CN101533609A - Electro-optic displays and methods for controlling the same - Google Patents

Electro-optic displays and methods for controlling the same Download PDF

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CN101533609A
CN101533609A CNA200910128714XA CN200910128714A CN101533609A CN 101533609 A CN101533609 A CN 101533609A CN A200910128714X A CNA200910128714X A CN A200910128714XA CN 200910128714 A CN200910128714 A CN 200910128714A CN 101533609 A CN101533609 A CN 101533609A
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voltage
electro
display
pixel
common electrode
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CN101533609B (en
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H·G·加特斯
K·R·阿蒙森
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E Ink Corp
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E Ink Corp
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Abstract

The invention relates to electro-optic display and method for controlling the same. The electro-optic display comprises a bistable electro-optic medium, a plurality of pixel electrodes, with associated non-linear elements, and a common electrode, disposed on opposed sides of the electro-optic medium. The display has a writing mode, in which at least two different voltages are applied to different pixel electrodes, and a non-writing mode in which the voltages applied to the pixel electrodes are controlled so that any image previously written on the electro-optic medium is substantially maintained. The display is arranged to apply to the common electrode a first voltage when the display is in its writing mode and a second voltage, different from the first voltage, when the display is in its non-writing mode.

Description

The method of electro-optic displays and operation electro-optic displays
The application is that application number is 200480023730.8, the applying date is on August 19th, 2004, denomination of invention is divided an application for the application for a patent for invention of " method of control electro-optic displays ".
Technical field
The present invention relates to control the method for electro-optic displays.In one aspect, the present invention relates in electro-optic displays, provide the reduction power rating, more particularly, relate to a kind of active matrix electro-optic displays that utilizes the bistable electro-optical medium, described display is equipped with the device that is used for controlling in the non-write state process of display the current potential of common electrode.On the other hand, the present invention relates to be used for controlling the method for electro-optic displays electrode voltage, more particularly, relate to the voltage method that is used to control the public preceding electrode that is applied to the active matrix electro-optic displays that utilizes the bistable electro-optical medium.
Background technology
Electro-optic displays comprises electro-optical material layer, refer to have the material of first and second different at least a optical characteristics show states with it at this term that uses on the traditional sense of imaging technique herein, described material is by applying electric field and change into its second show state from its first show state to described material.Although described optical characteristics generally is appreciable to the human eye color, but it can be another kind of optical characteristics, such as light transmission, reflectance, luminous, or under the situation of the display that designs for the machine reading, in the pseudo-colours that exceeds on the electromagnetic wavelength reflectance variation meaning of visible-range.
The ＂ of the term ＂ bistable of using on its traditional sense in imaging technique herein is meant that with ＂ bistable state ＂ display comprises the display element with first and second different at least a optical characteristics show states, and after making that any given element has driven by means of the addressing pulse of a limited duration, just take its first or second show state, after described addressing pulse finishes, described state will continue to change the several times at least of the minimum duration of the required addressing pulse of described status display module, for example, at least four times.Laid-open U.S. Patents application No.2002/0180687 shows, some electrophoretic display device (EPD) based on particle that can carry out the gray scale demonstration is stable at their extreme black and white state not only, and also be stable in their gray states of centre, the electro-optic displays situation of some other type also is like this.The display of described type should be called ＂ multistable ＂ rather than bistable state, although for simplicity, can not only cover bistable but also cover the multistable display with term ＂ bistable ＂ here.
The electro-optic displays that several types are arranged is known.For example, as in U.S. Patent No. 5,808,783; 5,777,782; 5,760,761; 6,054,071; 6,055,091; 6,097,531; 6,128,124; 6,137,467; With 6,147, described in 791, one type electro-optic displays is that the double-colored member type of rotation is (although the display of described type often is called ＂ rotation twin color ball ＂ display, it is a kind of appellation more accurately that but term ＂ rotates double-colored member ＂, because be not sphere at rotating member described in some above-mentioned patents).A kind of display like this uses a large amount of wisps (spherical in shape or cylindrical), and they have two or more cross sections, have different optical characteristic and internal dipole.These objects are suspended in the cavity of the full of liquid in the matrix, and described cavity filling liquid makes described object to rotate freely.Apply electric field thereon, thereby described object rotates to different positions and change object towards the cross section of watching the surface, the outward appearance of described display is changed.
The electro-optic displays of another kind of type uses electrochromic media, for example, take the electrochromic media of nanometer variable color film (nanochromic film) form to comprise the electrode that at least a portion ground is formed by semiconduction metal oxide and a plurality of dye molecule, reversible change color can take place in dye molecule, is attached on the described electrode; For example, see people such as O ' Regan B., Nature1991,353,737; And Wood D., Information Display, 18 (3), the article of 24 (March2002).Other sees Bach, people Adv.Mater. such as U., 2002,14 (11), 845 article.The nanometer variable color film of described type is also for example being described in U.S. Patent No. 6,301,038, the open No.WO01/27690 of international patent application and the U.S. Patent application 2003/0214695.The medium of described type generally also is bistable.
The electro-optic displays of another kind of type that has become the problem of broad research and exploitation for many years is based on the electrophoretic display device (EPD) of particle, and wherein a plurality of charged particles move by suspending liquid under electric field effects.Compare with LCD, electrophoretic display device (EPD) can have good attribute in brightness and contrast, wide wide viewing angle, bistable state and low-power consumption.Yet the long-term image quality problem of these displays has hindered their extensive employing.For example, the particle that constitutes electrophoretic display device (EPD) often precipitates, and causes these displays to fall short of serviceable life.
The patent and the application of recently disclosed many name applications with Massachusetts Institute of Technology (MIT) (MIT) and E Ink company, the description encapsulated electrophoretic medium.Such sealing medium comprises many Caplets, and wherein each itself comprises a kind of inner phase again, comprise movably particle of the electrophoresis that is suspended in the liquid suspension medium, and capsule wall surrounds described inner phase.Generally, they itself are maintained at described capsule in the polymeric binder, form a relevant layer that is positioned between two electrodes.The sealing medium of described type is for example, U.S. Patent No. 5,930,026; 5,961,804; 6,017,584; 6,067,185; 6,118,426; 6,120,588; 6,120,839; 6,124,851; 6,130,773; 6,130,774; 6,172,798; 6,177,921; 6,232,950; 6,249,721; 6,252,564; 6,262,706; 6,262,833; 6,300,932; 6,312,304; 6,312,971; 6,323,989; 6,327,072; 6,376,828; 6,377,387; 6,392,785; 6,392,786; 6,413,790; 6,422,687; 6,445,374; 6,445,489; 6,459,418; 6,473,072; 6,480,182; 6,498,114; 6,504,524; 6,506,438; 6,512,354; 6,515,649; 6,518,949; 6,521,489; 6,531,997; 6,535,197; 6,538,801; 6,545,291; 6,580,545; 6,639,578; 6,652,075; 6,657,772; 6,664,944; 6,680,725; 6,683,333; 6,704,133; 6,710,540; 6,721,083; 6,724,519; 6,727,881; 6,750,473; And6,753,999; With U.S. Patent Application Publication No.2002/0019081; 2002/0021270; 2002/0053900; 2002/0060321; 2002/0063661; 2002/0063677; 2002/0090980; 2002/0106847; 2002/0113770; 2002/0130832; 2002/0131147; 2002/0145792; 2002/0171910; 2002/0180687; 2002/0180688; 2002/0185378; 2003/0011560; 2003/0020844; 2003/0025855; 2003/0034949; 2003/0038755; 2003/0053189; 2003/0102858; 2003/0132908; 2003/0137521; 2003/0137717; 2003/0151702; 2003/0189749; 2003/0214695; 2003/0214697; 2003/0222315; 2004/0008398; 2004/0012839; 2004/0014265; 2004/0027327; 2004/0075634; 2004/0094422; 2004/0105036; With 2004/0112750; And the open No.WO 99/67678 of international patent application; WO 00/05704; WO 00/38000; WO 00/38001; WO 00/36560; WO 00/67110; WO 00/67327; WO 01/07961; WO 01/08241; WO 03/092077; WO 03/107315; With describe among the WO2004/049045.
