JP3847805B2

JP3847805B2 - Mold for optical element molding

Info

Publication number: JP3847805B2
Application number: JP28991794A
Authority: JP
Inventors: 靖行中居; 鉄夫桑原; 直宮崎; 正樹大森
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1994-11-24
Filing date: 1994-11-24
Publication date: 2006-11-22
Anticipated expiration: 2021-11-22
Also published as: JPH08151217A

Description

【０００１】
【産業上の利用分野】
本発明は、レンズ、プリズム等のガラスよりなる光学素子をガラス素材のプレス成形により製造するのに使用される型に関する。
【０００２】
【従来の技術】
研磨工程を必要としないでガラス素材のプレス成形によってレンズを製造する技術は、従来のレンズの製造において必要とされた複雑な工程をなくし、簡単かつ安価にレンズを製造することを可能とし、近来レンズのみならずプリズム、その他のガラスよりなる光学素子の製造に使用されるようになってきた。
【０００３】
このようなガラスの光学素子のプレス成形に使用される型材に要求される性質としては、硬さ、耐熱性、離型性、鏡面加工性等に優れていることが挙げられる。従来、この種の型材として、金属、セラミックス及びそれらをコーティングした材料等数多くの提案がされている。いくつかの例を挙げるならば、特開昭４９−５１１１２号公報には１３Ｃｒマルテンサイト鋼が、特開昭５２−４５６１３号公報にはＳｉＣ及びＳｉ₃ Ｎ₄ が、特開昭６０−２４６２３０号公報には超硬合金に貴金属をコーティングした材料が、また特開昭６１−１８３１３４号公報、特開昭６１−２８１０３０号公報、特開平１−３０１８６４号公報にはダイヤモンド薄膜またはダイヤモンド状炭素膜をコーティングした材料が、特開昭６４−８３５２９号公報には硬質炭素膜をコーティングした材料が提案されている。
【０００４】
【発明が解決しようとする課題】
しかし、１３Ｃｒマルテンサイト鋼は酸化し易く、更に高温下でＦｅがガラス中に拡散してガラスが着色するという欠点を持つ。また、ＳｉＣ，Ｓｉ₃ Ｎ₄ は一般的に酸化されにくいとされるが、高温下ではやはり酸化が起こり、表面にＳｉＯ₂ の膜が形成されるためガラスと融着を起こす。一方、貴金属をコーティングした材料は融着は起こしにくいが、極めて柔らかいため傷がつき易くまた変形し易い欠点を持つ。また、ＣＨ₃ ，ＣＨ₂ を含む炭化水素膜や黒鉛を蒸着したカーボン膜を超硬合金やセラミックス製の型母材上に成膜した型を成形に用いた場合、数ショット程度で膜が消耗してしまう。一方、硬質炭素膜は離型性に優れ、ガラスとの融着を起こさず、かつ高硬度で耐消耗性があり、型材としては良好なものの一つであるが、硬質炭素膜でも離型し難い場合がある。
【０００５】
第１の例として、プレス成形開始時から２０ショット程度までは硬質炭素膜が強い結合状態を維持し、グラファイトライクな部分がほとんどないため、離型し難い状態が続くという問題がある。
【０００６】
第２の例として、凸レンズ形状の場合には容易に離型する温度であっても、ある形状のメニスカスレンズでは離型しない。このような現象は次のような理由で起こると考えられる。型とレンズの離型現象は、それぞれ型、ガラスの熱膨張率差が起因していると考えられる。つまり、ガラスレンズのプレス成形後プロセス条件に従い徐冷する際、型、ガラスそれぞれの熱膨張率により収縮量が異るため型−ガラス界面に大きな剪断応力が働き、離型すると考えられる。しかし、レンズ形状が異なると型−ガラス界面に働く剪断応力が温度により大きく異なるため、ものによっては成形温度より３００℃以上低くしなければ離型しない場合がある。このように離型性が悪い、つまり離型温度が低いほど成形の１サイクルに時間がかかり、単位時間に作製できるレンズ数が制限され、コストアップにつながる。
【０００７】
【課題を解決するための手段及び作用】
本発明は、従来の離型膜の一つである硬質炭素膜上に、更に、離型性の良い炭化水素膜を被覆することにより、上述の問題を解決するものである。
【０００８】
すなわち、本発明は、ガラスよりなる光学素子のプレス成形に用いる成形用型において、型母材上に水素濃度が５〜３０ａｔｏｍｉｃ％の硬質炭素膜、及び膜厚が５ｎｍ以上５０ｎｍ未満で水素濃度が４０〜７０ａｔｏｍｉｃ％の炭化水素膜からなる成形表面をこの順に有することを特徴とする光学素子成形用型である。
【０００９】
以下にその作用を示す。
【００１０】
上記課題を解決するひとつの手段として、成形時の型とガラスの密着性を下げることが考えられる。従来の離型膜の一つである硬質炭素膜は結合性が高く、高温に長時間晒された場合に徐々に炭化し始めるのに対し、炭化水素膜は硬質炭素膜と比べ結合性が低く、高温になると炭化がすぐに促進され、カーボン特有の離型効果をもたらす。このように離型性の良い炭化水素膜を成形面に成膜することにより、上記に示したようなメニスカスレンズのようななかなか離型しない形状であっても離型が容易となる。また、硬質炭素膜が形成表面に成膜された型は、成形開始時にはまだ硬質炭素膜の炭化が始まっていないため、離型温度が低くなり成形の１サイクル当りにかかる時間が長くなる。しかし、炭化水素膜を被覆した型の場合、第１ショット目から高温での離型が可能となる。
【００１１】
【実施例】
［実施例１］（ＴｉＮ／ｉ−Ｃミキシング層、ＣＶＤ炭素膜）
図１及び図２は本発明に係る光学素子成形用型の一つの実施態様を示すものである。図１中１は超硬合金を用いた型母材、２はＴｉＮを用いた硬質物質からなる中間層、３は硬質炭素膜、４は炭化水素膜からなるガラス素材を成形する成形表面であり、５はガラス素材である。図２に示すように型の間に置かれたガラス素材５をプレス成形することによってレンズ等の光学素子６が形成される。
【００１２】
次に、本発明の光学素子成形用型について詳細に説明する。型母材としてＷＣ−Ｔｉ系超硬合金を所定の形状に加工した後、イオンプレーティングによりＴｉＮ膜を形成した後、成形面をＲｍａｘ．＝０．０２μｍに鏡面研磨したものを用いた。この型を良く洗浄したのち、図３に示すＩＢＤ（ＩｏｎＢｅａｍＤｅｐｏｓｉｔｉｏｎ）装置に設置した。図３中７は真空槽、８はイオンビーム装置、９はイオン化室、１０はガス導入口、１１はイオンビーム引き出しグリット、１２はイオンビーム、１３は型母材、１４は基板ホルダー及びヒーター、１５は排気口を示す。まず、ガス導入口１０よりアルゴンガス３５ｓｃｃｍをイオン化室に導入しイオン化した後、イオンビーム引き出しグリットに５００Ｖの電圧を印加してイオンビームを引き出し、型母材に５分間照射して成形表面の清浄化を行った。次に、ＣＨ₄ ：１５ｓｃｃｍ，Ｈ₂ ：３０ｓｃｃｍをイオン化室に導入してガス圧３．５×１０^-2Ｐａとし、加速電圧１０ｋＶでイオンビームを引き出し、成形面に照射して３５ｎｍのミキシング層を形成した。同条件で作製した分析サンプルのミキシング層をＸＰＳ（ＸｒａｙＰｈｏｔｏｅｌｅｃｔｒｏｎ
ｓｐｅｃｔｒｏｓｃｏｐｙ）により深さ方向分析した結果を図４に示す。図４により明らかなようにミキシング層の厚さは３５ｎｍで、炭素Ｃの濃度は表面側から型母材側に向かって減少している。一方、Ｔｉ及びＮ原子の濃度は表面側から型母材側に向かって増加している。以上の方法によりミキシング層を持つ硬質炭素膜を形成した。
