JP4158890B2

JP4158890B2 - Liquid crystal optical element and manufacturing method thereof

Info

Publication number: JP4158890B2
Application number: JP2002303271A
Authority: JP
Inventors: 和生福田
Original assignee: Nanox Corp
Current assignee: Nanox Corp
Priority date: 2002-10-17
Filing date: 2002-10-17
Publication date: 2008-10-01
Anticipated expiration: 2022-10-17
Also published as: JP2004138808A

Description

【０００１】
【発明の属する技術分野】
本発明は、液晶の光学異方性を用いた光学素子に関し、特に光通信素子に適した液晶光学素子とその製造方法に関する。
【０００２】
【従来の技術】
液晶の光学的異方性を利用した光学素子は、液晶表示素子として多く用いられている。その他の用途として、位相制御、偏光制御などの光学素子もあり、光通信素子への適用も試みられている。
【０００３】
液晶の誘電率異方性により、電界により液晶の配向方向を制御する場合には、２枚の透明導電膜付き基板の間に液晶を封入し、予め、透明導電膜上に塗布した配向膜により液晶を配向させておき、対向した透明導電膜間に電圧を印加することで、配向方向を変えることができる。
【０００４】
例えば、ネマティック液晶を用いた位相制御の場合には、液晶を面内で全て同じ方向となるようにホモジニアス配向として、液晶の屈折率異方性（複屈折率）△ｎと液晶層厚ｄの積△ｎｄを希望する位相差の長さに合わせる。この状態で、液晶の配向方向と垂直方向の偏光成分は、△ｎｄの位相差を持たせることができる。例えば、液晶の配向方向に４５°の直線偏光を入射させたとき、位相差が１／４波長であれば円偏光に、半波長であれば９０°の偏光方向に回転させるなど、偏光方向を変化させることができる。また、対向した透明導電膜に電圧を印加することで、液晶分子の向きを透明導電膜面に対して垂直方向に変えることで、この位相差を無くすことができる。
【０００５】
こうした液晶光学素子の特性を決める重要な因子は、液晶素子の△ｎｄであり、安定した特性を発揮させるためには、この値の安定性も要求される。
液晶光学素子の△ｎｄの値を安定化させるために液晶を封入した２枚の透明導電膜付き基板の間に電界を発生させることで行う方法が、千葉貴史、大寺康夫、川上彰二郎、「液晶回転波長板」、Ｏ plus Ｅ、第２０巻、第１０号、ｐ１１４５−１１５０に記載されており、また特開平１１−３８４５１号公報記載の発明では通信用に適したネマチック液晶を挟持した液晶光学素子として、屈折率異方性が０．２０以上であり、屈折率異方性と液晶部分の厚さの積が１．３μｍ以上であり、光学素子全体の厚さが１０μｍ〜２５０μｍである電界制御複屈折型の液晶素子を提案している。
【０００６】
【非特許文献１】
千葉貴史、大寺康夫、川上彰二郎、「液晶回転波長板」、Ｏ plus Ｅ、第２０巻、第１０号、ｐ１１４５−１１５０
【０００７】
【特許文献１】
特開平１１−３８４５１号公報
【０００８】
【発明が解決しようとする課題】
上記液晶光学素子の液晶セルは、図１０（ａ）に示すように２枚のガラス基板１、１’のシール部２で間隔が設けられた隙間に液晶Ｌが注入されているが、液晶光学素子の製作後に図１０（ｂ）に示すようにガラス基板１、１’の隙間であるギャップ（液晶層厚）が減少する性質がある。そのために、経時的に△ｎｄが減少してしまうという問題点があった。
これは、２枚のガラス基板１、１’の隙間に液晶Ｌを注入した後、経時的に液晶Ｌの体積が減少し、負圧が生じて結果的に基板間の距離を減少させるためである。
【０００９】
液晶表示パネルにおいては、前記２枚の基板１、１’の隙間の液晶Ｌ部分の体積減少による前記隙間の変化を避けるために、この隙間に液晶層厚と同じ程度の大きさを持つスペーサーを入れて、液晶Ｌの内部より２枚のガラス基板１、１’を支える方法が採られているが、光通信用の液晶素子では前記スペーサーをガラス基板１、１’間に入れると、スペーサーが光散乱の原因となり、エネルギーロスやスペーサーに基づく散乱光による干渉が生じる原因となるために採用できない。
【００１０】
また、液晶表示パネルに用いる液晶セルの大きさは約１０ｃｍ×１０ｃｍであるのに対して光通信用などに用いる液晶素子の液晶セルの大きさは約１ｃｍ×１ｃｍであるため、前記スペーサーをガラス基板１、１’間に入れることは有効利用面積を小さくしてしまうことからも不利である。
【００１１】
そのために、従来は液晶光学素子の製作後にエージングをして、液晶層厚の減少が一定幅を超えたものは除外することが行われていたが、製品のロスとなり、生産性を著しく低下させていた。また、最終的な液晶層厚の減少幅を見込んで、液晶を多めに注入するという方法も、液晶セルが小さいために効果が少ない。また、前記隙間の液晶部分の体積減少変動幅のバラツキによる液晶層厚のバラツキは避けられない。
【００１２】
このように、従来技術は液晶層厚が一定幅に入る最終液晶素子製品を得るための歩留まりが低いなどという問題点があった。
また、液晶セルは、液晶の体積がセルの大きさに比べて小さくなると、液晶のない空間部を発生し、該空間部がセルの厚さを戻す性質がある。液晶表示パネルにおいては、液晶のない前記空間部は表示に寄与しないばかりか、外観上も目立つため、重欠点として除外されている。
【００１３】
本発明の課題は、前記従来技術の問題点を克服し、生産性を低下させず、安定的に所定の液晶層厚を有する通信用などの光学素子としても十分使用できる液晶光学素子を得ることである。更に、本発明の課題は、液晶セルに液晶のない空間部が発生することを防止することである。
【００１４】
【課題を解決するための手段】
本発明の上記課題は次の解決手段で解決される。
請求項１記載の発明は、２枚の透明電極付き透明基板と、該２枚の透明基板を間隔を開けて重ね合わせ、該透明基板の対向する面の周辺部を仕切るシール部と、該シール部によって仕切られた２枚の透明基板間の空間内に液晶を封入して得られる液晶セルとを有する液晶光学素子において、前記液晶セルは、液晶が封入された液晶封入部と液晶が封入されていない空間部とが液晶が通過できる開口部を有するシール部により区画され、前記液晶封入部と前記空間部のシール部の基板間方向の厚みを変えることで、前記空間部における前記透明基板間の距離を液晶封入部における前記透明基板間の距離より大きくした液晶光学素子である。
【００１５】
液晶セルは、液晶の体積がセルの大きさに比べて小さくなると、液晶のない空間部を発生し、該空間部がセルの厚さを戻す性質がある。液晶表示パネルにおいては、液晶のない前記空間部は表示に寄与しないばかりか、外観上も目立つため、重欠点として除外されている。この空間部はセル内エアと呼ばれているが、この空間部内には空気があるとは限らない。
請求項１記載の発明をはじめ、本発明は、この空間部を積極的に用いることで完成した発明である。
【００１６】
本発明の光学素子の液晶セルは、例えば図１、図２に示す一方の透明基板１上に設けたシール部２の形状に示すように、光学素子としての有効な液晶Ｌが存在する領域（以後、液晶封入部３ということがある）とセル内エア領域（以後、空間部５と言うことがある）と液晶封入部３と空間部５の境界部にある狭い液晶流通可能な開口部６と液晶封入口３にある液晶注入口７を設けたシール部２を設けた構成である。
【００１７】
透明基板１の間の閉鎖領域であるセルに液晶Ｌを注入するとき、液晶Ｌが注入されない部分を残したり、後から発生させたりすることで積極的に空間部（液晶セル内エア領域）５を作製する。
【００１８】
液晶封入部３と空間部５との境界部にシール部２により狭い液晶流通可能な開口部６を設けておけば、液晶注入口７からシール部２内部に入った液晶Ｌは空間部５を容易に作ることができる。そして、液晶封入部３と空間部５とのシール部２の厚みを変えることで前記空間部における前記透明基板間の距離（ギャップ）を液晶封入部における前記透明基板間の距離（ギャップ）より大きくする。
【００１９】
本発明では空間部５の存在で液晶セルの厚さを所定の大きさに維持することができ、設計通りの光学特性を得ることができる。すなわち、透明基板１の剛性により透明基板１の平面を維持しながら、液晶Ｌの体積の変化に対しては、液晶Ｌの無い空間部５の気体の体積を変化させることで対応する。また、温度等や経時変化による液晶Ｌの体積に変化があっても、この空間部５の体積の変化により液晶Ｌの体積の変化に対応させて、液晶セルの液晶層厚を一定に維持することができる。空間部５の体積の変化により図１（ｂ）、図２に示すように空間部５のガス領域が増加することで液晶Ｌが収縮しないようにして液晶厚の変動を抑えることができる。
【００２０】
従来の液晶光学素子の液晶セルには、図１１に示すように透明基板１の周辺部に設けたシール部２と該シール部２内に図１等で示す空間部５が存在しないように液晶Ｌを充填させていた。従来の液晶光学素子では図１等で示す空間部５の存在がむしろ液晶光学素子の物性に悪影響を及ぼすので、前記空間部５を除くことが必要であったが、前記空間部５がない、液晶Ｌで完全に充填された液晶セル内では、液晶Ｌが収縮して図１０（ｂ）に示すように透明基板１、１’の中央部が凹状に窪むので、本発明では、むしろ空間部５を積極的に存在させて、液晶Ｌが収縮する部分を、この空間部５のガスの膨張部分で補い、透明基板１の変形を防止し、図１０（ａ）に示す断面形状のように透明基板１、１’を平坦な状態に維持することができる。
【００２１】
また、図１、図２に示す空間部５が光学素子として有効に機能する液晶封入部３に移動しないようにするために、狭い液晶流通用の開口部６を有するシール部２を設ける。
【００２２】
空間部５と液晶封入部３との境界部は液晶Ｌの表面張力により、該境界部の断面積が少なくなる所にとどまる。液晶Ｌが断面積の小さい部分に留まるため、空間部５の基板間距離（ギャップ）の大きい部分には気体（不活性ガスを用いる）がたまり、光学素子として有効な領域である液晶封入部３には移動しない。
更に、液晶封入部３と空間部５とのシール部２の厚みを変えることにより空間部５のセル厚を液晶封入部３のセル厚より厚くしておくことで、液晶の表面張力の効果により液晶が液晶封入部３に留まり、また気体は液晶層厚の厚い空間部５に留まるので、液晶封入部３には移動しない。
【００２３】
請求項２記載の発明は、前記空間部が液晶セルの周辺部または／およびコーナ部に設けられた請求項１記載の液晶光学素子である。
請求項２記載の発明によれば、光学素子として有効に機能する液晶封入部が液晶セルの中央部に広くとれるので、光学素子として利用できる面積が比較的大きくなる。
【００２４】
請求項３記載の発明は、液晶セル内に液晶を注入する液晶注入口を前記空間部から離れた位置の液晶封入部を区画するシール部に設けた請求項１又は２記載の液晶光学素子である。
【００２５】
請求項３記載の発明によれば、液晶封入部と空間部との境界部にある液晶流通可能な開口部は、液晶セルの液晶注入口よりできるだけ離れた部分とすることで、液晶が液晶セル内に注入される際に、最後に液晶が前記開口部に到達するようにしておき、その奥に液晶のない空間を残すことができる。また、前記開口部に液晶の侵入を阻む形状のシール部を形成することも有効である。
【００２６】
請求項４記載の発明は、前記シール部には、２つの透明基板の間隔を所定間隔に保つ所定の径を有するガラスファイバーが混入されている請求項１〜３のいずれかに記載の液晶光学素子である。
【００２７】
請求項４記載の発明によれば、液晶セルの基板間距離をシール部内にあるガラスファイバーにより所定の大きさに保つことができる。シール部を構成する合成樹脂に比べてガラスファイバーは変形率が小さいので、液晶セルの基板間距離をより正確に調整できる。
【００２８】
請求項５記載の発明は、前記空間部における前記透明基板間の距離と液晶封入部における前記透明基板間の距離との差が、０．２〜０．６μｍである請求項１〜４のいずれかに記載の液晶光学素子である。
前記ギャップ差を０．２〜０．６μｍとすることにより、空間部に液晶封入部から液晶が移動しないようにする。前記ギャップ差が０．２μｍ未満であると、実質的に基板間にギャップ差を設けることができず、また前記ギャップ差が０．６μｍを超えると、一つの液晶セル内に空間部と液晶封入部がそれぞれ異なるギャップを形成することが困難となる。
【００２９】
請求項６記載の発明は、前記空間部に圧力１０Ｐａ〜１００Ｐａの不活性ガスが存在する請求項１〜５のいずれかに記載の液晶光学素子である。
空間部の圧力を１０Ｐａ〜１００Ｐａとすることで、空間部内に十分の量の気体が存在することになり、安定して空間部を形成することができる。また、１００Ｐａを超えると空間部のスペースが大きくなり過ぎて好ましくない。
【００３０】
請求項７記載の発明は、液晶の複屈折率が０．１５〜０．２５で、液晶封入部の透明基板間の距離を８〜１３μｍとした請求項１〜６のいずれかに記載の液晶光学素子である。
複屈折率△ｎを０．１５〜０．２５とし、透明基板間の距離ｄを８〜１３μｍとすると△ｎｄの半分が光通信波長１．１μｍに近い値となるので、一波長分前後で変調するため、光通信用の光学素子として好都合である。
【００３１】
請求項８記載の発明は、２枚の透明基板の表面にそれぞれ透明導電膜と該透明導電膜に液晶配向膜を形成し、透明基板の周辺部にシール部材を用いて液晶注入口と液晶封入部と空間部と前記液晶封入部と空間部間の液晶通過口とを有する液晶セル用の領域を区画するシール部を形成し、前記液晶配向膜を互いに対向するように２枚の透明基板を間隔をあけて重ね合わせて配置し、液晶材料を前記液晶注入口から液晶セル領域内に１０〜１００Ｐａの減圧雰囲気下で注入し、液晶材料注入後に液晶注入口を樹脂で封止する液晶光学素子の製造方法であって、液晶注入部を区画するシール部を一方の透明基板に設け、空間部を区画するシール部を他方の透明基板に設け、その際に前記空間部における前記透明基板間の距離を前記液晶封入部における前記透明基板間の距離より大きくするために空間部を区画するシール部の厚みが液晶注入部を区画するシール部の厚みより厚くなるように形成し、その後前記２つの透明基板をそれぞれのシール部を向かい合わせて貼り合わせて、液晶注入口と液晶封入部と空間部と前記液晶封入部と空間部間の液晶通過口を有する液晶セル用の領域を前記２つのシール部で区画する液晶光学素子の製造方法である。
【００３２】
請求項８記載の発明によれば、シール部で囲まれた液晶セル内に液晶を前記液晶注入口から注入する際に、該液晶セル内に気体を存在させ、ここに液晶を注入して空間部を容易に作ることができる。
【００３３】
液晶材料を前記液晶注入口から液晶セル領域内に注入する際の圧力は、１０Ｐａ未満では空間部を形成する気体が圧力不足となり、十分なスペースを備えた空間部を形成することができず、１００Ｐａを超えると空間部のスペースが大きくなり過ぎて好ましくない。
また、液晶封入部より空間部の液晶セルの基板間距離を大きくした理由は、空間部のセル厚を液晶封入部のセル厚より厚くしておくことで、液晶の表面張力の効果により、透明基板間の距離（ギャップ）の小さい液晶層厚の薄い液晶封入部に液晶が留まり、気体は透明基板間の距離（ギャップ）の大きい液晶層厚の厚い空間部に溜まり、液晶封入部には移動しないためである。
【００３４】
請求項９記載の発明は、減圧雰囲気が不活性ガスで形成される請求項８記載の液晶光学素子の製造方法である。
請求項９記載の発明によれば、空間部に封入する気体は、液晶の劣化を防ぐために不活性ガスが望ましく、窒素、アルゴンなどがコストの面から有利であるが、これに限るものではない。
