JP3780082B2 - Active matrix liquid crystal display device - Google Patents

Description

で示すテトラカルボン酸二無水物からなるポリアミック酸の脱水閉環した有機高分子であり、その繰り返し構造の中のＲ及びＸに、−Ｏ−，−Ｓ−，−ＣＨ ₂ − , −Ｃ ( ＣＨ ₃ ) ₂ −，−Ｃ ( ＣＦ ₃ ) ₂ −，−ＳＯ ₂ − が合わせて３個以下の有機高分子であるアクティブマトリクス型液晶表示装置の構成を採る。
【００１１】
また上記構成において、前記配向制御膜表面のガラス転移温度Ｔｇが前記液晶層を形成する液晶組成物のネマティック−等方相転移温度Ｔ（Ｎ−Ｉ）以上であるアクティブマトリクス型液晶表示装置の構成を採る。
【００１２】
また上記構成において、前記配向制御膜と前記液晶層との界面における液晶分子に対する前記配向制御膜の表面のねじれ結合係数Ａ２が２０μＮ／ｍ以下であるアクティブマトリクス型液晶表示装置の構成を採る。
【００１３】
また上記構成において、前記一対の偏光板は、前記液晶層の屈折異方性をΔｎ、厚さをｄとしたときのパラメータｄ・Δｎが０ . ２μｍ＜ｄ・Δｎ＜０ . ５μｍを満たすアクティブマトリクス型液晶表示装置の構成を採る。
【００１４】
また上記構成において、前記有機高分子の重量平均分子量が１０ , ０００ 以上〜
３００ , ０００ 以下であるアクティブマトリクス型液晶表示装置の構成を採る。
【００１５】
また上記構成において、前記配向制御膜は光反応性材料層であるアクティブマトリクス型液晶表示装置の構成を採る。
【００１６】
また上記構成において、前記光反応性材料層は偏光を照射することにより前記液晶層の配向方向を制御するアクティブマトリクス型液晶表示装置の構成を採る。
【００１７】
また上記構成において、前記光反応性材料層は少なくとも１種類以上のジアゾベンゼン基またはその誘導体を含むポリマー及び／またはオリゴマを含有する有機高分子を含むアクティブマトリクス型液晶表示装置の構成を採る。
【００１８】
【発明の実施の形態】
まず、本発明の前提となる横電界方式の動作原理を図１を例に用いて説明する。図１（ａ),（ｂ）は横電界方式の液晶素子１画素内での液晶の動作を示す側断面を、図１（ｃ),（ｄ）はその正面図を表す。
【００１９】
電圧無印加時のセル側断面を図１（ａ）に、その時の正面図を図１（ｃ）に示す。一方の基板の内側に線状電極１，４が形成され、基板表面は対となる基板の双方とも配向膜５となっており、基板間には液晶組成物が挟持されている（この例ではその誘電異方性は正と仮定しているが、負の液晶組成物では液晶分子の長軸と短軸の方向を入れ換えるだけで横電界方式は同様に実現可能である）。
【００２０】
棒状の液晶分子６は、配向膜５との結合により両基板界面において共に電極１，４長手方向（図１（ｃ）正面図）に若干の角度をもつ方向１０の向きに配向制御されており、電界無印加時には液晶層内ではほぼ一様にこの初期配向方向を向いた状態となっている。ここで、画素電極４と共通電極１のそれぞれに異なる電位を与え、それらの間の電位差により液晶組成物層に電界９を印加すると、液晶組成物が持つ誘電異方性と電界との相互作用により図１（ｂ),（ｄ）に示したように液晶分子は電界方向にその向きを変える。このとき液晶組成物層の屈折異方性と偏光版８の作用により本液晶素子の光学特性が変化し、この変化により表示を行う。
【００２１】
図２は、横電界方式の液晶表示装置の電極間の印加電圧とその表示輝度との関係を模式的に示したグラフである。図２（ａ）の実線は初期の基本特性を示しており、（ｂ）の点線は典型的な残像（ＩＰＳ残像）を示す場合の電圧・輝度特性曲線を示している。このように残像，画像の焼き付け現象は、人間の視感度上、敏感な暗レベル又は中間調領域で顕著な輝度変動を示している。
【００２２】
ここで、残像現象のメカニズムについて考察する。
【００２３】
前記の配向膜と液晶分子の結合による配向規制力（結合力）は、配向膜材料やそのラビング処理条件等によって大きく異なることが知られているが、配向膜表面での液晶分子の配向変化の方向によっても異なる。表面にほぼ水平に配向した正の誘電率異方性を持つ液晶材料を考えると、電界印加により生じる基板表面の液晶分子の配向変化方向は、基板界面に対して電界がほぼ垂直に印加されるＴＮ方式では基板表面から立ち上がる方向（図３に示す極角方向）に、また基板界面に対して電界がほぼ平行に印加される横電界方式では基板面内方向（図３に示す面内のねじれ回転方向）となる。したがって、従来のＴＮ方式では液晶分子の極角方向の配向変化の戻り難さが画像の焼き付き，残像に対応し、またそれは上下の対電極付近に残留する直流電位に起因すると考えられている。一方、横電界方式では、画像の焼き付き，残像は基板面内方向の液晶分子のねじれ変形の戻り難さに相当する。また先に述べたように残像と画素電極近傍に残留する直流電位との相関が認められないことから、これは電気的な要因というよりはむしろ液晶／配向膜界面の相互作用に基づくと考えられる。
【００２４】
そこで本発明者らが鋭意検討した結果、横電界方式の画像の焼き付き，残像現象の発生は、電界印加による液晶分子の面内捻れ変形に基づき発生する回転トルクにより液晶分子の初期配向の方向１０を規制している配向膜表面が弾性変形し、その変形・クリープが高分子特有の（遅延弾性変形後の）弾性余効、すなわち残留した歪みとしてある有限の遅延時間とともに回復していく残像現象として、または永久変形としての画像の焼き付き現象として現れることが分かった。
【００２５】
したがって、このような残像現象の発生を低減する対策としては、（１）ツイスト弾性定数を小さな液晶組成物を用い面内捻れ変形による回転トルクの大きさを減少させること、または（２）配向膜の硬さ（弾性率）を増大させ、液晶分子の駆動による回転トルクの影響を受け難い高弾性高分子表面を形成することが有効である。さらには（３）液晶層の回転トルクが配向膜層に伝搬し難いように界面のねじれ結合の弱い状態を形成することが効果的である。
【００２６】
配向膜の高弾性率化を図るための具体策としては、配向膜を構成するポリマーの分子構造が剛直で直線性に富んだ構造であることが望ましく、また分子量をなるべく大きくするのが好ましい。さらには単分散系にするのが良い。また配向膜塗布・焼成硬化・ラビング配向処理後の光架橋反応により高次のネットワークを構築し力学的に強度を高めるのも良い。分子量を１０,０００ 以上に大きくすることによって、ポリマー鎖間の凝集力を増加させ弾性率の増加を図ることができる。しかし、一方で分子量が３００,０００ 以上に大きくなると、配向膜ワニスの融液状態でポリマー鎖の絡み合いが発生し、ポリマー鎖の密度の高いパッキングが妨げられることがある。
【００２７】
また高分子の分子軸の回転を可能にする結合基、−Ｏ−，−Ｓ−，−ＣＨ₂−,−Ｃ(ＣＨ₃)₂−，−ＳＯ₂− ，メタ結合，オルト結合が合わせて３個以下であることが望ましい。なぜならば、ポリマー主鎖間の拡散はほとんど起こらないが、上記のような結合基が多数存在すると分子軸回りの回転が容易となり局所的な熱運動が可能となるため、配向膜高分子の弾性率の低下を引き起こす結果となる。このような現象は弾性率の温度特性に現れる側鎖の副分散（Ｔｇ（ｂ））として知られている。また、従来のＴＮ方式に用いられる配向膜ではチルト角を制御するために直鎖アルキル基等の側鎖を導入する方法が用いられているが、横電界方式では視野角の広さを保持するためにも、また上記の観点からもチルト角を発生する直鎖アルキル基などの長鎖の枝分かれした側鎖官能基の少ないもの、またはかさ高い側鎖置換基を全く持たないポリマーが好適である。
【００２８】
またポリマー配向膜の弾性率は周囲の環境条件、特に温度により大きな影響を受けることが知られている。この観点から上記のような高弾性率配向膜の選定の指標として弾性率以外に配向膜高分子のガラス転移温度Ｔｇがある。このＴｇが高ければ高いほど配向膜の高い弾性率が保証されることになる。実際に用いる液晶セルでは配向膜と液晶の界面における界面Ｔｇと、用いる液晶のネマティック−等方相の転移温度Ｔ（Ｎ−Ｉ）の間に以下のような関係が考えられる。液晶の回転トルクの大きさは主に液晶のツイスト弾性定数Ｋ２に比例する。また液晶のツイスト弾性定数Ｋ２は液晶の温度上昇と共に徐々に低下し、ネマティック−等方相の相転移温度Ｔ（Ｎ−Ｉ）で急激に減少する。即ち、Ｔ（Ｎ−Ｉ）点以上では、液晶の回転トルクが非常に小さくなり、配向膜への応力負荷が著しく減少する。したがって、配向膜の表面または液晶層との界面近傍のガラス転移温度Ｔｇが液晶のＴ（Ｎ−Ｉ）温度よりも高い（Ｔｇ＞Ｔ（Ｎ−Ｉ））場合は、配向膜表面は非常に硬いガラス状態に近い状態として存在し、液晶の回転トルクによる弾性変形を受け難くなる。すなわち、横電界方式特有の残像（ＩＰＳ残像）が最小限に抑えられることになる。
【００２９】
以上のような観点から、本発明に用いる配向膜の合成材料であるアミン成分の化合物およびその他共重合可能な化合物は、例えば、芳香族ジアミンとしては、ｐ−フェニレンジアミン、ｍ−フェニレンジアミン、２，４−ジアミノトルエン、２，５−ジアミノトルエン、２，６−ジアミノトルエン、ジアミノデュレン、ベンジジン、Ｏ−トリジン、３，３−ジメトキシベンジジン、４，４″−ジアミノターフェニル、１，５−ジアミノナフタレン、２，７−ジアミノフルオレン、４，４′−ジアミノジフェニルエーテル、４，４′−ジアミノジフェニルスルフィド、４，４′−ジアミノジフェニルメタン、３，３′−ジメチル−４，４′−ジアミノジフェニルメタン、２，５−ジアミノピリジン、４，４′−ビス（ｐ−アミノフェノキシ）ビフェニル、２，２−ビス｛４−（ｐ−アミノフェノキシ）フェニル｝プロパン、２，２−ビス｛４−（ｐ−アミノフェノキシ）フェニル｝ヘキサフルオロプロパン、４，４′−ビス（ｍ−アミノフェノキシ）ジフェニルスルフォンなどが挙げられるが、これらに限定されるものではない。
【００３０】
一方、酸成分の化合物およびその他共重合可能な化合物は例えば、芳香族テトラカルボン酸二無水物としては、ピロメリット酸二無水物、メチル−ピロメリット酸二無水物、ジメチレントリメリテート酸二無水物、３，３′，４，４′−ベンゾフェノンテトラカルボン酸二無水物、３，３′，４，４′−ビフェニルテトラカルボン酸二無水物、ジメチレントリメリテート酸二無水物、２，３，６，７−ナフタレンテトラカルボン酸二無水物、３，３′，４，４′−ビフェニルスルホンテトラカルボン酸二無水物、３，３′，４，４′−ジフェニルエーテルテトラカルボン酸二無水物、３，３′，４，４′−ジフェニルメタンテトラカルボン酸二無水物、脂環式テトラカルボン酸二無水物としては、１，２，３，４−ブタンテトラカルボン酸二無水物、１，２，３，４−ビスシクロブタンテトラカルボン酸二無水物、１，２，３，４−シクロペンタンテトラカルボン酸二無水物、などが挙げられるが、これらに限定されるものではない。
【００３１】
また、溶剤については例えば極性を有するＮ−メチル−２−ピロリドン，ジメチルホルムアミド，ジメチルアセトアミド，ジメチルスルホキサイド，スルフォラン，ブチルラクトン，クレゾール，フェノール，シクロヘキサノン，ジメチルイミダゾリジノン，ジオキサン，テトラヒドロフラン，ブチルセルソルブ，ブチルセルソルブアセテート，アセトフェノンなどを用いることができる。
【００３２】
更に、有機高分子中に例えばγ−アミノプロピルトリエトキシシラン，δ−アミノプロピルメチルジエトキシシラン，Ｎ−β（アミノエチル）γ−アミノプロピルトリメトキシシランなどのアミノ系シランカップリング剤，エポキシ系シランカップリング剤，チタネートカップリング剤，アルミニウムアルコレート，アルミニウムキレート，ジルコニウムキレートなどの表面処理剤を混合もしくは反応することもできる。配向膜の形成は一般的なスピンコート，印刷，刷毛塗り，スプレー法などによって行うことができる。
【００３３】
用いる液晶としては、例えば４−置換フェニル−４′−置換シクロヘキサン，４−置換シクロヘキシル−４′−置換シクロヘキサン，４−置換フェニル−４′−置換ジシクロヘキサン，４−置換ジシクロヘキシル−４′−置換ジフェニル，４−置換−４″−置換ターフェニル，４−置換ビフェニル−４′−置換シクロヘキサン，２−（４−置換フェニル）−５−ピリミジン，２−（４−置換ジオキサン）−５−フェニル，４−置換安息香酸−４′−フェニルエステル，４−置換シクロヘキサンカルボン酸−４′−置換フェニルエステル，４−置換シクロヘキサンカルボン酸−４′−置換ビフェニルエステル，４−（４−置換シクロヘキサンカルボニルオキシ）安息香酸−４′−置換フェニルエステル，４−（４−置換シクロヘキシル）安息香酸−４′−置換フェニルエステル，４−（４−置換シクロヘキシル）安息香酸−４′−置換シクロヘキシルエステル，４−置換−４′−置換ビフェニル等を挙げることができ、これらの化合物の中でも、少なくても分子の一方の末端にアルキル基，アルコキシ基，アルコキシメチレン基，シアノ基，フッ素基，ジフッ素基，トリフッ素基を有する多成分系の混合液晶組成物が用いられる。
【００３４】
また、上記のようなラビング処理により配向制御をするポリイミド配向膜層ではなく、斜方蒸着法により配向能を持たせた無機配向膜を用いることにより解決することもできる。これにより、液晶組成物を昇温せず液晶相のまま注入しても配向むらが生じない程度の配向能が対基板の双方の基板表面上で得られ、また酸化シリコン等の無機材料の斜方蒸着により配向制御された表面の液晶分子については、一般的に用いられているラビング処理されたポリイミド配向膜上の液晶分子に較べて格段に弱いねじれ結合を示すことから、上記の弱いねじれ結合の効果により横電界方式特有の残像（ＩＰＳ残像）を低減することができる。
【００３５】
また、横電界方式の大きな利点の一つである広視野角特性は、基板表面における液晶分子のチルト角が小さいほど良好となり、チルト角が０°の時が理論的に最も広視野角となるが、ラビング処理により配向制御された有機配向膜の場合にはその表面上での液晶分子のチルト角を０°とすることが困難であるのに対して、酸化シリコン等の無機材料の斜方蒸着により配向制御された表面の液晶分子については、容易にチルト角をほぼ０°とすることが可能であることが知られており好都合である。
【００３６】
さらに、上記のような弱いねじれ結合を得るための別の配向膜材料として光反応性材料層、特に選択的に光化学反応を生じさせるように偏光光照射処理された光反応性配向膜を用いても良い。
【００３７】
光反応性配向膜は、従来一般的に、強いねじれ結合と十分な（数度以上）界面チルト角を付与することが困難とされてきた配向制御方法であるが、その弱いねじれ結合は本発明の実現に好都合であり、さらに横電界方式においては従来の
ＴＮ方式に代表される縦電界方式と異なり界面チルトが原理的に必要ないため、横電界方式との組み合わせにより量産性などの実用性を向上させることができる。
【００３８】
さらに、横電界方式においては、界面チルト角が小さいほど視角特性が良いことが知られており、上記の光反応性配向膜では界面チルト角が非常に小さな物となることは逆に好都合であり、良好な視角特性が期待できる。
【００３９】
また、このような光反応性の配向膜材料の中に光、または熱、または放射線の照射で硬化するポリマー前駆体を前もって混入させ、光配向処理と同時またはその前後に上記の硬化処理を行うことによって、光反応性配向膜の高弾性率化を可能とし横電界特有のＩＰＳ残像を更に低減することができる。また、上記のようなポリマー前駆体の混入以外の方法としては、光配向膜と基板の間に前記光配向膜よりも厚くかつ透明な有機高分子層を介在させ、配向膜全体の高弾性率化を図り、本発明の目的を達成することが可能である。
【００４０】
本発明を実施例により具体的に説明する。
【００４１】
（実施例１）
基板として、厚みが１.１mm で表面を研磨した透明なガラス基板を２枚用い、これらの基板のうち一方の基板の上に横電界が印加できる薄膜トランジスタおよび配線電極を形成し、更にその上の最表面に窒化シリコンからなる絶縁保護膜を形成した。薄膜トランジスタおよび各種電極の構造を図４に、基板面に垂直な方向から見た正面図と、正面図のＡ−Ａ′，Ｂ−Ｂ′における側断面図として示す。
