JP3777983B2

JP3777983B2 - Method for manufacturing glass article

Info

Publication number: JP3777983B2
Application number: JP2000567479A
Authority: JP
Inventors: 朋浩石原; 達彦齋藤; 裕一大賀
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 1998-08-31
Filing date: 1999-08-26
Publication date: 2006-05-24
Anticipated expiration: 2019-08-26
Also published as: KR20010073057A; AU5443799A; CN1152835C; GB2357500B; WO2000012438A1; GB2357500A; AU755861B2; GB0107542D0; CN1315924A

Description

【０００１】
【発明の属する技術分野】
本発明は高品質な大型のガラス物品及びその製造方法に関する。特に、長尺かつ外径のばらつきの小さい光ファイバ用ガラス母材及びその製法に関する。
【０００２】
【従来の技術】
フォトマスク用ガラス母材、光ファイバ用ガラス母材等のガラス物品は、気相軸付法（ＶＡＤ法）あるいは外付法（ＯＶＤ法）等の気相合成法により合成されたガラス微粒子堆積体を、加熱炉中で真空あるいは減圧雰囲気下で高温加熱処理し、透明化して製造される。高品質のガラス物品を得るためには、ガラス母材中への気泡の残留を極力無くし、かつ、その母材の外径を均一とすることが必要である。そのための方法として、加熱透明化工程を３工程に分け、それぞれの工程の温度を適切に制御する方法が提案されている（特開平６−２５６０３５号公報）。
【０００３】
この方法は、加熱処理中にガラス微粒子堆積体に残留するガスを除去する第１の加熱工程、前記第１の加熱工程の加熱温度より高く、前記堆積体の透明化温度より低い温度で加熱収縮させる第２の加熱工程、及び前記透明化温度で前記堆積体を透明化させる第３の加熱工程を含むことを特徴としている。また、この方法の第２の加熱工程において、ガラス微粒子堆積体を加熱する発熱体を上下方向に多段に分割しそれぞれ独立に温度を制御できるようにしている。下部の発熱体の温度が上部の発熱体の温度以上になるように設定することにより、ガラス物品の長手方向の外径変動を小さくする効果がある。近年、大量生産の必要性や製造工程の効率化の観点から、大型のガラス微粒子堆積体を使用して、長さが１０００ｍｍ以上かつ品質のすぐれた（気泡の残留がなく、外径の長手方向の変動が小さい）光ファイバ母材の製造方法の確立が望まれている。
【０００４】
本発明者らは、自重の影響が大きくなる長さ１０００ｍｍ以上の光ファイバ用ガラス母材では、前記第３の加熱工程のような高温（１４９０〜１６００℃）での加熱処理を行うと、外径の長手方向の変動が大きいという問題に気づいた。
また、本発明者らは、透明化温度が１４９０℃より低い温度の場合は、加熱時間が１時間以下であると、前記堆積体の透明化が難しく、前記堆積体の両端部に焼きのこし（完全に透明化されていない部分）ができるという問題に気づいた。
【０００５】
【発明が解決しようとする課題】
本発明は、大型のガラス微粒子堆積体から長手方向に外径が安定した大型の高品質のガラス物品を得ることができる製造方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
第１の発明は、気相合成法により合成したガラス微粒子堆積体を加熱炉に鉛直方向に挿入し、真空又は減圧雰囲気中で透明化温度より低い温度で加熱して、前記ガラス微粒子体に残留するガスを除去するとともに加熱収縮させる第１の加熱工程と、透明化温度で加熱して前記ガラス微粒子体を透明化させる第２の加熱工程とを有し、前記第２の加熱工程がガラス微粒子堆積体表面の温度が１４００〜１４８０℃となるように制御して７０分以上の所定の時間加熱し、第２の加熱工程の後にガラス物品を冷却する冷却工程を有する長さが１０００ｍｍ以上のガラス物品の製造方法に関する。
【０００７】
第２の発明は、前記第１の加熱工程が１０００〜１３００℃で１０Ｐａ以下の所定の真空度になるまで前記ガスの除去を行う脱気工程を有する第１の発明のガラス物品の製造方法に関する。
【０００８】
第３の発明は、前記第１の加熱工程が１０００〜１３００℃で１０Ｐａ以下の所定の真空度になるまでガスの除去を行う脱気工程と、１０Ｐａ以下の所定の真空度において１３００〜１４００℃で加熱する加熱収縮処理工程とからなる第１の発明のガラス物品の製造方法に関する。
【０００９】
第４の発明は、前記加熱炉は、長手方向の複数部分に対応してそれぞれ独立に制御されたヒータを備え、前記ガラス微粒子堆積体の温度を長手方向の複数部分に分けて制御する第１の発明のガラス物品の製造方法に関する。
【００１０】
第５の発明は、前記各加熱工程において、前記ヒータと前記ガラス微粒子堆積体とを隔離する炉心管の温度を測定し、その温度に基づいて各加熱工程の温度を制御する第１の発明のガラス物品の製造方法に関する。
【００１１】
第６の発明は、前記ガラス微粒子堆積体は透明ガラスロッドとその周囲に形成された多孔質ガラス部分からなる複合母材である第１の発明のガラス物品の製造方法に関する。
【００１２】
第７の発明は、前記第２の加熱工程において、前記ガラス微粒子堆積体表面の温度を上方から下方へ向かって連続的又は段階的に高くする第１の発明のガラス物品の製造方法に関する。
【００１３】
本発明の方法によれば、大型のガラス微粒子堆積体から、長さが１０００ｍｍ以上であり、外径の長手方向の変動が外径の長手方向の中央値に対して±２％以内という光ファイバ母材を容易に製造することができる。
【００１４】
【発明の実施の形態】
ＶＡＤ法あるいはＯＶＤ法などの気相合成法で得られたガラス微粒子堆積体は、第１の加熱工程において、真空又は減圧雰囲気中で、該堆積体に残留するガスの除去と該堆積体の加熱収縮処理を施される。この工程においては、１０００〜１３００℃の温度で１０Ｐａ以下の所定の真空度になるまでガスの除去を行い、その後に１０Ｐａ以下の所定の真空度で１３００〜１４００℃の温度で加熱収縮処理を行うことが好ましい。
【００１５】
前記第１の加熱工程後のガラス微粒子堆積体は、第２の加熱工程において、１４００〜１４８０℃の温度範囲で７０分以上加熱し、透明化される。加熱温度は、１４００〜１４８０℃と従来の透明化温度よりも低く設定することにより、自重による前記堆積体の引き延びが低減される。この場合、加熱温度が下がりやすい該堆積体の両端部においては、完全に透明化されない部分が発生することがあるが、加熱時間を７０分以上の所定の時間に設定することにより該堆積体の両端部を完全に透明化することができる。このように透明化温度を低くすることにより、長さが１０００ｍｍの大型の光ファイバ用ガラス母材では、母材外径の長手方向の変動が外径の長手方向の中央値に対し±２％以内にすることができる。
