JP4030136B2

JP4030136B2 - Glass lens mold, method for manufacturing the same, and glass lens molding method

Info

Publication number: JP4030136B2
Application number: JP14362695A
Authority: JP
Inventors: 慎一郎広田; 壮雄滝口; 紀士男菅原; 宏明高原
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 1995-06-09
Filing date: 1995-06-09
Publication date: 2008-01-09
Anticipated expiration: 2023-01-09
Also published as: JPH08337429A

Description

【０００１】
【産業上の利用分野】
本発明は、ガラスの精密プレス成形に用いられる成形用型及びその製造方法並びにガラスレンズ成形方法に関する。
【０００２】
【従来の技術】
近年、プレス後に被成形体のプレス面を研磨等の面仕上げ処理を施すまでもなくレンズとしての面精度が得られる精密プレス成形によって特に少なくとも一方の面が非球面をなした非球面ガラスレンズを製造する技術が種々検討されている。
【０００３】
ところで、この技術による非球面レンズの製造は、両凸レンズが中心であったが、最近、この技術によって非球面の凹メニスカスレンズや両凹レンズを製造したいという要請が高まってきている。なお、この種の凹メニスカスレンズや両凹レンズにおいては、各種のレンズ系に組み込むために、図５に示したように、光学機能面（光学的有効径領域）である凹面４１の外側に光軸と直交する平面部４３を設けることが必要とされる。
【０００４】
しかし、精密プレス成形によってこの様な凹メニスカスレンズ及び両凹レンズを製造する技術については、いまだ十分に検討されておらず、この成形に用いるための成形用型についてもその報告例は極めて少ない。
【０００５】
精密プレス成形を用いて上記凹メニスカスレンズを成形する方法として従来知られているのは、図６、図７、図８、図９及び図１０に示されるような方法であった。
【０００６】
図６〜１０に示される方法は、いずれも、胴型３０の成形室３０Ａ内に摺動可能に挿入配置された上型１０と下型２０との間の成形空間に成形材料をいれて成形するものである。このうち、図６〜７に示される方法は、成形後に、レンズの一方の側の外周部を研削加工して平面部４３を形成するものであり、図８〜１０に示される方法は、成形時に平面部４３をも同時に形成するものである。
【０００７】
図６〜７に示される方法は、レンズの凹面を成形するための上型１０の加工技術上の理由から結果的に、上型１０の外側領域の曲面が凸状曲面部１０１を略延長したような形状（図６）や、あるいは、砥石の摩耗を極力防いで凸状曲面部の要求精度を加工上において確保しやすくするために、レンズ有効径外での加工部をできるだけなくした形状（図７）にしたものである。これらの方法では、成形によって得られる成形体自体には平面部が形成されていないので、成形後にあらためて平面部を研削加工等によって形成する必要がある。
【０００８】
また、図８に示される方法は、レンズの凹面の有効径領域を成形する凸状曲面部１０１を有する上型１０の外側に円筒状の第２の上型１０３を嵌合してこの上型１０３によって平面部４３（図５参照）を成形するようにしたものである。
【０００９】
さらに、図９〜１０に示される方法は、胴型３０の上方部に小径部３０１を形成し、この小径部３０１に上型１０が嵌合されるようにし、小径部３０１の下方に大径部３０２を形成してこの大径部３０２に下型２０が嵌合されるようにし、上記小径部３０１と大径部３０２との境界段差面３０３によってレンズの平面部４３を成形するものである。この場合、図９に示される方法では、境界段差面３０３が上型１０の凸状曲面部１０１の外端仕切り線と一致するようにしたものであるのに対して、図１０に示される方法では、境界段差面３０３から上型１０の凸状曲面部１０１の外端仕切り線を下方に突出させたものである。
【００１０】
以上の通り、従来の方法は、いずれも、凹メニスカスレンズの凹面有効径領域４１を成形するための凸状曲面を有する成形型には、平面部４３を成形するための成形部が形成されていない。この理由は、次の通りである。
【００１１】
すなわち、まず、ガラスレンズの精密プレス成形用の型の材料としては、耐熱温度が高い材料であることが必要であることから、セラミックス、超硬合金、サーメット等の加工が容易でない硬脆材料が用いられる。それゆえ、凸状曲面に連続して平面部があるような比較的複雑な形状を精度よく加工する事は困難である。
【００１２】
凸状曲面部が球面である場合には、細かい面粗度と高い面精度を得るための研磨加工としていわゆる球面研磨機が一般的に用いられる。図１１に示されるように、この方法は、研削加工後の上型１０を回転装置５０によって回転させつつ凸状曲面部に接触させた研磨皿６０を揺動させることによって、研磨皿６０の表面に設けた研磨砥粒によって研磨するものである。この方法で研磨を行う場合には、研磨対象たる上型１０の形状としては、凸状曲面部の外側に研磨皿の揺動を阻害するような形状を設けることができず、したがって平面部を設けることもできない。
【００１３】
また、凸状曲面部が非球面の場合には、ＣＮＣ非球面加工機を使用するが、成形型が硬脆材料であるために砥石による研削加工法が採用される。砥石による研削加工では、加工面積が多いとその分砥石が摩耗し、目的の形状精度が得難くなるので、できるだけレンズの有効領域となる部分のみを加工して砥石の摩耗の少ない状態で所望の形状精度を確保する必要がある。その必然的結果としてレンズの有効領域以外は加工する必要のない図６〜１０に示されるような形状が採用されることになる。
【００１４】
【発明が解決しようとする課題】
ところで、本願発明者等の研究によれば、上述の従来の成形方法のうち、図６〜７に示される方法によって成形したレンズは、面精度が得られにくいことがわかった。これは、成形の際に、上型１０の凸状曲面の成形面による成形材料に対する押圧力がレンズ外周辺では外側に逃げてしまい、成形の際に下型２０の成形面の外周付近に対応する上型１０には成形面がないのでレンズの下面外周辺部分には上型１０からの成形圧力がほとんど加えられないからであるものと推察される。
【００１５】
以上のような傾向はレンズ凹面の曲率半径が小さいものほど顕著になる。また、成形後にレンズ凹面側の外周縁を研削除去する後加工によって平面部を形成するようにしていることから、成形体の段階ではその外周縁を十分に厚くしておかなければならない。このため、成形体の中心肉厚とコバ厚との差をどうしても大きいものにせざるを得なくなってそのことからも面精度が得にくいものと推察される。
【００１６】
しかも、成形後に研削除去加工が必要であることから工程数が多く製造コスト上も不利であった。
【００１７】
さらに図７に示される方法では、図１２に示したように、成形の際に上型１０の側面にもガラス材料が入り込む場合が少なくない。そうすると、冷却固化に際してガラスの収縮係数が成形型の収縮係数より大きいために、Ａ部で引っかかりが生じ、これによって面精度が悪化したり応力集中によってガラスにクラックがはいる場合も少なくないという問題もあった。
【００１８】
また、図８〜１０に示される方法は、成形によって平面部も形成されるので、図６〜７の方法のような欠点は一部解消される。しかしながら、レンズの凹状曲面部４１と平面部４３とが別部材の成形型で成形されるようになっているので、成形の際に別部材の成形型の接触部あるいは成形型と胴型との嵌合部の隙間等にガラス材料が入り込む場合が少なくない。これらの嵌合部の隙間にガラス材料が入り込むと、成形面の面精度が悪化する原因になるとともに、成形後にその部分が欠けてガラス屑が生じたり、あるいは、成形後の取り出しの際に引っかかりが生じて成形体を損傷したり、さらには、上型１０や胴型３０等の角部を損傷するおそれもあった。
【００１９】
本発明は、上述の背景のもとでなされたものであり、ガラスの精密プレスによって、少なくとも一方の光学機能面が凹面をなしたガラスレンズを歩留まり良く安定して成形することができる成形用型及びその製造方法並びにガラスレンズ成形方法を提供することを目的としている。
【００２０】
【課題を解決するための手段】
上述の課題を解決するために本発明にかかるガラスレンズ成形用型は、
（構成１）プレス後に被成形体のプレス面を研磨等の面仕上げ処理を施すことなくレンズの光学機能面にできるガラスの精密プレス成形によって少なくとも一方の光学機能面が凹面をなしたガラスレンズを成形する際に用いられる成形用型であって、前記プレスの際に前記ガラスレンズの凹面側の転写を行なうガラスレンズ成形用型において、
成形面が、前記ガラスレンズの凹面を成形するための凸状曲面部と、該凸状曲面部の周囲に該凸状曲面部から外側に連続して形成されて該凸状曲面部の中心軸とほぼ直交する平面に含まれる平面部と、前記凸状曲面部と平面部との境界部に形成された曲面部であって前記凸状曲面部から連続して滑らかに変化する曲面によって前記平面部に移行するように形成された境界曲面部と、を有することを特徴とする構成とし、
この構成１の態様として、
（構成２）構成１のガラスレンズ成形用型において、
前記凸状曲面部と境界曲面部との境界点における境界曲面部側の曲面の接平面が前記凸状曲面部の中心軸に対してなす角度をθ1 、前記境界点における凸状曲面部側の曲面の接平面が前記中心軸に対してなす角度をθ2 としたとき、
０°≦θ2 −θ1 ≦２５°
が成立するようにしたことを特徴とする構成とし、
また、本発明にかかるガラスレンズ成形用型の製造方法は、
（構成３）構成１又は２のガラスレンズ成形用型を製造するガラスレンズ成形用型の製造方法において、
成形用型の素材を荒加工して前記凸状曲面部、平面部及び境界曲面部を形成する荒加工工程と、これら各面を仕上げ研削加工する仕上研削工程とを有し、
前記仕上研削工程は、前記荒加工後の成形用型の素材を前記凸状曲面部の中心軸を回転軸として回転させながら、高速回転する仕上研削用砥石を前記成形用型の素材の仕上面に接触させつつ凸状曲面部の中心軸から外側に向けてまたは外側から中心軸に向けて所定の軌跡を描くように移動することによって行うことを特徴とする構成とし、
この構成３の態様として、
（構成４）構成３のガラスレンズ成形用型の製造方法において、
前記仕上研削工程では、前記凸状曲面部の研削に用いる砥石と、前記平面部部及び境界曲面部の研削に用いる砥石とを異ならしめたことを特徴とする構成とした。
【００２１】
さらに本発明にかかるガラスレンズ成形方法は、
（構成５）胴型内に摺動可能に設けた上型と下型との間に充填されたガラス素材を前記上型及び下型によってプレスしてガラスレンズを成形するガラスレンズ成形方法において、
前記上型又は下型の少なくとも一方に構成１又は２のガラスレンズ成形用型を用いると共に、前記上型及び下型の間に充填するガラス素材の量を、胴型、上型及び下型によって形成される容積より少なくすることを特徴とした構成としたものである。
【００２２】
【作用】
上述の構成１によれば、要するに、ガラスの精密プレス成形によって少なくとも一方の光学機能面が凹面をなしたガラスレンズを成形する際に用いられる成形用型であって、プレスの際にガラスレンズの凹面側の転写を行なうガラスレンズ成形用型において、その成形面の形状として、光学機能面を成形する凸状曲面部と平面部との境界部に境界曲面部を設けた形状としたものである。
【００２３】
これによって、まず、レンズの凹面部と平面部との双方の成形を行う成形面を有する成形型を、現在の加工技術を用いて製造することが可能になった。
【００２４】
また、上記形状にした成形型を用いて少なくとも一方の光学機能面が凹面をなしたガラスレンズを精密成形した場合には、特に平面部と境界曲面部の作用によって成形の際にガラス素材にかかる押圧力が比較的均等になり、その結果、この成形型に対向して設けられる成形型の成形面にガラス素材が均等に押圧されることになって、十分な面精度を有するガラスレンズが安定して得られるようになった。しかも、凸状曲面部と平面部との境界部に境界曲面部を設けたので上記成形型の表面にはレンズの凹面部と平面部との双方の成形を行う成形面が切れ目なくしかも滑らかに連続して形成されているので、応力集中の起こるような部分がなく、また、成形面にガラス材料が入り込むような隙間等がないと共に、成形後に欠けやすい角部を生じさせる形状もない。したがって、成形体にわれや欠け等を生ずることなく歩留まりよく安定してしかも迅速・ローコストにガラスレンズを得ることが可能になった。
【００２５】
その場合、構成２のように、凸状曲面部と境界曲面部との境界点における境界曲面部側の曲面の接平面が前記凸状曲面部の中心軸に対してなす角度をθ1 、境界点における凸状曲面部側の曲面の接平面が前記中心軸に対してなす角度をθ2 としたとき、０°≦θ2 −θ1 ≦２５°が成立するようにすることが望ましい。これは、０°＞θ2 −θ1 であると、加工方法によっては、凸状曲面部と平面部とをつなぐ境界曲面部を凸状曲面部から連続して滑らかに変化する曲面によって平面部に移行する曲面に加工することが事実上困難にな場合が生じ、また、θ2 −θ1 が２５°を超えると、凸状曲面部と境界曲面部１２との境界がはっきりした変曲点となり、凸状曲面部から連続して滑らかに変化する曲面によって平面部に移行する曲面にならなくなり、応力集中等が生じて好ましくないためである。
【００２６】
上述の構成３によれば、成形用型の素材を荒加工して前記凸状曲面部、平面部及び境界曲面部を形成する荒加工工程と、これら各面を仕上げ研削加工する仕上研削工程とを有し、前記仕上研削工程は、前記荒加工後の成形用型の素材を前記凸状曲面部の中心軸を回転軸として回転させながら、高速回転する仕上研削用砥石を前記成形用型の素材の仕上面に接触させつつ凸状曲面部の中心軸から外側に向けてまたは外側から中心軸に向けて所定の軌跡を描くように移動することによって行うようにしたことにより、構成１又は２の成形型を高精度の成形面を確保しつつ製造することが可能になった。即ち、回転する成形用型の素材の表面を、仕上研削用砥石が高速で回転しながら所定の軌跡を移動することで、成形用型の素材の回転と、仕上研削用砥石の高速回転とが相俟って、成形用型の成形面を高精度に仕上げることができる。
【００２７】
上述の構成３によれば、構成２に記載のガラスレンズ成形用型の製造方法において、前記仕上研削工程では、前記凸状曲面部の研削に用いる砥石と、前記平面部及び境界曲面部の研削に用いる砥石とを異ならしめるようにして、効率的かつローコストで製造可能になった。これは、レンズの光学機能面を成形する面であるために加工の際に高い面精度を要求される凸状曲面部を研削するには高精度で高価な砥石を用いて砥石の摩耗を最小限におさえることにより高精度面を得るが、平面部及び境界曲面部は光学機能面でないので、それほどの精度は必要でなく、その加工には凸状曲面部の加工に用いる砥石よりは荒くかつ多少摩耗した砥石を用いて比較的早い速度での加工をすることができ、全体として効率的で安価な加工が可能となる。高精度を要求される凸状曲面部を研磨する砥石は必要最小限の領域しか加工しないため、全体を加工する場合に比較して高価な砥石の摩耗が少ないので高精度の凸状曲面部が得られ、かつ、砥石の寿命を延ばすことができる。
【００２８】
上述の構成４によれば、上型又は下型の少なくとも一方に構成１に記載のガラスレンズ成形用型を用いると共に、前記上型及び下型の間に充填するガラス素材の量を、胴型、上型及び下型によって形成される容積より少なくするようにしたことにより、充填するガラス素材の量に多少のバラツキがあっても、成形の際にガラス素材が胴型と上型または下型との境目に生じる角部あるいは摺動部の隙間に入り込んで成形体の外端部に鋭い角部を形成して欠け等の原因を生じさせたりするおそれを除去しつつ、高精度のガラスレンズを成形することが可能になった。
【００２９】
【実施例】
（実施例１）
図１は本発明の実施例１にかかるガラスレンズ成形装置を示す模式的断面図である。以下、図１から図３を参照にしながら、まず実施例１にかかるガラスレンズ成形装置の構成を説明し、次に、この装置を構成するガラスレンズ成形用型の製造方法を説明する。
【００３０】
［ガラスレンズ成形用型の構成］
図１に示されるように、本実施例のガラスレンズ成形装置は上型１と下型２と胴型３とから構成されている。胴型３は上型１及び下型２を内部に摺動可能に挿入する円柱状成形室３Ａを有している。この円柱状成形室３Ａと上型１と下型２とで、凹メニスカスレンズを成形する成形空間を構成している。
【００３１】
上型１は、図２及び図３に示すように、その下側面（図３においては上側面）が成形面１Ａとなっている。この成形面１Ａは、ガラスレンズの凹面を成形するための凸状曲面部１１と、この凸状曲面部１１の周囲に凸状曲面部１１から外側に連続して形成されて凸状曲面部１１の中心軸Ｏとほぼ直交する平面上に含まれる平面部１３と、前記凸状曲面部１１と平面部１３との境界部に形成された曲面部分であって凸状曲面部１１から連続して滑らかに変化する曲面によって平面部１３に移行するように形成された境界曲面部１２とを有して構成されている。なお、中心軸Ｏは、上型１及び下型２等によってレンズ材料をレンズの形状に成形している際において、被成形体たるレンズの光学中心軸と一致する軸である。
【００３２】
