JP5332449B2 - Method for producing retardation film - Google Patents
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Description
本発明は、液晶性分子から形成された光学異方性層を有する位相差膜の製造方法に関する。 The present invention relates to a method for producing a retardation film having an optically anisotropic layer formed from liquid crystalline molecules.
液晶表示装置は、液晶セル、偏光素子および位相差膜（光学補償シート、位相差板ともいう）からなる。透過型液晶表示装置では、二枚の偏光素子を液晶セルの両側に取り付け、一枚または二枚の位相差膜を液晶セルと偏光素子との間に配置する。反射型液晶表示装置では、反射板、液晶セル、一枚の位相差膜、そして一枚の偏光素子の順に配置する。液晶セルは、棒状液晶性分子、それを封入するための二枚の基板および棒状液晶性分子に電圧を加えるための電極層からなる。液晶セルは、棒状液晶性分子の配向状態の違いで、透過型については、ＴＮ（Twisted Nematic）、ＩＰＳ（In-Plane Switching）、ＦＬＣ（Ferroelectric Liquid Crystal）、ＯＣＢ（Optically Compensatory Bend）、ＳＴＮ（Supper Twisted Nematic）、ＶＡ（Vertically Aligned）、ＥＣＢ（Electrically Controlled Birefringence ）、反射型については、ＴＮ、ＨＡＮ（Hybrid Aligned Nematic）、ＧＨ（Guest-Host）のような様々な表示モードが提案されている。 The liquid crystal display device includes a liquid crystal cell, a polarizing element, and a retardation film (also referred to as an optical compensation sheet or a retardation plate). In a transmissive liquid crystal display device, two polarizing elements are attached to both sides of a liquid crystal cell, and one or two retardation films are disposed between the liquid crystal cell and the polarizing element. In the reflection type liquid crystal display device, a reflection plate, a liquid crystal cell, one retardation film, and one polarizing element are arranged in this order. The liquid crystal cell is composed of a rod-like liquid crystal molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystal molecule. The liquid crystal cell is different in the alignment state of rod-like liquid crystal molecules. As for the transmissive type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (STN) Various display modes such as TN, HAN (Hybrid Aligned Nematic), and GH (Guest-Host) have been proposed for Supper Twisted Nematic (VA), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and reflective type. .
位相差膜は、画像着色を解消したり、視野角を拡大するために、様々な液晶表示装置で用いられている。特に視野角の問題については、ｎｘ＝ｎｙ＞ｎｚとなる屈折率異方性を有する位相差膜を液晶層と偏光板の間に配置すれば、斜め方向から観察する場合に生じる液晶層の複屈折を補償することが可能なことや、ｎｘ＞ｎｙ＝ｎｚの屈性率異方性を有する光学異方性層とｎｘ＝ｎｙ＞ｎｚの屈折率異方性を有する光学異方性層を少なくとも一層ずつ用いる構成や、ｎｘ＞ｎｙ＞ｎｚという二軸性の屈折率異方性を有する光学異方性層を少なくとも一層以上用いる構成とすれば、広視野角化が可能であることが知られている。（例えば特許文献１参照） The retardation film is used in various liquid crystal display devices in order to eliminate image coloring and to widen the viewing angle. In particular, regarding the problem of viewing angle, if a retardation film having a refractive index anisotropy satisfying nx = ny> nz is disposed between the liquid crystal layer and the polarizing plate, the birefringence of the liquid crystal layer that occurs when observing from an oblique direction is caused. At least one layer having an optical anisotropy layer having a refractive index anisotropy of nx> ny = nz and an optical anisotropic layer having a refractive index anisotropy of nx = ny> nz. It is known that a wide viewing angle can be obtained by using each of them, or using at least one optically anisotropic layer having biaxial refractive index anisotropy of nx> ny> nz. Yes. (For example, see Patent Document 1)
このような位相差膜としては延伸複屈折ポリマーフィルムが従来から使用されている。例えば特許文献１参照の複屈折ポリマーフィルムは、ｎｘ＞ｎｙ＞ｎｚという二軸性の屈折率異方性を有し、高分子の主鎖方向に芳香族環または芳香族複素環を持つため、主鎖に垂直方向と比べて屈折率が大きくなることから、分子として大きな複屈折を有すること、またその分子鎖が基板に平行に配向しやすいために、面内最大屈折率と厚み方向屈折率の差が大きいものが簡便に得られる。しかし、延伸が必要であることから、小面積の位相差膜を得るためには、延伸したフィルムを切り出して使用するといった不便さを有していた。また、厚み方向屈折率を小さくすることに限界があり、所望のリタデーションを得るために一定以上の膜厚を必要とするため、得られる位相差膜の膜厚が十分に薄くならないといった欠点もあり、薄膜化が進む液晶表示装置の部材としても限界がある。 As such a retardation film, a stretched birefringent polymer film has been conventionally used. For example, the birefringent polymer film of Patent Document 1 has a biaxial refractive index anisotropy of nx> ny> nz and has an aromatic ring or an aromatic heterocycle in the polymer main chain direction. Since the refractive index is higher than the direction perpendicular to the main chain, it has a large birefringence as a molecule, and the molecular chain tends to be oriented parallel to the substrate. A large difference is easily obtained. However, since stretching is necessary, in order to obtain a retardation film having a small area, there is an inconvenience that a stretched film is cut out and used. In addition, there is a limit to reducing the refractive index in the thickness direction, and since a film thickness of a certain level or more is required to obtain a desired retardation, there is a disadvantage that the film thickness of the obtained retardation film is not sufficiently reduced. Further, there is a limit as a member of a liquid crystal display device that is becoming thinner.
一方、透明支持体上に液晶性分子から形成された光学異方性層を有する位相差膜を使用することも提案されている。（例えば特許文献２、３参照）これらの方法は、任意の場所に塗布し位相差膜を形成できるため、小面積の位相差膜に適した方法である。
例えば特許文献２に記載の位相差膜は、透明支持体およびディスコティック液晶性分子から形成され、透明支持体が光学的一軸性または光学的二軸性を有し、ディスコティック液晶性分子の円盤面と透明支持体面との間の平均傾斜角が５゜未満の状態でディスコティック液晶性分子が配向した位相差膜である。また特許文献３に記載の位相差膜は、２枚の基板間に形成された光学異方体であって、一方の基板に対しては基板に略平行であって配向方向が異なる複数の配向領域を有し、他方の基板に対しては基板に略垂直な配向を有するハイブリッド構造を有する位相差膜である。
On the other hand, it has also been proposed to use a retardation film having an optically anisotropic layer formed from liquid crystalline molecules on a transparent support. (For example, refer to Patent Documents 2 and 3) Since these methods can be applied to an arbitrary place to form a retardation film, they are suitable for a retardation film having a small area.
For example, the retardation film described in Patent Document 2 is formed from a transparent support and a discotic liquid crystalline molecule, and the transparent support has optical uniaxiality or optical biaxiality. It is a retardation film in which discotic liquid crystal molecules are aligned in a state where an average inclination angle between the disk surface and the transparent support surface is less than 5 °. Further, the retardation film described in Patent Document 3 is an optical anisotropic body formed between two substrates, and a plurality of alignments having different alignment directions are substantially parallel to the substrate with respect to one substrate. The retardation film has a hybrid structure having a region and having an orientation substantially perpendicular to the substrate with respect to the other substrate.
しかしながら文献２に記載の位相差膜は２軸性を有する透明基板とその上に塗布された１軸性のディスコティック液晶層からなる擬似的な光学的２軸性を有するものであるため、広視野角化に限界があった。またその光学軸は透明基板の延伸条件によって定められ、延伸方向に制限があるため任意の方向に設定しうるものではないという問題があった。または文献３に記載の位相差膜は、ｘを位相差膜の面内での最大屈折率方向とし、ｙをｘに垂直な方向とし、ｚを厚み方向とし、ｎｘを前記ｘ方向の屈折率とし、ｎｙを前記ｙ方向の屈折率とし、ｎｚを前記ｚ方向の屈折率とした場合、ｎｘ＞ｎｙ＝ｎｚの関係を満たす一軸性の位相差膜であり、広視野角化に限界があるといった問題があった。 However, since the retardation film described in Document 2 has a pseudo optical biaxial property composed of a biaxial transparent substrate and a uniaxial discotic liquid crystal layer coated thereon, There was a limit to viewing angle. Further, the optical axis is determined by the stretching conditions of the transparent substrate, and there is a problem that it cannot be set in an arbitrary direction because the stretching direction is limited. Alternatively, in the retardation film described in Document 3, x is a maximum refractive index direction in the plane of the retardation film, y is a direction perpendicular to x, z is a thickness direction, and nx is a refractive index in the x direction. Where ny is the refractive index in the y direction and nz is the refractive index in the z direction, it is a uniaxial retardation film satisfying the relationship of nx> ny = nz, and there is a limit to widening the viewing angle. There was a problem.
本発明が解決しようとする課題は、ｎｘ＞ｎｙ＞ｎｚあるいはｎｘ＝ｎｙ＞ｎｚという屈折率異方性を有し、且つｎｚの値の小さい位相差膜を、液晶性分子を使用して簡便に得る方法を提供するものである。 A problem to be solved by the present invention is that a retardation film having a refractive index anisotropy of nx> ny> nz or nx = ny> nz and having a small nz value is easily obtained using liquid crystalline molecules. It provides a method to obtain.
