JP4882140B2 - Multi-domain liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-domain liquid crystal display device having high contrast and excellent in a visual angle characteristic, without increasing complex processes such as micro-fabrication process of a common electrode, and requiring a high degree of sticking technology. SOLUTION: In the multi-domain liquid crystal display device a control electrode 73 is connected with a source terminal 57 which is one of the terminals of a TFT 54 as a switching element, and a pixel electrode 71 with an opening part 74 formed therein has coupling capacitance 126 across the control electrode 73, and a divided signal voltage is applied to the pixel electrode 71 via the coupling capacitance 126.

Description

【００７６】
次に、表１に示したように制御電極電圧係数を変化させたＴＦＴ−ＬＣＤ（Liquid Crystal Device）を製造して表示動作を行ない、顕微鏡ならびに目視により観察した。表１の制御電極電圧係数の各値１．１、１．２、１．３、及び１．４、のそれぞれに対応する表示時の画素の顕微鏡写真を、図３１、図３２、図３３及び図３４に示した。図３１〜図３４から明らかなように、制御電極電圧係数の異なる各々のＴＦＴ−ＬＣＤにおいて、この発明及び参考発明の原理に基づくマルチドメイン液晶配向制御を実現することができた。特に、制御電極電圧係数が１．２以上、より好ましくは１．３以上の場合において、より正確に配向制御を実現することができた。これに対して、制御電極電圧係数が１．１と値の小さいＴＦＴ−ＬＣＤにおいては、目視観察により若干のざらつき感が見られた。
以上の結果から明らかなように、制御電極電圧係数については、その値が大きいほうが配向制御性が優れるが、これに伴って画素電極に印加される電圧は相対的に減少するため、駆動電圧あるいは明るさの点からは、制御電極電圧係数は大きくなり過ぎるのは望ましくない。これらのことを考慮すると、制御電極電圧係数は略１．３程度が最も好ましいと考えられる。
【００７７】
このように、この例の構成によっても、第１参考例において述べたのと略同様な効果を得ることができる。
【００７８】
◇第７参考例
参考発明の第７参考例では、第５参考例に示した図２３（ｗ）の適用例を基に、微小配向領域のサイズを異ならせた風数の実験用液晶セルを製造してそれぞれ比較検討した。ここで、微小配向領域とは、制御電極７３、画素電極７１の端部及び画素電極７１に設けられた開口部７４等の境界によって区切られる領域を示し、液晶が概ね単一の配向をとる領域を示している。
この例における図２３（ｗ）の適用例においては、一つの微小配向領域のサイズは略４０μｍ平方である。これを基に、微小配向領域サイズを略２０μｍ平方とした実験用液晶セルを製造した。比較例として、微小配向領域サイズを略４０μｍ平方とした実験用液晶セルも併せて製造した。これらの実験用液晶セルでは、ＴＦＴやゲートバスライン及びドレインバスライン等を省略し、制御電極７３と画素電極７２とのそれぞれに直接電圧を印加できる構造とした。
【００７９】
図３５はこの例の実験用液晶セルにおいて、暗状態から明状態に電圧を切り替えた後の顕微鏡写真を示している。図３５（ａ）は暗状態から明状態に電圧を切り替えた後２０ｍｓ放置した後の様子を示す写真、図３５(ｂ)は暗状態から明状態に電圧を切り替えた後１秒以上放置したあとの様子を示す写真である。
両写真を比較して明らかなように、この例では、電圧印加後、２０ｍｓ以内に定常状態の配向状態とほぼ等しい配向状態が得られ、配向の安定性と電気光学的応答特性が優れていることがわかった。応答時間の具体的な測定値は、暗→明が約１５ｍｓ、明→暗が約９ｍｓであった。
【００８０】
一方、図３６は比較例において、暗状態から明状態に電圧を切り替えた後の顕微鏡写真を示している。図３６（ａ）は暗状態から明状態に電圧を切り替えた後２０ｍｓ放置した後の様子を示す写真、図３６(ｂ)は暗状態から明状態に電圧を切り替えた後１秒以上放置したあとの様子を示す写真である。
両写真を比較して明らかなように、比較例では、電圧印加後、明るい定常状態の配向状態を得るまでに若干の時間を必要とすることがわかった。応答時間の具体的な測定値は、暗→明が約１４０ｍｓ、明→暗が約９ｍｓであった。
【００８１】
上述したようにこの例では、電気光学的応答特性については、微小配向領域サイズを小さく（２０μｍ平方）した方が、微小配向領域サイズを大きく（４０μｍ平方）した場合よりも優れていること確認された。しかしながら、素子全体の光透過率については、各微小領域境界に見られる暗線の密度の違いにより、微小領域配向領域サイズが大きいほうが好ましいことがわかった。すなわち、微小配向領域サイズを大きく（４０μｍ平方）とした方が、微小配向領域サイズを小さく（２０μｍ平方）した場合よりも実験用液晶セル全体での光透過率は高くなることが確認された。
【００８２】
微小配向領域サイズは、上記のような理由から、動画表示を行なうかどうかといった用途によって、また、目的とするＴＦＴ−ＬＣＤの画素ピッチとの兼ね合いを考慮して適宜選択できる。動画表示をおこなう場合には、略２０μｍ平方程度あるいはそれ以下、動画表示を行なわない場合は略４０μｍ平方程度あるいはそれ以上とすることが好ましい。もちろん用途によっては２０μｍ〜４０μｍ平方の範囲に設定してもよい。
【００８３】
このように、この例の構成によっても、第１参考例において述べたのと略同様な効果を得ることができる。
【００８４】
◇第８参考例
図３７は、参考発明の第８参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図、図３８は図３７のＨ−Ｈ’における模式的部分断面図、図３９は図３７のＩ−Ｉ’における模式的部分断面図である。この例のマルチドメイン液晶表示装置の構成が、上述した第１参考例の構成と大きく異なるところは、制御電極をスイッチング素子としてのＴＦＴのソース端子と一体的に形成するようにした点である。
すなわち、この例のマルチドメイン液晶表示装置は、図３７〜図３９に示すように、制御電極７３はＴＦＴ５４のソース端子５７と一体的にクロム等の不透明金属により形成されている。このように構成すると、既に述べたように、結合容量１２６の容量値を大きく形成した場合に、開口率の低下を招くことが懸念されるが、この例においては、その点も考慮して十分な開口率を確保できる構成になっている。具体的には、ゲート絶縁膜６１を介して制御電極７３より下層に結合容量電極１７１を形成して、この結合容量電極１７１と、層間絶縁膜６３を介して制御電極７３より上層に形成した画素電極７１とが、それぞれ制御電極７３との重畳部を有しており、互いにコンタクトホール１７２を通じて接続されている。図３７では、結合容量電極１７１の大部分が制御電極７３の下に隠れているので分かりにくいが、図３９から明らかなように、結合容量電極１７１は、略制御電極７３の形状に沿ってこの下側に配置されている。
【００８５】
この例によれば、制御電極７３の上下両側に結合容量１２６を形成できるので、結合容量１２６の容量値を大きくする場合にも、制御電極７３の面積をそれほど大きくしなくとも、十分な開口率を確保することができる。
この例では、制御電極７３を画素電極７１よりも下層に形成した例を示したが、逆に画素電極７１を制御電極７３の下層に形成することもでき、画素電極７１のさらに下層に配置した結合容量電極１７１と、上層の制御電極７３とをコンタクトホール１７２を通じて接続することにより、画素電極７１の上下両側に結合容量を形成することができる。
【００８６】
さらに、この例によれば、付加容量１２７に関しても、小さな重畳面積により十分な容量値を得るための構成を採用している。すなわち、コンタクトホール１７７において、接続端子１７６により共通容量ライン７２に接続された付加容量端子１７５、画素電極７１との重畳部により付加容量１２７を形成している。ここで、共通容量ライン７２はゲートバスライン５５と同層の金属膜により形成されており、付加容量端子１７５はドレインバスライン５６と同層の金属膜により形成されている。このように、付加容量端子１７５は共通容量ライン７２よりも画素電極７１に近い層に形成されているので、小さな重畳面積により十分な付加容量１２７の容量値を確保することができる。
【００８７】
この例では、層間絶縁膜６３を介して付加容量１２７を形成した例を示したが、ゲート絶縁膜６１を介して付加容量１２７を形成する構成とした場合であっても、これら２つの絶縁膜６３、６１を介した付加容量１２７を形成する構成よりも大きな容量値を確保しやすい。なお、小さな重畳面積で十分な容量値を得て開口率を確保するためには、上記のような層構造における工夫の他、例えば、ゲート絶縁膜６１あるいは層間絶縁膜６３の膜厚を薄くしたり、誘電率を大きくする等でも効果がある。
【００８８】
また、上記の開口率の確保に関する効果以外にも、この例においては、制御電極７３を金属膜により構成することにより、制御電極７３のパターニング精度を向上できるという効果もある。この理由は、通常、ＩＴＯ等の透明電極よりもＣｒ等の不透明金属のほうが、ウェットエッチングの精度が高いからである。この参考発明のマルチドメイン液晶表示装置においては、各々の電極の重畳部に形成される各容量の容量値が重要な設計パラメーターとなるため、重畳部の面積を決める各電極のパターニング精度の向上は重要である。
【００８９】
次に、図４１乃至図４３を参照して、この例のマルチドメイン液晶表示装置の製造方法について工程順に説明する。
まず、図４１（ａ）に示すように、ガラスから成る第１の基板１１上にクロムをスパッタ成膜した後、フォトリソグラフィ技術を用いてウェットエッチングによりクロムをパターニングして、ゲートバスライン５５、共通容量ライン７２、及び結合容量電極１７１を形成した。続いて、図４１（ｂ）に示すように、ＣＶＤ法を用いて窒化シリコンを成膜して、ゲート絶縁膜６１を一様に形成した。なお、ゲート絶縁膜６１は、例えば二酸化シリコン等でも良く、また窒化シリコンと酸化シリコンとの積層膜等でも良い。もちろん有機膜等でも構わない。次にＣＶＤ法によりアモルファスシリコン層を成膜し、フォトリソグラフィー技術を用いてドライエッチングによりパターニングして、アイランド状にＴＦＴ５４の活性層６４を形成した。
【００９０】
次に、図４２（ｃ）に示すように、クロムをスパッタ成膜した後、フォトグラフィ技術を用いてウェットエッチングによりパターニングして、ドレインバスライン５６、ドレイン端子５８、ソース端子５７、制御電極７３、付加容量端子１７５を形成した。続いて、図４２（ｄ）に示すように、窒化シリコンをＣＶＤ成膜して層間絶縁膜６３を一体的に一様に形成し、さらにフォトリソグラフィ技術を用いてドライエッチングにより層間絶縁膜６３及びゲート絶縁膜６１を連続的にパターニングして、コンタクトホール１７２、１７７を形成した。続いて、図４３に示すように、ＩＴＯをスパッタ成膜して、フォトリソグラフィ技術を用いてウェットエッチングによりパターニングして、フローティングの画素電極７１と接続端子１７６を形成した。なお、画素電極７１及び接続端子１７６を形成する工程において、ＩＴＯをウェットエッチングに代えてドライエッチングによりパターニングすることにより、パターニング精度を向上することができる。
【００９１】
上述したように、全部で５回のフォトリソグラフィ技術を用いる５ＰＲ工程により第１の基板１１を形成する。なお、詳しく説明しないが、この参考発明のマルチドメイン液晶表示装置において、表示領域周辺に設けられる、ゲートバスライン端子、ドレインバスライン端子、共通容量ライン接続部、静電保護トランジスタ等のすべての周辺素子についても、特にプロセスを追加することなく上記の工程と並行して同時に形成することができる。この詳細については、例えば特開平１０−２３２４０９号公報等に記載されている。なお、第２の基板１２の製造工程及び第１の基板１１と第２の基板１２との貼り合わせ工程等の、他のプロセスは、第１参考例の製造方法に準じて実施することができる。
【００９２】
このように、この例の構成によっても、第１参考例において述べたのと略同様な効果を得ることができる。
【００９３】
◇第９参考例
図４４は、参考発明の第９参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図、図４５は図４４のＫ−Ｋ’における模式的部分断面図、図４６は図４４のＬ−Ｌ’における模式的部分断面図である。この例のマルチドメイン液晶表示装置の構成が、上述した第１参考例の構成と大きく異なるところは、着目する画素の前段に対応するゲートバスラインに、放電用のＴＦＴを配置するようにした点である。
すなわち、この例のマルチドメイン液晶表示装置は、図４４〜図４６に示すよ
うに、特に図１５を参照して説明したこの発明の実施例の変形例において、着目する画素の前段に対応するゲートバスライン５５に、放電用のＴＦＴ１４１が配置されている。ここで、ＴＦＴ１４１を構成するゲート端子、ドレイン端子、ソース端子、活性層等は、表示用のＴＦＴ５４と同時に並行して形成することができる。ＴＦＴ１４１は、そのドレイン端子がコンタクトホール１４２を通して共通容量ライン７２に接続されており、ソース端子がコンタクトホール１４３を通して画素電極７１に接続されている。この構成によって、前段のゲートバスライン５５が選択された瞬間に共通容量ライン７２の電位を画素電極７１に書きこむことにより、画素電極７１に蓄積された電荷を放電させることができるようになる。
【００９４】
また、この例においては、画素電極７１に設けられた開口部７４のうち、下層に配置された制御電極７３からの制御電界が作用する開口部７４に対応する部位では、層間絶縁膜６３が除去された構成になっている。このような構成とすることにより、制御電極７３と液晶層との間にあった絶縁膜部分での電圧の損失がなくなり、制御電極７３からの電界が直接液晶層に印加される効果が得られる。また、層間絶縁膜６３の除去により形成される凹形状が、傾斜電界の作用による液晶分子の傾斜方向と整合するために、微小配向領域境界部における液晶の配向が安定する、といった効果が得られる。このような層間絶縁膜６３の除去は、表示領域周辺の端子部を露出させる工程と同時に並行して実施できるので、特に付加的な工程は必要としない。
