JP4776053B2

JP4776053B2 - Liquid crystal display

Info

Publication number: JP4776053B2
Application number: JP2000027297A
Authority: JP
Inventors: 一行久長
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2000-01-31
Filing date: 2000-01-31
Publication date: 2011-09-21
Anticipated expiration: 2020-01-31
Also published as: JP2001215513A

Description

【０００１】
【発明の属する技術分野】
本発明は半透過膜を設けた半透過型液晶表示装置に関し、とくに液晶パネルの設計（ツイスト角、光路差Δｎｄ）、位相差板の光路差Δｎｄおよび貼付角度ならびに偏光板の貼付角度の適正化に関するものである。
【０００２】
【従来の技術】
近年、液晶表示装置は小型もしくは中型の携帯情報端末やノートパソコンの他に、大型かつ高精細のモニターにまで使用されている。さらに携帯情報端末においては、屋外・屋内の双方に使用できる半透過型液晶表示装置が開発されている。
【０００３】
この半透過型液晶表示装置によれば、太陽光、蛍光灯などの外部照明によって反射型の装置として用いる場合と、バックライトを内部照明として装着した透過型の装置として用いる場合があり、双方の機能を併せもたせるために、半透過反射板を液晶パネルの裏面に配置するとともに、この半透過反射板の裏面側に偏光板とバックライトとを順次配置し、さらに半透過反射板と偏光板との間に透過表示時の着色を補償するための位相差板を配置した構造が提案されている（特開平８−２９２４１３号参照）。
【０００４】
図４は従来のＳＴＮ型単純マトリックスタイプの半透過型液晶表示装置１の概略断面図である。
【０００５】
この半透過型液晶表示装置１において、２は液晶パネルであって、対向配置した２枚のガラス基板のそれぞれの内面に、多くの透明電極を平行に配列し、さらに双方の平行透明電極群を両基板間で直交するように両ガラス基板を配し、そして、各平行透明電極群上に配向膜を形成し、ネマチック型液晶分子を両ガラス基板間で１８０°〜２７０°ツイスト配列させた構造である。
【０００６】
また、液晶パネル２の一方主面上には位相差板３と偏光板４とを順次積み重ね、他方主面上には位相差板５と偏光板６と半透過反射板７とを順次積み重ね、さらに半透過反射板７上にバックライト８を配設している。
【０００７】
そして、上記半透過型液晶表示装置１を反射型として使用する場合、半透過反射板７は反射膜となし、透過型として使用する場合に透過膜となす。
【０００８】
【発明が解決しようとする課題】
しかしながら、上記構成の半透過型液晶表示装置１を反射型として使用すると、液晶パネル２の液晶層と半透過反射板７との間に存在するガラス基板の厚みに起因し、視差が生じ、これによって像が二重に見える現象が発生し、さらに混色によって色再現性が低下するという課題がある。
【０００９】
本発明は上記事情に鑑みて完成されたものであり、その目的は反射型として使用しても高い輝度を達成し、さらに高コントラスト比（十分な色補償）が得られた高彩度の半透過型液晶表示装置を提供することにある。
【００１０】
本発明の他の目的は反射型および透過型の両機能を満足し得る程度にまで特性を高めた高性能な半透過型液晶表示装置を提供することにある。
【００１１】
【課題を解決するための手段】
本発明の液晶表示装置は、透明基板上に透明電極と配向層とを順次積層してなる２つの透明部材を、ツイスト角を２４０〜２６０°に、Δｎｄを８００〜９００ｎｍにしたスーパーツイストネマチック型液晶を介して貼り合わせてマトリックス状に画素を配列してなる液晶パネルの一方主面側に、光路差Δｎｄが６８０〜７００ｎｍの第一位相差板と、光路差Δｎｄが５７０〜５９０ｎｍの第二位相差板と、第一偏光板と、を順次積み重ね、液晶パネルの他方主面側に、光路差Δｎｄが１３０〜１５０ｎｍの第三位相差板と、第二偏光板と、バックライトと、を順次積み重ね、上記他方主面側の透明基板と透明電極との間に半透過膜を配設し、上記スーパーツイストネマチック型液晶における両面のラビング方向の平均値を基準にするとき、第一位相差板の延伸軸を５０〜６０°に、第二位相差板の延伸軸を１６５〜１７５°に、第一偏光板の吸収軸を５〜１５°に、第三位相差板の延伸軸を１３０〜１４０°に、第二偏光板の吸収軸を８５〜９５°に設定した。
【００１２】
本発明の他の液晶表示装置は、透明基板上に電極と配向層とを順次積層してなる２つの透明部材を、ツイスト角を２４０〜２６０°に、Δｎｄを８００〜９００ｎｍにしたスーパーツイストネマチック型液晶を介して貼り合わせてマトリックス状に画素を配列してなる液晶パネルの一方主面側に、光路差Δｎｄが６８０〜７００ｎｍの第一位相差板と、光路差Δｎｄが５７０〜５９０ｎｍの第二位相差板と、第一偏光板と、を順次積み重ね、液晶パネルの他方主面側に、光路差Δｎｄが１３０〜１５０ｎｍの第三位相差板と、第二偏光板と、バックライトと、を順次積み重ね、上記他方主面側の電極を半透過膜により形成し、上記スーパーツイストネマチック型液晶における両面のラビング方向の平均値を基準にするとき、第一位相差板の延伸軸を５０〜６０°に、第二位相差板の延伸軸を１６５〜１７５°に、第一偏光板の吸収軸を５〜１５°に、第三位相差板の延伸軸を１３０〜１４０°に、第二偏光板の吸収軸を８５〜９５°に設定した。
【００１３】
【発明の実施の形態】
以下、本発明の液晶表示装置を図１と図２により、本発明の他の液晶表示装置を図３により説明する。
例１
図１は液晶表示装置９の断面図であり、図２は液晶表示装置９の要部拡大断面図である。なお、図４に示す半透過型液晶表示装置１と同一部材には同一符号を付す。
【００１４】
図１において、液晶パネル２の一方主面上に、光散乱性板状体１０と、ポリカーボネイトなどからなる第一位相差板１１と、ポリカーボネイトなどからなる第二位相差板１２と、ヨウ素系の第一偏光板１３とを順次積み重ね、他方主面上にポリカーボネイトなどからなる第三位相差板１４とヨウ素系の第二偏光板１５とを順次積み重ねる。これらはアクリル系の材料からなる粘着材を用いて貼り付ける。さらに第二偏光板１５上にバックライト８を配設している。
【００１５】
第一位相差板１１、第二位相差板１２および第三位相差板１４はポリカーボネイトなどの合成樹脂フィルムを延伸したものを用いる。
【００１６】
上記光散乱性板状体１０は、たとえば大日本印刷（珠）製のＩＤＳ(Internal Diffusing Sheet)の光散乱膜があり、樹脂中にビーズ等を含有させたものである。その他に平板の表面に光散乱性の凹凸を設けてもよい。さらには第一位相差板１１とガラス基板とを貼り付ける粘着材中にビーズ等の微粒子を含有させてもよい。
【００１７】
図２に示す液晶パネル２において、１６はセグメント側のガラス基板、１７はコモン側のガラス基板であって、ガラス基板１６上には多数平行に配列したＩＴＯからなる透明電極１８と、ＳｉＯ₂ からなる絶縁層１９と、一定方向にラビングしたポリイミド樹脂からなる配向膜２０とを順次形成している。なお、絶縁層１９は形成しなくてもよい。
【００１８】
他方のガラス基板１７上には半透過膜２１を形成し、この半透過膜２１上にカラーフィルタ２２とブラックマトリックス２３とを形成している。カラーフィルタ２２などを容易に形成するために、半透過膜２１上にＳｉＯ₂ 層を介してカラーフィルタ２２を設けてもよい。上記カラーフィルタ２２は画素ごとに配し、各カラーフィルタ２２間にクロム金属もしくは感光性レジストのブラックマトリックス２３とを形成している。なお、ブラックマトリックス２３は必須不可欠ではなく、ブラックマトリックス２３を設けなくてもよい。
【００１９】
