JP4220729B2 - Liquid crystal light modulator and liquid crystal display device using the same - Google Patents

Liquid crystal light modulator and liquid crystal display device using the same Download PDF

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JP4220729B2
JP4220729B2 JP2002175899A JP2002175899A JP4220729B2 JP 4220729 B2 JP4220729 B2 JP 4220729B2 JP 2002175899 A JP2002175899 A JP 2002175899A JP 2002175899 A JP2002175899 A JP 2002175899A JP 4220729 B2 JP4220729 B2 JP 4220729B2
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liquid crystal
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light modulator
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crystal light
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英夫 藤掛
弘人 佐藤
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Japan Broadcasting Corp
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Description

【０００１】
【発明の属する技術分野】
本発明は液晶光変調器及びそれを用いた液晶表示装置に関し、特に、強誘電性液晶を用いて光強度を変調する液晶光変調器及びそれを用いた液晶表示装置に関する。
【０００２】
【従来の技術】
液晶膜に電界を加えて、液晶分子の配列状態を変化させるという液晶の電気光学効果を応用すると光変調器が容易に実現できる。液晶光変調器は、他の電気光学効果を示す無機結晶に比べて低電圧で動作し、比較的大きな面積のものを廉価に作ることができるため、ディスプレイ用の電気光学素子として近年注目されている。
【０００３】
このような液晶光変調器の１つとして、自発分極を持ちカイラルスメクティックＣ相を示す強誘電性液晶を、透明電極間の狭いギャップ（通常、２〜３μｍ）に充填し、液晶分子の配向を双安定化した表面安定化強誘電性液晶がある（参考文献１：Ｎ．Ａ．Ｃｌａｒｋ ａｎｄ Ｓ．Ｔ．Ｌａｎｇｅｒｗａｌｌ Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．，Ｖｏｌ．３６，Ｎｏ．１１，ｐｐ．８９９−９０１，１９８０）。
【０００４】
その場合、液晶分子は基板と水平な面内で配向膜の配向処理方向から、液晶材料固有のコーン角だけ傾いた２つの安定な配向状態を持ち、それらの２つの配向は、透明電極に加える電圧の極性を切り替えるとスイッチングする。この素子を偏光透過軸が直交した２つの偏光板で挟み、一方の偏光板の偏光透過軸を２方向の配向状態のいずれかに平行に設定することにより、双安定性の光変調動作が得られる。
【０００５】
液晶の複屈折効果を有効に利用して、高い透過率を得るためには、コーン角は２２．５度程度が望ましい。この分子配向スイッチングは、数十〜数百μｓｅｃの高速な光変調を可能にするため、高速動作が求められるフラットパネルディスプレイに有用である。
【０００６】
【発明が解決しようとする課題】
しかし、上記の液晶光変調器は液晶の分子配列が双安定のため、中間調表示が困難である。そのため、階調を必要とする画像表示に応用できない。また、液晶の配向が不連続となる配向欠陥（ジグザグ欠陥）が発生しやすく、それに伴う黒表示で光漏れにより、光変調のコントラスト比が低下するといった問題を抱えている。
【０００７】
本発明は、上記の点に鑑みてなされたもので、中間調表示を行うことができ面内均一性やコントラスト比に優れた液晶光変調器及びそれを用いた液晶表示装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
請求項１に記載の発明は、最大透過率が得られる理想的なコーン角が４５度であるのに対して４０度以上のコーン角を有し厚みが１μｍ以下であるカイラルスメクティックＣ相の強誘電性液晶膜と、