【００３５】
具体的には、チャンバー内で液晶注入前の液晶セル内の真空引きをする時に、チャンバーを低圧の前記窒素、アルゴンなどのガスで満たすことで空間部に不活性ガスを注入できる。
【００３８】
請求項１０記載の発明は、２つの透明基板の間隔を所定間隔に保つ所定の径を有するガラスファイバーをシール材に混入させてシール部を形成する請求項８又は９記載の液晶光学素子の製造方法である。
【００３９】
請求項１０記載の発明によれば、液晶セルの基板間距離をシール部内にあるガラスファイバーにより所定の大きさに保つことができる。シール部を構成する合成樹脂に比べてガラスファイバーは変形率が小さいので、液晶セルの基板間距離をより正確に調整できる。
【００４０】
請求項１１記載の発明は、請求項１〜７のいずれかの光学素子を、液晶セルの透明基板面が互いに平行になるように配置している光偏調素子である。
【００４１】
【発明の効果】
本発明によれば、液晶部分の体積変化を液晶の無い空間部のガスの体積変化で吸収できるので、液晶の体積が変動しても液晶層は一定の厚さに保つことができる。そのため、光学素子の特性を長期間一定に保つことができる。
更に、空間部を区画するシール部の厚みが液晶注入部を区画するシール部の厚みより厚くなるように形成し、液晶の無い空間部のセル厚を液晶部分のセル厚より厚くしておくことで、液晶の表面張力の効果により液晶が液晶部分に留まり、また気体は液晶層厚の厚い空間部に留まるので、液晶部分には移動しないため、液晶部分に液晶の無い空間部が発生することを防止できる。
【００４２】
【発明の実施の形態】
本発明の実施の形態について図面と共に説明する。
図１に示す液晶光学素子の製法について図３のフロー図と共に説明する。
【００４３】
工程１．２枚の透明導電膜付きガラス基板の準備：
７００Ω／平方のＩＴＯ透明導電膜を被覆した０．７ｍｍ厚のガラス基板（コーニング社製７０５９ガラス）を準備した。
【００４４】
工程２．ＩＴＯ電極のパターニング：
ＩＴＯ透明導電膜を、所定形状に塩酸を主成分とするエッチング水溶液を用いるフォトリソグラフ法により電極形成して透明基板とした。
【００４５】
工程３．液晶配向膜の形成：
ＩＴＯ電極形成した面にポリイミド前駆体溶液を塗布して、約２５０℃で３０分加熱してポリイミド重合体膜とした。液晶配向膜は、このポリイミド膜の表面にナイロン布を巻いた回転体を回転、移動させながら押し当ててポリイミド膜表面に一定方向に溝を形成する方法を採用した。
【００４６】
このとき、以下の工程５．の２枚のガラス基板の貼り合わせ工程で向き合う面が互いに反対方向を向くように、図４の矢印方向に示すラビングを逆方向となるように施し、２枚のガラス基板１，１’の貼り合わせ後にはツイストのないアンチパラレル配向のセルが形成できるようにした。
【００４７】
工程４．シール部の形成：
２枚の透明導電膜付きガラス基板にエポキシ樹脂（住友ベークライト（株）製商品名：ＥＲＳ−２１００）を所定形状にスクリーン印刷法により印刷した。
【００４８】
このとき、表側として用いる透明導電膜付きガラス基板１には図５（ａ）に示す平面形状の液晶だけが注入される光学素子として有効に機能する液晶封入部３を形成するためのシール部２をスクリーン印刷により印刷する。
【００４９】
シール部２には、液晶注入口７と空間部５にも液晶の一部を流し込むことができるような連通用開口部６も形成しておく。液晶注入口７のあるシール部２の辺とは反対側の長辺に連通用開口部６を形成しておく。
【００５０】
裏側として用いる透明導電膜付きガラス基板１’には図５（ｂ）に示す平面形状の空間部５を形成するためのシール部２’をスクリーン印刷により印刷する。
【００５１】
このとき前記表側のガラス基板１に形成した連通用開口部６に接続される連通用開口部６’をガラス基板１’にも形成しておく。
【００５２】
なお、シール部２、２’を形成する際には、シール部２、２’の貼り合わせ工程で液晶セルの基板間距離を保持するための直径約１２μｍのガラスファイバー１０（図６参照）を封入しておく。
【００５３】
また、シール部２とシール部２’で基板間方向の厚みに０．２μｍだけ差を付けることで、空間部５のセル厚を液晶封入部３のセル厚より厚くすることができ、液晶の表面張力の効果により、気体は液晶層厚の厚い空間部５に留まり、液晶封入部３には移動しなくする。
【００５４】
すなわち、液晶封入部３を形成するための図５（ａ）に示すシール部２の基板間方向の厚みは１２．０μｍとし、空間部５を形成するための図５（ｂ）に示すシール部２’の基板間方向の厚みは１２．２μｍとなるように調整する。
【００５５】
工程５．貼り合わせ：
２枚のガラス基板１、１’をシール部２、２’を介して貼り合わせ、１５０℃、９０分でシール部材を加熱硬化させることにより、液晶封入部３の区画を有する液晶セル構造を形成させる。前記加熱硬化後の液晶セルの基板間距離は、液晶封入部３より空間部５を大きく、それぞれ１２．０μｍと１２．２μｍとなる。
【００５６】
このとき、図６に２枚の透明基板１、１’の貼り合わせた状態の端部断面を示すように、液晶セルの基板間距離はシール部２内にあるガラスファイバー１０により所定の大きさに保つことができる。シール部２、２’を構成する合成樹脂に比べてガラスファイバー１０は変形率が小さいので、液晶セルの基板間距離をより正確に調整できる。
【００５７】
工程６．液晶の注入：
本工程６．の液晶の注入と次工程７．の液晶の封止は、図７に示すように液晶封止装置１２を用いて次のような手順で行う。
液晶封止装置１２に液晶Ｌを入れた皿状容器１３を置き、装置１２内の排気を行う（図７（ａ））。装置１２内が１Ｐａになるまで真空引きをした。その結果、液晶Ｌから溶けこんでいるガスが泡となって出てくる。これを１０分間放置して、泡が出なくなるのを待つ。
【００５８】
次いで、大気圧下で窒素ガスを装置１２内に導入した後、大気圧下で２枚のガラス基板１、１’を重ね合わせて得られるシール部２の液晶注入口７を下向きにして装置１２内におく（図７（ｂ））。
その後、液晶封止装置１２の密封を行ない、装置１２内を１Ｐａの圧力まで真空引きした後、窒素ガスを導入して１０Ｐａとした。
【００５９】
次いで、前記貼り合わせた２枚のガラス基板１、１’のシール部２の液晶注入口７を下向きにして皿状容器１３内の液晶Ｌ中に浸漬して、シール部２で囲まれ領域に液晶Ｌを注入させる。窒素を導入して５分後に大気圧に戻し、さらに３分間放置して、液晶封入部３の上側に位置する空間部５内部に窒素が存在した状態で液晶封入部２には液晶Ｌが充填される（図７（ｃ））。
その後、２枚に貼り合わせガラス基板１、１’を液晶Ｌを入れた皿状容器晶１３から引き上げる（図７（ｄ））。
用いた液晶は屈折率異方性△ｎが０．２３のネマチック液晶（メルク社製、Ｅ−６３）である。
【００６０】
工程７．液晶の封止：
液晶セルが形成されたガラス基板１，１’の組合せ体を液晶封止装置１２から取り出し、一方のガラス基板１から外圧を加えて基板間距離を減じ、その状態でＵＶ硬化樹脂ケミテック社（株）製商品名：ケミシール５Ｘ００９を封止剤として液晶注入口７に塗布した。封止剤が液晶セル内に侵入するように−１０℃で３分間放置した。次いで、紫外線炉に入れて、３０００ｍＪ／ｃｍ²の３９５ｎｍの紫外線を照射し、樹脂１４を硬化させて液晶注入口７を閉じた（図７（ｅ））。
【００６１】
完成した液晶セルが形成されたガラス基板１，１’の組合せ体を８０℃の雰囲気に１時間放置して、高温でのエイジングで基板間距離に変動が出やすい状態においた後に各々１００個ずつ、液晶層厚の変化を測定した。
【００６２】
２枚のガラス基板１、１’に設けたほぼ平面視で四角形状のシール部２内に液晶Ｌを充填して空間部５が存在しない液晶セルを用いたことを除いて、上記した本実施例の液晶セルの製法と同一条件で製造した従来の液晶セルと本発明の液晶セルを比較した結果を図８に示すが、従来技術で得た液晶セルの液晶層厚の変化が０．３μｍ以上であったのに対して本発明の液晶セルは、空間部５の領域は変化したが、液晶層厚の変化が０．３μｍを超えるものは皆無となった。
【００６３】
図２に示す液晶光学素子は図３とほぼ同様の工程で作製するが、シール部２、２’の形状が図１に示す液晶光学素子とは異なるので、その部分の作製工程について図９に示す。
【００６４】
図９（ａ）には外周側のシール部２の図面左右部分（実線）の基板間方向の厚みを１２．２μｍとして予め一方の基板１に形成し、図９（ｂ）の図面左右部分（点線）の内側のシール部２’（実線）と図面上下部分（実線）の外側のシール部２（実線）の基板間方向の厚みを１２．０μｍとして他方の基板１’に形成し、これらを向かい合わせにして液晶セルを形成した。
【００６５】
こうして、図２に示す空間部５のセル厚を液晶封入部３のセル厚より０．２μｍだけ厚くすることができ、液晶Ｌの表面張力の効果により、液晶Ｌは液晶封入部３に留まり、気体は液晶層厚の厚い空間部５に留まるので、液晶封入部３には移動しなくなる。
【００６６】
上記実施例では透明基板としてガラス基板を用いる例で説明したが、透明樹脂などを用いることもできる。
【００６７】
このように本実施例の液晶光学素子は、液晶層厚の変化が０．３μｍ未満であるので入射レーザー光の偏向角のばらつきなどがなく、光通信用素子として用いる場合に光通信波長が１．１μｍであるので、液晶層厚の変化が前記波長の１／４程度であることは有利である。
【００６８】
こうして本実施例の液晶光学素子は光通信用素子のみならず、偏波スタビライザー、偏波依存性計測用の偏波コントローラ、距離測定などのヘテロダイン計測のための周波数シフタなどに使用できる。
【図面の簡単な説明】
【図１】本発明の一実施例の液晶光学素子の一方のガラス基板を取り外した状態で他方のガラス基板上に形成される液晶セルの構造図である。
【図２】本発明の一実施例の液晶光学素子の一方のガラス基板を取り外した状態で他方のガラス基板上に形成される液晶セルの構造図である。
【図３】本発明の一実施例の液晶光学素子の製造プロセスの概略図である。
【図４】本発明の一実施例の液晶光学素子の製造プロセスでの液晶配向膜２枚のガラス基板の貼り合わせ面のラビング方向を示す図である。
【図５】本発明の一実施例の液晶光学素子の製造プロセスでの各ガラス基板上の形成するシール部の形状を示す図である。
【図６】本発明の一実施例の液晶光学素子の基板間のギャップを保持するためのシール部内に充填されるガラスファイバーを示す基板端部の断面図である。
【図７】本発明の一実施例の液晶光学素子の液晶注入・封止工程を説明する図である。
【図８】本発明の一実施例の液晶光学素子の基板間のギャップの減少幅の分布を示す図である。
【図９】図２に示す液晶光学素子の製造プロセスの図１に示す液晶光学素子の製造プロセスと異なる部分のガラス基板上に形成するシール部の形状を示す図である。
【図１０】本発明の一実施例の液晶光学素子の断面図（図１０（ａ））と従来技術の液晶光学素子の断面図（図１０（ｂ））である。
【図１１】従来の液晶光学素子の一方のガラス基板を取り外した状態で他方のガラス基板上に形成される液晶セルの構造図である。
【符号の説明】
１、１’ ガラス基板２、２’ シール部
３液晶封入部５空間部
６連通用開口部７液晶注入口
１０ガラスファイバー１２液晶封止装置
１３皿状容器１４樹脂
Ｌ液晶[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical element using the optical anisotropy of liquid crystal, and more particularly to a liquid crystal optical element suitable for an optical communication element and a method for manufacturing the same.
[0002]
[Prior art]
An optical element using the optical anisotropy of liquid crystal is often used as a liquid crystal display element. Other applications include optical elements such as phase control and polarization control, and application to optical communication elements has also been attempted.
[0003]
When the orientation direction of the liquid crystal is controlled by an electric field due to the dielectric anisotropy of the liquid crystal, the liquid crystal is sealed between two substrates with a transparent conductive film, and the orientation film previously applied on the transparent conductive film is used. The alignment direction can be changed by aligning the liquid crystal and applying a voltage between the opposing transparent conductive films.
[0004]
For example, in the case of phase control using a nematic liquid crystal, the liquid crystal is homogeneously aligned in the same direction in the plane, and the refractive index anisotropy (birefringence index) Δn of the liquid crystal and the liquid crystal layer thickness d are The product Δnd is adjusted to the desired phase difference length. In this state, the polarization component perpendicular to the alignment direction of the liquid crystal can have a phase difference of Δnd. For example, when 45 ° linearly polarized light is incident on the alignment direction of the liquid crystal, if the phase difference is ¼ wavelength, it is circularly polarized, and if it is half-wavelength, it is rotated in the 90 ° polarization direction. Can be changed. Moreover, this phase difference can be eliminated by changing the direction of the liquid crystal molecules in a direction perpendicular to the surface of the transparent conductive film by applying a voltage to the opposing transparent conductive film.
