JP2004269794A - Liquid crystal display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device at a low cost that has ability of easily repairing a defect of a liquid crystal composition in a gel state, has less thermal degradation when repaired and has enhanced aging stability. <P>SOLUTION: This liquid crystal display device 10 holds a liquid crystal composition 4, which contains (a) a liquid crystal substance that forms a nematic liquid crystal and (b) a gelatinizing agent of an organosiloxane having at least a hydrogen bonding site capable of gelatinizing the liquid crystal substance, so as to be sealed between at least a pair of substrates 1, 1. In the device 10, the liquid crystal-isotropic liquid phase transition temperature of the liquid crystal composition 4 is set to be higher than the sol-gel phase transition temperature. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

（式中、Ｒ_１〜Ｒ_５及びＸ，Ｙ，Ｚは、同一又は異なる一価の有機基であり、Ｘ，Ｙ，Ｚの少なくとも１つは、光学活性を有し水素結合部位を少なくとも１カ所以上有する一価の有機基である。また、ｎ，ｍ及びｌは自然数である。）
で示されるものであることを特徴とするものである。
【００１６】
請求項４に記載された発明は、請求項１〜３のいずれかに記載された発明において、前記ゲル化剤の含有量が、前記液晶性組成物が液晶ゲル状態で可視光に対して透明となる範囲のものであることを特徴とするものである。
【００１７】
請求項５に記載された発明は、請求項４に記載された発明において、前記ゲル化剤の含有量が、液晶物質に対して０．０５〜１．０重量％であることを特徴とするものである。
【００１８】
請求項６に記載された発明は、請求項１〜５のいずれかに記載された発明において、前記基板が、厚み２５０μｍ以下のプラスチック基板であることを特徴とするものである。
【００１９】
請求項７に記載された発明は、少なくとも一対の基板間に、（ａ）ネマチック液晶を形成する液晶物質と、（ｂ）前記液晶物質をゲル化する水素結合性部位を少なくとも１か所以上有するオルガノシロキサンからなるゲル化剤と、を含有する液晶性組成物を封じ込めた液晶表示素子の製造方法において、あらかじめ、該液晶物質と接する少なくとも一方の基板表面に該液晶物質をゲル化するゲル化剤の塗布部を形成した後、該液晶物質を一対の基板間に注入することを特徴とする液晶表示素子の製造方法である。
【００２０】
請求項８に記載された発明は、請求項７に記載された発明において、前記ゲル化剤の塗布部を液晶物質の注入部より離れた部分に形成することを特徴とするものである。
【００２１】
請求項９に記載された発明は、請求項７又は８に記載された発明において、前記液晶物質を、前記ゲル化剤が該液晶物質と混和しない温度において、注入することを特徴とするものである。
【００２２】
請求項１０に記載された発明は、請求項７〜９のいずれかに記載された発明において、前記一対の基板間に注入した液晶物質に加熱処理を施して、前記ゲル化剤を該液晶物質に混和させることにより、液晶性組成物とした後に、該液晶性組成物を冷却することを特徴とするものである。
【００２３】
請求項１１に記載された発明は、請求項７〜１０のいずれかに記載された発明において、一方の基板にギャップ材を設置し、そして、もう一方の基板に前記ゲル化剤の塗布部を形成して、これらを貼り合わせることを特徴とするものである。
【００２４】
【発明の実施の形態】
次に、本発明の実施の形態を図面に基づいて説明する。
図１は、本発明の一実施の形態を示す液晶表示素子の断面図であり、そして、図２は、図１のＡ−Ａ線断面図である。
【００２５】
図１において、１０は液晶表示素子である。液晶表示素子１０には、少なくとも一対の基板１，１の間に、（ａ）ネマチック液晶を形成する液晶物質と、（ｂ）前記液晶物質をゲル化する水素結合性部位を少なくとも１か所以上有するオルガノシロキサンからなるゲル化剤と、を含有する液晶性組成物４が封じ込められている。そして、この液晶性組成物４は、その液晶−等方性液体相転移温度がそのゾル−ゲル相転移温度より高いものとされている。
【００２６】
前記オルガノシロキサンにおける水素結合性部位は、次の式
−ＮＨ−Ｃ＊Ｈ（Ｒ）−ＣＯ− （１）
又は
−Ｃ＊Ｈ（Ｒ）ＮＨＣＯ− （２）
（式中、Ｒは一価の有機基を示し、そして、＊は光学活性部位を示す。）
で示される部分構造を有している。
【００２７】
本発明における「ゲル」は、三次元ネットワーク構造に溶剤が取り込まれた状態をさし、ゲル状態からゾル（溶液）状態へと可逆的に変化するものである。その場合、ゲル状態からゾル状態への変化が可能であれば、三次元ネットワーク構造の架橋部分の構造には限定を受けないが、その架橋構造は一般的に共有結合以外の二次的結合力によるものの場合が多い。本発明で用いるゲルのネットワーク構造は、分子間水素結合によるものであり、温度を上げることによりゲルのゾル化を引き起こすことができる。
【００２８】
本発明における「液晶物質」は、従来から液晶表示素子に用いられているネマティック液晶を示すビフェニル系、フェニルシクロヘキサン系等の液晶物質である。このような液晶物質を用いる液晶表示モードとしては、ＴＮ型、ＳＴＮ型、ＯＣＢ型、ＥＣＢ型等がある。これら一般的な表示モードだけでなく、ネマチックもしくはカイラルネマチックを利用した表示モードであれば、本発明の構成は適用できる。
【００２９】
上記したような「ネマチック液晶を形成する液晶物質とこれをゲル化するゲル化剤とからなる液晶性組成物」により形成されるゲルの表示素子への応用では、高分子分散型液晶のような散乱状態と透明状態との間での光スイッチング、もしくは、ＴＮ型、ＳＴＮ型のような旋光性や複屈折性を利用するために、その動作温度域において液晶性を有するゲル（液晶ゲル）であることが必要である。しかしながら、このゲル状態の液晶性組成物、即ち、液晶ゲルは、その流動性を消失させることにより、そのネットワーク構造の長期安定性を確保しているものであるので、強い機械的衝撃等でそのネットワーク構造が崩れることがある。このように、液晶ゲルのネットワーク構造が崩れた場合には、これを修復するために、液晶ゲルをゾル状態（ゲル化剤によるネットワーク構造がなくなって液晶と混和している状態）まで一旦加熱した後、冷却することにより再び安定な液晶ゲル状態にする必要がある。そこで、この液晶性組成物の二つの相転移温度（ネマチック液晶−等方性液体相転移点及びゾル−ゲル相転移点）の関係が重要になる。ネマチック液晶−等方性液体相転移点（以下、「Ｔｎｉ」と表記する。）とゾル−ゲル相転移点（以下、「Ｔｓｇ」と表記する。）との関係、並びに、その液晶性組成物の低温側からの相系列の変化を示すと、
▲１▼ Ｔｎｉ＜Ｔｓｇの場合 結晶−液晶ゲル−等方性ゲル−等方性ゾル
▲２▼ Ｔｎｉ＞Ｔｓｇの場合 結晶−液晶ゲル−液晶ゾル −等方性ゾル
となる。
【００３０】
液晶表示素子の動作温度範囲は、液晶ゲルを示す温度範囲に含まれている必要がある。ここで、前記▲１▼の場合、即ち、ＴｎｉがＴｓｇよりも低い場合の液晶ゲル組成物を調光層とした液晶表示素子において、発生した欠陥を修復するためには、そのゲルのネットワーク構造が一旦は消失するところの等方性ゾル状態を示す温度まで液晶ゲル組成物を加熱する必要がある。また、前記▲２▼の場合、即ち、ＴｎｉがＴｓｇよりも高い場合には、同様に、液晶ゲル組成物を液晶ゾル状態になるまで加熱することとなる。この２つの場合において、液晶ゾル及び等方性ゾルは、ゾル状態であることでは同じであるが、系として液晶性を持っているか、等方性であるかの違いがあり、そのために、加熱された液晶表示素子における劣化に異なる影響を与えることがわかった。
【００３１】
液晶表示素子のセル内での液晶性組成物は、配向剤、ギャップ材、シール剤、基板材料等の構成材料と接触している。これらの構成材料は、もちろん十分な精製が行われたものを使用しているが、幾分かの不純物を含有している。液晶性組成物は、有機溶剤としての側面も有しているので、高温になるほどその不純物の溶解能が高くなる。また、同じ温度でも、その液晶性組成物が等方液体相である場合には、液晶相を示しているのと比較して、容易に不純物を溶解するために、表示性能の急激な劣化に結びつくことが見いだされた。
【００３２】
このことから、液晶ゲルを調光層に用いた液晶表示素子においては、ＴｎｉがＴｓｇよりも高い構成とすることが、欠陥修復における表示劣化の抑制に効果的であることが理解できる。
【００３３】
ゲル状態の液晶性組成物、即ち、液晶ゲルの欠陥修復が、ゾル状態までの加熱と、その後の冷却による液晶ゲルの再生という簡易なプロセスでできるためには、そのゲル化剤が重要である。
【００３４】
本発明者らは、分子間水素結合によって物質をゲル化する性質を持ち、かつ、使用する液晶に溶解する低分子化合物のゲル化剤を提案した（前記特許文献６を参照。）。この「低分子化合物」とは、分子量分布を持たない化合物をさし、その分子量は、２０００ 以下、好ましくは、１０００ 〜２０００ である。このようなゲル化剤が、液晶物質を溶解し、かつ、分子間水素結合によって液晶物質をゲル化する分子量２０００ 以下、好ましくは、１０００ 〜２０００ の化合物とすることで、液晶層をより簡便なプロセスでゲル化できる化合物を有した液晶表示素子を提供することができた。
【００３５】
ここで具体的なゲル化剤として、分子間水素結合が可能な分子構造上の条件は、一般的には、アミド基（−ＮＨＣＯ −）、及び、アミノ基（−ＮＨ −）とカルボニル基（−ＣＯ −）との組み合わせを有するものが好ましく、これらの基以外に、カルバメート基、ウレア基、カルボキシル基、アルコキシ基、リン酸基、水酸基等があっても良く、これらの数、位置については限定されないとした。また、そのようなゲル化剤の中でも、特に、分子間水素結合が可能な基及びアルキレン基を１ 分子中にそれぞれ２ 個以上有する化合物が望ましく、アルキレン基としては、炭素数４ 以上、好ましくは６ 〜２０ の長鎖構造（分岐があっても良い）を持つ方が、液晶性物質への溶解性が高い。また、ゲル化剤は、キラル構造を有する化合物よりなるものが好ましいとした。それらの化合物としては、具体的には、前記特許文献１〜５及び特開平１１−２１５５６号公報に開示されているもの等が使用できるとした。
【００３６】
しかしながら、かようなゲル化剤（通常は室温で結晶性の固体である）においては、液晶物質との相溶性にあまり優れた化合物が少なく、その液晶組成物の製造過程において、液晶物質と混和させるために１２０℃前後の加熱温度が必要とされる場合が多かった。また、液晶表示素子として使用される温度域でそのゲル組織がある程度の長さを持つ繊維状の構造であることが知られている。そのため、ゲル化した当初はその長いゲル組織が組み合わさったネットワーク構造に液晶物質が取りこまれて流動性が消失しているが、時間の経過にともないネットワーク構造に取りこまれた液晶物質が徐々に染み出してくる。液晶物質の染み出しは、液晶組成物の透過率や屈折率のムラ、応答性のムラの原因となり表示品質を落とす要因となっていた。さらに、液晶ゲルの欠陥修復時にゾル−ゲル相転移温度より高い液晶ゾル状態になるべき温度域でのゲル化剤の溶解速度（ゲル化剤の水素結合が切れて液晶中に溶解する速度）が遅いために、混和させるための温度を高く設定したり、長時間にわたって加熱状態を保持する必要が生じるために、修復時の劣化の抑制効果が充分に発揮されないことがあった。
