JP2004125830A - Transflective liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display element which yields bright display in a transmissive mode, has high contrast, is able to be designed with reduced thickness and exhibits little viewing angle dependence. <P>SOLUTION: The transflective liquid crystal display element is equipped with: a first substrate with a transparent electrode; a second substrate with a transflective electrode having a reflective function region and a transmissive function region formed thereon; a nematic liquid crystal layer interposed between the first and second substrates; a first optically anisotropic element and a sheet of a polarizing plate disposed on the first substrate; and a second optically anisotropic element and a sheet of a polarizing plate disposed on the second substrate. The first optically anisotropic element consists of an optical retardation film which is a sheet of an aligned polymer film and of which the retardation values Re(λ) at 450, 550 and 650 nm wavelengths (λ) satisfy inequalities Re(450) < Re(550) < Re(650) and 0.2 ≤ Re(λ)/λ ≤ 0.3. Furthermore, the second optically anisotropic element is formed of a liquid crystalline polymer substance showing an optically positive uniaxiality and contains a liquid crystal film with a fixed nematic hybrid alignment formed in a liquid crystal state. <P>COPYRIGHT: (C)2004,JPO

Description

【００３８】
【化２】

【００３９】
上記式（１）において、Ｒ_１〜Ｒ_８はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜６の炭化水素基から選ばれる基を示し、Ｘは式（３）で示される基ある。また、上記式（２）において、Ｒ_９　〜Ｒ_１６はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる基を示し、Ｙは式（４）で示される基から選ばれる基を示す。
【００４０】
【化３】

【００４１】
【化４】

【００４２】
上記式（４）において、Ｒ_１７〜Ｒ_１９、Ｒ_２１及びＲ_２２はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる基を示し、Ｒ_２０及びＲ_２３はそれぞれ独立に炭素数１〜２０の炭化水素基から選ばれる基を示し、Ａｒは炭素数６〜１０のアリール基である。
【００４３】
この材料は、上記式（１）で表わされるフルオレン骨格を有する繰り返し単位と上記式（２）で表わされる繰り返し単位とからなるポリカーボネート共重合体、および上記式（１）で表わされるフルオレン骨格を有する繰り返し単位からなるポリカーボネートと上記式（２）で表わされる繰り返し単位からなるポリカーボネートとのブレンドポリマーである。共重合体の場合、上記式（１）および（２）で表わされる繰り返し単位はそれぞれ２種類以上組み合わせてもよく、組成物の場合も、上記繰り返し単位はそれぞれ２種類以上組み合わせてもよい。
【００４４】
上記式（１）において、Ｒ_１〜Ｒ_８はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜６の炭化水素基から選ばれる。かかる炭素数１〜６の炭化水素基としては、メチル基、エチル基、イソプロピル基、シクロヘキシル基等のアルキル基、フェニル基等のアリール基が挙げられる。この中で、水素原子、メチル基が好ましい。
上記式（２）において、Ｒ_９〜Ｒ_１６はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる。かかる炭素数１〜２２の炭化水素基としては、メチル基、エチル基、イソプロピル基、シクロヘキシル基等の炭素数１〜９のアルキル基、フェニル基、ビフェニル基、ターフェニル基等のアリール基が挙げられる。この中で、水素原子、メチル基が好ましい。
上記式（４）において、Ｒ_１７〜Ｒ_１９、Ｒ_２１及びＲ_２２はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる。かかる炭素数１〜２２の炭化水素基としては、メチル基、エチル基、イソプロピル基、シクロヘキシル基等の炭素数１〜９のアルキル基、フェニル基、ビフェニル基、ターフェニル基等のアリール基が挙げられる。この中で、水素原子、メチル基が好ましい。Ｒ_２０及びＲ_２３はそれぞれ独立に炭素数１〜２０の炭化水素基から選ばれ、またＡｒはフェニル基、ナフチル基等の炭素数６〜１０のアリール基である。
【００４５】
上記式（１）の含有率、すなわち共重合体の場合共重合組成、組成物の場合ブレンド組成比は、ポリカーボネート全体の３０〜９０モル％である。かかる範囲を外れた場合には、測定波長　４００〜７００ｎｍにおいて位相差絶対値が短波長ほど小さくなるということがない。上記式（１）の含有率は、ポリカーボネート全体の３５〜８５モル％が好ましく、４０〜８０モル％がより好ましい。ここで上記モル比は共重合体、ブレンドポリマーに関わらず、配向フィルムを構成するポリカーボネートのバルク全体で、例えば核磁気共鳴（ＮＭＲ）素子より求めることができる。
【００４６】
この材料におけるポリカーボネートとしては、下記式（５）で示される繰り返し単位と、下記式（６）で示される繰り返し単位とから構成されるポリカーボネート共重合体及び／またはポリカーボネート組成物（ブレンドポリマー）が好ましい。
【００４７】
【化５】

【００４８】
【化６】

【００４９】
上記式（５）において、Ｒ_２４及びＲ_２５はそれぞれ独立に水素原子またはメチル基から選ばれる基を示し、上記式（６）において、Ｒ_２６及びＲ_２７はそれぞれ独立に水素原子及びメチル基から選ばれる基を示し、Ｚは式（７）で示される基から選ばれる基を示す。
【００５０】
【化７】

【００５１】
さらに、下記式（８）〜（１２）で示される繰り返し単位からなる共重合体において、繰り返し単位（１２）の割合が４０〜７５モル％であるもの、下記式（９）及び（１２）で示される繰り返し単位からなる共重合体において（１２）の割合が３０〜７０モル％であるもの、下記式（１０）及び（１２）で示される繰り返し単位からなる共重合体において、（１２）の割合が３０〜７０モル％であるもの、下記式（８）及び（１１）で示される繰り返し単位からなる共重合体において、（１１）の割合が４０〜７５モル％であることがそれぞれより好ましい。
【００５２】
【化８】

【００５３】
最も好ましい材料はビスフェノールＡ（ＢＰＡ、上記式（８）に対応）　とビスクレゾールフルオレン（ＢＣＦ、上記式（１２）に対応）　を含む共重合体又は高分子ブレンドあるいはこれらの混合物であり、これらの成分の配合比はＢＣＦの含有率が５５〜７５モル％、より好ましくは５５〜７０モル％である。これらの材料において、より理想に近いλ／４板やλ／２板を得ることができる。
【００５４】
上記した共重合体及び／またはブレンドポリマーは公知の方法によって製造し得る。ポリカーボネートはジヒドロキシ化合物とホスゲンとの重縮合による方法、溶融重縮合法等が好適に用いられる。ブレンドの場合は、相溶性ブレンドが好ましいが、完全に相溶しなくても成分間の屈折率を合わせれば成分間の光散乱を抑え、透明性を向上させることが可能である。
【００５５】
本発明における高分子配向フィルムの材料高分子化合物の極限粘度は０．３〜２．０ｄｌ／ｇであることが好ましい。これより低粘度では脆くなり機械的強度が保てないといった問題があり、これより高粘度では溶液粘度が上がりすぎるため溶液製膜においてダイラインの発生等の問題や、重合終了時の精製が困難になるといった問題がある。
【００５６】
本発明における高分子配向フィルムは透明であることが好ましく、ヘイズ値は３％以下、全光線透過率は８５％以上であることが好ましい。また、前記高分子配向フィルム材料のガラス転移点温度は　１００℃以上、より好ましくは１２０℃以上であることが好ましい。さらに、フェニルサリチル酸、２−ヒドロキシベンゾフェノン、トリフェニルフォスフェート等の紫外線吸収剤や、色味を変えるためのブルーイング剤、酸化防止剤等を添加してもよい。
【００５７】
本発明における高分子配向フィルムは上記ポリカーボネートなどのフィルムを延伸等により配向させたフィルムを用いるものである。かかるフィルムの製造方法としては、公知の溶融押し出し法、溶液キャスト法等が用いられるが、膜厚むら、外観等の観点から溶液キャスト法がより好ましく用いられる。溶液キャスト法における溶剤としては、メチレンクロライド、ジオキソラン等が好適が用いられる。
また、延伸方法も公知の延伸方法を使用し得るが、好ましくは縦一軸延伸である。フィルム中には延伸性を向上させる目的で、公知の可塑剤であるジメチルフタレート、ジエチルフタレート、ジブチルフタレート等のフタル酸エステル、トリブチルフォスフェート等のリン酸エステル、脂肪族二塩基エステル、グリセリン誘導体、グリコール誘導体等を含有してもよい。延伸時には、先述のフィルム製膜時に用いた有機溶剤をフィルム中に残留させて延伸しても良い。この有機溶剤の量としてはポリマー固形分対比１〜２０質量％であることが好ましい。
【００５８】
また、上記可塑剤や液晶等の添加剤は、高分子配向フィルムの位相差波長分散を変化させ得るが、添加量は、ポリマー固形分対比１０質量％以下が好ましく、３質量％以下がより好ましい。
高分子配向フィルムの膜厚は特に限定されるものではないが、１μｍから４００μｍであることが好ましい。
【００５９】
高分子配向フィルムの位相差を短波長ほど小さくするためには、特定の化学構造を有することが必須条件であり、位相差波長分散はかなりの部分がその化学構造で決まるが、延伸条件、ブレンド状態等によっても変動することに留意されるべきである。
高分子配向フィルムは特に１枚の配向フィルムをもって波長依存性が少ない良好な４分の１波長板（λ／４板）を構成することができるものであるため、下記式（ＩＩ）を満たすものである。
０．２≦Ｒｅ（λ）／λ≦０．３　　　　　　　　　　（ＩＩ）
【００６０】
本発明に用いられる第２の光学異方素子は、光学的に正の一軸性を示す液晶性高分子物質、具体的には光学的に正の一軸性を示す液晶性高分子化合物または少なくとも１種の該液晶性高分子化合物を含有する光学的に正の一軸性を示す液晶性高分子組成物から成り、該液晶性高分子化合物または該液晶性高分子組成物が液晶状態において形成した平均チルト角が５゜〜３５゜のネマチックハイブリッド配向構造を固定化した液晶フィルム（Ａ）を少なくとも含み、可視光域で略４分の１波長の位相差を有する素子である。
【００６１】
