JP3817012B2

JP3817012B2 - Liquid crystal display device with coordinate detection function and drive circuit thereof

Info

Publication number: JP3817012B2
Application number: JP7155297A
Authority: JP
Inventors: 正三藤原; 武志奥野; 圭介津田; 智浅田
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1997-03-25
Filing date: 1997-03-25
Publication date: 2006-08-30
Anticipated expiration: 2017-03-25
Also published as: JPH10269020A

Description

【０００１】
【発明の属する技術分野】
本発明は、座標入力を行うタブレットをマトリクス型ディスプレイと一体化した座標検出機能付液晶表示装置とその駆動回路に関するものである。
【０００２】
【従来の技術】
従来のこの種の座標検出機能付液晶表示装置は、図11に示すブロック図のように構成されている。図11において、１は液晶パネル、２は検出用ペン、３は走査電極駆動回路、４は信号電極駆動回路、５は検出部、６は制御部、Ｒ(１〜m)は走査電極、Ｓ(１〜n)は信号電極である。また、図12は座標検出の原理とそのタイミングを示す図で、２は検出用ペン、ｒ１〜ｒ10，Ｓ１は液晶パネルの各電極、Ｃ１〜Ｃ10(Ｃａ)は検出用ペン２と電極ｒ１〜ｒ10(Ｓ１)の間に生じた静電容量結合、Ｐ１〜Ｐ７は検出走査パルス、Ｄ１は検出信号波形、Ｄ２は検出信号波形Ｄ１の微分波形である。
【０００３】
従来、液晶パネルの各電極をそのまま用いて座標検出を行う座標検出機能付液晶表示装置にあっては、１垂直走査期間(１フレーム)中に表示期間と検出期間とを設けて、液晶パネルの各走査電極，信号電極に対し順次検出走査パルスの印加を行うと、液晶パネルに近接した検出用ペン２と液晶パネルの電極間に生じた静電容量結合を介して、検出用ペン２に検出走査パルスによる検出信号波形Ｄ１が検出され、その検出タイミングからその座標位置を決定している。
【０００４】
さらに、図13は図11に示す座標検出機能付液晶表示装置における座標検出の各信号のタイミングチャートである。図13において、Ｖpは検出用ペン２に検出された検出信号波形、dＶp／dtは検出信号波形Ｖpの微分波形である。図13に示す検出信号波形Ｖpがピークに達した時間、あるいは微分波形dＶp／dtが０になった時間等から、検出用ペン２の位置を判別する。
【０００５】
前述した座標検出機能付液晶表示装置は主に単純マトリクス型液晶表示装置で実現する方法を説明したものである。最近ではアクティブマトリクス型液晶表示装置を用いて実現する方法も考案されている。アクティブマトリクス型液晶表示装置で実現する場合においても基本的な原理は単純マトリクス型液晶表示装置と同様である。しかし、従来のアクティブマトリクス型液晶表示装置の液晶パネルの場合には構造上の制約がある。以下、アクティブマトリクス型の液晶表示装置の液晶パネルを用いた場合の実現方法を説明する。
【０００６】
動作期間は単純マトリクス型表示装置の液晶パネルの場合と同様で、１フレームが表示期間と検出期間に分かれ、表示期間には表示動作を検出期間には検出動作を行う。さらに、検出期間ではＸ座標(行方向)検出期間とＹ座標(列方向)検出期間に分け、走査電極および信号電極に順次検出走査パルスを印加する。検出走査パルスが印加された各電極と検出用ペンの間の容量を介して信号を検出し、その信号の検出タイミングによってＸ、Ｙの座標値を決定する。ただし、一般的に従来のアクティブマトリクス型液晶表示装置の液晶パネルには以下の制約がある。
【０００７】
図14は従来のアクティブマトリクス型液晶表示装置の液晶パネルの構造を示す図である。図14に示すようにマトリクス状に配置された信号電極Ｓと走査電極Ｒの各交点に対応してスイッチング素子(ＴＦＴ)７と、スイッチング素子７に接続された画素電極Ｈが配置されるアレイ基板８があり。さらにアレイ基板８に対向して配置された対向基板９には、対向電極Ｃが一般的にはベタの電極として配置される。この液晶パネルは、表面には対向基板９、裏面にはアレイ基板８を配置するという構造をとる。このような配置であると、対向電極Ｃが走査電極Ｒや信号電極Ｓからの信号をシールドすることになるために、検出用ペンで検出信号を充分に得ることができない。また、充分な検出信号を得るためにアレイ基板８の面を表にすると、スイッチング素子７や走査電極Ｒ、信号電極Ｓの反射がある。これを防ぐためには各電極の配線やスイッチング素子７に反射防止用のブラックマトリクス層を設ける必要がある。
【０００８】
【発明が解決しようとする課題】
このように座標検出機能付液晶表示装置に用いられるアクティブマトリクス型液晶表示装置の液晶パネルでは構造上、液晶パネルの各電極からの信号が対向電極によってシールドされることで、微弱になり検出用ペンで検出することが困難であるという問題があった。また、液晶パネルのアレイ面を表側にしても各電極の配線やスイッチング素子の反射、あるいはその反射を防止するためにブラックマトリクス層を設けなければならないという問題があった。
【０００９】
本発明は、前記従来技術の問題点を解決することに指向するものであり、横電界方式のアクティブマトリクス型液晶表示装置の液晶パネルを採用し、対向電極によるシールド効果を軽減することにより、より精度の高い座標検出を行うことができる座標検出機能付液晶表示装置とその駆動回路を提供することを目的とする。
【００１０】
【課題を解決するための手段】
この目的を達成するために、本発明に係る座標検出機能付液晶表示装置は、マトリクス状に配置された複数の信号電極と走査電極およびその各交点に対応して設けられたスイッチング素子、スイッチング素子に接続された櫛形状の画素電極、および画素電極と咬合して形成され、各走査電極と平行な対向電極配線に接続された対向電極を有するアレイ基板と、アレイ基板に対向して配置された対向基板と、アレイ基板と対向基板に狭持された液晶層から成るアクティブマトリクス型の液晶パネルと、液晶パネルに有する走査電極，信号電極，対向電極に電圧を印加する各駆動手段と、液晶パネルに近接させたときに走査電極および信号電極との間に生じる静電容量結合を介して信号を検出する検出用導体と、検出用導体を通じて検出された信号から、検出用導体の位置を検出する検出手段を備えたことを特徴とする。
【００１１】
また、液晶パネルに近接させたときに対向電極および信号電極との間に生じる静電容量結合を介して信号を検出する検出用導体を備えたことを特徴とする。
【００１２】
また、前記座標検出機能付液晶表示装置の駆動回路には、表示期間に表示選択パルスを印加する走査電極を指定するための選択信号を、検出期間に検出走査パルスを印加する走査電極を指定するための選択信号を順次シフトして出力するシフトレジスタと、シフトレジスタの出力に応じて指定された電圧を選択し、走査電極に印加する選択手段を備えたことを特徴とする。
【００１３】
また、前記シフトレジスタは、検出期間に検出走査パルスを印加する前記対向電極配線を指定するための選択信号を順次シフトして出力し、前記選択手段は、シフトレジスタの出力に応じて指定された電圧を選択し、対向電極配線に印加することを特徴とする。
【００１４】
また、前記シフトレジスタは、表示期間に表示選択パルスを印加する走査電極を指定するための選択信号を順次シフトし、検出期間に検出走査パルスを印加する対向電極配線を指定するための選択信号を順次シフトして出力し、前記選択手段は、表示期間にシフトレジスタの出力に応じて指定された電圧を選択して走査電極に印加し、検出期間にシフトレジスタの出力に応じて指定された電圧を選択して対向電極配線に印加するように構成したものである。
【００１５】
前記構成における本発明の請求項１の記載によれば、液晶パネルのアレイ基板上に対向電極を設けたことで、検出用導体と液晶パネル間の対向電極によるシールド効果を軽減することができる。
【００１６】
また、本発明の請求項２の記載によれば、対向電極がアレイ基板の画素部分に配置されることから、検出用導体との静電容量結合において走査電極より大きな容量の対向電極を用いて、対向電極に検出走査パルスを走査させることで、より高い精度で検出することができる。
【００１７】
また、本発明の請求項３の記載によれば、検出走査パルスの電圧値をスイッチング素子が導通状態にならない値とすることで、画素電極に関係ない信号が印加されることを防ぐことができる。
【００１８】
また、本発明の請求項４または５の記載によれば、検出走査パルスの極性を１垂直走査期間毎に反転させることにより、印加される信号を交流化させることができる。
【００１９】
また、本発明の請求項６の記載によれば、表示期間と検出期間において走査電極に印加される各電圧を選択することができる。
【００２０】
また、本発明の請求項７の記載によれば、検出期間にのみ検出走査パルスを対向電極に印加することができる。
【００２１】
また、本発明の請求項８の記載によれば、表示期間に表示選択パルスを印加する走査電極を指定するシフトレジスタを検出期間に検出走査パルスを印加する対向電極配線を指定するシフトレジスタとしても使用できる。
【００２２】
また、本発明の請求項９または10の記載によれば、検出走査パルスの極性を１垂直走査期間毎に反転させることにより、印加される信号を交流化させることができる。
【００２３】
【発明の実施の形態】
以下、図面を参照して本発明における実施の形態を詳細に説明する。
図１は本発明の実施の形態における座標検出機能付液晶表示装置の液晶パネルに用いられるアレイ基板の各電極のパターン構成を示す部分平面図である。ここで、前記従来例を示す図14において説明した構成部材に対応し実質的に同等の機能を有するものには同一の符号を付してこれを示す。図１において、７はスイッチング素子(ＴＦＴ)、Ｇは走査電極、Ｓは信号電極、Ｃは対向電極、Ｃ′は対向電極Ｃが接続される対向電極配線、Ｈは画素電極である。このように構成されるアレイ基板において、表示期間には、走査電極ＧにＴＦＴ７を導通状態にする表示選択パルスが印加されると、ＴＦＴ７を通じて信号電極Ｓに印加された画像信号が画素電極Ｈに印加される。画素電極Ｈと対向電極Ｃとの電位差に応じて、液晶分子の配向状態が変化して画面の表示が行われる。
【００２４】
図２は本発明の実施の形態１における座標検出機能付液晶表示装置の概略構成を示すブロック図である。ここでも、前記従来例の図11で説明した構成部材に対応するものには同一の符号を付して、さらに以下の各図においても同様とする。図２において、１は図１に示すアレイ基板を有する液晶パネル、２は検出用導体である検出用ペン、４は信号電極駆動回路、５は検出用ペン２からの検出信号の変化を検出する検出部、６は検出部５や各駆動回路を制御する制御部、10は走査電極駆動回路、11は対向電極駆動回路、Ｇ(１〜m)は走査電極、Ｓ(１〜n)は信号電極、Ｃ(１〜m)は対向電極である。
【００２５】
また、図３は本実施の形態１における座標検出機能付液晶表示装置の座標検出の各信号を示すタイミングチャートである。図３に示すように１フレームには表示動作を行う表示期間と検出動作を行う検出期間とを設けている。さらに、図４は本実施の形態１における座標検出機能付液晶表示装置に使用する走査電極駆動回路の構成を示すブロック図である。図４において、12は表示選択パルスを印加する走査電極Ｇを指定する選択信号を順次シフトするシフトレジスタ、13は選択手段であるスイッチング回路、ＳＷ１は表示選択パルスの表示期間と検出期間とで電圧レベルを選択する第１選択回路、ＳＷ２は走査電極Ｇへの出力電圧を選択する第２選択回路、Ｑ(１〜m)はシフトレジスタ12の出力、Ｇ(１〜m)は走査電極、Ｖsは検出期間において検出走査パルスが印加される走査電極Ｇに印加する電圧、Ｖonは走査電極Ｇに印加されＴＦＴを導通状態にする時に印加する電圧、Ｖoffは走査電極Ｇに印加されＴＦＴを導通させない時に印加する電圧、ＳＥＬは表示期間と検出期間を示す信号、ＣＬＫはシフトレジスタの転送クロック、ＦＳはシフトレジスタのデータである選択信号である。
【００２６】
１フレームの表示期間において、ＳＥＬは“Ｈ”に設定され、図４に示す走査電極駆動回路のシフトレジスタ12に選択信号ＦＳが入力され、入力された転送クロックＣＬＫに同期してシフトレジスタ12により順次シフトされる。シフトレジスタ12の出力Ｑが“Ｈ”のとき、ＳＷ１はＶonを出力し、ＳＷ２は走査電極ＧにＳＷ１の出力を印加し、シフトレジスタ12の出力Ｑが“Ｌ”のとき、Ｖoffを走査電極Ｇに印加するように切り替わり、走査電極Ｇに図３で示すように順次表示選択パルスを印加し、信号電極Ｓには表示選択パルスに同期して表示画像データに応じた信号を印加する。また、対向電極Ｃには対向電圧を印加する。これらの動作により、画素の液晶分子の配向状態を変化させて表示を行う。
【００２７】
そして次の検出期間において、ＳＥＬは“Ｌ”に設定され、図４に示す走査電極駆動回路のシフトレジスタ12に選択信号ＦＳが入力され、入力される転送クロックＣＬＫに同期してシフトレジスタ12により、順次選択信号はシフトされる。シフトレジスタ12の出力Ｑが“Ｈ”のとき、ＳＷ１はＶsを出力し、ＳＷ２は走査電極ＧにＳＷ１の出力を印加し、シフトレジスタ12の出力Ｑが“Ｌ”のとき、Ｖoffを走査電極Ｇに印加するように切り替わり、図３で示すように行方向検出期間において、走査電極Ｇに順次検出走査パルスを印加する。
【００２８】
この場合、検出信号の強度を上げるために複数本の走査電極Ｇに同時に検出走査パルスを印加する。また、検出走査パルスの電圧値は画素のＴＦＴが導通状態にならないような値にする必要がある。図２に示す走査電極Ｇと検出用ペン２の間には静電容量結合が存在し、液晶パネル１上の検出用ペン２の位置に検出走査パルスが近づくと、図３に示す検出信号波形Ｖpのように検出用ペン２の電位が変化し、最も接近した時に最大となる。また、この検出用ペン２が検出した検出信号を微分回路を通して微分すると図３に示す微分波形dＶp／dtとなり、この微分波形dＶp／dtが正から負に変化する時点等を図２に示す検出部５で検出し、例えば、走査電極Ｇへの検出走査パルスの印加を開始した時点との時間差から、検出用ペン２が液晶パネルのどの走査電極Ｇ上に存在するかを決定する。
【００２９】
同様に、図３に示すように列方向検出期間において信号電極Ｓにも順次検出走査パルスを印加する。この場合も、検出信号の強度を上げるために複数本の信号電極Ｓに同時に検出走査パルスを印加する。図２の信号電極Ｓと検出用ペン２の間には静電容量結合が存在し、前記した行方向検出期間と同じように信号電極Ｓへの検出走査パルスの印加を開始した時点との時間差から、検出用ペン２が液晶パネル上のどの信号電極Ｓ上に存在するかを決定する。
【００３０】
なお、これらの出力電圧レベルは実施の形態１の説明で示した組み合わせに限定されるものではない。また、検出走査パルスを各フレーム毎に反転することにより、検出走査パルスにより液晶に印加されるＤＣ成分を解消することができる。
【００３１】
図５は本発明の実施の形態２における座標検出機能付液晶表示装置の概略構成を示すブロック図である。図５において、１は液晶パネル、２は検出用ペン、３は走査電極駆動回路、４は信号電極駆動回路、５は検出部、６は制御部、11′は対向電極駆動回路、Ｇ(１〜m)は走査電極、Ｓ(１〜n)は信号電極、Ｃ(１〜m)は対向電極である。図６は本実施の形態２における座標検出機能付液晶表示装置の座標検出の各信号を示すタイミングチャートである。１フレームに表示動作を行う表示期間と検出動作を行う検出期間を設けている。
【００３２】
また、図７は本実施の形態２における座標検出機能付液晶表示装置に使用する対向電極駆動回路の構成を示すブロック図である。図７において、14は検出走査パルスを印加する対向電極(対向電極配線)Ｃを指定する選択信号を順次シフトするシフトレジスタ、15はスイッチング回路、ＳＷは対向電極Ｃへの出力電圧を選択する選択回路、Ｑ(１〜m)はシフトレジスタ14の出力、Ｖcomは検出走査パルスが印加されない時に対向電極Ｃに印加される電圧、Ｖsは検出期間において検出走査パルスが印加される対向電極Ｃに印加する電圧、ＣＬＫはシフトレジスタの転送クロック、ＦＳはシフトレジスタのデータである選択信号である。
【００３３】
１フレームの表示期間においては、走査電極Ｇに図６で示すように順次表示選択パルスを印加し、信号電極Ｓには表示選択パルスに同期して表示画像データに応じた信号を印加する。また、図７に示す対向電極駆動回路においてスイッチング回路15からは電圧Ｖcomが出力され、対向電極Ｃに印加される。これらの動作により、画素の液晶分子の配向状態を変化させて表示を行う。
【００３４】
次に検出期間において、図７に示す対向電極駆動回路のシフトレジスタ14に選択信号ＦＳが入力され、入力された転送クロックＣＬＫに同期して、シフトレジスタ14により、順次選択信号はシフトされる。ＳＷはシフトレジスタ14からの出力Ｑが“Ｈ”の時にＶsを選択し、図６で示すように行方向検出期間において、対向電極Ｃに順次検出走査パルスを印加する。この場合、検出信号の強度を上げるために複数本の対向電極Ｃに同時に検出走査パルスを印加する。図５に示す対向電極Ｃと検出用ペン２の間には静電容量結合が存在し、液晶パネル１上の検出用ペン２の位置に検出走査パルスが近づくと、図６に示すように検出用ペン２の電位が変化し、最も接近した時に最大となる。この検出用ペン２が検出した検出信号波形Ｖpを微分回路を通して微分すると図６のような微分波形dＶp／dtとなり、微分波形が正から負に変化する時点等を図５の検出部５で検出し、例えば、対向電極Ｃへの検出走査パルスの印加を開始した時点との時間差から、検出用ペン２が液晶パネルのどの対向電極Ｃ上に存在するかを決定する。
【００３５】
同様に、図６で示すように列方向検出期間において信号電極Ｓに順次検出走査パルスを印加する。この場合も、検出信号の強度を上げるために複数本の信号電極Ｓに同時に検出走査パルスを印加する。図５の信号電極Ｓと検出用ペン２の間に静電容量結合が存在し、前記行方向検出期間の説明と同じように、図６に示す検出信号波形Ｖp，微分波形dＶp／dtが最大，正から負に変化する時点等を検出部５で検出し、信号電極Ｓへの検出走査パルスの印加を開始した時点との時間差から、検出用ペン２が液晶パネルのどの信号電極Ｓ上に存在するかを決定する。
【００３６】
