CN100437714C

CN100437714C - Methods for driving electro-optic displays

Info

Publication number: CN100437714C
Application number: CNB03813604XA
Authority: CN
Inventors: G·M·丹纳; K·R·阿蒙森; A·C·阿兰戈; J·B·埃温; R·W·泽纳
Original assignee: E Ink Corp
Current assignee: E Ink Corp
Priority date: 2002-06-13
Filing date: 2003-05-23
Publication date: 2008-11-26
Anticipated expiration: 2023-05-23
Also published as: HK1147340A1; EP1512137A2; JP2015099376A; HK1129484A1; AU2003239619A8; CN101373581A; JP2014063176A; CN104238227B; JP2005530201A; HK1205275A1; WO2003107315A2; JP4651383B2; CN1659618A; WO2003107315A3; CN104238227A; HK1147339A1; AU2003239619A1; CN101373581B

Abstract

A method for addressing a bistable electro-optic display having at least one pixel comprises applying an addressing pulse to drive the pixel to a first optical state; leaving the pixel undriven for a period of time, thereby permitting the pixel to assume a second optical state different from the first optical state; and applying to the pixel a refresh pulse which substantially restores the pixel to the first optical state, the refresh pulse being short relative to the addressing pulse.

Description

Be used to drive the method for electro-optic displays

The present invention relates to be used to drive the especially method and apparatus of bistable electro-optic displays of electro-optic displays.Method and apparatus of the present invention main (though unspecial) is used to drive the bistable electrophoretic display device (EPD).

The application relates to U.S. Patent No. 6,504, and 524 and No.6,531,997.The application also relates to common pendent International Application PCT/US02/10267 (publication number No.WO02/079869) and PCT/US02/37241.

The term " electric light " that is applied to material or display as used herein is its conventional sense in imaging technique, refer to material with first and second show states, at least a optical property difference of this first and second show state makes this material be converted to second show state from first show state by apply electric field to this material.Though this optical property is the appreciable color of human eye normally, but also can be other optical property, such as optical transmission, reflectivity, brightness or the demonstration of reading, counterfeit look on the electromagnetic reflectance varies meaning outside the visible range by machine.

The term of Shi Yonging " grey states " is its routine meaning in imaging technique herein, is meant the state between two extreme optical state of pixel, might not mean that the black and white between these two extremities changes.For example, described such electrophoretic display device (EPD) in a plurality of patents quoted below and the disclosed application, wherein extremity is white and dark blue, thus middle " grey states " actual will be light blue.In fact, as previously mentioned, the transformation between two extremities also may not be the variation on the color.

The term of Shi Yonging " bistable " and " bistability " are its routine meanings in the art herein, be meant the display that comprises display element with first and second show states, described first and second show states have a kind of optical property difference at least, make any point element be driven into and present its first or second show state by addressing pulse with finite duration, after addressing pulse stops, it is several times of times of minimum duration that change the required addressing pulse of state of this display element at least that this state will continue, and for example is four times of times at least.In the application that aforesaid common pendent sequence number is No.10/063236, illustrated: some based on particle can display gray scale electrophoretic display device (EPD) not only stable under its extreme black and white state, and stable under the grey states therebetween, the electro-optic displays of other type is like this equally.Such display is called " multistable " rather than bistable rightly, but term used herein for convenience's sake " bistable " covers bistable and multistable display.

Term used herein " impacts (impulse) " gets its conventional meaning: voltage is about the integration of time.Yet some bistable electro-optical mediums serve as charge sensor, can use another definition of impact for this medium, and promptly electric current is about the integration of time (equal applied total electrical charge).Serving as voltage-time shock transducer according to medium still is the electric charge shock transducer, should use the suitable definition about impacting.

Known polytype bistable electro-optic displays.One type electro-optic displays is for example in U.S. Patent No. 5,808,783,5,777,782,5,760,761,6,054,071,6,055,091,6,097,531,6,128,124,6,137, disclosed rotation two color component types (rotating bichromal member) are (though such display often is called as " rotating two chromospheres " display in 467 and 6,147,791, but because rotating element is not spherical in more above-mentioned patents, that term " rotates two color components " is more accurate).This display uses a large amount of corpusculums (being typically spherical or cylindric) and internal dipole, and these corpusculums have two or more different parts of optical characteristics.These corpusculums are suspended in the vacuole of the full of liquid in the matrix, and these vacuole fulls of liquid are so that these little physical efficiencys rotate freely.Apply electric field to this display, the appearance of this display changes, and therefore rotates these corpusculums to all places and change by observing those parts of the surperficial corpusculum of being seen.

The electro-optical medium of another kind of type uses electrochromic medium, the electrochromic medium of nanometer chromium (nanochromic) form of film for example, it comprise the electrode that forms by the semiconduction metal oxide to small part and a plurality of attached on this electrode can reversible color dye molecule; Referring to, for example, O ' Regan, Nature such as B. 1991,353,737; And Wood, D., Information Display, 18 (3), 24 (in March, 2002).And referring to Bach, U. waits Adv.Mater., 2002,14 (11), 845.For example among U.S. Patent No. 6,301,038 and the international application published No.WO 01/27690 such nanometer chromium thin film is being described also.

The electro-optic displays of the another kind of type of being researched and developed in a large number is based on the electrophoretic display device (EPD) of particle over several years, and wherein a plurality of charged particles pass the suspending liquid motion under electric field effects.Compare with LCD, the contribution of electrophoretic display device (EPD) is to have good brightness and contrast, wide visual angle, state bistability and low-power consumption.Yet the long-term image quality problem of these displays has hindered being extensive use of of they.For example, the particle that constitutes electrophoretic display device (EPD) trends towards sedimentation, causes the service life of these displays not enough.

Transfer in a large number or announce recently that they have described the electrophoretic media of encapsulation with the patent of Massachusetts science and engineering (MIT) and E Ink company application.The medium of this encapsulation comprises a large amount of folliculus, in wherein each folliculus comprises itself mutually and around the cyst wall of interior phase, but contain the particle that is suspended in the electrophoresis motion in the liquid suspension medium in wherein said mutually.Usually, these capsules itself are kept in the polymeric binder to form the adhesion layer between two electrodes.For example, in United States Patent (USP) N0.5,930,026; 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 published No.WO 99/67678; WO 00/05704; WO 00/20922; WO 00/26761; WO 00/38000; WO 00/38001; WO 00/36560; WO 00/67110; WO 00/67327; WO 01/07961; With the medium of having described such encapsulation among the WO01/08241.

Many above-mentioned patents and application recognize in the electrophoretic media of encapsulation can be with continuous replacement mutually around the wall that separates micro-capsule, thereby produce (polymer-dispersed) electrophoretic display device (EPD) of so-called polymer dispersed, wherein electrophoretic media comprises the droplet of separation of a plurality of electrophoretic fluid and the external phase of polymeric material, and relevant with each independent droplet even without the cyst membrane that separates, but the separation droplet of the electrophoretic fluid in the electrophoretic display device (EPD) of such polymer dispersed also can be considered to capsule or micro-capsule; Referring to, for example aforesaid 2002/0131147.Therefore, for the application's purpose, the subclass of the electrophoretic media that the electrophoretic media of this polymer dispersed is considered to encapsulate.

The electrophoretic display device (EPD) of encapsulation does not suffer the gathering and the precipitation failure mode of conventional electrophoretic part usually, and additional advantage is provided, such as can or being printed on various flexibilities and the stiff base the display coating.(use word " printing " to be intended to unrestrictedly comprise the printing and the coating of form of ownership: such as premeasuring (pre-metered) coating, slit or projection coating, slip or waterfall (cascade) coating, the showering of curtain formula of patch coating (patch die coating); Such as cutter (knife over roll) coating on roller, forward with the roll banding of reverse roll coating; The coating of gravure formula; Dip coated; Spraying; Crescent (meniscus) coating; Spin coating; Brush; Air knife is coated with; Silk-screen printing technique; Electrostatic printing process; Hot stamping dataller skill, ink-jet printing process; And other similar techniques.) therefore, the display of manufacturing can be flexible.In addition, owing to show that medium can print (make and in all sorts of ways), display itself can be made at an easy rate.

