JP4044213B2 - Optical glass - Google Patents
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- JP4044213B2 JP4044213B2 JP17672098A JP17672098A JP4044213B2 JP 4044213 B2 JP4044213 B2 JP 4044213B2 JP 17672098 A JP17672098 A JP 17672098A JP 17672098 A JP17672098 A JP 17672098A JP 4044213 B2 JP4044213 B2 JP 4044213B2
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【０００１】
【発明の属する技術分野】
本発明は、屈折率（ｎｄ）が１．６７〜１．７４未満、アッベ数（νｄ）が３５〜４５未満の範囲の光学定数を有し、耐失透性および化学的耐久性に優れ、プレス成形後、研削ないし研磨を必要とせずに光学素子を直接得ることができるモールドプレス成形に使用するのに適した新規な特定組成範囲のＢ2Ｏ3−ＳｉＯ2−Ｌｉ2Ｏ−ＣａＯ−Ｌａ2Ｏ3−ＴｉＯ2−ＺｒＯ2−Ｎｂ2Ｏ5系の光学ガラスに関する。
【０００２】
【従来の技術】
従来、前記範囲に近い光学定数を有するガラスとして、特公昭５３−４２３２７号公報には、ＳｉＯ2−ＣａＯ−Ｒ2Ｏ−ＴｉＯ2−Ｎｂ2Ｏ5系の眼鏡レンズ用ガラスが開示されているが、このガラスは、耐失透性が悪いため量産するには適していない。また、特公平５−３７９３５号公報には、Ｂ2Ｏ3−ＳｉＯ2−Ｌｉ2Ｏ−ＣａＯ−Ｌａ2Ｏ3−ＴｉＯ2−ＺｒＯ2−Ｎｂ2Ｏ5系のガラスが開示されているが、このガラスは、耐失透性および化学的耐久性が悪いうえ、平均線熱膨張係数が大きいため、加熱軟化したガラスをプレス成形して得たガラス成形品を冷却する際に、熱収縮により成形品が割れたり、成形面がガラス内部の熱収縮により引っ張られてへこむ現象、いわゆるヒケが生じたりするという問題点がある。また、特開昭５７−５１１４９号公報には、ＳｉＯ2−Ｂ2Ｏ3−Ｒ2Ｏ−ＣａＯ−ＴｉＯ2系のガラスが開示されているが、このガラスは、化学的耐久性は優れているものの、耐失透性が悪く、また、平均線熱膨張係数が充分に小さいとは言えず、上述した割れやヒケの問題を解決するには至っていない。
【０００３】
また、特開昭６０−２２１３３８号公報には、Ｂ2Ｏ3−Ｌａ2Ｏ3−Ｙ2Ｏ3−２価金属酸化物−Ｌｉ2Ｏ系のガラスが開示されている。このガラスは、金型の寿命を延ばす目的で低転移温度特性が付与されており、また、原料経済性に優れたガラスとするために、原料コストの高いＧｄ2Ｏ3およびＴａ2Ｏ5を任意成分としているが、Ｇｄ2Ｏ3およびＴａ2Ｏ5と同様に原料コストが高いＹ2Ｏ3を必須成分として含有しているため、原料経済性の向上が充分になされているとは言い難い。さらに、同号公報は、平均線熱膨張係数について何も記載しておらず、上述した割れやヒケの問題を解決する手段を示していない。また、特開昭５４−１６１６１９号公報には、ＳｉＯ2−Ｂ2Ｏ3−ＭｇＯおよび／またはＣａＯ−ＴｉＯ2−Ｌａ2Ｏ3−ＢａＯおよび／またはＳｒＯ系の眼鏡レンズ用ガラスが開示されているが、このガラスは、着色性が強い欠点があるうえ、屈折率（ｎｄ）が１．７７〜１．８１と本発明が目的とする屈折率の範囲と比べてかなり高い範囲にある。
【０００４】
【発明が解決しようとする課題】
本発明の目的は、上記従来技術の有する問題点を総合的に解決し、前記所望範囲の光学定数を有し、耐失透性および化学的耐久性に優れ、プレス成形後の冷却時に、成形品に熱収縮による割れやヒケ等の不良を生じることがなく、かつ、原料コストが安く経済性に優れた光学ガラスを提供することにある。
【０００５】
【課題を解決するための手段】
本発明者は、上記目的を達成するため鋭意試験研究を重ねた結果、ガラス形成酸化物の含有量を特定の範囲に限定した特定組成範囲のＢ2Ｏ3−ＳｉＯ2−Ｌｉ2Ｏ−ＣａＯ−Ｌａ2Ｏ3−ＴｉＯ2−ＺｒＯ2−Ｎｂ2Ｏ5系のガラスにおいて、前記所望範囲の光学定数を有し、耐失透性および化学的耐久性に優れ、プレス成形したガラス成形品を冷却する際、成形品に熱収縮による割れやヒケが生じず、かつ、プレス成形に適した粘性を有するガラスが得られることを見出し、本発明をなすに至った。
【０００６】