[0005]
An important factor that determines the characteristics of such a liquid crystal optical element is Δnd of the liquid crystal element, and the stability of this value is also required in order to exhibit stable characteristics.
In order to stabilize the value of Δnd of the liquid crystal optical element, a method of generating an electric field between two substrates with a transparent conductive film encapsulating liquid crystal is Takashi Chiba, Yasuo Ohtera, Shojiro Kawakami, “ Liquid crystal rotating wave plate ", O plus E, Vol. 20, No. 10, p1145-1150. In the invention described in JP-A-11-38451, a liquid crystal sandwiching nematic liquid crystal suitable for communication is used. As the optical element, the refractive index anisotropy is 0.20 or more, the product of the refractive index anisotropy and the thickness of the liquid crystal part is 1.3 μm or more, and the total thickness of the optical element is 10 μm to 250 μm. An electric field control birefringence type liquid crystal element has been proposed.
[0006]
[Non-Patent Document 1]
Takashi Chiba, Yasuo Ohtera, Shojiro Kawakami, “Liquid Crystal Rotating Waveplate”, O plus E, Vol. 20, No. 10, p1145-1150
[0007]
[Patent Document 1]
JP-A-11-38451
[0008]
[Problems to be solved by the invention]
In the liquid crystal cell of the liquid crystal optical element, as shown in FIG. 10 (a), the liquid crystal L is injected into the gap formed by the gap between the seal portions 2 of the two glass substrates 1, 1 ′. As shown in FIG. 10B, the gap (liquid crystal layer thickness) between the glass substrates 1 and 1 ′ is reduced after the device is manufactured. Therefore, there is a problem that Δnd decreases with time.
This is because after the liquid crystal L is injected into the gap between the two glass substrates 1 and 1 ′, the volume of the liquid crystal L decreases with time and negative pressure is generated, resulting in a decrease in the distance between the substrates. is there.
[0009]
In the liquid crystal display panel, in order to avoid the change of the gap due to the volume reduction of the liquid crystal L portion in the gap between the two substrates 1, 1 ′, a spacer having the same size as the liquid crystal layer thickness is provided in the gap. A method of supporting the two glass substrates 1 and 1 ′ from the inside of the liquid crystal L is adopted. In the liquid crystal element for optical communication, when the spacer is inserted between the glass substrates 1 and 1 ′, the spacer is It cannot be employed because it causes light scattering and causes interference due to energy loss and scattered light based on spacers.
[0010]
In addition, the size of the liquid crystal cell used for the liquid crystal display panel is about 10 cm × 10 cm, whereas the size of the liquid crystal cell of the liquid crystal element used for optical communication is about 1 cm × 1 cm. Inserting between the substrates 1 and 1 'is disadvantageous because it reduces the effective use area.
[0011]
For this reason, conventionally, aging was performed after the production of the liquid crystal optical element, and the liquid crystal layer thickness reduction exceeding a certain range was excluded, but this resulted in product loss and markedly reduced productivity. It was. In addition, the method of injecting a large amount of liquid crystal in anticipation of the final decrease in the liquid crystal layer thickness is less effective because the liquid crystal cell is small. Further, the variation in the liquid crystal layer thickness due to the variation in the volume decrease fluctuation range of the liquid crystal portion in the gap is unavoidable.
[0012]
  As described above, the conventional technique has a problem that the yield for obtaining the final liquid crystal element product in which the liquid crystal layer thickness falls within a certain range is low.
  In addition, when the volume of the liquid crystal is smaller than the size of the cell, the liquid crystal cell has a property that a space without liquid crystal is generated and the space returns the thickness of the cell. In the liquid crystal display panel, the space portion without liquid crystal not only contributes to display but also has a noticeable appearance, and is excluded as a serious defect.
[0013]
  The object of the present invention is to overcome the problems of the prior art and to obtain a liquid crystal optical element that can be used satisfactorily as an optical element for communication and the like having a predetermined liquid crystal layer thickness stably without reducing productivity. It is.Furthermore, the subject of this invention is preventing that the space part which does not have a liquid crystal generate | occur | produces in a liquid crystal cell.
[0014]
[Means for Solving the Problems]
  The above-mentioned problem of the present invention is solved by the following means.
  The invention described in claim 1 includes: two transparent substrates with transparent electrodes; a seal portion that divides the two transparent substrates at intervals, and divides peripheral portions of opposing surfaces of the transparent substrate; and the seal In a liquid crystal optical element having a liquid crystal cell obtained by enclosing a liquid crystal in a space between two transparent substrates partitioned by a portion, the liquid crystal cell includes a liquid crystal enclosing portion in which liquid crystal is encapsulated and a liquid crystal A space portion that is not separated by a seal portion having an opening through which liquid crystal can pass;By changing the thickness in the direction between the substrates of the sealing portion of the liquid crystal enclosing portion and the space portion,In the liquid crystal optical element, the distance between the transparent substrates in the space portion is larger than the distance between the transparent substrates in the liquid crystal sealing portion.
[0015]
When the volume of the liquid crystal is smaller than the size of the cell, the liquid crystal cell has a property that a space without liquid crystal is generated and the space returns the thickness of the cell. In the liquid crystal display panel, the space portion without liquid crystal not only contributes to display but also has a noticeable appearance, and is excluded as a serious defect. This space is called in-cell air, but air is not always present in this space.
In addition to the invention described in claim 1, the present invention is an invention completed by actively using this space portion.
[0016]
