JPH05142519A - Liquid crystal display device - Google Patents
Liquid crystal display deviceInfo
- Publication number
- JPH05142519A JPH05142519A JP30307891A JP30307891A JPH05142519A JP H05142519 A JPH05142519 A JP H05142519A JP 30307891 A JP30307891 A JP 30307891A JP 30307891 A JP30307891 A JP 30307891A JP H05142519 A JPH05142519 A JP H05142519A
- Authority
- JP
- Japan
- Prior art keywords
- liquid crystal
- ferroelectric liquid
- display device
- crystal display
- ferroelectric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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- Liquid Crystal (AREA)
- Liquid Crystal Display Device Control (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は１対の基板間に強誘電
性液晶を保持する強誘電性液晶素子からなる液晶表示装
置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device comprising a ferroelectric liquid crystal element holding a ferroelectric liquid crystal between a pair of substrates.
【０００２】[0002]
【従来の技術】強誘電性液晶は高速応答性、メモリ性等
の優れた特性をもっているため、従来より多くの研究が
なされ、その実用化が図られている。強誘電性液晶を用
いた液晶表示素子においては、その応答が印加電圧の極
性に依存するため、ネマティック液晶を用いた液晶表示
素子の場合のような交流駆動を行なうことはできず、所
望の表示特性たとえば明表示（白表示）、暗表示（黒表
示）を得るためには、正負いずれかの極性の電圧パルス
を印加する必要がある。しかしながら、液晶表示素子に
おいて、正負いずれかの電圧のみを印加することは、液
晶に対して直流電圧を印加することになり、液晶の電気
分解、不純物イオンの蓄積等による表示特性の劣化を生
じさせることとなる。そこで、多くの場合、所望の極性
の電圧パルスの前にその逆極性のパルスを印加する双極
性パルスによる駆動が行なわれている。2. Description of the Related Art Ferroelectric liquid crystals have excellent characteristics such as high-speed response and memory properties, and therefore, more research has been conducted than before and their practical application is being pursued. In a liquid crystal display element using a ferroelectric liquid crystal, the response depends on the polarity of the applied voltage, and therefore AC drive cannot be performed as in a liquid crystal display element using a nematic liquid crystal, and the desired display In order to obtain characteristics such as bright display (white display) and dark display (black display), it is necessary to apply a voltage pulse of either positive or negative polarity. However, in the liquid crystal display element, if only positive or negative voltage is applied, a direct current voltage is applied to the liquid crystal, which causes deterioration of display characteristics due to electrolysis of the liquid crystal, accumulation of impurity ions, and the like. It will be. Therefore, in many cases, driving is performed by a bipolar pulse in which a pulse having a reverse polarity is applied before a voltage pulse having a desired polarity.
【０００３】[0003]
【発明が解決しようとする課題】しかし、双極性パルス
を印加したときには、必ずいったんは逆の表示が成され
るため、表示素子としてはフリッカの発生、光デバイス
としての応用ではクロストークの発生、ＳＮ比の低下等
による表示特性の劣化が生ずる。また、パルス電圧印加
の場合には、電圧無印加時において実効的なチルト角が
低下するために、コントラスト比の低下が問題となって
いる。However, when a bipolar pulse is applied, the display is always reversed, so that flicker occurs as a display element and crosstalk occurs as an application as an optical device. Display characteristics are deteriorated due to a decrease in SN ratio or the like. In addition, in the case of applying a pulse voltage, the effective tilt angle is reduced when no voltage is applied, so that the contrast ratio is reduced.
【０００４】この発明は上述の課題を解決するためにな
されたもので、表示特性の劣化が生ずることがなく、コ
ントラスト比が大きい液晶表示装置を提供することを目
的としている。The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device having a large contrast ratio without deterioration of display characteristics.
【０００５】[0005]
【課題を解決するための手段】この目的を達成するた
め、この発明においては、１対の基板間に強誘電性液晶
を保持しかつそれぞれ独立に駆動が可能である強誘電性
液晶素子を２層積層し、上記強誘電性液晶素子には表示
データに応じて同相あるいは逆相の交流信号を印加す
る。To achieve this object, the present invention provides a ferroelectric liquid crystal element which holds a ferroelectric liquid crystal between a pair of substrates and can be driven independently of each other. A plurality of layers are stacked, and an in-phase or anti-phase alternating current signal is applied to the ferroelectric liquid crystal element according to display data.
