JP2004317738A

JP2004317738A - Ultra-violet light shielding element, its manufacture method and optical device

Info

Publication number: JP2004317738A
Application number: JP2003110551A
Authority: JP
Inventors: Kenji Inoue; 健二井上; Kenichi Ikeda; 健一池田
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-04-15
Filing date: 2003-04-15
Publication date: 2004-11-11

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacture method capable of manufacturing an ultraviolet light shielding element which suppresses the transmittance of ultraviolet light of 300 nm-400 nm to 1% or less and has a sharp transition gradient stably and accurately with excellent productivity. <P>SOLUTION: The ultraviolet light shielding element is made by laminating multilayer films containing high refractive index films 3 and low refractive index films 2 on a transparent substrate 1, wherein the light absorption coefficient of at least one film selected from the high refractive index films 3 and the low refractive index films 2 becomes 0.1 or more at a wavelength in the range of 300 nm-360 nm. By using a sputtering method for partially introducing oxygen to the film, a film of which the absorption coefficient k exceeds 0.1 at a wavelength in the middle of 300 nm-360 nm is manufactured, thereby, the film design containing thin films ≤30 nm is realized and the ultraviolet light shielding element which has a sharp transition gradient and suppresses ultraviolet light of 300-400 nm to 1% or less can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、可視光を透過し紫外光を遮蔽する紫外光遮蔽素子とその製造方法及び光学装置に関する。
【０００２】
【従来の技術】
可視光全域を利用する光学装置として、投射光学系を有するプロジェクターと撮像光学系を有するカメラとがあるが、これらの光学系には光源であるランプや太陽の発する紫外光が入射することで、様々な悪影響を被ることを防止するために、紫外光遮蔽素子が必要となっている。具体的にプロジェクターにおいては、光学系内にある有機材からなる偏光板、位相差板、液晶素子などの部材が、ランプから発せられる紫外光により損傷することが問題である。カメラにおいては、自然界に存在する紫外光が、光学系に入射して電荷結合素子（ＣＣＤ）や相補型金属酸化物半導体（ＣＭＯＳ）等の撮像素子に当たると感応して撮影画像を劣化させる問題がある。そのために、前記光学系内に紫外光遮蔽素子を使用して紫外光を遮蔽することが必要となっている。特にプロジェクターにおいては、至近距離にある高輝度ランプから発せられる非常に強い紫外光を受けるために、厳重に紫外光を遮蔽しなければ偏光板等の劣化が必至であり、２〜３種類の紫外光遮蔽素子を併用することが普通となっている。
【０００３】
図１０に液晶プロジェクターの光学系構成図を示す。光源であるランプ１０１は超高圧水銀ランプやキセノンランプ等が用いられ、前記ランプは可視光だけでなく紫外光も発光して、ランプ前方に配置するインテグレータ１０２に入射する。このインテグレータ以後の素子には偏光板、位相差板、接着剤等の有機物が複数箇所に用いられているので、インテグレータの入射面に第１の紫外光遮蔽膜を蒸着成膜する。あるいは後述するように紫外光遮蔽膜を蒸着で成膜することは難しく、高価なインテグレータを成膜不良として歩留まり低下させることが多いために、インテグレータへは紫外光遮蔽膜を成膜しないで、別途ガラス基板に成膜して紫外光遮蔽素子としてインテグレータとランプの間に配置することもある。ここで、紫外光遮蔽膜の遮蔽性能が充分でないために、若干量の紫外光が可視光とともに透過していく。
【０００４】
インテグレータ１０２を透過した光は、第２インテグレータ１０３、偏光変換素子１０４、折り返しミラー１０５を経て、第１ダイクロイックミラー１０６により、例えば赤色光は透過して赤色画像用の液晶素子に到達し、約５９０ｎｍ以下の緑から青色光は反射して第２ダイクロイックミラー１０７に入射する。第２ダイクロイックミラーでは例えば緑色光は反射されて緑色画像用の液晶素子に到達し、約５００ｎｍ以下の青色光は透過していく。この青色光路には前述した第１の紫外光遮蔽膜で漏れて透過してきた紫外光が含まれており、この先の青色画像用液晶素子とそれに付属する偏光板に照射されてしまい、液晶素子と偏光板が紫外光により損傷して劣化する問題がある。この問題を防ぐために、第２の紫外光遮蔽素子１０９を挿入したり、或いは図１０の位置に通常の全反射ミラーに変えて紫外光遮蔽ミラーを採用することが必要になっている。更には紫外光遮蔽素子１０９を用いる場合でも、透明ガラス基板に紫外光遮蔽膜を形成した素子では不充分で、基板自体を紫外光吸収特性を持つ特殊ガラスにしてその表面に紫外光遮蔽膜を形成した素子とする場合もある。このように、紫外光を遮蔽することは重要であり、従来の紫外光遮蔽膜の特性が不充分であることがわかる。現在の非常に高輝度なランプが用いられるプロジェクターの光学系においてはランプから出射される光の３００ｎｍから４００ｎｍの紫外光の透過率は１％に抑制しなければならない。１１０は液晶パネル、１１１は色合成プリズム、１１２は投射レンズである。
【０００５】
従来の紫外光遮蔽膜の成膜方法である蒸着について図１１を用いて説明する。真空槽１２０内の上方に位置する基板ホルダー１２１に成膜される基板１２２を載置する。成膜する膜の材料を下方のハース内に入れる。真空槽内を真空に排気し、ハース内の蒸着材料に電子銃で電子を照射して加熱溶融した材料が蒸発して上方の基板に付着することで成膜が行われる。蒸着する膜厚は、基板ホルダー１２１内に配置したモニター基板１２３に光学式膜厚計１２４から光を投光し基板から反射して帰ってくる光を検知することで計測が行われる。蒸発源は通常２箇所設けられており、誘電体である低屈折率材料と高屈折率材料の２種類の材料１２５，１２６を交互に蒸着して基板１２２上に積層することができる。この多層膜の各層の膜厚を所定の設計厚さに制御することにより紫外光遮蔽膜を得ることができる。
【０００６】
蒸着における高屈折率膜としては、酸化チタン、酸化タンタル、酸化ニオブ、酸化ジルコンなどが用いられ、低屈折率膜としては酸化珪素、弗化マグネシウムなどが用いられる。
【０００７】
紫外光遮蔽膜の特性は、４２０〜４３０ｎｍから約６８０ｎｍに亘る可視光を透過し、約４１０ｎｍからランプの発光領域である３００ｎｍ前後までの紫外光を遮蔽することが要求される。遮蔽帯から透過帯への遷移領域の波長は光学機器の設計仕様によって異なり、光の透過率が半値５０％になる半値波長は４１０ｎｍから４３０ｎｍの間に設定する。この遷移領域の勾配、透過帯の波長範囲と透過率、遮蔽帯の波長範囲と透過率とによって紫外光遮蔽膜の構成が変わってくる。
【０００８】