これら凸状曲面部１１、境界曲面部１２及び平面部１３は、プレス後に被成形体であるガラス素材の表面を精密プレス成形することができるように、高精度の表面仕上げを施している。即ち、プレス後のレンズ表面が、研磨等の面仕上げ処理を施すことなくそのままレンズの光学機能面等にすることができるように、上型１の成形面１Ａが高精度の表面仕上げを施されている。
【００３３】
凸状曲面部１１は曲率半径Ｒ₁の球面の一部として構成されている。この曲率半径Ｒ₁の大きさは製造するガラスレンズに要求される曲率半径に応じて設定される。
【００３４】
境界曲面部１２は、凸状曲面部１１の周囲に環状に形成され、その断面形状が曲率半径Ｒ₂の円の一部として構成されている。曲率半径Ｒ₂は、凸状曲面部１１の有効直径（レンズとして有効に使用される曲面の直径）にかからないように設定されている。
【００３５】
上型１の寸法を具体的数値を上げて説明すると、例えば上型１の外径は２８．０ｍｍ、凸状曲面部１１の曲率半径Ｒ₁は１２．９ｍｍ、その有効直径は１７．０ｍｍにとなっている。さらに、凸状曲面部１１と境界曲面部１２との境界部の直径は１７．７ｍｍ、境界曲面部１２と平面部１３との境界部の直径は２３．５ｍｍとなっている。また、境界曲面部１２の曲率半径Ｒ₂は６ｍｍとなっている。この上型１は超硬合金（タングステンカーバイド等）で構成されている。
【００３６】
下型２は、図１に示すように、その上側面が成形面２Ａとなっている。この成形面２Ａは前記上型１の成形面１Ａに対向して配設され、凹面状に形成されている。そして上型１の成形面１Ａと下型２の成形面２Ａとで、凹メニスカスレンズを製造するようになっている。成形面２Ａの寸法は、製造したいレンズの曲面に合せて適宜設定される。この下型２の成形面２Ａも、上型１の成形面１Ａと同様に、高精度の表面仕上げが施されている。
【００３７】
そして、上型１と下型２が胴型３の円柱状成形室３Ａ内に挿入された状態で、図示しない周知の加圧機構によって上型１が下方へ、下型２が上方へそれぞれ押圧されるようになっている。さらに、胴型３の周囲には図示しない周知の加熱機構が設けられ、上型１、下型２及び胴型３でできる成形空間に挿入されたガラス素材を加熱するようになっている。
【００３８】
［ガラスレンズ成形用型の製造方法］
以上のように構成されたガラスレンズ成形装置の上型１は、次のようにして製造する。
【００３９】
まず、荒加工工程として、ＣＮＣ超精密加工機を用いて、上型１となる素材を荒加工して大まかな面形状（球面又は非球面）に全体を形成する。これにより、凸状曲面部１１、境界曲面部１２及び平面部１３となる粗面を形成する。
【００４０】
次に、仕上研削工程として、ＣＮＣ超精密加工機で、凸状曲面部１１、境界曲面部１２及び平面部１３を高精度の仕上面に研削加工する。具体的には、次のようにして行なう。
【００４１】
前記荒加工工程で荒加工した後の素材を、中心軸Ｏを回転軸として低速（１００〜１０００ｒｐｍ程度）の速度で回転させる。この回転する素材の表面に仕上研削用砥石５を高速（１００００〜１０００００ｒｐｍ程度）で回転させながら移動させる。この場合、この高速回転する仕上研削用砥石５を、低速回転する素材の表面に接触させつつ中心軸Ｏから外側に向けて所定の軌跡を描くように正確に移動させる。この所定の軌跡とは、精密仕上げされた凸状曲面部１１、境界曲面部１２及び平面部１３の表面を辿る軌跡である。この軌跡に沿って仕上研削用砥石５を正確に移動させる。即ち、仕上研削用砥石５を、凸状曲面部１１では曲率半径１２．９ｍｍの円弧を描くように、境界曲面部１２では６ｍｍの円弧を描くように移動させる。平面部１３で中心軸Ｏに直交する直線上を移動させる。
【００４２】
仕上研削用砥石５としては円筒状又は円盤状の砥石を用い、中心軸Ｏに直交する回転軸に沿って回転させる。そして、仕上研削用砥石５を、前記回転軸と中心軸Ｏにそれぞれ直交する方向（外側方向）であって、前記所定の軌跡を描くように正確に移動させる。
【００４３】
その後、研磨装置で、少なくとも凸状曲面部１１のうち有効直径１７．０ｍｍ内を研磨する。好ましくは凸状曲面部１１と境界曲面部１２との境界部の直径１７．７ｍｍを僅かに越える領域まで研磨して上型１を得る。
【００４４】
［ガラスレンズ成形方法］
以上のようにして製造した上型１を成形装置にセットして、以下の方法でガラスレンズを成形した。
【００４５】
胴型３の円柱状成形室３Ａ内に下型２が下側から挿入された状態で、円柱状成形室３Ａの上側から成形材料たるガラス素材を配置する。このガラス素材は平凸形状をしており、その平面側を上にして円柱状成形室３Ａ内に配置する。このガラス素材の量は、上型１、下型２及び胴型３によって囲まれる容積を全部満たす量より少なくする。これは、成形時に上型１と胴型３との境界部に形成される角部にまではガラス素材が満たされないようにして成形後のガラスレンズに欠けやすい鋭い角部が生じないようにし、同時に、ガラス素材の過充填を防止して過充填によって生ずる寸法誤差を防止するためである。
【００４６】
次いで、加熱機構（図示せず）でこのガラス素材を加熱して軟化させる。そして、ガラス素材が所定の成形温度（ガラス粘度１０⁷〜１０¹²ポアズに対応する温度）まで上昇したら、加圧機構で上型１及び下型２の一方又は両方を加圧する。
【００４７】
上型１の成形面１Ａで加圧される部分では、凸状曲面部１１、境界曲面部１２及び平面部１３によって成形の際にこの成形面１Ａの転写が良好に行われると共に、この成形面１Ａによる転写の際にガラス素材にかかる押圧力が比較的均等になる。特に、境界曲面部１２の部分で応力の集中がなくほぼ均等な押圧力になる。その結果、この上型１に対向して設けられる下型２の成形面２Ａにガラス素材が均等に押圧されることになって、欠陥のない高精度の光学機能面が得られる。
【００４８】
次いで、加圧機構で加圧した状態で、または上型１の自重によりある程度の圧力をかけた状態で、ガラスの転移点以下までガラス素材を徐々に冷却する等の所定の処理を行って成形されたガラスレンズを得る。
【００４９】
（実施例２）
図４は実施例２にかかるガラスレンズ成形用型の製造方法の説明図である。以下、図４を参照にしながら実施例２にかかるガラスレンズ成形用型の製造方法を説明する。なお、この実施例は上型１の成形面１Ａを仕上げる仕上研削工程が異なる外は前記実施例１とほぼ同様である。また、本実施例の成形用型材料としては炭化ケイ素を用いた。
【００５０】
本実施例では、仕上研削用砥石として、２つの砥石５１，５２を用いる。第１砥石５１は、境界曲面部１２と平面部１３とを仕上げる砥石で、外周から中心軸Ｏへ向けて移動させる。第２砥石５２は凸状曲面部１１を仕上げる砥石で、中心軸Ｏから外周へ向けて移動させる。第１砥石５１は境界曲面部１２と平面部１３を仕上げる砥石であるため、高精度の仕上げが必要な第２砥石５２に比べて多少粗いもの又は場合によっては第２砥石として用いて多少摩耗したもの等を用いることができる。
【００５１】
荒加工を行なった後、ＣＮＣ超精密加工機で成形型用の素材を回転させながら、第１砥石５１を外周から中心軸Ｏへ向けて移動させる。最初は直線的に移動させて平面加工を行ない、平面部１３を仕上げる。具体的には、第１砥石５１を素材の最外周である直径２８ｍｍの位置から直径１８．６ｍｍの位置まで移動させる。次いで、この直径１８．６ｍｍの位置で、その直上１．０ｍｍの位置に中心をもつ曲率半径１．０ｍｍの円弧を描くように、第１砥石５１を移動させて、平面部１３及び境界曲面部１２を仕上げる。
【００５２】
次いで、第２砥石５２を、凸状曲面部１１の表面において、中心軸Ｏから外周に向けて曲率半径１２．９ｍｍの円弧を描くように移動させて、凸状曲面部１１を仕上げる。この第２砥石５２は凸状曲面部１１を仕上げる際に、直径１７．７ｍｍの点まで移動させる。この点で凸状曲面部１１の面と境界曲面部１２の面とが接続する。この加工の際、直径１７．７ｍｍの点における境界曲面部側の曲面の接平面（＝第１砥石５１による接平面）が中心軸Ｏに対してなす角度θ1 に比較して、この点における凸状曲面部側の曲面の接平面（＝第２砥石５２による接平面）が中心軸Ｏに対してなす角度θ2 を僅かに大きくなるように設定する。これは、第１砥石５１による接平面と中心軸Ｏのなす角度θ1 が、第２砥石５２による接平面と中心軸Ｏのなす角度θ2 より大きいと、それぞれの仕上面を直径１７．７ｍｍの点で接続させることができず、この加工は成り立たないためである。但し、Δθ＝θ2 −θ1 が２５°を超えると、凸状曲面部１１と境界曲面部１２との境界がはっきりした変曲点となるため、好ましくない。それゆえ、０°＜Δθ＝θ2 −θ1 ≦２５°とすることが望ましい。
【００５３】
次いで、凸状曲面部１１を仕上げた後、前記実施例１と同様に、研磨装置で凸状曲面部１１を研磨する。
【００５４】
以上のようにして製造した上型１をガラスレンズ成形装置に組み込んで、前記実施例１と同様にしてガラスレンズをプレス成形する。図１３はこのプレス成形の様子を示す図である。この実施例では、図１３に示されるように、上型１及び下型２の間に充填するガラス素材４の量を、胴型３、上型１及び下型２によって形成される容積内を完全に充満する量より少なくするようにした。これにより、成形されるガラス素材の外周部が成形型に接触しないようになっている。このため、充填するガラス素材４の量に多少のバラツキがあっても、成形の際にガラス素材４が胴型３と上型１または下型２との境目に生じる角部あるいは摺動部の隙間に入り込んで成形体の外端部に鋭い角部を形成して欠け等の原因を生じさせたりするおそれを除去しつつ、高精度のガラスレンズを成形することが可能になった。
【００５５】
以上のように、高い精度が要求される凸状曲面部１１を第２砥石５２で加工し、凸状曲面部１１ほどの精度が要求されない境界曲面部１２及び平面部１３を第１砥石５１で加工するようにしたので、全体を１つの砥石で仕上げる場合に比べて、各砥石５１，５２の摩耗を抑制することができ、これらの寿命を大幅に延ばすことができる。特に第２砥石５２の摩耗を抑制できることで、この摩耗の少ない第２砥石５２によって凸状曲面部１１の面を容易にかつ高い精度で仕上げることができる。これにより、第２砥石５２による仕上げ精度の高さを長期間維持することができるようになる。
【００５６】
なお、実施例１においては、仕上研削用砥石５を中心軸Ｏから外側の方向へ移動させたが、外側から中心軸Ｏの方向へ移動させるようにしてもよい。
【００５７】
また、前記各実施例では、凸状曲面部１１、境界曲面部１２及び平面部１３を有する成形型を上型１として用いが、下型２として用いてもよいことはいうまでもない。
【００５８】
さらに、各実施例では、説明を簡単にするために球面の凹メニスカスレンズを成形する場合について説明したが、本発明は、むしろ非球面レンズを製造する場合により効果的である。また、勿論、両凹メニスカスレンズの場合も前記各実施例同様の作用、効果を奏することができる。
【００５９】
【発明の効果】
以上詳述したように、本発明は、要するに、ガラスの精密プレス成形によって少なくとも一方の光学機能面が凹面をなしたガラスレンズを成形する際に用いられる成形用型の形状を、プレスの際にガラスレンズの凹面側の転写を行なうガラスレンズ成形用型において、その成形面の形状として、光学機能面を成形する凸状曲面部と平面部との境界部に凸状曲面部から連続して滑らかに変化する曲面によって前記平面部に移行する境界曲面部を設けた形状としたことにより、まず、レンズの凹面部と平面部との双方の成形を行う成形面を有する成形型を、現在の加工技術を用いて製造することが可能になった。また、上記形状にした成形型を用いて少なくとも一方の光学機能面が凹面をなしたガラスレンズを精密成形した場合には、特に平面部と境界曲面部の作用によって成形の際にガラス素材にかかる押圧力が比較的均等になり、その結果、この成形型に対向して設けられる成形型の成形面にガラス素材が均等に押圧されることになって、十分な面精度を有するガラスレンズが安定して得られるようになった。しかも、上記成形型の表面にはレンズの凹面部と平面部との双方の成形を行う成形面が切れ目なくしかも滑らかに連続して形成されているので、成形面にガラス材料が入り込むような隙間等がないと共に、成形後に欠けやすい角部を生じさせる形状もない。したがって、成形体にわれや欠け、応力集中等を生ずることなく歩留まりよく安定してしかも迅速・ローコストにガラスレンズを得ることが可能になった。
【図面の簡単な説明】
【図１】本発明の実施例１にかかるガラスレンズ成形用型を上型として用いたガラスレンズ成形装置の構成を示す模式的断面図である。
【図２】実施例１のガラスレンズ成形装置の上型の構成を示す模式的断面図である。
【図３】実施例１のガラスレンズ成形用型の製造方法にかかる仕上研削用砥石の移動を示す模式図である。
【図４】実施例２のガラスレンズ成形用型の製造方法にかかる仕上研削用砥石の移動を示す模式図である。
【図５】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である。
【図６】従来の凹メニスカスレンズを成形する方法の説明図である。
【図７】従来の凹メニスカスレンズを成形する方法の説明図である。
【図８】従来の凹メニスカスレンズを成形する方法の説明図である。
【図９】従来の凹メニスカスレンズを成形する方法の説明図である。
【図１０】従来の凹メニスカスレンズを成形する方法の説明図である。
【図１１】従来の成形型の加工方法の説明図である。
【図１２】図７の部分拡大図である。
【図１３】実施例２にかかるガラスレンズ製造方法の説明図である。
【符号の説明】
１…上型、１Ａ，２Ａ…成形面、２…下型、３…胴型、３Ａ…円柱状成形室、５…仕上研削用砥石、１１…凸状曲面部、１２…境界曲面部、１３…平面部、５１…第１砥石、５２…第２砥石。[0001]
[Industrial application fields]
The present invention relates to a molding die used for precision press molding of glass, a manufacturing method thereof, and a glass lens molding method.
[0002]
[Prior art]
In recent years, an aspherical glass lens in which at least one surface is aspherical by precision press molding, which can obtain surface accuracy as a lens without performing surface finishing processing such as polishing the pressed surface of the molded body after pressing. Various techniques for manufacturing have been studied.
[0003]
By the way, the manufacture of aspherical lenses by this technique has been centered on biconvex lenses, but recently there has been an increasing demand to manufacture aspherical concave meniscus lenses and biconcave lenses by this technique. In this type of concave meniscus lens and biconcave lens, as shown in FIG. 5, an optical axis is provided outside the concave surface 41, which is an optical functional surface (optical effective diameter region), for incorporation into various lens systems. It is necessary to provide a plane portion 43 orthogonal to the.
[0004]
However, the technology for manufacturing such concave meniscus lenses and biconcave lenses by precision press molding has not yet been fully studied, and there are very few examples of molds for use in this molding.
[0005]
Conventionally known methods for molding the concave meniscus lens using precision press molding are the methods shown in FIGS. 6, 7, 8, 9 and 10.
[0006]
