CN102208175B - The driving method of bistable liquid crystal display device - Google Patents

Abstract

In the driving of bistable liquid crystal display device, between pixel, can not rewrite display intrusively.First the liquid crystal layer of all pixels is made to become T structure with reset pulse 1.Then to the pixel maintaining T structure, between the first selecting period, in 2a, apply the voltage of below anchor ring damage threshold, to the pixel becoming U structure, between the first selecting period, in 5a, apply the voltage of more than anchor ring damage threshold.Then, between the second selecting period, in 2b, 5b, apply the voltage being less than anchor ring damage threshold, and then between the 3rd selecting period, apply the voltage of 0V.Like this, the fluidly control structure state of liquid crystal can not be caused.

Description

The driving method of bistable liquid crystal display device

Technical field

The present invention relates to the driving method of the liquid crystal indicator of bistable (bistable state) type, the hand particularly utilizing bistability switch simple matrix to drive levies the drive unit of nematic crystal display device.

Background technology

Now, twisted-nematic (TN) type liquid crystal, supertwist to row (STN) type liquid crystal, electrical control birefringent ECB type liquid crystal, to be vertical orientatedly widely used to liquid crystal indicators such as row (VA) type liquid crystal.These liquid crystal belong to monostable sizing, and when not applying electric field to liquid crystal layer, liquid crystal molecule becomes single structure (texture).When applying electric field to liquid crystal layer, the structure of liquid crystal molecule is out of shape continuously, and along with the distortion of structure, light characteristic changes.If there is not electric field in liquid crystal layer, just return to and stabilize to single structure.These liquid crystal indicators do not have storage effect.Therefore, need to use static drive, multipath transmission driving or driven with active matrix, drive continuously.On the other hand, bistable or multistable style keeping liquid crystal device have storage effect.Even if these liquid crystal indicators, under the state not applying electric field to liquid crystal layer, also can form different structures in box (cell).And, by applying specific electric field to liquid crystal layer, can change structure.This display device, once after determining structure, even if lose electric field, also can utilize its bistability, maintain the state of its structure.Therefore, image refreshing speed significantly declines, and power consumption reduces.

In recent years, the bistable liquid crystal indicator (such as with reference to patent documentation 1) using hand to levy nematic crystal is advocated.Fig. 5 is the dynamic schematic diagram of the liquid crystal molecule telling about bistable liquid crystal panel.As shown in the figure, first substrate 31 and second substrate 32 form electrode 33 respectively, and then the first alignment films 34 and the second alignment films 35 is set thereon.In the gap of first substrate 31 and second substrate 32, liquid crystal layer 6 is set.In this bistable liquid crystal panel, under the effect of alignment films liquid crystal molecule towards required towards.Here, the anchor ring power of the first alignment films 34 is greater than the second alignment films 35.Therefore, on the interface of the first alignment films 34, because the anchor ring power of the liquid crystal molecule of liquid crystal layer 6 is comparatively large, so liquid crystal molecule has angle a little, and on the interface of the second alignment films 35, because anchor ring power is less, so liquid crystal molecule roughly becomes level.When applying electric field to liquid crystal layer 6, on the interface of alignment films, although the anchor ring display of liquid crystal molecule is monostable qualitative, but can become U structure and these two steady state (SS)s of T structure as liquid crystal layer 6.U structure (uniform-texture) 7 is states of the arrangement of the same or distortion a little of liquid crystal molecule, and T structure (twisted-texture) 8 is the states arranged after twisted liquid crystal molecules.The about mutual deviation of distortion 180 ° of these two structures, can not coexist at identical position.The idiopathic spacing p0 of the liquid crystal molecule of nematic, just as the energy of the T structure of U structure with distortion identical in essence, maximum about 4 times of ground that can become the thickness d of box are selected.Like this, when not applying electric field, with there is not other the state with lower energy level with certain in U structure 7 and T structure 8 in stable condition (bistability).

Whichever structure, after destroying anchor ring, all will change from a structure to another structure.Apply stronger electric field from outside, destroy the anchor ring power of alignment layer surface, thus cause the conversion from U structure to T structure (or from T structure to U structure).Be no matter which state in U structure and T structure, after applying specific electric field, liquid crystal layer 6 just all becomes homeotropic texture (Homeotropic-texture, hereinafter referred to as " H structure ").By the electric field threshold value making liquid crystal layer become H structure 9, be defined as Vc (anchor ring damage threshold).Anchor ring damage threshold Vc depends on polar angle anchor ring energy (zenithal-anchoring-energy) Az that the material of alignment films is intrinsic and liquid crystal material.If apply the electric field of more than anchor ring damage threshold, then anchor ring is just destroyed.In addition, this electric field also impels the liquid crystal molecule in the near surface of alignment films to rearrange.Form H structure 9 until final, need this electric field to apply time enough.The minimum time is relevant to the physical characteristics applying the size (amplitude) of electric field, liquid crystal and alignment films.When electric field is applied in 1 ~ 3 millisecond or more, anchor ring damage threshold Vc can be defined with following formula 1.

(formula 1) Vc=d × Az/ (k33 × ε 0 × Δ ε) ^1/2in formula, d represents the thickness of liquid crystal cells; Az represents polar angle anchor ring energy; K33 represents the elastic torsion coefficient of liquid crystal; Δ ε represents the dielectric anisotropy of liquid crystal; ε 0 represents the dielectric constant in the vacuum of liquid crystal.

If apply this anchor ring damage threshold Vc, then alignment films interface liquid crystal molecule towards and vertical between angle just very little (such as less than 0.5 °), the stress that alignment films affects liquid crystal molecule is very low.Cut off in this condition after electric field, the liquid crystal molecule near alignment films just becomes unstable equilibrium state, be recover original towards or become rotate 180 ° of distortions in the opposite direction new structure in some.Finally become which structure, with apply electric signal shape, specifically return with this electric field (voltage) zero method closely bound up.

