JP4435362B2 - Light scattering sheet, light scattering composite sheet, and liquid crystal display element - Google Patents

Description

【００４３】
なお、共連続相構造を形成可能なポリマー系としては、ポリカーボネート系樹脂／ポリメタクリル酸メチル系も知られている。また、ＬＣＳＴ型の複合ポリマー系としては、スチレン−アクリロニトリル共重合体（ＡＳ樹脂）／ポリメタクリル酸メチル系、ＡＳ樹脂／ポリ（ε−カプロラクトン）系、ポリビニリデンフルオライド／イソタクチックポリメタクリル酸エチル系、ポリメタクリル酸メチル／ポリ塩化ビニル系なども挙げられる。ＵＣＳＴ型の複合ポリマー系としては、ポリスチレン／ポリメチルフェニルシロキサン系、ポリブタジエン／スチレン−ブタジエン共重合体（ＳＢＲ）系、ＡＳ樹脂／アクリロニトリル−ブタジエン共重合体（ＮＢＲ）系なども挙げられる。
【００４４】
第１のポリマーと第２のポリマーとの割合は、例えば、前者／後者＝１０／９０〜９０／１０（重量比）程度、好ましくは２０／８０〜８０／２０（重量比）程度、さらに好ましくは３０／７０〜７０／３０（重量比）程度、特に４０／６０〜６０／４０（重量比）程度である。ポリマーの構成比が一方に偏りすぎると、スピノーダル分解により共連続相を形成する時に、一方のポリマー相が非連続化しやすくなるため、シートを形成した場合に拡散光に指向性を付与できない。
【００４５】
なお、３以上の複数のポリマーでシートを形成する場合、各ポリマーの含有量は、通常、１〜９０重量％（例えば、１〜７０重量％、好ましくは５〜７０重量％、さらに好ましくは１０〜７０重量％）程度の範囲から選択できる。
【００４６】
前記光散乱層（光散乱シート）は、少なくとも共連続相構造を有している。共連続相構造は、共連続構造や三次元的に連続又は繋がった構造と称される場合があり、少なくとも２種の構成ポリマー相が連続している構造を意味する。
【００４７】
前記光散乱シートでは、少なくとも共連続相構造を有していればよく、共連続相構造と液滴相構造（独立又は孤立した相構造）とが混在した構造を有していてもよい。なお、スピノーダル分解において、相分離の進行に伴って、表面張力によりポリマー相が共連続相構造を形成し、さらに熱処理すると、連続相が自らの表面張力により非連続化し、液滴相構造（球状、真球状などの独立相の海島構造）となる。従って、相分離の程度によって、共連続相構造と液滴相構造との中間的構造、すなわち、上記共連続相から液滴相に移行する状態の相構造も形成できる。本発明では、ポリマー相が液滴相（独立又は孤立したほぼ真球形状の相）でない限り、上記中間的構造も共連続相構造という。
【００４８】
前記共連続相構造は、通常、シート面内において異方性が低減されており、実質的に等方性である。なお、等方性とは、シート面内のどの方向に対しても連続相による相分離構造のサイズ（平均相間距離）が等しいことを意味する。
【００４９】
なお、光散乱シートの相構造が共連続相構造と液滴構造との混在構造である場合、液滴相（独立ポリマー相）の割合は、例えば、３０％以下（体積比）、好ましくは１０％以下（体積比）であってもよい。共連続相構造の平面的又は立体的形状は特に制限されず、ネットワーク状、特にランダムなネットワーク状であってもよい。
【００５０】
なお、共連続相構造又は中間的構造は、通常、相間距離（同一相間の距離）に規則性を有する。そのため、シートに入射した光はブラッグ反射により特定方向に散乱光が指向する。従って、反射型液晶表示素子に装着しても、拡散光を一定の方向に指向させることができ（指向型拡散）、表示画面を高度に明るくすることができ、従来の粒子分散型の透過型光拡散シートでは解決できなかった問題点、すなわち、パネルへの光源（例えば、蛍光灯など）の映りを回避できる。
【００５１】
さらに、光散乱シートにおいて共連続相の平均相間距離は、例えば、１〜２０μｍ程度、好ましくは２〜１５μｍ程度、さらに好ましくは２〜１０μｍ程度である。平均相間距離が小さすぎると、拡散光の分布がガウス分布に近くなり、指向性を付与できない。また、平均相間距離が大きすぎると、拡散光の指向方向が直進光の方向とほぼ一致するため、光の拡散性が低下する。
【００５２】
なお、相間距離は、顕微鏡写真（共焦点レーザー顕微鏡など）の画像処理により測定できる。また、後述の拡散光の指向性の評価法と同様の方法により、拡散光強度が極大になる拡散角度θを測定し、下記のブラッグ反射条件の式より相間距離ｄを算出してもよい。
【００５３】
２ｄ・ｓｉｎ（θ／２）＝λ
（式中、ｄは相間距離を、θは拡散角度を、λは光の波長を示す）
光散乱シートの厚さは、例えば、１〜５００μｍ程度、好ましくは１〜３００μｍ程度（１０〜１５０μｍ程度、例えば、１０〜１００μｍ程度）、さらに好ましくは３〜１００μｍ程度（例えば、５〜５０μｍ、特に１０〜５０μｍ）程度であってもよい。シート厚みが薄すぎると、拡散光の強度が低下する。また、シート厚みが大きすぎると、拡散性が強くなりすぎ、指向性が低下する。また、反射型液晶表示素子に適用した場合に、素子の厚みや重量が増加するとともに、表示ボケが生じ、表示画面の精細性が低下する。なお、ポリマーの屈折率の差が小さい場合、シート厚みが大きい方が好ましく、反対に屈折率の差が大きい場合、シート厚みが小さい方が好ましい。
【００５４】
なお、後述するように、光散乱シートを基材シートと光散乱層とで構成する場合、光散乱層の厚みは、例えば、１〜１００μｍ程度、好ましくは５〜６０μｍ程度、さらに好ましくは１０〜４０μｍ程度であってもよい。
【００５５】
前記共連続相構造を有する光散乱シートを用いると、高い光散乱性が得られるだけでなく、拡散光に高い指向性を付与できる。拡散光の指向性は、例えば、図２に示すような、偏光板１、酢酸ビニル系粘着剤９、光拡散シート２、カラーフィルター８、ガラス板（厚さ１ｍｍ）１２、及びアルミニウム反射板５を積層した反射型ＬＣＤモデル装置を用いて測定できる。即ち、レーザー光照射器（ＮＩＨＯＮ ＫＡＧＡＫＵ ＥＮＧ ＮＥＯ−２０ＭＳ）１０により、この反射型ＬＣＤモデル装置に対して、正面方向から垂直にレーザー光を照射することにより、拡散角度θ１に対応する反射光の強度分布（拡散光の分布）を測定する。θ１＝０゜を中心とするガウス分布を示す光散乱シートに比べ、共連続相構造の光散乱シートを用いると、指向方向（例えば、θ１＝１〜６０゜（例えば、１〜３０゜）、好ましくは３〜６０゜（例えば、３〜２０゜）、さらに好ましくは５〜２０゜に強い極大分布を示す。このため、幅広い視野角で明るい液晶表示画像が得られる。
【００５６】
光散乱シートの透明性（全光線透過率）は、例えば、７０〜１００％程度、好ましくは８０〜１００％程度、さらに好ましくは９０〜１００％程度である。なお、全光線透過率は、日本電色工業（株）製のヘイズメーター（ＮＤＨ−３００Ａ）により測定できる。
【００５７】
前記光散乱シートのうち、特に好ましい光散乱シートは、特定の重量平均分子量［例えば、３００，０００以下（１０，０００〜３００，０００程度）、好ましくは１０，０００〜１５０，０００程度、さらに好ましくは１０，０００〜１２０，０００程度］の複数のポリマーにより構成されている。スピノーダル分解による共連続相の形成速度（発現速度）は、分子鎖の拡散により律速されるため、特定の分子量のポリマーを用いると、速やかに共連続相を形成できる。また、拡散光の強度を直進光の強度に対して相対的に高めることができる。このため、周囲の光を効果的に取り込むことができ、周囲からの入射光を効率よく散乱できる。そのため、明るい液晶表示画像が得られ、液晶表示の視認性を向上できる。図３は、拡散光の強度の測定方法を説明するための概略図である。すなわち、光散乱シート２の背面に配設されたレーザー光照射器（ＮＩＨＯＮ ＫＡＧＡＫＵＥＮＧ ＮＥＯ−２０ＭＳ）１０から、光散乱シート２に向けてレーザー光を照射する。レーザー光は、光散乱シート２で拡散されながら、光散乱シートの正面から出射する。拡散角θ３に応じて、この拡散光（拡散透過光）を検出器１１で検出することにより、拡散光の強度を測定できる。特定の重量平均分子量のポリマーで光散乱シートを構成した場合、直進透過光（θ３＝０゜）の強度Ｉ（θ0）と、極大の拡散透過光の強度Ｉ(θmax）との比Ｉ（θ0）／Ｉ（θmax）は、例えば、３０００／１〜１／１程度、、好ましくは５００／１〜１／１程度、さらに好ましくは１００／１〜５／１程度である。
【００５８】
なお、光散乱シートは、光散乱層単独で形成してもよく、必要に応じて、基材シート又はフィルム（透明支持体）と積層してもよい。透明支持体との積層により、シート強度を高くすることができる。
【００５９】
基材シート（透明支持体）を構成する樹脂としては、前記光散乱層を構成する樹脂と同様の樹脂が使用できる。また、共連続相構造を有する光散乱層の透明支持体として用いる場合、後述するように共連続相構造をスピノーダル分解により形成するため、基材シートもスピノーダル分解温度に対する耐熱性を有しているのが好ましい。好ましい基材シートとしては、例えば、セルロース誘導体（セルローストリアセテート（ＴＡＣ）、セルロースジアセテートなどのセルロースアセテートなど）、（メタ）アクリレート系樹脂、ビニルエステル系樹脂（ポリビニルアルコールなど）、ポリエステル系樹脂（ポリエチレンテレフタレート（ＰＥＴ）、ポリブチレンテレフタレート（ＰＢＴ）など）、ポリアリレート系樹脂、ポリスルホン系樹脂（ポリスルホン、ポリエーテルスルホン（ＰＥＳ）など）、ポリエーテルケトン系樹脂（ポリエーテルケトン（ＰＥＫ）、ポリエーテルエーテルケトン（ＰＥＥＫ）など）、ポリカーボネート系樹脂（ポリカーボネート（ＰＣ）など）、ポリオレフィン系樹脂（ポリエチレン、ポリプロピレンなど）、環状ポリオレフィン系樹脂（アートン(ARTON)、ゼオネックス(ZEONEX)など）、スチレン系樹脂（ポリスチレンなど）、ハロゲン含有樹脂（塩化ビニリデンなど）、などから得られるシートが挙げられる。これらシートは、１軸又は２軸に延伸されていてもよく、例えば、１軸延伸ＰＥＴシート、２軸延伸ＰＥＴシートなどのポリエステル延伸シートであってもよい。
【００６０】
なお、前記光散乱シート（又は基材シート）は、液晶画像をカラー化、高精細化する為に使用される偏光板や位相差板と同程度の熱膨張率を有するシートであってもよい。液晶表示素子において、偏光板や位相差板は光散乱シートと積層されることが多いため、光散乱シートの熱膨張率を偏光板や位相差板と同程度にすることで、熱膨張や熱収縮などに伴う光散乱シート（又は基材シート）と偏光板や位相差板との間の剥離の応力を抑制できる。例えば、偏光板や位相差板がセルロース誘導体で形成されている場合、光散乱層を構成する樹脂や基材シートに、セルロース誘導体（セルロースアセテートなど）を用いるのが好ましい。
【００６１】
また、液晶表示素子（特に、ＳＴＮ型液晶表示素子）には位相差板を用いる場合が多いため、位相差が小さい光散乱シートを用いるのが便利である。例えば、下記式で表される位相差（Ｒ；リターデーション）において、Ｒが５０ｎｍ以下、好ましくは３０ｎｍ以下の光散乱シートが使用できる。このような低位相差のシートは、例えば、光散乱層を構成する樹脂や基材シートにポリエーテルスルホン（ＰＥＳ）やセルローストリアセテート（ＴＡＣ）を用いることにより得ることができる。
【００６２】
Ｒ＝Δｎ×ｄ
（式中、Δｎはシートの複屈折を、ｄはシート厚みを示す）
なお、必要に応じて、位相差を有する光散乱シートであっても使用できる。例えば、位相差を有する基材シート（例えば、１軸延伸ＰＥＴシートなど）を用いて光散乱シートを形成した場合、光散乱シートは位相差を有する。また、共連続相構造を形成するために樹脂組成物をシート成形しスピノーダル分解したとき、場合によっては光散乱シートが位相差を有することがある。このような場合であっても、光散乱シートの配向軸を偏光板の偏光軸と一致させることにより、表示に障害が発生するのを防止できる。
【００６３】
なお、光散乱シートは、種々の添加剤、例えば、安定化剤（酸化防止剤、紫外線吸収剤、熱安定剤など）、可塑剤、着色剤（染料や顔料）、難燃剤、帯電防止剤、界面活性剤などを含有していてもよい。また、光散乱シートの表面には、必要により、種々のコーティング層、例えば、帯電防止層、防曇層、離型層などを形成してもよい。
【００６４】
［光散乱シートの製造方法］
前記共連続相構造の光散乱シートは、複数の屈折率の異なる成分からなる組成物（特に、樹脂組成物）をシート成形することにより、又は基材シート（透明性基材シート）に前記組成物層を塗布などにより積層することにより形成できる。なお、前記樹脂組成物は、通常、室温下で非相溶状態を維持可能であり、温度に依存して相分離が生じる。
【００６５】
より詳細には、共連続相構造を有する光散乱シートは、複数の屈折率の異なるポリマーからなる樹脂組成物を慣用の成形方法によりシート成形し、このシートをスピノーダル分解して、誘起された等方性の相分離構造（共連続相構造）を固定化することにより形成できる。また、前記複数のポリマーを略均一に分散した樹脂組成物を基材シート表面にコーティング又は溶融ラミネートし、必要に応じて、乾燥し、この積層シートをスピノーダル分解することによっても形成できる。
【００６６】
シート成形法は、例えば、ポリマー組成物の溶液（又はスラリー）を流延又はコーティングするキャスティング法やコーティング法、ポリマー組成物をガラス転移温度以上の温度で溶融混練してＴダイなどからシート状に押出成形する方法（Ｔダイ法、インフレーション法など）であってもよい。
【００６７】
スピノーダル分解は、前記屈折率の異なるポリマーからなる樹脂組成物層（又はシート）を、ポリマーのガラス転移温度以上の温度に加熱して相分離することにより行うことができる。例えば、樹脂組成物がＬＣＳＴ型の相分離性を示す場合、樹脂組成物層（又はシート）を下限臨界共溶温度（ＬＣＳＴ）以上の温度（例えば、ＬＣＳＴより１０〜１００℃、好ましくは２０〜８０℃程度高い温度）に加熱処理する方法、樹脂組成物がＵＣＳＴ型の相分離性を示す場合、上限臨界共溶温度（ＵＣＳＴ）以下の温度（例えば、ＵＣＳＴより１０〜５０℃、好ましくは２０〜４０℃程度低い温度）で熱処理、超音波処理する方法などが挙げられる。なお、熱処理温度は、例えば、８０〜３８０℃程度、好ましくは１４０〜３００℃程度の範囲から選択できる。なお、スピノーダル分解において、相分離の進行に伴って、表面張力によりポリマー相が共連続相構造を形成し、さらに熱処理すると、連続相が自らの表面張力により非連続化し、液滴相構造（球状、真球状などの独立相の海島構造）となる。従って、相分離の程度によって、共連続相構造と液滴相構造との中間的構造、すなわち、上記共連続相から液滴相に移行する状態の相構造も形成できる。
【００６８】
このようにしてスピノーダル分解により等方性の共連続相構造を形成したシートは、構成ポリマーのガラス転移温度以下（例えば、主たるポリマーのガラス転移温度以下）に冷却することにより、共連続相構造を固定化できる。なお、ＬＣＳＴ型のシートを冷却する場合、シートを急冷（例えば、３０℃以下、好ましくは１０℃以下の冷水での急冷）するのが好ましい。
【００６９】
このような方法では、スピノーダル分解を利用しているため、熱処理、冷却などの簡便な手段により低コストで共連続相構造を有するシートを形成できる。
【００７０】
［光散乱性複合シート］
本発明の光散乱性複合シートは、光散乱層で構成された光散乱シートの少なくとも一方の面に、他の機能層（偏光板、位相差板、光反射板、透明導電層など）が積層されている。光散乱シートを複合シート化すると、従来の液晶表示素子の機能層に代えて、複合シートを使用できるため、簡便に液晶表示素子に光散乱シートを導入できる。すなわち、液晶表示装置の製造ラインを変更することなく、コストを増大させることなく、更に歩留まりを低下することなく、高輝度高精細タイプの反射型液晶装置を製造することができる。また、複合シート用いると、後述するように、簡単に光散乱シートを液晶に近接でき、画像の視認性が向上する。
【００７１】
複合シートとしては、具体的には、光散乱シートと偏光板との積層シート、光散乱シートと位相差板との積層シート、光散乱シートと光反射板との積層シート、光散乱シートと透明導電層との積層シート（透明導電性シート）などの二層シート、この二層シートに、二層シートを構成する機能層と異なる機能層をさらに積層したシート（三層シート）（例えば、光散乱シートと偏光板と位相差板とで構成されている三層シート、特に、偏光板・光散乱シート・位相差板の順に貼合わされたシート、偏光板・位相差板・光散乱シートの順に貼り合わされたシートなどの偏光板が三層シートの表面に形成されているシートなど）などが例示できる。特に、三層シートを用いて液晶表示素子（例えば、ＳＴＮ液晶表示素子）を形成すると、液晶表示素子の製造において、各機能層の貼り合わせ工程を減らすことができる。
【００７２】
複合シートに用いる光散乱シートとしては、前記共連続相構造を有する光散乱シートを用いる場合が多いが、屈折率の異なる複数の固体成分（樹脂成分、無機成分など）により相分離構造が形成された光散乱層を有する限り特に制限されず、例えば、微粒子分散構造を有する光散乱シートであってもよい。なお、相分離構造（例えば、微粒子分散構造）を構成する複数の成分のうち、少なくとも２種の成分の屈折率差は、前記共連続相構造を構成する複数のポリマーの屈折率差と同様である。このような光散乱シートであっても、複合シートとして用いることにより、後述するように液晶画像の視認性を向上できる。
【００７３】
樹脂成分としては、前記共連続相構造を構成する樹脂と同様の樹脂が使用できる。
【００７４】
無機成分としては、透明又は半透明な無機成分が使用でき、例えば、酸化ケイ素（ガラスなど、特に、無アルカリガラス）、酸化ジルコニウム、酸化アルミ、酸化亜鉛、マイカ（雲母）などの無機酸化物、チッ化ホウ素などの無機窒素化物、弗化カルシウム、弗化マグネシウムなどの無機ハロゲン化物などが挙げられる。これら無機成分は、２種以上組み合わせて複合材として用いてもよく、例えば、マイカとチッ化ホウ素との複合材などが使用できる。
【００７５】
微粒子分散構造の光散乱層は、例えば、互いに屈折率が異なる透明ベース樹脂（前記樹脂成分で構成される透明ベース樹脂など）と微粒子成分（前記樹脂成分や無機成分で構成される微粒子など）とで構成されている。微粒子成分は、前記透明ベース樹脂に分散している。
【００７６】
好ましい透明ベース樹脂及び微粒子を構成する樹脂には、スチレン系樹脂（ポリスチレンなど）、（メタ）アクリル系樹脂、オレフィン系樹脂（ポリエチレン、ポリプロピレンなど）、ビニルエステル系樹脂、ビニルエーテル系樹脂、ポリカーボネート系樹脂、ポリスルホン系樹脂、ポリアミド系樹脂（ナイロン６、ナイロン１２、ナイロン６１２など）、セルロース誘導体（セルロースアセテートなど）などが挙げられる。
【００７７】
なお、微粒子分散構造では、高い光散乱性が得られるものの、拡散角が広角なほど光散乱性が小さくなる光散乱特性を示す場合がある。すなわち、拡散光の分布がガウス分布に近いため、拡散角が大きくなると、全体的に散乱光強度が低下し、表示画面の明るさが低下する場合がある。このため、透明ベース樹脂と微粒子成分（樹脂微粒子、無機微粒子など）との屈折率差、微粒子成分の粒子径、割合、粒子密度などを適宜調整して、後方散乱を抑制し、拡散光に指向性を付与してもよい。要求視野特性に対応した指向性を有するシートを用いると、外部光やフロントライトの光源を効率よく利用できる。
【００７８】
指向性を付与する場合、微粒子成分と前記透明ベース樹脂との屈折率差は、例えば、０．０１〜０．０６程度、好ましくは０．０１〜０．０５程度、さらに好ましくは０．０１〜０．０４程度である。
【００７９】
微粒子成分の平均粒径は、例えば、０．１〜１００μｍ程度、好ましくは１〜２０μｍ程度であってもよい。
【００８０】
微粒子成分と透明ベース樹脂との割合は、例えば、前者／後者＝１０／９０〜９０／１０（重量比）程度、好ましくは１５／８５〜６０／４０（重量比）程度、さらに好ましくは１５／８５〜４０／６０（重量比）程度であってもよい。
【００８１】
微粒子成分の平均粒子密度は、例えば、１〜１００（10¹⁰個／cm³）程度、好ましくは４〜８０（10¹⁰個／cm³）程度であってもよい。
【００８２】
なお、平均粒子密度は、例えば、平均粒径を測定し、下記式(I)により算出できる。
【００８３】
平均粒子密度(個／cm³）＝1cm³×Ｖs／［（4／3)π（Ｄs×10^-4／2）3］ (I)
（式中、Ｖsは光散乱層中の微粒子成分の割合（体積基準）を、πは円周率を、Ｄsは微粒子成分の粒径(μｍ）を示す）
複合シートに用いる光散乱シートは、前記共連続相構造の光散乱シートと同様に、光散乱層単独で構成してもよく、光散乱層と基材シート（透明支持体）とを積層することにより構成してもよい。なお、基材シートとしては、前記共連続相構造の光散乱シートの基材シートと同様のシートが使用できる。
【００８４】
また、複合シートに用いる光散乱シートの厚みは、前記共連続相構造の光散乱シートの厚みと同程度である。
【００８５】
なお、複合シートに用いる光散乱シートは、前記共連続相構造の光散乱シートと同様に、偏光板や位相差板と同程度の熱膨張率を有するシートで形成されたシートなどであってもよい。偏光板や位相差層と光散乱シートとを貼り合わせて複合シートを形成する場合、光散乱シートの熱膨張率を偏光板や位相差板と同程度にすることで、複合シートに、熱膨張や熱収縮などに伴う剥離の応力が発生するのを抑制できる。また、複合シートとして透明導電シート（光散乱シートと透明導電層との複合シート）を用いる場合であっても、液晶表示素子において、透明導電性シートは偏光板や位相差板と積層されることが多いため、剥離の応力の発生を抑制できる。
【００８６】
また、複合シートまたはこの複合シートに用いる光散乱シートは、前記共連続相構造の光散乱シートと同様に、位相差が小さい方が好ましいが、位相差を有していてもよい。
【００８７】
なお、微粒子分散構造の光散乱シートは、前記透明ベース樹脂と微粒子成分を含む混合物を用い、キャスティング法、溶融押出法などの慣用の方法に従って製造できる。なお、透明ベース樹脂と微粒子成分とを溶液にして成形する溶液製膜によってもシート成形できるが、好ましくは溶融した透明ベース樹脂に微粒子を分散して製膜する溶融製膜法より製造する。溶融製膜法によりシート化すると、安価にシート成形できる。
【００８８】
また、透明ベース樹脂と微粒子成分との混合物を基材シート表面にコーティングすることによっても、微粒子分散構造の光散乱シートを形成できる。
【００８９】
偏光板、位相差板及び反射板としては、液晶表示素子に用いる慣用の偏光板、位相差板または反射板が使用できる。例えば、偏光板は、ポリビニルアルコール製のフィルムであってもよい。位相差板は、例えば、ポリカーボネート製の位相差板である。反射板としては、例えば、金属箔（アルミ箔など）や金属（アルミニウムなど）が蒸着したプラスチックフィルムが使用できる。なお、反射板は、鏡面反射型の反射板であってもよく、光散乱性を有する反射板（表面が粗面処理された反射板など）であってもよい。
【００９０】
透明導電性シートを構成する透明導電層としては、導電性無機化合物で形成された層、例えば、金属酸化物層（ＩＴＯ（インジウム錫酸化物）、ＩｎＯ₂、ＳｎＯ₂、ＺｎＯなどの層）、金属層（Ａｕ、Ａｇ、Ｐｔ、Ｐｄなどの層）などが挙げられる。好ましい透明導電層は、ＩＴＯ層である。
【００９１】
透明導電層の厚みは、例えば、１００×１０^-8〜２，０００×１０^-8cm、好ましくは１００×１０^-8cm〜１，５００×１０^-8cm、さらに好ましくは１５０〜１，０００×１０^-8cm程度である。
【００９２】
透明導電層の表面抵抗は、例えば、１０〜１，０００Ω／□、好ましくは１５〜５００Ω／□、さらに好ましくは２０〜３００Ω／□である。
【００９３】
なお、光散乱シートが、光散乱層と基材シートとの積層シートの場合、透明導電層は、光散乱シートの光散乱層側に形成してもよく、基材シート側に形成してもよい。透明導電層を光散乱層側に形成すると、光散乱層を液晶層に近接できるため、高画質の表示画面を形成できる。一方、透明導電層を基材シート側に形成する場合、この透明導電シートを用いて後述の液晶表示素子を形成するときに、透明導電シートに配向膜を形成したり、光散乱シートに接着層を形成するなど、透明導電シートを高温処理する必要があるものの、基材シートの耐熱性が高い（例えば、ＰＥＳやＰＣのガラス転移温度は、それぞれ、約２２４℃及び約１４５℃である。また、ＰＥＴは結晶性が高く、ＴＡＣは耐熱性に優れている）ため、液晶表示素子の信頼性（安定性）を高めることができる。
【００９４】
また、透明導電シートは、光散乱シートの少なくとも一方の面に透明導電層が形成されていればよいため、他方の面は、未処理であってもよく、前記透明導電層以外の他の層、例えば、シートの静電気を除去するための静電気除去層（帯電防止層）が形成されていてもよい。静電気除去層を形成すると、この層に偏光板、位相差板、反射板などを貼りあわせる時に、静電気を有効に除去でき、液晶表示素子の品質低下を防止できる。
【００９５】
静電気除去層は、前記透明導電層と同様の成分で形成できる。静電気除去層の厚みは、例えば、１０〜５００オングストローム程度、好ましくは３０〜３００オングストローム程度である。また、静電気除去層の表面抵抗は、例えば、０．５〜１００ｋΩ／□程度、好ましくは１〜５０ｋΩ／□程度である。
【００９６】
透明導電シートは、導電層が形成されているにも拘わらず、前記光散乱シートと同程度の高い全光線透過率を示し、全光線透過率は、例えば、７０〜１００％程度、好ましくは８５〜９８％程度、さらに好ましくは９０〜９５％程度である。
【００９７】
なお、複合シートは、前記共連続相構造の光散乱シートと同様に、種々の添加剤を含有していてもよい。
【００９８】
複合シートの表面（透明導電シートの場合は、特に、透明導電層が形成されていない側の表面）には、必要により、種々のコーティング層、例えば、防曇層、離型層などを形成してもよい。
【００９９】
複合シートのシート厚みは、機能層の厚みに応じて選択できる。例えば、透明導電シートのシート厚みは、透明導電層の厚さが非常に薄いため、光散乱シートのシート厚みと同様であり、１〜５００μｍ程度、好ましくは１０〜４００μｍ程度、さらに好ましくは５０〜２００μｍ程度である。透明導電性シートの厚みが５００μｍを超えると、画像形成時に画像のシャープ性が低下する（画像ボケ）。また、透明導電性シートの厚みが１μｍ未満の場合、シートの強度や取扱い性が低下する。
【０１００】
複合シートは、例えば、拡散角度３〜６０゜程度、好ましくは５〜５０゜程度、さらに好ましくは１０〜４０゜程度（特に１０〜３０゜程度）に拡散光を指向可能であってもよい。
【０１０１】
［光散乱性複合シートの製造方法］
光散乱性複合シートのうち、偏光板、位相差板、光反射板などの透明導電層以外の機能層と光散乱シートとで複合シートを構成する場合、光散乱シート及び機能層のいずれか一方の表面に粘着剤を塗布し、光散乱シートと機能層層とを貼り合わせることにより複合シートを製造できる。例えば、光散乱シートの一方の面に粘着剤層を形成した後、機能層（偏光板、位相差板、反射板など）を貼りあわせることにより複合シートを形成できる。
【０１０２】
粘着剤としては、例えば（メタ）アクリル系樹脂、酢酸ビニル系樹脂、シリコーン系ポリマー、ポリエステル、ポリウレタン、合成ゴムなどが挙げられる。
【０１０３】
