JP4068507B2

JP4068507B2 - Lens manufacturing method

Info

Publication number: JP4068507B2
Application number: JP2003152045A
Authority: JP
Inventors: 知一徳永
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2003-05-29
Filing date: 2003-05-29
Publication date: 2008-03-26
Anticipated expiration: 2023-05-29
Also published as: JP2004351740A

Description

【０００１】
【発明の属する技術分野】
本発明はレンズの製造方法に関し、特に、凹面を有したレンズを成形するのに好適なレンズの製造方法に関するものである。
【０００２】
【従来の技術】
近年、デジタルカメラの高画質化、小型化に伴い、負メニスカスレンズを前玉等に使用することで、光学系の高画質化、小型化が推進されている。
【０００３】
本発明の実施の形態を示す図１を参照して、負メニスカスレンズ７は中心部より周縁部の肉厚が厚い。このような負メニスカスレンズ７を成形するのに、レンズ素材６を上下金型２、３により加熱しながらプレス成形した後、冷却する際、前記のような肉厚の差でレンズ凹面７ｂ側にひけるといった特性がある。このため、成形後の負メニスカスレンズ７は成形に続く冷却時に凸成形面２ａに喰らい付き、内部応力が残留する。この内部応力は図３に斜線を施した部分を除去する芯取り加工をした後の負メニスカスレンズ７に形状崩れをもたらす。このため、負メニスカスレンズ７の場合、ひけによる問題が生じない凸レンズに比して面精度を確保しにくく、生産効率は低い。そこで、所定の品質を維持しながらいかに生産性を高めるかが課題になっている。
【０００４】
これに対応するのに従来、加圧成形後の冷却工程にて上金型への加圧を解除するなどして上金型の自重のみが掛かる状態とすることにより前記喰らい付きを緩和し、面精度を得やすくする成形方法が知られている（例えば、特許文献１、２参照。）。
【０００５】
また、メニスカスレンズの凹面のように癖のあるレンズ面を成形する成形面を、前記癖を相殺する形状にして成形したり、癖のあるレンズ面を成形後に機械加工して所定の面精度に仕上げる方法も知られている（例えば、特許文献３参照。）。
【０００６】
【特許文献１】
特開昭６１−０２１９２７号公報
【０００７】
【特許文献２】
特開平１１−０４９５２３号公報
【０００８】
【特許文献３】
特開平０８−０４０７３２号公報
【０００９】
【発明が解決しようとする課題】
しかし、特許文献１、２に記載のもののように、冷却時に上金型の加圧を解除してフリーにする方法では、金型装置の構造が複雑になって高価につく。また、上金型は加圧部材など他の部材と離れて相互間に気体が入り込んで断熱層を形成するため上金型が放熱しにくく、加圧部材と接触したままの場合に比して冷却に長い時間が掛かる。特に、金型の背部から伝熱加熱、伝熱冷却を行う成形方法であると、加熱するのにも冷却時に離していた他部材の当接を待ってしか開始できないので、これによる時間遅れも加わり生産性に大きく影響する。
【００１０】
また、特許文献３に記載のもののように、癖のあるレンズ面を相殺する成形面を形成する方法は成形面の設計、管理が困難であるし、レンズの成形後に癖のあるレンズ面を機械加工する方法では、成形に問題はないが、機械加工のために製品コストが上昇する。
【００１１】
本発明の目的は、凹面を有するレンズであってもそれの凸成形面への喰らい付きを防止して面精度よく、また生産性よく成形できるレンズの製造方法を提供することにある。
【００１２】
【課題を解決するための手段】
上記の目的を達成するために、本発明のレンズ製造方法は、金型によりレンズ素材を加熱、加圧して所望の形状のレンズに成形する工程と、成形後の冷却に伴い、金型におけるレンズの有効径範囲を成形する第１成形面とその外側部分を成形する第２成形面とに、線熱膨張係数の差から、第１成形面が第２成形面よりも後退する段差を生じさせて金型の第１成形面と前記レンズとを分離する工程と、を備えたことを１つの特徴としている。
【００１３】
このような構成では、金型でレンズ素材を加熱、加圧して所望の形状のレンズに成形し、成形後は冷却する。この冷却に際して、金型におけるレンズの有効径範囲を成形する第１成形面とその外側部分を成形する第２成形面とが線熱膨張係数の差から段差を生じ、第１成形面が第２成形面よりも反レンズ側に移動する、つまり後退する。このため、第１成形面は第２成形面に当接しているレンズから後退し、レンズと分離される。この結果、第１成形面が凸成形面であって、それが成形したレンズの冷却時に凹面側へのひけが生じても、前記金型とレンズの分離によって従来のようにレンズが凸成形面に喰らいつくようなことを防止することができる。しかも、第１、第２成形面が協働してレンズの有効径外部分を含んだ片側全面の成形を満足しながら、レンズの有効径範囲を含んだ部分を第１の成形面１つによって成形するので、レンズが実用される有効径範囲内の成形上、成形面が２つに分かれることによる弊害を回避できる利点がある。
【００１４】
このような段差による金型とレンズの分離は上下金型の別なく、また、一対の金型の配置向きに関係なく達成することができる。しかし、レンズが重力で成形面の後退に追随する下金型や、形状やレンズとの材質的な関係からレンズが追随するか、追随する可能性のある条件の金型の場合に特に有効である。
【００１５】
本発明のレンズの製造方法は、また、上下金型間にレンズ素材を挿入する工程と、前記上下金型の少なくとも一方の金型を加熱し、双方型間で前記レンズ素材を規制部材による加圧規制位置まで加圧することにより、所望の形状のレンズに成形する工程と、成形後の冷却に伴い、前記規制部材と上下金型の少なくとも一方の金型との線熱膨張係数の差から、上下金型の少なくとも一方の金型とレンズとを分離する工程と、を備えたことを他の特徴としている。
【００１６】
このような構成では、少なくとも一方が加熱される上下金型間にレンズ素材を挿入して、このレンズ素材を加熱、加圧してレンズを成形する際、規制部材によって上下金型の加圧位置を規制することにより所望の形状のレンズを成形できるようにし、成形後は冷却する。この冷却に際して、上下金型の少なくとも一方は前記規制部材との線熱膨張係数の差から、規制部材による加圧位置規制状態のままでそれの成形面が後退する。これにより上下金型は開いてレンズと分離される。特に、この分離はレンズが重力で追随せず離れやすい上金型との間では確実に行われる。この結果、レンズから離れる成形面が凸成形面であって、それが成形したレンズの冷却時にその凹面側へのひけが生じても、従来のように凸成形面に喰らいつくようなことを防止することができる。しかも、レンズとの分離を図る成形面を複数に分割しなくてよい利点がある。
【００１７】
しかし、重力などによる追随を防止する操作の組み合わせによれば、下金型とこれに重力にて追随するレンズとの間などでも分離することができ、冷却に伴い金型とレンズを分離する工程に前記規制部材またはそれとは別の支持部材を利用して、線熱膨張係数の差からレンズの端部下面を規制部材または支持部材で支持し、下金型とレンズとを分離する工程であることを特徴とした、さらなる構成では、
前記規制部材によって規制された加圧位置のまま下金型の成形面が後退するとき、線熱膨張係数の差から規制部材または支持部材がレンズの端部下面を支持して、下金型の成形面の後退に追随しないようにするので、下金型とレンズとを分離することができる。規制部材または支持部材はレンズの端部を支持すればよく、レンズの有効径範囲を避けられるので、規制部材による支持がレンズに悪影響することはない。このような分離は一対の金型の配置向きに関係なく達成することができる。
【００２３】
本発明のそれ以上の目的および特徴は、以下の詳細な説明および図面によって明らかになる。本発明の各特徴は、それ単独で、あるいは種々な組み合わせで複合して採用することができる。
【００２４】
【発明の実施の形態】
以下、本発明に係るレンズの製造方法の実施の形態につき、図１〜図４を参照しながら詳細に説明する。以下の説明は本発明の具体例であって、特許請求の範囲の記載事項を限定するものではない。
【００２５】
本発明に係るレンズ製造方法の実施の形態では、図１、図２に例示する金型装置１や図４に例示する金型装置８などを用いて図３に例示するようなレンズ７を成形し、成形後に冷却する。このようにして製造したレンズ７は、その有効径範囲よりも外側にある図３に斜線を施して示した外側部分、つまり有効径外部分７ａを研削などして除去する芯取り加工を施す。例示したレンズ７は既述したように負メニスカスレンズであるが、これに限られることはなく、所望の形状のレンズ７に成形するようにできる。
【００２６】
