JP3981638B2 - Optical film, production method thereof, retardation film and polarizing plate using the same - Google Patents

Description

【０００９】
【化６】

【００１０】
本発明においてコレステリック層とは、前記層の構成分子がらせん構造をとり、そのらせん軸が面方向にほぼ垂直に配向している、いわゆる平面組織またはグランジャン組織と呼ばれる擬似層構造を有する層ということもできる。また、本発明において「構成分子がコレステリック構造をとっている」とは、例えば、液晶化合物が、コレステリック液晶相となっている場合には限定されず、液晶相では無いが、非液晶化合物が、前記コレステリック液晶相のようにねじれた状態で配向しているものも含む。
【００１１】
本発明らは、前記課題を解決すべく詳細な検討を行った。その結果、選択反射波長が４００ｎｍ以下、すなわち３３０ｎｍ〜４００ｎｍのコレステリック層を有する位相差板であっても、液晶化合物がらせん構造をとることによる選択反射が原因となって着色が生じ、この着色の影響によって、透過率の測定時における単体色相ｂ値が１．２以上となることがわかった。また、この位相差板を偏光板と貼合せた場合、クロスニコル状態で、法線方向における光漏れが全面に生じ、４２７ｎｍの直交透過率も、前記偏光板のみの直交透過率より０．２３５％も大きくなるという問題が生じることをつきとめた。目視でクロスニコル状態の黒表示を確認した結果、前面が青く見えるという現象もわかった。これらの結果から、このような光漏れは、選択反射が可視光範囲（約４００ｎｍ〜７００ｎｍ）に影響を及ぼすために生じると考え、３３０ｎｍ〜４００ｎｍの選択反射波長であっても、複屈折層として使用した場合、優れた表示品位をもつ液晶表示装置を形成することは困難であるとの知見を得たのである。
【００１２】
そこで、本発明者らは、さらに研究を重ねた結果、前記のような「液晶モノマー」と前記のようなカイラル剤とを使用し、この液晶モノマーとカイラル剤との配合割合をコントロールして、前記液晶モノマーをカイラル剤によってコレステリック構造に配向させた後、その配向を重合や架橋により固定することによって形成したコレステリック層であれば、前記選択反射波長帯域を１００ｎｍ〜３２０ｎｍに制御することができ、その範囲であれば、従来のような光漏れの問題を回避できることを見出したのである。なお、液晶モノマーを使用し、前記配合割合のコントロールすることによって、選択反射波長帯域が制御可能になることは、本発明者らが初めて見出したことである。
【００１３】
このように選択反射波長帯域が前記範囲に制御された光学フィルムであれば、例えば、従来のような選択反射が原因となる着色が防止される。つまり、選択反射波長が可視光波長（４００ｎｍ以上）に近いほど、可視光領域に影響を及ぼすため、光もれが発生し、それによって着色が見られるが、前記範囲に制御することによって光もれが抑制されるのである。このため、本発明の光学フィルムを位相差フィルムとして使用すれば、広い視野角範囲となり、正面方向および斜視方向のいずれにおいても優れた表示品位が達成できる。このため、液晶表示装置等の各種画像表示装置にも有用である。
【００１４】
次に、本発明の位相差フィルムは、前記本発明の光学フィルムを含む。また、本発明の偏光板は、前記本発明の位相差フィルムと偏光フィルムとを含み、特に光学補償用偏光板として有用である。さらに、前記本発明の位相差フィルムまたは偏光板は、液晶表示装置やエレクトロルミネッセンス（ＥＬ）装置等の各種画像表示装置に有用である。
【００１５】
【発明の実施の形態】
前述のように本発明の光学フィルムは、コレステリック層を含む光学フィルムであって、
前記層の構成分子が、コレステリック構造をとって配向しており、
前記層の選択反射波長帯域が、１００ｎｍ〜３２０ｎｍの範囲であり、
コレステリック層構成分子が非液晶ポリマーであって、前記非液晶ポリマーが、カイラル剤によってコレステリック構造をとって配向した液晶モノマーを重合または架橋したポリマーであり、
前記液晶モノマーが、下記式（４）で表される化合物、下記式（５）で表される化合物、下記式（６）で表される化合物、下記式（７）で表される化合物、下記式（８）で表される化合物、下記式（９）で表される化合物、下記式（１０）で表される化合物、下記式（１１）で表される化合物、下記式（１２）で表される化合物、下記式（１３）で表される化合物、下記式（１４）で表される化合物、下記式（１５）で表される化合物、下記式（１６）で表される化合物、下記式（１７）で表される化合物、下記式（１８）で表される化合物および下記式（１９）で表される化合物からなる群から選択される少なくとも１つの液晶モノマーであり、
前記カイラル剤が、下記式（２４）で表される化合物、下記式（２５）で表される化合物、下記式（２６）で表される化合物、下記式（２７）で表される化合物、下記式（２８）で表される化合物、下記式（２９）で表される化合物、下記式（３０）で表される化合物、下記式（３１）で表される化合物、下記式（３２）で表される化合物、下記式（３３）で表される化合物、下記式（３４）で表される化合物、下記式（３５）で表される化合物、下記式（３６）で表される化合物、下記式（３７）で表される化合物、下記式（３８）で表される化合物、下記式（３９）で表される化合物、下記式（４０）で表される化合物、下記式（４１）で表される化合物、下記式（４２）で表される化合物、下記式（４３）で表される化合物および下記式（４４）で表される化合物からなる群から選択される少なくとも１つのカイラル剤であり、
前記コレステリック層における液晶モノマーの割合が、７５〜９５重量％の範囲であり、
前記液晶モノマーに対するカイラル剤の割合が、５〜２３重量％の範囲であることを特徴とする。
【００１６】
【化７】

