および成形手段を有する、一般的なガラスの連続溶解・成形（試験）装置を用いて、Ｓ−ＢＳＬ７（オハラ硝種名）を溶解した。所望の配合組成とした原料を原料投入手段により、溶融ガラスの流出量と等価となるような量を投入し、所望の温度に制御された原料溶解槽、清澄槽、循環混合槽、攪拌槽を経た後、流出口から所定流量（この場合は２５０ｃｃ／ｍｉｎ）排出する。排出された溶融ガラスは成形型に受け、所定量排出したらガラスを切断し冷却され、後に加工・アニール等の工程を経て製品となる。
【００７０】
このときの循環混合工程については、内容積＝約８０００ｃｃ、槽内径Ｄ＝２０ｃｍ、溶液面高さＨ＝２０ｃｍ、循環混合筒内径ｄ＝１０ｃｍ、循環混合筒上端から溶液面までの距離ｈ１＝１ｃｍ、循環混合筒下端から循環混合槽底面までの距離ｈ２＝１ｃｍの条件の循環混合槽を使用し、循環混合筒内流量は１０００ｃｃ／ｍｉｎとなるよう、推進翼の回転数を調整した。溶解を開始してから約３時間で装置全体の操作条件が所定条件に達し、更に１時間後、この条件が安定して維持されていることを確認後、均質性確認用サンプルを連続的に１０個取得する。このサンプルを２４０ｍｍφ（半径）×８０ｍｍ^t（厚さ）のディスク状に加工し、干渉計により均質性を測定した。
【００７１】
上記の試験を第１〜第６の実施の形態の循環混合槽について行った結果、ブロック内の屈折率変動幅の平均値、および、ブロック間の屈折率変動幅の平均値（各ブロックの代表テストサンプルを精密示差屈折率計で測定した屈折率変動幅の平均）は次表に示ような値になった。表中、「実施例」の項目は第１〜第６の実施の形態の各番号を示している。「ブロック内の屈折率変動幅の平均値」の項目はブロック内の均質性、「ブロック間の屈折率変動幅の平均値」の項目はブロック間の均質性を示している。
【００７２】
【表１】

