JP3681114B2

JP3681114B2 - Manufacturing method of glass optical element

Info

Publication number: JP3681114B2
Application number: JP2001261775A
Authority: JP
Inventors: 浩之澤田; 順孝後藤; ゆか宮下
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2000-09-01
Filing date: 2001-08-30
Publication date: 2005-08-10
Anticipated expiration: 2021-08-30
Also published as: JP2002145630A

Description

【０００１】
【発明の属する技術分野】
本発明は、一方または両方の面が凹形状であって、例えば、中心肉厚ａと周辺肉厚ｂとの比ｂ／ａが１．５以上であるレンズを高い面精度で成形するガラス光学素子の製造方法に関する。
【０００２】
【従来の技術及び発明が解決すべき課題】
軟化したガラスを製品形状または製品形状に近似する形状を有する成形型を用いて加圧プレスして、研削や研磨をすることなく直接レンズを製造する方法(精密プレス法)が広く実用化されている。精密プレス法は、デジタルカメラやビデオカメラなど、さまざまな光学機器製品の光学系用レンズの製法として利用されている。精密プレス法においては、成形型の成形面をなるべく精密にガラスに転写する必要が有る。
【０００３】
しかし、一方または両方の面が凹形状のレンズは、ガラスに成形面を転写しても、ガラスが固化する間にガラスが一方の面の方向に反ってしまったり、いったん形成された転写面が悪化したりするために、十分な面精度が得られないことが有った。中心肉厚ａと周辺肉厚ｂとの比ｂ／ａが１．５以上であるレンズの成形においてはこの傾向が顕著であった。
【０００４】
そこで本発明の目的は、一方または両方の面が凹形状であるレンズであっても、高い面精度で成形できるガラス光学素子の製造方法を提供することにある。
【０００５】
【課題を解決するための手段】
本発明者らの検討の結果、レンズ形状のガラス成形品を徐冷する際に、一方の面が凹形状のレンズの場合、凹形状の面の冷却を反対側の面（平面又は凸面）の冷却より遅らせること、又、両方の面が凹形状のレンズの場合、曲率半径が小さい凹形状の面の冷却を反対側の曲率半径が大きい凹形状面の冷却より遅らせることで、上記課題を解決することを見出して本発明を完成した。
【０００６】
即ち、本発明は、加熱軟化した被成形ガラス素材を、得ようとするガラス光学子の光学的機能面を形成するための成形面を有する上型及び下型を含み、前記成形面の一方は凹面を形成するものであり、他方は凸面または平面を形成するものである成形型により加圧成形して、前記被成形ガラス素材に前記成形面を転写する工程（成形工程）、
前記成形型を冷却することにより成形したガラスをこのガラスのガラス転移温度(Tg)以下になるように冷却する工程（冷却工程）、
冷却されたガラスを前記成形型から取り出す工程（取り出し工程）、を含む一方の光学的機能面が凹面であるガラス光学素子の製造方法であって、
前記冷却を、成形面が凸面または平面を形成するものである型の温度ｔa２が、成形面が凹面を形成するものである型の温度ｔa1より先に、前記Tgに達するように行うことを特徴とする前記製造方法（第1の製造方法）に関する。
【０００７】
さらに本発明は、加熱軟化した被成形ガラス素材を、得ようとするガラス光学素子の光学的機能面を形成するための成形面を有する上型及び下型を含み、前記成形面の両方が凹面を形成するものである成形型により加圧成形して、前記被成形ガラス素材に前記成形面を転写する工程（以下、成形工程という）、
前記成形型を冷却することにより成形したガラスをこのガラスのガラス転移温度(Tg)以下になるように冷却する工程（以下、冷却工程という）、
冷却されたガラスを前記成形型から取り出す工程（以下、取り出し工程という）、を含む両方の光学的機能面が凹面であるガラス光学素子の製造方法であって、
前記冷却を、曲率半径が大きい方の成形面を有する型の温度ｔb２が、曲率半径が小さい方の成形面を有する型の温度ｔb１より先に、前記Tgに達するように行うことを特徴とする前記製造方法（第2の製造方法）に関する。
【０００８】
【発明の実施の形態】
以下本発明を詳細に説明する。
本発明の製造方法において製造の対象となるガラス光学素子は、例えば、一方または両方の面が凹形状であるレンズであることができる。特に本発明の製造方法は、中心肉厚ａと周辺肉厚ｂとの比ｂ／ａが１．５以上であるレンズの製造方法に適している。
そのようなレンズの例を図１に示す。図１の（Ａ）に示すレンズ１０は、一方の面Ｓ２が凹形状であり、他方の面Ｓ１は平面である。又、（Ｂ）に示すレンズ１１は、一方の面Ｓ２が凹形状であり、他方の面Ｓ１は凸面である。（Ｃ）に示すレンズ１２は、面Ｓ１及び面Ｓ２ともに凹形状である。但し、面Ｓ１の凹形状の曲率半径Ｒが、面Ｓ２の凹形状の曲率半径Ｒより大きい。さらに、（Ａ）〜（Ｃ）のいずれのレンズも、中心肉厚ａと周辺肉厚ｂとの比ｂ／ａが１．５以上であることができる。
【０００９】
尚、本発明の製造方法で製造対象とする凹メニスカスレンズ及び両凹レンズは、各種のレンズ系に組み込むために光学機能面(光学的有効領域)を有するものである。光学機能面(光学的有効領域)は、例えば、図２において４１として示す凹面であり、実際には、この凹面４１の外側に光軸と直交する平面部４３が設けられる。
【００１０】
一方または両方の面が凹形状であるレンズの場合、加圧プレス後、冷却の過程で歪みが緩和されると、一方の面が凹形状であるレンズの場合は、凹形状の面の曲率半径を小さくする方向に、また、両方の面が凹形状であるレンズの場合は、曲率半径の小さい凹形状の面の曲率半径を小さくする方向に形状変化を起こす。特に、比ｂ／ａが１．５以上であるレンズの場合に、この傾向が顕著である。しかし、比ｂ／ａが１．５未満のレンズの成形においても、同様の傾向はあり、比ｂ／ａが１．５未満のレンズの製造にも、本発明の製造方法は有効である。また、本発明の製造方法は、比ｂ／ａが１．５以上であるレンズに有効であるが、実用されているレンズの比ｂ／ａは、約３．５程度までである。但し、それを超える比ｂ／ａを有するレンズの成形も本発明の製造方法により可能である。
【００１１】
本発明の第1の製造方法は、図１の（Ａ）又は（Ｂ）に示すように、レンズの一方の面が平面又は凸面である場合が対象である。この場合、冷却工程における冷却を、成形面が凸面または平面を形成するものである型の温度ｔa２が、成形面が凹面を形成するものである型の温度ｔa1より先に、成形対象となっているガラスのガラス転移温度Tgに達するように行う。好ましくは温度ｔa２がTgに達したときに温度ｔa1は、温度ｔa２より５℃以上高くなるように冷却条件を設定する。特に好ましくは、温度ｔa２がTgに達したときに温度ｔa1は、温度ｔa２より好ましくは５℃〜４０℃、より好ましくは５〜３０℃、さらに好ましくは５〜２０℃以上高くなるように冷却条件を設定する。
