JP3766926B2 - Display device driving method, display device using the same, and portable device - Google Patents

Description

【０１１３】
そこで、画素電圧保持率Ｐとチラツキの知覚限界について詳細な検討を行った。図１０（ａ）に示すように、内側に透明電極４３を形成したガラス基板４２を２枚向かい合わせ、さらに透明電極４３・４３の間に液晶層４４を挟持したチラツキ評価用セル４１を作製した。そして、このチラツキ評価用セル４１の２つの透明電極４３・４３間に、信号発生装置４５から電圧を印加した。信号発生装置４５から出力される電圧波形を同図（ｂ）に示す。同図においてＶｓを３Ｖ、非選択期間Ｔを１６７ｍｓｅｃとし、Ｖｅを変化させる。チラツキ評価用セル４１は初めＶｓの電圧に充電されるが、徐々に電圧が低下してＶｅとなる。次に、−Ｖｓの電圧を印加するとチラツキ評価用セル４１の明るさが変化するが、このときの明るさの変化、すなわちチラツキを目視で確認する。
【０１１４】
ここで、Ｖｅ／Ｖｓが実際の液晶表示装置１における画素電圧保持率Ｐに相当する。画素電圧保持率Ｐとチラツキの発生状況について詳細に観察したところ、表２に示すような結果が得られた。
【０１１５】
【表２】

【０１１６】

である。
【０１１７】
これにより、休止期間Ｔ２を設けてもチラツキがない液晶パネル２を得るためには、画素電圧保持率Ｐ≧０．９とすればよいことが分かる。
【０１１８】
以上の構成の液晶表示装置１で低周波数駆動を行った場合の走査信号波形、データ信号波形、画素電極２７の電位、および反射電極２７ｂからの反射光強度を図１１（ａ）ないし（ｅ）に示す。なお、走査期間Ｔ１を１６．７ｍｓｅｃ、休止期間Ｔ２を１６７ｍｓｅｃとした。また、奇数回目の画像の書き込みでは奇数番目の走査信号線（Ｇ₁ ，Ｇ₃ ，…）を走査する場合にデータ信号線３２…を正極性、偶数番目の走査信号線（Ｇ₂ ，Ｇ₄ ，…）を走査する場合にデータ信号線３２…を負極性とし、偶数回目の画像の書き込みではその逆とした。こうすることにより、走査ライン方向に極性を反転させることができ、各画素には毎回極性反転した交流信号が入力される。
【０１１９】
同図（ａ）は、注目している画素の走査信号線３１の前段の走査信号線３１に出力される走査信号波形を、同図（ｂ）は注目している画素（自段）の走査信号線３１に出力される走査信号波形を、同図（ｃ）は注目している画素のデータ信号線３２に出力されるデータ信号波形を、同図（ｄ）は注目している画素の画素電極２７の電位を示す。同図（ａ）および（ｄ）から分かるように、前段の走査信号線３１に選択電圧が印加されているときに、画素電極２７の電位は安定している。このとき反射電極２７ｂからの反射光強度を測定したところ、同図（ｅ）に示すように反射光強度の変化はほとんど確認されなかった。また、目視による評価の結果でも、チラツキがなく均一で良好な表示品位が得られることが確認された。
【０１２０】
これに対し、図１２に示すように前段の走査信号線３１’…に補助容量用電極パッド２７ａ’…を対向させて補助容量を形成する従来のＣｓオンゲート構造では、図１３（ａ）ないし（ｅ）の結果が得られた。同図（ａ）および（ｄ）から分かるように、１ライン上の走査信号線３１’に選択電圧が印加されているときに、画素電極２７’の電位が大きく変動している。この結果、同図（ｅ）に示すように反射電極２７ｂ’からの反射光強度も変動してしまい、目視による評価の結果でもチラツキが知覚された。
【０１２１】
また、液晶表示装置１の消費電力を測定したところ、休止期間Ｔ２を設けずに駆動を行った場合には１６０ｍＷであったのに対し、休止期間Ｔ２を設けて駆動を行った場合には４０ｍＷとなり、大きく低減することが確認された。さらに、非走査期間を垂直帰線期間とし、１６．７ｍｓｅｃで繰り返し画像を書き換えるように切り換えたところ、画像が刻々と変化する通常の動画を表示させることができた。
【０１２２】
以上に述べたように、液晶表示装置１によれば、アクティブ素子を有する構成において、良好な表示品位を保ったまま低消費電力化を達成することができる。また、液晶表示装置１が反射電極２７ｂ…を備え、バックライトを必要としない反射型液晶表示装置であることから、３０Ｈｚ以下の駆動による低消費電力化の割合が大きい液晶表示装置となる。これは液晶パネルの裏面に反射部材が設けられている反射型液晶表示装置についても同様である。
【０１２３】
次に、液晶表示装置として、図４および図５を用いて説明した液晶表示装置１における液晶パネル２を、図１４および図１５に示す液晶パネル５１で置き換えた構成であり、透過反射両用型の液晶表示装置である。図１５のＢ−Ｂ断面図である図１４に示すように、液晶パネル５１は、液晶パネル２の反射防止膜１７およびカラーフィルタ１８が省略されるとともに、ガラス基板１２の下面に位相差板１５および偏光板１６がこの順で設けられた構成である。また、さらにその下方にバックライト５２が設けられている。また、補助容量用電極パッド５４ａはＩＴＯなどの透明電極で形成されており、層間絶縁膜２６および反射電極５４ｂに微細な凹凸はない。
【０１２４】
さらに、補助容量用電極パッド５４ａの上方にある反射電極５４ｂ…の一部には、層間絶縁膜２６を貫通する光透過穴５３が設けられている。この光透過穴５３がバックライト５２からの光の透過領域となっている。反射電極２７ｂ…によって光が反射される反射領域と、上記透過領域とはコンタクトホール２８を介して導通していて同電位であり、液晶層１３を駆動することが可能である。この液晶パネル５１で偏光モードで表示を行う場合、反射領域と透過領域との位相差の整合性を図る必要があることから、透過領域の液晶層１３の厚みｄ_T 、および反射領域の液晶層１３の厚みｄ_R とはｄ_T ≒２ｄ_R とするのが望ましい。
【０１２５】
また、図１５に図１４の液晶層１３より下方の部分を上方から見た図を示す。補助容量用電極パッド５４ａと反射電極５４ｂとを合わせて画素電極５４としている。各補助容量用電極パッド５４ａは補助容量配線３３と補助容量Ｃ_CSを形成しながらＴＦＴ１４の周囲に広範囲に形成されている。そして、矩形の光透過穴５３が、反射電極５４ｂおよび層間絶縁膜２６のうち、補助容量用電極パッド５４ａの上方で、かつ走査信号線３１と補助容量配線３３との上方を避けた位置に設けられている。
【０１２６】
上記の構成の液晶パネル５１とすれば、前述の液晶表示装置１で得られる効果に加えて、周囲光が多いときには反射型として、周囲光が少ないときにはバックライト５２を点灯して透過型と併用して利用することができるようになる。なお、液晶パネル２において、反射板を半透明としても同様の効果が得られる。
【０１２７】
以上、本実施の形態に係る表示装置の駆動方法とそれを用いた表示装置について述べてきたが、表示装置としてはアクティブマトリクス液晶表示装置に限らず、単純マルチプレックス液晶表示装置、ＥＬ（Electro Luminescence) 表示装置、ＰＤＰ(Plasma Display Panel)、ｇｉｒｉｃｏｎなどでもよい。また、上記の表示装置は、携帯電話、ポケットゲーム機、ＰＤＡ(Personal Digital Assistants) 、携帯ＴＶ、リモートコントロール、ノート型パーソナルコンピュータ、その他の携帯端末などに搭載可能である。これらの携帯機器はバッテリー駆動されることが多く、良好な表示品位を保ったままの低消費電力化が図れる表示装置を搭載していることにより、長時間駆動が容易になる。
【０１２８】
【発明の効果】
本発明の表示装置の駆動方法は、以上のように、画面を１回走査する走査期間よりも長い非走査期間であって、全走査信号線を非走査状態とする休止期間を設け、上記走査期間と上記休止期間との和を１垂直期間とする構成である。
【０１２９】
それゆえ、走査期間よりも長い休止期間が存在するために、垂直周波数が低い周波数となる。従って、明るさ、コントラスト、応答速度、階調性などの基本的な表示品位を確保することのできるマトリクス型の表示装置においては、データ信号の供給周波数に正比例して増加するデータ信号線ドライバの消費電力を上記表示品位を犠牲にすることなく容易にかつ大幅に削減することができる。
【０１３０】
以上により、明るさ、コントラスト、応答速度、階調性などの基本的な表示品位を満たした状態で、容易に十分な低消費電力化を図ることのできるマトリクス型の表示装置の駆動方法を提供することができるという効果を奏する。
【０１３１】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間を含めた非走査期間を複数種類の中から設定する構成である。
【０１３２】
それゆえ、静止画や動画など表示画像の種類に応じて画面を書き換える周期を変化させることができる。これにより、表示画像の種類ごとに最適な低消費電力化を図ることができるという効果を奏する。
【０１３３】
さらに本発明の表示装置の駆動方法は、以上のように、上記走査期間をＴ１、複数の上記非走査期間のうちで最短のものをＴ０１、Ｔ０１以外の任意のものをＴ０２としたとき、
（Ｔ１＋Ｔ０２）＝（Ｔ１＋Ｔ０１）×Ｎ（Ｎは２以上の整数）
の関係とする構成である。
【０１３４】
それゆえ、基準同期信号を非走査期間のそれぞれに共通化して利用することができ、簡単な回路を付加するだけで低周波数駆動が可能となって、新たに発生する消費電力を非常に小さくすることができるという効果を奏する。
【０１３５】
さらに本発明の表示装置の駆動方法は、以上のように、上記表示装置が上記データ信号の基となる画像データを蓄積する画像データ蓄積手段を有している場合に、上記休止期間に上記画像データ蓄積手段からの上記画像データの転送を停止させる構成である。
【０１３６】
それゆえ、休止期間において画像データ転送のための消費電力を削減することができる。これにより、表示装置全体の消費電力をさらに低減することができるという効果を奏する。
【０１３７】
さらに本発明の表示装置の駆動方法は、以上のように、上記データ信号の基となる画像データを上記表示装置に供給する画像データ供給手段がある場合に、上記休止期間に上記画像データ供給手段からの上記画像データの供給を受け付ける動作を上記表示装置に停止させる構成である。
【０１３８】
それゆえ、休止期間に画像データ供給手段からの画像データの供給を受け付ける動作を表示装置に停止させるので、休止期間において画像データ供給を受け付けるための消費電力を削減することができる。これにより、表示装置全体の消費電力をさらに低減することができるという効果を奏する。
【０１３９】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に、表示とは無関係なアナログ回路の動作を停止させる構成である。
【０１４０】
それゆえ、定常的に電力を消費している回路の消費電力を削減することができ、表示装置全体の消費電力をさらに低減することができるという効果を奏する。
【０１４１】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に、少なくとも上記データ信号線のドライバのアナログ回路の動作を停止させることを特徴としている。
【０１４２】
それゆえ、休止期間に少なくとも最も消費電力の大きいアナログ回路の動作を停止させるので、表示装置全体の消費電力を効率よく低減することができるという効果を奏する。
【０１４３】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に、全データ信号線を駆動するデータ信号ドライバに対して上記全データ信号線をハイインピーダンス状態とする構成である。
【０１４４】
それゆえ、休止期間において各データ信号線の電位を一定に保持することができる。従って、データ信号線と接続される画素電極を有するような液晶表示装置においてデータ信号線の電位変動によって生じる各画素のデータ保持状態の変化が抑制され、画面のチラツキが十分に抑制される。これにより、十分な低消費電力化とチラツキが十分に抑制された高表示品位とを両立させることのできるマトリクス型の表示装置の駆動方法を提供することができるという効果を奏する。
【０１４５】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に、上記全データ信号線をハイインピーダンス状態とした後に、表示とは無関係なアナログ回路の動作を停止させる構成である。
【０１４６】
それゆえ、休止期間にアナログ回路を介してデータ信号線がグランド電位となることを避けることができる。従って、アナログ回路の消費電力の削減を行いながら、画素のデータ保持状態の変化を抑制し、よりチラツキが抑制された高表示品位を達成することができるという効果を奏する。
【０１４７】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に、少なくとも上記データ信号線のドライバのアナログ回路の動作を停止させる構成である。
【０１４８】