なお、図７で示した駆動回路は一例にすぎず、液晶パネルの駆動方法や検出走査パルスの形態によってその構成は変わり、また表示期間と検出期間において、出力電圧が変更できればよい。また、出力電圧レベルは本実施の形態２で示した組み合わせに限定されるものではない。さらに、検出走査パルスをフレーム毎に反転することにより、検出走査パルスによる液晶に印加されるＤＣ成分を解消することができる。
【００３７】
図８は本発明の実施の形態３における座標検出機能付液晶表示装置の概略構成を示すブロック図である。図８において、１は液晶パネル、２は検出用ペン、４は信号電極駆動回路、５は検出部、６は制御部、16は走査および対向電極駆動回路、Ｇ(１〜m)は走査電極、Ｓ(１〜n)は信号電極、Ｃ(１〜m)は対向電極である。図９は本実施の形態３における座標検出機能付液晶表示装置の座標検出の各信号を示すタイミングチャートである。１フレームに表示動作を行う表示期間と検出動作を行う検出期間を設けている。
【００３８】
また、図10は本実施の形態３における座標検出機能付液晶表示装置に使用する走査および対向電極駆動回路の構成を示すブロック図である。図10において、17は検出走査パルスを印加する走査電極または対向電極を指定する選択信号を順次シフトするシフトレジスタ、18はスイッチング回路、ＳＷ１は走査電極Ｇへの出力電圧を選択する第１選択回路、ＳＷ２は対向電極Ｃへの出力電圧を選択する第２選択回路、Ｑ(１〜m)はシフトレジスタ17の出力、Ｖcomは検出走査パルスが印加されない時に対向電極Ｃに印加される電圧、Ｖsは検出期間において検出走査パルスが印加される対向電極Ｃに印加する電圧、Ｖonは走査電極Ｇに印加されＴＦＴを導通状態にする時に印加する電圧、Ｖoffは走査電極Ｇに印加されＴＦＴを導通させない時に印加する電圧、ＳＥＬは表示期間と検出期間を示す信号、ＣＬＫはシフトレジスタの転送クロック、ＦＳはシフトレジスタのデータである選択信号である。
【００３９】
１フレームの表示期間において、ＳＥＬは“Ｈ”に設定され、図10に示す走査および対向電極駆動回路のシフトレジスタ17に選択信号ＦＳが入力され、入力された転送クロックＣＬＫに同期してシフトレジスタ17により順次シフトされる。ＳＷ１はシフトレジスタ17の出力Ｑが“Ｈ”のときに、走査電極ＧにＶonを印加し、シフトレジスタ17の出力Ｑが“Ｌ”のときは走査電極ＧにＶoffを印加するように切り替わる。この動作の結果、走査電極Ｇに図９で示すように順次表示選択パルスが印加される。信号電極Ｓには表示選択パルスに同期して表示画像データに応じた信号が印加される。また、表示期間においてはＳＷ２は常にＶcomを選択し、対向電極ＣにはＶcomが印加される。
【００４０】
次に検出期間において、ＳＥＬは“Ｌ”に設定され、図10に示す走査および対向電極駆動回路のシフトレジスタ17に選択信号ＦＳが入力され、入力される転送クロックＣＬＫに同期してシフトレジスタ17により、順次選択信号はシフトされる。ＳＷ１は検出期間においてはＶoffを選択し、走査電極ＧにはＶoffが印加される。ＳＷ２はシフトレジスタ17の出力Ｑが“Ｈ”のときには対向電極ＣにＶsを印加し、シフトレジスタ17の出力Ｑが“Ｌ”のときは対向電極ＣにＶcomを印加するように切り替わる。この動作の結果、対向電極Ｃに図９で示す行方向検出期間のように順次検出走査パルスが印加される。この場合、検出信号の強度を上げるために複数本の対向電極Ｃに同時に検出走査パルスを印加する。
【００４１】
図８の対向電極Ｃと検出用ペン２の間には静電容量結合が存在し、液晶パネル１上の検出用ペン２の位置に検出走査パルスが近づくと、図９に示すように検出用ペン２の電位が変化し、最も接近した時に最大となる。この検出用ペン２が検出した検出信号波形Ｖpを微分回路を通して微分すると図９のような微分波形
dＶp／dtとなり、微分波形が正から負に変化する時点等を図８の検出部５で検出し、例えば、走査電極Ｇへの検出走査パルスの印加を開始した時点との時間差から、検出用ペン２が液晶パネル１のどの走査電極Ｇ上に存在するかを決定する。
【００４２】
同様に、図９で示す列方向検出期間のように信号電極Ｓに順次検出走査パルスを印加する。この場合も、検出信号の強度を上げるために複数本の信号電極に同時に検出走査パルスを印加する。信号電極Ｓと検出用ペン２の間には静電容量結合が存在し、前記行方向検出期間で説明したように検出用ペン２の検出信号を検出部５で検出し、信号電極Ｓへの検出走査パルスの印加を開始した時点との時間差から、検出用ペン２が液晶パネルのどの信号電極上に存在するかを決定する。
【００４３】
なお、図10で示した駆動回路も一例にすぎず、液晶パネルの駆動方法や検出走査パルスの電圧値等により、その構成は変わってくる。また、シフトレジスタ17が、表示期間では走査電極駆動回路のシフトレジスタとして、検出期間では対向電極駆動回路のシフトレジスタとして動作すればよい。さらに、出力電圧レベルは本実施の形態３で示した組み合わせに限定されるものではなく、検出走査パルスをフレーム毎に反転することにより、検出走査パルスにより液晶に印加されるＤＣ成分を解消することができる。
【００４４】
以上のことから、本発明の座標検出機能付液晶表示装置とその駆動回路によれば、アレイ基板上に画素電極を配置し、それに対向する基板上に対向電極を配置した従来のアクティブマトリクス型液晶パネルを採用する座標検出機能付液晶表示装置のように、検出用ペンと検出走査パルスが印加される電極の間に対向電極によるシールドがなくなり、検出用ペンに検出される信号の強度があがるので、より精度の良い座標検出を行うことができる。また、横電界方式の液晶パネルの構成上、対向電極は画素内にも存在することから、対向電極を検出用の電極として使用することにより、検出用電極と検出用ペンの間の結合容量をより大きく取ることができ、検出される信号の強度を上げることができる。
【００４５】
【発明の効果】
以上説明したように、本発明の請求項１記載の構成によれば、座標検出機能付液晶表示装置において、そのアレイ基板上に画素電極と対向電極を配置した横電界方式のアクティブマトリクス型液晶パネルを採用することにより、従来の座標検出機能付液晶表示装置のように検出用ペンと検出走査パルスが印加される電極の間に対向電極によるシールドがなく、検出用ペンに検出される信号の強度をあげることができるので、より精度の良い座標検出を行うことが可能となる。
【００４６】
また、本発明の請求項２記載の構成によれば、横電界方式の液晶パネルであることから対向電極は画素内にも存在することになり、対向電極を検出用の電極として使用することによって、検出用電極と検出用ペンの間の結合容量をより大きく取ることができ、検出用ペンに検出される信号の強度を上げることができる。
【００４７】
また、本発明の請求項３，４または５記載の構成によれば、検出走査パルスの電圧値をＴＦＴが導通状態とならない値とし、さらに１フレーム毎に検出走査パルスの極性を反転させることにより、画素電極に関係のない信号を印加されることがなく、印加される信号のＤＣ成分を解消することができる。
【００４８】
また、座標検出機能付液晶表示装置の駆動回路において、本発明の請求項６記載の構成によれば、１フレーム毎の表示期間と検出期間において走査電極に印加される各電圧を選択することができ、請求項７記載の構成によれば、検出期間のみ検出走査パルスを対向電極に印加することができ、請求項８記載の構成によれば、表示期間に表示選択パルスを走査電極へ、検出期間に検出走査パルスを対向電極(対向電極配線)へ切り替え印加することができ、画素電極に関係のない信号が印加されることなく、シフトレジスタを共用することも可能となり周辺回路を削減することができる。
【００４９】
また、本発明の請求項９または10記載の構成によれば、１フレーム毎に検出走査パルスの極性を反転させ、印加される信号のＤＣ成分を解消することができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の実施の形態における座標検出機能付液晶表示装置の液晶パネルに用いられるアレイ基板の各電極のパターン構成を示す部分平面図である。
【図２】本発明の実施の形態１における座標検出機能付液晶表示装置の概略構成を示すブロック図である。
【図３】本実施の形態１における座標検出機能付液晶表示装置の座標検出の各信号を示すタイミングチャートである。
【図４】本実施の形態１における座標検出機能付液晶表示装置に使用する走査電極駆動回路の構成を示すブロック図である。
【図５】本発明の実施の形態２における座標検出機能付液晶表示装置の概略構成を示すブロック図である。
【図６】本実施の形態２における座標検出機能付液晶表示装置の座標検出の各信号を示すタイミングチャートである。
【図７】本実施の形態２における座標検出機能付液晶表示装置に使用する対向電極駆動回路の構成を示すブロック図である。
【図８】本発明の実施の形態３における座標検出機能付液晶表示装置の概略構成を示すブロック図である。
【図９】本実施の形態３における座標検出機能付液晶表示装置の座標検出の各信号を示すタイミングチャートである。
【図１０】本実施の形態３における座標検出機能付液晶表示装置に使用する走査および対向電極駆動回路の構成を示すブロック図である。
【図１１】従来の座標検出機能付液晶表示装置の概略構成を示すブロック図である。
【図１２】座標検出の原理とそのタイミングを示す図である。
【図１３】従来の座標検出機能付液晶表示装置における座標検出の各信号のタイミングチャートである。
【図１４】従来のアクティブマトリクス型液晶表示装置の液晶パネルの構造を示す図である。
【符号の説明】
１…液晶パネル、２…検出用ペン、３，10…走査電極駆動回路、４…信号電極駆動回路、５…検出部、６…制御部、７…ＴＦＴ、８…アレイ基板、９…対向基板、 11，11′…対向電極駆動回路、 12，14，17…シフトレジスタ、 13，15，18…スイッチング回路、 16…走査および対向電極駆動回路。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device with a coordinate detection function in which a tablet for inputting coordinates is integrated with a matrix display, and a drive circuit thereof.
[0002]
[Prior art]
This type of conventional liquid crystal display device with a coordinate detection function is configured as shown in the block diagram of FIG. In FIG. 11, 1 is a liquid crystal panel, 2 is a detection pen, 3 is a scanning electrode drive circuit, 4 is a signal electrode drive circuit, 5 is a detection unit, 6 is a control unit, R (1 to m) is a scan electrode, S (1 to n) are signal electrodes. FIG. 12 is a diagram showing the principle and timing of coordinate detection. 2 is a detection pen, r1 to r10 and S1 are electrodes of the liquid crystal panel, C1 to C10 (Ca) are detection pen 2 and electrodes r1 to r1. Capacitive coupling generated during r10 (S1), P1 to P7 are detection scanning pulses, D1 is a detection signal waveform, and D2 is a differential waveform of the detection signal waveform D1.
[0003]
Conventionally, in a liquid crystal display device with a coordinate detection function that performs coordinate detection using each electrode of a liquid crystal panel as it is, a display period and a detection period are provided in one vertical scanning period (one frame). When the detection scanning pulse is sequentially applied to each scanning electrode and signal electrode, the detection pen 2 is detected via the capacitive coupling generated between the detection pen 2 close to the liquid crystal panel and the electrode of the liquid crystal panel. The detection signal waveform D1 by the scanning pulse is detected, and the coordinate position is determined from the detection timing.
[0004]
Further, FIG. 13 is a timing chart of each signal of coordinate detection in the liquid crystal display device with a coordinate detection function shown in FIG. In FIG. 13, Vp is a detection signal waveform detected by the detection pen 2, and dVp / dt is a differential waveform of the detection signal waveform Vp. The position of the detection pen 2 is determined from the time when the detection signal waveform Vp shown in FIG. 13 reaches the peak or the time when the differential waveform dVp / dt becomes zero.
[0005]
The above-described liquid crystal display device with a coordinate detection function mainly describes a method realized by a simple matrix type liquid crystal display device. Recently, a method has been devised that uses an active matrix liquid crystal display device. Even when the active matrix liquid crystal display device is used, the basic principle is the same as that of the simple matrix liquid crystal display device. However, the liquid crystal panel of the conventional active matrix type liquid crystal display device has structural limitations. A method for realizing the active matrix type liquid crystal display device using a liquid crystal panel will be described below.
[0006]
The operation period is the same as that of the liquid crystal panel of the simple matrix display device, and one frame is divided into a display period and a detection period, and a display operation is performed in the display period and a detection operation is performed in the detection period. Further, the detection period is divided into an X coordinate (row direction) detection period and a Y coordinate (column direction) detection period, and detection scan pulses are sequentially applied to the scan electrodes and the signal electrodes. A signal is detected through the capacitance between each electrode to which the detection scanning pulse is applied and the detection pen, and the X and Y coordinate values are determined based on the detection timing of the signal. However, the liquid crystal panel of the conventional active matrix liquid crystal display device generally has the following restrictions.
[0007]
