JP5632861B2 - Method for driving a bistable electro-optic display - Google Patents

Description

This application is related to the international application PCT / US02 / 37241. Publication WO 03
The entire contents of / 044765 are incorporated herein by reference.

The present invention relates to a method for driving an electro-optic display, and more particularly to a method for driving a bistable electro-optic display. The invention also relates to a drive device used in the method. More specifically, the present invention relates to a driving method and a driving device (controller) designed to allow a finer adjustment of the gray state of a pixel of an electro-optic display. The present invention also relates to a method that allows maintaining a direct current (DC) balance over a long period of drive impulses applied to an electrophoretic display. The present invention includes, but is not limited to, a particle-type electrophoretic display in which one or more kinds of charged particles are suspended in a liquid and moved in the liquid under the influence of an electric field to change the appearance of the display. Specifically intended for use.

The term “electro-optic” as applied to materials and displays is used in this application in the conventional sense of the imaging field and refers to first and second display states that differ in at least one optical property. The substance changes from the first display state to the second display state by an electric field applied to the substance. The optical properties are usually recognizable by the human eye, but in the case of other optical properties such as light transmission, reflectance, light emission, or machine-readable displays, the reflection of electromagnetic lengths outside the visible range. There is also the possibility of pseudo light due to a change in rate.

The term “gray state” is used in this application in the conventional sense of the image field and refers to the state between two extreme optical states of a pixel, which is not necessarily a transition between black and white. Does not mean. For example, in the electrophoretic displays described in the following registered patents and patent publications, the extreme state is white and dark blue, so the intermediate “gray state” is actually a light blue color. Also, as already mentioned, the transition between two extreme states may not be a color change at all.

The terms “bistable” and “bistability” are used in this application in the conventional sense of the display field, and the first and second displays differ in at least one optical property. Means a display composed of display elements having a state, and after a specific element is driven by an address pulse having a limit in duration, takes the first or second display state after the end of the address pulse, and The state lasts for at least several times the minimum duration of the address pulse required to change the state of the display element, for example at least four times. According to US Patent Application Publication No. 2002/0180687,
Some particle-type electrophoretic displays capable of gray scale display are stable not only in an extreme black / white state but also in an intermediate gray state, and the same applies to other types of electro-optic displays. This type of display is not a bistable type, but rather a "multistable type (mu
However, for the sake of convenience, the term “bistable” is used in this application to refer to both bistable and multistable displays.

The term “gamma voltage” in this application refers to an external voltage reference used by a driver to determine the voltage applied to a display pixel.
Of course, bistable electro-optic media do not display a one-to-one correlation between the applied voltage of the liquid crystal and the properties of the optical state, and the term “gamma voltage” as used in this application The meaning used in normal liquid crystal displays to determine the level and the inflection point on the output voltage curve is not exactly the same.

The term “impulse” is used in this application in the conventional sense of an integrated voltage over time. However, because some bistable electro-optic media operate as charge transducers, such media have another definition of impulse, the “integrated current over time” (equal to the total charge applied). ) May be used. Depending on whether the medium operates as a voltage-time transducer or a charge impulse transducer, an appropriate impulse definition should be used.

A plurality of types of electro-optic displays are known. Examples of such a type include US Pat. Nos. 5,808,783, 5,777,782, 5,760,761, and 6,054.
, 071, 6,055,091, 6,097,531, 6,128,124, 6
, 137, 467, 6, 147, 791, etc.
However, this type of display is often referred to as a “rotary two-color ball” display, but in the above patent, the rotating element is not necessarily spherical, and more accurately, it is a “rotating two-color element”) is there. The display described above uses a number of small objects (usually spherical or cylindrical) that have two or more parts with different optical properties and an internal dipole. By applying an electric field, the object rotates to various positions, and the appearance of the display changes as the part of the object visible from the screen changes. This type of electro-optic medium is usually bistable.

As another type of electro-optic display, an electrochromic medium, for example, a nanochromic film composed of an electrode formed at least partially from a semiconductor metal oxide and a large number of reversibly discolorable dye molecules attached to the electrode. Some use a form of electrochromic medium. As an example, “Nature 1991” 3 by O'Regan et al.
No. 53, page 737 and Wood's "Information Display" magazine 18 (
3) 24 pages (published March 2002), and Bach et al., “Advanced M
see pages 845, 14 (11), 2002, atterials. The above-mentioned types of nanochromic films are also disclosed in, for example, US Pat. No. 6,301,038, International Publication WO 0.
No. 1/27690, and U.S. Patent Application 2003/0214695.
This type of electro-optic medium is usually bistable.

Electro-optic displays that have been the subject of intense research and development for many years include particle-type electrophoretic displays in which a plurality of charged particles move through suspension under the influence of an electric field.
Compared with liquid crystal displays, electrophoretic displays have better brightness and contrast, wider viewing angles,
It has features such as state bistability and low power consumption. In any case, there is a problem with the long-term image quality of the display, so it has not been widely used. This is because, as an example, the particles constituting the electrophoretic display tend to deposit, resulting in an insufficient service life of the display.

Numerous patents and patent applications relating to microcapsule electrophoretic media assigned to the Massachusetts Institute of Technology (MIT) and E Ink, or both, have been published recently. The capsule medium is composed of a number of small capsules, and each capsule is composed of an inner phase containing electrophoretic movable particles suspended in a liquid suspension and a capsule wall surrounding the inner phase. . Usually, the capsules themselves are housed in a polymer binder to form an adhesion layer sandwiched between two electrodes. Such capsule media are described, for example, in the following documents: US Pat. Nos. 5,930,026, 5,961,804, 6,017,58.
4, 6,067,185, 6,118,426, 6,120,588, 6,12
0,839, 6,124,851, 6,130,773, 6,130,774,
6,172,798, 6,177,921, 6,232,950, 6,249,7
21、6、252、564、6、262、706、6、262、833、6、3
00,932, 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,
455,374, 6,455,489, 6,459,418, 6,473,072
No. 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, 6,538,80
No.1, 6,545,291, 6,580,545, 6,639,578, 6,65
2,075, 6,657,772, 6,664,944, 6,680,725,
6,683,333, 6,704,133, US Patent Application Publication 2002/00190
81, 2002/0021270, 2002/0053900, 2002/006
0321, 2002/0063661, 2002/0063677, 2002/0
090980, 2002/0106847, 2002/0113770, 2002
/ 0130832, 2002/0131147, 2002/0145792, 20
02/0171910, 2002/0180687, 2002/0180688,
2002/0185378, 2003/0011560, 2003/0011868
No., 2003/0020844, 2003/0025855, 2003/00349
49, 2003/0038755, 2003/0053189, 2003/009
6113, 2003/0102858, 2003/0132908, 2003/0
137521, 2003/0137717, 2003/0151702, 2003
/ 0189749, 2003/0214695, 2003/0214697, 20
03/0222315, 2004/0008398, 2004/0012839,
2004/0014265, 2004/0027327, International Publication No. WO 99 /
67678, WO 00/05704, WO 00/38000, WO 00/3
8001, WO 00/36560, WO 00/67110, WO 00/67
327, WO 01/07916, WO 01/08241, WO 03/092
077, WO 03 / 107,315.

In many of the above patents and patent applications, by replacing the wall surrounding the discontinuous capsule of the microcapsule electrophoretic medium with a continuous phase, the electrophoretic medium has a plurality of discontinuous electrophoretic liquid droplets and polymers. A so-called “polymer dispersion type electrophoretic display” composed of a continuous phase of the material is formed, and the discontinuous electrophoretic liquid droplets in the polymer dispersion type electrophoretic display are individually provided for each liquid droplet. It is recognized that even if it is not surrounded by a capsule membrane, it can be regarded as a capsule or a microcapsule. As an example, the above mentioned 2002/01311
See No. 47. Therefore, for the purposes of this application, the polymer dispersed electrophoretic display described above is considered a sub-species of microcapsule electrophoretic media.

In general, microcapsule electrophoretic displays do not suffer from failures such as accumulation and deposition like conventional electrophoretic devices, and can be printed and painted on a variety of flexible and rigid substrates. And offers new benefits. ("Print
The term “ting” includes, but is not limited to, all forms of printing and painting, including: patch die coating, slot and extrusion coating, slide and cascade coating, curtain coating, etc. Pay-per-use coating,
Roll coating such as KOR (knife) coating, roll coating, forward / reverse roll coating, dip coating, spray coating, uneven coating, spin coating, brush coating, air knife coating, silk screen printing, electrostatic printing, thermal printing Method, inkjet printing method, and other similar methods. Therefore, the resulting display may be flexible. Furthermore, since the display medium can be printed (using various methods), the display itself can be produced at low cost.

Related electrophoretic displays include so-called “microcell electrophoretic displays”. In the microcell electrophoretic display method, the charged particles and the suspension are contained in a plurality of cavities formed in a base medium (usually a polymer film) instead of being encapsulated. As an example, International Publication No. WO 0, assigned to Sipix Imaging.
See 2/01281 and US 2002/0075556.

Electrophoretic media are often opaque and operate in reflective mode (eg, in many electrophoretic media, because particles significantly block visible light transmission from the display). Many electrophoretic displays can operate in a so-called “shutter mode” where one display state is highly opaque and the other is translucent. As an example, the above-mentioned US Pat. No. 6,130
774 and 6,172,798 and U.S. Pat. Nos. 5,872,552 and 6,144.
361, 6,271,823, 6,225,971, 6,184,856. A dielectrophoretic display that is similar to an electrophoretic display but relies on various electric field strengths can operate in a similar mode. See U.S. Pat. No. 4,418,346.

Other electro-optic displays that exhibit bistable or multistable reactions of particle electrophoretic displays, as well as similar reactions, are in stark contrast to conventional liquid crystal (LC) displays. Twisted nematic (TN) liquid crystal is not bistable or multi-stable and operates as a voltage converter, so when a specific electric field is applied to a pixel of the display, the pixel regardless of the gray level previously displayed on the pixel To form a specific gray level. In addition, LC displays are only unidirectional (non-translucent or “dark” to translucent or “bright”), with the reverse transition from bright to dark achieved by reducing or reducing the electric field. It consists of the drive of. Finally, the gray level of the pixels of the LC display is not affected by the polarity of the electric field and is only affected by its scale. In fact, for technical reasons, commercially available LC
The display usually reverses the polarity of the drive area frequently.

Conversely, the bistable electro-optic display operates as an impulse converter in the approximate result obtained first, so the final state of the pixel is not only the applied electric field and the time the electric field is applied, It also depends on the pixel state before the electric field is applied. Moreover, in at least many particle electrophoretic displays, the impulse (based on eye or standard optics judgment) required to change a pixel with an equivalent change to gray level is not necessarily constant, and It has been known so far that it is not necessarily commutative. Take, for example, a display in which each pixel can display 0 (white), 1, 2, or 3 (black) gray levels that are effectively spaced apart. (The spacing between levels may be a straight line with a percentage reflectance based on eye or instrument measurements, or any other spacing method. For example, the spacing may be a straight line on L * (where L * is the normal Based on the following CIE definitions:
L * = 116 (R / R ₀ ) ¹ / ^3-16
In the formula, R is a reflectance and R ₀ is a standard reflectance value), and a specific gamma value may be selected. A gamma value of 2.2 is often used for monitors and the display of the present application is intended to replace the monitor, so an equivalent gamma value is preferred. ) Impulse required to change the pixel from level 0 to level 1 (hereinafter referred to as “0-1 transition” for convenience) is not the same as the impulse required for 1-2 transition or 2-3 transition It has been found that there are many cases. Furthermore, the impulse required for the 1-0 transition is not necessarily the same as the inverse of the 0-1 transition. Also, it seems that the impulse required for the 0-1 transition (for example) varies slightly according to the transition type of the specific pixel, 0-0-1, 1-0-1, or 3-0-1. Some systems display “memory” effects above. (In the above, x, y, z are all optical states 0, 1, 2, 3 and the notation “xyz” is the order of optical states accessed in order from early to late. Showing). The above problem can be reduced or overcome by driving all display pixels to one extreme state for a significant period of time before moving the pixel of interest to the next state, but the resulting plain "flash" Often unacceptable. For example, if an ebook reader wants to scroll down the text on the screen, if the screen frequently needs to display a black or white solid flash, it may be distracting or not knowing where you were reading there's a possibility that. Furthermore, such screen flashes can increase power consumption and reduce the operating time of the display. Finally, in at least some cases, the impulses required for a particular transition stay in a particular optical state with a particular pixel before a particular transition, as well as the display temperature and total operating time. It has become clear that the correction of these factors is desirable in order to ensure an accurate gray scale effect.

Furthermore, as can be easily seen from the above discussion, the drive requirements for bistable electro-optic media are:
It provides an unmodified driver designed for driving active matrix liquid crystal displays (AMLCD) and not suitable for bistable electro-optic media displays. However, the AMLCD
Drives are attractive for driving bistable electro-optic displays because they have a large allowable voltage range, are commercially available in high pin count (HPC) packages, are readily available, and are inexpensive. On the other hand, similar drivers specially designed for bistable electro-optic displays are quite expensive and require considerable design and production time. Therefore, since the cost and development time can be reduced by changing the configuration of the AMLCD driver for a bistable electro-optic display, the present invention aims to provide a method and a modified driver that enable this.

Also, as already mentioned, the present invention provides a long-term driving impulse applied to the display.
It also relates to a method of driving an electrophoretic display (EPID) that enables the C balance to be maintained. Microcapsule electrophoretic displays, and other electrophoretic displays, were accurately DC balanced to protect image stability, maintain symmetrical switching characteristics, and provide the effective maximum operating time of the display It has been found that for any particular display pixel, the integral current over time must be driven by zero over a long period of operation time. Conventional methods for maintaining accurate DC balance require a precisely tuned power supply, a precision voltage adjusted driver for gray levels, and a crystal oscillator for time adjustment. Providing it will greatly increase the cost of the display.

(Strictly speaking, DC balance should be measured “internally” taking into account the voltage received by the electro-optic medium itself. In practice, however, such internal measurements are measured in the hundreds of thousands of pixels. In reality, DC balance is measured using “external” surveying, ie, the applied voltage to the electrodes placed on both sides of the electro-optic medium, because it is impossible to perform in an active display with In addition, two assumptions are usually made when considering DC balance: First, for the most common reason, the conductivity of an electro-optic medium is not a polar function, but a constant voltage is applied. The pulse length is assumed to be appropriate for DC balance tracking recording, and then the conductivity of the electro-optic medium is proportional to the applied voltage, so it is assumed that impulses can be used for DC balance tracking recording. .)
In the following, the term “superframe” will be used to denote an array of continuously displayed scan frames necessary for all essential gray level changes from the initial image to the final image. Usually, the display update is activated only at the initial stage of one superframe.

In the above-mentioned WO 03/044765, each pixel displays at least three gray levels (the extreme black state and white state are regarded as two gray levels in the calculation of the gray level, as is conventional in the display field). A possible method of driving a bistable electro-optic display having a plurality of pixels is described. The method is
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
Receiving an input signal representing a desired final state of at least one display pixel, and generating an output signal representing an impulse required to convert the initial state of the single pixel into a desired final state, which is determined based on a lookup table; Consists of.

  This method is hereinafter referred to as “basic lookup table method” for convenience.

Based on the number of stored prior states, the number of lookup tables used in the lookup table method can be very large. As an extreme example, consider a look-up table method used for a display that displays 256 (2 ⁸ ) gray levels using an algorithm that considers an initial state, a final state, and two preceding states. The required 4D look-up table has 2 ³² inputs, and if each input requires 64 bits (8 bytes), for example, the total size of the look-up table will be about 32 gigabytes. If you save to a desktop computer, there is no problem with this size of data, but it can be a problem for mobile devices. In another aspect, the present invention provides a method for driving a bistable electro-optic display that achieves results similar to the look-up table method, but does not need to store multiple look-up tables.

One aspect of the present invention is that a portion of the display has a different bit depth than the rest of the display (ie,
The present invention relates to a driving method and a driving device of a bistable electro-optical display that can be operated at different gray scale levels. Figures 11A and 11B of WO 03/044765 mentioned above
According to the description of the serrated drive method illustrated in Fig. 1, the transition between successive images in the overall image flow of a bistable electro-optic display with multiple gray scale levels is
It will be apparent to those skilled in the art that it takes significantly more time than a similar image being driven in monochrome mode. Typically, a gray scale transition can take up to four times as much as the corresponding monochrome transition. A relatively slow grayscale transition is undesirable when the display is displaying a series of images, such as a series of photographs or successive pages of an ebook. However, in some cases, it is useful to quickly update only a limited area of the display. For example, when a user reviews a series of photos stored in a database using the display and enters keywords or other index terms into each photo to facilitate image retrieval from a later database, You may be able to endure even if the transition between successive photos is relatively slow. For example, if it takes 1-2 minutes to review each photo and select an index term, even if it takes 1-2 seconds to transfer between consecutive photos, there is no significant impact on user productivity. However, as anyone who has tried to start word processing software on a computer with insufficient processing power, it is very frustrating if the dialog box update that displays the entered index terms is delayed for 1-2 seconds. Can lead to many typos. Thus, in the above and similar situations, for quick transitions, it is an effective way for the dialog box to be driven in monochrome mode and the remaining display to continue to display in grayscale mode so that the image is accurately reproduced. The present invention provides a method and apparatus that enables it.