【００１７】
【化８】

【００１８】
前記選択反射波長帯域λ（ｎｍ）の中心波長は、例えば、コレステリック層が後述するように液晶モノマーを使用して形成されている場合、下記式で表すことができる。
λ＝ｎ・Ｐ
前記式において、ｎは、前記液晶モノマーの平均屈折率を示し、Ｐは前記コレステリック層のらせんピッチ（μｍ）を示す。前記平均屈折率ｎは、「（ｎ_o＋ｎ_e）／２」で表され、通常、１．４５〜１．６５の範囲であり、ｎ_oは、前記液晶モノマーの正常光屈折、ｎ_eは前記液晶モノマーの異常屈折率を示す。
【００１９】
前記選択反射波長帯域の上限は、前述のように３２０ｎｍ以下であり、好ましくは３００ｎｍ以下である。一方、選択反射波長帯域の下限は、前述のように１００ｎｍ以上であり、好ましくは１５０ｎｍ以上である。前記選択反射波長帯域が３２０ｎｍを超えると、可視光領域に選択反射波長帯域が入るため、例えば、前述のような着色や色抜けという問題が生じる。一方、前記選択反射波長帯域が１００ｎｍより小さい光学フィルムは、以下のような問題がある。すなわち、後述するように、本発明の光学フィルム製造時において、選択反射波長帯域の設定は、例えば、液晶モノマー等の構成材料とカイラル剤との添加割合を制御することによって行うことができる。そして、選択反射波長帯域を短波長側にシフトする手段として、例えば、カイラル剤添加量を増加する方法があるが、カイラル剤の添加量が増えると、液晶モノマー等の構成材料がコレステリック配向をとる温度範囲、すなわち液晶相となる温度範囲が非常に狭くなるのである。そのため、製造時において前記構成材料をコレステリック配向させるための温度制御を厳密に行うことが必要となり、製造が困難になるという問題があるためである。
【００２０】
本発明の光学フィルムは、例えば、前述のような３つの軸方向における屈折率（ｎｘ，ｎｙ，ｎｚ）を、ｎｘ≒ｎｙ＞ｎｚとすることが好ましい。このような光学フィルムは、いわゆるｎｅｇａｔｉｖｅ Ｃ−Ｐｌａｔｅの位相差板として使用することができる。
【００２１】
本発明において、前記コレステリック層の５９０ｎｍにおける面内位相差（Δｎｄ）は、例えば、２ｎｍ以下であり、好ましくは１．５ｎｍ以下である。前記面内位相差は、前記選択反射波長を１００ｎｍ〜３２０ｎｍの範囲に制御することによって、前述のような範囲に制御できる傾向にある。なお、前記面内位相差（Δｎｄ）とは、下記式で表される。下記式において「ｎｘ、ｎｙ」は、それぞれ前記図２と同様に、面内において垂直の関係にあるＸ軸方向およびＹ軸方向の屈折率であり、面内において最大値の屈折率を示す方向がＸ軸である。また、「ｄ」は膜厚を示す。
Δｎｄ＝（ｎｘ−ｎｙ）・ｄ
【００２２】
選択反射波長帯域を前記範囲に制御するために、前記コレステリック層は、カイラル剤を含む。本発明における前記カイラル剤とは、例えば、後述するような液晶モノマーや液晶ポリマーをコレステリック構造となるように配向する機能を有する化合物である。
【００２３】
これらのカイラル剤の中でも、そのねじり力が、１×１０^-6ｎｍ^-1・（ｗｔ％）^-1以上であることが好ましく、より好ましくは１×１０^-5ｎｍ^-1・（ｗｔ％）^-1以上であり、さらに好ましくは１×１０^-5〜１×１０^-2ｎｍ^-1・（ｗｔ％）^-1の範囲であり、特に好ましくは１×１０^-4〜１×１０^-3ｎｍ^-1・（ｗｔ％）^-1の範囲である。このようなねじり力のカイラル剤を使用すれば、例えば、形成されたコレステリック層のらせんピッチを、後述する範囲に制御でき、これによって前記選択反射波長帯域を、前記範囲に制御することが十分に可能となる。
【００２４】
なお、前記ねじり力とは、一般に、後述するような液晶モノマーや液晶ポリマー等の液晶材料にねじれを与え、らせん状に配向させる能力のことを示し、下記式で表すことができる。
ねじり力＝１／［コレステリックピッチ（ｎｍ）×カイラル剤重量比（ｗｔ％）］
【００２５】
前記式においてカイラル剤重量比とは、例えば、液晶モノマーまたは液晶ポリマーとカイラル剤とを含む混合物における前記カイラル剤の割合（重量比）をいい、下記式で表される。
カイラル剤重量比（ｗｔ％）＝ ［Ｘ／（Ｘ＋Ｙ）］×１００
Ｘ：カイラル剤重量
Ｙ：液晶モノマー重量または液晶ポリマー重量
【００２６】
また、前記コレステリック層におけるらせんピッチは、例えば、０．０１〜０．２５μｍの範囲が好ましく、より好ましくは０．０３〜０．２０μｍの範囲、特に好ましくは０．０５〜０．１５μｍの範囲である。前記らせんピッチが０．０１μｍ以上であれば、例えば、十分な配向性が得られ、０．２５μｍ以下であれば、例えば、可視光の短波長側における旋光性を十分に抑制できるため、偏光下で補償用の位相差フィルム等として使用する場合に、光漏れ等を十分に回避できる。そして、前述のようなねじり力のカイラル剤を使用すれば、形成されたコレステリック層のらせんピッチを前記範囲に制御できる。
【００２７】
本発明の光学フィルムは、前述のような範囲に選択反射波長帯域が制御されているため、その単体色相ｂ値が、例えば、１．２以下であり、着色が少なく、非常に優れた光学特性を示すといえる。前記単体色相ｂ値は、より好ましくは１．１以下であり、特に好ましくは１．０以下である。また、その直交色相ｂ値は、例えば、−０．５〜１．０であり、より好ましくは−０．３〜０．８であり、特に好ましくは−０．１〜０．８以下である。また、本発明の光学フィルムの４３０ｎｍにおける直交透過率は、例えば、０．１５以下であり、好ましくは０．１０以下であり、より好ましくは０．０８以下である。
【００２８】
なお、前記単体色相ｂ値は、ハンターＬａｂ表色系（Hunter, R. S.: J. Opt. Soc. Amer., 38, 661(A),1094(A)(1948); J.Opt. Soc. Amer., 48, 985(1958)）により規定される。具体的には、例えば、ＪＩＳ Ｋ ７１０５ ５．３に準じて、分光測定器または光電色彩計を用いて、試料の三刺激値（Ｘ、Ｙ、Ｚ）を測定し、これらの値をＬａｂ空間における色差公式として以下に示すＨｕｎｔｅｒの式に代入することによって、単体色相ｂ値が算出できる。この測定には、通常、Ｃ光源が使用される。例えば、積分球式分光透過率測定器（商品名ＤＯＴ−３Ｃ；村上色彩技術研究所製）によれば、透過率と共に単体色相ｂ値が測定できる。
単体色相ｂ＝７．０×（Ｙ−０．８４７Ｚ）／Ｙ^1/2
【００２９】
また、前記直交色相ｂ値は、以下のようにして測定できる。偏光板をクロスニコルに配置し、その間に前記光学フィルムを配置して、前述のようなハンターＬａｂ表色系に基づき、色相ｂ１を測定する。一方、光学フィルムを配置せず、クロスニコルに配置した偏光板のみで色相ｂ２を測定する。そして、色相ｂ１から色相ｂ２を差し引く（ｂ１−ｂ２）ことによって、直交色相ｂ値を求めることができる。
【００３０】
本発明において、前記構成分子は、例えば、非液晶ポリマーであって、前記非液晶ポリマーは、コレステリック構造をとって配向した液晶モノマーを重合または架橋したポリマーである。このような構成であれば、後述するように、前記モノマーが液晶性を示すため、コレステリック構造をとって配向させることができ、かつ、さらにモノマー間を重合等させることによって前記配向を固定できる。そして、液晶モノマーを使用するが、前記固定によって、重合したポリマーは非液晶性となる。このため、形成されたコレステリック層は、コレステリック液晶相のようなコレステリック構造をとるが、液晶分子から構成されていないため、例えば、液晶分子に特有の、温度変化による液晶相、ガラス相、結晶相への変化が起きることもない。したがって、そのコレステリック構造が温度変化に影響されない、極めて安定性に優れた光学フィルムとなり、例えば、特に光学補償用位相差フィルムとして有用であるといえる。
【００３１】
前記液晶モノマーは、前記の化学式で表されるモノマーである。このような液晶モノマーは、一般に、ネマチック性液晶モノマーであるが、本発明においては、前記カイラル剤によってねじりが付与され、最終的には、コレステリック構造をとるようになる。また、前記コレステリック層においては、配向固定のために、前記モノマー間が重合または架橋される必要があるため、前記モノマーは、重合性モノマーおよび架橋性モノマーの少なくとも一方を含むことが好ましい。
【００３２】
前記コレステリック層は、さらに、重合剤および架橋剤の少なくとも一方を含むことが好ましく、例えば、紫外線硬化剤、光硬化剤、熱硬化剤等の物質が使用できる。
【００３３】
前記コレステリック層における液晶モノマーの割合は、７５〜９５重量％の範囲であることが好ましく、より好ましくは８０〜９０重量％の範囲である。また、前記液晶モノマーに対するカイラル剤の割合は、５〜２３重量％の範囲であることが好ましく、より好ましくは１０〜２０重量％の範囲である。また、前記液晶モノマーに対する架橋剤または重合剤の割合は、０．１〜１０重量％の範囲であることが好ましく、より好ましくは０．５〜８重量％の範囲であり、特に好ましくは１〜５重量％の範囲である。
【００３４】
前記光学フィルムの厚みは、特に制限されないが、例えば、補償用等の位相差フィルムとして使用する場合、配向の乱れや透過率低下の防止、選択反射性、着色防止、生産性等の点から、０．１〜１０μｍの範囲であることが好ましく、より好ましくは０．５〜８μｍの範囲、特に好ましくは１〜５μｍの範囲である。
【００３５】
本発明の光学フィルムは、例えば、前述のようなコレステリック層のみから形成されてもよいが、さらに基板を含み、前記基板上に前記コレステリック層が積層された積層体であってもよい。
【００３６】
つぎに、本発明の光学フィルムの製造方法は、
コレステリック層を含み、前記層の構成分子が、コレステリック構造をとって配向している光学フィルムの製造方法であって、
前記式（４）で表される化合物、前記式（５）で表される化合物、前記式（６）で表される化合物、前記式（７）で表される化合物、前記式（８）で表される化合物、前記式（９）で表される化合物、前記式（１０）で表される化合物、前記式（１１）で表される化合物、前記式（１２）で表される化合物、前記式（１３）で表される化合物、前記式（１４）で表される化合物、前記式（１５）で表される化合物、前記式（１６）で表される化合物、前記式（１７）で表される化合物、前記式（１８）で表される化合物および前記式（１９）で表される化合物からなる群から選択される少なくとも１つの液晶モノマーと、前記式（２４）で表される化合物、前記式（２５）で表される化合物、前記式（２６）で表される化合物、前記式（２７）で表される化合物、前記式（２８）で表される化合物、前記式（２９）で表される化合物、前記式（３０）で表される化合物、前記式（３１）で表される化合物、前記式（３２）で表される化合物、前記式（３３）で表される化合物、前記式（３４）で表される化合物、前記式（３５）で表される化合物、前記式（３６）で表される化合物、前記式（３７）で表される化合物、前記式（３８）で表される化合物、前記式（３９）で表される化合物、前記式（４０）で表される化合物、前記式（４１）で表される化合物、前記式（４２）で表される化合物、前記式（４３）で表される化合物および前記式（４４）で表される化合物からなる群から選択される少なくとも１つのカイラル剤と、重合剤および架橋剤の少なくとも一方とを含み、かつ、前記液晶モノマーに対するカイラル剤の割合が５〜２３重量％の範囲である塗工液を配向基材上に展開して、展開層を形成する工程、
前記液晶モノマーがコレステリック構造をとった配向となるように、前記展開層に加熱処理を施す工程、および、
前記液晶モノマーの配向を固定して非液晶ポリマーのコレステリック層を形成するために、前記展開層に重合処理および架橋処理の少なくとも一方の処理を施す工程を含み、
前記コレステリック層における液晶モノマーの割合が、７５〜９５重量％の範囲であり、前記液晶モノマーに対するカイラル剤の割合が、５〜２３重量％の範囲である製造方法である。このような製造方法によれば、前述のような選択反射波長帯域である本発明の光学フィルムを製造できる。このように液晶モノマーとカイラル剤との配合割合をコントロールすることによって、前記選択反射波長帯域を１００ｎｍ〜３２０ｎｍの範囲に制御できることは、本発明者らが初めて見出したことである。
【００３７】
本発明の光学フィルムの製造方法の一例について、以下に具体的に説明する。まず、前記液晶モノマーと、前記カイラル剤と、前記架橋剤および重合剤の少なくとも一方とを含む塗工液を準備する。
【００３８】
前記液晶モノマーとしては、前記式（４）で表される化合物、前記式（５）で表される化合物、前記式（６）で表される化合物、前記式（７）で表される化合物、前記式（８）で表される化合物、前記式（９）で表される化合物、前記式（１０）で表される化合物、前記式（１１）で表される化合物、前記式（１２）で表される化合物、前記式（１３）で表される化合物、前記式（１４）で表される化合物、前記式（１５）で表される化合物、前記式（１６）で表される化合物、前記式（１７）で表される化合物、前記式（１８）で表される化合物または前記式（１９）で表される化合物があげられる。これらの液晶モノマーは、一種類でもよいし、二種類以上を併用してもよい。
【００３９】
前記液晶モノマーが液晶性を示す温度範囲は、その種類に応じて異なるが、例えば、４０〜１２０℃の範囲であることが好ましく、より好ましくは５０〜１００℃の範囲であり、特に好ましくは６０〜９０℃の範囲である。
【００４０】
前記カイラル化剤としては、前述のように、前記液晶モノマーにねじりを付与してコレステリック構造となるように配向させるものであり、重合性カイラル化剤であることが好ましく、前記式（２４）で表される化合物、前記式（２５）で表される化合物、前記式（２６）で表される化合物、前記式（２７）で表される化合物、前記式（２８）で表される化合物、前記式（２９）で表される化合物、前記式（３０）で表される化合物、前記式（３１）で表される化合物、前記式（３２）で表される化合物、前記式（３３）で表される化合物、前記式（３４）で表される化合物、前記式（３５）で表される化合物、前記式（３６）で表される化合物、前記式（３７）で表される化合物、前記式（３８）で表される化合物、前記式（３９）で表される化合物、前記式（４０）で表される化合物、前記式（４１）で表される化合物、前記式（４２）で表される化合物、前記式（４３）で表される化合物または前記式（４４）で表される化合物である。これらのカイラル剤は、一種類でもよいし、二種類以上を併用してもよい。
【００４１】
なお、これらのカイラル化合物は、ねじり力が１×１０^-6ｎｍ^-1・（ｗｔ％）^-1以上である。
【００４２】
前記重合剤および架橋剤としては、特に制限されないが、例えば、以下のようなものが使用できる。前記重合剤としては、例えば、ベンゾイルパーオキサイド（ＢＰＯ）、アゾビスイソブチロニトリル（ＡＩＢＮ）等が使用でき、前記架橋剤としては、例えば、イソシアネート系架橋剤、エポキシ系架橋剤、金属キレート架橋剤等が使用できる。これらはずれか一種類でもよいし、二種類以上を併用してもよい。
【００４３】
前記塗工液は、例えば、前記液晶モノマー等を、適当な溶媒に溶解・分散することによって調製できる。前記溶媒としては、特に制限されないが、例えば、例えば、クロロホルム、ジクロロメタン、四塩化炭素、ジクロロエタン、テトラクロロエタン、塩化メチレン、トリクロロエチレン、テトラクロロエチレン、クロロベンゼン、オルソジクロロベンゼン等のハロゲン化炭化水素類、フェノール、ｐ−クロロフェノール、ｏ−クロロフェノール、ｍ−クレゾール、ｏ−クレゾール、ｐ−クレゾールなどのフェノール類、ベンゼン、トルエン、キシレン、メトキシベンゼン、１，２−ジメトキシベンゼン等の芳香族炭化水素類、アセトン、メチルエチルケトン（ＭＥＫ）、メチルイソブチルケトン、シクロヘキサノン、シクロペンタノン、２−ピロリドン、Ｎ−メチル−２−ピロリドン等のケトン系溶媒、酢酸エチル、酢酸ブチルなどのエステル系溶媒、ｔ−ブチルアルコール、グリセリン、エチレングリコール、トリエチレングリコール、エチレングリコールモノメチルエーテル、ジエチレングリコールジメチルエーテル、プロピレングリコール、ジプロピレングリコール、２−メチル−２，４−ペンタンジオールのようなアルコール系溶媒、ジメチルホルムアミド、ジメチルアセトアミドのようなアミド系溶媒、アセトニトリル、ブチロニトリルのようなニトリル系溶媒、ジエチルエーテル、ジブチルエーテル、テトラヒドロフラン、ジオキサンのようなエーテル系溶媒、あるいは二硫化炭素、エチルセルソルブ、ブチルセルソルブ等が使用できる。これらの中でも好ましくは、トルエン、キシレン、メシチレン、ＭＥＫ、メチルイソブチルケトン、シクロヘキサノン、エチルセロソルブ、ブチルセロソルブ、酢酸エチル、酢酸ブチル、酢酸プロピル、酢酸エチルセロソルブである。これらの溶剤は、例えば、一種類でもよいし、二種類以上を混合して使用してもよい。
【００４４】
前記カイラル剤の添加割合は、例えば、所望のらせんピッチ、所望の選択反射波長帯域に応じて適宜決定されるが、前記液晶モノマーに対する添加割合は、５〜２３重量％の範囲であり、好ましくは１０〜２０重量％の範囲である。前述のように、液晶モノマーとカイラル剤との添加割合をこのように制御することによって、形成される光学フィルムの選択波長帯域を前述の範囲に設定できるのである。液晶モノマーに対するカイラル剤の割合が５重量％よりも小さい場合、形成される光学フィルムの選択反射波長帯域を低波長側に制御することが困難となる。また、前記割合が２３重量％よりも大きい場合は、液晶モノマーがコレステリック配向する温度範囲、すなわち前記液晶モノマーが液晶相となる温度範囲が狭くなるため、後述する配向工程における温度制御を厳密に行うことが必要となり、製造が困難となる。
【００４５】
例えば、同じねじり力のカイラル剤を使用した場合、液晶モノマーに対するカイラル剤の添加割合が多い方が、形成される選択反射波長帯域は低波長側となる。また、例えば、液晶モノマーに対するカイラル剤の添加割合が同じ場合には、例えば、カイラル剤のねじり力が大きい方が、形成される光学フィルムの選択反射波長帯域は、低波長側となる。具体例として、形成される光学フィルムの前記選択反射波長帯域を２００〜２２０ｎｍの範囲に設定する場合には、例えば、ねじり力が５×１０^-4ｎｍ^-1・（ｗｔ％）^-1のカイラル剤を、液晶モノマーに対して１１〜１３重量％となるように配合すればよく、前記選択反射波長帯域を２９０〜３１０ｎｍの範囲に設定する場合には、例えば、ねじれ力が５×１０^-4ｎｍ^-1・（ｗｔ％）^-1のカイラル剤を、液晶モノマーに対して７〜９重量％となるように配合すればよい。
【００４６】
また、前記液晶モノマーと前記カイラル剤との組み合わせとしては、特に制限されないが、具体的には、前記式（１０）のモノマー剤と、前記式（３８）のカイラル剤との組み合わせ、前記式（１１）のモノマー剤と、前記式（３９）のカイラル剤との組み合わせ等があげられる。
【００４７】
また、前記液晶モノマーに対する架橋剤または重合剤の添加割合は、例えば、０．１〜１０重量％の範囲であり、好ましくは０．５〜８重量％の範囲、より好ましくは１〜５重量％の範囲である。前記液晶モノマーに対する架橋剤または重合剤の割合が、０．１重量％以上であれば、例えば、コレステリック層の硬化が十分容易となり、また、１０重量％以下であれば、例えば、前記液晶モノマーがコレステリック配向する温度範囲、すなわち前記液晶モノマーが液晶相となる温度が十分な範囲となるため、後述する配向工程における温度制御がより一層容易となる。
【００４８】
また、前記塗工液には、例えば、必要に応じて各種添加物を適宜配合してもよい。前記添加物としては、例えば、老化防止剤、変性剤、界面活性剤、染料、顔料、変色防止剤、紫外線吸収剤等があげられる。これらの添加剤は、例えば、いずれか一種を添加してもよいし、二種類以上を併用してもよい。具体的に、前記老化防止剤としては、例えば、フェノール系化合物、アミン系化合物、有機硫黄系化合物、ホスフィン系化合物等、前記変性剤としては、例えば、グリコール類、シリコーン類やアルコール類等、従来公知のものがそれぞれ使用できる。また、前記界面活性剤は、例えば、光学フィルムの表面を平滑にするために添加され、例えば、シリコーン系、アクリル系、フッ素系等の界面活性剤が使用でき、特にシリコーン系が好ましい。
【００４９】
このように液晶モノマーを使用した場合、調製した塗工液は、例えば、塗工・展開等の作業性に優れた粘性を示す。前記塗工液の粘度は、通常、前記液晶モノマーの濃度や温度等に応じて異なるが、前記塗工液におけるモノマー濃度が前記範囲５〜７０重量％の場合、その粘度は、例えば、０．２〜２０ｍＰａ・ｓの範囲であり、好ましくは０．５〜１５ｍＰａ・ｓであり、特に好ましくは１〜１０ｍＰａ・ｓである。具体的には、前記塗工液におけるモノマー濃度が、３０重量％の場合、例えば、２〜５ｍＰａ・ｓの範囲であり、好ましくは３〜４ｍＰａ・ｓである。前記塗工液の粘度が０．２ｍＰａ・ｓ以上であれば、例えば、塗工液を走行することによる液流れの発生がより一層防止でき、また、２０ｍＰａ・ｓ以下であれば、例えば、表面平滑性がより一層優れ、厚みムラを一層防止でき、塗工性にも優れる。なお、前記粘度としては、温度２０〜３０℃における範囲を示したが、この温度には限定されない。
【００５０】
つぎに、前記塗工液を、配向基板上に塗布して展開層を形成する。
【００５１】
前記塗工液は、例えば、ロールコート法、スピンコート法、ワイヤバーコート法、ディップコート法、エクストルージョン法、カーテンコート法、スプレコート法等の従来公知の方法によって流動展開させればよく、この中でも、塗布効率の点からスピンコート、エクストルージョンコートが好ましい。
【００５２】
前記配向基板としては、前記液晶モノマーを配向できるものであれば特に制限されず、例えば、各種プラスチックフィルムやプラスチックシートの表面を、レーヨン布等でラビング処理したものが使用できる。前記プラスチックとしては、特に制限されないが、例えば、トリアセチルセルロース（ＴＡＣ）、ポリエチレン、ポリプロピレン、ポリ（４−メチルペンテン−１）等のポリオレフィン、ポリイミド、ポリイミドアミド、ポリエーテルイミド、ポリアミド、ポリエーテルエーテルケトン、ポリエーテルケトン、ポリケトンサルファイド、ポリエーテルスルホン、ポリスルホン、ポリフェニレンサルファイド、ポリフェニレンオキサイド、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート、ポリアセタール、ポリカーボネート、ポリアリレート、アクリル樹脂、ポリビニルアルコール、ポリプロピレン、セルロース系プラスチックス、エポキシ樹脂、フェノール樹脂等があげられる。また、アルミ、銅、鉄等の金属製基板、セラミック製基板、ガラス製基板等の表面に、前述のようなプラスチックフィルムやシートを配置したり、前記表面にＳｉＯ２斜方蒸着膜を形成したもの等も使用できる。また、前述のようなプラスチックフィルムやシートに、一軸延伸等の延伸処理を施した複屈折性を有する延伸フィルム等を配向膜として積層した積層体も、配向基板として使用することができる。さらに、基板自体が複屈折性を有する場合は、前述のようなラビング処理や、表面に複屈折性フィルムを積層すること等が不要であるため、好ましい。このように基板自体に複屈折性を付与する方法としては、基板の形成において、例えば、延伸処理の他に、キャスティングや押し出し成型等を行う方法があげられる。
【００５３】
続いて、前記展開層に加熱処理を施すことによって、液晶状態で前記液晶モノマーを配向させる。前記展開層には、前記液晶モノマーと共にカイラル剤が含まれているため、液晶相（液晶状態）となった液晶モノマーが、前記カイラル剤によってねじりを付与された状態で配向する。つまり、液晶モノマーがコレステリック構造（らせん構造）を示すのである。
【００５４】
前記加熱処理の温度条件は、例えば、前記液晶モノマーの種類、具体的には前記液晶モノマーが液晶性を示す温度に応じて適宜決定できるが、通常、４０〜１２０℃の範囲であり、好ましくは５０〜１００℃の範囲であり、より好ましくは６０〜９０℃の範囲である。前記温度が４０℃以上であれば、通常、十分に液晶モノマーを配向することができ、前記温度が１２０℃以下であれば、例えば、耐熱性の面において前述のような各種配向基材の選択性も広い。
【００５５】
次に、前記液晶モノマーが配向した前記展開層に架橋処理または重合処理を施すことによって、前記液晶モノマーとカイラル剤とを重合または架橋させる。これによって、液晶モノマーは、コレステリック構造をとって配向した状態のまま、相互に重合・架橋、またはカイラル剤と重合・架橋し、前記配向状態が固定される。そして、形成されたポリマーは、前記配向状態の固定によって、非液晶ポリマーとなる。
【００５６】
前記重合処理や架橋処理は、例えば、使用する重合剤や架橋剤の種類によって適宜決定できる。例えば、光重合剤や光架橋剤を使用した場合には、光照射を施し、紫外線重合剤や紫外線架橋剤を使用した場合には、紫外線照射を施せばよい。
【００５７】
このような製造方法によって、前記配向基板上に、コレステリック構造をとって配向した非液晶性ポリマーから形成された、選択反射波長帯域１００ｎｍ〜３２０ｎｍの光学フィルムが得られる。この光学フィルムは、前述のようにその配向が固定されているため非液晶性である。したがって、温度変化によって、例えば、液晶相、ガラス相、結晶相に変化することがなく、温度による配向変化が生じない。このため、温度に影響を受けることがない、高性能の位相差フィルムとして使用できる。また、選択反射波長帯域が前記範囲に制御されているため、前述のような光もれ等が抑制される。
【００５８】