【００３７】
本発明者らは、このような低分子化合物のゲル化剤による不具合を解決するために、さらなるゲル化剤の検討を行った結果、水素結合性部位を少なくとも１か所以上有するオルガノシロキサンのゲル化剤を用いることにより、微細で安定な液晶ゲル構造を保持し、製造時の高温加熱が不要で、修復時の液晶ゾルへの転移のための温度保持が短時間で済むことを見いだした。
【００３８】
本発明によれば、次の効果を奏する。
（１）本発明においては、ゲル化剤として水素結合性部位を有するオルガノシロキサンを用いてゲル組織を微細化したので、ゲル化剤と液晶物質との接触面積が大きくなり、そのために、ゲル化剤のネットワーク構造から液晶物質が染み出しにくくなり、よって、液晶表示素子の経時的安定性が向上する。
（２）本発明における会合性部位を有するオルガノシロキサン（ゲル化剤）は、液晶物質への溶解性が高く、液晶物質の種類にもよるが、おおむね１００℃程度未満で液晶物質と混和するので、液晶組成物の製造時の加熱温度が低くて済み、そのために、エネルギー的に効率良く製造ができる液晶組成物を備えた液晶表示素子を提供することができる。
（３）本発明においては、ゲル組織を微細化したので、ゲル化剤同士の凝集状態が比較的疎となり、そのために、液晶ゲル修復時の液晶ゾルへの転移に際してゾル−ゲル相転移温度以上での保持時間が短くても容易に均一な液晶ゾル状態を得ることができ、よって、修復による加熱での劣化がいっそう少ない液晶表示素子を提供することができる。
【００３９】
即ち、本発明によれば、少なくとも一対の基板間に、（ａ）ネマチック液晶を形成する液晶物質と、（ｂ）前記液晶物質をゲル化する水素結合性部位を少なくとも１か所以上有するオルガノシロキサンからなるゲル化剤と、を含有する液晶性組成物を封じ込めた液晶表示素子において、該液晶性組成物の液晶−等方性液体相転移温度がそのゾル−ゲル相転移温度より高いものとしたので、ゲル状態の液晶性組成物の欠陥修復が容易であり、かつ、修復時の加熱による劣化のいっそう少ない、しかも、経時的安定性の向上した液晶表示素子を低コストで提供することができる。
【００４０】
前記オルガノシロキサンにおける水素結合性部位は、次の式
−ＮＨ−Ｃ＊Ｈ（Ｒ）−ＣＯ− （１）
又は
−Ｃ＊Ｈ（Ｒ）ＮＨＣＯ− （２）
（式中、Ｒは一価の有機基を示し、そして、＊は光学活性部位を示す。）
で示される部分構造を有している。
このように、前記オルガノシロキサンにおける水素結合性部位が前記（１）又は（２）を有していると、分子間の結合が柔らかく、より溶解性に優れ、そして、液晶物質の電界応答性を下げない液晶組成物を備えた液晶表示素子を提供することができる。
【００４１】
分子間水素結合が可能な分子構造上の条件は、一般的にはアミド基（−ＮＨＣＯ−）、アミノ基（−ＮＨ−）とカルボニル基（−ＣＯ−）の組み合わせを有するものが好ましい。これ以外に、カルバメート基、ウレア基、カルボキシル基、アルコキシ基、リン酸基及び水酸基があってもよく、これらの数、位置については限定しない。そのような会合性部位の中でも、特に、式（１）及び（２）のようなアミノ基、カルボニル基及びアルキル基を有するものが好ましい。
【００４２】
より具体的には、高分子論文集、Ｖｏｌ．５２，Ｎｏ１２，Ｐ７７３（１９９５）、「オイルゲル化剤の開発とゲル化機構の解明」の項、並びに、高分子加工、４５巻１号，Ｐ２１（１９９６） 、「オイルゲル化剤」の項に記載される光学活性を有するゲル化剤の構造を有するものが好ましい。
【００４３】
具体的には、以下の構造のものが好ましい。
−（ＣＨ_２）_ｎ−ＣＯＮＨＣＨ（ｓ−Ｃ_４Ｈ_９）ＣＯＮＨＲ_５
（式中、ｎは２〜１８の整数であり、Ｒ_５ は炭素数が４〜２４のアルキル基である。）
−（ＣＨ_２）_ｎ−ＣＯＮＨＣＨ（ｉ−Ｃ_３Ｈ_７）ＣＯＮＨＣＨ（ｉ−Ｃ_３Ｈ_７）ＣＯＮＨＣＨＲ_５
（式中、ｎは２〜１８の整数であり、Ｒ_５ は炭素数が４〜２４のアルキル基である。）
【００４４】
【化３】

【００４５】
【化４】

（式中、ｎ，ｎ_１ は、２〜１８の整数であり、ｎ_２ ，ｎ_３ は、１〜９の整数でである。）
上記、会合性部位を持つ有機基は、高分子鎖に対してメチレン鎖（−ＣＨ_２ ）_ｎ −で結合されることが好ましく、その単位数は、高分子鎖の運動を妨げない面や会合体構築を妨げない面からｎ≧４であることが好ましい。
【００４６】
本発明におけるオルガノシロキサンは、次の式、
【化５】

（式中、Ｒ_１〜Ｒ_５及びＸ，Ｙ，Ｚは、同一又は異なる一価の有機基であり、Ｘ，Ｙ，Ｚの少なくとも１つは、光学活性を有し水素結合部位を少なくとも１カ所以上有する一価の有機基である。また、ｎ，ｍ及びｌは自然数である。）
で示されるものである。
このように、オルガノシロキサンが式（３）で示されているものであると、効果的に水素結合によるネットワーク構造が形成された（安定なゲル構造）液晶組成物を備えた液晶表示素子とすることができ、そのために、欠陥修復が容易であり、かつ、修復時の加熱による劣化が少ない液晶表示素子を提供することができる。
【００４７】
本発明で用いられる光学活性を有し水素結合性部位を有するオルガノシロキサンは、式（３）で表される構造を有しており、その水素結合性部位は、式中のＸ，Ｙ，Ｚで表される部位の少なくとも１ヶ所以上に存在する。この水素結合性部位は、好ましくは、前記式（１）及び（２）で示される構造を有している。この水素結合性部位は、シロキサン結合の側鎖又は末端に導入されていても良いし、側鎖と末端の両方に導入されていても良い。水素結合性部位がＸ，Ｙ，Ｚのうち複数か所に存在する場合は、それらが等しい構造であることが好ましい。また、ｍ及びｎは、側鎖にＲ_１ 及びＲ_４ をもつ単位構造と、側鎖にＲ_２ 及びＺをもつ単位構造と、の分子中での存在比率を表すものであり、分子中での結合の順番はそれぞれ連続して重合（ブロック共重合）していても良いし、ランダムに重合していても良い。
【００４８】
さらに好ましくは、Ｒ_１ 〜Ｒ_５ 及びＸ，Ｙ，Ｚのうち水素結合性部位でないものは、同一でも異なっていても良く、また、Ｈ或いは炭素数が１〜４のアルキル基、フェニル基である。また、シロキサン結合中のＳｉに付く有機基のうち、水素結合性部位が側鎖としてのみ存在する場合（Ｘ，Ｙ，ＺのうちＺのみが水素結合性である場合）に水素結合性部位Ｚの割合が低い時には、液晶組成物中の水素結合性オルガノシロキサンの濃度を高くして会合させることになるが、高濃度の会合性化合物は、液晶組成物の透過率及び応答性を下げる要因となりやすい。そのため、好ましくは、会合性部位Ｚの割合であるｎ／（ｍ＋ｎ）を０．３以上とすることで、少量の会合性化合物の添加により液晶物質を取り込むのに充分な会合構造を形成することができる。より好ましくは、ｎ／（ｍ＋ｎ）を０．５以上とすることでより効果的に本発明の目的を達成することができる。また、Ｘ，Ｙ，Ｚのうちの２か所以上が水素結合性部位を持つ有機基である場合には、それらが同一の基であればより好ましい。
【００４９】
また、水素結合性オルガノシロキサンの分子量が２０００以上であることにより、さらに安定な会合構造が形成された液晶組成物を備えた液晶表示素子を提供することができる。会合性化合物の分子量が小さい場合には、高分子鎖部の非晶質性を失いやすく、また、形成される会合体組織も粗いものになりやすく、しかも、会合構造の安定性も損なわれやすい。しかし、分子量が２０００以上であることにより、会合体組織が安定なことに加え、製造過程においてエネルギー的に有利になるとともに工業的にも扱いやすい。より好ましくは、水素結合性オルガノシロキサンの分子量は２０００以上である。オルガノシロキサンの分子鎖の繰り返し単位数｛式２中の記号で表すと（ｍ＋ｎ）×ｌ｝は５以上であることが好ましい。１０以上であればより一層好ましい。
【００５０】
本発明のゲル化剤によれば、液晶物質に対して０．０５〜１．０重量％の添加で液晶をゲル化することができる。液晶性組成物４におけるゲル化剤の含有量の最適値は液晶及びゲル化剤の種類によって異なるが、好ましくは、該液晶性組成物４が液晶ゲル状態で可視光に対して透明となる範囲、即ち、液晶が可視光に対して散乱しない範囲のものである。このような液晶性組成物４における水素結合性部位を少なくとも１か所以上有するオルガノシロキサンのゲル化剤の含有量は、液晶ゲル状態で可視光に対して透明となる範囲、好ましくは、０ ．０５〜１．０重量％であり、さらに好ましくは、０．０５〜０．５重量％である。このように、液晶性組成物４ におけるゲル化剤の含有量は、液晶性組成物４ が液晶ゲル状態で可視光に対して透明となる範囲のものであるので、表示不良の少ない液晶表示素子を提供できる。
【００５１】
液晶表示素子は、薄型であること、軽量であること、及び、省電力性に優れていること、等のために、数々の分野で利用されている。液晶表示素子は、携帯用電子機器の表示素子として、まさに、その特徴を十分に活かすものとして利用されている。液晶表示素子は、一般的には、２枚のガラス基板の間に液晶性組成物を挟みこんだ構成となっているが、基板をプラスチックフィルムにした場合には、薄型にできること、軽量にできること、さらには、耐衝撃性を向上できること、等のために、携帯用電子機器の表示素子に特に向いたものとなる。
【００５２】
本発明における基板１，１は、２５０μｍ以下のプラスチックフィルムである。従来、プラスチックフィルムを基板として液晶表示素子を作った場合において、局所的な機械的圧力等による配向欠陥や構造欠陥等が発生することがあったが、図１，２に示すように、本発明の液晶表示素子１０によれば、液晶性組成物４の液晶−等方性液体相転移温度がそのゾル−ゲル相転移温度より高いので、基板１が厚み２５０μｍ以下のプラスチックフィルムで構成されるものであっても、欠陥修復が容易であり、且つ、修復時の加熱による劣化が少ないものとなる。そして、プラスチックフィルムを基板１とする場合には、基板１の耐熱性が低いので、配向剤、ギャップ材、シール剤等の液晶表示素子の構成材料に対して低温で焼成、硬化させるようなプロセスを採用することになる。プラスチック基板は、ガラスを基板としたときよりも、配向剤、ギャップ材、シール剤等の液晶表示素子の構成材料からの不純物の溶出が多くなるが、本発明の液晶表示素子１０によれば、液晶性組成物４の液晶−等方性液体相転移温度がそのゾル−ゲル相転移温度より高いので、このようなプラスチック基板を用いた場合において不純物の溶出を低減することができる。
【００５３】
従来、液晶表示素子における両基板間への液晶物質の導入は、一般的には、減圧注入方式によって行われていた。即ち、従来においては、ゲル化している液晶性組成物をゾル化温度以上まで熱して液体状態とすることにより基板間に減圧注入していたが、この場合には、液晶性組成物の注入が終了するまでは液晶性組成物をゾル状態を保つ必要があるために、注入皿、基板などを加熱しておく必要が生じる。このような操作は、エネルギー的に不利であり、加熱装置等が必要となる上に、その制御も複雑となり、生産性を下げる要因となる。
【００５４】
これに対して、本発明では、少なくとも一対の基板１，１の間に、（ａ）ネマチック液晶を形成する液晶物質と、（ｂ）前記液晶物質をゲル化する水素結合性部位を少なくとも１か所以上有するオルガノシロキサンからなるゲル化剤と、を含有する液晶性組成物４を封じ込めた液晶表示素子１０の製造方法において、あらかじめ、該液晶物質と接する少なくとも一方の基板１，１の表面に該液晶物質をゲル化するゲル化剤の塗布部５を形成した後、該液晶物質を一対の基板１，１の間に注入する。少なくとも一方の基板１，１の表面に該液晶物質をゲル化するゲル化剤の塗布部５を形成するには、ゲル化剤を溶媒に溶かし、これを少なくとも一方の基板１ ，１ の上に塗布・乾燥させる。ゲル化剤の塗布には、従来公知のスピン塗布、デップ塗布、フレキソ印刷、ディスペンサー塗布等の手段が使用できる。所定の部位にゲル化剤を配置するには、フレキソ印刷、ディスペンサー塗布等の手段が望ましい。
【００５５】