Each of the methods shown in FIGS. 6 to 10 is formed by inserting a molding material into a molding space between the upper mold 10 and the lower mold 20 slidably inserted into the molding chamber 30A of the barrel mold 30. To do. Among these, the method shown in FIGS. 6 to 7 is to form the flat portion 43 by grinding the outer peripheral portion on one side of the lens after molding. The method shown in FIGS. Sometimes the flat portion 43 is formed at the same time.
[0007]
6 to 7, as a result, the curved surface of the outer region of the upper mold 10 substantially extends the convex curved surface portion 101 because of the processing technique of the upper mold 10 for forming the concave surface of the lens. In order to prevent wear of the grindstone as much as possible and make it easy to ensure the required accuracy of the convex curved surface part during processing, the shape with the processing part outside the lens effective diameter eliminated as much as possible ( FIG. 7). In these methods, since the flat part is not formed in the molded body itself obtained by molding, it is necessary to form the flat part again by grinding or the like after molding.
[0008]
Further, in the method shown in FIG. 8, a cylindrical second upper mold 103 is fitted to the outer side of the upper mold 10 having the convex curved surface portion 101 that molds the effective diameter area of the concave surface of the lens. The flat portion 43 (see FIG. 5) is formed by 103.
[0009]
Further, in the method shown in FIGS. 9 to 10, a small-diameter portion 301 is formed on the upper portion of the body mold 30, the upper die 10 is fitted to the small-diameter portion 301, and the large-diameter portion is formed below the small-diameter portion 301. A portion 302 is formed so that the lower mold 20 is fitted into the large diameter portion 302, and the flat surface portion 43 of the lens is formed by the boundary step surface 303 between the small diameter portion 301 and the large diameter portion 302. . In this case, in the method shown in FIG. 9, the boundary step surface 303 is made to coincide with the outer end partition line of the convex curved surface portion 101 of the upper mold 10, whereas the method shown in FIG. Then, the outer end partition line of the convex curved surface portion 101 of the upper mold 10 is protruded downward from the boundary step surface 303.
[0010]
As described above, in each of the conventional methods, a molding part for molding the flat surface portion 43 is formed on a molding die having a convex curved surface for molding the concave effective diameter region 41 of the concave meniscus lens. Absent. The reason for this is as follows.
[0011]
That is, first, as a material for a mold for precision press molding of a glass lens, it is necessary that the material has a high heat-resistant temperature. Therefore, there are hard and brittle materials such as ceramics, cemented carbide, and cermet that are not easily processed. Used. Therefore, it is difficult to accurately process a relatively complicated shape having a flat surface continuously with the convex curved surface.
[0012]
When the convex curved surface portion is a spherical surface, a so-called spherical polishing machine is generally used as a polishing process for obtaining fine surface roughness and high surface accuracy. As shown in FIG. 11, this method is performed by swinging the polishing dish 60 brought into contact with the convex curved surface portion while rotating the upper mold 10 after grinding by a rotating device 50. It grind | polishes with the abrasive grain provided in. When polishing by this method, the shape of the upper mold 10 to be polished cannot be provided on the outside of the convex curved surface portion so as to hinder the oscillation of the polishing dish. It cannot be provided.
[0013]
When the convex curved surface portion is aspherical, a CNC aspherical surface processing machine is used. However, since the mold is a hard and brittle material, a grinding method using a grindstone is employed. In grinding with a grindstone, if the machining area is large, the grindstone wears to that extent, making it difficult to obtain the desired shape accuracy. It is necessary to ensure shape accuracy. As a result, the shape shown in FIGS. 6 to 10 which does not need to be processed except for the effective area of the lens is adopted.
[0014]
[Problems to be solved by the invention]
By the way, according to the study by the inventors of the present application, it has been found that the lens molded by the method shown in FIGS. This is because the pressing force on the molding material by the convex curved molding surface of the upper mold 10 escapes to the outside at the outer periphery of the lens during molding, and corresponds to the vicinity of the outer periphery of the molding surface of the lower mold 20 at the molding. The upper mold 10 does not have a molding surface, so it is assumed that the molding pressure from the upper mold 10 is hardly applied to the outer peripheral portion of the lower surface of the lens.
[0015]
The tendency described above becomes more prominent as the radius of curvature of the concave lens surface is smaller. In addition, since the flat portion is formed by post-processing by grinding and removing the outer peripheral edge on the lens concave surface side after molding, the outer peripheral edge must be sufficiently thick at the stage of the molded body. For this reason, it is inevitable that the difference between the center thickness and the edge thickness of the molded body is inevitably large, and it is presumed that the surface accuracy is difficult to obtain.
[0016]
In addition, since grinding removal processing is necessary after molding, the number of steps is large, which is disadvantageous in terms of manufacturing cost.
[0017]
Furthermore, in the method shown in FIG. 7, as shown in FIG. 12, the glass material often enters the side surface of the upper mold 10 during molding. Then, since the shrinkage coefficient of the glass is larger than the shrinkage coefficient of the mold during the cooling and solidification, the portion A is caught, and thus the surface accuracy is deteriorated or the glass is often cracked due to stress concentration. There was also.
[0018]
Moreover, since the plane part is also formed by shaping | molding by the method shown by FIGS. 8-10, a fault like the method of FIGS. 6-7 is partly eliminated. However, since the concave curved surface portion 41 and the flat surface portion 43 of the lens are formed by separate molding tools, the contact portion of the molding die of another member or the molding die and the barrel die is formed during molding. In many cases, a glass material enters a gap or the like of the fitting portion. If glass material enters the gaps between these fitting parts, it will cause the surface accuracy of the molding surface to deteriorate, the part will be chipped after molding, or glass dust will be generated, or it will be caught when taken out after molding May occur, and the molded body may be damaged, and furthermore, corners of the upper mold 10 and the trunk mold 30 may be damaged.
[0019]
The present invention has been made under the above-mentioned background, and a molding die capable of stably molding a glass lens in which at least one optical functional surface is a concave surface with high precision by a glass precision press. And a method for manufacturing the same and a glass lens forming method.
[0020]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a glass lens molding die according to the present invention is:
