JP3687130B2 - Alignment dye film, production method thereof, polarizing element and liquid crystal display device - Google Patents

Description

ここで、Ｘ₁ 、Ｘ₂ はそれぞれ独立に下記の基から選ばれ、ｍは０〜８の整数である。
【化９】

Ａｒ₂ は下記の基から選ばれる。
【化１０】

【化１１】

（式中、Ｘ₁ は前記の定義と同じである。
また、Ａｒ₄ は下記の基から選ばれる。
【化１２】

【００１１】
［２］前記［１］記載の一般式（２）で表される構造を有するポリアゾ系色素材料の薄膜上に、一般式（１）で表される構造を有するポリアゾ系色素材料の薄膜を積層した薄膜であり、これら色素が一軸配向し、該薄膜が４００ｎｍ〜８００ｎｍの範囲に少なくとも１種の吸収ピークを持ち、該薄膜の厚みが１０ｎｍ以上１μｍ以下であり、少なくとも１種の該吸収ピーク波長の二色性比が４０以上であることを特徴とする配向色素膜。
［３］前記［１］記載の一般式（２）で表される構造を有する少なくとも一種のポリアゾ系色素材料と、一般式（１）で表される構造を有する少なくとも一種のポリアゾ系色素材料を、表面にフッ素系樹脂配向膜を有する基材上に気相から同時に蒸着することを特徴とする［１］記載の配向色素膜の製造方法。
【００１２】
［４］前記［１］記載の一般式（２）で表される構造を有するポリアゾ系色素材料の膜を、表面にフッ素系樹脂配向膜を有する基材上に気相から蒸着し、得られた蒸着膜上に一般式（１）で表される構造を有するポリアゾ系色素材料の膜を蒸着することを特徴とする［２］記載の配向色素膜の製造方法。
［５］表面に［１］記載の配向色素膜を有する高分子フィルムまたはガラス板もしくは透明電極を有するガラス板からなる偏光素子。
【００１３】
［６］表面に［２］記載の配向色素膜を有する高分子フィルムまたはガラス板もしくは透明電極を有するガラス板からなる偏光素子。
［７］電極を有する基板に挟持された、正の誘電率異方性を有し、電圧無印加時にほぼ水平にかつ螺旋軸を基板に垂直方向にほぼ９０°以上２７０°以下の間でねじれ配向した液晶層からなる液晶セルにおいて、その外側に［５］記載の偏光素子を配置したことを特徴とする液晶表示装置。
［８］電極を有する基板に挟持された、正の誘電率異方性を有し、電圧無印加時にほぼ水平にかつ螺旋軸を基板に垂直方向にほぼ９０°以上２７０°以下の間でねじれ配向した液晶層からなる液晶セルにおいて、その外側に［６］記載の偏光素子を配置したことを特徴とする液晶表示装置。
【００１４】
本発明では一般式（１）で表される構造を有するポリアゾ系色素と一般式（２）で表される構造を有するポリアゾ系色素とが使用される。
一般式（１）で表される構造を有するポリアゾ系色素は、いずれも剛直な直線状の分子構造を有しているが、得られる偏光素子の偏光性能の点でできるだけ完全な一軸配向を達成することが好ましい。そのためには、一般式（１）の範囲内でできるだけ細長い形状の剛直鎖（メソーゲン）を骨格とすることが好ましい。したがって、置換基Ｘ₁ 、Ｘ₂ はいずれも分子鎖末端のみに位置することが好ましい。
【００１５】
さらに具体的には、ポリアゾ系色素として、表１に示したＤ１からＤ９までの９種の色素を例示することができるが、これらの内では、Ｄ１、Ｄ６、Ｄ７、Ｄ８、Ｄ９で示される色素が好ましい。以下、これらの化合物をＤ１、Ｄ６、Ｄ７、Ｄ８、Ｄ９と表す。
【００１６】
【表１】

