JP4729750B2 - Optical glass and optical element - Google Patents

Description

ここで、ｎ_ｇ、ｎ_Ｆ、ｎ_Ｃはそれぞれスペクトル線のｇ線（光源Ｈｇ、波長４３５．８３５ｎｍ）、Ｆ線（光源Ｈ、波長４８６．１３ｎｍ）、Ｃ線（光源Ｈ、波長６５６．２７ｎｍ）に対するガラスの屈折率である。

以上のようにして算出したΔθｇ，Ｆの値がマイナスの場合、換言すれば、図１において、あるガラスの座標が直線Ｌより下方に位置している場合、そのガラスは負の異常分散性を有している。また、Δθｇ，Ｆの値がプラスの場合、すなわち、図１において、あるガラスの座標が直線Ｌより上方に位置している場合、そのガラスは正の異常分散性を有している。正、負いずれの場合も、Δθｇ，Ｆの絶対値が大きいほどそのガラスは大きな異常分散性を有している。
また、本発明の光学ガラスは、日本光学硝子工業会規格「光学ガラスのけい光度の測定方法」（ＪＯＧＩＳ０３−^１９７５）に基づき測定するガラスのけい光度が級１であってもよい。
本発明の第２の側面によれば、本発明の光学素子は、酸化物基準の質量％で、
ＳｉＯ_２ ３０〜５５％、
ＺｒＯ_２ ０．５〜１０％、
Ｎｂ_２Ｏ_５ ２０〜５０％、
Ｔａ_２Ｏ_５ １〜１５％、
Ｌｉ_２Ｏ ０〜２５％、
Ｎａ_２Ｏ ０〜２５％、
Ｋ_２Ｏ ０〜２５％、
ただし、Ｌｉ_２Ｏ＋Ｎａ_２Ｏ＋Ｋ_２Ｏ １２〜２５％、
ＭｇＯ ０〜 ５％未満、
ＣａＯ ０〜 ５％未満、
ＢａＯ ０〜 ５％未満、
ＺｎＯ ０〜 ５％未満、
ただし、ＭｇＯ＋ＣａＯ＋ＢａＯ＋ＺｎＯ ０〜 ５％未満、
Ｓｂ_２Ｏ_３ ０〜 １％
の範囲の各成分を含有し、ＳｒＯ、弗素及びＢ_２Ｏ_３を含有しない光学ガラスを用いて得られる。
図面の簡単な説明
図１は、本発明に係る各実施例のガラス、比較例のガラス及び基準のガラスのθｇ，Ｆ（部分分散比）対νｄ（アッベ数）を示す図である。
発明を実施するための最良の形態
前記のとおり、各成分の組成範囲を限定した理由は、次のとおりである。
ＳｉＯ_２成分は、ガラス形成酸化物であるとともに、ガラスの失透に対する安定性および化学的耐久性を向上させる成分であり、失透に対する安定性および化学的耐久性を維持するためには、３０％以上必要であるが、その量が５５％を超えるとガラスの粘性が高くなり溶融性が悪くなる。
また、特に溶融性が良く均質性が優れたガラスを得るためにはＳｉＯ_２成分の量を３０以上〜４７％未満の範囲とすることがより好ましい。
ＺｒＯ_２成分は、本発明において、ガラスに含有させることによって、ガラスの屈折率を高め、かつ、負の異常分散性を大きくする効果があることを見出した重要な成分であるが、その量が０．５％未満ではそれらの効果が得られず、また１０％を超えるとガラスが失透しやすくなり、安定なガラスを得難くなる。
Ｎｂ_２Ｏ_５成分は、所望の光学定数を維持するために欠くことができない成分であり、かつ、紫外線励起により生じるガラスのけい光（蛍光）の強さを低める効果を有する成分である。しかし、Ｎｂ_２Ｏ_５成分の量が２０％未満では所望の光学定数を維持することが困難となり、また、５０％を超えると光線透過性が悪化するとともに、ガラスが失透しやすくなる。
Ｔａ_２Ｏ_５成分は、ガラスに含有させることによって、所望範囲の光学定数を維持しつつ、負の異常分散性を大きくし、かつ、光線透過性および化学的耐久性を向上させる効果があるが、その量が１５％を超えると、溶融ガラス中に未溶融物を生じ、均質なガラスを得難くなる。
また、上記効果を十分に得るためには、Ｔａ_２Ｏ_５成分を１％以上含有させるべきである。
また、Ｎｂ_２Ｏ_５およびＴａ_２Ｏ_５成分は、ともに原料コストが高い成分であるため、両成分による上記効果を十分に得つつ、かつ、ガラスの製造コストを低く抑えるためには、両成分の合計量を５５％以下とすることがより好ましい。
