JP2004091592A - Nematic liquid crystal composition and liquid crystal display device using the same - Google Patents

Abstract

（式中、Ｒ^１〜Ｒ^４はＣ_１〜８のアルキル基等、環Ａ〜Ｇは１，４−シクロへキシレン，１，４−フェニレン，ピリミジン−２，５−ジイル等、Ｚ^１〜Ｚ^６は単結合，−ＣＯＯ−，−ＣＨ_２ＣＨ_２−等を表す。）で表される化合物からそれぞれ１種又は２種以上選ばれる化合物を含有し、なおかつネマチック相−等方性液体相転移温度（Ｔ_Ｎ−Ｉ）が６０℃以上１８０℃以下であり、屈折率の異方性（Δｎ）が０．０６〜０．３０の範囲であることを特徴とする液晶組成物及びこれを用いた液晶ディスプレイ。
【選択図】　なしAn object of the present invention is to provide a liquid crystal composition having a wider temperature range by simultaneously improving the temperature dependency and the frequency dependency of a threshold voltage, and to provide a liquid crystal display using the same which has good display characteristics in a wide temperature range. I do.
The general formula (1), the general formula (2) and the general formula (3)

(Wherein, R ^{1 to} R ⁴ are a C _1-8 alkyl group or the like, rings A to G are 1,4-cyclohexylene, 1,4-phenylene, pyrimidine-2,5-diyl, etc., Z ¹ to Z ⁶ represents a single bond, —COO—, —CH ₂ CH ₂ —, etc.), and contains one or more compounds selected from the group consisting of: a nematic phase and an isotropic liquid phase A liquid crystal composition characterized by having a transition temperature (T _NI ) of 60 ° C. or more and 180 ° C. or less and an anisotropy of refractive index (Δn) in a range of 0.06 to 0.30. The liquid crystal display used.
[Selection diagram] None

Description

（式中、Ｒ^１は炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数２〜８のアルケニル基又は炭素原子数２〜８のアルケニルオキシ基を表し、Ａ及びＢはそれぞれ独立に１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルを表し、ｉは０又は１を表し、Ｚ^１及びＺ^２はそれぞれ独立に単結合、−ＣＨ_２ＣＨ_２−、−ＣＯＯ−、−ＯＣＯ−又は−Ｃ≡Ｃ−を表す。）で表される化合物を１種又は２種以上を含有し、第２成分として、一般式（ＩＩ）
【０００９】
【化８】

（式中、Ｒ^２及びＲ^３はそれぞれ独立に炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数２〜８のアルケニル基、炭素原子数２〜８のアルケニルオキシ基を表し、Ｃ、Ｄ及びＥはそれぞれ独立に１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、２，５−ジフルオロ−１，４−フェニレン、２，３−ジフルオロ−１，４−フェニレン、２−メチル−１，４−フェニレン、３−メチル−１，４−フェニレン、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルを表し、ｊは０又は１を表し、Ｚ^３及びＺ^４はそれぞれ独立に単結合、−ＣＨ_２ＣＨ_２−、−ＣＯＯ−、−ＯＣＯ−、−Ｃ≡Ｃ−、−Ｃ＝Ｃ−、−ＣＦ＝ＣＦ−及び−ＣＨ＝Ｎ−Ｎ＝ＣＨ−を表す。）で表され化合物を１種又は２種以上を含有し、第３成分として、一般式（ＩＩＩ）
【００１０】
【化９】

【００１１】
（式中、Ｒ^４は炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数１〜８のアルコキシアルキル基、炭素原子数２〜８のアルケニル基、炭素原子数２〜８のアルケニルオキシ基を表し、Ｆ及びＧはそれぞれ独立に１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、２，３−ジフルオロ−１，４−フェニレン、２−メチル−１，４−フェニレン、３−メチル−１，４−フェニレン、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルを表し、Ｘ^１及びＸ^３はそれぞれ独立に水素原子、フッ素原子又は塩素原子を表し、Ｘ^２はそれぞれ独立にシアノ基、フッ素原子又は塩素原子を表し、Ｚ^５及びＺ^６はそれぞれ独立に単結合、−ＣＯＯ−、−ＯＣＯ−、−Ｃ≡Ｃ−又は−Ｃ_２Ｈ_４−を表し、ｋは０又は１を表す。）で表される化合物群から選ばれる１種又は２種以上の化合物を含有し、なおかつネマチック相−等方性液体相転移温度（Ｔ_Ｎ−Ｉ）が６０℃以上１８０℃以下であり、屈折率の異方性（Δｎ）が０．０６〜０．３０の範囲であることを特徴とする液晶組成物及びこの液晶組成物を用いた液晶表示素子を提供する。
【００１２】
一般式（Ｉ）の化合物は、ネマチック相上限温度が高く、また、液晶組成物の固体相又はスメクチック相−ネマチック相転移温度を低下させる効果が大きく、さらに、閾値電圧の温度依存性および周波数依存性が小さいが、閾値電圧を低下させる効果は充分に大きくない。そのため、誘電率異方性が比較的大きく、閾値電圧の温度依存性および周波数依存性が小さい一般式（ＩＩＩ）の化合物を同時に使用することにより、所望の閾値電圧を有し、閾値電圧の温度依存性および周波数依存性が小さくなる。さらに、低い粘性を有する一般式（ＩＩ）の化合物を同時に使用することにより、実際の使用に耐えうる粘性を得ることができ、そのうえ電流値を抑制し信頼性を高くすることを可能とする。
【００１３】
液晶表示素子にこのような液晶組成物を使用した場合、例えば１／３２〜１／４００デューティー（ｄｕｔｙ）、より好適には１／８０〜１／２５０デューティーのＳＴＮ−ＬＣＤの表示において特性改善に効果があり、情報量の増加やカラー表示に対して、より改善した高コントラストの液晶表示素子を提供することができる。
【００１４】
【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。
【００１５】
第１成分として一般式（Ｉ）から選ばれる化合物を１種もしくは２種以上を含有するが、１〜１０種が好ましく、１〜５種がさらに好ましい。一般式（Ｉ）において、一般式（Ｉ）の式中、ｉは０又は１を表すが、ｉが０である一般式（Ｉ−ａ）
【００１６】
【化１０】