Another aspect of the present invention relates to a method for achieving fine adjustment of gray levels of impulse driven image media without the need for fine adjustment of voltage. As already pointed out, some of the electrophoretic displays and other electro-optic displays show bistability, and the bistability is not infinite, so the image on the display gradually fades over time, so an image Is maintained over a long period of time, it is necessary to periodically refresh the image in order to restore the initial optical state of the image.

However, such an image refresh can itself cause problems. As described in the aforementioned US Pat. Nos. 6,531,997 and 6,504,524, if the display driving method is applied to the entire electro-optic medium, the electric field is applied to the net time average. If it is not zero or a zero approximation, a problem occurs and the operating time of the display is reduced. The driving method in which the electric field applied to the entire electro-optic medium on average over the net time is zero as a result is conveniently referred to as “DC balance driving method” or “DC
This is called “balance driving method”. If an image is maintained for a long time by applying a refreshing pulse, the pulse must be of the same polarity as the address pulse used to initially move to the optical state of interest to maintain the relevant display pixel. As a result, the drive system is unbalanced in DC balance.

The challenge in achieving accurate gray scale levels in impulse driven media is to apply the appropriate voltage impulse to achieve the desired gray tone. Satisfactory transitions between optical states can be achieved by fine-tuning the voltage across the drive waveform or in part. The need for accuracy can be understood from the following example. The current image consists of a half-black and half-white screen,
Take the case where the desired next image is a uniform gray between black and white as an example. To achieve a uniform gray level, the impulse used for the black-to-gray and white-to-gray transition must be fine-tuned so that the gray level achieved from black matches the gray level achieved from white. There is. If the final gray level achieved is a correlative element of the previous gray level recorded on the display, further tuning is necessary. For example, as already mentioned,
The optical state realized by the transition from black to gray is not only an applied waveform, but also a correlative element of the state accessed before the current black state. In this case, the display module preferably tracks the history of a part of the display, such as the preceding image state, and corrects the history of the preceding state by fine tuning of the waveform (see below for more discussion on this point). .

The fine tuning of the impulse can be achieved by adjusting the applied pulse width with high accuracy, and only 3 levels (0
, + V, −V). However, the fine tuning is not suitable for an active matrix display because it is necessary to increase the frame rate in order to realize a high pulse width resolution. High frame rate increases the power consumption of the display and imposes harsh conditions on electronic devices such as control devices and drive devices. Therefore, it is not desirable to operate an active matrix display at a frame rate significantly exceeding 60-75 Hz.

Impulse fine tuning can also be achieved when many finely spaced voltages are available. In order to realize the above in an active matrix drive, a source driver capable of outputting one of many usable voltages over at least a part of usable voltages is required. For example, a driver that outputs a voltage of -10 to +10 volts has two band voltages of 0 V, -10 to -7 volts, and 7 to 10 volts, and between -10 to -7 volts and 7 to 10 volts. It may be effective to set the total number of required voltage levels to 33 levels (see Table 1) by providing 16 voltage levels in between. Then, for example, the voltage of the last one or more scan frames in the address period is increased from +7 to +
Fine adjustment of the final optical state can be realized by changing between 10 volts or between -10 and -7 volts. The method is an example of a voltage regulation technique to achieve acceptable display performance.

  (Table 1: Example of voltage required for voltage regulation drive)

電圧調節テクニックの使用上の不利点は、ドライバである程度の電圧微調節ができる必
要があるという点である。ディスプレイモジュールのコストは２〜３レベルの電圧しかな
いドライバを使用することで削減できる。

The disadvantage of using voltage regulation techniques is that the driver needs to be able to make some voltage fine adjustments. The cost of the display module can be reduced by using a driver with only a few levels of voltage.

In other aspects, the present invention uses gray level drivers using only a few available voltages, especially when the impulse adjustment is too coarse to achieve the fine tuning required for acceptable display performance. Aiming to provide a method to achieve fine adjustment. In other words, this aspect of the present invention aims to provide a method for realizing fine adjustment of the gray level of an impulse-driven image medium without the need for fine adjustment of the voltage. The aspect of the present invention can be applied to, for example, an active matrix display including a source driver that can output only a voltage of a few levels.

In another aspect, the invention relates to a method for driving an electro-optic display using a drive scheme that includes at least some degree of direct current (DC) balance transition. For reasons detailed in the above-mentioned co-pending application, when driving an electro-optic display, DC balance is achieved.
That is, when the final optical state coincides with the initial optical state, it is preferable to use a drive system having such a characteristic that the integration of the applied voltage is always zero regardless of the arrangement of the optical states. By doing so, the net DC balance imbalance experienced by the electro-optic layer is necessarily bound to a known value.
For example, assume that the electro-optic layer is shifted from a white state to a black state using a pulse of 15 ms at 15 V. After the transition, the image layer has experienced a DC balance unbalanced impulse of 4.5V. Further, if a 300 ms pulse at -15 V was applied to return the film to white, the image layer would be DC over the entire series of white-to-black and black-to-white transitions.
It will be balanced.

It has also been found desirable to use a drive scheme in which at least some transition is itself DC balanced. Such a transition is hereinafter referred to as a “DC balance transition”. There is no net voltage impulse in the DC balance transition. A drive scheme waveform that uses only a DC balance transition leaves the electro-optic layer in a DC balanced state after each transition. For example, -15
It is assumed that a 300 ms pulse at 15 V is applied next to a 300 ms pulse at V, and the electro-optic layer is transferred from white to black. During the transition, the net voltage impulse of the electro-optic layer is zero. Then, if the electro-optic layer is transferred from black to white by applying a pulse of 300 ms at -15 V following a pulse of 300 ms at 15 V, the net voltage impulse during the transfer also becomes zero.

A drive system configured only with a DC balance transition element inevitably takes a DC balance waveform, but it is also possible to form a DC balance drive system including a DC balance transition and a DC balance unbalanced transition. Details follow below.

In one aspect, the present invention has a plurality of pixels each capable of displaying at least three gray levels,
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
Correction voltage data for each pixel is calculated based on at least one impulse previously applied to each pixel, storing correction voltage data representing the correction voltage for each display pixel,
Reception of an input signal representing a desired final state of at least one display pixel, and the pixel voltage is determined from the driving voltage determined from the initial and final states of the pixel and the lookup table, and the correction voltage data of the pixel The total correction voltage
Provided is a driving method of a bistable electro-optic display constituted by generating an output signal representing a pixel voltage applied to the pixel.

  This method is hereinafter referred to as the “correction voltage” method of the present invention for convenience.

In the correction voltage method, the correction voltage of each pixel is calculated based on at least one of the temporal preceding state of the pixel or the preceding gray level state of the pixel. The correction voltage of each pixel can be applied to the pixel during both the period in which the drive voltage is applied to the pixel and the stop period in which the drive voltage is not applied to the pixel.

For reasons detailed below, it is necessary to periodically update the correction voltage used in the correction voltage method of the present invention. The correction voltage for each pixel may be updated during each superframe (the period required for the complete address of the display). The correction voltage for each pixel is either (1) changing the preceding value of the correction voltage using a fixed algorithm independent of the pulse applied during the corresponding superframe, or (2) the corresponding superframe. It can be updated by increasing the value of step (1) by a numerical value determined by the pulse applied therein. In a preferred variant of the update method, the correction voltage of each pixel is either (1) equally dividing the preceding value of the correction voltage by a fixed constant, or (2) applied to the electro-optic medium during the relevant superframe. It is updated by increasing the value of step (1) by a numerical value that is sufficiently proportional to the total area under the voltage-time curve.

In the correction voltage method of the present invention, the correction voltage can also be applied in the form of an exponentially decreasing voltage applied at the end of at least one drive pulse.

The present invention also provides a device controller used in such a correction voltage method.
The controller
Saving a lookup table containing data representing impulses necessary to convert the initial gray level to the final gray level, saving data representing at least the initial state of each display pixel, and saving correction voltage data for each display pixel Storage means set up as
Input means for receiving an input signal representing a desired final state of at least one display pixel;
Saved data representing the initial state and look-up table of the pixel, a driving voltage necessary to change the initial state of the pixel to the desired final state is determined from the input signal, and further from the correction voltage data of the pixel, It comprises a calculating means for determining a correction voltage for the pixel and determining the pixel voltage from the sum of the drive voltage and the correction voltage, and an output means for generating an output signal representing the pixel voltage.

In the controller, the calculation means may be set to determine the correction voltage based on at least one of a temporal preceding state of the pixel or a preceding gray level state of the pixel. The output means may be set so that the correction voltage is applied to the pixel during both the period in which the drive voltage is applied to the pixel and the stop period in which the drive voltage is not applied to the pixel.

Further, in the controller, the calculation means may be set to update the correction voltage of each pixel during each super frame necessary for the complete address of the display. In the update, the calculation means changes (1) the correction voltage of each pixel to the preceding value of the correction voltage using a fixed algorithm independent of the pulse applied during the corresponding superframe. (2) It may be set to update by increasing the value of step (1) by the numerical value determined by the pulse applied during the corresponding superframe. In a preferred modification of the means, the calculating means divides the correction voltage of each pixel by (1) equally dividing the preceding value of the correction voltage by a fixed constant, or (2) an electro-optic medium during the corresponding superframe. Is set to be updated by increasing the value of step (1) by a value that is sufficiently proportional to the total area under the voltage-time curve applied to.

The output means of the controller may be set to apply the correction voltage in the form of an exponentially decreasing voltage applied at the end of at least one drive pulse.

In another aspect, the present invention has at least three different display states with a plurality of pixels arranged in a plurality of rows and columns, each pixel being uniquely defined at the intersection of a particular row and a particular column In order to change the display state of each pixel, a method for updating a bistable electro-optic display having driving means for applying an electric field independently of each pixel is provided. The method is
Storage of area data representing a specific area that is part of the display, but smaller than the entire area of the display
For each pixel, determine whether the pixel is within a specific area or outside the area,
The first driving method is applied to the pixels in the specific area, and the second driving method is applied to the pixels outside the specific area.

  This method is hereinafter referred to as the “specific region” method of the present invention for convenience.

In the specific area method, the first and second driving methods may have different bit depths. Specifically, one of the first and second drive methods may be monochrome and the other may be a gray scale having at least four different gray levels. The particular area may constitute a text box used to enter text on the display.

In another aspect, the invention has a plurality of pixels, each capable of displaying at least three gray levels,
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
From receiving an input signal representing a desired final state of at least one display pixel and generating an output signal representing an impulse required to convert the initial state of the pixel into the desired final state, which is determined based on a lookup table Configure
At least once transition from the initial state to the final state, the output signal constitutes a DC tuning unbalanced fine tuning sequence,
(A) has a non-zero net impulse;
(B) discontinuous,
(C) The DC reference pulse is a pulse of voltage V ₀ , and V ₀ is the maximum applied voltage in the fine tuning sequence, and is indicated by the same sign as the net impulse G of the fine tuning sequence, and the continuation of the reference pulse Resulting in a change in the gray level of the pixel that is quite different (usually more than 50% different) from the change from the optical state of the DC reference pulse where time is G / V ₀ ,
(D) The definition of the time reference pulse is a unipolar voltage pulse having the same duration as the fine tuning sequence, and the sign of the reference pulse gives a greater change to the gray level. Provided is a driving method for a bistable electro-optic display that ends up with a change in gray level of a pixel that is smaller in scale than the change (typically less than half).

This method (and similar methods defined below) is hereinafter referred to for convenience as the “non-contiguous address” method of the present invention. When the two methods need to be distinguished, they are called the “DC balanced unbalanced non-contiguous address” method and the “DC balanced non-contiguous address” method, respectively.

In a preferred form of the non-contiguous addressing method, the fine tuning sequence results in a pixel gray level change that is less than or equal to half the gray level change due to the time reference pulse.

The invention also has a plurality of pixels, each capable of displaying at least three gray levels,
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
From receiving an input signal representing a desired final state of at least one display pixel and generating an output signal representing an impulse required to convert the initial state of the pixel into the desired final state, which is determined based on a lookup table Configure
At least once transition from the initial state to the final state, the output signal constitutes a DC-balanced fine tuning sequence,
(A) has substantially zero net impulse;
(B) At any point in the fine tuning sequence, the gray level of the pixel is greater than or equal to about one third of the gray level difference between the two extreme optical states of the pixel from the original gray level of the fine tuning sequence. A method of driving a bistable electro-optic display that does not change is also provided.

In both forms of the non-contiguous addressing method of the present invention, the output signal typically consists of at least one unipolar drive pulse in addition to the fine tuning sequence. The discontinuous output signal may be an aperiodic signal. For most of the transitions in the lookup table, the net impulse of the output signal is non-zero and the signal is non-continuous. In at least one transition using a non-continuous output signal, the output signal has a voltage level of + V, 0, -V
Or preferably only pulses having a voltage level of 0 and one of + V and -V. In a preferred form of the method, in at least one transition using a non-continuous output signal, and preferably in the majority of transitions in the look-up table where the initial state and the final state of the pixel are different. The output signal consists of a pulse having a voltage level of 0 that precedes and follows at least two pulses having the same voltage level, either + V or −V. Preferably, the transfer table is DC balanced. Also, in at least one transition using a discontinuous output signal, the output signal may consist of a series of pulses that are integer multiples of a single interval.

The non-contiguous addressing method of the present invention further includes storing data representing at least one temporal preceding state of the pixel or / or at least one preceding gray level state of the pixel, and at least one of the pixel. It consists of generating the output signal based on a temporal preceding state and / or at least one preceding gray level state.

The invention includes a plurality of pixels each capable of displaying at least three gray levels, and an output signal that can change the pixel from an initial state to a final state is applied to each display pixel. In at least one transition where the initial state and the final state are different, the output signal is a zero that precedes and follows at least two pulses having the same voltage level of either + V or -V. A driving method for a bistable electro-optic display composed of pulses having a voltage level is also provided.

In another aspect, the invention includes a plurality of pixels each capable of displaying at least three gray levels, and applying an output signal that can change the pixels from an initial state to a final state to each display pixel. Also provided is a method of driving a bistable electro-optic display that is non-zero but DC balanced in at least one transition.

  This method is hereinafter referred to as the “DC balanced address” method of the present invention for convenience.

In the DC balanced address method, the output signal is at least once transferred.
A first set of pulses is composed of voltage pulses preceded by pulses of the same length but opposite signs. The output signal further constitutes a period of zero voltage between two pulses,
Alternatively, it is interrupted at a certain period of at least one pulse voltage zero. Furthermore, the output signal may constitute a second set of pulses that have the same length but the opposite sign. The second set of pulses may have a different pulse length than the first set of pulses. The first pulse of the second set of pulses may have a different polarity from the first pulse of the first set of pulses. The first set of pulses may appear between the first and second pulses of the second set of pulses.

Furthermore, in the DC balanced addressing method, in the transition described above, the output signal consists of at least one pulse element that can significantly move the pixel to one light rail.

As described in further detail below, the DC balanced addressing method of the present invention may utilize a combination of DC balance transition and DC balance unbalance transition. For example, in each transition where the initial state and final state of the pixel are similar, the output signal is non-zero but DC balanced, and in each transition where the initial state and final state of the pixel are not similar. ,
The output signal is DC unbalanced. In the addressing method, in each transition where the initial state and the final state of the pixel are not the same, in some cases, the format of the output signal is −x / ΔIP / x, where ΔIP is The impulse potential difference between the initial state and the final state of the pixel is shown, and -x and x are a set of pulses having the same length but opposite signs.

The DC balanced address method of the present invention further includes:
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
Receiving an input signal representing a desired final state of at least one display pixel, and generating an output signal representing an impulse required to convert the initial state of the single pixel into a desired final state, which is determined based on a lookup table; Consists of.

  The present invention also has at least one pixel,

（式中、Ｔは波形の長さを示し、積分は波形の継続期間にわたり、Ｖ（ｔ）は時間ｔの
関数としての波形電圧で、Ｍ（ｔ）は、ゼロ時に短パルスより派生する滞留時間依存性を
誘起するために、残留電圧の効果減少を特徴付けるメモリ関数である）が約１ボルト秒よ
り少なくなるような、画素への波形Ｖ（ｔ）の印加より構成する双安定型電気光学ディス
プレイの駆動方法も提供する。当該方法は、以下便宜上、本発明の「ＤＴＤ積分減少」法
と呼ぶ。望ましくは、Ｊは約０．５ボルト秒以下で、最も望ましくは約０．１ボルト秒以
下が良い。実際に、Ｊは出来るだけ小さな値、理想的にはゼロに設定するべきである。

(Where T is the length of the waveform, integration is the duration of the waveform, V (t) is the waveform voltage as a function of time t, and M (t) is a dwell derived from a short pulse at zero. Bistable electro-optic comprising application of waveform V (t) to the pixel such that the memory function that characterizes the reduced effect of residual voltage to induce time dependence is less than about 1 volt-second A display driving method is also provided. This method is hereinafter referred to as the “DTD integral reduction” method of the present invention for convenience. Preferably, J is less than about 0.5 volt seconds, and most desirably less than about 0.1 volt seconds. In practice, J should be set to the smallest possible value, ideally zero.