本発明に係るレンズの製造方法の実施の形態としては、金型装置１、８の上下金型２、３間に図２（ａ）、図４（ａ）に示すようにレンズ素材６を挿入する工程と、前記上下金型２、３の少なくとも一方を加熱し、双方間で前記レンズ素材６を図２（ａ）、図４（ａ）の状態から図２（ｂ）、図４（ｂ）に示すように規制部材９による加圧規制位置まで加圧して所望の形状のレンズ７に成形する工程とを備え、特に、成形後の冷却に伴い、前記規制部材９と上下金型２、３の少なくとも一方の金型との線熱膨張係数の差から、図２（ｂ）、図４（ｂ）の状態から図２（ｃ）、図４（ｃ）の状態に上下金型２、３の少なくとも一方の金型とレンズ７を分離する工程を備えている。
【００２７】
このように、少なくとも一方が加熱される上下金型２、３間にレンズ素材６を挿入して、このレンズ素材６を加熱、加圧してレンズ７を成形する際、規制部材９によって上下金型２、３の加圧位置を規制することにより所望の形状のレンズ７を成形することができる。成形後は冷却するが、この冷却に際して、上下金型２、３の少なくとも一方は前記規制部材９との線熱膨張係数の差から、規制部材９による加圧位置規制状態のままでそれの成形面２ａまたは３ａが後退する。これだけで、上下金型２、３は互いに開いてレンズ７と分離される。特に、この分離はレンズ７が重力で追随せず離れやすい上金型２との間では確実に行われる。この結果、レンズ７から離れる成形面２ａが図２、図４に例示するように凸成形面であって、それが成形したレンズ７の冷却時にその凹面７ａ側へのひけが生じても、従来のように凸成形面である成形面２ａに喰らいつくようなことを防止することができる。しかも、レンズ７との分離を図る成形面２ａなどを複数に分割しなくてよい利点がある。このような分離機構は上下金型２、３の双方の規制部材９との線熱膨張係数の違いから、それらの成形面２ａ、３ａの双方が後退する方式にても達成することができ、上下金型２、３の開き距離を大きくとりやすい。
【００２８】
なお、重力などによるレンズ７の下金型３の成形面３ａなどへの追随を防止する操作を組み合わせると、下金型３とこれに重力にて追随するレンズ７との間などでも分離することができる。これを達成するのに、本実施の形態の製造方法ではさらに、既述した冷却に伴い金型とレンズを分離する工程につき、線熱膨張係数の差からレンズ７の端部下面を図４に示す規制部材９または図２に示す支持部材４により図２（ｃ）、図４（ｃ）に示すように支持し、下金型３とレンズ７とを分離する工程としている。ここで、規制部材９または支持部材４がレンズ７の端部下面を支持するのは、それらに形成した成形面９ａまたは４ａであり、下金型３の成形面３ａと協働してレンズ７の下面を成形するものとしてある。これにより、レンズ７を規制部材９または支持部材４によって支持するために、レンズ７に余分な部分を設けて拡張するような不利は生じない。反面、レンズ７の下面を成形する成形面が下金型３の成形面３ａと規制部材９の成形面９ａまたは支持部材４の成形面４ａとに分割する必要はある。いずれを採用してもよい。また、成形面３ａは少なくともレンズ７の有効径範囲を成形すればレンズ７の有効径範囲の成形に成形面が分割することによる影響が生じない。従って、成形面３ａはレンズ７の有効径範囲を越えた部分をも成形することを妨げないし、成形面９ａまたは４ａはレンズ７を前記分離のために支持できればよく、レンズ７の有効径範囲外に対しどのように設定してもよい。
【００２９】
このような規制部材９または支持部材４は、レンズ７の成形後の冷却に際し、線熱膨張整数の差から下金型３が規制部材９によって規制された加圧位置のままでその成形面３ａが後退するとき、つまり下降するとき、線熱膨張係数の差から規制部材９の成形面９ａまたは支持部材４の成形面４ａによってレンズ７の端部下面を図２（ｃ）、図４（ｃ）に示すように支持し、下金型３の成形面３ａの後退にレンズ７が追随しないようにする。これにより、下金型３とレンズ７とを分離することができる。
【００３０】
なお、規制部材９または支持部材４はレンズ７の端部を支持すればよく、レンズ７の有効径範囲を避けられるので、規制部材９または支持部材４による支持がレンズ７に悪影響することはない。この場合、下金型３は規制部材９または支持部材４との線熱膨張係数の差から、規制部材９による加圧規制位置のままで成形面３ａが後退することを必須となるが、上金型２の側は必須とならない。しかし、線熱膨張係数の差から上金型２の成形面２ａが、規制部材９または支持部材４の成形面９ａまたは４ａに支持されたレンズ７から後退しないのでは、上金型２をレンズ７から分離できない。従って、上下金型２、３をレンズ７と分離するには、上下金型２、３の成形面２ａ、３ａ共に後退する線熱膨張係数の関係を満足する必要がある。
【００３１】
以上のような規制部材９または支持部材４による第２の成形面９ａまたは４ａに対し、下金型３による第１の成形面３ａが後退して、成形面３ａとレンズ７とを分離する機構は、一対の金型の配置向きに関係なく達成することができ、図２、図４に示す金型装置１、８の上下金型２、３の双方に対して同時に適用することができる。
【００３２】
また、このような分離機構は、第２の成形面９ａまたは４ａに対し、第１の成形面３ａが後退することによりできる図２（ｃ）、図４（ｃ）に示すような段差によって下金型３とレンズ７とを分離するものであるといえる。このような観点から、本実施の形態は、また、上下金型２、３によりレンズ素材６を加熱、加圧して所望の形状のレンズ７に成形する工程と、成形後の冷却に伴い、上下金型２、３の少なくとも一方側における、レンズ７の有効径範囲を含む部分を成形する第１成形面の一例である３ａと、その外側部分を成形する第２成形面の一例である成形面９ａまたは４ａとに、線熱膨張係数の差から、第１成形面３ａが第２成形面９ａまたは４ａよりも後退する段差を生じさせて成形面３ａと前記レンズ７を分離する工程と、を備えたレンズの製造方法をも提供している。
【００３３】
このような段差によるレンズ７との分離は、既述した規制部材９または支持部材４によりレンズ７を支持して分離を図る場合同様、上下金型２、３の別なく、また、一対の金型の配置向きに関係なく達成することができるが、レンズが重力で成形面の後退に追随する下金型３や、形状やレンズとの材質的な関係からレンズが追随するか、追随する可能性のある条件の金型の場合に特に有効である。
【００３４】
以下、図２、図４に示す金型装置１、８の具体例について、さらに詳述する。上下金型２、３は筒状の規制部材９内にその上下端から嵌め合わされて対向し合い、規制部材９による邪魔なしに相互間でレンズ素材６を加熱、加圧してレンズ７を成形することができる。上下金型２、３はそのフランジ部２ｄ、３ｄが規制部材９の上下端と対向し合い、レンズ７を成形する際に互いが図２（ｂ）、図４（ｂ）に示すように当接することで加圧位置を規制される。これによりレンズ素材６を所定の形状に成形することができる。
【００３５】
一般に、下金型３は規制部材９とともに固定側とし、上金型２を可動側として成形を行い、成形および冷却が終了する都度上金型２を規制部材９から上方へ抜き出して、製造したレンズ７を取り出せるようにする。しかし、これに限られることはない。規制部材９も上金型２と共に退避するようにもできるし、下金型３が可動側でも、上下金型２、３の双方が可動でもよい。
【００３６】
このような金型装置１、８で図３に示すような負メニスカスレンズを、凹面７ｂが上向きで凸面７ｃが下向きとなる姿勢のレンズ７として成形するのに、上金型２の成形面２ａを凸成形面、下金型３の成形面３ａを凹成形面としてある。レンズ７の成形後の冷却に際し、レンズ７の凹面７ｂが凸である成形面２ａに食いつかせないためには、上金型２とレンズ７との分離が必須となる。しかし、図２、図４に示す金型装置１、８では、上金型２とレンズ７との分離に加え、下金型３とレンズ７との分離をも規制部材９または支持部材４の成形面９ａまたは４ａによる支持方式にて図るようにしてある。
【００３７】
これを満足するのに、図２に示す金型装置１では、支持部材４は規制部材９の内周と下金型３の外周との間に嵌め合わされた筒型部材とし、規制部材９の途中高さ位置、下金型３の成形面３ａと並ぶ上端を成形面４ａとして、下金型３の成形面３ａと連なって既述したように協働し、レンズ７の下面を成形するようにしている。併せ、線熱膨張係数が「上下金型２、３」＞「規制部材９および支持部材４」の関係を満足して、前記成形とその後の冷却を行わせるようにしている。これにより、成形後の冷却の際、前記上下金型２、３と規制部材９との線熱膨張係数の違いから、上下金型２、３は規制部材９による加圧規制位置のままで、それらの成形面２ａ、３ａどうしが互いに後退して開く。このときレンズ７は上方に向け後退する、つまり上昇する上金型２の成形面２ａには重力にて追随せず確実に分離される。従って、図示するように成形面２ａが凸成形面であってもこれにより成形されたレンズ７の凹面７ｂが食らいつく問題はない。一方、下金型３の成形面３ａは下方に後退する、つまり下降するが、それだけではレンズ７は自重で追随する。しかし、前記支持部材４と下金型３との線熱膨張係数の違いから、下金型３ａの成形面３ａは支持部材４の成形面４ａに対して段差をなして下降するので、下金型３の成形面３ａは支持部材４の成形面４ａに支持されたレンズ７から確実に分離される。従って、下金型３の成形面３ａがもし、図２に示すのとは異なり凸成形面であってもレンズ７の食らいつきを防止することができる。
【００３８】
