JP2005070097A - Laminated optical film, elliptically polarizing plate, and image display device - Google Patents

Abstract

An object of the present invention is to display an image with a small tone-reversal region in which the change in color of the display image is suppressed even when the image is viewed from diagonal directions up, down, left, and right with respect to the normal direction of the screen of the image display device. To provide a laminated optical film that can be used.
At least the homeotropic alignment liquid crystal layer (1), the direction in which the refractive index in the film plane is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. represents the refractive index of the respective axial when the _{nx 2,} ny 2, nz _2, an optical film (2) which satisfies nx 2> ny ₂ ≒ nz _2,, optically negative uniaxial property A laminated optical film, characterized in that an optical film (3) formed of a material and having the material tilted is laminated.
[Selection] FIG.

Description

（ただし、Ｒ^１ は水素原子またはメチル基を、ａは１〜６の正の整数を、Ｘ^１ は−ＣＯ_２ −基または−ＯＣＯ−基を、Ｒ^２ はシアノ基、炭素数１〜６のアルコキシ基、フルオロ基または炭素数１〜６のアルキル基を、ｂおよびｃは１または２の整数を示す。）で表されるモノマーユニットがあげられる。
【００３３】
またモノマーユニット（ｂ）は、直鎖状側鎖を有するものであり、たとえば、一般式（ｂ）：
【化２】

（ただし、Ｒ^３ は水素原子またはメチル基を、Ｒ^４ は炭素数１〜２２のアルキル基、炭素数１〜２２のフルオロアルキル基、または一般式（ｂ１）：
【化３】

ただし、ｄは１〜６の正の整数を、Ｒ^５ は炭素数１〜６のアルキル基を示す。）で表されるモノマーユニットがあげられる。
【００３４】
また、モノマーユニット（ａ）とモノマーユニット（ｂ）の割合は、特に制限されるものではなく、モノマーユニットの種類によっても異なるが、モノマーユニット（ｂ）の割合が多くなると側鎖型液晶ポリマーが液晶モノドメイン配向性を示さなくなるため、（ｂ）／｛（ａ）＋（ｂ）｝＝０．０１〜０．８（モル比）とするのが好ましい。特に０．１〜０．５とするのがより好ましい。
【００３５】
またホメオトロピック配向液晶フィルムを形成しうる液晶ポリマーとしては、前記液晶性フラグメント側鎖を含有するモノマーユニット（ａ）と脂環族環状構造を有する液晶性フラグメント側鎖を含有するモノマーユニット（ｃ）を含有する側鎖型液晶ポリマーがあげられる。
【００３６】
前記モノマーユニット（ｃ）はネマチック液晶性を有する側鎖を有するものであり、たとえば、一般式（ｃ）：
【化４】

（ただし、Ｒ^６ 水素原子またはメチル基を、ｈは１〜６の正の整数を、Ｘ^２ は−ＣＯ_２ −基または−ＯＣＯ−基を、ｅとｇは１または２の整数を、ｆは０〜２の整数を、Ｒ^７ はシアノ基、炭素数１〜１２のアルキル基を示す。）で表されるモノマーユニットがあげられる。
【００３７】
また、モノマーユニット（ａ）とモノマーユニット（ｃ）の割合は、特に制限されるものではなく、モノマーユニットの種類によっても異なるが、モノマーユニット（ｃ）の割合が多くなると側鎖型液晶ポリマーが液晶モノドメイン配向性を示さなくなるため、（ｃ）／｛（ａ）＋（ｃ）｝＝０．０１〜０．８（モル比）とするのが好ましい。特に０．１〜０．６とするのがより好ましい。
【００３８】
ホメオトロピック配向液晶層（１）を形成しうる液晶ポリマーは、前記例示のモノマーユニットを有するものに限られず、また前記例示モノマーユニットは適宜に組み合わせることができる。
【００３９】
前記側鎖型液晶ポリマーの重量平均分子量（ＧＰＣ）は、２千〜１０万であるのが好ましい。重量平均分子量をかかる範囲に調整することにより液晶ポリマーとしての性能を発揮する。側鎖型液晶ポリマーの重量平均分子量が過少では配向層の成膜性に乏しくなる傾向があるため、重量平均分子量は２．５千以上とするのがより好ましい。一方、重量平均分子量が過多では液晶としての配向性に乏しくなって均一な配向状態を形成しにくくなる傾向があるため、重量平均分子量は５万以下とするのがより好ましい。
【００４０】
なお、前記例示の側鎖型液晶ポリマーは、前記モノマーユニット（ａ）、モノマーユニット（ｂ）、モノマーユニット（ｃ）に対応するアクリル系モノマーまたはメタクリル系モノマーを共重合することにより調製できる。なお、モノマーユニット（ａ）、モノマーユニット（ｂ）、モノマーユニット（ｃ）に対応するモノマーは公知の方法により合成できる。共重合体の調製は、例えばラジカル重合方式、カチオン重合方式、アニオン重合方式などの通例のアクリル系モノマー等の重合方式に準じて行うことができる。なお、ラジカル重合方式を適用する場合、各種の重合開始剤を用いうるが、そのうちアゾビスイソブチロニトリルや過酸化ベンゾイルなどの分解温度が高くもなく、かつ低くもない中間的温度で分解するものが好ましく用いられる。
【００４１】
前記側鎖型液晶ポリマーには、光重合性液晶化合物を配合して液晶性組成物として用いることができる。光重合性液晶化合物は、光重合性官能基として、たとえば、アクリロイル基またはメタクリロイル基等の不飽和二重結合を少なくとも１つ有する液晶性化合物であり、ネマチック液晶性のものが賞用される。かかる光重合性液晶化合物としては、前記モノマーユニット（ａ）となるアクリレートやメタクリレートを例示できる。光重合性液晶化合物として、耐久性を向上させるには、光重合性官能基を２つ以上有するものが好ましい。このような光重合性液晶化合物として、たとえば、下記化５：
【化５】