【００１６】
本発明に使用される加熱炉は、ガラス微粒子堆積体の温度を長手方向の複数部分に分けて制御するため、長手方向の複数部分に対応してそれぞれ独立に制御できる複数のヒータを備えることが好ましい。このようにすることによって、長尺のガラス微粒子堆積体を加熱する場合でも引き延びやすい部分と引き延びにくい部分の温度を適切に制御することができる。
【００１７】
ガラス微粒子堆積体を鉛直方向に挿入するたて型の加熱炉を使用する場合、高温での加熱処理の際に自重による引き延びが発生して外径が上部では細く、下部では太くなる傾向がある。そのような場合には、第２の加熱工程においてガラス微粒子堆積体表面の温度が上端から下方へ向かって連続的又は段階的に高くなるように制御するのが好ましい。
【００１８】
ガラス微粒子堆積体の透明化では、該堆積体を加熱炉のヒータから隔離するため、該堆積体はヒーターとの間にカーボン材等からなる炉心管を介して挿入される。
【００１９】
前記第１及び第２の加熱工程における温度制御は、放射温度計等の温度センサを使用してガラス微粒子堆積体表面の温度を測定し、その測定値に基づいてヒータの出力を制御することによって行うようにする。該堆積体表面の温度は炉心管の温度に近い温度となっていることが多く、その場合、より測定が容易な炉心管の温度を測定し、その測定値に基づいてヒータの出力を制御するようにしてもよい。
【００２０】
【実施例】
以下、実施例により本発明をさらに具体的に説明する。
（実施例１ａ）
ＶＡＤ法で合成した純シリカからなるガラス微粒子堆積体を図１に示す真空焼結炉を使用して本発明の方法に従い透明ガラス化した。図１の真空焼結炉において１はガラス微粒子堆積体、２は真空焼結炉本体、３は炉心管、４はヒータ、５は不活性ガス供給装置、６及び７はそれぞれ炉心管３及び炉本体２内へ供給する不活性ガスの流量計、８及び９はそれぞれ炉心管３及び炉本体２への不活性ガスの供給用配管、１０及び１１は炉内減圧用吸入ポンプ、１２及び１３はそれぞれ炉本体２及び炉心管３から排気するための配管、１４は母材１を支えるシード棒、１５は上蓋、１６は母材１の表面温度計測用の炉心管３まで貫通しているのぞき穴、１６′は炉心管３の温度計測用のぞき穴、１７は母材１の表面温度を計測する温度計、１８は炉心管３の温度を計測する温度計、１９は温度制御装置、２０はトラバース機である。なお、図では炉本体２及び炉心管３の両方にそれぞれ別々にガス供給、排気手段を設けているが、これらはどちらか一方のみとすることもできる。また、図には記載を省略したが配管８、９、１２、１３にはバルブが設けられており、これらのバルブの切替えで真空（減圧）排気又はガスの吹流しを行う。さらに、これも図示省略したが、温度計１８は温度制御装置１９にも接続されている。
【００２１】
ガラス微粒子堆積体１は、ＶＡＤ法で形成され、外径２００ｍｍ、重量３０ｋｇ、有効部長さ１５００ｍｍのものを使用した。真空焼結炉の温度を４００℃に保って該堆積体１を炉心管３に挿入し、上蓋１５で炉内を密封し、炉内圧力を１０Ｐａまで下げた。この状態で該堆積体１の全域における表面温度を１０℃／分の昇温速度で１３００℃まで上昇させて６０分間保持し、該堆積体１に残留したガスを十分に脱気した（脱気工程）。
次に該堆積体１の表面温度を５℃／分で上昇させ、１３５０℃で５０分間保持した（加熱収縮処理工程）。
次に該堆積体１の表面温度を５℃／分で上昇させ、該堆積体１の全域における表面温度を１４２０℃とした後、１００分間保持して透明化した（透明化工程）。
この後、ヒータでの加熱を停止して降温を続け、ガラス物品を冷却し（冷却工程）、６００℃で製品を取り出した。
得られたガラス物品の寸法を測定した結果、有効部長さ１４００ｍｍ全長にわたって外径は９０±０．５ｍｍ（外径変化率±０．５６％）であり、外径の長手方向の変動が小さく、良好な品質を有していた。
【００２２】
（実施例１ｂ）
また、実施例１ａのガラス微粒子堆積体１に代えて、中心部にＧｅがドープされ屈折率を高くし、外周部に純ＳｉＯ_２層を有する透明ガラスロッドの周囲に、ＶＡＤ法によりＳｉＯ_２の多孔質ガラス層を形成した実施例１ａと同寸法の複合母材を用いて、実施例１ａと同様に透明化したが、同様に良好な品質が得られた。
【００２３】
（実施例１ｃ）
また、ガラス微粒子堆積体１として、外径３００ｍｍ、有効部長さ１５００ｍｍ、重量６０ｋｇのものを使用し、実施例１ａと同様に脱気工程、加熱処理工程を行った後、該堆積体１の表面温度を５℃／分で上昇させ、該堆積体１の全域における表面温度を１４２０℃とした後、１８０分間保持して透明化した。
得られたガラス物品の寸法を測定した結果、有効部長さ１４００ｍｍ全長にわたって外径は１５０±１．２ｍｍ（外径変化率±０．６％）と良好な品質が得られた。
【００２４】
（比較例１ａ）
実施例１ａと同サイズのガラス微粒子堆積体１を、同じ設備により以下の条件で透明ガラス化した。すなわち、真空焼結炉の温度を４００℃に保って該堆積体１を炉心管３に挿入し、上蓋１５で炉内を密封し、炉内圧力を１０Ｐａまで下げた。この状態で該堆積体１の全域における表面温度を１０℃／分の昇温速度で１３００℃まで上昇させて６０分間保持し、該堆積体１に残留したガスを十分に脱気した（脱気工程）。
次に、該堆積体１の表面温度を５℃／分で上昇させ１３５０℃とし、同温度で５０分間保持した（加熱収縮処理工程）。
次に、該堆積体１の表面温度を５℃／分で上昇させ、該堆積体１の全域における表面温度を１５００℃とした後、６０分間保持して透明化した（透明化工程）。この後、ヒータでの加熱を停止して降温を続け、６００℃で製品を取り出した。得られたガラス物品の寸法を測定した結果、有効部長さ１４００ｍｍ全長にわたって外径は９０±４．５ｍｍ（外径変化率±５％）であり、外径の長手方向の変動が大きかった。
【００２５】
（比較例１ｂ）
実施例１ｃと同サイズのガラス微粒子堆積体１を使用し、比較例１ａと同じ条件で透明化した。得られたガラス物品の寸法を測定した結果、有効部長さ１５５０ｍｍ全長にわたって外径は１５０±５．０ｍｍ（外径変化率±３．３％）であり、外径の長手方向の変動が大きかった。
【００２６】
実施例１ａ及び比較例１ａの結果は、表１のとおりである。また、これらの例における長手方向に対する外径変動の傾向を図２に示す。第２の加熱工程（透明化工程）において、従来技術よりも低い１４００〜１４８０℃の範囲（好ましくは１４００〜１４４０℃の範囲）で７０分以上（好ましくは１００分以上、さらに好ましくは１５０分以上）保持して引き延びを防止することが、外径の安定化に重要であることがわかる。
実施例において、炉内の真空度を１０Ｐａとしているが、ガラス物品中の気泡の残留を防ぐため、この値は低い方が好ましく、９Ｐａ、８Ｐａであっても良い。
本発明の方法は、ガラス物品の自重が大きい場合、特に、自重が５０ｋｇ以上のものほど外径変動の低減に有効である。
【００２７】
【表１】