【００４２】
薄膜トランジスタ素子１４は画素電極（ソース電極）４，信号電極（ドレイン電極）３，走査電極（ゲート電極）１２およびアモルファスシリコン１３から構成される。共通電極１と走査電極１２、および信号電極３と画素電極４とはそれぞれ同一の金属層をパターン化して構成した。
【００４３】
画素電極４は正面図において、３本の共通電極１の間に配置されている。
【００４４】
画素ピッチは横方向（すなわち信号電極３間）は１００μｍ、縦方向（すなわち走査電極１２間）は３００μｍである。
【００４５】
電極幅は、複数画素間にまたがる配線電極である走査電極，信号電極，共通電極配線部（走査配線電極に並行に延びた部分）を広めにし、線欠陥を回避した。
幅はそれぞれ１０μｍ，８μｍ，８μｍである。
【００４６】
一方、開口率向上のために１画素単位で独立に形成した画素電極、および共通電極の信号配線電極の長手方向に延びた部分の幅は若干狭くし、それぞれ５μｍ，６μｍとした。これらの電極の幅を狭くしたことで異物などの混入により断線する可能性が高まるが、この場合１画素の部分的欠落ですみ、線欠陥には至らない。
【００４７】
信号電極３と共通電極１は絶縁膜を介して２μｍの間隔を設けた。
【００４８】
画素数は、６４０×３（Ｒ，Ｇ，Ｂ）本の信号配線電極と、４８０本の配線電極とにより６４０×３×４８０個とした。
【００４９】
用いた配向膜は、ｐ−フェニレンジアミン１.０ モル％をＮ−メチル−２−ピロリドン中に溶解させ、これにピロメリット酸二無水物１モル％を加えて２０℃で１２時間反応させて、標準ポリスチレン換算重量平均分子量が約100,000 、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ）が約１.６ のポリアミック酸ワニスを得た。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して２１０℃／３０分の熱処理を行い、約８００Åの緻密なポリイミド配向膜を形成した。
【００５０】
次に、ラビングローラに取り付けたバフ布で配向膜表面をラビング処理し、液晶配向膜を付与した。
【００５１】
もう一方の基板には、遮光層付きカラーフィルタを形成し、上記と同様に最表面にポリイミド配向膜を形成しラビング処理により液晶配向能を付与した。
【００５２】
本実施例では配向能を付与する方法としてラビング法を用いたが、それ以外の例えば紫外線硬化型樹脂溶液を塗布して配向膜とし、それに偏光紫外線光を照射して光化学反応を生じさせることにより液晶配向能を付与する方法や、水面上に展開した有機分子膜を基板上に引き上げて形成した配向性の良い多層膜を配向膜として用いる方法なども利用できる。
【００５３】
特に後者の二つの方法は、従来十分大きな界面チルト角を付与することが困難とされてきた配向制御方法であるが、横電界方式においては従来のＴＮ方式に代表される縦電界方式と異なり界面チルト角が原理的に必要ないため、横電界方式との組み合わせにより量産性などの実用性を向上させることができる。
【００５４】
次に、これらの２枚の基板をそれぞれの液晶配向能を有する表面を相対向させて、分散させた球形のポリマビ−ズからなるスペーサを介在させて、周辺部にシール剤を塗布し、セルを組み立てた。２枚の基板のラビング方向は互いにほぼ並行で、かつ印加横電界方向とのなす角度を７５゜とした。このセルに誘電異方性Δεが正でその値が１０.２(１ｋＨｚ，２０℃）であり、屈折率異方性Δｎが０.０７５(波長５９０ｎｍ，２０℃）、ねじれ弾性定数Ｋ２が７.０ｐＮ 、ネマティック−等方相転移温度Ｔ（Ｎ−Ｉ）が約７６℃のネマティック液晶組成物Ａを真空で注入し、紫外線硬化型樹脂からなる封止材で封止した。液晶層の厚み（ギャップ）は４.８μｍ の液晶パネルを製作した。このパネルのリタデーション（Δｎｄ）は、０.３６μｍ となる。このパネルを２枚の偏光板（日東電工社製G1220DU)で挾み、一方の偏光板の偏光透過軸を上記のラビング方向とほぼ並行とし、他方をそれに直交させた。その後、駆動回路，バックライトなどを接続してモジュール化し，アクティブマトリクス液晶表示装置を得た。本実施例では低電圧で暗表示，高電圧で明表示となるノーマリクローズ特性とした。
【００５５】
このように作製した液晶表示装置の画像の焼き付け，残像を定量的に測定するため、ホトダイオードを組み合わせたオシロスコープを用いて評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示、ここでは輝度が最大輝度の１０％となるように全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間として評価し、またウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【００５６】
その結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約２％であり、残像が消失するまでの時間は約５０ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００５７】
また、この液晶表示素子の液晶／配向膜界面のガラス転移温度Ｔｇを評価するため、ホットステージを用いて、上記輝度変動分ΔＢ／Ｂ（１０％）(残像強度)の温度依存性を測定した。その結果、室温から用いた液晶組成物Ａのネマティック−等方相転移温度Ｔ（Ｎ−Ｉ）近傍の約７３℃までの間は、輝度変動分ΔＢ／Ｂ（１０％）は約３％以下と一定の値を示した。さらに、この液晶組成物Ａとツイスト弾性定数，誘電率異方性Δεがほぼ同等で、Ｔ（Ｎ−Ｉ）点が１１５℃と高い別の液晶組成物Ｂを用い、それ以外の液晶セル形成プロセス，材料を全く同じにして作製した液晶表示素子を用いて、同様な界面Ｔｇの温度依存性を測定した。その結果、図５に示すように約１００℃を越えた付近で輝度変動分ΔＢ／Ｂ（１０％）が徐々に増加し、１１０℃では約１０％に達した。以上の結果から、本実施例に用いた液晶表示素子の界面Ｔｇは約１００℃と見積もられ、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）点７６℃よりも高いことが分かった。
【００５８】
（実施例２）
用いた配向膜以外は実施例１と同様にして、ｍ−フェニレンジアミン１.０ モル％をＮ−メチル−２−ピロリドン中に溶解させ、これに３，３′，４，４′−ジフェニルエーテルテトラカルボン酸二無水物１.０ モル％を加え４０℃で６時間反応させ、標準ポリスチレン換算重量平均分子量が約２１,０００ 、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ）が約１.８ のポリアミック酸ワニスを得た。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して２２５℃／３０分の熱処理を行い、約６００Åの緻密なポリイミド配向膜を形成した。
【００５９】
また、上記と同様な製法で得たポリイミド配向膜の表面弾性率を走査型粘弾性顕微鏡(Scanning Viscoelasticity Microscopy、ＳＶＭと略記する）装置を用いて評価した。ここで、表面弾性率測定の原理について簡単に説明する。ＳＶＭは、近年、一般に良く知られている原子間力顕微鏡(Atomic Force Microscopy、
ＡＦＭと略記する）装置を応用し、ＡＦＭの探針とサンプル表面に斥力が働く領域、すなわち探針が表面に変形を与える状態でピエゾ素子を用いてサンプルに強制的に正弦的振動（歪み）を与え、探針からの同じ周期の応答振動（応力）を検出する。この応力と歪み信号の振幅および位相差からサンプル表面の動的粘弾性関数を評価するものである（詳しくは、田中 敬二ほか，高分子論文集，５３巻（Ｎｏ.１０），１９９６，ｐ５８２.に記載されている）。
【００６０】
この装置を用いて、上記のポリイミド配向膜の１０Ｈｚの表面弾性率を測定した結果、約２.５ＧＰａ という値を得た。
【００６１】
実施例１と同様、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に測定するため、ホトダイオードを組み合わせたオシロスコープを用いて評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示、ここでは輝度が最大輝度の１０％となるように全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間として評価し、またウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【００６２】
その結果を輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約３％であり、残像が消失するまでの時間は約６２ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００６３】
また、実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約９０℃であり、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）＝７６℃以上であった。
【００６４】
（実施例３）
用いた配向膜以外は実施例１と同様にして、４，４′−ジアミノジフェニルメタン１.０ モル％をＮ−メチル−２−ピロリドンとジメチルアセトアミドの混合溶媒中に溶解させ、これに１，２，３，４−シクロペンタンテトラカルボン酸二無水物１.０ モル％を加え３０℃で１２時間反応させ、標準ポリスチレン換算重量平均分子量が約１２,０００〜２５０,０００のポリアミック酸ワニスを作製した。その後このワニスをゲル浸透クロマトグラフィを用いて重量平均分子量が約１５０,０００、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ）が１.５１の単分散ポリアミック酸ワニスに分集した。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して
２２０℃／３０分の熱処理を行い、約６００Åの緻密なポリイミド配向膜を形成した。
【００６５】
実施例１と同様、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に測定するため、ホトダイオードを組み合わせたオシロスコープを用いて評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示、ここでは輝度が最大輝度の１０％となるように全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間として評価し、またウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【００６６】
その結果を輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約２％であり、残像が消失するまでの時間は約４８ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００６７】
次にこの様にして得た液晶表示装置と同一の配向膜材料を用い、同一プロセスでガラス基板上に配向膜を形成、ラビング処理し、同一の液晶組成物を封入して液晶セルを作製し、フレデリックス転移法（ヤング，ローゼンブラッド，アプライド フィジックス レター，Ｖｏｌ.４３，１９８３，ｐ６２)により、界面における液晶分子と配向膜表面とのねじれ結合の強さを表す外挿長を測定すると、１.０μｍであった。
【００６８】
ここで、上記のフレデリックス転移法による外挿長の測定方法について、その原理を説明する。この測定方法は、液晶層と対となる２枚の基板の双方の界面におけるねじれ結合が等しい場合に近似的に得られる横電界方式における液晶分子の横電界に対する配向変化（フレデリックス転移）のしきい値電圧Ｖｃの液晶層の厚みｄへの依存性を表す（１）式（横山，モレキュラークリスタル アンド リキッドクリスタル，Ｖｏｌ.１６５ ，１９８８，ｐ２６５、および、大江，近藤，アプライド フィジックス レター，Ｖｏｌ.６７，１９９５，ｐ３８９５)より外挿長を測定する方法である。
【００６９】
（１／Ｖｃ）＝（ｄ＋２ｂ）×πｇ√（Δε／Ｋ２） （１）
ここで、ｄおよびｇはそれぞれ基板間ギャップ（液晶層の厚み），電極端間ギャップ、Ｋ２およびΔεはそれぞれ液晶組成物のツイスト弾性定数，誘電異方性で、ｂは配向膜表面のねじれ結合係数Ａ２を用いて次式で定義される界面における液晶分子と配向膜表面のねじれ結合の強さを表す外挿長である。
【００７０】
ｂ＝Ｋ２／Ａ２ （２）
この外挿長ｂは上記の配向膜表面でのねじれ結合が強いほど小さくなり、例えば配向膜表面で液晶分子の配向方向が固定されていると考えられるほど強い結合の場合には外挿長ｂは０と考えられる。
【００７１】
この式より、液晶層の厚みｄのみが異なる液晶セルを複数作成し、横（ｘ）軸にｄ、縦（ｙ）軸にそれらの液晶セルそれぞれについて測定した（１／Ｖｃ）をとり測定値をプロットすると、それらの点を直線で外挿したｙ切片が、−２ｂすなわち外挿長（この場合の係数２は上下界面が同じとした場合の双方からの外挿長への寄与を表す）を与える。
【００７２】
この測定方法では、原理的に外挿長が液晶層の厚みと同程度となる弱いねじれ結合の場合にのみ正確な測定が可能である。
【００７３】
より強いねじれ結合の場合にも適用可能な外挿長の測定方法としては、強電場法（横山，ファン スプラング，ジャーナルオブアプライドフィジックス，Vol.５７，１９８５，ｐ４５２）や、界面での微小ねじれを測定する方法（赤羽，金子，木村，ジャパニース ジャーナルオブ アプライドフィジックス，Ｖｏｌ．３５，１９９６，ｐ４４３４）などが知られているが、本発明の趣旨にある弱いねじれ結合の場合には、その測定値はこれらのどの測定法によっても大差ない値が十分な精度で得られる。
【００７４】
この様にして得られた外挿長から、上記の中心ギャップ４.６μｍ で計算すると、外挿長ｂのギャップｄに対する比率ｂ＊＝ｂ／ｄは０.２１７である。
【００７５】
配向膜表面でのねじれ結合係数Ａ２は、外挿長ｂと、液晶のねじれ弾性定数Ｋ２より（２）式から次式を用いて機械的に得ることが出来る。
【００７６】
Ａ２＝Ｋ２／ｂ （３）
従って、本実施例の場合には、Ａ２は７.０μＮ／ｍとなる。
【００７７】
（実施例４）
用いた配向膜以外は実施例１と同様にして、４−フルオロ−メタフェニレンジアミン１.０ モル％をＮ−メチル−２−ピロリドン中に溶解させ、これに３，３′，４，４′−ビスシクロブタンテトラカルボン酸二無水物１.０ モル％を加えて２０℃で８時間および１００℃で２時間反応させて、標準ポリスチレン換算重量平均分子量が約１７,０００、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ)が１.８５ のポリアミドイミドを得た。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して２００℃／３０分の熱処理を行い、約６００Åの緻密なポリアミドイミド配向膜を形成し、液晶層の厚みｄが４.２μｍ の液晶表示装置を作成した。
【００７８】
実施例１と同様、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に測定するため、ホトダイオードを組み合わせたオシロスコープを用いて評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示、ここでは輝度が最大輝度の１０％となるように全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間として評価し、またウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【００７９】