  In a preferred form of the method, J is calculated by the following formula:

式中、τは減衰（緩和）時間を示し、望ましくは約０．７から約１．３秒の間の値であ
る。
（項目１）
それぞれが少なくとも三つのグレーレベルを表示可能な複数の画素を持ち、
初期グレーレベルを最終グレーレベルに変換するのに必要なインパルスを表すデータを
含むルックアップテーブルの保存、
各表示画素の少なくとも初期状態を表すデータの保存、
少なくとも一表示画素の希望最終状態を表す入力信号の受信、および
当該一画素に印加される画素電圧を表す出力信号の生成から構成し、
いずれの画素の補正電圧も、各画素に以前印加された少なくとも一つのインパルスに基
づき計算される、各表示画素の当該補正電圧を表す補正電圧データの保存と、
当該画素電圧が、当該画素と当該ルックアップテーブルの当該初期・最終状態より決定
される駆動電圧と当該画素の当該補正電圧データより決定される補正電圧の合計である
ことにより特徴付けられる、
双安定型電気光学ディスプレイ駆動方法。
（項目２）
各画素の当該補正電圧が、当該画素の時間的先行状態あるいは当該画素の先行グレーレベ
ル状態の少なくとも一方の状態に基づき計算される項目１に記載の双安定型電気光学ディ
スプレイ駆動方法。
（項目３）
各画素の当該補正電圧が、当該画素に駆動電圧が印加される期間と当該画素に駆動電圧が
印加されない停止期間の両期間中に当該画素に印加される項目１に記載の双安定型電気光
学ディスプレイ駆動方法。
（項目４）
各画素の当該補正電圧が、当該ディスプレイの完全アドレスに必要な各スーパーフレーム
中に更新される項目１に記載の双安定型電気光学ディスプレイ駆動方法。
（項目５）
各画素の当該補正電圧が、（１）該当するスーパーフレーム中に印加されたパルスとは独
立した固定アルゴリズムを使用して当該補正電圧の先行値に変更を加えるか、（２）該当
するスーパーフレーム中に印加されたパルスにより決定される数値分だけステップ（１）
の値を増加させることにより更新される項目４に記載の双安定型電気光学ディスプレイ駆
動方法。
（項目６）
各画素の当該補正電圧が、（１）固定定数により当該補正電圧の先行値を等分するか、（
２）該当するスーパーフレーム中に電気光学媒体に印加された電圧・時間曲線下の総面積
に十分に比例する数値分だけステップ（１）の値を増加させることにより更新される項目
５に記載の双安定型電気光学ディスプレイ駆動方法。
（項目７）
当該補正電圧が、少なくとも一駆動パルスの終末で印加された指数関数的に減衰する電圧
という形式で印加される項目１に記載の双安定型電気光学ディスプレイ駆動方法。
（項目８）
初期グレーレベルを最終グレーレベルに変換するのに必要なインパルスを表すデータを含
むルックアップテーブルの保存、各表示画素の少なくとも初期状態を表すデータの保存、
並びに各表示画素の補正電圧データの保存するよう設定された保存手段、
少なくとも一表示画素の希望最終状態を表す入力信号を受信するための入力手段、
当該画素の初期状態とルックアップテーブルを表す保存データと、当該一画素の初期状
態を希望最終状態に変更するのに必要な駆動電圧を入力信号より決定し、さらに当該画素
の補正電圧データより、当該画素の補正電圧を決定し、駆動電圧と補正電圧の合計より画
素電圧を決定する計算手段、および
当該画素電圧を表す出力信号を生成するための出力手段、
より構成するデバイスコントローラ。
（項目９）
当該計算手段が、当該画素の時間的先行状態あるいは当該画素の先行グレーレベル状態の
少なくとも一つに基づいて当該補正電圧を決定するように設定された項目８に記載のデバ
イスコントローラ。
（項目１０）
当該出力手段が、当該画素に当該駆動電圧が印加される期間と当該画素に当該駆動電圧が
印加されない停止期間の両期間中に、当該画素に当該補正電圧を印加するように設定され
た項目８に記載のデバイスコントローラ。
（項目１１）
当該計算手段が、当該ディスプレイの完全アドレスに必要な各スーパーフレーム中に、各
画素の当該補正電圧を更新するように設定された項目８に記載のデバイスコントローラ。
（項目１２）
当該計算手段が、各画素の当該補正電圧を（１）該当するスーパーフレーム中に印加され
たパルスとは独立した固定アルゴリズムを使用して当該補正電圧の先行値に変更を加える
か、（２）該当するスーパーフレーム中に印加されたパルスにより決定される数値分だけ
ステップ（１）の値を増加させることにより更新するように設定された項目１１に記載の
デバイスコントローラ。
（項目１３）
当該計算手段が、各画素の当該補正電圧を（１）固定定数により当該補正電圧の先行値を
等分するか、（２）該当するスーパーフレーム中に電気光学媒体に印加された電圧・時間
曲線下の総面積に十分に比例する数値分だけステップ（１）の値を増加することにより更
新するように設定された項目１２に記載のデバイスコントローラ。
（項目１４）
当該出力手段が、少なくとも一駆動パルスの終末で印加された指数関数的に減少する電圧
という形式で、当該補正電圧を印加するように設定された項目８に記載のデバイスコント
ローラ。
（項目１５）
各画素が特定の行と特定の縦列の交点で独自に定義される、複数の行と縦列に配列された
複数の画素と、少なくとも三つの異なる表示状態を有する各画素の表示状態を変更するた
め、各画素とは独立して電場を印加する駆動手段を備え、
当該ディスプレイの全域よりは小さいが、一部を構成する特定領域を表す領域データの
保存、
各画素につき、当該画素が特定領域内か領域外かの決定、
当該特定領域内の画素への第一駆動方式の適用、および当該特定領域外の画素への第一
駆動方式とは異なる第二駆動方式の適用、
から構成する双安定型電気光学ディスプレイ更新方法。
（項目１６）
当該第一、第二駆動方式のビット深度が異なる項目１５に記載の双安定型電気光学ディス
プレイ更新方法。
（項目１７）
当該第一、第二駆動方式の一方式はモノクロで、他方式は少なくとも四つの異なるグレー
レベルを有するグレースケールである項目１６に記載の双安定型電気光学ディスプレイ更
新方法。
（項目１８）
当該特定領域が当該ディスプレイ上にテキストを入力するために使用されるテキストボッ
クスより構成される項目１５に記載の双安定型電気光学ディスプレイ更新方法。
（項目１９）
それぞれが少なくとも三つのグレーレベルを表示可能な複数の画素を持ち、
初期グレーレベルを最終グレーレベルに変換するのに必要なインパルスを表すデータを
含むルックアップテーブルの保存、
各表示画素の少なくとも初期状態を表すデータの保存、
少なくとも一表示画素の希望最終状態を表す入力信号の受信、および
ルックアップテーブルに基づき決定される、当該一画素の初期状態を希望最終状態へ変
換するのに必要なインパルスを表す出力信号の生成から構成し、
初期状態から最終状態への少なくとも一度の転移で、当該出力信号がＤＣバランス不平
衡の微同調シーケンスを構成し、当該微同調シーケンスは、
（ａ）非ゼロの正味インパルスを有し、
（ｂ）非連続的で、
（ｃ）ＤＣ基準パルスが電圧Ｖ_０のパルスで、Ｖ_０は当該微同調シーケンス中の最大印
加電圧であるが、当該微同調シーケンスの正味インパルスＧと同様の符号で示され、当該
基準パルスの継続時間がＧ／Ｖ_０であるところのＤＣ基準パルスの光学状態からの変化と
は著しく異なる当該画素のグレーレベル変化に終わり、
（ｄ）時間基準パルスの定義が、当該微同調シーケンスと同じ継続時間の単極電圧パル
スで、当該基準パルスの符号はグレーレベルにより大きな変化を与えるものであるところ
の当該時間基準パルスによるグレーレベル変化と比べ規模が小さい当該画素のグレーレベ
ル変化に終わる双安定型電気光学ディスプレイの駆動方法。
（項目２０）
当該微同調シーケンスが、時間基準パルスによるグレーレベル変化の半分以下の画素のグ
レーレベル変化に終わる項目１９に記載の双安定型電気光学ディスプレイの駆動方法。
（項目２１）
当該少なくとも一回の転移において、当該出力信号が、当該微同調シーケンスに加えて、
少なくとも一つの単極駆動パルスから構成する項目１９に記載の双安定型電気光学ディス
プレイの駆動方法。
（項目２２）
当該少なくとも一回の転移において、当該出力信号が非周期信号である項目１９に記載の
双安定型電気光学ディスプレイの駆動方法。
（項目２３）
当該ルックアップテーブルにおける転移の大部分において、当該出力信号の正味インパル
スは非ゼロで、当該信号は非連続的である項目１９に記載の双安定型電気光学ディスプレ
イの駆動方法。
（項目２４）
当該少なくとも一回の転移において、当該出力信号が電圧レベルが＋Ｖ、０、−Ｖである
パルスからのみ構成する項目１９に記載の双安定型電気光学ディスプレイの駆動方法。
（項目２５）
当該少なくとも一回の転移において、当該出力信号が電圧レベルが０と、＋ＶとーＶの内
一つを有するパルスからのみ構成する項目２３に記載の双安定型電気光学ディスプレイの
駆動方法。
（項目２６）
当該少なくとも一回の転移において、当該出力信号が、＋Ｖか−Ｖの内どちらか一つの同
じ電圧レベルを有する少なくとも二つのパルスに先行、および後行される０の電圧レベル
を有するパルスより構成する項目２５に記載の双安定型電気光学ディスプレイの駆動方法
。
（項目２７）
当該画素の当該初期状態と当該最終状態が異なる当該ルックアップテーブルにおける転移
の大部分において、当該出力信号が、＋Ｖか−Ｖの内どちらか一つの同じ電圧レベルを有
する少なくとも二つのパルスに先行、および後行される０の電圧レベルを有するパルスよ
り構成する項目２６に記載の双安定型電気光学ディスプレイの駆動方法。
（項目２８）
当該転移テーブルのＤＣバランスが取れている項目１９に記載の双安定型電気光学ディス
プレイの駆動方法。
（項目２９）
当該少なくとも一回の転移において、当該出力信号が、単一区間の整数の倍数である一連
のパルスから構成する項目１９に記載の双安定型電気光学ディスプレイの駆動方法。
（項目３０）
さらに、当該一画素の少なくとも一つの時間的先行状態あるいは／または当該一画素の少
なくとも一つの先行グレーレベル状態を表すデータの保存と、当該一画素の少なくとも一
つの時間的先行状態あるいは／または少なくとも一つの先行グレーレベル状態に基づく当
該出力信号の生成から構成する１９に記載の双安定型電気光学ディスプレイの駆動方法。
（項目３１）
それぞれが少なくとも三つのグレーレベルを表示可能な複数の画素を持ち、各表示画素に
画素を初期状態から最終状態に変更できる出力信号から印加することから構成し、画素の
初期状態と最終状態が異なる少なくとも一回の転移において、当該出力信号は、＋Ｖか−
Ｖの内どちらか一つの同じ電圧レベルを有する少なくとも二つのパルスに先行、および後
行される０の電圧レベルを有するパルスより構成する双安定型電気光学ディスプレイ駆動
方法。
（項目３２）
それぞれが少なくとも三つのグレーレベルを表示可能な複数の画素を持ち、
初期グレーレベルを最終グレーレベルに変換するのに必要なインパルスを表すデータを
含むルックアップテーブルの保存、
各表示画素の少なくとも初期状態を表すデータの保存、
少なくとも一表示画素の希望最終状態を表す入力信号の受信、および
ルックアップテーブルに基づき決定される、当該一画素の初期状態を希望最終状態へ変
換するのに必要なインパルスを表す出力信号の生成から構成し、
初期状態から最終状態への少なくとも一度の転移で、当該出力信号がＤＣバランスの取
れた微同調シーケンスを構成し、当該微同調シーケンスは、
（ａ）実質ゼロの正味インパルスを有し、
（ｂ）当該微同調シーケンスのどの時点においても、当該画素の当該グレーレベルが、
当該微同調シーケンス当初のグレーレベルから、当該画素の二つの極度光学状態間のグレ
ーレベルの差の約３分の１以上変化することはない双安定型電気光学ディスプレイの駆動
方法。
（項目３３）
当該少なくとも一回の転移において、当該出力信号が、当該微同調シーケンスに加えて、
少なくとも一つの単極駆動パルスから構成する項目３２に記載の双安定型電気光学ディス
プレイの駆動方法。
（項目３４）
それぞれが少なくとも三つのグレーレベルを表示可能な複数の画素を持ち、各表示画素に
画素を初期状態から最終状態に変更できる出力信号を印加することから構成し、少なくと
も一回の転移において、当該出力信号は非ゼロであるがＤＣバランスが取れている双安定
型電気光学ディスプレイ駆動方法。
（項目３５）
当該少なくとも一回の転移で、当該出力信号が、同長であるが符号が逆であるパルスによ
り先行される電圧パルスより構成する一組目のパルスを構成する項目３４に記載のＤＣバ
ランスの取れた双安定型電気光学ディスプレイの駆動方法。
（項目３６）
当該出力信号が、さらに二つのパルス間に電圧ゼロのある期間を構成する項目３５に記載
のＤＣバランスの取れた双安定型電気光学ディスプレイの駆動方法。
（項目３７）
少なくとも一パルスを電圧ゼロのある期間で中断する項目３５に記載のＤＣバランスの取
れた双安定型電気光学ディスプレイの駆動方法。
（項目３８）
当該少なくとも一回の転移で、当該出力信号が、さらに同長であるが符号が逆である二組
目のパルスを構成する項目３５に記載のＤＣバランスの取れた双安定型電気光学ディスプ
レイの駆動方法。
（項目３９）
当該二組目のパルスの長さが一組目のパルスと異なる項目３８に記載のＤＣバランスの取
れた双安定型電気光学ディスプレイの駆動方法。
（項目４０）
当該二組目のパルスの一つ目のパルスは、当該一組目のパルスの一つ目のパルスと極性が
異なる項目３８に記載のＤＣバランスの取れた双安定型電気光学ディスプレイの駆動方法
。
（項目４１）
当該一組目のパルスが、当該二組目のパルスの一つ目のパルスと二つ目のパルスの間に出
現する項目３８に記載のＤＣバランスの取れた双安定型電気光学ディスプレイの駆動方法
。
（項目４２）
当該少なくとも一回の転移で、当該出力信号が、一方の光レールへ画素をかなり移動でき
る少なくとも一つのパルス要素から構成する項目３４に記載のＤＣバランスの取れた双安
定型電気光学ディスプレイの駆動方法。
（項目４３）
当該画素の当該初期状態と当該最終状態が同様である各転移において、当該出力信号は非
ゼロであるがＤＣバランスが取れており、当該画素の当該初期状態と当該最終状態が同様
ではない各転移において、当該出力信号はＤＣバランス不平衡である項目３４に記載のＤ
Ｃバランスの取れた双安定型電気光学ディスプレイの駆動方法。
（項目４４）
当該画素の当該初期状態と当該最終状態が同様ではない各転移において、当該出力信号の
形式が−ｘ／ΔＩＰ／ｘであり、当該形式中、ΔＩＰは当該画素の当該初期状態と当該最
終状態間のインパルスポテンシャルの差を示し、−ｘとｘは同長であるが符号が逆である
一組のパルスを示す項目４３に記載のＤＣバランスの取れた双安定型電気光学ディスプレ
イの駆動方法。
（項目４５）
当該初期グレーレベルを最終グレーレベルに変換するのに必要なインパルスを表すデータ
を含むルックアップテーブルの保存、
各表示画素の少なくとも初期状態を表すデータの保存、
少なくとも一表示画素の希望最終状態を表す入力信号の受信、および
ルックアップテーブルに基づき決定される、当該一画素の当該初期状態を当該希望最終
状態へ変換するのに必要な当該インパルスを表す出力信号の生成
より、さらに構成する項目３４に記載のＤＣバランスの取れた双安定型電気光学ディスプ
レイの駆動方法。
（項目４６）
少なくとも一画素を持ち、

（式中、Ｔは波形の長さを示し、積分は波形の継続期間にわたり、Ｖ（ｔ）は時間ｔの
関数としての波形電圧で、Ｍ（ｔ）は、ゼロ時に短パルスより派生する滞留時間依存性を
誘起するために、残留電圧の効果減少を特徴付けるメモリ関数である）が約１ボルト秒よ
り少なくなるような、当該画素への波形Ｖ（ｔ）の印加より構成する双安定型電気光学デ
ィスプレイの駆動方法。
（項目４７）
Ｊが約０．５ボルト秒以下である項目４６に記載の双安定型電気光学ディスプレイの駆動
方法。
（項目４８）
Ｊが約０．１ボルト秒以下である項目４７に記載の双安定型電気光学ディスプレイの駆動
方法。
（項目４９）
Ｊが、

