JP3580994B2

JP3580994B2 - Liquid crystal display

Info

Publication number: JP3580994B2
Application number: JP27158597A
Authority: JP
Inventors: 満鹿野; 研次表
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1997-10-03
Filing date: 1997-10-03
Publication date: 2004-10-27
Anticipated expiration: 2017-10-03
Also published as: JPH11109334A

Description

【０００１】
【発明の属する技術分野】
本発明は液晶表示装置、特に全体の色相に対して補色となる色相の色素を添加したオーバーコート層を基板と透明電極との間に介在させた液晶表示装置に関する。
【０００２】
【従来の技術】
一般に、液晶表示装置の表示形態には、バックライトを備えた透過型と呼ばれるものと、反射型と呼ばれるものがある。反射型液晶表示装置は、太陽光、照明光等の外光だけを利用してバックライト無しで表示する液晶表示装置であり、例えば薄型で、軽量化が要求される携帯情報端末等に多く用いられている。
【０００３】
図３は、従来のＳＴＮ（スーパー・ツイステッド・ネマチック）方式の反射型液晶表示装置の一例を示すもので、この反射型液晶表示装置Ａは、上下に対向配置されたガラスからなる一対のガラス基板１、２と、それらの間に封止材により封入されたＳＴＮ方式の液晶層４と、上側ガラス基板１の上面側に上から順に設けられた偏光板５、位相差板６、７と、下側ガラス基板２の下面側に設けられた反射体１０とを具備して構成されている。この反射体１０は、例えば厚さ３００乃至５００μｍポリエステルフィルム等の樹脂又はガラスの基板８の表面に高さが数μｍの微細な凹凸部８ａを形成し、さらにその上にＡｌ、Ａｇなどからなる反射膜９が蒸着等により成膜されている。なお、反射体１０と前記ガラス基板２との突き合わせ面には、グリセリン等の光の屈折率に悪影響を与えることのない材質からなる粘着層１１が充填されている。
【０００４】
また、上側ガラス基板１の下面側にはＩＴＯ（インジウムスズ酸化物）からなる電極層１２とトップコート層１３と配向膜１４とが積層され、下側ガラス基板２の上面側にはカラー表示構造の場合に必要なカラーフィルタ層１５とオーバーコート層１６と電極層１７と配向膜１８とがそれぞれ積層されている。
【０００５】
前記従来の構造の反射型液晶表示装置Ａは、上側ガラス基板１の上方側からの入射光が液晶層４を透過した後に反射体１０の反射膜９で反射され、再度液晶層４を透過した後に上側ガラス基板１に戻る際に、液晶層４で光の偏光方向の変換を行い、反射光が前記偏光板６を通過できるか否かを切り換えることにより、明状態と暗状態を切り換えるようにしたものである。また、反射体１０の凹凸部８ａは、反射膜９を凹凸形状にすることにより、特定方向からの光の異常に高い反射を抑制し、視野角を広く、表示面の広範囲に亘って明るい表示を行えるようにしたものである。
【０００６】
【発明が解決しようとする課題】
ところで、前記ＳＴＮ方式は、電圧を印加したときの液晶の複屈折と電圧を印加していないときの液晶の複屈折との違いを表示に利用したものであるが、カラーフィルタ層１５によるカラー表示を実現するためには、無彩色（白黒）表示が必須である。そこで、位相差板６、７は液晶を透過する光の位相差を補償することにより表示が青や黄色に着色するのを防止するために用いられている。しかしながら、位相差板６、７自体の△ｎｄ（屈折率異方性△ｎと板厚ｄとの積）のコントロールが困難であり、且つ位相差板６、７の光学軸と偏光板５の偏光軸と角度を最適化するのが製造上難しい等の理由により、表示に色付きが生じ、完全に無彩色化することはできなかった。
【０００７】
そのために、従来、予め液晶層４に、色素が存在しないときの表示の色相に対して補色となるような色相の色素を添加する方法が提案されている。しかし、液晶層４に色素を入れた場合には、低温時に表示特性が劣化し、例えば外部温度が０℃以下になると、液晶の粘性がアップし、駆動電圧ＯＮ−ＯＦＦ時の液晶の応答性が著しく低下して、画面切り替えが不安定になる。また、常温（約２０℃）で長時間放置しておくと、液晶層４の一部が結晶化してしまい、表示不可能となる等の問題点があった。
【０００８】
本発明は上記問題点に鑑みなされたもので、液晶層に色素の添加を行うことなく表示の無彩色化が可能で、低温時や常温長時間放置後の特性の劣化のない液晶表示装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