（式中、Ｒは水素原子またはメチル基を、ＡおよびＤはそれぞれ独立して１，４−フェニレン基または１，４−シクロヘキシレン基を、Ｘはそれぞれ独立して−ＣＯＯ−基、−ＯＣＯ−基または−Ｏ−基を、Ｂは１，４−フェニレン基、１，４−シクロヘキシレン基、４，４’−ビフェニレン基または４，４’−ビシクロヘキシレン基を、ｍおよびｎはそれぞれ独立して２〜６の整数を示す。）で表される架橋型ネマチック性液晶モノマー等を例示できる。また、光重合性液晶化合物としては、前記化５における末端の「Ｈ_２ Ｃ＝ＣＲ−ＣＯ_２ −」を、ビニルエーテル基またはエポキシ基に置換した化合物や、「−（ＣＨ_２ ）_ｍ −」および／または「−（ＣＨ_２ ）_ｎ −」を「−（ＣＨ_２ ）_３ −Ｃ^＊ Ｈ（ＣＨ_３ ）−（ＣＨ_２ ）_２ −」または「−（ＣＨ_２ ）_２ −Ｃ^＊ Ｈ（ＣＨ_３ ）−（ＣＨ_２ ）_３ −」に置換した化合物を例示できる。
【００４２】
上記光重合性液晶化合物は、熱処理により液晶状態として、たとえば、ネマチック液晶層を発現させて側鎖型液晶ポリマーとともにホメオトロピック配向させることができ、その後に光重合性液晶化合物を重合または架橋させることによりホメオトロピック配向液晶フィルムの耐久性を向上させることができる。
【００４３】
液晶性組成物中の光重合性液晶化合物と側鎖型液晶ポリマーの比率は、特に制限されず、得られるホメオトロピック配向液晶フィルムの耐久性等を考慮して適宜に決定されるが、通常、光重合性液晶化合物：側鎖型液晶ポリマー（重量比）＝０．１：１〜３０：１程度が好ましく、特に０．５：１〜２０：１が好ましく、さらには１：１〜１０：１が好ましい。
【００４４】
前記液晶性組成物中には、通常、光重合開始剤を含有する。光重合開始剤は各種のものを特に制限なく使用できる。光重合開始剤としては、たとえば、チバスペシャルティケミカルズ社製のイルガキュア（Ｉｒｇａｃｕｒｅ）９０７，同１８４、同６５１、同３６９などを例示できる。光重合開始剤の添加量は、光重合液晶化合物の種類、液晶性組成物の配合比等を考慮して、液晶性組成物のホメオトロピック配向性を乱さない程度に加えられる。通常、光重合性液晶化合物１００重量部に対して、０．５〜３０重量部程度が好ましい。特に３重量部以上が好ましい。
【００４５】
ホメオトロピック配向液晶層（１）の作製は、基板上に、ホメオトロピック配向性側鎖型液晶ポリマーを塗工し、次いで当該側鎖型液晶ポリマーを液晶状態においてホメオトロピック配向させ、その配向状態を維持した状態で固定化することにより行う。また前記側鎖型液晶ポリマーと光重合性液晶化合物を含有してなるホメオトロピック配向液晶性組成物を用いる場合には、これを基板に塗工後、次いで当該液晶性組成物を液晶状態においてホメオトロピック配向させ、その配向状態を維持した状態で光照射することにより行う。
【００４６】
前記側鎖型液晶ポリマーまたは液晶性組成物を塗工する基板は、ガラス基板、金属箔、プラスチックシートまたはプラスチックフィルムのいずれの形状でもよい。プラスチックフィルムは配向させる温度で変化しないものであれば特に制限はなく，たとえば、ポリエチレンテレフタレート、ポリエチレンナフタレート等のポリエステル系ポリマー、ジアセチルセルロース、トリアセチルセルロース等のセルロース系ポリマー、ポリカーポネート系ポリマー、ポリメチルメタクリレート等のアクリル系ポリマー等の透明ポリマーからなるフィルムがあげられる。基板上に垂直配向膜は設けられていなくてもよい。基板の厚さは、通常、１０〜１０００μｍ程度である。
【００４７】
前記側鎖型液晶ポリマーまたは液晶性組成物を基板に塗工する方法は、当該側鎖型液晶ポリマーまたは液晶性組成物を溶媒に溶解した溶液を用いる溶液塗工方法または当該液晶ポリマーまたは液晶性組成物を溶融して溶融塗工する方法が挙げられるが、この中でも溶液塗工方法にて支持基板上に側鎖型液晶ポリマーまたは液晶性組成物の溶液を塗工する方法が好ましい。
【００４８】
上記の溶媒を用いて所望の濃度に調整した側鎖型液晶ポリマーまたは液晶性組成物の溶液を、基板上に塗工する方法としては、例えば、ロールコート法、グラビアコート法、スピンコート法、バーコート法などを採用することができる。塗工後、溶媒を除去し、基板上に液晶ポリマー層または液晶性組成物層を形成させる。溶媒の除去条件は、特に限定されず、溶媒をおおむね除去でき、液晶ポリマー層または液晶性組成物層が流動したり、流れ落ちたりさえしなければ良い。通常、室温での乾燥、乾燥炉での乾燥、ホットプレート上での加熱などを利用して溶媒を除去する。これらの塗工方法のなかでも本発明ではグラビアコート法を採用するのが、大面積を均一に塗工しやすい点で好ましい。
【００４９】
次いで、支持基板上に形成された側鎖型液晶ポリマー層または液晶性組成物層を液晶状態とし、ホメオトロピック配向させる。たとえば、側鎖型液晶ポリマーまたは液晶性組成物が液晶温度範囲になるように熱処理を行い、液晶状態においてホメオトロピック配向させる。熱処理方法としては、上記の乾燥方法と同様の方法で行うことができる。熱処理温度は、使用する側鎖型液晶ポリマーまたは液晶性組成物と支持基板の種類により異なるため一概には言えないが、通常６０〜３００℃、好ましくは７０〜２００℃の範囲において行う。また熱処理時間は、熱処理温度および使用する側鎖型液晶ポリマーまたは液晶性組成物や基板の種類によって異なるため一概には言えないが、通常１０秒〜２時間、好ましくは２０秒〜３０分の範囲で選択される。１０秒より短い場合、ホメオトロピック配向形成が十分に進行しないおそれがある。これらの配向温度、その処理時間のなかでも本発明では、配向温度８０〜１５０℃で、その処理時間を３０秒〜１０分間程度行うのが、作業性、量産性の点で好ましい。
【００５０】
熱処理終了後、冷却操作を行う。冷却操作としては、熱処理後のホメオトロピック配向液晶フィルムを、熱処理操作における加熱雰囲気中から、室温中に出すことによって行うことができる。また空冷、水冷などの強制冷却を行ってもよい。前記側鎖型液晶ポリマーのホメオトロピック配向層は、側鎖型液晶ポリマーのガラス転移温度以下に冷却することにより配向が固定化される。
【００５１】
液晶性組成物の場合には、このように固定化されたホメオトロピック液晶配向層に対して、光照射を行い光重合性液晶化合物を重合または架橋させて光重合性液晶化合物を固定化して、耐久性を向上したホメオトロピック配向液晶層を得る。光照射は、たとえば、紫外線照射により行う。紫外線照射条件は、十分に反応を促進するために、不活性気体雰囲気中とすることが好ましい。通常、約８０〜１６０ｍＷ／ｃｍ^２ の照度を有する高圧水銀紫外ランプが代表的に用いられる。メタハライドＵＶランプや白熱管などの別種ランプを使用することもできる。なお、紫外線照射時の液晶層表面温度が液晶温度範囲内になるように、コールドミラー、水冷その他の冷却処理あるいはライン速度を速くするなどして適宜に調整する。
【００５２】
このようにして、側鎖型液晶ポリマーまたは液晶性組成物の薄膜が生成され、配向性を維持したまま固定化することにより、ホメオトロピック配向液晶層（１）が得られる。本発明のホメオトロピック配向液晶フィルムの厚みは、特に制限されないが、塗工された前記側鎖型液晶ポリマーからなるホメオトロピック配向液晶フィルム層の厚みは０．５〜２００μｍ程度とするのが好ましい。０．５μｍ以下では膜厚が薄すぎるため厚み制御が困難である。２００μｍを超える場合には楕円偏光板として組み合わせて、画像表示装置に実施凹した場合に、上下左右の視野角が広がる方位がある一方、逆に狭くなる方位が発生してしまう場合がある。ホメオトロピック配向液晶層（１）は、基板から剥離して、または剥離することなく用いることができる。
【００５３】
光学フィルム（２）は、フィルム面内の屈折率が最大となる方向をＸ軸、Ｘ軸に垂直な方向をＹ軸、フィルムの厚さ方向をＺ軸とし、それぞれの軸方向の屈折率をｎｘ_２ 、ｎｙ_２ 、ｎｚ_２ とした場合に、ｎｘ_２ ＞ｎｙ_２ ≒ｎｚ_２ 、を満足するものを用いる。すなわち、三次元屈折率楕円体において一方向の主軸の屈折率が他の２方向の屈折率よりも大きい、光学的に正の一軸性を示す材料が用いられる。
【００５４】
光学フィルム（２）は、たとえば、高分子ポリマーフィルムを、面方向に一軸延伸処理することにより得られる。光学フィルム（２）を形成する高分子ポリマーとしては、たとえば、ポリカーボネート、ポリプロピレン等のポリオレフィン、ポリエチレンテレフタレート、ポリエチレンナフタレート等のポリエステル、ノルボルネン系ポリマー、ポリビニルアルコール、ポリビニルブチラール、ポリメチルビニルエーテル、ポリヒドロキシエチルアクリレート、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、メチルセルロース、ポリアリレート、ポリスルホン、ポリエーテルスルホン、ポリフェニレンスルファイド、ポリフェニレンオキサイド、ポリアリルスルホン、ポリビニルアルコール、ポリアミド、ポリイミド、ポリ塩化ビニル、トリアセチルセルロースなどのセルロース系ポリマー、アクリル系ポリマー、スチレン系ポリマーまたはこれらの二元系、三元系各種共重合体、グラフト共重合体、ブレンド物などがあげられる。これらのなかでもノルボルネン系ポリマーが好適である。
【００５５】
また、棒状ネマチック液晶性化合物を利用することもできる。棒状ネマチック液晶性化合物は傾斜配向させることができ、その傾斜配向状態は、その分子構造、配向膜の種類および光学異方性層内に適宜く加えられる添加剤（たとえば、可塑剤、バインダー、界面活性剤）の使用によって制御できる。
【００５６】
光学フィルム（２）の正面位相差（（ｎｘ_２ −ｎｙ_２ ）×ｄ_２ （厚さ：ｎｍ））は、０〜５００ｎｍであることが好ましく、１〜３５０ｎｍであることがさらに好ましい。厚み方向の位相差（（ｎｘ_２ −ｎｚ_２ ）×ｄ_２ ）は、０〜５００ｎｍであることが好ましく、１〜３５０ｎｍであることがさらに好ましい。
【００５７】
光学フィルム（２）の厚さ（ｄ_２ ）は特に制限されないが、１〜２００μｍが好ましく、さらに好ましくは２〜８０μｍである。
【００５８】
光学フィルム（２）として、λ／４板、λ／２板を用いる場合には、正面位相差が、それぞれ所定位相差になるように適宜に調整されたものが用いられる。
【００５９】
光学フィルム（３）を形成する、光学的に負の一軸性を示す材料とは、三次元屈折率楕円体において、一方向の主軸の屈折率が他の２方向の屈折率よりも小さい材料を示す。
【００６０】
光学的に負の一軸性を示す材料としては、たとえば、ポリイミド系材料や、ディスコティック液晶化合物などの液晶系材料があげられる。また、これらの材料を主成分とし、その他のオリゴマーやポリマーと混合、反応させて、負の一軸性を示す材料が傾斜配向した状態を固定化してフィルム状にしたものがあげられる。ディスコティック液晶化合物を用いる場合、液晶性分子の傾斜配向状態は、その分子構造、配向膜の種類および光学異方性層内に適宜加えられる添加剤（たとえば、可塑剤、バインダー、界面活性剤）の使用によって制御できる。
【００６１】
光学フィルム（３）のフィルム面内の屈折率が最大となる方向をＸ軸、Ｘ軸に垂直な方向をＹ軸、フィルムの厚さ方向をＺ軸とし、それぞれの軸方向の屈折率をｎｘ_３ 、ｎｙ_３ 、ｎｚ_３ とした場合に、光学フィルム（３）の正面位相差（（ｎｘ_３ −ｎｙ_３ ）×ｄ_３ （厚さ：ｎｍ））は、０〜２００ｎｍであることが好ましく、１〜１５０ｎｍであることがさらに好ましい。厚み方向の位相差（（ｎｘ_３ −ｎｚ_３ ）×ｄ_３ ）は、１０〜４００ｎｍであることが好ましく、５０〜３００ｎｍであることがさらに好ましい。
【００６２】
光学フィルム（３）の厚さ（ｄ_３ ）は特に制限されないが、１〜２００μｍが好ましく、さらに好ましくは、２〜１５０μｍである。
【００６３】
偏光板（Ｐ）は、通常、偏光子の片側または両側に保護フィルムを有するものである。偏光子は、特に制限されず、各種のものを使用できる。偏光子としては、たとえば、ポリビニルアルコール系フィルム、部分ホルマール化ポリビニルアルコール系フィルム、エチレン・酢酸ビニル共重合体系部分ケン化フィルム等の親水性高分子フィルムに、ヨウ素や二色性染料等の二色性物質を吸着させて一軸延伸したもの、ポリビニルアルコールの脱水処理物やポリ塩化ビニルの脱塩酸処理物等のポリエン系配向フィルム等があげられる。これらのなかでもポリビニルアルコール系フィルムを延伸して二色性材料（沃素、染料）を吸着・配向したものが好適に用いられる。偏光子の厚さも特に制限されないが、５〜８０μｍ程度が一般的である。
【００６４】
ポリビニルアルコール系フィルムをヨウ素で染色し一軸延伸した偏光子は、たとえば、ポリビニルアルコールをヨウ素の水溶液に浸漬することによって染色し、元長の３〜７倍に延伸することで作製することができる。必要に応じてホウ酸やヨウ化カリウムなどの水溶液に浸漬することもできる。さらに必要に応じて染色の前にポリビニルアルコール系フィルムを水に浸漬して水洗してもよい。ポリビニルアルコール系フィルムを水洗することでポリビニルアルコール系フィルム表面の汚れやブロッキング防止剤を洗浄することができるほかに、ポリビニルアルコール系フィルムを膨潤させることで染色のムラなどの不均一を防止する効果もある。延伸はヨウ素で染色した後に行っても良いし、染色しながら延伸してもよし、また延伸してからヨウ素で染色してもよい。ホウ酸やヨウ化カリウムなどの水溶液中や水浴中でも延伸することができる。
【００６５】
前記偏光子の片側または両側に設けられている保護フィルムには、透明性、機械的強度、熱安定性、水分遮蔽性、等方性などに優れるものが好ましい。前記保護フィルムの材料としては、例えばポリエチレンテレフタレートやポリエチレンナフタレート等のポリエステル系ポリマー、ジアセチルセルロースやトリアセチルセルロース等のセルロース系ポリマー、ポリメチルメタクリレート等のアクリル系ポリマー、ポリスチレンやアクリロニトリル・スチレン共重合体（ＡＳ樹脂）等のスチレン系ポリマー、ポリカーボネート系ポリマーなどがあげられる。また、ポリエチレン、ポリプロピレン、シクロ系ないしはノルボルネン構造を有するポリオレフィン、エチレン・プロピレン共重合体の如きポリオレフィン系ポリマー、塩化ビニル系ポリマー、ナイロンや芳香族ポリアミド等のアミド系ポリマー、イミド系ポリマー、スルホン系ポリマー、ポリエーテルスルホン系ポリマー、ポリエーテルエーテルケトン系ポリマー、ポリフェニレンスルフィド系ポリマー、ビニルアルコール系ポリマー、塩化ビニリデン系ポリマー、ビニルブチラール系ポリマー、アリレート系ポリマー、ポリオキシメチレン系ポリマー、エポキシ系ポリマー、あるいは前記ポリマーのブレンド物などが保護フィルムを形成するポリマーの例としてあげられる。その他、アクリル系やウレタン系、アクリルウレタン系やエポキシ系、シリコーン系等の熱硬化型ないし紫外線硬化型樹脂などをフィルム化したものなどがあげられる。
【００６６】
また、特開２００１−３４３５２９号公報（ＷＯ０１／３７００７）に記載のポリマーフィルム、たとえば、（Ａ）側鎖に置換および／または非置換イミド基を有する熱可塑性樹脂と、（Ｂ）側鎖に置換および／非置換フェニルならびにニトリル基を有する熱可塑性樹脂を含有する樹脂組成物があげられる。具体例としてはイソブチレンとＮ−メチルマレイミドからなる交互共重合体とアクリロニトリル・スチレン共重合体とを含有する樹脂組成物のフィルムがあげられる。フィルムは樹脂組成物の混合押出品などからなるフィルムを用いることができる。
【００６７】
偏光特性や耐久性などの点より、特に好ましく用いることができる保護フィルムは、表面をアルカリなどでケン化処理したトリアセチルセルロースフィルムである。保護フィルムの厚さは、適宜に決定しうるが、一般には強度や取扱性等の作業性、薄層性などの点より１０〜５００μｍ程度である。特に２０〜３００μｍが好ましく、３０〜２００μｍがより好ましい。
【００６８】
また、保護フィルムは、できるだけ色付きがないことが好ましい。したがって、Ｒｔｈ＝［（ｎｘ＋ｎｙ）／２−ｎｚ］・ｄ（ただし、ｎｘ、ｎｙはフィルム平面内の主屈折率、ｎｚはフィルム厚方向の屈折率、ｄはフィルム厚みである）で表されるフィルム厚み方向の位相差値が−９０ｎｍ〜＋７５ｎｍである保護フィルムが好ましく用いられる。かかる厚み方向の位相差値（Ｒｔｈ）が−９０ｎｍ〜＋７５ｎｍのものを使用することにより、保護フィルムに起因する偏光板の着色（光学的な着色）をほぼ解消することができる。厚み方向位相差値（Ｒｔｈ）は、さらに好ましくは−８０ｎｍ〜＋６０ｎｍ、特に−７０ｎｍ〜＋４５ｎｍが好ましい。
【００６９】
保護フィルムとしては、偏光特性や耐久性などの点より、トリアセチルセルロース等のセルロース系ポリマーが好ましい。特にトリアセチルセルロースフィルムが好適である。なお、偏光子の両側に保護フィルムを設ける場合、その表裏で同じポリマー材料からなる保護フィルムを用いてもよく、異なるポリマー材料等からなる保護フィルムを用いてもよい。前記偏光子と保護フィルムとは通常、水系粘着剤等を介して密着している。水系接着剤としては、ポリビニルアルコール系接着剤、ゼラチン系接着剤、ビニル系ラテックス系、水系ポリウレタン、水系ポリエステル等を例示できる。
【００７０】
前記保護フィルムとしては、ハードコート層や反射防止処理、スティッキング防止や、拡散ないしアンチグレアを目的とした処理を施したものを用いることができる。
【００７１】
ハードコート処理は偏光板表面の傷付き防止などを目的に施されるものであり、例えばアクリル系、シリコーン系などの適宜な紫外線硬化型樹脂による硬度や滑り特性等に優れる硬化皮膜を保護フィルムの表面に付加する方式などにて形成することができる。反射防止処理は偏光板表面での外光の反射防止を目的に施されるものであり、従来に準じた反射防止膜などの形成により達成することができる。また、スティッキング防止処理は隣接層との密着防止を目的に施される。
【００７２】