In the liquid crystal cell of the optical element of the present invention, for example, as shown in the shape of the seal portion 2 provided on one transparent substrate 1 shown in FIGS. Hereinafter, the liquid crystal enclosure 3 may be referred to), the in-cell air region (hereinafter may be referred to as space 5), and the narrow liquid crystal distribution opening 6 at the boundary between the liquid crystal enclosure 3 and space 5. And a seal portion 2 provided with a liquid crystal injection port 7 in the liquid crystal sealing port 3.
[0017]
When the liquid crystal L is injected into the cell which is a closed region between the transparent substrates 1, the space portion (air region in the liquid crystal cell) 5 is positively left by leaving a portion where the liquid crystal L is not injected or generating it later. Is made.
[0018]
  If an opening 6 capable of flowing a narrow liquid crystal by the seal portion 2 is provided at the boundary between the liquid crystal enclosing portion 3 and the space portion 5, the liquid crystal L that has entered the seal portion 2 from the liquid crystal injection port 7 passes through the space portion 5. Can be made easily. AndBy changing the thickness of the seal part 2 between the liquid crystal enclosure part 3 and the space part 5The distance (gap) between the transparent substrates in the space is made larger than the distance (gap) between the transparent substrates in the liquid crystal enclosure.
[0019]
In the present invention, the thickness of the liquid crystal cell can be maintained at a predetermined size due to the presence of the space portion 5, and optical characteristics as designed can be obtained. That is, the change of the volume of the liquid crystal L is handled by changing the volume of the gas in the space 5 without the liquid crystal L while maintaining the plane of the transparent substrate 1 by the rigidity of the transparent substrate 1. Further, even if the volume of the liquid crystal L changes due to temperature or the like, the liquid crystal layer thickness of the liquid crystal cell is kept constant in response to the change of the volume of the liquid crystal L due to the change of the volume of the space portion 5. be able to. As the volume of the space portion 5 changes, the gas region in the space portion 5 increases as shown in FIGS. 1B and 2, so that the liquid crystal L does not contract and the variation in the liquid crystal thickness can be suppressed.
[0020]
In the liquid crystal cell of the conventional liquid crystal optical element, as shown in FIG. 11, the liquid crystal so that the seal portion 2 provided in the peripheral portion of the transparent substrate 1 and the space portion 5 shown in FIG. L was charged. In the conventional liquid crystal optical element, since the presence of the space portion 5 shown in FIG. 1 or the like adversely affects the physical properties of the liquid crystal optical element, it is necessary to remove the space portion 5, but there is no space portion 5. In the liquid crystal cell completely filled with the liquid crystal L, the liquid crystal L contracts and the central portions of the transparent substrates 1 and 1 ′ are recessed in a concave shape as shown in FIG. The portion where the liquid crystal L contracts is made positive by the presence of the portion 5, and the expansion portion of the gas in the space portion 5 is supplemented to prevent the deformation of the transparent substrate 1, and the cross-sectional shape shown in FIG. In addition, the transparent substrates 1 and 1 'can be maintained in a flat state.
[0021]
  Also,In order to prevent the space portion 5 shown in FIGS. 1 and 2 from moving to the liquid crystal sealing portion 3 that effectively functions as an optical element, a seal portion 2 having a narrow liquid crystal distribution opening 6 is provided.
[0022]
  The boundary portion between the space portion 5 and the liquid crystal sealing portion 3 remains where the cross-sectional area of the boundary portion is reduced due to the surface tension of the liquid crystal L. Since the liquid crystal L remains in a portion having a small cross-sectional area, gas (using an inert gas) accumulates in a portion where the inter-substrate distance (gap) of the space portion 5 is large, and the liquid crystal encapsulating portion 3 which is an effective region as an optical element. Don't move on.
  Furthermore,By changing the thickness of the seal part 2 between the liquid crystal enclosure part 3 and the space part 5By making the cell thickness of the space portion 5 thicker than the cell thickness of the liquid crystal enclosure portion 3, the liquid crystal stays in the liquid crystal enclosure portion 3 due to the effect of the surface tension of the liquid crystal, and the gas enters the space portion 5 where the liquid crystal layer thickness is thick. Since it stays, it does not move to the liquid crystal enclosure 3.
[0023]
  Claim2In the invention described in the above, the space portion is provided in a peripheral portion or / and a corner portion of the liquid crystal cell.1Liquid crystal optical element.
  Claim2According to the described invention, since the liquid crystal encapsulating portion that effectively functions as an optical element can be widened in the center of the liquid crystal cell, the area that can be used as the optical element becomes relatively large.
[0024]
  Claim3In the described invention, a liquid crystal injection port for injecting liquid crystal into a liquid crystal cell is provided in a seal portion that partitions a liquid crystal sealing portion at a position away from the space portion.KetaClaim 1Or 2It is a liquid crystal optical element of description.
[0025]
  Claim3According to the described invention, the liquid crystal flow opening at the boundary between the liquid crystal enclosing portion and the space is made as far as possible from the liquid crystal injection port of the liquid crystal cell, so that the liquid crystal is injected into the liquid crystal cell. In this case, the liquid crystal finally reaches the opening, and a space without liquid crystal can be left behind. It is also effective to form a seal portion having a shape that prevents liquid crystal from entering the opening.
[0026]
  Claim4The described inventionThe liquid crystal optical element according to any one of claims 1 to 3, wherein a glass fiber having a predetermined diameter for keeping the interval between the two transparent substrates at a predetermined interval is mixed in the seal portion.It is.
[0027]
  Claim4According to the described invention,The distance between the substrates of the liquid crystal cell can be kept at a predetermined size by the glass fiber in the seal portion. Since the glass fiber has a smaller deformation rate than the synthetic resin constituting the seal portion, the distance between the substrates of the liquid crystal cell can be adjusted more accurately.
[0028]
  Claim5The described invention is a distance between the transparent substrates in the space portion.WhenDistance between the transparent substrates in the liquid crystal enclosureWhenThe difference is 0.2 to 0.6 μm.Any one of 1-4It is a liquid crystal optical element of description.