【００１２】
さらに、少なくとも成形工程終了時において、温度ｔa２は温度ｔa1より低いことが好ましく、より好ましくは、少なくとも成形工程終了時において、温度ｔa２は温度ｔa1より５℃以上低い。即ち、加圧終了時における成形型の温度を、平面又は凸面（Ｓ１）を成形する型の温度ｔa2が、凹面（Ｓ２）を成形する型の温度ｔa1より５℃以上低く（ｔa1−ｔa2≧５℃）なるようにする。
さらに、成形工程の開始から終了時まで、終始、温度ｔa２は温度ｔa1より低いことが好ましい。
【００１３】
また、本発明の第２の製造方法は、図１の（Ｃ）に示すような、両方の面が凹形状である場合が対象である。この場合、冷却工程における冷却を、曲率半径が大きい方の成形面を有する型の温度ｔb２が、曲率半径が小さい方の成形面を有する型の温度ｔb１より先に、前記Tgに達するように行う。好ましくは、温度ｔb２がTgに達したときに温度ｔb1は、温度ｔb２よりする５℃以上高くなるように冷却条件を設定する。特に好ましくは、温度ｔb２がTgに達したときに温度ｔb1は、温度ｔb２より好ましくは５℃〜４０℃、より好ましくは５〜３０℃、さらに好ましくは５〜２０℃以上高くなるように冷却条件を設定する。
【００１４】
さらに、少なくとも成形工程終了時において、温度ｔb２は温度ｔb１より低いことが好ましく、より好ましくは、少なくとも成形工程終了時において、温度ｔb２は温度ｔb１より５℃以上低い。即ち、加圧終了時における成形型の温度を、Ｒの小さい方の凹面（Ｓ２）を成形する型の温度ｔb１が、曲率半径Ｒの大きい方の凹面（Ｓ１）を成形する型の温度ｔb２より５℃以上高く（ｔb１−ｔb２≧５℃）なるようにする。
さらに、成形工程の開始から終了時まで、終始、温度ｔb２は温度ｔb１より低いことが好ましい。
【００１５】
本発明のガラス光学素子の製造方法は、(1)加熱軟化した被成形ガラス素材を、得ようとするガラス光学素子の光学的機能面を形成するための成形面を有する上型及び下型を含み、前記成形面の一方は凹面を形成するものであり、他方は凸面または平面を形成するものである成形型により加圧成形する（第１の製造方法）か、または、前記成形面の両方が凹面を形成するものである成形型により加圧成形して（第２の製造方法）、前記被成形ガラス素材に前記成形面を転写する成形工程、(2)前記成形型を冷却することにより成形したガラスをこのガラスのガラス転移温度(Tg)以下になるように冷却する冷却工程、(3)冷却されたガラスを前記成形型から取り出す取り出し工程を含む。
【００１６】
ガラス光学素子（例えば、ガラスレンズ）の加圧成形は、ガラス光学素子の光学的機能面を形成するための成形面を有する上型及び下型を含む成形型を用い、加圧成形工程及び冷却工程の所定の時点について、上型及び下型の間に所定の温度差を与えることを特徴とするものであり、それ以外の工程及び条件については、公知の方法をそのまま用いることかできる。精密プレス法によるガラスの成形方法は、一般に、ガラスプリフォームまたはガラスゴブ等のガラスレンズ素材をレンズの形状に対応する対向する成形面を有する上型及び下型を有する成形型に供給し、次いで所定の圧力及び時間、加圧成形し、加圧成形開始時、加圧成形途中、または加圧成形終了後に成形型とともに成形品を冷却し、所定の温度にまで冷却後、成形型から成形品を取り出すことからなる。成形型へのガラスレンズ素材の供給時及び加圧成形時のガラスレンズ素材及び成形型の温度条件は、レンズの材質、形状及び寸法等を考慮して適宜決定できる。
【００１７】
本発明においては、好ましくは初期加圧終了時において、ｔ１−ｔ２≧５℃となるように成形型の温度を調整する。ｔ１及びｔ２を有する成形型は、それぞれ上型及び下型のいずれであってもよい。但し、成形の容易さやガラス素材のセンタリングの容易さ等を考慮すると、一方の面が平面又は凸面であるレンズを成形する場合は、平面又は凸面（Ｓ１）を成形する型が下型であり、凹面（Ｓ２）を成形する型が上型であることが好ましい。また、両方の面が凹形状であるレンズを成形する場合は、曲率半径Ｒの大きい方の凹面（Ｓ１）を成形する型が下型であり、曲率半径Ｒの小さい方の凹面（Ｓ２）を成形する型が上型であることが適当である。
【００１８】
本発明の好ましい態様において、２つの型(上型、下型)の温度差（ｔ１−ｔ２）を５℃とするのは、少なくとも初期加圧終了時においてである。ここで、初期加圧とは、ガラスレンズ素材を成形型の成形面に対応した形状に成形するための加圧を意味する。本発明の製造方法では、初期加圧後に成形品に圧力（例えば、上型自重）をさらに加えることもできるが、初期加圧後に成形品に圧力を加えないで冷却することもできる。但し、ガラスを離型するまで成形品に圧力を加え続けることが好ましい。
【００１９】
２つの型(上型、下型)の温度差（例えば、ｔ１−ｔ２≧５℃）は、例えば、成形のための加圧開始時からつけておくことができる。具体的には、上型と下型とを異なる加熱条件下で加熱する。この状態を図３（Ａ）に示す。図中、（１）は加圧成形開始、（２）は初期加圧終了の時点である。図３（Ａ）では、加圧成形開始時（１）においてすでに、（ｔ１−ｔ２≧５℃）を満足する。また、成形のための加圧開始時には（ｔ１−ｔ２≧５℃）を満足しないが、成形のための加圧中に（ｔ１−ｔ２）≧５℃となるように成形型を温度制御することもできる。この場合、例えば、ｔ２を有する成形型を積極的に冷却することで、成形のための加圧中に（ｔ１−ｔ２）≧５℃とすることができる。この状態を図３（Ｂ）に示す。この図中でも、（１）は加圧成形開始、（２）は初期加圧終了の時点である。図３（Ｂ）では、加圧成形開始（１）の時点ではｔ１−ｔ２＜５℃であるが、ｔ２を有する成形型を積極的に冷却することで初期加圧終了の時点（２）において、（ｔ１−ｔ２≧５℃）を満足している。図３（Ｂ）においては、（１）の時点ではｔ１＝ｔ２であり、初期加圧終了の時点（２）において（ｔ１−ｔ２≧５℃）を満足するように調整することもできる。
【００２０】
好ましい態様の一つとして２つの型（上型及び下型）の温度差（ｔ１−ｔ２）が、少なくとも初期加圧終了時において５℃以上であれば、歪みの少ない良好な面精度を有するガラス光学素子（例えば、レンズ）を得ることができる。その場合、少なくとも初期加圧終了時における２つの成形型の温度差（ｔ１−ｔ２）は、好ましくは１０〜２０℃の範囲である。
【００２１】
本発明の方法においては、２つの成形型の温度差（ｔ１−ｔ２）は、平面又は凸面を成形する型または曲率半径Ｒの大きい方の凹面を成形する型の温度が少なくともＴｇになるまでは５℃以上になるように冷却することが、加圧プレス後、冷却工程で生じるガラス収縮の不均一さの低減及び歪みの量の減少をさせるという観点から好ましい。
