JP4045910B2 - Liquid crystal display - Google Patents

Description

【００９４】
本液晶表示装置１０にあっては、二つの液晶表示パネル１１Ｒ，１１Ｌを備えていることから、片面のみを更新する場合（曲線ｊ参照）と、両面を同時に更新する場合（曲線ｋ参照）とで環境温度の変化に応じて採用する特性曲線を変えるようにしている。
【００９５】
採用する特性曲線を変えるに当たっては、電源部の消費電力が過度に上昇したりピーク電流が過度に増大したりすることを防止するため、画面の更新所要時間が過度に短くならないように、また、駆動回路の性能が十分発揮できなくなるのを防止するため、選択パルスの幅が過度に小さくならないように特性曲線を選択する。さらに、両面更新時の更新所要時間の下限値が、片面更新時の更新所要時間の下限値よりも大きく、通常は、２倍よりも大きくなるように選択することが好ましい。さらにまた、画面の更新所要時間が必要以上に長くならないように選択することが好ましい。
【００９６】
即ち、片面のみを更新する場合は、画面の更新所要時間の下限値を２００ｍｓに設定し、これを下回ることのないように、また、画面の更新所要時間が長くなりすぎないように上限値を約６００ｍｓに設定し、これを上回ることのないように、温度変化に合わせて採用する曲線を変更する。具体的には、曲線ｊに示すように、低温域から２９℃までは特性曲線ａを採用し、２９℃を超えて３８℃までは特性曲線ｃを採用し、３８℃を超えると特性曲線ｆを採用する。なお、採用する特性曲線を切り換えるにあたっては、その特性曲線を採用した場合の選択パルス幅が小さくなりすぎないように考慮する。例えば、２９℃において特性曲線ａから特性曲線ｂに移すこともできるが、ここでは特性曲線ｂに移ると選択パルスの幅が小さくなりすぎるため、これを避ける意味で特性曲線ｃに移行させるようにしている。
【００９７】
一方、両面を同時に更新する場合は、画面の更新所要時間の下限値を６００ｍｓに設定し、これを下回ることのないように、また、画面の更新所要時間が長くなりすぎないように上限値を約１２００ｍｓに設定し、これを上回ることのないように、温度変化に合わせて採用する曲線を変更する。具体的には、曲線ｋに示すように、低温域から１１℃までは特性曲線ａを採用し、１１℃を超えて２２．５℃までは特性曲線ｂを採用し、２２．５℃を超えて２６℃までは特性曲線ｃを採用し、２６℃を超えて３２．５℃までは特性曲線ｄを採用し、３２．５℃を超えて３７℃までは特性曲線ｅを採用し、３７℃を超えて３９℃までは特性曲線ｆを採用し、３９℃を超えて４８℃までは特性曲線ｇを採用し、４８℃を超えて５８℃までは特性曲線ｈを採用し、５８℃を超えると特性曲線ｉを採用する。
【００９８】
このように、片面更新モードと両面更新モードとで、特性曲線の採用の仕方を異ならせることによって、（ａ）遅延期間の長さ（本例では、環境温度によってパルス群全体の長さが増減するので、正確には遅延期間の走査期間に対する割合）、（ｂ）駆動パルス群の互いのパルス幅の比（本例では、Ｔｓｐ／Ｔｓ（あるいはＴｓｓ／Ｔｓ））、（ｃ）駆動パルス群の互いのパルス幅の比固定での駆動パルス群全体の長さ、の少なくとも一つの変化の仕方が異なることとなる。
【００９９】
さらに詳細には、所定温度範囲内でＴｓｐ／Ｔｓが一定で、遅延期間の長さ（本例では、正確には遅延期間の走査期間に対する割合）が、環境温度が高くなるに従って大きくなるように変化させる。また、次の特性曲線に移るまでの所定温度範囲内では、駆動パルスの幅の比及びＴｓｐ／Ｔｓ（あるいはＴｓｓ／Ｔｓ）を一定に保ち、駆動パルス群全体の長さを変化させることとなる。
【０１００】
前記制御においては、環境温度が高温になるほど、駆動パルス群全体の長さを短くすると共に、Ｔｓｐ／Ｔｓ（あるいはＴｓｓ／Ｔｓ）が同じ値に保たれている温度範囲においては、環境温度が高温になるほど、遅延期間Ｔｄ（本例では、正確には遅延期間の走査期間に対する割合）を長く設定する。また、Ｔｓｐ／Ｔｓ（あるいはＴｓｓ／Ｔｓ）が同じ値に保たれる各温度範囲について高温の温度範囲ほどＴｓｐ／Ｔｓ（あるいはＴｓｓ／Ｔｓ）を大きい値に設定する。そして、環境温度に応じていずれの特性曲線を採用するかは、予めＲＯＭ５５に記憶させておき、温度センサ３１Ｒ，３１Ｌから取得される温度情報に基づいて所定の特性曲線を選択するように制御する。
【０１０１】
このように制御することで、複数の画面を同時に更新した場合でもピーク電流が過度に上昇することが抑制され、装置の損傷等の不具合を回避できる。
【０１０２】
（画面の更新例、図１７〜図１９参照）
ここで、左右の液晶表示パネル１１Ｒ，１１Ｌにおける画面の更新の様子を例示的に示す。図１７には両面更新モードにおけるページ送りの様子を示す。ここでは、３ページ及び４ページの表示から５ページ及び６ページの表示に更新されている。図１８には片面更新モードで右パネル１１Ｒのみを３ページの表示から４ページの表示へ更新する様子を示す。また、図１９には一の表示画面における部分更新モードの様子を示す。ここでは、色味調整のメニュー選択を実行する様子を示している。
【０１０３】
（制御手順、図２０〜図３１参照）
以下に、ＣＰＵ５１による本液晶表示装置１０の制御手順についてその主要な部分を説明する。
【０１０４】
図２０は制御のメインルーチンを示し、電源のオンによる起動時には、ステップＳ１で各種デバイスの状態やＲＡＭ５６に記憶されている各種パラメータ等を初期設定し、その後、ステップＳ２〜Ｓ９の処理を順次実行する。スリープ状態からの起床時にはステップＳ２から処理を開始する。
【０１０５】
なお、各種パラメータについては後述するが、これらのパラメータを記憶するメモリが不揮発性のものであれば起動時に初期設定することは不要である。
【０１０６】
ステップＳ２の入力処理では、操作パネルやタッチパネルの操作状況を把握する。ステップＳ３のモード判定処理では、入力された動作モード（片面更新モード、両面更新モード等）を判定する。ステップＳ４の描画極性決定処理では、これから描画する際の駆動パルスの極性を決定する（そのサブルーチンは以下に詳述する）。ステップＳ５の温度補償処理では、環境温度に応じた駆動パルスの補正を行う。ステップＳ６の描画処理では、所定の画像を液晶表示パネル上に表示する。ステップＳ７の通信処理では、通信ユニットを用いて外部機器との通信を行う。ステップＳ４の描画極性決定処理では、後述するように、決定した駆動パルスの極性データを複数のパラメータとしてメモリに記憶させる。そして、ステップＳ６の描画処理では、これらのパラメータが示す極性で画面の更新を行う。
【０１０７】
その後、ステップＳ８でスリープモードに入るか否かを判定し、ＹＥＳであればステップＳ９でスリープ処理を実行し、ＮＯであればステップＳ２へ戻る。
【０１０８】
図２１〜図２３はステップＳ４で実行される描画極性決定処理の第１例を示す。このサブルーチンで使用されるパラメータは以下のとおりである。
ＰＲ１：右パネルの前々回の描画極性を示す
ＰＲ２：右パネルの前回の描画極性を示す
ＰＬ１：左パネルの前々回の描画極性を示す
ＰＬ２：左パネルの前回の描画極性を示す
ＰＸ：これから更新しようとする描画極性を示す
ＰＸ１：部分更新モードでの１回目の描画極性を示す
ＰＸ２：部分更新モードでの２回目の描画極性を示す
ＮＲ：右パネルの部分更新回数を示す
ＮＬ：左パネルの部分更新回数を示す
【０１０９】
この第１例では、まず、ステップＳ１１で両面更新モードか否かを判定し、両面更新モードであれば、ステップＳ１２〜Ｓ１６でパラメータＰＲ１，ＰＲ２が正極性か負極性かを判定する。ＰＲ１及びＰＲ２が正極性であれば（ステップＳ１２でＹＥＳ）、ステップＳ１７でこれから更新しようとする描画極性を示すパラメータＰＸを負極性に設定する。ＰＲ１及びＰＲ２が負極性であれば（ステップＳ１３でＹＥＳ）、ステップＳ１８でパラメータＰＸを正極性に設定する。また、ＰＬ１及びＰＬ２が正極性であれば（ステップＳ１４でＹＥＳ）、ステップＳ１９でパラメータＰＸを負極性に設定する。ＰＬ１及びＰＬ２が負極性であれば（ステップＳ１５でＹＥＳ）、ステップＳ２０でパラメータＰＸを正極性に設定する。
【０１１０】
また、ＰＲ１，ＰＲ２，ＰＬ１，ＰＬ２が前記いずれの極性でもなければ（ステップＳ１５でＮＯ）、ステップＳ１６で前回の描画極性を示すパラメータＰＲ２の極性を判定し、正極性であればステップＳ２１でパラメータＰＸを負極性に設定し、負極性であればステップＳ２２でパラメータＰＸを正極性に設定する。
【０１１１】
次に、ステップＳ２３でパラメータＰＲ１をパラメータＰＲ２の内容に変更し、パラメータＰＬ１をパラメータＰＬ２の内容に変更し、かつ、パラメータＰＲ２，ＰＬ２をパラメータＰＸの内容に変更する。続いて、ステップＳ２４でパラメータＮＲ，ＮＬを０にリセットする。パラメータＮＲ，ＮＬは、部分更新時のクロストークによる画面濃度低下を防止する等の目的で左右のパネルの部分更新が所定回数に達したときに各パネルを全面更新するために使用されるが、その制御の詳細は省略する。
【０１１２】
片面更新モードが選択されている場合は（ステップＳ１１でＮＯ）、更新が選択されたパネルが右パネルか否かをステップＳ２５にて判定する。右パネルであれば、さらに、ステップＳ２６で部分更新モードか否かを判定し、部分更新モードであれば、ステップＳ２７でパラメータＰＲ２の極性を判定する。ＰＲ２が正極性であれば、ステップＳ２８でパラメータＰＸ１を負極性に設定すると共にパラメータＰＸ２を正極性に設定する。一方、ＰＲ２が負極性であれば、ステップＳ２９でパラメータＰＸ１を正極性に設定すると共にパラメータＰＸ２を負極性に設定する。本第１例にあっては、部分更新モードの場合、同じ部分更新領域を極性を変えて２回描画することにしている。次に、ステップＳ３０でパラメータＮＲに１を加算する。
【０１１３】
右パネルのみの全面更新モードであれば（ステップＳ２６でＮＯ）、ステップＳ３１でパラメータＰＲ２の極性を判定し、正極性であればステップＳ３２でパラメータＰＸを負極性に設定し、負極性であればステップＳ３３でＰＸを正極性に設定する。次に、ステップＳ３４でパラメータＰＲ１をパラメータＰＲ２の内容に変更し、かつ、パラメータＰＲ２をパラメータＰＸの内容に変更する。さらに、ステップＳ３５でパラメータＮＲを０にリセットする。
【０１１４】
一方、更新が選択されたパネルが左パネルであれば（ステップＳ２５でＮＯ）、ステップＳ３６で部分更新モードか否かを判定し、部分更新モードであれば、ステップＳ３７でパラメータＰＬ２の極性を判定する。ＰＬ２が正極性であれば、ステップＳ３８でパラメータＰＸ１を負極性に設定すると共にパラメータＰＸ２を正極性に設定する。一方、ＰＬ２が負極性であれば、ステップＳ３９でパラメータＰＸ１を正極性に設定すると共にパラメータＰＸ２を負極性に設定する。部分更新モードの場合、同じ部分更新領域を極性を変えて２回描画するためである。次に、ステップＳ４０でパラメータＮＬに１を加算する。
【０１１５】
左パネルのみの全面更新モードであれば（ステップＳ３６でＮＯ）、ステップＳ４１でパラメータＰＬ２の極性を判定し、正極性であればステップＳ４２でパラメータＰＸを負極性に設定し、負極性であればステップＳ４３でＰＸを正極性に設定する。次に、ステップＳ４４でパラメータＰＬ１をパラメータＰＬ２の内容に変更し、かつ、パラメータＰＬ２をパラメータＰＸの内容に変更する。さらに、ステップＳ４５でパラメータＮＬを０にリセットする。
【０１１６】
以上のフローチャートに従って各パラメータを設定することにより、両面更新や片面更新が混在しているにも拘わらず、メインルーチンにおける描画処理（ステップＳ６）の画面更新においては、同極性の駆動パルスでの更新が３回以上続くことが防止される。また、部分更新時には極性を変えて２回の描画が行われることとなり、全面更新と部分更新が混在していても同極性の駆動パルスでの更新が３回以上続くことが防止される。
【０１１７】
図２４〜図２６はステップＳ４で実行される描画極性決定処理の第２例を示す。このサブルーチンで新たに使用されるパラメータは以下のとおりである。
ＰＲＢ：右パネルの前回の部分更新モードでの描画極性を示す
ＰＬＢ：左パネルの前回の部分更新モードでの描画極性を示す
ＰＸＢ：これから部分更新しようとする描画極性を示す
【０１１８】
この第２例は、左右パネルの部分更新モードでの駆動パルスの極性をメモリしておき、部分更新領域が連続して同じ極性で描画されることを防止するようにしたものである。
【０１１９】
即ち、この第２例において、ステップＳ１１〜Ｓ２２，Ｓ２４は前記第１例で説明したステップＳ１１〜Ｓ２２，Ｓ２４と同様の処理を行う。ステップＳ２３ａでは前記ステップＳ２３と同じ処理に加えて、パラメータＰＲＢ，ＰＬＢをパラメータＰＸの内容に変更する。
【０１２０】
片面更新モードが選択され（ステップＳ１１でＮＯ）、それが右パネルであり（ステップＳ２５でＹＥＳ）、かつ、部分更新モードであれば（ステップＳ２６でＹＥＳ）、ステップＳ２７ａでパラメータＰＲＢの極性を判定する。ＰＲＢが正極性であれば、ステップＳ２８ａでパラメータＰＸＢを負極性に設定する。一方、ＰＲＢが負極性であれば、ステップＳ２９ａでパラメータＰＸＢを正極性に設定する。そして、ステップＳ４６でパラメータＰＲＢをパラメータＰＸＢの内容に変更する。本第２例にあっては、パラメータＰＲＢ，ＰＬＢ，ＰＸＢを導入することにより、部分更新領域を連続して同じ極性で描画することを防止している。次に、ステップＳ３０でパラメータＮＲに１を加算する。
【０１２１】
右パネルのみの全面更新モードの場合（ステップＳ２６でＮＯ）に実行されるステップＳ３１，Ｓ３２，Ｓ３３，Ｓ３５は前記第１例と同様である。但し、ステップＳ３４ａではパラメータＰＲＢをパラメータＰＸの内容に変更する処理が追加されている。
【０１２２】
一方、更新が選択されたパネルが左パネルであり（ステップＳ２５でＮＯ）、かつ、部分更新モードであれば（ステップＳ３６でＹＥＳ）、ステップＳ３７ａでパラメータＰＬＢの極性を判定する。ＰＬＢが正極性であれば、ステップＳ３８ａでパラメータＰＸＢを負極性に設定する。一方、ＰＬＢが負極性であれば、ステップＳ３９ａでパラメータＰＸＢを正極性に設定する。そして、ステップＳ４７でパラメータＰＬＢをパラメータＰＸＢの内容に変更する。部分更新領域を連続して同じ極性で描画することを防止するためである。次に、ステップＳ４０でパラメータＮＬに１を加算する。
【０１２３】
左パネルのみの全面更新モードの場合（ステップＳ３６でＮＯ）に実行されるステップＳ４１，Ｓ４２，Ｓ４３，Ｓ４５は前記第１例と同様である。但し、ステップＳ４４ａではパラメータＰＬＢをパラメータＰＸの内容に変更する処理が追加されている。
【０１２４】
本第２例においては、部分更新時における駆動パルスの極性をメモリに記憶しておくことにより、第１例のように部分更新時に複数回の更新を行わなくても、部分更新領域が連続して同じ極性で描画されるのを防止でき、更新動作が簡便になる。
【０１２５】
図２７〜図３１はステップＳ４で実行される描画極性決定処理の第３例を示す。このサブルーチンで新たに使用されるパラメータは以下のとおりである。
ＰＲＢ１：右パネルの前々回の部分更新モードでの描画極性を示す
ＰＲＢ２：右パネルの前回の部分更新モードでの描画極性を示す
ＰＬＢ１：左パネルの前々回の部分更新モードでの描画極性を示す
ＰＬＢ２：左パネルの前回の部分更新モードでの描画極性を示す
【０１２６】
この第３例は、左右のパネルを同時に部分更新する場合をも考慮して駆動パルスの極性を決定するようにしている。また、両面のパネルを同時に部分更新する場合に同じ極性での描画が３回以上続かないように描画極性を決定している。
【０１２７】
