JP3771429B2 - Ultraviolet absorbing glass and glass tube for fluorescent lamp using the same - Google Patents
Ultraviolet absorbing glass and glass tube for fluorescent lamp using the same Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は、紫外線吸収ガラスに関し、紫外線放射を伴う光源の外囲器、特に液晶ディスプレイ(以下LCDと称すことがある)等の表示デバイスのバックライトに用いられる蛍光ランプ用ガラス管に適したガラス及びこのガラスを用いた蛍光ランプ用ガラス管に関する。
【0002】
【従来の技術】
近年、マルチメディア関連機器のキーデバイスとしてLCDは広く用いられているが、その用途の拡大とともに軽量化、薄型化、高輝度化、低消費電力化などが求められるようになっている。特にパソコン用ディスプレイ、車載用表示装置、携帯情報端末等では高品位な表示品質が要求されている。一方、液晶表示素子自体は非発光であるため、上記のような用途では、蛍光ランプを光源とするバックライトを用いた透過型液晶表示素子が使用されている。
【0003】
上述のようにLCDに軽量化、薄型化、高輝度化、低消費電力化などが求められていることから、同様にバックライトにも一層の小型軽量化、高輝度化、低消費電力化が求められ、バックライト用蛍光ランプにおいては細管化、薄肉化が進展している。
【0004】
しかし、蛍光ランプの細管化、薄肉化は、機械的強度の低下、発熱量増大による電極部の温度上昇をもたらす。このため、バックライト用の蛍光ランプに使用されるガラス管には、より高強度で低膨張性であるガラスが必要とされている。
【0005】
従来、この種の蛍光ランプのガラス管には、照明用ガラスとしての実績があり加工性に優れた鉛ソーダ系の軟質ガラスが使用されてきた。ところが、バックライト用途で管径、肉厚が小さくなるに連れて、製品の信頼性において十分な強度や耐熱性を確保することが困難となり、鉛ソーダ系の軟質ガラスよりも熱的、機械的強度が高い硼珪酸系硬質ガラスを用いて蛍光ランプを作製することが検討され、気密封止可能な金属と硬質ガラスの組合せとして、従来からよく知られているコバール合金とコバール封着用ガラス又はタングステンとタングステン封着用ガラスを用いた蛍光ランプが開発され、商品化されている。ここで「コバール」とは、Fe−Ni−Co系合金を指すWestinghouse Ele.Corp.社の商標名であり、東芝社製KOV(商品名)など同等の他社製品を包含する意味で用いる。
【0006】
【発明が解決しようとする課題】
バックライト用蛍光ランプの発光原理は、一般照明用蛍光ランプと同様、蛍光管内の電極間放電により励起された水銀蒸気やキセノンガスが253.7nmの紫外線を放出し、管内壁面に塗布されている蛍光体が発光することによるものである。しかし、紫外線にはガラスに変色を引き起こす作用があることが知られており、紫外線に対して何の対策も取っていないガラスでは、紫外線照射によりソラリゼーションと呼ばれる変色作用を生ずる。蛍光管ガラスでソラリゼーションが起こると、結果としてランプ輝度の低下、発光色の変色となり、バックライトではLCDの表示が暗くなったり表示色が不鮮明になったりするなど表示品質の低下を招く。また、紫外線がバックライト用ガラス管を透過して管外に放出されると、LCD表示装置内部の樹脂部品等の材質劣化を促進させる問題がある。
【0007】
特に表示デバイスの薄型軽量化に有利なバックライト方式として、透明導光体の側端面に光源を配し、導光体の一面を反射・拡散処理して、光を多重反射させることにより面光源とするエッジライト方式が知られているが、この方式では構造上、導光体が必要なこと、軽量化のため導光体にはアクリル系樹脂等の樹脂部品が使用されることから、バックライト用光源からの紫外線漏洩は、導光体の劣化・着色による光透過率の低下をもたらし、光源近傍で樹脂の劣化が生ずると表示面全体の明るさが低下するため、上記蛍光管ガラスでのソラリゼーションとともに表示品質に与える影響が大きい。
【0008】
上記した鉛ソーダ系ガラスでは、ガラス成分として含有されている鉛が耐紫外線ソラリゼーション性、紫外線カット性能を有していたため、これらが問題となることはなかったが、硼珪酸系のコバール封着用ガラスやタングステン封着用ガラスは元来電子管や電子部品の封止に用いられていたもので、紫外線による作用に対してはガラス材質としての対策は取られておらず、紫外線ソラリゼーション、紫外線透過の問題が避けられなかった。
【0009】
このため、従来のコバール封着用ガラスまたはタングステン封着用ガラスを蛍光ランプ用外管に使用する場合、ガラス管内面に紫外線を反射又は吸収する成分であるAl2O3 やTiO2 のコーティングを行い、その上に蛍光体を塗布して多層膜を形成し、ガラスに達する紫外線の強度を弱めるといった措置も取られている。しかし、このような方法は、ガラス管の細径化にともなう塗布の困難化や塗布工程の増加によるコスト上昇が避けられない。
【0010】
以上のような背景から、コバール合金と封着可能な熱膨張係数を持ち、耐紫外線ソラリゼーション性を有するガラスとして特開平8−333132号公報、特開平9−110467号公報に開示のガラスが提案されている。これらのガラスはいずれも硼珪酸系ガラスにPbO,TiO2,Sb2 O3の少なくとも1種以上を添加することにより耐紫外線ソラリゼーション性を持たせたものである。
【0011】
これらのガラスにより紫外線によるソラリゼーションの問題は解消されるが、いずれのガラスも環境有害物質であるPbOの含有を許容しており、環境保護の観点からは好ましいとは言えない。また、蛍光ランプとして使用する場合の紫外線カットに対する配慮が十分とはいえず、前記した耐紫外線ソラリゼーション性付与成分の組合せ、含有量によっては励起された水銀等が発する253.7nmの有害紫外線を透過し、内装部品を劣化させるおそれがある。
【0012】
本発明は以上のような諸事情を考慮してなされたものであり、コバール合金またはタングステンとの良好な封着が可能で十分な耐紫外線ソラリゼーション性を持ち、かつ有害紫外線を透過しない紫外線吸収ガラス及びそれを用いた蛍光ランプ用ガラス管を提供することを目的とする。
【0013】
【課題を解決するための手段】
上記目的を達成するために、本発明は蛍光ランプ用ガラス管に用いられる紫外線吸収ガラスであって、質量%で、SiO 2 55〜78%、B 2 O 3 10〜25%、Fe2O30.001〜0.05%、WO3+Nb2O50.05〜5%、ZrO20.01〜3%を含有し、50℃〜ガラス転移点(Tg)までの温度範囲における平均線膨張係数が36〜57×10−7/℃である硼珪酸系ガラスからなり、波長253.7nmにおける肉厚1mmでの透過率が1%以下であり、以下の紫外線照射試験における劣化度が3%以下であることを特徴とする。ここで、前記紫外線照射試験における劣化度は、両面を光学研磨した肉厚1mmのガラス研摩面を主波長253.7nmの400W高圧水銀ランプから20cmの位置に対向させて配置し、300時間紫外線を照射した後、波長400nmにおける透過率(T1)を測定し、紫外線照射前の波長400nmにおける初期透過率(T0)からの劣化度を次式により求めたものである。
劣化度(%)=[(T0−T1)/T0]×100