【００２８】
（実施例２ａ）
実施例１ａと同サイズのガラス微粒子堆積体１を、実施例１ａと同じ設備、同じ温度条件で透明化した。ただし、本実施例においては透明化処理中の温度の制御を炉心管３の外表面温度を測定する温度計１８を用いて、炉心管３の温度を制御することによって行った。得られたガラス物品の寸法を測定した結果、有効部長さ１４００ｍｍ全長にわたって外径は９０±０．７ｍｍ（外径変化率±０．７８％）であり、外径の長手方向の変動が小さく、良好な品質を有していた。この結果から、該堆積体１の表面の温度を測定する代わりに、比較的測定の容易な炉心管の温度を測定しても問題のないことがわかる。
【００２９】
（実施例２ｂ）
実施例１ｃと同サイズのガラス微粒子堆積体１を使用し、実施例１ｃと同じ条件で透明化した。得られたガラス物品の寸法を測定した結果、有効部長さ１４１０ｍｍ全長にわたって外径は１５０±１．５ｍｍ（外径変化率±１．０％）と良好な品質が得られた。
【００３０】
（実施例３ａ）
実施例１ａと同サイズのガラス微粒子堆積体１を、図1の真空焼結炉と同形式で、ヒータ４を図３に示すように上段ヒータ４−１、中段ヒータ４−２及び下段ヒータ４−３の３段に分割して制御した真空焼結炉を使用して、実施例１ａと同様に透明化した。
該堆積体１は外径２００ｍｍ、有効部長さ１５６０ｍｍのものを使用した。真空焼結炉の温度を４００℃に保って該堆積体１を炉心管３に挿入し、上蓋１５で炉内を密封し、炉内圧力を１０Ｐａまで下げた。この状態で該堆積体１の全域における表面温度を１０℃／分の昇温速度で１３００℃まで上昇させて６０分間保持し、該堆積体１に残留したガスを十分に脱気した（脱気工程）。
次に該堆積体１の表面温度を１０℃／分で上昇させ、１３５０℃にして５０分間保持した（加熱収縮処理工程）。
【００３１】
次に上段ヒータ４−１の影響を強く受ける該堆積体１の範囲Ａの中心点における表面温度を５℃／分で上昇させて１４００℃に、中段ヒータ４−２の影響を強く受ける範囲Ｂの中心点における表面温度を７℃／分で上昇させて１４２０℃に、下段ヒータ４−３の影響を強く受ける範囲Ｃの中心点における表面温度を９℃／分で上昇させて１４４０℃にした後、１００分間保持して該堆積体１を透明化させた（透明化工程）。このときの温度分布はほぼ図３に示すとおりである。
この後、ヒータでの加熱を停止して降温を続け、ガラス物品を冷却し（冷却工程）、６００℃で製品を取り出した。
得られたガラス物品の外径を測定した結果、有効部長さ１４０５ｍｍ全長にわたって外径は９０±０．１ｍｍ（外径変化率±０．１１％）であり、外径の長手方向の変動が小さく、良好な品質を有していた。
【００３２】
（実施例３ｂ）
実施例３ａにおいて、該堆積体１の表面温度の制御を、各ヒーター位置に対応する炉心管３の表面温度を測定し制御することによっても、実施例３ａと同様の良好な品質が得られた（有効部長さ１４１７ｍｍ全長にわたって外径は９０±０．３ｍｍ（外径変化率±０．３３％））。
【００３３】
（実施例３ｃ）
実施例３ａのガラス微粒子堆積体１に代えて、中心部にＧｅがドープされ、外周部に純ＳｉＯ_２層を有する透明ガラスロッドの周囲にＶＡＤ法により純ＳｉＯ_２多孔質ガラス層を形成した実施例３ａと同寸法の複合母材を用いて、実施例３ａと同様に透明化したが、同様に良好な品質が得られた。
【００３４】
（実施例３ｄ）
実施例３ａにおいて、１３５０℃での加熱収縮処理を行っているが、なくても同様に良好な品質が得られた。
【００３５】
（実施例３ｅ）
実施例３ａにおいて、実施例３ａのガラス微粒子堆積体１に代えて、実施例１ｃと同サイズのガラス微粒子堆積体１を使用し、透明化工程で保持時間を１８０分間とした場合は、有効部長さ１３９０ｍｍ全長にわたって外径は１５０±０．７ｍｍ（外径変化率±０．４６％）同様に良好な品質が得られた。
【００３６】
（実施例３ｆ）
実施例３ｅにおいて、該堆積体１の表面温度の制御を、各ヒーター位置に対応する炉心管３の表面温度を測定し制御することによっても、実施例３ａと同様の良好な品質が得られた（有効部長さ１４００ｍｍ全長にわたって外径は１５０±１．０ｍｍ（外径変化率±０．６６％））。
【００３７】
（実施例３ｇ）
外径が３６５ｍｍ、有効部長さ１５６０ｍｍ、重量８０ｋｇのガラス微粒子堆積体１を、実施例３ｅと同じ設備、同じ条件で透明化した。得られたガラス物品の寸法を測定した結果、有効部長さ１４７０ｍｍ全長にわたり外径は１６３±１．５ｍｍ（外径変化率±０．９２％）であった。
【００３８】
（比較例２）
実施例３ｇと同サイズのガラス微粒子堆積体１を、実施例３ｅと同じ設備により以下の条件で透明ガラス化した。すなわち、真空焼結炉の温度を４００℃に保って該堆積体１を炉心管３に挿入し、上蓋１５で炉内を密封し、炉内圧力を１０Ｐａまで下げた。この状態で該堆積体１の全域における表面温度を１０℃／分の昇温速度で１３００℃まで上昇させて６０分間保持し、該堆積体１に残留したガスを十分に脱気した（脱気工程）。
【００３９】
次に、該堆積体１の表面温度を５℃／分で上昇させ１３５０℃とし、同温度で５０分間保持した（加熱収縮処理工程）。
次に該堆積体１の表面温度を１５℃／分で上昇させ、該堆積体１の全域における表面温度を１５００℃とした後、６０分間保持して透明化した（透明化工程）。この後、ヒータでの加熱を停止して降温を続け、６００℃で製品を取り出した。得られたガラス物品の寸法を測定した結果、有効部長さ１６６０ｍｍ全長にわたって外径は１５８±７ｍｍ（外径変化率±４．４３％）であり、外径の長手方向の変動が大きかった。
【図面の簡単な説明】
【図１】実施例で使用した真空焼結炉の装置構成を示す概略説明図である。
【図２】実施例１及び比較例１で得られた光ファイバ母材の長手方向における外径変化を示す図である。
【図３】実施例３における温度制御の状態を示す模式図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-quality large glass article and a method for producing the same. In particular, the present invention relates to a glass preform for an optical fiber that is long and has a small variation in outer diameter, and a method for producing the same.
[0002]
[Prior art]
Glass articles such as glass masks for photomasks and glass preforms for optical fibers are glass fine particle deposits synthesized by a gas phase synthesis method such as a gas phase axis method (VAD method) or an external method (OVD method). Is manufactured by heating at high temperature in a heating furnace in a vacuum or a reduced-pressure atmosphere to make it transparent. In order to obtain a high-quality glass article, it is necessary to eliminate the residual bubbles in the glass base material as much as possible and to make the outer diameter of the base material uniform. As a method therefor, a method has been proposed in which the heat-clearing step is divided into three steps and the temperature of each step is appropriately controlled (Japanese Patent Laid-Open No. 6-256035).
[0003]
This method includes a first heating step for removing gas remaining in the glass particulate deposit during the heat treatment, and heat shrinkage at a temperature higher than the heating temperature of the first heating step and lower than the transparency temperature of the deposit. And a third heating step for transparentizing the deposited body at the transparentizing temperature. Further, in the second heating step of this method, the heating element for heating the glass fine particle deposit is divided into multiple stages in the vertical direction so that the temperature can be controlled independently. By setting the temperature of the lower heating element to be equal to or higher than the temperature of the upper heating element, there is an effect of reducing the fluctuation of the outer diameter in the longitudinal direction of the glass article. In recent years, from the viewpoint of the necessity of mass production and the efficiency of the manufacturing process, using a large glass particulate deposit, the length is 1000 mm or more and the quality is excellent (there is no residual bubbles, the longitudinal direction of the outer diameter The establishment of a method for manufacturing an optical fiber preform is desired.