即ち、この第３例において、まず、ステップＳ１１で両面更新モードか否かを判定し、両面更新モードであれば、ステップＳ５１で部分更新モードか否かを判定する。部分更新モードであれば、ステップＳ５２〜Ｓ５６でパラメータＰＲＢ１，ＰＲＢ２が正極性か負極性かを判定する。ＰＲＢ１及びＰＲＢ２が正極性であれば（ステップＳ５２でＹＥＳ）、ステップＳ５７でこれから更新しようとする描画極性を示すパラメータＰＸＢを負極性に設定する。ＰＲＢ１及びＰＲＢ２が負極性であれば（ステップＳ５３でＹＥＳ）、ステップＳ５８でパラメータＰＸＢを正極性に設定する。また、ＰＬＢ１及びＰＬＢ２が正極性であれば（ステップＳ５４でＹＥＳ）、ステップＳ５９でパラメータＰＸＢを負極性に設定する。ＰＬＢ１及びＰＬＢ２が負極性であれば（ステップＳ５５でＹＥＳ）、ステップＳ６０でパラメータＰＸＢを正極性に設定する。
【０１２８】
また、ＰＲＢ１，ＰＲＢ２，ＰＬＢ１，ＰＬＢ２が前記いずれの極性でもなければ（ステップＳ５５でＮＯ）、ステップＳ５６で前回の描画極性を示すパラメータＰＲＢ２の極性を判定し、正極性であればステップＳ６１でパラメータＰＸＢを負極性に設定し、負極性であればステップＳ６２でパラメータＰＸＢを正極性に設定する。
【０１２９】
次に、ステップＳ６３でパラメータＰＲＢ１をパラメータＰＲＢ２の内容に変更し、パラメータＰＬＢ１をパラメータＰＬＢ２の内容に変更し、かつ、パラメータＰＲＢ２，ＰＬＢ２をパラメータＰＸＢの内容に変更する。続いて、ステップＳ６４でパラメータＮＲに１を加算し、パラメータＮＬに１を加算する。
【０１３０】
両面での全面更新モードであれば（ステップＳ５１でＮＯ）、ステップＳ１２〜Ｓ２２を実行する。ここでの処理は前記第１例で説明したステップＳ１２〜Ｓ２２と同様であり、その処理が終了すると、ステップＳ６５でパラメータＰＲ１をパラメータＰＲ２の内容に変更し、パラメータＰＬ１をパラメータＰＬ２の内容に変更し、かつ、パラメータＰＲ２，ＰＬ２をパラメータＰＸの内容に変更する。同時に、パラメータＰＲＢ１をパラメータＰＲＢ２の内容に変更し、パラメータＰＬＢ１をパラメータＰＬＢ２の内容に変更し、かつ、パラメータＰＲＢ２，ＰＬＢ２をパラメータＰＸＢの内容に変更する。続いて、ステップＳ６６でパラメータＮＲ，ＮＬを０にリセットする。
【０１３１】
片面更新モードが選択され（ステップＳ１１でＮＯ）、それが右パネルであり（ステップＳ２５でＹＥＳ）、かつ、部分更新モードであれば（ステップＳ２６でＹＥＳ）、ステップＳ２７ｂでパラメータＰＲＢ２の極性を判定する。ＰＲＢ２が正極性であれば、ステップＳ２８ｂでパラメータＰＸＢを負極性に設定する。一方、ＰＲＢ２が負極性であれば、ステップＳ２９ｂでパラメータＰＸＢを正極性に設定する。そして、ステップＳ４６ｂでパラメータＰＲＢ１をパラメータＰＲＢ２の内容に変更し、パラメータＰＲＢ２をパラメータＰＸＢの内容に変更する。次に、ステップＳ３０でパラメータＮＲに１を加算する。
【０１３２】
右パネルのみの全面更新モードの場合（ステップＳ２６でＮＯ）に実行されるステップＳ３１，Ｓ３２，Ｓ３３，Ｓ３５は前記第１例と同様である。但し、ステップＳ３４ｂではパラメータＰＲＢ１をパラメータＰＲＢ２の内容に変更し、パラメータＰＲＢ２をパラメータＰＸの内容に変更する処理が追加されている。
【０１３３】
一方、更新が選択されたパネルが左パネルであり（ステップＳ２５でＮＯ）、かつ、部分更新モードであれば（ステップＳ３６でＹＥＳ）、ステップＳ３７ｂでパラメータＰＬＢ２の極性を判定する。ＰＬＢ２が正極性であれば、ステップＳ３８ｂでパラメータＰＸＢを負極性に設定する。一方、ＰＬＢ２が負極性であれば、ステップＳ３９ｂでパラメータＰＸＢを正極性に設定する。そして、ステップＳ４７ｂでパラメータＰＬＢ１をパラメータＰＬＢ２の内容に変更し、パラメータＰＬＢ２をパラメータＰＸＢの内容に変更する。次に、ステップＳ４０でパラメータＮＬに１を加算する。
【０１３４】
左パネルのみの全面更新モードの場合（ステップＳ３６でＮＯ）に実行されるステップＳ４１，Ｓ４２，Ｓ４３，Ｓ４５は前記第１例と同様である。但し、ステップＳ４４ｂではパラメータＰＬＢ１をパラメータＰＬＢ２の内容に変更し、パラメータＰＬＢ２をパラメータＰＸの内容に変更する処理が追加されている。
【０１３５】
（他の実施形態）
なお、本発明に係る液晶表示装置は前記実施形態に限定するものではなく、その要旨の範囲内で種々に変更することができる。
【０１３６】
例えば、図２に示した液晶表示素子の構成、材料、製造方法等は任意であり、図２０〜図３１に示した制御手順の詳細も任意である。また、液晶表示素子は単層のものであってもよいし、２層や４層以上の液晶表示層が積層されたものであってもよい。
【０１３７】
特に、図１６のグラフに示した片面更新モード及び全面更新モードでの特性曲線ｊ，ｋは一例である。また、Ｔｓｓ／Ｔｓを特定の温度範囲ごとにステップ的に変化させることなく、全温度範囲において所定の曲線を描くように滑らかな特性で変化させてもよい。
【０１３８】
また、前記実施形態においては２画面の液晶表示装置について説明したが、本発明は三つ以上の画面を持つ液晶表示装置にも適用することが可能である。３画面以上を有する液晶表示装置の場合も、個々のパネルについて所定回数の駆動パルスの極性を記憶しこれに基づいて極性を決定すればよい。但し、３画面以上を有する液晶表示装置の場合、全数より少ない複数の画面を同時に更新することもあり得るため、２画面の液晶表示装置よりも各パネルの極性の履歴がばらつきやすくなる。従って、前々回よりもさらに遡って駆動パルスの極性を記憶させておくことが好ましい。部分更新については、前記実施形態と２画面構成の液晶表示装置と同様の制御を行えばよい。
【図面の簡単な説明】
【図１】本発明に係る液晶表示装置の一実施形態を示す斜視図。
【図２】前記液晶表示装置を構成する液晶表示素子の一例を示す断面図。
【図３】前記液晶表示素子の制御部を示すブロック図。
【図４】３層の液晶表示層を駆動するＩＣの配置を示すブロック図。
【図５】前記液晶表示素子に対する基本的な駆動波形を示すチャート図。
【図６】前記液晶表示素子の各画素に印加される駆動波形（奇数フレーム）を示すチャート図。
【図７】前記液晶表示素子の各画素に印加される駆動波形（偶数フレーム）を示すチャート図。
【図８】図６、図７に示した駆動波形（液晶を選択反射状態とする）の詳細を示すチャート図。
【図９】図６、図７に示した駆動波形（液晶を中間調表示状態とする）の詳細を示すチャート図。
【図１０】図６、図７に示した駆動波形（液晶を光透過状態とする）の詳細を示すチャート図。
【図１１】電源部の詳細（液晶を正極性で駆動する場合）を示すブロック図。
【図１２】電源部の詳細（液晶を負極性で駆動する場合）を示すブロック図。
【図１３】環境温度が変化した場合に走査電極へ印加される駆動波形を示すチャート図。
【図１４】ディレイドスキャン方式による駆動例１の駆動波形を示すチャート図。
【図１５】ディレイドスキャン方式による駆動例２の駆動波形を示すチャート図。
【図１６】遅延期間及びＴｓｓ／Ｔｓの各種設定値に関して、環境温度と走査時間との関係を示すグラフ。
【図１７】画面更新例（両面更新モード）の説明図。
【図１８】画面更新例（片面更新モード）の説明図。
【図１９】画面更新例（部分更新モード）の説明図。
【図２０】前記液晶表示装置の制御手順（メインルーチン）を示すフローチャート図。
【図２１】描画極性決定処理の第１例を示すフローチャート図。
【図２２】描画極性決定処理の第１例を示すフローチャート図、図２１の続き。
【図２３】描画極性決定処理の第１例を示すフローチャート図、図２２の続き。
【図２４】描画極性決定処理の第２例を示すフローチャート図。
【図２５】描画極性決定処理の第２例を示すフローチャート図、図２４の続き。
【図２６】描画極性決定処理の第２例を示すフローチャート図、図２５の続き。
【図２７】描画極性決定処理の第３例を示すフローチャート図。
【図２８】描画極性決定処理の第３例を示すフローチャート図、図２７の続き。
【図２９】描画極性決定処理の第３例を示すフローチャート図、図２８の続き。
【図３０】描画極性決定処理の第３例を示すフローチャート図、図２７の続き。
【図３１】描画極性決定処理の第３例を示すフローチャート図、図３０の続き。
【符号の説明】
１０…液晶表示装置
１１Ｒ，１１Ｌ…液晶表示パネル
３１Ｒ，３１Ｌ…温度センサ
５１…中央処理装置（ＣＰＵ）
５２…ＬＣＤコントローラ
７０…電源部
１００Ｒ，１００Ｌ…液晶表示素子
１１３，１１４…電極
１１６…カイラルネマチック液晶
１３１Ｒ，１３１Ｌ…走査駆動ＩＣ
１３２Ｒ，１３２Ｌ…信号駆動ＩＣ
Ｔｓ…選択期間
Ｔｓｐ…選択パルス印加期間
Ｔｄ…遅延期間
Ｔｓｓ…走査期間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including two display panels using liquid crystal as a display medium.
[0002]
[Prior art and issues]
In recent years, a reflective liquid crystal display element using a liquid crystal (mainly chiral nematic liquid crystal) exhibiting a cholesteric phase at room temperature as a medium for reproducing digital information into visible information can maintain a display without applying voltage. Various developments and researches have been focused on the advantages of low power consumption and low cost production.
[0003]
In order to display an image on this type of liquid crystal display panel, a reset period for resetting the liquid crystal to the homeotropic state, a selection period for selecting the liquid crystal to a desired state, and a state in which the liquid crystal is selected. There has been proposed a driving method including a sustain period for establishment.
[0004]
By the way, since the response speed with respect to the applied voltage of the chiral nematic liquid crystal increases as the environmental temperature rises, it is necessary to change the basic clock to increase the frequency of the drive pulse. However, when the frequency of the drive pulse is increased, there is a problem that the power consumption at the power source increases accordingly.
[0005]
Further, in an electronic book type liquid crystal display device having two display panels, when two screens are updated at the same time, the peak current may increase excessively, and measures to avoid it are necessary.
[0006]
Accordingly, an object of the present invention is to provide a liquid crystal display device that can suppress the increase in power consumption when two screens are updated simultaneously and the increase in power consumption accompanying an increase in environmental temperature as much as possible, and can use a battery with a small current supply capability. Is to provide.
[0007]
Configuration, operation and effect of the invention
In order to achieve the above object, a liquid crystal display device according to a first aspect of the invention is provided with a first display panel and a second display panel that use liquid crystal as a display medium, and for driving the first and second display panels. A driving circuit; a controller for controlling the driving circuit; and a temperature sensor for measuring an ambient temperature around the first and second display panels, each of the first and second display panels being a matrix. The drive circuit scans and drives each pixel of the first and second display panels for each scan line, and the controller includes the drive circuit A single-sided update mode for updating one of the screens of the first and second display panels and a double-sided update mode for simultaneously updating both screens of the first and second display panels can be selected. The controller changes the ratio of the delay period inserted between the scanning lines temporally adjacent to each scanning line in order with respect to the scanning period according to the environmental temperature, and the single-sided update mode and the double-sided update mode. The method of changing the ratio of the delay period to the scanning period is different.
