JP4035898B2 - Optical glass for press-molded lenses - Google Patents
Optical glass for press-molded lenses Download PDFInfo
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- JP4035898B2 JP4035898B2 JP23535998A JP23535998A JP4035898B2 JP 4035898 B2 JP4035898 B2 JP 4035898B2 JP 23535998 A JP23535998 A JP 23535998A JP 23535998 A JP23535998 A JP 23535998A JP 4035898 B2 JP4035898 B2 JP 4035898B2
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- temperature
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Classifications
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/12—Silica-free oxide glass compositions
- C03C3/16—Silica-free oxide glass compositions containing phosphorus
- C03C3/17—Silica-free oxide glass compositions containing phosphorus containing aluminium or beryllium
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
Description
【0001】
【産業上の利用分野】
本発明は比較的低温でプリフォームの熱間成形が可能で、かつプレス成形レンズに適した光学ガラスに関する。
【0002】
【従来の技術】
精密光学部品として、例えばレンズをプレス成形により製造する方式は近年広く使用されている。プレス成形は、それぞれ相対向する面が転写面となった下型及び上型を胴型内に設けるようにした成形型を用い、この成形型の下型と上型との間にガラス素材を配置した状態で加熱炉内に搬入して、この加熱炉内でガラス素材をプレス成形が可能な屈伏温度にまで加熱した上で、上下の型に加圧力を作用させてプレス成形することにより、ガラス素材に下型及び上型の転写面形状を転写するものである。プレス成形に用いられるガラス素材としては、レンズ形状にできるだけ近似した形状のプリフォームが用いられる。このプリフォームは熱間成形により形成され、ガラスを溶融状態にまで加熱してその溶融ガラスを所定量だけ型に受けることにより生成される。
【0003】
以上のことから、プレス成形に用いられるガラスの特性としては、まずプレス成形が可能な温度、つまり屈伏温度ができるだけ低いものを用いるのが望ましい。また、プリフォームを熱間成形するに当っては、ガラスの粘度が高い方が精度良く成形できることになる。従って、プレス成形に適したガラスとしては、屈伏温度(Ts)及び液相温度(L.T.)ができるだけ低いものが望まれる。
【0004】
ここで、屈折率(nd)が1.52〜1.62、アッベ数(νd)が59.0〜64.0の範囲の光学恒数を持つプレス成形レンズ用ガラスとして、P2O5−ZnO−Li2O系ガラス(特許2616980号公報)が知られている。この公知のガラスは屈伏温度が500℃以下というように低いことから、プレス成形レンズ用のプリフォームとしては優れた特性を有している。
【0005】
【発明が解決しようとする課題】
ところで、前述した公知のガラスの組成には、屈伏温度を下げるためにZnOを多量に含んでいる関係から、液相温度の上昇を招き、プリフォームの熱間成形時の精度が劣るという欠点がある。また、光ファイバー用のガラスとして、P2O5−ZnO−Li2O系ガラスを用いることが、特公平4−32015号公報に示されている。このガラスの組成としては、希土類酸化物を用いることにより屈折率を高くし、かつ転移点温度を下げるようにしている。ただし、希土類酸化物としてLa2O3 を用いていることから、レンズとして十分に耐失透性の良いガラスは得られていない。
【0006】
従って、本発明の目的は、 屈折率(nd)が1.56〜1.62で、アッベ数(νd)が56.0〜64.0の範囲の光学恒数を有し、しかもプレス成形レンズに適した低い屈伏温度を維持しつつ、 比較的低温でプリフォームの熱間成形が可能な光学ガラスを提供することにある。
【0007】
【課題を解決するための手段】
本発明者等は以上のような従来技術の欠点を解消すべく鋭意研究を行った結果、希土類酸化物としてLa2O3 の代わりにGd2O3 を加えたP2O5−ZnO−Li2O−Gd2O3 系が、低い屈伏温度を維持しつつ液相温度を著しく下げることを知見したことによって発明を完成するに至った。