[0004]
When the heat treatment at a high temperature (1490 to 1600 ° C.) as in the third heating step is performed on an optical fiber glass preform having a length of 1000 mm or more in which the influence of its own weight becomes large, the present inventors I noticed the problem of large variation in the longitudinal direction of the diameter.
In addition, when the transparentization temperature is lower than 1490 ° C., the present inventors have difficulty in clearing the deposit when the heating time is 1 hour or less, and baking is performed on both ends of the deposit ( I noticed that there was a problem that was not completely transparent.
[0005]
[Problems to be solved by the invention]
An object of this invention is to provide the manufacturing method which can obtain the large-sized high quality glass article with the outer diameter stabilized in the longitudinal direction from the large-sized glass particulate deposit.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, a glass particulate deposit synthesized by a vapor phase synthesis method is vertically inserted into a heating furnace, heated in a vacuum or a reduced pressure atmosphere at a temperature lower than a clearing temperature, and remains in the glass particulate. A first heating step for removing the gas to be heated and shrinking by heating, and a second heating step for heating the glass fine particle body at a transparent temperature to make the glass fine particle transparent, wherein the second heating step is a glass fine particle. A glass having a length of 1000 mm or more having a cooling step of controlling the temperature of the deposited body to be 1400 to 1480 ° C., heating for a predetermined time of 70 minutes or more, and cooling the glass article after the second heating step. The present invention relates to a method for manufacturing an article.
[0007]
2nd invention is related with the manufacturing method of the glass article of 1st invention which has the deaeration process which removes the said gas until the said 1st heating process becomes a predetermined vacuum degree of 10 Pa or less at 1000-1300 degreeC. .
[0008]
According to a third aspect of the present invention, there is provided a degassing step of removing gas until the first heating step reaches a predetermined vacuum level of 10 Pa or less at 1000 to 1300 ° C., and 1300 to 1400 ° C. at a predetermined vacuum level of 10 Pa or lower. It is related with the manufacturing method of the glass article of 1st invention which consists of a heat-shrink process process heated with.
[0009]
According to a fourth aspect of the present invention, the heating furnace includes a heater that is independently controlled corresponding to a plurality of portions in the longitudinal direction, and controls the temperature of the glass particulate deposit in a plurality of portions in the longitudinal direction. The present invention relates to a method for producing a glass article.
[0010]
According to a fifth aspect of the first aspect of the present invention, in each of the heating steps, the temperature of the core tube that separates the heater and the glass particulate deposit is measured, and the temperature of each heating step is controlled based on the temperature. The present invention relates to a method for manufacturing a glass article.
[0011]
6th invention is related with the manufacturing method of the glass article of 1st invention which is a composite base material in which the said glass particulate deposit body consists of a transparent glass rod and the porous glass part formed in the circumference | surroundings.
[0012]
7th invention is related with the manufacturing method of the glass article of 1st invention which raises the temperature of the said glass fine particle deposit | stacking body continuously or stepwise from upper direction to the downward direction in a said 2nd heating process.
[0013]