[0008]
In the liquid crystal display device according to the first aspect of the present invention, by adopting a delayed scan method in which a delay period is inserted between temporally adjacent scan lines for each scan line scanned in sequence, the drive frequency Can be reduced. That is, even when the environmental temperature rises, it is possible to suppress the drive pulse frequency from increasing, and to prevent an increase in power consumption of the power source. Further, the ratio of the delay period to the scanning period is changed according to the environmental temperature, and the ratio of the delay period to the scanning period is changed between the single-sided update mode and the double-sided update mode. The display panel can be driven under appropriate driving conditions by avoiding problems such as excessive increase in the peak current and the pulse width of the driving pulse becoming too small and exceeding the limit of the driving circuit.
[0009]
In the liquid crystal display device according to the first aspect of the invention, the first and second display panels perform display using selective reflection of a cholesteric liquid crystal phase, and a period in which a drive pulse is applied to the liquid crystal by the drive circuit Includes a reset period for resetting the liquid crystal to a homeotropic state, a selection period for selecting the liquid crystal to a desired state, and a sustain period for establishing the liquid crystal in a selected state, wherein the controller In the period, Tsp / Ts, which is a ratio of the length Tsp of the selection pulse application period, which is a period during which the selection pulse is applied to the pixels on the scan line, and the length Ts of the selection period is changed according to the environmental temperature, It is preferable to change the way of changing Tsp / Ts between the single-sided update mode and the double-sided update mode.
[0010]
By changing the Tsp / Ts according to the environmental temperature and changing the Tsp / Ts change method between the single-sided update mode and the double-sided update mode, the frequency of the drive pulse is increased or the peak current is excessive. The display panel can be driven under appropriate driving conditions.
[0011]
Further, the controller changes the ratio of the delay period to the scanning period while keeping the Tsp / Ts constant within the first temperature range, and Tsp / Ts within the second temperature range different from the first temperature range. It is preferable to keep the value constant at a value different from the first temperature range and to change the ratio of the delay period to the scanning period. Control when driving the display panel becomes easy. Further, it is preferable that the controller keeps the ratio of the drive pulse width and the Tsp / Ts constant within a predetermined temperature range, and changes the length of the entire drive pulse group. Similarly, control when driving the display panel is facilitated.
[0012]
Furthermore, the controller may change the Tsp / Ts so that the width of the selection pulse does not become smaller than a predetermined value. Alternatively, the controller may change the Tsp / Ts so that the time required for updating the screen does not become longer than a predetermined time. By controlling in this way, it is possible to prevent the update time from becoming too long and the operability to deteriorate.
[0013]
Furthermore, the controller may make the delay period different in each update mode so that the lower limit value of the update required time in the double-sided update mode is larger than the lower limit value of the update required time in the single-sided update mode. It is possible to more effectively prevent the peak current from increasing excessively in the double-sided update mode. In particular, the controller may vary the delay period in each update mode so that the lower limit value of the update required time in the double-sided update mode is larger than twice the lower limit value of the update required time in the single-sided update mode. preferable. It is possible to more reliably prevent the peak current from increasing excessively in the double-sided update mode.
[0014]
A liquid crystal display device according to a second aspect of the invention drives a first display panel and a second display panel that use liquid crystal as a display medium, and the first and second display panels are driven by drive pulses composed of a plurality of drive pulse groups. Drive circuit, a controller for controlling the drive circuit, and a temperature sensor for measuring ambient temperature around the first and second display panels, the first and second display panels being Each having a screen composed of a plurality of pixels arranged in a matrix; the drive circuit scans and drives each pixel of the first and second display panels for each scan line; and the controller drives the drive Selectable from single-sided update mode in which the circuit updates one of the screens of the first and second display panels, and double-sided update mode in which the screens of both the first and second display panels are updated simultaneously And (a) a ratio of a delay period inserted between temporally adjacent scan lines for each scan line scanned in order with respect to the scan period, and (b) each of the drive pulse groups. At least one of the ratio of the pulse width and (c) the length of the entire driving pulse group with the ratio of the pulse widths of the driving pulse groups fixed is changed according to the environmental temperature, and the single-sided update mode and the double-sided update mode And (a), (b), and (c) are changed in different ways.
[0015]
In the liquid crystal display device according to the second aspect of the present invention, (a) the ratio of the delay period inserted between the temporally adjacent scan lines to the scan period for each scan line scanned in sequence, (b) At least one of the ratio of the pulse widths of the drive pulse groups and (c) the length of the entire drive pulse group when the ratio of the pulse widths of the drive pulse groups is fixed is changed according to the environmental temperature. Thus, even when the environmental temperature rises, it is possible to prevent the drive pulse frequency from increasing, and to prevent an increase in power consumption of the power source. Further, by changing the change methods of (a), (b), and (c) between the single-sided update mode and the double-sided update mode, the peak current particularly in the double-sided update mode increases excessively, or the drive pulse The display panel can be driven under appropriate driving conditions by avoiding problems such as the pulse width being too small and exceeding the limit of the driving circuit.