なお、本発明の光学フィルムは、本発明者らが、前述のような液晶モノマーを使用することによって初めて実現できたものであるが、その製造方法は、このような方法には制限されず、前述のような液晶ポリマーを使用してもよい。なお、液晶モノマーを使用すれば、前記選択反射波長帯域をより一層制御し易いだけでなく、前述のように塗工液の粘度等の設定も容易なため、薄層の形成が一層容易になり、取り扱い性にも非常に優れる。また、形成されたコレステリック層も、その表面が平坦性に優れたものとなる。このため、より一層優れた品質であり、かつ、薄型化の光学フィルムが形成できるといえる。
【００５９】
また、前記光学フィルムは、例えば、前記配向基板から剥離して、そのまま前述のような補償用等の位相差フィルムとして使用してもよいし、前記配向基板に積層された状態で、位相差板として使用することもできる。
【００６０】
前記光学フィルムと前記配向基板との積層体として使用する際には、前記配向基板は、透光性のプラスチックフィルムであることが好ましい。前記プラスチックフィルムとしては、例えば、ＴＡＣ等のセルロース系、ポリエチレン、ポリプロピレン、ポリ（４−メチルペンテン−１）等のポリオレフィン、ポリイミド、ポリアミドイミド、ポリアミド、ポリエーテルイミド、ポリエーテルエーテルケトン、ポリケトンサルファイド、ポリエーテルスルホン、ポリスルホン、ポリフェニレンサルファイド、ポリフェニレンオキサイド、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート、ポリアセタール、ポリカーボネート、ポリアリレート、アクリル樹脂、ポリビニルアルコール、ポリプロピレン、セルロース系プラスチック、エポキシ樹脂、フェノール樹脂、ポリノルボルネン、ポリエステル、ポリスチレン、ポリ塩化ビニル、ポリ塩化ビニリデン、液晶ポリマー等から形成されるフィルムがあげられる。これらのフィルムは、光学的に等方性であっても、異方性であっても差し支えない。これらのプラスチックフィルムの中でも、耐溶剤性や耐熱性の観点から、例えば、ポリプロピレン、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から形成された各フィルムが好ましい。
【００６１】
前述のような透光性配向基板は、例えば、単層でもよいが、例えば、強度、耐熱性、ポリマーや液晶モノマーの密着性を向上する点から、異種ポリマーを積層した積層体であってもよい。
【００６２】
また、複屈折による位相差を生じないものでもよいし、例えば、偏光分離層で反射された光の偏光状態の解消を目的として、複屈折による位相差を生じるものであってもよい。このような偏光状態の解消は、光利用効率の向上や、光源光との同一化によって、視覚による色相変化の抑制に友好である。前記複屈折による位相差を生じる透明基板としては、例えば、各種ポリマー製の延伸フィルム等が使用でき、厚み方向の屈折率を制御したものであってもよい。前記制御は、例えば、ポリマーフィルムを熱収縮フィルムと接着して、加熱延伸すること等によって行うことができる。
【００６３】
前記プラスチックフィルムの厚みは、通常、５μｍ〜５００μｍ、好ましくは１０〜２００μｍであり、好ましくは１５〜１５０μｍである。前記厚みが５μｍ以上であれば、基板として十分な強度を有するため、例えば、製造時に破断する等の問題の発生を防止できる。
【００６４】
また、前記光学フィルムを前記配向基板（以下、「第１の基板」という）から他の基板（以下、「第２の基板」という）に転写し、前記第２の基板に前記光学フィルムを積層した状態で、例えば、位相差板として使用することもできる。具体的には、前記第２の基板の少なくとも一方の表面に接着剤層または粘着剤層（以下、「接着剤層等」という）を積層し、この接着剤層等を、前記第１の基板上の光学フィルムと接着してから、前記第１の基板を前記光学フィルムから剥離すればよい。
【００６５】
この場合、前記塗工液を展開する配向基板としては、例えば、その透光性や厚み等には制限されず、耐熱性や強度の点から選択することが好ましい。
【００６６】
一方、前記第２の基板は、例えば、耐熱性等については制限されない。例えば、透光性基板や、透光性保護フィルム等が好ましく、具体的には、透明なガラスやプラスチックフィルム等があげられる。前記プラスチックフィルムとしては、例えば、ポリメチルメタクリレート、ポリスチレン、ポリカーボネート、ポリエーテルスルホン、ポリフェニレンサルファイド、ポリアリレート、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、ポリオレフィン、トリアセチルセルロース、ノルボルネン系樹脂、エポキシ樹脂、ポリビニルアルコール系樹脂等のフィルムがあげられる。この他にも、例えば、特開２００１−３４３５２９号公報（ＷＯ０１／３７００７）に記載のポリマーフィルムがあげられる。このポリマー材料としては、例えば、側鎖に置換または非置換のイミド基を有する熱可塑性樹脂と、側鎖に置換または非置換のフェニル基ならびにニトリル基を有す熱可塑性樹脂を含有する樹脂組成物が使用でき、例えば、イソブテンとＮ−メチレン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有する樹脂組成物があげられる。前記ポリマーフィルムは、例えば、前記樹脂組成物の押出成形物であってもよい。この他にも、コーティング偏光子を第２の偏光子として使用することもできる。
【００６７】
また、前記第２の基板は、例えば、光学的に等方性であることが好ましいが、前記光学フィルムの用途に応じて、光学的異方性であってもよい。このような光学的異方性を有する第２の基板としては、例えば、前記プラスチックフィルムに延伸処理等を施した位相差フィルムや、光散乱性を有する光散乱フィルム、回折能を有する回折フィルム、偏光フィルム等でもよい。
【００６８】
なお、前記コレステリック層と前記各種透光性基板等との積層体とする場合、前記コレステリック層は、前記透光性基板の両面に積層してもよいし、その積層数も、一層でもよいし、二層以上であってもよい。
【００６９】
本発明の光学フィルムは、さらに、その表面に粘着層や接着層が積層されてもよい。このように粘着層等を積層することによって、例えば、偏光板等の他の光学層や、液晶セル等の部材との積層が容易になり、光学フィルムの剥離を防止することができる。
【００７０】
前記接着層の材料としては、特に制限されないが、例えば、アクリル系、ビニルアルコール系、シリコーン系、ポリエステル系、ポリウレタン系、ポリエーテル系等のポリマー製接着剤や、イソシアネート系接着剤、ゴム系接着剤等が使用できる。また、前記粘着層の材料としては、特に制限されないが、例えば、アクリル系、シリコーン系、ポリエステル系、ゴム系等の粘着剤が使用できる。また、これらの材料に、微粒子を含有させて光拡散性を示す層としてもよい。これらの中でも、例えば、吸湿性や耐熱性に優れる材料が好ましい。このような性質であれば、例えば、液晶表示装置に使用した場合に、吸湿による発泡や剥離、熱膨張差等による光学特性の低下や、液晶セルの反り等を防止でき、高品質で耐久性にも優れる表示装置となる。
【００７１】
本発明の偏光フィルムや位相差フィルムは、前述のように、単独で使用してもよいし、必要に応じて、他の光学部材と組み合わせた積層体として、各種の光学用途に供してもよい。具体的には、光学補償部材等として、特に液晶表示素子の光学補償部材として有用である。前記他の光学部材としては、例えば、他の屈折率構造を有する位相差フィルム、液晶フィルム、光散乱フィルム、回折フィルム、偏光フィルム等があげられる。
【００７２】
つぎに、本発明の偏光板は、前記本発明の位相差フィルム（本発明の偏光フィルムも含む）と偏光フィルムとを含む偏光板である。
【００７３】
前記偏光板の一例としては、例えば、偏光フィルム（偏光子）の少なくとも一方の表面に、接着層または粘着層（以下、「接着層等」ともいう）を介して保護層が積層され、前記位相差フィルムが、前記保護層上に接着層を介して積層された構造である。前記保護層は、前記偏光フィルムの片面のみ、または、両面に積層してもよく、両面に積層する場合には、例えば、同じ種類の透明保護層を使用しても、異なる種類の透明保護層を使用してもよい。また、前記位相差フィルムは、偏光子の片面に積層されても両面に積層されてもよく、この積層は前記保護層を介してもよいし、直接であってもよい。また、本発明の位相差フィルムに加えて、さらに他の位相差フィルムが積層されてもよい。
【００７４】
前記偏光フィルムとしては、特に制限されず、例えば、従来公知の方法により、各種フィルムに、ヨウ素や二色性染料等の二色性物質を吸着させて染色し、架橋、延伸、乾燥することによって調製したもの等が使用できる。この中でも、自然光を入射させると直線偏光を透過するフィルムが好ましく、光透過率や偏光度に優れるものが好ましい。前記二色性物質を吸着させる各種フィルムとしては、例えば、ＰＶＡ系フィルム、部分ホルマール化ＰＶＡ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、セルロース系フィルム等の親水性高分子フィルム等があげられ、これらの他にも、例えば、ＰＶＡ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配向フィルム等も使用できる。これらの中でも、好ましくはＰＶＡ系フィルムである。また、前記偏光フィルムの厚みは、通常、１〜８０μｍの範囲であるが、これには限定されない。
【００７５】
前記保護層としては、特に制限されず、従来公知の透明フィルムを使用できるが、例えば、透明性、機械的強度、熱安定性、水分遮断性、等方性などに優れるものが好ましい。このような透明保護層の材質の具体例としては、トリアセチルセルロール等のセルロース系樹脂や、ポリエステル系、ポリカーボネート系、ポリアミド系、ポリイミド系、ポリエーテルスルホン系、ポリスルホン系、ポリスチレン系、ポリノルボルネン系、ポリオレフィン系、アクリル系、アセテート系等の透明樹脂等があげられる。また、前記アクリル系、ウレタン系、アクリルウレタン系、エポキシ系、シリコーン系等の熱硬化型樹脂または紫外線硬化型樹脂等もあげられる。この中でも、偏光特性や耐久性の点から、表面をアルカリ等でケン化処理したＴＡＣフィルムが好ましい。
【００７６】
また、特開２００１−３４３５２９号公報（ＷＯ０１／３７００７）に記載のポリマーフィルムがあげられる。このポリマー材料としては、例えば、側鎖に置換または非置換のイミド基を有する熱可塑性樹脂と、側鎖に置換または非置換のフェニル基ならびにニトリル基を有す熱可塑性樹脂を含有する樹脂組成物が使用でき、例えば、イソブテンとＮ−メチレン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有する樹脂組成物があげられる。なお、前記ポリマーフィルムは、例えば、前記樹脂組成物の押出成形物であってもよい。
【００７７】
また、前記保護層は、例えば、色付きが無いことが好ましい。具体的には、下記式で表されるフィルム厚み方向の位相差値（Ｒｔｈ）が、−９０ｎｍ〜＋７５ｎｍの範囲であることが好ましく、より好ましくは−８０ｎｍ〜＋６０ｎｍであり、特に好ましくは−７０ｎｍ〜＋４５ｎｍの範囲である。前記位相差値が−９０ｎｍ〜＋７５ｎｍの範囲であれば、十分に保護フィルムに起因する偏光板の着色（光学的な着色）を解消できる。なお、下記式において、ｎｘ，ｎｙ，ｎｚおよびｄは、前述と同様である。
Ｒｔｈ＝［［（ｎｘ＋ｎｙ）／２］−ｎｚ］・ｄ
【００７８】
また、前記透明保護層は、さらに光学補償機能を有するものでもよい。このように光学補償機能を有する透明保護層としては、例えば、液晶セルにおける位相差に基づく視認角の変化が原因である、着色等の防止や、良視認の視野角の拡大等を目的とした公知のものが使用できる。具体的には、例えば、前述した透明樹脂を一軸延伸または二軸延伸した各種延伸フィルムや、液晶ポリマー等の配向フィルム、透明基材上に液晶ポリマー等の配向層を配置した積層体等があげられる。これらの中でも、良視認の広い視野角を達成できることから、前記液晶ポリマーの配向フィルムが好ましく、特に、ディスコティック系やネマチック系の液晶ポリマーの傾斜配向層から構成される光学補償層を、前述のトリアセチルセルロースフィルム等で支持した光学補償位相差板が好ましい。このような光学補償位相差板としては、例えば、富士写真フィルム株式会社製「ＷＶフィルム」等の市販品があげられる。なお、前記光学補償位相差板は、前記位相差フィルムやトリアセチルセルロースフィルム等のフィルム支持体を２層以上積層させることによって、位相差等の光学特性を制御したもの等でもよい。
【００７９】
前記透明保護層の厚みは、特に制限されず、例えば、位相差や保護強度等に応じて適宜決定できるが、通常、５ｍｍ以下であり、好ましくは１ｍｍ以下、より好ましくは１〜５００μｍ以下、特に好ましくは５から１５０μｍの範囲である
【００８０】
前記透明保護層は、例えば、偏光フィルムに前記各種透明樹脂を塗布する方法、前記偏光フィルムに前記透明樹脂製フィルムや前記光学補償位相差板等を積層する方法等の従来公知の方法によって適宜形成でき、また市販品を使用することもできる。
【００８１】
また、前記透明保護層は、さらに、例えば、ハードコート処理、反射防止処理、スティッキングの防止や拡散、アンチグレア等を目的とした処理等が施されたものでもよい。前記ハードコート処理とは、偏光板表面の傷付き防止等を目的とし、例えば、前記透明保護層の表面に、硬化型樹脂から構成される、硬度や滑り性に優れた硬化被膜を形成する処理である。前記硬化型樹脂としては、例えば、シリコーン系、ウレタン系、アクリル系、エポキシ系等の紫外線硬化型樹脂等が使用でき、前記処理は、従来公知の方法によって行うことができる。スティッキングの防止は、隣接する層との密着防止を目的とする。前記反射防止処理とは、偏光板表面での外光の反射防止を目的とし、従来公知の反射防止層等の形成により行うことができる。
【００８２】
前記アンチグレア処理とは、偏光板表面において外光が反射することによる、偏光板透過光の視認妨害を防止すること等を目的とし、例えば、従来公知の方法によって、前記透明保護層の表面に、微細な凹凸構造を形成することによって行うことができる。このような凹凸構造の形成方法としては、例えば、サンドブラスト法やエンボス加工等による粗面化方式や、前述のような透明樹脂に透明微粒子を配合して前記透明保護層を形成する方式等があげられる。
【００８３】
前記透明微粒子としては、例えば、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、酸化アンチモン等があげられ、この他にも導電性を有する無機系微粒子や、架橋または未架橋のポリマー粒状物等から構成される有機系微粒子等を使用することもできる。前記透明微粒子の平均粒径は、特に制限されないが、例えば、０．５〜２０μｍの範囲である。また、前記透明微粒子の配合割合は、特に制限されないが、一般に、前述のような透明樹脂１００質量部あたり２〜７０質量部の範囲が好ましく、より好ましくは５〜５０質量部の範囲である。
【００８４】
前記透明微粒子を配合したアンチグレア層は、例えば、透明保護層そのものとして使用することもでき、また、透明保護層表面に塗工層等として形成されてもよい。さらに、前記アンチグレア層は、偏光板透過光を拡散して視角を拡大するための拡散層（視覚補償機能等）を兼ねるものであってもよい。
【００８５】
なお、前記反射防止層、スティッキング防止層、拡散層、アンチグレア層等は、前記透明保護層とは別個に、例えば、これらの層を設けたシート等から構成される光学層として、偏光板に積層してもよい。
【００８６】
前記偏光フィルムと前記透明保護層との接着方法は、特に制限されず、従来公知の方法によって行うことができる。一般には、前述と同様の粘着剤や接着剤等が使用でき、その種類は、前記偏光フィルムや透明保護層の材質等によって適宜決定できる。前述のような粘着剤、接着剤は、例えば、湿度や熱の影響によっても剥がれ難く、光透過率や偏光度にも優れる。具体的には、前記偏光フィルムがポリビニルアルコール系フィルムである場合、例えば、接着処理の安定性等の点から、ポリビニルアルコール系接着剤が好ましい。これらの接着剤や粘着剤は、例えば、そのまま偏光フィルムや透明保護層の表面に塗布してもよいし、前記接着剤や粘着剤から構成されたテープやシートのような層を前記表面に配置してもよい。また、例えば、水溶液として調製した場合、必要に応じて、他の添加剤や、酸等の触媒を配合してもよい。
【００８７】
本発明の位相差フィルムと前記偏光フィルムとの積層方法は、特に制限されず、前述のような接着層や粘着層等を用いた従来公知の方法が採用できる。また、偏光フィルムに位相差フィルム（本発明の光学フィルム）を形成することもできる。例えば、前記透明保護層を透明基板として、その一方の表面に配向基板を形成し、この配向基板上にコレステリック層を形成する。そして、前記透明保護層の他方の表面に偏光フィルムを接着し、前記偏光フィルムの他方の表面に、さらに透明保護層を接着することもできる。
【００８８】
本発明の偏光板は、前記本発明の位相差板と同様に、液晶セル等の他の部材への積層が容易になることから、さらに粘着層を有していることが好ましく、前記偏光板の片面または両面に配置することができる。また、その材質としては、前述と同様のものが使用できる。前記偏光板表面への前記粘着剤層の形成は、例えば、各種材料の溶液または溶融液を、流延や塗工等の展開方式により、前記偏光板の所定の面に直接添加して層を形成する方式や、同様にして後述するセパレータ上に粘着剤層を形成させて、それを前記偏光板の所定面に移着する方式等によって行うことができる。なお、このような層は、偏光板のいずれの表面に形成してもよく、例えば、偏光板における前記位相差板の露出面に形成してもよい。
【００８９】
このように偏光板に設けた粘着剤層の表面が露出する場合は、前記粘着層を実用に供するまでの間、汚染防止等を目的として、セパレータによって前記表面をカバーすることが好ましい。このセパレータは、前記透明保護フィルム等のような適当なフィルムに、必要に応じて、シリコーン系、長鎖アルキル系、フッ素系、硫化モリブデン等の剥離剤による剥離コートを設ける方法等によって形成できる。
【００９０】
前記粘着剤層は、例えば、単層体でもよいし、積層体でもよい。前記積層体としては、例えば、異なる組成や異なる種類の単層を組み合わせた積層体を使用することもできる。また、前記偏光板の両面に配置する場合は、例えば、それぞれ同じ粘着剤層でもよいし、異なる組成や異なる種類の粘着剤層であってもよい。
【００９１】
前記粘着剤層の厚みは、例えば、偏光板の構成等に応じて適宜に決定でき、一般には、１〜５００μｍである。
【００９２】
前記粘着剤層を形成する粘着剤としては、例えば、光学的透明性に優れ、適度な濡れ性、凝集性や接着性の粘着特性を示すものが好ましい。具体的な例としては、アクリル系ポリマーやシリコーン系ポリマー、ポリエステル、ポリウレタン、ポリエーテル、合成ゴム等のポリマーを適宜ベースポリマーとして調製された粘着剤等があげられる。
【００９３】
前記粘着剤層の粘着特性の制御は、例えば、前記粘着剤層を形成するベースポリマーの組成や分子量、架橋方式、架橋性官能基の含有割合、架橋剤の配合割合等によって、その架橋度や分子量を調節するというような、従来公知の方法によって適宜行うことができる。
【００９４】
なお、本発明の位相差フィルムや偏光板、この他にも、例えば、偏光フィルム、透明保護フィルム、光学層等、また粘着層や接着層等の各層は、例えば、サリチル酸エステル系化合物、ベンゾフェノン系化合物、ベンゾトリアゾール系化合物、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による処理等によって紫外線吸収能を持たせたものなどであってもよい。
【００９５】
本発明の位相差フィルムや偏光板は、前述のように、液晶表示装置等の各種表示装置に使用できる。前記液晶表示装置の形成は、従来公知の方法で行うことができる。すなわち、前記液晶表示装置は、一般に、液晶セルと偏光板等の光学素子、必要に応じて照明システム等の構成部品を適宜組立て、駆動回路を組込むこと等によって形成されるが、本発明においては本発明の位相差フィルムや偏光板を使用する以外は、特に限定されない。液晶セルについても、例えば、ＴＮ型やＳＴＮ型、π型等の任意のタイプのセルが使用できる。
【００９６】
具体的には、本発明の位相差板や本発明の偏光板を、液晶セルの片側または両側に配置した液晶表示装置があげられる。前記液晶セルの両側に、位相差板や偏光板を設ける場合、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。また、液晶表示装置の形成に際しては、例えば、さらに、拡散板、アンチグレア層、反射防止層、保護板、プリズムアレイシート、レンズアレイシート、光拡散板、バックライト、反射板、半透過反射板、輝度向上板等、適宜な部品を適宜な位置に、１層または２層以上配置してもよい。
【００９７】
また、本発明の偏光板は、例えば、インライン測定によりマーキングできるため、例えば、偏光子を裁断（チップカット）した直後の外観検査や梱包などオフライン工程が不要となり、一貫して液晶表示装置やエレクトロルミネッセンス表示装置に貼り合わせるインハウス製造が可能となる。これにより、例えば、表示装置の低コスト化を図ることができ、かつ、その製造工程の管理も容易となるため、工業的価値は大である。
【００９８】
なお、本発明の光学フィルムや偏光板は、前述のような液晶表示装置には限定されず、例えば、エレクトロルミネッセンス（ＥＬ）ディスプレイ、プラズマディスプレイ（ＰＤ）、ＦＥＤ（電界放出ディスプレイ：Ｆｉｅｌｄ Ｅｍｉｓｓｉｏｎ Ｄｉｓｐｌａｙ）等の自発光型表示装置にも使用できる。
【００９９】
つぎに、本発明の位相差フィルムおよび偏光板は、有機や無機のエレクトロルミネッセンス装置にも、前記液晶表示装置と同様にして、用いることができる。
【０１００】
一般に、有機エレクトロルミネッセンス（有機ＥＬ）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ＥＬ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、あるいは前記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、またあるいは前記正孔注入層、前記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。
【０１０１】
前記有機ＥＬ装置は、通常、前記透明電極と前記金属電極とに電圧を印加することによって、前記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質を励起し、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。
【０１０２】
有機ＥＬ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あることが好ましく、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などの金属電極が使用できる。
【０１０３】
このような構成の有機ＥＬ装置において、有機発光層は、通常、厚み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できる。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装置の表示面が鏡面のように見える。
【０１０４】
電圧の印加によって発光する前記有機発光層の表面側に透明電極を備えるとともに、前記有機発光層の裏面側に金属電極を備えた有機ＥＬ発光体を含む有機ＥＬ装置において、例えば、透明電極の表面側に偏光板を設け、前記透明電極と偏光板との間に位相差板を設けてもよい。この偏光板や位相差板として、本発明の偏光板や位相差フィルムが適用できる。
【０１０５】
前記位相板および偏光板は、外部から入射して金属電極で反射してきた光を偏光させ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、位相板を１／４波長板で構成し、かつ偏光板と位相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。
【０１０６】
すなわち、この有機ＥＬ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板により、一般に楕円偏光となるが、特に位相板が１／４波長板であり、しかも偏光板と位相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。
【０１０７】
この円偏光は、通常、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、位相板で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。
【０１０８】
【実施例】
つぎに、本発明について、以下の実施例および比較例を用いてさらに説明する。なお、本発明は、これらの実施例のみに限定されるものではない。
【０１０９】
（実施例１）
下記化学式（１０）に示すネマチック液晶モノマー９０重量部、下記式（３８）に示すねじり力５．５×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤１０重量部、ＵＶ重合開始剤（商品名イルガキュア９０７：チバスペシャリティーケミカルズ社製、以下同じ）５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを７０℃で３分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。そして、前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、２００〜２２０ｎｍであった。
【０１１０】
【化９】