上記半透過膜２１は光透過性と光反射性の双方の特性を具備しており、しかも、２枚の偏光板の間に挟んだ時に位相差を生じないようにする。また、半透過膜２１は鏡面性であっても、散乱性を有していてもよく、散乱性を具備させるには、樹脂等により凹凸形状を設け、その上に半透過膜を形成することで得られるが、このように光散乱性の半透過膜２１を形成した場合には、後記の光散乱性板状体１０を設けなくてもよい。
【００２０】
また、半透過膜２１は金属層や誘電体層により形成する。金属層を用いた場合にはＡｌ、Ｃｒ、ＳＵＳ系、Ａｇにより構成し、光透過性と光反射性の双方を満たすために、膜厚を５０〜３００Åにするとよく、さらに光透過性を重視する場合には５０〜１５０Åに、光反射性を重視する場合には１５０〜３００Åにするとよい。誘電体層を使用した場合には、たとえば高屈折率材料のＴｉＯ₂ 膜と低屈折率材料のＳｉＯ₂ 膜とを交互に積層した膜でよく、このような積層を５０Å〜１２０００Åの厚みで形成するとよい。そして、かかる構成の半透過膜２１はガラス基板などの透明な支持板に設ける。また、金属層でもって形成する方が単一の材料を用いるという点で低コストになり、さらにスパッタリング法により容易に安定して高品質な膜形成ができるという点でよい。
【００２１】
上記カラーフィルタ２２は、顔料分散方式、すなわちあらかじめ顔料により調合された感光性レジストを基板上に塗布し、フォトリソグラフィにより形成している。図中のＲ、Ｇ、Ｂの各表示はそれぞれ赤、緑、青に着色したカラーフィルタ２２であることを示す。
【００２２】
その上にアクリル系樹脂からなるオーバーコート層２４と、多数平行に配列したＩＴＯからなる透明電極２５とを形成している。この透明電極２５は上記透明電極１８と直交している。しかも、透明電極２５上に一定方向にラビングしたポリイミド樹脂からなる配向膜２６を形成している。なお、透明電極２５と配向膜２６との間にＳｉＯ₂ 等からなる絶縁層を介在させてもよい。
【００２３】
また、上記のように形成した各ガラス基板１６、１７をたとえば２００〜２７０°の角度でツイストされたカイラルネマチック液晶からなる液晶層２７を介してシール剤２８により貼り合わせる。さらにまた、両ガラス基板１６、１７間には液晶層２７の厚みを一定にするためにスペーサ２９を多数個配している。なお、本例の液晶パネル２では絶縁層１９、オーバーコート層２４を設けているが、それを設けなくてもよい。
【００２４】
かくして上記構成の液晶表示装置９を反射型として用いた場合には、太陽光、蛍光灯などの外部照明による照射光は第一偏光板１３と第二位相差板１２と第一位相差板１１と光散乱性板状体１０と液晶パネル２とを順次通過し、さらに半透過膜２１でもって反射され、その反射光が液晶パネル２を通過し、光散乱性板状体１０と第一位相差板１１と第二位相差板１２と第一偏光板１３とを通過することで、ガラス基板１７や第三偏光板１４、第二偏光板１５を通過しないので輝度が高くなる。
【００２５】
とくに、このようにガラス基板１７上に半透過膜２１を形成すると、反射型として使用してもガラス基板１７を通過しなくなり、これにより、ガラス基板１７に起因する表示が二重に見えるという現象が生じなくなる。
【００２６】
また、液晶表示装置９を透過型として用いた場合には、バックライト８の照射光が第二偏光板１５と第三位相差板１４と半透過膜２１とを順次通過し、液晶パネル２を通って光散乱性板状体１０と第一位相差板１１と第二位相差板１２と第一偏光板１３とを順次通過し、これによって第二偏光板１５を通過した光は第三位相差板１４で偏光状態を変え、その結果、上記の反射型にて使用した液晶パネル２を、そのままの条件で透過型にも使用することができ、さらに液晶層２７のツイスト角、液晶層２７の光路差Δｎｄ、偏光板１３、１５の吸収軸、位相差板１１、１２、１４の光路差Δｎｄおよび延伸軸を本発明にて規定する所定の範囲に設定することで、反射型および透過型のいずれの場合でも十分な色補償が得られ、高彩度で、かつ安定した鮮明な色表示ができた。
【００２７】
しかも、本発明の液晶表示装置９によれば、半透過膜２１が鏡面性を具備している場合には、光散乱性板状体１０を液晶パネル２と第一位相差板１１との間に設けることで、反射型として用いると、半透過膜２１でもって反射された反射光は光散乱性板状体１０でもって正反射方向以外の方向にも散乱され、これによって画像表示の視野角が大きくなり、反射時の表示特性が改善される。
【００２８】
また、半透過膜２１が散乱性を有しているのであれば、その散乱機能により同様に正反射方向以外の方向にも散乱され、これによって画像表示の視野角が大きくなり、反射時の表示特性が改善される。
【００２９】
さらに半透過膜２１を内部に配置したことで、視差がなくなり、二重像、色の混色による色再現性の低下が解消された。
例２
本発明の他の液晶表示装置３０を図３により説明する。なお、例１の液晶表示装置９と同一箇所には同一符号を付す。
【００３０】
この液晶表示装置３０においては、液晶表示装置９にて設けた半透過膜２１に代えて透明電極１８を半透過膜でもって形成し（図中、電極１８ａと記す）、このように兼用することでコストが低減できる。その半透過膜用の電極１８ａは金属膜で形成する。ただし、バックライト８の配設部位は上記液晶表示装置９と反対側にする。
【００３１】
上記構成の液晶表示装置３０についても反射型として使用すると、輝度が高くなり、さらに透過型として用いた場合にも反射型にて使用した液晶パネルをそのままの条件で透過型にも使用でき、反射型および透過型のいずれの場合でも安定した鮮明な色表示ができ、しかも、例１と同様に二重に見える現象がなくなった。さらに偏光サングラスを通してパネルを見た場合においても良好な表示が得られた。
【００３２】
また、基板１６上に半透過膜２１を形成し、その上に絶縁層、透明電極１８、絶縁層１９、配向膜２０を形成した構成でも同じ効果が得られる。
好適な設計条件
図５は液晶層２１のツイスト角を２４０〜２６０°、光路差△ｎｄを８００〜９００ｎｍにして、両配向膜２０、２６での双方のラビング方向の平均ラビング方向を基準にして、各位相差板１１、１２、１４の延伸軸および各偏光板１３、１５の吸収軸の各角度（反時計回り）を表示面から見た場合を示す。なお、位相差板１１、１２、第一偏光板１３は半透過膜形成基板の対向基板に、位相差板１４、第二偏光板１５は半透過膜形成基板に配設する。
【００３３】
本発明においては、下記のように設定する。
第一位相差板１１
光路差Δｎｄ：６８０〜７００ｎｍ、好適には６８５〜６９５ｎｍ
延伸軸：５０〜６０°、好適には５２〜５８°
第二位相差板１２
光路差Δｎｄ：５７０〜５９０ｎｍ、好適には５７５〜５８５ｎｍ
延伸軸：１６５〜１７５°、好適には１６７〜１７３°
第一偏光板１３
吸収軸：５〜１５°、好適には７〜１３°
第三位相差板１４
光路差Δｎｄ：１３０〜１５０ｎｍ、好適には１３５〜１４３ｎｍ
延伸軸：１３０〜１４０°、好適には１３２〜１３８°
第二偏光板１５
吸収軸：８５〜９５°、好適には８７〜９３°
上記のように設定することで、反射型として使用した場合、高い輝度を達成し、さらに高コントラスト比（十分な色補償）が得られた。そして、反射型とした使用した液晶表示装置を透過型に使用した場合でも十分な色補償が得られ、反射型もしくは透過型のいずれにしても高彩度の表示が実現できた。また、偏光サングラスを通してパネルを見た場合においても良好な表示が得られた。
【００３４】
【実施例】
（実施例１）
各液晶表示装置９、３０を透過型および反射型に使用した場合の輝度を測定したところ、表１に示すような結果が得られた。比較例として図４の半透過型液晶表示装置１を用いた。
【００３５】
色度および輝度の測定にはミノルタ製ＣＳ−１００を使用し、透過型の場合には一定の色度および輝度を有する同一のバックライトを使用し、反射型の場合には同一光源を液晶パネルに対し一定の角度で照射することで、それぞれの色度と輝度を測定した。
【００３６】
【表１】