Ｌｉ_２Ｏ、Ｎａ_２ＯおよびＫ_２Ｏの各成分は、いずれも、ガラスの溶融を促進する効果があり、これらの成分を添加することにより、ガラス化範囲を拡大させることができる。さらに、これらの成分には、ガラスに負の異常分散性を与える効果があるが、これらの成分の１種または２種以上の合計量が１２％未満であると、上記各効果が十分に得られなくなる。また、これらの成分の１種または２種以上の合計量が２５％を超えると、ガラスの化学的耐久性が劣化するとともに、ガラスが失透しやすくなる。特に化学的耐久性が優れたガラスを得るためには、これらの各成分の量を、それぞれ、１５％までとすることがより好ましい。また、これらの成分のうちＬｉ_２Ｏ成分は、特に負の異常分散性を大きくする効果が大きいため、０．５％以上添加することがより好ましい。
ＢａＯ、ＣａＯ、ＭｇＯおよびＺｎＯの各成分は、光学定数の調整、ガラスの溶融性、耐失透性および化学的耐久性の向上のため任意に添加し得るが、これらの成分の一種または二種以上の合計量が５％以上であると、かえってガラスが失透しやすくなるうえ、化学的耐久性も劣化する。特に化学的耐久性および耐失透性が優れたガラスを得るためには、これらの成分の一種または二種以上の合計量を４％までとすることが、より好ましい。Ｓｂ_２Ｏ_３成分は、ガラスを清澄、均質化するための脱泡剤として任意に添加しうるが、その量は１％までで十分である。
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．２６）の組成ならびに従来公知のＳｉＯ_２−Ｎｂ_２Ｏ_５−Ｒ_２Ｏ−ＲＯ系のガラスの比較例（Ｎｏ．Ａ、Ｎｏ．Ｂ）の組成およびＳｉＯ_２−Ａｌ_２Ｏ_３−ＰｂＯ−Ｂ_２Ｏ_３系のガラスの比較例（Ｎｏ．Ｃ、Ｎｏ．Ｄ）の組成を表２〜表９に示す。また、これらのガラスの光学定数（ｎｄ、νｄ）、部分分散比（θｇ，Ｆ）、異常分散性（Δθｇ，Ｆ）、耐酸性のクラス（ＳＲ）、反射損失を含む分光透過率８０％を示す光線の波長（Ｔ_８０；単位ｎｍ）およびけい光度も表２〜表９に示す。また、図１（θｇ，Ｆ対νｄを示す図）に、上記実施例（Ｎｏ．１〜Ｎｏ．２６）のガラスが示すθｇ，Ｆおよびνｄの座標を●印、上記比較例（Ｎｏ．Ａ、Ｎｏ．Ｂ）のガラスが示すθｇ，Ｆおよびνｄの座標を■印、上記比較例（Ｎｏ．Ｃ、Ｎｏ．Ｄ）のガラスが示すθｇ，Ｆおよびνｄの座標を▲印で示した。なお、異常分散性を示すΔθｇ，Ｆの値は、前述の方法により算出したものである。 また、耐酸性を示すクラス（ＳＲ）は、国際標準化機構ＩＳＯ８４２４：１９９６（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は、所定の酸処理液中におけるガラス試料が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ものである。ＳＲが１、２、３および４の場合は、ｐＨ０．３の硝酸溶液を用いて、それぞれ、ガラス試料の侵食に、１００を超えるｈ、１００ｈ〜１０ｈ、１０ｈ未満から１ｈまで、および１ｈ未満から０．１ｈまでを要したことを示す。また、ＳＲが５、５１、５２および５３の場合は、ｐＨ４．６の酢酸緩衝液を用いて、それぞれ、ガラス試料の侵食に、１０を超えるｈ、１０ｈ〜１ｈ、１ｈ未満から０．１ｈまで、および０．１ｈ未満を要したことを示す。したがって、ＳＲのクラスの値が小さいほどガラスの耐酸性が高く、化学的耐久性が優れていることを示す。
また、Ｔ_８０は、対面研磨した厚さ１０ｍｍのガラス試料について測定した結果を示したものである。
また、けい光度（蛍光度）の測定は、日本光学硝子工業会規格「光学ガラスのけい光度の測定方法」（ＪＯＧＩＳ０３−^１９７５）に基づいて行なった。標準試料として、日本光学硝子工業会指定のフリントガラスを用い、実施例および比較例のガラス試料および上記標準試料に、主波長が３６５ｎｍの紫外線を照射して生じたけい光の強さを測定した。けい光度は、けい光の強さの測定値から、標準試料に対する各ガラス試料のけい光の強さの比を求め、比が１．５以上の場合を級３、０．７以上から１．５未満の範囲にある場合を級２、０．７未満の場合を級１として示したものである。

