CN104238227B - Method for addressing bistable electro-optical medium - Google Patents

Abstract

A method of for addressing bistable electro-optical medium, wherein apply the alternating electric field with offset to the medium.To have the advantages that the waveform elements of offset are not needing to addressing pulse accurate timing relative to other waveform elements.

Description

Method for addressing bistable electro-optical medium

The application be the first time divisional application for the following PCT international application submitted on May 23rd, 2003 again Divisional application: international application no PCT/US03/16434, national application number 03813604.X, entitled " for driving The method of dynamic electro-optic displays ", first time divisional application application No. is 200810215240.8, it is entitled " for driving The method of dynamic electro-optic displays ".

Technical field

The present invention relates to the method and apparatus for driving electro-optic displays especially bistable electro-optic displays.Of the invention Method and apparatus main (although unspecial) are for driving bistable electrophoretic display device (EPD).

Background technique

This application involves United States Patent (USP) No.6,504,524 and No.6,531,997.The application further relates to common undecided International Application Serial No. PCT/US02/10267(publication number No.WO 02/079869) and PCT/US02/37241.

Term " electric light " as used herein applied to material or display is its conventional sense in imaging technique, Refer to the material with the first and second display states, at least one optical property of the first and second displays state is not Together, the material is made to be converted to the second display state from the first display state by applying electric field to the material.Although this is optical Matter is usually the appreciable color of human eye, but is also possible to other optical properties, such as optical transmission, reflectivity, brightness, Or the display by machine reading, the counterfeit color in the reflectivity changes meaning of the electromagnetic wave except visible range.

Term " grey states " used herein is its conventional meaning in imaging technique, refers to two between pixel State between extreme optical state does not necessarily mean that the black-white transition between the two extremities.For example, being referenced below Multiple patents and published application in describe such electrophoretic display device (EPD), wherein extremity is white and dark blue, thus Intermediate " grey states " will be actually light blue.In fact, as previously mentioned, the transformation between two extremities may also root This is not the variation in color.

Term " bistable " used herein and " bistability " are its conventional meanings in the art, are referred to including having The display of the display element of first and second display states, the first and second displays at least a kind of optical property of state Difference, so that any point element is driven by the addressing pulse with finite duration, that its first or second is presented is aobvious Show state, after addressing pulse termination, it is addressing pulse needed for changing the state of the display element which, which will last at least, Several times of times of minimum duration are for example, at least four times of times.In common pendent Serial No. above-mentioned Show in the application of No.10/063236: some electrophoretic display device (EPD)s for capableing of display gray scale based on particle are not only in its pole Stablize under the black and white state at end, and stablize under grey states therebetween, the electro-optic displays of other type are same So.Such display is properly called " multistable " rather than bistable, but used herein for convenience's sake Term " bistable " covering bistable and multistable display.

Term " impact (impulse) " used herein takes it routinely to look like: integral of the voltage about the time.However, Some bistable electro-optical mediums serve as charge sensor, this medium can be used another definition of impact, i.e. electric current closes In the integral of time (equal to the total electrical charge applied).Voltage-vs-time shock transducer or charge impact are served as according to medium Sensor should use the definition appropriate about impact.

A plurality of types of bistable electro-optic displays known.A type of electro-optic displays are for example in United States Patent (USP) No.5,808,783、5,777,782、5,760,761、6,054,071、6,055,091、6,097,531、6,128,124、6, Disclosed in 137,467 and 6,147,791 two color component type of rotation (rotating bichromal member) (although Such display is commonly referred to as " two chromospheres of rotation " display, but due to the rotating element in above-mentioned some patents It is not spherical, so term " two color components of rotation " is more acurrate).This display is (typically spherical using a large amount of corpusculums Or cylindric) and internal dipole, two or more parts that these corpusculums have optical characteristics different.These corpusculums suspend In hydraulically full vacuole in matrix, these vacuoles are hydraulically full so that these small physical efficiencys rotate freely.To the display Apply electric field, the appearance variation of the display, therefore rotates these corpusculums to various positions and change through observation surface institute Those of corpusculum seen part.

Another type of electro-optical medium uses electrochromic medium, such as nanometer chromium (nanochromic) form of film Electrochromic medium comprising the electrode that is at least partly formed by semiconducting metal oxides and multiple be attached to the electrode On the dye molecule for capableing of reversible color；See, e.g., O ' Regan, the Nature such as B. 1991,353,737；And Wood, D., Information Display, 18(3), 24(2002 March).And referring to Bach, U., wait Adv. Mater., 2002,14(11), 845.In such as United States Patent (USP) No.6,301,038 and international application published No.WO 01/ Such nanometer chromium thin film is also illustrated in 27690.

It is over several years the electrophoretic display device (EPD) based on particle by the another type of electro-optic displays of numerous studies and exploitation, Plurality of charged particle passes through suspension liquid movement under the influence of electric fields.Compared with liquid crystal display, electrophoretic display device (EPD) Contribution is there is good brightness and contrast, wide viewing angle, state bi-stability and low-power consumption.However, these displays Long-term image quality problem hinder being widely used for they.For example, the particle for constituting electrophoretic display device (EPD) is intended to settle, lead Cause the service life of these displays inadequate.

It largely transfers or has been announced recently with the patent that Massachusetts science and engineering (MIT) and E Ink company apply, they are described The electrophoretic media of encapsulation.The medium of this encapsulation includes a large amount of folliculus, and wherein each folliculus itself includes interior phase and ring Around the cyst wall of interior phase, wherein the interior phase contain be suspended in liquid suspending medium can electrophoresis motion particle.In general, these Capsule itself is stored in polymeric binder to form the adhesion layer being located between two electrodes.For example, in United States Patent (USP) NO.5, 930,026; 5,961,804; 6,017,584; 6,067,185;6,118,426;6,120,588;6,120,839;6,124, 851;6,130,773;6,130,774; 6,172,798; 6,177,921; 6,232,950; 6,249,721; 6,252, 564; 6,262,706; 6,262,833; 6,300,932; 6,312,304; 6,312,971; 6,323,989; 6,327, 072; 6,376,828; 6,377,387; 6,392,785; 6,392,786; 6,413,790; 6,422,687; 6,445, 374; 6,445,489; 6,459,418; 6,473,072; 6,480,182; 6,498,114; 6,504,524; 6,506, 438; 6,512,354; 6,515,649; 6,518,949; 6,521,489; 6,531,997; 6,535,197; 6,538, 801;With 6,545,291 and U.S. Patent Application Publication No.200210019081;2002/0021270;2002/ 0053900;2002/0060321;2002/0063661;2002/0063677;2002/0090980;2002/0106847; 2002/0113770;200210130832;2002/0131147;2002/0145792;2002/0154382,2002/ 0171910;2002/0180687;2002/0180688;2002/0185378;2003/0011560;2003/0011867; 2003/0011868;2003/0020844;2003/0025855;2003/0034949;2003/0038755 and international application Announce No.WO 99/67678; WO 00/05704; WO00/20922; WO 00/26761; WO 00/38000; WO 00/ 38001; WO 00/36560; WO00/67110; WO 00/67327; WO 01/07961;It is retouched in WO 01/08241 The medium of such encapsulation is stated.

Many above-mentioned patents and application recognize that the wall around separation micro-capsule in the electrophoretic media of encapsulation can the company of using Continuous mutually replacement, thus generate (polymer-dispersed) electrophoretic display device (EPD) of so-called polymer dispersion, wherein electrophoresis Medium includes the continuous phase of the isolated droplet and polymer material of multiple electrophoretic fluids, and even if the cyst membrane not separated It is related to each individual droplet, but the separation droplet of the electrophoretic fluid in the electrophoretic display device (EPD) of such polymer dispersion can also To be considered as capsule or micro-capsule；See, e.g. above-mentioned 2002/0131147.Therefore, for the purpose of the application, this polymerization The electrophoretic media of object dispersion is considered as the subclass of the electrophoretic media of encapsulation.