【００１７】
一般式（２）で表される色素を複合することで偏光素子として有用な特に良好な配向が得られる。配向の点で一般式（２）におけるＸ₁ の構造としては、得られる色素膜の配向の点で水素またはアルキル基を使用することが好ましい。アルキル基の長さを表す一般式（２）におけるｎとしては、０〜８であり、０〜５が好ましく、２〜３がさらに好ましい。さらに具体的には、表１で示したＤ１０を例示することができる。
【００１８】
使用する色素に必要な純度は、不純物の種類によって異なる。不純物の種類によってはかなり純度が低下しても配向が低下しない場合もあるが、一般には純度が高いことが好ましい。不純物の種類にもよるが、純度は好ましくは９０ｗｔ％以上１００ｗｔ％以下であり、さらに好ましくは９５ｗｔ％以上１００ｗｔ％以下であり、特に好ましくは９９ｗｔ％以上１００ｗｔ％以下である。
【００１９】
本発明の配向色素膜は高配向を特徴とするが、該配向色素膜は一般式（１）で表される構造を有する色素と一般式（２）で表される構造を有する色素の双方で構成され、複数の色素を膜内に含有する状態としては単一層内に複数の色素をほぼ均等に含有してもよいし、各々の色素膜を積層して一つの膜としてもよい。
【００２０】
複数色素を単一層内にほぼ均等に含有させる方法として、フッ素系樹脂の配向膜の上に複数の該色素を気相から同時に蒸着する方法が挙げられる。
また、各々の色素膜を積層して一つの膜とする方法として、まず一般式（２）で表される構造を有する色素をフッ素系樹脂配向膜を設けた基板上に気相から蒸着し、次に形成した色素膜上に一般式（１）で表される構造を有する別の色素を蒸着する工程を繰り返して複数の色素の多層膜を得る方法が挙げられる。
【００２１】
フッ素系樹脂の配向膜は公知の方法で作成できるが、特に米国特許５１８０４７０号記載の方法を用いることにより高配向の膜が得られる。具体的には、加熱下において基板にフッ素系樹脂の塊を圧力をかけてこすりつけることにより作成できる。
【００２２】
配向膜に用いられるフッ素系樹脂としては、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリ３フッ化エチレン、ポリフッ化ビニリデン（以下、ＰＶＤＦと記すことがある。）、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（以下、ＰＦＡと記すことがある。）、テトラフルオロエチレン−エチレン共重合体等が例示されるが、ＰＴＦＥが好ましい。
【００２３】
このときの基板の加熱温度は、樹脂とこすりつける基板の種類によるが、樹脂の分解温度以下であって、１００℃以上３５０℃以下が好ましい。樹脂がＰＴＦＥであり、こすりつける基板がガラスの場合、好ましくは１３０℃以上３４０℃以下であり、さらに好ましくは２５０℃以上３４０℃以下であり、特に好ましくは３００℃以上３４０℃以下である。
【００２４】
こすりつける圧力は樹脂とこすりつける基板の種類により適宜選択できる。樹脂がＰＴＦＥであり、こすりつける基板がガラスの場合、均一で配向特性に優れた配向膜を得るためには、０．５ｋｇｆ／ｃｍ² 以上４０ｋｇｆ／ｃｍ² 以下が好ましく、５ｋｇｆ／ｃｍ² 以上２０ｋｇｆ／ｃｍ² 以下がさらに好ましい。
【００２５】
こすりつける速度も樹脂とこすりつける基板の種類により適宜選択できる。樹脂がＰＴＦＥであり、こすりつける基板がガラスの場合、均一で配向特性に優れた配向膜を得るためには、０. ０１ｃｍ／秒以上１０ｃｍ／秒以下が好ましく、０. ０１ｃｍ／秒以上０. ５ｃｍ／秒以下がさらに好ましい。
【００２６】
配向膜の厚さが薄すぎると上に堆積する色素膜は配向しなくなるので好ましくなく、一方、配向膜の厚さが厚すぎると可視域での吸収が大きくなって偏光素子としての透過率を下げてしまうので好ましくない。よって、フッ素系樹脂の配向膜の厚さは好ましくは１ｎｍ〜１μｍ、さらに好ましくは１ｎｍ〜０. ２μｍ、特に好ましくは１ｎｍ〜５０ｎｍである。
【００２７】
配向膜をこすりつける基板は、配向色素膜をそのまま偏光素子として使用する場合には、可視光に対して透明で平滑なものが用いられ、ガラス、透明電極［（Ｉｎｄｉｕｍ−Ｔｉｎ Ｏｘｉｄｅ）、Ｉｎ₂ Ｏ₃ 、ＳｎＯ₂ など］を被覆したガラス、ポリエチレンテレフタレート、ポリカーボネート等が例示される。
【００２８】
また、生成する配向色素膜を剥離したり他の基板に転写して用いる場合には、上記の基材に加えて、金属板、金属ロールも使用できる。この場合、金属材料として表面にＮｉ等の金属をメッキした材料も使用できる。
【００２９】
ただし、得られる配向色素膜の配向の点で３００℃以上３４０℃以下の温度でＰＴＦＥをこすりつけることが特に好ましいので、この場合配向膜をこすりつける基板は３００℃以上の熱に十分に耐えるものであることが好ましい。このような基板として、ガラス、透明電極［（Ｉｎｄｉｕｍ−Ｔｉｎ Ｏｘｉｄｅ）、Ｉｎ₂ Ｏ₃ 、ＳｎＯ₂ など］を被覆したガラス、金属板、金属ロール等が例示される。金属材料の場合、表面にＮｉ等の金属をメッキした材料も使用できるが、メッキを施される下地の材料も３００℃以上の熱に十分に耐えることが好ましい。
【００３０】
同時蒸着による配向色素膜の製造では、一般式（１）および一般式（２）で表される色素群から任意の色素を選択して組み合わせることができる。組み合わせに際しては、所望の色になるようにその配合比率を調整することができる。
【００３１】
同時蒸着による配向色素膜の製造方法としては、色素を分解温度以下で加熱することにより昇華させてフッ素系樹脂配向膜を設けた基板上に堆積させる方法が挙げられる。よって、色素は蒸発に必要な加熱により分解しないで昇華するものが用いられるが、蒸発源の温度を色素の分解温度以下とする必要がある。具体的な温度は、色素の構造により異なるが、ポリアゾ系色素の一般的な特徴から４００℃以下が好ましく、３５０℃以下がさらに好ましい。
【００３２】
同時蒸着時の真空度は大気圧以下を使用することができるが、色素の加熱温度を下げるために、また蒸発源と基板の距離を確保する意味でできるだけ真空の状態に排気することが好ましい。具体的には10^-4ｔｏｒｒ以下が好ましく、10^-5ｔｏｒｒ以下がさらに好ましい。
【００３３】
同時蒸着の場合、一般式（２）で表される色素の含有量を高くすると偏光性能の良い膜が得られる。この場合、一般式（２）で表される色素の含有量として５０％以上１００％以下が好ましいが、６０％以上１００％以下がさらに好ましく、７０％以上１００％以下が特に好ましい
【００３４】
同時蒸着の場合の配向色素膜の最適膜厚は、色素の二色性や、モル吸光係数、膜中の色素の配向度にもより調整する必要があるが、一般にピンホールがなく、均一な薄膜を形成するという観点からは厚い方がよく、高配向度とするためには薄くすることが有利である。また、薄すぎると単体透過率が大きすぎるため、偏光素子として用いても十分な性能が得られない。よって、膜厚は、通常１０ｎｍ以上１μｍ以下、好ましくは２０ｎｍ以上０. ４μm 以下、さらに好ましくは２０ｎｍ以上０．２μm 以下である。
【００３５】
色素膜を積層して一つの配向色素膜とする場合、一般式（２）で表される構造を有する色素膜上に積層される一般式（１）で表される構造を有する色素膜の層数は、積層する層の配向の点で少ないことが好ましい。一般に１〜４層が使用できるが、１〜３層が好ましく、１層がさらに好ましい。
【００３６】
積層する場合、各色素膜の膜厚を調整することで得られる色素膜の色調が変化するので、所望の色調が得られるように膜厚を調整する。ただし、各色素膜の膜厚は各色素の配向に著しく影響するので、配向を損なわないような注意が必要である。具体的には一般式（２）で表される構造を有する色素膜の膜厚をある範囲に収めることが好ましい。色素の二色性や、モル吸光係数でも調整することが好ましいが、通常１０ｎｍ以上０. ４μｍ以下、好ましくは２０ｎｍ以上０. ２μm 以下、さらに好ましくは２０ｎｍ以上０．２μm 以下である。
【００３７】
また、該配向色素膜は、４００ｎｍ〜８００ｎｍの範囲に少なくとも１種の吸収ピークを持ち、少なくとも１種の吸収ピーク波長での二色性比が４０以上、好ましくは６０以上、さらに好ましくは８０以上である。さらに、単体透過率が３５％以上８０％以下であることが好ましい。
【００３８】
本発明においては、偏光素子として用いる場合に不可欠な配向色素膜に加えて、他の機能を有する膜を積層してもよく、例えば、最上部に保護膜としてエポキシ樹脂や光硬化樹脂等の薄膜を形成してもよい。
【００３９】
本発明の配向色素膜は容易に偏光素子として利用できる。最も単純な使用方法は、本発明の配向色素膜を透明な基板上に形成されたフッ素樹脂配向膜上に形成してそのまま偏光素子とするものである。
【００４０】
一方、本配向色素膜は転写して偏光素子とすることもできる。この場合の製造方法は、一旦基材上に配向色素膜を形成した後、より接着性の高い別の基材に強く押し当てる、または加熱しながら押し当てることにより転写する方法、表面に接着剤をつけた別の基材を張り付けて剥離することにより転写する方法等が例示される。
【００４１】
本発明の液晶表示装置の構造を説明する。本発明の配向色素膜からなる偏光素子を用いて液晶表示装置を作成するには、液晶セルの外側に、必要な大きさの偏光素子を組み込めばよい。図１に本発明の液晶表示装置の一例の概略図を示す。図１において、１は本発明の偏光素子、２はガラス基板、３は透明電極、４は絶縁性の液晶配向制御膜、５は液晶層、６はスペーサーである。ただし、図１は本発明の液晶表示装置に最低必要な基本的構成のみを示すに過ぎず、必要に応じ他の構成要素を含むことができる。このような構成要素として、カラーフィルタ、薄膜トランジスタ、防眩フィルムなどが例示される。
【００４２】
透明電極３は、液晶層側のガラス基板２上に被覆されており、通常ＩＴＯ（Ｉｎｄｉｕｍ−Ｔｉｎ Ｏｘｉｄｅ）、Ｉｎ₂ Ｏ₃ 、ＳｎＯ₂ などが用いられている。透明電極３の液晶層側５には、絶縁性の液晶配向制御膜が設置されている。この際、液晶配向制御膜がそれ単独で充分な絶縁性を有する場合には、配向膜のみでよいが、必要に応じて液晶配向制御膜の下に絶縁層を設置し、その両者で絶縁性配向膜としてもかまわない。
【００４３】
液晶配向制御膜としては、有機物、無機物、低分子、高分子など、公知のものを使用することができる。高分子化合物としては、例えば、ポリイミド、ポリアミド、ポリアミドイミド、ポリビニルアルコール、ポリスチレン、ポリエステル、ポリエステルイミドや種々のフォトレジストなどを必要に応じて用いることができる。
【００４４】
また、これらの高分子物質を液晶配向制御膜として用いた場合には、必要に応じてこれら膜の表面を、ガーゼやアセテート植毛布などを用いて、一方向にこする、いわゆるラビング処理を行なうことによって液晶分子の配向をより一層促進することができる。
絶縁膜としては、例えば、チタン酸化物、アルミニウム酸化物、ジルコニウム酸化物、シリコン酸化物、シリコン窒化物などを用いることができる。
【００４５】
