JP3829338B2 - Surface crystallized high-strength glass, its production method and its use - Google Patents
Surface crystallized high-strength glass, its production method and its use Download PDFInfo
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- JP3829338B2 JP3829338B2 JP29168794A JP29168794A JP3829338B2 JP 3829338 B2 JP3829338 B2 JP 3829338B2 JP 29168794 A JP29168794 A JP 29168794A JP 29168794 A JP29168794 A JP 29168794A JP 3829338 B2 JP3829338 B2 JP 3829338B2
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
- C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
- C03C10/0036—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents
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Description
【０００１】
【産業上の利用分野】
本発明は、表面結晶化高強度ガラス、その製法及びその用途に関する。
【０００２】
【従来の技術】
従来、ガラスの表面を結晶化させて、その結晶の熱膨張率が母ガラスよりも小さいことを利用すると、表面に圧縮応力が発生し、ガラスの強度が向上することが知られている。オルコットら（米国特許Ｎｏ．２９９８６７５）は、はじめてガラスを熱処理することで表面に結晶化した薄い圧縮層を発生させて高い強度のガラスを製造した。オルコットらのガラス組成は６５〜７２重量％のＳｉＯ２、４重量％以上のＬｉ２Ｏ、２２．５〜３０重量％のＡｌ２Ｏ３でＬｉ２Ｏ／Ａｌ２Ｏ３比が０．３以下であり、結晶核として０．１〜３．５重量％のＴｉＯ２、０．１〜５重量％のＢ２Ｏ３、０．４〜２重量％のＮａ２Ｏと、０．５〜１０重量％のＰｂＯのなかの最低１種類を含むことを特徴としている。同ガラスは８００℃前後で数時間熱処理され、熱処理の間に表面にベータユークリプタイトの結晶層が析出する。ベータユークリプタイトの熱膨張係数は母ガラスよりも小さいため、冷却時に表面に均一な圧縮応力が発生し、ガラスの強度が上昇する。オルコットら（米国特許Ｎｏ．３２５３９７５）はその後組成を以下の通り修正している。即ち、５２〜６５重量％のＳｉＯ２、４重量％以上のＬｉ２Ｏ、４０重量％以下のＡｌ２Ｏ３でＬｉ２Ｏ／Ａｌ２Ｏ３比が０．３以下である。しかし、強度上昇に寄与する表面結晶層は前と同様のベータユークリプタイトであり、充分に高い透明性を有するとはいえない。
【０００３】
ウィルマイト（ｗｉｌｌｅｍｉｔｅ）層の結晶化による表面結晶化ガラスは英国特許Ｎｏ．１１０８４７３と同１１０８４７６に見られる。これらのガラス組成は３２〜５４重量％のＳｉＯ２、２４〜５６重量％のＡｌ２Ｏ３であり、結晶核として０．５〜６重量％のＰ２Ｏ５、０．５〜４重量％のＭｏＯ３、１．５〜７．５重量％のＺｒＯ２のなかの最低１種類を含むことを特徴としている。しかし、結晶化後の同ガラスは不透明である。
【０００４】
ベアルら（米国特許Ｎｏ．４８１４２９７）は上記とは異なった組成の、微細なベータユークリプタイトまたはベータクォーツが固溶した結晶層を有する表面結晶化ガラスを発明している。その組成は５５〜６７重量％のＳｉＯ２、２２〜２８重量％のＡｌ２Ｏ３、５〜７重量％のＬｉ２Ｏ、０〜２重量％のＮａ２Ｏ、０〜１０重量％のＺｎＯであり、加えてアルカリ金属酸化物がＡｌ２Ｏ３に対してモル比で１以上であり、ＳｉＯ２とＡｌ２Ｏ３のモル比が４である。
【０００５】
さらに、表面結晶化ガラスに関する最も新しい特許である米国特許Ｎｏ．５０８４３２８（ファインら、１９９２年）にはマグネシウム・アルミノシリケート系ガラスにおいて、ベータクォーツの表面結晶圧縮応力層を持つガラスが示されており、その組成は、５０〜７０重量％のＳｉＯ２、１６〜２８重量％のＡｌ２Ｏ３、５〜１０重量％のＭｇＯ、２．５〜５重量％のＬｉ２Ｏ、３．５〜１２重量％のＺｎＯである。このガラスの強度向上は急冷による物理強化とベータクォーツ表面層による圧縮応力との複合によっている。
【０００６】
