JP2008102363A - Nd filter and light quantity adjusting device using the same - Google Patents
Nd filter and light quantity adjusting device using the same Download PDFInfo
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- JP2008102363A JP2008102363A JP2006285466A JP2006285466A JP2008102363A JP 2008102363 A JP2008102363 A JP 2008102363A JP 2006285466 A JP2006285466 A JP 2006285466A JP 2006285466 A JP2006285466 A JP 2006285466A JP 2008102363 A JP2008102363 A JP 2008102363A
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- Optical Elements Other Than Lenses (AREA)
- Physical Vapour Deposition (AREA)
Abstract
Description
本発明はＮＤフィルタ及びこれを用いた光量絞り装置に関する。ＮＤ（ニュートラルデンシティ）フィルタは、光量絞り用として可視域全般に渡り均一に透過光量を減衰させる目的で使用するものである。 The present invention relates to an ND filter and a light quantity reduction device using the ND filter. The ND (neutral density) filter is used for the purpose of attenuating the transmitted light amount uniformly over the entire visible range for light amount reduction.
従来よりカメラやビデオなどの撮像系において、被写体輝度が高過ぎる時は絞りを最小径に絞っても（開口径を最小にしても）感光面へ所定量以上の光量が入射してしまう場合がある。この為、撮像系の一部にＮＤフィルタを装着して感光面への入射光量を規制することがしばしば行われている。この場合、ＮＤフィルタの分光特性は単に入射光量を減少させるということから、可視領域全般に亘り均一な透過率を有していることが必要となっている。カメラやビデオなどの撮像系においては、可視域全般に亘り均一に光量を減衰させる目的で以前からプラスチックフィルムベースのＮＤフィルタが用いられてきた。特に近年では光学特性及び耐久性に優れたプラスチックフィルムベースでその上に光学多層薄膜を積層したＮＤフィルタが多用される様になってきており、特許文献１及び２に記載されている。
特許文献１に記載されたＮＤフィルタは、透明フィルム基材として、アセチルセルロースやポリエチレンテレフタレート（ＰＥＴ）を使っている。また特許文献２に記載されたＮＤフィルタは、ポリプロピレン、ポリエステル、ポリスチレン、ポリ塩化ビニリデン、ポリエチレン、ポリエチレンテレフタレートなどの透明フィルム基材を用いている。 The ND filter described in Patent Document 1 uses acetyl cellulose or polyethylene terephthalate (PET) as a transparent film substrate. The ND filter described in Patent Document 2 uses a transparent film substrate such as polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, or polyethylene terephthalate.
しかしながら、上述した樹脂材料は、比較的ヘイズ値やリタデーション値が大きく、撮像系の解像度劣化要因になるという問題がある。例えば薄膜積層方式のＮＤフィルタの基材として通常使用されるポリエステル系フィルムは、ロール作成時の張付き防止のため、表面に透明ビーズ等で凹凸を形成する必要があり、ヘイズ値が比較的高くなって光散乱の度合いが大きくなる。また内部複屈折率も大きく、リタデーション値が比較的高い。この様に従来から多用されているポリエステル系フィルムはヘイズ値及びリタデーション値が無視出来ない程度の範囲にあり、撮像光学系の解像度を劣化させる要因となっていた。 However, the above-described resin material has a problem that the haze value and the retardation value are relatively large, which causes a resolution deterioration factor of the imaging system. For example, a polyester film usually used as a base material for a thin film lamination type ND filter needs to have irregularities formed on its surface with transparent beads or the like to prevent sticking during roll creation, and has a relatively high haze value. As a result, the degree of light scattering increases. Also, the internal birefringence is large and the retardation value is relatively high. Thus, the polyester film which has been frequently used in the past has a range in which the haze value and the retardation value cannot be ignored, and has been a factor of degrading the resolution of the imaging optical system.
透明フィルム基材の上に光学薄膜を積層したＮＤフィルタのほか、透明樹脂基材に染料もしくは顔料を練り込んだタイプのＮＤフィルタも知られている。このタイプのＮＤフィルタは、ヘイズ値及びリタデーション値が比較的低いトリアセチルセルロース（ＴＡＣ）フィルムを基材に使用している。しかしながら、ＴＡＣフィルムは高温多湿環境下での形状ならびに寸法変形が大きく、また透過率特性のばらつきも大きいことなどから、近年の高性能な撮像系では適用困難となっていた。 In addition to an ND filter in which an optical thin film is laminated on a transparent film substrate, a type of ND filter in which a dye or pigment is kneaded into a transparent resin substrate is also known. This type of ND filter uses a triacetyl cellulose (TAC) film having a relatively low haze value and retardation value as a substrate. However, since the TAC film has a large shape and dimensional deformation in a high temperature and high humidity environment and a large variation in transmittance characteristics, it has been difficult to apply to a recent high performance imaging system.