【0014】
本発明において、上記構成を規定した理由を以下に説明する。まず、硼珪酸系ガラスは、従来の鉛ソーダ系軟質ガラスに比べて機械的強度、耐熱性に優れており、蛍光管の細径・薄肉化に有利であるため、基本組成として硼珪酸系のガラスを使用する。
【0015】
次に、平均線膨張係数を36〜57×10−7/℃としたのは、この範囲であれば、コバール合金の平均熱膨張係数60.9×10−7/℃またはタングステン平均熱膨張係数45×10−7/℃と比較的近い値で、かつこれら封着金属よりもやや低めの値とすることが可能となり、ガラスの固着点以下での膨張・収縮挙動が類似していることから封着金属との良好かつ信頼性の高い封着性が得られる。特にコバール合金は400℃台後半で膨張曲線が屈曲するため、ガラスの転移点を低下させて膨張曲線をコバール合金に近似させることが必要であり、ガラスのコバール合金との封着性を評価するためにはこの温度域までの熱膨張係数を評価する必要がある。平均線膨張係数が前記範囲を外れると、コバールとの整合性が悪く、封着部でのクラックやリークの原因となって蛍光ランプとして信頼性のあるものが得られない。
【0016】
また以上のような硼珪酸系ガラスにFe2O30.001〜0.05%、WO3+Nb2O50.05〜5%、ZrO2 0.01〜3%を必須成分として含有させた理由は以下のとおりである。Fe2O3は紫外線吸収が顕著であるため添加するが、前記下限値未満では紫外線カット効果が認めらず、前記上限値を越えると耐紫外線ソラリゼーション性にマイナスの影響が現れるので好ましくない。より好ましくは0.003〜0.03%である。
【0017】
WO3、Nb2O5は耐紫外線ソラリゼーション性、紫外線カット性能を付与する目的で添加するが、これらの合量が5%を越えるとガラスが失透し易くなって均質性の悪化を生じるるとともに、バッチコストの極端な上昇を伴うため経済的観点からも好ましくない。また0.05%未満では、耐紫外線ソラリゼーション性、紫外線カット性能等の特性が十分に得られない。これら成分合量での添加量は、好ましくは0.1〜5%、より好ましくは0.1〜3%の範囲である。WO3、Nb2O5は特に紫外線によるソラリゼーションを抑制する作用が強いため、WO3、Nb2O5のいずれかを必須成分とする。単独で含有させる場合の各成分の好ましい含有量は、WO3が0.05〜5%、より好ましくは0.1〜3%、Nb2O5が0.05〜5%、より好ましくは0.1〜3%の範囲である。また、WO3、Nb2O5各成分単独での含有量が増加すると、固有の吸収によりガラスに着色傾向が見られることがあるため、各成分のより好ましい範囲内でWO3、Nb2O5を合せて添加することが好ましい。これによりソラリゼーション防止効果がより強化されるとともに不要な着色を与えないガラスを得ることができる。
【0018】
ZrO2 は、ガラスの化学的耐久性の改善及び分相抑制に効果が期待できるが、その含有量が0.01%未満ではその効果が十分でなく、3%を越えるとガラスが不均一になりやすく、細管に成形した際に肉厚や寸法の精度がばらつく原因になるので好ましくない。特に硼珪酸系ガラスにおいて、Fe2O3、WO3、Nb2O5、Bi2O3、CeO2等のガラスに着色を与えることのある成分を含有している場合、溶融成形工程でガラスに分相が生じると、分相部分が起点となって着色が現れることがあるため、本発明においてはガラスの着色防止のためにも必要な成分である。
【0019】
また、上述のように本発明のガラスをLCD表示装置等のバックライト用蛍光ランプに使用した場合、紫外線がガラス管を透過して管外に放出されると、LCD表示装置内部の樹脂部品等の材質劣化を促進させ、製品寿命や信頼性を低下させる原因になるため、本発明では上記成分により紫外線カット特性を持たせ、ガラスを肉厚1mmに光学研磨した状態で、波長253.7nmにおける紫外線透過率を1%以下としている。実際の蛍光ランプにおけるガラス肉厚はさらに薄いが、この程度まで紫外線透過が抑えられていれば、実用上問題は生じない。可視光の透過に影響を及ぼさず、より好ましい品質レベルを求めるのであれば、肉厚1mmで0.1%以下にすることができる。
【0020】
また、本発明において、紫外線照射試験における劣化度を上記のように定めた理由は次のとおりである。普通、強紫外線源の近傍にガラスを曝す促進試験では、1時間〜数時間で着色傾向(着色し易いガラスか否か)は確認できるが、100時間を越えるとその程度は次第に緩やかになり、300時間経過時点ではほぼソラリゼーションによる着色限界に近い状態を確認することができる。このため、実製品における長期間使用時の透過率低下の影響をより正確に把握できる。このときの透過率評価波長400nmは、明るさに最も影響を与え易いと考えられる波長を選択した。このような条件の試験における透過率の劣化度が3%以下であれば、蛍光ランプ用ガラス管に起因するLCD表示の暗化を使用者が認識し得ない程度に抑えることができ、実用的な表示品質を維持できる。
【0021】
また、本発明は、前記硼珪酸系ガラスが、質量%で、SiO2 65〜78%、Al2 O3 3〜10%、B2 O3 10〜25%、Li2 O+Na2 O+K2 O 5〜12%、Fe2O3 0.001〜0.03%、WO3+Nb2O50.05〜5%、ZrO2 0.01〜3%を含有し、30℃〜400℃までの温度範囲における平均線膨張係数が36〜45×10−7/℃であることを特徴とする。
【0022】
また、本発明は、前記硼珪酸系ガラスが、質量%で、SiO2 55〜70%、Al2 O3 1〜5%、B2 O3 10〜25%、Li2 O+Na2 O+K2 O 8〜15%、Fe2O3 0.001〜0.03%、WO3+Nb2O50.05〜5%、ZrO2 0.01〜3%を含有し、℃50℃〜ガラス転移点(Tg)までの温度範囲における平均線膨張係数が46〜57×10−7/℃であることを特徴とする。ここで、各成分の含有量を上記のように限定した理由を以下に説明する。
【0023】
SiO2は、はガラスの網目形成成分であるが、78%を超えるとガラスの溶融性、加工性が悪化し、55%未満ではガラスの化学的耐久性が低下する。化学的耐久性の低下はウェザリング、ヤケ等の原因となり蛍光ランプの輝度低下、色むら発生の原因となる。また、コバール合金と封着される用途に使用する場合には、55〜70%、タングステンと封着される用途に使用する場合には、65〜78%とすることが好ましい。これによりガラスの線膨張係数を各封着金属と近似の適正な値に保ちリーク、クラック等のない封着を可能にする。
【0024】
Al2 O3はガラスの化学的耐久性を改善する作用があるが、10%を超えると脈理の発生など溶融性に問題が生じ、ダンナー法による管成形の際スリーブ部分での失透の原因となる。また1%未満では分相が発生し成形性に問題を生じるとともにガラスの化学的耐久性の低下をもたらす。好ましくは1〜7%の範囲である。また、コバール合金と封着される用途に使用する場合には、1〜5%、タングステンと封着される用途に使用する場合には、4〜7%とすることがより好ましい。
【0025】
B2 O3は溶融性向上および粘度調整の目的で用いられる成分であるが、25%を超えるとガラスの化学的耐久性が低下し、長期間の使用によりウェザリングを生じる。またB2 O3が10%未満では溶融性の悪化、粘度上昇によるコバールとの封着性悪化等の問題を生じる。好ましくは12〜24%である。
【0026】