以上、ガラスの表面に結晶層を析出させ、その熱膨張係数を母ガラスよりも小さくすることにより表面に圧縮応力を発生させてガラスの強度を向上させようとする試みは多くなされてきているが、その結晶層はベータユークリプタイト、ベータクォーツ、ウィルマイトに限定されている。また、結晶層と母ガラスの屈折率が異なるために、充分な可視光線透過率が得られず、得られたガラスは不透明であるという欠点があった。どの特許においても具体的な可視光線透過率については言及しておらず、透明と記述されたファインらによる組成（米国特許Ｎｏ．５０８４３２８）について、追試を行ったところ、同ガラスは研磨後でも７５％以下の低い可視光線透過率しか得られていない。さらに結晶層の母ガラスへの固溶性に関する検討がなされておらず、その結果結晶層と母ガラスの熱膨張係数の差が小さくなって充分な強度上昇が得られず、急冷による物理強化と組み合わせることにより高強度化を達成しているものが多い。
【０００７】
以上のように、表面結晶化による高強度ガラスを提供する手法はいくつかあるが、物理強化を用いずに高い強度を与え、かつ高い可視光線透過率を満足するガラス組成及び製造方法は見出されていない。
【０００８】
【発明が解決しようとする課題】
本発明の目的は、従来技術が有する前述の問題点をすなわち、物理強化なしでも充分に大きい強度を有するとともに可視光線透過率の高い、すなわち透明な表面結晶化ガラスを提供しようとするものである。
【０００９】
【課題を解決するための手段】
本発明は、組成が６２〜７５重量％のＳｉＯ２、４〜８重量％のＬｉ２Ｏ、１５〜２２重量％のＡｌ２Ｏ３、４．４〜８重量％のＺｎＯ、２〜７重量％のＺｒＯ２、０〜１．５重量％のＭｇＯ、０〜２重量％のＣａＯ、０〜１０重量％のＮａ２Ｏ＋Ｋ２Ｏからなり、Ｌｉ ２ ＯとＡｌ ２ Ｏ ３ のモル比が０．９〜１．１の範囲であるガラスであって、前記ガラス表面にベータスポジュメンを含む薄い結晶層を有する表面結晶化高強度ガラス、その製法及びその用途を提供する。
【００１０】
本発明における表面結晶化高強度ガラスは、ガラス表面に熱膨張係数の小さい薄い結晶層を有し、中央部がガラス層である。この結晶層としては、ガラスの透明性を特に高くできる点でベータスポジュメンが用いられる。この表面の結晶層の厚さは数μｍ〜６０μｍである。
【００１１】
次に本発明のガラスの組成の限定理由を説明する。
【００１２】
ＳｉＯ２、Ｌｉ２Ｏ及びＡｌ２Ｏ３は表面結晶を構成する基本部分であり、ＳｉＯ２はガラス相において網目構造を形成する主成分でもある。ＳｉＯ２の含有量が６０重量％未満では結晶化時に変形が起こり形状を保持できない。７５重量％を超えると結晶化が遅くなり、また、ガラスの溶融性が悪くなるため、均質なガラスを得ることが困難となる。ＳｉＯ２は上記範囲中、６２重量％以上である。また、７０重量％以下であることが好ましく、６５．２重量％であることが最適である。
【００１３】
Ｌｉ２Ｏの含有量は、３重量％未満では表面の結晶析出が充分ではなく、８重量％を超えると結晶粒が大きくなり、可視光線透過率が低下する。Ｌｉ２Ｏは上記範囲中、４重量％以上である。また、６重量％以下であることが好ましく、最も高い透過率を得るには５．４重量％が最適である。
【００１４】
Ａｌ２Ｏ３ の含有量は、１５重量％未満では結晶析出が充分ではなく、２２重量％を超えると溶解が困難となるとともに結晶粒が大きくなって、可視光線透過率が低下する。Ａｌ２Ｏ３は上記範囲中、１５〜２１重量％であることが好ましく、さらに最も高い透過率と圧縮応力を得るには１８．２重量％が最適である。
【００１５】
ＺｎＯは結晶核の形成剤として加えられる。その含有量が２重量％未満では析出結晶が充分ではなく、充分な圧縮応力が得られない。一方、８重量％を超えると体積結晶化が起こる。ＺｎＯは上記範囲中、４．５〜７重量％とされて、充分細かい結晶を析出させて高い可視光線透過率と圧縮応力を得るには４．４重量％とされる。
【００１６】
ＺｒＯ２ を含有することにより、ガラスの透明性を高くできるベータスポジュメンを表面に析出させることができる。ただし、その含有量が７重量％を超えると体積結晶化が起こり強度が低下する。ＺｒＯ２は上記範囲中、２重量％以上とされる。また、５重量％以下であることが好ましく、充分細かい結晶を析出させるには４．０重量％であることが最適である。
【００１７】
ＭｇＯは必須成分ではないが、含有することにより、ガラスの溶融性を向上させることができる。しかし、ＭｇＯは結晶相と母ガラスの界面近傍に固溶して、両者の熱膨張率の違いを低下させる働きがあるため、１．５重量％を超えると表面に析出する結晶の熱膨張係数が大きくなり、充分な圧縮応力が得られない。ＭｇＯは上記範囲中、０．１〜０．７重量％であることが好ましく、高い圧縮応力を得るには０．７重量％であることが最適である。
【００１８】