(Configuration 1) A glass lens in which at least one optical functional surface is concave by precision press molding of glass that can be made into an optical functional surface of a lens without subjecting the press surface of the molded body to a surface finishing process such as polishing after pressing. In a mold for molding used for molding, a mold for molding a glass lens that performs transfer on the concave side of the glass lens during the pressing,
A convex curved surface portion for molding the concave surface of the glass lens, and a central axis of the convex curved surface portion formed continuously from the convex curved surface portion around the convex curved surface portion. A plane portion included in a plane substantially orthogonal to the curved surface portion, and a curved surface portion formed at a boundary portion between the convex curved surface portion and the planar portion, and the curved surface continuously and smoothly changing from the convex curved surface portion. A boundary curved surface portion formed so as to transition to a portion,
As an aspect of this configuration 1,
(Configuration 2) In the glass lens molding die of Configuration 1,
The angle formed by the tangent plane of the curved surface on the boundary curved surface side at the boundary point between the convex curved surface portion and the boundary curved surface portion with respect to the central axis of the convex curved surface portion is θ1, When the angle formed by the tangent plane of the curved surface with respect to the central axis is θ2,
0 ° ≦ θ2 −θ1 ≦ 25 °
Is a feature characterized by the fact that
In addition, the method for producing a glass lens mold according to the present invention includes:
(Configuration 3) In the method for manufacturing a glass lens molding die for manufacturing the glass lens molding die of Configuration 1 or 2,
A roughing process for roughing a forming mold material to form the convex curved surface part, a flat surface part and a boundary curved surface part, and a finish grinding process for finish grinding each of these surfaces;
In the finish grinding step, a finish grinding wheel that rotates at a high speed while rotating the raw material of the molding die after the rough machining around the central axis of the convex curved surface portion is used as the finish surface of the raw material of the molding die. It is performed by moving so as to draw a predetermined trajectory from the central axis of the convex curved surface part toward the outside or from the outside toward the central axis while being in contact with
As an aspect of this configuration 3,
(Configuration 4) In the method for manufacturing the glass lens molding die of Configuration 3,
In the finish grinding step, the grindstone used for grinding the convex curved surface portion is different from the grindstone used for grinding the flat surface portion and the boundary curved surface portion.
[0021]
Furthermore, the glass lens molding method according to the present invention includes:
(Configuration 5) In a glass lens molding method of molding a glass lens by pressing a glass material filled between an upper mold and a lower mold slidably provided in a body mold with the upper mold and the lower mold,
The glass lens molding die of Configuration 1 or 2 is used for at least one of the upper die and the lower die, and the amount of the glass material to be filled between the upper die and the lower die is determined by the barrel die, the upper die, and the lower die. The configuration is characterized in that the volume is smaller than the formed volume.
[0022]
[Action]
According to the above-described configuration 1, in short, it is a molding die used when molding a glass lens in which at least one optical functional surface has a concave surface by precision press molding of glass. In the glass lens molding die for transferring the concave surface, the shape of the molding surface is such that a boundary curved surface portion is provided at the boundary between the convex curved surface portion and the flat surface portion for molding the optical functional surface. .
[0023]
Thereby, first, it became possible to manufacture a mold having a molding surface for molding both the concave surface portion and the flat surface portion of the lens by using the current processing technique.
[0024]
In addition, when a glass lens having at least one optical function surface made concave is precisely molded using the molding die having the above shape, it is applied to the glass material at the time of molding, particularly by the action of the flat surface portion and the boundary curved surface portion. The pressing force becomes relatively uniform, and as a result, the glass material is uniformly pressed against the molding surface of the molding die provided opposite to this molding die, so that the glass lens having sufficient surface accuracy is stable. To get it. In addition, since the boundary curved surface portion is provided at the boundary portion between the convex curved surface portion and the flat surface portion, the molding surface for molding both the concave surface portion and the flat surface portion of the lens is smooth and smooth on the surface of the mold. Since it is formed continuously, there is no portion where stress concentration occurs, and there is no gap or the like that allows the glass material to enter the molding surface, and there is no shape that generates corners that are easily chipped after molding. Therefore, it has become possible to obtain a glass lens stably and quickly with low yield without causing cracks or chipping in the molded body, and at a low cost.
[0025]
In this case, as in Configuration 2, the angle formed by the tangent plane of the curved surface on the boundary curved surface side at the boundary point between the convex curved surface portion and the boundary curved surface portion with respect to the central axis of the convex curved surface portion is θ1, It is preferable that 0 ° ≦ θ2−θ1 ≦ 25 ° is established, where θ2 is an angle formed by the tangent plane of the curved surface on the convex curved surface side with respect to the central axis. If 0 °> θ2 −θ1, depending on the processing method, the boundary curved surface portion connecting the convex curved surface portion and the flat surface portion is shifted to the flat surface portion by a curved surface that continuously changes smoothly from the convex curved surface portion. If θ2−θ1 exceeds 25 °, the boundary between the convex curved surface portion and the boundary curved surface portion 12 becomes a clear inflection point. This is because the curved surface continuously and smoothly changing from the curved surface portion does not become a curved surface that shifts to the flat surface portion, and stress concentration occurs, which is not preferable.
[0026]
According to the above-described configuration 3, a roughing process for roughing a forming mold material to form the convex curved surface part, a flat surface part, and a boundary curved surface part, and a finish grinding process for finish grinding each of these surfaces; And the finish grinding step comprises rotating a grinding wheel for grinding at a high speed while rotating the raw material of the molding die after the roughing process with the central axis of the convex curved portion as a rotation axis. Configuration 1 or 2 by performing the movement so as to draw a predetermined locus from the center axis of the convex curved surface portion toward the outside or from the outside toward the center axis while being in contact with the finished surface of the material. It is now possible to manufacture a mold of this type while ensuring a highly accurate molding surface. That is, by rotating a predetermined trajectory while the grinding wheel for finishing grinding rotates at a high speed on the surface of the material for the rotating molding die, rotation of the molding die material and high-speed rotation of the grinding wheel for finishing grinding are performed. Together, the molding surface of the mold can be finished with high accuracy.