前記アクリル系粘着剤を形成する（メタ）アクリル系樹脂としては、例えば、（メタ）アクリル酸エステル（エチルアルコール、ｎ−プロピルアルコール、イソプロピルアルコールなどの炭素数が２〜１４程度のアルコールと（メタ）アクリル酸とのエステル）の単独又は共重合体が挙げられる。
【０１０４】
なお、液晶表示素子の製造工程において複合シートを簡便に貼り付けるために、複合シートの表面（例えば、光散乱シートの機能層との非接触面）に前記粘着剤を塗布してもよい。また、粘着剤の表面は、一般の機能シートと同様に、離型性フィルムが貼付されていてもよい。
【０１０５】
複合シートの機能層の表面は保護フィルムにより保護してもよい。
【０１０６】
一方、透明導電シートは、光散乱シートの表面に、慣用の方法、例えば、スパッタリング法、真空蒸着法、イオンプレーティング法、コーティング法などにより透明導電層を形成することにより得ることができる。なお、真空蒸着法により透明導電層を形成する場合（ＩＴＯを蒸着する場合など）、光散乱シート表面に予めＳｉＯ₂などの非導電性無機化合物を蒸着したり、熱硬化性樹脂やＵＶ硬化性樹脂などを予めコーティングしてアンカーコート層を形成した後で、透明導電層を蒸着することが多い。これら前処理により、透明導電層の強度や耐久性を向上できる。
【０１０７】
［反射型液晶表示素子］
本発明の反射型液晶表示素子は、透明導電層（電極）及びこの透明導電層を支持する基板（電極支持基板）を有する透明性フロント電極板と、導電層（電極）及びこの導電層を支持する基板（電極支持基板）を有するバック電極板とが導電層を対向して配設され、この両電極板の間に液晶が封入された液晶セルを有しており、この液晶セルの前方には偏光板が配設されている。なお、通常、バック電極板の背面には光反射板が配設されているとともに、前記偏光板は前方からの光の入射路及び反射路内に配設されている。そして、本発明では、液晶表示素子の画像の視認性を向上するため、光散乱シート（前記複合シートに用いる光散乱シート、例えば、共連続相構造の光散乱シート、微粒子分散構造の光散乱シートなど）を用いて液晶表示素子を構成している。この光散乱シートは、下記（i)〜(iii)のいずれかである。
【０１０８】
(i)偏光板とフロント電極板との間に配設された光散乱シート
(ii)バック電極板とこのバック電極板の後方に配設された反射板との間に配設された光散乱シート
(iii)基板としての光散乱シート
このような反射型液晶表示素子を用いると、光散乱シートを液晶に近接して配設できるため、画像の不明瞭性（ボケ）を防止して視認性を高めることができる。また、光散乱シートが反射型液晶表示素子の表面に露出しないので、外部から機械的または化学的影響を受けることが少なく、光散乱層が損傷する虞がない。さらに、反射型液晶表示素子の表面に耐久性の優れた偏光板が形成されているため、反射型液晶表示素子の品質を長期間に亘って維持できる。
【０１０９】
例えば、図１は、偏光板と液晶セルとの間に光散乱シートが配設されたカラー表示用の液晶表示素子（i)の例を示す概略断面図である。図１の反射型ＬＣＤは、透明導電層（図示せず）を有する一対の透明性電極板７ａ、７ｂ（ガラス板など）の間に封入された液晶６（液晶層など）を備えた液晶セル１２において、一方の透明性電極板（バック電極板）７ｂには、入射光を反射するための反射板５（例えば、鏡面反射板などの反射層）が積層されている。また、液晶セル１２の他方の透明性電極板（フロント電極板）７ａには、カラー表示のためのカラーフィルター８を介して、光散乱シート（この例では、共連続相構造の光散乱シート）２が積層されている。また、光散乱シート２の他方の面には、反射光を偏光するための偏光板１が積層されている。なお、反射型ＬＣＤをモノクロ表示に使用する場合、前記カラーフィルターは必ずしも必要ではない。
【０１１０】
偏光板と透明導電層との間に光散乱シートを配設すると、観察者側のフロント面から入射した光（入射光）を拡散（散乱）できるだけでなく、反射板５により反射した光をも再度拡散（散乱）できる。このように、２回に亘って光を散乱できるため、反射板５の鏡面反射を十分に防止できる。
【０１１１】
なお、偏光板と透明導電層との間に光散乱シートを配設する場合、入射光を液晶よりも後方で反射できる限り反射板は必ずしも必要ではなく、例えば、バック電極板の導電層を光反射性導電層（例えば、金属層が蒸着したガラス板など）であってもよい。図７は、光反射性導電層を有する液晶表示素子の概略断面図である。この液晶表示素子は、透明性フロント電極（インジウム錫酸化物薄膜などの透明導電層）４ａとフロント基板（厚み１mmのガラス板など）２２ａとを有するフロント電極板７ａと、バック電極（導電層）４ｃとバック基板（厚み1mmのガラス板など）２２ｂとを有するバック電極板７ｃと、この両電極板７ａ、７ｃの間に封入された液晶層６とで構成された液晶セル１２を有している。そして、バック電極（導電層）４ｃは、アルミニウム薄膜で形成された光反射性バック電極である。なお、液晶セル１２のフロント側には、粘着剤層９２を介して光散乱シート２が積層され、この光散乱シート２の表面には、粘着剤層９１を介して偏光板１が積層されている。光反射性背面電極で反射性液晶表示素子を形成すると、液晶表示素子を薄型化できる。
【０１１２】
また、ＴＦＴ型の液晶表示素子の場合には必ずしも必要ではないものの、ＳＴＮ（Super Twisted Nematic）液晶表示素子の場合には、偏光板とフロント電極板との間には位相差板を配設してもよい。光散乱シートは偏光板と位相差板との間に配設してもよいが、好ましくは位相差板とフロント電極板（又は液晶セル）との間に配設できる。例えば、図９は、位相差板とフロント電極板との間に光散乱シートを配設した液晶表示素子の概略断面図である。図９の液晶表示素子は、前記図７と同様の液晶セル１２のフロント電極板７ａに、粘着剤層９２を介して光散乱シート２を貼り付け、この光散乱シート２の表面に粘着剤層９３を介して位相差板３を貼り付け、さらにこの位相差板３の表面に粘着剤層９１を介して偏光板１を貼り付けることにより形成できる。位相差板３とフロント電極板７ａとの間に光散乱シート２を配設すると、偏光板１と位相差板３との間に光散乱シート２を配設する場合に比べ、液晶に光散乱シートを近接させることができ、画像の明瞭性をさらに高めることができる。
【０１１３】
図１１は、バック電極板と反射板との間に光散乱シートを配設した液晶表示素子(ii)の概略断面図である。この液晶表示素子は、フロント基板（厚み１００μｍのプラスチックシートなど）２２ａと、バック基板（厚み１００μｍのプラスチックシートなど）２２ｂと、この両基板の間に封入された液晶層６とで構成された液晶セル１２を有している。また、前記両基板において、液晶側の表面には透明性フロント電極（インジウム錫酸化物薄膜など）４ａ、４ｂが形成されている。そして、この液晶セル１２の後方には、粘着剤層９５を有する反射板５が配設され、この反射板５と液晶セル１２との間に粘着剤層９２により光散乱シート２が貼り付けられている。バック電極板７ｂと反射板５との間に光散乱シート２を配設した場合も、前記偏光板１とフロント電極板７ａとの間に光散乱シート２を配設する場合と同様に、入射光と反射光とを散乱でき、反射板５の鏡面反射を十分に防止できる。
【０１１４】
図４は、基板を光散乱シートで形成した液晶表示素子（iii）の概略断面図である。この液晶表示素子は、液晶セル１２の前方に位相差板３を介して偏光板１が積層されており、液晶セル１２の後方には反射板５が積層されている。そして、液晶セル１２では、基板（電極支持基板）２２ａ、２２ｂとして、基材シート２３ａ、２３ｂに光散乱層２１ａ、２１ｂが積層された光散乱シート（フロント電極板）２ａ、２ｂを使用しており、これら両基板（光散乱シート）のうち液晶側の表面には透明導電層４ａ、４ｂが形成されている。
【０１１５】
このような液晶表示素子を用いると、光散乱シートで基板（電極支持基板）を構成できるため、光散乱層（光散乱シート）などを別個に設ける必要がない。このため、明るい画面が得られるにも拘わらず、液晶表示素子の厚みを薄くできる。さらに、液晶表示素子の厚みを薄くすることにより、液晶画像と光散乱層の画像との両方の画像が形成されるのを十分に防止でき、よりシャープな画像を形成でき、極めて鮮明で高品質な表示画面を得ることができる。
【０１１６】
なお、光散乱シートで基板を構成する場合、必ずしもフロント基板２２ａとバック基板２２ｂとの両方の基板を光散乱シート２で形成する必要はなく、いずれか一方が光散乱シート２で形成されていればよい。例えば、バック基板２２ｂを光散乱シート２ｂで形成する場合、フロント基板７ａとしては、光散乱性を有さない透明性基板を使用してもよい。
【０１１７】
また、フロント基板２２ａを光散乱シート２ａで形成する場合も、フロント基板７ａとして、光散乱性を有さない透明性基板が使用できる。さらに、フロント基板２２ａを光散乱シート２ａで形成する場合、バック電極（導電層）４ｂは、光反射性電極であってもよく、光反射性電極を用いる場合、反射板５は必ずしも必要ではない。
【０１１８】
光散乱シートとしては、好ましくは共連続相構造の光散乱シートが使用できる。共連続相構造の光散乱シートを用いて反射型ＬＣＤを構成すると、反射光に拡散性を付与しながら、散乱光を一定の方向に指向させることができるため、画面表示を明るくすることができる。特に、カラー表示であっても十分な明るさを確保できるので、カラー反射型液晶表示素子に有利に形成できる。なお、光散乱シートとして共連続相構造の光散乱シートを使用する場合、反射光に指向性を付与できるため、透過型液晶表示素子（反射板に代えて、バックライトを用いた液晶表示素子）であっても広い視野角に亘って明るい液晶画像を表示できる。また、光散乱シートとして共連続相構造の光散乱シートを使用する場合、光散乱シートの配設位置は特には限定されない。
【０１１９】
偏光板１、位相差板３、反射板５及び透明導電層４ａ、４ｂは前記複合シートと同様である。
【０１２０】
透明導電層が形成された電極板（光透過性電極板）としては、ガラスやプラスチック（前記基材シートと同様のプラスチックシートなど）などの基板（透明性基板）の表面に、前記透明導電シート（光散乱性透明導電シート）と同様にして透明導電層を形成した電極板が使用できる。
【０１２１】
また、光反射性導電層が形成された電極板（光反射性電極板）は、前記フロント電極板と同様の基板に、金属層（光反射性導電層）を蒸着することにより形成できる。光反射性導電層は粗面処理されていてもよい。なお、粗面処理は、例えば、蒸着条件を適当に選択することにより、または慣用の粗面化方法により行うことができる。粗面処理した光反射性バック電極板を用いると、液晶表示素子において、液晶に電圧を印加できるとともに、入射光を鏡面反射することなく、適度に散乱して反射できる。
【０１２２】
なお、導電層（透明導電層、光反射性導電層など）は、ストライプ状にパターン処理され、ストライプ状電極を構成している。この導電層のパターン処理は、フォトリソグラフ加工などのレジスト形成法により、または導電層にエッチングを施すことにより行うことができる。また、フロント電極板のストライプ状電極と、バック電極板のストライプ状電極とが、互いに交叉（例えば、直交）するように両電極板は配設されていてもよい。
【０１２３】
さらに、この両導電層には、液晶を反射型液晶に適する配向（前記図７、９、１１及び４のような１枚偏光板方式では、主に垂直配向）を発生させるため、配向膜を塗布乾燥し、ラビングしてもよい。配向膜にはポリイミド系の垂直配向膜が主に用いられる。
【０１２４】
前記液晶セル１２は、例えば、スクリーン印刷により、電極板７ａ、７ｂの導電層側の表面にシール部分を形成（印刷）し、当該シール部の上にスペーサ１３を配設し、このスペーサー１３を挟んで２枚の電極板７ａ、７ｂを貼りあわせることにより形成できる。液晶は、前記貼り合わせにより形成された空間部（セル内）に、真空注入法などの慣用の方法によって注入できる。また、注入口は封止剤（紫外線硬化型の封止剤など）により封止可能である。
【０１２５】
液晶表示素子は、１つの偏光板を用いた偏光板１枚方式の反射型ＬＣＤに限られず、異なる偏光性を有する２つの偏光板を用いた偏光板２枚方式の反射型ＬＣＤであってもよい。また、偏光板１枚方式の反射型ＬＣＤは、例えば、１枚の偏光板と、種々のモード（ツイストネマチック液晶を用いたモード、Ｒ−ＯＣＢ（Optically Compensated Bend) モード、平行配向モードなど）を組み合わせた反射型ＬＣＤであってもよい。
【０１２６】
前記液晶表示素子は、偏光板、光散乱シート、液晶セル、及び必要に応じて位相差板や光反射板などを互い粘着剤（接着剤）で貼り合わせることにより形成できる。なお、偏光板、光散乱シート、位相差板、及び光散乱板は、通常、予め表面（両面又は片面）に粘着剤層が形成されている。なお、光散乱層と基材シートとで構成された光散乱シートの片面に粘着剤層を形成する場合、光散乱層を保護するため、光散乱層側の表面に粘着剤層（接着剤層）を形成することが多い。
【０１２７】
偏光板、光散乱シート、位相差板、及び光散乱板の片面に粘着剤層を形成すると、簡便に液晶表示素子を形成できる。例えば、偏光板と光散乱シートと液晶セルとを貼り合わせて液晶表示素子を製造する場合、偏光板の粘着剤（接着剤）で光散乱シートと偏光板とを貼りあわせることができる。このため、光散乱シートの片面に形成された粘着剤により、光散乱シートと位相差板又は液晶セル（フロント電極板）とを張り合わせることにより液晶表示素子を製造できる。
【０１２８】
また、偏光板、位相差板、光散乱シート及び液晶セルを張り合わせて液晶表示素子を製造する場合も、位相差板の粘着剤（接着剤）で光散乱シートと位相差板とを貼りあわせることができる。そして、光散乱シートの片面に形成された粘着剤により、光散乱シートと液晶セル（フロント基板）とを貼り合わせることができる。なお、必要に応じて、光散乱シートの粘着剤により光散乱シートと位相差板とを貼り合わせ、位相差板の粘着剤により位相差板と液晶セル（フロント基板）とを貼り合わせてもよい。そして、偏光板の粘着剤により、偏光板を位相差板又は光散乱シートと貼り合わせることにより液晶表示素子を製造できる。
【０１２９】
さらに、光透過性バック電極板と光散乱シートと反射板とを貼り合わせる場合には、この反射板の粘着剤（接着剤）で反射板と光散乱シートとを貼りあわせることができる。このため、光散乱シートの片面に形成された粘着剤により、光散乱シートとバック電極板とを張り合わせることができる。また、前記液晶セルのフロント面に、粘着剤層が形成された位相差板、及び粘着剤層が形成された偏光板を順次貼り合わせることにより、液晶表示素子を製造できる。
【０１３０】
また、偏光板、光散乱シート、位相差板、及び光散乱板の両面に粘着剤層を形成する場合、特に光散乱シートの両面に粘着剤層が形成する場合、粘着剤層の成面を識別する必要なくシートを貼り付けることができ、製造工程が簡便となり、接着強度も向上する。
【０１３１】
前記液晶表示素子の製造工程において、前記複合シート（光散乱シートと偏光板との積層シート、光散乱シートと位相差板との積層シート、光散乱シートと反射板との積層シート、光散乱シートと透明導電層との積層シート（透明導電性シート）など）を用いてもよい。例えば、前記図７の液晶表示素子は、偏光板１と光散乱シート２を積層した複合シート（図６）を用いることにより、前記図９の液晶表示素子は、位相差板３と光散乱シート２を積層した複合シート（二層シート）（図８）又はこのシートの位相差板３にさらに偏光板１を積層した複合シート（三層シート）（図１２）を用いることにより、図１１の液晶表示素子は、光散乱シート２と反射板５とを積層した複合シート（図１１）を用いることにより、図４の液晶表示素子は光散乱シート２の表面に透明導電層４を形成した透明導電性シート（図１６）を用いることにより製造できる。このような複合シートを用いると、従来の液晶表示素子の製造ラインを変更することなく、反射型液晶表示装置を製造できる。
【０１３２】
なお、複合シートを用いて液晶表示素子を製造する場合、好ましくは、複合シートの光散乱シートを液晶に近接するように、複合シートを液晶セルに配設（貼り付け）する。例えば、光散乱シートと偏光板（又は位相差板）との複合シートを液晶セルの観察者側に配設して反射型液晶表示素子を構成する場合、光散乱シートを液晶セルに向けて（すなわち、偏光板（又は位相差板）を観察者側に向けて）複合シートを配設（貼り合わせ）するのが好ましい。光散乱シートを液晶に近接するように複合シートを配設すると、画像の明瞭性をさらに高めることができる。
【０１３３】
本発明の光散乱シート、複合シートまたは液晶表示素子を用いると、液晶表示画面の視認性を向上できる。このため、反射型ＬＣＤ、特に携帯型情報機器の液晶表示装置に好適に利用できる。また、本発明の光散乱シートの製造方法によると、スピノーダル分解により光散乱シートを製造しているため指向性拡散シートを簡便に製造できる。
【０１３４】
【発明の効果】
本発明の光散乱シート、複合シート、及び液晶表示素子によれば、反射光に指向性を付与できるため、または液晶セルに近接して光散乱シートを配設することが可能であるため、液晶画像の視認性を向上できる。また、本発明の複合シートによれば、光散乱シートと液晶表示素子の機能層とが複合化されているため、液晶表示素子の製造ラインを変更することなく、コストを増大させることなく、かつ歩留まりを低下させることなく、液晶表示素子の鏡面反射を防止して、画像の視認性を向上できる。特に、透明導電性シートを用いると、導電性を有しているため、液晶表示素子の電極板を構成でき、薄型で高画質な液晶表示素子を簡便かつ低コストに得ることができる。さらに、本発明の液晶表示素子によれば、液晶画像の視認性を向上できるだけでなく、光散乱シートが偏光板よりも背面に配設されているため、液晶表示素子の表面の耐傷性を向上でき、低コストで液晶表示素子の耐久性を向上できる。
【０１３５】
【実施例】
以下に、実施例に基づいて本発明をより詳細に説明するが、本発明はこれらの実施例によって限定されるものではない。
【０１３６】
なお、実施例及び比較例では、下記の樹脂、偏光板、位相差板を使用した。
【０１３７】
［樹脂］
ＰＭＭＡ−１：ポリメタクリル酸メチル（三菱レイヨン（株）製、「ＢＲ−８７」、重量平均分子量（Ｍw）＝２５，０００、屈折率＝１．４９）
ＰＭＭＡ−２：ポリメタクリル酸メチル（三菱レイヨン（株）製、「ＢＲ−８３」、重量平均分子量（Ｍw）＝４０，０００、屈折率＝１．４９）
ＰＭＭＡ−３：ポリメタクリル酸メチル（三菱レイヨン（株）製、「ＢＲ−８０」、重量平均分子量（Ｍw）＝９５，０００、屈折率＝１．４９）
ＰＭＭＡ−４：ポリメタクリル酸メチル（三菱レイヨン（株）製、「ＢＲ−８８」、重量平均分子量（Ｍw）＝４８０，０００、屈折率＝１．４９）
ＰＭＭＡ−５：ポリメタクリル酸メチル（ＰＭＭＡ）系粒子（積水化学（株）製、「ＭＢＸ−２」）
ＳＡＮ−１：スチレン−アクリロニトリル共重合体（テクノポリマー（株）製、「２９０−ＺＦ」、重量平均分子量（Ｍw）＝６９，０００、屈折率＝１．５７）
ＳＡＮ−２：スチレン−アクリロニトリル共重合体（テクノポリマー（株）製、「ＳＡＮ−Ｔ」、重量平均分子量（Ｍw）＝１０７，０００、屈折率＝１．５７）
ＳＡＮ−３：スチレン−アクリロニトリル共重合体（テクノポリマー（株）製、「ＳＡＮ−Ｌ」、重量平均分子量（Ｍw）＝１００，０００、屈折率＝１．５７）
ＳＡＮ−４：スチレン−アクリロニトリル共重合体（ダイセル化学工業（株）製、「０８０」、重量平均分子量（Ｍw）＝１１０，０００、屈折率＝１．５５）
ＳＡＮ−５：スチレン−アクリロニトリル共重合体（ダイセル化学工業（株）製、「０８０ＳＦ」、重量平均分子量（Ｍw）＝１１０，０００、屈折率＝１．５５）
ＣＥＬ−１：セルローストリアセテート（ダイセル化学工業（株）製、「ＬＴ−１０５」）
ＰＥＴＧ−１：ポリエチレンテレフタレート系非晶性コポリエステル（Eastman Chemical 社製、「Eastar PETG 6763」、屈折率＝１．５６７）
ＧＰＰＳ−１：汎用ポリスチレン（ダイセル化学工業（株）製、「ＧＰＰＳ ♯３０」、屈折率＝１．５８９）
ＰＥＳ−１：ポリエーテルスルホンシート（住友化学工業（株）製、厚み＝１００μｍ）
［偏光板］
偏光板Ａ：液晶表示用偏光フィルム（日東電工（株）製、「ＮＰＦ」）
偏光板Ｂ：ヨウ素を吸着した一軸延伸ポリビニルアルコールフィルムの一方の面に粘着剤層が形成され、他方の面が、粗面化処理及び表面加工処理した後保護フィルム（トリアセチルセルロースフィルム）で保護されている偏光板。なお、液晶表素子の製造工程において、保護フィルムは偏光板から剥がされる。
【０１３８】
［位相差板］
位相差板Ａ：液晶表示用位相差フィルム（日東電工（株）製、「ＮＲＦ」）
位相差板Ｂ：ポリカーボネート樹脂製位相差フィルム
［反射板］
反射板Ａ：樹脂シートにアルミニウムを厚み１００μｍで蒸着し、このアルミニウム蒸着面に粘着剤を塗布したシート
反射板Ｂ：表面に粘着剤層が形成されたアルミ箔（厚み５０μｍ）
実施例１
ポリメタクリル酸メチル（ＰＭＭＡ−４）５０重量部とスチレン−アクリロニトリル共重合体（ＳＡＮ−４）５０重量部とを塩化メチレン／メタノール混合溶媒（９／１、重量比）４００重量部に溶解した。溶液をガラス板上に流延することにより、厚さ８μｍのシート層を形成した。ガラス板を２８０℃のホットプレート上で、1 分間加熱した。熱処理後、ガラス板とシートとを、冷水浴に浸漬した。シートをガラス板から剥離し、枠に張り付け、乾燥した（厚さ１０μｍ）。得られたシートを透過型光学顕微鏡により観察したところ、シートは共連続相構造と液滴相構造との中間的構造を有し、連続相の平均相間距離は約６μｍであった。また、シートの全光線透過率は９３％であった。透過型光学顕微鏡により観察された相構造の模式図を図１９に示す。
【０１３９】
実施例２
熱処理温度を２５０℃、熱処理時間を３分とする以外は、実施例１と同様にした。得られたシートを透過型光学顕微鏡により観察したところ、共連続相構造と液滴相構造との中間的構造を有しており、平均相間距離は約６μｍであった。
【０１４０】
参考例１
セルローストリアセテート（ＣＥＬ−１）のフレーク８０重量部を塩化メチレン／メタノール混合溶媒（９／１、重量比）９００重量に溶解した。溶液にＰＭＭＡ系微粒子（ＰＭＭＡ−５）２０重量部を混合し、流延、キャストし、１５０μｍのシートを得た。得られたシートを透過型光学顕微鏡により観察したところ、液滴相構造を有しており、液滴の平均直径は３μｍであった。また、シートの全光線透過率は９２％であった。
【０１４１】
実施例１、２及び参考例１で得られた光拡散シートの性能を、以下の方法に従って評価した。
【０１４２】
（指向性１）
得られた光拡散シートを用いて、図２の反射型ＬＣＤモデル装置を構成した。正面方向から垂直にレーザー光（ＮＩＨＯＮ ＫＡＧＡＫＵ ＥＮＧ ＮＥＯ−２０ＭＳ）を照射し、拡散角度θ１に対応する反射光の強度（拡散強度）を測定した。測定結果を図２１に示す。図２１から明らかなように、液滴相構造（海島構造）を有する参考例１の微粒子分散型光拡散シートがガウス分布型の拡散強度を示すのに対し、実施例のシートは特定方向（拡散角度約７°）に拡散光が指向している。
（指向性２）
図２と同様の反射型ＬＣＤモデル装置を構成し、斜め方向からスポットライト白色光を照射し、垂直方向に反射する光の強度を測定した（図５）。入射角度（拡散角度θ２）に対応する垂直方向の反射光の強度を以下の基準に従って評価した。
【０１４３】
Ａ：明るい
Ｂ：ふつう
Ｃ：暗い
結果を表２に示す。
【０１４４】
【表２】

【０１４５】
表２から明らかなように、実施例の透過型光拡散シートは、所定の拡散角度（入射角度）に対して高い指向性を有している。
【０１４６】
実施例３
熱処理温度を２３０℃、熱処理時間を１０分、シート厚みを１４μｍとする以外は、実施例１と同様にした。得られたシートを透過型光学顕微鏡により観察した。シートは共連続相構造を有しており、連続相の平均相間距離は約６μｍであった。この共連続相構造の模式図を図２０に示す。
【０１４７】
実施例４
シート厚みを８μｍとする以外は、実施例３と同様にした。得られたシートを透過型光学顕微鏡で観察したところ、共連続相構造を有し、連続相の平均相間距離は約４μｍであった。
【０１４８】
実施例５
シート厚みを１０μｍとする以外は、実施例３と同様にした。得られたシートを透過型光学顕微鏡で観察したところ、共連続相構造を有し、連続相の平均相間距離は約４μｍであった。
【０１４９】
実施例６
熱処理時間を７分とする以外は実施例５と同様にした。得られたシートを透過型光学顕微鏡で観察したところ、共連続相構造を有し、連続相の平均相間距離は約３μｍであった。
【０１５０】
実施例７
熱処理時間を１４分とする以外は実施例５と同様にした。得られたシートを透過型光学顕微鏡で観察したところ、共連続相構造と液滴相構造との中間的構造を有し、連続相の平均相間距離は約６μｍであった。
【０１５１】
実施例３〜７で得られたシートの指向性を、実施例１と同様にして評価した（指向性２）。結果を表３に示す。
【０１５２】
【表３】

【０１５３】
表３から明らかなように、実施例の透過型光拡散シートは、所定の拡散角度（入射角度）に対して高い指向性を有している。
【０１５４】
実施例８〜１３
ポリメタクリル酸メチル（ＰＭＭＡ−１〜４）及びスチレンアクリロニトリル共重合体（ＳＡＮ−１〜３）を表４に示す割合に従って配合し、溶剤（酢酸エチル）に溶解混合した後、得られた溶液（ドープ）をバーコート法により、支持体の無アルカリガラス上に流延し、一昼夜風乾させ、所定厚みのシートを作成した。このあと、ガラス板上のシートごとオーブンに入れ、表４に記載された温度及び時間で熱処理した。熱処理後、ガラス板ごと冷水に浸漬した。シートをガラス板から剥離し乾燥させて、光散乱シートを得た。こうして得られた光散乱シートについて、下記の方法に従って、全光線透過率、光散乱性、直進光／拡散光比、及び明るさについて評価した。
【０１５５】
（全光線透過率）
ＪＩＳ Ｋ７１０５に準拠して、ヘーズメーター（日本電色工業（株）製、ＮＤＨ−３００Ａ）を用いて全光線透過率（透過率）を測定した。
【０１５６】
（光散乱性）
図３に示すレーザー光散乱自動測定装置（日本科学エンジニリング（株）製）を用いて、光散乱シートに対して垂直方向より光が入射する時の散乱特性（散乱角度に対する散乱光（拡散光）の強度）を測定した。
【０１５７】
（直進光／拡散光比（Ｉ（θ0）／Ｉ（θmax））
前記光散乱性試験により、散乱角度に対して光散乱強度をプロットし、シートを直進透過した直進透過光の強度Ｉ（θ0）と、極大の散乱光（拡散光）の強度Ｉ（θmax）との比を求めた。
【０１５８】
（明るさ）
図２と同様の反射型ＬＣＤモデル装置を構成し、斜め方向からスポットライト白色光を照射し、垂直方向に反射する光の強度を測定した（図５）。入射角度（拡散角度θ２）に対応する垂直方向の反射光の強度を以下の基準に従って評価した。
【０１５９】
ＡＡ：実施例１３より、極めて明るい
Ａ：実施例１３より、さらに明るい
Ｂ：明るい
結果を表４、表５、図２２、及び図２３に示す
【０１６０】
【表４】

【０１６１】
【表５】

【０１６２】
表４及び表５から明らかなように、実施例８〜１３の光散乱シートを用いると、液晶の表示画像を明るくできる。特に、特定の分子量のポリマーで構成された実施例８〜１２の光散乱シートは、高い全光線透過率、低い直進光／拡散光比（Ｉ（θ0）／Ｉ（θmax））を有しており、効果的に外部光を取り込むことができる。このため、液晶画像の明るさも極めて優れている。
【０１６３】
実施例１４
