JPH0442659B2

JPH0442659B2 -

Info

Publication number: JPH0442659B2
Application number: JP32054687A
Authority: JP
Inventors: Masanori Fujita
Original assignee: Seikosha KK
Current assignee: Seikosha KK
Priority date: 1987-12-18
Filing date: 1987-12-18
Publication date: 1992-07-14
Also published as: JPH01161319A

Description

【発明の詳細な説明】（産業上の利用分野）本発明は光プリンタ用液晶シヤツタの駆動方法
に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for driving a liquid crystal shutter for an optical printer.

（従来の技術）最近、例えば光プリンタ用液晶シヤツタとして
高速応答性を有する強誘電液晶の開発が進められ
ている。(Prior Art) Recently, ferroelectric liquid crystals with high-speed response have been developed as liquid crystal shutters for optical printers, for example.

強誘電液晶の光学モードとしては、複屈折型光
学モードおよびゲストホスト型光学モードがあ
る。これらを駆動する場合、従来のTN型液晶と
異なり、電界の印加方向によつて光学応答状態
（開閉状態）を制御するため、TN型液晶で用い
られていた駆動方法が利用できず、特殊な駆動方
法を必要とするものである。 The optical modes of ferroelectric liquid crystals include birefringent optical mode and guest-host optical mode. When driving these, unlike conventional TN-type liquid crystals, the optical response state (open/closed state) is controlled by the direction of electric field application, so the driving method used for TN-type liquid crystals cannot be used, and special This requires a driving method.

さらに液晶シヤツタの寿命を考えると、直流成
分がシヤツタ素子に印加され続けるのは好ましく
なく、その点も考慮した駆動方法が必要になつて
くる。 Furthermore, considering the lifespan of the liquid crystal shutter, it is undesirable for a direct current component to be continuously applied to the shutter element, and a driving method that takes this point into account is required.

そこでシヤツタ素子に直流を印加し続けない方
法として、電圧−Ｖ／＋Ｖと、＋Ｖ／−Ｖの直流
パルスでそれぞれ開状態を閉状態を書き込む２パ
ルス法を用いる。または電圧＋Ｖと−Ｖで開状態
と閉状態を書き込む方法を用いることが考えられ
ている。 Therefore, as a method of not continuing to apply direct current to the shutter element, a two-pulse method is used in which an open state and a closed state are written using direct current pulses of voltages -V/+V and +V/-V, respectively. Alternatively, it is considered to use a method of writing open and closed states using voltages +V and -V.

（発明が解決しようとする問題点）しかし、前者の駆動方法を光プリンタ用液晶シ
ヤツタに用いた場合には、電圧−Ｖ／＋Ｖと、電
圧＋Ｖ／−Ｖではそれぞれ開／閉と閉／開の状態
になつてコントラストがとれず実用的でない。こ
れに対して後者の駆動方法を用いれば、コントラ
ストはとれるが＋Ｖまたは−Ｖが続けて印加され
る場合があつて、駆動用の透明電極が還元されて
黒ずんでしまつたり、液晶の劣化を引き起こすと
いう問題があつた。(Problem to be solved by the invention) However, when the former driving method is used for a liquid crystal shutter for an optical printer, the voltage -V/+V and the voltage +V/-V are respectively open/close and close/open. This is not practical because the contrast cannot be maintained. On the other hand, if the latter driving method is used, the contrast can be maintained, but +V or -V may be continuously applied, which may reduce the transparent electrode for driving and darken it, or cause deterioration of the liquid crystal. There was a problem with causing it.

本発明の目的は、長時間駆動しても透明電極の
黒変、液晶の劣化等を引き起こすことを排除し、
コントラストを高めることにある。 The purpose of the present invention is to eliminate blackening of transparent electrodes, deterioration of liquid crystal, etc. even when driven for a long time,
The purpose is to increase contrast.

（問題点を解決するための手段）本発明の特徴は、電界の印加方向によつて分子
の配向状態を異にし、かつ２つの異なる光学的安
定状態を有する液晶を用いてシヤツタ素子を形成
し、シヤツタ素子の前回の開閉状態指定データと
今回の開閉状態指定データとを比較して両者が不
一致のときに、そのシヤツタ素子に第１または第
２の直流パルスを印加して指定された開閉状態と
し、その後は印加電圧をＯに保持するものであ
り、第１および第２の直流パルスは、互いに逆極
性で対称波形とすることにより、上記目的を達成
している。(Means for Solving the Problems) A feature of the present invention is that a shutter element is formed using a liquid crystal that has two different optically stable states in which the orientation of molecules changes depending on the direction of application of an electric field. , compare the previous opening/closing state designation data of the shutter element with the current opening/closing state designation data, and if the two do not match, apply the first or second DC pulse to the shutter element to set the designated opening/closing state. After that, the applied voltage is maintained at O, and the above object is achieved by making the first and second DC pulses have opposite polarities and symmetrical waveforms.