毛先押し込み量が０．４ｍｍ以上のラビング処理により形成され、前記強誘電性液晶膜を挟み液晶分子を配向させる一対の配向膜と、
前記強誘電性液晶膜と前記一対の配向膜とを挟む一対の透明電極と、
前記強誘電性液晶膜と前記一対の配向膜と前記一対の透明電極を挟んで配置され偏光透過軸が直交する一対の偏光板と、
前記一対の透明電極間に印加して光透過率を連続的に変化させる両極性の直流電圧の電圧源とを有することにより、
透明基板上に塗布した配向膜の影響が強くなって双安定特性が消失し、印加電圧に応じて透過率が連続的に変化して中間調表示を行うことができる。
【００１０】
請求項２に記載の発明は、請求項１記載の液晶光変調器において、
前記一対の配向膜は、高プレチルト配向膜であることにより、
配向欠陥が生じにくくなり、面内均一性やコントラスト比に優れた液晶光変調器を構成できる。
【００１１】
請求項３に記載の発明は、請求項１または２記載の液晶光変調器において、
前記一対の配向膜は、配向処理方向が逆方向であることにより、
配向欠陥が生じにくくなり、面内均一性やコントラスト比に優れた液晶光変調器を構成できる。
【００１２】
請求項４に記載の発明は、請求項１乃至３のいずれか記載の液晶光変調器において、
前記一対の偏光板は、いずれか一方の偏光透過軸が、前記一対の配向膜の配向処理方向と平行であることにより、
印加電圧に応じて透過率を連続的に変化させることが可能となる。
【００１３】
【発明の実施の形態】
以下に本発明の実施の形態を説明する。図１は本発明の液晶光変調器の一実施例の構成を示す模式図である。同図中、自発分極をもつカイラルスメクティックＣ相を示す強誘電性液晶膜１が、配向膜３ａを付着させた透明電極４ａと配向膜３ｂを付着させた透明電極４ｂに挟まれて配設される。透明電極４ａ，４ｂそれぞれは透明基板５ａ、５ｂに付着させて形成されている。透明電極４ａ、４ｂはリード線６ａ、６ｂを介して、両極性電圧を供給できる電圧源７に接続されている。
【００１４】
透明基板５ａの強誘電性液晶膜１とは逆側に配設された入射側の偏光板８ａは、強誘電性液晶１の液晶分子２の長軸方向の偏光透過軸を有しており、透明基板５ｂの強誘電性液晶膜１とは逆側に配設された出射側の偏光板８ｂは、強誘電性液晶１の液晶分子２の長軸方向と直交する方向の偏光透過軸を有している。
【００１５】
入射光９は、入射側の偏光板８ａを透過することにより、強誘電性液晶１の液晶分子２の長軸方向に偏光され、強誘電性液晶膜１に入射する。この入射光は強誘電性液晶膜１で偏光状態が制御されたのち、他方の透明基板５ｂを通し出射側の偏光板８ｂを透過透過することにより、強度変調された出射光１０となる。
【００１６】
すなわち２つの偏光板８ａ、８ｂの偏光透過軸を直交させ、偏光板８ａ、８ｂのいずれか一方の偏光透過軸を配向膜３ａ，３ｂの配向処理方向と平行にすることにより、電圧源７による極性及び電圧強度の制御により、液晶分子２の配向方向が透明基板５ａ，５ｂの面内で連続的に変化して、光透過率が連続的に変化するアナログ的な光変調機能が得られる。
【００１７】
強誘電性液晶膜１には、４０度以上（理想的には４５度）のコーン角をもたせることにより、入射光に対する複屈折効果を高めることができ、高い光利用率が期待できる。アナログ的な分子配向変化を得るためには、液晶分子２の分子配向が配向膜３ａ，３ｂの配向処理方向に安定化されるように、配向膜３ａ，３ｂの配向力を強くするか、もしくは強誘電性液晶膜１の厚みを１μｍ以下と薄くして、配向膜３ａ，３ｂの影響を強めることができる。これにより、透明基板上に塗布した配向膜の影響が強くなり、強誘電性液晶膜１の双安定特性が消失する。
【００１８】
強誘電性液晶膜１の厚みは、２μｍ程度でも液晶分子配向が可能であるが、コーン角が広い強誘電性液晶膜では分子配向のスイッチング軸が面内でぶれやすくなり、配向欠陥が生じやすくなる。しかし１μｍ以下であれば、配向欠陥を大幅に低減することが可能となる。すなわち、強誘電性液晶膜１の膜厚を減少させれば、液晶分子２の分子配向を安定化することができる。
【００１９】
更に、配向膜３ａ，３ｂとして高プレチルト配向膜を用いて、液晶分子２を透明基板５ａ，５ｂから起こして配向させることにより（例えば、透明基板５ａ，５ｂと液晶分子２のなす角度であるチルト角は１０度程度）、更に配向欠陥を減らして、面内均一性やコントラスト比を高めることができる。この場合、２つの配向膜３ａ，３ｂの配向処理は逆方向（アンチパラレル）が効果的である。しかし、平行配向であっても一定の欠陥抑制が期待できる。
【００２０】
強誘電性液晶１の分子配向を一方向に安定化する配向膜３ａ，３ｂには、摩擦（ラビング）処理、もしくは偏光紫外光の照射による配向処理を施されたポリイミド樹脂、ポリビニルアルコール樹脂、斜方蒸着されたＳｉＯ、ＳｉＯ２のいずれかの配向膜を用いることができる。
【００２１】
