JP3994450B2 - Manufacturing method of optical diffraction grating and optical head device using the same - Google Patents
Manufacturing method of optical diffraction grating and optical head device using the same Download PDFInfo
- Publication number
- JP3994450B2 JP3994450B2 JP15722296A JP15722296A JP3994450B2 JP 3994450 B2 JP3994450 B2 JP 3994450B2 JP 15722296 A JP15722296 A JP 15722296A JP 15722296 A JP15722296 A JP 15722296A JP 3994450 B2 JP3994450 B2 JP 3994450B2
- Authority
- JP
- Japan
- Prior art keywords
- substrate
- diffraction grating
- optical
- light
- photoresist
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Landscapes
- Liquid Crystal (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
- Optical Head (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、ＣＤ（コンパクト・ディスク）、ＣＤ−ＲＯＭ、ビデオディスク等の光ディスク及び光磁気ディスク等の光学記録媒体に光学的情報を書き込んだり、光学的情報を読み取るための光ヘッド装置に好適な光学回折格子の製造方法及びそれを用いた光ヘッド装置に関する。
【０００２】
【従来の技術】
従来、光ディスク及び光磁気ディスク等の光学記録媒体に光学的情報を書き込んだり、光学的情報を読み取る光ヘッド装置としては、光学記録媒体の記録面から反射された信号光を検出部へ導光（ビームスプリット）する光学部品としてプリズム式ビームスプリッタを用いたものと、回折格子又はホログラム素子を用いたものとが知られていた。
【０００３】
この光ヘッド装置用の回折格子又はホログラム素子は、ガラスやプラスチック基板上に、矩形の断面を有する矩形格子（レリーフ型）をドライエッチイング法又は射出成形法よって形成し、これによって光を回折しビームスプリット機能を付与していた。
【０００４】
また、この光の利用効率が１０％程度の等方性回折格子よりも光の利用効率を上げようとした場合、偏光を利用することが考えられる。偏光を利用しようとすると、プリズム式ビームスプリッタにλ／４板を組み合わせて、往路（光源から光学記録媒体へ向かう方向）及び復路（光学記録媒体から光検出器へ向かう方向）の効率を上げて往復効率を上げる方法があった。
【０００５】
しかし、プリズム式偏光ビームスプリッタは高価であり、他の方式が模索されていた。一つの方式としてＬｉＮｂＯ３等の複屈折結晶の平板を用い、表面に異方性回折格子を形成し偏光選択性をもたせる方法が知られている。しかし、複屈折結晶自体が製造が困難であり高価であり、民生分野への適用は困難であった。
【０００６】
等方性回折格子は、前述のように、利用効率が往路で５０％程度、復路で２０％程度であるため、往復での利用効率が１０％程度しか得られなかった。
【０００７】
さらに、これらのものは単に効率が低いだけでなく、格子が左右対称形状を持つ回折格子であるため、＋１次光の回折効率と−１次光の回折効率がほぼ等しかった。光検出器が複数設けられて両方で検出する場合には、両方の回折効率がほぼ等しいことは有利であるが、１個の光検出器の場合には必ずしも有利ではない。
【０００８】
すなわち、光ヘッドの小型化のために光検出器を１個とすることが提案されており、この場合には２方向に同じ程度の光量で光が回折されることは、光の利用効率からみて有利ではない。２方向に回折された光のうち、光検出器を設けた側に回折する光の光量を増加させることが有利となる。このため、一方の回折光を他方よりも多くすることが望まれていた。
【０００９】
【発明が解決しようとする課題】
このためには、回折格子の凹凸の短手方向が左右非対称な回折格子を使用する必要がある。しかし、この非対称な回折格子はもともとかなり微細なピッチの回折格子ということもあり、きわめて製造が難しいものであった。このため、生産性が高い非対称な回折格子の製造方法が望まれていた。
【００１０】
本発明は、このような課題を解消し、複数の回折光のうち、１方の回折光の利用効率の高い光学回折格子を容易に製造する製造方法の提供を目的とする。
【００１１】
【課題を解決するための手段】
本発明は、基板の表面に格子状の凸部が形成された光学回折格子の製造方法において、基板の表面にフォトレジストを形成し、このフォトレジストを、フォトレジストが形成された側から所望のパターンが得られるように定めた照射角度でフォトマスクを通して斜め露光し、現像することにより残存したフォトレジストの格子の短手方向の側面が非対称になるようにし、次いでドライエッチングすることにより、エッチングにより残存した凸部の格子の短手方向の側面が非対称になるようにしたことを特徴とする光学回折格子の製造方法を提供する。
【００１２】
また、基板として透明材料膜を設けた基板を用い、エッチングにより残存した透明材料膜の凸部の格子の短手方向の側面が非対称になるようにしたことを特徴とする上記光学回折格子の製造方法、及び、凸部の側面が非対称になるよう形成された基板を第１の基板とし、この第１の基板と第２の基板との間に光学的異方性材料を充填したことを特徴とする上記光学回折格子の製造方法を提供する。
【００１４】