【００７３】
【発明の効果】
以上のように、本発明の高均質ガラスの製造方法によれば、循環混合筒の内側と外側に沿った溶融ガラスの還流によって、溶融ガラスの屈折率の時間的な平均化を行うことが出来ると共に、溶融ガラスの流入又は流出を循環混合筒内に直接行うことにより、循環混合槽の流入口から流出口へのショートパスが回避されるなど、従来の技術（循環混合槽内の循環混合筒で還流を行う形式の技術）にあった幾つかの不具合を解消して、その攪拌性能を飛躍的に向上させることが出来る。従って、屈折率変動幅の許容誤差が１０^-7オーダーの高均質ガラスの製造に応用でき、且つ、型に流し込まれる溶融ガラスの屈折率の時間的変化も十分に小さくすることが可能となる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の高均質ガラスの製造装置を示す概要図である。
【図２】循環混合槽のバリエーションを示すもので、（ａ）は第１の実施の形態の循環混合槽、（ｂ）は第２の実施の形態の循環混合槽を示す概要図である。
【図３】循環混合槽のバリエーションを示すもので、（ａ）は第３の実施の形態の循環混合槽、（ｂ）は第４の実施の形態の循環混合槽を示す概要図である。
【図４】循環混合槽のバリエーションを示すもので、（ａ）は第５の実施の形態の循環混合槽、（ｂ）は第６の実施の形態の循環混合槽を示す概要図である。
【図５】循環混合槽の内部に循環混合筒を備えた形式の従来の高均質ガラス製造装置を示す断面図である。
【符号の説明】
２溶解槽
３清澄槽
４攪拌槽
１０循環混合装置（第１の実施の形態）
１２循環混合筒
１４槽接続管
１５筒直結管
１８推進・攪拌手段
２０循環混合装置（第２の実施の形態）
２４槽接続管
２５筒直結管
３０循環混合装置（第３の実施の形態）
３４槽接続管
３５筒直結管
４０循環混合装置（第４の実施の形態）
４４槽接続管
４５筒直結管
５０循環混合装置（第５の実施の形態）
５２循環混合筒
５２ａ貫通口
５４槽接続管
５５筒直結管
５８推進・攪拌手段（２方向推進手段）
６０循環混合装置（第６の実施の形態）
６４槽接続管
６５筒直結管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a highly homogeneous glass such as used in an optical system of a stepper for semiconductor production.
[0002]
[Prior art]
As a method for producing optical glass, for example, after performing a melting step of melting a glass raw material, a clarification step of clarifying the molten glass, and a stirring step of stirring the molten glass, the glass is molded by molding or the like. Manufacturing methods are generally known. In the clarification step, for example, bubbles and gases are removed, and in the stirring step, the local and global refractive indexes of the molten glass are made uniform.
[0003]
By the way, for example, in an optical glass (high homogeneity glass) used for an optical system of a stepper for semiconductor manufacturing, the refractive index fluctuation range from one end to one end of a glass product is 10. ^-7 It is being sought to be within the range of orders.
[0004]
In order to produce such highly homogeneous glass, many proposals related to the stirring process and the refining process have been made. For example, Japanese Patent Application Laid-Open No. 56-140030 discloses a method in which a specific barrier is provided at the neck of a melting furnace and the molten glass stream is stirred by the barrier to homogenize as a proposal in the stirring step. . Japanese Patent Laid-Open No. 5-208830 discloses a method for performing defoaming and homogenization by stirring molten glass in a reduced pressure state as a proposal in a clarification step. In JP-A-58-88126, JP-A-61-21922, and JP-A-2-48422, a stirring blade is devised as a proposal regarding the stirring process.
However, the refractive index fluctuation range is 10 by only the proposal related to the stirring step and the clarification step. ^-7 The production of highly homogeneous glass that falls within the tolerance of the order could not be achieved.
[0005]
Furthermore, many proposals related to the above-described stirring process and clarification process are intended to achieve local homogenization of molten glass or homogenization in a relatively small stirring tank, and the range to be homogenized is very large. It was not a thing. That is, when the molten glass poured into the mold through the clarification step and the stirring step is viewed with a temporal change, the temporal change in the refractive index is relatively large.
Therefore, when manufacturing multiple glass products (same type glass products) continuously, or when manufacturing glass products in lot production, changes in refractive index between each product or changes in refractive index between lots. Had the problem of becoming relatively large.
[0006]
In order to reduce the temporal change in the refractive index of the molten glass with respect to this problem, for example, as shown in FIG. Japanese Patent Publication No. 31-1681 The technology has been proposed.
In this technique, molten glass is sent to a mixing tank (circulation mixing tank) P3 via a transfer channel P2, and after stirring globally in the mixing tank P3, local stirring is performed in the stirring channel P8. After that, the molten glass is fed from the feeding port P12 to the mold or the like.
[0007]
Global stirring in the mixing tank P3 is performed by refluxing the molten glass up and down by a reflux mechanism (propulsion blade P4, reflux pipe P5 as a circulating and mixing cylinder). Then, a larger amount of molten glass than the amount flowing into the stirring channel P8 from the mixing tank P3 is refluxed in the mixing tank P3, whereby the molten glass flowing into the stirring channel P8, and further from the feeding port P12. It is intended to reduce the temporal change in the refractive index of the molten glass being fed.
[0008]
The auxiliary pipe P10 circulates the remaining glass remaining in the stirring flow path P8 when the molten glass is intermittently charged into the mixing tank P3 in batch processing or the like. It is not used when processing. In the case of continuous treatment, the molten glass in the auxiliary pipe P10 is solidified to close the auxiliary pipe P10.
[0009]
[Problems to be solved by the invention]
As a result of investigation and confirmation by the inventors about the above technique, the following various problems occur, and the temporal change in the refractive index of the molten glass cannot be sufficiently reduced to a desired level. The conclusion has been reached.
[0010]
That is, in the method of refluxing the molten glass in the mixing tank P3, the glass flow entering the stirring device P1 and the temperature of the glass in the mixing tank P3 must be substantially the same. Due to the difference in specific gravity due to the difference, for example, if the temperature of the molten glass that flows in is low, the amount of glass that passes through the wall of the mixing tank P3 without stirring and enters the stirring channel P8 without stirring becomes large. On the contrary, if the temperature of the glass flowing in is high, the glass stays on the upper surface of the mixing tank P3, and the glass on the outer peripheral portion of the upper surface of the mixing tank P3 enters the stirring channel P8 without being stirred.
[0011]
Further, even if the temperature of the molten glass that flows in and the temperature of the molten glass in the mixing tank P3 are the same, the propulsion blade P4 causes a flow in the rotating direction in the molten glass in the mixing tank P3, and a part of the molten glass that flows in The phenomenon that the unmixed molten glass stays around the upper wall of the mixing tank P3 due to the centrifugal force and then reaches the vicinity of the upper surface of the stirring channel P8 is drawn into the stirring channel P8 as it is. The problem of reducing the homogeneity of the molten glass occurs.
[0012]
Further, the method of refluxing the molten glass in the mixing tank P3 has a drawback that it is difficult to arbitrarily control the amount of reflux of the molten glass. Therefore, this method is performed by continuously melting, outflowing and molding the glass. When trying to use it for various processes, the following problems occur. That is, if the outflow amount of the molten glass is increased, the ratio of the recirculation amount to the outflow amount is reduced and it becomes difficult to reduce the refractive index fluctuation due to the recirculation, but in order to avoid this, the propulsion blade P4 is rotated at a high speed. If this is done, a high load is applied to the reflux mechanism (propulsion blade P4, reflux pipe P5), causing a risk of breakage of the reflux mechanism, and even if this is avoided in terms of equipment, the propulsion blade P4 in the mixing tank P3. Since a vortex is generated on the top and bubbles are entrained from the vortex, it is not possible to take a method of securing a reflux amount by high rotation after all. Further, if the rotation direction of the propulsion blade P4 is reversed to reverse the direction of circulation so as to prevent only the vortex on the propulsion blade P4, the flow of molten glass by the stirring means P7 rotating at high speed and the molten glass due to reflux The direction of the circulation is the same, and the molten glass that has flowed into the mixing tank P3 short-passes without flowing through and flows into the stirring flow path P8, conversely increasing the refractive index fluctuation. It will be.