ＣａＯは必須成分ではないが、含有することにより、ガラスの溶融性を向上させることができる。しかし、その含有量が２重量％を超えると、透明性を損なう結晶が析出しやすくなる。
【００１９】
Ｎａ２Ｏ及びＫ２Ｏは必須成分ではないが、含有することにより、溶解性を改善することができる。その含有量が合量で１０重量％を超えると、ベータスポジュメンの低膨張結晶相が析出しなくなり、目的とする強度が得られなくなる。Ｎａ２Ｏ＋Ｋ２Ｏの含有量は、上記範囲中、８重量％以下であることが好ましく、さらに高い可視光線透過率と圧縮応力を得るためには、Ｎａ２Ｏの含有量が０．７重量％であり、Ｋ２Ｏの含有量が１．０重量％である時が最適である。
【００２０】
また、ベータスポジュメンを有効に析出させるには、Ｌｉ２ＯとＡｌ２Ｏ３のモル比が０．９〜１．１の範囲とされ、１であることが最適である。
【００２１】
上記ガラスにおいて、可視光線透過率が７５％以上であるものは、強度が高く可視光線透過率が高いことを要求される分野に好適に使用することができる。
【００２２】
かかるガラスは、次のようにして製造される。常法にしたがって、目標組成になるように各原料を調合し、これを１６００〜１７００℃に加熱してガラス化する。次いでこの溶融ガラスを清澄した後所定の形状に成形する。その際板ガラスに成形する場合は、ロールアウト法、フロート法、プレス法等が使用される。また、ファイバーに成形する場合は、白金製のピンホールから引き出す方法が使用される。かくして成形されたガラスは、ガラス転移点温度以上軟化点温度以下の温度範囲で所定時間保持され、表面に薄い結晶層が生成される。この温度は具体的には６００〜８５０℃の温度範囲にあり、保持時間は３０分間〜８時間程度である。特に薄いガラスの場合には、あらじめ、５５０〜６５０℃程度に１０〜４８時間保持して予備加熱し、結晶核を形成すると表面の結晶層が析出しやすくなる。さらに、薄いガラスの場合には結晶を析出するための保持時間を上記範囲内において短い時間を採用する。
【００２３】
本発明の表面結晶化ガラスは通常のガラスと同程度の可視光線透過率をもち、かつ強度が高いため、より高い強度が要求される建築用、自動車用ガラスに適用することにより、大きな利点が得られる。すなわち、同一厚さで使用すれば数倍の強度を発現することができ、また同一強度を発現するための厚さは数分の１になるために大幅な軽量化が可能である。さらに、通常の急冷による物理強化では強度の上昇が困難であった薄板やファイバーについても可視光線透過率を保持しつつ高強度化が可能であり、太陽電池のカバーガラスや繊維強化複合材料用の強化繊維として応用が可能である。
【００２４】
【実施例】
［実施例１］
表１に、本発明の実施例（例３）及び比較例（例４、５）、参考例（例１、２）として検討した５種類のガラス組成を示す。
【００２５】
表１に記載されたとおりのガラス組成になるように、各組成の原料粉体２００ｇを白金製の坩堝に投入した後、１６５０〜１６７５℃大気中にて４時間、撹拌しながら溶解した。比較例（例５）では溶解性が悪いが、本発明の例３では、通常のソーダライムガラスと同程度の溶解性があり、製造上の問題はないことを確認した。均一に溶解した各組成のガラスは、カーボンの型に流し込んで、約１０ｃｍ角で厚さ５ｍｍ程度の板に成形・冷却した。得られた板のガラス転移点温度は各組成によって異なるため、それらをＤＴＡにて測定した。成形後の各ガラスを、表２に記載の熱処理温度、保持時間保持し表面に結晶層を析出した。その後６０℃／ｈｒのゆっくりした速度で冷却した。かくして得られたガラスについて、可視光線透過率及び表面の圧縮応力を測定し、その結果を、表２の可視光線透過率の欄、圧縮応力の欄にそれぞれ示した。圧縮応力の測定は、偏光顕微鏡によった。また、表面の結晶層について、Ｘ線により調査した結果、例１、２は、ベータスポジュメン以外の結晶が主体であり、例３はベータスポジュメンが主体であり、その厚さは、いずれも約５０μｍであることを確認した。比較例である例４は、中央部まで全体にベータスポジュメン以外の結晶が析出したいわゆる体積結晶であり、例５は表面に５μｍのベータスポジュメン以外の結晶層が析出していた。
【００２６】
例１〜３では、高い可視光線透過率と大きい圧縮応力が確認されており、中でも例３の組成が最も良い値を示した。これに対し、例４では高い圧縮応力は測定されたものの、ＳｉＯ２含有量が少ないために熱処理時に変形が起こり、可視光線透過率は測定できなかった。また、例５では、溶解性が悪く、得られたガラスの可視光線透過率や圧縮応力も不充分であった。
【００２７】
最も良い結果が得られた例３については、強度試験片を作成し、実際の強度を測定した。ＪＩＳ Ｒ１６０１に定められた３点曲げ強さ試験で測定した。曲げスパンは３０ｍｍ、荷重の負荷速度は０．５ｍｍ／ｍｉｎである。強度試験片の大きさは３×４×４０ｍｍとし、１６本の試験片を作成した。同形状に機械加工後、８本について表２の例３の条件にて表面結晶化処理を行った。試験片の結晶化処理前後の平均強度及び標準偏差の結果を表３に示す。