ここで、ネマチックハイブリッド配向とは、液晶分子がネマチック配向しており、このときの液晶分子のダイレクターとフィルム平面のなす角がフィルム上面と下面とで異なった配向形態を言う。したがって、上面界面近傍と下面界面近傍とで該ダイレクターとフィルム平面との成す角度が異なっていることから、該フィルムの上面と下面との間では該角度が連続的に変化しているものといえる。
またネマチックハイブリッド配向状態を固定化したフィルムは、液晶分子のダイレクターがフィルムの膜厚方向のすべての場所において異なる角度を向いている。したがって当該フィルムは、フィルムという構造体として見た場合、もはや光軸は存在しない。
【００６２】
また本発明でいう平均チルト角とは、液晶フィルムの膜厚方向における液晶分子のダイレクターとフィルム平面との成す角度の平均値を意味するものである。本発明に供される液晶フィルムは、フィルムの一方の界面付近ではダイレクターとフィルム平面との成す角度が、絶対値として通常２０゜〜９０゜、好ましくは３０゜〜７０゜の角度をなしており、当該面の反対においては、絶対値として通常０゜〜２０゜、好ましくは０゜〜１０゜の角度を成しており、その平均チルト角は、絶対値として通常５゜〜４５゜、好ましくは７゜〜４０゜、さらに好ましくは１０゜〜３８゜、最も好ましくは１５゜〜３５゜である。平均チルト角が上記範囲から外れた場合、コントラストの低下等の恐れがあり望ましくない。なお平均チルト角は、クリスタルローテーション法を応用して求めることができる。
【００６３】
本発明に用いられる第２の光学異方素子を構成する液晶フィルム（Ａ）は、光学的に正の一軸性を示す液晶性高分子物質より実質的に形成され、該液晶性高分子物質が液晶状態において形成したネマチックハイブリッド配向状態を固定化したものであれば、その製造方法については特に制限はない。例えば、低分子液晶を液晶状態においてネマチックハイブリッド配向に形成後、光架橋や熱架橋によって固定化して得られる液晶フィルムや、高分子液晶を液晶状態においてネマチックハイブリッド配向に形成後、冷却することによって当該配向を固定化して得られる液晶フィルムを用いることができる。なお本発明でいう液晶フィルムとは、フィルム自体が液晶性を呈するか否かを問うものではなく、低分子液晶、高分子液晶などの液晶物質をフィルム化することによって得られるものを意味する。
【００６４】
また液晶フィルム（Ａ）が、半透過反射型液晶表示素子に対してより好適な視野角改良効果を発現するための該フィルムの膜厚は、対象とする液晶表示素子の方式や種々の光学パラメーターに依存するので一概には言えないが、通常０．２μｍ〜１０μｍ、好ましくは０．３μｍ〜５μｍ、特に好ましくは０．５μｍ〜２μｍの範囲である。膜厚が０．２μｍ未満の時は、十分な補償効果が得られない恐れがある。また膜厚が１０μｍを越えるとディスプレーの表示が不必要に色づく恐れがある。
【００６５】
次に、図１から図３を用いて液晶フィルム（Ａ）からなる光学異方素子の上下、該光学異方素子のチルト方向および液晶セル層のプレチルト方向をそれぞれ以下に定義する。
まず図１および図２において、液晶フィルム（Ａ）からなる光学異方素子の上下を、該光学異方素子を構成する液晶フィルム（Ａ）のフィルム界面近傍における液晶分子ダイレクターとフィルム平面との成す角度によってそれぞれ定義すると、液晶分子のダイレクターとフィルム平面との成す角度が鋭角側で２０〜９０度の角度を成している面をｂ面とし、該角度が鋭角側で０〜２０度の角度を成している面をｃ面とする。
この光学異方素子のｂ面から液晶フィルム層を通してｃ面を見た場合、液晶分子ダイレクターとダイレクターのｃ面への投影成分が成す角度が鋭角となる方向で、かつ投影成分と平行な方向を光学異方素子のチルト方向と定義する。
次いで図３において、通常、液晶セル層のセル界面では、駆動用低分子液晶はセル界面に対して平行ではなくある角度もって傾いており一般にこの角度をプレチルト角と言うが、セル界面の液晶分子のダイレクターとダイレクターの界面への投影成分とがなす角度が鋭角である方向で、かつダイレクターの投影成分と平行な方向を液晶セル層のプレチルト方向と定義する。
【００６６】
また、第２の光学異方素子は、他の高分子延伸フィルムやまたはネマチック配向を固定化した液晶フィルム（Ｂ）と組み合わせても使用することができる。
高分子延伸フィルムとしては、一軸性あるいは二軸性を示すような物質で、例えば、ポリカーボネート（ＰＣ）、ポリメタクリレート（ＰＭＭＡ）、ポリビニルアルコール（ＰＶＡ）、日本合成ゴム（株）製のＡＲＴＯＮ（商品名）フィルムなどの延伸フィルムを使用することができる。この場合も、コストアップの問題を勘案すれば、液晶フィルム１枚と高分子延伸フィルム１枚の組み合わせが実用上好ましい。
【００６７】
液晶フィルム（Ｂ）は、ネマチック配向状態が固定化されたものであれば、如何様な液晶から形成されたものであっても構わない。例えば低分子液晶を液晶状態においてネマチック配向に形成後、光架橋や熱架橋によって固定化して得られる液晶フィルムや、高分子液晶を液晶状態においてネマチック配向に形成後、冷却することによって当該配向を固定化して得られる液晶フィルムを用いることができる。なお本発明でいう液晶フィルム（Ｂ）とは、液晶フィルム（Ａ）と同様にフィルム自体が液晶性を呈するか否かを問うものではなく、低分子液晶、高分子液晶などの液晶物質をフィルム化することによって得られるものを意味する。
【００６８】
また第２の光学異方素子に含まれる液晶フィルムとしては、液晶フィルム単体として使用することも可能であり、支持基板として透明プラスチックフィルムを設けて使用することも可能である。液晶フィルム単体として使用する場合は、該偏光板を作製するときに用いるポリエステルやトリアセチルセルロース等の透明プラスチックフィルムに液晶フィルムを積層した後、偏光板と一体化することにより作製できる。
【００６９】
本発明の第２の光学異方素子のリターデーション値（複屈折Δｎと膜厚ｄとの積）について説明する。
液晶フィルム（Ａ）の法線方向から見た場合の面内の見かけのリターデーション値としては、ネマチックハイブリッド配向したフィルムでは、ダイレクターに平行な方向の屈折率（以下ｎｅと呼ぶ）と垂直な方向の屈折率（以下ｎｏと呼ぶ）が異なっているおり、ｎｅからｎｏを引いた値を見かけ上の複屈折率とした場合、見かけ上のリターデーション値は見かけ上の複屈折率と絶対膜厚との積で与えられるとする。この見かけ上のリターデーション値は、エリプソメトリー等の偏光光学測定により容易に求めることができる。
【００７０】
前記第２の光学異方素子が、ネマチックハイブリッド配向を固定化した液晶フィルム（Ａ）のみから構成される場合と、液晶フィルム（Ａ）と高分子延伸フィルムまたはネマチック配向を固定化した液晶フィルム（Ｂ）とを組み合わせた場合に分けて説明する。
ネマチックハイブリッド配向した液晶フィルム（Ａ）のみから構成される場合、液晶フィルム（Ａ）の見かけ上のリターデーション値は、５５０ｎｍの単色光に対して、通常、７０ｎｍ〜１８０ｎｍ、好ましくは９０ｎｍ〜１６０ｎｍ、特に好ましくは１２０ｎｍ〜１５０ｎｍの範囲にすることにより、良好な円偏光特性が得られる。見かけのリターデーション値が７０ｎｍ未満、あるいは１８０ｎｍより大きい時は、液晶表示素子に不必要な色付きが生じる恐れがある。
【００７１】
液晶フィルム（Ａ）と高分子延伸フィルムまたは液晶フィルム（Ｂ）とを組み合わせた場合は、特開平１０−０６８８１６号公報に記載のように、５５０ｎｍの単色光での複屈折光の位相差が略１／４波長である１／４波長板と５５０ｎｍの単色光での複屈折光の位相差が略１／２波長である１／２波長板とを、それらの遅相軸が交差した状態で貼り合わせることにより、良好な円偏光特性が得られる。１／４波長板のリターデーション値は、通常、７０ｎｍ〜１８０ｎｍ、好ましくは９０ｎｍ〜１６０ｎｍ、特に好ましくは１２０ｎｍ〜１５０ｎｍの範囲である。１／２波長板のリターデーション値は、通常１８０ｎｍ〜３２０ｎｍ、好ましくは２００ｎｍ〜３００ｎｍ、特に好ましくは２２０ｎｍ〜２８０ｎｍの範囲である。１／４波長板と１／２波長板のリターデーション範囲が上記から外れた場合、液晶表示素子に不必要な色付きが生じる恐れがある。
【００７２】
１／４波長板の遅相軸と１／２波長板の遅相軸のなす角度は、通常、鋭角側で４０度〜９０度、好ましくは５０度〜８０度、特に好ましくは５５度〜７５度の範囲である。
ネマチックハイブリッド配向を固定化した液晶フィルム（Ａ）は、１／４波長板に使用しても良いし、１／２波長板に使用してもよい。
１／４波長板に液晶フィルム（Ａ）を使用する場合は、１／２波長板には高分子延伸フィルムまたは液晶フィルム（Ｂ）を使用し、１／２波長板に液晶フィルム（Ａ）を使用する場合は、１／４波長板に高分子延伸フィルムまたは液晶フィルム（Ｂ）を使用すれば良い。
【００７３】
第２の光学異方素子として、液晶フィルム（Ａ）１枚のみを半透過反射型液晶表示素子に用いる場合について説明する。液晶フィルム（Ａ）は液晶セルの第２の基板と偏光板との間に配置するのが好ましい。ここで液晶フィルム（Ａ）の配置条件について図６を用いて説明する。
図６の液晶セル１５における、上側基板のプレチルト方向に重ね合わさる直線および下側基板のプレチルト方向に重ね合わさる直線を、それぞれ仮定する。この２つの直線を同一平面に投影し、このとき直線が交差する点を中心として形成される４つの角度のうち、鋭角側の２つの角度が、それぞれ左右対称の角度となるような直線を引く。この直線を、本発明において２等分線と定義する。なお上側基板のプレチルト方向に重ね合わさる直線と下側基板のプレチルト方向に重ね合わさる直線とが重ね合わさる場合（すなわち、２つの直線が平行の場合）は、その重ね合わさる直線が、本発明で言う２等分線となる。
この２等分線と液晶フィルム（Ａ）のチルト方向を基準とする直線成分との成す角度が、通常、絶対値として０度〜３０度、好ましくは０度〜２０度、さらに好ましくは０度〜１０度、もっとも好ましくは概ね０度となるように配置することが望ましい。両者のなす角度が３０度より大きい場合、十分な視野角補償効果が得られない恐れがある。
【００７４】
次に、第２の光学異方素子として液晶フィルム（Ａ）１枚と高分子延伸フィルム１枚あるいは液晶フィルム（Ｂ）１枚を組み合わせて半透過反射型液晶表示素子に用いる場合について説明する。
液晶フィルム（Ａ）の配置は上述の１枚のみを使用する場合と同様の配置にすることが好ましい。すなわち、液晶フィルム中の液晶性高分子のチルト方向と前記２等分線の方向とがおおむね一致することが好ましい。チルト方向とプレチルト方向のなす角度は０度から３０度の範囲が好ましく、より好ましくは０度から２０度の範囲であり、特に好ましくは０度から１０度の範囲である。
【００７５】
本発明の半透過反射型液晶表示素子において、光拡散層、バックライト、光制御フィルム、導光板、プリズムシートとしては、特に制限されず公知のものを使用することができる。
本発明の半透過反射型液晶表示素子は、前記した構成部材以外にも他の構成部材を付設することができる。例えば、カラーフィルターを本発明の液晶表示素子に付設することにより、色純度の高いマルチカラー又はフルカラー表示を行うことができるカラー液晶表示素子を作製することができる。
【００７６】
【発明の効果】
本発明の半透過反射型液晶表示素子は、透過モードにおける表示が明るく、高コントラストであり、薄く設計することが可能であり、視野角依存性が少ないという特徴を有する。
【００７７】
【実施例】
以下、本発明を実施例および比較例によりさらに詳細に説明するが、本発明はこれらに限定されるものではない。なお、本実施例におけるリターデーションΔｎｄは特に断りのない限り波長５５０ｎｍにおける値とする。
【００７８】
［実施例１］
本発明の半透過反射型液晶表示素子の概略については図４を用いて、実施例１の構成については図５を用いて説明する。
第２の基板８にＡｌ等の反射率の高い材料で形成された反射電極６とＩＴＯ等の透過率の高い材料で形成された透明電極７とが設けられ、第１の基板３に対向電極４が設けられ、反射電極６及び透過電極７と対向電極４との間に正の誘電率異方性を示す液晶材料からなる液晶層５が挟持されている。第１の基板３の対向電極４が形成された側の反対面に第１の光学異方素子２及び偏光板１が設けられており、第２の基板８の反射電極６及び透過電極７が形成された面の反対側に第２の光学異方素子９及び偏光板１０が設けられている。偏光板１０の背面側にはバックライト１１が設けられている。