その結果を輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約２％であり、残像が消失するまでの時間は約５５ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００８０】
また、実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約１０５℃であり、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）＝７６℃以上であった。さらに実施例２同様の走査型粘弾性顕微鏡(ＳＶＭ)装置を用いて、上記のポリイミド配向膜の５０Ｈｚの表面弾性率を測定した結果、約５ＧＰａという値を得た。
【００８１】
（実施例５）
用いた配向膜材料以外は、実施例１と同様にして、液晶層の厚み（ギャップ）ｄが５.０μｍの液晶パネルを作製した。このパネルのリタデ−ション（Δｎｄ)は、０.３７５μｍとなる。
【００８２】
配向膜材料は、薄膜トランジスタ側の基板には、窒化シリコンからなる絶縁保護膜の上の最表面に酸化シリコンからなる無機配向制御層を斜方蒸着法により形成した無機配向膜材料を用いた。
【００８３】
斜方蒸着は、液晶配向のチルト角をほぼ０°するため、基板法線より６０°の方向となるように蒸着方向を規制するルーバー（高分子学会編，新高分子実験学，第１０巻：高分子の物性（３）−表面，界面と膜・輸送−，２３３ｐ）を用いて行った。
【００８４】
もう一方の基板には、遮光層付きカラーフィルタを形成し、最表面にポリイミド配向膜を形成した後、ラビングローラに取り付けたバフ布で配向膜表面をラビング処理し、液晶配向膜を付与した。
【００８５】
ポリイミド配向膜は溶剤可溶型のポリイミド前駆体である日立化成製ＰＩＱの溶液を基板表面上に印刷形成した後、２１０℃／３０分の熱処理を行う事により形成した。
【００８６】
また、実施例３と同じくフレデリックス転移法により外挿長ｂを測定すると１.６μｍであった。
【００８７】
ポリイミド配向膜ＰＩＱをラビングした表面と液晶分子とのねじれ結合は非常に強く、この界面での外挿長がほぼ０であることが別途行った実験より知られていることから、上記の外挿長はそのほとんどが、酸化シリコンを斜方蒸着して形成した無機配向膜側の寄与であると考えられる。
【００８８】
上記のギャップ５.０μｍ で計算すると外挿長ｂのギャップに対する比率ｂ＊は０.３２になり、配向膜表面でのねじれ結合係数Ａ２は、４.３８μＮ／ｍであった。
【００８９】
実施例１と同様、ウインドウパターンを用いて、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に評価した結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約３％であり、残像が消失するまでの時間は約５０ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００９０】
（実施例６）
用いた配向膜以外は実施例１と同様にして、ジアミン化合物として、ジアゾベンゼン基を含有する
【００９１】
【化２】

【００９２】
と４，４′−ジアミノジフェニルメタンを等モル比で混入した物を用い、ピロメリット酸二無水物及び／或いは１，２，３，４−シクロブタンテトラカルボン酸二無水物の酸無水物にポリアミック酸として合成し、基板表面に塗布後、２００℃，３０分の焼成，イミド化を行い、波長４２０ｎｍの偏光光照射を行った。
【００９３】
その後、実施例１と同様にネマティック液晶組成物を封入後、１００℃，１０分のアニーリングを施し、上記の照射偏光方向に対してほぼ垂直方向に液晶配向を得た。このようにして、液晶層の厚みｄが４.０μｍの液晶表示装置を得た。
実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約８５℃であり、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）＝７６℃以上であった。また、実施例１と同様、ウインドウパターンを用いて、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に評価した結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約３％であり、残像が消失するまでの時間は約５０ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００９４】
また、実施例３と同じくフレデリックス転移法により外挿長ｂを測定すると１.０μｍ であった。したがって、外挿長ｂのギャップに対する比率ｂ＊は0.25である。また、用いた液晶組成物のねじれ変形に対する弾性定数Ｋ２の値と、上記の外挿長ｂの測定値から、本実施例の配向膜表面でのねじれ結合定数Ａ２は５.０μＮ／ｍとなる。
【００９５】
（実施例７）
用いた配向膜以外は実施例６と同様にして、ジアミン化合物として、スチルベン基を含有する
【００９６】
【化３】

【００９７】
と４，４′−ジアミノジフェニルメタンを等モル比で混入した物を用い、ピロメリット酸二無水物及び／或いは１，２，３，４−シクロブタンテトラカルボン酸二無水物の酸無水物にポリアミック酸として合成し、基板表面に塗布後、２１０℃，３０分の焼成，イミド化を行い、波長３０８ｎｍの偏光光照射を行った。
【００９８】
その後、実施例１と同様にネマティック液晶組成物を封入後、１００℃，１０分のアニーリングを施し、上記の照射偏光方向に対してほぼ垂直方向に液晶配向を得た。このようにして、液晶層の厚みｄが４.０μｍの液晶表示装置を得た。
実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約８０℃であり、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）＝７６℃以上であった。また、実施例１と同様、ウインドウパターンを用いて、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に評価した結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約３％であり、残像が消失するまでの時間は約４８ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【００９９】
（実施例８）
実施例７と同様のスチルベン基を有するジアミン化合物に加えアセチレン基を有するジアミン化合物と、４，４′−ジアミノジフェニルメタンを等モル比で混入した物を用い、ピロメリット酸二無水物及び／或いは１，２，３，４−シクロブタンテトラカルボン酸二無水物の酸無水物にポリアミック酸として合成し、基板表面に塗布後、２１０℃，３０分の焼成、イミド化を行い、ＸｅＣｌ₂ ガスのエキシマレーザを用い波長３０８ｎｍの偏光光照射を行った。
【０１００】
その後、実施例１と同様にネマティック液晶組成物を封入後、１００℃，１０分のアニーリングを施し、上記の照射偏光方向に対してほぼ垂直方向に液晶配向を得た。このようにして、液晶層の厚みｄが４.０μｍの液晶表示装置を得た。
実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約１００℃であり、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）＝７６℃以上であった。また、実施例１と同様、ウインドウパターンを用いて、このように作製した液晶表示装置の画像の焼き付け，残像を定量的に評価した結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約２％であり、残像が消失するまでの時間は約４０ミリ秒でここで用いた液晶の立ち下がり応答時間約３５ミリ秒とほとんど同じであった。目視による画質残像検査においても、画像の焼き付け，残像による表示むらも一切見られず、高い表示特性が得られた。このように上記配向膜を使用することにより画像の焼き付き，残像の表示不良が低減される液晶表示素子を得ることができた。
【０１０１】
（比較例１）
２，２−ビス｛４−（ｐ−アミノフェノキシ）フェニル｝プロパン１.０ モル％、３，３′，４，４′−ベンゾフェノンテトラカルボン酸二無水物１.０ モル％をＮ−メチル−２−ピロリドン中で２０℃で１０時間重合して、標準ポリスチレン換算重量平均分子量が約２００,０００ 、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ）が約１.９ のポリアミック酸ワニスを得た。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して２２０℃／３０分の熱処理を行い、約８００Åの緻密なポリイミド配向膜を形成した。
【０１０２】
次に、この配向膜材料を用いて実施例１と同様に液晶表示装置を作成し、液晶表示装置の画像の焼き付け，残像を定量的に測定評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示に全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間、及びウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【０１０３】
その結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約５％と大きく、残像が消失するまでの時間も約６０分掛かり、目視による画質残像検査においても、明らかな画像の焼き付け，残像による表示むらとして確認された。このように上記配向膜を使用することにより画像の焼き付き，残像による表示不良が目立った。
【０１０４】
また、実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約５８℃であり、用いた液晶組成物ＡのＴ(Ｎ−Ｉ)＝７６℃以下であった。さらに実施例２同様の走査型粘弾性顕微鏡(ＳＶＭ)装置を用いて、上記のポリイミド配向膜の１０Ｈｚの表面弾性率を測定した結果、約０.１ＧＰａという値を得た。
【０１０５】
（比較例２）
２，２−ビス〔４−（ｐ−アミノフェノキシ）フェニル〕オクタン０.５ モル％、４，４′−ジアミノジフェニルメタン０.５ モル％、３，３′，４，４′，−ビフェニルテトラカルボン酸二無水物１.０ モル％をＮ−メチル−２−ピロリドン中で２０℃で８時間重合して、標準ポリスチレン換算重量平均分子量が約 ４０,０００、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ）が約１.８のポリアミック酸ワニスを得た。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して２００℃／３０分の熱処理を行い、約８００Åの緻密なポリイミド配向膜を形成した。
【０１０６】
次に、この配向膜材料を用いて実施例１と同様に液晶表示装置を作成し、液晶表示装置の画像の焼き付け，残像を定量的に測定評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示に全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間、及びウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【０１０７】
その結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約８％と大きく、残像が消失するまでの時間も約１２０分掛かり、目視による画質残像検査においても、明らかな画像の焼き付け，残像による表示むらとして確認された。このように上記配向膜を使用することにより画像の焼き付き，残像による表示不良が目立った。
【０１０８】
また、実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約６０℃であり、用いた液晶組成物ＡのＴ（Ｎ−Ｉ）＝７６℃以下であった。さらに実施例２同様の走査型粘弾性顕微鏡（ＳＶＭ）装置を用いて、上記のポリイミド配向膜の１０Ｈｚの表面弾性率を測定した結果、約０.０８ＧＰａという値を得た。
【０１０９】
（比較例３）
２，２−ビス〔４−（ｐ−アミノフェノキシ）フェニル〕ヘキサフルオロプロパン１.０ モル％、４，４′−ジアミノジフェニルエ−テル１.０ モル％をＮ−メチル−２−ピロリドン中で２０℃で６時間重合して、標準ポリスチレン換算重量平均分子量が約４０００、重量平均分子量／数平均分子量（Ｍｖ／Ｍｎ）が約３.５ のポリアミック酸ワニスを得た。このワニスを６％濃度に希釈してγ−アミノプロピルトリエトキシシランを固形分で０.３ 重量％添加後、印刷形成して２００℃／３０分の熱処理を行い、約９００Åの緻密なポリイミド配向膜を形成した。
【０１１０】
次に、この配向膜材料を用いて実施例１と同様に液晶表示装置を作成し、液晶表示装置の画像の焼き付け，残像を定量的に測定評価した。まず、画面上に最大輝度でウインドウのパターンを３０分間表示し、その後、残像が最も目立つ中間調表示に全面を切り換え、ウインドウのエッジ部のパターンが消えるまでの時間を残像時間、及びウインドウの残像部分と周辺中間調部分の輝度Ｂの輝度変動分の大きさΔＢ／Ｂ（１０％）を残像強度として評価した。但し、ここで許容される残像強度は３％以下である。
【０１１１】
その結果、輝度変動分である残像強度ΔＢ／Ｂ（１０％）は約２０％と大きく、残像が消失するまでの時間も約１００分掛かり、目視による画質残像検査においても、明らかな画像の焼き付け，残像による表示むらとして確認された。このように上記配向膜を使用することにより画像の焼き付き，残像による表示不良が目立った。
【０１１２】
また、実施例１同様の方法で、この液晶／配向膜の界面Ｔｇを評価した結果、この界面Ｔｇは約５０℃であり、用いた液晶組成物ＡのＴ(Ｎ−Ｉ)＝７６℃以下であった。さらに実施例２同様の走査型粘弾性顕微鏡(ＳＶＭ)装置を用いて、上記のポリイミド配向膜の１０Ｈｚの表面弾性率を測定した結果、約０.１ＧＰａという値を得た。
【０１１３】
【発明の効果】
本発明によれば、基板に対してほぼ平行な方向に電界を液晶層に印加して動作させるＩＰＳ−ＴＦＴ−ＬＣＤの固有の問題である画像の焼き付き，残像現象の低減が可能になり、画像の焼き付き，残像現象による表示むらの少ない高画質で量産性の優れたアクティブマトリクス型液晶表示装置を提供することが可能になる。
【図面の簡単な説明】
【図１】本発明の液晶表示装置における液晶の動作を示す図である。
【図２】本発明の電気光学特性を説明する図であり、（ａ）は基本的な電圧・輝度特性、（ｂ）は残像現象を示している電圧・輝度特性を示す図である。
【図３】液晶分子と基板表面との極結合とねじれ結合を示す図である。
【図４】本発明の薄膜トランジスタ，電極，配線の構造を示す図であり、（ａ）は正面図、（ｂ),（ｃ）は側断面図を示す。
【図５】残像強度の温度依存性を示す。
【符号の説明】
１…共通電極（コモン電極）、２…ゲ−ト絶縁膜、３…信号電極（ドレイン電極）、４…画素電極（ソ−ス電極）、５…配向膜、６…液晶組成物層中の液晶分子、７…基板、８…偏光板、９…電界、１０…界面上の分子長軸配向方向（ラビング方向）、１１…偏光板偏光透過軸方向、１２…走査電極(ゲート電極)、１３…アモルファスシリコン、１４…薄膜トランジスタ素子。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an active matrix liquid crystal display device, and more particularly to a lateral electric field type active matrix liquid crystal display device that drives an liquid crystal by generating an electric field substantially parallel to a substrate plane.