により計算され、式中、τが減少（緩和）時間を示す項目４６に記載の双安定型電気光学
ディスプレイの駆動方法。
（項目５０）
Ｔが約０．７から約１．３秒の間の値である項目４９に記載のプロセス。

In the equation, τ represents the decay (relaxation) time, and is preferably a value between about 0.7 and about 1.3 seconds.
(Item 1)
Each having a plurality of pixels capable of displaying at least three gray levels,
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
Receiving at least one input signal representing a desired final state of a display pixel and generating an output signal representing a pixel voltage applied to the one pixel;
Correction voltage data for any pixel is calculated based on at least one impulse previously applied to each pixel, storing correction voltage data representing the correction voltage for each display pixel; and
The pixel voltage is characterized by the sum of the drive voltage determined from the initial and final states of the pixel and the lookup table and the correction voltage determined from the correction voltage data of the pixel.
Bistable electro-optic display driving method.
(Item 2)
The bistable electro-optic display driving method according to item 1, wherein the correction voltage of each pixel is calculated based on at least one of a temporal preceding state of the pixel and a preceding gray level state of the pixel.
(Item 3)
Item 2. The bistable electro-optic according to item 1, wherein the correction voltage of each pixel is applied to the pixel during both the period in which the drive voltage is applied to the pixel and the stop period in which the drive voltage is not applied to the pixel. Display driving method.
(Item 4)
2. The bistable electro-optic display driving method according to item 1, wherein the correction voltage of each pixel is updated during each super frame necessary for a complete address of the display.
(Item 5)
The correction voltage of each pixel is either (1) changing the preceding value of the correction voltage using a fixed algorithm independent of the pulse applied during the corresponding superframe, or (2) the corresponding superframe. Step (1) by the numerical value determined by the pulse applied during
5. The bistable electro-optic display driving method according to item 4, which is updated by increasing the value of.
(Item 6)
Whether the correction voltage of each pixel divides the preceding value of the correction voltage by a fixed constant (1)
2) The item according to item 5, which is updated by increasing the value of step (1) by a numerical value sufficiently proportional to the total area under the voltage-time curve applied to the electro-optic medium during the corresponding superframe. Bistable electro-optic display driving method.
(Item 7)
The bistable electro-optic display driving method according to item 1, wherein the correction voltage is applied in the form of an exponentially decaying voltage applied at the end of at least one driving pulse.
(Item 8)
Storing a lookup table containing data representing impulses needed to convert the initial gray level to the final gray level; storing data representing at least the initial state of each display pixel;
And storage means set to store correction voltage data of each display pixel,
Input means for receiving an input signal representing a desired final state of at least one display pixel;
Saved data representing the initial state and look-up table of the pixel, a driving voltage necessary to change the initial state of the pixel to the desired final state is determined from the input signal, and further from the correction voltage data of the pixel, Calculating means for determining a correction voltage of the pixel and determining the pixel voltage from the sum of the drive voltage and the correction voltage; and output means for generating an output signal representing the pixel voltage;
Device controller that consists of more.
(Item 9)
9. The device controller according to item 8, wherein the calculation means is set to determine the correction voltage based on at least one of a temporal preceding state of the pixel or a preceding gray level state of the pixel.
(Item 10)
Item 8 in which the output means is set to apply the correction voltage to the pixel during both the period in which the drive voltage is applied to the pixel and the stop period in which the drive voltage is not applied to the pixel. Device controller as described in.
(Item 11)
9. The device controller according to item 8, wherein the calculation means is set to update the correction voltage of each pixel during each super frame necessary for the complete address of the display.
(Item 12)
The calculation means changes the correction voltage of each pixel using a fixed algorithm independent of the pulse applied during the corresponding superframe (1) or (2) 12. The device controller according to item 11, which is set to be updated by increasing the value of step (1) by a numerical value determined by a pulse applied during the corresponding superframe.
(Item 13)
The calculation means equally divides the correction voltage of each pixel by (1) a preceding value of the correction voltage by a fixed constant, or (2) a voltage / time curve applied to the electro-optic medium during the corresponding superframe. 13. The device controller according to item 12, which is set to be updated by increasing the value of step (1) by a numerical value which is sufficiently proportional to the total area below.
(Item 14)
Item 9. The device controller of item 8, wherein the output means is set to apply the correction voltage in the form of an exponentially decreasing voltage applied at the end of at least one drive pulse.
(Item 15)
To change the display state of each pixel having at least three different display states and a plurality of pixels arranged in a plurality of rows and columns, each pixel being uniquely defined at the intersection of a specific row and a specific column , Comprising driving means for applying an electric field independently of each pixel;
Storage of area data representing a specific area that is part of the display, but smaller than the entire area of the display
For each pixel, determine whether the pixel is within a specific area or outside the area,
Application of the first drive method to pixels within the specific region, and application of a second drive method different from the first drive method to pixels outside the specific region;
A bi-stable electro-optic display update method comprising:
(Item 16)
Item 16. The bistable electro-optic display update method according to item 15, wherein the bit depths of the first and second drive systems are different.
(Item 17)
Item 17. The bistable electro-optic display updating method according to item 16, wherein one of the first and second driving methods is monochrome, and the other method is grayscale having at least four different gray levels.
(Item 18)
16. The bistable electro-optic display updating method according to item 15, wherein the specific area is composed of a text box used for inputting text on the display.
(Item 19)
Each having a plurality of pixels capable of displaying at least three gray levels,
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
From receiving an input signal representing a desired final state of at least one display pixel and generating an output signal representing an impulse required to convert the initial state of the pixel into the desired final state, which is determined based on a lookup table Configure
At least once transition from the initial state to the final state, the output signal constitutes a DC tuning unbalanced fine tuning sequence,
(A) has a non-zero net impulse;
(B) discontinuous,
(C) The DC reference pulse is a pulse of voltage V ₀ , and V ₀ is the maximum applied voltage in the fine tuning sequence, and is indicated by the same sign as the net impulse G of the fine tuning sequence. Resulting in a change in the gray level of the pixel that is significantly different from the change from the optical state of the DC reference pulse where the duration is G / V ₀ ,
(D) The definition of the time reference pulse is a unipolar voltage pulse having the same duration as the fine tuning sequence, and the sign of the reference pulse gives a greater change to the gray level. A driving method for a bistable electro-optic display that ends with a change in gray level of the pixel, which is smaller than the change.
(Item 20)
Item 20. The driving method for a bistable electro-optic display according to Item 19, wherein the fine tuning sequence ends with a gray level change of a pixel that is less than half of the gray level change caused by the time reference pulse.
(Item 21)
In the at least one transition, the output signal is added to the fine tuning sequence,
Item 20. The method for driving a bistable electro-optic display according to item 19, comprising at least one unipolar drive pulse.
(Item 22)
Item 20. The driving method of the bistable electro-optic display according to Item 19, wherein the output signal is an aperiodic signal in the at least one transition.
(Item 23)
20. A method for driving a bistable electro-optic display according to item 19, wherein, for most of the transitions in the look-up table, the net impulse of the output signal is non-zero and the signal is non-continuous.
(Item 24)
Item 20. The driving method of the bistable electro-optic display according to item 19, wherein the output signal is composed only of pulses whose voltage levels are + V, 0, and -V in at least one transition.
(Item 25)
24. A driving method of a bistable electro-optic display according to item 23, wherein the output signal is composed only of a pulse having a voltage level of 0 and one of + V and −V in at least one transition.
(Item 26)
In the at least one transition, the output signal consists of a pulse having a voltage level of 0 preceding and following at least two pulses having the same voltage level of either + V or -V. 26. A driving method of a bistable electro-optic display according to item 25.
(Item 27)
In most of the transitions in the look-up table where the initial state and the final state of the pixel are different, the output signal precedes at least two pulses having the same voltage level of either + V or -V; 27. A driving method of a bistable electro-optic display according to item 26, further comprising a pulse having a voltage level of 0 to be followed.
(Item 28)
Item 20. The driving method of the bistable electro-optic display according to Item 19, wherein the transfer table is DC balanced.
(Item 29)
20. The driving method of a bistable electro-optic display according to item 19, wherein, in the at least one transition, the output signal is composed of a series of pulses that are integer multiples of a single interval.
(Item 30)
Further, storage of data representing at least one temporal preceding state of the pixel or / or at least one preceding gray level state of the pixel, and at least one temporal preceding state or / or at least one of the pixel. 20. A driving method for a bistable electro-optic display according to 19, comprising generating the output signal based on two preceding gray level states.
(Item 31)
Each pixel has a plurality of pixels capable of displaying at least three gray levels, and each pixel is applied with an output signal that can change the pixel from the initial state to the final state. The initial state and the final state of the pixel are different. In at least one transition, the output signal is + V or −
A method of driving a bistable electro-optic display comprising a pulse having a voltage level of 0 that precedes and follows at least two pulses having the same voltage level of any one of V.
(Item 32)
Each having a plurality of pixels capable of displaying at least three gray levels,
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level,
Storage of data representing at least the initial state of each display pixel;
From receiving an input signal representing a desired final state of at least one display pixel and generating an output signal representing an impulse required to convert the initial state of the pixel into the desired final state, which is determined based on a lookup table Configure
At least once transition from the initial state to the final state, the output signal constitutes a DC-balanced fine tuning sequence,
(A) has substantially zero net impulse;
(B) At any point in the fine tuning sequence, the gray level of the pixel is
A driving method for a bistable electro-optic display in which the gray level difference between the two extreme optical states of the pixel does not change by more than about one third from the initial gray level of the fine tuning sequence.
(Item 33)
In the at least one transition, the output signal is added to the fine tuning sequence,
33. A driving method of a bistable electro-optic display according to item 32, comprising at least one monopolar driving pulse.
(Item 34)
Each pixel has a plurality of pixels capable of displaying at least three gray levels, and each display pixel is configured by applying an output signal capable of changing the pixel from an initial state to a final state, and at least one transition is performed with the output A bistable electro-optic display driving method in which the signal is non-zero but DC balanced.
(Item 35)
Item 35. The DC balance according to item 34, wherein at least one transition, the output signal constitutes a first set of pulses composed of voltage pulses preceded by pulses having the same length but the opposite sign. A driving method for a bistable electro-optic display.
(Item 36)
36. The method for driving a DC-balanced bistable electro-optic display according to item 35, wherein the output signal further constitutes a period in which the voltage is zero between two pulses.
(Item 37)
36. The method of driving a DC balanced bistable electro-optic display according to item 35, wherein at least one pulse is interrupted in a period of zero voltage.
(Item 38)
36. Driving a DC-balanced bistable electro-optic display according to item 35, wherein the output signal further comprises the second set of pulses having the same length but the opposite sign in the at least one transition. Method.
(Item 39)
39. The driving method of a bistable electro-optic display with DC balance according to Item 38, wherein the length of the second set of pulses is different from that of the first set of pulses.
(Item 40)
39. The method of driving a bistable electro-optic display with DC balance according to Item 38, wherein the first pulse of the second set of pulses is different in polarity from the first pulse of the first set of pulses.
(Item 41)
39. A method of driving a DC balanced bistable electro-optic display according to item 38, wherein the first set of pulses appears between the first pulse and the second pulse of the second set of pulses. .
(Item 42)
35. A method of driving a DC balanced bistable electro-optic display according to item 34, wherein the output signal comprises at least one pulse element capable of moving the pixel considerably to one light rail by at least one transition. .
(Item 43)
In each transition where the initial state and the final state of the pixel are similar, the output signal is non-zero but DC balanced, and the initial state and the final state of the pixel are not similar. 35, wherein the output signal is DC unbalanced.
C-balanced bistable electro-optic display driving method.
(Item 44)
In each transition where the initial state and the final state of the pixel are not the same, the format of the output signal is −x / ΔIP / x, where ΔIP is between the initial state and the final state of the pixel. 45. A driving method of a DC balanced bistable electro-optic display according to item 43, which shows a pair of pulses having the same length, but having the opposite sign.
(Item 45)
A lookup table containing data representing the impulses needed to convert the initial gray level to the final gray level;
Storage of data representing at least the initial state of each display pixel;
Reception of an input signal representing a desired final state of at least one display pixel, and an output signal representing the impulse necessary for converting the initial state of the pixel into the desired final state, which is determined based on a lookup table 35. A method of driving a bistable electro-optic display with DC balance according to item 34, further comprising:
(Item 46)
Have at least one pixel,

(Where T is the length of the waveform, integration is the duration of the waveform, V (t) is the waveform voltage as a function of time t, and M (t) is a dwell derived from a short pulse at zero. A bistable electric power composed of the application of the waveform V (t) to the pixel so that the time dependence is induced, which is a memory function that characterizes the reduced effect of the residual voltage (less than about 1 volt-second). Driving method of optical display.
(Item 47)
47. A method for driving a bistable electro-optic display according to item 46, wherein J is about 0.5 volt second or less.
(Item 48)
48. The method of driving a bistable electro-optic display according to item 47, wherein J is about 0.1 volt second or less.
(Item 49)
J

47. A driving method of a bistable electro-optic display according to item 46, wherein τ indicates a decrease (relaxation) time, calculated by:
(Item 50)
50. The process of item 49, wherein T is a value between about 0.7 and about 1.3 seconds.

1A to 1E are diagrams showing five waveforms that can be used in the non-contiguous address method of the present invention. FIG. 2 illustrates the problem of addressing an electro-optic display using multiple frames of unipolar voltage. FIG. 3 is a diagram illustrating one method for solving the problem of FIG. 2 using the non-contiguous addressing method of the present invention. FIG. 4 is a diagram showing a second method for solving the problem of FIG. 13 by using the non-contiguous address method of the present invention. FIG. 5 is a diagram showing waveforms that can be used in the non-contiguous addressing method of the present invention. FIG. 6 is a diagram illustrating a basic waveform that can be modified in accordance with the present invention to generate the waveform of FIG. FIG. 7 illustrates the problem of addressing an electro-optic display using multiple frames of unipolar voltage while maintaining DC balance. FIG. 8 is a diagram illustrating one method for solving the problem of FIG. 7 using the non-contiguous addressing method of the present invention. FIG. 9 is a diagram showing a second method for solving the problem of FIG. 7 by using the non-contiguous address method of the present invention. FIG. 10 is a diagram showing gray levels obtained on an electro-optic display of only 4 gray levels without using the non-contiguous addressing method of the present invention as described in the following examples. FIG. 11 is a diagram showing gray levels obtained from a display similar to FIG. 10 using various non-contiguous address sequences. FIG. 12 is a diagram showing gray levels obtained from a display similar to that of FIG. 10 using a driving scheme modified based on the non-contiguous addressing method of the present invention. FIG. 13 shows a simple DC balance waveform that can be used to drive an electro-optic display. FIG. 14 shows two changes to the waveform of FIG. 13 to incorporate a period of zero voltage. FIG. 15 is a diagram illustrating two changes to the waveform of FIG. 13 to incorporate a period of zero voltage. FIG. 16 is a diagram schematically illustrating how the waveform of FIG. 13 can be modified to apply a set of drive pulses. FIG. 17 is a diagram showing one waveform formed by changing the waveform of FIG. 13 by the method shown in FIG. Figure 18 is a method shown in FIG. 16 is a diagram showing a second waveform which is formed by changing the waveform of FIG. 13. FIG. 19 is a diagram schematically showing how the waveform of FIG. 18 can be further modified to apply the third set of drive pulses. 20 is a diagram showing one waveform formed by changing the waveform of FIG. 18 by the method shown in FIG. FIG. 21 is a diagram illustrating one preferred DC balance unbalanced waveform that can be used in conjunction with a DC balance waveform to provide a complete look-up table for use in the method of the present invention. FIG. 22 is a graph showing a decrease in residence time dependency that can be realized by the correction voltage method of the present invention. FIG. 23 is a graph showing an effect of residence time dependency in an electro-optic display.

From the foregoing, it is apparent that the present invention makes various different improvements to the driving method of the electro-optic display and the device controller and other apparatuses for realizing the driving method. In the following description, the various different improvements provided by the present invention will usually be described separately, but in practice, a single display may utilize one or more important methods, eg, It is natural for those familiar with the image field that a display using the non-contiguous addressing method also uses a specific area method.

The ideal addressing method for impulse-driven electro-optic displays, called the so-called “general grayscale image flow” method, is where the controller directs each writing of the image so that each pixel directly transitions from the initial gray level to the final gray level. It may initially appear as if it is a way of organizing. Inevitably, however, writing images to an impulse-driven display can be error prone. As mentioned previously, the actual errors encountered include the following:
(A) Prior state dependency: The impulse required to switch a pixel to a new optical state depends not only on the initial optical state and the desired optical state, but also on the previous optical state of the pixel.

(B) Residence time dependence: The impulse required to switch a pixel to a new optical state depends on the time the pixel spent under various optical states. The obvious nature of this dependence is not well understood, but in general, the longer the pixel remains in the current optical state, the greater the required impulse.

(C) Temperature dependence: The impulse required to switch the pixel to the new optical state is highly temperature dependent.

(D) Humidity dependence: The impulse required to switch a pixel to a new optical state is highly dependent on ambient humidity, at least for some electro-optic displays.