本発明の液晶表示装置は、対向する上下の透明基板のそれぞれの対向面に、少なくとも透明電極及び配向膜を順に設け、少なくとも何れか一方の前記透明基板と前記透明電極との間に、所望のパターンを有するカラーフィルタと、該カラーフィルタのパターンによりもたらされる凹凸を平坦化するとともに前記カラーフィルタ及び前記透明基板を覆うオーバーコート層を介在させ、上下の透明基板の前記配向膜間に液晶層を設けてなり、全体の色相に対して補色となる色相の色素を前記オーバーコート層に添加したことにある。従って、色素の添加が液晶層に悪影響を与えることが無く、表示面の無彩色化が可能となる。この色素としては、液晶表示装置の色調の補色関係にある色調を呈する顔料が好ましい。この顔料としては、アゾ系顔料、フタロシアン系顔料等を使用できる。
本発明の液晶表示装置は、対向する上下の透明基板の上側透明基板の対向面に、所望のパターンを有するカラーフィルタと、該カラーフィルタのパターンによりもたらされる凹凸を平坦化するとともに前記カラーフィルタと前記透明基板を覆うオーバーコート層と、透明電極と、配向膜とを順に設け、前記下側透明基板の対向面に少なくとも透明電極及び配向膜を順に設けるとともに、上下の透明基板の前記配向膜間に液晶層を設けてなり、全体の色相に対して補色となる色相の色素を前記オーバーコート層に添加したことを特徴とする。
【００１０】
また、本発明は、対向する上下の透明基板の下側透明基板の対向面に、凹凸を有する反射体と、該反射体の凹凸を平坦化するオーバーコート層と、透明電極及び配向膜を順に設け、前記上側透明基板の対向面に少なくとも透明電極及び配向膜を順に設けると共に、該上側透明基板の外側に位相差板と偏光板とを順に設け、上下の透明基板の前記配向膜間に液晶層を設けてなり、全体の色相に対して補色となる色相の色素を前記オーバーコート層に添加したことにある。反射体内蔵型の液晶表示装置において、無彩色化が可能となる。色素としては、上記顔料を使用することができる。
本発明の液晶表示装置は、前記偏光板の偏光軸が、上側透明基板に設けられた配向膜の配向方向に対してなす角度を配向方向から反時計回りに４０°であり、前記位相差板が第１の位相差板及び第２の位相差板の２層からなるとともに、第１の位相差板の遅相軸が上側配向膜の配向方向に対してなす角度を配向方向から反時計回りに８０゜であり、第２の位相差板の遅相軸が前記第１の位相差板の遅相軸に対してなす角度を第１の位相差板の遅相軸から反時計回りに１０°であり、前記補色となる色相の色素が、アゾ系の赤色顔料及びフタロシアニン系の赤色顔料であることを特徴とする
また、本発明は、前記色素を０．１乃至０．４重量％添加したことで、表示面の無彩色化に好適である。
更に本発明の液晶表示装置は、対向する上下の透明基板の下側透明基板の対向面に、凹凸を有する反射体と、該反射体の凹凸を平坦化するオーバーコート層と、透明電極及び配向膜を順に設け、前記上側透明基板の対向面に少なくともカラーフィルタ層とオーバーコート層と透明電極及び配向膜を順に設けると共に、該上側透明基板の外側に位相差板と偏光板とを順に設け、上下の透明基板の前記配向膜間にＳＴＮ液晶層を設けてなり、全体の色相に対して補色となる色相の色素を前記反射体の凹凸を平坦化するオーバーコート層に添加する一方、前記偏光板の偏光軸が、上側透明基板に設けられた配向膜の配向方向に対してなす角度を配向方向から反時計回りに４０°とし、前記位相差板を第１の位相差板及び第２の位相差板の２層から構成するとともに、第１の位相差板の遅相軸が上側配向膜の配向方向に対してなす角度を配向方向から反時計回りに８０゜とし、第２の位相差板の遅相軸が前記第１の位相差板の遅相軸に対してなす角度を第１の位相差板の遅相軸から反時計回りに１０°とし、前記補色となる色相の色素として、アゾ系の赤色顔料及びフタロシアニン系の青色顔料を０．１乃至０．４重量％添加したことを特徴とする。
【００１１】
【発明の実施の形態】
以下、図面により本発明の液晶表示装置の一実施形態について説明する。
図１は、本発明の液晶表示装置をＳＴＮ方式の反射型カラー液晶表示装置に適用した実施形態をを示す断面図である。
この実施形態の反射型液晶装置は、対向する上下のガラス基板２２、２３の下側ガラス基板２３（下側透明基板）の対向面に反射体２７、第１のオーバーコート層２８、コモン電極２９（透明電極）及び配向膜３１が順に設けられ、上側ガラス基板２２の対向面にカラーフィルター層３２、第２のオーバーコート層３３、セグメント電極３４（透明電極）及び配向膜３０が順に設けられ、更に、前記上下のガラス基板２２、２３の配向膜３０、３１間にＳＴＮの液晶層３５が設けられた概略構成である。更に上側ガラス基板２２上に、第１及び第２の位相差板２４及び２５と、偏光板２６とが順次積層されている。
【００１２】
配向膜３０、３１は、膜厚が約０．２μｍで、通常使用されてる透明な配向膜が用いられ、例えば、ポリイミドなどの高分子膜がラビング処理されたものである。