[0002]
[Prior art]
The display of the liquid crystal display device is performed by applying an electric field to the liquid crystal molecules in the liquid crystal layer sandwiched between the substrates to change the alignment direction of the liquid crystal molecules, thereby changing the optical characteristics of the liquid crystal layer.
[0003]
A conventional active matrix type liquid crystal display device is typified by a twisted nematic (TN) display method in which the direction of the electric field applied to the liquid crystal is set in a direction substantially perpendicular to the substrate interface and performs display using the optical rotation of the liquid crystal. The On the other hand, a method (transverse electric field method) in which the direction of the electric field applied to the liquid crystal using the comb electrode is made substantially parallel to the substrate surface and the birefringence of the liquid crystal is used is shown in, for example, JP-A-5-505247 proposes. This lateral electric field method has advantages such as a wide viewing angle and a low load capacity compared to the conventional TN method, and is a promising technology as an active matrix liquid crystal display device.
[0004]
With the recent rapid response of liquid crystal display devices, a display defect called an image burn-in phenomenon called an afterimage of a liquid crystal display element has occurred. This image burn-in phenomenon, that is, the afterimage problem, is usually used when a region with a significantly slow response occurs compared to the liquid crystal response speed of about 50 milliseconds. These occurrences in the conventional TN type liquid crystal display device are due to accumulation of direct current charges at the liquid crystal alignment film interface of each pixel and change in effective voltage. That is, it occurs because the effective voltage applied to the liquid crystal layer changes because the potential at the time of applying the voltage is not canceled within the response time at the interface between the alignment film on the pixel electrode or the liquid crystal alignment film. . The correlation between such an afterimage phenomenon and the residual DC voltage component has been studied, and now it is starting to be understood that the afterimage phenomenon is improved as the residual DC voltage is reduced. Therefore, a conventional TN type alignment film is required to have a property that DC charges are difficult to accumulate, that is, an alignment film having a small residual DC voltage component.
[0005]
[Problems to be solved by the invention]
On the other hand, even in the horizontal electric field method, an image burn-in (afterimage) phenomenon occurs, causing a decrease in black level, a decrease in contrast, a gradation inversion between adjacent pixels, and a decrease in image quality and yield, resulting in a decrease in mass productivity. There's a problem. Therefore, when the DC voltage remaining on the pixel electrode correlated with the afterimage phenomenon in the conventional TN method was also measured for this horizontal electric field method, (1) the residual DC voltage value between the liquid crystal display element in which the afterimage was generated and the one not to be generated. It has been found that there is almost no significant difference between the two, and (2) in this lateral electric field method, there is a case where image burn-in persists semipermanently and causes a significant decrease in contrast. Also, when examining the alignment direction of the liquid crystal in the afterimage and burn-in area, it is rotated by a subtle angle from the initially set alignment direction to the driving alignment direction and has not completely returned to the initial alignment direction. I understood. From the above points, the afterimage and burn-in phenomenon of this horizontal electric field method is considered to be based on the afterimage mechanism unique to the horizontal electric field method, which is completely different from the conventional TN method. There is a need for a solution. Hereinafter, this afterimage is referred to as an IPS (In-Plane Switching) afterimage.
[0006]
Accordingly, an object of the present invention is to provide an active matrix liquid crystal display device with high image quality, in which there is little display unevenness due to image sticking afterimage phenomenon in an active matrix liquid crystal display device using a horizontal electric field method.
[0007]
Another object of the present invention is to provide a high-quality active matrix liquid crystal display device excellent in mass productivity.
[0008]
[Means for Solving the Problems]
  Means for solving the problems of the present invention will be described below.
[0009]
  In the present invention, an active matrix liquid crystal display device having a plurality of switching elements, at least one of which is transparent, a liquid crystal layer disposed between the pair of substrates, and one of the pair of substrates. An electrode structure for generating an electric field in the liquid crystal layer formed on the substrate and having a component predominantly parallel to the substrate surface, and on each surface in contact with the liquid crystal layer on the pair of substrates And a pair of polarizing plates disposed so as to sandwich the pair of substrates, and a glass transition temperature Tg at an interface between the liquid crystal layer and the alignment control film is the liquid crystal. Nematic-isotropic phase transition temperature T of the liquid crystal composition forming the layer ( NI ) That is the above, and at least one of the pair of orientation control films has the chemical formula H ₂ N-R-NH ₂ And the chemical formula
[0010]
[Chemical 1]

Is a polyamic acid dehydrated ring-closed organic polymer composed of tetracarboxylic dianhydride represented by the formula: wherein R and X in the repetitive structure have -O-, -S-, -CH ₂ − , -C ( CH _Three ) ₂ -, -C ( CF _Three ) ₂ -, -SO ₂ − The configuration of the active matrix type liquid crystal display device is composed of 3 or less organic polymers.
[0011]
  Further, in the above-described configuration, a configuration of an active matrix liquid crystal display device in which the glass transition temperature Tg on the surface of the alignment control film is equal to or higher than the nematic-isotropic phase transition temperature T (NI) of the liquid crystal composition forming the liquid crystal layer. Take.
[0012]
  Further, in the above configuration, an active matrix liquid crystal display device in which the torsional coupling coefficient A2 of the surface of the alignment control film with respect to liquid crystal molecules at the interface between the alignment control film and the liquid crystal layer is 20 μN / m or less is employed.