【０１１１】
（実施例２）
実施例１と同様にして、前記化学式（１０）に示すネマチック液晶モノマー９２重量部、前記化学式（３８）に示すねじり力５．５×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤８重量部、ＵＶ重合開始剤５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを８０℃で３分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、２９０〜３１０ｎｍであった。
【０１１２】
（実施例３）
実施例１と同様にして、前記化学式（１０）に示すネマチック液晶モノマー９１重量部、前記式（３８）に示すねじり力５．５×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤９重量部、ＵＶ重合開始剤５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを８０℃で３分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、２４０〜２６０ｎｍであった。
【０１１３】
（実施例４）
実施例１と同様にして、下記化学式（１１）に示すネマチック液晶モノマー８７重量部、下記式（３９）に示すねじり力６．０×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤１３重量部、ＵＶ重合開始剤５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを７０℃で３分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、１９０〜２１０ｎｍであった。
【０１１４】
【化１０】

【０１１５】
（実施例５）
実施例１と同様にして、前記化学式（１１）に示すネマチック液晶モノマー８３重量部、前記式（３９）に示すねじり力６．０×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤１７重量部、ＵＶ重合開始剤５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを６０℃で５分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、１４０〜１６０ｎｍであった。
【０１１６】
（比較例１）
前記化学式（１１）に示すネマチック液晶モノマー８０重量部、下記式（４４）に示すねじり力５．８×１０^-5ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤２０重量部、ＵＶ重合開始剤５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを７０℃で３分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、３３０〜３５０ｎｍであった。
【０１１７】
【化１１】

【０１１８】
（比較例２）
前記化学式（１１）に示すネマチック液晶モノマー７５重量部、前記式（３９）に示すねじり力６．０×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤２５重量部、ＵＶ重合開始剤５重量部およびメチルエチルケトン３００重量部を混合し、この混合物を配向基板（厚み７５μｍ：ポリエステルフィルム）上に塗布した。そして、これを６０℃で５分間加熱処理することによって、前記モノマーを配向させた後、紫外線照射によって前記モノマーを重合させ、その配向を固定した。前記配向基板を除去することによって、厚み約２μｍの完全透明で平滑な位相差フィルムが得られた。この位相差フィルムは、ｎｘ≒ｎｙ＞ｎｚの複屈折層であり、その選択反射波長帯域は、７０〜９０ｎｍであった。
【０１１９】
前記実施例１〜５、比較例１および２で作製した位相差フィルムについて、積分球式分光透過率測定器（商品名ＤＯＴ−３Ｃ；村上色彩技術研究所製）を用いて、前記位相差フィルムの透過率および色相（単体ｂ）を測定した。さらに、前記各種位相差フィルムを、偏光度９９．９５％の二枚の偏光板（日東電工（株）製、商品名ＨＥＧ１４２５ＤＵ）をクロスニコルに配置した間に挿入し、そのときの法線方向の透過率（直交透過率）および色相（直交ｂ）を測定した。なお、直交透過率と色相（直交ｂ）については、前記位相差フィルムを配置せずに、クロスニコルに配置した偏光板のみについても同様に測定を行い、前述のように偏光板のみの測定値を差し引いて算出した。
【０１２０】
また、平行ニコル回転法を原理とする位相差計（王子計測機器社製、商品名ＫＯＢＲＡ２１−ＡＤＨ）にて、前記各種位相差板の位相差を測定し、この結果より前述のｎｘ、ｎｙ、ｎｚを算出してΔｎｄを求めた。
【０１２１】
これらの結果を下記表１および表２に示す。また、図１に、前記各種位相差フィルムの選択反射波長と透過率との関係を示す。
【０１２２】
【表１】

【０１２３】
【表２】

【０１２４】
前記表１より、本発明の位相差フィルムは単体色相ｂ値が略１．０以下であり、単体色相ｂ値が約１．３である比較例１と比べて、極めて着色が少なかった。また、面内位相差（Δｎｄ）も、比較例１が４ｎｍであるのに対して、その半分以下の値（１．６ｎｍ以下）に抑制できた。この結果から、実施例の位相差フィルムは、面内位相差のバラツキがほとんどなく、着色の影響もない、光学的に優れた複屈折層であることがわかる。また、前記表２より、比較例１の位相差フィルムの直交透過率が０．２３５％であるのに対して、実施例の位相差フィルムの直交透過率は０．１％以下と、比較例１の半分以下の値となり、優れた偏光特性を示した。また、実施例の位相差フィルムは、比較例に比べて、直交色相ｂ値の絶対値が極めて低いことから、可視光領域における光漏れが殆んど起きていないことがわかる。なお、比較例２については、配向自体が不良なため、測定不可能であった。
【０１２５】
また、前記実施例１で作製した位相差フィルムを、垂直配向モードの液晶セルの両面に接着し、さらに前記両位相差フィルムの表面に、偏光板（商品名ＳＥＧ１２２４ＤＵ：日東電工社製）をクロスニコルとなるようにそれぞれ配置して液晶表示装置を作製した。そして、その表示特性を目視で確認した。その結果、正面と斜視の広い視角範囲において、コントラストや、表示の均質性が優れており、良好な表示品位であることがわかった。
【０１２６】
（実施例６）
（１）塗工液の調製
前記式（１０）に示す重合性ネマチック液晶モノマー９０重量部、前記式（３８）に示すねじり力５．５×１０^-4ｎｍ^-1・（ｗｔ％）^-1の重合性カイラル剤１０重量％およびＵＶ重合開始剤５重量部を、溶媒メチルエチルケトン３００重量部に溶解して、塗工液を調製した。前記塗工液の粘度は、３．２ｍＰａ・ｓであった。
【０１２７】
（２）偏光板の作製
ヨウ素を含有するＰＶＡ系フィルムからなる偏光子（厚み３０μｍ）の両面にＴＡＣ製保護層（厚み８０μｍ）をアクリル系粘着剤により積層して、偏光板を作製した。
【０１２８】
一方、高延伸ＰＥＴフィルム（商品名Ｔ−６０：帝人社製、厚み７５μｍ）の片面に前記塗工液を塗工し、７０℃で１分間加熱処理を施すことによって、前記モノマーを配向させた後、紫外線照射によってモノマーを重合して、その配向を固定した。これによって、前記ＰＥＴフィルム上に厚み３μｍの位相差フィルム（補償層）が形成された。この位相差フィルムの選択反射波長帯域は２００〜２２０ｎｍであった。
【０１２９】
次に、前記偏光板の一方の表面に、アクリル製接着剤層を介して、前記ＰＥＴフィルム上の位相差フィルムを接着した。そして、この積層体から、前記ＰＥＴフィルムを剥離することによって、補償層付偏光板を作製した。
【０１３０】
この補償層付偏光板を、垂直配向モードの液晶セルの視認側に、前記補償層が接するように接着した。一方、前記液晶セルのバックライト側には、位相差フィルムを積層しなかった他は同様にして調製した偏光板を接着した。このようにして作製した液晶表示装置について、その表示特性を目視で確認した結果、正面と斜視の広い視角範囲において、コントラストや、表示の均質性が優れており、良好な表示品位であることがわかった。
【０１３１】
【発明の効果】
以上のように、選択反射波長帯域が１００ｎｍ〜３２０ｎｍである本発明の光学フィルムであれば、例えば、位相差フィルムや偏光板等の光学素子として、液晶表示装置等の各種表示装置に使用した場合、着色等の問題がないため、表示ムラがなく、優れた表示特性を達成できる。
【図面の簡単な説明】
【図１】 本発明の実施例における、各波長における透過率の変化を示すグラフである。
【図２】 屈折率の軸方向を示す概略図である。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an optical film, a manufacturing method thereof, a retardation film and a polarizing plate using the optical film, and an image display device using the optical film.
[0002]
[Prior art]
  In general, a liquid crystal display device has polarizers disposed on both sides of a liquid crystal cell holding liquid crystal. Conventionally, in order to visually compensate for a phase difference due to birefringence of the liquid crystal cell in a front direction and a perspective direction, A birefringent layer is disposed between the liquid crystal cell and the polarizer. As this birefringent layer, there is usually a negative birefringent layer in which cholesteric liquid crystal molecules are aligned on an alignment substrate and the refractive index (nx, ny, nz) satisfies a negative uniaxiality “nx = ny> nz”. in use. The index of refraction (nx, ny, nz) indicates the refractive index in the three axial directions of the birefringent layer, respectively. Specifically, in the schematic diagram of FIG. 2, the axial direction of the refractive index (nx, ny, nz) in the birefringent layer is indicated by an arrow. Refractive indexes nx, ny, and nz indicate the refractive indexes in the X-axis, Y-axis, and Z-axis directions, respectively, as described above, and as shown in the figure, the X-axis indicates the maximum refractive index in the plane. The Y axis is an axial direction perpendicular to the X axis in the plane, and the Z axis is a thickness direction perpendicular to the X axis and the Y axis.
[0003]
  As such a birefringent layer, for example, a compensation plate in which a liquid crystal polymer coating solution is applied on an alignment substrate and the liquid crystal polymer is cholesterically aligned is disclosed (for example, see Patent Document 1). Specifically, for example, there is a birefringent layer composed of a cholesteric liquid crystal polymer in which the product of the helical pitch and refractive index of the cholesteric structure is 400 nm or less, and viewing angle compensation is performed by this birefringent layer. (For example, refer to Patent Document 2). And in the said patent document 2, in order to satisfy | fill the characteristic that the said liquid crystal polymer which shows the cholesteric liquid crystal phase orientated substantially parallel with respect to the board | substrate is substantially isotropic with respect to visible light in a plane, It is disclosed that the size of the cholesteric pitch needs to be smaller than the visible light wavelength (about 400 nm to 800 nm). Further, it is disclosed that, for example, the product of the refractive index of the birefringent phase and the helical pitch needs to be smaller than 400 nm in order to prevent coloring due to selective reflection due to the liquid crystal polymer having a cholesteric structure. Has been.
[0004]
[Patent Document 1]
Japanese Patent No. 2660601
[Patent Document 2]
JP-A-3-67219
[0005]
[Problems to be solved by the invention]
  However, even with a retardation plate having a cholesteric layer as described above, there is a problem that coloring due to selective reflection is seen and an excellent display quality cannot be obtained when used in a liquid crystal display device or the like. there were.
[0006]
  Accordingly, an object of the present invention is to provide an optical film having a cholesteric layer in which coloring due to selective reflection is reduced, for example.
[0007]
[Means for Solving the Problems]
To achieve the above object, the optical film of the present invention is an optical film including a cholesteric layer,
The constituent molecules of the layer are oriented with a cholesteric structure,
The selective reflection wavelength band of the layer is in the range of 100 nm to 320 nm,
The cholesteric layer constituting molecule is a non-liquid crystal polymer, and the non-liquid crystal polymer is a polymer obtained by polymerizing or crosslinking a liquid crystal monomer having a cholesteric structure oriented by a chiral agent,
  The liquid crystal monomer is a compound represented by the following formula (4), a compound represented by the following formula (5), a compound represented by the following formula (6), a compound represented by the following formula (7), the following A compound represented by the formula (8), a compound represented by the following formula (9), a compound represented by the following formula (10), a compound represented by the following formula (11), and a formula represented by the following formula (12) A compound represented by the following formula (13), a compound represented by the following formula (14), a compound represented by the following formula (15), a compound represented by the following formula (16), and the following formula At least one liquid crystal monomer selected from the group consisting of a compound represented by (17), a compound represented by the following formula (18), and a compound represented by the following formula (19);
  The chiral agent is a compound represented by the following formula (24), a compound represented by the following formula (25), a compound represented by the following formula (26), a compound represented by the following formula (27), the following A compound represented by the formula (28), a compound represented by the following formula (29), a compound represented by the following formula (30), a compound represented by the following formula (31), a formula represented by the following formula (32) The compound represented by the following formula (33), the compound represented by the following formula (34), the compound represented by the following formula (35), the compound represented by the following formula (36), the following formula The compound represented by (37), the compound represented by the following formula (38), the compound represented by the following formula (39), the compound represented by the following formula (40), and the following formula (41) A compound represented by the following formula (42), a compound represented by the following formula (43), and In at least one chiral agent selected from the group consisting of compounds represented by (44)Yes,
  The proportion of liquid crystal monomer in the cholesteric layer is in the range of 75 to 95% by weight,
The ratio of the chiral agent to the liquid crystal monomer is in the range of 5 to 23% by weight.It is characterized by being.
[0008]
[Chemical formula 5]