上述した従来の技術の課題に鑑み、本発明は信頼性が高く且つ撮像光学系に用いても解像度の劣化することのない耐久性に優れたＮＤフィルタを提供することを目的とする。かかる目的を達成するために以下の手段を講じた。即ち本発明は、光吸収膜と誘電体膜を透明基材上に積層したＮＤフィルタにおいて、前記透明基材は、ノルボルネン類をモノマーとして合成され主鎖に脂環構造を持つ非晶質透明フィルムであり、前記非晶質透明フィルムは、少なくとも可視域で透明であり、ヘイズ値が１％以下で、リタデーション値が２０ｎｍ以下であることを特徴とする。 In view of the above-described problems of the conventional technology, an object of the present invention is to provide an ND filter having high reliability and excellent durability that does not deteriorate resolution even when used in an imaging optical system. In order to achieve this purpose, the following measures were taken. That is, the present invention relates to an ND filter in which a light absorption film and a dielectric film are laminated on a transparent substrate, wherein the transparent substrate is synthesized using norbornene as a monomer and has an alicyclic structure in the main chain. The amorphous transparent film is transparent at least in the visible range, has a haze value of 1% or less, and a retardation value of 20 nm or less.
好ましくは前記非晶質透明フィルムは、その厚みが５０μｍ〜２００μｍの範囲にある。又前記光吸収膜は、Ｔｉ，Ｃｒ，Ｎｉ，ＮｉＣｒ，ＮｉＦｅ及びＮｉＴｉから選択される単体若しくはその化合物からなる。又前記誘電体膜は、ＳｉＯ２、Ａｌ２Ｏ３、ＭｇＦ２、ＴｉＯ２及びＣｅＯ２から選択される誘電体材料からなる。かかるＮＤフィルタは光量絞り装置に好適である。 Preferably, the amorphous transparent film has a thickness in the range of 50 μm to 200 μm. The light absorbing film is made of a simple substance selected from Ti, Cr, Ni, NiCr, NiFe and NiTi or a compound thereof. The dielectric film is made of a dielectric material selected from SiO 2 , Al 2 O 3 , MgF 2 , TiO 2 and CeO 2 . Such an ND filter is suitable for a light quantity diaphragm device.
本発明によれば、光吸収膜と誘電体膜を透明基材上に積層したＮＤフィルタにおいて、非晶質透明フィルムを透明基材に用いている。この非晶質透明フィルムは可視域で透明であり、且つヘイズ値を１％以下としリタデーション値を２０ｎｍ以下に抑えることが出来る。この様にヘイズ値及びリタデーション値がともに低い非晶質透明フィルムを基材に用いることで、撮像光学系に適用しても解像度の劣化がないＮＤフィルタを提供することが出来る。しかもこの非晶質透明フィルムを基材としその上に光吸収膜と誘電体膜を積層したＮＤフィルタは耐環境性に優れており、高温多湿下でも光学特性や物理特性が変化しない。低ヘイズ値及び低リタデーション値を示す非晶質透明フィルムを用いることで、ＮＤフィルタ挿入時にも解像度が劣化することのない耐久性に優れた撮像光学系を実現することが可能になる。 According to the present invention, in the ND filter in which the light absorption film and the dielectric film are laminated on the transparent substrate, the amorphous transparent film is used as the transparent substrate. This amorphous transparent film is transparent in the visible region, and can have a haze value of 1% or less and a retardation value of 20 nm or less. In this way, by using an amorphous transparent film having a low haze value and retardation value as a base material, it is possible to provide an ND filter that does not deteriorate in resolution even when applied to an imaging optical system. In addition, an ND filter in which an amorphous transparent film is used as a base material and a light absorption film and a dielectric film are laminated thereon has excellent environmental resistance, and optical characteristics and physical characteristics do not change even under high temperature and high humidity. By using an amorphous transparent film exhibiting a low haze value and a low retardation value, it becomes possible to realize an imaging optical system with excellent durability that does not deteriorate the resolution even when an ND filter is inserted.
