KR20190101488A - Driving Methods for Color Display Devices - Google Patents

Abstract

The present invention relates to driving methods for a color display device capable of displaying high quality color states. The display device utilizes an electrophoretic fluid comprising three types of pigment particles with different optical properties and provides for displaying, at the viewing surface, the colors of the three types of particles as well as the colors of the binary mixtures thereof. .

Description

Driving Methods for Color Display Devices

Reference to Related Applications

This application claims priority to US Patent Application No. 15 / 496,604, filed April 25, 2017, and published as US Patent Publication No. 2017/0263176, both of which are incorporated herein by reference in their entirety. . The contents of all other US patents and published applications mentioned below are all incorporated herein by reference.

Field of invention

The present invention relates to driving methods for color display devices for displaying high quality color states.

In order to achieve a color display, color filters are often used. The most common approach is to add color filters on top of the black / white sub-pixels of the pixelated display to display red, green and blue colors. When a red color is desired, the green and blue sub-pixels change to a black state so that the only color displayed is red. When a blue color is desired, the green and red sub-pixels change to a black state so that the only color displayed is blue. When a green color is desired, the red and blue sub-pixels change to a black state so that the only color displayed is green. When a black state is desired, all three sub-pixels change to a black state. When a white state is desired, the three sub-pixels change to red, green and blue, respectively, so that the white state is shown to the viewer.

The main disadvantage of this technique is that the white state is quite blurry because each of the sub-pixels has a reflectance of about one third (1/3) of the desired white state. To compensate for this, a quarter sub-pixel may be added that can only display black and white states so that the white level is doubled at the expense of a red, green or blue color level (where each sub-pixel is Only 1/4 of the area of pixels). Brighter colors can be achieved by adding light from white pixels, but this is accomplished at the expense of color gamut to make the colors very bright and unsaturated. Similar results can be achieved by reducing the color saturation of the three sub-pixels. Even with these approaches, the white level is usually substantially less than half that of a black and white display, allowing for display devices such as e-readers or displays that require well-readable black-white brightness and contrast. Make it an impossible choice.

A first aspect of the invention is a drive method for an electrophoretic display, wherein the electrophoretic display comprises a first surface on a viewing side, a second surface on a non-viewing side and an electrophoretic fluid Wherein the electrophoretic fluid comprises pigment particles of a first type, pigment particles of a second type and pigment particles of a third type, all of the pigment particles being dispersed in a liquid,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display during a first period of time, the first drive voltage being a polarity that drives the pigment particles of the first type towards the first surface; Applying the first driving voltage, thereby causing the pixel to display the optical properties of the pigment particles of the first type at the first surface;

(ii) applying a second drive voltage to the pixel for a second period of time, the second drive voltage having a polarity to drive the third type of pigment particles towards the first surface, whereby a third at the first surface Applying the second driving voltage to drive the pixel towards the optical properties of the pigment particles of the type; And

A method of driving an electrophoretic display, comprising repeating steps (i) and (ii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged. In one embodiment, the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage. In one embodiment, steps (i) and (ii) are repeated at least four times. In one embodiment, the method further comprises a shaking waveform before step (i). In one embodiment, the method further comprises driving the pixel with the full optical properties of the pigment particles of the first type after the shaking waveform but before step (i). In one embodiment, the first time period is 40 to 140 msec, the second time period is at least 460 msec, and steps (i) and (ii) are repeated at least seven times.

A second aspect of the invention relates to a method for driving an electrophoretic display as described above but comprising an additional step, the further step being: after step (ii) but with steps (i) and not applying any drive voltage to the pixel for a third time period prior to repeating (ii); And repeating steps (i), (ii) and (iii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged. In one embodiment, the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage. In one embodiment, steps (i), (ii) and (iii) are repeated at least four times. In one embodiment, the method further comprises a shaking waveform prior to step (i). In one embodiment, the method further comprises driving the pigment particles of the first type to the full color state after the shaking waveform but before step (i).

A third aspect of the invention is a drive method for an electrophoretic display, wherein the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, the electrophoretic fluid being the first Pigment particles of the type, pigment particles of the second type and pigment particles of the third type, all of which are dispersed in a liquid,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,

The method relates to a driving method for the electrophoretic display, having a voltage insensitive range of at least 0.7 V.

A fourth aspect of the invention relates to a driving method for an electrophoretic display, in accordance with the first aspect of the invention but comprising additional steps, which further steps are as follows:

(iii) applying no drive voltage to the pixel for a third time period after step (i) but before step (ii);

(iv) applying no drive voltage to the pixel for a fourth time period after step (ii) but before repeating the steps; And

Repeating steps (i) to (iv).

In one embodiment, the pigment particles of the first type may be negatively charged and the pigment particles of the second type may be positively charged. In one embodiment, the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage. In one embodiment, steps (i) to (iv) are repeated at least three times. In one embodiment, the method further comprises a shaking waveform prior to step (i). In one embodiment, the method further comprises driving the pixel to a full color state of pigment particles of the first type after the shaking waveform but before step (i).