[0009]
[Chemical 6]

[0010]
  In the present invention, the cholesteric layer refers to a layer having a pseudo-layer structure called a so-called planar structure or Grandian structure in which the constituent molecules of the layer have a helical structure and the helical axis is oriented substantially perpendicular to the plane direction. You can also Further, in the present invention, “the constituent molecules have a cholesteric structure” is not limited to a case where the liquid crystal compound is in a cholesteric liquid crystal phase, for example. Also included are those that are aligned in a twisted state, such as the cholesteric liquid crystal phase.
[0011]
  The present inventors have conducted detailed studies to solve the above-described problems. As a result, even when the retardation plate has a cholesteric layer having a selective reflection wavelength of 400 nm or less, that is, 330 nm to 400 nm, coloring occurs due to selective reflection due to the liquid crystal compound having a helical structure. It was found that the single hue b value at the time of measuring the transmittance was 1.2 or more due to the influence. Further, when this retardation plate is bonded to the polarizing plate, light leakage in the normal direction occurs in the crossed Nicol state on the entire surface, and the 427 nm orthogonal transmittance is 0.235 from the orthogonal transmittance of the polarizing plate alone. I found out that the problem of a large percentage would arise. As a result of visually confirming the black display in the crossed Nicols state, it was also found that the front surface looks blue. From these results, it is considered that such light leakage occurs because selective reflection affects the visible light range (about 400 nm to 700 nm). Even at a selective reflection wavelength of 330 nm to 400 nm, the birefringent layer is used. It has been found that it is difficult to form a liquid crystal display device having excellent display quality when used.
[0012]
  Therefore, the present inventors conducted further research,As above"Liquid crystal monomer"With the above-mentioned chiral agentA cholesteric layer formed by controlling the blending ratio of the liquid crystal monomer and the chiral agent, aligning the liquid crystal monomer into a cholesteric structure with the chiral agent, and then fixing the orientation by polymerization or crosslinking. If it exists, it has been found that the selective reflection wavelength band can be controlled to 100 nm to 320 nm, and within this range, the conventional light leakage problem can be avoided. The present inventors have found for the first time that the selective reflection wavelength band can be controlled by using a liquid crystal monomer and controlling the blending ratio.
[0013]
  Thus, if the optical film has the selective reflection wavelength band controlled within the above range, for example, the conventional coloring caused by selective reflection can be prevented. In other words, the closer the selective reflection wavelength is to the visible light wavelength (400 nm or more), the more the visible light region is affected, and therefore light leakage occurs and coloration is observed. This is suppressed. For this reason, if the optical film of this invention is used as a retardation film, it will become a wide viewing angle range, and the outstanding display quality can be achieved in any of a front direction and a perspective direction. Therefore, it is also useful for various image display devices such as liquid crystal display devices.
[0014]
Next, the retardation film of the present invention includes the optical film of the present invention. The polarizing plate of the present invention includes the retardation film of the present invention and a polarizing film, and is particularly useful as a polarizing plate for optical compensation. Furthermore, the retardation film or polarizing plate of the present invention is useful for various image display devices such as liquid crystal display devices and electroluminescence (EL) devices.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
  As described above, the optical film of the present invention is an optical film including a cholesteric layer,
The constituent molecules of the layer are oriented with a cholesteric structure,
The selective reflection wavelength band of the layer is in the range of 100 nm to 320 nm,
The cholesteric layer constituting molecule is a non-liquid crystal polymer, and the non-liquid crystal polymer is a polymer obtained by polymerizing or crosslinking a liquid crystal monomer having a cholesteric structure oriented by a chiral agent,
  The liquid crystal monomer is a compound represented by the following formula (4), a compound represented by the following formula (5), a compound represented by the following formula (6), a compound represented by the following formula (7), the following A compound represented by the formula (8), a compound represented by the following formula (9), a compound represented by the following formula (10), a compound represented by the following formula (11), and a formula represented by the following formula (12) A compound represented by the following formula (13), a compound represented by the following formula (14), a compound represented by the following formula (15), a compound represented by the following formula (16), and the following formula At least one liquid crystal monomer selected from the group consisting of a compound represented by (17), a compound represented by the following formula (18), and a compound represented by the following formula (19);
  The chiral agent is a compound represented by the following formula (24), a compound represented by the following formula (25), a compound represented by the following formula (26), a compound represented by the following formula (27), the following A compound represented by the formula (28), a compound represented by the following formula (29), a compound represented by the following formula (30), a compound represented by the following formula (31), a formula represented by the following formula (32) The compound represented by the following formula (33), the compound represented by the following formula (34), the compound represented by the following formula (35), the compound represented by the following formula (36), the following formula The compound represented by (37), the compound represented by the following formula (38), the compound represented by the following formula (39), the compound represented by the following formula (40), and the following formula (41) A compound represented by the following formula (42), a compound represented by the following formula (43), and In at least one chiral agent selected from the group consisting of compounds represented by (44)Yes,
  The proportion of liquid crystal monomer in the cholesteric layer is in the range of 75 to 95% by weight,
The ratio of the chiral agent to the liquid crystal monomer is in the range of 5 to 23% by weight.It is characterized by being.
[0016]
[Chemical 7]

[0017]
[Chemical 8]