[0013]
  In the above configuration, the pair of polarizing plates has a parameter d · Δn of 0 when the refractive anisotropy of the liquid crystal layer is Δn and the thickness is d. . 2 μm <d · Δn <0 . The configuration of an active matrix liquid crystal display device satisfying 5 μm is adopted.
[0014]
  In the above structure, the organic polymer has a weight average molecular weight of 10 , 000 more than~
300 , 000 The following active matrix type liquid crystal display device is employed.
[0015]
  In the above configuration, the alignment control film has a configuration of an active matrix liquid crystal display device which is a photoreactive material layer.
[0016]
  In the above structure, the photoreactive material layer adopts a structure of an active matrix liquid crystal display device in which the alignment direction of the liquid crystal layer is controlled by irradiating polarized light.
[0017]
  In the above configuration, the photoreactive material layer has a configuration of an active matrix type liquid crystal display device including an organic polymer containing a polymer and / or an oligomer containing at least one diazobenzene group or a derivative thereof.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
First, the principle of operation of the horizontal electric field method, which is the premise of the present invention, will be described using FIG. 1 as an example. FIGS. 1A and 1B are side cross-sectional views showing the operation of the liquid crystal in one pixel of a horizontal electric field type liquid crystal element, and FIGS. 1C and 1D are front views thereof.
[0019]
FIG. 1A shows a cell side cross-section when no voltage is applied, and FIG. 1C shows a front view at that time. The linear electrodes 1 and 4 are formed inside one substrate, the substrate surfaces are both alignment films 5 in the paired substrates, and a liquid crystal composition is sandwiched between the substrates (in this example, The dielectric anisotropy is assumed to be positive, but in the case of a negative liquid crystal composition, the transverse electric field method can be similarly realized by simply switching the major axis and minor axis directions of the liquid crystal molecules).
[0020]
The alignment of the rod-like liquid crystal molecules 6 is controlled in the direction of the direction 10 having a slight angle in the longitudinal direction of the electrodes 1 and 4 (FIG. 1 (c) front view) at the interface between both substrates by bonding with the alignment film 5. When no electric field is applied, the initial alignment direction is almost uniformly oriented in the liquid crystal layer. Here, when different potentials are applied to the pixel electrode 4 and the common electrode 1 and an electric field 9 is applied to the liquid crystal composition layer due to the potential difference therebetween, the interaction between the dielectric anisotropy of the liquid crystal composition and the electric field is applied. Thus, as shown in FIGS. 1B and 1D, the liquid crystal molecules change their directions in the direction of the electric field. At this time, the optical characteristics of the liquid crystal element change due to the refractive anisotropy of the liquid crystal composition layer and the action of the polarizing plate 8, and display is performed by this change.
[0021]
FIG. 2 is a graph schematically showing the relationship between the applied voltage between the electrodes of the horizontal electric field type liquid crystal display device and the display luminance. The solid line in FIG. 2A indicates the initial basic characteristic, and the dotted line in FIG. 2B indicates a voltage / luminance characteristic curve in the case of a typical afterimage (IPS afterimage). As described above, the afterimage and image burn-in phenomenon show remarkable luminance fluctuations in a sensitive dark level or halftone region in terms of human visibility.
[0022]
Here, the mechanism of the afterimage phenomenon is considered.
[0023]
The alignment regulation force (bonding force) due to the bonding between the alignment film and the liquid crystal molecules is known to vary greatly depending on the alignment film material and the rubbing treatment conditions, but the alignment change of the liquid crystal molecules on the alignment film surface is known. It depends on the direction. Considering a liquid crystal material with positive dielectric anisotropy that is oriented almost horizontally on the surface, the direction of the change in the orientation of the liquid crystal molecules on the substrate surface caused by the application of an electric field is such that the electric field is applied almost perpendicular to the substrate interface. In the TN system, in the direction rising from the substrate surface (polar angle direction shown in FIG. 3), and in the lateral electric field system in which the electric field is applied substantially parallel to the substrate interface, the substrate in-plane direction (in-plane twist shown in FIG. 3). Rotation direction). Therefore, in the conventional TN system, the difficulty in returning the orientation change of the liquid crystal molecules in the polar angle direction corresponds to image burn-in and afterimage, and it is considered that this is caused by the DC potential remaining near the upper and lower counter electrodes. On the other hand, in the horizontal electric field method, image burn-in and afterimage correspond to difficulty in returning torsional deformation of liquid crystal molecules in the in-plane direction of the substrate. In addition, as described above, since there is no correlation between the afterimage and the DC potential remaining in the vicinity of the pixel electrode, this is considered to be based on the interaction between the liquid crystal / alignment film interface rather than an electrical factor. .
[0024]
Therefore, as a result of intensive studies by the present inventors, the occurrence of image sticking and afterimage phenomenon in the lateral electric field type image is caused by the direction 10 of the initial alignment of the liquid crystal molecules due to the rotational torque generated based on the in-plane torsional deformation of the liquid crystal molecules due to the applied electric field. The surface of the alignment film that regulates the deformation is elastically deformed, and its deformation / creep is an elastic aftereffect (after delayed elastic deformation), that is, an afterimage phenomenon that recovers with a finite delay time as a residual strain. As a result, it has been found that it appears as an image burn-in phenomenon as a permanent deformation.
[0025]
Therefore, as countermeasures for reducing the occurrence of such an afterimage phenomenon, (1) a liquid crystal composition having a small twist elastic constant is used to reduce the magnitude of rotational torque due to in-plane torsional deformation, or (2) an alignment film It is effective to increase the hardness (elastic modulus) of the film and to form a highly elastic polymer surface that is hardly affected by the rotational torque due to the driving of liquid crystal molecules. Furthermore, (3) it is effective to form a weakly twisted interface at the interface so that the rotational torque of the liquid crystal layer is difficult to propagate to the alignment layer.
[0026]
As a specific measure for increasing the modulus of elasticity of the alignment film, it is desirable that the molecular structure of the polymer constituting the alignment film is a rigid and highly linear structure, and it is preferable to increase the molecular weight as much as possible. Furthermore, a monodispersed system is preferable. It is also possible to build a higher-order network by a photocrosslinking reaction after alignment film coating, baking and curing, and rubbing alignment treatment to increase the strength dynamically. By increasing the molecular weight to 10,000 or more, it is possible to increase the cohesive force between polymer chains and increase the elastic modulus. However, when the molecular weight is increased to 300,000 or more, entanglement of polymer chains may occur in the melt state of the alignment film varnish, and packing with a high density of polymer chains may be hindered.
[0027]
In addition, -O-, -S-, -CH, a linking group that enables rotation of the molecular axis of the polymer₂-, -C (CH_Three)₂-, -SO₂-It is desirable that the total number of meta bonds and ortho bonds is 3 or less. This is because diffusion between polymer main chains hardly occurs, but if there are many bonding groups as described above, rotation around the molecular axis is facilitated and local thermal motion becomes possible. As a result, the rate drops. Such a phenomenon is known as side chain sub-dispersion (Tg (b)) that appears in the temperature characteristic of the elastic modulus. In addition, in a conventional alignment film used in the TN system, a method of introducing a side chain such as a linear alkyl group is used to control the tilt angle, but in the horizontal electric field system, a wide viewing angle is maintained. Therefore, from the above viewpoint, a polymer having few long-chain branched side-chain functional groups such as a linear alkyl group that generates a tilt angle or a polymer having no bulky side-chain substituents is preferable. .
[0028]
Further, it is known that the elastic modulus of the polymer alignment film is greatly influenced by ambient environmental conditions, particularly temperature. From this point of view, there is a glass transition temperature Tg of the alignment film polymer in addition to the elastic modulus as an index for selecting the alignment film having a high elastic modulus as described above. The higher the Tg, the higher the elastic modulus of the alignment film is guaranteed. In the liquid crystal cell actually used, the following relationship can be considered between the interface Tg at the interface between the alignment film and the liquid crystal and the transition temperature T (NI) of the nematic-isotropic phase of the liquid crystal used. The magnitude of the rotational torque of the liquid crystal is mainly proportional to the twist elastic constant K2 of the liquid crystal. Further, the twist elastic constant K2 of the liquid crystal gradually decreases as the temperature of the liquid crystal increases, and rapidly decreases at the nematic-isotropic phase transition temperature T (NI). That is, above the T (N-I) point, the rotational torque of the liquid crystal becomes very small, and the stress load on the alignment film is significantly reduced. Therefore, when the glass transition temperature Tg in the vicinity of the surface of the alignment film or the liquid crystal layer is higher than the T (NI) temperature of the liquid crystal (Tg> T (NI)), the alignment film surface is very It exists as a state close to a hard glass state, and is less susceptible to elastic deformation due to the rotational torque of the liquid crystal. That is, the afterimage (IPS afterimage) peculiar to the horizontal electric field method can be minimized.
[0029]
From the above viewpoint, the compound of the amine component and the other copolymerizable compound which are synthetic materials for the alignment film used in the present invention include, for example, p-phenylenediamine, m-phenylenediamine, 2 , 4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, diaminodurene, benzidine, O-tolidine, 3,3-dimethoxybenzidine, 4,4 "-diaminoterphenyl, 1,5-diamino Naphthalene, 2,7-diaminofluorene, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2, , 5-Diaminopyridine, 4,4'-bis (p-aminophenoxy) bi , 2,2-bis {4- (p-aminophenoxy) phenyl} propane, 2,2-bis {4- (p-aminophenoxy) phenyl} hexafluoropropane, 4,4′-bis (m-amino) Examples thereof include, but are not limited to, phenoxy) diphenylsulfone.
[0030]
On the other hand, the acid component compound and other copolymerizable compounds include, for example, pyromellitic dianhydride, methyl-pyromellitic dianhydride, dimethylene trimellitic acid dianhydride. Anhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, dimethylene trimellitate dianhydride, 2 , 3,6,7-Naphthalenetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenylsulfone tetracarboxylic dianhydride, 3,3', 4,4'-diphenyl ether tetracarboxylic dianhydride 3,3 ', 4,4'-diphenylmethanetetracarboxylic dianhydride and alicyclic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride. Examples include water, 1,2,3,4-biscyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, and the like. Absent.
[0031]
Examples of the solvent include polar N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane, butyllactone, cresol, phenol, cyclohexanone, dimethylimidazolidinone, dioxane, tetrahydrofuran, and butyl cell. Solv, butyl cellosolve acetate, acetophenone, etc. can be used.
[0032]
Furthermore, in organic polymers, for example, γ-aminopropyltriethoxysilane, δ-aminopropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and other amino silane coupling agents, epoxy Surface treatment agents such as silane coupling agents, titanate coupling agents, aluminum alcoholates, aluminum chelates, and zirconium chelates can also be mixed or reacted. The alignment film can be formed by general spin coating, printing, brushing, spraying, or the like.
[0033]
Examples of the liquid crystal to be used include 4-substituted phenyl-4'-substituted cyclohexane, 4-substituted cyclohexyl-4'-substituted cyclohexane, 4-substituted phenyl-4'-substituted dicyclohexane, 4-substituted dicyclohexyl-4'-substituted diphenyl. , 4-substituted-4 ″ -substituted terphenyl, 4-substituted biphenyl-4′-substituted cyclohexane, 2- (4-substituted phenyl) -5-pyrimidine, 2- (4-substituted dioxane) -5-phenyl, 4 -Substituted benzoic acid-4'-phenyl ester, 4-substituted cyclohexanecarboxylic acid-4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid-4'-substituted biphenyl ester, 4- (4-substituted cyclohexanecarbonyloxy) benzoic acid Acid-4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid -4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid-4'-substituted cyclohexyl ester, 4-substituted-4'-substituted biphenyl, and the like. Also, a multicomponent mixed liquid crystal composition having an alkyl group, alkoxy group, alkoxymethylene group, cyano group, fluorine group, difluorine group, or trifluorine group at one end of the molecule is used.
[0034]
In addition, instead of the polyimide alignment film layer whose alignment is controlled by the rubbing treatment as described above, the problem can be solved by using an inorganic alignment film having an alignment ability by oblique deposition. As a result, an alignment ability that does not cause alignment unevenness even when the liquid crystal composition is injected without changing the temperature of the liquid crystal phase is obtained on both substrate surfaces of the substrate, and the tilt of an inorganic material such as silicon oxide is obtained. The liquid crystal molecules on the surface whose orientation is controlled by side vapor deposition show much weaker torsional bonds compared to the liquid crystal molecules on polyimide alignment films that are generally used for rubbing treatment. As a result, the afterimage (IPS afterimage) peculiar to the horizontal electric field method can be reduced.
