JP4088705B2 - Liquid crystal display element - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、液晶表示素子、特に強誘電性液晶表示素子に関する。
【０００２】
【従来の技術】
クラーク及びラガーウオルにより提案された強誘電性液晶を用いた液晶表示素子（特開昭５６−１０７２１６号に記載）は双安定性を有し、且つ電界の変化に対する応答が高速であることから、大画面で高精細な液晶表示素子としての応用が期待されている。しかしながら、双安定性を有していることから、中間調の表示が困難という問題があった。
【０００３】
これを解決する技術として、我々は先に強誘電性液晶と液晶性（メタ）アクリレートモノマーを含有する液晶組成物を液晶セル中に注入した後、該組成物が強誘電液晶性をしめす温度において直流電圧を印加しながら紫外線を照射し、液晶性（メタ）アクリレートモノマーを高分子化させることによって得られる高分子安定化強誘電性液晶素子を提案した。この素子においては、強誘電性液晶の双安定性は消失するので、中間調の表示が可能になる。そして、この高分子安定化強誘電性液晶素子に電圧を印加していない時の液晶分子の配向方向は、配向膜の容易軸（液晶分子が配向しやすい軸）方向から紫外線照射の際に印加していた直流電圧の極性によって決定する向きに、ある角度だけずれた状態となっている。この角度をメモリー角度と定義すると、通常、このメモリー角度は強誘電性液晶自体のチルト角より若干小さな値となる。従って、紫外線照射の際に印加していた直流電圧と同極性の直流電圧を印加すれば、ある電圧以上では、強誘電性液晶の配向方向は配向膜の容易軸に対してメモリー角度より大きな角度をなすようになる。双安定性は消失しているので、電圧を印加しなくなれば、強誘電性液晶は再び、配向膜の容易軸に対してメモリー角度をなすように配列する。一方、この高分子安定化強誘電性液晶素子に、紫外線照射の際に印加していた直流電圧に対して異極性の直流電圧を印加すると、直流電圧の絶対値に比例して、配向膜の容易軸に対して、今度はメモリー角の方向とは反対方向に、強誘電性液晶の配向方向が傾いていく。この場合でも、双安定性は消失しているので、電圧を印加しなくなれば、強誘電性液晶は再び、配向膜の容易軸に対してメモリー角度をなすように配列する。
【０００４】
以上のような動作原理から、この高分子安定化強誘電性液晶表示素子では、絶対値が等しい直流電圧を印加しても、強誘電性液晶分子のふれ角の絶対値が等しくならない。つまり素子として動作させた時、絶対値がおなじ直流電圧を印加しても、おなじ光透過率が得られず、表示がちらついてしまうという問題があった。
【０００５】
【本発明が解決しようとする課題】
本発明が解決しようとする課題は、高分子安定化強誘電性液晶を用いた素子においてちらつきの問題がない、高品位表示が可能な液晶表示素子を提供することにある。
【０００６】
【課題を解決するための手段】
本発明は前記課題を解決するために、
１．配向制御膜を付与した一対の電極付基板間に液晶層を挟持することにより構成される単位画素及びバックライト光源を有する液晶表示素子において、該液晶層が少なくとも液晶性（メタ）アクリレートの光硬化物及び強誘電性液晶を含有し、電圧無印加時における該強誘電性液晶の容易軸からの配向角度が一定角度Ｔであり、且つ該バックライト光源の光強度が該液晶層に印加する電圧に応じて調節可能であることを特徴とする液晶表示素子。
２．電圧無印加時における強誘電性液晶の容易軸からの配向角度Ｔが絶対値で３度以上を有することを特徴とする上記１記載の液晶表示素子。
３．液晶性（メタ）アクリレートが一般式（Ｉ）
【０００７】
【化３】
（式中、Ｘは水素原子又はメチル基を表し、ｎは０又は１の整数を表し、６員環Ａ、Ｂ及びＣはそれぞれ独立的に、