[0018]
  For example, when the cholesteric layer is formed using a liquid crystal monomer as described later, the center wavelength of the selective reflection wavelength band λ (nm) can be expressed by the following formula.
  λ = n · P
  In the above formula, n represents the average refractive index of the liquid crystal monomer, and P represents the helical pitch (μm) of the cholesteric layer. The average refractive index n is “(n_o+ N_e) / 2 ", usually in the range of 1.45 to 1.65, n_oIs the normal light refraction of the liquid crystal monomer, n_eIndicates an extraordinary refractive index of the liquid crystal monomer.
[0019]
  As described above, the upper limit of the selective reflection wavelength band is 320 nm or less, and preferably 300 nm or less. On the other hand, the lower limit of the selective reflection wavelength band is 100 nm or more as described above, and preferably 150 nm or more. When the selective reflection wavelength band exceeds 320 nm, the selective reflection wavelength band enters the visible light region, and thus, for example, the above-described problems of coloring and color loss occur. On the other hand, the optical film having the selective reflection wavelength band smaller than 100 nm has the following problems. That is, as will be described later, at the time of manufacturing the optical film of the present invention, the selective reflection wavelength band can be set, for example, by controlling the addition ratio of a constituent material such as a liquid crystal monomer and a chiral agent. As a means for shifting the selective reflection wavelength band to the short wavelength side, for example, there is a method of increasing the amount of chiral agent added. However, as the amount of chiral agent added increases, constituent materials such as liquid crystal monomers take cholesteric alignment. The temperature range, that is, the temperature range for the liquid crystal phase becomes very narrow. For this reason, it is necessary to strictly control the temperature for cholesteric orientation of the constituent materials at the time of manufacturing, which makes it difficult to manufacture.
[0020]
  In the optical film of the present invention, for example, it is preferable that the refractive indexes (nx, ny, nz) in the three axial directions as described above satisfy nx≈ny> nz. Such an optical film can be used as a so-called negative C-Plate retardation plate.
[0021]
  In the present invention, the in-plane retardation (Δnd) at 590 nm of the cholesteric layer is, for example, 2 nm or less, preferably 1.5 nm or less. The in-plane retardation tends to be controlled in the above-described range by controlling the selective reflection wavelength in the range of 100 nm to 320 nm. The in-plane retardation (Δnd) is expressed by the following formula. In the following formula, “nx, ny” is the refractive index in the X-axis direction and the Y-axis direction that are perpendicular to each other in the same manner as in FIG. 2, and the direction showing the maximum refractive index in the surface. Is the X axis. “D” indicates a film thickness.
    Δnd = (nx−ny) · d
[0022]
  In order to control the selective reflection wavelength band to the above range, the cholesteric layer includes a chiral agent.Include. The said chiral agent in this invention is a compound which has the function to orientate a liquid crystal monomer and a liquid crystal polymer which are mentioned later, for example so that it may become a cholesteric structure.
[0023]
  Among these chiral agents, the twisting force is 1 × 10^-6nm^-1・ (Wt%)^-1Or more, more preferably 1 × 10^-Fivenm^-1・ (Wt%)^-1Above, more preferably 1 × 10^-Five~ 1x10^-2nm^-1・ (Wt%)^-1And particularly preferably 1 × 10^-Four~ 1x10^-3nm^-1・ (Wt%)^-1Range. If such a chiral agent having a twisting force is used, for example, the helical pitch of the formed cholesteric layer can be controlled within the range described later, and thereby the selective reflection wavelength band can be sufficiently controlled within the range. It becomes possible.
[0024]
  The torsional force generally indicates the ability to twist a liquid crystal material such as a liquid crystal monomer or a liquid crystal polymer as will be described later and align it in a spiral shape, and can be expressed by the following formula.
  Torsional force = 1 / [Cholesteric pitch (nm) × Chiral agent weight ratio (wt%)]
[0025]
  In the above formula, the weight ratio of the chiral agent means, for example, the ratio (weight ratio) of the chiral agent in the mixture containing the liquid crystal monomer or liquid crystal polymer and the chiral agent, and is represented by the following formula.
  Chiral agent weight ratio (wt%) = [X / (X + Y)] × 100
      X: Chiral agent weight
      Y: Liquid crystal monomer weight or liquid crystal polymer weight
[0026]
  The helical pitch in the cholesteric layer is preferably in the range of 0.01 to 0.25 μm, more preferably in the range of 0.03 to 0.20 μm, and particularly preferably in the range of 0.05 to 0.15 μm. is there. If the helical pitch is 0.01 μm or more, for example, sufficient orientation is obtained, and if it is 0.25 μm or less, for example, the optical rotation on the short wavelength side of visible light can be sufficiently suppressed. When using as a retardation film for compensation, light leakage and the like can be sufficiently avoided. If a chiral agent having a twisting force as described above is used, the helical pitch of the formed cholesteric layer can be controlled within the above range.
[0027]
  In the optical film of the present invention, since the selective reflection wavelength band is controlled in the above-described range, the single hue b value is, for example, 1.2 or less, little coloring, and very excellent optical characteristics. It can be said that it shows. The single hue b value is more preferably 1.1 or less, and particularly preferably 1.0 or less. The orthogonal hue b value is, for example, −0.5 to 1.0, more preferably −0.3 to 0.8, and particularly preferably −0.1 to 0.8 or less. . Moreover, the orthogonal transmittance | permeability in 430 nm of the optical film of this invention is 0.15 or less, for example, Preferably it is 0.10 or less, More preferably, it is 0.08 or less.
[0028]
  The single hue b value is determined by Hunter Lab color system (Hunter, RS: J. Opt. Soc. Amer., 38, 661 (A), 1094 (A) (1948); J. Opt. Soc. Amer. , 48, 985 (1958)). Specifically, for example, according to JIS K 7105 5.3, tristimulus values (X, Y, Z) of a sample are measured using a spectrophotometer or a photoelectric colorimeter, and these values are measured in Lab space. By substituting into the Hunter equation shown below as the color difference formula in, a single hue b value can be calculated. For this measurement, a C light source is usually used. For example, according to the integrating sphere type spectral transmittance measuring device (trade name DOT-3C; manufactured by Murakami Color Research Laboratory), the single hue b value can be measured together with the transmittance.
Single unit hue b = 7.0 × (Y−0.847Z) / Y^1/2
[0029]
  The orthogonal hue b value can be measured as follows. A polarizing plate is arranged in crossed Nicols, and the optical film is arranged therebetween, and the hue b1 is measured based on the Hunter Lab color system as described above. On the other hand, the hue b2 is measured only with a polarizing plate arranged in crossed Nicols without arranging an optical film. The orthogonal hue b value can be obtained by subtracting the hue b2 from the hue b1 (b1-b2).
[0030]
  In the present invention, the constituent molecule is, for example, a non-liquid crystal polymer, and the non-liquid crystal polymer is a polymer obtained by polymerizing or crosslinking a liquid crystal monomer having a cholesteric structure.It is.With such a configuration, as will be described later, since the monomer exhibits liquid crystallinity, it can be oriented with a cholesteric structure, and the orientation can be fixed by further polymerizing the monomers. Then, although a liquid crystal monomer is used, the polymerized polymer becomes non-liquid crystalline due to the fixing. For this reason, the formed cholesteric layer has a cholesteric structure like a cholesteric liquid crystal phase, but is not composed of liquid crystal molecules. For example, the liquid crystal phase, glass phase, There will be no change to. Accordingly, the cholesteric structure is an optical film that is not affected by temperature changes and is extremely stable, and can be said to be particularly useful as a retardation film for optical compensation, for example.
[0031]
  The liquid crystal monomer isIt is a monomer represented by the above chemical formula. Such a liquid crystal monomer is generally a nematic liquid crystal monomer.In the aboveTwist is imparted by the chiral agent, and finally a cholesteric structure is taken. Further, in the cholesteric layer, the monomers need to be polymerized or cross-linked in order to fix the orientation. Therefore, the monomer preferably contains at least one of a polymerizable monomer and a cross-linkable monomer.
[0032]
  The cholesteric layer preferably further contains at least one of a polymerization agent and a crosslinking agent. For example, substances such as an ultraviolet curing agent, a photocuring agent, and a thermosetting agent can be used.
[0033]
  The proportion of the liquid crystal monomer in the cholesteric layer is preferably in the range of 75 to 95% by weight, more preferably in the range of 80 to 90% by weight. The ratio of the chiral agent to the liquid crystal monomer is preferably in the range of 5 to 23% by weight, and more preferably in the range of 10 to 20% by weight. Further, the ratio of the crosslinking agent or the polymerization agent to the liquid crystal monomer is preferably in the range of 0.1 to 10% by weight, more preferably in the range of 0.5 to 8% by weight, and particularly preferably 1 to 1% by weight. It is in the range of 5% by weight.
[0034]
  Although the thickness of the optical film is not particularly limited, for example, when used as a retardation film for compensation or the like, from the viewpoints of orientation disorder and prevention of transmittance reduction, selective reflectivity, coloring prevention, productivity, etc. It is preferably in the range of 0.1 to 10 μm, more preferably in the range of 0.5 to 8 μm, and particularly preferably in the range of 1 to 5 μm.
[0035]
  For example, the optical film of the present invention may be formed of only the cholesteric layer as described above, but may further include a substrate, and may be a laminate in which the cholesteric layer is laminated on the substrate.
[0036]
  Next, the method for producing the optical film of the present invention includes:
  A method for producing an optical film comprising a cholesteric layer, wherein the constituent molecules of the layer have a cholesteric structure and are oriented,
  In the compound represented by the formula (4), the compound represented by the formula (5), the compound represented by the formula (6), the compound represented by the formula (7), the formula (8) A compound represented by the formula (9), a compound represented by the formula (10), a compound represented by the formula (11), a compound represented by the formula (12), A compound represented by formula (13), a compound represented by formula (14), a compound represented by formula (15), a compound represented by formula (16), and a formula represented by formula (17) At least one liquid crystal monomer selected from the group consisting of the compound represented by formula (18) and the compound represented by formula (19), and the compound represented by formula (24), The compound represented by the formula (25), the compound represented by the formula (26), the formula (27) A compound represented by formula (28), a compound represented by formula (29), a compound represented by formula (30), a compound represented by formula (31), In the compound represented by the formula (32), the compound represented by the formula (33), the compound represented by the formula (34), the compound represented by the formula (35), the formula (36) A compound represented by the formula (37), a compound represented by the formula (38), a compound represented by the formula (39), a compound represented by the formula (40), At least selected from the group consisting of a compound represented by formula (41), a compound represented by formula (42), a compound represented by formula (43) and a compound represented by formula (44) Including one chiral agent and at least one of a polymerization agent and a crosslinking agent, , The step of the proportion of the chiral agent to the liquid crystal monomer is to expand the coating solution is in the range of 5 to 23 wt% on the alignment substrate to form a development layer,
  Heat-treating the spreading layer so that the liquid crystal monomer has an orientation having a cholesteric structure, and
  In order to fix the orientation of the liquid crystal monomer and form a cholesteric layer of a non-liquid crystal polymer, the development layer includes a step of performing at least one of a polymerization treatment and a crosslinking treatment.See
  The ratio of the liquid crystal monomer in the cholesteric layer is in the range of 75 to 95% by weight, and the ratio of the chiral agent to the liquid crystal monomer is in the range of 5 to 23% by weight.It is a manufacturing method. According to such a manufacturing method, the optical film of the present invention having the selective reflection wavelength band as described above can be manufactured. Thus, the present inventors have found for the first time that the selective reflection wavelength band can be controlled in the range of 100 nm to 320 nm by controlling the blending ratio of the liquid crystal monomer and the chiral agent.
[0037]
  An example of the method for producing the optical film of the present invention will be specifically described below. First, a coating liquid containing the liquid crystal monomer, the chiral agent, and at least one of the crosslinking agent and the polymerization agent is prepared.
[0038]
  As the liquid crystal monomer,In the compound represented by the formula (4), the compound represented by the formula (5), the compound represented by the formula (6), the compound represented by the formula (7), the formula (8) A compound represented by the formula (9), a compound represented by the formula (10), a compound represented by the formula (11), a compound represented by the formula (12), A compound represented by formula (13), a compound represented by formula (14), a compound represented by formula (15), a compound represented by formula (16), and a formula represented by formula (17) A compound represented by formula (18) or a compound represented by formula (19)Is given. One kind of these liquid crystal monomers may be used, or two or more kinds may be used in combination.
[0039]
  The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type, but is preferably in the range of 40 to 120 ° C., more preferably in the range of 50 to 100 ° C., and particularly preferably 60. It is the range of -90 degreeC.
[0040]
  As the chiral agent, the aforementionedSo that the liquid crystalThis is to twist the monomer and align it so that it has a cholesteric structure.Yes, polymerizablePreferably a chiral agent,In the compound represented by the formula (24), the compound represented by the formula (25), the compound represented by the formula (26), the compound represented by the formula (27), the formula (28) A compound represented by the formula (29), a compound represented by the formula (30), a compound represented by the formula (31), a compound represented by the formula (32), A compound represented by formula (33), a compound represented by formula (34), a compound represented by formula (35), a compound represented by formula (36), and a formula represented by formula (37) A compound represented by formula (38), a compound represented by formula (39), a compound represented by formula (40), a compound represented by formula (41), and the formula The compound represented by (42), the compound represented by the formula (43) or the formula (44) It is a compound. One kind of these chiral agents may be used, or two or more kinds thereof may be used in combination.
[0041]
In addition,These chiral compounds have a torsional force of 1 × 10^-6nm^-1・ (Wt%)^-1That's it.
[0042]
  The polymerizing agent and the crosslinking agent are not particularly limited, and for example, the following can be used. Examples of the polymerization agent include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking. An agent can be used. These may be either one of them, or two or more of them may be used in combination.
[0043]
  The coating liquid can be prepared, for example, by dissolving and dispersing the liquid crystal monomer and the like in an appropriate solvent. Examples of the solvent include, but are not limited to, for example, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenol, p- Phenols such as chlorophenol, o-chlorophenol, m-cresol, o-cresol, p-cresol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, acetone, methyl ethyl ketone (MEK), ketone solvents such as methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone and N-methyl-2-pyrrolidone, and esters such as ethyl acetate and butyl acetate Solvent, alcohol solvent such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, dimethylformamide Amide solvents such as dimethylacetamide, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, or carbon disulfide, ethyl cellosolve, butyl cellosolve, etc. Can be used. Among these, toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl acetate cellosolve are preferable. These solvents may be, for example, one kind or a mixture of two or more kinds.
[0044]
  The addition ratio of the chiral agent is appropriately determined according to, for example, a desired helical pitch and a desired selective reflection wavelength band, and the addition ratio to the liquid crystal monomer is in the range of 5 to 23% by weight, preferably It is in the range of 10 to 20% by weight. As described above, by controlling the addition ratio of the liquid crystal monomer and the chiral agent in this way, the selected wavelength band of the optical film to be formed can be set within the above-mentioned range. When the ratio of the chiral agent to the liquid crystal monomer is smaller than 5% by weight, it becomes difficult to control the selective reflection wavelength band of the formed optical film to the low wavelength side. When the ratio is greater than 23% by weight, the temperature range in which the liquid crystal monomer is cholesterically aligned, that is, the temperature range in which the liquid crystal monomer is in the liquid crystal phase is narrowed. Manufacturing becomes difficult.
[0045]
  For example, when a chiral agent having the same torsional force is used, the selective reflection wavelength band to be formed is on the lower wavelength side when the addition ratio of the chiral agent to the liquid crystal monomer is larger. For example, when the addition ratio of the chiral agent to the liquid crystal monomer is the same, for example, the selective reflection wavelength band of the formed optical film is on the lower wavelength side when the twisting force of the chiral agent is larger. As a specific example, when the selective reflection wavelength band of the optical film to be formed is set in a range of 200 to 220 nm, for example, the twisting force is 5 × 10 5.^-Fournm^-1・ (Wt%)^-1The chiral agent may be blended so as to be 11 to 13% by weight with respect to the liquid crystal monomer. When the selective reflection wavelength band is set in the range of 290 to 310 nm, for example, the twisting force is 5 × 10 5.^-Fournm^-1・ (Wt%)^-1The chiral agent may be blended so as to be 7 to 9% by weight with respect to the liquid crystal monomer.
[0046]
  Further, the combination of the liquid crystal monomer and the chiral agent is not particularly limited. Specifically, the combination of the monomer agent of the formula (10) and the chiral agent of the formula (38), the formula ( And a combination of the monomer agent of 11) and the chiral agent of the above formula (39).
[0047]
  Moreover, the addition ratio of the crosslinking agent or the polymerization agent with respect to the liquid crystal monomer is, for example, in the range of 0.1 to 10% by weight, preferably in the range of 0.5 to 8% by weight, more preferably 1 to 5% by weight. RangeIs. If the ratio of the crosslinking agent or the polymerization agent to the liquid crystal monomer is 0.1% by weight or more, for example, curing of the cholesteric layer is sufficiently easy, and if it is 10% by weight or less, for example, the liquid crystal monomer is Since the temperature range in which the cholesteric alignment is performed, that is, the temperature at which the liquid crystal monomer becomes a liquid crystal phase is in a sufficient range, temperature control in the alignment step described later is further facilitated.
[0048]
  Moreover, you may mix | blend various additives with the said coating liquid suitably as needed, for example. Examples of the additive include an anti-aging agent, a modifier, a surfactant, a dye, a pigment, a discoloration inhibitor, and an ultraviolet absorber. Any one of these additives may be added, or two or more of them may be used in combination. Specifically, as the anti-aging agent, for example, phenol compounds, amine compounds, organic sulfur compounds, phosphine compounds, etc., and as the modifier, for example, glycols, silicones, alcohols, etc. A well-known thing can be used, respectively. The surfactant is added, for example, to smooth the surface of the optical film. For example, a surfactant such as silicone, acrylic or fluorine can be used, and silicone is particularly preferable.
[0049]
  Thus, when a liquid crystal monomer is used, the prepared coating liquid shows the viscosity excellent in workability | operativity, such as coating and expansion | deployment, for example. The viscosity of the coating liquid usually varies depending on the concentration and temperature of the liquid crystal monomer, but when the monomer concentration in the coating liquid is in the range of 5 to 70% by weight, the viscosity is, for example, 0. The range is 2 to 20 mPa · s, preferably 0.5 to 15 mPa · s, and particularly preferably 1 to 10 mPa · s. Specifically, when the monomer concentration in the coating solution is 30% by weight, for example, the range is 2 to 5 mPa · s, and preferably 3 to 4 mPa · s. If the viscosity of the coating liquid is 0.2 mPa · s or more, for example, generation of a liquid flow by running the coating liquid can be further prevented, and if the viscosity is 20 mPa · s or less, for example, the surface Smoothness is further improved, thickness unevenness can be further prevented, and coating properties are also excellent. In addition, as said viscosity, although the range in the temperature of 20-30 degreeC was shown, it is not limited to this temperature.
[0050]
  Next, the coating liquid is applied onto the alignment substrate to form a spread layer.
[0051]
  The coating liquid may be flow-deployed by a conventionally known method such as a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, a spray coating method, Of these, spin coating and extrusion coating are preferred from the viewpoint of coating efficiency.
[0052]
  The alignment substrate is not particularly limited as long as the liquid crystal monomer can be aligned. For example, a substrate obtained by rubbing the surface of various plastic films or plastic sheets with a rayon cloth or the like can be used. The plastic is not particularly limited. For example, polyolefin such as triacetyl cellulose (TAC), polyethylene, polypropylene, poly (4-methylpentene-1), polyimide, polyimide amide, polyether imide, polyamide, polyether ether. Ketone, polyether ketone, polyketone sulfide, polyethersulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulosic plastic And epoxy resins and phenol resins. Also, a plastic film or sheet as described above is disposed on the surface of a metal substrate such as aluminum, copper, or iron, a ceramic substrate, or a glass substrate, or a SiO2 oblique vapor deposition film is formed on the surface. Etc. can also be used. Moreover, the laminated body which laminated | stacked the above-mentioned plastic film and sheet | seat on the oriented film etc. which gave the birefringent property etc. which performed the extending | stretching processes, such as uniaxial stretching, can also be used as an oriented substrate. Further, when the substrate itself has birefringence, it is preferable because the rubbing treatment as described above or the lamination of a birefringent film on the surface is unnecessary. As a method for imparting birefringence to the substrate itself as described above, for example, in the formation of the substrate, there is a method of performing casting, extrusion molding, or the like in addition to the stretching treatment.
[0053]
  Subsequently, the liquid crystal monomer is aligned in a liquid crystal state by subjecting the spread layer to a heat treatment. Since the spread layer contains a chiral agent together with the liquid crystal monomer, the liquid crystal monomer in a liquid crystal phase (liquid crystal state) is aligned in a state where a twist is imparted by the chiral agent. That is, the liquid crystal monomer exhibits a cholesteric structure (helical structure).
[0054]
  The temperature condition of the heat treatment can be appropriately determined according to, for example, the type of the liquid crystal monomer, specifically the temperature at which the liquid crystal monomer exhibits liquid crystallinity, but is usually in the range of 40 to 120 ° C., preferably It is the range of 50-100 degreeC, More preferably, it is the range of 60-90 degreeC. If the temperature is 40 ° C. or higher, the liquid crystal monomer can usually be sufficiently aligned, and if the temperature is 120 ° C. or lower, for example, selection of various alignment substrates as described above in terms of heat resistance. The nature is also wide.
[0055]
  Next, the liquid crystal monomer and the chiral agent are polymerized or crosslinked by performing a crosslinking treatment or a polymerization treatment on the spread layer in which the liquid crystal monomer is aligned. As a result, the liquid crystal monomer is polymerized / crosslinked with each other while being aligned with a cholesteric structure, or polymerized / crosslinked with a chiral agent, and the alignment state is fixed. The formed polymer becomes a non-liquid crystal polymer by fixing the alignment state.
[0056]
  The polymerization treatment and the crosslinking treatment can be appropriately determined depending on, for example, the kind of the polymerization agent and the crosslinking agent to be used. For example, when a photopolymerization agent or a photocrosslinking agent is used, light irradiation is performed, and when an ultraviolet polymerization agent or an ultraviolet crosslinking agent is used, ultraviolet irradiation is performed.
[0057]
  By such a manufacturing method, an optical film having a selective reflection wavelength band of 100 nm to 320 nm formed from a non-liquid crystalline polymer having a cholesteric structure and aligned on the alignment substrate can be obtained. This optical film is non-liquid crystalline because its orientation is fixed as described above. Therefore, the change in temperature does not change, for example, to a liquid crystal phase, a glass phase, or a crystal phase, and an orientation change due to temperature does not occur. For this reason, it can be used as a high-performance retardation film that is not affected by temperature. Further, since the selective reflection wavelength band is controlled within the above range, the above-described light leakage or the like is suppressed.
[0058]
  The optical film of the present invention was first realized by the present inventors by using the liquid crystal monomer as described above, but its production method is not limited to such a method, Liquid crystal polymers as described above may be used. If a liquid crystal monomer is used, not only the selective reflection wavelength band can be controlled more easily, but also the viscosity of the coating liquid can be easily set as described above, so that the formation of a thin layer becomes easier. Also, it is very easy to handle. In addition, the formed cholesteric layer also has excellent surface flatness. For this reason, it can be said that it is the quality which was further excellent, and a thin optical film can be formed.
[0059]
  Further, the optical film may be peeled off from the alignment substrate and used as a retardation film for compensation as described above, or in a state of being laminated on the alignment substrate, It can also be used as
[0060]
  When used as a laminate of the optical film and the alignment substrate, the alignment substrate is preferably a translucent plastic film. Examples of the plastic film include celluloses such as TAC, polyolefins such as polyethylene, polypropylene, poly (4-methylpentene-1), polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyketone sulfide, Polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulose plastic, epoxy resin, phenol resin, polynorbornene , Polyester, polystyrene, polyvinyl chloride, polyvinyl chloride Down, the film may be mentioned that is formed from a liquid crystal polymer or the like. These films can be optically isotropic or anisotropic. Among these plastic films, from the viewpoint of solvent resistance and heat resistance, for example, each film formed from polypropylene, polyethylene terephthalate, or polyethylene naphthalate is preferable.
[0061]
  The translucent alignment substrate as described above may be, for example, a single layer, but may be, for example, a laminate in which different types of polymers are laminated from the viewpoint of improving strength, heat resistance, and adhesion between polymers and liquid crystal monomers. Good.
[0062]
  The phase difference due to birefringence may not be generated, or for example, the phase difference due to birefringence may be generated for the purpose of eliminating the polarization state of the light reflected by the polarization separation layer. Such elimination of the polarization state is friendly to suppression of visual hue change by improving the light utilization efficiency and making it the same as the light source light. As the transparent substrate that generates the phase difference due to the birefringence, for example, stretched films made of various polymers can be used, and the refractive index in the thickness direction may be controlled. The control can be performed, for example, by adhering a polymer film to a heat-shrink film and heating and stretching.
[0063]
  The thickness of the plastic film is usually 5 μm to 500 μm, preferably 10 to 200 μm, and preferably 15 to 150 μm. If the thickness is 5 μm or more, it has sufficient strength as a substrate, and therefore, for example, it is possible to prevent problems such as breakage during manufacturing.
[0064]
  Also, the optical film is transferred from the alignment substrate (hereinafter referred to as “first substrate”) to another substrate (hereinafter referred to as “second substrate”), and the optical film is laminated on the second substrate. In this state, for example, it can be used as a phase difference plate. Specifically, an adhesive layer or a pressure-sensitive adhesive layer (hereinafter referred to as “adhesive layer or the like”) is laminated on at least one surface of the second substrate, and this adhesive layer or the like is used as the first substrate. After adhering to the upper optical film, the first substrate may be peeled from the optical film.
[0065]
  In this case, the alignment substrate on which the coating liquid is developed is not limited to its translucency, thickness, etc., and is preferably selected from the viewpoints of heat resistance and strength.
[0066]
  On the other hand, the second substrate is not limited in terms of heat resistance, for example. For example, a translucent substrate, a translucent protective film, and the like are preferable, and specific examples include transparent glass and plastic films. Examples of the plastic film include polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, polyarylate, polyethylene terephthalate, polyethylene naphthalate, polyolefin, triacetyl cellulose, norbornene resin, epoxy resin, and polyvinyl alcohol resin. And the like. In addition to this, for example, polymer films described in JP-A-2001-343529 (WO01 / 37007) can be mentioned. Examples of the polymer material include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. For example, a resin composition having an alternating copolymer composed of isobutene and N-methylenemaleimide and an acrylonitrile / styrene copolymer can be used. The polymer film may be, for example, an extruded product of the resin composition. In addition, a coating polarizer can also be used as the second polarizer.
[0067]
  The second substrate is preferably optically isotropic, for example, but may be optically anisotropic depending on the use of the optical film. As the second substrate having such optical anisotropy, for example, a retardation film obtained by subjecting the plastic film to stretching treatment, a light scattering film having light scattering properties, a diffraction film having diffraction ability, A polarizing film or the like may be used.
[0068]
  In addition, when it is set as the laminated body of the said cholesteric layer and the said various translucent board | substrates, the said cholesteric layer may be laminated | stacked on both surfaces of the said translucent board | substrate, and the lamination | stacking number may be one layer. Two or more layers may be used.
[0069]
  The optical film of the present invention may further have an adhesive layer or an adhesive layer laminated on the surface thereof. By laminating the adhesive layer and the like in this way, for example, lamination with other optical layers such as a polarizing plate and members such as a liquid crystal cell can be facilitated, and peeling of the optical film can be prevented.
[0070]
  The material of the adhesive layer is not particularly limited. For example, an adhesive made of a polymer such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, or polyether, an isocyanate adhesive, or a rubber adhesive. An agent can be used. The material of the adhesive layer is not particularly limited, and for example, acrylic, silicone, polyester, rubber-based adhesives can be used. Alternatively, these materials may contain fine particles to form a layer exhibiting light diffusibility. Among these, for example, a material excellent in hygroscopicity and heat resistance is preferable. With such a property, for example, when used in a liquid crystal display device, it can prevent foaming and peeling due to moisture absorption, deterioration of optical characteristics due to a difference in thermal expansion, warpage of the liquid crystal cell, etc., and high quality and durability. The display device is also excellent.
[0071]
  As described above, the polarizing film and the retardation film of the present invention may be used alone, or may be used for various optical applications as a laminate in combination with other optical members as necessary. . Specifically, it is useful as an optical compensation member or the like, particularly as an optical compensation member for a liquid crystal display element. Examples of the other optical member include a retardation film having another refractive index structure, a liquid crystal film, a light scattering film, a diffraction film, and a polarizing film.
[0072]
  Next, the polarizing plate of the present invention is a polarizing plate including the retardation film of the present invention (including the polarizing film of the present invention) and a polarizing film.
[0073]
  As an example of the polarizing plate, for example, a protective layer is laminated on at least one surface of a polarizing film (polarizer) via an adhesive layer or an adhesive layer (hereinafter also referred to as “adhesive layer”). The phase difference film has a structure laminated on the protective layer via an adhesive layer. The protective layer may be laminated on only one side or both sides of the polarizing film. When laminating on both sides, for example, even if the same type of transparent protective layer is used, different types of transparent protective layers are used. May be used. Moreover, the said retardation film may be laminated | stacked on the single side | surface of a polarizer, or may be laminated | stacked on both surfaces, and this lamination | stacking may be through the said protective layer, and may be direct. In addition to the retardation film of the present invention, another retardation film may be further laminated.
[0074]
  The polarizing film is not particularly limited. For example, by a conventionally known method, a dichroic substance such as iodine or a dichroic dye is adsorbed and dyed on various films, crosslinked, stretched, and dried. The prepared one can be used. Among these, a film that transmits linearly polarized light when natural light is incident is preferable, and a film that is excellent in light transmittance and degree of polarization is preferable. Examples of the various films for adsorbing the dichroic substance include hydrophilic polymer films such as PVA films, partially formalized PVA films, ethylene / vinyl acetate copolymer partially saponified films, and cellulose films. In addition to these, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products can also be used. Among these, PVA film is preferable. Moreover, although the thickness of the said polarizing film is the range of 1-80 micrometers normally, it is not limited to this.
[0075]
  The protective layer is not particularly limited, and a conventionally known transparent film can be used. For example, a protective layer having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. Specific examples of the material for such a transparent protective layer include cellulose resins such as triacetyl cellulose, polyester, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, and polynorbornene. Transparent resins such as polyethylene, polyolefin, acrylic, and acetate. Further, examples thereof include thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins. Among these, a TAC film whose surface is saponified with alkali or the like is preferable from the viewpoint of polarization characteristics and durability.
[0076]
  Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) is mention | raise | lifted. Examples of the polymer material include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. For example, a resin composition having an alternating copolymer composed of isobutene and N-methylenemaleimide and an acrylonitrile / styrene copolymer can be used. The polymer film may be, for example, an extruded product of the resin composition.
[0077]
  Moreover, it is preferable that the said protective layer does not have coloring, for example. Specifically, the retardation value (Rth) in the film thickness direction represented by the following formula is preferably in the range of −90 nm to +75 nm, more preferably −80 nm to +60 nm, and particularly preferably −70 nm. It is in the range of ˜ + 45 nm. When the retardation value is in the range of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate due to the protective film can be sufficiently eliminated. In the following formula, nx, ny, nz, and d are the same as described above.
Rth = [[(nx + ny) / 2] −nz] · d
[0078]
  The transparent protective layer may further have an optical compensation function. As described above, the transparent protective layer having an optical compensation function is intended to prevent coloring or increase the viewing angle for good viewing caused by a change in viewing angle based on a phase difference in a liquid crystal cell, for example. A well-known thing can be used. Specifically, for example, various stretched films obtained by uniaxially or biaxially stretching the above-described transparent resin, alignment films such as liquid crystal polymers, and laminates in which alignment layers such as liquid crystal polymers are arranged on a transparent substrate. It is done. Among these, the alignment film of the liquid crystal polymer is preferable because it can achieve a wide viewing angle with good visual recognition, and in particular, the optical compensation layer composed of the inclined alignment layer of a discotic or nematic liquid crystal polymer is used as described above. An optical compensation retardation plate supported by a triacetyl cellulose film or the like is preferable. Examples of such an optical compensation retardation plate include commercially available products such as “WV film” manufactured by Fuji Photo Film Co., Ltd. The optical compensation retardation plate may be one in which optical properties such as retardation are controlled by laminating two or more film supports such as the retardation film and triacetyl cellulose film.
[0079]
  The thickness of the transparent protective layer is not particularly limited, and can be appropriately determined according to, for example, the phase difference or the protective strength, but is usually 5 mm or less, preferably 1 mm or less, more preferably 1 to 500 μm, particularly Preferably in the range of 5 to 150 μm
[0080]
  The transparent protective layer is appropriately formed by a conventionally known method such as a method of applying the various transparent resins to a polarizing film, a method of laminating the transparent resin film, the optical compensation retardation plate, or the like on the polarizing film. It is also possible to use a commercial product.
[0081]
  The transparent protective layer may be further subjected to, for example, a hard coat treatment, an antireflection treatment, a treatment for preventing sticking or diffusion, antiglare, and the like. The hard coat treatment is for the purpose of preventing scratches on the surface of the polarizing plate, for example, a treatment for forming a cured film having excellent hardness and slipperiness composed of a curable resin on the surface of the transparent protective layer. It is. As the curable resin, for example, a silicone-based, urethane-based, acrylic-based, or epoxy-based ultraviolet curable resin can be used, and the treatment can be performed by a conventionally known method. The purpose of preventing sticking is to prevent adhesion between adjacent layers. The antireflection treatment is intended to prevent reflection of external light on the surface of the polarizing plate, and can be performed by forming a conventionally known antireflection layer or the like.
[0082]
  The anti-glare treatment is intended to prevent visual interference of the light transmitted through the polarizing plate due to reflection of external light on the surface of the polarizing plate, for example, on the surface of the transparent protective layer by a conventionally known method, This can be done by forming a fine uneven structure. Examples of a method for forming such a concavo-convex structure include a roughening method by sandblasting or embossing, a method of forming the transparent protective layer by blending transparent fine particles in the transparent resin as described above, and the like. It is done.
[0083]
  Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like. In addition, conductive inorganic fine particles, crosslinked or uncrosslinked Organic fine particles composed of polymer particles and the like can also be used. The average particle size of the transparent fine particles is not particularly limited, but is, for example, in the range of 0.5 to 20 μm. The blending ratio of the transparent fine particles is not particularly limited, but is generally preferably in the range of 2 to 70 parts by mass and more preferably in the range of 5 to 50 parts by mass per 100 parts by mass of the transparent resin as described above.
[0084]
  The antiglare layer containing the transparent fine particles can be used as, for example, the transparent protective layer itself, or may be formed as a coating layer on the surface of the transparent protective layer. Furthermore, the anti-glare layer may also serve as a diffusion layer (visual compensation function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
[0085]
  The antireflection layer, anti-sticking layer, diffusion layer, anti-glare layer, etc. are laminated on the polarizing plate as an optical layer composed of, for example, a sheet provided with these layers, separately from the transparent protective layer. May be.
[0086]
  The adhesion method between the polarizing film and the transparent protective layer is not particularly limited, and can be performed by a conventionally known method. In general, the same pressure-sensitive adhesives and adhesives as described above can be used, and the type thereof can be appropriately determined depending on the material of the polarizing film and the transparent protective layer. The pressure-sensitive adhesives and adhesives as described above are hardly peeled off due to, for example, the influence of humidity and heat, and are excellent in light transmittance and degree of polarization. Specifically, when the polarizing film is a polyvinyl alcohol-based film, for example, a polyvinyl alcohol-based adhesive is preferable from the viewpoint of the stability of the adhesion treatment. These adhesives and pressure-sensitive adhesives, for example, may be directly applied to the surface of the polarizing film or the transparent protective layer, or a layer such as a tape or sheet composed of the adhesive or pressure-sensitive adhesive is disposed on the surface. May be. For example, when prepared as an aqueous solution, other additives and catalysts such as acids may be blended as necessary.
[0087]
  A method for laminating the retardation film of the present invention and the polarizing film is not particularly limited, and a conventionally known method using an adhesive layer, an adhesive layer, or the like as described above can be employed. Moreover, retardation film (optical film of this invention) can also be formed in a polarizing film. For example, using the transparent protective layer as a transparent substrate, an alignment substrate is formed on one surface thereof, and a cholesteric layer is formed on the alignment substrate. And a polarizing film can be adhere | attached on the other surface of the said transparent protective layer, and a transparent protective layer can further be adhere | attached on the other surface of the said polarizing film.
[0088]
  Like the retardation plate of the present invention, the polarizing plate of the present invention preferably has an adhesive layer because it can be easily laminated on other members such as a liquid crystal cell. Can be placed on one or both sides. Further, the same materials as described above can be used. The pressure-sensitive adhesive layer is formed on the surface of the polarizing plate by, for example, adding a solution or melt of various materials directly to a predetermined surface of the polarizing plate by a developing method such as casting or coating. It can be performed by a method of forming, a method of forming a pressure-sensitive adhesive layer on a separator, which will be described later, and transferring it to a predetermined surface of the polarizing plate. Such a layer may be formed on any surface of the polarizing plate, for example, on the exposed surface of the retardation plate in the polarizing plate.
[0089]
  Thus, when the surface of the adhesive layer provided in the polarizing plate is exposed, it is preferable to cover the surface with a separator for the purpose of preventing contamination until the adhesive layer is put to practical use. This separator can be formed by, for example, a method of providing a release coat with a release agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide on an appropriate film such as the transparent protective film.
[0090]
  For example, the pressure-sensitive adhesive layer may be a single layer or a laminate. As the laminate, for example, a laminate in which different compositions or different types of single layers are combined can be used. Moreover, when arrange | positioning on the both surfaces of the said polarizing plate, the same adhesive layer may respectively be sufficient, for example, a different composition and a different kind of adhesive layer may be sufficient.
[0091]
  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to, for example, the configuration of the polarizing plate, and is generally 1 to 500 μm.
[0092]
  As the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer, for example, one that is excellent in optical transparency and exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties is preferable. Specific examples include pressure-sensitive adhesives prepared by appropriately using polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers as base polymers.
[0093]
  Control of the adhesive property of the pressure-sensitive adhesive layer is, for example, the degree of cross-linking depending on the composition and molecular weight of the base polymer forming the pressure-sensitive adhesive layer, the crosslinking method, the content ratio of the crosslinkable functional group, the blending ratio of the crosslinking agent, and the like. It can be suitably carried out by a conventionally known method such as adjusting the molecular weight.
[0094]
  In addition to the retardation film and polarizing plate of the present invention, in addition to this, for example, a polarizing film, a transparent protective film, an optical layer, and each layer such as an adhesive layer and an adhesive layer are, for example, salicylic acid ester compounds, benzophenone compounds A compound, an benzotriazole-based compound, a cyanoacrylate-based compound, a nickel complex-based compound, or the like that has been provided with ultraviolet absorbing ability by treatment with an ultraviolet absorbent or the like may be used.
[0095]
  The retardation film and polarizing plate of the present invention can be used for various display devices such as a liquid crystal display device as described above. The liquid crystal display device can be formed by a conventionally known method. That is, the liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell and an optical element such as a polarizing plate, and an illumination system as necessary, and incorporating a drive circuit. There is no particular limitation except that the retardation film or polarizing plate of the present invention is used. As the liquid crystal cell, for example, any type of cell such as a TN type, STN type, or π type can be used.
[0096]
  Specifically, there is a liquid crystal display device in which the retardation plate of the present invention or the polarizing plate of the present invention is disposed on one side or both sides of a liquid crystal cell. When providing a phase difference plate and a polarizing plate on both sides of the liquid crystal cell, they may be the same or different. In forming the liquid crystal display device, for example, further, a diffusion plate, an antiglare layer, an antireflection layer, a protective plate, a prism array sheet, a lens array sheet, a light diffusion plate, a backlight, a reflection plate, a transflective plate, One layer or two or more layers may be disposed at appropriate positions such as a brightness enhancement plate.
[0097]
  In addition, since the polarizing plate of the present invention can be marked by, for example, in-line measurement, for example, an offline process such as appearance inspection and packing immediately after cutting (chip cutting) of the polarizer is not required, and a liquid crystal display device or an electro In-house manufacturing to be bonded to the luminescence display device becomes possible. Thereby, for example, the cost of the display device can be reduced, and the manufacturing process can be easily managed. Therefore, the industrial value is great.
[0098]
  The optical film and the polarizing plate of the present invention are not limited to the above-described liquid crystal display device. For example, an electroluminescence (EL) display, a plasma display (PD), an FED (Field Emission Display). It can also be used for self-luminous display devices such as.
[0099]
  Next, the retardation film and polarizing plate of the present invention can be used in organic and inorganic electroluminescence devices in the same manner as the liquid crystal display device.
[0100]
  In general, in an organic electroluminescence (organic EL) 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 EL 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 or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Also known are structures having various combinations such as a laminate of the light-emitting layer and an electron injection layer composed of a perylene derivative, or the like, or a laminate of the hole injection layer, the light-emitting layer, and the electron injection layer. Yes.
[0101]
  In the organic EL device, holes and electrons are usually injected into the organic light emitting layer by applying a voltage to the transparent electrode and the metal electrode, and energy generated by recombination of these holes and electrons. Excites the phosphor and emits light on the principle that it emits light when the excited phosphor returns 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.
[0102]
  In an organic EL device, at least one of the electrodes is preferably transparent in order to extract light emitted from the organic light emitting layer. Usually, a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. Used. 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 can be used.
[0103]
  In the organic EL device having such a configuration, the organic light emitting layer is usually formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer can transmit 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 device looks like a mirror surface.
[0104]
  In an organic EL device including an organic EL light emitting device that includes a transparent electrode on the surface side of the organic light emitting layer that emits light when a voltage is applied and includes a metal electrode on the back surface side of the organic light emitting layer, for example, the surface of the transparent electrode On the sidePolarizerAnd a retardation plate may be provided between the transparent electrode and the polarizing plate. As the polarizing plate or retardation plate, the polarizing plate or retardation film of the present invention can be applied.
[0105]
  Since the phase 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 phase plate with a quarter-wave plate and adjusting the angle between the polarization directions of the polarizing plate and the phase plate to π / 4.
[0106]
  In other words, only the linearly polarized light component of the external light incident on the organic EL device is transmitted through the polarizing plate. This linearly polarized light is generally elliptically polarized light by the phase plate, but is particularly circularly polarized when the phase plate is a quarter wave plate and the angle between the polarization direction of the polarizing plate and the phase plate is π / 4. .
[0107]
  This circularly polarized light is normally transmitted through the transparent substrate, transparent electrode, and organic thin film, reflected by the metal electrode, and again transmitted through the organic thin film, transparent electrode, transparent substrate, and the phase plate.soIt becomes linearly polarized light again. 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.
[0108]
【Example】
Next, the present invention will be further described using the following examples and comparative examples. In addition, this invention is not limited only to these Examples.
[0109]
  Example 1
  90 parts by weight of a nematic liquid crystal monomer represented by the following chemical formula (10), and a twisting force of 5.5 × 10 5 represented by the following formula (38)^-Fournm^-1・ (Wt%)^-110 parts by weight of a polymerizable chiral agent, 5 parts by weight of a UV polymerization initiator (trade name Irgacure 907: manufactured by Ciba Specialty Chemicals, the same shall apply hereinafter) and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was aligned with an alignment substrate (thickness 75 μm: Polyester film). And this was heat-processed at 70 degreeC for 3 minute (s), and after orientating the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. Then, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained by removing the alignment substrate. This retardation film was a birefringent layer of nx≈ny> nz, and the selective reflection wavelength band was 200 to 220 nm.
[0110]
[Chemical 9]