【００９５】
このように、この例の構成によっても、第１参考例において述べたのと略同様な効果を得ることができる。
【００９６】
以上、この発明の実施例を図面により詳述してきたが、具体的な構成はこの実施例に限られるものではなく、この発明の要旨を逸脱しない範囲の設計の変更などがあってもこの発明に含まれる。例えばスイッチング素子として動作させる素子としてはＴＦＴを使用する例で説明したが、これに限らずＭＩＭ(Metal Insulator Metal)素子等のダイオードを使用してもよい。また、画素電極及び制御電極を構成する透明電極としてはＩＴＯを使用する例で説明したが、これに限らずネサ膜（酸化錫膜）等の他の材料を使用することも可能である。また、制御電極を透明電極で構成する場合には、一部のみに透明電極を用いるようにしてもよい。また、ゲートバスライン、ソース端子、ドレイン端子等を構成する金属としてはクロムを使用する例で説明したが、これに限らずモリブデン、タンタルあるいはこれらの合金等の他の材料を使用することも可能である。
【００９７】
【発明の効果】
以上説明したように、この発明によれば、各画素毎に設けられた制御電極を、各画素毎に設けられたスイッチング素子で駆動するため、その画素が明表示、暗表示、あるいは中間表示となっても、それに応じて制御電極電位が制御され、よって、制御電極から広がるように発生する斜め方向の電界により液晶のドメイン形成を確実に制御できる。さらに、画素電極には結合容量を介して制御電極電圧の分圧が印加されるため、１個のスイッチング素子だけで制御電極と画素電極との２つの電極電位を制御することができる。
したがって、共通電極の微細加工工程等の煩雑な工程を増加させたり、高度な貼り合わせ技術を要求することなく、高コントラストで、視角特性の優れたマルチドメイン液晶表示装置を提供することができる。
【図面の簡単な説明】
【図１】 参考発明の第１参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図である。
【図２】 図１のＡ−Ａ’における模式的部分断面図である。
【図３】 図１のＢ−Ｂ’における模式的部分断面図である。
【図４】 図１のＣ−Ｃ’における模式的部分断面図である。
【図５】 同マルチドメイン液晶表示装置の画素の等価回路図である。
【図６】 同マルチドメイン液晶表示装置の製造方法を工程順に示す工程図である。
【図７】 同マルチドメイン液晶表示装置の製造方法を工程順に示す工程図である。
【図８】 参考発明の第２参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図である。
【図９】 図８のＤ−Ｄ’における模式的部分断面図である。
【図１０】 図８のＥ−Ｅ’における模式的部分断面図である。
【図１１】 同マルチドメイン液晶表示装置におけるマルチドメイン状の液晶配向を模式的に示す図である。
【図１２】 同マルチドメイン液晶表示装置におけるマルチドメイン状の配向状態に対応する透過光の様子を模式的に示す図である。
【図１３】 この発明の一実施例であるマルチドメイン液晶表示装置の構成を示す模式的部分断面図である。
【図１４】 同マルチドメイン液晶表示装置の画素の等価回路図である。
【図１５】 同マルチドメイン液晶表示装置の変形例の画素の等価回路図である。
【図１６】 参考発明の第３参考例であるマルチドメイン液晶表示装置の構成を示す模式的部分断面図である。
【図１７】 参考発明の第４参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図である。
【図１８】 図１７のＦ−Ｆ’における模式的部分断面図である。
【図１９】 図１７のＧ−Ｇ’における模式的部分断面図である。
【図２０】 参考発明の第５参考例であるマルチドメイン液晶表示装置の画素電極と制御電極との組み合わせ例の平面形状を示す図である。
【図２１】 同マルチドメイン液晶表示装置の画素電極と制御電極との組み合わせ例において、基本的な構成の平面形状を示す図である。
【図２２】 同マルチドメイン液晶表示装置の画素電極と制御電極との組み合わせ例において、基本的な構成の平面形状を示す図である。
【図２３】 同基本的な構成を同マルチドメイン液晶表示装置に適用した例の平面形状を示す図である。
【図２４】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図２５】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図２６】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図２７】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図２８】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図２９】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図３０】 同マルチドメイン液晶表示装置の画素の配向状態を示す顕微鏡写真である。
【図３１】 参考発明の第６参考例であるマルチドメイン液晶表示装置の表示時の画素の顕微鏡写真である。
【図３２】 同マルチドメイン液晶表示装置の表示時の画素の顕微鏡写真である。
【図３３】 同マルチドメイン液晶表示装置の表示時の画素の顕微鏡写真である。
【図３４】 同マルチドメイン液晶表示装置の表示時の画素の顕微鏡写真である。
【図３５】 参考発明の第７参考例であるマルチドメイン液晶表示装置の実験用液晶セルの暗状態から明状態に電圧を切り替えた後の顕微鏡写真ある。
【図３６】 同マルチドメイン液晶表示装置の比較用液晶セルの暗状態から明状態に電圧を切り替えた後の顕微鏡写真ある。
【図３７】 参考発明の第８参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図である。
【図３８】 図３７のＨ−Ｈ’における模式的部分断面図である。
【図３９】 図３７のＩ−Ｉ’における模式的部分断面図である。
【図４０】 図３７のＪ−Ｊ’における模式的部分断面図である。
【図４１】 同マルチドメイン液晶表示装置の製造方法を工程順に示す工程図である。
【図４２】 同マルチドメイン液晶表示装置の製造方法を工程順に示す工程図である。
【図４３】 同マルチドメイン液晶表示装置の製造方法を工程順に示す工程図である。
【図４４】 参考発明の第９参考例であるマルチドメイン液晶表示装置の画素の構成を示す模式的平面図である。
【図４５】 図４４のＫ−Ｋ’における模式的部分断面図である。
【図４６】 図４５のＬ−Ｌ’における模式的部分断面図である。
【図４７】 従来のマルチドメイン液晶表示装置の画素の構成を示す模式的部分断面図である。
【符号の説明】
１１ 第１の基板
１２ 第２の基板
２０ 液晶
２１ 液晶分子
５４ ＴＦＴ（スイッチング素子）
５５ ゲートバスライン
５６ ドレインバスライン
５７ ソース端子
５８ ドレイン端子
５９、１４２、１４３、１４９、１７２、１７７ コンタクトホール
６１ ゲート絶縁膜
６２ 半導体膜
６３ 層間絶縁膜
６４ 活性層（半導体層）
６５ ＴＦＴの保護膜
７１ 画素電極
７２ 共通容量ライン
７３ 制御電極
７４ 開口部
７５ 容量端子
７６ 開口部もしくは画素電極端部
８１ 共通電極
９１ 色層
９２ オーバーコート層
９３ 遮光層
１２５ 液晶容量
１２６ 結合容量
１２７ 付加容量
１３５ 結合抵抗
１４１ ＴＦＴ（放電用素子）
１７１ 結合容量電極
１７５ 付加容量端子
１７６ 接続端子
Ｅ１ 液晶駆動電界[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a multi-domain liquid crystal display device, and more particularly to a multi-domain liquid crystal display device having excellent viewing angle characteristics.
[0002]
[Prior art]
  In a twisted nematic (hereinafter referred to as “TN”) type liquid crystal display device that has been widely used in the past, a “white” display state when no voltage is applied, in which liquid crystal molecules are twisted parallel to the substrate surface From the “white” display state, the liquid crystal molecules gradually change from the “white” display state to the “black” display state by changing the orientation vector direction in the electric field direction according to the applied voltage. However, there is a problem that the viewing angle of the TN liquid crystal display device is narrow due to the behavior of the liquid crystal molecules due to this voltage application. This problem of a narrow viewing angle becomes particularly significant in the rising direction of liquid crystal molecules in halftone display.
[0003]
  As a method for improving the visual field characteristics of a liquid crystal display device, a technique as disclosed in Japanese Patent Application Laid-Open No. 6-43461 has been proposed. FIG. 47 is a schematic partial cross-sectional view illustrating an example of the configuration of a liquid crystal display device according to the technique disclosed in the publication. In this technique, a liquid crystal cell in which liquid crystal 21 having negative dielectric anisotropy is homeotropically aligned (vertically) is prepared, and two polarizing plates (not shown) installed so that their polarization axes are orthogonal to each other. By using a common electrode 81 sandwiched between them and having an opening 74, the electric field is concentrated obliquely in each pixel, thereby making each pixel two or more domains, so-called multi-domains, and improving viewing angle characteristics. ing. In this technique, if necessary, an optical compensator can be used to improve the black viewing angle characteristic. Furthermore, not only homeotropically aligned liquid crystal cells but also TN aligned cells use a common electrode having an opening to generate an oblique electric field and divide each pixel into two or more domains. The viewing angle characteristics have been improved.
[0004]
  In the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-199190, an opening (alignment control window) is provided in the common electrode, and an alignment control electrode is provided so as to surround the pixel electrode. The liquid crystal domain is stabilized by emphasizing the electric field.
[0005]
  In addition, in Japanese Patent Application Laid-Open No. 7-230097, an alignment control electrode integrated with a gate line is provided on a pixel electrode, and each pixel is made into two or more liquid crystal domains by an oblique electric field from the alignment control electrode. It has improved.
[0006]
  Further, the technique disclosed in Japanese Patent Laid-Open No. 10-20323 discloses a technique for forming a plurality of liquid crystal domains by providing an opening in a pixel electrode and disposing a control electrode at the position of the opening. Yes.