【００１３】
次に、硬質炭素膜層上の炭化水素膜の形成方法について述べる。図５は炭化水素膜を成膜する薄膜堆積装置の概略構成を示す模式図である。図５中１６は真空槽、１７は排気口、１８はガス導入口、１９は型母材を保持するためのドーム状ホルダー、２０は型母材を加熱するためのヒーター、２１は被覆膜厚を測定するための水晶モニタ、２２は高周波印加用アンテナである。なお、２３は上記ホルダーに保持されている型母材である。
【００１４】
良く洗浄された硬質炭素膜及びＴｉＮを成膜した型母材をドーム状ホルダーに取り付け、ヒーター２０で３００℃に加熱し、排気口１７より排気を行い真空槽１６内を１×１０^-3Ｐａ以下になるまで減圧した後に、ガス導入口１８からアルゴンガスを５×１０^-2Ｐａとなるまで導入し、高周波印加用アンテナ２２に３００Ｗの高周波を印加して高周波放電を行い型母材２３のプラズマクリーニングを行った。その後、アルゴンガスの導入を停止し１×１０^-3Ｐａの真空度に戻してガス導入口１８からＣＨ₄ ガスを１×１０^-1Ｐａになるまで導入した。そして、高周波印加用アンテナ２２に５００Ｗの高周波を印加して高周波放電を行い、約３０ｎｍ厚の被覆膜を形成した。なお、本発明による離型効果が現れるためには膜厚が最低５ｎｍ必要であり、また５０ｎｍ以上では光学素子の外観に不良が発生する場合があった。
【００１５】
ここで形成された炭化水素膜の赤外吸収分光分析（ＩＲ）の結果を図６に示す。図６に示すように該炭化水素膜はＣＨ₃ ，ＣＨ₂ の吸収が見られるのに対し、図８に示す硬質炭素膜のＩＲの結果から、図６の炭化水素膜に見られるＣＨ₃ 、ＣＨ₂ の吸収がほとんど確認できなかった。また、該炭化水素膜の水素濃度は４０〜７０ａｔｏｍｉｃ％であったことからも、炭化水素膜の水素の多くはＣＨ₃ ＣＨ₂ 等の基の状態で結合していると考えられる。一方、硬質炭素膜の水素濃度は５〜３０ａｔｏｍｉｃ％であるが、上記のようにＣＨ₃ ，ＣＨ₂ の吸収が少ないことから、膜中水素はダングリングボンドの端に結合していると考えられる。
【００１６】
次に、本発明による光学素子成形用型によってプレス成形を行った例を示す。図７は成形装置であり、図中５１は真空槽本体、５２はそのフタ、５３は光学素子を成形するための上型、５４はその下型、５５は上型を押えるための上型押え、５６は胴型、５７は型ホルダー、５８はヒーター、５９は下型を突き上げる突き上げ棒、６０は該突き上げ棒を作動するエアシリンダ、６１は油回転ポンプ、６２、６３、６４はバルブ、６５は不活性ガス流入パイプ、６６はバルブ、６７はリークバルブ、６８はバルブ、６９は温度センサ７０は水冷パイプ、７１は真空槽を支持する台を示す。レンズを製作する工程を次に述べる。クラウン系光学ガラス（ＳＫ１２）を所定の両に調整したゴブを型のキャビティー内に置き、これを装置内に設置する。そしてガラス素材を投入した型を装置内に設置してから真空槽５１のフタ５２を閉じ、水冷パイプ７０に水を流し、ヒーター５８に電流を流す。このとき窒素ガス用バルブ６６及び６８は閉じ、排気系バルブ６２、６３、６４も閉じている。なお、油回転ポンプ６１は常に回転している。バルブ６２を開け排気を開始してから１Ｐａ以下になったらバルブ６２を閉じ、バルブ６６を開いて窒素ガスをボンベより真空槽内に導入する。所定の温度になったらエアシリンダ６０を作動させて１．５Ｐａの圧力で１分間加圧する。圧力を解除した後、冷却速度−５℃／ｍｉｎで転移点以下になるまで冷却し、その後は−２０℃／ｍｉｎ以上の速度で冷却を行い２００℃以下に下がったらバルブ６６を閉じ、リークバルブ６３を開いて真空槽５１内に空気を導入する。それからフタ５２を開け上型押えをはずして成形物を取り出す。上記のようにしてクラウン光学ガラス（軟化点Ｓｐ＝６７２℃、転移点Ｔｇ＝５５０℃）を使用して図４に示すレンズを用いた。
【００１７】
本発明による光学素子成形用型を用いることによりプレス成形の第１ショット目の離型温度（プレス成形後の徐冷時に、光学素子が型から剥れる温度）が従来の硬質炭素膜が成形表面である型と比較して７０℃上昇した（本発明による型の離型温度：５３０℃）。プレス成形第１ショットの離型温度の上昇が本発明により可能となったため、成形のタクト短縮が可能となった。
【００１８】
以上のようなプレス行程により３０００回成形した後の型部材の成形面及び成形された光学素子の表面粗さ、並びに型部材と成形された光学素子との離型性は良好であった。特に、型部材の成形面について光学顕微鏡、走査電子顕微鏡（ＳＥＭ）で観察しても傷やクラック等の欠陥やガラス成分の反応析出物、ガラスの融着はなかった。
【００１９】
また、光学素子形状が両凹レンズ、凸メニスカスレンズ、凹メニスカスレンズとなる各光学素子成形用型を上記と同等の方法で作製した結果、従来の硬質炭素膜より離型性の良いことが確認された。特に図９に示すような凸メニスカスレンズの場合、従来の硬質炭素膜の場合、３５０℃まで型から光学素子が離型しない場合があったが、本発明の光学素子成形用型を使用した場合、安定して５００℃以上での離型が可能となった。上記各種形状の連続成形も実施例１前半に記した両凸レンズ同様、３０００回成形を行っても全く問題はなかった。
【００２０】
また、本発明型でランタン系ガラス（ＬａＫ１２）やＳＦ系ガラス（ＳＦ８）を成形したがクラウン系ガラス（ＳＫ１２）と同様３０００回成形を行っても全く問題はなく、優れた離型効果が確認された。
【００２１】
［実施例２］（ＴｉＮ／ｉ−Ｃミキシング層、イオンビーム炭素膜）
本発明では型母材、中間層であるＴｉＮ，硬質炭素膜は上記実施例１と同等の方法で作製したので、成形表面である炭化水素膜の作製方法について詳細に述べる。実施例１では高周波を用い、ＣＨ₄ プラズマを発生させ炭化水素膜の成膜を行ったが、本発明ではイオンビームを用い炭化水素膜を型母材状に形成したものである。成膜装置は実施例１に示した硬質炭素膜を形成したＩＢＤ装置を用いることができる。そのため本発明では硬質炭素膜形成と炭化水素膜形成が連続してできる。実施例１と同様にＷＣ−Ｔｉ系超硬合金状にＴｉＮ及び硬質炭素膜を成膜した後、図３に示す硬質炭素膜を成膜した装置中で連続して炭化水素膜を成膜した。
【００２２】
以下に炭化水素の成膜方法について述べる。まず、ＣＨ₄ ：２０ｓｃｃｍをイオン化室に導入してガス圧４．０×１０^-2Ｐａとし、ＣＨ₄ ガスをイオン化した後、イオンビーム引き出しグリットに２００Ｖの電圧を印加し、イオンビームを引き出し、基板ホルダーに−１００Ｖのバイアス電圧をかけ硬質炭素膜上に炭化水素膜を約３０ｎｍ成膜した。次に、本発明による光学素子成形用型によってプレス成形を実施例１と同様に行った。その結果、本発明による光学素子成形用型を用いることによりプレス成形の第１ショット目の離型温度が従来の硬質炭素膜が成形表面である型と比較して５０℃上昇した。（本発明による型の離型温度：５２０℃）プレス成形第１ショット目の離型温度の上昇が本発明により可能となったため、成形のタクト短縮が可能となった。また、３０００回成形した後の型部材の成形面及び成形された光学素子の表面粗さ、並びに型部材と成形された光学素子との離型性は良好であった。特に、型部材の成形面について光学顕微鏡、走査電子顕微鏡（ＳＥＭ）で観察しても傷やクラック等の欠陥やガラス成分の反応析出物、ガラスの融着はなかった。
【００２３】