強誘電性液晶膜１の材料としては、入射光の偏光状態を大きく制御できるように、液晶の屈折率異方性△ｎ（△ｎ＝異常光屈折率ｎｅ−常光屈折率ｎｏ）が大きい方が好ましい。
【００２２】
そのため、屈折率異方性の大きなシッフ塩基系強誘電性液晶、アゾ系強誘電性液晶、アゾキシ系強誘電性液晶、ビフェニル系強誘電性液晶、エステル系強誘電性液晶、もしくはフェニルピリミジン系強誘電性液晶などが適している。また、自発分極が大きな強誘電性液晶材料を用いることにより、高速応答と低電圧駆動が可能となる。
【００２３】
透明電極４ａ，４ｂとしては、錫をドープした酸化インジウム（ＩＴＯ：Ｉｎ２Ｏ３：Ｓｎ）などが好適である。透明電極４ａ，４ｂを付着させる透明基板５ａ，５ｂには、ガラスもしくはプラスティックフィルムを用いることができ、プラスティックフィルムを透明基板５ａ，５ｂに用いた場合には、液晶光変調器をフレキシブルにすることが可能である。また、透明基板５ａ，５ｂで挟まれた強誘電性液晶１の膜厚は、球状のスペーサを分散するか、フォトリソグラフィーで樹脂製の微細構造物を形成することにより、一定に保つことが可能である。
【００２４】
このような液晶光変調器と、蛍光管、冷陰極管、発光ダイオードなどのバックライトを組み合わせることにより、動画表示に適した高速な液晶表示装置を構成することができる。また、液晶光変調器に反射板を組み合わせて用いるか、内蔵させることにより、反射型ディスプレイを構成することも可能である。
【００２５】
実施例として、強誘電性液晶膜１にチッソ社、液晶組成物（コーン角度４２．９度、カイラルピッチ１４μｍ）を用いて作製した液晶光変調器について述べる。作製方法は以下の通りである。
【００２６】
まず、透明ガラスを用いた２枚の透明基板５ａ，５ｂに、それぞれ厚み７２ｎｍのＩｎ２Ｏ３：Ｓｎを蒸着して透明電極４ａ，４ｂを形成し、さらに透明電極４ａ，４ｂ上にスピンコート法によって高プレチルト用ポリイミド（ＪＳＲ社ＪＡＬＳ−２４６−Ｒ４）を塗布し、厚み５０ｎｍの配向膜３ａ，３ｂを形成した。この配向膜３ａ，３ｂを微細なレーヨンブラシ（安川加工社、ＹＡ−２０−ＲＷ）で一方向にラビングした。
【００２７】
２枚の配向膜３ａ，３ｂ付きの透明基板５ａ，５ｂを配向方向が逆方向になるように、１μｍ径もしくは１．８μｍ径もしくは２．５μｍ径の球状スペーサを介在させて重ね合わせギャップを形成した。そのギャップに、１００℃で加熱した強誘電性液晶１を注入し、室温に戻して液晶配向の均一性を偏光顕微鏡により観察した。
【００２８】
ラビング強度が強く、レーヨンブラシの毛先押し込み量が０．４ｍｍと大きくした場合、膜厚の減少による液晶配向の均一化が見られた。強誘電性液晶膜１の膜厚が２．５μｍではランダムな分子配向となったが、強誘電性液晶膜１の膜厚を薄くして１．８μｍにすると配向した液晶領域が現れ始め、さらに薄く膜厚１μｍにすると、ラビング方向に一様に配向した液晶領域が観察された。
【００２９】
しかし、ラビング強度が弱く、レーヨンブラシの毛先押し込み量が０．２ｍｍと小さくした場合、配向組織の改善効果は低いことが分かった。配向処理を強くして透明基板５ａ，５ｂ間のギャップを膜厚１μｍと薄くすることにより、配向欠陥が減少した結果、コントラスト比が膜厚１．８μｍの２０：１から、膜厚１μｍの２５０：１に大幅に改善できた。
【００３０】
図２は、電圧源７により印加直流電圧を−５Ｖ〜＋５Ｖまで変化させたときの透過光強度変化を示す。印加電圧に応じて透過光の強度が連続的に変化して、Ｖ字状の光変調特性が確認された。また、試作した素子の応答時間（立上がり時間＋立下り時間）は０．６ｍｓｅｃと高速であり、動画用の表示材料に好適である。
【００３１】
このように、広いコーン角を有する強誘電性液晶膜を用い、膜厚を薄くすることで、表示の一様性やコントラスト比に優れ、高速なアナログ変調が可能な液晶光変調器および液晶表示装置を提供することができる。従って、本発明の液晶光変調器や液晶表示装置は、フラットパネルディスプレイに好適であり、本発明を用いることにより階調を伴う動画表示が可能となる。
【００３２】
【発明の効果】
上述の如く、請求項１に記載の発明によれば、透明基板上に塗布した配向膜の影響が強くなって双安定特性が消失し、印加電圧に応じて透過率が連続的に変化して中間調表示を行うことができる。
【００３４】
また、請求項２に記載の発明によれば、配向欠陥が生じにくくなり、面内均一性やコントラスト比に優れた液晶光変調器を構成できる。
【００３５】
また、請求項３に記載の発明によれば、配向欠陥が生じにくくなり、面内均一性やコントラスト比に優れた液晶光変調器を構成できる。
【００３６】
また、請求項４に記載の発明によれば、印加電圧に応じて透過率を連続的に変化させることが可能となる。
【図面の簡単な説明】
【図１】本発明の液晶光変調器の一実施例の構成を示す模式図である。