When electric field is periodically declined, flowing (power on the fluid mechanics of liquid crystal molecule) becomes minimum, liquid crystal molecule near the alignment films of stronger anchor ring tends to balance state lentamente, carrying out after elasticity is combined with the liquid crystal molecule of central authorities, liquid crystal molecule rotates towards identical direction.This motion, to more weak anchor ring side substrate diffusion, promptly rotates towards identical direction one by one, forms the same state (U structure 7) in box.

On the other hand, when electric field is declined sharp, such as, after carrying out switch motion at short notice, just near the alignment films of stronger anchor ring, respond to stronger flowing.This flowing, to liquid crystal layer transmission, arrives the surface of the alignment films of more weak anchor ring.On the surface of the alignment films of more weak anchor ring, the power on fluid mechanics is greater than anchor ring power, becomes the T structure 8 of distortion.Like this, if control the electric field applied to each pixel, it just can be made to change from a structure to another structure.

Present use Fig. 6, tells about the electric field that structure is changed.Fig. 6 is the schematic diagram representing the voltage waveform being applied to liquid crystal layer.Fig. 6 (a), (b) make its waveform changed from U structure to T structure.In Fig. 6 (a), during τ 1, apply the potential pulse P1 being greater than anchor ring damage threshold.During the pulsewidth of waveform and τ 1, it is 2 ~ 3 milliseconds.During this τ 1, become H structure from U structure.Then, during τ 2, the potential pulse P2 of Δ V lower than potential pulse P1 is applied.Promptly reduce this voltage difference delta V, thus in the very strong flowing of liquid crystal layer internal induction, become T structure.During generating the τ 2 needed for T structure, be about 1/10 during τ 1, maximum also need 500 microsecond.Potential difference (PD) Δ V depends on the difference of potential pulse P1 and P2 applied during τ 1 and τ 2.In an experiment, when potential pulse P1 is 24V, potential pulse P2 is below 8V.Again then, during τ 3, apply 0V.If carry out the continuous action of this τ 1 ~ τ 2 ~ τ 3, then change to T structure from U structure via H structure.In Fig. 6 (b), to illustrate during making τ 2 and potential difference (PD) during τ 3 be greater than τ 1 during and potential difference (PD) during τ 2 time situation.During τ 1, become H structure from U structure, during τ 2, become T structure from H structure.At this moment, potential pulse P2 is made to be more than anchor ring damage threshold.Specifically, P2 is made just can to obtain identical effect after the degree of more than 10V.

Fig. 6 (c), (d) are waveforms when making it change from T structure to U structure.With equally above-mentioned, during τ 1, apply the potential pulse P1 being greater than anchor ring damage threshold.During this τ 1, become H structure from U structure.Then, during τ 2, it is made to reduce lentamente.Fig. 6 (c) illustrates the situation reducing voltage during τ 2 skewedly, and Fig. 6 (d) illustrates the situation reducing voltage stepwise.The situation reducing voltage is desirable skewedly, but normally makes it reduce stepwise.Specifically, when potential pulse P1 is 16V, potential pulse P2 is more than 8V below 12V.Again then, during τ 3, apply 0V.If carry out the continuous action of this τ 1 ~ τ 2 ~ τ 3, then change to U structure from T structure via H structure.Like this, become which structure, depend on to apply which type of voltage during τ 2.

Then, the driving method of the bistable liquid crystal panel of dot matrix type is told about.Fig. 7 illustrates the signal waveform being applied to bistable liquid crystal panel.Fig. 7 (a) illustrates the common signal (COM) being applied to public electrode, Fig. 7 (b) illustrates the block signal (SEG) being applied to segmented electrode, and Fig. 7 (c) illustrates voltage between public-segmentation, is namely applied to the waveform (COM-SEG) of the liquid crystal layer clamped with public electrode and segmented electrode.In figure, the waveform in left side is the situation making the pixel of public electrode and segmented electrode intersection become U structure, and the waveform on right side is the situation making this pixel become T structure.Fig. 7 (d) schematically shows the relation of the state applying waveform and liquid crystal molecule.

First, the waveform in left side is told about.If apply the common signal shown in Fig. 7 (a) and the block signal shown in Fig. 7 (b), then pixel (liquid crystal layer) is applied in the voltage waveform shown in Fig. 7 (c).Because be applied to+the V of liquid crystal layer ,-V to become anchor ring more than damage threshold Vc, no matter so which kind of structure the liquid crystal layer before applying signal is, be also all H structure during applying-V to liquid crystal layer.Become the effect of the waveform of 0V stepwise at the next one under, cause more weak liquid crystal flowing, become U structure in the stage till 0V current potential that arrives.On the other hand, the waveform on right side is told about.No matter which kind of structure the liquid crystal layer before applying signal is, be also all H structure during applying-V to liquid crystal layer, this is same with the waveform in left side.During the next one, maintain potential difference (PD) to a certain degree, arrive 0V rapidly.At this moment, along with the flowing of larger liquid crystal, change from H structure to TH structure.As known in the figure: be no matter that the situation becoming U structure of left and right becomes T structure situation, although common signal is identical, but block signal is different.The display of liquid crystal panel, a concentric line of signal and the signal condition of all segmentations is selected according to being supplied to, determine the black and white (state of structure) of a line, scan all concentric lines successively, thus determine the display (black and white) of whole picture.In the moment of carrying out scanning, only select signal to the concentric line supply of in whole picture.To the voltage waveform of remaining most concentric line supply non-select signal.At this moment the waveform being applied to liquid crystal layer is not the waveform causing anchor ring to destroy, so maintain by the structure selecting signal deciding.This series of actions, by control circuit (MPU) control COM driver, SEG driver and carrying out.Like this, all concentric line of scanning bistable LCDs, determine display after, even under the state not applying public and segmentation, also keep display image.In other words, after write image, even if cut off the electricity supply, the image of bistable LCDs also maintains display.Therefore, although need electric power when rewriting, also can show (such as with reference to patent documentation 2) even without electric power later.