【００７９】
膜厚方向の平均チルト角が２８度のネマチックハイブリッド配向が固定化された膜厚０．７７μｍの液晶フィルム１３を作製し、図５に示したような配置で以下に示すＴＮ型の半透過反射型液晶表示素子を作製した。
使用した液晶セル１５は、液晶材料としてＺＬＩ−１６９５（Ｍｅｒｃｋ社製）を用い、液晶層厚は反射電極領域６（反射表示部）で３．５μｍ、透過電極領域７（透過表示部）で４．０μｍとした。液晶層の基板両界面のプレチルト角は２度であり、液晶セルのツイスト角は左ねじれの７０度、液晶セルのΔｎｄは、反射表示部で略２３０ｎｍ、透過表示部で略２６２ｎｍであった。
【００８０】
液晶セル１５の観察者側（図の上側）に偏光板１（厚み約１８０μｍ；住友化学工業（株）製ＳＱＷ−８６２）を配置し、偏光板１と液晶セル１５との間に、第１の光学異方素子２として、本発明の要件である式（Ｉ）及び式（ＩＩ）を満たす帝人（株）製の一軸延伸した高分子延伸フィルム（製品名ピュアエース）２を配置した。高分子延伸フィルム２の△ｎｄは略１２０ｎｍであった。
また、第２の光学異方素子９として、観察者から見て液晶セル１５の後方に液晶フィルム１３及び一軸延伸したポリカーボネートフィルムからなる高分子延伸フィルム１４を配置し、更に背面に偏光板１０を配置した。ハイブリッドネマチック配向構造を固定化した液晶フィルム１３の△ｎｄは１３５ｎｍ、高分子延伸フィルム１４の△ｎｄは２７５ｎｍであった。
偏光板１及び１０の吸収軸、第１の光学異方体２及び高分子延伸フィルム１４の遅相軸、液晶セル１５の両界面のプレチルト方向、液晶フィルム１３のチルト方向は図６に記載した条件で配置した。
【００８１】
図７は、バックライト点灯時（透過モード）での、白表示０Ｖ、黒表示６Ｖの透過率の比（白表示）／（黒表示）をコントラスト比として、全方位からのコントラスト比を示している。
図８は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の左右方向での透過率の視野角特性を示している。
図９は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の上下方向での透過率の視野角特性を示している。
図７〜９から特に透過モードにおいて良好な視野角特性を持っていることが分かった。
【００８２】
［実施例２］
膜厚方向の平均チルト角が２８度のネマチックハイブリッド配向が固定化された膜厚０．６０μｍの液晶フィルム１３を作製し、図５に示したような配置で以下に示すＥＣＢ型の半透過反射型液晶表示素子を作製した。
使用した液晶セル１６は、液晶材料としてＺＬＩ−１６９５（Ｍｅｒｃｋ社製）を用い、液晶層厚は反射電極領域６（反射表示部）で２．１μｍ、透過電極領域７（透過表示部）で４．９μｍとした。液晶層の基板両界面のプレチルト角は２度であり、液晶セルのΔｎｄは、反射表示部で略１３８ｎｍ、透過表示部で略３２１ｎｍのホモジニアス配向とした。
【００８３】
液晶セル１６の観察者側（図の上側）に偏光板１（厚み約１８０μｍ；住友化学工業（株）製ＳＱＷ−８６２）を配置し、偏光板１と液晶セル１６との間に、第１の光学異方素子２として、本発明の要件である式（Ｉ）及び式（ＩＩ）を満たす帝人（株）製のポリカーボネートからなる一軸延伸した高分子延伸フィルム（製品名ピュアエース）２を配置した。高分子延伸フィルム２の△ｎｄは略１１５ｎｍであった。
また、第２の光学異方素子９として配置したハイブリッドネマチック配向構造を固定化した液晶フィルム１３の△ｎｄは１０５ｎｍ、高分子延伸フィルム１４の△ｎｄは２７０ｎｍであった。
偏光板１及び１０の吸収軸、第１の光学異方体２及び高分子延伸フィルム１４の遅相軸、液晶セル１６の両界面のプレチルト方向、液晶フィルム１３のチルト方向は図１０に記載した条件で配置した。
【００８４】
図１１は、バックライト点灯時（透過モード）での、白表示０Ｖ、黒表示６Ｖの透過率の比（白表示）／（黒表示）をコントラスト比として、全方位からのコントラスト比を示している。
図１２は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の左右方向での透過率の視野角特性を示している。
図１３は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の上下方向での透過率の視野角特性を示している。
図１１〜１３から、ＥＣＢ型でもＴＮ型と同様、特に透過モードにおいて良好な視野角特性を持っていることが分かった。
【００８５】
［比較例１］
図１４の配置図に示したように、液晶フィルム１３の代わりにポリカーボネート１７（Δｎｄが略１３０ｎｍ）を用い、ポリカーボネート１４のΔｎｄを２６０ｎｍとし、液晶セル１５の背面側に配置した偏光板１０の吸収軸、高分子延伸フィルム１４及び１７の遅相軸を図１５に記載した条件で配置にした以外は、実施例１と同様の液晶表示素子を作製した。
【００８６】
図１６は、バックライト点灯時（透過モード）での、白表示０Ｖ、黒表示６Ｖの透過率の比（白表示）／（黒表示）をコントラスト比として、全方位からのコントラスト比を示している。
図１７は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の左右方向での透過率の視野角特性を示している。
図１８は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の上下方向での透過率の視野角特性を示している。
【００８７】
視野角特性について、実施例１と比較例１を比較する。
全方位の等コントラスト曲線を図７と図１６で比較すると、ハイブリッドネマチック構造を持つ液晶フィルム１３を用いることにより、広い視野角特性が得られていることが分かる。
また、透過モードでの欠点となる左右、上下方向の階調特性を図８、９と図１７，１８で比較すると、ハイブリッドネマチック構造を持つ液晶フィルムを用いることにより、反転特性が大幅に改善されていることが分かる。
【００８８】
［比較例２］
図１４の配置図に示したように、液晶フィルム１３の代わりにポリカーボネート１７（Δｎｄが略１１０ｎｍ）を用い、ポリカーボネート１４のΔｎｄを２７０ｎｍとし、液晶セル１６の背面側に配置した偏光板１０の吸収軸、高分子延伸フィルム１４及び１７の遅相軸を図１９に記載した条件で配置にした以外は、実施例２と同様の液晶表示素子を作製した。
【００８９】
図２０は、バックライト点灯時（透過モード）での、白表示０Ｖ、黒表示６Ｖの透過率の比（白表示）／（黒表示）をコントラスト比として、全方位からのコントラスト比を示している。
図２１は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の左右方向での透過率の視野角特性を示している。
図２２は、バックライト点灯時（透過モード）での、白表示０Ｖから黒表示６Ｖまで６階調表示した時の上下方向での透過率の視野角特性を示している。
【００９０】
視野角特性について、実施例２と比較例２を比較する。
全方位の等コントラスト曲線を図１１と図２０で比較すると、ハイブリッドネマチック構造を持つ液晶フィルム１３を用いることにより、広い視野角特性が得られていることが分かる。
また、透過モードでの欠点となる左右、上下方向の階調特性を図１２、１３と図２１、２２で比較すると、ハイブリッドネマチック構造を持つ液晶フィルムを用いることにより、反転特性が大幅に改善されていることが分かる。
本実施例では、カラーフィルターの無い形態で実験を行ったが、液晶セル中にカラーフィルターを設ければ、良好なマルチカラー、またはフルカラー表示ができることは言うまでもない。
【００９１】
【図面の簡単な説明】
【図１】液晶分子のチルト角及びツイスト角を説明するための概念図である。
【図２】第２の光学異方素子を構成する液晶性フィルムの配向構造の概念図である。
【図３】液晶セルのプレチルト方向を説明する概念図である。
【図４】本発明の半透過反射型液晶表示素子を模式的に表した断面図である。
【図５】実施例１及び実施例２の半透過反射型液晶表示素子を模式的に表した断面図である。
【図６】実施例１における偏光板の吸収軸、液晶セルのプレチルト方向、高分子延伸フィルムの遅相軸および液晶フィルムのチルト方向の角度関係を示した平面図である。
【図７】実施例１における半透過反射型液晶表示素子を全方位から見た時のコントラスト比を示す図である。
【図８】実施例１における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の左右方位の透過率の視野角特性を示す図である。
【図９】実施例１における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の上下方位の透過率の視野角特性を示す図である。
【図１０】実施例２における偏光板の吸収軸、液晶セルのプレチルト方向、高分子延伸フィルムの遅相軸および液晶フィルムのチルト方向の角度関係を示した平面図である。
【図１１】実施例２における半透過反射型液晶表示素子を全方位から見た時のコントラスト比を示す図である。
【図１２】実施例２における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の左右方位の透過率の視野角特性を示す図である。
【図１３】実施例２における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の上下方位の透過率の視野角特性を示す図である。
【図１４】比較例１及び比較例２の半透過反射型液晶表示素子を模式的に表した断面図である。
【図１５】比較例１における偏光板の吸収軸、液晶セルのプレチルト方向及び高分子延伸フィルムの遅相軸の角度関係を示した平面図である。
【図１６】比較例１における半透過反射型液晶表示素子を全方位から見た時のコントラスト比を示す図である。
【図１７】比較例１における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の左右方位の透過率の視野角特性を示す図である。
【図１８】比較例１における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の上下方位の透過率の視野角特性を示す図である。
【図１９】比較例２における偏光板の吸収軸、液晶セルのプレチルト方向及び高分子延伸フィルムの遅相軸の角度関係を示した平面図である。
【図２０】比較例２における半透過反射型液晶表示素子を全方位から見た時のコントラスト比を示す図である。
【図２１】比較例２における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の左右方位の透過率の視野角特性を示す図である。
【図２２】比較例２における半透過反射型液晶表示素子を０Ｖから６Ｖまで７階調表示した時の上下方位の透過率の視野角特性を示す図である。
【符号の説明】
１：偏光板
２：第１の光学異方素子
３：第１の基板
４：対向電極
５：液晶層
６：反射電極
７：透過電極
８：第２の基板
９：第２の光学異方素子
１０：偏光板
１１：バックライト
１２，１５，１６：液晶セル
１４，１７：高分子延伸フィルム
１３：液晶フィルム[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal having both a reflection type and a transmission type used for OA equipment such as a word processor and a personal computer, portable information equipment such as an electronic organizer and a mobile phone, or a camera-integrated VTR equipped with a liquid crystal monitor. It relates to a display element.