本発明者らは、二色性染料を含有する薄膜層に、偏光軸をｘ−ｙ面内で回転させながら偏光紫外線を照射することで、該薄膜層上に設けた重合性基を有する棒状液晶化合物を含有する重合性液晶組成物層が、ｎｘ＞ｎｙ＞ｎｚあるいはｎｘ＝ｎｙ＞ｎｚという屈折率異方性を有して配向し、該重合性液晶組成物層を重合させることで、ｎｘ＞ｎｙ＞ｎｚあるいはｎｘ＝ｎｙ＞ｎｚの屈折率異方性を有する位相差膜が得られることを見出した。 The inventors of the present invention irradiate a thin film layer containing a dichroic dye with polarized ultraviolet rays while rotating the polarization axis in the xy plane, thereby forming a rod-like shape having a polymerizable group provided on the thin film layer. A polymerizable liquid crystal composition layer containing a liquid crystal compound is aligned with a refractive index anisotropy of nx> ny> nz or nx = ny> nz, and polymerizing the polymerizable liquid crystal composition layer, It has been found that a retardation film having a refractive index anisotropy of nx> ny> nz or nx = ny> nz can be obtained.
即ち本発明は、ｘ−ｙ面内方向に略平行であり、且つ、ｘ−ｙ面内方向屈折率ｎｘ及びｎｙが厚み方向ｚの屈折率ｎｚよりも大きい位相差膜の製造方法であって、
二色性染料を含有する薄膜層に、偏光軸をｘ−ｙ面内で回転させながら偏光紫外線を照射する工程Ａと、該薄膜層上に重合性基を有する棒状液晶化合物を含有する重合性液晶組成物層を形成する工程Ｂと、重合性基を有する液晶化合物を硬化させる工程Ｃとを有する位相差膜の製造方法を提供する。
（但しｘは位相差膜の面内での最大屈折率方向を表し、ｙはｘに垂直な方向を表し、ｚは厚み方向を表す）
That is, the present invention is a method for producing a retardation film that is substantially parallel to the xy in-plane direction and has xy in-plane direction refractive indexes nx and ny larger than the refractive index nz in the thickness direction z. ,
A process for irradiating a thin film layer containing a dichroic dye with polarized ultraviolet rays while rotating the polarization axis in the xy plane, and a polymerizability containing a rod-like liquid crystal compound having a polymerizable group on the thin film layer There is provided a method for producing a retardation film, which comprises a step B for forming a liquid crystal composition layer and a step C for curing a liquid crystal compound having a polymerizable group.
(Where x represents the maximum refractive index direction in the plane of the retardation film, y represents the direction perpendicular to x, and z represents the thickness direction)
また本発明は、基板上に、二色性染料を含有する液晶配向層と、前記液晶配向層により配向された状態で重合してなる液晶組成物の重合体からなる層とを有し、ｎｘ＞ｎｙ＞ｎｚの関係を満たす位相差膜を提供する。（但し、ｘは位相差膜の面内での最大屈折率方向を表し、ｙはｘに垂直な方向を表し、ｚは厚み方向を表し、ｎｘは前記ｘ方向の屈折率を表し、ｎｙは前記ｙ方向の屈折率を表し、ｎｚは前記ｚ方向の屈折率を表す） Further, the present invention includes a liquid crystal alignment layer containing a dichroic dye on a substrate, and a layer made of a polymer of a liquid crystal composition that is polymerized in a state aligned by the liquid crystal alignment layer, nx A retardation film satisfying a relationship of> ny> nz is provided. (Where x represents the maximum refractive index direction in the plane of the retardation film, y represents the direction perpendicular to x, z represents the thickness direction, nx represents the refractive index in the x direction, and ny represents (Y represents the refractive index in the y direction, and nz represents the refractive index in the z direction)
本発明により、ｎｘ＞ｎｙ＞ｎｚという二軸性の屈折率異方性を有する位相差膜を、液晶性分子を使用して簡便に得ることができる。
本発明の製造方法は、ｎｚの制御範囲が広く、より小さな値にできる。具体的には、本発明の製造方法により、ｎｙがｎｚより大きく、且つｎｘ−ｎｚが０．０６以上である、ｎｚがｎｘやｎｙに比べて非常に小さい位相差膜を得ることが可能である。このため膜厚を薄くすることができ、結果的に得られる液晶表示装置の厚みを薄くすることが可能である。
According to the present invention, a retardation film having a biaxial refractive index anisotropy of nx>ny> nz can be easily obtained using liquid crystalline molecules.
The manufacturing method of the present invention has a wide control range of nz and can be set to a smaller value. Specifically, by the production method of the present invention, it is possible to obtain a retardation film in which ny is larger than nz and nx-nz is 0.06 or more, and nz is very small compared to nx and ny. is there. Therefore, the film thickness can be reduced, and the thickness of the resulting liquid crystal display device can be reduced.
（二色性染料を含有する薄膜層）
本発明において、二色性染料を含有する薄膜層とは、具体的には、基板上に二色性染料を含有する塗膜を設けた薄膜層である。
二色性染料とは、光二色性に起因するワイゲルト効果による分子の配向誘起もしくは異性化反応（例：アゾベンゼン基）、二量化反応（例：シンナモイル基）、光架橋反応（例：ベンゾフェノン基）、あるいは光分解反応（例：ポリイミド基）のような、液晶配向能の起源となる光反応を生じる基（以下、光配向性基と略す）を表す。
中でも、光二色性に起因するワイゲルト効果による分子の配向誘起もしくは異性化反応、二量化反応、あるいは光架橋反応を利用したものが、配向性に優れ、重合性液晶化合物を簡単に配向させることができ好ましい。
光配向性基としては特に限定されないが、中でも、Ｃ＝Ｃ、Ｃ＝Ｎ、Ｎ＝Ｎ、及びＣ＝Ｏからなる群より選ばれる少なくとも一つの二重結合（但し、芳香環を形成する二重結合を除く）を有する基が特に好ましく用いられる。
なお、本発明において、ワイゲルト効果とは、遷移モーメントを有する分子の配向方向が、入射光の偏光方向に対して該分子の持つ遷移モーメントが垂直となるように変化することをいう。
(Thin film layer containing dichroic dye)
In the present invention, the thin film layer containing a dichroic dye is specifically a thin film layer provided with a coating film containing a dichroic dye on a substrate.
Dichroic dye means molecular orientation induction or isomerization reaction (eg azobenzene group), dimerization reaction (eg cinnamoyl group), photocrosslinking reaction (eg benzophenone group) due to Weigert effect due to photodichroism Alternatively, it represents a group (hereinafter abbreviated as a photoalignment group) that causes a photoreaction that is the origin of liquid crystal alignment ability, such as a photodecomposition reaction (eg, polyimide group).
Among them, those utilizing molecular orientation induction or isomerization reaction, dimerization reaction, or photocrosslinking reaction due to the Weigert effect resulting from photodichroism are excellent in orientation and can easily align polymerizable liquid crystal compounds. This is preferable.
The photo-alignment group is not particularly limited, but among them, at least one double bond selected from the group consisting of C = C, C = N, N = N, and C = O (however, it forms two aromatic rings). A group having (excluding a heavy bond) is particularly preferably used.
In the present invention, the Weigert effect means that the orientation direction of a molecule having a transition moment changes so that the transition moment of the molecule is perpendicular to the polarization direction of incident light.
これらの光配向性基として、Ｃ＝Ｃ結合を有する基としては、例えば、ポリエン基、スチルベン基、スチルバゾ−ル基、スチルバゾリウム基、シンナモイル基、ヘミチオインジゴ基、カルコン基等の構造を有する基が挙げられる。Ｃ＝Ｎ結合を有する基としては、芳香族シッフ塩基、芳香族ヒドラゾン等の構造を有する基が挙げられる。Ｎ＝Ｎ結合を有する基としては、アゾベンゼン基、アゾナフタレン基、芳香族複素環アゾ基、ビスアゾ基、ホルマザン基等の構造を有する基や、アゾキシベンゼンを基本構造とするものが挙げられる。Ｃ＝Ｏ結合を有する基としては、ベンゾフェノン基、クマリン基、アントラキノン基等の構造を有する基が挙げられる。これらの基は、アルキル基、アルコキシ基、アリ−ル基、アリルオキシ基、シアノ基、アルコキシカルボニル基、ヒドロキシル基、スルホン酸基、ハロゲン化アルキル基等の置換基を有していても良い。
中でも、光異性化反応により光配向性を示すアゾベンゼン基又はアントラキノン基、あるいは、光二量化反応により光配向性を示すベンゾフェノン基、シンナモイル基、カルコン基、又はクマリン基が、光配向に必要な偏光の照射量が少なく、かつ得られた光配向膜の熱安定性、経時安定性が優れているため、特に好ましい。中でも、アゾベンゼン基が好ましい。
中でも、アゾベンゼン誘導体を含有する組成物がもっとも好ましい。アゾベンゼン誘導体による光配向膜は、光照射に伴う化学結合の生成や、分解を伴う他の配向膜とは異なり一旦光で配向した後も再配向が可能である。従って、一旦膜全体を特定の方向に配向させた後、フォトマスクを用いて光が照射された部分のみ別の方向に配向させることができるので、簡便に、かつ精度良くパターン配向領域を得ることができる。
Examples of groups having a C═C bond as these photo-alignable groups include groups having a structure such as a polyene group, a stilbene group, a stilbazole group, a stilbazolium group, a cinnamoyl group, a hemithioindigo group, and a chalcone group. It is done. Examples of the group having a C═N bond include groups having a structure such as an aromatic Schiff base and an aromatic hydrazone. Examples of the group having an N═N bond include groups having a structure such as an azobenzene group, an azonaphthalene group, an aromatic heterocyclic azo group, a bisazo group, a formazan group, and those having a basic structure of azoxybenzene. Examples of the group having a C═O bond include groups having a structure such as a benzophenone group, a coumarin group, and an anthraquinone group. These groups may have a substituent such as an alkyl group, an alkoxy group, an aryl group, an allyloxy group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, a sulfonic acid group, and a halogenated alkyl group.
