JP3608768B2

JP3608768B2 - Glass optical element press molding apparatus and glass optical element molding method

Info

Publication number: JP3608768B2
Application number: JP12921898A
Authority: JP
Inventors: 忠幸藤本; 慎一郎広田; 紀士男菅原; 伸司波田
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 1997-05-13
Filing date: 1998-05-12
Publication date: 2005-01-12
Anticipated expiration: 2018-05-12
Also published as: JPH1129333A

Description

【０００１】
【発明の属する技術分野】
本発明はガラス光学素子の成形装置及び成形方法、特に複数のガラス光学素子を同時に成形するための成形装置及び成形方法に関する。
【０００２】
【従来の技術】
軟化ガラスが融着せず、鏡面加工が可能な型材料を精密加工した成形型を用いて、高精度のレンズ等のガラス光学素子を成形する方法が近年注目され、種々開発されている。この方法において、生産効率を向上させるために、複数の成形型を用いて複数のガラス光学素子を同時にプレス成形することが検討されている。
【０００３】
例えば、特開昭６３−１７０２２５号公報には、円盤形の上、下の金型に４個の上下キャビティダイを、各キャビティダイの中心が金型の中心から同一半径上で、等間隔になるように配置し、各下キャビティダイ上に被成形ガラス素材をセットして、金型の周縁に巻回した誘導加熱コイルにより金型を誘導加熱し、金型からの熱伝導でキャビティダイおよび被成形ガラス素材を加熱し、プレス成形することが示されている。
一方、特開平７−３３４５２号公報には、図１２に示すように、直列に配列したガラス材料成形用の上型部材５０２及び下型部材５０３を備えた胴型５０１を、該上型部材５０２及び下型部材５０３の列に並行に配した熱源５０７により加熱し、プレス成形をするように構成した光学素子の成形装置が提案されている。
【０００４】
【発明が解決しようとする課題】
高精度のレンズ等のガラス光学素子をプレス成形するには、成形型の成形面における温度が均一であることが重要であり、例えば２〜３℃以内の温度分布であることが必要とされる。しかしながら、特開昭６３−１７０２２５号の方法では金型の周縁部が誘導加熱され、その熱が金型中心方向へ伝導して金型全体を加熱することになるため、金型の周縁部が高く中心部が低い温度分布が生じ、キャビティダイ成形面の温度分布も、金型の周縁部側で高く中心部側で低いものとなる。その結果、成形時に成形材料が金型の周縁部側に伸び、キャビティダイからはみ出すという問題があった。また、中心部側では逆にのび不良が生じやすく、結果として不良品を生じることがあった。また、成形品はこの温度分布のためにアスが生じやすい問題があった。
【０００５】
特開平７−３３４５２号の装置は、図１２に示すように、２列に配列した成形型をこれに平行な加熱源を用いて胴型を加熱することにより加熱するものであるため、加熱源側は高温となり胴型の中心側は低温となり、上記と同様の問題があった。また、特開平７−３３４５２の装置では密閉容器内でガラス素材の自動供給および成形品の取出しが行えるものの、加熱ゾーンで型と被成形ガラス素材を加熱するものであるため、必ずしも成形のサイクルタイムは短いものではなかった。
【０００６】
そこで本発明は、上記問題を解決し、複数の成形型を均一に加熱してプレス成形を行い、面精度及び表面品質の良好なガラス光学素子を製造し得るプレス成形装置及びプレス成形方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明では上記課題を解決するために、上型及び下型からなる成形型と、該成形型を支持する母型と、前記母型の周囲に巻回された前記成形型を加熱するための加熱手段を有する成形装置において、
前記母型が長尺形状であって、かつ一定の幅を有し、
該母型に前記成形型複数個を長手方向に等間隔に一列に、成形型の中心が母型の中心線上に位置するように設け、かつ
少なくとも母型の短手方向端部での前記加熱手段と母型との距離が一定であることを特徴とするガラス光学素子用成形装置が提供される。
さらに、本発明においては、複数個の加熱軟化した被成形ガラス素材を、長尺形状の母型に長手方向に沿って一列に配列された、上型及び下型からなる複数個の成形型で同時に加圧成形することからなる光学素子の成形方法において、
前記複数個の成形型のそれぞれが、前記母型の周囲に巻回された加熱手段により加熱された母型からの熱伝導によって加熱され、かつこの加熱が、少なくとも各成形型の水平断面における対向する２つの位置が実質的に均等に熱せられるように行われることを特徴とする光学素子の成形方法が提供される。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
本発明の成形装置は、成形型を支持する母型が長尺形状であって、かつ一定の幅を有し、該母型に前記成形型複数個を長手方向に等間隔に一列に、成形型の中心が母型の中心線上に位置するように設け、さらに少なくとも母型の短手方向端部での前記加熱手段と母型との距離が一定であることが特徴である。本発明では、このような構造とすることにより、各成形型の成形面に加熱手段からの距離の違いによる温度分布が生じることを極力防止でき、その結果、面精度及び表面品質の良好なガラス光学素子を複数個同時に成形することができる。上記長尺形状の母型は、好ましくは両端部が略半円状になっていることが、両端部に近い成形型への加熱が均一にできるという観点から好ましい。
【０００９】
１つの母型に設けられる成形型の数は、特に制限はなく、ガラス光学素子の形状や寸法等を考慮して適宜決定できる。但し、生産効率と生産技術とを考慮すると、２個以上、１０個以下程度であることが好ましい。しかし、１０個以上であっても勿論良い。
本発明の成形装置において、成形型の形状や構造及び材質は、公知のものであることができ、例えば、特開平８−１３３７５８号に記載のものを挙げることができる。具体的には、成形型として炭化ケイ素焼結体にＣＶＤ法により炭化ケイ素膜を形成した後、イオンプレーティング法によりｉ−カーボン膜を形成したものを用いることができる。さらに、ケイ素、窒化ケイ素、炭化タングステン、酸化アルミニウムと炭化チタンのサーメットや、これらの表面にダイヤモンド、耐熱金属、貴金属合金、或いは炭化物、窒化物、硼化物、酸化物などのセラミックスなどを被覆したものも使用することができる。但し、ｉ−カーボン膜等の炭素系膜は離型性がよい点で特に有利である。
【００１０】
加熱手段は公知の種々のものから選択でき、成形時に母型の周囲に接触状態または非接触状態で位置するように母型の周囲に巻回される。加熱手段は、誘導加熱コイルのような誘導加熱手段であり、成形時に母型の周囲に非接触状態で位置するように母型の形状に倣って巻回されているのが好ましい。尚、誘導加熱コイル等の誘導加熱手段は公知のものから適宜選択できる。
加熱手段として誘導加熱手段を用いることにより、繰り返し成形する場合に、成形型の昇温を素早く行うことが出来るため、成形のサイクルタイムを短くできるという利点がある。さらには、誘導加熱手段は、温度の再現性が極めて良いため、精密な温度制御が可能であるという利点もある。
【００１１】
本発明の成形装置において、加熱手段が誘導加熱コイルである場合、少なくとも母型の短手方向端部での前記加熱手段と母型との距離が一定であることで、誘導加熱コイルからの母型へのエネルギーを均一に与えることができ、成形型の均一加熱を可能にする。さらに、長尺形状であって、かつ一定の幅を有す母型に、成形型を各成形型の中心が母型の中心線上に位置するように設けるることで、誘導加熱コイルにより母型の発熱を長手方向で左右対照にすることができる。さらに、母型の長手方向に一列に設けられた成形型を等間隔にすることで、成形型の間で母型から受け取る熱量を均一にすることができる。
そして、本発明の成形装置では上記要件を満たすことで、特に、加熱手段が誘導加熱コイルである場合であっても、複数の成形型を均一に加熱してプレス成形を行い、面精度及び表面品質の良好なガラス光学素子を製造することがでるようになる。
【００１２】
また、本発明のプレス成形装置は、誘導加熱コイルによる成形型の加熱を均一に行うために、母型の長手方向の一方または両方から気体を吹きつける手段を設けることができる。成形型３０１ｂの長手方向の両方に気体を吹きつける手段３０８を設けた場合を図９に示す。成形型に吹きつけるための気体には特に制限はないが、例えば、窒素のような不活性ガスを用いることができる。
【００１３】