また、図４に示す金型装置８では、図２に示す金型装置１での支持部材４の成形面４ａに代えて、規制部材９の内周の途中高さ部に形成した成形面９ａを採用している。この成形面９ａは規制部材９の内周途中で、下金型３の成形面３ａと並ぶ段差部をなし、下金型３の成形面３ａと連なって既述したように協働し、レンズ７の下面を成形するようにしている。併せ、線熱膨張係数が「上下金型２、３」＞「規制部材９」の関係を満足したものとしている。これにより、成形後の冷却の際、前記上下金型２、３と規制部材９との線熱膨張係数の違いから、上下金型２、３は規制部材９による加圧規制位置のままで、それらの成形面２ａ、３ａどうしが互いに後退して開く。このときレンズ７は上方に向け後退する、つまり上昇する上金型２の成形面２ａには重力にて追随せず確実に分離される。従って、図示するように成形面２ａが凸成形面であってもこれにより成形されたレンズ７の凹面７ｂが食らいつく問題はない。一方、下金型３の成形面３ａは下方に後退する、つまり下降するが、それだけではレンズ７は自重で追随する。しかし、前記規制部材９と下金型３との線熱膨張係数の違いから、下金型３ａの成形面３ａは規制部材９の成形面９ａに対して段差をなして下降するので、下金型３の成形面３ａは規制部材９の成形面９ａに支持されたレンズ７から確実に分離される。従って、下金型３の成形面３ａがもし、図４に示すのとは異なり凸成形面であってもレンズ７の食らいつきを防止することができる。
【００３９】
なお、規制部材９あるいは支持部材４の成形面９ａまたは４ａの高さに対する下金型３の成形面３ａは、図２（ａ）、図４（ａ）に示すように予め低くしておき、前記加熱成形時に前記線熱膨張係数の違いから、双方の成形面９ａまたは４ａと成形面３ａとの高さがほぼ一致するように配慮する。これにより、下金型３と線熱膨張係数の違う規制部材９や支持部材４に形成した成形面９ａまたは４ａにてレンズ７の有効径より外側部分７ａを成形するのに、この成形面９ａまたは４ａに対して低くしておいた下金型３の成形面３ａの高さの違いを、加熱成形時の規制部材９や支４と下金型３との前記線熱膨張係数の違い応じた膨張差によりほぼ一致させられる。この結果、下金型３と規制部材９や支持部材４との線熱膨張係数が異なることによって双方の成形面９ａまたは４ａと成形面３ａが形成するレンズ面に許容範囲を超える段差ができて成形の邪魔になりレンズ７の周縁の成形に支障を来すようなことを防止することができる。
【００４０】
また、前記規制部材９の成形面９ａや支持部材４の成形面４ａの傾斜角度は、下金型３の成形面３ａの周縁部の傾斜角度とほぼ同一とする。これにより、下金型３と規制部材９や支持部材４とが別部材であっても、それらの成形面４ａまたは９ａと成形面３ａの境界部で傾斜が大きく異なって成形の邪魔になってレンズ７の周縁の成形に支障を来したり、成形したレンズ７の前記境界部で極端に傾斜角度が異なるようなことを防止することができる。
【００４１】
なお、前記規制部材９や支持部材４は炭化タングステン、上下金型２、３が規制部材９や支持部材４よりも線熱膨張係数が大きな炭化タングステン、ＳｉＣ、Ｓｉ₃Ｎ₄、Ａｌ₂Ｏ₃、ＺｒＯ₂、サーメットのいずれかであるのが好適である。
【００４２】
ここで、図１、図２に示す金型装置１での実施例を示すと、成形するレンズ７はガラス材料よりなる凹面７ｂと凸面７ｃとを有したメニスカスレンズであって、記述したように凹面７ｂを上にして成形するようにしている。しかし、反対向きでもよいし、凹面７ｂどうしのレンズ７でもよい。レンズ素材６はホウケイ酸ガラスで、ガラス転移点が５１０℃、線熱膨張係数が１００℃〜３００℃で９０×１０^-7／℃のもので、直径１５ｍｍ、中心厚み４ｍｍに研磨加工されたプリフォーム材を用いた。
【００４３】
一方、上下金型２、３には炭化タングステン（ＷＣ−Ｃｏ）の焼結体をＨＩＰ処理したものを用いた。線熱膨張係数は５７×１０^-7／℃である。また、規制部材９および支持部材４には炭化タングステン（ＷＣ−Ｔｉ−ＴａＣ）の焼結体を用いた。線熱膨張係数は４７×１０^-7／℃である。
【００４４】
図２（ａ）に示す状態で窒素雰囲気中にある上下金型２、３の間にレンズ素材６をセットし、レンズ素材６の温度が５８０℃になるまで加熱する。ガラス素材６の温度が５８０℃になるとレンズ素材６の粘度は１０⁹ポアズになっている。この温度で、１５０Ｋｇ／ｃｍ²の圧力をかけ７０秒間プレスした。このときの金型装置１とレンズ素材６との状態を図２（ｂ）に示している。
【００４５】
下金型３の成形面３ａは線熱膨張係数が支持部材４よりも大きいため、支持部材４の成形面４ａとほぼ同一高さ（２〜３μｍ程度の段差内）になる。従って、レンズ素材６は段差による邪魔なく支持部材４の側にスムーズに変形することができ、レンズ素材６の周縁部が支持部材４の成形面４ａに掛かるまで変形されレンズ７に成形される。
【００４６】
この後、プレス圧力を５０Ｋｇ／ｃｍ²まで減圧して金型装置１とともにレンズ７を３００℃まで冷却した。このときの冷却速度は０．８５℃／秒〜１．５ ℃／秒である。このときの金型装置１とレンズ７との状態を図２（ｃ）に示してある。この冷却時にレンズ７および金型装置１は収縮するが、上金型２の線熱膨張係数が規制部材９よりも大きいので、規制部材９による加圧位置規制状態のまま成形面２ａが上方に後退する。併せて、レンズ７の線熱膨張係数が上金型２の線熱膨張係数より大きいので厚みは小さいが幾分上面が下降する。これにより、レンズ７と上金型２の成形面２ａとの間に隙間（２〜３μｍ程度）が生じ、レンズ７と上金型２は離型する。また、下金型３の線熱膨張係数が支持部材４よりも大きく、支持部材４の成形面４ａよりも成形面３ａが下降し、かつ、レンズ７の周縁部は支持部材４で受け止められた状態を保つので、下金型３の成形面３ａとレンズ７とが離型する。
【００４７】
離型後、取り出したレンズ７を図３に示す斜線部分を除去して芯取り加工し、負メニスカスレンズを得た。このとき、下金型３と支持部材４との境目は芯取り加工時に除去されるので、この境目に多少の段差が生じていても問題はない。得られた負メニスカスレンズの形状精度を調べたところ、ニュートン２本以内、アスクセ０．５本以内の良好なレンズ７であった。
【００４８】
支持部材４の成形面４ａに傾斜はなしで説明したが、レンズ７の周縁の傾斜角度にほぼ等しい傾斜角度に設定することができる。図示する例ではレンズ７の周縁の傾斜角度が２５度であるので、０度〜２５度程度、あるいは２５度よりも少し大き目に設定することができる。
【００４９】
さらに、上下金型２、３の材料を炭化タングステン（ＷＣ−Ｃｏ）にした場合について説明したが、線熱膨張係数は３０〜９５×１０^-7／℃のものが望ましく、これを満足する他の材料、例えば、ＳｉＣ、Ｓｉ₃Ｎ₄、Ａｌ₂Ｏ₃、ＺｒＯ₂、サーメット等を使用することができる。
【００５０】
次に、図４に示す金型装置８での実施例について説明すると、成形するレンズ７はガラス材料よりなる凹面７ｂと凸面７ｃとを有したメニスカスレンズであって、記述したように凹面７ｂを上にして成形するようにしている。しかし、反対向きでもよいし、凹面７ｂどうしのレンズ７でもよい。レンズ素材６はホウケイ酸ガラスで、ガラス転移点が５１０℃、線熱膨張係数が１００℃〜３００℃で９０×１０^-7／℃のもので、直径１５ｍｍ、中心厚み４ｍｍに研磨加工されたプリフォーム材を用いた。
【００５１】
一方、上下金型２、３には炭化タングステン（ＷＣ−Ｃｏ）の焼結体をＨＩＰ処理したものを用いた。線熱膨張係数は５７×１０^-7／℃である。また、規制部材９には炭化タングステン（ＷＣ−Ｔｉ−ＴａＣ）の焼結体を用いた。線熱膨張係数は４７×１０^-7／℃である。
【００５２】
図４（ａ）に示す状態で窒素雰囲気中にある上下金型２、３の間にレンズ素材６をセットし、レンズ素材６の温度が５８０℃になるまで加熱する。レンズ素材６の温度が５８０℃になるとレンズ素材６の粘度は１０⁹ポアズになっている。この温度で、１５０Ｋｇ／ｃｍ²の圧力をかけ７０秒間プレスした。このときの金型装置１とレンズ素材６との状態を図４（ｂ）に示している。
【００５３】
下金型３の成形面３ａは線熱膨張係数が規制部材９よりも大きいため、規制部材９の成形面９ａとほぼ同一高さ（２〜３μｍ程度の段差内）になる。従って、レンズ素材６は段差による邪魔なく規制部材９の側にスムーズに変形することができ、レンズ素材６の周縁部が規制部材９の成形面９ａに掛かるまで変形されレンズ７に成形される。
【００５４】
この後、プレス圧力を５０Ｋｇ／ｃｍ²まで減圧して金型装置１とともにレンズ７を３００℃まで冷却した。このときの冷却速度は０．８５℃／秒〜１．５ ℃／秒である。このときの金型装置１とレンズ７との状態を図４（ｃ）に示してある。この冷却時にレンズ７および金型装置１は収縮するが、上金型２の線熱膨張係数が規制部材９よりも大きいので、規制部材９による加圧位置規制状態のまま成形面２ａが上方に後退する。併せて、レンズ７の線熱膨張係数が上金型２の線熱膨張係数より大きいので厚みは小さいが幾分上面が下降する。これにより、レンズ７と上金型２の成形面２ａとの間に隙間（２〜３μｍ程度）が生じ、レンズ７と上金型２は離型する。また、下金型３の線熱膨張係数が規制部材９よりも大きく、その成形面９ａよりも成形面３ａが下降し、かつ、レンズ７の周縁部は規制部材９の成形面９ａで受け止められた状態を保つので、下金型３の成形面３ａとレンズ７とが離型する。
【００５５】