【００３７】
輝度については、比較例の透過型および反射型をそれぞれ１．００として、相対値でもってあらわした。
【００３８】
表１の結果から明らかなとおり、本発明の液晶表示装置９、３０によれば、いずれも透過型もしくは反射型の双方ともに輝度を高めることができた。とくに例２の液晶表示装置３０は例１の液晶表示装置９に比べ、透過型および反射型の双方ともに輝度を顕著に高めることができた。
（実施例２）
本例においては、例１の液晶表示装置９について、第一位相差板１１（光路差Δｎｄ：６８０〜７００ｎｍ）の延伸軸、第二位相差板１２（光路差Δｎｄ：５７０〜５９０ｎｍ）の延伸軸、第一偏光板１３の吸収軸、第三位相差板１４（光路差Δｎｄ：１３０〜１５０ｎｍ）の延伸軸、第二偏光板１５の吸収軸を、それぞれ幾とおりにも変えて、種々の液晶表示装置９を作製し、装置Ｎｏ．１〜２１を得た。そして、これら各装置を（実施例１）にて用いた測定方法でもってコントラストを測定したところ、表２に示すような結果が得られた。
【００３９】
【表２】

【００４０】
この結果から明らかなとおり、本発明の装置Ｎｏ．１〜３、６、７、１０、１１、１４、１５、１８、１９については、反射時のコントラストが１２．５以上、透過時のコントラストが１７．５以上という優れた値が得られた。
【００４１】
これに対し装置４、５は第一偏光板が本発明の範囲外であり、装置８、９は第二位相差板が本発明の範囲外であり、装置１２、１３は第一位相差板が本発明の範囲外であり、装置１６、１７は第三位相差板が本発明の範囲外であることで、反射時のコントラストおよび透過時のコントラストが低くなっている。さらに装置２０、２１についても第二偏光板が本発明の範囲外であることで、透過時のコントラストが低くなっている。
（実施例３）
本例においては、例２の液晶表示装置３０について、第一位相差板１１（光路差Δｎｄ：６８０〜７００ｎｍ）の延伸軸、第二位相差板１２（光路差Δｎｄ：５７０〜５９０ｎｍ）の延伸軸、第一偏光板１３の吸収軸、第三位相差板１４（光路差Δｎｄ：１３０〜１５０ｎｍ）の延伸軸、第二偏光板１５の吸収軸を、それぞれ幾とおりにも変えて、種々の液晶表示装置３０を作製し、装置Ｎｏ．２２〜４２を得た。そして、これら各装置を（実施例１）にて用いた測定方法でもってコントラストを測定したところ、表３に示すような結果が得られた。
【００４２】
【表３】