しかし、前記蒸着法により紫外光遮蔽膜を得るには幾つもの課題が存在し、その課題を回避する取り組みとして、下記特許文献１が提案されている。第一に、紫外光遮蔽膜の分光透過率曲線における遷移勾配を急峻にする程、また透過帯を広く透過率を高くする程、遮蔽帯を広く透過率を下げる程に、多層膜の層数が増し３０層以上の非常に多層になり、また各層の膜厚誤差が紫外光遮蔽膜の光学特性を劣化させる敏感度も増していくので、製造が困難になる。第２に、蒸着は前述のように加熱溶融した材料が蒸発して浮遊した粒子を基板に付着させるものであり、膜の密度が低く、屈折率が変動しやすく、基板に対する付着力も比較的弱い。ハース内の材料の溶融状態や、真空槽内壁の付着物や吸着ガスの状態により、成膜された膜の屈折率が変動しやすい。膜の屈折率が変動すれば積層した紫外光遮蔽膜の特性も変動する。第３に、前記のように不安定なプロセスであるので成膜速度も不安定であり、インプロセスでの膜厚計測が不可欠であるが、一般の光学多層膜と異なり紫外光遮蔽膜はその膜厚計測の精度が良くない。ここで膜の屈折率をｎ、物理的膜厚をｄ、光の波長をλとすると、膜の光学的膜厚ＤはＤ＝ｎ×ｄ×４／λで表され、高屈折率膜の光学的膜厚Ｈを１Ｈ＝ｎ×ｄ×４／λとし、低屈折率膜の光学的膜厚Ｌを１Ｌ＝ｎ×ｄ×４／λとする。モニター基板は安価で品質が良いことから、青色ガラスと通称されるソーダライムガラスや白板ガラスと通称される硼珪酸ガラスが用いられており、どちらも屈折率は約１．５２である。モニター基板１２３に投光して光学式膜厚計１２４で反射光を受光する場合、成膜前のモニター基板だけの光量に対して、高屈折率膜の場合は反射光が増加していき計測光波長λのλ／４の膜厚をピークに減少してλ／２で元の光量に戻ってから再び増加を繰り返す正弦波状の光量変化を示し、低屈折率膜の場合は初めに光量減少していきλ／４で増加に転ずる逆パターンの正弦波状光量変化を示す。このモニター基板上の膜厚に伴う光量変化を利用して成膜中の膜厚を計測する。多層膜における１層毎の所定の膜厚に対してモニター光量が幾らかを予め計算しておき、その光量に達した瞬間に蒸着を停止することで膜厚を制御する。前述したように蒸着においては膜の屈折率が不安定に変動するために、モニター光量も膜の屈折率に依存して変動する。この誤差を少しでも減少させるために、モニター光量変化のピークに到達した時にピーク光量に対する所定膜厚の光量を成膜中に瞬時に算出してピークを少し過ぎた光量の時に蒸着停止させるように設定すると比較的に光学的膜厚の精度が良い。しかしながら紫外光遮蔽膜は、一般的な可視光用光学薄膜よりも各層の膜が薄く、モニター光量のピークに達する前や、光量変化が緩慢で膜厚に対する敏感度が悪いピーク付近で蒸着を停止させることになり、膜厚制御精度が悪化するという問題がある。
【０００９】
そして各層の設計膜厚が不均一でばらばらでは光学式膜厚計による膜厚制御性も悪く再現性が劣る為に、できるだけ同程度の膜厚を規則的に繰り返す膜構成が用いられており、それが紫外光遮蔽膜の設計自由度を制限し、元々の設計性能の劣化や、それを補うための層数増加を余儀なくされている。更には薄い膜ほど膜厚制御性が劣るために薄い膜を避けた膜構成にしなければならないことも、設計の制限と性能劣化の原因であり問題である。
【００１０】
下記特許文献１の技術は、上記課題の対策であり、二つの解決手段を提案している。その一つは、モニター基板は遮蔽せず紫外光遮蔽膜を成膜する基板に対して膜付着量を遮蔽する補正板を設置して、モニター基板よりも紫外光遮蔽膜基板の付着膜厚を４０％〜１５％少なくする手段である。これはつまり蒸発した材料の成膜を阻害して成膜速度が低下させ、蒸着材料の利用効率も低下し、生産効率の低下とコストアップを引き起こす。そして紫外光遮蔽膜の設計膜厚に対してモニター基板での制御膜厚が１５〜４０％増えるだけであり、一般の光学薄膜に比べて各層の膜厚が低く光学式膜厚計での制御精度の向上度合いが小さい。もう一つの手段は、膜構成における繰り返し交互層における高屈折率膜の光学的膜厚Ｈと低屈折率膜の光学的膜厚Ｌの比をＨ／Ｌ又はＬ／Ｈを１．２〜２．０として、厚い方の膜を先にモニター基板に成膜し光学式膜厚計の光量変化のピーク越えさせることにし、薄い方の膜は厚い方の膜の上に重ねて成膜してモニター光量を計測することでピーク越えさせようとするものである。
【００１１】
【特許文献１】
特開２００２−２５８０３５号公報
【００１２】
【発明が解決しようとする課題】
しかし、前記従来の方法では、高屈折率膜と低屈折率膜の膜厚に大きな制限を設ける為に設計自由度が小さく充分な設計性能を得ることが難しい。そのために膜層数を増やして設計せざるを得ず、その結果として、製造困難度とコストが増すことになる。またモニター基板に２層を積層するために、２層目の計測精度は１層目の膜の光学定数の変動と膜厚制御誤差が重畳して不安定になるという問題がある。
【００１３】
本発明は、前記従来の問題を解決するため、生産性良く安定して高精度な紫外光遮蔽素子とその製造方法およびこれを用いた光学装置を提供することを目的とする。
【００１４】
【課題を解決するための手段】
前記目的を達成するため、本発明の紫外光遮蔽素子は、透明基板上に、高屈折率膜と低屈折率膜とを含む膜を多層積層した紫外光遮蔽素子であって、前記高屈折率膜及び低屈折率膜から選ばれる少なくとも一つ膜の光吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあることを特徴とする。
【００１５】
本発明の紫外光遮蔽素子の製造方法は、低屈折率膜用と高屈折率膜用の少なくとも２種類のターゲットをスパッタして透明基板に成膜し、前記基板を酸化領域に搬送し、スパッタ膜を酸化処理して酸化膜とする紫外光遮蔽素子の製造方法であって、前記酸化膜の少なくとも１種類の膜を、光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御することを特徴とする。
【００１６】
次に本発明の別の紫外光遮蔽素子の製造方法は、前記低屈折率膜用と高屈折率膜用の２種類のターゲットをスパッタして基板に成膜を行う際、前記スパッタ領域に酸素ガスを導入し酸化物を基板に付着させる反応性スパッタ方式を用い、前記酸化膜の少なくとも１種類の膜の光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御することを特徴とする。
【００１７】
次に本発明の光学装置は、光源と、光源から出射された光を画像信号に変換する光変換装置と、前記変換した画像光を投射する投射光学系とを備え、前記光源と光変換装置との間に、ターゲットをスパッタして成膜する高屈折率膜と低屈折率膜とを積層し、少なくとも一方の膜の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜を有する紫外光遮蔽素子を配置することを特徴とする。
【００１８】
本発明の別の光学装置は、外部の光を取り込んで結像させる撮像光学系と、撮像素子との間に、ターゲットをスパッタして成膜する高屈折率膜と低屈折率膜とを積層し、少なくとも一方の膜の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜を有する紫外光遮蔽素子を配置することを特徴とする。
【００１９】
【発明の実施の形態】
本発明の紫外光遮蔽素子は、多層積層膜を構成する高屈折率膜及び低屈折率膜から選ばれる少なくとも一つ膜の光吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある。これにより、３００ｎｍから４００ｎｍの紫外光の透過率を１％以下に抑えて、かつ急峻な遷移勾配を持つ紫外光遮蔽素子を、安定して精度良く生産性良く製作することが可能になり、プロジェクターの部品点数削減と長寿命化を実現できる。また撮像光学系においては色むら等の画質劣化を抑止することができる。
【００２０】
上記の光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜としては、五酸化ニオブ、二酸化チタン、五酸化タンタル、二酸化ジルコニウムが好適である。また、物理的膜厚が３０ｎｍより薄い膜を含むことが好ましく、特に物理的膜厚が２０ｎｍ以下であることが好適である。さらに層数が２０層以上６０層以下であることが好ましく、特に３０層以上であることが好適である。
【００２１】
可視光と紫外光の境界付近の透過率が１０％から９０％に遷移する波長幅が１５ｎｍ以下であることが好ましく、特に１０ｎｍ以下であることが好適である。可視光から紫外光へかけて透過率が１％以下に低下する波長が４０５から４２０ｎｍの間にあり且つ３００ｎｍの波長まで透過率が１％以下であることが好ましい。
【００２２】
上記の紫外光遮蔽素子における透明基板が板ガラスであることが好ましい。又は、上記紫外光遮蔽素子における透明基板として少なくとも片面にレンズアレイを有するガラス基板であることが好ましい。
【００２３】
次に、本発明方法においては、酸化領域へ酸素ガスを導入し圧力を０．０５Ｐａ〜５Ｐａの範囲にすることが好ましい。酸素を入れないと膜の酸化に必要な酸素が不足して酸化不充分で吸収係数が過大になり不透明な膜になる傾向となる。逆に酸素過多では酸化が進みすぎて吸収係数が過小で紫外光遮蔽効果が薄くなる傾向となる。
【００２４】
さらに酸素プラズマを発生させる印加電力を１ｋＷ〜１０ｋＷが好ましい。酸化領域への印可電力過小だと酸素プラズマが弱く膜の酸化が不十分で吸収係数過大になる傾向となる。逆に電力過大になると、酸化過多となり、吸収係数が過小となる傾向がある。
【００２５】
また、成膜速度を０．１〜２．０ｎｍ／ｓとすることが好適である。成膜速度過小だと膜が酸化される時間が十分にあり、酸化が進みすぎて吸収係数過小になる傾向となる。逆に成膜速度過大であると、酸化過少になり、吸収係数が過大になる傾向となる。
【００２６】
本発明の別の製造方法においては、反応性スパッタにおいては、導入するガスにおける酸素の体積比率を０．１〜０．８に設定することが好適である。酸素導入量により吸収係数を制御することができる。
【００２７】
本発明の光学装置においては、光変換装置は、ランプの出射光を３色の帯域に分離する色分離光学系と、分離した各色の画像信号に変換する素子と、前記変換した各色画像を合成する色合成光学系とで構成することが好ましい。前記画像信号変換素子が液晶パネルかもしくはデジタルミラーデバイス（ＤｉｇｉｔａｌＭｉｒｒｏｒＤｅｖｉｃｅ）が用いられる。また上記光変換装置は、ランプの出射光を３色以上の色帯域に時系列分離する色分離光学系と、分離した各色の画像信号に変換する素子とで構成することが好ましい。
【００２８】
以下、具体的な実施形態について、図面を参照しながら説明する。
【００２９】
（実施の形態１）
図１は本発明の一実施例を示す図である。透明な基板１の表面に低屈折率膜２と高屈折率膜３とを交互に積層した紫外光遮蔽膜を形成している。図１の膜構成を表１に示す。設計波長は３６０ｎｍとし、基板は光学ガラスＢＫ７、低屈折率膜として二酸化珪素、高屈折率膜として五酸化ニオブを用いた。
【００３０】
【表１】

