CN1025454C

CN1025454C - Ferroelectric liquid crystal display and its multiplex addressing method

Info

Publication number: CN1025454C
Application number: CN91105533A
Authority: CN
Inventors: J·R·休斯; E·P·雷恩斯
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1990-08-07
Filing date: 1991-08-07
Publication date: 1994-07-13
Anticipated expiration: 2006-08-07
Also published as: GB2262831A; WO1992002925A1; GB9017316D0; JP3356430B2; DE69119771T2; GB9301627D0; GB2262831B; CA2088770A1; DE69119771D1; MY108630A; EP0542804A1; JPH05509419A; CA2088770C; CN1058850A; KR930701803A; KR100231216B1; EP0542804B1

Abstract

A ferroelectric liquid crystal element is addressed by the row and column electrodes of the X, Y matrix display element. Row electrodes are sequentially applied with strobe waveforms, and column electrodes are applied with data waveforms. An addressing waveform is received on each display element, causing it to transition to one of two transition states. Two different switching characteristics are generated with two addressing waveforms. The display operates at voltages above which at least one switching characteristic has the shortest response time at a voltage value. The data waveform is a pulse that alternates positive and negative. The strobe waveform causes the addressing of adjacent row electrodes to overlap. A strobe or blanking pulse is used to switch display elements to one state and some display elements to another state.

Description

Multiplex addressing of ferro-electric liquid crystal displays

The present invention relates to the multiplex addressing (multiplex addressing) of ferroelectric liquid Crystal.This class display adopts the inclination hand to levy C, I or the F type liquid crystal material of saucer-like configuration (chiral smectic).

Liquid crystal device is the liquid crystal material of installing skim between two glass slides normally.Be formed with euphotic electrode on the inside surface of two slide glasses.When adding voltage on these electrodes, the electric field that is produced has changed the molecules align of liquid crystal molecule.The variation of molecules align is to be easy to observedly, and this has become the principle of work of plurality of liquid crystals display device.

In ferroelectric liquid crystal devices, each liquid crystal molecule is changed its arrangement mode by alive polarity between two different orientations.These devices have certain bistable degree, and have the tendency that keeps a kind of transition status in two kinds of transition statuses, till being transformed into another transition status.This performance makes us carry out multiplex addressing to sizable display.

Common multiplex's display has many X of being arranged in usually, the display unit of Y matrix format, and promptly picture dot supplies to show for example usefulness of alphanumeric character.Matrix format is by making each electrode on the slide glass form a series of row electrodes, makes each electrode on another slide glass form that a series of column electrodes form.Intersection point between each row and each row just forms addressable unit or picture dot.Also have other matrix form as you know, for example polar coordinates (r-θ) and seven lines digital indicators etc.

Multiplex addressing has many different schemes.These schemes have a common characteristic, add voltage successively toward each row and each column electrode exactly, are gate voltage (strobe voltage).When pressing, add suitable voltage for all row electrodes, be data voltage (data voltage) toward each row electrode by-election energising.The difference of different schemes is the shape of gate voltage and data voltage waveform.

European patent application 0,306,203 have introduced a kind of multiplex addressing scheme that ferroelectric liquid Crystal is used.In this patented claim, gate voltage is the unipolar pulse of polarity alternation, and the waveform of two data voltages is the opposite square wave of is-symbol then.The width of strobe pulse is half of data waveform cycle.With gate voltage and the molecules align mode that suitable data voltage combines and just can change liquid crystal material.

Other addressing scheme has introduction: GB2,146,473-A in following document; GB-2,173,336A; GB-2,173,337-A; GB-2,173,629-A; WO89/05025; The article that people such as Harada write at S.I.D Digest Paper8.4 131-134 page or leaf in 1985; With people such as Lagerwall at IEEE in 1985, the article of delivering on the IDRC 213-221 page or leaf; P, people such as Maltese be at Proc1988IEEE, the article of writing on the IDRC 98-101 page or leaf that is entitled as " the quick addressing of ferroelectric liquid crystals display board ".

Strobe pulse with two opposite in signs can make liquid crystal material change between two state together with a data waveform.Not so also can make liquid crystal material be transformed into a kind of state and cooperate with a suitable data pulse and make each picture dot rotate back into another kind of state selectively with blanking pulse with an independent strobe pulse.For keeping total D. C. value is zero, regularly alternately change the symbol of blanking pulse and strobe pulse.

Usually, the amplitude of these blanking pulses is bigger than strobe pulse, and the time that applies is also long than strobe pulse, so just can make liquid crystal material no matter in two data waveforms which be added on any one intersection point and can both change its state.Blanking pulse can apply before strobe pulse line by line, perhaps once just whole display was carried out blanking, perhaps simultaneously to one group of horizontal blanking of advancing.

It is to adopt voltage (V) to equate but opposite polarity blanking pulse with the product VT of time (t) and the VT product of strobe pulse that a kind of known blanking scheme is arranged.The amplitude of blanking pulse is half of strobe pulse, and application time is the twice of strobe pulse.These values guarantee blanking and strobe pulse need not regularly change its polarity just can make total DC component this zero.Experiment shows, this scheme poor performance.

The another kind of known arrangement of blanking pulse is in European patent EP 0,378, introduction arranged in 293.This scheme has adopted balance strobe pulse (its cycle identical polar is opposite) commonly used, and together with similar dc balance blanking pulse (its cycle identical polar is opposite), wherein the width of blanking pulse can be the several times of gate width.This scheme need not regularly change blanking and gating waveform, and just can to make total DC component be zero.

These characteristics of dc balance particular importance in the projection display because if want to make the gap between each picture dot to be transformed into a kind of optical states, is not just allowed regular change polarity.

A problem of existing display is composite display (complex display) is addressed the needed time.In order to drive composite display, need address display fast with visual frame frequency speed.Addressing can also improve contrast ratio fast, thereby makes train wave shape be in corresponding high frequency state.But only improving the volume specific rate might not make transfer process correctly carry out.Purpose of the present invention will shorten exactly matrix display is addressed the needed time, improves to show contrast.