またアンチグレア処理は偏光板の表面で外光が反射して偏光板透過光の視認を阻害することの防止等を目的に施されるものであり、例えばサンドブラスト方式やエンボス加工方式による粗面化方式や透明微粒子の配合方式などの適宜な方式にて保護フィルムの表面に微細凹凸構造を付与することにより形成することができる。前記表面微細凹凸構造の形成に含有させる微粒子としては、例えば平均粒径が０．５〜５０μｍのシリカ、アルミナ、チタニア、ジルコニア、酸化錫、酸化インジウム、酸化カドミウム、酸化アンチモン等からなる導電性のこともある無機系微粒子、架橋又は未架橋のポリマー等からなる有機系微粒子などの透明微粒子が用いられる。表面微細凹凸構造を形成する場合、微粒子の使用量は、表面微細凹凸構造を形成する透明樹脂１００重量部に対して一般的に２〜５０重量部程度であり、５〜２５重量部が好ましい。アンチグレア層は、偏光板透過光を拡散して視角などを拡大するための拡散層（視角拡大機能など）を兼ねるものであってもよい。
【００７３】
なお、前記反射防止層、スティッキング防止層、拡散層やアンチグレア層等は、保護フィルムそのものに設けることができるほか、別途光学層として透明保護層とは別体のものとして設けることもできる。
【００７４】
粘着剤層（ａ）を形成する粘着剤は特に制限されないが、例えばアクリル系重合体、シリコーン系ポリマー、ポリエステル、ポリウレタン、ポリアミド、ポリエーテル、フッ素系やゴム系などのポリマーをベースポリマーとするものを適宜に選択して用いることができる。特に、アクリル系粘着剤の如く光学的透明性に優れ、適度な濡れ性と凝集性と接着性の粘着特性を示して、耐候性や耐熱性などに優れるものが好ましく用いうる。
【００７５】
粘着剤層の形成は、適宜な方式で行うことができる。その例としては、例えばトルエンや酢酸エチル等の適宜な溶剤の単独物又は混合物からなる溶媒にベースポリマーまたはその組成物を溶解又は分散させた１０〜４０重量％程度の粘着剤溶液を調製し、それを流延方式や塗工方式等の適宜な展開方式で前記基板または液晶フィルム上に直接付設する方式、あるいは前記に準じセパレータ上に粘着剤層を形成してそれを前記液晶層上移着する方式などがあげられる。
【００７６】
また粘着剤層には、例えば天然物や合成物の樹脂類、特に、粘着性付与樹脂や、ガラス繊維、ガラスビーズ、金属粉、その他の無機粉末等からなる充填剤や顔料、着色剤、酸化防止剤などの粘着層に添加されることの添加剤を含有していてもよい。また微粒子を含有して光拡散性を示す粘着剤層などであってもよい。
【００７７】
粘着剤層の厚さは、使用目的や接着力などに応じて適宜に決定でき、一般には１〜５００μｍであり、５〜２００μｍが好ましく、特に１０〜１００μｍが好ましい。
【００７８】
粘着剤層の露出面に対しては、実用に供するまでの間、その汚染防止等を目的にセパレータが仮着されてカバーされる。これにより、通例の取扱状態で粘着層に接触することを防止できる。セパレータとしては、上記厚さ条件を除き、例えばプラスチックフィルム、ゴムシート、紙、布、不織布、ネット、発泡シートや金属箔、それらのラミネート体等の適宜な薄葉体を、必要に応じシリコーン系や長鎖アルキル系、フッ素系や硫化モリブデン等の適宜な剥離剤でコート処理したものなどの、従来に準じた適宜なものを用いうる。
【００７９】
なお、上記光学フィルム、粘着剤層などの各層には、例えばサリチル酸エステル系化合物やべンゾフェノール系化合物、ベンゾトリアゾール系化合物やシアノアクリレート系化合物、ニッケル錯塩系化合物等の紫外線吸収剤で処理する方式などの方式により紫外線吸収能をもたせることができる。
【００８０】
本発明の楕円偏光板は、画像表示装置において好適に用いられる。たとえば、反射半透過型の液晶表示装置などの各種装置の形成に好ましく用いうる。反射半透過型液晶表示装置等は携帯型情報通信機器、パーソナルコンピュータとして好適に利用される。反射型半透過型液晶表示装置を形成する場合、本発明による楕円偏光板は、液晶セルの視認側に配置される。
【００８１】
図１９は、図４乃至図６、図１１乃至図１４に示す本発明の楕円偏光板（Ｐ１）を、反射半透過型液晶表示装置において、液晶セル（Ｌ）のバックライト（ＢＬ）側に粘着剤層を介して配置したものである。下側（バックライト側）の液晶セル（Ｌ）に積層する楕円偏光板（Ｐ１）の側は特に制限されないが、楕円偏光板（Ｐ１）の偏光板（Ｐ）が液晶セル（Ｌ）側から最も離れるようにするのが好ましい。液晶セル（Ｌ）には、液晶が封入されている。上側の液晶セル基板には透明電極が設けられており、下側の液晶セル基板には電極を兼ねる反射層が設けられている。一方、上側にも楕円偏光板（Ｐ２）を有する。楕円偏光板（Ｐ２）も、偏光板（Ｐ）が液晶セル（Ｌ）側から最も離れるようにするのが好ましい。その他各種光学フィルムを用いることができる。下側の液晶セル基板の下部には、反射半透過型液晶表示装置に用いられる、バックライトシステム（ＢＬ）を有する。
【００８２】
なお、本発明の積層光学フィルムや楕円偏光板を、液晶表示装置等に実装する際には、光学フィルム（３）において、光学的に負の一軸性を示す材料の平均光軸（傾斜配向している平均角度）が、液晶セル（電圧印加時）のミッドプレーンにおける液晶分子の配向方向とほぼ同じ方向を向くように配置するのが好ましい。
【００８３】
上記図１９の反射半透過型液晶表示装置は、液晶セルの一例を示したものであり、本発明の積層光学フィルム、楕円偏光板はその他各種の液晶表示装置に適用できる。
【００８４】
反射型偏光板は、偏光板に反射層を設けたもので、視認側（表示側）からの入射光を反射させて表示するタイプの液晶表示装置などを形成するためのものであり、バックライト等の光源の内蔵を省略できて液晶表示装置の薄型化を図りやすいなどの利点を有する。反射型偏光板の形成は、必要に応じ、前記透明保護フィルム等を介して偏光板の片面に金属等からなる反射層を付設する方式などの適宜な方式にて行うことができる。
【００８５】
反射型偏光板は、偏光板に反射層を設けたもので、視認側（表示側）からの入射光を反射させて表示するタイプの液晶表示装置などを形成するためのものであり、バックライト等の光源の内蔵を省略できて液晶表示装置の薄型化を図りやすいなどの利点を有する。反射型偏光板の形成は、必要に応じ、前記透明保護フィルム等を介して偏光板の片面に金属等からなる反射層を付設する方式などの適宜な方式にて行うことができる。
【００８６】
反射型偏光板の具体例としては、必要に応じマット処理した透明保護フィルムの片面に、アルミニウム等の反射性金属からなる箔や蒸着膜を付設して反射層を形成したものなどがあげられる。
【００８７】
反射板は前記偏光板の透明保護フィルムに直接付与する方式に代えて、その透明フィルムに準じた適宜なフィルムに反射層を設けてなる反射シートなどとして用いることもできる。なお反射層は、通常、金属からなるので、その反射面が透明保護フィルムや偏光板等で被覆された状態の使用形態が、酸化による反射率の低下防止、ひいては初期反射率の長期持続の点や、保護層の別途付設の回避の点などより好ましい。
【００８８】
なお、半透過型偏光板は、上記において反射層で光を反射し、かつ透過するハーフミラー等の半透過型の反射層とすることにより得ることができる。半透過型偏光板は、通常液晶セルの裏側に設けられ、液晶表示装置などを比較的明るい雰囲気で使用する場合には、視認側（表示側）からの入射光を反射させて画像を表示し、比較的暗い雰囲気においては、半透過型偏光板のバックサイドに内蔵されているバックライト等の内蔵光源を使用して画像を表示するタイプの液晶表示装置などを形成できる。すなわち、半透過型偏光板は、明るい雰囲気下では、バックライト等の光源使用のエネルギーを節約でき、比較的暗い雰囲気下においても内蔵光源を用いて使用できるタイプの液晶表示装置などの形成に有用である。
【００８９】
また、偏光板と輝度向上フィルムを貼り合わせた偏光板は、通常液晶セルの裏側サイドに設けられて使用される。輝度向上フィルムは、液晶表示装置などのバックライトや裏側からの反射などにより自然光が入射すると所定偏光軸の直線偏光または所定方向の円偏光を反射し、他の光は透過する特性を示すもので、輝度向上フィルムを偏光板と積層した偏光板は、バックライト等の光源からの光を入射させて所定偏光状態の透過光を得ると共に、前記所定偏光状態以外の光は透過せずに反射される。この輝度向上フィルム面で反射した光を更にその後ろ側に設けられた反射層等を介し反転させて輝度向上フィルムに再入射させ、その一部又は全部を所定偏光状態の光として透過させて輝度向上フィルムを透過する光の増量を図ると共に、偏光子に吸収させにくい偏光を供給して液晶表示画像表示等に利用しうる光量の増大を図ることにより輝度を向上させうるものである。すなわち、輝度向上フィルムを使用せずに、バックライトなどで液晶セルの裏側から偏光子を通して光を入射した場合には、偏光子の偏光軸に一致していない偏光方向を有する光は、ほとんど偏光子に吸収されてしまい、偏光子を透過してこない。すなわち、用いた偏光子の特性によっても異なるが、およそ５０％の光が偏光子に吸収されてしまい、その分、液晶画像表示等に利用しうる光量が減少し、画像が暗くなる。輝度向上フィルムは、偏光子に吸収されるような偏光方向を有する光を偏光子に入射させずに輝度向上フィルムで一旦反射させ、更にその後ろ側に設けられた反射層等を介して反転させて輝度向上フィルムに再入射させることを繰り返し、この両者間で反射、反転している光の偏光方向が偏光子を通過し得るような偏光方向になった偏光のみを、輝度向上フィルムは透過させて偏光子に供給するので、バックライトなどの光を効率的に液晶表示装置の画像の表示に使用でき、画面を明るくすることができる。
【００９０】
輝度向上フィルムと上記反射層等の間に拡散板を設けることもできる。輝度向上フィルムによって反射した偏光状態の光は上記反射層等に向かうが、設置された拡散板は通過する光を均一に拡散すると同時に偏光状態を解消し、非偏光状態となる。すなわち、拡散板は偏光を元の自然光状態にもどす。この非偏光状態、すなわち自然光状態の光が反射層等に向かい、反射層等を介して反射し、再び拡散板を通過して輝度向上フィルムに再入射することを繰り返す。このように輝度向上フィルムと上記反射層等の間に、偏光を元の自然光状態にもどす拡散板を設けることにより表示画面の明るさを維持しつつ、同時に表示画面の明るさのむらを少なくし、均一で明るい画面を提供することができる。かかる拡散板を設けることにより、初回の入射光は反射の繰り返し回数が程よく増加し、拡散板の拡散機能と相俟って均一の明るい表示画面を提供することができたものと考えられる。
【００９１】
前記の輝度向上フィルムとしては、例えば誘電体の多層薄膜や屈折率異方性が相違する薄膜フィルムの多層積層体の如き、所定偏光軸の直線偏光を透過して他の光は反射する特性を示すもの、コレステリック液晶ポリマーの配向フィルムやその配向液晶層をフィルム基材上に支持したものの如き、左回り又は右回りのいずれか一方の円偏光を反射して他の光は透過する特性を示すものなどの適宜なものを用いうる。
【００９２】
従って、前記した所定偏光軸の直線偏光を透過させるタイプの輝度向上フィルムでは、その透過光をそのまま偏光板に偏光軸を揃えて入射させることにより、偏光板による吸収ロスを抑制しつつ効率よく透過させることができる。一方、コレステリック液晶層の如く円偏光を投下するタイプの輝度向上フィルムでは、そのまま偏光子に入射させることもできるが、吸収ロスを抑制する点よりその円偏光を位相差板を介し直線偏光化して偏光板に入射させることが好ましい。なお、その位相差板として１／４波長板を用いることにより、円偏光を直線偏光に変換することができる。
【００９３】
可視光域等の広い波長範囲で１／４波長板として機能する位相差板は、例えば波長５５０ｎｍの淡色光に対して１／４波長板として機能する位相差層と他の位相差特性を示す位相差層、例えば１／２波長板として機能する位相差層とを重畳する方式などにより得ることができる。従って、偏光板と輝度向上フィルムの間に配置する位相差板は、１層又は２層以上の位相差層からなるものであってよい。
【００９４】
なお、コレステリック液晶層についても、反射波長が相違するものの組み合わせにして２層又は３層以上重畳した配置構造とすることにより、可視光領域等の広い波長範囲で円偏光を反射するものを得ることができ、それに基づいて広い波長範囲の透過円偏光を得ることができる。
【００９５】
また、偏光板は、上記の偏光分離型偏光板の如く、偏光板と２層又は３層以上の光学層とを積層したものからなっていてもよい。従って、上記の反射型偏光板や半透過型偏光板と位相差板を組み合わせた反射型楕円偏光板や半透過型楕円偏光板などであってもよい。
【００９６】
液晶表示装置の形成は、従来に準じて行いうる。すなわち液晶表示装置は一般に、液晶セルと光学素子、及び必要に応じての照明システム等の構成部品を適宜に組立てて駆動回路を組込むことなどにより形成される。本発明の楕円偏光板を用いる点を除いて特に限定はなく、従来に準じうる。液晶セルについても、例えばＴＮ型やＳＴＮ型、π型などの任意なタイプのものを用いうる。
【００９７】
液晶セルの裏側には、照明システムにバックライトあるいは反射板を用いたものなどの適宜な液晶表示装置を形成することができる。その場合、本発明の楕円偏光板は液晶セルの片側又は両側に設置することができる。両側に光学素子を設ける場合、それらは同じものであってもよいし、異なるものであってもよい。さらに、液晶表示装置の形成に際しては、例えば拡散板、アンチグレア層、反射防止膜、保護板、プリズムアレイ、レンズアレイシート、光拡散板、バックライトなどの適宜な部品を適宜な位置に１層又は２層以上配置することができる。
【００９８】
次いで有機エレクトロルミネセンス装置（有機ＥＬ表示装置）について説明する。一般に、有機ＥＬ表示装置は、透明基板上に透明電極と有機発光層と金属電極とを順に積層して発光体（有機エレクトロルミネセンス発光体）を形成している。ここで、有機発光層は、種々の有機薄膜の積層体であり、例えばトリフェニルアミン誘導体等からなる正孔注入層と、アントラセン等の蛍光性の有機固体からなる発光層との積層体や、あるいはこのような発光層とペリレン誘導体等からなる電子注入層の積層体や、またあるいはこれらの正孔注入層、発光層、および電子注入層の積層体等、種々の組み合わせをもった構成が知られている。
【００９９】
有機ＥＬ表示装置は、透明電極と金属電極とに電圧を印加することによって、有機発光層に正孔と電子とが注入され、これら正孔と電子との再結合によって生じるエネルギーが蛍光物資を励起し、励起された蛍光物質が基底状態に戻るときに光を放射する、という原理で発光する。途中の再結合というメカニズムは、一般のダイオードと同様であり、このことからも予想できるように、電流と発光強度は印加電圧に対して整流性を伴う強い非線形性を示す。
【０１００】
有機ＥＬ表示装置においては、有機発光層での発光を取り出すために、少なくとも一方の電極が透明でなくてはならず、通常酸化インジウムスズ（ＩＴＯ）などの透明導電体で形成した透明電極を陽極として用いている。一方、電子注入を容易にして発光効率を上げるには、陰極に仕事関数の小さな物質を用いることが重要で、通常Ｍｇ−Ａｇ、Ａｌ−Ｌｉなどの金属電極を用いている。
【０１０１】
このような構成の有機ＥＬ表示装置において、有機発光層は、厚さ１０ｎｍ程度ときわめて薄い膜で形成されている。このため、有機発光層も透明電極と同様、光をほぼ完全に透過する。その結果、非発光時に透明基板の表面から入射し、透明電極と有機発光層とを透過して金属電極で反射した光が、再び透明基板の表面側へと出るため、外部から視認したとき、有機ＥＬ表示装置の表示面が鏡面のように見える。
【０１０２】
電圧の印加によって発光する有機発光層の表面側に透明電極を備えるとともに、有機発光層の裏面側に金属電極を備えてなる有機エレクトロルミネセンス発光体を含む有機ＥＬ表示装置において、透明電極の表面側に偏光板を設けるとともに、これら透明電極と偏光板との間に位相差板を設けることができる。
【０１０３】
位相差板および偏光板は、外部から入射して金属電極で反射してきた光を偏光する作用を有するため、その偏光作用によって金属電極の鏡面を外部から視認させないという効果がある。特に、位相差板を１ ／４ 波長板で構成し、かつ偏光板と位相差板との偏光方向のなす角をπ／４ に調整すれば、金属電極の鏡面を完全に遮蔽することができる。
【０１０４】
すなわち、この有機ＥＬ表示装置に入射する外部光は、偏光板により直線偏光成分のみが透過する。この直線偏光は位相差板により一般に楕円偏光となるが、とくに位相差板が１ ／４ 波長板でしかも偏光板と位相差板との偏光方向のなす角がπ／４ のときには円偏光となる。
【０１０５】
この円偏光は、透明基板、透明電極、有機薄膜を透過し、金属電極で反射して、再び有機薄膜、透明電極、透明基板を透過して、位相差板に再び直線偏光となる。そして、この直線偏光は、偏光板の偏光方向と直交しているので、偏光板を透過できない。その結果、金属電極の鏡面を完全に遮蔽することができる。
【０１０６】
【実施例】
以下に実施例をあげて本発明の一態様について説明するが、本発明は実施例に限定されないことはいうまでもない。
【０１０７】
なお、各光学フィルムの屈折率、位相差の測定は、フィルム面内と厚さ方向の主屈折率ｎｘ、ｎｙ、ｎｚを自動複屈折測定装置（王子計測機器株式会社製，自動複屈折計ＫＯＢＲＡ２１ＡＤＨ）により、λ＝５９０ｎｍにおける特性を測定した。
【０１０８】
光学フィルム（３）において、傾斜配向している光学材料の平均光軸と光学フィルム（３）の法線方向からなす傾斜角度は、光学フィルム（３）を遅相軸を軸として、左右に−５０°〜５０°傾け、前記測定装置で位相差を測定し、最小の位相差を示す角度の絶対値とした。また前記測定においては、測定器の光源からの光の入射方向とフィルム面内に対する法線が一致した時の測定角を０°とした。
【０１０９】
（ホメオトロピック配向液晶層（１））
【化６】