[0013]
That is, according to the above technique, although the refractive index is temporally averaged by refluxing the molten glass by the reflux mechanism (propulsion blade P4, reflux pipe P5), the above-described problems occur. Specifically, the refractive index fluctuation range cannot be lowered, and the refractive index fluctuation range is 10%. ^-7 It is not applicable to the production of high order homogenous glass.
[0014]
The present invention has been made in view of the above circumstances, and the allowable error of the refractive index fluctuation range is 10. ^-7 It can be used for the production of high-order glass of the order, and the temporal change of the refractive index of the molten glass poured into the mold is made sufficiently small in order to reduce the change of the refractive index between multiple products and between production lots. An object of the present invention is to provide a method for producing highly homogeneous glass capable of satisfying the requirements.
[0015]
[Means for Solving the Problems]
To solve the above problem,
The invention according to claim 1 is a method for producing a highly homogeneous glass including a circulating mixing step of homogenizing molten glass,
A circulating mixing tank for homogenizing the molten glass;
Contained in the circulating mixing tank Both ends A circulating mixing cylinder having an opening in
A propulsion means disposed in the circulation mixing cylinder and imparting a driving force to the molten glass in the circulation mixing cylinder;
The circulating mixing cylinder from outside the circulating mixing tank Side wall A tube directly connected to the tube,
A tank connection pipe connected to the circulating mixing tank from outside the circulating mixing tank;
Use a circulating mixing device with
In the circulating and mixing step,
Let the molten glass of the previous step flow through the cylinder direct connection pipe and flow into the circulation mixing cylinder,
The molten glass is propelled in the circulating and mixing cylinder, and the molten glass is refluxed in a reflux path along the inside and outside of the circulating and mixing cylinder.
It was set as the method including the process which flows out the molten glass outside the said circulation mixing cylinder to the following process through the said tank connection pipe.
[0016]
According to this high homogenous glass manufacturing method, in addition to the temporal averaging of the refractive index of the molten glass by the reflux of the molten glass rotating along the inside and outside of the circulating mixing cylinder, the molten glass Inflow directly into the circulating and mixing cylinder via the cylinder direct connection pipe, and outflow of the molten glass from the outside of the circulating and mixing cylinder via the tank connection pipe. The following inconveniences in the technique of refluxing with the internal circulation mixing cylinder) can be solved and the stirring performance can be improved.
[0017]
That is, in the conventional one, there is a problem that a part of the molten glass that has flowed moves along the wall of the circulating mixing tank and flows out without entering the circulating mixing cylinder. Since the inflow of the molten glass is performed inside the circulation mixing cylinder and the outflow is performed outside the circulation mixing cylinder, the molten glass does not flow out through a short path along the wall as in the conventional case.
[0018]
Also, in the conventional one, the short path as described above is likely to occur, so the propulsion direction cannot be raised upward, and thus the vortex is likely to occur and the propulsive force cannot be increased greatly, In the present invention, the short path avoidance action is similarly exerted even if the propulsion direction of the molten glass is reversed, so that the propulsion direction is directed upward to prevent the generation of vortex, and the propulsive force is increased to increase the melting glass. The amount of reflux can be increased. That is, the reflux direction and reflux speed of the molten glass can be arbitrarily selected, and the stirring action is greatly improved.
[0019]
Further, in the conventional case, when the temperature of the molten glass that flows in is higher than the molten glass in the tank, the molten glass that flows in may stay in the upper layer and adversely affect the invention. Then, even when there is a temperature change of the flowing molten glass, the flowing molten glass is forcibly propelled by the circulating mixing cylinder (if the propulsion means also has a stirring action, the stirring is forcibly performed). Therefore, the above stay phenomenon can be avoided. Moreover, since the reflux rate of the molten glass can be increased as described above, the above stagnation phenomenon can be avoided.
As described above, according to the method for producing a highly homogeneous glass of the present invention, the stirring property is good, the temporal averaging of the refractive index is performed reliably, and the homogenization of the molten glass can be improved. . Therefore, the tolerance of the refractive index is 10 ^-7 It can be used for the production of high-order glass of the order, and the change in refractive index can be reduced between a plurality of products or between production lots.
[0020]
Moreover, like the manufacturing method of the highly homogeneous glass of Claim 2, the molten glass of the front process of the said circulation mixing process is made to flow in the outside of the said circulation mixing cylinder through the said tank connection pipe | tube, and molten glass is added in the said circulation mixing cylinder. The molten glass may be refluxed by a reflux path that rotates along the inside and outside of the circulating and mixing cylinder, and the molten glass in the circulating and mixing cylinder may be passed through the cylinder direct connection pipe to flow out to the next step. By this manufacturing method, the same effect as that of the first aspect of the invention can be obtained.
[0021]
In addition, it is preferable to add an agitating function to the propelling means in addition to the propelling means, so that the molten glass that is refluxed is also locally agitated, and the refractive index is averaged by the reflux. Further, the agitation treatment may be performed in the circulation mixing tank, and various known techniques can be applied to the agitation treatment, and the place where the agitation treatment is performed is also inside and outside the circulation mixing cylinder, and It is possible to select the inside of the pipe directly connected pipe or the tank connecting pipe as appropriate.
[0026]
Claims 3 Like the described invention,
In a plan view perpendicular to the central axis of the circulating mixing cylinder, a circulating mixing apparatus in which d / D is 0.2 to 0.8, where D is the inner diameter of the circulating mixing tank and d is the inner diameter of the circulating mixing cylinder. Preferably, those having a d / D of 0.4 to 0.6 are preferably used.
[0027]
When the inner diameter d of the circulating and mixing cylinder is made smaller than the inner diameter D of the circulating and mixing tank, the outer reflux speed becomes lower than the inner reflux speed of the circulating and mixing cylinder, and the stirring efficiency is lowered. On the other hand, when the inner diameter d of the circulating and mixing cylinder is made larger than the inner diameter D of the circulating and mixing tank, the load on the propulsion means increases and the reflux efficiency decreases.
When the efficiency of both is expressed as a comprehensive index, there is a peak in the range of d / D = 0.2 to 0.8, and further in the range of d / D = 0.4 to 0.6. It is preferable to set to.
[0028]