Among them, an azobenzene group or anthraquinone group that exhibits photoalignment by a photoisomerization reaction, or a benzophenone group, a cinnamoyl group, a chalcone group, or a coumarin group that exhibits photoalignment by a photodimerization reaction, are polarized light necessary for photoalignment. This is particularly preferable because the irradiation amount is small, and the obtained photo-alignment film has excellent thermal stability and stability over time. Of these, an azobenzene group is preferable.
Among these, a composition containing an azobenzene derivative is most preferable. A photo-alignment film made of an azobenzene derivative can be re-orientated even after it is once aligned with light, unlike other alignment films that involve generation or decomposition of chemical bonds accompanying light irradiation. Therefore, once the entire film is oriented in a specific direction, only a portion irradiated with light can be oriented in another direction using a photomask, so that a pattern orientation region can be obtained easily and accurately. Can do.
アゾベンゼン誘導体としては、例えば、特開２００２−２５０９２４号公報に記載の化合物や、ＳＩＤ０１ Ｄｉｇｅｓｔ，１１７０（２００１）に記載の化合物を使用することができる。該化合物は、数種類を混合して使用することもできる。 As the azobenzene derivative, for example, a compound described in JP-A No. 2002-250924 or a compound described in SID01 Digest, 1170 (2001) can be used. These compounds can be used in combination of several kinds.
これらのアゾベンゼン誘導体は、適当な良溶媒に溶解し、スピンコート法、エクストルージョン法、グラビアコーティング法、ダイコーティング法、バーコーティング法、アプリケータ法などの塗布法やフレキソ印刷法等の方法で後述の基板上に塗布する。溶媒としては特に限定はないが、ガラス等の基板に対する光配向膜用化合物の溶液の塗布性が良好で、かつ、均一な膜が得られるので、Ｎ−メチルピロリドン、ブチルセロソルブ、ガンマ−ブチロラクトン、ジメチルホルムアミドなどが特に好ましい。
溶媒は、基板に塗布した後揮発除去されるので、使用する場合は、化合物（Ｃ）の固形分濃度が少なくとも０．２質量％以上となることが必要である。中でも、０．３〜１０質量％の範囲が特に好ましい。また、本発明の効果を損なわない範囲で、ポリビニルアルコ−ルやポリイミド等の高分子材料を混合することもできる。
These azobenzene derivatives are dissolved in a suitable good solvent and are described later by methods such as spin coating, extrusion, gravure coating, die coating, bar coating, applicator and other application methods and flexographic printing methods. Apply onto the substrate. The solvent is not particularly limited, but the coating property of the photo alignment film compound solution on a substrate such as glass is good and a uniform film can be obtained. Therefore, N-methylpyrrolidone, butyl cellosolve, gamma-butyrolactone, dimethyl Formamide and the like are particularly preferable.
Since the solvent is volatilized and removed after being applied to the substrate, the solid content concentration of the compound (C) needs to be at least 0.2% by mass or more when used. Especially, the range of 0.3-10 mass% is especially preferable. In addition, a polymer material such as polyvinyl alcohol or polyimide can be mixed within a range not impairing the effects of the present invention.
二色性染料を含有する塗膜の膜厚は、薄くした方が配向処理に用いる紫外線エネルギーを低く抑えることができ、生産速度を高められるので好ましいが、あまり薄すぎると基板の表面平滑性または表面特性の影響を受けやすく、配向の均一性が悪くなる。従って１〜２００ｎｍが好ましく、５〜１００ｎｍが尚好ましく、１０〜４０ｎｍが最も好ましい。 As for the film thickness of the coating film containing the dichroic dye, it is preferable that the film thickness is reduced because the ultraviolet energy used for the alignment treatment can be kept low and the production speed can be increased. It is easily affected by surface characteristics, and the uniformity of orientation is deteriorated. Therefore, 1-200 nm is preferable, 5-100 nm is still more preferable, and 10-40 nm is the most preferable.
（基板）
基板としては実質的に透明であれば材質に特に限定はなく、ガラス、セラミックス、プラスチック等を使用することができる。プラスチック基板としてはセルロ−ス、トリアセチルセルロ−ス、ジアセチルセルロ−ス等のセルロ−ス誘導体、ポリシクロオレフィン誘導体、ポリエチレンテレフタレ−ト、ポリエチレンナフタレ−ト等のポリエステル、ポリプロピレン、ポリエチレン等のポリオレフィン、ポリカーボネート、ポリビニルアルコ−ル、ポリ塩化ビニル、ポリ塩化ビニリデン、ナイロン、ポリスチレン、ポリアクリレート、ポリメチルメタクリレ−ト、ポリエーテルサルホン、ポリアリレートなどを用いることができる。
(substrate)
The substrate is not particularly limited as long as it is substantially transparent, and glass, ceramics, plastics, and the like can be used. Examples of plastic substrates include cellulose derivatives such as cellulose, triacetyl cellulose, diacetyl cellulose, polycycloolefin derivatives, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polypropylene, and polyethylene. Polyolefin, polycarbonate, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, nylon, polystyrene, polyacrylate, polymethyl methacrylate, polyether sulfone, polyarylate and the like can be used.
（工程Ａ）
工程Ａは、ｎｘ＝ｎｙ＞ｎｚあるいはｎｘ＞ｎｙ＞ｎｚなる屈折率を有する位相差膜とするための光配向膜を得る工程である。具体的には、前記二色性染料を含有する薄膜層に、偏光軸をｘ−ｙ面内で回転させながら偏光紫外線を照射して光配向膜を得る。
偏光紫外線は、使用する二色性染料が吸収しうる波長が好ましく、例えばアゾベンゼン誘導体を使用する場合、アゾベンゼンのπ→π＊遷移による強い吸収帯に対応する波長３５０〜５００ｎｍの範囲の紫外光もしくは可視光が特に好ましい。照射光の光源としては、キセノンランプ、高圧水銀ランプ、超高圧水銀ランプ、メタルハライドランプ、紫外光レーザー等が挙げられる。特に超高圧水銀ランプはほぼ点光源であるため、平行光を得ることが容易であることから特に好ましい。前記光源からの光を偏光フィルタや偏光プリズムを通すことで直線偏光を得ることができる。
(Process A)
Step A is a step of obtaining a photo-alignment film for forming a retardation film having a refractive index of nx = ny> nz or nx>ny> nz. Specifically, the photo-alignment film is obtained by irradiating the thin film layer containing the dichroic dye with polarized ultraviolet rays while rotating the polarization axis in the xy plane.
The polarized ultraviolet light preferably has a wavelength that can be absorbed by the dichroic dye to be used. For example, when an azobenzene derivative is used, ultraviolet light having a wavelength in the range of 350 to 500 nm corresponding to a strong absorption band due to the π → π * transition of azobenzene or Visible light is particularly preferred. Examples of the light source for irradiation light include a xenon lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, and an ultraviolet laser. In particular, since an ultra-high pressure mercury lamp is almost a point light source, it is particularly preferable because it is easy to obtain parallel light. Linearly polarized light can be obtained by passing light from the light source through a polarizing filter or a polarizing prism.
（ｎｘ＝ｎｙ＞ｎｚなる屈折率を有する光配向膜を得る方法）
ｘ−ｙ面に垂直な方向から偏光紫外線を照射された光配向膜はその上に形成された液晶層の液晶分子をｘ−ｙ面に平行で特定の方位角方向に配向させる規制力を有する。従って光配向膜に照射する偏光紫外線の電場の振動方向（偏光軸）をｘ−ｙ面に平行なまま面内で回転させると、配向規制力の方向が特定の方位角方向を向くことなく全方向に向いた、即ち面内配向させる規制力を有する配向膜となる。この配向膜の上に液晶層を形成する（後述の工程Ｂ）と面内配向した液晶層を得ることができる。
前記二色性染料を含有する薄膜層に照射する偏光紫外線の偏光軸の回転速度は光配向膜の有する配向規制力を発現させるに要する光照射量に応じて最適速度が異なる。即ちあまり回転速度が遅いと配向規制力を生起するに十分な紫外線照射量が常に照射されることになるため、照射を止めた最後の偏光軸方向に対応した配向規制力が発現する。即ちこの配向膜の上に液晶層を積層したとすると最後の照射の偏光軸に対応した方向に液晶層が配向し、面内配向ではなくｘ−ｙ面内の特定の方位角に配向した位相差膜となる。これを防ぐためには回転速度を大きくしたり、紫外線照射強度を小さくしたり、その両方を組み合わせ積算光量を少なくする等の方法がある。
(Method for obtaining a photo-alignment film having a refractive index of nx = ny> nz)
The photo-alignment film irradiated with polarized ultraviolet rays from a direction perpendicular to the xy plane has a regulating force to align the liquid crystal molecules of the liquid crystal layer formed thereon in a specific azimuth direction parallel to the xy plane. . Therefore, when the oscillation direction (polarization axis) of the electric field of polarized ultraviolet light irradiating the photo-alignment film is rotated in the plane while being parallel to the xy plane, the direction of the orientation regulating force is not directed to a specific azimuth direction. The alignment film has a regulating force that is oriented in the direction, that is, in-plane orientation. When a liquid crystal layer is formed on this alignment film (step B described later), an in-plane aligned liquid crystal layer can be obtained.
The rotation speed of the polarization axis of polarized ultraviolet light irradiated to the thin film layer containing the dichroic dye varies depending on the amount of light irradiation required to develop the alignment regulating force of the photo-alignment film. That is, if the rotational speed is too low, an ultraviolet irradiation amount sufficient to cause the alignment regulating force is always irradiated, so that the alignment regulating force corresponding to the last polarization axis direction where the irradiation is stopped appears. That is, if a liquid crystal layer is laminated on this alignment film, the liquid crystal layer is aligned in the direction corresponding to the polarization axis of the last irradiation, and is not in-plane alignment but in a specific azimuth angle in the xy plane. It becomes a phase difference film. In order to prevent this, there are methods such as increasing the rotational speed, decreasing the ultraviolet irradiation intensity, or combining both of them to reduce the integrated light quantity.
