CN102789764B

CN102789764B - Methods for driving bistable electro-optic displays

Info

Publication number: CN102789764B
Application number: CN201210168809.6A
Authority: CN
Inventors: R·W·泽赫纳; H·G·加特斯; A·C·阿兰戈; K·R·阿穆德森; J·F·欧; A·N·克奈安; J·L·扎勒斯基
Original assignee: E Ink Corp
Current assignee: E Ink Corp
Priority date: 2001-11-20
Filing date: 2002-11-20
Publication date: 2015-05-27
Anticipated expiration: 2022-11-20
Also published as: EP2916312A1; JP2017049608A; EP2916312B1; JP2015064588A; CN1589462A; JP5618811B2; WO2003044765A2; HK1142162A1; JP2007249230A; AU2002366174A1; CN102789758A; EP2916312A8; JP2012098733A; JP4852478B2; WO2003044765A3; AU2002366174A8; HK1176454A1; JP2007249231A; JP2011128625A; JP5758440B2

Abstract

A bistable electro-optic display has a plurality of pixels, each of which is capable of displaying at least three gray levels. The display is driven by a method comprising: storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level; storing data representing at least an initial state of each pixel of the display; receiving an input signal representing a desired final state of at least one pixel of the display; and generating an output signal representing the impulse necessary to convert the initial state of the one pixel to the desired final state thereof, as determined from the look-up table. The invention also provides a method for reducing the remnant voltage of an electro-optic display.

Description

Drive the method for bistable electro-optic displays

The application is the applying date is on November 20th, 2002, and application number is 200910163444.6, and denomination of invention is the divisional application of the application of " method driving bistable electro-optic displays ".

The present invention relates to a kind of device driving the method for bistable electro-optic displays and this method to use.More properly, the present invention relates to a kind of driving method and device controller for the grey states of electro-optic displays pixel more accurately can be controlled.The invention still further relates to a kind of method that driving pulse making to be provided to electrophoretic display device (EPD) keeps long-term DC (DC) to balance.The present invention is especially used for using together with the electrophoretic display device (EPD) based on particle, but is not limited thereto, and in such a display, the charged particle of one or more types hangs in a liquid and moves with the display changing display in a liquid under the influence of electric fields.

On the one hand, the present invention relates to the device that the circuit for driving liquid crystal displays can be used to drive the electro-optical medium of the polar sensitive for provided electric field, wherein liquid crystal material is insensitive to polarity.

Used as the term " electric light " for material or display here, in image technique, the implication of its routine relates to a kind of material with the first and second at least different in a kind of optical characteristics display states, by applying electric field to this material, this material changes to its second display state from its first display state.Although the identifiable design color of this optical characteristics normally human eye, but it also can be other optical characteristics, such as optical transport, reflectivity, brightness or the electromagnetic wavelength reflectivity when for machine-readable display outside visible-range change the pseudo-colours in meaning.

Term " grey states " used here implication of its routine in image technique relates to a kind of state in the middle of two extreme (extreme) optical states of pixel, and need not mean that the Hei-Bai between two extremities changes.Such as, it is white and dark blue electrophoretic display device (EPD) that several patent spoken of below and open application describe its extremity, and like this, " grey states " is in fact exactly pale blue.In fact, as already noted, the conversion between two extremities can not be a kind of color transformed.

The implication of term " bistable state " used here and " bistability " their routines in the art relates to a kind of display, this display comprises the display unit at least in a kind of optical characteristics with the first and second different display states, like this when rely on the addressing pulse of finite time complete to arbitrary to the driving of limiting-members with after presenting its first or second display state, after addressing pulse terminates, this state can continue at least several times of times (several times), at least four times of times of the addressing pulse shortest time such as a change needed for display unit state.Shown in the CO-PENDING application (simultaneously see corresponding international application open NO.WO02/079869) being the patent application serial numbers 10/063236 that on April 2nd, 2002 submits to, some have the electrophoretic display device (EPD) of gray level not only in their extreme black and white state based on particle, and be also stable at their intermediate grey states, this is suitable for the electro-optic displays of some other types equally.Relative to bistable state, it is more suitable for being called " multistable " such display, although term " bistable state " can here for containing bistable state and multistable display usually.

The term " gamma electric voltage " here used is the external voltage reference that finger actuator is used for determining to provide to displayer pixel voltage.Can be appreciated that bistable state electro-optical medium is not shown as the type corresponding to one-one relationship between provided voltage and liquid crystal optics status flag, it is equally accurate to be here unlike in conventional LCD device the use of term " gamma electric voltage ", and in conventional LCD device, gamma electric voltage determines the flex point in electric pressure/output voltage curve.

Term " pulse " used here refers to the integration of voltage relative to the time by the implication of its routine.But some bistable state electro-optical mediums as charge sensor, and for such medium, can use the definition of an alternative paired pulses, i.e. electric current integration in time (it equals provided total charge dosage).The suitable definition of paired pulses depends on that medium is as voltage-time impulse sensor or charge pulse sensor.

The bistable electro-optic displays of known several types.The electro-optic displays of one type is rotating bichromal element type, such as, at U.S. Patent number 5808783; 5777782; 5760761; 6054071; 6055091; 6097531; 6128124; 6137467; With (although such display is often called as " rotating bichromal ball " display, term " rotating bichromal unit " is more accurate, because it is not spherical for rotating unit in more above-mentioned patents) described in 6147791.So a kind of display use has two or more in a large number the corpusculum of different optical characteristic part (section) and an interior dipole (being generally spherical or cylindrical).These corpusculums are suspended in the vacuole being full of liquid being arranged in matrix, because vacuole is full of liquid, so corpusculum can rotate freely.The presentation of this display becomes by applying electric field to it, and then corpusculum is rotated to various position and changes the part of the corpusculum seen from a sightingpiston.

The electro-optical medium of another kind of type uses a kind of electrochromic media, such as with an electrochromic media for receiving look form membrane, described film comprise be at least partially the electrode that is made up of metal oxide semiconductor and multiple depend on electrode can the dye molecule of reversible color; See such as O ' Regan, B., wait the Nature 1991,353,737 of people; And Wood, D., InformationDisplay, 18 (3), 24 (in March, 2002).Also see Bach, U., the Adv.Mater. of people can be waited, 2002,14 (11), 845.Such receiving look film also has introduction, such as, at U.S. Patent number 6301038, the open NO.WO01/27690 of international application and its CO-PENDING all at the series application NO.60/365368 that on March 18th, 2002 submits to; 60/365369 and 60/365385; All at the series application NO.60/319279 that on May 31st, 2002 submits to; 60/319280 and 60/319281 and on July 31st, 2002 submit to series application NO.60/319438.

Conscientiously studied and another kind electro-optic displays developed for many years is electrophoretic display device (EPD) based on particle, wherein multiple charged particle moves through suspending liquid under the influence of electric fields.Compare with liquid crystal display, electrophoretic display device (EPD) has excellent brightness and contrast, wide visual angle, the characteristic of bistable state state and low-power consumption.But, the problem of these displays in long-term image quality has hindered widely using of they.Such as, the particle of composition electrophoretic display device (EPD) is easy to precipitation, causes the serviceable life of these displays not enough.

Under Massachusetts Institute of Technology (MIT) (MIT) and E Ink exabyte or transfer its multiple describe encapsulation electrophoretic medium patents and application disclosing in the recent period.Such encapsulation medium comprises multiple little endosome (capsule), each endosome itself comprises one and includes the improved interior phase of the electrophoresis be suspended in liquid suspension medium (internal phase), and in one body wall round interior phase.Usually, itself remains in polymer adhesive and is positioned at two interelectrode binding layers (coherent layer) to form one by endosome.Such encapsulation medium is described, such as U.S. Patent number 5930026 in following file; 5961804; 6017584; 6067185; 6118426; 6120588; 6120839; 6124851; 6130773; 6130774; 6172798; 6177921; 6232950; 6249721; 6252564; 6262706; 6262833; 6300932; 6312304; 6312971; 6323989; 6327072; 6376828; 6377387; 6392785; 6392786; 6413790; 6422687; 6445374; 6445489 and 6459418; And U.S. Patent Application Publication No. 2001/0045934; 2002/0019081; 2002/0021270; 2002/0053900; 2002/0060321; 2002/0063661; 2002/0063677; 2002/0090980; 2002/106847; 2002/0113770; 2002/0130832; 2002/0131147 and 2002/0154382, and International Publication No. WO99/53373; WO99/59101; WO99/67678; WO 00/05704; WO00/20922; WO 00/38000; WO00/38001; WO00/36560; WO00/20922; WO00/36666; WO00/67110; WO00/67327; WO01/07961; WO01/08241; WO01/17029 and WO01/17041.

Multiple patent above mentioned and application are recognized and can be substituted in wall round discrete microbody (microcapsule) in the electrophoretic medium of encapsulation by a kind of continuous phase, manufacture a kind of so-called dispersin polymerization body electrophoretic display device (EPD) thus, electrophoretic medium comprises the discrete droplets of many electrophoresis liquid and the continuous phase of polymeric material in such a display, even if the discrete each independent droplet of endosome film discord combines, the discrete droplets of the electrophoresis liquid in such dispersin polymerization volumetric display can regard endosome or microbody as; For example, see WO01/02899, the 10th page of 6-19 is capable.Also the CO-PENDING series application NO.09/683903 submitted on February 28th, 2002 can be illustrated in, and corresponding International Application Serial No. PCT/US02/06393.Therefore, in order to the object of the application, such dispersin polymerization body electrophoretic medium is counted as subspecies of the electrophoretic medium encapsulated.

The electrophoretic display device (EPD) of encapsulation can not suffer grumeleuse and the precipitation defective pattern of conventional electrophoretic equipment usually, and provides further advantage, such as, in various flexibility and rigid substrates, print or apply the ability of display.(use of word " printing " is printing and the coating that will comprise whole form, comprises (but not limiting to so): such as post-chip mouth mould coating, slit or Extrusion Coating, slides or classification coating, the coating of metering in advance of curtain coating; Such as, on cutter roller coat, forward or the oppositely roller coat of roller coat, notch board applies; Immersion coating; Spraying; Meniscus applies; Spin coating; Brush; Air knife applies; Serigraphy process; Xeroprinting process; Temperature-sensitive printing treatment; Ink jet printing process; With other similar techniques.) display obtained thus can be flexible.In addition, print because display medium (can use various method), therefore display itself can become cheap.

A kind of electrophoretic display device (EPD) of respective type is so-called " microcell electrophoretic display ".In microcell electrophoretic display, charged particle and suspending liquid be not be encapsulated in microbody but remain on be formed in normally polymer film mounting medium in multiple cavitys in.Such as, see being all the open NO.WO02/01281 of international application transferring Sipix Imaging company, and disclosed U. S. application NO.2002-0075556.

Striking contrast is defined based on the similar characteristics of the bistable state of the electrophoretic display device (EPD) of particle or multistable characteristic and the performance of other electro-optic displays and traditional liquid crystal (" LC ") display.Twisted nematic liquid crystal is not bistable state or multistable but as voltage sensor, so no matter be originally present in the gray level on pixel and the pixel to this display provides an electric field set, pixel produces a gray level of specifying.In addition, liquid crystal display only carries out in a direction driving (from non-transmissive or " black " to transmissive or " bright "), from bright state to the reverse transformation of black state by reducing or removing electric field to realize.Finally, the polarity of gray level to electric field of liquid crystal display pixel is insensitive, and only to its magnitude, and in fact for technical reason, and commercial liquid crystal display often drives the polarity of electric field with interval upset frequently.

By comparison, first approximate part, bistable electro-optic displays is as pulse transducer, so the end-state of pixel not only depends on the time of applied field and applied field, but also depends on the state applying pixel before electric field.In addition, have been found that now, at least many based in the electro-optic displays of particle, the pulse changed needed for a given pixel by the equal change of (as judged by eyes or normalized optical instrument) in gray level needs not to be constant, and they also need not to be interchangeable.Such as, imagine a kind of display, its each pixel can show for 0 (in vain), and the gray level of 1,2,3 (black) is relatively good at certain intervals.(interval between gray level can in reflection coefficient number percent linearly, as by eyes or instrument surveyed, but other also can be used to distribute.Such as, distribution can in L* linearly, or can be selected to provide a specific gamma value; The gamma value of 2.2, through being usually used in monitor, wherein with the alternative of this display as monitor, can use similar gamma value as required.) have been found that by pixel from the pulse needed for the change (being hereinafter called for simplicity " 0-1 conversion ") of 0 grade to 1 grade often and 1-2 or 2-3 change needed for different.And, 1-0 conversion needed for pulse need not with contrary 0-1 change identical.In addition, a kind of " storages " effect of some systems performance display, like this (such as) pulse needed for 0-1 conversion depends on whether particular pixels experiences 0-0-1,1-0-1 or 3-0-1 changes and changes a little.(wherein, symbol " x-y-z " represents the sequence of the optical states of accessing in chronological order, and x, y, z are optical states 0,1,2 or 3 here.Although) can by with a basic cycle all pixel driving of display being alleviated to one of extremity before by required pixel driving to another state or overcoming these problems, the pure color " flicker " produced is often unacceptable; Such as, the reader of e-book may need the text of books to roll under screen, if display needs black or pure white with interval flashing frequently, that reader may be made or lose dizzy his position.In addition, this flicker of display adds power consumption and can reduce the serviceable life of display.Finally, have been found that, at least in some cases, a certain particular conversion required pulse is by temperature and display total operating time, and particular pixels remained on the impact of the time of a certain particular optical state before given conversion, in order to ensure gray-scale rendition accurately, need to compensate these factors.