すなわち、上記目的を達成するための本発明の請求項１に記載の光学ガラスの特徴は、重量％で、Ｂ2Ｏ3 ２０．５〜３５％、ＳｉＯ2 １７．５〜３０％、ただし、Ｂ2Ｏ3＋ＳｉＯ2 ４２〜６０％、Ｌｉ2Ｏ ３．５〜７％、Ｎａ2Ｏ ０〜５％、Ｋ2Ｏ ０〜５％、ＭｇＯ ０〜１０％、ＣａＯ ９〜２３％、ＢａＯ ０〜４％、ＺｎＯ ０〜１０％、Ｌａ2Ｏ3 １５＜〜３０％、Ｇｄ2Ｏ3 ０〜１５％、ＴｉＯ2 ４〜１４％、ＺｒＯ2 １〜１０％、Ｎｂ2Ｏ5 １〜２０％、Ａｌ2Ｏ3 ０〜５％およびＳｂ2Ｏ3 ０〜１％の組成からなるところにある。
【０００７】
また、上記目的を達成するための本発明の請求項２に記載の光学ガラスの特徴は、重量％で、Ｂ2Ｏ3 ２１〜３５％、ＳｉＯ2 １８〜３０％、ただし、Ｂ2Ｏ3＋ＳｉＯ2 ４２〜６０％、Ｌｉ2Ｏ ３．５〜７％、Ｎａ2Ｏ ０〜５％、Ｋ2Ｏ ０〜５％、ＭｇＯ ０〜１０％、ＣａＯ １０〜２３％、ＢａＯ ０〜４％、ＺｎＯ ０〜１０％、Ｌａ2Ｏ3 １６〜２８％、Ｇｄ2Ｏ3 ０〜１５％、ＴｉＯ2 ４〜１３％、ＺｒＯ2 １〜１０％、Ｎｂ2Ｏ5 １〜２０％、Ａｌ2Ｏ3 ０〜５％およびＳｂ2Ｏ3 ０〜１％の組成からなり、屈折率（ｎｄ）が１．６７〜１．７４未満、アッベ数（νｄ）が３５〜４５未満の範囲の光学定数を有し、平均線熱膨張係数（α×１０-7／℃）が９０×１０-7／℃未満であるところにある。
【０００８】
【発明の実施の形態】
本発明にかかる光学ガラスの各成分の組成範囲を前記のとおり限定した理由は、次のとおりである。
Ｂ2Ｏ3成分は、ガラス形成酸化物であり、ガラスの屈折率を高めるために比較的多量のＬａ2Ｏ3成分を安定に導入するのに必要な成分であるが、Ｂ2Ｏ3成分の量が２０．５％未満ではガラスの失透傾向が大きくなってガラスが不安定になり、また、３５％を超えると、本発明の目標とする光学定数が得られなくなる。Ｂ2Ｏ3成分の量の特に好ましい範囲は２１〜３５％である。
【０００９】
ＳｉＯ2成分は、ガラス形成酸化物であり、ガラスの粘性を高め、プレス成形を容易にする効果があるが、その量が１７．５％未満では、上記効果が充分に得られず、プレス成形が難しくなるうえ、ガラスの化学的耐久性および耐失透性が悪化する。また、３０％を超えるとガラスの溶融性が悪くなるとともに失透傾向が大きくなる。ＳｉＯ2成分の量の特に好ましい範囲は、１８〜３０％である。また、Ｂ2Ｏ3およびＳｉＯ2成分の合計量が４２％未満では、ガラスの耐失透性および化学的耐久性が悪化するうえ、ガラスの平均線熱膨張係数が大きくなり、プレス成形したガラス成形品を冷却する際、熱収縮により成形品に割れやヒケが生じやすくなる。また、それらの成分の合計量が６０％を超えると、本発明の目標とする光学定数が得られなくなる。
【００１０】
Ｌｉ2Ｏ成分は、ガラス溶融の際、ＳｉＯ2原料の溶融を促進し、かつ、失透傾向を小さくする効果があり、上記効果を得るために３．５％以上含有させる必要があるが、７％を超えるとかえって失透傾向が大きくなり、また、ガラスの化学的耐久性が悪化する。
【００１１】
ＣａＯ成分は、失透傾向を抑制して安定なガラスを得るために９％以上含有させる必要があるが、２３％を超えるとかえって失透傾向が大きくなる。ＣａＯ成分の量の特に好ましい範囲は１０〜２３％である。
【００１２】
Ｌａ2Ｏ3成分は、ガラスの屈折率を高める効果がある成分であり、その量が１５％以下では本発明の目標とする光学定数が得られず、３０％を超えるとガラスの失透傾向が大きくなる。Ｌａ2Ｏ3成分の量の特に好ましい範囲は１６〜２８％である。
【００１３】
ＴｉＯ2成分は、ガラスの安定性を維持しつつ、屈折率を高める効果があるが、その量が４％未満では本発明の目標とする所望の光学定数を得ることができず、また、１４％を超えるとガラスの失透傾向が増大するうえ、着色が著しくなる。ＴｉＯ2成分の量は１３％までとすることが特に好ましい。
【００１４】
ＺｒＯ2成分は、ガラスの屈折率を高め、かつ、Ｎｂ2Ｏ5成分と共存させることにより、化学的耐久性を向上させる効果があるが、その量が１％未満ではそれらの効果が充分でなく、また、１０％を超えるとガラスの溶融性が悪化し、そのうえ失透傾向が増大する。
【００１５】
Ｎｂ2Ｏ5成分は、上述したＺｒＯ2成分と共存させることにより、ガラスの化学的耐久性を高める効果があり、本発明のガラスにおいて欠くことのできない成分であり、また、屈折率を高める効果もあり、上記共存効果を得るとともに、本発明の目標とする所望の光学定数を得るためには、１％以上含有させる必要があるが、本発明の目標とする屈折率を維持し、かつ、原料コストの上昇を抑えるためには、その量は２０％までとすべきである。