A kind of electrophoretic display device (EPD) of correlation type is so-called " microcell electrophoretic display ".In microcell electrophoretic display, charged particle and suspension are not sealed in the micro-capsule but remain in a plurality of chambeies that are formed in the carrier medium (normally polymer film).Referring to, for example, international application published No.WO 02/01281 and disclosed U. S. application No.2002-0075556 (transfer Sipix Imaging, Inc.)

Though electrophoretic display device (EPD) normally opaque (because the basic block visible light transmission display of these particles device) and under reflective-mode, working, but electrophoretic display device (EPD) can be in so-called " shutter mode (shutter mode) " down work, and particle is arranged in the display transverse movement to make display have one be the show state of an opaque show state and a printing opacity substantially in this pattern.Referring to, for example, aforesaid U.S. Patent No. 6,130,774 and 6,172,798, and U.S. Patent No. 5,872,552,6,144,361,6,271,823,6,225,971 and 6,184,856.Be similar to electrophoretic display device (EPD), but the dielectrophoretic displays that depends on the electric field intensity variation can worked under the pattern similarly also; Referring to U.S. Patent No. 4,418,346.The electro-optic displays of other type also can be worked under shutter mode.

Based on the bistable of the electrophoretic display device (EPD) of particle or the similar performance of multistable performance and other electro-optic displays, form distinct contrast with the performance of traditional liquid crystal (LC) display.The performance of twisted nematic liquid crystal is not bistable or multistable, but serves as voltage sensor, and a feasible pixel to this display applies given voltage can produce a specific gray level in this pixel, and irrelevant with the gray level that before appeared on this pixel.In addition, only a direction (from non-transmission or " secretly " to transmission or " bright ") driving LC display, the reverse transformation from brighter state to darker state is by reducing or eliminating the electric field realization.At last, the gray level of the pixel of LC display is insensitive to the polarity of electric field, and only to its magnitude, and in fact for technical reason, coml LC display is usually with the reversal of poles of frequent interval with driving electric field.With first approximate contrast be, bistable electro-optic displays is served as shock transducer, thus the end-state of pixel not only depends on the electric field that is applied and applies time of this electric field, also depends on the state of this pixel before applying electric field.

Though point out the front, the electro-optic displays performance bistability of electrophoresis and other type, but this bistability is not hard-core, image on this class display slowly weakens in time, if thereby image will keep the long cycle, this image must periodic refresh, writes the fashionable optical states that it has for the first time so that image returned to.

Yet, this image refresh the problem that may cause himself.As aforesaid U.S. Patent No. 6,531,997 and 6,504,524 are discussed, and on average apply electric field if drive the method for this display is not produced as zero (or near zero) on whole electro-optical medium net time, may encounter problems and the mission life of this display reduces.On whole electro-optical medium, be produced as the driving method that zero net time on average applies electric field and typically refer to " dc balance " or " DC balance ".If keep image for a long time by applying refresh pulse, then the polarity of these pulses need to be driven into the polarity of addressing pulse of the optical states that is keeping identical with being used for related pixel with this display, and this causes the uneven drive scheme of DC.

According to a further aspect in the invention, have been found that the image on then can refresh display reduces and the relevant harmful effect of DC imbalance drive scheme simultaneously if use short pulse to realize refreshing.

Another aspect of the present invention relates to such problem of handling: the driving of aforesaid bistable electro-optic displays requires to cause the conventional ADS driving method that is used to drive LCD to be unsuitable for this bistable electro-optic displays.In addition, U.S. Patent No. 6,531 as described above, 997 and 6,504,524 are discussed, on average apply electric field if drive the method for this display is not produced as zero (or near zero) on whole electro-optical medium net time, may encounter problems and the mission life of this display reduces.On whole electro-optical medium, be produced as the driving method that zero net time on average applies electric field and typically refer to " dc balance " or " DC balance ".LCD also can run into similar problem, but because this class display is insensitive to the polarity of the electric field that applied, and have the arbitrarily ability of reversed polarity thereupon, make that the DC equilibrium problem is not very important in LCD.Yet, the DC balance need in the drive scheme of design bistable electro-optic displays (wherein electro-optical medium is to the polar sensitive of the electric field that applied), be significant consideration.

Therefore, another aspect of the present invention relates to the method and apparatus that drives electro-optic displays, and this method and apparatus has reached the specific (special) requirements of bi-stable display previously discussed.Some method and apparatus of the present invention is mainly used in and produces accurate gray scale rendition in bi-stable display.

Therefore, on the one hand, the invention provides and be used for the method that addressing has the bistable electro-optic displays of at least one pixel, this method comprises: apply addressing pulse to drive described pixel to first optical states;

In a period of time, keep described pixel not to be driven, allow described pixel to present to be different from second optical states of first optical states thus;

Apply refresh pulse to described pixel, this refresh pulse returns to first optical states with described pixel substantially, and is shorter with respect to this refresh pulse of addressing pulse.

Of the present invention for convenience's sake hereinafter this is called as " refresh pulse " of the present invention method on the one hand.

In this refresh pulse method, the impact of refresh pulse is not more than impact about 20% of addressing pulse usually, it is desirable to be not more than the about 10% of this impact, and preferably is not more than 5% of this impact.Owing to reason as explained below, the difference between common first and second optical states is no more than the L of an about unit ^*(L wherein ^*Has common CIE definition); It is desirable to the L that this difference is no more than about 0.5 unit ^*, and preferably be no more than the L of about 0.2 unit ^*Can apply a plurality of refresh pulses to this pixel at interval with rule.

In a kind of form of this refresh pulse method, after applying refresh pulse, apply second addressing pulse to this display, this second addressing pulse drives this pixel to the 3rd optical states that is different from first and second optical states, and wherein the impact that is applied by second addressing pulse is following two sums: (a) this pixel is driven into the required impact of the 3rd optical states from first optical states, and (b) and in an algebraic sum equal and opposite in direction that is applied to the refresh pulse on this pixel between first and second addressing pulses and an opposite polarity impact.But second addressing pulse may be to change the voltage constant duration.In comprising the display of a plurality of pixels, second addressing pulse can be a blanking pulse, and it is with all pixel drive to one extreme optical states of this display.In the preferred form that this " blanking pulse/refresh pulse " handled, this display comprises a plurality of pixels, first addressing pulse is applied to each pixel, and first group of pixel becomes in vain and second group of pixel becomes black so that drive, at least one refresh pulse is applied to each pixel, and apply to this display afterwards and make first blanking pulse of all pixel blackening and second blanking pulse that drives all pixel Cheng Bai, these two blanking pulses apply with any order all can.The impact that is applied to each pixel of first group during first blanking pulse is following two sums: (a) drive this pixel from white to black required impact, and (b) and between first addressing pulse and first blanking pulse, be applied to the algebraic sum equal and opposite in direction of refresh pulse of this pixel but an opposite polarity impact.Similar, the impact that is applied to each pixel of second group during second blanking pulse is following two sums: (a) drive this pixel from black to white required impact, and (b) and between first addressing pulse and first blanking pulse, be applied to the algebraic sum equal and opposite in direction of refresh pulse of this pixel but an opposite polarity impact.

Refresh pulse method of the present invention can be used for the electro-optical medium of aforesaid any kind.Therefore, in the method, display can be rotation two color components or an electrochromic display device (ECD), perhaps electrophoretic display device (EPD), the electrophoretic display device (EPD) that it is desirable to encapsulate.

On the other hand, the invention provides a kind of method that is used for addressing bistable electro-optical medium, this method comprises to this medium and applies the have direct current offset alternating-current pulse of (offset).

On the other hand, the invention provides a kind of method of addressing bistable electro-optical medium, this method comprises to this medium and applies alternating-current pulse, and changes the frequency of this pulse and at least one in the duty cycle, thereby changes the optical states of this electro-optical medium with this alternating-current pulse.