[0027]
According to the above-described configuration 3, in the glass lens molding die manufacturing method according to the configuration 2, in the finish grinding step, the grindstone used for grinding the convex curved surface portion, and the grinding of the planar portion and the boundary curved surface portion This makes it possible to manufacture efficiently and at a low cost by making the grindstone used in the above different. This is the surface that molds the optical functional surface of the lens, so it is necessary to use a high-precision and expensive grindstone to minimize the wear of the grindstone to grind convex curved surfaces that require high surface accuracy during processing. High accuracy surface can be obtained by limiting, but the plane part and the boundary curved surface part are not optical functional surfaces, so much precision is not necessary, and the processing is rougher than the grindstone used for processing the convex curved surface part and Processing can be performed at a relatively high speed using a somewhat worn grindstone, and efficient and inexpensive processing as a whole becomes possible. A grinding wheel that polishes a convex curved surface that requires high precision processes only the minimum necessary area, so there is less wear on the expensive grinding wheel than when machining the whole, so a high precision convex curved surface is required. And the life of the grindstone can be extended.
[0028]
According to the above-described configuration 4, the glass lens molding die described in the configuration 1 is used for at least one of the upper die and the lower die, and the amount of the glass material filled between the upper die and the lower die is determined as the barrel die. Since the volume formed by the upper mold and the lower mold is smaller, the glass material is molded into the body mold and the upper mold or the lower mold even when there is some variation in the amount of the glass material to be filled. A high-precision glass lens that eliminates the possibility of causing sharp corners at the outer edge of the molded body by entering the gaps between the corners or sliding parts that occur at the boundary between them and causing the cause of chipping, etc. It became possible to mold.
[0029]
【Example】
Example 1
FIG. 1 is a schematic cross-sectional view showing a glass lens molding apparatus according to Example 1 of the present invention. Hereinafter, with reference to FIGS. 1 to 3, the configuration of the glass lens molding apparatus according to Example 1 will be described first, and then the method for manufacturing the glass lens molding mold constituting the apparatus will be described.
[0030]
[Configuration of Glass Lens Mold]
As shown in FIG. 1, the glass lens molding apparatus of the present embodiment includes an upper mold 1, a lower mold 2, and a body mold 3. The body mold 3 has a cylindrical molding chamber 3A into which the upper mold 1 and the lower mold 2 are slidably inserted. The cylindrical molding chamber 3A, the upper mold 1 and the lower mold 2 constitute a molding space for molding a concave meniscus lens.
[0031]
As shown in FIGS. 2 and 3, the upper die 1 has a molding surface 1 </ b> A on its lower side surface (upper side surface in FIG. 3). 1 A of this shaping | molding surface is formed in the convex curved surface part 11 for shape | molding the concave surface of a glass lens, and the convex curved surface part 11 is continuously formed in the circumference | surroundings of this convex curved surface part 11 from the convex curved surface part 11 outside. And a curved surface portion formed at a boundary portion between the convex curved surface portion 11 and the flat surface portion 13 continuously from the convex curved surface portion 11. It has a boundary curved surface portion 12 formed so as to move to the flat surface portion 13 by a smoothly changing curved surface. The central axis O is an axis that coincides with the optical central axis of the lens that is a molded object when the lens material is molded into the shape of the lens by the upper mold 1 and the lower mold 2 or the like.
[0032]
The convex curved surface portion 11, the boundary curved surface portion 12, and the flat surface portion 13 are subjected to high-precision surface finishing so that the surface of the glass material that is a molded body can be precision press-molded after pressing. In other words, the molding surface 1A of the upper mold 1 is subjected to high-precision surface finishing so that the lens surface after pressing can be used as it is without being subjected to surface finishing treatment such as polishing. ing.
[0033]
The convex curved surface portion 11 has a curvature radius R ₁ It is comprised as a part of spherical surface. This radius of curvature R ₁ Is set according to the radius of curvature required for the glass lens to be manufactured.
[0034]
The boundary curved surface portion 12 is formed in an annular shape around the convex curved surface portion 11, and its cross-sectional shape has a radius of curvature R. ₂ As part of the circle. Radius of curvature R ₂ Is set so as not to affect the effective diameter of the convex curved surface portion 11 (the diameter of a curved surface that is effectively used as a lens).
[0035]
Explaining the dimensions of the upper mold 1 with specific numerical values, for example, the outer diameter of the upper mold 1 is 28.0 mm, and the curvature radius R of the convex curved surface portion 11 is, for example. ₁ Is 12.9 mm, and its effective diameter is 17.0 mm. Further, the diameter of the boundary portion between the convex curved surface portion 11 and the boundary curved surface portion 12 is 17.7 mm, and the diameter of the boundary portion between the boundary curved surface portion 12 and the flat surface portion 13 is 23.5 mm. In addition, the radius of curvature R of the boundary curved surface portion 12 ₂ Is 6 mm. The upper mold 1 is made of a cemented carbide (tungsten carbide or the like).
[0036]
As shown in FIG. 1, the upper surface of the lower mold 2 is a molding surface 2A. The molding surface 2A is disposed to face the molding surface 1A of the upper mold 1 and is formed in a concave shape. A concave meniscus lens is manufactured by the molding surface 1A of the upper mold 1 and the molding surface 2A of the lower mold 2. The dimension of the molding surface 2A is appropriately set according to the curved surface of the lens to be manufactured. Similarly to the molding surface 1A of the upper mold 1, the molding surface 2A of the lower mold 2 is also given a high-precision surface finish.
[0037]
Then, with the upper mold 1 and the lower mold 2 inserted into the cylindrical molding chamber 3A of the body mold 3, the upper mold 1 is pressed downward and the lower mold 2 is pressed upward by a well-known pressurizing mechanism (not shown). It has come to be. Further, a well-known heating mechanism (not shown) is provided around the body mold 3 so as to heat the glass material inserted into the molding space formed by the upper mold 1, the lower mold 2 and the body mold 3.
[0038]
[Method of manufacturing glass lens mold]
The upper mold 1 of the glass lens molding apparatus configured as described above is manufactured as follows.
[0039]