以下図面を参照して本発明の実施の形態を詳細に説明する。図１は、本発明にかかる薄膜型ＮＤフィルタの基本的な構成を示す模式的な断面図である。図示するように、本ＮＤフィルタは、光吸収膜３、５と誘電体膜２、４、６を透明基材１上に積層した薄膜型となっている。特徴事項として、この透明基材１は、ノルボルネン類をモノマーとして合成された主鎖に脂環構造をもつ非晶質透明フィルムである。この非晶質透明フィルムは、少なくとも可視域で透明であり、低ヘイズ値で且つ低リタデーション値を有する点に特徴がある。具体的には、非晶質透明フィルムはヘイズ値が１％以下でリタデーション値が２０ｎｍ以下である。ヘイズ値は、透明性を測る目安となる。ヘイズ値は試験片の散乱光線透過率を全光線透過率で割ったものを百分率で表したものである。又リタデーションとは複屈折性媒体を透過する振動方向が直交する２つの直線偏光成分について、一方を基準として測った位相遅れをいう。上記の定義から明らかなように、ヘイズ値は透明フィルムの光散乱性を示す尺度であり、低ヘイズであるほど光散乱が少ない。またリタデーション値は透明フィルムの複屈折性を示す尺度であり、低リタデーションであるほど複屈折が生ぜず、光学歪が少ない。光散乱や複屈折は撮像系の解像度劣化の大きな要因である。非晶質透明フィルムは低ヘイズで低リタデーションに特徴があり、光散乱や複屈折が少ないため、撮像光学系の解像度を劣化させることがない。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a basic configuration of a thin-film ND filter according to the present invention. As shown in the figure, this ND filter is a thin film type in which light absorption films 3 and 5 and dielectric films 2, 4 and 6 are laminated on a transparent substrate 1. As a feature, the transparent substrate 1 is an amorphous transparent film having an alicyclic structure in the main chain synthesized using norbornenes as monomers. This amorphous transparent film is characterized in that it is transparent at least in the visible range, has a low haze value, and a low retardation value. Specifically, the amorphous transparent film has a haze value of 1% or less and a retardation value of 20 nm or less. The haze value is a measure for measuring transparency. The haze value is a percentage obtained by dividing the scattered light transmittance of the test piece by the total light transmittance. Retardation is a phase delay measured with respect to one of two linearly polarized light components having orthogonal vibration directions that pass through a birefringent medium. As is clear from the above definition, the haze value is a scale indicating the light scattering property of the transparent film, and the lower the haze, the less the light scattering. The retardation value is a measure showing the birefringence of the transparent film. The lower the retardation, the less the birefringence and the less the optical distortion. Light scattering and birefringence are major causes of resolution degradation of the imaging system. The amorphous transparent film is characterized by low haze and low retardation, and has little light scattering and birefringence, so that the resolution of the imaging optical system is not deteriorated.
非晶質透明フィルムは、撮像光学系のＮＤフィルタに用いる場合、その厚みは５０μｍ〜２００μｍの範囲が適当である。但し本発明はこれに限られるものではなく、撮像光学系用途以外に使う場合、非晶質透明フィルムの厚みは数μｍ〜数ｍｍの範囲でも差し支えない。 When the amorphous transparent film is used for an ND filter of an imaging optical system, the thickness is suitably in the range of 50 μm to 200 μm. However, the present invention is not limited to this, and when used for purposes other than the imaging optical system, the thickness of the amorphous transparent film may be in the range of several μm to several mm.
光吸収膜３，５は、Ｔｉ，Ｃｒ，Ｎｉ，ＮｉＣｒ，ＮｉＦｅ及びＮｉＴｉから選択される単体もしくはその化合物からなる。誘電体膜２，４，６は、ＳｉＯ２、Ａｌ２Ｏ３、ＭｇＦ２、ＴｉＯ２及びＣｅＯ２から選択される誘電体材料からなる。この様に透明フィルムからなる基材１の上に成膜する薄膜は、吸収膜３，５と誘電体膜（透明膜）２，４，６の交互層で、要求される光学特性に合わせて膜の層数や膜の厚みが調整される。場合によっては、透明基材１の裏面に反射防止膜を形成してもよい。あるいは表面と同じように裏面にも吸収膜と誘電体膜の交互層を形成してもよい。 The light absorbing films 3 and 5 are made of a simple substance selected from Ti, Cr, Ni, NiCr, NiFe and NiTi or a compound thereof. Dielectric films 2, 4 and 6, a dielectric material selected from SiO 2, Al 2 O 3, MgF 2, TiO 2 and CeO 2. Thus, the thin film formed on the base material 1 made of a transparent film is an alternating layer of absorption films 3 and 5 and dielectric films (transparent films) 2, 4 and 6, in accordance with required optical characteristics. The number of layers and the thickness of the film are adjusted. In some cases, an antireflection film may be formed on the back surface of the transparent substrate 1. Alternatively, an alternating layer of an absorption film and a dielectric film may be formed on the back surface as well as the front surface.
図２はノルボルネンの化学構造式を示す。前述したように、非晶質透明樹脂は、図２に示したノルボルネンまたはその誘導体をモノマーとして合成されたポリマーである。 FIG. 2 shows the chemical structural formula of norbornene. As described above, the amorphous transparent resin is a polymer synthesized using norbornene or a derivative thereof shown in FIG. 2 as a monomer.
図３は、非晶質透明樹脂の代表的な例を示す構造式である。構造式（Ａ）、（Ｂ）及び（Ｃ）は、いずれもノルボルネン類をモノマーとして構成され主鎖に脂環構造を有する。 FIG. 3 is a structural formula showing a typical example of an amorphous transparent resin. Structural formulas (A), (B) and (C) are all composed of norbornene as a monomer and have an alicyclic structure in the main chain.