（実施例）本発明の一実施例を図面に基づいて説明する。(Example) An embodiment of the present invention will be described based on the drawings.

第１，２図は液晶セルの一例を示すもので、所
定の間隙で対向する２枚のガラス１，２の対向す
る面のうちの一方の対向面には、透明電極よりな
るコモン電極１１が形成されている。コモン電極
１１は金属膜例えばクロム膜１２で前面が覆われ
ており、クロム膜には千鳥状に２列に配列してシ
ヤツタとしての窓１２ａ…が開設してある。また
他方の対向面には、透明電極よりなるセグメント
電極２１…が窓１２ａ…と対向する位置に形成し
てある。ガラス１と２との間隙内には、電界の印
加方向によつて分子の配向状態を異にし、かつ２
つの異なる光学的安定状態を有する強誘電液晶３
が封入されている。４，５は偏光板である。これ
により各セグメント電極と窓を介して対向するコ
モン電極とに挟まれて多数のシヤツタ素子が千鳥
状に２列に配列して構成されている。Ｃはコモン
端子であり、Ｓ１〜Snはセグメント端子である。 Figures 1 and 2 show an example of a liquid crystal cell, in which a common electrode 11 made of a transparent electrode is mounted on one of the opposing surfaces of two glasses 1 and 2 facing each other with a predetermined gap. It is formed. The front surface of the common electrode 11 is covered with a metal film such as a chrome film 12, and the chrome film has windows 12a arranged in two rows in a staggered manner as shutters. On the other opposing surface, segment electrodes 21 made of transparent electrodes are formed at positions facing the windows 12a. In the gap between glasses 1 and 2, molecules have different orientation states depending on the direction of electric field application, and 2
Ferroelectric liquid crystal with two different optical stable states 3
is included. 4 and 5 are polarizing plates. As a result, a large number of shutter elements are arranged in two rows in a staggered manner, sandwiched between each segment electrode and a common electrode facing each other through a window. C is a common terminal, and S1 to Sn are segment terminals.

第３図はシヤツタ素子に開状態および閉状態を
書き込むための電圧波形を示すもので、コモン端
子Ｃには常時電圧Ｏが供給されている。これに対
しセグメント端子Ｓ１〜Snには、シヤツタ素子
の開閉状態を変化させるときにのみ、電圧Ｖの第
１の信号またはこれと逆極性で対称波形の電圧−
Ｖの第２の信号を供給し、それ以外のときは電圧
Ｏを供給するものである。 FIG. 3 shows voltage waveforms for writing open and closed states into the shutter element, and the common terminal C is constantly supplied with voltage O. On the other hand, only when changing the opening/closing state of the shutter element, the segment terminals S1 to Sn receive the first signal of voltage V or the voltage - of the opposite polarity and symmetrical waveform.
A second signal of V is supplied, and a voltage of O is supplied at other times.

すなわちシヤツタ素子の前回の開閉状態指定デ
ータを記憶する記憶回路（図示せず。）の出力と
今回の開閉状態を指定する開閉状態指定データと
を比較し、両者が不一致のときにのみ、今回の開
閉状態指定データに基いて第１の信号または第２
の信号を供給するものである。 In other words, the output of a memory circuit (not shown) that stores the previous open/close state designation data of the shutter element is compared with the open/close state designation data that designates the current open/close state, and only when the two do not match, the current open/close state is determined. The first signal or the second signal based on the open/close state designation data.
It supplies the signal.

したがつて、閉状態から開状態に変化すべきシ
ヤツタ素子には電圧Ｖの第１の直流パルスＰ１が
印加され、開状態に書き込まれる。開状態から閉
状態に変化すべきシヤツタ素子には電圧−Ｖの第
２の直流パルスＰ２が印加され、閉状態に書き込
まれる。 Therefore, the first DC pulse P1 of voltage V is applied to the shutter element to be changed from the closed state to the open state, and the shutter element is written into the open state. A second DC pulse P2 of voltage -V is applied to the shutter element to be changed from the open state to the closed state, and the shutter element is written into the closed state.

この書込み終了後は電圧Ｏが印加され、その開
閉状態が保持される。 After this writing is completed, voltage O is applied and the open/closed state is maintained.

また開閉状態の変化しないシヤツタ素子には電
圧Ｏを印加しておくことによりその開閉状態が保
持される。 Further, by applying a voltage O to the shutter element whose open/closed state does not change, its open/closed state is maintained.