それゆえ、休止期間に少なくとも最も消費電力の大きいアナログ回路の動作を停止させるので、表示装置全体の消費電力を効率よく低減することができるという効果を奏する。
【０１４９】
さらに本発明の表示装置の駆動方法は、以上のように、上記全データ信号線をハイインピーダンス状態とする前に、上記全データ信号線を、全画素のデータ保持状態の変化が平均して最小となる電位とする構成である。
【０１５０】
それゆえ、ラインごとに画素のデータ保持状態が異なる場合でも、画面全体としてデータ保持状態の変化が略最小となり、よりチラツキが抑制された高表示品位を達成することができるという効果を奏する。
【０１５１】
また、本発明の表示装置は、以上のように、前記所定の発明に記載の表示装置の駆動方法を実行する制御手段を有している構成である。
【０１５２】
それゆえ、明るさ、コントラスト、応答速度、階調性などの基本的な表示品位を満たした状態で、容易に十分な低消費電力化を図ることのできるマトリクス型の表示装置を提供することができるという効果を奏する。
【０１５３】
また、本発明の表示装置は、以上のように、前記所定の発明に記載の表示装置の駆動方法を実行する制御手段を有している構成である。
【０１５４】
それゆえ、十分な低消費電力化とチラツキが十分に抑制された高表示品位とを両立させることのできるマトリクス型の表示装置を提供することができるという効果を奏する。
【０１５５】
さらに本発明の表示装置の駆動方法は、以上のように、上記表示装置が、画素電極と対向電極との間に液晶が介在して形成される電気容量に、走査信号線から供給される走査信号によって選択状態となったアクティブ素子を介し、データ信号線から供給されるデータ信号に基づいた電荷が周期的に書き込まれる画素がマトリクス状に配置された液晶表示素子を有する液晶表示装置である構成である。
【０１５６】
それゆえ、明るさ、コントラスト、応答速度、階調性などの基本的な表示品位を満たした状態で、容易に十分な低消費電力化を図ることのできるアクティブマトリクス型の液晶表示装置の駆動方法を提供することができるという効果を奏する。
【０１５７】
さらに本発明の表示装置の駆動方法は、以上のように、上記表示装置が、画素電極と対向電極との間に液晶が介在して形成される電気容量に、走査信号線から供給される走査信号によって選択状態となったアクティブ素子を介し、データ信号線から供給されるデータ信号に基づいた電荷が周期的に書き込まれる画素がマトリクス状に配置された液晶表示素子を有する液晶表示装置である構成である。
【０１５８】
それゆえ、十分な低消費電力化とチラツキが十分に抑制された高表示品位とを両立させることのできるアクティブマトリクス型の表示装置の駆動方法を提供することができるという効果を奏する。
【０１５９】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に上記対向電極を、上記対向電極に上記走査期間に直流電圧を印加する場合には上記走査期間の上記対向電極と同電位とし、上記対向電極に上記走査期間に交流電圧を印加する場合には上記交流電圧の振幅中心の電位とする構成である。
【０１６０】
それゆえ、休止期間に各画素と対向電極との容量結合に起因した画素電極の電位変動が抑制される。従って、画素のデータ保持状態の変化が抑制され、チラツキが抑制された高表示品位を達成することができるという効果を奏する。
【０１６１】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間に、上記アクティブ素子のＯＦＦ抵抗値を最大とする非選択電圧を全走査信号線に印加する構成である。
【０１６２】
それゆえ、休止期間において、データ信号線への漏れ電流による画素電極の電位変動が抑制される。これにより、走査ラインごとに画素の電位が異なる場合でも、画素のデータ保持状態の変化が抑制され、チラツキが抑制された高表示品位を達成することができるという効果を奏する。
【０１６３】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間を１６．７ｍｓｅｃ以上２ｓｅｃ以下とする構成である。
【０１６４】
それゆえ、休止期間を６０Ｈｚの走査期間以上に相当する１６．７ｍｓｅｃ以上としてデータ信号線ドライバの消費電力を削減することができるとともに、休止期間を２ｓｅｃ以下とすることにより、液晶およびアクティブ素子からの漏れ電流によって画素電極の電位が変動することによるチラツキが抑制され、高表示品位を達成することができるという効果を奏する。
【０１６５】
さらに本発明の表示装置の駆動方法は、以上のように、上記休止期間を５０ｍｓｅｃ以上１ｓｅｃ以下とする構成である。
【０１６６】
それゆえ、休止期間を５０ｍｓｅｃ以上としてデータ信号線ドライバの消費電力を大幅に削減することができるとともに、休止期間を１ｓｅｃ以下とすることにより、液晶およびアクティブ素子からの漏れ電流によって画素電極の電位が変動することによるチラツキが大きく抑制され、より高表示品位を達成することができるという効果を奏する。
【０１６７】
さらに本発明の表示装置は、以上のように、前記所定の発明に表示装置の駆動方法を実行する制御手段を有している構成である。
【０１６８】
それゆえ、明るさ、コントラスト、応答速度、階調性などの基本的な表示品位を満たした状態で、容易に十分な低消費電力化を図ることのできるアクティブマトリクス型の液晶表示装置を提供することができるという効果を奏する。
【０１６９】
さらに本発明の表示装置は、以上のように、前記所定の発明に記載の表示装置の駆動方法を実行する制御手段を有している構成である。
【０１７０】
それゆえ、十分な低消費電力化とチラツキが十分に抑制された高表示品位とを両立させることのできるアクティブマトリクス型の液晶表示装置を提供することができるという効果を奏する。
【０１７１】
さらに本発明の表示装置は、以上のように、上記液晶表示素子には、上記画素電極との間で上記画素の補助容量を形成する補助容量電極が上記走査信号線の位置を避けて設けられている構成である。
【０１７２】
それゆえ、走査信号線と画素電極との電気容量結合を無視することができ、この状態で制御手段により休止期間を設定して液晶表示素子の駆動を行えば、Ｃｓオンゲート構造で補助容量を形成していた場合と異なり、１ライン上の走査信号線の電位変動による画素電極の電位変動は生じなくなる。これにより、長い休止期間を設定してもチラツキが抑制された高表示品位を得ることができるという効果を奏する。
【０１７３】
さらに本発明の表示装置は、以上のように、上記液晶表示素子の画素電圧保持率を、上記画素電極と上記対向電極との間の電気容量をＣ_LC、上記補助容量をＣ_CS、上記アクティブ素子の非選択期間をＴ、上記書き換え周波数における非選択期間Ｔ３後の液晶電圧保持率をＨｒ（Ｔ）、書き込み直後の上記画素電極と上記対向電極との電位差をＶ、上記アクティブ素子の非選択時の抵抗値をＲ、Ｖ₁ ＝Ｖ−｛Ｖ・（１−Ｈｒ（Ｔ））×Ｃ_LC／（Ｃ_LC＋Ｃ_CS）｝として、
Ｐ＝Ｖ₁ ・ｅｘｐ［−Ｔ／｛（Ｃ_LC＋Ｃ_CS）・Ｒ｝］／Ｖ
と表したときに、Ｐ≧０．９である構成である。
【０１７４】
それゆえ、走査信号線数をｎ、走査期間をＴ１、非走査期間をＴ０とすれば、非選択期間Ｔ＝（Ｔ１＋Ｔ０）−Ｔ１／ｎと表されるので、非走査期間Ｔ０を休止期間に設定しても、選択期間中にデータ信号線から印加された画素の電圧が、非選択期間Ｔを通して９０％以上の電圧保持率で保持される。従って、非選択期間Ｔにおいて画素電極の電位変動がほとんど生じない。これにより、長い休止期間を設定してもよりチラツキのない安定した表示品位が得られるという効果を奏する。
【０１７５】
さらに本発明の表示装置は、以上のように、上記液晶表示素子は周囲光を用いて反射型表示を行う反射部材を有している構成である。
【０１７６】
それゆえ、バックライトを必要としない反射型液晶表示装置とするので、休止期間を設定した駆動による低消費電力化の割合が大きくなるという効果を奏する。
【０１７７】
さらに本発明の液晶表示装置は、以上のように、上記反射部材は上記画素電極の少なくとも一部である構成である。
【０１７８】
それゆえ、画素電極の少なくとも一部が反射型液晶表示装置の反射電極となるので、別途反射部材は必要なく、装置を構成する部材の種類を減らすことが可能であるという効果を奏する。
【０１７９】
さらに本発明の表示装置は、以上のように、上記反射部材に光透過用の穴が設けられている、または上記反射部材が半透明である構成である。
【０１８０】
それゆえ、反射透過両用型の液晶表示装置とするので、周囲光が多いときには反射型として、周囲光が少ないときにはバックライトを点灯するなど透過型と併用して利用することができるという効果を奏する。
【０１８１】
また、本発明の携帯機器は、以上のように、前記所定の発明に記載の表示装置が搭載されている構成である。
【０１８２】
それゆえ、明るさ、コントラスト、応答速度、階調性などの基本的な表示品位を満たした状態で、容易に十分な低消費電力化を図ることのできる携帯機器を提供することができ、バッテリーによる長時間駆動が容易になるという効果を奏する。
【０１８３】
また、本発明の携帯機器は、以上のように、前記所定の発明に記載の表示装置が搭載されている構成である。
【０１８４】
それゆえ、十分な低消費電力化とチラツキが十分に抑制された高表示品位とを両立させることのできる携帯機器を提供することができ、バッテリーによる長時間駆動が容易になるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の一実施の形態における表示装置の駆動方法を説明するタイミングチャートである。
【図２】図１の表示装置の駆動方法が適用される表示装置の構成を示すシステムブロック図である。
【図３】図２の表示装置のデータ信号ドライバの内部構成を示す回路図である。
【図４】図２の表示装置の液晶パネルの構成を示す断面図である。
【図５】図２の表示装置の液晶パネルの構成を示す平面透視図である。
【図６】（ａ）および（ｂ）は、図５の等価回路を示す回路図である。
【図７】液晶の特性を示すグラフである。
【図８】ＴＦＴのＯＦＦ抵抗の特性を示すグラフである。
【図９】電荷を十分に保持することができない場合の画素電極電位の変化と反射光強度の変化とを説明する説明図である。
【図１０】（ａ）および（ｂ）は、液晶パネルの特性を評価する方法を説明する説明図である。
【図１１】（ａ）ないし（ｅ）は、図５の液晶パネルの信号および特性を示すタイミングチャートである。
【図１２】図５の液晶パネルの比較例の構成を示す平面透視図である。
【図１３】（ａ）ないし（ｅ）は、図１２の液晶パネルの信号および特性を示すタイミングチャートである。
【図１４】図４の液晶パネルの変形例の構成を示す断面図である。
【図１５】図４の液晶パネルの変形例の構成を示す平面透視図である。
【図１６】マトリクス型表示装置の構成を示すブロック図である。
【図１７】従来の表示装置の駆動方法を説明するタイミングチャートである。
【図１８】垂直帰線期間を説明する説明図である。
【符号の説明】
１ 液晶表示装置（表示装置）
２ 液晶パネル（液晶表示素子）
３ ゲートドライバ
４ ソースドライバ（データ信号線のドライバ）
５ コントロールＩＣ（制御手段）
６ 画像メモリ（画像データ蓄積手段）
７ ＧＳＰ変換回路
１３ 液晶層（液晶）
１４ ＴＦＴ（アクティブ素子）
１９ 透明共通電極（対向電極）
２７ 画素電極
２７ａ 補助容量用電極パッド
２７ｂ 反射電極
３１ 走査信号線
３２ データ信号線
３３ 補助容量配線（補助容量電極）
５１ 液晶パネル（液晶表示素子）
５３ 光透過穴（光透過用の穴）
５４ 画素電極
５４ａ 補助容量用電極パッド
５４ｂ 反射電極
Ｃ_CL 液晶容量（電気容量）
Ｃ_CS 補助容量
Ｔ 非選択期間
Ｔ１ 走査期間
Ｔ２ 休止期間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to low power consumption of a matrix display device.
[0002]
[Prior art]
In recent years, application of liquid crystal display devices to word processors, laptop personal computers, pocket televisions, and the like is rapidly progressing. In particular, a reflective liquid crystal display device that displays light by reflecting light incident from the outside among liquid crystal display devices does not require a backlight, so it consumes less power, is thin, and can be reduced in weight. Attention has been paid.