これらの液晶配向制御膜や絶縁膜を形成する方法としては、必要に応じて、それら用いる物質によって最適な方法を用いることができる。例えば、高分子物質の場合には、その高分子物質またはその前駆体を、それらの物質を溶解できる溶媒に溶解後、スクリーン印刷法、スピンナー塗布法、浸漬法などの方法で塗布することができる。無機物質の場合には、浸漬法、蒸着法、斜方蒸着法などを用いることができる。これら絶縁性配向膜の厚みとしては、特に限定するものではないが、好ましくは１ｎｍ〜２μｍ、さらに好ましくは２ｎｍ〜１００ｎｍである。
【００４６】
これら液晶配向制御膜４および透明電極３を設置した二枚のガラス基板２は、スペーサー６を介して所定の間隔に保持される。スペーサーとしては、所定の直径または厚みを有する、ビーズ、ファイバーまたはフィルム状の絶縁性の材料を用いることができる。具体的にはシリカ、アルミナ、高分子物質（ポリスチレン等）が例示できる。これらスペーサー６を２枚のガラス基板２で挾持し、周囲を例えばエポキシ系接着剤等を用いてシールした後、液晶を封入することができる。
【００４７】
一般に二枚のガラス基板の外側には、それぞれ偏光素子が必要であるので二枚の本発明の配向色素膜からなる偏光素子が設置される。しかし、２枚の一方を他の種類の偏光素子とすることも目的によっては可能である。また、液晶層に二色性色素を含ませて使用するいわゆるゲストホスト型の液晶素子の場合には、片側の偏光素子を省き、もう一方の偏光素子を本発明の偏光素子とする。図１には二枚の偏光素子を用いた場合が例示されている。
【００４８】
透明電極３は、適当なリード線が接続されており、外部の駆動回路に接続されている。外部の駆動回路の一部を、液晶セル上に形成した薄膜トランジスタ回路（通称ＴＦＴ）とすると、極めて性能の高い表示素子ができるので特に有用である。
【００４９】
【実施例】
以下本発明の実施例を示すが、本発明はこれらによって限定されるものではない。
なお、本発明における二色性比とは、特定の波長における、配向色素膜の配向方向に平行な方向の偏光の吸光度（Ａ１）と、配向色素膜の配向方向と直交する方向の偏光の吸光度（Ａ２）を測定し、次の式により求めたものであり、特に吸収ピーク波長での値を用いた。吸光度の値としては、基材による吸収を差し引いて、配向色素膜単独のものを用いた。
【数１】
二色性比＝Ａ１／Ａ２
【００５０】
実施例１
＜配向膜の形成＞
米国特許５１８０４７０号記載の方法を用いることにより、ＰＴＦＥの配向膜を得た。具体的には、約３００℃に加熱したガラス基板（２．５ｃｍ×８．０ｃｍ）上に、同様に加熱した長さ２ｃｍ直径１．０ｃｍのＰＴＦＥの円柱の側面たる曲面を押しつけ、基板を０．１ｃｍ／秒の速度で移動することにより、幅２．０ｃｍ×長さ７．０ｃｍのＰＴＦＥ配向膜を得た。この際、円柱は５ｋｇｆの圧力で基板に押しつけた。基板との接触面積を観察すると約０. ４ｃｍ² であった。
＜色素膜の形成＞
得られたＰＴＦＥ配向膜上に、ポリアゾ系色素であるＤ１０（日本感光色素社製、商品名Ｇ２０５）とポリアゾ系色素であるＤ６（日本感光色素社製、商品名Ｇ２３２）を同時に蒸着した。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる配向色素膜の厚さは、約１００ｎｍであった。このとき、Ｄ１０の蒸着速度はＤ６の３倍であった。
＜二色性比の評価＞
３００ｎｍ〜７００ｎｍの範囲の偏光吸光度を測定すると、５１０ｎｍに吸収ピークがあった。吸収ピークでの二色性比は４０以上であった。
また、得られる配向色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、良好なコントラストを示す。
【００５１】
実施例２
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上に、ポリアゾ系色素であるＤ１０（日本感光色素社製、商品名Ｇ２０５）とポリアゾ系色素であるＤ１を同時に蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる配向色素膜の厚さは、約１００ｎｍである。このとき、Ｄ１０の蒸着速度はＤ１の３倍である。
＜二色性比の評価＞
３００ｎｍ〜７００ｎｍの範囲の偏光吸光度を測定すると、５１０ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上である。
また、得られる配向色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、良好なコントラストを示す。
【００５２】
実施例３
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上にポリアゾ系色素であるＤ１０（日本感光色素社製、商品名Ｇ２０５）とポリアゾ系色素であるＤ７を同時に蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる複合色素膜の厚さは、約５０ｎｍである。
＜二色性比の評価＞
３００ｎｍ〜７００ｎｍの範囲の偏光吸光度を測定すると、４９５ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上である。
また、得られる配向色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、良好なコントラストを示す。
【００５３】
実施例４
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上に、ポリアゾ系色素であるＤ１０（日本感光色素社製、商品名Ｇ２０５）とポリアゾ系色素であるＤ９とを同時に蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる配向色素膜の厚さは、約１００ｎｍである。このとき、Ｄ１０の蒸着速度はＤ９の３倍である。
【００５４】
＜二色性比の評価＞
３００ｎｍから７００ｎｍの範囲の偏光吸光度を測定すると、５１０ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上である。
また、得られる配向色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、良好なコントラストを示す。
【００５５】
実施例５
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上に、Ｄ１０（日本感光色素社製、商品名Ｇ２０５）を蒸着した。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られた色素膜の厚さは、約１００ｎｍであった。次にこの膜上にＤ６（日本感光色素製Ｇ２３２）を蒸着した。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約５０ｎｍであった。
＜二色性比の評価＞
３００ｎｍから７００ｎｍの範囲の偏光吸光度を測定すると、５１０ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上であった。
また、得られた色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、無色と赤色の変化を示し、良好なコントラストを示す。
【００５６】
実施例６
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上に、Ｄ１０（日本感光色素社製、商品名Ｇ２０５）を蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約５０ｎｍである。次にこの膜上にＤ１を蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約５０ｎｍである。
＜二色性比の評価＞
３００ｎｍ〜７００ｎｍの範囲の偏光吸光度を測定すると、４９５ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上である。
また、得られる色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、無色と赤色の変化を示し、良好なコントラストを示す。
【００５７】
実施例７
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上に、Ｄ１０（日本感光色素社製、商品名Ｇ２０５）を蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約１００ｎｍである。次にこの膜上にＤ７を蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約５０ｎｍである。
＜二色性比の評価＞
３００ｎｍ〜７００ｎｍの範囲の偏光吸光度を測定すると、５１０ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上である。
また、得られる色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、無色と赤色の変化を示し、良好なコントラストを示す。
【００５８】
実施例８
＜色素膜の形成＞
実施例１と同様にして得たＰＴＦＥ配向膜上に、Ｄ１０（日本感光色素社製、商品名Ｇ２０５）を蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約５０ｎｍである。次にこの膜上にＤ８を蒸着する。蒸着の際の真空度は、１０^-5Ｔｏｒｒ以下であり、得られる色素膜の厚さは、約５０ｎｍである。
【００５９】
＜二色性比の評価＞
３００ｎｍ〜７００ｎｍの範囲の偏光吸光度を測定すると、４９５ｎｍに吸収ピークがある。吸収ピークでの二色性比は４０以上である。
また、得られる色素膜をＴＮ型液晶セルの両側に９０°捩じって配置し、ＴＮ型液晶セルを駆動すると、無色と赤色の変化を示し、良好なコントラストを示す。
【００６０】
【発明の効果】
本発明の配向色素膜は、複数の種類の色素からなる二色性比の高い配向色素膜であり、本発明の製造方法で容易に作成でき、それを用いた偏光素子を液晶表示装置に用いた場合には、高コントラストの画像が得られる。
【図面の簡単な説明】
【図１】本発明の液晶表示装置の一例の概略図。
【符号の説明】
１………偏光素子
２………ガラス基板
３………透明電極
４………絶縁性の液晶配向制御膜
５………液晶層
６………スペーサー[0001]
[Industrial application fields]