表２〜表９に示されるとおり、本発明の実施例のガラス（Ｎｏ．１〜Ｎｏ．２６）は、いずれも所望範囲内の屈折率（ｎｄ）およびアッベ数（νｄ）を有している。また、本発明の実施例のガラス（Ｎｏ．１〜Ｎｏ．２６）は、比較例Ｎｏ．Ａおよび比較例Ｎｏ．Ｂのガラスと比べ絶対値が大きい負のΔθｇ，Ｆの値を示し、大きな負の異常分散性を有している。一方、比較例Ｎｏ．Ｃおよび比較例Ｎｏ．Ｄのガラスは、大きな負の異常分散性を有しているが、本発明の実施例のガラス（Ｎｏ．１〜Ｎｏ．２６）は、いずれも、耐酸性のクラス（ＳＲ）が１であり、比較例Ｎｏ．Ｃおよび比較例Ｎｏ．Ｄのガラスと比べ、耐酸性が格段に優れ、化学的耐久性が優れていることが分かる。さらに、比較例（Ｎｏ．Ａ〜Ｎｏ．Ｄ）のガラスのけい光度が級３であるのに対し、本発明の実施例のガラス（Ｎｏ．１〜Ｎｏ．２６）は、いずれも、けい光度が級１であり、紫外線励起により生じるけい光の強度が非常に小さいことがわかる。
また、反射損失を含む分光透過率８０％を示す光線の波長（Ｔ_８０）は、３７７〜３３８ｎｍの範囲にあり、紫外域における光線透過性に優れていることが分かる。
また、実施例Ｎｏ．１のガラスは、屈伏点（Ａｔ）が５４９℃、転移点（Ｔｇ）が４９７℃であり、実施例Ｎｏ．１９のガラスは、屈伏点（Ａｔ）が５６２℃、転移点（Ｔｇ）が５０６℃であって、ともに低温軟化性を有しており、低温でプレス成形できる。従って、これらのガラスをプレス成形する時に、ガラスの金型への焼き付きや、金型成形面の酸化による損耗が生じにくい。そのため、実施例Ｎｏ．１及びＮｏ．１９のガラスは、精密プレス成形、すなわち、ガラスを高精度な成形面をもつ金型でプレス成形し、成形後、ガラスに研削や研磨を施すことなく、直接、レンズ等の光学素子を得ることができるプレス成形に使用するガラスとして好適である。
なお、本発明にかかる上記実施例（Ｎｏ．１〜Ｎｏ．２６）のガラスは、酸化物、炭酸塩および硝酸塩等の通常の光学ガラス用原料を所定の割合となるように秤量し、混合した後、白金坩堝等に投入し、ガラス組成による溶融性に応じて、１１００〜１３５０℃の温度で２〜４時間、溶融、脱泡し、攪拌均質化した後、降温してから金型等に鋳込み徐冷することにより、均質性の優れたガラスを容易に得ることができる。
また、本発明の光学素子は、精密プレス成形等の公知の方法によって、これらの光学ガラスを用いて製造できる。
産業上の利用可能性
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ＳｉＯ_２−ＺｒＯ_２−Ｎｂ_２Ｏ_５−Ｔａ_２Ｏ_５−Ｒ_２Ｏ（Ｒは、Ｌｉ、ＮａおよびＫから選ばれる１種または２種以上）系のガラスであるから、屈折率（ｎｄ）が１．６０〜１．７８、アッベ数（νｄ）が２９〜４５の範囲の光学定数および大きな負の異常分散性を有し、優れた化学的耐久性および均質性を有しており、各種光学機器のレンズ等として用いるのに好適である。また、本発明の光学ガラスは、ＧｅＯ_２等の原料が非常に高価な成分を含有せず、かつ、環境対策にコストを要するＰｂＯを含有していないため経済的に有利である。さらに、本発明の光学ガラスは、紫外域における光線透過性に優れ、かつ、紫外線励起によるけい光度が小さく、低けい光性を有しているため、蛍光測定用溶液セル、固体撮像素子のカバーガラス、蛍光顕微鏡の対物レンズ等の低けい光性が要求されるガラス部材として用いるのにも適している。また、低温軟化性を有しているため、プレス成形したガラスを研削または研磨をすることなく、そのままレンズ等の光学素子として使用することができる精密プレス成形用のガラスとしても適している。
【図面の簡単な説明】
図１は、本発明に係る各実施例のガラス、比較例のガラス及び基準のガラスのθｇ，Ｆ（部分分散比）対νｄ（アッベ数）を示す図である。TECHNICAL FIELD This invention does not contain PbO, has a refractive index (nd) of 1.60 to 1.78, an Abbe number (νd) of 29 to 45, and a large negative anomaly. The present invention relates to an optical glass having dispersibility and an optical element obtained from the optical glass.