【００２２】
本発明の製造方法の成形工程における初期加圧は例えば、294×10⁴〜3432×10⁴Paで行うことができ、加圧時間は例えば、30〜300秒間とすることができる。さらに、冷却工程において、２次加圧することができ（２次加圧することが好ましく）、２次加圧は196×10⁴〜2450×10⁴Paで行うことができ、加圧時間は例えば、30〜300秒間とすることができる。２次加圧の圧の大きさは初期加圧より小さいことが好ましい。２次加圧は、初期加圧に引続き行うことが好ましく、ガラスの温度がガラスのＴｇより50℃程度低い温度になるまで行うことが好ましい。さらに、本発明の製造方法では、２次加圧後、成形型から成形したガラスを取り出すまでの間、最終加圧をすることができ、最終加圧は、0.0098×10⁴〜4.9×10⁴Paで行うことができる。
【００２３】
【実施例】
以下本発明を実施例により詳細に説明する。
以下の実施例１〜３及び比較例１〜２では、図４に示す成形装置を用いた。
図４に示す成形装置は、函体２１ａによって密閉された加熱成形室２１内に、上型２２と下型２３が配置され、この上型２２と下型２３は、それぞれ断熱ベース２９、３０を介して上部固定軸２４と下部可動軸２５の先端に固定されている。下部可動軸２５は図示していない加圧シリンダに連結され、加圧時に上昇駆動される。
各実施例及び比較例ともに、初期加圧を588×10⁴Paで2分間、２次加圧を294×10⁴Paで3分間行った。
また、断熱ベース２９及び３０は、上型２２及び下型２３を独立に冷却するための、冷却用ガスの吹き出し口３１及び３２をそれぞれ有する。ガスの供給は上下独立にコントロールすることが出来、上型２２と下型２３の冷却スピードを変えることが出来る。冷却用のガスは、不活性ガスである。
【００２４】
実施例１
図５に示す形状の一方が凹面（曲率半径Ｒ＝４ｍｍ）であり、他方が凸面（曲率半径Ｒ＝５０ｍｍ）のガラスレンズ（比ｂ／ａ＝２．９、凹メニスカスレンズ）を製造した。凹面を上型で形成し、凸面を下型で成形した。ガラス素材としてはＮｂＦＤ１３（Ｔｇ＝５３５℃、Ｔｓ＝５７０℃）を用いた。成形の条件は表１に示す。
上型（凹面を形成する）の温度、下型（凸面を形成する）の温度、及び加圧圧力の各経時変化を図８に示す。加圧成形開始時の上型の温度(ta1)は６１０℃であり、下型の温度(ta2)は５９０℃であり、両者の温度差は２０℃であった。加圧成形中、この温度は維持され、初期加圧終了時の上型の温度(ta1)も６１０℃であり、下型の温度(ta2)も５９０℃であり、両者の温度差は２０℃であった。さらに、冷却が進み、下型の温度(ta2)がガラス素材のＴｇ＝５３５℃に達したときの上型の温度(ta1)は５４５℃であり、両者の温度差は10℃であった。さらに、２次加圧終了時の下型の温度(ta2)と上型 (ta1)の温度差は４℃であった。
【００２５】
実施例２
図６に示す形状の一方が凹面（曲率半径Ｒ＝１７ｍｍ）であり、他方が凸面（曲率半径Ｒ＝２３ｍｍ）のガラスレンズ（比ｂ／ａ＝２．５、凹メニスカスレンズ）を製造した。凹面を上型で形成し、凸面を下型で成形した。ガラス素材としてはＬａＣ１３（Ｔｇ＝５２０℃、Ｔｓ＝５６０℃）を用いた。成形の条件は表１に示す。
上型（凹面を形成する）の温度、下型（凸面を形成する）の温度、及び加圧圧力の各経時変化を図９に示す。加圧成形開始時の上型の温度(ta1)は６００℃であり、下型の温度(ta2)は５８０℃であり、両者の温度差は２０℃であった。加圧成形中、上型の温度を徐々に低くし、初期加圧終了時の上型の温度(ta1)は５９０℃であり、下型の温度(ta2)は５８０℃であり、両者の温度差は１０℃であった。さらに、冷却が進み、下型の温度(ta2)がガラス素材のＴｇ＝５２０℃に達したときの上型の温度(ta1)は５２８℃であり、両者の温度差は8℃であった。さらに、２次加圧終了時の下型の温度(ta2)と上型 (ta1)の温度差は１℃であった。
【００２６】
実施例３
図７に示す形状の一方が凹面（曲率半径Ｒ＝３８ｍｍ）であり、他方が凹面（曲率半径Ｒ＝１８０ｍｍ）のガラスレンズ（比ｂ／ａ＝３．０、両凹レンズ）を製造した。Ｒの小さい凹面を上型で形成し、Ｒの大きい凹面を下型で成形した。ガラス素材としてはＬａＣ１３（Ｔｇ＝５２０℃、Ｔｓ＝５６０℃）を用いた。成形の条件は表１に示す。
上型（Ｒの小さい凹面を形成する）の温度、下型（Ｒの大きい凹面を形成する）の温度、及び加圧圧力の各経時変化を図１０に示す。加圧成形開始時の上型の温度(tb1)は６００℃であり、下型の温度(tb2)は５８０℃であり、両者の温度差は２０℃であった。加圧成形中、上型の温度(tb1)を徐々に低くし、初期加圧終了時の上型の温度(tb1)は５９５℃であり、下型の温度(tb2)は５８０℃であり、両者の温度差は１５℃であった。さらに、冷却が進み、下型の温度(tb2)がガラス素材のＴｇ＝５２０℃に達したときの上型の温度(tb1)は５３０℃であり、両者の温度差は10℃であった。さらに、２次加圧終了時の下型の温度と上型 (tb1)の温度差は２℃であった。
【００２７】
比較例１
表１に示すように上型温度を下型温度と同一にした以外は、実施例１と同様にしてガラスレンズを成形した。上型の温度、下型の温度、及び加圧圧力の各経時変化を図１１に示す。加圧成形開始時の上型の温度(ta1)は６００℃であり、下型の温度(ta2)も６００℃であり、両者の温度差は０℃であった。加圧成形中もこの温度を維持し、初期加圧終了時の上型の温度(ta1)は６００℃であり、下型の温度(ta2)は６００℃であり、両者の温度差は０℃であった。さらに、冷却が進み、下型の温度(ta2)がガラス素材のＴｇ＝５３５℃に達したときの上型の温度(ta1)は535℃であり、両者の温度差は0℃であった。さらに、２次加圧終了時の下型の温度(ta2)と上型 (ta1)の温度差は０℃であった。
【００２８】
比較例２
表１に示すように上型温度を下型温度より低くした以外は、実施例１と同様にしてガラスレンズを成形した。上型の温度、下型の温度、及び加圧圧力の各経時変化を図１２に示す。加圧成形開始時の上型の温度(ta1)は５９５℃であり、下型の温度(ta2)は６０５℃であり、両者の温度差は−１０℃であった。加圧成形中、上型の温度(ta1)を徐々に高くし、初期加圧終了時の上型の温度(ta1)は６００℃であり、下型の温度(ta2)は６０５℃であり、両者の温度差は−５℃であった。さらに、冷却が進み、下型の温度(ta2)がガラス素材のＴｇ＝５３５℃に達したときの上型の温度(ta1)は５３３℃であり、両者の温度差は-2℃であった。さらに、２次加圧終了時の下型の温度(ta2)と上型 (ta1)の温度差は０℃であった。
【００２９】
実施例１〜３及び比較例１〜２で得られたガラスレンズの面精度を図１３に示す。表１中の面精度が良好とは、有効径（光学的有効径領域：干渉縞に写っている約８０％の領域が有効径）の内において干渉縞に「アス、クセ」が認められない物を意味する。
【００３０】
【表１】