[0003]
Conventional reflective liquid crystal display devices can be used for segment display systems that can display only simple numbers and pictograms used in watches and the like, as well as complex displays such as personal computers and portable information terminals. These are roughly divided into a simple multiplex driving method and an active matrix driving method using active elements such as TFT (Thin Film Transistor). It is desirable to reduce power consumption in each method.
[0004]
As a method for reducing the power consumption of the segment display method, Japanese Patent Application Laid-Open No. 5-232447 discloses that the common electrode and the segment electrode are stable at the same potential during standby, that is, when no image is displayed in which the entire white display or the entire black display is performed. It is disclosed that a solid white display or a black solid display is performed. Japanese Patent Laid-Open No. 2-10492 discloses a method for reducing the power consumption of a driving circuit by setting a MOS transistor that directly drives a liquid crystal during standby to a high impedance state. All of these technologies are aimed at segment-display liquid crystal display devices, so their ideographic performance is limited to displaying simple numbers and pictograms, and complex information such as personal computers and personal digital assistants. It is impossible to apply to devices that display
[0005]
In addition, it is difficult to use such a driving method for a matrix type liquid crystal display device. Specifically, for example, in the case of a 4 × 4 matrix type liquid crystal display device as shown in FIG. 16, the scanning signals supplied to the scanning signal lines G (0) to G (3) are as shown in FIG. The selection voltage is sequentially applied to the scanning signal lines G (0) to G (3). Electric charges corresponding to the data are written in the respective pixels by supplying data signals to the data signal lines S (0) to S (3) in synchronization with the scanning signals for the respective lines thus selected. Then, after scanning the last line, as shown in FIG. 18, the scanning is started again from the first line after a short time blanking period. Since this vertical blanking period is a period of time originally provided for returning the electron beam from the electron gun inside the CRT to the original position, there is no need for the liquid crystal display device. However, in order to reproduce a normal television image or the like on a liquid crystal display device, it is provided to maintain compatibility with a television image signal such as NTSC.
[0006]
As described above, in the case of a matrix type liquid crystal display device, a plurality of pixels whose data signal lines are arranged in the vertical direction of the screen must be sequentially driven, and one pixel corresponding to the segment output of the segment display system is used. There is no data signal output for driving only the pixels. For this reason, even if charges are written in the pixels on the bottom line of one screen and the data display line and the counter electrode of the pixel are kept in a high impedance state by applying the segment display driving method, For other pixels, the written charge is not held, and a stable display cannot be obtained.
[0007]
Among the matrix type liquid crystal display devices, those of the simple multiplex drive type are basically 2 sized and have a sufficiently low power consumption of about 10 mW to 15 mW, but are basically low in brightness and contrast and low in response speed. There is a problem with the display quality. On the other hand, the active drive method using TFTs, etc. has high brightness and contrast, high response speed and sufficient basic display quality, but the power consumption is about 100mW to 150mW even with a size of about 2 type. It was not satisfactory enough.
[0008]
On the other hand, research and development for sufficiently low power consumption and good display quality has been energetically performed so far, for example, Japanese Utility Model Laid-Open No. 60-50573 and Japanese Patent Laid-Open No. 10-10489. A method for reducing power consumption is disclosed in the publication. The methods of these publications focus on the transmission method of television signals, and use the fact that there is no data in the vertical blanking period and stop the operation of the peripheral drive circuit during the vertical blanking period. Is to be reduced.
[0009]
Another method is disclosed in JP-A-9-107563. This relates to a reduction in power consumption of a field-sequential stereoscopic image display head-mounted display having two liquid crystal panels corresponding to left and right eyes. In one field period, only one liquid crystal panel is driven and the other liquid crystal panel is driven. The liquid crystal panel is stopped, and the display is performed by alternately switching the driving for each field period.
[0010]
As yet another method, a multi-field driving method has been proposed in SID '95 Proceedings p249 to p252 and JP-A-3-271795. This is because the scanning of one screen is divided into a plurality of times every other scanning signal line or every other scanning signal line, and the polarity of the voltage of the data signal line is not reversed during one scanning. The power consumption of the line driver is reduced. Another object of the present invention is to realize a display without flickering as a whole by offsetting the change in brightness, i.e. flickering, generated in each line with the flickering of adjacent lines of opposite polarity.
[0011]
Further, as in the method disclosed in Japanese Patent Laid-Open No. 6-342148, for example, a ferroelectric liquid crystal is used for the liquid crystal panel to provide a memory property, and the drive frequency (refresh rate) is reduced to reduce power consumption. There is also a way to do it.
[0012]
[Problems to be solved by the invention]
However, in the method of stopping the operation of the peripheral drive circuit during the vertical blanking period, the vertical blanking period is only about 8% of the total time as described in Japanese Utility Model Laid-Open No. 60-50573. The power consumption that can be reduced during this period is only about 5%.
[0013]
In the method disclosed in Japanese Patent Laid-Open No. 9-107563, one of the liquid crystal panels is driven during all field periods, and power consumption does not increase and cannot be reduced. Further, by using a left and right binocular head mounted display, refreshing is always performed on one of the displays, and thus an image with less flicker is obtained. However, in general, a liquid crystal display device can provide a flicker-free display when driven at 30 Hz, particularly about 45 Hz or more. Therefore, when this method is applied to a method of directly viewing one liquid crystal panel, flicker is easily perceived.
[0014]
Further, even if multi-field driving is performed, flickering is generated for each line, and flickering is actually perceived even if offset by adjacent lines, and the visibility is remarkably lowered. In addition, the drive frequency is only slightly reduced, and the reduction in power consumption is not sufficient. Further, in the multi-field driving method, since one screen is divided into a plurality of subfields and scanning is performed every other line or every other scanning signal line, an image is temporarily stored in a frame memory and then driven to scan. It is necessary to read a signal corresponding to the signal line, and the circuit configuration is inevitably complicated. Therefore, there is a drawback that the peripheral circuit is enlarged and the cost is increased.
[0015]
Further, in the method disclosed in Japanese Patent Application Laid-Open No. 6-342148, since the ferroelectric liquid crystal is basically a binary (monochrome) display, gradation display cannot be performed and a natural image cannot be displayed. Furthermore, since a high-level panel manufacturing technique is required to make a ferroelectric liquid crystal into a panel, it is difficult to realize it and has not been put into practical use until today.
[0016]
As described above, in the driving method of the conventional matrix type liquid crystal display device, sufficient power consumption can be easily reduced while satisfying basic display quality such as brightness, contrast, response speed, and gradation. I couldn't. Furthermore, the conventional driving method of the matrix type liquid crystal display device cannot achieve both a sufficiently low power consumption and a high display quality without flickering. These problems are not limited to liquid crystal display devices, but can also be said for matrix display devices in general.
[0017]
The present invention has been made in view of the above-described conventional problems, and its purpose is to easily achieve a sufficiently low level while satisfying basic display quality such as brightness, contrast, response speed, and gradation. It is an object to provide a method for driving a matrix display device capable of reducing power consumption, a display device using the method, and a portable device. Another object of the present invention is to provide a driving method for a matrix type display device capable of achieving both a sufficiently low power consumption and a high display quality in which flicker is sufficiently suppressed, and a display device using the same. As well as providing portable devices.
[0018]
[Means for Solving the Problems]
In order to solve the above problems, the display device driving method of the present invention selects and scans each line of the screen in which pixels are arranged in a matrix by using a plurality of scanning signal lines. In a driving method of a display device in which a data signal is supplied from a data signal line to a pixel of a line for display, the scanning signal line is non-scanned in a non-scanning period longer than a scanning period for scanning the screen once. It is characterized in that there is a pause period to be in a state, and the sum of the scanning period and the pause period is one vertical period.
[0019]
According to the above invention, the scanning period and the pause period in which all the scanning signal lines are in the non-scanning state longer than the scanning period are repeated every vertical period. For example, if the scanning period is set to a time equivalent to a normal 60 Hz, there is a pause period longer than that, so that the vertical frequency is lower than 30 Hz. The scanning period and the pause period may be appropriately set according to the degree of movement in an image to be displayed such as a still image or a moving image. Since all the scanning signal lines are in a non-scanning state during the idle period, the data signal supply frequency can be reduced. Therefore, in an active matrix type liquid crystal display device, such as a matrix type display device that can ensure basic display quality such as brightness, contrast, response speed, and gradation, it is directly proportional to the data signal supply frequency. Thus, the increased power consumption of the data signal line driver can be easily and significantly reduced without sacrificing the display quality.
[0020]
As described above, a driving method of a matrix type display device that can easily achieve sufficient power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation is provided. can do.
[0021]
Further, the display device driving method of the present invention is characterized in that the non-scanning period including the pause period is set from a plurality of types in order to solve the above-mentioned problem.
[0022]
According to the above invention, since the non-scanning period including the pause period is switched to a plurality of types, the cycle of rewriting the screen can be changed according to the type of display image such as a still image or a moving image. As a result, it is possible to achieve optimum power consumption reduction for each type of display image.
[0023]
Further, in order to solve the above problems, the driving method of the display device of the present invention sets the scanning period to T1, the shortest of the plurality of non-scanning periods to T01, and any other than T01 to T02. When
(T1 + T02) = (T1 + T01) × N (N is an integer of 2 or more)
It is characterized by the relationship.
[0024]
According to the above invention, the frame period using each of the plurality of non-scanning periods is an integral multiple of the frame period using the shortest non-scanning period. For example, when driving at normal 60 Hz, T1 is 16.7 msec or less. If T01 is a vertical blanking period and T02 is set to the relationship of the above equation, the screen data signal transferred at 60 Hz may be sampled once every integer. Therefore, the reference synchronization signal can be used in common for each non-scanning period, and low frequency driving can be achieved by simply adding a simple circuit, so that newly generated power consumption can be greatly reduced. Can do.
[0025]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention includes the pause period when the display device has image data storage means for storing image data as a basis of the data signal. The transfer of the image data from the image data storage means is stopped.
[0026]
According to the above invention, since the transfer of the image data from the image data storage means is stopped during the pause period, it is possible to reduce the power consumption for the image data transfer during the pause period. Thereby, the power consumption of the entire display device can be further reduced.
[0027]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention includes the image data supply unit that supplies the display device with image data serving as a basis of the data signal. The display device stops the operation of accepting the supply of the image data from the data supply means.
[0028]
According to the above invention, since the display device stops the operation of accepting the supply of image data from the image data supply means during the suspension period, the power consumption for accepting the supply of image data during the suspension period can be reduced. Thereby, the power consumption of the entire display device can be further reduced.
[0029]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention is characterized in that the operation of an analog circuit unrelated to display is stopped during the pause period.
[0030]
According to the above-described invention, the operation of the analog circuit that is irrelevant to the display in the idle period is stopped among the analog circuits included in the data signal line driver and its control circuit. Therefore, it is possible to reduce power consumption of a circuit that constantly consumes power, and further reduce power consumption of the entire display device.
[0031]
Further, the display device driving method of the present invention is characterized in that the operation of at least the analog circuit of the driver of the data signal line is stopped during the pause period in order to solve the above-described problem.
[0032]
According to the above invention, since the operation of the analog circuit with the largest power consumption is stopped at least during the idle period, the power consumption of the entire display device can be efficiently reduced.
[0033]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention sets all the data signal lines to a high impedance state with respect to the data signal driver that drives all the data signal lines during the pause period. It is a feature.
[0034]
According to the above invention, all the data signal lines are disconnected from the data signal driver during the idle period so that the data signal driver is in a high impedance state, so that the potential of each data signal line is kept constant during the idle period. can do. Therefore, the potential fluctuation of the data signal line, such as the potential fluctuation of the pixel electrode due to capacitive coupling between the data signal line and the pixel electrode, which occurs in a liquid crystal display device having a pixel electrode connected to the data signal line. The change in the data holding state of each pixel caused by the above is suppressed, and the flickering of the screen is sufficiently suppressed. As a result, it is possible to provide a method for driving a matrix display device that can achieve both low power consumption and high display quality in which flicker is sufficiently suppressed.
[0035]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention stops the operation of the analog circuit unrelated to display after setting all the data signal lines to a high impedance state during the pause period. It is characterized by.
[0036]
According to the above invention, after all the data signal lines are set to the high impedance state, the operation of the analog circuit unrelated to the display of the pause period is stopped, so that the data signal line is grounded via the analog circuit during the pause period. Can be avoided. Therefore, it is possible to suppress the change in the data holding state of the pixel while reducing the power consumption of the analog circuit, and to achieve high display quality in which flicker is further suppressed.