上記非晶質透明樹脂としては、飽和非晶質透明樹脂が好ましく、例えば、ノルボルネン系モノマーの開環（共）重合体の水素添加物、ノルボルネン系モノマーと他のオレフィン系モノマーとの付加共重合体、ノルボルネン系モノマー同士の付加共重合体及びこれらの誘導体等が挙げられる。これらの非晶質透明樹脂は、単独で用いられても良いし、２種類以上が併用されても良い。 The amorphous transparent resin is preferably a saturated amorphous transparent resin, such as a hydrogenated product of a ring-opening (co) polymer of a norbornene monomer, or an addition copolymer of a norbornene monomer and another olefin monomer. Examples thereof include addition copolymers, addition copolymers of norbornene monomers, and derivatives thereof. These amorphous transparent resins may be used alone or in combination of two or more.
上記ノルボルネン系モノマーは、ノルボルネン環を有するものであれば特に限定されないが、耐熱性、低線膨張率等に優れた成形品が得られることから、三環体以上の多環ノルボルネン系モノマーを用いることが好ましい。上記ノルボルネン系モノマーの具体例としては、例えば、ノルボルネン、ノルボルナジエン等の二環体；ジシクロペンタジエン、ジヒドロキシペンタジエン等の三環体；テトラシクロドデセン等の四環体；シクロペンタジエン三量体等の五環体；テトラシクロペンタジエン等の七環体；これらのメチル、エチル、プロピル、ブチル等のアルキル、ビニル等のアルケニル、エチリデン等のアルキリデン、フェニル、トリル、ナフチル等のアリール等の置換体；さらにこれらのエステル基、エーテル基、シアノ基、ハロゲン原子、アルコキシカルボニル基、ピリジル基、水酸基、カルボン酸基、アミノ基、無水酸基、シリル基、エポキシ基、アクリル基、メタクリル基等の炭素、水素以外の元素を含有する基、いわゆる極性基を有する置換体等が挙げられ、なかでも、入手が容易であり、反応性に優れ、得られる成形品の耐熱性が優れることから、三環体、四環体及び五環体のノルボルネン系モノマーが好適に用いられる。これらのノルボルネン系モノマーは、単独で用いられても良いし、２種類以上が併用されても良い。 The norbornene-based monomer is not particularly limited as long as it has a norbornene ring, but since a molded product having excellent heat resistance, low linear expansion coefficient, etc. is obtained, a tricyclic or higher polycyclic norbornene-based monomer is used. It is preferable. Specific examples of the norbornene-based monomer include bicyclic products such as norbornene and norbornadiene; tricyclic products such as dicyclopentadiene and dihydroxypentadiene; tetracyclic products such as tetracyclododecene; cyclopentadiene trimer and the like. Pentacycles; heptacycles such as tetracyclopentadiene; alkyls such as methyl, ethyl, propyl and butyl; alkenyls such as vinyl; alkylidenes such as ethylidene; and substituents such as aryls such as phenyl, tolyl and naphthyl; These ester groups, ether groups, cyano groups, halogen atoms, alkoxycarbonyl groups, pyridyl groups, hydroxyl groups, carboxylic acid groups, amino groups, hydroxyl-free groups, silyl groups, epoxy groups, acrylic groups, methacrylic groups, etc. other than carbon and hydrogen Groups containing these elements, so-called polar group substituents, etc. Gerare, among others, it is readily available, excellent reactivity, since the heat resistance of the molded article obtained is excellent, tricyclic body, norbornene-based monomer tetracyclic body and pentacyclic body is preferably used. These norbornene monomers may be used alone or in combination of two or more.
上記ノルボルネン系モノマーの開環（共）重合体の水素添加物としては、上記ノルボルネン系モノマーを公知の方法で開環重合させた後、残留している二重結合が水素添加されているものが広く用いられる。これは、ノルボルネン系モノマーの単独重合体であっても良いし、異種のノルボルネン系モノマーの共重合体であっても良い。 Examples of the hydrogenated product of the ring-opening (co) polymer of the norbornene monomer include those obtained by subjecting the norbornene monomer to ring-opening polymerization by a known method and then hydrogenating the remaining double bonds. Widely used. This may be a homopolymer of norbornene monomers or a copolymer of different norbornene monomers.
また、上記ノルボルネン系モノマーと他のオレフィン系モノマーとの付加共重合体としては、ノルボルネン系モノマーとα−オレフィンとの共重合体が挙げられる。上記α−オレフィンとしては、炭素数２〜２０、好ましくは２〜１０のα−オレフィン、例えば、エチレン、プロピレン、１−ブテン、３−メチル−１−ブテン、１−ペンテン、３−メチル−１−ペンテン、４−メチル−１−ペンテン、１−ヘキセン、１−オクテン、１−デセン、１−ドデセン、１−テトラデセン、１−ヘキサデセン等が挙げられ、なかでも、共重合性が高いことから、エチレンが好ましく、他のα−オレフィンをノルボルネン系モノマーと共重合させる場合にも、エチレンが存在している方が共重合性が高められる。 Moreover, as an addition copolymer of the said norbornene-type monomer and another olefin-type monomer, the copolymer of a norbornene-type monomer and an alpha olefin is mentioned. Examples of the α-olefin include α-olefins having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, and 3-methyl-1. -Pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and the like, and among them, the copolymerizability is high. Ethylene is preferable, and also when other α-olefin is copolymerized with a norbornene-based monomer, the presence of ethylene improves the copolymerizability.