According to the method of the present invention, an optical fiber having a length of 1000 mm or more and a variation in the longitudinal direction of the outer diameter within ± 2% with respect to the median value in the longitudinal direction of the outer diameter from a large glass particulate deposit. The base material can be easily manufactured.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the first heating step, the glass fine particle deposit obtained by the vapor phase synthesis method such as the VAD method or the OVD method is used to remove the gas remaining in the deposit and to heat the deposit in a vacuum or a reduced pressure atmosphere. Shrinkage treatment is applied. In this step, the gas is removed at a temperature of 1000 to 1300 ° C. until a predetermined vacuum level of 10 Pa or lower, and then a heat shrinking process is performed at a temperature of 1300 to 1400 ° C. at a predetermined vacuum level of 10 Pa or lower. It is preferable.
[0015]
In the second heating step, the glass particulate deposit after the first heating step is heated in the temperature range of 1400 to 1480 ° C. for 70 minutes or more to be transparent. By setting the heating temperature to 1400 to 1480 ° C., which is lower than the conventional clearing temperature, extension of the deposited body due to its own weight is reduced. In this case, there may occur a portion that is not completely transparent at both end portions of the deposited body where the heating temperature tends to decrease. However, by setting the heating time to a predetermined time of 70 minutes or more, Both ends can be made completely transparent. Thus, by lowering the transparency temperature, in a large glass preform for an optical fiber having a length of 1000 mm, the longitudinal variation of the outer diameter of the preform is ± 2% with respect to the median value of the outer diameter in the longitudinal direction. Can be within.
[0016]
The heating furnace used in the present invention is provided with a plurality of heaters that can be controlled independently corresponding to the plurality of portions in the longitudinal direction in order to control the temperature of the glass particulate deposit in a plurality of portions in the longitudinal direction. preferable. By doing in this way, even when heating a long glass fine particle deposit body, the temperature of the part which is easy to extend and the part which is difficult to extend can be controlled appropriately.
[0017]
When using a vertical heating furnace that inserts a glass particle deposit in the vertical direction, it tends to stretch due to its own weight during heat treatment at high temperatures, and the outer diameter tends to be thin at the top and thick at the bottom. is there. In such a case, in the second heating step, it is preferable to control the temperature of the surface of the glass fine particle deposit so as to increase continuously or stepwise from the upper end to the lower side.
[0018]
When the glass particulate deposit is made transparent, the deposit is isolated from the heater of the heating furnace, and the deposit is inserted between the heater and a heater core tube made of a carbon material or the like.
[0019]
The temperature control in the first and second heating steps is performed by measuring the temperature of the surface of the glass particulate deposit using a temperature sensor such as a radiation thermometer and controlling the output of the heater based on the measured value. To do. The temperature of the surface of the deposit is often close to the temperature of the core tube. In this case, the temperature of the core tube, which is easier to measure, is measured, and the output of the heater is controlled based on the measured value. You may do it.
[0020]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1a
A glass fine particle deposit made of pure silica synthesized by the VAD method was made into a transparent glass according to the method of the present invention using a vacuum sintering furnace shown in FIG. In the vacuum sintering furnace of FIG. 1, 1 is a glass particulate deposit, 2 is a vacuum sintering furnace body, 3 is a furnace core tube, 4 is a heater, 5 is an inert gas supply device, and 6 and 7 are the furnace core tube 3 and the furnace, respectively. Inert gas flowmeters to be supplied into the main body 2, 8 and 9 are pipes for supplying inert gas to the furnace core tube 3 and the furnace