ポリメタクリル酸メチル（ＰＭＭＡ−４）５０重量部とスチレン−アクリロニトリル共重合体（ＳＡＮ−４）５０重量部とを塩化メチレン／メタノール混合溶媒（９／１、重量比）４００重量部に溶解した。溶液をポリエーテルスルホンシート（ＰＥＳ−１）上に流延することにより、厚さ１１５μｍのコーティングシートを形成した。このコーティングシートを２３０℃で１０分間加熱した。熱処理後、コーティングシートとを、冷水浴に浸漬し、十分に乾燥した。得られたシートを透過型光学顕微鏡により観察したところ、シートは共連続相構造と液滴相構造との中間的構造を有し、連続相の平均相間距離は約６μｍであった。また、シートの全光線透過率は９３％であった。
【０１６４】
偏光板（偏光板Ａ）１の粘着剤層９１により、偏光板１と前記共連続相構造のシート（光散乱シート２）のポリエーテルスルホンシート層とを貼り合わせ、この光散乱シート２の表面（光散乱層）にアクリル系粘着剤層９２を塗布し、乾燥することにより複合シートＡ（積層シート）（図６）を製造した。なお、偏光板１の表面は保護フィルム（図示せず）で、粘着剤層９２の表面はシリコン系離型剤を塗布したＰＥＴフィルム（厚み５０μｍ）（離型フィルム）で保護した。
【０１６５】
複合シートＡ表面の保護フィルム及び離型フィルムを剥離し、粘着剤層９２により複合シートＡを液晶セル１２に貼り付けることにより、図７の液晶表示素子を製造した。なお、液晶セル１２のフロント基板２２ａ及びバック基板２２ｂには、ガラス板（厚み１ｍｍ）を、透明のフロント電極４ａにはインジウム錫酸化物薄膜を、光反射性バック電極４ｃにはアルミニウム薄膜を用いた。
【０１６６】
偏光板１と光散乱シート２とを積層した複合シートＡを用いているため、液晶表示素子の偏光板貼り付け工程において複合シートＡを貼り付けることができ、液晶表示素子の製造ラインを変更することなく光散乱シート２を有する液晶表示素子を製造できた。このため、コストを増大させることなく、かつ歩留まりを低下させることなく、鏡面反射の防止可能な画像の視認性が向上した反射型液晶表示素子を製造できた。
【０１６７】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。
【０１６８】
実施例１５
液晶セル１２の表面に光散乱シート２をはりあわせた後、この光散乱シート２の表面に偏光板１を貼り付けることにより図７に示す反射型液晶表示素子を形成した。
【０１６９】
実施例１４に比べると製造工程が複雑化するものの、この液晶表示素子は実施例１４と同様に、表示画像の視認性に優れていた。
【０１７０】
参考例２
位相差板（位相差板Ａ）３の粘着剤層９３により、位相差板３と光散乱シート（参考例１の光散乱シート）２とを貼り合わせた。光散乱シート２の表面にアクリル系粘着剤層９２を塗布し、乾燥することにより複合シートＢ（積層シート）（図８）を製造した。なお、位相差板３の表面は保護フィルム（図示せず）で、粘着剤層９２の表面はシリコン系離型剤を塗布したＰＥＴフィルム（厚み５０μｍ）（離型フィルム）で保護した。
【０１７１】
複合シートＢの保護フィルム及び離型フィルムを剥離し、粘着剤層９２により複合シートＢを液晶セル１２に貼り付けた後、この複合シートＢの表面に偏光板（偏光板Ａ）を貼り付けることにより図９の液晶表示素子を製造した。なお、液晶セル１２のフロント基板２２ａ及びバック基板２２ｂには、ガラス板（厚み１ｍｍ）を、透明のフロント電極４ａにはインジウム錫酸化物薄膜を、光反射性バック電極４ｃにはアルミニウム薄膜を用いた。
【０１７２】
位相差板３と光散乱シート１との複合シートＢを用いているため、液晶表示素子の位相差板貼り付け工程において複合シートＢを貼り付けることができ、液晶表示素子の製造ラインを変更することなく光散乱シートを有する液晶表示素子を製造できた。このため、コストを増大させることなく、かつ歩留まりを低下させることなく、鏡面反射の防止可能な画像の視認性が向上した反射型液晶表示素子を製造できた。
【０１７３】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。
【０１７４】
参考例３
透明ベース樹脂としての非晶性コポリエステル（ＰＥＴＧ−１）９０重量部と、微粒子分散成分としての熱可塑性樹脂（ＧＰＰＳ−１）１０重量部とをそれぞれ７０℃で４時間乾燥した後、バンバリーミキサーで混練した。混練した樹脂組成物を押出機に供給し、２４０℃で溶融し、Ｔダイからシート状に押し出し成形し、表面温度２５℃の冷却ドラムで冷却個化した（溶融製膜）。得られたシート（光散乱シート２）の厚みは１２０μｍであり、全光線透過率は９１％であった。
【０１７５】
反射板（反射板Ａ）５の粘着剤層９５により、反射板５と前記微粒子分散構造のシート（光散乱シート２）とを貼り合わせ、この光散乱シート２の表面にアクリル系粘着剤層９２を塗布し、乾燥することにより複合シートＣ（積層シート）（図１０）を製造した。なお、反射板５の表面は保護フィルム（図示せず）で、粘着剤層９２の表面はシリコン系離型剤を塗布したＰＥＴフィルム（厚み５０μｍ）（離型フィルム）で保護した。
【０１７６】
複合シートＣ表面の保護フィルム及び離型フィルムを剥離し、粘着剤層９２により複合シートＣを液晶セル１２の背面に貼り付け、また液晶セル１２の観察者側の面に位相差板３及び偏光板１を貼り付けることにより図１１の液晶表示素子を製造した。なお、液晶セル１２のフロント基板２２ａ及びバック基板２２ｂには、プラスチックシート（ＰＥＳ−１）を用い、透明のフロント電極４ａ及びバック電極４ｂとしてインジウム錫酸化物薄膜製ストライプ状透明電極を形成した。
【０１７７】
反射板５と光散乱シート２とを積層した複合シートＣを用いているため、液晶表示素子の反射板貼り付け工程において複合シートＣを貼り付けることができ、液晶表示素子の製造ラインを変更することなく光散乱シート２を有する液晶表示素子を製造できた。このため、コストを増大させることなく、かつ歩留まりを低下させることなく、鏡面反射の防止可能な画像の視認性が向上した反射型液晶表示素子を製造できた。
【０１７８】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。
【０１７９】
実施例１６
偏光板（偏光板Ａ）１の粘着剤層９１により偏光板１と位相差板（位相差板Ｂ）３とを貼り合わせ、この位相差板３の粘着剤層９３により位相差板３と光散乱シート（実施例１４の光散乱シート）２とを貼り合わせた。光散乱シート２の表面にアクリル系粘着剤層９２を塗布し、乾燥することにより複合シートＤ（積層シート）（図１２）を製造した。なお、偏光板１の表面は保護フィルム（図示せず）で、粘着剤層９２の表面はシリコン系離型剤を塗布したＰＥＴフィルム（厚み５０μｍ）（離型フィルム）で保護した。
【０１８０】
偏光板１、位相差板３及び光散乱シート２とを積層した複合シートＤを用いて液晶表示素子を製造したところ、液晶表示素子の偏光板の貼り付け工程及び位相差板貼り付け工程に代えて、ワンステップで複合シートＤを貼り付けることができ、液晶表示素子の製造ラインを簡略化して光散乱シート２を有する液晶表示素子を製造できた。このため、コストを低減し、かつ歩留まりを低下させることなく、鏡面反射の防止可能な画像の視認性が向上した反射型液晶表示素子を製造できた。
【０１８１】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。
【０１８２】
参考例４
参考例１の光散乱シート２の面に、スパッタリングによりＩＴＯの透明導電層４（厚み４５０オングストローム）を形成することにより、図１３の透明導電シートを得た。透明導電層の表面抵抗は１００Ω／□であった。シート厚み、全光線透過率、及び光散乱性は、参考例１の光散乱シートと同様であった。
【０１８３】
参考例５
参考例４の透明導電シートの透明導電層非形成面（非蒸着面）に、スパッタリングによりＩＴＯの静電気除去層（厚み５０オングストローム）を形成することにより、静電気除去層１３と、透明導電層４及び光散乱シート２とが積層した透明導電シートを得た（図１４）。静電気除去層の表面抵抗は２０ｋΩ／□であった。シート厚み、全光線透過率、及び光散乱性は、参考例４の光散乱シートと同様であった。
【０１８４】
実施例１７
ポリメタクリ酸メチル（ＰＭＭＡ−４）５０重量部とスチレン−アクリロニトリル共重合体（ＳＡＮ−５）５０重量部を塩化メチレン／メタノール混合溶媒（９／１（重量比）に溶解した。この溶液をポリエーテルスルホンシート（ＰＥＳ−１）上に流延し、乾燥した後、２３０℃で１０分間熱処理した。冷水中に浸漬して冷却した後、十分に乾燥することにより光散乱シート（シート厚み１１５μｍ、全光線透過率９３％）を得た。この光散乱シートを透過型顕微鏡により観察したところ、シートは共連続相構造を有しており、連続相の平均相間距離は約６μｍであった。この光散乱シートは、拡散角度約７゜に拡散光を指向可能であった。
【０１８５】
光散乱シートの共連続相側の表面に、ＩＴＯをスパッタリングして、厚み４５０オングストロームの透明導電層を形成することにより、基材シート２３と光散乱層２１の積層体の光散乱層側に透明導電層４が積層した透明導電シート（図１５）を得た。透明導電層の表面抵抗は１００Ωであった。シート厚み、全光線透過率、及び光散乱性は、前記透明導電層形成前の光散乱シートと同様であった。
【０１８６】
実施例１８
光散乱シートのＰＥＳ面（共連続相非形成面）に透明導電層を形成する以外は、実施例１７と同様にして透明導電シート（図１６）を得た。透明導電層の厚みは４５０オングストロームであり、表面抵抗は１００Ω／□であった。シート厚み、全光線透過率、及び光散乱性は、実施例１７の光散乱シートと同様であった。
【０１８７】
実施例１９
実施例１８で得られた透明導電シートを、フォトリソグラフ加工により透明導電層をストライプ状にパターン処理し、この処理シートをフロント基板及びバック基板として用いることにより、図４のＳＴＮ型の反射型プラスチック液晶表示素子を形成した。偏光板１には偏光板Ａを、位相差板３には位相差板Ａを、反射板５には反射板Ｂを用いた。液晶表示素子の厚みは約６５０μｍであった。
【０１８８】
蛍光燈の照明下でこの反射型プラスチック液晶表示素子を用いて画面表示したところ、鏡面反射に対応する拡散角度０゜の反射光を低減し、拡散光に指向性を付与できた。また、画像ボケの少ないシャープな画像を形成でき、コントラストの高い鮮明な表示画面が観察された。
【０１８９】
参考例６
フロント基板及びバック基板として下記のシートを用い、フロント基板に実施例１７の光散乱シート２を積層する以外は、実施例１９と同様にして反射型プラスチック液晶表示素子を形成した（図１７）。液晶表示素子の厚みは約７７０μｍであった。
【０１９０】
（フロント電極板及びバック電極板）
ポリエーテルスルホンシート（ＰＥＳ−１）の一方の面に、実施例１７と同様にしてＩＴＯの透明導電層（厚み４５０オングストローム）を形成した。このシートの透明導電層を、フォトリソグラフ加工によりストライプ状にパターン処理することにより、フロント電極板７ａ及びバック電極板７ｂ用シートを形成した。
【０１９１】
蛍光灯の照明下で実施例１９（図４）と参考例６（図１７）の反射型プラスチック液晶表示素子の画面表示を比較したところ、実施例１９の反射型プラスチック液晶表示素子では、蛍光灯の像が全く確認されず、画像の視認性に優れていた。
【０１９２】
実施例１９及び参考例６から明らかなように、参考例４及び５、並びに実施例１７〜１９の液晶表示素子では、透明導電シートは、光散乱性を有するだけでなく、液晶表示素子の電極板として使用できるため、別途光散乱シートを用いる必要がない。このため、液晶表示素子の厚みを薄くでき、実施例１９と参考例６とを比較した場合、約１２０μｍ薄型化できる。このため、画像ボケを防止して、シャープかつコントラストの高い鮮明な表示画面を得ることができる。
【０１９３】
実施例２０
偏光板１として偏光板Ｂを用い、予め積層シートＡを形成することなく液晶セル１２のフロント電極支持板２２ａに光散乱シート２を貼り付け、さらにこの光散乱シート２の表面に偏光板１を貼り付ける以外は、実施例１４と同様にして図７の反射型液晶表示素子を形成した。
【０１９４】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。さらに、反射型液晶表示素子の表面（偏光板１）はスチールウール（♯００００）でこすっても、殆ど傷がつかなかった。
【０１９５】
比較例１
液晶セル１２のフロント基板２２ａに偏光板（偏光板Ｂ）１を貼り付け、さらにこの偏光板１の表面に光散乱シート２を貼り付ける以外は、実施例２０と同様にして図１８の反射型液晶表示素子を製造した。
【０１９６】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、光散乱シート２により鏡面反射は低減しているものの、実施例２０の液晶表示素子に比べて表示画面が不明瞭であった。さらに、反射型液晶表示素子の表面（光散乱シート２）をスチールウール（♯００００）でこすると、傷がついた。
【０１９７】
参考例７
光散乱シート２として参考例１の光散乱シートを用いる以外は、実施例２０と同様にして反射型液晶表示素子を製造した。
【０１９８】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。さらに、反射型液晶表示素子の表面（偏光板１）はスチールウール（♯００００）でこすっても、殆ど傷がつかなかった。
【０１９９】
参考例８
偏光板１として偏光板Ｂを、位相差板３として位相差板Ｂを、反射板５として反射板Ｂを用い、予め積層シートＤを形成することなく、液晶セル１２のフロント側に偏光板１及び位相差板３を貼り付け、液晶セル１２の背面に光散乱シート２及び反射板５を貼り付ける以外は参考例３と同様にして図１１の反射型液晶表示素子を製造した。なお、光散乱シート２は僅かにリターデーションを有しているため、光散乱シート２の配向軸を偏光板の偏光軸に一致させるようにして、光散乱シート２を背面電極の基板に貼り合わせた。
【０２００】
蛍光燈の照明下、この反射型液晶表示素子の表示画像を目視で確認すると、鏡面反射は低減しており、明瞭性に優れたコントラストの高い鮮明な表示画面が観察された。さらに、反射型液晶表示素子の表面（偏光板１）はスチールウール（♯００００）でこすっても、殆ど傷がつかなかった。
【図面の簡単な説明】
【図１】図１は本発明の液晶表示素子の一例を示す概略断面図である。
【図２】図２は光散乱シートの指向性の評価方法を説明するための概略図である。
【図３】図３は、光散乱シートの直進透過光及び拡散透過光の強度の測定方法を説明するための概略図である。
【図４】図４は本発明の液晶表示素子の他の例を示す概略断面図である。
【図５】図５は光散乱シートの指向性の他の評価方法を説明するための概略図である。
【図６】図６は本発明の複合シートの一例を示す概略断面図である。
【図７】図７は本発明の液晶表示素子のさらに他の例を示す概略断面図である。
【図８】図８は本発明の複合シートの他の例を示す概略断面図である。
【図９】図９は本発明の液晶表示素子の別の例を示す概略断面図である。
【図１０】図１０は本発明の複合シートのさらに他の例を示す概略断面図である。
【図１１】図１１は本発明の液晶表示素子のさらに別の例を示す概略断面図である。
【図１２】図１２は本発明の複合シートの別の例を示す概略断面図である。
【図１３】図１３は本発明の複合シートのさらに別の例を示す概略断面図である。
【図１４】図１４は本発明の複合シートの他の例を示す概略断面図である。
【図１５】図１５は本発明の複合シートのさらに他の例を示す概略断面図である。
【図１６】図１６は本発明の複合シートの別の例を示す概略断面図である。
【図１７】 図１７は参考例６の液晶表示素子の概略断面図である。
【図１８】図１８は比較例１の液晶表示素子の概略断面図である。
【図１９】図１９は実施例１で得られたシートの透過型光学顕微鏡の測定結果を示す模式図である。
【図２０】図２０は実施例３で得られたシートの透過型光学顕微鏡の測定結果を示す模式図である。
【図２１】図２１は光散乱シートの指向性を示すグラフである。
【図２２】図２２は光散乱シートの直進透過光と拡散透過光の強度の測定結果を示す片対数グラフである。
【図２３】図２３は光散乱シートの直進透過光と拡散透過光の強度の測定結果を示すグラフである。
【符号の説明】
１…偏光板
２、２ａ、２ｂ…光散乱シート
３…位相差板
４、４ａ、４ｂ、４ｃ…導電層
５…反射板
７ａ、７ｂ、７ｃ…電極板
１２…液晶セル
２１、２１ａ、２１ｂ…光散乱層
２２ａ、２２ｂ…基板
２３、２３ａ、２３ｂ…基材シート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light scattering sheet (film) useful for displaying a high-luminance screen in a liquid crystal display element, a method for producing the same, a composite sheet using the sheet, a liquid crystal display element, and production of the light scattering sheet. Regarding the method.
[0002]
[Prior art]
Liquid crystal display elements (LCDs) are widely used in display units of electrical products such as personal computers (personal computers), word processors, liquid crystal televisions, watches, and calculators. Since the liquid crystal itself does not emit light, a backlight for illuminating the liquid crystal part from the back surface is used except for low-luminance applications such as a clock and a calculator.
[0003]
Recently, networking of information has been progressing through the development of information communication infrastructure such as the Internet and the fusion of communication devices with computers. With networking, access to information is not subject to time and location constraints. In order to efficiently use such a network, portable information terminals such as PDA (Personal Digital Assistance) are currently being developed. Also, instead of notebook computers, development of thinner and lighter mobile computers is underway.
[0004]
Since these devices are required to be portable, it is necessary to achieve both longer battery driving time and thinner and smaller communication devices. Therefore, the display used for these portable information communication devices is required to be thin and light and to have low power consumption. In particular, in order to achieve low power consumption, a method of brightening the display unit using natural light is considered instead of a conventional method using a backlight. A reflection type liquid crystal display element is most promising as such a display. In particular, in order to cope with the diversification of information accompanying the advancement of multimedia in the future, there is a demand for an inexpensive reflective liquid crystal display element capable of color display and high-quality display (high-definition display).
[0005]
Various elements such as TN type (Twisted Nematic type) and STN type (Super Twisted Nematic type) are known as reflective liquid crystal display elements, but polarizing plates are used for color display and high-definition display. The type (single polarizing plate type) is advantageous. For example, the R-OCB mode in which the liquid crystal layer is HAN (Hybrid Aligned Nematic) alignment has excellent characteristics in terms of low voltage, wide viewing angle, high-speed response, intermediate color display, high contrast, and the like. An active matrix type liquid crystal display element such as a TFT (Thin Film Transistor) that controls all the pixels one by one is generally used as a display element capable of forming a fine display on the screen. However, an active matrix type liquid crystal display element such as a TFT type needs to form several hundreds of thousands or more transistors on a substrate, and thus a liquid crystal display element of a glass substrate needs to be used. On the other hand, a liquid crystal display element of STN (Super Twisted Nematic) type is cheaper than TFT type because it uses a rod-shaped electrode to display a matrix type image, and plastic as the electrode substrate (support substrate). A substrate can be used, and a reflective plastic liquid crystal display element can be formed.
[0006]
In a reflective liquid crystal display element, in order to give brightness to the screen, light (natural light, external light) incident on the liquid crystal layer is efficiently captured, and the light is reflected by the reflector so that the visibility is not impaired. It scatters light (prevents total reflection). If sufficient brightness cannot be obtained even by maximizing the use of natural light or external light due to the influence of the usage environment, etc., light is emitted from the side of the display surface of the liquid crystal display element. A front light may be used. As the reflecting plate, a light reflecting back electrode using a light reflecting electrode, a laminate in which a reflecting plate is formed on the substrate surface of the electrode plate, or the like can be used. For example, in Japanese Laid-Open Patent Publication No. 63-228887, Photofabrication Symposium '92 sponsored by the Japan Printing Society, the basic technology of reflective liquid crystal display elements and metal thin films with surface irregularities are applied as back electrodes (lower electrodes). Liquid crystal display elements that prevent total reflection and expand the viewing angle of the display surface have been introduced. However, since such a reflective liquid crystal display element scatters reflected light while avoiding specular reflection, the reflector (or the light-reflecting back electrode) is appropriately roughened and requires advanced processing technology. High cost. Further, when the display element is colored, a color filter is used in addition to the polarizing plate. In the color filter, the ratio of the loss of reflected light is large, and the diffusion plate method cannot give sufficient brightness to the display screen. In colorization, it is particularly important to provide high luminance by directional diffusion that directs diffused light in a certain direction. In order to increase the directivity by the diffuse reflection plate method, it is necessary to precisely control the shape and distribution of the uneven portions of the reflection plate, which increases the cost.