【０００６】この場合、２層の上記強誘電性液晶素子を
挾んで偏光板を設け、上記偏光板をクロスニコル状態に
してもよい。In this case, a polarizing plate may be provided by sandwiching the two-layered ferroelectric liquid crystal element, and the polarizing plate may be in a crossed Nicols state.
【０００７】また、２層の上記強誘電性液晶素子の配向
方向を一致させ、少なくとも一方の上記偏光板の偏光軸
を上記強誘電性液晶素子の強誘電性液晶分子の電圧印加
時の配向方向と平行としてもよい。Further, the alignment directions of the two layers of the ferroelectric liquid crystal element are made to coincide with each other, and the polarization axis of at least one of the polarizing plates is set to the alignment direction of the ferroelectric liquid crystal molecules of the ferroelectric liquid crystal element when a voltage is applied. It may be parallel to.
【０００８】また、上記強誘電性液晶素子のチルト角を
約４５°としてもよい。The tilt angle of the ferroelectric liquid crystal element may be about 45 °.
【０００９】[0009]
【作用】この液晶表示装置においては、印加電圧を同相
とするか逆相とするかで明暗表示が可能となるから、交
流駆動が可能であり、また連続した電圧印加によっても
表示が反転することはなく、さらに連続した電圧印加に
より安定した実効的チルト角が確保できる。In this liquid crystal display device, bright and dark display can be performed by changing the applied voltage to the same phase or opposite phase, so that it can be driven by alternating current, and the display can be reversed by continuous voltage application. In addition, a stable effective tilt angle can be secured by applying a continuous voltage.
【００１０】[0010]
【実施例】以下、この発明の実施例を図を用いて説明す
る。Embodiments of the present invention will be described below with reference to the drawings.
【００１１】図１はこの発明に係る液晶表示装置の概略
を示す構成図である。この液晶表示装置においては、同
一構成の強誘電性液晶素子１１、１２が積層されてお
り、強誘電性液晶素子１１、１２の対応する各画素は位
置合わせがなされており、この液晶表示装置に入射する
光は２つの画素を通過して光学的作用を受けることにな
る。ここで、強誘電性液晶素子１１、１２は通常の液晶
表示素子から偏光板を除いたものであり、１対のガラス
基板、各々のガラス基板上に設けられた透明電極、透明
電極間に保持された強誘電性液晶、セル厚を保つスペー
サ、強誘電性液晶を配向させる配向膜等から構成されて
おり、強誘電性液晶素子１１、１２の強誘電性液晶分子
のチルト角は４５°である。また、強誘電性液晶素子１
１、１２を挾んで偏光板１３、１４が設けられており、
偏光板１３、１４はクロスニコル状態をとっている。そ
して、強誘電性液晶素子１１、１２は配向方向が一致す
るように配置され、図２(ａ)、(ｂ)に示すように、強誘
電性液晶素子１１、１２の強誘電性液晶分子２３、２４
の電圧印加時の２つの安定位置は入力光に対して重なる
ように配置されており、さらに２つの安定位置の一方は
クロスニコル状態にある偏光板１３、１４の偏光軸２
１、２２の１つと一致するように配置されている。そし
て、液晶表示素子１１、１２に同相の交流電圧（矩形波
電圧）を印加した場合には、液晶表示装置としての実効
的なチルト角は１層の強誘電性液晶素子１１、１２の真
のチルト角と一致するが、液晶表示素子１１、１２に逆
相の電圧を印加した場合には、実効的なチルト角は真の
チルト角の半分になる。FIG. 1 is a block diagram showing the outline of a liquid crystal display device according to the present invention. In this liquid crystal display device, ferroelectric liquid crystal elements 11 and 12 having the same structure are laminated, and corresponding pixels of the ferroelectric liquid crystal elements 11 and 12 are aligned. The incident light passes through the two pixels and is optically affected. Here, the ferroelectric liquid crystal elements 11 and 12 are obtained by removing a polarizing plate from a normal liquid crystal display element, and include a pair of glass substrates, a transparent electrode provided on each glass substrate, and a space between the transparent electrodes. The ferroelectric liquid crystal molecules of the ferroelectric liquid crystal elements 11 and 12 have a tilt angle of 45 °. is there. In addition, the ferroelectric liquid crystal element 1
Polarizing plates 13 and 14 are provided sandwiching 1 and 12,
The polarizing plates 13 and 14 are in a crossed Nicol state. Then, the ferroelectric liquid crystal elements 11 and 12 are arranged so that the alignment directions thereof coincide with each other. As shown in FIGS. 2A and 2B, the ferroelectric liquid crystal molecules 23 of the ferroelectric liquid crystal elements 11 and 12 are arranged. , 24
The two stable positions when the voltage is applied are arranged so as to overlap with the input light, and one of the two stable positions is the polarization axis 2 of the polarizing plates 13 and 14 in the crossed Nicols state.