The present invention comprises the following steps: a kind of method that the formed ferroelectric liquid crystal matrix display of each intersection point of first group of electrode and second group of electrode carries out multiplex addressing

Respectively each electrode in first group of electrode is addressed, this addressing can equal zero to keep total DC component value by applying on the occasion of applying the strobe pulse that polarity regularly changes again and carry out with the pulse gate waveform of negative value or by applying a blanking pulse earlier;

One in two data waveforms synchronously is added on each electrode in second group of electrode with strobe pulse, two data waveforms alternately get on the occasion of and negative value, one data waveform is opposite with the phase place of another data waveform, and the cycle of data waveform (2ts) is the twice in single strobe pulse cycle (ts);

It is characterized in that: in time prolong the concluding time of each strobe pulse, thereby with symbol and the suitable pulse of size to each intersection point addressing, make each complete demonstration addressing cycle of this intersection point once enter desired show state, and to make total DC component value be zero.

Strobe pulse can be earlier zero at period 1 ts, then greater than time of ts for example (1.5,2.0,2.5,3.0 or more than) xts strobe pulse in season be voltage (master) pulse of non-zero.The voltage of gating waveform also can be non-vanishing in a ts cycle, and polarity and remaining strobe pulse are identical or different; The amplitude of this first potential pulse is adjustable, so that temperature compensation to be provided.The voltage of gating waveform then can be not equal to zero in polarity a period of time opposite with the principal voltage pulse, this section period can be for example greater than, be equal to or less than ts.

By making strobe pulse consistent, liquid crystal material is changed between two state with suitable data waveform.Not so also can make liquid crystal material convert one of them state to, again by making a strobe pulse and a suitable data waveform one cause selected picture dot to go back to another state with a blanking pulse.

Blanking pulse can divide two parts, and the polarity of first is opposite with second portion.Two parts of blanking pulse are arranged to such an extent that the VT product of its voltage time product VT and single gating is lumped together the DC component value is equalled zero.

The duration that prolongs strobe pulse means carries out repeat to address (RA) in turn to each electrode in first group of electrode.This width of commutation pulse that repeated broadening does not effectively simultaneously influence other waveform, thereby has shortened the T.T. that whole display is addressed, and makes each picture dot that is in two kinds of different switching states keep good contrast ratio.

Each strobe pulse can be immediately following with the strobe pulse that links to each other less prepulsing (prepulse) back of identical or contrary sign being arranged at one.This prepulsing can be used as the portion temperature compensation in order to change the conversion characteristic of liquid crystal material.In this case, detect the temperature of liquid crystal material, and suitably regulate the amplitude of prepulsing.

And then the pulse of opposite in sign after each strobe pulse.

Multiplex addressing LCD of the present invention comprises:

One liquid crystal cell, make by the liquid crystal material that one deck is contained between the two elements wall, liquid crystal material is the material that the inclination hand is levied saucer-like configuration, has negative dielectric anisotropic, be formed with the electrode of first series on the wall of the element wall of loading electrode, be formed with the electrode of second series on another element wall, each electrode is configured to make its collective to form the matrix of being made up of addressable point of crossing, one of them element wall through surface treatment so that surperficially align with liquid crystal molecule along a direction;

First group of electrode excitation circuit is in order to be added to the gating waveform successively on each electrode in first group of electrode;

Second group of electrode excitation circuit is in order to be added to data waveform on second group of electrode;

Waveform generator is added to gating waveform and two data waveforms on the exciting circuit in order to generation;

Control device with the order with the control data waveform, thereby draws desired display graphics;

It is characterized in that a data waveform generator and a gate pulse ganerator are arranged, the former has equal magnitude and frequency but the waveform of opposite in sign in order to produce two groups, and each data waveform all comprises the DC pulse of symbol alternation; The latter lasts longer than the strobe pulse in half data waveform cycle in order to generation, and each strobe pulse all lasts till the addressing cycle of next electrode always.

This display also can comprise a temperature sensor, in order to detect the temperature of display; And a voltage regulator, in order to regulate the size of addressing voltage.

The liquid crystal conversion characteristic is carried out simple analysis (" liquid crystal ",, the 6th volume, the 3rd phase, 341-347 page or leaf in 1989) can draw the expression formula of following electric field, under this electric field, liquid crystal material the response time-response time of voltage transitions characteristic is the shortest:

Wherein Emin be liquid crystal material the response time-the response time electric field the most in short-term of voltage transitions characteristic, ∈ ₀Be the specific inductive capacity of free space, △ ∈ is (bearing) dielectric anisotropy of liquid crystal material, and θ is the taper angle of liquid crystal material, and Ps is a spontaneous polarization strength.

This simple analysis is only applicable to some liquid crystal material, and their Ps and △ ∈ value can be regulated, to reach desired operating voltage.Nearest research work (the article of being write at " the refining chemicals II of electronics industry, the nineties is in chemically application " 130-146 page or leaf referring to EP Raynes that is entitled as " the display physics of the nineties "; Jones, Raynes and Towler are at the paper of delivering in the international symposium of ferroelectric liquid crystals for the third time that U.S. Bonlder Colerado university holds 24-28 day in June, 1991 that is entitled as " importance of ferroelectric liquid crystal devices dielectric biaxiality ") show, make a minimum value to occur in response time-voltage characteristic, the dielectric biaxiality is very important factor.The data of Figure 16 described below-20 obtain from experiment.