FIG. 14 is a diagram showing a structure of a liquid crystal panel of a conventional active matrix liquid crystal display device. As shown in FIG. 14, an array substrate on which switching elements (TFTs) 7 and pixel electrodes H connected to the switching elements 7 are arranged corresponding to the intersections of the signal electrodes S and the scanning electrodes R arranged in a matrix. There are eight. Further, the counter electrode C is generally disposed as a solid electrode on the counter substrate 9 disposed to face the array substrate 8. This liquid crystal panel has a structure in which a counter substrate 9 is disposed on the front surface and an array substrate 8 is disposed on the back surface. With such an arrangement, the counter electrode C shields the signal from the scanning electrode R and the signal electrode S, so that a detection signal cannot be sufficiently obtained with the detection pen. Further, when the surface of the array substrate 8 is turned upside down in order to obtain a sufficient detection signal, the switching element 7, the scanning electrode R, and the signal electrode S are reflected. In order to prevent this, it is necessary to provide a black matrix layer for reflection prevention on the wiring of each electrode and the switching element 7.
[0008]
[Problems to be solved by the invention]
In this way, in the liquid crystal panel of the active matrix type liquid crystal display device used for the liquid crystal display device with a coordinate detection function, the signal from each electrode of the liquid crystal panel is shielded by the counter electrode due to the structure, and the detection pen is weakened. There was a problem that it was difficult to detect with. Further, even when the array surface of the liquid crystal panel is on the front side, there is a problem that a black matrix layer must be provided in order to prevent the reflection of the wiring of each electrode and the switching element or the reflection.
[0009]
The present invention is directed to solving the problems of the prior art, and adopts a liquid crystal panel of a horizontal electric field type active matrix type liquid crystal display device to reduce the shielding effect by the counter electrode, thereby further improving the shielding effect. It is an object of the present invention to provide a liquid crystal display device with a coordinate detection function capable of performing highly accurate coordinate detection, and a drive circuit thereof.
[0010]
[Means for Solving the Problems]
In order to achieve this object, a liquid crystal display device with a coordinate detection function according to the present invention includes a plurality of signal electrodes and scanning electrodes arranged in a matrix, and switching elements and switching elements provided corresponding to the intersections thereof. A comb-shaped pixel electrode connected to each other, an array substrate having a counter electrode connected to a counter electrode wiring parallel to each scanning electrode, and arranged opposite to the array substrate. An active matrix type liquid crystal panel composed of a counter substrate, an array substrate and a liquid crystal layer sandwiched between the counter substrate, scanning electrodes, signal electrodes, driving means for applying a voltage to the counter electrode, and a liquid crystal panel A detection conductor for detecting a signal through capacitive coupling generated between the scan electrode and the signal electrode when the sensor is brought close to the signal, and a signal detected through the detection conductor. From, characterized in that it comprises a detection means for detecting a position of the detection conductor.
[0011]
In addition, a detection conductor is provided that detects a signal through capacitive coupling generated between the counter electrode and the signal electrode when being brought close to the liquid crystal panel.
[0012]
In addition, in the driving circuit of the liquid crystal display device with the coordinate detection function, a selection signal for designating a scan electrode to which a display selection pulse is applied in the display period is designated, and a scan electrode to which the detection scan pulse is applied in the detection period is designated. A shift register that sequentially shifts and outputs a selection signal for selection, and a selection unit that selects a voltage designated according to the output of the shift register and applies the selected voltage to the scan electrode.
[0013]
The shift register sequentially shifts and outputs a selection signal for designating the counter electrode wiring to which the detection scanning pulse is applied in a detection period, and the selection unit is designated according to the output of the shift register. A voltage is selected and applied to the counter electrode wiring.
[0014]
The shift register sequentially shifts a selection signal for designating a scan electrode to which a display selection pulse is applied in a display period, and a selection signal for designating a counter electrode wiring to which a detection scan pulse is applied in a detection period. The selection means selects the voltage specified according to the output of the shift register during the display period and applies it to the scan electrode during the display period, and the voltage specified according to the output of the shift register during the detection period. Is selected and applied to the counter electrode wiring.
[0015]
According to the first aspect of the present invention in the above configuration, the shield effect by the counter electrode between the detection conductor and the liquid crystal panel can be reduced by providing the counter electrode on the array substrate of the liquid crystal panel.
[0016]
According to the second aspect of the present invention, since the counter electrode is disposed in the pixel portion of the array substrate, the counter electrode having a capacitance larger than that of the scanning electrode is used for capacitive coupling with the detection conductor. By making the counter electrode scan the detection scanning pulse, it can be detected with higher accuracy.
[0017]
According to the third aspect of the present invention, by setting the voltage value of the detection scanning pulse to a value that does not cause the switching element to become conductive, it is possible to prevent the application of a signal that is not related to the pixel electrode. .
[0018]
According to the fourth or fifth aspect of the present invention, the applied signal can be converted into an alternating current by inverting the polarity of the detection scanning pulse every vertical scanning period.
[0019]
According to the sixth aspect of the present invention, each voltage applied to the scan electrode can be selected in the display period and the detection period.
[0020]
According to the seventh aspect of the present invention, the detection scanning pulse can be applied to the counter electrode only during the detection period.
[0021]
According to the eighth aspect of the present invention, the shift register that specifies the scan electrode to which the display selection pulse is applied during the display period may be used as the shift register that specifies the counter electrode wiring to which the detection scan pulse is applied during the detection period. Can be used.
[0022]
In addition, according to the ninth or tenth aspect of the present invention, the applied signal can be converted into an alternating current by inverting the polarity of the detection scanning pulse every vertical scanning period.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial plan view showing a pattern configuration of each electrode of an array substrate used in a liquid crystal panel of a liquid crystal display device with a coordinate detection function according to an embodiment of the present invention. Here, components having substantially the same functions corresponding to the components described in FIG. 14 showing the conventional example are denoted by the same reference numerals. In FIG. 1, 7 is a switching element (TFT), G is a scanning electrode, S is a signal electrode, C is a counter electrode, C 'is a counter electrode wiring to which the counter electrode C is connected, and H is a pixel electrode. In the array substrate configured as described above, when a display selection pulse for turning on the TFT 7 is applied to the scanning electrode G in the display period, an image signal applied to the signal electrode S through the TFT 7 is applied to the pixel electrode H. Applied. Depending on the potential difference between the pixel electrode H and the counter electrode C, the alignment state of the liquid crystal molecules changes, and the screen is displayed.