  By setting the gap difference to 0.2 to 0.6 μm, the liquid crystal is prevented from moving from the liquid crystal enclosure to the space. If the gap difference is less than 0.2 μm, it is not possible to substantially provide a gap difference between the substrates. If the gap difference exceeds 0.6 μm, a space portion and liquid crystal are enclosed in one liquid crystal cell. It becomes difficult to form gaps with different parts.
[0029]
  Claim6The invention according to claim 1 is characterized in that an inert gas having a pressure of 10 Pa to 100 Pa exists in the space.5The liquid crystal optical element according to any one of the above.
  By setting the pressure in the space portion to 10 Pa to 100 Pa, a sufficient amount of gas exists in the space portion, and the space portion can be formed stably. On the other hand, if it exceeds 100 Pa, the space portion becomes too large, which is not preferable.
[0030]
  Claim7In the invention described in claim 1, the birefringence of the liquid crystal is 0.15 to 0.25, and the distance between the transparent substrates of the liquid crystal encapsulating portion is 8 to 13 μm.6The liquid crystal optical element according to any one of the above.
  If the birefringence Δn is 0.15 to 0.25 and the distance d between the transparent substrates is 8 to 13 μm, half of Δnd is close to the optical communication wavelength of 1.1 μm. Since it modulates, it is convenient as an optical element for optical communication.
[0031]
  Claim8In the described invention, a transparent conductive film and a liquid crystal alignment film are formed on the surfaces of two transparent substrates, respectively, and a liquid crystal injection port, a liquid crystal sealing portion, and a space are formed using a sealing member around the transparent substrate. A liquid crystal cell region having a liquid crystal enclosing portion and a liquid crystal passage opening between the space portion and a liquid crystal cell region is formed, and the two transparent substrates are spaced apart so that the liquid crystal alignment films face each other A method of manufacturing a liquid crystal optical element in which a liquid crystal material is injected into the liquid crystal cell region from the liquid crystal injection port in a reduced pressure atmosphere of 10 to 100 Pa, and the liquid crystal injection port is sealed with a resin after the liquid crystal material is injected In this case, a seal part for partitioning the liquid crystal injection part is provided on one transparent substrate, and a seal part for partitioning the space part is provided on the other transparent substrate.In order to make the distance between the transparent substrates in the space portion larger than the distance between the transparent substrates in the liquid crystal sealing portionThe thickness of the seal part that divides the space part is formed to be thicker than the thickness of the seal part that divides the liquid crystal injection part, and then the two transparent substrates are bonded to each other with the seal parts facing each other.,A liquid crystal optical element manufacturing method in which a liquid crystal cell region having a liquid crystal injection port, a liquid crystal sealing portion, a space portion, and a liquid crystal passage portion between the liquid crystal sealing portion and the space portion is partitioned by the two seal portions.
[0032]
  Claim8According to the described invention, when the liquid crystal is injected into the liquid crystal cell surrounded by the seal portion from the liquid crystal injection port, the gas is present in the liquid crystal cell, and the liquid crystal is injected into the liquid crystal cell to facilitate the space portion. Can be made.
[0033]
  The pressure when injecting the liquid crystal material into the liquid crystal cell region from the liquid crystal injection port is less than 10 Pa, the gas forming the space becomes insufficient in pressure, and the space with sufficient space cannot be formed, If it exceeds 100 Pa, the space is too large, which is not preferable.
  Also, the reason why the distance between the substrates of the liquid crystal cell in the space part is made larger than the liquid crystal enclosure part is that the cell thickness in the space part is made thicker than the cell thickness of the liquid crystal enclosure part. The liquid crystal stays in the liquid crystal enclosure with a small liquid crystal layer thickness with a small distance (gap) between the substrates, and the gas accumulates in a thick liquid crystal layer with a large distance (gap) between the transparent substrates and moves to the liquid crystal enclosure. It is because it does not.
[0034]
  Claim9The invention as described in claim 1, wherein the reduced-pressure atmosphere is formed of an inert gas.8It is a manufacturing method of the liquid crystal optical element of description.
  Claim9According to the described invention, the gas sealed in the space is preferably an inert gas in order to prevent deterioration of the liquid crystal, and nitrogen, argon, etc. are advantageous from the viewpoint of cost, but are not limited thereto.
[0035]
Specifically, when evacuating the liquid crystal cell before liquid crystal injection in the chamber, an inert gas can be injected into the space by filling the chamber with a low-pressure gas such as nitrogen or argon.
[0038]
  Claim10In the invention described in the above, the sealing portion is formed by mixing glass fiber having a predetermined diameter for keeping the interval between the two transparent substrates at a predetermined interval into the sealing material.8 or 9It is a manufacturing method of the liquid crystal optical element of description.
[0039]
  Claim10According to the described invention, the distance between the substrates of the liquid crystal cell can be maintained at a predetermined size by the glass fiber in the seal portion. Since the glass fiber has a smaller deformation rate than the synthetic resin constituting the seal portion, the distance between the substrates of the liquid crystal cell can be adjusted more accurately.
[0040]
  Claim 11The invention described in claims 1 to7These optical elements are light modulating elements in which the transparent substrate surfaces of the liquid crystal cell are arranged in parallel to each other.
[0041]
【The invention's effect】
  According to the present invention, since the volume change of the liquid crystal portion can be absorbed by the volume change of the gas in the space without the liquid crystal, the liquid crystal layer can be kept constant even if the volume of the liquid crystal varies. Therefore, the characteristics of the optical element can be kept constant for a long time.