【０００９】
【化４】
を表し、ｍは１〜４の整数を表し、Ｙ1及びＹ2はそれぞれ独立的に、単結合、−ＣＨ2ＣＨ2−、−ＣＨ2Ｏ−、−ＯＣＨ2−、−ＣＯＯ−、−ＯＣＯ−、−Ｃ≡Ｃ−、−ＣＨ＝ＣＨ−、−ＣＦ＝ＣＦ−、−（ＣＨ2）4−、−ＣＨ2ＣＨ2ＣＨ2Ｏ−、−ＯＣＨ2ＣＨ2ＣＨ2−、−ＣＨ＝ＣＨ−ＣＨ2ＣＨ2−、−ＣＨ2ＣＨ2−ＣＨ＝ＣＨ−を表し、Ｙ3は単結合、−Ｏ−、−ＣＯＯ−、−ＯＣＯ−を表し、Ｚは水素原子、ハロゲン原子、シアノ基、炭素原子数１〜２０のアルキル基又は炭素原子数２〜２０のアルケニル基を表す。）で表されることを特徴とする上記１又は２記載の液晶表示素子。
４．一般式（Ｉ）において、Ｘは水素原子を表し、ｎは０を表し、６員環Ａ及びＣはそれぞれ独立的に１，４−フェニレン基、又は１，４−トランスシクロヘキシル基を表し、Ｙ1は単結合又は−Ｃ≡Ｃ−を表し、Ｙ3は単結合を表し、Ｚはハロゲン原子、シアノ基あるいは炭素原子数１〜２０のアルキル基を表すことを特徴とする上記３記載の液晶表示素子。
５．能動素子で駆動されることを特徴とする上記１乃至４記載の液晶表示素子。６．バックライト光源が冷陰極管もしくは発光ダイオードであることを特徴とする上記１乃至５記載の液晶表示素子。
を上記課題の解決手段として見出した。
【００１１】
【発明の実施の形態】
以下に本発明の一例について説明する。
本発明者らは上記課題を解決するため鋭意検討した結果、かかる課題がバックライト光源の強度を変調することによって解決できることを見いだし、本発明を提供するに至った。
【００１２】
即ち、本発明は配向制御膜を付与した一対の電極付基板間に液晶層を挟持することにより構成された単位画素及びバックライト光源を有する液晶表示素子において、該液晶層が少なくとも液晶性（メタ）アクリレートの光硬化物及び強誘電性液晶を含有し、電圧無印加時における該強誘電性液晶の容易軸からの配向角度が一定角度Ｔであり、且つ該バックライト光源の光強度が該液晶層に印加する電圧に応じて調節可能であることを特徴とする液晶表示素子を提供する。尚、本発明でいう容易軸とは、液晶が配向しやすい軸方向のことを意味し、例えば、配向処理法としてラビング法を用いた場合は、ラビング方向に沿った軸のことを指す。
【００１３】
バックライト光源の強度を、液晶層に印加する電圧に関係無く、一定にした場合、印加電圧−光透過率特性は図１のようになる。この図からわかるように、負の電圧印加時には、光透過率が小さくなってしまっている。本発明では、このように光透過率が小さくなってしまう極性の電圧を印加する際には、バックライト光源からの光強度を強めることによって、絶対値がおなじ直流電圧を印加した場合、同じ光透過率が得られるよう補償している。図２は本発明の液晶表示素子に関するものであり、負の電圧印加時にバックライト光源の強度を正の電圧印加時の３．５倍に強めた場合の印加電圧−誘電率特性の例であり、ほぼ良好な補償がなされているのがわかる。
【００１４】
このようなバックライト強度の変調による光透過率の補償は、電圧無印加時における液晶分子の容易軸からの角度Ｔの絶対値が３度以上の場合、特に有効である。
【００１５】
液晶層中における液晶性（メタ）アクリレート化合物の光硬化物の濃度は、０．１から１０重量％に調節するのが好ましく、０．５から７重量％に調節するのがさらに好ましく、１から５重量％が特に好ましい。液晶層中における液晶性（メタ）アクリレート光硬化物の濃度が０．１％より低いと、強誘電性液晶の双安定性が消失せず、中間調の表示が困難になる。また１０％より多いと、駆動電圧が増大してしまう。光硬化性組成物中に含有される液晶性（メタ）アクリレートとしては、液晶骨格と重合性官能基を分子内に有する化合物であれば特に制限なく用いることができるが、中間調表示と低電圧駆動を両立するためには、重合性官能基と液晶骨格の間にメチレンスペーサーが無い、単官能液晶性アクリレートを用いるのが好ましい。このような化合物としては、例えば一般式（Ｉ）