【００４３】
この結果から明らかなとおり、本発明の装置Ｎｏ．２２〜２４、２７、２８、３１、３２、３５、３６、３９、４０については、反射時のコントラストが１４．２以上、透過時のコントラストが１８．８以上という優れた値が得られた。
【００４４】
これに対し装置２５、２６は第一偏光板が本発明の範囲外であり、装置２９、３０は第二位相差板が本発明の範囲外であり、装置３３、３４は第一位相差板が本発明の範囲外であり、装置３７、３８は第三位相差板が本発明の範囲外であることで、反射時のコントラストおよび透過時のコントラストが低くなっている。さらに装置４１、４２についても第二偏光板が本発明の範囲外であることで、透過時のコントラストが低くなっている。
なお、本発明は上記実施形態例に限定されるものでなく、本発明の要旨を逸脱しない範囲内で種々の変更や改善などは何ら差し支えない。
【００４５】
たとえば、上記の実施形態においては、ＳＴＮ型単純マトリックスタイプのカラー液晶表示装置でもって説明しているが、そのほかにモノクロのＳＴＮ型単純マトリックスタイプの液晶表示装置であっても同様な作用効果が得られる。
【００４６】
【発明の効果】
以上のとおり、本発明によれば、透明基板上に透明電極と配向層とを順次積層してなる２つの透明部材を、ツイスト角とΔｎｄを規定したスーパーネマチック型液晶を介して貼り合わせてマトリックス状に画素を配列し、透明基板と透明電極との間に半透過膜を配設してなる液晶パネルの一方主面側に、光路差Δｎｄと延伸軸を規定した第一位相差板と、光路差Δｎｄと延伸軸を規定した第二位相差板と、吸収軸を規定した第一偏光板とを順次積み重ね、他方主面側に光路差Δｎｄと延伸軸を規定した第三位相差板と、吸収軸を規定した第二偏光板と、バックライトとを順次積み重ねたことで、反射型として用いた場合には、外部照明による照射光は第一偏光板と第二位相差板と第一位相差板と光散乱性の板状体と液晶パネルとを順次通過し、さらに半透過膜でもって反射され、その反射光が液晶パネルを通過することで、他方の第二偏光板を通過しなくなり、これによって輝度が高くなり、一方、透過型として用いた場合には、バックライトの照射光が第二偏光板と第三位相差板と半透過膜とを順次通過し、液晶パネルを通り、これによって上記の反射型にて使用したパネルを、そのままの条件で透過型にも使用することができ、反射型もしくは透過型のいずれの場合でも安定した鮮明な色表示ができ、色補償が十分となり、その結果、反射型および透過型の両機能を満足し得る程度にまで特性を高めた高性能な半透過型液晶表示装置が提供できた。
【００４７】
また、本発明の他の液晶表示装置においても、スーパーネマチック型液晶、第一位相差板、第二位相差板、第一偏光板、第三位相差板、第二偏光板を同様に規定することで、反射型として用いた場合に輝度が高くなり、一方、透過型として用いた場合に反射型にて使用した液晶パネルを、そのままの条件で透過型にも使用することができ、反射型もしくは透過型のいずれの場合でも安定した鮮明な色表示ができ、色補償が十分となり、その結果、反射型および透過型の両機能を満足し得る程度にまで特性を高めた高性能な半透過型液晶表示装置が提供できた。
【図面の簡単な説明】
【図１】本発明の液晶表示装置の断面概略図である。
【図２】本発明の液晶表示装置の要部拡大断面図である。
【図３】本発明の他の液晶表示装置の要部拡大断面図である。
【図４】従来の液晶表示装置の断面概略図である。
【図５】位相差板の延伸軸と偏光板の吸収軸の表示面から見た各角度を示す説明図である。
【符号の説明】
２液晶パネル
８バックライト
９、３０液晶表示装置
１０光散乱性板状体
１１第一位相差板
１２第二位相差板
１３第一偏光板
１４第三位相差板
１５第二偏光板
１６、１７ガラス基板
１８、２５透明電極
１８ａ半透過膜で形成した電極
２０、２６配向膜
２１半透過膜
２２カラーフィルタ
２７液晶層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transflective liquid crystal display device provided with a transflective film, and in particular, optimization of liquid crystal panel design (twist angle, optical path difference Δnd), optical path difference Δnd and pasting angle of a phase difference plate, and pasting angle of a polarizing plate. It is about.
[0002]
[Prior art]
In recent years, liquid crystal display devices have been used for large-sized and high-definition monitors in addition to small or medium-sized portable information terminals and notebook computers. Further, for portable information terminals, transflective liquid crystal display devices that can be used both outdoors and indoors have been developed.
[0003]
According to this transflective liquid crystal display device, there are a case where it is used as a reflection type device by external illumination such as sunlight and fluorescent lamp, and a case where it is used as a transmission type device equipped with a backlight as internal illumination. In order to combine the functions, a transflective plate is disposed on the back side of the liquid crystal panel, and a polarizing plate and a backlight are sequentially disposed on the back side of the transflective plate. There has been proposed a structure in which a phase difference plate for compensating coloring at the time of transmissive display is arranged (see JP-A-8-292413).
[0004]
FIG. 4 is a schematic cross-sectional view of a conventional STN type simple matrix type transflective liquid crystal display device 1.
[0005]
In the transflective liquid crystal display device 1, reference numeral 2 denotes a liquid crystal panel, in which a large number of transparent electrodes are arranged in parallel on the inner surfaces of two opposing glass substrates, and both parallel transparent electrode groups are arranged. A structure in which both glass substrates are arranged so as to be orthogonal between both substrates, an alignment film is formed on each parallel transparent electrode group, and nematic liquid crystal molecules are twisted between 180 ° and 270 ° between both glass substrates. It is.
[0006]
Further, the phase difference plate 3 and the polarizing plate 4 are sequentially stacked on one main surface of the liquid crystal panel 2, and the phase difference plate 5, the polarizing plate 6 and the transflective plate 7 are sequentially stacked on the other main surface, Further, a backlight 8 is disposed on the transflective plate 7.
[0007]
When the transflective liquid crystal display device 1 is used as a reflective type, the transflective plate 7 is a reflective film, and when used as a transmissive type, it is a transmissive film.
[0008]
[Problems to be solved by the invention]
However, when the transflective liquid crystal display device 1 having the above-described configuration is used as a reflective type, parallax occurs due to the thickness of the glass substrate existing between the liquid crystal layer of the liquid crystal panel 2 and the transflective plate 7. This causes a phenomenon that the image looks double, and there is a problem that color reproducibility deteriorates due to color mixing.
[0009]
The present invention has been completed in view of the above circumstances, and its purpose is to achieve high luminance even when used as a reflection type, and to achieve a high contrast ratio (sufficient color compensation) and a high-saturation transflective type. The object is to provide a liquid crystal display device.
[0010]
Another object of the present invention is to provide a high-performance transflective liquid crystal display device whose characteristics are improved to such an extent that both functions of the reflective type and the transmissive type can be satisfied.
[0011]
[Means for Solving the Problems]
The liquid crystal display device of the present invention is a super twist nematic type in which two transparent members obtained by sequentially laminating a transparent electrode and an alignment layer on a transparent substrate have a twist angle of 240 to 260 ° and Δnd of 800 to 900 nm. A first retardation plate having an optical path difference Δnd of 680 to 700 nm and a second retardation plate having an optical path difference Δnd of 570 to 590 nm are formed on one main surface side of a liquid crystal panel in which pixels are arranged in a matrix by being bonded via a liquid crystal. and the retardation plate, and the first polarizing plate, sequentially stacked on the other main surface side of the liquid crystal panel, the optical path difference Δnd and the third retardation plate of 130～150Nm, and a second polarizer, a backlight, a When the semi-transmission film is disposed between the transparent substrate on the other main surface side and the transparent electrode and the average value in the rubbing direction of both surfaces in the super twist nematic liquid crystal is used as a reference , Stretching axis of retardation plate is 50-60 °, stretching axis of second retardation plate is 165-175 °, absorption axis of first polarizing plate is 5-15 °, stretching axis of third retardation plate Was set to 130 to 140 °, and the absorption axis of the second polarizing plate was set to 85 to 95 °.