本発明で製造される光学回折格子は、光源からの光をこの光学回折格子を通して光学記録媒体上に照射することにより、情報の書き込み及び／又は情報の読み取りを行う光ヘッド装置に好適に用いられる。
【００１５】
本発明では、レジストパターンをフォトマスクで露光するときに、斜め方向から露光することによって、透明基板の表面に左右非対称な格子状（ストライプ状）の凸部を形成する。さらに、このようにして形成された凸部を有する基板を用いて２枚の基板間に光学異方性を有する液晶を充填して使用する。これにより、片側回折効率の高い光学回折格子を容易に製造できる。
【００１６】
本発明では、基板自体を直接エッチングして凸部を形成して用いてもよいが、エッチングの深さ、分布、終点検出の点からみて、基板表面に透明材料膜を形成して用いることが好ましい。
【００１７】
【発明の実施の形態】
本発明では、基板自体の表面又は透明材料膜を設けた基板の表面にフォトレジストを形成し、このフォトレジストを、フォトレジストが形成された側から所望のパターンが得られるように定めた照射角度でフォトマスクを通して斜め露光し、現像することにより残存したフォトレジストの格子の短手方向の側面が非対称になるようにし、次いでドライエッチングすることにより、エッチングにより残存した凸部の格子の短手方向の側面が非対称になるようにする。
【００１８】
図２は、従来の光学回折格子の製造する主要工程を示す。（Ａ）はフォトレジストを露光現像した状態を示す断面図であり、（Ｂ）はそれを用いて透明材料膜をドライエッチングした状態を示す断面図である。１１は基板、１２は透明材料膜、１３はフォトレジスト、１４はエッチング後の透明材料膜を示す。
【００１９】
このように通常の露光、現像、エッチングを行うと、透明材料膜は格子のストライプの短手方向（図の左右方向）の凸部の左右の側面はほぼ同じ傾斜角となり、左右が対称になる。このような形状の光学回折格子は、回折光の光量が＋１次と−１次とでほぼ等しくなる。これは左右に複数の光検出器を設けて光学記録媒体からの反射光を検出する場合には好適である。
【００２０】
しかし、一方にしか光検出器を設けない場合には、光検出器を設ける側にのみ多くの光が回折する方が有利である。また、両方に光検出器を設けるが、その目的が異なり、一方の光検出器への光量の方が多く要求される場合も同様である。このため、本発明の製造方法で製造された光学回折格子を用いる光ヘッド装置では光検出器が１個のみのものに限定されない。
【００２１】
図１は、本発明の光学回折格子を製造する主要工程を示し、基板表面に透明材料膜を形成した例を示す。（Ａ）はフォトレジストを露光現像した状態を示す断面図であり、（Ｂ）はそれを用いて透明材料膜をドライエッチングした状態を示す断面図である。１は基板、２は透明材料膜、３はフォトレジスト、４はエッチング後の透明材料膜を示す。
【００２２】
このように通常の露光、現像、エッチングを行うと、透明材料膜は格子のストライプの短手方向（図の左右方向）の凸部の左右の側面は異なる傾斜角となり、左右が非対称になる。このような形状の光学回折格子は、回折光の光量が＋１次と−１次とで異なることになる。これは左右のいずれかに１個の光検出器を設けて光学記録媒体からの反射光を検出する場合には、光量を有効利用できるので好適である。
【００２３】
本発明で用いる基板は、ガラス等の透明基板である。この透明基板はそのまま用いて基板表面をエッチングして凸部を形成することもできるが、この図の例のように、透明基板上に、ＳｉＯＮ、ＳｉＯ２等の透明材料膜を、反応性スパッタ法、蒸着法、プラズマＣＶＤ法等によって形成して用いることが好ましい。
【００２４】
液晶等の光学的異方性材料を充填して用いない場合には、透明材料膜と基板との界面での反射を低減するために、この透明材料膜の屈折率は、基板の屈折率とほぼ一致させることが好ましい。
【００２５】
液晶等の光学的異方性材料を充填して用いる場合には、透明材料膜の屈折率は液晶等の常光屈折率又は異常光屈折率とほぼ等しくすることが好ましい。さらに、基板との界面での反射を低減するために、この透明材料膜の屈折率を、基板の屈折率とほぼ一致させることが好ましい。
【００２６】
この透明材料膜２の上にフォトレジストをスピンコート法等により積層し、そのフォトレジストに、フォトマスクを通して光を照射する。この際に、光を斜め方向から照射し、その後現像することにより、残存したフォトレジスト３のストライプの短手方向（図の左右方向）の凸部の左右の側面は異なる傾斜角となり、左右が非対称になる。この例では、左側の側面はほぼ垂直、右側の側面は傾斜面にされている。
【００２７】
この斜め方向からの光照射は、斜め方向から光を照射して行う。この斜めからの照射の角度は、所望のパターンが得られるように実験的に定めればよいが、おおむね垂直方向から１０〜６０°程度傾斜するようにすればよい。具体的には、たとえば、図３に示すような方法で行えばよい。図３は、斜め方向からの光照射工程を示す側面図である。
【００２８】
通常の露光は垂直方向から行うので、光源としては同じ構造の露光装置を用いて、その光路中にプリズムを挿入して、光路を斜め方向に折り曲げている。図３において、２１は基板、２２は透明材料膜、２３はフォトレジスト、２５はマスク、２６はプリズム、２７Ａは垂直方向の入射光、２７Ｂはプリズム内の光、２７Ｃはプリズム通過後の光の進行方向を示す。
【００２９】
斜め方向からの露光は、これは代表的な露光方法であるが、これに限定されない。たとえば、複数のプリズムが並んで設けられているプリズムアレー構造や、鏡の反射を用いた方法等公知の光学部品を用いて斜め方向から光を照射するようにすればよい。
【００３０】
次いで、この非対称のフォトレジストを用いて、基板自体又は透明材料膜のドライエッチングを行う。このドライエッチングは、基板自体又は透明材料膜をエッチングできるものを用いてエッチングすればよい。この際、透明材料膜はエッチングするが基板はエッチングしにくい材料を用いることにより、エッチングを制御しやすくなり、エッチング深さ等の点で好ましい。
【００３１】