In one aspect, the present invention seeks to provide a kind of method and controller, can without the need to carrying out pure color flicker with interval frequently and provide gray level accurately to electro-optic displays over the display.

In addition, as being easy to find out from describe above, the driving of bistable state electro-optical medium requires to make the driver for driving active matrix liquid crystal display (AMLCD) to design not revise the display be unsuitable for for based on bistable state electro-optical medium.But, such AMLCD driver is commercially easy to obtain, there is large allowable voltage scope and the encapsulation of high pin count, there is the basis that can be purchased off the shelf, low price, therefore such AMLCD driver is attractive for driving bistable electro-optic displays, and customize similar for the driver based on bistable state electro-optical medium display in fact can be more expensive, also to take Basic Design and manufacturing time.Therefore, amendment AMLCD driver has the advantage on cost and construction cycle for bistable electro-optic displays, the present invention seeks to provide and can meet a kind of method of this point and the driver of amendment.

Equally, as already mentioned, the present invention relates to the method for drive cataphoresis display, make the driving pulse being provided to electrophoretic display device (EPD) keep long-term DC (DC) balance.What have been found that encapsulation needs the waveform balanced with precise dc to drive (namely with other electrophoretic display device (EPD), integration for display arbitrary particular pixels Current versus time will remain zero in the whole expanded period of display operation) to keep image stabilization, maintain symmetrical switching characteristic and the maximum service life (MSL) of display is provided.The power supply supply that the conventional method needs balanced for keeping precise dc accurately control, for the precise voltage modulating driver of gray scale and the crystal oscillator for timing, top and like the cost considerably increasing display is provided.

And, even if add parts expensive like this, still do not realize real DC balance.Empirically find, many electrophoretic mediums have asymmetric current/voltage (I/V curve), although the present invention is not by any restriction of this understanding, believe that this skew curve is attributed to electrochemical voltage source in media as well.In both cases voltage is carefully controlled as time accurately consistent even if this skew curve means, not identical when electric current and this medium of (supposing black) is addressed to relative extreme optical state (supposing white) when medium is addressed to an extreme optical state.

Have been found that now that the unbalanced degree of direct current in the electrophoretic medium used in the display can be found out by measuring open electrochemical current potential (being hereinafter called for convenience " residual voltage (the remnant voltage) " of medium).When the residual voltage of pixel is zero, it has been just good DC balance.If residual voltage is just, be exactly that direct current in positive dirction is non-equilibrium.If residual voltage is negative, be exactly that direct current is in a negative direction non-equilibrium.The present invention uses residual voltage data to balance to keep the long-term DC of display.

Therefore, in one aspect, the invention provides a kind of method driving bistable electro-optic displays, described display has multiple pixel, wherein each can show at least three gray levels (as in conventional display technology, extremely black and white state is considered in order to the gray level of two for calculating gray level).This method comprises:

Store a question blank, it preserves expression will change the data of an initial grey levels to a final gray level required pulse;

Store the data representing at least one original state of each pixel of display;

Receive the input signal that one of at least one pixel representing display expects end-state; With

Produce an output signal, represent the pulse needed for the end-state original state of described pixel being transformed into it and expecting, as from as described in determine in question blank.

This method is for simplicity hereinafter referred to as " question blank method " of the present invention.

The present invention also provides a kind of device controller made in this way.This controller comprises:

Memory storage, represents will change an initial grey levels to the question blank of final gray level required pulse data and the data of at least one original state of each pixel representing display for storing to preserve;

Input media, for receiving the input signal of an expectation end-state of at least one pixel representing display;

Calculation element, the pulse needed for the end-state of hoping for determining the change of the original state of a described pixel to expire from input signal, the data of the original state of the described pixel of expression stored and question blank; And

For generation of the output unit of the output signal of the described pulse of expression.

The present invention also provides a kind of method driving bistable electro-optic displays, and described display has multiple pixel, and wherein each can show at least three gray levels.The method comprises:

Produce an output signal, represent the pulse original state of described pixel being transformed into it and expecting needed for end-state, as from as described in determine in question blank, output signal represents the time cycle that will be supplied to the substantially invariable driving voltage of described pixel.

Calculation element, for determining the change of the original state of a described pixel to expire the pulse of hoping needed for end-state from input signal, the data of the original state of the described pixel of expression stored and question blank; And

For generation of the output unit of the output signal of the described pulse of expression, output signal represents the time cycle that will be supplied to the substantially invariable driving voltage of described pixel.

In yet another aspect, the invention provides a kind of device controller using the inventive method.This controller comprises:

Memory storage, represents will change the question blank of at least one initial condition data of an initial grey levels to each pixel of the question blank of final gray level required pulse data and expression display for storing to preserve;

For generation of the output unit of the output signal of the described pulse of expression, output signal represents multiple pulse at least middle change of one of voltage and duration, and after a predetermined period of time expires, output signal is expressed as no-voltage.

In yet another aspect, the invention provides a kind of drive circuit with the output line of drive electrode for being connected to electro-optic displays.This drive circuit comprises the first input media, will be placed on (n+1) bit digital of signal voltage on drive electrode and polarity for receiving multiple expression; And for the secondary input device of receive clock signal.One receives clock signal, and drive circuit is just presented at selected voltage on its output line.In a preferred form of this drive circuit, selected voltage can be between R and R+V 2 ⁿin individual discrete voltage any one or between R and R-V 2 ⁿany one in individual discrete voltage, wherein R is predetermined reference voltage (the normally voltage of the public front electrode of Active Matrix Display, as being described in more detail below), V be this drive circuit determine (assert) with the maximum differential pressure of reference voltage.Voltage selected by these can be that linear distribution is within the scope of R ± V, also can be nonlinear way distribution, this is non-linear can be controlled by two or more gamma electric voltage being positioned at particular range, and each gamma electric voltage defines the linear conditions (regime) between gamma electric voltage and adjacent gamma value or reference voltage.

In yet another aspect, the invention provides a kind of drive circuit with the output line of drive electrode for being connected to electro-optic displays.This drive circuit comprises the first input media, will be placed on 2 bit digital (2-bitnumber) of signal voltage on drive electrode and polarity for receiving multiple expression; And for the secondary input device of receive clock signal.One receives clock signal, and drive circuit is just presented at voltage selected from R+V, R and R-V (wherein R and V is as defined above) on its output line.

In yet another aspect, the invention provides a kind of method driving bistable electro-optic displays method, particularly drive cataphoresis display, described display shows a residual voltage.The method comprises:

A () provides the first driving pulse to the pixel of display;

B () measures the residual voltage of pixel after the first driving pulse; And

C () provides the second driving pulse at the rear of measurement of residual voltage to pixel, the residual voltage measured by dependence controls the size of the second driving pulse to reduce the residual voltage of pixel.

This method is hereinafter in order to conveniently be called " residual voltage " of the present invention method.

Fig. 1 represents apparatus of the present invention, the display driven by this device and the schematic diagram of associated apparatus, is designed to the structure showing whole system;

Fig. 2 is the schematic block diagram of the controller unit shown in Fig. 1, and describes the output signal produced by this unit;

Fig. 3 represents that the controller unit shown in Fig. 1 and 2 produces the schematic block diagram of the mode of a certain output signal shown in Fig. 2;

Figure 4 and 5 represent that the different reference voltage of two kinds of may be used for display shown in Fig. 1 is arranged;

Fig. 6 represents the schematic diagram weighed between width modulation and voltage modulated method in look-up-table method of the present invention;

Fig. 7 is the block diagram for customization (custom) driver in look-up-table method of the present invention;

Fig. 8 is the process flow diagram that the program can run by controller unit shown in Fig. 1 and 2 is described;

Fig. 9 and 10 illustrates two kinds of drive arrangements of the present invention;

Figure 11 A and 11B illustrates two parts of the third drive arrangements of the present invention.

As pointed out above, question blank part of the present invention provides method and controller for driving electro-optic displays, and described display has multiple pixel, and wherein each can show at least three gray levels.The present invention may be used for the electro-optic displays with greater number gray level certainly, such as 4,8,16 or more.

Similarly, as described above, drive bistable electro-optic displays to need and be generally used for the method that driving liquid crystal displays (LCD) is entirely different.In conventional (non-cholesteric) LCD, apply the specific voltage in enough cycle to pixel, pixel can be made to obtain a particular gray level.And, the magnitude of liquid crystal material only to electric field, and insensitive to its polarity.By comparison, bistable electro-optic displays is as pulse transducer, so not man-to-man mapping between applying voltage and acquisition grey states; Pixel must be applied to change with " initially " grey states of corresponding pixel for the pulse (with voltage thus) obtaining a given grey states.In addition, because bistable electro-optic displays needs in the two directions (white to black, and black in white) to drive, so need polarity and the size of specifying required pulse.

Here, need to consider to define some terms as used herein according to its conventional sense in display technique.Most of discussion below concentrates on one or more pixels of the single gradation conversion (that is, from a kind of gray scale to alternative change) of experience from " initially " state to " finally " state.Obviously, original state and end-state are appointed as and are only considered the single conversion studied, and in most of the cases, pixel has lived through conversion before " initially " state, and also will through conversion after " finally " state.As explanation below, some embodiments of the present invention not only can consider the initial of pixel and end-state, also can consider pixel existing " front " state before reaching original state.Here need to distinguish between front state multiple, term " first in front state " is used in reference to corresponding pixel and there is the state that (non-zero) before original state changes, term " second in front state " is used in reference to corresponding pixel and there is a state changed at the first (non-zero) before front state, the like.Term " non-zero conversion " is used in reference to " conversion " that realize the change of at least one gray units; Term " zero conversion " is used in reference to " conversion " (although other pixel of display can experience non-zero conversion simultaneously) of any change not producing selected pixel gray level.

As those skilled in the art are easy to find out, a simple embodiment of method of the present invention only can consider original state and the end-state of each pixel, and in this case, question blank is two-dimentional.But, as already noted, some electro-optical mediums show storage effect, and such medium is needs, when producing output signal, the original state not only considering each pixel being needed for this medium, but also (at least) will consider that first of this pixel in front state, in this case, question blank is three-dimensional.In some cases, may need to consider the more than one in front state of each pixel, cause in question blank, have four (if only considering that first and second in front states) or more dimension thus.

From form mathematical terms, the present invention can regard as and comprise an algorithm, provide about the initial of electric light pixel and final and (optionally) in the information of front state, and the information of (optional-vide infra in discuss in more detail) relevant physical state of display, function V (t) that may be used for pixel and change with the end-state being implemented to expectation can be produced.From this form viewpoint, controller of the present invention can regard in fact a physical embodiments of this algorithm as, and controller is used as the interface between the equipment and electro-optic displays of desired display information.

Temporarily ignoring physical state information, according to the present invention, is question blank or transition matrix this algorithm coding.This matrix has the one dimension of each end-state for expecting, and uses each dimension being used for other state (initial and any in front state) in the calculation.The key element of matrix can comprise to be used for electro-optical medium function V (t).

The key element of question blank or transition matrix can have various ways.In some cases, each key element can comprise single number.Such as, electro-optic displays can use the high-accuracy voltage modulating driver circuit that can export the multiple different voltages upper and lower at reference voltage, and provides required voltage with the predetermined period of a standard to pixel simply.In this case, each entry in question blank simply can have the form of individual integer, and this integer is specified will provide to given pixel for which voltage.In another case, each key element can comprise a series of numbers of the diverse location relating to waveform.Such as, the embodiments of the invention be described below use single or double prepulses waveform, and specify such required pulse to it may be noted that several numbers of the diverse location of waveform.What talk about equally below is embodiments of the invention, and it selects in the several process in multiple sub-scan period in a complete scan, by providing a predetermined voltage and effective apply pulse length modulated to pixel.In such embodiments, the key element of transition matrix can have several the forms indicating whether to apply predetermined voltage in every sub-scan period of corresponding conversion.Finally, as described in more detail below, in some cases, such as temperature compensation display can be the form (or, the coefficient of the various items that in fact more definite is in such function) of function more easily for the key element of question blank.