Patent documentation 1: Jap.P. No. 3293138 publication

Patent documentation 2: Japanese Unexamined Patent Publication 2004-4552 publication

Summary of the invention

As mentioned above, applied to be greater than the potential pulse of anchor ring damage threshold Vc during τ 1 after in the past, during τ 2, giving segmented electrode for becoming the current potential of required structure, during τ 3, then applying the voltage of 0V.Like this, liquid crystal dynamically just under the effect of the current potential of anchor ring more than damage threshold Vc, first become H structure, change to T structure or U structure from the displaying contents of this H structure according to image.As mentioned above, when becoming T structure from H structure change, produce flowing, the interference so the U structure adjacent with T structure is flowed.Like this, in the pixel with regard to Cheng Wei U structure, mix the state of T structure, made the arrangement disorder of liquid crystal molecule.Particularly the pixel on the edge of pixel or the border of display frame is very eye-catching.Like this, the display just producing display state light or dense in picture is irregular.Particularly with the tartan of 1 single point bit reversal display (grid pattern) or black display more time, show irregular very eye-catching.Therefore, the object of the invention is to realize in face, not producing the irregular bistable liquid crystal indicator of display.

Therefore, in the driving method of bistable liquid crystal indicator of the present invention, possess successively: during initialization, in order to make the liquid crystal layer of all pixels become T structure, and applying has the reset pulse that anchor ring destruction is worth above voltage; Between the first selecting period, the liquid crystal layer becoming the pixel of U structure to change applies anchor ring destruction and is worth above voltage or is worth following voltage to the liquid crystal layer applying anchor ring destruction of the pixel maintaining T structure; Between the second selecting period, apply anchor ring destruction to liquid crystal layer and be worth following voltage, in order to avoid cause flowing in the liquid crystal molecule of liquid crystal layer; And the 3rd between selecting period, the liquid crystal layer to all pixels applies 0V.By this driving method, during initialization, the liquid crystal layer of all pixels is all rewritten into T structure; Between the first selecting period and between the second selecting period, decision is that change becomes U structure or maintains T structure.And then, between the 3rd selecting period, apply 0V voltage, thus maintain U structure or T structure.Like this, when obtaining T structure, between the selecting period till from the first to the three, because do not apply anchor ring destruction to be worth above voltage, the flowing of liquid crystal can not be caused.

And then, to make to be longer than between the 3rd selecting period between the first selecting period and sum between the second selecting period.In addition, between also during initialization and between the first selecting period, during being set to the liquid crystal layer applying 0V of all pixels.

And then, in order to will the waveform interchangeization of liquid crystal layer be applied to, repeatedly to carry out between the first selecting period and between the second selecting period after, move on between the 3rd selecting period.In addition, between the second selecting period, the waveform that current potential changes stepwise can be applied.

And then, according to the temperature information from temperature sensor, determine the magnitude of voltage that applies between the first selecting period or during applying, the magnitude of voltage that applies between the second selecting period or during applying, between the 3rd selecting period at least one.

(invention effect)

According to driving method of the present invention, even if when making pixel be T structure, liquid crystal flowing also can not be produced, so the limit end of display pixel or the limit end of display frame can not mix the display of T structure and U structure.Therefore, it is possible to carry out there is no irregular uniform display.In addition, in matrix driving, also between pixel, can not rewrite display intrusively.And then, in icon (icon), symbol display or segmentation display, also can until the edge of display pixel shows brightly.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the drive waveforms telling about embodiment 1.

Fig. 2 is the schematic diagram of the drive waveforms telling about embodiment 2.

Fig. 3 is the schematic diagram of the drive waveforms telling about embodiment 3.

Fig. 4 is the circuit block diagram of bistable liquid crystal indicator.

Fig. 5 is the schematic diagram of the configuration state telling about liquid crystal layer.

Fig. 6 tells about existingly to execute alive schematic diagram.

Fig. 7 is the schematic diagram telling about existing drive waveforms.

Embodiment

In the driving method of bistable liquid crystal indicator of the present invention, first apply reset pulse to all display pixels, make liquid crystal layer become T structure.Then, the higher potential pulse (being decided to be between the first selecting period during being applied by this voltage) of more than the pixel applying anchor ring damage threshold of U structure is become to hope change.Then, before being reduced to 0V, apply the voltage (being decided to be between the second selecting period during being applied by this voltage) lower than anchor ring damage threshold Vc.When applying this waveform to liquid crystal layer, between the first selecting period, become H structure from the change of T structure, become U structure finishing the phase change between the second selecting period.After just finishing between the second selecting period, the voltage of 0V is applied predetermined time period, maintain U structure.Be called during the voltage applying this 0V between line signal stand-down or between the 3rd selecting period.Like this, can change in the configuration state of the first to the 3rd selecting period chien shih liquid crystal.On the other hand, the pixel maintaining T structure to hope applies the voltage lower than anchor ring damage threshold Vc between the first selecting period.And then, between the second selecting period, also apply the voltage lower than anchor ring damage threshold Vc.When applying this waveform to liquid crystal layer, the T structure formed by reset pulse all can not change the structure that becomes other and maintain T structure between the first selecting period or between the second selecting period.And then after just terminating between the second selecting period, arrange between line signal stand-down (between the 3rd selecting period), online signal applies the voltage of 0V between stand-down.Maintain T structure thus.