【００３１】
表１に示すように、初期加圧終了時点において、上型温度（凹面を形成する）を下型温度（凸面を形成する）より高くする（成形面が凸面または平面を形成するものである型の温度ｔa２が、成形面が凹面を形成するものである型の温度ｔa1より先に、Tgに達する）ことにより、一方または両方の面が凹形状であっても、良好な面精度を有するガラス光学素子を得ることができる。
【００３２】
【発明の効果】
本発明の成形方法によれば、一方または両方の面が凹形状であって、中心肉厚ａと周辺肉厚ｂとの比ｂ／ａが２以上であるレンズであっても、高い面精度を有するガラスレンズを提供することができる。
【図面の簡単な説明】
【図１】本発明の製造方法において製造の対象となるガラス光学素子（Ａ）、（Ｂ）及び（Ｃ）を示す。
【図２】光学機能面外側の一方の側に光軸と直交する平面部を設けた凹メニスカスレンズの説明図。
【図３】本発明の製造方法における２つの型(上型、下型)の温度の典型的な経時変化を示す。
【図４】実施例１〜３及び比較例１〜２に用いた成形装置の概略図。
【図５】実施例１で製造したガラスレンズの説明図。
【図６】実施例２で製造したガラスレンズの説明図。
【図７】実施例３で製造したガラスレンズの説明図。
【図８】実施例１における上型の温度、下型の温度、及び加圧圧力の各経時変化。
【図９】実施例２における上型の温度、下型の温度、及び加圧圧力の各経時変化。
【図１０】実施例３における上型の温度、下型の温度、及び加圧圧力の各経時変化。
【図１１】比較例１における上型の温度、下型の温度、及び加圧圧力の各経時変化。
【図１２】比較例２における上型の温度、下型の温度、及び加圧圧力の各経時変化。
【図１３】実施例１〜３及び比較例１〜２で得られたガラスレンズの面精度を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass optical for molding a lens having one surface or both surfaces having a concave shape, for example, a lens having a ratio b / a of a central thickness a to a peripheral thickness b of 1.5 or more with high surface accuracy. The present invention relates to a method for manufacturing an element.
[0002]
[Prior art and problems to be solved by the invention]
A method (precision press method) that directly pressurizes softened glass using a mold having a product shape or a shape that approximates the product shape and directly manufactures the lens without grinding or polishing has been widely put into practical use. Yes. The precision press method is used as a manufacturing method of lenses for optical systems of various optical equipment products such as digital cameras and video cameras. In the precision press method, it is necessary to transfer the molding surface of the mold to the glass as precisely as possible.
[0003]
However, if one or both of the lenses have a concave shape, even if the molding surface is transferred to the glass, the glass will warp in the direction of one surface while the glass is solidified, or the transfer surface once formed In some cases, sufficient surface accuracy could not be obtained due to deterioration. This tendency was conspicuous in the molding of a lens in which the ratio b / a between the central thickness a and the peripheral thickness b was 1.5 or more.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a glass optical element that can be molded with high surface accuracy even if the lens has one or both surfaces that are concave.
[0005]
[Means for Solving the Problems]
As a result of the study by the present inventors, when slowly cooling a lens-shaped glass molded product, when one surface is a concave lens, cooling of the concave surface is performed on the opposite surface (planar or convex). The above problem can be solved by delaying the cooling of the concave surface having a small radius of curvature, and delaying the cooling of the concave surface having a large radius of curvature on the opposite side by delaying the cooling. As a result, the present invention has been completed.
[0006]
That is, the present invention includes an upper mold and a lower mold having a molding surface for forming an optically functional surface of a glass optical element to be obtained by heating and softening a glass material to be molded, and one of the molding surfaces is A step of forming a concave surface, the other being pressure-formed by a mold that forms a convex surface or a flat surface, and transferring the molding surface to the glass material to be molded (molding step);
A step (cooling step) of cooling the glass formed by cooling the mold so as to be equal to or lower than the glass transition temperature (Tg) of the glass;
A method of producing a glass optical element in which one optical functional surface including a step of taking out cooled glass from the mold (extraction step) is a concave surface,
The cooling is performed such that the temperature ta2 of the mold whose molding surface forms a convex surface or a flat surface reaches the Tg before the temperature ta1 of the mold whose molding surface forms a concave surface. The above manufacturing method (first manufacturing method).
[0007]
Furthermore, the present invention includes an upper mold and a lower mold having a molding surface for forming an optical functional surface of a glass optical element to be obtained, and the molding surface is concave. A step of pressure-molding with a molding die that forms the above, and transferring the molding surface to the glass material to be molded (hereinafter referred to as a molding step),
A step of cooling the glass formed by cooling the mold so as to be equal to or lower than the glass transition temperature (Tg) of the glass (hereinafter referred to as a cooling step),
A step of taking out the cooled glass from the mold (hereinafter referred to as a take-out step), and a method for producing a glass optical element in which both optical functional surfaces are concave surfaces,
The cooling is performed such that the temperature tb2 of the mold having the molding surface having the larger curvature radius reaches the Tg before the temperature tb1 of the mold having the molding surface having the smaller curvature radius. The present invention relates to the manufacturing method (second manufacturing method).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
The glass optical element to be manufactured in the manufacturing method of the present invention can be, for example, a lens whose one or both surfaces are concave. In particular, the manufacturing method of the present invention is suitable for a lens manufacturing method in which the ratio b / a between the central thickness a and the peripheral thickness b is 1.5 or more.
An example of such a lens is shown in FIG. In the lens 10 shown in FIG. 1A, one surface S2 has a concave shape, and the other surface S1 has a flat surface. In the lens 11 shown in (B), one surface S2 is concave and the other surface S1 is convex. In the lens 12 shown in (C), both the surface S1 and the surface S2 are concave. However, the concave curvature radius R of the surface S1 is larger than the concave curvature radius R of the surface S2. Further, in any of the lenses (A) to (C), the ratio b / a between the central thickness a and the peripheral thickness b can be 1.5 or more.
