JP3966943B2 - Opaque quartz glass and manufacturing method thereof - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は不透明石英ガラスに関し、特に、熱遮断性及び透明石英ガラスとの接合性に優れた不透明石英ガラス及びその製造方法に関する。
【０００２】
【従来の技術】
従来の不透明石英ガラスの製造方法は、珪酸質原料粉末を加熱溶融しガラス化する方法であり、その加熱溶融の方式として、アルゴン−酸素プラズマ炎、酸水素炎などの火炎中で溶融させるベルヌーイ法、あるいは容器に充填したシリカを高真空下で加熱溶融する真空溶融法などがある。不透明石英ガラスの原料としては、従来より、天然の珪石または低品位の水晶が用いられている。これらの原料中には、多数の微細な気泡が包含されており、原料が溶融されたとき、気泡はそのまま残留し、不透明石英ガラスが得られる。しかしながら、近年、半導体分野においてＬＳＩの高集積化が進むに伴い、使用する原材料に対する高純度化の要求が厳しくなり、従来は低純度品が使用されていた分野においても、高純度品が求められ始めた。代表的な分野がフランジ材であり、不透明で、かつ、高純度の石英ガラス、すなわち、高純度不透明石英ガラスの供給が望まれている。しかし、従来から用いられている不透明石英ガラス製造用の天然原料は、微細な気泡と共に多量の不純物を含有している。これらの不純物を除去することは極めて困難であって、精製による高純度化は不可能であると言われている。一方、比較的高純度の水晶は、結晶中に存在する気泡−特に、微細気泡の量が少ないので、溶融しても不透明度が高まらず、得られた石英ガラスは半透明なものになるに過ぎない。
【０００３】
その改良方法として、アルカリ（土類）金属、ＦｅおよびＡｌの各元素の含有率が低く、多数の微細気泡を包含し、気化性成分としてシラノール基を特定の範囲の濃度で均一に含有した高純度の非晶質シリカを火炎溶融することによる方法が提案されている（特開平６−２４７７１）。
【０００４】
しかしながら、この方法によれば、ＩＣ封止材用シリカフィラーやシリカガラス粉製造用の母材インゴットのような簡単な形状の石英ガラス製品しか直接製造出来ず、フランジ状、円筒状、中空角柱状、スクリュウー状、ターボチャージャー状、角状水槽又はたらい状のような複雑な形状を有する石英ガラス製品を製造するには、多大の削り出し等の後加工が必要となり、石英ガラスの利用率が低くなり、結果として製造コストの上昇を招く。
【０００５】
別の新しい不透明石英ガラスとして、高純度に精製された結晶質石英粉末をアンモニア雰囲気中で加熱してアンモニア化し、不活性ガス雰囲気下で加熱溶融する製造法により、気泡の径を小さくするが、気泡の数量を多くし、不透明石英ガラスの単位体積当りの総気泡断面積を大きくして、耐熱性が向上した不透明石英ガラスが提案されている（特開平７−６１８２７及び特開平７−３００３４１）。しかしながら、この方法では、不透明石英ガラスの密度、気泡径、気泡量は原料粉末の粒子径、粒子径分布、溶融容器に充填した時の充填状態に非常に敏感に反応するために再現性良く気泡制御することが容易ではなく、表面と内部で気泡径や気泡量が大きく異なるなどの問題がある。また、石英ガラス中の窒素元素含有量が大きく、この石英ガラスの欠損部の補修で火炎加工する場合、ガラス基質中から窒素ガスが気泡として遊離し、補修箇所が凸凹になったり、補修箇所の不透明度が他の箇所と異なるなど、寸法精度上及び外観上、好ましくない事態が発生する。さらに、透明石英ガラス部材と火炎接合する場合、両者の窒素元素含有濃度が大きく違い、接合がうまくいかない。
【０００６】
他の不透明石英ガラスの製造法として、珪石、珪砂、α−クォーツ、クリストバライトなどの珪酸質原料粉末に、発泡剤として炭素、窒化ケイ素などの微粉末を添加して加熱溶融する方法が提案されている（たとえば、特開平４−６５３２８号公報）。しかしながら、この方法では、前記手法のような問題は回避し得るが、酸水素炎で溶融するために得られるガラスにＯＨ基が取り込まれやすく高温での粘性が低下し、高温で長時間使用する半導体製造用治具などの用途には不利である。また、固体粒子の混合や固相反応・分解反応などが関与し、溶融体中に微細気泡を均一に分散させるように制御することが困難である。更に、火炎溶融法では、火炎中での微粒子の滞留時間が極めて短いので反応を完結することが困難であり、添加された発泡剤が溶融体中に異物として残留することがある。また、珪酸質原料と発泡剤とが反応して溶融体が着色する現象が起こるという問題点がある。
【０００７】
以上の様に、いずれの先行特許においても各々未だに解決されない課題を有している。
【０００８】
【発明が解決しようとする課題】
本願発明はこれらの課題を解決することを目的としてなされたものであり、気泡が均一に分散され、高温粘性及び熱遮断性が優れた不透明石英ガラスを容易に製造する方法を提供することにある。また、この不透明石英ガラスは、フランジ状を初め、円筒状、中空角柱状、スクリュウー状、ターボチャージャー状、角状水槽状又は“たらい状”の様な複雑な形状を直接製造することが可能であり、また、石英ガラス中の窒素元素含有量を小さくして、この石英ガラスの欠損部の補修で火炎加工する場合、ガラス基質中から窒素ガスが気泡として遊離せず、補修箇所の外面を滑らかにすることができ、透明石英ガラス部材と火炎接合する場合、両者の窒素元素含有濃度が近いので、接合がうまくいく新規な不透明石英ガラスを提供することも本願発明の目的とする。
【０００９】
【課題を解決するための手段】
製造方法として、上記の珪石、珪砂、α−クォーツ、クリストバライトなどの珪酸質原料粉末に、発泡剤として炭素、窒化ケイ素などの微粉末を添加して加熱溶融する方法（特開平４−６５３２８号公報）と類似の方法を採用し、平均粒子径が１０〜５００μｍの比較的安価な粗いシリカ粉末に窒化ケイ素粉末を、シリカ粉末１００重量部に対して窒化ケイ素粉末０．００１〜０．０５重量部を混合分散させた出発原料粉末を、複雑な形状を有する耐熱性型に充填し、真空雰囲気下で、当該出発原料を溶融する温度以上１９００℃以下の温度まで加熱し、ガラス化及び発泡による気泡生成を行う製造方法を採用することにより、気泡が均一に分散され、高温粘性及び熱遮断性に優れただけでなく、鋳込み成形等の繁雑な粉末成形を行わずに、耐熱性型の形状をフランジ状を初め、円筒状、中空角柱状、スクリュウー状、ターボチャージャー状、角状水槽状又は“たらい状”の様な複雑な形状を適宜選択することで最終製品に近いガラス体を直接製造することが可能であり、後加工が必要であっても簡単で済む。
【００１０】
以下、本発明をさらに詳細に説明する。
【００１１】
［１］出発原料
出発原料としては、シリカ粉末と窒化ケイ素粉末により得られる混合粉末である。
【００１２】
（ａ）シリカ粉末
本発明で使用されるシリカ粉末としては、含有金属不純物としてＮａ，Ｋ，Ｍｇ，Ｃａ，Ｆｅが各々独立して１ｐｐｍ以下とした高純度な結晶質又は非晶質シリカ粉末を用いることが好ましい。この理由としては、本発明の方法により得られる不透明石英ガラスを加熱すると、蒸気圧の低い不純物が飛散する傾向があり、不透明石英ガラス自体が一部結晶化して破損しやすくなったり、着色してしまったりするのを避けるためである。このような高純度なシリカ粉末は、合成法によったり、天然原料を精製したりすることより得られる。例えば、非晶質シリカ粉末を合成法により得るには、アルカリ金属ケイ酸塩水溶液（水ガラス）を酸と反応させることによりアルカリ金属を除去してシリカを得る方法、ＳｉＣｌ4を加水分解してシリカとする方法、シリコンアルコキシドを加水分解してシリカとする方法が挙げられるが、工業的規模の生産には、Ｎａ，Ｋ，Ｌｉ等のアルカリ金属と二酸化ケイ素からなるアルカリ金属ケイ酸塩水溶液（水ガラス）を硫酸，硝酸，塩酸等の無機酸と反応させる方法で得られるものが好適である。又、結晶質シリカ粉末を天然原料より得るには、天然水晶をフッ酸処理する方法等により得ることができる。