Obviously question blank used in some embodiments of the invention can become very large.For an extreme example, imagine and consider that initial, final sum two is used for 256 (2 at the algorithm of front state by a kind of ⁸) operation of the present invention of gray level display.Required four-dimensional question blank has 2 ³²individual entry.If each entry needs (hypothesis) 64 (8 byte), so the total amount of question blank can be about 32G byte.Although what problem is the data storing so large quantity on desktop computer do not have, just may have problems in portable equipment.But the size of in fact so large question blank can reduce greatly.Under many circumstances, have been found that and only have the type of waveform of little number to need a large amount of different switching, the length of the independent pulse of such as common waveform changes between different switching.Therefore, can comprise by making each entry the length reducing independent entry in question blank with lower part: (a) sensing be used to specify one of the peanut type of waveform that will use at the second table discal patch object pointer; And (b) specifies common waveform how to be the relevant parameter changing the peanut of change.

Can be pre-determined in question blank discal patch object value by an experience optimal processing.Substantially, pixel is set to corresponding original state, there is provided a roughly the same pulse of expectation end-state needing according to estimation to obtain, and the end-state measuring pixel is to determine reality and to expect the deviation between end-state, if this deviation exists.Then this process can repeat until deviation is less than predetermined value with modulating pulse, and this can be determined by the function of the instrument for measuring end-state.When considering the method in front state of one or more pixel, except original state, when pixel state the original state for determining pulse and whole in front state in constant, the general pulse first determined needed for particular conversion, then considers that different to carry out " accurate adjustment " in front state to this pulse be easily.

Paired pulses modulation when the present invention expects to be provided in the change of the total operating time considering temperature and/or display, and due to " aging " of some electro-optical mediums and the change of their states may need after long period of operation the compensation to the running time.Such modulation can one or both methods realize.First, extended look-up table can be carried out by the additional dimension of often kind of variable for considering when calculating output signal.Obviously, when the continuous variable of processing example as temperature and operation, in order to question blank being remained in a specific finite size, need to quantize continuous variable.In order to find out the waveform that will be applied to pixel, calculation element can select question blank entry as the form closest to measured temperature simply.Alternatively, in order to provide temperature compensation more accurately, calculation element can find two adjacent question blank entries in the continuous variable both sides recorded, and applies a suitable interpolation algorithm and obtain entry needed for the variable intermediate value place recorded.Such as, hypothesis matrix comprises the temperature entry increased progressively with 10 DEG C.If the display temperature of reality is 25 DEG C, so calculating can be found the entry of 20 DEG C and 30 DEG C and use this intermediate value of two.Notice that the characteristic variations due to the electro-optical medium together with temperature is not often linear, so the entry for temperature setting that question blank stores can not linearly distribute; Such as, the change of many electro-optical medium temperature mostly accelerates at high temperature place, and the spacing being therefore in question blank 20 DEG C at low temperature is just enough, and the spacing of 5 DEG C can meet the demands at high temperature place.

It is a kind of that what compensate for temperature/running time can system of selection be use with the functional form of physical descriptor or perhaps in the question blank entry of the more severity factor of such function Plays item.The situation of modulating the display of drive scheme service time is considered for simple, wherein by providing the constant voltage of a variant time length (arbitrary polarity) to control each conversion to each pixel, therefore, save the correction of any environmental variance, each entry in question blank only can comprise the single signed number of duration and its polarity representing the constant voltage that will apply.If need for the such display of temperature variation correction, be so the time T of constant voltage that particular conversion and needing applies on temperature t _tprovided by following formula:

T _t＝T ₀+AΔt+B(Δt) ²

Wherein T ₀be the time needed at some standard temperature places, normally display estimates the mid point of operating temperature range, and Δ t is at t with at T ₀difference between measured temperature, the entry in question blank can comprise T ₀and the value of A and B for the particular conversion that relates to given entry, and calculation element can use these coefficients to calculate the T at measured temperature place _t.Be pushed into more at large, the question blank entry being suitable for corresponding initial and end-state found out by calculation element, then uses and calculates by the function of this entry definition the suitable output signal considering other and need the variable of consideration.

Associated temperature for temperature compensation calculating is the temperature of the electro-optical medium in corresponding pixel; and this temperature can be obviously different with environment temperature; particularly when display will be used for outdoor application, such as sunlight causes the temperature of electro-optical medium layer to be in fact higher than environment temperature by front fender effect there.In fact, such as, when huge bulletin template outdoor signage, if under the part of display falls into the shade of adjacent building, other parts are then in sunlight, and the temperature on so same display between different pixel can be different.Therefore, may to need in electrooptic layer or contiguous its embed one or more electric heating occasionally other temperature sensor to detect the actual temperature of this layer.When large display, also may need to be defined in method of interpolation between the temperature that recorded by many temperature sensors to estimate the temperature of each particular pixels.Finally, when the large display by many module compositions that can replace separately, method of the present invention and controller can specify the different running times for the pixel in disparate modules.

Method of the present invention and controller it is also conceivable to the residence time (namely pixel maintains the cycle of a non-zero conversion) of the particular pixels that will drive.Have been found that at least in some cases, the pulse needed for given conversion is along with the residence time change of pixel in its optical states.Like this, just expect or the pulse for given conversion must be changed at the function of the residence time of its initial optical state as pixel.In order to complete it, question blank can comprise an additional dimension being used to indicate the residence time of pixel in its initial optical state by a counter index.In addition, controller needs containing an additional storage for the counter of each pixel in display.This also needs a read clock, and it is increased to arrange interval by the count value being stored in each pixel.The length at interval must be the integral multiple of display frame-period, therefore must be not less than a frame period.The size of counter and clock frequency can be decided by the pulse elapsed time length of change used and necessary temporal resolution.Such as, for each pixel store 4 digit counters can allow pulse in 4 second cycle (4 seconds × 4 times counting/second=16 time counting=4) with the interval variation of 0.25 second.Can reset once there is particular event this counter, such as pixel be transformed into a kind of new state.Once reach its maximal value, counter can be set to " upset " to zero count, or keep its maximal value until it is cleared.

Certainly can according to needing any physical parameter that other has detectable effect of pulse consideration of any one producing electro-optical medium or more particular conversion to change question blank method of the present invention.Such as, if find that electro-optical medium is to humidity sensitive, can change this method with the correction of combining environmental humidity.

For bistable state electro-optical medium, question blank can have following characteristics, and for zero initial identical with the end-state conversion of any pixel, entry is zero, or in other words, does not have voltage and be applied on pixel.As an inevitable outcome, if display does not have pixel to change in given interval, just pulse need not be applied.This can realize super low-power consumption operation, also ensure that electro-optical medium can not excessively drive when showing still image.Generally, question blank only can retain the information about non-zero conversion.In other words, for two images, I and I+1, if given pixel is in identical state in I and I+1, so state I+1 would not be stored in front state table, and until the conversion of pixel experience just can store information again.

Be apparent as the professional for modern electronic technology field, controller of the present invention can have various physical form.And any routine data processing element can be used.Such as, universal digital computer can be used to realize this method, this computing machine with combine for the numeral from computing machine being exported the suitable equipment (such as, one or more digital analog converter, " DAC ") being converted to suitable pixel voltage.Optionally, method of the present invention can realize by using special IC (ASIC).Especially, controller of the present invention can have the form of video card, and it can be inserted in PC the existing display screen that the image produced by computer is presented at replace such as LCD or as on the electric light screen supplemented of existing display screen.Due in the lucky technical merit in the image processing arts of structure of controller of the present invention, so its circuit details need not be described in detail at this.

The preferred physical embodiments of controller of the present invention is a kind of timing controller integrated circuit (IC).This IC receives input image data and exports the control signal being used for Data Collection and selecting drive IC, to produce suitable voltage to produce the image of expectation on pixel.This IC can receive view data by the memory buffer unit of access preservation view data, or can receive the signal for driving traditional LCD, therefrom extracts view data.It can also receive the serial signal preserved arbitrarily it and need the necessary pulse computing information performed.On the other hand, this timing controller can use software simulating, or is combined into a part of CPU.This timing controller can also have the ability of the external parameter of any impact display operation of measuring such as temperature.

Controller can operate as follows.The memory controller question blank that can obtain in memory.For each pixel successively, initial, the final sum (optionally) that are necessary all provide as input at front and physical state information.Then these status informations are for calculating the index in question blank.When the temperature quantized or other are revised, the rreturn value from this inquiry can be a voltage, or the array of voltages of a relative time.Controller can repeat this operation for two bracketing temperature in question blank, then carries out interpolation between these values.For algorithm temperature adjustmemt, the rreturn value of question blank has one or more parameters, then as mentioned above, can substitute into an equation together to determine the appropriate format of driving pulse by synthermal for these parameters.This program can realize in a similar fashion for other any system variable of driving pulse real-time change that needs.One or more such system variable can be determined by the value or the memory be stored in EPROM such as arranging programmable resistance on a display panel in order to the performance of optimizing display when structure.

An important feature of this display controller is that it does not resemble most of display, in most of actual conditions, need several complete reading scan to complete an image update.Several scannings needed for an image update should form one and can not be interrupted unit.If display controller and image source synchronous operation, so this controller must ensure that the data for calculating provided pulse keep constant in whole scanning.This can realize with one or both methods.First, input image data can be stored in an independent impact damper (alternatively, if display controller accesses display buffer by dual-ported memory, it should block the access from CPU) by display controller.Secondly, in first time scanning, the pulse of calculating can be stored in a pulse buffer by controller.The benefit of this second option is that each conversion is only carried out once for the house-keeping (overhead) of scanning panel, and for keeping the data scanned directly to export from impact damper.

Optionally, image update can with a kind of synchronous mode process.In general, although generally the complete conversion produced once between two images can spend and scans several times, pixel can start in the centre of frame to change or overturn the conversion started separately.In order to realize this, controller must be remembered for which part of the whole conversion of given pixel to complete.If receive the request of the optical states of the pixel of change one not in current conversion, so the counter of this pixel can be cleared, and this pixel can start conversion in the next frame.If pixel is effectively in conversion when receiving a new request, then controller can provide an algorithm to determine how to arrive new state from current frame intermediateness.For the normal image stream of 1, a kind of possible algorithm provides a pulse overturning polarity simply, and it is through amplifying and having and the duration identical in prepulse part provided.

In order to make the minimum power needed for operation display, and the picture steadiness of electro-optical medium is maximized, in time not having pixel to change in the display, this display controller can stop the scanning of display and reduces to be applied to the voltage of all pixels or make it close to zero.Very advantageously, when display is in " maintenance " state, this display controller can be closed to the power supply of its corresponding line and row driver, can make minimise power consumption like this.In this scheme, when asking pixel conversion next time, this driver can be reactivated.

Accompanying drawing 1 schematically shows the device of the present invention used together with associated apparatus.Whole devices (being usually designated as 10) shown in Fig. 1 comprise an image source, the PC 12 exporting expression view data on data line 14 as shown in.Data line 14 can be the general type of any one and can be an independent data line or bus; Such as, data line 14 can comprise USB (universal serial bus) (USB), serial, parallel, I EEE-1394 or other line.The data of placing on online 14 can be conventional replacement response image formats, such as bitmap (BMP), Tagged Image File (TIF) Format (TIF), GIF (GIF) or associating (Jooint) motion picture expert group version (JPEG) file.But optionally, the data of placing on online 14 can be the signal forms for driving video equipment; Such as, many computers provide a kind of for driving the video frequency output of external display, and the signal in this output may be used for the present invention.Can recognize that the present invention's device described below performs basic document format conversion and/or decoding possibly the technician of image processing field, to use dissimilar available input signals, but such conversion and/or decoding are known to those skilled in the art, therefore, only can be described from this point device of the present invention: the view data as its original input has been transformed into as the manageable form of device of the present invention.

As described in detail later, data line 14 extends to controller unit 16 of the present invention.This controller unit 16 produces one group of output signal and produce second group of signal on independent data bus 20 on data bus 18.Data bus 18 is connected to two row (or grid) drivers 22, and data bus 20 is connected to multiple row (or source) driver 24 (number of the row driver in FIG greatly reduces for the ease of representing).The operation of row and column driver control bistable electro-optic displays 26.