が好ましい。一般式（Ｉ−ａ）において、Ｒ^１は炭素原子数２〜８のアルキル基、アルコキシル基、アルケニル基又はアルケニルオキシ基を表すが、炭素原子数２〜８のアルキル基又はアルケニル基が好ましい。Ｚ^７は単結合又は−ＣＨ_２ＣＨ_２−を表すが、単結合がより好ましい。Ａは、１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルを表すが、１，４−シクロヘキシレン、１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルが好ましく、１，４−シクロヘキシレン、１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、ピリミジン−２，５−ジイルがより好ましい。
【００１７】
複数種の該化合物を含有することは、所望の屈折率異方性、誘電率異方性、ネマチック相‐等方性液体相転移温度又はコントラストなどを調整するときに特に効果的である。一般式（Ｉ）及び一般式（Ｉ−ａ）の化合物の含有率が５〜５０質量％の範囲であるが、５〜４０質量％の範囲が好ましく、５〜３５質量％がより好ましい。
【００１８】
第２成分として一般式（ＩＩ）
【化１１】

から選ばれる化合物を１種又は２種以上を含有するが、１〜２０種が好ましく、１〜１５種がさらに好ましい。一般式（ＩＩ）は、具体的には、一般式（ＩＩ−ａ）又は一般式（ＩＩ−ｂ）で表される化合物が好ましい。
【化１２】

【００１９】
一般式（ＩＩ−ａ）及び一般式（ＩＩ−ｂ）において、Ｒ^２、Ｒ^３はそれぞれ独立的に炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数２〜８のアルケニル基又は炭素原子数２〜８のアルケニルオキシ基を表すが、炭素原子数１〜８のアルキル基、炭素原子数２〜８のアルケニル基が好ましく、炭素原子数１〜６のアルキル基、炭素原子数２〜６のアルケニル基がより好ましく、１〜５のアルキル基又はアルケニル基として式（ａ）〜（ｅ）が特に好ましい。
【化１３】

（右端にて環と結合しているものとする。）
Ｈ、Ｉ、Ｊはそれぞれ独立に１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、２，６−ジフルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、２−メチル−１，４−フェニレン、３−メチル−１，４−フェニレンを表すが、１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレンが好ましい。Ｋ及びＬはそれぞれ独立に１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、２，６−ジフルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、２−メチル−１，４−フェニレン、３−メチル−１，４−フェニレンを表すが、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、２−メチル−１，４−フェニレン、３−メチル−１，４−フェニレンが好ましい。Ｚ^８は単結合、−ＣＨ_２ＣＨ_２−、−ＣＯＯ−、−ＯＣＯ−、−Ｃ＝Ｃ−、−ＣＦ＝ＣＦ−又は−ＣＨ＝Ｎ−Ｎ＝ＣＨ−を表すが、単結合、−ＣＨ_２ＣＨ_２−、−Ｃ＝Ｃ−又は−ＣＨ＝Ｎ−Ｎ＝ＣＨ−が好ましい。Ｚ^９は単結合、−ＣＨ_２ＣＨ_２−、−ＣＯＯ−又は−ＯＣＯ−を表すが、単結合、−ＣＨ_２ＣＨ_２−又は−ＯＣＯ−が好ましい。
【００２０】
低粘性化により高速応答性を図る場合は、一般式（ＩＩ−ａ）が有用であり、薄セル化に伴う高Δｎを図る場合は、一般式（ＩＩ−ｂ）が有用である。ｊは０又は１を表すが、ネマチック相液晶相の温度範囲を広くする場合は、ｊは１が好ましく、粘性を低下させる場合は、ｊは０であることが好ましい。
【００２１】
一般式（ＩＩ−ａ）の好ましい例は、一般式（ＩＩ−ａ−１）〜一般式（ＩＩ−ａ−１１）で表される化合物である。
【化１４】

（式中、Ｒ^５及びＲ^６はそれぞれ独立的に炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数２〜８のアルケニル基又は炭素原子数２〜８のアルケニルオキシ基を表す）
【００２２】
一般式（ＩＩ−ｂ）の好ましい例は、一般式（ＩＩ−ｂ−１）〜一般式（ＩＩ−ｂ−１５）で表される化合物である。
【化１５】

【００２３】
（式中、Ｒ^５及びＲ^６はそれぞれ独立的に炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数２〜８のアルケニル基又は炭素原子数２〜８のアルケニルオキシ基を表す）
一般式（ＩＩ）、一般式（ＩＩ−ａ）および般式（ＩＩ−ｂ）の化合物の含有率は５〜９０質量％の範囲であるが、５〜８０質量％の範囲が好ましく、１０〜７０質量％がより好ましい。
【００２４】
第３成分として、一般式（ＩＩＩ）から選ばれる化合物を１種又は２種以上を含有するが、２種以上が好ましく、２種〜２０種がさらに好ましく、３種〜１５種が特に好ましい。一般式（ＩＩＩ）は、具体的には、一般式（ＩＩＩ−ａ）又は一般式（ＩＩＩ−ｂ）で表される化合物が好ましい。
【化１６】