[0012]
Another liquid crystal display device of the present invention is a super twist nematic in which two transparent members formed by sequentially laminating an electrode and an alignment layer on a transparent substrate have a twist angle of 240 to 260 ° and Δnd of 800 to 900 nm. A first retardation plate having an optical path difference Δnd of 680 to 700 nm and a first retardation plate having an optical path difference Δnd of 570 to 590 nm on one main surface side of a liquid crystal panel in which pixels are arranged in a matrix by being bonded via a type liquid crystal. sequentially stacking a second retardation plate, a first polarizing plate, and the other main surface side of the liquid crystal panel, and the third retardation plate optical path difference Δnd is 130～150Nm, and a second polarizer, and a backlight, sequentially stacked, the other main surface side of the electrode is formed by a semi-permeable membrane, when referenced to the average value of both sides of the rubbing direction of the upper Symbol super twisted nematic liquid crystal, the stretching axis of the first retardation plate To 50 to 60 °, the stretching axis of the second retardation plate to 165 to 175 °, the absorption axis of the first polarizing plate to 5 to 15 °, and the stretching axis of the third retardation plate to 130 to 140 °. The absorption axis of the second polarizing plate was set to 85 to 95 °.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the liquid crystal display device of the present invention will be described with reference to FIGS. 1 and 2, and another liquid crystal display device of the present invention will be described with reference to FIG.
Example 1
FIG. 1 is a cross-sectional view of the liquid crystal display device 9, and FIG. 2 is an enlarged cross-sectional view of the main part of the liquid crystal display device 9. The same members as those of the transflective liquid crystal display device 1 shown in FIG.
[0014]
In FIG. 1, on one main surface of the liquid crystal panel 2, a light scattering plate-like body 10, a first retardation plate 11 made of polycarbonate, a second retardation plate 12 made of polycarbonate, etc., an iodine-based plate The first polarizing plate 13 is sequentially stacked, and the third retardation plate 14 made of polycarbonate or the like and the iodine-based second polarizing plate 15 are sequentially stacked on the other main surface. These are attached using an adhesive material made of an acrylic material. Further, a backlight 8 is disposed on the second polarizing plate 15.
[0015]
As the first retardation plate 11, the second retardation plate 12, and the third retardation plate 14, a stretched synthetic resin film such as polycarbonate is used.
[0016]
The light-scattering plate-like body 10 has, for example, a light scattering film of IDS (Internal Diffusing Sheet) manufactured by Dai Nippon Printing Co., Ltd., and contains beads or the like in a resin. In addition, light scattering irregularities may be provided on the surface of the flat plate. Furthermore, fine particles such as beads may be contained in the adhesive material for bonding the first retardation plate 11 and the glass substrate.
[0017]
In the liquid crystal panel 2 shown in FIG. 2, 16 is a glass substrate on the segment side, 17 is a glass substrate on the common side, and a transparent electrode 18 made of ITO arranged in parallel on the glass substrate 16 and SiO _2. An insulating layer 19 and an alignment film 20 made of polyimide resin rubbed in a certain direction are sequentially formed. The insulating layer 19 may not be formed.
[0018]
A semi-transmissive film 21 is formed on the other glass substrate 17, and a color filter 22 and a black matrix 23 are formed on the semi-transmissive film 21. In order to easily form the color filter 22 and the like, the color filter 22 may be provided on the semi-transmissive film 21 via a SiO ₂ layer. The color filter 22 is provided for each pixel, and a black matrix 23 of chromium metal or photosensitive resist is formed between the color filters 22. Note that the black matrix 23 is not essential, and the black matrix 23 may not be provided.
[0019]
The semi-transmissive film 21 has both light-transmitting and light-reflecting characteristics, and prevents a phase difference when it is sandwiched between two polarizing plates. Further, the semi-transmissive film 21 may be specular or scattering, and in order to provide the scattering property, an uneven shape is provided with a resin or the like, and a semi-transmissive film is formed thereon. However, when the light-scattering semi-transmissive film 21 is formed in this way, the light-scattering plate-like body 10 described later need not be provided.
[0020]
The semi-transmissive film 21 is formed of a metal layer or a dielectric layer. When a metal layer is used, it is composed of Al, Cr, SUS, Ag, and the film thickness should be 50 to 300 mm in order to satisfy both light transmittance and light reflectivity. When it is necessary, it is preferably 50 to 150 mm, and when light reflectivity is important, it is preferably 150 to 300 mm. When the dielectric layer is used, for example, a film in which a TiO ₂ film of a high refractive index material and a SiO ₂ film of a low refractive index material are alternately laminated may be used, and such a lamination is formed with a thickness of 50 mm to 12000 mm. Good. The semi-permeable membrane 21 having such a configuration is provided on a transparent support plate such as a glass substrate. Further, the formation with a metal layer is cheaper in that a single material is used, and furthermore, a high-quality film can be formed easily and stably by a sputtering method.
[0021]
The color filter 22 is formed by photolithography using a pigment dispersion method, that is, a photosensitive resist previously prepared with a pigment is applied on a substrate. Each display of R, G, and B in the figure indicates that the color filter 22 is colored red, green, and blue, respectively.
[0022]
On top of this, an overcoat layer 24 made of acrylic resin and a transparent electrode 25 made of ITO arranged in parallel are formed. The transparent electrode 25 is orthogonal to the transparent electrode 18. In addition, an alignment film 26 made of polyimide resin rubbed in a certain direction is formed on the transparent electrode 25. Note that an insulating layer made of SiO ₂ or the like may be interposed between the transparent electrode 25 and the alignment film 26.
[0023]
Further, the