[0035]
In addition, the wide viewing angle characteristic, which is one of the great advantages of the lateral electric field method, becomes better as the tilt angle of the liquid crystal molecules on the substrate surface is smaller, and the theoretically widest viewing angle is obtained when the tilt angle is 0 °. However, in the case of an organic alignment film whose alignment is controlled by rubbing, it is difficult to set the tilt angle of liquid crystal molecules on the surface to 0 °, while the oblique direction of inorganic materials such as silicon oxide It is known and convenient that the liquid crystal molecules on the surface whose orientation is controlled by vapor deposition can easily have a tilt angle of approximately 0 °.
[0036]
Further, as another alignment film material for obtaining the weak torsional bond as described above, a photoreactive material layer, in particular, a photoreactive alignment film subjected to polarized light irradiation treatment so as to selectively generate a photochemical reaction is used. Also good.
[0037]
The photoreactive alignment film is an alignment control method that has conventionally been difficult to impart a strong twisted bond and a sufficient (more than several degrees) interface tilt angle. In the horizontal electric field method,
Unlike the vertical electric field method typified by the TN method, interface tilt is not necessary in principle, and practicality such as mass productivity can be improved by combining with the horizontal electric field method.
[0038]
Furthermore, in the lateral electric field method, it is known that the viewing angle characteristic is better as the interface tilt angle is smaller. On the contrary, it is advantageous that the photoreactive alignment film has a very small interface tilt angle. Good viewing angle characteristics can be expected.
[0039]
In addition, a polymer precursor that is cured by irradiation with light, heat, or radiation is mixed in advance in the photoreactive alignment film material, and the above-described curing process is performed simultaneously with or before and after the photo-alignment process. As a result, the elastic modulus of the photoreactive alignment film can be increased, and the IPS afterimage peculiar to the transverse electric field can be further reduced. Also, as a method other than the mixing of the polymer precursor as described above, an organic polymer layer thicker and transparent than the photo-alignment film is interposed between the photo-alignment film and the substrate, and the high elasticity modulus of the entire alignment film It is possible to achieve the object of the present invention.
[0040]
The present invention will be specifically described with reference to examples.
[0041]
(Example 1)
Two transparent glass substrates having a thickness of 1.1 mm and polished surfaces are used as substrates, and a thin film transistor and a wiring electrode to which a lateral electric field can be applied are formed on one of these substrates. An insulating protective film made of silicon nitride was formed on the outermost surface. The structure of the thin film transistor and various electrodes are shown in FIG. 4 as a front view as seen from a direction perpendicular to the substrate surface, and as a side sectional view taken along the lines AA ′ and BB ′ of the front view.
[0042]
The thin film transistor element 14 includes a pixel electrode (source electrode) 4, a signal electrode (drain electrode) 3, a scanning electrode (gate electrode) 12, and amorphous silicon 13. The common electrode 1 and the scanning electrode 12, and the signal electrode 3 and the pixel electrode 4 are configured by patterning the same metal layer.
[0043]
The pixel electrode 4 is disposed between the three common electrodes 1 in the front view.
[0044]
The pixel pitch is 100 μm in the horizontal direction (that is, between the signal electrodes 3), and 300 μm in the vertical direction (that is, between the scanning electrodes 12).
[0045]
As for the electrode width, the scanning electrodes, signal electrodes, and common electrode wiring portions (portions extending in parallel with the scanning wiring electrodes), which are wiring electrodes extending between a plurality of pixels, are widened to avoid line defects.
The widths are 10 μm, 8 μm, and 8 μm, respectively.
[0046]
On the other hand, in order to improve the aperture ratio, the width of the pixel electrode formed independently for each pixel and the portion of the common electrode extending in the longitudinal direction of the signal wiring electrode were slightly narrowed to 5 μm and 6 μm, respectively. Narrowing the width of these electrodes increases the possibility of disconnection due to the inclusion of foreign matter or the like. In this case, however, only one pixel is partially missing and no line defect is caused.
[0047]
The signal electrode 3 and the common electrode 1 are spaced by 2 μm through an insulating film.
[0048]
The number of pixels was set to 640 × 3 × 480 with 640 × 3 (R, G, B) signal wiring electrodes and 480 wiring electrodes.
[0049]
The alignment film used was prepared by dissolving 1.0 mol% of p-phenylenediamine in N-methyl-2-pyrrolidone, adding 1 mol% of pyromellitic dianhydride thereto, and reacting at 20 ° C. for 12 hours. A polyamic acid varnish having a weight average molecular weight of about 100,000 in terms of standard polystyrene and a weight average molecular weight / number average molecular weight (Mv / Mn) of about 1.6 was obtained. This varnish was diluted to a concentration of 6%, and 0.3% by weight of γ-aminopropyltriethoxysilane was added as a solid content, followed by printing, heat treatment at 210 ° C./30 minutes, and a dense polyimide orientation of about 800 mm. A film was formed.
[0050]
Next, the alignment film surface was rubbed with a buff cloth attached to a rubbing roller to give a liquid crystal alignment film.
[0051]
On the other substrate, a color filter with a light shielding layer was formed, a polyimide alignment film was formed on the outermost surface in the same manner as described above, and liquid crystal alignment ability was imparted by rubbing treatment.
[0052]
In this example, the rubbing method was used as a method for imparting alignment ability, but other than that, for example, an ultraviolet curable resin solution was applied to form an alignment film, and polarized ultraviolet light was irradiated to cause a photochemical reaction. A method of imparting liquid crystal alignment ability, a method of using a multilayer film with good alignment formed by pulling an organic molecular film developed on the water surface on the substrate, and the like can also be used.
[0053]
In particular, the latter two methods are orientation control methods that have conventionally been difficult to provide a sufficiently large interface tilt angle. However, in the horizontal electric field method, the interface is different from the vertical electric field method represented by the conventional TN method. Since the tilt angle is not necessary in principle, practicality such as mass productivity can be improved by combination with the horizontal electric field method.
[0054]
Next, a sealant is applied to the periphery of these two substrates with the surfaces having the liquid crystal alignment ability facing each other and interposing spacers made of dispersed spherical polymer beads. Assembled. The rubbing directions of the two substrates were substantially parallel to each other, and the angle formed with the applied lateral electric field direction was 75 °. This cell has a positive dielectric anisotropy Δε and a value of 10.2 (1 kHz, 20 ° C.), a refractive index anisotropy Δn of 0.075 (wavelength 590 nm, 20 ° C.), and a torsional elastic constant K2 of 7 Nematic liquid crystal composition having a nematic-isotropic phase transition temperature T (NI) of about 76 ° C.AWas injected in a vacuum and sealed with a sealing material made of an ultraviolet curable resin. A liquid crystal panel having a liquid crystal layer thickness (gap) of 4.8 μm was manufactured. The retardation (Δnd) of this panel is 0.36 μm. This panel was sandwiched between two polarizing plates (G1220DU manufactured by Nitto Denko Corporation), and the polarizing transmission axis of one polarizing plate was substantially parallel to the rubbing direction, and the other was perpendicular to the rubbing direction. Thereafter, a drive circuit, a backlight, and the like were connected and modularized to obtain an active matrix liquid crystal display device. In this embodiment, a normally closed characteristic is obtained in which dark display is performed at a low voltage and bright display is performed at a high voltage.
[0055]
In order to quantitatively measure the image sticking and afterimage of the liquid crystal display device thus manufactured, evaluation was performed using an oscilloscope combined with a photodiode. First, the window pattern is displayed on the screen at the maximum brightness for 30 minutes, and then the halftone display in which the afterimage is most noticeable. Here, the entire surface is switched so that the brightness is 10% of the maximum brightness, and the pattern of the edge portion of the window is displayed. The time until disappearance was evaluated as the afterimage time, and the magnitude ΔB / B (10%) of the luminance fluctuation of the luminance B of the afterimage portion of the window and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0056]
As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation is about 2%, and the time until the afterimage disappears is about 50 milliseconds, and the fall response time of the liquid crystal used here is about 35 milliseconds. It was almost the same as the second. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0057]
Further, in order to evaluate the glass transition temperature Tg at the liquid crystal / alignment film interface of the liquid crystal display element, the temperature dependence of the luminance variation ΔB / B (10%) (afterimage intensity) was measured using a hot stage. . As a result, the liquid crystal composition used from room temperatureAThe luminance variation ΔB / B (10%) showed a constant value of about 3% or less up to about 73 ° C. near the nematic-isotropic phase transition temperature T (NI). Further, this liquid crystal compositionALiquid crystal composition having a high T (N-I) point of 115 ° C.BThe temperature dependence of the same interface Tg was measured using a liquid crystal display device manufactured using the same liquid crystal cell forming process and materials other than that. As a result, as shown in FIG. 5, the luminance fluctuation ΔB / B (10%) gradually increased near about 100 ° C., and reached about 10% at 110 ° C. From the above results, the interface Tg of the liquid crystal display element used in this example is estimated to be about 100 ° C., and the liquid crystal composition used isAThe T (N-I) point was found to be higher than 76 ° C.
[0058]
(Example 2)
Except for the alignment film used, 1.0 mol% of m-phenylenediamine was dissolved in N-methyl-2-pyrrolidone in the same manner as in Example 1, and 3,3 ′, 4,4′-diphenyl ether tetra Carboxylic acid dianhydride 1.0 mol% was added, and it was made to react at 40 degreeC for 6 hours, the standard polystyrene conversion weight average molecular weight is about 21,000, and a weight average molecular weight / number average molecular weight (Mv / Mn) is about 1.8. A polyamic acid varnish was obtained. This varnish was diluted to a concentration of 6%, and 0.3% by weight of γ-aminopropyltriethoxysilane was added as a solid content, followed by printing, heat treatment at 225 ° C./30 minutes, and a dense polyimide orientation of about 600 mm. A film was formed.
[0059]
Further, the surface elastic modulus of the polyimide alignment film obtained by the same production method as described above was evaluated using a scanning viscoelasticity microscope (abbreviated as SVM). Here, the principle of surface elastic modulus measurement will be briefly described. In recent years, the SVM has been widely known as an atomic force microscope (Atomic Force Microscopy,
Applying the device (abbreviated as AFM), the area where repulsive force acts on the AFM probe and the sample surface, that is, forcing the sample into sinusoidal vibration (distortion) using a piezo element while the probe deforms the surface And response vibration (stress) of the same period from the probe is detected. The dynamic viscoelasticity function of the sample surface is evaluated from the amplitude and phase difference of the stress and strain signals (for details, see Keiji Tanaka et al., Polymer Journal, Vol. 53 (No. 10), 1996, p582. It is described in).
[0060]
As a result of measuring the surface elastic modulus of 10 Hz of the polyimide alignment film using this apparatus, a value of about 2.5 GPa was obtained.
[0061]
In the same manner as in Example 1, in order to quantitatively measure image sticking and afterimage of the liquid crystal display device thus manufactured, evaluation was performed using an oscilloscope combined with a photodiode. First, the window pattern is displayed on the screen at the maximum brightness for 30 minutes, and then the halftone display in which the afterimage is most noticeable. Here, the entire surface is switched so that the brightness is 10% of the maximum brightness, and the pattern of the edge portion of the window is displayed. The time until disappearance was evaluated as the afterimage time, and the magnitude ΔB / B (10%) of the luminance fluctuation of the luminance B of the afterimage portion of the window and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0062]
As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation is about 3%, and the time until the afterimage disappears is about 62 milliseconds, and the fall response time of the liquid crystal used here is about 35 milliseconds. It was almost the same as the second. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0063]
Further, as a result of evaluating the interface Tg of the liquid crystal / alignment film in the same manner as in Example 1, the interface Tg was about 90 ° C., and T (N—I) of the liquid crystal composition A used was 76 ° C. or higher. Met.