このように、開閉状態を変化するときにのみ、
シヤツタ素子を所望の開閉状態にするための直流
パルスが印加されるため、シヤツタ素子に印加さ
れる第１および第２の直流パルスＰ１，Ｐ２は第
４図のように、互いに逆極性で対称波形となり、
偏つた直週電圧が印加されることがない。 In this way, only when changing the open/close state,
Since a DC pulse is applied to bring the shutter element into the desired open/close state, the first and second DC pulses P1 and P2 applied to the shutter element have opposite polarities and symmetrical waveforms, as shown in Figure 4. Then,
Unbalanced weekly voltage is not applied.

ところで、直流パルスのパルス幅とパルス高Ｖ
は、強誘電液晶の発生分極の大きさや液晶セル厚
との関係で、開状態あるいは閉状態が得られるよ
うに適宜設定される。 By the way, the pulse width and pulse height V of the DC pulse
is appropriately set so as to obtain an open state or a closed state depending on the magnitude of polarization generated in the ferroelectric liquid crystal and the thickness of the liquid crystal cell.

また上記の説明では、＋側の電圧によつて開状
態、−側の電圧によつて閉状態となるとしたが、
逆に＋側の電圧で閉状態、−側の電圧で開状態と
なるようにしてもよい。 Also, in the above explanation, the positive voltage causes the open state, and the negative voltage causes the closed state.
Conversely, a voltage on the + side may cause the cap to be in the closed state, and a voltage on the minus side may cause the cap to be in the open state.

ところで、各電極に供給する信号は上記に限る
ものではなく、種々の変更が可能であり、また必
要に応じて適宜バイアス電圧を加えるようにして
もよい。 By the way, the signals supplied to each electrode are not limited to those described above, and various changes can be made, and a bias voltage may be applied as necessary.

（発明の効果）本発明によれば、開閉状態を変化するときにの
み、互いに逆極性で対称波形の第１または第２の
直流パルスを印加して画素を所望の開閉状態に
し、それ以外のときは電圧Ｏを印加するようにし
たので、画素には交互に逆極性の直流パルスが印
加されることになり、長時間駆動しても透明電極
が黒ずんだり液晶が劣化したりすることがない。
しかもコントラストを高くとれるため、高性能の
液晶シヤツタと実現することができる。(Effects of the Invention) According to the present invention, only when changing the open/close state, the first or second DC pulses with opposite polarities and symmetrical waveforms are applied to bring the pixel into the desired open/close state; Since a voltage of O was applied at the time, DC pulses of opposite polarity were alternately applied to the pixels, so the transparent electrodes would not darken or the liquid crystal would deteriorate even if driven for a long time. .
Moreover, since it can achieve high contrast, it can be realized as a high-performance liquid crystal shutter.

[Brief explanation of drawings]

第１図は液晶セルの一例を示した一部切欠正面
図、第２図は第１図−線断面図、第３図は本
発明を実現するための電圧波形を示した説明図、
第４図は１つのシヤツタ素子に印加される電圧波
形に１例を示したタイムチヤートである。３……液晶、１１……コモン電極、１２ａ……
窓、２１……セグメント電極、Ｐ１……第１の直
流パルス、Ｐ２……第２の直流パルス。 FIG. 1 is a partially cutaway front view showing an example of a liquid crystal cell, FIG. 2 is a sectional view taken along the line shown in FIG. 1, and FIG. 3 is an explanatory diagram showing voltage waveforms for realizing the present invention.
FIG. 4 is a time chart showing an example of a voltage waveform applied to one shutter element. 3...Liquid crystal, 11...Common electrode, 12a...
Window, 21... Segment electrode, P1... First DC pulse, P2... Second DC pulse.

Claims

[Claims] 1. A liquid crystal that changes the orientation state of its molecules depending on the direction of application of an electric field and has two different optically stable states is interposed between one common electrode and a plurality of segment electrodes to form a plurality of liquid crystals. In a method for driving a liquid crystal shutter for an optical printer formed with a shutter element, a desired signal is always supplied to a common electrode, and the previous opening/closing state designation data of each shutter element stored in a storage means and each shutter element are stored. and the current opening/closing state designation data using comparison means, and selectively supplying either the first signal or the second signal to the segment electrode of the shutter element where the two do not match. , applies either the first DC pulse or the second DC pulse to the shutter element to bring it into the specified open/close state, and after applying the first or second DC pulse,
The voltage applied to the shutter element is maintained at O by supplying the desired signal to the segment electrode, and the first DC pulse and the second DC pulse are
A method for driving a liquid crystal shutter for an optical printer, characterized by having mutually opposite polarities and symmetrical waveforms.