By this driving method, the pixel of the pixel of U structure and T structure can be made to be mingled in display frame.At this moment T configuration state, can not become T structure after H structure change.Therefore, liquid crystal molecule does not cause flowing and can obtain T structure.Like this, the impact that would not be flowed of U structure.

In addition, concentric line is driven by selecting successively.Needs apply the voltage lower than anchor ring damage threshold Vc to the concentric line of nonselection mode all the time.

In addition, can be longer than and set to sum between the first selecting period and between the second selecting period between line signal stand-down.

[embodiment 1]

Then, the driving method of the bistable liquid crystal panel of the present embodiment is told about.Fig. 1 illustrates the drive waveforms being applied to and using bistable hand to levy the lattice lcd panel of nematic liquid crystal.Fig. 1 (a) illustrates the signal being applied to segmented line (SEG1), Fig. 1 (b) illustrates the signal being applied to concentric line (COM1), Fig. 1 (c) illustrates the waveform of the intersection point being applied to COM1 and SEG1, Fig. 1 (d) illustrates the signal being applied to COM2, and Fig. 1 (e) illustrates the waveform of the intersection point being applied to COM2 and SEG1.

The pixel being applied in the waveform shown in Fig. 1 (c) becomes T structure, and the pixel being applied in the waveform shown in Fig. 1 (e) becomes U structure.No matter which kind of situation, is all first apply reset pulse 1, whole liquid crystal panel is changed to T structure.In fact, the divided reset signal S1 shown in Fig. 1 (a) is supplied segmented line, the common reset signal C1 shown in Fig. 1 (b) is supplied concentric line.Such as make V0=30, V5=GND (0V).The waveform synthesizing these signals becomes centered by 0V, has the reset pulse 1 of the amplitude of 2 times of V0.Under the effect of reset pulse 1, after the square wave of positive level+4, apply the square wave of negative level-4.Like this, do not apply direct current to liquid crystal layer, charge component can not be detained in liquid crystal layer.Here, anchor ring destruction value+Vc is between potential level+4 and potential level+3.

Then, being just applied with in the time interval D after reset pulse 1, common signal and block signal is made to be all V5.Like this, 0V is applied to pixel also as shown in Fig. 1 (c).It is waveform 3 between stand-down of applying between online signal stand-down.Between this stand-down, waveform 3 is whole after the change of T structure, in order to make this in stable condition necessary.

Below, according to Fig. 1 (a) ~ (c), tell about the waveform applied to the pixel maintaining T structure.The concrete example of the signal to SEG1 supply is first told about according to Fig. 1 (a).After divided reset signal S1, alternative supply S2 signal and S4 signal.S2 signal maintains T structure together with the common signal of selection mode, and S4 signal makes U structure change together with the common signal of selection mode.S2 signal is corresponding with the time interval E and F, and magnitude of voltage is V34; S4 signal is corresponding with the time interval H and I, and magnitude of voltage is V0.After S2 signal and S4 signal the time interval G, J magnitude of voltage become V5.The concrete example of the signal to COM1 supply is told about again according to Fig. 1 (b).After common reset signal C1, supply C2 signal, then supplies C4 signal.Magnitude of voltage V5 is got between each signal, corresponding with waveform between stand-down.Because drive concentric line, so supply C2 signal between the selecting period of concentric line according to line order.In other words, the time interval E, F of COM1 are between selecting period, supply C4 signal after this time, until terminate to all concentric lines write image.Like this, the liquid crystal layer of the pixel intersected to COM1 and SEG1 applies the waveform shown in Fig. 1 (c).In order to maintain T structure, the waveform shown in Fig. 1 (c), after reset pulse 1, is formed with the current potential of anchor ring below disintegration voltage Vc.In the time interval E, F, the liquid crystal layer to this pixel applies first shown in Fig. 1 (c) and selects waveform 2.Here, between the first selecting period of the first selection waveform 2, the voltage level of 2a is "-2 ", and between the second selecting period, the voltage level of 2b is "+1 ".First selects waveform 2 must to form with the voltage level becoming anchor ring below damage threshold Vc.Specifically, 2a between the first selecting period, is decided to be the approximately voltage of about-4V and the waveform widths of about 1 millisecond; 2b between the second selecting period, is decided to be the approximately voltage of about+2 ~+4V and the waveform widths of 50 ~ 500 microseconds.Because the applying voltage of the best and time become along with environment temperature, so setting after considering it.Then, and then between the second selecting period after 2b, become between line signal stand-down, in this time interval G, namely the voltage becoming level 0V become waveform 3 between stand-down.Apply this first to liquid crystal layer and select waveform 2 and between stand-down during waveform 3, because maintain T structure, so do not produce liquid crystal flowing.At this moment, finally applying the time of waveform 3 between stand-down, is the time of being longer than 2b sum between 2a and the second selecting period between the first selecting period.Specifically, more than 2 milliseconds are set as.

After between the line signal stand-down shown in time interval G in FIG, the liquid crystal layer to this pixel alternately applies the synthetic waveform of the S4 signal shown in the C4 signal (non-selection common waveform) shown in Fig. 1 (b) and Fig. 1 (b) or S2 signal.In other words, continue to apply the non-selection period waveform 4 shown in Fig. 1 (c), until to all concentric lines write view data.Here, waveform 4 is square waves of voltage level-2 or+2 non-selection period.In non-selection period of different voltage levels between waveform 4, namely the voltage applying 0V apply waveform 3 between stand-down.Like this, after making whole face become T structure with initial reset pulse 1, make waveform 3, first between stand-down select waveform 2, waveform 3 and then at the waveform 4 and number of times of waveform 3 remaining line number repeatedly between stand-down of non-selection period thereafter between stand-down, thus maintain T structure.