A fifth aspect of the invention is a drive method for an electrophoretic display, wherein the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, the electrophoretic fluid being a common electrode And sandwiched between a layer of pixel electrodes and comprising pigment particles of a first type, pigment particles of a second type and pigment particles of a third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying said first drive voltage having the same polarity as one type of pigment particles;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage being a pigment particle of the second type to drive the pixel towards the color state of the pigment particles of the second type on the viewing side. Applying the second driving voltage having the same polarity as the above; And

A method of driving an electrophoretic display, comprising repeating steps (i) and (ii).

In one embodiment, the method further includes a wait time for which no drive voltage is applied. In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged. In one embodiment, the second time period is at least twice as long as the first time period. In one embodiment, steps (i) and (ii) are repeated at least three times. In one embodiment, the method further comprises a shaking waveform prior to step (i). In one embodiment, the method further comprises driving the pixel to a full color state of pigment particles of the second type after the shaking waveform but before step (i).

A sixth aspect of the invention is a drive method for an electrophoretic display, wherein the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, the electrophoretic fluid being a common electrode And sandwiched between a layer of pixel electrodes and comprising pigment particles of a first type, pigment particles of a second type and pigment particles of a third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel toward the color state of the pigment particles of the second type on the viewing side. Applying said first drive voltage having the same polarity as the two types of pigment particles;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage being a pigment particle of the first type to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying the second driving voltage having the same polarity as the above;

(iii) applying no driving voltage to the pixel during the third time period; And

A method of driving an electrophoretic display, comprising repeating steps (i), (ii) and (iii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged. In one embodiment, steps (i), (ii) and (iii) are repeated at least three times. In one embodiment, the amplitude of the second drive voltage is equal to the amplitude of the drive voltage required to drive the pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, or vice versa. Do. In one embodiment, the amplitude of the second drive voltage is higher than the amplitude of the drive voltage required to drive the pixel from the color state of the first type of pigment particles to the color state of the second type of pigment particles, or vice versa. . In one embodiment, the method further comprises a shaking waveform. In one embodiment, the method further comprises driving the pixel to a full color state of pigment particles of the first type after the shaking waveform but before step (i).

A seventh aspect of the invention is a drive method for an electrophoretic display, wherein the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, the electrophoretic fluid being a common electrode And sandwiched between a layer of pixel electrodes and comprising pigment particles of a first type, pigment particles of a second type and pigment particles of a third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first time period, the first drive voltage being of the second type to drive the pixel towards the color state of the pigment particles of the second type. Applying the first driving voltage having the same polarity as the pigment particles and having a first time period not sufficient to drive a pixel in a full color state of pigment particles of a second type at the viewing side;

(ii) applying a second drive voltage to the pixel for a second period of time, the second drive voltage being at the viewer side to drive the pixel towards the mixed state of the first and second types of pigment particles; Applying said second drive voltage having the same polarity as the pigment particles of the type; And

A method of driving an electrophoretic display, comprising repeating steps (i) and (ii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged. In one embodiment, the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage. In one embodiment, steps (i) and (ii) are repeated at least four times. In one embodiment, the method further comprises a shaking waveform prior to step (i). In one embodiment, the method further comprises driving the pixel to a full color state of pigment particles of the first type after the shaking waveform but before step (i).

The fourth driving method of the present invention may be applied to the pixel in the color state of the pigment particles of the first type or may be applied to the pixel in the color state other than the color state of the pigment particles of the first type.

The invention also provides driving methods for displaying mixtures of optical properties of two of three particles in electrophoretic display fluids as previously described. This first "mixed property" method is:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage having a polarity driving the pigment particles of the first type towards the first surface, whereby the pixel Applying said first drive voltage to cause display of the optical properties of pigment particles of a first type at this first surface;

(ii) applying a second drive voltage to the pixel for a second period of time, the second drive voltage having a polarity to drive the third type of pigment particles towards the first surface, whereby a third at the first surface Applying the second driving voltage to drive the pixel towards the optical properties of the pigment particles of the type; And

(iii) applying a third drive voltage during a third time period, wherein the third drive voltage has the same polarity as the first drive voltage, and the third time period is shorter than the first time period, thereby at the viewing surface. Applying the third drive voltage, creating a mixture of optical properties of the first and third types of particles.

In this first mixed feature method, the duration of the third time period may be about 20 to about 80%, and preferably about 20 to about 40% of the duration of the first time period. The shaking waveform may be applied before step (i), and the driving voltage driving the pigment particles of the first type towards the first surface may be applied before the shaking waveform.

The second "mixed properties" method is:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage having a polarity driving the pigment particles of the second type towards the first surface, whereby the pixel Applying the first drive voltage, causing the display of the optical properties of the pigment particles of the second type on the first surface;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage having the same polarity as the first driving voltage, but having a magnitude less than the first driving voltage, thereby at the first surface. Driving a third type of pigment particles and applying a second drive voltage, which produces a mixture of optical properties of the second and third types of particles at the first surface.