【００１６】
以下の各成分は、必要に応じて、本発明のガラスに任意に添加し得る。
Ｎａ2ＯおよびＫ2Ｏ成分は、いずれも、本発明の目標とする所望の屈折率を維持し得る範囲内で、ガラスの溶融性向上のため、それぞれ、５％まで添加できる。ＭｇＯ、ＢａＯおよびＺｎＯ成分は、いずれも、ガラスの耐失透性や化学的耐久性を悪化させない範囲内で、光学定数の調整のため、それぞれ、１０％、４％および１０％まで添加できる。Ｇｄ2Ｏ3成分は、光学定数の調整や、ガラスの耐失透性の改善のため添加し得るが、原料コストの上昇を抑えるためその量は１５％までとすべきであり、添加しないことが特に好ましい。Ａｌ2Ｏ3成分は、ガラスの化学的耐久性を向上させるとともに、粘性を高めプレス成形を容易にするが、その量が５％を超えるとガラスの失透傾向が増大する。Ｓｂ2Ｏ3成分は、ガラス溶融時に脱泡、清澄を促進する効果があるが、その量は１％までで充分である。
【００１７】
【実施例】
次に、本発明の光学ガラスにかかる実施例について説明する。本発明の光学ガラスの実施例（Ｎｏ．１〜Ｎｏ．１０）、前記従来のＢ2Ｏ3−ＳｉＯ2−Ｌｉ2Ｏ−ＣａＯ−Ｌａ2Ｏ3−ＴｉＯ2−ＺｒＯ2−Ｎｂ2Ｏ5系のガラスの比較例（Ｎｏ．ＡおよびＮｏ．Ｂ）および前記従来のＳｉＯ2−Ｂ2Ｏ3−Ｒ2Ｏ−ＣａＯ−ＴｉＯ2系のガラスの比較例（Ｎｏ．ＣおよびＮｏ．Ｄ）をこれらのガラスの屈折率（ｎｄ）、アッベ数（νｄ）および耐失透性試験結果とともに表１および表２に示した。表１および表２における耐失透性試験は、あらかじめ調合したガラス原料バッチを３００ｃｃの白金坩堝に投入し、電気炉中で各ガラス試料の溶融性の難易度に応じて１２００〜１３００℃で２時間溶融した後、降温して、各試料を９００℃および８５０℃でそれぞれ１時間保温した後、炉外に取り出して失透の有無を顕微鏡により観察したもので、その結果、失透が見られなかったガラス試料○印で、また、失透が見られたものは×印で示す。
【００１８】
また、上記実施例（Ｎｏ．１〜Ｎｏ．１０）および上記比較例（Ｎｏ．ＡおよびＮｏ．Ｂ）のガラスの耐酸性（ＳＲ値）を表３に示した。なお、上記ＳＲ値は、国際標準化機構 ＩＳＯ ８４２４：１９９６（Ｅ）の測定方法に準拠し、測定して得た結果を示したものである。ここでＳＲ値は所定の酸処理液中において、ガラス試料が０．１μｍの侵食を受けるのに要した時間（ｈ）によって等級付けした値である。表３中のＳＲ値＝５、５１および５３は、ｐＨ＝４．６の酢酸緩衝液を用いて０．１μｍの侵食を受けるのに要した時間（ｈ）が、それぞれ、ｈ＞１０、ｈ＝１〜１０およびｈ＜０．１であることを示す。したがって、ＳＲ値が小さいほどガラスの耐酸性は高く、化学的耐久性に優れていることを示す。
【００１９】
また、上記実施例（Ｎｏ．１〜Ｎｏ．３）および上記比較例（Ｎｏ．Ａ〜Ｎｏ．Ｄ）のガラスの１００〜３００℃の温度範囲における平均線熱膨張係数（α×１０-7／℃）を表４に示す。
【００２０】
【表１】
【表２】
【表３】
【表４】
上記表１および表２に見られるとおり、本発明の実施例のガラスは、いずれも、所望の範囲の光学定数を有し、かつ、上述した耐失透性試験結果の結果、失透が認められず、上記比較例のガラス（Ｎｏ．Ａ〜Ｎｏ．Ｄ）と比べて耐失透性が優れている。また、上記表３に見られるとおり、本発明の実施例のガラスは、いずれも、上記比較例のガラス（Ｎｏ．ＡおよびＮｏ．Ｂ）と比べて、ＳＲ値が小さく、耐酸性が高く、化学的耐久性が優れている。
さらに、上記表４に見られるとおり、本発明の実施例のガラス（Ｎｏ．１〜Ｎｏ．３）は、いずれも、上記比較例のガラス（Ｎｏ．Ａ〜Ｎｏ．Ｄ）と比べて平均線熱膨張係数（α×１０-7／℃）が小さく、比較例の従来のガラスと比べて、加熱軟化したガラスをプレス成形した後の冷却時におけるガラスの熱収縮が小さいことが分かる。
以上、表１〜表４に見られるとおり、本発明の実施例のガラスは、優れた化学的耐久性を維持しつつ、比較例の従来のガラスよりも、耐失透性が優れ、かつ、小さい平均線熱膨張係数（α×１０-7／℃）を有しており、比較例の従来のガラスの欠点が総合的に改善されていることが分かる。
【００２５】
なお、本発明の上記実施例のガラスは、酸化物、炭酸塩、硝酸塩等の通常の光学ガラス用原料を秤量混合し、これを白金坩堝等を用いて、約１２００℃〜１３００℃で、約３〜４時間、溶融、清燈し、攪拌、均質化した後、予熱した型に鋳込み、徐冷することにより容易に製造することができる。また、上記実施例のガラスは、いずれも、溶融性に優れ、泡、脈理のない高均質のガラスを容易に得ることができるうえ、適度に高い粘性を有しているため、プレス成形作業も容易に行うことができる。