Li2 O、Na2 O、K2 Oは、融剤として作用し、ガラスの溶融性を改善するとともに粘度、熱膨張係数の調整に用いられる成分であるが、これら成分の合量が15%を超える場合は熱膨張係数が大きくなりすぎ、また化学的耐久性が悪化する。他方、5%未満では膨張係数の大幅な低下、粘度の大幅な上昇を伴いコバールとの封着が困難となる。また、各成分の含有量は、Li2 Oを0〜5%、Na2 Oを0〜8%、K2 Oを 2〜12%とすることが好ましい。それぞれの含有量が各上限値を超える場合は熱膨張係数が大きくなりすぎたり、化学的耐久性を悪化させたりする。また蛍光ランプの点灯中Na2 Oは水銀と反応しアマルガムを形成することが知られており、ガラス中の過剰なNa2 Oは蛍光ランプ中で有効に作用する水銀量を結果として減らすことになるため、水銀使用量削減の環境的観点からもNa2 Oの上記上限値を超える添加は好ましくなく、より好ましくは0〜4.5%である。また、コバール合金と封着される用途に使用する場合には、8〜15%、タングステンと封着される用途に使用する場合には、5〜12%とすることが好ましい。各下限値未満では膨張係数が大幅に低下し、粘度の大幅な上昇によりコバール合金またはタングステンとの良好な封着ができなくなる。なお、Fe2O3、Sb2 O3、ZrO2については上述のとおりである。
【0027】
また本発明は、上記紫外線吸収ガラスを管状に成形してなる蛍光ランプ用ガラス管である。上述のように本発明に係るガラスは、コバール合金との封着性に優れ、十分な耐紫外線ソラリゼーション性及び紫外線吸収性を有するので、蛍光ランプからの紫外線漏洩がなく、ガラスの紫外線着色によりランプ輝度や演色性が損なわれにくい蛍光ランプ用ガラス管得られる。また、ガラス管の外径が0.7〜5mm、肉厚が0.07〜0.6mmであり、表示デバイスのバックライト用光源に用いられることを特徴とする。外径、肉厚が前記上限値を越えると、現在のバックライト使用製品における薄型・軽量化の要請を満たすことができず、下限値未満になると成形精度の安定性や耐衝撃強度の点で充分な信頼性をもった製品を低廉な価格で供給することが難しくなる。
【0028】
さらに、本発明は導光体を介して表示面を照射するエッジライト方式のバックライト用光源に好適に用いられる。上述のとおり、本発明の蛍光ランプ用ガラス管は、紫外線吸収性能に優れるため、樹脂製導光体を使用するエッジライト方式のバックライト用光源に用いた場合でも、導光体の紫外線による劣化、透過率低下を生じにくく、初期の明るさを長期間維持できる。
【0029】
本発明のガラスを溶融するにあたって使用する清澄剤に特に制限はなく、一般的に用いられるSb2 O3、NaCl、Na2SO4等が使用できる。ただし、Sb2 O3はその含有量が多くなると、金属封着等の熱加工時にガラスが黒化する原因となり、蛍光ランプの輝度低下、発光色の変色、色むらを引き起こすので注意が必要である。
【0030】
さらに、ガラスの耐候性、溶融性、失透性などを改善する目的でZnO,CaO,MgO,SrO,P2O5,F−などの成分を本発明の所期の特性を損なわない範囲で添加することも可能である。
【0031】
【発明の実施の形態】
以下に本発明の実施の形態について説明する。本発明のガラス及び該ガラスを用いた蛍光ランプ用ガラス管は次のようにして作成することができる。まず上記組成範囲、たとえば、SiO2 68%, Al2O3 3.5%,Li2O 1%,Na2O 0.5%,K2O 8.3%,B2O3 18%,WO30.2%,Sb2O30.3%,ZrO2 0.2%、Fe2O30.01%となるように秤量・混合した原料混合物を溶融炉において加熱溶融し、ダンナー法あるいは一度管状に成形されたガラスをリドローする等の既知の管引き成形法によって所望の外径、肉厚を有する蛍光ランプ用ガラス管を得る。
【0032】
【実施例】
次に、本発明の蛍光ランプ用ガラス管につき実施例に基づいて詳細に説明する。表1ないし表3に本発明の実施例および比較例を示す。試料No.1〜15はコバール合金との封着を想定した本発明の実施例、No.16,17はその比較例、又No.18〜27はタングステンとの封着を想定した実施例、No.28,29はその比較例である。なお、表中の組成は質量%で示してある。表中記載のガラスは、表に示す酸化物組成となるよう珪砂、各金属の炭酸塩、硝酸塩、水酸化物等の原料粉末を秤量・混合し、それぞれ含有成分によって選択された清澄方法により白金坩堝もしくは石英坩堝を用いて1450℃で5時間溶融した。その後、充分に攪拌・清澄したガラスを矩形枠内に流出させ、徐冷後に以下に示す評価項目に合せて所望の形状に加工したサンプルを作成した。なお酸化清澄の場合はSb2O3を、還元清澄の場合はNaClを清澄剤として用いた。
【0033】
表中に示した項目について説明すると、熱膨張係数およびガラスの転移点は、各ガラスを直径4mm、長さ20mmの円柱に加工したサンプルを用い熱機械分析装置(TMA)で測定した。このとき熱膨張係数については、後述する温度範囲における平均線膨張係数を測定し、コバール合金については合せて同じ温度範囲における金属の平均線膨張係数も記載した。ガラスと封着金属との熱膨張係数差が大きくなると、封着部からのリークやクラックの発生原因となり、蛍光ランプ用としては使用できない。特に、コバール合金は400℃台後半で膨張曲線が屈曲するため、ガラスの転移点を低下させて膨張曲線をコバール合金に近似させることが必要であり、ガラスのコバール合金との封着性を評価するためには、この温度域までの熱膨張係数がコバール合金と同等又はやや低めであることが好ましい。このため、コバール合金との封着を想定した実施例No.1〜15のガラスは、この温度域を含む50℃〜各ガラスの転移点(Tg)までの温度範囲における熱膨張係数を評価した。一方、タングステンとの封着を想定した実施例No.18〜27のガラスは30〜400℃の温度範囲における熱膨張係数を評価した。
【0034】
耐紫外線ソラリゼーション性試験による透過率の劣化度は、各ガラスサンプルを一辺30mm角の板状にカットし、厚さが1mmとなるよう両面光学研磨加工した試料を、主波長253.7nmの400W高圧水銀ランプから20cmの位置に研摩面を対向させて配置し、300時間紫外線を照射した後、波長400nmにおける透過率(T1)を測定し、紫外線照射前の波長400nmにおける初期透過率(T0)からの劣化率を透過率劣化度として、劣化度(%)=[(T0−T1)/T0]×100により求めた値で示した。
【0035】
また、耐紫外線ソラリゼーション性試験に供する前の前記試料で、波長253.7nmの透過率を測定した値を合わせて示した。
【0036】
【表1】
【0037】
【表2】
【0038】
【表3】
【0039】
表から明らかなように、本発明の実施例であるNo.1〜15の各試料は、いずれもその熱膨張係数がコバールの平均熱膨張係数60.9×10−7/℃と比較的近い値で、かつコバール合金よりもやや低めの値を示しており、ガラスの固着点以下での膨張・収縮挙動が類似していることからコバール合金との良好かつ信頼性の高い封着性が得られる。また、本発明の実施例であるNo.18〜27の各試料は、いずれもその熱膨張係数がタングステンの平均熱膨張係数45×10−7/℃と比較的近い値で、かつタングステンよりもやや低めの値を示しており、タングステンとの良好かつ信頼性の高い封着性が得られる。また、波長253.7nmの透過率が極めて低く、有害紫外線をほとんど透過しない。さらに、紫外線照射による透過率劣化度も0.5%以下に抑えられており、非常に高い耐紫外線ソラリゼーション性を有していた。