本発明によれば、あらかじめ、該液晶物質と接する少なくとも一方の基板１，１の表面に該液晶物質をゲル化するゲル化剤の塗布部５を形成した後、該液晶物質を一対の基板１，１の間に注入するので、減圧注入時の過熱を必要とせず、また、煩雑な温度制御も不要となり、しかも、従来の装置がそのまま使用できる。そのために、本発明によれば、調光層にゲル状の液晶性組成物４を有するいっそう均一な表示が可能となると共に、欠陥修復が容易となる液晶表示素子を効率良く低コストで製造できる。
【００５６】
本発明においては、前記ゲル化剤の塗布部５は、液晶物質の注入部６より離れた部分に形成される。このように、前記ゲル化剤の塗布部５を液晶物質の注入部６より離れた部分に形成すると、液晶物質の注入時に、ゲル化剤による液晶の流入阻害がなく、そのために、注入時間のばらつき等のない安定な液晶表示素子を製造することができる。
【００５７】
また、本発明においては、前記液晶物質は、前記ゲル化剤が該液晶物質と混和しない温度において注入される。前記液晶物質を前記ゲル化剤が該液晶物質と混和しない温度において注入すると、均一な表示ができる液晶表示素子を製造することができる。即ち、本発明においては、水素結合性部位を少なくとも１か所以上有するオルガノシロキサンのゲル化剤は、液晶物質を基板間に注入する温度では、該液晶物質と混和しないものである。このように、一対の基板１ ，１ の間に注入した液晶物質に加熱処理を施して、前記ゲル化剤を該液晶物質に混和させ、液晶性組成物４とした後に、該液晶性組成物４を冷却することにより、混和の温度が低くできると共に、加熱時間が短く液晶組成物の劣化が少ない、かつ表示不良の少ない液晶表示素子が製造される。
【００５８】
前記「ゲル化剤が液晶物質に混和しない」という意味は、所定の液晶物質の注入時間内での混和が避けられれば良いという意味であり、その温度においてまったく混和しないという意味ではない。ゲル化剤が液晶物質に混和するものであると、基板１ ，１ の上に配置したゲル化剤によって液晶の注入と同時にゲル化が開始してしまい、注入の妨げとなったり、ゲル化剤が液晶の注入とともに移動して、ゲル化剤の濃度が基板上で不均一になる可能性がある。このような場合に作製された表示素子では、均一な表示ができなくなる。この現象を防ぐために、混和が起こらないゲル化剤と液晶の組み合わせを選ぶことが必要である。
【００５９】
本発明においては、前記一対の基板１，１の間に注入した液晶物質に加熱処理を施して、前記ゲル化剤を該液晶物質に混和させることにより、液晶性組成物とした後に、該液晶性組成物を冷却する。このように、前記一対の基板１，１の間に注入した液晶物質に加熱処理を施して、前記ゲル化剤を該液晶物質に混和させることにより、液晶性組成物とした後に、該液晶性組成物を冷却すると、短時間で表示不良の少ない液晶表示素子を製造することができ、また、液晶表示素子における表示欠陥を修復することが可能となる。
【００６０】
液晶物質とゲル化剤を基板１ ，１ の間に封入後この混合物を加熱すると、均一な等方性溶液となる。本発明によれば、かかる等方性溶液を冷却することにより、光学的には液晶の異方性を持つゲル状の液晶性組成物、即ち、液晶ゲルを得ることができる。かかる液晶ゲルは、水素結合性のネットワーク構造を持つことにより、長期安定性により優れたものとなる。それ故、液晶物質の注入が完了した後は、ゲル化剤が液晶物質に溶解するように、温度を一旦ゾル−ゲル相転移温度以上になるまで加熱してからゲル化する温度以下にまで冷却することにより、短時間で、表示不良の少ない液晶表示素子を提供することができる。また、このように形成されたゲル状の液晶性組成物は、水素結合性のネットワーク構造を持っているので、「熱などの刺激に応じて水素結合が切れたり再びネットワークを形成したりする」という構造変化を可逆的に起こすことができる。即ち、ゲル状の液晶性組成物を再度加熱することにより等方性溶液に戻り、そして、この等方性溶液を再度冷却すると液晶ゲルとなるので、液晶表示素子における表示欠陥を修復することが可能となる。さらに、本発明で作製されるゲル状の液晶性組成物は、電界の強度の変化に応じて配向が変化し、明確な電界応答性を示す。
【００６１】
一般に、減圧注入により液晶表示素子を作製する場合は、基板間距離を一定にするためにギャップ材を使用している。このギャップ材は両基板を貼り付ける前に、少なくともいずれか一方の基板上に存在させておくものである。ギャップ材の配置方法には、乾式散布、湿式散布及びスクリーン印刷などがある。乾式散布は、ギャップ剤を直接に基板に吹き付けるものであり、湿式散布は、溶媒にギャップ材を分散させたものを基板上に吹き付けて散布するものである。また、ゲル化剤を配置した基板に、前記したような方式でギャップ材を吹き付けると、ゲル化剤の有無によりギャップ材の付着状態が異なるため、結果として、基板の面内でのギャップ材の均一な配置ができない。さらに、ゲル化剤を配置した基板にスクリーン印刷でギャップ材を配置する場合、印刷時にスクリーン版とゲル化剤が接触し、ゲル化剤がスクリーン版に転写してしまう。この結果、所定のゲル化剤濃度の液晶ゲルを形成できず、所望の性能の素子が作製できない。しかしながら、本発明によれば、電極２を備えた一方の基板１にギャップ材を設置し、そして、もう一方の基板１に前記ゲル化剤の塗布部５を配置して、これらを貼り合わせたので、貼り合わせた基板１ ，１ の間にギャップ材を均一に配置でき、しかも、ムラのない液晶表示素子１０ を製造することができる。
【００６２】
本発明において使用されるシール剤３としては、従来から液晶表示素子に用いられている材料、具体的には、光硬化性のアクリル系樹脂、エポキシ系樹脂等を用いることができる。また、本発明において使用される基板としては、従来から液晶表示素子の基板として用いられている透明な材料を用いることができる。ガラス等の剛直な材料、プラスチックフィルム等の柔軟な材料のいずれも用いることができる。
【００６３】
【実施例】
以下、実施例を示して、本発明を具体的に説明するが、本発明は下記の実施例に制限されるものではない。
【００６４】
（実施例１）
（１）寸法が３０ｍｍ×４０ｍｍの一対のガラスよりなる基板にＩＴＯ電極層を形成し、次に、配向処理膜としてポリイミドを積層した後、それらの表面をラビング処理した。そして、これらの基板の一方の基板にはシール剤としてアミン硬化エポキシ樹脂中をディスペンサー塗布し、そして、他の基板には５μｍ粒径のシリカビーズをイソプロピルアルコール溶媒に分散して約１００個／ｍｍ^２ の密度で散布した。これらの２枚の基板は、互いのラビング方向が反平行になるようにシール剤で貼り合わせて固定・硬化することによりセルを作製した。
（２）ゲル化剤として、次の式
【化６】

で示されるオルガノシロキサン（分子量約６０００）を用意し、そして、液晶として、Ｔｎｉが８３℃であるネマチック液晶（ＬＣ１）を用意した。そして、これらを混合して得た混合物を１００℃のオーブンで１０分間放置して、等方性液体状態でネマチック液晶物質とゲル化剤を十分に混和させた液晶性組成物を準備した。この液晶性組成物のゲル化剤濃度は、１．０重量％に調整した。この液晶性組成物のＴｎｉ約８２℃であり、液晶物質単独でのＴｎｉとほぼ同じであった。また、そのＴｓｇは６８ ℃であった。
（３）前記セルを液晶注入用真空装置に移し、０．００２Ｔｏｒｒまで減圧した後に、液晶皿にセルの液晶注入口を付けてセル外部を常圧に戻し、続いて、液晶性組成物をこのセル中に注入した。この液晶性組成物のセル中への注入は、セル及び液晶皿を液晶ゾル状態である７５ ℃に加熱して行った。
（４）このように液晶性組成物を注入した後、液晶性組成物の注入口部を封止剤で塞ぎ硬化することにより、ゲル状の液晶性組成物が存在する液晶表示素子を得た。
【００６５】
このようにして得た液晶表示素子は、そのゲル状の液晶部分が可視光に対して透明であり（透過率約８７％）、偏光板のクロスニコル下で観察すると、液晶が均一なホモジニアス配向していることが確認できた。また、この液晶セルに５Ｖ、６４Ｈｚの交流電圧を印加したところ、液晶が均一に正常に作動した。次に、そのセル表面を１１φの鉄球で押圧する試験を繰り返した。この試験で、液晶の配向が乱れたことによる欠陥が発生した時点で、この液晶素子を７５℃の液晶ゾル状態まで加熱してそのまま２分保持後、室温まで冷却したところ、試験前の無欠陥な状態に復帰した。この欠陥修復の操作を３００回繰り返したが、液晶素子の外観、電界応答特性に変化は見られなかった。
【００６６】
（実施例２）
（１）実施例１と同様に基板として、寸法が３０ｍｍ×４０ｍｍのガラスよりなる基板を用いて、セルを作製した。
（２）Ｔｎｉが３５．２℃のネマチック液晶（ＬＣ２）とゲル化剤（Ｇ１）を混合し、１２０℃のオーブン中に３０分放置し、等方性液体状態で、液晶とゲル化剤を十分に混和させた液晶性組成物を準備し、その液晶性組成物のゲル化剤濃度を０．２ｍｏｌ％に調整した。この液晶性組成物のＴｎｉは約３５℃であり液晶物質単独での転移点とほぼ同じであった。また、Ｔｓｇは８０℃であった。
（３）セルを液晶注入用真空装置に移し、０．００２Ｔｏｒｒまで減圧した後に、液晶皿にセルの液晶注入口を付けてセル外部を常圧に戻し、続いて、液晶性組成物をセル中に導入した。この液晶性組成物のセル中への注入は、セル及び液晶皿を等方性ゾル状態である８５℃に加熱して行った。
（４）このように液晶性組成物をセル中に注入した後、注入口部を封止剤で塞ぎ硬化することにより、ゲル状の液晶性組成物が存在する液晶表示素子を得た。
【００６７】
このようにして得た液晶表示素子は、そのゲル状の液晶部分が可視光に対して透明であり、偏光板のクロスニコル下で観察すると、液晶が均一なホモジニアス配向していることが確認できた。また、この液晶セルに５Ｖ、６４Ｈｚの交流電圧を印加したところ、液晶が均一に正常に作動した。次に、そのセル表面を１１φの鉄球で押圧する試験を繰り返した。この試験で、液晶の配向が乱れたことによる欠陥が発生した時点で、この液晶素子を７５℃の液晶ゾル状態まで加熱してそのまま２分保持後、室温まで冷却したところ、試験前の無欠陥な状態に復帰した。この欠陥修復の操作を３００回繰り返したが、液晶素子の外観、電界応答特性に変化は見られなかった。しかし、電界応答特性において、その動作電圧が大きく上昇した。このセルのインピーダンス測定を実施したところ、液晶性組成物層の比抵抗が低下していることが判明した。これは液晶性組成物層に何らかの不純物が混入したことを示唆している。
【００６８】
（実施例３）
実施例１において、寸法が３０ｍｍ×４０ｍｍのガラス基板に変えて、ＩＴＯを表面に持つポリエーテルサルフォンシート（ＰＥＳ：住友ベークライト製、厚み１５０ミクロン）を用いて、セルを作製した。ネマチック液晶（ＬＣ１）、ゲル化剤（Ｇ１）等の材料及び構成は実施例１と同様とした。このセルに実施例１と同様の押圧試験を実施し、欠陥修復操作を繰り返してみた。繰り返し回数は３００回とした。試験後、フィルム基板面の押圧部の一部に、へこみ跡などの外観変化が見られたが（表示特性上で問題にならないレベルであった。）、電界応答特性には変化が見られなかった。
【００６９】
（実施例４）
（１）寸法が３０ｍｍ×４０ｍｍの一対のガラスよりなる基板にＩＴＯ電極層を形成し、配向処理膜としてポリイミドを積層した後、それらの表面をラビング処理した。これらの基板の一方の基板には、ゲル化剤としてＧ１を溶剤に溶かしたものを、図２に示される部分にディスペンサーで定量塗布して、乾燥させた。そして、ゲル化剤を塗布した部分の外側に、シール剤としてアミン硬化エポキシ樹脂中をディスペンサー塗布した。次に、他の一方の基板には５μｍ粒径のシリカビーズをイソプロピルアルコール溶媒に分散して約１００個／ｍｍ^２ の密度で散布した。これらの２枚の基板は、互いのラビング方向が反平行になるように貼り合わせて固定・硬化することによりセルを作製した。
（２）このように作成したセルを液晶注入用真空装置に移し、０．００２Ｔｏｒｒまで減圧した後に、液晶皿にセルの液晶注入口を付けてセル外部を常圧に戻し、液晶物質（ＬＣ１）をセル中に導入した。
（３）このように液晶物質（ＬＣ１）をセル中に注入した後、注入口部を封止剤で塞ぎ硬化することにより、液晶表示素子を得た。
【００７０】
この液晶表示素子では、８０℃まで加熱してゲル化剤と液晶物質を溶かして液晶ゾルとした後、室温まで冷却することにより、ゲル状の液晶性組成物が存在する液晶表示素子とすることができた。この液晶性組成物のゲル化剤濃度は、１．０重量％になるように、ゲル化剤の塗布量を調節しておいたので、得られた液晶表示素子は、実施例１で作製したものと同等の特性を示し、欠陥修復試験の結果も同じものであった。