(E) Mechanical consistency: The impulse required to switch a pixel to a new optical state may be affected by mechanical diversity in the display, such as the thickness of the electro-optic medium and the associated laminating adhesive. Other mechanical inconsistencies may arise from unavoidable diversity in manufacturing batches of media, manufacturing tolerances, material diversity, and the like.

(F) Voltage error: Due to some inevitable errors in the voltage supplied by the driver, the impulses actually applied to the pixels are slightly different from those theoretically applied.

A typical grayscale image flow suffers from the “error accumulation” phenomenon. For example, suppose that temperature dependence causes a 0.2 L * error in the positive direction for each transition. After 50 transfers, the error accumulates to 10L *. Perhaps more realistically, if the average error of each transition, expressed as the difference between the theoretical reflectance of the display and the actual reflectance, is ± 0.2 L *,
After 100 consecutive transitions, the average deviation of the pixel from the expected state is 2L *. This deviation is apparent to the average observer of certain types of images.

The error accumulation phenomenon is applicable not only to errors due to temperature but also to other types of errors. Although the error can be corrected, accuracy is limited. For example, the temperature error can be corrected by a temperature sensor and a look-up table. However, since the resolution of the temperature sensor is limited, a temperature slightly different from the temperature read by the electro-optic medium may be read. Similarly, the preceding state dependency can be corrected by storing the preceding state and the multi-dimensional transition matrix, but the controller memory limits the number of states that can be recorded and the size of the transition matrix that can be stored. There is a limit to the correction.

Therefore, general grayscale image flow requires very precise control of applied impulses to provide good results, and in the current state of electro-optic display technology, general grayscale image flow is a commercial display. Has been experimentally found to be usually inappropriate.

Almost all electro-optic displays have a built-in reset (error limit) mechanism, an extreme (usually black and white) optical state that functions as a “light rail”. After a certain impulse is applied to a pixel of an electro-optic display, the pixel cannot become whiter (or blacker). For example, in a microcapsule electro-optic display, after applying a certain impulse, all the electrophoretic particles are forced against each other or against the capsule wall and cannot move, so that the limited optical state Or a light rail is produced. In such media, the size and charge of the electrophoretic particles vary, so some particles reach the rail before other particles, and the impulse required when the final optical state of the transition is extremely close to the black / white state. In the case of a transition that decreases in accuracy and ends near the center of the optical region of the pixel, a “soft rail” phenomenon occurs, in which the required optical accuracy increases dramatically. Needless to say, in a purely general grayscale image flow drive scheme, the gray level of a particular pixel can change to infinity without touching any light rail, so that drive scheme depends on the light rail. Therefore, the gray level error cannot be prevented.

As described in the above-mentioned US Pat. Nos. 6,504,524 and 6,531,997, in many electro-optic media, particularly particle-type electrophoretic media, it is necessary to drive the media for a long period of time. It is desirable to use a direct current (DC) balanced drive system in the sense that the algebraic sum of the currents passing through the pixels should be zero or as close to zero as possible. It should be designed with standards in mind. More precisely, the look-up table should be designed to provide DC balance for the entire array of transitions starting and ending in one extreme optical state (black, white) of the pixel. According to the above, since the impulse required for a specific transition from gray to gray, such as the current passing through the pixel, is fairly constant, this DC balancing may seem initially impossible to achieve. However, this is only true for the approximation results obtained first, and at least in a particle-type electrophoretic medium (similar to other electro-optic media), (for example) five spaced 50 ms pulses It has been experimentally found that the effect applied to the pixel is not the same as applying a 250 ms pulse of the same voltage. Therefore, there is some flexibility in the current passing through the pixel to achieve a certain transition, and this flexibility helps to achieve DC balance. For example, the lookup table of the present invention can store multiple impulses per transition, as well as the value of the total current provided by each of the impulses, and the controller can have a certain lead time (pixel) for each pixel. A register set to store the algebraic sum of the impulses applied to the pixel (such as when it was last in a black state) can be maintained. When a particular pixel is moved from a white or gray state to a black state, the controller examines the register associated with that pixel and adjusts the DC balance in the entire array of transitions from the previous black state to the next black state. Determine the current required to achieve and zero the associated resistor, or at least make the residue as small as possible (in this case, the associated resistor holds the value of that residue and is applied during a later transition The impulse required for the transition from white to gray to black is selected from a number of stored impulses. Obviously, by repeating this process, accurate DC balance over a long period of time can be achieved for each pixel.

The following discussion regarding the various aspects of the present invention presupposes the full content of the aforementioned patent WO 03/044765, particularly familiarity with the various waveforms disclosed in that patent. Various methods of the present invention
It is natural for those familiar with the display field that the basic look-up table method described in the above-mentioned patent WO 03/044765 can be modified to add various optional functions (temperature correction, service life correction, humidity correction, etc.). It is obvious. The various methods of the present invention reduce the amount of data to be stored in the look-up table, so that the aforementioned patent WO 03/04476 can be used.
The method described in No. 5 may be used. Furthermore, since the data constituting the lookup table can be handled as a general multidimensional data set, (a) the size of storage required for the data set, (b) the amount of calculation required for data extraction, or (c) the relevant To reduce one or more of the time required to locate and extract a particular element from a set, any standard function or algorithm known to those familiar with data storage and data processing ,
It can also be used in symbolic methods. The storage technology includes, for example, representation of a data set as a combination of a hash function, lossless / lossy compression, and a basis function.

(Discontinuous address method)
The fine adjustment of the gray level in the method of the present invention can be realized by the non-contiguous address method of the present invention. As described above, there are two main forms of the non-contiguous address method: a DC balance unbalanced form and a DC balanced form. The DC balance unbalanced form achieves at least one transition between gray levels with an output signal having a non-zero net impulse (i.e., the lengths of the positive and negative segments are not equal), so internally DC balance Is not removed and is discontinuous (that is, the pulse has a zero voltage portion or a different polarity). The output signal used in the non-contiguous addressing method may or may not be aperiodic (ie, composed of repeating units such as + / − / + / − and ++ / −− / ++ / −−). May or may not be configured).

The non-continuous waveform (hereinafter referred to as a “fine tuning” or “FT” waveform) does not have a frame of different polarity and / or a display (usually the display is applied to the pixels of the electro-optic medium) A pixel electrode associated with each pixel and a number of pixels, typically a front electrode extending across the front of the display, so that the electric field generated is determined by the voltage difference between the associated pixel electrode and the front electrode With respect to the front side effective voltage (which is an active matrix display), it may contain only three levels of voltage: + V, 0, -V. Alternatively, the FT waveform can include any one of the above-described waveforms (such as n-prepulse) to which a non-continuous waveform is applied, including three or more levels of voltage.

The FT waveform is (usually) dependent on one or more previous image states and is subject to standard pulse width modulation (
It is used to realize a change smaller than the change in optical state that can be realized by PWM) technology. (Thus, the actual FT waveform used is different in the look-up table due to the transition, so it is claimed to use alternating polarity pulses, for example, to prevent electrophoretic particles from adhering to surfaces such as capsule walls. (In contrast to some prior art waveforms.)
In a preferred form of the non-contiguous addressing method, all the combinations of waveforms necessary to achieve the total acceptable optical transition (“transition matrix”) of the display are provided, at least one waveform is the FT waveform of the present invention, The combination of waveforms is DC balanced, and in another preferred form of the non-contiguous addressing method, the length of all voltage segments is an integer multiple of a single interval (“frame time”). Means a part of a waveform with a constant voltage.

The non-contiguous addressing method of the present invention has a waveform that is expected to be zero in many impulse-driven electro-optic media and therefore theoretically not to have a full change in the gray level of the pixel. Because of the non-linear effect on the nature of the medium, it actually has a slight change in the gray level. Compared with a simple PWM drive system or driver with limited pulse width and / or pulse length change power. , Based on the discovery that a finer adjustment of the gray level can be achieved. The pulse causing the “fine tuning” waveform as described above is different from the “main driving” pulse causing the main change in the gray level, and the main driving pulse can be preceded or followed. In some cases, the fine adjustment pulse and the main drive pulse may be either a single block of fine adjustment pulses at a single point of the main drive pulse sequence, or may be single or small at multiple points of the main drive pulse sequence. Mixing may be done by placing a group of fine tuning pulses.

The non-consecutive address method can be applied in general. However, the drive method using a source driver having three voltage outputs (positive, negative, zero) and a waveform composed of the following three waveform elements is mainly used as an example. Described (because the necessary modifications to the present invention for use with other types of drivers and waveform elements are believed to be easily understood by those familiar with electro-optic display technology):
1) Saturation pulse: with a voltage of one sign, or one sign and zero volts, with a reflectivity of one extreme optical state (light rail, dark state called black state in this application and bright state called white state in this application) A frame sequence that moves to the vicinity,
2) Set pulse: a frame sequence that has a voltage of one sign, or one sign and zero volts, and transitions the reflectivity to the desired gray level (black, white, or intermediate gray level),
3) FT sequence: A frame sequence having a voltage individually selected to be positive, negative or zero so that the amount of movement of the optical state of the ink is significantly reduced compared to a single code sequence of the same length. An example of an F drive sequence with a total length of 5 scan frames is
[+-++-] (here, the voltage of each frame is indicated by positive voltage +, voltage zero is 0, and negative voltage is-), [−−0 ++], [00000], [00+ −0], [0− + 00
]. The above sequence is shown schematically in the above order in FIGS. 1A to 1E, where the circles in the figure represent the start and end points of the FT sequence, and there are five scan frames between each point. To do.

The FT sequence is used to allow fine adjustment of the optical state, as described above, or a unipolar (single sign) voltage but a different net voltage impulse (the impulse is a voltage applied over time). Used to make changes to a state similar to the optical state of a sequence having (defined as integral). Therefore, the FT sequence in the waveform can be used as a means for achieving DC balance.

First, a method for realizing fine adjustment of the optical state using the FT sequence will be described. In FIG. 2, optical states that can be realized with a unipolar voltage of 0, 1, 2, 3, or more are shown schematically as points on the reflectivity axis. From the figure, it can be seen that the length of the monopolar pulse can be selected to achieve the reflectivity shown as the corresponding point on the axis. However, there are times when it is desired to realize the gray level indicated by the “target” that is not very close to the gray level in FIG. 2. In this case, the final state realized after using the unipolar drive pulse is obtained using the FT sequence. The reflectance can be finely tuned to a desired state by fine tuning or fine tuning the initial state and then using a monopolar drive pulse.

The first example of the FT sequence shown in FIG. 3 shows an example in which the FT sequence is used after two-pulse single-pole driving. The FT sequence is used to fine tune the final optical state to the target state. As shown in FIG. 2, FIG. 3 shows the optical states that can be realized with a large number of scan frames as black circles.
It also shows the light change induced by the sequence.

A second example of the FT sequence is shown in FIG. In the figure, first, using the FT sequence,
The optical state is finely tuned to a position where the desired optical state can be realized by the monopolar drive sequence. The optical states that can be realized after using the FT sequence are indicated by white circles in FIG.

The FT sequence can also be used with a rail-stable grayscale (RSGS) waveform as shown in FIGS. 11A and 11B of the aforementioned patent WO 03/044765. R
The essence of the SGS waveform is that there is a limited number of gray to gray transition tolerances that can be performed before a particular pixel is moved to one extreme optical state. Thus, the waveform frequently transitions to the extreme optical state (called the light rail) to reduce optical errors while maintaining DC balance (where DC balance is zero net voltage impulse, details below) As described in). A well-divided grayscale can be achieved using the waveform by selecting a fine adjustment voltage for one or more scan frames. However, when the fine adjustment voltage cannot be used, fine tuning must be realized by using another method and preferably maintaining DC balance. FT sequences can be used to achieve that goal.

First, each transition has an annular shape composed of 0, 1, and 2 saturation pulses (pulses that transfer pixels to one light rail) followed by the set pulses (pulses that move the pixels to the desired gray level). Consider a rail-stable grayscale waveform. Each waveform element is symbolized to show how the FT sequence can be used in this waveform: “sat” indicates a saturation pulse, “set” indicates a set pulse, and “N” indicates an FT drive sequence. Show. The three basic forms of the annular rail stable gray scale are:
set (WO 03/044765, transition 1104 in FIG. 11A, etc.)
sat-set (WO 03/044765, transition 1106/1108 in FIG. 11A, etc.)
sat-sat'-set (WO 03/044765, transition 1116 / in FIG. 11A)
1118/1120 etc.)
And sat and sat ′ denote two different saturation pulses.

Changing the first form above with an FT sequence produces the following waveform:
N-set
set-N
That is, whether the FT sequence follows the set pulse or the same element is reversed.

Changing the second form above with one or two FT sequences produces, for example, the following FT change waveform:
N-sat-set
sat-N-set
sat-set-N
sat-N-set-N ′
N-sat-set-N ′
N-sat-N'-set
N-sat-N'-set-N "
Among the above, N, N ′, and N ″ are three FT sequences and may or may not be different.

The change of the second form described above can be realized by interspersing FT sequences between three waveform elements basically according to the form described above. Some examples include the following:
N-sat-sat'-set
N-sat-sat'-set-N '
sat-N-sat'-N'-set-N "
N-sat-N′-sat′-N ″ -set-N ″ ′
Another basic waveform that can be changed by the FT sequence is a single-pulse slideshow grayscale that drives to black (or white). In the waveform, the optical state is first shifted to the light rail and then to the desired image. Each transition waveform is shown symbolically in either of the following two sequences:
sat-set
set
The above waveform can be modified by inserting FT drive sequence elements in the same way as previously described for rail-stable grayscale sequences, resulting in the following sequence:
sat-set-N
sat-N-set
Such.

The above two examples show an example in which FT sequences are inserted before and after the saturation pulse and set pulse elements of the waveform. It may also be effective to insert an FT sequence in the middle of a saturation pulse or set pulse. That is, the basic sequence:
sat-set
Will be changed to the following format:
{Sat, part I} -N- {sat, part II} -set
Or
sat- {set, part I} -N- {set, part II}
As already mentioned, it has become clear that the optical state of many electro-optic media realized after a series of transitions is sensitive to the preceding optical state and the elapsed time in the preceding optical state,
A method for correcting the preceding state and the preceding residence time by appropriately adjusting the transition waveform has been reported. By using the FT sequence in a similar manner, the preceding optical state and the preceding dwell time can be corrected.

To describe the concept in more detail, consider the gray level sequence displayed on a particular pixel. The level is denoted as R ₁ , R ₂ , R ₃ , R _4, etc., R ₁ represents the next desired (final) gray level of the transition under consideration, R ₂ represents the initial gray level of the transition, R ₃ represents the first preceding gray level, R ₄ represents the second preceding gray level, and so on. Thus, the gray level sequence is represented as:
R _n R _{n over} 1 _{R n-2.} . . . . . R ₃ R ₂ R ₁
The dwell time preceding gray level i is denoted D _i . D _i can represent the number of scan frames staying in the gray level i.

The above FT sequence may be selected as appropriate for the transition from the current gray level to the desired gray level. Thus, in its simplest form, the FT sequence is a function of the current and desired gray levels and is represented symbolically by the following equation:
N = N (R ₂ , R ₁ )
Indicates that the FT sequence N depends on R ₂ or R ₁ .

To improve device performance and reduce the variation in residual gray level, especially related to previous images,
It is effective to fine-tune the transition waveform. Many FT sequences can be used to implement the adjustment, but different FT sequences yield different final optical states, and different FT sequences can be selected for different optical histories of a pixel. For example, to correct the first preceding image (R ₃ ), an FT sequence depending on R ₃ can be selected and is represented by the following equation:
N = N (R ₃ , R ₂ , R ₁ )
That is, the FT sequence can be selected based on R ₃ as well as R ₁ and R ₂ .

Generalizing the concept, the FT sequence can depend on any number of preceding gray levels and / or any number of preceding dwell times and is represented by the following formula:
N = N (D _m , D _m−1 ,... D ₃ , D ₂ ; R _n , R _n−1 ,... R ₃ , R ₂ , R ₁ )
In the equation, D _k represents the time spent at the gray level R _k , and the number of optical states n does not need to be equal to the number of residence times m required for the FT decision function. Thus, the FT sequence can be a function of the previous image or / or the previous / current gray level dwell time.

As a special example of the concept, it is known that the final optical state to be realized is changed by inserting a scan frame having a voltage of zero into an originally unipolar pulse. For example, the optical state realized after the sequence of FIG. 5 in which a zero voltage scan frame is inserted is the corresponding single pole of FIG. 6 where there is no zero voltage scan frame but the total impulse is equivalent to the sequence of FIG. The optical state realized after the sequence is slightly different.

It has been found that the influence of a particular pulse on the final optical state depends on the length of the delay time between the pulse and the preceding pulse. Therefore, fine tuning of the waveform can be realized by inserting a zero voltage frame between the pulse elements.

The present invention extends the use of FT drive elements and the insertion of zero voltage scan frames to unipolar drive elements in other corrugated structures. Other examples include, but are not limited to,
When transitioning from one optical state to another optical state, slideshow-type grayscale waveforms of double prepulses (including triple prepulses, quadruple prepulses, etc.) and rail stable grayscale waveforms that access both optical rails included. The FT sequence can also be used for general image flow grayscale waveforms where there is a direct transition between gray levels.