Background Art In an optical lens system, chromatic aberration with respect to dichroic light is a normal optical glass that does not have large anomalous dispersion, and is removed by using a combination of two normal optical glasses having different Abbe numbers. Can do. However, for other color lights, the chromatic aberration shown as the secondary spectrum still remains. Therefore, correction of these secondary spectra, particularly correction from the blue region to the ultraviolet region of visible light, is desired in terms of lens design. The secondary spectrum can be considerably reduced by combining an optical glass exhibiting a large positive anomalous dispersion and an optical glass exhibiting a large negative anomalous dispersion.
Conventionally, as an optical glass having an optical constant in the above range and having negative anomalous dispersion, SiO ₂ —Al ₂ O ₃ —PbO—B ₂ O ₃ disclosed in Japanese Patent Publication No. 45-2311 is disclosed. A glass based on SiO ₂ and an SiO ₂ —Al ₂ O ₃ —PbO—B ₂ O ₃ —Sb ₂ O ₃ based glass disclosed in JP-A-48-74516 are known. However, since these glasses contain a large amount of PbO, there is a problem that the density is high and the weight is increased, which is disadvantageous in use. In addition, there is a problem that the cost required for environmental measures when manufacturing, processing and discarding these glasses is high. Furthermore, these glasses are not sufficiently chemically durable.
On the other hand, as a glass containing no PbO, Japanese Patent Publication No. 51-34407 discloses SiO ₂ , B ₂ O ₃ and GeO ₂ as glass forming materials, and Li ₂ O, ZnO, ZrO ₂ and Ta. A composition glass containing ₂ O ₅ is disclosed. However, this glass is economically disadvantageous because the raw material contains a large amount of very expensive GeO ₂ and Ta ₂ O ₅ as components for obtaining a desired refractive index and negative anomalous dispersion. . Moreover, the meltability of the glass is also difficult, and it is difficult to obtain a homogeneous glass.
Japanese Patent Publication No. 58-46459 discloses SiO ₂ —Nb having an optical constant in the range of refractive index (nd) of 1.61 to 1.80 and Abbe number (dispersion value) (νd) of 28 to 43. _{A 2} O ₅ —R ₂ O—RO-based glass is disclosed. However, this publication does not suggest anything about anomalous dispersion of glass.
Further, JP-A-10-130033 and JP-A No. _10-265238, glass _{SiO 2 -B 2 O 3 -ZrO 2} -Nb 2 O 5 system is disclosed. However, since these glasses all contain a relatively large amount of B ₂ O ₃ as an essential component, they have a large negative anomalous dispersibility, but the glass structure becomes weak and the chemical durability is not sufficient. There is a drawback.
The purpose of the present invention is a glass that eliminates the disadvantages found in the above prior art, does not contain components that require cost for environmental measures such as PbO, and does not contain GeO ₂ as an essential component, which has a high raw material cost, Refractive index (nd) has an optical constant in the range of 1.60 to 1.78, Abbe number (νd) in the range of 29 to 45, large negative anomalous dispersion, chemical durability and homogeneity The object is to provide an optical glass having excellent properties. Another object of the present invention is to provide an optical element obtained from the optical glass.
To solve the disclosure above problems of the present invention, the present inventors as a result of extensive research, _SiO 2 -ZrO specific composition range _{2 -Nb 2 O 5 -Ta 2 O} 5 -R 2 O ( R is one or more selected from Li, Na and K) glass, and has found that the object can be achieved, and has led to the present invention.