【００１６】
【化５】
（式中、Ｘは水素原子又はメチル基を表し、ｎは０又は１の整数を表し、６員環Ａ、Ｂ及びＣはそれぞれ独立的に、
【００１８】
【化６】
を表し、ｍは１〜４の整数を表し、Ｙ1及びＹ2はそれぞれ独立的に、単結合、−ＣＨ2ＣＨ2−、−ＣＨ2Ｏ−、−ＯＣＨ2−、−ＣＯＯ−、−ＯＣＯ−、−Ｃ≡Ｃ−、−ＣＨ＝ＣＨ−、−ＣＦ＝ＣＦ−、−（ＣＨ2）4−、−ＣＨ2ＣＨ2ＣＨ2Ｏ−、−ＯＣＨ2ＣＨ2ＣＨ2−、−ＣＨ＝ＣＨ−ＣＨ2ＣＨ2−、−ＣＨ2ＣＨ2−ＣＨ＝ＣＨ−を表し、Ｙ3は単結合、−Ｏ−、−ＣＯＯ−、−ＯＣＯ−を表し、Ｚは水素原子、ハロゲン原子、シアノ基あるいは炭素原子数１〜２０のアルキル基、アルケニル基を表す。）で表されるものを挙げることができる。その中でも特に、上記一般式（Ｉ）において、Ｘは水素原子を表し、ｎは０を表し、６員環Ａ及びＣはそれぞれ独立的に、１，４−フェニレン基、又は１，４−トランスシクロヘキシル基を表し、Ｙ1は単結合又は−Ｃ≡Ｃ−を表し、Ｙ3は単結合を表し、Ｚはハロゲン原子、シアノ基あるいは炭素原子数１〜２０のアルキル基又はアルコキシ基を表す化合物が室温付近の液晶相を発現しやすく、また扱いやすいため特に好ましい。また、環Ａ，Ｂ，Ｃのいずれかにピリミジン環を導入した化合物は、スメクチック液晶相を発現しやすく、強誘電性液晶への相溶性にすぐれるため、好適に使用することができる。このような液晶性（メタ）アクリレート化合物の具体的な例としては、式（１）〜（２１）に挙げた化合物が好ましいが、本発明の液晶組成物において使用することができる単官能（メタ）アクリレートはこれらに限定されるものではない。
【００２０】
【化７】
【化８】
【化９】
（上記中、シクロヘキサン環はトランスシクロヘキサン環を表し、またＣは結晶相、Ｎはネマチック相、Ｓはスメクチック相、Ｉは等方性液体相を表し、数字は相転移温度を表す。）これらの化合物の中でも、光学活性基を有する（１６）や（１７）の化合物を利用すると、螺旋ピッチの微調整や、駆動電圧低減の効果が期待できるので、これらも特に好適に使用することができる。
【００２４】
液晶層中に含有される強誘電性液晶は、通常この技術分野で強誘電性液晶と認識されるものであれば、特に制限なく使用することができるが、強誘電性液晶組成物はカイラルスメクチックＣ相より上の温度領域でスメクチックＡ相及びネマチック相を呈するものを使用するのが好ましい。
【００２５】
配向制御膜は従来用いられているラビング処理を施したポリイミド配向膜を特に制限なく用いることができる。またポリビニルシンナメート薄膜やポリイミド薄膜等に偏光紫外線を照射した、ラビング処理を施していない配向制御膜も用いることができる。
【００２６】
液晶層の厚さは、使用する強誘電液晶の屈折率の異方性にも依存するが、１から２０ミクロンであることが好ましく、１．５から１０ミクロンがさらに好ましく、１．５から６ミクロンが特に好ましい。
【００２７】
本発明の液晶表示素子は、双安定性を有していないため、能動素子を用いて駆動するのが好ましいが、能動素子の中でも特に、ＴＦＴ（薄膜トランジスタ）素子、ＭＩＭ（メタルインシュレーターメタル）素子、薄膜ダイオード等が好ましい。
【００２８】
本発明の液晶表示素子に用いるバックライトとしては、冷陰極管又は発光ダイオード（ＬＥＤ）が好ましい。本液晶表示素子は応答速度が早い強誘電性液晶を使用しているので、例えば赤、青、緑色の３色を発色するバックライトを時間分割により、それぞれの発光時間と強度を変調すれば、カラーフィルターを使用することなくカラー化することも可能になる。勿論、バックライトとして白色の冷陰極管を、カラーフィルターと共に用いても支障なくカラー化することも可能である。