[0009]
The concave meniscus lens and the biconcave lens to be manufactured by the manufacturing method of the present invention have an optical functional surface (optically effective area) for incorporation into various lens systems. The optical functional surface (optically effective area) is, for example, a concave surface shown as 41 in FIG. 2, and actually a flat surface portion 43 orthogonal to the optical axis is provided outside the concave surface 41.
[0010]
In the case of a lens having a concave shape on one or both surfaces, after the pressure press, if the distortion is relieved during the cooling process, the radius of curvature of the concave surface in the case of a lens having a concave shape on one surface In the case of a lens in which both surfaces have a concave shape, the shape changes in the direction to decrease the curvature radius of the concave surface having a small curvature radius. This tendency is particularly remarkable in the case of a lens having a ratio b / a of 1.5 or more. However, the same tendency is found in the molding of a lens having a ratio b / a of less than 1.5, and the production method of the present invention is effective for the production of a lens having a ratio b / a of less than 1.5. The manufacturing method of the present invention is effective for lenses having a ratio b / a of 1.5 or more, but the ratio b / a of lenses in practical use is up to about 3.5. However, a lens having a ratio b / a exceeding that can be molded by the production method of the present invention.
[0011]
The first manufacturing method of the present invention is intended for the case where one surface of the lens is a flat surface or a convex surface as shown in FIG. 1 (A) or (B). In this case, the cooling in the cooling process is performed on the molding temperature ta2 whose molding surface forms a convex surface or a flat surface before the mold temperature ta1 whose molding surface forms a concave surface. The glass transition temperature Tg of the glass is reached. Preferably, the cooling condition is set so that the temperature ta1 is higher than the temperature ta2 by 5 ° C. or more when the temperature ta2 reaches Tg. Particularly preferably, the cooling condition is such that when the temperature ta2 reaches Tg, the temperature ta1 is higher than the temperature ta2 by 5 to 40 ° C, more preferably 5 to 30 ° C, and even more preferably 5 to 20 ° C or more. Set.
[0012]
Further, at least at the end of the molding process, the temperature ta2 is preferably lower than the temperature ta1, and more preferably at least at the end of the molding process, the temperature ta2 is 5 ° C. or more lower than the temperature ta1. That is, the temperature of the mold at the end of pressurization is such that the temperature ta2 of the mold for molding the flat surface or the convex surface (S1) is 5 ° C. lower than the temperature ta1 of the mold for molding the concave surface (S2) (ta1-ta2 ≧ 5 ° C).
Furthermore, it is preferable that the temperature ta2 is lower than the temperature ta1 from start to finish.
[0013]
Further, the second manufacturing method of the present invention is intended for the case where both surfaces are concave as shown in FIG. In this case, the cooling in the cooling step is performed so that the temperature tb2 of the mold having the molding surface with the larger curvature radius reaches the Tg before the temperature tb1 of the mold having the molding surface with the smaller curvature radius. . Preferably, the cooling condition is set so that when the temperature tb2 reaches Tg, the temperature tb1 is 5 ° C. higher than the temperature tb2. Particularly preferably, when the temperature tb2 reaches Tg, the cooling condition is such that the temperature tb1 is higher than the temperature tb2 by 5 to 40 ° C, more preferably 5 to 30 ° C, and even more preferably 5 to 20 ° C or more. Set.
[0014]
Further, at least at the end of the molding step, the temperature tb2 is preferably lower than the temperature tb1, and more preferably at least at the end of the molding step, the temperature tb2 is 5 ° C. or more lower than the temperature tb1. That is, the temperature of the mold at the end of pressurization is the temperature of the mold that molds the concave surface (S 1 ) with the larger radius of curvature R, the temperature tb1 of the mold that molds the concave surface (S 2 ) with the smaller R. It should be higher than tb2 by 5 ° C. or more (tb1-tb2 ≧ 5 ° C.).
Furthermore, it is preferable that the temperature tb2 is lower than the temperature tb1 from start to finish.
[0015]
The method for producing a glass optical element of the present invention comprises (1) an upper mold and a lower mold having molding surfaces for forming an optical functional surface of a glass optical element to be obtained by heating and softening a glass material to be molded. wherein one of said molding surface is to form a concave surface and the other pressure molding by molds and forms a convex or plane (first manufacturing method), or, both of the molding surface (2) cooling the molding die by pressure molding with a molding die that forms a concave surface (second manufacturing method) and transferring the molding surface to the glass material to be molded; A cooling step of cooling the formed glass so as to be equal to or lower than the glass transition temperature (Tg) of the glass; and (3) a step of taking out the cooled glass from the mold.
[0016]