[0037]
Further, the display device driving method of the present invention is characterized in that the operation of at least the analog circuit of the driver of the data signal line is stopped during the pause period in order to solve the above-described problem.
[0038]
According to the above invention, since the operation of the analog circuit with the largest power consumption is stopped at least during the idle period, the power consumption of the entire display device can be efficiently reduced.
[0039]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention provides an average change in the data holding state of all the pixels before setting all the data signal lines to the high impedance state. do it minimum It is characterized by having a potential that becomes
[0040]
According to the above invention, all the data signal lines are averaged by the change in the data holding state of all the pixels. minimum A high impedance state is obtained after the potential becomes. For example, in a liquid crystal display device in which liquid crystal is interposed between a pixel electrode connected to a data signal line and the counter electrode, the amplitude of the AC voltage is applied to all the data signal lines when an AC voltage is applied to the counter electrode. The center potential is set to the same potential as the counter electrode when a DC voltage is applied to the counter electrode. In this case, even if a pixel having a positive potential and a pixel electrode having a negative potential are mixed in AC driving, the change in the charge retention state of all the pixels due to capacitive coupling between the data signal line and the pixel electrode, that is, the data retention state On average change minimum It becomes. As a result, even when the pixel data retention state differs from line to line, the change in the data retention state of the entire screen is substantially minimized, and a high display quality in which flicker is further suppressed can be achieved.
[0041]
In order to solve the above-mentioned problems, the display device of the present invention is characterized by having a control means for executing the display device driving method described in the predetermined invention.
[0042]
According to the above invention, a matrix type display device that can easily achieve sufficiently low power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation is provided. Can be provided.
[0043]
In order to solve the above-mentioned problems, the display device of the present invention is characterized by having a control means for executing the display device driving method described in the predetermined invention.
[0044]
According to the above invention, it is possible to provide a matrix type display device that can achieve both low power consumption and high display quality in which flicker is sufficiently suppressed.
[0045]
Furthermore, in order to solve the above problem, the display device driving method according to the present invention supplies, from the scanning signal line, the electric capacity formed by the display device with a liquid crystal interposed between the pixel electrode and the counter electrode. Liquid crystal display device having a liquid crystal display element in which pixels are periodically written with charges based on a data signal supplied from a data signal line through an active element selected by a scanning signal It is characterized by being.
[0046]
According to the above invention, an active matrix type liquid crystal display that can easily achieve sufficiently low power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation. A method for driving the apparatus can be provided.
[0047]
Furthermore, in order to solve the above problem, the display device driving method according to the present invention supplies, from the scanning signal line, the electric capacity formed by the display device with a liquid crystal interposed between the pixel electrode and the counter electrode. Liquid crystal display device having a liquid crystal display element in which pixels are periodically written with charges based on a data signal supplied from a data signal line through an active element selected by a scanning signal It is characterized by being.
[0048]
According to the above-described invention, it is possible to provide a driving method of an active matrix display device that can achieve both low power consumption and high display quality in which flicker is sufficiently suppressed.
[0049]
Further, in order to solve the above-described problem, the display device driving method of the present invention is configured so that the counter electrode is applied during the pause period, and the counter electrode during the scan period when a DC voltage is applied to the counter electrode during the scan period. When the AC voltage is applied to the counter electrode during the scanning period, the potential is set to the potential at the amplitude center of the AC voltage.
[0050]
According to the above invention, by setting the potential of the counter electrode in the rest period as described above, fluctuations in the potential of the pixel electrode due to capacitive coupling between each pixel and the counter electrode are suppressed. Therefore, it is possible to achieve high display quality in which changes in the data holding state of the pixels are suppressed and flickering is suppressed.
[0051]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention sets the OFF resistance value of the active element during the pause period. maximum The non-selection voltage is applied to all scanning signal lines.
[0052]
According to the above invention, the OFF resistance value of the active element is set in the rest period in which all the scanning signal lines are in the non-scanning state. maximum Therefore, the potential fluctuation of the pixel electrode due to the leakage current to the data signal line is suppressed. As a result, even when the pixel potential differs for each scanning line, a change in the data holding state of the pixel is suppressed, and high display quality with reduced flickering can be achieved.
[0053]
Furthermore, in order to solve the above-described problem, the display device driving method of the present invention is characterized in that the pause period is set to 16.7 msec or more and 2 sec or less.
[0054]
According to the above invention, the power consumption of the data signal line driver is reduced by setting the pause period to 16.7 msec or more corresponding to the 60 Hz scanning period or more. By setting the rest period to 2 sec or less, flickering due to fluctuations in the potential of the pixel electrode due to leakage current from the liquid crystal and the active element is suppressed, and high display quality can be achieved.
[0055]
Furthermore, in order to solve the above problem, the display device driving method of the present invention is characterized in that the pause period is set to 50 msec or more and 1 sec or less.
[0056]
According to the above invention, the power consumption of the data signal line driver is greatly reduced by setting the pause period to 50 msec or more. By setting the rest period to 1 sec or less, flicker due to fluctuations in the potential of the pixel electrode due to leakage current from the liquid crystal and the active element is greatly suppressed, and higher display quality can be achieved.
[0057]
Furthermore, in order to solve the above-mentioned problems, the display device of the present invention is characterized in that the predetermined invention has a control means for executing a method for driving the display device.
[0058]
According to the above invention, an active matrix type liquid crystal display that can easily achieve sufficiently low power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation. An apparatus can be provided.
[0059]
Further, in order to solve the above-mentioned problems, the display device of the present invention is characterized by having a control means for executing the display device driving method described in the predetermined invention.
[0060]
According to the above invention, it is possible to provide an active matrix liquid crystal display device that can achieve both low power consumption and high display quality with sufficiently reduced flickering.
[0061]
Further, in order to solve the above problems, the display device of the present invention avoids the position of the scanning signal line in the liquid crystal display element by using an auxiliary capacitance electrode that forms an auxiliary capacitance of the pixel with the pixel electrode. It is characterized by being provided.
[0062]
According to the above invention, since the auxiliary capacitance electrode forming the auxiliary capacitance of the pixel is provided avoiding the position of the scanning signal line, the capacitive coupling between the scanning signal line and the pixel electrode can be ignored. Therefore, in this state, if the liquid crystal display element is driven by setting a pause period by the control means, unlike the case where the auxiliary capacitor is formed with the Cs on-gate structure, the pixel due to the potential fluctuation of the scanning signal line on one line. The potential fluctuation of the electrode does not occur. Thereby, even if a long rest period is set, high display quality in which flickering is suppressed can be obtained.
[0063]
Further, in order to solve the above problems, the display device of the present invention has a pixel voltage holding ratio of the liquid crystal display element, and an electric capacity between the pixel electrode and the counter electrode. _LC , The auxiliary capacity is C _CS T is the non-selection period of the active element, Hr (T) is the liquid crystal voltage holding ratio after the non-selection period T3 at the rewrite frequency, V is the potential difference between the pixel electrode and the counter electrode immediately after writing, and the active element The resistance value when R is not selected is R, V ₁ = V- {V · (1-Hr (T)) × C _LC / (C _LC + C _CS )}
P = V ₁ Exp [-T / {(C _LC + C _CS ) ・ R}] / V
It is characterized by P ≧ 0.9.
[0064]
According to the above invention, when the number of scanning signal lines is n, the scanning period is T1, and the non-scanning period is T0, the non-selection period T = (T1 + T0) −T1 / n is expressed. Is set to the rest period, the voltage of the pixel applied from the data signal line during the selection period is held at a voltage holding ratio of 90% or more throughout the non-selection period T. Therefore, the potential fluctuation of the pixel electrode hardly occurs in the non-selection period T. As a result, a stable display quality without flickering can be obtained even when a long pause period is set.
[0065]
Furthermore, in order to solve the above-described problems, the display device of the present invention is characterized in that the liquid crystal display element has a reflective member that performs a reflective display using ambient light.
[0066]
According to the above invention, since the reflective liquid crystal display device does not require a backlight, the ratio of low power consumption by driving with a pause period is increased.
[0067]
Furthermore, in order to solve the above problems, the liquid crystal display device of the present invention is characterized in that the reflecting member is at least a part of the pixel electrode.
[0068]
According to the above invention, since the reflective member is at least a part of the pixel electrode, that is, at least a part of the pixel electrode becomes a reflective electrode of the reflective liquid crystal display device, no additional reflective member is required, and the device is configured. It is possible to reduce the types of members to be performed.
[0069]
Furthermore, in order to solve the above-mentioned problems, the display device of the present invention is characterized in that a hole for transmitting light is provided in the reflecting member, or the reflecting member is translucent.
[0070]
According to the above invention, since the liquid crystal display device of both reflection and transmission is used, it can be used as a reflection type when there is a lot of ambient light and in combination with a transmission type such as turning on a backlight when there is little ambient light. .
[0071]
Further, in order to solve the above problems, the mobile device of the present invention is characterized in that the display device described in the predetermined invention is mounted.
[0072]
According to the above invention, it is possible to provide a portable device that can easily achieve sufficient power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation. And can be driven for a long time by a battery.
[0073]
Moreover, in order to solve the above-mentioned problems, the mobile device of the present invention is characterized in that the display device described in the predetermined invention is mounted.
[0074]
According to the above invention, it is possible to provide a portable device that can achieve both a sufficiently low power consumption and a high display quality in which flickering is sufficiently suppressed, and the battery can be easily driven for a long time.
[0075]
DETAILED DESCRIPTION OF THE INVENTION
A driving method of a display device of the present invention, a display device using the same, and an embodiment that embodies a portable device will be described below with reference to FIGS.
[0076]
FIG. 2 shows a system block diagram of a liquid crystal display device 1 as a display device according to the present embodiment. The liquid crystal display device 1 includes a liquid crystal panel 2, a gate driver 3, a source driver 4, a control IC 5, and an image memory 6. The liquid crystal panel 2 includes a screen composed of pixels arranged in a matrix, a plurality of scanning signal lines for selecting and scanning the screen in a line-sequential manner, and a plurality of data for supplying data signals to the pixels on the selected line. And a signal line. The scanning signal line and the data signal line are orthogonal to each other. The gate driver 3 is a scanning signal line driver, and outputs a voltage corresponding to each of the selection period and the non-selection period to each scanning signal line of the liquid crystal panel 2. The source driver 4 is a data signal line driver that outputs a data signal to each data signal line of the liquid crystal panel 2 and supplies image data to each of the pixels on the selected scanning signal line.
[0077]
The control IC 5 receives the image data stored in the image memory 6 inside the computer or the like, delivers the gate start pulse signal GSP and the gate clock signal GCK to the gate driver 3, and RGB gradation data to the source driver 4. The source start pulse signal SP, the source latch strobe signal SLS, and the source clock signal SCK are distributed. All these signals are synchronized, and when the frequency of each signal is expressed by adding f in front of the signal name, the relationship between these frequencies is generally
fGSP <fGCK = fSP <fSCK
It has become. In the case of so-called pseudo double speed drive, fGCK> fSP. The image data stored in the image memory 6 as the image data storage means is data that is the basis of the data signal. In addition, the control IC 5 has a function as a control unit that executes a driving method of the display device according to the present embodiment which will be described later.
[0078]
The gate driver 3 starts scanning the liquid crystal panel 2 in response to the gate start pulse signal GSP received from the control IC 5, and sequentially applies a selection voltage to each scanning signal line according to the gate clock signal GCK. Based on the source start pulse signal SP received from the source driver 4 and the control IC 5, the transmitted gradation data of each pixel is stored in a register in accordance with the source clock signal SCK, and the liquid crystal panel 2 is in accordance with the next source latch strobe signal SLS. Gradation data is written to each data signal line.