これにより、図１（Ｂ）で示すような非対称な透明材料膜４の凸部を形成できる。この透明材料膜４の凸部は、フォトレジスト３の形状にほぼ似た形状になる。この例においては、透明材料膜４の凸部の左側の側面はほぼ垂直、右側の側面は傾斜面にされている。
【００３２】
この非対称な凸部の格子を設けた基板は、それ自体として形成した光学回折格子として使用できる。また、この非対称な凸部の格子を設けた基板と他の基板との間に液晶等の光学的異方性材料を充填して光学回折格子として使用できる。また、上記の例では透明材料膜を設けた基板を用いた例を中心にして説明したが、基板自体をエッチングして凸部を形成した基板を用いることもできる。
【００３３】
図４は、液晶を用いた光学回折格子の例の断面図である。図４において、３１は基板、３４は非対称な形状の凸部の透明材料膜、３５は他の基板、３６は２枚の基板の周囲を封止するシール材、３７は液晶を示す。
【００３４】
この液晶を用いた場合、基板を配向処理して液晶を特定方向に配列させておくことが有利である。たとえば、液晶分子の長手方向が図４の前後方向（紙面に垂直方向）になるように配向処理した基板を用い、液晶の屈折率のいずれかとこの透明材料膜の屈折率とが一致するようにすると、高い回折効率が得られ好ましい。
【００３５】
この液晶の配向処理は、ＳｉＯ等の無機膜の斜め蒸着をしたり、ポリイミド、ポリアミド、ＳｉＯ２等の膜を形成してラビング処理したりすればよい。さらに、必要に応じて電極を形成して、一部の液晶を電圧の印加により配向状態を変えて光学回折格子としての機能を可変にしたりしてもよい。具体的には、電圧印加状態により、光学回折格子の回折能力を変化させたり、開口率を変えたり、旋光性を変えたり、焦点距離を変るようにしてもよい。
【００３６】
この非対称な凸部の格子を形成した光学回折格子は、光ヘッド装置に好適に用いられる。光ヘッド装置において、この光学回折格子は光源と光学記録媒体との間に配置して用いられる。具体的な構成としては、図５に示す構成がある。図５において、４１はレーザダイオード等の光源、４２は光学回折格子、４３は１／４λ板のような位相差板、４４は対物レンズ、４５は光学記録媒体、４６は光検出器、４７Ａ、４７Ｂは回折光を示す。
【００３７】
この例では、非対称の光学回折格子で回折光４７Ａよりも４７Ｂの方が光量が多くなるので、回折光４７Ｂ側にのみ光検出器が設けられている。片側のみに光検出器が設けられているので、その側のみ光量が多くなればよい。このため、光源４１の光量は少なくて済むので、光ヘッド装置の小型化、低消費電力化というメリットを有する。
【００３８】
なお、この光ヘッド装置の例は、代表例を示すにすぎず、これに限定されない。たとえば、これにプリズムや鏡を付加して、光路を曲げたり、対物レンズを交換可能にしたり、液晶レンズ等で焦点距離を変えたりして異なる焦点位置の光学記録媒体を読み書きできるようにしてもよい。また、光のビームを３ビームに分けるために別個の回折格子を付加してもよい。
【００３９】
【実施例】
［実施例１］
屈折率１．５２のガラス基板上に、透明材料膜として屈折率１．４４のＳｉＯ２膜を６００ｎｍの厚さに真空蒸着法により成膜した。このＳｉＯ２膜上にスピンコートにより２μｍ厚のポジ型フォトレジストを塗布し、プリベークを実施した。その後、通常の密着／近接露光装置を使用し、４μｍピッチのマスクパターンを用いて密着露光を実施した。
【００４０】
その際、フォトマスク上に、屈折率約１．５のアクリル樹脂製直角プリズムをマスク上に配置することにより、上方より垂直に入射する紫外光を約２５°の入射角でフォトレジストに露光した。この後、現像及びポストベークを実施し、フォトレジストの立ち上がり角が、約８５°及び約６０°の非対称形状のフォトレジストのパターンを作製した。
【００４１】
この後、Ｃ２Ｆ６及びＯ２の混合ガスを用いたリアクティブイオンエッチング（ＲＩＥ）法によりドライエッチングを行い、フォトレジストの非対称形状をＳｉＯ２膜にも形成されるようにした。その後、残存するフォトレジストを除去し、非対称のＳｉＯ２膜の凸部を有する光学回折格子を実現した。
【００４２】
得られた光学回折格子は、波長６５０ｎｍの半導体レーザ光に対し、＋１次約１２％、−１次約１％の非対称比約１０、透過率約５０％の特性を示した。
【００４３】
［実施例２］
屈折率１．５２のガラス基板上に、屈折率１．５２のＳｉＯＮ膜を１．８μｍの厚さにプラズマＣＶＤ法により成膜した。ＳｉＯＮ膜上にスピンコートにより２．５μｍ厚のポジ型フォトレジストを塗布し、プリベークを実施した。その後、４μｍピッチのマスクパターンを用いて密着露光を実施した。
【００４４】
その際、フォトマスク上に、屈折率１．８５のガラス直角プリズムをマスク上に配置することにより、上方より垂直に入射する紫外光を約６０°の入射角でフォトレジストに露光した。この後、現像及びポストベークを実施し、フォトレジストの立ち上がり角が、約８５°及び約６０°の非対称形状のフォトレジストのパターンを作製した。
【００４５】
この後、Ｃ２Ｆ６及びＯ２の混合ガスを用いたＲＩＥ法によりドライエッチングを行い、フォトレジストの非対称形状をＳｉＯＮ膜にも形成されるようにした。残存するフォトレジストを除去した基板及び対向ガラス基板に反射防止膜をコーティングした後、ポリイミドを塗布焼成し配向膜を形成した。
【００４６】
ラビング配向処理の後、これらの基板を８μｍのスペーサを含むシール材で周辺を熱圧着し、常光屈折率１．５２、異常光屈折率１．７７のネマチック液晶を充填し注入口を封止した。
【００４７】
作製した偏光依存性回折格子は、波長６５０ｎｍの半導体レーザ光に対し、Ｓ偏光の半導体レーザ光に対し＋１次約５０％、−１次約１５％の非対称比約３．３の特性を示した。またＰ偏光の半導体レーザ光に対しては、９５％の透過率を示した。
【００４８】
この光学回折格子を図５に示す光ヘッド装置に組み込んで使用したところ、光源からの往路の光は光学回折格子を高効率でそのまま通過し、復路の光は光学回折格子で回折され、光検出器のある方への光量が多い回折光が得られた。
【００４９】
【発明の効果】