液晶層３５は、上側と下側ガラス基板２２、２３の内側に設けられた上下の配向膜３０、３１と、これら配向膜３０、３１を所定の間隔を隔てて接合する図示を省略したシール材とに囲まれた領域内に封入された常温でネマチック状態となる液晶分子からなり、この液晶分子は１８０゜以上、好ましくは２４０゜ねじれて配向されたスーパーツイステッドネマチックタイプ（ＳＴＮ）のものが用いられている。
【００１３】
上側ガラス基板２２は、液晶表示装置の種類によって異なるが、ソーダライムガラスなどからなり、その厚さは０．３ｍｍ以上とされるのが好ましい。厚みが０．３ｍｍ未満であると機械的強度が小さくなるからである。
第２のオーバーコート層３３は、カラーフィルタ層３２による凹凸を平坦化するために３〜４μｍの膜厚に設けられたもので、カラーフィルタ層３２と密着性の高いポリビニルアルコールやアクリル系樹脂などの有機材料からなる。
カラーフィルタ層３２は、レッド、ブルー、グリーンの３原色の各画素がフォトリソグラフィーや印刷法などの方法により所望のパターン通りに形成されてなるもので、このカラーフィルタ層３２には、上記３原色の周りに線状のブラックマスクがパターンニングされていても良い。
【００１４】
下側ガラス基板２３としては、液晶表示装置の種類によって異なるが、この実施形態では、ナトリウムなどのアルカリ金属の酸化物を含んだソーダライムガラスなどが用いられ、その厚みは、機械的強度から０．１ｍｍ以上とされるのが好ましい。また、ここでの下側ガラス基板２３のコモン電極２９側の面には、凹凸を有する粗面が形成されており、反射体２７は、下側ガラス基板２３の粗面の表面に形成されたＡｌ膜等の金属膜からなるものである。反射体２７は、入射した光を反射させるとともに拡散させることにより、視野角を大きくするためのものである。このような反射体内蔵型の反射型液晶装置は、下側ガラス基板２３に厚みによる視差の問題を考慮する必要がない。
【００１５】
第１のオーバーコート層２８は、反射体２７による凹凸を平坦化するために設けられたもので、膜厚が３〜４μｍのアクリル系材料からなるものである。
そこで、第１のオーバーコート層２８には、予め色素が添加され、液晶表示装置全体の色相（着色）を無彩色化したものである。オーバーコート層２８は比較的膜の厚さが厚く、色素の均一な分散が容易である。前記色素の種類は、赤色、青色又は黄色顔料からなり、その材料としては、アゾ系、フタロシアン系等を使用することができる。
用いる色素の種類としては、液晶表示装置全体の色相（着色）に対して、補色の関係にある色の顔料を選択すれば良く、例えば、装置全体の色相が黄色の場合は補色の赤色及び青色顔料を、色相が緑の場合は補色の赤色顔料のみを、色相が青色の場合は補色の黄色及び赤色顔料を用いることができる。
また、色素の添加量としては、０．１乃至０．４重量％が好ましく、２種類の顔料を用いる場合には、各色素をそれぞれ０．１乃至０．４重量％を添加することにより、装置全体の色相の無彩色化を果たすことができる。
なお、第１のオーバーコート層２８に色素を添加することで説明したが、第２のオーバーコート層３３に色素を添加して装置全体を無彩色化し得ることは勿論である。
【００１６】
【実施例】
以下、本発明を実施例及び比較例により、さらに具体的に説明するが、本発明はこれらの実施例のみに限定されるものではない。
図１に示した実施形態の反射型液晶表示装置において、第１のオーバーコート層２８に添加する色素の添加量を違えたものを準備し、その分光特性について調べた。
上下の配向膜３０、３１としては、ＰＳＩ−２５０１（商品名：チッソ株式会社製）を用い、ツイスト角が２４０度になるように配向処理を行った。また、液晶セルの厚みは、５．２μｍであり、△ｎｄは８６１ｎｍ（測定波長５８９ｎｍ）であった。
第１と第２の位相差板２４と２５としては、ポリカーボネートからなるものを用い、位相差をそれぞれ２１７ｎｍとした。
偏光板２６としては、ＮＰＦ−ＥＧ１２２５ＤＵ（商品名：日東電工株式会社製）を用いた。
【００１７】
そして、偏光板２６の偏光軸が上配向膜３０の配向方向に対してなす角度を配向方向から反時計回りに４０°、第１の位相差板２４の遅相軸が上配向膜３０の配向方向に対してなす角度を配向方向から反時計回りに８０°、第２の位相差板２５の遅相軸が前記第１の位相差板２４の遅相軸に対してなす角度を第１の位相差板２４の遅相軸から反時計回りに１０°とした。
【００１８】
第１のオーバーコート層２８として、アクリル系ポリマー（商品名ＪＳＳ６６９９Ｇ、日本合成ゴム株式会社製）を用いた。色素としては、アゾ系の赤色顔料（商品名Ｃ．Ｉ．１２４９０、住友化学株式会社製）、フタロシアニン系の青色顔料（商品名Ｃ．Ｉ．４４０４５−ｌａｋｅ、大日精化株式会社製）をそれぞれ用いた。
そこで、下記表１に示すように、第１のオーバーコート層２８へ添加する色素の添加量を変えた５種類の前記液晶表示装置を作成し、それぞれの分光特性を調べた。
【００１９】