また、光学素子形状が両凹レンズ、凸メニスカスレンズ、凹メニスカスレンズとなる各光学素子成形用型を上記と同等の方法で作製した結果、従来の硬質炭素膜より離型性の良いことが確認された。特に図９に示すような凸メニスカスレンズの場合、従来の硬質炭素膜の場合、３５０℃まで型から光学素子が離型しない場合があったが、本発明の光学素子成形用型を使用した場合、安定して５００℃以上での離型が可能となった。上記各種形状の連続成形も実施例１前半に記した両凸レンズ同様、３０００回成形を行っても全く問題はなかった。
【００２４】
また、本発明型でランタン系ガラス（ＬａＫ１２）やＳＦ系ガラス（ＳＦ８）を成形したがクラウン系ガラス（ＳＫ１２）と同様３０００回成形を行っても全く問題はなく、優れた離型効果が確認された。
【００２５】
［実施例３］（ＣＶＤＳｉＣ／ｉ−Ｃミキシング層、ＣＶＤ炭素膜）
本発明では型母材として常圧焼結ＳｉＣを用い、これを所定の形状に加工した後、硬質物質からなる中間層形成、及び表面の緻密化のため型母材ＳｉＣ上にＣＶＤによるＳｉＣ膜を成膜し、成形面をＲｍａｘ．＝０．０２に鏡面研磨したものを用いた。この型を良く洗浄した後、実施例１と同様図３に示すＩＢＤ装置に設置し、硬質炭素膜を実施例１と同条件でミキシング層３５ｎｍとなるように成膜を行った。次に、炭化水素膜を実施例１と同装置、同条件で３０ｎｍの膜厚で成膜を行った。
【００２６】
次に、本発明による光学素子成形用型によってプレス成形を実施例１と同様に行った。その結果、本発明による光学素子成形用型を用いることによりプレス成形の第１ショット目の離型温度が従来の硬質炭素膜が成形表面である型と比較して６０℃上昇した。（本発明による型の離型温度：５３０℃）プレス成形第１ショット目の離型温度の上昇が本発明により可能となったため、成形のタクト短縮が可能となった。また、３０００回成形した後の成形面及び成形された光学素子の表面粗さ、並びに型部材と成形された光学素子との離型性は良好であった。特に、型部材の成形面について光学顕微鏡、走査電子顕微鏡（ＳＥＭ）で観察しても傷やクラック等の欠陥やガラス成分の反応析出物、ガラスの融着はなかった。
【００２７】
また、光学素子形状が両凹レンズ、凸メニスカスレンズ、凹メニスカスレンズとなる各光学素子成形用型を上記と同等の方法で作製した結果、従来の硬質炭素膜より離型性の良いことが確認された。特に図９に示すような凸メニスカスレンズの場合、従来の硬質炭素膜の場合、３５０℃まで型から光学素子が離型しない場合があったが、本発明の光学素子成形用型を使用した場合、安定して５００℃以上での離型が可能となった。上記各種形状の連続成形も実施例１前半に記した両凸レンズ同様、３０００回成形を行っても全く問題はなかった。
【００２８】
また、本発明型でランタン系ガラス（ＬａＫ１２）やＳＦ系ガラス（ＳＦ８）を成形したがクラウン系ガラス（ＳＫ１２）と同様３０００回成形を行っても全く問題はなく、優れた離型効果が確認された。
【００２９】
［実施例４］（ダイヤモンド／ｉ−Ｃミキシング層、ＣＶＤ炭素膜）
型母材としてＷＣ−Ｔｉ系超硬合金を所定の形状に加工した後、プラズマＣＶＤによりダイヤモンド膜を成膜した後、成形面をＲｍａｘ．＝０．０２μｍに鏡面研磨したものを用いた。この型を良く洗浄した後、実施例１と同様図３に示すＩＢＤ装置に設置し、硬質炭素膜を実施例１と同条件でミキシング層３５ｎｍとなるように成膜を行った。次に、炭化水素膜を実施例１と同装置、同条件で３０ｎｍの膜厚で成膜を行った。
【００３０】
次に、本発明による光学素子成形用型によってプレス成形を実施例１と同様に行った。その結果、本発明による光学素子成形用型を用いることによりプレス成形の第１ショット目の離型温度が従来の硬質炭素膜が成形表面である型と比較して６０℃上昇した。（本発明による型の離型温度：５００℃）プレス成形第１ショット目の離型温度の上昇が本発明により可能となったため、成形のタクト短縮が可能となった。また、３０００回成形した後の型部材の成形面及び成形された光学素子の表面粗さ、並びに型部材と成形された光学素子との離型性は良好であった。特に、型部材の成形面について光学顕微鏡、走査電子顕微鏡（ＳＥＭ）で観察しても傷やクラック等の欠陥やガラス成分の反応析出物、ガラスの融着はなかった。
【００３１】
また、光学素子形状が両凹レンズ、凸メニスカスレンズ、凹メニスカスレンズとなる各光学素子成形用型を上記と同等の方法で作製した結果、従来の硬質炭素膜より離型性の良いことが確認された。特に図９に示すような凸メニスカスレンズの場合、従来の硬質炭素膜の場合、３５０℃まで型から光学素子が離型しない場合があったが、本発明の光学素子成形用型を使用した場合、安定して５００℃以上での離型が可能となった。上記各種形状の連続成形も実施例１前半に記した両凸レンズ同様、３０００回成形を行っても全く問題はなかった。
【００３２】
また、本発明型でランタン系ガラス（ＬａＫ１２）やＳＦ系ガラス（ＳＦ８）を成形したがクラウン系ガラス（ＳＫ１２）と同様３０００回成形を行っても全く問題はなく、優れた離型効果が確認された。
【００３３】
［実施例５］（ＣＶＤＳｉＮ／ｉ−Ｃミキシング層、ＣＶＤ炭素膜）
型母材としてＳｉ₃ Ｎ₄ セラミックスを所定の形状に加工した後、プラズマＣＶＤによりダイヤモンド膜を成膜した後、成形面をＲｍａｘ．＝０．０２に鏡面研磨したものを用いた。この型を良く洗浄したのち、実施例１と同様図３に示すＩＢＤ装置に設置し、硬質炭素膜を実施例１と同条件でミキシング層３５ｎｍとなるように成膜を行った。次に、炭化水素膜を実施例１と同装置、同条件で３０ｎｍの膜厚で成膜を行った。
【００３４】
次に、この光学素子成形用型によってプレス成形を実施例１と同様に行った。その結果、本発明による光学素子成形用型を用いることによりプレス成形の第１ショット目の離型温度が従来の硬質炭素膜が成形表面である型と比較して６０℃上昇した。（本発明による型の離型温度：５１０℃）プレス成形第１ショット目の離型温度の上昇が本発明により可能となったため、成形のタクト短縮が可能となった。また、３０００回成形した後の型部材の成形面及び成形された光学素子の表面粗さ、並びに型部材と成形された光学素子との離型性は良好であった。特に、型部材の成形面について光学顕微鏡、走査電子顕微鏡（ＳＥＭ）で観察しても傷やクラック等の欠陥やガラス成分の反応析出物、ガラスの融着はなかった。
【００３５】
また、光学素子形状が両凹レンズ、凸メニスカスレンズ、凹メニスカスレンズとなる各光学素子成形用型を上記と同等の方法で作製した結果、従来の硬質炭素膜より離型性の良いことが確認された。特に図９に示すような凸メニスカスレンズの場合、従来の硬質炭素膜の場合、３５０℃まで型から光学素子が離型しない場合があったが、本発明の光学素子成形用型を使用した場合、安定して５００℃以上での離型が可能となった。上記各種形状の連続成形も実施例１前半に記した両凸レンズ同様、３０００回成形を行っても全く問題はなかった。
【００３６】
また、本発明型でランタン系ガラス（ＬａＫ１２）やＳＦ系ガラス（ＳＦ８）を成形したがクラウン系ガラス（ＳＫ１２）と同様３０００回成形を行っても全く問題はなく、良離型効果が確認された。
【００３７】
以下実施例６〜７９については実施例１〜５を含め表１〜４にまとめる。
【００３８】
なお、中間層材料であるＴａＮ、ＺｒＮ，ＨｆＮ、ＴｉＣ、ＴａＣ、ＺｒＣ、ＨｆＣ、ＴｉＣＮ、ＴａＣＮ、ＺｒＣＮ及びＨｆＣＮの膜は、イオンプレーティング及びスパッタリングにより成膜した。
【００３９】
また、型母材材料であるサーメットはＴｉＮ−ＴｉＣ系のものを、ステンレスは高膨張鋼材である日立金属製ＹＨＤ５０ＦＭ（α＝１７×１０^-6）等を用いた。
【００４０】
【表１】