That is, in order to achieve the above object, according to the first aspect of the present invention, the optical glass of the present invention has a mass% based on an oxide,
SiO ₂ 30~55%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
Li ₂ O 0-25%,
Na ₂ O 0-25%,
K ₂ O 0-25%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0 to less than 5%,
CaO 0 to less than 5%,
BaO 0 to less than 5%,
ZnO 0 to less than 5%,
However, MgO + CaO + BaO + ZnO 0 to less than 5%,
Sb ₂ O ₃ 0 to 1%
In the range, each component is contained, and SrO, fluorine and B ₂ O ₃ are not contained.
The optical glass of the present invention is in mass% based on oxide,
SiO ₂ 30~55%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
However, Nb ₂ O ₅ + Ta ₂ O ₅ is 55% or less,
Li ₂ O 0.5~15%,
Na ₂ O 0-15%,
K ₂ O 0-15%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0 to less than 5%,
CaO 0 to less than 5%,
BaO 0 to less than 5%,
ZnO 0 to less than 5%,
However, MgO + CaO + BaO + ZnO 0 to less than 5%,
Sb ₂ O ₃ 0 to 1%
These components may be contained without containing SrO, fluorine and B ₂ O ₃ .
Further, the optical glass of the present invention is in mass% based on oxide,
SiO ₂ 30 to less than 47%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
However, Nb ₂ O ₅ + Ta ₂ O ₅ is 55% or less,
Li ₂ O 0.5~15%,
Na ₂ O 0-15%,
K ₂ O 0-15%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0-4%,
CaO 0-4%,
BaO 0-4%,
ZnO 0-4%,
However, MgO + CaO + BaO + ZnO 0-4%,
Sb ₂ O ₃ 0 to 1%
These components may be contained without containing SrO, fluorine and B ₂ O ₃ .
The optical glass of the present invention has optical constants in the range of refractive index (nd) of 1.60 to 1.78 and Abbe number (νd) of 29 to 45, and the values of Δθg and F indicating anomalous dispersion are It may be −0.0009 or less.
Here, the value of Δθg, F indicating anomalous dispersion is calculated by the following method. First, the partial dispersion ratio (θg, F) is obtained by the following equation (Equation 1). Of the normal optical glasses, two glass types having the partial dispersion ratio (θg, F) and Abbe number (νd) shown in Table 1 below, NSL7 and PBM2 (both OHARA Glass Co., Ltd.) are selected as references. . As shown in FIG. 1, the vertical axis indicates the partial dispersion ratio (θg, F), the horizontal axis indicates the Abbe number (νd), and the coordinates (θg, F) of these two glass types indicated by ○ in FIG. , Νd) are connected by a straight line L. Then, the difference (Δθg, F) in the ordinate between the coordinates (θg, F, νd) of the glass to be compared and the straight line L is set as a value indicating the partial dispersion ratio of the glass, that is, a value indicating anomalous dispersion. is there.

_{Here, n g, n F, n} C each g-ray spectral line (light source Hg, wavelength 435.835 nm), F line (light source H, wavelength 486.13 nm), C line (light source H, wavelength 656.27nm ) Is the refractive index of the glass.

When the value of Δθg, F calculated as described above is negative, in other words, in FIG. 1, when the coordinates of a certain glass are located below the straight line L, the glass exhibits negative anomalous dispersion. Have. When the values of Δθg and F are positive, that is, when the coordinates of a certain glass are located above the straight line L in FIG. 1, the glass has positive anomalous dispersion. In both positive and negative cases, the larger the absolute value of Δθg, F, the greater the anomalous dispersion of the glass.
In addition, the optical glass of the present invention is, Kei luminosity of glass to be measured on the basis of the Japan Optical Glass Industry Association standard "method of measuring the Kei intensity of optical glass" (JOGIS03- ¹⁹⁷⁵⁾ may be of Class 1.
According to the second aspect of the present invention, the optical element of the present invention is in mass% based on oxide,
SiO ₂ 30~55%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
Li ₂ O 0-25%,
Na ₂ O 0-25%,
K ₂ O 0-25%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0 to less than 5%,
CaO 0 to less than 5%,
BaO 0 to less than 5%,
ZnO 0 to less than 5%,
However, MgO + CaO + BaO + ZnO 0 to less than 5%,
Sb ₂ O ₃ 0 to 1%
It is obtained by using an optical glass containing each component in the range of SrO, fluorine and B ₂ O ₃ .