Attention is directed to the fact that the insertion of a zero voltage frame is considered a specific example of FT sequence insertion, which is all zero, as the special case has been found to be effective in changing the final optical state.

The above discussion has focused on the use of FT sequences to achieve gray level fine tuning. From now on, the use of the FT sequence for achieving DC balance will be considered. F
The T-sequence can be used to change the level of DC balance imbalance in the waveform (preferably to reduce or eliminate DC balance imbalance). DC balance means that the net voltage impulse of all fully circuit gray level sequences (sequences starting and ending at similar gray levels) is zero. The FT sequence can (a) change the optical state in the same way as a saturation pulse or set pulse, but it has a very different net voltage impulse, or (b) causes a slight change in the optical state, but eventually DC Taking advantage of the fact that the balance is unbalanced, the waveform DC
Balance can be achieved or the DC balance imbalance can be reduced.

The following example shows how DC balance can be achieved using FT sequences. In this example, the pulse length of the set pulse can vary, specifically 1, 2, 3 scan frames or more. The final gray level realized in each of the plurality of scan frames is shown in FIG. 7, where the number below each point indicates the number of scan frames used to achieve the gray level.

FIG. 7 shows the optical states that can be used with positive voltage scan frames in a unipolar drive, where the number specifies the number of unipolar frames used to achieve the final gray level. In this example, it is assumed that a voltage impulse consisting of a total of two positive voltage frames is required to maintain DC balance. The desired (target) gray level can be achieved with three scan frames of impulses, but in doing so the system remains DC unbalanced for one frame. On the other hand, DC balance can be achieved by using two positive voltage scan frames instead of three scan frames, but the final optical state will deviate significantly from the target.

One way to achieve DC balance is to use two positive voltage frames to move the electro-optic medium to near the desired gray level, and then to achieve a DC balanced FT sequence (FT sequence with zero net voltage impulse). There is a way to use and make final adjustments to get close enough to the target gray level. The method is shown schematically in FIG. 8, in which the target gray is represented by two scan frames followed by a FT sequence with a net voltage impulse selected to make the appropriate change in the optical state. Level is realized.

Alternatively, use three positive voltage scan frames with unipolar drive to move the reflectivity to the target optical state and the final DC balance imbalance is equivalent to one negative voltage scan frame. There is a method using one FT sequence. If an FT sequence is used in which the final optical state hardly changes, the final optical state remains accurate and the DC balance is restored. Such an example is shown in FIG. Of course, usually F
Since the use of the T sequence has some influence on the DC balance as well as the adjustment of the optical state, the above two examples are extreme examples.

For illustrative purposes only, the following example is presented below to illustrate an experimental use of an FT sequence according to the present invention.

(Use of FT sequence in annular RSGS waveform)
This example shows the improvement of the optical performance of the waveform through the use of an FT sequence aimed at achieving 4 gray level (2 bit) addresses in a single pixel display. The display uses a microcapsule type electrophoretic medium, and is configured substantially based on the method described in the paragraphs [0069] to [0076] of the aforementioned 2002/0180687.

The waveform voltage was applied to the pixels based on a transition matrix (lookup table) to achieve a gray level sequence within a 2 bit (4 state) gray scale. As described above, the transition matrix and the look-up table are a set of rules for applying a voltage to a pixel in order to shift from a gray level in a gray scale to another gray level.

The waveform was constrained by voltage and timing, and only three voltage levels, -15V, 0V, and + 15V, were applied to the entire pixel. Also, in order to stimulate an active matrix drive with a frame rate of 50 Hz, a voltage was applied at 20 ms intervals. The tuning algorithm was used repeatedly to optimize the waveform, i.e., to achieve the conditions that minimize the evolution in the actual optical state of each of the 4 gray levels across the test sequence.

In the first experiment, a circular rail stable grayscale (cRSGS) waveform was optimized using a simple saturation and set pulse. In determining the transition matrix, consideration of the preceding state was limited to the initial (R ₂ ) and desired final (R ₁ ) gray levels, and the waveform was DC balanced throughout. Minimum impulse available for tuning (20 ms at 15V) is rough, since the R ₂ leading state in the transition matrix lacked was expected fairly low quality grades from the waveform.

The behavior of the transition matrix was verified by switching test pixels in a “five-perfect” gray-level sequence, including a sequence of five, all gray levels arranged randomly. (A set of five sequence elements is 0-1-0-2-3 or 2-1-3-0.
In a sequence of five gray levels, such as -3, 0, 1, 2, 3 indicate the four available gray levels. ) In a perfect transition matrix, the reflectivity of each of the four gray levels is always exactly the same no matter when each gray level of the random sequence appears. In a realistic transition matrix, the reflectivity at each gray level varies considerably. In reality, FIG.
This bar graph shows the poor performance of the transfer matrix constrained by voltage and timing.
The measured reflectivity of the various manifestations of each target gray level is very varied. The cRSGS waveform optimized without the FT sequence developed in this part of the experiment is hereinafter referred to as a basic waveform.

The FT sequence was then incorporated into the cRSGS waveform. In this experiment, the FT sequence was limited to 5 scan frames and contained only a DC balanced FT sequence. At each transition, the FT sequence was placed at the end of the basic waveform. That is, the waveform of each transition took one of the following forms:
set-N
sat-set-N
sat-sat'-set-N
In order to successfully incorporate FT sequence elements into the waveform, the next two steps are to confirm the effect on the optical state of the various FT sequences at each gray level and to select the FT sequence to be applied to the various waveform elements. It was necessary.

To see the effect on the optical state of various FT sequences at each gray level,
An “effect” experiment was conducted. First, a consistent starting point was established by repeatedly switching the electrophoretic medium between the black and white light rails. Then the film is in this application referred to as the optical state R _2, is moved to the four first level of the gray levels (0, 1, 2, 3), the other gray levels (the further FT sequence is applied Appropriate basic waveforms were applied to transfer R ₂ to one of the levels (referred to as R _{1 in the} application). The step was repeated for all 51 DC balanced 5 frame FT sequences and the final optical state was recorded for each FT sequence. The FT sequence was then organized based on the respective final reflectance. The process was repeated for all combinations of initial (R ₂ ) and final (R ₁ ) gray levels. The final gray level 1 (R ₁ = 1) and the current gray level 0,
The order of the FT sequences of _2, 3 (R ₂ = 0, _2, 3) is shown in Tables 2 to 4 in order, and the corresponding FT sequence is shown in the column titled “Frame 1” to “Frame 5”. The potential applied during the five consecutive frames is expressed in volts. The final optical state realized in the waveform using various FT sequences is shown by the curves in FIG. From the figure, it can be seen that the FT sequence can be used to make a significant change in the final optical state without any change in the net voltage impulse, and that the final optical state can be fine-tuned with the FT sequence having five scan frames. The

  (Table 2: Final optical states of gray levels 0 to 1 in various FT sequences)

（表３：様々なＦＴシーケンスにおけるグレーレベル２〜１の最終光学状態）

(Table 3: Final optical states of gray levels 2-1 in various FT sequences)

（表４：様々なＦＴシーケンスにおけるグレーレベル３〜１の最終光学状態）

(Table 4: Final optical states at gray levels 3 to 1 in various FT sequences)

次に、表２〜４と図１１（特に表２のシーケンス３３、表３のシーケンス４９、および
表４のシーケンス４）に示される結果と他のグレーレベルの類似物を用いて選択されたＦ
Ｔシーケンスを使用して、ｃＲＳＧＳ波形が構成された。図１１のｙ軸上の〜３６．９と
〜３７．５Ｌ＊間部は、ＤＣバランスの取れたＦＴシーケンスで使用可能になった同じ最
終（Ｒ_１）状態と異なる初期（Ｒ_２）状態の光反射率間の重複部を示す。したがって、Ｒ
_１＝１のターゲットグレーレベルは３７．２Ｌ＊で選択され、本ターゲットに最も近い最
終光学状態を提示する各Ｒ_２のＦＴシーケンスが選択された。本プロセスは他の最終光学
状態（Ｒ_１＝０、２、３）に対しても反復された。

Next, F selected using the results shown in Tables 2-4 and FIG. 11 (especially, Sequence 33 in Table 2, Sequence 49 in Table 3, and Sequence 4 in Table 4) and other gray level analogs.
A cRSGS waveform was constructed using the T sequence. ～36.9 and ～37.5L * The inter on the y-axis in FIG. 11, the same final made available by FT sequences came off the DC balance _{(R 1)} state and different initial _{(R 2)} Condition The overlap part between light reflectivities is shown. Therefore, R
A target gray level of ₁ = 1 was selected at 37.2 L *, and each R ₂ FT sequence that presented the final optical state closest to this target was selected. This process was repeated for the other final optical states (R ₁ = 0, 2, 3).

Finally, the resulting waveform was examined using the pseudo-random sequence described above that contained all the five-level concentration state history. The sequence includes 324 important transitions. Using the cRSGS waveform modified by the chosen FT sequence, all transitions in the sequence were realized and the reflectivity of each realized optical state was recorded. The realized optical state is shown in FIG. From a comparison between FIG. 12 and FIG. 10, it is clear that the reflectance spread at each gray level is significantly reduced by incorporating the FT sequence.

In summary, in terms of non-contiguous addressing, the present invention can either (i) change the optical state, or (ii) achieve a DC balance of the waveform, or at least change the degree of DC balance imbalance in the waveform. A plurality of FT sequences are provided that allow the means to As described above, the FT sequence can be defined somewhat mathematically, for example, for a form in which the DC balance of the method is unbalanced.

(A) Use of an FT sequence with an unbalanced DC balance that results in a change in the optical state that is significantly different from the change in the optical state of the DC reference pulse. The “DC reference pulse” is a pulse of voltage V ₀ , and V ₀ is a voltage corresponding to the maximum voltage amplitude applied during the FT sequence, and has the same sign as the net impulse of the FT sequence. It is. The net impulse of a sequence is the area under the voltage-time curve and is represented by the symbol G. The duration of the reference pulse is represented by T = G / _{V 0.} The FT sequence is used to introduce a DC balance imbalance that is significantly different from the net DC balance imbalance of the reference pulse.

(B) Use of an FT sequence with an unbalanced DC balance that results in a change in optical state that is significantly smaller than the change in optical state achieved with a time reference pulse. The definition of the “time reference pulse” is a voltage pulse having a single sign equivalent in duration to the FT sequence, but the sign of the reference pulse is chosen so that the change in the optical state is maximized. That is,
If the electro-optic medium is close to the white state, a negative voltage pulse may only bring the electro-optic medium closer to the white state, but a positive voltage pulse strongly changes the electro-optic medium to the black state. There is. In this case, the sign of the reference pulse is positive. This type of FT
The purpose of the pulse is to adjust the net voltage impulse (eg, to achieve DC balance) without strongly affecting the optical state.

In terms of non-contiguous addressing, the present invention is based on the concept of using one or more FT sequences between or within the pulse elements of a transition waveform, and FT to offset the effects of preceding gray level and preceding dwell time. Also relevant to concepts using sequences. As a specific example of the present invention, there is an example in which a zero voltage frame is inserted in one pulse element of a waveform or between a plurality of pulse elements in order to change the final optical state.

In terms of non-contiguous addressing, the present invention provides a fine tuning of the waveform to achieve the desired gray level with the desired accuracy, and a source driver that cannot fine tune the voltage, especially a source driver having only two or three voltage levels. It also allows a means to bring a waveform closer to DC balance (ie zero net voltage impulse in all annular transition movements to various gray levels).

(DC balance type address method)
The sawtooth drive scheme shown in FIGS. 11A and 11B of the above-mentioned WO 03/044765 says that for any given pixel, there will only be a limited number of transitions while passing through the black state continuously. In fact, and the fact that one pixel actually passes through the black state on average only half of all transitions, it is worth noting that it is suitable for use in balancing DC.

However, as already mentioned, the DC balance method according to the present invention is not limited to balancing the sum of impulses applied to the electro-optic medium during continuous transition, It also allows for “internally” balancing at least some of the transitions experienced by the display pixel. The method will be described in detail below.

The DC balanced addressing method of the present invention relates to a DC balanced transition that is effective for driving impulse driven electro-optic media, such as microcapsule electrophoresis for displays. The method can be applied to an active matrix type display having a source driver that can output only a voltage of a few levels, for example. Although other types of drivers can be used, much of the detailed description below focuses on examples using source drivers with three voltage outputs (positive, negative, and zero).

In the following description of the DC balanced addressing method of the present invention, the gray level of the electro-optic medium is represented by 1 to N as in the above description of the other aspects of the present invention. Here, 1 indicates the darkest state, N indicates the brightest state, and the intermediate states are numbered from the darkest to the brightest. The drive system for impulse driven image media uses a set of rules to achieve the transition from the initial gray level to the final gray level. As shown in Table 5 for each of the 16 transitions that can be achieved with a 2-bit (4 gray level) grayscale display, the drive scheme can be expressed as a voltage as a function of time for each transition.

  (Table 5)

表５でＶ_ｉｊ（ｔ）は、グレーレベルｉからグレーレベルｊへの転移に使用される波形
を示す。ＤＣバランス転移とは、波形Ｖ_ｉｊ（ｔ）の時間積分値がゼロとなる転移である
。

In Table 5, V _ij (t) represents the waveform used for the transition from gray level i to gray level j. The DC balance transition is a transition in which the time integral value of the waveform V _ij (t) becomes zero.

The term “optical rails” has already been defined to mean the extreme optical state of an electro-optic medium, but hereinafter “pushing the medium towards or into one light rail” "Is used. Here, the term “toward the (optical rail)” means that a voltage is applied so as to move the optical state of the medium toward one optical rail. The term “push” means that the voltage pulse has sufficient duration and amplitude to bring the optical state of the electro-optic medium closer to one light rail. The sentence “pushing into one light rail” does not necessarily mean that the light rail state at the end of the pulse is achieved, but the optical state at the end of the pulse is considerably more than the final optical state. It should be noted that it means close. For example, taking an electro-optic medium with an optical rail at 1% reflectivity and 50% point, it can be seen that a 300 ms pulse moves from the final optical state (from reflectivity 1%) to reflectivity 50%. ing. In this case, applying a 200 ms pulse may be considered to push the display into a high reflectivity light rail, even though the reflectivity ultimately achieved is only 45%. The duration of 200 ms is long compared to the time required to cross the large optical range, for example, the middle part when the optical range is divided into one third.
A 0 ms pulse is considered to push the medium into one light rail (in this case 200 m
s is longer than the pulse required to cross the range of one third of the reflectivity width in the middle of the medium, that is, the range of 17% to 34% reflectivity. )
Three types of DC balance transitions according to the DC balance type address method of the present invention, and a composite drive system using both DC balance transitions and DC balance unbalance transitions will be described below.
In the following description, for convenience, each pulse is represented by a number, and the size of the number indicates the length of the duration. If the number is a positive number, the pulse is a positive voltage, and if the number is a negative number, the pulse is a negative voltage. Thus, for example, if the usable voltage is + 15V, 0V, -15V and the duration of the pulse is measured in milliseconds (ms), a pulse with the property x = 300 is 300 m.
s represents a pulse of 15V, and a pulse having the property x = −60 is −15V in 60 ms.
Represents a pulse.

(Type I)
In the simplest first DC balance transition of the present invention, as shown in FIG. 13, the voltage pulse (x) is preceded by a voltage pulse (-x) of the same duration and opposite sign. (note:
Since the value of x itself may be negative, positive and negative pulses may appear in the reverse order of FIG. )
As described above, according to the non-contiguous address method of the present invention, the effect of the waveform used for transition is
It has been found that it changes due to the presence of a period of zero voltage (actual time delay) in the middle of any pulse contained in the waveform, or before appearance. FIG. 1 shows a modification of the waveform of FIG.
4 and FIG. In FIG. 14, a time delay is inserted between the two pulses of FIG.
On the other hand, in FIG. 15, a time delay is inserted in the middle of the second pulse in FIG. 13, that is, the second pulse in FIG. 13 is divided into two pulses by the time delay. It is. As described above, a time delay can be introduced into a certain waveform in order to realize an optical state that cannot be realized without the time delay. The time delay can also be used for fine tuning of the final optical state. In the active matrix drive, the time resolution of each pulse is determined by the scanning speed of the display, and therefore the fine tuning capability is important. The time resolution due to the scanning speed may be so coarse that an accurate final optical state cannot be achieved without some additional fine tuning means. While the time delay provides a small amount of fine tuning for the final optical state, other features as described below provide an additional means of coarse and fine tuning of the final optical state.

(Type II)
As shown symbolically in FIG. 16, the type II waveform comprises the type I waveform and a pair of positive and negative pulses (pulses y and -y) inserted at a certain point. These y and -y pulses do not need to be continuous, and may exist at different points in the basic waveform. The type II waveform has two particularly effective forms.