上記の化６（式中の数字はモノマーユニットのモル％を示し、便宜的にブロック体で表示している、重量平均分子量５０００）に示される側鎖型液晶ポリマー５重量部、ネマチック液晶相を示す重合性液晶（Ｐａｌｉｏｃｏｌｏｒ ＬＣ２４２，ＢＡＳＦ製）２０重量部および光開始剤（イルガキュア９０７，チバスペシャルティケミカルズ社製）を前記重合性液晶に対して３重量部を、シクロへキサノン７５重量部に溶解した溶液を調製した。そして、当該溶液を、レシチンを塗布したポリエチレンテレフタレート基材にバーコーターにて塗布し、１００℃で１０分間、乾燥配向させた後、メタルハライドランプにて１ｍＪ／ｃｍ^２ の光を照射し、厚さ約０．７μｍのホメオトロピック配向液晶層を得た。ホメオトロピック配向液晶層の厚み方向位相差は、−７０ｎｍであった。
【０１１０】
（光学フィルム（２））
厚さ１００μｍのノルボルネン系無延伸フィルム（ＪＳＲ株式会社製，製品名アートン）を、１７０℃で１．３倍に一軸延伸した。得られた延伸フィルムは、厚さ：８０μｍ、正面位相差：１４０ｎｍ、厚み方向の位相差：１４０ｎｍであった。この延伸フィルムを光学フィルム（２（１））とした。
【０１１１】
また、厚さ１００μｍのノルボルネン系無延伸フィルム（ＪＳＲ株式会社製，製品名アートン）を、１７０℃で１．６倍に一軸延伸した。得られた延伸フィルムは、厚さ：７０μｍ、正面位相差：２８０ｎｍ、厚み方向の位相差：２８０ｎｍであった。この延伸フィルムを光学フィルム（２（２））とした。
【０１１２】
（光学フィルム（３））
富士写真フィルム株式会社製のＷＶＳＡ１２Ｂ（厚さ：１１０μｍ）を用いた。当該フィルムは、ディスコティック液晶を支持体に塗布することにより作製されたものであり、正面位相差：３０ｎｍ、厚み方向の位相差：１６０ｎｍであり、傾斜配向している平均光軸の傾斜角度：２０°、であった。
【０１１３】
実施例１
（積層光学フィルム）
上記で得られたホメオトロピック配向液晶フィルム（１）、光学フィルム（２（１））、光学フィルム（３）とを、図１に示すように、粘着剤層（アクリル系粘着剤，厚さ３０μｍ）を介しに積層して積層光学フィルムを得た。
【０１１４】
（楕円偏光板）
上記積層光学フィルムに、図４に示すように、偏光板（日東電工（株）製，ＳＥＧ１４６５ＤＵ）を粘着剤層（アクリル系粘着剤，厚さ３０μｍ）を介して貼り合わせて楕円偏光板を得た。なお、貼り合わせは、偏光板の吸収軸に対して光学フィルム（２（１））の遅相軸が３０°に交差するように行った。
【０１１５】
実施例２
実施例１において、積層光学フィルムの積層順を図２に示すように、楕円偏光板の積層順を図５に示すように変えたこと以外は実施例１と同様にして、積層光学フィルムおよび楕円偏光板を得た。
【０１１６】
実施例３
実施例１において、積層光学フィルムの積層順を図３に示すように、楕円偏光板の積層順を図６に示すように変えたこと以外は実施例１と同様にして、積層光学フィルムおよび楕円偏光板を得た。
【０１１７】
実施例４
（積層光学フィルム）
上記で得られたホメオトロピック配向液晶フィルム（１）、光学フィルム（２（１））、光学フィルム（２（２））、光学フィルム（３）とを、図７に示すように、粘着剤層（アクリル系粘着剤，厚さ３０μｍ）を介しに積層して積層光学フィルムを得た。なお、貼り合わせは、光学フィルム（２（１））および光学フィルム（２（２））板の遅相軸が７５°に交差するように行った。
【０１１８】
（楕円偏光板）
上記積層光学フィルムに、図１１に示すように、偏光板（日東電工（株）製，ＳＥＧ１４６５ＤＵ）を粘着剤層（アクリル系粘着剤，厚さ３０μｍ）を介して貼り合わせて楕円偏光板を得た。なお、貼り合わせは、偏光板の吸収軸に対して光学フィルム（２（１））の遅相軸が３０°に交差するように行った。
【０１１９】
実施例５
実施例４において、積層光学フィルムの積層順を図１０に示すように、楕円偏光板の積層順を図１４に示すように変えたこと以外は実施例４と同様にして、積層光学フィルムおよび楕円偏光板を得た。
【０１２０】
実施例６
実施例４において、積層光学フィルムの積層順を図９に示すように、楕円偏光板の積層順を図１３に示すように変えたこと以外は実施例４と同様にして、積層光学フィルムおよび楕円偏光板を得た。
【０１２１】
実施例７
実施例４において、積層光学フィルムの積層順を図８に示すように、楕円偏光板の積層順を図１２に示すように変えたこと以外は実施例４と同様にして、積層光学フィルムおよび楕円偏光板を得た。
【０１２２】
比較例１
偏光板、光学フィルム（２（１））およびホメオトロピック配向液晶フィルム（１）を用い、図１５に示すように、粘着剤層を介して偏光板に貼り合わせて楕円偏光板を得た。なお、貼り合わせは、偏光板の吸収軸に対して光学フィルム（２（１））の遅相軸が４５°に交差するように行った。
【０１２３】
比較例２
偏光板、光学フィルム（２（１））および光学フィルム（３）を用い、図１６に示すように、粘着剤層を介して偏光板に貼り合わせて楕円偏光板を得た。なお、貼り合わせは、偏光板の吸収軸に対して光学フィルム（２（１））の遅相軸が３０°に交差するように行った。
【０１２４】
比較例３
偏光板、光学フィルム（２（１））、光学フィルム（２（２））および光学フィルム（３）を用い、図１７に示すように、粘着剤層を介して偏光板に貼り合わせて楕円偏光板を得た。なお、貼り合わせは、偏光板の吸収軸に対して光学フィルム（２（２））の遅相軸が３０°に交差するように行った。
【０１２５】
参考例１
偏光板、光学フィルム（２（１））および光学フィルム（２（２））を用い、図１８に示すように、粘着剤層を介して偏光板に貼り合わせて楕円偏光板を得た。なお、貼り合わせは、偏光板の吸収軸に対して光学フィルム（２（２））の遅相軸が３０°に交差するように行った。
【０１２６】
（評価）
実施例、比較例で得られた楕円偏光板を、図１９に示すように、反射半透過型ＴＦＴ−ＴＮ型液晶表示装置のバックライト側の楕円偏光板（Ｐ１）として実装した。一方、参考例１で作製した楕円偏光板を視認側の楕円偏光板（Ｐ２）として実装した。楕円偏光板（Ｐ１）、楕円偏光板（Ｐ２）はいずれも、偏光板側が液晶セル（Ｌ）側から最も離れた積層位置となるように実装した。
【０１２７】
次いで、上記液晶表示装置に、白画像、黒画像を表示させて、ＥＬＤＩＭ社製のＥＺｃｏｎｔｒａｓｔ１６０Ｄにて、正面および上下左右、視野角０〜７０°におけるＸＹＺ表示系におけるＹ値、ｘ値、ｙ値を測定した。
【０１２８】
そのときのコントラスト（Ｙ値（白画像）／Ｙ値（黒画像））の値が１０以上となる角度を視野角とした。結果を表１に示す。
【０１２９】
また、白画像について、画面の正面の色度（ｘ_０ ，ｙ_０ ）に対して上下左右にそれぞれ４０°傾斜したとき色度（ｘ_４０，ｙ_４０）の色度変化量を比較評価した。色度変化量は下記式にて求めた。結果を表１に示す。
色度変化量＝√｛（ｘ_４０−ｘ_０ ）^２ ＋（ｙ_４０−ｙ_０ ）^２ ｝
【０１３０】
【表１】