The electrophoretic display device (EPD) of encapsulation is usually not subjected to aggregation and the settling failure mode of conventional electrophoretic part, and mentions For other advantage, such as display can be coated with or is printed in various flexible and rigid basements.It (uses word " printing " It is intended to printing and coating unlimitedly including form of ownership: such as premeasuring of patch coating (patch die coating) (pre-metered) coating, gap or protrusion coating, sliding or waterfall (cascade) coating, curtain showering；Such as knife is in roller Upper (knife over roll) coating, the forward roll banding with reverse roll coating；Gravure；Dip coated；Spraying； Crescent (meniscus) coating；Spin coating；It brushes；Air cutter painting；Silk-screen printing technique；Electrostatic printing process；Thermally printed technique, spray Ink print technique；And other similar techniques.) therefore, manufactured display can be flexible.Further, since display matchmaker Matter can print and (use various methods), and display itself can be manufactured inexpensively.

A kind of electrophoretic display device (EPD) of correlation type is so-called " microcell electrophoretic display ".In microcell electrophoretic display In, charged particle and suspension are not sealed in micro-capsule and are held in and are formed in carrier medium (usually polymer film) Interior is multiple intracavitary.See, e.g., international application published No.WO 02/01281 and disclosed U. S. application No.2002- 0075556(transfers Sipix Imaging, Inc.).

Although electrophoretic display device (EPD) be usually opaque (since these particles stop visible light-transmissive display substantially) simultaneously And work in a reflective mode enabling, but electrophoretic display device (EPD) can work at so-called " shutter mode (shutter mode) ", It is substantially opaque display state that particle, which is arranged at transverse movement in display display is made to have one, in the mode With the display state of a light transmission.See, e.g., United States Patent (USP) No.6 above-mentioned, 130,774 and 6,172,798 and the U.S. Patent No.5,872,552,6,144,361,6,271,823,6,225,971 and 6,184,856.Similar to electrophoretic display device (EPD), but The dielectrophoretic displays for being to rely on electric field strength variation can also work in a similar mode；Referring to United States Patent (USP) No.4, 418,346.Other types of electro-optic displays can also work in shutter mode.

The similar performance of the bistable of electrophoretic display device (EPD) based on particle or multistable performance and other electro-optic displays, with The performance of traditional liquid crystal (LC) display forms distinct contrast.The not instead of bistable or multistable of the performance of twisted nematic liquid crystal, fills Work as voltage sensor, so that a specific ash can be generated in the pixel by applying given voltage to a pixel of this display Grade is spent, and it is unrelated with the gray level previously appeared in the pixel.In addition, only in one direction (from non-transmissive or " dark " to thoroughly Penetrate or " bright ") on drive LC display, be by reducing or disappearing from brighter state to the reverse transformation than darker state Except electric field is realized.Finally, the gray level of the pixel of LC display is insensitive to the polarity of electric field, only to its magnitude, and in fact On border for technical reasons, commercial LC display is usually inverted the polarity of driving electric field with frequent interval.With first Approximation contrasts, and bistable electro-optic displays serve as shock transducer, so that the end-state of pixel is depended not only upon and applied The electric field added and the time for applying the electric field, also rely on the state of the pixel before applying electric field.

Although front has been pointed out, electrophoresis and other types of electro-optic displays show bistability, this bistable Property be not without limitation, the image on this class display slowly weakens at any time, thus if image will keep long week Phase, the image must be periodically refreshed, the optical states that it has when being written for the first time so that image to be restored to.

However, the problem of refreshing of this image may cause its own.As United States Patent (USP) No.6,531 above-mentioned, 997 and 6,504,524 are discussed, (or are connect if the method that drives the display is not produced as zero on entire electro-optical medium Nearly net time zero) averagely applies electric field, and the working life that can be potentially encountered problem and the display is reduced.In entire electric light matchmaker Zero net time is produced as in matter averagely to apply the driving method of electric field and typically refer to " DC balance " or " DC balance ".If logical Application refresh pulse is crossed to keep image for a long time, then the polarity of these pulses is needed and is used for the related pixel of the display Drive the polarity of the addressing pulse of the optical states kept identical, this leads to DC imbalance drive scheme.

Summary of the invention

According to another aspect of the present invention, it has been found that refresh if realized using short pulse, it can be with refresh display On image, while reducing relevant to DC imbalance drive scheme deleterious effects.

Another aspect of the present invention relates to processing such problems: the driving of bistable electro-optic displays above-mentioned requires to cause Conventional drive method for driving LCD is unsuitable for this bistable electro-optic displays.In addition, such as aforesaid U.S. Patent No.6, 531,997 and 6,504,524 are discussed, if the method for driving the display is not produced as zero on entire electro-optical medium The net time of (or close to zero) averagely applies electric field, and the working life that can be potentially encountered problem and the display is reduced.Entire Zero net time is produced as on electro-optical medium averagely to apply the driving method of electric field and typically refer to " DC balance " or " DC balance ". LCD can also encounter similar problem, but since polarity of this class display to the electric field applied is insensitive, and have therewith It is capable of the ability of random reversed polarity, so that DC equilibrium problem is not critically important in an lcd.However, the needs of DC balance are being set Counting in the drive scheme of bistable electro-optic displays (wherein polar sensitive of the electro-optical medium to the electric field applied) is important consideration Factor.

Therefore, another aspect of the present invention relates to the method and apparatus of driving electro-optic displays, this method and device reach The particular/special requirement of bi-stable display previously discussed.Certain method and apparatus of the invention are mainly used in bi-stable display Generate accurate gray scale rendition.

Therefore, on the one hand, the present invention provides for addressing the bistable electro-optic displays at least one pixel Method, this method comprises: applying addressing pulse to drive the pixel to the first optical states；

It keeps the pixel not driven whithin a period of time, thus allows the pixel to present and be different from the first optics shape Second optical states of state；

Apply refresh pulse to the pixel, which is restored to the first optical states, phase for the pixel substantially The refresh pulse is shorter for addressing pulse.

This aspect of the invention is referred to as " refresh pulse " method of the invention for the sake of hereinafter for convenience.

In the refresh pulse method, the impact of refresh pulse is usually more than about the 20% of the impact of addressing pulse, reason That thinks is no more than about the 10% of the impact, and is preferably no greater than the 5% of the impact.Due to as explained below, usually Difference between first and second optical states is no more than the L of about unit^*(wherein L^*It is defined with common CIE)；Reason That think is the L that the difference is no more than about 0.5 unit^*, and the L of preferably no more than about 0.2 unit^*.It can be between rule Every applying multiple refresh pulses to the pixel.