【図２】印加直流電圧を変化させたときの透過光強度変化を示す図である。
【符号の説明】
１ 強誘電性液晶膜
２ 液晶分子
３ａ，３ｂ 配向膜
４ａ，４Ｂ 透明電極
５ａ，５ｂ 透明基板
６ａ、６ｂ リード線
７ 電圧源
８ａ，８ｂ 偏光板
９ 入射光
１０ 出射光[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal light modulator and a liquid crystal display device using the same, and more particularly to a liquid crystal light modulator that modulates light intensity using a ferroelectric liquid crystal and a liquid crystal display device using the same.
[0002]
[Prior art]
An optical modulator can be easily realized by applying the electro-optic effect of liquid crystal, in which an electric field is applied to the liquid crystal film to change the alignment state of liquid crystal molecules. Liquid crystal light modulators have been attracting attention as electro-optic elements for displays in recent years because they operate at a lower voltage than other inorganic crystals exhibiting electro-optic effects and can be made inexpensively with relatively large areas. Yes.
[0003]
As one of such liquid crystal light modulators, a ferroelectric liquid crystal having spontaneous polarization and exhibiting a chiral smectic C phase is filled in a narrow gap (usually 2 to 3 μm) between transparent electrodes, and the orientation of liquid crystal molecules is adjusted. There are bistable surface-stabilized ferroelectric liquid crystals (Reference 1: NA Clark and ST Langerwall Appl. Phys. Lett., Vol. 36, No. 11, pp. 899-901. 1980).
[0004]
In that case, the liquid crystal molecules have two stable alignment states inclined by the cone angle specific to the liquid crystal material from the alignment processing direction of the alignment film in a plane parallel to the substrate, and these two alignments are added to the transparent electrode. Switching occurs when the polarity of the voltage is switched. By sandwiching this element between two polarizing plates whose polarization transmission axes are orthogonal to each other and setting the polarization transmission axis of one of the polarizing plates in parallel to one of two orientation states, a bistable light modulation operation can be obtained. It is done.