On the other hand, the invention provides the method that drives bistable electro-optic displays, this display comprises a plurality of pixels that are arranged in a plurality of row and a plurality of row; A plurality of column electrodes, each column electrode is relevant with one of these a plurality of row; A plurality of row electrodes, each row electrode is relevant with one of these a plurality of row; And drive unit, be arranged for selecting each in the column electrode successively and during the selection of any given column electrode, applying selected voltage, so that pixel in the addressing row relevant and the delegation that on this display, writes needed image with selected column electrode to the row electrode.This method comprises:

First image is write display;

Receive representative and will write the data of second image on this display;

This first and second image and the row of this display is divided into first group and second group relatively, at least one the pixel difference in first group row between first and second images, pixel is identical between first and second images in second group row; And

Column electrode by a select progressively and first group of line correlation writes second image, and apply voltage to the row electrode only writing first group of row, thereby on this display, form second image.

On the other hand, the invention provides electro-optic displays with a plurality of pixels, in these pixels at least one comprises area different a plurality of sub-pixels mutually, and this display comprises drive unit, is arranged for changing independently of each other the optical states of described sub-pixel.In this display, its area of at least two sub-pixels that it is desirable in these sub-pixels differs 2 times substantially.

Describe the preferred embodiments of the present invention now with reference to accompanying drawing, but preferred embodiment only is exemplary, in the accompanying drawing:

The curve map of Fig. 1 shows in the display that uses the DC pulse addressing with pulse length modulation gray level over time;

The curve map of Fig. 2 is similar to Fig. 1, be to use the DC pulse addressing with pulse-height modulation display gray level over time;

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

The curve map of Fig. 4 is similar to Fig. 1, be the alternating-current pulse addressing with duty cycle modulation used according to the invention display gray level over time;

The curve map of Fig. 5 shows in the display that uses two prepulsing magic lantern (slideshow) waveform addressing gray level over time;

The curve map of Fig. 6 shows in the display that uses the addressing of single prepulsing magic lantern waveform gray level over time;

Fig. 7 A and 7B show may arranging of sub-pixel in the single pixel of display of the present invention.

Point out as front, the invention provides many improvement of the structure of the method for addressing electro-optical medium and display and these displays. To sequentially describe various aspects of the present invention now, but will be appreciated that single electro-optical medium or display can utilize a more than aspect of the present invention. For example, single electro-optic displays can use the AC pulsed drive with DC skew, and also uses refresh pulse.

Refresh pulse method of the present invention

As previously mentioned, the invention provides a kind of method, the method refreshes image on this display by apply the new pulse of whisk broom to electro-optic displays. Therefore, in the method for the invention, at first the pixel to bi-stable display applies addressing pulse, and this addressing pulse is enough to change the optical states of this pixel. Keeping this display after not driven a period of time, apply refresh pulse to this pixel, this refresh pulse is shorter with respect to this addressing pulse. Usually, the impact that refresh pulse applies is not more than 20% (it is desirable to be not more than 10%, and preferably be not more than 5%) of the impact that addressing pulse applies. For example, if pixel need to continue the addressing pulse of the 15V of 500 milliseconds (msec), refresh pulse can be 15V, continue 10 milliseconds (msec), its impact be addressing pulse impact 2%.

Should consider that human eye adjusts the time of refresh pulse in the method to the sensitivity of the minor variations of unexpected optical states. Human eye has relative patience for the gradually decay of image, so that, for example, usually measure as brightness L^*(defined by common CIE; Referring to, Hunt for example, R.W.G.Measuring Color, 3rd edition, Fountain Press, Kingston-upon-Thames, England (1998). (ISBN 0863433871)) the bistability of electro-optical medium of required time, two units of maximum (or minimum of a value of black state) variation of the white optical state of after addressing pulse finishes, observing. Yet when applying refresh pulse to display, the brightness of related pixel occurs to change suddenly, and substantially less than 1 L of unit^*Sudden change be easy to be discovered by human eye. According to the interval between the refresh pulse, the variation of the image that is caused by these pulses may show as " flicker " in image, and this flicker is disliked for most of observer. Other discernable variation in the image that causes for fear of this flicker or by refresh pulse, expectation be interval between selective addressing pulse and the first refresh pulse or the interval between the continuous refresh pulse so that each refresh pulse causes minimum variation in image. Therefore, the L that is caused by single refresh pulse^*Variation should be less than about 1 L of unit^*, it is desirable to less than about 0.5 unit, and more preferably less than about 0.2 unit.

Although the refresh pulse that uses in this method can be introduced some DC in drive scheme during applying this refresh pulse uneven, but be not precluded within the long-term DC balance of acquisition in this drive scheme, and have been found that the long-term but not DC balance of short-term is the principal element of the working life of decision electro-optic displays. In order to obtain this long-term DC balance, after applying one or more refresh pulses, the pixel that has received these refresh pulses can be driven to its opposite optical states by " conversion " or the second addressing pulse, and can be adjusted at the impact that applies in this inversion address pulse so that DC balance (perhaps minimum at least DC is uneven) to be provided in the whole cycle that begins since the first addressing pulse, this adjustment is by adjusting the impact of this second addressing pulse, wherein the adjustment amount size equal and polarity in contrast to the algebraical sum that between these two addressing pulses, is applied to the refresh pulse of this pixel. For example, consider a display, it can be by applying ± impact of 15V, 500 milliseconds (msec) and changing between white and black light state. The pixel of supposing this display at first by apply 500 milliseconds (msec)+15V impacts and bleaches from black, and the white state of this pixel subsequently by apply at set intervals 10 milliseconds (msec)+10 refresh pulses of 15V are held. If behind these 10 refresh pulses, expectation makes this pixel get back to its black optic state, this can by apply 600 (rather than 500) millisecond (msec)-the 15V addressing pulse realizes, thereby all realized the DC balance between tour at the whole Hei-Bai of this pixel-Hei.

The such adjustment that changes addressing pulse can realize when new images writes on this display and therefore must change the optical states of some pixel. Perhaps, can during applying " blanking pulse " to this display, carry out this adjustment. Discuss among the PCT/US02/37241 as the aforementioned, usually must or expect to apply so-called " blanking pulse " with the rule time interval to electro-optic displays; This blanking pulse comprises at first all pixel drivers to one extreme optical state of this display (for example, white state), then drives all pixels to opposite optical states (for example, black), then writes needed image. The advantage that realizes this adjustment during blanking pulse is, all pixels can be substantially at one time by the DC balance; The technology of using the front to describe in detail, the pixel that in the image formerly (firm incipient image before the blanking pulse) is black can be the DC balance during with the blanking pulse of all pixel driver Cheng Bai, and is that white pixel can be the DC balance during the blanking pulse that all pixel drivers is become black in the image formerly. Equally, realize that during blanking pulse the advantage of this adjustment is, do not need clearly to know since its previous addressing pulse to begin how many refresh pulses are each independent pixel received; Suppose to refresh black and white pixel (fact of case is usually like this) every the identical time interval, and when changing, inserts each image blanking pulse, each pixel will need identical adjustment (except polarity) during this blanking pulse, this adjustment determines by work the quantity that is applied to the refresh pulse on this display since this previous blanking pulse. Equally, the impact that applies adjust ash-grey transformation in this display during realizes that during blanking pulse the DC balance provides a kind of this refresh pulse method is applied to have mode more than the electro-optic displays of two gray levels, because obviously may cause the undesired error of gray level.

Refresh pulse method of the present invention can as the substitute of the additive of the bistability that increases electro-optical medium or with its combination. For example, the electrophoretic media that the present invention can describe in aforesaid 2002/0180687 is used, and this medium has the suspension that polymer dissolving or that disperse is wherein arranged, and wherein this polymer increases the bistability of medium.

Provide following Example now,, an embodiment of refresh pulse method of the present invention is shown only by the mode of explanation.