離型後、取り出したレンズ７を図３に示す斜線部分を除去して芯取り加工し、負メニスカスレンズを得た。このとき、下金型３と規制部材９との境目は芯取り加工時に除去されるので、この境目に多少の段差が生じていても問題はない。得られた負メニスカスレンズの形状精度を調べたところ、ニュートン２本以内、アスクセ０．５本以内の良好なレンズ７であった。
【００５６】
規制部材９の成形面９ａの傾斜角度はなしで説明したが、レンズ７の周縁の傾斜角度にほぼ等しい傾斜角度に設定することができる。図示する例ではレンズ７の周縁の傾斜角度が２５度であるので、０度〜２５度程度、あるいは２５度よりも少し大き目に設定することができる。
【００５７】
さらに、上下金型２、３の材料を炭化タングステン（ＷＣ−Ｃｏ）にした場合について説明したが、線熱膨張係数は３０〜９５×１０^-7／℃のものが望ましく、これを満足する他の材料、例えば、ＳｉＣ、Ｓｉ₃Ｎ₄、Ａｌ₂Ｏ₃、ＺｒＯ₂、サーメット等を使用することができる。
【００５８】
【発明の効果】
本発明の１つの特徴のレンズ成形方法によれば、金型でレンズ素材を加熱、加圧して所望の形状のレンズに成形し、成形後は冷却する。この冷却に際して、金型におけるレンズの有効径範囲を含む部分を成形する第１成形面とその外側部分を成形する第２成形面とが線熱膨張係数の差から段差を生じ、第１成形面が第２成形面よりも反レンズ側に移動する、つまり後退する。このため、第１成形面は第２成形面に当接しているレンズから後退し、レンズと分離される。この結果、第１成形面が凸成形面であって、それが成形したレンズの冷却時に凹面側へのひけが生じても、前記金型とレンズの分離によって従来のようにレンズが凸成形面に喰らいつくようなことを防止することができる。しかも、第１、第２成形面が協働してレンズの有効径外部分を含んだ片側全面の成形を満足しながら、レンズの有効径範囲を含んだ部分を第１の成形面１つによって成形するので、レンズが実用される有効径範囲内の成形上、成形面が２つに分かれることによる弊害を回避できる利点がある。
【００５９】
本発明の他の特徴のレンズの製造方法によれば、少なくとも一方が加熱される上下金型間にレンズ素材を挿入して、このレンズ素材を加熱、加圧してレンズを成形する際、規制部材によって上下金型の加圧位置を規制することにより所望の形状のレンズを成形できるようにし、成形後は冷却する。この冷却に際して、上下金型の少なくとも一方は前記規制部材との線熱膨張係数の差から、規制部材による加圧位置規制状態のままでそれの成形面が後退する。これにより上下金型は開いてレンズと分離される。特に、この分離はレンズが重力で追随せず離れやすい上金型との間では確実に行われる。この結果、レンズから離れる成形面が凸成形面であって、それが成形したレンズの冷却時にその凹面側へのひけが生じても、従来のように凸成形面に喰らいつくようなことを防止することができる。しかも、レンズとの分離を図る成形面を複数に分割しなくてよい利点がある。
【００６０】
冷却に伴い金型とレンズを分離する工程に前記規制部材またはそれとは別の支持部材を利用して、線熱膨張係数の差からレンズの端部下面を規制部材または支持部材で支持し、下金型とレンズとを分離する工程とした、さらなる構成によれば、
前記規制部材によって規制された加圧位置のまま下金型の成形面が後退するとき、線熱膨張係数の差から規制部材または支持部材がレンズの端部下面を支持して、下金型の成形面の後退に追随しないようにするので、下金型とレンズとを分離することができる。規制部材または支持部材はレンズの端部を支持すればよく、レンズの有効径範囲を避けられるので、規制部材による支持がレンズに悪影響することはない。このような分離は一対の金型の配置向きに関係なく達成することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る１つの実施例を示す金型装置の断面図。
【図２】図１の装置によるレンズの成形工程を示し、その（ａ）はレンズ素材をセットした状態の断面図、その（ｂ）は加熱成形時の断面図、その（ｃ）は成形後の冷却時の断面図。
【図３】図２の成形工程によって得られたレンズの芯取り加工を行う際の説明図。
【図４】別の金型装置によるレンズの成形工程を示し、その（ａ）はレンズ素材をセットした状態の断面図、その（ｂ）は加熱成形時の断面図、その（ｃ）は成形後の冷却時の断面図。
【符号の説明】
１金型装置
２上金型
３下金型
４支持部材
９規制部材
２ａ、３ａ、４ａ、９ａ成形面
６レンズ素材
７レンズ
７ａ有効径の外側部分
７ｂ凹面
７ｃ凸面[0001]
BACKGROUND OF THE INVENTION
The present invention is a method of manufacturing a lens. To the law In particular, a method of manufacturing a lens suitable for molding a lens having a concave surface To the law It is related.
[0002]
[Prior art]
In recent years, with the increase in image quality and miniaturization of digital cameras, the use of a negative meniscus lens for the front lens or the like has promoted the improvement in image quality and miniaturization of optical systems.
[0003]
Referring to FIG. 1 showing the embodiment of the present invention, the negative meniscus lens 7 has a thicker peripheral edge than the center. In order to mold such a negative meniscus lens 7, when the lens material 6 is press-molded while being heated by the upper and lower molds 2, 3 and then cooled, the lens concave surface 7 b side is caused by the thickness difference as described above. There are characteristics such as sinking. For this reason, the negative meniscus lens 7 after molding bites into the convex molding surface 2a during cooling subsequent to molding, and internal stress remains. This internal stress causes the shape of the negative meniscus lens 7 after being centered to remove the hatched portion in FIG. For this reason, in the case of the negative meniscus lens 7, it is difficult to ensure surface accuracy and the production efficiency is low as compared with a convex lens that does not cause a problem due to sink marks. Thus, how to increase productivity while maintaining a predetermined quality has become an issue.
[0004]
To cope with this, conventionally, the biting of the upper mold is reduced by releasing the pressurization to the upper mold in the cooling step after pressure molding, etc. A molding method for easily obtaining surface accuracy is known (for example, see Patent Documents 1 and 2).
[0005]
In addition, a molding surface that molds a wrinkled lens surface such as a concave surface of a meniscus lens is shaped to cancel the wrinkles, or the wrinkled lens surface is machined after molding to a predetermined surface accuracy. A finishing method is also known (see, for example, Patent Document 3).