[0002]
[Prior art]
2. Description of the Related Art In recent years, expectations for market expansion as displays of portable information terminal devices, which can make full use of the thin and lightweight characteristics of liquid crystal display devices, are increasing. Since portable electronic devices are usually driven by batteries, it is important to reduce power consumption. For this reason, as a liquid crystal display element for portable use, a reflective liquid crystal display element that does not use a backlight that consumes a large amount of power or does not need to use it at all times can be used. Has received particular attention.
[0003]
As a reflection type liquid crystal display device, a two-plate type reflection type liquid crystal display device in which a liquid crystal cell is sandwiched between a pair of polarizing plates and a reflecting plate is further disposed outside is widely used for monochrome display. More recently, a reflective type liquid crystal display device having a single polarizer, in which a liquid crystal layer is sandwiched between a polarizer and a reflective plate, has been put to practical use because it is brighter in principle and easier to color than the dual polarizer type. . In a reflection type liquid crystal display device having a single polarizing plate, a quarter wave plate is used as a retardation plate disposed between the polarizing plate and the liquid crystal cell so as to have a substantially circular polarizing plate function. A normally white reflective liquid crystal display device is realized by setting the thickness of the liquid crystal layer in the inside to approximately one-quarter wavelength (for example, see Patent Documents 1 and 2).
[0004]
In order to provide good circular polarization characteristics, a quarter-wave plate used as a retardation plate has a quarter-wave plate in which the phase difference of birefringent light of 550 nm monochromatic light is approximately a quarter wavelength. It has been proposed to use at least two or more retardation films composed of a half-wave plate having a birefringent light having a retardation of approximately 波長 wavelength with a 550 nm monochromatic light. 3).
[0005]
However, since these reflective liquid crystal display elements usually perform display using external light, they have a disadvantage that the display becomes difficult to see when used in a dark environment. As a technique for solving this problem, in a reflection type liquid crystal display element having a single polarizing plate, a semi-transmissive reflector having a property of transmitting a part of incident light is used instead of the reflector, and a backlight is used. A transflective liquid crystal display device provided with such a device has been proposed (for example, see Patent Document 4). In this case, it can be used as a reflection type (reflection mode) using external light when the backlight is not lit, and as a transmission type (transmission mode) with the backlight lit in a dark environment.
[0006]
In this transflective liquid crystal display device of a single polarizing plate type, it is necessary to make substantially circularly polarized light enter the liquid crystal cell through the transflective layer in the transmissive mode. It is necessary to arrange a circularly polarizing plate comprising a stretched polymer film and a polarizing plate between the transflective layer and the backlight. However, in the transmission mode liquid crystal display device, the problem of the viewing angle that the display color changes or the display contrast is reduced when viewed obliquely due to the refractive index anisotropy of the liquid crystal molecules can be essentially avoided. On the other hand, with a circularly polarizing plate using a stretched polymer film, it is essentially difficult to increase the viewing angle.
In recent years, there has been an increasing demand for thinner and lighter portable information terminal devices, and there has been an increasing demand for thinner and lighter members used for displays of portable information terminal devices. However, in the case of stretched polymer films, there is a limit to the reduction in thickness due to manufacturing problems.
[0007]
[Patent Document 1]
JP-A-6-11711
[Patent Document 2]
WO 98/4320 pamphlet
[Patent Document 3]
JP-A-10-68816
[Patent Document 4]
JP-A-10-206846
[0008]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a transflective liquid crystal display element which can be designed to have a bright display, a high contrast, a small thickness and a small viewing angle dependence in a transmission mode.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, a first substrate having a transparent electrode, a second substrate having a transflective electrode in which a region having a reflective function and a region having a transmissive function are formed, A nematic liquid crystal layer sandwiched between a substrate and the second substrate; and a first optically anisotropic element provided on a surface of the first substrate opposite to a surface in contact with the liquid crystal layer, and one sheet. A transflective liquid crystal display comprising a polarizing plate, a second optically anisotropic element provided on the surface of the second substrate opposite to the surface in contact with the liquid crystal layer, and one polarizing plate; In the element
The first optically anisotropic element is a retardation film composed of one polymer oriented film, and has retardation values at wavelengths (λ) of 450 nm, 550 nm, and 650 nm of Re (450), Re (550), and Re (550), respectively. When Re (650), the film is made of a retardation film satisfying the following formulas (I) and (II);
Re (450) <Re (550) <Re (650) (I)
0.2 ≦ Re (λ) /λ≦0.3 (II)
The second optically anisotropic element is substantially formed of at least one sheet of an optically positive uniaxial liquid crystalline polymer, and the liquid crystal polymer forms a nematic hybrid alignment formed in a liquid crystal state. The present invention relates to a transflective liquid crystal display device including a fixed liquid crystal film (A).
[0010]
According to a second aspect of the present invention, in the transflective liquid crystal display element described above, the second optically anisotropic element is substantially more than at least one liquid crystal polymer material having optically positive uniaxiality. Wherein the liquid crystalline polymer substance is composed of a liquid crystal film (A) in which a nematic hybrid alignment formed in a liquid crystal state is fixed, and at least one stretched polymer film. And a transflective liquid crystal display device.
[0011]
According to a third aspect of the present invention, in the transflective liquid crystal display element described above, the second optically anisotropic element is substantially more than at least one optically positive uniaxial liquid crystalline polymer. And a liquid crystal film (A) in which the nematic hybrid alignment formed by the liquid crystal polymer substance in a liquid crystal state is fixed to at least one optically positive uniaxial liquid crystal polymer substance. And a liquid crystal film (B) in which the liquid crystalline polymer substance is formed in a liquid crystal state and in which the nematic alignment is fixed, and the transflective liquid crystal display element as described above.
[0012]
A fourth feature of the present invention is that the liquid crystal film (A) is a liquid crystal film in which a liquid crystal material is nematic hybrid aligned in a liquid crystal state, and the nematic hybrid alignment is glass-fixed by cooling from the state. And a transflective liquid crystal display device as described above.
[0013]
A fifth aspect of the present invention is that the liquid crystal film (A) is a liquid crystal film in which a liquid crystal material is nematic hybrid aligned in a liquid crystal state and the nematic hybrid alignment is fixed by a crosslinking reaction. The present invention relates to a transflective liquid crystal display device.
[0014]
A sixth aspect of the present invention is that the liquid crystal layer thickness of the region having the reflection function and the liquid crystal layer thickness of the region having the transmission function are different, and the liquid crystal layer thickness of the region having the reflection function is smaller than the liquid crystal layer thickness of the region having the transmission function. And a transflective liquid crystal display device as described above.
[0015]
A seventh aspect of the present invention relates to the above-mentioned transflective liquid crystal display element, which uses an ECB (Electrically Controlled Birefringence) system.
An eighth aspect of the present invention relates to the above-mentioned transflective liquid crystal display device, wherein a TN (Twisted Nematic) system is used.
A ninth aspect of the present invention relates to the transflective liquid crystal display element described above, wherein a HAN (Hybrid Aligned Nematic) system is used.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The transflective liquid crystal display element of the present invention, when viewed from the observer side, includes a polarizing plate, a first optically anisotropic element, a liquid crystal cell, a second optically anisotropic element, a polarizing plate, and a backlight. If necessary, members such as a light diffusion layer, a light control film, a light guide plate, and a prism sheet can be further added. In a liquid crystal display device of this type, it is possible to use both a reflection mode and a transmission mode by installing a backlight behind.
[0017]
Next, the liquid crystal cell used in the present invention will be described.
The liquid crystal cell used in the present invention has a first substrate having a transparent electrode, a second substrate having a transflective electrode in which a region having a reflective function and a region having a transmissive function are formed, It comprises a first substrate and a nematic liquid crystal layer sandwiched between the second substrate.
[0018]
The liquid crystal cell includes a semi-transmissive reflective layer in which a region having a reflective function and a region having a transmissive function are formed, but the region having a reflective function is a reflective display portion for performing reflective display, and the region having a transmissive function is transmissive. It becomes a transmissive display unit that performs display.
It is preferable that the thickness of the liquid crystal layer of the reflective display portion of the liquid crystal cell is smaller than that of the transmissive display portion. The reason will be described below.
First, the transmissive display in the transmissive display unit when the liquid crystal layer thickness is set to a layer thickness suitable for reflective display will be described. When a liquid crystal layer suitable for reflective display is set, the amount of change in the polarization state due to a change in the orientation due to an external field such as an electric field of the liquid crystal layer depends on the amount of light incident through the liquid crystal layer from the observer side. Then, the light is reflected again by the liquid crystal layer and emitted to the observer side, so that the liquid crystal layer reciprocates and a sufficient contrast ratio can be obtained. However, in this setting, in the transmissive display section, the amount of change in the polarization state of the light passing through the liquid crystal layer is insufficient. For this reason, in addition to the polarizing plate installed on the observer side of the liquid crystal cell used for reflective display, even if the polarizing plate used only for transmissive display is installed on the back of the liquid crystal cell viewed from the observer side, the transmissive display section Sufficient display cannot be obtained. That is, when the alignment condition of the liquid crystal layer is set to the alignment condition of the liquid crystal layer suitable for the reflective display portion, the transmissive display portion has insufficient lightness, or even if the lightness is sufficient, the transmittance of the dark display is low. Does not decrease, and a contrast ratio sufficient for display cannot be obtained.
[0019]
More specifically, when performing the reflective display, the liquid crystal in the liquid crystal layer is applied by the applied voltage so that a phase difference of approximately 波長 wavelength is given to the light passing through the liquid crystal layer only once. Is controlled. When the transmissive display is performed by performing the voltage modulation for providing the liquid crystal layer thickness suitable for the reflective display, that is, the phase modulation of 1/4 wavelength, the transmittance of the transmissive display unit in the dark display is sufficiently reduced. However, when the transmissive display section performs bright display, light having about half the luminous intensity is absorbed by the polarizing plate on the light emission side, and sufficient bright display cannot be obtained. Further, when an optical element such as a polarizing plate or a phase difference compensator is arranged to increase the brightness when the transmissive display unit is in a bright display, the brightness when the transmissive display unit is in a dark display becomes the brightness in the bright display. And the contrast ratio of the display becomes insufficient.
[0020]
Conversely, in order to set the thickness of the liquid crystal layer to a condition suitable for transmissive display, it is necessary to apply voltage modulation to the liquid crystal layer so that a phase difference of 波長 wavelength is given to light transmitted through the liquid crystal layer. is there. Therefore, in order to use both the reflected light and the transmitted light for display with high resolution and excellent visibility, the liquid crystal layer thickness of the reflective display portion needs to be smaller than the liquid crystal layer thickness of the transmissive display portion. . Ideally, the thickness of the liquid crystal layer in the reflective display section is preferably about half the thickness of the liquid crystal layer in the transmissive display section.
[0021]
As the liquid crystal cell system, a TN (Twisted Nematic) system, an STN (Super Twisted Nematic) system, an ECB (Electrically Controlled Birefringence) system, an IPS (In-Plane Switching), a VoIP (Internal Plane), and a VA (Opt. Birefringence system, HAN (Hybrid Aligned Nematic) system, ASM (Axially Symmetric Aligned Microcell) system, halftone gray scale system, domain division system, display system using ferroelectric liquid crystal, antiferroelectric liquid crystal, etc. Method.