[0016]
In the liquid crystal display device according to a second aspect of the present invention, it is preferable that the controller keeps (a) and (b) constant and changes (c) within a predetermined temperature range. Control when driving the display panel becomes easy.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described with reference to the accompanying drawings.
[0018]
(Refer to the overall configuration of the liquid crystal display device, FIG. 1)
As an embodiment of the liquid crystal display device according to the present invention, an electronic book type liquid crystal display device 10 having two screens shown in FIG.
[0019]
The liquid crystal display device 10 includes a liquid crystal display panel 11R that forms a right page and a liquid crystal display panel 11L that forms a left page. Each panel 11R and 11L has a full-color liquid crystal described below in housings 12R and 12L. Display elements 100R and 100L are accommodated. The casings 12R and 12L are connected by a hinge 13 at the center, and can be opened and closed between a closed state in which two screens overlap and an open state in which two screens are arranged.
[0020]
The lower sections of the housings 12R and 12L are configured as operation panels 20R and 20L, and include a power key 21 for turning on / off the main power, a menu key 22 for executing menu display, and a determination for instructing command determination. Key 23, cursor movement keys 24R and 24L, key 25 for selecting a mode for updating only the right side, key 26 for selecting a mode for updating only the left side, and a key for selecting a mode for simultaneously updating both sides 27 is provided.
[0021]
The housings 12R and 12L incorporate temperature sensors 31R and 31L and speakers 32R and 32L for measuring the environmental temperature of the liquid crystal display elements 100R and 100L. The housing 12R is provided with an antenna 33 for transmitting and receiving communication radio waves. A slot 34 for mounting the recording medium 35 is provided in the housing 12L. The recording medium 35 stores book data to be displayed on the display panels 11R and 11L, and a semiconductor memory, an optical disk, a removable hard disk, or the like is used. Data to be displayed is also input to the liquid crystal display device 10 through the antenna 33. Furthermore, a control unit 50 (described below) including a drive circuit for driving the liquid crystal display elements 100R and 100L is housed in the housings 12R and 12L.
[0022]
(Liquid crystal display element, see FIG. 2)
Here, the liquid crystal display elements 100R and 100L will be described. Each of the liquid crystal display elements 100R and 100L has the configuration shown in FIG. 2, and is a reflection type full-color liquid crystal display element by a simple matrix driving system in which display layers 111R, 111G, and 111B including liquid crystal exhibiting a cholesteric phase are laminated.
[0023]
In the liquid crystal display elements 100R and 100L, a red display layer 111R that performs display by switching between a red selective reflection and a transparent state is disposed on the light absorption layer 121, and a green selective reflection and a transparent state are switched thereon. A green display layer 111G that performs display is stacked, and a blue display layer 111B that displays by switching between blue selective reflection and a transparent state is stacked thereon.
[0024]
The display layers 111R, 111G, and 111B sandwich the liquid crystal 116 and the spacer 117 between the transparent substrates 112 made of resin, glass, or the like on which the transparent electrodes 113 and 114 are formed, respectively, and both the substrates 112 are made of resin columnar structures 115. It is glued. An insulating film 118 and an alignment control film 119 are provided on the transparent electrodes 113 and 114 as necessary. A sealing material 120 for sealing the liquid crystal 116 is provided on the outer peripheral portion (outside the display area) of the substrate 112.
[0025]
The transparent electrodes 113 and 114 are connected to the scanning drive ICs 131R and 131L and the signal drive ICs 132R and 132L shown in FIG. 3, respectively, and a predetermined pulse voltage is applied to the transparent electrodes 113 and 114, respectively. In response to the applied voltage, the display is switched between a transparent state in which the liquid crystal 116 transmits visible light and a selective reflection state in which visible light having a specific wavelength is selectively reflected.
[0026]
The transparent electrodes 113 and 114 provided in the display layers 111R, 111G, and 111B are each composed of a plurality of strip electrodes arranged in parallel at fine intervals, and the orientation of the strip electrodes is viewed from a plane. They are opposed to each other at right angles. The upper and lower strip electrodes are sequentially energized. That is, display is performed by sequentially applying voltages to the liquid crystals 116 in a matrix. This is called matrix driving, and the portions where the electrodes 113 and 114 intersect constitute each pixel. By performing such matrix driving for each display layer, a full color image is displayed on the liquid crystal display element 100.
[0027]
Specifically, in a liquid crystal display element in which a liquid crystal exhibiting a cholesteric phase is sandwiched between two substrates, display is performed by switching the liquid crystal state between a planar state and a focal conic state. When the liquid crystal is in a planar state, light having a wavelength λ = P · n is selectively reflected when the spiral pitch of the cholesteric liquid crystal is P and the average refractive index of the liquid crystal is n. In the focal conic state, the incident light is scattered when the selective reflection wavelength of the cholesteric liquid crystal is in the infrared light region, and when it is shorter than that, the scattering becomes weak and substantially visible light is transmitted. Therefore, by setting the selective reflection wavelength in the visible light region and providing a light absorption layer on the opposite side of the element from the observation side, selective reflection color display in the planar state and black display in the focal conic state are possible. . In addition, by setting the selective reflection wavelength in the infrared light region and providing a light absorption layer on the side opposite to the observation side of the element, light in the infrared light region is reflected in the planar state but the wavelength in the visible light region. Because of the transmission of light, black display is possible, and white display by scattering is possible in the focal conic state.
[0028]
In the liquid crystal display elements 100R and 100L in which the display layers 111R, 111G, and 111B are stacked, the blue display layer 111B and the green display layer 111G are in a transparent state in which the liquid crystal is in a focal conic arrangement, and the red display layer 111R is in a planar arrangement. The red display can be performed by using the selective reflection state. Further, the blue display layer 111B is in a transparent state in which the liquid crystal is in a focal conic arrangement, and the green display layer 111G and the red display layer 111R are in a selective reflection state in which the liquid crystal is in a planar arrangement, thereby performing yellow display. Can do. Similarly, red, green, blue, white, cyan, magenta, yellow, and black can be displayed by appropriately selecting a transparent state and a selective reflection state as the state of each display layer. Further, by selecting an intermediate selective reflection state as the state of each display layer 111R, 111G, 111B, an intermediate color can be displayed and can be used as a full color display element.
[0029]
As the liquid crystal 116, those showing a cholesteric liquid crystal phase at room temperature are preferable, and a chiral nematic liquid crystal obtained by adding a sufficient amount of a chiral material to show a cholesteric liquid crystal phase to the nematic liquid crystal is particularly preferable.
[0030]
A chiral material is an additive having an action of twisting molecules of a nematic liquid crystal when added to the nematic liquid crystal. By adding a chiral material to the nematic liquid crystal, a spiral structure of liquid crystal molecules having a predetermined twist interval is generated, thereby exhibiting a cholesteric liquid crystal phase.
[0031]
In addition, by using this type of chiral nematic liquid crystal as a display medium, a liquid crystal display panel having a so-called memory property that can maintain a display state semi-permanently when no voltage is applied can be obtained. Therefore, it is possible to continue displaying images while the CPU of the control unit 50 is in the sleep mode.
[0032]
The liquid crystal display layer is not necessarily limited to this configuration, and the resin structure may be a dam-like structure or may be omitted from the resin structure. Further, a liquid crystal display is used as a so-called polymer dispersion type liquid crystal composite film in which liquid crystal is dispersed in a conventionally known polymer three-dimensional network structure or a polymer three-dimensional network structure is formed in the liquid crystal. It is also possible to construct layers.
[0033]
(Control section and drive circuit, see FIGS. 3 and 4)
The pixel configuration of the liquid crystal display elements 100R and 100L is represented by a matrix of a plurality of scanning electrodes R1, R2 to Rm and signal electrodes C1, C2 to Cn (m and n are natural numbers), respectively, as shown in FIG. Is done. Scan electrodes R1, R2 to Rm are connected to output terminals of scan drive ICs 131R and 131L, and signal electrodes C1, C2 to Cn are connected to output terminals of signal drive ICs 132R and 132L.
[0034]
The scanning drive ICs 131R and 131L output a selection signal to a predetermined one of the scanning electrodes R1, R2 to Rm to be in a selected state, while outputting non-selection signals to the other electrodes to be in a non-selected state. The scan drive ICs 131R and 131L sequentially apply selection signals to the scan electrodes R1, R2 to Rm while switching the electrodes at predetermined time intervals. On the other hand, the signal driving ICs 132R and 132L simultaneously output signals corresponding to image data to the signal electrodes C1, C2 to Cn in order to rewrite each pixel on the scanning electrodes R1, R2 to Rm in the selected state. For example, when the scan electrode Ra is selected (a is a natural number satisfying a ≦ m), the pixels LRa-C1 to LRa-Cn at the intersections of the scan electrode Ra and the signal electrodes C1, C2 to Cn are simultaneously rewritten. It is done. Thereby, the voltage difference between the scan electrode and the signal electrode in each pixel becomes the rewrite voltage of the pixel, and each pixel is rewritten in accordance with this rewrite voltage.
[0035]
Image rewriting is performed by sequentially selecting all scanning lines. In the case of partial rewriting, only specific scanning lines may be sequentially selected so as to include a portion to be rewritten. Thereby, only a necessary part can be rewritten in a short time.
[0036]
The control unit 50 includes a central processing unit (CPU) 51 that performs overall control, an LCD controller 52 that controls the driving IC, an image processing device 53 that performs various processes on image data, an image memory 54 that stores image data, The ROM 55 stores a control program and various data, and the RAM 56 stores various data.
[0037]
The CPU 51 is connected with operation panels 20R and 20L, temperature sensors 31R and 31L, speakers 32R and 32L, a communication unit 61, a reader / writer 62 for the recording medium 35, a touch panel 63, and front lights 64R and 64L. Each of these devices exchanges necessary signals with the CPU 51 and is controlled by the CPU 51.
[0038]
Power is supplied from the power supply unit 70 to the drive ICs 131R, 131L, 132R, and 132L. The LCD controller 52 controls the drive ICs 131R, 131L, 132R, and 132L based on the image data stored in the image memory 54, and sequentially applies voltages between the scan electrodes and the signal electrodes of the liquid crystal display elements 100R and 100L, thereby Write. The CPU 51 acquires environmental temperature information from the temperature sensors 31R and 31L and temporarily stores it in the RAM 56. The ROM 55 stores information for determining how to set the selection pulse application period Tsp and the selection period Ts described below according to the environmental temperature.
[0039]
The CPU 51 has a sleep mode. When necessary processing such as screen update, communication with the outside, access to the recording medium 35 is completed, the CPU 51 shifts to the sleep mode. In the sleep mode, only the minimum necessary functions such as operation detection of the operation panels 20R and 20L are executed, and other functions are stopped to reduce energy consumption.
[0040]
As shown in FIG. 4, the scanning drive ICs 131R and 131L are provided in common for each display layer, and the signal drive ICs 132R and 132L are provided for each display layer. If the drive voltages of the display layers are substantially equal, the scan drive ICs 131R and 131L can be shared, which is advantageous in terms of cost. Of course, the scanning drive ICs 131R and 131L may be provided for each display layer, or the signal drive ICs 132R and 132L may be provided in common for each display layer.
[0041]
The driving method described below relates to driving of one display layer, but it goes without saying that the same driving method is applied to each display layer.