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing θg, F (partial dispersion ratio) vs. νd (Abbe number) of the glass of each example according to the present invention, the glass of a comparative example, and the reference glass.
BEST MODE FOR CARRYING OUT THE INVENTION As described above, the reasons for limiting the composition range of each component are as follows.
The SiO ₂ component is a glass-forming oxide and is a component that improves the stability and chemical durability against devitrification of the glass. In order to maintain the stability and chemical durability against devitrification, 30 % Or more is necessary, but if the amount exceeds 55%, the viscosity of the glass increases and the meltability deteriorates.
In order to obtain a glass having particularly good meltability and excellent homogeneity, it is more preferable that the amount of the SiO ₂ component is in the range of 30 to less than 47%.
In the present invention, the ZrO ₂ component is an important component that has been found to have an effect of increasing the refractive index of the glass and increasing the negative anomalous dispersibility by being contained in the glass. If it is less than 0.5%, those effects cannot be obtained, and if it exceeds 10%, the glass tends to devitrify and it is difficult to obtain a stable glass.
The Nb ₂ O ₅ component is an indispensable component for maintaining a desired optical constant, and is a component having an effect of reducing the intensity of fluorescence (fluorescence) of glass generated by ultraviolet excitation. However, if the amount of the Nb ₂ O ₅ component is less than 20%, it is difficult to maintain a desired optical constant, and if it exceeds 50%, the light transmittance deteriorates and the glass tends to devitrify.
When Ta ₂ O ₅ component is contained in glass, it has the effect of increasing negative anomalous dispersibility and improving light transmittance and chemical durability while maintaining the optical constant in a desired range. If the amount exceeds 15%, an unmelted product is produced in the molten glass, and it becomes difficult to obtain a homogeneous glass.
Further, in order to sufficiently obtain the above effect, the Ta ₂ O ₅ component should be contained at 1% or more.
In addition, since both Nb ₂ O ₅ and Ta ₂ O ₅ components are components having high raw material costs, both components can be used in order to sufficiently obtain the above-described effects of both components and to keep the manufacturing cost of glass low. More preferably, the total amount of is 55% or less.
Each component of Li ₂ O, Na ₂ O and K ₂ O has an effect of promoting melting of the glass, and the vitrification range can be expanded by adding these components. Furthermore, these components have an effect of imparting negative anomalous dispersion to the glass. However, when the total amount of one or more of these components is less than 12%, the above effects can be sufficiently obtained. It becomes impossible. If the total amount of one or more of these components exceeds 25%, the chemical durability of the glass deteriorates and the glass tends to devitrify. In particular, in order to obtain a glass having excellent chemical durability, the amount of each of these components is more preferably up to 15%. Of these components, the Li ₂ O component is more preferably added in an amount of 0.5% or more because it has a particularly large effect of increasing negative anomalous dispersion.
Each component of BaO, CaO, MgO and ZnO can be optionally added to adjust the optical constant, improve the meltability, devitrification resistance and chemical durability of the glass. One or two of these components can be added. If the total amount is 5% or more, the glass tends to be devitrified, and the chemical durability is deteriorated. In particular, in order to obtain a glass excellent in chemical durability and devitrification resistance, it is more preferable to set the total amount of one or more of these components to 4%. The Sb ₂ O ₃ component can be optionally added as a defoaming agent for clarifying and homogenizing the glass, but up to 1% is sufficient.