[0022]
In the case of the TN mode, the twist direction of the liquid crystal layer may be left-handed or right-handed. The twist angle is desirably 90 degrees or less, and more desirably 70 degrees or less. If the angle is larger than 90 degrees, unnecessary coloring may occur on the liquid crystal display element.
The driving method of the liquid crystal cell is not particularly limited. The passive matrix method used for STN-LCD and the like, the active matrix method using an active electrode such as a TFT (Thin Film Transistor) electrode, a TFD (Thin Film Diode) electrode, Any driving method such as a plasma addressing method may be used.
[0023]
The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the material exhibiting liquid crystallinity constituting the liquid crystal layer is oriented in a specific orientation. Specifically, a transparent substrate in which the substrate itself has a property of aligning liquid crystal, a transparent substrate in which the substrate itself lacks alignment ability, and an alignment film or the like having a property of aligning liquid crystal is provided. Can also be used. In addition, known electrodes such as ITO can be used for the electrodes of the liquid crystal cell. The electrode can be usually provided on the surface of the transparent substrate in contact with the liquid crystal layer. When a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.
[0024]
The material exhibiting liquid crystallinity that forms the liquid crystal layer is not particularly limited, and examples thereof include ordinary various low-molecular liquid crystal substances, high-molecular liquid crystal substances, and mixtures thereof that can form various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystalline substance, and the like can be added to these as long as the liquid crystallinity is not impaired.
[0025]
The region having a reflective function (hereinafter, sometimes referred to as a reflective layer) included in the transflective electrode is not particularly limited, and may be a metal such as aluminum, silver, gold, chromium, or platinum, an alloy containing them, or an oxide. An oxide such as magnesium, a dielectric multilayer film, a liquid crystal exhibiting selective reflection, a combination thereof, or the like can be given. These reflective layers may be flat or curved. In addition, the reflective layer is made to have a diffuse reflection property by processing the surface shape such as the uneven shape, the one having both electrodes on the electrode substrate on the side opposite to the observer side of the liquid crystal cell, and a combination thereof. May be used.
[0026]
The polarizing plate used in the present invention is not particularly limited as long as the object of the present invention can be achieved, and a normal polarizing plate used in a liquid crystal display device can be appropriately used. Specifically, iodine and / or a dichroic dye is applied to a hydrophilic polymer film made of a PVA-based material such as polyvinyl alcohol (PVA) or partially acetalized PVA or a partially saponified ethylene-vinyl acetate copolymer. And a polarizing film composed of a polyene oriented film such as a dehydrated product of PVA or a dehydrochlorinated product of polyvinyl chloride. Further, a reflective polarizing film can also be used.
The polarizing plate may be used alone or a polarizing film provided with a transparent protective layer or the like on one or both sides of the polarizing film for the purpose of improving strength, improving moisture resistance, improving heat resistance, and the like. good. Examples of the transparent protective layer include those obtained by laminating a transparent plastic film such as polyester or triacetyl cellulose directly or via an adhesive layer, an application layer of a transparent resin, and a photocurable resin layer such as an acrylic or epoxy resin. . When these transparent protective layers are coated on both sides of the polarizing film, different protective layers may be provided on both sides.
[0027]
The first optically anisotropic element used in the present invention, when the retardation values at wavelengths (λ) of 450 nm, 550 nm and 650 nm are Re (450), Re (550) and Re (650), respectively, is represented by the following formula ( It is a retardation film composed of one polymer oriented film satisfying I) and formula (II).
Re (450) <Re (550) <Re (650) (I)
0.2 ≦ Re (λ) /λ≦0.3 (II)
A retardation film that satisfies the above formula (I), that is, a retardation film composed of one polymer oriented film having a smaller retardation value as the wavelength becomes shorter, is obtained by a polymer oriented film that satisfies the following condition (A) or (B). be able to.
[0028]
(A) (1) Form a polymer unit having a positive refractive index anisotropy (hereinafter referred to as a first monomer unit) and a polymer compound having a negative refractive index anisotropy. A film comprising a polymer compound containing a monomer unit (hereinafter, referred to as a second monomer unit), wherein (2) a polymer compound based on the first monomer unit, Re (450) / Re ( 550) is an oriented film that is smaller than Re (450) / Re (550) of the polymer compound based on the second monomer unit and (3) has a positive refractive index anisotropy.
[0029]
(B) (1) A monomer unit forming a polymer compound having a positive refractive index anisotropy (hereinafter, referred to as a first monomer unit) and a polymer compound having a negative refractive index anisotropy are formed. A film comprising a polymer compound containing a monomer unit (hereinafter, referred to as a second monomer unit), wherein (2) a polymer compound based on the first monomer unit, Re (450) / Re ( 550) is an oriented film which is larger than Re (450) / Re (550) of the polymer compound based on the second monomer unit and (3) has a negative refractive index anisotropy.
[0030]
As an example of an embodiment that satisfies the above conditions (A) and (B), there is one that satisfies the following conditions (C) and (D).
(C) (1) a blend polymer comprising a polymer compound having a positive refractive index anisotropy and a polymer compound having a negative refractive index anisotropy and / or a polymer having a positive refractive index anisotropy A film comprising a copolymer comprising a monomer unit forming a compound and a monomer unit forming a polymer compound having a negative refractive index anisotropy, wherein (2) the positive refractive index anisotropy Re (450) / Re (550) of the polymer having the negative refractive index anisotropy is smaller than Re (450) / Re (550) of the polymer having the negative refractive index anisotropy, and (3) the positive refraction is obtained. An oriented film having anisotropy.
[0031]
(D) (1) A blend polymer comprising a polymer compound having a positive refractive index anisotropy and a polymer compound having a negative refractive index anisotropy and / or a polymer having a positive refractive index anisotropy A film comprising a copolymer comprising a monomer unit forming a compound and a monomer unit forming a polymer compound having a negative refractive index anisotropy, wherein (2) the positive refractive index anisotropy Re (450) / Re (550) of the polymer compound having a negative refractive index anisotropy is larger than Re (450) / Re (550) of the polymer compound having the negative refractive index anisotropy, and (3) negative refraction. An oriented film having anisotropy.
Here, the polymer compound having a positive or negative refractive index anisotropy refers to a polymer compound that gives an oriented film having a positive or negative refractive index anisotropy.
[0032]
In the present invention, the polymer oriented film used for the first optically anisotropic element may be made of a blend polymer or a copolymer as described above. The polymer material constituting the polymer oriented film may be a blend polymer or a copolymer satisfying the above conditions, and is a thermoplastic polymer having excellent heat resistance, good optical performance, and capable of forming a solution. For example, one type or two or more types can be appropriately selected from polymers such as polyarylate, polyester, polycarbonate, polyolefin, polyether, polysulfine, polysulfone, and polyethersulfone. However, if the water absorption of the oriented film is not less than 1% by weight, there is a problem in practical use as a retardation film. Therefore, the film material must have a water absorption of 1% by weight or less, preferably 0.5% by weight or less. It is important to choose to meet.
[0033]
In the case of a blend polymer, it is preferable that the refractive index of the compatible blend or each of the high molecular compounds is substantially equal, since the polymer needs to be optically transparent. Specific combinations of the blend polymer include, for example, polymethyl methacrylate as a polymer having negative optical anisotropy, and polyvinylidene fluoride, polyethylene oxide, or vinylidene as a polymer having positive optical anisotropy. Combination of fluoride-trifluoroethylene copolymer, polyphenylene oxide as a polymer having positive optical anisotropy, and polystyrene as a polymer having negative optical anisotropy, styrene-lauroylmaleimide copolymer, Styrene-cyclohexylmaleimide copolymer or a combination of styrene-phenylmaleimide copolymer, styrene-maleic anhydride copolymer having negative optical anisotropy and polycarbonate having positive optical anisotropy, Has optical anisotropy of Acrylonitrile - butadiene copolymer and acrylonitrile having a negative optical anisotropy - Styrene copolymer to favorably used, but is not limited thereto. In particular, from the viewpoint of transparency, a combination of polystyrene and polyphenylene oxide such as poly (2,6-dimethyl-1,4-phenylene oxide) is preferable. In the case of such a combination, the ratio of the polystyrene preferably accounts for 67% by weight or more and 75% by weight or less of the whole.
[0034]
As the copolymer, for example, butadiene-styrene copolymer, ethylene-styrene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, polycarbonate copolymer, polyester copolymer, A polyester carbonate copolymer, a polyarylate copolymer, or the like can be used. In particular, since a segment having a fluorene skeleton can have negative optical anisotropy, a polycarbonate copolymer, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, or the like having a fluorene skeleton is more preferably used.
[0035]
A polycarbonate copolymer produced by reacting a bisphenol with a phosgene or a carbonate-forming compound such as diphenyl carbonate has excellent transparency, heat resistance, and productivity, and can be particularly preferably used. The polycarbonate copolymer is preferably a copolymer containing a structure having a fluorene skeleton. The component having a fluorene skeleton is preferably contained in an amount of 1 to 99 mol%.
[0036]
A preferred material for the oriented film of the present invention comprises an oriented film of polycarbonate composed of a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2). The repeating unit represented by 1) accounts for 30 to 90 mol% of the entire polycarbonate, and the repeating unit represented by the above formula (2) is a material that accounts for 70 to 10 mol% of the whole.
[0037]
Embedded image

[0038]
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[0039]
In the above formula (1), R ₁ ~ R ₈ Each independently represents a group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms, and X is a group represented by the formula (3). In the above formula (2), R ₉ ~ R ₁₆ And each independently represents a group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and Y represents a group selected from the groups represented by the formula (4).
[0040]
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[0041]
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[0042]
In the above formula (4), R ₁₇ ~ R ₁₉ , R ₂₁ And R ₂₂ Each independently represents a group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms; ₂₀ And R ₂₃ Each independently represents a group selected from a hydrocarbon group having 1 to 20 carbon atoms, and Ar is an aryl group having 6 to 10 carbon atoms.
[0043]
This material has a polycarbonate copolymer comprising a repeating unit having a fluorene skeleton represented by the above formula (1) and a repeating unit represented by the above formula (2), and a fluorene skeleton represented by the above formula (1). It is a blend polymer of a polycarbonate comprising a repeating unit and a polycarbonate comprising a repeating unit represented by the above formula (2). In the case of a copolymer, two or more kinds of the repeating units represented by the above formulas (1) and (2) may be used in combination, and in the case of a composition, two or more kinds of the above repeating units may be used in combination.
[0044]
In the above formula (1), R ₁ ~ R ₈ Are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include an alkyl group such as a methyl group, an ethyl group, an isopropyl group and a cyclohexyl group, and an aryl group such as a phenyl group. Of these, a hydrogen atom and a methyl group are preferred.
In the above formula (2), R ₉ ~ R ₁₆ Are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group having 1 to 22 carbon atoms include an alkyl group having 1 to 9 carbon atoms such as a methyl group, an ethyl group, an isopropyl group and a cyclohexyl group, and an aryl group such as a phenyl group, a biphenyl group and a terphenyl group. Can be Of these, a hydrogen atom and a methyl group are preferred.
In the above formula (4), R ₁₇ ~ R ₁₉ , R ₂₁ And R ₂₂ Are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group having 1 to 22 carbon atoms include an alkyl group having 1 to 9 carbon atoms such as a methyl group, an ethyl group, an isopropyl group and a cyclohexyl group, and an aryl group such as a phenyl group, a biphenyl group and a terphenyl group. Can be Of these, a hydrogen atom and a methyl group are preferred. R ₂₀ And R ₂₃ Are each independently selected from hydrocarbon groups having 1 to 20 carbon atoms, and Ar is an aryl group having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group.
