JP4024907B2

JP4024907B2 - Optical glass

Info

Publication number: JP4024907B2
Application number: JP25430797A
Authority: JP
Inventors: 宗雄中原
Original assignee: Ohara Inc
Current assignee: Ohara Inc
Priority date: 1997-09-03
Filing date: 1997-09-03
Publication date: 2007-12-19
Anticipated expiration: 2017-09-03
Also published as: JPH1179781A

Description

【０００１】
【発明の属する技術分野】
本発明は、屈折率（ｎｄ）が１．６０〜１．６８、アッベ数（νｄ）が５５以上の光学恒数を有する光学ガラスに関する。
【０００２】
【従来の技術】
従来、前記範囲の光学恒数を有する光学ガラスとして、例えば、ＳｉＯ₂、Ｂ₂Ｏ₃およびＢａＯを基本的成分とするガラスが知られている。この組成系のガラスは、溶融時の安定性に優れているものの化学的耐久性が非常に劣っており、ガラスの研磨および洗浄工程や、レンズとしての長期間にわたる使用過程において、ガラス表面にヤケや風化作用による侵蝕が生じやすく、上記従来のガラスの加工および使用に際しては特別な注意を要した。また、上記従来のガラスは、ＢａＯ成分を比較的多量に含有しているため比重が大きくなる傾向があり、さらに、調合原料を溶融する際にＳｉＯ₂成分が融液表面に分離しやすく、均質なガラスが得にくいという問題点がある。
【０００３】
【発明が解決しようとする課題】
本発明の目的は、上記従来技術に見られる諸欠点を解消し、前記所定の範囲の光学恒数を有し、溶融性および化学的耐久性が優れ、Ｙ₂Ｏ₃、Ｇｄ₂Ｏ₃およびＴａ₂Ｏ₅のような原料価格の高い成分を含有しない、もしくは、必須成分としない、失透が生じにくい安定な光学ガラスを提供することにある。
【０００４】
【課題を解決するための手段】
本発明者は、前記課題を解決するために鋭意試験研究を重ねた結果、特定組成範囲のＳｉＯ₂−Ｂ₂Ｏ₃―ＣａＯ−Ｌａ₂Ｏ₃系ガラスに、Ａｌ₂Ｏ₃およびＬｉ₂Ｏを必須成分として添加することによって、前記目的を達成し得ることを見いだし本発明をなすに至った。
【０００５】
すなわち、前記目的を達成するための本発明の光学ガラスは、請求項１に記載のとおり、重量％で、ＳｉＯ₂ ５＜〜２０％、Ｂ₂Ｏ₃ ４０〜５０％（４０％を除く）、Ａｌ₂Ｏ₃ ０．１〜１０％未満、Ｌａ₂Ｏ₃ １６．５〜３０％、ＣａＯ１０〜３０％、Ｌｉ₂Ｏ０．１〜２％未満、Ｎａ₂Ｏ０〜１．９％、Ｋ₂Ｏ０〜１．９％、ただし、Ｒ₂Ｏ（Ｒ₂ＯはＬｉ₂Ｏ、Ｎａ₂ＯおよびＫ₂Ｏ）の合計量０．１〜２％未満、ＭｇＯ０〜５％、ＳｒＯ０〜５％、ＢａＯ０〜１５％、ＺｎＯ０〜１５％ＴｉＯ₂ ０〜３％、ＺｒＯ₂ ０〜５％、Ｎｂ₂Ｏ₅ ０〜５％、Ｔａ₂Ｏ₅ ０〜５％、ＷＯ₃ ０〜５％、Ｓｂ₂Ｏ₃ ０〜１％およびＦ₂ ０〜５％を含有し、Ｙ ₂ Ｏ ₃ を含有しないことを特徴とする。
【０００６】