【００７１】
（実施例５）
実施例４において、寸法が３０ｍｍ×４０ｍｍのガラス基板に変えて、ＩＴＯを表面に持つポリエーテルサルフォンシート（ＰＥＳ：住友ベークライト製、厚み１５０ミクロン）を用いて、同様のセルを作製した。このようにして作製したセルは、実施例３で作製したセルと同等であり、特性上の差異も見られなかった。
【００７２】
【発明の効果】
（１）請求項１に記載された発明によれば、少なくとも一対の基板間に、（ａ）ネマチック液晶を形成する液晶物質と、（ｂ）前記液晶物質をゲル化する水素結合性部位を少なくとも１か所以上有するオルガノシロキサンからなるゲル化剤と、を含有する液晶性組成物を封じ込めた液晶表示素子において、該液晶性組成物の液晶−等方性液体相転移温度がそのゾル−ゲル相転移温度より高いものとしたので、ゲル状態の液晶性組成物の欠陥修復が容易であり、かつ、修復時の加熱による劣化のいっそう少ない、しかも、経時的安定性の向上した液晶表示素子を低コストで提供することができる。
【００７３】
（２）請求項２に記載された発明によれば、前記オルガノシロキサンにおける水素結合性部位が前記（１）又は（２）を有しているので、分子間の結合が柔らかく、より溶解性に優れ、そして、液晶物質の電界応答性を下げない液晶組成物を備えた液晶表示素子を提供することができる。
（３）請求項３に記載された発明によれば、オルガノシロキサンが式（３）で示されているものであるので、効果的に水素結合によるネットワーク構造が形成された（安定なゲル構造）液晶組成物を備えた液晶表示素子とすることができ、そのために、欠陥修復が容易であり、かつ、修復時の加熱による劣化が少ない液晶表示素子を提供することができる。
【００７４】
（４）請求項４，５に記載された発明によれば、オルガノシロキサンのゲル化剤の含有量は、液晶ゲル状態で可視光に対して透明となる範囲、好ましくは、０．０５〜１．０重量％であるので、表示不良の少ない液晶表示素子を提供できる。
（５）請求項６に記載された発明によれば、液晶性組成物の液晶−等方性液体相転移温度がそのゾル−ゲル相転移温度より高いので、基板が厚み２５０μｍ以下のプラスチックフィルムで構成されるものであっても、欠陥修復が容易であり、且つ、修復時の加熱による劣化が少ないものとなる。
【００７５】
（６）請求項７に記載された発明によれば、あらかじめ、該液晶物質と接する少なくとも一方の基板の表面に該液晶物質をゲル化するゲル化剤の塗布部を形成した後、該液晶物質を一対の基板間に注入するので、減圧注入時の過熱を必要とせず、また、煩雑な温度制御も不要となり、しかも、従来の装置がそのまま使用できる。
（７）請求項８に記載された発明によれば、前記ゲル化剤の塗布部を液晶物質の注入部より離れた部分に形成するので、液晶物質の注入時に、ゲル化剤による液晶の流入阻害がなく、そのために、注入時間のばらつき等のない安定な液晶表示素子を製造することができる。
【００７６】
（８）請求項９に記載された発明によれば、前記液晶物質を前記ゲル化剤が該液晶物質と混和しない温度において注入するので、均一な表示ができる液晶表示素子を製造することができる。
（９）請求項１０に記載された発明によれば、前記一対の基板間に注入した液晶物質に加熱処理を施して、前記ゲル化剤を該液晶物質に混和させることにより、液晶性組成物とした後に、該液晶性組成物を冷却するので、短時間で表示不良の少ない液晶表示素子を製造することができ、また、液晶表示素子における表示欠陥を修復することが可能となる。
【００７７】
（１０）請求項１１に記載された発明によれば、一方の基板にギャップ材を設置し、そして、もう一方の基板に前記ゲル化剤の塗布部を形成して、これらを貼り合わせたので、貼り合わせた基板の間にギャップ材を均一に配置でき、しかも、ムラのない液晶表示素子を製造することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態を示す液晶表示素子の断面図である。
【図２】図１のＡ−Ａ線断面図である。
【符号の説明】
１ 基板
２ 電極
３ シール剤
４ 液晶性組成物
５ ゲル化剤の塗布部
６ 液晶物質の注入部
１０ 液晶表示素子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly, to a liquid crystal display device in which a liquid crystal gel composition having lost fluidity is enclosed in a light control layer portion and a method for manufacturing the same.
[0002]
[Prior art]
A liquid crystal display element using a gel-like substance exhibiting liquid crystal properties has already been proposed (for example, see Patent Documents 1 to 6).
[0003]
Further, a polymer-dispersed liquid crystal device in which a liquid crystal is arranged in a network structure or a capsule structure of a polymer resin using a nematic liquid crystal has been proposed. Such a polymer-dispersed liquid crystal device can be easily manufactured because (a) a bright image can be displayed without using a polarizing plate, (b) a wide viewing angle, and (c) no alignment treatment of the liquid crystal is required. Although there were advantages such as (1), high precision is required for temperature and light intensity when curing the polymer resin, and (2) defect repair because the polymer resin is cured. Are not possible, and (3) it is impossible to display halftones due to the occurrence of hysteresis when voltage is applied.
[0004]
In order to solve these problems, a liquid crystal display device comprising a liquid crystal composition in a gel state containing a low molecular compound having a perfluoroalkyl group and a liquid crystal substance has been proposed (Patent Document 1 and Patent Document 1). Reference 2). By using this liquid crystalline composition in a gel state (hereinafter, referred to as “liquid crystal gel”) in the production of a display element, display without generation of hysteresis becomes possible, and high contrast comparable to that of a TN type liquid crystal cell is realized. Was. In addition, it was a great merit that the defect of the network of the liquid crystal gel could be repaired by a simple operation of heating to above the sol-gel phase transition temperature and then cooling. However, since the sol-gel phase transition temperature of the liquid crystalline composition is 110 to 120 ° C., when the temperature for repairing the defect is about 130 ° C. and the repair of the defect is repeated, the high temperature sol-state liquid crystalline composition is obtained. There is a problem that a display failure occurs due to the incorporation of impurities into the product, and the liquid crystal composition showing a gel state shows a gel state at room temperature. There is also a problem that the cell must be heated to a temperature higher than the sol-gel phase transition temperature of the liquid crystal composition.
[0005]
In the examples of Patent Document 1 and Patent Document 2, the liquid crystalline composition is heated to 100 to 180 ° C., which is higher than the sol-gel phase transition temperature, to obtain an isotropic liquid. The liquid is injected in a vacuum into a liquid crystal cell heated to the same temperature. However, in a vacuum, when a high-temperature liquid crystalline composition is injected into a liquid crystal cell maintained at a high temperature, the composition fluctuates due to volatilization of a high vapor pressure component of the liquid crystalline composition and material deterioration occurs due to continuous production at a high temperature. Further, in a process such as cell heating under vacuum, there is a problem that the productivity is poor because energy efficiency is deteriorated.