Above-mentioned many patents and application are recognized, the wall portion that surrounds discrete micro-capsule in encapsulated electrophoretic medium can replace with external phase, thereby, produce a kind of so-called ＂ polymer-dispersed electrophoretic display ＂, wherein said electrophoretic medium comprises a plurality of discrete electrophoresis droplets and the external phase of polymeric material, and the discrete electrophoresis droplet in such polymer-dispersed electrophoretic display can be regarded as capsule or micro-capsule, although the discrete capsule film that is not associated with each independent drop; For example, see above-mentioned 2002/0131147.Correspondingly, for the application's purpose, such polymer-dispersed electrophoretic media is counted as the subclass of encapsulated electrophoretic medium.
Encapsulated electrophoretic display does not generally have traditional electrophoresis device to assemble and the problem of precipitation failure mode, and in addition, it also has such as can or being coated on advantage on the substrate of various flexibilities and rigidity the display printing.Want to comprise whole forms of printing and coating when using ＂ printing ＂ one speech, include, but is not limited to: scheduled volume (pre-metered) coating, such as repairing punch die coating, slit or extrusion coated, slip or lamination coating, sheltering coating; Print roll coating is such as knife over roll coating, two-way print roll coating; The intaglio plate coating; Dip-coating; Spraying; Meniscus (meniscus) coating; Spin coating; Brush; The air knife coating; Serigraphy is handled; Xeroprinting is handled; The hot stamping brush is handled; Ink jet printing is handled; And other similar techniques.Thereby the display of gained can be flexible.In addition, because display medium can print (utilizing various methods), so display itself can be with cheap cost production.
The electrophoretic medium that has two above type electrophoresis particles in the single capsule has been described in above-mentioned some patent of E Ink and MIT and application.For current purpose, so many granule mediums are counted as the subclass of two granule mediums.
A kind of electrophoretic display device (EPD) of correlation type is so-called ＂ micro element electrophoretic display device (EPD) ＂.In the micro element electrophoretic display device (EPD), charged particle and suspending liquid are not sealed in the capsule, but maintain in the mounting medium, generally are in a plurality of holes that form in the thin polymer film.For example, see open No.WO 02/01281 of international patent application and U.S. Patent Application Publication No.2002/0075556, both all transfer Sipix Imaging, Inc. (company).
Although electrophoretic medium is opaque often (for example, because in many electrophoretic mediums, particle block visible light basically sees through described display), and operate under the reflection mode, many electrophoretic display device (EPD)s may operate under the so-called ＂ optical gate mode ＂, one of them show state is opaque basically, and one is printing opacity.For example, see above-mentioned U.S. Patent No. 6,130,774 and 6,172,798 and U.S. Patent No. 5,872,552; 6,144,361; 6,271,823; 6,225,971; And 6,184,856.Be similar to electrophoretic display device (EPD), but depend on electric field intensity change dielectrophoretic displays, may operate under the similar mode; See U.S. Patent No. 4,418,346.The electro-optic displays of other type perhaps also can operate under the optical gate mode.
In order to obtain the high resolving power electro-optic displays, each pixel of described display must be able to be addressed, and don't disturbs neighbor.An approach that reaches this purpose is the array that non-linear element is set, and it can be transistor or diode, has the nonlinear element that at least one is associated with each pixel of described display.The pixel on related pixel next door or addressing electrode are connected to the driving circuit that is used to control described display operation by nonlinear element.Be equipped with the display of such nonlinear element to be called ＂ active matrix ＂ display.
Generally, such Active Matrix Display adopts two dimension (＂ XY ＂) addressing scheme, has many data lines and many selection wires, and each pixel is defined by the intersection point of a data line and a selection wire uniquely.By applying voltage to a specific selection wire, just (the supposition here of selected delegation, described selection wire defines the row of described matrix, and described data line definition row, this is arbitrarily, can do opposite appointment in case of necessity but obviously), adjust the voltage on data line or the alignment, so that make the pixel in the described select row that required optic response is provided.Thereby the pixel electrode voltage in the select row rises to and approaches, but the voltage on (owing to the reason that the following describes) inaccurate data line that is associated that equals them.By applying voltage to next bar selection wire, selected next line pixel is so that write whole display line by line then.
When described nonlinear element is transistor (generally being thin film transistor (TFT) (TFT)), traditional way is that data and selection wire and transistor are arranged on a side of electro-optical medium, and the single common electrode of the extension of crossing over many pixels and general whole display is arranged on an opposite side of electro-optical medium.For example, see above-mentioned WO 00/67327, it describes a such structure, wherein data line is connected to the source electrode of tft array, pixel electrode is connected to the drain electrode of described TFT, and selection wire is connected to the grid of described TFT, and single common electrode is arranged on the opposite side of electro-optical medium.Described common electrode operated by rotary motion is watched face (that is, the surface of the display that the observer watches) described display.In writing the display process, common electrode remains under the fixing voltage, is called ＂ common electrode voltage ＂ or ＂ common plane voltage ＂, and generally is abbreviated as ＂ V COM＂.Common plane voltage can have any value easily, because it is the difference between common plane voltage and the voltage that is applied to the optical states that influences the different pixel of electro-optical medium on the different pixel electrodes.The electro-optical medium of most of type is to polarity and the electric field amplitude sensitivity that applied, thereby, must be driven into voltage to pixel electrode above and below common plane voltage.For example, common plane voltage can be 0, and pixel electrode changes from-V to+V, and wherein V is any maximum voltage arbitrarily.As another program, common practices be common plane voltage is remained on+V/2 on, and allow pixel electrode change from 0 to+V.
Important use of bistable electro-optical medium is on portable electron device, and such as PDA(Personal Digital Assistant) and cellular telephone, wherein the electric battery life-span is an important consideration, thereby hope reduces the power consumption of display as far as possible.LCD is not bistable, so image writes such display, if want described image still as seen, must constantly refresh.The power that like this constantly consumes in the refresh process at figure is the main leakage point of electric battery.Otherwise bistable electro-optic displays only need write once, and after this bistable medium will be kept one period considerable time of image, and needn't anyly refresh, thereby, reduce the power consumption of display widely.For example, the electrophoretic display device (EPD) based on particle shows that image can be adhered to several hours even several days.
Thereby, between image update, stop to scan the active matrix bistable electro-optic displays, help saving electric power.In some cases, cut off fully and be used for driving the driver of described display and the power supply of common plane circuit, even can save more electric power.
But, must realize non-writing mode (, being called ＂ non-scanning ＂ or ＂ zero energy ＂ mode) and remarkable as another program.The described display of design and running in such a way, that is, described electro-optical medium display it (scanning) mode that writes and its non-writing mode between do not experience great voltage amplitude transition when switching.