The present invention relates to an alignment dye film useful for a polarizing element, a manufacturing method thereof, a polarizing element using the same, and a liquid crystal display device. Specifically, the present invention relates to an alignment dye film composed of a plurality of types of polyazo dichroic dyes, a method for producing the same, and a high-performance polarizing element and a liquid crystal display device using the same.
[0002]
[Prior art]
A polarizing element is widely used as an indispensable element for displaying on a liquid crystal display (hereinafter sometimes referred to as LCD). Currently, a polarizing element is produced by adsorbing iodine or a plurality of types of dichroic dyes to stretched and oriented polyvinyl alcohol (hereinafter sometimes referred to as PVA) or a derivative film thereof.
[0003]
Among these, a polarizing film using iodine as a polarizing element has excellent initial polarization performance in a wide wavelength range, but is weak against water and heat, and is durable when used for a long time under high temperature and high humidity conditions. There was a problem with sex. In order to increase the durability, various measures such as a protective film have been taken, but it is not sufficient. Moreover, although the polarizing element which adsorb | sucked the dye is excellent in durability with respect to water and a heat | fever compared with the thing which adsorb | sucked iodine, its polarization performance is inferior. In this case, the polarization performance is secured in a wide wavelength range by using a plurality of types of dyes.
[0004]
Full color LCDs have been developed very actively. In these LCDs, a high contrast ratio is required for the liquid crystal cell in order to display various colors. One effective method for increasing the contrast ratio of the liquid crystal cell is to improve the polarization performance of the polarizing element used in a wide wavelength range.
[0005]
Color filters are used to make the liquid crystal cell full color. In this case, the amount of transmitted light is very small due to light absorption by the polarizing element and the color filter. In order to obtain a bright LCD, a strong backlight must be used, and there are problems such as a rise in temperature of the liquid crystal cell and an increase in power consumption.
[0006]
In other words, in order to manufacture a high-performance full-color LCD, it has excellent polarization performance, maintains a very high degree of polarization, achieves a high contrast ratio, enhances image quality, and has durability to withstand temperature rise due to backlight. A polarizing element is extremely useful.
[0007]
On the other hand, J.H. C. Wittmann et al. Have shown that an oriented PTFE thin film can be obtained by rubbing polytetrafluoroethylene (hereinafter sometimes referred to as PTFE) onto a glass substrate under heating while applying pressure. It has been reported that alkanes, liquid crystal molecules, polymers, oligomers, inorganic salts, and the like can be aligned on this film as an alignment film [Nature 352, 414 (1991)].
[0008]
As described above, a polarizing element having high polarization performance and durability required for a high-performance full-color LCD is not yet known. A dichroic dye dyed on a stretched oriented polymer is excellent in durability but has insufficient polarization characteristics. This is a problem resulting from insufficient orientation of dichroic dye molecules in the prior art. That is, if almost perfect uniaxial orientation is achieved with a dichroic dye, the polarization performance can be dramatically improved and this problem can be achieved. Therefore, there is a demand for a dichroic dye film that is easy to manufacture and uniaxially oriented, and a method for manufacturing the same.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide an alignment dye film having a high dichroic ratio composed of a plurality of kinds of dyes, a manufacturing method thereof, a high-contrast and high-performance polarizing element and a liquid crystal display device using the same.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have reached the present invention.
That is, this invention consists of the invention described below.
[1] A thin film comprising at least one polyazo dye material having a structure represented by the general formula (1) and at least one polyazo dye material having a structure represented by the general formula (2), These dyes are uniaxially oriented, the thin film has at least one absorption peak in the range of 400 nm to 800 nm, the thickness of the thin film is from 10 nm to 1 μm, and the dichroic ratio of at least one of the absorption peak wavelengths Is an alignment dye film characterized by being 40 or more.
[Chemical 7]
Ar ₁ -N = N-Ar ₂ -N = N-Ar _Three (1)
(Wherein Ar ₁ , Ar _Three Are independently selected from the following groups.
[Chemical 8]