[0005]
In order to effectively use the birefringence effect of the liquid crystal and obtain high transmittance, the cone angle is preferably about 22.5 degrees. Since this molecular orientation switching enables high-speed optical modulation of several tens to several hundreds of μsec, it is useful for flat panel displays that require high-speed operation.
[0006]
[Problems to be solved by the invention]
However, the liquid crystal light modulator is difficult to display halftone because the liquid crystal molecular alignment is bistable. Therefore, it cannot be applied to image display that requires gradation. Further, alignment defects (zigzag defects) in which the alignment of the liquid crystal becomes discontinuous are likely to occur, and there is a problem that the contrast ratio of light modulation is reduced due to light leakage in black display.
[0007]
The present invention has been made in view of the above points, and provides a liquid crystal light modulator that can perform halftone display and has excellent in-plane uniformity and contrast ratio, and a liquid crystal display device using the same. Objective.
[0008]
[Means for Solving the Problems]
According to one aspect of the present invention, the strength of the chiral smectic C phase thickness have a cone angle of at least 40 degrees with respect to the ideal cone angle is 45 degrees the maximum transmittance is obtained is 1μm or less A dielectric liquid crystal film;
A pair of alignment films formed by rubbing treatment with a hair tip pushing amount of 0.4 mm or more, and aligning liquid crystal molecules with the ferroelectric liquid crystal film interposed therebetween;
A pair of transparent electrodes sandwiching the ferroelectric liquid crystal film and the pair of alignment films;
A pair of polarizing plates arranged with the ferroelectric liquid crystal film, the pair of alignment films, and the pair of transparent electrodes sandwiched therebetween, and whose polarization transmission axes are orthogonal to each other;
By having a voltage source of a bipolar DC voltage applied between the pair of transparent electrodes to continuously change the light transmittance ,
The influence of the alignment film applied on the transparent substrate becomes stronger, the bistable characteristics disappear, and the transmittance changes continuously according to the applied voltage, so that halftone display can be performed.
[0010]
The invention described in claim 2 is the liquid crystal light modulator according to claim 1 ,
The pair of alignment films are high pretilt alignment films,
An alignment defect is less likely to occur, and a liquid crystal light modulator excellent in in-plane uniformity and contrast ratio can be configured.
[0011]
The invention according to claim 3 is the liquid crystal light modulator according to claim 1 or 2 ,
In the pair of alignment films, the alignment treatment direction is opposite,
An alignment defect is less likely to occur, and a liquid crystal light modulator excellent in in-plane uniformity and contrast ratio can be configured.
[0012]
According to a fourth aspect of the present invention, in the liquid crystal light modulator according to any one of the first to third aspects,
In the pair of polarizing plates, any one polarization transmission axis is parallel to the alignment treatment direction of the pair of alignment films,
It becomes possible to continuously change the transmittance according to the applied voltage.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram showing the configuration of an embodiment of the liquid crystal light modulator of the present invention. In the figure, a ferroelectric liquid crystal film 1 exhibiting a chiral smectic C phase having spontaneous polarization is disposed between a transparent electrode 4a to which an alignment film 3a is attached and a transparent electrode 4b to which an alignment film 3b is attached. The The transparent electrodes 4a and 4b are formed by being attached to the transparent substrates 5a and 5b, respectively. The transparent electrodes 4a and 4b are connected to a voltage source 7 that can supply bipolar voltages via lead wires 6a and 6b.
[0014]
An incident-side polarizing plate 8a disposed on the opposite side of the transparent substrate 5a from the ferroelectric liquid crystal film 1 has a polarization transmission axis in the major axis direction of the liquid crystal molecules 2 of the ferroelectric liquid crystal 1; The output-side polarizing plate 8b disposed on the opposite side of the transparent substrate 5b from the ferroelectric liquid crystal film 1 has a polarization transmission axis in a direction perpendicular to the major axis direction of the liquid crystal molecules 2 of the ferroelectric liquid crystal 1. is doing.
[0015]
Incident light 9 is polarized in the major axis direction of the liquid crystal molecules 2 of the ferroelectric liquid crystal 1 by being transmitted through the polarizing plate 8 a on the incident side, and is incident on the ferroelectric liquid crystal film 1. After the polarization state of the incident light is controlled by the ferroelectric liquid crystal film 1, the incident light is transmitted through the polarizing plate 8 b on the emission side through the other transparent substrate 5 b to become intensity-modulated emission light 10.