In a kind of form of the refresh pulse method, after applying refresh pulse, applies second to the display and seek Location pulse, second addressing pulse drive the pixel to the third optical states for being different from the first and second optical states, and its In by the impact that the second addressing pulse is applied be the sum of following two :(a) the pixel is driven from the first optical states to the Impact needed for three optical states, and the refresh pulse (b) and between the first and second addressing pulses being applied in the pixel Algebraical sum it is equal in magnitude and it is opposite polarity one impact.Second addressing pulse may be that voltage is constant but the duration becomes Change.In the display for including multiple pixels, the second addressing pulse can be blanking pulse, by all pixels of the display It drives to an extreme optical states.In a preferred form of this " blanking pulse/refresh pulse " processing, the display Device includes multiple pixels, the first addressing pulse be applied to each pixel so as to drive first group of pixel at white and second group of pixel at Black, at least one refresh pulse is applied to each pixel, and the backward display apply so that all pixels blackening first Blanking pulse and the second blanking pulse for driving all pixels Cheng Bai, the two blanking pulses apply in any order. The impact that each first group of pixel is applied to during the first blanking pulse is the sum of following two :(a) drive the pixel from Impact needed for white to black, and (b) and between the first addressing pulse and the first blanking pulse it is applied to the refreshing arteries and veins of the pixel The algebraical sum of punching is equal in magnitude but opposite polarity one is impacted.It is similar, each second is applied to during the second blanking pulse The impact of the pixel of group is the sum of following two :(a) the pixel is driven to be sought from black to white required impact, and (b) with first The algebraical sum that the refresh pulse of the pixel is applied between location pulse and the first blanking pulse is equal in magnitude but opposite polarity one A impact.

Refresh pulse method of the invention can be used for any kind of electro-optical medium above-mentioned.Therefore, in the method, Display can be two color components of rotation or electrochromic display device (ECD) or electrophoretic display device (EPD), it is generally desirable to which the electrophoresis of encapsulation is aobvious Show device.

On the other hand, the present invention provides a kind of method for addressing bistable electro-optical medium, and this method includes to the medium Apply the alternating-current pulse with direct current offset (offset).

On the other hand, the present invention provides a kind of method of addressing bistable electro-optical medium, this method includes applying to the medium Add alternating-current pulse, and at least one of frequency and duty cycle for changing the pulse, to change the electricity with the alternating-current pulse The optical states of optical media.

On the other hand, the present invention provides the method for driving bistable electro-optic displays, which includes being arranged in multiple rows With multiple pixels of multiple column；Multiple row electrodes, each row electrode are related to one of multiple row；Multiple column electrodes, it is each A column electrode is related to one of multiple column；And driving device, it is arranged for successively selecting each of row electrode simultaneously And nematic electrode applies selected voltage during the selection of any given row electrode, to address and selected row electrode A line of pixel in relevant row and image required for being written on the display.This method comprises:

Display is written into first image；

Receive the data for representing and will writing the second image on the display；

Compare first and second image and the row of the display is divided into first group and second group, in first group of row In at least one pixel between the first and second images it is different, in pixel phase between the first and second images in second group of row Together；And

The second image is written by only sequential selection row electrode relevant to first group of row, and applies voltage to column electricity Pole is only to write first group of row, to form the second image on the display.

On the other hand, the present invention provides the electro-optic displays with multiple pixels, and at least one of these pixels include The mutually different multiple sub-pixels of area, which includes driving device, is arranged for changing the son independently of each other The optical states of pixel.In such a display, it is generally desirable to which at least two sub-pixels its area in these sub-pixels is basic 2 times of difference.

Detailed description of the invention

It is now described with reference to the drawings the preferred embodiment of the present invention, it is preferred that embodiment is only exemplary, it is attached In figure:

The curve of Fig. 1 show using have pulse length modulation DC pulse address display in gray level with The variation of time；

The curve graph of Fig. 2 is similar to Fig. 1, is the ash of the display addressed using the DC pulse with pulse-height modulation Degree grade changes with time；

The curve graph of Fig. 3 is similar to Fig. 1, is the display of the alternating-current pulse addressing used according to the invention with direct current offset The gray level of device changes with time；

The curve graph of Fig. 4 is similar to Fig. 1, is the aobvious of the alternating-current pulse addressing used according to the invention with duty cycle modulation Show that the gray level of device changes with time；

The curve of Fig. 5 shows gray level in the display addressed using double prepulses magic lantern (slideshow) waveform It changes with time；

The curve of Fig. 6 shows the change of gray level at any time in the display using single prepulsing magic lantern waveform addressing Change；

Fig. 7 A and 7B show the possibility arrangement of the sub-pixel in the single pixel of display of the invention.

Specific embodiment

It has already been indicated that the present invention provides the method and these displays of addressing electro-optical medium and display as before Many improvement of structure.Various aspects of the invention are described into sequence now, but it would be recognized that single electro-optical medium or aobvious In terms of showing that device can use more than one of the invention.For example, the AC arteries and veins with DC offset can be used in single electro-optic displays Punching driving, and also use refresh pulse.

Refresh pulse method of the invention

As previously mentioned, the present invention provides a kind of method, this method is brushed by applying short refresh pulse to electro-optic displays Image on the new display.Therefore, in the method for the invention, apply addressing pulse to the pixel of bi-stable display first, The addressing pulse is enough to change the optical states of the pixel.After keeping the display not by driving a period of time, to the pixel Apply refresh pulse, the refresh pulse is shorter relative to the addressing pulse.It is sought in general, the impact that refresh pulse is applied is not more than Preferably the 20%(for the impact that location pulse is applied is not more than 10%, and preferably no greater than 5%).For example, if pixel needs Continue the addressing pulse of the 15V of 500 milliseconds (msec), refresh pulse can be 15V, continue 10 milliseconds (msec), impact It is the 2% of the impact of addressing pulse.

Human eye is contemplated that the sensitivity of the minor change of unexpected optical states to adjust refresh pulse in this method Time.Human eye has opposite patience for the gradually decaying of image, so that, for example, usually measurement is used as brightness L^*(by leading to Normal CIE defines to define；See, e.g. Hunt, R.W.G. Measuring Color, 3rd edition, Fountain Press, Kingston-upon-Thames, England (1998) (ISBN 0 86,343 387 1)) required time electricity The bistability of optical media, maximum value (or the black state for the white optical state observed after terminating from addressing pulse Minimum value) two units of variation.However, suddenly change occurs for the brightness of related pixel when applying refresh pulse to display, And approximately less than 1 unit L^*Mutation be easy to be detected by human eye.According to the interval between refresh pulse, by these pulses The variation of caused image may show as " flashing " in the picture, and this flashing is disagreeable for most of observer 's.In order to avoid other discernable variations in this flashing or the image as caused by refresh pulse, it may be desirable to which selection is sought The interval between interval or continuous refresh pulse between location pulse and the first refresh pulse, so that each refresh pulse is being schemed Cause the smallest variation as in.Therefore, the L as caused by single refresh pulse^*Variation should be less than about 1 unit L^*, preferably It is less than about 0.5 unit, and is more preferably less than about 0.2 unit.

Although refresh pulse used in this method can introduce in drive scheme during applying the refresh pulse DC is uneven, but is not precluded within and obtains long-term DC balance in the drive scheme, and have been found that long-term rather than short-term DC Balance is to determine the principal element of the working life of electro-optic displays.In order to obtain this long-term DC balance, applying one Or after multiple refresh pulses, the pixel that these refresh pulses have been received can be driven by " conversion " or the second addressing pulse The optical states opposite to its, and the adjustable impact applied in the inversion address pulse is since the first addressing pulse It is provided in the whole cycle of beginning DC balance (or at least minimum DC is uneven), which is by adjusting the second addressing arteries and veins The impact of punching, wherein adjustment amount size is equal to and polarity is in contrast to the refreshing for being applied to the pixel between the two addressing pulses The algebraical sum of pulse.For example, it is contemplated that a display, can be existed by the impact of application ± 15V, 500 milliseconds (msec) Change between white and black optical states.Assuming that the pixel of the display passes through the+15V impact of 500 milliseconds of application (msec) first And it is white from blacking, and the white state of the pixel then passes through the 10 of+15V for applying 10 milliseconds (msec) at regular intervals Refresh pulse and be kept.If it is expected that the pixel is made to return to its black optic state, this can be with after this 10 refresh pulses By applying 600(rather than 500) -15V the addressing pulse of millisecond (msec) is realized, thus the pixel it is entire it is black - DC balance is all realized during transformation white-black.