【0040】
これに対し比較例であるNo.17、28の試料は紫外線照射による透過率劣化が大きく、No.16,29の試料は波長253.7nmの透過率が高いものであった。
【0041】
なお、上記実施例では、蛍光ランプ用ガラス管について説明したが、本発明に係る紫外線吸収ガラスは、たとえば、バルブ状に吹成して水銀ランプ等の外囲器に使用しても、光源からの有害紫外線を有効にカットし、紫外線によるガラスの着色がない優れた特性を有し、その他にも耐熱性、耐紫外線性を要求される様々な形状・用途に用いることができる。また、本発明に係るガラスは、環境有害物質であるPbOを含有しなくとも充分な紫外線カット特性及び耐紫外線ソラリゼーション性を有するため、環境負荷の低減にも貢献できる。
【0042】
【発明の効果】
以上のように本発明の紫外線吸収ガラスは、紫外線カット特性に優れ、コバール合金との封着に適した熱膨張係数を持ち、しかも優れた耐紫外線ソラリゼーション性を有するため、紫外線発生を伴う光源の外囲器等に好適し、透過率の劣化を小さく抑えることができる。
【0043】
また、本発明の紫外線吸収ガラスを用いた蛍光ランプ用ガラス管は、紫外線カット特性にも優れているため、液晶ディスプレイ等の表示デバイスのバックライト用蛍光ランプに用いた場合でも表示装置内部の樹脂部品等の材質を劣化させることがなく、表示装置の経時特性、信頼性を向上させる。[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to an ultraviolet absorbing glass, and is a glass suitable for a glass tube for a fluorescent lamp used for a backlight of a display device such as a liquid crystal display (hereinafter, referred to as LCD). And a glass tube for a fluorescent lamp using the glass.
[0002]
[Prior art]
In recent years, LCDs have been widely used as key devices for multimedia-related equipment, but with the expansion of their applications, there are demands for weight reduction, thickness reduction, high brightness, low power consumption, and the like. In particular, high-quality display quality is required for personal computer displays, in-vehicle display devices, portable information terminals, and the like. On the other hand, since the liquid crystal display element itself does not emit light, a transmissive liquid crystal display element using a backlight using a fluorescent lamp as a light source is used in the above-described applications.
[0003]
As described above, LCDs are required to be lighter, thinner, higher brightness, lower power consumption, etc., so the backlight is also becoming smaller, lighter, higher brightness, and lower power consumption. Accordingly, the fluorescent lamps for backlights are becoming thinner and thinner.
[0004]
However, the thinning and thinning of the fluorescent lamp cause a decrease in mechanical strength and an increase in the temperature of the electrode part due to an increase in the amount of heat generated. For this reason, the glass tube used for the fluorescent lamp for backlights requires glass having higher strength and lower expansion.
[0005]
Conventionally, as a glass tube of this type of fluorescent lamp, lead soda-based soft glass having a track record as illumination glass and excellent workability has been used. However, as the tube diameter and wall thickness become smaller in backlight applications, it becomes difficult to ensure sufficient strength and heat resistance in terms of product reliability, which is more thermal and mechanical than lead soda-based soft glass. It has been studied to produce a fluorescent lamp using a high-strength borosilicate hard glass, and a well-known Kovar alloy and Kovar sealing glass or tungsten as a combination of a metal and a hard glass that can be hermetically sealed. And fluorescent lamps using tungsten sealing glass have been developed and commercialized. Here, “Kovar” is a trade name of Westinghouse Ele. Corp. indicating an Fe—Ni—Co-based alloy, and is used to include equivalent products of other companies such as KOV (trade name) manufactured by Toshiba.