【００２６】
【発明の効果】
上述のとおり、本発明にかかる光学ガラスは、ガラス形成酸化物の含有量を特定の範囲に限定した特定組成範囲のＢ2Ｏ3−ＳｉＯ2−Ｌｉ2Ｏ−ＣａＯ−Ｌａ2Ｏ3−ＴｉＯ2−ＺｒＯ2−Ｎｂ2Ｏ5系のガラスであるから、前記所望範囲の光学定数を有し、耐失透性および化学的耐久性に優れ、適度に高い粘性を有しているため、プレス成形が容易であるうえ、平均線熱膨張係数（α×１０-7／℃）が小さいため、プレス成形したガラス成形品を冷却する際、成形品に熱収縮による割れやヒケが生じず、プレス成形歩留まりを向上せることができる。また、溶融性が優れているため、泡、脈理等のない均質なガラスを容易に製造することができきるうえ、Ｙ2Ｏ3のように原料価格の高い成分や、ＰｂＯやＡｓ2Ｏ3のように環境対策上の廃棄物処理に高いコストを要する成分を含有していないので、製造コストや廃棄物処理コストの点でも有利である。[0001]
BACKGROUND OF THE INVENTION
The present invention has an optical constant with a refractive index (nd) of less than 1.67 to 1.74 and an Abbe number (νd) of less than 35 to 45, and is excellent in devitrification resistance and chemical durability. B 2 O 3 —SiO 2 —Li 2 O—CaO— having a novel specific composition range suitable for use in mold press molding in which an optical element can be directly obtained without requiring grinding or polishing after press molding la 2 O 3 -TiO 2 -ZrO 2 -Nb 2 O 5 systems for optical glass.
[0002]
[Prior art]
Conventionally, as a glass having optical constants close to the range, in JP-B-53-42327, glass SiO 2 -CaO-R 2 O- TiO 2 -Nb 2 O 5 system of the spectacle lens is disclosed However, this glass is not suitable for mass production because of its poor devitrification resistance. Further, Japanese Patent Kokoku 5-37935, B 2 is O 3 -SiO 2 -Li 2 O- CaO-La 2 O 3 -TiO 2 -ZrO 2 -Nb 2 O 5 based glass is disclosed This glass has poor devitrification resistance and chemical durability, and also has a large average linear thermal expansion coefficient. Therefore, when glass molded products obtained by press-molding heat-softened glass are cooled, the glass shrinks due to thermal shrinkage. There is a problem that the molded product is broken or a phenomenon that the molding surface is pulled due to thermal contraction inside the glass, that is, a so-called sink occurs. Japanese Patent Application Laid-Open No. 57-51149 