また、本発明の光学ガラスの好ましい態様は、請求項２に記載のとおり、重量％で、ＳｉＯ₂ ８〜１５％、Ｂ₂Ｏ₃ ４０〜５０％（４０％を除く）、ただし、ＳｉＯ₂＋Ｂ₂Ｏ₃ ５０％以上、Ａｌ₂Ｏ₃ ０．３〜５％、Ｌａ₂Ｏ₃ １８〜２５％、ＣａＯ１８〜２５％、Ｌｉ₂Ｏ０．１〜２％未満、Ｎａ₂Ｏ０〜２％未満、Ｋ₂Ｏ０〜２％未満、ただし、Ｒ₂Ｏ（Ｒ₂ＯはＬｉ₂Ｏ、Ｎａ₂ＯおよびＫ₂Ｏ）の合計量０．１〜２％未満、ＭｇＯ０〜５％、ＳｒＯ０〜５％、ＢａＯ０〜１０％、ＺｎＯ０〜１０％ＺｒＯ₂ ０〜５％、Ｔａ₂Ｏ₅ ０〜５％、Ｓｂ₂Ｏ₃ ０〜０．５％およびＦ₂ ０〜５％を含有し、Ｙ ₂ Ｏ ₃ 、ＴｉＯ₂、Ｎｂ₂Ｏ₅およびＷＯ₃を含有しないことを特徴とする。
【０００７】
また、本発明の光学ガラスの好ましい態様は、請求項３に記載のとおり、重量％で、ＳｉＯ₂ ８〜１５％、Ｂ₂Ｏ₃ ４０〜５０％（４０％を除く）、Ａｌ₂Ｏ₃ ０．３〜５％、Ｌａ₂Ｏ₃ １８〜２５％、ＣａＯ１８〜２５％、Ｌｉ₂Ｏ０．１〜２％未満、Ｎａ₂Ｏ０〜２％未満、Ｋ₂Ｏ０〜２％未満、ただし、Ｒ₂Ｏ（Ｒ₂ＯはＬｉ₂Ｏ、Ｎａ₂ＯおよびＫ₂Ｏ）の１種または２種以上の合計量０．１〜２％未満、ＭｇＯ０〜５％、ＳｒＯ０〜５％、ＢａＯ０〜１０％、ただし、上記Ｒ₂ＯとＲＯ（ＲＯはＣａＯ、ＭｇＯ、ＳｒＯおよびＢａＯ）との合計量１９％以上、ＺｎＯ０〜１０％ＺｒＯ₂ ０〜５％、Ｔａ₂Ｏ₅ ０〜５％、Ｓｂ₂Ｏ₃ ０〜０．５％およびＦ₂ ０〜５％を含有し、Ｙ ₂ Ｏ ₃ 、ＴｉＯ₂、Ｎｂ₂Ｏ₅およびＷＯ₃を含有しないところにある。
【０００８】
また、本発明の光学ガラスの特に好ましい態様は、請求項４に記載のとおり、重量％で、ＳｉＯ₂ ８〜１５％、Ｂ₂Ｏ₃ ４０〜５０％（４０％を除く）、ただし、ＳｉＯ₂＋Ｂ₂Ｏ₃ ５０％以上、Ａｌ₂Ｏ₃ ０．３〜５％、Ｌａ₂Ｏ₃ １８〜２５％、ＣａＯ１８〜２５％、Ｌｉ₂Ｏ０．１〜２％未満、Ｎａ₂Ｏ０〜２％未満、Ｋ₂Ｏ０〜２％未満、ただし、Ｒ₂Ｏ（Ｒ₂ＯはＬｉ₂Ｏ、Ｎａ₂ＯおよびＫ₂Ｏ）の１種または２種以上の合計量０．１〜２％未満、ＭｇＯ０〜５％、ＳｒＯ０〜５％、ＢａＯ０〜１０％、ただし、上記Ｒ₂ＯとＲＯ（ＲＯはＣａＯ、ＭｇＯ、ＳｒＯおよびＢａＯ）との合計量１９％以上、ＺｎＯ０〜１０％ＺｒＯ₂ ０〜５％、Ｔａ₂Ｏ₅ ０〜５％、Ｓｂ₂Ｏ₃ ０〜０．５％およびＦ₂ ０〜５％を含有し、Ｙ ₂ Ｏ ₃ 、ＴｉＯ₂、Ｎｂ₂Ｏ₅およびＷＯ₃を含有しないことを特徴とする。
【０００９】
【発明の実施の形態】
本発明の光学ガラスにおいて、各成分を前記組成範囲に限定した理由を以下に述べる。
ＳｉＯ₂およびＢ₂Ｏ₃成分は、ガラス形成酸化物であり、本発明において、ガラス化範囲を広くし、かつ、ガラスに適度な粘度を持たせるのに有効である。ＳｉＯ₂成分は、その量が５％以下では上記効果が不十分であり、２０％を超えると混合原料の溶融性が悪くなり、未溶融物を生じやすくなる。また、Ｂ₂Ｏ₃成分は、その量が３５％未満の場合および５５％を超える場合、所望の屈折率のガラスを得にくくなる。特に均質性の良いガラスを得るためには、ＳｉＯ₂成分の量を８〜１５％、Ｂ₂Ｏ₃成分の量を４０〜５０％とすることが好ましい。さらに、一段と安定なガラスを得るためには、ＳｉＯ₂成分およびＢ₂Ｏ₃成分の合計量を５０％以上とすることがより好ましい。