光照射した後の前記二色性染料を含有する薄膜層の配向状態は例えばオーダーパラメータで表すことができる。オーダーパラメータは偏光紫外線の積算光量と共に増大しやがて飽和値に到達する。この状態の配向膜に更に同じ方向の偏光軸を有する紫外線を照射してもオーダーパラメータの値は変化しない。この飽和配向状態を与える紫外線の積算光量を飽和積算光量とする。飽和積算光量は使用する配向剤により異なる。照射する偏光紫外線はその偏光の消光比が有限の値であるため、偏光軸の方位角は正確に一方向でなくその中央方向を含んだある幅に分布することになる。偏光軸を回転させながら紫外線を照射する場合、この分布幅と回転速度に応じた照射量が、ある方向への配向処理に用いられた偏光紫外線の積算光量となる。従って回転する偏光軸を有する紫外線は回転速度が遅かったり照射強度が強すぎたりすると飽和紫外線量に近い量またはそれ以上の照射量を与えやすい。このような照射条件で照射を止めると、回転の最後に光配向層に照射された偏光軸の方向に応じた配向状態を与えることになる。従って面内配向状態を与える光配向膜を得るためには、照射量があまり大きくならないよう、紫外線照射強度はなるべく小さく、回転速度はなるべく大きくすべきである。回転速度を大きくすることにより、異なった偏光軸を有する偏光を繰り返し照射することができ面内配向の均一性を向上させることが可能となる。照射量の好ましい範囲は、偏光軸が方位角方向に１８０°回転する間に飽和積算光量の１/１０未満であり、好ましくは１/５０以下、更に好ましくは１/１００以下の配向状態となる照射量とすべきであり、それ以上となるような偏光紫外線の照射強度と回転速度では均一な面内配向は実現できない。また照射偏光の偏光軸の回転速度は、一回の配向処理時に偏光軸が１回転以上することが好ましく、更に好ましくは２回転以上、更に好ましくは５回転以上となるようにすべきである。
特にフィルム上に塗布された前記二色性染料を含有する薄膜層に連続的に光照射する場合には、紫外線が照射される時間内に異なった偏光軸の偏光紫外線が複数回照射されるように偏光軸の回転数とフィルムの搬送速度を調整する必要がある。
The orientation state of the thin film layer containing the dichroic dye after the light irradiation can be expressed by an order parameter, for example. The order parameter increases with the cumulative amount of polarized ultraviolet light, and eventually reaches a saturation value. Even if the alignment film in this state is further irradiated with ultraviolet rays having the polarization axis in the same direction, the value of the order parameter does not change. The integrated light quantity of ultraviolet rays that gives this saturated orientation state is defined as the saturated integrated light quantity. The amount of saturated integrated light varies depending on the alignment agent used. Since the polarized ultraviolet ray to be irradiated has a finite value of the extinction ratio of the polarized light, the azimuth angle of the polarization axis is not distributed exactly in one direction but in a certain width including the central direction. In the case of irradiating ultraviolet rays while rotating the polarization axis, the irradiation amount according to the distribution width and the rotation speed becomes the integrated light amount of the polarized ultraviolet rays used for the alignment processing in a certain direction. Accordingly, if the rotation speed of the ultraviolet ray having a rotating polarization axis is slow or the irradiation intensity is too strong, it is easy to give an irradiation amount close to or more than the saturation ultraviolet ray amount. When the irradiation is stopped under such irradiation conditions, an alignment state corresponding to the direction of the polarization axis irradiated to the photo-alignment layer at the end of the rotation is given. Therefore, in order to obtain a photo-alignment film that gives an in-plane alignment state, the ultraviolet irradiation intensity should be as small as possible and the rotation speed should be as large as possible so that the irradiation dose does not become too large. By increasing the rotation speed, it is possible to repeatedly irradiate polarized light having different polarization axes, and to improve the uniformity of in-plane orientation. A preferable range of the irradiation amount is less than 1/10 of the saturated integrated light amount while the polarization axis is rotated 180 ° in the azimuth direction, preferably 1/50 or less, more preferably 1/100 or less. Uniform in-plane orientation cannot be realized with the irradiation intensity and rotation speed of polarized ultraviolet light that should be an irradiation amount or more. Further, the rotation speed of the polarization axis of the irradiated polarized light should preferably be 1 rotation or more, more preferably 2 rotations or more, and even more preferably 5 rotations or more in one alignment treatment.
In particular, when the thin film layer containing the dichroic dye coated on the film is continuously irradiated with light, polarized ultraviolet rays having different polarization axes are irradiated a plurality of times within the irradiation time of the ultraviolet rays. In addition, it is necessary to adjust the rotation speed of the polarization axis and the film conveyance speed.
偏光軸の回転する偏光紫外線を得るためには、紫外線照射ランプの下に偏光板を設け、偏光板を光軸が回転軸となるように回転させればよい。その際、偏光軸が光配向層のｘ−ｙ面に対し略平行、即ち光軸がｘ−ｙ面に垂直である必要がある。偏光板としては誘電体多層膜からなる偏光フィルタや、マイクログリッドからなる偏光フィルタあるいはグラントムソン、グランテーラーなどの偏光プリズムを用いることができる。紫外線照射ランプと偏光板を同時に回転させても良いが、その場合はランプに接続するケーブルや排気装置を回転に対応させなければならず大掛かりな装置となる欠点がある。 In order to obtain polarized ultraviolet light whose polarization axis rotates, a polarizing plate is provided under the ultraviolet irradiation lamp, and the polarizing plate may be rotated so that the optical axis becomes the rotation axis. At that time, it is necessary that the polarization axis is substantially parallel to the xy plane of the photo-alignment layer, that is, the optical axis is perpendicular to the xy plane. As the polarizing plate, a polarizing filter made of a dielectric multilayer film, a polarizing filter made of a microgrid, or a polarizing prism such as Glan Thompson or Grant Taylor can be used. The ultraviolet irradiation lamp and the polarizing plate may be rotated at the same time, but in that case, there is a drawback that a cable and an exhaust device connected to the lamp must be adapted to the rotation, resulting in a large-scale device.
回転する偏光軸を有する偏光を照射するには円偏光を照射する方法もある。即ち、紫外線の円偏光を光配向膜上に照射すれば、偏光軸が光の周波数で回転する偏光を照射することになり、この場合には面内配向の均一性を向上するために異なった偏光軸を有する偏光を繰り返し照射することが自動的に行われることになる。面内均一性の高い状態を実現するためには円偏光の回転面が光配向層のｘ−ｙ面に対し平行である必要があることは前述の通りである。紫外線の照射強度については偏光軸の回転数が非常に大きいので通常の紫外線ランプを使用する限りでは事実上制限は無いが、照射量の好ましい範囲は、偏光軸が１８０°回転する間に飽和積算光量の１/１０未満、好ましくは１/５０以下、更に好ましくは１/１００以下の配向状態となる照射量であることに変わりは無い。円偏光を照射するためには、紫外線照射ランプの下に偏光板と１/４波長板とをこの順番で設け、１/４波長板の遅相軸と偏光板の吸収軸とが４５°の角度となるように設置すればよい。 There is also a method of irradiating circularly polarized light to irradiate polarized light having a rotating polarization axis. That is, when the circularly polarized light of ultraviolet rays is irradiated onto the photo-alignment film, the polarized light whose polarization axis rotates at the frequency of the light is irradiated, and in this case, different in order to improve the uniformity of in-plane alignment. Repeated irradiation with polarized light having a polarization axis is automatically performed. As described above, in order to realize a state with high in-plane uniformity, the plane of rotation of circularly polarized light needs to be parallel to the xy plane of the photo-alignment layer. As for the irradiation intensity of ultraviolet rays, since the rotation speed of the polarization axis is very large, there is practically no limitation as long as a normal ultraviolet lamp is used. However, the preferable range of irradiation amount is saturated integration while the polarization axis rotates 180 °. There is no change in the amount of irradiation with which the alignment state is less than 1/10 of the light amount, preferably 1/50 or less, and more preferably 1/100 or less. In order to irradiate circularly polarized light, a polarizing plate and a quarter wave plate are provided in this order under the ultraviolet irradiation lamp, and the slow axis of the quarter wave plate and the absorption axis of the polarizing plate are 45 °. What is necessary is just to install so that it may become an angle.
また偏光軸が直交する二つの紫外線を用いて当量の積算光量となるように照射してもよい。ここで当量とは、直交する二つの紫外線を同時に照射するのであれば等量を意味する。しかし逐次照射するのであれば始めに照射した偏光紫外線の積算光量を１００とした時、次に照射する直交する方向への２回目の積算光量は１６０〜１８０程度が適当である。即ち２回目の照射は１回目の照射の効果を打ち消しながら直交方向への配向成分を生み出す必要があるため等量ではなく大目の照射量となる。しかしながらこの方法は面内配向を実現する偏光紫外線の当量を再現性よく照射することが困難な場合がある。 Moreover, you may irradiate so that it may become an equivalent integrated light quantity using the two ultraviolet-rays by which a polarization axis orthogonally crosses. Here, the equivalent means an equivalent amount if two orthogonal ultraviolet rays are irradiated simultaneously. However, if sequential irradiation is performed, assuming that the integrated light amount of the polarized ultraviolet light irradiated first is 100, the second integrated light amount in the orthogonal direction to be irradiated next is suitably about 160 to 180. That is, since the second irradiation needs to generate an orientation component in the orthogonal direction while canceling the effect of the first irradiation, the second irradiation is not an equal amount but a large irradiation amount. However, in this method, it may be difficult to irradiate the equivalent amount of polarized ultraviolet rays that achieve in-plane orientation with good reproducibility.