[0007]
Further, in order to scatter reflected light and impart high brightness, a method is disclosed in which the liquid crystal layer has a dispersed structure in which liquid crystal and polymer are dispersed in place of the light diffusing reflector (special feature). (Kaihei 6-258624). A liquid crystal display element that uses a transmissive light scattering sheet instead of the diffuse reflector is also known.
[0008]
For example, a method of forming a light-scattering transparent resin layer inside or outside a liquid crystal cell is known. JP-A-7-98452 discloses a transparent resin layer (light scattering) containing dispersed fine particles between an electrode of an electrode plate and a substrate (electrode support substrate) as a display element in which a light diffusion layer is formed in a liquid crystal cell. A display element in which a layer is formed is disclosed. Japanese Patent Application Laid-Open No. 7-318926 discloses a display element in which a light diffusion layer in which liquid crystalline polymers are randomly oriented is formed between a support plate having a transparent electrode and a liquid crystal layer. On the other hand, in Japanese Patent Application Laid-Open No. 7-261171, as a display element in which a light diffusion layer is formed outside a liquid crystal cell, a polarizing film is formed on the outer surface of an electrode plate, and the refractive index is different on the surface of the polarizing film. A display element in which a light scattering layer in which the above resins are dispersed in a phase-separated state is formed is disclosed. Japanese Patent Publication No. 61-8430 also discloses a liquid crystal display element in which a light scattering layer is laminated on the surface of a polarizing layer formed on the front side of a liquid crystal cell. However, the polarizing plate usually has a highly completed surface hardening characteristic and an appropriate anti-glare characteristic. Therefore, if a light scattering layer is formed on the surface of the polarizing plate, the surface of the display element (that is, the light scattering sheet) is easily damaged, the visibility of the display screen is lowered, and the image quality of the reflective liquid crystal display element is lowered. To do. In particular, it is difficult to maintain image quality over a long period of time. Further, since both the liquid crystal image and the image from the light scattering layer are formed, the sharpness of the image is deteriorated (image blur) and the image quality is deteriorated. In addition, in order to impart directivity to the transmission type light scattering sheet, a sheet resin polymerized using a hologram is known (Abstracts of the Annual Meeting of the Liquid Crystal Society of Japan in 1998). However, the manufacturing method is complicated and the cost is low. Become high.
[0009]
In JP-A-7-27904 and JP-A-9-113902, a particle scattering sheet having a sea-island structure composed of plastic beads and a transparent resin is formed between a backlight and a liquid crystal cell. Such a transmission type liquid crystal display device is known.
[0010]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a light scattering sheet (or film) capable of high-quality liquid crystal display, a light scattering composite sheet (or film), a liquid crystal display element, and a method for producing the light scattering sheet. It is in.
[0011]
Another object of the present invention is to produce a light scattering sheet (or film), a light scattering composite sheet (or film), a liquid crystal display element, and the light scattering sheet capable of imparting diffusivity and directivity to reflected light. It is to provide a method.
[0012]
Still another object of the present invention is to provide a light-scattering composite sheet (or film) useful for producing a high-luminance and high-definition liquid crystal display element at low cost, and a liquid crystal display using the composite sheet (or film). It is to provide an element.
[0013]
Another object of the present invention is to provide a liquid crystal display element capable of maintaining high quality over a long period of time.
[0014]
Still another object of the present invention is to provide a method by which a directional diffusion sheet (or film) can be easily produced.
[0015]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the present inventors have been able to easily form an isotropic bicontinuous phase structure (biconbinuous) by spinodal decomposition using a plurality of resins having different refractive indexes. It has been found that when a sheet having such a co-continuous phase structure is used, high directivity can be imparted to diffused light. In addition, when the present inventors form a composite sheet with a polarizing plate, a retardation plate, a reflector, or a transparent conductive layer and a light scattering sheet, not only high image quality is obtained, but also a liquid crystal display element is easily and inexpensively I found out that Furthermore, the present inventors have found that the durability of the reflective liquid crystal display device can be improved and a highly accurate image can be obtained by installing the light scattering sheet at a specific position of the reflective liquid crystal display device. Based on the above findings, the present inventors have completed the present invention.
[0016]
  That is, the present inventionofThe light scattering sheet is composed of a light scattering layer in which an isotropic co-continuous phase structure is formed by a plurality of polymers having different refractive indexes. The average interphase distance between the co-continuous phases is, for example, about 1 to 20 μm, and the difference in refractive index between the plurality of polymers is, for example, about 0.01 to 0.2. The plurality of polymers may exhibit a lower critical eutectic temperature (LCST) type phase separation. The critical eutectic temperature of the composition composed of a plurality of polymers is, for example, about 50 to 300 ° C. The weight average molecular weight of the polymer may be about 10,000 to 300,000. Examples of the polymer include styrene resins, (meth) acrylic resins, vinyl ether resins, halogen-containing resins, polycarbonate resins, polyester resins, polyamide resins, silicone resins, cellulose derivatives, rubbers, and elastomers. . The light scattering sheet of the present invention isTotal raysThe transmittance is 70 to 100%, and incident light can be diffused isotropically. The diffused light has a maximum value at a diffusion angle of 3 to 60 °. For example, when the transmitted light of the light scattering sheet is plotted against the diffusion angle (θ), the ratio (I (θ 0) between the intensity I (θ 0) of the straight transmitted light and the intensity I (θ max) of the maximum diffuse transmitted light ) / I (θmax)) may be about 3000/1 to 1/1.
[0017]
  The light scattering composite sheet of the present invention isSaidAt least one selected from a polarizing plate, a retardation plate, a light reflection plate, and a transparent conductive layer is formed on at least one surface of the light scattering sheet formed of the light scattering layer. Light scattering layerOf multiple polymersThe difference in refractive index may be about 0.01 to 0.2..
[0018]
  The liquid crystal display element of the present invention isSaidConsists of a light scattering sheet having a light scattering layer. in frontThe light scattering sheet is disposed at a specific position of the reflective liquid crystal display element. That is, the reflective liquid crystal display device includes a transparent front electrode plate having a transparent conductive layer and a substrate supporting the transparent conductive layer, and a back electrode plate having a conductive layer and a substrate supporting the conductive layer. The liquid crystal cell is disposed so as to face each other and in which liquid crystal is sealed between the conductive layers of both electrode plates. A polarizing plate is disposed in front of the liquid crystal cell. And it has at least 1 light-scattering sheet among following (i)-(iii).
[0019]
  (i) a light scattering sheet disposed between the polarizing plate and the front electrode plate
  (ii) A light scattering sheet disposed between the back electrode plate and a reflector disposed behind the back electrode plate
  (iii) Light scattering sheet as a substrateG.
[0020]
The present invention also includes a method for producing a light scattering sheet in which a composition composed of a plurality of polymers having different refractive indexes is formed into a sheet, and an isotropic bicontinuous phase structure is formed by spinodal decomposition.
[0021]
In the present specification, the “sheet” means a two-dimensional structure regardless of the thickness, and is used to include a film.
[0022]
The term “light scattering sheet having a bicontinuous phase structure” is used to mean a light scattering sheet having an intermediate structure between the bicontinuous phase structure and the droplet phase structure.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
[Light scattering sheet]
The light scattering layer constituting the light scattering sheet (transmission type light scattering sheet) is composed of a plurality of polymers having different refractive indexes, and usually in a use atmosphere (especially at a room temperature of about 10 to 30 ° C.) It has a separation structure (such as a co-continuous phase structure described later). When such a sheet is used, diffusibility and directivity can be imparted to the reflected light. In order to enhance light diffusibility, a plurality of polymers can be used in combination so that the difference in refractive index is, for example, about 0.01 to 0.2, preferably about 0.1 to 0.15. If the difference in refractive index is less than 0.01, a sheet having diffuse light with sufficient intensity cannot be obtained. On the other hand, if the difference in refractive index is greater than 0.2, directivity cannot be imparted to the diffused light.
[0024]
Examples of the polymer include styrene resins, (meth) acrylic resins, vinyl ester resins, vinyl ether resins, halogen-containing resins, olefin resins, polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, Polysulfone resins (such as homopolymers of sulfones such as dihalodiphenylsulfone (polyethersulfone), copolymers of the sulfones with aromatic diols such as bisphenol A (polysulfone), etc.), polyphenylene ether resins (2 , 6-xylenol and other phenolic polymers), cellulose derivatives (cellulose esters, cellulose carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.) Rubber or elastomer (polybutadiene, diene rubbers such as polyisoprene, styrene - butadiene copolymer, acrylonitrile - butadiene copolymer, acrylic rubber, urethane rubber, silicone rubber, etc.) can be chosen a suitable combination and the like. Multiple polymers are usually selected from styrene resin, (meth) acrylic resin, vinyl ether resin, halogen-containing resin, polycarbonate resin, polyester resin, polyamide resin, cellulose derivative, silicone resin, rubber or elastomer it can.