[0006]
[Patent Document 1]
JP 61-021927 A
[0007]
[Patent Document 2]
JP 11-049523 A
[0008]
[Patent Document 3]
Japanese Patent Laid-Open No. 08-040732
[0009]
[Problems to be solved by the invention]
However, in the method of releasing the pressure of the upper mold during cooling, such as those described in Patent Documents 1 and 2, the structure of the mold apparatus becomes complicated and expensive. In addition, the upper mold is separated from other members such as a pressure member, and gas enters between them to form a heat insulating layer, so that the upper mold is less likely to dissipate heat, compared to the case where it remains in contact with the pressure member. Cooling takes a long time. In particular, in the molding method in which heat transfer heating and heat transfer cooling are performed from the back of the mold, heating can only be started after waiting for the contact of other members that have been separated during cooling. In addition, it greatly affects productivity.
[0010]
In addition, the method of forming a molding surface that cancels a wrinkled lens surface, such as that described in Patent Document 3, makes it difficult to design and manage the molding surface. In the processing method, there is no problem in molding, but the product cost increases due to machining.
[0011]
The object of the present invention is to manufacture a lens that can be molded with good surface accuracy and high productivity by preventing biting of the convex molding surface even if the lens has a concave surface. The law It is to provide.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the lens manufacturing method of the present invention includes a step of heating and pressing a lens material with a mold to form a lens having a desired shape, and a lens in the mold along with cooling after molding. Due to the difference in the coefficient of linear thermal expansion, a difference in level between the first molding surface and the second molding surface is caused between the first molding surface that molds the effective diameter range and the second molding surface that molds the outer portion thereof. And a step of separating the first molding surface of the mold and the lens.
[0013]
In such a configuration, a lens material is heated and pressurized with a mold to form a lens having a desired shape, and then cooled after molding. During this cooling, the first molding surface that molds the effective diameter range of the lens in the mold and the second molding surface that molds the outer portion thereof produce a step due to the difference in linear thermal expansion coefficient, and the first molding surface is the second molding surface. It moves to the side opposite the lens from the molding surface, that is, moves backward. For this reason, the first molding surface is retracted from the lens in contact with the second molding surface and separated from the lens. As a result, even if the first molding surface is a convex molding surface and sinking to the concave surface occurs during cooling of the molded lens, the lens is convexly molded as in the prior art by separating the mold and the lens. It is possible to prevent such a thing from eating. In addition, the first and second molding surfaces cooperate to satisfy the molding of the entire surface on one side including the outer portion of the effective diameter of the lens, while the portion including the effective diameter range of the lens is formed by one first molding surface. Since molding is performed, there is an advantage that adverse effects caused by splitting the molding surface into two parts can be avoided in molding within the effective diameter range in which the lens is practically used.
[0014]
Separation of the mold and the lens by such a step can be achieved regardless of the upper and lower molds and regardless of the arrangement direction of the pair of molds. However, it is particularly effective for lower molds where the lens follows the retraction of the molding surface due to gravity, and molds that follow or may follow the lens due to the shape and material relationship with the lens. is there.
[0015]
The method for manufacturing a lens of the present invention also includes a step of inserting a lens material between upper and lower molds, heating at least one mold of the upper and lower molds, and adding the lens material between both molds by a regulating member. From the difference in linear thermal expansion coefficient between the regulating member and at least one of the upper and lower molds, with the step of molding into a lens having a desired shape by pressurizing to the pressure regulation position, and cooling after molding, Another feature is that it includes a step of separating the lens from at least one of the upper and lower molds.
[0016]
In such a configuration, when a lens material is inserted between upper and lower molds, at least one of which is heated, and this lens material is heated and pressed to mold the lens, the pressure member is positioned by the regulating member. By restricting, a lens having a desired shape can be molded and cooled after molding. At the time of this cooling, at least one of the upper and lower molds retreats its molding surface in a state where the pressure position is regulated by the regulating member due to the difference in the coefficient of linear thermal expansion with the regulating member. As a result, the upper and lower molds are opened and separated from the lens. In particular, this separation is surely performed between the upper mold and the lens that does not follow due to gravity and is easily separated. As a result, the molding surface away from the lens is a convex molding surface, and even if sinks to the concave surface occur when the molded lens cools, it prevents it from biting into the convex molding surface as before. can do. Moreover, there is an advantage that the molding surface for separation from the lens need not be divided into a plurality of parts.
[0017]
However, according to the combination of operations to prevent following by gravity etc., it is possible to separate even between the lower mold and the lens following by this, and the process of separating the mold and the lens with cooling Further, using the restriction member or another support member, the lower surface of the lens end is supported by the restriction member or the support member from the difference in coefficient of linear thermal expansion, and the lower mold and the lens are separated. In a further configuration, characterized by
When the molding surface of the lower mold moves backward with the pressure position regulated by the regulation member, the regulation member or the support member supports the lower surface of the end of the lens from the difference in linear thermal expansion coefficient. Since it does not follow the retreat of the molding surface, the lower mold and the lens can be separated. The restriction member or the support member only needs to support the end of the lens, and the effective diameter range of the lens can be avoided, so that the support by the restriction member does not adversely affect the lens. Such separation can be achieved regardless of the orientation of the pair of molds.
[0023]
Further objects and features of the present invention will become apparent from the following detailed description and drawings. Each feature of the present invention can be used alone or in combination in various combinations.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the manufacturing method of the lens according to the present invention Legal The embodiment will be described in detail with reference to FIGS. The following description is a specific example of the present invention and does not limit the matters described in the claims.
[0025]
In the embodiment of the lens manufacturing method according to the present invention, the lens 7 illustrated in FIG. 3 is molded using the mold apparatus 1 illustrated in FIGS. 1 and 2, the mold apparatus 8 illustrated in FIG. And cooling after molding. The lens 7 manufactured in this way is subjected to a centering process in which the outer portion shown by hatching in FIG. 3 outside the effective diameter range, that is, the effective diameter outer portion 7a is removed by grinding or the like. The lens 7 illustrated is a negative meniscus lens as described above, but is not limited to this, and can be formed into a lens 7 having a desired shape.
[0026]
As an embodiment of the lens manufacturing method according to the present invention, the lens material 6 is inserted between the upper and lower molds 2 and 3 of the mold apparatus 1 and 8 as shown in FIGS. 2 (a) and 4 (a). And at least one of the upper and lower molds 2 and 3 is heated, and the lens material 6 is moved between the two from the state of FIGS. 2 (a) and 4 (a) to FIGS. 2 (b) and 4 (b). ) To form a lens 7 having a desired shape by pressurizing to a pressure regulating position by the regulating member 9, and in particular, with the cooling after molding, the regulating member 9 and the upper and lower molds 2, 3, the upper and lower molds 2 are changed from the state of FIGS. 2B and 4B to the state of FIGS. 2C and 4C. 3 is provided with a step of separating the lens 7 from at least one of the molds 3.
[0027]
In this way, when the lens material 6 is inserted between the upper and lower molds 2 and 3 to which at least one is heated and the lens material 6 is heated and pressed to mold the lens 7, the upper and lower molds are formed by the regulating member 9. The lens 7 having a desired shape can be formed by regulating the pressure positions of a few. Although cooling is performed after molding, at the time of this cooling, at least one of the upper and lower molds 2, 3 is molded in a state where the pressure position is regulated by the regulating member 9 due to the difference in linear thermal expansion coefficient with the regulating member 9. The surface 2a or 3a is retracted. With this alone, the upper and lower molds 2 and 3 are opened from each other and separated from the lens 7. In particular, this separation is surely performed between the upper mold 2 where the lens 7 does not follow due to gravity and is easily separated. As a result, the molding surface 2a that is separated from the lens 7 is a convex molding surface as illustrated in FIGS. 2 and 4, and even if a sink to the concave surface 7a side occurs when the molded lens 7 is cooled, Thus, it is possible to prevent biting on the molding surface 2a which is a convex molding surface. In addition, there is an advantage that the molding surface 2a and the like for separation from the lens 7 need not be divided into a plurality of parts. Such a separation mechanism can be achieved even in a system in which both of the molding surfaces 2a and 3a recede from the difference in linear thermal expansion coefficient between the upper and lower molds 2 and 3 and the regulating members 9 of both. It is easy to increase the opening distance between the upper and lower molds 2 and 3.