discloses SiO 2 —B 2 O 3 —R 2 O—CaO—TiO 2 glass, which is excellent in chemical durability. However, the devitrification resistance is poor, and the average linear thermal expansion coefficient cannot be said to be sufficiently small, so that the above-described problems of cracks and sink marks have not been solved.
[0003]
JP-A-60-221338 discloses a B 2 O 3 —La 2 O 3 —Y 2 O 3 -divalent metal oxide—Li 2 O glass. This glass is provided with a low transition temperature characteristic for the purpose of extending the life of the mold, and Gd 2 O 3 and Ta 2 O 5, which have high raw material costs, are used in order to make the glass excellent in raw material economics. Although it is an optional component, it contains Y 2 O 3, which has a high raw material cost as an essential component, as in Gd 2 O 3 and Ta 2 O 5 , so it is said that the raw material economy has been sufficiently improved. hard. Further, the publication does not describe anything about the average linear thermal expansion coefficient, and does not indicate means for solving the above-described problems of cracks and sink marks. Japanese Patent Application Laid-Open No. 54-161619 discloses SiO 2 —B 2 O 3 —MgO and / or CaO—TiO 2 —La 2 O 3 —BaO and / or SrO-based glasses lenses. However, this glass has a drawback that it has a strong coloring property and has a refractive index (nd) of 1.77 to 1.81, which is considerably higher than the target refractive index range of the present invention.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to comprehensively solve the above-mentioned problems of the prior art, have an optical constant in the above desired range, excellent in devitrification resistance and chemical durability, and molded during cooling after press molding. An object of the present invention is to provide an optical glass that does not cause defects such as cracks and sink marks due to heat shrinkage, has low raw material costs, and is economical.