It is arranged so as to coincide with one of Nos. 1 and 22. When an in-phase alternating voltage (rectangular wave voltage) is applied to the liquid crystal display elements 11 and 12, the effective tilt angle of the liquid crystal display device is the true tilt angle of the one-layer ferroelectric liquid crystal elements 11 and 12. Although it matches the tilt angle, the effective tilt angle becomes half of the true tilt angle when a voltage of opposite phase is applied to the liquid crystal display elements 11 and 12.
【００１２】ところで、液晶表示装置においては、偏光
板がクロスニコル状態のとき、液晶セル厚をｄ、チルト
角をθ、屈折率異方性をΔｎ、透過光の波長をλとする
と、透過光強度Ｉは次式で表される。In the liquid crystal display device, when the polarizing plate is in the crossed Nicols state, if the liquid crystal cell thickness is d, the tilt angle is θ, the refractive index anisotropy is Δn, and the wavelength of the transmitted light is λ, then the transmitted light is The intensity I is expressed by the following equation.
【００１３】 Ｉ＝Ｉ0・sin2４θ・sin2(π・Δｎ・ｄ／λ) (１) (１)式より複屈折モードではチルト角θが２２.５°の
ときにコントラスト比が最大になることがわかる。I = I 0 · sin 2 4θ · sin 2 (π · Δn · d / λ) (1) From the equation (1), the maximum contrast ratio is obtained when the tilt angle θ is 22.5 ° in the birefringence mode. It turns out that
【００１４】このため、印加電圧が同相の場合には、実
効的なチルト角は４５°となるから、強誘電性液晶分子
２３、２４の安定点の移動量は９０°となり、しかも強
誘電性液晶分子２３、２４の電圧印加時の２つの安定位
置は入力光に対して重なるように配置されており、さら
に２つの安定位置の一方は偏光軸２１、２２の１つと一
致するように配置されているから、安定位置のもう一方
も偏光軸２１、２２のもう一方と一致する。したがっ
て、印加電圧が同相の場合には、図２(ａ)、(ｂ)に示す
ように、印加電圧の正負に関わらず、強誘電性液晶分子
２３、２４は常に同じ偏光軸２１、２２上にあるから、
光学的な透過特性は変化せず、暗状態となる。一方、印
加電圧が逆相の場合には、その実効的なチルト角は２
２.５°となるから、上記複屈折モードにおける最適チ
ルト角となるので、明状態をとり続けることになる。す
なわち、図２(ｃ)、(ｄ)に示すように、２層の強誘電性
液晶分子２３、２４は常に反対側の偏光軸２１、２２と
一致するように動くから、実効的な強誘電性液晶分子２
３、２４の位置は常に２つの偏光軸２１、２２の中間に
あるので、明状態となる。Therefore, when the applied voltages are in phase, the effective tilt angle is 45 °, so that the amount of movement of the stable points of the ferroelectric liquid crystal molecules 23 and 24 is 90 °, and the ferroelectricity is high. The two stable positions of the liquid crystal molecules 23 and 24 when a voltage is applied are arranged so as to overlap with the input light, and one of the two stable positions is arranged to coincide with one of the polarization axes 21 and 22. Therefore, the other stable position also coincides with the other polarization axes 21 and 22. Therefore, when the applied voltages are in phase, as shown in FIGS. 2 (a) and 2 (b), the ferroelectric liquid crystal molecules 23 and 24 are always on the same polarization axes 21 and 22 regardless of whether the applied voltage is positive or negative. Because
The optical transmission characteristics do not change, and a dark state is set. On the other hand, when the applied voltage has a reverse phase, the effective tilt angle is 2
Since it is 2.5 °, the optimum tilt angle in the above-mentioned birefringence mode is obtained, so that the bright state is maintained. That is, as shown in FIGS. 2C and 2D, since the two layers of ferroelectric liquid crystal molecules 23 and 24 always move so as to match the polarization axes 21 and 22 on the opposite side, the effective ferroelectric Liquid crystal molecule 2
Since the positions of 3 and 24 are always in the middle of the two polarization axes 21 and 22, they are in the bright state.