[0042]
(Driving principle and basic driving waveform, see Fig. 5)
First, the basic principle of the method for driving the liquid crystal display element will be described. In addition, although the basic drive waveform shown here demonstrates using a positive pulse waveform, it may be negative or may use an alternating pulse waveform.
[0043]
FIG. 5 shows basic drive waveforms output from the scan drive ICs 131R and 131L to the scan electrodes. This driving method is roughly composed of a reset period Trs, a selection period Ts, a sustain period Trt, and a display period Ti (also referred to as a crosstalk period). The selection period Ts further includes a selection pulse application period Tsp, a pre-selection period Tsz, and a post-selection period Tsz ′, and Ts− (Tsz + Tsz ′) is the scanning period Tss.
[0044]
In the basic drive waveform, a reset pulse of + V1 is applied in the reset period Trs. In the selection period Ts, a + V2 selection pulse is applied in the selection pulse application period Tsp. The pre-selection period Tsz and the post-selection period Tsz ′ are periods of zero voltage. Further, a sustain pulse of + V3 is applied during the sustain period.
[0045]
The operation of the liquid crystal is as follows. First, when a reset pulse of + V1 is applied in the reset period Trs, the liquid crystal is reset to a homeotropic state. Next, the selection pulse application period Tsp is reached through the previous selection period Tsz (the liquid crystal is slightly twisted back). By changing the waveform of the selection pulse applied here, it is possible to finally select the liquid crystal for each pixel from the planar state, the focal conic state, and the mixed state (halftone display).
[0046]
First, the case where the planar state is selected will be described. In this case, a selection pulse having a predetermined energy is applied in the selection pulse application period Tsp, and the liquid crystal is brought into a homeotropic state again. Thereafter, in the post-selection period Tsz ′, the liquid crystal is in a state where the twist is slightly returned. After that, when a sustain pulse of + V3 is applied in the sustain period Trt, the liquid crystal in which the twist is slightly returned in the previous post-selection period Tsz ′ is untwisted again by the sustain pulse, and is homeotropic. It becomes a state. Here, the liquid crystal in the homeotropic state becomes the planar state by setting the voltage to zero, and is fixed in the planar state.
[0047]
On the other hand, when the focal conic state is finally selected, a selection pulse having a smaller energy than that when the planar state is selected in the selection pulse application period Tsp is applied. Then, in the post-selection period Tsz ′, the liquid crystal returns to the twisted state and the helical pitch is expanded about twice.
[0048]
Thereafter, a sustain pulse of + V3 is applied in the sustain period Trt. The liquid crystal whose twist has returned in the post-selection period Tsz ′ transitions to the focal conic state by applying this sustain pulse. Here, the liquid crystal in the focal conic state is fixed in the focal conic state even if the voltage is zero.
[0049]
As described above, the final display state of the liquid crystal can be selected based on the energy of the selection pulse applied during the selection pulse application period Tsp. Also, halftone display is possible by adjusting the voltage value and pulse width of the selected pulse.
[0050]
(Example of driving, see FIGS. 6 to 10)
6 and 7 show the pulse waveforms output from the scan drive ICs 131R and 131L to the scan electrodes (shown by rows 1 and 28), and one signal electrode (shown by the column b) from the signal drive ICs 132R and 132L. An output pulse waveform and a pulse waveform applied to the liquid crystal of each pixel (indicated by LCD1, LCD2 to LCD28) by superimposing these pulse waveforms are shown.
[0051]
In this driving example, the polarity of the pulse waveform to be applied is changed every time one frame of the image is updated, the driving waveform of the odd frame to which the positive polarity is applied is applied to FIG. 6, and the negative polarity is applied to FIG. The drive waveform of the even frame is shown.
[0052]
The scan driving ICs 131R and 131L scan a plurality of voltages supplied from the power supply unit 70, here, the reset voltage (+ V1, -V1), the selection voltage (+ V2, -V2), and the sustain voltage (+ V3, -V3). Applied to R1, R2... Rm. The voltage of the reset pulse is, for example, + 40V or −40V, the voltage of the selection pulse is, for example, + 15V or −15V, and the voltage of the sustain pulse is, for example, + 25V or −25V.
[0053]
The signal drive ICs 132R and 132L apply the rewrite signal voltage ± V4 supplied from the power supply unit 70 to the signal electrodes C1, C2 to Cn. The voltage of the rewrite signal pulse is, for example, + 3V or -3V.
[0054]
6 and 7, a selection pulse is sequentially applied to a plurality of scanning electrodes (rows 1, 2 to 28), and a rewrite signal pulse is applied to one of the plurality of signal electrodes (column b). Is shown.
[0055]
The signal pulse waveform applied to the column b is shown here so that pulses having energy for selecting the selective reflection state of the liquid crystal are sequentially applied in any scanning period Tss for ease of illustration. Yes. At the time of actual screen update, the waveform of the rewrite signal pulse changes according to the image data, and a pulse having a waveform for selecting each of the liquid crystal in the transparent state, the selective reflection state, or the mixed state is applied in each scanning period Tss. The
[0056]
By applying the above driving pulses, the pulse voltages having the waveforms shown in FIGS. 6 and 7 are applied to the pixels LCD1, LCD2 to LCD28. A rewrite signal pulse is applied as a crosstalk pulse from each signal electrode to each pixel. In FIGS. 6 and 7, the region to which the crosstalk pulse is applied is indicated by a bold line. However, this crosstalk pulse has a low voltage value and does not substantially affect the liquid crystal state. Accordingly, it can be said that a substantially single polarity driving pulse is applied to the liquid crystal within one frame.
[0057]
In the reset period Trs, a reset pulse (+ V1 for odd frames, -V1 for even frames) is applied. In the selection period Ts, a selection pulse (+ V2 in the odd frame and −V2 in the even frame) is applied in the selection pulse application period Tsp. Further, in the period Tsp, the rewrite signal pulse ± V4 is superimposed from the signal driving ICs 132R and 132L. This signal pulse ± V4 is a voltage set based on the image data. Here, it is a rectangular pulse having a duty ratio of 50% in the signal pulse application period Tw and the same absolute value of the positive and negative voltages.
[0058]
The voltage is zero in the pre-selection period Tsz and the post-selection period Tsz ′. Further, a sustain pulse (+ V3 for odd frames and -V3 for even frames) is applied in the sustain period Trt.
[0059]
In this driving example, each scan electrode is selected on the basis of the length of the scan period Tss, and when the scan period Tss in the previous scan electrode ends, the selection pulse application period Tsp of the next scan electrode is started. The
[0060]
In this driving example, the polarity of the driving pulse applied to the scanning electrode is set to a single polarity in the odd-numbered frame and the even-numbered frame, and is inverted every time each frame is drawn. In this way, when control is performed so that a single polarity voltage is applied in each frame, the time during which the single polarity state continues can be set relatively long. As a result, as compared with the case where an alternating voltage whose polarity changes periodically in a very short time is applied as the voltage applied to the liquid crystal, the substantial repetition frequency of the applied voltage can be lowered and the scan electrode can be supplied. The voltage value of the drive pulse to be applied can be halved. Therefore, the power consumption of the power supply unit 70 is significantly reduced.
[0061]
Note that the scanning method in this driving example may be either progressive scanning in which scanning is sequentially performed for each scanning line, or interlace scanning in which an image of one frame is divided into a plurality of fields and interlaced scanning is performed. Good. In the case of interlaced scanning, generation of a black band (the background light absorption layer 121 is observed as black) due to the liquid crystal being in a substantially transparent state from the start of applying the reset pulse to the end of applying the sustain pulse is suppressed, Visibility when updating the screen is improved.
[0062]
Next, details of drive waveforms in the drive example will be described with reference to FIGS. FIG. 8 to FIG. 10 show the waveform of the selection pulse applied to row a, which is one of rows 1 to 28, and the rewrite signal pulse applied to column b, in odd frames (plus frames). The waveform and the voltage waveform applied to the pixel LCDx with these pulses superimposed are shown including the crosstalk pulse. FIG. 8 shows a waveform when the liquid crystal is finally selected in the maximum selective reflection state, FIG. 9 shows a waveform when the liquid crystal is finally selected in the halftone display state, and FIG. 10 shows the waveform when the liquid crystal is finally selected. Shows the waveform when the transparent state is selected.
[0063]
Specifically, the waveform of the pulse applied to the pixel LCDx in the selection period Ts is changed by changing the phase of the signal pulse of ± V4, and any one of the planar state, the focal conic state, and the mixed state is selected. Have decided.
[0064]
Here, the selection pulse applied to the row a has an application period Tsp of ½ the scanning period Ts, and the signal pulse applied to the column b has a duty ratio of 50% in the application period Tw. The rectangular pulses have the same absolute value of the positive and negative voltages.
[0065]
As shown by thick lines in FIGS. 6 and 7, all the pixels are subjected to crosstalk due to the signal pulse applied to the signal electrode. However, in this driving example, the signal pulse applied to the column b is a rectangular pulse having a duty ratio of 50% and the same absolute value of the positive and negative voltages. Therefore, in FIG. 8, FIG. 9, and FIG. In the reset period Trs, the effective voltage is √ {[((V1 + V4) 2+ (V1−V4) 2] / 2}, and the effective voltage is √ {[(V3 + V4) 2+ (V3) in the sustain period Trt. -V4) 2] / 2} and constant.
[0066]
As a result, the voltage applied to the liquid crystal of each pixel can be made substantially constant while being affected by the crosstalk pulse, and shadowing that normally occurs in the image due to the crosstalk pulse is suppressed. Is done.
[0067]
(Details of the power supply unit, see FIGS. 11 and 12)
Details of the power supply unit 70 shown in FIG. 3 are shown in FIGS. The power supply unit 70 includes a power supply 71, power supply switching circuits 75R and 75L, and a capacitor inserted at a predetermined location. The power supply 71 has nine terminals for outputting predetermined drive pulses to the scan drive ICs 131R and 131L, that is, + V1, + V2L, -V2L, -V1, -V3, GND, -V2R, + V2R, and + V3. . The power supply 71 has three terminals for outputting predetermined signal pulses to the signal driving ICs 132R and 132L, that is, + V4, GND, and -V4. The voltage value of the pulse output from these terminals can be finely adjusted within a predetermined range.
[0068]
The power supply switching circuits 75R and 75L include four switching elements SW1R to SW4R and SW1L to SW4L. One end of these switching elements is connected to predetermined terminals of the scanning drive ICs 131R and 131L, and the other end is connected to the terminal of the power source 71.
[0069]
Terminals ± V1, ± V3, and GND are connected in parallel to each of power supply switching circuits 75R and 75L. Terminals ± V2R and ± V2L for applying a selection pulse are independently connected to the power supply switching circuits 75R and 75L. The voltage values output from the terminals ± V2R and ± V2L are set so as to eliminate the characteristic difference between the liquid crystal display elements 100R and 100L based on the previously measured characteristics. Fine adjustment of the voltage value may be performed as an adjustment before shipment, or the user of the liquid crystal display device may be able to adjust.
[0070]
The scan drive ICs 131R and 131L have a built-in logic level shifter that is a circuit that shifts the potential back to 0V for compensation when the potential changes, where the terminal GND should be 0V.
[0071]
In the middle of the connection lines for supplying the drive pulse voltages + V1, + V2, + V3, -V1, -V2, and -V3 to the scan electrodes, voltage stabilization connected to the terminal GND corresponding to those voltages. A capacitor is connected. Further, a voltage stabilizing capacitor connected to the terminal GND corresponding to these voltages is connected to the signal electrodes in the middle of the connection lines for supplying the signal pulse voltages + V4 and -V4.