[0064]
(Example 3)
Except for the alignment film used, 1.0 mol% of 4,4′-diaminodiphenylmethane was dissolved in a mixed solvent of N-methyl-2-pyrrolidone and dimethylacetamide in the same manner as in Example 1, , 3,4-cyclopentanetetracarboxylic dianhydride (1.0 mol%) was added and reacted at 30 ° C. for 12 hours to prepare a polyamic acid varnish having a standard polystyrene equivalent weight average molecular weight of about 12,000 to 250,000. . Thereafter, the varnish was collected by gel permeation chromatography into a monodispersed polyamic acid varnish having a weight average molecular weight of about 150,000 and a weight average molecular weight / number average molecular weight (Mv / Mn) of 1.51. This varnish was diluted to a concentration of 6%, 0.3% by weight of γ-aminopropyltriethoxysilane was added as a solid content, and then printed.
A heat treatment at 220 ° C./30 minutes was performed to form a dense polyimide alignment film of about 600 mm.
[0065]
In the same manner as in Example 1, in order to quantitatively measure image sticking and afterimage of the liquid crystal display device thus manufactured, evaluation was performed using an oscilloscope combined with a photodiode. First, the window pattern is displayed on the screen at the maximum brightness for 30 minutes, and then the halftone display in which the afterimage is most noticeable. Here, the entire surface is switched so that the brightness is 10% of the maximum brightness, and the pattern of the edge portion of the window is displayed. The time until disappearance was evaluated as the afterimage time, and the magnitude ΔB / B (10%) of the luminance fluctuation of the luminance B of the afterimage portion of the window and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0066]
As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation is about 2%, and the time until the afterimage disappears is about 48 milliseconds, and the fall response time of the liquid crystal used here is about 35 milliseconds. It was almost the same as the second. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0067]
Next, using the same alignment film material as the liquid crystal display device obtained in this way, an alignment film is formed on the glass substrate by the same process, rubbed, and the same liquid crystal composition is sealed to produce a liquid crystal cell. When an extrapolated length representing the strength of torsional coupling between the liquid crystal molecules and the alignment film surface at the interface is measured by the Fredericks transition method (Young, Rosenblad, Applied Physics Letter, Vol. 43, 1983, p62). It was 0.0 μm.
[0068]
Here, the principle of the extrapolation length measurement method by the Fredericks transition method will be described. In this measurement method, the orientation change (Frederix transition) of the liquid crystal molecules with respect to the transverse electric field in the transverse electric field method obtained approximately when the torsional coupling at the interface between the two substrates paired with the liquid crystal layer is the same is obtained. Expression (1) representing the dependence of the threshold voltage Vc on the thickness d of the liquid crystal layer (Yokoyama, Molecular Crystal and Liquid Crystal, Vol. 165, 1988, p265, and Oe, Kondo, Applied Physics Letter, Vol. 67) , 1995, p3895).
[0069]
(1 / Vc) = (d + 2b) × πg√ (Δε / K2) (1)
Here, d and g are the gap between the substrates (the thickness of the liquid crystal layer), the gap between the electrode ends, K2 and Δε are the twist elastic constant and dielectric anisotropy of the liquid crystal composition, respectively, and b is the torsional coupling of the alignment film surface It is an extrapolation length that represents the strength of torsional coupling between the liquid crystal molecules and the alignment film surface at the interface defined by the following equation using the coefficient A2.
[0070]
b = K2 / A2 (2)
This extrapolation length b becomes smaller as the torsional coupling on the alignment film surface becomes stronger. For example, in the case of such a strong bond that the orientation direction of liquid crystal molecules is considered fixed on the alignment film surface, the extrapolation length b Is considered zero.
[0071]
From this formula, a plurality of liquid crystal cells having different liquid crystal layer thickness d only are prepared, and the measured value is (1 / Vc) measured for each of the liquid crystal cells on the horizontal (x) axis and on the vertical (y) axis. , The y-intercept obtained by extrapolating these points with a straight line is -2b, that is, extrapolation length (the coefficient 2 in this case represents the contribution to the extrapolation length from both when the upper and lower interfaces are the same) give.
[0072]
In this measuring method, accurate measurement is possible only in the case of weak torsional coupling in which the extrapolation length is substantially the same as the thickness of the liquid crystal layer.
[0073]
As an extrapolation length measurement method that can be applied even in the case of stronger torsional coupling, the strong electric field method (Yokoyama, Fun Sprang, Journal of Applied Physics, Vol. 57, 1985, p452), and micro-twisting at the interface can be used. The measurement method (Akabane, Kaneko, Kimura, Japan Journal of Applied Physics, Vol. 35, 1996, p4434) is known, but in the case of weak torsional coupling within the meaning of the present invention, the measured value is Values that do not differ greatly by any of these measurement methods can be obtained with sufficient accuracy.
[0074]
When the extrapolation length obtained in this way is calculated with the center gap of 4.6 μm, the ratio b * = b / d of the extrapolation length b to the gap d is 0.217.
[0075]
The torsional coupling coefficient A2 on the alignment film surface can be mechanically obtained from the equation (2) using the following equation from the extrapolation length b and the torsional elastic constant K2 of the liquid crystal.
[0076]
A2 = K2 / b (3)
Therefore, in this embodiment, A2 is 7.0 μN / m.
[0077]
(Example 4)
Except for the alignment film used, 1.0 mol% of 4-fluoro-metaphenylenediamine was dissolved in N-methyl-2-pyrrolidone in the same manner as in Example 1, and 3,3 ′, 4,4 ′ was dissolved therein. -1.0 mol% of biscyclobutanetetracarboxylic dianhydride was added and reacted at 20 ° C for 8 hours and at 100 ° C for 2 hours, the weight average molecular weight of standard polystyrene conversion was about 17,000, weight average molecular weight / number average A polyamideimide having a molecular weight (Mv / Mn) of 1.85 was obtained. This varnish was diluted to a concentration of 6%, and γ-aminopropyltriethoxysilane was added in an amount of 0.3% by weight, followed by printing, heat treatment at 200 ° C./30 minutes, and a dense polyamideimide of about 600 mm. An alignment film was formed, and a liquid crystal display device having a liquid crystal layer thickness d of 4.2 μm was prepared.
[0078]
In the same manner as in Example 1, in order to quantitatively measure image sticking and afterimage of the liquid crystal display device thus manufactured, evaluation was performed using an oscilloscope combined with a photodiode. First, the window pattern is displayed on the screen at the maximum brightness for 30 minutes, and then the halftone display in which the afterimage is most noticeable. Here, the entire surface is switched so that the brightness is 10% of the maximum brightness, and the pattern of the edge portion of the window is displayed. The time until disappearance was evaluated as the afterimage time, and the magnitude ΔB / B (10%) of the luminance fluctuation of the luminance B of the afterimage portion of the window and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0079]
As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation is about 2%, and the time until the afterimage disappears is about 55 milliseconds, and the fall response time of the liquid crystal used here is about 35 milliseconds. It was almost the same as the second. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0080]
Further, the interface Tg of the liquid crystal / alignment film was evaluated in the same manner as in Example 1. As a result, the interface Tg was about 105 ° C., and T (NI) = 76 ° C. or higher of the liquid crystal composition A used. Met. Furthermore, using the same scanning viscoelastic microscope (SVM) apparatus as in Example 2, the surface elastic modulus at 50 Hz of the polyimide alignment film was measured, and as a result, a value of about 5 GPa was obtained.
[0081]
(Example 5)
A liquid crystal panel having a liquid crystal layer thickness (gap) d of 5.0 μm was prepared in the same manner as in Example 1 except for the alignment film material used. The retardation (Δnd) of this panel is 0.375 μm.
[0082]
As the alignment film material, an inorganic alignment film material in which an inorganic alignment control layer made of silicon oxide was formed on the outermost surface of the insulating protective film made of silicon nitride by oblique deposition was used for the substrate on the thin film transistor side.
[0083]
In oblique deposition, a louver that regulates the deposition direction so that the tilt angle of the liquid crystal orientation is almost 0 ° so that it is 60 ° from the normal of the substrate (edited by the Society of Polymer Science, New Polymer Experiments, Volume 10: Polymer physical properties (3) —surface, interface and membrane / transport—, 233p).
[0084]
On the other substrate, a color filter with a light shielding layer was formed, a polyimide alignment film was formed on the outermost surface, and then the alignment film surface was rubbed with a buff cloth attached to a rubbing roller to give a liquid crystal alignment film.
[0085]
The polyimide alignment film was formed by printing a solution of PIQ made by Hitachi Chemical, which is a solvent-soluble polyimide precursor, on the substrate surface, followed by heat treatment at 210 ° C./30 minutes.
[0086]
Further, when the extrapolation length b was measured by the Fredericks transition method as in Example 3, it was 1.6 μm.
[0087]
Since the torsional bond between the surface on which the polyimide alignment film PIQ is rubbed and the liquid crystal molecules is very strong and the extrapolation length at this interface is almost zero, it is known from the experiment conducted separately. Most of the length is considered to be due to the inorganic alignment film formed by oblique deposition of silicon oxide.
[0088]
When calculated with the above gap of 5.0 μm, the ratio b * of the extrapolation length b to the gap was 0.32, and the torsional coupling coefficient A2 on the alignment film surface was 4.38 μN / m.
[0089]
As in Example 1, the image pattern of the liquid crystal display device manufactured in this way and the afterimage were quantitatively evaluated using the window pattern. As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance variation was about The time until the afterimage disappeared was about 50 milliseconds, which was almost the same as the fall response time of the liquid crystal used here, about 35 milliseconds. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0090]
(Example 6)
A diazobenzene group is contained as a diamine compound in the same manner as in Example 1 except for the alignment film used.
[0091]
[Chemical formula 2]

[0092]
And 4,4'-diaminodiphenylmethane mixed at an equimolar ratio, and polyamic acid is added to pyromellitic dianhydride and / or 1,2,3,4-cyclobutanetetracarboxylic dianhydride acid anhydride After being applied to the substrate surface, baking and imidization were performed at 200 ° C. for 30 minutes, and irradiation with polarized light having a wavelength of 420 nm was performed.
[0093]
Then, after encapsulating the nematic liquid crystal composition in the same manner as in Example 1, annealing was performed at 100 ° C. for 10 minutes to obtain a liquid crystal alignment in a direction substantially perpendicular to the irradiation polarization direction. Thus, a liquid crystal display device having a liquid crystal layer thickness d of 4.0 μm was obtained.
The interface Tg of the liquid crystal / alignment film was evaluated in the same manner as in Example 1. As a result, the interface Tg was about 85 ° C., and T (N−I) of the liquid crystal composition A used was 76 ° C. or higher. It was. In addition, as in Example 1, the image pattern of the liquid crystal display device thus manufactured using the window pattern and the afterimage were quantitatively evaluated. As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation was obtained. Was about 3%, and the time until the afterimage disappeared was about 50 milliseconds, which was almost the same as the fall response time of the liquid crystal used here of about 35 milliseconds. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0094]
Further, when the extrapolation length b was measured by the Fredericks transition method in the same manner as in Example 3, it was 1.0 μm. Therefore, the ratio b * of the extrapolation length b to the gap is 0.25. Further, from the value of the elastic constant K2 with respect to the torsional deformation of the liquid crystal composition used and the measured value of the extrapolation length b, the torsional coupling constant A2 on the alignment film surface of this example is 5.0 μN / m. .
[0095]
(Example 7)
Except for the alignment film used, the diamine compound contains a stilbene group in the same manner as in Example 6.
[0096]
[Chemical Formula 3]

[0097]
And 4,4'-diaminodiphenylmethane mixed at an equimolar ratio, and polyamic acid is added to pyromellitic dianhydride and / or 1,2,3,4-cyclobutanetetracarboxylic dianhydride acid anhydride After being applied to the substrate surface, baking and imidization were performed at 210 ° C. for 30 minutes, and irradiation with polarized light with a wavelength of 308 nm was performed.
[0098]
Then, after encapsulating the nematic liquid crystal composition in the same manner as in Example 1, annealing was performed at 100 ° C. for 10 minutes to obtain a liquid crystal alignment in a direction substantially perpendicular to the irradiation polarization direction. Thus, a liquid crystal display device having a liquid crystal layer thickness d of 4.0 μm was obtained.