また、本発明のプレス成形装置では、加熱手段としての誘導加熱コイルは、母型の長手方向の端部を除き、母型の周囲に非接触状態で位置するように母型の形状に倣って巻回されることもできる。このような態様の例を図１０に模式的に示す。例えば、長手方向端部での加熱手段と母型との距離が、短手方向端部での加熱手段と母型との距離より大きくすることができる。図１０の（ａ）は、母型の長手方向の端部付近では、誘導加熱コイル３０７ｂを母型から遠ざけ、母型の長手方向の端部３０９ｂが加熱されないようにした。また、図１０の（ｂ）では、母型の長手方向の端部３０９ｂを除く側部のみに誘導加熱コイル３０７ｂを配置した。これにより、長手方向の端部に近い成形型の加熱と中央部の成形型の加熱とをより均一化することができる。尚、図１０の（ｂ）の場合、２つの誘導加熱コイルは、同一または別々の回路で温度調節することができる。
【００１４】
上記と同様の理由から、成形型との接触部から端部までの母型の幅を、短手方向より長手方向で大きくすることができる。この状態を図１１に示す。図中、母型の長手方向の端部３０９ｂを長めにすることで、誘導加熱コイル３０７ｂにより加熱された母型の熱が、両端の成形型３０３１及び３０３６に伝わりにくくすることもできる。
尚、上記の図に基づく説明は下型についてのものであるが、上型についても同様とすることができる。
【００１５】
長尺形状の母型は、一の母型で上型及び下型を支持するものであってもよく、また、上型を支持する上母型と下型を支持する下母型に分割されているものであっても良い。一の母型で支持する場合、上型及び下型の少なくとも一方は該母型に対して上下動可能である。この場合、例えば、母型をプレスの下軸上に位置し、上型の上面をプレスの上軸に取り付けたプレスへッドで押圧することにより、プレスを行い得る。上下に分割されている母型の場合、上母型及び下母型を、少なくとも一方が上下動可能であるプレスの上軸及び下軸に取り付けてプレスを行い得る。
【００１６】
誘導加熱コイルは、成形時の母型の位置に配置されるが、母型が上下に分割されている場合、好ましくは各々の母型の周囲に位置するように２個設けられる。上下のコイルは、被成形材料の供給及び成形品の取り出しが可能なように、適当な間隔を開けて配置するのが好ましい。
尚、成形型を支持する母型の材質は公知のものであることができる。成形型を支持する母型の材質は、例えば、ステンレス合金、鋳鉄、タングステン合金、モリブデン合金等を挙げることができる。
【００１７】
本発明の装置において、好ましくは、上型と下型との軸ずれを防止するためのスリーブが、前記上型、下型、上母型及び下母型のいずれかに設けられる。例えば、下型の外周にスリーブ部材を装着し、スリーブ部材の内側に上型が挿入し得る構成とすることができる。
【００１８】
本発明の成形装置は、前記複数の成形型に複数の被成形用ガラス素材を同時に供給するための割型皿をさらに設けることができる。さらに、この割型皿は気体を上方に吹き出し、被成形用ガラス素材を浮上させるための細孔を有するものであることができる。このような被成形用ガラス素材浮上用の割型皿は、特開平８−１３３７５８号に浮上治具として記載のものを挙げることができる。
本発明の成形装置については、実施例においてさらに具体的に説明する。
【００１９】
本発明の成形方法は、複数個の加熱軟化した被成形ガラス素材を、長尺形状の母型に長手方向に沿って一列に配列された、上型及び下型からなる複数の成形型で同時に加圧成形することからなる光学素子の成形方法である。本発明の成形方法に用いる成形型の形状や構造及び材質等、さらには、成形条件等は、公知のものであることができ、例えば、特開平８−１３３７５８号に記載のものを挙げることができる。
複数個の加熱軟化した被成形ガラス素材を、複数の成形型で同時に加圧成形する場合、複数の成形型の間で熱的条件が同一であり、かつ各成形型において、成形面の温度が成形面の中心から等距離にある位置においては同一であることが好ましい。
【００２０】
本発明の成形方法では、複数の成形型が長尺形状の母型に長手方向に沿って一列に配列され、かつ前記母型の周囲に巻回された加熱手段により加熱された母型からの熱伝導によって、各成形型が加熱されることから、複数の成形型の間での熱的条件を同一にすることを可能にしている。
さらに、本発明の成形方法では、前記複数個の成形型のそれぞれが、前記母型の周囲に巻回された加熱手段により加熱された母型からの熱伝導によって加熱され、かつこの加熱は、少なくとも各成形型の水平断面における対向する２つの位置が実質的に均等に加熱されるように行われることを特徴とする。
【００２１】
このような成形型の加熱を可能にする成形装置として、前記本発明の成形装置を挙げることができる。即ち、前記母型が長尺形状であって、かつ一定の幅を有し、該母型に前記成形型複数個を長手方向に等間隔に一列に、成形型の中心が母型の中心線上に位置するように設け、さらに少なくとも母型の短手方向端部での前記加熱手段と母型との距離が一定である装置を用いることができる。
【００２２】
加熱手段は、母型をより均一に加熱できるという観点から誘導加熱コイルであることが好ましい。成形型はその周囲を母型で覆われており、母型からの熱伝導によって過熱される。母型から伝えられる熱が１つの成形型について水平断面における対向する２つの位置で異なると、成形型の成形面の中心から等距離にある位置において温度分布（温度差）が生じることになり、面精度及び表面品質の良好なガラス光学素子を得ることは困難である。そこで、本発明の方法では、各成形型の水平断面における対向する２つの位置が実質的に均等に加熱されるように成形型の加熱を行う。このような成形型の加熱方式とすることで、各成形型の成形面の中心から等距離にある位置においての温度の違いを極力抑制でき、その結果、面精度及び表面品質の良好なガラス光学素子を複数個同時に成形することができる。
【００２３】
さらに、複数の成形型の間での熱的条件を同一にするという観点からは、誘導加熱コイルによる成形型の加熱を均一に行うために、成形型の加熱時に母型の長手方向の一方または両方から気体を吹きつけることもできる。成形型に吹きつけるための気体には特に制限はないが、例えば、窒素のような不活性ガスを用いることができる。さらに、図１０及び１１に示すようにな装置を用いることで複数の成形型の加熱を均一に行うこともできる。
【００２４】
本発明のプレス成形は、例えばプレスの上軸及び／又は下軸を駆動して成形型を誘導加熱コイル内に配置した後、誘導加熱を行い、被成形材料が成形温度まで昇温した後、上軸及び／又は下軸を駆動してさらに上型と下型をプレスすることにより行い得る。
被成形ガラス素材は、成形型に供給した後に加熱軟化しても良いが、好ましくは予め加熱軟化した状態で成形型に供給する。加熱軟化した状態で供給する場合は、成形型を予め加熱しておくことが好ましい。
特に本発明の成形方法においては、予め加熱軟化した被成形ガラス素材が、成形型に供給され、成形型に供給される被成形ガラス素材の温度が成形型の温度より高いことが、表面欠陥等のないガラス光学素子を、比較的短いサイクル時間で製造できるという観点から好ましい。
【００２５】
例えば、ガラス素材を該ガラス素材の粘度が１０^９ポアズ未満に相当する温度加熱して軟化させることができる。ガラス素材の粘度が１０^９ポアズ未満であるとで、１０^９ポアズ以上の粘度に相当する温度に予熱した成形型でガラス素材を分に変形させて成形することが可能である。成形型の温度を比較的低温にして成するには、ガラス素材は、好ましくは１０^５．５〜１０^７．６ポアズに相当する温度加熱して軟化させることが適当である。
成形型の予熱の温度は、前記ガラス素材の粘度が１０^９〜１０^１２ポアズに相当る温度とすることができる。粘度が１０^１２ポアズに相当する温度未満では、ガラ素材を大きく伸ばして、コバ厚の薄いガラス成形体を得ることが難しくなり、ま、高面精度が得にくく、粘度が１０^９ポアズに相当する温度を超える温度では、形のサイクルタイムが必要以上に長くなり、また、成形型の寿命が短くなる。
【００２６】
被成形ガラスの成形型への供給は、吸着パッド等公知の供給手段を用いうるが、被成形ガラスを加熱軟化した状態で供給する場合は、浮上皿、好ましくは割型式浮上皿を用い得る。例えば、支持アーム上に長手方向一列に配置された複数の割型式浮上皿上に、下方から噴出する気流により浮上させて、加熱軟化した複数の被成形ガラス素材を、浮上させて搬送し、前記下型の直上で該浮上皿を分割して被成形ガラス素材を落下させることによりガラス素材を供給し得る。このような浮上皿は、例えば、特開平８−１３３７５８号に記載の物を用いることができる。
【００２７】
ガラス素材が、その自重によって変形する程の低粘性域においては、加熱の際にガラス素材を保持する治具とガラスの融着を防止するのは容易ではない。治具の内部からガスを噴出する浮上皿を用い、ガラス素材を気流により浮上させると、治具面とガラス両面にガスのレイヤーが形成され、このため治具とガラスが反応することなく、加熱軟化することが可能となる。更にガラス素材がプリフォームの場合、プリフォームの形状を概ね維持しつつ加熱軟化することができる。また、ガラス素材がガラスゴブであり、不規則な形状で表面にシワ等の表面欠陥がある場合でも、加熱軟化しながら気流により浮上させることで、形状を整え、表面欠陥を消去することも可能である。
【００２８】
ガラス素材の浮上のために用いる気流となるガスとしては、特に制限はない。但し、加熱したガラス素材が治具と反応しないこと、さらに、加熱した治具の酸化による劣化を防止するという観点から、非酸化性ガスであることが好ましく、例えば窒素等であることが適当である。還元性のガス、例えば水素ガス等を添加することもできる。