これらの非晶質透明樹脂は公知であり、商業的に入手できる。商業的に入手できる非晶質透明樹脂の具体例としては、例えば、ジェイエスアール社製の商品名「アートン」シリーズ、日本ゼオン社製の商品名「ゼオノア」シリーズ、三井化学社製の商品名「アペル」シリーズ等が挙げられる。 These amorphous transparent resins are known and commercially available. Specific examples of commercially available amorphous transparent resins include, for example, the product name “Arton” series manufactured by JSR Corporation, the product name “ZEONOR” series manufactured by Zeon Corporation, and the product name “Mitsui Chemicals” "Apel" series.
図４は、種々の透明フィルムを基材として作成したＮＤフィルタの透過波面観察結果を示す写真である。（Ａ）はＰＥＴフィルムを基材としたＮＤフィルタのサンプルである。（Ｂ）はポリエチレンナフタレート（ＰＥＮ）フィルムを基材にしたＮＤフィルタのサンプルである。（Ｃ）はＴＡＣフィルムを基材にしたＮＤフィルタのサンプルである。（Ｄ）は本発明にしたがって非晶質透明フィルムを基材にしたサンプル写真である。４つのサンプルを比較すれば明らかなように、非晶質透明フィルムを基材にしたＮＤフィルタは、他のサンプルに比べ干渉縞の歪が少ない良好な結果を得ている。４つのＮＤフィルタサンプルを実際に撮像光学系に組み込んで評価した結果、従来のＲＥＴフィルムを基材にしたＮＤフィルタではクリア出来なかった解像度を、非晶質透明フィルムを基材にしたＮＤフィルタで満足することが出来た。また非晶質透明フィルムを基材にしたＮＤフィルタを環境試験に投入した結果、光学特性及び形状の安定性などに関し、実用上問題がないことが確認された。 FIG. 4 is a photograph showing transmission wavefront observation results of ND filters prepared using various transparent films as base materials. (A) is a sample of an ND filter using a PET film as a base material. (B) is a sample of an ND filter based on a polyethylene naphthalate (PEN) film. (C) is a sample of an ND filter using a TAC film as a base material. (D) is a sample photograph using an amorphous transparent film as a base material according to the present invention. As is clear from the comparison of the four samples, the ND filter based on the amorphous transparent film has a good result with less interference fringe distortion than the other samples. As a result of evaluation by actually incorporating four ND filter samples into the imaging optical system, the resolution that could not be cleared by the conventional ND filter based on the RET film was obtained using the ND filter based on the amorphous transparent film. I was satisfied. Moreover, as a result of putting an ND filter having an amorphous transparent film as a base material into an environmental test, it was confirmed that there was no practical problem with respect to optical characteristics and shape stability.
図５は、本発明にかかるＮＤフィルタの実施例を示す断面図である。図示する様に、本ＮＤフィルタ０は、光吸収膜３，５と誘電体膜２，４，６を透明基材１上に積層した薄膜型となっている。光吸収膜３，５は、金属材料を原料として蒸着により成膜されたものである。酸素を含む混合ガスを成膜時に導入し、真空度を１×１０-3Ｐａないし１×１０-2Ｐａの間で一定に維持した状態で金属材料の酸化物を生成している。換言すると、吸収膜３，５は、金属とその酸化物とで構成された複合材料構成となっている。好ましくは、光吸収膜３，５と誘電体膜２，４，６を透明基材１に積層した後、酸素を１０％以上含む酸素雰囲気で加熱し、光学特性の変化を飽和させるとよい。一方、誘電体膜２，４，６はＳｉＯ2及びＡｌ2Ｏ3から形成される。この場合、誘電体膜２，４，６及び光吸収膜３，５を所定の膜厚及び所定の順番で積層して反射防止機能を付与することができる。 FIG. 5 is a sectional view showing an embodiment of the ND filter according to the present invention. As shown in the figure, the ND filter 0 is a thin film type in which light absorbing films 3 and 5 and dielectric films 2, 4 and 6 are laminated on a transparent substrate 1. The light absorption films 3 and 5 are formed by vapor deposition using a metal material as a raw material. A mixed gas containing oxygen is introduced at the time of film formation, and an oxide of a metal material is generated in a state where the degree of vacuum is kept constant between 1 × 10 −3 Pa and 1 × 10 −2 Pa. In other words, the absorption films 3 and 5 have a composite material structure composed of a metal and its oxide. Preferably, after the light absorbing films 3 and 5 and the dielectric films 2, 4 and 6 are laminated on the transparent substrate 1, heating is performed in an oxygen atmosphere containing 10% or more of oxygen to saturate the change in optical characteristics. On the other hand, the dielectric films 2, 4 and 6 are made of SiO 2 and Al 2 O 3 . In this case, the dielectric films 2, 4, 6 and the light absorption films 3, 5 can be laminated in a predetermined film thickness and in a predetermined order to provide an antireflection function.