【図面の簡単な説明】
【図１】本発明の積層光学フィルムの断面図の一態様である。
【図２】本発明の積層光学フィルムの断面図の一態様である。
【図３】本発明の積層光学フィルムの断面図の一態様である。
【図４】本発明の楕円偏光板の断面図の一態様である。
【図５】本発明の楕円偏光板の断面図の一態様である。
【図６】本発明の楕円偏光板の断面図の一態様である。
【図７】本発明の積層光学フィルムの断面図の一態様である。
【図８】本発明の積層光学フィルムの断面図の一態様である。
【図９】本発明の積層光学フィルムの断面図の一態様である。
【図１０】本発明の積層光学フィルムの断面図の一態様である。
【図１１】本発明の楕円偏光板の断面図の一態様である。
【図１２】本発明の楕円偏光板の断面図の一態様である。
【図１３】本発明の楕円偏光板の断面図の一態様である。
【図１４】本発明の楕円偏光板の断面図の一態様である。
【図１５】比較例の楕円偏光板の断面図の一態様である。
【図１６】比較例の楕円偏光板の断面図の一態様である。
【図１７】比較例の楕円偏光板の断面図の一態様である。
【図１８】参考例の楕円偏光板の断面図の一態様である。
【図１９】実施例の反射半透過型液晶表示装置例の断面図である。
【符号の説明】
１：ホメオトロピック配向液晶層
２：ｎｘ_２ ＞ｎｙ_２ ≒ｎｚ_２ 、を満足する光学フィルム
３：負の一軸性を示す材料を傾斜配向させてなる光学フィルム
ａ：粘着剤層
Ｐ：偏光板
Ｌ：液晶セル
ＢＬ：バックライト[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated optical film. The laminated optical film of the present invention can be used as various optical films such as a retardation plate, a viewing angle compensation film, an optical compensation film, an elliptically polarizing plate, and a brightness enhancement film alone or in combination with other optical films. In particular, the laminated optical film of the present invention is useful when used as an elliptically polarizing plate by being laminated with a polarizing plate. The present invention also relates to a liquid crystal display device using the laminated optical film, an elliptically polarizing plate, and the like, an organic EL (electroluminescence) display device, an image display device such as a PDP. As described above, the laminated optical film and the elliptically polarizing plate of the present invention can be applied to various liquid crystal display devices and the like. It is preferably used.
[0002]
[Prior art]
Conventionally, for a reflective transflective liquid crystal display device or the like, a broadband retardation plate functioning as a λ / 4 plate or a λ / 2 plate is preferably used for incident light (visible light region) having a broadband wavelength region. Has been. As such a broadband retardation plate, a laminated film is proposed in which a plurality of polymer films having optical anisotropy are laminated with their optical axes crossed. In these laminated films, the optical axes of two or more stretched films are crossed to realize a broad band (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).
[0003]
However, even when the broadband retardation plate described in Patent Documents 1 to 3 described above is used, when the image is viewed from the upper, lower, left, and right oblique directions with respect to the normal direction of the screen of the display device, There is a drawback that the color appearance of one display screen changes, or the tone is inverted such that the white image and the black image are inverted.
[0004]
[Patent Document 1]
JP-A-5-100114 [Patent Document 2]
JP-A-10-68816 [Patent Document 3]
Japanese Patent Laid-Open No. 10-90521
[Problems to be solved by the invention]
According to the present invention, even when an image is viewed from an oblique direction that is up, down, left, and right with respect to the normal direction of the screen of the image display device, a change in the color of the display image is suppressed, and an image with a small gradation inversion region is displayed. An object of the present invention is to provide a laminated optical film that can be used.
[0006]
Another object of the present invention is to provide an elliptically polarizing plate in which the laminated optical film and a polarizing plate are laminated. Furthermore, an object of the present invention is to provide an image display device using the laminated optical film and the elliptically polarizing plate.
[0007]
[Means for solving problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by a laminated optical film shown below, and have completed the present invention.
[0008]
That is, the present invention includes at least a homeotropic alignment liquid crystal layer (1),
The direction in which the refractive index in the film plane is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. The refractive indexes in the respective axial directions are nx ₂ , ny ₂ , nz ₂ and an optical film (2) satisfying nx ₂ > ny ₂ ≈nz ₂ ,
The present invention relates to a laminated optical film characterized by being laminated with an optical film (3) that is formed of a material exhibiting optically negative uniaxial properties and in which the material is inclined and oriented.
[0009]
In the laminated optical film of the present invention, the retardation in the thickness direction can be controlled by the homeotropic alignment liquid crystal layer (1), and the change in color appearance when viewed from an oblique direction can be suppressed. The laminated optical film of the present invention is useful as a retardation plate that compensates for a wide viewing angle. An image display device such as a liquid crystal display device to which the laminated optical film is applied can realize a wide viewing angle, and even when the display screen is viewed from an oblique direction, the color change of the display image is suppressed, and anyone tone inversion region It is possible to display an image with little. The laminated optical film of the present invention can also satisfy a wide band required as a retardation plate.
[0010]
In the laminated optical film, the optical film (2) is preferably a film formed from a polymer having a norbornene skeleton. A film formed from a polymer having a norbornene skeleton is preferable from the viewpoint of excellent durability under high temperature and high temperature and high humidity conditions.
[0011]
In the laminated optical film, the homeotropic alignment liquid crystal layer (1) has an in-plane refractive index maximum direction as an X axis, a direction perpendicular to the X axis as a Y axis, and a thickness direction as a Z axis. When the refractive index in the axial direction is nx ₁ , ny ₁ , nz ₁ ,
Thickness direction retardation: {((nx ₁ + ny ₁ ) / 2) −nz ₁ } × d (thickness: nm) is preferably −10 nm to −500 nm.
[0012]
In order to suppress a change in color when viewed obliquely, the phase difference in the thickness direction of the homeotropic alignment liquid crystal layer (1) is preferably −10 nm to −500 nm, and preferably −30 nm to −300 nm. More preferably. Furthermore, −50 nm to −200 nm is preferable.
[0013]
In the laminated optical film, the material that forms the optical film (3) and exhibits optically negative uniaxiality is preferably a discotic liquid crystal compound. A material that exhibits optically negative uniaxiality is not particularly limited, but a discotic liquid crystal compound is preferable because it is easy to control the tilt alignment and is a general material and relatively inexpensive.
[0014]
In the laminated optical film, the material that forms the optical film (3) and exhibits optically negative uniaxiality has an inclination angle between the average optical axis and the normal direction of the optical film (3) of 5 ° to 5 °. It is preferable that the inclined orientation is in the range of 50 °.
[0015]
As described above, the optical film (3) is used as a laminated optical film combined with the optical film (1) whose three-dimensional refractive index is controlled, but the inclination angle of the optical film (3) is controlled to 5 ° or more. Thus, the effect of widening the viewing angle when mounted on a liquid crystal display device or the like is great. On the other hand, by controlling the tilt angle to be 50 ° or less, the viewing angle is good in any direction (four directions) up, down, left and right, and the viewing angle may be improved or worsened depending on the direction. Can be suppressed. From this viewpoint, the inclination angle is preferably 10 ° to 30 °.
[0016]
It should be noted that the optically negative optical material (for example, discotic liquid crystalline molecules) may have a uniform tilt (tilt) orientation that does not change with distance from the film plane. It may change with the distance between the material and the film plane.
[0017]
In the laminated optical film, a λ / 4 plate can be used as the optical film (2). When the optical film (2) is a λ / 4 plate, it can be laminated with a polarizing plate to form an elliptical polarizing plate.
[0018]
In the laminated optical film, two or more optical films (2) can be laminated. When two or more optical films (2) are laminated, the homeotropic alignment liquid crystal layer (1) is preferably laminated so as to be positioned between two or more optical films (2) laminated. . When two or more optical films (2) are laminated as described above and laminated in the above arrangement, the viewing angle is more widened, which is preferable.
[0019]
Moreover, the optical film (2) laminated | stacked two or more can laminate | stack a (lambda) / 4 board and a (lambda) / 2 board. The optical film (2) can function as a λ / 4 plate as a whole by laminating two or more λ / 4 plates or λ / 2 plates.
[0020]
The present invention also relates to an elliptically polarizing plate characterized in that the laminated optical film and a polarizing plate are laminated.
[0021]
As the elliptically polarizing plate, for example, a polarizing plate, an optical film (2), a homeotropic alignment liquid crystal layer (1), and an optical film (3) laminated in this order are suitable in terms of a wide viewing angle. In addition, the elliptically polarizing plate, for example, a laminate in which a polarizing plate, a homeotropic alignment liquid crystal layer (1), an optical film (2), and an optical film (3) are laminated in this order is preferable in terms of a wide viewing angle.
[0022]
When the λ / 4 plate and the λ / 2 plate are laminated as the optical film (2), the elliptically polarizing plate is laminated in the order of the λ / 2 plate and the λ / 4 plate from the polarizing plate side. It is preferable. When laminated in such an arrangement, the viewing angle is more widened, which is preferable. Further, when the λ / 4 plate and the λ / 2 plate are laminated as the optical film (2), the elliptically polarizing plate has a λ / 2 plate, a homeotropic alignment liquid crystal layer (1), λ, / 4 plates and those laminated in the order of the optical film (3) are preferred. In addition, a laminate in which a λ / 2 plate, a λ / 4 plate, a homeotropic alignment liquid crystal layer (1), and an optical film (3) are laminated in this order from the polarizing plate side is also preferable.
[0023]
Furthermore, the present invention relates to an image display device in which the laminated optical film or the elliptically polarizing plate is laminated. The elliptically polarizing plate or the like is disposed on a liquid crystal cell in a liquid crystal display device, or a metal electrode in an organic EL display device.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The laminated optical film and the elliptically polarizing plate of the present invention will be described below with reference to the drawings.
[0025]
As shown in FIGS. 1 to 3, in the laminated optical film of the present invention, a homeotropic alignment liquid crystal layer (1), an optical film (2), and an optical film (3) are laminated. As a laminated optical film, FIG. 1 and FIG. 2 are preferable in terms of a wide viewing angle. In order to make these laminated optical films into elliptical polarizing plates, a λ / 4 plate (2 (1)) is used as the optical film (2).
[0026]
A polarizing plate (P) can be laminated on the laminated optical film to form an elliptically polarizing plate. The laminating position of the polarizing plate (P) is not particularly limited, but in the case of the laminated optical film of FIGS. 1 to 3, it can be laminated as shown in FIGS. 4 to 6. In particular, as shown in FIGS. 4 and 5, when an elliptical polarizing plate in the stacking order in which the optical film (3) is positioned on the opposite side of the polarizing plate (P) is mounted on the liquid crystal display device, This is preferable in terms of a wider viewing angle.
[0027]
In the laminated optical film of FIGS. 1 to 3, the case where one optical film (2) is used is exemplified, but in the laminated optical film of the present invention, two or more optical films (2) can be used. In this case, the two or more laminated optical films are arranged by changing the lamination angle of the optical axes according to the wavelength characteristics of the optical film (2) to be used so as to function as a λ / 4 plate as a whole. 7 to 10 illustrate a case where a λ / 4 plate (2 (1)) and a λ / 2 plate (2 (2)) are laminated as the optical film (2). 7 to 9 show the case where two optical films (2) are laminated in order in the laminated optical film of FIGS. When two optical films (2) are laminated, a homeotropic alignment liquid crystal layer (1) is disposed between the two optical films (2) as shown in FIG. From the point of view, it is preferable.
[0028]
11 to 14 are elliptically polarizing plates in which a polarizing plate (P) is laminated on the laminated optical films of FIGS. 7 to 10. Further, the position where the polarizing plate (P) is laminated with respect to the laminated optical film is not particularly limited, but as shown in FIGS. 11 to 15, the optical film (2) is a λ / 4 plate (2 (1)) and λ In the case of using the / 2 plate (2 (2)), the λ / 2 plate (2 (2)) and the λ / 4 plate (2 (1)) are laminated in this order from the polarizing plate (P) side. It is preferable to use an elliptically polarizing plate from the viewpoint of a wide viewing angle.
[0029]
1 to 14, the homeotropic alignment liquid crystal layer (1), the optical film (2), the optical film (3) and the polarizing plate (P) are the pressure-sensitive adhesive layer (a). It is laminated through. One layer may be sufficient as an adhesive layer (a), and it can be set as the overlapping form of two or more layers.
[0030]
The homeotropic alignment liquid crystal layer (1) is obtained by aligning a liquid crystal material with, for example, a vertical alignment agent. As a liquid crystal compound that can be homeotropically aligned, for example, a nematic liquid crystal compound is known. An outline of the liquid crystal compound alignment technique is described in, for example, Chemical Review 44 (Surface Modification, Edited by The Chemical Society of Japan, pages 156 to 163).
[0031]
The liquid crystal material for the homeotropic alignment liquid crystal layer (1) includes, for example, a monomer unit (a) having a positive refractive index anisotropy and containing a liquid crystal fragment side chain and a non-liquid crystal fragment side chain. It can be formed by a side chain type liquid crystal polymer containing the monomer unit (b). The side-chain liquid crystal polymer can realize homeotropic alignment of the liquid crystal polymer without using a vertical alignment film.
[0032]
The monomer unit (a) has a side chain having nematic liquid crystallinity, for example, the general formula (a):
[Chemical 1]