【００１０】
Ａｌ₂Ｏ₃成分は、ガラスの化学的耐久性の向上や粘度の調整、および失透に対する安定化に効果がある。しかし、その量が０．１％未満では、上記効果が十分でなく、また、１０％以上になると、かえって失透性が増大し好ましくない。より好ましい量は０．３〜５％である。
【００１１】
Ｌａ₂Ｏ₃成分は、ガラスの化学的耐久性および耐失透性を向上させるとともに、分散をあまり大きくすることなしに屈折率を高め、高屈折率を有する安定なガラスを得るのに有効な成分である。その量が１６．５％未満であるとガラスの化学的耐久性や耐失透性が不十分であり、また３０％を超えると所望の屈折率が得られなくなる。所望の光学恒数を有し、かつ、失透のない均質なガラスを得るには、Ｌａ₂Ｏ₃成分の量が１８〜２５％の範囲であることがより好ましい。
【００１２】
ＣａＯ成分は、ガラスの化学的耐久性、耐失透性およびガラス原料の溶融性を向上するのに効果がある。ＣａＯ成分の量が１０％未満では上記効果が十分でなく、また、所望の光学恒数を得がたい。また、その量が３０％を超えるとかえって失透化傾向が増大し好ましくない。ＣａＯ成分のより好ましい量は１８〜２５％である。
【００１３】
Ｌｉ₂Ｏ成分は、ガラス原料の溶融を促進するのに有効である。上記効果を得るためには、その量は０．１〜２％未満で十分であり、２％以上では、ガラス中に結晶が析出する傾向が増大するので好ましくない。また、Ｌｉ₂Ｏ成分の一部をＮａ₂ＯおよびＫ₂Ｏ成分の一方または両方で置き換えることが可能である。
【００１４】
ＭｇＯ、ＳｒＯ、ＢａＯおよびＺｎＯの各成分は、ガラスの屈折率やアッベ数の調整、ガラス原料の溶融性の向上および耐失透性の改善のために有効であり、ＭｇＯおよびＳｒＯ成分をそれぞれ５％まで、また、ＢａＯおよびＺｎＯ成分をそれぞれ１５％まで加えることができる。なお、ＢａＯおよびＺｎＯ成分の量は、それぞれ１０％までとすることが、より好ましい。さらに、Ｒ₂Ｏ成分（Ｒ₂ＯはＬｉ₂Ｏ、Ｎａ₂ＯおよびＫ₂Ｏ）とＲＯ成分（ＲＯはＣａＯ、ＭｇＯ、ＳｒＯおよびＢａＯ）との合計量は、１９％以上とすることが、より好ましい。
【００１５】
本発明のガラスには、屈折率やアッベ数の調整またはガラスの安定性向上のために、ＴｉＯ₂、ＺｒＯ₂、Ｎｂ₂Ｏ₅、Ｔａ₂Ｏ₅およびＷＯ₃の各成分を任意に添加し得るが、それらの量は、ＴｉＯ₂成分は３％まで、ＺｒＯ₂、Ｎｂ₂Ｏ₅、Ｔａ₂Ｏ₅およびＷＯ₃の各成分は、それぞれ５％までで十分である。しかし、ＴｉＯ₂、Ｎｂ₂Ｏ₅およびＷＯ₃成分は、短波長側におけるガラスの光線透過率を低くする傾向があるので、これらの成分を含有しないほうがより好ましい。
【００１６】
Ｓｂ₂Ｏ₃成分は、ガラス溶融の際の清澄剤として任意に添加し得るが、その量は１％以下で十分であり、より適当な量は０．５％以下である。
また、本発明のガラスには、上記金属酸化物の各金属元素の弗化物を１種または２種以上添加してもよい。その量はＦ₂として５％までである。
【００１７】
【実施例】
次に、本発明にかかる光学ガラスの好適な実施例（Ｎｏ．１〜Ｎｏ．２０）をこれらのガラスの屈折率（ｎｄ）およびアッベ数（νｄ）とともに表１および表２に示す。
【００１８】
【表１】