[0006]
[Problems to be solved by the invention]
The light emission principle of the fluorescent lamp for the backlight is the same as that of the general illumination fluorescent lamp. Mercury vapor or xenon gas excited by the inter-electrode discharge in the fluorescent tube emits 253.7 nm ultraviolet light and is applied to the inner wall surface of the tube. This is because the phosphor emits light. However, it is known that ultraviolet rays have a function of causing discoloration in glass, and in a glass that does not take any measures against ultraviolet rays, a discoloration action called solarization is caused by ultraviolet irradiation. When solarization occurs in the fluorescent tube glass, the result is a decrease in lamp brightness and a discoloration of the emission color, and in the backlight, the display quality is degraded, such as the LCD display becoming dark or the display color becoming unclear. Further, when ultraviolet rays pass through the backlight glass tube and are emitted to the outside of the tube, there is a problem of accelerating material deterioration of resin parts and the like inside the LCD display device.
[0007]
As a backlight system that is particularly advantageous for thin and light display devices, a light source is arranged on the side end face of the transparent light guide, and one surface of the light guide is reflected and diffused to make multiple reflections of light. The edge light method is known, but this method requires a light guide due to its structure, and the light guide uses resin parts such as acrylic resin for weight reduction. Ultraviolet light leakage from the light source for light causes a decrease in light transmittance due to deterioration and coloring of the light guide, and if the resin deteriorates in the vicinity of the light source, the brightness of the entire display surface decreases. The effect on display quality is great along with solarization.
[0008]
In the above lead soda-based glass, lead contained as a glass component had ultraviolet solarization resistance and UV-cutting performance, so these did not pose a problem, but borosilicate Kovar sealing glass Glass for sealing tungsten and tungsten was originally used for sealing electron tubes and electronic components. No countermeasures were taken against the effects of ultraviolet rays as a glass material, and there were problems of ultraviolet solarization and ultraviolet transmission. It was inevitable.
[0009]
For this reason, when using conventional Kovar sealing glass or tungsten sealing glass for an outer tube for a fluorescent lamp, coating the inner surface of the glass tube with Al 2 O 3 or TiO 2 that reflects or absorbs ultraviolet rays, On top of that, a measure is taken such that a phosphor is applied to form a multilayer film to reduce the intensity of ultraviolet rays reaching the glass. However, such a method inevitably increases the cost due to the difficulty in coating and the increase in the coating process as the diameter of the glass tube is reduced.
[0010]
From the above background, glasses disclosed in JP-A-8-333132 and JP-A-9-110467 have been proposed as glasses having a thermal expansion coefficient that can be sealed with Kovar alloy and having ultraviolet solarization resistance. ing. All of these glasses are provided with ultraviolet solarization resistance by adding at least one of PbO, TiO 2 and Sb 2 O 3 to borosilicate glass.
[0011]
Although these glasses eliminate the problem of solarization due to ultraviolet rays, any glass allows the inclusion of PbO, which is an environmentally hazardous substance, and is not preferable from the viewpoint of environmental protection. In addition, it cannot be said that sufficient consideration is given to UV protection when used as a fluorescent lamp, and it transmits harmful UV rays of 253.7 nm emitted by excited mercury or the like depending on the combination and content of the above-mentioned UV-proof solarization resistance-imparting components. There is a risk of deteriorating interior parts.
[0012]
The present invention has been made in view of the above circumstances, and is an ultraviolet absorbing glass that can be satisfactorily sealed with Kovar alloy or tungsten, has sufficient ultraviolet solarization resistance, and does not transmit harmful ultraviolet rays. And it aims at providing the glass tube for fluorescent lamps using the same.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an ultraviolet absorbing glass used for a glass tube for a fluorescent lamp, wherein the glass has a mass% of SiO 2. 55-78%, B 2 O 3 10 to 25%, Fe 2 O 3 0.001 to 0.05%, WO 3 + Nb 2 O 5 0.05 to 5%, ZrO 2 0.01 to 3%, and 50 ° C. to glass transition point ( Tg) is a borosilicate glass having an average linear expansion coefficient of 36 to 57 × 10 −7 / ° C. in the temperature range up to Tg), and the transmittance at a wavelength of 253.7 nm at a thickness of 1 mm is 1% or less. The degree of deterioration in the ultraviolet irradiation test is 3% or less. Here, the degree of deterioration in the ultraviolet irradiation test was determined by placing a 1 mm thick glass polished surface optically polished on both sides facing a position 20 cm from a 400 W high-pressure mercury lamp having a principal wavelength of 253.7 nm, After the irradiation, the transmittance (T 1 ) at a wavelength of 400 nm was measured, and the degree of deterioration from the initial transmittance (T 0 ) at a wavelength of 400 nm before ultraviolet irradiation was obtained by the following equation.
Degree of degradation (%) = [(T 0 −T 1 ) / T 0 ] × 100
[0014]
The reason why the above configuration is defined in the present invention will be described below. First, borosilicate glass is superior in mechanical strength and heat resistance compared to conventional lead soda-based soft glass, and is advantageous in reducing the diameter and thickness of fluorescent tubes. Use glass.
[0015]
Next, if the average linear expansion coefficient is 36 to 57 × 10 −7 / ° C. within this range, the average thermal expansion coefficient of Kovar alloy is 60.9 × 10 −7 / ° C. or the average thermal expansion coefficient of tungsten. It is possible to make the value relatively close to 45 × 10 −7 / ° C. and slightly lower than these sealing metals, and the expansion / contraction behavior below the fixing point of the glass is similar. Good and reliable sealing properties with the sealing metal can be obtained. In particular, the expansion curve of the Kovar alloy bends in the latter half of 400 ° C. Therefore, it is necessary to lower the glass transition point to approximate the expansion curve to the Kovar alloy, and the sealing property of the glass with the Kovar alloy is evaluated. Therefore, it is necessary to evaluate the thermal expansion coefficient up to this temperature range. If the average linear expansion coefficient is out of the above range, the consistency with Kovar is poor, and a reliable fluorescent lamp cannot be obtained due to cracks and leaks at the sealing portion.