【００１３】
シリカ粉末の平均粒子径としては、耐熱性型に充填しやすいように流動性を付与するために１０〜５００μｍの範囲である。平均粒子径が１０μｍ未満の場合では粉末の流動性が低下し均一に粉末を充填することが困難であり、５００μｍを越える場合では粒子間の空隙が大きくなり不透明石英ガラス中に３００μｍ以上の巨大な気泡が発生する原因となり好ましくない。
【００１４】
本発明の方法により得られる不透明石英ガラス中の気泡径はシリカ粉末の平均粒子径に依存するため、平均粒子径の調整による気泡径制御が可能である。すなわち、より微細な気泡を得ようとする場合には微粒子からなる粉末を、粗い気泡を得ようとする場合には粗粒子からなる粉末を用いるとよい。
【００１５】
（ｂ）窒化ケイ素粉末
窒化ケイ素粉末としては、四塩化ケイ素、シリコン、シリカ等を原料とし、それらを窒化することにより得られる高純度のものを使用することが好ましい。この理由としては、本発明の方法により得られる不透明石英ガラスより不純物が飛散してしまったり、不透明石英ガラス自体が一部結晶化して破損しやすくなったり、着色してしまったりするのを避けるためである。
【００１６】
又、窒化ケイ素粉末の量としては、シリカ粉末１００重量部に対して窒化ケイ素粉末０．００１〜０．０５重量部である。０．００１重量部未満の場合には発泡による気泡の生成量が少なくなり充分な熱遮断性が得られず好ましくない。０．０５重量部を越える場合には発泡による気泡の生成量が多くなり得られる不透明石英ガラスの機械強度が悪くなるため好ましくない。もう一つの理由として、０．０５重量部を越えると石英ガラス基質中に含まれる窒素元素濃度が５０ｐｐｍ以上となり、得られたガラスを火炎加工など再加熱した際に石英ガラス基質から窒素ガスが遊離し、気泡量や気泡径が増大するため、不透明石英ガラスの白色度が変化してしまう。また、窒化ケイ素粉末の平均粒子径としては、０．１〜１μｍであることが好ましく、０．１〜０．５μｍであることが更に好ましい。この理由は、平均粒子径がこの範囲にあれば、気泡が粗大化したり、気泡量が激減してしまうこともなく、更に、粉末が凝集してシリカ粉末との混合において均一に混合できなくなるのを避けるためである。
【００１７】
［２］混合分散
シリカ粉末と窒化ケイ素粉末よりなる原料粉末中の窒化ケイ素粉末の分散の度合いは発泡時の気泡径及びその分布に影響を及ぼすため、窒化ケイ素粉末の凝集がないように混合する必要がある。混合の際に用いる器具としては窒化ケイ素粉末が分散できるものであれば特に限定されないが、例えば、乳鉢、ボールミル等が例示できる。更に、窒化ケイ素粉末の分散を良好にするために分散媒を用いる湿式法が好ましく用いられる。分散媒としては、例えば、水、アルコール等が例示できる。
【００１８】
［３］容器への充填
次に、得られた混合粉末を耐熱性型に充填する。ここで使用する耐熱性型としては、本発明の目的を達し得るものであればその材質、形状等は特に限定されるものではない。例えば、材質としては、シリカと反応しにくい性質を有するカーボン、窒化ホウ素、炭化ケイ素等が好ましく用いられる。さらに耐熱性型の内面と混合粉末との滑りを良好にするためにカーボンフェルトまたはカーボンペーパー等を用いて、充填及び加熱を実施することが好ましい。混合粉末の充填密度としては、耐熱性型に均一に充填するために０．７〜１．８ｇ／ｃｍ3が好ましく、また、均一に発泡させるために充填密度が均一になるように充填することが好ましい。耐熱性型の形状は、ガラス化、気泡生成後のガラスの形状が耐熱性型の形状と実質的に同じとなるため、所望の形状の不透明石英ガラスを得るように任意に選ぶことができる。
【００１９】
［４］ガラス化及び気泡生成
窒化ケイ素粉末中の窒化ケイ素成分を十分に分解し、発泡による気泡生成後の石英ガラスをほぼ完全なガラス状態とするため、耐熱性型に充填した混合粉末を加熱する。この加熱処理において用いられる加熱装置としては、原料粉末をガラス状態とするに要する加熱能力を有するものであれば特に限定されるものではないが、電気炉等が例示できる。混合粉末は加熱装置内において原料が溶融しうる温度以上１９００℃以下の温度にて加熱される。原料が溶融しうる温度は、原料に非晶質シリカ粉末を使用する場合は、クリストバライトを経由し、常圧で１７１３℃となるが、原料に結晶質石英粉末を使用すると、クリストバライトを経由しにくく、溶融温度がこの温度より低くなります。
【００２０】
この原料が溶融しうる温度未満の温度で加熱した場合、原料が溶融せず、又、非晶質シリカ粉末を原料とした場合には、加熱中、原料の一部もくしは全部が非晶質シリカから結晶質であるクリストバライトに転移していると、クリストバライトが溶融しきれずに残り、ガラスが割れやすくなるため好ましくない。又、１９００℃を越える温度で加熱すると、気泡が粗大化するために得られるガラスの密度は低下し、所定の形状、寸法に機械加工を施すのに必要な機械的強度が得られないため好ましくない。また、加熱処理の時間としては原料が全量溶融しガラス化できる時間であれば特に制限はないが、加熱温度に左右され一定しないが、通常１時間で充分である。
【００２１】
加熱昇温過程においては、粉末充填体が開気孔状態から閉気孔状態に転じ、次いで、閉気孔状態の粉末充填体がガラスに変態するまで真空雰囲気とする。その真空度は絶対圧１０ｍｍＨｇ以下であることが好ましい。この理由としては、原料粉末中の窒化ケイ素成分とシリカ成分の反応により生成し、石英ガラス中に固溶する窒素元素の脱離ガス及び分解ガスのみを独立気泡中に存在させることによりガラス全体にわたって気泡の分布を均一にすることができるからである。
【００２２】
真空雰囲気は、開気孔状態であった粉末充填体が閉気孔状態に転じ、ガラスへ変態した時点で解除され、不活性ガスが導入される。不活性ガスとしては、本発明の方法において使用される耐熱性型、原料、生成物とは実質的に反応性を有しないものであれば特に制限なく用いることができ、例えば、窒素、アルゴン、ヘリウム等が使用できる。特に、経済性、気密性を考慮して窒素、アルゴンが好ましく用いられる。導入する不活性ガスの圧力としては、得られたガラスを火炎加工など再加熱するにあたり、ガラス中の気泡の膨脹、収縮など不安定な挙動を防ぐために通常常圧が用いられるが、やや加圧された状態でもさしつかえない。所望によりやや減圧された状態にすることもできる。
【００２３】
［５］不透明石英ガラス
上記工程で得られる不透明石英ガラスの特性としては、機械強度を高め加工性に優れるように又はガラス面の精度を良くするために、見掛密度１．７〜２．１ｇ／ｃｍ3、平均気泡径１０〜１００μｍであることが好ましい。
【００２４】
本発明の不透明石英ガラスの製造方法において、ガラス中に含まれる独立気泡の径及び量を制御する因子としては、窒化ケイ素粉末添加量、シリカ粉末の粒子径及びその分布、溶融温度、導入ガス圧力が挙げられる。例えば、見掛密度１．９５〜２．０５ｇ／ｃｍ3、平均気泡径５０〜７０μｍ、気泡量７×１０5〜８×１０5個／ｃｍ3を有する熱遮断性に優れた不透明石英ガラスを得るには、窒化ケイ素粉末添加量０．０１〜０．０２重量部（シリカ粉末１００重量部に対して）、シリカ粉末の平均粒子径１００〜２００μｍ（粒子径分布：１０〜６００μｍ）、溶融温度１８００〜１８５０℃、導入ガス圧力１．０〜２．０ｋｇｆ／ｃｍ2の範囲を選ぶとよい。さらに、高い熱遮断性と同時に、より平滑な表面が得られる見掛密度２．０５〜２．１２ｇ／ｃｍ3、平均気泡径３０〜５０μｍ、気泡量１〜２×１０6個／ｃｍ3を有する不透明石英ガラスを得るには、窒化ケイ素粉末添加量０．００５〜０．０２重量部（シリカ粉末１００重量部に対して）、シリカ粉末の平均粒子径５０〜１００μｍ（粒子径分布：１０〜２００μｍ）、溶融温度１７５０〜１８５０℃、導入ガス圧力１．０〜２．０ｋｇｆ／ｃｍ2の範囲を選ぶとよい。気泡を支配する最も大きい因子はシリカ粉末の粒度であり、より微細な粒度のシリカ粉末を用いることにより、気泡径が小さくかつ気泡量が多い熱遮断性に優れた不透明石英ガラスとすることができる。