【0008】
而して、本発明によるガラスの組成を重量%で表すと、
P2O5 48〜58%
Al2O3 1〜 3%
Li2O 1〜 4%
Na2O 0〜 4%
MgO 0〜 5%
CaO 0〜10%
SrO 0〜10%
BaO 2〜15%
ただし、MgO+CaO+SrO+BaOの合量 8〜20%
ZnO 18〜32%
Gd2O3 1〜 5%
ZrO2 0〜 1%
Nb2O5 0〜 2%
である。
【0009】
本発明の光学ガラスの組成における各成分範囲を以上のように検定した理由は次の通りである。
【0010】
まず、P2O5 はガラスの骨格を構成する主成分であるが、 本願の目的とする光学恒数、つまり屈折率(nd)1.56〜1.62、アッベ数(νd)56.0〜64.0の範囲の光学恒数を得るために、このP2O5 の含量は48% 〜58%に限定される。
【0011】
Al2O3 は1%以上添加することにより液相温度を下げ、耐候性を向上させる。しかし3%を超えると逆に液相温度を上昇させる。
【0012】
Li2Oは屈伏温度の低温度化に必要な成分で1%以上必要である。ただし、添加量が4%を超えると液相温度の上昇を招くことになる。
【0013】
Na2Oを少量添加すると、屈伏温度と液相温度を改善する上で有効である。ただし、4%を超えると液相温度が逆に上昇するとともに耐候性が悪化する。
【0014】
BaOはアッベ数を高く保持し液相温度の低いガラスを得るのに必須であり、少なくとも2%以上必要だが、添加量が15%を超えると屈伏温度が上昇するので望ましくはない。
【0015】
MgO,CaO,SrOは液相温度の改善と光学恒数の調整を行う上で有効である。ただし、それらが各々5%,10%,15%を超えると液相温度が上がってしまう。また、所望の屈伏温度と液相温度を得るということから、MgO,CaO,SrO,BaOの合量は8〜20%に限定される。
【0016】
ZnOは屈伏温度が低くかつ屈折率が比較的高いガラスを得るのに有効な成分であり18%以上必要だが、32%を超えると液相温度が上昇するとともに所望のアッベ数を得るのが困難になる。
【0017】
Gd2O3は既に説明したように、液相温度を下げるのに有効であり、かつ耐候性改善の効果もあり、1%以上必要である。ただし、Gd2O3 の添加量が5%を超えると逆に液相温度が上昇する。
【0018】
ZrO2 ,Nb2O5 は耐候性を改善する効果が大きいので、必要に応じて微量添加される。ただし、ZrO2 が1%を超えると液相温度が上昇し、Nb2O5が2%を超えると所望のアッベ数を維持できなくなる。
【0019】
【実施例】
次に本発明に係る実施組成例および前記従来の光学ガラスの比較組成例を、屈折率(nd)、アッベ数(νd)、屈状温度(Ts)、液相温度(L.T.)の測定結果とともに表1,2に示す。表2の比較例No.7は表1の実施例No.1のGd2O3 をLa2O3 に置き換えた組成であり、比較例No.8は実施例No.5のGd2O3 をLa2O3 に置き換えた組成である。
【0020】
表記の光学ガラスは、P2O5 原料として正燐酸またはメタ燐酸塩を用い、他の成分についてはメタ燐酸塩、炭酸塩、硝酸塩、酸化物等を用い、 これらの原料を所定の割合に調合して白金製るつぼに投入し、1000〜1200℃の電気炉にて溶融、 攪拌均質化してから鉄製型に流し込み徐冷することにより得る。
【0021】
表中の屈折率(nd)、アッベ数(νd)は、速度−10K/hourにて徐冷した場合の結果である。屈状温度(Ts)は熱膨張測定機を用いて5K/minで昇温した場合の結果である。また、液相温度(L.T.)は500〜1000℃の温度勾配のついた失透試験装置に30分保持した後、倍率100倍の偏光顕微鏡で結晶の有無を観察して得た結果である。
【0022】
【表1】
【0023】
【表2】
以上の表1,2に見られるとおり、Gd2O3 はLa2O3 と比較して液相温度を下げるのに有効であることがわかる。 その結果、 表1に見られるように、本発明の光学ガラスはいずれも440℃以下の屈状温度(Ts)を維持しつつ液相温度(L.T.)を870℃以下に下げることが可能である。
【0024】
【発明の効果】
本発明のP2O5−ZnO−Li2O−Gd2O3 系光学ガラスは、屈折率(nd)1.56〜1.62、アッベ数(νd)56.0〜64.0の範囲の光学恒数の範囲の光学恒数を有し、しかもプレス成形レンズに適した440℃以下の屈状温度(Ts)を維持しつつ、870℃以下の液相温度(L.T.)を有しているため、比較的低い温度でプリフォームの熱間成形を行うことができる等といった効果を奏する。[0001]
[Industrial application fields]
The present invention relates to an optical glass capable of hot forming a preform at a relatively low temperature and suitable for a press-molded lens.