[0016]
Further, Fe 2 O 3 0.001 to 0.05%, WO 3 + Nb 2 O 5 0.05 to 5%, ZrO 2 is added to the above borosilicate glass. The reason for containing 0.01 to 3% as an essential component is as follows. Fe 2 O 3 is added because it absorbs significantly ultraviolet rays. However, if it is less than the lower limit, no ultraviolet blocking effect is observed, and if it exceeds the upper limit, a negative effect on ultraviolet solarization resistance appears. More preferably, it is 0.003 to 0.03%.
[0017]
WO 3 and Nb 2 O 5 are added for the purpose of imparting UV solarization resistance and UV-cutting performance. However, if the total amount exceeds 5%, the glass tends to be devitrified and the uniformity is deteriorated. At the same time, the batch cost is extremely increased, which is not preferable from an economic viewpoint. On the other hand, if it is less than 0.05%, characteristics such as ultraviolet solarization resistance and ultraviolet cut performance cannot be obtained sufficiently. The addition amount in the total amount of these components is preferably 0.1 to 5%, more preferably 0.1 to 3%. Since WO 3 and Nb 2 O 5 are particularly effective in suppressing solarization due to ultraviolet rays, either WO 3 or Nb 2 O 5 is an essential component. Preferred content of each component in the case of containing alone, WO 3 is 0.05 to 5%, more preferably 0.1 to 3% Nb 2 O 5 is from 0.05 to 5%, more preferably 0 0.1 to 3% of range. In addition, when the content of each of the WO 3 and Nb 2 O 5 components alone is increased, the glass tends to be colored due to inherent absorption. Therefore, within the more preferable range of each component, WO 3 and Nb 2 O It is preferable to add 5 together. As a result, the effect of preventing solarization is further strengthened, and a glass that does not give unnecessary coloring can be obtained.
[0018]
ZrO 2 Can be expected to improve the chemical durability of the glass and suppress phase separation, but if its content is less than 0.01%, the effect is not sufficient, and if it exceeds 3%, the glass tends to be non-uniform. This is not preferable because the thickness and dimensional accuracy vary when formed into a thin tube. In particular, when the borosilicate glass contains a component that may give color to the glass, such as Fe 2 O 3 , WO 3 , Nb 2 O 5 , Bi 2 O 3 , CeO 2 , the glass in the melt molding process. When phase separation occurs in the glass, coloring may appear starting from the phase separation portion. Therefore, in the present invention, it is a necessary component for preventing coloration of the glass.
[0019]
In addition, when the glass of the present invention is used for a backlight fluorescent lamp such as an LCD display device as described above, if ultraviolet rays are transmitted through the glass tube and emitted outside the tube, resin parts inside the LCD display device, etc. In the present invention, ultraviolet rays are cut by the above components and the glass is optically polished to a thickness of 1 mm at a wavelength of 253.7 nm. The ultraviolet transmittance is 1% or less. Although the glass thickness in an actual fluorescent lamp is even thinner, there is no practical problem as long as UV transmission is suppressed to this extent. If a more desirable quality level is desired without affecting visible light transmission, the thickness can be reduced to 0.1% or less at a thickness of 1 mm.
[0020]
In the present invention, the reason why the degree of deterioration in the ultraviolet irradiation test is determined as described above is as follows. Usually, in the accelerated test in which the glass is exposed to the vicinity of a strong ultraviolet ray source, the coloring tendency (whether it is easy to color) can be confirmed in 1 hour to several hours, but the degree gradually decreases after 100 hours. When 300 hours have elapsed, it is possible to confirm a state that is almost close to the limit of coloring due to solarization. For this reason, the influence of the transmittance | permeability fall at the time of long-term use in a real product can be grasped | ascertained more correctly. As the transmittance evaluation wavelength 400 nm at this time, a wavelength considered to have the most influence on brightness was selected. If the degree of transmittance deterioration in a test under such conditions is 3% or less, the darkening of the LCD display caused by the glass tube for a fluorescent lamp can be suppressed to a level that the user cannot recognize, which is practical. Display quality can be maintained.
[0021]
Further, according to the present invention, the borosilicate glass is, by mass%, SiO 2 65 to 78%, Al 2 O 3 3 to 10%, B 2 O 3 10 to 25%, Li 2 O + Na 2 O + K 2 O 5. ~12%, Fe 2 O 3 0.001 to 0.03%, WO 3 + Nb 2 O 5 0.05 to 5%, ZrO 2 It contains 0.01 to 3%, and an average linear expansion coefficient in a temperature range from 30 ° C. to 400 ° C. is 36 to 45 × 10 −7 / ° C.
[0022]
Further, the present invention, the borosilicate glass, in mass%, SiO 2 55~70%, Al 2 O 3 1~5%, B 2 O 3 10~25%, Li 2 O + Na 2 O + K 2 O 8 ~15%, Fe 2 O 3 0.001 to 0.03%, WO 3 + Nb 2 O 5 0.05 to 5%, ZrO 2 It contains 0.01 to 3%, and the average linear expansion coefficient in the temperature range from 50 ° C. to the glass transition point (Tg) is 46 to 57 × 10 −7 / ° C. Here, the reason which limited content of each component as mentioned above is demonstrated below.
[0023]
SiO 2 is a glass network-forming component. However, if it exceeds 78%, the meltability and workability of the glass deteriorate, and if it is less than 55%, the chemical durability of the glass decreases. A decrease in chemical durability causes weathering, burns, etc., and causes a decrease in luminance and color unevenness of the fluorescent lamp. Moreover, when using it for the use sealed with a Kovar alloy, it is preferable to set it as 65-78% when using it for the use sealed with tungsten. As a result, the linear expansion coefficient of the glass is maintained at an appropriate value approximate to that of each sealing metal, and sealing without leaks, cracks and the like is enabled.
[0024]
Al 2 O 3 has the effect of improving the chemical durability of the glass. However, if it exceeds 10%, problems such as the occurrence of striae will occur in the meltability, and devitrification in the sleeve part will occur when the tube is formed by the Danner method. Cause. On the other hand, if it is less than 1%, phase separation occurs, which causes a problem in formability and lowers the chemical durability of the glass. Preferably it is 1 to 7% of range. Moreover, when using it for the use sealed with a Kovar alloy, it is more preferable to set it as 4 to 7% when using it for the use sealed with tungsten.
[0025]
B 2 O 3 is a component used for the purpose of improving the meltability and adjusting the viscosity. However, if it exceeds 25%, the chemical durability of the glass is lowered, and weathering occurs due to long-term use. On the other hand, if the B 2 O 3 content is less than 10%, problems such as poor meltability and poor sealability with Kovar due to increased viscosity are caused. Preferably it is 12 to 24%.