(Type II: Special case A)
In this particular form, the -y and y pulse pair is positioned before the -x and x pulse pair.
When the signs of x and y are reversed as shown in FIG. 17, it is known that fine tuning of the final optical state is possible even if the duration of y is adjusted to some extent. Therefore, it is possible to adjust the value of x for coarse adjustment of the final optical state of the electro-optic medium and adjust the value of y for final adjustment. This is presumably because the y pulse extends the -x pulse, and as a result, the degree to which the electro-optic medium is pushed into one optical rail changes. It is known that the final optical state can be fine-tuned after a certain pulse (in this case, an x pulse) is applied depending on the degree to which the electro-optic medium is pushed into one light rail. Yes.

(Type II: Special case B)
For the reasons described above, it has been found useful to use a waveform having at least one pulsed element that is long enough to significantly move the electro-optic medium to one optical rail. Also, for a more aesthetic transition, it is desirable to implement the final optical state from a closer light rail since only a short final pulse is required to achieve a gray level close to one light rail. . This type of waveform requires at least one long pulse to move to an optical rail, and further requires one short pulse to achieve the final optical state near the optical rail. Although it cannot have a type I structure,
A special case of a type II waveform can realize this type of waveform. FIG. 18 shows an example of this type of waveform, where the y pulse is located after the -x / x pulse pair and the -y pulse is located before the pulse pair. Since the final optical state is very sensitive to the magnitude of y, in this type of waveform, the last y pulse is coarsely tuned. On the other hand, since the final optical state is not so strongly influenced by the degree of movement to the normal light rail, the x pulse performs fine tuning.

(Type III)
In the third type (type III) of the DC balanced waveform of the present invention, another set of DC balanced pulses (z and -z) is added to the waveform as schematically shown in FIG.
Is introduced. A preferred example of the type III waveform is shown in FIG. For the reasons described below, this type of waveform is useful for fine tuning the final optical state. Taking the situation where there are no z and -z pulses (ie, the type II waveform above) as an example, the x pulse element is used for fine tuning, increasing x reduces the final optical state and decreases x. The final optical state is then increased. However, reducing x below a certain point is sufficient to place the electro-optic medium in the light rail,
This is not desirable because it cannot be brought close to the level necessary for the stability of the waveform. To avoid this problem, instead of reducing x, adding a -z and z pulse pair, as shown in FIG. 20, extends the -x pulse (actually) without changing the x pulse. Is possible. Note that z has the opposite sign to x. The z pulse extends the -x pulse, and the -z pulse keeps the net impulse of transition to zero, i.e., the transition is DC balanced.

Of course, the type I, II, and III waveforms described above can be modified in various ways. It is also possible to add other pulse pairs to the waveform for a more general structure. The effect of the new additional pulse pair decreases as the number of pulse elements increases, but the resulting waveform is a natural extension of type I, II, and III waveforms. Also, as described above, one or more time delays can be inserted at various points in the waveform in the same manner as shown in FIGS. As mentioned earlier, the time delay during the pulse is effective for fine tuning because it affects the resulting final optical state. Furthermore, the appearance of the transition can also be changed by changing the position of a certain transition element in relation to other elements in the same transition or other transition elements by insertion of a time delay. The time delay can also be used to align certain transition elements in the waveform and may be useful for certain display modules with specific control capabilities. Considering the fact that a small change in the order of applied pulses can cause a large change in the subsequent optical state, it is possible to replace all or part of the one-pulse arrangement described above or repeat such a replacement. Alternatively, the output signal may be formed by inserting a zero volt period once or more at any one position of the above pulse arrangement. Furthermore, these replacement and insertion operators (eg, a zero volt portion is inserted before a replacement and then a zero volt portion is inserted) may be combined in any order. It should be noted that all the pulse sequences formed by such a deformation operation maintain the essential characteristic of net impulse zero.

Finally, the DC balance transition can also be combined with the DC balance unbalance transition to form a drive scheme. For example, co-pending application 60/481 filed July 2, 2003
No. 053 includes -TM (R1, R2) [IP (R1) -IP (R2)] TM (R1,
A preferred waveform of type R2) is described, where [IP (R1) -IP (R2)]
Represents the difference in impulse potential between the initial and final states of the transition, and the other two terms represent DC balanced pulse pairs. Hereinafter, for convenience, the waveform is referred to as a −x / ΔIP / x waveform and is illustrated in FIG. The waveform is suitable for transitions between various optical states, but not well suited for zero transitions where the initial and final states are the same. In the present embodiment, a type II waveform as shown in FIGS. 17 and 18 is used for such zero transition. Table 6 shows the complete form of the waveform in symbols. From the table, the −x / ΔIP / x waveform is used for the non-zero transition and is type II.
It can be seen that this waveform is used for zero transition.

  (Table 6)

ＤＣバランス転移は初期及び最終グレーレベルが同じである「リーディング・ダイアゴ
ナル（ｌｅａｄｉｎｇ ｄｉａｇｏｎａｌ）型」転移だけに限定されているが、当該ＤＣ
バランス型アドレス法は、当然ながら当該タイプの転移マトリクスだけに限られるもので
はない。グレーレベルの制御を最大限に改善するには、ＤＣバランス転移の数を極力多く
することが望ましい。しかしながら、使用する特定の電気光学媒体によっては、例えば黒
や白へ、または黒や白からの転移、即ちグレーレベル１や４といった極度グレーレベルへ
の転移またはそういった極度グレーレベルからの転移を伴った転移のＤＣバランスを取る
ことが困難な場合がある。その上、どの転移のＤＣバランスを取るか決定する際、転移マ
トリクス全体を不平衡にしないこと、つまり同じグレーレベルから開始・終了する閉ルー
プのＤＣバランスが不平衡である転移マトリクスを形成しないことが重要である。例えば
、グレーレベルの０または１レベルの変化だけを含んだ転移のＤＣバランスは取れている
が、その他の転移はＤＣバランスが取れていないなどの規則は好ましくない。なぜなら、
こういった規則は、次の例で示すように、転移マトリクス全体のバランスを不平衡にする
からである。２−４−３−２というグレーレベルのシーケンスを実施している画素は、２
−４（ＤＣバランス不平衡）、４−３（ＤＣバランスが取れている）、３−２（ＤＣバラ
ンスが取れている）という転移を経過するので、全体のループのＤＣバランスが不平衡と
なる。上記の対立する二つの要求間で現実的な妥協を図るには、中間グレーレベル（レベ
ル２と３）だけが関与する場合にＤＣバランス転移を用い、転移が極度グレーレベル（レ
ベル１か４）で開始・終了する場合にはＤＣバランス不平衡転移を用いる方法がある。言
うまでもなく、当該規則で選択される中間グレーレベルは、使用する具体的な電気光学媒
体とコントローラによって異なるであろう。例えば、３ビット（８グレーレベル）のディ
スプレイでは、グレーレベル２〜７（または、場合によって３〜６）で開始・終了する全
ての転移にはＤＣバランス転移を用い、グレーレベル１または８（あるいは１、２、７、
８）で開始・終了する全ての転移にはＤＣバランス不平衡転移を用いることが可能な場合
がある。

DC balance transitions are limited to “leading diagonal” transitions where the initial and final gray levels are the same.
Naturally, the balanced addressing method is not limited to this type of transfer matrix. To maximize gray level control, it is desirable to maximize the number of DC balance transitions. However, depending on the particular electro-optic medium used, there was a transition, for example to black or white, or from black or white, i.e. a transition to or from such an extreme gray level as gray level 1 or 4. It may be difficult to balance the DC of the transition. In addition, when determining which transition to be DC balanced, do not unbalance the entire transition matrix, that is, do not form a transition matrix in which the closed-loop DC balance starting and ending from the same gray level is unbalanced. is important. For example, a rule such that the DC balance of the transition including only the change of the gray level of 0 or 1 is balanced, but the other transition is not DC balanced is not preferable. Because
This is because these rules make the balance of the entire transfer matrix unbalanced, as shown in the following example. A pixel that performs a gray level sequence of 2-4-3-2 is 2
-4 (DC balance unbalance), 4-3 (DC balance is taken), and 3-2 (DC balance is taken), the DC balance of the entire loop becomes unbalanced. . To achieve a realistic compromise between the two conflicting requirements above, use the DC balance transition when only intermediate gray levels (levels 2 and 3) are involved, and the transition is extremely gray level (level 1 or 4). In the case of starting and ending in step 1, there is a method using DC balance unbalanced transition. Needless to say, the intermediate gray level selected in the rule will depend on the specific electro-optic medium and controller used. For example, on a 3-bit (8 gray level) display, use DC balance transitions for all transitions starting and ending at gray levels 2-7 (or 3-6 in some cases) and gray levels 1 or 8 (or 1, 2, 7,
It may be possible to use a DC balance disequilibrium transition for all transitions starting and ending in 8).

From the above, in order to realize a desired gray level with high accuracy using a source driver that cannot finely tune a voltage, particularly a source driver that has only a voltage of 2 to 3 levels,
It will be appreciated that the C-balanced addressing method allows fine tuning of the waveform and further allows the acquisition of means by which the waveform transition can have a zero net voltage. It is believed that transitions with a DC balanced waveform provide better performance than transitions with a DC unbalanced waveform, and the present invention generally has, but is not limited to, only a few levels of voltage. This is applied to an active matrix display module using a source driver. The present invention is also applied to an active matrix display module using a source driver having a plurality of voltage levels.

The DC balance type address method of the present invention provides still another effect. As mentioned above
In some driving methods of the present invention, the transition matrix is a function of variables such as the length of time elapsed since the last update and the temperature of the display medium, in addition to the preceding optical state. In the above case, it is very difficult to maintain DC balance using DC balance unbalance transition. As an example, consider a display that transitions repeatedly from white to black at 25 ° C. and then from black to white at 0 ° C., a slower than normal response with a longer pulse length is usually indicated at lower temperatures. As a result, the display falls into a white balance of DC balance imbalance. On the other hand, if all transitions are internally balanced, various transition matrices can be freely mixed and used without being affected by DC balance imbalance.

(Specific domain method)
The undesired effect of the reset method as described above is to update partly, not entirely, that is, select the part of the display to be rewritten in “local” or pixel units, and only the part that changes between successive images. There is a possibility that it can be further reduced by rewriting. For example, a series of images in which a relatively small object moves in a large static background is not uncommon, as can be seen in a diagram showing a part of a mechanical device or an accident analysis diagram. To use partial update, the display controller must compare the final image with the initial image to determine which parts have changed between the two images and therefore need to be rewritten. The controller identifies a rectangular area with vertical and horizontal axes along the grid of pixels that contains one or more local, usually pixels that need to be updated, or simply updated. Necessary pixels may be specified individually. Any of the drive schemes described above can be used to update only local or individual pixels that have been identified as being rewritten as described above. The partial update method described above can greatly reduce the power consumption of the display.

Furthermore, as already mentioned, the specific area method of the present invention provides a specific area method that allows updating of a bistable electro-optic display using separate update methods for different areas of the display.

Several electro-optic displays are known that can drive a full display in 1-bit mode or grayscale mode, but if such a display is set to 1-bit mode, a 1-bit overall image flow (GIF) waveform is generated. To update. On the other hand, when the display is set to the gray scale mode, even when only 1-bit information is updated in a specific display area, the update is performed using a multi-prepulse slide show waveform or another low-speed waveform. .

The electro-optic display has two more commands within the controller: a “DEFINE REGION” command and a “CLEAR ALL” command.
By defining a “REGIONS)” command, it can be modified to perform the specific area method of the present invention. Usually, the “specify area” command uses position information sufficient as an independent variable to completely specify a rectangular area in the display, such as the upper right corner and the lower left corner of the specific area. The command may have another independent variable that specifies the bit depth at which the region is set, but if the specific region is always monochrome, the final independent variable is a simple region specific region method. Then it is not necessary. The bit depth set by the final independent variable naturally takes precedence over all the bit depths previously set for the region. As another method, the “specify region” command can also specify a series of points forming a vertex of a polygon. The “Erase All Region” command does not take an independent variable and simply resets the entire display to a predetermined single bit depth, or the bit depth of the entire display screen after erasure from among the applicable bit depths. Sometimes it takes a single independent variable that specifies what to do.

Of course, the specific area method of the present invention is not limited to the use of only two areas, but can provide more areas as needed. For example, in an image editing program, the image being edited is displayed in the main area at all bit depths, an information display area (such as a box that displays the current cursor position) and a dialog box area (such as user text input) ) May be effective to display in 1-bit mode. In the following, the present invention will be described primarily with respect to a method using two regions, since the modified method of enabling more than one region will be readily apparent to those familiar with the structure of the display controller.

The controller maintains an array of storage elements such that each storage element corresponds to each pixel of the display, and each element represents the current bit depth of its corresponding pixel, in order to track the depth of the various regions Memorize the numerical value. For example, XV that can operate in 1-bit or 2-bit mode
The GA (800 × 600) display can use 1-bit elements arranged in 800 × 600 (0 of each element indicates a 1-bit mode, and 1 indicates a 2-bit mode). In such a controller, the “specify region” command sets an element corresponding to the specific region of the display to a desired bit depth, and the “delete all region” command sets all elements of the array to the same single numerical value ( Reset to the default value or the value determined by the command's independent variable).

Another method is to ensure DC balance when certain areas are identified or erased.
Or, for example, as described above, the controller updates the pixels in the region to transition the display from one mode to another for the purpose of adjusting the optical state of the pixel in the FT sequence.

When a display is operating in a specific area mode, when a new image is sent to the controller, the display needs to be rewritten. There are three cases:
1. In the new image, only the pixels within a specific (for example) 1-bit region have changed. In this case, a 1-bit (high-speed) waveform can be used to update the display.

2. In the new image, only the pixels in the unspecified (grayscale) area changed. In this case, it is necessary to use a grayscale (slow) waveform to update the display (note, of course, there are no pixels that change within a particular area, so a particular area, eg, a dialog box being rewritten Readability is not an issue).

3. In the new image, the pixels in both the specified and unspecified areas have changed. in this case,
Grayscale pixels are updated using a grayscale waveform, and 1-bit pixels are updated using a 1-bit waveform (short 1 to match the length of the grayscale update waveform.
The bit waveform must be correctly filled with zeros).

Prior to scanning the display, the controller can perform the following logic verification to determine which of the above cases exist (as defined, a 1-bit number corresponds to each pixel,
Based on the assumption that the mode of the pixel is stored).

(Old_image XOR new_image)> 0: Display pixel has been changed (Old_image XOR new_image) AND mode_arra
y> 0: the gray scale pixel has been changed (Old_image XOR new_image) AND (NOT mode
_Array)> 0: Monochrome pixel changed While the display is being scanned by the controller, in case 1 or case 2, a look-up table with one waveform can be used for all pixels. The reason is that assuming that no transition in 1-bit mode is the same as no transition in grayscale mode, a zero volt voltage is applied to the unchanged pixels (in other words, both waveforms are partially updated). Because there is.
Conversely, if the grayscale waveform is globally updated (every pixel is updated every time the display is updated), the controller has a pixel in the correct area to determine whether the globally updated waveform is available. Need to investigate. In case 3, when scanning is performed for the purpose of determining which waveform the controller uses, it is necessary to check the numerical value of the bit array representing the mode of each pixel.

Alternatively, if the black / white brightness achieved in 1-bit mode is similar to that achieved in grayscale mode, in case 3 above, the grayscale waveform can be used for all pixels of the display, There is no need for function transfer between the 1-bit waveform and the grayscale waveform.

As described above, the specific area method of the present invention can be used with any selection function of the basic lookup table method.

The main advantage of the specific area method of the present invention is that a 1-bit high-speed waveform can be used for displays that display already written grayscale images. In the general display controller of the prior art, the display can display only one of the gray scale mode and the 1-bit mode at any time. It is possible to write a 1-bit image in grayscale mode, but the waveform in grayscale mode is very slow. In addition, a host system (system, usually a computer system) that provides images to the controller
The specific domain method of the present invention is essentially transparent to the host system because it does not need to tell the controller which waveform to use. Finally, if the specific area method can display both grayscale and 1-bit waveforms on the display at the same time, if both waveforms are used in other methods, the update is performed twice separately. There is a need to do.

(More general considerations on waveforms)
The above drive scheme can be modified in various ways based on the characteristics of the particular electro-optic display used. For example, in some cases, the above-described driving method can largely eliminate the reset procedure. For example, the electro-optic medium used is bistable over time (that is, the gray level of the written pixel changes only very slowly over time) and the pixel stays in the initial gray state If the impulse required for a particular transition does not change significantly with the time taken, the look-up is made so that the transition from one gray state to another is directly performed without interfering feedback from the black / white state. If you arrange the table and perform a display reset only if a significant amount of time passes and the pixel gradually “drifts” from its nominal gray level, resulting in a noticeable error in the displayed image Good. Therefore, for example, when a certain user uses the display of the present invention for reading an electronic book, a number of information screens can be displayed before the display needs to be reset. By using the appropriate waveform and driver, it is possible to display thousands of information screens before resetting is necessary. I know.

As will be readily appreciated by those familiar with display technology, the apparatus of the present invention can be effectively provided alone, with a number of different drive schemes that can be used under a variety of conditions. For example, the above-mentioned WO
In the drive scheme shown in FIGS. 9 and 10 of 03/044765, the reset pulse consumes most of the total power consumption of the display, so the controller minimizes grayscale errors by frequently resetting the display. There may be a first drive method to suppress and a second drive method to reset the display from time to time by allowing a larger error in gray scale while reducing power consumption. Switching between the two drive systems is
Can be done manually or based on external factors. For example, if the display is used in a laptop computer, the first drive method can be used while the computer is operating on the main power source and the second drive method can be used while the computer is operating on internal power.