At first sight, appear if to row driver pack into mid-point voltage (that is, the voltage of the mid point of these driver usable range), and not having to stop the gate drivers clock under the chosen situation of grid circuit, can be the way that an acceptable is realized described non-writing mode.But this can cause stable state DC bias current to be applied on the electro-optical medium in practice.Any Active Matrix Display all has and is called as the problem that the logical ＂ of ＂ grid feedthrough or ＂ flyback ＂ cause, wherein the voltage that pixel electrode reached is from some quantity of corresponding row (data) voltage input skew (general 0.5-2V).Described grid feedthrough effect is that the scanning by grid (selection) circuit causes, works by the coupling electrical network between gate line and the source electrode line/pixel electrode.Thereby the voltage that in fact is applied on the pixel electrode moves to negative direction from described row driver voltage because of the grid feedthrough in scanning process.Generally, common plane voltage from its nominal value to the fixing quantity of negative direction skew, so that allow the grid feedthrough to be offset being applied on the voltage of described pixel electrode.When stopping to scan, because the skew that the grid feedthrough causes can not occur, described then row driver mid-point voltage is higher than the required value of generation zero-voltage difference between described common plane and pixel electrode.TFT will under the described bias voltage between described alignment and described pixel electrode the disconnection off-state characteristic according to them correspondingly produce leakage current, and described electric current will flow to common electrode by electro-optical medium from described pixel electrode.The mobile voltage that will produce again of described electric current itself across electro-optical medium, and described voltage is undesirable, because it may be at the described optical states of upsetting electro-optical medium non-write cycle in the process like this, and also may cause material lifetime to shorten and electro-optical medium in the gathering of electric charge, this will negatively influence the optical states that scanning recovers afterwards image subsequently.(show that if be not long-term DC balance by its electric current, some electro-optical medium is subjected to passive influence at least, and such DC is unbalance may cause shortening mission life and other undesirable influences).
In addition, although at first sight, as if when preparing, disconnect the power supply of driving circuit for non-writing mode, only need to disconnect the circuit that bias voltage is provided, or the power circuit of disconnection from such circuit to described driver, but in practice, any one in these two measures all provides undesirable voltage transient to described electro-optical medium probably; Such voltage transient except that other factors, may be by existing stray capacitance caused in traditional active matrix driving circuit.
Summary of the invention
In one aspect, the present invention makes every effort to provide in electro-optic displays realization non-writing mode, and enters and withdraw from equipment and the method that does not cause undesirable voltage transient in the non-writing mode process on described electro-optical medium in described display switching.The present invention also makes every effort to be provided at the non-writing mode of realization in the electro-optic displays, and does not cause undesirable equipment and the method that the voltage deviation of negative influence may be arranged described medium on described electro-optical medium.
Others of the present invention relate to the method for measuring and revising voltage deviation.The source of grid feed-trough voltage has been described above.It is desirable to, the two ends that described grid feed-trough voltage is crossed over all pixels in array and can balance out by described common electrode voltage is applied side-play amount about equally.But, be difficult to apply the bias voltage of almost just offsetting described feed-trough voltage to common electrode.In order to do like this, a kind of device must to be set to determine whether described bias voltage mates described feed-trough voltage exactly, and produce, be provided with and adjust described bias voltage.It is desirable to, described feed-trough voltage is known in advance, and described bias voltage can for good and all and inexpensively be set when making the display electronic circuit.In practice, described electronic circuit and display require bias voltage is done some adjustment after being assembled into last device.
In traditional LCD (LCD), the adjustment of bias voltage can be undertaken by vision; When applying incorrect bias voltage, eyes will be discovered the flicker of display.Adjust by the operator then, change the simulation potentiometer till flicker disappears.
But in based on the electrophoretic display device (EPD) of particle and in the bistable electro-optic displays of most of other type, incorrect bias voltage can not cause any to the visible influence of human eye, unless described bias voltage error is very big.Thereby sizable error can continue and visually invisible on the bias voltage, and these sizable errors do not carry over if do not proofread and correct, and then these sizable errors may have injurious effects to display.Therefore, be desirable to provide very much method beyond some visual observation and detect error in the described bias voltage.In addition, the error of even now in case detect and survey, just can be revised on the same ground with LCD by hand, and so manual correction inconvenience preferably provides some automatically to adjust the way of bias voltage.
The present invention makes every effort to be provided for measuring and revising the equipment and the method for bias voltage.The present invention extends to manual and automatic bearing calibration.
Therefore, in one aspect, the invention provides a kind of electro-optic displays, it comprises:
The bistable electro-optical dielectric layer;
A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer,
The nonlinear element that at least one is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode;
Common electrode, it is in a side opposite with pixel electrode on the electro-optical medium layer; And
The common electrode control device, it is arranged to apply voltage to common electrode,
Described display has: writing mode, and wherein said pixel driving device is added to two different voltages on the pixel electrodes different in described each pixel electrode at least, thereby image is write electro-optical medium; And non-writing mode, wherein said pixel driving device control is applied to the voltage on the described pixel electrode, and any image that writes described electro-optical medium before making is all preserved basically.
Described common electrode control device is arranged to apply first voltage to common electrode, and when described display is in its non-writing mode, apply second voltage that is different from first voltage when described display is in its writing mode.
For simplicity, display of the present invention can be called the variable common plane voltage display of ＂ ＂ hereinafter.Such display has two main modification.In two modification, described common electrode all remains on the predetermined voltage in said write mode process.(this does not get rid of the possibility that described display can have an above writing mode, is applied on the described common electrode at different voltages under the different writing modes.) for example, as in above-mentioned 2003/0137521, discussing, sometimes may preferably use so-called ＂ top plan to switch ＂, wherein said common electrode (for example) 0 and+switch between the V, and the voltage that is applied to described pixel electrode simultaneously changes to+V from 0, when described common electrode is in 0, processed pixels transformation in one direction, and when described common electrode be in+during V, handle the transformation on other direction, for example, if supposition is a black/white display, according to the characteristic of described electro-optical medium, when described common electrode is in 0, can handle the transformation that bleaches (that is, the transformation that the last state of wherein said pixel is brighter than initial state), and when described common electrode be in+during V, can handle the transformation (that is, the transformation that the last state of wherein said pixel is darker than initial state) of blackening.But, in the first main transformer type, when the non-writing mode of described display, the voltage on the described common electrode remains on the fixing ＂ value of a ＂ (adjustment of the method that this may stand to describe below) by described common electrode is connected on voltage supply line or other circuit.In the second main transformer type, when non-writing mode that described display is in, described utility voltage and external voltage source disconnect, and are allowed to the ＂ ＂ that floats.When distinguishing between must these two modification of discussion below, the former is called the two common plane voltage display ＂ of ＂, and the latter will be called the ＂ common electrode display ＂ that floats.
Two common plane voltage displays can comprise:
First voltage supply line, it is arranged to supply with first voltage;
Second voltage supply line, it is arranged to supply with second voltage;
Output line;
Switching device shifter, one that is used for described first and second voltage supply lines is connected to described output line; And
Control line, it is connected to described switching device shifter and is configured to receive the control signal with first or second value,
Described switching device shifter is arranged to output line is connected to first voltage supply line, and when control signal has second value, output line is connected to second voltage supply line when described control signal has first value.
In two common plane voltage displays of described form, described output line can be to be connected to described common electrode.In this case, described display may also comprise at least one sensor pixel, the latter has the sensor associated pixel electrode, and described sensor pixel electrode is configured to receive second voltage, and described at least one sensor pixel is connected to second voltage supply line.Described display can also comprise differential amplifier, and its positive input terminal is connected at least one sensor pixel; And its output is connected to its negative input end and second voltage supply line.
As another program, described output line can be arranged to control the mid point of pixel driving device voltage range.If as described at above-mentioned WO 00/67327, capacitor is associated with each pixel electrode, an electrode of each capacitor is configured to receive the voltage same with described common electrode.
The common electrode display that floats can comprise:
Voltage supply line, it is arranged to supply first voltage;
Output line is connected to described common electrode;
Switching device shifter is used for described voltage supply line is connected to output line; Or be used for described output line and described voltage supply line are disconnected.
Control line is connected to described switching device shifter, and is configured to receive the control signal with first or second value,
Switching device shifter is arranged to when control signal has first value output line is connected to voltage supply line, and when control signal has second value, output line and voltage supply line is disconnected.
Of the present invention pair of common plane voltage display generally comprises the bias voltage supply circuit, the latter is arranged to supply first and second voltages, and described display can be equipped with when described display is in its non-writing mode, is used to disconnect the device of described bias voltage supply circuit.Described pixel electrode can be arranged in that described bias voltage supply circuit disconnects and power up in the reception voltage identical with described common electrode.