Below, the waveform being applied to the pixel becoming U structure from T Structural Transformation is told about.The liquid crystal layer of pixel that here COM2 and SEG1 intersects is for conversion into U structure.Fig. 1 (d) is the signal of supply COM2, and Fig. 1 (e) is the waveform that the liquid crystal layer of the pixel intersected to COM2 and SEG1 applies.As shown in Fig. 1 (d), after common reset signal C1, supply C4 signal to COM2, then supply C2 signal.Because drive concentric line, so staggered between the selecting period of COM1 and COM2 according to line order.In other words, the time interval H, I of COM2 are between selecting period, supply C4 signal after this time, until terminate to all concentric lines write image.

The state of the liquid crystal layer of the pixel that COM2 and SEG1 intersects is told about with reference to Fig. 1 (e).First, when the time interval, B, C applied reset pulse 1, liquid crystal layer becomes T structure.Then, the time interval H, I between the selecting period of COM2 apply second and select waveform 5.Second selects waveform 5 to need to comprise the voltage level becoming anchor ring more than damage threshold Vc.Second selection waveform 5 is the synthetic waveforms of the Professional Association signal C2 shown in the block signal S4 and Fig. 1 (d) shown in Fig. 1 (a).Between the first selecting period of the second selection waveform 5, the voltage level of 5a is "-4 ", is the voltage level of anchor ring more than damage threshold Vc.Between the second selecting period, the voltage level of 5b is "-3 ", is the voltage level of anchor ring below damage threshold Vc.To follow closely between the second selecting period after 5b, become between line signal stand-down, in this time interval J, apply the voltage (i.e. waveform 3 between stand-down) of level 0V.When liquid crystal layer to T structure applies this second selection waveform 5, between the first selecting period, in 5a, anchor ring is destroyed, and becomes H structure.Then, between end second selecting period, in the stage of 5b, become U structure.This is because the difference of the voltage applied between 5b and line signal stand-down between the difference of voltage that between the first selecting period, between 5a and the second selecting period, 5b applies and the second selecting period is all less than anchor ring damage threshold Vc.Like this, the liquid crystal layer of T structure, under the effect of the second selection waveform 5, becomes U structure through H structure.Then, between stand-down waveform 3 effect under, maintain U structure.And then, although with after-applied non-selection period waveform 4 and waveform 3 between stand-down, because be configured to the voltage into anchor ring below damage threshold Vc, so just maintain U structure.

Specifically, the voltage sets that 5a between the first selecting period applies is become about-13V ~-20V, application time setting is become about 1 millisecond.In addition, between the second selecting period in 5b, setting becomes the voltage of about-8V ~-13V and the time of 50 ~ 500 microseconds.Between line signal stand-down, G is longer than the time sum of 5b between 5a and the second selecting period between the first selecting period.Specifically, setting becomes more than 2 milliseconds.In addition, the time interval E and H, F and I, G and J are identical time widths.After time interval J, make non-selection period waveform 4 and number of times of the line number that waveform 3 is left repeatedly between stand-down.In addition, as shown in Fig. 1 (c), (e) because non-selection period waveform 4 alternately to appear at+side and-side, so liquid crystal layer can not be subject to the impact of flip-flop.

Here, the structure of bistable liquid crystal panel is told about.The polarization plate with the absorption axle forming the angle of about 45 degree with orientation angles of bistable liquid crystal panel, parallel (Nicol) configuration in the both sides of liquid crystal layer.When liquid crystal layer is T structure, transmissivity uprises, if observed with reflective-mode, just becomes white display.This is because in T structure, less there is phase differential and intactly by the cause of polarization plate in rectilinearly polarized light.On the other hand, when liquid crystal layer is U structure, liquid crystal molecule shows greatly 0 degree of arrangement, produces the phase differential of Δ nd.Such as, when the long-pending setting of the refractive index n of liquid crystal and thickness of liquid crystal layer d being become wavelength X/2, rectilinearly polarized light just produces the phase differential of 180 degree, orientation rotation 90 degree.Like this, during parallel Nicol configuration, due to transmissivity step-down, just become black display so observe with reflective-mode.In other words, utilize in T structure for white, show for black pattern in U structure.In addition, when carrying out the polarization plate configuration of cross Nicols, just to become in T structure as black display, be white display in U structure, compared with parallel Nicol, the display of reversing can be carried out.Tell about the situation of the formation of parallel Nicol configuration polarization plate below.

Fig. 3 is the circuit structure schematically showing bistable liquid crystal indicator.Bistable liquid crystal panel 30 common driver 41 of the concentric line of driving horizontal direction, the segment drivers 42 of the segmented line of driving vertical direction, generation drive the power circuit 43 of current potential (V0, V12, V34, V5, VCX), control control circuit (MPU) 44 driving of common driver 41 and segment drivers 42 and power circuit 43.Control circuit 44 supplies the control signal of common driver 41 and segment drivers 42, and common STN driving circuit is same.In other words, to common driver 41 input initialization signal (RESETX), the signal (C-data) determining scanning timing, write clock (CL), interchangeization signal (FRCOM) and display erase signal (DispOffx), to segment drivers 42 input initialization signal (RESETX), display viewdata signal (S-data), write clock (XCK), interchangeization signal (FRSEG) and display erase signal (DispOffx).In addition, temperature sensor 45 is connected with control circuit (MPU) 44.Power circuit 43 is loaded among common driver 41, and then also loads segment drivers 42, thus an IC can be made.First, MPU44 carries out following program (sequence): from temperature sensor 45, read ambient temperature value, from the thermometer be stored in MPU, obtain each information of voltage, set after the value meeting table is supplied to power supply 43 and export each current potential (V0, V12, Vcx, V34, V5).Meanwhile, from thermometer, also obtain the width information in each time interval, when successively exporting, determine pulsewidth at every turn.Then, according to these information, drive liquid crystal panel with the pulsewidth conformed to temperature.