気流の流量は、気流を吹き出す口の形状やガラス素材の形状及び重量等を考慮して適宜変更できる。通常の場合、ガス流量は０．００５〜２０リットル／分の範囲がガラス素材の浮上に適している。但し、ガス流量が０．００５リットル／分未満であると、ガラス素材の重量が３００ｍｇ以上の場合、ガラス素材を十分に浮上させることができない場合がある。また、ガス流量が２０リットル／分を超えると、ガラス重量が２０００ｍｇ以上の場合でも、浮上治具上のガラスが大きく揺れて、加熱の際にガラス素材がプリフォームの場合、その形状が変化することがあるからである。
さらにガラス素材の加熱軟化の条件は、ガラスの種類等により適宜変えることができ、軟化したガラス素材に必要とされる粘度となるように調整される。
【００２９】
プリフォームの気流による浮上は、例えば、プリフォームの径より小さいか、等しいか、または大きい開口径を有する上方開口部から上方に流出する気流により行うことができる。
【００３０】
さらに、上記のように割型式浮上皿を用いる場合、下型の中央部に心ずれせずに落下させるために、前記被成形ガラス素材を、前記浮上皿と下型の間に配置した心ずれ防止ファンネル部材の開口を通して落下させることもできる。
また、落下した被成形ガラス素材の下型中央部からの位置ずれを直すためにガイド手段により幅寄せを行うことにより心ずれを補正することもできる。
【００３１】
本発明の成形方法において適用できる被成形ガラス素材の形状としては、例えば、球形状、マーブル形状等を挙げることができる。また、被成形ガラス素材の材質や成形により得られる光学素子の形状等には特に制限はない。本発明の成形方法により得られるガラス光学素子としては、例えば、非球面または球面の両凸レンズ、凸メニスカスレンズ、凹メニスカスレンズ等を挙げることができる。
【００３２】
本発明の成形方法において、押圧成形の条件等には特に制限はなく、ガラス素の温度及び成形型の温度等を考慮して適宜決定することができる。通常３０〜２０ｋｇ／ｃｍ^２の圧力で、３〜６０秒間、好ましくは５〜３０秒間押圧すること成形することができる。又、プリフォーム及びゴブの温度、成形型の温度、並び離型の温度も適宜選択できる。
【００３３】
【実施例】
以下、本発明の装置及び方法を実施例により、図面に基づいてさらに説明する。
実施例１
図１は本実施例のプレス成形装置の上型、下型及び母型の組み付け状態を示す断面図であり、図に示すように本実施例のプレス成形装置においては、長尺形状の母型１により上下動可能に支持された４組の上型２、下型３からなる成形型を用いる。上型２および下型３は超硬合金製であり、成形面には貴金属合金薄膜が被覆されている。母型１はタングステン合金製であり、超硬合金よりわずかに大きい熱膨張係数を有する。５は上型２及び下型３を備えた母型１をプレス成形室内に搬送するためのトレーである。６は各々の成形型において成形品の肉厚が一定になるように、各成形型の寸法に応じて厚さを調整するために、下型の下面に設けられたスペーサーである。本実施例のプレス成形装置は、さらに図２に示すように、上型と下型をプレスするためのプレス手段の上主軸９及び下主軸８と、成形時の誘導加熱を行うための誘導加熱コイル７を有する。誘導加熱コイル７は長尺形状の母型の周囲を取り巻く形状で巻回されている。
【００３４】
上記成形装置により、バリウムホウケイ酸ガラス（転移点５１４ ℃、屈伏点５４５ ℃）の球状プリフォーム４を用いて、外径１５ｍｍの両凸レンズを成形した。
球状プリフォーム４を、母型１内の上型２と下型３の間にセットし、この母型１をトレー５に載置して、不活性雰囲気に保たれた成形装置内に入れ、成形装置の下主軸８上にトレー５と共に配置した。その後、下主軸８を上昇させ、下型３を成形装置の誘導加熱コイル７の内側に上昇させた（図２ａ、ｂ）。高周波のパワーを入れ、タングステン合金製の母型１を誘導加熱し、被成形ガラス素材を５９６ ℃（ガラス粘度が１０^８ポアズに相当する温度）に加熱した後、下主軸を更に上昇し、上型の上面を上主軸のヘッド９に押し当てることにより、軟化したプリフォームを加圧した（図２ｃ）。その後、ガラス転移点以下まで冷却した後、下主軸を下降させ、成形品を成形用型と共に成形装置の外へ取り出した。
各型の成形面の温度分布は良好であり、偏ったのび方をすることがなく、アスの少ない面精度の良好なレンズが得られた。
【００３５】
実施例２
炭化珪素製の上下型を用い、成形面に炭素系薄膜を被覆し、図３に示すように下型１０３外周面にスリーブ１１０を設けた以外は実施例１と同様の成形装置により、実施例１と同様の両凸レンズを成形した。スリーブ１１０は、プレス時に上型１０２と嵌合して上下型の軸ずれを防止すると共にレンズの側面を形成するためのものであり、上下型と同様炭化珪素に炭素系薄膜を被覆してある。実施例１と同様の条件で成形を行ったところ、熱伝導のよいスリーブが上下型の外周を取り囲むことによって、成形面の温度分布がより良くなるため、実施例１以上に高精度のレンズが得られた。
【００３６】
実施例３
本実施例の成形装置においては、図４に示すように、長尺形状の上母型２０１ａ及び下母型２０１ｂが、各々プレスの上主軸２０９及び下主軸２０８に取り付けられており、上母型２０１ａ及下母型２０１ｂには、各々４個の上型２０２及び下型２０３が取り付けられている。さらに、上型２０２の外周には、下型と狭いクリアランスで嵌合して滑動することによりレンズの上下面の軸ずれを防止するスリーブ２１０が設けられている。上母型２０１ａの両側には、ガイドピン２１１が突設され、これに対応して下母型２０１ｂには、ガイド孔２１２が設けられている。上母型２０１ａ及び下母型２０１ｂは、タングステン合金により形成し、上型２０２及び下型２０３並びにスリーブ２１０は実施例２と同様の材質により形成した。
【００３７】
この装置を用いて、バリウムホウケイ酸ガラス（転移点５１４ ℃、屈伏点５４５ ℃）をプレスして外径１５ｍｍの両凸形状のレンズ（１面が球面、他の１面が非球面）を成形した。マーブル形状に熱間成形された表面欠陥のないプリフォーム２０４を４７０ ℃に予熱し、成形室の下方にて約４７０ ℃に予熱された下母型２０１ｂの４個の下型２０３上に吸着パッド（図示せず）を用いて４個同時に移送した。直ちに、下母型２０１ｂを上昇し４７０ ℃の上母型に組み込んだ（図４ａ）。この時、下型２０３がガイドピン２１１とガイド孔２１２にガイドされ、その後各スリーブ２１０が各下型２０３に嵌合する。高周波誘導加熱により上下母型２０１ａ，２０１ｂをガラス粘度１０^８ポアズに相当する５９６ ℃に昇温した。均熱化した後、下母型２０１ｂを上昇させて７０Ｋｇ／ｃｍ^２の圧力でプレスした（図４Ｃ）。次に、型および成形されたレンズをガラスの転移点以下になるまで５０℃／分の冷却速度で冷却した。このときガラスの収縮に対して上型２０２が追随し、上型自重のみかかった状態で冷却された。すなわち冷却中はレンズの上面と上型の接触が保たれていた。
【００３８】
各型において、加熱及び冷却がほぼ均等に行われた。４９０ ℃で下母型２０１ｂを下降させて離型し、そのまま下母型２０１ｂを成形室の下まで下降させ、吸着パッドを用いて４個のレンズを取り出した。取り出したレンズは必要に応じ、その後アニールする場合もある。得られたレンズは高面精度で、表面品質も良好で、心取り後の偏心も良好であった。
【００３９】
実施例４
本実施例の成形装置においては、長尺形状の上母型及び下母型に各々６個の上型及び下型が組み込まれている以外は実施例３と同様の構造の母型及び成形型を用いて、直径１０ｍｍの両凸レンズを成形した。
本実施例の装置においては、図６に示すように上母型３０１ａ（不図示）及び下母型３０１ｂの長尺形状を倣った形に巻回された誘導加熱コイルが２箇所（３０７ａ（不図示）、３０７ｂ）、即ち上母型３０１ｂ（不図示）及び下母型３０１ｂの周囲に設けられている。高周波パワーは、下側を制御し、上側は下側に対して何％かを設定できるようにした。上側のコイルと下側のコイルの間には２０ｍｍの隙間を設けた。
【００４０】
６個の球状プリフォーム３０４を、図５に示す開閉可能な支持アーム３１４上に直線上に１列配置（上下型の間隔と等間隔に配置）された６個の割型式浮上皿３１５（グラッシーカーボン製）上で、下方から噴出する気流により、浮上させて加熱、軟化（特開平８−１３３７５８号参照）させた（図７ａ参照）。その後、支持アーム３１４を上下の誘導加熱コイル３０７の間に挿入し、複数の下型３０３の直上に配置して、支持アーム３１４を素早く開くことにより、複数の浮上皿３１５を左右に分割し、複数のプリフォーム３０４を、浮上皿３１５からそれぞれに対応する下型３０３上に同時に落下させることにより、下型３０３上に供給した（図７ｂ）。プリフォーム３０４が各下型３０３の中央部に心ずれせずにより確実に落下するように、浮上皿３１５と下型３０３の間に図６に平面形状を、また図７に断面形状を示すファンネル状部材３１６を挟んで落下させることが好ましい。
【００４１】
その後、直ちに支持アームおよびファンネルを下型上から後退させ、高周波パワーを切り、下母型を上昇させて７０Ｋｇ／ｃｍ²の圧力でプレスした。ガラスにかかる圧力は上型自重のみとし、ガラスの転移点以下まで冷却し、その後下母型を約２０ｍｍ下降して離型し、吸着パット（図示せず）を上下の誘導加熱コイルの間に挿入し成形品を同時に取り出した。そして上下の母型温度は高周波パワーにより直ちにプレス開始温度に回復させ、次の成形を同様にして行った。本実施例の成形条件の例を表１に示す。
【００４２】
【表１】