【００２５】
このようにして得られた不透明石英ガラスは、外観が白色であれば特に限定されるものではないが、その特性として、気泡が均一に分散されており、例えば、波長３００〜９００ｎｍの光を照射した場合の直線透過率が低くなることで不透明となることが確認できる。この直線透過率としては、熱遮断性を確保するために、ガラスの厚みが１ｍｍ以上において、３００〜９００ｎｍの光を照射した場合の直線透過率が３％以下であることが好ましい。
【００２６】
このような直線透過率を有する不透明石英ガラスは、気泡を有することでガラスの熱伝導性が低くなると共に、熱線を散乱させることによりその効果が増幅される。従って、直線透過率を低くする、すなわち熱線を散乱させ易くすることで熱遮断性に優れた不透明石英ガラスとすることができる。
【００２７】
又、本発明の方法は、原料及び溶融工程においてガラスにＯＨ基を取り込むものではないため、高温における粘性が高い優れた不透明石英ガラスとすることができるものである。
【００２８】
【実施例】
本発明を以下の実施例により更に詳細に説明するが、本発明はこれに限定されるものではない。なお不純物の分析等は以下により行った。
【００２９】
〜不純物の分析〜
結晶質シリカ粉末をＩＣＰ法により分析した。
【００３０】
〜Ｘ線回折〜
不透明石英ガラスを切断機を用いて２０ｍｍ×１０ｍｍ×２ｍｍ（厚み）の大きさに切断し、測定用サンプルとした。これをＸ線回折装置（マックサイエンス社製、型式：ＭＸＰ３）を使用し、サンプルのガラス状態を観察した。得られた回折パターン中における石英、クリストバライト等の結晶に起因する回折ピークの有無によりガラス状態を確認した。
【００３１】
〜見掛密度〜
不透明石英ガラスを切断機を用いて３０ｍｍ×３０ｍｍ×１０ｍｍ（厚み）の大きさに切断し、測定用サンプルとした。これを電子天秤（メトラー社製、型式：ＡＴ２６１）を使用し、アルキメデス法により見掛密度を測定した。
【００３２】
〜平均気泡径及び気泡量〜
不透明石英ガラスを切断機を用いて３０ｍｍ×１０ｍｍ×０．３ｍｍ（厚み）の大きさの測定用サンプルとした。これを目盛り付レンズのある偏光顕微鏡（オリンパス社製、型式：ＢＨ−２）を使用し、サンプル中の気泡径及び気泡量を測定した。平均気泡径については、カウントした気泡を完全球形と見なしてその総体積を算出し、それを気泡数で除して得た平均体積からさらに平均直径を算出し、これを平均気泡径とした。
【００３３】
〜粒子径〜
粉末の粒子径分布及び平均粒子径は、レ−ザ−回折散乱法ＣＯＵＬＴＥＲ ＬＳ−１３０（ＣＯＵＬＴＥＲ ＥＬＥＣＴＲＯＮＩＣＳ社製）により測定した。〜充填密度〜
粉末の充填密度は、所定の重量の粉末を耐熱性型に充填し、粉末が占める体積を測定し、粉末重量をその体積で除して求めた。
【００３４】
〜空洞の確認〜
ガラスを切断機を用いて切断し、目視にて切断面を観察した。
【００３５】
〜光透過率〜
石英ガラスを切断機を用いて切断し、さらに厚み方向の両面を＃１２００のアルミナ砥粒で研磨して３０ｍｍ×１０ｍｍ×１ｍｍ（厚み）の大きさの測定用サンプルとした。これを分光光度計（日立製作所社製、型式：ダブルビーム分光光度計２２０型）を使用し、サンプルの厚み方向に３００，５００，７００，９００ｎｍの波長の光を照射したときの直線透過率を測定した。
【００３６】
〜ガラス基質中の窒素元素濃度〜
石英ガラスを乳鉢を用いて十分に粉砕して粉末状にした。これを硝酸−フッ酸、硫酸を用いて加圧分解し、蒸留分離後、イオンクロマトグラフ法により測定した。
【００３７】
〜気泡総断面積〜
気泡が完全球体であると仮定し、その直径を含む円の面積の総和で定義され、平均気泡径から平均気泡断面積を算出し、これに気泡量を乗じて算出した。
【００３８】
実施例１
平均粒子径３００μｍで３０〜５００μｍの範囲の粒子径分布を有する天然水晶粉末（ユミニン製、商品名：ＩＯＴＡ−５）を公知の方法であるフッ酸処理により高純度化したもの（以降、石英粉末という）を原料粉末として用いた。四塩化ケイ素から公知の方法であるアンモニア処理法により得られた窒化ケイ素粉末（宇部興産製、商品名：ＳＮ−Ｅ１０、平均粒子径０．５μｍ）を、石英粉末１００重量部に対して０．０１重量部となるように秤取し、石英粉末１００重量部に対して５０重量部のエタノールに投入した後、撹拌と同時に超音波振動を与えて十分に分散させた。得られた窒化ケイ素分散液に石英粉末を投入し、十分に撹拌し混合した。次に、真空エバポレータを用いてエタノールを除去、乾燥して石英粉末と窒化ケイ素粉末の混合粉末（以降、混合粉末という）を得た。混合粉末３００ｇを、内面に厚さ２ｍｍのカーボンフェルトを貼付けたカーボン製るつぼ（外径：１３０ｍｍ、内径：１００ｍｍ、深さ：５０ｍｍ）内に充填した。この時の充填密度は１．４ｇ／ｃｍ3であった。るつぼを電気炉内に入れ、１×１０-3ｍｍＨｇの真空雰囲気にした後、室温から１８００℃まで３００℃／時間の割合で昇温した。１８００℃に１０分間保持した後、電気炉内の圧力が常圧（１ｋｇｆ／ｃｍ2）に達するまで窒素ガスを導入し加熱を終了した。このようにして得られた不透明石英ガラスをＸ線回折によりガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００３９】
【表１】
【表２】
【表３】
実施例２
実施例１における石英粉末を乾式ボールミルを用いて粉砕し、さらにふるいによる粒度調整を行い、平均粒子径が５０μｍで１０〜２００μｍの範囲の粒子径分布を有するものを得た。この石英粉末を用い、窒化ケイ素粉末の混合量を、石英粉末１００重量部に対して０．０３重量部として混合粉末を得た。この混合粉末３００ｇを、実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は１．４ｇ／ｃｍ3であった。これを実施例１と同様の条件で加熱し、不透明石英ガラスを得た。この不透明石英ガラスをＸ線回折によりガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００４３】
実施例３
実施例１における石英粉末を乾式ボールミルを用いて粉砕し、さらにふるいによる粒度調整を行い、平均粒子径が５０μｍで１０〜２００μｍの範囲の粒子径分布を有するものとした。この石英粉末を用いて実施例１と同一の条件で混合粉末を作製した。
【００４４】
この混合粉末３００ｇを、実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は１．２ｇ／ｃｍ3であった。これを実施例１の条件で加熱し、不透明石英ガラスを得た。この不透明石英ガラスをＸ線回折によってガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００４５】
実施例４
実施例１の条件において加熱温度を１８５０℃とした以外は同様の条件にて実施した。得られた不透明石英ガラスをＸ線回折によってガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００４６】
実施例５
実施例１の加熱条件において、１８００℃に１０分間保持した後、電気炉内の圧力が２．０ｋｇｆ／ｃｍ2に達するまで窒素ガスを導入し加熱を終了した以外は同様の条件にて実施した。得られた不透明石英ガラスをＸ線回折によってガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００４７】
実施例６