Device is in FIG selected to represent various available cell, and it is most suitable for a kind of experimental " breadboard " unit.In the business of reality manufactures, as in the conventional portable computer and personal digital assistant of assembling LCD, controller 16 can become the part of the Same Physical unit of display 26 usually, and image source also can become the part of this physical location.Same, the present invention represents in FIG and mainly describes in conjunction with a kind of Active Matrix Display structure below, this display device structure has the independent common transparent electrode on the side of electrooptic layer, and this public electrode extends through whole pixels of display.Usually, this public electrode between electrooptic layer and observer and formed an observer by its viewing display sightingpiston.Be placed the pixel capacitors matrix arranged with row and column in the opposite side of electrooptic layer, uniquely determine each pixel capacitors by the infall of going separately with independent row like this.Thus, by changing the voltage being provided to corresponding pixel electrode relative to the voltage (being generally expressed as " Vcom ") being provided to public front electrode, the electric field stood by each pixel of electrooptic layer is controlled.Each pixel capacitors at least with one transistor is connected, normally thin film transistor (TFT).On every row, the grid of transistor is connected on one of line driver 22 through independent prolongation column electrode.On every row the source electrode of transistor through independent prolongation row Electrode connection on one of row driver 24.The drain electrode of each transistor is directly connected in pixel capacitors.Be appreciated that grid is random to row and source electrode to the distribution arranged, just as the distribution of source electrode and drain electrode, can reverse.But following description can suppose conventional distribution.

In operation, line driver 22 applies voltage to grid, has one like this and only have the transistor of a line to be conducting in arbitrary preset time.Meanwhile, row driver 24 provides predetermined voltage to each row electrode.Thus, the voltage being applied to row driver is only provided in a line of pixel capacitors, writes the image that (or writing at least partly) a line is expected like this on electro-optical medium.Then line driver switching makes the transistor turns in next line, and a different set of voltage is applied to row electrode, write next line image.

It is emphasized that and the invention is not restricted to such Active Matrix Display.As long as determine the precision waveform for each pixel of image according to the present invention, any handover scheme can be used to provide waveform to pixel.Such as, the present invention can use the scheme of a kind of so-called " Direct driver ", and wherein independent drive wire is supplied to each pixel.In principle, the present invention can also use a kind of passive-matrix drive scheme for some LCD, but it should be noted that, because (namely many bistable state electro-optical mediums lack switching threshold, as long as provide one to prolong macrocyclic very little electric field, this medium will change optical states), drive so such medium is unsuitable for passive-matrix.But, owing to it seems that the present invention finds that it is mainly used in Active Matrix Display, so the present invention is mainly described with reference to such display at this.

Controller unit 16 (Fig. 1) has two major functions.The first, use method of the present invention, controller calculates and will change to from initial pictures the two-dimensional matrix that final image must be applied to the pulse (or waveform) displayer pixel.The second, use the conventional drives designed for LCD to drive bistable electro-optic displays, controller 16 calculates and will apply to expect the whole timing signals needed for pulse in pixel capacitors from this dither matrix.

As shown in Figure 2, the controller unit 16 in FIG has two major parts, and namely a buffer memory represents that controller 16B will be written to the frame buffer 16A of the final image data of display 26 (Fig. 1), and controller itself, is designated as 16B.Controller 16B from impact damper 16A one by one pixel read data produce various signals as described below at data bus 18 and 20.

Signal shown in Fig. 2 is as follows:

Six magnitudes of voltage (obviously, figure place in the signal can change according to particular row and column driver used) of D0:D5-pixel

POL-is relative to the pixel polarity of Vcom (vide infra)

START-places a start bit to start the loading of pixel value in row driver 24

The horizontal-drive signal of HSYNC-breech lock row driver

PCLK-switches the pixel clock of start bit along line driver

Start bit is loaded into the vertical synchronizing signal of line driver by VSYNC-

The output enabling signal of OE-breech lock line driver.

In these signals, although the definite timing of these signals can change according to used accurate electro-optical medium certainly, because line scanning method in shown device is in FIG identical with LCD scan method in principle, so VSYNC with OE being provided to line driver 22 is substantially the same with the corresponding signal being provided to line driver in conventional thin film transistor，Bao Mojingtiguan.Similar, for START, HSYNC and PCLK, although their timing can change according to the accurate electro-optical medium used, these signals being provided to row driver are substantially the same with the corresponding signal being provided to row driver in conventional thin film transistor，Bao Mojingtiguan.Therefore, can think that there is no need to further describe these outputs signal.

Controller 16B shown in Fig. 3 represents in fig. 2 in a highly schematic fashion produces the method for D0:D5 and POL signal.As mentioned above, controller 16B stores and represents final image 120 (this image expects write display), writes the initial pictures 122 of display and selectable one or more data at front image 123 writing display before initial pictures in advance.Embodiments of the invention shown in Fig. 3 store two such at front image 123.(obviously, the storage of necessary data can at controller 16B or in an external data storage device.Controller 16B uses particular pixels (as shown in Fig. 3 shade, be expressed as the first row first pixel) initial, final and at front image 120, the data of 122 and 123 are as the pointer entering question blank 124, and this question blank provides the state that will change this pixel must be applied to the value of the pulse of particular pixels to the expectation gray level in final image.Synthesis from question blank 124 is exported and is provided to from the output of frame counter 126 the voltage v. frame array 128 that produces D0:D5 and POL signal.

Controller 16B is designed to use together with TFT lcd driver, and this driver is equipped with the pixel reverse circuit usually changing adjacent image point polarity relative to end face.The pixel at interval can be designed as by even number and odd number and is connected to the two opposite sides of voltage ladder.In addition, the polarity of driver input for switching even number and odd number pixel of " polarity " is labeled as.Driver provides together with four or more gamma electric voltage grade, arranges to above-mentioned electric pressure the slope local can determining voltage-class curve.The exemplary with the commercial integrated circuit (IC) of these features is KS0652 300/309 passage TFT-LCD Source drives of Samsung.As mentioned above, the display that drive is used in the public electrode on electro-optical medium side, is applied to the Voltage Reference of this public electrode as " end face voltage " or " Vcom ".

In the embodiment of as shown in Figure 4, the reference voltage of driver is arranged as end face voltage and is positioned in the half of the maximum voltage (Vmax) that driver can provide, namely

Vcom＝Vmax/2

And gamma electric voltage is arranged as in the upper and lower linear change of end face voltage.(gamma electric voltage of a Figure 4 and 5 hypothesis odd number is drawn, thus such as in the diagram gamma electric voltage VGMA (n/2+1/2) equal Vcom.If there is the gamma electric voltage of an even number, VGMA (n/2) and VGMA (n/2+1) arranges and equals Vcom.Similar, in Figure 5, if there is the gamma electric voltage of an even number, VGMA (n/2) and VGMA (n/2+1) arranges and equals ground voltage Vs s).Obtain pulse length all needed for conversion to decide by being dispensing by the maximum impulse that Vmax/2 sets up needed for new images.This pulse can be converted into frame number by being multiplied by reading scan rate.Then necessary frame number is multiplied by 2 to provide even number and the odd-numbered frame of a great deal of.These even numbers and odd-numbered frame can corresponding to polarity position relative to this frame be set to high or low.For each pixel in every frame, controller 16B must provide a kind of algorithm, is even number or odd number with (1) pixel; (2) for considered frame, polarity position is high or low; (3) pulse desired by is just or bears; And (4) expect that the size of pulse inputs as it.Then algorithm determines that can this pixel addressed with the polarity expected in this frame again.If so, just suitable driving voltage (pulse length) is provided to this pixel.If not, then this pixel is parked in end face voltage (Vmax/2) to be located at hold mode, in this frame, does not wherein have electric field to be applied to pixel.

Such as, consider two adjacent image points in display, an odd image element 1 and an icon element 2.And suppose when polarity position is high time, odd image element can access positive drive voltage range (namely on end face voltage), and icon element can access negative voltage (namely below end face voltage).If pixel 1 and 2 all needs to drive with positive pulse, so following order must be there is:

A (), in positive polarity frame, drive pixel 1 with positive voltage, pixel 2 remains on end face voltage; With

B (), in negative polarity frame, pixel 1 remains on end face voltage, and drive pixel 2 with positive voltage.

Although general frame can replace (that is, mutually replacing) with the positive-negative polarity of 1: 1, this is optional; Such as, all odd-numbered frame can flock together, and are and then all even frame.This can cause the alternate column of driving display in the group that can be separated at two.

The major advantage of the present embodiment is to switch public front electrode during operation.This major advantage is that the maximum drive voltage of available electro-optical medium is the half of driver maximum voltage, and every a line only can drive the time of 50%.Like this, under identical maximum drive voltage, the refresh time of this display is four times of electro-optical medium switching time.

In the second embodiment of this form of the present invention, the gamma electric voltage of driver is arranged as shown in Figure 5, and public electrode switches between V=0 and V=Vmax.The gamma electric voltage in this way arranged allows to drive icon element and odd image element with single direction simultaneously, but needs public electrode to be switched to the driving polarity close to contrary.In addition, because this layout is about end face voltage symmetry, therefore to the specific input of driver can cause identical voltage be provided to odd image element or icon plain on.In this case, the input of algorithm is size and the symbol of desired pulse, and the polarity of end face.If corresponding to expecting that the symbol of pulse arranges current public electrode, then this value exports exactly.If expect that pulse is in contrary direction, so this pixel is arranged on end face voltage, in this frame, does not have electric field to be applied on this pixel like this.

As previously described in a prior embodiment, in the present embodiment can by calculating the necessary length of driving pulse divided by maximum impulse with maximum drive voltage, and this value is converted into frame number by being multiplied by display refresh rates.Frame number must be double so that the fact that display can only drive corresponding to end face to be in one direction described at every turn again.

The major advantage of the second embodiment is the full voltage that can use driver, and can drive all output at once.But two frames need to drive in the opposite direction.Thus, under identical maximum drive voltage, the refresh time of this display is the twice of the switching time of electro-optical medium.Its major defect needs to switch public electrode, and this may cause at electro-optical medium, the transistor be connected with pixel capacitors or the less desirable voltage noise in both.

In any embodiment, gamma electric voltage is generally all distributed between the maximum voltage of driver and end face voltage with linear gradient.Depend on the design of driver, can really produce top voltage in output in order to ensure driver, one or more gamma electric voltage in end face value may be needed.

Above to needing the restriction making method of the present invention be suitable for for the conventional drives of LCD design to make reference.More specifically, the row driver of conventional LCD, particularly supertwist is to row (STN) LCD (can control higher voltage than the row driver of other type), one of two voltages can only be applied to drive wire, because whole needs that Here it is to the non-sensitive liquid crystal material of polarity in arbitrary preset time.Contrary, for driving the electro-optic displays to polar sensitive, minimum needs three actuator electrical voltage levels.This actuator voltage needed for three take opposing top voltage as the V-of negative driving pixel, take opposing top voltage as the V+ of positive driving pixel, and keep pixel to be the voltage of 0V at the opposing top voltage of identical display state.

But, method of the present invention can realize with such conventional LCD driver, in order to necessary pulse will be provided to the pixel of electro-optic displays, the controller that provides is arranged to provide a suitable contact potential series to one or more row driver and relative line driver.

This method has two primary variabless.In the first variable, all provided pulses must have+I, one of three values of-I or 0, wherein:

+I＝-(-I)＝Vapp×t _pulse

Wherein Vapp is the provided voltage on end face voltage, and t _pulseit is pulse length in seconds.This variable only allows display to operate with scale-of-two (black/white) pattern.In second variable, the pulse provided can change to-I from+I, but must be the integral multiple of Vapp/freq, and wherein freq is the refreshing frequency of display.

This aspect of the present invention utilizes the following fact pointed out, conventional LCD driver is designed to frequency interval upset polarity to avoid some undesirably but the effect that may produce in the display.Therefore, such driver is designed to the polarity or the control voltage that receive self-controller, and it can be high or be low.When being shown to be a low control voltage, output voltage on arbitrary given driver output line can adopt may needed for three voltages outside one of two, for example V1 or V2, and when being shown to be a high control voltage, output voltage on arbitrary given driver output line can adopt one of different in three voltages that may need two, for example V2 or V3.Thus, two only outside three required voltages can be addressed at arbitrary special time, and three whole voltages just can obtain in different time.These three required voltages can meet following relational expression usually:

V2＝(V 3+V1)/2

V1 can or close to logically.

In this method of the present invention, display can by scanning 2 × t _pulse× freq time.For these half scanned (that is, for t _pulse× the scanning of freq time), the output of driver can be set to V1 or V2, it can equal-V and Vcom usually respectively.Thus, in these scannings, pixel or driving are negative, or remain on identical display state.For second half of scanning, driver can be outputted to V2 or V3, it can equal Vcom and+V usually respectively.In these scannings, pixel or driving are just, or remain on identical display state.Table 1 below illustrates these options how to combine to produce in the driving of either direction or a hold mode; The negative driving just driving and can obtain bright state that certainly can obtain black state is accordingly a kind of function of specific electro-optical medium used.