Claims

4 As stated
The circulating mixing cylinder is arranged at both ends up and down,
The solution surface height of the molten glass filled in the circulating mixing tank during the circulating mixing step is H,
The distance from the lower end of the upper opening of the circulating mixing cylinder to the height of the solution surface of the molten glass is h1,
The distance from the upper end of the lower opening of the circulation mixing cylinder to the bottom of the circulation mixing tank is h2,
h1 / H from 0 to 0.5,
Preferably h2 / H is set to 0.02 to 0.5,
More preferably,
h1 / H from 0.05 to 0.4,
h2 / H may be set to 0.05 to 0.4.
[0029]
When the distance h1 from the solution surface to the lower end of the upper opening of the circulating and mixing cylinder is increased with respect to the solution surface height H, the reflux rate above the circulating and mixing cylinder is lowered, and a stagnation phenomenon of molten glass is likely to occur. . Further, when the distance h2 from the bottom of the circulating mixing tank to the upper end of the lower opening of the circulating mixing cylinder is increased with respect to the height H of the solution surface, the reflux rate below the circulating mixing cylinder decreases, and the molten glass stays. The phenomenon tends to occur. On the other hand, when the distance h2 is reduced, the solution glass is difficult to flow.
When the above action is expressed as a comprehensive index, there is a peak in the range of h1 / H = 0 to 0.5, and further h1 / H = 0.05 to 0.4. It is effective. In addition, there is a peak in the range of h2 / H = 0.02 to 0.5, and further h2 / H = 0.05 to 0.4, and it is effective to set the peak in this range.
[0030]

Claims

5 The flow rate of the molten glass passing through the circulating mixing cylinder is 2.0 times or more of the flow rate of the molten glass flowing out through the cylinder direct connection pipe or the tank connection pipe as in the method for producing highly homogeneous glass described Preferably, it is 3.0 to 80.0 times, and more preferably 4.0 to 60.0 times.
[0031]
In order to perform temporal averaging of the refractive index of the molten glass by refluxing along the inside and outside of the circulation mixing cylinder, the above reflux flow rate is 2.0 times or more the flow rate of the molten glass flowing out of the circulation mixing tank. The more it is necessary, the more the refractive index can be averaged over time. On the other hand, if the reflux flow rate is too high, the production efficiency is reduced.
Considering the efficiency of both, it is appropriate to set the reflux flow rate and the outflow flow rate from the circulating mixing tank to the above ranges. Preferably it is 3.0-80.0 times, More preferably, it is 4.0-60.0 times.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings of FIGS.
[First Embodiment]
FIG. 1 shows a first embodiment of the present invention. High homogeneous glass production equipment FIG.
[0033]
High-homogeneous glass manufacturing apparatus of this embodiment 100 Is a method for producing a highly homogeneous glass according to the present invention, and is constituted by connecting a dissolution tank 2, a clarification tank 3, a circulating mixing device 10, and a stirring tank 4 via

communication pipes

5, 6, and 7. The Moreover, although not shown in figure, the temperature of the raw material injection | throwing-in apparatus which introduce | transduces glass raw material into the dissolution tank 2 by predetermined amount, and each tank (The dissolution tank 2, the clarification tank 3, the circulating mixing tank 10A, the stirring tank 4) is controlled. A temperature control device and a molding device that has a molding die and molds molten glass discharged from the stirring vessel 4 are provided.
[0034]
The dissolution tank 2 and the clarification tank 3 are general ones having a function of melting the glass raw material to be charged and a function of removing, for example, bubbles and gases from the molten glass, and various conventional techniques are applied. Is possible.
The stirring tank 4 is for eliminating small striae of the molten glass, and various conventional techniques such as a form in which the molten glass is locally stirred by the stirring means 8 can be applied. A discharge port 9 is provided on the downstream side of the stirring tank 4.
[0035]
The circulating mixing apparatus 10 is according to the present invention, and an enlarged view thereof is shown in FIG. 2A. The circulating mixing tank 10A, the circulating mixing cylinder 12, the tank connection pipe 14, the cylinder direct connection pipe 15, and the propulsion / It comprises stirring means 18 and the like.
[0036]
The circulating mixing tank 10A has a substantially cylindrical shape with a central axis oriented vertically, and has a bottom 10B. The circulating and mixing tank is not limited to a cylindrical shape and can be changed as appropriate.
The circulating mixing cylinder 12 has a substantially cylindrical shape with a central axis oriented vertically, and has an inner diameter d in a range of d / D = 0.4 to 0.6 with respect to an inner diameter D of the circulating mixing tank 10A. Used. The circulating and mixing cylinder 12 is disposed at the approximate center of the circulating and mixing tank 10A, and its upper and lower ends are open. In addition, a plurality of

openings

12a, 12a,...
[0037]
The positions of the upper and lower ends of the opening of the circulating and mixing cylinder 12 are h1, the distance between the lower end of the upper opening and the molten glass solution surface, and the distance between the upper end of the lower opening and the bottom 10B of the circulating mixing tank 10A, h2. The height of the solution surface of the molten glass from the bottom portion 10B is H, and h1 / H = 0.05 to 0.4 and h2 / H = 0.05 to 0.4.
[0038]
The tank connection pipe 14 is a pipe for discharging molten glass from the circulation mixing device 10, and one end side is connected to the wall portion of the circulation mixing tank 10 A, and the other end side is connected to the stirring tank 4 through the communication pipe 7. Yes.
The cylinder direct connection pipe 15 is a pipe for allowing molten glass to flow into the circulation mixing device 10, and one end side is connected to the clarification tank 3 via the communication pipe 6, and the other end side is connected to the side wall portion of the circulation mixing cylinder 12. Yes.
[0039]
The tank connection pipe 14 and the cylinder direct connection pipe 15 are connected, for example, at positions opposite to each other when viewed in the horizontal direction and above the middle stage in the vertical direction. That is, the path length is increased in the reflux path that rotates along the inside and outside of the circulating and mixing cylinder 12. With this arrangement, a short path of molten glass from the inlet to the outlet of the circulating and mixing device 10 is reliably avoided.
When the propulsion direction by the propulsion / stirring means 18 is reversed, the tank connection pipe 14 and the cylinder direct connection pipe 15 are connected to a position below the middle stage in the vertical direction, so that The path length from the inlet to the outlet can be increased.
[0040]
The propulsion / stirring means 18 includes, for example, propulsion blades 18a and 18a, stirring