ケイ酸ナトリウムと酸を反応させた後、加熱処理して得た平均粒子径３００μｍで５０〜１０００μｍの範囲の粒子径分布を有する非晶質シリカ粉末（日東化学工業製、商品名：シリカエースＡ）を乾式ボールミルを用いて粉砕し、ふるいによる分級を行い、平均粒子径が１８０μｍで１０〜６００μｍの範囲の粒子径分布を有するものを得、これを原料粉末として用いた。四塩化ケイ素から公知の方法であるアンモニア処理法により得られた窒化ケイ素粉末（宇部興産製、商品名：ＳＮ−Ｅ１０、平均粒子径０．５μｍ）を、非晶質シリカ粉末１００重量部に対して０．０１重量部となるように秤取し、非晶質シリカ粉末１００重量部に対して５０重量部のエタノールに投入した後、撹拌と同時に超音波振動を与えて十分に分散させた。得られた窒化ケイ素分散液に非晶質シリカ粉末を投入し、十分に撹拌し混合した。次に、真空エバポレータを用いてエタノールを除去、乾燥して非晶質シリカ粉末と窒化ケイ素粉末の混合粉末（以降、混合粉末という）を得た。混合粉末３００ｇを、内面に厚さ２ｍｍのカーボンフェルトを貼付けたカーボン製るつぼ（外径：１３０ｍｍ、内径：１００ｍｍ、深さ：５０ｍｍ）内に充填した。この時の充填密度は０．８１ｇ／ｃｍ3であった。るつぼを電気炉内に入れ、１×１０-3ｍｍＨｇの真空雰囲気にした後、室温から１８００℃まで３００℃／時間の割合で昇温した。１８００℃に１０分間保持した後、電気炉内の圧力が常圧（１ｋｇｆ／ｃｍ2）に達するまで窒素ガスを導入し加熱を終了した。このようにして得られた不透明石英ガラスをＸ線回折によりガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００４８】
実施例７
実施例６における非晶質シリカ原料粉末に対する窒化ケイ素粉末の混合量を、非晶質シリカ粉末１００重量部に対して０．０２重量部として混合粉末を得た。この混合粉末３００ｇを、実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は０．８１ｇ／ｃｍ3であった。これを実施例１と同様の条件で加熱し、不透明石英ガラスを得た。この不透明石英ガラスをＸ線回折によりガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００４９】
実施例８
実施例６における非晶質シリカ原料粉末を、平均粒子径が２５０μｍで１０〜８００μｍの範囲の粒子径分布を有するものとした。得られた混合粉末３００ｇを、実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は０．７９ｇ／ｃｍ3であった。これを実施例１の条件で加熱し、不透明石英ガラスを得た。この不透明石英ガラスをＸ線回折によってガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示した。
【００５０】
実施例９
シリコンアルコキシドと水とを反応させた後、加熱処理して得た平均粒子径１７０μｍで３０〜４００μｍの範囲の粒子径分布を有する非晶質シリカ粉末（三菱化学製、商品名：ＭＫＣシリカ ＰＳ３００Ｌ）を原料粉末として用いた。この非晶質シリカ粉末に対する窒化ケイ素粉末（宇部興産製、商品名：ＳＮ−Ｅ１０、平均粒子径０．５μｍ）の混合量を、シリカ粉末１００重量部に対して０．０１重量部となるように秤取し、実施例１と同じ方法で混合粉末を得た。この混合粉末３００ｇを実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は０．８１ｇ／ｃｍ3であった。これを実施例１と同様の条件で加熱し、不透明石英ガラスを得た。このようにして得られた不透明石英ガラスをＸ線回折によりガラス状態であることを確認した。このガラスを前記記載の方法により評価し、その結果として、見掛密度、平均気泡径、気泡量を表１に、気泡総断面積及び光透過率を表２に示した。また、ガラス基質中の窒素元素濃度を表３に示す。
【００５１】
このように実施例１〜９により得られた不透明石英ガラスをスライスして顕微鏡により観察すると、気泡が均一に分散していることが分かった。また、これらのガラスを電気炉に入れ、窒素ガスで常圧（１ｋｇｆ／ｃｍ2）に保ち、１８００℃に１０分間保持して加熱処理した。加熱処理後のガラスをスライスして顕微鏡観察したところ、気泡の状態は加熱処理前と変わらなかった。
【００５２】
比較例１
実施例１における石英粉末を、乾式ボールミルを用いて粉砕し、さらにこれをエタノール中に分散させて沈降速度の差異による粒度調整を行い、平均粒子径が５μｍで１〜１０μｍの範囲の粒子径分布を有するものを得た。この石英粉末を用いて実施例１と同一の条件で混合粉末を作製した。
【００５３】
得られた混合粉末３００ｇを、実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は０．９ｇ／ｃｍ3であった。これを実施例１と同様の条件で加熱し、石英ガラスを得た。この石英ガラスをＸ線回折によってガラス状態であることを確認した。しかしながら、このガラスの見掛密度は１．２ｇ／ｃｍ3と低く、ガラスを切断して内部を調べると直径２〜５ｍｍ程度の空洞が点在していた。
【００５４】
比較例２
実施例６における非晶質シリカ原料粉末を、平均粒子径が７００μｍで５００〜１０００μｍの範囲の粒子径分布を有するものにして実施した。得られた混合粉末３００ｇを、実施例１と同じカーボン製るつぼ内に充填した。この時の充填密度は０．７８ｇ／ｃｍ3であった。これを実施例１と同様の条件で加熱し、石英ガラスを得た。この石英ガラスをＸ線回折によってガラス状態であることを確認した。しかしながら、このガラスの見掛密度は１．４ｇ／ｃｍ3と低く、ガラス内部に直径０．５〜１ｍｍ程度の空洞が点在していた。
【００５５】
比較例３
実施例６において、加熱温度を１９５０℃とした以外は同様の条件にて実施した。得られた石英ガラスをＸ線回折によってガラス状態であることを確認した。しかしながら、このガラスの見掛密度は１．５ｇ／ｃｍ3と低く、平均気泡径は２００μｍに達しており、非常に脆いガラスであった。
【００５６】
比較例４
実施例１において、窒化ケイ素粉末の混合量を、石英粉末１００重量部に対して０．０６重量部とした以外は同様の条件にて実施した。得られた石英ガラスをＸ線回折によってガラス状態であることを確認した。このガラスの見掛密度は１．７ｇ／ｃｍ3であった。ガラス基質中の窒素元素濃度を表３に示した。
【００５７】
このガラスを電気炉に入れ、窒素ガスで常圧（１ｋｇｆ／ｃｍ2）に保ち、１８００℃に１０分間保持して加熱処理した。加熱処理後のガラスは加熱処理前に比べて白色度が増していた。これをスライスして顕微鏡観察したところ、気泡量、気泡径はともに加熱処理前のものに比べて増大していた。
【００５８】
【発明の効果】
本発明の不透明石英ガラスは、シリカ粉末に、窒化ケイ素粉末を添加し加熱することにより、シリカ粉末のガラス化及び窒化ケイ素粉末の分解による発泡によるものであるため、アルカリ金属等の不純物の混入を防止することができる。更に、シリカ粉末の粒子径、窒化ケイ素粉末の混合量を調節したり、加熱温度を調節することにより、得られる不透明石英ガラスの気泡径や見掛密度を制御することができる。また、耐熱性型の形状とほぼ同様の形状のガラスを得ることができるため、所望の形状に近似した耐熱性型に原料粉末を充填し、ガラス化することにより、最終製品形状を得るために行う研削等の機械加工工程を大幅に削減することが可能になる。また、ガラス基質中の窒素元素濃度が低いので、火炎加工などの再加熱処理を施しても、再発泡による不透明石英ガラスの白色度の変化を抑制できる。
【００５９】
また、透明石英ガラス部材と火炎加工で接合する場合、窒素元素濃度が近いので、接合部付近における双方のガラスに変質がなく、割れなどの恐れがなく良好な接合が可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an opaque quartz glass, and more particularly to an opaque quartz glass excellent in heat shielding properties and bondability with transparent quartz glass and a method for producing the same.