As mentioned above, when iting is desirable to become U structure (black display), apply between the first selecting period anchor ring more than damage threshold Vc ± 4 level; When wishing to maintain T structure (showing in vain), apply between the first selecting period anchor ring below damage threshold Vc ± 2 level.In addition, between the second selecting period, no matter when all apply the voltage level of anchor ring below damage threshold Vc.Between the 3rd selecting period after following closely between the second selecting period, apply the voltage level (i.e. waveform 3 between stand-down) of 0V.And then, even if in non-selection period, also to clip between line signal stand-down and to apply the voltage level (± 2 level) of anchor ring below damage threshold Vc.Like this, between the first selecting period, be applied in the pixel of the voltage level of anchor ring more than damage threshold Vc, just changed to U structure (black display) from T structure (showing in vain); The pixel being applied in the voltage level of anchor ring below damage threshold Vc between the first selecting period then continues to maintain T structure (showing in vain).In addition, these shape informations and reset pulse equally, utilize temperature sensor to read ambient temperature data, obtain voltage and the width information of the waveform conformed to this temperature, waveform is reflected from the thermometer preset.This driving owing to can not obtain T structure, so do not produce the flowing of liquid crystal after H structure change.Therefore, also interference can not be produced between the pixels.Like this, just successfully can rewrite, not cause display interference between the pixels.The waveform applied due to non-selection period does not reach anchor ring damage threshold, so structure is constant.Bistable liquid crystal panel 30 scans concentric line successively according to the amount of a picture, thus determines the display of whole picture.After as described above image being write bistable liquid crystal panel 30, even if make common electric voltage and segmentation voltage be GND, make bistable liquid crystal panel 30 become without applying state, also can keep the display image write.In other words, after write image, the display image of bistable liquid crystal panel 30 can also be maintained even if cut off the electricity supply.Like this, although need electric power during write, can show under the state of unregulated power later.

[embodiment 2]

Then, Fig. 2 is used to tell about the driving method of the present embodiment.Fig. 2 represents the schematic diagram being applied to and using bistable hand to levy the drive waveforms of the lattice lcd panel of nematic liquid crystal.Detailed content between the first selecting period of formation first selection waveform and the second selection waveform and between the second selecting period, and the difference of embodiment 1.In other words, in the present embodiment, between the first selecting period, between 12a and the second selecting period, 12b selects each in waveform appearance twice at one.Other is identical with embodiment 1, so suitably omit telling about of repetition.

Fig. 2 (a) illustrates the signal being applied to segmented line (SEG1), Fig. 2 (b) illustrates the signal being applied to concentric line (COM1), Fig. 2 (c) illustrates the waveform of the intersection point being applied to COM1 and SEG1, Fig. 2 (d) illustrates the signal being applied to COM2, and Fig. 2 (e) illustrates the waveform of the intersection point being applied to COM2 and SEG1.In the present embodiment, the pixel being applied in the waveform shown in Fig. 2 (c) becomes T structure, and the pixel being applied in the waveform shown in Fig. 2 (e) becomes U structure.

The waveform applied to the pixel (intersection point of COM1 and SEG1) maintaining T structure is first told about according to Fig. 2 (c).First, the reset pulse 1 of the composite wave of divided reset signal S1 and common reset signal C1 is applied to pixel.Because reset pulse 1 has the voltage of anchor ring destruction more than value Vc, so liquid crystal layer becomes T structure.After during following the initialization applying reset pulse 1 closely, arrange between line signal stand-down.Online signal applies waveform 3 (current potential of 0V) between stand-down between stand-down.Between this stand-down waveform 3 be in order to make whole towards T structure change after stablize necessary.

Then, apply the composite wave of S12 signal and C12 signal to pixel first selects waveform 12.C12 signal is the signal applied between the selecting period of concentric line.In order to maintain T structure, forming first with the current potential of anchor ring below disintegration voltage Vc and selecting waveform 12.In the present embodiment, be level+2 in time interval E, in time interval F for level-1, in time interval G for level-2, be the waveform of level+1 in time interval H.And, select after waveform 12 first, between setting line signal stand-down, to apply the voltage (between stand-down waveform 3) of 0V during this period.Like this, in during time interval E ~ H, the potential level of anchor ring below damage threshold Vc must be set.Utilize this waveform, maintain T structure.Therefore, liquid crystal layer does not produce flowing.Specifically, between the first selecting period in 12a, set the approximately ± voltage of about 4V and the time of about 1 millisecond, between the second selecting period, potential level ± 1 of 12b sets the voltage of ± 2 ~ ± about 4V and the waveform widths of 50 ~ 500 microseconds.Here, between the first selecting period, 12a is the time interval E and G, and between the second selecting period, 12b is the time interval F and H.So, can think the first selection waveform 12 be by between the first selecting period between 12a and the second selecting period one group of 12b repeatedly carried out twice.Here, line signal compares until the time of time interval E ~ H is long between stand-down, is specifically preferably more than 2 milliseconds.

Below tell about the signal supplied to SEGI and COM1 to obtain this first selection waveform 12.As shown in Fig. 2 (a), the Segmented electrical corrugating of S12 signal is V12, the waveform becoming V34 in the time interval G and H in the initial time interval E and F.Then, following closely in the time interval I after S12 signal, V5 is applied.The time interval E, F and the time interval G, H reversed by with FRSEG signal.In addition, as shown in Fig. 2 (b), the common electric voltage waveform of C12 signal be in initial time interval E for V0, in time interval F for Vcx, be V5, the waveform becoming Vcx in time interval H in time interval G.Then, following closely in the time interval I after C12 signal, V5 is applied.The time interval E, F and the time interval G, H reversed by with FRCOM signal.Here, anchor ring destruction value Vc is between potential level ± 4 and ± 3, between V12 and V34.In addition, V0=30V, V5=GND (0V) is such as made.