【００２５】
一般式（ＩＩＩ−ａ）及び一般式（ＩＩＩ−ｂ）において、Ｒ^４は炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシル基、炭素原子数２〜８のアルケニル基又は炭素原子数２〜８のアルケニルオキシ基を表すが、炭素原子数１〜８のアルキル基、炭素原子数２〜８のアルケニル基が好ましい。Ｆ及びＧはそれぞれ独立に１，４−シクロヘキシレン、１，４−フェニレン、２−フルオロ−１，４−フェニレン、３−フルオロ−１，４−フェニレン、２，５−ジフルオロ−１，４−フェニレン、２，３−ジフルオロ−１，４−フェニレン、２−メチル−１，４−フェニレン、３−メチル−１，４−フェニレン、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルを表すが、１，４−シクロヘキシレン、１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン、ピリミジン−２，５−ジイル、ナフタレン−２，６−ジイル、デカヒドロナフタレン−２，６−ジイル又は１，２，３，４−テトラヒドロナフタレン−２，６−ジイルが好ましく、１，４−シクロヘキシレン、１，４−フェニレン、３−フルオロ−１，４−フェニレン、３，５−ジフルオロ−１，４−フェニレン又はピリミジン−２，５−ジイルがより好ましい。Ｚ^１０は単結合、−ＣＨ_２ＣＨ_２−、−ＣＯＯ−又は−ＯＣＯ−を表すが、単結合又は−ＣＯＯ−が好ましい。Ｘ^１及びＸ^３はそれぞれ独立に水素原子、フッ素原子又は塩素原子を表すが、水素原子又はフッ素原子が好ましい。Ｘ^２はシアノ基、フッ素原子又は塩素原子を表すが、シアノ基又はフッ素原子が好ましい。
一般式（ＩＩＩ）及び一般式（ＩＩＩ−ａ）、（ＩＩＩ−ｂ）の化合物の含有率が５〜５０質量％の範囲であるが、５〜４５質量％の範囲が好ましく、５〜４０質量％の範囲がより好ましい。
【００２６】
この液晶組成物はネマチック相上限温度が６０℃以上であることを特徴とするが、７５℃以上が好ましく、８０℃以上がより好ましく、８５℃以上が特に好ましい。Δｎは０．０６〜０．３０の範囲であることを特徴とするが、０．０８〜０．２２が好ましく、０．１０〜０．２０が更に好ましい範囲であり、０．１２〜０．１８の範囲がＳＴＮ−ＬＣＤのセル厚の設計に特に好ましい。誘電率異方性（Δε）は、３以上４０以下が好ましい。閾値電圧が１．５Ｖ〜１．９Ｖの場合は５≦Δε≦１２の範囲がより好ましく、閾値電圧が１．２Ｖ〜１．６Ｖの場合は８≦Δε≦１６の範囲がより好ましく、閾値電圧が０．８Ｖ〜１．３Ｖの場合は１２≦Δε≦３０の範囲がより好ましい。
【００２７】
本発明の液晶組成物は、上記の化合物以外に、通常のネマチック液晶、スメクチック液晶、コレステリック液晶、２色性色素などを含有していてもよい。又、ＴＮ−ＬＣＤのリバースツイストドメイン防止のためやＳＴＮ−ＬＣＤの螺旋構造を誘起するため、カイラル剤を添加しても良い。カイラル剤は通常市販されているものを使用することができる。例えば、コレステリルノナノエート（ＣＮ）、メルク社製Ｓ−８１１、Ｒ−８１１、ＣＢ−１５、Ｃ−１５などが挙げられる。温度上昇によって誘起螺旋ピッチが長くなるものと短くなるものが知られているが、これらの一方を１種あるいは２種以上を用いても良く、両者を組み合わせて１種あるいは２種以上用いても良い。例えば、ＴＮ−ＬＣＤ、ＳＴＮ−ＬＣＤ、ＴＦＴ−ＬＣＤにおいては、基板間の厚みｄと誘起螺旋ピッチｐの商ｄ／ｐは、０．００１〜２４の範囲から選ぶことができるが、０．０１〜１２の範囲が好ましく、０．１〜２の範囲がより好ましく、０．１〜１．５の範囲が更に好ましく、０．１〜１の範囲が更により好ましく、０．１〜０．８の範囲が特に好ましい。
上記ネマチック液晶組成物はＴＮ−ＬＣＤ、ＳＴＮ−ＬＣＤ、ＯＣＢ−ＬＣＤ、高分子分散型液晶表示素子、フェーズチェンジ型コレステリック液晶表示素子に有用であるが、ＳＴＮ−ＬＣＤに特に有用である。また、透過型あるいは反射型の液晶表示素子に用いることができる。
【００２８】
本発明のＳＴＮ液晶表示素子は目的に応じて、ねじり角を１８０°から２７０°の範囲で選択することができ、２２０°から２６０°が好ましい。本発明の液晶組成物を使用することにより、閾値電圧Ｖｔｈが１．８Ｖ以下で、閾値電圧の温度依存性ｄＶ／ｄＴ（温度：−２０〜６０℃）が２．８ｍＶ／℃以下で、閾値電圧の周波数依存性ｄＶ／ｄＦ（１ｋＨｚ／６４Ｈｚ）が−２０℃において１．０８以下で、急峻性（Ｖｓａｔ／Ｖｔｈ）が１．１０以下（コントラストが４．５以上）である液晶表示素子が得られた。このようなＳＴＮ液晶表示素子は、例えば、１／６０〜１／４００　Ｄｕｔｙ、より好適には１／８０〜１／２５０　Ｄｕｔｙの表示において、温度や周波数の変化による表示品位の悪化が小さく、高いコントラストを有したものである。
【００２９】
【実施例】
以下、実施例を挙げて本発明を更に詳述するが、本発明はこれらの実施例に限定されるものではない。又、以下の実施例及び比較例の組成物における「％」は『質量％』を意味する。
【００３０】
実施例中、測定した特性は以下の通りである。
Ｔ_Ｎ−Ｉ　　　　：ネマチック相−等方性液体相転移温度（℃）
Ｔ_{→ Ｎ}　　　　：固体相又はスメクチック相−ネマチック相転移温度（℃）
Ｖｔｈ　　　　　：２５℃でセル厚８．３μｍのＴＮ−ＬＣＤを構成した時、透過率が１０％変化するのに必要な電圧（Ｖ）
Δｎ　　　　　：複屈折率（２５℃）
η　　　　　　：２５℃での回転粘度（ｍＰａ・ｓ）
ＳＴＮ−ＬＣＤ表示素子の作成は以下のように行った。ネマチック液晶組成物にカイラル物質「Ｓ−８１１」（メルク社製）を添加して混合液晶を調製し、対向する平面透明電極上に「サンエバー１５０」（日産化学社製）の有機膜をラビングして配向膜を形成したツイスト角２４０度のＳＴＮ−ＬＣＤ表示用セルに注入した。なお、カイラル物質はカイラル物質の添加による混合液晶の固有らせんピッチＰと表示用セルのセル厚ｄが、Δｎ・ｄ＝０．９０、ｄ／Ｐ＝０．５０となるように添加した。
【００３１】
Ｖｔｈ（ＳＴＮ）　：２５℃での閾値電圧（透過率が１０％変化するのに必要な電圧）（Ｖ）
Ｖｓａｔ（ＳＴＮ）：２５℃での飽和値電圧（透過率が９０％変化するのに必要な電圧）（Ｖ）
γ　　　：２５℃での急峻性　　Ｖｓａｔ（ＳＴＮ）／Ｖｔｈ（ＳＴＮ）
ＣＲ　　　：２４０°ツイストのＳＴＮ−ＬＣＤに液晶組成物を真空注入し、１／２００　Ｄｕｔｙ、１／１６バイアスの駆動波形で駆動したときのコントラスト
Ｉｒ　　　：２４０°ツイストのＳＴＮ−ＬＣＤに液晶組成物を真空注入し８０℃、１００時間加熱後の電流値（μＡ／ｃｍ^２）
ｄＶ／ｄＴ　　　：−２０〜６０℃における閾値電圧の温度依存性（１ｋＨｚ、ｍＶ／℃）（Ｖｔｈ（−２０℃）−Ｖｔｈ（６０℃））／８０
Ｖｆ比（−２０）　　　：−２０℃における閾値電圧の周波数依存性（Ｖｔｈ（１ｋＨｚ）／Ｖｔｈ（６４Ｈｚ））化合物記載に下記の略号を使用する。
−ｎ　数字　：−Ｃ_ｎＨ_２ｎ＋１　（アルキル側鎖は数字、代表するときはＲとする。）
−Ｏｎ　　　　　：−ＯＣ_ｎＨ_２ｎ＋１
−ｎｄｍ　　　　：−（Ｃ_ｎＨ_２ｎ＋１−ＣＨ＝ＣＨ−（ＣＨ_２）_ｍ−１）
ｎｄｍ−　　　　：Ｃ_ｎＨ_２ｎ＋１−ＣＨ＝ＣＨ−（ＣＨ_２）_ｍ−１−
−Ｏｄ（ｍ）ｎ　：−Ｏ（Ｃ_ｎＨ_２ｎ＋１−ＣＨ＝ＣＨ−（ＣＨ_２）_ｍ−２）
ｄ（ｍ）ｎＯ−　：Ｃ_ｎＨ_２ｎ＋１−ＣＨ＝ＣＨ−（ＣＨ_２）_ｍ−２Ｏ−
連結基
−ＶＯ−　：−ＣＯＯ−　　　　　　　　　　　　　　　　−Ｔ−　　：−Ｃ≡Ｃ−
−２−　　：−ＣＨ_２ＣＨ_２−
置換基
−ＣＮ　　　：−Ｃ≡Ｎ　　　　　　　　　　　−Ｆ　　：−Ｆ
環
Ｐｈ　：１，４−フェニレン基　　　　　　　　　　　　　Ｐｈ１：３−フルオロ−１，４−フェニレン基
Ｐｈ２：３，５−ジフルオロ−１，４−フェニレン基
Ｐｈ３：３−フルオロ−５−クロロ−１，４−フェニレン基
Ｍａ　：ピリミジン−２，５−ジイル基
Ｃｙ　：１，４−シクロヘキシレン基
【００３２】
（実施例１、比較例１、比較例２、比較例３）
ネマチック液晶組成物Ｎｏ．１を調製し、この組成物の諸特性を測定した結果を比較例１と共に表１に示す。
【表１】