rods

18b and 18b, and a motor 18c that rotates the propulsion blades 18a and 18a. The molten glass in the circulating and mixing cylinder 12 is rotated by the rotation of the propulsion blades 18a and 18a. And agitating the molten glass in the circulating mixing cylinder 12 by rotation of the stirring

rods

18b, 18b (or including the propelling blades 18a, 18a) to make the local refractive index of the molten glass uniform, For example, the refractive index in the horizontal direction is made uniform.
[0041]
The propulsion blades 18a and 18a and the stirring

rods

18b and 18b have rotation diameters close to the inner surface of the circulating and mixing cylinder 12, so that the molten glass passing through the circulating and mixing cylinder 12 is mixed with the stirring blades 18a and 18a. 18a and the stirring

rods

18b and 18b are prevented from refluxing through the outside of the rotational diameter range without being stirred.
[0042]
The manufacturing method of the highly homogeneous glass which concerns on this invention is implemented as follows using the manufacturing apparatus 100 of the above structures.
[0043]
That is, a glass raw material that is equivalent to the outflow amount of the molten glass is continuously fed into the melting tank 2 by the raw material charging device, the melting process of the glass raw material in the melting tank 2, and the molten glass in the clarification tank 3 A clarification step, a circulating and mixing step of molten glass in the circulating mixing tank 10A, and a molten glass stirring step in the stirring tank 4 are successively performed, and the homogenized molten glass is continuously discharged from the discharge port 9. Go.
[0044]
During the above-described series of processes, when the molten glass enters the communication pipe 6 and is pumped to the circulation mixing device 10 after being clarified in the clarification tank 3, the molten glass first passes through the cylinder direct connection pipe 15 and is circulated and mixed. 12 and is propelled downward while being stirred, for example, in the horizontal direction by the propulsion / stirring means 18.
The propelled molten glass reaches the lower end of the circulating and mixing cylinder 12, and then is dispersed in the horizontal direction and turns to the outside of the circulating and mixing cylinder 12. Thereafter, the molten glass rises outside the circulating and mixing cylinder 12 to the vicinity of the solution surface. It reaches the inside of the circulating and mixing cylinder 12 again and is propelled downward. And it recirculate | refluxs many times in the path | route which turns along the inner side and the outer side of such a circulation mixing cylinder 12. FIG.
[0045]
Here, the rotation speed of the propulsion / stirring means 18 is controlled so that the reflux amount of the molten glass is 4.0 times to 60.0 times the outflow amount of the molten glass.
During the reflux of the molten glass, a part of the refluxed molten glass flows out from the circulating mixing tank 10A through the tank connection pipe 14, while the same amount of molten glass flows into the circulating mixing cylinder 12 as the outflow amount. It is stirred. That is, since the molten glass that has flowed into the circulating and mixing apparatus 10 is gradually discharged while being stirred by the above reflux, the refractive index of the molten glass is averaged over time.
[0046]
Thereafter, further, local stirring is performed in the stirring tank 4 to remove small striae, and then the homogenized molten glass is discharged from the discharge port 9. The discharged molten glass is received by, for example, a mold, cut and cooled when discharged by a predetermined amount, and glass products are manufactured through processes such as processing and annealing.
[0047]
As described above, according to the manufacturing method of the highly homogeneous glass of this embodiment, the refractive index of the molten glass is averaged over time by the reflux that rotates along the inside and the outside of the circulation mixing cylinder 12. It is possible to reduce the refractive index variation between a plurality of products and between production lots.
[0048]
Further, in the circulating and mixing apparatus 10, the molten glass is directly introduced into the circulating and mixing cylinder 12 through the cylinder direct connection pipe 15, while the molten glass that flows out flows out from the wall portion of the circulating and mixing tank 10A. Stirring performance can be avoided because the molten glass that has flowed in moves along the wall and flows out without reflux, as it was in the technology of refluxing with a circulating mixing cylinder in the circulating mixing tank. Can be improved.
[0049]
Further, even if the direction of rotation of the propulsion / stirring means 18 is reversed and the propulsion direction is directed upward, a short path as in the prior art does not occur. Therefore, the propulsion force is generated with the propulsion direction facing upward and without generating vortex. Can be increased. That is, the reflux direction and the reflux speed can be arbitrarily selected, and the stirring performance is greatly improved.
Further, in the circulating and mixing apparatus 10, the molten glass flows directly into the circulating and mixing cylinder 12 and is forcedly propelled and stirred, and the reflux direction and the reflux speed of the molten glass can be arbitrarily selected. Even when there is a temperature change in the glass, problems such as a stagnation phenomenon that existed in the prior art are avoided, and the stirring performance is improved.
[0050]
Therefore, according to the method for producing a highly homogeneous glass of the present invention, the stirring property is good, the refractive index is temporally averaged, and the homogenization of the molten glass can be improved. Tolerance of 10 ^-7 It can be used for the production of high-order glass of order, and the change in refractive index can be reduced between a plurality of products and between production lots.
[0051]
In addition, this invention is not restricted to the manufacturing method of the highly homogeneous glass of this embodiment, For example, the process performed other than a circulation mixing process is various other than a melt | dissolution process, a clarification process, a stirring process, etc. Conventional techniques can be applied, and the order of these steps can be changed as appropriate. The stirring process in the circulating and mixing apparatus 10 is not limited to the process performed in the circulating and mixing cylinder 12 together with the propulsion process. For example, the stirring process is performed on the outside of the circulating and mixing cylinder 12, the tank connection pipe 14, the cylinder direct connection pipe 15, or the like. In addition, as the type of the stirring process, various conventional techniques can be applied in addition to the stirring by the stirring