【００２８】
この結果から、最適組成を用いれば、結晶化により約５倍の強度上昇が得られ、かつ高い可視光線透過率が保たれることが分かる。
【００２９】
［実施例２］
さらに、同ガラスの用途として、建築用及び自動車用のガラスを想定し、３００ｍｍ角の板を成形し、強度測定を行った。ガラスとして表１の例３のものと同一のものを使用し、板厚を通常板厚の半分の１．５ｍｍとなるように成形後、所定の熱処理を行って表面に均一な結晶層を析出させた。この結晶層はベータスポジュメンであった。こうして得られた板及びソーダライムガラスの強度をリング−オン−リング法にて測定した。リング−オン−リング法とは、直径８０ｍｍの下リング上にガラスを載置し、その上に直径３０ｍｍの上リングを載置し、上リングより荷重を印加し、ガラスが破壊した時の破壊加重を強度として測定する方法である。その結果を表４に示す。通常のソーダライムガラスと比較して板厚が半分にもかかわらず、破壊荷重は約１．６倍となっており、本ガラスを用いることによって高強度化と軽量化が同時に実現できたことが分かる。
【００３０】
［実施例３］
さらに、表１の例３と同一の組成のガラスを用いて、太陽電池のカバーガラスとして用いられる厚さ０．３ｍｍの薄板を作成し、表面に結晶層を析出し、破壊荷重と可視光線透過率を測定した。表５には通常使用されているソーダライムガラスと前述の表１の例３の組成にて作製した薄板の特性を比較して示す。破壊荷重は前述の実施例２と同様、リング−オン−リング法にて測定した。なお、本実施例ではより高い可視光線透過率を得るために表面結晶化後に表面を研磨しており、その結果、前述の表２に比べて高い可視光線透過率が得られている。この結果から明らかなように、本結晶化ガラスを使用することにより、通常のソーダライムガラスと同程度の可視光線透過率を保持しつつ強度を２倍以上とすることが可能である。
【００３１】
［実施例４］
また、表１の例３と同一の組成のガラスを用いて、厚さ２ｍｍの腕時計用のガラスを試作し、表面に結晶層を析出した。そのガラス及びソーダライムガラスについてビッカース硬度と可視光線透過率とを測定した。その結果を表６に示す。同表より明らかなように、本実施例によるガラスは、ビッカース硬度がソーダライムガラスと比べて２倍以上大きく、耐擦傷性に優れている。しかも可視光線透過率は、ソーダライムガラスとほとんど変わらない。またこのガラスを棒状に成形し、同一の条件で表面に結晶を析出した。この棒について曲げ強度を測定した結果、３００ＭＰａであり充分な強度を有する。
【００３２】
［実施例５］
もう一つの応用例として、表面結晶化ガラスとしてファイバー形状に成形したものを、繊維強化プラスチックの補強材料として使用した結果を示す。表１の例３のガラスを溶融した後、白金製のピンホールから引き出すことにより紡糸を行い、太さ約φ７０μｍの繊維を得た。長繊維用として、数百本の同繊維を長さ約２００ｍｍに切りそろえてから電気炉にて所定の熱処理を実施（７３０℃、１時間保持）し、表面に薄い結晶層を生成した。この結晶層はベータスポジュメンであった。また、短繊維用として、長さ１〜３ｍｍ程度に切断してチョップドストランドを作り、長繊維同様熱処理を実施して、表面結晶ファイバーとした。これらのファイバーをポリエステル樹脂中に含浸して板形状とし繊維強化ポリエステル板を成型した。板厚は２ｍｍで、常温硬化後に６０℃、１時間のキュアーを実施した。こうして得られた板から長さ１５０ｍｍ、幅１０ｍｍの短冊系試験片を切り出し、引張試験により平滑材強度を測定した。また、平滑材の中央部片側に深さ４ｍｍ、幅０．５ｍｍのスリット状の切り欠けを設けた試験片も作成し、切り欠け材強度も測定した。試験片本数は各５本である。得られた結果を通常のＥガラスファイバーを使用して作製した試験片の結果と比較して表７に示す。同表から強化繊維として本表面結晶化ガラスを使用すると繊維強化ポリエステル板の強度が約２０〜５０％向上することが分かる。
【００３３】
【表１】
【表２】
【表３】
【表４】
【表５】
【表６】
【表７】
【発明の効果】
本発明によれば、強度が高く、可視光線透過率が高いガラスが提供される。かかるガラスは、建築用ガラス、自動車用ガラス、太陽電池カバーガラス、磁気ディスク基板用ガラス、ガラスフアイバー、時計用カバーガラスに適する。[0001]
[Industrial application fields]
The present invention relates to a surface crystallized high-strength glass, a method for producing the same, and a use thereof.