Variable common plane voltage display of the present invention can utilize the above-mentioned electro-optical medium of any kind.Thereby, in described display, described electrooptic layer can comprise rotation double-colored member or electrochromism display medium or a kind of electrophoresis material based on particle, comprises suspending liquid and a plurality of charged particle that is suspended in the suspending liquid and can moves by it when described electrophoresis material applies electric field.Such electrophoretic medium can be the sealing electrophoresis material, and wherein suspending liquid and charged particle are sealed in a plurality of capsules, and each capsule has capsule wall; Perhaps can be the micro element type, wherein suspending liquid and charged particle maintain in a plurality of unit that form in the substrate.
The present invention also provides a kind of method of operating electro-optic displays, and described electro-optic displays comprises: the bistable electro-optical dielectric layer; A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer, and each pixel electrode has at least one nonlinear element that is associated with it; And common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer.Described method comprises:
Apply first voltage to described common electrode, and simultaneously at least two different voltages are added on the pixel electrodes different in described each pixel electrode, thereby image is write described electro-optical medium; And
Apply second voltage that is different from described first voltage to described common electrode, and control simultaneously is applied to the voltage on the described pixel electrode, makes that any any image that writes described electro-optical medium is in the past all preserved basically.
The present invention also provides a kind of operation electro-optic displays method, and described electro-optic displays comprises: the bistable electro-optical dielectric layer; A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer, and each pixel electrode has at least one nonlinear element that is associated with it; Common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer; And voltage supply line, be used for providing voltage to described common electrode.Described method comprises:
Apply first voltage to described common electrode, and simultaneously at least two different voltages are added on the pixel electrodes different in described each pixel electrode, thereby image is write on the described electro-optical medium; And
Control is applied to the voltage of described pixel electrode, and any image that writes described electro-optical medium before making is all preserved basically, and simultaneously described common electrode is disconnected from described voltage supply line, thereby allows the voltage on the described common electrode to float.
As already noted, others of the present invention relate to and are used to measure and revise equipment and the method that bias voltage is used.Thereby, in yet another aspect, the invention provides a kind of electro-optic displays, it comprises:
The bistable electro-optical dielectric layer;
A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer, and at least one pixel electrode is the sensor pixel electrode;
The nonlinear element that at least one is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode, and described pixel driving device is arranged to apply predetermined voltage at least one sensor pixel electrode;
Common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer; And
Measurement mechanism, it is configured to receive described predetermined voltage and the voltage on described at least one sensor pixel, and determines the difference between them.
The present invention also provides a kind of electro-optic displays, it comprises:
The bistable electro-optical dielectric layer;
A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer;
The nonlinear element that at least one is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode;
Common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer;
The common electrode voltage feed lines, it is arranged to supply at least one voltage;
Switching device shifter, it is connected to described common electrode to described voltage supply line, and described switching device shifter has: mode of operation, wherein said voltage supply line is connected to described common electrode; And test mode, wherein said voltage source and described common electrode disconnect, thereby allow the voltage on the described common electrode to float,
Described pixel driving device is arranged to supply single predetermined voltage by described nonlinear element to whole pixel electrodes when described switching device shifter is in its test mode,
Described display also comprises measurement mechanism, and it is arranged to receive described single predetermined voltage and the voltage on described common electrode when described switching device shifter is in its test mode, so that determine the difference between them.
The present invention also provides a kind of electro-optic displays, and it comprises:
The bistable electro-optical dielectric layer;
A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer, and at least one pixel electrode is the sensor pixel electrode;
The nonlinear element that at least one is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode, and described pixel driving device is arranged to apply predetermined voltage to described at least one sensor pixel electrode;
Common electrode, it is in a described electro-optical medium layer side opposite with described pixel electrode; And
The common electrode voltage control device, it is configured to receive the signal of the voltage of representative on described at least one sensor pixel electrode, and is applied to voltage on the described common electrode according to described signal change.
At last, the invention provides a kind of method of operating electro-optic displays, described electro-optic displays comprises: the bistable electro-optical dielectric layer; A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer; The nonlinear element that at least one is associated with each pixel electrode; Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode; Common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer.Described method comprises:
Apply predetermined voltage by means of described pixel driving device to whole pixel electrodes of described display;
The described predetermined voltage of storage representative and in the value that applies the difference between the voltage that appears at common electrode in the described predetermined voltage process to pixel electrode; And
After this value according to described storage applies voltage to described common electrode, and applies pixel electrode voltage simultaneously, and described pixel electrode voltage causes image is write described electro-optical medium.
Description of drawings
Fig. 1 is the partial circuit figure of of the present invention pair of common plane voltage display;
Fig. 2 is the partial circuit figure of unsteady common electrode display of the present invention;
Fig. 3 is the partial circuit figure that is used for realizing at large-scale Active Matrix Display the prototype circuit of Fig. 1 basic circuit and some others of the present invention;
Fig. 4 is the partial circuit figure of revision of two common plane voltage displays of the use sensor pixel of Fig. 1;
Fig. 5 is the partial circuit figure that is equipped with the display of the device that is used to measure feed-trough voltage;
Fig. 6 is the partial circuit figure of revision of the display of being equipped with of Fig. 2 device that is used to measure feed-trough voltage;
Fig. 7 utilizes external unit to adjust so that the partial circuit figure of a kind of display of the present invention of compensating feed through voltage;
Fig. 8 is the partial circuit figure of a kind of display of the present invention, wherein the compensation of feed-trough voltage is carried out at the inner utilization sensor pixel;
Fig. 9 is the partial circuit figure of the display revision of Fig. 1, is equipped with the device that is used for compensating feed through voltage;
Figure 10 is the partial circuit figure of a kind of display of the present invention, wherein the compensation of feed-trough voltage is carried out with digital form.
Embodiment
As showing, the present invention has several different aspects, relates to display and be used for the method controlling the electro-optic displays electrode voltage and be used to measure and revise feed-trough voltage in such display.Usually describe different aspect of the present invention below respectively, but will appreciate that single kind of display may utilize the more than one aspect of the present invention; For example, the display of Fig. 6 uses unsteady common electrode display of the present invention and feed-trough voltage measurement aspect simultaneously.
As discussed above, the subject matter that the present invention makes every effort to handle is: by the grid feedthrough cause each voltage that driving circuit applies to the nonlinear element of electro-optic displays (may be called hereinafter " the row driving voltage ", because as showing, although in that to select the Active Matrix Display one-row pixels to write constantly at any one traditionally be arbitrarily basically) between difference, be applied on the described pixel electrode to row (data) electrode then and produce the required different voltage of different voltages (these voltages can be called ＂ pixel electrode voltage ＂ hereinafter), described pixel electrode voltage is that to produce required transformation on the pixel of described select row required.
Fig. 1 is the partial circuit figure of two common plane voltage displays of recommendation of the present invention, and illustrates common electrode control device (usually being denoted as 100).Control device 100 comprises first voltage supply line 102, second voltage supply line 104 and output line 106.Control device 100 also comprises the switching device shifter of following form: be arranged on first switch S 1 between first voltage supply line 102 and the output line 106 and be arranged on second switch S2 between second voltage supply line 102 and the output line 106.As shown in Figure 1, switch S 1 and S2 are connected to control line 108, and switch S 2 is directly connected to control line 108 by line 110, and switch S 1 is connected to control line 108 by phase inverter 112 simultaneously.Output line 106 is connected to the common electrode (not shown) of bistable electro-optic displays.
Voltage supply line 102 and 104 all is connected to bias voltage supply circuit (not shown, but belong to traditional type, it is that the technician of Active Matrix Display is familiar with).The bias voltage supply circuit provides voltage V by lead 102 COM, voltage V COMBe the normal voltage of common electrode in (scanning) mode that the writes process of described display, and be the mid point of pixel electrode voltage scope basically.In addition, the bias voltage supply circuit provides voltage V by lead 104 SM, voltage V SMBe the correct voltage of common electrode in the non-writing mode process of display, and be arranged on the mid point of row driver voltage range basically.Thereby, V COMAnd V SMDiffer a quantity that equals the grid feed voltage of display.