本発明によれば、非対称な構造を有する光学回折格子を生産性良く製造できる。特に、露光の光の方向を斜めにするのみでよいので、既存の製造装置を容易に流用して製造できる。このため、プリズムの付加というような既存の製造ラインのわずかな変更で容易に製造でき、従来型の対称な構造を有する光学回折格子との併産も簡単なので、生産性がきわめてよい。
【００５０】
この非対称な構造を有する光学回折格子は、複数の回折光のうち、１つの回折光の利用効率を高くできるので、光ヘッド装置の小型化、低消費電力化に有用である。
発明は、本発明の効果を損しない範囲内で、種々の応用ができる。
【図面の簡単な説明】
【図１】本発明の光学回折格子の製造工程を示す断面図。
【図２】従来の対称な構造を有する光学回折格子の製造工程を示す断面図。
【図３】本発明の斜め方向からの光照射工程を示す側面図。
【図４】本発明の液晶を用いた光学回折格子の例の断面図。
【図５】本発明の光学回折格子を用いた光ヘッド装置の代表的な例の模式図。
【符号の説明】
１：基板
２：透明材料膜
３：フォトレジスト
４：透明材料膜[0001]
BACKGROUND OF THE INVENTION
The present invention is suitable for an optical head device for writing optical information on an optical recording medium such as an optical disc such as a CD (compact disc), a CD-ROM, a video disc, and a magneto-optical disc, and for reading the optical information. The present invention relates to an optical diffraction grating manufacturing method and an optical head device using the same.
[0002]
[Prior art]
Conventionally, as an optical head device for writing optical information on an optical recording medium such as an optical disk and a magneto-optical disk or reading optical information, signal light reflected from the recording surface of the optical recording medium is guided to a detection unit ( As optical parts for beam splitting, those using a prism type beam splitter and those using a diffraction grating or a hologram element are known.
[0003]
In this diffraction grating or hologram element for an optical head device, a rectangular grating (relief type) having a rectangular cross section is formed on a glass or plastic substrate by a dry etching method or an injection molding method, thereby diffracting light. A beam split function was added.
[0004]
In addition, it is conceivable to use polarized light when trying to increase the light use efficiency more than the isotropic diffraction grating having the light use efficiency of about 10%. When using polarized light, a prism type beam splitter is combined with a λ / 4 plate to increase the efficiency of the forward path (direction from the light source to the optical recording medium) and the return path (direction from the optical recording medium to the photodetector). There was a way to increase the round trip efficiency.
[0005]
However, prismatic polarization beam splitters are expensive, and other methods have been sought. As one method, a method is known in which a flat plate of birefringent crystal such as LiNbO 3 is used, and an anisotropic diffraction grating is formed on the surface to provide polarization selectivity. However, the birefringent crystal itself is difficult to manufacture and expensive, and it has been difficult to apply to the consumer field.