【００２９】
【実施例】
以下、本発明の実施例を示し、本発明を更に詳細に説明する。しかしながら、本発明は実施例に限定されるものではない。
（実施例）
縦１．５ｃｍ、横１ｃｍの長方形のＩＴＯ（インジウムチンオキサイド）透明電極を形成した厚さ１．１ｍｍのガラス基板上に、ポリイミド膜「ＲＮ−１１９９」（日産化学製）を３００オングストロームの厚さで形成した後、ラビング処理を施してポリイミド配向膜付きガラス基板を得た。このようにして得た２枚のポリイミド配向膜付き基板を、配向膜が形成された面が内側になるようにして２．０ミクロンの間隔をもって対向させて液晶セル（Ａ）を作製した。この時、液晶セルをなす２枚の基板のラビング方向は、パラレル方向になるように設定した。
【００３０】
次に、化合物（１）
【００３１】
【化１０】
５０重量部及び化合物（４）
【００３３】
【化１１】
５０重量部及び光重合開始剤「イルガキュアー６５１」（チバガイギー社製）１重量部からなる液晶性アクリレート組成物（ａ）を調製した。この液晶性アクリレート組成物（ａ）は、室温でネマチック液晶相を示し、透明点は４１℃であった。
【００３５】
次に液晶セル（Ａ）を８０℃に保ちながら、調製した液晶性アクリレート組成物（ａ）２重量％及び強誘電性液晶「ＺＬＩ−４６５４−１００」（メルク社製）９８重量％からなる液晶組成物を注入した。その後、温度を室温まで下げ、液晶組成物をカイラルスメクチックＣ相まで転移させた。次に透明電極間に４Ｖの電圧を印加しながら、６０ｍＪ／ｃｍ2の紫外線を照射した。紫外線照射後、液晶分子の配向を電圧無印加状態において偏光顕微鏡で調べたところ、液晶分子は容易軸から右に８度傾いていることがわかった。次にセルの両側に偏光フィルムを貼った。この時、片面の偏光フィルムの偏光軸は、容易軸から右に８度傾いた方向と平行方向に、もう片面の偏光フィルムの偏光軸は、容易軸から右に８度傾いた方向と直角方向をなすようした。このようにして作製した素子に、赤、青、緑色の３色の発光ダイオードを組み合わせ、白色のバックライトとして取り付けた。これら３色の発光ダイオードの点灯回路に、液晶層への電圧印加回路からの出力との同期回路を付与し、液晶層への印加電圧の極性によって、発光ダイオードの出力を可変できるようにした。液晶層への印加電圧が正の場合に対して、負の場合は発光ダイオードの光出力が３．６倍になるように設定した後、液晶層に振幅が正負０から４Ｖの範囲で周波数２０Ｈｚの方形波を印加したところ、ちらつきのない中間調表示が得られることを確かめることができた。
（比較例）
実施例１で作製した液晶素子において、バックライトの点灯同期回路の機能を働かせないように設定することによって、液晶層への印加電圧の極性が変わっても発光ダイオードからの出力が変化しないようにした。液晶層に振幅が正負０から４Ｖの範囲で周波数２０Ｈｚの方形波を印加したところ、中間調表示はできたものの、ちらつきが観察された。
【００３６】
【発明の効果】
本発明の液晶表示素子は、高分子安定化型液晶表示素子であり、中間調表示が可能で、且つ表示のちらつきがない。従って、能動素子と組み合わせることによって高品位の表示を達成できる。
【図面の簡単な説明】
【図１】バックライト光源の光強度が、液晶層に印加する電圧に応じて変化しない液晶表示素子の電圧に対する光透過特性の例。
【図２】バックライト光源の光強度が、液晶層に印加する電圧に応じて変化する本発明の液晶表示素子の電圧に対する光透過特性の例。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display element, and more particularly to a ferroelectric liquid crystal display element.