（ｎｘ＞ｎｙ＞ｎｚなる屈折率を有する光学異方体の形成方法）
前述の通り、第一回目の照射として偏光紫外線の偏光軸を回転させて照射したり、直交させて照射することによりｘ−ｙ面内に配向した光学異方体（ｎｘ＝ｎｙ＞ｎｚ）を得ることができる。このような面内配向を誘起するような偏光紫外線照射を行った後、第二回目の照射としてｘ−ｙ面内の特定の方向に偏光軸を有する偏光紫外線を照射すればｎｘ＞ｎｙ＞ｎｚなる光学異方体を得ることができる。この場合、２回目の偏光紫外線の積算光量は、偏光紫外線の飽和積算光量の１/１０以上が必要である。
偏光紫外線の偏光軸を回転させて照射する際、円偏光ではなく楕円偏光を照射すれば楕円の長軸方向に強度の強い紫外線が照射されることになる。楕円偏光の軸比を制御することにより紫外線の振動方向による強度差を与え、配向膜の面内のある方向に配向方向を与えることが可能である。長軸と短軸との積算光量の差は偏光紫外線の飽和積算光量の１/１０以上必要であるのは上記と同様である。
(Method for forming an optical anisotropic body having a refractive index of nx>ny> nz)
As described above, an optical anisotropic body (nx = ny> nz) oriented in the xy plane by rotating the polarizing axis of polarized ultraviolet rays for irradiation as the first irradiation or by irradiating the polarized ultraviolet rays at right angles. Can be obtained. After irradiating polarized ultraviolet light that induces such in-plane orientation, if irradiating polarized ultraviolet light having a polarization axis in a specific direction in the xy plane as the second irradiation, nx>ny> nz An optical anisotropic body can be obtained. In this case, the accumulated light quantity of the polarized ultraviolet light for the second time needs to be 1/10 or more of the saturated accumulated light quantity of the polarized ultraviolet light.
When irradiation is performed with the polarization axis of polarized ultraviolet light rotated, if ultraviolet light is irradiated instead of circularly polarized light, strong ultraviolet light is irradiated in the major axis direction of the ellipse. By controlling the axial ratio of elliptically polarized light, it is possible to give an intensity difference depending on the vibration direction of the ultraviolet rays and to give the orientation direction in a certain direction in the plane of the orientation film. The difference between the accumulated light quantity between the major axis and the minor axis is required to be 1/10 or more of the saturated accumulated light quantity of polarized ultraviolet light as described above.
使用する二色性染料が、光二色性に起因するワイゲルト効果による分子の配向誘起もしくは異性化反応を作用機構とするものである場合には、該二色性染料を含有する薄膜層に偏光紫外線を全く照射しない場合にもｘ−ｙ面内に配向した光学異方体を得ることができる。しかしながらこの場合にはｚ方向への配向成分も存在するため、面内への配向状態が高い面内異方体が形成できない。
また、該二色性染料を用いた配向膜に、偏光軸をｘ−ｙ面内で回転させずに、例えば、紫外線の振動方向がランダムである光をｘ−ｙ面に垂直な方向（ｚ方向）から照射すると、該二色性染料の分子は吸収するエネルギーが最低になる方向に配向し、ｚ方向への配向成分が増すためｘ−ｙ面内への配向状態が高い面内異方体が形成できない。更に照射量を大きくすればｚ方向への配向成分が増し配向膜上の液晶層はｎｚ＞ｎｘ＝ｎｙなる位相差膜となる。
When the dichroic dye to be used has a mechanism of molecular orientation induction or isomerization reaction due to the Weigert effect resulting from photodichroism, polarized UV light is applied to the thin film layer containing the dichroic dye. Even when no is irradiated, an optical anisotropic body oriented in the xy plane can be obtained. However, in this case, since an orientation component in the z direction also exists, an in-plane anisotropic body having a high in-plane orientation state cannot be formed.
Further, without rotating the polarization axis in the xy plane on the alignment film using the dichroic dye, for example, light having a random vibration direction of ultraviolet rays is directed in a direction perpendicular to the xy plane (z Direction), the molecules of the dichroic dye are oriented in the direction that minimizes the energy to be absorbed, and the orientation component in the xy plane increases because the orientation component in the z direction increases. The body cannot be formed. If the irradiation dose is further increased, the alignment component in the z direction increases, and the liquid crystal layer on the alignment film becomes a retardation film satisfying nz> nx = ny.
（工程Ｂ 該薄膜層上に重合性基を有する棒状液晶化合物を含有する重合性液晶組成物層を形成する）
（重合性基を有する棒状液晶化合物）
本発明で使用する重合性基を有する棒状液晶化合物は、単独又は他の液晶化合物との組成物において液晶性を示す、重合性官能基を有する化合物であれば特に限定はない。例えば、Ｈａｎｄｂｏｏｋ ｏｆ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌｓ （Ｄ． Ｄｅｍｕｓ， Ｊ． Ｗ． Ｇｏｏｄｂｙ， Ｇ． Ｗ． Ｇｒａｙ， Ｈ． Ｗ． Ｓｐｉｅｓｓ， Ｖ． Ｖｉｌｌ編集、Ｗｉｌｅｙ−ＶＣＨ 社発行、１９９８年）、季刊化学総説Ｎｏ．２２、液晶の化学（日本化学会編、１９９４年）、あるいは、特開平７−２９４７３５号公報、特開平８−３１１１号公報、特開平８−２９６１８号公報、特開平１１−８００９０号公報、特開平１１−１４８０７９号公報、特開２０００−１７８２３３号公報、特開２００２−３０８８３１号公報、特開２００２−１４５８３０号公報に記載されているような、１，４−フェニレン基、１，４−シクロヘキシレン基等の構造が複数繋がったメソゲンと呼ばれる剛直な部位と、（メタ）アクリロイル基、ビニルオキシ基、エポキシ基といった重合性官能基とを有する棒状重合性液晶化合物があげられる。
(Step B: Forming a polymerizable liquid crystal composition layer containing a rod-like liquid crystal compound having a polymerizable group on the thin film layer)
(Bar-shaped liquid crystal compound having a polymerizable group)
The rod-shaped liquid crystal compound having a polymerizable group used in the present invention is not particularly limited as long as it is a compound having a polymerizable functional group that exhibits liquid crystallinity alone or in a composition with another liquid crystal compound. For example, Handbook of Liquid Crystals (D. Demus, J. W. Goodbye, GW Gray, H. W. Spiss, V. Vill, edited by Wiley-VCH, 1998), Quarterly Chemical Review. 22, Liquid Crystal Chemistry (Edited by Chemical Society of Japan, 1994), or JP-A-7-294735, JP-A-8-3111, JP-A-8-29618, JP-A-11-80090, 1,4-phenylene group, 1,4-cyclohexene, as described in Kaihei 11-148079, JP-A 2000-178233, JP-A 2002-308831, and JP-A 2002-145830. Examples thereof include a rod-like polymerizable liquid crystal compound having a rigid site called a mesogen in which a plurality of structures such as a sylene group are connected and a polymerizable functional group such as a (meth) acryloyl group, a vinyloxy group, and an epoxy group.
（光重合開始剤）
前記重合性液晶化合物を重合させる際には、公知慣用の光重合開始剤や熱重合開始剤を配合することが好ましい。
光重合開始剤としては、例えば１−ヒドロキシシクロヘキシルフェニルケトン（チバ・スペシャルティ・ケミカルズ社製「イルガキュア１８４」）、１−（４−イソプロピルフェニル）−２−ヒドロキシ−２−メチルプロパン−１−オン（メルク社製「ダロキュア１１１６」）、２−メチル−１−［（メチルチオ）フェニル］−２−モリホリノプロパン−１（チバ・スペシャルティ・ケミカルズ社製「イルガキュア９０７」）、ベンジルメチルケタ−ル（チバ・スペシャルティ・ケミカルズ社製「イルガキュア６５１」）。２，４−ジエチルチオキサントン（日本化薬社製「カヤキュアＤＥＴＸ」）とｐ−ジメチルアミノ安息香酸エチル（日本化薬社製「カヤキュアＥＰＡ」）との混合物、アシルフォスフィンオキシド（ＢＡＳＦ社製「ルシリンＴＰＯ」）、などが挙げられる。一方、熱重合開始剤としては、例えば、ベンゾイルパ−オキサイド、ビス（４−ｔ−ブチルシクロヘキシル）パーオキシジカーボネート、ｔ−ブチルパ−オキシベンゾエイト、メチルエチルケトンパ−オキサイド等の有機過酸化物、２，２’−アゾビスイソブチロニトリル等のアゾニトリル化合物、２，２’−アゾビス（２−メチル−Ｎ−フェニルプロピオン−アミヂン）ジハイドロクロライド等のアゾアミヂン化合物、２，２’アゾビス｛２−メチル−Ｎ−［１，１−ビス（ヒドロキシメチル）−２−ヒドロキシエチル］プロピオンアミド｝等のアゾアミド化合物、２，２’アゾビス（２，４，４−トリメチルペンタン）等のアルキルアゾ化合物等を使用することができる。これらの重合開始剤の使用量は組成物に対して１０質量％以下が好ましく、０．５〜５質量％が特に好ましい。（以下、前記重合性液晶化合物と重合開始剤等を含有する組成物を、重合性液晶組成物と略す。）
(Photopolymerization initiator)
When polymerizing the polymerizable liquid crystal compound, it is preferable to blend a known and commonly used photopolymerization initiator or thermal polymerization initiator.
Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (“Irgacure 184” manufactured by Ciba Specialty Chemicals), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one ( “Darocur 1116” manufactured by Merck & Co.), 2-methyl-1-[(methylthio) phenyl] -2-morpholinopropane-1 (“Irgacure 907” manufactured by Ciba Specialty Chemicals), benzylmethylketal ( “Irgacure 651” manufactured by Ciba Specialty Chemicals). Mixture of 2,4-diethylthioxanthone (“Kayacure DETX” manufactured by Nippon Kayaku Co., Ltd.) and ethyl p-dimethylaminobenzoate (“Kayacure EPA” manufactured by Nippon Kayaku Co., Ltd.), acylphosphine oxide (“Lucillin” manufactured by BASF TPO "), and the like. On the other hand, examples of the thermal polymerization initiator include organic peroxides such as benzoyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, t-butyl peroxybenzoate, and methyl ethyl ketone peroxide. Azonitrile compounds such as 2′-azobisisobutyronitrile, azoamidin compounds such as 2,2′-azobis (2-methyl-N-phenylpropion-amidin) dihydrochloride, 2,2′azobis {2-methyl- Use azoamide compounds such as N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, alkylazo compounds such as 2,2′azobis (2,4,4-trimethylpentane), and the like. Can do. The amount of these polymerization initiators used is preferably 10% by mass or less, particularly preferably 0.5 to 5% by mass, based on the composition. (Hereinafter, a composition containing the polymerizable liquid crystal compound and a polymerization initiator is abbreviated as a polymerizable liquid crystal composition.)
前記薄膜層上に重合性基を有する棒状液晶化合物を含有する重合性液晶組成物層を形成させるには、スピンコ−ティング法、エクストルージョン法、グラビアコーティング法、ダイコーティング法、バーコーティング法、アプリケータ法などの塗布法やフレキソ法などの印刷法等、公知の方法を使用できる。
膜厚は目的とする位相差膜により異なるが、概ね０．１μｍ〜１０μｍが好ましい。
In order to form a polymerizable liquid crystal composition layer containing a rod-like liquid crystal compound having a polymerizable group on the thin film layer, a spin coating method, an extrusion method, a gravure coating method, a die coating method, a bar coating method, an application Known methods such as a coating method such as a coating method and a printing method such as a flexo method can be used.
The film thickness varies depending on the target retardation film, but is generally preferably 0.1 μm to 10 μm.
（工程Ｃ 重合性基を有する液晶化合物を硬化させる）
前記工程１、工程２を経て、配向させた状態の重合性液晶組成物層を重合固定化させる方法としては、活性エネルギー線を照射する方法や熱重合法等が挙げられるが、加熱を必要とせず、室温で反応が進行することから活性エネルギー線を照射する方法が好ましく、中でも、操作が簡便なことから、紫外線等の光を照射する方法が好ましい。照射時の温度は、重合性液晶組成物が液晶相を保持できる温度とし、重合性液晶組成物の熱重合の誘起を避けるため、可能な限り２５℃以下とすることが好ましい。尚、液晶組成物は、通常、昇温過程において、Ｃ（固相）−Ｎ（ネマチック）転移温度（以下、Ｃ−Ｎ転移温度と略す。）から、Ｎ−Ｉ転移温度範囲内で液晶相を示す。一方、降温過程においては、熱力学的に非平衡状態を取るため、Ｃ−Ｎ転移温度以下でも凝固せず液晶状態を保つ場合がある。この状態を過冷却状態という。本発明においては、過冷却状態にある液晶組成物も液晶相を保持している状態に含めるものとする。紫外線照射強度は、１Ｗ／ｍ２〜１０ｋＷ／ｍ２の範囲が好ましい。特に、１０Ｗ／ｍ２〜２ｋＷ／ｍ２の範囲が好ましい。紫外線強度が１Ｗ／ｍ２未満の場合、重合を完了させるのに多大な時間がかかる。一方、２ｋＷ／ｍ２を超える強度では、重合性液晶組成物中の液晶分子が光分解する傾向にあることや、重合熱が多く発生して重合中の温度が上昇し、重合性液晶のオーダーパラメータが変化して、重合後のフィルムのリタデーションに狂いが生じる可能性がある。このような紫外線の最適な積算光量は、重合性液晶に添加した光開始剤の吸収効率、添加量及び重合性液晶の置かれている雰囲気などにより異なるが、概ね１００Ｊ／ｍ２〜１００ｋＪ／ｍ２が好ましく、特に１ｋＪ／ｍ２〜４０ｋＪ／ｍ２が好ましい。
また照射する紫外線は光配向膜に照射した偏光紫外線と同じ偏光軸の方向を有する偏光が望ましい。これは本工程で照射する紫外線により光配向層の配向方向が影響を受ける可能性を排除するためである。
(Step C: curing the liquid crystal compound having a polymerizable group)
Examples of the method for polymerizing and fixing the aligned polymerizable liquid crystal composition layer through the steps 1 and 2 include a method of irradiating active energy rays and a thermal polymerization method, but heating is required. However, the method of irradiating active energy rays is preferable because the reaction proceeds at room temperature, and among them, the method of irradiating light such as ultraviolet rays is preferable because the operation is simple. The temperature at the time of irradiation is preferably set to 25 ° C. or less as much as possible in order to avoid the induction of thermal polymerization of the polymerizable liquid crystal composition so that the polymerizable liquid crystal composition can maintain the liquid crystal phase. The liquid crystal composition usually has a liquid crystal phase in the range from the C (solid phase) -N (nematic) transition temperature (hereinafter abbreviated as C-N transition temperature) to the NI transition temperature in the temperature rising process. Indicates. On the other hand, in the temperature lowering process, a non-equilibrium state is taken thermodynamically, so that the liquid crystal state may be maintained without being solidified even at a temperature lower than the CN transition temperature. This state is called a supercooled state. In the present invention, the liquid crystal composition in a supercooled state is also included in the state in which the liquid crystal phase is retained. The ultraviolet irradiation intensity is preferably in the range of 1 W / m 2 to 10 kW / m 2 . In particular, a range of 10 W / m 2 to 2 kW / m 2 is preferable. When the ultraviolet intensity is less than 1 W / m 2 , it takes a lot of time to complete the polymerization. On the other hand, when the strength exceeds 2 kW / m 2 , liquid crystal molecules in the polymerizable liquid crystal composition tend to be photodegraded, or a large amount of polymerization heat is generated to increase the temperature during polymerization. The parameter may change, and the retardation of the film after polymerization may be distorted. The optimum integrated light quantity of such ultraviolet rays varies depending on the absorption efficiency of the photoinitiator added to the polymerizable liquid crystal, the added amount, the atmosphere in which the polymerizable liquid crystal is placed, and the like, but is generally 100 J / m 2 to 100 kJ / m. 2 are preferred, especially 1kJ / m 2 ~40kJ / m 2 is preferred.
Further, it is desirable that the ultraviolet rays to be irradiated be polarized light having the same polarization axis direction as that of the polarized ultraviolet rays irradiated to the photo-alignment film. This is to eliminate the possibility that the alignment direction of the photo-alignment layer is affected by the ultraviolet rays irradiated in this step.
得られた位相差膜の膜厚は目的とする位相差により異なるが薄いほど好ましい。膜厚制御の容易さと重合性液晶硬化膜の複屈折の大きさを考えると、二色性染料を含有する薄膜層と重合性液晶層との好ましい膜厚は０．１〜２０μｍが好ましく、０．１〜１０μｍが尚好ましく、０．１〜５μｍが最も好ましい。 The thickness of the obtained retardation film varies depending on the target retardation, but is preferably as thin as possible. Considering the ease of controlling the film thickness and the birefringence of the polymerizable liquid crystal cured film, the preferred film thickness of the thin film layer containing the dichroic dye and the polymerizable liquid crystal layer is preferably 0.1 to 20 μm. 1 to 10 μm is more preferable, and 0.1 to 5 μm is most preferable.
以下、実施例及び比較例を用いて本発明を更に詳細に説明する。しかしながら、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.
（二色性染料を含有する薄膜層用組成物（Ａ）の調整）
式（１）で表される化合物５０質量部と式（２）で表される化合物を５０質量部ずつ混合し、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテルからなる混合溶媒に溶解して（１）と（２）からなる固体分が０．５質量％溶液とした。この溶液を孔径０．４５μｍのフィルタ−で濾過し、二色性染料を含有する組成物溶液（Ａ）とした。尚、薄膜用組成物（Ａ）の飽和積算光量は１ｋＪ／ｍ２であった。
(Preparation of thin film layer composition (A) containing dichroic dye)
50 parts by mass of the compound represented by the formula (1) and 50 parts by mass of the compound represented by the formula (2) are mixed and dissolved in a mixed solvent composed of ethylene glycol monoethyl ether and ethylene glycol monobutyl ether (1 ) And (2) was a 0.5 mass% solution. This solution was filtered through a filter having a pore diameter of 0.45 μm to obtain a composition solution (A) containing a dichroic dye. The thin film composition (A) had a saturated integrated light amount of 1 kJ / m 2 .
（重合性液晶組成物の調製）
式（３）及び式（４）で表される化合物を、質量比が５０：５０になるように混合して重合性液晶組成物を調製し、これに塩素化ポリプロピレンを重合性液晶組成物１００質量部に対し０．６質量部を混合した。この重合性液晶組成物９６質量部にチバスペシャリティケミカルズ（株）製の光重合開始剤「イルガキュア９０７」４質量部、キシレンとシクロヘキシルアセテートとからなる混合溶媒３９５質量部を混合し、孔径０．４５μｍのフィルタ−で濾過して重合性液晶組成物溶液（Ｂ）とした。該重合性液晶組成物溶液（Ｂ）から該混合溶媒を蒸発させた後の液晶組成物は、２５℃において液晶相を示した。よって、以下の実施例では該液晶組成物を２５℃において用いた。
(Preparation of polymerizable liquid crystal composition)
A polymerizable liquid crystal composition is prepared by mixing the compounds represented by the formulas (3) and (4) so that the mass ratio is 50:50, and chlorinated polypropylene is added to the polymerizable liquid crystal composition 100. 0.6 parts by mass was mixed with respect to parts by mass. 96 parts by mass of this polymerizable liquid crystal composition was mixed with 4 parts by mass of a photopolymerization initiator “Irgacure 907” manufactured by Ciba Specialty Chemicals Co., Ltd. and 395 parts by mass of a mixed solvent composed of xylene and cyclohexyl acetate, and a pore size of 0.45 μm. To obtain a polymerizable liquid crystal composition solution (B). The liquid crystal composition after evaporating the mixed solvent from the polymerizable liquid crystal composition solution (B) exhibited a liquid crystal phase at 25 ° C. Therefore, in the following examples, the liquid crystal composition was used at 25 ° C.