First, as a roughing process, a CNC ultra-precision machine is used to rough-process the material to be the upper mold 1 to form a rough surface shape (spherical or aspherical) as a whole. As a result, rough surfaces to be the convex curved surface portion 11, the boundary curved surface portion 12, and the flat surface portion 13 are formed.
[0040]
Next, as a finishing grinding step, the convex curved surface portion 11, the boundary curved surface portion 12 and the flat surface portion 13 are ground to a highly accurate finished surface with a CNC ultra-precision processing machine. Specifically, this is performed as follows.
[0041]
The material after roughing in the roughing step is rotated at a low speed (about 100 to 1000 rpm) with the central axis O as a rotation axis. The grinding wheel 5 for finish grinding is moved to the surface of the rotating material while rotating at a high speed (about 10,000 to 100,000 rpm). In this case, the finishing grinding wheel 5 rotating at high speed is accurately moved so as to draw a predetermined locus from the central axis O toward the outside while contacting the surface of the material rotating at low speed. The predetermined trajectory is a trajectory that follows the surfaces of the convex curved surface portion 11, the boundary curved surface portion 12, and the flat surface portion 13 that are precisely finished. The grinding wheel 5 for finish grinding is accurately moved along this locus. That is, the finish grinding wheel 5 is moved so as to draw an arc having a curvature radius of 12.9 mm on the convex curved surface portion 11 and a 6 mm arc on the boundary curved surface portion 12. The flat part 13 is moved on a straight line orthogonal to the central axis O.
[0042]
A cylindrical or disc-shaped grindstone is used as the finish grinding grindstone 5 and is rotated along a rotation axis orthogonal to the central axis O. Then, the finish grinding wheel 5 is accurately moved so as to draw the predetermined trajectory in a direction (outward direction) orthogonal to the rotation axis and the central axis O, respectively.
[0043]
Thereafter, at least the inside of the effective diameter 17.0 mm of the convex curved surface portion 11 is polished by a polishing apparatus. Preferably, the upper die 1 is obtained by polishing to a region slightly exceeding the diameter of 17.7 mm at the boundary between the convex curved surface portion 11 and the boundary curved surface portion 12.
[0044]
[Glass lens molding method]
The upper mold 1 manufactured as described above was set in a molding apparatus, and a glass lens was molded by the following method.
[0045]
In the state where the lower mold 2 is inserted from the lower side into the cylindrical molding chamber 3A of the body mold 3, a glass material as a molding material is arranged from the upper side of the cylindrical molding chamber 3A. This glass material has a plano-convex shape, and is disposed in the cylindrical molding chamber 3A with its plane side up. The amount of the glass material is set smaller than the amount that fills the entire volume surrounded by the upper mold 1, the lower mold 2, and the trunk mold 3. This prevents the glass material from being filled up to the corner formed at the boundary between the upper mold 1 and the body mold 3 at the time of molding so that a sharp corner that is easily chipped in the molded glass lens does not occur. At the same time, the glass material is prevented from being overfilled to prevent dimensional errors caused by overfilling.
[0046]
Next, the glass material is heated and softened by a heating mechanism (not shown). The glass material has a predetermined molding temperature (glass viscosity of 10 ⁷ -10 ¹² When the temperature rises to a temperature corresponding to the pores, one or both of the upper mold 1 and the lower mold 2 are pressurized by a pressurizing mechanism.
[0047]
In the portion to be pressed by the molding surface 1A of the upper mold 1, the molding surface 1A is satisfactorily transferred during molding by the convex curved surface portion 11, the boundary curved surface portion 12 and the flat surface portion 13, and this molding surface. The pressure applied to the glass material during the transfer by 1A becomes relatively uniform. In particular, there is no concentration of stress at the boundary curved surface portion 12, and the pressure is almost uniform. As a result, the glass material is evenly pressed against the molding surface 2A of the lower mold 2 provided to face the upper mold 1, and a highly accurate optical function surface without defects is obtained.
[0048]
Next, in a state where the pressure is applied by the pressure mechanism or in a state where a certain amount of pressure is applied by the weight of the upper mold 1, a predetermined treatment such as gradually cooling the glass material to below the glass transition point is performed. Get a glass lens.
[0049]
(Example 2)
FIG. 4 is an explanatory diagram of a method for producing a glass lens mold according to the second embodiment. Hereinafter, a method for manufacturing a glass lens molding die according to Example 2 will be described with reference to FIG. This embodiment is substantially the same as the first embodiment except that the finishing grinding process for finishing the molding surface 1A of the upper die 1 is different. In addition, silicon carbide was used as the mold material of this example.
[0050]
In this embodiment, two grindstones 51 and 52 are used as the grindstone for finish grinding. The first grindstone 51 is a grindstone that finishes the boundary curved surface portion 12 and the flat surface portion 13 and is moved from the outer periphery toward the central axis O. The second grindstone 52 is a grindstone that finishes the convex curved surface portion 11 and is moved from the central axis O toward the outer periphery. Since the first grindstone 51 is a grindstone that finishes the boundary curved surface portion 12 and the flat surface portion 13, it is somewhat rougher than the second grindstone 52 that requires high-precision finishing, or in some cases, used as the second grindstone and is somewhat worn. A thing etc. can be used.
[0051]
After performing the rough machining, the first grindstone 51 is moved from the outer periphery toward the central axis O while rotating the material for the mold using a CNC ultra-precision machine. Initially, the flat surface processing is performed by moving linearly to finish the flat surface portion 13. Specifically, the 1st grindstone 51 is moved from the position of diameter 28mm which is the outermost periphery of a raw material to the position of diameter 18.6mm. Next, the first grindstone 51 is moved so as to draw an arc having a radius of curvature of 1.0 mm centered at a position of 1.0 mm immediately above the position at a diameter of 18.6 mm, and the flat surface portion 13 and the boundary curved surface portion. Finish 12
[0052]