[0002]
[Prior art]
Conventionally, it is known that when the surface of glass is crystallized and the thermal expansion coefficient of the crystal is smaller than that of the mother glass, compressive stress is generated on the surface and the strength of the glass is improved. Olcott et al. (US Pat. No. 2,998,675) produced a high strength glass by first heat treating the glass to generate a thin compressed layer crystallized on the surface. Olcott et al glass composition of SiO 2 65 to 72 wt%, 4 wt% or more of Li 2 O, the Li 2 O / Al 2 O 3 ratio of 22.5 to 30 wt% of Al 2 O 3 0.3 0.1 to 3.5 wt% TiO 2 , 0.1 to 5 wt% B 2 O 3 , 0.4 to 2 wt% Na 2 O as crystal nuclei, 0.5 to It is characterized by containing at least one of 10% by weight of PbO. The glass is heat-treated at around 800 ° C. for several hours, and a beta-eucryptite crystal layer is deposited on the surface during the heat treatment . Since the coefficient of thermal expansion of beta-eucryptite is smaller than that of the mother glass, a uniform compressive stress is generated on the surface during cooling, and the strength of the glass increases . Olcott et al. (US Pat. No. 3,253,975) subsequently modified the composition as follows. That is, 52 to 65 wt% SiO 2 , 4 wt% or more Li 2 O, 40 wt% or less Al 2 O 3 and the Li 2 O / Al 2 O 3 ratio is 0.3 or less . However, the surface crystal layer that contributes to an increase in strength is the same beta-eucryptite as before, and cannot be said to have sufficiently high transparency.
[0003]
Surface crystallized glass by crystallization of a willemite layer is described in British Patent No. 1108473 and 1108476. These glass composition 32-54 wt% SiO 2, a Al 2 O 3 of 24 to 56 wt%, 0.5-6 wt% of P 2 O 5 as a crystal nucleus, 0.5-4 wt% MoO 3 , and at least one of 1.5 to 7.5% by weight of ZrO 2 is included. However, the glass after crystallization is opaque.
[0004]
Bear et al. (US Pat. No. 4,814,297) invented a surface crystallized glass having a composition different from the above and having a crystal layer in which fine betaeucryptite or beta quartz is dissolved. Its composition 55-67 wt% of SiO 2, 22 to 28 wt% of Al 2 O 3, 5~7 wt% of Li 2 O, 0 to 2 wt% of Na 2 O, 0% by weight of ZnO , and the added alkali metal oxide is 1 or more in molar ratio to Al 2 O 3, molar ratio of SiO 2 and Al 2 O 3 is Ru 4 der.
[0005]
In addition, U.S. Pat. 5084328 (Fine et al., 1992) in magnesium-aluminosilicate glass in, there is shown a glass having a surface crystal compressive stress layer of beta quartz, its composition, 50-70 wt% of SiO 2,. 16 to 28 wt% Al 2 O 3, 5 to 10 wt% of MgO, 2.5 to 5 wt% of Li 2 O, 3.5 to 12 wt% of ZnO. This glass strength improvement is due to a combination of physical strengthening by rapid cooling and compressive stress by the beta quartz surface layer.
[0006]
As described above , many attempts have been made to improve the strength of the glass by generating a compressive stress on the surface by precipitating a crystal layer on the surface of the glass and making its thermal expansion coefficient smaller than that of the mother glass. The crystal layer is limited to beta eucryptite, beta quartz and Wilmite. Further, in the refractive index of the crystal layer and mother glass is different, not sufficient visible light transmittance is obtained, the obtained glass had a disadvantage that it is opaque. None of the patents mentions the specific visible light transmittance, and a further examination was made on the composition by Fine et al. Described as transparent (US Pat . No. 5,084,328) . Only a low visible light transmittance of less than 10% is obtained. Further crystal layer Study solid solubility to the mother glass is not made of, as a result sufficient strength increase the difference in the thermal expansion coefficient of the crystal layer and mother glass is decreased can not be obtained, physically strengthened by rapid cooling Many have achieved high strength by combining with.