[0007]
  Japanese Patent Application Laid-Open No. 10-301114 discloses a liquid crystal cell in which a liquid crystal having a negative dielectric constant is homeotropically aligned, and a protrusion is provided on the alignment film, and the protrusion controls the tilt direction of the liquid crystal when a voltage is applied. A technique has been devised that operates by dividing into two or more liquid crystal domains.
[0008]
[Problems to be solved by the invention]
  However, among these techniques, a technique having an opening in a common electrode as disclosed in Japanese Patent Application Laid-Open No. 6-43461 is necessary in a normal manufacturing process of a monodomain type TN liquid crystal display device. However, there is a problem that “a fine processing process such as a photoresist process for the common electrode” is required, and an advanced bonding technique for the upper and lower substrates is required. This problem is particularly serious in the case of an active matrix liquid crystal display device using a switching element such as a thin film transistor (TFT). That is, in a normal active matrix liquid crystal display device, a switching element (active element) such as a thin film transistor is manufactured on one transparent substrate (TFT substrate), and therefore a microfabrication process such as a photoresist process is required. This is only a TFT substrate on one side for manufacturing a switching element, and it is not necessary to perform fine processing on the electrode on the other transparent substrate (counter substrate) side, which is usually called “common electrode”, and a common electrode is formed on the entire surface. It has only been done. However, in the prior art having an opening in the common electrode, a fine processing step such as a photoresist process is required for the “common electrode” that is not normally required for fine processing, and the number of steps increases. Advanced bonding technology for the upper and lower substrates is required.
[0009]
  From such a problem, for example, a technique for providing an opening or a slit in the pixel electrode on the TFT substrate side where a switching element such as a TFT is formed to generate an oblique electric field to control the alignment of the liquid crystal can be considered. . This is because the pixel electrode on the TFT substrate side originally requires patterning, and in this case, no additional process is required. However, the liquid crystal domain cannot be stably controlled in this configuration. This is because the gradient of the electric field around the opening when the common electrode is provided with an opening as disclosed in Japanese Patent Laid-Open No. 6-43461 is aligned with the gradient direction of the electric field around the pixel electrode (see FIG. 47). On the other hand, when the opening is provided in the pixel electrode on the TFT substrate side, the gradient of the electric field around the opening does not match the direction of the gradient of the electric field around the pixel electrode.
[0010]
  As disclosed in Japanese Patent Laid-Open No. 7-199190, when the control electrode is provided around the pixel electrode, it is possible to emphasize the gradient of the electric field around the pixel electrode. In the substrate on the side, an opening must be provided in the common electrode, and the above-described problem needs to be solved.
[0011]
  On the other hand, as described in JP-A-7-230097, an oblique electric field can be generated by arranging a control electrode on a pixel electrode and appropriately determining the potential of the control electrode. However, at the time of so-called inversion driving in which the polarity of the pixel electrode potential is inverted at a constant period, the state of occurrence of the oblique electric field also changes due to the change in the polarity of the pixel electrode potential, so that the liquid crystal domain cannot be controlled stably and reliably. Further, in this configuration, since the control electrode is integrated with the gate bus line, the control electrode potential cannot be changed according to the lighting / non-lighting of the pixel, that is, the pixel is not lighted (dark display). Sometimes an electric field in an oblique direction is generated in the control electrode potential, and this electric field causes light leakage around the control electrode, leading to a decrease in display contrast. When a light shielding layer is provided to shield this light leakage, the aperture ratio is significantly reduced. Further, normally, since a DC voltage is applied to the common electrode in the gate bus line during a period excluding the selection period, when the control electrode is integrated with the gate bus line, the display region is displayed. A DC voltage is continuously applied to the inner liquid crystal layer, which causes a problem of deteriorating the reliability of the display element.
[0012]
  The technique of providing an opening in a pixel electrode and disposing a control electrode at that position as disclosed in Japanese Patent Laid-Open No. 10-20323 also has means for controlling the control electrode potential for each pixel during display operation. Therefore, there is a problem that the liquid crystal domain cannot be controlled stably and reliably as in the technique described in JP-A-7-230097.
[0013]
  As means for solving the above-described problems in the techniques described in JP-A-7-230097 and JP-A-10-20323, for example, control electrodes provided individually for each pixel are provided. Although a method of controlling with individual switching elements provided in the pixel is conceivable, in this configuration, it is necessary to provide individual switching elements and drain bus lines corresponding to the pixel electrode and the control electrode. The configuration is complicated, which is not realistic in terms of manufacturing cost and manufacturing yield.
[0014]
  In addition, in the method of providing protrusions on the alignment film as described in JP-A-10-301114, the effect of area division by the protrusions works only in the vicinity of the protrusions. Therefore, in order to realize reliable region division, a protrusion must be provided not only on the alignment film on the TFT substrate on one side where the switching element is formed, but also on the alignment film on the counter substrate side. In addition, there is a problem that both substrates need to be accurately bonded.
[0015]
  The present invention has been made in view of the above-described circumstances, and increases the problems of the conventional technology as described above, that is, complicated processes such as the microfabrication process of the common electrode, or requires an advanced bonding technique. Therefore, an object of the present invention is to provide a multi-domain liquid crystal display device having high contrast and excellent viewing angle characteristics.
[0016]
[Means for Solving the Problems]
  To solve the above problem,The configuration of the present invention is as follows:A liquid crystal sandwiched between a pair of substrates, a plurality of gate bus lines formed on one side of the substrate and extending in the horizontal direction, and a plurality of drain bus lines extending in the vertical direction. It is arranged in a matrix corresponding to each intersection of the gate bus line and the drain bus line, and an electric field in an oblique direction is generated in each of the pixels with respect to the switching element, the pixel electrode, and the liquid crystal. And a control electrode for forming a plurality of alignment regions in one pixel. The control electrode is connected to one terminal of the switching element, and the pixel electrode is connected to the control electrode. A coupling capacitor between the drain electrode and the control electrode via the corresponding switching element when the corresponding gate bus line is selected. A signal voltage is applied to the pixel electrode, and the divided voltage of the signal voltage is applied to the pixel electrode via the coupling capacitance, and is further accumulated in the pixel electrode between the pixel electrode and the control electrode. And a resistance element for discharging the generated charge.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below with reference to the drawings. The description will be made specifically using examples.It should be noted that an embodiment of the invention related to the divisional application of this application (hereinafter referred to as reference invention) will be described in view of the depth of relevance. The description will be made specifically using a reference example.
[0018]
FirstreferenceExample
  FIG.referenceFirst of the inventionreferenceFIG. 2 is a schematic partial cross-sectional view taken along the line AA ′ in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line BB ′ in FIG. 4 is a schematic partial cross-sectional view taken along line CC ′ of FIG. 1, FIG. 5 is an equivalent circuit diagram of a pixel of the multi-domain liquid crystal display device, and FIGS. It is process drawing which shows the manufacturing method of a domain liquid crystal display device in order of a process.
  As shown in FIGS. 1 to 5, the multi-domain liquid crystal display device of this example has a region surrounded by a plurality of gate bus lines 55 extending in the horizontal direction and a plurality of drain bus lines 56 extending in the vertical direction. One pixel is constituted by a unit, and each pixel is repeatedly arranged in a matrix in the vertical and horizontal directions on the first substrate 11.
[0019]
  Each pixel has a TFT 54, a pixel electrode 71, and a control electrode 73. The TFT 54 has a bottom gate structure in which the gate is disposed below the source and drain, and amorphous silicon, polysilicon, or the like can be used as an active layer (semiconductor layer), and is formed by a self-alignment technique. Can do. The pixel electrode 71 is electrically floating, and a coupling capacitor 126 and an additional capacitor 127 are formed through the control electrode 73 and the common capacitor line 72 through the interlayer insulating film 63 and the gate insulating film 61, respectively. The TFT 54 is covered with a protective insulating film 65. The interlayer insulating film 63, the gate insulating film 61, and the protective insulating film 65 are made of silicon nitride or the like. Here, the common capacitor line 72 is provided to add capacitance to the pixel electrode 71.
[0020]
  The capacitances of the coupling capacitor 126 and the additional capacitor 127 can be set to desired values according to parameters such as the material, size, and thickness of the interlayer insulating film 63 and the gate insulating film 61. The pixel electrode 71 and the control electrode 73 are made of transparent electrodes, and materials such as ITO (Indium Tin Oxide) are used. The control electrode 73 is connected to the source terminal 57 of the TFT 54. The control electrode 73 can be formed integrally with the source terminal of the TFT 54. The gate bus line 55, the source terminal 57, the drain terminal 58, and the common capacitor line 72 are made of a metal film such as chromium. A common electrode 81 is formed on the second substrate 12 and is superimposed on the first substrate 11 so as to face the first substrate 11 with a predetermined interval. A liquid crystal 20 is sandwiched between the substrates 11 and 12. The TFT 54 is shown as a bottom gate structure.4 ReferenceAs an example, a top gate structure in which the gate is disposed at an upper position than the source and drain may be used.
[0021]
  In this example, a common capacitance line 72 for adding capacitance to the pixel electrode 71 is provided. However, the coupling capacitance 126 between the pixel electrode 71 and the control electrode 73 in FIG. If the required potential difference is obtained between the pixel electrode 71 and the liquid crystal capacitor 125 between the common electrode 81, the common capacitor line 72 is not particularly required.
[0022]
  In this example, at the moment when the gate bus line 55 is selected, the signal voltage is written from the drain bus line 56 to the control electrode 73 connected to the source terminal 57 via the TFT 54. At this time, the potential of the floating pixel electrode 71 is determined to be a predetermined potential between the control electrode 73 and the common capacitor line 72 according to the capacitance ratio of the coupling capacitor 126, the additional capacitor 127, and the liquid crystal capacitor 125. For example, the common capacitance line 72 may be configured to have the same potential as the common electrode 81 on the second substrate 12, or may be connected to a previous gate bus line or the like.
  In this example, the potential relationship between the control electrode 73, the pixel electrode 71, and the common electrode 81 is in the order shown in this list or vice versa, so that it occurs between the pixel electrode 71 and the control electrode 73 and the common electrode 81. As shown in FIG. 3, the liquid crystal drive electric field E <b> 1 is generated obliquely so as to spread outward from the control electrode 73.
[0023]
  Hereinafter, the operation will be described taking as an example the case of a VA (Vertical Alignment) mode in which liquid crystal having a negative dielectric anisotropy is homeotropically aligned. The alignment state of the liquid crystal 20 (or liquid crystal molecules 21) interposed between the first substrate 11 and the second substrate 12 is changed by the liquid crystal driving electric field E1. In this example, since the liquid crystal driving electric field E1 is generated so as to spread outward from the control electrode 73 as described above, the liquid crystal molecules 21 are in different directions on both sides of the control electrode 73 as shown in FIGS. The orientation direction is changed. For this reason, regions (liquid crystal domains) in which the liquid crystal molecules 21 are inclined differently compensate each other for viewing angle characteristics, and as a whole, good and favorable viewing angle characteristics can be obtained. In the description here, the liquid crystal viewed in bulk is referred to as the liquid crystal 20 and the individual liquid crystal molecules are described as the liquid crystal molecules 21 for the sake of convenience.referenceIt is not very important in the invention.
[0024]
  As described above, in this example, the operation mode of the liquid crystal 20 has been described in the case of the VA mode in which a liquid crystal having negative dielectric anisotropy is homeotropically aligned. It may be a TN mode in which liquid crystal is twisted and aligned with a refractive index anisotropy, or a homogeneous mode in which liquid crystal having a positive dielectric anisotropy is uniformly aligned. In the case of the TN mode, the liquid crystal may have a spontaneous chirality or a non-spontaneous chirality. In the case of the non-spontaneous chirality, the liquid crystal driving electric field E1 can be operated by being divided into a plurality of regions having different chiral directions. In order to stabilize the liquid crystal domain, it is also possible to mix a polymer compound with the liquid crystal. Alternatively, a monomer can be added to the liquid crystal to create a domain, and then polymerized to stabilize the domain.