Example 1

This example uses the display of the anti-charge type medium of two particles that contains encapsulation, and this medium comprises polymer-coated titanium dioxide white particles and polymer-coated black particles, and suspending liquid is not painted.This display is substantially according to " method B " preparation of describing in aforesaid 2002/0180687 [0061]-[0068] section.

Zhi Bei display comprises a plurality of pixels as previously mentioned, can use continue 500 milliseconds (msec) ± the 15V addressing pulse changes these pixels between the black and white optical states.The bistability of this display is limited, and white optical state changes 2L in the environment around ^*Only about 15sec of needed time of unit.Yet, determine on the experience by apply 4sec/min ± the new pulse of whisk broom (duty cycle is approximately 6.7%) of 15V can keep this white and black optic state indefinitely.In order to avoid flicker in the standard picture (containing the black and white zone) that real test is provided and in these experiments, uses, after 500 milliseconds of (msec) addressing pulses of beginning, every about 100 milliseconds (msec) to the black and white pixel of this display apply 7 milliseconds of (msec) duration ± refresh pulse of 15V.

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

Scheme 480:

Use described standard picture to this display addressing, and use aforesaid refresh pulse that this image was kept 480 minutes.Apply a series of blanking pulses then, and the circulation of repetitive addressing and refresh pulse.Whenever do not apply the DC equalizing pulse.After 83 hours the work, apply a series of blanking pulse, and what test this display then has been the white and the separate areas of black respectively.Be retained as in the zone table below of this display of white with " 480W " expression at test period, and be that the zone of black is with " 480D " expression.The addressing pulse zone that each is tested of 500 milliseconds (msec) by standard is driven into its white optical state, and measures its number percent reflectance value; This value is represented with " w% " in table.Allow each tested zone under the situation that does not apply any refresh pulse, to keep 15sec then, after this interval of 15 seconds, measure L ^*Variation; Resulting L ^*Variation be called " bright maintenance difference (brightholding difference) ", in described table with " bhdl " expression.After applying other blanking pulse, the addressing pulse zone that each is tested of 500 milliseconds (msec) by standard is driven into its black optic state, and measures its number percent reflectance value; This value is represented with " d% " in described table.Allow each tested zone under the situation that does not apply any refresh pulse, to keep 15 seconds then, after this interval of 15 seconds, measure L ^*Variation, resulting L ^*Variation be called " secretly keeping difference ", in described table with " dhdl " expression.

Scheme 60:

This scheme is identical with scheme 480, and just image only kept 60 minutes before applying blanking pulse." 60W " expression is used in the zone that remains this display of white during this test period in following table, and remains zone " 60D " expression of black.

Scheme 10:

In this scheme, write image in the mode identical, and use and scheme 480 identical refresh pulses kept 10 minutes with scheme 480.Apply opposite polarity 40sec pulse then with this display of DC balance, this image is rewritten then, and repeats this circulation." 10W " expression is used in the zone that remains this display of white during this test period in following table, and remains zone " 10D " expression of black.

Scheme 1:

This scheme is identical with scheme 10, and just image only is held 1 minute, applies 4 seconds the 2nd DC equalizing pulse then, and repeats this circulation." 1W " expression is used in the zone that remains this display of white during this test period in following table, and remains zone " 1D " expression of black.

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

Table 1

	480W	480D	60W	60D
	480W	480D	60W	60D	w％	37.90	30.63	38.21	38.47
d％	2.89	2.69	3.03	2.45	w％	37.90	30.63	38.21	38.47
d％	2.89	2.69	3.03	2.45	dhdl	2.05	0.64	4.79	1.05
bbdl	-1.34	-4.06	-0.47	-2.72	dhdl	2.05	0.64	4.79	1.05
bbdl	-1.34	-4.06	-0.47	-2.72		10W	10D	1W	1D
w％	37.31	37.39	37.20	37.20		10W	10D	1W	1D
w％	37.31	37.39	37.20	37.20	d％	2.75	2.75	3.14	3.13
dhdl	0.89	0.84	0.98	0.99	d％	2.75	2.75	3.14	3.13
dhdl	0.89	0.84	0.98	0.99	bhdl	-2.24	-2.30	-2.02	-1.98

Find out that from the data of table 1 in highly uneven scheme 480, the white states reflectivity between the zone of this display that remains white and black during test period is obviously different, and the bright and dark difference that keeps is also significantly different.Therefore, this highly uneven drive scheme produces the basic variation of the optical states of this display, and is far from other effect of following this non-equilibrium drive scheme possible, such as the damage to electrode.Equally, shown as the difference in the bright and dark maintenance difference, this imbalance drive scheme is introduced " biasing " to this display, also keeps white after the zone of promptly long-term maintenance white trends towards, and keeps the zone of black to trend towards keeping afterwards black for a long time.Never the result who obtains in the balance scheme 60 is similarly, but is not so significantly (just as expected).What contrast is that DC balance scheme 10 and 1 does not show difference substantially between the black and white zone of maintenance.

Therefore, these test demonstration, as long as long-term DC balance is to be produced by the blanking pulse that separates, can negative effect not arranged to the attribute of this display by the temporary transient DC imbalance of using the new pulse of whisk broom to cause so.

The electrophoretic media of using in refresh pulse method of the present invention can adopt same parts and the manufacturing technology in aforesaid EInk and MIT patent and the application, and the reader can and apply for to obtain further information with reference to these patents.

The fundamental element of gray level drive waveforms (comprise and use the AC pulse)

As aforesaid U.S. Patent No. 6,531,997 and 6,504, described in 524, current many displays make electro-optical medium saturated by applying sufficiently long potential pulse of duration, thereby (for example are converted to another extreme optical state from an extreme optical state, to in vain, vice versa from black); For example in electro-optical medium, make charged particle from start to finish forward or the rear electrode motion based on particle.Need not allow the middle gray state to exist up to the become tradition of saturated this electro-optical medium of ability addressing of this optical states.The electro-optic displays that obtains gray level provides significant advantage on image volume and picture quality.

For convenience, the voltage waveform or the drive scheme that can obtain gray level in bistable electro-optic displays is called " gray level waveform " or " gray scale drive scheme " hereinafter.The basic gray level waveform elements that can use in this gray level waveform or drive scheme has 5; Term " gray level waveform elements " is meant the potential pulse or the sequence of voltage pulses that can change in the optical states of electro-optic displays.Itself can produce gray level the gray level waveform elements, and the one or more gray level waveform elements that are arranged in particular sequence form the gray level drive waveforms together.The gray level drive waveforms can be converted to another from a grey states with the pixel of display.The sequence of one or more drive waveforms constitutes drive scheme, and this scheme can show any grayscale image sequence on display.

The drive waveforms element is divided into two classes, promptly direct current (DC) potential pulse with exchange (AC) potential pulse.In both of these case, the parameter that can change of pulse is pulse height and pulse length.

Though producing the key of gray level optical states in electro-optical medium depends on voltage and is applied to mode on this medium, but this medium keeps the ability of described gray level optical states important too in the gray level addressing scheme in case after not applying voltage, and this ability will depend on the characteristic of this medium, in fact will depend on all greyscale transitions attributes.In this application, the electrophoretic media based on particle of main reference encapsulation is discussed the gray level addressing scheme, but think that for the technician in the described medium technical field it is conspicuous that the attribute of considering other type of bistable electro-optical medium carries out necessary modification to this scheme.

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

The DC pulse of pulse length modulation

One of the simplest method of the grey states of realizing ideal is to stop addressing being in from a kind of extreme optical state and being converted to pixel among the another kind of extreme optical state.In Fig. 1 of accompanying drawing, interpolation illustrates the waveform elements that is used for producing in the electrophoretic media (shown in the major part of this figure) of encapsulation the DC pulse length modulation of greyscale transitions.(herein and the display that uses in the following subsequent experimental make according to aforementioned 2002/0180687 [0061]-[0068] section described " method B " substantially.) three pulses using are respectively that 15V continues 200,400 and 600 milliseconds (msec), and three curves that produce are by mark correspondingly; Different in time scale in noting in the illustration and the master map.Therefore, for the difference variation of reflectivity, pulse height is fixed and the duration variation of pulse.In Fig. 1, the reflectivity of the pixel of having drawn (according to these potential pulses that applied, its reflective condition is from the black gray scale that changes to different stage) is change curve in time; Long as can be seen pulse length produces bigger reflectance varies.