【００４３】
いずれの成形条件においても品質の良好なレンズが連続して得られた。本実施例の方法によると、非常に速い生産速度で、高い効率で、多量のレンズが連続生産できる。
【００４４】
実施例５
本実施例ではプリフォームとして、マーブル形状に熱間成形されたプリフォーム４０４を用いた。球状プリフォームの場合は、実施例４で説明したように落下時にファンネルでガイドすることが非常に有効であったが、マーブル形状のプレイフォームの場合、下型中心からずれる場合がある。そこで、落下したプリフォームの下型中央部からの位置ずれを直すためにガイド手段４１７により幅寄せを行った。ガイド手段４１７としては、プリフォーム径よりわずかに大きい内径の円形開口４１８を有する部材が用いられた。このガイド手段４１７を、開口４１８の中心が下型４０３の中心と合うように被せた（図７参照）。ずれたプリフォーム４０４の周縁部に部材が当たることにより、プリフォーム４０４は中心位置に滑り、これにより幅寄せが行われる。その後、プレス成形を行うことにより、偏肉の少ないレンズが得られた。他の条件については実施例４と同様である。
【００４５】
【発明の効果】
本発明のプレス成形装置においては、複数の成形型を直線状一列に配列し、これに対して両側から誘導加熱を生じさせるため、各成形型を均一に加熱してプレス成形を行うことができる。このため、部分的なのび不良等の問題が生じることなく、面精度が高く、かつ表面品質の良好なガラス光学素子を得ることができる。
【図面の簡単な説明】
【図１】本発明の一実施例のプレス成形装置の組み付け状態を示す断面図。
【図２】図１のプレス成形装置の成形時の状態を示す説明図。
【図３】本発明の他の実施例のプレス成形装置の組み付け状態を示す断面図。
【図４】本発明の他の実施例のプレス成形装置の成形時の状態を示す説明図。
【図５】本発明の他の実施例に用いる成形材料供給手段を示す上面図。
【図６】本発明の他の実施例の装置を示す上面図。
【図７】図６の装置を示す断面図。
【図８】本発明の他の実施例の成形材料供給方法を示す断面図。
【図９】本発明のプレス成形装置を示す上面図。
【図１０】本発明のプレス成形装置を示す上面図。
【図１１】本発明のプレス成形装置を示す上面図。
【図１２】従来例のプレス成形装置を示す図。
【符号の説明】
１母型
２上型
３下型
７誘導加熱コイル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass optical element molding apparatus and molding method, and more particularly to a molding apparatus and molding method for simultaneously molding a plurality of glass optical elements.
[0002]
[Prior art]
In recent years, various methods have been developed for molding glass optical elements such as high-precision lenses using a mold in which a softened glass is not fused and a mold material that can be mirror-finished is precisely processed. In this method, in order to improve production efficiency, it has been studied to simultaneously press mold a plurality of glass optical elements using a plurality of molds.
[0003]
For example, in Japanese Patent Laid-Open No. 63-170225, four upper and lower cavity dies are placed on a disk-shaped upper and lower mold, and the center of each cavity die is at the same radius from the center of the mold at equal intervals. The glass material to be molded is set on each lower cavity die, the die is induction-heated by an induction heating coil wound around the periphery of the die, and the cavity die and the heat are transmitted from the die. It is shown that a glass material to be molded is heated and press-molded.
On the other hand, in Japanese Patent Application Laid-Open No. 7-33452, as shown in FIG. 12, a body mold 501 provided with an upper mold member 502 and a lower mold member 503 for forming a glass material arranged in series is provided. In addition, there has been proposed an optical element molding apparatus that is configured to perform press molding by heating with a heat source 507 arranged in parallel to the row of lower mold members 503.
[0004]
[Problems to be solved by the invention]
In order to press-mold a glass optical element such as a high-precision lens, it is important that the temperature on the molding surface of the mold is uniform, for example, a temperature distribution within 2 to 3 ° C. is required. . However, in the method of Japanese Patent Laid-Open No. 63-170225, the periphery of the mold is induction-heated, and the heat is conducted toward the center of the mold to heat the entire mold. A high temperature distribution is generated at the center portion, and the temperature distribution on the cavity die molding surface is high at the peripheral portion side of the mold and low at the center portion side. As a result, there is a problem that the molding material extends to the peripheral edge side of the mold during molding and protrudes from the cavity die. On the other hand, on the side of the center part, it is easy to cause a defective extension, resulting in a defective product. Further, the molded product has a problem that asses are likely to occur due to this temperature distribution.
[0005]
As shown in FIG. 12, the apparatus disclosed in Japanese Patent Application Laid-Open No. 7-33452 heats the molds arranged in two rows by heating the barrel mold using a heating source parallel thereto. The side became high temperature and the center side of the body mold became low temperature. Further, the apparatus disclosed in Japanese Patent Laid-Open No. 7-33452 can automatically supply a glass material and take out a molded product in an airtight container. However, the mold and the glass material to be molded are heated in a heating zone. Was not short.
[0006]
Accordingly, the present invention provides a press molding apparatus and a press molding method capable of solving the above-mentioned problems and manufacturing a glass optical element having good surface accuracy and surface quality by uniformly heating a plurality of molds and performing press molding. The purpose is to do.
[0007]
[Means for Solving the Problems]
In the present invention, in order to solve the above-mentioned problems, a mold composed of an upper mold and a lower mold, a mother mold supporting the mold, and the mold wound around the mother mold are heated. In a molding apparatus having a heating means,
The matrix has an elongated shape and a certain width;
A plurality of the molds are provided in the matrix in a line at equal intervals in the longitudinal direction, and the center of the mold is positioned on the center line of the matrix; and
There is provided a glass optical element molding apparatus characterized in that a distance between the heating means and the mother die is constant at least at a short-side end of the mother die.
Further, in the present invention, a plurality of heat-softened glass materials to be formed are formed by a plurality of forming molds composed of an upper mold and a lower mold, which are arranged in a line along a longitudinal direction on an elongated mother mold. In the molding method of the optical element consisting of pressure molding at the same time,
Each of the plurality of molding dies is heated by heat conduction from the mother die heated by heating means wound around the mother die, and this heating is at least in the horizontal section of each molding die. There is provided a method for molding an optical element, wherein the two positions are heated so as to be substantially evenly heated.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
In the molding apparatus of the present invention, a matrix that supports the mold has an elongated shape and has a certain width, and a plurality of the molds are molded in the matrix in a row at equal intervals in the longitudinal direction. The mold is provided so that the center of the mold is located on the center line of the mother mold, and the distance between the heating means and the mother mold at least in the short-side end of the mother mold is constant. In the present invention, by adopting such a structure, it is possible to prevent the occurrence of temperature distribution due to the difference in distance from the heating means on the molding surface of each mold as much as possible. As a result, the glass having good surface accuracy and surface quality A plurality of optical elements can be molded simultaneously. It is preferable from the viewpoint that the long base is preferably semi-circular at both ends so that heating to the mold near the both ends can be made uniform.
[0009]
The number of molds provided in one mother mold is not particularly limited, and can be appropriately determined in consideration of the shape and dimensions of the glass optical element. However, in consideration of production efficiency and production technology, the number is preferably about 2 or more and 10 or less. However, of course, it may be 10 or more.
In the molding apparatus of the present invention, the shape, structure and material of the mold can be known, and examples include those described in JP-A-8-133758. Specifically, a silicon carbide sintered body formed on a silicon carbide sintered body by a CVD method and then an i-carbon film formed by an ion plating method can be used as a mold. In addition, cermets of silicon, silicon nitride, tungsten carbide, aluminum oxide and titanium carbide, and their surfaces coated with diamond, refractory metals, noble metal alloys, or ceramics such as carbides, nitrides, borides, oxides, etc. Can also be used. However, carbon-based films such as i-carbon films are particularly advantageous in that they have good releasability.
[0010]
The heating means can be selected from various known ones, and is wound around the mother die so as to be positioned in a contact state or a non-contact state around the mother die at the time of molding. The heating means is an induction heating means such as an induction heating coil, and is preferably wound around the shape of the mother die so as to be positioned in a non-contact state around the mother die at the time of molding. The induction heating means such as an induction heating coil can be appropriately selected from known ones.
By using the induction heating means as the heating means, it is possible to quickly raise the temperature of the mold when repeatedly molding, and there is an advantage that the molding cycle time can be shortened. Furthermore, the induction heating means has an advantage that precise temperature control is possible because the temperature reproducibility is very good.
[0011]
In the molding apparatus of the present invention, when the heating means is an induction heating coil, the distance between the heating means and the mother die at least at the short-side end of the mother die is constant, so that the mother from the induction heating coil is The energy to the mold can be uniformly applied, and the mold can be uniformly heated. Furthermore, by providing a molding die in a long shape and having a certain width so that the center of each molding die is located on the center line of the mother die, an induction heating coil can be used for the mother die. The left and right heat generation can be contrasted in the longitudinal direction. Furthermore, the amount of heat received from the mother die can be made uniform between the molding dies by arranging the molding dies provided in a row in the longitudinal direction of the mother die at equal intervals.
In the molding apparatus of the present invention, the above requirements are satisfied. In particular, even when the heating means is an induction heating coil, a plurality of molds are uniformly heated to perform press molding, and surface accuracy and surface It becomes possible to manufacture a glass optical element with good quality.
[0012]
Further, the press molding apparatus of the present invention can be provided with means for blowing gas from one or both of the longitudinal directions of the mother die in order to uniformly heat the molding die by the induction heating coil. FIG. 9 shows a case where means 308 for blowing gas is provided in both the longitudinal directions of the mold 301b. Although there is no restriction | limiting in particular in the gas for blowing on a shaping | molding die, For example, inert gas like nitrogen can be used.
[0013]
Further, in the press molding apparatus of the present invention, the induction heating coil as the heating means follows the shape of the mother die so that it is positioned in a non-contact state around the mother die except for the end portion in the longitudinal direction of the mother die. It can also be wound. An example of such an embodiment is schematically shown in FIG. For example, the distance between the heating means and the mother die at the end portion in the longitudinal direction can be made larger than the distance between the heating means and the mother die at the edge portion in the short direction. In FIG. 10A, the induction heating coil 307b is moved away from the mother die in the vicinity of the longitudinal end of the mother die so that the longitudinal end 309b of the mother die is not heated. In FIG. 10B, the induction heating coil 307b is disposed only on the side portion excluding the end portion 309b in the longitudinal direction of the mother die. As a result, the heating of the mold near the end in the longitudinal direction and the heating of the mold at the center can be made more uniform. In the case of FIG. 10B, the temperature of the two induction heating coils can be adjusted by the same or different circuits.