Referring now to accompanying drawing, content of the present invention only is described by way of example.In the accompanying drawing:

Fig. 1 is the X of time-multiplex addressing, the synoptic diagram of Y matrix;

Fig. 2 is the amplification profile of Fig. 1 display part;

Fig. 3 is the log-log graph of time to the relation of voltage, shows the conversion characteristic for the saucer-like configuration material of two variform addressing waveforms;

Fig. 4-8 shows spendable various gating and data waveform figure;

Fig. 9 shows the oscillogram that the gating waveform is correct on Fig. 4 basis;

Figure 10 shows the oscillogram of blanking, gating and data;

Figure 11 shows gating, data and the addressing waveform that uses in the prior art display;

Figure 12 a, b show the oscillogram to 4X4 picture dot display shown in Figure 13;

Figure 13 is 4 * 4 cell arrays, can see that some point of crossing changes " conducting " state over to, and remaining point of crossing then is in " ending " state;

Figure 14,15 shows the graph of relation of contrast ratio and institute's making alive pulse width of two kinds of different materials;

Figure 16-the 20th, the time with the log-log graph of alive relation, show a kind of material in the conversion characteristic that applies under the different wave situation;

Figure 21,22 shows various blanking, gating and data waveform;

Figure 23,24 shows the capable waveform and the train wave shape of prior art display;

Figure 25,26 shows and revises used capable waveform and the train wave shape of Fig. 6.

Display 1 shown in Fig. 1,2 comprises two

glass walls

2,3, uses the distance of the at interval about 1-6 micron of distance piece of spaced ring 4 and/or distribution each other.

Two wall inner faces are formed with the

electrode member

5,6 that transparent tin oxide is made.Can see that these electrodes embark on journey into row and arrange to form X, Y matrix, but also can get other form.Illustrate, be used for getting radially and curved shape of r, θ display, and seven digital lines displays are got the segmentation form.

Between

wall

2,3 and the spaced ring 4 one deck liquid crystal material 7 is housed.

The front and back of element 1 are provided with polarizer 8,9.The

driver

10 and 11 of row and column is added to voltage signal on the element.Two groups of waveforms that produce are added on the row, column driver 10,11.Gating waveform generator 12 provides capable waveform, and 13 in data waveform generator is added to " conducting " and " ending " waveform on the row driver 11.The The whole control of timing and display format is undertaken by steering logic unit 14.The temperature of liquid crystal layer 7 is measured by thermopair 15, and the output of thermopair 15 is fed on the gate pulse ganerator 12.The output of thermopair 15 can be directly or through proportioning element 16(rom chip for example by programming) be fed on the generator, to change the part of strobe pulse or data waveform.

Before assembling, by known mode element wall is carried out surface treatment, for example apply skim polyimide or polyamide, carry out drying, solidify in case of necessity and on single direction R1, R2, rub with cloth (for example rayon fabrics).Not so also can fixed inclination evaporation go up for example silicon monoxide of skim.These processing are arranged the liquid crystal molecule surface.Arrangement/frictional direction R1, R2 can be parallel to each other or not parallel.When adding suitable unidirectional voltage, molecule is arranged along a direction among D1 and the D2 according to the polarity of voltage.Angle between D1 and the D2 is advisable with about miter angle.When not having added electric field, each molecule is got third side between R1, R2 and D1, the D2 direction to arrangement.

This device can transmission or the reflection mode work.Under preceding a kind of mode,, thereby form desired display graphics for example from the optionally transmission or stopped of the light of osram lamp by this device.Under reflecting operating mode, mirror is being settled in second polarizer 9 back, and light reflected back is on every side passed element 1 and two polarizers.Can also can work with transmission mode work by making the reflective display that can make of minute surface part in the reflection mode.

Liquid crystal material 7 can add pleochroic dye.In the case, only need a polarizer, the desirable 4-10 micron of the thickness of coating.

The liquid crystal material that is suitable for has:

Be numbered the product (can buy from Britain Merck Ltd Poole company) of SCE8 in the Merck company product sample, the Ps of this product is about 5 millimicros storehouse/square centimeter (nc/cm in the time of 30 ℃ ²), dielectric anisotropy is about-2.0, and phase sequence is: Sc59 ℃ Sa79 ℃ N98 ℃.

Potpourri A contains 5% racemization adulterant (racemic dopant) and 3% hand and levies adulterant (chiral dopant) in the matrix (host);

Potpourri B contains 9.5% racemization adulterant and 3.5% hand and levies adulterant in the matrix.

* number expression chirality, no * person represents that material is the racemization type.

Potpourri A, the B Ps in the time of 30 ℃ all is about 7 millimicros storehouse/square centimeter, and dielectric anisotropy is about-2.3.

The phase sequence of potpourri A is Sc100 ℃ Sa111 ℃ N136 ℃.

The phase sequence of potpourri B is Sc87 ℃ Sa118 ℃ N132 ℃.

The liquid crystal material at row and column electrode crossings place is changed by adding addressing voltage.This addressing voltage is added to data waveform Vd combination acquisition on the row electrode simultaneously by gating waveform Vs is added on the column electrode.

That is Vr=Vs-Vd,

Wherein Vr=addresses the instantaneous value of waveform;

The instantaneous value of Vs=gating waveform;

The instantaneous value of Vd=data waveform.

Hand is levied inclination saucer-like configuration material and is changed according to the product of voltage and time.Fig. 3 shows this specific character.The voltage time product of curve top can make the liquid crystal material conversion, and the curve below then is the non-conversion district.The symbol that is noted that conversion characteristic and voltage is irrelevant, and promptly liquid crystal material is all convertible under the positive voltage of given amplitude or negative voltage.The direction of liquid crystal material conversion depends on the polarity of voltage.

Two curves have been shown, because conversion characteristic depends on the form of addressing potential pulse combination among Fig. 3.Top curve is to obtain when and then addressing voltage arranged after the little prepulsing of opposite in sign, follows a bigger positive pulse after for example little negative pulse.The performance that adds liquid crystal material when following a big negative pulse after the little positive pulse is identical.Above transformation or the response time of this curve ordinary representation under a certain voltage the shortest.This is different with (1) formula provided, because conversion characteristic changes because of prepulsing.Little prepulsing can be called leading pulse (LP), and bigger addressing pulse then can be called the pulse of smearing (Tp).Above curve be the curve of Lp/Tp ratio when being negative value.