[0028]
When the operation for preventing the lens 7 from following the molding surface 3a of the lower mold 3 due to gravity or the like is combined, separation between the lower mold 3 and the lens 7 that follows this due to gravity is also possible. Can do. In order to achieve this, in the manufacturing method of the present embodiment, the lower surface of the end of the lens 7 is shown in FIG. 4 due to the difference in linear thermal expansion coefficient in the process of separating the mold and the lens with the cooling described above. As shown in FIGS. 2 (c) and 4 (c), the lower mold 3 and the lens 7 are separated from each other by the regulating member 9 shown in FIG. 2 or the support member 4 shown in FIG. Here, the regulating member 9 or the supporting member 4 supports the lower surface of the end portion of the lens 7 by the molding surface 9 a or 4 a formed on the lens 7, and in cooperation with the molding surface 3 a of the lower mold 3, the lens 7. The lower surface of the sheet is formed. Thereby, in order to support the lens 7 by the restricting member 9 or the support member 4, there is no disadvantage that the lens 7 is provided with an extra portion for expansion. On the other hand, the molding surface for molding the lower surface of the lens 7 needs to be divided into the molding surface 3 a of the lower mold 3 and the molding surface 9 a of the regulating member 9 or the molding surface 4 a of the support member 4. Either may be adopted. Further, if at least the effective diameter range of the lens 7 is formed on the molding surface 3a, the molding surface is not affected by the division of the molding surface in the molding of the effective diameter range of the lens 7. Accordingly, the molding surface 3a does not prevent molding of a portion beyond the effective diameter range of the lens 7, and the molding surface 9a or 4a only needs to support the lens 7 for the separation, and is outside the effective diameter range of the lens 7. May be set in any way.
[0029]
Such a regulating member 9 or the supporting member 4 is formed on the molding surface 3a while the lower mold 3 remains in the pressure position regulated by the regulating member 9 due to the difference of the linear thermal expansion integer when the lens 7 is cooled after molding. 2 retreats, that is, descends, the lower surface of the end portion of the lens 7 is lowered by the molding surface 9a of the regulating member 9 or the molding surface 4a of the support member 4 due to the difference in coefficient of linear thermal expansion. ) So that the lens 7 does not follow the retreat of the molding surface 3a of the lower mold 3. Thereby, the lower mold 3 and the lens 7 can be separated.
[0030]
The restriction member 9 or the support member 4 only needs to support the end portion of the lens 7 and the effective diameter range of the lens 7 can be avoided. Therefore, the support by the restriction member 9 or the support member 4 does not adversely affect the lens 7. . In this case, the lower mold 3 is required to move the molding surface 3a backward in the pressure regulation position by the regulation member 9 due to the difference in linear thermal expansion coefficient with the regulation member 9 or the support member 4. The mold 2 side is not essential. However, if the molding surface 2a of the upper mold 2 does not retreat from the lens 7 supported by the molding surface 9a or 4a of the regulating member 9 or the support member 4 due to the difference in linear thermal expansion coefficient, Cannot be separated from 7. Therefore, in order to separate the upper and lower molds 2 and 3 from the lens 7, it is necessary to satisfy the relationship of the linear thermal expansion coefficient that causes the molding surfaces 2 a and 3 a of the upper and lower molds 2 and 3 to recede.
[0031]
A mechanism for separating the molding surface 3a and the lens 7 by retracting the first molding surface 3a by the lower mold 3 with respect to the second molding surface 9a or 4a by the regulating member 9 or the support member 4 as described above. Can be achieved regardless of the orientation of the pair of molds, and can be applied to both the upper and lower molds 2 and 3 of the mold apparatus 1 and 8 shown in FIGS.
[0032]
Such a separation mechanism is lowered by a step as shown in FIGS. 2 (c) and 4 (c), which is formed by retracting the first molding surface 3a with respect to the second molding surface 9a or 4a. It can be said that the mold 3 and the lens 7 are separated. From this point of view, the present embodiment also has a process in which the lens material 6 is heated and pressurized by the upper and lower molds 2 and 3 to form the lens 7 having a desired shape, and the upper and lower molds are cooled with the cooling after the molding. 3a, which is an example of a first molding surface for molding a portion including the effective diameter range of the lens 7, on at least one side of the molds 2, 3, and a molding surface, which is an example of a second molding surface for molding the outer portion thereof A step of separating the molding surface 3a and the lens 7 by causing a step in which the first molding surface 3a recedes from the second molding surface 9a or 4a due to the difference in linear thermal expansion coefficient between 9a and 4a. Also provided is a method of manufacturing the provided lens.
[0033]
The separation from the lens 7 due to such a level difference is the same as when the lens 7 is supported by the regulating member 9 or the support member 4 described above and the separation is made between the upper and lower molds 2 and 3 and a pair of metal molds. This can be achieved regardless of the orientation of the mold, but the lens can follow or follow the lower mold 3 where the lens follows the retraction of the molding surface due to gravity, and the material relationship between the shape and the lens. This is particularly effective in the case of molds with specific conditions.
[0034]
Hereinafter, specific examples of the mold apparatuses 1 and 8 shown in FIGS. 2 and 4 will be described in more detail. The upper and lower molds 2 and 3 are fitted into the cylindrical regulating member 9 from the upper and lower ends so as to face each other, and the lens material 6 is heated and pressurized between them without obstruction by the regulating member 9 to form the lens 7. be able to. The upper and lower molds 2, 3 have flange portions 2 d, 3 d facing the upper and lower ends of the regulating member 9, and when molding the lens 7, they are brought into contact with each other as shown in FIGS. 2 (b) and 4 (b). The pressurization position is regulated by contact. Thereby, the lens material 6 can be formed into a predetermined shape.
[0035]
In general, the lower mold 3 is formed with the restricting member 9 as a fixed side, and the upper mold 2 is formed as a movable side, and the upper mold 2 is extracted upward from the restricting member 9 every time molding and cooling are completed. The lens 7 can be taken out. However, it is not limited to this. The restricting member 9 can also be retracted together with the upper mold 2, or the lower mold 3 can be movable, or both the upper and lower molds 2, 3 can be movable.
[0036]
In order to mold a negative meniscus lens as shown in FIG. 3 with the mold apparatuses 1 and 8 as the lens 7 in such a posture that the concave surface 7b faces upward and the convex surface 7c faces downward, the molding surface 2a of the upper mold 2 is formed. Is a convex molding surface, and the molding surface 3a of the lower mold 3 is a concave molding surface. When the lens 7 is cooled after molding, the upper mold 2 and the lens 7 must be separated so that the concave surface 7b of the lens 7 cannot be caught on the convex molding surface 2a. However, in the mold apparatuses 1 and 8 shown in FIGS. 2 and 4, in addition to the separation between the upper mold 2 and the lens 7, the lower mold 3 and the lens 7 are separated from each other by the regulating member 9 or the support member 4. It is designed so as to be supported by the molding surface 9a or 4a.
[0037]
In order to satisfy this, in the mold apparatus 1 shown in FIG. 2, the support member 4 is a cylindrical member fitted between the inner periphery of the restriction member 9 and the outer periphery of the lower mold 3. In the middle height position, the upper end aligned with the molding surface 3a of the lower mold 3 is used as the molding surface 4a, and the lower surface of the lens 7 is molded in cooperation with the molding surface 3a of the lower mold 3 as described above. I have to. In addition, the linear thermal expansion coefficient satisfies the relationship of “upper and lower molds 2 and 3”> “regulating member 9 and support member 4”, and the molding and the subsequent cooling are performed. Thereby, at the time of cooling after molding, the upper and lower molds 2 and 3 remain in the pressure regulation position by the regulation member 9 because of the difference in linear thermal expansion coefficient between the upper and lower molds 2 and 3 and the regulation member 9. The molding surfaces 2a and 3a are retracted and opened. At this time, the lens 7 retreats upward, that is, the molding surface 2 a of the upper mold 2 that rises is reliably separated without following the gravity. Therefore, even if the molding surface 2a is a convex molding surface as shown in the drawing, there is no problem that the concave surface 7b of the lens 7 molded thereby bites. On the other hand, the molding surface 3a of the lower mold 3 retreats downward, that is, descends, but the lens 7 follows with its own weight by itself. However, because of the difference in the coefficient of linear thermal expansion between the support member 4 and the lower mold 3, the molding surface 3 a of the lower mold 3 a is lowered with a step with respect to the molding surface 4 a of the support member 4. The molding surface 3 a of the mold 3 is reliably separated from the lens 7 supported by the molding surface 4 a of the support member 4. Therefore, even if the molding surface 3a of the lower mold 3 is a convex molding surface unlike the case shown in FIG. 2, the lens 7 can be prevented from biting.