【００１５】したがって、図３に示すように、２層の強
誘電性液晶素子１１、１２に同相の信号を印加したとき
には、透過光量は小となって、暗状態をとり、また２層
の強誘電性液晶素子１１、１２に逆相の信号を印加した
ときには、透過光量は大となって、明状態をとる。この
ため、強誘電性液晶素子に表示データに応じて同相ある
いは逆相の交流電圧を印加すれば、データを表示するこ
とができる。また、強誘電性液晶素子１１、１２には正
負の連続電圧が印加されており、交流駆動が可能であ
る。Therefore, as shown in FIG. 3, when signals of the same phase are applied to the two-layered ferroelectric liquid crystal elements 11 and 12, the amount of transmitted light becomes small and a dark state is obtained, and the two-layered ferroelectric liquid crystal elements are strong. When signals of opposite phases are applied to the dielectric liquid crystal elements 11 and 12, the amount of transmitted light becomes large and a bright state is obtained. Therefore, data can be displayed by applying in-phase or anti-phase AC voltage to the ferroelectric liquid crystal element according to the display data. Further, positive and negative continuous voltages are applied to the ferroelectric liquid crystal elements 11 and 12, and AC driving is possible.
【００１６】このように、強誘電性液晶素子１１、１２
への印加電圧を同相とするか逆相とするかで明暗表示が
可能となるから、交流駆動が可能であるので、強誘電性
液晶素子１１、１２の液晶の電気分解、不純物イオンの
蓄積等による表示特性の劣化が生ずることはなく、また
連続した電圧印加によっても表示が反転することはない
ので、フリッカ等が生じないため、表示特性の劣化が生
ずることがなく、さらに連続した電圧印加により安定し
た実効的チルト角が確保できるので、コントラスト比が
大きくなる。Thus, the ferroelectric liquid crystal elements 11 and 12 are
Brightness and darkness can be displayed depending on whether the voltages applied to the same phase or the opposite phase are applied, and therefore AC driving is possible. Therefore, electrolysis of liquid crystals of the ferroelectric liquid crystal elements 11 and 12, accumulation of impurity ions, etc. The display characteristics are not deteriorated due to, and the display is not inverted by the continuous application of voltage, so that flicker does not occur and the display characteristics are not deteriorated. Since a stable and effective tilt angle can be secured, the contrast ratio becomes large.
【００１７】なお、上述実施例においては、強誘電性液
晶素子１１、１２のチルト角を４５°としたが、この発
明においては強誘電性液晶素子のチルト角は必ずしも正
確に４５°である必要はなく、(１)式で示される透過光
強度Ｉさらにはコントラスト比に対する要求条件に応じ
て、４５°からずれたチルト角をもつ強誘電性液晶素子
を用いることも可能である。また、上述実施例において
は、偏光板１３、１４がクロスニコル状態をとっている
場合について説明したが、２枚の偏光板の偏光軸が平行
である場合にもこの発明を適用することができ、この場
合には２層の強誘電性液晶素子１１、１２に同相の信号
を印加したときには、明状態をとり、２層の強誘電性液
晶素子１１、１２に逆相の信号を印加したときには、暗
状態をとる。Although the tilt angles of the ferroelectric liquid crystal elements 11 and 12 are set to 45 ° in the above embodiment, the tilt angle of the ferroelectric liquid crystal elements is not necessarily 45 ° in the present invention. Alternatively, it is possible to use a ferroelectric liquid crystal element having a tilt angle deviated from 45 ° depending on the requirements for the transmitted light intensity I and the contrast ratio expressed by the equation (1). Further, in the above-mentioned embodiment, the case where the polarizing plates 13 and 14 are in the crossed Nicols state has been described, but the present invention can be applied to the case where the polarizing axes of the two polarizing plates are parallel. In this case, when in-phase signals are applied to the two-layered ferroelectric liquid crystal elements 11 and 12, a bright state is obtained, and when opposite-phased signals are applied to the two-layered ferroelectric liquid crystal elements 11 and 12. , Get dark.