Next, the second grindstone 52 is moved so as to draw an arc having a radius of curvature of 12.9 mm from the central axis O toward the outer periphery on the surface of the convex curved surface portion 11 to finish the convex curved surface portion 11. The second grindstone 52 is moved to a point having a diameter of 17.7 mm when the convex curved surface portion 11 is finished. At this point, the surface of the convex curved surface portion 11 and the surface of the boundary curved surface portion 12 are connected. In this processing, the convexity at this point is compared with the angle θ1 formed by the tangential plane of the curved surface on the boundary curved surface portion side at the point having a diameter of 17.7 mm (= the tangential plane by the first grindstone 51) with respect to the central axis O. The angle θ2 formed by the tangential plane of the curved surface on the curved surface portion side (= the tangential plane by the second grindstone 52) with respect to the central axis O is set to be slightly larger. This is because if the angle θ1 formed between the tangent plane by the first grindstone 51 and the central axis O is larger than the angle θ2 formed by the tangential plane by the second grindstone 52 and the central axis O, the respective finished surfaces have a point of 17.7 mm in diameter. This is because the process cannot be established. However, if Δθ = θ 2 −θ 1 exceeds 25 °, the boundary between the convex curved surface portion 11 and the boundary curved surface portion 12 becomes a clear inflection point, which is not preferable. Therefore, it is desirable that 0 ° <Δθ = θ2−θ1 ≦ 25 °.
[0053]
Subsequently, after finishing the convex curved surface part 11, the convex curved surface part 11 is grind | polished with a grinding | polishing apparatus similarly to the said Example 1. FIG.
[0054]
The upper mold 1 manufactured as described above is incorporated into a glass lens molding apparatus, and a glass lens is press-molded in the same manner as in Example 1. FIG. 13 is a view showing a state of this press molding. In this embodiment, as shown in FIG. 13, the amount of the glass material 4 filled between the upper mold 1 and the lower mold 2 is set within the volume formed by the barrel mold 3, the upper mold 1 and the lower mold 2. The amount was less than the full charge. Thereby, the outer peripheral part of the glass raw material shape | molded is made not to contact a shaping | molding die. For this reason, even if there is some variation in the amount of the glass material 4 to be filled, the corners or sliding portions of the glass material 4 generated at the boundary between the body mold 3 and the upper mold 1 or the lower mold 2 during molding. It has become possible to mold a high-precision glass lens while eliminating the possibility of entering into the gap and forming sharp corners at the outer end of the molded body to cause a cause such as chipping.
[0055]
As described above, the convex curved surface portion 11 that requires high accuracy is processed by the second grindstone 52, and the boundary curved surface portion 12 and the flat surface portion 13 that do not require as high accuracy as the convex curved surface portion 11 are processed by the first grindstone 51. Since it processed, compared with the case where the whole is finished with one grindstone, abrasion of each grindstone 51 and 52 can be suppressed and these lifetimes can be extended significantly. In particular, since the wear of the second grindstone 52 can be suppressed, the surface of the convex curved surface portion 11 can be easily finished with high accuracy by the second grindstone 52 with less wear. Thereby, the high finishing precision by the 2nd grindstone 52 can be maintained for a long period of time.
[0056]
In the first embodiment, the finishing grinding wheel 5 is moved from the central axis O toward the outer side, but may be moved from the outer side toward the central axis O.
[0057]
In each of the above embodiments, the mold having the convex curved surface portion 11, the boundary curved surface portion 12 and the flat surface portion 13 is used as the upper die 1, but it goes without saying that it may be used as the lower die 2.
[0058]
Further, in each embodiment, the case where a spherical concave meniscus lens is molded has been described for the sake of simplicity. However, the present invention is more effective when an aspherical lens is manufactured. Of course, in the case of a biconcave meniscus lens, the same operations and effects as those in the above embodiments can be obtained.
[0059]
【The invention's effect】
As described above in detail, the present invention is, in short, the shape of the molding die used when molding a glass lens having at least one optical functional surface made concave by precision press molding of glass. In a glass lens molding die for transferring the concave side of a glass lens, the shape of the molding surface is smooth continuously from the convex curved surface portion to the boundary between the convex curved surface portion and the flat surface portion that molds the optical functional surface. By forming a boundary curved surface portion that transitions to the flat surface portion by a curved surface that changes to a first, a molding die having a molding surface for molding both the concave surface portion and the flat surface portion of the lens is first processed. It became possible to manufacture using technology. In addition, when a glass lens having at least one optical function surface made concave is precisely molded using the molding die having the above shape, it is applied to the glass material at the time of molding, particularly by the action of the flat surface portion and the boundary curved surface portion. The pressing force becomes relatively uniform, and as a result, the glass material is uniformly pressed against the molding surface of the molding die provided opposite to this molding die, so that the glass lens having sufficient surface accuracy is stable. To get it. In addition, since the molding surface for molding both the concave surface portion and the flat surface portion of the lens is formed on the surface of the molding die continuously and smoothly, there is a gap that allows the glass material to enter the molding surface. In addition, there is no shape that produces corners that are easily chipped after molding. Accordingly, it has become possible to obtain a glass lens stably and quickly with low yield without causing cracks, chipping, stress concentration, etc. in the molded body.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a configuration of a glass lens molding apparatus using a glass lens molding die according to Example 1 of the present invention as an upper mold.
FIG. 2 is a schematic cross-sectional view showing the configuration of the upper mold of the glass lens molding apparatus of Example 1. FIG.
3 is a schematic diagram showing movement of a grinding wheel for finish grinding according to the method for manufacturing a glass lens molding die of Example 1. FIG.
4 is a schematic diagram showing movement of a grinding wheel for finish grinding according to a method for manufacturing a glass lens molding die of Example 2. FIG.
FIG. 5 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. 6 is an explanatory diagram of a method for forming a conventional concave meniscus lens.
FIG. 7 is an explanatory diagram of a method of forming a conventional concave meniscus lens.
FIG. 8 is an explanatory diagram of a method of forming a conventional concave meniscus lens.
FIG. 9 is an explanatory diagram of a method of forming a conventional concave meniscus lens.
FIG. 10 is an explanatory diagram of a method of forming a conventional concave meniscus lens.
FIG. 11 is an explanatory view of a conventional molding die processing method.
12 is a partially enlarged view of FIG. 7;
13 is an explanatory diagram of a glass lens manufacturing method according to Example 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Upper die, 1A, 2A ... Molding surface, 2 ... Lower die, 3 ... Body die, 3A ... Cylindrical molding chamber, 5 ... Grinding wheel for finish grinding, 11 ... Convex curved surface part, 12 ... Boundary curved surface part, 13 ... a plane part, 51 ... 1st whetstone, 52 ... 2nd whetstone.