[0026]
Li 2 O, Na 2 O, and K 2 O are components that act as fluxes, improve the meltability of the glass, and are used to adjust the viscosity and thermal expansion coefficient. The total amount of these components is 15%. If it exceeds 1, the thermal expansion coefficient becomes too large and the chemical durability deteriorates. On the other hand, if it is less than 5%, it will be difficult to seal with Kovar with a significant decrease in expansion coefficient and a significant increase in viscosity. The content of each component, 0 to 5% of Li 2 O, 0 to 8% of Na 2 O, it is preferred to 2-12% of K 2 O. When each content exceeds each upper limit, the thermal expansion coefficient becomes too large, or the chemical durability is deteriorated. It is also known that Na 2 O reacts with mercury to form amalgam during the operation of the fluorescent lamp, and excessive Na 2 O in the glass results in a reduction in the amount of mercury that acts effectively in the fluorescent lamp. Therefore, also from the environmental viewpoint of reducing the amount of mercury used, addition of Na 2 O exceeding the above upper limit is not preferable, and more preferably 0 to 4.5%. Moreover, when using it for the use sealed with Kovar alloy, it is preferable to set it as 5 to 12% when using for the use sealed with tungsten. If it is less than each lower limit value, the expansion coefficient is significantly reduced, and a satisfactory increase in viscosity cannot be achieved with Kovar alloy or tungsten. Note that Fe 2 O 3 , Sb 2 O 3 and ZrO 2 are as described above.
[0027]
Moreover, this invention is a glass tube for fluorescent lamps formed by shape | molding the said ultraviolet absorption glass in the shape of a tube. As described above, the glass according to the present invention is excellent in sealing property with Kovar alloy and has sufficient UV solarization resistance and UV absorption, so that there is no UV leakage from the fluorescent lamp, and the lamp is colored by UV coloring of the glass. A glass tube for a fluorescent lamp is obtained in which the luminance and color rendering are not easily impaired. The glass tube has an outer diameter of 0.7 to 5 mm and a thickness of 0.07 to 0.6 mm, and is used as a light source for a backlight of a display device. If the outer diameter and wall thickness exceed the above upper limits, it will not be possible to meet the demands for reducing the thickness and weight of current products using backlights. If the outer diameter and wall thickness are less than the lower limits, molding accuracy will be stable and impact strength will be reduced. It becomes difficult to supply a product with sufficient reliability at a low price.
[0028]
Furthermore, the present invention is suitably used for an edge light type backlight light source that irradiates a display surface through a light guide. As described above, the glass tube for a fluorescent lamp of the present invention is excellent in ultraviolet absorption performance. Therefore, even when it is used for a light source for an edge-light type backlight using a resin light guide, the light guide is deteriorated by ultraviolet light. It is difficult to cause a decrease in transmittance, and the initial brightness can be maintained for a long time.
[0029]
The fining agent used for melting the glass of the present invention is not particularly limited, and commonly used Sb 2 O 3 , NaCl, Na 2 SO 4 and the like can be used. However, if Sb 2 O 3 content is increased, it will cause the glass to blacken during heat processing such as metal sealing, and this will cause a decrease in the brightness of the fluorescent lamp, discoloration of the emission color, and color unevenness. is there.
[0030]
Furthermore, components such as ZnO, CaO, MgO, SrO, P 2 O 5 and F − are added within the range not impairing the intended characteristics of the present invention for the purpose of improving the weather resistance, meltability, devitrification, etc. of the glass. It is also possible to add.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The glass of the present invention and the glass tube for a fluorescent lamp using the glass can be produced as follows. First, the above composition range, for example, SiO 2 68%, Al 2 O 3 3.5%, Li 2 O 1%, Na 2 O 0.5%, K 2 O 8.3%, B 2 O 3 18%, WO 3 0.2%, Sb 2 O 3 0.3%, ZrO 2 Known tube drawing, such as 0.2%, Fe 2 O 3 0.01%, and the raw material mixture weighed and mixed in a melting furnace is heated and melted in a melting furnace to redraw the glass once formed into a tubular shape. A fluorescent tube glass tube having a desired outer diameter and thickness is obtained by a molding method.
[0032]
【Example】
Next, the glass tube for a fluorescent lamp of the present invention will be described in detail based on examples. Tables 1 to 3 show examples and comparative examples of the present invention. Sample No. Nos. 1 to 15 are examples of the present invention assuming sealing with a Kovar alloy, 16 and 17 are comparative examples, and Nos. 18 to 27 are examples in which sealing with tungsten is assumed. 28 and 29 are comparative examples. In addition, the composition in a table | surface is shown by the mass%. The glass listed in the table is prepared by weighing and mixing raw materials such as silica sand, carbonates, nitrates, and hydroxides of the respective metals so that the oxide composition shown in the table is obtained, and then refining the platinum by the refining method selected according to the components contained therein. It was melted at 1450 ° C. for 5 hours using a crucible or a quartz crucible. Thereafter, the sufficiently stirred and clarified glass was allowed to flow out into the rectangular frame, and after slow cooling, a sample processed into a desired shape according to the evaluation items shown below was created. In the case of oxidation clarification, Sb 2 O 3 was used as a clarifier, and in the case of reduction clarification, NaCl was used as a clarifier.
[0033]
The items shown in the table will be described. The thermal expansion coefficient and the glass transition point were measured with a thermomechanical analyzer (TMA) using samples obtained by processing each glass into a cylinder having a diameter of 4 mm and a length of 20 mm. At this time, for the thermal expansion coefficient, the average linear expansion coefficient in the temperature range described later was measured, and for the Kovar alloy, the average linear expansion coefficient of the metal in the same temperature range was also described. If the difference in coefficient of thermal expansion between the glass and the sealing metal becomes large, it may cause leaks and cracks from the sealing part and cannot be used for fluorescent lamps. In particular, since the expansion curve of the Kovar alloy bends in the upper 400 ° C range, it is necessary to lower the glass transition point and approximate the expansion curve to the Kovar alloy, and evaluate the sealing property of the glass with the Kovar alloy. In order to achieve this, it is preferable that the thermal expansion coefficient up to this temperature range is equal to or slightly lower than that of the Kovar alloy. For this reason, Example No. assuming sealing with Kovar alloy. The glass of 1-15 evaluated the thermal expansion coefficient in the temperature range from 50 degreeC including this temperature range to the transition point (Tg) of each glass. On the other hand, in Example No. assuming sealing with tungsten. 18-27 glass evaluated the thermal expansion coefficient in the temperature range of 30-400 degreeC.