main body

2, 10 and 11 are suction pumps for depressurizing the furnace, and 12 and 13 are Piping for exhausting from the furnace body 2 and the

core tube

3, 14 is a seed rod for supporting the base material 1, 15 is an upper lid, and 16 is a peephole penetrating to the core tube 3 for measuring the surface temperature of the base material 1. , 16 'is a peephole for measuring the temperature of the

core tube

3, 17 is a thermometer for measuring the surface temperature of the

base material

1, 18 is a thermometer for measuring the temperature of the

core tube

3, 19 is a temperature control device, and 20 is a traverse. Machine. In the figure, gas supply and exhaust means are provided separately for both the furnace body 2 and the furnace core tube 3, but only one of them may be provided. Although not shown in the figure,

valves

8, 9, 12, and 13 are provided with valves, and vacuum (decompression) exhaust or gas blowing is performed by switching these valves. Further, although not shown, the thermometer 18 is also connected to the temperature control device 19.
[0021]
The glass fine particle deposit 1 was formed by the VAD method, and had an outer diameter of 200 mm, a weight of 30 kg, and an effective part length of 1500 mm. The deposit 1 was inserted into the furnace core tube 3 while maintaining the temperature of the vacuum sintering furnace at 400 ° C., the inside of the furnace was sealed with the upper lid 15, and the furnace pressure was reduced to 10 Pa. In this state, the surface temperature of the entire area of the deposit 1 is increased to 1300 ° C. at a rate of temperature increase of 10 ° C./min and held for 60 minutes, and the gas remaining in the deposit 1 is sufficiently degassed (degassed) Process).
Next, the surface temperature of the deposited body 1 was increased at 5 ° C./min and held at 1350 ° C. for 50 minutes (heating shrinkage treatment step).
Next, the surface temperature of the deposited body 1 was increased at 5 ° C./min, the surface temperature of the entire area of the deposited body 1 was set to 1420 ° C., and then kept for 100 minutes to be transparent (transparentizing step).
Thereafter, the heating with the heater was stopped, the temperature was continuously lowered, the glass article was cooled (cooling step), and the product was taken out at 600 ° C.
As a result of measuring the dimensions of the obtained glass article, the outer diameter is 90 ± 0.5 mm (outer diameter change rate ± 0.56%) over the entire length of the effective part length of 1400 mm, and the fluctuation in the longitudinal direction of the outer diameter is small, Had good quality.
[0022]
(Example 1b)
Further, instead of the glass fine particle deposit 1 of Example 1a, the central portion is doped with Ge, the refractive index is increased, and the periphery of a transparent glass rod having a pure SiO ₂ layer on the outer peripheral portion is made of SiO ₂ by the VAD method. Using a composite base material having the same dimensions as Example 1a in which the porous glass layer was formed, it was made transparent in the same manner as Example 1a, but good quality was obtained in the same manner.
[0023]
(Example 1c)
Further, the glass fine particle deposit 1 having an outer diameter of 300 mm, an effective part length of 1500 mm, and a weight of 60 kg was used, and after performing a deaeration process and a heat treatment process in the same manner as in Example 1a, the surface of the deposit 1 The temperature was raised at 5 ° C./min, the surface temperature of the entire area of the deposited body 1 was set to 1420 ° C., and then kept for 180 minutes to be transparent.
As a result of measuring the dimensions of the obtained glass article, the outer diameter was 150 ± 1.2 mm (outer diameter change rate ± 0.6%) over the entire length of the effective portion length of 1400 mm, and good quality was obtained.
[0024]
(Comparative Example 1a)
The glass fine particle deposit 1 having the same size as that of Example 1a was made into a transparent glass under the following conditions using the same equipment. That is, while keeping the temperature of the vacuum sintering furnace at 400 ° C., the deposit 1 was inserted into the furnace core tube 3, the inside of the furnace was sealed with the upper lid 15, and the furnace pressure was lowered to 10 Pa. In this state, the surface temperature of the entire area of the deposit 1 is increased to 1300 ° C. at a rate of temperature increase of 10 ° C./min and held for 60 minutes, and the gas remaining in the deposit 1 is sufficiently degassed (degassed) Process).
Next, the surface temperature of the deposited body 1 was increased at 5 ° C./min to 1350 ° C. and held at the same temperature for 50 minutes (heating shrinkage treatment step).
Next, the surface temperature of the deposited body 1 was increased at 5 ° C./min to set the surface temperature of the entire area of the deposited body 1 to 1500 ° C., and then kept transparent for 60 minutes (clearing step). Thereafter, heating with the heater was stopped, the temperature was continuously lowered, and the product was taken out at 600 ° C. As a result of measuring the dimensions of the obtained glass article, the outer diameter was 90 ± 4.5 mm (outer diameter change rate ± 5%) over the entire length of the effective part length of 1400 mm, and the longitudinal variation of the outer diameter was large.
[0025]
(Comparative Example 1b)
The glass fine particle deposit 1 having the same size as that of Example 1c was used, and it was made transparent under the same conditions as in Comparative Example 1a. As a result of measuring the dimensions of the obtained glass article, the outer diameter was 150 ± 5.0 mm (outer diameter change rate ± 3.3%) over the entire length of the effective part length of 1550 mm, and the longitudinal variation of the outer diameter was large. .
[0026]
The results of Example 1a and Comparative Example 1a are as shown in Table 1. Moreover, the tendency of the outer diameter fluctuation | variation with respect to the longitudinal direction in these examples is shown in FIG. In the second heating step (clearing step), it is 70 minutes or more (preferably 100 minutes or more, more preferably 150 minutes or more) in the range of 1400 to 1480 ° C. (preferably in the range of 1400 to 1440 ° C.) lower than the prior art. It can be seen that holding and preventing stretching is important for stabilizing the outer diameter.
In the examples, the degree of vacuum in the furnace is set to 10 Pa. However, in order to prevent bubbles from remaining in the glass article, this value is preferably low, and may be 9 Pa or 8 Pa.
The method of the present invention is more effective in reducing fluctuations in the outer diameter when the weight of the glass article is large, particularly when the weight of the glass article is 50 kg or more.
[0027]
[Table 1]