[0005]
[Means for Solving the Problems]
The present inventor has conducted extensive research to achieve the above object, a specific composition range for limiting the content of the glass-forming oxides in a specific range B 2 O 3 -SiO 2 -Li 2 O-CaO in -La 2 O 3 -TiO 2 -ZrO 2 -Nb 2 O 5 based glass, has optical constants of the desired range, the devitrification resistance and excellent chemical durability, a glass molded article obtained by press molding Upon cooling, the present inventors have found that a glass having a viscosity suitable for press molding can be obtained without cracking or sinking due to heat shrinkage in the molded product.
[0006]
That is, the optical glass according to claim 1 of the present invention for achieving the above object is characterized in that, by weight, B 2 O 3 20.5 to 35%, SiO 2 17.5 to 30%, B 2 O 3 + SiO 2 42~60 %, Li 2 O 3.5~7%, Na 2 O 0~5%, K 2 O 0~5%, 0~10% MgO, CaO 9~23%, BaO 0~4%, 0~10% ZnO, La 2 O 3 15 <~30%, Gd 2 O 3 0~15%, TiO 2 4~14%, ZrO 2 1~10%, Nb 2 O 5 1~ 20%, Al 2 O 3 0-5% and Sb 2 O 3 0-1%.
[0007]
The feature of the optical glass according to claim 2 of the present invention for achieving the above object, in weight%, B 2 O 3 21~35% , SiO 2 18~30%, however, B 2 O 3 + SiO 2 42~60%, Li 2 O 3.5~7%, Na 2 O 0~5%, K 2 O 0~5%, 0~10% MgO, CaO 10~23%, BaO 0~4% ZnO 0-10%, La 2 O 3 16-28%, Gd 2 O 3 0-15%, TiO 2 4-13%, ZrO 2 1-10%, Nb 2 O 5 1-20%, Al 2 O 3 consists 0-5% and Sb 2 O 3 0 to 1% of the composition, less than the refractive index (nd) of 1.67 to 1.74, the optical constant in the range Abbe number ([nu] d) of less than 35 to 45 The average coefficient of linear thermal expansion (α × 10 −7 / ° C.) is less than 90 × 10 −7 / ° C.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The reason why the composition range of each component of the optical glass according to the present invention is limited as described above is as follows.
B 2 O 3 component is a glass forming oxide is a component necessary for stably introducing a relatively large amount of La 2 O 3 component to increase the refractive index of the glass, B 2 O 3 component If the amount is less than 20.5%, the devitrification tendency of the glass becomes large and the glass becomes unstable, and if it exceeds 35%, the optical constant targeted by the present invention cannot be obtained. A particularly preferable range of the amount of the B 2 O 3 component is 21 to 35%.
[0009]
The SiO 2 component is a glass-forming oxide and has the effect of increasing the viscosity of the glass and facilitating press molding. However, if the amount is less than 17.5%, the above effect cannot be obtained sufficiently, and press molding is performed. Is difficult, and the chemical durability and devitrification resistance of the glass deteriorate. On the other hand, if it exceeds 30%, the meltability of the glass deteriorates and the tendency to devitrification increases. A particularly preferable range of the amount of the SiO 2 component is 18 to 30%. Further, if the total amount of B 2 O 3 and SiO 2 components is less than 42%, the devitrification resistance and chemical durability of the glass are deteriorated, and the average linear thermal expansion coefficient of the glass is increased. When the molded product is cooled, cracks and sink marks are likely to occur in the molded product due to heat shrinkage. If the total amount of these components exceeds 60%, the optical constant targeted by the present invention cannot be obtained.
[0010]
The Li 2 O component has the effect of promoting melting of the SiO 2 raw material and reducing the devitrification tendency during glass melting, and in order to obtain the above effect, it is necessary to contain 3.5% or more, On the other hand, if it exceeds 7%, the tendency of devitrification increases, and the chemical durability of the glass deteriorates.
[0011]
The CaO component needs to be contained in an amount of 9% or more in order to suppress the tendency to devitrification and obtain a stable glass, but if it exceeds 23%, the tendency to devitrification increases. A particularly preferable range of the amount of the CaO component is 10 to 23%.
[0012]
The La 2 O 3 component is a component having an effect of increasing the refractive index of the glass. If the amount is 15% or less, the optical constant targeted by the present invention cannot be obtained, and if it exceeds 30%, the glass tends to devitrify. Becomes larger. A particularly preferred range of the amount of La 2 O 3 component is 16 to 28%.