Such adjustment of transformation addressing pulse can be write in new images must change on the display and therefore Realization when becoming the optical states of certain pixels.Alternatively, the adjustment can be carried out during applying " blanking pulse " to the display. Discussed in PCT/US02/37241 as the aforementioned, it is often necessary to or expectation is spaced at regular times to electro-optic displays and applies So-called " blanking pulse "；This blanking pulse includes first by all pixels driving of the display to an extreme optical shape State (for example, white state) then drives all pixels to opposite optical states (for example, black), then writes required figure Picture.The advantages of adjustment is realized during blanking pulse be, what all pixels can be balanced in the same time by DC substantially；Make The technology being described in detail with front is that the pixel of black exists in image (just incipient image before blanking pulse) previous By all pixels driving at can be during white blanking pulse DC balance, and be in image previous white pixel exist All pixels, which are driven, can be DC balance during the blanking pulse at black.Equally, the tune is realized during blanking pulse Whole advantage is do not need clearly to know each individually pixel has received how many since its previous addressing pulse starts Refresh pulse；Assuming that refreshing black and white pixel (fact of case is usually such) every identical time interval, and every Secondary image is inserted into blanking pulse when changing, each pixel will be needed during the blanking pulse identical adjustment (in addition to polarity it Outside), which is determined by the quantity for acting the refresh pulse being applied on the display since the previous blanking pulse.Equally, It realizes that DC balance provides during blanking pulse a kind of the refresh pulse method to be applied to more than two gray level The mode of electro-optic displays, because adjusting the impact applied during ash-grey transformation in such a display obviously may cause ash Spend the undesired error of grade.

Refresh pulse method of the invention may be used as increase electro-optical medium bistability additive substitute or It is in connection.For example, the present invention can with above-mentioned 2002/0180687 described in electrophoretic media be used together, the medium tool There is the suspension for wherein having dissolution or dispersion polymer, wherein the polymer increases the bistability of medium.

Following example is provided now, and only by the mode of explanation, one of refresh pulse method of the invention is shown Embodiment.

Example 1

The example uses the display of the sub- counter charges type medium of double grains containing encapsulation, which includes polymer-coated Titanium oxide white particles and polymer-coated black particles, and suspension is uncolored.The display is essentially according to above-mentioned It is prepared by " method B " described in 2002/0180687 [0061]-[0068] section.

The display prepared as previously described, including multiple pixels, ± 15V for being able to use lasting 500 milliseconds (msec) are sought Location pulse changes these pixels between black and white optical states.The bistability of the display is limited, the ring around White optical state changes 2L in border^*The only about 15sec of time required for unit.However, empirically determining by applying 4sec/ The short refresh pulse (duty cycle the is approximately 6.7%) of ± 15V of min can indefinitely keep the white and black optic shape State.In order to provide the test of reality and in these experiments avoid in the standard picture (containing black and white region) that uses Flashing, after 500 milliseconds of (msec) addressing pulses of beginning, every about 100 milliseconds (msec) black to the display Apply the refresh pulse of ± 15V of 7 milliseconds of (msec) duration with white pixel.

In order to determine the effect in each period of DC imbalance drive scheme on display, 4 kinds of drive schemes are tested:

Scheme 480:

The display is addressed using the standard picture, and the image is kept for 480 points using refresh pulse above-mentioned Clock.Then apply a series of blanking pulses, and the circulation of repetitive addressing and refresh pulse.Whenever DC parallel vein is not applied Punching.After work in 83 hours, apply a series of blanking pulse, and then test the display has been white respectively With the isolated region of black.It is used in following table in the region for being maintained as the display of white dduring test " 480W " is indicated, and has been region " 480D " expression of black.It will by the addressing pulse of 500 milliseconds (msec) of standard Its white optical state is arrived in each tested region driving, and measures its percent reflectivity value；The value is used in table " w% " is indicated.Then the region for allowing each to be tested keeps 15sec in the case where not applying any refresh pulse, at this L is measured after 15 seconds intervals^*Variation；Obtained L^*Variation be referred to as " bright holding difference (bright holding Difference) ", indicated in the table with " bhdl ".After applying other blanking pulse, pass through 500 millis of standard Each tested region driving is arrived its black optic state by the addressing pulse of second (msec), and measures its percent reflection Rate value；The value uses " d% " to indicate in the table.Then the region for allowing each to be tested is not applying any refresh pulse In the case of kept for 15 seconds, measure L after 15 seconds intervals^*Variation, obtained L^*Variation be referred to as it is " dark to keep poor Not ", it is indicated in the table with " dhdl ".

Scheme 60:

The program is identical as scheme 480, and only image is only kept 60 minutes before applying blanking pulse.In test week The region that the display of white is remained during phase uses " 60W " to indicate in the following table, and " 60D " is used in the region for remaining black It indicates.

Scheme 10:

In this scenario, image, and use refreshing identical with scheme 480 are written in a manner of identical with scheme 480 Pulse is kept for 10 minutes.Then apply opposite polarity 40sec pulse and the display is balanced with DC, then the image is rewritten, And repeat the circulation.The region that the display of white is remained during the test period uses " 10W " to indicate in the following table, and The region for remaining black is indicated with " 10D ".

Scheme 1:

The program is identical as scheme 10, and only image is only kept 1 minute, then applies the 2nd DC equalizing pulse in 4 seconds, And repeat the circulation.The region that the display of white is remained during the test period uses " 1W " to indicate in the following table, and The region for remaining black is indicated with " 1D ".

The result obtained in these experiments is as shown in table 1 below.

Table 1

Find out from the data of table 1, in height imbalance scheme 480, white and black are remained during test period The display region between the significantly different and bright and dark holding difference of white state reflectivity it is also dramatically different.Therefore, Height imbalance drive scheme generates the basic variation of the optical states of the display, and far from this non-equilibrium driving The possible other effects of scheme, such as to the damage of electrode.It equally, should as shown by the bright and dark difference kept in difference Uneven drive scheme introduces " biasing " and arrives the display, i.e., the long-term region for keeping white also keeps white after being intended to, And black is kept after keeping the region of black to be intended to for a long time.It is never being obtained in balance scheme 60 the result is that similar, but It is not so significant (as would be expected).It contrasts, DC balance scheme 10 and 1 is between the region for keeping black and white Substantially it does not show to distinguish.

Therefore, as long as these experiments show that long-term DC balance is generated by the blanking pulse separated, then by using Temporary DC imbalance caused by short refresh pulse will not have negative effect to the attribute of the display.

The electrophoretic media used in refresh pulse method of the invention can using E Ink above-mentioned and MIT patent and Same parts and manufacturing technology in application, reader can be with reference to these patents and application to obtain further information.

The basic element (including using AC pulse) of gray level drive waveforms

As United States Patent (USP) No.6 above-mentioned, 531,997 and 6, described in 504,524, current many displays pass through Apply duration sufficiently long voltage pulse be saturated electro-optical medium, to be converted to from an extreme optical state another A extreme optical state (for example, from black to white, vice versa)；Such as in the electro-optical medium based on particle, make charged particle From beginning to end to front or rear electrode movement.Until the optical states become saturation and just address the tradition of the electro-optical medium to need not permit Perhaps intermediate grey states exist.The electro-optic displays of acquisition gray level provide significant excellent in image volume and picture quality Point.