[0079]
The control IC 5 includes a GSP conversion circuit 7 for setting the pulse interval of the gate start pulse signal GSP. The pulse interval of the gate start pulse signal GSP is about 16.7 msec when the display frame frequency is a normal 60 Hz. For example, the GSP conversion circuit 7 can increase the pulse interval of the gate start pulse signal GSP to 167 msec. Assuming that the scanning period T1 for one screen remains normal, about 9/10 of the above-described pulse interval is a period during which all scanning signal lines are in a non-scanning state. As described above, in the GSP conversion circuit 7, the non-scanning period until the gate start pulse signal GSP is input to the gate driver 3 again after the scanning period T1 ends may be set to be longer than the scanning period T1. it can. A non-scanning period longer than the scanning period T1 is referred to as a pause period T2. The scanning signal line G when the pause period T2 is set as the non-scanning period ₁ ~ G _n The waveform of the scanning signal supplied to is shown in FIG. In the figure, when n = 4, the non-scanning period is set to a pause period T2 longer than the scanning period T1 in place of the vertical blanking period in comparison with the conventional scanning signal waveform shown in FIG. It can be seen that the vertical period representing the field is longer.
[0080]
When the GSP conversion circuit 7 sets the pause period T2 as the non-scanning period, one vertical period is the sum of the scanning period T1 and the pause period T2. For example, when the scanning period T1 is set to a time equivalent to a normal 60 Hz, there is a pause period T2 longer than that, so the vertical frequency becomes a frequency lower than 30 Hz. The scanning period T1 and the non-scanning period may be appropriately set according to the degree of movement in an image to be displayed such as a still image or a moving image, and the GSP conversion circuit 7 sets a plurality of non-scanning periods according to the content of the image. Be able to. At least one of the non-scanning periods is a pause period T2. In the figure, the GSP conversion circuit 7 changes the setting of the non-scanning period according to the non-scanning period setting signals M1 and M2 inputted from the outside. Although the number of non-scanning period setting signals may be arbitrary, for example, if these two types of non-scanning period setting signals M1 and M2 are logic signals, four non-scanning periods can be set.
[0081]
By providing the pause period T2, the number of times the screen is rewritten, that is, the supply frequency of the data signal output from the source driver 4 can be reduced, so that the power for charging the pixels can be reduced. Therefore, when the liquid crystal display device 1 is an active matrix type liquid crystal display device capable of ensuring basic display quality such as brightness, contrast, response speed, and gradation, the rest period T2 is set as the non-scanning period. Is set, the power consumption of the data signal line driver, which increases in direct proportion to the data signal supply frequency, can be easily and sufficiently reduced without sacrificing the display quality.
[0082]
For this reason, the non-scanning period may be set to the long pause period T2 for a display with no movement such as a still image or a display with little movement even with a moving image. For a moving image with a lot of movement, the non-scanning period may be set to a short pause period T2 or a non-scanning period shorter than the pause period T2. For example, if a non-scanning period that is sufficiently short with respect to a scanning period of 16.7 msec is set, the drive frequency is equivalent to a normal 60 Hz, so that a sufficiently fast moving image can be displayed. On the other hand, if the non-scanning period is set to a long pause period T2 of 3333 msec, it is possible to reduce the power consumption by rewriting the screen while maintaining the basic display quality for still images and moving images with little movement. it can. That is, the liquid crystal panel 2 can be used by switching between a moving image display and a low power consumption display. As described above, since the cycle of rewriting the screen can be changed in accordance with the type of display image such as a still image or a moving image, it is possible to achieve optimum low power consumption for each type of display image.
[0083]
In addition, when the shortest of the plurality of non-scanning periods is T01 and any other than T01 is T02,
(T1 + T02) = (T1 + T01) × N (N is an integer of 2 or more) (1)
In other words, the frame period using each of the plurality of non-scanning periods is preferably an integer multiple of the frame period using the shortest non-scanning period T01. For example, when driving at normal 60 Hz, T1 is 16.7 msec or less. If T01 is set as the vertical blanking period and T02 is set in the relationship of the expression (1), the screen data signal transferred at 60 Hz may be sampled once every integer. Therefore, the reference synchronization signal can be used in common for each non-scanning period, and low frequency driving can be achieved by simply adding a simple circuit, so that newly generated power consumption can be greatly reduced. Can do.
[0084]
In setting the non-scanning period, a plurality of non-scanning period setting signals may be input to the GSP conversion circuit 7 as in this example, or the non-scanning period adjustment signal may be input to the GSP conversion circuit 7. A volume, a switch for selection, and the like may be provided. Of course, a volume for adjusting the non-scanning period, a switch for selection, and the like may be provided on the outer peripheral surface of the housing of the liquid crystal display device 1 so that the user can easily set. The GSP conversion circuit 7 may have any configuration that can change the non-scanning period to a desired setting in accordance with at least an external instruction. In FIG. 2, the GSP conversion circuit 7 is incorporated in the control IC 5. However, the configuration is not limited to this, and the GSP conversion circuit 7 may be provided independently of the control IC 5.
[0085]
Next, a method for further reducing power consumption when the pause period T2 is set will be described.
[0086]
There are logic circuits inside the gate driver 3 and the source driver 4, and each consumes power to operate the internal transistors. For this reason, the power consumption is proportional to the number of times the transistor operates, and is proportional to the clock frequency. Since all the scanning signal lines are in a non-scanning state during the pause period T2, signals other than the gate start pulse signal GSP such as the gate clock signal GCK, the source start pulse signal SP, and the source clock signal SCK are supplied to the gate driver 3 and the source driver. By not inputting to 4, it becomes unnecessary to operate the logic circuit inside the gate driver 3 and the source driver 4, so that power consumption can be reduced accordingly.
[0087]
On the other hand, when the source driver 4 is a digital driver that handles a digital data signal, a gradation generation circuit 8 is provided as shown in FIG. 3, and based on the gradation signal sent from the control IC 5, A power supply voltage V is obtained by a resistance division method using a voltage dividing resistor 8a and a switching element 8b. _DD The gradation voltage is selected from Thereafter, the current is amplified by the buffer 9 and output to each data signal line. As described above, there are analog circuits such as the gradation generation circuit 8 and the buffer 9 in which current constantly flows inside the source driver 4. When the source driver 4 is an analog driver that handles analog data signals, a sampling hold circuit and a buffer exist as analog circuits. Further, there may be an analog circuit inside the control IC 5.
[0088]
Since the power consumption of the analog circuit does not depend on the driving frequency, the power consumption cannot be reduced only by stopping the operation of the logic circuit in the gate driver 3 and the source driver 4. Therefore, by stopping these analog circuits during the suspension period T2 and disconnecting the analog circuits from the power source, the power consumption of the analog circuits can be reduced, and the power consumption of the entire liquid crystal display device 1 can be further reduced. . When the liquid crystal display device 1 is an active matrix liquid crystal display device, a non-selection voltage is applied to the pixel from the gate driver 3 during the pause period T2, and therefore, an analog circuit to be stopped is associated with the gate driver 3 at a minimum. What is not to be performed, that is, what is unrelated to the display in the suspension period T2 may be used. By stopping at least the analog circuit of the source driver 4, the operation of the analog circuit with the largest power consumption is stopped, so that the power consumption of the entire liquid crystal display device 1 can be efficiently reduced.
[0089]
In addition, since no data is written to the pixels in the pause period T2, power consumption for image data transfer in the pause period T2 can be reduced by stopping the transfer of the image data from the image memory 6 in the pause period T2. it can. For stopping the transfer of the image data, for example, the control IC 5 requests the image memory 6 to stop the transfer of the image data based on the non-scanning period setting signals M1 and M2. Thereby, the power consumption of the entire liquid crystal display device 1 can be further reduced while the transfer stop control is easy.
[0090]
In some cases, image data supply means for supplying image data to the liquid crystal display device 1 from the outside is provided. In this case, the image memory 6 may be provided inside the liquid crystal display device 1 or may not be provided. Under such conditions, it is possible to cause the liquid crystal display device 1 to stop the operation of accepting the supply of image data from the image data supply means during the suspension period T2. For example, the input part of the control IC 5 is set to high impedance with respect to the image data supply side based on the non-scan period setting signals M1 and M2. Thereby, the power consumption in the said input part can be reduced. Thus, by stopping the operation of accepting the supply of image data from the image data supply means during the suspension period T2, the liquid crystal display device 1 can reduce the power consumption for accepting the supply of image data during the suspension period T2. it can. Therefore, the power consumption of the entire liquid crystal display device 1 can be further reduced.
[0091]
Next, a method for achieving high display quality in which flickering of the screen is sufficiently suppressed when the pause period T2 is set will be described.
[0092]
First, all the data signal lines are disconnected from the source driver 4 during the idle period T2, and the source driver 4 is brought into a high impedance state. In this way, the potential of each data signal line can be kept constant during the pause period T2. Therefore, the data signal line such as the potential fluctuation of the pixel electrode caused by the capacitive coupling between the data signal line and the pixel electrode, which occurs when the liquid crystal display device 1 includes the pixel electrode connected to the data signal line, is used. The change in the data holding state of each pixel caused by the potential fluctuation is suppressed, and flicker is sufficiently suppressed. Thereby, it is possible to achieve both low power consumption and high display quality in which flicker is sufficiently suppressed.
[0093]
Further, as described above, when the operation of the analog circuit in the buffer 9 of the source driver 4 is stopped in order to reduce power consumption, the buffer 9 becomes the ground potential. Then, the data signal line connected to the buffer 9 also becomes the ground potential at the same time, and when the liquid crystal display device 1 has a pixel electrode connected to the data signal line, the pixel electrode caused by capacitive coupling Potential fluctuation occurs. Therefore, after all the data signal lines are set to the high impedance state, the operation of the analog circuit unrelated to the display in the pause period T2 is stopped. Therefore, it is possible to suppress the change in the data holding state of the pixel while reducing the power consumption of the analog circuit, and to achieve high display quality in which flicker is further suppressed.
[0094]
Furthermore, all the data signal lines are averaged by the change in the data holding state of all the pixels. minimum It is more preferable that the high impedance state is obtained after the potential becomes. For example, if the liquid crystal display device 1 has a configuration in which a liquid crystal is interposed between a pixel electrode connected to a data signal line and the counter electrode, all data signal lines are applied to an AC voltage applied to the counter electrode. The potential at the amplitude center of the AC voltage is set to the same potential as the counter electrode when a DC voltage is applied to the counter electrode. In this case, even if a pixel having a positive potential and a pixel electrode having a negative potential are mixed in AC driving, the change in the charge retention state of all the pixels due to capacitive coupling between the data signal line and the pixel electrode, that is, the data retention state On average change minimum It becomes. As a result, even when the pixel data retention state differs from line to line, the change in the data retention state of the entire screen is substantially minimized, and a high display quality in which flicker is further suppressed can be achieved.
[0095]
Next, a specific configuration example of the liquid crystal panel 2 of the liquid crystal display device 1 will be described.
[0096]
FIG. 4 shows a cross-sectional configuration of the liquid crystal panel 2. This figure corresponds to an AA cross-sectional view of FIG. The liquid crystal panel 2 is a reflective active matrix liquid crystal panel, and a liquid crystal layer 13 such as a nematic liquid crystal is sandwiched between two glass substrates 11 and 12, and TFTs 14 as active elements are formed on the glass substrate 12. It has a basic configuration. In this embodiment, a TFT is used as an active element, but an MIM (Metal Insulator Metal) or an FET other than a TFT can also be used. On the upper surface of the glass substrate 11, a phase difference plate 15, a polarizing plate 16, and an antireflection film 17 for controlling the state of incident light are provided in this order. On the lower surface of the glass substrate 11, an RGB color filter 18 and a transparent common electrode 19 as a counter electrode are provided in this order. The color filter 18 enables color display.
[0097]
In each TFT 14, a part of the scanning signal line provided on the glass substrate 12 is used as a gate electrode 20, and a gate insulating film 21 is formed thereon. An i-type amorphous silicon layer 22 is provided at a position facing the gate electrode 20 with the gate insulating film 21 interposed therebetween, and n channel so as to sandwich the channel region of the i-type amorphous silicon layer 22. ⁺ Two type amorphous silicon layers 23 are formed. One n ⁺ A data electrode 24 forming a part of a data signal line is formed on the upper surface of the type amorphous silicon layer 23, and the other n ⁺ A drain electrode 25 is formed extending from the upper surface of the type amorphous silicon layer 23 to the upper surface of the flat portion of the gate insulating film 21. One end of the drain electrode 25 opposite to the extraction start position is connected to a rectangular auxiliary capacitance electrode pad 27a facing the auxiliary capacitance wiring 33 as shown in FIG. An interlayer insulating film 26 is formed on the upper surface of the TFTs 14, and reflective electrodes 27 b are provided on the upper surface of the interlayer insulating film 26. The reflective electrodes 27b are reflective members for performing reflective display using ambient light. In order to control the direction of light reflected by the reflective electrodes 27b, fine irregularities are formed on the surface of the interlayer insulating film 26.