[0024]
FIG. 2 is a block diagram showing a schematic configuration of the liquid crystal display device with a coordinate detection function according to the first embodiment of the present invention. Here, the same reference numerals are assigned to the components corresponding to those of the conventional example described with reference to FIG. 11, and the same applies to the following drawings. In FIG. 2, 1 is a liquid crystal panel having the array substrate shown in FIG. 1, 2 is a detection pen that is a detection conductor, 4 is a signal electrode drive circuit, and 5 is a change in detection signal from the detection pen 2. A detection unit, 6 is a control unit for controlling the detection unit 5 and each drive circuit, 10 is a scan electrode drive circuit, 11 is a counter electrode drive circuit, G (1 to m) is a scan electrode, and S (1 to n) is a signal. Electrodes C (1 to m) are counter electrodes.
[0025]
FIG. 3 is a timing chart showing signals for coordinate detection of the liquid crystal display device with a coordinate detection function according to the first embodiment. As shown in FIG. 3, one frame is provided with a display period for performing a display operation and a detection period for performing a detection operation. FIG. 4 is a block diagram showing the configuration of a scan electrode driving circuit used in the liquid crystal display device with a coordinate detection function in the first embodiment. In FIG. 4, 12 is a shift register that sequentially shifts a selection signal that designates a scanning electrode G to which a display selection pulse is applied, 13 is a switching circuit as selection means, and SW1 is a voltage between the display period and the detection period of the display selection pulse. A first selection circuit for selecting a level, SW2 is a second selection circuit for selecting an output voltage to the scan electrode G, Q (1 to m) is an output of the shift register 12, G (1 to m) is a scan electrode, Vs Is a voltage applied to the scanning electrode G to which a detection scanning pulse is applied in the detection period, Von is a voltage applied to the scanning electrode G to make the TFT conductive, and Voff is applied to the scanning electrode G and does not make the TFT conductive. Voltage applied at times, SEL is a signal indicating a display period and a detection period, CLK is a transfer clock of the shift register, and FS is a selection signal which is data of the shift register.
[0026]
In the display period of one frame, SEL is set to “H”, the selection signal FS is input to the shift register 12 of the scan electrode driving circuit shown in FIG. 4, and the shift register 12 synchronizes with the input transfer clock CLK. Shifted sequentially. When the output Q of the shift register 12 is “H”, SW1 outputs Von, SW2 applies the output of SW1 to the scan electrode G, and when the output Q of the shift register 12 is “L”, Voff is the scan electrode. As shown in FIG. 3, a display selection pulse is sequentially applied to the scanning electrode G, and a signal corresponding to display image data is applied to the signal electrode S in synchronization with the display selection pulse. A counter voltage is applied to the counter electrode C. By these operations, display is performed by changing the alignment state of the liquid crystal molecules of the pixel.
[0027]
In the next detection period, SEL is set to “L”, the selection signal FS is input to the shift register 12 of the scan electrode driving circuit shown in FIG. 4, and the shift register 12 synchronizes with the input transfer clock CLK. The selection signal is sequentially shifted. When the output Q of the shift register 12 is “H”, SW1 outputs Vs, SW2 applies the output of SW1 to the scan electrode G, and when the output Q of the shift register 12 is “L”, Voff is the scan electrode. The detection scan pulses are sequentially applied to the scan electrodes G in the row direction detection period as shown in FIG.
[0028]
In this case, in order to increase the intensity of the detection signal, the detection scan pulse is simultaneously applied to the plurality of scan electrodes G. Further, the voltage value of the detection scanning pulse needs to be set to a value that prevents the TFT of the pixel from being turned on. Capacitive coupling exists between the scanning electrode G and the detection pen 2 shown in FIG. 2, and when the detection scanning pulse approaches the position of the detection pen 2 on the liquid crystal panel 1, the detection signal waveform shown in FIG. The potential of the detection pen 2 changes like Vp, and becomes the maximum when approaching closest. Further, when the detection signal detected by the detection pen 2 is differentiated through a differentiating circuit, a differential waveform dVp / dt shown in FIG. 3 is obtained, and the time when the differential waveform dVp / dt changes from positive to negative is detected in FIG. The detection pen 2 determines which scan electrode G of the liquid crystal panel is present from the time difference from the time point detected by the unit 5 and, for example, the time when the application of the detection scan pulse to the scan electrode G is started.
[0029]
Similarly, detection scan pulses are sequentially applied to the signal electrodes S in the column direction detection period as shown in FIG. Also in this case, a detection scanning pulse is simultaneously applied to the plurality of signal electrodes S in order to increase the intensity of the detection signal. Capacitive coupling exists between the signal electrode S and the detection pen 2 in FIG. 2, and the time difference from the time when the application of the detection scanning pulse to the signal electrode S is started as in the above-described row direction detection period. Thus, it is determined on which signal electrode S on the liquid crystal panel the detection pen 2 is present.
[0030]
These output voltage levels are not limited to the combinations shown in the description of the first embodiment. Further, by inverting the detection scan pulse for each frame, the DC component applied to the liquid crystal by the detection scan pulse can be eliminated.
[0031]
FIG. 5 is a block diagram showing a schematic configuration of a liquid crystal display device with a coordinate detection function according to Embodiment 2 of the present invention. In FIG. 5, 1 is a liquid crystal panel, 2 is a detection pen, 3 is a scanning electrode drive circuit, 4 is a signal electrode drive circuit, 5 is a detection unit, 6 is a control unit, 11 'is a counter electrode drive circuit, and G (1 ˜m) are scanning electrodes, S (1˜n) are signal electrodes, and C (1˜m) are counter electrodes. FIG. 6 is a timing chart showing each signal of coordinate detection of the liquid crystal display device with a coordinate detection function in the second embodiment. A display period for performing a display operation and a detection period for performing a detection operation are provided in one frame.
[0032]
FIG. 7 is a block diagram showing a configuration of a counter electrode driving circuit used in the liquid crystal display device with a coordinate detection function in the second embodiment. In FIG. 7, 14 is a shift register that sequentially shifts a selection signal designating a counter electrode (counter electrode wiring) C to which a detection scanning pulse is applied, 15 is a switching circuit, and SW is a selection for selecting an output voltage to the counter electrode C. Circuit, Q (1-m) is the output of the shift register 14, Vcom is a voltage applied to the counter electrode C when no detection scan pulse is applied, and Vs is applied to the counter electrode C to which the detection scan pulse is applied in the detection period A voltage to be transmitted, CLK is a transfer clock of the shift register, and FS is a selection signal which is data of the shift register.