rods

18b and 18b. In addition, the detailed structure and method specifically shown can be changed as appropriate without departing from the spirit of the invention.
[0052]
[Other embodiments]
The manufacturing method of the highly homogeneous glass of the present invention may have various variations with respect to the arrangement and action of the cylinder direct connection pipe and the tank connection pipe in the circulation mixing apparatus, and the propulsion direction of the molten glass in the circulation mixing cylinder. Hereinafter, these variations will be described. Note that the configuration other than the circulating mixing device and the processing other than the circulating mixing step are the same as those in the first embodiment, and a description thereof will be omitted. In the circulating and mixing apparatus, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[0053]
FIG. 2B is a schematic diagram showing the circulation mixing device 20 according to the second embodiment.
The circulating and mixing apparatus 20 of the second embodiment is different from that of the first embodiment in the connection destination of the tank connecting pipe 24 and the cylinder direct connecting pipe 25.
[0054]
The tank connection pipe 24 is a pipe for allowing molten glass to flow into the circulation mixing device 20, and one end side is connected to the clarification tank 3 via the communication pipe 6, and the other end side is connected to the side wall portion of the circulation mixing tank 20 A. Yes.
The cylinder direct connection pipe 25 is a pipe for flowing molten glass from the circulation mixing device 20, one end side is connected to the wall portion of the circulation mixing cylinder 12, and the other end side is connected to the stirring tank 4 via the communication pipe 7. Yes.
[0055]
In such a circulation mixing process using the circulation mixing device 20, the molten glass fed from the clarification tank 3 first flows into the outside of the circulation mixing cylinder 12, and then goes around the outside and inside of the circulation mixing cylinder 12. The mixture is stirred while refluxing and gradually flows out from the inside of the circulating and mixing cylinder 12. And the refractive index of a molten glass is averaged temporally by this recirculation | reflux.
[0056]
FIG. 3A is a schematic diagram showing a circulation mixing device 30 according to the third embodiment.
The circulating and mixing apparatus 30 of the third embodiment is different from that of the first embodiment in the arrangement of the tank connection pipe 34 and the cylinder direct connection pipe 35.
[0057]
The tank connection pipe 34 is a pipe for flowing molten glass into the circulation mixing device 30, one end side is connected to the clarification tank 3 via the communication pipe 6, and the other end side is connected to the lower end portion of the side wall portion of the circulation mixing tank 30 A. It is connected.
The cylinder direct connection pipe 35 is a pipe for the molten glass to flow out from the circulation mixing device 30, and one end side is connected to the lower end portion of the wall portion of the circulation mixing cylinder 12, and the other end side is connected to the stirring tank 4 through the communication pipe 7. It is connected.
[0058]
That is, the arrangement of the tank connection pipe 34 and the cylinder direct connection pipe 35 is, for example, the longest path length in the recirculation path that is located on the opposite side in the horizontal direction and that runs along the inside and the outside of the circulation mixing cylinder 12. It has become an arrangement. With this arrangement, a short path of molten glass from the inlet to the outlet of the circulating and mixing device 30 is reliably avoided.
[0059]
FIG. 3B is a schematic diagram showing a circulating and mixing device 40 according to the fourth embodiment.
The circulation mixing device 40 of the fourth embodiment is different from that of the first embodiment in the arrangement of the tank connection pipe 44 and the cylinder direct connection pipe 45 and the propulsion direction by the propulsion / stirring means 18.
[0060]
The tank connection pipe 44 is a pipe for allowing molten glass to flow into the circulation mixing device 40, one end side of which is connected to the clarification tank 3 via the communication pipe 6, and the other end side is a solution surface S in the side wall portion of the circulation mixing tank 40 A. It is connected to the position near.
The cylinder direct connection pipe 45 is a pipe for the molten glass to flow out from the circulation mixing device 40, and one end side is connected to the upper end portion of the wall portion of the circulation mixing cylinder 12, and the other end side is connected to the stirring tank 4 through the communication pipe 7. It is connected.
[0061]
In other words, the arrangement of the tank connection pipe 44 and the cylinder direct connection pipe 45 is the longest in the recirculation path around the inside and outside of the circulation mixing cylinder 12 when the propulsion direction by the propulsion / stirring means 18 is the upward direction. The arrangement becomes longer. With this arrangement, a short path of molten glass from the inlet to the outlet of the circulating and mixing device 40 is reliably avoided.
[0062]
FIG. 4A is a schematic diagram showing a circulation mixing device 50 according to the fifth embodiment.
The circulatory mixing device 50 of the fifth embodiment is the first embodiment in terms of the structure of the circulatory mixing cylinder 52, the configuration of the propulsion / stirring means 58, and the arrangement of the tank connection pipe 54 and the cylinder direct connection pipe 55. Different from that.
[0063]
The circulating and mixing cylinder 52 is the same in size and shape as that of the first embodiment, but a plurality of through-holes 52a are provided in the middle step.
The propulsion / stirring means 58 exerts a propulsive force in different directions between the upper stage and the lower stage. For example, a propulsion blade 58a that applies a propulsive force in the forward direction by rotation from the middle stage to the upper stage is provided from the middle stage to the lower stage. Is provided with a propulsion blade 58b for applying a propulsive force in the opposite direction by rotation. These propulsion blades 58a and 58b have overlapping portions in the middle stage so that convection of the molten glass between the upper and lower layers can be promoted.
[0064]
The tank connection pipe 54 is a pipe for allowing molten glass to flow into the circulation mixing device 50, and one end side is connected to the clarification tank 3 via the communication pipe 6, and the other end side is connected to the middle stage of the side wall portion of the circulation mixing tank 50 A. Has been.