Table 1 is with the drive sequences of the maintenance acquisition bi-directional drive pulse of STN driver

There is multiple distinct methods to arrange two of this drive scheme parts (that is, two dissimilar scannings or " frame ").Such as, the frame of two types can replace.In fact in driving in the opposite direction in the frame replaced, if carried out with high refresh rate, so electro-optical medium can show luminous and dimmed simultaneously.Optionally, all frames of a type can occur before any one of Second Type frame; This can cause a kind of driving external characteristic of two steps.Certainly other layout is also fine; The frame of two or more opposite types is followed for such as two with the frame of a more type.In addition, if do not have pixel to need to drive in one of both direction, so can cancel the frame of this polarity, 50% ground reduces driving time.

When the first variable can only produce binary picture, the second variable can provide the image with multi-grey level.This is by realizing in conjunction with the drive scheme of the above-mentioned width modulation to different pixel.In this case, again to scanning of a display 2 × t _pulse× freq time, but in these enough scannings, only provide driving voltage to ensure to obtain the pulse desired by particular pixels to arbitrary particular pixels.Such as, for each pixel, can record provided total pulse, when pixel reaches the pulse of its expectation, in the scanning below all, this pixel can remain on end face voltage.For the pixel needing to drive to be less than total scanning time, the time of drive part (namely, the time portion of pulse is provided in the display state of for a change pixel, relative with the retaining part that provided voltage simply maintains the display state of pixel) can be distributed in a variety of ways in total time.Such as, whole drive parts can be set to start in beginning place of total time, or whole drive parts can change into the end of T.T. timing complete.As in the first variable, if the pulse that the arbitrary time in the second variable no longer includes particular polarity needs to be supplied to arbitrary pixel, the scanning that this polar impulse is provided so can be cancelled.This may mean that whole pulse can be shortened, such as, if the maximum impulse provided with positive and negative direction is less than maximum permission pulse.

Take situation about highly simplifying for illustrative purposes, suppose that the above-mentioned grey scale solutions being used for display has four gray levels, i.e. black (0 grade), dark gray (1 grade), bright gray scale (2 grades) and white (3 grades).A kind of possible drive scheme of such display is summarized in table 2 below.

Table 2

Frame No.	1	2	3	4	5	6
							Parity	Very	Even	Very	Even	Very	Even
Conversion
							0-3	+	0	+	0	+	0
0-2	+	0	+	0	0	0
							0-1	+	0	0	0	0	0
0-0	0	0	0	0	0	0
							3-0	0	-	0	-	0	-
2-0	0	-	0	-	0	0
							1-0	0	-	0	0	0	0

Although the frame of more more number usually can be used in practice, for convenience of description, suppose only to use six frames in this drive scheme.These frames are alternately odd and even number.Be tending towards white conversion (that is, gray level increase conversion) only to drive in odd-numbered frame, and be tending towards black conversion (that is, gray level reduce conversion) and only drive in even frame.Do not drive in the frame of pixel arbitrary, it remains on the voltage identical with public front electrode, as indicated by " 0 " in table 2.For 0-3 (Hei-Bai) conversion, in each odd-numbered frame, a pulse being tending towards white (that is, pixel capacitors being remained on one trends towards increasing pixel gray level voltage relative to public front electrode) in frame 1,3 and 5, can be provided.On the other hand, for 0-2 (black in bright gray scale) conversion, only in frame 1 and 3, provide a pulse being tending towards white, and pulse is not provided in frame 5; That yes is random for this, such as, can apply one and be tending towards white pulse and do not apply pulse in frame 3 in frame 1 and 5.For 0-1 (black in dark gray) conversion, only apply a pulse being tending towards white at frame 1 frame, and do not apply pulse at frame 3 and 5 frame; In addition, this is also random, such as, can apply one in frame 3 and be tending towards white pulse, and not apply pulse at frame 1 and 5 frame.

Being tending towards black conversion is process with a kind of method being very similar to the conversion being tending towards white accordingly, only applies in the even frame of this drive scheme except this is tending towards black pulse.Believe and drive the technician in electro-optic displays field can be readily appreciated that the method for unshowned conversion in table 2 by description above.

Above-mentioned pulse group can be independence (stand-along) conversion between two images, or they also can be parts for the designed pulse train for completing image conversion (as with magic lantern (slide-show) waveform).

Although emphasis to be placed on and of the present invention to have allowed to use for use together with LCD and in the method for conventional drives that designs above, but the present invention also can use the driver of customization and a kind of driver for accurately controlling grey states in electro-optic displays, and introduces the realization of the no write de-lay of display now with reference to Fig. 6 and 7.

As mentioned above, first, many electro-optical mediums are in response to a potential pulse, and this pulse can be expressed as V timing t (or more conventional, by the integration of V relative to t), and wherein V is the voltage being applied to pixel, and t applies this voltage institute elapsed time.Thus, the modulation to the potential pulse length being applied to display can be passed through, or pass through executing alive modulation, or the combination both them obtains grey states.

When the width modulation of Active Matrix Display, available impulse width resolution is the inverse of display refresh rate.In other words, for the display of 100Hz refresh rate, pulse length can be sub-divided into the interval of 10ms.This is because in each scanning in display the addressing of each pixel once, exactly when in that a line, the selection line of pixel is activated time.In all the other times, as described in above-mentioned WO01/07961, the voltage on pixel can be maintained by holding capacitor.Along with the response speed of electro-optical medium accelerates, can be more and more precipitous relative to the slope of the reflectance curve of time.Thus, in order to maintain identical gray level resolution, the refresh rate of display must corresponding increase.The increase of refresh rate causes higher power consumption, final if expectation transistor and driver becoming impossible in the shorter and shorter time to the charging of pixel and line capacitance.

In yet another aspect, in voltage modulated display, pulse resolution is just determined by the number of voltage level, and independent of the speed of electro-optical medium.By utilizing the nonlinear Distribution of electric pressure to increase effective resolution, they concentrate on the most precipitous place of the voltage/reflectivity responses of electro-optical medium.

Accompanying drawing 6 schematically illustrates the balance between width modulation (PWM) and voltage modulated (VM) mode.Horizontal axis repre-sents pulse width, and vertical axes representative voltage.Reflectivity as the electrophoretic display device (EPD) based on particle of the function of these two parameters is expressed as one with the expression district of the difference of 1L* and contour map at interval in display reflects brightness, and wherein L* has the definition of conventional ICE:

L*＝116(R/R ₀) ^1/3-16

Wherein R is reflectivity, and R0 is the value of a standard reflectivity.(empirically find that difference in 1L* brightness is significant just for mean value theme in double excitation test.) the specific electrophoretic medium based on particle used in this experiment of summing up in figure 6 has response time of the 200ms at maximum voltage (16V) place as shown in the figure.

The effect of independent width modulation can be determined by the segment crossed along top level, and the effect of individual voltage modulation is by checking that the vertical edge on right side is found out.From this segment it is clear that, if use the display of this particular medium to be drive with the refresh rate of 100Hz in width modulation (PWM) pattern, so the reflectivity in ± 1L* can not be obtained in the mid gray regions of profile steepest.In voltage modulated (VM) pattern, the reflectivity obtained in ± 1L* can need 128 grades of equally spaced voltage levels, runs (certain, to suppose that the voltage holding capability provided by capacitor is sufficiently high) with the low frame frequency to 5Hz simultaneously.In addition, these two kinds of methods can be combined and obtain same precision with less voltage level.In order to reduce required voltage progression further, can by they in figure 6 shown in middle the steep part of curve concentrated and sparse in exterior lateral area.This can come with the input gamma electric voltage of peanut.In order to reduce required voltage progression further, they can be concentrated in favourable value.Such as, if use very little voltage can not meet the grey states conversion of any expectation in distributed address-time, so such small voltage is otiose for realizing conversion.Select the voltage's distribiuting getting rid of such small voltage that allowed voltage can be made to have more favourable distribution.

As noted above, because bistable electro-optic displays is for the polar sensitive of the electric field applied, so unlike done in an lcd in continuous print frame (image) polarity of upset driving voltage, and frame, pixel and line upset are all unnecessary, and in fact can have the opposite effect.Such as, the lcd driver with pixel upset carries the voltage changing polarity in the frame replaced.Like this, the pulse of suitable polarity only may be carried in the frame of half.This is not problem in an lcd, because liquid crystal material is insensitive to polarity, but in bistable electro-optic displays, needs the time addressing electro-optical medium of twice.

Similar, because bistable electro-optic displays is pulse transducer instead of voltage sensor, so display integral voltage error in time, this can cause the pixel of display to depart from the large skew of their expectation optical states.This makes to use the driver with high voltage precision to become very important, the tolerance of recommendation ± 3mV or less.

In order to enable driver carry out the display panel of the monochromatic XGA (1024*768) of addressing with the refresh rate of 75Hz, need the maximum pixel clock rate of a 60Hz; Obtain such clock frequency in the present art.

As already mentioned, be the stability of their images based on the electrophoresis of particle and a major advantage of other similar bistable electro-optic displays, and then have an opportunity to run display with extremely low power consumption.Utilize this chance substantially, the power supply of driver can be disabled to when image does not change.Therefore, driver can be designed as when not producing any stray voltage on the output line and carrys out power down in the controllable mode of one.Because enter and leave such " sleep " pattern can become a kind of common event, thus power down and the order that powers on fast as much as possible, and minimum influence to be had on the serviceable life of driver.

In addition, an output pin making driver all should be had to be the input pin of Vcom, all pixels can remain on their current optical states when driver not power down by it.

Driver of the present invention is useful, wherein such as, in particular for driving high resolving power medium, the portable display of high information capacity, 7 inches of (178mm) diagonal line XGA monochrome displays.In order to the number of integrated circuit required in such high resolution panel minimizes, need use to have every sheet and encapsulate the driver that high number (such as, 324) exports.Also need this driver to have one operate in the option under other pattern one or more of and there is less output enable.Carrier package (TCP) the integrated circuit method for optimizing put on a display panel, the size so just needing to arrange driver to export and place the use being beneficial to this method.

This driver is typically used in and carrys out drive medium active matrix board with the little voltage to about 30V.Therefore, this driver needs the capacitive load that can drive about 100PF.

Give the block diagram of preferred driver (being usually designated as 200) of the present invention in fig. 7.Driver 200 comprises shift register 202, data register 204, data latches 206, digital analog converter (DAC) 208 and output buffer 210.This driver is different from those and is generally used for driving places of LCD to be to it provide a polarity position relevant to each pixel of display, and produces one in the upper and lower output of end face voltage by the control of corresponding polarity position.

Originally provide in the signal description of preferred driver table 3 below:

Driver 200 operates in the following manner.First, a starting impulse is provided to make shift register 202 reset to an initial state by setting (for example) DIO1 as height.(can be readily understood that for Display Driver those skilled in the art, the various DIOx input provided to shift register can make driver and have together with display that varying number arranges to use, but arbitrary given display is only used in these inputs, and by low for being forever restricted to of other.) now shift register operate with the usual manner used in an lcd; In each CLK1 pulse place, have one in 162 outputs of shift register 202 and only have one to uprise, other maintenance low level, and this high level output converts a position when each CLK1 pulse.As Fig. 7 schematically shows, 162 of shift register 202 export in each be connected to two inputs of data register 204, one very input and one occasionally input.

Display controller (comparison diagram 2) provides polar signal D0POL and D1POL of two six digit pulse value D0 (0:5) and D1 (0:5) and two single positions in the input of data register 204.At the rising edge of each time clock CLK1, export in conjunction with (high level) selected by shift register 202, two seven figure places (D0POL+D0 (0:5) and D1POL+D1 (0:5)) are written in the register of data register 204.Thus, after 162 time clock CLK1,324 seven figure places (pulse value relative to for complete a line in a frame display) are written in 324 registers in data register 204.

At the rising edge of each time clock LCK2, these 324 seven figure places are sent to data latches 206 from data register 204.These numbers be placed in data latches 206 are read by DAC208, and in a usual manner, the corresponding analogue value is placed on the output of DAC208, and the row electrode of display is fed to through impact damper 210, there they are supplied to the pixel capacitors in a line selected in the usual way by line driver (not shown).But, it is pointed out that, by polarity position D0POL or D1POL be written in data latches 206 to control the polarity of each row electrode corresponding to Vcom, these polarity can not change by the usual manner as used in an lcd between adjacent column electrode like this.