【００４１】
【表２】

【００４２】
【表３】

【００４３】
【表４】

【００４４】
【発明の効果】
以上説明したように本発明の光学素子成形用型によれば、型母材上に成膜した硬質炭素膜上に炭化水素膜を設けたことにより、以下の諸問題の解決に成功した。
【００４５】
第一に光学素子成形初期ショットから約２０ショットまでの間に生じる離型性が悪い状態を、成形初期ショットから良好な離型状態にすることができた。これにより成形サイクルタイムを従来より大幅に短くすることができ、時間当りの生産数を向上でき、また離型性が悪い状態に発生する型の破損を極力押えることが可能となった。
【００４６】
第二に従来の硬質炭素膜でも離型し難い凸メニスカスレンズ形状であっても、本発明による光学素子成形用型を用いることにより、離型性が向上した。これにより従来プレス成形終了後３００℃まで冷却が必要であって形状でも、５３０℃での離型が可能となり成形サイクルタイムの飛躍的な短縮を可能にした。
【００４７】
本発明により得られた光学素子成形用型を用いることにより、生産性の向上とコストダウンを実現することが可能となった。
【図面の簡単な説明】
【図１】本発明に係る光学素子成形用型の一例を示す断面図で、プレス成形前の状態を示す。
【図２】本発明に係る光学素子成形用型の一例を示す断面図で、プレス成形後の状態を示す。
【図３】本発明の実施例で用いるイオンビーム成膜装置を示す概略図である。
【図４】本発明に係る光学素子成形用型の中間層と硬質炭素膜の間に生成したミキシング層の光電分光分析（ＸＰＳ）によるデプスプロファイルを示す図である。
【図５】本発明の実施例で用いる高周波放電タイプ成膜装置を示す概略図である。
【図６】本発明に係る成膜表面に高周波放電方式で成膜した炭化水素膜の赤外分光分析（ＦＴ−ＩＲ）の結果を示すグラフである。
【図７】本発明に係る光学素子成形用型を使用するレンズの成形装置を示す断面図で非連続である。
【図８】本発明に係る成形表面にイオンビーム成膜装置で成膜した硬質炭素膜の赤外分光分析（ＦＴ−ＩＲ）の結果を示すグラフである。
【図９】本発明に係る光学素子成形用型の一例を示す断面図で、プレス成形前の状態を示す。
【符号の説明】
１型母材
２中間層
３硬質炭素膜
４炭化水素膜
５ガラス素材
６光学素子
７真空層
８イオンビーム装置
９イオン化室
１０ガス導入口
１１イオンビーム引き出しグリット
１２イオンビーム
１３型母材
１４基板ホルダー及びヒーター
１５排気口
１６真空槽
１７排気口
１８ガス導入口
１９ドーム状ホルダー
２０ヒーター
２１水晶モニタ
２２高周波印加用アンテナ
２３型母材
５１真空槽
５２真空槽のフタ
５３上型
５４下型
５５上型押え
５６胴型
５７型ホルダー
５８ヒーター
５９下型を突き上げる突き上げ棒
６０エアシリンダー
６１油回転ポンプ
６２、６３、６４バルブ
６５不活性ガス導入バルブ
６６バルブ
６７リークパイプ
６８バルブ
６９温度センサ
７０水冷パイプ
７１真空槽を支持する台[0001]
[Industrial application fields]
The present invention relates to a mold used for manufacturing an optical element made of glass such as a lens and a prism by press molding a glass material.
[0002]
[Prior art]
The technology for manufacturing lenses by press molding of glass materials without the need for polishing processes eliminates the complicated processes required in conventional lens manufacturing, making it possible to manufacture lenses easily and inexpensively. Not only lenses but also prisms and other optical elements made of glass have come to be used.
[0003]
Properties required for a mold material used for press molding of such a glass optical element include excellent hardness, heat resistance, releasability, and mirror surface workability. Conventionally, as this type of mold material, many proposals such as metals, ceramics and materials coated with them have been made. Some examples include 13Cr martensitic steel in JP-A-49-51112, SiC and Si ₃ N ₄ in JP-A-52-45613, and JP-A-60-246230. Japanese Laid-Open Patent Publication No. 6-183134, Japanese Laid-Open Patent Publication No. 61-281030, and Japanese Laid-Open Patent Publication No. 1-301864 disclose a diamond thin film or a diamond-like carbon film. JP-A 64-83529 proposes a material coated with a hard carbon film.
[0004]
[Problems to be solved by the invention]
However, 13Cr martensitic steel is easy to oxidize, and further has the disadvantage that Fe diffuses into the glass at a high temperature and the glass is colored. In addition, SiC and Si ₃ N ₄ are generally considered to be hardly oxidized, but oxidation also occurs at a high temperature, and a SiO ₂ film is formed on the surface, which causes fusion with glass. On the other hand, a material coated with a noble metal is difficult to cause fusion, but has a drawback that it is very soft and easily damaged and easily deformed. In addition, when a mold in which a hydrocarbon film containing CH ₃ or CH ₂ or a carbon film deposited with graphite is deposited on a cemented carbide or ceramic mold base material is used for molding, the film will be consumed in several shots. Resulting in. On the other hand, a hard carbon film is excellent in releasability, does not cause fusion with glass, has high hardness and wear resistance, and is a good mold material. It may be difficult.
[0005]
As a first example, there is a problem that the hard carbon film maintains a strong bonding state from the start of press molding to about 20 shots, and there is almost no graphite-like portion, so that it remains difficult to release.
[0006]
As a second example, in the case of a convex lens shape, even if the temperature is easily released, a meniscus lens having a certain shape does not release. Such a phenomenon is considered to occur for the following reason. It is considered that the mold and lens release phenomenon is caused by the difference in thermal expansion coefficient between the mold and glass. That is, when the glass lens is slowly cooled according to the post-press molding process conditions, the amount of shrinkage varies depending on the coefficient of thermal expansion of each of the mold and the glass, so that a large shearing stress acts on the mold-glass interface and the mold is released. However, if the lens shape is different, the shear stress acting on the mold-glass interface varies greatly depending on the temperature. Therefore, depending on the object, the mold may not be released unless the temperature is lowered by 300 ° C. or more. Thus, the lower the mold release property, that is, the lower the mold release temperature, the longer one cycle of molding takes, and the number of lenses that can be manufactured per unit time is limited, leading to an increase in cost.
[0007]
[Means and Actions for Solving the Problems]
The present invention solves the above-mentioned problems by coating a hard carbon film, which is one of conventional mold release films, with a hydrocarbon film having a good mold release property.
[0008]
That is, the present invention provides a mold for use in press molding of the optical element made of glass, the mold base material on the hydrogen concentration 5～30Atomic% of the hard carbon film, and the film thickness is the hydrogen concentration of less than 50nm or 5nm An optical element molding die having a molding surface made of a hydrocarbon film of 40 to 70 atomic% in this order.
[0009]
The action is shown below.
[0010]
As one means for solving the above problems, it is conceivable to lower the adhesion between the mold and the glass during molding. A hard carbon film, which is one of the conventional release films, has high bonding properties, and gradually begins to carbonize when exposed to high temperatures for a long time, whereas hydrocarbon films have lower bonding properties than hard carbon films. When the temperature is high, carbonization is immediately promoted, resulting in a release effect peculiar to carbon. By forming a hydrocarbon film having good releasability on the molding surface in this way, it is easy to release even a shape that does not release easily such as the meniscus lens described above. Also, in the mold in which the hard carbon film is formed on the forming surface, the carbonization of the hard carbon film has not yet started at the start of molding, so that the mold release temperature is lowered and the time required for one molding cycle is increased. However, in the case of a mold coated with a hydrocarbon film, the mold can be released at a high temperature from the first shot.