[0016]
That is, the polarization transmission axes of the two polarizing plates 8a and 8b are orthogonal to each other, and the polarization transmission axis of one of the polarizing plates 8a and 8b is made parallel to the alignment treatment direction of the alignment films 3a and 3b. By controlling the polarity and voltage intensity, an analog light modulation function is obtained in which the alignment direction of the liquid crystal molecules 2 continuously changes in the plane of the transparent substrates 5a and 5b, and the light transmittance continuously changes.
[0017]
By providing the ferroelectric liquid crystal film 1 with a cone angle of 40 degrees or more (ideally 45 degrees), the birefringence effect on incident light can be enhanced, and a high light utilization rate can be expected. In order to obtain an analog molecular alignment change, the alignment force of the alignment films 3a and 3b is increased so that the molecular alignment of the liquid crystal molecules 2 is stabilized in the alignment treatment direction of the alignment films 3a and 3b, or The influence of the alignment films 3a and 3b can be increased by reducing the thickness of the ferroelectric liquid crystal film 1 to 1 μm or less. Thereby, the influence of the alignment film applied on the transparent substrate becomes strong, and the bistable characteristics of the ferroelectric liquid crystal film 1 disappear.
[0018]
Liquid crystal molecular alignment is possible even when the thickness of the ferroelectric liquid crystal film 1 is about 2 μm. However, in a ferroelectric liquid crystal film having a wide cone angle, the switching axis of the molecular alignment tends to fluctuate in the plane and alignment defects are likely to occur. Become. However, if it is 1 μm or less, alignment defects can be greatly reduced. That is, if the film thickness of the ferroelectric liquid crystal film 1 is reduced, the molecular orientation of the liquid crystal molecules 2 can be stabilized.
[0019]
Further, by using a high pretilt alignment film as the alignment films 3a and 3b, the liquid crystal molecules 2 are raised from the transparent substrates 5a and 5b and aligned (for example, a tilt that is an angle formed by the transparent substrates 5a and 5b and the liquid crystal molecules 2). The angle is about 10 degrees), and the alignment defects can be further reduced to increase the in-plane uniformity and the contrast ratio. In this case, the reverse direction (anti-parallel) is effective for the alignment treatment of the two alignment films 3a and 3b. However, a certain defect suppression can be expected even in the parallel orientation.
[0020]
The alignment films 3a and 3b for stabilizing the molecular alignment of the ferroelectric liquid crystal 1 in one direction are subjected to a rubbing process or an alignment process by irradiation with polarized ultraviolet light, a polyvinyl alcohol resin, an oblique film Either a vapor-deposited alignment film of SiO or SiO 2 can be used.
[0021]
As the material of the ferroelectric liquid crystal layer 1, so that it can greatly control the polarization state of the incident light, the refractive index anisotropy of the liquid crystal △ n (△ n = extraordinary refractive index n e - ordinary refractive index n o) is Larger is preferable.
[0022]
Therefore, Schiff base ferroelectric liquid crystal, azo ferroelectric liquid crystal, azoxy ferroelectric liquid crystal, biphenyl ferroelectric liquid crystal, ester ferroelectric liquid crystal, or phenyl pyrimidine strong Dielectric liquid crystals are suitable. In addition, by using a ferroelectric liquid crystal material having a large spontaneous polarization, high-speed response and low-voltage driving are possible.
[0023]
As the transparent electrodes 4a and 4b, indium oxide doped with tin (ITO: In 2 O 3 : Sn) or the like is suitable. Glass or plastic film can be used for the transparent substrates 5a and 5b to which the transparent electrodes 4a and 4b are attached. When the plastic film is used for the transparent substrates 5a and 5b, the liquid crystal light modulator should be flexible. Is possible. The film thickness of the ferroelectric liquid crystal 1 sandwiched between the transparent substrates 5a and 5b can be kept constant by dispersing spherical spacers or forming resin microstructures by photolithography. It is.