【００２０】
作製した上記５種類の液晶表示装置の分光特性を図２にグラフで示す。分光特性は、光源からの白色光をこの液晶表示装置に対して入射角０度で入射したときの反射光を受光角０度で受光して測定した。
図２において、横軸を波長、縦軸を反射率で示してあり、前記表１の比較例及び実施例のａ〜ｅがそれぞれグラフ中の細い実線ａ、破線ｂ、太い実線ｃ、一点鎖線ｄ及び二点鎖線ｅに対応している。細い実線ａは色素が無添加の場合であり、特に赤と青の波長帯域の光をよく透過し、全体として黄色に着色している。そして、この黄色と補色関係にある赤顔料と青顔料の添加量が増加するに従って、光の波長４５０〜６５０ｎｍ帯域の透過率が減少することが分かる。グラフｃ及びｄに示すように赤色及び青色顔料のそれぞれの添加量が０．１乃至０．４重量％の範囲内であると、光の前記波長帯域が同レベルとなり、波長依存性をなくすことができ、ほぼ無彩色化できる。なお、さらに添加量を増やし０．５重量％になると、赤紫色に着色し且つ表示全体が暗くなり使用できなくなる。
【００２１】
なお、上記実施例では、色素が無添加の場合に液晶表示装置の表示面が黄色に着色し、その補色関係にある赤色及び青色顔料を添加したもので説明した。しかし、本発明は、表示面が他の色相を有する液晶表示装置にも適用可能であり、表示面が緑の色相の液晶表示装置には、その補色関係にある赤色顔料のみを、また、表示面が青の色相の液晶表示装置には、その補色関係にある黄色及び赤色顔料を上述したように同様な量添加すればよく、例えば、アゾ系の黄色顔料としては、Ｃ．Ｉ．１１６７０（商品名：大日精化株式会社製）を用いることができる。
【００２２】
【発明の効果】
以上説明したように本発明の液晶表示装置は、対向する上下の透明基板のそれぞれの対向面に、少なくとも透明電極及び配向膜を順に設け、少なくとも何れか一方の前記透明基板の該透明基板と前記透明電極との間に、カラーフィルタ又は凹凸を有する反射体と、オーバーコート層とを介在させ、上下の透明基板の前記配向膜間に液晶層を設けてなり、全体の色相に対して補色となる色相の色素を前記オーバーコート層に添加したものであり、表示面の色相を色素により無彩色化することが可能となる。また、前記色素をオーバーコート層に添加したものであるため、液晶層に色素の添加を行うことなく表示の無彩色化が可能で、低温時や常温長時間放置後の特性の劣化のない液晶表示装置を提供することができ、従来の液晶層へ添加したものに比較して特性の劣化が無いために長寿命化が図れる。更に、オーバーコート層は他の膜と比較して厚く色素を均一に分散しやすいと云う効果も奏する。
更に本発明において、上側透明基板の外側に位相差板と偏光板とを順に設け、偏光板の偏光軸が、上側透明基板に設けられた配向膜の配向方向に対してなす角度を配向方向から反時計回りに４０°とし、第１の位相差板の遅相軸を上側配向膜の配向方向に対してなす角度を配向方向から反時計回りに８０゜とし、第２の位相差板の遅相軸を第１の位相差板の遅相軸に対してなす角度を第１の位相差板の遅相軸から反時計回りに１０°とし、補色となる色相の色素として、アゾ系の赤色顔料及びフタロシアニン系の赤色顔料であるならば、表示面の色相を色素により無彩色化することが可能となる。
また、前記色素を０．１乃至０．４重量％添加したことで、表示面の無彩色化に好適な特徴を有する。
更に本発明において、対向する上下の透明基板の下側透明基板の対向面に、凹凸を有する反射体と、該反射体の凹凸を平坦化するオーバーコート層と、透明電極及び配向膜を順に設け、前記上側透明基板の対向面に少なくともカラーフィルタ層とオーバーコート層と透明電極及び配向膜を順に設けると共に、該上側透明基板の外側に位相差板と偏光板とを順に設け、上下の透明基板の前記配向膜間にＳＴＮ液晶層を設けてなり、全体の色相に対して補色となる色相の色素を前記反射体の凹凸を平坦化するオーバーコート層に添加する一方、前記偏光板の偏光軸が、上側透明基板に設けられた配向膜の配向方向に対してなす角度を配向方向から反時計回りに４０°とし、前記位相差板を第１の位相差板及び第２の位相差板の２層から構成するとともに、第１の位相差板の遅相軸が上側配向膜の配向方向に対してなす角度を配向方向から反時計回りに８０゜とし、第２の位相差板の遅相軸が前記第１の位相差板の遅相軸に対してなす角度を第１の位相差板の遅相軸から反時計回りに１０°とし、前記補色となる色相の色素として、アゾ系の赤色顔料及びフタロシアニン系の青色顔料を０．１乃至０．４重量％添加した構成ならば、光の波長４５０〜６５０ｎｍ帯域の透過率を同レベルとすることができ、波長依存性を無くすることができ、表示色の色調を無彩色にすることを確実にできるものである。
また、前記色素をオーバーコート層に添加したものであるため、液晶層に色素の添加を行うことなく表示の無彩色化が可能で、低温時や常温長時間放置後の特性の劣化のない液晶表示装置を提供することができ、従来の液晶層へ添加したものに比較して特性の劣化が無いために長寿命化が図れる。更に、オーバーコート層は他の膜と比較して厚く色素を均一に分散しやすいと云う効果も奏する。
【図面の簡単な説明】
【図１】本発明をＳＴＮ方式の反射型液晶表示装置に適用した実施の形態を示す断面図である。
【図２】本発明の実施例と比較例の反射型液晶表示装置のそれぞっれの分光特性を示すグラフである。
【図３】従来の反射型液晶表示装置の概略構成を示す断面図である。
【符号の説明】
２２上側ガラス基板（上側透明基板）
２３下側ガラス基板（下側透明基板）
２４第１の位相差板
２５第２の位相差板
２６偏光板
２７反射体
２８第１のオーバーコート層
２９、３４透明電極
３０、３１配向膜
３３第２のオーバーコート層
３５液晶層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which an overcoat layer containing a dye having a hue complementary to the entire hue is interposed between a substrate and a transparent electrode.
[0002]
[Prior art]
In general, display modes of a liquid crystal display device include a transmission type including a backlight and a reflection type. A reflection type liquid crystal display device is a liquid crystal display device that performs display without a backlight using only external light such as sunlight and illumination light, and is often used for a portable information terminal or the like which is required to be thin and lightweight. Have been.
[0003]
FIG. 3 shows an example of a conventional STN (super twisted nematic) type reflection type liquid crystal display device. This reflection type liquid crystal display device A is composed of a pair of glass substrates made of glass which are vertically arranged to face each other. 1 and 2, an STN-type liquid crystal layer 4 sealed with a sealing material therebetween, a polarizing plate 5, and retardation plates 6, 7 provided in order from the top on the upper surface side of the upper glass substrate 1, And a reflector 10 provided on the lower surface side of the lower glass substrate 2. The reflector 10 has fine irregularities 8a having a height of several μm formed on the surface of a resin or glass substrate 8 such as a polyester film having a thickness of 300 to 500 μm, for example, and further includes Al, Ag, and the like. The reflection film 9 is formed by vapor deposition or the like. An abutting surface between the reflector 10 and the glass substrate 2 is filled with an adhesive layer 11 made of a material such as glycerin which does not adversely affect the refractive index of light.
[0004]
An electrode layer 12 made of ITO (indium tin oxide), a top coat layer 13, and an alignment film 14 are laminated on the lower surface of the upper glass substrate 1, and a color display structure is formed on the upper surface of the lower glass substrate 2. In this case, the necessary color filter layer 15, overcoat layer 16, electrode layer 17, and alignment film 18 are laminated.
[0005]
In the reflection type liquid crystal display device A having the conventional structure, the incident light from the upper side of the upper glass substrate 1 is reflected by the reflection film 9 of the reflector 10 after passing through the liquid crystal layer 4 and transmitted through the liquid crystal layer 4 again. When returning to the upper glass substrate 1 later, the liquid crystal layer 4 changes the polarization direction of the light, and switches whether or not the reflected light can pass through the polarizing plate 6, thereby switching between the bright state and the dark state. It was done. In addition, the uneven portion 8a of the reflector 10 suppresses abnormally high reflection of light from a specific direction by forming the reflective film 9 into an uneven shape, widens the viewing angle, and displays a bright image over a wide range of the display surface. Can be performed.
[0006]
[Problems to be solved by the invention]
By the way, the STN method utilizes the difference between the birefringence of the liquid crystal when a voltage is applied and the birefringence of the liquid crystal when no voltage is applied for display. In order to realize the above, achromatic (black and white) display is indispensable. Therefore, the retardation plates 6 and 7 are used to prevent the display from being colored blue or yellow by compensating for the phase difference of the light transmitted through the liquid crystal. However, it is difficult to control △ nd (product of refractive index anisotropy と n and plate thickness d) of retardation plates 6 and 7 themselves, and it is difficult to control the optical axes of retardation plates 6 and 7 and polarizing plate 5. For reasons such as difficulty in optimizing the polarization axis and the angle in terms of manufacturing, the display is colored, and it is not possible to completely achromatic.
[0007]