[0006]
As described above, since the use efficiency of the isotropic diffraction grating is about 50% in the forward path and about 20% in the return path, the utilization efficiency in the round trip is only about 10%.
[0007]
Furthermore, since these are not only low in efficiency but also a diffraction grating having a symmetrical shape, the diffraction efficiency of the + 1st order light and the diffraction efficiency of the −1st order light are almost equal. When a plurality of photodetectors are provided to detect both, it is advantageous that both diffraction efficiencies are approximately equal, but it is not necessarily advantageous in the case of a single photodetector.
[0008]
That is, it has been proposed that one optical detector be used for the miniaturization of the optical head, and in this case, light is diffracted by the same amount of light in two directions from the light utilization efficiency. This is not advantageous. Of the light diffracted in two directions, it is advantageous to increase the amount of light diffracted to the side where the photodetector is provided. For this reason, it has been desired to increase one diffracted light more than the other.
[0009]
[Problems to be solved by the invention]
For this purpose, it is necessary to use a diffraction grating in which the lateral direction of the concave and convex portions of the diffraction grating is asymmetrical. However, this asymmetrical diffraction grating was originally a diffraction grating with a very fine pitch, and was extremely difficult to manufacture. Therefore, an asymmetric diffraction grating manufacturing method with high productivity has been desired.
[0010]
An object of the present invention is to solve such a problem and to provide a manufacturing method for easily manufacturing an optical diffraction grating with high utilization efficiency of one of the diffracted lights.
[0011]
[Means for Solving the Problems]
The present invention relates to a method of manufacturing an optical diffraction grating in which a grating-like convex portion is formed on a surface of a substrate, and a photoresist is formed on the surface of the substrate, and the photoresist is desired from the side on which the photoresist is formed. By obliquely exposing through a photomask at a predetermined irradiation angle so that a pattern can be obtained and developing, the lateral side surface of the remaining photoresist lattice becomes asymmetric, and then dry etching is performed by etching. Provided is a method for manufacturing an optical diffraction grating, characterized in that the lateral side surface of the remaining convex portion grating is asymmetrical.
[0012]
A manufacturing method of the optical diffraction grating according to claim 1, wherein a substrate provided with a transparent material film is used as a substrate, and the lateral surface of the convex portion of the transparent material film remaining by etching is asymmetric in the lateral direction. The method and the substrate formed so that the side surfaces of the convex portions are asymmetrical are used as a first substrate, and an optically anisotropic material is filled between the first substrate and the second substrate. A method for producing the optical diffraction grating is provided.
[0014]
The optical diffraction grating manufactured by the present invention is suitably used for an optical head device that writes information and / or reads information by irradiating light from a light source onto the optical recording medium through the optical diffraction grating. .
[0015]
In the present invention, when the resist pattern is exposed with a photomask, it is exposed from an oblique direction, thereby forming a left-right asymmetric lattice (stripe-shaped) convex portion on the surface of the transparent substrate. Further, the substrate having the convex portions formed in this way is used by filling a liquid crystal having optical anisotropy between the two substrates. Thereby, an optical diffraction grating with high one-side diffraction efficiency can be easily manufactured.
[0016]
In the present invention, the substrate itself may be directly etched to form a convex portion, but from the viewpoint of etching depth, distribution, and end point detection, a transparent material film may be formed on the substrate surface. preferable.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a photoresist is formed on the surface of the substrate itself or the surface of the substrate provided with a transparent material film, and the irradiation angle is determined so that a desired pattern can be obtained from the side on which the photoresist is formed. in oblique exposure through a photomask, the lateral direction of the side surface of the grating of photoresist remaining by development is to become asymmetric, then by dry etching, lateral direction of the grid of protrusions remaining etching So that the sides are asymmetric.
[0018]
FIG. 2 shows a main process for manufacturing a conventional optical diffraction grating. (A) is sectional drawing which shows the state which exposed and developed the photoresist, (B) is sectional drawing which shows the state which dry-etched the transparent material film | membrane using it. 11 is a substrate, 12 is a transparent material film, 13 is a photoresist, and 14 is a transparent material film after etching.
[0019]
When the normal exposure, development, and etching are performed in this way, the transparent material film has the same inclination angle on the left and right side surfaces of the convex portion in the short direction of the lattice stripe (left and right in the figure), and the left and right sides are symmetrical. . In the optical diffraction grating having such a shape, the amount of diffracted light is approximately equal between the + 1st order and the −1st order. This is suitable when a plurality of photodetectors are provided on the left and right sides to detect reflected light from the optical recording medium.
[0020]
However, when a photodetector is provided only on one side, it is advantageous that a large amount of light is diffracted only on the side where the photodetector is provided. Although both are provided with photodetectors, the purpose is different, and the same is true when more light is required for one of the photodetectors. For this reason, the optical head device using the optical diffraction grating manufactured by the manufacturing method of the present invention is not limited to one having only one photodetector.