[0014]
For the same reason as described above, the width of the mother die from the contact portion to the end portion with the mold can be made larger in the longitudinal direction than in the lateral direction. This state is shown in FIG. In the drawing, by making the end 309b in the longitudinal direction of the mother mold longer, it is possible to make it difficult for the heat of the mother mold heated by the induction heating coil 307b to be transmitted to the molding dies 3031 and 3036 at both ends.
In addition, although the description based on said figure is about a lower mold | type, it is the same also about an upper mold | type.
[0015]
The long-shaped mother die may be a single mother die that supports the upper die and the lower die, and is divided into an upper mother die that supports the upper die and a lower mother die that supports the lower die. May be. In the case of supporting with one mother die, at least one of the upper die and the lower die can move up and down with respect to the mother die. In this case, for example, the press can be performed by positioning the mother die on the lower shaft of the press and pressing the upper surface of the upper die with a press head attached to the upper shaft of the press. In the case of a mother die that is divided vertically, the upper mother die and the lower mother die can be attached to the upper and lower shafts of a press that can move up and down at least one of them.
[0016]
The induction heating coil is arranged at the position of the mother die at the time of molding. When the mother die is divided into upper and lower parts, two induction heating coils are preferably provided so as to be located around each mother die. The upper and lower coils are preferably arranged at an appropriate interval so that the material to be molded can be supplied and the molded product can be taken out.
The material of the mother die that supports the mold can be a known material. Examples of the material of the mother die that supports the forming die include stainless steel alloy, cast iron, tungsten alloy, molybdenum alloy, and the like.
[0017]
In the apparatus according to the present invention, preferably, a sleeve for preventing axial misalignment between the upper mold and the lower mold is provided in any of the upper mold, the lower mold, the upper mother mold, and the lower mother mold. For example, a sleeve member can be attached to the outer periphery of the lower mold, and the upper mold can be inserted inside the sleeve member.
[0018]
The molding apparatus of the present invention can further include a split plate for simultaneously supplying a plurality of glass materials for molding to the plurality of molds. Further, the split plate can have pores for blowing gas upward to float the glass material for molding. Examples of such a mold plate for floating a glass material for molding include those described in JP-A-8-133758 as a floating jig.
The molding apparatus of the present invention will be described more specifically in the examples.
[0019]
In the molding method of the present invention, a plurality of heat-softened glass materials to be molded are simultaneously arranged in a plurality of molding molds composed of an upper mold and a lower mold, which are arranged in a line along a longitudinal direction on an elongated mother mold. An optical element molding method comprising pressure molding. The shape, structure, material, and the like of the mold used in the molding method of the present invention, as well as the molding conditions, can be known, and examples include those described in JP-A-8-133758. it can.
When a plurality of heat-softened glass materials to be softened are simultaneously pressure-molded in a plurality of molds, the thermal conditions are the same among the molds, and the temperature of the molding surface in each mold is From the center of the molding surfaceetcIt is preferable that the position is the same at a distance.
[0020]
In the molding method of the present invention, a plurality of molding dies are arranged in a line along the longitudinal direction on a long-shaped mother die, and from the mother die heated by heating means wound around the mother die. Since each mold is heated by heat conduction, it is possible to make the thermal conditions the same among a plurality of molds.
Further, in the molding method of the present invention, each of the plurality of molding dies is heated by heat conduction from a mother die heated by a heating means wound around the mother die, and this heating is performed by: It is characterized in that it is performed so that at least two opposing positions in the horizontal cross section of each mold are heated substantially evenly.
[0021]
Examples of the molding apparatus that enables heating of such a mold include the molding apparatus of the present invention. That is, the mother die has a long shape and has a certain width, and a plurality of the molding dies are arranged in a row at equal intervals in the longitudinal direction, and the center of the molding die is on the center line of the mother die. Further, an apparatus can be used in which the distance between the heating means and the mother die is constant at least at the short-side end of the mother die.
[0022]
The heating means is preferably an induction heating coil from the viewpoint that the mother die can be heated more uniformly. The periphery of the molding die is covered with a mother die and is overheated by heat conduction from the mother die. If the heat transferred from the mother mold is different at two opposing positions in the horizontal section for one mold, it will be from the center of the molding surface of the mold.etcA temperature distribution (temperature difference) occurs at a position at a distance, and it is difficult to obtain a glass optical element with good surface accuracy and surface quality. Therefore, in the method of the present invention, the mold is heated so that two opposing positions in the horizontal cross section of each mold are heated substantially uniformly. By adopting such a mold heating method, from the center of the molding surface of each moldetcA difference in temperature at a position at a distance can be suppressed as much as possible, and as a result, a plurality of glass optical elements having good surface accuracy and surface quality can be molded simultaneously.
[0023]
Further, from the viewpoint of making the thermal conditions among the plurality of molds the same, in order to uniformly heat the mold by the induction heating coil, Gas can be blown from both. Although there is no restriction | limiting in particular in the gas for blowing on a shaping | molding die, For example, inert gas like nitrogen can be used. Further, by using such an apparatus as shown in FIGS. 10 and 11, a plurality of molds can be heated uniformly.
[0024]
In the press molding of the present invention, for example, after driving the upper shaft and / or the lower shaft of the press to place the mold in the induction heating coil, induction heating is performed, and after the material to be molded is heated to the molding temperature, It can be performed by driving the upper shaft and / or the lower shaft and further pressing the upper die and the lower die.
The glass material to be molded may be heated and softened after being supplied to the mold, but is preferably supplied to the mold in a preheated and softened state. When supplying in a heat-softened state, it is preferable to heat the mold in advance.
Particularly in the molding method of the present invention, a glass material to be molded that has been softened by heating in advanceBut,Supply to moldIsThe temperature of the glass material to be molded supplied to the mold is preferably higher than the temperature of the mold from the viewpoint that a glass optical element free from surface defects can be produced in a relatively short cycle time.
[0025]
For example, if a glass material has a viscosity of 10⁹It can be softened by heating at a temperature corresponding to less than Poise. The viscosity of the glass material is 10⁹If it is less than poise, 10⁹It is possible to mold the glass material by deforming it with a mold preheated to a temperature corresponding to a viscosity equal to or higher than Poise. In order to achieve the mold at a relatively low temperature, the glass material is preferably 10^5.5-10^7.6It is appropriate to soften by heating at a temperature corresponding to Poise.
The preheating temperature of the mold is such that the viscosity of the glass material is 10⁹-10¹²The temperature can be equivalent to Poise. Viscosity is 10¹²Below the temperature corresponding to Poise, it is difficult to obtain a glass molded product with a thin edge by greatly stretching the glass material, and it is difficult to obtain high surface accuracy and a viscosity of 10⁹At temperatures exceeding the temperature corresponding to Poise, the cycle time of the shape becomes longer than necessary, and the life of the mold is shortened.
[0026]
For supplying the glass to be molded to the mold, known supply means such as a suction pad can be used, but when the glass to be molded is supplied in a heat-softened state, a floating plate, preferably a split mold type floating plate can be used. For example, on a plurality of split type levitation plates arranged in a line in the longitudinal direction on a support arm, a plurality of glass materials to be molded that are levitated by an air current jetted from below and heated and softened are conveyed and conveyed, The glass material can be supplied by dividing the floating dish directly above the lower mold and dropping the glass material to be molded. As such a floating dish, for example, the one described in JP-A-8-133758 can be used.
[0027]
In a low-viscosity region where the glass material is deformed by its own weight, it is not easy to prevent the glass holding the glass material from fusing with each other during heating. When a glass plate is levitated by an air flow using a levitation dish that ejects gas from the inside of the jig, a gas layer is formed on both the jig surface and the glass surface. It becomes possible to soften. Furthermore, when the glass material is a preform, it can be softened by heating while generally maintaining the shape of the preform. In addition, even if the glass material is glass gob and there are surface defects such as wrinkles in the irregular shape, it is possible to prepare the shape and erase the surface defects by floating by air flow while softening with heat. is there.
[0028]
There is no restriction | limiting in particular as gas used as the airflow used for the float of a glass raw material. However, from the viewpoint of preventing the heated glass material from reacting with the jig and preventing deterioration of the heated jig due to oxidation, it is preferably a non-oxidizing gas, for example, nitrogen. is there. A reducing gas such as hydrogen gas can also be added.