Tested display to the end response of the potential pulse that applied rapidly, and its optical states stops to develop.On micro-level, can suppose that electrophoresis particle stops immediately from the migration of an electrode to another electrode, and keep being suspended in the centre position in the capsule.

The DC greyscale drive pulse advantage of pulse length modulation is the speed that reaches desirable grey states.

The DC pulse of pulse-height modulation

Another method that obtains desirable grey states is to use a voltage lower than needed voltage to come address pixel to make an extreme optical state of this pixel be converted to another extreme optical state fully.In Fig. 2 of accompanying drawing, interpolation illustrates the waveform elements that is used for producing in the electrophoretic media (shown in the major part of this figure) of encapsulation the DC pulse-height modulation of greyscale transitions.Potential pulse length is fixed on maximal voltage level and changes the needed time span of this medium fully.Three pulses using are respectively 5,10 and 15V, continue 500 milliseconds (msec), and three curves of generation are also by mark correspondingly; Different in time scale in noting in the illustration and the master map.Therefore, for the difference variation of reflectivity, pulse length is fixed and the height change of pulse.In Fig. 2 of accompanying drawing, the reflectivity of the pixel of having drawn (according to these potential pulses that applied, its reflective condition is from the black gray scale that changes to different stage) is change curve in time; Bigger as can be seen pulse height produces bigger reflectance varies.

Can suppose that electrophoresis particle passes through suspending liquid with lower speed under lower voltage, and when stopping to apply driving voltage, keep suspending.

The advantage of the DC greyscale drive pulse of pulse-height modulation is the accurate control to the grey states that obtains.

AC pulse with DC offset modulation

The gray level of the electrophoretic media of aforesaid encapsulation drives and has been subjected to vibration (AC) electric field effects; Use the transition mechanisms of this AC field to be assumed to the mechanism that is different from realization in the DC of above-mentioned identical medium drives fully.In Fig. 3 of accompanying drawing, interpolation illustrates the AC pulse of DC offset modulation waveform elements, is used for producing greyscale transitions in the electrophoretic media of the encapsulation shown in the major part of this figure.Under any circumstance, the frequency of AC composition (approximately 10Hz) is set in a value, this value allows particle in response to this oscillating field, and the size and Orientation of DC skew (for three curves among Fig. 3, demonstration be 0 ,-1 or-2.5V) determine the final grey states that obtains of this pixel.As among the figure of front, the time scale in the interior illustration is different from the time scale in the master map.In Fig. 3, the reflectivity of the pixel of having drawn (according to these potential pulses that applied, its reflective condition is from the black gray scale that changes to different stage) is change curve in time; Big as can be seen DC skew produces bigger reflectance varies.

In case apply the AC field, electrophoresis particle vibrates in suspending liquid, and this vibration is as the cyclical variation that is superimposed upon the reflectivity in the whole variation of reflectivity and observed motion, and this left side at Fig. 3 is easy to find out.Yet,, just can clean influence be arranged to reflectivity up to applying the DC skew.Under the influence of DC skew, reflectivity after waveform applies a period of time near steady state value.As if having a kind of restoring force to resist mutually, otherwise particle will continue to flow to cell-wall with the power that is applied on the particle owing to the DC offset voltage.This restoring force may be because the motion of the fluid between cyst wall and the particle and/or since particle directly and the effect between the cell-wall.Consistent with other waveform elements, remove that the stability of optical states remains constant behind the voltage.

The advantage of AC waveform elements is to reach specific reflectivity state by the parameter of specified waveform element, and the DC waveform elements can only make reflectance varies.Having the AC waveform elements of DC skew do not need to be to the addressing pulse accurate timing with respect to the advantage of other AC waveform elements.

The AC pulse of duty cycle modulation

The another kind of mode of using oscillating field to introduce the DC biasing is the modulation duty cycle.In Fig. 4, interpolation illustrates the AC pulse of duty cycle modulation, and this pulse is used for producing the greyscale transitions of the major part of this figure.In each of these pulses, voltage is set to maximal value, and duty cycle (voltage is at the number percent of the time of positive dirction or negative direction) decision reflectivity.Three duty cycles using are 50%, 47% and 40%, as shown in Figure 4.As among the figure of front, the time scale of using in interior illustration is different from the time scale in the master map.In the figure, the reflectivity of the pixel of having drawn (according to these potential pulses that applied, its reflective condition changes to different grey level from black) curve over time.

As can be seen from Figure 4, identical with the AC/DC shift pulse that is used to produce curve shown in Fig. 3, curve shown in Figure 4 reaches steady state value after pulse applies a period of time.Therefore, consistent with the AC/DC skew, use the duty cycle modulation, as if there is a kind of restoring force, it forces particle to leave cell-wall, keeps grey states constant.The physical mechanism of this restoring force and previously discussed similar.Equally, grey states stops to change immediately after stopping to apply pulse.

The advantage of the AC waveform of duty cycle modulation do not need to be voltage modulated.

Warbled AC pulse

The another kind of method that realizes the AC greyscale transitions is to apply such AC field to electro-optical medium: this AC field causes the optical states vibration of this medium, stops this AC field then in circulation on the point that obtains ideal reflectivity.Voltage can be set to maximal value, changes the AC frequency to obtain greater or lesser reflectivity range.The amplitude of frequency decision reflectivity vibration.

When this method be applied to encapsulate based on the electrophoretic media of particle the time, electrophoresis particle by near oscillatory response their initial position in the AC field.Because usually reflectivity does not reach extreme black or white light and learns state, minimize with interaction between the cell-wall and reflectivity is relative linear to the response of applying voltage.

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

By pulse in conjunction with the above-mentioned type, can develop multiple waveform elements, each comprises unique changing the mechanism, and therefore provides to drive the different electro-optical medium the whole bag of tricks with different switching characteristic.

In concrete an application of above-mentioned drive scheme principle, use pulse-length modulation and AC pulse with the middle gray state in the acquisition electro-optic displays, otherwise this display can only obtain black and white state.

Discussed owing to top, very expectation can obtain gray level in electro-optic displays.Yet, suppose that the pulse-length modulation that a large amount of gray levels need have high frame frequency driver or driver that can voltage modulated arbitrarily (needs high frame frequency that pulse width " is cut " and becomes a plurality of intervals, therefore accurate gating pulse width, and then accurately control gray level).In these two kinds of drivers any is substantially all higher than simple three grades of (tri-level) driver costs, described three grades of drivers can only make the electromotive force of the single pixel of display be configured to respect to public front electrode potential+V ,-V and 0 (V is any work potential), and it is generally used for driving the display that can only show black and white state.