Below curve be before addressing voltage, to obtain during a little prepulsing with symbol first, and then a bigger positive pulse is promptly arranged after little positive pulse.Also draw same curve when after little negative pulse, following a big negative pulse.Below the Lp/Tp ratio of curve for just.Following its shape of curve is different with top curve.The volt-time curve of some liquid crystal material may not have minimum value.

The shape difference of two curves, thereby display just can in so many words be worked under the quite wide duration of scope.This is by making work in the zone of display between two curves (example zone as shown by hatching in FIG.) reach.The addressing voltage that each point of crossing to be converted adapts with shape and following curve and voltage and pulse width are in this curve top addresses.Those point of crossing that need not to change receive its shape and top curve adapts and voltage and pulse width are in the addressing voltage of this curve below, or receive only data waveform voltage.This will introduce below in more detail.

Fig. 4 shows gating, data and the addressing waveform of one embodiment of the invention.To begin in the time of ts be zero to the gating waveform lasting, and then is+3 in the time of lasting twice ts.Each capable in turn (i.e. frame period in a period of time) all is like this.The next part of gating waveform is zero in the time of lasting a ts, then is+3 in the time of lasting twice ts.This is applicable to each row in turn in the frame period for the moment too.Display all addresses the time in frame period when needing two.+ 3 ,-3 values are just for illustrating the voltage cell that provides, and just provide actual value when relating to concrete material later on.

Data waveform can be named as " conducting " data and " ending " data arbitrarily, or D1 and D2." conducting " data last first ts in the time its value be+1 earlier, then next ts in the time its value be-1, carry out so repeatedly; Promptly " conducting " data are that amplitude is 1, be the alternating signal of 2ts the same period." end " data similarly, its value is to be-1 when just beginning, then for+1; Promptly opposite with " conducting " data.The first of data waveform (for example concerning " conducting " data, its value is for+1, and the time of lasting is ts) and first's (be that its value is zero, the time of lasting is ts) of gating waveform overlap.

The addressing waveform be gating and data waveform and.Positive strobe pulse has with the combination of " conducting " data :-1,4,2,1 ,-1,1 etc.The conversion characteristic of before numerical value 4, guaranteeing liquid crystal material first for one-1 by Fig. 3 above a curve controlled.Negative strobe pulse has with the combination of " conducting " data :-1 ,-2 ,-4,1 ,-1,1 etc.Symbol gets up to guarantee the following curve controlled of the conversion characteristic of liquid crystal material by Fig. 3 with big (4) pulsion phase less pulse combined together.Equally, just strobe pulse draws 1,2,4 ,-1,1 etc. with " ending " data combination; Negative strobe pulse draws 1 ,-4 ,-2 ,-1,1 ,-1 etc. with " ending " data combination.

When not receiving strobe pulse, each row ground connection promptly receives no-voltage.Each row is not to receive " conducting " data to receive " ending " data exactly from start to finish.Its effect is that all point of crossing receive the caused alternating signal of data waveform when not addressed.This makes each point of crossing obtain AC bias, and helps liquid crystal material to keep its transition status.Improving the AC bias value can make contrast improve because of the known interchange stabilization described in " Proc 4 th IDRC " 217-220 page or leaf in 1984.

AC bias can provide from for example one 50 kilo hertzs power supply in addition, directly is added on those each row that does not receive strobe pulse.Figure 14 and 15 shows the influence to contrast ratio of the size of AC bias concerning material SCE8 and potpourri A and pulse width.From these figure as can be seen, intrinsic contrast ratio (CR) is measured as the function of a-c cycle, and at this moment element is changed between two bistable state; Intrinsic contrast ratio also is to measure when the various varying level of AC bias simultaneously.

Fig. 5 to 8 shows other gating waveform.Among Fig. 5, the gating waveform was zero before this, lasted the time of 1 * ts, was 3 then, lasted the time of 3 * ts, then was its opposite situation.Among Fig. 6, the gating waveform was zero before this, lasted the time of 1 * ts, was 3 then, lasted the time of 4 * ts, then was its reverse situation.Among Fig. 7, the gating waveform was zero before this, lasted the time of 1 * ts, was 3 then, lasted the time of 2 * ts, was-1 again, lasted the time of 1 * ts, then was its opposite situation.

Fig. 8 becomes from Fig. 4, has adopted the prepulsing of non-zero in the gating waveform.As shown in the figure, the first of gating waveform is between-1 and 1, rather than the null value of Fig. 4.The same among the remainder of gating waveform and Fig. 4, promptly amplitude is 3, lasts the time of twice ts.So the addressing waveform that draws is: first pulse under first and second electric fields all between-2 and-1.The effect of this prepulsing is the position that changes the transformation curve of Fig. 3 etc.The value that changes prepulsing can change the shape and the upright position of each curve, and this describes with reference to Figure 16 and 17 below.Below table 8 represented situation about changing with temperature switching time.The amplitude that changes prepulsing can reduce this variation.

Fig. 9 is the modification of Fig. 4.In this modification, the gating waveform is zero in the time at first ts, is 3 in the time of next 1.5ts.1.5ts this time only is for example, any greater than ts until approximately the time of 5ts can adopt.

Figure 10 shows that to last the 4ts amplitude be 4 single blanking pulse.This blanking pulse makes all point of crossing all be transformed into a kind of transition status.Be transformed into another transition status with the strobe pulse point of crossing that some is selected then.Periodically making the sign-inverted of blanking and strobe pulse, is zero thereby make total DC voltage component.Each scheme of Fig. 4-8 all can adopt blanking pulse and single strobe pulse.Blanking and gating system have such benefit, and promptly whole display can address in an independent field time.

As a comparison, Figure 11 shows gating, data and the addressing waveform of prior art displaying scheme, and this is the scheme of a monopulse addressing.