The flow rate of the airflow can be changed as appropriate in consideration of the shape of the mouth for blowing the airflow, the shape and weight of the glass material, and the like. In a normal case, a gas flow rate in the range of 0.005 to 20 liters / minute is suitable for floating a glass material. However, if the gas flow rate is less than 0.005 liter / min, the glass material may not be sufficiently levitated when the weight of the glass material is 300 mg or more. When the gas flow rate exceeds 20 liters / minute, even when the glass weight is 2000 mg or more, the glass on the floating jig is greatly shaken, and when the glass material is a preform during heating, the shape changes. Because there are things.
Furthermore, the conditions for heat softening of the glass material can be appropriately changed depending on the type of glass and the like, and are adjusted so as to have a viscosity required for the softened glass material.
[0029]
The levitation by the air flow of the preform can be performed, for example, by an air flow flowing upward from an upper opening having an opening diameter smaller than, equal to, or larger than the diameter of the preform.
[0030]
Further, when using the split type floating dish as described above, the glass material to be molded is placed between the floating dish and the lower mold in order to drop the center of the lower mold without being misaligned. It can also be dropped through the opening of the prevention funnel member.
Moreover, in order to correct the position shift from the lower mold center part of the glass molding material which fell, the center shift | offset | difference can also be correct | amended by performing width alignment by a guide means.
[0031]
Examples of the shape of the glass material to be molded that can be applied in the molding method of the present invention include a spherical shape and a marble shape. Moreover, there is no restriction | limiting in particular in the shape of the optical element obtained by the material of a to-be-molded glass raw material, or shaping | molding. Examples of the glass optical element obtained by the molding method of the present invention include an aspherical or spherical biconvex lens, a convex meniscus lens, and a concave meniscus lens.
[0032]
In the molding method of the present invention, there are no particular limitations on the conditions for press molding, and the conditions can be appropriately determined in consideration of the temperature of the glass element, the temperature of the mold, and the like. Usually 30-20kg / cm²It can be formed by pressing at a pressure of 3 to 60 seconds, preferably 5 to 30 seconds. Further, the temperature of the preform and gob, the temperature of the mold, and the temperature of the mold release can be selected as appropriate.
[0033]
【Example】
Hereinafter, the apparatus and method of the present invention will be further described with reference to the drawings by way of examples.
Example 1
FIG. 1 is a cross-sectional view showing an assembled state of an upper die, a lower die and a mother die of a press molding apparatus according to the present embodiment. As shown in FIG. A molding die comprising four sets of an upper die 2 and a lower die 3 supported by 1 so as to be movable up and down is used. The upper mold 2 and the lower mold 3 are made of cemented carbide, and the molding surfaces are covered with a noble metal alloy thin film. The mother die 1 is made of a tungsten alloy and has a slightly larger thermal expansion coefficient than that of the cemented carbide. Reference numeral 5 denotes a tray for conveying the mother die 1 including the upper die 2 and the lower die 3 into the press molding chamber. Reference numeral 6 denotes a spacer provided on the lower surface of the lower mold in order to adjust the thickness according to the dimension of each mold so that the thickness of the molded product is constant in each mold. As shown in FIG. 2, the press molding apparatus of the present embodiment further includes an upper main shaft 9 and a lower main shaft 8 for pressing means for pressing the upper mold and the lower mold, and induction heating for performing induction heating at the time of molding. A coil 7 is provided. The induction heating coil 7 is wound in a shape that surrounds the periphery of an elongated mother die.
[0034]
A biconvex lens having an outer diameter of 15 mm was molded using the spherical preform 4 of barium borosilicate glass (transition point 514 ° C., yield point 545 ° C.) by the molding apparatus.
The spherical preform 4 is set between the upper mold 2 and the lower mold 3 in the mother mold 1, this mother mold 1 is placed on the tray 5, and placed in a molding apparatus maintained in an inert atmosphere, It was arranged with the tray 5 on the lower main shaft 8 of the molding apparatus. Thereafter, the lower main shaft 8 was raised, and the lower die 3 was raised inside the induction heating coil 7 of the molding apparatus (FIGS. 2a and 2b). The high frequency power is applied, the tungsten alloy matrix 1 is induction-heated, and the glass material to be molded is 596 ° C. (with a glass viscosity of 10⁸After heating to a temperature corresponding to Poise, the lower main spindle was further raised, and the upper surface of the upper mold was pressed against the head 9 of the upper main spindle to pressurize the softened preform (FIG. 2c). Then, after cooling to below the glass transition point, the lower main spindle was lowered, and the molded product was taken out of the molding apparatus together with the molding die.
The temperature distribution on the molding surface of each mold was good, and the lens did not spread unevenly, and a lens with good surface accuracy with little asperity was obtained.
[0035]
Example 2
A molding apparatus similar to that of Example 1 was used except that an upper and lower mold made of silicon carbide was used, the molding surface was covered with a carbon-based thin film, and a sleeve 110 was provided on the outer peripheral surface of the lower mold 103 as shown in FIG. A biconvex lens similar to 1 was molded. The sleeve 110 is for fitting with the upper mold 102 at the time of pressing to prevent the axial displacement of the upper and lower molds and to form the side surface of the lens. Like the upper and lower molds, a silicon thin film is coated on silicon carbide. . When molding was performed under the same conditions as in Example 1, the sleeve with good heat conduction surrounds the outer periphery of the upper and lower molds, so that the temperature distribution on the molding surface becomes better. Obtained.
[0036]
Example 3
In the molding apparatus of the present embodiment, as shown in FIG. 4, a long upper mold 201a and a lower mold 201b are respectively attached to an upper main shaft 209 and a lower main shaft 208 of the press. Four upper molds 202 and lower molds 203 are attached to 201a and lower mother mold 201b, respectively. Further, a sleeve 210 is provided on the outer periphery of the upper die 202 to prevent axial misalignment of the upper and lower surfaces of the lens by fitting and sliding with the lower die with a narrow clearance. Guide pins 211 are projected on both sides of the upper mother die 201a, and correspondingly, guide holes 212 are provided in the lower mother die 201b. The upper mother die 201a and the lower mother die 201b were formed of a tungsten alloy, and the upper die 202, the lower die 203, and the sleeve 210 were formed of the same material as in Example 2.
[0037]
Using this device, barium borosilicate glass (transition point 514 ° C, yield point 545 ° C) is pressed to form a biconvex lens (one surface is spherical and the other is aspheric) with an outer diameter of 15 mm. did. The preform 204 which is hot-formed into a marble shape and has no surface defects is preheated to 470 ° C., and suction pads are placed on the four lower molds 203 of the lower mother die 201b preheated to about 470 ° C. below the molding chamber. (Not shown) were used to simultaneously transfer 4 pieces. Immediately, the lower mother die 201b was raised and incorporated into the upper mother die at 470 ° C. (FIG. 4a). At this time, the lower mold 203 is guided by the guide pins 211 and the guide holes 212, and then the respective sleeves 210 are fitted into the respective lower molds 203. The upper and lower mother dies 201a and 201b are made to have a glass viscosity of 10 by high frequency induction heating.⁸The temperature was raised to 596 ° C. corresponding to Poise. After soaking, the lower base 201b is raised to 70Kg / cm²(FIG. 4C). Next, the mold and the molded lens were cooled at a cooling rate of 50 ° C./min until the temperature was below the glass transition point. At this time, the upper mold 202 followed the shrinkage of the glass and cooled in a state where only the upper mold weight was applied. That is, the contact between the upper surface of the lens and the upper mold was maintained during cooling.
[0038]
In each mold, heating and cooling were performed almost evenly. The lower mother die 201b was lowered at 490 ° C. to release the mold, and the lower mother die 201b was lowered to the bottom of the molding chamber as it was, and four lenses were taken out using the suction pad. The taken out lens may be annealed afterwards if necessary. The obtained lens had high surface accuracy, good surface quality, and good decentration after centering.
[0039]
Example 4
In the molding apparatus of the present embodiment, a mother mold and a mold having the same structure as those of the third embodiment except that six upper molds and lower molds are incorporated in the long upper mold and the lower mold, respectively. Was used to mold a biconvex lens with a diameter of 10 mm.
In the apparatus of the present embodiment, as shown in FIG. 6, two induction heating coils (307a (not shown) are wound in a shape imitating the long shape of the upper mother die 301a (not shown) and the lower mother die 301b. 307b), that is, around the upper mother die 301b (not shown) and the lower mother die 301b. The high frequency power was controlled on the lower side, and the upper side could be set to a percentage of the lower side. A gap of 20 mm was provided between the upper coil and the lower coil.
[0040]
Six split preforms 315 (glassy) in which six spherical preforms 304 are linearly arranged on a support arm 314 that can be opened and closed as shown in FIG. 5 (arranged at equal intervals with the upper and lower molds). The air was blown up and heated and softened (refer to Japanese Patent Laid-Open No. 8-133758) (see FIG. 7a). Thereafter, the support arm 314 is inserted between the upper and lower induction heating coils 307, arranged directly above the plurality of lower molds 303, and the support arm 314 is quickly opened to divide the plurality of floating dishes 315 into left and right, A plurality of preforms 304 were simultaneously supplied onto the lower mold 303 by dropping them from the floating tray 315 onto the corresponding lower mold 303 (FIG. 7b). A funnel having a planar shape in FIG. 6 and a cross-sectional shape in FIG. 7 between the floating plate 315 and the lower die 303 so that the preform 304 is surely dropped to the center of each lower die 303 without being misaligned. It is preferable to drop it with the member 316 interposed therebetween.
[0041]
Immediately after that, the support arm and funnel are retracted from above the lower mold, the high frequency power is turned off, and the lower mother mold is raised to 70 kg / cm.²Pressing at a pressure of The pressure applied to the glass is only the upper mold weight, cooled to below the glass transition point, the lower mother mold is lowered by about 20 mm and released, and the suction pad (not shown) is placed between the upper and lower induction heating coils. InsertMoldingWere taken out at the same time. The upper and lower mold temperatures were immediately restored to the press start temperature by the high frequency power, and the next molding was performed in the same manner. Table 1 shows an example of molding conditions of this example.
[0042]
[Table 1]