[0007]
As described above, there are several methods for providing high-strength glass by surface crystallization. However, a glass composition and a production method that provide high strength without using physical strengthening and satisfy high visible light transmittance have been found. It has not been.
[0008]
[Problems to be solved by the invention]
The object of the present invention is to provide the above-mentioned problems of the prior art, that is, to provide a surface crystallized glass having a sufficiently high strength without physical strengthening and a high visible light transmittance, that is, a transparent surface crystallized glass. .
[0009]
[Means for Solving the Problems]
The present invention has a composition of 6 2 to 75 wt% SiO 2 , 4 to 8 wt% Li 2 O, 15 to 22 wt% Al 2 O 3 , 4.4 to 8 wt% ZnO, 2 to 7 wt% of ZrO 2, 0 to 1.5 wt% of MgO, 0 to 2 wt% of CaO, of 0-10 wt% Na 2 O + K 2 O Tona is, the molar ratio of Li 2 O and Al 2 O 3 there a glass area by der of 0.9 to 1.1, surface crystallized high-strength glass having a thin crystalline layer comprising beta-spodumene to said glass surface and provides the preparation and use thereof.
[0010]
Contact Keru surface crystallized high strength glass in the present invention, the glass surface has a small thin crystalline layer coefficient of thermal expansion, the central portion is a glass layer. As this crystal layer , beta spodium is used in that the transparency of the glass can be made particularly high. The thickness of the crystal layer on this surface is several μm to 60 μm.
[0011]
Next, the reasons for limiting the composition of the glass of the present invention will be described.
[0012]
SiO 2 , Li 2 O and Al 2 O 3 are basic parts constituting the surface crystal, and SiO 2 is also a main component forming a network structure in the glass phase. If the content of SiO 2 is less than 60% by weight, deformation occurs during crystallization and the shape cannot be maintained. If it exceeds 75% by weight, the crystallization will be slow, and the meltability of the glass will deteriorate, making it difficult to obtain a homogeneous glass. SiO 2 is in the above range is 62 wt% or more. Moreover, it is preferable that it is 70 weight% or less , and it is optimal that it is 65.2 weight%.
[0013]
When the content of Li 2 O is less than 3% by weight, crystal precipitation on the surface is not sufficient, and when it exceeds 8% by weight, the crystal grains become large and the visible light transmittance is lowered. Li 2 O is in the above range is 4% by weight or more. Further, it is preferably 6% by weight or less , and 5.4% by weight is optimal for obtaining the highest transmittance.
[0014]
The content of Al 2 O 3, in less than 15% by weight is not sufficient that sintering crystallization unloading, with dissolution exceeds 22 wt% it becomes difficult becomes crystal grains is large, you decrease visible light transmission . Al 2 O 3 is preferably 15 to 21 wt % in the above range, and 18.2 wt % is optimal for obtaining the highest transmittance and compressive stress.
[0015]
ZnO is added as a crystal nucleus forming agent. If the content is less than 2% by weight, the precipitated crystals are not sufficient and sufficient compressive stress cannot be obtained. On the other hand, if it exceeds 8% by weight, volume crystallization occurs. During ZnO above range, 4.5 to 7 is the weight%, Ru is by precipitating sufficiently fine crystals having high visible light transmittance and 4.4% by weight to obtain a compressive stress.
[0016]
By containing ZrO 2 , beta spodumene that can increase the transparency of the glass can be deposited on the surface. However, if its content exceeds 7% by weight, volume crystallization occurs and the strength decreases. ZrO 2 is 2 % by weight or more in the above range . Further, it is preferably 5% by weight or less , and is optimally 4.0% by weight in order to precipitate sufficiently fine crystals.
[0017]
MgO is not an essential component, by containing, can Rukoto to improve the meltability of the glass. However, MgO dissolves in the vicinity of the interface between the crystal phase and the mother glass and reduces the difference in the coefficient of thermal expansion between the two. Therefore, the thermal expansion coefficient of the crystals that precipitate on the surface exceeds 1.5% by weight. , And sufficient compressive stress cannot be obtained. MgO is in the above range is preferably from 0.1 to 0.7 wt%, to obtain a high compressive stress is optimal to be 0.7 wt%.
[0018]
CaO is not an essential component, but by containing, can Rukoto to improve the meltability of the glass. However, when the content exceeds 2% by weight, crystals that impair transparency tend to precipitate.
[0019]
Na 2 O and K 2 O is not an 必 Sunari minutes, but by containing, can improve the solubility. If the total content exceeds 10% by weight, the low-expansion crystal phase of beta spodumene does not precipitate and the intended strength cannot be obtained. The content of Na 2 O + K 2 O is preferably 8% by weight or less in the above range, and in order to obtain higher visible light transmittance and compressive stress, the content of Na 2 O is 0.8. It is optimal when the content is 7% by weight and the content of K 2 O is 1.0% by weight .