[0034]
The degree of transmittance deterioration by the ultraviolet solarization resistance test was determined by cutting each glass sample into a 30 mm square plate and performing double-sided optical polishing so that the thickness was 1 mm, and a 400 W high pressure with a main wavelength of 253.7 nm. The polishing surface is placed 20 cm away from the mercury lamp and irradiated with ultraviolet rays for 300 hours, and then the transmittance (T 1 ) at a wavelength of 400 nm is measured, and the initial transmittance (T 0 ) at a wavelength of 400 nm before ultraviolet irradiation. ) As the transmittance deterioration degree, and is indicated by a value obtained by the deterioration degree (%) = [(T 0 −T 1 ) / T 0 ] × 100.
[0035]
In addition, the values obtained by measuring the transmittance at a wavelength of 253.7 nm in the sample before being subjected to the ultraviolet solarization resistance test are also shown.
[0036]
[Table 1]
[0037]
[Table 2]
[0038]
[Table 3]
[0039]
As is apparent from the table, No. 1 as an example of the present invention. Each of the samples 1 to 15 has a coefficient of thermal expansion that is relatively close to the average coefficient of thermal expansion of Kovar 60.9 × 10 −7 / ° C., and is slightly lower than that of Kovar alloy. Since the expansion and contraction behaviors below the fixing point of the glass are similar, a good and reliable sealing property with the Kovar alloy can be obtained. In addition, No. which is an embodiment of the present invention. Each of the samples 18 to 27 has a coefficient of thermal expansion that is relatively close to an average thermal expansion coefficient of 45 × 10 −7 / ° C. of tungsten and is slightly lower than that of tungsten. Good and reliable sealing performance. Moreover, the transmittance | permeability of wavelength 253.7nm is very low, and hardly transmits harmful ultraviolet rays. Furthermore, the degree of transmittance deterioration due to ultraviolet irradiation was also suppressed to 0.5% or less, and it had very high resistance to ultraviolet solarization.
[0040]
On the other hand, No. which is a comparative example. Samples Nos. 17 and 28 have large transmittance deterioration due to ultraviolet irradiation. Samples 16 and 29 had high transmittance at a wavelength of 253.7 nm.
[0041]
In addition, although the glass tube for fluorescent lamps has been described in the above embodiment, the ultraviolet absorbing glass according to the present invention can be used, for example, from a light source even when blown into a bulb shape and used in an envelope such as a mercury lamp. It effectively cuts harmful UV rays, has excellent characteristics that the glass is not colored by UV rays, and can be used in various shapes and applications that require heat resistance and UV resistance. In addition, the glass according to the present invention has sufficient ultraviolet cut characteristics and ultraviolet solarization resistance even without containing PbO, which is an environmentally hazardous substance, and thus can contribute to a reduction in environmental load.
[0042]
【The invention's effect】
As described above, the UV-absorbing glass of the present invention is excellent in UV-cutting properties, has a thermal expansion coefficient suitable for sealing with Kovar alloy, and has excellent UV solarization resistance. It is suitable for an envelope or the like, and the deterioration of transmittance can be suppressed to a small level.
[0043]
In addition, since the glass tube for a fluorescent lamp using the ultraviolet absorbing glass of the present invention is excellent also in the ultraviolet cut characteristic, even when used in a fluorescent lamp for a backlight of a display device such as a liquid crystal display, the resin inside the display device The time-dependent characteristics and reliability of the display device are improved without deteriorating the material such as parts.
Claims (7)
ただし、前記紫外線照射試験における劣化度は、両面を光学研磨した肉厚1mmのガラス研摩面を主波長253.7nmの400W高圧水銀ランプから20cmの位置に対向させて配置し、300時間紫外線を照射した後、波長400nmにおける透過率(T1)を測定し、紫外線照射前の波長400nmにおける初期透過率(T0)からの劣化度を次式により求めたもの。
劣化度(%)=[(T0−T1)/T0]×100 It is an ultraviolet absorbing glass used for a glass tube for a fluorescent lamp , and is SiO 2 in mass%. 55-78%, B 2 O 3 10 to 25%, Fe 2 O 3 0.001 to 0.05%, WO 3 + Nb 2 O 5 0.05 to 5%, ZrO 2 0.01 to 3%, and the average linear expansion coefficient is 36 to It is made of borosilicate glass at 57 × 10 −7 / ° C., has a transmittance of 1% or less at a thickness of 1 mm at a wavelength of 253.7 nm, and a deterioration degree of 3% or less in the following ultraviolet irradiation test. Ultraviolet absorbing glass characterized by
However, the degree of deterioration in the ultraviolet irradiation test was determined by placing a 1 mm thick glass polished surface optically polished on both sides facing a 20 cm position from a 400 W high-pressure mercury lamp with a principal wavelength of 253.7 nm and irradiating with ultraviolet rays for 300 hours. Then, the transmittance (T 1 ) at a wavelength of 400 nm was measured, and the degree of deterioration from the initial transmittance (T 0 ) at a wavelength of 400 nm before ultraviolet irradiation was obtained by the following equation.
Degree of degradation (%) = [(T 0 −T 1 ) / T 0 ] × 100
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JP2002293571A (en) * | 2001-03-30 | 2002-10-09 | Nippon Electric Glass Co Ltd | Glass for illumination |
US7517822B2 (en) | 2002-05-16 | 2009-04-14 | Schott Ag | UV-blocking borosilicate glass, the use of the same, and a fluorescent lamp |
TW200500314A (en) * | 2003-05-30 | 2005-01-01 | Asahi Glass Co Ltd | Glass sheet for display substrate |
JP2005041729A (en) * | 2003-07-28 | 2005-02-17 | Nippon Electric Glass Co Ltd | Illuminating glass |
DE202005004487U1 (en) * | 2004-07-12 | 2005-11-24 | Schott Ag | System for backlighting displays or screens |
JP2006089342A (en) * | 2004-09-24 | 2006-04-06 | Asahi Techno Glass Corp | Glass for fluorescent lamp |
WO2006090801A1 (en) * | 2005-02-25 | 2006-08-31 | Japan Science And Technology Agency | Glass composition containing bismuth and method of amplifying signal light therewith |
WO2006103942A1 (en) | 2005-03-25 | 2006-10-05 | Asahi Techno Glass Corporation | Ultraviolet absorbing glass, glass tube for fluorescent lamp using same, and method for producing ultraviolet absorbing glass for fluorescent lamp |
JP2007210851A (en) * | 2006-02-10 | 2007-08-23 | Asahi Techno Glass Corp | Glass tube for fluorescent lamp |
JP5540506B2 (en) * | 2009-01-16 | 2014-07-02 | 旭硝子株式会社 | Window glass for solid-state image sensor package |
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