[0006]
Further, in the embodiment of the invention disclosed in Patent Document 4, a liquid crystal gel using an amino acid-based gelling agent is applied not only to a polymer dispersed liquid crystal device but also to a TN type liquid crystal light control layer. Since the liquid crystal composition constituting the liquid crystal sol has a higher sol-gel phase transition temperature than the liquid crystal-isotropic liquid phase transition temperature, it exhibits liquid crystallinity even in repairing alignment defects of the liquid crystal gel. It has to be heated to a high temperature to a non-isotropic sol state. For this reason, there is a problem that display defects occur when the alignment defects of the liquid crystal gel are repeatedly repaired. Further, since the liquid crystal composition showing a gel state is in a gel state at room temperature, when the operation of injecting this into a liquid crystal cell, the liquid crystal composition and the sol-gel of the liquid crystal composition are used. There is a problem that heating must be performed at a temperature higher than the phase transition temperature.
[0007]
In the examples of Patent Document 3 and Patent Document 4, spin coating, a bar coater, a roll coater, or the like is performed on one of the substrates with a heated isotropic liquid of a liquid crystalline composition and a gelling agent. It is described that the isotropic liquid is applied by using an isotropic liquid. However, the isotropic liquid loses its fluidity when the temperature is lower than the sol-gel phase transition temperature. There has been a problem that it is necessary to devise a process such as keeping the substrate and the coating apparatus at a high temperature so that the ionic liquid is not cooled during the coating.
[0008]
Therefore, the present inventors have proposed a liquid crystal display device in which a liquid crystal composition containing a liquid crystal material forming a nematic liquid crystal between a pair of substrates provided with electrodes and a gelling agent for gelling the same is sealed. The liquid crystal composition in a gel state obtained by setting the liquid crystal-isotropic liquid phase transition temperature of the liquid crystal composition higher than its sol-gel phase transition temperature can be easily repaired and repaired. A liquid crystal display element that is less likely to deteriorate due to heating during heating has been proposed (see Patent Document 6).
[0009]
In such a liquid crystal display element, deterioration of the liquid crystal material due to heating during restoration was reduced by controlling the transition temperature. However, depending on the type of the gelling agent, the liquid crystal sol state higher than the sol-gel phase transition temperature for restoration was reduced. In some cases, the dissolution rate of the gelling agent (the rate at which the gelling agent breaks hydrogen bonds and dissolves in the liquid crystal) is slow in the temperature range where And the temperature for mixing the liquid crystal material is set high, so that the liquid crystal material is kept in a heated state for a long time, and the effect of suppressing the deterioration of the liquid crystal material due to heating during restoration becomes insufficient. There was a problem.
[0010]
Further, in such a liquid crystal display element, since the stability of gelation of the liquid crystal composition is poor, the liquid crystal substance incorporated in the gel network structure gradually permeates over time, For this reason, there has been a problem that unevenness in transmittance and refractive index of the liquid crystal composition and unevenness in response occur.
[0011]
[Patent Document 1]
JP-A-5-216015
[Patent Document 2]
JP-A-8-254688
[Patent Document 3]
JP-A-11-52341
[Patent Document 4]
JP-A-11-256164
[Patent Document 5]
JP 2000-239663 A
[Patent Document 6]
JP 2002-156665 A
[0012]
[Problems to be solved by the invention]
The present invention aims to solve such a problem.
That is, the present invention provides a liquid crystal display element which is easy to repair a defect in a liquid crystalline composition in a gel state, has less deterioration due to heating during repair, and has improved stability over time at low cost. The first object of the present invention is to provide a method for manufacturing a liquid crystal display device capable of efficiently and inexpensively manufacturing a liquid crystal display device having a gel-like liquid crystal composition in a dimming layer and capable of more uniform display. The second purpose is to provide.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 provides (a) a liquid crystal material that forms a nematic liquid crystal between at least a pair of substrates, and (b) a hydrogen bonding material that gels the liquid crystal material. A gelling agent comprising an organosiloxane having at least one site, and a liquid crystal display device containing a liquid crystal composition containing the liquid crystal composition, wherein a liquid crystal-isotropic liquid phase transition temperature of the liquid crystal composition is A liquid crystal display device characterized by having a higher sol-gel phase transition temperature.
[0014]
The invention described in claim 2 is the invention according to claim 1, wherein the hydrogen bonding site is represented by the following formula:
-NH-C * H (R) -CO- (1)
Or
-C * H (R) NHCO- (2)
(In the formula, R represents a monovalent organic group, and * represents an optically active site.)
Is characterized by having a partial structure represented by
[0015]
The invention described in claim 3 is the invention according to claim 1 or 2, wherein the organosiloxane is represented by the following formula:
Embedded image

(Where R₁~ R₅And X, Y, and Z are the same or different monovalent organic groups, and at least one of X, Y, and Z is a monovalent organic group having optical activity and having at least one hydrogen bonding site. is there. Further, n, m and l are natural numbers. )
Is characterized by the following.
[0016]
The invention described in claim 4 is the invention according to any one of claims 1 to 3, wherein the content of the gelling agent is such that the liquid crystalline composition is transparent to visible light in a liquid crystal gel state. Is characterized by the following range.
[0017]
The invention described in claim 5 is the invention described in claim 4, wherein the content of the gelling agent is 0.05 to 1.0% by weight based on the liquid crystal substance. Things.
[0018]
The invention described in claim 6 is the invention described in any one of claims 1 to 5, wherein the substrate is a plastic substrate having a thickness of 250 µm or less.
[0019]
The invention described in claim 7 has (a) a liquid crystal substance forming a nematic liquid crystal and (b) at least one hydrogen bonding site for gelling the liquid crystal substance between at least one pair of substrates. A method of manufacturing a liquid crystal display device containing a liquid crystal composition containing an organosiloxane gelling agent, wherein the gelling agent gels the liquid crystal material on at least one substrate surface in contact with the liquid crystal material in advance Forming a coated portion of the liquid crystal material, and injecting the liquid crystal material between a pair of substrates.
[0020]
The invention described in claim 8 is the invention described in claim 7, wherein the application portion of the gelling agent is formed in a portion remote from a liquid crystal substance injection portion.
[0021]
According to a ninth aspect of the present invention, in the liquid crystal display device according to the seventh or eighth aspect, the liquid crystal material is injected at a temperature at which the gelling agent does not mix with the liquid crystal material. is there.
[0022]
According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, the liquid crystal material injected between the pair of substrates is subjected to a heat treatment so that the gelling agent is added to the liquid crystal material. And then cooling the liquid crystal composition after the liquid crystal composition is formed.
[0023]
The invention described in claim 11 is the invention according to any one of claims 7 to 10, wherein a gap material is provided on one substrate, and the application portion of the gelling agent is provided on the other substrate. It is characterized by forming and bonding these.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
[0025]
In FIG. 1, reference numeral 10 denotes a liquid crystal display element. The liquid crystal display element 10 has (a) a liquid crystal material forming a nematic liquid crystal and (b) at least one hydrogen bonding site for gelling the liquid crystal material between at least one pair of substrates 1 and 1. And a gelling agent comprising an organosiloxane having the same. The liquid crystal composition 4 has a liquid crystal-isotropic liquid phase transition temperature higher than the sol-gel phase transition temperature.
[0026]
The hydrogen bonding site in the organosiloxane is represented by the following formula:
-NH-C * H (R) -CO- (1)
Or
-C * H (R) NHCO- (2)
(In the formula, R represents a monovalent organic group, and * represents an optically active site.)
Has a partial structure represented by
[0027]
The “gel” in the present invention refers to a state in which a solvent is taken into a three-dimensional network structure, and reversibly changes from a gel state to a sol (solution) state. In that case, the structure of the cross-linking part of the three-dimensional network structure is not limited as long as the state can be changed from the gel state to the sol state, but the cross-linking structure is generally a secondary bonding force other than a covalent bond. Often due to. The network structure of the gel used in the present invention is based on intermolecular hydrogen bonds. The gel can be turned into a sol by increasing the temperature.
[0028]
The "liquid crystal substance" in the present invention is a liquid crystal substance such as a biphenyl-based or phenylcyclohexane-based liquid crystal which shows a nematic liquid crystal conventionally used in a liquid crystal display device. As a liquid crystal display mode using such a liquid crystal material, there are a TN mode, an STN mode, an OCB mode, an ECB mode, and the like. The configuration of the present invention can be applied to not only these general display modes but also display modes utilizing nematic or chiral nematic.
[0029]
As described above, in the application of a gel formed by a liquid crystal composition comprising a liquid crystal substance forming a nematic liquid crystal and a gelling agent for gelling the same to a display element, a polymer dispersion type liquid crystal may be used. In order to use optical switching between the scattering state and the transparent state, or optical rotation or birefringence such as TN type and STN type, a gel (liquid crystal gel) having liquid crystallinity in the operating temperature range. It is necessary to be. However, since the liquid crystalline composition in the gel state, that is, the liquid crystal gel, secures the long-term stability of the network structure by losing its fluidity, the liquid crystalline composition is subjected to strong mechanical impact or the like. The network structure may collapse. When the network structure of the liquid crystal gel collapses, the liquid crystal gel is once heated to a sol state (a state in which the network structure due to the gelling agent has disappeared and is mixed with the liquid crystal) in order to repair the network structure. Thereafter, it is necessary to make the liquid crystal gel state stable again by cooling. Therefore, the relationship between the two phase transition temperatures (nematic liquid crystal-isotropic liquid phase transition point and sol-gel phase transition point) of this liquid crystalline composition becomes important. Relationship between a nematic liquid crystal-isotropic liquid phase transition point (hereinafter, referred to as “Tni”) and a sol-gel phase transition point (hereinafter, referred to as “Tsg”), and the liquid crystal composition thereof The change of the phase series from the low temperature side of
(1) When Tni <Tsg Crystal-liquid crystal gel-isotropic gel-isotropic sol
(2) When Tni> Tsg Crystal-liquid crystal gel-liquid crystal sol-isotropic sol
Becomes
[0030]
The operating temperature range of the liquid crystal display element needs to be included in the temperature range showing the liquid crystal gel. Here, in the case of the above (1), that is, in the case where the liquid crystal gel composition in which the Tni is lower than Tsg is used as the light control layer, in order to repair the generated defect, the gel network structure is required. It is necessary to heat the liquid crystal gel composition to a temperature at which an isotropic sol state, which disappears once. In the case of the above (2), that is, when Tni is higher than Tsg, the liquid crystal gel composition is similarly heated until it becomes a liquid crystal sol state. In these two cases, the liquid crystal sol and the isotropic sol are the same in the sol state, but there is a difference whether the system has liquid crystallinity or isotropic. It has been found that this has a different effect on the deterioration of the liquid crystal display device.
[0031]
The liquid crystalline composition in the cell of the liquid crystal display element is in contact with constituent materials such as an alignment agent, a gap material, a sealant, and a substrate material. These constituent materials are of course sufficiently purified, but contain some impurities. Since the liquid crystal composition also has an aspect as an organic solvent, the higher the temperature is, the higher the solubility of the impurities becomes. Also, at the same temperature, when the liquid crystalline composition is in an isotropic liquid phase, it readily dissolves impurities as compared to a liquid crystal phase, so that the display performance deteriorates sharply. It was found to be connected.
[0032]
From this, it can be understood that a configuration in which Tni is higher than Tsg in a liquid crystal display element using a liquid crystal gel for the light control layer is effective in suppressing display deterioration in defect repair.
[0033]
The gelling agent is important in order that a liquid crystalline composition in a gel state, that is, a defect repair of a liquid crystal gel can be performed by a simple process of heating to a sol state and then regenerating the liquid crystal gel by cooling thereafter. .