glass substrates

16 and 17 formed as described above are bonded together by a sealant 28 via a liquid crystal layer 27 made of chiral nematic liquid crystal twisted at an angle of, for example, 200 to 270 °. Furthermore, a large number of spacers 29 are arranged between the

glass substrates

16 and 17 in order to make the thickness of the liquid crystal layer 27 constant. In addition, although the insulating layer 19 and the overcoat layer 24 are provided in the liquid crystal panel 2 of this example, it is not necessary to provide them.
[0024]
Thus, when the liquid crystal display device 9 having the above-described configuration is used as a reflection type, the irradiation light from the external illumination such as sunlight or fluorescent lamp is the first polarizing plate 13, the second retardation plate 12, and the first retardation plate 11. , The light scattering plate-like body 10 and the liquid crystal panel 2 are sequentially passed, and further reflected by the semi-transmissive film 21, and the reflected light passes through the liquid crystal panel 2, and the light scattering plate-like body 10 and the first place. By passing through the phase difference plate 11, the second phase difference plate 12, and the first polarizing plate 13, the luminance is increased because the glass substrate 17, the third polarizing plate 14, and the second polarizing plate 15 are not passed.
[0025]
In particular, when the semi-transmissive film 21 is formed on the glass substrate 17 as described above, even if it is used as a reflection type, it does not pass through the glass substrate 17, thereby causing a phenomenon that the display due to the glass substrate 17 looks double. Will not occur.
[0026]
Further, when the liquid crystal display device 9 is used as a transmission type, the irradiation light of the backlight 8 sequentially passes through the second polarizing plate 15, the third retardation plate 14 and the semi-transmissive film 21, and passes through the liquid crystal panel 2. The light passing through the light scattering plate 10, the first retardation plate 11, the second retardation plate 12, and the first polarizing plate 13 sequentially passes, and thus the light that has passed through the second polarizing plate 15 is third. The polarization state is changed by the phase difference plate 14, and as a result, the liquid crystal panel 2 used in the reflection type can be used in the transmission type under the same conditions, and the twist angle of the liquid crystal layer 27 and the liquid crystal layer 27 can be used. By setting the optical path difference Δnd, the absorption axis of the

polarizing plates

13 and 15, the optical path difference Δnd of the

retardation plates

11, 12, and 14 and the stretching axis to the predetermined ranges defined in the present invention, the reflection type and the transmission type In any case, sufficient color compensation is obtained, high saturation, and stability A clear color display was achieved.
[0027]
In addition, according to the liquid crystal display device 9 of the present invention, when the semi-transmissive film 21 has a specularity, the light scattering plate 10 is disposed between the liquid crystal panel 2 and the first retardation plate 11. Therefore, when used as a reflection type, the reflected light reflected by the semi-transmissive film 21 is scattered by the light scattering plate-like body 10 in directions other than the regular reflection direction, and thereby the viewing angle of image display. Increases and the display characteristics during reflection are improved.
[0028]
Further, if the semi-transmissive film 21 has a scattering property, it is similarly scattered in directions other than the regular reflection direction by the scattering function, thereby increasing the viewing angle of the image display, and the display at the time of reflection. The characteristics are improved.
[0029]
Furthermore, by disposing the semi-transmissive film 21 inside, the parallax is eliminated, and the deterioration of the color reproducibility due to the double image and color mixing is eliminated.
Example 2
Another liquid crystal display device 30 of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same location as the liquid crystal display device 9 of Example 1. FIG.
[0030]
In this liquid crystal display device 30, instead of the semi-transmissive film 21 provided in the liquid crystal display device 9, the transparent electrode 18 is formed of a semi-transmissive film (denoted as an electrode 18a in the figure), and is used in this way. The cost can be reduced. The semi-permeable membrane electrode 18a is formed of a metal film. However, the portion where the backlight 8 is disposed is opposite to the liquid crystal display device 9.
[0031]
When the liquid crystal display device 30 having the above configuration is also used as a reflective type, the luminance is increased, and even when the liquid crystal display device 30 is used as a transmissive type, the liquid crystal panel used in the reflective type can be used in the transmissive type as it is. In both cases of the mold and the transmissive type, stable and clear color display was possible, and the phenomenon of being doubled as in Example 1 was eliminated. Furthermore, when the panel was viewed through polarized sunglasses, a good display was obtained.
[0032]
Further, the same effect can be obtained by a configuration in which the semi-transmissive film 21 is formed on the substrate 16 and the insulating layer, the transparent electrode 18, the insulating layer 19, and the alignment film 20 are formed thereon.
Preferred design conditions Fig. 5 shows an average rubbing direction of both rubbing directions in both