The interface Tg of the liquid crystal / alignment film was evaluated in the same manner as in Example 1. As a result, the interface Tg was about 80 ° C., and T (N−I) of the liquid crystal composition A used was 76 ° C. or higher. It was. In addition, as in Example 1, the image pattern of the liquid crystal display device thus manufactured using the window pattern and the afterimage were quantitatively evaluated. As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation was obtained. Was about 3%, and the time until the afterimage disappeared was about 48 milliseconds, which was almost the same as the fall response time of the liquid crystal used here of about 35 milliseconds. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0099]
(Example 8)
Using a diamine compound having an acetylene group in addition to a diamine compound having a stilbene group as in Example 7 and 4,4'-diaminodiphenylmethane mixed in an equimolar ratio, pyromellitic dianhydride and / or 1 , 2,3,4-cyclobutanetetracarboxylic dianhydride, synthesized as polyamic acid, applied to the substrate surface, baked at 210 ° C. for 30 minutes, imidized, XeCl₂Irradiation with polarized light having a wavelength of 308 nm was performed using a gas excimer laser.
[0100]
Then, after encapsulating the nematic liquid crystal composition in the same manner as in Example 1, annealing was performed at 100 ° C. for 10 minutes to obtain a liquid crystal alignment in a direction substantially perpendicular to the irradiation polarization direction. Thus, a liquid crystal display device having a liquid crystal layer thickness d of 4.0 μm was obtained.
The interface Tg of the liquid crystal / alignment film was evaluated in the same manner as in Example 1. As a result, the interface Tg was about 100 ° C., and T (N−I) of the liquid crystal composition A used was 76 ° C. or higher. It was. In addition, as in Example 1, the image pattern of the liquid crystal display device thus manufactured using the window pattern and the afterimage were quantitatively evaluated. As a result, the afterimage intensity ΔB / B (10%) corresponding to the luminance fluctuation was obtained. Was about 2%, and the time until the afterimage disappeared was about 40 milliseconds, which was almost the same as the fall response time of the liquid crystal used here of about 35 milliseconds. Even in visual image quality afterimage inspection, no image burn-in and display unevenness due to afterimage were observed, and high display characteristics were obtained. Thus, by using the alignment film, it was possible to obtain a liquid crystal display element in which image burn-in and afterimage display defects were reduced.
[0101]
(Comparative Example 1)
2,2-bis {4- (p-aminophenoxy) phenyl} propane 1.0 mol%, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride 1.0 mol% were added to N-methyl- Polymerization was performed in 2-pyrrolidone at 20 ° C. for 10 hours to obtain a polyamic acid varnish having a standard polystyrene equivalent weight average molecular weight of about 200,000 and a weight average molecular weight / number average molecular weight (Mv / Mn) of about 1.9. . This varnish was diluted to a concentration of 6%, and 0.3 wt% of γ-aminopropyltriethoxysilane was added as a solid content, followed by printing, heat treatment at 220 ° C / 30 minutes, and a dense polyimide orientation of about 800 mm. A film was formed.
[0102]
Next, using this alignment film material, a liquid crystal display device was prepared in the same manner as in Example 1, and image printing and afterimage of the liquid crystal display device were quantitatively measured and evaluated. First, the window pattern is displayed on the screen at maximum brightness for 30 minutes, and then the entire screen is switched to the halftone display where the afterimage is most noticeable. The time until the edge pattern disappears is the afterimage time and the afterimage of the window. The magnitude ΔB / B (10%) of the luminance variation of the luminance B between the portion and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0103]
As a result, the afterimage intensity ΔB / B (10%), which is a luminance fluctuation, is as large as about 5%, and it takes about 60 minutes until the afterimage disappears. This was confirmed as display unevenness due to afterimages. By using the alignment film as described above, image sticking and display defects due to afterimages were conspicuous.
[0104]
Further, as a result of evaluating the interface Tg of the liquid crystal / alignment film in the same manner as in Example 1, the interface Tg was about 58 ° C., and T (N−I) = 76 ° C. or less of the liquid crystal composition A used. Met. Furthermore, using the same scanning viscoelastic microscope (SVM) apparatus as in Example 2, the surface elastic modulus at 10 Hz of the polyimide alignment film was measured. As a result, a value of about 0.1 GPa was obtained.
[0105]
(Comparative Example 2)
2,2-bis [4- (p-aminophenoxy) phenyl] octane 0.5 mol%, 4,4′-diaminodiphenylmethane 0.5 mol%, 3,3 ′, 4,4 ′,-biphenyltetracarboxylic 1.0 mol% of acid dianhydride was polymerized in N-methyl-2-pyrrolidone at 20 ° C. for 8 hours to obtain a standard polystyrene equivalent weight average molecular weight of about 40,000, weight average molecular weight / number average molecular weight (Mv / A polyamic acid varnish having a Mn) of about 1.8 was obtained. This varnish was diluted to a concentration of 6%, and 0.3% by weight of γ-aminopropyltriethoxysilane was added as a solid content, followed by printing, heat treatment at 200 ° C./30 minutes, and a dense polyimide orientation of about 800 mm. A film was formed.
[0106]
Next, using this alignment film material, a liquid crystal display device was prepared in the same manner as in Example 1, and image printing and afterimage of the liquid crystal display device were quantitatively measured and evaluated. First, the window pattern is displayed on the screen at maximum brightness for 30 minutes, and then the entire screen is switched to the halftone display where the afterimage is most noticeable. The time until the edge pattern disappears is the afterimage time and the afterimage of the window. The magnitude ΔB / B (10%) of the luminance variation of the luminance B between the portion and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0107]
As a result, the afterimage intensity ΔB / B (10%), which is the luminance fluctuation, is as large as about 8%, and it takes about 120 minutes until the afterimage disappears. Even in the visual image afterimage inspection, a clear image is printed. This was confirmed as display unevenness due to afterimages. By using the alignment film as described above, image sticking and display defects due to afterimages were conspicuous.
[0108]
Further, the interface Tg of the liquid crystal / alignment film was evaluated in the same manner as in Example 1. As a result, the interface Tg was about 60 ° C., and T (NI) = 76 ° C. or less of the liquid crystal composition A used. Met. Furthermore, using the same scanning viscoelastic microscope (SVM) apparatus as in Example 2, the surface elastic modulus at 10 Hz of the polyimide alignment film was measured, and as a result, a value of about 0.08 GPa was obtained.
[0109]
(Comparative Example 3)
1.0 mol% of 2,2-bis [4- (p-aminophenoxy) phenyl] hexafluoropropane and 1.0 mol% of 4,4′-diaminodiphenyl ether in N-methyl-2-pyrrolidone Polymerization was carried out at 20 ° C. for 6 hours to obtain a polyamic acid varnish having a standard polystyrene equivalent weight average molecular weight of about 4000 and a weight average molecular weight / number average molecular weight (Mv / Mn) of about 3.5. This varnish was diluted to a concentration of 6%, 0.3% by weight of γ-aminopropyltriethoxysilane was added as a solid content, then printed and heat-treated at 200 ° C./30 minutes for a dense polyimide orientation of about 900 mm. A film was formed.
[0110]
Next, using this alignment film material, a liquid crystal display device was prepared in the same manner as in Example 1, and image printing and afterimage of the liquid crystal display device were quantitatively measured and evaluated. First, the window pattern is displayed on the screen at maximum brightness for 30 minutes, and then the entire screen is switched to the halftone display where the afterimage is most noticeable. The time until the edge pattern disappears is the afterimage time and the afterimage of the window. The magnitude ΔB / B (10%) of the luminance variation of the luminance B between the portion and the peripheral halftone portion was evaluated as the afterimage intensity. However, the allowable afterimage intensity is 3% or less.
[0111]
As a result, the afterimage intensity ΔB / B (10%), which is a luminance variation, is as large as about 20%, and it takes about 100 minutes until the afterimage disappears. Even in visual image afterimage inspection, a clear image is printed. This was confirmed as display unevenness due to afterimages. By using the alignment film as described above, image sticking and display defects due to afterimages were conspicuous.
[0112]
Further, the interface Tg of the liquid crystal / alignment film was evaluated in the same manner as in Example 1. As a result, the interface Tg was about 50 ° C., and T (N−I) = 76 ° C. or less of the liquid crystal composition A used. Met. Furthermore, using the same scanning viscoelastic microscope (SVM) apparatus as in Example 2, the surface elastic modulus at 10 Hz of the polyimide alignment film was measured. As a result, a value of about 0.1 GPa was obtained.
[0113]
【The invention's effect】
According to the present invention, it is possible to reduce image sticking and afterimage phenomenon, which are problems inherent to an IPS-TFT-LCD that operates by applying an electric field to a liquid crystal layer in a direction substantially parallel to the substrate. It is possible to provide an active matrix liquid crystal display device with high image quality and excellent mass productivity with little display unevenness due to image sticking and afterimage phenomenon.
[Brief description of the drawings]
FIG. 1 is a diagram showing an operation of a liquid crystal in a liquid crystal display device of the present invention.
2A and 2B are diagrams illustrating electro-optical characteristics of the present invention, in which FIG. 2A is a diagram illustrating basic voltage / luminance characteristics, and FIG. 2B is a diagram illustrating voltage / luminance characteristics indicating an afterimage phenomenon;
FIG. 3 is a diagram showing polar coupling and torsional coupling between liquid crystal molecules and a substrate surface.
4A and 4B are diagrams showing a structure of a thin film transistor, an electrode, and a wiring according to the present invention, where FIG. 4A is a front view, and FIGS. 4B and 2C are side sectional views.
FIG. 5 shows the temperature dependence of afterimage intensity.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Common electrode (common electrode), 2 ... Gate insulating film, 3 ... Signal electrode (drain electrode), 4 ... Pixel electrode (source electrode), 5 ... Alignment film, 6 ... In liquid crystal composition layer Liquid crystal molecules, 7 ... substrate, 8 ... polarizing plate, 9 ... electric field, 10 ... molecular long axis orientation direction (rubbing direction) on the interface, 11 ... polarizing plate transmission axis direction, 12 ... scanning electrode (gate electrode), 13 ... Amorphous silicon, 14 ... Thin film transistor element.

Claims (8)

An active matrix liquid crystal display device having a plurality of switching elements,
A pair of substrates at least one of which is transparent;
A liquid crystal layer disposed between the pair of substrates;
An electrode structure that is formed on one of the pair of substrates and generates an electric field in the liquid crystal layer having a component that is predominantly parallel to the substrate surface;
A pair of alignment control films formed on respective surfaces in contact with the liquid crystal layer on the pair of substrates;
A pair of polarizing plates arranged to sandwich the pair of substrates,
Nematic liquid crystal composition having a glass transition temperature Tg of the interface between the orientation control film and the liquid crystal layer forms the liquid crystal layer - Ri isotropic phase transition temperature T (N-I) or Der,
At least one of the pair of alignment control films includes a diamine compound represented by the chemical formula H ₂ N—R—NH ₂ and a chemical formula

A polyamic acid dehydrated ring-closed organic polymer composed of tetracarboxylic dianhydride represented by the formula: wherein R and X in the repeating structure are represented by —O—, —S—, —CH ₂ — , —C ( CH ₃ ) ₂ −, −C ( CF ₃ ) ₂ −, −SO ₂ − An active matrix type liquid crystal display device comprising three or less organic polymers.   2. The active matrix liquid crystal display device according to claim 1, wherein a glass transition temperature Tg of the surface of the alignment control film is equal to or higher than a nematic-isotropic phase transition temperature T (NI) of the liquid crystal composition forming the liquid crystal layer.   2. The active matrix liquid crystal display device according to claim 1, wherein a torsional coupling coefficient A2 of the surface of the alignment control film with respect to liquid crystal molecules at an interface between the alignment control film and the liquid crystal layer is 20 μN / m or less.   2. The active film according to claim 1, wherein the pair of polarizing plates satisfy the parameter d · Δn satisfying 0.2 μm <d · Δn <0.5 μm when the refractive anisotropy of the liquid crystal layer is Δn and the thickness is d. Matrix type liquid crystal display device. 2. The active matrix liquid crystal display device according to claim 1 , wherein the organic polymer has a weight average molecular weight of 10,000 to 300,000.   2. The active matrix liquid crystal display device according to claim 1, wherein the alignment control film is a photoreactive material layer. 7. The active matrix liquid crystal display device according to claim 6 , wherein the photoreactive material layer controls the alignment direction of the liquid crystal layer by irradiating polarized light. 8. The active matrix liquid crystal display device according to claim 7 , wherein the photoreactive material layer includes an organic polymer containing a polymer and / or an oligomer containing at least one diazobenzene group or a derivative thereof.

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