Control line 108 receives single bifurcation control signal from the control circuit (not shown), and described control signal has to be write fashionable first, the low or value of writing and display at display and do not write fashionable second, high or non-value of writing.When display was in its writing mode (that is, update image), the control signal by lead 108 kept low, makes switch S 1 connect, and switch S 2 disconnects, and output line 106 and common electrode are directly connected to second voltage supply line 104, and received voltage V SMIn non-writing mode process, row driver also can be set to voltage V by whole pixel electrodes SM, thereby, between pixel electrode and common electrode, set up no-voltage.
As already noted, the output line 106 of Fig. 1 circuit is connected to the common electrode of the display that is associated.But as another program, output line 106 can be connected to the circuit of the mid point that is used for controlling the voltage range that row driver uses.When output line connects with this substitute mode, control signal will make that when display is in its writing mode output line 106 receives voltage V from top with reference to the described state counter-rotating of Fig. 1 SM, and when display was in its non-writing mode, output line 106 received voltage V COM(certainly, as another program, by keep same control signal overturn from control line 108 to switch S 1 with being connected of S2, make S1 be directly connected to line 108, and S2 is connected to line 108 by phase inverter 112.) in this case, common electrode all will receive V any time COM
The circuit that is connected to common electrode with output line 106 or is connected to the mid point that is used for controlling the voltage range that row driver uses is irrelevant, if pixel electrode is equipped with the memory capacitor that is associated, described as above-mentioned WO 00/67327, preferably present and be fed to the same voltage of voltage of common electrode to the counter electrode of pixel capacitor (that is, be not in the electrode for capacitors of same voltage) with their pixel electrode that is associated.
Its output line 106 is connected to the circuit shown in Figure 1 of the common electrode of display, may display write and non-writing mode between in the transforming process, make electro-optical medium experience some little, undesirable voltage transient.For example, in recommending operation method, when scanning the last time, display changes over to before its non-writing mode, and all row driver all is set to voltage V SMBecause former explanation, actual pixel voltage will be different from V slightly SM, because display still stands the grid feedthrough this moment, and pixel voltage in fact equals V COM, with the identical voltage that in scanning process, is applied on the common electrode.Then, if described common electrode switches to voltage V by circuit 100 immediately SM, then electro-optical medium equals experience to the transition that the grid feed-trough voltage is present in pixel electrode, and along with the leakage by pixel transistor and electro-optical medium, pixel electrode is charged to voltage V SM, described transition decays gradually.Obviously, preferably eliminate described voltage transient, or reduce it as far as possible.Similarly, when display when its non-writing mode switches to its writing mode, will produce little voltage transient.When circuit shown in Figure 1 is used for controlling the mid point of the voltage range of being used by row driver, can switch to its non-writing mode or produce voltage transient mutually on the contrary along with the writing mode of display from it.
Fig. 2 is the partial circuit figure of the unsteady common electrode display of recommendation of the present invention, and illustrates common electrode control device (usually being denoted as 200).Control device 200 usually is similar to control device shown in Figure 1 100 and comprises: voltage supply line 202, it provides voltage V by the bias control circuit (not shown) COM Output line 206, it is connected to the common electrode (not shown) of display; Switch S 3, it is these two lines and be used for the control line 208 of operation of gauge tap S3 and link together.Be present in control device 100 phase inverters 112 because from the control device 200 of Fig. 2, saved, so the control signal on the lead 208 need be reversed from the state on the lead 108, make that switch S 3 is connected in the writing mode process of display, and common electrode receives V by switch S 3 and output line 206 from voltage supply line 202 COM
When display was in its non-writing mode, switch S 3 disconnected, and common electrode and bias voltage supply circuit disconnect, thereby allowed the unsteady ＂ of ＂.In the process that common electrode floats like this, as has been described, all the row electrode all remains on V SM, leak and all to be charged to voltage V to pixel electrode and common electrode at last by pixel transistor and the electric current by electro-optical medium SM, thereby, stay zero electric field at the electro-optical medium two ends.Will find out, be similar to drive unit 100, display it writing mode and non-writing mode between when switching, drive unit shown in Figure 2 200 produces little voltage transient, and described transition lasts till that always voltage on pixel electrode and the common electrode is with till the aforesaid way equilibrium or resetting.
Fig. 3 is the partial circuit figure that is used for realizing at large-scale Active Matrix Display the basic circuit of Fig. 1 and some other side's of the present invention prototype circuit (usually being denoted as 300).Now, only describe those parts that Fig. 3 is similar to the circuit of Fig. 1, the remainder of Fig. 3 will be described with reference to the aspect of the present invention of implementing them below.
Circuit 300 comprise control line 108 ' and lead 110 ', they just are similar to the corresponding circuit in Fig. 1.Circuit 300 also comprise phase inverter 112 ', be similar to the phase inverter 112 in Fig. 1, but provide by integrated circuit (IC) NC7SZ04M5.Anti-phase output on the pin 1 of described IC is fed to the pin (C4) of IC 320, and IC 320 is tetrad switches of DG201B type.Lead 110 ' be connected to same pin of chip 1 (C1).The S4/D4/C4 of IC 320 (pin 6,7 and 8) section is corresponding to the switch S among Fig. 11, and the pin 7 (D4) of IC 320 be connected to output line 106 ', output line 106 ' be connected to the again common electrode of display.
Fig. 3 also illustrates and is used for producing the input voltage V that common electrode control device of the present invention uses COMAnd V IMThe part of bias control circuit.Shown in the lower right of Fig. 3, as the signal V of the ceiling voltage that is used for driving row driver SHBe fed to voltage divider, the latter comprises resistance R 5 and the R6 that resistance equates, and is V SHR5 of half and the voltage between the R6 are fed to the pin 10 (positive input terminal) of the IC 330 of operational amplifier OPA 4243.Export the negative input end that is fed back on its pin 9 at IC 330 pins 8 resulting amplifiers, also be fed to the circuit that comprises resistance R 4 and capacitor C3, described RC circuit between resistance R 4 and capacitor C3 by tap, so that as the voltage V of other local usefulness that circuit 300 is provided of describing below SMCapacitor C3 is in a conventional manner as accumulator, so that burning voltage V SM
The voltage V of Chan Shenging like this SMBe fed to the pin 11 (S3) of IC 320; High voltage enables the control corresponding pin 9 (C3) that (HVEN) signal (be used for control Driver Circuit powering on or down) is fed to IC 320, and the result on the pin 10 (D3) export be connected to output line 106 '.Voltage V SMAlso be fed to the variable voltage divider that comprises potentiometer R9 and resistance R 10, this voltage that is present between R9 and the RIO is fed to the pin 3 (positive input terminal) of IC 330 as being denoted as V by resistance R 1 COM_REFSignal.Corresponding output feeds back on its pin 2 on IC 330 pins 1 negative input end and conduct are denoted as V COMThe signal of _ DRIVE is fed to the pin 6 (S4) of IC 320.
Lead 106 ' on signal (as has been described, can be V COMOr V SM, depend on line 108 ' on the value of control signal) be fed to the pin 5 (positive input terminal) of IC 330.Corresponding output on IC 330 pins 7 feeds back to the negative input end on its pin 6, also as being denoted as V COMThe signal of _ PANEL_BUF3 is fed to the pin 2 (S1) of IC 320.As already noted, the pin 1 (C1) of IC 320 by lead 110 ' reception from control line 108 ' signal.Corresponding output on the pin 2 (D1) of IC320 is fed to the circuit that comprises resistance R 2 and capacitor C1, and the voltage that exists between resistance R 2 and the capacitor C1 is as above-mentioned signal V COM_REFBe fed to the pin 3 of IC 330.Capacitor C1 is in a conventional manner as accumulator, so that burning voltage V COM_REF(therefore circuit shown in Figure 3 is arranged for different modes for test objective rather than large-scale production design.The described circuit of design makes generally only to have one of R1 and R2 constantly at any one like this.R1 does not exist if R2 exists, and then described circuit can work in the mode identical with following Fig. 9 circuit basically; When R1 exists and R2 when not existing, described circuit is to work in the mode identical with the circuit of following Fig. 7 basically.)