  Furthermore,The thickness of the seal part that divides the space part is formed to be thicker than the thickness of the seal part that divides the liquid crystal injection part,By making the cell thickness of the space without liquid crystal thicker than the cell thickness of the liquid crystal part, the liquid crystal stays in the liquid crystal part due to the effect of the surface tension of the liquid crystal, and the gas stays in the space part with a thick liquid crystal layer thickness. Since it does not move to the liquid crystal portion, it is possible to prevent the generation of a space portion without liquid crystal in the liquid crystal portion.
[0042]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
A method for manufacturing the liquid crystal optical element shown in FIG. 1 will be described with reference to the flowchart of FIG.
[0043]
Step 1. Preparation of two glass substrates with transparent conductive films:
A 0.7 mm thick glass substrate (Corning 7059 glass) coated with 700 Ω / square ITO transparent conductive film was prepared.
[0044]
Step 2. ITO electrode patterning:
An ITO transparent conductive film was formed into an electrode by a photolithographic method using an etching aqueous solution containing hydrochloric acid as a main component in a predetermined shape to obtain a transparent substrate.
[0045]
Step 3. Formation of liquid crystal alignment film:
A polyimide precursor solution was applied to the surface on which the ITO electrode was formed and heated at about 250 ° C. for 30 minutes to obtain a polyimide polymer film. For the liquid crystal alignment film, a method of forming a groove in a certain direction on the polyimide film surface by pressing a rotating body wound with a nylon cloth on the surface of the polyimide film while rotating and moving it was adopted.
[0046]
At this time, the following process 5. 4 so that the surfaces facing each other in the bonding process of the two glass substrates are opposite to each other, and the rubbing shown in the arrow direction in FIG. After the alignment, an anti-parallel alignment cell without twist was formed.
[0047]
Step 4. Formation of seal part:
An epoxy resin (trade name: ERS-2100, manufactured by Sumitomo Bakelite Co., Ltd.) was printed on two glass substrates with a transparent conductive film in a predetermined shape by a screen printing method.
[0048]
At this time, the sealing part 2 for forming the liquid crystal encapsulating part 3 that effectively functions as an optical element into which only the planar liquid crystal shown in FIG. Is printed by screen printing.
[0049]
In the seal portion 2, a communication opening 6 is also formed so that a part of the liquid crystal can be poured into the liquid crystal inlet 7 and the space 5. A communication opening 6 is formed on the long side opposite to the side of the seal portion 2 where the liquid crystal injection port 7 is provided.
[0050]
On the glass substrate 1 ′ with a transparent conductive film used as the back side, a seal portion 2 ′ for forming the planar space portion 5 shown in FIG. 5B is printed by screen printing.
[0051]
At this time, a communication opening 6 ′ connected to the communication opening 6 formed in the front glass substrate 1 is also formed in the glass substrate 1 ′.
[0052]
When forming the seal portions 2, 2 ′, a glass fiber 10 having a diameter of about 12 μm (see FIG. 6) for maintaining the distance between the substrates of the liquid crystal cell in the bonding process of the seal portions 2, 2 ′ is used. Enclose.
[0053]
Further, by making a difference of 0.2 μm in the thickness between the substrates in the seal portion 2 and the seal portion 2 ′, the cell thickness of the space portion 5 can be made larger than the cell thickness of the liquid crystal encapsulating portion 3, and the liquid crystal Due to the effect of the surface tension, the gas stays in the space portion 5 where the liquid crystal layer is thick and does not move to the liquid crystal enclosure portion 3.
[0054]
That is, the thickness in the inter-substrate direction of the seal portion 2 shown in FIG. 5A for forming the liquid crystal sealing portion 3 is 12.0 μm, and the seal portion shown in FIG. 5B for forming the space portion 5. The thickness in the 2 ′ inter-substrate direction is adjusted to 12.2 μm.
[0055]
Step 5. Bonding:
The two glass substrates 1 and 1 ′ are bonded together through the seal portions 2 and 2 ′, and the seal member is heated and cured at 150 ° C. for 90 minutes to form a liquid crystal cell structure having a partition of the liquid crystal encapsulating portion 3 Let The distance between the substrates of the liquid crystal cell after the heat curing is 12.0 μm and 12.2 μm, respectively, in the space 5 larger than the liquid crystal encapsulating part 3.
[0056]
At this time, the distance between the substrates of the liquid crystal cell is set to a predetermined size by the glass fiber 10 in the seal portion 2 as shown in the end cross section of the two transparent substrates 1 and 1 ′ bonded together in FIG. Can be kept in. Since the deformation rate of the glass fiber 10 is smaller than that of the synthetic resin constituting the seal portions 2 and 2 ′, the distance between the substrates of the liquid crystal cell can be adjusted more accurately.
[0057]
Step 6. Liquid crystal injection:
Step 6 6. Liquid crystal injection and next process The liquid crystal is sealed in the following procedure using the liquid crystal sealing device 12 as shown in FIG.
The dish-like container 13 containing the liquid crystal L is placed in the liquid crystal sealing device 12, and the inside of the device 12 is exhausted (FIG. 7A). Vacuum was drawn until the inside of the apparatus 12 reached 1 Pa. As a result, the gas dissolved from the liquid crystal L comes out as bubbles. Let this stand for 10 minutes and wait for the bubbles to disappear.
[0058]
Next, after introducing nitrogen gas into the apparatus 12 under atmospheric pressure, the apparatus 12 is placed with the liquid crystal injection port 7 of the seal portion 2 obtained by superposing the two glass substrates 1 and 1 ′ under the atmospheric pressure facing downward. (FIG. 7B).
Thereafter, the liquid crystal sealing device 12 was sealed, the inside of the device 12 was evacuated to a pressure of 1 Pa, and nitrogen gas was introduced to 10 Pa.
[0059]
Next, the liquid crystal injection port 7 of the seal portion 2 of the two glass substrates 1 and 1 ′ bonded together is immersed downward in the liquid crystal L in the dish-like container 13, and is surrounded by the seal portion 2. Liquid crystal L is injected. 5 minutes after nitrogen is introduced, the pressure is returned to atmospheric pressure, and is further left for 3 minutes. The liquid crystal enclosure 2 is filled with liquid crystal L in a state where nitrogen is present in the space 5 located above the liquid crystal enclosure 3. (FIG. 7C).