【００１８】[0018]
【発明の効果】以上説明したように、この発明に係る表
示装置においては、交流駆動が可能であるから、液晶の
電気分解、不純物イオンの蓄積等による表示特性の劣化
が生ずることはなく、また連続した電圧印加によっても
表示が反転することはないから、フリッカ等が生じない
ので、表示特性の劣化が生ずることがなく、さらに連続
した電圧印加により安定した実効的チルト角が確保でき
るから、コントラスト比が大きくなる。このように、こ
の発明の効果は顕著である。As described above, since the display device according to the present invention can be driven by an alternating current, deterioration of display characteristics due to electrolysis of liquid crystal, accumulation of impurity ions, etc. does not occur. Since the display is not inverted by continuous voltage application, flicker does not occur, display characteristics do not deteriorate, and a stable effective tilt angle can be secured by continuous voltage application. The ratio becomes large. As described above, the effect of the present invention is remarkable.
【図１】この発明に係る液晶表示装置の概略を示す構成
図である。FIG. 1 is a configuration diagram showing an outline of a liquid crystal display device according to the present invention.
【図２】図１に示した液晶表示装置を構成する２層の強
誘電性液晶素子内の強誘電性液晶分子の相対的な位置関
係を模式的に示す図である。2 is a diagram schematically showing a relative positional relationship of ferroelectric liquid crystal molecules in a two-layer ferroelectric liquid crystal element that constitutes the liquid crystal display device shown in FIG.
【図３】図１に示した液晶表示装置の動作を示すための
図である。FIG. 3 is a diagram showing an operation of the liquid crystal display device shown in FIG.
１１、１２…強誘電性液晶素子 １３、１４…偏光板 11, 12 ... Ferroelectric liquid crystal element 13, 14 ... Polarizing plate
Claims (4)
それぞれ独立に駆動が可能である強誘電性液晶素子を２
層積層し、上記強誘電性液晶素子に表示データに応じて
同相あるいは逆相の交流信号を印加することを特徴とす
る液晶表示装置。1. A ferroelectric liquid crystal device which holds a ferroelectric liquid crystal between a pair of substrates and can be driven independently of each other.
A liquid crystal display device comprising a plurality of laminated layers, wherein an in-phase or anti-phase alternating current signal is applied to the ferroelectric liquid crystal element according to display data.
板を設け、上記偏光板をクロスニコル状態にしたことを
特徴とする請求項１に記載の液晶表示装置。2. The liquid crystal display device according to claim 1, wherein a polarizing plate is provided by sandwiching the two layers of the ferroelectric liquid crystal element, and the polarizing plate is in a crossed Nicol state.
一致させ、少なくとも一方の上記偏光板の偏光軸を上記
強誘電性液晶素子の強誘電性液晶分子の電圧印加時の配
向方向と平行としたことを特徴とする請求項２に記載の
液晶表示装置。3. The alignment directions of the two layers of the ferroelectric liquid crystal element are made to coincide with each other, and the polarization axis of at least one of the polarizing plates is the alignment direction of the ferroelectric liquid crystal molecules of the ferroelectric liquid crystal element when a voltage is applied. The liquid crystal display device according to claim 2, wherein the liquid crystal display device is parallel to the liquid crystal display device.
°としたことを特徴とする請求項１に記載の液晶表示装
置。4. The tilt angle of the ferroelectric liquid crystal device is about 45.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set at 0 °.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30307891A JPH05142519A (en) | 1991-11-19 | 1991-11-19 | Liquid crystal display device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30307891A JPH05142519A (en) | 1991-11-19 | 1991-11-19 | Liquid crystal display device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05142519A true JPH05142519A (en) | 1993-06-11 |
Family
ID=17916631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30307891A Pending JPH05142519A (en) | 1991-11-19 | 1991-11-19 | Liquid crystal display device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05142519A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007125628A1 (en) * | 2006-04-28 | 2007-11-08 | Sharp Kabushiki Kaisha | Liquid crystal display device, its driving method and electronic device |
| US8009248B2 (en) | 2005-09-30 | 2011-08-30 | Sharp Kabushiki Kaisha | Liquid crystal display and television receiver |
| US8279375B2 (en) | 2007-04-16 | 2012-10-02 | Sharp Kabushiki Kaisha | Display apparatus, driving apparatus of display apparatus, and electronic device |
-
1991
- 1991-11-19 JP JP30307891A patent/JPH05142519A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8009248B2 (en) | 2005-09-30 | 2011-08-30 | Sharp Kabushiki Kaisha | Liquid crystal display and television receiver |
| WO2007125628A1 (en) * | 2006-04-28 | 2007-11-08 | Sharp Kabushiki Kaisha | Liquid crystal display device, its driving method and electronic device |
| US8279375B2 (en) | 2007-04-16 | 2012-10-02 | Sharp Kabushiki Kaisha | Display apparatus, driving apparatus of display apparatus, and electronic device |
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