[0011]
【Example】
[Example 1] (TiN / i-C mixing layer, CVD carbon film)
1 and 2 show an embodiment of an optical element molding die according to the present invention. In FIG. 1, 1 is a mold base material using cemented carbide, 2 is an intermediate layer made of a hard material using TiN, 3 is a hard carbon film, and 4 is a molding surface for molding a glass material made of a hydrocarbon film. Reference numeral 5 denotes a glass material. As shown in FIG. 2, an optical element 6 such as a lens is formed by press-molding a glass material 5 placed between molds.
[0012]
Next, the optical element molding die of the present invention will be described in detail. After processing a WC-Ti cemented carbide as a mold base material into a predetermined shape, a TiN film is formed by ion plating, and then the molding surface is Rmax. = 0.02 μm mirror-polished was used. After this mold was washed well, it was placed in an IBD (Ion Beam Deposition) apparatus shown in FIG. In FIG. 3, 7 is a vacuum chamber, 8 is an ion beam apparatus, 9 is an ionization chamber, 10 is a gas inlet, 11 is an ion beam extraction grid, 12 is an ion beam, 13 is a mold base material, 14 is a substrate holder and heater, Reference numeral 15 denotes an exhaust port. First, after argon gas 35 sccm is introduced into the ionization chamber from the gas inlet 10 and ionized, a voltage of 500 V is applied to the ion beam extraction grit to extract the ion beam, and the mold base material is irradiated for 5 minutes to clean the molding surface. Made. Next, CH ₄ : 15 sccm and H ₂ : 30 sccm are introduced into the ionization chamber to a gas pressure of 3.5 × 10 ⁻² Pa, an ion beam is extracted at an acceleration voltage of 10 kV, and the molding surface is irradiated to a 35 nm mixing layer. Formed. The mixing layer of the analysis sample prepared under the same conditions is designated as XPS (Xray Photoelectron).
The result of depth direction analysis by spectroscopy is shown in FIG. As apparent from FIG. 4, the thickness of the mixing layer is 35 nm, and the concentration of carbon C decreases from the surface side toward the mold base material side. On the other hand, the concentration of Ti and N atoms increases from the surface side toward the mold base material side. A hard carbon film having a mixing layer was formed by the above method.
[0013]
Next, a method for forming a hydrocarbon film on the hard carbon film layer will be described. FIG. 5 is a schematic diagram showing a schematic configuration of a thin film deposition apparatus for forming a hydrocarbon film. In FIG. 5, 16 is a vacuum chamber, 17 is an exhaust port, 18 is a gas inlet, 19 is a dome-shaped holder for holding the mold base material, 20 is a heater for heating the mold base material, and 21 is a coating film. A quartz crystal monitor 22 for measuring the thickness is an antenna for applying a high frequency. Reference numeral 23 denotes a mold base material held by the holder.
[0014]
A well-cleaned hard carbon film and a mold base material on which TiN is formed are attached to a dome-shaped holder, heated to 300 ° C. by a heater 20, evacuated from an exhaust port 17, and the inside of the vacuum chamber 16 is 1 × 10 ⁻³ Pa. After the pressure is reduced to below, argon gas is introduced from the gas inlet 18 until the pressure reaches 5 × 10 ⁻² Pa, and a high frequency of 300 W is applied to the high frequency applying antenna 22 to perform high frequency discharge and Plasma cleaning was performed. Thereafter, the introduction of argon gas was stopped, the degree of vacuum was returned to 1 × 10 ⁻³ Pa, and CH ₄ gas was introduced from the gas introduction port 18 until 1 × 10 ⁻¹ Pa was reached. Then, a high frequency of 500 W was applied to the high frequency applying antenna 22 to perform high frequency discharge, and a coating film having a thickness of about 30 nm was formed. In order to exhibit the mold release effect according to the present invention, the film thickness is required to be at least 5 nm, and when it is 50 nm or more, the appearance of the optical element may be defective.
[0015]
The result of infrared absorption spectroscopy (IR) of the hydrocarbon film formed here is shown in FIG. The hydrocarbon film as shown in FIG. 6 while the absorption of CH _3, CH ₂ is seen from the IR analysis of the hard carbon film shown in FIG. 8, CH ₃ found in hydrocarbon film in FIG. 6, Almost no absorption of CH ₂ could be confirmed. Further, since the hydrogen concentration of the hydrocarbon film was 40 to 70 atomic%, it is considered that most of the hydrogen in the hydrocarbon film is bonded in a group state such as CH ₃ CH ₂ . On the other hand, the hydrogen concentration of the hard carbon film is 5 to 30 atomic%. However, since the absorption of CH ₃ and CH ₂ is small as described above, it is considered that the hydrogen in the film is bonded to the end of the dangling bond. .
[0016]
Next, an example in which press molding is performed using the optical element molding die according to the present invention will be described. FIG. 7 shows a molding apparatus, in which 51 is a vacuum chamber body, 52 is a lid, 53 is an upper mold for molding an optical element, 54 is a lower mold, and 55 is an upper mold presser for pressing the upper mold. , 56 is a barrel mold, 57 is a mold holder, 58 is a heater, 59 is a thrust bar that pushes up the lower mold, 60 is an air cylinder that operates the thrust bar, 61 is an oil rotary pump, 62, 63, and 64 are valves, 65 Is an inert gas inflow pipe, 66 is a valve, 67 is a leak valve, 68 is a valve, 69 is a temperature sensor 70 is a water-cooled pipe, and 71 is a table that supports a vacuum chamber. The process for manufacturing the lens will be described next. A gob prepared by adjusting the crown optical glass (SK12) to both predetermined positions is placed in a cavity of a mold, and this is placed in the apparatus. After the mold filled with the glass material is installed in the apparatus, the lid 52 of the vacuum chamber 51 is closed, water is supplied to the water cooling pipe 70, and current is supplied to the heater 58. At this time, the