[0002]
[Prior art]
As a precision optical component, for example, a method of manufacturing a lens by press molding has been widely used in recent years. Press molding uses a molding die in which a lower die and an upper die each having a surface facing each other as a transfer surface are provided in a body die, and a glass material is placed between the lower die and the upper die. By carrying it into the heating furnace in the state of being placed and heating the glass material to a yield temperature where press molding is possible in this heating furnace, by applying pressure to the upper and lower molds and press molding, The transfer surface shape of the lower mold and the upper mold is transferred to a glass material. As a glass material used for press molding, a preform having a shape as close as possible to the lens shape is used. This preform is formed by hot forming, and is produced by heating the glass to a molten state and receiving the molten glass in a predetermined amount.
[0003]
From the above, it is desirable that the glass used for press molding should have a temperature at which press molding can be performed, that is, a material having the lowest yield temperature. In addition, when the preform is hot-formed, the glass having a higher viscosity can be formed with higher accuracy. Therefore, a glass suitable for press molding is desired to have as low a yield temperature (Ts) and a liquidus temperature (LT) as possible.
[0004]
Here, as a glass for press-molded lenses having an optical constant having a refractive index (nd) of 1.52 to 1.62 and an Abbe number (νd) of 59.0 to 64.0, P 2 O 5 − ZnO—Li 2 O-based glass (Japanese Patent No. 2616980) is known. This known glass has an excellent characteristic as a preform for a press-molded lens because the deformation temperature is as low as 500 ° C. or less.
[0005]
[Problems to be solved by the invention]
By the way, the above-mentioned known glass composition has a drawback in that since it contains a large amount of ZnO in order to lower the yield temperature, the liquidus temperature rises and the accuracy during hot forming of the preform is inferior. is there. Japanese Patent Publication No. 4-32015 discloses the use of P 2 O 5 —ZnO—Li 2 O-based glass as glass for optical fibers. As the composition of this glass, a rare earth oxide is used to increase the refractive index and lower the transition temperature. However, since La 2 O 3 is used as a rare earth oxide, a glass having sufficiently good devitrification resistance as a lens has not been obtained.
[0006]
Accordingly, an object of the present invention is to provide an optical constant having a refractive index (nd) of 1.56 to 1.62, an Abbe number (νd) of 56.0 to 64.0, and a press-molded lens. It is an object of the present invention to provide an optical glass capable of hot forming a preform at a relatively low temperature while maintaining a low deformation temperature suitable for the above.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to eliminate the drawbacks of the prior art as described above, the present inventors have found that P 2 O 5 —ZnO—Li in which Gd 2 O 3 is added instead of La 2 O 3 as a rare earth oxide. The inventors have found that the 2 O—Gd 2 O 3 system significantly lowers the liquidus temperature while maintaining a low yielding temperature, thereby completing the invention.