【００１９】
【表２】

【００２０】
上記表１および表２の実施例の光学ガラスは、いずれも、溶融性に優れ、泡や脈理のない均質なガラスが得ることができ、失透に対する安定性も優れている。また、前記従来のＳｉＯ₂、Ｂ₂Ｏ₃およびＢａＯを基本成分とするガラスと比較し、化学的耐久性が優れ、比重が小さい。
本発明にかかる上記実施例の光学ガラスは、酸化物、炭酸塩、水酸化物、硝酸塩及び弗化物等の通常の光学ガラス原料を秤量混合し、白金ルツボ等を用いて、約１２００℃から１４００℃で約２から４時間、溶融、清澄、攪拌した後、予熱した金型等に鋳込み、徐冷することにより、容易に製造することができる。
【００２１】
【発明の効果】
以上述べたとおり、本発明の光学ガラスは、特定組成範囲のＳｉＯ₂−Ｂ₂Ｏ₃―ＣａＯ−Ｌａ₂Ｏ₃系ガラスに、Ａｌ₂Ｏ₃およびＬｉ₂Ｏを必須成分として添加したガラスであり、屈折率（ｎｄ）が１．６０〜１．６８、アッベ数（νｄ）が５５以上の範囲の光学恒数を有し、溶融性および化学的耐久性が優れ、失透が生じにくい安定かつ均質な光学ガラスを得ることができる。さらに本発明の光学ガラスは、原料価格の高いＹ₂Ｏ₃およびＧｄ₂Ｏ₃成分を含有せず、Ｔａ₂Ｏ₅成分を必須成分としておらず、安価に製造し得るという点においても有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical glass having an optical constant having a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 55 or more.
[0002]
[Prior art]
Conventionally, as an optical glass having an optical constant in the above range, for example, a glass containing SiO ₂ , B ₂ O ₃ and BaO as basic components is known. Glass of this composition system is excellent in stability at the time of melting, but its chemical durability is very inferior, and the glass surface is burned in the polishing and cleaning process of the glass and in the use process for a long time as a lens. Erosion due to weathering is likely to occur, and special care was required when processing and using the conventional glass. In addition, the above-mentioned conventional glass tends to increase in specific gravity because it contains a relatively large amount of the BaO component. Further, when melting the preparation raw material, the SiO ₂ component is easily separated on the melt surface and is homogeneous. There is a problem that it is difficult to obtain a glass.
[0003]
[Problems to be solved by the invention]
The object of the present invention is to eliminate the above-mentioned drawbacks found in the prior art, to have the optical constants in the predetermined range, excellent in meltability and chemical durability, Y ₂ O ₃ , Gd ₂ O ₃ and It is an object of the present invention to provide a stable optical glass which does not contain a component with a high raw material price such as Ta ₂ O ₅ or does not make it an essential component and hardly causes devitrification.
[0004]
[Means for Solving the Problems]
As a result of intensive studies and studies to solve the above problems, the present inventor has added Al ₂ O ₃ and Li ₂ O to SiO ₂ —B ₂ O ₃ —CaO—La ₂ O ₃ glass having a specific composition range. It was found that the above-mentioned object can be achieved by adding as an essential component, and the present invention has been made.
[0005]
That is, the optical glass of the present invention for achieving the above object is, as described in claim 1, expressed by weight%, SiO ₂ 5 <˜20%, B ₂ O ₃ 40-50% (excluding 40%). , Al ₂ O ₃ less than _{_{0.1~10%, La 2 O 3 16.5~30}} %, CaO 10~30%, Li 2 O less than 0.1~2%, Na ₂ O 0~1.9% , K ₂ O 0 to 1.9%, provided that the total amount of R ₂ O (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) is less than 0.1 to 2%, MgO 0 to 5%, SrO 0~5%, BaO 0~15%, 0~15% TiO 2 0~3% ZnO, ZrO 2 0~5%, Nb 2 O 5 0~5%, Ta 2 O 5 0~5%, WO ₃ 0 to 5%, Sb ₂ O ₃ 0 to 1% and F ₂ 0 to 5% are contained, and Y ₂ O ₃ is not contained .
[0006]
Further, a preferred embodiment of the optical glass of the present invention, (excluding 40%) as described in claim 2, in _{weight%, SiO 2 8~15%, B} 2 O 3 40~50%, however, SiO ₂ + B ₂ O ₃ 50% or more, Al ₂ O ₃ 0.3-5%, La ₂ O ₃ 18-25%, CaO 18-25%, Li ₂ O 0.1-2%, Na ₂ O 0 Less than 2%, K ₂ O 0 to less than 2%, except that the total amount of R ₂ O (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) is less than 0.1 to 2%, MgO 0 to 5 %, SrO 0-5%, BaO 0-10%, ZnO 0-10% ZrO ₂ 0-5%, Ta ₂ O ₅ 0-5%, Sb ₂ O ₃ 0-0.5% and F ₂ 0 It is characterized by containing 5% and not containing Y ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ and WO ₃ .
[0007]
Further, a preferred embodiment of the optical glass of the present invention, (excluding 40%) as described in claim 3, in _{weight%, SiO 2 8~15%, B} 2 O 3 40~50%, Al 2 O 3 _{_{0.3~5%, La 2 O 3 18~25}} %, CaO 18~25%, Li 2 O less than 0.1~2%, Na ₂ O less than 0 to 2%, K less than ₂ O 0 to 2% However, the total amount of one or more of R ₂ O (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) is less than 0.1 to 2%, MgO 0 to 5%, SrO 0 to 5%, BaO 0-10%, provided that the total amount of R ₂ O and RO (RO is CaO, MgO, SrO and BaO) is 19% or more, ZnO 0-10% ZrO ₂ 0-5%, Ta ₂ O ₅ 0 to 5%, contains Sb ₂ O ₃ 0~0.5% and F ₂ 0 to 5%, a _{_{_{Y 2 O 3, TiO 2,}}} Nb 2 O 5 and WO ₃ There is to do not have.
[0008]