(Wherein R ¹ represents a hydrogen atom or a methyl group, a represents a positive integer of 1 to 6, X ¹ represents a —CO ₂ — group or —OCO— group, R ² represents a cyano group, and has 1 to 6 carbon atoms. An alkoxy group, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, and b and c each represent an integer of 1 or 2.).
[0033]
The monomer unit (b) has a linear side chain. For example, the monomer unit (b) has the general formula (b):
[Chemical 2]

(However, the ^{R 3} is a hydrogen atom or a methyl group, ^{R 4} is an alkyl group having 1 to 22 carbon atoms, fluoroalkyl group having 1 to 22 carbon atoms, or the general formula, (b1):
[Chemical 3]

However, d is a positive integer from 1 to 6, ^{R 5} represents an alkyl group having 1 to 6 carbon atoms. ) Monomer units.
[0034]
Further, the ratio of the monomer unit (a) to the monomer unit (b) is not particularly limited and varies depending on the type of the monomer unit. However, when the ratio of the monomer unit (b) is increased, the side chain type liquid crystal polymer is changed. In order to stop showing liquid crystal monodomain orientation, it is preferable to set it as (b) / {(a) + (b)} = 0.01-0.8 (molar ratio). In particular, 0.1 to 0.5 is more preferable.
[0035]
The liquid crystal polymer capable of forming a homeotropic alignment liquid crystal film includes a monomer unit (a) containing the liquid crystalline fragment side chain and a monomer unit (c) containing a liquid crystalline fragment side chain having an alicyclic ring structure. And a side chain type liquid crystal polymer.
[0036]
The monomer unit (c) has a side chain having nematic liquid crystallinity, for example, the general formula (c):
[Formula 4]

(Provided that the ^{R 6} hydrogen atom or a methyl group, h is 1 to 6 positive integer, ^{X 2} is -CO ₂ - group or -OCO- group, e and g is 1 or 2 an integer, f Represents an integer of 0 to 2, and R ⁷ represents a cyano group and an alkyl group having 1 to 12 carbon atoms.).
[0037]
Further, the ratio of the monomer unit (a) to the monomer unit (c) is not particularly limited and varies depending on the type of the monomer unit. However, when the ratio of the monomer unit (c) is increased, the side chain type liquid crystal polymer is changed. Since the liquid crystal monodomain orientation is not exhibited, it is preferable that (c) / {(a) + (c)} = 0.01 to 0.8 (molar ratio). In particular, 0.1 to 0.6 is more preferable.
[0038]
The liquid crystal polymer that can form the homeotropic alignment liquid crystal layer (1) is not limited to those having the above-described monomer units, and the above-mentioned monomer units can be appropriately combined.
[0039]
The side chain type liquid crystal polymer preferably has a weight average molecular weight (GPC) of 2,000 to 100,000. By adjusting the weight average molecular weight to such a range, performance as a liquid crystal polymer is exhibited. When the weight average molecular weight of the side chain type liquid crystal polymer is too small, the film forming property of the alignment layer tends to be poor. Therefore, the weight average molecular weight is more preferably 2.5000 or more. On the other hand, if the weight average molecular weight is excessive, the orientation as a liquid crystal tends to be poor and it becomes difficult to form a uniform alignment state. Therefore, the weight average molecular weight is more preferably 50,000 or less.
[0040]
The illustrated side chain type liquid crystal polymer can be prepared by copolymerizing an acrylic monomer or a methacrylic monomer corresponding to the monomer unit (a), the monomer unit (b), and the monomer unit (c). The monomers corresponding to the monomer unit (a), the monomer unit (b), and the monomer unit (c) can be synthesized by a known method. The copolymer can be prepared, for example, according to a polymerization method such as a conventional acrylic monomer such as a radical polymerization method, a cationic polymerization method, and an anionic polymerization method. When applying the radical polymerization method, various polymerization initiators can be used. Among them, decomposition temperatures such as azobisisobutyronitrile and benzoyl peroxide are not high and are not low. Those are preferably used.
[0041]
The side-chain liquid crystal polymer can be used as a liquid crystal composition by blending a photopolymerizable liquid crystal compound. The photopolymerizable liquid crystal compound is a liquid crystal compound having at least one unsaturated double bond such as an acryloyl group or a methacryloyl group as a photopolymerizable functional group, and a nematic liquid crystal compound is awarded. Examples of such photopolymerizable liquid crystal compounds include acrylates and methacrylates that serve as the monomer unit (a). As the photopolymerizable liquid crystal compound, those having two or more photopolymerizable functional groups are preferable for improving durability. As such a photopolymerizable liquid crystal compound, for example,
[Chemical formula 5]