[0045]
The content of the above formula (1), that is, the copolymer composition in the case of a copolymer and the blend composition ratio in the case of a composition is 30 to 90 mol% of the entire polycarbonate. When the value is out of this range, the absolute value of the phase difference does not decrease as the wavelength becomes shorter at a measurement wavelength of 400 to 700 nm. The content of the above formula (1) is preferably 35 to 85 mol%, more preferably 40 to 80 mol% of the entire polycarbonate. Here, the above molar ratio can be determined by, for example, a nuclear magnetic resonance (NMR) element for the entire bulk of the polycarbonate constituting the oriented film regardless of the copolymer or the blend polymer.
[0046]
The polycarbonate in this material is preferably a polycarbonate copolymer and / or a polycarbonate composition (blend polymer) composed of a repeating unit represented by the following formula (5) and a repeating unit represented by the following formula (6). .
[0047]
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[0048]
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[0049]
In the above formula (5), R ₂₄ And R ₂₅ Each independently represents a group selected from a hydrogen atom or a methyl group; in the above formula (6), R ₂₆ And R ₂₇ Each independently represents a group selected from a hydrogen atom and a methyl group, and Z represents a group selected from the group represented by the formula (7).
[0050]
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[0051]
Further, in a copolymer comprising repeating units represented by the following formulas (8) to (12), a copolymer having a proportion of the repeating unit (12) of 40 to 75 mol%, and a copolymer represented by the following formulas (9) and (12): In the copolymer comprising the repeating unit represented by the following formula (10) and the copolymer comprising the repeating unit represented by the following formulas (10) and (12): It is more preferable that the proportion of (11) is 40 to 75 mol% in the copolymer having the proportion of 30 to 70 mol% and the copolymer comprising the repeating units represented by the following formulas (8) and (11). .
[0052]
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[0053]
The most preferable material is a copolymer or a polymer blend containing bisphenol A (BPA, corresponding to the above formula (8)) and biscresol fluorene (BCF, corresponding to the above formula (12)) or a mixture thereof. The compounding ratio of the components is such that the BCF content is 55 to 75 mol%, and more preferably 55 to 70 mol%. With these materials, it is possible to obtain a λ / 4 plate and a λ / 2 plate that are more ideal.
[0054]
The above-mentioned copolymer and / or blend polymer can be produced by a known method. As the polycarbonate, a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method, and the like are suitably used. In the case of a blend, a compatible blend is preferable, but even if they are not completely compatible, light scattering between the components can be suppressed and transparency can be improved by adjusting the refractive index between the components.
[0055]
The intrinsic viscosity of the material polymer compound of the polymer oriented film in the invention is preferably from 0.3 to 2.0 dl / g. If the viscosity is lower than this, there is a problem that the material becomes brittle and the mechanical strength cannot be maintained. Problem.
[0056]
The polymer oriented film in the present invention is preferably transparent, and has a haze value of 3% or less and a total light transmittance of 85% or more. Further, the glass transition temperature of the polymer oriented film material is preferably 100 ° C. or higher, more preferably 120 ° C. or higher. Further, an ultraviolet absorber such as phenylsalicylic acid, 2-hydroxybenzophenone, and triphenyl phosphate, a bluing agent for changing color, and an antioxidant may be added.
[0057]
The polymer oriented film in the present invention uses a film obtained by orienting a film of the above polycarbonate or the like by stretching or the like. As a method for producing such a film, a known melt extrusion method, a solution casting method, or the like is used, and a solution casting method is more preferably used from the viewpoints of uneven film thickness and appearance. As the solvent in the solution casting method, methylene chloride, dioxolane or the like is preferably used.
In addition, a known stretching method can be used for the stretching method, but it is preferably longitudinal uniaxial stretching. In the film for the purpose of improving the stretchability, known plasticizers dimethyl phthalate, diethyl phthalate, phthalate esters such as dibutyl phthalate, phosphate esters such as tributyl phosphate, aliphatic dibasic esters, glycerin derivatives, It may contain a glycol derivative or the like. At the time of stretching, the film may be stretched while the organic solvent used at the time of film formation is left in the film. The amount of the organic solvent is preferably 1 to 20% by mass based on the polymer solid content.
[0058]
Further, the above-mentioned additives such as the plasticizer and the liquid crystal can change the wavelength dispersion of the retardation of the polymer oriented film, but the addition amount is preferably 10% by mass or less, more preferably 3% by mass or less based on the solid content of the polymer. .
The thickness of the polymer oriented film is not particularly limited, but is preferably 1 μm to 400 μm.
[0059]
In order to make the retardation of the polymer oriented film smaller as the wavelength becomes shorter, it is essential to have a specific chemical structure.Wavelength dispersion of the retardation is largely determined by its chemical structure. It should be noted that it varies depending on the state and the like.
Since a polymer oriented film can form a good quarter-wave plate (λ / 4 plate) having a small wavelength dependence particularly with one oriented film, it satisfies the following formula (II). It is.
0.2 ≦ Re (λ) /λ≦0.3 (II)
[0060]
The second optically anisotropic element used in the present invention is a liquid crystalline polymer substance having an optically positive uniaxial property, specifically, a liquid crystalline polymer compound having an optically positive uniaxial property or at least one liquid crystalline polymer compound having an optically positive uniaxial property. Comprising an optically positive uniaxial liquid crystalline polymer composition containing the liquid crystalline polymer compound, wherein the liquid crystalline polymer compound or the liquid crystalline polymer composition is formed in a liquid crystal state. A device having at least a liquid crystal film (A) in which a nematic hybrid alignment structure having a tilt angle of 5 ° to 35 ° is fixed, and having a phase difference of about a quarter wavelength in the visible light region.
[0061]
Here, the nematic hybrid alignment refers to an alignment mode in which liquid crystal molecules are in a nematic alignment, and the angle between the director of the liquid crystal molecules and the film plane is different between the upper surface and the lower surface of the film. Therefore, since the angle formed between the director and the film plane is different between the vicinity of the upper surface interface and the vicinity of the lower surface interface, the angle is continuously changed between the upper surface and the lower surface of the film. I can say.
In a film in which the nematic hybrid alignment state is fixed, directors of liquid crystal molecules are oriented at different angles in all places in the film thickness direction. Thus, the film no longer has an optical axis when viewed as a film structure.
[0062]
The average tilt angle in the present invention means the average value of the angle between the director of liquid crystal molecules and the plane of the film in the thickness direction of the liquid crystal film. In the liquid crystal film used in the present invention, the angle formed between the director and the film plane near one interface of the film usually forms an angle of 20 ° to 90 °, preferably 30 ° to 70 ° as an absolute value. On the opposite side of the plane, an absolute value usually forms an angle of 0 ° to 20 °, preferably 0 ° to 10 °, and the average tilt angle is usually 5 ° to 45 ° as an absolute value, It is preferably between 7 ° and 40 °, more preferably between 10 ° and 38 °, and most preferably between 15 ° and 35 °. When the average tilt angle is out of the above range, the contrast may be lowered, which is not desirable. The average tilt angle can be obtained by applying a crystal rotation method.
[0063]
The liquid crystal film (A) constituting the second optically anisotropic element used in the present invention is substantially formed of a liquid crystal polymer material having optically positive uniaxiality. There is no particular limitation on the manufacturing method as long as the nematic hybrid alignment state formed in the liquid crystal state is fixed. For example, a liquid crystal film obtained by forming a low-molecular liquid crystal in a nematic hybrid orientation in a liquid crystal state and then immobilized by photocrosslinking or thermal crosslinking, or a polymer liquid crystal formed in a nematic hybrid orientation in a liquid crystal state, and then cooled. A liquid crystal film obtained by fixing the orientation can be used. In the present invention, the liquid crystal film does not matter whether the film itself exhibits liquid crystallinity, but means a film obtained by forming a liquid crystal material such as a low-molecular liquid crystal and a high-molecular liquid crystal into a film.
[0064]
In order for the liquid crystal film (A) to exhibit a more favorable viewing angle improving effect on the transflective liquid crystal display device, the film thickness of the film depends on the type of the target liquid crystal display device and various optical parameters. Although it cannot be said unconditionally, it is usually in the range of 0.2 μm to 10 μm, preferably 0.3 μm to 5 μm, particularly preferably 0.5 μm to 2 μm. When the thickness is less than 0.2 μm, there is a possibility that a sufficient compensation effect cannot be obtained. If the film thickness exceeds 10 μm, the display may be unnecessarily colored.
[0065]
Next, the upper and lower sides of the optically anisotropic element made of the liquid crystal film (A), the tilt direction of the optically anisotropic element, and the pretilt direction of the liquid crystal cell layer are defined below with reference to FIGS.
First, in FIGS. 1 and 2, the upper and lower sides of the optically anisotropic element composed of the liquid crystal film (A) are positioned between the liquid crystal molecule director and the film plane near the film interface of the liquid crystal film (A) constituting the optically anisotropic element. When each angle is defined by the angle formed, the surface formed by the angle between the director of the liquid crystal molecules and the film plane forms an angle of 20 to 90 degrees on the acute angle side is defined as b surface, and the angle is 0 to 20 degrees on the acute angle side. Is defined as a c-plane.
When the c-plane is viewed from the b-plane of the optically anisotropic element through the liquid crystal film layer, the angle formed by the liquid crystal molecule director and the projection component of the director on the c-plane is an acute angle and is parallel to the projection component. The direction is defined as the tilt direction of the optically anisotropic element.
Next, in FIG. 3, at the cell interface of the liquid crystal cell layer, the driving low-molecular liquid crystal is not parallel to the cell interface but tilts at an angle, and this angle is generally called a pretilt angle. Is defined as a pretilt direction of the liquid crystal cell layer, in which the angle between the director and the projection component on the interface of the director is an acute angle and is parallel to the projection component of the director.
[0066]
Further, the second optically anisotropic element can be used in combination with another stretched polymer film or a liquid crystal film (B) in which nematic alignment is fixed.
As the polymer stretched film, a material exhibiting uniaxial or biaxial properties, such as polycarbonate (PC), polymethacrylate (PMMA), polyvinyl alcohol (PVA), ARTON (product of Nippon Synthetic Rubber Co., Ltd.) Name) Stretched films such as films can be used. Also in this case, in consideration of the problem of cost increase, a combination of one liquid crystal film and one stretched polymer film is practically preferable.
[0067]
The liquid crystal film (B) may be formed from any liquid crystal as long as the nematic alignment state is fixed. For example, a liquid crystal film obtained by forming a low-molecular liquid crystal in a nematic orientation in a liquid crystal state and then immobilized by photocrosslinking or thermal crosslinking, or a liquid crystal polymer in a nematic orientation in a liquid crystal state and then cooling to fix the orientation. A liquid crystal film obtained by conversion can be used. The liquid crystal film (B) in the present invention does not mean whether the film itself exhibits liquid crystallinity as in the case of the liquid crystal film (A). Means what is obtained by
[0068]
The liquid crystal film included in the second optically anisotropic element can be used as a single liquid crystal film, or can be used by providing a transparent plastic film as a support substrate. When used as a single liquid crystal film, it can be manufactured by laminating a liquid crystal film on a transparent plastic film such as polyester or triacetyl cellulose used for manufacturing the polarizing plate, and then integrating the film with the polarizing plate.