[0008]
Thus, when the composition of the glass according to the present invention is expressed in weight%,
P 2 O 5 48~58%
Al 2 O 3 1-3%
Li 2 O 1-4%
Na 2 O 0-4%
MgO 0-5%
CaO 0-10%
SrO 0-10%
BaO 2-15%
However, the total amount of MgO + CaO + SrO + BaO 8-20%
ZnO 18-32%
Gd 2 O 3 1-5%
ZrO 2 0 to 1%
Nb 2 O 5 0-2%
It is.
[0009]
The reason why each component range in the composition of the optical glass of the present invention was tested as described above is as follows.
[0010]
First, P 2 O 5 is a main component constituting the skeleton of the glass, but the optical constants of the present application, that is, refractive index (nd) 1.56-1.62, Abbe number (νd) 56.0. In order to obtain an optical constant in the range of ˜64.0, the content of P 2 O 5 is limited to 48% to 58%.
[0011]
Al 2 O 3 is added at 1% or more to lower the liquidus temperature and improve the weather resistance. However, if it exceeds 3%, the liquidus temperature is raised.
[0012]
Li 2 O is a component necessary for lowering the yield temperature, and 1% or more is necessary. However, when the addition amount exceeds 4%, the liquidus temperature is increased.
[0013]
Addition of a small amount of Na 2 O is effective in improving the yield temperature and liquidus temperature. However, if it exceeds 4%, the liquidus temperature rises conversely and the weather resistance deteriorates.
[0014]
BaO is essential for obtaining a glass having a high Abbe number and a low liquidus temperature, and is required to be at least 2% or more. However, if the added amount exceeds 15%, the deformation temperature is undesirably increased.
[0015]
MgO, CaO, and SrO are effective in improving the liquid phase temperature and adjusting the optical constant. However, if they exceed 5%, 10%, and 15%, respectively, the liquidus temperature rises. Moreover, since the desired yield temperature and liquidus temperature are obtained, the total amount of MgO, CaO, SrO, and BaO is limited to 8 to 20%.
[0016]
ZnO is an effective component for obtaining a glass having a low yield temperature and a relatively high refractive index, and is required to be 18% or more. However, if it exceeds 32%, the liquidus temperature rises and it is difficult to obtain a desired Abbe number. become.
[0017]
As already described, Gd 2 O 3 is effective for lowering the liquidus temperature, and also has an effect of improving weather resistance, and needs to be 1% or more. However, when the amount of Gd 2 O 3 added exceeds 5%, the liquidus temperature increases.
[0018]
ZrO 2 and Nb 2 O 5 have a great effect of improving the weather resistance, and are added in small amounts as necessary. However, if ZrO 2 exceeds 1%, the liquidus temperature rises, and if Nb 2 O 5 exceeds 2%, the desired Abbe number cannot be maintained.
[0019]
【Example】
Next, an example composition according to the present invention and a comparative composition example of the above-described conventional optical glass have a refractive index (nd), Abbe number (νd), bent temperature (Ts), and liquidus temperature (LT). It shows in Table 1, 2 with a measurement result. Comparative Example No. 2 in Table 2 7 is an example No. 7 in Table 1. No. 1 Gd 2 O 3 is replaced with La 2 O 3 . 8 shows Example No. No. 5 Gd 2 O 3 is replaced with La 2 O 3 .
[0020]
The optical glass indicated uses orthophosphoric acid or metaphosphate as the P 2 O 5 raw material, and metaphosphorate, carbonate, nitrate, oxide, etc. are used for the other components, and these raw materials are prepared in a predetermined ratio. Then, it is put into a platinum crucible, melted in a 1000 to 1200 ° C. electric furnace, homogenized with stirring, poured into an iron mold and gradually cooled.
[0021]
The refractive index (nd) and Abbe number (νd) in the table are the results when cooling slowly at a speed of −10 K / hour. The bent temperature (Ts) is the result when the temperature is increased at 5 K / min using a thermal expansion measuring machine. The liquidus temperature (LT) was obtained by observing the presence or absence of crystals with a polarizing microscope at a magnification of 100 times after being held in a devitrification test apparatus with a temperature gradient of 500 to 1000 ° C. for 30 minutes. It is.