Again then, the waveform applied to the pixel (intersection point of COM2 and SEG1) maintained after being for conversion into U structure is told about according to Fig. 2 (e).Here the waveform shown in is the synthetic waveform of the SEG1 signal of Fig. 2 (a) and the COM2 signal of Fig. 2 (d).Same with Fig. 2 (c), the reset pulse 1 of the composite wave of divided reset signal S1 and common reset signal C1 is first applied to pixel.Because reset pulse 1 has the voltage of anchor ring destruction more than value Vc, so liquid crystal layer becomes T structure.After being just applied with reset pulse 1, apply waveform 3 between stand-down.Waveform 3 between the stand-down in this time interval D is necessary in order to make it stablize after the change of T structure all pixels.In COM2, owing to being between non-selecting period after (being equivalent to time interval D) between line signal stand-down, so apply non-selection waveform 14.Non-selection waveform 14 must be formed with the voltage of anchor ring below damage threshold Vc.Then, apply the composite wave of S14 signal and C12 signal to pixel second selects waveform 15.C12 signal is the signal applied between the selecting period of concentric line.Second selects waveform 15 also with the first to select waveform 12 same, can think by between the first selecting period between 15a and the second selecting period one group of 15b repeatedly carried out twice.Between the first selecting period in 15a, apply the voltage of anchor ring more than damage threshold Vc.Between this first selecting period in 15a, liquid crystal layer becomes H structure from T structure.Then, between the second selecting period in 15b, after applying the voltage of anchor ring below damage threshold Vc, apply voltage and the waveform 3 between stand-down of 0V.Like this, liquid crystal layer becomes U structure from H structure, maintains U structure.Through this driving, liquid crystal can not be produced and fluidly obtain U structure.

In the present embodiment, non-selection period waveform 14 be potential level-2 in the time interval E and F, be potential level+2 in the time interval G and H.Specifically, the voltage of setting ± 4V ~ ± about 8V.In addition, second selects waveform 15 to be potential level+4 in time interval J (between the first selecting period 15a), potential level+3 in time interval K (between the second selecting period 15b), be potential level-4 in time interval L (between the first selecting period 15a) subsequently, be potential level-3 in time interval M (between the second selecting period 15b).Specifically, between the first selecting period, potential level ± 4 of 15a are ± 13V ~ ± about 20V, are set as about 1 millisecond; Between the second selecting period, potential level ± 3 of 15b are ± 8V ~ ± about 13V, are set as 50 ~ 500 microseconds.Between the first selecting period, between the second selecting period, use the time data obtained from thermometer.In addition, line signal was longer than between stand-down until the time of time interval E ~ H.Specifically, preferably more than 2 milliseconds.In addition, the width between non-selection period and line stand-down following closely, with between selecting period with line stand-down following closely between width identical.In addition, the time interval E and J, F and K, G and L, H and M, I and N each be identical time width.

From above-mentioned waveform: when making U structure change, between the first selecting period, apply potential level ± 4 of anchor ring more than damage threshold Vc; When maintaining T structure, between the first selecting period, apply potential level ± 2 of anchor ring below damage threshold Vc.In addition, no matter which kind of structure, between the second selecting period, all apply potential level ± 2 of anchor ring below damage threshold Vc, between line signal stand-down thereafter, apply waveform between stand-down.Utilize this waveform, can not cause liquid crystal in picture, fluidly there is T structure and U structure.

In addition, 12b, 15b between 12a, 15a and the second selecting period between the first selecting period, make polarity on the contrary repeatedly.And then, non-selection period waveform 14 also same with embodiment 1, in+side and-top-cross for occurring.Like this, owing to being applied to the waveform of liquid crystal layer by interchange, so liquid crystal layer is not by the impact of flip-flop.

[embodiment 3]

Again then, Fig. 3 is used to tell about the driving method of the present embodiment.Fig. 3 is the schematic diagram representing the drive waveforms being applied to lattice lcd panel.In this point of sectionalization between the second selecting period selecting waveform and the second selection waveform by first, and embodiment 2 is different.Other is identical with embodiment 2 or 1, so suitably omit telling about of repetition.

Fig. 3 (a) illustrates the signal being applied to segmented line (SEG1), Fig. 3 (b) illustrates the signal being applied to concentric line (COM1), Fig. 3 (c) illustrates the waveform of the intersection point being applied to COM1 and SEG1, Fig. 3 (d) illustrates the signal being applied to COM2, and Fig. 3 (e) illustrates the waveform of the intersection point being applied to COM2 and SEG1.In the present embodiment, the pixel being applied in the waveform shown in Fig. 3 (c) also becomes T structure, and the pixel being applied in the waveform shown in Fig. 3 (e) becomes U structure.No matter which kind of situation is all the reset pulse 1 of the composite wave first applying divided reset signal S1 and common reset signal C1 to pixel.Because reset pulse 1 has the voltage of anchor ring destruction more than value Vc, so liquid crystal layer becomes T structure.After during following the initialization applying reset pulse 1 closely, arrange between line signal stand-down.Online signal applies waveform 3 (current potential of 0V) between stand-down between stand-down.The T Stability Analysis of Structures that between this stand-down, waveform 3 utilizes reset pulse 1 to make to have changed.Then, COM1 becomes between selecting period, and COM2 becomes non-selection period.