alignment films

20 and 26, with a twist angle of the liquid crystal layer 21 of 240 to 260 ° and an optical path difference Δnd of 800 to 900 nm. As a reference, the angles (counterclockwise) of the stretching axes of the

retardation plates

11, 12, and 14 and the absorption axes of the

polarizing plates

13 and 15 are shown as viewed from the display surface. The retardation plates 11 and 12 and the first polarizing plate 13 are disposed on the counter substrate of the semi-transmissive film forming substrate, and the retardation plate 14 and the second polarizing plate 15 are disposed on the semi-transmissive film forming substrate.
[0033]
In the present invention, settings are made as follows.
First retardation plate 11
Optical path difference Δnd: 680 to 700 nm, preferably 685 to 695 nm
Stretch axis: 50-60 °, preferably 52-58 °
Second retardation plate 12
Optical path difference Δnd: 570 to 590 nm, preferably 575 to 585 nm
Stretch axis: 165 to 175 °, preferably 167 to 173 °
First polarizing plate 13
Absorption axis: 5-15 °, preferably 7-13 °
Third retardation plate 14
Optical path difference Δnd: 130 to 150 nm, preferably 135 to 143 nm
Stretch axis: 130-140 °, preferably 132-138 °
Second polarizing plate 15
Absorption axis: 85-95 °, preferably 87-93 °
By setting as described above, when used as a reflection type, high luminance was achieved, and a higher contrast ratio (sufficient color compensation) was obtained. Further, even when the liquid crystal display device used as the reflection type is used as the transmission type, sufficient color compensation can be obtained, and high-saturation display can be realized in either the reflection type or the transmission type. Also, good display was obtained when the panel was viewed through polarized sunglasses.
[0034]
【Example】
Example 1
When the luminance was measured when each of the liquid crystal display devices 9 and 30 was used as a transmission type and a reflection type, the results shown in Table 1 were obtained. As a comparative example, the transflective liquid crystal display device 1 of FIG. 4 was used.
[0035]
Minolta CS-100 is used for measurement of chromaticity and luminance, the same backlight having a certain chromaticity and luminance is used for the transmission type, and the same light source is used for the liquid crystal panel for the reflection type. The chromaticity and brightness of each were measured by irradiating at a constant angle.
[0036]
[Table 1]

[0037]
The luminance was expressed as a relative value, assuming that the transmission type and the reflection type of the comparative example were each 1.00.
[0038]
As is clear from the results in Table 1, according to the liquid crystal display devices 9 and 30 of the present invention, it was possible to increase the luminance of both the transmission type and the reflection type. In particular, the liquid crystal display device 30 of Example 2 was able to significantly increase the luminance of both the transmissive type and the reflective type as compared with the liquid crystal display device 9 of Example 1.
(Example 2)
In this example, with respect to the liquid crystal display device 9 of Example 1, the extension axis of the first retardation plate 11 (optical path difference Δnd: 680 to 700 nm) and the extension of the second retardation plate 12 (optical path difference Δnd: 570 to 590 nm). The axis, the absorption axis of the first polarizing plate 13, the stretching axis of the third retardation plate 14 (optical path difference Δnd: 130 to 150 nm), and the absorption axis of the second polarizing plate 15 are changed in various ways, and various A liquid crystal display device 9 was manufactured, and device no. 1-21 were obtained. Then, when the contrast was measured by the measuring method using these devices in (Example 1), the results shown in Table 2 were obtained.
[0039]
[Table 2]

[0040]
As is apparent from the results, the apparatus No. For 1 to 3, 6, 7, 10, 11, 14, 15, 18, and 19, excellent values were obtained such that the contrast at reflection was 12.5 or more and the contrast at transmission was 17.5 or more.
[0041]
In contrast, the devices 4 and 5 have the first polarizing plate outside the scope of the present invention, the devices 8 and 9 have the second retardation plate outside the scope of the present invention, and the

devices

12 and 13 have the first retardation plate. Is outside the scope of the present invention, and the

devices

16 and 17 have a low contrast at the time of reflection and a contrast at the time of transmission because the third retardation plate is outside the scope of the present invention. Furthermore, the contrast at the time of transmission is low because the second polarizing plate is out of the scope of the present invention in the

devices

20 and 21 as well.
(Example 3)
In this example, for the liquid crystal display device 30 of Example 2, the stretching axis of the first retardation plate 11 (optical path difference Δnd: 680 to 700 nm) and the stretching of the second retardation plate 12 (optical path difference Δnd: 570 to 590 nm). The axis, the absorption axis of the first polarizing plate 13, the stretching axis of the third retardation plate 14 (optical path difference Δnd: 130 to 150 nm), and the absorption axis of the second polarizing plate 15 are changed in various ways, and various A liquid crystal display device 30 was manufactured, and device no. 22-42 were obtained. Then, when the contrast was measured by the measurement method using each of these devices in (Example 1), the results shown in Table 3 were obtained.
[0042]
[Table 3]