The cylinder direct connection pipe 55 is a pipe for the molten glass to flow out from the circulation mixing device 50, and one end side is connected to the middle part of the wall portion of the circulation mixing cylinder 52, and the other end side is connected to the stirring tank 4 via the communication pipe 7. It is connected.
[0065]
In such a circulating mixing process using the circulating mixing device 50, the molten glass fed from the clarification tank 3 first flows into the outer middle stage of the circulating mixing cylinder 52 and then moves up and down according to the molten glass being refluxed. Divided. Then, reflux is performed along the inner and outer sides of the circulation mixing cylinder 52 through the through-hole 52a above the middle stage of the circulation mixing tank 50A, and passes through the through-hole 52a below the middle stage of the circulation mixing tank 50A. Then, reflux is performed that rotates along the inside and outside of the circulating and mixing cylinder 52. During the reflux, mixing of the upper layer molten glass and the lower layer molten glass is also performed in the inner middle step of the circulating mixing cylinder 52. During the reflux, the molten glass gradually flows out from the inside of the circulating and mixing cylinder 52.
[0066]
According to the manufacturing method of the highly homogeneous glass of the fifth embodiment, since the circulation path of the molten glass in the circulation mixing cylinder 52 is shortened, the mixing of the molten glass is promoted, and the circulation mixing tank 50A Mixing of the upper and lower molten glass is also promoted.
[0067]
FIG. 4B is a schematic view showing a circulating and mixing device 60 according to the sixth embodiment.
The circulating and mixing device 60 of the sixth embodiment differs from that of the fifth embodiment in the rotation direction of the propulsion / stirring means 58 and the connection destination of the tank connection pipe 64 and the cylinder direct connection pipe 65.
The rotation direction of the propelling / stirring means 58 is the reverse of the fifth embodiment, and the molten glass is propelled from the middle to the upper and lower stages.
The tank connection pipe 64 is a pipe for allowing molten glass to flow out from the circulation mixing device 60, and one end side is connected to the middle stage of the wall portion of the circulation mixing tank 60 A, and the other end side is connected to the stirring tank 4 through the communication pipe 7. It is connected.
The cylinder direct connection pipe 65 is a pipe for allowing molten glass to flow into the circulation mixing device 60, and one end side is connected to the clarification tank 3 via the communication pipe 6, and the other end side is connected to the middle stage of the side wall portion of the circulation mixing cylinder 52. Has been.
[0068]
In such a circulating mixing process using the circulating mixing device 60, the molten glass fed from the clarification tank 3 first flows into the inner middle stage of the circulating mixing cylinder 52, and then is driven by the propulsive force of the propulsion / stirring means 58. Divided vertically, one rises and the other descends. Then, reflux is performed along the inner and outer sides of the circulating mixing cylinder 52 through the through hole 52a above the middle stage of the circulating mixing tank 60A, and passes through the through hole 52a below the middle stage of the circulating mixing tank 60A. Then, reflux is performed that rotates along the inside and outside of the circulating and mixing cylinder 52. During these refluxes, mixing of the upper-layer molten glass and the lower-layer molten glass is also performed at the outer middle stage portion of the circulation mixing cylinder 52. During the reflux, the molten glass gradually flows out from the outside of the circulating and mixing cylinder 52. In addition, it is preferable for the homogenization to add various stirring means to the propulsion / stirring means 58 similarly to the stirring / propulsion means 18.
[0069]
【Example】
General glass having raw material charging means, raw material dissolution tank, clarification tank, circulating mixing tank, stirring tank, outlet, communication pipe connecting these tanks, temperature control device for each tank, molten glass cutting means and molding means S-BSL7 (Ohara glass type name) was dissolved using a continuous melting / molding (test) apparatus. A raw material having a desired composition is charged by a raw material charging means in an amount equivalent to the outflow amount of molten glass, and a raw material dissolution tank, a clarification tank, a circulating mixing tank, and a stirring tank controlled at a desired temperature are provided. After that, a predetermined flow rate (250 cc / min in this case) is discharged from the outlet. The discharged molten glass is received by a molding die, and when a predetermined amount is discharged, the glass is cut and cooled, and later becomes a product through processes such as processing and annealing.
[0070]
Regarding the circulation mixing step at this time, the internal volume = about 8000 cc, the tank inner diameter D = 20 cm, the solution surface height H = 20 cm, the circulation mixing tube inner diameter d = 10 cm, the distance h1 = 1 cm from the upper end of the circulation mixing tube to the solution surface. The number of rotations of the propulsion blades was adjusted so that the flow rate in the circulating and mixing cylinder was 1000 cc / min using a circulating and mixing tank with a distance h2 = 1 cm from the lower end of the circulating and mixing cylinder to the bottom of the circulating and mixing tank. Approximately 3 hours after the start of dissolution, the operating conditions of the entire apparatus reached the specified conditions. After another hour, after confirming that these conditions were stably maintained, samples for homogeneity confirmation were continuously added. Acquire 10 pieces. This sample is 240mmφ (radius) x 80mm ^t (Thickness) was processed into a disk shape, and homogeneity was measured with an interferometer.
[0071]
As a result of performing the above test on the circulating mixing tank of the first to sixth embodiments, the average value of the refractive index fluctuation range in the block and the average value of the refractive index fluctuation range between the blocks (representative of each block) The average of the refractive index fluctuation range obtained by measuring the test sample with a precision differential refractometer was as shown in the following table. In the table, the item “Example” indicates the number of each of the first to sixth embodiments. The item “average value of the refractive index fluctuation range within the block” indicates the homogeneity within the block, and the item “average value of the refractive index fluctuation range between the blocks” indicates the homogeneity between the blocks.
[0072]
[Table 1]