For convenience, the voltage waveform or drive scheme that can obtain gray level in bistable electro-optic displays are hereinafter It is referred to as " gray level waveform " or " gray scale drive scheme ".It can be used in this gray level waveform or drive scheme Basic gray level waveform elements have 5；Term " gray level waveform elements " is referred in the optical states of electro-optic displays Generate the voltage pulse or sequence of voltage pulses of variation.Gray level waveform elements itself can generate gray level, be arranged in specific One or more gray level waveform elements of sequence are formed together gray level drive waveforms.Gray level drive waveforms can will be shown The pixel of device from a gray state transitions to another.The Sequence composition drive scheme of one or more drive waveforms, the party Case can show any grayscale image sequence over the display.

Drive waveforms element is divided into two classes, i.e., direct current (DC) voltage pulse with exchange (AC) voltage pulse.In both feelings In condition, the parameter that can change of pulse is pulse height and pulse length.

Although generating the side for depending critically on voltage and being applied on the medium of gray level optical states in electro-optical medium Formula, but the medium keeps the ability of the gray level optical states after not applying voltage in gray scale addressing scheme No less important, and the ability will depend on the characteristic of the medium, in fact will depend on all greyscale transitions attributes.In this Shen Please in, by Primary Reference encapsulation gray scale addressing scheme is discussed based on the electrophoretic media of particle, but it is believed that for described For technical staff in medium technical field, it is contemplated that the other types of attribute of bistable electro-optical medium carries out this scheme Necessary modification is obvious.

The infrastructure elements of gray level drive waveforms are as follows:

The DC pulse of pulse length modulation

One of the simplest method for realizing ideal grey states is off addressing and is in from a kind of extreme optical state The pixel being converted among another extreme optical state.In figure 1 of the accompanying drawings, interpolation is shown for the electrophoresis in encapsulation The waveform elements of the DC pulse length modulation of greyscale transitions are generated in medium (as shown in the major part of the figure).(this is sentenced And display used in following subsequent experimentals is essentially according to aforementioned 2002/0180687 [0061]-[0068] Duan Suoshu " method B " manufacture.) three pulses using are that 15V continues 200,400 and 600 milliseconds (msec), and three generated respectively Curve is marked accordingly；The difference in time scale and master map in paying attention in illustration.Therefore, the difference of reflectivity is become Change, pulse height is fixed and the duration of pulse changes.In Fig. 1, the reflectivity of pixel is depicted (according to this applied A little voltage pulses, gray scale of the reflective condition from blacking to different stage) change over time curve；It can be seen that longer pulse Length generates biggish reflectivity changes.

Tested display responds rapidly the end of the voltage pulse applied, and its optical states stops developing. In micro- grade, it can be assumed that electrophoresis particle stops the migration from an electrode to another electrode immediately, and keeps suspending In intracapsular middle position.

The DC greyscale drive pulse advantage of pulse length modulation is to reach the speed of desired gray level state.

The DC pulse of pulse-height modulation

Another method for obtaining desired gray level state is to address picture than required lower voltages using one Element makes an extreme optical state of the pixel be converted to another extreme optical state completely.In Fig. 2 of attached drawing, interior illustration Show the DC pulse height for generating greyscale transitions in the electrophoretic media (as shown in the major part of the figure) of encapsulation The waveform elements of modulation.Voltage pulse length is fixed on that change the time required for the medium completely with maximal voltage level long Degree.Three pulses used are 5,10 and 15V respectively, are continued 500 milliseconds (msec), and three curves of generation are also by correspondingly Label；The difference in time scale and master map in paying attention in illustration.Therefore, the difference of reflectivity is changed, pulse length It fixes and the height change of pulse.In Fig. 2 of attached drawing, the reflectivity of pixel is depicted (according to these voltage arteries and veins applied Punching, gray scale of the reflective condition from blacking to different stage) change over time curve；It can be seen that biggish pulse height generates Biggish reflectivity changes.

It assume that electrophoresis particle passes through suspension at lower voltages with lower speed, and driven when stopping applying It keeps suspending when dynamic voltage.

The advantages of DC greyscale drive pulse of pulse-height modulation is the accurate control to the grey states of acquirement.

AC pulse with DC offset modulation

The gray level driving of the electrophoretic media of encapsulation above-mentioned has been subjected to the influence of oscillation (AC) electric field；Use this AC The transition mechanisms of field are assumed to be totally different from the mechanism realized in the DC driving of above-mentioned identical medium.In Fig. 3 of attached drawing In, interpolation illustrates the AC pulse of DC offset modulation waveform elements, the electricity for encapsulation shown in the major part in the figure Greyscale transitions are generated in swimming medium.Under any circumstance, the frequency (about 10Hz) of AC ingredient is set in a value, which permits Perhaps particle is in response to the oscillating field, and DC offset size and Orientation (for three curves in Fig. 3, it is shown that 0, -1 or - 2.5V) determine the grey states that the pixel finally obtains.As in previous drawings, the time scale in interior illustration is different from master Time scale in figure.In Fig. 3, the reflectivity of pixel is depicted (according to these voltage pulses applied, reflective condition Gray scale from blacking to different stage) change over time curve；It can be seen that larger DC offset generates biggish reflectivity changes.

Once applying AC, electrophoresis particle vibrates in suspension, and this vibrate is as being superimposed upon reflectivity The cyclically-varying of reflectivity in entire variation and the movement observed, this is readily seen on the left of Fig. 3.However, straight To DC offset is applied, can just there are net impacts to reflectivity.Under the influence of DC offset, reflectivity is after waveform applies a period of time Close to steady state value.Seem there is a kind of restoring force is opposite with the power being applied on particle due to DC offset voltage to resist, otherwise, particle will Continue to flow to cell-wall.This restoring force may be due to the movement of the fluid between cyst wall and particle and/or since particle is straight Connect the effect between cell-wall.It is consistent with other waveform elements, remove optical states after voltage stability remain it is constant.

The advantages of waveform elements is that specific reflectivity state can be reached by the parameter of specified waveform element, and DC waveform elements can only make reflectivity changes.Have the advantages that the AC waveform elements of DC offset exist relative to other AC waveform elements In not needing to addressing pulse accurate timing.

The AC pulse of duty cycle modulation

Another kind is modulation duty cycle using the mode that oscillating field introduces DC biasing.In Fig. 4, interpolation shows duty The AC pulse of modulation is spent, which is used to generate the greyscale transitions in the major part of the figure.In each of these pulses In, voltage is set as maximum value, and duty cycle (percentage of the voltage in the time of positive direction or negative direction) determines reflectivity.Make Three duty cycles are 50%, 47% and 40%, as shown in Figure 4.When as in previous drawings, used in the interior illustration Between scale be different from master map in time scale.In the figure, depict pixel (according to these voltage pulses for being applied, Reflective condition is from blacking to different grey levels) reflectivity versus time curve.

Figure 4, it is seen that it is identical as generating the AC/DC shift pulse of curve shown in Fig. 3, it is shown in Fig. 4 Curve reaches steady state value after pulse has applied a period of time.Therefore, consistent with AC/DC offset, using duty cycle modulation, seemingly There are a kind of restoring forces, and particle is forced to leave cell-wall, keep grey states constant.The physical mechanism of the restoring force is with before Face discusses similar.Equally, grey states stop changing immediately after stopping applying pulse.

The advantages of AC waveform of duty cycle modulation, is not needing voltage modulated.