[0025]
Styrenic resins include styrene monomers alone or copolymers (polystyrene, styrene-α-methylstyrene copolymer, styrene-vinyltoluene copolymer, etc.), styrene monomers and other polymerizable monomers. Copolymers with monomers ((meth) acrylic monomers, maleic anhydride, maleimide monomers, dienes, etc.) are included. Examples of the styrene-based copolymer include a styrene-acrylonitrile copolymer (AS resin), a copolymer of styrene and a (meth) acrylic monomer [styrene-methyl methacrylate copolymer, styrene-methacrylic acid. Methyl- (meth) acrylic acid ester copolymer, styrene-methyl methacrylate- (meth) acrylic acid copolymer, etc.], styrene-maleic anhydride copolymer and the like. Preferred styrenic resins include polystyrene, copolymers of styrene and (meth) acrylic monomers [copolymers based on styrene and methyl methacrylate such as styrene-methyl methacrylate copolymer], AS resin, styrene-butadiene copolymer and the like are included.
[0026]
As the (meth) acrylic resin, the above (meth) acrylic monomer alone or a copolymer, or a copolymer of a (meth) acrylic monomer and a copolymerizable monomer can be used. Examples of (meth) acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, (Meth) acrylic acid C such as hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate_1-10Alkyl; aryl (meth) acrylates such as phenyl (meth) acrylate; hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; glycidyl (meth) acrylate; N, N-dialkyl Examples include aminoalkyl (meth) acrylate; (meth) acrylonitrile. Examples of the copolymerizable monomer include the styrene monomer, vinyl ester monomer, maleic anhydride, maleic acid, and fumaric acid. These monomers can be used alone or in combination of two or more.
[0027]
Examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate-acrylic acid ester- (meth) acrylic. Examples include acid copolymers, methyl methacrylate- (meth) acrylic acid ester copolymers, (meth) acrylic acid ester-styrene copolymers (such as MS resin). Preferred (meth) acrylic resins include poly (meth) acrylic acid C such as methyl poly (meth) acrylate._1-5Examples thereof include methyl methacrylate resins containing alkyl as a main component (especially about 50 to 100% by weight, preferably about 70 to 100% by weight) of methyl methacrylate.
[0028]
Examples of vinyl ester resins include vinyl ester monomers alone or copolymers (polyvinyl acetate, polyvinyl propionate, etc.), copolymers of vinyl ester monomers and copolymerizable monomers ( Vinyl acetate-vinyl chloride copolymer, vinyl acetate- (meth) acrylic ester copolymer, etc.) or derivatives thereof. Examples of the vinyl ester resin derivative include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl acetal resin, and the like.
[0029]
Examples of vinyl ether resins include vinyl C such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, and vinyl t-butyl ether._1-10Alkyl ether homo- or copolymer, vinyl C_1-10Examples include copolymers of alkyl ethers and copolymerizable monomers (such as vinyl alkyl ether-maleic anhydride copolymers).
[0030]
Examples of the halogen-containing resin include polyvinyl chloride, polyvinylidene fluoride, vinyl chloride-vinyl acetate copolymer, vinyl chloride- (meth) acrylate ester copolymer, vinylidene chloride- (meth) acrylate ester copolymer, and the like. Can be mentioned.
[0031]
Examples of the olefin resin include homopolymers of olefins such as polyethylene and polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meta ) Copolymers such as acrylic acid ester copolymers.
[0032]
Polycarbonate resins include aromatic polycarbonates based on bisphenols (such as bisphenol A) and aliphatic polycarbonates such as diethylene glycol bisallyl carbonate.
[0033]
Polyester resins include aromatic polyesters using aromatic dicarboxylic acids such as terephthalic acid (poly C such as polyethylene terephthalate and polybutylene terephthalate)._2-4Alkylene terephthalate and poly C_2-4Homopolyester such as alkylene naphthalate, C_2-4Alkylene terephthalate and / or C_2-4And copolyesters containing an alkylene naphthalate unit as a main component (for example, 50% by weight or more), aliphatic polyesters using aliphatic dicarboxylic acids such as adipic acid, and the like. Polyester resins also include lactone homo- or copolymers such as ε-caprolactone.
[0034]
Examples of polyamide resins include aliphatic polyamides such as nylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11 and nylon 12, dicarboxylic acids (for example, terephthalic acid, isophthalic acid, adipic acid, etc.) and diamines ( Examples thereof include polyamides obtained from hexamethylenediamine and metaxylylenediamine). The polyamide-based resin may be a lactam homopolymer or copolymer such as ε-caprolactam, and is not limited to homopolyamide but may be copolyamide.
[0035]
Among cellulose derivatives, cellulose esters include, for example, aliphatic organic acid esters (cellulose acetate such as cellulose diacetate and cellulose triacetate; cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate). C_1-6Organic acid esters), aromatic organic acid esters (cellulose phthalate, cellulose benzoate, etc.)_7-12Aromatic aromatic esters) and inorganic acid esters (for example, cellulose phosphate, cellulose sulfate and the like), and mixed acid esters such as acetic acid and cellulose nitrate esters may be used. Cellulose derivatives include cellulose carbamates (for example, cellulose phenyl carbamate), cellulose ethers (for example, cyanoethyl cellulose; hydroxy-C such as hydroxyethyl cellulose, hydroxypropyl cellulose)._2-4Alkylcellulose; C such as methylcellulose and ethylcellulose_1-6Alkylcellulose; carboxymethylcellulose or a salt thereof, benzylcellulose, acetylalkylcellulose, etc.).
[0036]
Preferred polymers include, for example, styrene resins, (meth) acrylic resins, vinyl ether resins, halogen-containing resins, polycarbonate resins, polyester resins, polyamide resins, cellulose derivatives, silicone resins, and rubbers or elastomers. Is included. Further, a preferable polymer may be a thermoplastic polymer having moldability, film-forming property, or transparency (for example, styrene resin, (meth) acrylic resin, etc.).
[0037]
The glass transition temperature of the polymer can be selected from the range of, for example, about −100 to 250 ° C., preferably about −50 to 230 ° C., and more preferably about 0 to 200 ° C. (for example, about 50 to 150 ° C.). From the viewpoint of sheet strength and rigidity, the glass transition temperature of at least one of the constituent polymers is 50 ° C. or higher (for example, about 70 to 200 ° C.), preferably 80 ° C. or higher (for example, 80 to 170 ° C.). It is advantageous that Further, from the viewpoint of sheet formability, the glass transition temperature of the constituent polymer is 250 ° C. or lower (for example, 70 to 200 ° C.), preferably 200 ° C. or lower (for example, 80 to 180 ° C.).
[0038]
The weight average molecular weight of the polymer is not particularly limited, but is, for example, 1,000,000 or less (about 10,000 to 1,000,000), preferably about 10,000 to 700,000, more preferably 10, It is about 000 to 50,000.
[0039]
The light scattering sheet is configured by combining a plurality of polymers that exhibit both compatibility and incompatibility (phase separation) at or above the glass transition temperature of each polymer. That is, when a coexistence system of a plurality of polymers is configured, a plurality of polymers having temperature dependency in which phase separation (or compatibility) changes depending on temperature can be used. The temperature dependence of phase separation (or compatibility) is a coexisting system of high temperature phase separation type (lower critical solution temperature (LCST) type, lower critical solution temperature) that is compatible at low temperature and incompatible at high temperature. (Composite polymer system) or a low temperature phase separation type (upper critical solution temperature (UCST) type, upper critical solution temperature) coexisting system showing incompatibility at low temperature and compatibility at high temperature may be used. LCST type phase separation is preferred. By using a plurality of polymers exhibiting such phase separation properties, the phase separation structure can be adjusted by spinodal decomposition, and a bicontinuous phase structure can be formed.
[0040]
When a plurality of polymers constitute an LCST type or UCST type coexistence system, the lower limit or upper limit critical eutectic temperature (critical temperature of compatible / incompatible) is higher than the ambient temperature in which the light scattering sheet is used. For example, it is about 50-300 degreeC, Preferably it is about 70-250 degreeC, More preferably, it is about 80-250 degreeC (for example, 100-220 degreeC), and is about 80-230 degreeC normally. In general, a composite polymer system including a soft polymer (silicone resin, rubber, elastomer, etc.) often exhibits UCST-type compatibility.
[0041]
When a plurality of polymers are composed of two types of polymers (first polymer and second polymer), the combination of the first polymer and the second polymer is not particularly limited. For example, when the first polymer is a styrene resin (polystyrene, styrene-acrylonitrile copolymer, etc.), the second polymer is a polycarbonate resin, a (meth) acrylic resin, a vinyl ether resin, a rubber, an elastomer, or the like. It may be. Note that the temperature dependence of the compatibility depends on LCST, UCST, glass transition temperature, polymer molecular weight, and the like, so that an appropriate combination of polymers can be easily selected by experiment. For reference, an example of a combination of polymers is shown in Table 1.
[0042]
[Table 1]

[0043]
A polycarbonate resin / polymethyl methacrylate system is also known as a polymer system capable of forming a co-continuous phase structure. LCST type composite polymer systems include styrene-acrylonitrile copolymer (AS resin) / polymethyl methacrylate, AS resin / poly (ε-caprolactone) system, polyvinylidene fluoride / isotactic polymethacrylic acid. Examples include ethyl-based and polymethyl methacrylate / polyvinyl chloride-based. Examples of the UCST type composite polymer system include polystyrene / polymethylphenylsiloxane system, polybutadiene / styrene-butadiene copolymer (SBR) system, AS resin / acrylonitrile-butadiene copolymer (NBR) system, and the like.
[0044]
The ratio of the first polymer to the second polymer is, for example, the former / the latter = about 10/90 to 90/10 (weight ratio), preferably about 20/80 to 80/20 (weight ratio), and more preferably Is about 30/70 to 70/30 (weight ratio), particularly about 40/60 to 60/40 (weight ratio). If the composition ratio of the polymer is too biased to one side, when forming a co-continuous phase by spinodal decomposition, one of the polymer phases is likely to be discontinuous. Therefore, when a sheet is formed, directivity cannot be imparted to diffused light.
[0045]
In addition, when forming a sheet | seat with a 3 or more polymer, content of each polymer is 1 to 90 weight% normally (for example, 1 to 70 weight%, Preferably it is 5 to 70 weight%, More preferably, it is 10 (About 70% by weight).
[0046]
The light scattering layer (light scattering sheet) has at least a co-continuous phase structure. The co-continuous phase structure may be referred to as a co-continuous structure or a three-dimensional continuous or connected structure, and means a structure in which at least two constituent polymer phases are continuous.
[0047]
The light scattering sheet only needs to have at least a co-continuous phase structure, and may have a structure in which a co-continuous phase structure and a droplet phase structure (independent or isolated phase structure) are mixed. In spinodal decomposition, as the phase separation progresses, the polymer phase forms a co-continuous phase structure due to surface tension, and when further heat-treated, the continuous phase becomes discontinuous due to its own surface tension, resulting in a droplet phase structure (spherical Independent phase sea-island structure such as true sphere). Therefore, depending on the degree of phase separation, an intermediate structure between the co-continuous phase structure and the droplet phase structure, that is, a phase structure in a state of transition from the co-continuous phase to the droplet phase can be formed. In the present invention, the intermediate structure is also referred to as a co-continuous phase structure unless the polymer phase is a droplet phase (independent or isolated substantially spherical shape).
[0048]
The bicontinuous phase structure is generally isotropic with reduced anisotropy in the sheet plane. In addition, isotropic means that the size (average interphase distance) of the phase separation structure by the continuous phase is equal in any direction in the sheet surface.
[0049]
When the phase structure of the light scattering sheet is a mixed structure of a co-continuous phase structure and a droplet structure, the ratio of the droplet phase (independent polymer phase) is, for example, 30% or less (volume ratio), preferably 10 % Or less (volume ratio) may be sufficient. The planar or three-dimensional shape of the co-continuous phase structure is not particularly limited, and may be a network shape, particularly a random network shape.
[0050]
In addition, the co-continuous phase structure or the intermediate structure usually has regularity in the interphase distance (distance between the same phases). Therefore, the light incident on the sheet is scattered light directed in a specific direction by Bragg reflection. Therefore, even when mounted on a reflective liquid crystal display element, diffused light can be directed in a certain direction (directional diffusion), the display screen can be made highly bright, and the conventional particle dispersion type transmission type Problems that cannot be solved by the light diffusion sheet, that is, reflection of a light source (for example, a fluorescent lamp) on the panel can be avoided.
[0051]
Furthermore, the average interphase distance of the co-continuous phase in the light scattering sheet is, for example, about 1 to 20 μm, preferably about 2 to 15 μm, and more preferably about 2 to 10 μm. If the average interphase distance is too small, the diffused light distribution is close to a Gaussian distribution, and directivity cannot be imparted. On the other hand, if the average interphase distance is too large, the directional direction of the diffused light substantially coincides with the direction of the straight-ahead light, so that the light diffusibility decreases.
[0052]
The interphase distance can be measured by image processing of a micrograph (such as a confocal laser microscope). Further, the diffusion angle θ at which the diffused light intensity is maximized may be measured by a method similar to a method for evaluating the directivity of diffused light described later, and the interphase distance d may be calculated from the following Bragg reflection condition equation.
[0053]
2d · sin (θ / 2) = λ
(Where d is the interphase distance, θ is the diffusion angle, and λ is the wavelength of the light)
The thickness of the light scattering sheet is, for example, about 1 to 500 μm, preferably about 1 to 300 μm (about 10 to 150 μm, for example, about 10 to 100 μm), more preferably about 3 to 100 μm (for example, 5 to 50 μm, particularly 10 to 50 μm). When the sheet thickness is too thin, the intensity of the diffused light is reduced. On the other hand, if the sheet thickness is too large, the diffusibility becomes too strong and the directivity is lowered. Further, when applied to a reflective liquid crystal display element, the thickness and weight of the element increase, display blurring occurs, and the fineness of the display screen decreases. In addition, when the difference of the refractive index of a polymer is small, the one where a sheet | seat thickness is large is preferable, and when the difference of a refractive index is large conversely, the one where a sheet thickness is small is preferable.
[0054]
As will be described later, when the light scattering sheet is composed of a base sheet and a light scattering layer, the thickness of the light scattering layer is, for example, about 1 to 100 μm, preferably about 5 to 60 μm, and more preferably 10 to 10 μm. It may be about 40 μm.
[0055]
When the light scattering sheet having the co-continuous phase structure is used, not only high light scattering properties can be obtained, but also high directivity can be imparted to diffused light. The directivity of the diffused light is, for example, as shown in FIG. 2, a polarizing plate 1, a vinyl acetate adhesive 9, a light diffusing sheet 2, a color filter 8, a glass plate (thickness 1 mm) 12, and an aluminum reflector 5. Can be measured by using a reflection type LCD model device in which is laminated. That is, the intensity of the reflected light corresponding to the diffusion angle θ1 is obtained by irradiating the reflective LCD model device with the laser beam perpendicularly from the front direction by the laser beam irradiator (NIHON KAGAKU ENG NEO-20MS) 10. Measure the distribution (diffuse light distribution). Compared with a light scattering sheet having a Gaussian distribution centered on θ1 = 0 °, when a light scattering sheet having a co-continuous phase structure is used, the directivity direction (for example, θ1 = 1-60 ° (for example, 1-30 °), The maximum distribution is preferably 3 to 60 ° (for example, 3 to 20 °), more preferably 5 to 20 °, so that a bright liquid crystal display image can be obtained with a wide viewing angle.
[0056]
The transparency (total light transmittance) of the light scattering sheet is, for example, about 70 to 100%, preferably about 80 to 100%, and more preferably about 90 to 100%. The total light transmittance can be measured with a haze meter (NDH-300A) manufactured by Nippon Denshoku Industries Co., Ltd.
[0057]
Among the light scattering sheets, a particularly preferable light scattering sheet is a specific weight average molecular weight [for example, 300,000 or less (about 10,000 to 300,000), preferably about 10,000 to 150,000, and more preferably. Is composed of a plurality of polymers of about 10,000 to 120,000. Since the formation rate (expression rate) of the bicontinuous phase by spinodal decomposition is limited by the diffusion of the molecular chain, the bicontinuous phase can be formed quickly by using a polymer having a specific molecular weight. In addition, the intensity of the diffused light can be increased relative to the intensity of the straight light. For this reason, ambient light can be taken in effectively and incident light from the periphery can be efficiently scattered. Therefore, a bright liquid crystal display image can be obtained and the visibility of the liquid crystal display can be improved. FIG. 3 is a schematic diagram for explaining a method for measuring the intensity of diffused light. That is, laser light is irradiated toward the light scattering sheet 2 from a laser light irradiator (NIHON KAGAKUENG NEO-20MS) 10 disposed on the back surface of the light scattering sheet 2. The laser light is emitted from the front of the light scattering sheet while being diffused by the light scattering sheet 2. The intensity of the diffused light can be measured by detecting the diffused light (diffused transmitted light) with the detector 11 according to the diffusion angle θ3. When the light scattering sheet is composed of a polymer having a specific weight average molecular weight, the ratio I (θ0) between the intensity I (θ0) of the linearly transmitted light (θ3 = 0 °) and the intensity I (θmax) of the maximum diffuse transmitted light ) / I (θmax) is, for example, about 3000/1 to 1/1, preferably about 500/1 to 1/1, and more preferably about 100/1 to 5/1.
[0058]
In addition, a light-scattering sheet may be formed in a light-scattering layer independent, and may be laminated | stacked with a base material sheet or a film (transparent support body) as needed. By lamination with the transparent support, the sheet strength can be increased.
[0059]
As resin which comprises a base material sheet (transparent support body), resin similar to resin which comprises the said light-scattering layer can be used. In addition, when used as a transparent support of a light scattering layer having a co-continuous phase structure, the base sheet also has heat resistance to the spinodal decomposition temperature because the co-continuous phase structure is formed by spinodal decomposition as described later. Is preferred. Examples of preferable base sheet include cellulose derivatives (cellulose triacetate (TAC), cellulose acetate such as cellulose diacetate), (meth) acrylate resins, vinyl ester resins (polyvinyl alcohol, etc.), polyester resins (polyethylene). Terephthalate (PET), polybutylene terephthalate (PBT), etc.), polyarylate resins, polysulfone resins (polysulfone, polyethersulfone (PES), etc.), polyether ketone resins (polyether ketone (PEK), polyether ether) Ketone (PEEK), polycarbonate resin (polycarbonate (PC), etc.), polyolefin resin (polyethylene, polypropylene, etc.), cyclic polyolefin resin (Ar) Down (ARTON), such as Zeonex (ZEONEX)), and styrene-based resin (polystyrene), a halogen-containing resin (vinylidene chloride), and a sheet obtained from such. These sheets may be uniaxially or biaxially stretched, and may be, for example, a stretched polyester sheet such as a uniaxially stretched PET sheet or a biaxially stretched PET sheet.
[0060]
The light scattering sheet (or base material sheet) may be a sheet having a thermal expansion coefficient comparable to that of a polarizing plate or a retardation plate used for colorizing and increasing the definition of a liquid crystal image. . In a liquid crystal display element, a polarizing plate or a retardation plate is often laminated with a light scattering sheet. Therefore, by making the thermal expansion coefficient of the light scattering sheet comparable to that of a polarizing plate or a retardation plate, The stress of peeling between the light scattering sheet (or substrate sheet) and the polarizing plate or the retardation plate accompanying shrinkage can be suppressed. For example, when a polarizing plate or a retardation plate is formed of a cellulose derivative, it is preferable to use a cellulose derivative (such as cellulose acetate) for the resin or the base sheet that constitutes the light scattering layer.
[0061]
In addition, since a retardation plate is often used for a liquid crystal display element (particularly an STN type liquid crystal display element), it is convenient to use a light scattering sheet having a small phase difference. For example, in the phase difference (R; retardation) represented by the following formula, a light scattering sheet having R of 50 nm or less, preferably 30 nm or less can be used. Such a low retardation sheet can be obtained, for example, by using polyethersulfone (PES) or cellulose triacetate (TAC) for a resin or a base sheet constituting the light scattering layer.
[0062]
R = Δn × d
(In the formula, Δn represents the birefringence of the sheet, and d represents the sheet thickness)
Note that a light scattering sheet having a phase difference can be used as necessary. For example, when a light scattering sheet is formed using a base material sheet having a phase difference (for example, a uniaxially stretched PET sheet), the light scattering sheet has a phase difference. Further, when the resin composition is formed into a sheet and subjected to spinodal decomposition in order to form a co-continuous phase structure, the light scattering sheet may have a phase difference in some cases. Even in such a case, by causing the alignment axis of the light scattering sheet to coincide with the polarization axis of the polarizing plate, it is possible to prevent the display from being obstructed.
[0063]
In addition, the light scattering sheet includes various additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, etc.), plasticizers, colorants (dyes and pigments), flame retardants, antistatic agents, It may contain a surfactant or the like. Moreover, you may form various coating layers, for example, an antistatic layer, an anti-fogging layer, a mold release layer etc. on the surface of a light-scattering sheet as needed.
[0064]
[Method for producing light scattering sheet]
The light-scattering sheet having the co-continuous phase structure is formed by molding a composition (particularly a resin composition) composed of a plurality of components having different refractive indexes, or into a base sheet (transparent base sheet). It can be formed by laminating physical layers by coating or the like. In addition, the said resin composition can maintain an incompatible state normally at room temperature, and phase separation arises depending on temperature.
[0065]
More specifically, the light scattering sheet having a co-continuous phase structure is a resin composition composed of a plurality of polymers having different refractive indexes formed by a conventional molding method, and this sheet is induced by spinodal decomposition, etc. It can be formed by immobilizing an isotropic phase separation structure (co-continuous phase structure). Alternatively, the resin composition in which the plurality of polymers are substantially uniformly dispersed may be coated or melt-laminated on the surface of the base sheet, dried as necessary, and spinodal decomposition of the laminated sheet.
[0066]
Sheet molding methods include, for example, a casting method or a coating method in which a solution (or slurry) of a polymer composition is cast or coated, and the polymer composition is melt-kneaded at a temperature higher than the glass transition temperature to form a sheet from a T die. An extrusion molding method (T-die method, inflation method, etc.) may also be used.