Where X ₁ , X ₂ Are each independently selected from the following groups, and m is an integer of 0-8.
[Chemical 9]

Ar ₂ Is selected from the following groups.
[Chemical Formula 10]

Embedded image

(Where X ₁ Is the same as defined above.
Ar _Four Is selected from the following groups.
Embedded image

[0011]
[2] A thin film of a polyazo dye material having a structure represented by the general formula (1) is laminated on a thin film of a polyazo dye material having a structure represented by the general formula (2) described in [1]. The thin film has a uniaxial orientation, the thin film has at least one absorption peak in the range of 400 nm to 800 nm, the thickness of the thin film is from 10 nm to 1 μm, and at least one absorption peak wavelength. An alignment dye film characterized by having a dichroic ratio of 40 or more.
[3] At least one polyazo dye material having a structure represented by the general formula (2) described in [1], and at least one polyazo dye material having a structure represented by the general formula (1). The method for producing an oriented dye film according to [1], wherein vapor deposition is simultaneously performed from a gas phase on a substrate having a fluororesin orientation film on the surface.
[0012]
[4] Obtained by vapor-depositing a film of a polyazo dye material having the structure represented by the general formula (2) described in [1] from a gas phase on a substrate having a fluororesin alignment film on the surface. The method for producing an oriented dye film according to [2], wherein a film of a polyazo dye material having a structure represented by the general formula (1) is deposited on the deposited film.
[5] A polarizing element comprising a polymer film having the alignment dye film according to [1] on the surface, a glass plate, or a glass plate having a transparent electrode.
[0013]
[6] A polarizing element comprising a polymer film having the alignment dye film according to [2] on the surface, a glass plate, or a glass plate having a transparent electrode.
[7] A positive dielectric anisotropy sandwiched between substrates having electrodes, twisted between approximately 90 ° and 270 ° in a substantially horizontal direction when no voltage is applied, and a helical axis perpendicular to the substrate. In a liquid crystal cell comprising an aligned liquid crystal layer, the polarizing element described in [5] is disposed outside thereof, and a liquid crystal display device.
[8] A positive dielectric anisotropy sandwiched between substrates having electrodes, twisted between approximately 90 ° and 270 ° in the horizontal direction when no voltage is applied and the helical axis perpendicular to the substrate. A liquid crystal display device comprising a liquid crystal cell comprising an aligned liquid crystal layer, wherein the polarizing element according to [6] is disposed outside the liquid crystal cell.
[0014]
In the present invention, a polyazo dye having a structure represented by the general formula (1) and a polyazo dye having a structure represented by the general formula (2) are used.
All of the polyazo dyes having the structure represented by the general formula (1) have a rigid linear molecular structure, but achieve as complete uniaxial orientation as possible in terms of the polarization performance of the obtained polarizing element. It is preferable to do. For that purpose, it is preferable to use a rigid straight chain (mesogen) as long as possible within the range of the general formula (1) as a skeleton. Thus, the substituent X ₁ , X ₂ Are preferably located only at the molecular chain ends.
[0015]
More specifically, as the polyazo dye, nine kinds of dyes D1 to D9 shown in Table 1 can be exemplified, and among these, D1, D6, D7, D8, and D9 are shown. A dye is preferred. Hereinafter, these compounds are represented as D1, D6, D7, D8, and D9.
[0016]
[Table 1]