【００３３】
実施例１において、一般式（Ｉ−ａ）の化合物に対応する３−Ｃｙ−Ｐｈ３−ＣＮ、一般式（ＩＩ−ａ）及び一般式（ＩＩＩ）に対応する化合物を使用した液晶組成物Ｎｏ．１を作製した。その結果、比較例と比べ、閾値電圧の温度依存性ｄＶ／ｄＴが良好な特性を示しており、閾値電圧の周波数依存性（Ｖｆ比）においても、−２０℃において、より１に近い値となっており周波数による閾値電圧の変化が小さいことがわかる。また、Ｔ_{→ Ｎ}が、比較例より約−１０℃も低下しており、素子の駆動温度範囲が大きく広がっている。比較例１においては、一般式（Ｉ−ａ）を使用しない液晶組成物の結果であるが、コントラストは実施例１と同等の特性が得られているが、室温から−２０℃の閾値電圧の温度依存性ｄＶ／ｄＴ及び閾値電圧の周波数依存性（Ｖｆ比）が大きく悪いものとなっている。さらに、比較例２においては、一般式（Ｉ−ａ）のように末端がフロオロ基、クロル基、シアノ基の３つ置換基ではなく、フルオロ基、フルオロ基、シアノ基の３つの置換基を有する５−Ｐｈ−ＶＯ−Ｐｈ２−ＣＮを使用した場合であるが、ｄＶ／ｄＴは良好な結果を与えているが、（Ｖｆ比）が並びに加熱後の電流値が大きく悪いものとなっている。
【００３４】
（実施例２）
さらに、ネマチック液晶組成物Ｎｏ．２を調製し、これらの組成物の諸特性を測定した結果を表２に示す。
【表２】