Therefore, conventionally, a method has been proposed in which a dye having a hue that is complementary to the hue of display when no dye is present is added to the liquid crystal layer 4 in advance. However, when a dye is added to the liquid crystal layer 4, the display characteristics deteriorate at a low temperature. For example, when the external temperature becomes 0 ° C. or lower, the viscosity of the liquid crystal increases, and the response of the liquid crystal at the time of driving voltage ON-OFF is increased. And the screen switching becomes unstable. Further, if the liquid crystal layer 4 is left at room temperature (about 20 ° C.) for a long time, a part of the liquid crystal layer 4 is crystallized, so that there is a problem that display cannot be performed.
[0008]
The present invention has been made in view of the above problems, and a liquid crystal display device capable of achromatic display without adding a dye to a liquid crystal layer and having no deterioration in characteristics at a low temperature or after standing at room temperature for a long time. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In the liquid crystal display device of the present invention, at least a transparent electrode and an alignment film are sequentially provided on respective opposing surfaces of the upper and lower transparent substrates facing each other, and at least one of the transparent substrate and the transparent electrode has a desired structure. A color filter having a pattern, and an overcoat layer that covers the color filter and the transparent substrate while flattening unevenness caused by the pattern of the color filter, and forming a liquid crystal layer between the alignment films of the upper and lower transparent substrates. This is because a dye having a hue complementary to the whole hue is added to the overcoat layer. Therefore, the addition of the dye does not adversely affect the liquid crystal layer, and the display surface can be made achromatic. As the pigment, a pigment exhibiting a color tone having a complementary color relation to the color tone of the liquid crystal display device is preferable. As the pigment, an azo pigment, a phthalocyanine pigment or the like can be used.
The liquid crystal display device of the present invention has a color filter having a desired pattern on the upper transparent substrate facing the upper and lower transparent substrates, and flattening the unevenness caused by the pattern of the color filter and the color filter. An overcoat layer covering the transparent substrate, a transparent electrode, and an alignment film are sequentially provided, and at least a transparent electrode and an alignment film are sequentially provided on the opposing surface of the lower transparent substrate, and between the alignment films of the upper and lower transparent substrates. And a colorant having a hue complementary to the entire hue is added to the overcoat layer.
[0010]
Further, the present invention provides a reflector having irregularities on an opposing surface of a lower transparent substrate facing the upper and lower transparent substrates , an overcoat layer for flattening the irregularities of the reflector , a transparent electrode and an alignment film in order. And at least a transparent electrode and an alignment film are sequentially provided on the opposing surface of the upper transparent substrate, and a retardation plate and a polarizing plate are sequentially provided outside the upper transparent substrate, and a liquid crystal is provided between the alignment films of the upper and lower transparent substrates. A layer having a hue complementary to the entire hue is added to the overcoat layer. In a liquid crystal display device with a built-in reflector, achromaticity can be achieved. As the pigment, the above pigment can be used.
In the liquid crystal display device of the present invention, an angle formed by the polarization axis of the polarizing plate with respect to the alignment direction of the alignment film provided on the upper transparent substrate is 40 ° counterclockwise from the alignment direction; Is composed of two layers, a first retardation plate and a second retardation plate, and the angle formed by the slow axis of the first retardation plate with respect to the orientation direction of the upper orientation film is counterclockwise from the orientation direction. The angle formed by the slow axis of the second retardation plate with respect to the slow axis of the first retardation plate is 10 ° counterclockwise from the slow axis of the first retardation plate. And the complementary hue dye is an azo red pigment or a phthalocyanine red pigment . In the present invention, the dye may be 0.1 to 0.1. The addition of 4% by weight is suitable for making the display surface achromatic.
Further, the liquid crystal display device of the present invention comprises a reflector having irregularities on the opposing surfaces of the lower transparent substrates facing the upper and lower transparent substrates, an overcoat layer for flattening the irregularities of the reflector, a transparent electrode and alignment. Films are sequentially provided, and at least a color filter layer, an overcoat layer, a transparent electrode, and an alignment film are sequentially provided on the facing surface of the upper transparent substrate, and a retardation plate and a polarizing plate are sequentially provided outside the upper transparent substrate, An STN liquid crystal layer is provided between the alignment films of the upper and lower transparent substrates, and a dye having a hue complementary to the whole hue is added to the overcoat layer for flattening the unevenness of the reflector, while the polarization is added. The angle between the polarization axis of the plate and the orientation direction of the orientation film provided on the upper transparent substrate is set to 40 ° counterclockwise from the orientation direction, and the retardation plate is a first retardation plate and a second retardation plate. It consists of two layers of retardation plate At the same time, the angle between the slow axis of the first retardation plate and the orientation direction of the upper alignment film is set to 80 ° counterclockwise from the orientation direction, and the slow axis of the second retardation plate is The angle between the slow axis of the first retardation plate and the slow axis of the first retardation plate is set to 10 ° counterclockwise, and azo red pigment and phthalocyanine are used as the complementary hue dyes. Blue pigment is added in an amount of 0.1 to 0.4% by weight.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a liquid crystal display device of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment in which the liquid crystal display device of the present invention is applied to an STN type reflective color liquid crystal display device.
In the reflection type liquid crystal device of this embodiment, a reflector 27, a first overcoat layer 28, and a common electrode 29 are provided on opposing surfaces of a lower glass substrate 23 (lower transparent substrate) of upper and