[0017]
By combining the dye represented by the general formula (2), particularly good orientation useful as a polarizing element can be obtained. X in general formula (2) in terms of orientation ₁ As the structure, it is preferable to use hydrogen or an alkyl group in view of the orientation of the resulting dye film. As n in General formula (2) showing the length of an alkyl group, it is 0-8, 0-5 are preferable and 2-3 are more preferable. More specifically, D10 shown in Table 1 can be exemplified.
[0018]
The purity required for the dye used depends on the type of impurity. Depending on the type of impurity, even if the purity is considerably lowered, the orientation may not be lowered. However, it is generally preferable that the purity is high. Although it depends on the type of impurities, the purity is preferably 90 wt% or more and 100 wt% or less, more preferably 95 wt% or more and 100 wt% or less, and particularly preferably 99 wt% or more and 100 wt% or less.
[0019]
The oriented dye film of the present invention is characterized by high orientation, and the oriented dye film includes both a dye having a structure represented by the general formula (1) and a dye having a structure represented by the general formula (2). As a state of being configured and containing a plurality of dyes in a film, a plurality of dyes may be contained almost uniformly in a single layer, or each dye film may be laminated to form a single film.
[0020]
As a method of containing a plurality of dyes almost uniformly in a single layer, a method of simultaneously depositing a plurality of dyes from a gas phase on a fluororesin alignment film can be mentioned.
In addition, as a method of laminating the respective dye films to form one film, first, a dye having a structure represented by the general formula (2) is vapor-deposited from a vapor phase on a substrate provided with a fluororesin alignment film, Next, a method of obtaining a multilayer film of a plurality of dyes by repeating the step of depositing another dye having a structure represented by the general formula (1) on the formed dye film can be mentioned.
[0021]
The fluororesin alignment film can be prepared by a known method, but a highly oriented film can be obtained by using the method described in US Pat. No. 5,180,470. Specifically, it can be produced by rubbing a block of fluorine-based resin under pressure while applying pressure.
[0022]
Examples of the fluororesin used for the alignment film include polytetrafluoroethylene (PTFE), polytrifluoride ethylene, polyvinylidene fluoride (hereinafter sometimes referred to as PVDF), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Examples thereof include a coalescence (hereinafter sometimes referred to as PFA), a tetrafluoroethylene-ethylene copolymer, and the like, and PTFE is preferable.
[0023]
The heating temperature of the substrate at this time depends on the type of the substrate to be rubbed with the resin, but is not higher than the decomposition temperature of the resin and is preferably 100 ° C. or higher and 350 ° C. or lower. When the resin is PTFE and the substrate to be rubbed is glass, it is preferably 130 ° C. or higher and 340 ° C. or lower, more preferably 250 ° C. or higher and 340 ° C. or lower, and particularly preferably 300 ° C. or higher and 340 ° C. or lower.
[0024]
The pressure for rubbing can be appropriately selected depending on the kind of resin and the substrate to be rubbed. In the case where the resin is PTFE and the substrate to be rubbed is glass, 0.5 kgf / cm is required to obtain a uniform alignment film with excellent alignment characteristics. ² 40 kgf / cm ² The following is preferable, 5 kgf / cm ² 20 kgf / cm ² More preferred are:
[0025]
The rubbing speed can also be appropriately selected depending on the type of resin and the substrate to be rubbed. When the resin is PTFE and the substrate to be rubbed is glass, in order to obtain a uniform alignment film having excellent alignment characteristics, 0.01 cm / second to 10 cm / second is preferable, and 0.01 cm / second to 0.00 cm. 5 cm / second or less is more preferable.
[0026]
If the alignment film is too thin, the dye film deposited on the alignment film will not be aligned, which is not preferable. On the other hand, if the alignment film is too thick, absorption in the visible region increases and the transmittance as a polarizing element is increased. Since it lowers, it is not preferable. Therefore, the thickness of the fluororesin alignment film is preferably 1 nm to 1 μm, more preferably 1 nm to 0.2 μm, and particularly preferably 1 nm to 50 nm.
[0027]
As the substrate for rubbing the alignment film, when the alignment dye film is used as it is as a polarizing element, a transparent and smooth substrate for visible light is used, and glass, transparent electrode [(Indium-Tin Oxide), In ₂ O _Three , SnO ₂ Etc.], polyethylene terephthalate, polycarbonate and the like.
[0028]
In addition, when the alignment dye film to be formed is peeled off or transferred to another substrate, a metal plate or a metal roll can be used in addition to the above-mentioned base material. In this case, a material having a surface plated with a metal such as Ni can also be used as the metal material.
[0029]
However, since it is particularly preferable to rub PTFE at a temperature of 300 ° C. or higher and 340 ° C. or lower in terms of the orientation of the obtained alignment dye film, the substrate on which the alignment film is rubbed is sufficiently resistant to heat of 300 ° C. or higher. It is preferable that As such a substrate, glass, transparent electrode [(Indium-Tin Oxide), In ₂ O _Three , SnO ₂ Etc.], a metal plate, a metal roll, and the like. In the case of a metal material, a material having a surface plated with a metal such as Ni can also be used, but it is preferable that the underlying material to be plated should sufficiently withstand heat of 300 ° C. or higher.
[0030]
In the production of the alignment dye film by co-evaporation, any dye can be selected and combined from the dye group represented by the general formula (1) and the general formula (2). In combination, the blending ratio can be adjusted so as to obtain a desired color.
[0031]
Examples of a method for producing an alignment dye film by simultaneous vapor deposition include a method in which a dye is sublimated by heating at a decomposition temperature or lower and deposited on a substrate provided with a fluororesin alignment film. Accordingly, a dye that sublimes without being decomposed by heating necessary for evaporation is used, but the temperature of the evaporation source needs to be equal to or lower than the decomposition temperature of the dye. Although specific temperature changes with structures of a pigment | dye, 400 degrees C or less is preferable from the general characteristic of a polyazo dye, and 350 degrees C or less is still more preferable.
[0032]
The degree of vacuum at the time of co-evaporation can be less than atmospheric pressure, but it is preferable to evacuate to a vacuum as much as possible in order to lower the heating temperature of the dye and to secure the distance between the evaporation source and the substrate. Specifically, 10 ^-Four preferably less than torr, 10 ^-Five More preferably, it is less than torr.
[0033]
In the case of co-evaporation, a film having good polarization performance can be obtained by increasing the content of the dye represented by the general formula (2). In this case, the content of the dye represented by the general formula (2) is preferably 50% or more and 100% or less, more preferably 60% or more and 100% or less, and particularly preferably 70% or more and 100% or less.
[0034]
The optimum film thickness of the alignment dye film in the case of co-evaporation needs to be adjusted according to the dichroism of the dye, the molar extinction coefficient, and the degree of orientation of the dye in the film. From the viewpoint of forming a thin film, it is better to make it thicker, and it is advantageous to make it thinner in order to achieve a high degree of orientation. On the other hand, if the thickness is too thin, the single transmittance is too large, so that sufficient performance cannot be obtained even when used as a polarizing element. Therefore, the film thickness is usually from 10 nm to 1 μm, preferably from 20 nm to 0.4 μm, and more preferably from 20 nm to 0.2 μm.
[0035]
When the dye films are laminated to form one oriented dye film, the layer of the dye film having the structure represented by the general formula (1) laminated on the dye film having the structure represented by the general formula (2) The number is preferably small in terms of the orientation of the layers to be laminated. Generally 1 to 4 layers can be used, but 1 to 3 layers are preferable, and 1 layer is more preferable.
[0036]
In the case of stacking, since the color tone of the dye film obtained by adjusting the film thickness of each dye film changes, the film thickness is adjusted so that a desired color tone is obtained. However, since the film thickness of each dye film significantly affects the orientation of each dye, care must be taken not to impair the orientation. Specifically, it is preferable to keep the film thickness of the dye film having the structure represented by the general formula (2) within a certain range. Although it is preferable to adjust also by the dichroism of a pigment | dye and a molar extinction coefficient, they are 10 nm or more and 0.4 micrometer or less normally, Preferably they are 20 nm or more and 0.2 micrometers or less, More preferably, they are 20 nm or more and 0.2 micrometers or less.
[0037]
The alignment dye film has at least one absorption peak in the range of 400 nm to 800 nm, and has a dichroic ratio of at least one absorption peak wavelength of 40 or more, preferably 60 or more, more preferably 80 or more. It is. Further, the single transmittance is preferably 35% or more and 80% or less.
[0038]
In the present invention, in addition to the alignment dye film indispensable when used as a polarizing element, a film having other functions may be laminated, for example, a thin film such as an epoxy resin or a photo-curing resin as a protective film on the top. May be formed.
[0039]
The alignment dye film of the present invention can be easily used as a polarizing element. In the simplest method of use, the alignment dye film of the present invention is formed on a fluororesin alignment film formed on a transparent substrate and used as it is as a polarizing element.
[0040]
On the other hand, the alignment dye film can be transferred to a polarizing element. The manufacturing method in this case is a method in which an oriented dye film is once formed on a substrate and then strongly pressed against another substrate having higher adhesiveness, or transferred by pressing while heating, an adhesive on the surface For example, a method of transferring by pasting and peeling off another base material with a mark is exemplified.
[0041]
The structure of the liquid crystal display device of the present invention will be described. In order to produce a liquid crystal display device using a polarizing element comprising the alignment dye film of the present invention, a polarizing element having a required size may be incorporated outside the liquid crystal cell. FIG. 1 shows a schematic diagram of an example of the liquid crystal display device of the present invention. In FIG. 1, 1 is a polarizing element of the present invention, 2 is a glass substrate, 3 is a transparent electrode, 4 is an insulating liquid crystal alignment control film, 5 is a liquid crystal layer, and 6 is a spacer. However, FIG. 1 shows only a basic configuration that is at least necessary for the liquid crystal display device of the present invention, and may include other components as necessary. Examples of such components include color filters, thin film transistors, and antiglare films.