[0025]
  As shown in FIG. 4, by forming an appropriate opening 74 in the pixel electrode 71, the formation of the liquid crystal domain can be made more reliable. The opening 74 may be formed in a window shape or may be formed so as to be cut from one side or both sides of the pixel electrode 71. Of course, even if the opening 74 is not provided.referenceThe object of the invention can be achieved. No. described later3 ReferenceAs an example, a color layer (not shown) or a light shielding layer (not shown) may be provided on the first substrate 11 or the second substrate 12. Note that a part or the whole of the common capacitance line 72 can be formed of a transparent electrode.
[0026]
  Next, with reference to FIG. 6 and FIG. 7, the manufacturing method of the multi-domain liquid crystal display device of this example is demonstrated in order of a process.
  First, as shown in FIG. 6A, chromium is sputter-deposited on the entire surface of the first substrate 11 made of glass, and the chrome is patterned into a desired shape by using a photolithography technique. 55 and a common capacitor line 72 were formed. Subsequently, a silicon nitride film was formed on the entire surface by CVD (Chemical Vapor Deposition) to form a gate insulating film 61.
[0027]
  Next, as shown in FIG. 6B, after an amorphous silicon film was formed on the entire surface by the CVD method, the active layer 64 was formed by patterning the amorphous silicon into a desired shape by a photolithography technique. Next, after chromium was sputter-deposited on the entire surface, the chromium was patterned into a desired shape by a photolithography technique to form a drain bus line 56, a drain terminal 58, and a source terminal 57. Next, after ITO was sputtered over the entire surface, the ITO was patterned into a desired shape by a photolithography technique to form a pixel electrode 71 having an opening 74. The pixel electrode 71 is floating as described above. Thus, a TFT 54 was formed on the first substrate 11.
[0028]
  Next, as shown in FIG. 7C, after a silicon nitride film is formed on the entire surface by a CVD method, the silicon nitride is patterned into a desired shape by a photolithography technique to protect the interlayer insulating film 63 and the TFT 54. A film 65 was formed, and a contact hole 59 was formed so as to expose the source terminal 57. In this case, the interlayer insulating film 63 and the protective insulating film 65 may be integrally formed. Next, after ITO was formed on the entire surface by sputtering, the ITO was patterned into a desired shape by a photolithography technique to form the control electrode 73. The control electrode 73 is connected to the source terminal 57 through the contact hole 59.
[0029]
  Next, as shown in FIG. 7D, R (Red), G (Green), and B (Black) color layers and a black matrix (see FIG. 7) are formed on the second substrate 12 made of glass by a printing method or the like. (Not shown), and ITO was sputter-deposited thereon, and then the ITO was patterned into a desired shape by a photolithography technique to form the common electrode 81.
[0030]
  An alignment film (not shown) for vertical alignment was formed on each of the first substrate 11 and the second substrate 12 prepared as described above. SE-1211 manufactured by Nissan Chemical Co., Ltd. was used as the alignment film material. Next, a sealant (not shown) is applied linearly on the first substrate 11, and a spherical spacer (not shown) is sprayed on the second substrate 12, so that the two substrates 11, 12 are connected to each other. The sealing material was cured by bonding and heating. Next, after the structure in which the first substrate 11 and the second substrate 12 are integrated by the sealing material is cut into individual panel shapes, nematic liquid crystal having a negative dielectric anisotropy is injected from the injection hole. After the injection, the injection hole was sealed with a photocurable resin. Next, after attaching a negative compensation film on both sides of the panel, a deflecting plate is further attached on both sides so that the transmission axes thereof are orthogonal to each other, and a peripheral drive circuit is attached to form a module. The multi-domain liquid crystal display device of this example as shown in FIG.
[0031]
  The planar shape of each component of the multi-domain liquid crystal display device manufactured by the above manufacturing method is as shown in FIG. 1, and the size of the pixel is approximately 100 μm horizontal × 300 μm vertical. The planar shape of each component is not limited to the shape of FIG. 1, and various shapes can be considered as shown in FIG.
[0032]
  In the multi-domain liquid crystal display device of this example, when the deflecting plates are arranged so that their transmission axes are orthogonal to each other, the tilt direction of the liquid crystal molecules 21 in both main liquid crystal alignment regions is the deflection plate transmitting axes on both sides. In order to match the bisecting direction, that is, the vertical, horizontal, and horizontal directions, a good bright state can be displayed by applying the liquid crystal driving electric field E1, but dark lines are generated at the boundaries between the liquid crystal alignment regions. There is. The cause of the dark line will be described in the second section below.referenceThis will be explained with an example. When generation of dark lines becomes a problem, an optically anisotropic medium called a quarter-wave plate is inserted between the polarizing plate and the liquid crystal 20 so that circular deflection is incident on the liquid crystal layer. By configuring, the generation of dark lines can be eliminated. In this case, the control electrode 73 may be formed of a transparent electrode.
[0033]
  Thus, according to the multi-domain liquid crystal display device of this example, the control electrode 73 is connected to the source terminal 57 which is one terminal of the TFT 54 serving as a switching element, and the pixel electrode 71 in which the opening 74 is formed is Since the coupling capacitor 126 is provided between the control electrode 73 and the pixel electrode 71 is applied with a signal voltage divided voltage via the coupling capacitor 126, the pixel electrode 71 is provided around the control electrode 73 and the pixel electrode 71 during operation. The liquid crystal can be operated by being divided into a plurality of regions by the action of the generated oblique electric field.
  Therefore, it is possible to provide a multi-domain liquid crystal display device having high contrast and excellent viewing angle characteristics without increasing complicated processes such as a microfabrication process of a common electrode or requiring an advanced bonding technique.
[0034]
◇ SecondreferenceExample
  FIG.referenceSecond inventionreferenceFIG. 9 is a schematic partial cross-sectional view taken along the line DD ′ of FIG. 8, and FIG. 10 is a schematic partial cross-sectional view taken along the line EE ′ of FIG. It is. The configuration of the multi-domain liquid crystal display device of this example is the first described above.referenceA significant difference from the configuration of the example is that the control electrode is formed to be lower than the pixel electrode through the interlayer insulating film.
  That is, in the multi-domain liquid crystal display device of this example, as shown in FIGS. 8 to 10, pixels (structure shown in FIG. 8) are repeatedly arranged in a matrix in the vertical and horizontal directions on the first substrate 11. In addition, a control electrode 73 made of ITO or the like is formed below the pixel electrode 71 made of ITO or the like via an interlayer insulating film 63 made of silicon nitride or the like. The pixel electrode 71 is a first electrodereferenceFloating as in the example. The control electrode 73 can be formed integrally with the source terminal 57 of the TFT 54. In this case, it is advantageous in the manufacturing process, but the source terminal 57 is usually formed of an opaque metal such as chromium as described above. Therefore, the disadvantage that the light transmittance of the element is reduced is unavoidable. On the other hand, when the control electrode 73 is formed of a transparent electrode such as ITO as described above, as shown in FIG. 8, for example, the overlapping portion with the pixel electrode 71 so that the capacitance value of the coupling capacitor 126 becomes sufficiently large. A sufficient aperture ratio can be secured even if a large is taken.
[0035]
  In this example, the control electrode 73 is below the pixel electrode 71 as described above, but the pixel electrode 71 is provided with the opening 74, and the electric field from the control electrode 73 acts on the liquid crystal through the opening 74. Therefore, the liquid crystal can be operated by being divided into a plurality of regions. The firstreferenceSimilar to the example, the present invention can be applied not only to the bottom gate structure but also to the top gate structure.
  Other than this, the first mentioned abovereferenceIt is almost the same as the example. Therefore, in FIG. 8 to FIG. 10, the same reference numerals are given to the respective parts corresponding to the constituent parts of FIG. 1 to FIG.
[0036]
  The opening 74 of the pixel electrode 71 in this example is the firstreferenceSimilarly to the example, it may be formed in a window shape or may be formed so as to be cut from one side or both sides of the pixel electrode 71. In addition to the region where the electric field from the control electrode 73 is applied to the pixel electrode 71, the liquid crystal domain can be more reliably formed by providing an appropriate opening 74. In the opening 74 where the electric field from the control electrode 73 acts, the liquid crystal driving electric field E1 acts so as to spread from the opening 74, but when the control electrode 73 does not exist in the opening 74, or FIG. 8 or FIG. When the common capacitance line 72 is present in the opening 74 as shown in FIG. 5, the liquid crystal driving electric field E <b> 1 acts so as to converge to the center of the width of the opening 74.
[0037]
  FIG. 11 is a diagram schematically showing the multi-domain liquid crystal alignment in this example, and shows the alignment state of the portion including the pixel electrode 71 and the control electrode 73 of FIG. As shown in FIG. 11, regions where the liquid crystal molecules 21 are inclined in different directions are formed with the opening 74 of the pixel electrode 71 as a boundary, and the alignment of the liquid crystal molecules 21 is caused by the elasticity of the liquid crystal at each region boundary. The direction changes continuously.
[0038]
  In this example, deflecting plates are arranged on the outer sides of the first substrate 11 and the second substrate, respectively. Various combinations of the transmission axis directions of the deflecting plates on both sides are possible. Among them, the deflection in which the transmission axes on both the deflecting plates are orthogonal to each other and the tilt directions of the liquid crystal molecules 21 in the main liquid crystal alignment regions are orthogonal. By disposing the plate transmission axis so as to coincide with the azimuth that bisects, a bright and high-contrast display can be realized. Furthermore, by inserting an optical compensator of a type called a negative compensator whose in-plane refractive index is larger than the refractive index in the surface normal direction between the liquid crystal and the deflection plate, The viewing angle characteristics can be improved.
[0039]
  FIG. 12 schematically shows the state of transmitted light corresponding to the multi-domain alignment state in this example, and includes the pixel electrode 71 and the control electrode 73 of FIG. The state of the transmitted light of the part is shown. Here, although the pixel electrode 71 and the control electrode 73 are transparent electrodes, the common capacitance line 72 is usually formed of an opaque metal such as chromium as described above. Actually, no light is transmitted, but in order to explain the relationship between the liquid crystal alignment state and the light transmission, the light shielding by the common capacitance line 72 is ignored.
[0040]
  In FIG. 12, the deflection plates are arranged so as to be orthogonal to each other so that their transmission axes are in the diagonal direction of the figure. In such an arrangement, in each of the main liquid crystal alignment regions, the tilt direction of the liquid crystal molecules 21 coincides with the direction that bisects the polarizing plate transmission axes on both sides, that is, the upper, lower, left, and right directions in the figure. Therefore, a good bright state can be displayed by applying the liquid crystal driving electric field E1, but a dark line 25 as shown in FIG. 12 is generated at the boundary portion of each liquid crystal alignment region. This dark line 25 corresponds to a portion where the tilt direction of the liquid crystal molecules 21 coincides with the deflection plate transmission axis direction. With respect to the direction of the transmission axis of the deflecting plate, even if the liquid crystal is tilted in that direction, light is not transmitted, and therefore a dark line 25 as shown in FIG. 12 is generated.
[0041]
  Although the dark line 25 as described above does not cause a significant problem in display, for example, when a voltage is applied to change from a black display state with no voltage applied to a white display state, a temporary change in orientation, Next to the change in which the liquid crystal molecules 21 are tilted in the direction defined by the electric field from the control electrode 73, a secondary alignment change in which the liquid crystal molecules 21 change their tilt directions may occur. May be a problem. In this case, after the dark line 25 is generated, the shape and width thereof are changed. The time scale of the secondary orientation change is slower than that of the temporary orientation change, causing a change in light transmittance with time of the pixel. There are roughly two patterns of change in light transmittance over time. One is a case where the change from black to white is substantially delayed, which causes afterimages. On the contrary, there is a case where the brightness changes once so that it becomes brighter and then gradually becomes darker. In this case, the brightness of the display in a steady state is insufficient.