lower glass substrates

22 and 23 facing each other. (Transparent electrode) and an orientation film 31 are sequentially provided, and a color filter layer 32, a second overcoat layer 33, a segment electrode 34 (transparent electrode) and an orientation film 30 are sequentially provided on a surface facing the upper glass substrate 22, Further, this is a schematic configuration in which an STN liquid crystal layer 35 is provided between the

alignment films

30 and 31 of the upper and

lower glass substrates

22 and 23. Further, on the upper glass substrate 22, first and

second retardation plates

24 and 25 and a polarizing plate 26 are sequentially laminated.
[0012]
Each of the

alignment films

30 and 31 has a thickness of about 0.2 μm, and is a transparent alignment film that is usually used. For example, a polymer film such as polyimide is rubbed.
The liquid crystal layer 35 includes upper and

lower alignment films

30 and 31 provided inside the upper and

lower glass substrates

22 and 23, and a sealing material (not shown) for joining the

alignment films

30 and 31 at a predetermined interval. And a liquid crystal molecule which is in a nematic state at normal temperature and enclosed in a region surrounded by the above. Have been.
[0013]
The upper glass substrate 22 is made of soda lime glass or the like, although it differs depending on the type of liquid crystal display device, and preferably has a thickness of 0.3 mm or more. When the thickness is less than 0.3 mm, the mechanical strength is reduced.
The second overcoat layer 33 is provided with a thickness of 3 to 4 μm in order to flatten the unevenness due to the color filter layer 32, and has a high adhesion to the color filter layer 32 such as polyvinyl alcohol and acrylic resin. Of organic materials.
The color filter layer 32 is formed by forming pixels of three primary colors of red, blue, and green according to a desired pattern by a method such as photolithography or a printing method. May be patterned with a linear black mask.
[0014]
As the lower glass substrate 23, although it depends on the type of liquid crystal display device, in this embodiment, soda lime glass or the like containing an oxide of an alkali metal such as sodium is used. .1 mm or more. Here, a rough surface having irregularities is formed on the surface of the lower glass substrate 23 facing the common electrode 29, and the reflector 27 is formed on the rough surface of the lower glass substrate 23. It is made of a metal film such as an Al film. The reflector 27 serves to increase the viewing angle by reflecting and diffusing incident light. In such a reflective liquid crystal device with a built-in reflector, there is no need to consider the problem of parallax due to the thickness of the lower glass substrate 23.
[0015]
The first overcoat layer 28 is provided for flattening unevenness due to the reflector 27, and is made of an acrylic material having a thickness of 3 to 4 μm.
Therefore, a dye is added to the first overcoat layer 28 in advance, and the hue (color) of the entire liquid crystal display device is made achromatic. The overcoat layer 28 has a relatively large film thickness and facilitates uniform dispersion of the dye. The type of the dye is a red, blue or yellow pigment, and as the material thereof, an azo type, a phthalocyanine type, or the like can be used.
As the kind of the pigment to be used, a pigment having a color complementary to the hue (coloring) of the entire liquid crystal display device may be selected. For example, when the hue of the entire device is yellow, complementary colors of red and blue are used. When the hue is green, only the complementary red pigment can be used, and when the hue is blue, the complementary yellow and red pigments can be used.
The amount of the dye added is preferably 0.1 to 0.4% by weight, and when two types of pigments are used, 0.1 to 0.4% by weight of each dye is added. The hue of the entire apparatus can be made achromatic.
Although the description has been made by adding a dye to the first overcoat layer 28, it is a matter of course that the entire device can be rendered achromatic by adding a dye to the second overcoat layer 33.
[0016]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to only these Examples.
In the reflection type liquid crystal display device of the embodiment shown in FIG. 1, a different type of dye added to the first overcoat layer 28 was prepared, and its spectral characteristics were examined.
PSI-2501 (trade name, manufactured by Chisso Corporation) was used as the upper and

lower alignment films

30 and 31, and alignment processing was performed so that the twist angle was 240 degrees. The thickness of the liquid crystal cell was 5.2 μm, and Δnd was 861 nm (measurement wavelength: 589 nm).
The first and