[0033]
In the display period of one frame, a display selection pulse is sequentially applied to the scanning electrode G as shown in FIG. 6, and a signal corresponding to display image data is applied to the signal electrode S in synchronization with the display selection pulse. In the counter electrode drive circuit shown in FIG. 7, the voltage Vcom is output from the switching circuit 15 and applied to the counter electrode C. By these operations, display is performed by changing the alignment state of the liquid crystal molecules of the pixel.
[0034]
Next, in the detection period, the selection signal FS is input to the shift register 14 of the counter electrode driving circuit shown in FIG. 7, and the selection signal is sequentially shifted by the shift register 14 in synchronization with the input transfer clock CLK. SW selects Vs when the output Q from the shift register 14 is “H”, and sequentially applies detection scanning pulses to the counter electrode C in the row direction detection period as shown in FIG. In this case, a detection scanning pulse is simultaneously applied to a plurality of counter electrodes C in order to increase the intensity of the detection signal. Capacitive coupling exists between the counter electrode C and the detection pen 2 shown in FIG. 5, and when the detection scanning pulse approaches the position of the detection pen 2 on the liquid crystal panel 1, detection is performed as shown in FIG. When the electric potential of the pen 2 changes and approaches the maximum, it becomes maximum. When the detection signal waveform Vp detected by the detection pen 2 is differentiated through a differentiating circuit, a differential waveform dVp / dt as shown in FIG. 6 is obtained, and the time when the differential waveform changes from positive to negative is detected by the detection unit 5 in FIG. Then, for example, the counter electrode C of the liquid crystal panel on which the detection pen 2 is present is determined from the time difference from the time when the application of the detection scanning pulse to the counter electrode C is started.
[0035]
Similarly, detection scan pulses are sequentially applied to the signal electrodes S in the column direction detection period as shown in FIG. Also in this case, a detection scanning pulse is simultaneously applied to the plurality of signal electrodes S in order to increase the intensity of the detection signal. Capacitive coupling exists between the signal electrode S and the detection pen 2 in FIG. 5, and the detection signal waveform Vp and the differential waveform dVp / dt shown in FIG. The detection unit 2 detects when the detection unit 5 changes from positive to negative, and the time difference from the time when the application of the detection scanning pulse to the signal electrode S is started. Determine if it exists.
[0036]
Note that the driving circuit shown in FIG. 7 is merely an example, and the configuration thereof varies depending on the driving method of the liquid crystal panel and the form of the detection scanning pulse, and it is sufficient that the output voltage can be changed between the display period and the detection period. Further, the output voltage level is not limited to the combination shown in the second embodiment. Further, by inverting the detection scanning pulse for each frame, the DC component applied to the liquid crystal due to the detection scanning pulse can be eliminated.
[0037]
FIG. 8 is a block diagram showing a schematic configuration of a liquid crystal display device with a coordinate detection function according to Embodiment 3 of the present invention. In FIG. 8, 1 is a liquid crystal panel, 2 is a detection pen, 4 is a signal electrode driving circuit, 5 is a detection unit, 6 is a control unit, 16 is a scanning and counter electrode driving circuit, and G (1 to m) is a scanning electrode. , S (1-n) are signal electrodes, and C (1-m) are counter electrodes. FIG. 9 is a timing chart showing signals for coordinate detection of the liquid crystal display device with a coordinate detection function according to the third embodiment. A display period for performing a display operation and a detection period for performing a detection operation are provided in one frame.
[0038]
FIG. 10 is a block diagram showing the configuration of the scanning and counter electrode drive circuit used in the liquid crystal display device with a coordinate detection function in the third embodiment. In FIG. 10, 17 is a shift register for sequentially shifting a selection signal for designating a scan electrode or a counter electrode to which a detection scan pulse is applied, 18 is a switching circuit, and SW1 is a first selection circuit for selecting an output voltage to the scan electrode G. , SW2 is a second selection circuit for selecting an output voltage to the counter electrode C, Q (1 to m) is an output of the shift register 17, Vcom is a voltage applied to the counter electrode C when no detection scan pulse is applied, Vs Is a voltage applied to the counter electrode C to which a detection scanning pulse is applied in the detection period, Von is a voltage applied to the scanning electrode G to make the TFT conductive, and Voff is applied to the scanning electrode G and does not make the TFT conductive. SEL is a signal indicating a display period and a detection period, CLK is a transfer clock of the shift register, and FS is a selection signal that is data of the shift register. .
[0039]
In a display period of one frame, SEL is set to “H”, a selection signal FS is input to the shift register 17 of the scanning and counter electrode driving circuit shown in FIG. 10, and the shift register is synchronized with the input transfer clock CLK. 17 is sequentially shifted. SW1 is switched so that Von is applied to the scanning electrode G when the output Q of the shift register 17 is "H", and Voff is applied to the scanning electrode G when the output Q of the shift register 17 is "L". As a result of this operation, a display selection pulse is sequentially applied to the scan electrode G as shown in FIG. A signal corresponding to display image data is applied to the signal electrode S in synchronization with the display selection pulse. In the display period, SW2 always selects Vcom, and Vcom is applied to the counter electrode C.
[0040]
Next, in the detection period, SEL is set to “L”, the selection signal FS is input to the shift register 17 of the scanning and counter electrode driving circuit shown in FIG. 10, and the shift register 17 is synchronized with the input transfer clock CLK. Thus, the selection signal is sequentially shifted. SW1 selects Voff during the detection period, and Voff is applied to the scan electrode G. SW2 is switched so that Vs is applied to the counter electrode C when the output Q of the shift register 17 is "H", and Vcom is applied to the counter electrode C when the output Q of the shift register 17 is "L". As a result of this operation, detection scanning pulses are sequentially applied to the counter electrode C as in the row direction detection period shown in FIG. In this case, a detection scanning pulse is simultaneously applied to a plurality of counter electrodes C in order to increase the intensity of the detection signal.
[0041]
Capacitive coupling exists between the counter electrode C and the detection pen 2 in FIG. 8, and when the detection scanning pulse approaches the position of the detection pen 2 on the liquid crystal panel 1, as shown in FIG. The potential of the pen 2 changes and becomes maximum when the pen 2 is closest. When the detection signal waveform Vp detected by the detection pen 2 is differentiated through a differentiation circuit, a differentiated waveform as shown in FIG.