The invention provides a kind of drive scheme, this scheme can make the intermediate grey scales between deceiving of three grades of drivers generation bistable electro-optic displays and the white level.The easiest understanding from following table 2 of this drive scheme, this has expressed the voltage that is applied during the successive frame of all kinds transformation in this display of the present invention:

Table 2

	0	1	2	3	4	5	6	...	N-1	N
	0	1	2	3	4	5	6	...	N-1	N	White to black	+ V	+ V	+ V	+ V	+ V	+ V	+ V	...	+V	+ V
Black in white	- V	- V	- V	- V	- V	- V	- V	...	-V	- V	White to black	+ V	+ V	+ V	+ V	+ V	+ V	+ V	...	+V	+ V
Black in white	- V	- V	- V	- V	- V	- V	- V	...	-V	- V	White to ash	+ V	+ V	+ V	+ V	- V	+ V	- V	...	+V	- V
Black in ash	- V	- V	- V	- V	+ V	- V	+ V	...	-V	+ V	White to ash	+ V	+ V	+ V	+ V	- V	+ V	- V	...	+V	- V
Black in ash	- V	- V	- V	- V	+ V	- V	+ V	...	-V	+ V	Ash is to black	+ V	+ V	+ V	0	0	0	0	0	0	0
Ash is to white	- V	- V	- V	0	0	0	0	0	0	0	Ash is to black	+ V	+ V	+ V	0	0	0	0	0	0	0

From top table 2 as can be seen, the same the transformation from black to white (vice versa) and scale-of-two (the having only black/white) display.On the other hand, the transformation to gray scale has two parts.First is square waveform pulse (that is, a plurality of frames of same potential), and it has suitable polarity and length approaching as far as possible middle gray brightness that needs so that the reflectivity of electro-optical medium becomes.Degree of accuracy with this step may will be subjected to the frame frequency restriction of display.The second portion of addressing pulse comprises the potential pulse of the positive and negative that quantity equates, the width of each pulse equals a frame.With reference to Fig. 3 and 4 described, the front is verified as preceding: the surge medium based on particle that the AC square wave is applied to encapsulation causes that this medium " relaxation " is to some " middle gray " state.Therefore, no matter previous pulse history, the second portion of pulse will make all pixels become identical uniform middle gray state.Use has the short pulse of suitable polarity and realizes being addressed to from grey states black or white.

More generally, the AC of this pulse part does not change polarity at every frame, but can be with lower frequency transitions, is accompanied by that (frequency=frame frequency/2n) voltage carries out alternation every a frame (frequency=frame frequency/4) or common every n frame.

Therefore, the invention provides a kind of method, this method is only used simple three grades of drivers and is not used complexity and expensive voltage modulated driver, produces single gray level in other binary electro-optic displays.

In second concrete application of above-mentioned drive scheme principle, the invention provides the set of two-dimentional transition matrix, wherein how each the element regulation in the matrix arrives final optical states (using " column index is represented " herein) from initial optical state (using " row index " expression herein, though be apparent that distributing to capable initial optical state is arbitrarily).Each element of this matrix is by a series of waveform elements (as defined above) structure, and usually for n position gray level display device, this matrix will comprise 2 ^(2N)Individual element.Matrix of the present invention has counted such consideration, such as needs (as previously discussed) to the DC balance of drive scheme, in some electro-optical medium, " memory " effect is minimized (promptly, the effect that applies the result of certain pulses to pixel not only depends on the current state of this pixel, also depend on some original state), thereby produce uniform optical states and, under the restriction of driven with active matrix scheme, work simultaneously the maximization of the rate of transformation of display.The present invention also provides a kind of method, is used for determining for any certain electric optical media each optimal value of the element of this matrix.For this matrix and their application in driving electro-optic displays, the reader can be with reference to aforesaid PCTUS02/37241.

With regard to aforesaid pulse-length modulation (PWM), current preferred wave shape form of the present invention is as described below.Yet, use the AC modulation of pulse-height modulation or above-mentioned various mixed types also can obtain same or analogous result, and can in single waveform, use various different type of modulation, for example, for the pulse-length modulation of all parts except the decline of pulse, what follow later is back-page voltage modulated to this pulse.

Of the present invention preceding two waveforms that describe below are " magic lantern " waveforms, and it got back to black state from a grey states before being addressed to next grey states.This waveform is the most compatible with the display update scheme of a wherein blanking of whole screen (as in slide projector).

Two prepulsing magic lantern waveforms

In this waveform, its preferred form has been shown among Fig. 5 of accompanying drawing, use partial pulse at first the pixel of electro-optical medium to be driven into (shown in 100) initial (first) grey states from deceiving.For the from then on initial grey states of pixel is changed to different expectation (second) grey states, at first pixel is driven into white (102) from first grey states, then from vain to black (104).At last, apply suitable pulse to reach second grey states 106.Keep whole DC balance in order to ensure such waveform, the length sum of the white pulse at the addressing pulse at 106 places and 102 places must equal the length of the Bai at 104 places-Hei pulse.The maximal value of the medium fringe time that these waveform needs are three times (that is, single pixel is learned state-transition from black light and learned the required time of state to white light, and perhaps vice versa) is implemented in the transformation between any two any gray scales, therefore is called as the 3X waveform.

Single prepulsing magic lantern waveform

In this waveform, its preferred form has been shown among Fig. 6 of accompanying drawing, use partial pulse at first with the pixel of electro-optical medium from black (shown in 110) initial (first) grey states that is driven into, two prepulsing waveforms of discussing in the mode of employing and top the 6th part are identical.For this pixel is changed to different (second) grey states of expecting from initial grey states, at first this pixel is driven into black (112) from first grey states, apply suitable pulse to arrive second grey states 114 then.Obviously, before second transformation, this pixel will be got back to black 116 once more.Such waveform keeps the DC balance of whole waveform, and this is because equal (except polarity) respectively in 110 and 114 impacts that apply in 112 and 116 impacts that apply.This waveform needs the maximal value of medium fringe time of twice being implemented in any two transformations between the grey states arbitrarily, therefore is called as the 2X waveform.

Gray scale-greyscale waveforms

Replace to use above-mentioned magic lantern waveform, can be by directly coming its addressing and refresh display without black or white state from a grey states to another grey states.Because tangible illusion (promptly black and/or white " flicker ") is not followed in this transformation, so it is called as " gray scale-gray scale " addressing.Have the gray scale-greyscale waveforms of two kinds of principal modes, i.e. DC balance and DC imbalance.

In the gray scale-greyscale waveforms of DC balance, be implemented in transformation between these two states by being applied between two grey states the necessary modulating pulse of conversion with precise length.Electro-optical medium is black or white state without any centre.Because maximum impulse length equals the addressing time of ink, this waveform is also referred to as the 1X waveform.In order to keep the DC balance, for the display with n grey states, available free parameter has n-1 in the optimization of the transformation matrix relevant with any specific waveforms.This causes excessive limited systems.For example, change and to equate and relative pulse (that is, except polarity, 2-3 must be identical with 3-2) for opposite transformation.

Uneven gray scale-the greyscale waveforms of DC is basic identical with the situation of DC balance, and just pulse length no longer is subjected to the constraint of DC equilibrium-limited.So 2 in transformation matrix ^(2N)In each can be independent of all other variations.

Various waveform discussed above can be in Active Matrix Display the addressing gray level, use in PDA(Personal Digital Assistant) and e-book are used is crucial for electro-optical medium for this.These waveforms minimize the memory effect in the electro-optical medium, and this memory can cause the image ghost image.By selecting optimal burst length and order, can in the minimum number pulse, obtain desirable gray-scale optical state.

Selective row drives

Another aspect of the present invention relates to by selecting to drive the row of this display, improves the performance of active matrix bistable electro-optic displays.

As previously mentioned, and discuss in more detail in patent and the application as the aforementioned, in order on traditional LC D, to keep needed image, must refresh the entire image zone continuously, this is not bistable because of common liquid crystal, and if do not refresh on the LCD image in a short period of time the image on the LCD will weaken.Technician as active matrix field is known, in this display, the realization that refreshes continuously be by: use line driver to open the transistorized grid relevant with the one-row pixels of this display, on row driver (being connected to the transistorized source electrode in every row of this display), apply the electromotive force that the relevant portion of the required image on this display is write the pixel in the selected row, and therefore write the selected row of this display.Line driver is selected the next line of this display then and is repeated this process, and row just is recycled and refreshes like this.(line driver is assigned to gate electrode and row driver is assigned to the source electrode is conventional, but also is arbitrarily substantially, certainly puts upside down if desired.)

Because LCD needs refreshing continuously of image, the only part of shown image changes the part that is used as whole refresh process and handles.In the display that refreshes continuously, do not need to provide the more new portion of image; Because in fact per second all has several times new images write display (under the situation of LCD), any variation of the parts of images of the display of feeding manifests effect short at interval automatically on this display.Therefore, the custom circuit of having developed that is used for LCD does not provide the only renewal of parts of images.