[0002]
[Prior art]
A conventional method for producing opaque quartz glass is a method in which siliceous raw material powder is heated and melted to vitrify, and as a method of heating and melting, Bernoulli method of melting in a flame such as argon-oxygen plasma flame or oxyhydrogen flame Alternatively, there is a vacuum melting method in which silica filled in a container is heated and melted under high vacuum. Conventionally, natural silica or low-quality quartz has been used as a raw material for opaque quartz glass. These raw materials contain many fine bubbles, and when the raw materials are melted, the bubbles remain as they are, and opaque quartz glass is obtained. However, in recent years, with the progress of high integration of LSI in the semiconductor field, the demand for high purity of raw materials to be used has become strict, and high purity products are required even in the field where low purity products have been used conventionally. I started. A typical field is flange material, and it is desired to supply opaque and high-purity quartz glass, that is, high-purity opaque quartz glass. However, conventionally used natural raw materials for producing opaque quartz glass contain a large amount of impurities together with fine bubbles. It is said that removal of these impurities is extremely difficult, and high purity by purification is impossible. On the other hand, relatively high-purity quartz crystal has a small amount of bubbles, especially fine bubbles, in the crystal, so that the opacity does not increase even when melted, and the resulting quartz glass becomes translucent. Not too much.
[0003]
As an improved method, the content of each element of alkali (earth) metal, Fe and Al is low, including a large number of fine bubbles, and containing a silanol group uniformly as a vaporizable component in a specific range of concentration. A method by flame-melting pure amorphous silica has been proposed (Japanese Patent Laid-Open No. 6-24771).
[0004]
However, according to this method, only a silica glass product having a simple shape such as a silica filler for IC encapsulant or a base material ingot for producing silica glass powder can be directly produced, and a flange shape, a cylindrical shape, and a hollow prism shape In order to produce quartz glass products with complicated shapes such as screw shape, turbocharger shape, square water tank or tub shape, post-processing such as a large amount of cutting is required, and the utilization rate of quartz glass is low As a result, the manufacturing cost increases.
[0005]
As another new opaque quartz glass, a crystalline quartz powder purified to a high purity is heated in an ammonia atmosphere to be ammoniated, and heated to melt in an inert gas atmosphere to reduce the bubble diameter. There has been proposed an opaque quartz glass having an improved heat resistance by increasing the number of bubbles and increasing the total bubble cross-sectional area per unit volume of the opaque quartz glass (JP-A-7-61827 and JP-A-7-300341). . However, in this method, the density, bubble size, and bubble volume of opaque quartz glass react very sensitively to the particle size, particle size distribution of the raw material powder, and the filling state when filled in the melting vessel, so that the bubbles are reproducible. It is not easy to control, and there are problems such as the bubble diameter and the amount of bubbles being greatly different between the surface and inside. In addition, when the nitrogen content in quartz glass is large and flame processing is performed by repairing the defect part of this quartz glass, nitrogen gas is liberated as bubbles from the glass substrate, and the repaired part becomes uneven or the repaired part An unfavorable situation occurs in terms of dimensional accuracy and appearance, such as the opacity being different from other parts. Furthermore, when flame bonding is performed with a transparent quartz glass member, the nitrogen element-containing concentrations of the two are greatly different, and bonding is not successful.
[0006]
As another opaque quartz glass manufacturing method, a method of heating and melting by adding fine powders such as carbon and silicon nitride as a foaming agent to siliceous raw material powders such as silica, silica sand, α-quartz and cristobalite has been proposed. (For example, JP-A-4-65328). However, in this method, problems such as those described above can be avoided, but OH groups are easily incorporated into the glass obtained by melting with an oxyhydrogen flame, and the viscosity at high temperature is lowered, and the glass is used for a long time at high temperature. This is disadvantageous for applications such as semiconductor manufacturing jigs. Moreover, mixing of solid particles, solid phase reaction / decomposition reaction, and the like are involved, and it is difficult to control the fine bubbles to be uniformly dispersed in the melt. Furthermore, in the flame melting method, since the residence time of the fine particles in the flame is extremely short, it is difficult to complete the reaction, and the added foaming agent may remain as a foreign substance in the melt. Further, there is a problem that a phenomenon occurs in which the melt is colored by the reaction between the siliceous raw material and the foaming agent.
[0007]
As described above, each of the prior patents has a problem that has not yet been solved.
[0008]
[Problems to be solved by the invention]
The present invention has been made for the purpose of solving these problems, and it is an object of the present invention to provide a method for easily producing an opaque quartz glass in which bubbles are uniformly dispersed and high-temperature viscosity and thermal barrier properties are excellent. . In addition, this opaque quartz glass can be directly manufactured in a complicated shape such as a flange shape, a cylindrical shape, a hollow prism shape, a screw shape, a turbocharger shape, a square water tank shape or a “tub shape”. Yes, when the nitrogen element content in the quartz glass is reduced and flame processing is performed by repairing the defective part of this quartz glass, nitrogen gas does not release as bubbles from the glass substrate, and the outer surface of the repaired part is smooth It is also an object of the present invention to provide a novel opaque quartz glass that can be joined well because the nitrogen element-containing concentrations of the transparent quartz glass member and the transparent quartz glass member are close.
[0009]
[Means for Solving the Problems]
As a production method, a fine powder such as carbon or silicon nitride is added as a foaming agent to the above siliceous raw material powder such as silica stone, silica sand, α-quartz, cristobalite and the like (Japanese Patent Laid-Open No. 4-65328). The silicon nitride powder is applied to a relatively inexpensive coarse silica powder having an average particle diameter of 10 to 500 μm, and 0.001 to 0.05 parts by weight of the silicon nitride powder with respect to 100 parts by weight of the silica powder. The starting material powder mixed and dispersed in a heat-resistant mold having a complicated shape, In a vacuum atmosphere, heat the starting material to a temperature not lower than 1900 ° C. and higher than the melting temperature. By adopting a manufacturing method that generates bubbles by vitrification and foaming, the bubbles are evenly dispersed and not only have excellent high-temperature viscosity and thermal barrier properties, but also do not perform complicated powder molding such as casting. The end product can be selected by appropriately selecting a complicated shape such as a flange shape, cylindrical shape, hollow prism shape, screw shape, turbocharger shape, square water tank shape or “tub shape” as the shape of the heat resistant mold. A near glass body can be manufactured directly, and even if post-processing is required, it is easy.
[0010]
Hereinafter, the present invention will be described in more detail.
[0011]
[1] Starting material
The starting material is a mixed powder obtained from silica powder and silicon nitride powder.
[0012]
(A) Silica powder
As the silica powder used in the present invention, it is preferable to use high-purity crystalline or amorphous silica powder in which Na, K, Mg, Ca, and Fe are each independently contained at 1 ppm or less as the contained metal impurities. This is because when the opaque quartz glass obtained by the method of the present invention is heated, impurities with low vapor pressure tend to scatter, and the opaque quartz glass itself is partly crystallized and easily broken or colored. This is to avoid being cheated. Such high-purity silica powder can be obtained by a synthesis method or by refining natural raw materials. For example, in order to obtain amorphous silica powder by a synthesis method, a method of obtaining silica by removing an alkali metal by reacting an alkali metal silicate aqueous solution (water glass) with an acid, SiCl Four There are a method of hydrolyzing the alkoxide to silica and a method of hydrolyzing the silicon alkoxide to the silica, but for industrial scale production, an alkali metal composed of alkali metal such as Na, K, Li and silicon dioxide. What is obtained by the method of making silicate aqueous solution (water glass) react with inorganic acids, such as a sulfuric acid, nitric acid, and hydrochloric acid, is suitable. Moreover, in order to obtain crystalline silica powder from a natural raw material, it can be obtained by a method of treating natural quartz with hydrofluoric acid.