[0069]
The retardation value (product of birefringence Δn and film thickness d) of the second optically anisotropic element of the present invention will be described.
The apparent retardation value in the plane when viewed from the normal direction of the liquid crystal film (A) is, in the case of a nematic hybrid-oriented film, a refractive index perpendicular to the director (hereinafter, referred to as ne). The refractive index in the direction (hereinafter referred to as no) is different, and when the value obtained by subtracting no from ne is the apparent birefringence, the apparent retardation value is the apparent birefringence and the absolute film thickness. Let it be given by the product of the thickness. This apparent retardation value can be easily obtained by polarization optical measurement such as ellipsometry.
[0070]
The case where the second optically anisotropic element is composed of only the liquid crystal film (A) in which the nematic hybrid alignment is fixed, the case in which the liquid crystal film (A) and the polymer stretched film or the liquid crystal film in which the nematic alignment is fixed ( The case where B) is combined will be described separately.
When the liquid crystal film (A) is composed of only the nematic hybrid-aligned liquid crystal film (A), the apparent retardation value of the liquid crystal film (A) is generally 70 nm to 180 nm, preferably 90 nm to 160 nm with respect to 550 nm monochromatic light. Particularly preferably, in the range of 120 nm to 150 nm, good circular polarization characteristics can be obtained. When the apparent retardation value is smaller than 70 nm or larger than 180 nm, there is a possibility that unnecessary coloring may occur in the liquid crystal display device.
[0071]
When the liquid crystal film (A) and the polymer stretched film or the liquid crystal film (B) are combined, as described in JP-A-10-068816, the phase difference of the birefringent light in the monochromatic light of 550 nm is substantially equal. A １ ／ wavelength plate having a 波長 wavelength and a 波長 wavelength plate having a birefringent light having a phase difference of approximately 波長 wavelength in monochromatic light having a wavelength of 550 nm, with their slow axes crossing each other. By bonding, good circular polarization characteristics can be obtained. The retardation value of the quarter-wave plate is usually in the range of 70 nm to 180 nm, preferably 90 nm to 160 nm, particularly preferably 120 nm to 150 nm. The retardation value of the half-wave plate is usually in the range of 180 nm to 320 nm, preferably 200 nm to 300 nm, particularly preferably 220 nm to 280 nm. When the retardation ranges of the ４ wavelength plate and the 波長 wavelength plate deviate from the above, unnecessary coloring may occur in the liquid crystal display element.
[0072]
The angle between the slow axis of the quarter-wave plate and the slow axis of the half-wave plate is usually 40 to 90 degrees, preferably 50 to 80 degrees, particularly preferably 55 to 75 on the acute angle side. Range of degrees.
The liquid crystal film (A) in which the nematic hybrid alignment is fixed may be used for a 波長 wavelength plate or a 波長 wavelength plate.
When the liquid crystal film (A) is used for the 波長 wavelength plate, a polymer stretched film or a liquid crystal film (B) is used for the 波長 wavelength plate, and the liquid crystal film (A) is used for the 波長 wavelength plate. When used, a polymer stretched film or a liquid crystal film (B) may be used for a 波長 wavelength plate.
[0073]
A case where only one liquid crystal film (A) is used for a transflective liquid crystal display element as the second optical anisotropic element will be described. The liquid crystal film (A) is preferably disposed between the second substrate of the liquid crystal cell and the polarizing plate. Here, the arrangement condition of the liquid crystal film (A) will be described with reference to FIG.
In the liquid crystal cell 15 of FIG. 6, a straight line overlapping in the pretilt direction of the upper substrate and a straight line overlapping in the pretilt direction of the lower substrate are assumed. These two straight lines are projected on the same plane, and a straight line is drawn such that two angles on the acute angle side are respectively left-right symmetrical angles among four angles formed around a point where the straight lines intersect. . This straight line is defined as a bisector in the present invention. When a straight line overlapping in the pretilt direction of the upper substrate and a straight line overlapping in the pretilt direction of the lower substrate are overlapped (that is, when two straight lines are parallel), the overlapping straight line is referred to as 2 in the present invention. It becomes an equal line.
The angle formed by the bisector and the linear component with respect to the tilt direction of the liquid crystal film (A) is usually 0 to 30 degrees, preferably 0 to 20 degrees, and more preferably 0 degree as an absolute value. It is desirable to arrange so as to be 10 to 10 degrees, most preferably approximately 0 degrees. If the angle between them is greater than 30 degrees, there is a possibility that a sufficient viewing angle compensation effect cannot be obtained.
[0074]
Next, a case in which one liquid crystal film (A) and one polymer stretched film or one liquid crystal film (B) are used as a second optically anisotropic element in a transflective liquid crystal display element will be described.
The arrangement of the liquid crystal film (A) is preferably the same as that in the case where only one sheet is used. That is, it is preferable that the tilt direction of the liquid crystalline polymer in the liquid crystal film substantially coincides with the direction of the bisector. The angle between the tilt direction and the pretilt direction is preferably in the range of 0 to 30 degrees, more preferably in the range of 0 to 20 degrees, and particularly preferably in the range of 0 to 10 degrees.
[0075]
In the transflective liquid crystal display device of the present invention, the light diffusion layer, the backlight, the light control film, the light guide plate, and the prism sheet are not particularly limited, and known materials can be used.
The transflective liquid crystal display element of the present invention may be provided with other constituent members in addition to the constituent members described above. For example, by attaching a color filter to the liquid crystal display element of the present invention, a color liquid crystal display element capable of performing multicolor or full-color display with high color purity can be manufactured.
[0076]
【The invention's effect】
The transflective liquid crystal display device of the present invention is characterized in that the display in the transmissive mode is bright, has high contrast, can be designed to be thin, and has little dependence on the viewing angle.
[0077]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In this embodiment, the retardation Δnd is a value at a wavelength of 550 nm unless otherwise specified.
[0078]
[Example 1]
An outline of the transflective liquid crystal display device of the present invention will be described with reference to FIG. 4, and the configuration of the first embodiment will be described with reference to FIG.
A second substrate 8 is provided with a reflective electrode 6 formed of a material having a high reflectance such as Al and a transparent electrode 7 formed of a material having a high transmittance such as ITO, and a counter electrode is formed on the first substrate 3. A liquid crystal layer 5 made of a liquid crystal material having a positive dielectric anisotropy is sandwiched between the reflection electrode 6 and the transmission electrode 7 and the counter electrode 4. The first optically anisotropic element 2 and the polarizing plate 1 are provided on the surface of the first substrate 3 opposite to the side on which the counter electrode 4 is formed, and the reflection electrode 6 and the transmission electrode 7 of the second substrate 8 are The second optically anisotropic element 9 and the polarizing plate 10 are provided on the side opposite to the formed surface. A backlight 11 is provided on the back side of the polarizing plate 10.
[0079]
A liquid crystal film 13 having a thickness of 0.77 μm and having a fixed nematic hybrid orientation having an average tilt angle of 28 degrees in the film thickness direction was prepared, and the TN type semi-transmissive reflection shown below was arranged in the arrangement shown in FIG. A liquid crystal display device was manufactured.
The used liquid crystal cell 15 uses ZLI-1695 (manufactured by Merck) as a liquid crystal material, and has a liquid crystal layer thickness of 3.5 μm in the reflective electrode area 6 (reflective display section) and 4 μm in the transmissive electrode area 7 (transmissive display section). 0.0 μm. The pretilt angle of the liquid crystal layer at both interfaces of the substrate was 2 degrees, the twist angle of the liquid crystal cell was 70 degrees with a left-hand twist, and the Δnd of the liquid crystal cell was approximately 230 nm in the reflective display portion and approximately 262 nm in the transmissive display portion.
[0080]
The polarizing plate 1 (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) is arranged on the viewer side (upper side of the figure) of the liquid crystal cell 15, and the first plate is disposed between the polarizing plate 1 and the liquid crystal cell 15. As the optically anisotropic element 2, a uniaxially stretched polymer stretched film (product name Pure Ace) 2 manufactured by Teijin Limited that satisfies the formulas (I) and (II), which are the requirements of the present invention, was disposed. Δnd of the stretched polymer film 2 was approximately 120 nm.
Further, as the second optically anisotropic element 9, a liquid crystal film 13 and a polymer stretched film 14 made of a uniaxially stretched polycarbonate film are arranged behind the liquid crystal cell 15 as viewed from an observer, and a polarizing plate 10 is further provided on the back side. Placed. Δnd of the liquid crystal film 13 in which the hybrid nematic alignment structure was fixed was 135 nm, and Δnd of the stretched polymer film 14 was 275 nm.
FIG. 6 shows the absorption axes of the polarizing plates 1 and 10, the slow axes of the first optically anisotropic body 2 and the polymer stretched film 14, the pretilt directions of both interfaces of the liquid crystal cell 15, and the tilt direction of the liquid crystal film 13. Arranged under conditions.
[0081]
FIG. 7 shows the contrast ratio from all directions, with the ratio of the transmittance of white display 0 V and black display 6 V (white display) / (black display) as the contrast ratio when the backlight is turned on (transmission mode). I have.
FIG. 8 shows the viewing angle characteristics of the transmissivity in the left and right directions when displaying six gradations from white display 0 V to black display 6 V when the backlight is turned on (transmission mode).
FIG. 9 shows the viewing angle characteristics of the transmittance in the vertical direction when six gradations are displayed from 0 V for white display to 6 V for black display when the backlight is turned on (transmission mode).
From FIGS. 7 to 9, it was found that good viewing angle characteristics were obtained particularly in the transmission mode.
[0082]
[Example 2]
A liquid crystal film 13 having a thickness of 0.60 μm and having a fixed nematic hybrid orientation having an average tilt angle of 28 degrees in the film thickness direction was prepared, and the following ECB-type semi-transmissive reflection was arranged in the arrangement shown in FIG. A liquid crystal display device was manufactured.
The liquid crystal cell 16 used was ZLI-1695 (manufactured by Merck) as a liquid crystal material, and the liquid crystal layer thickness was 2.1 μm in the reflective electrode area 6 (reflective display section) and 4 μm in the transmissive electrode area 7 (transmissive display section). 0.9 μm. The pretilt angle at both interfaces of the liquid crystal layer and the substrate was 2 degrees, and the Δnd of the liquid crystal cell was a homogeneous alignment of about 138 nm in the reflective display section and about 321 nm in the transmissive display section.
[0083]
A polarizing plate 1 (about 180 μm thick; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the viewer side (upper side of the figure) of the liquid crystal cell 16, and a first plate is provided between the polarizing plate 1 and the liquid crystal cell 16. A uniaxially stretched polymer stretched film (product name Pure Ace) 2 made of polycarbonate manufactured by Teijin Limited satisfying the formulas (I) and (II), which are the requirements of the present invention, is disposed as the optically anisotropic element 2 of the present invention. did. Δnd of the stretched polymer film 2 was approximately 115 nm.
Further, Δnd of the liquid crystal film 13 in which the hybrid nematic alignment structure arranged as the second optically anisotropic element 9 was fixed was 105 nm, and Δnd of the stretched polymer film 14 was 270 nm.