[0024]
By combining such a liquid crystal light modulator with a backlight such as a fluorescent tube, a cold cathode tube, or a light emitting diode, a high-speed liquid crystal display device suitable for moving image display can be configured. In addition, it is also possible to configure a reflective display by using a liquid crystal light modulator in combination with a reflection plate or by incorporating it.
[0025]
As an example, a liquid crystal light modulator manufactured using a liquid crystal composition (cone angle: 42.9 degrees, chiral pitch: 14 μm) from Chisso Corporation for the ferroelectric liquid crystal film 1 will be described. The manufacturing method is as follows.
[0026]
First, two transparent substrates 5a using a transparent glass, in 5b, the thicknesses 72nm In 2 O 3: Sn transparent electrode 4a by depositing, 4b is formed, further the transparent electrode 4a, spin coated onto a 4b A high pretilt polyimide (JALS-246-R4, manufactured by JSR) was applied by a method to form alignment films 3a and 3b having a thickness of 50 nm. The alignment films 3a and 3b were rubbed in one direction with a fine rayon brush (Yaskawa Processing Co., Ltd., YA-20-RW).
[0027]
A transparent gap 5a, 5b with two alignment films 3a, 3b is formed with a 1 μm diameter, 1.8 μm diameter, or 2.5 μm diameter spherical spacer interposed so that the alignment direction is reversed. did. The ferroelectric liquid crystal 1 heated at 100 ° C. was injected into the gap, returned to room temperature, and the uniformity of liquid crystal alignment was observed with a polarizing microscope.
[0028]
When the rubbing strength was strong and the push-in amount of the rayon brush was increased to 0.4 mm, the liquid crystal alignment was uniform due to the decrease in film thickness. The ferroelectric liquid crystal film 1 has a random molecular orientation when the film thickness is 2.5 μm, but when the film thickness of the ferroelectric liquid crystal film 1 is reduced to 1.8 μm, the aligned liquid crystal region starts to appear. When the film thickness was reduced to 1 μm, a liquid crystal region uniformly aligned in the rubbing direction was observed.
[0029]
However, it was found that when the rubbing strength is weak and the tip pushing amount of the rayon brush is as small as 0.2 mm, the effect of improving the oriented structure is low. As a result of reducing the alignment defects by strengthening the alignment treatment and reducing the gap between the transparent substrates 5a and 5b to a film thickness of 1 μm, the contrast ratio is from 20: 1 with a film thickness of 1.8 μm to 250 with a film thickness of 1 μm. : 1 was greatly improved.
[0030]
FIG. 2 shows changes in transmitted light intensity when the applied DC voltage is changed from −5 V to +5 V by the voltage source 7. The intensity of the transmitted light continuously changed according to the applied voltage, and V-shaped light modulation characteristics were confirmed. The response time (rise time + fall time) of the prototyped device is as fast as 0.6 msec, which is suitable for a display material for moving images.
[0031]
In this way, a liquid crystal light modulator and a liquid crystal display capable of high-speed analog modulation with excellent display uniformity and contrast ratio by using a ferroelectric liquid crystal film having a wide cone angle and reducing the film thickness. An apparatus can be provided. Therefore, the liquid crystal light modulator and the liquid crystal display device of the present invention are suitable for a flat panel display, and moving image display with gradation can be performed by using the present invention.
[0032]
【The invention's effect】
As described above, according to the invention described in claim 1, the influence of the alignment film coated on the transparent substrate is strengthened, the bistable characteristic is lost, and the transmittance continuously changes according to the applied voltage. Halftone display can be performed.
[0034]
In addition, according to the second aspect of the present invention, alignment defects are less likely to occur, and a liquid crystal light modulator excellent in in-plane uniformity and contrast ratio can be configured.
[0035]
In addition, according to the third aspect of the present invention, alignment defects are less likely to occur, and a liquid crystal light modulator excellent in in-plane uniformity and contrast ratio can be configured.
[0036]
In addition, according to the invention described in claim 4 , it is possible to continuously change the transmittance according to the applied voltage.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an embodiment of a liquid crystal light modulator of the present invention.