[0098]
Further, each reflective electrode 27 b is electrically connected to the drain electrode 25 through a contact hole 28 provided in the interlayer insulating film 26. That is, the voltage applied from the data electrode 24 and controlled by the TFT 14 is applied from the drain electrode 25 to the reflective electrode 27b through the contact hole 28, and the liquid crystal layer is applied by the voltage between the reflective electrode 27b and the transparent common electrode 19. 13 is driven. That is, the storage capacitor electrode pad 27 a and the reflective electrode 27 b are electrically connected to each other, and liquid crystal is interposed between the reflective electrode 27 b and the common transparent electrode 19. As described above, the auxiliary capacitor electrode pad 27 a and the reflective electrode 27 b constitute the pixel electrode 27. In the case of a transmissive liquid crystal display device, a transparent electrode arranged so as to correspond to each of the electrodes is a pixel electrode.
[0099]
Further, the liquid crystal panel 2 includes a scanning signal line 31 for supplying a scanning signal to the gate electrode 20 of the TFT 14 as shown in FIG. Data signal lines 32 for supplying data signals to the data electrodes 24 are provided on the glass substrate 12 so as to be orthogonal to each other. Further, auxiliary capacity wirings 33 as auxiliary capacity electrodes for forming auxiliary capacity of the pixels are provided between the auxiliary capacity electrode pads 27a. The auxiliary capacitance wirings 33 are located on the glass substrate 12 at positions other than the scanning signal lines 31 and are partially paired with the auxiliary capacitance electrode pads 27a with the gate insulating film 21 interposed therebetween. It is provided in parallel. Not only in this case, the auxiliary capacitance lines 33... Need only be provided avoiding the positions of the scanning signal lines 31. In the figure, the reflective electrodes 27b are partially omitted so as to clarify the positional relationship between the auxiliary capacitor electrode pads 27a and the auxiliary capacitor wires 33. Further, the irregularities on the surface of the interlayer insulating film 26 in FIG. 4 are not shown in FIG.
[0100]
An equivalent circuit for one pixel in the liquid crystal panel 2 having the above-described configuration is shown in FIGS. FIG. 5A shows a liquid crystal capacitance C formed by sandwiching the liquid crystal layer 13 between the transparent common electrode 19 and the reflective electrode 27b. _LC And the auxiliary capacitance C formed by sandwiching the gate insulating film 21 between the auxiliary capacitance electrode pad 27a and the auxiliary capacitance wiring 33. _CS Are connected to the TFT 14, and the transparent common electrode 19 and the auxiliary capacitance wiring 33 are equivalent circuits with a constant DC potential. FIG. 4B shows the liquid crystal capacitance C. _LC An alternating voltage Va is applied to the transparent common electrode 19 through a buffer, and the auxiliary capacitance C _CS This is an equivalent circuit in which an AC voltage Vb is applied to the auxiliary capacitance wiring 33 via a buffer. The AC voltage Va and the AC voltage Vb have the same voltage amplitude and the same phase. Therefore, in this case, the potential of the transparent common electrode 19 and the potential of the auxiliary capacitance wiring 33 vibrate in the same phase. In addition, as shown in FIG. _LC And auxiliary capacity C _CS May be connected in parallel, and a common AC voltage may be applied via a buffer instead of a constant DC potential.
[0101]
Next, a driving method in the case where the suspension period T2 is provided for the liquid crystal panel 2 having the above configuration will be described.
[0102]
6 (a) and 6 (b), a selection voltage is applied to the scanning signal line 31 to turn on the TFT 14, and the liquid crystal capacitance C from the data signal line 32 is turned on. _LC And auxiliary capacity C _CS A data signal is applied to each of them. Next, by applying a non-selection voltage to the scanning signal line 31 to turn off the TFT 14, the liquid crystal capacitance C _LC And auxiliary capacity C _CS The charge written in and is held. Here, as described above, the auxiliary capacitance C of the pixel _CS Since the auxiliary capacitor wiring 33 for forming the capacitor is provided so as to avoid the position of the scanning signal line 31, the capacitive coupling between the scanning signal line 31 and the auxiliary capacitor electrode pad 27a can be ignored in these equivalent circuits. . Accordingly, in this state, if the liquid crystal panel 2 is driven with the rest period T2 set by the control IC 5, unlike the case where the auxiliary capacitor is formed with the Cs on-gate structure, the pixel electrode 27 of the pixel electrode 27 due to the potential fluctuation of the scanning signal line in the previous stage is formed. No potential fluctuation occurs.
[0103]
By setting the pause period T2 to drive at a low frequency, the polarity inversion frequency of the data signal is reduced, and the power consumption of the data signal driver, in this case, the source driver 4 is sufficiently reduced. Further, by suppressing the potential fluctuation of the pixel electrode 27, it is possible to obtain a high display quality in which flickering is suppressed even when a long pause period T2 is set.
[0104]
6A, when a DC voltage is applied to the transparent common electrode 19 in the scanning period T1, the transparent common electrode 19 is set to the same potential as the transparent common electrode 19 in the scanning period T1 in the pause period T2. . Alternatively, when an AC voltage is applied to the transparent common electrode 19 during the scanning period T1 as shown in FIG. 5B, the transparent common electrode 19 is set to the potential at the amplitude center of the AC voltage during the rest period T2. In this way, by setting the potential of the transparent common electrode 19 as described above during the rest period T2, fluctuations in the potential of the pixel electrode 27 due to capacitive coupling between each pixel and the counter electrode are suppressed. Therefore, it is possible to achieve high display quality in which changes in the data holding state of the pixels are suppressed and flickering is suppressed.
[0105]
Next, a driving method based on the analysis result of the characteristics of the liquid crystal panel 2 with a diagonal size of 0.1 m, 240 scanning signal lines 31 and 320 data signal lines 320 × 3 will be described. FIG. 7 shows the results of measuring the non-scanning period dependence of the liquid crystal voltage holding ratio Hr for the liquid crystal (ZLI-4792 manufactured by Merck) used for the liquid crystal layer 13. As can be seen from the figure, the liquid crystal voltage holding ratio Hr gradually decreases greatly to 92% when the non-scanning period is 2 sec and 80% when 3 sec. When the non-scanning period is 3 sec, the pixel voltage holding ratio P, which will be described later, is 88%, and the pixel voltage holding ratio P is preferably 90% or more, so the non-scanning period is preferably 2 sec or less. If the non-scanning period is 16.7 msec or more, the non-scanning period becomes the pause period T2 for the scanning period of 16.7 msec of 60 Hz.
[0106]
Therefore, by setting the pause period T2 to 16.7 msec or more, the power consumption of the source driver 4 can be reduced as compared with the case of 60 Hz driving, and by setting it to 2 sec or less, the leakage current from the liquid crystal and the TFT 14 is reduced. Flickering due to fluctuations in the potential of the pixel electrode 27 is suppressed, and high display quality can be achieved. More preferably, the rest period T2 is set to 50 msec or more and 1 sec or less. By setting the pause period T2 to 50 msec or more, the power consumption of the source driver 4 can be greatly reduced, and by setting the pause period T2 to 1 sec or less, the leakage current from the liquid crystal and the TFT 14 causes a leakage current from the pixel electrode 27. Flickering due to potential fluctuation is greatly suppressed, and higher display quality can be achieved.
[0107]
FIG. 8 shows the result of measuring the relationship between the OFF resistance value of the TFT 14 and the potential of the gate electrode 20 of the TFT 14, that is, the potential of the scanning signal line 31. The OFF voltage of the TFT 14 is normally about −10V, and even if this fluctuates slightly, if the liquid crystal voltage holding ratio Hr and the OFF resistance value of the TFT 14 become insufficient, the liquid crystal capacitance C _LC And auxiliary capacity C _CS The charges written in and are remarkably leaked during the non-selection period of the TFT 14, and the potential of the pixel electrode 27 varies as shown in FIG. 9, and the reflected light intensity from the reflective electrode 27b varies. That is, flickering occurs.
[0108]
Therefore, during the rest period T2, the OFF resistance value of the TFT 14 is set to maximum A non-selection voltage is applied to all the scanning signal lines 31. This non-selection voltage is about −8V in FIG. In the rest period T2 in which all the scanning signal lines 31 are in the non-scanning state, the OFF resistance value of the TFT 14 is set. maximum Therefore, the potential fluctuation of the pixel electrode 27 due to the leakage current to the data signal line 32 is suppressed. As a result, even when the pixel potential differs for each scanning line, a change in the data holding state of the pixel is suppressed, and high display quality with reduced flickering can be achieved.
[0109]
In addition, by applying a non-selection voltage to all the scanning signal lines 31 in this way, a signal other than the gate start pulse signal GSP is delivered to the gate driver 3 and the source driver 4 as they are during the idle period T2, unlike the above. Even when the source driver 4 outputs a data signal to the data signal line of the liquid crystal panel 2, the potential of the pixel electrode 27 is held and the display does not change.
[0110]
Next, the pixel voltage holding ratio P related to the potential of the pixel electrode 27 and the intensity of reflected light from the reflective electrode 27b is
P = V ₁ Exp [-T / {(C _LC + C _CS R}] / V (2)
It is represented by However,
V ₁ = V- {V · (1-Hr (T)) × C _LC / (C _LC + C _CS )}
T: Non-selection period of TFT14
Hr (T): Liquid crystal voltage holding ratio after non-selection period T in FIG.
V: Potential difference between the pixel electrode 27 and the transparent common electrode 19 immediately after writing
R: OFF resistance value of TFT 14 in FIG.
It is. V ₁ Exp [-T / {(C _LC + C _CS ) · R}] is the potential difference between the pixel electrode 27 and the transparent common electrode 19 after time T from writing. Further, when the number of scanning signal lines is n, the scanning period is T1, and the non-scanning period is T0, the non-selection period T = (T1 + T0) −T1 / n.
[0111]
For example, the liquid crystal voltage holding ratio Hr (T) when T = 180 msec, the resistance value when the TFT 14 is not selected, that is, the OFF resistance value R, and the liquid crystal capacitance C _LC , And auxiliary capacity C _CS Is set as shown in Table 1, and the pixel voltage holding ratio P is calculated from the equation (2), it becomes 99.7%.
[0112]
[Table 1]

[0113]
Therefore, a detailed study was performed on the pixel voltage holding ratio P and the flicker perception limit. As shown in FIG. 10 (a), a flicker evaluation cell 41 was produced in which two glass substrates 42 with transparent electrodes 43 formed on the inside face each other and a liquid crystal layer 44 was sandwiched between the transparent electrodes 43 and 43. . A voltage was applied from the signal generator 45 between the two transparent electrodes 43 and 43 of the flicker evaluation cell 41. The voltage waveform output from the signal generator 45 is shown in FIG. In the drawing, Vs is 3 V, the non-selection period T is 167 msec, and Ve is changed. The flicker evaluation cell 41 is initially charged to a voltage of Vs, but the voltage gradually decreases to Ve. Next, when a voltage of −Vs is applied, the brightness of the flicker evaluation cell 41 changes. At this time, the brightness change, that is, flicker is visually confirmed.
[0114]
Here, Ve / Vs corresponds to the pixel voltage holding ratio P in the actual liquid crystal display device 1. When the pixel voltage holding ratio P and flicker occurrence were observed in detail, the results shown in Table 2 were obtained.
[0115]
[Table 2]

[0116]

It is.
[0117]
Thus, it can be seen that the pixel voltage holding ratio P ≧ 0.9 may be obtained in order to obtain the liquid crystal panel 2 that does not flicker even when the pause period T2 is provided.
[0118]
11A to 11E show the scanning signal waveform, the data signal waveform, the potential of the pixel electrode 27, and the reflected light intensity from the reflecting electrode 27b when the liquid crystal display device 1 having the above configuration is driven at a low frequency. Shown in The scanning period T1 was 16.7 msec, and the rest period T2 was 167 msec. In the odd-numbered image writing, the odd-numbered scanning signal lines (G ₁ , G _Three ,..., The data signal lines 32... Are positive and the even-numbered scanning signal lines (G ₂ , G _Four ,...) Has a negative polarity in the data signal lines 32, and vice versa for even-numbered image writing. By doing so, the polarity can be inverted in the scanning line direction, and an AC signal whose polarity is inverted every time is input to each pixel.