Figure 21 and 22 shows addressing scheme of the present invention, and having adopted and having made total DC component value is zero blanking pulse and single strobe pulse.

Among Figure 21, blanking pulse divides two parts, and the symbol of prepulsing is opposite with main pulse and blanking pulse.The effect of prepulsing is to offset DC component, is zero.The value of prepulsing is 3, lasts the time of 4ts, and the time of 6ts is lasted followed by-3 values in the back.Strobe pulse is earlier zero, lasts the time of 1ts, and the time of 1 o'clock 2ts is gone through followed by being 3 in the back; This strobe pulse is the same with the strobe pulse of Fig. 4.Data waveform D1, D2 also with Fig. 4 in the same.Blanking and D1 or D2 combination make negative Vt product become big, and this product makes all picture dots in the addressing row be transformed into " ending " state.Strobe pulse and D2 combination make desired each picture dot be transformed into " conducting " state, and this is in the above referring to speaking of in the explanation that Fig. 4 did.

Figure 22 and Figure 21 are similar, but the shape difference of blanking pulse.The prepulsing amplitude of this blanking pulse is 3, lasts the time of 4ts, the back followed by be-4.5, last the time of 4ts.The amplitude of strobe pulse is 3, lasts the time of 2ts, the same with among Fig. 4.Can see that blanking pulse and D1 and D2 combination make negative Vt product become big, this product makes all addressing row be transformed into " ending " state.Here selected picture dot also is transformed into " conducting " state by strobe pulse and D2.

Figure 21 and 22 blanking pulse can use with the strobe pulse of other form shown in Fig. 5-9, arrange amplitude and/or Vt product to such an extent that to make total DC component value be zero.Situation about changing with for example temperature for first time slot of the sort of gating of Fig. 8 for example is total the amplitude of feedback and/or main blanking pulse is also regulated to such an extent that the DC component value that makes remains zero in advance.

Blanking pulse is ahead of how much can changing of strobe pulse, but corresponding to response time, contrast and the visible flicker level of display an optimum position is arranged.It is representational that blanking pulse begins than Zao six row of strobe pulse, but this depends on the various parameters of material and the details situation of multiplex's scheme.

The matrix array that Figure 12 a, b illustrate 4 * 4 addresses employed waveform, wherein shows information shown in Figure 13.Here arbitrarily selected solid round dot is represented the electrode crossings of " conducting ", and promptly display element is not marked the point of crossing of round dot and represented to be in " ending " state.Addressing scheme is the addressing scheme that Fig. 4 adopted.

Successively will be just or the leading strobe pulse be added on each row of 1 to 4, this has just formed first.After the leading strobe pulse addressed last column, the strobe pulse of will bearing or smear successively was added to each row of 1 to 4, and this has just formed second.Should be noted that, be can be overlapping between row and the row.For example, the 3rd ts time of the 1st row occurred simultaneously with the 2nd capable first ts time.This overlapping situation is more noticeable when the gating waveform shown in display employing Fig. 5 and 6.

" conducting " data that data waveform is added to the 1st row remain unchanged, because each point of crossing always " conducting " in the row.Equally, the data waveform that is added to the 2nd row is " ending " data, and because all point of crossing in the 2nd row all are " ending ", thereby remain unchanged.The data waveform that is added to the 3rd row is " ending " data when the 1st and the 2nd row is in adressed state, become " conducting " data when the 3rd row is in adressed state, changes back to " ending " data then when the 4th row is in adressed state.In other words, the 3rd row receive " ending " data, last the time of 4 * ts, receive " conducting " data, last the time of 2 * ts, receive " ending " data, last 2 * ts, the cycle is a field time, and promptly positive strobe pulse addresses the needed time to every row.Concerning the 4th row, data waveform is " ending " data, lasts 2ts equally; " conducting " data are lasted 2ts; " end " data, last 2ts; " conducting " data are lasted 2ts.When adding negative strobe pulse, repeat said process, last another field duration.Forming a frame period need two field duration with the addressing of finishing display.Repeat said process, till the new display graphics of needs.

Figure 12 b shows the addressing waveform that draws.The 1st row the 1st row (R1, C1) do not change during first field duration, carry out because the conversion of material is a top curve by Fig. 3, and time and added voltage level is the below that is in transformation curve by the liquid crystal material of point of crossing.On the contrary, liquid crystal material was changed during second field duration, and at this moment voltage/time value is less to be changed liquid crystal material owing to following curve of Fig. 3 requires.This reasoning also is applicable to point of crossing R1, C2, and the liquid crystal material of this point of crossing was changed during first field duration.

As for point of crossing R3, C3, liquid crystal material since during first field duration added time do not reach desired high value of curve above Fig. 3, thereby during second field duration, change.Point of crossing R4, C4 at the end changes in second field duration when negative strobe pulse adds.

Be added to the 4th shape that lists waveform and brought a difficult problem.Owing to show the form get on-off-on-off, thus the cycle of data waveform be the 1st twice that is listed as for example.This means contrast ratio such as Figure 14, reduced like that shown in 15 that at this moment pulse width increases (frequency is low), thereby contrast ratio is obviously descended.In addition, the addressing pulse is not changed but is had very big amplitude and the commutation pulse than small magnitude in second field to form obvious contrast in first., change reliably, just need make between two transformation curves for example shown in Figure 3 has very big gap for this reason.

The intrinsic contrast of contrast ratio (CR) curve representation one display among Figure 14 (potpourri A) and Figure 15 (potpourri SEC8) when being added with under the AC bias situation between two bistable state position conversion.Obviously, make good contrast and evenly, preferably make display in the short plateau work of pulse width.Because the multiplex's AC bias from train wave shape can have the variable frequency component relevant with the picture dot form, thereby the contrast of display may change.This is under the situation that a kind of state (highest frequency component) and each picture dot alternately be in inverse state (lowest frequency components) the most noticeable at all picture dots, at this moment a factor of both differences is arranged in the train wave shape frequency.Figure 12 and 13 shows the 1st and the 4th row and is in both of these case.