Thereafter, the two glass substrates 1, 1 'are pulled up from the dish-like container crystal 13 containing the liquid crystal L (FIG. 7D).
The liquid crystal used is nematic liquid crystal (E-63 manufactured by Merck & Co., Inc.) having a refractive index anisotropy Δn of 0.23.
[0060]
Step 7. Liquid crystal sealing:
The combination of the glass substrates 1 and 1 ′ on which the liquid crystal cell is formed is taken out from the liquid crystal sealing device 12, the external pressure is applied from one glass substrate 1 to reduce the distance between the substrates, and UV curable resin Chemtech Co., Ltd. ) Product name: Chemiseal 5X009 was applied to the liquid crystal inlet 7 as a sealant. The sealant was left at −10 ° C. for 3 minutes so as to enter the liquid crystal cell. Next, put it in a UV furnace and 3000 mJ / cm²Was irradiated with UV light of 395 nm to cure the resin 14 and close the liquid crystal injection port 7 (FIG. 7E).
[0061]
100 pieces each after the glass substrate 1,1 ′ combination body on which the completed liquid crystal cell is formed is left in an atmosphere of 80 ° C. for 1 hour and placed in a state in which the distance between the substrates is likely to change due to high temperature aging. The change in the liquid crystal layer thickness was measured.
[0062]
This embodiment described above, except that a liquid crystal cell in which the liquid crystal L is filled in the rectangular seal portion 2 provided in the two glass substrates 1 and 1 ′ in a substantially plan view and the space portion 5 does not exist is used. FIG. 8 shows a result of comparison between the conventional liquid crystal cell manufactured under the same conditions as the manufacturing method of the liquid crystal cell of the example and the liquid crystal cell of the present invention, and the change in the liquid crystal layer thickness of the liquid crystal cell obtained by the conventional technique is 0.3 μm. In contrast to the above, in the liquid crystal cell of the present invention, the region of the space portion 5 was changed, but there was no change in the thickness of the liquid crystal layer exceeding 0.3 μm.
[0063]
The liquid crystal optical element shown in FIG. 2 is manufactured in substantially the same process as in FIG. 3, but the shape of the seal portions 2 and 2 ′ is different from that of the liquid crystal optical element shown in FIG. Show.
[0064]
In FIG. 9A, the thickness in the inter-substrate direction of the left and right portions (solid line) of the outer peripheral seal portion 2 in the drawing is set to 12.2 μm in advance on one substrate 1, and the left and right portions of FIG. The thickness of the seal part 2 ′ (solid line) inside the dotted line) and the seal part 2 (solid line) outside the upper and lower parts of the drawing (solid line) in the direction between the substrates is set to 12.0 μm on the other substrate 1 ′. A liquid crystal cell was formed facing each other.
[0065]
In this way, the cell thickness of the space portion 5 shown in FIG. 2 can be made 0.2 μm thicker than the cell thickness of the liquid crystal enclosure portion 3, and the liquid crystal L remains in the liquid crystal enclosure portion 3 due to the effect of the surface tension of the liquid crystal L. Since the gas stays in the space portion 5 where the liquid crystal layer is thick, the gas does not move to the liquid crystal sealing portion 3.
[0066]
In the above embodiment, the glass substrate is used as the transparent substrate. However, a transparent resin or the like can also be used.
[0067]
As described above, the liquid crystal optical element of this example has a change in the thickness of the liquid crystal layer of less than 0.3 μm, so there is no variation in the deflection angle of the incident laser light, and the optical communication wavelength is 1 when used as an optical communication element. Since it is 0.1 μm, it is advantageous that the change in the thickness of the liquid crystal layer is about ¼ of the wavelength.
[0068]
Thus, the liquid crystal optical element of this embodiment can be used not only for an optical communication element but also for a polarization stabilizer, a polarization controller for measuring polarization dependence, a frequency shifter for heterodyne measurement such as distance measurement, and the like.
[Brief description of the drawings]
FIG. 1 is a structural diagram of a liquid crystal cell formed on another glass substrate with one glass substrate removed of a liquid crystal optical element of one embodiment of the present invention.
FIG. 2 is a structural diagram of a liquid crystal cell formed on the other glass substrate with one glass substrate removed of the liquid crystal optical element of one embodiment of the present invention.
FIG. 3 is a schematic view of a manufacturing process of a liquid crystal optical element of one embodiment of the present invention.
FIG. 4 is a diagram showing a rubbing direction of a bonding surface of two glass substrates of a liquid crystal alignment film in a manufacturing process of a liquid crystal optical element according to an embodiment of the present invention.
FIG. 5 is a view showing the shape of a seal portion formed on each glass substrate in the manufacturing process of the liquid crystal optical element of one embodiment of the present invention.
FIG. 6 is a cross-sectional view of a substrate end portion showing glass fibers filled in a seal portion for maintaining a gap between the substrates of the liquid crystal optical element of one embodiment of the present invention.
FIG. 7 is a diagram illustrating a liquid crystal injection / sealing process of the liquid crystal optical element of one embodiment of the present invention.
FIG. 8 is a diagram showing a distribution of a reduction width of a gap between substrates of a liquid crystal optical element according to an embodiment of the present invention.
9 is a diagram showing a shape of a seal portion formed on a glass substrate at a portion different from the manufacturing process of the liquid crystal optical element shown in FIG. 1 in the manufacturing process of the liquid crystal optical element shown in FIG.
FIG. 10 is a cross-sectional view (FIG. 10A) of a liquid crystal optical element according to an embodiment of the present invention and a cross-sectional view of a conventional liquid crystal optical element (FIG. 10B).
FIG. 11 is a structural diagram of a liquid crystal cell formed on another glass substrate with one glass substrate removed from a conventional liquid crystal optical element.
[Explanation of symbols]
1, 1 'glass substrate 2, 2' seal part
3 Liquid crystal enclosure 5 Space
6 Opening for communication 7 Liquid crystal injection port
10 Glass fiber 12 Liquid crystal sealing device
13 Dish container 14 Resin
L liquid crystal