【００３１】
表１の屈折率、吸収係数、光学的膜厚は設計波長３６０ｎｍの値であり、これらの値は分散と呼ばれる波長依存性があり、波長によって異なる値になる。本実施例においては、可視光の４３０ｎｍから６８０ｎｍの領域で透過率が９６％以上で、紫外光３００〜４０５ｎｍの領域で透過率が１％以下、紫外光から可視光に向けて透過率が上がっていく遷移領域の透過率５０％にあたる波長のことを半値と称して半値４２０ｎｍに設計仕様を設定している。
【００３２】
この膜構成において、完全に膜を酸化させて吸収係数をほぼ０に近い値の膜を用いた場合は、図２に示す分光特性となり、波長３２０ｎｍ以下の領域で急に透過率が悪化し３１４ｎｍでは３６％もの紫外光を透過してしまい、紫外光遮蔽機能が大幅に低下する。またこの場合、物理膜厚２０ｎｍ以下の膜が６層もあり、光学式膜厚計で膜厚制御しながら蒸着して設計通りの特性を得ることは困難であった。
【００３３】
しかし、成膜方法や膜の特性などに着目して鋭意検討した結果、少なくとも一方の膜の吸収係数ｋが０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜を有する紫外光遮蔽膜を用いることにより、紫外光遮蔽素子の分光透過率が図３に示すように大きく改善することを見いだした。
【００３４】
五酸化ニオブの光波長λに対する屈折率ｎと吸収係数ｋの関係を示すグラフを図４に示す。図４の細い実線が屈折率、太い実線が波長３００ｎｍに対する吸収係数ｋが０．１１である五酸化ニオブの吸収係数、波線は吸収係数が０．１を越えるのは３２５ｎｍである五酸化ニオブの吸収係数を示している。吸収係数が０．１を越える波長が３００ｎｍから３６０ｎｍの範囲にあれば、図３のように３００から４００ｎｍの紫外光の透過率を最大でも０．９％と１％以下に抑制することができた。さらに波長３２５ｎｍで吸収係数が０．１を越える五酸化ニオブを用いる場合には、３００から４００ｎｍの紫外光の透過率を最大でも０．２％と高い遮蔽能力を発揮できた。
【００３５】
ここで比較例として図１２に示す分光透過率の特性は、従来の膜のように各層の物理的膜厚を３０ｎｍ以上にしたものである。このように３９０から４００ｎｍ付近の紫外光が１％を超えており、４１５ｎｍで１０％に達し、また４３０ｎｍ付近の可視光透過率が９０％前後に下がっており充分な特性を得ることが出来ない。
【００３６】
本実施の形態のように物理的膜厚が３０ｎｍ以下の薄い膜や、さらに薄い２０ｎｍ以下の蒸着では制御が困難な薄い膜を用いることで、３００から４００ｎｍの紫外光全域に亘って透過率を下げつつ、紫外光から可視光へ向かって透過率が上がっていく遷移領域の勾配を急峻にすることができる。透過率が１０％から９０％に遷移する波長幅を１５ｎｍ以下やさらに急峻な１０ｎｍ以下にすることが可能になり、図３の例では４１５ｎｍから４２３．５ｎｍの８．５ｎｍにすることができた。
【００３７】
ここで比較例として図１３に示す分光透過率の特性は、１９層の紫外光遮蔽膜のものである。このように３８９ｎｍ以上から紫外光透過率が１％を超え、４０９ｎｍで１０％に達し、４２７ｎｍで９０％になっており、１０％から９０％への遷移波長幅が１８ｎｍと緩慢な勾配である。また可視光の透過率も大きく変動して良くない。これに対して広い範囲の紫外光遮蔽性能と急峻な遷移勾配を得るためには多層膜の層数を２０層以上にすれば可能になり、また多くても６０層を越えると特性改善は実質的に小さくかつ成膜時間が長くなり生産性が低下する傾向となる。
【００３８】
次に上記の紫外光遮蔽素子を得るための手段について、図５に原理図を、図６にスパッタ装置の概要図を示す。第１真空槽１６は、図６では一部だけが簡易表示されているが開閉可能な真空槽であり、大気開放して円筒状の基板ホルダー６に透明な基板１を取り付けてから真空排気し、真空状態で基板を第１真空槽１６から第２真空槽１５に搬送してさらに所定の圧力まで真空排気を行ってからスパッタ成膜を始める。
【００３９】
図５に示す第１スパッタ領域１２には、低屈折率膜の元となる珪素であるターゲット４を備えており、ターゲット背面には図示していないが磁石と電力を供給する電極装置が備えられている。なお、ターゲット４とターゲット５については、図６のように各２個のターゲット電極を対にしたデュアルターゲット構成であれば交流電圧を印加してターゲット表面の帯電を防いで安定な放電ができるが、各１個ずつのターゲット電極を備えて放電させる方式でも良い。第１スパッタ領域１２には、アルゴンガスを１００ｓｃｃｍ導入し、圧力０．２Ｐａにてターゲットに交流で６ｋＷの電力を印加すると、アルゴンのプラズマ放電が発生してスパッタが始まる。プラズマ内のアルゴンイオン７が磁力によりターゲット４に衝突し、ターゲットから弾き飛ばされた粒子８が基板１に付着する。このスパッタ領域にて付着したばかりの膜は、珪素が周辺雰囲気に存在する酸素とある程度結合した酸化珪素である。アルゴンガスだけでなく酸素ガスも導入すれば膜の酸化度合いは増すが、成膜速度が減少する傾向にあるので生産効率の点から最適な条件に設定すれば良い。基板１は基板ホルダー６の回転に伴い酸化領域１４に搬送される。その途中で第２スパッタ領域１３を通過するが、通常は第２のターゲット５でのスパッタ成膜は行わない。酸化領域１４には酸素ガスを２００ｓｃｃｍ導入し、圧力を０．３Ｐａにする。アンテナ９により窓１０を介して高周波電力５ｋＷ印加することにより、酸素プラズマを発生させる。そして基板上の膜が、酸素プラズマ中の酸素イオンや酸素ラジカルの粒子１１に晒されて、酸化膜、つまり二酸化珪素膜が形成できる。
【００４０】
同様に第２スパッタ領域１３には、高屈折率膜の元であるニオブからなるターゲット５が備えられており、アルゴンガス１００ｓｃｃｍと酸素ガス５ｓｃｃｍとを合わせて導入して圧力０．３Ｐａの状態にする。ここで導入する酸素ガスはニオブの酸化を補助するためであり、後の酸化処理の条件と合わせて最適な酸化度合いで、最適な吸収係数が得られるように設定するものであり、酸素ガスを導入しない場合もある。交流の電力４ｋＷを印加して放電しターゲットをスパッタする。基板上にはある程度酸化したニオブ膜が形成され、すぐに基板ホルダーの回転に伴い酸化領域１４に搬送され、酸素プラズマに晒されて五酸化ニオブ膜が得られる。そして各層の膜厚に対して成膜速度に応じた所定の時間のスパッタを行うことにより低屈折率膜と高屈折率膜を交互に積層した紫外光遮蔽膜を基板上に形成した紫外光遮蔽素子を得ることができる。
【００４１】
上述のようなスパッタ方式によれば、加速されたアルゴンイオンに弾き飛ばされた粒子は強いエネルギーを有しており、これが基板に付着してできた膜は緻密で付着力も強い安定した膜となる。そのため、膜の屈折率が多層膜の初めから終わりまで、またバッチ間においても蒸着よりも安定した膜が得られる。また、膜厚制御性が膜厚に関係なく薄い膜でも高い膜厚精度が得られる。このように膜の光学定数と膜厚が安定しているので、各層の膜厚が薄く且つ層数が多くて蒸着では困難であった紫外光遮蔽膜を設計通りの特性で精度良く安定して作ることが可能になる。
【００４２】
五酸化ニオブ膜の吸収係数ｋについて、真空排気してから酸化領域へ酸素ガスを導入した状態の圧力は、０．０５Ｐａから１０Ｐａの範囲が好適である。これより小さな圧力では膜の酸化度合いが不足して吸収係数が過大になり可視光透過率が低下することと酸素プラズマ濃度が薄く不安定になる傾向となる。また１０Ｐａより大きな圧力では、膜の酸化が進みすぎて吸収係数ｋが過小になり紫外光の透過率が上がってしまい、また酸素ガスが酸化領域内に留まらずスパッタ領域に到達する量が過大でターゲット表面が酸化して成膜速度が遅くなる傾向となる。
【００４３】
また、酸素プラズマを発生させる印可電力にも吸収係数は影響を受け、印加電力が１ｋＷ未満では酸化度合いが不足して可視光透過率が低下し、１０ｋＷより大きければ酸化が進みすぎて紫外光透過率が上がる傾向となる。また、成膜速度については、０．１ｎｍ／ｓ未満では、基板ホルダー１回転あたりの膜厚が非常に薄くなり、少しの酸素プラズマでも容易に酸化膜となるので、吸収係数ｋが過小になり紫外光透過率が上がる傾向となる。逆に１．２ｎｍ／ｓ以上では１回転あたりに酸化しなければならない原子の量が過大で酸化度合いが不足し可視光透過率が低下する傾向となる。
【００４４】
なお、本発明は図６に示すスパッタ装置の構成に限定されるものではなく、スパッタ領域や酸化領域を囲む仕切がない構成、基板ホルダーが概円盤状の回転体であり第１と第２のターゲット及び酸化領域が同じ向きに並列する構成などであっても有効である。
【００４５】
次に本発明の光学装置の一例について、図７を用いて説明する。これは液晶プロジェクターの一例である。超高圧水銀ランプか又はキセノンランプである光源３１から光が出射される。出射光は光の強度分布が偏っているので均一化するために第１インテグレータ３２と第２インテグレータ３３とで均一な強度分布に調整する。ここで、第１インテグレータ３２を基板として前述の紫外光遮蔽膜を形成してあるので、第１インテグレータ自体が紫外光遮蔽素子となっており、図３のように４０７．５ｎｍから３００ｎｍまで透過率１％以下に、また４１５ｎｍまで１０％以下に抑えられた急峻な遷移勾配を持っているので、第１インテグレータ３２以後は紫外光が遮蔽されて無くすことができる。また薄い膜も高精度に、全層の膜の屈折率も安定しているので、成膜不良が激減し高価なインテグレータの歩留まりを落とすことなく成膜することができる。
【００４６】
第２インテグレータ３３は偏光変換素子３４と接しており、偏光変換素子には有機材料である波長板が用いられており、従来の紫外光遮蔽素子では遮蔽しきれなかった紫外光により前記波長板が２０００時間程度の長期間経過すると損傷劣化していたが、本装置では５０００時間でも損傷劣化がなく長寿命化することができた。そして偏光変換素子以後は折り返しミラー３５を経て第１ダイクロイックミラー３６に入射し、本例では約５９０ｎｍ以下の緑から青色光は反射して、赤色光を透過して赤色画像用の液晶パネルに入射する。緑から青色光は第２ダイクロイックミラー３７に入射し、約５００ｎｍ以下の青色光は透過し、緑色光は反射して緑色画像用の液晶パネルに入射する。青色光は折り返しミラー３８を経て青色画像用の液晶パネル３９に入射する。従来ならばこの青色光に紫外光が含まれていたのでもう一つの紫外光遮蔽素子が組み込まれていたが、本発明では１個の紫外光遮蔽素子だけで充分に紫外光を遮蔽できるので青色光の光路の紫外光遮蔽素子を除去することが実現できる。さらに青色画像用液晶パネル自体とその近傍の有機材料からなる偏光板も従来より長い５０００時間以上の長寿命化ができる。
【００４７】
各色の液晶パネルで変換した画像は、色合成プリズム３９で合成されて投射レンズ４１にて投射される。以上の光学装置構成により、紫外光遮蔽素子が１個だけで部品点数が少なく小型化とコストダウンが可能になり、且つ画像劣化の寿命が長い装置とすることができる。なお本発明は、図７の構成に限定されず、プリズムで色分離する光学系、ダイクロイックミラーで合成する光学系、カラーホイールで時系列に色分離する光学系、反射型液晶パネルを用いた光変換装置、デジタル・ミラー・デバイスを用いた光変換装置などに対しても有効である。
【００４８】
（実施の形態２）
本発明の別の実施形態について図８を用いて説明する。透明な基板２１が円盤状の基板ホルダー２２に取り付けられている。真空槽内を真空排気してから第１スパッタ領域２６にアルゴンガスを５０ｓｃｃｍと酸素ガスを１０ｓｃｃｍ導入して０．７Ｐａの圧力にする。第１スパッタ領域には低屈折率膜の元となる珪素からなるターゲット２３を備え、高周波電力を印加して反応性スパッタを行う。スパッタ領域に導入する酸素量が多いので珪素ターゲットの最表面は酸化状態にあり、またスパッタされて基板に付着した時も酸化が進んで二酸化珪素の膜が得られる。同様に第２スパッタ領域２８には、高屈折率膜の元になるタンタルからなるターゲット２７を備え、アルゴンガス５０ｓｃｃｍと酸素ガス２５ｓｃｃｍを導入して１Ｐａの圧力にする。酸素ガス量が多いのでタンタルターゲットの最表面は酸化状態にあり、またスパッタされて基板に付着した時も酸化が進んで五酸化タンタルの膜が得られる。このように低屈折率膜のスパッタ成膜と高屈折率膜のスパッタ成膜とを所定の膜厚に対して成膜速度に応じた所定の時間行うことにより紫外光遮蔽膜を基板上に形成した紫外光遮蔽素子を得ることができる。
【００４９】
この実施形態は、スパッタ領域に導入するガスにおける体積比率が０．１未満であれば膜の酸化が不充分で可視光の透過率が低下してしまう。酸素ガスの比率が０．１から１．１の範囲であれば五酸化ニオブ膜の吸収係数ｋを０．１以上に制御することができる。そして酸素ガスの比率が１．１以上であれば五酸化ニオブの吸収係数が過小になり、紫外光の透過率が上がって紫外光遮蔽降下が大きく低下する。
【００５０】
本実施形態においても実施形態１のスパッタ方式と同様に、緻密で屈折率が安定した膜を、膜厚に影響されず薄い膜でも高精度に成膜することができるので、物理的膜厚３０ｎｍ以下の特に２０ｎｍ以下の非常に薄い膜でも精度良く成膜可能になり、蒸着では困難であった紫外光遮蔽膜を形成した紫外光遮蔽素子を得ることができる。
【００５１】
さらに本実施形態では図９に示す光学装置に、上記の紫外光遮蔽素子３１を、レンズ３３ａ〜３３ｄからなる撮像光学系とＣＣＤからなる撮像素子３２の間に導入することにより、紫外光にＣＣＤが感応して撮像画像の品質が劣化するという問題を解決することができた。３４はハウジングである。
【００５２】
【発明の効果】
以上のように本発明により、３００ｎｍから４００ｎｍの紫外光の透過率を１％以下に抑え、かつ急峻な遷移勾配を持つ紫外光遮蔽素子を、安定して精度良く生産性良く製作することが可能になり、プロジェクターの部品点数削減と長寿命化を実現できる。また撮像光学系においては色むら等の画質劣化を抑止することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態における多層積層膜の模式的断面図。