The time when the differential waveform changes from positive to negative is detected by the detection unit 5 in FIG. 8, and for example, the detection time is detected from the time difference from the time when the application of the detection scan pulse to the scan electrode G is started. The scanning electrode G of the liquid crystal panel 1 on which the pen 2 is present is determined.
[0042]
Similarly, detection scan pulses are sequentially applied to the signal electrodes S as in the column direction detection period shown in FIG. Also in this case, the detection scanning pulse is simultaneously applied to the plurality of signal electrodes in order to increase the intensity of the detection signal. Capacitive coupling exists between the signal electrode S and the detection pen 2, and the detection signal of the detection pen 2 is detected by the detection unit 5 as described in the row direction detection period, and the signal to the signal electrode S is detected. It is determined on which signal electrode of the liquid crystal panel the detection pen 2 is present based on the time difference from the time when the application of the detection scanning pulse is started.
[0043]
Note that the drive circuit shown in FIG. 10 is merely an example, and the configuration varies depending on the driving method of the liquid crystal panel, the voltage value of the detection scanning pulse, and the like. Further, the shift register 17 may operate as a shift register of the scan electrode driver circuit in the display period and as a shift register of the counter electrode driver circuit in the detection period. Further, the output voltage level is not limited to the combination shown in the third embodiment, and the DC component applied to the liquid crystal by the detection scanning pulse is eliminated by inverting the detection scanning pulse for each frame. Can do.
[0044]
As described above, according to the liquid crystal display device with a coordinate detection function and the drive circuit thereof according to the present invention, the conventional active matrix type liquid crystal in which the pixel electrode is arranged on the array substrate and the counter electrode is arranged on the opposite substrate. Like a liquid crystal display with a coordinate detection function that uses a panel, there is no shield due to the counter electrode between the detection pen and the electrode to which the detection scan pulse is applied, and the intensity of the signal detected by the detection pen increases. More accurate coordinate detection can be performed. In addition, because of the configuration of the horizontal electric field type liquid crystal panel, the counter electrode is also present in the pixel. Therefore, by using the counter electrode as a detection electrode, the coupling capacitance between the detection electrode and the detection pen is increased. It can be made larger and the intensity of the detected signal can be increased.
[0045]
【The invention's effect】
As described above, according to the configuration of the first aspect of the present invention, in the liquid crystal display device with a coordinate detection function, the horizontal electric field type active matrix liquid crystal panel in which the pixel electrode and the counter electrode are arranged on the array substrate. By adopting, there is no shield by the counter electrode between the detection pen and the electrode to which the detection scan pulse is applied as in the conventional liquid crystal display device with coordinate detection function, and the intensity of the signal detected by the detection pen Therefore, more accurate coordinate detection can be performed.
[0046]
According to the configuration of the second aspect of the present invention, since the liquid crystal panel is a horizontal electric field type, the counter electrode is also present in the pixel, and the counter electrode is used as a detection electrode. The coupling capacitance between the detection electrode and the detection pen can be increased, and the intensity of the signal detected by the detection pen can be increased.
[0047]
According to the configuration of claim 3, 4 or 5 of the present invention, the voltage value of the detection scan pulse is set to a value at which the TFT does not become conductive, and the polarity of the detection scan pulse is inverted every frame. A signal unrelated to the pixel electrode is not applied, and the DC component of the applied signal can be eliminated.
[0048]
In the driving circuit of the liquid crystal display device with a coordinate detection function, according to the configuration of claim 6 of the present invention, each voltage applied to the scan electrode can be selected in the display period and the detection period for each frame. According to the configuration of claim 7, the detection scan pulse can be applied to the counter electrode only during the detection period. According to the configuration of claim 8, the display selection pulse is detected to the scan electrode during the display period. The detection scan pulse can be switched and applied to the counter electrode (counter electrode wiring) during the period, and it is possible to share a shift register without applying a signal unrelated to the pixel electrode, thereby reducing peripheral circuits Can do.
[0049]
Further, according to the configuration of the ninth or tenth aspect of the present invention, there is an effect that the polarity of the detection scanning pulse is inverted every frame and the DC component of the applied signal can be eliminated.
[Brief description of the drawings]
FIG. 1 is a partial plan view showing a pattern configuration of each electrode of an array substrate used in a liquid crystal panel of a liquid crystal display device with a coordinate detection function in an embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of a liquid crystal display device with a coordinate detection function according to the first embodiment of the present invention.
FIG. 3 is a timing chart showing each signal of coordinate detection of the liquid crystal display device with a coordinate detection function in the first embodiment.
4 is a block diagram showing a configuration of a scan electrode driving circuit used in the liquid crystal display device with a coordinate detection function in the first embodiment. FIG.
FIG. 5 is a block diagram showing a schematic configuration of a liquid crystal display device with a coordinate detection function according to a second embodiment of the present invention.
FIG. 6 is a timing chart showing signals for coordinate detection of the liquid crystal display device with a coordinate detection function according to the second embodiment.
7 is a block diagram showing a configuration of a counter electrode driving circuit used in the liquid crystal display device with a coordinate detection function in the second embodiment. FIG.
FIG. 8 is a block diagram showing a schematic configuration of a liquid crystal display device with a coordinate detection function according to a third embodiment of the present invention.
FIG. 9 is a timing chart showing coordinates detection signals of the liquid crystal display device with a coordinate detection function according to the third embodiment.
FIG. 10 is a block diagram showing a configuration of a scanning and counter electrode drive circuit used in a liquid crystal display device with a coordinate detection function in a third embodiment.
FIG. 11 is a block diagram showing a schematic configuration of a conventional liquid crystal display device with a coordinate detection function.
FIG. 12 is a diagram showing the principle of coordinate detection and its timing.
FIG. 13 is a timing chart of each signal of coordinate detection in a conventional liquid crystal display device with a coordinate detection function.
FIG. 14 is a diagram showing a structure of a liquid crystal panel of a conventional active matrix type liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal panel, 2 ... Detection pen, 3, 10 ... Scanning electrode drive circuit, 4 ... Signal electrode drive circuit, 5 ... Detection part, 6 ... Control part, 7 ... TFT, 8 ... Array substrate, 9 ... Opposite substrate 11, 11 ′... Counter electrode drive circuit, 12, 14, 17... Shift register, 13, 15, 18.