Fig. 8 is the process flow diagram that a program can run by the controller unit shown in Fig. 1 and 2 is described.This program (being generally designated as 300) for using together with look-up-table method of the present invention (hereinafter having more detailed description), and wherein in each image write or when refreshing, all pixels of display are wiped free of and addressing more again.

Program starts from controller initialized " powering on " step 302, and this is the result of user's input usually, and such as user presses the power button of personal digital assistant (PDA).Step 302 also can cause by with under type, such as, the opening of PDA box (can by mechanical pick-up device or photoelectric sensor to detect this opening), input pen leaves the movement of its shelf on PDA, move when user picks up PDA detection, or when the hand of user is close to the close detection carrying out during PDA detecting.Next step 304 is " reset " steps, wherein by all pixel driven of display to the black of them and white state.Have been found that at least in some electro-optical mediums, over the display in the write successively of image, this " flicker " of pixel is for guaranteeing that accurate grey states is required.Also find usually at least to need glimmer for 5 times (calculating each time continuously black and white state is once flicker), or in some cases more times.The number of times of flicker is more, and time and the energy of cost in this step are more, and the time simultaneously had to pass through before user can see the image of expectation over the display is thus also longer.Therefore, just wish to make the number of times of flicker little as much as possible when meeting and writing accurate grey states supply in image subsequently.At the end of reset process 304, all pixel of display is all in identical black or white state.

Next step is write or " sending image " step, and its middle controller 16 sends signal with the method said respectively to row and column driver 22 and 24 (Fig. 1 and Fig. 2), writes the image of expectation thus over the display.Because display is bistable, so once image write, do not need to rewrite at once, and thus after write image, controller interrupts the write of row and column driver to display by arranging blanking signal (such as in the figure 7 signal BL being set to height) usually.

Present controller enters one by step 308, the 310 and 312 judgement circulations formed.In step 308, controller 16 checks whether computing machine 12 (Fig. 1) asks the display of a new images.If so, controller continues, and will be written to the image wipe of display within step 306 in an erase step 314, the state arrived at the end of thus display being turned back to reset process 304 substantially.Controller turns back to step 304 from erase step 314, resets foregoing, and continues the new image of write.

If do not need the new images being written to display in step 308, controller proceeds to step 310, determines that when the image kept over the display is more than a predetermined period there.Known to the technician in display technique, the image be written on bistable media is not keep indefinite duration, and image can fade away gradually (that is, contrast reduces).In addition; in the electro-optical medium of some types; particularly electrophoretic medium, often can weigh between the writing speed and bistable state of medium because several hours and within several days, keep bistable medium substantially than only keep several seconds or a few minutes bistable medium there is the longer write time.Therefore, although continuous rewriting electro-optical medium not needing to resemble in situation in an lcd, in order to provide the image with good contrast, need to carry out refreshed image with the interval of (for example) a few minutes.Thus, controller judges whether exceeded predetermined refresh interval since writing the time that image starts to have pass by within step 306 in the step 310, if, controller proceeds to erase step 314 and then arrives reset process 304, reset as mentioned above, and continue identical image to be rewritten on display.

(program in fig. 8 can become use local simultaneously and rewrite with overall, as hereinafter described in more detail.If like this, step 310 will change into and determines the need of local or totally rewrite.If in the program of conversion, in step 310 place, program judges that predetermined time does not expire, and will not operate.If but the schedule time arrives, step 310 can not the erasing of calling graph picture at once and rewriting, but only arrange an instruction generally to the renewal of next image than more effective mark (term usually in computing machine) partly.Program arrives step 306 in the next time, certification mark, if be provided with this mark, then to the overall rewriting of image with then remove this and mark.But if this mark is not set, then just to the Local Gravity of image with effect.)

If judge that refresh interval does not also exceed in the step 310, controller proceeds to step 312, has judged whether the time of closing display and/or image source there.In order to preserve energy in a portable device, controller can not allow a single image to refresh down indefinitely, as shown in Figure 8 can one extend without the operating cycle after terminator.Therefore, judge whether predetermined " closedown " cycle (being greater than refresh interval above-mentioned) expires after the new image rewriting of front image (instead of) is written to display in step 310 controller, if, as represented by 314, program determination.Step 314 can comprise the power down of image source.That is, after such program determination, user can also access the image of slowly desalinating over the display.If also do not exceed this closedown cycle, then controller turns back to step 308 from step 312.

Only method is by way of example introduced the various possible waveform being used for performing look-up-table method of the present invention.But, first will introduce the general provisions of some waveforms used in the present invention.

The waveform showing the bistable display of foregoing storage effect can be divided into two main classes, i.e. offset-type and non-compensated.In offset-type waveform, consider that arbitrary storage effect in the pixel carries out minute adjustment to whole pulse.Such as, the pixel of the series conversion of an experience gray level 1-3-4-2 can receive a pulse changed for 4-2 slightly different compared with the pixel changed of experience 1-2-4-2.Such impulse compensation can pass through regulating impulse length, and other change that voltage or the V (t) by pulse distribute is carried out.In non-compensated waveform, without any any behave front status information (being different from original state) of consideration.In non-compensation waveform, the pixel of all experience 2-4 conversion can receive identical pulse.In order to make non-compensated wave shape successful operation, one of two conditions must be met.One is that electro-optical medium must not performance storage effect in its blocked operation, or changes any storage effect must effectively eliminated in pixel at every turn.

Generally, non-compensation waveform is best suited for the system can only carrying out thick pulse resolution.Be such as the display with three grades of drivers, or only have the display of 2-3 position voltage conversion capabilities.Compensating waveform and need accurate pulse regulation, is impossible by such system.Obviously, when rough pulse system is preferably limited to non-compensation waveform, the system with Precision Pulse adjustment can realize the waveform of this two type.

The simplest non-compensation waveform is 1 normal image stream (1 GIF).In 1 GIF, display conversion arrives the next one reposefully from a pure black white image.Can carry out as follows simply the transformation rule of this sequence: if image is changed to black from white cut, then provide pulse I.If it is switched to white from black, then provide the pulse of opposite polarity ,-I.If image keeps identical state, then do not provide pulse to pixel.As specified above, pulse polarity can rely on the respective function (function) of material for the mapping of the polarity of voltage of system.

The another kind of non-compensation waveform that can produce gray level image is non-offset-type n prepulsing magic lantern (n-PPSS).This non-compensation magic lantern (slide show) waveform has three essential parts.First, erasing pixel is to a unique optical states, normally white or black.Then, pixel is driven backward or forward between two optical states, usual or white and black.Finally, pixel is addressed to the new optical states that can be grey states more than.Finally (or write) pulse is called as addressing pulse, and other pulse (the first (or erasing) pulse and middle (or blanking) pulse) is collectively referred to as prepulsing.Such waveform can describe with reference to Fig. 9 and 10 below.

Prepulsing magic lantern waveform can be divided into two citation forms, have odd number prepulsing and have even number prepulsing.For the situation of odd number prepulsing, the erasing pulse meeting polarity that equal and relative direct preceding write pulse (or see Fig. 9 and following description) is contrary in pulse.In other words, if pixel is written to ash from black, erasing pulse can make pixel turn back to black state.When even number prepulsing, the pulse that erasing pulse can have the polarity identical with direct preceding write pulse and can equal from black to white needed for complete conversion in the pulse sum of front write pulse and erasing pulse.In other words, if pixel is from black write when even number prepulsing, so must be erased to white.

After erasing pulse, waveform comprises zero or even number blanking pulse.The normally equal but opposite polarity pulse of these blanking pulses, being arranged to first pulse is the polarity contrary with erasing pulse.These pulses be generally equal to whole black-white pulse, but this is not necessary condition.Also can only need pulse to the pulse with equal but opposite polarity pulse-can the be paired great changes linked together, i.e.+I ,-I ,+0.1I ,-0.1I ,+4I ,-4I.

The pulse finally provided is write pulse.To the selection of this pulse only based on desired optical states (do not rely on current state, or any in front state).Generally, this pulse meeting is with grey states value monotone increasing or minimizing, but this is optional.Design because this waveform is in particular the use of rough pulse system, such as, so the mapping of one group of expectation grey states in the possible pulse choice of peanut generally can be included in the selection of write pulse, 4 grey states in 9 kinds of pulses that may apply.

The inspection of non-compensation n the prepulsing magic lantern waveform of dual numbers or odd number form can demonstrate write pulse always from identical direction, namely from black or from vain.This is the key character of this waveform.Principle due to non-compensation waveform is cannot for guaranteeing that pixel reaches identical optical states and paired pulses length compensates accurately, so can not look to reaching consistent optical states when setting about from contrary extreme optical state (black or white).Therefore, for one of these forms that can be designated as " from black " and " confession ", there are two kinds of possible polarity.

A major defect of this type waveforms is to have the optical flicker of greatly amplifying between images.As with reference to Fig. 9 and 10 hereinafter as described in, can be that the conversion of half pixel upgrades order by super frame tim e, and to improve with high resolving power staggered scanning pixel.Possible pattern comprises every (every) other row, every other row, or inspection plate pattern.Note, this does not also mean that and uses relative polarity, and namely " from black " is to " confession ", because this can cause not mating of on adjacent image point gray scale.As an alternative, can by with to half pixel (namely, first group of pixel completes erasing pulse, and then second group of pixel starts erasing pulse and first group of pixel starts the first blanking pulse) postpone more NEW BEGINNING with one " superframe " the frame group of the maximum length that Hei-Bai upgrades (one equal) and realize.Consider synchronous, this needs for increasing a superframe total update time.

First can find out that Perfected process of the present invention can be called " ordinary gamma image stream ", its middle controller arranges the write of each image, and each like this pixel directly can be transformed into its final gray level from its initial grey levels.But in fact, ordinary gamma image stream faces the problem from the accumulation of error.Due to following practical work, such as, by driver, the change etc. of the production of electro-optical medium on thickness causes the change being difficult to avoid on voltage exports, and is applied to the inevitable and theoretical demand of pulse in arbitrary given gradation conversion and there is difference.Supposing that the average error changed at often kind is expressed as display in difference terms that is theoretical and actual frame reflectivity is ± 0.2L*.Through 100 continuously conversions, pixel can demonstrate a mean deviation from the 2L* state desired by them; This skew is obvious in the image of some type for general viewers.In order to avoid this problem, need the drive scheme used in the present invention to be arranged to before an extreme optical state (black or white), arbitrary given pixel can only experience the gradation conversion of a predetermined maximum number.After being applied with certain pulses on electro-optical medium, these extreme optical state are as " fence ", and medium can not become more black or whiter.Thus, the conversion next time always from extreme optical state from the optical states accurately known, can effectively compensate for any error in front accumulation.By extreme optical state, the minimized various technology of the optical effect of such one section of pixel be will be described below.

First, have black (0 grade) referring now to one, dull gray (1 grade), bright ash (2 grades) and white (3 grades) optical states, use pulse modulation technology and as the conversion query table as shown in following table 4 realize conversion simple two gray scale systems, introduce simple drive scheme useful in the present invention.

Table 4

Conversion	Pulse	Conversion	Pulse
				0-0	0	0-0	0
0-1	n	1-0	-n
				0-2	2n	2-0	-2n
0-3	3n	3-0	-3n

Wherein n is a number according to particular display, but and-n represents that has the pulse with pulse n equal length opposite polarity.The also end of further hypothesis reset pulse 304 in fig. 8, all pixel of display is all black (0 grade).Therefore, as described below, all conversions are all occurred by a black state in centre, only have those to be effective to this grey states or from the conversion of this grey states.Like this, required question blank size obviously reduces, and the scale factor obviously according to the question blank size reduced can increase along with the number of display gray level.

Fig. 9 shows a pixel relevant with the drive scheme of Fig. 8 and changes.In the beginning of reset process 304, pixel is in a certain random greyscale.In reset process 304, by pixel driven to three black states and two white states in centre, terminate in its black state.Then write for the suitable gray level of the first image to pixel at 306 places, suppose it is 1 grade.During the display of this identical image, this pixel keeps a period of time in this level; The length of display cycle substantially reduces for convenience of explanation in fig .9.Sometimes a new images needs write, in this, pixel turns back to black (0 grade) in erase step 308, then in the second reset process being appointed as 304 ', 6 times alternately white and black reset pulses are passed through, like this in this reset process 304 ' end, pixel has turned back to black state.Finally, in the second write state being appointed as 306 ', write one for the suitable gray level of the second image to pixel, suppose it is 2 grades.

That yes is possible for many different drive scheme in Fig. 9.Figure 10 illustrates a kind of useful change.Step 304 in Fig. 10,306 with 308 the same with in Fig. 9.But, in step 304 ' in, employ 5 reset pulses (obviously also can use the odd number impulse that different), like this in step 304 ' end, pixel is at white state (3 grades), and in the second write step 306 ', the write of pixel is realization instead of realize from resembling black state described in fig .9 from white state.Such consecutive image is just alternately from the black state of pixel and the write of white state.