FIG. 2 is a diagram showing a change in transmitted light intensity when an applied DC voltage is changed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ferroelectric liquid crystal film 2 Liquid crystal molecule 3a, 3b Alignment film 4a, 4B Transparent electrode 5a, 5b Transparent substrate 6a, 6b Lead wire 7 Voltage source 8a, 8b Polarizing plate 9 Incident light 10 Output light

Claims (7)

最大透過率が得られる理想的なコーン角が４５度であるのに対して４０度以上のコーン角を有し厚みが１μｍ以下であるカイラルスメクティックＣ相の強誘電性液晶膜と、
毛先押し込み量が０．４ｍｍ以上のラビング処理により形成され、前記強誘電性液晶膜を挟み液晶分子を配向させる一対の配向膜と、
前記強誘電性液晶膜と前記一対の配向膜とを挟む一対の透明電極と、
前記強誘電性液晶膜と前記一対の配向膜と前記一対の透明電極を挟んで配置され偏光透過軸が直交する一対の偏光板と、
前記一対の透明電極間に印加して光透過率を連続的に変化させる両極性の直流電圧の電圧源とを有することを特徴とする液晶光変調器。A ferroelectric liquid crystal layer of the chiral smectic C phase thickness is 1μm or less ideal cone angle which the maximum transmittance is obtained have a cone angle of at least 40 degrees with respect to a 45 °,
A pair of alignment films formed by rubbing treatment with a hair tip pushing amount of 0.4 mm or more, and aligning liquid crystal molecules with the ferroelectric liquid crystal film interposed therebetween;
A pair of transparent electrodes sandwiching the ferroelectric liquid crystal film and the pair of alignment films;
A pair of polarizing plates arranged with the ferroelectric liquid crystal film, the pair of alignment films, and the pair of transparent electrodes sandwiched therebetween, and whose polarization transmission axes are orthogonal to each other;
A liquid crystal light modulator comprising: a bipolar voltage source that is applied between the pair of transparent electrodes to continuously change the light transmittance . 請求項１記載の液晶光変調器において、
前記一対の配向膜は、高プレチルト配向膜であることを特徴とする液晶光変調器。The liquid crystal light modulator according to claim 1 .
The liquid crystal light modulator according to claim 1, wherein the pair of alignment films are high pretilt alignment films. 請求項１または２記載の液晶光変調器において、
前記一対の配向膜は、配向処理方向が逆方向であることを特徴とする液晶光変調器。The liquid crystal light modulator according to claim 1 or 2 ,
The pair of alignment films is a liquid crystal light modulator, wherein the alignment treatment direction is opposite. 請求項１乃至３のいずれか記載の液晶光変調器において、
前記一対の偏光板は、いずれか一方の偏光透過軸が、前記一対の配向膜の配向処理方向と平行であることを特徴とする液晶光変調器。In the liquid crystal optical modulator according to any one of claims 1 to 3,
One of the pair of polarizing plates has a polarization transmission axis parallel to the alignment treatment direction of the pair of alignment films. 請求項１乃至４のいずれか記載の液晶光変調器において、
前記配向膜は、ラビング配向処理または偏光紫外線光の照射による光配向処理を施されたポリイミド樹脂、ポリビニルアルコール樹脂、及び斜方蒸着処理されたＳｉＯ、ＳｉＯ２のいずれかであることを特徴とする液晶光変調器。The liquid crystal light modulator according to any one of claims 1 to 4 ,
The alignment film may be one of polyimide resin, polyvinyl alcohol resin, and obliquely vapor-deposited SiO, SiO 2 subjected to rubbing alignment treatment or photo-alignment treatment by irradiation with polarized ultraviolet light. Liquid crystal light modulator. 請求項１乃至５のいずれか記載の液晶光変調器において、
前記透明電極は、ガラスもしくはプラスティックフィルムの透明基板に付着させて形成したことを特徴とする液晶光変調器。In the liquid crystal optical modulator according to any of claims 1 to 5,
The liquid crystal light modulator, wherein the transparent electrode is formed by adhering to a transparent substrate of glass or plastic film. 請求項１乃至６のいずれか記載の液晶光変調器を用いて表示を行うことを特徴とする液晶表示装置。The liquid crystal display device characterized by performing display using a liquid crystal light modulator according to any one of claims 1 to 6.
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