[0002]
[Prior art]
A liquid crystal display device using ferroelectric liquid crystal proposed by Clark and Lagerwall (described in Japanese Patent Laid-Open No. 56-107216) has bistability and has a high response to changes in electric field. Application as a high-definition liquid crystal display element with a screen is expected. However, since it has bistability, there is a problem that halftone display is difficult.
[0003]
As a technique for solving this problem, we first injected a liquid crystal composition containing a ferroelectric liquid crystal and a liquid crystalline (meth) acrylate monomer into a liquid crystal cell, and then at a temperature at which the composition exhibits ferroelectric liquid crystallinity. We proposed a polymer-stabilized ferroelectric liquid crystal device obtained by irradiating ultraviolet rays while applying a DC voltage to polymerize a liquid crystalline (meth) acrylate monomer. In this element, since the bistability of the ferroelectric liquid crystal is lost, halftone display is possible. The orientation direction of the liquid crystal molecules when no voltage is applied to the polymer-stabilized ferroelectric liquid crystal element is applied during the ultraviolet irradiation from the easy axis direction of the alignment film (the axis in which the liquid crystal molecules are easily oriented). The direction is determined by the polarity of the DC voltage, and is shifted by a certain angle. When this angle is defined as a memory angle, this memory angle is usually slightly smaller than the tilt angle of the ferroelectric liquid crystal itself. Therefore, if a DC voltage having the same polarity as the DC voltage applied during UV irradiation is applied, the orientation direction of the ferroelectric liquid crystal is larger than the memory angle with respect to the easy axis of the alignment film above a certain voltage. It comes to make. Since the bistability has disappeared, if the voltage is not applied, the ferroelectric liquid crystal is arranged again at a memory angle with respect to the easy axis of the alignment film. On the other hand, when a DC voltage having a different polarity from the DC voltage applied at the time of ultraviolet irradiation is applied to the polymer-stabilized ferroelectric liquid crystal element, the alignment film is in proportion to the absolute value of the DC voltage. With respect to the easy axis, the orientation direction of the ferroelectric liquid crystal is now inclined in the direction opposite to the memory angle direction. Even in this case, since the bistability has disappeared, if the voltage is not applied, the ferroelectric liquid crystal is arranged again so as to form a memory angle with respect to the easy axis of the alignment film.
[0004]
From the above operation principle, in this polymer-stabilized ferroelectric liquid crystal display element, even if a DC voltage having the same absolute value is applied, the absolute values of the deflection angles of the ferroelectric liquid crystal molecules are not equal. That is, when operated as an element, even when a DC voltage having the same absolute value is applied, the same light transmittance cannot be obtained and the display flickers.
[0005]
[Problems to be solved by the present invention]
The problem to be solved by the present invention is to provide a liquid crystal display element capable of high-quality display without causing a flickering problem in an element using a polymer-stabilized ferroelectric liquid crystal.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention
1. In a liquid crystal display element having a unit pixel and a backlight light source configured by sandwiching a liquid crystal layer between a pair of electrodes-attached substrates provided with an alignment control film, the liquid crystal layer is at least liquid-cured (meth) acrylate photocured A voltage at which the orientation angle from the easy axis of the ferroelectric liquid crystal is a constant angle T when no voltage is applied, and the light intensity of the backlight source is applied to the liquid crystal layer. A liquid crystal display element which can be adjusted according to the above.
2. 2. The liquid crystal display element as described in 1 above, wherein the orientation angle T from the easy axis of the ferroelectric liquid crystal when no voltage is applied has an absolute value of 3 degrees or more.
3. Liquid crystalline (meth) acrylate is represented by the general formula (I)
[0007]
[Chemical 3]
(In the formula, X represents a hydrogen atom or a methyl group, n represents an integer of 0 or 1, and the 6-membered rings A, B and C are each independently,
[0009]
[Formula 4]
M represents an integer of 1 to 4, Y 1 and Y 2 are each independently a single bond, —CH 2 CH 2 —, —CH 2 O—, —OCH 2 —, —COO—, — OCO—, —C≡C—, —CH═CH—, —CF═CF—, — (CH 2 ) 4 —, —CH 2 CH 2 CH 2 O—, —OCH 2 CH 2 CH 2 —, —CH ═CH—CH 2 CH 2 —, —CH 2 CH 2 —CH═CH—, Y 3 represents a single bond, —O—, —COO—, —OCO—, Z represents a hydrogen atom, a halogen atom, A cyano group, an alkyl group having 1 to 20 carbon atoms, or an alkenyl group having 2 to 20 carbon atoms is represented. 3. The liquid crystal display element as described in 1 or 2 above, wherein
4). In the general formula (I), X represents a hydrogen atom, n represents 0, the 6-membered rings A and C each independently represent a 1,4-phenylene group or a 1,4-transcyclohexyl group, and Y 1 represents a single bond or —C≡C—, Y 3 represents a single bond, and Z represents a halogen atom, a cyano group, or an alkyl group having 1 to 20 carbon atoms. Display element.