【図２】従来の比較例の波長と透過率の関係を示す光学特性図。
【図３】本発明の第１の実施形態における波長と透過率の関係を示す光学特性図。
【図４】本発明の第１の実施形態における波長と屈折率及び吸収係数の関係を示す光学特性図。
【図５】本発明の第１の実施形態における多層積層膜の製造工程を示す模式的断面図。
【図６】本発明の第１の実施形態における多層積層膜の製造装置を示す模式的断面図。
【図７】本発明の第１の実施形態における液晶プロジェクターの模式的構成図。
【図８】本発明の第２の実施形態における多層積層膜の製造工程を示す模式的断面図。
【図９】本発明の第２の実施形態における光学装置模式的断面図。
【図１０】従来の液晶プロジェクターの模式的構成図。
【図１１】従来の紫外光遮蔽膜の成膜方法である蒸着を示す説明図。
【図１２】比較例の分光透過率の特性図。
【図１３】比較例の分光透過率の特性図。
【符号の説明】
１透明基板
２低屈折率膜
３高屈折率膜
４，５ターゲット
６ホルダー
７アルゴンイオン
８粒子
９アンテナ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultraviolet light shielding element that transmits visible light and blocks ultraviolet light, a method of manufacturing the same, and an optical device.
[0002]
[Prior art]
As an optical device that utilizes the entire visible light range, there are a projector having a projection optical system and a camera having an imaging optical system.These optical systems are configured such that a lamp as a light source and ultraviolet light emitted by the sun enter the optical system. In order to prevent various adverse effects, an ultraviolet light shielding element is required. Specifically, in a projector, there is a problem that members such as a polarizing plate, a retardation plate, and a liquid crystal element made of an organic material in an optical system are damaged by ultraviolet light emitted from a lamp. In a camera, when ultraviolet light existing in the natural world enters an optical system and strikes an imaging device such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), there is a problem that a captured image is sensitively deteriorated. is there. Therefore, it is necessary to shield ultraviolet light by using an ultraviolet light shielding element in the optical system. Particularly, in a projector, since extremely strong ultraviolet light emitted from a high-intensity lamp at a close distance is received, unless the ultraviolet light is strictly shielded, deterioration of a polarizing plate or the like is inevitable. It is common to use a light shielding element together.
[0003]
FIG. 10 shows an optical system configuration diagram of a liquid crystal projector. An ultra-high pressure mercury lamp, a xenon lamp, or the like is used as a lamp 101 as a light source. The lamp emits not only visible light but also ultraviolet light, and enters an integrator 102 disposed in front of the lamp. Since organic materials such as a polarizing plate, a retardation plate, and an adhesive are used in a plurality of places in the elements after the integrator, a first ultraviolet light shielding film is deposited and formed on the incident surface of the integrator. Alternatively, as described later, it is difficult to form an ultraviolet light shielding film by vapor deposition, and the yield is often lowered as a film formation defect of an expensive integrator. In some cases, a film is formed on a glass substrate and disposed as an ultraviolet light shielding element between an integrator and a lamp. Here, since the shielding performance of the ultraviolet light shielding film is not sufficient, a small amount of ultraviolet light is transmitted together with visible light.
[0004]
The light transmitted through the integrator 102 passes through the second integrator 103, the polarization conversion element 104, and the folding mirror 105, and is transmitted by the first dichroic mirror 106, for example, red light to reach the liquid crystal element for red image, and has a wavelength of about 590 nm. The following green to blue light is reflected and enters the second dichroic mirror 107. In the second dichroic mirror, for example, green light is reflected and reaches the liquid crystal element for green image, and blue light of about 500 nm or less is transmitted. The blue light path contains the ultraviolet light leaked and transmitted by the first ultraviolet light shielding film described above, and is radiated to the blue image liquid crystal element and the polarizing plate attached to the blue image liquid crystal element. There is a problem that the polarizing plate is damaged and deteriorated by ultraviolet light. In order to prevent this problem, it is necessary to insert the second ultraviolet light shielding element 109 or to use an ultraviolet light shielding mirror at the position shown in FIG. 10 instead of a normal total reflection mirror. Furthermore, even when the ultraviolet light shielding element 109 is used, an element in which an ultraviolet light shielding film is formed on a transparent glass substrate is insufficient, and the substrate itself is made of a special glass having an ultraviolet light absorbing characteristic, and the ultraviolet light shielding film is formed on the surface thereof. In some cases, it is a formed element. As described above, it is important to shield ultraviolet light, and it is understood that the characteristics of the conventional ultraviolet light shielding film are insufficient. In the current optical system of a projector using a very high-intensity lamp, the transmittance of light emitted from the lamp to ultraviolet light of 300 nm to 400 nm must be suppressed to 1%. 110 is a liquid crystal panel, 111 is a color combining prism, and 112 is a projection lens.
[0005]
A conventional method of forming an ultraviolet light shielding film, vapor deposition, will be described with reference to FIG. A substrate 122 on which a film is to be formed is placed on a substrate holder 121 located above the vacuum chamber 120. The material of the film to be formed is put in the lower hearth. The inside of the vacuum chamber is evacuated to a vacuum, and an electron gun irradiates the evaporation material in the hearth with electrons with an electron gun to evaporate the heated and melted material to adhere to an upper substrate, thereby forming a film. The film thickness to be vapor-deposited is measured by projecting light from the optical film thickness meter 124 onto the monitor substrate 123 disposed in the substrate holder 121 and detecting light returning from the substrate. Usually, two evaporation sources are provided, and two kinds of