[0038]
Moreover, in the mold apparatus 8 shown in FIG. 4, it replaces with the molding surface 4a of the support member 4 in the mold apparatus 1 shown in FIG. 2, and the molding surface 9a formed in the middle height part of the inner periphery of the control member 9 Is adopted. The molding surface 9a forms a step portion aligned with the molding surface 3a of the lower mold 3 in the middle of the inner periphery of the restricting member 9, and cooperates as described above in connection with the molding surface 3a of the lower mold 3. The lower surface of 7 is molded. In addition, the linear thermal expansion coefficient satisfies the relationship of “upper and lower molds 2 and 3”> “regulating member 9”. Thereby, at the time of cooling after molding, the upper and lower molds 2 and 3 remain in the pressure regulation position by the regulation member 9 because of the difference in linear thermal expansion coefficient between the upper and lower molds 2 and 3 and the regulation member 9. The molding surfaces 2a and 3a are retracted and opened. At this time, the lens 7 retreats upward, that is, the molding surface 2 a of the upper mold 2 that rises is reliably separated without following the gravity. Therefore, even if the molding surface 2a is a convex molding surface as shown in the drawing, there is no problem that the concave surface 7b of the lens 7 molded thereby bites. On the other hand, the molding surface 3a of the lower mold 3 retreats downward, that is, descends, but the lens 7 follows with its own weight by itself. However, the molding surface 3a of the lower mold 3a descends with a step with respect to the molding surface 9a of the regulating member 9 due to the difference in the linear thermal expansion coefficient between the regulating member 9 and the lower mold 3. The molding surface 3a of the mold 3 is reliably separated from the lens 7 supported by the molding surface 9a of the regulating member 9. Therefore, the molding surface 3a of the lower mold 3 can be prevented from biting the lens 7 even if it is a convex molding surface unlike the case shown in FIG.
[0039]
Note that the molding surface 3a of the lower mold 3 with respect to the height of the molding surface 9a or 4a of the regulating member 9 or the support member 4 is previously lowered as shown in FIGS. 2 (a) and 4 (a). At the time of the heat molding, due to the difference in the coefficient of linear thermal expansion, consideration is given so that the heights of both the molding surfaces 9a or 4a and the molding surface 3a are substantially the same. Thereby, in order to mold the outer portion 7a from the effective diameter of the lens 7 with the molding surface 9a or 4a formed on the regulating member 9 or the support member 4 having a different linear thermal expansion coefficient from that of the lower mold 3, this molding surface 9a Alternatively, the difference in the height of the molding surface 3a of the lower mold 3 that is lower than that of 4a depends on the difference in the linear thermal expansion coefficient between the regulating member 9 and the support 4 and the lower mold 3 at the time of heat molding. It is almost matched by the difference in expansion. As a result, a difference in linear thermal expansion coefficient between the lower mold 3 and the regulating member 9 or the support member 4 results in a step exceeding the allowable range on the lens surfaces formed by both the molding surfaces 9a or 4a and the molding surface 3a. It is possible to prevent the formation of the peripheral edge of the lens 7 from being obstructed during the molding.
[0040]
In addition, the inclination angle of the molding surface 9 a of the regulating member 9 and the molding surface 4 a of the support member 4 is substantially the same as the inclination angle of the peripheral edge of the molding surface 3 a of the lower mold 3. As a result, even if the lower mold 3 and the regulating member 9 and the support member 4 are separate members, the inclination is greatly different at the boundary between the molding surface 4a or 9a and the molding surface 3a, which obstructs the molding. It is possible to prevent the peripheral edge of the lens 7 from being hindered from being formed, and the inclination angle from being extremely different at the boundary portion of the molded lens 7 can be prevented.
[0041]
The regulating member 9 and the supporting member 4 are tungsten carbide, and the upper and lower molds 2 and 3 are tungsten carbide, SiC, Si having a larger linear thermal expansion coefficient than the regulating member 9 and the supporting member 4. _Three N _Four , Al ₂ O _Three , ZrO ₂ Or cermet is preferred.
[0042]
Here, according to the embodiment of the mold apparatus 1 shown in FIGS. 1 and 2, the lens 7 to be molded is a meniscus lens having a concave surface 7b and a convex surface 7c made of a glass material, as described above. Molding is performed with the concave surface 7b facing up. However, the opposite direction may be sufficient, and the lens 7 between the concave surfaces 7b may be sufficient. The lens material 6 is borosilicate glass having a glass transition point of 510 ° C. and a linear thermal expansion coefficient of 100 ° C. to 300 ° C. and 90 × 10. ^-7 A preform material polished at a temperature of 15 ° C. and a center thickness of 4 mm was used.
[0043]
On the other hand, as the upper and lower molds 2 and 3, a tungsten carbide (WC-Co) sintered body subjected to HIP treatment was used. Linear thermal expansion coefficient is 57 × 10 ^-7 / ° C. Further, a sintered body of tungsten carbide (WC—Ti—TaC) was used for the regulating member 9 and the support member 4. Linear thermal expansion coefficient is 47 × 10 ^-7 / ° C.
[0044]
In the state shown in FIG. 2A, the lens material 6 is set between the upper and lower molds 2 and 3 in a nitrogen atmosphere and heated until the temperature of the lens material 6 reaches 580 ° C. When the temperature of the glass material 6 reaches 580 ° C., the viscosity of the lens material 6 is 10 ⁹ It is poise. At this temperature, 150 kg / cm ² Was pressed for 70 seconds. The state of the mold apparatus 1 and the lens material 6 at this time is shown in FIG.
[0045]
Since the molding surface 3 a of the lower mold 3 has a linear thermal expansion coefficient larger than that of the support member 4, the molding surface 3 a has almost the same height as the molding surface 4 a of the support member 4 (within a step of about 2 to 3 μm). Therefore, the lens material 6 can be smoothly deformed to the side of the support member 4 without being obstructed by the step, and the lens material 6 is deformed and molded into the lens 7 until the peripheral edge of the lens material 6 hits the molding surface 4 a of the support member 4.
[0046]
After this, the pressing pressure is 50 kg / cm. ² The lens 7 was cooled to 300 ° C. together with the mold apparatus 1 under reduced pressure. The cooling rate at this time is 0.85 ° C./sec to 1.5 ° C./sec. The state of the mold apparatus 1 and the lens 7 at this time is shown in FIG. During this cooling, the lens 7 and the mold apparatus 1 contract, but since the linear thermal expansion coefficient of the upper mold 2 is larger than that of the regulating member 9, the molding surface 2 a remains upward while the pressurized position is regulated by the regulating member 9. fall back. In addition, since the linear thermal expansion coefficient of the lens 7 is larger than the linear thermal expansion coefficient of the upper mold 2, the thickness is small but the upper surface is somewhat lowered. Thereby, a gap (about 2 to 3 μm) is generated between the lens 7 and the molding surface 2a of the upper mold 2, and the lens 7 and the upper mold 2 are released. Moreover, the linear thermal expansion coefficient of the lower mold 3 is larger than that of the support member 4, the molding surface 3 a is lowered from the molding surface 4 a of the support member 4, and the peripheral portion of the lens 7 is received by the support member 4. Since the state is maintained, the molding surface 3a of the lower mold 3 and the lens 7 are released.
[0047]
After releasing, the removed lens 7 was centered by removing the hatched portion shown in FIG. 3 to obtain a negative meniscus lens. At this time, since the boundary between the lower mold 3 and the support member 4 is removed during the centering process, there is no problem even if a slight level difference is generated at this boundary. When the accuracy of the shape of the obtained negative meniscus lens was examined, it was found to be a good lens 7 with no more than 2 Newtons and no more than 0.5 Axes.
[0048]
Although the molding surface 4 a of the support member 4 has been described without being inclined, it can be set to an inclination angle substantially equal to the inclination angle of the peripheral edge of the lens 7. In the illustrated example, since the inclination angle of the periphery of the lens 7 is 25 degrees, it can be set to about 0 to 25 degrees or slightly larger than 25 degrees.
[0049]
Furthermore, although the case where the material of the upper and lower molds 2, 3 is tungsten carbide (WC-Co) has been described, the linear thermal expansion coefficient is 30 to 95 × 10. ^-7 / ° C is desirable, and other materials satisfying this, for example, SiC, Si _Three N _Four , Al ₂ O _Three , ZrO ₂ , Cermet etc. can be used.
[0050]
Next, the embodiment of the mold apparatus 8 shown in FIG. 4 will be described. The lens 7 to be molded is a meniscus lens having a concave surface 7b and a convex surface 7c made of a glass material, and the concave surface 7b is formed as described. I try to mold it up. However, the opposite direction may be sufficient, and the lens 7 between the concave surfaces 7b may be sufficient. The lens material 6 is borosilicate glass having a glass transition point of 510 ° C. and a linear thermal expansion coefficient of 100 ° C. to 300 ° C. and 90 × 10. ^-7 A preform material polished at a temperature of 15 ° C. and a center thickness of 4 mm was used.
[0051]
On the other hand, as the upper and lower molds 2 and 3, a tungsten carbide (WC-Co) sintered body subjected to HIP treatment was used. Linear thermal expansion coefficient is 57 × 10 ^-7 / ° C. Further, a tungsten carbide (WC—Ti—TaC) sintered body was used for the regulating member 9. Linear thermal expansion coefficient is 47 × 10 ^-7 / ° C.
[0052]
In the state shown in FIG. 4A, the lens material 6 is set between the upper and lower molds 2 and 3 in a nitrogen atmosphere and heated until the temperature of the lens material 6 reaches 580 ° C. When the temperature of the lens material 6 reaches 580 ° C., the viscosity of the lens material 6 is 10 ⁹ It is poise. At this temperature, 150 kg / cm ² Was pressed for 70 seconds. The state of the mold apparatus 1 and the lens material 6 at this time is shown in FIG.