Common electrode control device shown in Fig. 4 (usually being denoted as 400) is the modification of control device 100 shown in Figure 1, but is to use the one or more ＂ sensor ＂ pixels that are arranged on display itself.Control device 400 comprises lead 402,406,408 and 410, and phase inverter 412 and switch S 1 and S2 work in identical with corresponding part (integers) in the control device 100 shown in Figure 1 basically mode all.But, second voltage input end 404 of control device 400 ' not to provide voltage V simply by described bias control circuit SMOn the contrary, the voltage supply on the sensor pixel 414 is to the positive input terminal of differential amplifier 416, and the output of amplifier be fed to simultaneously its negative input end and line 404 '.
The mode of the row or column of the part outside that sensor pixel 414 is generally seen with the user of display easily is arranged on the zone of display.For example, the extra row that sensor pixel 414 can be used as pixel is provided with, and is generally hidden by the bezel of display.The control circuit of display is set like this, so that utilize voltage V SMConstantly write the pixel electrode of sensor pixel, as has been described, voltage V SMBe returned be transported to second voltage supply line 404 '.
As conspicuous for the technician who drives electro-optic displays, control device 400 is operated in the mode that is quite analogous to control device shown in Figure 1 100.Differential amplifier 416 is used for cushioning the voltage from sensor pixel 414.When display is in its writing mode, control device 100 as shown in Figure 1, switch S 1 is connected and switch S 2 disconnections, makes common electrode receive voltage V COMWhen display when its writing mode is converted to its non-writing mode, during the last end of scan of display, control signal uprises, and makes switch S 1 disconnect and switch S 2 is connected.This moment, the voltage on the sensor pixel 414 equals V COM, make it not produce voltage transient, because common electrode is connected to the output of amplifier 416.After this, the pixel electrode (comprising sensor pixel 414) when display little by little is charged to voltage V by the leakage by pixel transistor in the mode of having described SMThe time, the connection between sensor pixel 414 and the common electrode guarantees the lucky voltage that is present in described pixel electrode of following the tracks of of the voltage on the common electrode, making does not have electric field to exist at the electro-optical medium two ends.But, when display when its non-writing mode switches to its writing mode, will produce a little voltage transient.
Can revise control device 400 like this, make common electrode always be connected to sensor pixel 414, suppose that sensor pixel is set like this to make always with voltage V SMThey are write.This configuration has the additional benefit that allows the automatic fine tuning of common plane voltage.If when display be in its non-writing mode only use when (as at control device 400) sensor pixel and also as described in voltage on the pixel only send to common electrode, so, described sensor pixel can be described array common pixel (that is, rather than the sensor special pixel image pixel).
Embodiments of the invention shown in Fig. 1 to 4 depend on analog line.But, can also carry out with digital form the control of the required common plane voltage of variable common plane voltage display of the present invention.For example, common electrode can be connected to digital/analog converter (DAC), makes output controlled by display controller.Like this, display writing mode and non-writing in both processes, can be set to any required value by common plane voltage.But the hardware that digital embodiment needs is generally than the needed costliness of above-mentioned simulation embodiment, and makes common electrode follow the difficult more difficulty of process that the driver mid-point voltage descends in driver power down process and occur error easily.
In other embodiments of the invention, common plane voltage or the voltage that is applied to pixel electrode can be set up by software design in the non-writing mode process of display, thereby, the analog line of describing before removing from; Instead, in described non-writing mode process, select common plane voltage or be applied to the voltage of pixel electrode, make the electric field at electro-optical medium two ends reduce to minimum.Generally, when utilizing the modern digital driving circuit, there is one to compare V SMMore near V COMDigital voltage can use, especially if the digital resolution height of described driver.For example, investigate a display, wherein row driver uses 0 to 30 volt scope, makes V SMBe 15 volts, and supposition V COMBe 14 volts (15 volts deduct by caused 1 volt of grid feedthrough), and driver provide six voltage resolution and linear fully Control of Voltage.If the output of row driver rests on V in non-writing mode process SM(15 volts), then electro-optical medium will stand by 1 volt of electric field that difference causes between pixel electrode and the common electrode.But row driver can provide 14.063 volts voltage (descending from VSM two digits ladder), and if voltage puts on pixel electrode in non-writing mode process, then electro-optical medium only stands the electric field that the 63mV difference between pixel and the common electrode causes.This electric field that reduces widely at the electro-optical medium two ends will be acceptable under most of situation.
In other words, can select digital addressable voltage for row driver in many cases, by under non-writing mode, selecting the digital addressable voltage of the most close common plane voltage, can reduce the electric field at electro-optical medium two ends during the non-writing mode of display greatly
As showing, variable common plane voltage display of the present invention can be equipped with device that the non-writing mode process that is used at display breaks the bias voltage supply circuit (as described above, use referring to signal HVEN among Fig. 3), thereby, additional power save is provided on sizable degree.But,, wish very then to guarantee that common plane voltage can not be different from the voltage of pixel electrode in disconnection of bias voltage supply circuit and the power up significantly if disconnect the bias voltage supply circuit.This can be by still being realized with the driven pixel electrode of VSM by row driver in disconnection of bias voltage supply circuit and power up.When doing like this, common electrode should be directly connected to V SMVoltage or be arranged to follow V SMVoltage is so that change along with the change of described voltage.This can utilize any one circuit shown in Fig. 1 and 2 to reach.Utilize the circuit of Fig. 1, common electrode can switch to voltage V simply SMUtilize the circuit of Fig. 2, in power up at voltage V SMDuring change, common electrode will be allowed to float.In these circuit any one all can reduce to minimum to the voltage transient that electro-optical medium experienced, but circuit shown in Figure 4 is eliminated such transition fully.In a kind of like this layout, it may be difficult using digital to analog converter (DAC) to control common plane voltage.
In case the power supply of bias voltage supply circuit disconnects, the power supply of logical circuit also may disconnect, and after this may cut off the power supply of operational amplifier, and analog switch generally is used as the part of control circuit.Realize that the operations necessary sequence requires the electronic circuit of described display to comprise suitable power supply order hardware, and will appropriate software be set at display controller.
The technician of display Driving technique will appreciate that, when display powers on after bias voltage supply circuit and the following electricity of driver, before electro-optical medium can begin update image, system requirements considerable time (perhaps 10-100 millisecond) encouraged again.In some application (for example, when display is used as information symbol in airport, station or similar position), described time delay as a result is not horrible.But in other is used (for example, when display is used as e-book), if often repeat, then described time delay as a result may be horrible.In a kind of application in back, rational trading off is between the response (wherein bias voltage supply circuit and driver are still powered) that can obtain from the non-substantially writing mode of display and the additional power save (wherein bias voltage supply circuit and/or driver under) that can obtain from a ＂ dormancy ＂ mode, in case no longer require image update, just must allow display enter non-substantially writing mode, but only after non-substantially writing mode continues one period considerable time, just allow display enter sleep mode.For example, if display is as the books of electronics, then can select to enter the time delay before the sleep mode, make display not enter sleep mode, and user's reading simultaneously is by the single page (moment carries out basically to make the renewal that obtains down one page) of image setting, but when reading a few minutes that the user disconnects him for example so that when handling call, display just can enter sleep mode.As another program, (for example, if display is just as portable computer or cellular telephone auxiliary screen under) the control, then the following electricity of bias voltage supply circuit and driver can be controlled by host computer system if display is in host computer system; Note that in this case host computer system need allow when display powers on, send new image to display and occurred time delay in the past.