[0021]
FIG. 1 shows the main steps for producing the optical diffraction grating of the present invention, and shows an example in which a transparent material film is formed on the substrate surface. (A) is sectional drawing which shows the state which exposed and developed the photoresist, (B) is sectional drawing which shows the state which dry-etched the transparent material film | membrane using it. Reference numeral 1 denotes a substrate, 2 denotes a transparent material film, 3 denotes a photoresist, and 4 denotes a transparent material film after etching.
[0022]
When normal exposure, development, and etching are performed in this way, the transparent material film has a different inclination angle on the left and right side surfaces of the convex portion in the short direction of the lattice stripe (left and right in the figure), and the left and right sides become asymmetric. In the optical diffraction grating having such a shape, the amount of diffracted light differs between the + 1st order and the −1st order. This is preferable because the amount of light can be used effectively when one photodetector is provided on either the left or right side to detect the reflected light from the optical recording medium.
[0023]
The substrate used in the present invention is a transparent substrate such as glass. Although this transparent substrate can be used as it is, the substrate surface can be etched to form convex portions. However, as shown in the example of this figure, a transparent material film such as SiON or SiO 2 is formed on the transparent substrate by reactive sputtering. It is preferably formed and used by a method, a vapor deposition method, a plasma CVD method or the like.
[0024]
When an optically anisotropic material such as liquid crystal is not filled and used, in order to reduce reflection at the interface between the transparent material film and the substrate, the refractive index of the transparent material film is equal to the refractive index of the substrate. It is preferable to make them substantially coincide.
[0025]
When an optically anisotropic material such as liquid crystal is filled and used, the refractive index of the transparent material film is preferably substantially equal to the ordinary light refractive index or the extraordinary light refractive index of the liquid crystal or the like. Furthermore, in order to reduce reflection at the interface with the substrate, it is preferable to make the refractive index of the transparent material film substantially coincide with the refractive index of the substrate.
[0026]
A photoresist is laminated on the transparent material film 2 by spin coating or the like, and the photoresist is irradiated with light through a photomask. At this time, by irradiating light from an oblique direction and then developing, the left and right side surfaces of the convex portion in the short direction (left and right direction in the figure) of the stripe of the remaining photoresist 3 have different inclination angles. It becomes asymmetric. In this example, the left side surface is substantially vertical and the right side surface is inclined.
[0027]
The light irradiation from the oblique direction is performed by irradiating light from the oblique direction. The angle of the oblique irradiation may be determined experimentally so as to obtain a desired pattern, but it may be generally inclined by about 10 to 60 ° from the vertical direction. Specifically, for example, the method shown in FIG. FIG. 3 is a side view showing a light irradiation process from an oblique direction.
[0028]
Since normal exposure is performed from the vertical direction, an exposure apparatus having the same structure as the light source is used, a prism is inserted in the optical path, and the optical path is bent obliquely. In FIG. 3, 21 is a substrate, 22 is a transparent material film, 23 is a photoresist, 25 is a mask, 26 is a prism, 27A is incident light in a vertical direction, 27B is light in the prism, and 27C is light after passing through the prism. Indicates the direction of travel.
[0029]
The exposure from the oblique direction is a typical exposure method, but is not limited to this. For example, light may be irradiated from an oblique direction using a known optical component such as a prism array structure in which a plurality of prisms are arranged side by side, or a method using mirror reflection.
[0030]
Next, dry etching of the substrate itself or the transparent material film is performed using the asymmetric photoresist. This dry etching may be performed using a material that can etch the substrate itself or the transparent material film. At this time, by using a material that etches the transparent material film but is difficult to etch the substrate, it becomes easier to control the etching, which is preferable in terms of etching depth and the like.
[0031]
Thereby, the convex part of the asymmetric transparent material film | membrane 4 as shown in FIG.1 (B) can be formed. The convex portion of the transparent material film 4 has a shape substantially similar to the shape of the photoresist 3. In this example, the left side surface of the convex portion of the transparent material film 4 is substantially vertical, and the right side surface is inclined.
[0032]
The substrate provided with the asymmetrical convex grating can be used as an optical diffraction grating formed as such. In addition, an optically anisotropic material such as liquid crystal can be filled between a substrate provided with the asymmetric convex grating and another substrate and used as an optical diffraction grating. In the above example, the description is centered on an example in which a substrate provided with a transparent material film is used. However, a substrate in which a convex portion is formed by etching the substrate itself can also be used.
[0033]
FIG. 4 is a cross-sectional view of an example of an optical diffraction grating using liquid crystal. In FIG. 4, 31 is a substrate, 34 is a transparent material film having an asymmetrical convex portion, 35 is another substrate, 36 is a sealing material for sealing the periphery of two substrates, and 37 is a liquid crystal.
[0034]
When this liquid crystal is used, it is advantageous to align the liquid crystal in a specific direction by aligning the substrate. For example, using a substrate that has been aligned so that the longitudinal direction of the liquid crystal molecules is in the front-rear direction of FIG. 4 (perpendicular to the paper surface), one of the refractive indices of the liquid crystals and the refractive index of the transparent material film match. Then, high diffraction efficiency is obtained and preferable.