[0067]
Spinodal decomposition can be carried out by heating the resin composition layer (or sheet) composed of polymers having different refractive indices to a temperature equal to or higher than the glass transition temperature of the polymer to cause phase separation. For example, when the resin composition exhibits LCST type phase separation, the resin composition layer (or sheet) is heated to a temperature equal to or higher than the lower critical solution temperature (LCST) (for example, 10 to 100 ° C., preferably 20 to 20 ° C. from the LCST). When the resin composition exhibits a UCST type phase separation, the temperature is not higher than the upper critical solution temperature (UCST) (for example, 10 to 50 ° C., preferably 20 ° C. from UCST). And a method of heat treatment and ultrasonic treatment at a temperature of about -40 ° C). In addition, the heat processing temperature can be selected from the range of about 80-380 degreeC, for example, Preferably about 140-300 degreeC. In spinodal decomposition, as the phase separation progresses, the polymer phase forms a co-continuous phase structure due to surface tension, and when further heat-treated, the continuous phase becomes discontinuous due to its own surface tension, resulting in a droplet phase structure (spherical Independent phase sea-island structure such as true sphere). Therefore, depending on the degree of phase separation, an intermediate structure between the co-continuous phase structure and the droplet phase structure, that is, a phase structure in a state of transition from the co-continuous phase to the droplet phase can be formed.
[0068]
The sheet in which the isotropic bicontinuous phase structure is formed by spinodal decomposition in this way is cooled to the glass transition temperature of the constituent polymer or lower (for example, the glass transition temperature of the main polymer or lower), thereby forming the bicontinuous phase structure. Can be fixed. When cooling an LCST type sheet, it is preferable to quench the sheet (for example, quenching with cold water of 30 ° C. or lower, preferably 10 ° C. or lower).
[0069]
In such a method, since spinodal decomposition is used, a sheet having a co-continuous phase structure can be formed at low cost by simple means such as heat treatment and cooling.
[0070]
[Light scattering composite sheet]
In the light scattering composite sheet of the present invention, another functional layer (a polarizing plate, a retardation plate, a light reflecting plate, a transparent conductive layer, etc.) is laminated on at least one surface of the light scattering sheet composed of the light scattering layer. Has been. When the light scattering sheet is made into a composite sheet, the composite sheet can be used in place of the functional layer of the conventional liquid crystal display element, so that the light scattering sheet can be easily introduced into the liquid crystal display element. That is, it is possible to manufacture a high-brightness, high-definition type reflective liquid crystal device without changing the production line of the liquid crystal display device, without increasing the cost, and without further reducing the yield. In addition, when a composite sheet is used, as will be described later, the light scattering sheet can be easily brought close to the liquid crystal, and the visibility of the image is improved.
[0071]
Specifically, as a composite sheet, a laminated sheet of a light scattering sheet and a polarizing plate, a laminated sheet of a light scattering sheet and a retardation plate, a laminated sheet of a light scattering sheet and a light reflecting plate, a light scattering sheet and a transparent sheet A two-layer sheet such as a laminated sheet (transparent conductive sheet) with a conductive layer, a sheet (three-layer sheet) in which a functional layer different from the functional layer constituting the two-layer sheet is further laminated on the two-layer sheet (for example, light A three-layer sheet composed of a scattering sheet, a polarizing plate and a retardation plate, in particular, a sheet laminated in the order of a polarizing plate, a light scattering sheet, and a retardation plate, in the order of a polarizing plate, a retardation plate, and a light scattering sheet And a sheet in which a polarizing plate such as a laminated sheet is formed on the surface of a three-layer sheet. In particular, when a liquid crystal display element (for example, an STN liquid crystal display element) is formed using a three-layer sheet, it is possible to reduce the bonding process of each functional layer in manufacturing the liquid crystal display element.
[0072]
As the light scattering sheet used for the composite sheet, the light scattering sheet having the bicontinuous phase structure is often used, but a phase separation structure is formed by a plurality of solid components (resin component, inorganic component, etc.) having different refractive indexes. The light scattering layer is not particularly limited as long as it has a light scattering layer, and may be, for example, a light scattering sheet having a fine particle dispersed structure. Of the plurality of components constituting the phase separation structure (for example, the fine particle dispersion structure), the difference in refractive index between at least two components is the same as the difference in refractive index between the plurality of polymers constituting the co-continuous phase structure. is there. Even if it is such a light-scattering sheet, the visibility of a liquid crystal image can be improved by using as a composite sheet so that it may mention later.
[0073]
As the resin component, the same resin as that constituting the co-continuous phase structure can be used.
[0074]
As the inorganic component, a transparent or translucent inorganic component can be used. For example, inorganic oxides such as silicon oxide (glass, particularly alkali-free glass), zirconium oxide, aluminum oxide, zinc oxide, mica (mica), Examples thereof include inorganic nitrides such as boron nitride, inorganic halides such as calcium fluoride and magnesium fluoride. Two or more of these inorganic components may be used in combination as a composite material. For example, a composite material of mica and boron nitride can be used.
[0075]
The light scattering layer having a fine particle dispersed structure includes, for example, a transparent base resin (such as a transparent base resin composed of the resin component) and a fine particle component (fine particles composed of the resin component or inorganic component) having different refractive indexes. It consists of The fine particle component is dispersed in the transparent base resin.
[0076]
Preferred transparent base resins and resins constituting the fine particles include styrene resins (polystyrene, etc.), (meth) acrylic resins, olefin resins (polyethylene, polypropylene, etc.), vinyl ester resins, vinyl ether resins, polycarbonate resins. , Polysulfone resins, polyamide resins (nylon 6, nylon 12, nylon 612, etc.), cellulose derivatives (cellulose acetate, etc.), and the like.
[0077]
In addition, although the fine particle dispersion structure can obtain high light scattering properties, it may exhibit light scattering properties in which the light scattering properties become smaller as the diffusion angle becomes wider. That is, since the diffused light distribution is close to a Gaussian distribution, when the diffusion angle increases, the scattered light intensity generally decreases and the brightness of the display screen may decrease. For this reason, the difference in refractive index between the transparent base resin and the fine particle components (resin fine particles, inorganic fine particles, etc.), the particle diameter, ratio, and particle density of the fine particle components are appropriately adjusted to suppress backscattering and direct to diffused light. Sexuality may be imparted. If a sheet having directivity corresponding to the required visual field characteristics is used, external light or a light source of front light can be used efficiently.
[0078]
When imparting directivity, the difference in refractive index between the fine particle component and the transparent base resin is, for example, about 0.01 to 0.06, preferably about 0.01 to 0.05, and more preferably 0.01 to It is about 0.04.
[0079]
The average particle diameter of the fine particle component may be, for example, about 0.1 to 100 μm, preferably about 1 to 20 μm.
[0080]
The ratio of the fine particle component to the transparent base resin is, for example, the former / the latter = about 10/90 to 90/10 (weight ratio), preferably about 15/85 to 60/40 (weight ratio), and more preferably 15 / It may be about 85 to 40/60 (weight ratio).
[0081]
The average particle density of the fine particle component is, for example, 1 to 100 (10^TenPiece / cm^Three) Grade, preferably 4-80 (10^TenPiece / cm^Three) Degree.
[0082]
The average particle density can be calculated, for example, by measuring the average particle size and using the following formula (I).
[0083]
Average particle density (pieces / cm^Three) = 1cm^Three× Vs / [(4/3) π (Ds × 10^-Four/ 2) 3] (I)
(In the formula, Vs represents the ratio (volume basis) of the fine particle component in the light scattering layer, π represents the circular ratio, and Ds represents the particle size (μm) of the fine particle component.)
The light-scattering sheet used for the composite sheet may be composed of a light-scattering layer alone, similarly to the light-scattering sheet having the co-continuous phase structure, and the light-scattering layer and the base sheet (transparent support) are laminated. You may comprise by. In addition, as a base material sheet, the sheet | seat similar to the base material sheet of the light-scattering sheet of the said co-continuous phase structure can be used.
[0084]
Moreover, the thickness of the light-scattering sheet used for the composite sheet is approximately the same as the thickness of the light-scattering sheet having the bicontinuous phase structure.
[0085]
The light scattering sheet used for the composite sheet may be a sheet formed of a sheet having a thermal expansion coefficient similar to that of a polarizing plate or a retardation plate, similar to the light scattering sheet having the bicontinuous phase structure. Good. When a composite sheet is formed by laminating a polarizing plate or retardation layer and a light scattering sheet, the thermal expansion coefficient of the light scattering sheet is made to be about the same as that of the polarizing plate or retardation plate, thereby expanding the thermal expansion of the composite sheet. It is possible to suppress the occurrence of peeling stress due to heat shrinkage. Further, even when a transparent conductive sheet (a composite sheet of a light scattering sheet and a transparent conductive layer) is used as the composite sheet, in the liquid crystal display element, the transparent conductive sheet is laminated with a polarizing plate or a retardation plate. Since there are many, generation | occurrence | production of the stress of peeling can be suppressed.
[0086]
In addition, the composite sheet or the light scattering sheet used for this composite sheet preferably has a smaller phase difference, like the light scattering sheet having the bicontinuous phase structure, but may have a phase difference.
[0087]
The light scattering sheet having a fine particle dispersed structure can be produced according to a conventional method such as a casting method or a melt extrusion method using the mixture containing the transparent base resin and the fine particle component. The sheet can also be formed by solution casting in which the transparent base resin and the fine particle component are molded into a solution, but it is preferably manufactured by a melt film forming method in which fine particles are dispersed to form a film in a molten transparent base resin. When a sheet is formed by the melt film forming method, the sheet can be formed at low cost.
[0088]
Further, a light scattering sheet having a fine particle dispersed structure can also be formed by coating the base sheet surface with a mixture of a transparent base resin and a fine particle component.
[0089]
As the polarizing plate, the retardation plate and the reflection plate, a conventional polarizing plate, retardation plate or reflection plate used for a liquid crystal display element can be used. For example, the polarizing plate may be a film made of polyvinyl alcohol. The retardation plate is, for example, a polycarbonate retardation plate. As the reflector, for example, a metal film (such as aluminum foil) or a plastic film on which a metal (such as aluminum) is deposited can be used. The reflection plate may be a specular reflection type reflection plate, or may be a reflection plate having light scattering properties (such as a reflection plate whose surface is roughened).
[0090]
As a transparent conductive layer constituting the transparent conductive sheet, a layer formed of a conductive inorganic compound, for example, a metal oxide layer (ITO (indium tin oxide), InO)₂, SnO₂, ZnO, etc.), metal layers (Au, Ag, Pt, Pd, etc.). A preferred transparent conductive layer is an ITO layer.
[0091]
The thickness of the transparent conductive layer is, for example, 100 × 10^-8~ 2,000 × 10^-8cm, preferably 100x10^-8cm to 1,500 × 10^-8cm, more preferably 150 to 1,000 × 10^-8It is about cm.
[0092]
The surface resistance of the transparent conductive layer is, for example, 10 to 1,000 Ω / □, preferably 15 to 500 Ω / □, and more preferably 20 to 300 Ω / □.
[0093]
In addition, when the light scattering sheet is a laminated sheet of a light scattering layer and a base sheet, the transparent conductive layer may be formed on the light scattering layer side of the light scattering sheet or may be formed on the base sheet side. Good. When the transparent conductive layer is formed on the light scattering layer side, the light scattering layer can be brought close to the liquid crystal layer, so that a high-quality display screen can be formed. On the other hand, when forming the transparent conductive layer on the base sheet side, when forming a liquid crystal display element to be described later using this transparent conductive sheet, an alignment film is formed on the transparent conductive sheet, or an adhesive layer is formed on the light scattering sheet. Although the transparent conductive sheet needs to be subjected to a high temperature treatment such as forming a glass substrate, the substrate sheet has high heat resistance (for example, the glass transition temperatures of PES and PC are about 224 ° C. and about 145 ° C., respectively). PET has high crystallinity and TAC has excellent heat resistance), so that the reliability (stability) of the liquid crystal display element can be improved.
[0094]
Moreover, since the transparent conductive sheet should just have the transparent conductive layer formed in at least one surface of the light-scattering sheet, the other surface may be untreated and other layers other than the said transparent conductive layer For example, a static electricity removing layer (antistatic layer) for removing static electricity from the sheet may be formed. When a static electricity removing layer is formed, static electricity can be effectively removed when a polarizing plate, a retardation plate, a reflecting plate, or the like is bonded to this layer, and quality deterioration of the liquid crystal display element can be prevented.
[0095]
The static electricity removing layer can be formed of the same components as the transparent conductive layer. The thickness of the static electricity removing layer is, for example, about 10 to 500 angstroms, preferably about 30 to 300 angstroms. The surface resistance of the static electricity removing layer is, for example, about 0.5 to 100 kΩ / □, preferably about 1 to 50 kΩ / □.
[0096]
The transparent conductive sheet exhibits a high total light transmittance as high as that of the light scattering sheet, although the conductive layer is formed, and the total light transmittance is, for example, about 70 to 100%, preferably 85. It is about -98%, More preferably, it is about 90-95%.
[0097]
In addition, the composite sheet may contain various additives like the light scattering sheet having the bicontinuous phase structure.
[0098]
On the surface of the composite sheet (in the case of a transparent conductive sheet, in particular, the surface on the side where the transparent conductive layer is not formed), various coating layers such as an antifogging layer and a release layer are formed as necessary. May be.
[0099]
The sheet thickness of the composite sheet can be selected according to the thickness of the functional layer. For example, the sheet thickness of the transparent conductive sheet is the same as the sheet thickness of the light scattering sheet because the thickness of the transparent conductive layer is very thin, and is about 1 to 500 μm, preferably about 10 to 400 μm, and more preferably 50 to It is about 200 μm. When the thickness of the transparent conductive sheet exceeds 500 μm, the sharpness of the image is lowered during image formation (image blur). Moreover, when the thickness of a transparent conductive sheet is less than 1 micrometer, the intensity | strength and handleability of a sheet | seat fall.
[0100]
For example, the composite sheet may be capable of directing diffused light at a diffusion angle of about 3 to 60 °, preferably about 5 to 50 °, more preferably about 10 to 40 ° (particularly about 10 to 30 °).
[0101]
[Method for producing light-scattering composite sheet]
Among the light scattering composite sheets, when a composite sheet is composed of a functional layer other than a transparent conductive layer such as a polarizing plate, a retardation plate, and a light reflecting plate, and the light scattering sheet, either the light scattering sheet or the functional layer A composite sheet can be produced by applying a pressure-sensitive adhesive to the surface and bonding the light scattering sheet and the functional layer layer together. For example, a composite sheet can be formed by forming a pressure-sensitive adhesive layer on one surface of a light scattering sheet and then bonding a functional layer (a polarizing plate, a retardation plate, a reflecting plate, etc.).
[0102]
Examples of the adhesive include (meth) acrylic resin, vinyl acetate resin, silicone polymer, polyester, polyurethane, and synthetic rubber.
[0103]
Examples of the (meth) acrylic resin forming the acrylic pressure-sensitive adhesive include, for example, (meth) acrylic acid esters (ethyl alcohol, n-propyl alcohol, isopropyl alcohol, etc. ) Ester with acrylic acid) homopolymers or copolymers.
[0104]
In addition, in order to attach a composite sheet simply in the manufacturing process of a liquid crystal display element, you may apply | coat the said adhesive to the surface (For example, non-contact surface with the functional layer of a light-scattering sheet). In addition, a release film may be attached to the surface of the pressure-sensitive adhesive similarly to a general functional sheet.
[0105]
The surface of the functional layer of the composite sheet may be protected by a protective film.
[0106]
On the other hand, the transparent conductive sheet can be obtained by forming a transparent conductive layer on the surface of the light scattering sheet by a conventional method such as sputtering, vacuum deposition, ion plating, or coating. In addition, when forming a transparent conductive layer by a vacuum evaporation method (when depositing ITO, etc.), SiO2 is previously formed on the surface of the light scattering sheet.₂In many cases, a transparent conductive layer is vapor-deposited after depositing a non-conductive inorganic compound such as a thermosetting resin or UV curable resin in advance to form an anchor coat layer. These pretreatments can improve the strength and durability of the transparent conductive layer.
[0107]
[Reflective liquid crystal display element]
The reflective liquid crystal display element of the present invention comprises a transparent front electrode plate having a transparent conductive layer (electrode) and a substrate (electrode support substrate) that supports the transparent conductive layer, a conductive layer (electrode), and the conductive layer. A back electrode plate having a substrate (electrode support substrate) to be disposed is disposed opposite to the conductive layer, and a liquid crystal cell in which liquid crystal is sealed is provided between the two electrode plates. A plate is provided. Normally, a light reflection plate is disposed on the back surface of the back electrode plate, and the polarizing plate is disposed in the light incident path and reflection path from the front. In the present invention, in order to improve the visibility of the image of the liquid crystal display element, a light scattering sheet (a light scattering sheet used for the composite sheet, for example, a light scattering sheet having a co-continuous phase structure, a light scattering sheet having a fine particle dispersion structure) Etc.) to form a liquid crystal display element. This light scattering sheet is any of the following (i) to (iii).
[0108]
(i) a light scattering sheet disposed between the polarizing plate and the front electrode plate
(ii) A light scattering sheet disposed between the back electrode plate and a reflector disposed behind the back electrode plate
(iii) Light scattering sheet as substrate
When such a reflection type liquid crystal display element is used, the light scattering sheet can be disposed close to the liquid crystal, so that the ambiguity (blurring) of the image can be prevented and the visibility can be improved. Further, since the light scattering sheet is not exposed on the surface of the reflective liquid crystal display element, the light scattering sheet is hardly affected from the outside by mechanical or chemical effects, and there is no possibility that the light scattering layer is damaged. Furthermore, since a polarizing plate having excellent durability is formed on the surface of the reflective liquid crystal display element, the quality of the reflective liquid crystal display element can be maintained over a long period of time.
[0109]
For example, FIG. 1 is a schematic cross-sectional view showing an example of a liquid crystal display element (i) for color display in which a light scattering sheet is disposed between a polarizing plate and a liquid crystal cell. 1 is a liquid crystal cell including a liquid crystal 6 (liquid crystal layer or the like) sealed between a pair of transparent electrode plates 7a and 7b (glass plate or the like) having a transparent conductive layer (not shown). In FIG. 12, a reflection plate 5 (for example, a reflection layer such as a specular reflection plate) for reflecting incident light is laminated on one transparent electrode plate (back electrode plate) 7b. The other transparent electrode plate (front electrode plate) 7a of the liquid crystal cell 12 is provided with a light scattering sheet (in this example, a light scattering sheet having a co-continuous phase structure) through a color filter 8 for color display. 2 are stacked. A polarizing plate 1 for polarizing reflected light is laminated on the other surface of the light scattering sheet 2. When the reflective LCD is used for monochrome display, the color filter is not always necessary.
[0110]
When a light scattering sheet is disposed between the polarizing plate and the transparent conductive layer, not only can the light (incident light) incident from the front surface on the viewer side be diffused (scattered), but also the light reflected by the reflector 5 can be reflected. It can be diffused (scattered) again. Thus, since light can be scattered twice, the specular reflection of the reflecting plate 5 can be sufficiently prevented.
[0111]
When a light scattering sheet is disposed between the polarizing plate and the transparent conductive layer, a reflector is not necessarily required as long as incident light can be reflected behind the liquid crystal. For example, the conductive layer of the back electrode plate is light-transmitted. A reflective conductive layer (for example, a glass plate on which a metal layer is deposited) may be used. FIG. 7 is a schematic cross-sectional view of a liquid crystal display element having a light reflective conductive layer. This liquid crystal display element includes a front electrode plate 7a having a transparent front electrode (a transparent conductive layer such as an indium tin oxide thin film) 4a and a front substrate (a glass plate having a thickness of 1 mm) 22a, and a back electrode (conductive layer). A liquid crystal cell 12 including a back electrode plate 7c having a 4c and a back substrate (a glass plate having a thickness of 1 mm, etc.) 22b, and a liquid crystal layer 6 sealed between the electrode plates 7a and 7c. Yes. The back electrode (conductive layer) 4c is a light reflective back electrode formed of an aluminum thin film. The light scattering sheet 2 is laminated on the front side of the liquid crystal cell 12 via an adhesive layer 92, and the polarizing plate 1 is laminated on the surface of the light scattering sheet 2 via an adhesive layer 91. Yes. When a reflective liquid crystal display element is formed with a light reflective back electrode, the liquid crystal display element can be thinned.
[0112]
  In the case of an STN (Super Twisted Nematic) liquid crystal display element, a retardation plate is disposed between the polarizing plate and the front electrode plate, although this is not always necessary in the case of a TFT type liquid crystal display element. May. lightThe scattering sheet may be disposed between the polarizing plate and the retardation plate, but is preferably disposed between the retardation plate and the front electrode plate (or liquid crystal cell). For example, FIG. 9 is a schematic cross-sectional view of a liquid crystal display element in which a light scattering sheet is disposed between a retardation plate and a front electrode plate. In the liquid crystal display element of FIG. 9, the light scattering sheet 2 is attached to the front electrode plate 7 a of the liquid crystal cell 12 similar to that of FIG. 7 via the adhesive layer 92, and the adhesive layer is formed on the surface of the light scattering sheet 2. It can be formed by attaching the retardation plate 3 via 93 and further attaching the polarizing plate 1 to the surface of the retardation plate 3 via the adhesive layer 91. When the light scattering sheet 2 is disposed between the retardation plate 3 and the front electrode plate 7a, light is scattered in the liquid crystal as compared with the case where the light scattering sheet 2 is disposed between the polarizing plate 1 and the retardation plate 3. The sheets can be brought close to each other, and the clarity of the image can be further enhanced.