引き続き図５を参照して、ＮＤフィルタ０の具体的な膜構成を説明する。まず透明基材１は、厚みが０．１ｍｍ（１００μｍ）の非晶質透明フィルムからなる。本実施例では、日本ゼオン社製のゼオノアフィルムを用いている。 With reference to FIG. 5, the specific film configuration of the ND filter 0 will be described. First, the transparent substrate 1 is made of an amorphous transparent film having a thickness of 0.1 mm (100 μm). In this example, a ZEONOR film manufactured by Nippon Zeon Co., Ltd. is used.
透明基材１の上に形成された第１の誘電体膜２はＳｉＯ2からなり、その物理膜厚は７５．８ｎｍである。その上に成膜された第１の光吸収膜３は、金属Ｔｉとその酸化物ＴｉＯｘとで構成されており、物理膜厚は２０．０ｎｍである。その上に成膜された第２の誘電体膜４はＡｌ2Ｏ3からなり、その物理膜厚は３８．７ｎｍである。その上に成膜された第２の光吸収膜５は、同じく金属Ｔｉとその酸化物ＴｉＯｘの混合物からなり、物理膜厚は３８．０ｎｍである。その上に成膜された第３の誘電体膜６は、ＳｉＯ2からなりその物理膜厚は６６．４ｎｍである。尚、係る積層構成は例示であって、本発明の範囲を限定するものではない。光学薄膜の場合、通常使用波長において透明なセラミックス材料を誘電体膜と表現している。光の干渉効果が現われる厚さ（波長の数倍程度）の誘電体膜を積層することで、入射する光線の光学特性（反射量、透過量、偏光、位相など）を自由に調節することができる。本実施形態では、図５に示す層構成とすることで、ＮＤフィルタに反射防止機能を付与している。一方光吸収膜は、使用波長領域において文字通り光を吸収する働きがあり、可視域では通常金属を用いる。本発明では、特に金属材料にその酸化物を導入することで、光学特性並びに物理特性を改善している。 The first dielectric film 2 formed on the transparent substrate 1 is made of SiO 2 and has a physical film thickness of 75.8 nm. The first light absorption film 3 formed thereon is composed of metal Ti and its oxide TiOx, and has a physical film thickness of 20.0 nm. The second dielectric film 4 formed thereon is made of Al 2 O 3 and has a physical film thickness of 38.7 nm. The second light absorption film 5 formed thereon is also made of a mixture of metal Ti and its oxide TiOx, and has a physical film thickness of 38.0 nm. The third dielectric film 6 formed thereon is made of SiO 2 and has a physical film thickness of 66.4 nm. Note that such a stacked configuration is an example and does not limit the scope of the present invention. In the case of an optical thin film, a ceramic material that is transparent at a normal use wavelength is expressed as a dielectric film. By laminating a dielectric film with a thickness (several times the wavelength) at which the light interference effect appears, the optical characteristics (reflection amount, transmission amount, polarization, phase, etc.) of the incident light can be freely adjusted. it can. In the present embodiment, an antireflection function is imparted to the ND filter by adopting the layer configuration shown in FIG. On the other hand, the light-absorbing film literally absorbs light in the used wavelength region, and usually uses metal in the visible region. In the present invention, the optical characteristics and physical characteristics are improved particularly by introducing the oxide into the metal material.
図６は、図５に示したＮＤフィルタの作成に使用する真空蒸着装置の一例を示す模式的なブロック図である。図示する様に、本装置は真空チャンバ１１を主体に構成されており、その上には膜厚モニタ１２と膜厚制御器１３が取り付けられている。チャンバ１１内には処理対象となる基材を支持固定する基材ホルダ１４と、膜厚測定用基材１５、と蒸着源１６とが組み込まれている。膜厚モニタ１２は光源と分光器と受光器とを備えている。分光器から出射した光は膜厚測定用基材１５に入射し、これから反射した光が受光器に入射し、その出力が膜厚制御器１３に送られる。この様に、膜厚をリアルタイムでモニタすることにより、基材上に所望の厚みの光吸収膜や誘電体膜を成膜する様にしている。 FIG. 6 is a schematic block diagram showing an example of a vacuum vapor deposition apparatus used for creating the ND filter shown in FIG. As shown in the figure, this apparatus is mainly composed of a vacuum chamber 11 on which a film thickness monitor 12 and a film thickness controller 13 are attached. A chamber holder 14 for supporting and fixing a substrate to be processed, a film thickness measuring substrate 15, and a vapor deposition source 16 are incorporated in the chamber 11. The film thickness monitor 12 includes a light source, a spectroscope, and a light receiver. The light emitted from the spectroscope enters the film thickness measurement substrate 15, the light reflected therefrom enters the light receiver, and the output is sent to the film thickness controller 13. Thus, by monitoring the film thickness in real time, a light absorption film or a dielectric film having a desired thickness is formed on the substrate.