The bed thickness that Figure 16 shows in the element of parallel friction is the time logarithmic curve of 1.8 microns the conversion characteristic of liquid crystal material SCE8 under 250 ℃.The coordinate axis of curve is respectively logarithm ts value and logarithm pulse amplitude magnitude of voltage.

Each curve is to obtain in the demarcation element of simulation addressing waveform shown in Figure 4.Two kinds of different addressing waveforms have been adopted.First waveform, the waveform I is a little negative pulse (amplitude is-1), and the duration that adds pulse is ts, then is a bigger positive pulse (amplitude is 5), and the duration that adds pulse is 2ts, and promptly Lp/Tp ratio is-0.166.After a period of time that through superpotential is zero volt, then be opposite situation, i.e. a little positive pulse (amplitude is 1) and a bigger negative pulse (amplitude is-5).Also added one 50 kilo hertzs square-wave signal during this external addressing, AC bias is provided thus and simulates a data waveform.Small-pulse effect is 0.166 of a big pulse value under employed all voltage levels of curve plotting.This first addressing waveform has provided a top curve.The time value of this curve top can make the element conversion, and the value of curve below then can not make the element conversion.

Second addressing waveform, the waveform II, amplitude was 1 to last the little positive pulse of ts before this, and then the back is that an amplitude is 4 to last the bigger positive pulse of 2ts.After no-voltage after a while, waveform changes opposite situation over to.Small-pulse effect is 0.25 of big pulse value, i.e. Lp/Tp=0.25.Here also add 50 kilo hertzs signal, so that AC bias to be provided.This second addressing waveform provided a following curve.The time value of this curve top can make the element conversion, and the value of curve below can not make the element conversion.Under the situation of gate voltage Vs=50 volt, data voltage Vd=10 volt, working range is the Vs-Vd=40 volt, changes when 52 microseconds, and the Vs+Vd=60 volt is changed when about 480 microseconds.

Figure 17 show with Figure 16 in the time voltage response of employed identical addressing scheme (being the addressing scheme of Fig. 4), but as among Fig. 8, in the gating waveform, adopted little prepulsing to improve.As can be seen from Figure 17, the effect of prepulsing is that the upright position of curve is moved.This can be in order to carry out temperature compensation: offset curve because of moving that temperature variation causes by changing the prepulsing value.

Above the simulation addressing waveform of a curve be no-voltage of lasting ts first, then be that to last the 2ts amplitude be 6 bigger positive pulse, i.e. Lp/Tp=0.After ts is in no-voltage at interval after a while, add opposite pulse, make total DC voltage remain zero.For AC bias is provided, 50 kilo hertzs of waveforms are superposeed up.

Below the addressing waveform of a curve then be first one last the little positive pulse that the ts amplitude equals 1, then being one, to last the 2ts amplitude be 2 bigger positive pulse, i.e. Lp/Tp=0.5.After this, conversely with its polarity.For AC bias is provided, 50 kilo hertzs of waveforms are superposeed up.

Vs=50, the working range of each curve is as follows during Vd=10: a following curve is Vs-Vd=40, when 42 microseconds, change, above a curve be Vs+Vd=60, when about 500 microseconds, change.

Figure 18 is similar to Figure 16, and liquid crystal cell is identical, but adopts Fig. 5 to address the analog waveform of waveform.Therefore the addressing waveform of a top curve is-1,6,4,6(Lp/Tp=-0.166); Below the addressing waveform of a curve be 1,4,6,4(Lp/Tp=0.25).Vs=50, during Vd=10, below a curve when 38 microseconds, change, above curve when about 210 microseconds, change.

Figure 19 and Figure 16 are similar, have same liquid crystal cell, but adopt Fig. 7 to address the analog waveform of waveform.The addressing waveform promptly indicates the curve that "+" number each point forms as shown in the figure, and its value is-1,6,6 ,-6(Lp/Tp=-0.166), to indicate its value of curve that " 0 " number each point forms be 1,4,4 ,-4.Its transfer process complexity, because a top curve has a new zone (re-entrant area), in this district, liquid crystal material is not to change when main pulse occurs but conversion when the pulse of smearing occurs.Vs=50, during Vd=10, below a curve Vs-Vd=40 when 58 to 240 microseconds, change, transfer process is carried out when occurring smearing pulse greater than 300 microseconds the time again.Above a curve Vs+Vd=60 in the time of 60 volts, do not change.The multiplex of main pulse takes place between 58 and 240 microseconds, and the multiplex of the pulse of smearing then takes place greater than 300 microseconds the time.

For the purpose of contrast, the log characteristic curve of the time of general monopulse addressing scheme has been shown among Figure 20, this scheme be with the same liquid crystal cell of Figure 11 in adopted the gating of Figure 11 and the analog waveform of data waveform.Above the simulation addressing waveform of a curve be to last the negative pulse that the ts amplitude is 1 unit, then be to last the positive pulse that the ts amplitude is 6 units.Below the addressing waveform of a curve then for to last the positive pulse that the ts amplitude is 1 unit, then be to last the positive pulse that the ts amplitude is 4 units.Here pulse amplitude in unit with the expression relative value; Each curve is to draw under the voltage that is exemplified.Vs=50, during Vd=10, below a curve Vs-Vd=40 when 80 microseconds, change, above curve Vs+Vd=60 then when about 950 microseconds, change.

After the characteristic of having introduced various different liquid crystal material displays and different addressing waveform, following some detailed problems of interview.We have made a kind of testing element of single picture dot, and address with 50 row display simulation waveforms.Respectively address magnitude of voltage for providing, chosen different gatings, Vs and data, the voltage magnitude of Vd, thus make changing voltage be in the top of a curve below Fig. 3, but not changing voltage is in the below of a curve above Fig. 3, regulate the microsecond value of ts in addition, conversion shows to provide clearly.Do the liquid crystal cell work in the zone shown in Fig. 3 hacures of having guaranteed like this.Contrast ratio CR is at the ratio of the light that transmits under a certain transition status with the light that transmits under another transition status; This is measuring of display resolution.CR measures under pulse width ultimate value ts or specific ts value.CR can make its transmission quantity corresponding to minimum reach optimum condition by a dislocation in the directed factor in the liquid crystal is adjusted to.