The pressure molding of a glass optical element (for example, a glass lens) is performed by using a molding die including an upper mold and a lower mold having a molding surface for forming an optical functional surface of the glass optical element, and a pressure molding process and cooling. A predetermined temperature difference is given between the upper mold and the lower mold at a predetermined point in the process, and a publicly known method can be used as it is for the other processes and conditions. In general, a glass molding method using a precision press method is to supply a glass lens material such as a glass preform or a glass gob to a molding die having an upper die and a lower die having opposing molding surfaces corresponding to the shape of the lens, and then a predetermined mold. Pressure and time, pressure molding, and at the start of pressure molding, during pressure molding, or after pressure molding, the molded product is cooled together with the molding die, cooled to a predetermined temperature, and then the molded product is removed from the molding die. It consists of taking out. The temperature conditions of the glass lens material and the mold during supply of the glass lens material to the mold and during pressure molding can be determined as appropriate in consideration of the lens material, shape, dimensions, and the like.
[0017]
In the present invention, the temperature of the mold is preferably adjusted so that t1−t2 ≧ 5 ° C. at the end of the initial pressurization. The mold having t1 and t2 may be either an upper mold or a lower mold. However, considering the ease of molding, the ease of centering the glass material, etc., when molding a lens whose one surface is a plane or convex surface, the mold for molding the plane or convex surface (S1) is the lower mold, The mold for molding the concave surface (S2) is preferably an upper mold. When molding a lens having both concave surfaces, the mold for molding the concave surface (S1) having the larger curvature radius R is the lower mold, and the concave surface (S2) having the smaller curvature radius R is used. It is appropriate that the mold to be molded is an upper mold.
[0018]
In a preferred embodiment of the present invention, the temperature difference (t1−t2) between the two molds (upper mold and lower mold) is set to 5 ° C. at least at the end of the initial pressurization. Here, the initial and pressurization means pressurization for molding a glass lens material into a shape corresponding to the molding surface of the mold. In the production method of the present invention, pressure (for example, the upper mold weight) can be further applied to the molded product after the initial pressurization, but can be cooled without applying pressure to the molded product after the initial pressurization. However, it is preferable to continue to apply pressure to the molded product until the glass is released.
[0019]
The temperature difference (for example, t1−t2 ≧ 5 ° C.) between the two molds (upper mold and lower mold) can be applied from the start of pressurization for molding, for example. Specifically, the upper mold and the lower mold are heated under different heating conditions. This state is shown in FIG. In the figure, (1) is the start of pressure molding, and (2) is the end of initial pressurization. In FIG. 3A, (t1−t2 ≧ 5 ° C.) is already satisfied at the start of pressure molding (1). Also, the temperature of the mold is controlled so that (t1-t2) ≧ 5 ° C. during pressurization for molding, although (t1-t2 ≧ 5 ° C.) is not satisfied at the start of pressurization for molding. You can also. In this case, for example, (t1−t2) ≧ 5 ° C. can be achieved during pressurization for molding by positively cooling the mold having t2. This state is shown in FIG. In this figure, (1) is the start of pressure molding and (2) is the end of initial pressurization. In FIG. 3B, t1−t2 <5 ° C. at the time of pressure molding start (1), but at the time of completion of initial pressure (2) by positively cooling the mold having t2. (T1-t2 ≧ 5 ° C.). In FIG. 3B, t1 = t2 at the time of (1), and it can be adjusted to satisfy (t1−t2 ≧ 5 ° C.) at the time (2) of the end of the initial pressurization.
[0020]
As one of preferred embodiments, a glass having good surface accuracy with little distortion if the temperature difference (t1-t2) between the two molds (upper mold and lower mold) is at least 5 ° C. at the end of the initial pressurization. An optical element (for example, a lens) can be obtained. In that case, the temperature difference (t1−t2) between the two molds at least at the end of the initial pressurization is preferably in the range of 10 to 20 ° C.
[0021]
In the method of the present invention, the temperature difference (t1-t2) between the two molds is such that the temperature of the mold that molds the flat surface or the convex surface or the mold that molds the concave surface with the larger radius of curvature R is at least Tg. Cooling to 5 ° C. or higher is preferable from the viewpoint of reducing the non-uniformity of glass shrinkage and the amount of distortion after the pressing and pressing in the cooling step.
[0022]
The initial pressurization in the molding step of the production method of the present invention can be performed, for example, at 294 × 10 ^{4 to} 3432 × 10 ⁴ Pa, and the pressurization time can be, for example, 30 to 300 seconds. Further, in the cooling step, secondary pressurization can be performed (preferably secondary pressurization), and the secondary pressurization can be performed at 196 × 10 ^{4 to} 2450 × 10 ⁴ Pa, and the pressurization time is, for example, It can be 30 to 300 seconds. The magnitude of the secondary pressure is preferably smaller than the initial pressure. The secondary pressurization is preferably performed subsequent to the initial pressurization, and is preferably performed until the glass temperature is about 50 ° C. lower than the glass Tg. Furthermore, in the production method of the present invention, after the secondary pressurization, the final pressurization can be performed until the molded glass is taken out from the mold, and the final pressurization is 0.0098 × 10 ^{4 to} 4.9 × 10 ^4. Can be done with Pa.
[0023]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
In the following Examples 1-3 and Comparative Examples 1-2, the shaping | molding apparatus shown in FIG. 4 was used.
In the molding apparatus shown in FIG. 4, an upper mold 22 and a lower mold 23 are arranged in a thermoforming chamber 21 sealed by a box 21a. The upper mold 22 and the lower mold 23 are provided with