[0028]
Example 2a
The glass particulate deposit 1 having the same size as that of Example 1a was made transparent under the same equipment and the same temperature conditions as in Example 1a. However, in the present embodiment, the temperature during the transparency treatment was controlled by controlling the temperature of the core tube 3 using the thermometer 18 that measures the outer surface temperature of the core tube 3. As a result of measuring the dimensions of the obtained glass article, the outer diameter is 90 ± 0.7 mm (outer diameter change rate ± 0.78%) over the entire length of the effective portion length of 1400 mm, and the fluctuation in the longitudinal direction of the outer diameter is small, Had good quality. From this result, it can be seen that there is no problem even if the temperature of the core tube, which is relatively easy to measure, is measured instead of measuring the temperature of the surface of the deposit 1.
[0029]
(Example 2b)
The glass fine particle deposit 1 having the same size as that of Example 1c was used, and it was made transparent under the same conditions as in Example 1c. As a result of measuring the dimension of the obtained glass article, the outer diameter was 150 ± 1.5 mm (outer diameter change rate ± 1.0%) over the entire length of the effective part length of 1410 mm, and good quality was obtained.
[0030]
(Example 3a)
The glass fine particle deposit 1 having the same size as that of Example 1a is formed in the same format as the vacuum sintering furnace of FIG. 1, and the heater 4 is shown in FIG. Using a vacuum sintering furnace controlled by dividing into three stages of -3, it was made transparent in the same manner as in Example 1a.
The deposit 1 had an outer diameter of 200 mm and an effective part length of 1560 mm. The deposit 1 was inserted into the furnace core tube 3 while maintaining the temperature of the vacuum sintering furnace at 400 ° C., the inside of the furnace was sealed with the upper lid 15, and the furnace pressure was reduced to 10 Pa. In this state, the surface temperature of the entire area of the deposit 1 is increased to 1300 ° C. at a rate of temperature increase of 10 ° C./min and held for 60 minutes, and the gas remaining in the deposit 1 is sufficiently degassed (degassed) Process).
Next, the surface temperature of the deposit 1 was increased at 10 ° C./min, and maintained at 1350 ° C. for 50 minutes (heating shrinkage treatment step).
[0031]
Next, the surface temperature at the center point of the range A of the deposit 1 that is strongly influenced by the upper heater 4-1 is increased at 5 ° C./min to 1400 ° C., and the range B that is strongly influenced by the middle heater 4-2. The surface temperature at the center point of No. 4 was increased at 7 ° C./min to 1420 ° C., and the surface temperature at the center point of the range C strongly affected by the lower heater 4-3 was increased at 9 ° C./min to 1440 ° C. Thereafter, the deposit 1 was made transparent by being held for 100 minutes (transparency process). The temperature distribution at this time is substantially as shown in FIG.
Thereafter, the heating with the heater was stopped, the temperature was continuously lowered, the glass article was cooled (cooling step), and the product was taken out at 600 ° C.
As a result of measuring the outer diameter of the obtained glass article, the outer diameter is 90 ± 0.1 mm (outer diameter change rate ± 0.11%) over the entire length of the effective portion 1405 mm, and the fluctuation of the outer diameter in the longitudinal direction is small. Had good quality.
[0032]
(Example 3b)
In Example 3a, the same good quality as in Example 3a was obtained by controlling the surface temperature of the deposit 1 by measuring and controlling the surface temperature of the core tube 3 corresponding to each heater position. (Outer diameter is 90 ± 0.3 mm over the entire length of the effective portion 1417 mm (outer diameter change rate ± 0.33%)).
[0033]
(Example 3c)
In place of the glass fine particle deposit 1 of Example 3a, a pure SiO ₂ porous glass layer was formed by a VAD method around a transparent glass rod doped with Ge at the center and having a pure SiO ₂ layer at the outer periphery. Using a composite base material having the same dimensions as in Example 3a, it was made transparent in the same manner as in Example 3a, but good quality was obtained in the same manner.
[0034]
(Example 3d)
In Example 3a, the heat-shrinkage treatment at 1350 ° C. was performed, but good quality was obtained even without it.
[0035]
Example 3e
In Example 3a, instead of the glass fine particle deposit 1 of Example 3a, when the glass fine particle deposit 1 of the same size as Example 1c is used and the holding time is 180 minutes in the clarification step, the effective length The outer diameter was 150 ± 0.7 mm over the entire length of 1390 mm (outer diameter change rate ± 0.46%), and good quality was obtained as well.
[0036]
(Example 3f)
In Example 3e, the same good quality as in Example 3a was obtained by controlling the surface temperature of the deposit 1 by measuring and controlling the surface temperature of the core tube 3 corresponding to each heater position. (Outer diameter is 150 ± 1.0 mm (outer diameter change rate ± 0.66%) over the entire effective portion length of 1400 mm).
[0037]
(Example 3g)
The glass fine particle deposit 1 having an outer diameter of 365 mm, an effective portion length of 1560 mm, and a weight of 80 kg was made transparent using the same equipment and the same conditions as in Example 3e. As a result of measuring the dimensions of the obtained glass article, the outer diameter was 163 ± 1.5 mm (outer diameter change rate ± 0.92%) over the entire length of the effective portion 1470 mm.
[0038]
(Comparative Example 2)
The glass fine particle deposit 1 having the same size as that of Example 3g was made into a transparent glass under the following conditions using the same equipment as Example 3e. That is, while keeping the temperature of the vacuum sintering furnace at 400 ° C., the deposit 1 was inserted into the furnace core tube 3, the inside of the furnace was sealed with the upper lid 15, and the furnace pressure was lowered to 10 Pa. In this state, the surface temperature of the entire area of the deposited body 1 is increased to 1300 ° C. at a rate of temperature increase of 10 ° C./min and held for 60 minutes to sufficiently degas the gas remaining in the deposited body 1 (degassing). Process).
[0039]
Next, the surface temperature of the deposited body 1 was increased at 5 ° C./min to 1350 ° C., and held at that temperature for 50 minutes (heating shrinkage treatment step).
Next, the surface temperature of the deposited body 1 was increased at 15 ° C./min to set the surface temperature of the entire area of the deposited body 1 to 1500 ° C., and then kept transparent for 60 minutes (clearing step). Thereafter, heating with the heater was stopped, the temperature was continuously lowered, and the product was taken out at 600 ° C. As a result of measuring the dimensions of the obtained glass article, the outer diameter was 158 ± 7 mm (outer diameter change rate ± 4.43%) over the entire length of the effective part length of 1660 mm, and the fluctuation of the outer diameter in the longitudinal direction was large.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing a device configuration of a vacuum sintering furnace used in Examples.
FIG. 2 is a diagram showing changes in the outer diameter in the longitudinal direction of the optical fiber preforms obtained in Example 1 and Comparative Example 1.
3 is a schematic diagram showing a state of temperature control in Embodiment 3. FIG.