Warbled AC pulse

Another method for realizing AC greyscale transitions is to apply such AC: the AC to electro-optical medium to cause the matchmaker The optical states of matter vibrate, and then terminate the AC on the point for obtaining ideal reflectivity in the circulating cycle.Voltage can be set to Maximum value changes AC frequency to obtain greater or lesser reflectivity range.Frequency determines the amplitude of reflectivity oscillation.

When this method is applied to the electrophoretic media based on particle of encapsulation, electrophoresis particle passes through in their initial bit It sets and oscillates around in response to AC.Since usual reflectivity is not up to extremely black or white optical states, the phase between cell-wall Interaction minimum and reflectivity are opposite linears to applied alive response.

The advantages of warbled AC pulse is not need voltage modulated.

By combining the pulse of the above-mentioned type, multiple waveforms element can be developed, each includes unique interpreter System thus provides the various methods of different electro-optical mediums that driving has different switching characteristic.

In a concrete application of above-mentioned drive scheme principle, using pulse width modulation and AC pulse to obtain electric light Intermediate grey states in display, otherwise the display can only obtain black and white state.

Due to being discussed above, it would be highly desirable to gray level can be obtained in electro-optic displays.However, false If a large amount of gray level needs the pulse width arbitrarily with high frame frequency driver or the driver for capableing of voltage modulated, modulation (is needed It wants high frame frequency by pulse width " cutting " at multiple intervals, therefore can accurately control pulse width, and then accurately control gray scale Grade).It is any substantially all higher than simple three-level (tri-level) driver cost in both drivers, described three Grade driver can only make the potential of the single pixel of display be configured to+V ,-V and 0 relative to public front electrode potential (V is any work potential), and it is commonly used for the display that driving is only able to display black and white state.

The present invention provides a kind of drive scheme, the program can make three-level driver generate the black of bistable electro-optic displays and Intermediate grey scales between white grade.The drive scheme is most easily understood by from following table 2, and the table show in of the invention this The voltage applied during the successive frame of various types transformation in kind display:

Table 2

From table 2 above as can be seen that from black to white the transformation of (vice versa) and binary system (only black/white) display In as.On the other hand, to the transformation of gray scale, there are two parts.First part is square waveform pulse (that is, same potential is more A frame), with polarity appropriate and length so that the reflectivity of electro-optical medium becomes the middle gray as close possible to needs Brightness.The accuracy for the step for having may be limited the frame frequency by display.The second part of addressing pulse includes number The voltage pulse of equal positive and negative is measured, the width of each pulse is equal to a frame.Described in Fig. 3 and 4 as described previously with reference to, before It is verified: to cause the medium " relaxation " to certain " middle grays " the surge medium based on particle that AC square wave is applied to encapsulation State.Therefore, regardless of previous pulse history, the second part of pulse will make all pixels become identical uniform middle gray State.It is black or white using being addressed to appropriate polar short pulse realization from grey states.

More generally, the part AC of the pulse does not change polarity in every frame, but can be changed with lower frequency, adjoint Every a frame (frequency=frame frequency/4) or usually every n frame (frequency=frame frequency/2n) voltage carries out alternation.

Therefore, the present invention provides a kind of method, and simple three-level driver is used only without the use of complicated and high in this method Expensive voltage modulated driver generates single gray level in other binary electro-optic displays.

In second concrete application of above-mentioned drive scheme principle, the present invention provides the set of two-dimentional transition matrix, Wherein each element in matrix defines how (to be indicated with " row index " herein, although it is apparent that dividing from initial optical state The initial optical state of dispensing row is arbitrary) reach final optical states (using " column index expression " herein).The matrix it is every A element is constructed by a series of waveform elements (as defined above), and generally for n gray level displays, which will be wrapped Containing 2^(2N)A element.Matrix of the invention has been included in such consideration, such as to the needs of the DC balance of drive scheme (such as preceding institute Discuss), " memory " effect is minimized (that is, applying the effect of the result of certain pulses to pixel in certain electro-optical mediums The current state for depending not only upon the pixel also relies on certain original states), thus generate uniform optical states and will show Show that the rate of transformation of device maximizes, while working under the limitation of active matrix drive scheme.Present invention provides a kind of sides Method, the optimal value of each single item for determining the element in this matrix for any specific electro-optical medium.For this matrix And their applications in driving electro-optic displays, reader can refer to PCTUS02/37241 above-mentioned.

For pulse width above-mentioned modulates (PWM), currently preferred waveform is as described below.However, using The AC of pulse-height modulation or above-mentioned various mixed types modulation can also obtain the same or similar as a result, and can be Various types of modulation is used in single waveform, for example, for all parts other than the decline of pulse Pulse width modulation, what is be followed by is the back-page voltage modulated to the pulse.

The first two waveform of invention described below is " magic lantern " waveform, before being addressed to next grey states from One grey states returns to black state.This waveform and the display update side for wherein entirely shielding a blanking (such as in slide projector) Case is most compatible.

Double prepulses magic lantern waveform

In the waveform, its preferred form is shown in Fig. 5 of attached drawing, using partial pulse initially by the picture of electro-optical medium Element is from black driving to (as shown at 100) initial (first) grey states.In order to by pixel from this initial gray state change to To white (102), then from white to black different expectation (second) grey states first drive pixel from the first grey states (104).Finally, applying pulse appropriate 106 to reach the second grey states.In order to ensure the holding of such waveform Whole DC is balanced, and the sum of the length of white pulse at addressing pulse and 102 at 106 is necessarily equal to the pulse white-black at 104 Length.The waveform needs the medium fringe time of three times (that is, single pixel is converted to white optical states institute from black optical states The time needed, or vice versa) maximum value realize the transformation between any gray scale of any two, therefore referred to as 3X Waveform.

Single prepulsing magic lantern waveform

In the waveform, its preferred form is shown in Fig. 6 of attached drawing, using partial pulse initially by the picture of electro-optical medium Element from black driving to (as shown at 110) initial (first) grey states, by the way of with discussed in the 6th part above it is double Prepulsing waveform is identical.In order to by the pixel from initial gray state change to different desired (second) grey states, first The pixel is driven from the first grey states to black (112), then applies pulse appropriate 114 to reach the second gray scale shape State.Obviously, before the second transformation, which will turn again to black 116.Such waveform keeps the DC of entire waveform Balance, this is because the impact applied 112 and 116 is respectively equal to the impact that (other than polarity) applies 110 and 114. The waveform needs the maximum value of twice of medium fringe time to realize the transformation between the arbitrary grey states of any two, Therefore referred to as 2X waveform.

Gray scale-greyscale waveforms

Instead of using above-mentioned magic lantern waveform, can by directly from a grey states to another grey states without It is addressed by black or white state and updates display.Since to be not accompanied by apparent illusion (i.e. black and/or white for this transformation " flashing "), so it is referred to as " gray scale-gray scale " addressing.In the presence of there are two types of gray scale-greyscale waveforms of principal mode, i.e. DC Balance and DC are uneven.

In gray scale-greyscale waveforms of DC balance, have by being applied between two grey states necessary to conversion The transformation between the two states is realized in the modulation pulse of precise length.Electro-optical medium is without any centre is black or white shape State.Since maximum impulse length is equal to the addressing time of ink, this waveform is also referred to as 1X waveform.In order to keep DC to balance, For the display with n grey states, the available freedom in the optimization of transformation matrix relevant to any specific waveforms Parameter has n-1.This leads to the system being excessively limited.Equal and phase is needed for example, changing for opposite transformation Pair pulse (that is, other than polarity, 2-3 must be identical as 3-2).

The case where uneven gray scale-greyscale waveforms are balanced with DC substantially is identical, and only pulse length is no longer influenced by DC balance The constraint of limitation.Therefore 2 in transformation matrix^(2N)Each single item in can change independently of all other.