[0020]
In order to precipitate beta spodumene effectively, the molar ratio of Li 2 O to Al 2 O 3 is in the range of 0.9 to 1.1, and is optimally 1.
[0021]
In the above glass, those having a visible light transmittance of 75% or more can be suitably used in fields requiring high strength and high visible light transmittance.
[0022]
Such glass is manufactured as follows. In accordance with a conventional method, each raw material is prepared so that it may become a target composition, and this is heated to 1600-1700 degreeC and vitrified. Next, the molten glass is clarified and then formed into a predetermined shape. At that time, when forming into a sheet glass, a roll-out method, a float method, a press method or the like is used. In the case of forming the fiber, a method drawn from pinholes made of platinum is used. The glass thus formed is held for a predetermined time in a temperature range between the glass transition temperature and the softening temperature, and a thin crystal layer is formed on the surface. This temperature is specifically in the temperature range of 600 to 850 ° C., and the holding time is about 30 minutes to 8 hours. In particular, in the case of a thin glass, if a crystal nucleus is formed by preliminarily holding it at about 550 to 650 ° C. for 10 to 48 hours to form a crystal nucleus, the surface crystal layer is likely to be precipitated. Further, in the case of thin glass, a short time is employed for the retention time for crystal precipitation within the above range.
[0023]
Since the surface crystallized glass of the present invention has a visible light transmittance comparable to that of ordinary glass and has a high strength, it has a great advantage when applied to architectural and automotive glass where higher strength is required. can get. That is, it is possible to express several times stronger if used in the same thickness, also the thickness for expressing the same strength can have a large width lightweight to become fraction. Furthermore, it is possible to increase the strength of thin plates and fibers that have been difficult to increase in strength by physical quenching by ordinary rapid cooling while maintaining the visible light transmittance. It can be applied as a reinforcing fiber.
[0024]
【Example】
[Example 1]
Table 1 shows five types of glass compositions studied as examples (Example 3), comparative examples (Examples 4 and 5) of the present invention , and reference examples (Examples 1 and 2) .
[0025]
After putting 200 g of raw material powder of each composition into a platinum crucible so as to have a glass composition as described in Table 1, it was dissolved in the atmosphere at 1650 to 1675 ° C. with stirring for 4 hours. In Comparative Example (Example 5), the solubility was poor, but in Example 3 of the present invention, it was confirmed that the solubility was comparable to that of ordinary soda lime glass and there was no problem in production. The uniformly melted glass of each composition was poured into a carbon mold and formed into a plate having a thickness of about 10 cm square and a thickness of about 5 mm and cooled. Since the glass transition temperature of the obtained plate differs depending on each composition, they were measured by DTA. Each glass after molding was kept at the heat treatment temperature and holding time shown in Table 2 to deposit a crystal layer on the surface. Thereafter, it was cooled at a slow rate of 60 ° C./hr. The glass thus obtained was measured for visible light transmittance and surface compressive stress, and the results are shown in the column of visible light transmittance and the column of compressive stress in Table 2, respectively. The compressive stress was measured with a polarizing microscope. Moreover, as a result of investigating the surface crystal layer by X-ray, Examples 1 and 2 are mainly crystals other than beta spojumen, Example 3 is mainly beta spojumen, and its thickness is Both were confirmed to be about 50 μm. Example 4, which is a comparative example, is a so-called volume crystal in which crystals other than beta-spodumene are precipitated all the way to the center, and Example 5 has a crystal layer other than beta-spodumene of 5 μm deposited on the surface.
[0026]
In Examples 1 to 3 are large compressive stress and high visible light transmittance check showed the most have good value composition of among others Example 3. On the other hand, in Example 4, although a high compressive stress was measured, since the SiO 2 content was small, deformation occurred during the heat treatment, and the visible light transmittance could not be measured. Moreover, in Example 5, the solubility was poor, and the visible light transmittance and compressive stress of the obtained glass were insufficient.
[0027]
For Example 3 where the best result was obtained, a strength test piece was prepared and the actual strength was measured. It was measured by a three-point bending strength test defined in JIS R 1601. The bending span is 30 mm and the load speed of the load is 0.5 mm / min. The size of the strength test piece was 3 × 4 × 40 mm, and 16 test pieces were prepared. After machining into the same shape, surface crystallization treatment was performed on 8 pieces under the conditions of Example 3 in Table 2. Table 3 shows the results of the average strength and standard deviation before and after the crystallization treatment of the test piece .
[0028]
From this result, it can be seen that, if the optimum composition is used, an increase in strength of about 5 times is obtained by crystallization, and a high visible light transmittance is maintained.