[0034]
The present inventors have proposed a gelling agent for a low-molecular compound having a property of gelling a substance by intermolecular hydrogen bonding and dissolving in a liquid crystal to be used (see Patent Document 6). The "low molecular weight compound" refers to a compound having no molecular weight distribution, and has a molecular weight of 2,000 or less, preferably 1,000 to 2,000. Such a gelling agent is a compound having a molecular weight of 2,000 or less, preferably 1,000 to 2,000, which dissolves the liquid crystal substance and gels the liquid crystal substance by intermolecular hydrogen bonding, so that the liquid crystal layer can be more easily formed. A liquid crystal display device having a compound that can be gelled by a process can be provided.
[0035]
Here, as a specific gelling agent, conditions on the molecular structure capable of forming an intermolecular hydrogen bond generally include an amide group (—NHCO—), an amino group (—NH—), and a carbonyl group ( Those having a combination with -CO-) are preferable, and in addition to these groups, there may be a carbamate group, a urea group, a carboxyl group, an alkoxy group, a phosphate group, a hydroxyl group, and the like. It was not limited. Further, among such gelling agents, in particular, compounds having two or more groups capable of intermolecular hydrogen bonding and two or more alkylene groups in one molecule are desirable, and the alkylene group has 4 or more carbon atoms, preferably Those having a long-chain structure of 6 to 20 (which may have branches) have higher solubility in liquid crystal substances. The gelling agent is preferably made of a compound having a chiral structure. As those compounds, specifically, those disclosed in Patent Documents 1 to 5 and JP-A-11-21556 can be used.
[0036]
However, in such a gelling agent (usually a crystalline solid at room temperature), there are few compounds having very good compatibility with the liquid crystal material, and the compound is miscible with the liquid crystal material during the production process of the liquid crystal composition. In many cases, a heating temperature of about 120 ° C. is required to perform the heating. It is also known that the gel structure has a fibrous structure having a certain length in a temperature range used as a liquid crystal display element. For this reason, at the beginning of gelation, the liquid crystal substance is incorporated into the network structure composed of the long gel structure and the fluidity is lost, but as the time elapses, the liquid crystal substance incorporated into the network structure gradually decreases. Oozing out. Exudation of the liquid crystal material causes unevenness in transmittance and refractive index of the liquid crystal composition and unevenness in response, which is a factor of deteriorating display quality. Furthermore, the dissolution rate of the gelling agent (the rate at which the hydrogen bond of the gelling agent breaks and dissolves in the liquid crystal) in the temperature range where the liquid crystal sol state should be higher than the sol-gel phase transition temperature when the liquid crystal gel is repaired is determined. Because of the slowness, it is necessary to set a high temperature for mixing or to maintain a heated state for a long time, so that the effect of suppressing deterioration during restoration may not be sufficiently exhibited.
[0037]
The present inventors have conducted further studies on a gelling agent to solve such a problem caused by the gelling agent of a low molecular compound, and as a result, have found that a gel of an organosiloxane having at least one hydrogen bonding site is obtained. It has been found that the use of the agent keeps a fine and stable liquid crystal gel structure, does not require high-temperature heating during production, and can maintain the temperature for the transition to the liquid crystal sol during repair in a short time.
[0038]
According to the present invention, the following effects can be obtained.
(1) In the present invention, the gel structure is refined by using an organosiloxane having a hydrogen bonding site as a gelling agent, so that the contact area between the gelling agent and the liquid crystal substance is increased, and therefore, the gelation The liquid crystal material is less likely to exude from the network structure of the agent, and thus the stability over time of the liquid crystal display element is improved.
(2) The organosiloxane (gelling agent) having an associative site in the present invention has a high solubility in a liquid crystal substance, and depends on the type of the liquid crystal substance, but is generally miscible with the liquid crystal substance at less than about 100 ° C. In addition, it is possible to provide a liquid crystal display device including a liquid crystal composition which can be manufactured with high energy efficiency because the heating temperature at the time of manufacturing the liquid crystal composition is low.
(3) In the present invention, since the gel structure is refined, the state of aggregation between the gelling agents becomes relatively sparse, so that the transition to the liquid crystal sol at the time of liquid crystal gel repair is at or above the sol-gel phase transition temperature. Even when the holding time is short, a uniform liquid crystal sol state can be easily obtained, so that a liquid crystal display element with less deterioration due to heating due to restoration can be provided.
[0039]
That is, according to the present invention, (a) a liquid crystal material forming a nematic liquid crystal, and (b) an organosiloxane having at least one hydrogen bonding site for gelling the liquid crystal material between at least one pair of substrates. And a liquid crystal display element containing a liquid crystal composition containing the liquid crystal composition, wherein the liquid crystal-isotropic liquid phase transition temperature of the liquid crystal composition is higher than its sol-gel phase transition temperature. Therefore, it is easy to repair defects in the liquid crystalline composition in the gel state, and it is possible to provide a liquid crystal display element with less deterioration due to heating at the time of repair and improved stability over time at low cost. .
[0040]
The hydrogen bonding site in the organosiloxane is represented by the following formula:
-NH-C * H (R) -CO- (1)
Or
-C * H (R) NHCO- (2)
(In the formula, R represents a monovalent organic group, and * represents an optically active site.)
Has a partial structure represented by
As described above, when the hydrogen bonding site in the organosiloxane has the above (1) or (2), the bonding between molecules is soft, the solubility is more excellent, and the electric field response of the liquid crystal material is improved. A liquid crystal display device including a liquid crystal composition which does not lower the liquid crystal composition can be provided.
[0041]
In general, the conditions for the molecular structure capable of forming an intermolecular hydrogen bond are preferably those having a combination of an amide group (—NHCO—) and an amino group (—NH—) and a carbonyl group (—CO—). In addition, there may be a carbamate group, a urea group, a carboxyl group, an alkoxy group, a phosphoric acid group and a hydroxyl group, and the number and position of these groups are not limited. Among such associative sites, those having an amino group, a carbonyl group and an alkyl group as shown in formulas (1) and (2) are particularly preferable.
[0042]
More specifically, Polymer Collection, Vol. 52, No. 12, P773 (1995), "Development of Oil Gelling Agent and Elucidation of Gelation Mechanism", and Polymer Processing, Vol. 45, No. 1, P21 (1996), "Oil Gelling Agent" Those having a structure of a gelling agent having optical activity to be obtained are preferable.
[0043]
Specifically, those having the following structures are preferable.
− (CH₂)_n-CONHCH (s-C₄H₉) CONHR₅
(Wherein, n is an integer of 2 to 18;₅  Is an alkyl group having 4 to 24 carbon atoms. )
− (CH₂)_n-CONHCH (i-C₃H₇) CONHCH (i-C₃H₇) CONCHHR₅
(Wherein, n is an integer of 2 to 18;₅  Is an alkyl group having 4 to 24 carbon atoms. )
[0044]
Embedded image

[0045]
Embedded image

(Where n, n₁  Is an integer of 2 to 18, and n₂  , N₃  Is an integer of 1 to 9. )
The organic group having an associative site is a methylene chain (—CH₂  )_n  It is preferable that the number of units is n ≧ 4 from the viewpoint of not hindering the movement of the polymer chain or hindering the assembly.
[0046]
The organosiloxane of the present invention has the following formula:
Embedded image

(Where R₁~ R₅And X, Y, and Z are the same or different monovalent organic groups, and at least one of X, Y, and Z is a monovalent organic group having optical activity and having at least one hydrogen bonding site. is there. Further, n, m and l are natural numbers. )
It is shown by.
As described above, when the organosiloxane is represented by the formula (3), a liquid crystal display device including a liquid crystal composition in which a network structure is effectively formed by hydrogen bonding (stable gel structure) is obtained. Therefore, it is possible to provide a liquid crystal display element in which defect repair is easy and deterioration due to heating during repair is small.
[0047]
The organosiloxane having an optical activity and a hydrogen bonding site used in the present invention has a structure represented by the formula (3), and the hydrogen bonding site is represented by X, Y, Z in the formula. Are present in at least one of the sites represented by This hydrogen bonding site preferably has a structure represented by the above formulas (1) and (2). This hydrogen bonding site may be introduced into the side chain or terminal of the siloxane bond, or may be introduced into both the side chain and the terminal. When the hydrogen bonding site is present at a plurality of positions among X, Y and Z, it is preferable that they have the same structure. Further, m and n represent R in the side chain.₁  And R₄  And a side chain with R₂  Represents the abundance ratio in the molecule of the unit structure having the formula and Z. The order of bonding in the molecule may be either continuous polymerization (block copolymerization) or random polymerization. May be.
[0048]
More preferably, R₁  ~ R₅  And X, Y, and Z that are not hydrogen-bonding sites may be the same or different, and are H or an alkyl group having 1 to 4 carbon atoms or a phenyl group. Further, in the organic group attached to Si in the siloxane bond, when the hydrogen bonding site exists only as a side chain (when only Z of X, Y, and Z is hydrogen bonding), the hydrogen bonding site Z When the ratio is low, the concentration of the hydrogen-bonding organosiloxane in the liquid crystal composition is increased to cause the association, but the high concentration of the associative compound becomes a factor that lowers the transmittance and the responsiveness of the liquid crystal composition. Cheap. Therefore, preferably, the ratio n / (m + n), which is the ratio of the associative site Z, is set to 0.3 or more to form an associative structure sufficient for incorporating a liquid crystal substance by adding a small amount of the associative compound. Can be. More preferably, the object of the present invention can be more effectively achieved by setting n / (m + n) to 0.5 or more. When two or more of X, Y and Z are organic groups having a hydrogen bonding site, it is more preferable that they are the same group.
[0049]
When the molecular weight of the hydrogen-bonding organosiloxane is 2,000 or more, a liquid crystal display device including a liquid crystal composition having a more stable association structure can be provided. If the molecular weight of the associative compound is small, the amorphous property of the polymer chain portion is easily lost, and the formed aggregate structure is likely to be coarse, and the stability of the associated structure is also easily impaired. . However, when the molecular weight is 2,000 or more, the aggregate structure is stable, and it is advantageous in energy in the production process and is industrially easy to handle. More preferably, the molecular weight of the hydrogen bonding organosiloxane is 2000 or more. The number of repeating units of the molecular chain of the organosiloxane {(m + n) × l} as represented by the symbol in Formula 2 is preferably 5 or more. A value of 10 or more is more preferable.
[0050]
According to the gelling agent of the present invention, liquid crystals can be gelled by adding 0.05 to 1.0% by weight to the liquid crystal substance. The optimum value of the content of the gelling agent in the liquid crystal composition 4 varies depending on the type of the liquid crystal and the gelling agent, but preferably, the range in which the liquid crystal composition 4 is transparent to visible light in a liquid crystal gel state. That is, it is in a range where the liquid crystal does not scatter visible light. The content of the organosiloxane gelling agent having at least one hydrogen bonding site in such a liquid crystal composition 4 is in a range that is transparent to visible light in a liquid crystal gel state, and preferably 0.1 to 0.1. It is from 0.05 to 1.0% by weight, and more preferably from 0.05 to 0.5% by weight. As described above, the content of the gelling agent in the liquid crystal composition 4 is within a range in which the liquid crystal composition 4 is transparent to visible light in a liquid crystal gel state, and therefore, the liquid crystal display element with few display defects Can be provided.
[0051]
2. Description of the Related Art Liquid crystal display elements are used in various fields because they are thin, light, and excellent in power saving. A liquid crystal display element is used as a display element of a portable electronic device, which is a device that fully utilizes its features. A liquid crystal display element generally has a configuration in which a liquid crystal composition is sandwiched between two glass substrates, but when the substrate is made of a plastic film, it can be made thinner and lighter. Further, since the shock resistance can be improved, it is particularly suitable for a display element of a portable electronic device.