In following each table, the information that voltage/time curve of the reach of time ts and Figure 16-20 provides does not meet very much.Reason has three aspects.At first, employed analog form is not fully suitable concerning all situations of display graphics among Figure 16-20.Secondly, under the situation of pulse width than long and the corresponding length of frame time, because instantaneous the carrying out of conversion, operating personnel can find out scintillation, and this may be interpreted as does not have due to the multiplex addressing.The 3rd, when pulse width was longer, the contrast ratio step-down was seen Figure 14 and 15.For example, CR is 2 when 200 microseconds, is difficult to therefore determine whether liquid crystal material is in transition status.

25 ℃ of following bed thickness are 1.8 microns SCE8 liquid crystal material

Table 1, the addressing scheme of Fig. 4

Vs Vd ts CR

50 5 36-53 8-7

50 7.5 46-115 45-15

40 10 46-88 77-21.5

50 10 57-140 71-9.5

Table 2, the addressing scheme of Fig. 5

50 7.5 40-73 26-11

40 10 34-57 64-23

50 10 47-100 67-17

Table 3, the addressing scheme of Fig. 7

50 5 44-280 17.5-5.4

50 7.5 62-225 62-5

40 10 56-186 87-5.8

50 10 69-213 70-4.8

Table 4, the addressing scheme of Figure 11 (monopulse)

50 5 65-450 23-3

50 7.5 75-480 65-2.2

40 10 95-345 49-2.7

50 10 83-370 63-2.3

30 ℃ of following bed thickness are 1.7 microns potpourri B

Table 5, the addressing scheme of Fig. 4

Vs Vd ts CR(is when minimum ts)

50 10 22-78 51

50 7.5 17-82 33

40 10 16-47 56

Fig. 6, the addressing scheme of Fig. 5

50 10 20-68 51

50 7.5 14-62 24

40 10 13-36 53

40 7.5 10-37 7.2

45 7.5 10-42 10

Fig. 7, the addressing scheme of Fig. 7

50 10 24-80 52

50 7.5 19-98 35

40 10 18-66 68

Table 8, the addressing scheme of Fig. 4 under different temperatures

50 10 39-123 48 25℃

50 10 21-73 59 30℃

50 10 12-43 58 35℃

50 10 7-25 26 40℃

50 10 5-10 5 45℃

Table 9, the addressing scheme of Fig. 5 under different temperatures

50 10 18-64 52 30℃

50 10 8-20 13 40℃

50 10 8-37 44 35℃

50 10 35-120 48 25℃

Table 10, Figure 11 addressing scheme (monopulse) under 30 ℃

50 10 28-93 47

50 7-5 24-148 33

40 10 32-120 44

30 ℃ of following bed thickness are 1.7 microns potpourri A

Table 11, the addressing scheme of Fig. 4

40 10 39-100 46

50 10 59-120 26

Table 12, the addressing scheme of Fig. 5

40 10 33-85 48

50 10 52-110 30

Table 13, the addressing scheme of Fig. 7

40 10 40-150 46

50 10 64-220 23

Table 14, the addressing scheme of Figure 11 (monopulse)

40 10 56-150 32

50 10 66-300 22

No. 917 Merck Company Material product samples

30 ℃ of temperature; The Vs=60 volt; The Vd=15 volt

Table 15

Addressing scheme Figure 11 Fig. 4 Fig. 5 Fig. 7

During the fastest crack, microsecond 27 15 12 17

During the longest crack, microsecond 116 37 28 70

Working range (time) 4.3X 2.5X 2.3X 4.1X

Contrast ratio (CR) 41 84 80 76

Width (%) 63 63 60 63

Working range is: during the longest crack/and during the fastest crack

Brightness (%) is to compare under the situation that does not have liquid crystal cell between the parallel polarization device.

Material RSRE A206: 30 ℃ of temperature, Vs=30 volt, Vd=10 volt.

Table 16

Addressing scheme Figure 11 Fig. 4 Fig. 5

During the fastest crack, microsecond 60 27 20

Working range (time)＞2X 2.6X 2.2X 1X

Contrast ratio (CR) 14 48 55

Brightness (%) 77 67 60

Material RSRE A206 is: AS500:A151 1:1+5% adulterant

AS500:A151 1: the 1+5% adulterant

2% hand is levied

3% racemization

* number expression chirality, no * person represents that material is racemization.

Therefore in the display of reality, when it can not effectively be changed, then should look it and reach time upper limit.This is possibly than much shorter switching time of reality.

In ferroelectric liquid crystal devices, well-known, can apply the crest voltage that additional waveform reduces row and column by giving column electrode and row electrode.Therefore, display of the present invention also can comprise additional waveform generator, in order to producing additional waveform, and it is added on the two arrays of electrodes.

For example, Figure 23-24 shows two kinds of different schemes that reduce the crest voltage of monopulse drive system of the prior art shown in Figure 9.

Among Figure 23, gating (OK) waveform is alternately to be in zero and be positive pulse Vs in other 1ts in 1ts in first, then is zero and be negative pulse-Vs in another ts in 1ts in second.Additional waveform is positive Vs/2 at the 1st field interval, then at second is-Vs/2.Can see, the gating waveform that draws Vs/2 and-change between the Vs/2.Data (row) waveform is Vd and-pulse that Vd replaces, and the duration respectively is 1ts.The additional waveform that is added to each row is Vs/2 in the time of first, then in the time of second is-Vs/2.Can see, the data waveform that is drawn Vd+Vs/2 and-change between (Vs/2+Vd).The effect of additional waveform is to reduce for example 50 volts to 35 volts crest voltage.