[0043]
As is apparent from the results, the apparatus No. For 22 to 24, 27, 28, 31, 32, 35, 36, 39, and 40, excellent values were obtained in which the contrast at reflection was 14.2 or more and the contrast at transmission was 18.8 or more.
[0044]
On the other hand, the devices 25 and 26 have the first polarizing plate outside the scope of the present invention, the

devices

29 and 30 have the second retardation plate outside the scope of the present invention, and the devices 33 and 34 have the first retardation plate. Is outside the scope of the present invention, and the devices 37 and 38 have a low contrast at the time of reflection and a contrast at the time of transmission because the third retardation plate is outside the scope of the present invention. Furthermore, the contrast at the time of transmission is low because the second polarizing plate is out of the range of the present invention in the devices 41 and 42 as well.
It should be noted that the present invention is not limited to the above embodiment, and various modifications and improvements can be made without departing from the scope of the present invention.
[0045]
For example, in the above embodiment, the STN type simple matrix type color liquid crystal display device has been described. However, the same effect can be obtained with a monochrome STN type simple matrix type liquid crystal display device. It is done.
[0046]
【The invention's effect】
As described above, according to the present invention, two transparent members obtained by sequentially laminating a transparent electrode and an alignment layer on a transparent substrate are bonded together via a super nematic liquid crystal that defines a twist angle and Δnd. A first retardation plate defining an optical path difference Δnd and a stretching axis on one main surface side of a liquid crystal panel in which pixels are arranged in a shape and a transflective film is disposed between a transparent substrate and a transparent electrode; A second retardation plate that defines an optical path difference Δnd and a stretching axis, and a first polarizing plate that defines an absorption axis, and a third retardation plate that defines an optical path difference Δnd and a stretching axis on the other main surface side; When the second polarizing plate having the absorption axis and the backlight are sequentially stacked, when used as a reflection type, the irradiation light from the external illumination is the first polarizing plate, the second retardation plate, and the first. Pass sequentially through the retardation plate, light-scattering plate and liquid crystal panel, Further, the light is reflected by the semi-transmissive film, and the reflected light passes through the liquid crystal panel, so that it does not pass through the other second polarizing plate, thereby increasing the brightness. On the other hand, when used as a transmissive type The light emitted from the backlight sequentially passes through the second polarizing plate, the third retardation plate and the semi-transmissive film, passes through the liquid crystal panel, and passes through the panel used in the reflection type as it is. It can also be used for molds, and can display stable and clear colors in either reflection type or transmission type, providing sufficient color compensation, and as a result, it can satisfy both functions of reflection type and transmission type. We were able to provide a high-performance transflective liquid crystal display device with improved characteristics.
[0047]
In the other liquid crystal display device of the present invention, the super nematic liquid crystal, the first retardation plate, the second retardation plate, the first polarizing plate, the third retardation plate, and the second polarizing plate are similarly defined. Therefore, when used as a reflective type, the brightness increases. On the other hand, when used as a transmissive type, the liquid crystal panel used in the reflective type can also be used in the transmissive type under the same conditions. Or, in any case of the transmissive type, stable and clear color display is possible, and color compensation is sufficient, and as a result, high-performance semi-transmissive with improved characteristics to the extent that both functions of the reflective type and transmissive type can be satisfied. Type liquid crystal display device could be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a liquid crystal display device of the present invention.
FIG. 2 is an enlarged cross-sectional view of a main part of the liquid crystal display device of the present invention.
FIG. 3 is an enlarged cross-sectional view of a main part of another liquid crystal display device of the present invention.
FIG. 4 is a schematic cross-sectional view of a conventional liquid crystal display device.
FIG. 5 is an explanatory diagram showing angles seen from the display surface of the stretching axis of the retardation film and the absorption axis of the polarizing plate.
[Explanation of symbols]
2 Liquid crystal panel 8 Backlight 9, 30 Liquid crystal display device 10 Light scattering plate-like body 11 First retardation plate 12 Second retardation plate 13 First polarizing plate 14 Third retardation plate 15

Second polarizing plates

16, 17 Glass substrates 18 and 25 Transparent

electrode 18a Electrodes

20 and 26 formed of a semi-transmissive film Alignment film 21 Semi-transmissive film 22 Color filter 27 Liquid crystal layer

Claims

Two transparent members obtained by sequentially laminating a transparent electrode and an alignment layer on a transparent substrate are bonded to each other via a super twist nematic liquid crystal having a twist angle of 240 to 260 ° and Δnd of 800 to 900 nm. Jo to the one main surface side of a liquid crystal panel formed by arranging pixels,
A first retardation plate having an optical path difference Δnd of 680 to 700 nm;
A second retardation plate having an optical path difference Δnd of 570 to 590 nm;
Sequentially stacking a first polarizer, a,
On the other main surface side of the liquid crystal panel ,
A third retardation plate having an optical path difference Δnd of 130 to 150 nm;
A second polarizing plate;
Sequentially stacked and the backlight, the,
A semi-permeable membrane is disposed between the transparent substrate on the other main surface side and the transparent electrode,
When the average value of the rubbing direction on both sides in the super twist nematic liquid crystal is used as a reference ,
The stretching axis of the first retardation plate is 50-60 °,
The stretching axis of the second retardation plate is 165 to 175 °,
The absorption axis of the first polarizing plate is 5 to 15 °,
The stretching axis of the third retardation plate is 130 to 140 °,
Set the absorption axis of the second polarizer 85 to 95 °, the liquid crystal display device.

Two transparent members obtained by sequentially laminating an electrode and an alignment layer on a transparent substrate are bonded together via a super twist nematic liquid crystal having a twist angle of 240 to 260 ° and Δnd of 800 to 900 nm. on one main surface side of a liquid crystal panel formed by arranging pixels in,
A first retardation plate having an optical path difference Δnd of 680 to 700 nm;
A second retardation plate having an optical path difference Δnd of 570 to 590 nm;
Sequentially stacking a first polarizer, a,
On the other main surface side of the liquid crystal panel ,
A third retardation plate having an optical path difference Δnd of 130 to 150 nm;
A second polarizing plate ;
Sequentially stacked and the backlight, the,
The electrode on the other main surface side is formed of a semipermeable membrane,
When based on the average value of the rubbing direction of the double-sided in the upper Symbol super twisted nematic liquid crystal,
The stretching axis of the first retardation plate is 50-60 °,
The stretching axis of the second retardation plate is 165 to 175 °,
The absorption axis of the first polarizing plate is 5 to 15 °,
The stretching axis of the third retardation plate is 130 to 140 °,
Set the absorption axis of the second polarizer 85 to 95 °, the liquid crystal display device.