下記に示す実施例で得られた位相差膜の複屈折は、自動複屈折計（コブラ２１ＡＤＨ（王子計測機器（株）製））を用い、５８９．３ｎｍの波長で測定した。フィルム面内の複屈折をｎｘ−ｎｙとし、厚さ方向の複屈折をｎｘ−ｎｚとして表１に結果を示した。 The birefringence of the retardation film obtained in the examples shown below was measured at a wavelength of 589.3 nm using an automatic birefringence meter (Cobra 21ADH (manufactured by Oji Scientific Instruments)). The results are shown in Table 1, where the in-plane birefringence is nx-ny and the birefringence in the thickness direction is nx-nz.
（実施例１）
ＴＡＣフィルムをコロナ処理した後、二色性染料を含有する組成物溶液（Ａ）をダイコータにより連続成膜し、８０℃で乾燥して膜厚１７ｎｍの二色性染料を含有する薄膜層を形成した。これに第一回目の照射として面内配向を誘起するため、薄膜層付きのＴＡＣフィルムを搬送しながら、直線偏光紫外線の偏光軸を回転させて該薄膜層面の法線方向から照射した。偏光軸の回転した偏光は紫外線ランプの下に偏光板を置き、フィルム面に平行な回転面で偏光板を回転することにより得ている。この時フィルムの搬送速度は０．５ｍ／分であり紫外線の照射領域を通過するに要する時間は２５秒であった。照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は５Ｗ／ｍ２ 、偏光軸の回転速度は１０回転／分であった。
次いで第２回目の照射として、前記光照射後の薄膜層付きのＴＡＣフィルムを搬送しながら、偏光の振動方向がフィルムの長手方向に対し７５°傾いており、偏光軸が回転していない直線偏光紫外線を照射し、光配向層（Ａ−１）を得た。この時、照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は４Ｗ／ｍ２であり、紫外線の照射領域を通過するに要する時間は２５秒であった。
光配向層（Ａ−１）上に重合性液晶組成物溶液（Ｂ）をダイコータにより塗布し、６０℃で乾燥した。偏光軸が回転していない偏光紫外線をその振動方向がフィルムの長手方向に対し７５°となるよう照射した。照射は空気雰囲気下で行い、積算光量が６ｋＪ／ｍ２ となるよう照射し、遅相軸のフィルムの長手方向に対する方位角が１６５°の位相差膜（１）を得た。
Example 1
After corona treatment of the TAC film, a composition solution (A) containing a dichroic dye is continuously formed by a die coater and dried at 80 ° C. to form a thin film layer containing a dichroic dye having a thickness of 17 nm. did. In order to induce in-plane orientation as the first irradiation, the film was irradiated from the normal direction of the surface of the thin film layer by rotating the polarization axis of the linearly polarized ultraviolet light while transporting the TAC film with the thin film layer. Polarized light whose polarization axis has been rotated is obtained by placing a polarizing plate under an ultraviolet lamp and rotating the polarizing plate on a plane of rotation parallel to the film surface. At this time, the film conveyance speed was 0.5 m / min, and the time required to pass through the ultraviolet irradiation region was 25 seconds. The irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, the irradiation intensity was 5 W / m 2 , and the rotation speed of the polarization axis was 10 rotations / minute.
Next, as the second irradiation, linearly polarized light in which the vibration direction of polarized light is inclined by 75 ° with respect to the longitudinal direction of the film while the TAC film with the thin film layer after the light irradiation is conveyed and the polarization axis is not rotated. The photo-alignment layer (A-1) was obtained by irradiating with ultraviolet rays. At this time, the irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, the irradiation intensity was 4 W / m 2 , and the time required to pass through the ultraviolet irradiation region was 25 seconds.
The polymerizable liquid crystal composition solution (B) was applied on the photo-alignment layer (A-1) with a die coater and dried at 60 ° C. Polarized ultraviolet light whose polarization axis is not rotated was irradiated so that the vibration direction was 75 ° with respect to the longitudinal direction of the film. Irradiation was performed in an air atmosphere so that the integrated light amount was 6 kJ / m 2, and a retardation film (1) having an azimuth angle of 165 ° with respect to the longitudinal direction of the slow axis film was obtained.
（実施例２）
ＴＡＣフィルムをコロナ処理した後、二色性染料を含有する組成物溶液（Ａ）をダイコータにより連続成膜し、８０℃で乾燥して膜厚１７ｎｍの二色性染料を含有する薄膜層を形成した。これに面内配向を誘起するため、薄膜層付きのＴＡＣフィルムを搬送しながら、直線偏光紫外線の偏光軸を回転させて該層面の法線方向から照射し光配向層（Ａ−２）を得た。偏光軸の回転した偏光は紫外線ランプの下に偏光板を置き、フィルム面に平行な回転面で偏光板を回転することにより得ている。この時フィルムの搬送速度は０．５ｍ／分であり紫外線の照射領域を通過するに要する時間は２５秒であった。照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は５Ｗ／ｍ２ 、偏光軸の回転速度は１０回転／分であった。
光配向層（Ａ−２）上に重合性液晶組成物溶液（Ｂ）をダイコータにより塗布し、６０℃で乾燥した。偏光ではない紫外線を空気雰囲気下、積算光量が６ｋＪ／ｍ２ となるよう照射し、位相差膜（２）を得た。
(Example 2)
After corona treatment of the TAC film, a composition solution (A) containing a dichroic dye is continuously formed by a die coater and dried at 80 ° C. to form a thin film layer containing a dichroic dye having a thickness of 17 nm. did. In order to induce in-plane alignment, the photo-alignment layer (A-2) is obtained by rotating the polarization axis of the linearly polarized ultraviolet light and irradiating from the normal direction of the layer surface while transporting the TAC film with the thin film layer. It was. Polarized light whose polarization axis has been rotated is obtained by placing a polarizing plate under an ultraviolet lamp and rotating the polarizing plate on a plane of rotation parallel to the film surface. At this time, the film conveyance speed was 0.5 m / min, and the time required to pass through the ultraviolet irradiation region was 25 seconds. The irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, the irradiation intensity was 5 W / m 2 , and the rotation speed of the polarization axis was 10 rotations / minute.
The polymerizable liquid crystal composition solution (B) was applied on the photo-alignment layer (A-2) with a die coater and dried at 60 ° C. The phase difference film (2) was obtained by irradiating ultraviolet rays that were not polarized light in an air atmosphere so that the integrated light amount was 6 kJ / m 2 .
（参考例３）
ＴＡＣフィルムをコロナ処理した後、二色性染料を含有する組成物溶液（Ａ）をダイコータにより連続成膜し、８０℃で乾燥して膜厚１７ｎｍの二色性染料を含有する薄膜層を形成した。薄膜層付きのＴＡＣフィルムを搬送しながら、円偏光紫外線をフィルム面の法線方向から照射した。円偏光紫外線は偏光板と該光配向層との間に１／４波長板を置くことにより得ている。この時フィルムの搬送速度は０．５ｍ／分であり紫外線の照射領域を通過するに要する時間は２５秒であった。照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は２０Ｗ／ｍ２であった。
次いで第２回目の照射として前記光照射後の薄膜層付きのＴＡＣフィルムを搬送しながら、直線偏光の振動方向がフィルムの長手方向に対し７５°傾いており、偏光軸が回転していない偏光紫外線を照射し光配向層（Ａ−３）を得た。この時、照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は４Ｗ／ｍ２であり、紫外線の照射領域を通過するに要する時間は２５秒であった。
光配向層（Ａ−３）上に重合性液晶組成物溶液（Ｂ）をダイコータにより塗布し、６０℃で乾燥した。偏光軸が回転していない偏光紫外線をその振動方向がフィルムの長手方向に対し７５°となるよう照射した。照射は空気雰囲気下で行い、積算光量が６ｋＪ／ｍ２となるよう照射し、遅相軸のフィルムの長手方向に対する方位角が１６５°の位相差膜（３）を得た。
( Reference Example 3)
After corona treatment of the TAC film, a composition solution (A) containing a dichroic dye is continuously formed by a die coater and dried at 80 ° C. to form a thin film layer containing a dichroic dye having a thickness of 17 nm. did. While conveying the TAC film with a thin film layer, circularly polarized ultraviolet rays were irradiated from the normal direction of the film surface. Circularly polarized ultraviolet light is obtained by placing a quarter wave plate between the polarizing plate and the photo-alignment layer. At this time, the film conveyance speed was 0.5 m / min, and the time required to pass through the ultraviolet irradiation region was 25 seconds. The irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, and the irradiation intensity was 20 W / m 2 .
Next, while conveying the TAC film with the light-irradiated thin film layer as the second irradiation, the polarized ultraviolet light whose oscillation direction of linearly polarized light is inclined by 75 ° with respect to the longitudinal direction of the film and whose polarization axis is not rotated. Was obtained to obtain a photo-alignment layer (A-3). At this time, the irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, the irradiation intensity was 4 W / m 2 , and the time required to pass through the ultraviolet irradiation region was 25 seconds.