Figure 24 shows the another kind of scheme that can replace Figure 23.With top the same, normal strobe pulse is earlier zero in first field time, lasts 1ts, is positive Vs then, lasts 1ts, then is earlier zero in second field time, lasts 1ts, is-Vs to last 1ts then.Added additional waveform is to be the square waveform of 2ts in the cycle in first field time, then then adds the waveform opposite with it in second field time, each waveform all Vs/2 and-change between the Vs/2.The gating that draws (OK) waveform as shown in the figure.Equally, data (row) waveform be+Vd and-square waveform that changes between the Vd.Additional waveform and be added to column electrode on the same.The data that draw (row) waveform as shown in the figure, this waveform Vs/2+Vs and-change between (Vs/2+Vd).This equally also make display the required usefulness of driver crest voltage from for example 50 volts be reduced to 35 volts.

Figure 23 and 24 principle equally also are applicable to the addressing scheme of above-mentioned Fig. 4-8.Figure 25 shows the situation of this respect, and this is a modification to Fig. 5.In first field time, strobe pulse is earlier zero, lasts 1ts, then for Vs, lasts 3ts.In second field time, strobe pulse is earlier zero, lasts 1ts, then is-Vs, lasts 3ts.There is shown the 1st, 2,3, the 4 gating waveforms of going that 4 row show; Express two different gating waveforms of the 4th row among the figure, its reason will illustrate below.Being added to the additional waveform of row (and also being added to row) electrode, as shown in the figure, is Vs/2 in first field time, in second field time is then-Vs/2.As can be seen, the capable waveform of first row that draws is-Vs/2 to last 1ts in first and second field time; Vs/2 lasts 3ts;-Vs/2 lasts 4ts; Vs/2 lasts 1ts;-Vs/2 lasts 3ts and Vs/2, lasts 4ts.From the gating waveform and the additional waveform that are drawn and be expressed as the capable row of 4a as can be seen, this waveform has+and-the big peak value of 3Vs/2.The reason of this phenomenon is that strobe pulse length has prolonged, and overlaps onto in the adjacent field.For addressing this problem, can make the 4th row keep hidden, perhaps use the zero gate voltage shown in 4b to address.In the more practical example that for example 128 row show, the waveform that is produced is programmed by 128 row are shown, but in the scheme of Figure 25, has only used 127 row.Even adopt longer strobe pulse as shown in Figure 6, also can be that row even more capable the keeping that has need not.Figure 26 shows the waveform that is added on each row electrode.The same among data 1 and reverse data 2 thereof and Fig. 5.Additional waveform is Vs/2 in first field time, in second field time is-Vs/2.As can be seen, the train wave shape that draws ± change between (Vd+Vs/2).Therefore concerning the scheme of Fig. 5, under the situation that Vs=50 volt and Vd=10 lie prostrate, Figure 25,26 scheme make crest voltage be reduced to 35 volts.

Claims

1, the formed ferroelectric liquid crystal matrix display in a kind of each point of crossing to first group of electrode and second group of electrode carries out the method for multiplex addressing, comprises the following steps:

2, the method for claim 1, it is characterized in that the gating waveform is a no-voltage in the time of first ts, is nonzero value voltage in a period of time greater than ts, then the some ts in a frame period of expression are no-voltage in the time, then are opposite polarity similar waveform again.

3, the method for claim 1 is characterized in that, the gating waveform is nonzero value voltage in the time at first ts, and this voltage is less than next voltage, and amplitude is variable, to compensate the liquid crystal material conversion characteristic with variation of temperature.

4, the method for claim 1 is characterized in that, adopts two opposite polarity strobe pulses when each point of crossing is addressed.

5, method as claimed in claim 4 is characterized in that, adds the another one waveform to two arrays of electrodes, to reduce to be added to the crest voltage on each electrode.

6, the method for claim 1 is characterized in that, blanking pulse has two opposite polarity parts, and the voltage time product of its voltage time product (Vt) and strobe pulse lumps together the DC component value is equalled zero.

7, a kind of multiplex addressing LCD comprises:

It is characterized in that a data waveform generator and a gate pulse ganerator are arranged, the former has equal magnitude and frequency but the waveform of opposite in sign in order to produce two groups, and each data waveform all comprises the DC pulse of symbol alternation; The latter is in order to produce two opposite polarity strobe pulses or blanking pulse and opposite polarity strobe pulse, and the duration of strobe pulse is bigger than half data waveform cycle, and lasts till the addressing time of next electrode always;

And carry out such arrangement: to each point of crossing addressing, make each complete demonstration addressing cycle of point of crossing once enter desired show state with symbol and the suitable pulse of size, and to make total DC component value be zero.

8, display as claimed in claim 7, it is characterized in that, the gating waveform generator is designed so that it produces no-voltage in first time cycle ts, in greater than a period of time of ts, produce nonzero value voltage then, then the some ts in a frame period of expression are no-voltage in the time, then are opposite polarity similar waveform again.

9, display as claimed in claim 8 is characterized in that, it also comprises additional waveform generator, in order to producing additional waveform, and this additional waveform is added on the two arrays of electrodes.

10, display as claimed in claim 7 is characterized in that, it also comprises a temperature sensor, in order to detect the temperature of display; And a voltage regulator, in order to regulate the size of addressing voltage.

11, display as claimed in claim 10, it is characterized in that, the gating waveform generator is designed so that it produces nonzero value voltage in first time cycle ts, this voltage is less than the next voltage that adjoins, but and its amplitude and symbol change, so that compensation liquid crystal material conversion characteristic makes its unlikely being acted upon by temperature changes.

12, display as claimed in claim 7, it is characterized in that, the gating waveform generator is designed so that its generation has the blanking pulse of two opposite polarity parts, and the voltage time product of its voltage time product (vt) and strobe pulse lumps together total DC component value of waveform is equalled zero.