heat insulating bases

29 and 30, respectively. Via the upper fixed shaft 24 and the lower movable shaft 25. The lower movable shaft 25 is connected to a pressure cylinder (not shown), and is driven to rise when pressurized.
In each example and comparative example, initial pressurization was performed at 588 × 10 ⁴ Pa for 2 minutes, and secondary pressurization was performed at 294 × 10 ⁴ Pa for 3 minutes.
The

heat insulating bases

29 and 30 have cooling gas outlets 31 and 32 for cooling the upper mold 22 and the lower mold 23 independently. The gas supply can be controlled independently of the upper and lower sides, and the cooling speed of the upper mold 22 and the lower mold 23 can be changed. The cooling gas is an inert gas.
[0024]
Example 1
A glass lens (ratio b / a = 2.9, concave meniscus lens) having one concave surface (curvature radius R = 4 mm) and the other convex surface (curvature radius R = 50 mm) was manufactured. The concave surface was formed with the upper mold, and the convex surface was molded with the lower mold. NbFD13 (Tg = 535 ° C., Ts = 570 ° C.) was used as the glass material. The molding conditions are shown in Table 1.
FIG. 8 shows changes over time in the temperature of the upper mold ( forming the concave surface), the temperature of the lower mold ( forming the convex surface), and the pressurizing pressure. The temperature (ta1) of the upper mold at the start of pressure molding was 610 ° C., the temperature (ta2) of the lower mold was 590 ° C., and the temperature difference between them was 20 ° C. During press molding, this temperature is maintained, the upper die temperature (ta1) at the end of the initial pressurization is 610 ° C, the lower die temperature (ta2) is also 590 ° C, and the temperature difference between them is 20 ° C. Met. Furthermore, when the cooling progressed and the temperature (ta2) of the lower mold reached Tg = 535 ° C. of the glass material, the temperature (ta1) of the upper mold was 545 ° C., and the temperature difference between them was 10 ° C. Furthermore, the temperature difference between the lower mold temperature (ta2) and the upper mold (ta1) at the end of the secondary pressurization was 4 ° C.
[0025]
Example 2
A glass lens (ratio b / a = 2.5, concave meniscus lens) having one concave surface (curvature radius R = 17 mm) and the other convex surface (curvature radius R = 23 mm) was manufactured. The concave surface was formed with the upper mold, and the convex surface was molded with the lower mold. LaC13 (Tg = 520 ° C., Ts = 560 ° C.) was used as the glass material. The molding conditions are shown in Table 1.
FIG. 9 shows changes over time in the temperature of the upper mold ( forming the concave surface), the temperature of the lower mold ( forming the convex surface), and the pressurizing pressure. The temperature (ta1) of the upper mold at the start of pressure molding was 600 ° C., the temperature (ta2) of the lower mold was 580 ° C., and the temperature difference between them was 20 ° C. During press molding, the temperature of the upper mold is gradually lowered, the temperature (ta1) of the upper mold at the end of the initial pressurization is 590 ° C, and the temperature (ta2) of the lower mold is 580 ° C. The difference was 10 ° C. Further, when the cooling progressed and the temperature (ta2) of the lower mold reached Tg = 520 ° C. of the glass material, the temperature (ta1) of the upper mold was 528 ° C., and the temperature difference between them was 8 ° C. Furthermore, the temperature difference between the lower mold temperature (ta2) and the upper mold (ta1) at the end of the secondary pressurization was 1 ° C.
[0026]
Example 3
A glass lens (ratio b / a = 3.0, biconcave lens) in which one of the shapes shown in FIG. 7 is a concave surface (curvature radius R = 38 mm) and the other is a concave surface (curvature radius R = 180 mm) was manufactured. A concave surface with a small R was formed with an upper mold, and a concave surface with a large R was molded with a lower mold. LaC13 (Tg = 520 ° C., Ts = 560 ° C.) was used as the glass material. The molding conditions are shown in Table 1.
FIG. 10 shows changes over time in the temperature of the upper die ( forming a concave surface having a small R), the temperature of the lower die ( forming a concave surface having a large R), and the pressurizing pressure. The temperature (tb1) of the upper mold at the start of pressure molding was 600 ° C., the temperature (tb2) of the lower mold was 580 ° C., and the temperature difference between them was 20 ° C. During press molding, the upper mold temperature (tb1) is gradually lowered, the upper mold temperature (tb1) at the end of the initial pressurization is 595 ° C, and the lower mold temperature (tb2) is 580 ° C. The temperature difference between the two was 15 ° C. Further, the cooling progressed, and when the lower mold temperature (tb2) reached Tg = 520 ° C. of the glass material, the upper mold temperature (tb1) was 530 ° C., and the temperature difference between them was 10 ° C. Furthermore, the temperature difference between the lower mold and the upper mold (tb1) at the end of the secondary pressurization was 2 ° C.
[0027]
Comparative Example 1
As shown in Table 1, a glass lens was molded in the same manner as in Example 1 except that the upper mold temperature was the same as the lower mold temperature. FIG. 11 shows changes with time in the temperature of the upper mold, the temperature of the lower mold, and the pressurizing pressure. The temperature (ta1) of the upper mold at the start of pressure molding was 600 ° C., the temperature (ta2) of the lower mold was also 600 ° C., and the temperature difference between them was 0 ° C. This temperature is maintained during pressure molding, the temperature of the upper die (ta1) at the end of the initial pressurization is 600 ° C, the temperature of the lower die (ta2) is 600 ° C, and the temperature difference between them is 0 ° C. Met. Further, when the cooling progressed and the lower mold temperature (ta2) reached Tg = 535 ° C. of the glass material, the upper mold temperature (ta1) was 535 ° C., and the temperature difference between them was 0 ° C. Further, the temperature difference between the lower mold temperature (ta2) and the upper mold (ta1) at the end of the secondary pressurization was 0 ° C.
[0028]
Comparative Example 2
As shown in Table 1, a glass lens was molded in the same manner as in Example 1 except that the upper mold temperature was lower than the lower mold temperature. FIG. 12 shows changes over time in the temperature of the upper mold, the temperature of the lower mold, and the pressurizing pressure. The temperature (ta1) of the upper die at the start of pressure molding was 595 ° C, the temperature (ta2) of the lower die was 605 ° C, and the temperature difference between the two was -10 ° C. During press molding, the upper mold temperature (ta1) is gradually increased, the upper mold temperature (ta1) at the end of the initial pressurization is 600 ° C, and the lower mold temperature (ta2) is 605 ° C. The temperature difference between the two was −5 ° C. Furthermore, when the cooling progressed and the temperature (ta2) of the lower mold reached Tg = 535 ° C. of the glass material, the temperature (ta1) of the upper mold was 533 ° C., and the temperature difference between them was −2 ° C. . Further, the temperature difference between the lower mold temperature (ta2) and the upper mold (ta1) at the end of the secondary pressurization was 0 ° C.
[0029]
The surface accuracy of the glass lenses obtained in Examples 1 to 3 and Comparative Examples 1 and 2 is shown in FIG. The surface accuracy in Table 1 means that the interference fringes do not show “Ass, habits” within the effective diameter (optical effective diameter region: the effective diameter is about 80% of the region shown in the interference fringes). Means a thing.
[0030]
[Table 1]