[0022]
[Table 1]
[0023]
[Table 2]
As can be seen from Tables 1 and 2 above, it can be seen that Gd 2 O 3 is effective in lowering the liquidus temperature as compared with La 2 O 3 . As a result, as shown in Table 1, all of the optical glasses of the present invention can reduce the liquidus temperature (LT) to 870 ° C. or lower while maintaining the bending temperature (Ts) of 440 ° C. or lower. Is possible.
[0024]
【The invention's effect】
The P 2 O 5 —ZnO—Li 2 O—Gd 2 O 3 optical glass of the present invention has a refractive index (nd) of 1.56 to 1.62 and an Abbe number (νd) of 56.0 to 64.0. The liquid phase temperature (LT) of 870 ° C. or lower is maintained while maintaining the bending temperature (Ts) of 440 ° C. or lower, which is suitable for a press-molded lens. Since it has, there exists an effect that a preform can be hot formed at a relatively low temperature.
Claims (1)
P2O5 48〜58%
Al2O3 1〜 3%
Li2O 1〜 4%
Na2O 0〜 4%
MgO 0〜 5%
CaO 0〜10%
SrO 0〜10%
BaO 2〜15%
ただし、MgO+CaO+SrO+BaOの合量 8〜20%
ZnO 18〜32%
Gd2O3 1〜 5%
ZrO2 0〜 1%
Nb2O5 0〜 2%
からなり、屈伏温度(Ts)が440℃以下、液相温度(L.T.)が870℃以下で、屈折率(nd)が1.56〜1.62、アッベ数(νd)が56.0〜64.0である光学ガラス。% By weight P 2 O 5 48-58%
Al 2 O 3 1-3%
Li 2 O 1-4%
Na 2 O 0-4%
MgO 0-5%
CaO 0-10%
SrO 0-10%
BaO 2-15%
However, the total amount of MgO + CaO + SrO + BaO 8-20%
ZnO 18-32%
Gd 2 O 3 1-5%
ZrO 2 0 to 1%
Nb 2 O 5 0-2%
The yield temperature (Ts) is 440 ° C. or lower, the liquidus temperature (LT) is 870 ° C. or lower, the refractive index (nd) is 1.56 to 1.62, and the Abbe number (νd) is 56. Optical glass that is 0-64.0.
Priority Applications (1)
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JP23535998A JP4035898B2 (en) | 1998-08-21 | 1998-08-21 | Optical glass for press-molded lenses |
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JP23535998A JP4035898B2 (en) | 1998-08-21 | 1998-08-21 | Optical glass for press-molded lenses |
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JP2000072474A JP2000072474A (en) | 2000-03-07 |
JP4035898B2 true JP4035898B2 (en) | 2008-01-23 |
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DE10239572B3 (en) * | 2002-08-23 | 2004-01-08 | Schott Glas | Lead-free and preferably arsenic-free optical heavy crown glasses and their use |
JP2004168593A (en) * | 2002-11-20 | 2004-06-17 | Minolta Co Ltd | Optical glass |
US7157391B2 (en) * | 2002-12-27 | 2007-01-02 | Hoya Corporation | Optical glass, preform for press molding and optical element |
JP4162532B2 (en) * | 2003-04-18 | 2008-10-08 | Hoya株式会社 | Optical glass, press-molding preform and manufacturing method thereof, optical element and manufacturing method thereof |
JP4442168B2 (en) * | 2003-09-10 | 2010-03-31 | コニカミノルタオプト株式会社 | Optical glass and optical element |
JP6540706B2 (en) | 2014-09-05 | 2019-07-10 | 株式会社ニコン | Optical glass, optical element using optical glass, optical device |
CN114853338A (en) * | 2017-06-20 | 2022-08-05 | 成都光明光电有限责任公司 | Low melting point glass |
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1998
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