(In the formula, R is a hydrogen atom or a methyl group, A and D are each independently 1,4-phenylene group or 1,4-cyclohexylene group, and X is each independently a —COO— group or —OCO group. -Group or -O- group, B is 1,4-phenylene group, 1,4-cyclohexylene group, 4,4'-biphenylene group or 4,4'-bicyclohexylene group, and m and n are each And a cross-linked nematic liquid crystal monomer represented by the following formula: Examples of the photopolymerizable liquid crystal compound include compounds in which the terminal “H ₂ C═CR—CO ₂ —” in Chemical Formula 5 is substituted with a vinyl ether group or an epoxy group, “— (CH ₂ ) _m —” and / Or “— (CH ₂ ) _n —” to “— (CH ₂ ) ₃ —C ^* H (CH ₃ ) — (CH ₂ ) ₂ —” or “— (CH ₂ ) ₂ —C ^* H (CH ₃ )-(CH ₂ ) ₃ — ”.
[0042]
The photopolymerizable liquid crystal compound can be converted into a liquid crystal state by heat treatment, for example, by developing a nematic liquid crystal layer and homeotropically aligning with the side chain type liquid crystal polymer, and then polymerizing or crosslinking the photopolymerizable liquid crystal compound. As a result, the durability of the homeotropic alignment liquid crystal film can be improved.
[0043]
The ratio of the photopolymerizable liquid crystal compound and the side chain type liquid crystal polymer in the liquid crystal composition is not particularly limited and is appropriately determined in consideration of the durability of the obtained homeotropic alignment liquid crystal film. Photopolymerizable liquid crystal compound: side chain type liquid crystal polymer (weight ratio) = about 0.1: 1 to 30: 1 is preferable, 0.5: 1 to 20: 1 is particularly preferable, and 1: 1 to 10: is more preferable. 1 is preferred.
[0044]
The liquid crystalline composition usually contains a photopolymerization initiator. Various photopolymerization initiators can be used without particular limitation. Examples of the photopolymerization initiator include Irgacure 907, 184, 651, and 369 manufactured by Ciba Specialty Chemicals. The addition amount of the photopolymerization initiator is added to such an extent that the homeotropic orientation of the liquid crystalline composition is not disturbed in consideration of the type of the photopolymerized liquid crystal compound, the blending ratio of the liquid crystalline composition, and the like. Usually, about 0.5-30 weight part is preferable with respect to 100 weight part of photopolymerizable liquid crystal compounds. Particularly preferred is 3 parts by weight or more.
[0045]
The homeotropic alignment liquid crystal layer (1) is produced by coating a homeotropic alignment side chain type liquid crystal polymer on a substrate, then aligning the side chain type liquid crystal polymer in a liquid crystal state, and changing the alignment state. This is done by immobilizing in a maintained state. When a homeotropic alignment liquid crystalline composition comprising the side chain liquid crystal polymer and the photopolymerizable liquid crystal compound is used, this is applied to a substrate, and then the liquid crystalline composition is homeomorphized in a liquid crystal state. A tropic alignment is performed, and light irradiation is performed while maintaining the alignment state.
[0046]
The substrate on which the side chain type liquid crystal polymer or liquid crystalline composition is applied may have any shape of a glass substrate, a metal foil, a plastic sheet, or a plastic film. The plastic film is not particularly limited as long as it does not change with the temperature at which it is oriented. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, Examples thereof include a film made of a transparent polymer such as an acrylic polymer such as polymethyl methacrylate. The vertical alignment film may not be provided on the substrate. The thickness of the substrate is usually about 10 to 1000 μm.
[0047]
The side chain type liquid crystal polymer or liquid crystal composition is applied to the substrate by a solution coating method using a solution obtained by dissolving the side chain type liquid crystal polymer or liquid crystal composition in a solvent, or the liquid crystal polymer or liquid crystal property. Although the method of melt | dissolving and melt-coating a composition is mentioned, Among these, the method of coating the solution of a side chain type liquid crystal polymer or a liquid crystalline composition on a support substrate by a solution coating method is preferable.
[0048]
Examples of the method for applying a solution of a side chain type liquid crystal polymer or liquid crystal composition adjusted to a desired concentration using the above-mentioned solvent on a substrate include a roll coating method, a gravure coating method, a spin coating method, A bar coat method or the like can be employed. After coating, the solvent is removed, and a liquid crystal polymer layer or a liquid crystal composition layer is formed on the substrate. The conditions for removing the solvent are not particularly limited, as long as the solvent can be generally removed and the liquid crystal polymer layer or the liquid crystal composition layer does not flow or even flow down. Usually, the solvent is removed by drying at room temperature, drying in a drying furnace, heating on a hot plate, or the like. Among these coating methods, the gravure coating method is preferably used in the present invention because it is easy to uniformly coat a large area.
[0049]
Next, the side chain type liquid crystal polymer layer or liquid crystal composition layer formed on the supporting substrate is brought into a liquid crystal state and homeotropically aligned. For example, heat treatment is performed so that the side chain type liquid crystal polymer or the liquid crystalline composition is in the liquid crystal temperature range, and homeotropic alignment is performed in the liquid crystal state. The heat treatment can be performed by the same method as the above drying method. The heat treatment temperature varies depending on the type of the side chain type liquid crystal polymer or liquid crystalline composition to be used and the support substrate, and cannot be generally stated, but is usually in the range of 60 to 300 ° C, preferably 70 to 200 ° C. The heat treatment time varies depending on the heat treatment temperature and the type of the side chain type liquid crystal polymer or liquid crystal composition or substrate used, but cannot be generally stated, but is usually in the range of 10 seconds to 2 hours, preferably 20 seconds to 30 minutes. Selected. If it is shorter than 10 seconds, homeotropic alignment formation may not proceed sufficiently. Among these orientation temperatures and treatment times, in the present invention, it is preferable from the viewpoint of workability and mass productivity that the treatment time is about 30 seconds to 10 minutes at an orientation temperature of 80 to 150 ° C.
[0050]
After the heat treatment is completed, a cooling operation is performed. As the cooling operation, the homeotropic alignment liquid crystal film after the heat treatment can be performed by taking it out from the heating atmosphere in the heat treatment operation to room temperature. Moreover, you may perform forced cooling, such as air cooling and water cooling. The orientation of the homeotropic alignment layer of the side chain type liquid crystal polymer is fixed by cooling to the glass transition temperature or lower of the side chain type liquid crystal polymer.
[0051]
In the case of a liquid crystalline composition, the homeotropic liquid crystal alignment layer thus fixed is irradiated with light to polymerize or crosslink the photopolymerizable liquid crystal compound to fix the photopolymerizable liquid crystal compound, A homeotropic alignment liquid crystal layer with improved durability is obtained. Light irradiation is performed by, for example, ultraviolet irradiation. The ultraviolet irradiation conditions are preferably in an inert gas atmosphere in order to sufficiently promote the reaction. Usually, a high-pressure mercury ultraviolet lamp having an illuminance of about 80 to 160 mW / cm ² is typically used. Different types of lamps such as metahalide UV lamps and incandescent tubes can also be used. It should be noted that the liquid crystal layer surface temperature at the time of ultraviolet irradiation is appropriately adjusted by, for example, a cold mirror, water cooling or other cooling treatment, or by increasing the line speed.
[0052]
In this way, a thin film of a side chain type liquid crystal polymer or a liquid crystalline composition is produced, and the homeotropic alignment liquid crystal layer (1) is obtained by fixing it while maintaining the alignment. The thickness of the homeotropic alignment liquid crystal film of the present invention is not particularly limited, but the thickness of the homeotropic alignment liquid crystal film layer composed of the coated side chain type liquid crystal polymer is preferably about 0.5 to 200 μm. If the thickness is 0.5 μm or less, it is difficult to control the thickness because the film thickness is too thin. When it exceeds 200 μm, it is combined as an elliptically polarizing plate, and when it is recessed in the image display device, there are cases where the vertical and horizontal viewing angles are widened, but conversely, narrowing directions are generated. The homeotropic alignment liquid crystal layer (1) can be used with or without peeling from the substrate.
[0053]
In the optical film (2), the direction in which the in-plane refractive index is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. When nx ₂ , ny ₂ , and nz ₂ are satisfied, those satisfying nx ₂ > ny ₂ ≈nz ₂ are used. That is, in the three-dimensional refractive index ellipsoid, a material exhibiting optically positive uniaxiality in which the refractive index of the principal axis in one direction is larger than the refractive indexes in the other two directions is used.
[0054]
The optical film (2) can be obtained, for example, by subjecting a polymer film to uniaxial stretching in the surface direction. Examples of the polymer that forms the optical film (2) include polyolefins such as polycarbonate and polypropylene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, norbornene polymers, polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, and polyhydroxyethyl. Cellulose polymers such as acrylate, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyvinyl chloride, and triacetyl cellulose Acrylic polymer, styrene polymer These binary and ternary various copolymers, graft copolymers, and any blend thereof. Of these, norbornene-based polymers are preferred.
[0055]
A rod-like nematic liquid crystalline compound can also be used. The rod-like nematic liquid crystalline compound can be tilted and the tilted alignment state is determined depending on the molecular structure, the type of the alignment film, and an additive (for example, a plasticizer, a binder, an interface). Can be controlled by the use of an activator).
[0056]
The front phase difference ((nx ₂ −ny ₂ ) × d ₂ (thickness: nm)) of the optical film (2) is preferably 0 to 500 nm, and more preferably 1 to 350 nm. The thickness direction retardation ((nx ₂ −nz ₂ ) × d ₂ ) is preferably 0 to 500 nm, and more preferably 1 to 350 nm.
[0057]
The thickness of the optical film _{(2) (d} 2) is not particularly limited but is preferably 1 to 200 [mu] m, more preferably from 2 to 80 [mu] m.
[0058]
When a λ / 4 plate or a λ / 2 plate is used as the optical film (2), a film in which the front phase difference is appropriately adjusted so as to have a predetermined phase difference is used.
[0059]
The optically negative uniaxial material forming the optical film (3) is a material in which the refractive index of the principal axis in one direction is smaller than the refractive index in the other two directions in the three-dimensional refractive index ellipsoid. Show.
[0060]
Examples of the optically negative uniaxial material include polyimide materials and liquid crystal materials such as discotic liquid crystal compounds. In addition, a material in which these materials are the main components and mixed and reacted with other oligomers or polymers to fix a state in which a material exhibiting negative uniaxiality is tilt-oriented is fixed to form a film. When a discotic liquid crystal compound is used, the tilted alignment state of the liquid crystalline molecules is determined depending on the molecular structure, the type of alignment film, and additives that are appropriately added to the optically anisotropic layer (eg, plasticizer, binder, surfactant). Can be controlled by using.
[0061]
The direction in which the refractive index in the film plane of the optical film (3) is the maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. ₃ , ny ₃ , nz ₃ , the front phase difference ((nx ₃ −ny ₃ ) × d ₃ (thickness: nm)) of the optical film (3) is preferably 0 to 200 nm, More preferably, it is 1-150 nm. The thickness direction retardation ((nx ₃ −nz ₃ ) × d ₃ ) is preferably 10 to 400 nm, and more preferably 50 to 300 nm.
[0062]
The thickness (d ₃ ) of the optical film (3) is not particularly limited, but is preferably 1 to 200 μm, and more preferably 2 to 150 μm.
[0063]
The polarizing plate (P) usually has a protective film on one side or both sides of the polarizer. The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And polyene-based oriented films such as those obtained by adsorbing a volatile substance and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.
[0064]
A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.
[0065]
The protective film provided on one side or both sides of the polarizer preferably has excellent transparency, mechanical strength, thermal stability, moisture shielding properties, isotropic properties, and the like. Examples of the material of the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymers, and the like. Examples thereof include styrene polymers such as (AS resin) and polycarbonate polymers. Polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Examples of polymers that form protective films include polymer blends. Other examples include films made of thermosetting or ultraviolet curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone.
[0066]
Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing an unsubstituted phenyl and a thermoplastic resin having a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.
[0067]
A protective film that can be particularly preferably used in terms of polarization characteristics and durability is a triacetylcellulose film whose surface is saponified with an alkali or the like. Although the thickness of a protective film can be determined suitably, generally it is about 10-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 20-300 micrometers is especially preferable, and 30-200 micrometers is more preferable.
[0068]
Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a retardation value in the film thickness direction of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.
[0069]
As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of aqueous adhesives include polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, and the like.
[0070]
As the protective film, a hard coat layer, an antireflection treatment, an anti-sticking treatment, or a treatment subjected to diffusion or anti-glare treatment can be used.
[0071]
Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.
[0072]
The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
[0073]
The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.
[0074]
The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer (a) is not particularly limited, but for example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer as a base polymer Can be appropriately selected and used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.
[0075]
The pressure-sensitive adhesive layer can be formed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method of attaching it directly on the substrate or liquid crystal film by an appropriate development method such as a casting method or a coating method, or forming an adhesive layer on a separator according to the above and transferring it onto the liquid crystal layer The method to do.
[0076]
The pressure-sensitive adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, fillers and pigments made of glass fibers, glass beads, metal powders, other inorganic powders, coloring agents, oxidation agents, and the like. You may contain the additive added to adhesion layers, such as an inhibitor. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.
[0077]
The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.
[0078]
A separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination until it is put into practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.
[0079]
In addition, each layer such as the optical film and the pressure-sensitive adhesive layer is treated with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It is possible to provide ultraviolet absorbing ability by this method.
[0080]
The elliptically polarizing plate of the present invention is suitably used in an image display device. For example, it can be preferably used for forming various devices such as a reflective transflective liquid crystal display device. A reflective transflective liquid crystal display device or the like is suitably used as a portable information communication device or a personal computer. In the case of forming a reflective transflective liquid crystal display device, the elliptically polarizing plate according to the present invention is disposed on the viewing side of the liquid crystal cell.
[0081]
FIG. 19 shows the elliptically polarizing plate (P1) of the present invention shown in FIGS. 4 to 6 and 11 to 14 on the backlight (BL) side of the liquid crystal cell (L) in the reflective transflective liquid crystal display device. It is arranged via an adhesive layer. The side of the elliptically polarizing plate (P1) laminated on the lower (backlight side) liquid crystal cell (L) is not particularly limited, but the polarizing plate (P) of the elliptically polarizing plate (P1) is from the liquid crystal cell (L) side. It is preferable to be the farthest away. Liquid crystal is sealed in the liquid crystal cell (L). The upper liquid crystal cell substrate is provided with a transparent electrode, and the lower liquid crystal cell substrate is provided with a reflective layer that also serves as an electrode. On the other hand, an elliptically polarizing plate (P2) is also provided on the upper side. The elliptically polarizing plate (P2) is also preferably arranged such that the polarizing plate (P) is farthest from the liquid crystal cell (L) side. Various other optical films can be used. A lower part of the lower liquid crystal cell substrate has a backlight system (BL) used for a reflective transflective liquid crystal display device.
[0082]
When the laminated optical film or elliptically polarizing plate of the present invention is mounted on a liquid crystal display device or the like, in the optical film (3), an average optical axis (inclined alignment) of a material that exhibits optically negative uniaxiality. The average angle of the liquid crystal cell (when a voltage is applied) is preferably arranged so as to face the same direction as the alignment direction of the liquid crystal molecules in the midplane of the liquid crystal cell (when voltage is applied).
[0083]
The reflective transflective liquid crystal display device of FIG. 19 shows an example of a liquid crystal cell, and the laminated optical film and the elliptically polarizing plate of the present invention can be applied to various other liquid crystal display devices.
[0084]
A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one surface of the polarizing plate via the transparent protective film or the like, if necessary.
[0085]
A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one surface of the polarizing plate via the transparent protective film or the like, if necessary.
[0086]
Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary.
[0087]
The reflection plate can be used as a reflection sheet in which a reflection layer is provided on an appropriate film according to the transparent film instead of the method of directly applying to the transparent protective film of the polarizing plate. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.
[0088]
The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.
[0089]
Moreover, the polarizing plate which bonded the polarizing plate and the brightness enhancement film is normally provided and used on the back side of the liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.
[0090]
A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.
[0091]
The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.
[0092]
Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that emits circularly polarized light such as a cholesteric liquid crystal layer, it can be incident on a polarizer as it is, but from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.
[0093]
A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.
[0094]
In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.
[0095]
Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.
[0096]
The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by assembling components such as a liquid crystal cell, an optical element, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the elliptically polarizing plate of this invention, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.
[0097]
On the back side of the liquid crystal cell, an appropriate liquid crystal display device such as a lighting system using a backlight or a reflector can be formed. In that case, the elliptically polarizing plate of this invention can be installed in the one side or both sides of a liquid crystal cell. When optical elements are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.
[0098]
Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.
[0099]
In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.
[0100]
In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.
[0101]
In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.
[0102]
In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.
[0103]
Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a 1/4 wavelength plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .
[0104]
That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a 1/4 wavelength plate and the angle between the polarization direction of the polarizing plate and the phase difference plate is π / 4. .
[0105]
This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.
[0106]
【Example】
Examples of the present invention will be described below with reference to examples, but the present invention is not limited to the examples.
[0107]
The refractive index and retardation of each optical film are measured using the automatic birefringence measuring device (manufactured by Oji Scientific Instruments Co., Ltd., automatic birefringence meter KOBRA21ADH) using the main refractive indices nx, ny and nz in the film plane and in the thickness direction. ), The characteristics at λ = 590 nm were measured.
[0108]
In the optical film (3), the tilt angle formed from the average optical axis of the optical material that is tilt-oriented and the normal direction of the optical film (3) is to the left and right with the optical film (3) as the slow axis. The phase difference was measured with the measuring device at an angle of 50 ° to 50 °, and the absolute value of the angle indicating the minimum phase difference was obtained. In the measurement, the measurement angle when the incident direction of light from the light source of the measuring instrument coincided with the normal to the film plane was set to 0 °.
[0109]
(Homeotropic alignment liquid crystal layer (1))
[Chemical 6]