[0031]
As shown in Table 1, at the end of the initial pressurization, the upper mold temperature ( forming the concave surface) is set higher than the lower mold temperature ( forming the convex surface) (the molding surface forms a convex surface or a flat surface). Glass having good surface accuracy even if one or both surfaces are concave, because the temperature ta2 of the mold reaches Tg before the temperature ta1 of the mold whose forming surface forms a concave surface). An optical element can be obtained.
[0032]
【The invention's effect】
According to the molding method of the present invention, even in a lens in which one or both surfaces are concave and the ratio b / a between the central thickness a and the peripheral thickness b is 2 or more, high surface accuracy is achieved. The glass lens which has can be provided.
[Brief description of the drawings]
FIG. 1 shows glass optical elements (A), (B) and (C) to be manufactured in the manufacturing method of the present invention.
FIG. 2 is an explanatory diagram of a concave meniscus lens in which a flat portion perpendicular to the optical axis is provided on one side outside the optical functional surface.
FIG. 3 shows a typical time-dependent change in temperature of two molds (upper mold and lower mold) in the production method of the present invention.
4 is a schematic view of a molding apparatus used in Examples 1 to 3 and Comparative Examples 1 and 2. FIG.
5 is an explanatory diagram of a glass lens manufactured in Example 1. FIG.
6 is an explanatory diagram of a glass lens manufactured in Example 2. FIG.
7 is an explanatory diagram of a glass lens manufactured in Example 3. FIG.
8 shows changes over time in the temperature of the upper mold, the temperature of the lower mold, and the pressurizing pressure in Example 1. FIG.
FIG. 9 shows changes over time in the temperature of the upper mold, the temperature of the lower mold, and the pressurization pressure in Example 2.
10 shows changes over time in the temperature of the upper mold, the temperature of the lower mold, and the pressurizing pressure in Example 3. FIG.
11 shows changes over time in the temperature of the upper mold, the temperature of the lower mold, and the pressurizing pressure in Comparative Example 1. FIG.
12 shows changes over time in the temperature of the upper mold, the temperature of the lower mold, and the pressurizing pressure in Comparative Example 2. FIG.
FIG. 13 shows the surface accuracy of the glass lenses obtained in Examples 1 to 3 and Comparative Examples 1 and 2.

Claims

An upper mold and a lower mold having a molding surface for forming an optical functional surface of a glass optical element to be obtained by heating and softening a glass material to be obtained, and one of the molding surfaces forms a concave surface. Yes, the other is pressure-molded by a molding die that forms a convex surface or a flat surface, and the step of transferring the molding surface to the glass material to be molded (hereinafter referred to as molding step),
A step of cooling the glass formed by cooling the mold so as to be equal to or lower than the glass transition temperature (Tg) of the glass (hereinafter referred to as a cooling step),
A step of taking out the cooled glass from the mold (hereinafter referred to as a taking-out step), and a method for producing a glass optical element in which one optical functional surface is a concave surface,
The cooling is performed such that the temperature ta2 of the mold whose molding surface forms a convex surface or a flat surface reaches the Tg before the temperature ta1 of the mold whose molding surface forms a concave surface. Said manufacturing method.

The manufacturing method according to claim 1, wherein when the temperature ta2 reaches Tg, the temperature ta1 is 5 ° C or more higher than the temperature ta2.

At least at the end of pressure molding in the molding step, the temperature t a 2 is temperature t a1 The manufacturing method of Claim 1 or 2 lower.

At least at the end of pressure molding in the molding step, the temperature t a 2 is temperature t a1 The production method according to any one of claims 1 to 3, which is lower by 5 ° C or more.

From the start to the end of pressure molding in the molding process, temperature t a 2 is temperature t a1 The manufacturing method of Claim 3 or 4 lower.

The temperature t between the end of pressure forming in the forming step and the end of the cooling step a1 And temperature t a The manufacturing method as described in any one of Claims 1-5 by which the difference with 2 becomes small gradually.

A glass material to be molded that has been softened by heating includes an upper mold and a lower mold having a molding surface for forming an optical functional surface of a glass optical element to be obtained, and both of the molding surfaces form concave surfaces. A step of molding by pressure using a certain mold and transferring the molding surface to the glass material to be molded (molding step);
A step (cooling step) of cooling the glass formed by cooling the mold so as to be equal to or lower than the glass transition temperature (Tg) of the glass;
A method of producing a glass optical element in which both optical functional surfaces including a step of taking out cooled glass from the mold (extraction step) are concave surfaces,
The cooling is performed such that the temperature tb2 of the mold having the molding surface having the larger curvature radius reaches the Tg before the temperature tb1 of the mold having the molding surface having the smaller curvature radius. The manufacturing method.

The manufacturing method according to claim 7 , wherein when the temperature tb2 reaches Tg, the temperature tb1 is 5 ° C or more higher than the temperature tb2.

The manufacturing method according to claim 7 or 8 , wherein the temperature tb2 is lower than the temperature tb1 at least at the end of pressure molding in the molding step.

The process according to at least the Te pressing end odor in the molding process, temperature tb2 is any one of 5 ° C. or more lower claims 7-9 than temperature tb1.

Wherein to the end from the start of pressing in the molding step, the final start, temperature tb2 manufacturing method according to a low claim 9 or 10 than the temperature tb1.

Between the time pressing ends in the molding step until the cooling step is completed, the difference becomes smaller gradually with the temperature tb1 and temperature tb2, the production method according to any one of claims 7-11.

After pressing ends in the molding step, successively to the pressure in the molding process, manufacturing according to any one of claims 1 to 12 for secondary pressure at a pressure less than the pressure in the molding process Method.

The manufacturing method according to any one of claims 1 to 13 , wherein the glass optical element has a ratio b / a between a center thickness a and a peripheral thickness b of 1.5 or more.

The process according to the glass optical element, any one of claims 1 to 14 which is a concave meniscus lens.

Wherein the glass material, the manufacturing method according to any one of reheating claims 1-15 is intended and the glass preform.