In the change of the another drive scheme shown in Fig. 9 and 10, erase step 308 not black according to driving pixel but white (3 grades) realize.Then in reset process, under white state, even number reset pulse is added to pixel end, write second image from white state.As the drive scheme at Figure 10, black state and white state write continuous print image alternately from pixel in this programme.

Be appreciated that above in all schemes, according to the characteristic of the electro-optical medium used, the number of reset pulse and duration can change.Similar, can change with voltage modulated instead of width modulation the pulse being applied to pixel.

The black lightning showed over the display in the reset process of above-mentioned drive scheme and white dodge for user that yes is visible, and may not like for a lot of user.In order to reduce the visual effect of this reset process, easily the pixel of display can be divided into two (or more) group, and provide dissimilar reset pulse to different groups.More particularly, if need to use reset pulse drive any given black and white between the pixel that replaces, easily pixel can be divided at least two groups, and arrange drive scheme make one group of pixel driving for white and simultaneously another group drive as black.This two groups the space distribution provided is that selection meticulously and pixel are all enough little, user experiences reset process just as gradation intervals (preferably some slight flashing) over the display, and such gradation intervals induces one to detest unlike a series of black and white flicker usually.

Such as, in such " two groups of resets " step of a kind of form, the pixel on odd column can be assigned as " very " group, and the pixel in even column is assigned to second " idol " group.Then odd number pixel can be used in the drive scheme shown in Fig. 9, and even pixels can use the mutation of this drive scheme, and wherein in erase step, pixel is not be driven to black state but white state.Then these two groups of pixels all can experience even number reset pulse in reset process 304 ', substantially can separate 180 degree of phase places like this, and display are shown as ash in whole reset process for this reset pulse of two groups.Finally, in step 306 ' the second image address period, odd number pixel is from the black end-state being driven into them, and even pixels is from being driven into their end-state in vain.In order to ensure each pixel that resets in the same way in the very long time (and the method resetted like this does not cause any noise over the display), it is favourable between consecutive image, switching this drive scheme for controller, like this when a series of new images is written to display, each pixel is alternately written to its end-state from black and white state.

Obviously, can use and form first group by the pixel in odd-numbered line and pixel in even number line forms the similar scheme of second group.In another similar drive scheme, first group of pixel be included in odd column and odd-numbered line, and even column and even number line, and second group of pixel be included in odd column and even number line, and even column and odd-numbered line, press checkerboard pattern and arrange for such two groups.

Replace or except pixel being divided into two groups and arranging reset pulse in a group and the difference 180 degree of phase places in another group, pixel can be divided into the group being used in different reset pulses distinct in quantity and pulsed frequency.Such as, one group can use 6 pulsed reset sequences as shown in Figure 9, and second group of 12 pulse that can use similar doubled frequency.In a more accurate scheme, pixel can be divided into four groups, and but first and second groups use 6 pulse protocol difference 180 degree phase places each other, and third and fourth group uses 12 pulse protocol but differ 180 degree of phase places each other.

The another program of the adverse effect reducing reset process is illustrated as now with reference to Figure 11 A and 11B.In this scenario, pixel is divided into two groups again, by drive scheme shown in Figure 11 A the first (even number) group and press second (odd number) group of the drive scheme shown in Figure 11 B.Equally in this scenario, all gray levels in black and white centre are divided into first group of the contiguous dull gray level against black level, and second group of the contiguous bright grey level against white level, be the same for two groups of this point-scores of pixel.Expect but not necessarily, there is in these two groups the gray level of identical number; If there is odd number gray level, so intergrade can be randomly assigned to arbitrary group.For convenience of explanation, Figure 11 A and 11B illustrates that this drive scheme provides 8 grades of gray scale displays, is appointed as the grade of 0 (black) to 7 (in vain); Gray level 1,2 and 3 is dull gray levels, and gray level 4,5 and 6 is bright grey levels.

In the drive scheme of Figure 11 A and 11B, the conversion according between following rule control gray scale:

A () first, even number set pixel, in the conversion to dull gray level, the final pulse provided always one be tending towards white pulse (namely, one have tend to pixel from its black state to the pulse of the polarity of its white state-driven), otherwise in the conversion to bright grey level, the final pulse provided always one be tending towards black pulse.

(b) secondly, odd number group pixel, in the conversion to dull gray level, the final pulse provided always one be tending towards black pulse, and in the conversion to bright grey level, the final pulse provided always one be tending towards white pulse.

C (), when all, after obtaining white state, being tending towards black pulse can only after being tending towards white pulse, and after obtaining black state, and being tending towards white pulse can only after being tending towards black pulse.

D () even pixels singlely can not be tending towards black pulse and is driven into black from a dull gray level by one, odd number pixel also can not use one to be singlely tending towards white pulse from bright grey level in vain.(obviously, in both cases, one can only be used finally to be tending towards white pulse and to obtain white state, also can only finally be tending towards black pulse with one and obtain black state.)

The application of these rules allows a conversion realized between gray scale maximum in use three continuous print pulses.Such as, Figure 11 A shows through from black (0 grade) to an even pixels of the conversion of gray level 1.This obtains with the independent white pulse (be certainly expressed as in Figure 11 A one positive slope) that is tending towards being designated as 1102.Then, pixel driving to gray level 3.Because gray level 3 is dull gray levels, with good grounds rule (a) it must be tending towards white pulse by one and realize, and 1 grade thus/3 grades conversions can be controlled by the independent white pulse 1104 that is tending towards, it has a pulse difference with pulse 1102.

Now pixel driving is arrived gray level 6.Because this is a bright gray level, according to rule (a), it must be tending towards black pulse by one and realizes.Therefore, the application of rule (a) and (c) needs the conversion being realized 3 grades/6 grades by two pulse trains, namely one first is tending towards white pulse 1106 pixel driving to white (7 grades), and and then one is tending towards black pulse 1108 pixel from 7 grades of second of being driven into 6 grades of expectation.

Then pixel driving to gray level 4.Because this is a bright gray level, according to a foregoing very similar theory for 1 grade/3 grades conversions, independent be tending towards the conversion that black pulse 1110 realizes 6 grades/4 grades by one.Ensuing conversion is to 3 grades.Because this is a dull gray level, according to a foregoing very similar theory for 3 grades/6 grades conversions, the conversion of 4 grades/3 grades is controlled by two pulse trains, namely one first is tending towards black pulse 1112 pixel driving to black (0 grade), and and then one is tending towards white pulse 1114 pixel from 0 grade of second of being driven into 3 grades of expectation.

Final conversion shown in Figure 11 A is the conversion from 3 grades to 1 grade.Because this is a dull gray level, according to rule (a), it must be tending towards white pulse by one and realizes.Therefore, application rule (a) and (c), 3 grades/1 grade conversion must be controlled by a three-pulse sequence, this pulse train comprises one and pixel driving first is tending towards white pulse 1116 to white (7 grades), pixel driving second is tending towards black pulse 1118 to black (0 grade) by one, and one by pixel from the black pulse 1120 being driven into the 3rd of expectation 1 grade of state and being tending towards white.

Figure 11 B shows the sequence of the 0-1-3-6-4-3-1 grey states as the even pixels in Figure 11 A that an odd number pixel realizes.But can see, pulse train used is very different.Rule (b) needs to be tending towards black pulse by one and realizes a dull gray level 1 grade.Therefore, 0-1 conversion is, by one, pixel driving first is tending towards white pulse 1122 to white (7 grades), follow one by pixel from 7 grades be driven into 1 grade of expectation be tending towards that black pulse 1124 realizes.1-3 changes needs three-pulse sequence, pixel driving first is tending towards black pulse 1126 to black (0 grade) by one, pixel driving second is tending towards white pulse to white (7 grades) by one, and a pulse 1130 that pixel is driven into the 3rd of 3 grades of expectation is tending towards black from 7 grades.Ensuing conversion is to being 6 grades of bright grey level, according to rule (b), this is tending towards white pulse by one to realize, and 3 grades/6 grades conversions are comprised pixel driving to be tending towards black pulse 1132 and one by the two pulse trains realizations of pixel driving to 6 grades of expectation be tending towards white pulse 1134 to black (0 grade).6 grades/4 grades conversions are realized by a three-pulse sequence, namely pixel driving is tending towards white pulse 1136 to white (7 grades) by one, pixel driving is tending towards black pulse 1138 to black (0 grade) by one, and one by pixel driving to 4 grades that expect be tending towards white pulse 1140.4 grades/3 grades conversions are comprised pixel driving to be tending towards white pulse 1142 to white (7 grades), and and then pixel driving realizes to two pulse trains of 3 grades of expectation be tending towards black pulse 1144 by one.Finally, 3 grades/1 grade conversion is realized by the independent black pulse 1146 that is tending towards.

Can find out that this drive scheme guarantees that each pixel is gone along " sawtooth " shape from Figure 11 A and 11B, wherein not changing in nyctitropic situation (although obviously pixel can in arbitrary intermediate grey scales static short or long cycle) each pixel from black be transformed into white, and black from being transformed in vain when not change direction subsequently.Thus, rule (c) above and (d) can be replaced by single rule (e) below:

(e) once pixel by a single polarity pulse from an extreme optical state (namely, white or black) drive to contrary extreme optical state, so before it arrives foregoing contrary extreme optical state, pixel no longer receives the pulse of opposite polarity.

Thus this drive scheme guarantee a pixel at most only experience equal (N-1)/2 time number object and change, wherein N is being driven into the number of grayscale levels before an extreme optical state; The serial distortion that the slight errors (in the voltage such as provided by driver, unavoidable minor swing causes) that this prevent in each conversion is ad infinitum gathered in a gray level image is obvious degree for observer.In addition, this drive scheme is designed to even number and odd number pixel always arrives given intermediate grey scales the other way around, that is, the final pulse in sequence is be tending towards white and be tending towards black in another case in one case.If keep the effective coverage of the even number of basic equal amount and the display of odd number pixel to be written to a single gray level one, so " reverse direction " characteristic can make the flicker in this region minimize.

Other is driven in two discrete groups to the drive scheme of pixel, for described similar reason above, when performing the sawtooth drive scheme of Figure 11 A and 11B, concentrate one's energy to arrange pixel by even number and odd number group.This arrangement needs to guarantee that on display, any substantially adjacent region will keep the odd and even number pixel of basic equal number, and the full-size of the adjacent image point block of identical group will enough littlely make general viewers to offer an explanation easily.As mentioned above, these requirements can be met with checker board pattern arrangement two group of pixels.Random screen technology also may be used for the arrangement of two groups of pixels.But in sawtooth drive scheme, the use of checker board pattern can be tending towards the power consumption increasing display.In arbitrary given row in such pattern, adjacent image point can belong to contrary group, and all stand at all pixels in the adjacent area of the basic size of same grey level transition (general case), in arbitrary preset time, adjacent image point is tending towards the pulse needing opposite polarity.When each new row will be write, the pulse of opposite polarity is provided to need the row to display (source) electrode discharge and recharge to continuous pixel in arbitrary row.The technician in Active Matrix Display field is driven all to know, the electric discharge of row electrode and to recharge be a principal element of power consumption for displays.Therefore, chessboard distribution makes the power consumption of display be tending towards increasing.

To avoid between the adjacent area of identical group of large pixel reasonably compromise to be that the pixel in every group is distributed into rectangle in power consumption and expectation, the pixel in this rectangle all only continues several pixel along these row in same column.With such arrangement, when overwritten area has identical gray level, only have and just can need the electric discharge of row electrode when being switched to another rectangle from a rectangle and recharging.Desirable rectangle is 1 × 4 pixel, and the rectangle be arranged in adjacent column can not terminate in the same row, that is, the rectangle in adjacent column can have different " phase place ".In each row, rectangle can realize with method that is random or circulation to the distribution of phase place.

A benefit of the sawtooth drive scheme shown in Figure 11 A and 11B is, as a part for display whole updating, any monochromatic areas of image can be black in white or upgrade to black Sing plus in vain with one simply.The maximum time spent for rewriteeing such monochromatic areas just rewrites the half needing the maximum time of transition region between gray scale, and the use of this feature is conducive to the character as user's input, the quick renewal of the characteristics of image such as drop-down menu.Controller can check image upgrade the need of the conversion between any gray scale; If do not needed, need the image-region rewritten can use fast monochrome generation patterns to rewrite.Thus, user can have input character, and the quick renewal of other and user interaction features of drop-down menu and display, it seamlessly coordinates with the slower renewal of ordinary gamma image.