[0042]
The transparent electrode 3 is coated on the glass substrate 2 on the liquid crystal layer side, and is usually ITO (Indium-Tin Oxide), In ₂ O _Three , SnO ₂ Etc. are used. An insulating liquid crystal alignment control film is provided on the liquid crystal layer side 5 of the transparent electrode 3. In this case, if the liquid crystal alignment control film alone has sufficient insulation, only the alignment film may be used, but if necessary, an insulating layer is provided under the liquid crystal alignment control film, and both of them are insulative. An alignment film may be used.
[0043]
As the liquid crystal alignment control film, known materials such as organic substances, inorganic substances, low molecules, and polymers can be used. As the polymer compound, for example, polyimide, polyamide, polyamideimide, polyvinyl alcohol, polystyrene, polyester, polyesterimide, various photoresists, and the like can be used as necessary.
[0044]
In addition, when these polymer substances are used as liquid crystal alignment control films, the surface of these films is rubbed in one direction with gauze, acetate flocking cloth, or the like as necessary. As a result, the alignment of the liquid crystal molecules can be further promoted.
As the insulating film, for example, titanium oxide, aluminum oxide, zirconium oxide, silicon oxide, silicon nitride, or the like can be used.
[0045]
As a method for forming these liquid crystal alignment control films and insulating films, an optimum method can be used depending on the materials used, if necessary. For example, in the case of a polymer substance, the polymer substance or a precursor thereof can be dissolved in a solvent capable of dissolving the substance and then applied by a method such as a screen printing method, a spinner coating method, or a dipping method. . In the case of an inorganic substance, an immersion method, a vapor deposition method, an oblique vapor deposition method, or the like can be used. The thickness of these insulating alignment films is not particularly limited, but is preferably 1 nm to 2 μm, and more preferably 2 nm to 100 nm.
[0046]
The two glass substrates 2 provided with the liquid crystal alignment control film 4 and the transparent electrode 3 are held at a predetermined interval via a spacer 6. As the spacer, a bead, fiber, or film-like insulating material having a predetermined diameter or thickness can be used. Specific examples include silica, alumina, and polymer substances (polystyrene, etc.). After these spacers 6 are held between two glass substrates 2 and the periphery is sealed using, for example, an epoxy adhesive, liquid crystal can be sealed.
[0047]
In general, since a polarizing element is necessary for each of the two glass substrates, two polarizing elements made of the alignment dye film of the present invention are installed. However, depending on the purpose, one of the two sheets may be another type of polarizing element. In the case of a so-called guest-host type liquid crystal element used by including a dichroic dye in a liquid crystal layer, one side of the polarizing element is omitted and the other polarizing element is used as the polarizing element of the present invention. FIG. 1 illustrates the case where two polarizing elements are used.
[0048]
The transparent electrode 3 is connected to an appropriate lead wire and is connected to an external drive circuit. When a part of the external drive circuit is a thin film transistor circuit (commonly referred to as TFT) formed on a liquid crystal cell, it is particularly useful because a display element with extremely high performance can be obtained.
[0049]
【Example】
Examples of the present invention will be described below, but the present invention is not limited thereto.
The dichroic ratio in the present invention refers to the absorbance (A1) of polarized light in a direction parallel to the alignment direction of the alignment dye film and the absorbance of polarization in a direction orthogonal to the alignment direction of the alignment dye film at a specific wavelength. (A2) was measured and obtained by the following formula, and in particular, the value at the absorption peak wavelength was used. As the absorbance value, the alignment dye film alone was used after subtracting the absorption by the base material.
[Expression 1]
Dichroic ratio = A1 / A2
[0050]
Example 1
<Formation of alignment film>
By using the method described in US Pat. No. 5,180,470, an alignment film of PTFE was obtained. Specifically, on the glass substrate (2.5 cm × 8.0 cm) heated to about 300 ° C., a curved surface which is the side surface of a PTFE cylinder heated in the same manner and having a length of 2 cm and a diameter of 1.0 cm is pressed. By moving at a speed of 0.1 cm / second, a PTFE alignment film having a width of 2.0 cm and a length of 7.0 cm was obtained. At this time, the cylinder was pressed against the substrate with a pressure of 5 kgf. When the contact area with the substrate is observed, it is about 0.4 cm. ² Met.
<Formation of dye film>
On the obtained PTFE alignment film, a polyazo dye D10 (trade name G205, manufactured by Nippon Photosensitive Dye) and a polyazo dye D6 (trade name G232, manufactured by Nippon Photosensitive Dye) were simultaneously deposited. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting alignment dye film was about 100 nm. At this time, the deposition rate of D10 was three times that of D6.
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm was measured, there was an absorption peak at 510 nm. The dichroic ratio at the absorption peak was 40 or more.
Further, when the obtained alignment dye film is twisted by 90 ° on both sides of the TN liquid crystal cell and the TN liquid crystal cell is driven, good contrast is exhibited.
[0051]
Example 2
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, D10 which is a polyazo dye (manufactured by Nippon Photosensitizer Co., Ltd., trade name G205) and D1 which is a polyazo dye are vapor-deposited simultaneously. The degree of vacuum during deposition is 10 ^-Five It is equal to or less than Torr, and the thickness of the resulting oriented dye film is about 100 nm. At this time, the deposition rate of D10 is three times that of D1.
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 510 nm. The dichroic ratio at the absorption peak is 40 or more.
Further, when the obtained alignment dye film is twisted by 90 ° on both sides of the TN liquid crystal cell and the TN liquid crystal cell is driven, good contrast is exhibited.
[0052]
Example 3
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, a polyazo dye D10 (trade name G205, manufactured by Nippon Photosensitive Dye) and a polyazo dye D7 are vapor-deposited simultaneously. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting composite dye film is about 50 nm.
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 495 nm. The dichroic ratio at the absorption peak is 40 or more.
Further, when the obtained alignment dye film is twisted by 90 ° on both sides of the TN liquid crystal cell and the TN liquid crystal cell is driven, good contrast is exhibited.
[0053]
Example 4
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, D10 as a polyazo dye (trade name G205, manufactured by Nippon Senshoku Dye Co., Ltd.) and D9 as a polyazo dye are simultaneously deposited. The degree of vacuum during deposition is 10 ^-Five It is equal to or less than Torr, and the thickness of the resulting oriented dye film is about 100 nm. At this time, the deposition rate of D10 is three times that of D9.
[0054]
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 510 nm. The dichroic ratio at the absorption peak is 40 or more.
Further, when the obtained alignment dye film is twisted by 90 ° on both sides of the TN liquid crystal cell and the TN liquid crystal cell is driven, good contrast is exhibited.
[0055]
Example 5
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, D10 (manufactured by Nippon Photosensitizer Co., Ltd., trade name G205) was deposited. The degree of vacuum during deposition is 10 ^-Five The thickness of the obtained dye film was about 100 nm. Next, D6 (Nippon Senshoku Dye G232) was vapor-deposited on this film. The degree of vacuum during deposition is 10 ^-Five The thickness of the obtained dye film was about 50 nm.
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 510 nm. The dichroic ratio at the absorption peak was 40 or more.
Further, when the obtained dye film is twisted 90 ° on both sides of the TN type liquid crystal cell and the TN type liquid crystal cell is driven, it shows a change of colorless and red and shows a good contrast.
[0056]
Example 6
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, D10 (trade name G205, manufactured by Nippon Photosensitizer Co., Ltd.) is deposited. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting dye film is approximately 50 nm. Next, D1 is vapor-deposited on this film. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting dye film is approximately 50 nm.
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 495 nm. The dichroic ratio at the absorption peak is 40 or more.
Further, when the obtained dye film is twisted 90 ° on both sides of the TN type liquid crystal cell and the TN type liquid crystal cell is driven, it shows a change of colorless and red and shows a good contrast.
[0057]
Example 7
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, D10 (trade name G205, manufactured by Nippon Photosensitizer Co., Ltd.) is deposited. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting dye film is about 100 nm. Next, D7 is vapor-deposited on this film. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting dye film is approximately 50 nm.
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 510 nm. The dichroic ratio at the absorption peak is 40 or more.
Further, when the obtained dye film is twisted 90 ° on both sides of the TN type liquid crystal cell and the TN type liquid crystal cell is driven, it shows a change of colorless and red and shows a good contrast.
[0058]
Example 8
<Formation of dye film>
On the PTFE alignment film obtained in the same manner as in Example 1, D10 (trade name G205, manufactured by Nippon Photosensitizer Co., Ltd.) is deposited. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting dye film is approximately 50 nm. Next, D8 is vapor-deposited on this film. The degree of vacuum during deposition is 10 ^-Five The thickness of the resulting dye film is approximately 50 nm.
[0059]
<Evaluation of dichroic ratio>
When the polarization absorbance in the range of 300 nm to 700 nm is measured, there is an absorption peak at 495 nm. The dichroic ratio at the absorption peak is 40 or more.
Further, when the obtained dye film is twisted 90 ° on both sides of the TN type liquid crystal cell and the TN type liquid crystal cell is driven, it shows a change of colorless and red and shows a good contrast.
[0060]
【The invention's effect】
The alignment dye film of the present invention is an alignment dye film having a high dichroic ratio composed of a plurality of types of dyes, and can be easily prepared by the production method of the present invention. If there is, a high-contrast image is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view of an example of a liquid crystal display device of the present invention.
[Explanation of symbols]
1 ... Polarizing element
2 ……… Glass substrate
3 ... Transparent electrode
4 .... Insulating liquid crystal alignment control film
5 .... Liquid crystal layer
6 ……… Spacer