[0052]
The substrates 1, 1 in the present invention are plastic films of 250 μm or less. Conventionally, when a liquid crystal display device was manufactured using a plastic film as a substrate, alignment defects and structural defects sometimes occurred due to local mechanical pressure and the like. However, as shown in FIGS. According to the liquid crystal display element 10 of the above, since the liquid crystal-isotropic liquid phase transition temperature of the liquid crystalline composition 4 is higher than its sol-gel phase transition temperature, the substrate 1 is made of a plastic film having a thickness of 250 μm or less. Even in this case, the defect can be easily repaired, and the deterioration due to heating at the time of repairing is small. When a plastic film is used as the substrate 1, the substrate 1 has a low heat resistance. Therefore, a process of baking and curing the constituent materials of the liquid crystal display element such as an alignment agent, a gap material, and a sealant at a low temperature. Will be adopted. The plastic substrate has a greater amount of impurities eluted from the constituent materials of the liquid crystal display device such as an alignment agent, a gap material, and a sealant than when glass is used as the substrate, but according to the liquid crystal display device 10 of the present invention, Since the liquid crystal-isotropic liquid phase transition temperature of the liquid crystal composition 4 is higher than its sol-gel phase transition temperature, elution of impurities can be reduced when such a plastic substrate is used.
[0053]
Conventionally, the introduction of a liquid crystal substance between both substrates in a liquid crystal display element has generally been performed by a reduced pressure injection method. That is, conventionally, the gelled liquid crystal composition was heated to a temperature higher than the solization temperature to be in a liquid state and injected under reduced pressure between the substrates. In this case, the injection of the liquid crystal composition was not performed. Until the termination, the liquid crystalline composition needs to be kept in a sol state, so that it is necessary to heat the injection dish, the substrate, and the like. Such an operation is disadvantageous in terms of energy, requires a heating device and the like, and also complicates the control thereof, which causes a decrease in productivity.
[0054]
On the other hand, in the present invention, (a) a liquid crystal substance forming a nematic liquid crystal and (b) at least one hydrogen bonding site for gelling the liquid crystal substance are provided between at least one pair of substrates 1 and 1. In a method for manufacturing a liquid crystal display element 10 in which a liquid crystal composition 4 containing a gelling agent comprising an organosiloxane having at least one part is encapsulated, the surface of at least one of the substrates 1, 1 in contact with the liquid crystal material is previously coated on the surface. After forming the application portion 5 of the gelling agent for gelling the liquid crystal material, the liquid crystal material is injected between the pair of substrates 1 and 1. In order to form a coating portion 5 of a gelling agent for gelling the liquid crystal substance on the surface of at least one of the substrates 1, 1, the gelling agent is dissolved in a solvent, and the solution is placed on at least one of the substrates 1, 1. Apply and dry. For applying the gelling agent, conventionally known means such as spin coating, dip coating, flexographic printing, and dispenser coating can be used. In order to dispose the gelling agent at a predetermined site, means such as flexographic printing or dispenser application is desirable.
[0055]
According to the present invention, after a coating portion 5 of a gelling agent for gelling the liquid crystal material is formed on the surface of at least one of the substrates 1 and 1 in contact with the liquid crystal material, the liquid crystal material is added to the pair of substrates 1 and 1. , 1 so that it is not necessary to overheat at the time of injection under reduced pressure, it is not necessary to perform complicated temperature control, and the conventional apparatus can be used as it is. Therefore, according to the present invention, a more uniform display having the gel-like liquid crystalline composition 4 in the dimming layer can be performed, and a liquid crystal display device that facilitates defect repair can be efficiently manufactured at low cost. .
[0056]
In the present invention, the application portion 5 of the gelling agent is formed at a portion separated from the liquid crystal substance injection portion 6. As described above, when the gelling agent application portion 5 is formed at a portion remote from the liquid crystal material injection portion 6, the liquid crystal material is not hindered from flowing into the liquid crystal by the gelling agent when the liquid crystal material is injected. It is possible to manufacture a stable liquid crystal display element without variation or the like.
[0057]
Further, in the present invention, the liquid crystal substance is injected at a temperature at which the gelling agent does not mix with the liquid crystal substance. By injecting the liquid crystal material at a temperature at which the gelling agent is immiscible with the liquid crystal material, a liquid crystal display device capable of uniform display can be manufactured. That is, in the present invention, the organosiloxane gelling agent having at least one hydrogen bonding site is immiscible with the liquid crystal substance at a temperature at which the liquid crystal substance is injected between the substrates. As described above, the liquid crystal material injected between the pair of substrates 1 and 1 is subjected to a heat treatment so that the gelling agent is mixed with the liquid crystal material to form a liquid crystal composition 4. By cooling 4, a mixing temperature can be lowered, and a liquid crystal display element with a short heating time, less deterioration of the liquid crystal composition, and less display defects can be manufactured.
[0058]
The meaning that "the gelling agent does not mix with the liquid crystal substance" means that it is only necessary to avoid the mixing of the predetermined liquid crystal substance within the injection time, but does not mean that it does not mix at all at the temperature. If the gelling agent is miscible with the liquid crystal substance, the gelling agent disposed on the substrates 1 and 1 starts gelation at the same time as the liquid crystal is injected. May move with the injection of the liquid crystal, and the concentration of the gelling agent may be non-uniform on the substrate. A display element manufactured in such a case cannot provide uniform display. In order to prevent this phenomenon, it is necessary to select a combination of a gelling agent and a liquid crystal that does not cause miscibility.
[0059]
In the present invention, the liquid crystal material injected between the pair of substrates 1 and 1 is subjected to a heat treatment, and the gelling agent is mixed with the liquid crystal material to form a liquid crystal composition. Cool the neutral composition. In this way, the liquid crystal material injected between the pair of substrates 1 and 1 is subjected to a heat treatment, and the gelling agent is mixed with the liquid crystal material to form a liquid crystal composition. When the composition is cooled, a liquid crystal display element with few display defects can be manufactured in a short time, and a display defect in the liquid crystal display element can be repaired.
[0060]
When the mixture is heated after enclosing the liquid crystal substance and the gelling agent between the substrates 1, 1, a uniform isotropic solution is obtained. According to the present invention, by cooling such an isotropic solution, a gel-like liquid crystalline composition having optically liquid crystal anisotropy, that is, a liquid crystal gel can be obtained. Such a liquid crystal gel has excellent long-term stability by having a hydrogen bonding network structure. Therefore, after the injection of the liquid crystal material is completed, the temperature is once heated to a temperature higher than the sol-gel phase transition temperature and then cooled to a temperature lower than the gelation temperature so that the gelling agent dissolves in the liquid crystal material. By doing so, a liquid crystal display element with few display defects can be provided in a short time. In addition, since the gel-like liquid crystalline composition thus formed has a network structure of a hydrogen bond, “the hydrogen bond is cut off or a network is formed again in response to a stimulus such as heat”. Such a structural change can be caused reversibly. That is, the gel-like liquid crystalline composition is returned to the isotropic solution by heating again, and the isotropic solution is cooled again to form a liquid crystal gel, so that a display defect in the liquid crystal display element can be repaired. It becomes possible. Furthermore, the gel-like liquid crystalline composition produced in the present invention changes its orientation in accordance with the change in electric field strength, and shows a clear electric field response.
[0061]
Generally, when a liquid crystal display element is manufactured by injection under reduced pressure, a gap material is used to keep the distance between substrates constant. This gap material is present on at least one of the substrates before the two substrates are bonded. Examples of the method of arranging the gap material include dry spraying, wet spraying, and screen printing. The dry spraying is to spray a gap agent directly onto a substrate, and the wet spraying is to spray a dispersion of a gap material in a solvent onto a substrate. Further, when the gap material is sprayed on the substrate on which the gelling agent is disposed in the above-described manner, the adhesion state of the gap material differs depending on the presence or absence of the gelling agent. As a result, the gap material in the plane of the substrate is consequently formed. Uniform arrangement is not possible. Furthermore, when a gap material is arranged on a substrate on which a gelling agent is arranged by screen printing, the screen plate and the gelling agent come into contact during printing, and the gelling agent is transferred to the screen plate. As a result, a liquid crystal gel having a predetermined gelling agent concentration cannot be formed, and an element having desired performance cannot be produced. However, according to the present invention, the gap material is provided on one substrate 1 provided with the electrodes 2, and the application portion 5 of the gelling agent is disposed on the other substrate 1, and these are adhered. Therefore, the gap material can be arranged uniformly between the bonded substrates 1 1 and 1, and the liquid crystal display element 10 2 having no unevenness can be manufactured.
[0062]
As the sealant 3 used in the present invention, a material conventionally used for a liquid crystal display element, specifically, a photocurable acrylic resin, an epoxy resin, or the like can be used. Further, as the substrate used in the present invention, a transparent material conventionally used as a substrate of a liquid crystal display element can be used. Any of a rigid material such as glass and a flexible material such as a plastic film can be used.
[0063]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.
[0064]
(Example 1)
(1) An ITO electrode layer was formed on a pair of glass substrates each having a size of 30 mm × 40 mm, and then polyimide was laminated as an alignment treatment film, and the surfaces thereof were rubbed. Then, one of these substrates is coated with an amine-cured epoxy resin as a sealant by a dispenser, and silica beads having a particle size of 5 μm are dispersed in an isopropyl alcohol solvent to about 100 / mm.²  Sprayed at a density of These two substrates were bonded together with a sealant so that their rubbing directions were antiparallel to each other, and were fixed and cured to produce a cell.
(2) As a gelling agent, the following formula
Embedded image

Was prepared, and as a liquid crystal, a nematic liquid crystal (LC1) having a Tni of 83 ° C. was prepared. Then, a mixture obtained by mixing these was left in an oven at 100 ° C. for 10 minutes to prepare a liquid crystal composition in which a nematic liquid crystal substance and a gelling agent were sufficiently mixed in an isotropic liquid state. The gelling agent concentration of this liquid crystalline composition was adjusted to 1.0% by weight. The Tni of the liquid crystal composition was about 82 ° C., which was almost the same as the Tni of the liquid crystal substance alone. Its Tsg was 68 ° C.
(3) The cell was transferred to a liquid crystal injection vacuum apparatus, and after reducing the pressure to 0.002 Torr, the liquid crystal injection port of the cell was attached to the liquid crystal dish and the outside of the cell was returned to normal pressure. Injected into the cell. The liquid crystal composition was injected into the cell by heating the cell and the liquid crystal dish to 75 ° C., which is a liquid crystal sol.
(4) After injecting the liquid crystal composition in this way, the injection port of the liquid crystal composition is closed with a sealing agent and cured to obtain a liquid crystal display element having the gel liquid crystal composition. .
[0065]
In the liquid crystal display device thus obtained, the gel-like liquid crystal portion is transparent to visible light (transmittance of about 87%), and when observed under crossed Nicols of a polarizing plate, the liquid crystal has a uniform homogeneous alignment. I was able to confirm that. When an AC voltage of 5 V and 64 Hz was applied to the liquid crystal cell, the liquid crystal uniformly operated normally. Next, the test of pressing the cell surface with an 11φ iron ball was repeated. In this test, when a defect occurred due to the disorder of the liquid crystal orientation, the liquid crystal element was heated to a liquid crystal sol state at 75 ° C., held for 2 minutes, and then cooled to room temperature. Returned to a normal state. This defect repairing operation was repeated 300 times, but no change was observed in the appearance and electric field response characteristics of the liquid crystal element.