(Correction voltage method)
The corrected voltage method and apparatus of the present invention provides further changes to the basic look-up table method and apparatus of the present invention. Details are described below.

As described above, the correction voltage method and apparatus of the present invention attempt to achieve a result similar to the basic lookup table method described above without having to store a very large lookup table. The size of the lookup table increases rapidly with increasing number of predecessors, depending on which lookup table is indexed. Therefore, as mentioned above, the increase in the number of preceding states used to select the impulse to achieve the desired transition in a bistable electro-optic display involves practical and cost constraints. Come on.

In the correction voltage method and apparatus of the present invention, the required look-up table size is reduced and correction voltage data is stored for each pixel of the display. The correction voltage data is
Calculated according to at least one impulse previously applied to the pixel. The voltage finally applied to the pixel is the sum of the drive voltage selected from the look-up table by a normal method and the correction voltage determined from the correction voltage data of the pixel. In practice, the correction voltage data adds “correction” to the pixel that is otherwise performed by adding an index to the look-up table for one or more preceding states.

The look-up table used in the correction voltage method may have any of the forms described above. Therefore, the look-up table may be a simple two-dimensional table that considers only the initial state and the final state of the pixel for the corresponding transition. Alternatively, the look-up table may take into account one or more of the temporal preceding state of the pixel or the preceding gray level state of the pixel. The correction voltage may take into account only the correction voltage data stored for the corresponding pixel, but in some cases, may take into account one or more temporal preceding states or preceding gray level states. The correction voltage can be applied to the pixel not only during a period during which the drive voltage is applied to the pixel but also during a stop period during which the drive voltage is not applied.

The exact method for determining the correction voltage data may vary greatly depending on the characteristics of the bistable electro-optic medium used. Generally, in a method determined by the drive voltage applied to the pixel during the current scan frame or during one or more scan frames,
The correction voltage data is periodically changed. In a preferred embodiment of the present invention, the correction voltage data is composed of a single numerical value (register) corresponding to each display pixel.

In one preferred embodiment of the present invention, the scan frames are grouped into superframes in the manner described above, so the display update is only initiated at the start of the superframe. One super frame is composed of, for example, 10 display scan frames. Therefore, in a display with a scanning speed of 50 Hz, one display scanning speed is 20 ms, and one super frame scanning speed is 200 ms. In each super frame during the display update, correction voltage data corresponding to each pixel is updated. The update has two configurations, and the order is as follows.

(1) changing the leading value using a fixed algorithm independent of the pulses applied during the relevant superframe;
(2) Only the numerical value determined by the pulse applied during the corresponding superframe,
Increasing the numerical value of step (1) above.

In one particularly preferred embodiment of the invention, steps (1) and (2) are performed as follows.

  (1) Equally divide the leading value by a fixed constant which is conveniently 2.

(2) The numerical value of step (1) is increased by a numerical value proportional to the total area under the voltage / time curve applied to the electro-optic medium during the corresponding superframe.

In the above step (2), the increment may be exactly proportional to the area under the voltage-time curve of the voltage applied during the corresponding superframe or may be simply proportional. For example, as described in detail below with reference to FIG. 22, the increment may be “quantized” into a finite set of classifications for all applicable waveforms. Here, each classification includes all waveforms having an increase in step (2) determined by the total area sandwiched between the two boundary lines and the classification to which the applied waveform belongs.

Here, the following example is given. The display used was one microcapsule electrophoretic display with a 2-bit gray scale, and the driving method used for the display is shown in Table 7 below, considering only the initial and final states of the desired transition. A two-dimensional lookup table was used. In the table, the column heading indicates the desired final state, the row heading indicates the initial state, and the numerical value of each square indicates the voltage value V applied to the pixel for a predetermined time.

  (Table 7)

本発明の補正電圧法を実行できるように、単一の数値で示すレジスタが各表示画素に割
り振られた。表７に示された様々なインパルスは分類され、表８に示すように、各インパ
ルスに付き一つのパルス分類が指定された。

A register represented by a single numerical value is assigned to each display pixel so that the correction voltage method of the present invention can be implemented. The various impulses shown in Table 7 were classified, and as shown in Table 8, one pulse classification was assigned for each impulse.

  (Table 8)

各スーパーフレーム中に、各画素に対応した数値レジスタが２で等分され、次いで表１
３に示した当該スーパーフレーム中に該当する画素に印加するパルスの数値だけ増加され
た。当該スーパーフレーム中に各画素に印加された電圧は、表１２に示す駆動電圧と下式
から得られる補正電圧Ｖ_ｃｏｍｐとの合計である。

During each superframe, the numeric registers corresponding to each pixel are equally divided by two, then Table 1
It is increased by the numerical value of the pulse applied to the corresponding pixel during the superframe shown in FIG. The voltage applied to each pixel during the super frame is the sum of the drive voltage shown in Table 12 and the correction voltage V _comp obtained from the following equation.

V _comp = A * (pixel register)
In the equation, the value of the pixel register is a numerical value read from the register corresponding to the corresponding pixel, and A
Is a predetermined constant.

As a result of conducting a proof experiment in the laboratory on the preferred correction voltage method of the present invention, several single pixel displays using a microcapsule electrophoresis medium sandwiched between parallel electrodes have a black state and a white state. It was driven with a +/− 15 V square wave pulse at 300 ms between states. Here, light-transmitting ITO was used for the front parallel electrode. The display started from the white state, moved to the black state, opened the dwell time, and then returned to the white state. As shown in FIG. 22 of the accompanying drawings, the brightness of the final white state was found to be a function of the staying state. Therefore, the microcapsule electrophoretic medium has high sensitivity to the residence time, and the white L * fluctuated by about 3 units depending on the length of the residence time.

In order to present the effect of the correction voltage method of the present invention, the experiment was repeated.
A correction voltage composed of a voltage that decays exponentially from the end of each drive pulse was applied to each pulse. The applied voltage was the sum of the drive voltage and the correction voltage. As shown in FIG. 22, when the correction voltage is used, the white state is more uniform than the uncorrected pulse even if the residence time varies. Thus, using the correction voltage according to the present invention,
The experiment revealed that the sensitivity of the microcapsule electrophoresis medium to the residence time can be significantly reduced.

The correction voltage method of the present invention can use any selection function of the basic lookup table method.

From the above, it will be appreciated that the present invention can provide a method for controlling the operation of an electro-optic display, which is well suited to the characteristics of bistable particle electrophoretic displays and similar displays.

Furthermore, from the above, according to the present invention, there is provided a method for controlling the operation of an electro-optic display, wherein the gray scale can be accurately adjusted without passing through an inconvenient state where the entire display is frequently flushed to one extreme optical state. It will be appreciated that a control method that can be controlled can be provided. In addition, the present invention enables accurate control of the display while reducing power consumption of the display regardless of changes in temperature and operating time of the display. Since the controller of the present invention can be composed of commercially available parts, the above advantages can be realized at low cost.

(DTD integral reduction method)
As already mentioned, it has been found that, at least in some cases, the impulse required for a certain transition depends on the residence time of the pixel under certain optical conditions in a bistable electro-optic display. This phenomenon, which has not been taken up in the prior literature, is hereinafter referred to as “residence time dependence” or “DTD”. Due to the above properties, the impulse applied to a transition is
It may be desirable to vary as a function of the residence time of the pixel in its initial optical state, or in practice it may be necessary in some cases.

Hereinafter, the phenomenon of the residence time dependency will be described in more detail with reference to FIG. 23 of the accompanying drawings. FIG. 23 shows pixel reflectivity as a function of time for a series of transitions represented by R ₃ → R ₂ → R ₁ , where each R _k term represents a gray level in the gray level sequence, R with a large index precedes R with a small index. R ₃ to R ₂ transition and R ₂ to R
The transition to ₁ is also illustrated. DTD is the variation in the final optical state R _{1 that} results from the variation in time that has elapsed in the optical state R ₂ , referred to as the residence time. The DTD integral reduction method of the present invention provides a method of reducing the residence time dependency in driving a bistable electro-optic display.

The present invention is in no way limited to any theory on its origin, but the residual electric field experienced by electro-optic media appears to be a major cause of DTD. The residual electric field is a residual pulse of the driving pulse applied to the medium. The discussion on the residual voltage resulting from the applied pulse is well prevalent, and the residual voltage is simply a scalar potential that corresponds to the residual electric field in a normal way that is compatible with electrostatics theory. The residual voltage may cause the optical state of the display film to drift over time. Moreover, since the residual voltage may change the effectiveness of the drive voltage to be applied next, as a result, the final optical state realized after application of the subsequent pulse is also changed. Thus, the residual voltage from one transition waveform is
The final state obtained after application of the trailing waveform may be different from the final state where the two transitions are fairly independent of each other. “Substantially independent” means that the two transitions are sufficiently far apart in time that the residual voltage of the first transition waveform is substantially attenuated before the application of the second transition waveform. .

From the measurement of the residual voltage due to the transition waveform applied to the electro-optic medium and other single pulses, it has been found that the residual voltage decays over time. The attenuation is monotonic and does not appear to be a simple exponential decay. However, according to the approximate results obtained, it is considered that most of the microcapsule type electrophoretic media examined follow an exponential function with an attenuation time constant of about 1 second, and other bistable electro-optic media. Is expected to show a similar decay time.

  Therefore, the DTD integral reduction method of the present invention has at least one pixel,

（式中、Ｔは波形の長さを示し、積分は波形の継続期間にわたり、Ｖ（ｔ）は時間ｔの関
数としての波形電圧で、Ｍ（ｔ）は、ゼロ時に短パルスより派生する滞留時間依存性を誘
起するために、残留電圧の効果減少を特徴付けるメモリ関数である）が約１ボルト秒より
少なくなるような、画素への波形Ｖ（ｔ）の印加より構成する双安定型電気光学ディスプ
レイの駆動方法も提供する。望ましくは、Ｊは約０．５ボルト秒以下で、最も望ましくは
約０．１ボルト秒以下が良い。実際、Ｊは出来るだけ小さな値、理想的にはゼロに設定す
るべきである。

(Where T is the length of the waveform, integration is the duration of the waveform, V (t) is the waveform voltage as a function of time t, and M (t) is a dwell derived from a short pulse at zero. Bistable electro-optic comprising application of waveform V (t) to the pixel such that the memory function that characterizes the reduced effect of residual voltage to induce time dependence is less than about 1 volt-second A display driving method is also provided. Preferably, J is less than about 0.5 volt seconds, and most desirably less than about 0.1 volt seconds. In fact, J should be set to the smallest possible value, ideally zero.

By forming a composite pulse, the waveform can be designed to provide a very low value of J, so that the DTD is very small. For example, a long negative voltage pulse (with the same voltage amplitude but different sign) preceding a short positive voltage pulse significantly reduces the DTD. It is believed that the two pulses leave two residual voltages of opposite signs (although the present invention is in no way limited to such an opinion). If the ratio of the two pulse lengths is set correctly, the residual voltages of the two pulses can cancel each other for the most part. The appropriate ratio of the two pulse lengths is determined by the memory function of the residual voltage.

  In the presently preferred embodiment of the present invention, J is calculated as:

式中、τは実験的に求められた最適な減衰（緩和）時間を示す。

In the equation, τ represents an optimum decay (relaxation) time obtained experimentally.

For some microcapsule electrophoretic media, it has been experimentally found that waveforms that produce small J values produce particularly low values of DTD, while waveforms that have particularly large J values also increase DTD. In fact, τ is set to 1 second, which is approximately the same as the measured decay time of the residual voltage after applying the voltage pulse, and there is a good correlation between the multiple J values obtained as a result of calculation by the above equation (2). It has been.

Thus, the method described in the patents and patent applications described above can be applied to each transition from one gray level to another (or at least most of the transitions in the lookup table).
It is effective to use a waveform realized by a waveform that produces a low value of J. This J
Is preferably zero, but at least for the microcapsule electrophoretic media described in the above patents and patent applications, as long as the value of J is less than about 1 volt-second at room temperature
It has been experimentally found that the resulting residence time dependence is also very small.

As described above, the present invention provides a waveform with a small calculated value of J for any transition as a waveform for realizing a transition between a series of optical states. The calculation of the J value is performed using a memory function that is assumed to be monotonously decreasing. The memory function is not arbitrarily determined, but can be estimated by observing the residence time dependence of the display film on a single voltage pulse or a composite voltage pulse. For example, in order to realize the transition from the first optical state to the second optical state, a voltage pulse is applied to the display film, a dwell time is set, and then a second voltage pulse is applied to the second film. There is a method for realizing the transition from the voltage pulse to the third voltage pulse. By observing changes in the third optical state as a function of residence time, the shape of the memory function can be determined roughly. The memory function has a form that is roughly similar to the difference between the third optical state and its long residence time value as a function of residence time. The memory function will then be applied in the above form and will have a single amplitude when its independent variable is zero.
In the above method, only the memory function is approximately obtained, and the form of the measured memory function is expected to change slightly for various final optical states.
The overall characteristics of the memory function should be similar for different optical states. However, if there is a large difference in form depending on the final optical state, the most suitable form of memory function for adoption is obtained when the third optical state is in the middle third of the optical range of the display medium. It is what By measuring the decay of the residual voltage after applying the voltage pulse, the overall characteristics of the memory function should be estimated.

Although the memory function estimation method described above is not precise, it has been found that even a J value calculated from an approximate memory is a good guideline for a waveform having a low DTD. As described above, an effective memory function exhibits the overall characteristics of DTD time dependence. For example, an exponential memory function with a 1 second decay time has been found to be effective in predicting waveforms that provide low DTD. Even if the decay time is changed to 0.7 seconds or 1.3 seconds, the effectiveness of the J value for the role of predicting a waveform having a low DTD is not impaired. However, the effectiveness of the prediction effect of a memory function that remains 1 without being attenuated is considerably low, and a memory function having a very short decay time such as 0.05 seconds is not effective for predicting a waveform with a low DTD. There wasn't.

The above waveforms in FIGS. 19 and 20 are examples of waveforms that decrease the value of J, but in these waveforms, the x, y, and z pulses are all significantly shorter in duration than the decay time characteristic of the memory function. The waveform is composed of continuous pulse elements having opposite signs, and the residual voltages of the pulse elements almost cancel each other, so that the waveform functions effectively when the above conditions are satisfied. For x and y values that are not significantly shorter than the decay time that is specific to the memory function, waveforms with opposite signs of x and y tend to provide small J values. The various pulse elements actually produce a residual voltage that cancels or greatly cancels after the waveform is applied, so that the duration of the x and y pulses actually allows a very small J value. Sometimes.

It is clear from the above that the J value of a waveform can be changed by inserting a period of zero voltage in the waveform or adjusting the length of a period of zero voltage already present in the waveform. In this way, various waveforms can be used while the J value is always kept near zero.

The DTD integral reduction method of the present invention can be widely applied. The waveform structure can be devised and expressed by a plurality of parameters, and the J value of the waveform is calculated according to the value of the parameter, and an appropriate parameter value is selected to minimize the J value, whereby the waveform DTD Can be reduced.

Claims (2)

A method of driving a bistable electro-optic display having a plurality of pixels, each of the pixels being capable of displaying at least three gray levels, the method comprising:
Storing a lookup table containing data representing the impulses required to convert the initial gray level to the final gray level;
Storing at least data representing an initial state of each pixel of the display;
Receiving an input signal representative of a desired final state of at least one pixel of the display;
Generating an output signal representing an impulse necessary to convert the initial state of the one pixel to the desired final state, as determined from the look-up table;
For at least one transition from the initial state to the final state, the output signal consists only of pulses having voltage levels of + V, 0, −V, and the output signal is a fine tuning of DC unbalance. Sequence, and the fine tuning sequence is
(A) has a non-zero net impulse G;
(B) has a pulse containing a zero voltage or opposite polarity part;
(C) providing a change in the gray level of the pixel that is substantially different from a change in the optical state of the DC reference pulse, the DC reference pulse being a voltage V pulse, where V is applied during the fine tuning sequence. Has the same sign as the non-zero net impulse G of the fine tuning sequence, and the duration of the DC reference pulse is G / V,
(D) providing a change in the gray level of the pixel that is smaller in magnitude than the change in gray level caused by the time reference pulse, the time reference pulse being a unipolar voltage pulse of the same duration as the fine tuning sequence; Where the sign of the time reference pulse gives a greater change in gray level;
The method wherein the net impulse G is determined by calculating the area under the voltage level-time curve. A method of driving a bistable electro-optic display having a plurality of pixels, each of the plurality of pixels being capable of displaying at least three gray levels, the method comprising: For at least one transition in which the initial state and the final state of the pixel are different, including applying an output signal that is effective in changing the pixel from an initial state to a final state. The output signal consists only of pulses having voltage levels of + V, 0, −V, which are preceded by the first two pulses and then the second two pulses. And the first two pulses have a voltage level of either + V or −V, and the second two pulses are the first two pulses and Have opposite voltage levels .

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