[0013]
The TiO 2 component has the effect of increasing the refractive index while maintaining the stability of the glass. However, if the amount is less than 4%, the desired optical constant targeted by the present invention cannot be obtained. If it exceeds 50%, the tendency of devitrification of the glass increases and the coloring becomes remarkable. The amount of the TiO 2 component is particularly preferably up to 13%.
[0014]
The ZrO 2 component has an effect of improving the chemical durability by increasing the refractive index of the glass and coexisting with the Nb 2 O 5 component. However, if its amount is less than 1%, these effects are sufficient. Further, if it exceeds 10%, the meltability of the glass deteriorates, and the devitrification tendency increases.
[0015]
The Nb 2 O 5 component has the effect of increasing the chemical durability of the glass by coexisting with the above-described ZrO 2 component, is an indispensable component in the glass of the present invention, and also has an effect of increasing the refractive index. In order to obtain the above-mentioned coexistence effect and to obtain the desired optical constant targeted by the present invention, it is necessary to contain 1% or more, maintaining the refractive index targeted by the present invention, and In order to suppress the increase in raw material costs, the amount should be up to 20%.
[0016]
The following components can be optionally added to the glass of the present invention as necessary.
Both Na 2 O and K 2 O components can be added up to 5% in order to improve the meltability of the glass within the range in which the desired refractive index targeted by the present invention can be maintained. Any of MgO, BaO and ZnO components can be added up to 10%, 4% and 10%, respectively, in order to adjust the optical constant within a range not deteriorating the devitrification resistance and chemical durability of the glass. The Gd 2 O 3 component can be added to adjust the optical constants or improve the devitrification resistance of the glass, but the amount should be up to 15% in order to suppress an increase in raw material costs, and should not be added. Is particularly preferred. The Al 2 O 3 component improves the chemical durability of the glass and increases the viscosity to facilitate press molding. However, if the amount exceeds 5%, the tendency of the glass to devitrify increases. The Sb 2 O 3 component has an effect of promoting defoaming and clarification when the glass is melted, but the amount is sufficient up to 1%.
[0017]
【Example】
Next, the Example concerning the optical glass of this invention is described. Example of the optical glass of the present invention (No.1~No.10), the conventional B 2 O 3 -SiO 2 -Li 2 O-CaO-La 2 O 3 -TiO 2 -ZrO 2 -Nb 2 O 5 Comparative example glass system comparative example glass (No. a and No.B) and the conventional SiO 2 -B 2 O 3 -R 2 O-CaO-TiO 2 system (No. C and No. D) Are shown in Tables 1 and 2 together with the refractive index (nd), Abbe number (νd) and devitrification resistance test results of these glasses. In the devitrification resistance test in Table 1 and Table 2, a glass raw material batch prepared in advance was put into a 300 cc platinum crucible, and the temperature was 1200 to 1300 ° C. depending on the difficulty of melting of each glass sample in an electric furnace. After melting for a period of time, the temperature was lowered, each sample was kept at 900 ° C. and 850 ° C. for 1 hour, and then taken out of the furnace and observed for the presence of devitrification with a microscope. As a result, devitrification was observed. The glass sample which did not exist, and the thing which devitrification was seen is shown by x mark.
[0018]
In addition, Table 3 shows the acid resistance (SR value) of the glass of the examples (No. 1 to No. 10) and the comparative examples (No. A and No. B). The SR value is a result obtained by measuring in accordance with the measuring method of International Organization for Standardization ISO 8424: 1996 (E). Here, the SR value is a value graded according to the time (h) required for the glass sample to undergo erosion of 0.1 μm in a predetermined acid treatment solution. The SR values in Table 3 = 5, 51 and 53 indicate that the time (h) required to undergo erosion of 0.1 μm using an acetate buffer with pH = 4.6 is h> 10, h, respectively. = 1-10 and h <0.1. Therefore, the smaller the SR value, the higher the acid resistance of the glass and the better the chemical durability.
[0019]
Moreover, the average linear thermal expansion coefficient ((alpha) * 10 < -7 > /) in the temperature range of 100-300 degreeC of the glass of the said Example (No.1-No.3) and the said comparative example (No.A-No.D). ° C) is shown in Table 4.