[0035]
The alignment treatment of the liquid crystal may be performed by obliquely depositing an inorganic film such as SiO, or by performing a rubbing process by forming a film of polyimide, polyamide, SiO 2 or the like. Furthermore, an electrode may be formed as needed, and the function as an optical diffraction grating may be made variable by changing the alignment state of some liquid crystals by applying a voltage. Specifically, the diffraction capability of the optical diffraction grating, the aperture ratio, the optical rotation, or the focal length may be changed depending on the voltage application state.
[0036]
The optical diffraction grating in which the asymmetric convex grating is formed is preferably used for an optical head device. In the optical head device, the optical diffraction grating is used by being disposed between a light source and an optical recording medium. As a specific configuration, there is a configuration shown in FIG. In FIG. 5, 41 is a light source such as a laser diode, 42 is an optical diffraction grating, 43 is a retardation plate such as a 1 / 4λ plate, 44 is an objective lens, 45 is an optical recording medium, 46 is a photodetector, 47A, 47B indicates diffracted light.
[0037]
In this example, the light amount of 47B is larger than that of diffracted light 47A by an asymmetric optical diffraction grating, and therefore a photodetector is provided only on the diffracted light 47B side. Since the photodetector is provided only on one side, the amount of light only needs to increase on that side. For this reason, since the light quantity of the
[0038]
In addition, the example of this optical head apparatus shows only a representative example, and is not limited to this. For example, by adding a prism or mirror to this, the optical path can be bent, the objective lens can be exchanged, or the focal length can be changed with a liquid crystal lens, etc. so that optical recording media at different focal positions can be read and written. Good. A separate diffraction grating may be added to divide the light beam into three beams.
[0039]
【Example】
[Example 1]
A SiO 2 film having a refractive index of 1.44 was formed as a transparent material film to a thickness of 600 nm on a glass substrate having a refractive index of 1.52 by a vacuum deposition method. A 2 μm-thick positive photoresist was applied onto the SiO 2 film by spin coating and prebaked. Thereafter, using a normal contact / proximity exposure apparatus, contact exposure was performed using a 4 μm pitch mask pattern.
[0040]
At that time, by placing an acrylic resin right-angle prism having a refractive index of about 1.5 on the photomask on the photomask, ultraviolet light incident vertically from above was exposed to the photoresist at an incident angle of about 25 °. . Thereafter, development and post-baking were performed, and a photoresist pattern having an asymmetric shape with a rising angle of about 85 ° and about 60 ° of the photoresist was produced.
[0041]
Thereafter, dry etching was performed by a reactive ion etching (RIE) method using a mixed gas of C 2 F 6 and O 2 so that an asymmetric shape of the photoresist was also formed on the SiO 2 film. Thereafter, the remaining photoresist was removed to realize an optical diffraction grating having a convex portion of an asymmetric SiO 2 film.
[0042]
The obtained optical diffraction grating showed characteristics of an asymmetry ratio of about 10 and a transmittance of about 50% with respect to a semiconductor laser beam having a wavelength of 650 nm, about + 1st order about 12%, -1st order about 1%.
[0043]
[Example 2]
A SiON film having a refractive index of 1.52 was formed to a thickness of 1.8 μm on a glass substrate having a refractive index of 1.52 by a plasma CVD method. A 2.5 μm-thick positive photoresist was applied onto the SiON film by spin coating and prebaked. Thereafter, contact exposure was performed using a 4 μm pitch mask pattern.
[0044]
At that time, a glass rectangular prism having a refractive index of 1.85 was disposed on the photomask, so that the ultraviolet light incident vertically from above was exposed to the photoresist at an incident angle of about 60 °. Thereafter, development and post-baking were performed, and a photoresist pattern having an asymmetric shape with a rising angle of about 85 ° and about 60 ° of the photoresist was produced.
[0045]
Thereafter, dry etching was performed by an RIE method using a mixed gas of C 2 F 6 and O 2 so that an asymmetric shape of the photoresist was also formed on the SiON film. After coating the anti-reflective film on the substrate from which the remaining photoresist was removed and the counter glass substrate, polyimide was applied and baked to form an alignment film.
[0046]
After the rubbing alignment treatment, the periphery of these substrates was thermocompression bonded with a sealing material containing a spacer of 8 μm, filled with nematic liquid crystal having an ordinary light refractive index of 1.52 and an extraordinary light refractive index of 1.77, and the injection port was sealed. .
[0047]
The produced polarization-dependent diffraction grating exhibited a characteristic of an asymmetry ratio of about 3.3 with respect to a semiconductor laser beam having a wavelength of 650 nm, that is, about + 1st order about 50% and about -1st order about 15% with respect to S-polarized semiconductor laser light. . Further, the transmittance was 95% for P-polarized semiconductor laser light.
[0048]
When this optical diffraction grating is incorporated in the optical head device shown in FIG. 5 and used, the forward light from the light source passes through the optical diffraction grating with high efficiency, and the return light is diffracted by the optical diffraction grating to detect light. A diffracted light with a large amount of light directed toward the vessel was obtained.
[0049]
【The invention's effect】
According to the present invention, an optical diffraction grating having an asymmetric structure can be manufactured with high productivity. In particular, since it is only necessary to make the direction of exposure light oblique, it is possible to manufacture by using an existing manufacturing apparatus easily. For this reason, since it can be easily manufactured with a slight modification of an existing manufacturing line such as addition of a prism, and it can be easily combined with an optical diffraction grating having a conventional symmetrical structure, the productivity is very good.