[0043]
Under any molding condition, lenses having good quality were continuously obtained. According to the method of this embodiment, a large number of lenses can be continuously produced at a very high production rate and with high efficiency.
[0044]
Example 5
In this example, a preform 404 hot-formed into a marble shape was used as the preform. In the case of a spherical preform, as described in Example 4, it was very effective to guide with a funnel at the time of dropping, but in the case of a marble-shaped play form, there is a case where it deviates from the center of the lower mold. Therefore, in order to correct the positional deviation from the center of the lower mold of the dropped preform, the guide means 417 performed width adjustment. As the guide means 417, a member having a circular opening 418 having an inner diameter slightly larger than the preform diameter was used. This guide means 417 was placed so that the center of the opening 418 was aligned with the center of the lower mold 403 (see FIG. 7). When the member hits the peripheral edge of the shifted preform 404, the preform 404 slides to the center position, and thereby the width is adjusted. Then, a lens with little uneven thickness was obtained by performing press molding. Other conditions are the same as in the fourth embodiment.
[0045]
【The invention's effect】
In the press molding apparatus of the present invention, a plurality of molding dies are arranged in a straight line, and induction heating is generated from both sides thereof. . For this reason, it is possible to obtain a glass optical element with high surface accuracy and good surface quality without causing problems such as partial stretch failure.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an assembled state of a press molding apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing a state during molding of the press molding apparatus of FIG. 1;
FIG. 3 is a cross-sectional view showing an assembled state of a press molding apparatus according to another embodiment of the present invention.
FIG. 4 is an explanatory view showing a state during molding of a press molding apparatus according to another embodiment of the present invention.
FIG. 5 is a top view showing a molding material supply means used in another embodiment of the present invention.
FIG. 6 is a top view showing an apparatus according to another embodiment of the present invention.
7 is a cross-sectional view showing the apparatus of FIG.
FIG. 8 is a cross-sectional view showing a molding material supply method according to another embodiment of the present invention.
FIG. 9 is a top view showing the press molding apparatus of the present invention.
FIG. 10 is a top view showing the press molding apparatus of the present invention.
FIG. 11 is a top view showing the press molding apparatus of the present invention.
FIG. 12 is a view showing a conventional press molding apparatus.
[Explanation of symbols]
1 Mother mold
2 Upper mold
3 Lower mold
7 Induction heating coil