Claims

Two transparent substrates with a transparent electrode, the two transparent substrates are overlapped with a gap, and a seal portion that partitions the periphery of the opposing surface of the transparent substrate, and two sheets separated by the seal portion In a liquid crystal optical element having a liquid crystal cell obtained by enclosing a liquid crystal in a space between transparent substrates,
In the liquid crystal cell, a liquid crystal sealing portion in which liquid crystal is sealed and a space portion in which liquid crystal is not sealed are partitioned by a seal portion having an opening through which liquid crystal can pass.
The distance between the transparent substrates in the space portion is made larger than the distance between the transparent substrates in the liquid crystal enclosure portion by changing the thickness between the liquid crystal enclosure portion and the seal portion of the space portion in the direction between the substrates. Liquid crystal optical element.

The liquid crystal optical element according to claim 1, wherein the space portion is provided in a peripheral portion or / and a corner portion of the liquid crystal cell.

3. The liquid crystal optical element according to claim 1, wherein a liquid crystal injection port for injecting liquid crystal into the liquid crystal cell is provided in a seal portion that partitions a liquid crystal sealing portion at a position away from the space portion.

The liquid crystal optical element according to any one of claims 1 to 3, wherein a glass fiber having a predetermined diameter that keeps the interval between the two transparent substrates at a predetermined interval is mixed in the seal portion.

5. The difference between the distance between the transparent substrates in the space and the distance between the transparent substrates in the liquid crystal sealing portion is 0.2 to 0.6 μm. Liquid crystal optical element.

The liquid crystal optical element according to claim 1, wherein an inert gas having a pressure of 10 Pa to 100 Pa is present in the space portion.

7. The liquid crystal optical element according to claim 1, wherein the birefringence of the liquid crystal is 0.15 to 0.25, and the distance between the transparent substrates of the liquid crystal encapsulating portion is 8 to 13 [mu] m.

A transparent conductive film and a liquid crystal alignment film are formed on the surfaces of the two transparent substrates, respectively, and a liquid crystal injection port, a liquid crystal sealing portion, a space portion, and the liquid crystal sealing are formed using a sealing member on the periphery of the transparent substrate. A liquid crystal cell area having a liquid crystal passage opening between the liquid crystal cell and the liquid crystal cell is formed, and two transparent substrates are arranged with a gap therebetween so that the liquid crystal alignment films face each other. The liquid crystal material is injected from the liquid crystal injection port into the liquid crystal cell region under a reduced pressure atmosphere of 10 to 100 Pa, and the liquid crystal injection port is sealed with a resin after the liquid crystal material is injected.
A sealing part for partitioning the liquid crystal injection part is provided on one transparent substrate, and a sealing part for partitioning the space part is provided on the other transparent substrate, and at that time, the distance between the transparent substrates in the space part is determined in the liquid crystal sealing part. In order to make it larger than the distance between the transparent substrates, the thickness of the seal part that divides the space part is formed to be thicker than the thickness of the seal part that divides the liquid crystal injection part, and then the two transparent substrates are connected to the respective seal parts. the combined face each other bonding, characterized by defining the regions of the liquid crystal cell in the two seal portions having a liquid crystal inlet and liquid crystal filling portion and the space portion between the liquid crystal passage port between the liquid crystal filling portion and the space portion A method for producing a liquid crystal optical element.

9. The method for producing a liquid crystal optical element according to claim 8, wherein the reduced-pressure atmosphere is formed of an inert gas.

10. The method of manufacturing a liquid crystal optical element according to claim 8, wherein the sealing portion is formed by mixing glass fibers having a predetermined diameter that keeps the interval between the two transparent substrates at a predetermined interval into the sealing material.

8. An optical modulation element, wherein the optical element according to claim 1 is disposed such that the transparent substrate surfaces of the liquid crystal cell are parallel to each other.