nitrogen gas valves

66 and 68 are closed, and the

exhaust system valves

62, 63 and 64 are also closed. The oil rotary pump 61 is always rotating. When the pressure becomes 1 Pa or less after the valve 62 is opened and exhaust is started, the valve 62 is closed and the valve 66 is opened to introduce nitrogen gas into the vacuum chamber from the cylinder. When the temperature reaches a predetermined temperature, the air cylinder 60 is operated to pressurize at a pressure of 1.5 Pa for 1 minute. After releasing the pressure, cooling is performed at a cooling rate of −5 ° C./min until the transition point or lower, and then cooling is performed at a rate of −20 ° C./min or higher. 63 is opened to introduce air into the vacuum chamber 51. Then, the lid 52 is opened and the upper mold retainer is removed, and the molded product is taken out. The lens shown in FIG. 4 was used using the crown optical glass (softening point Sp = 672 ° C., transition point Tg = 550 ° C.) as described above.
[0017]
By using the optical element molding die according to the present invention, the mold release temperature of the first shot of press molding (the temperature at which the optical element peels from the mold during slow cooling after press molding) is the surface of the conventional hard carbon film. Compared with the mold which is, it rose by 70 ° C. (mold release temperature of the mold according to the invention: 530 ° C.). Since the present invention can increase the mold release temperature of the first press molding, the tact time of molding can be shortened.
[0018]
The molding surface of the mold member and the surface roughness of the molded optical element after being molded 3000 times by the press process as described above, and the releasability between the mold member and the molded optical element were good. In particular, even when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), there were no defects such as scratches and cracks, reaction deposits of glass components, and glass fusion.
[0019]
In addition, as a result of producing each optical element molding die whose optical element shape is a biconcave lens, a convex meniscus lens, and a concave meniscus lens by the same method as above, it was confirmed that the mold has better releasability than the conventional hard carbon film. It was. In particular, in the case of a convex meniscus lens as shown in FIG. 9, in the case of a conventional hard carbon film, the optical element may not be released from the mold up to 350 ° C., but when the optical element molding die of the present invention is used The mold release at 500 ° C. or higher was possible stably. Similar to the biconvex lens described in the first half of Example 1, the continuous molding of the various shapes described above had no problem even if it was performed 3000 times.
[0020]
In addition, lanthanum-based glass (LaK12) and SF-based glass (SF8) were molded with the mold of the present invention. However, as with crown-based glass (SK12), there was no problem at all, and an excellent release effect was confirmed. It was done.
[0021]
[Example 2] (TiN / i-C mixing layer, ion beam carbon film)
In the present invention, the mold base material, the TiN as the intermediate layer, and the hard carbon film were produced by the same method as in Example 1 above, so the method for producing the hydrocarbon film as the molding surface will be described in detail. In Example 1, a high frequency was used to generate a CH ₄ plasma to form a hydrocarbon film, but in the present invention, a hydrocarbon film is formed into a mold base using an ion beam. As the film forming apparatus, the IBD apparatus in which the hard carbon film shown in the first embodiment is formed can be used. Therefore, in the present invention, hard carbon film formation and hydrocarbon film formation can be performed continuously. In the same manner as in Example 1, after depositing TiN and a hard carbon film in the form of a WC-Ti cemented carbide, a hydrocarbon film was continuously formed in the apparatus for forming the hard carbon film shown in FIG. .
[0022]
The hydrocarbon film forming method is described below. First, CH ₄ : 20 sccm is introduced into the ionization chamber to a gas pressure of 4.0 × 10 ⁻² Pa. After ionizing the CH ₄ gas, a voltage of 200 V is applied to the ion beam extraction grid to extract the ion beam, A bias voltage of −100 V was applied to the substrate holder to form a hydrocarbon film of about 30 nm on the hard carbon film. Next, press molding was performed in the same manner as in Example 1 using the optical element molding die according to the present invention. As a result, by using the mold for molding an optical element according to the present invention, the mold release temperature in the first shot of press molding was increased by 50 ° C. compared with the mold in which the conventional hard carbon film is the molding surface. (Mold release temperature of the mold according to the present invention: 520 ° C.) Since the present invention can increase the mold release temperature in the first shot of press molding, the tact time of molding can be shortened. Further, the molding surface of the mold member after molding 3000 times, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good. In particular, even when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), there were no defects such as scratches and cracks, reaction deposits of glass components, and glass fusion.
[0023]
In addition, as a result of producing each optical element molding die whose optical element shape is a biconcave lens, a convex meniscus lens, and a concave meniscus lens by the same method as above, it was confirmed that the mold has better releasability than the conventional hard carbon film. It was. In particular, in the case of a convex meniscus lens as shown in FIG. 9, in the case of a conventional hard carbon film, the optical element may not be released from the mold up to 350 ° C., but when the optical element molding die of the present invention is used The mold release at 500 ° C. or higher was possible stably. Similar to the biconvex lens described in the first half of Example 1, the continuous molding of the various shapes described above had no problem even if it was performed 3000 times.
[0024]
In addition, lanthanum-based glass (LaK12) and SF-based glass (SF8) were molded with the mold of the present invention. However, as with crown-based glass (SK12), there was no problem at all, and an excellent release effect was confirmed. It was done.
[0025]
[Example 3] (CVD SiC / i-C mixing layer, CVD carbon film)
In the present invention, atmospheric pressure sintered SiC is used as a mold base material, which is processed into a predetermined shape, and then an SiC film formed by CVD on the mold base material SiC for forming an intermediate layer made of a hard material and densifying the surface. And forming the molding surface with Rmax. What was mirror-polished to 0.02 was used. After this mold was thoroughly cleaned, it was placed in the IBD apparatus shown in FIG. 3 as in Example 1, and a hard carbon film was formed under the same conditions as in Example 1 so as to have a mixing layer of 35 nm. Next, a hydrocarbon film was formed to a thickness of 30 nm under the same apparatus and conditions as in Example 1.
[0026]