FIG. 10 shows the absorption axes of the polarizing plates 1 and 10, the slow axis of the first optically anisotropic body 2 and the stretched polymer film 14, the pretilt directions of both interfaces of the liquid crystal cell 16, and the tilt direction of the liquid crystal film 13. Arranged under conditions.
[0084]
FIG. 11 shows the contrast ratio from all directions, with the ratio of the transmittance of white display 0 V and black display 6 V (white display) / (black display) as the contrast ratio when the backlight is turned on (transmission mode). I have.
FIG. 12 shows the viewing angle characteristics of the transmissivity in the left and right directions when displaying six gradations from 0 V for white display to 6 V for black display when the backlight is turned on (transmission mode).
FIG. 13 shows the viewing angle characteristics of the transmittance in the vertical direction when six gradations are displayed from 0 V for white display to 6 V for black display when the backlight is turned on (transmission mode).
From FIGS. 11 to 13, it was found that the ECB type has good viewing angle characteristics, particularly in the transmission mode, similarly to the TN type.
[0085]
[Comparative Example 1]
As shown in the layout diagram of FIG. 14, polycarbonate 17 (Δnd is approximately 130 nm) is used instead of the liquid crystal film 13, the Δnd of the polycarbonate 14 is set to 260 nm, and the absorption of the polarizing plate 10 arranged on the back side of the liquid crystal cell 15. A liquid crystal display device similar to that of Example 1 was produced except that the axes and the slow axes of the stretched polymer films 14 and 17 were arranged under the conditions shown in FIG.
[0086]
FIG. 16 shows the contrast ratio from all directions, with the ratio of the transmittance of white display 0 V and black display 6 V (white display) / (black display) as the contrast ratio when the backlight is turned on (transmission mode). I have.
FIG. 17 shows the viewing angle characteristics of the transmissivity in the left and right directions when displaying six gradations from white display 0 V to black display 6 V when the backlight is turned on (transmission mode).
FIG. 18 shows the viewing angle characteristics of the transmittance in the vertical direction when six gradations are displayed from 0 V for white display to 6 V for black display when the backlight is turned on (transmission mode).
[0087]
Example 1 and Comparative Example 1 are compared for viewing angle characteristics.
Comparing the omnidirectional isocontrast curves between FIG. 7 and FIG. 16, it can be seen that a wide viewing angle characteristic is obtained by using the liquid crystal film 13 having the hybrid nematic structure.
Comparing the horizontal and vertical gradation characteristics, which are the drawbacks in the transmission mode, between FIGS. 8 and 9 and FIGS. 17 and 18, the inversion characteristics are greatly improved by using the liquid crystal film having the hybrid nematic structure. You can see that.
[0088]
[Comparative Example 2]
As shown in the arrangement diagram of FIG. 14, polycarbonate 17 (Δnd is approximately 110 nm) is used in place of the liquid crystal film 13, Δnd of the polycarbonate 14 is set to 270 nm, and the absorption of the polarizing plate 10 arranged on the back side of the liquid crystal cell 16 is performed. A liquid crystal display device similar to that of Example 2 was produced except that the axes and the slow axes of the stretched polymer films 14 and 17 were arranged under the conditions shown in FIG.
[0089]
FIG. 20 shows the contrast ratio from all directions, with the ratio of the transmittance of white display 0 V and black display 6 V (white display) / (black display) as the contrast ratio when the backlight is turned on (transmission mode). I have.
FIG. 21 shows the viewing angle characteristics of the transmissivity in the left-right direction when six gradations are displayed from 0 V for white display to 6 V for black display when the backlight is turned on (transmission mode).
FIG. 22 shows the viewing angle characteristics of the transmittance in the vertical direction when six gradations are displayed from 0 V for white display to 6 V for black display when the backlight is turned on (transmission mode).
[0090]
Example 2 and Comparative Example 2 are compared for viewing angle characteristics.
Comparing the omnidirectional isocontrast curves between FIG. 11 and FIG. 20, it can be seen that a wide viewing angle characteristic is obtained by using the liquid crystal film 13 having the hybrid nematic structure.
In addition, comparing the horizontal and vertical gradation characteristics, which are disadvantages in the transmission mode, between FIGS. 12 and 13 and FIGS. 21 and 22, the inversion characteristics are greatly improved by using the liquid crystal film having the hybrid nematic structure. You can see that.
In this embodiment, the experiment was performed without a color filter. However, if a color filter is provided in a liquid crystal cell, it goes without saying that a good multi-color or full-color display can be performed.
[0091]
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a tilt angle and a twist angle of a liquid crystal molecule.
FIG. 2 is a conceptual diagram of an alignment structure of a liquid crystal film constituting a second optically anisotropic element.
FIG. 3 is a conceptual diagram illustrating a pretilt direction of a liquid crystal cell.
FIG. 4 is a cross-sectional view schematically showing a transflective liquid crystal display device of the present invention.
FIG. 5 is a cross-sectional view schematically illustrating a transflective liquid crystal display device of Examples 1 and 2.
FIG. 6 is a plan view showing an angle relationship among an absorption axis of a polarizing plate, a pretilt direction of a liquid crystal cell, a slow axis of a stretched polymer film, and a tilt direction of a liquid crystal film in Example 1.
FIG. 7 is a diagram showing a contrast ratio when the transflective liquid crystal display element in Example 1 is viewed from all directions.
FIG. 8 is a diagram showing viewing angle characteristics of transmissivity in the left and right directions when the transflective liquid crystal display element in Example 1 displays seven gradations from 0V to 6V.
FIG. 9 is a diagram showing viewing angle characteristics of transmittance in the vertical direction when the transflective liquid crystal display element in Example 1 displays seven gradations from 0V to 6V.
FIG. 10 is a plan view showing an angle relationship among an absorption axis of a polarizing plate, a pretilt direction of a liquid crystal cell, a slow axis of a stretched polymer film, and a tilt direction of a liquid crystal film in Example 2.
FIG. 11 is a diagram showing a contrast ratio when the transflective liquid crystal display element in Example 2 is viewed from all directions.
FIG. 12 is a diagram showing viewing angle characteristics of transmissivity in the left-right azimuth when the transflective liquid crystal display device in Example 2 displays seven gradations from 0 V to 6 V.
FIG. 13 is a view showing the viewing angle characteristics of the transmittance in the vertical direction when the transflective liquid crystal display element in Example 2 displays seven gradations from 0 V to 6 V.
FIG. 14 is a cross-sectional view schematically illustrating a transflective liquid crystal display element of Comparative Examples 1 and 2.
FIG. 15 is a plan view showing an angle relationship among an absorption axis of a polarizing plate, a pretilt direction of a liquid crystal cell, and a slow axis of a stretched polymer film in Comparative Example 1.
FIG. 16 is a diagram showing a contrast ratio when the transflective liquid crystal display element in Comparative Example 1 is viewed from all directions.
FIG. 17 is a view showing the viewing angle characteristics of the transmissivity in the left-right azimuth when the transflective liquid crystal display element in Comparative Example 1 displays seven gradations from 0 V to 6 V.
FIG. 18 is a view showing viewing angle characteristics of transmittance in the vertical direction when the transflective liquid crystal display element in Comparative Example 1 displays seven gradations from 0V to 6V.
FIG. 19 is a plan view showing an angle relationship among an absorption axis of a polarizing plate, a pretilt direction of a liquid crystal cell, and a slow axis of a stretched polymer film in Comparative Example 2.
FIG. 20 is a diagram showing a contrast ratio when the transflective liquid crystal display element in Comparative Example 2 is viewed from all directions.
FIG. 21 is a diagram showing viewing angle characteristics of transmissivity in the left-right azimuth when the transflective liquid crystal display element in Comparative Example 2 displays seven gradations from 0 V to 6 V.
FIG. 22 is a view showing the viewing angle characteristics of the transmittance in the vertical direction when the transflective liquid crystal display element in Comparative Example 2 displays seven gradations from 0 V to 6 V.
[Explanation of symbols]
1: Polarizing plate
2: First optically anisotropic element
3: First substrate
4: Counter electrode
5: Liquid crystal layer
6: reflective electrode
7: Transmission electrode
8: Second substrate
9: second optically anisotropic element
10: Polarizing plate
11: Backlight
12, 15, 16: liquid crystal cell
14, 17: polymer stretched film
13: Liquid crystal film

Claims (9)

A first substrate having a transparent electrode, a second substrate having a transflective electrode in which a region having a reflective function and a region having a transmissive function are formed, the first substrate and the second substrate A nematic liquid crystal layer sandwiched therebetween, a first optically anisotropic element provided on a surface of the first substrate opposite to a surface in contact with the liquid crystal layer, and one polarizing plate; A transflective liquid crystal display device comprising a second optically anisotropic element and one polarizing plate provided on a surface of the second substrate opposite to a surface in contact with the liquid crystal layer,
The first optically anisotropic element is a retardation film composed of one polymer oriented film, and the retardation values at wavelengths (λ) of 450 nm, 550 nm and 650 nm are Re (450), Re (550) and Re (450), respectively. (650), a retardation film satisfying the following formulas (I) and (II);
Re (450) <Re (550) <Re (650) (I)
0.2 ≦ Re (λ) /λ≦0.3 (II)
The second optically anisotropic element is substantially formed of at least one sheet of an optically positive uniaxial liquid crystalline polymer, and the liquid crystal polymer forms a nematic hybrid alignment formed in a liquid crystal state. A transflective liquid crystal display device comprising a fixed liquid crystal film (A). 2. The transflective liquid crystal display element according to claim 1, wherein said second optically anisotropic element is substantially formed of at least one optically positive uniaxial liquid crystalline polymer. 2. The transflective film according to claim 1, wherein the conductive polymer material comprises a liquid crystal film (A) in which a nematic hybrid alignment formed in a liquid crystal state is fixed, and at least one stretched polymer film. Liquid crystal display device. 2. The transflective liquid crystal display element according to claim 1, wherein said second optically anisotropic element is substantially formed of at least one optically positive uniaxial liquid crystalline polymer. A liquid crystal film (A) in which a nematic hybrid alignment formed in a liquid crystal state is formed of at least one optically positive uniaxial liquid crystalline polymer, 2. The transflective liquid crystal display device according to claim 1, wherein the liquid crystal polymer material comprises a liquid crystal film (B) formed in a liquid crystal state and having a fixed nematic orientation. 4. The liquid crystal film according to claim 1, wherein the liquid crystal film (A) is a liquid crystal film in which a liquid crystal material is nematic hybrid aligned in a liquid crystal state and the nematic hybrid alignment is glass-fixed by cooling from the state. A transflective liquid crystal display device according to any one of the above items. The liquid crystal film (A) is a liquid crystal film in which a liquid crystal material is nematic hybrid aligned in a liquid crystal state and the nematic hybrid alignment is fixed by a crosslinking reaction. Transflective liquid crystal display device. 2. A liquid crystal layer thickness of a region having a reflection function and a liquid crystal layer thickness of a region having a transmission function are different, and a liquid crystal layer thickness of the region having a reflection function is smaller than a liquid crystal layer thickness of the region having a transmission function. 3. The transflective liquid crystal display device according to item 1. 2. The transflective liquid crystal display device according to claim 1, wherein an ECB (Electrically Controlled Birefringence) system is used. 2. The transflective liquid crystal display device according to claim 1, wherein a TN (Twisted Nematic) method is used. The transflective liquid crystal display device according to claim 1, wherein a HAN (Hybrid Aligned Nematic) system is used.

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