5. 5. The liquid crystal display element as described in any one of 1 to 4 above, which is driven by an active element. 6). 6. The liquid crystal display element as described in any one of 1 to 5 above, wherein the backlight source is a cold cathode tube or a light emitting diode.
Has been found as means for solving the above problems.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An example of the present invention will be described below.
As a result of intensive studies to solve the above problems, the present inventors have found that such problems can be solved by modulating the intensity of the backlight light source, and have provided the present invention.
[0012]
That is, the present invention relates to a liquid crystal display element having a unit pixel and a backlight light source that are configured by sandwiching a liquid crystal layer between a pair of electrodes-attached substrates provided with an alignment control film, and the liquid crystal layer has at least liquid crystallinity (metabolism). ) A photocured product of acrylate and a ferroelectric liquid crystal, the orientation angle from the easy axis of the ferroelectric liquid crystal when no voltage is applied is a constant angle T, and the light intensity of the backlight light source is the liquid crystal Provided is a liquid crystal display element which can be adjusted according to a voltage applied to a layer. In the present invention, the easy axis means an axial direction in which the liquid crystal is easily aligned. For example, when a rubbing method is used as an alignment treatment method, it indicates an axis along the rubbing direction.
[0013]
When the intensity of the backlight light source is constant irrespective of the voltage applied to the liquid crystal layer, the applied voltage-light transmittance characteristic is as shown in FIG. As can be seen from this figure, when a negative voltage is applied, the light transmittance is reduced. In the present invention, when applying a voltage having such a polarity that the light transmittance is reduced, the same light is applied when the same absolute value is applied by increasing the light intensity from the backlight light source. Compensation is made to obtain transmittance. FIG. 2 relates to the liquid crystal display element of the present invention, and is an example of applied voltage-dielectric constant characteristics when the intensity of the backlight light source is increased to 3.5 times that when a positive voltage is applied when a negative voltage is applied. It can be seen that almost good compensation has been made.
[0014]
Such light transmittance compensation by modulating the backlight intensity is particularly effective when the absolute value of the angle T from the easy axis of the liquid crystal molecules when no voltage is applied is 3 degrees or more.
[0015]
The concentration of the photocured liquid crystalline (meth) acrylate compound in the liquid crystal layer is preferably adjusted to 0.1 to 10% by weight, more preferably 0.5 to 7% by weight. 5% by weight is particularly preferred. If the concentration of the liquid crystalline (meth) acrylate photocured product in the liquid crystal layer is lower than 0.1%, the bistability of the ferroelectric liquid crystal does not disappear and halftone display becomes difficult. If it exceeds 10%, the drive voltage increases. The liquid crystalline (meth) acrylate contained in the photocurable composition can be used without particular limitation as long as it is a compound having a liquid crystal skeleton and a polymerizable functional group in the molecule. In order to achieve both driving, it is preferable to use a monofunctional liquid crystal acrylate having no methylene spacer between the polymerizable functional group and the liquid crystal skeleton. Examples of such a compound include the general formula (I)
[0016]
[Chemical formula 5]
(In the formula, X represents a hydrogen atom or a methyl group, n represents an integer of 0 or 1, and the 6-membered rings A, B and C are each independently,
[0018]
[Chemical 6]
M represents an integer of 1 to 4, Y 1 and Y 2 are each independently a single bond, —CH 2 CH 2 —, —CH 2 O—, —OCH 2 —, —COO—, — OCO—, —C≡C—, —CH═CH—, —CF═CF—, — (CH 2 ) 4 —, —CH 2 CH 2 CH 2 O—, —OCH 2 CH 2 CH 2 —, —CH ═CH—CH 2 CH 2 —, —CH 2 CH 2 —CH═CH—, Y 3 represents a single bond, —O—, —COO—, —OCO—, Z represents a hydrogen atom, a halogen atom, A cyano group or an alkyl group or alkenyl group having 1 to 20 carbon atoms is represented. ) Can be mentioned. Among them, in the general formula (I), X represents a hydrogen atom, n represents 0, and the 6-membered rings A and C are each independently a 1,4-phenylene group or 1,4-trans A compound that represents a cyclohexyl group, Y 1 represents a single bond or —C≡C—, Y 3 represents a single bond, and Z represents a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group. Is particularly preferable because it easily develops a liquid crystal phase around room temperature and is easy to handle. A compound in which a pyrimidine ring is introduced into any one of rings A, B, and C can be suitably used because it easily develops a smectic liquid crystal phase and is excellent in compatibility with a ferroelectric liquid crystal. As specific examples of such liquid crystal (meth) acrylate compounds, the compounds listed in the formulas (1) to (21) are preferable, but monofunctional (meta) that can be used in the liquid crystal composition of the present invention. ) Acrylate is not limited to these.