[0066]
(Example 2)
(1) In the same manner as in Example 1, a cell was manufactured using a glass substrate having a size of 30 mm × 40 mm as the substrate.
(2) A nematic liquid crystal (LC2) having a Tni of 35.2 ° C. and a gelling agent (G1) are mixed, and the mixture is allowed to stand in an oven at 120 ° C. for 30 minutes. A liquid crystal composition sufficiently mixed was prepared, and the gelling agent concentration of the liquid crystal composition was adjusted to 0.2 mol%. The Tni of this liquid crystalline composition was about 35 ° C., which was almost the same as the transition point of the liquid crystal substance alone. Tsg was 80 ° C.
(3) The cell was transferred to a vacuum apparatus for injecting liquid crystal, and after the pressure was reduced to 0.002 Torr, the liquid crystal injection port of the cell was attached to the liquid crystal dish, and the outside of the cell was returned to normal pressure. Introduced. The liquid crystal composition was injected into the cell by heating the cell and the liquid crystal dish to 85 ° C., which is an isotropic sol state.
(4) After the liquid crystal composition was injected into the cell as described above, the injection port was closed with a sealing agent and cured to obtain a liquid crystal display device in which the gel liquid crystal composition was present.
[0067]
In the liquid crystal display device thus obtained, the gel-like liquid crystal part is transparent to visible light, and when observed under crossed Nicols of the polarizing plate, it can be confirmed that the liquid crystal has a uniform homogeneous orientation. Was. When an AC voltage of 5 V and 64 Hz was applied to the liquid crystal cell, the liquid crystal uniformly operated normally. Next, the test of pressing the cell surface with an 11φ iron ball was repeated. In this test, when a defect occurred due to the disorder of the liquid crystal alignment, the liquid crystal element was heated to a liquid crystal sol state at 75 ° C., held for 2 minutes, and then cooled to room temperature. Returned to a normal state. This defect repairing operation was repeated 300 times, but no change was observed in the appearance and electric field response characteristics of the liquid crystal element. However, in the electric field response characteristics, the operating voltage increased significantly. When the impedance of this cell was measured, it was found that the specific resistance of the liquid crystalline composition layer was lowered. This suggests that some impurities were mixed in the liquid crystal composition layer.
[0068]
(Example 3)
In Example 1, a cell was produced using a polyethersulfone sheet (PES: manufactured by Sumitomo Bakelite, 150 μm in thickness) having ITO on the surface instead of a glass substrate having a size of 30 mm × 40 mm. Materials and configurations such as a nematic liquid crystal (LC1) and a gelling agent (G1) were the same as in Example 1. The same pressing test as in Example 1 was performed on this cell, and the defect repair operation was repeated. The number of repetitions was 300. After the test, a change in appearance such as a dent mark was observed in a part of the pressed portion on the film substrate surface (a level that was not a problem in display characteristics), but no change was observed in the electric field response characteristics. Was.
[0069]
(Example 4)
(1) An ITO electrode layer was formed on a substrate made of a pair of glasses each having a size of 30 mm × 40 mm, and polyimide was laminated as an alignment treatment film, and then their surfaces were rubbed. One of these substrates was prepared by dissolving G1 in a solvent as a gelling agent in a fixed amount on a portion shown in FIG. 2 with a dispenser and dried. Then, the inside of the amine-cured epoxy resin was applied as a sealant by a dispenser to the outside of the portion where the gelling agent was applied. Next, silica beads having a particle diameter of 5 μm were dispersed in an isopropyl alcohol solvent on the other one of the substrates, so that about 100 beads / mm.²  Sprayed at a density of The two substrates were bonded and fixed and cured so that the rubbing directions were antiparallel to each other, thereby producing a cell.
(2) The cell thus prepared was transferred to a liquid crystal injection vacuum device, and after reducing the pressure to 0.002 Torr, the liquid crystal injection hole was attached to the liquid crystal dish and the outside of the cell was returned to normal pressure, and the liquid crystal material (LC1) Was introduced into the cell.
(3) After injecting the liquid crystal material (LC1) into the cell as described above, the injection port was closed with a sealing agent and cured to obtain a liquid crystal display element.
[0070]
In this liquid crystal display element, the gelling agent and the liquid crystal material are dissolved by heating to 80 ° C. to form a liquid crystal sol, and then cooled to room temperature to obtain a liquid crystal display element having a gel-like liquid crystalline composition. Was completed. The applied amount of the gelling agent was adjusted so that the concentration of the gelling agent in this liquid crystalline composition was 1.0% by weight, and thus the obtained liquid crystal display device was manufactured in Example 1. The properties were equivalent to those of the test pieces, and the results of the defect repair test were also the same.
[0071]
(Example 5)
In Example 4, a similar cell was manufactured using a polyethersulfone sheet (PES: manufactured by Sumitomo Bakelite, 150 μm in thickness) having ITO on the surface instead of a glass substrate having a size of 30 mm × 40 mm. The cell manufactured in this manner was equivalent to the cell manufactured in Example 3, and no difference in characteristics was observed.
[0072]
【The invention's effect】
(1) According to the first aspect of the present invention, (a) a liquid crystal substance forming a nematic liquid crystal and (b) at least a hydrogen bonding site for gelling the liquid crystal substance are provided between at least a pair of substrates. A gelling agent comprising one or more organosiloxanes, wherein the liquid crystal composition contains a liquid crystal composition, and the liquid crystal composition has a liquid crystal-isotropic liquid phase transition temperature of the sol-gel phase. Since the temperature is higher than the transition temperature, it is easy to repair defects in the liquid crystalline composition in the gel state, and the deterioration due to heating during the repair is further reduced. Can be provided at cost.
[0073]
(2) According to the invention described in claim 2, since the hydrogen bonding site in the organosiloxane has the above (1) or (2), the bonding between molecules is soft and the solubility is higher. A liquid crystal display device including a liquid crystal composition which is excellent and does not lower the electric field response of the liquid crystal material can be provided.
(3) According to the invention described in claim 3, since the organosiloxane is represented by the formula (3), a network structure is effectively formed by hydrogen bonding (stable gel structure). A liquid crystal display device including a liquid crystal composition can be provided. Therefore, it is possible to provide a liquid crystal display device in which defect repair is easy and deterioration due to heating during repair is small.
[0074]
(4) According to the invention as set forth in claims 4 and 5, the content of the organosiloxane gelling agent is in a range in which the liquid crystal gel state is transparent to visible light, preferably 0.05 to 1. Since the content is 0.0% by weight, a liquid crystal display element with less display defects can be provided.
(5) According to the invention described in claim 6, since the liquid crystal composition has a liquid crystal-isotropic liquid phase transition temperature higher than its sol-gel phase transition temperature, the substrate is made of a plastic film having a thickness of 250 μm or less. Even if it is configured, the defect can be easily repaired, and the deterioration due to heating at the time of repairing is small.
[0075]
(6) According to the invention described in claim 7, after a coating portion of a gelling agent for gelling the liquid crystal material is formed on at least one surface of the substrate in contact with the liquid crystal material, the liquid crystal material is formed. Is injected between a pair of substrates, so that overheating is not required at the time of vacuum injection, complicated temperature control is not required, and a conventional apparatus can be used as it is.
(7) According to the invention as set forth in claim 8, since the application portion of the gelling agent is formed at a portion remote from the injection portion of the liquid crystal substance, the inflow of the liquid crystal by the gelling agent during the injection of the liquid crystal material. There is no hindrance, and therefore, a stable liquid crystal display element having no variation in injection time can be manufactured.
[0076]
(8) According to the ninth aspect of the present invention, the liquid crystal material is injected at a temperature at which the gelling agent is not mixed with the liquid crystal material, so that a liquid crystal display device capable of uniform display can be manufactured. .
(9) According to the invention as set forth in claim 10, the liquid crystal material injected between the pair of substrates is subjected to a heat treatment, and the gelling agent is mixed with the liquid crystal material, whereby the liquid crystal composition is obtained. After the liquid crystal composition is cooled, a liquid crystal display element with less display defects can be manufactured in a short time, and a display defect in the liquid crystal display element can be repaired.
[0077]
(10) According to the invention as set forth in claim 11, the gap material is provided on one substrate, and the application portion of the gelling agent is formed on the other substrate, and these are bonded together. In addition, a gap material can be uniformly arranged between the bonded substrates, and a liquid crystal display element without unevenness can be manufactured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquid crystal display element according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line AA of FIG.
[Explanation of symbols]
1 substrate
2 electrodes
3 Sealant
4 Liquid crystal composition
5 Application part of gelling agent
6. Injection part of liquid crystal substance
10 Liquid crystal display device

Claims (11)

(A) a liquid crystal material forming a nematic liquid crystal, and (b) a gelling agent comprising an organosiloxane having at least one hydrogen bonding site for gelling the liquid crystal material, between at least a pair of substrates. What is claimed is: 1. A liquid crystal display device containing a liquid crystal composition, wherein the liquid crystal composition has a liquid crystal-isotropic liquid phase transition temperature higher than its sol-gel phase transition temperature. The hydrogen bonding site has the following formula: -NH-C * H (R) -CO- (1)
Or -C * H (R) NHCO- (2)
(In the formula, R represents a monovalent organic group, and * represents an optically active site.)
The liquid crystal display device according to claim 1, having a partial structure represented by the following formula. The organosiloxane has the following formula:

(Wherein, R _{1 to} R ₅ and X, Y, and Z are the same or different monovalent organic groups, and at least one of X, Y, and Z has optical activity and has at least one hydrogen bonding site. It is a monovalent organic group having at least three positions, and n, m and l are natural numbers.)
The liquid crystal display device according to claim 1, wherein: The liquid crystal display according to any one of claims 1 to 3, wherein the content of the gelling agent is in a range where the liquid crystalline composition is transparent to visible light in a liquid crystal gel state. element. The liquid crystal display device according to claim 4, wherein the content of the gelling agent is 0.05 to 1.0% by weight based on the liquid crystal material. The liquid crystal display device according to any one of claims 1 to 5, wherein the substrate is a plastic substrate having a thickness of 250 µm or less. (A) a liquid crystal material forming a nematic liquid crystal, and (b) a gelling agent comprising an organosiloxane having at least one hydrogen bonding site for gelling the liquid crystal material, between at least a pair of substrates. In a method for manufacturing a liquid crystal display device containing a liquid crystal composition containing the liquid crystal material, a coating portion of a gelling agent for gelling the liquid crystal material is formed on at least one substrate surface in contact with the liquid crystal material, and then the liquid crystal is formed. A method for manufacturing a liquid crystal display element, comprising injecting a substance between a pair of substrates. 8. The method according to claim 7, wherein the application portion of the gelling agent is formed at a portion away from the injection portion of the liquid crystal material. 9. The method according to claim 7, wherein the liquid crystal material is injected at a temperature at which the gelling agent does not mix with the liquid crystal material. The liquid crystal material injected between the pair of substrates is subjected to a heat treatment, and the gelling agent is mixed with the liquid crystal material to form a liquid crystal composition, and then the liquid crystal composition is cooled. The method for manufacturing a liquid crystal display device according to claim 7. The liquid crystal according to any one of claims 7 to 10, wherein a gap material is provided on one of the substrates, and a coating portion of the gelling agent is formed on the other substrate, and these are adhered to each other. A method for manufacturing a display element.

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