[0053]
Since the molding surface 3 a of the lower mold 3 has a linear thermal expansion coefficient larger than that of the regulating member 9, the molding surface 3 a has almost the same height as the molding surface 9 a of the regulating member 9 (within a step of about 2 to 3 μm). Accordingly, the lens material 6 can be smoothly deformed toward the regulating member 9 without being interrupted by the step, and the lens material 6 is deformed and molded into the lens 7 until the peripheral edge of the lens material 6 hits the molding surface 9 a of the regulating member 9.
[0054]
After this, the pressing pressure is 50 kg / cm. ² The lens 7 was cooled to 300 ° C. together with the mold apparatus 1 under reduced pressure. The cooling rate at this time is 0.85 ° C./sec to 1.5 ° C./sec. The state of the mold apparatus 1 and the lens 7 at this time is shown in FIG. During this cooling, the lens 7 and the mold apparatus 1 contract, but since the linear thermal expansion coefficient of the upper mold 2 is larger than that of the regulating member 9, the molding surface 2 a remains upward while the pressurized position is regulated by the regulating member 9. fall back. In addition, since the linear thermal expansion coefficient of the lens 7 is larger than the linear thermal expansion coefficient of the upper mold 2, the thickness is small but the upper surface is somewhat lowered. Thereby, a gap (about 2 to 3 μm) is generated between the lens 7 and the molding surface 2a of the upper mold 2, and the lens 7 and the upper mold 2 are released. Further, the coefficient of linear thermal expansion of the lower mold 3 is larger than that of the regulating member 9, the molding surface 3 a is lowered from its molding surface 9 a, and the peripheral portion of the lens 7 is received by the molding surface 9 a of the regulating member 9. Therefore, the molding surface 3a of the lower mold 3 and the lens 7 are released from each other.
[0055]
After releasing, the removed lens 7 was centered by removing the hatched portion shown in FIG. 3 to obtain a negative meniscus lens. At this time, since the boundary between the lower mold 3 and the regulating member 9 is removed during the centering process, there is no problem even if a slight level difference is generated at this boundary. When the accuracy of the shape of the obtained negative meniscus lens was examined, it was found to be a good lens 7 with no more than 2 Newtons and no more than 0.5 Axes.
[0056]
Although the inclination angle of the molding surface 9a of the restricting member 9 has been described as being none, it can be set to an inclination angle substantially equal to the inclination angle of the periphery of the lens 7. In the illustrated example, since the inclination angle of the periphery of the lens 7 is 25 degrees, it can be set to about 0 to 25 degrees or slightly larger than 25 degrees.
[0057]
Furthermore, although the case where the material of the upper and lower molds 2, 3 is tungsten carbide (WC-Co) has been described, the linear thermal expansion coefficient is 30 to 95 × 10. ^-7 / ° C is desirable, and other materials satisfying this, for example, SiC, Si _Three N _Four , Al ₂ O _Three , ZrO ₂ , Cermet etc. can be used.
[0058]
【The invention's effect】
According to the lens molding method of one aspect of the present invention, a lens material is heated and pressurized with a mold to form a lens having a desired shape, and then cooled after molding. During this cooling, a first molding surface that forms a portion including the effective diameter range of the lens in the mold and a second molding surface that molds the outer portion thereof cause a step due to the difference in coefficient of linear thermal expansion. Moves to the side opposite the lens from the second molding surface, that is, moves backward. For this reason, the first molding surface is retracted from the lens in contact with the second molding surface and separated from the lens. As a result, even if the first molding surface is a convex molding surface and sinking to the concave surface occurs during cooling of the molded lens, the lens is convexly molded as in the prior art by separating the mold and the lens. It is possible to prevent such a thing from eating. In addition, the first and second molding surfaces cooperate to satisfy the molding of the entire surface on one side including the outer portion of the effective diameter of the lens, while the portion including the effective diameter range of the lens is formed by one first molding surface. Since molding is performed, there is an advantage that adverse effects caused by splitting the molding surface into two parts can be avoided in molding within the effective diameter range in which the lens is practically used.
[0059]
According to the lens manufacturing method of another aspect of the present invention, when a lens material is inserted between upper and lower molds, at least one of which is heated, and the lens material is heated and pressurized to form a lens, a regulating member By restricting the pressurization position of the upper and lower molds, a lens having a desired shape can be molded and cooled after molding. At the time of this cooling, at least one of the upper and lower molds retreats its molding surface in a state where the pressure position is regulated by the regulating member due to the difference in the coefficient of linear thermal expansion with the regulating member. As a result, the upper and lower molds are opened and separated from the lens. In particular, this separation is surely performed between the upper mold and the lens that does not follow due to gravity and is easily separated. As a result, the molding surface away from the lens is a convex molding surface, and even if sinks to the concave surface occur when the molded lens cools, it prevents it from biting into the convex molding surface as before. can do. Moreover, there is an advantage that the molding surface for separation from the lens need not be divided into a plurality of parts.
[0060]
The regulating member or another supporting member is used in the process of separating the mold and the lens along with cooling, and the lower surface of the lens end is supported by the regulating member or the supporting member from the difference in linear thermal expansion coefficient. According to the further configuration, which is the process of separating the mold and the lens,
When the molding surface of the lower mold moves backward with the pressure position regulated by the regulation member, the regulation member or the support member supports the lower surface of the end of the lens from the difference in linear thermal expansion coefficient. Since it does not follow the retreat of the molding surface, the lower mold and the lens can be separated. The restriction member or the support member only needs to support the end of the lens, and the effective diameter range of the lens can be avoided, so that the support by the restriction member does not adversely affect the lens. Such separation can be achieved regardless of the orientation of the pair of molds.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a mold apparatus showing an example according to an embodiment of the present invention.
2 shows a lens molding process by the apparatus of FIG. 1, in which (a) is a cross-sectional view of a state in which a lens material is set, (b) is a cross-sectional view during heat molding, and (c) is after molding. Sectional drawing at the time of cooling.
FIG. 3 is an explanatory diagram when performing the centering processing of the lens obtained by the molding process of FIG. 2;
FIGS. 4A and 4B show a lens molding process using another mold apparatus, wherein FIG. 4A is a sectional view of a lens material set, FIG. 4B is a sectional view during heat molding, and FIG. 4C is molding. Sectional drawing at the time of subsequent cooling.
[Explanation of symbols]
1 Mold equipment
2 Upper mold
3 Lower mold
4 Support members
9 Regulatory members
2a, 3a, 4a, 9a Molded surface
6 Lens material
7 Lens
7a Effective diameter outer part
7b Concave
7c Convex surface

Claims

金型によりレンズ素材を加熱、加圧して所望の形状のレンズに成形する工程と、
成形後の冷却に伴い、金型におけるレンズの有効径範囲を成形する第１成形部と、その外側部分を成形する第２成形面とに、線熱膨張係数の差から、第１成形面が第２成形面よりも後退する段差を生じさせて金型の第１成形面と前記レンズとを分離する工程と、
を備えたことを特徴とするレンズの製造方法。Heating and pressing the lens material with a mold to form a lens of a desired shape;
Due to the difference in coefficient of linear thermal expansion, the first molding surface is formed between the first molding part that molds the effective diameter range of the lens in the mold and the second molding surface that molds the outer part thereof with cooling after molding. Separating the first molding surface of the mold and the lens by causing a step which is retracted from the second molding surface;
A method for producing a lens, comprising:

上下金型間にレンズ素材を挿入する工程と、
前記上下金型の少なくとも一方の金型を加熱し、双方間で前記レンズ素材を規制部材による加圧規制位置まで加圧することにより、所望の形状のレンズに成形する工程と、
成形後の冷却に伴い、前記規制部材と上下金型の少なくとも一方の金型との線熱膨張係数の差から、上下金型の少なくとも一方の金型とレンズとを分離する工程と、
を備えたことを特徴とするレンズの製造方法。Inserting a lens material between the upper and lower molds;
Heating at least one mold of the upper and lower molds and pressurizing the lens material to a pressure regulating position by a regulating member between the two, thereby forming a lens having a desired shape;
With the cooling after molding, the step of separating at least one mold of the upper and lower molds and the lens from the difference in linear thermal expansion coefficient between the restriction member and at least one of the upper and lower molds;
A method for producing a lens, comprising:

冷却に伴い金型とレンズを分離する工程は、線熱膨張係数の差からレンズの端部下面を規制部材またはそれとは別の支持部材で支持し、下金型とレンズとを分離する工程であることを特徴とする請求項２に記載のレンズの製造方法。 The process of separating the mold and the lens along with cooling is a process of separating the lower mold and the lens by supporting the lower surface of the end of the lens with a regulating member or another support member from the difference in linear thermal expansion coefficient. The method for manufacturing a lens according to claim 2, wherein the lens is provided.