[0119]
FIG. 4A shows the scanning signal waveform output to the scanning signal line 31 preceding the scanning signal line 31 of the pixel of interest, and FIG. 4B shows the scanning of the pixel of interest (own stage). The scanning signal waveform output to the signal line 31, FIG. 6C shows the data signal waveform output to the data signal line 32 of the pixel of interest, and FIG. 4D shows the pixel of the pixel of interest. The potential of the electrode 27 is shown. As can be seen from FIGS. 9A and 9D, when the selection voltage is applied to the preceding scanning signal line 31, the potential of the pixel electrode 27 is stable. At this time, when the intensity of the reflected light from the reflective electrode 27b was measured, almost no change in the reflected light intensity was confirmed as shown in FIG. In addition, it was confirmed that a uniform and good display quality can be obtained with no flickering as a result of visual evaluation.
[0120]
On the other hand, as shown in FIG. 12, in the conventional Cs on-gate structure in which the auxiliary capacitor electrode pads 27a ′ are made to face the scanning signal lines 31 ′ in the preceding stage to form the auxiliary capacitors, FIGS. The result of e) was obtained. As can be seen from FIGS. 4A and 4D, when the selection voltage is applied to the scanning signal line 31 ′ on one line, the potential of the pixel electrode 27 ′ fluctuates greatly. As a result, the intensity of the reflected light from the reflective electrode 27b ′ also fluctuated as shown in FIG. 9E, and flicker was perceived even as a result of visual evaluation.
[0121]
Further, when the power consumption of the liquid crystal display device 1 was measured, it was 160 mW when the driving was performed without providing the pause period T2, whereas it was 40 mW when the driving was performed with the pause period T2. Thus, it was confirmed that it was greatly reduced. Furthermore, when the non-scanning period was set as the vertical blanking period and switching was performed so that the image was rewritten repeatedly at 16.7 msec, it was possible to display a normal moving image with the image changing every moment.
[0122]
As described above, according to the liquid crystal display device 1, it is possible to achieve low power consumption while maintaining good display quality in a configuration having active elements. Further, since the liquid crystal display device 1 is a reflection type liquid crystal display device that includes the reflective electrodes 27b and does not require a backlight, the liquid crystal display device has a large ratio of low power consumption by driving at 30 Hz or less. The same applies to a reflective liquid crystal display device in which a reflective member is provided on the back surface of the liquid crystal panel.
[0123]
Next, as a liquid crystal display device, the liquid crystal panel 2 in the liquid crystal display device 1 described with reference to FIGS. 4 and 5 is replaced with a liquid crystal panel 51 shown in FIGS. It is a liquid crystal display device. As shown in FIG. 14 which is a BB cross-sectional view of FIG. 15, in the liquid crystal panel 51, the antireflection film 17 and the color filter 18 of the liquid crystal panel 2 are omitted. The polarizing plate 16 is provided in this order. Further, a backlight 52 is provided below the backlight 52. Further, the auxiliary capacitor electrode pad 54a is formed of a transparent electrode such as ITO, and the interlayer insulating film 26 and the reflective electrode 54b have no fine irregularities.
[0124]
Further, a light transmission hole 53 penetrating the interlayer insulating film 26 is provided in a part of the reflective electrode 54b... Above the auxiliary capacitance electrode pad 54a. This light transmission hole 53 is a transmission region of light from the backlight 52. The reflective region where the light is reflected by the reflective electrodes 27b and the transmissive region are electrically connected through the contact hole 28 and have the same potential, and the liquid crystal layer 13 can be driven. When the liquid crystal panel 51 performs display in the polarization mode, it is necessary to match the phase difference between the reflective region and the transmissive region, and thus the thickness d of the liquid crystal layer 13 in the transmissive region. _T , And the thickness d of the liquid crystal layer 13 in the reflective region _R Is d _T ≒ 2d _R Is desirable.
[0125]
FIG. 15 shows a view of the portion below the liquid crystal layer 13 of FIG. 14 as viewed from above. The auxiliary capacitor electrode pad 54 a and the reflective electrode 54 b are combined to form a pixel electrode 54. Each auxiliary capacitor electrode pad 54a includes an auxiliary capacitor line 33 and an auxiliary capacitor C. _CS It is formed in a wide range around the TFT 14 while forming. A rectangular light transmission hole 53 is provided in the reflective electrode 54 b and the interlayer insulating film 26 at a position above the auxiliary capacitance electrode pad 54 a and avoiding the upper side of the scanning signal line 31 and the auxiliary capacitance wiring 33. It has been.
[0126]
In the liquid crystal panel 51 having the above configuration, in addition to the effects obtained by the liquid crystal display device 1 described above, the reflective type is used when there is a lot of ambient light, and the backlight 52 is turned on when the ambient light is low. Can be used. In the liquid crystal panel 2, the same effect can be obtained even if the reflecting plate is made translucent.
[0127]
The display device driving method and the display device using the display device according to the present embodiment have been described above. However, the display device is not limited to an active matrix liquid crystal display device, and a simple multiplex liquid crystal display device, EL (Electro Luminescence), or the like. ) A display device, PDP (Plasma Display Panel), giricon, etc. may be used. The display device can be mounted on a mobile phone, a pocket game machine, a PDA (Personal Digital Assistants), a mobile TV, a remote control, a notebook personal computer, and other mobile terminals. These portable devices are often driven by a battery, and are equipped with a display device capable of reducing power consumption while maintaining good display quality, thereby facilitating long-time driving.
[0128]
【The invention's effect】
As described above, the driving method of the display device of the present invention is a non-scanning period longer than the scanning period for scanning the screen once, and provides a pause period in which all scanning signal lines are in a non-scanning state. The sum of the period and the pause period is one vertical period.
[0129]
Therefore, since there is a pause period longer than the scanning period, the vertical frequency becomes a low frequency. Therefore, in a matrix type display device that can ensure basic display quality such as brightness, contrast, response speed, and gradation, a data signal line driver that increases in direct proportion to the data signal supply frequency. The power consumption can be easily and significantly reduced without sacrificing the display quality.
[0130]
As described above, a driving method of a matrix type display device that can easily achieve sufficient power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation is provided. There is an effect that can be done.
[0131]
Furthermore, the display device driving method of the present invention is configured to set the non-scanning period including the pause period from a plurality of types as described above.
[0132]
Therefore, the cycle of rewriting the screen can be changed according to the type of display image such as a still image or a moving image. As a result, there is an effect that it is possible to achieve optimum power consumption reduction for each type of display image.
[0133]
Furthermore, as described above, the driving method of the display device of the present invention is such that when the scanning period is T1, the shortest of the plurality of non-scanning periods is T01, and any one other than T01 is T02.
(T1 + T02) = (T1 + T01) × N (N is an integer of 2 or more)
It is the structure made into this relationship.
[0134]
Therefore, the reference synchronization signal can be used in common for each non-scanning period, and a low frequency drive can be achieved by adding a simple circuit, and the newly generated power consumption is extremely reduced. There is an effect that can be.
[0135]
Furthermore, as described above, the display device driving method according to the present invention is configured such that, when the display device has image data storage means for storing image data as a basis of the data signal, the image is displayed during the pause period. In this configuration, the transfer of the image data from the data storage means is stopped.
[0136]
Therefore, it is possible to reduce power consumption for image data transfer during the suspension period. As a result, the power consumption of the entire display device can be further reduced.
[0137]
Further, the display device driving method according to the present invention provides the image data supply means in the pause period when there is image data supply means for supplying the display device with the image data as the basis of the data signal as described above. The display device is configured to stop the operation of accepting the supply of the image data from the display device.
[0138]
Therefore, since the display device stops the operation of accepting the supply of image data from the image data supply means during the suspension period, it is possible to reduce the power consumption for accepting the supply of image data during the suspension period. As a result, the power consumption of the entire display device can be further reduced.
[0139]
Further, as described above, the display device driving method of the present invention is configured to stop the operation of the analog circuit unrelated to display during the pause period.
[0140]
Therefore, it is possible to reduce the power consumption of the circuit that constantly consumes the power, and it is possible to further reduce the power consumption of the entire display device.
[0141]
Further, as described above, the driving method of the display device of the present invention is characterized in that the operation of at least the analog circuit of the driver of the data signal line is stopped during the pause period.
[0142]
Therefore, since the operation of the analog circuit with the largest power consumption is stopped at least during the suspension period, the power consumption of the entire display device can be efficiently reduced.
[0143]
Furthermore, as described above, the driving method of the display device of the present invention is configured such that all the data signal lines are in a high impedance state with respect to the data signal driver that drives all the data signal lines during the pause period.
[0144]
Therefore, the potential of each data signal line can be kept constant during the pause period. Accordingly, in a liquid crystal display device having a pixel electrode connected to the data signal line, a change in the data holding state of each pixel caused by a fluctuation in the potential of the data signal line is suppressed, and flickering of the screen is sufficiently suppressed. As a result, there is an effect that it is possible to provide a driving method for a matrix type display device capable of achieving both a sufficiently low power consumption and a high display quality in which flicker is sufficiently suppressed.
[0145]
Furthermore, as described above, the driving method of the display device of the present invention is configured to stop the operation of the analog circuit unrelated to display after all the data signal lines are set in a high impedance state during the pause period.
[0146]
Therefore, it can be avoided that the data signal line becomes the ground potential through the analog circuit during the idle period. Therefore, while reducing the power consumption of the analog circuit, it is possible to suppress a change in the data holding state of the pixel and achieve a high display quality in which flicker is further suppressed.
[0147]
Further, as described above, the driving method of the display device of the present invention is configured to stop the operation of at least the analog circuit of the driver of the data signal line during the pause period.
[0148]
Therefore, since the operation of the analog circuit with the largest power consumption is stopped at least during the suspension period, the power consumption of the entire display device can be efficiently reduced.
[0149]
Furthermore, as described above, the driving method of the display device according to the present invention averages all the data signal lines with the change in the data holding state of all the pixels before setting all the data signal lines to the high impedance state. minimum The potential is such that
[0150]
Therefore, even when the pixel data retention state differs from line to line, the change in the data retention state of the entire screen is substantially minimized, and a high display quality with further reduced flickering can be achieved.
[0151]
In addition, as described above, the display device of the present invention has a control unit that executes the method for driving the display device according to the predetermined invention.
[0152]
Therefore, it is possible to provide a matrix display device that can easily achieve sufficient power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation. There is an effect that can be done.
[0153]
In addition, as described above, the display device of the present invention has a control unit that executes the method for driving the display device according to the predetermined invention.
[0154]
Therefore, there is an effect that it is possible to provide a matrix type display device that can achieve both a sufficiently low power consumption and a high display quality in which flicker is sufficiently suppressed.
[0155]
Furthermore, in the display device driving method of the present invention, as described above, the display device is supplied with a scanning signal line from a scanning signal line to a capacitance formed by interposing a liquid crystal between a pixel electrode and a counter electrode. A liquid crystal display device having a liquid crystal display element in which pixels in which charges based on a data signal supplied from a data signal line are periodically written via an active element selected by a signal are arranged in a matrix It is.
[0156]
Therefore, a driving method of an active matrix type liquid crystal display device which can easily achieve sufficiently low power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation. There is an effect that can be provided.
[0157]
Furthermore, in the display device driving method of the present invention, as described above, the display device is supplied with a scanning signal line from a scanning signal line to a capacitance formed by interposing a liquid crystal between a pixel electrode and a counter electrode. A liquid crystal display device having a liquid crystal display element in which pixels in which charges based on a data signal supplied from a data signal line are periodically written via an active element selected by a signal are arranged in a matrix It is.
[0158]
Therefore, there is an effect that it is possible to provide a driving method of an active matrix display device that can achieve both low power consumption and high display quality with sufficiently reduced flickering.
[0159]
Further, as described above, the driving method of the display device according to the present invention is the same as that of the counter electrode in the scanning period when the counter electrode is applied during the pause period and a DC voltage is applied to the counter electrode during the scanning period. In the case where an AC voltage is applied to the counter electrode during the scanning period, a potential at the amplitude center of the AC voltage is used.
[0160]
Therefore, the potential fluctuation of the pixel electrode due to capacitive coupling between each pixel and the counter electrode is suppressed during the pause period. Therefore, it is possible to achieve a high display quality in which changes in the data holding state of the pixels are suppressed and flickering is suppressed.