materials

125 and 126 of a low-refractive-index material and a high-refractive-index material, which are dielectric materials, can be alternately deposited and laminated on the substrate 122. By controlling the film thickness of each layer of the multilayer film to a predetermined design thickness, an ultraviolet light shielding film can be obtained.
[0006]
Titanium oxide, tantalum oxide, niobium oxide, zircon oxide, and the like are used as the high refractive index film in vapor deposition, and silicon oxide, magnesium fluoride, and the like are used as the low refractive index film.
[0007]
The characteristics of the ultraviolet light shielding film are required to transmit visible light from 420 to 430 nm to about 680 nm, and to shield ultraviolet light from about 410 nm to about 300 nm, which is a light emission region of the lamp. The wavelength in the transition region from the shielding band to the transmission band varies depending on the design specification of the optical device, and the half-value wavelength at which the light transmittance becomes 50% at half-value is set between 410 nm and 430 nm. The configuration of the ultraviolet light shielding film changes depending on the gradient of the transition region, the wavelength range and transmittance of the transmission band, and the wavelength range and transmittance of the shielding band.
[0008]
However, there are several problems in obtaining an ultraviolet light shielding film by the vapor deposition method, and Patent Document 1 below has been proposed as an approach to avoid the problems. First, the number of layers of the multilayer film increases as the transition gradient in the spectral transmittance curve of the ultraviolet light shielding film becomes steeper, the transmission band becomes wider and the transmittance becomes higher, and the shielding band becomes wider and the transmittance becomes lower. This increases the number of layers, resulting in a very multilayer structure of 30 layers or more, and the thickness error of each layer also increases the sensitivity of deteriorating the optical characteristics of the ultraviolet light shielding film, making the production difficult. Secondly, vapor deposition involves heating and melting the material and evaporating the suspended particles onto the substrate as described above. The film has a low density, the refractive index tends to fluctuate, and the adhesion to the substrate is relatively low. weak. The refractive index of the formed film tends to fluctuate depending on the melting state of the material in the hearth, the state of the deposit on the inner wall of the vacuum chamber, and the state of the adsorbed gas. If the refractive index of the film changes, the characteristics of the laminated ultraviolet light shielding film also change. Thirdly, since the process is unstable as described above, the film forming rate is also unstable, and the film thickness measurement in-process is indispensable. The accuracy of film thickness measurement is not good. Here, assuming that the refractive index of the film is n, the physical film thickness is d, and the wavelength of light is λ, the optical film thickness D of the film is represented by D = n × d × 4 / λ. The optical thickness H is 1H = n × d × 4 / λ, and the optical thickness L of the low refractive index film is 1L = n × d × 4 / λ. Since the monitor substrate is inexpensive and has good quality, soda lime glass commonly called blue glass and borosilicate glass commonly called white plate glass are used, and both have a refractive index of about 1.52. When the light is projected on the monitor substrate 123 and the reflected light is received by the optical film thickness meter 124, the reflected light is increased and measured for the high-refractive-index film with respect to the light amount of only the monitor substrate before film formation. The film thickness of λ / 4 of the light wavelength λ decreases to a peak, returns to the original light amount at λ / 2, and then increases again. The light amount changes like a sinusoidal wave. Then, a sinusoidal light amount change in an inverse pattern which gradually increases at λ / 4 is shown. The film thickness during film formation is measured using the change in the amount of light accompanying the film thickness on the monitor substrate. The monitor light amount is calculated in advance for a predetermined film thickness of each layer in the multilayer film, and the film thickness is controlled by stopping vapor deposition at the moment when the monitor light amount is reached. As described above, since the refractive index of the film fluctuates in an unstable manner during vapor deposition, the amount of monitor light also fluctuates depending on the refractive index of the film. In order to reduce this error as much as possible, when reaching the peak of the monitor light amount change, the light amount of the predetermined film thickness with respect to the peak light amount is calculated instantaneously during film formation, and the vapor deposition is stopped when the light amount slightly exceeds the peak. When set, the precision of the optical film thickness is relatively good. However, the ultraviolet light shielding film is thinner than the general optical thin film for visible light, and stops vapor deposition before reaching the peak of the monitor light amount or near the peak where the light amount change is slow and sensitivity to the film thickness is poor. Therefore, there is a problem that the accuracy of controlling the film thickness is deteriorated.
[0009]
If the design thickness of each layer is non-uniform and disparate, the film thickness controllability by the optical film thickness meter is poor and the reproducibility is inferior. This limits the degree of freedom in designing an ultraviolet light shielding film, and it is necessary to deteriorate the original design performance and increase the number of layers to compensate for the deterioration. Furthermore, the thinner the film, the worse the controllability of the film thickness, so that it is necessary to adopt a film structure avoiding the thin film, which is a problem because it limits the design and deteriorates the performance.
[0010]
The technique of Patent Document 1 listed below is a measure for solving the above problem, and proposes two solutions. One of them is to install a compensating plate to block the amount of film deposition on the substrate on which the ultraviolet light shielding film is formed without blocking the monitor substrate, and to reduce the thickness of the ultraviolet light shielding film substrate attached to the monitor substrate. This is a means of reducing by 40% to 15%. This means that the deposition of the evaporated material is hindered, the deposition rate is reduced, the utilization efficiency of the vapor deposition material is reduced, and the production efficiency is reduced and the cost is increased. The control film thickness on the monitor substrate only increases by 15 to 40% with respect to the design film thickness of the ultraviolet light shielding film, and the film thickness of each layer is lower than that of a general optical thin film, and the control by the optical film thickness meter is performed. The degree of improvement in accuracy is small. Another means is to set the ratio of the optical film thickness H of the high refractive index film and the optical film thickness L of the low refractive index film in the repetitive alternating layer in the film configuration to H / L or L / H of 1.2 to 2 0.0, the thicker film is first formed on the monitor substrate so that the peak of the change in the amount of light of the optical film thickness meter is exceeded, and the thinner film is formed by overlapping the thicker film. The peak is exceeded by measuring the amount of monitor light.
[0011]
[Patent Document 1]
JP-A-2002-258035
[0012]
[Problems to be solved by the invention]
However, in the above-mentioned conventional method, since the thicknesses of the high refractive index film and the low refractive index film are largely limited, it is difficult to obtain sufficient design performance with a small degree of freedom in design. For this reason, the number of film layers must be increased for designing, and as a result, manufacturing difficulty and cost increase. In addition, since two layers are stacked on the monitor substrate, there is a problem that the measurement accuracy of the second layer becomes unstable due to the fluctuation of the optical constant of the first layer and the error in controlling the film thickness.
[0013]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a stable and highly accurate ultraviolet light shielding element with good productivity, a method of manufacturing the same, and an optical device using the same, in order to solve the conventional problem.
[0014]
[Means for Solving the Problems]
In order to achieve the object, the ultraviolet light shielding element of the present invention is an ultraviolet light shielding element in which a film including a high refractive index film and a low refractive index film is laminated on a transparent substrate in a multilayer manner, wherein the high refractive index The wavelength at which the light absorption coefficient of at least one film selected from a film and a low refractive index film is 0.1 or more is in the range of 300 nm to 360 nm.
[0015]
The method for manufacturing an ultraviolet light shielding element of the present invention comprises the steps of: sputtering at least two types of targets for a low refractive index film and a high refractive index film to form a film on a transparent substrate; transferring the substrate to an oxidized region; What is claimed is: 1. A method for manufacturing an ultraviolet light shielding element comprising: oxidizing a film to form an oxide film, wherein at least one kind of the oxide film has a wavelength at which a light absorption coefficient is 0.1 or more in a range of 300 nm to 360 nm. The control is performed as described in (1).
[0016]
Next, another method of manufacturing an ultraviolet light shielding element according to the present invention is characterized in that when two kinds of targets for the low refractive index film and the high refractive index film are sputtered to form a film on a substrate, oxygen is added to the sputtered region. Using a reactive sputtering method in which a gas is introduced and an oxide is attached to a substrate, the wavelength at which the light absorption coefficient of at least one of the oxide films is 0.1 or more is in the range of 300 nm to 360 nm. It is characterized by controlling.
[0017]
Next, the optical device of the present invention includes a light source, a light conversion device that converts light emitted from the light source into an image signal, and a projection optical system that projects the converted image light. A high-refractive-index film and a low-refractive-index film, which are formed by sputtering a target, are stacked, and the wavelength at which the absorption coefficient of at least one of the films is 0.1 or more is in the range of 300 nm to 360 nm. An ultraviolet light shielding element having a thin film is provided.
[0018]
Another optical device of the present invention is a device in which a high-refractive-index film and a low-refractive-index film formed by sputtering a target are stacked between an imaging optical system that captures external light to form an image and an imaging element. Further, an ultraviolet light shielding element having a thin film having a wavelength in the range of 300 nm to 360 nm at which the absorption coefficient of at least one film is 0.1 or more is arranged.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The ultraviolet light shielding element of the present invention has a wavelength at which a light absorption coefficient of at least one film selected from a high refractive index film and a low refractive index film constituting a multilayer laminated film is 0.1 or more in a range of 300 nm to 360 nm. is there. This makes it possible to suppress the transmittance of ultraviolet light from 300 nm to 400 nm to 1% or less and to produce an ultraviolet light shielding element having a steep transition gradient stably, accurately and with high productivity. The number of parts can be reduced and the service life can be extended. Further, in the image pickup optical system, it is possible to suppress image quality deterioration such as color unevenness.
[0020]
Niobium pentoxide, titanium dioxide, tantalum pentoxide, and zirconium dioxide are suitable for the thin film having a wavelength at which the light absorption coefficient of 0.1 or more is in the range of 300 nm to 360 nm. Further, it is preferable to include a film whose physical film thickness is smaller than 30 nm, and it is particularly preferable that the physical film thickness is 20 nm or less. Further, the number of layers is preferably 20 or more and 60 or less, and more preferably 30 or more.
[0021]
The wavelength width at which the transmittance near the boundary between visible light and ultraviolet light transitions from 10% to 90% is preferably 15 nm or less, and particularly preferably 10 nm or less. It is preferable that the wavelength at which the transmittance decreases to 1% or less from visible light to ultraviolet light is between 405 and 420 nm, and the transmittance is 1% or less up to a wavelength of 300 nm.
[0022]
It is preferable that the transparent substrate in the above-mentioned ultraviolet light shielding element is a sheet glass. Alternatively, a glass substrate having a lens array on at least one surface is preferable as the transparent substrate in the ultraviolet light shielding element.
[0023]
Next, in the method of the present invention, it is preferable that oxygen gas is introduced into the oxidized region and the pressure is in the range of 0.05 Pa to 5 Pa. If oxygen is not added, the oxygen required for the oxidation of the film becomes insufficient, the oxidation becomes insufficient, the absorption coefficient becomes excessive, and the film tends to be opaque. Conversely, if there is too much oxygen, the oxidation will proceed too much and the absorption coefficient will be too small, tending to reduce the ultraviolet light shielding effect.
[0024]
Further, the applied power for generating oxygen plasma is preferably 1 kW to 10 kW. If the power applied to the oxidized region is too small, the oxygen plasma is weak, the oxidation of the film is insufficient, and the absorption coefficient tends to be too large. Conversely, when the power becomes excessive, the oxidation tends to be excessive, and the absorption coefficient tends to be too small.
[0025]
Further, it is preferable that the film formation rate is 0.1 to 2.0 nm / s. If the film formation rate is too low, the film is oxidized for a sufficient time, and the oxidation proceeds too much, and the absorption coefficient tends to be too small. Conversely, if the deposition rate is too high, the oxidation tends to be too low and the absorption coefficient tends to be too high.
[0026]
In another manufacturing method of the present invention, in the reactive sputtering, it is preferable to set the volume ratio of oxygen in the introduced gas to 0.1 to 0.8. The absorption coefficient can be controlled by the amount of oxygen introduced.
[0027]
In the optical device according to the aspect of the invention, the light conversion device includes a color separation optical system that separates the light emitted from the lamp into three color bands, an element that converts the separated light into image signals of each color, and combines the converted color images. It is preferable to use a color synthesizing optical system. The image signal conversion element is a liquid crystal panel or a digital mirror device. It is preferable that the light conversion device includes a color separation optical system that separates outgoing light of the lamp into three or more color bands in time series, and an element that converts the separated light into image signals of each color.
[0028]
Hereinafter, specific embodiments will be described with reference to the drawings.
[0029]
(Embodiment 1)
FIG. 1 shows an embodiment of the present invention. An ultraviolet light shielding film in which low refractive index films 2 and high refractive index films 3 are alternately laminated on the surface of a transparent substrate 1 is formed. Table 1 shows the film configuration of FIG. The design wavelength was 360 nm, the substrate was optical glass BK7, silicon dioxide was used as the low refractive index film, and niobium pentoxide was used as the high refractive index film.
[0030]
[Table 1]