By as can be seen above-mentioned, the embodiment of the recommendation of variable common plane voltage display of the present invention can provide the power consumption that reduces electro-optic displays greatly and don't influence the image that has write display, and electro-optical medium is exposed to may be to the method and apparatus of the harmful voltage transient of medium.
In case above-mentioned discussion concentrates on equipment and method that known grid feed-trough voltage of the present invention just is used to compensate the influence of described voltage.For example, for the description of control device shown in Figure 1 100 operations, supposed grid feed-trough voltage (V in the past COMAnd V SMBetween difference) known, therefore give V COMSuitable value known, and have suitable circuit can be used for formation voltage V on first voltage supply line COMNow notice being turned to be used to measure the grid feed-trough voltage and to adjust display circuit has suitable voltage to can be used to compensate the method for grid feed-trough voltage so that guarantee.
First challenge will be any specific combination at panel, driver, sweep speed and other correlative factors, accurately measure the amplitude of feed-trough voltage.Although the present invention does not get rid of other method of use, the measuring method of two type of recommendation is sensor pixel and unsteady common electrode.
Described sensor pixel method is used the one or more sensor pixels on the display, and the sole purpose of these pixels provides the indication of required feed-trough voltage.For example, discuss with reference to Fig. 4 as top, can be at the pel array edge, exceed the edge in the active pixel zone (that is, the zone that is used for display image of display) of design, increase one or more pixels.These sensor pixels are identical with active pixel, and just conductive path is connected to described panel edges to sensor pixel along a bit, is connected to measuring system here.All sensors pixel on the described panel can link together with lead, and is upgraded by the controller that has same magnitude of voltage in the panel scanning process.Be used for upgrading the required value of pixel and, obtain representative value by measurement about feed-trough voltage from the difference between the measured value of sensor pixel.
Fig. 5 represents to be used for a simple circuit (usually being denoted as 500) of this purpose.Relatively will find out Fig. 5 and Fig. 4, the circuit of Fig. 5 is substantially similar to the part of the control device 400 of Fig. 4, except the destination of last output signal and for fear of repetition be each several part (integers) among Fig. 5 provide with Fig. 4 in identical label.Fig. 5 circuit comprises a plurality of sensor pixels 414 and differential amplifier 416.But the output of amplifier 416 sends to metering circuit by lead 404 ＂.Relation between given control device 400 and the circuit 500, just will appreciate that, the sensor pixel measuring method can be by temporarily the lead 404 of control device 400 ' being connected to metering circuit carries out, measure (because switch S 1 disconnects in measuring process and implement the grid feed-trough voltage simultaneously, this moment, lead 402 needn't connect), after this adjust the voltage V that is provided with on the lead 402 according to the measured value of grid feed-trough voltage COM
As another program, can measure the grid feed-trough voltage by the following method: allow common electrode float (that is, it and all conductor disconnections), and upgrade one period sufficiently long cycle of whole pixel electrode array with single voltage, so that allow electric current common electrode is charged to the voltage that equals pixel electrode voltage by the leakage of electro-optical medium layer.Then, metering circuit can be measured the difference between the output voltage of the row driving voltage voltage of drive source polar curve (scan period be used for) and unsteady public electrode, and thereby the area weighted mean value of definite grid feed-trough voltage.
Fig. 6 represents to be used to implement the simple circuit (usually being denoted as 600) of described process of measurement.More just can find out Fig. 6 and Fig. 2 and 5, circuit 600 is the control device 200 of Fig. 2 basically, its modification is: add differential amplifier 416 ' and be directed to lead 404 ＂ of metering circuit from amplifier, amplifier 416 ', the operation method of lead 404 ＂ and metering circuit is the same with counterpart among Fig. 5, and correspondingly the different piece among Fig. 5 is numbered.Might be connected to suitable test cell by output line 206 temporarily, comprise differential amplifier and metering circuit, carry out process of measurement control device shown in Figure 2 200.In the process of measurement process, should be arranged to cut-off switch S3 to the control signal on the lead 208, thereby common electrode is disconnected from its driving circuit.Similarly, S3 also can be used to provide a display ＂ dormancy ＂ state, as described above.
Employing or sensor pixel or unsteady common electrode measuring method for fear of produce error in the measured value of grid feed-trough voltage, need a kind of low-down method of measuring from the output voltage of sensor pixel or common electrode of leakage current.The voltage measurement method of such recommendation will be connected the high impedance voltage follower circuit between sensor pixel or common electrode and the described metering circuit.
Now use description to adjust the voltage input so that adjust the method for actual measurement grid feed-trough voltage.The most direct way of compensating feed through voltage (and measuring such voltage really) is, in case display fully and its driver be assembled together, just display is connected to external unit.Fig. 7 represents to be applicable to the circuit (usually being denoted as 700) of this purpose, it is included in the basic controlling device of type shown in Figure 2, and comprising voltage supply line 202, control line 208, switch S 3 and output line 206, they are all identical with corresponding part among Fig. 2.For suitable V is provided on lead 202 COMValue, handle electrokinetic potential device P1 is connected between voltage V1 and the V2, makes the output of described potentiometer sliding contact on lead 720 can cover the V corresponding with possible feed-trough voltage gamut COMThe scope of value.Lead 720 is connected to the positive input terminal of voltage follower, and described voltage follower comprises differential amplifier 722, and the latter's output terminal is connected to lead 202 and negative input end thereof simultaneously.The output 202 of amplifier also is connected to external measurement devices 726 by lead 724, and the latter also receives common electrode voltage by lead 728 from lead 206.
For suitable V being set for the voltage input lead 202 in the circuit 700 COMValue, can be set under the situation of their mid-point voltage (often being 0V) type scanner continuously at whole pixel electrodes, and be arranged to the control signal on the lead 208 make switch S 3 to keep disconnecting, and display and the driving circuit disconnection that forms by potentiometer P1 and amplifier 722.The output voltage of amplifier 722 on the common electrode voltage that exists on external unit 726 measurements and the comparison lead 206 and 728 and lead 202 and 724.The operator rotates the sliding contact of P1, up to the difference between external test facility 726 indication (by green glow, ring sound or other signal) these two voltages be in can accept within the scope till.
As showing, the circuit 300 of Fig. 3 comprises the circuit of type shown in Figure 7 really, and the combination of potentiometer R9 and resistance R 10 replaces potentiometer P1, and pin 1/2/3 part of IC 330 replaces amplifier 722.
Potentiometer P1 among Fig. 7 can replace with digital regulation resistance.The interface that testing apparatus can be by special use or automatically adjust the value of potentiometer then by controller, up to measure difference in the difference of regulation till.Potentiometer can or have nonvolatile memory or last setting value is stored in the controller and each display is used for the described potentiometer of initialization when powering on.No matter under any situation, described potentiometer can be arranged on the display module printed circuit board (PCB), rather than on controller board, because feed-trough voltage becomes with display, rather than become with controller; Thereby, described potentiometer is set like this allows exchange control unit in the middle of each display.
Can replace potentiometer P1 with dissimilar circuit.For example, can be arranged in parallel resistive trace or resistor and to its optionally cut, perforation or laser ablation adjust described voltage setting value.As another program, digital-to-analog mechanism can be used for this purpose such as R-2R stairing circuit, the pulse-modulator that is coupled to low-pass filter or real D/A.Described external unit can be finished measurement and compare, and the while control unit interface, so that adjust the digital-to-analog device.In case determine last setting, it just can be stored in the controller or be installed among the little EEPROM or other nonvolatile memory on the display module printed circuit board (PCB).