second retardation plates

24 and 25 were made of polycarbonate, and each had a retardation of 217 nm.
As the polarizing plate 26, NPF-EG1225DU (trade name: manufactured by Nitto Denko Corporation) was used.
[0017]
The angle between the polarization axis of the polarizing plate 26 and the alignment direction of the upper alignment film 30 is 40 ° counterclockwise from the alignment direction, and the slow axis of the first retardation plate 24 is The angle with respect to the direction is 80 ° counterclockwise from the orientation direction, and the angle between the slow axis of the second retardation plate 25 and the slow axis of the first retardation plate 24 is the first angle. The angle was set to 10 ° counterclockwise from the slow axis of the phase difference plate 24.
[0018]
As the first overcoat layer 28, an acrylic polymer (trade name: JSS6699G, manufactured by Nippon Synthetic Rubber Co., Ltd.) was used. Examples of the pigment include an azo red pigment (trade name: CI 12490, manufactured by Sumitomo Chemical Co., Ltd.) and a phthalocyanine blue pigment (trade name: CI.44045-lake, manufactured by Dainichi Seika Co., Ltd.) Using.
Therefore, as shown in Table 1 below, five types of the liquid crystal display devices were prepared in which the amount of the dye added to the first overcoat layer 28 was changed, and their respective spectral characteristics were examined.
[0019]

[0020]
FIG. 2 is a graph showing the spectral characteristics of the five types of liquid crystal display devices manufactured. The spectral characteristics were measured by receiving reflected light at a light receiving angle of 0 degree when white light from a light source was incident on the liquid crystal display device at an incident angle of 0 degree.
In FIG. 2, the horizontal axis represents wavelength, and the vertical axis represents reflectance, and a to e in Comparative Examples and Examples in Table 1 are thin solid lines a, broken lines b, thick solid lines c, and dashed lines in the graphs, respectively. d and the two-dot chain line e. The thin solid line a indicates the case where no pigment is added, and particularly, light in the red and blue wavelength bands is well transmitted, and is colored yellow as a whole. It can be seen that the transmittance of the light in the wavelength band of 450 to 650 nm decreases as the addition amount of the red pigment and the blue pigment having a complementary color relationship with yellow increases. As shown in the graphs c and d, when the addition amount of each of the red and blue pigments is in the range of 0.1 to 0.4% by weight, the wavelength band of the light becomes the same level, and the wavelength dependency is eliminated. And can be almost achromatic. In addition, when the addition amount is further increased to 0.5% by weight, it is colored reddish purple and the whole display becomes dark, and cannot be used.
[0021]
In the above-described embodiment, the display surface of the liquid crystal display device is colored yellow when no pigment is added, and red and blue pigments, which are complementary to each other, are added. However, the present invention is also applicable to a liquid crystal display device having a display surface having another hue, and a liquid crystal display device having a display surface with a green hue includes only a red pigment having a complementary color relationship, A liquid crystal display device having a blue hue may be added with yellow and red pigments having a complementary color relationship in the same amount as described above. For example, azo-based yellow pigments include C.I. I. 11670 (trade name: manufactured by Dainichi Seika Co., Ltd.) can be used.
[0022]
【The invention's effect】
As described above, the liquid crystal display device of the present invention is provided with at least a transparent electrode and an alignment film in order on each of the opposing upper and lower transparent substrates, and the transparent substrate and the transparent substrate of at least one of the transparent substrates. between the transparent electrode, and a reflector having a color filter or irregularities, is interposed between the overcoat layer, it is provided a liquid crystal layer between the alignment layer of the upper and lower transparent substrates, a complementary color for the entire hue A dye having the following hue is added to the overcoat layer, and the hue on the display surface can be made achromatic by the dye. In addition, since the dye is added to the overcoat layer, the display can be made achromatic without adding the dye to the liquid crystal layer, and the liquid crystal does not degrade at low temperatures or after standing at room temperature for a long time. A display device can be provided, and a longer lifetime can be achieved because there is no deterioration in characteristics as compared with a conventional device added to a liquid crystal layer. Further, the overcoat layer is thicker than other films, and has an effect of easily dispersing the dye uniformly.
Further, in the present invention, a retardation plate and a polarizing plate are sequentially provided outside the upper transparent substrate, and the polarization axis of the polarizing plate forms an angle from the alignment direction with respect to the alignment direction of the alignment film provided on the upper transparent substrate. The angle between the slow axis of the first phase difference plate and the orientation direction of the upper alignment film is set to 80 ° counterclockwise from the orientation direction, and the angle of the slow axis of the first phase difference plate is set to 80 °. The angle between the slow axis of the first retardation plate and the slow axis of the first retardation plate is set to 10 ° counterclockwise from the slow axis of the first retardation plate. If it is a pigment or a phthalocyanine-based red pigment, the hue on the display surface can be made achromatic by using a pigment.
Further, by adding the dye in an amount of 0.1 to 0.4% by weight, it has a feature suitable for making the display surface achromatic.
Further, in the present invention, a reflector having unevenness, an overcoat layer for flattening the unevenness of the reflector, a transparent electrode and an alignment film are provided in this order on the opposing surfaces of the lower transparent substrate facing the upper and lower transparent substrates. At least a color filter layer, an overcoat layer, a transparent electrode and an alignment film are sequentially provided on the opposing surface of the upper transparent substrate, and a retardation plate and a polarizing plate are sequentially provided outside the upper transparent substrate. A STN liquid crystal layer is provided between the alignment films, and a dye having a hue complementary to the whole hue is added to the overcoat layer for flattening the unevenness of the reflector, while the polarization axis of the polarizing plate is added. However, the angle formed with respect to the alignment direction of the alignment film provided on the upper transparent substrate is set to 40 ° counterclockwise from the alignment direction, and the phase difference plate is formed of a first phase difference plate and a second phase difference plate. When composed of two layers Further, the angle formed by the slow axis of the first retardation film with respect to the orientation direction of the upper alignment film is set to 80 ° counterclockwise from the orientation direction, and the slow axis of the second retardation film is The angle between the slow axis of the first retardation plate and the slow axis of the first retardation plate is set to 10 ° counterclockwise, and azo red pigment and phthalocyanine are used as the complementary hue dyes. In the case where a blue pigment of 0.1 to 0.4% by weight is added, the transmittance in the wavelength band of light of 450 to 650 nm can be made the same level, the wavelength dependency can be eliminated, and the display can be performed. The color tone can be made achromatic.
In addition, since the dye is added to the overcoat layer, the display can be made achromatic without adding the dye to the liquid crystal layer, and the liquid crystal does not degrade at low temperatures or after standing at room temperature for a long time. A display device can be provided, and a longer lifetime can be achieved because there is no deterioration in characteristics as compared with a conventional device added to a liquid crystal layer. Further, the overcoat layer is thicker than other films, and has an effect of easily dispersing the dye uniformly.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment in which the present invention is applied to an STN reflective liquid crystal display device.
FIG. 2 is a graph showing the spectral characteristics of each of the reflective liquid crystal display devices according to an example of the present invention and a comparative example.
FIG. 3 is a cross-sectional view illustrating a schematic configuration of a conventional reflective liquid crystal display device.
[Explanation of symbols]
22 Upper glass substrate (upper transparent substrate)
23 Lower glass substrate (Lower transparent substrate)
24 First retardation plate 25 Second retardation plate 26 Polarizing plate 27 Reflector 28