The polymerizable liquid crystal composition solution (B) was applied on the photo-alignment layer (A-3) with a die coater and dried at 60 ° C. Polarized ultraviolet light whose polarization axis is not rotated was irradiated so that the vibration direction was 75 ° with respect to the longitudinal direction of the film. Irradiation was performed in an air atmosphere, and irradiation was performed so that the integrated light amount was 6 kJ / m 2. Thus, a retardation film (3) having an azimuth angle of 165 ° with respect to the longitudinal direction of the slow axis film was obtained.
（比較例１）
ＴＡＣフィルムをコロナ処理した後、二色性染料を含有する組成物溶液（Ａ）をダイコータにより連続成膜し、８０℃で乾燥して膜厚１７ｎｍの二色性染料を含有する薄膜層を形成した。薄膜層付きのＴＡＣフィルムを搬送しながら、偏光の振動方向がフィルムの長手方向に対し７５°傾いており、偏光軸が回転していない偏光紫外線を照射し光配向層（ＡＨ−１）を得た。この時、照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は４Ｗ／ｍ２であり、紫外線の照射領域を通過するに要する時間は２５秒であった。
光配向層（ＡＨ−１）上に重合性液晶組成物溶液（Ｂ）をダイコータにより塗布し、６０℃で乾燥した。偏光軸が回転していない偏光紫外線をその振動方向がフィルムの長手方向に対し７５°となるよう照射した。照射は空気雰囲気下で行い、積算光量が６ｋＪ／ｍ２ となるよう照射し、遅相軸のフィルムの長手方向に対する方位角が１６５°の位相差膜（Ｈ１）を得た。
(Comparative Example 1)
After corona treatment of the TAC film, a composition solution (A) containing a dichroic dye is continuously formed by a die coater and dried at 80 ° C. to form a thin film layer containing a dichroic dye having a thickness of 17 nm. did. While conveying a TAC film with a thin film layer, the polarization direction of polarization is tilted by 75 ° with respect to the longitudinal direction of the film, and the polarized light with the polarization axis not rotating is irradiated to obtain a photo-alignment layer (AH-1). It was. At this time, the irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, the irradiation intensity was 4 W / m 2 , and the time required to pass through the ultraviolet irradiation region was 25 seconds.
The polymerizable liquid crystal composition solution (B) was applied on the photo-alignment layer (AH-1) with a die coater and dried at 60 ° C. Polarized ultraviolet light whose polarization axis is not rotated was irradiated so that the vibration direction was 75 ° with respect to the longitudinal direction of the film. Irradiation was performed in an air atmosphere, and irradiation was performed so that the integrated light amount was 6 kJ / m 2. Thus, a retardation film (H1) having an azimuth angle of 165 ° relative to the longitudinal direction of the slow axis film was obtained.
（比較例２）
ＴＡＣフィルムをコロナ処理した後、二色性染料を含有する組成物溶液（Ａ）をダイコータにより連続成膜し、８０℃で乾燥して膜厚１７ｎｍの二色性染料を含有する薄膜層を形成した。薄膜層付きのＴＡＣフィルムを搬送しながら、偏光の振動方向がフィルムの長手方向に対し７５°傾いており、偏光軸が回転していない偏光紫外線を照射し光配向層（ＡＨ−２）とした。この時、照射した偏光紫外線は３６５ｎｍのバンドパスフィルターを透過しており、その照射強度は４０Ｗ／ｍ２であり、紫外線の照射領域を通過するに要する時間は２５秒であった。
光配向層（ＡＨ−２）上に、重合性液晶組成物溶液（Ｂ）をダイコータにより塗布し、６０℃で乾燥した。偏光ではない紫外線を空気雰囲気下、積算光量が６ｋＪ／ｍ２ となるよう照射し、位相差膜（Ｈ２）を得た。
(Comparative Example 2)
After corona treatment of the TAC film, a composition solution (A) containing a dichroic dye is continuously formed by a die coater and dried at 80 ° C. to form a thin film layer containing a dichroic dye having a thickness of 17 nm. did. While transporting a TAC film with a thin film layer, the polarization vibration direction is inclined by 75 ° with respect to the longitudinal direction of the film, and the polarized UV light whose polarization axis does not rotate is irradiated to form a photo-alignment layer (AH-2). . At this time, the irradiated polarized ultraviolet rays were transmitted through a 365 nm band pass filter, the irradiation intensity was 40 W / m 2 , and the time required to pass through the ultraviolet irradiation region was 25 seconds.
The polymerizable liquid crystal composition solution (B) was applied on the photo-alignment layer (AH-2) with a die coater and dried at 60 ° C. Ultraviolet light that is not polarized light was irradiated in an air atmosphere so that the integrated light amount was 6 kJ / m 2 to obtain a retardation film (H2).
（比較例３）
ＴＡＣフィルムをコロナ処理した後、二色性染料を含有する組成物溶液（Ａ）をダイコータにより連続成膜し、８０℃で乾燥して膜厚１７ｎｍの二色性染料を含有する薄膜層を形成した。これに重合性液晶組成物溶液（Ｂ）をダイコータにより塗布し、６０℃で乾燥した。偏光ではない紫外線を空気雰囲気下、積算光量が６ｋＪ／ｍ２ となるよう照射し、位相差膜（Ｈ３）を得た。
表１に、実施例１〜３，比較例１〜２の位相差膜の複屈折の結果をまとめた。
(Comparative Example 3)
After corona treatment of the TAC film, a composition solution (A) containing a dichroic dye is continuously formed by a die coater and dried at 80 ° C. to form a thin film layer containing a dichroic dye having a thickness of 17 nm. did. The polymerizable liquid crystal composition solution (B) was applied to this with a die coater and dried at 60 ° C. A retardation film (H3) was obtained by irradiating ultraviolet light that was not polarized light in an air atmosphere so that the integrated light amount was 6 kJ / m 2 .
Table 1 summarizes the results of birefringence of the retardation films of Examples 1 to 3 and Comparative Examples 1 and 2.
この結果、光配向層の配向処理として偏光軸を回転させて処理して得た位相差膜は、重合性液晶分子がｘ−ｙ面内に略平行に配向し、ｎｙがｎｚより大きく、且つｎｘ−ｎｚが０．０６以上の大きい値を有するものであった。即ち実施例１及び３の方法により得られた位相差膜はｎｘ＞ｎｙ＞ｎｚの性質を有し、実施例２の方法により得られた位相差膜はｎｘ＝ｎｙ＞ｎｚの性質を有する位相差膜であった。これは複屈折が大きいため薄膜化が可能であり、薄型の液晶表示装置にも対応させることが可能である。
一方、比較例１及び比較例２は、偏光軸を回転させずに偏光紫外線を照射して位相差膜を作成した例であるが、この方法では、３次元的に等方性となる傾向があり、ｎｘ＞ｎｙ＞ｎｚまたはｎｘ＝ｎｙ＞ｎｚであり且つｎｘ−ｎｚの大きな、即ちｎｚの非常に小さい位相差膜を得ることができなかった。なお比較例３は紫外線を照射しない、即ち二色性染料を含有する薄膜層を光配向させない例であるが、ｎｘ＞ｎｙ＞ｎｚまたはｎｘ＝ｎｙ＞ｎｚであり且つｎｘ−ｎｚの大きな、即ちｎｚの非常に小さい位相差膜を得ることができなかった。
As a result, in the retardation film obtained by rotating the polarization axis as the alignment treatment of the photo-alignment layer, the polymerizable liquid crystal molecules are aligned substantially parallel in the xy plane, ny is larger than nz, and nx-nz had a large value of 0.06 or more. That is, the retardation film obtained by the methods of Examples 1 and 3 has a property of nx>ny> nz, and the retardation film obtained by the method of Example 2 has a property of nx = ny> nz. It was a phase difference film. Since this has a large birefringence, it can be made thin and can be applied to a thin liquid crystal display device.
On the other hand, Comparative Example 1 and Comparative Example 2 are examples in which a retardation film is formed by irradiating polarized ultraviolet rays without rotating the polarization axis, but this method tends to be three-dimensionally isotropic. In other words, a retardation film satisfying nx>ny> nz or nx = ny> nz and having a large nx−nz, that is, a very small nz could not be obtained. Comparative Example 3 is an example in which ultraviolet rays are not irradiated, that is, a thin film layer containing a dichroic dye is not photo-aligned, but nx>ny> nz or nx = ny> nz and nx−nz is large, that is, A retardation film having a very small nz could not be obtained.
Claims (3)
二色性染料を含有する薄膜層に、光軸がｘ−ｙ面内に垂直となるように配置した偏光板を光軸が回転軸となり、かつ一回の配向処理時に当該偏光板が２回転以上回転するように回転させながら偏光紫外線を照射する工程Ａと、該薄膜層上に重合性基を有する棒状液晶化合物を含有する重合性液晶組成物層を形成する工程Ｂと、重合性基を有する液晶化合物を硬化させる工程Ｃとを有することを特徴とする、位相差膜の製造方法。
（但しｘは位相差膜の面内での最大屈折率方向を表し、ｙはｘに垂直な方向を表し、ｚは厚み方向を表す） A method for producing a retardation film that is substantially parallel to an xy in-plane direction and has xy in-plane direction refractive indexes nx and ny larger than a refractive index nz in a thickness direction z,
A polarizing plate is arranged on a thin film layer containing a dichroic dye so that the optical axis is perpendicular to the xy plane. The optical axis is the rotational axis, and the polarizing plate rotates twice during one orientation treatment. a step a of irradiating polarized ultraviolet rays while rotating to rotate above, step B of forming a polymerizable liquid crystal composition layer containing a rod-like liquid crystal compound having a polymerizable group in the thin film layer, a polymerizable group And a step C for curing the liquid crystal compound having the method.
(Where x represents the maximum refractive index direction in the plane of the retardation film, y represents the direction perpendicular to x, and z represents the thickness direction)
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