Claims

A plurality of signal electrodes and scanning electrodes arranged in a matrix, switching elements provided corresponding to the intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and occlusion with the pixel electrodes , An array substrate having a counter electrode connected to a counter electrode wiring parallel to each scanning electrode, a counter substrate disposed to face the array substrate, and a liquid crystal layer sandwiched between the array substrate and the counter substrate An active matrix type liquid crystal panel comprising:
Via capacitive coupling generated between each scanning means, signal electrode, and counter electrode of the liquid crystal panel, which applies voltage to the scanning electrode, and the scanning electrode and the signal electrode when the liquid crystal panel is brought close to the driving means. A detection conductor for detecting the signal and a detection means for detecting the position of the detection conductor from the signal detected through the detection conductor,
One vertical scanning period is composed of a display period and a detection period. In the display period, a display selection pulse for sequentially turning on the switching element is applied to the scanning electrodes, and display image data is synchronized with the display selection pulse. An image signal according to the above is applied to the signal electrode, the image signal is written to the pixel electrode through the switching element, and is substantially parallel to the array substrate and the counter substrate between the pixel electrode and the counter electrode. By generating an electric field, the arrangement of liquid crystal molecules is changed, and display image data is displayed.
In the detection period, a detection scan pulse is sequentially applied to the scan electrode and the signal electrode, and when the detection conductor is brought close to the liquid crystal panel, the detection conductor is interposed between the scan electrode and the signal electrode. A change in voltage generated in the detection conductor is detected through the generated capacitive coupling, and a position of the detection conductor on the liquid crystal panel is detected from the time when the change is detected. Liquid crystal display device with coordinate detection function.