[0031]
The refractive index, absorption coefficient, and optical film thickness in Table 1 are values at a design wavelength of 360 nm, and these values have a wavelength dependency called dispersion, and differ depending on the wavelength. In the present embodiment, the transmittance is 96% or more in the region of 430 nm to 680 nm of visible light, the transmittance is 1% or less in the region of 300 to 405 nm of ultraviolet light, and the transmittance increases from ultraviolet light to visible light. The wavelength corresponding to a transmittance of 50% in the transition region going forward is called a half value, and the design specification is set to a half value of 420 nm.
[0032]
In this film configuration, when the film is completely oxidized and a film having an absorption coefficient close to 0 is used, the spectral characteristics shown in FIG. 2 are obtained, and the transmittance suddenly deteriorates in the region of a wavelength of 320 nm or less to 314 nm. In this case, as much as 36% of the ultraviolet light is transmitted, and the ultraviolet light shielding function is greatly reduced. In this case, there are also six layers having a physical film thickness of 20 nm or less, and it is difficult to obtain characteristics as designed by vapor deposition while controlling the film thickness using an optical film thickness meter.
[0033]
However, as a result of intensive studies focusing on the film forming method and film characteristics, an ultraviolet light shielding film having a thin film whose wavelength at which the absorption coefficient k of at least one film is 0.1 or more is in the range of 300 nm to 360 nm is obtained. It has been found that the spectral transmittance of the ultraviolet light shielding element is greatly improved as shown in FIG.
[0034]
FIG. 4 is a graph showing the relationship between the refractive index n and the absorption coefficient k with respect to the light wavelength λ of niobium pentoxide. The thin solid line in FIG. 4 indicates the refractive index, the thick solid line indicates the absorption coefficient of niobium pentoxide having an absorption coefficient k of 0.11 at a wavelength of 300 nm, and the dashed line indicates the absorption coefficient of niobium pentoxide whose absorption coefficient exceeds 0.1 at 325 nm. The absorption coefficient is shown. If the wavelength whose absorption coefficient exceeds 0.1 is in the range of 300 nm to 360 nm, the transmittance of ultraviolet light of 300 to 400 nm can be suppressed to 0.9% or less and 1% or less as shown in FIG. Was. Further, when niobium pentoxide having a wavelength of 325 nm and an absorption coefficient exceeding 0.1 was used, a high shielding ability of a maximum of 0.2% in the transmittance of ultraviolet light of 300 to 400 nm was exhibited.
[0035]
Here, the characteristics of the spectral transmittance shown in FIG. 12 as a comparative example are obtained by setting the physical film thickness of each layer to 30 nm or more as in a conventional film. As described above, the ultraviolet light around 390 to 400 nm exceeds 1%, reaches 10% at 415 nm, and the visible light transmittance around 430 nm decreases to around 90%, and it is not possible to obtain sufficient characteristics. .
[0036]
By using a thin film having a physical film thickness of 30 nm or less as in this embodiment or a thin film which is difficult to control with a thinner vapor deposition of 20 nm or less, the transmittance can be increased over the entire range of 300 to 400 nm ultraviolet light. While decreasing, the gradient of the transition region where the transmittance increases from the ultraviolet light to the visible light can be made steep. The wavelength width at which the transmittance transitions from 10% to 90% can be reduced to 15 nm or less or even steeply 10 nm or less. In the example of FIG. 3, the wavelength width can be reduced from 415 nm to 423.5 nm to 8.5 nm. .
[0037]
Here, the spectral transmittance characteristic shown in FIG. 13 as a comparative example is that of a 19-layer ultraviolet light shielding film. As described above, the transmittance of ultraviolet light from 389 nm or more exceeds 1%, reaches 10% at 409 nm, and reaches 90% at 427 nm. The transition wavelength width from 10% to 90% is a gentle gradient of 18 nm. . In addition, the transmittance of the visible light also fluctuates greatly, which is not good. On the other hand, in order to obtain a wide range of ultraviolet light shielding performance and a steep transition gradient, it is possible to increase the number of the multilayer films to 20 or more. Therefore, the film formation time is prolonged, and the productivity tends to decrease.
[0038]
Next, regarding the means for obtaining the above-mentioned ultraviolet light shielding element, FIG. 5 shows a principle diagram, and FIG. 6 shows a schematic diagram of a sputtering apparatus. The first vacuum chamber 16 is a vacuum chamber that can be opened and closed, although only a part of the vacuum chamber is simply shown in FIG. 6. The first vacuum chamber 16 is opened to the atmosphere, the transparent substrate 1 is mounted on the cylindrical substrate holder 6, and then the vacuum chamber is evacuated. Then, the substrate is transferred from the first vacuum chamber 16 to the second vacuum chamber 15 in a vacuum state, evacuated to a predetermined pressure, and then sputter deposition starts.
[0039]
The first sputtering region 12 shown in FIG. 5 includes a target 4 which is silicon as a source of the low refractive index film, and a magnet and an electrode device (not shown) for supplying power are provided on the back surface of the target. ing. As for the targets 4 and 5, as shown in FIG. 6, if a dual target configuration is used in which two target electrodes are paired, an AC voltage is applied to prevent charging of the target surface, thereby enabling stable discharge. Alternatively, a system may be provided in which each target electrode is provided for discharging. When 100 sccm of argon gas is introduced into the first sputtering region 12 and a power of 6 kW is applied to the target at a pressure of 0.2 Pa by alternating current, argon plasma discharge is generated and sputtering starts. The argon ions 7 in the plasma collide with the target 4 by magnetic force, and the particles 8 repelled from the target adhere to the substrate 1. The film just deposited in the sputter region is silicon oxide in which silicon is combined to some extent with oxygen present in the surrounding atmosphere. When oxygen gas as well as argon gas is introduced, the degree of oxidation of the film increases, but the film formation rate tends to decrease. Therefore, optimal conditions may be set in terms of production efficiency. The substrate 1 is transported to the oxidized area 14 with the rotation of the substrate holder 6. While passing through the second sputtering region 13 on the way, the sputtering target is not usually formed on the second target 5. Oxygen gas is introduced into the oxidized region 14 at 200 sccm, and the pressure is set to 0.3 Pa. Oxygen plasma is generated by applying a high-frequency power of 5 kW through the window 10 by the antenna 9. Then, the film on the substrate is exposed to particles 11 of oxygen ions and oxygen radicals in the oxygen plasma, so that an oxide film, that is, a silicon dioxide film can be formed.
[0040]
Similarly, the second sputtering region 13 is provided with a target 5 made of niobium, which is a source of the high refractive index film, and is supplied with a mixture of 100 sccm of argon gas and 5 sccm of oxygen gas to form a state of a pressure of 0.3 Pa. I do. The oxygen gas introduced here is for assisting the oxidation of niobium, and is set so as to obtain an optimal absorption coefficient with an optimal oxidation degree in accordance with the conditions of the subsequent oxidation treatment. Not always introduced. The target is sputtered by discharging by applying an AC power of 4 kW. A niobium film that has been oxidized to some extent is formed on the substrate, and is immediately transferred to the oxidized region 14 with the rotation of the substrate holder, and is exposed to oxygen plasma to obtain a niobium pentoxide film. An ultraviolet light shielding film in which a low-refractive-index film and a high-refractive-index film are alternately laminated on the substrate by performing sputtering for a predetermined time according to the film forming speed with respect to the film thickness of each layer. An element can be obtained.
[0041]
According to the sputtering method described above, the particles repelled by the accelerated argon ions have strong energy, and the film formed by adhering to the substrate is a stable film having a dense and strong adhesive force. Become. Therefore, a film whose refractive index is stable from the beginning to the end of the multilayer film and between batches can be obtained as compared with vapor deposition. Further, high film thickness accuracy can be obtained even with a thin film whose film thickness controllability is independent of the film thickness. Since the optical constants and the film thickness of the film are stable in this way, the ultraviolet light shielding film, which is difficult to perform by evaporation because the thickness of each layer is small and the number of layers is large, can be stably precisely formed with the characteristics as designed. It becomes possible to make.
[0042]
Regarding the absorption coefficient k of the niobium pentoxide film, the pressure in the state where oxygen gas is introduced into the oxidation region after evacuation is preferably in the range of 0.05 Pa to 10 Pa. If the pressure is lower than this, the degree of oxidation of the film becomes insufficient, the absorption coefficient becomes excessive, the visible light transmittance decreases, and the oxygen plasma concentration tends to be thin and unstable. At a pressure higher than 10 Pa, the oxidation of the film proceeds too much, the absorption coefficient k becomes too small, the transmittance of ultraviolet light increases, and the amount of oxygen gas that does not stay in the oxidation region and reaches the sputtering region is too large. The target surface is oxidized, and the film forming rate tends to be slow.