Next, press molding was performed in the same manner as in Example 1 using the optical element molding die according to the present invention. As a result, by using the optical element molding die according to the present invention, the mold release temperature in the first shot of press molding was increased by 60 ° C. as compared with the mold in which the conventional hard carbon film was the molding surface. (Mold release temperature of the mold according to the present invention: 530 ° C.) The mold release temperature of the first shot of press molding can be increased by the present invention, so that the tact time of molding can be shortened. Further, the molding surface after molding 3000 times, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good. In particular, even when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), there were no defects such as scratches and cracks, reaction deposits of glass components, and glass fusion.
[0027]
In addition, as a result of producing each optical element molding die whose optical element shape is a biconcave lens, a convex meniscus lens, and a concave meniscus lens by the same method as above, it was confirmed that the mold has better releasability than the conventional hard carbon film. It was. In particular, in the case of a convex meniscus lens as shown in FIG. 9, in the case of a conventional hard carbon film, the optical element may not be released from the mold up to 350 ° C., but when the optical element molding die of the present invention is used The mold release at 500 ° C. or higher was possible stably. Similar to the biconvex lens described in the first half of Example 1, the continuous molding of the various shapes described above had no problem even if it was performed 3000 times.
[0028]
In addition, lanthanum-based glass (LaK12) and SF-based glass (SF8) were molded with the mold of the present invention. However, as with crown-based glass (SK12), there was no problem at all, and an excellent release effect was confirmed. It was done.
[0029]
[Example 4] (Diamond / i-C mixing layer, CVD carbon film)
After processing a WC-Ti cemented carbide as a mold base material into a predetermined shape, a diamond film was formed by plasma CVD, and the molding surface was subjected to Rmax. = 0.02 μm mirror-polished was used. After this mold was thoroughly cleaned, it was placed in the IBD apparatus shown in FIG. 3 as in Example 1, and a hard carbon film was formed under the same conditions as in Example 1 so as to have a mixing layer of 35 nm. Next, a hydrocarbon film was formed to a thickness of 30 nm under the same apparatus and conditions as in Example 1.
[0030]
Next, press molding was performed in the same manner as in Example 1 using the optical element molding die according to the present invention. As a result, by using the optical element molding die according to the present invention, the mold release temperature in the first shot of press molding was increased by 60 ° C. as compared with the mold in which the conventional hard carbon film was the molding surface. (Mold release temperature of the mold according to the present invention: 500 ° C.) Since the present invention makes it possible to increase the mold release temperature in the first shot of press molding, the tact time of the molding can be shortened. Further, the molding surface of the mold member after molding 3000 times, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good. In particular, even when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), there were no defects such as scratches and cracks, reaction deposits of glass components, and glass fusion.
[0031]
In addition, as a result of producing each optical element molding die whose optical element shape is a biconcave lens, a convex meniscus lens, and a concave meniscus lens by the same method as above, it was confirmed that the mold has better releasability than the conventional hard carbon film. It was. In particular, in the case of a convex meniscus lens as shown in FIG. 9, in the case of a conventional hard carbon film, the optical element may not be released from the mold up to 350 ° C., but when the optical element molding die of the present invention is used The mold release at 500 ° C. or higher was possible stably. Similar to the biconvex lens described in the first half of Example 1, the continuous molding of the various shapes described above had no problem even if it was performed 3000 times.
[0032]
In addition, lanthanum-based glass (LaK12) and SF-based glass (SF8) were molded with the mold of the present invention. However, as with crown-based glass (SK12), there was no problem at all, and an excellent release effect was confirmed. It was done.
[0033]
[Example 5] (CVDSiN / i-C mixing layer, CVD carbon film)
After processing Si ₃ N ₄ ceramics as a mold base material into a predetermined shape, a diamond film was formed by plasma CVD, and the molding surface was subjected to Rmax. What was mirror-polished to 0.02 was used. After this mold was thoroughly washed, it was placed in the IBD apparatus shown in FIG. 3 as in Example 1, and a hard carbon film was formed to have a mixing layer of 35 nm under the same conditions as in Example 1. Next, a hydrocarbon film was formed to a thickness of 30 nm under the same apparatus and conditions as in Example 1.
[0034]
Next, press molding was performed in the same manner as in Example 1 using this optical element molding die. As a result, by using the optical element molding die according to the present invention, the mold release temperature in the first shot of press molding was increased by 60 ° C. as compared with the mold in which the conventional hard carbon film was the molding surface. (Mold release temperature of the mold according to the present invention: 510 ° C.) The mold release temperature in the first shot of press molding can be increased by the present invention, so that the tact time of molding can be shortened. Further, the molding surface of the mold member after molding 3000 times, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good. In particular, even when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), there were no defects such as scratches and cracks, reaction deposits of glass components, and glass fusion.
[0035]
In addition, as a result of producing each optical element molding die whose optical element shape is a biconcave lens, a convex meniscus lens, and a concave meniscus lens by the same method as above, it was confirmed that the mold has better releasability than the conventional hard carbon film. It was. In particular, in the case of a convex meniscus lens as shown in FIG. 9, in the case of a conventional hard carbon film, the optical element may not be released from the mold up to 350 ° C., but when the optical element molding die of the present invention is used The mold release at 500 ° C. or higher was possible stably. Similar to the biconvex lens described in the first half of Example 1, the continuous molding of the various shapes described above had no problem even if it was performed 3000 times.
[0036]
In addition, lanthanum glass (LaK12) and SF glass (SF8) were molded with the mold of the present invention, but there was no problem even if it was molded 3000 times like crown glass (SK12), and a good mold release effect was confirmed. It was.
[0037]
Examples 6 to 79 are summarized in Tables 1 to 4 including Examples 1 to 5 below.
[0038]
The films of TaN, ZrN, HfN, TiC, TaC, ZrC, HfC, TiCN, TaCN, ZrCN, and HfCN, which are intermediate layer materials, were formed by ion plating and sputtering.
[0039]
Moreover, the cermet which is a mold base material was TiN-TiC, and the stainless steel was YHD50FM (α = 17 × 10 ⁻⁶ ) made by Hitachi Metals which is a high expansion steel material.
[0040]
[Table 1]