[0042]
  As described above, when the generation of the dark line 25 becomes a problem, an optically anisotropic medium called a quarter-wave plate is inserted between the deflection plate and the liquid crystal 20, and a circle is formed in the liquid crystal layer. The generation of the dark line 25 can also be eliminated by configuring so that the deflection is incident. In this example, since the control electrode 73 is formed of a transparent electrode,Dark lineThe elimination of 25 leads to an improvement in element transmittance and response characteristics. As the quarter-wave plate, a stretched film such as polycarbonate can be used as a single layer or laminated, and it is preferable to arrange the optical axes on both sides of the liquid crystal layer so that their optical axes are orthogonal to each other. In the case of using a laminate of a plurality of stretched films, called a broadband quarter-wave plate, it is preferable to arrange the corresponding layers on both sides of the liquid crystal layer so as to be orthogonal to each other.
[0043]
  In addition, even when there is a change in transmittance that once brightens and then gradually darkens in the normal drive system, a black display is inserted for each frame of the display for the purpose of sharpening the image during movie display Such a change with time does not cause a problem when driving is performed.
[0044]
  Also in this example, the operation of the liquid crystal 20 is the first.referenceIt is done in much the same way as the example. Here, particularly in the homogeneous mode, a compensation film having negative refractive index anisotropy (the refractive index of the optical axis is small) is set so that the optical axis coincides with the optical axis of the liquid crystal when no voltage is applied. When used in the normally black mode, good viewing angle characteristics can be obtained. At this time, it is preferable that the retardation of the compensation film and the retardation of the liquid crystal layer are opposite in sign and have the same absolute value. It is also possible to improve display contrast and viewing angle characteristics using a biaxial compensation film.
[0045]
  The manufacturing method of the multi-domain liquid crystal display device of this example is the first described with reference to FIGS.referenceIt can be carried out according to that in the examples. That is, in FIG. 6B, the control electrode 73 is formed instead of the pixel electrode 71, and in FIG. 7C, the pixel electrode 71 is formed instead of the control electrode 73. . An opening 74 is also formed when the pixel electrode 71 is patterned.
  The planar shape of each component of the multi-domain liquid crystal display device manufactured by the manufacturing method as described above is as shown in FIG. 6, and the size of the pixel is approximately 100 μm wide × 300 μm vertically. The planar shape of each component is not limited to the shape shown in FIG. 6, and various shapes are possible as shown in FIG.
[0046]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0047]
◇Example
  FIG. 13 illustrates the present invention.oneSchematic partial sectional view showing the configuration of a multi-domain liquid crystal display device which is an embodiment (firstreferenceFIG. 14 is an equivalent circuit diagram of a pixel of the multi-domain liquid crystal display device. The configuration of the multi-domain liquid crystal display device of this example is the first described above.referenceA significant difference from the configuration of the example is that the pixel electrode is formed so as not to be completely floating.
  That is, the multi-domain liquid crystal display device of this example is controlled with the pixel electrode 71 as shown in FIG. 14 in order to prevent charges from being accumulated in the pixel electrode 71 for some reason as shown in FIGS. For example, a first coupling resistor 135 having a substantially finite resistance value is connected between the electrode 73 and the coupling capacitor 126 in parallel.referenceInstead of the interlayer insulating film 63 of the example, a semiconductor film 62 such as amorphous silicon is formed. A desired resistance value can be obtained by doping the semiconductor film 62 with appropriate impurity ions.
[0048]
  When a resistor is connected in parallel to the additional capacitor 127 in FIG. 14, a semiconductor film 62 such as amorphous silicon is formed between the common capacitor line 72 and the pixel electrode 71 instead of the interlayer insulating film 63 in the same manner as described above. A finite coupling resistance may be connected by forming. The coupling resistor 135 is accumulated so as to prevent a display burn-in due to the influence of the electric charge accumulated in the pixel electrode 71 and an afterimage exceeding the response time of the liquid crystal when a moving image is displayed. The value is set so that the electric charge is discharged. Depending on how the liquid crystal display device is used, the discharge can be completed within a one-frame display period, or the discharge can be completed by a pause of several seconds to several minutes.
  Other than this, the first mentioned abovereferenceIt is almost the same as the example. Therefore, in FIG.13 and FIG.14, the same number is attached | subjected to each part corresponding to the component of FIGS. 1-5, and the description is abbreviate | omitted.
[0049]
  The manufacturing method of the multi-domain liquid crystal display device of this example is the first described with reference to FIGS.referenceIt can be carried out according to that in the examples. That is, in the process according to FIG. 6B and FIG. 7C, after depositing amorphous silicon on the entire surface by the CVD method, the amorphous silicon is patterned into a desired shape by the photolithography technique to form the active layer 64. At the time of formation, the semiconductor film 62 may be patterned and formed into a desired shape at the same time.
[0050]
  FIG. 15 is an equivalent circuit showing a pixel of a modification of the multi-domain liquid crystal display device of this example. In this modified example, as shown in the figure, the TFT 141 is formed so as to connect each pixel electrode 71 and the common capacitance line 72, and the gate of the TFT 141 is connected to the previous gate bus line 55, whereby the previous stage is connected. The electric charge accumulated in the pixel electrode 71 can be discharged by writing the potential of the common capacitance line 72 to the pixel electrode 71 at the moment when the gate bus line 55 is selected.
[0051]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0052]
◇ No.3 ReferenceExample
  FIG.referenceInvention No.3 ReferenceSchematic partial sectional view showing the configuration of an example multi-domain liquid crystal display device (firstreference(Corresponding to FIG. 2 in the example). The configuration of the multi-domain liquid crystal display device of this example is the first described above.referenceA significant difference from the configuration of the example is that the pixel electrode and the control electrode are formed on the color layer and the light shielding layer.
  That is, in the multi-domain liquid crystal display device of this example, as shown in FIG. 16, the color layer 91 and the light shielding layer 93 are formed on the first substrate 11, and the pixel electrode 71 and the control electrode 73 are arranged thereon. The pixel electrode 71 is opposed to the common capacitor line 72 through the capacitor terminal 75.
  Other than this, the first mentioned abovereferenceIt is almost the same as the example. Therefore, in FIG. 16, the same numbers are assigned to the components corresponding to the components in FIGS.
[0053]
  The manufacturing method of the multi-domain liquid crystal display device of this example is the first described with reference to FIGS.referenceIt can be carried out according to that in the examples. That is, in the process according to FIGS. 6B and 7C, after the active layer 64 is formed, chromium is formed on the entire surface by sputtering, and then chromium is patterned into a desired shape by a photolithography technique. Thus, the drain terminal line 56, the drain terminal 58, and the source terminal 57 were formed, and at the same time, the capacitor terminal 75 was formed. Further, a protective insulating film 65 of the TFT 54 is formed of silicon nitride, a light shielding layer 93 is formed using a black resist, and an R, G, B color layer 91 is formed using a color resist. Subsequently, an overcoat layer 92 was formed and planarized to form a pixel electrode 71, an interlayer insulating film 63, and a control electrode 73. The control electrode 73 is connected to the source terminal 57 and the pixel electrode 71 is connected to the capacitor terminal 75 through contact holes, respectively. The pixel electrode 73 is floating while being connected to the capacitor terminal 75.
[0054]
  By forming the semiconductor film 62 between the pixel electrode 71 and the control electrode 73,Of this inventionIt is possible not to make the pixel electrode 71 completely floating as in the embodiment.
[0055]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0056]
◇ No.4 ReferenceExample
  FIG.referenceInvention No.4 ReferenceFIG. 18 is a schematic partial sectional view taken along line FF ′ of FIG. 17, and FIG. 19 is a schematic part taken along line GG ′ of FIG. It is sectional drawing. The configuration of the multi-domain liquid crystal display device of this example is the first described above.referenceA significant difference from the configuration of the example is that a TFT as a switching element is formed in a top gate structure.
  That is, in the multi-domain liquid crystal display device of this example, as shown in FIGS. 17 to 19, the TFT 54 is formed in a top gate structure in which the gate bus line 55 is disposed above the source terminal 57 and the drain terminal 58. Has been.
  Other than this, the first mentioned abovereferenceIt is almost the same as the example. Therefore, in FIG. 17 to FIG. 19, the parts corresponding to the constituent parts of FIG. 1 to FIG.
[0057]
  The manufacturing method of the multi-domain liquid crystal display device of this example is the first described with reference to FIGS.referenceIt can be carried out according to that in the examples. That is, in the process according to FIGS. 6A to 7C, the drain bus line 56, the drain terminal 58, and the source terminal 57 are formed by patterning and patterning chromium on the first substrate 11. The control electrode 73 was formed at the same time, and then an amorphous silicon layer, an insulating layer, and a chromium sputtered film were formed, and these were collectively patterned to form the TFT 54. Further, an interlayer insulating film 63 made of silicon nitride was formed, and then ITO was sputtered and patterned to form a pixel electrode 71. The pixel electrode 71 is floating, and an opening 74 is provided in alignment with the position of the control electrode 73. Next, a gate insulating film 61 and a common capacitance line 72 were formed by continuously sputtering silicon oxide and ITO and patterning them together.
[0058]
  According to this example, only the structure of the TFT 54 is changed from the bottom gate structure to the top gate structure, and the second structure described with reference to FIG.referenceA multi-domain similar to the example can be formed.
[0059]
  Again, by forming the semiconductor film 62 instead of the interlayer insulating film 63 between the pixel electrode 71 and the control electrode 73 or the gate insulating film 61 between the pixel electrode 71 and the common capacitor line 72,Of this inventionIt is possible not to make the pixel electrode 71 completely floating as in the embodiment.
[0060]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0061]
◇ No.5 ReferenceExample
  FIG.referenceInvention No.5 ReferenceFIG. 21 and FIG. 22 are diagrams showing a planar shape of a combination example of a pixel electrode and a control electrode of a multi-domain liquid crystal display device as an example, and FIGS. 21 and 22 are a combination example of a pixel electrode and a control electrode of the multi-domain liquid crystal display device FIG. 23 is a diagram showing a planar shape of a basic configuration, and FIG. 23 is a diagram showing a planar shape of an example in which the basic configuration is applied to the multi-domain liquid crystal display device.
  That is, various examples of combinations of the pixel electrode 71 and the control electrode 73 of the multi-domain liquid crystal display device of this example are conceivable as shown in FIGS.
  Here, the basic configuration examples of FIGS. 21 (i) to 21 (n) and FIGS. 22 (o) to 22 (r) and the planar shapes of the application examples of FIGS. The electrode 73 is projected onto a certain plane. In particular, the control electrode 73 is drawn only in a portion visible from the opening 74 provided on the pixel electrode 71.
[0062]
  In this example, the positional relationship between the control electrode 73, the opening 74 provided on the pixel electrode 71, and the end of the pixel electrode 71 is important. In order to explain these positional relationships, the positional relationship on the plan view will be described. First, using the unit electrodes shown in FIGS. 21 (i) to (n), basic combinations of the pixel electrode 71, the control electrode 73, and the ends of the pixel electrode 71 are shown in FIGS. 21 (a) to (r). Next, an application example in which these unit electrodes are applied to an actual liquid crystal display device will be described with reference to FIGS. For the sake of explanation, the pixel electrode 71 and the control electrode 73 will be described as if they were on the same plane, but in the multi-domain liquid crystal display device of this example, both electrodes 71 and 73 are on different planes. If conduction is ensured through a contact hole or the like, a configuration in which part or all of these electrodes 71 and 73 are on the same plane is also possible.