[0072]
FIG. 11 shows a case where the drive pulses supplied to the left and right liquid crystal display elements 100R and 100L are set to positive polarity, and FIG. 12 shows a case where the drive pulse is set to negative polarity. In either case, the CPU 51 controls the switching elements of the power supply switching circuits 75R and 75L.
[0073]
That is, the switching elements SW1R to SW4R and SW1L to SW4L are simultaneously switched to the positive polarity side (contact 1 side shown in FIG. 11) or the negative polarity side (contact 2 side shown in FIG. 12) under the instruction from the CPU 51. It is done.
[0074]
When each switching element is switched to the contact 1 side, positive voltages + V1, + V2R, and + V3 are supplied from the power supply 71 to the scan driving IC 131R that drives the right liquid crystal display element 100R, and the left liquid crystal display. Positive voltages + V1, + V2L, and + V3 are supplied from a power supply 71 to a scan driving IC 131L that drives the element 100L.
[0075]
When each switching element is switched to the contact 2 side, negative voltages -V1, -V2R, -V3 are supplied from the power source 71 to the scanning drive IC 131R that drives the right liquid crystal display element 100R, and the left side The negative voltages -V1, -V2L, -V3 are supplied from the power source 71 to the scan driving IC 131L that drives the liquid crystal display element 100L.
[0076]
In the drive circuit including the power supply unit 70 configured as described above, the control unit 50 switches the voltage supplied to the scan drive ICs 131R and 131L between the positive polarity and the negative polarity every time one frame is drawn. The frame is controlled so that it has a single polarity and is inverted between positive and negative every frame. According to such a driving circuit and control method, it is possible to realize driving that can prevent adverse effects such as deterioration of the liquid crystal with a simple circuit configuration.
[0077]
Further, in this drive circuit, the voltage ± V2 is supplied from independent power supply terminals to the left and right liquid crystal display elements 100R and 100L, so the difference in characteristics between the display elements 100R and 100L (liquid crystal layer thickness and composition) Variation) can be easily corrected. Also, if the ambient temperature differs between the left and right liquid crystal display elements (for example, environmental temperature imbalance due to battery heat generation when the battery is installed only on one housing) Can be corrected.
[0078]
Further, in this drive circuit, the voltages supplied to the scan drive ICs 131R and 131L are switched in polarity using the power supply switching circuits 75R and 75L, so that the scan drive ICs 131R and 131L have four values with low breakdown voltage. Cheaper ones can be used.
[0079]
In the driving example, the polarity inversion of the driving pulse is executed for each drawing of one frame, but various other inversion modes may be adopted. For example, when the liquid crystal is hardly deteriorated or when the liquid crystal is allowed to deteriorate to some extent, the liquid crystal may be inverted every several frames. Alternatively, if it is desired to suppress the deterioration of the liquid crystal as much as possible, it is inverted during scanning of one scanning line, inverted every scanning line, inverted every several scanning lines, inverted every field, every few fields It may be reversed.
[0080]
(Relationship between temperature and drive frequency, see FIG. 13)
As described above, the chiral nematic liquid crystal has different responsiveness to the driving pulse depending on the temperature change. That is, the response speed of the liquid crystal is slow in the low temperature range and fast in the high temperature range. Therefore, in the present embodiment, each pulse (reset pulse, selection pulse) of the drive pulse group applied to each liquid crystal display element 100R, 100L for each predetermined temperature range based on the environmental temperature detected by the temperature sensors 31R, 31L. The length of the entire drive pulse group is changed in a state where the ratio of the pulse width of the pulse, the sustain pulse, and the rewrite signal pulse is kept constant.
[0081]
That is, since the response speed of the liquid crystal increases as the temperature rises, the scanning period Tss corresponding to the scanning time for one line is set shorter as the temperature rises. Accordingly, the reset period Trs, the selection period Ts, and the sustain period Trt are also changed at the same rate. Such a change may be achieved by modulating the frequency of the basic clock signal generated by the basic clock generation means built in the LCD controller 52 or the like, for example, according to an instruction from the CPU 51. Alternatively, the clock signal count number and the frequency division ratio may be increased or decreased.
[0082]
As shown in FIG. 13, the mode of change of the drive pulse group based on the change of the environmental temperature is as follows. In the first temperature range from (K-20) ° C. to K ° C., Tss / Ts = 1/3 (Tsp / Ts = 1/6), and the length of the entire drive pulse group is shortened. Further, in the second temperature range exceeding K ° C. and reaching (K + 10) ° C., Tss / Ts = 1/1 (Tsp / Ts = 1/2) is maintained as the temperature rises. Reduce the overall length of the drive pulse group. Here, it is illustrated that the temperature change is measured in units of 0.1 ° C.
[0083]
Thus, when changing the length of the entire drive pulse group, while changing the rate of change for each predetermined temperature range, the rate of change may be set constant within each temperature range, or Even within the range, the change rate may be continuously changed with the temperature change. In the former case, control becomes simple, and in the latter case, finer control is possible with respect to temperature changes.
[0084]
(Delayed scan method drive example 1, see FIG. 14)
Next, a driving example 1 based on a so-called delayed scan method in which a delay period is inserted between temporally adjacent scan lines for one scan line that is sequentially scanned in either progressive scan or interlace scan will be described. . As shown in FIG. 14, the driving example 1 has a delay period Td set to 2 units (a scanning period Tss is set to 1 unit), and is referred to as a 1-2 delay here.
[0085]
In FIG. 14 (FIG. 15 is also the same), rows 1 to 4 show basic drive waveforms applied to the respective scan electrodes, and columns show signal waveforms applied to the signal electrodes. LCD1 to LCD4 show pulse waveforms applied to the liquid crystal of each pixel.
[0086]
In this driving example 1, the liquid crystal is driven on the same principle as the driving examples shown in FIGS. 5 to 10, and a delay unit Td of 2 units is inserted for each scanning line scanned in sequence. Here, the delay period Td delays the pulse application timing to the scan electrode by 2 units, and delays the pulse application timing to the signal electrode in accordance with this, and while the pulse application is delayed, both electrodes are zeroed. This is achieved by keeping the potential.
[0087]
When the delay period Td is set to 2 units or more, the influence of crosstalk can be eliminated and image degradation can be more effectively suppressed. That is, when attention is paid to the pixel LCD 3 in the driving example 1, crosstalk occurs in the period A, the pre-selection period B, the post-selection period D, and the period E that is the leading end of the sustain period. Not. According to the study by the present inventors, when crosstalk occurs in the periods A, B, D, and E, the density of the image that is finally displayed is affected by the density of the update target pixel. It has been found that it is visually recognized as a ghost when displayed. This phenomenon is significant when the application of crosstalk is at the end of the reset period or at the front end of the sustain period, and is more prominent in the pre-selection period and the post-selection period than in the reset period and sustain period. It has also been found that. In the driving example 1, the selection pulse application period Tsp is delayed by two units for each scan line, so that the application of the crosstalk pulse in the periods A, B, D, and E is avoided for all the scan lines. As a result, generation of ghosts due to crosstalk during periods A, B, D, and E is eliminated.
[0088]
(Refer to drive example 2 using the delayed scan method, FIG. 15)
Next, driving example 2 using the delayed scan method will be described. In this driving example 2, as shown in FIG. 15, the delay period Td is set to 3 units (the scanning period Tss is 1 unit), and is referred to as 1-3 delay here.
[0089]
Also in this driving example 2, when attention is paid to the pixel LCD 3, it can be seen that no crosstalk occurs in the periods A, B, D, and E.
[0090]
(Change based on delay period and temperature of Tss / Ts, see FIG. 16)
Here, control for changing the length of the delay period Td and the ratio of Tss / Ts described in FIG. 13 based on the environmental temperature will be described.
[0091]
Use a group of drive pulses (reset pulse, selection pulse, sustain pulse) with a constant voltage value in advance, and fix the ratio of the pulse width of each drive pulse to obtain the appropriate display density for various environmental temperatures. Measure the length of the entire pulse group shown. Based on this, a characteristic curve indicating the length of the entire proper pulse group with respect to various environmental temperatures is created. At this time, a plurality of characteristic curves are created by variously changing the length of the delay period Td and Tss / Ts (Tsp / Ts). Then, by changing the characteristic curve to be used for each predetermined temperature range, the screen is updated without significantly increasing the update required time and the peak current flowing through the drive circuit.
[0092]
FIG. 16 shows characteristic curves a to i which are the basis of the control created in this way, the horizontal axis is the environmental temperature (horizontal axis), and the vertical axis is the time required for updating the screen. The time from application of the selection pulse to the scan line to the end of application of the selection pulse to the last scan line is represented. Each characteristic curve a to i has the specifications shown in Table 1 below. Incidentally, the characteristic curve shown in FIG. 16 is created at 25 ° C. with a reset period Trs of 48 ms, a selection period Ts of 0.6 ms, a sustain period Trt of 48 ms, and 1024 scanning lines.
[0093]
[Table 1]

[0094]
Since the present liquid crystal display device 10 includes two liquid crystal display panels 11R and 11L, when only one side is updated (see curve j) and when both sides are updated simultaneously (see curve k). The characteristic curve to be adopted is changed according to the environmental temperature.
[0095]
When changing the characteristic curve to be adopted, in order to prevent the power consumption of the power supply unit from excessively rising and the peak current from increasing excessively, in order to prevent the screen update time from becoming excessively short, In order to prevent the performance of the driving circuit from being sufficiently exhibited, the characteristic curve is selected so that the width of the selection pulse does not become excessively small. Further, it is preferable that the lower limit value of the update time required for the double-sided update is larger than the lower limit value of the update required time for the single-sided update, and is usually larger than twice. Furthermore, it is preferable that the time required for updating the screen is selected so as not to be longer than necessary.
[0096]
That is, when updating only one side, the lower limit value of the screen update required time is set to 200 ms, and the upper limit value is set so that the screen update required time does not become too long. The curve to be adopted is changed according to the temperature change so that it is set to about 600 ms and does not exceed this. Specifically, as shown by the curve j, the characteristic curve a is adopted from the low temperature range to 29 ° C., the characteristic curve c is adopted from 29 ° C. to 38 ° C., and the characteristic curve f is exceeded when it exceeds 38 ° C. Is adopted. Note that, when switching the characteristic curve to be employed, it is considered that the selection pulse width when the characteristic curve is employed is not too small. For example, it is possible to shift from the characteristic curve a to the characteristic curve b at 29 ° C. Here, however, since the width of the selection pulse becomes too small when moving to the characteristic curve b, the characteristic curve c is shifted to avoid this. ing.
[0097]
On the other hand, when updating both sides at the same time, set the lower limit value of the screen update required time to 600 ms, and set the upper limit value so that the screen update required time does not become too long. The curve to be adopted is changed in accordance with the temperature change so that it is set to about 1200 ms and does not exceed this. Specifically, as shown by the curve k, the characteristic curve a is adopted from the low temperature range to 11 ° C., and the characteristic curve b is adopted from 11 ° C. to 22.5 ° C., exceeding 22.5 ° C. The characteristic curve c is adopted up to 26 ° C., the characteristic curve d is adopted up to 32.5 ° C. above 26 ° C., and the characteristic curve e is adopted up to 37 ° C. above 32.5 ° C. The characteristic curve f is adopted up to 39 ° C. above, the characteristic curve g is adopted up to 39 ° C. up to 48 ° C., the characteristic curve h is adopted up to 48 ° C. above 58 ° C., and over 58 ° C. And the characteristic curve i is adopted.