Claims (8)

A thin film comprising at least one polyazo dye material having a structure represented by the general formula (1) and at least one polyazo dye material having a structure represented by the general formula (2). Uniaxially oriented, the thin film has at least one absorption peak in the range of 400 nm to 800 nm, the thickness of the thin film is 10 nm or more and 1 μm or less, and the dichroic ratio of at least one absorption peak wavelength is 40 or more An alignment dye film characterized by the following.

(In the formula, Ar ₁ and Ar ₃ are each independently selected from the following groups.

Here, X ₁ and X ₂ are each independently selected from the following groups, and m is an integer of 0 to 8.

Ar ₂ is selected from the following groups.

(Wherein X ₁ is the same as defined above).
Ar ₄ is selected from the following groups.

A thin film obtained by laminating a thin film of a polyazo dye material having a structure represented by the general formula (1) on a thin film of a polyazo dye material having a structure represented by the general formula (2) according to claim 1. These dyes are uniaxially oriented, the thin film has at least one absorption peak in the range of 400 nm to 800 nm, the thickness of the thin film is 10 nm to 1 μm, and at least one dichroism of the absorption peak wavelength. An alignment dye film characterized by having a ratio of 40 or more. At least one polyazo dye material having a structure represented by the general formula (2) according to claim 1 and at least one polyazo dye material having a structure represented by the general formula (1) are provided on the surface with fluorine. The method for producing an oriented dye film according to claim 1, wherein vapor deposition is simultaneously performed from a gas phase on a base material having a resin-based orientation film. A film of a polyazo dye material having a structure represented by the general formula (2) according to claim 1 is vapor-deposited from a gas phase on a substrate having a fluororesin alignment film on the surface, and on the obtained vapor-deposited film 3. A method for producing an oriented dye film according to claim 2, wherein a film of a polyazo dye material having a structure represented by the general formula (1) is deposited. A polarizing element comprising a polymer film having the alignment dye film according to claim 1 on the surface, a glass plate, or a glass plate having a transparent electrode. A polarizing element comprising a polymer film having the alignment dye film according to claim 2 on the surface, a glass plate, or a glass plate having a transparent electrode. A liquid crystal sandwiched between substrates having electrodes and having a positive dielectric anisotropy and twisted and aligned between approximately 90 ° and 270 ° in a horizontal direction with no spiral and a helical axis perpendicular to the substrate. A liquid crystal display device comprising a polarizing element according to claim 5 arranged outside the liquid crystal cell comprising a layer. A liquid crystal sandwiched between substrates having electrodes and having a positive dielectric anisotropy and twisted and aligned between approximately 90 ° and 270 ° in a horizontal direction with no spiral and a helical axis perpendicular to the substrate. A liquid crystal display device comprising a polarizing element according to claim 6 arranged outside thereof in a liquid crystal cell comprising layers.

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