[0113]
FIG. 11 is a schematic cross-sectional view of a liquid crystal display element (ii) in which a light scattering sheet is disposed between a back electrode plate and a reflection plate. This liquid crystal display element includes a liquid crystal layer composed of a front substrate (such as a 100 μm thick plastic sheet) 22a, a back substrate (such as a 100 μm thick plastic sheet) 22b, and a liquid crystal layer 6 sealed between the two substrates. It has a cell 12. In both the substrates, transparent front electrodes (such as indium tin oxide thin films) 4a and 4b are formed on the surface on the liquid crystal side. A reflective plate 5 having an adhesive layer 95 is disposed behind the liquid crystal cell 12, and the light scattering sheet 2 is pasted between the reflective plate 5 and the liquid crystal cell 12 by an adhesive layer 92. ing. Even when the light scattering sheet 2 is disposed between the back electrode plate 7b and the reflection plate 5, the light scattering sheet 2 is incident as in the case where the light scattering sheet 2 is disposed between the polarizing plate 1 and the front electrode plate 7a. Light and reflected light can be scattered, and specular reflection of the reflecting plate 5 can be sufficiently prevented.
[0114]
FIG. 4 is a schematic cross-sectional view of a liquid crystal display element (iii) having a substrate formed of a light scattering sheet. In this liquid crystal display element, a polarizing plate 1 is laminated in front of a liquid crystal cell 12 via a phase difference plate 3, and a reflecting plate 5 is laminated behind the liquid crystal cell 12. In the liquid crystal cell 12, light scattering sheets (front electrode plates) 2a and 2b in which light scattering layers 21a and 21b are laminated on base material sheets 23a and 23b are used as substrates (electrode support substrates) 22a and 22b. Transparent conductive layers 4a and 4b are formed on the surface of the liquid crystal side of both the substrates (light scattering sheets).
[0115]
When such a liquid crystal display element is used, a substrate (electrode support substrate) can be configured with a light scattering sheet, and thus it is not necessary to separately provide a light scattering layer (light scattering sheet) or the like. For this reason, the thickness of the liquid crystal display element can be reduced despite a bright screen. Furthermore, by reducing the thickness of the liquid crystal display element, it is possible to sufficiently prevent both the liquid crystal image and the image of the light scattering layer from being formed, and a sharper image can be formed. Display screen can be obtained.
[0116]
When the substrate is constituted by the light scattering sheet, it is not always necessary to form both the front substrate 22a and the back substrate 22b with the light scattering sheet 2, and one of them is formed with the light scattering sheet 2. That's fine. For example, when the back substrate 22b is formed of the light scattering sheet 2b, a transparent substrate having no light scattering property may be used as the front substrate 7a.
[0117]
Also when the front substrate 22a is formed of the light scattering sheet 2a, a transparent substrate having no light scattering property can be used as the front substrate 7a. Further, when the front substrate 22a is formed of the light scattering sheet 2a, the back electrode (conductive layer) 4b may be a light reflective electrode, and when the light reflective electrode is used, the reflection plate 5 is not necessarily required. .
[0118]
As the light scattering sheet, a light scattering sheet having a bicontinuous phase structure is preferably used. When a reflective LCD is configured using a light scattering sheet having a co-continuous phase structure, the scattered light can be directed in a certain direction while imparting diffusivity to the reflected light, so that the screen display can be brightened. . In particular, since sufficient brightness can be ensured even in color display, it can be advantageously formed in a color reflective liquid crystal display element. When a light scattering sheet having a co-continuous phase structure is used as the light scattering sheet, directivity can be imparted to the reflected light, so that a transmissive liquid crystal display element (a liquid crystal display element using a backlight instead of a reflector) Even so, a bright liquid crystal image can be displayed over a wide viewing angle. Moreover, when using the light-scattering sheet of a co-continuous phase structure as a light-scattering sheet, the arrangement | positioning position of a light-scattering sheet is not specifically limited.
[0119]
The polarizing plate 1, the phase difference plate 3, the reflecting plate 5, and the transparent conductive layers 4a and 4b are the same as the composite sheet.
[0120]
As an electrode plate (light transmissive electrode plate) on which a transparent conductive layer is formed, the transparent conductive sheet is formed on the surface of a substrate (transparent substrate) such as glass or plastic (plastic sheet similar to the base sheet). An electrode plate having a transparent conductive layer formed in the same manner as the (light-scattering transparent conductive sheet) can be used.
[0121]
The electrode plate (light reflective electrode plate) on which the light reflective conductive layer is formed can be formed by vapor-depositing a metal layer (light reflective conductive layer) on the same substrate as the front electrode plate. The light reflective conductive layer may be roughened. The roughening treatment can be performed, for example, by appropriately selecting vapor deposition conditions or by a conventional roughening method. When the light-reflecting back electrode plate subjected to the rough surface treatment is used, a voltage can be applied to the liquid crystal in the liquid crystal display element, and incident light can be appropriately scattered and reflected without being specularly reflected.
[0122]
Note that the conductive layer (transparent conductive layer, light-reflective conductive layer, or the like) is patterned in a stripe shape to form a striped electrode. The patterning of the conductive layer can be performed by a resist forming method such as photolithography, or by etching the conductive layer. In addition, both the electrode plates may be arranged so that the stripe electrode on the front electrode plate and the stripe electrode on the back electrode plate cross each other (for example, orthogonal).
[0123]
Further, in both the conductive layers, an alignment film is formed in order to generate an alignment suitable for the reflective liquid crystal (mainly a vertical alignment in the single polarizing plate system as in FIGS. 7, 9, 11 and 4). It may be applied and dried and rubbed. As the alignment film, a polyimide-based vertical alignment film is mainly used.
[0124]
The liquid crystal cell 12 forms (prints) a seal portion on the surface of the electrode layer 7a, 7b on the conductive layer side by screen printing, for example, and a spacer 13 is disposed on the seal portion. It can be formed by bonding two electrode plates 7a and 7b together. The liquid crystal can be injected into a space (in the cell) formed by the bonding by a conventional method such as a vacuum injection method. The injection port can be sealed with a sealant (such as an ultraviolet curable sealant).
[0125]
The liquid crystal display element is not limited to a single-polarization-type reflective LCD using a single polarizing plate, but may be a dual-polarization-type reflective LCD using two polarizing plates having different polarization properties. Good. In addition, a reflection type LCD with a single polarizing plate has, for example, one polarizing plate and various modes (mode using twisted nematic liquid crystal, R-OCB (Optically Compensated Bend) mode, parallel alignment mode, etc.). A combined reflective LCD may also be used.
[0126]
The liquid crystal display element can be formed by pasting together a polarizing plate, a light scattering sheet, a liquid crystal cell, and a retardation plate, a light reflection plate, and the like with an adhesive (adhesive) as necessary. In addition, as for a polarizing plate, a light-scattering sheet, a phase difference plate, and a light-scattering plate, the adhesive layer is normally formed in the surface (both surfaces or single side | surface) previously. In addition, when forming an adhesive layer in the single side | surface of the light-scattering sheet comprised by the light-scattering layer and the base material sheet, in order to protect a light-scattering layer, an adhesive layer (adhesive layer) on the surface of the light-scattering layer side ) Is often formed.
[0127]
When an adhesive layer is formed on one side of a polarizing plate, a light scattering sheet, a retardation plate, and a light scattering plate, a liquid crystal display element can be easily formed. For example, when a liquid crystal display element is manufactured by bonding a polarizing plate, a light scattering sheet, and a liquid crystal cell, the light scattering sheet and the polarizing plate can be bonded with an adhesive (adhesive) of the polarizing plate. For this reason, a liquid crystal display element can be manufactured by bonding together a light-scattering sheet and a phase difference plate or a liquid crystal cell (front electrode plate) with the adhesive formed in the single side | surface of the light-scattering sheet.
[0128]
In addition, when a liquid crystal display element is manufactured by bonding a polarizing plate, a retardation plate, a light scattering sheet, and a liquid crystal cell, the light scattering sheet and the retardation plate are bonded together with an adhesive (adhesive) for the retardation plate. Can do. And a light-scattering sheet and a liquid crystal cell (front substrate) can be bonded together with the adhesive formed in the single side | surface of a light-scattering sheet. If necessary, the light scattering sheet and the phase difference plate may be bonded together with the light scattering sheet adhesive, and the phase difference plate and the liquid crystal cell (front substrate) may be bonded together with the phase difference plate adhesive. . And a liquid crystal display element can be manufactured by bonding a polarizing plate with a phase difference plate or a light-scattering sheet with the adhesive of a polarizing plate.
[0129]
Further, when the light transmissive back electrode plate, the light scattering sheet, and the reflection plate are bonded together, the reflection plate and the light scattering sheet can be bonded together with an adhesive (adhesive) of the reflection plate. For this reason, a light-scattering sheet and a back electrode plate can be bonded together with the adhesive formed in the single side | surface of a light-scattering sheet. In addition, a liquid crystal display element can be manufactured by sequentially bonding a retardation plate on which a pressure-sensitive adhesive layer is formed and a polarizing plate on which a pressure-sensitive adhesive layer is formed on the front surface of the liquid crystal cell.
[0130]
Moreover, when forming an adhesive layer on both surfaces of a polarizing plate, a light scattering sheet, a retardation plate, and a light scattering plate, especially when an adhesive layer is formed on both surfaces of the light scattering sheet, the surface of the adhesive layer is formed. A sheet can be affixed without the need for identification, the manufacturing process is simplified, and the adhesive strength is improved.
[0131]
In the manufacturing process of the liquid crystal display element, the composite sheet (a laminated sheet of a light scattering sheet and a polarizing plate, a laminated sheet of a light scattering sheet and a retardation plate, a laminated sheet of a light scattering sheet and a reflective plate, a light scattering sheet) A laminated sheet (transparent conductive sheet or the like) of a transparent conductive layer and the like may be used. For example, the liquid crystal display element of FIG. 7 uses a composite sheet (FIG. 6) in which a polarizing plate 1 and a light scattering sheet 2 are laminated, so that the liquid crystal display element of FIG. 11 by using a composite sheet (two-layer sheet) laminated with 2 (FIG. 8) or a composite sheet (three-layer sheet) obtained by further laminating the polarizing plate 1 on the retardation plate 3 of this sheet (FIG. 12). The liquid crystal display element uses a composite sheet (FIG. 11) in which the light scattering sheet 2 and the reflecting plate 5 are laminated, so that the liquid crystal display element in FIG. 4 has a transparent conductive layer 4 formed on the surface of the light scattering sheet 2. It can be manufactured by using a conductive sheet (FIG. 16). When such a composite sheet is used, a reflective liquid crystal display device can be manufactured without changing the production line of a conventional liquid crystal display element.
[0132]
In the case of manufacturing a liquid crystal display element using a composite sheet, the composite sheet is preferably disposed (attached) to the liquid crystal cell so that the light scattering sheet of the composite sheet is close to the liquid crystal. For example, when a reflective liquid crystal display element is configured by disposing a composite sheet of a light scattering sheet and a polarizing plate (or retardation plate) on the viewer side of the liquid crystal cell, the light scattering sheet is directed toward the liquid crystal cell ( That is, it is preferable to dispose (bond) the composite sheet (with the polarizing plate (or retardation plate) facing the viewer). When the composite sheet is disposed so that the light scattering sheet is close to the liquid crystal, the clarity of the image can be further improved.
[0133]
When the light scattering sheet, composite sheet or liquid crystal display element of the present invention is used, the visibility of the liquid crystal display screen can be improved. For this reason, it can be suitably used for a reflective LCD, particularly a liquid crystal display device of a portable information device. Moreover, according to the manufacturing method of the light-scattering sheet of this invention, since the light-scattering sheet is manufactured by spinodal decomposition, a directional diffusion sheet can be manufactured simply.
[0134]
【The invention's effect】
According to the light scattering sheet, the composite sheet, and the liquid crystal display element of the present invention, the directivity can be imparted to the reflected light, or the light scattering sheet can be disposed close to the liquid crystal cell. The visibility of the image can be improved. Further, according to the composite sheet of the present invention, the light scattering sheet and the functional layer of the liquid crystal display element are combined, so that the production line of the liquid crystal display element is not changed, the cost is not increased, and Without lowering the yield, it is possible to prevent mirror reflection of the liquid crystal display element and improve image visibility. In particular, when a transparent conductive sheet is used, since it has conductivity, an electrode plate of a liquid crystal display element can be formed, and a thin and high-quality liquid crystal display element can be obtained easily and at low cost. Furthermore, according to the liquid crystal display element of the present invention, not only the visibility of the liquid crystal image can be improved, but also the scratch resistance of the surface of the liquid crystal display element is improved because the light scattering sheet is disposed behind the polarizing plate. The durability of the liquid crystal display element can be improved at low cost.
[0135]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[0136]
In the examples and comparative examples, the following resins, polarizing plates, and retardation plates were used.
[0137]
[resin]
PMMA-1: Polymethylmethacrylate (manufactured by Mitsubishi Rayon Co., Ltd., “BR-87”, weight average molecular weight (Mw) = 25,000, refractive index = 1.49)
PMMA-2: polymethyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., “BR-83”, weight average molecular weight (Mw) = 40,000, refractive index = 1.49)
PMMA-3: polymethyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., “BR-80”, weight average molecular weight (Mw) = 95,000, refractive index = 1.49)
PMMA-4: Polymethyl methacrylate (Mitsubishi Rayon Co., Ltd., “BR-88”, weight average molecular weight (Mw) = 480,000, refractive index = 1.49)
PMMA-5: Polymethyl methacrylate (PMMA) -based particles (manufactured by Sekisui Chemical Co., Ltd., “MBX-2”)
SAN-1: Styrene-acrylonitrile copolymer (manufactured by Technopolymer Co., Ltd., “290-ZF”, weight average molecular weight (Mw) = 69,000, refractive index = 1.57)
SAN-2: Styrene-acrylonitrile copolymer (manufactured by Technopolymer Co., Ltd., “SAN-T”, weight average molecular weight (Mw) = 107,000, refractive index = 1.57)
SAN-3: Styrene-acrylonitrile copolymer (manufactured by Technopolymer Co., Ltd., “SAN-L”, weight average molecular weight (Mw) = 100,000, refractive index = 1.57)
SAN-4: Styrene-acrylonitrile copolymer (manufactured by Daicel Chemical Industries, “080”, weight average molecular weight (Mw) = 110,000, refractive index = 1.55)
SAN-5: Styrene-acrylonitrile copolymer (manufactured by Daicel Chemical Industries, “080SF”, weight average molecular weight (Mw) = 110,000, refractive index = 1.55)
CEL-1: Cellulose triacetate (manufactured by Daicel Chemical Industries, “LT-105”)
PETG-1: Polyethylene terephthalate amorphous copolyester (Eastman Chemical, “Eastar PETG 6763”, refractive index = 1.567)
GPPS-1: General-purpose polystyrene (manufactured by Daicel Chemical Industries, “GPPS # 30”, refractive index = 1.589)
PES-1: polyethersulfone sheet (manufactured by Sumitomo Chemical Co., Ltd., thickness = 100 μm)
[Polarizer]
Polarizing plate A: Polarizing film for liquid crystal display (“NPF” manufactured by Nitto Denko Corporation)
Polarizing plate B: A pressure-sensitive adhesive layer is formed on one surface of a uniaxially stretched polyvinyl alcohol film adsorbing iodine, and the other surface is protected with a protective film (triacetylcellulose film) after roughening treatment and surface treatment treatment. A polarizing plate. In the manufacturing process of the liquid crystal surface element, the protective film is peeled off from the polarizing plate.
[0138]
[Phase difference plate]
Retardation plate A: retardation film for liquid crystal display (“NRF” manufactured by Nitto Denko Corporation)
Phase difference plate B: Polycarbonate resin phase difference film
[a reflector]
Reflector A: A sheet in which aluminum is vapor-deposited on a resin sheet with a thickness of 100 μm and an adhesive is applied to the aluminum vapor-deposited surface
Reflector B: Aluminum foil with a pressure-sensitive adhesive layer formed on the surface (thickness 50 μm)
Example 1
50 parts by weight of polymethyl methacrylate (PMMA-4) and 50 parts by weight of a styrene-acrylonitrile copolymer (SAN-4) were dissolved in 400 parts by weight of a methylene chloride / methanol mixed solvent (9/1, weight ratio). The solution was cast on a glass plate to form a sheet layer having a thickness of 8 μm. The glass plate was heated on a hot plate at 280 ° C. for 1 minute. After the heat treatment, the glass plate and the sheet were immersed in a cold water bath. The sheet was peeled from the glass plate, attached to a frame and dried (thickness 10 μm). When the obtained sheet was observed with a transmission optical microscope, the sheet had an intermediate structure between a co-continuous phase structure and a droplet phase structure, and the average interphase distance of the continuous phase was about 6 μm. The total light transmittance of the sheet was 93%. A schematic diagram of the phase structure observed with a transmission optical microscope is shown in FIG.
[0139]
Example 2
Example 1 was repeated except that the heat treatment temperature was 250 ° C. and the heat treatment time was 3 minutes. When the obtained sheet was observed with a transmission optical microscope, it had an intermediate structure between a bicontinuous phase structure and a droplet phase structure, and the average interphase distance was about 6 μm.
[0140]
Reference example 1
80 parts by weight of cellulose triacetate (CEL-1) flakes were dissolved in 900 parts by weight of a methylene chloride / methanol mixed solvent (9/1, weight ratio). The solution was mixed with 20 parts by weight of PMMA fine particles (PMMA-5), cast and cast to obtain a 150 μm sheet. When the obtained sheet was observed with a transmission optical microscope, it had a droplet phase structure, and the average diameter of the droplets was 3 μm. The total light transmittance of the sheet was 92%.
[0141]
The performance of the light diffusion sheets obtained in Examples 1 and 2 and Reference Example 1 was evaluated according to the following method.
[0142]
(Direction 1)
The reflection type LCD model device of FIG. 2 was configured using the obtained light diffusion sheet. Laser light (NIHON KAGAKA ENG NEO-20MS) was irradiated vertically from the front direction, and the intensity of the reflected light (diffusion intensity) corresponding to the diffusion angle θ1 was measured. The measurement results are shown in FIG. As is clear from FIG. 21, the fine particle-dispersed light diffusion sheet of Reference Example 1 having a droplet phase structure (sea-island structure) exhibits a Gaussian distribution-type diffusion strength, whereas the sheet of the example has a specific direction (diffusion). Diffuse light is directed at an angle of about 7 °.
(Direction 2)
A reflective LCD model device similar to that shown in FIG. 2 was constructed, spotlight white light was irradiated from an oblique direction, and the intensity of light reflected in the vertical direction was measured (FIG. 5). The intensity of the reflected light in the vertical direction corresponding to the incident angle (diffusion angle θ2) was evaluated according to the following criteria.
[0143]
A: Bright
B: Normally
C: Dark
The results are shown in Table 2.
[0144]
[Table 2]

[0145]
As is clear from Table 2, the transmissive light diffusion sheet of the example has high directivity with respect to a predetermined diffusion angle (incident angle).
[0146]
Example 3
Example 1 was repeated except that the heat treatment temperature was 230 ° C., the heat treatment time was 10 minutes, and the sheet thickness was 14 μm. The obtained sheet was observed with a transmission optical microscope. The sheet had a co-continuous phase structure, and the average interphase distance of the continuous phase was about 6 μm. A schematic diagram of this co-continuous phase structure is shown in FIG.
[0147]
Example 4
Example 3 was repeated except that the sheet thickness was 8 μm. When the obtained sheet was observed with a transmission optical microscope, it had a co-continuous phase structure, and the average interphase distance of the continuous phase was about 4 μm.
[0148]
Example 5
Example 3 was performed except that the sheet thickness was 10 μm. When the obtained sheet was observed with a transmission optical microscope, it had a co-continuous phase structure, and the average interphase distance of the continuous phase was about 4 μm.
[0149]
Example 6
Example 5 was repeated except that the heat treatment time was 7 minutes. When the obtained sheet was observed with a transmission optical microscope, it had a co-continuous phase structure, and the average interphase distance between the continuous phases was about 3 μm.
[0150]
Example 7
Example 5 was repeated except that the heat treatment time was 14 minutes. When the obtained sheet was observed with a transmission optical microscope, it had an intermediate structure between a co-continuous phase structure and a droplet phase structure, and the average interphase distance of the continuous phase was about 6 μm.
[0151]
The directivity of the sheets obtained in Examples 3 to 7 was evaluated in the same manner as in Example 1 (Directivity 2). The results are shown in Table 3.
[0152]
[Table 3]

[0153]
As is apparent from Table 3, the transmissive light diffusion sheet of the example has high directivity with respect to a predetermined diffusion angle (incident angle).
[0154]
Examples 8-13
Polymethylmethacrylate (PMMA-1 to 4) and styrene acrylonitrile copolymer (SAN-1 to 3) were blended according to the ratio shown in Table 4, dissolved and mixed in a solvent (ethyl acetate), and then the resulting solution ( The dope was cast on an alkali-free glass as a support by a bar coating method, and air-dried all day and night to prepare a sheet having a predetermined thickness. Thereafter, the sheet on the glass plate was placed in an oven and heat treated at the temperature and time described in Table 4. After the heat treatment, the entire glass plate was immersed in cold water. The sheet was peeled from the glass plate and dried to obtain a light scattering sheet. The light scattering sheet thus obtained was evaluated for total light transmittance, light scattering property, straight light / diffuse light ratio, and brightness according to the following methods.
[0155]
(Total light transmittance)
Based on JIS K7105, the total light transmittance (transmittance) was measured using a haze meter (NDH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.).
[0156]
(Light scattering)
Using the laser light scattering automatic measuring apparatus (manufactured by Nihon Kagaku Engineering Co., Ltd.) shown in FIG. )).
[0157]
(Straight light / diffuse light ratio (I (θ0) / I (θmax))
By the light scattering test, the light scattering intensity is plotted against the scattering angle, the intensity I (θ0) of the straight transmitted light that has passed straight through the sheet, and the intensity I (θmax) of the maximum scattered light (diffused light) The ratio of was calculated.
[0158]
(Brightness)
A reflective LCD model device similar to that shown in FIG. 2 was constructed, spotlight white light was irradiated from an oblique direction, and the intensity of light reflected in the vertical direction was measured (FIG. 5). The intensity of the reflected light in the vertical direction corresponding to the incident angle (diffusion angle θ2) was evaluated according to the following criteria.
[0159]
AA: Brighter than Example 13
A: Brighter than Example 13
B: Bright
The results are shown in Table 4, Table 5, FIG. 22 and FIG.