[0063]
  In the unit electrode of FIG. 21 (i), the pixel electrode 71 is square and the control electrode 73 is disposed along one side of the pixel electrode 71, and the remaining three sides of the pixel electrode 71 are openings or pixel electrode ends. It is characterized by being part 76.
  In the unit electrode of FIG. 21 (j), the pixel electrode 71 is square and the control electrode 73 is disposed along two sides of the pixel electrode 71. The remaining two sides of the pixel electrode 71 are openings or pixel electrode ends. It is characterized by being part 76.
  In the unit electrode of FIG. 21 (k), the pixel electrode 71 is square and the control electrode 73 is disposed along the three sides of the pixel electrode 71, and the remaining one side of the pixel electrode 71 is an opening or a pixel electrode end. It is characterized by being part 76.
  In the unit electrode of FIG. 21 (l), the pixel electrode 71 is triangular, and the control electrode 73 is arranged along two sides of the pixel electrode 71. The remaining one side of the pixel electrode 71 is an opening or a pixel electrode end. It is characterized by being part 76.
  In the unit electrode of FIG. 21 (m), the pixel electrode 71 is triangular and the control electrode 73 is disposed along one side of the pixel electrode 71, and the remaining two sides of the pixel electrode 71 are openings or pixel electrode ends. It is characterized by being part 76.
  In the unit electrode of FIG. 21 (n), the pixel electrode 71 is pentagonal, and the control electrode 73 is arranged along two sides of the pixel electrode 71, and the remaining three sides of the pixel electrode 71 are openings or pixel electrode ends. It is characterized by being part 76.
[0064]
  Next, an example in which the unit electrodes of FIGS. 21 (i) to (n) are applied to a multi-domain liquid crystal display device having a repeating unit of pixels: approximately horizontal 100 μm × vertical 300 μm is illustrated in FIGS. This will be described with reference to an application example.
  The application example of FIG. 23 (s) uses several unit electrodes of FIG. 21 (i). That is, the unit electrode (i) and the unit electrode in which the unit electrode (i) is axisymmetric with respect to the control electrode 73 are arranged so as to share the control electrode 73 to form an electrode like the electrode (o). Then, two electrodes (o) were used to form one pixel electrode of the multi-domain liquid crystal display device. The reason for using the electrode (o) is to control the direction of the liquid crystal in approximately two directions by the oblique electric field from the control electrode 73 and the oblique electric fields at the left and right ends of the electrode (o). In the application example of FIG. 23S, the control electrode 73 is made parallel to the long side of the pixel. Note that, when applied to a multi-domain liquid crystal display device, the pixel electrode 71 is not divided by the control electrode 73 as shown in the electrode (o), but the pixel electrode 71 on one pixel is equipotential. A joint is provided. The junction is provided so that the pixel electrode 71 on one pixel is equipotential. The electrode (o) is the application example of FIG. 23 (t), and the unit electrode (l) is of FIG. 23 (u). In the application example, the unit electrode (j) is the application example of FIG. 23 (w), the unit electrode (k) and the unit electrode (n) are the application example of FIG. 23 (x), the unit electrode (i), and the unit electrode. The same applies when (l) and the unit electrode (j) are applied to the application example of FIG.
[0065]
  In the application example of FIG. 23 (t), five electrodes (o) are arranged so that the control electrode 73 is parallel to the short side of the pixel to form one pixel electrode of the multi-domain liquid crystal display device.
  The application example of FIG. 23 (u) is composed of unit electrodes (l). First, four unit electrodes (l) are arranged so as to share the control electrode 73 with each other to form an electrode like the electrode (p), and a multi-domain liquid crystal display device using the two electrodes (p) One pixel electrode. The reason why the unit electrode (l) and the electrode (p) are used is that the unit electrode (l) is formed by three oblique electric fields, that is, an oblique electric field from the two control electrodes 73 of the unit electrode (l) and an oblique electric field at the pixel end. This is because the upper alignment is controlled in approximately one direction, and the unit electrode (l) is arranged like the electrode (p) to control the direction of the liquid crystal in approximately four directions.
[0066]
  The application example of FIG. 23 (v) is composed of a unit electrode (l) and a unit electrode (m). Four unit electrodes (m) were arranged so that the control electrode 73 was on the outside, and shaped like an electrode (q). An electrode (q) is disposed between two electrodes (p) to form one pixel electrode of a multi-domain liquid crystal display device. However, in the application example of FIG. 23 (v), in order to obtain alignment consistency between the electrode (p) and the electrode (q), the electrode (p) among the control electrodes 73 outside the electrode (q). The part which touches is removed. Thus, basically, the unit electrodes (i) to (n) are used to form the pixel electrodes. However, in order to achieve alignment alignment as described above, the shape of the unit electrodes is partially changed. It is also possible.
[0067]
  The application example of FIG. 23 (w) is composed of unit electrodes (j). The shape of the unit electrode (j) is substantially square, and the four unit electrodes (j) are arranged so as to share the control electrode 73 to form the shape of the electrode (r). Three electrodes (r) were used to form one pixel electrode of the multi-domain liquid crystal display device. The reason why the unit electrode (j) and the electrode (r) are used is that the electrode (r) is formed by the four oblique electric fields of the oblique electric field from the two control electrodes 73 of the unit electrode (j) and the oblique electric field at the two pixel end portions. This is because the orientation of the liquid crystal is controlled in approximately one direction, and the unit electrode (j) is arranged like the electrode (r) to control the direction of the liquid crystal in approximately four directions. In the application example of FIG. 23 (w), the number of electrodes (r) is three, but the number of electrodes (r) is not limited to this and can be arbitrarily designed according to the pixel size and application.
[0068]
  The application example of FIG. 23 (x) is composed of two unit electrodes (k) and two unit electrodes (n). The square of the unit electrode (k) was a trapezoid. The control electrode 73 was placed on the upper base of the trapezoid, and the two unit electrodes (k) were arranged so as to share the upper base. The unit electrode (n) is arranged on the oblique side portion of the electrode formed in this way so as to share the unit electrode (k) and the control electrode 73. When combining, in order to achieve alignment consistency, the upper base of the trapezoid, that is, a part of the control electrode 73 is hidden. As a result, an electrode that appears as if the “Y” -type and “Y” -type inverted control electrodes 73 are arranged on the rectangular pixel electrode 71 is formed. This was used as one pixel electrode of the multi-domain liquid crystal display device.
[0069]
  The application example shown in FIG. 23 (y) is formed of three types of unit electrodes: a unit electrode (i), a unit electrode (l), and a unit electrode (j). In the application example of FIG. 23 (y), the unit electrode (i) is a trapezoid, the unit electrode (l) is a right isosceles triangle with a right angle between the control electrodes 73, and the unit electrode (j) is A parallelogram was used. The hypotenuse of the unit electrode (l) is in contact with the upper base (opening) of the unit electrode (i), and the lower base of the unit electrode (i) and the unit electrode (j) share the control electrode 73. . Several electrodes thus formed were used as one pixel electrode of a multi-domain liquid crystal display device. In addition, since a right isosceles triangle is used for a part of the minute pixel electrode, the control electrode 73 and the opening 74 inside the pixel electrode 71 have an angle of about 45 ° or about 135 ° with respect to the short side of the pixel. There is no.
  In any of the application examples of FIGS. 23 (s) to (y), the pixel electrode is basically formed by using the unit electrode, but in order to obtain alignment consistency in the entire pixel, It is also possible to partially change the shape of the unit electrode.
  A multi-domain liquid crystal display device having a pixel electrode designed as described above was manufactured. The details of this control electrodereferenceIt can be implemented according to that of the example.
[0070]
  The alignment states of the application examples of FIGS. 23 (s) to (y) described above are shown in micrographs in FIGS. In FIG. 24 to FIG. 27 and FIG. 29, the two polarizing plates are arranged in such a manner that the absorption axes of the polarizing plates are orthogonal to each other, and the absorption axis of one polarizing plate is relative to the long side of the pixel. The direction is approximately 45 °. 28 and 30, the two polarizing plates are arranged in such a manner that the absorption axes of the polarizing plates are orthogonal to each other, and the absorption axis of one of the polarizing plates is approximately 0 ° with respect to the long side of the pixel. It is in the direction.
[0071]
  According to this example, the effect of the oblique electric field from the peripheral portion of the control electrode 73, the peripheral portion of the opening 74, and the peripheral portion of the pixel electrode 71 in any of the application examples of FIGS. As a result, a good multi-domain liquid crystal alignment was obtained.
  In particular, the pattern of the application example of FIG. 23 (w) has good viewing angle characteristics, high transmittance, and excellent stability. In the application example of FIG. 23 (w), since the shape of the unit electrode (j) is substantially square, the liquid crystal is tilted along the diagonal direction. Therefore, the alignment direction differs by approximately 90 ° between the adjacent unit electrodes (j). On the electrode (r), the four-fold symmetrical orientation is defined by the “+” type control electrode 73.
[0072]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0073]
◇ No.6 ReferenceExample
  referenceInvention No.6 ReferenceIn the example,5 ReferenceIn the application example of FIG. 23 (w) shown as an example, the influence on the orientation controllability when the control electrode voltage coefficient (control electrode voltage / pixel electrode voltage) is varied was compared. Here, the pixel electrode voltage and the control electrode voltage indicate the voltages of the pixel electrode 71 and the control electrode 73 based on the voltage of the common electrode 81.
  As described above, the voltage ratio between the pixel electrode voltage and the control electrode voltage is such that the coupling capacitor 126 between the pixel electrode 71 and the control electrode 73, the additional capacitor 127 between the pixel electrode 71 and the common capacitor line 72, and It is determined by the ratio with the liquid crystal capacitor 125. Here, when the voltage of the common capacitor line 72 is the same as that of the common electrode 81, (control electrode voltage coefficient) = {(capacitance value of the liquid crystal capacitor 125) + (capacitance value of the coupling capacitor 126) + ( (Capacitance value of additional capacitor 127)} / (capacitance value of coupling capacitor 126).
[0074]
  Although the liquid crystal capacitance 125 varies depending on the change of the alignment state, the liquid crystal capacitance 125 is considered as the maximum value for simplicity. That is, when calculating the capacitance value of the liquid crystal capacitor 125, the larger value of the relative permittivity of the liquid crystal is selected from the relative permittivity corresponding to the direction perpendicular to the liquid crystal molecular axis and the relative permittivity corresponding to the direction perpendicular to the liquid crystal molecular axis. It was decided to use. In this example, the control electrode voltage coefficient is varied by changing the capacitance value of the coupling capacitor 126. Since the coupling capacitor 126 is formed at the overlapping portion of the pixel electrode 71 and the control electrode 73, the capacitance of the coupling capacitor 126 is determined by the area of the overlapping portion, the film thickness of the interlayer film between the electrodes 71 and 73, and the relative dielectric constant. Although the value is determined, here, an example is shown in which the area of the overlapping portion of the control electrode 73 and the pixel electrode 71 is changed as shown in Table 1 below. The interlayer film between the electrodes 71 and 73 was silicon nitride having a thickness of about 200 nm formed by CVD. The relative dielectric constant of the silicon nitride film is approximately 6.4.