【００３５】
実施例２は、優れた閾値電圧の温度依存性、優れた周波数依存性及び広い温度範囲を有し、更に、低粘性、高コントラスト、高信頼性等の諸特性にも優れるものであることがわかる。
【００３６】
【発明の効果】
本発明の液晶材料の組み合わせにより、閾値電圧の温度依存性や周波数依存性を同時に改善し、より広い温度範囲を有するで液晶組成物を提供することができる。本発明の液晶ディスプレイは広い温度範囲で良好な表示特性を達成することを可能にし、情報量の増加やカラー表示に対して、より改善した高コントラストで高信頼性の液晶表示素子を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nematic liquid crystal composition useful as a liquid crystal display material, and a liquid crystal display device using the same.
[0002]
[Prior art]
Among liquid crystal display elements, a twisted nematic liquid crystal display element (hereinafter, referred to as TN-LCD) and a super twisted nematic liquid crystal display element (hereinafter, referred to as STN-LCD) are used as display devices for a wide range of applications. In addition, various characteristics are required in accordance with application development. In a portable terminal display (Personal Digital Assistance), good display characteristics are required in a wider temperature range.
[0003]
One of the important characteristics improvement issues of the TN-LCD and the STN-LCD as described above is improvement in contrast. With the rapid expansion of applications of LCDs, LCDs are not only used indoors, but also used outdoors where temperature conditions are severe, such as displays for computer portable terminals, in-vehicle instruments, and displays used outdoors. Has increased. For this reason, there has been a problem that the display contrast is lowered due to a change in the temperature of the environment in which the LCD is placed, and that the display quality is deteriorated due to the lowering of the contrast at a low temperature and the lowering of the response speed.
[0004]
For portable display terminals, STN-LCDs capable of displaying a large amount of information and exhibiting good display characteristics in a wide operating temperature range are required. On the other hand, a method of reducing the influence of the use temperature by adding an electric temperature compensation circuit to the drive circuit has been performed. However, adding an extra circuit has led to a reduction in yield due to complication of the process and the like. For this reason, it is required that the threshold voltage of the liquid crystal display element be hardly affected by the operating temperature in the operating temperature range. Furthermore, in time-division driving for displaying a large amount of information, it is required that the threshold voltage of the STN-LCD does not fluctuate due to a change in the frequency of the drive voltage depending on the number of time divisions and display contents. That is, there is a demand for an STN-LCD in which the temperature dependence and the frequency dependence of the threshold voltage are simultaneously small in the operating temperature range. If these characteristics can be achieved, it is possible to obtain a good display independent of the placed environmental temperature even under a severe temperature environment such as outdoors. On the other hand, for example, improvement methods such as those disclosed in JP-A-4-296387, JP-A-7-209624, JP-A-9-157654, WO89 / 08102, WO91 / 08184 have been proposed. Japanese Patent Application Laid-Open No. 2000-96059 proposes a method of improving the frequency dependency. However, the degree of simultaneously improving the temperature dependence and the frequency dependence of the threshold voltage of the STN-LCD by these improvement methods cannot be said to be sufficient, and even now, liquid crystal compounds capable of high time-division driving in which these are improved, There is a need for a proposal for a liquid crystal composition or STN-LCD.
[0005]
On the other hand, JP-A-9-202740 discloses a compound represented by the general formula (I), which is an essential component of the present invention, but there is no disclosure of specific physical properties by using this compound. When the compound represented by the general formula (I) is mixed with a specific compound and used as a liquid crystal composition, there is no suggestion that the temperature dependency and the frequency dependency of the threshold voltage are improved.
[0006]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a liquid crystal composition which has improved temperature dependency and frequency dependency of a threshold voltage at the same time and has a liquid crystal stability in a wide low temperature range, and a high contrast liquid crystal using the same. It is to provide a display element.
[0007]
[Means for Solving the Problems]
The present invention has studied liquid crystal compositions using various liquid crystal compounds in order to solve the above-mentioned problems, and as a result, has completed the following invention.
[0008]
As the first component, the general formula (I)
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(Wherein, R ¹ represents an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms or an alkenyloxy group having 2 to 8 carbon atoms, A and B are each independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4- Phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6 -Diyl, i represents 0 or 1, and Z ¹ and Z ² each independently represent a single bond, —CH ₂ CH ₂ —, —COO—, —OCO—, or —C≡C—. One or more compounds represented by Contains two or more kinds, and as a second component, a compound represented by the general formula (II)
[0009]
Embedded image

(Wherein, R ² and R ³ are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, Represents an alkenyloxy group, wherein C, D and E each independently represent 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 5-difluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, pyridine-2,5-diyl, Represents pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, and j is 0 or 1 Represents Z ³ and ^{Z 4} are each independently a single _{bond, -CH 2 CH 2 -, -} COO -, - OCO -, - C≡C -, - C = C -, - CF = CF- and -CH = N- N = CH-), wherein one or more compounds are represented by the general formula (III)
[0010]
Embedded image

[0011]
(Wherein, R ⁴ is an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkoxyalkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a carbon atom Represents an alkenyloxy group of Formulas 2 to 8, wherein F and G each independently represent 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene , 3,5-difluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, pyridine-2,5 - represents diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, ^{X 1} Fine X ³ each independently represent a hydrogen atom, a fluorine atom or a chlorine atom, X ² is independently a cyano group, a fluorine atom or a chlorine atom, Z ⁵ and Z ⁶ single bond independently, -COO- , --OCO -, - C≡C- or _-C 2 _{H 4} - represents, k contains one or more compounds selected from the group of compounds represented by representing) 0 or 1,. In addition, the nematic phase-isotropic liquid phase transition temperature (T _NI ) is 60 ° C. or more and 180 ° C. or less, and the anisotropy (Δn) of the refractive index is in the range of 0.06 to 0.30. Disclosed are a liquid crystal composition and a liquid crystal display device using the liquid crystal composition.
[0012]
The compound of the general formula (I) has a high nematic phase maximum temperature, a large effect of lowering a solid phase or a smectic phase-nematic phase transition temperature of a liquid crystal composition, and further has a temperature dependence and a frequency dependence of a threshold voltage. However, the effect of lowering the threshold voltage is not sufficiently large. Therefore, by simultaneously using the compound of the general formula (III) having a relatively large dielectric anisotropy and a small temperature dependency and a small frequency dependency of the threshold voltage, the compound has a desired threshold voltage, The dependence and the frequency dependence are reduced. Furthermore, by simultaneously using the compound of the general formula (II) having a low viscosity, it is possible to obtain a viscosity that can withstand actual use, and furthermore, it is possible to suppress a current value and increase reliability.
[0013]
When such a liquid crystal composition is used in a liquid crystal display device, for example, the characteristic is improved in the display of an STN-LCD having a duty of 1/32 to 1/400, more preferably 1/80 to 1/250. It is possible to provide a liquid crystal display element having an effect and an improved high contrast with respect to an increase in the amount of information and color display.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of the present invention will be described.
[0015]
One or more compounds selected from the general formula (I) are contained as the first component, but 1 to 10 are preferable, and 1 to 5 are more preferable. In the general formula (I), in the general formula (I), i represents 0 or 1, and the general formula (Ia) in which i is 0
[0016]
Embedded image