[0161]
Furthermore, in the display device driving method of the present invention, as described above, the OFF resistance value of the active element is set during the idle period. maximum The non-selection voltage is applied to all scanning signal lines.
[0162]
Therefore, the potential fluctuation of the pixel electrode due to the leakage current to the data signal line is suppressed during the pause period. Thereby, even when the potential of the pixel is different for each scanning line, the change in the data holding state of the pixel is suppressed, and an effect of achieving high display quality in which flickering is suppressed can be achieved.
[0163]
Furthermore, the driving method of the display device of the present invention has a configuration in which the pause period is 16.7 msec or more and 2 sec or less as described above.
[0164]
Therefore, the power consumption of the data signal line driver can be reduced by setting the pause period to 16.7 msec or more, which corresponds to the 60 Hz scanning period or more, and by setting the pause period to 2 sec or less, Flickering due to fluctuations in the potential of the pixel electrode due to leakage current is suppressed, and an effect is achieved that high display quality can be achieved.
[0165]
Furthermore, the display device driving method of the present invention has a configuration in which the pause period is set to 50 msec to 1 sec as described above.
[0166]
Therefore, the power consumption of the data signal line driver can be significantly reduced by setting the pause period to 50 msec or more, and by setting the pause period to 1 sec or less, the potential of the pixel electrode is reduced by the leakage current from the liquid crystal and the active element. Flickering due to fluctuation is greatly suppressed, and an effect is achieved that higher display quality can be achieved.
[0167]
Furthermore, as described above, the display device of the present invention is configured to have a control means for executing the method for driving the display device according to the predetermined invention.
[0168]
Therefore, an active matrix liquid crystal display device that can easily achieve sufficient power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation is provided. There is an effect that can be.
[0169]
Furthermore, as described above, the display device of the present invention has a control unit that executes the method for driving the display device according to the predetermined invention.
[0170]
Therefore, it is possible to provide an active matrix type liquid crystal display device capable of achieving both a sufficiently low power consumption and a high display quality in which flicker is sufficiently suppressed.
[0171]
Further, as described above, in the display device of the present invention, the liquid crystal display element is provided with the auxiliary capacitance electrode that forms the auxiliary capacitance of the pixel with the pixel electrode, avoiding the position of the scanning signal line. It is the composition which is.
[0172]
Therefore, the capacitive coupling between the scanning signal line and the pixel electrode can be ignored. In this state, if the liquid crystal display element is driven by setting the pause period by the control means, the auxiliary capacitance is formed with the Cs on-gate structure. Unlike the above case, the potential fluctuation of the pixel electrode due to the potential fluctuation of the scanning signal line on one line does not occur. Thereby, there is an effect that it is possible to obtain a high display quality in which flickering is suppressed even when a long rest period is set.
[0173]
Furthermore, as described above, the display device according to the present invention has a pixel voltage holding ratio of the liquid crystal display element, and an electric capacity between the pixel electrode and the counter electrode. _LC , The auxiliary capacity is C _CS T is the non-selection period of the active element, Hr (T) is the liquid crystal voltage holding ratio after the non-selection period T3 at the rewrite frequency, V is the potential difference between the pixel electrode and the counter electrode immediately after writing, and the active element The resistance value when R is not selected is R, V ₁ = V- {V · (1-Hr (T)) × C _LC / (C _LC + C _CS )}
P = V ₁ Exp [-T / {(C _LC + C _CS ) ・ R}] / V
This is a configuration in which P ≧ 0.9.
[0174]
Therefore, if the number of scanning signal lines is n, the scanning period is T1, and the non-scanning period is T0, the non-selection period T = (T1 + T0) −T1 / n is obtained. Even if it is set, the voltage of the pixel applied from the data signal line during the selection period is held at a voltage holding ratio of 90% or more throughout the non-selection period T. Therefore, the potential fluctuation of the pixel electrode hardly occurs in the non-selection period T. Thereby, there is an effect that a stable display quality without flickering can be obtained even if a long rest period is set.
[0175]
Furthermore, as described above, the display device of the present invention has a configuration in which the liquid crystal display element includes a reflective member that performs reflective display using ambient light.
[0176]
Therefore, since the reflective liquid crystal display device does not require a backlight, there is an effect that the ratio of power consumption reduction by driving with a set rest period is increased.
[0177]
Furthermore, as described above, the liquid crystal display device of the present invention has a configuration in which the reflecting member is at least a part of the pixel electrode.
[0178]
Therefore, since at least a part of the pixel electrode serves as a reflective electrode of the reflective liquid crystal display device, there is no need for a separate reflective member, and there is an effect that the types of members constituting the device can be reduced.
[0179]
Furthermore, as described above, the display device of the present invention has a configuration in which a hole for light transmission is provided in the reflection member, or the reflection member is translucent.
[0180]
Therefore, the reflection / transmission liquid crystal display device can be used as a reflection type when there is a lot of ambient light, and can be used in combination with a transmission type such as turning on a backlight when there is little ambient light. .
[0181]
Further, as described above, the portable device of the present invention has a configuration in which the display device according to the predetermined invention is mounted.
[0182]
Therefore, it is possible to provide a portable device that can easily achieve sufficient power consumption while satisfying basic display quality such as brightness, contrast, response speed, and gradation, and a battery. There is an effect that it is easy to drive for a long time.
[0183]
Further, as described above, the portable device of the present invention has a configuration in which the display device according to the predetermined invention is mounted.
[0184]
Therefore, it is possible to provide a portable device that can achieve both a sufficiently low power consumption and a high display quality in which flicker is sufficiently suppressed, and an effect of facilitating long-time driving by a battery is achieved.
[Brief description of the drawings]
FIG. 1 is a timing chart illustrating a method for driving a display device according to an embodiment of the present invention.
2 is a system block diagram illustrating a configuration of a display device to which the display device driving method of FIG. 1 is applied. FIG.
3 is a circuit diagram showing an internal configuration of a data signal driver of the display device of FIG. 2;
4 is a cross-sectional view showing a configuration of a liquid crystal panel of the display device of FIG.
5 is a perspective plan view showing a configuration of a liquid crystal panel of the display device of FIG. 2. FIG.
6A and 6B are circuit diagrams showing an equivalent circuit of FIG.
FIG. 7 is a graph showing characteristics of liquid crystal.
FIG. 8 is a graph showing characteristics of TFT OFF resistance.
FIG. 9 is an explanatory diagram for explaining a change in pixel electrode potential and a change in reflected light intensity when a sufficient charge cannot be held.
FIGS. 10A and 10B are explanatory diagrams illustrating a method for evaluating the characteristics of a liquid crystal panel. FIGS.
11A to 11E are timing charts showing signals and characteristics of the liquid crystal panel of FIG.
12 is a plan perspective view showing a configuration of a comparative example of the liquid crystal panel of FIG. 5. FIG.
FIGS. 13A to 13E are timing charts showing signals and characteristics of the liquid crystal panel of FIG.
14 is a cross-sectional view showing a configuration of a modified example of the liquid crystal panel of FIG.
FIG. 15 is a plan perspective view showing a configuration of a modification of the liquid crystal panel of FIG. 4;
FIG. 16 is a block diagram illustrating a configuration of a matrix display device.
FIG. 17 is a timing chart illustrating a method for driving a conventional display device.
FIG. 18 is an explanatory diagram for explaining a vertical blanking period.
[Explanation of symbols]
1 Liquid crystal display device (display device)
2 Liquid crystal panel (liquid crystal display element)
3 Gate driver
4 Source driver (data signal line driver)
5 Control IC (control means)
6 Image memory (image data storage means)
7 GSP conversion circuit
13 Liquid crystal layer (liquid crystal)
14 TFT (active element)
19 Transparent common electrode (counter electrode)
27 Pixel electrode
27a Auxiliary capacitor electrode pad
27b Reflective electrode
31 Scanning signal line
32 Data signal line
33 Auxiliary capacitance wiring (auxiliary capacitance electrode)
51 Liquid crystal panel (Liquid crystal display element)
53 Light transmission hole (hole for light transmission)
54 Pixel electrode
54a Auxiliary Capacitor Electrode Pad
54b Reflective electrode
C _CL Liquid crystal capacity (electric capacity)
C _CS Auxiliary capacity
T non-selection period
T1 scanning period
T2 suspension period

Claims (20)

A display in which each line of a screen in which pixels are arranged in a matrix is selected and scanned sequentially by a plurality of scanning signal lines, and data signals are supplied from the data signal lines to the pixels of the selected lines for display. In the driving method of the apparatus,
A non-scanning period longer than a scanning period for scanning the screen once, and a pause period in which all scanning signal lines are in a non-scanning state is provided, and a sum of the scanning period and the pause period is defined as one vertical period,
In the pause period, all the data signal lines are set to a high impedance state with respect to the data signal driver that drives all the data signal lines ,
A driving method of a display device, characterized in that, before setting all data signal lines to a high impedance state, all the data signal lines are set to a potential at which a change in a data holding state of all pixels is averaged to be a minimum .   2. The display device driving method according to claim 1, wherein a non-scanning period including the pause period is set from a plurality of types. When the scanning period is T1, the shortest of the plurality of non-scanning periods is T01, and any one other than T01 is T02,
(T1 + T02) = (T1 + T01) × N (N is an integer of 2 or more)
The display device driving method according to claim 2, wherein:   When the display device has image data storage means for storing image data as a basis of the data signal, the transfer of the image data from the image data storage means is stopped during the pause period. A method for driving a display device according to claim 1.   When there is image data supply means for supplying image data that is the basis of the data signal to the display device, the operation for accepting the supply of the image data from the image data supply means is stopped in the display device during the pause period. The display device driving method according to claim 1, wherein the display device driving method is performed.   6. The drive of a display device according to claim 1, wherein after all the data signal lines are set in a high impedance state during the pause period, the operation of the analog circuit unrelated to display is stopped. Method.   7. The method of driving a display device according to claim 6, wherein the operation of at least the analog circuit of the driver of the data signal line is stopped during the pause period. 8. A display device comprising control means for executing the method for driving the display device according to claim 1 . From the data signal line through the active element selected by the scanning signal supplied from the scanning signal line to the capacitance formed by interposing the liquid crystal between the pixel electrode and the counter electrode in the display device. 8. A display according to claim 1, which is a liquid crystal display device having a liquid crystal display element in which pixels in which charges based on a supplied data signal are periodically written are arranged in a matrix. Device driving method. When the counter electrode is applied to the counter electrode during the pause period and a DC voltage is applied to the counter electrode during the scan period, the counter electrode is set to the same potential as the counter electrode during the scan period, and an AC voltage is applied to the counter electrode during the scan period. The display device driving method according to claim 9 , wherein in this case, a potential at the center of amplitude of the AC voltage is used. 11. The method for driving a display device according to claim 9 , wherein a non-selection voltage that maximizes an OFF resistance value of the active element is applied to all scanning signal lines during the idle period. 12. The display device driving method according to claim 9, wherein the pause period is 16.7 msec or more and 2 sec or less. 13. The display device driving method according to claim 12 , wherein the pause period is 50 msec or more and 1 sec or less. 14. A display device comprising control means for executing the method for driving the display device according to claim 9 . 15. The liquid crystal display element according to claim 14 , wherein an auxiliary capacitance electrode that forms an auxiliary capacitance of the pixel with the pixel electrode is provided avoiding the position of the scanning signal line. Display device. The pixel voltage holding ratio of the liquid crystal display element is defined as follows: the capacitance between the pixel electrode and the counter electrode is CLC, the auxiliary capacitance is CCS, the non-selection period of the active element is T, and the non-selection period at the rewrite frequency The liquid crystal voltage holding ratio after completion of T is Hr (T), the potential difference between the pixel electrode and the counter electrode immediately after writing is V, the resistance value when the active element is not selected is R, and V ₁ = V− {V・ (1-Hr (T)) × C _LC / (C _LC + C _CS )}
P = V ₁ · exp [−T / {(C _LC + C _CS ) · R}] / V
The display device according to claim 15 , wherein P ≧ 0.9. The display device according to claim 14 , wherein the liquid crystal display element includes a reflective member that performs reflective display using ambient light. The display device according to claim 17 , wherein the reflecting member is at least a part of the pixel electrode. The display device according to claim 17 or 18 , wherein the reflecting member is provided with a light transmitting hole, or the reflecting member is translucent. A portable device comprising the display device according to any one of claims 8, 14, 15, 16, 17, 18, and 19 .

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