5 parts by weight of the side chain type liquid crystal polymer represented by the above chemical formula 6 (the number in the formula represents the mol% of the monomer unit and is expressed as a block body for the sake of convenience), and the nematic liquid crystal phase. 20 parts by weight of the polymerizable liquid crystal (Paliocolor LC242, manufactured by BASF) and 3 parts by weight of the photoinitiator (Irgacure 907, manufactured by Ciba Specialty Chemicals) were dissolved in 75 parts by weight of cyclohexanone. A solution was prepared. And after apply | coating the said solution to the polyethylene terephthalate base material which apply | coated the lecithin with a bar coater and carrying out dry orientation at 100 degreeC for 10 minutes, 1 mJ / cm < ² > light was irradiated with a metal halide lamp, thickness A homeotropic alignment liquid crystal layer having a thickness of about 0.7 μm was obtained. The thickness direction retardation of the homeotropic alignment liquid crystal layer was −70 nm.
[0110]
(Optical film (2))
A norbornene-based unstretched film having a thickness of 100 μm (manufactured by JSR Corporation, product name Arton) was uniaxially stretched 1.3 times at 170 ° C. The obtained stretched film had a thickness of 80 μm, a front phase difference of 140 nm, and a thickness direction retardation of 140 nm. This stretched film was designated as an optical film (2 (1)).
[0111]
In addition, a norbornene-based unstretched film having a thickness of 100 μm (manufactured by JSR Corporation, product name Arton) was uniaxially stretched 1.6 times at 170 ° C. The obtained stretched film had a thickness of 70 μm, a front phase difference of 280 nm, and a thickness direction retardation of 280 nm. This stretched film was designated as an optical film (2 (2)).
[0112]
(Optical film (3))
WVSA12B (thickness: 110 μm) manufactured by Fuji Photo Film Co., Ltd. was used. The film is prepared by applying a discotic liquid crystal to a support, and has a front phase difference of 30 nm, a thickness direction retardation of 160 nm, and an inclination angle of an average optical axis that is inclined and aligned: 20 °.
[0113]
Example 1
(Laminated optical film)
The homeotropic alignment liquid crystal film (1), the optical film (2 (1)), and the optical film (3) obtained above were bonded to an adhesive layer (acrylic adhesive, thickness 30 μm as shown in FIG. ) To obtain a laminated optical film.
[0114]
(Ellipse polarizing plate)
As shown in FIG. 4, a polarizing plate (manufactured by Nitto Denko Corporation, SEG1465DU) is bonded to the laminated optical film via an adhesive layer (acrylic adhesive, thickness 30 μm) to obtain an elliptical polarizing plate. It was. Bonding was performed so that the slow axis of the optical film (2 (1)) intersected with 30 ° with respect to the absorption axis of the polarizing plate.
[0115]
Example 2
In Example 1, the laminated optical film and the elliptical film were laminated in the same manner as in Example 1 except that the laminated order of the laminated optical films was changed as shown in FIG. 2, and the laminated order of the elliptically polarizing plates was changed as shown in FIG. A polarizing plate was obtained.
[0116]
Example 3
In Example 1, the laminated optical film and the elliptical film were laminated in the same manner as in Example 1 except that the laminated order of the laminated optical films was changed as shown in FIG. 3 and the laminated order of the elliptically polarizing plates was changed as shown in FIG. A polarizing plate was obtained.
[0117]
Example 4
(Laminated optical film)
As shown in FIG. 7, the homeotropic alignment liquid crystal film (1), the optical film (2 (1)), the optical film (2 (2)), and the optical film (3) obtained above are used as an adhesive layer. A laminated optical film was obtained by laminating via (acrylic adhesive, thickness 30 μm). In addition, bonding was performed so that the slow axis of an optical film (2 (1)) and an optical film (2 (2)) board might cross | intersect at 75 degrees.
[0118]
(Ellipse polarizing plate)
As shown in FIG. 11, a polarizing plate (manufactured by Nitto Denko Corporation, SEG1465DU) is bonded to the laminated optical film via an adhesive layer (acrylic adhesive, thickness 30 μm) to obtain an elliptical polarizing plate. It was. Bonding was performed so that the slow axis of the optical film (2 (1)) intersected with 30 ° with respect to the absorption axis of the polarizing plate.
[0119]
Example 5
In Example 4, the laminated optical film and the elliptical film were laminated in the same manner as in Example 4 except that the laminated order of the laminated optical films was changed as shown in FIG. 10 and the laminated order of the elliptically polarizing plates was changed as shown in FIG. A polarizing plate was obtained.
[0120]
Example 6
In Example 4, the laminated optical film and the elliptical optical film were laminated in the same manner as in Example 4 except that the laminated order of the laminated optical films was changed as shown in FIG. 9, and the laminated order of the elliptically polarizing plates was changed as shown in FIG. A polarizing plate was obtained.
[0121]
Example 7
In Example 4, the laminated optical film and the elliptical optical film were laminated in the same manner as in Example 4 except that the laminated order of the laminated optical films was changed as shown in FIG. 8 and the laminated order of the elliptically polarizing plates was changed as shown in FIG. A polarizing plate was obtained.
[0122]
Comparative Example 1
Using the polarizing plate, the optical film (2 (1)), and the homeotropic alignment liquid crystal film (1), as shown in FIG. 15, it bonded to the polarizing plate through the adhesive layer, and obtained the elliptically polarizing plate. Note that the bonding was performed such that the slow axis of the optical film (2 (1)) intersected at 45 ° with respect to the absorption axis of the polarizing plate.
[0123]
Comparative Example 2
Using the polarizing plate, the optical film (2 (1)), and the optical film (3), as shown in FIG. 16, it bonded together to the polarizing plate through the adhesive layer, and obtained the elliptically polarizing plate. Bonding was performed so that the slow axis of the optical film (2 (1)) intersected with 30 ° with respect to the absorption axis of the polarizing plate.
[0124]
Comparative Example 3
Using a polarizing plate, an optical film (2 (1)), an optical film (2 (2)), and an optical film (3), as shown in FIG. I got a plate. Bonding was performed so that the slow axis of the optical film (2 (2)) intersected with 30 ° with respect to the absorption axis of the polarizing plate.
[0125]
Reference example 1
Using the polarizing plate, the optical film (2 (1)) and the optical film (2 (2)), as shown in FIG. 18, it was bonded to the polarizing plate through an adhesive layer to obtain an elliptical polarizing plate. Bonding was performed so that the slow axis of the optical film (2 (2)) intersected with 30 ° with respect to the absorption axis of the polarizing plate.
[0126]
(Evaluation)
As shown in FIG. 19, the elliptically polarizing plates obtained in the examples and comparative examples were mounted as the elliptically polarizing plate (P1) on the backlight side of the reflective transflective TFT-TN type liquid crystal display device. On the other hand, the elliptically polarizing plate produced in Reference Example 1 was mounted as the elliptical polarizing plate (P2) on the viewing side. The elliptically polarizing plate (P1) and the elliptically polarizing plate (P2) were both mounted such that the polarizing plate side was the most distant from the liquid crystal cell (L) side.
[0127]
Next, a white image and a black image are displayed on the liquid crystal display device, and the Y value, x value, and y value in the XYZ display system at the front, top, bottom, left, and right, and viewing angles of 0 to 70 ° are displayed on EZcontrast 160D manufactured by ELDIM. Was measured.
[0128]
The angle at which the contrast (Y value (white image) / Y value (black image)) at that time was 10 or more was defined as the viewing angle. The results are shown in Table 1.
[0129]
For the white image, the chromaticity change amount of the chromaticity (x ₄₀ , y ₄₀ ) was compared and evaluated when the white image was tilted by 40 ° vertically and horizontally with respect to the chromaticity (x ₀ , y ₀ ) in front of the screen. The amount of change in chromaticity was determined by the following formula. The results are shown in Table 1.
Chromaticity change amount = √ {(x ₄₀ −x ₀ ) ² + (y ₄₀ −y ₀ ) ² }
[0130]
[Table 1]

[Brief description of the drawings]
FIG. 1 is an embodiment of a cross-sectional view of a laminated optical film of the present invention.
FIG. 2 is an embodiment of a cross-sectional view of the laminated optical film of the present invention.
FIG. 3 is an embodiment of a cross-sectional view of the laminated optical film of the present invention.
FIG. 4 is one embodiment of a cross-sectional view of the elliptically polarizing plate of the present invention.
FIG. 5 is an embodiment of a cross-sectional view of the elliptically polarizing plate of the present invention.
FIG. 6 is one embodiment of a cross-sectional view of the elliptically polarizing plate of the present invention.
FIG. 7 is an embodiment of a cross-sectional view of the laminated optical film of the present invention.
FIG. 8 is an embodiment of a cross-sectional view of the laminated optical film of the present invention.
FIG. 9 is an embodiment of a cross-sectional view of the laminated optical film of the present invention.
FIG. 10 is an embodiment of a cross-sectional view of the laminated optical film of the present invention.
FIG. 11 is one embodiment of a cross-sectional view of the elliptically polarizing plate of the present invention.
FIG. 12 is a cross-sectional view of an elliptically polarizing plate of the present invention.
FIG. 13 is one embodiment of a cross-sectional view of the elliptically polarizing plate of the present invention.
FIG. 14 is one embodiment of a cross-sectional view of the elliptically polarizing plate of the present invention.
FIG. 15 is one embodiment of a cross-sectional view of an elliptically polarizing plate of a comparative example.
FIG. 16 is an embodiment of a cross-sectional view of an elliptically polarizing plate of a comparative example.
FIG. 17 is one embodiment of a cross-sectional view of an elliptically polarizing plate of a comparative example.
FIG. 18 is a cross-sectional view of an elliptically polarizing plate of a reference example.
FIG. 19 is a cross-sectional view of an example of a reflective transflective liquid crystal display device according to an embodiment.
[Explanation of symbols]
1: Homeotropic alignment liquid crystal layer 2: Optical film satisfying nx ₂ > ny ₂ ≈ nz ₂ : Optical film formed by obliquely aligning a material exhibiting negative uniaxiality: Adhesive layer P: Polarizing plate L : Liquid crystal cell BL: Backlight

Claims (16)

At least a homeotropic alignment liquid crystal layer (1);
The direction in which the refractive index in the film plane is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. The refractive indexes in the respective axial directions are nx ₂ , ny ₂ , nz ₂ and an optical film (2) satisfying nx ₂ > ny ₂ ≈nz ₂ ,
An optical film (3) formed of a material exhibiting optically negative uniaxial properties, and the material is inclined and oriented, is laminated. The laminated optical film according to claim 1, wherein the optical film (2) is a film formed from a polymer having a norbornene skeleton. In the homeotropic alignment liquid crystal layer (1), the direction in which the in-plane refractive index is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction is the Z axis. When nx ₁ , ny ₁ , and nz ₁ are set,
3. The thickness direction retardation: {((nx ₁ + ny ₁ ) / 2) −nz ₁ } × d (thickness: nm) is −10 nm to −500 nm. 3. Laminated optical film. The laminated optical film according to any one of claims 1 to 3, wherein the optically negative uniaxial material forming the optical film (3) is a discotic liquid crystal compound. The material that forms the optical film (3) and exhibits optically negative uniaxiality is inclined in the range of 5 ° to 50 ° with an inclination angle between the average optical axis and the normal direction of the optical film (3). The laminated optical film according to claim 1, wherein the laminated optical film is oriented. The laminated optical film according to any one of claims 1 to 5, wherein a λ / 4 plate is laminated as the optical film (2). Two or more optical films (2) are laminated | stacked, The laminated | multilayer optical film in any one of Claims 1-5 characterized by the above-mentioned. The laminated optical film according to claim 7, wherein the homeotropic alignment liquid crystal layer (1) is laminated so as to be positioned between two or more laminated optical films (2). The laminated optical film according to claim 7 or 8, wherein the two or more laminated optical films (2) are obtained by laminating a λ / 4 plate and a λ / 2 plate. The laminated optical film of Claims 1-9 and the polarizing plate are laminated | stacked, The elliptically polarizing plate characterized by the above-mentioned. The elliptically polarizing plate according to claim 10, wherein the polarizing plate, the optical film (2), the homeotropic alignment liquid crystal layer (1), and the optical film (3) are laminated in this order. 11. The elliptically polarizing plate according to claim 10, wherein a polarizing plate, a homeotropic alignment liquid crystal layer (1), an optical film (2), and an optical film (3) are laminated in this order. The λ / 4 plate and the λ / 2 plate are laminated as the optical film (2), and the λ / 2 plate and the λ / 4 plate are laminated in this order from the polarizing plate side. The elliptically polarizing plate in any one of 10-12. As the optical film (2), a λ / 4 plate and a λ / 2 plate are laminated. From the polarizing plate side, a λ / 2 plate, a homeotropic alignment liquid crystal layer (1), a λ / 4 plate, an optical film (3 The elliptically polarizing plate according to claim 10, which is laminated in the order of As the optical film (2), a λ / 4 plate and a λ / 2 plate are laminated. From the polarizing plate side, a λ / 2 plate, a λ / 4 plate, a homeotropic alignment liquid crystal layer (1), an optical film (3 The elliptically polarizing plate according to claim 10, which is laminated in the order of An image display device comprising the laminated optical film according to any one of claims 1 to 9 and the elliptically polarizing plate according to any one of claims 10 to 15.

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