[0160]
[Table 4]

[0161]
[Table 5]

[0162]
As apparent from Tables 4 and 5, when the light scattering sheets of Examples 8 to 13 are used, the liquid crystal display images can be brightened. In particular, the light scattering sheets of Examples 8 to 12 composed of a polymer having a specific molecular weight have a high total light transmittance and a low straight light / diffuse light ratio (I (θ0) / I (θmax)). Therefore, external light can be taken in effectively. For this reason, the brightness of the liquid crystal image is extremely excellent.
[0163]
Example 14
50 parts by weight of polymethyl methacrylate (PMMA-4) and 50 parts by weight of a styrene-acrylonitrile copolymer (SAN-4) were dissolved in 400 parts by weight of a methylene chloride / methanol mixed solvent (9/1, weight ratio). The solution was cast on a polyethersulfone sheet (PES-1) to form a coating sheet having a thickness of 115 μm. This coating sheet was heated at 230 ° C. for 10 minutes. After the heat treatment, the coating sheet was immersed in a cold water bath and sufficiently dried. When the obtained sheet was observed with a transmission optical microscope, the sheet had an intermediate structure between a co-continuous phase structure and a droplet phase structure, and the average interphase distance of the continuous phase was about 6 μm. The total light transmittance of the sheet was 93%.
[0164]
The pressure-sensitive adhesive layer 91 of the polarizing plate (polarizing plate A) 1 bonds the polarizing plate 1 and the polyethersulfone sheet layer of the co-continuous phase structure sheet (light scattering sheet 2), and the surface of the light scattering sheet 2 The acrylic pressure-sensitive adhesive layer 92 was applied to the (light scattering layer) and dried to produce a composite sheet A (laminated sheet) (FIG. 6). The surface of the polarizing plate 1 was protected with a protective film (not shown), and the surface of the pressure-sensitive adhesive layer 92 was protected with a PET film (thickness 50 μm) (release film) coated with a silicon release agent.
[0165]
The protective film and the release film on the surface of the composite sheet A were peeled off, and the composite sheet A was adhered to the liquid crystal cell 12 with the adhesive layer 92, whereby the liquid crystal display element of FIG. Note that a glass plate (thickness 1 mm) is used for the front substrate 22a and the back substrate 22b of the liquid crystal cell 12, an indium tin oxide thin film is used for the transparent front electrode 4a, and an aluminum thin film is used for the light reflective back electrode 4c. It was.
[0166]
Since the composite sheet A in which the polarizing plate 1 and the light scattering sheet 2 are laminated is used, the composite sheet A can be attached in the polarizing plate attaching step of the liquid crystal display element, and the production line of the liquid crystal display element is changed. The liquid crystal display element which has the light-scattering sheet 2 was able to be manufactured without this. For this reason, a reflective liquid crystal display element with improved image visibility capable of preventing specular reflection could be manufactured without increasing the cost and without reducing the yield.
[0167]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed.
[0168]
Example 15
After the light scattering sheet 2 was bonded to the surface of the liquid crystal cell 12, the reflective liquid crystal display element shown in FIG. 7 was formed by attaching the polarizing plate 1 to the surface of the light scattering sheet 2.
[0169]
Although the manufacturing process is complicated as compared with Example 14, this liquid crystal display element was excellent in the visibility of the display image as in Example 14.
[0170]
  Reference example 2
  The phase difference plate 3 and the light scattering sheet (light scattering sheet of Reference Example 1) 2 were bonded together with the pressure-sensitive adhesive layer 93 of the phase difference plate (phase difference plate A) 3. The composite sheet B (laminated sheet) (FIG. 8) was manufactured by apply | coating the acrylic adhesive layer 92 to the surface of the light-scattering sheet 2, and drying. The surface of the retardation film 3 was protected with a protective film (not shown), and the surface of the pressure-sensitive adhesive layer 92 was protected with a PET film (thickness 50 μm) (release film) coated with a silicon release agent.
[0171]
After the protective film and the release film of the composite sheet B are peeled off and the composite sheet B is attached to the liquid crystal cell 12 by the adhesive layer 92, a polarizing plate (polarizing plate A) is attached to the surface of the composite sheet B. Thus, the liquid crystal display element of FIG. 9 was manufactured. Note that a glass plate (thickness 1 mm) is used for the front substrate 22a and the back substrate 22b of the liquid crystal cell 12, an indium tin oxide thin film is used for the transparent front electrode 4a, and an aluminum thin film is used for the light reflective back electrode 4c. It was.
[0172]
Since the composite sheet B of the retardation film 3 and the light scattering sheet 1 is used, the composite sheet B can be attached in the retardation plate attaching process of the liquid crystal display element, and the production line of the liquid crystal display element is changed. A liquid crystal display element having a light scattering sheet could be produced without any problems. For this reason, a reflective liquid crystal display element with improved image visibility capable of preventing specular reflection could be manufactured without increasing the cost and without reducing the yield.
[0173]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed.
[0174]
  Reference example 3
  90 parts by weight of amorphous copolyester (PETG-1) as a transparent base resin and 10 parts by weight of a thermoplastic resin (GPPS-1) as a fine particle dispersion component were each dried at 70 ° C. for 4 hours, and then Banbury mixer Kneaded. The kneaded resin composition was supplied to an extruder, melted at 240 ° C., extruded from a T-die into a sheet, and cooled and individualized with a cooling drum having a surface temperature of 25 ° C. (melt film formation). The obtained sheet (light scattering sheet 2) had a thickness of 120 μm and a total light transmittance of 91%.
[0175]
The reflective plate 5 and the sheet having the fine particle dispersion structure (light scattering sheet 2) are bonded together by the adhesive layer 95 of the reflective plate (reflecting plate A) 5, and the acrylic adhesive layer 92 is attached to the surface of the light scattering sheet 2. Was applied and dried to produce a composite sheet C (laminated sheet) (FIG. 10). The surface of the reflector 5 was protected with a protective film (not shown), and the surface of the adhesive layer 92 was protected with a PET film (thickness 50 μm) (release film) coated with a silicon-based release agent.
[0176]
The protective film and the release film on the surface of the composite sheet C are peeled off, and the composite sheet C is attached to the back surface of the liquid crystal cell 12 by the adhesive layer 92. The liquid crystal display element of FIG. 11 was manufactured by affixing the plate 1. Note that a plastic sheet (PES-1) was used for the front substrate 22a and the back substrate 22b of the liquid crystal cell 12, and striped transparent electrodes made of an indium tin oxide thin film were formed as the transparent front electrode 4a and the back electrode 4b.
[0177]
Since the composite sheet C in which the reflector 5 and the light scattering sheet 2 are laminated is used, the composite sheet C can be attached in the reflector attaching process of the liquid crystal display element, and the production line of the liquid crystal display element is changed. The liquid crystal display element which has the light-scattering sheet 2 was able to be manufactured without this. For this reason, a reflective liquid crystal display element with improved image visibility capable of preventing specular reflection could be manufactured without increasing the cost and without reducing the yield.
[0178]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed.
[0179]
  Example 16
  The polarizing plate 1 and the retardation plate (retardation plate B) 3 are bonded together by the adhesive layer 91 of the polarizing plate (polarizing plate A) 1, and the retardation plate 3 and light are bonded by the adhesive layer 93 of the retardation plate 3. A scattering sheet (light scattering sheet of Example 14) 2 was bonded. An acrylic pressure-sensitive adhesive layer 92 was applied to the surface of the light scattering sheet 2 and dried to produce a composite sheet D (laminated sheet) (FIG. 12). The surface of the polarizing plate 1 was protected with a protective film (not shown), and the surface of the pressure-sensitive adhesive layer 92 was protected with a PET film (thickness 50 μm) (release film) coated with a silicon release agent.
[0180]
When the liquid crystal display element was manufactured using the composite sheet D which laminated | stacked the polarizing plate 1, the phase difference plate 3, and the light-scattering sheet 2, it replaced with the sticking process of the polarizing plate of a liquid crystal display element, and a phase difference plate sticking process. Thus, the composite sheet D could be attached in one step, and the liquid crystal display element having the light scattering sheet 2 could be manufactured by simplifying the production line of the liquid crystal display element. For this reason, it was possible to manufacture a reflective liquid crystal display element with improved image visibility capable of preventing specular reflection without reducing cost and yield.
[0181]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed.
[0182]
  Reference example 4
  By forming the ITO transparent conductive layer 4 (thickness: 450 Å) by sputtering on the surface of the light scattering sheet 2 of Reference Example 1, the transparent conductive sheet of FIG. 13 was obtained. The surface resistance of the transparent conductive layer was 100Ω / □. The sheet thickness, total light transmittance, and light scattering property were the same as those of the light scattering sheet of Reference Example 1.
[0183]
  Reference Example 5
  Reference example 4By forming a static electricity removal layer (thickness 50 angstrom) of ITO by sputtering on the transparent conductive layer non-formation surface (non-deposition surface) of the transparent conductive sheet, the static electricity removal layer 13, the transparent conductive layer 4, and the light scattering sheet A transparent conductive sheet laminated with 2 was obtained (FIG. 14). The surface resistance of the static electricity removing layer was 20 kΩ / □. Sheet thickness, total light transmittance, and light scattering areReference example 4This was the same as the light scattering sheet.
[0184]
  Example17
  50 parts by weight of polymethyl methacrylate (PMMA-4) and 50 parts by weight of styrene-acrylonitrile copolymer (SAN-5) were dissolved in a methylene chloride / methanol mixed solvent (9/1 (weight ratio). It was cast on a sulfone sheet (PES-1), dried, and then heat treated for 10 minutes at 230 ° C. After being immersed in cold water and cooled, it was sufficiently dried to obtain a light scattering sheet (sheet thickness 115 μm, total When the light scattering sheet was observed with a transmission microscope, the sheet had a co-continuous phase structure, and the average interphase distance between the continuous phases was about 6 μm. The scattering sheet was able to direct diffused light at a diffusion angle of about 7 °.
[0185]
A transparent conductive layer having a thickness of 450 angstroms is formed by sputtering ITO on the surface of the light scattering sheet on the co-continuous phase side, so that the transparent body is transparent on the light scattering layer side of the laminate of the base sheet 23 and the light scattering layer 21. A transparent conductive sheet (FIG. 15) on which the conductive layer 4 was laminated was obtained. The surface resistance of the transparent conductive layer was 100Ω. The sheet thickness, total light transmittance, and light scattering property were the same as those of the light scattering sheet before forming the transparent conductive layer.
[0186]
  Example18
  Example except that a transparent conductive layer is formed on the PES surface (non-continuous-phase surface) of the light scattering sheet17In the same manner, a transparent conductive sheet (FIG. 16) was obtained. The thickness of the transparent conductive layer was 450 Å, and the surface resistance was 100Ω / □. Sheet thickness, total light transmittance, and light scattering properties are examples.17This was the same as the light scattering sheet.
[0187]
  Example19
  Example18The STN-type reflective plastic liquid crystal display element shown in FIG. 4 is obtained by patterning the transparent conductive sheet obtained in the above in the form of stripes by photolithographic processing and using the processed sheet as a front substrate and a back substrate. Formed. Polarizing plate A was used for polarizing plate 1, retardation plate A was used for retardation plate 3, and reflecting plate B was used for reflecting plate 5. The thickness of the liquid crystal display element was about 650 μm.
[0188]
When this reflective plastic liquid crystal display element was used to display a screen under the illumination of a fluorescent lamp, reflected light with a diffusion angle of 0 ° corresponding to specular reflection was reduced, and directivity was imparted to the diffused light. In addition, a sharp image with little image blur could be formed, and a clear display screen with high contrast was observed.
[0189]
  Reference example6
  The following sheets are used as the front substrate and the back substrate, and the embodiment is applied to the front substrate.17Except for laminating the light scattering sheet 2 of Example19In the same manner, a reflective plastic liquid crystal display element was formed (FIG. 17). The thickness of the liquid crystal display element was about 770 μm.
[0190]
  (Front electrode plate and back electrode plate)
  Example on one surface of polyethersulfone sheet (PES-1)17In the same manner, an ITO transparent conductive layer (thickness: 450 Å) was formed. The transparent conductive layer of this sheet was patterned into a stripe shape by photolithography, thereby forming sheets for the front electrode plate 7a and the back electrode plate 7b.
[0191]
  Example under fluorescent lighting19(Fig. 4) and reference examples6When the screen display of the reflective plastic liquid crystal display element of FIG.19In the reflective plastic liquid crystal display element, no fluorescent lamp image was confirmed, and the image visibility was excellent.
[0192]
  Example19And reference examples6As is clear fromReference Examples 4 and 5, andExample 17~19In the liquid crystal display element, the transparent conductive sheet not only has a light scattering property but also can be used as an electrode plate of the liquid crystal display element, so that it is not necessary to use a separate light scattering sheet. Therefore, the thickness of the liquid crystal display element can be reduced.19And reference examples6Can be reduced by about 120 μm. For this reason, image blurring can be prevented and a sharp display screen with high contrast can be obtained.
[0193]
  Example 20
  A polarizing plate B is used as the polarizing plate 1, and the light scattering sheet 2 is attached to the front electrode support plate 22 a of the liquid crystal cell 12 without forming the laminated sheet A in advance. A reflective liquid crystal display element of FIG. 7 was formed in the same manner as in Example 14 except that the attachment was performed.
[0194]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed. Further, even when the surface of the reflective liquid crystal display element (polarizing plate 1) was rubbed with steel wool (# 0000), it was hardly damaged.
[0195]
  Comparative Example 1
  Example 2 except that the polarizing plate (polarizing plate B) 1 is attached to the front substrate 22a of the liquid crystal cell 12, and the light scattering sheet 2 is attached to the surface of the polarizing plate 1.0The reflective liquid crystal display element shown in FIG.
[0196]
  When the display image of the reflective liquid crystal display element is visually confirmed under the illumination of a fluorescent lamp, although the specular reflection is reduced by the light scattering sheet 2, Example 20The display screen was unclear compared with the liquid crystal display element. Further, the surface of the reflective liquid crystal display element (light scattering sheet 2) was scratched with steel wool (# 0000).
[0197]
  Reference Example 7
  Example 2 except that the light scattering sheet of Reference Example 1 is used as the light scattering sheet 20A reflective liquid crystal display device was manufactured in the same manner as described above.
[0198]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed. Further, even when the surface of the reflective liquid crystal display element (polarizing plate 1) was rubbed with steel wool (# 0000), it was hardly damaged.
[0199]
  Reference Example 8
  The polarizing plate 1 is used as the polarizing plate 1, the retardation plate B is used as the retardation plate 3, and the reflecting plate B is used as the reflecting plate 5. And the phase difference plate 3 and the light scattering sheet 2 and the reflection plate 5 are adhered to the back surface of the liquid crystal cell 12Reference example 3The reflective liquid crystal display element shown in FIG. Since the light scattering sheet 2 has a slight retardation, the light scattering sheet 2 is bonded to the back electrode substrate so that the alignment axis of the light scattering sheet 2 coincides with the polarization axis of the polarizing plate. It was.
[0200]
When the display image of the reflective liquid crystal display element was visually confirmed under the illumination of a fluorescent lamp, the specular reflection was reduced, and a clear display screen with excellent contrast and high contrast was observed. Further, even when the surface of the reflective liquid crystal display element (polarizing plate 1) was rubbed with steel wool (# 0000), it was hardly damaged.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a liquid crystal display element of the present invention.
FIG. 2 is a schematic view for explaining a method for evaluating directivity of a light scattering sheet.
FIG. 3 is a schematic diagram for explaining a method of measuring the intensity of straight transmitted light and diffuse transmitted light of a light scattering sheet.
FIG. 4 is a schematic sectional view showing another example of the liquid crystal display element of the present invention.
FIG. 5 is a schematic diagram for explaining another evaluation method of directivity of a light scattering sheet.
FIG. 6 is a schematic cross-sectional view showing an example of the composite sheet of the present invention.
FIG. 7 is a schematic sectional view showing still another example of the liquid crystal display element of the present invention.
FIG. 8 is a schematic sectional view showing another example of the composite sheet of the present invention.
FIG. 9 is a schematic sectional view showing another example of the liquid crystal display element of the present invention.
FIG. 10 is a schematic sectional view showing still another example of the composite sheet of the present invention.
FIG. 11 is a schematic cross-sectional view showing still another example of the liquid crystal display element of the present invention.
FIG. 12 is a schematic sectional view showing another example of the composite sheet of the present invention.
FIG. 13 is a schematic sectional view showing still another example of the composite sheet of the present invention.
FIG. 14 is a schematic sectional view showing another example of the composite sheet of the present invention.
FIG. 15 is a schematic sectional view showing still another example of the composite sheet of the present invention.
FIG. 16 is a schematic sectional view showing another example of the composite sheet of the present invention.
FIG. 17 is a reference example.6It is a schematic sectional drawing of this liquid crystal display element.
18 is a schematic cross-sectional view of a liquid crystal display element of Comparative Example 1. FIG.
FIG. 19 is a schematic diagram showing the measurement results of the sheet obtained in Example 1 with a transmission optical microscope.
FIG. 20 is a schematic diagram showing measurement results of a sheet obtained in Example 3 using a transmission optical microscope.
FIG. 21 is a graph showing the directivity of the light scattering sheet.
FIG. 22 is a semi-logarithmic graph showing the measurement results of the intensity of straight transmitted light and diffuse transmitted light of a light scattering sheet.
FIG. 23 is a graph showing the measurement results of the intensity of the straight transmitted light and diffuse transmitted light of the light scattering sheet.
[Explanation of symbols]
1 ... Polarizing plate
2, 2a, 2b ... Light scattering sheet
3 ... retardation plate
4, 4a, 4b, 4c ... conductive layer
5 ... Reflector
7a, 7b, 7c ... electrode plate
12 ... Liquid crystal cell
21, 21a, 21b ... Light scattering layer
22a, 22b ... substrate
23, 23a, 23b ... base material sheet

Claims (18)

Refractive index is different from each other and styrene resin, (meth) acrylic resin, vinyl ether resin, halogen-containing resin, polycarbonate resin, polyester resin, polyamide resin, silicone resin, cellulose derivative, and rubber or elastomer. A light scattering sheet comprising a light scattering layer in which an isotropic bicontinuous phase structure is formed by a plurality of selected polymers, wherein incident light diffuses isotropically, and a diffusion angle of 3 to 60 ° The diffused light intensity has a maximum value, the total light transmittance is 70 to 100%, and when the transmitted light of the light scattering sheet is plotted against the diffusion angle (θ), the intensity I (θ0) of the straight transmitted light ) And the intensity I (θ _max ) of the maximum diffuse transmitted light (I (θ 0 ) / I (θ _max )) is 3000/1 to 1/1 .   The light scattering sheet according to claim 1, wherein an average interphase distance between co-continuous phases is 1 to 20 μm.   The light scattering sheet according to claim 1, wherein the difference in refractive index between the plurality of polymers is 0.01 to 0.2.   The light-scattering sheet of Claim 1 comprised by the some polymer which shows the phase-separation property of a lower critical solution temperature (LCST) type.   The light-scattering sheet according to claim 4, wherein a critical eutectic temperature of the composition composed of a plurality of polymers is 50 to 300 ° C.   The light scattering sheet according to claim 1, wherein the light scattering sheet comprises a plurality of polymers having a weight average molecular weight of 10,000 to 300,000.   The first polymer and the second polymer are different in refractive index from each other, and the first polymer and the second polymer are lower critical solution temperature (LCST) type or upper critical solution temperature (UCST) type. The light scattering sheet according to claim 1, wherein the ratio of the first polymer and the second polymer is the former / the latter = 10/90 to 90/10 (weight ratio).   The light scattering sheet according to claim 7, wherein the lower critical solution temperature is 80 to 250 ° C.   The light scattering sheet according to claim 1, wherein an average inter-phase distance of the co-continuous phases is 2 to 10 µm, and the sheet thickness is 1 to 300 µm.   The light-scattering composite sheet in which at least 1 type chosen from the polarizing plate, the phase difference plate, the light reflection board, and the transparent conductive layer is formed in the at least one surface of the light-scattering sheet of Claim 1. The light-scattering composite sheet according to claim 10 , wherein the light-scattering composite sheet comprises a light-scattering sheet, a polarizing plate, and a retardation plate, wherein the polarizing plate is formed on the surface of the three-layer sheet. The light-scattering composite sheet according to claim 10 , wherein the light-scattering sheet is composed of a plurality of polymers having a refractive index difference of 0.01 to 0.2. A transparent front electrode plate having a transparent conductive layer and a substrate for supporting the transparent conductive layer, and a back electrode plate having a conductive layer and a substrate for supporting the conductive layer are disposed so that the conductive layers face each other. In a reflection type liquid crystal display device comprising a liquid crystal cell in which liquid crystal is sealed between conductive layers of both electrode plates and a polarizing plate disposed in front of the liquid crystal cell, the following (i) to (iii) A reflective liquid crystal display element having at least one light scattering sheet.
(i) The light scattering sheet according to claim 1, which is disposed between the polarizing plate and the front electrode plate.
(ii) The light scattering sheet according to claim 1, wherein the light scattering sheet is disposed between the back electrode plate and a reflection plate disposed behind the back electrode plate.
(iii) The light scattering sheet according to claim 1 as a substrate. Retardation plate is arranged between the polarizing plate and the liquid crystal cell, the light-scattering sheet according to claim 13, characterized in that disposed or between the phase difference plate and the liquid crystal cell of the polarizing plate and the retardation plate Liquid crystal display element. A light-scattering sheet, a polarizing plate, a retardation plate, at least one selected from the light reflection plate and the transparent conductive layer functional layer according to claim 13, wherein the light-scattering composite sheet constituted are arranged in Liquid crystal display element.   A liquid crystal display element comprising a liquid crystal cell in which liquid crystal is sealed and a polarizing plate disposed in front of the liquid crystal cell, the liquid crystal display element having a light scattering sheet according to claim 1.   A method for producing a light-scattering sheet, comprising forming a composition comprising a plurality of polymers having different refractive indexes from each other and forming an isotropic co-continuous phase structure by spinodal decomposition. 18. The production method according to claim 17 , wherein a sheet having LCST type phase separation is heated to a temperature lower than the lower critical eutectic temperature to form a co-continuous phase structure.

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