[0111]
  (Example 2)
  In the same manner as in Example 1, 92 parts by weight of the nematic liquid crystal monomer represented by the chemical formula (10) and the twisting force 5.5 × 10 represented by the chemical formula (38)^-Fournm^-1・ (Wt%)^-18 parts by weight of the polymerizable chiral agent, 5 parts by weight of the UV polymerization initiator, and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was applied onto an alignment substrate (thickness 75 μm: polyester film). And this was heat-processed at 80 degreeC for 3 minute (s), and after aligning the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. By removing the alignment substrate, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained. This retardation film was a birefringent layer of nx≈ny> nz, and its selective reflection wavelength band was 290 to 310 nm.
[0112]
  (Example 3)
  In the same manner as in Example 1, 91 parts by weight of the nematic liquid crystal monomer represented by the chemical formula (10) and the twisting force 5.5 × 10 represented by the formula (38)^-Fournm^-1・ (Wt%)^-19 parts by weight of the polymerizable chiral agent, 5 parts by weight of the UV polymerization initiator, and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was applied onto an alignment substrate (thickness 75 μm: polyester film). And this was heat-processed at 80 degreeC for 3 minute (s), and after aligning the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. By removing the alignment substrate, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained. This retardation film was a birefringent layer of nx≈ny> nz, and its selective reflection wavelength band was 240 to 260 nm.
[0113]
  Example 4
  In the same manner as in Example 1, 87 parts by weight of a nematic liquid crystal monomer represented by the following chemical formula (11), and a torsional force 6.0 × 10 represented by the following formula (39)^-Fournm^-1・ (Wt%)^-113 parts by weight of the polymerizable chiral agent, 5 parts by weight of the UV polymerization initiator and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was applied onto an alignment substrate (thickness 75 μm: polyester film). And this was heat-processed at 70 degreeC for 3 minute (s), and after orientating the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. By removing the alignment substrate, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained. This retardation film was a birefringent layer of nx≈ny> nz, and the selective reflection wavelength band thereof was 190 to 210 nm.
[0114]
[Chemical Formula 10]