[0098]
In this way, by changing the way of adopting the characteristic curve between the single-sided update mode and the double-sided update mode, (a) the length of the delay period (in this example, the length of the entire pulse group increases or decreases depending on the environmental temperature). Therefore, to be precise, the ratio of the delay period to the scanning period), (b) the ratio of the pulse widths of the drive pulse groups (in this example, Tsp / Ts (or Tss / Ts)), (c) the drive pulse group At least one change in the length of the entire drive pulse group with a fixed ratio of the pulse widths of the two is different.
[0099]
More specifically, Tsp / Ts is constant within a predetermined temperature range, and the length of the delay period (in this example, precisely the ratio of the delay period to the scanning period) is increased as the environmental temperature increases. Change. Further, within the predetermined temperature range until the next characteristic curve is reached, the ratio of the drive pulse width and Tsp / Ts (or Tss / Ts) are kept constant, and the length of the entire drive pulse group is changed. .
[0100]
In the control, as the environmental temperature becomes higher, the length of the entire drive pulse group is shortened, and in the temperature range where Tsp / Ts (or Tss / Ts) is kept at the same value, the environmental temperature is higher. The longer the delay period Td (in this example, the ratio of the delay period to the scanning period) is set longer. Further, for each temperature range in which Tsp / Ts (or Tss / Ts) is maintained at the same value, Tsp / Ts (or Tss / Ts) is set to a larger value as the temperature range is higher. Then, which characteristic curve is to be used according to the environmental temperature is stored in advance in the ROM 55 and controlled so as to select a predetermined characteristic curve based on the temperature information acquired from the temperature sensors 31R and 31L. .
[0101]
By controlling in this way, even when a plurality of screens are updated at the same time, an excessive increase in peak current is suppressed, and problems such as damage to the apparatus can be avoided.
[0102]
(Refer to screen update examples, see FIGS. 17-19)
Here, the state of the screen update in the left and right liquid crystal display panels 11R and 11L is exemplarily shown. FIG. 17 shows the state of page feed in the duplex update mode. Here, the display of the third page and the fourth page is updated to the display of the fifth page and the sixth page. FIG. 18 shows a state in which only the right panel 11R is updated from the 3-page display to the 4-page display in the single-sided update mode. FIG. 19 shows a partial update mode on one display screen. Here, a state in which menu selection for color adjustment is executed is shown.
[0103]
(Control procedure, see FIGS. 20 to 31)
Below, the main part is demonstrated about the control procedure of this liquid crystal display device 10 by CPU51.
[0104]
FIG. 20 shows a main routine of control. At the time of startup by turning on the power, the state of various devices and various parameters stored in the RAM 56 are initialized at step S1, and then the processes of steps S2 to S9 are sequentially executed. To do. When waking up from the sleep state, the process starts from step S2.
[0105]
Although various parameters will be described later, if the memory for storing these parameters is non-volatile, it is not necessary to perform initial setting at the time of startup.
[0106]
In the input process of step S2, the operation status of the operation panel or the touch panel is grasped. In the mode determination process in step S3, the input operation mode (single-sided update mode, double-sided update mode, etc.) is determined. In the drawing polarity determination process in step S4, the polarity of the drive pulse for drawing is determined (the subroutine will be described in detail below). In the temperature compensation process in step S5, the drive pulse is corrected according to the environmental temperature. In the drawing process in step S6, a predetermined image is displayed on the liquid crystal display panel. In the communication process in step S7, communication with an external device is performed using a communication unit. In the drawing polarity determination process in step S4, the polarity data of the determined drive pulse is stored in the memory as a plurality of parameters, as will be described later. In the drawing process in step S6, the screen is updated with the polarities indicated by these parameters.
[0107]
Then, it is determined whether or not the sleep mode is entered in step S8. If YES, the sleep process is executed in step S9. If NO, the process returns to step S2.
[0108]
21 to 23 show a first example of the drawing polarity determination process executed in step S4. The parameters used in this subroutine are as follows:
PR1: Shows the previous drawing polarity of the right panel
PR2: Indicates the previous drawing polarity of the right panel
PL1: Shows the previous drawing polarity of the left panel
PL2: Indicates the previous drawing polarity of the left panel
PX: Indicates the drawing polarity to be updated
PX1: Indicates the first drawing polarity in the partial update mode
PX2: Indicates the second drawing polarity in the partial update mode
NR: Indicates the number of partial updates on the right panel
NL: Indicates the number of partial updates on the left panel
[0109]
In this first example, first, it is determined whether or not it is a double-sided update mode in step S11, and if it is the double-sided update mode, it is determined whether or not the parameters PR1 and PR2 are positive or negative in steps S12 to S16. If PR1 and PR2 are positive (YES in step S12), the parameter PX indicating the drawing polarity to be updated is set to negative in step S17. If PR1 and PR2 are negative (YES in step S13), the parameter PX is set to positive in step S18. If PL1 and PL2 are positive (YES in step S14), the parameter PX is set to negative in step S19. If PL1 and PL2 are negative (YES in step S15), the parameter PX is set to positive in step S20.
[0110]
If PR1, PR2, PL1, PL2 are not in any of the above polarities (NO in step S15), the polarity of the parameter PR2 indicating the previous drawing polarity is determined in step S16, and if positive, the parameter is determined in step S21. PX is set to negative polarity, and if negative, the parameter PX is set to positive polarity in step S22.
[0111]
Next, in step S23, the parameter PR1 is changed to the content of the parameter PR2, the parameter PL1 is changed to the content of the parameter PL2, and the parameters PR2 and PL2 are changed to the content of the parameter PX. Subsequently, the parameters NR and NL are reset to 0 in step S24. The parameters NR and NL are used to completely update each panel when the partial update of the left and right panels reaches a predetermined number of times for the purpose of preventing a decrease in screen density due to crosstalk at the time of partial update. Details of the control are omitted.
[0112]
If the single-sided update mode is selected (NO in step S11), it is determined in step S25 whether or not the panel for which updating has been selected is the right panel. If it is the right panel, it is further determined in step S26 whether or not it is the partial update mode. If it is in the partial update mode, the polarity of the parameter PR2 is determined in step S27. If PR2 is positive, in step S28, the parameter PX1 is set to negative polarity and the parameter PX2 is set to positive polarity. On the other hand, if PR2 is negative, in step S29, the parameter PX1 is set to positive polarity and the parameter PX2 is set to negative polarity. In the first example, in the partial update mode, the same partial update area is drawn twice with different polarities. Next, 1 is added to the parameter NR in step S30.
[0113]
If it is the full update mode only for the right panel (NO in step S26), the polarity of the parameter PR2 is determined in step S31. If it is positive, the parameter PX is set to negative in step S32, and if negative. In step S33, PX is set to positive polarity. Next, in step S34, the parameter PR1 is changed to the content of the parameter PR2, and the parameter PR2 is changed to the content of the parameter PX. Further, the parameter NR is reset to 0 in step S35.
[0114]
On the other hand, if the panel selected to be updated is the left panel (NO in step S25), it is determined in step S36 whether or not it is the partial update mode, and if it is the partial update mode, the polarity of parameter PL2 is determined in step S37. To do. If PL2 is positive, the parameter PX1 is set to negative polarity and the parameter PX2 is set to positive polarity in step S38. On the other hand, if PL2 is negative, in step S39, the parameter PX1 is set to positive polarity and the parameter PX2 is set to negative polarity. This is because in the partial update mode, the same partial update area is drawn twice with the polarity changed. Next, 1 is added to the parameter NL in step S40.
[0115]
If it is the full update mode only for the left panel (NO in step S36), the polarity of the parameter PL2 is determined in step S41. If it is positive, the parameter PX is set to negative in step S42. In step S43, PX is set to positive polarity. Next, in step S44, the parameter PL1 is changed to the content of the parameter PL2, and the parameter PL2 is changed to the content of the parameter PX. Further, the parameter NL is reset to 0 in step S45.
[0116]
By setting each parameter according to the above flow chart, the screen update of the drawing process (step S6) in the main routine is performed with the same polarity drive pulse even though both-side update and one-side update are mixed. Is prevented from continuing three times or more. In addition, at the time of partial update, drawing is performed twice while changing the polarity, and even if full update and partial update are mixed, it is prevented that the update with the same polarity drive pulse continues three or more times.
[0117]
24 to 26 show a second example of the drawing polarity determination process executed in step S4. The parameters newly used in this subroutine are as follows.
PRB: Indicates the drawing polarity in the previous partial update mode on the right panel
PLB: Indicates the drawing polarity in the previous partial update mode on the left panel
PXB: Indicates the drawing polarity to be partially updated
[0118]
In the second example, the polarities of the drive pulses in the partial update mode of the left and right panels are stored in memory to prevent the partial update areas from being drawn continuously with the same polarity.
[0119]
That is, in this second example, steps S11 to S22 and S24 perform the same processing as steps S11 to S22 and S24 described in the first example. In step S23a, in addition to the same processing as in step S23, the parameters PRB and PLB are changed to the contents of the parameter PX.
[0120]
If single-sided update mode is selected (NO in step S11), it is the right panel (YES in step S25), and if it is the partial update mode (YES in step S26), the polarity of parameter PRB is determined in step S27a. To do. If PRB is positive, the parameter PXB is set to negative in step S28a. On the other hand, if PRB is negative, the parameter PXB is set to positive in step S29a. In step S46, the parameter PRB is changed to the content of the parameter PXB. In the second example, by introducing the parameters PRB, PLB, and PXB, it is possible to prevent the partial update area from being continuously drawn with the same polarity. Next, 1 is added to the parameter NR in step S30.
[0121]
Steps S31, S32, S33, and S35 executed in the full update mode only for the right panel (NO in step S26) are the same as in the first example. However, in step S34a, a process for changing the parameter PRB to the content of the parameter PX is added.
[0122]
On the other hand, if the panel selected to be updated is the left panel (NO in step S25) and if it is the partial update mode (YES in step S36), the polarity of the parameter PLB is determined in step S37a. If PLB is positive, the parameter PXB is set to negative in step S38a. On the other hand, if PLB is negative, the parameter PXB is set to positive in step S39a. In step S47, the parameter PLB is changed to the content of the parameter PXB. This is to prevent the partial update area from being continuously drawn with the same polarity. Next, 1 is added to the parameter NL in step S40.
[0123]
Steps S41, S42, S43, and S45 executed in the full update mode only for the left panel (NO in step S36) are the same as in the first example. However, in step S44a, a process for changing the parameter PLB to the content of the parameter PX is added.
[0124]
In the second example, the polarity of the drive pulse at the time of partial update is stored in the memory, so that the partial update area is continuous even without performing multiple updates at the time of partial update as in the first example. Thus, drawing with the same polarity can be prevented, and the updating operation is simplified.
[0125]
27 to 31 show a third example of the drawing polarity determination process executed in step S4. The parameters newly used in this subroutine are as follows.
PRB1: Indicates the drawing polarity in the partial update mode just before the right panel
PRB2: Shows the drawing polarity in the previous partial update mode on the right panel
PLB1: Indicates the drawing polarity in the partial update mode just before the left panel
PLB2: Shows the drawing polarity in the previous partial update mode on the left panel
[0126]
In the third example, the polarity of the drive pulse is determined in consideration of the case where the left and right panels are partially updated simultaneously. In addition, when the double-sided panel is partially updated at the same time, the drawing polarity is determined so that drawing with the same polarity does not continue three times or more.