Examples Next, compositions of preferred examples (No. 1 to No. 26) of the optical glass according to the present invention and comparative examples of conventionally known SiO ₂ —Nb ₂ O ₅ —R ₂ O—RO-based glasses. (No. a, No.B) Comparative example glass composition and _{SiO 2 -Al 2 O 3 -PbO-} B 2 O 3 system (No. C, No. D) the composition of Table 2 to Table 9 Show. Also, the optical constants (nd, νd), partial dispersion ratio (θg, F), anomalous dispersion (Δθg, F), acid resistance class (SR), and spectral transmittance 80% including reflection loss of these glasses are obtained. Tables 2 to 9 also show the wavelength of light (T ₈₀ ; unit nm) and fluorescence. Further, in FIG. 1 (a diagram showing θg, F vs. νd), the coordinates of θg, F and νd shown by the glass of the above examples (No. 1 to No. 26) are marked with ●, and the comparative example (No. A The coordinates of θg, F and νd indicated by the glass of No. B) are indicated by ▪, and the coordinates of θg, F and νd indicated by the glass of the comparative example (No. C, No. D) are indicated by ▲. The value of Δθg, F indicating anomalous dispersion is calculated by the method described above. The class (SR) indicating acid resistance indicates the results obtained by measurement in accordance with the measurement method of International Standardization Organization ISO 8424: 1996 (E). Here, SR is graded according to the time (h) required for a glass sample in a predetermined acid treatment solution to undergo erosion of 0.1 μm. When SR is 1, 2, 3 and 4, the nitric acid solution with pH 0.3 is used to attack the glass sample for more than 100 h, 100 h to 10 h, less than 10 h to 1 h, and less than 1 h, respectively. It shows that it took up to 0.1h. Moreover, when SR is 5, 51, 52 and 53, the pH 4.6 is used for the erosion of the glass sample, respectively, for erosion of the glass sample from more than 10 h, from 10 h to 1 h, from less than 1 h to 0.1 h. , And less than 0.1 h. Therefore, the smaller the SR class value, the higher the acid resistance of the glass and the better the chemical durability.
Further, T ₈₀ is a diagram showing the results of measurement for the glass sample having a thickness of 10mm which faces polished.
In addition, measurement of silicon luminous intensity (fluorescence) was carried out on the basis of the Japan Optical Glass Industry Association standard "method of measuring the Kei intensity of optical glass" (JOGIS03- ^1975). The flint glass designated by the Japan Optical Glass Industry Association was used as the standard sample, and the intensity of the fluorescence produced by irradiating the glass samples of Examples and Comparative Examples and the standard sample with ultraviolet rays having a main wavelength of 365 nm was measured. . For the fluorescence intensity, the ratio of the fluorescence intensity of each glass sample to the standard sample is obtained from the measured value of the fluorescence intensity. A case of less than 5 is shown as class 2, and a case of less than 0.7 is shown as class 1.

As shown in Tables 2 to 9, the glasses (No. 1 to No. 26) of the examples of the present invention all have a refractive index (nd) and an Abbe number (νd) within a desired range. . Moreover, the glass (No.1-No.26) of the Example of this invention is comparative example No.1. A and Comparative Example No. It has a negative Δθg, F value that is larger than that of B glass and has a large negative anomalous dispersion. On the other hand, Comparative Example No. C and Comparative Example No. Although the glass of D has a large negative anomalous dispersibility, all of the glasses (No. 1 to No. 26) of the examples of the present invention have an acid resistance class (SR) of 1. Comparative Example No. C and Comparative Example No. It can be seen that the acid resistance is remarkably excellent and the chemical durability is excellent as compared with the glass of D. Furthermore, while the fluorescence of the glass of the comparative examples (No. A to No. D) is class 3, the glasses of the examples of the present invention (No. 1 to No. 26) are all fluorescent. Is class 1, and it can be seen that the intensity of fluorescence generated by ultraviolet excitation is very small.
The wavelength of the light beam which indicates an 80% spectral transmittance including reflection loss _{(T 80)} is in the range of 377～338Nm, it can be seen that excellent light transmittance in the ultraviolet region.
In addition, Example No. The glass of No. 1 has a yield point (At) of 549 ° C. and a transition point (Tg) of 497 ° C. No. 19 has a yield point (At) of 562 ° C. and a transition point (Tg) of 506 ° C., both of which have low-temperature softening properties and can be press-molded at a low temperature. Therefore, when these glasses are press-molded, the glass is not easily burned into the mold or worn out due to oxidation of the mold surface. Therefore, Example No. 1 and no. Glass No. 19 is precision press-molded, that is, the glass is press-molded with a mold having a high-precision molding surface, and after molding, an optical element such as a lens can be obtained directly without grinding or polishing the glass. It is suitable as a glass used for press molding.
In addition, the glass of the said Example (No.1-No.26) concerning this invention measured and mixed the raw materials for optical glasses, such as an oxide, carbonate, and nitrate, so that it might become a predetermined | prescribed ratio. After that, it is put into a platinum crucible, etc., melted and degassed at a temperature of 1100 to 1350 ° C. for 2 to 4 hours according to the meltability of the glass composition, homogenized with stirring, and then cooled to a mold or the like. By casting and cooling slowly, glass with excellent homogeneity can be easily obtained.
The optical element of the present invention can be produced using these optical glasses by a known method such as precision press molding.