Is preferred. In the general formula (Ia), R ¹ represents an alkyl group having 2 to 8 carbon atoms, an alkoxyl group, an alkenyl group or an alkenyloxy group, preferably an alkyl group or an alkenyl group having 2 to 8 carbon atoms. Z ⁷ represents a single bond or _-CH 2 CH ₂ - represents a single bond is more preferable. A is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, pyridine- Represents 2,5-diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl Is 1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, naphthalene-2,6 -Diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl is preferred, and 1,4-cyclohexylene, Ren, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, pyrimidine-2,5-diyl are more preferable.
[0017]
The inclusion of a plurality of such compounds is particularly effective when adjusting the desired refractive index anisotropy, dielectric anisotropy, nematic phase-isotropic liquid phase transition temperature or contrast. The content of the compounds of the general formulas (I) and (Ia) is in the range of 5 to 50% by mass, preferably in the range of 5 to 40% by mass, and more preferably in the range of 5 to 35% by mass.
[0018]
General formula (II) as the second component
Embedded image

The compound contains one or more compounds selected from the group consisting of, but preferably 1 to 20, and more preferably 1 to 15. Specifically, the compound represented by formula (II) is preferably a compound represented by formula (II-a) or (II-b).
Embedded image

[0019]
In the general formulas (II-a) and (II-b), R ² and R ³ each independently represent an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, or a carbon atom. Represents an alkenyl group having 2 to 8 carbon atoms or an alkenyloxy group having 2 to 8 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, and preferably having 1 to 6 carbon atoms. Alkyl groups and alkenyl groups having 2 to 6 carbon atoms are more preferable, and formulas (a) to (e) are particularly preferable as the alkyl group or alkenyl group having 1 to 5 carbon atoms.
Embedded image

(It shall be connected to the ring at the right end.)
H, I, and J each independently represent 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro-1, Represents 4-phenylene, 3,5-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, but 1,4-cyclohexylene, 1,4- Phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene are preferred. K and L are each independently 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, 3,5-difluoro Represents 1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, but 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro- 1,4-phenylene, 2-methyl-1,4-phenylene and 3-methyl-1,4-phenylene are preferred. Z ⁸ represents a single _{bond, -CH 2 CH 2 -, -} COO -, - OCO -, - C = C -, - CF = CF- or represents a -CH = N-N = CH-, a single bond, - _{CH 2 CH 2 -, - C} = C- or -CH = N-N = CH- are preferred. Z ⁹ represents a single _bond, -CH ₂ CH 2 -, - COO- or -OCO- represents a single bond, _-CH 2 CH ₂ - or -OCO- are preferred.
[0020]
The general formula (II-a) is useful for achieving high-speed response by reducing the viscosity, and the general formula (II-b) is useful for achieving a high Δn accompanying thinning of cells. j represents 0 or 1, but j is preferably 1 when the temperature range of the nematic phase liquid crystal phase is widened, and j is preferably 0 when the viscosity is reduced.
[0021]
Preferred examples of the general formula (II-a) are compounds represented by the general formulas (II-a-1) to (II-a-11).
Embedded image

(Wherein, R ⁵ and R ⁶ are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms or 2 to 8 carbon atoms. Represents an alkenyloxy group)
[0022]
Preferred examples of the general formula (II-b) are compounds represented by the general formulas (II-b-1) to (II-b-15).
Embedded image

[0023]
(Wherein, R ⁵ and R ⁶ are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms or 2 to 8 carbon atoms. Represents an alkenyloxy group)
The content of the compounds of the general formulas (II), (II-a) and (II-b) is in the range of 5 to 90% by mass, preferably 5 to 80% by mass, 70 mass% is more preferable.
[0024]
As the third component, one or more compounds selected from the general formula (III) are contained, but two or more are preferable, 2 to 20 are more preferable, and 3 to 15 are particularly preferable. Specifically, the compound represented by formula (III) is preferably a compound represented by formula (III-a) or (III-b).
Embedded image