[0075]
[Table 1]

[0076]
  Next, as shown in Table 1, a TFT-LCD (Liquid Crystal Device) in which the control electrode voltage coefficient was changed was manufactured, displayed, and observed with a microscope and visually. The photomicrographs of the pixels at the time of display corresponding to the control electrode voltage coefficient values 1.1, 1.2, 1.3, and 1.4 in Table 1 are shown in FIGS. This is shown in FIG. As is apparent from FIGS. 31 to 34, the present invention is applied to each TFT-LCD having a different control electrode voltage coefficient.And reference inventionThe multi-domain liquid crystal alignment control based on the principle of can be realized. In particular, when the control electrode voltage coefficient is 1.2 or more, more preferably 1.3 or more, the orientation control can be realized more accurately. On the other hand, in the TFT-LCD having a small control electrode voltage coefficient of 1.1, a slight roughness was observed by visual observation.
  As is clear from the above results, the control electrode voltage coefficient has a higher orientation controllability when the value is larger. However, since the voltage applied to the pixel electrode is relatively decreased along with this, the drive voltage or From the viewpoint of brightness, it is not desirable that the control electrode voltage coefficient becomes too large. Considering these, it is considered that the control electrode voltage coefficient is most preferably about 1.3.
[0077]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0078]
◇ No.7 ReferenceExample
  referenceInvention No.7 ReferenceIn the example,5 ReferenceBased on the application example of FIG. 23 (w) shown in the example, experimental liquid crystal cells with different wind sizes with different micro-alignment regions were manufactured and compared. Here, the micro-alignment region refers to a region delimited by the boundaries of the control electrode 73, the end of the pixel electrode 71, the opening 74 provided in the pixel electrode 71, and the like, and the region where the liquid crystal has a substantially single alignment. Is shown.
  In the application example of FIG. 23 (w) in this example, the size of one micro-alignment region is approximately 40 μm square. Based on this, an experimental liquid crystal cell having a micro-alignment region size of approximately 20 μm square was manufactured. As a comparative example, an experimental liquid crystal cell having a micro-alignment region size of approximately 40 μm square was also manufactured. In these experimental liquid crystal cells, the TFT, the gate bus line, the drain bus line, and the like are omitted, and a voltage can be directly applied to the control electrode 73 and the pixel electrode 72, respectively.
[0079]
  FIG. 35 shows a micrograph after switching the voltage from the dark state to the bright state in the experimental liquid crystal cell of this example. FIG. 35A is a photograph showing the state after leaving the voltage for 20 ms after switching the voltage from the dark state to the bright state, and FIG. 35B is after leaving the voltage for one second or more after switching the voltage from the dark state to the bright state. It is a photograph showing the state of.
  As is clear from comparison between the two photographs, in this example, an alignment state almost equal to the steady state alignment state is obtained within 20 ms after voltage application, and the alignment stability and electro-optical response characteristics are excellent. I understood it. Specific measurements of response time were about 15 ms for dark → light and about 9 ms for light → dark.
[0080]
  On the other hand, FIG. 36 shows a micrograph after switching the voltage from the dark state to the bright state in the comparative example. FIG. 36A is a photograph showing the state after being left for 20 ms after switching the voltage from the dark state to the bright state, and FIG. 36B is after leaving the voltage for more than 1 second after switching the voltage from the dark state to the bright state. It is a photograph showing the state of.
  As is clear from comparison between the two photographs, it was found that in the comparative example, it takes some time to obtain a bright steady state alignment state after voltage application. Specific measurements of response time were about 140 ms from dark to light and about 9 ms from light to dark.
[0081]
  As described above, in this example, regarding the electro-optic response characteristics, it is confirmed that the smaller micro-alignment region size (20 μm square) is superior to the larger micro-alignment region size (40 μm square). It was. However, with regard to the light transmittance of the entire device, it has been found that a larger micro-region alignment region size is preferable due to the difference in dark line density seen at each micro-region boundary. That is, it was confirmed that the light transmittance of the whole experimental liquid crystal cell was higher when the micro-alignment region size was increased (40 μm square) than when the micro-alignment region size was decreased (20 μm square).
[0082]
  For the reasons described above, the micro-alignment region size can be selected as appropriate depending on the use of whether or not to perform moving image display and considering the balance with the pixel pitch of the target TFT-LCD. When displaying moving images, it is preferably about 20 μm square or less, and when not displaying moving images, it is preferably about 40 μm square or more. Of course, depending on the application, it may be set in the range of 20 μm to 40 μm square.
[0083]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0084]
◇ No.8 ReferenceExample
  FIG.referenceInvention No.8 ReferenceFIG. 38 is a schematic partial cross-sectional view taken along line HH ′ of FIG. 37, and FIG. 39 is a schematic part taken along line II ′ of FIG. 37. It is sectional drawing. The configuration of the multi-domain liquid crystal display device of this example is the first described above.referenceA significant difference from the configuration of the example is that the control electrode is formed integrally with the source terminal of the TFT as a switching element.
  That is, in the multi-domain liquid crystal display device of this example, as shown in FIGS. 37 to 39, the control electrode 73 is formed of an opaque metal such as chromium integrally with the source terminal 57 of the TFT. With such a configuration, as described above, there is a concern that the aperture ratio may be lowered when the capacitance value of the coupling capacitor 126 is formed large. In this example, however, this point is also taken into consideration. It is the structure which can ensure a sufficient aperture ratio. Specifically, a coupling capacitor electrode 171 is formed below the control electrode 73 via the gate insulating film 61, and the coupling capacitor electrode 171 and a pixel formed above the control electrode 73 via the interlayer insulating film 63. Each of the electrodes 71 has an overlapping portion with the control electrode 73 and is connected to each other through a contact hole 172. In FIG. 37, it is difficult to understand because most of the coupling capacitance electrode 171 is hidden under the control electrode 73, but as is clear from FIG. 39, the coupling capacitance electrode 171 substantially follows the shape of the control electrode 73. Located on the lower side.
[0085]
  According to this example, since the coupling capacitance 126 can be formed on both upper and lower sides of the control electrode 73, even when the capacitance value of the coupling capacitance 126 is increased, a sufficient aperture ratio can be obtained without increasing the area of the control electrode 73 so much. Can be secured.
  In this example, the control electrode 73 is formed below the pixel electrode 71, but conversely, the pixel electrode 71 can be formed below the control electrode 73 and disposed below the pixel electrode 71. By connecting the coupling capacitor electrode 171 and the upper control electrode 73 through the contact hole 172, a coupling capacitor can be formed on both upper and lower sides of the pixel electrode 71.
[0086]
  Furthermore, according to this example, the configuration for obtaining a sufficient capacitance value with a small overlapping area is also adopted for the additional capacitor 127. That is, in the contact hole 177, the additional capacitor 127 is formed by the overlapping portion of the additional capacitor terminal 175 connected to the common capacitor line 72 by the connection terminal 176 and the pixel electrode 71. Here, the common capacitor line 72 is formed of the same metal film as the gate bus line 55, and the additional capacitor terminal 175 is formed of the same metal film as the drain bus line 56. Thus, since the additional capacitance terminal 175 is formed in a layer closer to the pixel electrode 71 than the common capacitance line 72, a sufficient capacitance value of the additional capacitance 127 can be ensured with a small overlapping area.
[0087]
  In this example, the additional capacitor 127 is formed through the interlayer insulating film 63. However, even if the additional capacitor 127 is formed through the gate insulating film 61, these two insulating films are formed. It is easy to secure a larger capacitance value than the configuration in which the additional capacitor 127 is formed via the capacitors 63 and 61. In order to obtain a sufficient capacitance value with a small overlapping area and ensure the aperture ratio, for example, the gate insulating film 61 or the interlayer insulating film 63 is made thinner in addition to the device in the layer structure as described above. It is also effective to increase the dielectric constant.
[0088]
  In addition to the effect related to securing the aperture ratio, the patterning accuracy of the control electrode 73 can be improved by configuring the control electrode 73 with a metal film in this example. This is because the accuracy of wet etching is usually higher for an opaque metal such as Cr than a transparent electrode such as ITO. thisreferenceIn the multi-domain liquid crystal display device of the invention, since the capacitance value of each capacitor formed in the overlapping portion of each electrode is an important design parameter, it is important to improve the patterning accuracy of each electrode that determines the area of the overlapping portion. is there.
[0089]
  Next, with reference to FIGS. 41 to 43, a manufacturing method of the multi-domain liquid crystal display device of this example will be described in the order of steps.
  First, as shown in FIG. 41A, after chromium is sputter-deposited on the first substrate 11 made of glass, the chromium is patterned by wet etching using a photolithography technique, and the gate bus line 55, A common capacitor line 72 and a coupling capacitor electrode 171 were formed. Subsequently, as shown in FIG. 41B, a silicon nitride film was formed using a CVD method to form a gate insulating film 61 uniformly. The gate insulating film 61 may be, for example, silicon dioxide, or a laminated film of silicon nitride and silicon oxide. Of course, an organic film or the like may be used. Next, an amorphous silicon layer was formed by a CVD method and patterned by dry etching using a photolithography technique to form an active layer 64 of the TFT 54 in an island shape.
[0090]
  Next, as shown in FIG. 42 (c), chromium is sputtered and then patterned by wet etching using a photolithography technique to form a drain bus line 56, a drain terminal 58, a source terminal 57, and a control electrode 73. The additional capacitor terminal 175 was formed. Subsequently, as shown in FIG. 42 (d), silicon nitride is formed by CVD to form the interlayer insulating film 63 integrally and uniformly, and by dry etching using photolithography technology, the interlayer insulating film 63 and The gate insulating film 61 was continuously patterned to form contact holes 172 and 177. Subsequently, as shown in FIG. 43, ITO was sputtered and patterned by wet etching using a photolithography technique to form floating pixel electrodes 71 and connection terminals 176. In the step of forming the pixel electrode 71 and the connection terminal 176, patterning accuracy can be improved by patterning ITO by dry etching instead of wet etching.
[0091]
  As described above, the first substrate 11 is formed by the 5PR process using the photolithography technique five times in total. Although not explained in detail, thisreferenceIn the multi-domain liquid crystal display device of the invention, a process is added especially to all peripheral elements such as a gate bus line terminal, a drain bus line terminal, a common capacitance line connection part, and an electrostatic protection transistor provided around the display region. It can form simultaneously with said process, without said. Details of this are described in, for example, Japanese Patent Laid-Open No. 10-232409. Other processes such as the manufacturing process of the second substrate 12 and the bonding process of the first substrate 11 and the second substrate 12 are the same as the first process.referenceIt can implement according to the manufacturing method of an example.
[0092]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0093]
◇ No.9 ReferenceExample
  FIG.referenceInvention No.9 ReferenceFIG. 45 is a schematic partial sectional view taken along the line KK ′ of FIG. 44, and FIG. 46 is a schematic part taken along the line LL ′ of FIG. 44. It is sectional drawing. The configuration of the multi-domain liquid crystal display device of this example is the first described above.referenceA significant difference from the configuration of the example is that a discharge TFT is arranged on the gate bus line corresponding to the previous stage of the pixel of interest.
  That is, the multi-domain liquid crystal display device of this example is shown in FIGS.
In particular, as described with reference to FIG.Of this inventionIn the modification of the embodiment, a discharge TFT 141 is disposed on the gate bus line 55 corresponding to the previous stage of the pixel of interest. Here, a gate terminal, a drain terminal, a source terminal, an active layer, and the like constituting the TFT 141 can be formed in parallel with the TFT 54 for display. The TFT 141 has a drain terminal connected to the common capacitor line 72 through the contact hole 142, and a source terminal connected to the pixel electrode 71 through the contact hole 143. With this configuration, the electric charge accumulated in the pixel electrode 71 can be discharged by writing the potential of the common capacitance line 72 to the pixel electrode 71 at the moment when the previous gate bus line 55 is selected.