But, it is desirable to, display need not carried out the adjustment program when being connected to external unit, but have a kind of adjustment capability of inside, adjust its common electrode voltage and (or more precisely, adjust the side-play amount of described voltage from the mid point of described drive voltage range, so that reserve the grid feedthrough), thereby, save time and eliminate potential error when making, and allow repeatedly to adjust again.The simple circuit (usually being denoted as 800) that provides such ＂ inside to adjust ＂ is illustrated in Fig. 8.Circuit 800 is the remodeling of circuit 700 shown in Figure 7 basically, wherein lead 724 and 728, external measurement devices 726 and potentiometer P1 all save, and replace in order to the lower part: a plurality of sensor pixels 414 (described above being equal to) and signal adjustment unit 830 with reference to Fig. 4, the input end of signal adjustment unit 830 is arranged to receive voltages from sensor pixel 414, and its output by lead 720 ' be fed to amplifier 722 '.
Circuit 800 does not also require the feed-trough voltage digitizing of will survey.Instead, sensor pixel is used for providing in the mode the same with control device shown in Figure 4 400 real-time measurement values of the needed voltage of common electrode, the active region of display variable image Data Update, but constantly use V SM(mid point of row driver voltage range (often being 0V)) writes sensor pixel.The aanalogvoltage that sensor pixel 414 produces randomly by signal adjustment unit 830 filtering and be used for by by amplifier 722 ' and the voltage follower circuit that lead 206 is provided with drive common electrode.
Fig. 9 illustrates the inner ＂ of adjustment of another ＂ method, and it does not require the existence of sensor pixel.Circuit shown in Figure 9 (usually being denoted as 900) can be regarded as from the circuit 800 of Fig. 8 by saving sensor pixel 414 and signal adjustment unit 830, and with between the positive input terminal that is connected amplifier 722 ＂ and the ground and replace deriving by the capacitor C1 that switch S 4 is connected to output line 206.Switch S 4 receives control signal by lead 932 from lead 208, and inserts phase inverter 912 simultaneously between control line 208 and switch S 3.(because the existence of phase inverter 912 is compared with circuit 800, the control signal on the lead 208 need be reversed on circuit 900.Certainly, as another program, phase inverter can insert in the lead 932, and control signal still remains unchanged.)
Circuit 900 operations are as follows.At first, type scanner under following situation: all the row electrode is set to V SM, switch S 4 is connected and switch S 3 disconnections, makes capacitor C1 be charged to common electrode voltage V COMThen, change the signal on the control line 208, connect S3, and simultaneously actual image is write display so that disconnect S4.Under the situation that S4 disconnects, the voltage follower that is provided with by amplifier 722 ＂ guarantees that the voltage that is stored in capacitor C1 also appears at lead 202 and 206, thereby, appear on the common electrode.If be necessary, can between S4 and C1, insert additional voltage follower.Thereby the combination of switch S 4 and capacitor C1 plays simulation sampling and holding circuit, and its output is used for driving common electrode in the display renewal process.Described method has individual shortcoming, for the voltage on the capacitor C1 is maintained on the required value, requires several blank frames, perhaps even before each image update, carry out periodic scanning, and the scanning of such blank frame can increase the time that image update is used.
As showing, circuit 300 shown in Figure 3 is to prepare for proofreading and correct the grid feedthrough in a kind of mode that is similar to circuit shown in Figure 9 900, it is identical with capacitor C1 in the circuit 900 that capacitor C1 in the circuit plays a part, and in circuit 300, switch described HVEN signal, replace the switch S 4 in the circuit 900.
Form contrast with analog sampling of using in the circuit 900 and maintenance method, digitial controller can play its digital-to-analog mechanism effect, makes voltage deviation at V SMAnd V COMBetween, closely mate described feed-trough voltage.The circuit of described type (usually being denoted as 1000) is illustrated among Figure 10.Can be considered as circuit 1000 remodeling of circuit shown in Figure 7 700, potentiometer P1 is replaced by digital to analog converter 934, and its slave controller 936 receives the numeral input.In addition, external measurement devices 726 is replaced by comparer 938, the output that its positive input terminal receives from amplifier 722 by lead 924, and the negative input end of comparer 938 is connected to output line 206 by lead 928 simultaneously.The output of comparer 938 is fed to controller 936.
Determine suitable voltage V COMSo that be arranged on the lead 202 and 206 in the circuit 1000, this is to carry out in a kind of circuit 900 used modes that usually are similar to.Controller 936 is adjusted control signal on the leads 208 so that cut-off switch S3, and is set to V at whole row drivers SMSituation under display is carried out one or many scanning.The controller 936 at first output of digital to analog converter 934 is set to the ultimate value of its scope, then or sequentially step is by the whole possible output valve of digital to analog converter 934, perhaps (perhaps preferably) uses approximation technique one by one, obtain two output valves of digital to analog converter 934, the single position output of comparer 938 changes between described two output valves.Then, the output of controller 936 digital to analog converters 934 is set in these two values, and switch S 3 is connected, and the renewal of beginning display epigraph.According to the accuracy and the resolution of described circuit, described program reduces the value V that in fact is arranged on the output line 206 COMRequire in V in theory SMValue between difference, and the grid feed-trough voltage is reduced to low to acceptable level.
In circuit 1000, comparer 938 can be replaced by total weighted-voltage D/A converter, but sees the analog comparator 938 of recommending use single from cost.
From the above, will find out, the invention provides the equipment and the method for the feed-trough voltage that is used to measure and compensate electro-optic displays, thereby, avoid issuable harmful at such display if described feed-trough voltage can not get accurate compensation.

Claims (3)

1. electro-optic displays, it comprises:
The bistable electro-optical dielectric layer;
Be arranged on a plurality of pixel electrodes of a side of described electro-optical medium layer;
At least one nonlinear element that is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode;
Common electrode, it is in a described electro-optical medium layer side opposite with described pixel electrode;
Common electrode voltage feed lines (202), it is arranged to supply at least one voltage;
Switching device shifter (S3), it is connected to described common electrode to described voltage supply line (202), and described switching device shifter (S3) has: running status, wherein said voltage supply line (202) is connected to described common electrode; And test mode, wherein said voltage supply line (202) disconnects with described common electrode, thereby allows the voltage on the described common electrode to float,
Pixel driving device, it is arranged to when described switching device shifter is in its test mode, supplies single predetermined voltage by described nonlinear element to whole pixel electrodes,
Described display also comprises: measurement mechanism (726), it is arranged to when described switching device shifter (S3) is in its test mode, receives described single predetermined voltage and the voltage on the described common electrode, and determines the difference between them.
2. method of operating electro-optic displays, described electro-optic displays comprises:
The bistable electro-optical dielectric layer;
Be arranged on a plurality of pixel electrodes of a side of described electro-optical medium layer;
At least one nonlinear element that is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode;
Common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer;
Described method comprises:
By means of described pixel drive dress predetermined voltage is put on the whole described pixel electrode that is applied to described display;
The described predetermined voltage of storage representative and in the value that applies difference between the described voltage that appears in the described predetermined voltage process on the described common electrode to described pixel electrode; And
After this voltage of the value that depends on described storage is added on the described common electrode, and applies described pixel electrode voltage simultaneously, make image be written into described electro-optical medium.
3. electro-optic displays, it comprises:
The bistable electro-optical dielectric layer;
A plurality of pixel electrodes, they are arranged on a side of described electro-optical medium layer, and at least one in the described pixel electrode is sensor pixel electrode (414);
At least one nonlinear element that is associated with each pixel electrode;
Pixel driving device, it is arranged to apply voltage by described nonlinear element to described pixel electrode, described pixel driving device be arranged in the sensor pixel electrode at least one apply predetermined voltage;
Common electrode, it is in a side opposite with described pixel electrode on the described electro-optical medium layer; And
Measurement mechanism, it is configured to receive described predetermined voltage and the voltage at least one sensor pixel, and determines the difference between them.
CN200910128714XA 2003-08-19 2004-08-19 Electro-optic displays and methods for controlling the same Expired - Fee Related CN101533609B (en)

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