Claims

A molding die used when molding a glass lens in which at least one optical function surface is concave by precision press molding,
A convex surface for molding the concave surface of the glass lens, and a flat surface portion formed around the convex curved surface and included in a plane substantially orthogonal to the optical center axis of the convex curved surface If, Yes and the convex curved surface portion and forming boundary curved portion as a curved surface portion formed on the boundary shifts to the plane portion by a curved surface that changes from the convex curved surface portions of the planar portion And
An angle formed by the tangent plane of the curved surface on the boundary curved surface side at the boundary point between the convex curved surface portion and the boundary curved surface portion with respect to the central axis of the convex curved surface portion is θ1. , Of the curved surface on the convex curved surface side at the boundary point
The angle formed by the tangent plane with respect to the central axis is θ2 When
0 ° ≦ θ2 -Θ1 ≦ 25 °
Is formed so that
The molding surface is moved so as to draw a predetermined trajectory while contacting a rotating cylindrical grindstone while contacting the molding die material while rotating the central axis of the molding die material as a rotation axis. In this case, the glass lens mold is characterized in that it is ground by changing the angle formed by the rotation axis of the grindstone with the movement of the grindstone with respect to a plane substantially orthogonal to the optical center axis. .

A molding die used for molding a glass lens having at least one optical function surface formed into a concave surface by precision press molding, wherein the molding surface is a convex curved surface portion for molding the concave surface of the glass lens; A planar portion formed around the convex curved surface portion and included in a plane substantially orthogonal to the optical center axis of the convex curved surface portion; and a curved surface formed at a boundary portion between the convex curved surface portion and the planar portion. A boundary curved surface portion formed so as to transition to the flat surface portion by a curved surface that changes from the convex curved surface portion ,
An angle formed by the tangent plane of the curved surface on the boundary curved surface side at the boundary point between the convex curved surface portion and the boundary curved surface portion with respect to the central axis of the convex curved surface portion is θ1. , Of the curved surface on the convex curved surface side at the boundary point
The angle formed by the tangent plane with respect to the central axis is θ2 When
0 ° ≦ θ2 -Θ1 ≦ 25 °
Is formed so that
The molding surface is moved so as to draw a predetermined trajectory while rotating the central axis of the molding die material as the rotation axis while bringing the cylindrical edge portion of the rotating cylindrical grinding stone into contact with the molding die material. A glass lens molding die characterized by being ground by grinding.

3. The glass lens molding die according to claim 1 , wherein the molding die material is made of a hard and brittle material including ceramics, cemented carbide, or cermet.

A molding die used for molding a glass lens having at least one optical function surface formed into a concave surface by precision press molding, wherein the molding surface is a convex curved surface portion for molding the concave surface of the glass lens; A planar portion formed around the convex curved surface portion and included in a plane substantially orthogonal to the optical center axis of the convex curved surface portion; and a curved surface formed at a boundary portion between the convex curved surface portion and the planar portion. a part and a formation boundary curved portion so as to transition to the flat portion by a curved surface that changes from the convex curved surface portion, the boundary curved portion at the boundary point between the convex curved surface portion and the boundary curved portion The angle formed by the tangent plane of the curved surface on the side with respect to the central axis of the convex curved surface portion is θ1 , The angle formed by the tangent plane of the curved surface on the convex curved surface side at the boundary point with respect to the central axis is θ2 When
0 ° ≦ θ2 -Θ1 ≦ 25 °
There a formed Ru method for manufacturing a glass lens mold to stand,
While rotating the molding surface about the central axis of the molding die material as a rotation axis, the rotating cylindrical grinding wheel is moved so as to draw a predetermined trajectory while contacting the molding die material, and the movement In this case, the glass lens molding die manufacturing method is characterized in that grinding is performed by changing an angle formed by a rotation axis of the grindstone with a movement of the grindstone with respect to a plane substantially orthogonal to the optical center axis.

A molding die used for molding a glass lens having at least one optical function surface formed into a concave surface by precision press molding, wherein the molding surface is a convex curved surface portion for molding the concave surface of the glass lens; A planar portion formed around the convex curved surface portion and included in a plane substantially orthogonal to the optical center axis of the convex curved surface portion; and a curved surface formed at a boundary portion between the convex curved surface portion and the planar portion. a part and a formation boundary curved portion so as to transition to the flat portion by a curved surface that changes from the convex curved surface portion, the boundary curved portion at the boundary point between the convex curved surface portion and the boundary curved portion The angle formed by the tangent plane of the curved surface on the side with respect to the central axis of the convex curved surface portion is θ1 , The angle formed by the tangent plane of the curved surface on the convex curved surface side at the boundary point with respect to the central axis is θ2 When
0 ° ≦ θ2 -Θ1 ≦ 25 °
There a formed Ru method for manufacturing a glass lens mold to stand,
While rotating the molding surface with the central axis of the molding die material as the rotation axis, the cylindrical surface of the rotating cylindrical grinding wheel is moved so as to draw a predetermined locus while contacting the molding die material. A method for manufacturing a glass lens molding die, characterized in that grinding is performed.

6. The method for manufacturing a glass lens molding die according to claim 4, wherein the convex curved surface portion is ground by moving the grindstone from the central axis of the molding die material toward the outer periphery. .

The molding surface, said mold material, as the rotation axis center axis of the mold material, while rotating at a speed of 100～1000Rpm, any claim 4-6, characterized in that the grinding A method for producing a glass lens mold according to claim 1.

The glass lens molding die according to any one of claims 5 to 8, wherein the molding surface is ground by bringing a grinding wheel rotating at 10,000 to 100,000 rpm into contact with the molding die material. Production method.

9. The method according to claim 4 , wherein a first grindstone is used for grinding the convex curved surface portion, and a second grindstone is used for grinding the flat surface portion and the boundary curved surface portion. A method for producing a mold for molding a glass lens.

A glass material is disposed in a molding apparatus provided with at least one of an upper mold or a lower mold with the molding mold according to any one of claims 1 to 3 or the molding mold manufactured by the manufacturing method according to claims 4 to 9. A method for producing a glass lens, comprising pressure-molding a glass material in a state of being heated to a predetermined temperature and softened.

In the molding apparatus, the upper mold and the lower mold are slidably provided in the barrel mold, and the amount of the glass material disposed between the upper mold and the lower mold is determined by the barrel mold, the upper mold, and the lower mold. The manufacturing method according to claim 10 , wherein the volume is smaller than the volume formed by the step.

A meniscus lens manufactured by the manufacturing method according to claim 10 or 11 .