[0127]
That is, in this third example, first, it is determined whether or not it is the double-sided update mode in step S11. If it is the double-sided update mode, it is determined whether or not it is the partial update mode in step S51. If it is the partial update mode, it is determined in steps S52 to S56 whether the parameters PRB1 and PRB2 are positive or negative. If PRB1 and PRB2 are positive (YES in step S52), the parameter PXB indicating the drawing polarity to be updated is set to negative in step S57. If PRB1 and PRB2 are negative (YES in step S53), parameter PXB is set to positive in step S58. If PLB1 and PLB2 are positive (YES in step S54), the parameter PXB is set to negative in step S59. If PLB1 and PLB2 are negative (YES in step S55), parameter PXB is set to positive in step S60.
[0128]
If PRB1, PRB2, PLB1, and PLB2 are not in any of the above polarities (NO in step S55), the polarity of parameter PRB2 indicating the previous drawing polarity is determined in step S56, and if positive, the parameter is determined in step S61. PXB is set to negative polarity, and if negative, the parameter PXB is set to positive polarity in step S62.
[0129]
Next, in step S63, the parameter PRB1 is changed to the contents of the parameter PRB2, the parameter PLB1 is changed to the contents of the parameter PLB2, and the parameters PRB2 and PLB2 are changed to the contents of the parameter PXB. Subsequently, in step S64, 1 is added to the parameter NR, and 1 is added to the parameter NL.
[0130]
If it is the full-surface update mode on both sides (NO in step S51), steps S12 to S22 are executed. The processing here is the same as steps S12 to S22 described in the first example. When the processing ends, in step S65, the parameter PR1 is changed to the content of the parameter PR2, and the parameter PL1 is changed to the content of the parameter PL2. In addition, the parameters PR2 and PL2 are changed to the contents of the parameter PX. At the same time, the parameter PRB1 is changed to the contents of the parameter PRB2, the parameter PLB1 is changed to the contents of the parameter PLB2, and the parameters PRB2 and PLB2 are changed to the contents of the parameter PXB. Subsequently, parameters NR and NL are reset to 0 in step S66.
[0131]
If single-sided update mode is selected (NO in step S11), it is the right panel (YES in step S25), and if it is the partial update mode (YES in step S26), the polarity of parameter PRB2 is determined in step S27b. To do. If PRB2 is positive, the parameter PXB is set to negative in step S28b. On the other hand, if PRB2 is negative, the parameter PXB is set to positive in step S29b. In step S46b, the parameter PRB1 is changed to the content of the parameter PRB2, and the parameter PRB2 is changed to the content of the parameter PXB. Next, 1 is added to the parameter NR in step S30.
[0132]
Steps S31, S32, S33, and S35 executed in the full update mode only for the right panel (NO in step S26) are the same as in the first example. However, in step S34b, processing for changing the parameter PRB1 to the content of the parameter PRB2 and changing the parameter PRB2 to the content of the parameter PX is added.
[0133]
On the other hand, if the panel selected to be updated is the left panel (NO in step S25) and if it is the partial update mode (YES in step S36), the polarity of parameter PLB2 is determined in step S37b. If PLB2 is positive, the parameter PXB is set to negative in step S38b. On the other hand, if PLB2 is negative, the parameter PXB is set to positive in step S39b. In step S47b, the parameter PLB1 is changed to the content of the parameter PLB2, and the parameter PLB2 is changed to the content of the parameter PXB. Next, 1 is added to the parameter NL in step S40.
[0134]
Steps S41, S42, S43, and S45 executed in the full update mode only for the left panel (NO in step S36) are the same as in the first example. However, in step S44b, a process for changing the parameter PLB1 to the content of the parameter PLB2 and changing the parameter PLB2 to the content of the parameter PX is added.
[0135]
(Other embodiments)
The liquid crystal display device according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist.
[0136]
For example, the configuration, material, manufacturing method, and the like of the liquid crystal display element shown in FIG. 2 are arbitrary, and the details of the control procedure shown in FIGS. 20 to 31 are also arbitrary. The liquid crystal display element may be a single layer or may be a laminate of two or four or more liquid crystal display layers.
[0137]
In particular, the characteristic curves j and k in the single-sided update mode and the full-side update mode shown in the graph of FIG. 16 are examples. Further, Tss / Ts may be changed with smooth characteristics so as to draw a predetermined curve in the entire temperature range without changing stepwise for each specific temperature range.
[0138]
In the above-described embodiment, the liquid crystal display device having two screens has been described. However, the present invention can also be applied to a liquid crystal display device having three or more screens. In the case of a liquid crystal display device having three or more screens, the polarity of a predetermined number of drive pulses for each panel may be stored and the polarity determined based on this. However, in the case of a liquid crystal display device having three or more screens, a plurality of screens less than the total number may be updated at the same time, so that the polarity history of each panel is more likely to vary than in a two-screen liquid crystal display device. Therefore, it is preferable to memorize the polarity of the drive pulse further retroactively. For the partial update, the same control as in the liquid crystal display device with the two-screen configuration may be performed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a liquid crystal display device according to the present invention.
FIG. 2 is a cross-sectional view showing an example of a liquid crystal display element constituting the liquid crystal display device.
FIG. 3 is a block diagram showing a control unit of the liquid crystal display element.
FIG. 4 is a block diagram showing an arrangement of ICs for driving three liquid crystal display layers.
FIG. 5 is a chart showing basic drive waveforms for the liquid crystal display element.
FIG. 6 is a chart showing drive waveforms (odd frames) applied to each pixel of the liquid crystal display element.
FIG. 7 is a chart showing drive waveforms (even frames) applied to each pixel of the liquid crystal display element.
FIG. 8 is a chart showing details of a drive waveform (a liquid crystal is in a selective reflection state) shown in FIGS. 6 and 7;
FIG. 9 is a chart showing details of the drive waveforms shown in FIGS. 6 and 7 (the liquid crystal is in a halftone display state).
FIG. 10 is a chart showing details of the driving waveform (the liquid crystal is in a light transmission state) shown in FIGS. 6 and 7;
FIG. 11 is a block diagram illustrating details of a power supply unit (when liquid crystal is driven with positive polarity).
FIG. 12 is a block diagram showing details of a power supply unit (when liquid crystal is driven with negative polarity).
FIG. 13 is a chart showing drive waveforms applied to the scan electrodes when the environmental temperature changes.
FIG. 14 is a chart showing driving waveforms of driving example 1 using a delayed scan method;
FIG. 15 is a chart showing drive waveforms of drive example 2 using a delayed scan method;
FIG. 16 is a graph showing the relationship between the environmental temperature and the scanning time with respect to the delay period and various set values of Tss / Ts.
FIG. 17 is an explanatory diagram of a screen update example (double-sided update mode).
FIG. 18 is an explanatory diagram of a screen update example (single-sided update mode).
FIG. 19 is an explanatory diagram of a screen update example (partial update mode).
FIG. 20 is a flowchart showing a control procedure (main routine) of the liquid crystal display device.
FIG. 21 is a flowchart showing a first example of a drawing polarity determination process.
22 is a flowchart showing a first example of drawing polarity determination processing, and is a continuation of FIG.
23 is a flowchart showing a first example of drawing polarity determination processing, and is a continuation of FIG.
FIG. 24 is a flowchart showing a second example of drawing polarity determination processing.
FIG. 25 is a flowchart showing a second example of the drawing polarity determination process, and is a continuation of FIG.
FIG. 26 is a flowchart showing a second example of the drawing polarity determination process, continued from FIG.
FIG. 27 is a flowchart showing a third example of the drawing polarity determination process.
FIG. 28 is a flowchart showing a third example of the drawing polarity determination process, and is a continuation of FIG.
29 is a flowchart showing a third example of the drawing polarity determination process, and is a continuation of FIG.
30 is a flowchart showing a third example of the drawing polarity determination process, and is a continuation of FIG.
FIG. 31 is a flowchart showing a third example of the drawing polarity determination process, and is a continuation of FIG.
[Explanation of symbols]
10. Liquid crystal display device
11R, 11L ... Liquid crystal display panel
31R, 31L ... Temperature sensor
51. Central processing unit (CPU)
52 ... LCD controller
70 ... Power supply
100R, 100L ... Liquid crystal display element
113, 114 ... electrodes
116 ... chiral nematic liquid crystal
131R, 131L ... Scanning drive IC
132R, 132L ... signal drive IC
Ts ... Selection period
Tsp: Selection pulse application period
Td: Delay period
Tss ... Scanning period

Claims (5)

A first display panel and a second display panel that use liquid crystal as a display medium; a drive circuit for driving the first and second display panels; a controller for controlling the drive circuit; A temperature sensor for measuring the ambient temperature around the second display panel,
Each of the first and second display panels includes a screen composed of a plurality of pixels arranged in a matrix,
The drive circuit scans and drives each pixel of the first and second display panels for each scan line;
The controller selects a single-sided update mode in which the drive circuit updates one of the screens of the first and second display panels, and a double-sided update mode in which both the screens of the first and second display panels are updated simultaneously. Is possible,
Further, the controller changes a ratio of a delay period inserted between temporally adjacent scanning lines with respect to the scanning period for each scanning line sequentially scanned according to the environmental temperature, and the single-sided update mode and double-sided update. Differently changing the ratio of the delay period to the scanning period depending on the mode,
A liquid crystal display device. The first and second display panels perform display using selective reflection of a cholesteric liquid crystal phase,
A period for applying a driving pulse to the liquid crystal by the driving circuit includes a reset period for resetting the liquid crystal to a homeotropic state, a selection period for selecting the liquid crystal to a desired state, and establishing the liquid crystal in a selected state. Has a maintenance period,
The controller sets Tsp / Ts, which is a ratio of the length Tsp of the selection pulse application period, which is a period during which the selection pulse is applied to the pixels on the scan line, in the selection period, to the environmental temperature. And changing the way of changing Tsp / Ts between the single-sided update mode and the double-sided update mode,
The liquid crystal display device according to claim 1. The controller changes the ratio of the delay period to the scanning period while keeping the Tsp / Ts constant within the first temperature range, and changes the Tsp / Ts within the second temperature range different from the first temperature range. 3. A liquid crystal display device according to claim 2, wherein the liquid crystal display device is fixed at a value different from the temperature range of 1, and the ratio of the delay period to the scanning period is changed. A first display panel and a second display panel that use liquid crystal as a display medium, a drive circuit for driving the first and second display panels with a drive pulse composed of a plurality of drive pulse groups, and a control of the drive circuit And a temperature sensor for measuring an ambient temperature around the first and second display panels,
Each of the first and second display panels includes a screen composed of a plurality of pixels arranged in a matrix,
The drive circuit scans and drives each pixel of the first and second display panels for each scan line;
The controller selects a single-sided update mode in which the drive circuit updates one of the screens of the first and second display panels and a double-sided update mode in which both the screens of the first and second display panels are updated simultaneously. Is possible,
The controller further includes: (a) a ratio of a delay period inserted between temporally adjacent scan lines for each scan line scanned in order to a scan period; and (b) a mutual pulse width of the drive pulse group. At least one of the ratio, (c) the length of the entire drive pulse group with the ratio of the pulse widths of the drive pulse groups fixed, is changed according to the environmental temperature, Different ways of changing (a), (b), (c),
A liquid crystal display device. 5. The liquid crystal display device according to claim 4, wherein the controller keeps the (a) and (b) constant and changes the (c) within a predetermined temperature range.

Images