[0094]
  Further, in this example, the interlayer insulating film 63 is removed at a portion corresponding to the opening 74 where the control electric field from the control electrode 73 disposed in the lower layer of the opening 74 provided in the pixel electrode 71 acts. It has been configured. By adopting such a configuration, the loss of voltage in the insulating film portion between the control electrode 73 and the liquid crystal layer is eliminated, and an effect that the electric field from the control electrode 73 is directly applied to the liquid crystal layer is obtained. Further, since the concave shape formed by removing the interlayer insulating film 63 is aligned with the tilt direction of the liquid crystal molecules due to the action of the tilt electric field, the effect of stabilizing the liquid crystal alignment at the micro-alignment region boundary is obtained. . Since the removal of the interlayer insulating film 63 can be performed in parallel with the step of exposing the terminal portion around the display region, no additional step is required.
[0095]
  Thus, even with the configuration of this example, the firstreferenceThe same effect as described in the example can be obtained.
[0096]
  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the present invention can be changed even if there is a design change without departing from the gist of the present invention. include. For example, the example in which the TFT is used as the switching element has been described. However, the present invention is not limited to this, and a diode such as an MIM (Metal Insulator Metal) element may be used. Moreover, although the example which uses ITO was demonstrated as the transparent electrode which comprises a pixel electrode and a control electrode, it is not restricted to this, It is also possible to use other materials, such as a nesa film | membrane (tin oxide film). Further, when the control electrode is formed of a transparent electrode, the transparent electrode may be used for only a part. Moreover, although the example which uses chromium was demonstrated as a metal which comprises a gate bus line, a source terminal, a drain terminal, etc., other materials, such as not only this but molybdenum, tantalum, or these alloys, can also be used. It is.
[0097]
【The invention's effect】
  As described above, according to the present invention, since the control electrode provided for each pixel is driven by the switching element provided for each pixel, the pixel is displayed in a bright display, a dark display, or an intermediate display. Even so, the control electrode potential is controlled accordingly, and therefore, the formation of the liquid crystal domains can be reliably controlled by the oblique electric field generated so as to spread from the control electrode. Furthermore, since the divided voltage of the control electrode voltage is applied to the pixel electrode via the coupling capacitance, the two electrode potentials of the control electrode and the pixel electrode can be controlled with only one switching element.
  Therefore, it is possible to provide a multi-domain liquid crystal display device having high contrast and excellent viewing angle characteristics without increasing complicated processes such as a microfabrication process of a common electrode or requiring an advanced bonding technique.
[Brief description of the drawings]
[Figure 1]referenceFirst of the inventionreferenceIt is a typical top view which shows the structure of the pixel of the multi domain liquid crystal display device which is an example.
FIG. 2 is a schematic partial cross-sectional view taken along line A-A ′ of FIG.
FIG. 3 is a schematic partial cross-sectional view taken along B-B ′ of FIG. 1;
FIG. 4 is a schematic partial cross-sectional view taken along C-C ′ of FIG. 1;
FIG. 5 is an equivalent circuit diagram of a pixel of the multi-domain liquid crystal display device.
FIG. 6 is a process drawing showing the manufacturing method of the multi-domain liquid crystal display device in the order of steps.
FIG. 7 is a process drawing showing the manufacturing method of the multi-domain liquid crystal display device in the order of steps.
[Fig. 8]referenceSecond inventionreferenceIt is a typical top view which shows the structure of the pixel of the multi domain liquid crystal display device which is an example.
9 is a schematic partial cross-sectional view taken along the line D-D ′ of FIG. 8. FIG.
10 is a schematic partial cross-sectional view taken along line E-E ′ of FIG. 8. FIG.
FIG. 11 is a diagram schematically showing multi-domain liquid crystal alignment in the multi-domain liquid crystal display device.
FIG. 12 is a diagram schematically showing a state of transmitted light corresponding to a multi-domain alignment state in the multi-domain liquid crystal display device.
FIG. 13 shows the present invention.oneIt is a typical fragmentary sectional view which shows the structure of the multi domain liquid crystal display device which is an Example.
FIG. 14 is an equivalent circuit diagram of a pixel in the multi-domain liquid crystal display device.
FIG. 15 is an equivalent circuit diagram of a pixel of a modification of the multi-domain liquid crystal display device.
FIG. 16referenceInvention No.3 ReferenceIt is a typical fragmentary sectional view which shows the structure of the multi domain liquid crystal display device which is an example.
FIG. 17referenceInvention No.4 ReferenceIt is a typical top view which shows the structure of the pixel of the multi domain liquid crystal display device which is an example.
FIG. 18 is a schematic partial cross-sectional view taken along the line F-F ′ of FIG.
19 is a schematic partial cross-sectional view taken along line G-G ′ of FIG.
FIG. 20referenceInvention No.5 ReferenceIt is a figure which shows the planar shape of the example of a combination of the pixel electrode and control electrode of the multi domain liquid crystal display device which is an example.
FIG. 21 is a diagram illustrating a planar shape of a basic configuration in a combination example of a pixel electrode and a control electrode of the multi-domain liquid crystal display device.
FIG. 22 is a diagram illustrating a planar shape of a basic configuration in a combination example of a pixel electrode and a control electrode of the multi-domain liquid crystal display device.
FIG. 23 is a diagram showing a planar shape of an example in which the same basic configuration is applied to the multi-domain liquid crystal display device.
FIG. 24 is a micrograph showing the alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 25 is a micrograph showing an alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 26 is a micrograph showing the alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 27 is a micrograph showing the alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 28 is a micrograph showing the alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 29 is a micrograph showing an alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 30 is a micrograph showing an alignment state of pixels of the multi-domain liquid crystal display device.
FIG. 31referenceInvention No.6 ReferenceIt is the microscope picture of the pixel at the time of the display of the multi domain liquid crystal display device which is an example.
FIG. 32 is a photomicrograph of pixels during display of the multi-domain liquid crystal display device.
FIG. 33 is a photomicrograph of pixels during display of the multi-domain liquid crystal display device.
FIG. 34 is a photomicrograph of pixels during display of the multi-domain liquid crystal display device.
FIG. 35referenceInvention No.7 ReferenceIt is the microscope picture after switching the voltage from the dark state of the liquid crystal cell for experiment of the multi-domain liquid crystal display device which is an example to the bright state.
FIG. 36 is a photomicrograph after switching the voltage from the dark state to the bright state of the comparative liquid crystal cell of the multi-domain liquid crystal display device.
FIG. 37referenceInvention No.8 ReferenceIt is a typical top view which shows the structure of the pixel of the multi domain liquid crystal display device which is an example.
38 is a schematic partial cross-sectional view taken along the line H-H ′ of FIG. 37. FIG.
39 is a schematic partial cross-sectional view taken along the line I-I ′ of FIG. 37. FIG.
40 is a schematic partial cross-sectional view taken along the line J-J ′ of FIG. 37. FIG.
FIG. 41 is a process drawing showing the manufacturing method of the multi-domain liquid crystal display device in order of processes.
FIG. 42 is a process drawing showing the manufacturing method of the multi-domain liquid crystal display device in order of processes.
FIG. 43 is a process drawing showing the manufacturing method of the multi-domain liquid crystal display device in order of processes.
FIG. 44referenceInvention No.9 ReferenceIt is a typical top view which shows the structure of the pixel of the multi domain liquid crystal display device which is an example.
45 is a schematic partial cross-sectional view taken along the line K-K ′ of FIG. 44. FIG.
46 is a schematic partial cross-sectional view taken along line L-L ′ of FIG. 45. FIG.
FIG. 47 is a schematic partial cross-sectional view showing a configuration of a pixel of a conventional multi-domain liquid crystal display device.
[Explanation of symbols]
    11 First substrate
    12 Second substrate
    20 LCD
    21 Liquid crystal molecules
    54 TFT (switching element)
    55 Gate bus line
    56 Drain bus line
    57 Source terminal
    58 Drain terminal
    59, 142, 143, 149, 172, 177 Contact hole
    61 Gate insulation film
    62 Semiconductor film
    63 Interlayer insulation film
    64 Active layer (semiconductor layer)
    65 TFT protective film
    71 pixel electrode
    72 Common capacity line
    73 Control electrode
    74 opening
    75 capacity terminal
    76 Opening or pixel electrode edge
    81 Common electrode
    91 color layers
    92 Overcoat layer
    93 Shading layer
  125 LCD capacity
  126 coupling capacity
  127 Additional capacity
  135 Coupling resistance
  141 TFT (Discharge element)
  171 Coupling capacitance electrode
  175 Additional capacity terminal
  176 connection terminal
    E1 LCD drive electric field

Claims (18)

A liquid crystal sandwiched between a pair of substrates, a plurality of gate bus lines formed on one side of the substrate and extending in the horizontal direction, and a plurality of drain bus lines extending in the vertical direction. It is arranged in a matrix corresponding to each intersection of the gate bus line and the drain bus line, and an electric field oblique to the liquid crystal is generated in each of the pixels. A multi-domain liquid crystal display device comprising a control electrode for forming a plurality of alignment regions in one pixel,
The control electrode is connected to one terminal of the switching element, the pixel electrode has a coupling capacitance with the control electrode,
When the corresponding gate bus line is selected, a signal voltage is applied to the control electrode from the corresponding drain bus line via the corresponding switching element, and the signal voltage is applied to the pixel electrode via the coupling capacitance. And a partial pressure of
A multi-domain liquid crystal display device, further comprising a resistance element for discharging electric charges accumulated in the pixel electrode between the pixel electrode and the control electrode.   The multi-domain liquid crystal display device according to claim 1, wherein the pixel electrode and the control electrode are configured such that the pixel electrode is a lower layer through an insulating film.   2. The multi-domain liquid crystal display device according to claim 1, further comprising a common capacitance line for adding capacitance to the pixel electrode.   4. The multi-domain liquid crystal display device according to claim 3, wherein an additional capacitor having a predetermined capacitance is provided between the pixel electrode and the common capacitor line.   2. The multi-domain liquid crystal display device according to claim 1, wherein at least a part of the control electrode comprises a transparent electrode.   The multi-domain according to claim 1, further comprising a quarter-wave plate on both sides of the liquid crystal, the optical axes of the quarter-wave plates being arranged to be orthogonal to each other. Liquid crystal display device.   7. The multi-domain liquid crystal display device according to claim 1, wherein the switching element is a bottom gate TFT.   7. The multi-domain liquid crystal display device according to claim 1, wherein the switching element is a TFT having a top gate structure.   3. The multi-domain liquid crystal display device according to claim 2, wherein the switching element is a TFT having a bottom gate structure, and the insulating film is formed integrally with an insulating film for protecting the TFT.   3. The multi-domain liquid crystal display device according to claim 2, wherein the switching element is a TFT having a top gate structure, and the insulating film is formed integrally with an insulating film for protecting the TFT.   The multi-domain liquid crystal display device according to claim 7, 8, 9, or 10, wherein the control electrode is formed integrally with a source terminal of the TFT.   The multi-domain liquid crystal display device according to claim 1, wherein the resistance element has a substantially finite resistance value.   4. The multi-domain liquid crystal display device according to claim 3, further comprising a resistive element having a substantially finite resistance value between the pixel electrode and the common capacitance line.   2. The multi-domain liquid crystal display device according to claim 1, wherein the operation mode of the liquid crystal is a TN mode in which liquid crystal having positive dielectric anisotropy is twisted and aligned.   The multi-domain liquid crystal display device according to claim 14, wherein the liquid crystal is spontaneous chiral.   The multi-domain liquid crystal display device according to claim 14, wherein the liquid crystal is non-spontaneous chiral.   2. The multi-domain liquid crystal display device according to claim 1, wherein the operation mode of the liquid crystal is a homogeneous mode in which liquid crystals having positive dielectric anisotropy are uniformly aligned.   2. The multi-domain liquid crystal display device according to claim 1, wherein the operation mode of the liquid crystal is a VA mode in which a liquid crystal having negative dielectric anisotropy is homeotropically (vertically) aligned.

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