Further, particularly preferred embodiments of the optical glass of the present invention are as described in claim 4 in terms of weight%, SiO ₂ 8-15%, B ₂ O ₃ 40-50% (excluding 40%) , but SiO 2 ₂ + B ₂ O ₃ 50% or more, Al ₂ O ₃ 0.3-5%, La ₂ O ₃ 18-25%, CaO 18-25%, Li ₂ O 0.1-2%, Na ₂ O 0 less than to 2% K ₂ O less than 0-2%, provided that, R ₂ O (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) 1 or more kinds of the total amount 0.1 of Less than 2%, MgO 0-5%, SrO 0-5%, BaO 0-10%, provided that the total amount of R ₂ O and RO (RO is CaO, MgO, SrO and BaO) is 19% or more, ZnO _{0~10% ZrO 2 0~5%, Ta} 2 O 5 0~5%, contain Sb ₂ O ₃ 0~0.5% and F ₂ 0~5%, Y ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ and WO ₃ are not contained.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The reason why each component of the optical glass of the present invention is limited to the above composition range will be described below.
The SiO ₂ and B ₂ O ₃ components are glass-forming oxides, and are effective in widening the vitrification range and imparting an appropriate viscosity to the glass in the present invention. When the amount of the SiO ₂ component is 5% or less, the above effect is insufficient. When the amount exceeds 20%, the meltability of the mixed raw material is deteriorated and an unmelted product is likely to be generated. Further, when the amount of the B ₂ O ₃ component is less than 35% or exceeds 55%, it becomes difficult to obtain a glass having a desired refractive index. In order to obtain glass with particularly good homogeneity, it is preferable that the amount of the SiO ₂ component is 8 to 15% and the amount of the B ₂ O ₃ component is 40 to 50%. Furthermore, in order to obtain a more stable glass, the total amount of the SiO ₂ component and the B ₂ O ₃ component is more preferably 50% or more.
[0010]
The Al ₂ O ₃ component is effective in improving the chemical durability of the glass, adjusting the viscosity, and stabilizing against devitrification. However, if the amount is less than 0.1%, the above effect is not sufficient, and if it is 10% or more, devitrification increases, which is not preferable. A more preferred amount is 0.3 to 5%.
[0011]
The La ₂ O ₃ component improves the chemical durability and devitrification resistance of the glass and increases the refractive index without increasing the dispersion too much, and is effective in obtaining a stable glass having a high refractive index. It is an ingredient. If the amount is less than 16.5%, the chemical durability and devitrification resistance of the glass are insufficient, and if it exceeds 30%, the desired refractive index cannot be obtained. In order to obtain a homogeneous glass having a desired optical constant and no devitrification, the amount of La ₂ O ₃ component is more preferably in the range of 18 to 25%.
[0012]
The CaO component is effective in improving the chemical durability, devitrification resistance, and meltability of the glass raw material. If the amount of the CaO component is less than 10%, the above effect is not sufficient, and it is difficult to obtain a desired optical constant. Moreover, when the amount exceeds 30%, the devitrification tendency increases, which is not preferable. A more preferable amount of the CaO component is 18 to 25%.
[0013]
The Li ₂ O component is effective for promoting the melting of the glass raw material. In order to obtain the above effect, the amount is sufficient to be less than 0.1 to 2%, and if it is 2% or more, the tendency of crystals to precipitate in the glass increases, which is not preferable. Also, a part of the Li ₂ O component can be replaced with one or both of the Na ₂ O and K ₂ O components.
[0014]
Each component of MgO, SrO, BaO and ZnO is effective for adjusting the refractive index and Abbe number of glass, improving the meltability of glass raw materials and improving devitrification resistance. %, And up to 15% each of BaO and ZnO components. The amounts of the BaO and ZnO components are more preferably up to 10% each. Furthermore, the total amount of the R ₂ O component (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) and the RO component (RO is CaO, MgO, SrO and BaO) may be 19% or more. More preferable.
[0015]
In order to adjust the refractive index and the Abbe number or improve the stability of the glass, the glass of the present invention may optionally contain TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ components. However, it is sufficient that the amount of TiO ₂ component is 3% and that of ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ components is 5% each. However, since TiO ₂ , Nb ₂ O ₅ and WO ₃ components tend to lower the light transmittance of the glass on the short wavelength side, it is more preferable not to contain these components.
[0016]
The Sb ₂ O ₃ component can be optionally added as a fining agent during glass melting, but its amount is sufficient to be 1% or less, and a more appropriate amount is 0.5% or less.
Moreover, you may add 1 type, or 2 or more types of the fluoride of each metal element of the said metal oxide to the glass of this invention. The amount is up to 5% as F _2.
[0017]
【Example】
Next, preferred examples (No. 1 to No. 20 ) of the optical glass according to the present invention are shown in Tables 1 and 2 together with the refractive index (nd) and Abbe number (νd) of these glasses.
[0018]
[Table 1]