[0029]
[Example 2]
Further, as the application of the glass, assuming architectural and automotive glass, a plate of 300mm square and formed shapes were strength measurement. Using the same as those in Table 1 of Example 3 as a glass, after forming the shape such that the thickness and normal thickness one half of 1.5mm of uniform crystal layer on a surface by performing a predetermined heat treatment Was precipitated. This crystal layer was a beta-spodumene. The strength of the plate and soda lime glass thus obtained was measured by a ring-on-ring method. In the ring-on-ring method , glass is placed on a lower ring having a diameter of 80 mm, an upper ring having a diameter of 30 mm is placed thereon, a load is applied from the upper ring, and the glass breaks when it breaks. This is a method of measuring weight as intensity. The results are shown in Table 4. Although the plate thickness is half that of normal soda lime glass, the breaking load is about 1.6 times, and the use of this glass has made it possible to achieve high strength and light weight at the same time. I understand.
[0030]
[Example 3]
Furthermore, using a glass having the same composition as Example 3 in Table 1, a 0.3 mm-thick thin plate used as a cover glass for a solar cell was prepared, a crystal layer was deposited on the surface, and a breaking load and visible light transmission were achieved. The rate was measured. Table 5 shows a comparison of the characteristics of a soda lime glass that is usually used and a thin plate produced with the composition of Example 3 in Table 1 described above. The breaking load was measured by the ring-on-ring method as in Example 2 described above. In this example , in order to obtain a higher visible light transmittance, the surface is polished after the surface crystallization, and as a result, a higher visible light transmittance is obtained as compared with Table 2 described above. As is apparent from this result, by using this crystallized glass, it is the strength while retaining the usual soda-lime glass as much visible light transmittance can be more than doubled.
[0031]
[Example 4]
Moreover, using a glass having the same composition as that of Example 3 in Table 1, a glass for a watch having a thickness of 2 mm was made as a prototype, and a crystal layer was deposited on the surface. The Vickers hardness and visible light transmittance of the glass and soda lime glass were measured. The results are shown in Table 6. As is clear from the table, the glass according to this example has a Vickers hardness of 2 times or more larger than that of soda lime glass, and is excellent in scratch resistance. Moreover, the visible light transmittance is almost the same as that of soda lime glass. Further, this glass was formed into a rod shape, and crystals were precipitated on the surface under the same conditions. As a result of measuring the bending strength of this bar, it is 300 MPa and has sufficient strength.
[0032]
[Example 5]
As another application example, a material obtained by forming the shape in the fiber shape as the surface of crystallized glass, shows the results of using as a reinforcing material for the fiber-reinforced plastic. After melting the glass of Example 3 in Table 1, spinning was performed by pulling it out from a platinum pinhole to obtain a fiber having a thickness of about φ70 μm. For long fibers, several hundreds of the same fibers were cut to a length of about 200 mm and then subjected to a predetermined heat treatment in an electric furnace (730 ° C., held for 1 hour) to form a thin crystal layer on the surface. This crystal layer was beta-spodumene. Further, as a short fiber 維用, it makes chopped strands were cut to a length of about 1 to 3 mm, to implement the long fibers similar heat treatment was the surface crystal fiber. These fibers were impregnated into a polyester resin to form a plate shape, and a fiber-reinforced polyester plate was molded. The plate thickness was 2 mm, and curing at 60 ° C. for 1 hour was performed after curing at room temperature. A strip-type test piece having a length of 150 mm and a width of 10 mm was cut out from the plate thus obtained, and the smooth material strength was measured by a tensile test. Moreover, the test piece which provided the slit-shaped notch of depth 4mm and width 0.5mm on the center part piece side of the smooth material was also created, and notch material strength was also measured. The number of test pieces is 5 each. The obtained results are shown in Table 7 in comparison with the results of test pieces prepared using ordinary E glass fibers. It can be seen from the table that the strength of the fiber-reinforced polyester plate is improved by about 20 to 50% when this surface crystallized glass is used as the reinforcing fiber.
[0033]
[Table 1]
[ Table 2 ]
[Table 3]
[ Table 4 ]
[Table 5]
[ Table 6 ]
[ Table 7 ]
【The invention's effect】
According to the present invention, a glass having high strength and high visible light transmittance is provided. Such glass is suitable for architectural glass, automotive glass, solar cell cover glass, magnetic disk substrate glass, glass fiber, and watch cover glass.
Claims (10)
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-
1994
- 1994-11-25 JP JP29168794A patent/JP3829338B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101760039B1 (en) * | 2015-12-28 | 2017-07-31 | 한국세라믹기술원 | Li2O-Al2O3-SiO2 transparent crystallized glass and the manufacturing method of the same |
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|---|---|
| JPH08151228A (en) | 1996-06-11 |
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