Contrast, bistable electro-optic displays does not need to refresh continuously, and in fact this refreshing continuously be harmful to, and this is because unnecessarily increased the energy consumption of display.In addition, during this refreshing, grid (OK) circuit may pass to pixel electrode with the capacitive voltage spike pulse, and any actuator voltage error or uncompensated grid feedthrough biased error may be accumulated; All of these factors taken together causes undesirable transformation of the optical states of display picture element.Therefore, in bistable electro-optic displays, it is desirable to provide some devices to be used to upgrade parts of images and need not rewrite entire image on display, an aspect of of the present present invention relates to the bistable electro-optic displays of being furnished with this " partial update " device.According to the present invention, this consecutive image by relatively will writing this display, be identified in row different in these two images and only the identified row of addressing realize.

In the method, in order to realize the partial update of display, only identification comprises the row of the display of the pixel that its optical states will change.In a preferred form of this method, for every row of display, display controller (referring to aforesaid PCT/US02/37241) is checked all desirable pixel electrode output voltages.If for this row, all output voltages equal the electromotive force V of the public preceding electrode of this display _Com(that is), the then synchronous (V of controller output if there is not pixel to need to rewrite in that row _Sync) pulse and data value is not written into row driver, and do not issue corresponding output enable (OE) order.The net effect of doing like this is that the token position of line driver is delivered to the next line of display and does not activate current line.Data only are written into row driver, and output enable is only for the row statement that wherein has at least one pixel to be rewritten.

The invention provides two kinds of different advantages.At first, for the pixel that is not rewritten, can eliminate a lot of stray voltage sources.Do not have capacitive grid spike (gate spike) for these pixels, and in the frame that pixel is not addressed, the error of row driver voltage can not be delivered to this pixel.Since with liquid crystal phase relatively, a lot of electro-optical medium resistivity are low relatively, electrophoretic media especially, pixel electrode will trend towards relaxing towards actual front (front plane) voltage, therefore keep the hold mode of electro-optical medium.Secondly, the minimise power consumption of display.For each row that is not rewritten, corresponding grid line does not need to be recharged.In addition, when output is not written into the row electrode of display, has also eliminated and crossed over the extra power consumption that display interface device comes mobile data.

Area of space shake (dither)

Foregoing aspect of the present invention relates to the waveform that is used to drive electro-optic displays.The performance of this display also can change by the structural change that changes base plate, and one or more pixels (preferably each pixel) that this relates on the one hand with display of the present invention are divided into a plurality of sub-pixels with different area.

Mention as preceding, wish very much in electro-optic displays, to provide gray level.Also can obtain this gray level to the grey states between two extremity by pixel drive with this display.Yet, if this medium can not obtain the intermediateness of ideal quantity, if perhaps this display is driven by the driver of the intermediateness that ideal quantity can not be provided, then must obtain the state of ideal quantity with other method, of the present invention this is related to this purpose and the spatial jitter used on the one hand.

A display can be divided into a plurality of " logic " pixel, and wherein each can show gray scale or other optical states of ideal quantity.Yet, obviously in each logical pixel a more than physically separated zone can appear, in fact this is common for color monitor utilization " panchromatic " logical pixel, and each of described " panchromatic " logical pixel comprises have primary colours three sub-pixels of (for example red, green, blue); Referring to for example aforesaid 2002/0180688.Similarly, can use the combination of sub-pixel to obtain gray level as logical pixel, each in the sub-pixel can binary change.For example, comprise that 4 controlled logical pixel with sub-pixel of the same area of independence can be used for providing 2 gray levels.Yet for any situation more than 1 or 2 gray level, the quantity of sub-pixel becomes greatly inconveniently, because 1 of the every increase of gray level, the quantity of required sub-pixel doubles.

The invention provides a kind of electro-optic displays, it has at least one pixel, and this pixel comprises a plurality of sub-pixels, and these sub-pixels have different areas.In a preferred embodiment of the invention, the area of at least two sub-pixels differs 2 times substantially.Therefore, for example, logical pixel may have the sub-pixel that area is 1X, 2X and 4X, and wherein X is an arbitrary area.Such logical pixel schematically shows in Fig. 7 of accompanying drawing A.This logical pixel only uses three electrodes to obtain 3-position gray level, will need 8 sub-pixels and use the sub-pixel that equates on area to obtain identical 3-position gray level.

When each sub-pixel is driven, the part of its reflection or transmission incident light, and the part amount is by the area decision of this sub-pixel.If reflection/transmission is average on the zone of this logical pixel, then obtain to drive the binary weights of area, therefore obtain the gray level of spatial jitter.

The area of sub-pixel is arbitrarily.The reflectivity weighting of sub-pixel shown in Fig. 7 A.(this is for the L that waits stepping if use nonlinear weight ^*Perhaps gamma correction gray scale is fit at interval), this area will correspondingly change.

Except the relative area of considering them, also should think over the shape of sub-pixel.Simple bulk as shown in Figure 7A allows array of sub-pixels simply to be shaped, but under certain conditions, these sub-pixels may the observed person be differentiated.Equally, if the intergrade gray scale (thereby (such as) in each logical pixel, have only the zone 4 of Fig. 7 A to be driven) be presented on the big zone (covering a lot of logical pixel), the observer will see line or the grid graph that occurs from the sub-pixel figure.

The resolution that increases logical pixel will reduce these problems, but need extra pixels in a large number because pixel quantity be with resolution square and increase.On the contrary, can reduce the observability of sub-pixel and/or the problem of eye diagram by the mutual sub-pixel (for example as shown in Fig. 7 B) that intersects; Notice that this figure is intended to illustrate mutual intersection.Be inaccurate and represent the relative area of sub-pixel.The cross one another figure that much is similar to Fig. 7 B can be used for improving picture quality.

The another kind of method of handling the problem of sub-pixel observability and/or eye diagram is the random orientation sub-pixel.For example, in pel array, each pixel is by the arrangement of subpixels shown in Fig. 7 A, and single pixel may have each in 4 possibility directions of arranging shown in Fig. 7 A at random." randomization " of this sub pixel helps partition graph and makes them more be difficult for seeing for the observer.

Though the embodiments of the invention shown in Fig. 7 A and the 7B produce 3-position gray level, are appreciated that the present invention can be by increasing the gray level that extra sub-pixel produces any figure place simply.

The advantage of this aspect of the present invention is as follows:

(a) electro-optical medium itself does not need to have gray level; Basically display can be the black/white display, and the open and close sub-pixel is to produce gray level.In scanning array, can obtain to control by extra row driver (for the row of equal number) is provided for necessity of sub-pixel.This has reduced the requirement to electro-optical medium; For example, do not need to worry to exceed may the drifting about of gray level of electro-optical medium after its mission life.

(b) do not need complicated row driver; The present invention and the simple binary level driver compatibility of using in a lot of traditional monitors of using.Therefore, help using the various electro-optical mediums of easy acquisition, cheap " finished product " parts.Some produce the method for gray levels need be to row electrode working voltage modulating driver, this driver be not widely available and than the manufacturing of binary level driver more expensive/more difficult.

(c) be used to use the design of thin film transistor (TFT) (TFT) of active matrix array of the present invention needed more difficult unlike panchromatic, in panchromatic each pixel have three sub-pixels (for example, RGB), and need offer the data volume of various parts can be not bigger yet.Therefore in implementing active matrix base plate of the present invention, do not need development new technologies.

Miscellaneous technology

In the most traditional driven with active matrix scheme of electro-optic displays, the change in voltage of pixel electrode on the display base plate is so that apply required voltage on pixel.End face keeps specific voltage usually, and it is favourable that this specific voltage is considered to for address pixel.For example, if the data line voltage that offers pixel electrode at zero volt and voltage V ₀Between change, then end face will remain on V ₀/ 2, so that allow the voltage drop on the pixel that V is all arranged on both direction ₀/ 2 is so big.

According to an aspect of the present invention, the voltage of end face can change to strengthen the addressing of electro-optical medium.For example, end face voltage can remain zero volt in case allow total pixel voltage fall (end face negative pixel voltage) low to-V ₀Rising end face voltage is to V ₀, allowing pixel voltage to fall has V ₀So big.These bigger voltage drops allow electro-optical medium addressing quickly.