[0025]
In the general formulas (III-a) and (III-b), R ⁴ is an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or It represents an alkenyloxy group having 2 to 8 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms and an alkenyl group having 2 to 8 carbon atoms. F and G are each independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,5-difluoro-1,4- Phenylene, 2,3-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, Represents naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, but 1,4-cyclohexylene, 1,4-phenylene , 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene- , 6-Diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl is preferred, and 1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5 -Difluoro-1,4-phenylene or pyrimidine-2,5-diyl is more preferred. Z ¹⁰ is a single _{bond, -CH 2 CH 2 -, -} COO- or represents a -OCO-, single bond or -COO- are preferred. X ¹ and X ³ each independently represent a hydrogen atom, a fluorine atom or a chlorine atom, preferably a hydrogen atom or a fluorine atom. X ² represents a cyano group, a fluorine atom or a chlorine atom, preferably a cyano group or a fluorine atom.
The content of the compounds of the general formulas (III) and (III-a) and (III-b) is in the range of 5 to 50% by mass, preferably 5 to 45% by mass, and 5 to 40% by mass. % Is more preferable.
[0026]
This liquid crystal composition is characterized in that the maximum temperature of the nematic phase is 60 ° C. or higher, preferably 75 ° C. or higher, more preferably 80 ° C. or higher, and particularly preferably 85 ° C. or higher. Δn is in the range of 0.06 to 0.30, preferably 0.08 to 0.22, more preferably 0.10 to 0.20, and 0.12 to 0.20. A range of 18 is especially preferred for STN-LCD cell thickness designs. The dielectric anisotropy (Δε) is preferably 3 or more and 40 or less. When the threshold voltage is 1.5 V to 1.9 V, the range of 5 ≦ Δε ≦ 12 is more preferable, and when the threshold voltage is 1.2 V to 1.6 V, the range of 8 ≦ Δε ≦ 16 is more preferable. Is 0.8 V to 1.3 V, the range of 12 ≦ Δε ≦ 30 is more preferable.
[0027]
The liquid crystal composition of the present invention may contain a normal nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal, a dichroic dye, and the like, in addition to the above compounds. In addition, a chiral agent may be added to prevent a reverse twist domain of the TN-LCD and to induce a helical structure of the STN-LCD. As the chiral agent, a commercially available chiral agent can be used. For example, cholesteryl nonanoate (CN), S-811, R-811, CB-15, C-15 manufactured by Merck, and the like can be mentioned. It is known that the induced helical pitch becomes longer and shorter as the temperature rises, but one or two or more of these may be used, or one or two or more of them may be used in combination. good. For example, in TN-LCD, STN-LCD, and TFT-LCD, the quotient d / p of the thickness d between the substrates and the induced helical pitch p can be selected from the range of 0.001 to 24, but is 0.01 to 0.01. To 12, preferably 0.1 to 2, more preferably 0.1 to 1.5, even more preferably 0.1 to 1, more preferably 0.1 to 0.8. Is particularly preferred.
The nematic liquid crystal composition is useful for TN-LCDs, STN-LCDs, OCB-LCDs, polymer dispersed liquid crystal display devices, and phase-change cholesteric liquid crystal display devices, but is particularly useful for STN-LCDs. Further, it can be used for a transmissive or reflective liquid crystal display device.
[0028]
The twist angle of the STN liquid crystal display device of the present invention can be selected from the range of 180 ° to 270 °, and preferably from 220 ° to 260 °. By using the liquid crystal composition of the present invention, the threshold voltage Vth is 1.8 V or less, the temperature dependence dV / dT (temperature: −20 to 60 ° C.) of the threshold voltage is 2.8 mV / ° C. or less, A liquid crystal display device having a frequency dependence dV / dF (1 kHz / 64 Hz) of 1.08 or less at −20 ° C. and a steepness (Vsat / Vth) of 1.10 or less (contrast of 4.5 or more) at −20 ° C. Obtained. In such an STN liquid crystal display element, for example, in display of 1/60 to 1/400 Duty, more preferably 1/80 to 1/250 Duty, deterioration of display quality due to changes in temperature and frequency is small and high. It has contrast.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Further, “%” in the compositions of the following Examples and Comparative Examples means “% by mass”.
[0030]
The characteristics measured in the examples are as follows.
T _NI : Nematic phase-isotropic liquid phase transition temperature (° C.)
T _{→ N} : solid phase or smectic phase-nematic phase transition temperature (° C.)
Vth: voltage (V) required for 10% change in transmittance when a TN-LCD having a cell thickness of 8.3 μm is formed at 25 ° C.
Δn: birefringence (25 ° C.)
η: rotational viscosity at 25 ° C. (mPa · s)
The STN-LCD display element was prepared as follows. A chiral substance “S-811” (manufactured by Merck) is added to the nematic liquid crystal composition to prepare a mixed liquid crystal, and an organic film of “San Ever 150” (manufactured by Nissan Chemical Industries) is rubbed on the opposed flat transparent electrode. It was injected into a STN-LCD display cell having a twist angle of 240 degrees on which an alignment film was formed. The chiral substance was added so that the intrinsic helical pitch P of the mixed liquid crystal and the cell thickness d of the display cell by the addition of the chiral substance were Δn · d = 0.90 and d / P = 0.50.
[0031]
Vth (STN): threshold voltage at 25 ° C. (voltage required for 10% change in transmittance) (V)
Vsat (STN): Saturation voltage at 25 ° C. (voltage required for 90% change in transmittance) (V)
γ: steepness at 25 ° C. Vsat (STN) / Vth (STN)
CR: A liquid crystal composition was vacuum-injected into a 240 ° twisted STN-LCD and driven by a 1/200 duty, 1/16 bias driving waveform. Ir: The liquid crystal composition was injected into a 240 ° twisted STN-LCD. Current value after vacuum injection and heating at 80 ° C for 100 hours (μA / cm ² )
dV / dT: temperature dependence of threshold voltage at −20 to 60 ° C. (1 kHz, mV / ° C.) (Vth (−20 ° C.) − Vth (60 ° C.)) / 80
Vf ratio (−20): Frequency dependency of threshold voltage at −20 ° C. (Vth (1 kHz) / Vth (64 Hz)) The following abbreviations are used to describe compounds.
-N numbers: _-C n _{H 2n + 1} (alkyl side chains numbers, when representative and R.)
-On: _-OC n _{H 2n + 1
-Ndm :-( C n H 2n + 1} -CH = CH- (CH 2) m-1)
_{ndm-: C n H 2n + 1} -CH = CH- (CH 2) m-1 -
_{-Od (m) n: -O (} C n H 2n + 1 -CH = CH- (CH 2) m-2)
_{d (m) nO-: C n} H 2n + 1 -CH = CH- (CH 2) m-2 O-
Linking group -VO-: -COO- -T-: -C≡C-
-2-: _{-CH 2} CH 2 -
Substituent -CN: -C≡N -F: -F
Ring Ph: 1,4-phenylene group Ph1: 3-fluoro-1,4-phenylene group Ph2: 3,5-difluoro-1,4-phenylene group Ph3: 3-fluoro-5-chloro-1,4-phenylene Group Ma: pyrimidine-2,5-diyl group Cy: 1,4-cyclohexylene group
(Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3)
Nematic liquid crystal composition No. Table 1 shows the results of measuring various properties of this composition together with Comparative Example 1.
[Table 1]