[0019]
[Table 2]

[0020]
The optical glasses of the examples in Table 1 and Table 2 are both excellent in meltability, capable of obtaining a homogeneous glass free from bubbles and striae, and excellent in stability against devitrification. Further, compared with the conventional glass containing SiO ₂ , B ₂ O ₃ and BaO as basic components, the chemical durability is excellent and the specific gravity is small.
The optical glass of the above embodiment according to the present invention is prepared by weighing and mixing ordinary optical glass raw materials such as oxides, carbonates, hydroxides, nitrates and fluorides, and using a platinum crucible or the like, from about 1200 ° C. to 1400 ° C. After melting, clarifying, stirring for about 2 to 4 hours at ° C., it can be easily produced by casting into a preheated mold or the like and gradually cooling.
[0021]
【The invention's effect】
As described above, the optical glass of the present invention is a glass in which Al ₂ O ₃ and Li ₂ O are added as essential components to a SiO ₂ —B ₂ O ₃ —CaO—La ₂ O ₃ glass having a specific composition range. Yes, with an optical constant in the range of refractive index (nd) of 1.60 to 1.68 and Abbe number (νd) of 55 or more, excellent meltability and chemical durability, and stable devitrification A homogeneous optical glass can be obtained. Furthermore, the optical glass of the present invention does not contain Y ₂ O ₃ and Gd ₂ O ₃ components, which are expensive raw materials, and does not contain a Ta ₂ O ₅ component as an essential component, and is useful in that it can be manufactured at low cost. is there.