[0043]
In addition, the absorption coefficient is also affected by the applied power for generating oxygen plasma. When the applied power is less than 1 kW, the degree of oxidation is insufficient and the visible light transmittance is reduced. When the applied power is more than 10 kW, the oxidation proceeds too much to transmit ultraviolet light. Rate tends to rise. When the deposition rate is less than 0.1 nm / s, the film thickness per one rotation of the substrate holder becomes extremely thin, and even a little oxygen plasma easily becomes an oxide film, so that the absorption coefficient k becomes too small. The ultraviolet light transmittance tends to increase. Conversely, at 1.2 nm / s or more, the amount of atoms that must be oxidized per rotation is too large, the degree of oxidation is insufficient, and the visible light transmittance tends to decrease.
[0044]
The present invention is not limited to the configuration of the sputtering apparatus shown in FIG. 6, but has a configuration in which there is no partition surrounding the sputtered region and the oxidized region. It is effective even if the target and the oxidized region are arranged in parallel in the same direction.
[0045]
Next, an example of the optical device of the present invention will be described with reference to FIG. This is an example of a liquid crystal projector. Light is emitted from a light source 31 that is an ultra-high pressure mercury lamp or a xenon lamp. Since the intensity distribution of the emitted light is biased, the first integrator 32 and the second integrator 33 adjust the intensity distribution so as to be uniform. Here, since the above-mentioned ultraviolet light shielding film is formed using the first integrator 32 as a substrate, the first integrator itself is an ultraviolet light shielding element, and has a transmittance from 407.5 nm to 300 nm as shown in FIG. Since it has a steep transition gradient of 1% or less and 10% or less up to 415 nm, the ultraviolet light after the first integrator 32 can be shielded and eliminated. In addition, since a thin film has high accuracy and the refractive index of the film of all layers is stable, film formation defects are drastically reduced, and a film can be formed without lowering the yield of an expensive integrator.
[0046]
The second integrator 33 is in contact with the polarization conversion element 34, and a wavelength plate that is an organic material is used for the polarization conversion element, and the wavelength plate is formed by ultraviolet light that cannot be completely shielded by a conventional ultraviolet light shielding element. Although damage and deterioration were observed after a long period of time of about 2000 hours, this apparatus was able to extend the life without damage and deterioration even after 5000 hours. After the polarization conversion element, the light enters the first dichroic mirror 36 via the folding mirror 35. In this example, green to blue light of about 590 nm or less is reflected, red light is transmitted, and enters the liquid crystal panel for red image. I do. The green to blue light is incident on the second dichroic mirror 37, the blue light of about 500 nm or less is transmitted, and the green light is reflected and incident on the liquid crystal panel for green image. The blue light is incident on a liquid crystal panel 39 for a blue image via a folding mirror 38. Conventionally, this blue light contained ultraviolet light, so another ultraviolet light shielding element was incorporated. However, in the present invention, only one ultraviolet light shielding element can sufficiently block ultraviolet light, so Removal of the ultraviolet light shielding element in the optical path of light can be realized. Further, the blue image liquid crystal panel itself and a polarizing plate made of an organic material in the vicinity thereof can also have a longer life of 5000 hours or more than the conventional one.
[0047]
The images converted by the liquid crystal panels of each color are combined by the color combining prism 39 and projected by the projection lens 41. With the above optical device configuration, only one ultraviolet light shielding element is used, the number of components is small, miniaturization and cost reduction are possible, and a device with a long life of image deterioration can be provided. The present invention is not limited to the configuration shown in FIG. 7, but includes an optical system for color separation by a prism, an optical system for synthesis by a dichroic mirror, an optical system for color separation in a time series by a color wheel, and light using a reflective liquid crystal panel. It is also effective for a conversion device, a light conversion device using a digital mirror device, and the like.
[0048]
(Embodiment 2)
Another embodiment of the present invention will be described with reference to FIG. A transparent substrate 21 is mounted on a disk-shaped substrate holder 22. After evacuating the vacuum chamber, 50 sccm of argon gas and 10 sccm of oxygen gas are introduced into the first sputtering region 26 to a pressure of 0.7 Pa. The first sputtering region is provided with a target 23 made of silicon which is a source of a low refractive index film, and performs high frequency power to perform reactive sputtering. Since the amount of oxygen introduced into the sputter region is large, the outermost surface of the silicon target is in an oxidized state, and when sputtered and adhered to the substrate, the oxidation proceeds and a silicon dioxide film is obtained. Similarly, the second sputtering region 28 is provided with a target 27 made of tantalum, which is a source of the high refractive index film, and a pressure of 1 Pa is introduced by introducing 50 sccm of argon gas and 25 sccm of oxygen gas. Since the amount of oxygen gas is large, the outermost surface of the tantalum target is in an oxidized state, and when sputtered and adhered to the substrate, oxidation proceeds, and a tantalum pentoxide film is obtained. In this way, the ultraviolet light shielding film is formed on the substrate by performing the sputter deposition of the low-refractive-index film and the sputter deposition of the high-refractive-index film for a predetermined film thickness for a predetermined time in accordance with a film formation rate. The obtained ultraviolet light shielding element can be obtained.
[0049]
In this embodiment, if the volume ratio of the gas introduced into the sputtering region is less than 0.1, the oxidation of the film is insufficient and the transmittance of visible light is reduced. If the ratio of oxygen gas is in the range of 0.1 to 1.1, the absorption coefficient k of the niobium pentoxide film can be controlled to 0.1 or more. If the ratio of oxygen gas is 1.1 or more, the absorption coefficient of niobium pentoxide becomes too small, the transmittance of ultraviolet light increases, and the drop in ultraviolet light shielding greatly decreases.
[0050]
In the present embodiment, as in the case of the sputtering method of the first embodiment, a dense and stable film having a stable refractive index can be formed with high accuracy even if the thickness is small regardless of the film thickness. It is possible to accurately form even an extremely thin film having a thickness of 20 nm or less, and to obtain an ultraviolet light shielding element having an ultraviolet light shielding film which is difficult to be formed by vapor deposition.
[0051]
Further, in the present embodiment, the ultraviolet light shielding element 31 is introduced between the imaging optical system including the lenses 33a to 33d and the imaging element 32 including the CCD in the optical device illustrated in FIG. Was able to solve the problem that the quality of the captured image was degraded in response to the problem. 34 is a housing.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress the transmittance of ultraviolet light from 300 nm to 400 nm to 1% or less and to manufacture an ultraviolet light shielding element having a steep transition gradient stably, accurately and with high productivity. Thus, the number of parts of the projector can be reduced and the life of the projector can be prolonged. Further, in the image pickup optical system, it is possible to suppress image quality deterioration such as color unevenness.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a multilayer laminated film according to a first embodiment of the present invention.
FIG. 2 is an optical characteristic diagram showing a relationship between wavelength and transmittance of a conventional comparative example.
FIG. 3 is an optical characteristic diagram showing a relationship between wavelength and transmittance according to the first embodiment of the present invention.
FIG. 4 is an optical characteristic diagram showing a relationship between a wavelength, a refractive index, and an absorption coefficient according to the first embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing a manufacturing process of the multilayer laminated film according to the first embodiment of the present invention.
FIG. 6 is a schematic sectional view showing an apparatus for manufacturing a multilayer laminated film according to the first embodiment of the present invention.
FIG. 7 is a schematic configuration diagram of a liquid crystal projector according to the first embodiment of the present invention.
FIG. 8 is a schematic cross-sectional view showing a manufacturing process of a multilayer laminated film according to a second embodiment of the present invention.
FIG. 9 is a schematic sectional view of an optical device according to a second embodiment of the present invention.
FIG. 10 is a schematic configuration diagram of a conventional liquid crystal projector.
FIG. 11 is an explanatory view showing vapor deposition which is a conventional method for forming an ultraviolet light shielding film.
FIG. 12 is a characteristic diagram of spectral transmittance of a comparative example.
FIG. 13 is a characteristic diagram of spectral transmittance of a comparative example.
[Explanation of symbols]
1 Transparent substrate
2 Low refractive index film
3 High refractive index film
4,5 target
6 holder
7 Argon ion
8 particles
9 Antenna