More generally, advantageously end face voltage not only can be set at voltage zero and V ₀, also can be set to other voltage.For example, advantageously consistent with the pixel-pixel voltage that is applied by base plate, the time that applies the overall situation on electro-optical medium changes voltage.

Knownly in electro-optic displays, provide capacitor, so that fill same voltage with selecting circuit at pixel electrode with between by the electrode that extends to form of selecting circuit; As the aforementioned described in the WO01/07961, this electric capacity the rate of decay that has reduced the electric field on the pixel after removing driving voltage is provided.Convenient at another, the present invention has the electro-optic displays of holding capacitor, and this holding capacitor is formed between pixel electrode and (second) electrode, and the selection circuit that the voltage of described (second) electrode can be independent of this display changes.In a preferred embodiment, second electrode is followed end face voltage, that is, the difference of its voltage and end face only is a constant that does not rely on the time.Compare with the holding capacitor that overlaps to form between the selection circuit of having gone, provide such capacitor to significantly reduce the capacitive voltage spike of pixel experience by adjacent (before) of pixel electrode and this display of control.

Another aspect of the present invention relates to the harmful transformation that reduces or eliminates electro-optical medium by selection and data line.

As discussed above, selection and data line are the primary elements of active matrix panel, and they provide pixel electrode is charged to the required voltage of expectation value.Yet selection and data line may have the deleterious effect that changes the electro-optical medium adjacent with this data line.By using black mask the observer to be hidden, can eliminate the harmful optics artifact that causes by this transformation by the zone that data line and/or selection wire change.Yet, provide this black mask need be with the front of display with thereafter in the face of neat, and reduced the electro-optical medium part that is exposed to the observer.The result compares with the situation of not using black mask and being obtained, and display is darker and contrast is lower.

In another aspect of the present invention, little by data line side direction is in one direction prolonged, thus make them during normal display operation, can not carry out sizable addressing to adjacent electro-optical medium, thus the use of black mask avoided.This has been avoided the needs to black mask.

The modification that related fields of the present invention relate to the use of passivated electrodes and are used to drive the drive scheme of electro-optical medium.In in its film between two electrodes, impacting the electro-optical medium that drives can be by electrical addressing.Usually, electrode contacts with electro-optical medium.Yet, even there is dielectric material between one or two electrode and this medium with long electronics relaxation time, also can this electrode of addressing.For fear of interacting at the base plate of display device or the contrary chemistry or the galvanochemistry of front, the passivation of one or two electrode may need; Referring to aforesaid WO00/38001.Keep the ability of the voltage on the electro-optical medium to reduce greatly though the appearance of dielectric layer makes, if this dielectric layer is suitably designed, voltge surge still can be applied to this medium and this medium can pass through these voltge surge addressing.

Yes that voltage on the pixel electrode realizes by changing in the change of the optical states of electro-optical medium.This voltage changes the voltage that causes on the electro-optical medium, and by medium because electric charge leaks the voltage attenuation that makes on the electro-optical medium.If external dielectric layers (that is, the dielectric layer between this medium and the electrode) is enough thin and resistivity electro-optical medium is enough big, then the voltge surge on this medium will be enough to cause that the optical states of this medium changes on demand.Therefore the electronically addressing of the electro-optical medium by dielectric layer is possible.Yet this addressing scheme is different from the electro-optical medium that its electrode of addressing and this medium directly contact, because under latter event, by applying voltage addressing medium on pixel, and in the previous case, is to realize addressing by causing to change in pixel voltage.In each variation, electro-optical medium experience voltge surge.

At last, the invention provides the drive scheme of crosstalking that is used for reducing the active matrix electro-optic displays.

Crosstalk between pixel (optical states that pixel of addressing influences other pixel) be harmful to, this has multiple reason to cause.A reason is that electric current limited under off state flows through transistor.Because the electric current of off state leaks, and provides voltage (being intended to the pixel of charging) to charge to the transistor in the non-selection row to data line.Solution is to use the transistor with low cut-off state electric current.

Another crosstalk sources is that the electric current between neighbor leaks.Electric current can spill by the element of base plate, or spills by the electro-optical medium that contacts with base plate.This solution of crosstalking is the big base plate of clearance for insulation between a kind of pixel electrode of design.The leakage current of the big more generation in gap is more little.

As has been noted, the preferred type that is used for the present invention's electro-optical medium is the electrophoretic media based on particle of encapsulation.This electrophoretic media of using in method and apparatus of the present invention can be used identical parts and the manufacturing technology described in the patent of front E Ink and MIT and application, and the reader can and apply for to obtain further information with reference to these patents.

Claims

1, a kind ofly be used for the method that addressing has the bistable electro-optic displays of at least one pixel, this method comprises:

Apply addressing pulse to drive this pixel to first optical states; With

In a period of time, keep this pixel not to be driven, allow described pixel to present to be different from second optical states of first optical states thus;

This method is characterised in that, applies refresh pulse to this pixel, and this refresh pulse returns to this pixel its first optical states substantially, and this refresh pulse is shorter with respect to addressing pulse.

2, method according to claim 1 is characterized in that, refresh pulse has 20% impact of the impact that is not more than this addressing pulse.

3, method according to claim 1 is characterized in that, refresh pulse has 10% impact of the impact that is not more than this addressing pulse.

4, method according to claim 1 is characterized in that, refresh pulse has 5% impact of the impact that is not more than this addressing pulse.

5, according to each described method in the aforementioned claim, it is characterized in that the difference between first and second optical states is no more than the L of 1 unit ^*

6, according to each described method among the claim 1-4, it is characterized in that the difference between first and second optical states is no more than the L of 0.5 unit ^*

7, according to each described method among the claim 1-4, it is characterized in that the difference between first and second optical states is no more than the L of 0.2 unit ^*

8, according to each described method among the claim 1-4, it is characterized in that a plurality of refresh pulses are applied to this pixel at interval with rule.

9, according to each described method among the claim 1-4, it is characterized in that, after applying refresh pulse, apply second addressing pulse to this display, this second addressing pulse drives this pixel to the 3rd optical states that is different from first and second optical states, and the impact that is wherein applied by second addressing pulse is following two sums: (a) drive this pixel from the required impact of first optical states to the, three optical states; And (b) equate but opposite polarity impact with the algebraic sum amplitude of the refresh pulse that between first and second addressing pulses, is applied to pixel.

10, method according to claim 9 is characterized in that, the voltage constant of second addressing pulse but duration change.

11, method according to claim 9 is characterized in that, this display comprises a plurality of pixels, and second addressing pulse comprises the blanking pulse with all pixel drive to one extreme optical state of this display.

12, according to each described method among the claim 1-4, it is characterized in that, this display comprises a plurality of pixels, first addressing pulse is applied to each pixel so that with first group of pixel drive Cheng Bai, and second group of pixel drive become black, apply at least one refresh pulse to each pixel, and apply to this display afterwards and all pixels are become the first black blanking pulse and second blanking pulse of all pixel drive Cheng Bai, these two blanking pulses can apply with any order, and the impact that wherein during first blanking pulse, is applied to each first group of pixel be below two and: (a) with this pixel from being driven into black needed impact in vain, and (b) equate but opposite polarity impact with the algebraic sum amplitude that between first addressing pulse and first blanking pulse, is applied to the refresh pulse of this pixel, and the impact that during second blanking pulse, is applied to each second group of pixel be below two and: (c) this pixel is driven into white needed impact from black, and (d) equate but opposite polarity impact with the algebraic sum amplitude that between first addressing pulse and first blanking pulse, is applied to the refresh pulse of this pixel

According to each described method among the claim 1-4, it is characterized in that 13, this display is rotation dichromatism parts or electrochromic display device (ECD).

14, according to each described method among the claim 1-4, it is characterized in that this display is an electrophoretic display device (EPD).

15, method according to claim 14 is characterized in that, this display is the electrophoretic display device (EPD) of encapsulation.