First overcoat layer

29, 34

Transparent electrodes

30, 31 Alignment film 33 Second overcoat layer 35 Liquid crystal layer

Claims

At least a transparent electrode and an alignment film are sequentially provided on each of the opposing upper and lower transparent substrates, and a color filter having a desired pattern is provided between at least one of the transparent substrate and the transparent electrode. A liquid crystal layer is provided between the alignment films of the upper and lower transparent substrates while flattening the unevenness caused by the pattern of the color filter and interposing an overcoat layer that covers the color filter and the transparent substrate, thereby providing an overall hue. A liquid crystal display device characterized in that a dye having a hue that is a complementary color is added to the overcoat layer.

A color filter having a desired pattern on an upper transparent substrate facing the upper and lower transparent substrates facing each other, and an overcoat layer that flattens irregularities caused by the pattern of the color filter and covers the color filter and the transparent substrate. And, a transparent electrode, and an alignment film are sequentially provided, and at least the transparent electrode and the alignment film are sequentially provided on the opposing surface of the lower transparent substrate, and a liquid crystal layer is provided between the alignment films of the upper and lower transparent substrates, A liquid crystal display device, wherein a dye having a hue complementary to the entire hue is added to the overcoat layer.

On the opposing surface of the lower transparent substrate facing the upper and lower transparent substrates, a reflector having irregularities, an overcoat layer for flattening the irregularities of the reflector , a transparent electrode and an alignment film are sequentially provided, and the upper transparent substrate is provided. At least a transparent electrode and an alignment film are sequentially provided on the opposing surface, a retardation plate and a polarizing plate are sequentially provided outside the upper transparent substrate, and a liquid crystal layer is provided between the alignment films of the upper and lower transparent substrates, A liquid crystal display device, wherein a dye having a hue complementary to the entire hue is added to the overcoat layer.

The polarization axis of the polarizing plate is 40 ° counterclockwise from the alignment direction with respect to the alignment direction of the alignment film provided on the upper transparent substrate, and the phase difference plate has a first phase difference plate and The second phase difference plate has two layers, and the angle between the slow axis of the first phase difference plate and the orientation direction of the upper alignment film is 80 ° counterclockwise from the orientation direction. The angle between the slow axis of the phase difference plate and the slow axis of the first phase difference plate is 10 ° counterclockwise from the slow axis of the first phase difference plate, and the complementary color is obtained. The liquid crystal display device according to claim 3, wherein the hue pigment is an azo red pigment or a phthalocyanine red pigment.

5. The liquid crystal display device according to claim 1, wherein the dye is added in an amount of 0.1 to 0.4% by weight.

On the opposing surface of the lower transparent substrate facing the upper and lower transparent substrates, a reflector having irregularities, an overcoat layer for flattening the irregularities of the reflector, a transparent electrode and an alignment film are sequentially provided, and the upper transparent substrate is provided. At least a color filter layer, an overcoat layer, a transparent electrode, and an alignment film are sequentially provided on the opposite surface of the substrate, and a retardation plate and a polarizing plate are sequentially provided outside the upper transparent substrate. A STN liquid crystal layer, and a dye having a hue complementary to the entire hue is added to the overcoat layer for flattening the unevenness of the reflector,
The polarization axis of the polarizing plate, the angle formed with respect to the orientation direction of the orientation film provided on the upper transparent substrate is 40 ° counterclockwise from the orientation direction, the first retardation plate and the first retardation plate The second phase difference plate is composed of two layers, and the angle formed by the slow axis of the first phase difference plate with respect to the orientation direction of the upper alignment film is set to 80 ° counterclockwise from the orientation direction. The angle between the slow axis of the phase difference plate and the slow axis of the first phase difference plate is set to 10 ° counterclockwise from the slow axis of the first phase difference plate, A liquid crystal display device comprising 0.1 to 0.4% by weight of an azo red pigment and a phthalocyanine blue pigment as a dye.