Between selecting period, apply first shown in Fig. 3 (c) to COM1 and select waveform 22.First selection waveform 22 is composite waves of S22 signal and C22 signal.C22 signal is the signal supplied between the selecting period of concentric line.Because form first with the current potential of anchor ring below disintegration voltage Vc to select waveform 22, maintain T structure.Same with embodiment 2, can think the first selection waveform 22 be by between the first selecting period between 22a and the second selecting period one group of 22b repeatedly carried out twice.Although form 22a between the first selecting period with a current potential (-pulse), 3 current potentials (3 periods) are used to form 22b between the second selecting period in the present embodiment.Fig. 3 illustrates concrete current potential.Select after waveform 22 first, waveform 3 through between stand-down, apply non-selection period waveform 24.Because non-selection period waveform 24 is also formed with the current potential of anchor ring below disintegration voltage Vc, so continue to maintain T structure.

As shown in Fig. 3 (e), before second selects waveform 25, to COM2 applying waveform of non-selection period 24.This, waveform 24 was composite waves of S22 signal and C24 signal non-selection period.Because with the current potential formation waveform of non-selection period 24 of anchor ring below disintegration voltage Vc, so maintain T structure.Second selection waveform 25 is composite waves of S24 signal and C22 signal.Same with embodiment 2, can think the second selection waveform 25 be by between the first selecting period between 25a and the second selecting period one group of 25b repeatedly carried out twice.Although form 25a between the first selecting period with a current potential (-pulse), 3 current potentials (3 periods) are used to form 25b between the second selecting period in the present embodiment.Second selects waveform 25 25a between the first selecting period to apply the voltage of anchor ring more than disintegration voltage Vc.Therefore, H structure is become from the change of T structure.Then, through applying between the second selecting period of current potential reduced stepwise after 25b, become between line signal stand-down.In other words, drive with becoming 0V after reducing the current potential of 25a between the first selecting period gradually.Like this, liquid crystal layer becomes U structure from H structure change.Fig. 3 illustrates concrete current potential.

As shown in Figure 3, when U structure is changed, between the first selecting period, voltage level ± 5 of more than anchor ring damage threshold in 25a, are applied.When maintaining T structure, between the first selecting period, in 25a, apply voltage level ± 2 level of below anchor ring damage threshold.No matter which kind of situation, applies the voltage level of below anchor ring damage threshold in 25b between the second selecting period all after 25a continue between the first selecting period, in order to avoid structure change.And, between the second selecting period after 25b, between setting line signal stand-down.

As the present embodiment, when make voltage steps scalariform in 25b between the second selecting period reducing, easily become U structure from T structure.Voltage can be reduced skewedly.

The present invention is not limited to the various embodiments described above, in the scope not exceeding main idea of the present invention, can carry out various change and improvement.Even the waveform beyond shown in embodiment, also identical effect can be obtained.Such as by controlling pulsewidth, even if be not that the waveform reducing voltage stepwise also can obtain identical effect.It and anchor ring disintegration voltage value and pulsewidth have close relationship, particularly during low temperature, increase pulsewidth, voltage can be made quite low.At this moment, high withstand voltage driver is not used can to obtain same action effect yet.

Because if after carrying out that driving of the various embodiments described above, do not cause the flowing of liquid crystal, easily become U structure, the yield rate of LCD can be improved.In addition, in matrix driving, also display can not rewritten intrusively between the pixels.And then, even icon, Charactes Display or segmentation display (8 words of numeral or the Greek of letter) also can until the edge of display pixel show brightly.

Description of reference numerals

1 reset pulse; 2,12,22 first waveform is selected; Waveform between 3 stand-downs; 4,14,24 non-selection period waveform; 5,15,25 second waveform is selected; 6 liquid crystal layers; 7U structure; 8T structure; 9H structure; 30 bistable liquid crystal panels; 31 first substrates; 32 second substrates; 33 electrodes; The anchor ring alignment films of the last 34; 35 more weak anchor ring alignment films; 41 common drivers; 42 segment drivers; 43 power circuits; 44 control parts; 45 temperature sensors; 2a, 5a first is between selecting period; 2b, 5b second is between selecting period.

Claims (7)

1. a driving method for bistable liquid crystal display device, is characterized in that, possesses successively:

During initialization, in order to make the liquid crystal layer of all pixels become T structure, and applying has the reset pulse that anchor ring destruction is worth above voltage;

Between the first selecting period, the liquid crystal layer becoming the pixel of U structure to change applies anchor ring destruction and is worth above voltage, and is worth following voltage to the liquid crystal layer applying anchor ring destruction of the pixel maintaining T structure;

Between the second selecting period, the liquid crystal layer of the liquid crystal layer becoming the pixel of described U structure to change and the pixel maintaining described T structure applies described anchor ring destruction and is worth following voltage, in order to avoid cause flowing in the liquid crystal molecule of described liquid crystal layer; And

Between the 3rd selecting period, the liquid crystal layer to described all pixels applies 0V.

2. the driving method of bistable liquid crystal display device as claimed in claim 1, is characterized in that: between during described initialization and between described first selecting period, during being set to the liquid crystal layer applying 0V of described all pixels.

3. the driving method of bistable liquid crystal display device as claimed in claim 2, it is characterized in that: in order to will the waveform interchangeization of described liquid crystal layer be applied to, repeatedly to carry out between described first selecting period and between described second selecting period after, move on between the 3rd selecting period.

4. the driving method of bistable liquid crystal display device as claimed in claim 2, is characterized in that: between described second selecting period, applies the waveform that current potential changes stepwise.

5. the driving method of the bistable liquid crystal display device according to any one of Claims 1 to 4, is characterized in that: to make to be longer than between described 3rd selecting period between the first selecting period and sum between the second selecting period.

6. the driving method of bistable liquid crystal display device as claimed in claim 2, is characterized in that: according to temperature information, determines the magnitude of voltage that applies between described first selecting period or between described second selecting period or during applying.

7. the driving method of bistable liquid crystal display device as claimed in claim 6, is characterized in that: according to described temperature information, determines between described 3rd selecting period.