A plurality of signal electrodes and scanning electrodes arranged in a matrix, switching elements provided corresponding to the intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and occlusion with the pixel electrodes , An array substrate having a counter electrode connected to a counter electrode wiring parallel to each scanning electrode, a counter substrate disposed to face the array substrate, and a liquid crystal layer sandwiched between the array substrate and the counter substrate An active matrix type liquid crystal panel comprising:
Via the capacitive coupling generated between each of the drive means for applying a voltage to the scanning electrode, signal electrode, and counter electrode of the liquid crystal panel, and the counter electrode and the signal electrode when it is brought close to the liquid crystal panel. A detection conductor for detecting the signal and a detection means for detecting the position of the detection conductor from the signal detected through the detection conductor,
One vertical scanning period is composed of a display period and a detection period. In the display period, a display selection pulse for sequentially turning on the switching element is applied to the scanning electrodes, and display image data is synchronized with the display selection pulse. An image signal according to the above is applied to the signal electrode, the image signal is written to the pixel electrode through the switching element, and is substantially parallel to the array substrate and the counter substrate between the pixel electrode and the counter electrode. By generating an electric field, the arrangement of liquid crystal molecules is changed, and display image data is displayed.
In the detection period, a detection scanning pulse is sequentially applied to the counter electrode and the signal electrode, and when the detection conductor is brought close to the liquid crystal panel, the detection conductor is interposed between the counter electrode and the signal electrode. A change in voltage generated in the detection conductor is detected through the generated capacitive coupling, and a position of the detection conductor on the liquid crystal panel is detected from the time when the change is detected. Liquid crystal display device with coordinate detection function.

2. The liquid crystal display device with a coordinate detection function according to claim 1, wherein the voltage value of the detection scan pulse applied to the scan electrode in the detection period is a value at which the switching element does not enter a conductive state.

4. The liquid crystal display device with a coordinate detection function according to claim 1, wherein the polarity of the detection scanning pulse applied to the scanning electrode is reversed every vertical scanning period in the detection period.

3. The liquid crystal display device with a coordinate detection function according to claim 2, wherein in the detection period, the polarity of the detection scanning pulse applied to the counter electrode is reversed every vertical scanning period.

A plurality of signal electrodes and scanning electrodes arranged in a matrix, switching elements provided corresponding to the intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and occlusion with the pixel electrodes An array substrate having a counter electrode connected to a counter electrode wiring that is wired in parallel with each scanning electrode, a counter substrate disposed opposite to the array substrate, and the array substrate and the counter substrate Has an active matrix type liquid crystal panel consisting of liquid crystal layers,
One vertical scanning period is composed of a display period and a detection period. In the display period, a display selection pulse for sequentially turning on the switching element is applied to the scanning electrodes, and display image data is synchronized with the display selection pulse. An image signal according to the above is applied to the signal electrode, the image signal is written to the pixel electrode through the switching element, and is substantially parallel to the array substrate and the counter substrate between the pixel electrode and the counter electrode. By generating an electric field, the arrangement of liquid crystal molecules is changed to display display image data. During the detection period, a detection scan pulse is sequentially applied to the scan electrode and the signal electrode, and a detection conductor is applied to the liquid crystal panel. Is generated in the detection conductor through capacitive coupling generated between the detection conductor and the scanning electrode and the signal electrode Detecting a change in pressure, from the time of detecting the variation, in the coordinate detection-capable liquid crystal display device for detecting a position on said liquid crystal panel of the detection conductor,
A selection signal for designating the scan electrode to which the display selection pulse is applied is sequentially shifted during the display period, and a selection for designating the scan electrode to which the detection scan pulse is applied during the detection period A liquid crystal display with a coordinate detection function, comprising: a shift register that sequentially shifts and outputs a signal; and a selection unit that selects a voltage specified according to the output of the shift register and applies the selected voltage to the scan electrode. Device drive circuit.

A plurality of signal electrodes and scanning electrodes arranged in a matrix, switching elements provided corresponding to the intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and occlusion with the pixel electrodes An array substrate having a counter electrode connected to a counter electrode wiring that is wired in parallel with each scanning electrode, a counter substrate disposed opposite to the array substrate, and the array substrate and the counter substrate Has an active matrix type liquid crystal panel consisting of liquid crystal layers,
One vertical scanning period is composed of a display period and a detection period. In the display period, a display selection pulse for sequentially turning on the switching element is applied to the scanning electrodes, and display image data is synchronized with the display selection pulse. An image signal in accordance with is applied to the signal electrode, the image signal is written to the pixel electrode through the switching element, and is substantially parallel to the array substrate and the counter substrate between the pixel electrode and the counter electrode. By generating a simple electric field, the arrangement of liquid crystal molecules is changed, and display image data is displayed. During the detection period, detection scanning pulses are sequentially applied to the counter electrode and the signal electrode, and the liquid crystal panel is used for detection. When the conductor is brought close to the detection conductor, it is generated in the detection conductor through capacitive coupling generated between the detection conductor and the counter electrode and the signal electrode. That detects a change in voltage, from the time of detecting the variation, in the coordinate detection-capable liquid crystal display device for detecting a position on said liquid crystal panel of the detection conductor,
In the detection period, a shift register that sequentially shifts and outputs a selection signal for designating the counter electrode wiring to which the detection scan pulse is applied, and a voltage designated according to the output of the shift register are selected. A drive circuit for a liquid crystal display device with a coordinate detection function, comprising: selection means for applying to the counter electrode wiring.

A plurality of signal electrodes and scanning electrodes arranged in a matrix, switching elements provided corresponding to the intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and occlusion with the pixel electrodes An array substrate having a counter electrode connected to a counter electrode wiring that is wired in parallel with each scanning electrode, a counter substrate disposed opposite to the array substrate, and the array substrate and the counter substrate Has an active matrix type liquid crystal panel consisting of liquid crystal layers,
One vertical scanning period is composed of a display period and a detection period. In the display period, a display selection pulse for sequentially turning on the switching element is applied to the scanning electrodes, and display image data is synchronized with the display selection pulse. An image signal in accordance with is applied to the signal electrode, the image signal is written to the pixel electrode through the switching element, and is substantially parallel to the array substrate and the counter substrate between the pixel electrode and the counter electrode. By generating a simple electric field, the arrangement of liquid crystal molecules is changed, and display image data is displayed. During the detection period, detection scanning pulses are sequentially applied to the counter electrode and the signal electrode, and the liquid crystal panel is used for detection. When the conductor is brought close to the detection conductor, it is generated in the detection conductor through capacitive coupling generated between the detection conductor and the counter electrode and the signal electrode. That detects a change in voltage, from the time of detecting the variation, in the coordinate detection-capable liquid crystal display device for detecting a position on said liquid crystal panel of the detection conductor,
In the display period, a selection signal for designating the scan electrode to which the display selection pulse is applied is sequentially shifted, and in the detection period, the counter electrode wiring to which the detection scan pulse is applied is designated. A shift register that sequentially shifts and outputs a selection signal, and a voltage designated according to the output of the shift register is selected and applied to the scan electrode in the display period, and the shift is applied in the detection period. A drive circuit for a liquid crystal display device with a coordinate detection function, comprising selection means for selecting a voltage designated according to an output of a register and applying the selected voltage to the counter electrode wiring.

7. The drive circuit for a liquid crystal display device with a coordinate detection function according to claim 6, wherein in the detection period, the polarity of the detection scan pulse applied to the scan electrode is inverted every one vertical scan period.

9. The driving circuit for a liquid crystal display device with a coordinate detection function according to claim 7, wherein the polarity of the detection scanning pulse applied to the counter electrode is inverted every vertical scanning period in the detection period.