As described above INDUSTRIAL APPLICABILITY The optical glass of the present _{invention, SiO 2 -ZrO 2 -Nb 2 O} 5 -Ta 2 O 5 -R 2 O (R a specific composition range, Li, Na and K 1 type or two or more types of glass selected from the group consisting of optical constants having a refractive index (nd) of 1.60 to 1.78 and an Abbe number (νd) of 29 to 45 and a large negative anomaly. It has dispersibility, has excellent chemical durability and homogeneity, and is suitable for use as a lens of various optical instruments. In addition, the optical glass of the present invention is economically advantageous because the raw material such as GeO ₂ does not contain a very expensive component and does not contain PbO that is costly for environmental measures. Furthermore, the optical glass of the present invention is excellent in light transmittance in the ultraviolet region, has low fluorescence due to ultraviolet excitation, and has low fluorescence. It is also suitable for use as a glass member requiring low fluorescence such as glass and an objective lens of a fluorescence microscope. Further, since it has a low temperature softening property, it is also suitable as a glass for precision press molding that can be used as an optical element such as a lens as it is without grinding or polishing the press molded glass.
[Brief description of the drawings]
FIG. 1 is a diagram showing θg, F (partial dispersion ratio) versus νd (Abbe number) of the glass of each example according to the present invention, the glass of the comparative example, and the reference glass.

Claims (7)

% By mass based on oxide,
SiO ₂ 30~55%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
Li ₂ O 0-25%,
Na ₂ O 0-25%,
K ₂ O 0-25%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0 to less than 5%,
CaO 0 to less than 5%,
BaO 0 to less than 5%,
ZnO 0 to less than 5%,
However, MgO + CaO + BaO + ZnO 0 to less than 5%,
Sb ₂ O ₃ 0 to 1%
An optical glass characterized in that it contains each component in the range, and does not contain SrO, fluorine and B ₂ O ₃ . % By mass based on oxide,
SiO ₂ 30~55%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
However, Nb ₂ O ₅ + Ta ₂ O ₅ is 55% or less,
Li ₂ O 0.5~15%,
Na ₂ O 0-15%,
K ₂ O 0-15%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0 to less than 5%,
CaO 0 to less than 5%,
BaO 0 to less than 5%,
ZnO 0 to less than 5%,
However, MgO + CaO + BaO + ZnO 0 to less than 5%,
Sb ₂ O ₃ 0 to 1%
_2. The optical glass according to claim 1, which contains each component in the above range and does not contain SrO, fluorine and B ₂ O ₃ . % By mass based on oxide,
SiO ₂ 30 to less than 47%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
However, Nb ₂ O ₅ + Ta ₂ O ₅ is 55% or less,
Li ₂ O 0.5~15%,
Na ₂ O 0-15%,
K ₂ O 0-15%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0-4%,
CaO 0-4%,
BaO 0-4%,
ZnO 0-4%,
However, MgO + CaO + BaO + ZnO 0-4%,
Sb ₂ O ₃ 0 to 1%
_2. The optical glass according to claim 1, which contains each component in the above range and does not contain SrO, fluorine and B ₂ O ₃ . The refractive index (nd) has an optical constant in the range of 1.60 to 1.78, the Abbe number (νd) in the range of 29 to 45, and the values of Δθg and F indicating anomalous dispersion are −0.0009 or less. The optical glass according to claim 1, 2, or 3. The optical glass according to claim 1, which is substantially free of PbO. % By mass based on oxide,
SiO ₂ 30~55%,
ZrO ₂ 0.5-10%,
Nb ₂ O ₅ 20-50%,
Ta ₂ O ₅ 1-15%,
Li ₂ O 0-25%,
Na ₂ O 0-25%,
K ₂ O 0-25%,
_{However, Li 2 O + Na 2 O} + K 2 O 12~25%,
MgO 0 to less than 5%,
CaO 0 to less than 5%,
BaO 0 to less than 5%,
ZnO 0 to less than 5%,
However, MgO + CaO + BaO + ZnO 0 to less than 5%,
Sb ₂ O ₃ 0 to 1%
An optical element characterized by being obtained using an optical glass containing each component in the range described above and containing no SrO, fluorine and B ₂ O ₃ . "Measurement method of silicate luminous intensity of optical glass" (JOGIS03- ¹⁹⁷⁵⁾ silicate luminous intensity of the glass to be measured based on the characterized in that it is a Grade 1 claims the first term of the Japan Optical Glass Industrial Standard, paragraph 2 or 4. Optical glass according to item 3.

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