Claims

A glass particulate deposit synthesized by a gas phase synthesis method is vertically inserted into a heating furnace and heated at a temperature lower than the transparent temperature in a vacuum or reduced pressure atmosphere to remove the gas remaining in the glass particulate. A first heating step for heat shrinking, and a second heating step for heating the glass fine particle body to be transparent by heating at a clearing temperature, wherein the temperature of the surface of the glass fine particle deposit is determined by the second heating step. A glass article having a length of 1000 mm or more, characterized by having a cooling step of controlling the temperature to 1400 to 1480 ° C. and heating for a predetermined time of 70 minutes or more and cooling the glass article after the second heating step Manufacturing method.

2. The glass article according to claim 1, further comprising a deaeration step in which the gas is removed until the first heating step has a predetermined degree of vacuum of 10 Pa or less at 1000 to 1300 ° C. 3. Production method.

A degassing step for removing gas until the first heating step at 1000 to 1300 ° C. reaches a predetermined vacuum level of 10 Pa or less, and a heat shrinking process for heating at 1300 to 1400 ° C. at a predetermined vacuum level of 10 Pa or lower. The method for producing a glass article according to claim 1, comprising a step.

The heating furnace includes a heater that is independently controlled corresponding to a plurality of portions in the longitudinal direction, and controls the temperature of the glass particulate deposit in a plurality of portions in the longitudinal direction. A method for producing a glass article according to item 1.

The temperature of a furnace core tube that separates the heater and the glass fine particle deposit is measured, and the temperature of each heating step is controlled based on the temperature. Production method.

2. The method for producing a glass article according to claim 1, wherein the glass particulate deposit is a composite base material comprising a transparent glass rod and a porous glass portion formed around the transparent glass rod.

2. The method for producing a glass article according to claim 1, wherein in the second heating step, the temperature of the surface of the glass particulate deposit is increased continuously or stepwise from above to below. .