チャンバ１１には真空計ゲージ部１７、真空計制御部１８、ガス導入ユニット１９及び排気ユニット２０が接続している。本実施例では、チャンバ１１内の真空度を一定に保つ為に、ＡＰＣ方式を採用している。具体的には、真空計ゲージ部１７及び真空計制御部１８を介してフィードバックをかけ、ガス導入ユニット１９を制御して、チャンバ１１内に導入される混合ガスの量を調整している。但し、本発明はこれに限られるものではなく、導入量をニードルバルブにて一定に調整する方式を採用してもよい。 A vacuum gauge gauge unit 17, a vacuum gauge control unit 18, a gas introduction unit 19 and an exhaust unit 20 are connected to the chamber 11. In the present embodiment, the APC method is adopted in order to keep the degree of vacuum in the chamber 11 constant. Specifically, feedback is applied through the vacuum gauge unit 17 and the vacuum gauge controller 18 to control the gas introduction unit 19 and adjust the amount of the mixed gas introduced into the chamber 11. However, the present invention is not limited to this, and a method of adjusting the introduction amount to be constant with a needle valve may be adopted.
図７は、図６に示した真空蒸着装置を用いて、図５に示したＮＤフィルタを作成する場合の成膜条件を表わした表図である。図示する様に、基材温度は１００℃としている。又、チャンバの到達真空度は１×１０-3Ｐａに設定している。ここで、光吸収膜３，５を成膜する為に、原料としてＴｉを用い、蒸着速度は１ｎｍ／ｓｅｃに設定している。Ｔｉを蒸着する際に導入するガスとして、本実施例では窒素と酸素を４：１で混合した空気を用いている。但し、本発明はこれに限られるものではなく、一般的には酸素を５０％以下の割合で含有する混合ガスが用いられる。尚、酸素を含有した混合ガスを導入した場合の蒸着真空度は、４×１０-3Ｐａに設定した。但し、本発明はこれに限られるものではなく、一般に１×１０-3Ｐａ〜１×１０-2Ｐａの間で一定に維持すれば、良好な光学特性並びに物理特性を有し且つ金属とその酸化物の混合物よりなる光吸収膜を成膜することができる。次に、誘電体膜２，６を成膜する場合には、蒸着源としてＳｉＯ2を用い、蒸着速度は１ｎｍ／ｓｅｃに設定している。ＳｉＯ2を成膜する場合には特に反応性のガスを導入していない。又、誘電体膜４の成膜には、蒸着源としてＡｌ2Ｏ3を用い蒸着速度を１ｎｍ／ｓｅｃに設定している。この場合も、反応性ガスは特に導入しない。 FIG. 7 is a table showing film forming conditions when the ND filter shown in FIG. 5 is created using the vacuum vapor deposition apparatus shown in FIG. As shown in the drawing, the substrate temperature is set to 100 ° C. The ultimate vacuum in the chamber is set to 1 × 10 −3 Pa. Here, in order to form the light absorption films 3 and 5, Ti is used as a raw material, and the deposition rate is set to 1 nm / sec. In this embodiment, air in which nitrogen and oxygen are mixed at a ratio of 4: 1 is used as a gas introduced when depositing Ti. However, the present invention is not limited to this, and generally a mixed gas containing oxygen at a ratio of 50% or less is used. In addition, the vapor deposition vacuum degree at the time of introduce | transducing the mixed gas containing oxygen was set to 4 * 10 < -3 > Pa. However, the present invention is not limited to this, and generally has good optical characteristics and physical characteristics as long as it is kept constant between 1 × 10 −3 Pa and 1 × 10 −2 Pa, and the metal and its A light absorption film made of a mixture of oxides can be formed. Next, the case of forming the dielectric film 2 and 6, the SiO 2 used as a deposition source, the deposition rate is set to 1 nm / sec. When depositing SiO 2 , no reactive gas is introduced. In forming the dielectric film 4, Al 2 O 3 is used as a vapor deposition source and the vapor deposition rate is set to 1 nm / sec. Also in this case, no reactive gas is particularly introduced.
図８は、図５に示したＮＤフィルタの光学特性を表しており、透過率、反射率及び透過濃度を測定した結果を示すグラフである。なおこの測定結果は、図５に示したＮＤフィルタに熱処理を加えて安定化した後のデータである。この熱処理では、窒素と酸素の混合比が４：１の酸化雰囲気（大気）中で、８０℃に５０時間放置した。但し、本発明はこれに限られるものではなく、一般的な熱処理条件は酸素濃度が１０％以上のガスで、熱処理温度は基材に損傷を与えない程度で設定する。一般的には、酸素濃度を増やし高温加熱をした方が、光学特性の経時変化を出し切る上では効果的である。グラフに示す様に、熱処理後では可視域において波長依存性はなく均一に透過光を減衰し、フィルタ面での反射を抑えたＮＤフィルタを得ることができた。 FIG. 8 shows the optical characteristics of the ND filter shown in FIG. 5, and is a graph showing the results of measurement of transmittance, reflectance, and transmission density. The measurement results are data after the ND filter shown in FIG. 5 is stabilized by heat treatment. In this heat treatment, the substrate was left at 80 ° C. for 50 hours in an oxidizing atmosphere (air) having a mixing ratio of nitrogen and oxygen of 4: 1. However, the present invention is not limited to this, and a general heat treatment condition is a gas having an oxygen concentration of 10% or more, and the heat treatment temperature is set so as not to damage the substrate. In general, increasing the oxygen concentration and heating at a high temperature is more effective in keeping up the optical characteristics with time. As shown in the graph, after the heat treatment, it was possible to obtain an ND filter that has no wavelength dependence in the visible region and uniformly attenuates transmitted light and suppresses reflection on the filter surface.