[0020]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
As can be seen from Table 1 and Table 2 above, the glasses of the examples of the present invention all have a desired range of optical constants, and as a result of the devitrification resistance test results described above, devitrification is recognized. The devitrification resistance is superior to the glasses of the above comparative examples (No. A to No. D). In addition, as seen in Table 3 above, the glasses of the examples of the present invention all have a small SR value and high acid resistance compared to the glasses of the comparative examples (No. A and No. B), Excellent chemical durability.
Furthermore, as seen in Table 4 above, the glasses (No. 1 to No. 3) of the examples of the present invention are all average lines compared to the glasses of the comparative examples (No. A to No. D). It can be seen that the thermal expansion coefficient (α × 10 −7 / ° C.) is small, and the thermal shrinkage of the glass during cooling after press-molding the heat-softened glass is smaller than that of the conventional glass of the comparative example.
As described above, as seen in Tables 1 to 4, the glass of the examples of the present invention is superior in devitrification resistance than the conventional glass of the comparative example, while maintaining excellent chemical durability, and It has a small average linear thermal expansion coefficient (α × 10 −7 / ° C.), and it can be seen that the defects of the conventional glass of the comparative example are improved comprehensively.
[0025]
In addition, the glass of the said Example of this invention measured and mixed the raw materials for optical glasses, such as an oxide, carbonate, nitrate, and this about about 1200 to 1300 degreeC using a platinum crucible etc., and about It can be easily manufactured by melting, clarifying, stirring and homogenizing for 3 to 4 hours, then casting into a preheated mold and slow cooling. In addition, the glasses of the above examples are excellent in meltability, can easily obtain highly homogeneous glass free from bubbles and striae, and have a reasonably high viscosity. Can also be done easily.
[0026]
【The invention's effect】
As described above, the optical glass according to the present invention is B 2 O 3 —SiO 2 —Li 2 O—CaO—La 2 O 3 —TiO having a specific composition range in which the content of the glass-forming oxide is limited to a specific range. Since it is a 2- ZrO 2 —Nb 2 O 5 -based glass, it has an optical constant in the desired range, is excellent in devitrification resistance and chemical durability, and has a reasonably high viscosity. Because it is easy to mold and the average linear thermal expansion coefficient (α × 10 -7 / ° C) is small, when the glass molded product that has been press-molded is cooled, the molded product is not cracked or sinked by heat shrinkage. The molding yield can be improved. In addition, because of its excellent meltability, it is possible to easily produce a homogeneous glass free from bubbles and striae, as well as high-priced components such as Y 2 O 3 , PbO and As 2 O. As shown in 3 , it does not contain components that require high costs for waste disposal due to environmental measures, which is advantageous in terms of manufacturing costs and waste disposal costs.
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17672098A JP4044213B2 (en) | 1998-06-09 | 1998-06-09 | Optical glass |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17672098A JP4044213B2 (en) | 1998-06-09 | 1998-06-09 | Optical glass |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000001329A JP2000001329A (en) | 2000-01-07 |
| JP4044213B2 true JP4044213B2 (en) | 2008-02-06 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP17672098A Expired - Fee Related JP4044213B2 (en) | 1998-06-09 | 1998-06-09 | Optical glass |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3555681B2 (en) * | 2001-10-29 | 2004-08-18 | 日本電気硝子株式会社 | Glass for mold press molding |
| JP4453328B2 (en) * | 2003-10-09 | 2010-04-21 | 日本電気硝子株式会社 | Mold press molding glass and method for producing the same |
| JP4703168B2 (en) | 2004-11-09 | 2011-06-15 | 株式会社オハラ | Optical glass |
| JP5056291B2 (en) * | 2007-09-13 | 2012-10-24 | コニカミノルタアドバンストレイヤー株式会社 | Optical glass and optical element |
| JP5727689B2 (en) * | 2008-03-31 | 2015-06-03 | 株式会社オハラ | Optical glass, optical element and optical instrument |
| CN108290771A (en) * | 2015-11-24 | 2018-07-17 | 旭硝子株式会社 | Optical glass |
| US20210114918A1 (en) * | 2017-02-01 | 2021-04-22 | Ohara Inc. | Optical glass, preform and optical element |
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1998
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