[0020]
[Chemical 7]
[Chemical 8]
[Chemical 9]
(In the above, the cyclohexane ring represents a transcyclohexane ring, C represents a crystalline phase, N represents a nematic phase, S represents a smectic phase, I represents an isotropic liquid phase, and the number represents a phase transition temperature.) Among the compounds, when the compounds (16) and (17) having an optically active group are used, the effect of fine adjustment of the helical pitch and reduction of the driving voltage can be expected, and these can be particularly preferably used.
[0024]
The ferroelectric liquid crystal contained in the liquid crystal layer can be used without particular limitation as long as it is normally recognized as a ferroelectric liquid crystal in this technical field, but the ferroelectric liquid crystal composition is a chiral smectic. It is preferable to use a material exhibiting a smectic A phase and a nematic phase in a temperature region above the C phase.
[0025]
As the alignment control film, a conventionally used polyimide alignment film subjected to rubbing treatment can be used without particular limitation. In addition, an alignment control film which is not subjected to rubbing treatment and which is irradiated with polarized ultraviolet rays on a polyvinyl cinnamate thin film, a polyimide thin film, or the like can also be used.
[0026]
The thickness of the liquid crystal layer depends on the anisotropy of the refractive index of the ferroelectric liquid crystal used, but is preferably 1 to 20 microns, more preferably 1.5 to 10 microns, and 1.5 to 6 Micron is particularly preferred.
[0027]
Since the liquid crystal display element of the present invention does not have bistability, it is preferably driven using an active element. Among active elements, a TFT (thin film transistor) element, a MIM (metal insulator metal) element, A thin film diode or the like is preferable.
[0028]
As the backlight used in the liquid crystal display element of the present invention, a cold cathode tube or a light emitting diode (LED) is preferable. Since this liquid crystal display element uses a ferroelectric liquid crystal with a fast response speed, for example, if the backlight that develops three colors of red, blue, and green is time-divided to modulate the respective emission time and intensity, Colorization is also possible without using a color filter. Of course, even if a white cold cathode fluorescent lamp is used together with a color filter as a backlight, it can be colored without any problem.
[0029]
【Example】
Hereinafter, the present invention will be described in further detail with reference to examples. However, the present invention is not limited to the examples.
(Example)
A polyimide film “RN-1199” (manufactured by Nissan Chemical Industries) having a thickness of 300 Å is formed on a 1.1 mm thick glass substrate on which a rectangular ITO (indium tin oxide) transparent electrode having a length of 1.5 cm and a width of 1 cm is formed. Then, a rubbing treatment was performed to obtain a glass substrate with a polyimide alignment film. The two substrates with the polyimide alignment film thus obtained were made to face each other with an interval of 2.0 microns so that the surface on which the alignment film was formed was on the inside, thereby producing a liquid crystal cell (A). At this time, the rubbing direction of the two substrates constituting the liquid crystal cell was set to be parallel.