[0013]
The average particle diameter of the silica powder is in the range of 10 to 500 μm in order to impart fluidity so that the heat resistant mold can be easily filled. When the average particle diameter is less than 10 μm, the fluidity of the powder is lowered and it is difficult to uniformly fill the powder, and when it exceeds 500 μm, the voids between the particles become large and the opaque quartz glass has a huge size of 300 μm or more. This is not preferable because it causes bubbles.
[0014]
Since the bubble diameter in the opaque quartz glass obtained by the method of the present invention depends on the average particle diameter of the silica powder, the bubble diameter can be controlled by adjusting the average particle diameter. That is, it is preferable to use a powder composed of fine particles when trying to obtain finer bubbles, and a powder composed of coarse particles when obtaining coarse bubbles.
[0015]
(B) Silicon nitride powder
As the silicon nitride powder, it is preferable to use a high purity powder obtained by nitriding silicon tetrachloride, silicon, silica or the like as a raw material. The reason for this is to prevent impurities from being scattered from the opaque quartz glass obtained by the method of the present invention, or the opaque quartz glass itself is partially crystallized and easily damaged or colored. It is.
[0016]
The amount of silicon nitride powder is 0.001 to 0.05 parts by weight of silicon nitride powder with respect to 100 parts by weight of silica powder. When the amount is less than 0.001 part by weight, the amount of bubbles generated due to foaming is reduced, and a sufficient thermal barrier property cannot be obtained. When the amount exceeds 0.05 parts by weight, the amount of bubbles generated by foaming increases, and the resulting opaque quartz glass has a poor mechanical strength. Another reason is that when it exceeds 0.05 parts by weight, the concentration of nitrogen element contained in the quartz glass substrate becomes 50 ppm or more, and when the obtained glass is reheated such as flame processing, nitrogen gas is liberated from the quartz glass substrate. However, since the amount of bubbles and the bubble diameter increase, the whiteness of the opaque quartz glass changes. The average particle size of the silicon nitride powder is preferably 0.1 to 1 μm, and more preferably 0.1 to 0.5 μm. The reason for this is that if the average particle diameter is in this range, bubbles will not become coarse or the amount of bubbles will not be drastically reduced, and furthermore, the powder will aggregate and be unable to be mixed uniformly with the silica powder. Is to avoid.
[0017]
[2] Mixed dispersion
Since the degree of dispersion of the silicon nitride powder in the raw material powder composed of silica powder and silicon nitride powder affects the bubble diameter and its distribution during foaming, it is necessary to mix so that the silicon nitride powder does not aggregate. The instrument used for mixing is not particularly limited as long as the silicon nitride powder can be dispersed, and examples thereof include a mortar and a ball mill. Furthermore, in order to improve the dispersion of the silicon nitride powder, a wet method using a dispersion medium is preferably used. Examples of the dispersion medium include water and alcohol.
[0018]
[3] Filling the container
Next, the obtained mixed powder is filled into a heat resistant mold. The material, shape, etc. of the heat-resistant mold used here are not particularly limited as long as the object of the present invention can be achieved. For example, as a material, carbon, boron nitride, silicon carbide or the like having a property that hardly reacts with silica is preferably used. Furthermore, in order to improve the sliding between the inner surface of the heat resistant mold and the mixed powder, it is preferable to perform filling and heating using carbon felt or carbon paper. The packing density of the mixed powder is 0.7 to 1.8 g / cm in order to uniformly fill the heat-resistant mold. Three It is also preferable to perform filling so that the packing density is uniform in order to foam uniformly. The shape of the heat-resistant mold can be arbitrarily selected so as to obtain an opaque quartz glass having a desired shape because the glass shape after vitrification and bubble generation is substantially the same as the shape of the heat-resistant mold.
[0019]
[4] Vitrification and bubble generation
In order to sufficiently decompose the silicon nitride component in the silicon nitride powder and bring the quartz glass after the generation of bubbles by foaming into an almost complete glass state, the mixed powder filled in the heat resistant mold is heated. The heating device used in this heat treatment is not particularly limited as long as it has the heating ability required to bring the raw material powder into a glass state, and an electric furnace or the like can be exemplified. The mixed powder is heated in the heating device at a temperature not lower than the temperature at which the raw material can be melted and not higher than 1900 ° C. When amorphous silica powder is used as a raw material, the temperature at which the raw material can be melted is 1713 ° C. at normal pressure via cristobalite. However, when crystalline quartz powder is used as a raw material, it is difficult to pass through cristobalite. The melting temperature will be lower than this temperature.
[0020]
When heated at a temperature lower than the temperature at which this raw material can be melted, the raw material does not melt, and when amorphous silica powder is used as the raw material, some or all of the raw material is amorphous during heating. When the crystalline silica is transferred to crystalline cristobalite, the cristobalite cannot be melted and remains, and the glass is liable to break. Further, heating at a temperature exceeding 1900 ° C. is preferable because the density of the glass obtained is reduced because the bubbles are coarsened, and the mechanical strength necessary for machining into a predetermined shape and size cannot be obtained. Absent. The time for the heat treatment is not particularly limited as long as the entire raw material can be melted and vitrified. However, although it depends on the heating temperature and is not constant, one hour is usually sufficient.
[0021]
During the heating and heating process, the powder filler changes from an open pore state to a closed pore state. , Next, a vacuum atmosphere is maintained until the powder filling in a closed pore state is transformed into glass. To do. The degree of vacuum is preferably 10 mmHg or less. The reason for this is that only the desorption gas and decomposition gas of nitrogen element produced by the reaction between the silicon nitride component and the silica component in the raw material powder and dissolved in the quartz glass are present in the closed cells, so that the entire glass is covered. This is because the distribution of bubbles can be made uniform.
[0022]
In the vacuum atmosphere, the powder packing that was in the open pore state changed to the closed pore state. , When it is transformed into glass, it is released and an inert gas is introduced. As the inert gas, any heat-resistant type, raw material, and product used in the method of the present invention can be used without particular limitation as long as they are not substantially reactive. For example, nitrogen, argon, Helium or the like can be used. In particular, nitrogen and argon are preferably used in consideration of economy and airtightness. As the pressure of the inert gas to be introduced, normal pressure is usually used to prevent unstable behavior such as expansion and contraction of bubbles in the glass when the obtained glass is reheated such as flame processing. Even if it is done, it doesn't matter. If desired, the pressure can be reduced slightly.
[0023]
[5] Opaque quartz glass
The characteristics of the opaque quartz glass obtained in the above process include an apparent density of 1.7 to 2.1 g / cm in order to increase mechanical strength and excel in workability or to improve the accuracy of the glass surface. Three The average cell diameter is preferably 10 to 100 μm.
[0024]
In the method for producing an opaque quartz glass of the present invention, the factors controlling the diameter and amount of closed cells contained in the glass include silicon nitride powder addition amount, silica powder particle size and distribution, melting temperature, and introduced gas pressure. Is mentioned. For example, the apparent density is 1.95 to 2.05 g / cm Three , Average bubble diameter 50-70 μm, bubble volume 7 × 10 Five ~ 8x10 Five Piece / cm Three In order to obtain an opaque quartz glass having an excellent thermal barrier property, the amount of silicon nitride powder added is 0.01 to 0.02 parts by weight (based on 100 parts by weight of silica powder), and the average particle diameter of silica powder is 100 to 200 μm. (Particle size distribution: 10 to 600 μm), melting temperature 1800 to 1850 ° C., introduction gas pressure 1.0 to 2.0 kgf / cm 2 Choose a range. Furthermore, an apparent density of 2.05 to 2.12 g / cm at which a smoother surface can be obtained simultaneously with a high thermal barrier property. Three , Average bubble diameter 30-50 μm, bubble volume 1-2 × 10 6 Piece / cm Three In order to obtain an opaque quartz glass having a particle size of 0.005 to 0.02 parts by weight of silicon nitride powder (relative to 100 parts by weight of silica powder), an average particle size of silica powder of 50 to 100 μm (particle size distribution: 10). -200 μm), melting temperature 1750-1850 ° C., introduction gas pressure 1.0-2.0 kgf / cm 2 Choose a range. The largest factor governing the bubbles is the particle size of the silica powder, and by using a finer particle size silica powder, it is possible to obtain an opaque quartz glass with a small bubble diameter and a large amount of bubbles and excellent heat blocking properties. .