Claims

In _{weight%, SiO 2 5 <~20%} , ( excluding _{_{40%) 2 O 3 40~50%}} B, Al 2 O 3 less than _{_{0.1~10%, La 2 O 3 16.5~30}} %, CaO 10~30%, Li ₂ O less than _{0.1~2%, Na 2 O 0~1.9%} , K 2 O 0~1.9%, provided that, R _₂ O (R ₂ O is Li ₂ O , Na ₂ O and K ₂ O) less than 0.1-2%, MgO 0-5%, SrO 0-5%, BaO 0-15%, ZnO 0-15% TiO ₂ 0-3%, _{_{ZrO 2 0~5%, Nb 2 O}} 5 0~5%, Ta 2 O 5 0~5%, WO 3 0~5%, contain Sb ₂ O ₃ 0~1% and F ₂ 0 to 5% Optical glass characterized by not containing Y ₂ O ₃ .

2. The optical glass according to claim 1, wherein, by weight, SiO _{2 is} 8 to 15%, B ₂ O _{3 is} 40 to 50% (excluding 40%) , but SiO ₂ + B ₂ O _{3 is} 50% or more, Al ₂ O ₃ 0.3-5%, La ₂ O ₃ 18-25%, CaO 18-25%, Li ₂ O 0.1-2%, Na ₂ O 0-1.9%, K ₂ O 0- 1.9%, provided that the total amount of R ₂ O (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) is less than 0.1-2%, MgO 0-5%, SrO 0-5%, BaO 0-10%, ZnO 0-10% ZrO ₂ 0-5%, Ta ₂ O ₅ 0-5%, Sb ₂ O ₃ 0-0.5% and F ₂ 0-5% , Y ₂ An optical glass characterized by not containing O ₃ , TiO ₂ , Nb ₂ O ₅ and WO ₃ .

In the optical glass according to claim 1, in weight%, SiO ₂ 8~15%, (excluding _{_{40%) 2 O 3 40~50%}} B, Al 2 O 3 0.3~5%, La 2 O _{3 18~25%, CaO 18~25%,} Li 2 O less than _{0.1~2%, Na 2 O 0~1.9%} , K 2 O 0~1.9%, provided that, R ₂ O (R ₂ O is a total amount of one or more of Li ₂ O, Na ₂ O and K ₂ O 0.1 to 2%, MgO 0 to 5%, SrO 0 to 5%, BaO 0 to 10% However, the total amount of R ₂ O and RO (RO is CaO, MgO, SrO and BaO) is 19% or more, ZnO 0 to 10% ZrO ₂ 0 to 5%, Ta ₂ O ₅ 0 to 5%, Sb ₂ O ₃ containing 0 to 0.5% and F ₂ 0 to 5%, optical, characterized in that it does not contain a _{_{_{Y 2 O 3, TiO 2,}}} Nb 2 O 5 and WO ₃ Russ.

2. The optical glass according to claim 1, wherein, by weight, SiO _{2 is} 8 to 15%, B ₂ O _{3 is} 40 to 50% (excluding 40%) , but SiO ₂ + B ₂ O _{3 is} 50% or more, Al ₂ O ₃ 0.3-5%, La ₂ O ₃ 18-25%, CaO 18-25%, Li ₂ O 0.1-2%, Na ₂ O 0-1.9%, K ₂ O 0- 1.9%, provided that the total amount of one or more of R ₂ O (R ₂ O is Li ₂ O, Na ₂ O and K ₂ O) is less than 0.1 to 2%, MgO 0 to 5% , SrO 0-5%, BaO 0-10%, provided that the total amount of R ₂ O and RO (RO is CaO, MgO, SrO and BaO) is 19% or more, ZnO 0-10% ZrO ₂ 0-5 %, Ta ₂ O ₅ 0-5%, Sb ₂ O ₃ 0-0.5% and F ₂ 0-5% , Y ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ and Optical glass characterized by not containing WO ₃ .