Claims

透明基板上に、高屈折率膜と低屈折率膜とを含む膜を多層積層した紫外光遮蔽素子であって、
前記高屈折率膜及び低屈折率膜から選ばれる少なくとも一つ膜の光吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあることを特徴とする紫外光遮蔽素子。An ultraviolet light shielding element in which a film including a high refractive index film and a low refractive index film is multilayered on a transparent substrate,
An ultraviolet light shielding element, wherein a wavelength at which a light absorption coefficient of at least one film selected from the high refractive index film and the low refractive index film is 0.1 or more is in a range of 300 nm to 360 nm.

前記光吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜が、五酸化ニオブ、二酸化チタン、五酸化タンタル及び二酸化ジルコニウムから選ばれる少なくとも一つの酸化膜である請求項１に記載の紫外光遮蔽素子。The thin film in which the wavelength at which the light absorption coefficient is 0.1 or more is in the range of 300 nm to 360 nm is at least one oxide film selected from niobium pentoxide, titanium dioxide, tantalum pentoxide, and zirconium dioxide. The ultraviolet light shielding element as described in the above.

前記高屈折率膜及び低屈折率膜から選ばれる少なくとも一つ膜の物理的膜厚が、３０ｎｍより薄い層の膜を含む請求項１または２に記載の紫外光遮蔽素子。3. The ultraviolet light shielding element according to claim 1, wherein a physical thickness of at least one film selected from the high refractive index film and the low refractive index film includes a film having a thickness smaller than 30 nm.

前記物理的膜厚が２０ｎｍより薄い層の膜を含む請求項３に記載の紫外光遮蔽素子。4. The ultraviolet light shielding device according to claim 3, wherein the physical film thickness includes a film having a thickness smaller than 20 nm.

前記多層膜の層数が２０層以上６０層以下である請求項１〜４のいずれかに記載の紫外光遮蔽素子。The ultraviolet light shielding element according to any one of claims 1 to 4, wherein the number of layers of the multilayer film is 20 or more and 60 or less.

前記多層膜の層数が３０層以上である請求項５に記載の紫外光遮蔽素子。The ultraviolet light shielding element according to claim 5, wherein the number of layers of the multilayer film is 30 or more.

前記紫外光遮蔽素子の紫外光から可視光への境界付近の透過率が１０％から９０％に遷移する波長幅が、１５ｎｍ以下である請求項１〜６のいずれかに記載の紫外光遮蔽素子。The ultraviolet light shielding element according to any one of claims 1 to 6, wherein the wavelength width at which the transmittance of the ultraviolet light shielding element near the boundary from ultraviolet light to visible light transitions from 10% to 90% is 15 nm or less. .

前記紫外光遮蔽素子の紫外光から可視光への境界付近の透過率が１０％から９０％に遷移する波長幅が、１０ｎｍ以下である請求項７に記載の紫外光遮蔽素子。8. The ultraviolet light shielding element according to claim 7, wherein a wavelength width at which the transmittance of the ultraviolet light shielding element near the boundary from ultraviolet light to visible light transitions from 10% to 90% is 10 nm or less. 9.

前記紫外光遮蔽素子の可視光から紫外光へかけて透過率が１％以下に低下する波長が４０５から４２０ｎｍの間にあり、且つ前記透過率が１％以下に達する波長から３００ｎｍの波長まで透過率が１％以下である請求項１〜８のいずれかに記載の紫外光遮蔽素子。The wavelength at which the transmittance of the ultraviolet light shielding element falls to 1% or less from visible light to ultraviolet light is between 405 and 420 nm, and the wavelength is between 300 nm and 300 nm. The ultraviolet light shielding element according to claim 1, wherein the ratio is 1% or less.

前記透明基板が板状ガラスである請求項１〜９のいずれかに記載の紫外光遮蔽素子。The ultraviolet light shielding element according to claim 1, wherein the transparent substrate is a sheet glass.

前記透明基板が、少なくとも片面にレンズアレイを有するガラス基板である請求項１〜９のいずれかに記載の紫外光遮蔽素子。The ultraviolet light shielding element according to any one of claims 1 to 9, wherein the transparent substrate is a glass substrate having a lens array on at least one surface.

低屈折率膜用と高屈折率膜用の少なくとも２種類のターゲットをスパッタして透明基板に成膜し、前記基板を酸化領域に搬送し、スパッタ膜を酸化処理して酸化膜とする紫外光遮蔽素子の製造方法であって、
前記酸化膜の少なくとも１種類の膜を、光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御することを特徴とする紫外光遮蔽素子の製造方法。At least two types of targets for a low-refractive-index film and a high-refractive-index film are sputtered to form a film on a transparent substrate, the substrate is conveyed to an oxidized region, and the sputtered film is oxidized to form an oxide film. A method for manufacturing a shielding element,
A method of manufacturing an ultraviolet light shielding element, wherein at least one kind of the oxide film is controlled so that a wavelength at which a light absorption coefficient is 0.1 or more is in a range of 300 nm to 360 nm.

前記光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御する方法が、前記酸化領域へ酸素ガスを導入し、圧力を０．０５Ｐａ以上５Ｐａ以下である請求項１２に記載の紫外光遮蔽素子の製造方法。The method of controlling the wavelength at which the light absorption coefficient is 0.1 or more to be in the range of 300 nm to 360 nm, introducing oxygen gas into the oxidized region, and setting the pressure to 0.05 Pa or more and 5 Pa or less. 13. The method for producing an ultraviolet light shielding element according to item 12.

前記光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御する方法が、前記酸化領域における酸化処理の際、印加電力を１ｋＷ以上１０ｋＷ以下に制御して酸素プラズマを発生させる方法である請求項１２に記載の紫外光遮蔽素子の製造方法。The method of controlling the wavelength at which the light absorption coefficient becomes 0.1 or more to be in the range of 300 nm to 360 nm is performed by controlling the applied power to 1 kW or more and 10 kW or less during the oxidation treatment in the oxidation region. The method for producing an ultraviolet light shielding element according to claim 12, which is a method for generating the ultraviolet light.

前記光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御する方法が、前記低屈折率膜と高屈折率膜の各膜の成膜速度を０．１〜２．０ｎｍ／ｓである請求項１２に記載の紫外光遮蔽素子の製造方法。The method of controlling the wavelength at which the light absorption coefficient is 0.1 or more to be in the range of 300 nm to 360 nm is performed by controlling the film forming speed of each of the low refractive index film and the high refractive index film to 0.1 to 0.1 nm. The method for manufacturing an ultraviolet light shielding element according to claim 12, wherein the speed is 2.0 nm / s.

前記低屈折率膜用と高屈折率膜用の２種類のターゲットをスパッタして基板に成膜を行う際、
前記スパッタ領域に酸素ガスを導入し酸化物を基板に付着させる反応性スパッタ方式を用い、前記酸化膜の少なくとも１種類の膜の光の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にあるように制御することを特徴とする紫外光遮蔽素子の製造方法。When forming two types of targets for the low refractive index film and the high refractive index film by sputtering,
Using a reactive sputtering method in which an oxygen gas is introduced into the sputtering region to attach an oxide to a substrate, a wavelength at which the light absorption coefficient of at least one of the oxide films is 0.1 or more is from 300 nm to 360 nm. A method for manufacturing an ultraviolet light shielding element, wherein the ultraviolet light shielding element is controlled to be within a range.

反応性スパッタにおいてスパッタ領域に導入するガスにおける酸素の体積比率を０．１〜１．１に設定する請求項１６に記載の紫外光遮蔽素子の製造方法。17. The method for manufacturing an ultraviolet light shielding element according to claim 16, wherein a volume ratio of oxygen in a gas introduced into a sputtering region in reactive sputtering is set to 0.1 to 1.1.

光源と、光源から出射された光を画像信号に変換する光変換装置と、前記変換した画像光を投射する投射光学系とを備え、
前記光源と光変換装置との間に、ターゲットをスパッタして成膜する高屈折率膜と低屈折率膜とを積層し、少なくとも一方の膜の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜を有する紫外光遮蔽素子を配置することを特徴とする光学装置。A light source, a light conversion device that converts light emitted from the light source into an image signal, and a projection optical system that projects the converted image light,
A high-refractive-index film and a low-refractive-index film formed by sputtering a target are stacked between the light source and the light conversion device, and the wavelength at which the absorption coefficient of at least one of the films is 0.1 or more is 300 nm. An optical device, comprising an ultraviolet light shielding element having a thin film in a range of 3 to 360 nm.

前記光変換装置は、光源の出射光を３色の帯域に分離する色分離光学系と、分離した各色の画像信号に変換する素子と、前記変換した各色画像を合成する色合成光学系とで構成する請求項１８に記載の光学装置。The light conversion device includes a color separation optical system that separates outgoing light from a light source into three color bands, an element that converts the separated light into image signals of each color, and a color synthesis optical system that combines the converted color images. The optical device according to claim 18, wherein the optical device is configured.

前記光変換装置は、光源の出射光を３色以上の色帯域に時系列分離する色分離光学系と、分離した各色の画像信号に変換する素子とで構成する請求項１８に記載の光学装置。19. The optical device according to claim 18, wherein the light conversion device includes a color separation optical system that time-separates light emitted from the light source into three or more color bands, and an element that converts the light into image signals of the separated colors. .

外部の光を取り込んで結像させる撮像光学系と、撮像素子との間に、ターゲットをスパッタして成膜する高屈折率膜と低屈折率膜とを積層し、少なくとも一方の膜の吸収係数が０．１以上となる波長が３００ｎｍから３６０ｎｍの範囲にある薄膜を有する紫外光遮蔽素子を配置することを特徴とする光学装置。A high-refractive-index film and a low-refractive-index film, which are formed by sputtering a target, are stacked between an imaging optical system that captures external light to form an image and an imaging device, and an absorption coefficient of at least one of the films is formed. An optical device, comprising: an ultraviolet light shielding element having a thin film having a wavelength in a range of 300 nm to 360 nm in which the wavelength is 0.1 or more.