Various waveforms discussed above can address gray level in Active Matrix Display, this is for electro-optical medium a Use in personal digital assistant (PDA) and e-book application is crucial.These waveforms imitate the memory in electro-optical medium It should minimize, this memory will lead to image ghost image.It, can be in minimum number pulse by selection optimal burst length and sequence Middle acquisition desired gray level optical states.

Selective row driving

Another aspect of the present invention relates to the row for driving the display by selection, Lai Gaishan active matrix bistable electro-optical is aobvious Show the performance of device.

As previously mentioned, and as the aforementioned patent and application in discuss in more detail, in order on traditional LC D keep required for Image, it is necessary to it is continuous to refresh whole image region, this is because usually liquid crystal is not bistable, and if do not refresh on LCD Image of the image in a short period of time on LCD will weaken.As well known to the technical staff in active matrix field, at this In kind display, the realization continuously refreshed is to pass through: relevant to the one-row pixels of the display to open using line driver The grid of transistor applies in row driver (source electrode of the transistor in each column for being connected to the display) by the display The potential of the pixel in selected row is written in the relevant portion of required image on device, and therefore writes the selected row of the display.Row Then driver selects the next line of the display and repeats the process, such row is just refreshed by circulation.(line driver is specified To gate electrode and row driver is assigned to source electrode is conventional, but is also arbitrary substantially, can of course be run if necessary ?.)

Since LCD needs the continuous refreshing of image, the only part of displayed image changes by as entire refresh process Part handle.In the display continuously refreshed, do not need to provide the update part of image；Because actually per second have New images are write display (in case of an lcd) several times, and any variation of the parts of images for display of feeding is in short interval Automatically show effect on the display.Therefore, the custom circuit for LCD developed does not provide only part image It updates.

Correspondingly, bistable electro-optic displays do not need continuously to refresh, and actually it is this it is continuous refreshing be it is harmful, This is because unnecessarily increasing the energy consumption of display.In addition, grid (row) route may will hold during this refreshing Property voltage spike pass to pixel electrode, and any actuator voltage error or uncompensated grid feedthrough biased error may Accumulation；All of these factors taken together leads to the undesirable transformation of the optical states of display picture element.Therefore, in bistable electro-optic displays In, it is generally desirable to some devices are provided and are used to update parts of images without rewriteeing whole image over the display, the present invention Relate in one aspect to the bistable electro-optic displays equipped with this " part update " device.According to the present invention, this by comparing will It writes the consecutive image of the display, identify row different in the two images and only addresses the row being identified to come in fact It is existing.

In the method, in order to realize that the part of display updates, the picture that only identification will change comprising its optical states The row of the display of element.In a preferred form of this method, for every row of display, display controller is (referring to preceding The PCT/US02/37241 stated) check all ideal pixel electrode output voltages.If for the row, all output voltage etc. In the potential V of the public preceding electrode of the display_com(that is, if not having pixel to need to rewrite in that row), controller output are same Walk (V_sync) pulse do not issue without data value is loaded into row driver and corresponding export enabled (OE) order.It does so Net effect is that the token position of line driver is transmitted to the next line of display without activating current line.Data are only loaded into column driving Device, and export enabled only for the row statement for wherein thering is at least one pixel to need to be rewritten.

The present invention provides two different advantages.Firstly, for the pixel being not overwritten, many stray electricals can be eliminated Potential source.There is no capacitive grid spike (gate spike) for these pixels, and in the frame that pixel is not addressed, row driver electricity The error of pressure is not transferred to the pixel.Since compared with liquid crystal, many electro-optical medium resistivity are relatively low, especially electrophoresis Medium, pixel electrode would tend to relax towards practical front (front plane) voltage, therefore maintain the holding of electro-optical medium State.Secondly, the power consumption of display minimizes.For the every a line being not overwritten, corresponding grid line is not required to be charged.This Outside, when output is not loaded into the column electrode of display, the extra power consumption for carrying out mobile data across display interface device is also eliminated.

Area of space shakes (dither)

Mentioned-above aspect of the invention is related to the waveform for driving electro-optic displays.The performance of this display It can be changed by changing the structure change of bottom plate, this aspect of the invention is related to one or more pixels of display (preferably each pixel) is divided into multiple sub-pixels with different area.

As being before already mentioned above, therefore it is highly desirable to provide gray level in electro-optic displays.It can also be by by the picture of the display Element driving obtains the gray level to the grey states between two extremity.However, if the medium cannot obtain Ideal quantity intermediate state, or if the display is driven by the driver that cannot provide the intermediate state of ideal quantity It is dynamic, then the state of ideal quantity must be obtained with other methods, this aspect of the invention is related to using for this purpose Spatial jitter.

One display can be divided into multiple " logic " pixels, wherein each can show ideal quantity gray scale or Other optical states.It may be evident, however, that the physically separated region of more than one can occur in each logical pixel, it is in fact right In color monitor utilization " panchromatic " logical pixel, this is common, and each of " panchromatic " logical pixel includes having base Three sub-pixels of color (such as red, green, blue)；See, for example, above-mentioned 2002/0180688.Similarly, sub-pixel can be used Combination gray level is obtained as logical pixel, each of sub-pixel being capable of binary transition.E.g., including 4 independences The controllable logical pixel with sub-pixel of the same area can be used for providing 2 gray levels.However, for being more than 1 or 2 ash Any situation of grade is spent, the quantity of sub-pixel inconveniently becomes larger, because gray level is every to increase by 1, the number of required sub-pixel Amount doubles.

The present invention provides a kind of electro-optic displays, has at least one pixel, which includes multiple sub-pixels, these Sub-pixel has different areas.In a preferred embodiment of the invention, the area of at least two sub-pixels differs 2 substantially Times.Thus, for example, it is the sub-pixel of 1X, 2X and 4X that logical pixel, which may have area, wherein X is arbitrary area.This seed type Logical pixel schematically shown in Fig. 7 A of attached drawing.The logical pixel only uses three electrodes and obtains 3- gray levels, and 8 sub-pixels will be needed by obtaining identical 3- gray level using equal sub-pixel on area.

When each sub-pixel is driven, a part of reflection or transmission incident light, and partial amount is by the sub-pixel Area determines.If reflection/transmission is average on the region of the logical pixel, the binary weight of driving area is obtained Weight, therefore obtain the gray level of spatial jitter.

The area of sub-pixel is arbitrary.Sub-pixel shown in Fig. 7 A is weighted with reflectivity.If it is desired that with non-linear Weighting (this L for equal steppings^*Or gamma correction gradation intervals are suitable), which will correspondingly change.

Other than considering their relative area, the shape of sub-pixel should be also thought over.Letter as shown in Figure 7A Single bulk allows array of sub-pixels simply to shape, but under certain conditions, these sub-pixels may observed person's resolution.Together Sample, if intergrade gray scale (thus (such as) only has the region 4 of Fig. 7 A to be driven in each logical pixel) be shown in it is big Region (covering many logical pixels) on, observer will be seen from the line occurred from sub-pixel figure or grid graph.

The resolution ratio for increasing logical pixel will reduce these problems, but need a large amount of additional pixels, because of pixel number Amount be with resolution ratio square and increase.On the contrary, can be subtracted by the sub-pixel that intersects (such as shown in fig.7b) The problem of visibility and/or eye diagram of few sub-pixel；Notice that the figure is intended to show to intersect, be inaccurate representative The relative area of sub-pixel.Many cross one another figures similar to Fig. 7 B can be used to improving image quality.