As described in the patent application serial numbers 09/561424 and 09/520743 of CO-PENDING above, in a lot of electro-optical medium, particularly based on the electrophoretic medium of particle, direct current (DC) balance for driving the drive scheme of such medium to have in whole expanded period meaning is desirable, zero or as far as possible close to zero, the design of drive scheme of the present invention will be devoted to this standard is should be by the algebraic sum of the electric current of particular pixels.More specifically, the question blank used in the present invention will be designed to make any conversion sequence of the extreme optical state (black or white) starting or end at pixel should be DC balance.According to mentioned above, can first find out due to this pulse, so it is substantially constant for changing required electric current between arbitrary specific gray scale thus by pixel, so such DC balance may not realize.But, this is just genuine for first approximation, empirically find, at least when the electrophoretic medium based on particle (and being genuine equally in the situation of other electro-optical medium), (for example) provides the effect of the 50ms pulse at 5 intervals and provides the different of identical voltage 250ms pulse to pixel to pixel.Therefore, for obtain given conversion and by the electric current of pixel in have that some are flexible, this flexibility may be used for the acquisition participating in DC balance.Such as, the multiple pulses being used for given conversion can store together with the total current value provided by each in these pulses by the question blank used in the present invention, controller can keep one to work from certain the register being provided to the pulse algebraic sum of pixel for storing in the front time (such as, rising since pixel being maintained black state) for each pixel.When will a particular pixels from white or grey states is driven into black state time, controller can check the register relevant to this pixel, determine the electric current needed for DC balance from original black state to the whole conversion sequence of black state on the horizon, and select to store for one of some pulses needed for white/ash to black conversion, corresponding registers accurately can be reduced to zero by any one in them, or be at least reduced to residual value (wherein corresponding registers can keep this residual value and is added on provided electric current in next one conversion) little as far as possible.Can find out that the application repeatedly of this process can obtain the accurate long-term DC balance of each pixel.

It should be noted that the sawtooth drive scheme shown in Figure 11 A and 11B is very suitable for using such DC balance technology, can only through the conversion of effective quantity because this drive scheme is guaranteed between the continuing through of any given pixel through black state, and in the conversion of its half, have a pixel can by black state in fact on an average.

By the ill-effect using local instead of overall renewal can reduce reset process further, namely by only rewriteeing the part only changed between consecutive image in display, the part that will rewrite can be selected on " locally " region or the basis of pixel one by one.Such as, when such as illustrate component movement in plant equipment figure or in the figure of accident reconstruction, be not difficult to find a series of images of wherein smaller object relative to larger static background movement.In order to use local updating, controller needs final image to compare with initial pictures and determines which region is different and then need rewriting between the two figures.Controller can determine one or more regional area, be generally have with pixel grillages row limit preserve the rectangular area that will upgrade pixel, or can only determine need upgrade independently pixel.The arbitrary drive scheme described thus may be used for only upgrading the regional area or independently pixel determined as needing to rewrite.Such local updating scheme fully can reduce the power consumption of display.

Feature according to certain electric optical display unit used can change above-mentioned drive scheme in a variety of ways.Such as, many reset process can be saved in above-mentioned drive scheme in some cases.Such as, if electro-optical medium used be very macrocyclic bistable state (namely, the gray level of write pixel is only with time variations slowly), and the pulse change needed for the particular conversion of carrying out with this cycle for the pixel being in its initial gray state is little, question blank can be arranged to the intervention not turning back to black or white state and the conversion directly realized between grey states, after a basic cycle, only when pixel can cause the reset just carrying out display during the appreciable error of present image from " skew " gradually of their nominal gray level.Thus, such as, if display of the present invention is used as electronic book reader by user, before the reset needing display, it can show the information of many screens, empirically, have been found that and use suitable waveform and driver, can show before needing to reset as the information more than 1000 screens, so in fact can not need to reset between the usual read period to electronic book reader.

The personnel in display technique field are easy to find out that isolated system of the present invention can at different conditions for providing with many different drive schemes.Such as, due in the drive scheme shown in Fig. 9 and 10, reset pulse consumes part very little in display total power consumption, so can come together to provide controller with the first drive scheme of frequency interval reset display, gamma error is made to minimize like this, and only with the alternative plan of longer interval reset display, allowed larger error like this but reduced power consumption.Manually or by means of external parameter can realize the switching between two schemes; Such as, if display is used as portable computer, the first drive scheme can be used when computer runs on primary power, and can alternative plan be used when computer runs on internal cell power supply.

According to noted earlier, can find out and the invention provides a kind of driver controlled for electro-optic displays operation, it is very suitable for the feature of bistable electro phoretic display based on particle and similar display.

According to noted earlier, can find out the invention provides and a kind ofly control method that electro-optic displays runs and controller, it allows when not needing whole display with the accurate control of frequency interval to gray scale when the flicker of the inconvenience of its extremity.The present invention also, while reduction power consumption for displays, allows the accurate control of display regardless of temperature and the change of its running time.Because controller can use available parts commercially to form, so can realize these advantages at an easy rate.

In residual voltage method of the present invention, expect by high impedance voltage measuring equipment to realize the measurement of residual voltage, such as a kind of metal-oxide semiconductor (MOS) (MOS) comparer.When display a kind ofly has little pixel, such as per inch 100 point (DPI) matrix display, wherein each pixel has 10 ^-4square inch or about 6 × 10mm ²area, when so single pixel resistance arrive 10 ¹²during the quantitative value of ohm, comparer needs to have extremely low input current.But suitable comparer is easy to commercially obtain; Such as, the INA111 chip as the Texas Instrument with the input current being only about 20pA is suitable.(technically, this integrated circuit is a kind of instrumentation amplifier, but if its output enters a Schmidt trigger, it can be used as a comparer and uses.) for the display with large single pixel, large Direct driver display (specifying below) such as indicating, each pixel may have the region of several square centimeters, not very high to the requirement of comparer, substantially all business FET input comparators can use, such as, from the LF311 comparer of National Semiconductor.

Personnel for electronic display technology field are easy to find out; in order to expense and other reason; the electronic console of large-scale production can have the driver of special IC (ASIC) form usually; in such display, comparer can provide as a part of ASIC usually.Although this approach can need the feedback circuit be provided in ASIC, this has the advantage making the power supply of ASIC and oscillating part simpler and less on area.If need 3 grades of normal image stream drivers, this method can also make the drive part of ASIC simpler and less on area.Thus, this method can reduce the cost of ASIC usually.

Easily, use one to provide driving voltage, make pixel electrical short or floating driver to provide driving pulse.When using such driver, on each addressing period realizing DC balance correction, pixel is addressed, and then electrical short floats.(term " addressing period " conventional sense in electro-optic displays technology refers to the total cycle needed for over the display from the first image change to the second image as used herein.As noted above, due to electrophoretic display device (EPD) lower be generally tens to the switch speed of the hundreds of millisecond order of magnitude, an independent addressing period can comprise the scanning of many complete displays.) after of short duration time delay, comparer for measuring the residual voltage by pixel, and determines it is just or negative on symbol.If residual voltage is just, so controller can extend the cycle (or increasing its voltage a little) of negative addressing pulse a little in next addressing period.If but residual voltage is negative, so controller can extend the cycle (or increasing its voltage a little) of positive addressing voltage pulse a little in next addressing period.

Thus, electro-optical medium is just being placed on a kind of feedback circulation of switching regulator by residual voltage method of the present invention, by regulating the length of addressing pulse by residual voltage towards zero driving.When residual voltage close to zero time, media table reveals desirable performance and the life-span of raising.Especially, of the present invention use allows to improve the control to gray scale.As noted, seen that the gray level obtained in electro-optic displays is one and starts gray level and the pulse that provides, and display is at the function of front state.Believe that one of reason of this " history " effect in (although the present invention not by this restriction believed) gray level is the electric field that residual voltage acts on electro-optical medium and experiences; The actual electric field affecting medium state is the virtual voltage sum applied by electrode and residual voltage.Thus, ensure that the electric field experienced by electro-optical medium accurately corresponds to the voltage provided through electrode according to the control of the present invention to residual voltage, allow the control improving gray scale thus.

Residual voltage method of the present invention is particularly useful in the display of so-called " Direct driver " type, this display is divided into each a series of pixels providing separate mesh electrode, and this display comprises further for the independent switching device shifter controlling to be applied to the voltage of each separate mesh electrode.Such Direct driver display is useful for the display of the limited character group of text or other such as many numeral, and is especially described in aforementioned International Publication No. 00/05704.But residual voltage method of the present invention can also be used for the display of other type, such as, have the Active Matrix Display of transistor matrix, wherein at least one transistor is connected with each pixel of display.Pixel capacitors is connected to source electrode by the gate line of the thin film transistor (TFT) (TFT) of the driving used in such Active Matrix Display.Residual voltage is compared and is less than grid voltage (absolute value of residual voltage generally can not more than 0.5V), and therefore gate drive voltage can conducting TFT all the time.Then source electrode line can be that electricity floats, and is connected to MOS comparer, allows the residual voltage of each independent pixel reading Active Matrix Display thus.

Although it should be noted that residual voltage on the pixel of electrophoretic display device (EPD) closely can connect with the degree of electric current of the pixel flowing through DC balance, zero residual voltage need not mean desirable DC balance.But from practical point of view, this has no difference because be residual voltage instead of DC balance history to the adverse effect that herein means out be responsible for.

Personnel for display technique field are easy to find out, object due to residual voltage method of the present invention reduces residual voltage and direct current imbalance, so this method need not use in each addressing period of display, it provides to prevent the long-term direct current formed in particular pixels uneven with suitable frequency.Such as, the display using " refreshing " or " blanking " pulse with interval is needed if a kind of, so in refreshing or blanking pulse, all pixels are driven to identical display state, normally a kind of extreme display state (or, more generally, can first by all pixel driving to one of extreme display state, then arrive another extreme display state again), this method of the present invention can refreshing or blanking pulse in use.

Although residual voltage method of the present invention has carried out description roughly in the application of encapsulated electrophoretic display, this method also may be used for encapsulation electrophoretic display device (EPD), and the display of other type, such as, show the electrochromic display device (ECD) of residual voltage.

Described in above, can find out that residual voltage method of the present invention provides a kind of for driving the method for electrophoresis and other electro-optic displays, it is in the display serviceable life providing increase, strengthen action pane and long-term display optical performance while, decrease the expense of the pixel DC balance equipment needed thereby for guaranteeing display.

Claims

1. one kind drives the method for bistable electro-optic displays, described display comprises bistable state electric light dielectric layer, is arranged on the side of described electro-optical medium layer and the first and second pixel capacitors limiting the first and second pixels of described display and the public electrode be arranged on the opposite side of described electro-optical medium layer, and described method comprises:

A first public electrode voltages is applied on public electrode by (), first gamma electric voltage is applied in described first pixel capacitors, and described first public electrode voltages is applied in described second pixel capacitors, thus be applied on described first pixel of described display with a direction by electric field, and there is no that electric field is applied on the second pixel; And

B the second public electrode voltages being different from described first public electrode voltages is applied on described public electrode by (), described second public electrode voltages is applied in described first pixel capacitors, and the second gamma electric voltage is applied in described second pixel capacitors, thus substantially do not apply electric field on described first pixel of described display, and electric field is applied on described second pixel of described display with contrary direction.

2. method as claimed in claim 1, wherein said displaying appliance has the device for generation of multiple different gamma electric voltage, described first public electrode voltages is set to maximum gamma electric voltage and described second public electrode voltages is set to minimum gamma electric voltage.

3. method as claimed in claim 2, is wherein arranged on described gamma electric voltage between described first and second public electrode voltages with linear gradient.

4. method according to claim 1, wherein repeatedly repeats step (a) and (b) in a rewriting period of display.

5. method according to claim 4, the applying step (a) wherein replaced in continuous print rewriting period and (b).

6. bistable electro-optic displays comprise bistable state electric light dielectric layer, be arranged on the side of described electro-optical medium layer and limit the first and second pixels of described display the first and second pixel capacitors, be arranged on the public electrode on the opposite side of described electro-optical medium layer and the display controller for controlling the voltage be applied on described first and second pixel capacitors and public electrode, described controller is set to:

7. display according to claim 6, there is the device for generating multiple different gamma electric voltage, and wherein said display controller is set to described first public electrode voltages to be arranged to equal maximum gamma electric voltage, and described second public electrode voltages is arranged to equal minimum gamma electric voltage.

8. display according to claim 7, wherein said gamma electric voltage is set to linear gradient.

9. display according to claim 7, wherein said controller is set to repeatedly repeat (a) and (b) in a rewriting period of described display.

10. display according to claim 9, wherein said controller is set to alternately apply (a) and (b) in continuous print rewriting period.