[0073]
【The invention's effect】
As described above, according to the method for producing highly homogeneous glass of the present invention, the refractive index of the molten glass can be averaged over time by the reflux of the molten glass along the inside and outside of the circulating and mixing cylinder. At the same time, the conventional technique (circulating mixing cylinder in the circulating mixing tank) prevents the short path from the inlet to the outlet of the circulating mixing tank by directly performing the inflow or outflow of the molten glass into the circulating mixing cylinder. This eliminates some of the problems that existed in the technique of refluxing and improves the agitation performance dramatically. Therefore, the tolerance of the refractive index fluctuation range is 10 ^-7 It can be applied to the production of high-order glass of the order, and the temporal change in the refractive index of the molten glass poured into the mold can be sufficiently reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an apparatus for producing highly homogeneous glass according to a first embodiment of the present invention.
FIGS. 2A and 2B show variations of the circulating and mixing tank, where FIG. 2A is a schematic diagram showing the circulating and mixing tank of the first embodiment, and FIG. 2B is a schematic diagram showing the circulating and mixing tank of the second embodiment;
FIGS. 3A and 3B show variations of the circulating mixing tank, in which FIG. 3A is a schematic diagram showing the circulating mixing tank of the third embodiment, and FIG. 3B is a schematic diagram showing the circulating mixing tank of the fourth embodiment;
4A and 4B show variations of the circulating mixing tank, where FIG. 4A is a schematic diagram showing a circulating mixing tank according to a fifth embodiment, and FIG. 4B is a schematic diagram showing a circulating mixing tank according to a sixth embodiment.
FIG. 5 is a cross-sectional view showing a conventional high-homogeneous glass manufacturing apparatus of a type provided with a circulating mixing cylinder inside a circulating mixing tank.
[Explanation of symbols]
2 Dissolution tank
3 clarification tank
4 Mixing tank
10 Circulating and mixing device (first embodiment)
12 Circulating and mixing cylinder
14 tank connection pipe
15 Tube direct connection pipe
18 Propulsion / stirring means
20 Circulating and mixing device (second embodiment)
24 tank connection pipe
25 Tube direct connection pipe
30 Circulating and mixing device (third embodiment)
34 tank connection pipe
35 Tube direct connection pipe
40 Circulating and mixing device (fourth embodiment)
44 tank connection pipe
45 Tube direct connection pipe
50 Circulating mixer (fifth embodiment)
52 Circulating and mixing cylinder
52a Through-hole
54 tank connection pipe
55 Tube direct connection pipe
58 Propulsion / stirring means (two-way propulsion means)
60 Circulating mixer (sixth embodiment)
64 tank connection pipe
65 Tube direct connection pipe

Claims

A method for producing a highly homogeneous glass including a circulation mixing step for homogenizing molten glass,
A circulating mixing tank for homogenizing the molten glass;
A circulating and mixing cylinder housed in the circulating and mixing tank and having openings on both end sides ;
A propulsion means disposed in the circulation mixing cylinder and imparting a driving force to the molten glass in the circulation mixing cylinder;
A pipe directly connected to the side wall of the circulating and mixing cylinder from outside the circulating and mixing tank;
A circulation mixing device having a tank connection pipe connected to the circulation mixing tank from the outside of the circulation mixing tank;
In the circulating and mixing step,
Let the molten glass of the previous step flow through the cylinder direct connection pipe and flow into the circulation mixing cylinder,
The molten glass is propelled in the circulating and mixing cylinder, and the molten glass is refluxed in a reflux path along the inside and outside of the circulating and mixing cylinder.
A method for producing high-homogeneous glass, comprising a process of causing molten glass outside the circulating and mixing cylinder to flow out to the next step through the tank connection pipe.

A method for producing a highly homogeneous glass comprising a circulating and mixing step of homogenizing molten glass using the circulating and mixing device according to claim 1,
In the circulating and mixing step,
Let the molten glass of the previous process flow out of the circulating and mixing cylinder through the tank connecting pipe,
The molten glass is propelled in the circulating and mixing cylinder and the molten glass is refluxed in a reflux path along the inside and outside of the circulating and mixing cylinder.
A method for producing high-homogeneous glass, comprising a process of passing the molten glass in the circulating and mixing tube through the tube directly connected tube to the next step.

In a plan view perpendicular to the central axis of the circulating mixing cylinder,
The inner diameter of the circulating mixing tank is D,
Assuming that the inner diameter of the circulating mixing cylinder is d,
The method for producing highly homogeneous glass according to claim 1 or 2 , wherein a circulating mixing device having d / D of 0.2 to 0.8 is used.

The circulating mixing cylinder is arranged at both ends up and down,
The solution surface height of the molten glass filled in the circulating mixing tank during the circulating mixing step is H,
The distance from the lower end of the upper opening of the circulating mixing cylinder to the height of the solution surface of the molten glass is h1,
The distance from the upper end of the lower opening of the circulation mixing cylinder to the bottom of the circulation mixing tank is h2,
h1 / H is 0 to 0.5,
The method for producing highly homogeneous glass according to any one of claims 1 to 3 , wherein h2 / H is set to a condition of 0.02 to 0.5.

Claim 1-4, characterized in that the relative flow rate of the molten glass flowing out through the cylinder direct pipe or tank connecting tube, 2.0 times or more the flow rate of molten glass passing through the circulation mixing tube The manufacturing method of the highly homogeneous glass in any one of.