[0115]
  (Example 5)
  In the same manner as in Example 1, 83 parts by weight of the nematic liquid crystal monomer represented by the chemical formula (11), and the twisting force 6.0 × 10 represented by the formula (39).^-Fournm^-1・ (Wt%)^-117 parts by weight of the polymerizable chiral agent, 5 parts by weight of the UV polymerization initiator, and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was applied onto an alignment substrate (thickness 75 μm: polyester film). And this was heat-processed at 60 degreeC for 5 minute (s), and after aligning the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. By removing the alignment substrate, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained. This retardation film was a birefringent layer of nx≈ny> nz, and the selective reflection wavelength band thereof was 140 to 160 nm.
[0116]
  (Comparative Example 1)
  80 parts by weight of a nematic liquid crystal monomer represented by the chemical formula (11), and a twisting force of 5.8 × 10 5 represented by the following formula (44)^-Fivenm^-1・ (Wt%)^-120 parts by weight of the polymerizable chiral agent, 5 parts by weight of the UV polymerization initiator, and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was applied onto an alignment substrate (thickness 75 μm: polyester film). And this was heat-processed at 70 degreeC for 3 minute (s), and after orientating the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. By removing the alignment substrate, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained. This retardation film was a birefringent layer of nx≈ny> nz, and the selective reflection wavelength band thereof was 330 to 350 nm.
[0117]
Embedded image

[0118]
(Comparative Example 2)
  75 parts by weight of a nematic liquid crystal monomer represented by the chemical formula (11), and a torsional force 6.0 × 10 represented by the formula (39)^-Fournm^-1・ (Wt%)^-125 parts by weight of the polymerizable chiral agent, 5 parts by weight of the UV polymerization initiator, and 300 parts by weight of methyl ethyl ketone were mixed, and this mixture was applied onto an alignment substrate (thickness 75 μm: polyester film). And this was heat-processed at 60 degreeC for 5 minute (s), and after aligning the said monomer, the said monomer was polymerized by ultraviolet irradiation and the orientation was fixed. By removing the alignment substrate, a completely transparent and smooth retardation film having a thickness of about 2 μm was obtained. This retardation film was a birefringent layer of nx≈ny> nz, and the selective reflection wavelength band was 70 to 90 nm.
[0119]
  About the retardation film produced in Examples 1-5 and Comparative Examples 1 and 2, the retardation film was measured using an integrating sphere type spectral transmittance measuring device (trade name DOT-3C; manufactured by Murakami Color Research Laboratory). The transmittance and hue (unit b) were measured. Further, the various retardation films were inserted between two polarizing plates having a degree of polarization of 99.95% (manufactured by Nitto Denko Corporation, trade name HEG1425DU) arranged in crossed Nicols, and the normal direction at that time The transmittance (orthogonal transmittance) and hue (orthogonal b) were measured. The orthogonal transmittance and hue (orthogonal b) were measured in the same manner for only the polarizing plate arranged in crossed Nicols without arranging the retardation film, and the measured value of the polarizing plate only as described above. Was subtracted.
[0120]
  Moreover, the phase difference of each said phase difference plate was measured with the phase difference meter (the product name KOBRA21-ADH by the Oji Scientific Instruments company) based on a parallel Nicol rotation method, and the above-mentioned nx, ny, nz was calculated to obtain Δnd.
[0121]
  These results are shown in Tables 1 and 2 below. FIG. 1 shows the relationship between the selective reflection wavelength and the transmittance of the various retardation films.
[0122]
[Table 1]

[0123]
[Table 2]

[0124]
  From Table 1 above, the retardation film of the present invention had a single hue b value of about 1.0 or less, and was very little colored compared to Comparative Example 1 in which the single hue b value was about 1.3. Further, the in-plane retardation (Δnd) was suppressed to a value less than half (1.6 nm or less) compared to 4 nm in Comparative Example 1. From this result, it can be seen that the retardation films of Examples are optically excellent birefringent layers with little variation in in-plane retardation and no influence of coloring. Moreover, from the said Table 2, while the orthogonal transmittance | permeability of the retardation film of the comparative example 1 is 0.235%, the orthogonal transmittance | permeability of the retardation film of an Example is 0.1% or less, and a comparative example The value was less than half of 1, indicating excellent polarization characteristics. Moreover, since the retardation film of an Example has the extremely low absolute value of orthogonal hue b value compared with a comparative example, it turns out that the light leakage in visible region has hardly occurred. In Comparative Example 2, measurement was impossible because the alignment itself was poor.
[0125]
  Further, the retardation film produced in Example 1 was adhered to both surfaces of a liquid crystal cell in a vertical alignment mode, and a polarizing plate (trade name SEG1224DU: manufactured by Nitto Denko Corporation) was crossed on the surfaces of both retardation films. A liquid crystal display device was manufactured by arranging each so as to be Nicol. And the display characteristic was confirmed visually. As a result, it was found that the contrast and display uniformity were excellent in a wide viewing angle range between the front and the perspective, and the display quality was good.
[0126]
(Example 6)
(1) Preparation of coating solution
  90 parts by weight of a polymerizable nematic liquid crystal monomer represented by the formula (10), and a twisting force of 5.5 × 10 5 represented by the formula (38)^-Fournm^-1・ (Wt%)^-1A coating solution was prepared by dissolving 10% by weight of the polymerizable chiral agent and 5 parts by weight of a UV polymerization initiator in 300 parts by weight of the solvent methyl ethyl ketone. The viscosity of the coating solution was 3.2 mPa · s.
[0127]
(2) Production of polarizing plate
  A protective plate made of TAC (thickness 80 μm) was laminated on both surfaces of a polarizer (thickness 30 μm) made of a PVA-based film containing iodine to prepare a polarizing plate.
[0128]
  On the other hand, the above-mentioned coating liquid was applied to one side of a highly stretched PET film (trade name T-60: manufactured by Teijin Ltd., thickness 75 μm), and the monomer was oriented by performing a heat treatment at 70 ° C. for 1 minute. Thereafter, the monomer was polymerized by ultraviolet irradiation to fix its orientation. As a result, a retardation film (compensation layer) having a thickness of 3 μm was formed on the PET film. The selective reflection wavelength band of this retardation film was 200 to 220 nm.
[0129]
  Next, the retardation film on the PET film was bonded to one surface of the polarizing plate via an acrylic adhesive layer. And the polarizing plate with a compensation layer was produced by peeling the said PET film from this laminated body.
[0130]
  This polarizing plate with a compensation layer was bonded so that the compensation layer was in contact with the viewing side of the liquid crystal cell in the vertical alignment mode. On the other hand, a polarizing plate prepared in the same manner except that no retardation film was laminated was adhered to the backlight side of the liquid crystal cell. As a result of visually confirming the display characteristics of the liquid crystal display device thus manufactured, the contrast and display uniformity are excellent in a wide viewing angle range between the front and the perspective, and the display quality is good. all right.
[0131]
【The invention's effect】
  As described above, the optical film of the present invention having a selective reflection wavelength band of 100 nm to 320 nm, for example, when used in various display devices such as a liquid crystal display device as an optical element such as a retardation film or a polarizing plate. Since there is no problem such as coloring, there is no display unevenness and excellent display characteristics can be achieved.
[Brief description of the drawings]
FIG. 1 is a graph showing a change in transmittance at each wavelength in an example of the present invention.
FIG. 2 is a schematic diagram showing an axial direction of a refractive index.

Claims (25)

An optical film including a cholesteric layer,
The constituent molecules of the layer are oriented with a cholesteric structure,
The selective reflection wavelength band of the layer is in the range of 100 nm to 320 nm,
The cholesteric layer constituting molecule is a non-liquid crystal polymer, and the non-liquid crystal polymer is a polymer obtained by polymerizing or crosslinking a liquid crystal monomer having a cholesteric structure oriented by a chiral agent,
The liquid crystal monomer is a compound represented by the following formula (4), a compound represented by the following formula (5), a compound represented by the following formula (6), a compound represented by the following formula (7), the following A compound represented by the formula (8), a compound represented by the following formula (9), a compound represented by the following formula (10), a compound represented by the following formula (11), and a formula represented by the following formula (12) A compound represented by the following formula (13), a compound represented by the following formula (14), a compound represented by the following formula (15), a compound represented by the following formula (16), and the following formula At least one liquid crystal monomer selected from the group consisting of a compound represented by (17), a compound represented by the following formula (18), and a compound represented by the following formula (19);
The chiral agent is a compound represented by the following formula (24), a compound represented by the following formula (25), a compound represented by the following formula (26), a compound represented by the following formula (27), the following A compound represented by the formula (28), a compound represented by the following formula (29), a compound represented by the following formula (30), a compound represented by the following formula (31), a formula represented by the following formula (32) The compound represented by the following formula (33), the compound represented by the following formula (34), the compound represented by the following formula (35), the compound represented by the following formula (36), the following formula The compound represented by (37), the compound represented by the following formula (38), the compound represented by the following formula (39), the compound represented by the following formula (40), and the following formula (41) A compound represented by the following formula (42), a compound represented by the following formula (43), and (44) at least one chiral agent selected from the group consisting of compounds represented by,
The proportion of liquid crystal monomer in the cholesteric layer is in the range of 75 to 95% by weight,
The optical film whose ratio of the chiral agent with respect to the said liquid-crystal monomer is the range of 5-23 weight% .

The optical film according to claim 1, wherein the cholesteric layer contains a chiral agent having a twisting force of 1 × 10 ⁻⁶ nm ⁻¹ · (wt%) ⁻¹ or more.   The optical film according to claim 1, wherein a helical pitch in the cholesteric layer is in a range of 0.01 to 0.25 μm.   The optical film according to claim 1, wherein the cholesteric layer further contains at least one of a polymerization agent and a crosslinking agent.   The optical film according to any one of claims 1 to 4, wherein a ratio of the crosslinking agent or the polymerization agent to the liquid crystal monomer is in the range of 0.1 to 10% by weight.   The optical film according to claim 1, wherein the liquid crystal monomer is a liquid crystal monomer represented by the formula (10), and the chiral agent is a chiral agent represented by the formula (38). .   The optical film according to claim 1, wherein the liquid crystal monomer is a liquid crystal monomer represented by the formula (11), and the chiral agent is a chiral agent represented by the formula (39). .   The optical film according to claim 1, further comprising a substrate, wherein the cholesteric layer is laminated on the substrate.   The optical film according to claim 8, wherein the substrate is an alignment substrate.   The optical film according to claim 9, wherein the alignment substrate is a substrate having an alignment film on a surface thereof.   The optical film according to claim 8, wherein the substrate is a transparent substrate. A method for producing an optical film comprising a cholesteric layer, wherein the constituent molecules of the layer have a cholesteric structure and are oriented,
A compound represented by the following formula (4), a compound represented by the following formula (5), a compound represented by the following formula (6), a compound represented by the following formula (7), and the following formula (8): A compound represented by the following formula (9), a compound represented by the following formula (10), a compound represented by the following formula (11), a compound represented by the following formula (12), A compound represented by the formula (13), a compound represented by the following formula (14), a compound represented by the following formula (15), a compound represented by the following formula (16), and a formula represented by the following formula (17) A compound represented by the following formula (18) and at least one liquid crystal monomer selected from the group consisting of a compound represented by the following formula (19), a compound represented by the following formula (24), The compound represented by the following formula (25), the compound represented by the following formula (26), the following formula (27 A compound represented by the following formula (28), a compound represented by the following formula (29), a compound represented by the following formula (30), a compound represented by the following formula (31), A compound represented by the following formula (32), a compound represented by the following formula (33), a compound represented by the following formula (34), a compound represented by the following formula (35), and the following formula (36) A compound represented by the following formula (37), a compound represented by the following formula (38), a compound represented by the following formula (39), a compound represented by the following formula (40), At least selected from the group consisting of a compound represented by the formula (41), a compound represented by the following formula (42), a compound represented by the following formula (43) and a compound represented by the following formula (44) One chiral agent and at least one of a polymerization agent and a crosslinking agent, , The step of the proportion of the chiral agent to the liquid crystal monomer is to expand the coating solution is in the range of 5 to 23 wt% on the alignment substrate to form a development layer,
Heat-treating the spreading layer so that the liquid crystal monomer has an orientation having a cholesteric structure, and
In order to fix the orientation of the liquid crystal monomer and form a cholesteric layer of a non-liquid crystal polymer, the development layer includes a step of performing at least one of a polymerization treatment and a crosslinking treatment ,
The proportion of liquid crystal monomer in the cholesteric layer is in the range of 75 to 95% by weight,
The manufacturing method of the optical film whose ratio of the chiral agent with respect to the said liquid-crystal monomer is the range of 5 to 23 weight% .

The manufacturing method according to claim 12, wherein the torsional force of the chiral agent is 1 × 10 ⁻⁶ nm ⁻¹ · (wt%) ⁻¹ or more.   The production method according to claim 12 or 13, wherein a ratio of the polymerization agent or the crosslinking agent to the liquid crystal monomer is in the range of 0.1 to 10% by weight.   The manufacturing method according to any one of claims 12 to 14, wherein the polymerization treatment or the crosslinking treatment is at least one treatment selected from the group consisting of an ultraviolet irradiation treatment, a light irradiation treatment, and a heat treatment.   The manufacturing method according to claim 12, wherein the alignment substrate is a substrate having an alignment film on a surface thereof.   The method according to any one of claims 12 to 16, wherein the alignment substrate is a transparent substrate.   A transparent substrate having an adhesive layer on at least one surface is prepared, the cholesteric layer formed on the alignment substrate is bonded to the adhesive layer of the transparent substrate, and the alignment substrate is removed from the spreading layer. The manufacturing method as described in any one of Claims 12-17 including the process to peel.   The method according to any one of claims 17 and 18, wherein the material of the transparent substrate is at least one substance selected from the group consisting of a cellulose polymer, a norbornene polymer, and a polyvinyl alcohol polymer.   The manufacturing method according to any one of claims 12 to 19, wherein the liquid crystal monomer is a liquid crystal monomer represented by the formula (10), and the chiral agent is a chiral agent represented by the formula (38). .   The manufacturing method according to claim 12, wherein the liquid crystal monomer is a liquid crystal monomer represented by the formula (11), and the chiral agent is a chiral agent represented by the formula (39). .   The optical film manufactured by the manufacturing method of the optical film as described in any one of Claims 12-21.   A retardation film comprising at least one of the optical film according to any one of claims 1 to 11 and the optical film according to claim 22.   A polarizing plate comprising the retardation film according to claim 23 and a polarizing film.   An image display device comprising at least one optical member selected from the group consisting of the optical film according to claim 22, the retardation film according to claim 23, and the polarizing plate according to claim 24.

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