Another method of the problem of processing sub-pixel visibility and/or eye diagram is randomly oriented sub-pixel.For example, In pixel array, each pixel may have row shown in Fig. 7 A by arrangement of subpixels as shown in Figure 7 A, single pixel at random Each of 4 possible directions of column." randomization " of this sub-pixel facilitates partition graph and makes them for seeing The person of examining less is clear to.

Although the embodiment of the present invention shown in fig. 7 A and 7B generates 3- gray levels, it will be understood that the present invention can be with The gray level of any digit is generated by simply increasing additional sub-pixel.

The advantages of this aspect of the present invention, is as follows:

(a) electro-optical medium itself is not needed with gray level；Substantially display can be black/white display, and open and close Sub-pixel is to generate gray level.It, can be by providing additional row driver in scanning array (for the row of identical quantity) To obtain necessity control for sub-pixel.It reduce the requirements to electro-optical medium；For example, needing not worry about beyond its work The possibility drift of the gray level of electro-optical medium after service life.

(b) row driver complicated is not needed；The present invention with simply using used in many traditional monitors two into Grade driver processed is compatible.Therefore, be conducive to using the various electro-optical mediums being easy to get, cheap " finished product " component.Some productions The method of raw gray level needs to use voltage modulated driver to column electrode, and this driver is not widely available and ratio two The manufacture of system grade driver is more expensive/it is more difficult.

(c) design for the thin film transistor (TFT) (TFT) using active matrix array of the invention is required unlike panchromatic Be more difficult, there are three sub-pixel (for example, RGB) for each pixel in panchromatic, and are provided to the data volume of various parts It will not be bigger.Therefore exploitation new technology is not needed in implementing active matrix backplane of the invention.

Miscellaneous technology

In most traditional active matrix drive scheme of electro-optic displays, the voltage of pixel electrode becomes on display bottom plate Change to apply required voltage in pixel.Top surface generally remains specific voltage, which is considered for addressing picture Element is advantageous.For example, provided that giving the data line voltage of pixel electrode in zero volt and voltage V₀Between change, then top surface It will remain in V₀/ 2, to allow the voltage drop in pixel to have V in two directions₀/ 2 is so big.

According to an aspect of the present invention, the voltage of top surface can change to reinforce the addressing of electro-optical medium.For example, top surface Voltage can remain zero volt to allow total pixel voltage to drop (top surface negative pixel voltage) as low as-V₀.Increase top surface electricity It is depressed into V₀, allowing pixel voltage to drop has V₀It is so big.These bigger voltage drops allow electro-optical medium quickly to address.

More generally, it is advantageous that top surface voltage can not only be set as voltage zero and V₀, can also be set to other Voltage.For example, it can be advantageous to consistent with the pixel-pixel voltage applied by bottom plate, when applying global on electro-optical medium Between change voltage.

It is known to provide capacitor between pixel electrode and the electrode extended to form by selection route in electro-optic displays Device, to fill same voltage with selection route；Described in WO 01/07961 as the aforementioned, the offer of this capacitor reduces The rate of decay of electric field after removing driving voltage in pixel.In another convenience, the present invention has the electric light of storage Display, the storage are formed between pixel electrode and (second) electrode, and the voltage of (second) electrode can be only Stand on the selection route variation of the display.In a preferred embodiment, second electrode follows top surface voltage, that is, its voltage A constant independent of the time is only in that with the difference of top surface.With the phase by pixel electrode and the control display The storage overlapped to form between the selection route of adjacent (previous) row compares, and provides such capacitor significantly Reduce the capacitive voltage spike of pixel experience.

Another aspect of the present invention relates to harmful transformations by selecting to reduce or eliminate electro-optical medium with data line.

As discussed above, it selects and data line is the primary element of active matrix panel, they are provided pixel electrode Voltage needed for being charged to desired value.However, selection and data line, which may have, changes the electro-optical medium adjacent with the data line Adverse effect.Observer will be hidden by the region of data line and/or selection line transformation, can be disappeared by using black mask Except the deleterious optical artifact as caused by this transformation.However, provide this black mask need will before display with thereafter In face of neat, and reduce the electro-optical medium part for being exposed to observer.The result is that with black mask situation obtained is not used It compares, display is darker and contrast is lower.

In another aspect of the invention, by keeping the laterally extension of data line in one direction small, so that it Will not carry out sizable addressing to adjacent electro-optical medium during normal display operation, so as to avoid making for black mask With.This avoids the needs to black mask.

The use and the drive scheme for driving electro-optical medium that a related fields of the invention are related to passivated electrodes Modification.When in its film between two electrodes, the electro-optical medium for impacting driving can be by electrical addressing.In general, electric Pole is contacted with electro-optical medium.However, even if existing between one or two electrode and the medium with long the electron relaxation time Dielectric material can also address the electrode.In order to avoid the inverse chemistry or electrochemistry in the bottom plate of display device or front are mutual Effect, the passivation of one or two electrode may be needed；Referring to WO 00/38001 above-mentioned.Although the appearance of dielectric layer So that the ability of the voltage on electro-optical medium is kept to greatly reduce, but if the dielectric layer is appropriately designed, voltge surge It still can apply to the medium and the medium can be addressed by these voltge surges.

What the change of the optical states of electro-optical medium was certainly realized by the voltage changed on pixel electrode.The voltage changes Becoming leads to voltage on electro-optical medium, and makes due to charge leakage the voltage attenuation on electro-optical medium by medium.If outer Portion's dielectric layer (that is, dielectric layer between the medium and an electrode) sufficiently thin and electro-optical medium resistivity is sufficiently large, then should Voltge surge on medium will be enough to cause the optical states of the medium to change as needed.Therefore pass through the electro-optical medium of dielectric layer Electronically addressing be possible.However, the addressing scheme is different from addressing the electro-optical medium that its electrode is directly contacted with the medium, It is by pixel because in the latter case, addressing medium by applying voltage in pixel, and in the previous case Variation is caused to realize addressing in voltage.In each variation, electro-optical medium undergoes voltge surge.

Finally, the present invention is provided to reduce the drive scheme of the crosstalk in active matrix electro-optic displays.

Pixel-level fusion (one pixel of addressing influences the optical states of other pixels) be it is harmful, this is that there are many reasons Caused by.One the reason is that there is limited electric current to flow through transistor in the off case.It is right due to the current leakage of off state Data line provides voltage (being intended to the pixel that charges) and may charge to the transistor in non-selection row.Solution be using Transistor with low OFF-state current.

Another crosstalk sources is the current leakage between adjacent pixel.Electric current can be leaked out by the element of bottom plate, or be passed through It is leaked out with the electro-optical medium of contacts baseplate.The solution of this crosstalk is that a kind of design between pixel electrode clearance for insulation is big Bottom plate.The leakage current of the bigger generation in gap is smaller.

As has been noted, the preferred type for the electro-optical medium in the present invention is the electricity based on particle of encapsulation Swimming medium.The patent such as front E Ink and MIT can be used in this electrophoretic media used in methods and apparatus of the present invention With identical component and manufacturing technology described in application, reader can be with reference to these patents and application to obtain further letter Breath.

Claims (2)

1. a kind of method for addressing bistable electrophoretic media, the bistable electrophoretic media, which contains, to be suspended in liquid suspending medium Can electrophoresis motion particle, which is characterized in that apply the alternating electric field that there is DC to deviate, wherein institute to the bistable electrophoretic media The size and Orientation for stating DC offset determines the grey states that the pixel finally obtains, and wherein larger DC offset generation is biggish Reflectivity changes.

2. according to the method described in claim 1, wherein the electric field is applied to bistable electrophoretic media, until the bistable electrophoresis The gray level of medium is constant.