[0041]
[Table 2]

[0042]
[Table 3]

[0043]
[Table 4]

[0044]
【The invention's effect】
As described above, according to the optical element molding die of the present invention, the following problems were successfully solved by providing the hydrocarbon film on the hard carbon film formed on the mold base material.
[0045]
First, it was possible to change the state of poor releasability occurring between the initial optical element molding shot to about 20 shots and the favorable release state from the initial molding shot. As a result, the molding cycle time can be significantly shortened compared to the prior art, the number of production per hour can be improved, and the breakage of the mold that occurs when the mold release property is poor can be suppressed as much as possible.
[0046]
Secondly, even if it is a convex meniscus lens shape that is difficult to release even with a conventional hard carbon film, the releasability is improved by using the optical element molding die according to the present invention. As a result, it is necessary to cool to 300 ° C. after the end of conventional press molding, and the mold can be released at 530 ° C., and the molding cycle time can be drastically shortened.
[0047]
By using the optical element molding die obtained by the present invention, it becomes possible to improve productivity and reduce costs.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an optical element molding die according to the present invention, showing a state before press molding.
FIG. 2 is a cross-sectional view showing an example of an optical element molding die according to the present invention, showing a state after press molding.
FIG. 3 is a schematic view showing an ion beam film forming apparatus used in an embodiment of the present invention.
FIG. 4 is a diagram showing a depth profile by photoelectric spectroscopic analysis (XPS) of a mixing layer formed between an intermediate layer of an optical element molding die according to the present invention and a hard carbon film.
FIG. 5 is a schematic view showing a high-frequency discharge type film forming apparatus used in an embodiment of the present invention.
FIG. 6 is a graph showing the results of infrared spectroscopic analysis (FT-IR) of a hydrocarbon film formed by a high frequency discharge method on the film formation surface according to the present invention.
FIG. 7 is a cross-sectional view showing a lens molding apparatus using the optical element molding die according to the present invention, which is discontinuous.
FIG. 8 is a graph showing the results of infrared spectroscopic analysis (FT-IR) of a hard carbon film formed on the molding surface according to the present invention by an ion beam film forming apparatus.
FIG. 9 is a cross-sectional view showing an example of an optical element molding die according to the present invention, showing a state before press molding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Type | mold base material 2 Intermediate | middle layer 3 Hard carbon film 4 Hydrocarbon film 5 Glass material 6 Optical element 7 Vacuum layer 8 Ion beam apparatus 9 Ionization chamber 10 Gas inlet 11 Ion beam extraction grid 12 Ion beam 13 Type base material 14 Substrate holder And heater 15 exhaust port 16 vacuum chamber 17 exhaust port 18 gas introduction port 19 dome-shaped holder 20 heater 21 crystal monitor 22 high frequency applying antenna 23 mold base material 51 vacuum chamber 52 vacuum chamber lid 53 upper mold 54 lower mold 55 upper mold Presser 56 Body mold 57 Mold holder 58 Heater 59 Pushing rod for pushing up the lower mold 60 Air cylinder 61

Oil rotary pump

62, 63, 64 Valve 65 Inert gas introduction valve 66 Valve 67 Leak pipe 68 Valve 69 Temperature sensor 70 Water cooling pipe 71 Vacuum Stand that supports the tank

Claims

In a molding die used for press molding of an optical element made of glass, a hard carbon film having a hydrogen concentration of 5 to 30 atomic% and a carbonization having a thickness of 5 nm to less than 50 nm and a hydrogen concentration of 40 to 70 atomic% on the mold base material. An optical element molding die having a molding surface made of a hydrogen film in this order.

The optical element molding die according to claim 1, further comprising an intermediate layer made of a hard substance between the die base material and the hard carbon film.

The elements constituting the intermediate layer formed by ion beam mixing between the intermediate layer and the hard carbon film decrease toward the hard carbon film, and the carbon included in the hard carbon film decreases toward the intermediate layer. The mold for molding an optical element according to claim 2, further comprising a mixing layer.

The mold for molding an optical element according to claim 1, wherein the mold base material is selected from cemented carbide, cermet, stainless steel, silicon nitride, and silicon carbide.

The intermediate layer material is selected from TiN, TaN, ZrN, HfN, TiC, TaC, ZrC, HfC, TiCN, TaCN, ZrCN, HfCN, SiC formed by CVD, SiN formed by CVD, and diamond. The mold for molding an optical element as described.

2. The mold for molding an optical element according to claim 1, wherein the hard carbon film is selected from a diamond thin film, a diamond-like carbon film, and a hydrogenated amorphous carbon film.

The mold for molding an optical element according to claim 1, wherein the hydrocarbon film as the molding surface is a film formed by plasma CVD.

2. The mold for molding an optical element according to claim 1, wherein the hydrocarbon film as a molding surface is a film formed by an ion beam.