[0025]
The opaque quartz glass thus obtained is not particularly limited as long as the appearance is white, but as a characteristic, bubbles are uniformly dispersed, for example, irradiation with light having a wavelength of 300 to 900 nm. It can be confirmed that it becomes opaque when the linear transmittance is reduced. As the linear transmittance, in order to ensure heat-shielding properties, it is preferable that the linear transmittance is 3% or less when the glass is irradiated with light of 300 to 900 nm in a thickness of 1 mm or more.
[0026]
The opaque quartz glass having such a linear transmittance has bubbles, thereby lowering the thermal conductivity of the glass and amplifying the effect by scattering the heat rays. Therefore, it is possible to obtain an opaque quartz glass having excellent heat blocking properties by reducing the linear transmittance, that is, making it easy to scatter heat rays.
[0027]
Moreover, since the method of the present invention does not incorporate OH groups into the glass in the raw materials and the melting step, it can be an excellent opaque quartz glass having high viscosity at high temperature.
[0028]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Impurity analysis and the like were performed as follows.
[0029]
~ Analysis of impurities ~
Crystalline silica powder was analyzed by ICP method.
[0030]
~ X-ray diffraction ~
The opaque quartz glass was cut into a size of 20 mm × 10 mm × 2 mm (thickness) using a cutting machine to obtain a measurement sample. An X-ray diffractometer (manufactured by Mac Science, model: MXP3) was used to observe the glass state of the sample. The glass state was confirmed by the presence or absence of diffraction peaks due to crystals such as quartz and cristobalite in the obtained diffraction pattern.
[0031]
~ Apparent density ~
The opaque quartz glass was cut into a size of 30 mm × 30 mm × 10 mm (thickness) using a cutting machine to obtain a measurement sample. An apparent density was measured by an Archimedes method using an electronic balance (Model: AT261 manufactured by Mettler).
[0032]
~ Average bubble diameter and bubble volume ~
An opaque quartz glass was used as a measurement sample having a size of 30 mm × 10 mm × 0.3 mm (thickness) using a cutting machine. Using a polarizing microscope with a calibrated lens (Olympus, model: BH-2), the bubble diameter and bubble amount in the sample were measured. Regarding the average bubble diameter, the total volume was calculated by regarding the counted bubbles as a perfect sphere, and the average diameter was further calculated from the average volume obtained by dividing it by the number of bubbles, and this was taken as the average bubble diameter.
[0033]
~Particle size~
The particle size distribution and average particle size of the powder were measured by a laser diffraction scattering method COULTER LS-130 (manufactured by COULTER ELECTRONICS). ~ Packing density ~
The packing density of the powder was obtained by filling a heat-resistant mold with a predetermined weight of powder, measuring the volume occupied by the powder, and dividing the powder weight by the volume.
[0034]
~ Confirmation of cavity ~
The glass was cut using a cutting machine, and the cut surface was observed visually.
[0035]
~ Light transmittance ~
Quartz glass was cut using a cutting machine, and both surfaces in the thickness direction were polished with # 1200 alumina abrasive grains to obtain a measurement sample having a size of 30 mm × 10 mm × 1 mm (thickness). Using a spectrophotometer (Hitachi, Ltd., model: double beam spectrophotometer type 220), the linear transmittance when irradiating light with a wavelength of 300, 500, 700, 900 nm in the thickness direction of the sample is obtained. It was measured.
[0036]
~ Nitrogen element concentration in glass substrate ~
Quartz glass was sufficiently pulverized using a mortar to form a powder. This was subjected to pressure decomposition using nitric acid-hydrofluoric acid and sulfuric acid, and after distillation separation, it was measured by an ion chromatography method.
[0037]
-Total cross-sectional area of bubbles-
Assuming that the bubble is a perfect sphere, it was defined as the sum of the areas of the circle including its diameter, and the average bubble cross-sectional area was calculated from the average bubble diameter, and this was multiplied by the bubble amount.
[0038]
Example 1
A natural crystal powder (product name: IOTA-5, manufactured by Yuminin) having an average particle size of 300 μm and a particle size distribution in the range of 30 to 500 μm, which has been purified by hydrofluoric acid treatment, which is a known method (hereinafter, quartz powder) Was used as a raw material powder. Silicon nitride powder (trade name: SN-E10, product name: SN-E10, manufactured by Ube Industries, Ltd.) obtained from silicon tetrachloride by an ammonia treatment method, which is a publicly known method, is added to 0.1 parts by weight of quartz powder. It weighed so that it might become 01 weight part, and after putting into 50 weight part ethanol with respect to 100 weight part of quartz powder, ultrasonic vibration was given simultaneously with stirring and it fully disperse | distributed. Quartz powder was put into the obtained silicon nitride dispersion and sufficiently stirred and mixed. Next, ethanol was removed using a vacuum evaporator and dried to obtain a mixed powder of quartz powder and silicon nitride powder (hereinafter referred to as mixed powder). 300 g of the mixed powder was filled into a carbon crucible (outer diameter: 130 mm, inner diameter: 100 mm, depth: 50 mm) with a carbon felt having a thickness of 2 mm attached to the inner surface. The packing density at this time is 1.4 g / cm. Three Met. Put the crucible in the electric furnace, 1 × 10 -3 After the vacuum atmosphere of mmHg, the temperature was raised from room temperature to 1800 ° C. at a rate of 300 ° C./hour. After holding at 1800 ° C. for 10 minutes, the pressure in the electric furnace is normal pressure (1 kgf / cm 2 Nitrogen gas was introduced until heating was completed. The opaque quartz glass thus obtained was confirmed to be in the glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0039]
[Table 1]
[Table 2]
[Table 3]
Example 2
The quartz powder in Example 1 was pulverized using a dry ball mill, and the particle size was adjusted by sieving to obtain an average particle size of 50 μm and a particle size distribution in the range of 10 to 200 μm. Using this quartz powder, the amount of silicon nitride powder mixed was 0.03 part by weight with respect to 100 parts by weight of quartz powder to obtain a mixed powder. 300 g of this mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 1.4 g / cm. Three Met. This was heated under the same conditions as in Example 1 to obtain an opaque quartz glass. This opaque quartz glass was confirmed to be in a glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0043]
Example 3
The quartz powder in Example 1 was pulverized using a dry ball mill, and the particle size was adjusted by sieving, so that the average particle size was 50 μm and had a particle size distribution in the range of 10 to 200 μm. Using this quartz powder, a mixed powder was produced under the same conditions as in Example 1.