[0050]
Since the optical diffraction grating having this asymmetric structure can increase the use efficiency of one diffracted light among a plurality of diffracted lights, it is useful for reducing the size and power consumption of the optical head device.
The present invention can be applied in various ways within a range not impairing the effects of the present invention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a manufacturing process of an optical diffraction grating of the present invention.
FIG. 2 is a cross-sectional view showing a manufacturing process of a conventional optical diffraction grating having a symmetric structure.
FIG. 3 is a side view showing a light irradiation process from an oblique direction according to the present invention.
FIG. 4 is a cross-sectional view of an example of an optical diffraction grating using the liquid crystal of the present invention.
FIG. 5 is a schematic view of a typical example of an optical head device using the optical diffraction grating of the present invention.
[Explanation of symbols]
1: Substrate 2: Transparent material film 3: Photoresist 4: Transparent material film
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15722296A JP3994450B2 (en) | 1996-06-18 | 1996-06-18 | Manufacturing method of optical diffraction grating and optical head device using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15722296A JP3994450B2 (en) | 1996-06-18 | 1996-06-18 | Manufacturing method of optical diffraction grating and optical head device using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1010307A JPH1010307A (en) | 1998-01-16 |
| JP3994450B2 true JP3994450B2 (en) | 2007-10-17 |
Family
ID=15644901
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15722296A Expired - Fee Related JP3994450B2 (en) | 1996-06-18 | 1996-06-18 | Manufacturing method of optical diffraction grating and optical head device using the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3994450B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4614193B2 (en) * | 1999-11-09 | 2011-01-19 | スタンレー電気株式会社 | Reflective display |
| JP4636573B2 (en) * | 2000-10-31 | 2011-02-23 | オプトレックス株式会社 | Method for forming light diffusion layer of reflective liquid crystal display device |
| JP3859473B2 (en) | 2001-08-30 | 2006-12-20 | シャープ株式会社 | Stamper manufacturing method |
| JP2005353207A (en) * | 2004-06-11 | 2005-12-22 | Ricoh Co Ltd | Polarizing hologram element, optical pickup device, and manufacturing method for them |
| JP2007264555A (en) * | 2006-03-30 | 2007-10-11 | Brother Ind Ltd | Transmission type diffraction element and eyeball projection type display device using the same |
| JP5806129B2 (en) * | 2012-01-17 | 2015-11-10 | トヨタ自動車株式会社 | Semiconductor device and manufacturing method thereof |
| CN106772734A (en) * | 2017-01-03 | 2017-05-31 | 中国科学院上海光学精密机械研究所 | The asymmetric pattern reflection type optical grid of broadband high-diffraction efficiency |
-
1996
- 1996-06-18 JP JP15722296A patent/JP3994450B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1010307A (en) | 1998-01-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6271966B1 (en) | Optical head device including an optically anisotropic diffraction grating and process for its production | |
| US6304312B1 (en) | Optical head, method of manufacturing the same, and diffraction element suitable therefor | |
| JP4043058B2 (en) | Manufacturing method of diffraction element used in optical head device | |
| JP3994450B2 (en) | Manufacturing method of optical diffraction grating and optical head device using the same | |
| JP3624561B2 (en) | Optical modulation element and optical head device | |
| JP3711652B2 (en) | Polarization diffraction element and optical head device using the same | |
| JP3598703B2 (en) | Optical head device and manufacturing method thereof | |
| JP3947828B2 (en) | Optical head device and manufacturing method thereof | |
| JP2541548B2 (en) | Diffraction grating type optical polarizer | |
| JP4179645B2 (en) | Optical head device and driving method thereof | |
| JP3596152B2 (en) | Method of manufacturing optical modulation element and method of manufacturing optical head device | |
| JP3528381B2 (en) | Optical head device | |
| JP3713778B2 (en) | Optical head device | |
| JP3648581B2 (en) | Polarization diffraction grating, aperture control device using the same, aperture control method, and optical head device | |
| JP3509399B2 (en) | Optical head device | |
| JP3550873B2 (en) | Optical head device | |
| JPH05196813A (en) | Diffraction grating type optical polarizing element | |
| JPH09274188A (en) | Optical modulation element and optical head device | |
| JPH10188332A (en) | Optical head device | |
| JP4420990B2 (en) | Optical head device | |
| KR100223860B1 (en) | Optical pickup for different disc type | |
| JPH09185837A (en) | Optical head device | |
| JP4364083B2 (en) | Optical head device | |
| JPH09198698A (en) | Production of optical head device | |
| JPH09127335A (en) | Manufacture of optical head device and optical head device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20040823 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20060110 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060306 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20060404 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060526 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20070313 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20070509 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20070710 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20070723 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100810 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100810 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100810 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110810 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110810 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120810 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120810 Year of fee payment: 5 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120810 Year of fee payment: 5 |
|
| R371 | Transfer withdrawn |
Free format text: JAPANESE INTERMEDIATE CODE: R371 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120810 Year of fee payment: 5 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130810 Year of fee payment: 6 |
|
| LAPS | Cancellation because of no payment of annual fees |