Claims

In a molding apparatus having a molding die composed of an upper die and a lower die, a mother die supporting the molding die, and a heating means for heating the molding die wound around the mother die,
The matrix has an elongated shape and a certain width;
A plurality of the molds are arranged in a row on the mother mold so that the center of the mold is located on the center line of the mother mold, and at least the heating means and the mother mold at the end in the short direction of the mother mold A molding apparatus for glass optical elements, characterized in that the distance is constant.

2. The molding apparatus according to claim 1, wherein a plurality of molding dies are provided on the mother die in a line at equal intervals in the longitudinal direction so that the center of the molding die is located on the center line of the mother die.

3. The molding apparatus according to claim 1, wherein the heating means is an induction heating coil.

The molding apparatus according to any one of claims 1 to 3, further comprising means for blowing gas on a longitudinal end portion of the matrix.

The molding apparatus according to claim 4, wherein the amount of gas sprayed is adjusted by a flow controller.

The distance between the heating means and the mother die at the end portion in the longitudinal direction is larger than the distance between the heating means and the mother die at the edge portion in the short direction. Molding equipment.

The molding apparatus according to any one of claims 1 to 3, wherein the width of the mother die from the contact portion to the end portion with the molding die is larger in the longitudinal direction than in the lateral direction.

The long-shaped mother die is divided into an upper mother die that supports the upper die and a lower mother die that supports the lower die, and at least one of them can be moved up and down. The shaping | molding apparatus of any one.

The molding apparatus according to any one of claims 1 to 8, wherein the mother die is divided into an upper mother die and a lower mother die, and the heating means is arranged to heat the upper die and the lower die, respectively.

The sleeve according to any one of claims 1 to 9, wherein the upper die, the lower die, the upper mother die, and the lower mother die are each provided with a sleeve for preventing vertical axis misalignment. The molding apparatus as described.

Transporting a plurality of molds to a plurality of glass material and for the molded simultaneously, provided further split mold dish for supplying, according to claim 1-10, characterized in that the supply is carried out by dividing the dish The shaping | molding apparatus of any one.

In the molding method of the glass optical element,
A molding apparatus comprising: a mold composed of an upper mold and a lower mold; a mother mold that supports the mold; and a heating unit that heats the mold wound around the mother mold.
The matrix has an elongated shape and a certain width;
A plurality of the molds are arranged in a row on the mother mold so that the center of the mold is located on the center line of the mother mold; and
The method is characterized in that molding is performed using a glass optical element molding apparatus in which a distance between the heating means and the mother die is fixed at least at a short-side end of the mother die.

Because a plurality of heat-softened glass materials to be heat-softened are simultaneously pressure-molded in a plurality of molds composed of an upper mold and a lower mold arranged in a line along the longitudinal direction on a long-shaped mother mold In the optical element molding method,
Each of the plurality of molding dies is heated by heat conduction from the mother die heated by heating means wound around the mother die, and this heating is at least the center of the molding surface of each molding die. On the other hand, the method for molding an optical element is performed such that two opposing positions are heated substantially uniformly.

The molding method according to claim 13, wherein the heating means is an induction heating coil.

Supplying a glass material to be molded into the mold, with respect to the center of the molding surface of each mold, two positions opposing the heating with the mold by the heating means so as to be substantially uniformly heated The molding method according to claim 13 or 14, characterized in that

The glass material for molding softened by preheating is supplied to the mold heated by the heating means, and at the start of pressure molding, the temperature of the softened glass for molding is higher than the temperature of the heated mold And the mold is heated so that the two opposing positions are heated substantially uniformly with respect to the center of the molding surface of each mold, and then the pressure is applied to mold the optical element. The molding method according to claim 13 or 14, characterized in that:

Supplying a plurality of glass material to be molded to the plurality of mold, in any one of claims 13 to 16, characterized in that it is carried out by dropping the glass material to be molded simultaneously onto the mold The forming method as described.

Claim glass material for the molded, has as many openings of the mold, characterized in that for dropping the lower mold through misalignment prevention of the funnel member provided between the floating plates and the lower mold 17 The forming method according to 1.

Multiple glass optical elements are formed by supplying a plurality of heat-softened glass materials to be molded to a plurality of molds including an upper mold and a lower mold, and then simultaneously press-molding the plurality of molds. A way to
Arranging the plurality of glass materials to be molded in a row and heat-softening;
Supplying the glass material for molding onto the lower mold by simultaneously dropping the heat-softened glass material for molding onto the lower molds of the plurality of molding dies arranged in a line; and the supply A method for molding a glass optical element, comprising a step of press-molding a glass material that has been pressed with the molding die.

A plurality of glass optical elements are formed by supplying a plurality of heat-softened glass materials to be molded to a plurality of molds including an upper mold and a lower mold, and then simultaneously press-molding with the plurality of molds. A method,
Heat-softening on a split plate in which the plurality of glass materials to be molded are arranged in a row,
By dividing the split plate on the lower molds of the plurality of molds arranged in a row and simultaneously dropping the plurality of glass materials for molding softened by heating, A method for molding a glass optical element, comprising: a step of supplying a glass material for molding; and a step of press-molding the supplied glass material to be molded with the molding die.

The split plate is a split type floating plate;
The step of heating and softening the plurality of glass forming materials is performed on a split-type levitation plate in which the plurality of glass forming materials are arranged in a row while being floated by an air current,
21. The method of molding a glass optical element according to claim 19 or 20 , wherein the step of supplying the glass material for molding onto the lower mold is performed by dividing the floating dish.

The press molding, wherein carried out by press molding at the molding mold heated to a temperature of the glass material for the molded heated softened to a temperature corresponding to a viscosity of less than 10 ⁹ poises, corresponding to a viscosity of more than 10 ⁹ poises Item 22. The method for molding a glass optical element according to any one of Items 19 to 21 .

Said plurality of mold are arranged in a row in the matrix, the molding type claims is heated by heat conduction from the inductively heated mold by induction heating coils winding the mother mold 19-22 The glass optical element molding method according to any one of the above.