[0044]
300 g of this mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 1.2 g / cm Three Met. This was heated under the conditions of Example 1 to obtain an opaque quartz glass. This opaque quartz glass was confirmed to be in a glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0045]
Example 4
It implemented on the conditions similar to the conditions of Example 1 except having made heating temperature 1850 degreeC. The obtained opaque quartz glass was confirmed to be in a glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0046]
Example 5
In the heating condition of Example 1, after holding at 1800 ° C. for 10 minutes, the pressure in the electric furnace was 2.0 kgf / cm. 2 Was carried out under the same conditions except that nitrogen gas was introduced and heating was terminated. The obtained opaque quartz glass was confirmed to be in a glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0047]
Example 6
Amorphous silica powder having an average particle size of 300 μm and a particle size distribution in the range of 50 to 1000 μm obtained by reacting sodium silicate and acid (Nitto Chemical Industries, trade name: Silica Ace A) ) Was pulverized using a dry ball mill and classified by sieving to obtain a powder having an average particle size of 180 μm and a particle size distribution in the range of 10 to 600 μm, which was used as a raw material powder. Silicon nitride powder (trade name: SN-E10, manufactured by Ube Industries, average particle size 0.5 μm) obtained from silicon tetrachloride by an ammonia treatment method, which is a known method, is added to 100 parts by weight of amorphous silica powder. Then, it was weighed to 0.01 parts by weight, put into 50 parts by weight of ethanol with respect to 100 parts by weight of the amorphous silica powder, and then sufficiently dispersed by applying ultrasonic vibration simultaneously with stirring. Amorphous silica powder was added to the obtained silicon nitride dispersion, and the mixture was sufficiently stirred and mixed. Next, ethanol was removed using a vacuum evaporator and dried to obtain a mixed powder of amorphous silica powder and silicon nitride powder (hereinafter referred to as mixed powder). 300 g of the mixed powder was filled into a carbon crucible (outer diameter: 130 mm, inner diameter: 100 mm, depth: 50 mm) with a carbon felt having a thickness of 2 mm attached to the inner surface. The packing density at this time is 0.81 g / cm. Three Met. Put the crucible in the electric furnace, 1 × 10 -3 After the vacuum atmosphere of mmHg, the temperature was raised from room temperature to 1800 ° C. at a rate of 300 ° C./hour. After holding at 1800 ° C. for 10 minutes, the pressure in the electric furnace is normal pressure (1 kgf / cm 2 Nitrogen gas was introduced until heating was completed. The opaque quartz glass thus obtained was confirmed to be in the glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0048]
Example 7
A mixed powder was obtained by setting the mixing amount of the silicon nitride powder to the amorphous silica raw material powder in Example 6 to 0.02 parts by weight with respect to 100 parts by weight of the amorphous silica powder. 300 g of this mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 0.81 g / cm. Three Met. This was heated under the same conditions as in Example 1 to obtain an opaque quartz glass. This opaque quartz glass was confirmed to be in a glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0049]
Example 8
The amorphous silica raw material powder in Example 6 had a particle size distribution in the range of 10 to 800 μm with an average particle size of 250 μm. 300 g of the obtained mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 0.79 g / cm. Three Met. This was heated under the conditions of Example 1 to obtain an opaque quartz glass. This opaque quartz glass was confirmed to be in a glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. In addition, Table 3 shows the nitrogen element concentration in the glass substrate.
[0050]
Example 9
Amorphous silica powder having an average particle size of 170 μm and a particle size distribution in the range of 30 to 400 μm obtained by reacting silicon alkoxide and water (Mitsubishi Chemical, trade name: MKC silica PS300L) Was used as a raw material powder. The mixing amount of silicon nitride powder (trade name: SN-E10, average particle size 0.5 μm, manufactured by Ube Industries) with respect to this amorphous silica powder is 0.01 parts by weight with respect to 100 parts by weight of silica powder. The mixed powder was obtained in the same manner as in Example 1. 300 g of this mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 0.81 g / cm. Three Met. This was heated under the same conditions as in Example 1 to obtain an opaque quartz glass. The opaque quartz glass thus obtained was confirmed to be in the glass state by X-ray diffraction. This glass was evaluated by the method described above. As a result, the apparent density, average bubble diameter, and bubble volume are shown in Table 1, and the total cross-sectional area and light transmittance are shown in Table 2. Table 3 shows the nitrogen element concentration in the glass substrate.
[0051]
Thus, when the opaque quartz glass obtained by Examples 1-9 was sliced and observed with the microscope, it turned out that the bubble is disperse | distributing uniformly. In addition, these glasses are put into an electric furnace, and normal pressure (1 kgf / cm 2) with nitrogen gas. 2 And kept at 1800 ° C. for 10 minutes for heat treatment. When the glass after the heat treatment was sliced and observed with a microscope, the state of bubbles was not different from that before the heat treatment.
[0052]
Comparative Example 1
The quartz powder in Example 1 is pulverized using a dry ball mill, and further dispersed in ethanol to adjust the particle size according to the difference in sedimentation speed, and the average particle size is 5 μm and the particle size distribution is in the range of 1 to 10 μm. Obtained. Using this quartz powder, a mixed powder was produced under the same conditions as in Example 1.
[0053]
300 g of the obtained mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 0.9 g / cm. Three Met. This was heated under the same conditions as in Example 1 to obtain quartz glass. This quartz glass was confirmed to be in a glass state by X-ray diffraction. However, the apparent density of this glass is 1.2 g / cm. Three When the glass was cut and the inside was examined, cavities having a diameter of about 2 to 5 mm were scattered.
[0054]
Comparative Example 2
The amorphous silica raw material powder in Example 6 was carried out with an average particle size of 700 μm and a particle size distribution in the range of 500 to 1000 μm. 300 g of the obtained mixed powder was filled in the same carbon crucible as in Example 1. The packing density at this time is 0.78 g / cm. Three Met. This was heated under the same conditions as in Example 1 to obtain quartz glass. This quartz glass was confirmed to be in a glass state by X-ray diffraction. However, the apparent density of this glass is 1.4 g / cm. Three However, cavities having a diameter of about 0.5 to 1 mm were scattered inside the glass.
[0055]
Comparative Example 3
In Example 6, it implemented on the same conditions except the heating temperature having been 1950 degreeC. The obtained quartz glass was confirmed to be in the glass state by X-ray diffraction. However, the apparent density of this glass is 1.5 g / cm. Three The average bubble diameter reached 200 μm, which was very brittle glass.
[0056]
Comparative Example 4
In Example 1, it implemented on the same conditions except having made the mixing amount of the silicon nitride powder 0.06 weight part with respect to 100 weight part of quartz powder. The obtained quartz glass was confirmed to be in the glass state by X-ray diffraction. The apparent density of this glass is 1.7 g / cm. Three Met. The nitrogen element concentration in the glass substrate is shown in Table 3.
[0057]
This glass is put into an electric furnace and nitrogen gas is used for normal pressure (1 kgf / cm 2 And kept at 1800 ° C. for 10 minutes for heat treatment. The whiteness of the glass after the heat treatment was higher than that before the heat treatment. When this was sliced and observed with a microscope, both the amount of bubbles and the bubble diameter were increased compared to those before the heat treatment.
[0058]
【The invention's effect】
The opaque quartz glass of the present invention is produced by adding silicon nitride powder to silica powder and heating to vitrify the silica powder and foaming due to decomposition of the silicon nitride powder. Can be prevented. Furthermore, the bubble diameter and apparent density of the obtained opaque quartz glass can be controlled by adjusting the particle diameter of the silica powder, the mixing amount of the silicon nitride powder, and adjusting the heating temperature. In addition, since a glass having a shape substantially similar to the shape of the heat-resistant mold can be obtained, the final product shape can be obtained by filling the heat-resistant mold that approximates the desired shape with raw material powder and vitrifying it. It is possible to greatly reduce machining processes such as grinding. In addition, since the nitrogen element concentration in the glass substrate is low, the change in whiteness of the opaque quartz glass due to re-foaming can be suppressed even if reheating treatment such as flame processing is performed.
[0059]
Moreover, when joining with a transparent quartz glass member by flame processing, since nitrogen element density | concentration is near, both glass near a junction part does not change in quality, There is no fear of a crack, and favorable joining is attained.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17194897A JP3966943B2 (en) | 1996-07-04 | 1997-06-27 | Opaque quartz glass and manufacturing method thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17459696 | 1996-07-04 | ||
| JP8-254351 | 1996-09-26 | ||
| JP25435196 | 1996-09-26 | ||
| JP8-174596 | 1996-09-26 | ||
| JP17194897A JP3966943B2 (en) | 1996-07-04 | 1997-06-27 | Opaque quartz glass and manufacturing method thereof |
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| Publication Number | Publication Date |
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| JPH10152332A JPH10152332A (en) | 1998-06-09 |
| JP3966943B2 true JP3966943B2 (en) | 2007-08-29 |
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| JP3693772B2 (en) * | 1996-12-17 | 2005-09-07 | 東ソー株式会社 | Method for producing opaque quartz glass cylinder |
| JP3839537B2 (en) * | 1997-01-21 | 2006-11-01 | 東ソー株式会社 | Production method of opaque quartz glass containing fine bubbles |
| DE19962452B4 (en) * | 1999-12-22 | 2004-03-18 | Heraeus Quarzglas Gmbh & Co. Kg | Process for the production of opaque quartz glass |
| JP6379508B2 (en) * | 2014-02-17 | 2018-08-29 | 東ソー株式会社 | Opaque quartz glass and method for producing the same |
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