[0033]
In Example 1, 3-Cy-Ph3-CN corresponding to the compound of the general formula (Ia), and the liquid crystal composition No. 1 using the compound corresponding to the general formula (II-a) and the general formula (III). 1 was produced. As a result, as compared with the comparative example, the temperature dependency dV / dT of the threshold voltage shows good characteristics, and the frequency dependency (Vf ratio) of the threshold voltage is closer to 1 at -20 ° C. It can be seen that the change in the threshold voltage due to the frequency is small. In addition, T _{→ N} is lower by about −10 ° C. than that of the comparative example, and the driving temperature range of the element is greatly expanded. Comparative Example 1 is a result of a liquid crystal composition not using the general formula (Ia). The contrast is similar to that of Example 1, but the threshold voltage is from room temperature to −20 ° C. The temperature dependence dV / dT and the frequency dependence of the threshold voltage (Vf ratio) are significantly poor. Furthermore, in Comparative Example 2, instead of three substituents having a terminal of a fluoro group, a chloro group, and a cyano group as in the general formula (Ia), three substituents of a fluoro group, a fluoro group, and a cyano group were used. In the case where 5-Ph-VO-Ph2-CN is used, dV / dT gives good results, but (Vf ratio) and the current value after heating are large and poor. .
[0034]
(Example 2)
Further, the nematic liquid crystal composition No. Table 2 shows the results of measuring the properties of these compositions.
[Table 2]

[0035]
Example 2 has excellent temperature dependence of threshold voltage, excellent frequency dependence and a wide temperature range, and also has excellent characteristics such as low viscosity, high contrast, and high reliability. Understand.
[0036]
【The invention's effect】
By the combination of the liquid crystal materials of the present invention, the temperature dependency and the frequency dependency of the threshold voltage can be simultaneously improved, and a liquid crystal composition having a wider temperature range can be provided. The liquid crystal display of the present invention makes it possible to achieve good display characteristics over a wide temperature range, and to provide a liquid crystal display element with improved high contrast and high reliability for an increase in the amount of information and color display. Can be.

Claims (9)

As the first component, the general formula (I)

(Wherein, R ¹ represents an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms or an alkenyloxy group having 2 to 8 carbon atoms, A and B are each independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4- Phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6 -Diyl, i represents 0 or 1, and Z ¹ and Z ² each independently represent a single bond, —CH ₂ CH ₂ —, —COO—, —OCO—, or —C≡C—. One or more compounds represented by Contains two or more kinds, and as a second component, a compound represented by the general formula (II)

(Wherein, R ² and R ³ are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, Represents an alkenyloxy group, wherein C, D and E each independently represent 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 5-difluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, pyridine-2,5-diyl, Represents pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, and j is 0 or 1 Represents Z ³ and ^{Z 4} are each independently a single _{bond, -CH 2 CH 2 -, -} COO -, - OCO -, - C≡C -, - C = C -, - CF = CF- and -CH = N- N = CH-), wherein one or more compounds are represented by the general formula (III)

(Wherein, R ⁴ is an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkoxyalkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a carbon atom Represents an alkenyloxy group of Formulas 2 to 8, wherein F and G each independently represent 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene , 3,5-difluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, pyridine-2,5 - represents diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, ^{X 1} Fine X ³ each independently represent a hydrogen atom, a fluorine atom or a chlorine atom, X ² is independently a cyano group, a fluorine atom or a chlorine atom, Z ⁵ and Z ⁶ single bond independently, -COO- , --OCO -, - C≡C- or _-C 2 _{H 4} - represents, k contains one or more compounds selected from the group of compounds represented by representing) 0 or 1,. In addition, the nematic phase-isotropic liquid phase transition temperature (T _NI ) is 60 ° C. or more and 180 ° C. or less, and the anisotropy (Δn) of the refractive index is in the range of 0.06 to 0.30. Characteristic liquid crystal composition. The compound of the general formula (I) has a content of 5 to 50% by mass, the compound of the general formula (II) has a content of 5 to 90% by mass, and the compound of the general formula (III) The liquid crystal composition according to claim 1, wherein the content of is in the range of 5 to 50% by mass. General formula (Ia) as general formula (I)

(Wherein, R ¹ represents an alkyl group having 2 to 8 carbon atoms, an alkoxyl group, an alkenyl group or an alkenyloxy group, and A represents 1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1, 4-phenylene, 3,5-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4- (It represents tetrahydronaphthalene-2,6-diyl, and Z ⁷ each independently represents a single bond or —CH ₂ CH ₂ —.)
The liquid crystal composition according to claim 1, comprising a compound represented by the formula: General formula (II-a) or general formula (II-b) as general formula (II)

(Wherein, R ² and R ³ are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, Represents an alkenyloxy group, and H, I and J each independently represent 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, Represents 6-difluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, and K and L are each independently 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene , 2- It represents chill-1,4-phenylene or 3-methyl-1,4-phenylene, ^{Z 8} represents a single bond, -CH2CH2 -, - COO -, - OCO -, - C = C -, - CF = CF- or represents -CH = N-N = CH-, Z 9 represents a single _bond, -CH ₂ CH _{2 -,} - represents COO- or -OCO-, claim 1 j is containing represents) 0 or 1. 4. The liquid crystal composition according to any one of items 1 to 3. General formula (III-a) or general formula (III-b) as general formula (III)

(Wherein, R ⁴ represents an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkenyloxy group having 2 to 8 carbon atoms, F and G are each independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4- Phenylene, 2,3-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, Represents naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, Z ¹⁰ represents a single bond, —CH ₂ CH ₂ —, -COO Or an -OCO-, ^{X 1} and ^{X 3} each independently represents a hydrogen atom, a fluorine atom or a chlorine atom, ^{X 2} is claim 1 containing represents.) A cyano group, a fluorine atom or a chlorine atom The liquid crystal composition according to any one of the above. The liquid crystal composition according to claim 1, having a dielectric anisotropy (Δε) of 3 or more and 40 or less. A liquid crystal display device using the liquid crystal composition according to claim 1. A super-twisted nematic (STN) liquid crystal display device using the liquid crystal composition according to claim 1 and having a twist angle of 180 ° to 270 °. A twisted nematic (TN) liquid crystal display device using the liquid crystal composition according to claim 1 and having a twist angle of 80 ° to 130 °.