図９は、本発明にかかるＮＤフィルタをカメラ用絞り装置に適用した模式図である。一対に形成された内の１枚を示した絞り羽根１００の凹部には、ＮＤフィルタ１０５が接着剤１０６または熱溶着などにより固設されている。絞り羽根１００は駆動部１０３により、支持ピン１０４の周りを回動して、開口部１０１を開閉するように構成されている。前述したように、絞り羽根１００に装着されたＮＤフィルタは低ヘイズ値で低リタデーション値を示す非晶質透明フィルムを基材にしている。この非晶質透明フィルムは光散乱が少なく屈折率の異方性も小さい。よってＮＤフィルタ使用時も解像度が劣化することのない耐久性に優れた撮像光学系を提供することが可能である。 FIG. 9 is a schematic diagram in which the ND filter according to the present invention is applied to a camera diaphragm device. An ND filter 105 is fixed to the concave portion of the diaphragm blade 100 showing one of the pair formed by an adhesive 106 or heat welding. The aperture blade 100 is configured to rotate around the support pin 104 by the drive unit 103 to open and close the opening 101. As described above, the ND filter mounted on the diaphragm blade 100 is based on an amorphous transparent film having a low haze value and a low retardation value. This amorphous transparent film has little light scattering and low refractive index anisotropy. Therefore, it is possible to provide an imaging optical system with excellent durability that does not deteriorate the resolution even when the ND filter is used.
０・・・ＮＤフィルタ、１・・・透明基材、２・・・誘電体膜、３・・・光吸収膜、４・・・誘電体膜、５・・・光吸収膜、６・・・誘電体膜 DESCRIPTION OF SYMBOLS 0 ... ND filter, 1 ... Transparent base material, 2 ... Dielectric film, 3 ... Light absorption film, 4 ... Dielectric film, 5 ... Light absorption film, 6 ...・ Dielectric film
Claims (5)
前記透明基材は、ノルボルネン類をモノマーとして合成され主鎖に脂環構造を持つ非晶質透明フィルムであり、
前記非晶質透明フィルムは、少なくとも可視域で透明であり、ヘイズ値が１％以下で、リタデーション値が２０ｎｍ以下であることを特徴とするＮＤフィルタ。 In an ND filter in which a light absorption film and a dielectric film are laminated on a transparent substrate,
The transparent substrate is an amorphous transparent film synthesized with norbornene as a monomer and having an alicyclic structure in the main chain,
The ND filter, wherein the amorphous transparent film is transparent at least in a visible region, has a haze value of 1% or less, and a retardation value of 20 nm or less.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009282088A (en) * | 2008-05-20 | 2009-12-03 | Sumitomo Metal Mining Co Ltd | Absorption type multi-layer film nd filter and method for manufacturing the same |
| JP2010156765A (en) * | 2008-12-26 | 2010-07-15 | Jsr Corp | Nd filter, method of manufacturing the same and method of controlling transmittance of light using them |
| JP2010266661A (en) * | 2009-05-14 | 2010-11-25 | Canon Electronics Inc | Optical filter, and image capturing apparatus using the same |
| WO2016035452A1 (en) * | 2014-09-03 | 2016-03-10 | 日本電波工業株式会社 | Neutral density filter |
| CN113544493A (en) * | 2019-03-05 | 2021-10-22 | 宽腾矽公司 | Optical absorption filter for integrated devices |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004037548A (en) * | 2002-06-28 | 2004-02-05 | Nisca Corp | Nd filter, its manufacture method and diaphragm device incorporating nd filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004037548A (en) * | 2002-06-28 | 2004-02-05 | Nisca Corp | Nd filter, its manufacture method and diaphragm device incorporating nd filter |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009282088A (en) * | 2008-05-20 | 2009-12-03 | Sumitomo Metal Mining Co Ltd | Absorption type multi-layer film nd filter and method for manufacturing the same |
| JP2010156765A (en) * | 2008-12-26 | 2010-07-15 | Jsr Corp | Nd filter, method of manufacturing the same and method of controlling transmittance of light using them |
| JP2010266661A (en) * | 2009-05-14 | 2010-11-25 | Canon Electronics Inc | Optical filter, and image capturing apparatus using the same |
| WO2016035452A1 (en) * | 2014-09-03 | 2016-03-10 | 日本電波工業株式会社 | Neutral density filter |
| CN113544493A (en) * | 2019-03-05 | 2021-10-22 | 宽腾矽公司 | Optical absorption filter for integrated devices |
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