[0030]
Next, compound (1)
[0031]
[Chemical Formula 10]
50 parts by weight and compound (4)
[0033]
Embedded image
A liquid crystalline acrylate composition (a) comprising 50 parts by weight and 1 part by weight of a photopolymerization initiator “Irgacure 651” (manufactured by Ciba Geigy) was prepared. This liquid crystalline acrylate composition (a) exhibited a nematic liquid crystal phase at room temperature and had a clearing point of 41 ° C.
[0035]
Next, while maintaining the liquid crystal cell (A) at 80 ° C., a liquid crystal composed of 2% by weight of the prepared liquid crystal acrylate composition (a) and 98% by weight of the ferroelectric liquid crystal “ZLI-4654-100” (manufactured by Merck). The composition was injected. Thereafter, the temperature was lowered to room temperature, and the liquid crystal composition was transferred to the chiral smectic C phase. Next, 60 mJ / cm 2 of ultraviolet rays was irradiated while applying a voltage of 4 V between the transparent electrodes. After UV irradiation, the orientation of the liquid crystal molecules was examined with a polarizing microscope in the absence of applied voltage, and it was found that the liquid crystal molecules were tilted 8 degrees to the right from the easy axis. Next, polarizing films were pasted on both sides of the cell. At this time, the polarization axis of the polarizing film on one side is parallel to the direction tilted 8 degrees to the right from the easy axis, and the polarizing axis of the polarizing film on the other side is perpendicular to the direction tilted 8 degrees to the right from the easy axis. I tried to make. The thus produced element was combined with light emitting diodes of three colors, red, blue and green, and attached as a white backlight. The lighting circuit for the light emitting diodes of these three colors is provided with a synchronizing circuit with the output from the voltage application circuit to the liquid crystal layer so that the output of the light emitting diode can be varied depending on the polarity of the voltage applied to the liquid crystal layer. In contrast to the case where the voltage applied to the liquid crystal layer is positive, in the case where the voltage is negative, the light output of the light emitting diode is set to be 3.6 times, and then the frequency is 20 Hz in the range of positive / negative amplitude from 0 to 4V. When a square wave was applied, it was confirmed that a halftone display without flickering was obtained.
(Comparative example)
In the liquid crystal element manufactured in Example 1, the output from the light emitting diode does not change even if the polarity of the voltage applied to the liquid crystal layer changes by setting the backlight lighting synchronization circuit so as not to function. did. When a square wave having a frequency of 20 Hz with an amplitude ranging from 0 to 4 V in amplitude was applied to the liquid crystal layer, flicker was observed although halftone display was possible.
[0036]
【The invention's effect】
The liquid crystal display element of the present invention is a polymer-stabilized liquid crystal display element that can display halftones and has no display flicker. Therefore, high-quality display can be achieved by combining with active elements.
[Brief description of the drawings]
FIG. 1 shows an example of light transmission characteristics with respect to the voltage of a liquid crystal display element in which the light intensity of a backlight light source does not change according to the voltage applied to the liquid crystal layer.
FIG. 2 shows an example of light transmission characteristics with respect to the voltage of the liquid crystal display element of the present invention in which the light intensity of the backlight light source changes according to the voltage applied to the liquid crystal layer.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12637398A JP4088705B2 (en) | 1998-05-08 | 1998-05-08 | Liquid crystal display element |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12637398A JP4088705B2 (en) | 1998-05-08 | 1998-05-08 | Liquid crystal display element |
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| JPH11326961A JPH11326961A (en) | 1999-11-26 |
| JP4088705B2 true JP4088705B2 (en) | 2008-05-21 |
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| JP12637398A Expired - Fee Related JP4088705B2 (en) | 1998-05-08 | 1998-05-08 | Liquid crystal display element |
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| KR100542082B1 (en) * | 1999-12-20 | 2006-01-10 | 엘지.필립스 엘시디 주식회사 | Method for fabricating a liquid crystal cell |
| KR20010065035A (en) * | 1999-12-21 | 2001-07-11 | 구본준, 론 위라하디락사 | Method for fabrication a liquid crystal display device |
| JP4524827B2 (en) * | 2000-01-17 | 2010-08-18 | 旭硝子株式会社 | Acrylic acid derivative compound |
| GB2360603A (en) * | 2000-03-20 | 2001-09-26 | Cambridge 3D Display Ltd | Planar optical waveguide and float glass process |
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