In this second mixed characteristic method, the duration of the second time period may be about 100 to about 150% of the duration of the first time period. The shaking waveform may be applied before step (i), and the driving voltage driving the pigment particles of the first type towards the first surface may be applied before the shaking waveform.

The third "mixed character" method is:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage having a polarity driving the pigment particles of the first type towards the first surface, whereby the pixel Applying said first drive voltage to cause display of the optical properties of pigment particles of a first type at this first surface;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage applying the second driving voltage having a polarity to drive the third type of pigment particles towards the first surface; Making; And

Repeating steps (i) and (ii),

The durations of steps (i) and (ii) and the magnitudes of the voltages applied in the steps are determined by the optical of one of the first and second types of particles and the third type of particles at the first surface. Adjusted to produce a mixture of properties.

In this third mixed characteristic method, the shaking waveform may be applied before step (i), and the driving voltage for driving the pigment particles of the first type towards the first surface may be applied before the shaking waveform. .

1 is a schematic cross-sectional view through an electrophoretic display fluid useful in the drive methods of the present invention.
2 (A), (B) and (C) are schematic cross sectional views similar to the schematic cross sectional view of FIG. 1, showing positions of particles in black, white and red (colored) states of the display fluid, respectively. do.
3 illustrates a typical waveform for driving a pixel from the white state of FIG. 2B to the red state of FIG. 2C.
4 illustrates a waveform that may be used to replace a portion of the waveform of FIG. 3 at period t3 to achieve the first drive method of the present invention.
5 and 6 illustrate waveforms generated by modifying the waveform of FIG. 3 to the partial waveform of FIG. 4 to achieve the first driving method of the present invention.
FIG. 7 illustrates a second waveform that may be used to replace a portion of the waveform of FIG. 3 at period t3 to achieve the second drive method of the present invention.
8 and 9 illustrate waveforms generated by modifying the waveform of FIG. 3 to the partial waveform of FIG. 7 to achieve the second driving method of the present invention.
10A and 10B illustrate the optical results produced by the third drive method of the present invention. FIG. 10A demonstrates the relationship of applied drive voltage to optical state performance (a *) based on the waveform of FIG. 3, and FIG. 10B shows the applied drive based on the modification of the waveform of FIG. 3 to the partial waveform of FIG. 4. The relationship of voltage to optical state performance (a *) is demonstrated.
FIG. 11 illustrates a waveform that may be used to replace a portion of the waveform of FIG. 3 at period t3 to achieve the fourth drive method of the present invention.
12 and 13 illustrate waveforms generated by modifying the waveform of FIG. 3 to the partial waveform of FIG. 11 to achieve the fourth driving method of the present invention.
FIG. 14 shows a typical waveform for driving a pixel from the white state of FIG. 2B to the black state of FIG. 2A.
FIG. 15 illustrates a waveform that may be added to the end of the waveform of FIG. 14 to achieve a fifth driving method of the present invention.
16 illustrates a composite waveform combining the waveforms of FIGS. 14 and 15 to achieve a fifth driving method of the present invention.
FIG. 17 shows a typical waveform for driving the pixel to the white state of FIG. 2B.
18A and 18B illustrate two waveforms that may be used to replace a portion of the waveform of FIG. 17 at period t17 to achieve the sixth driving method of the present invention.
19A and 19B show waveforms generated by modifying the waveform of FIG. 17 to the partial waveform of FIG. 18A or 18B, respectively, to achieve the sixth driving method of the present invention.
20A and 20B are schematic cross sectional views similar to the schematic cross sectional diagram of FIG. 1, showing positions of particles in black and gray states of the display fluid, respectively.
21 illustrates a typical waveform for driving a pixel in the gray state of FIG. 20B.
FIG. 22 illustrates a waveform that may be used to replace a portion of the waveform of FIG. 21 at period t23 to achieve the seventh drive method of the present invention.
FIG. 23 illustrates a composite waveform combining the waveforms of FIGS. 21 and 22 to achieve the seventh driving method of the present invention.
24 illustrates waveforms used in the eighth drive method of the present invention.
25 illustrates a composite waveform combining the waveforms of FIGS. 14 and 24 to achieve an eighth drive method of the present invention.
26A and 26B illustrate the generation of its gray state starting from the white state of the pixel.
(B) and (D) illustrate the generation of its gray state starting from the black state of the pixel.
27 illustrates waveforms useful for driving a display from a white state to a bright red state in a first mixed characteristic driving method of the present invention.
Figure 28 illustrates waveforms useful for driving a display in a dark red state in the second mixed characteristic drive method of the present invention.
29 illustrates a second waveform useful for driving a display in a dark red state in the third mixed characteristic driving method of the present invention.

The present invention relates to driving methods for color display devices.

The device utilizes an electrophoretic fluid as shown in FIG. 1. The fluid comprises three types of pigment particles dispersed in a liquid, typically a dielectric solvent or solvent mixture. For ease of illustration, the three types of pigment particles may be referred to as white particles 11, black particles 12 and colored particles 13. Chromic particles are non-white and non-black.

However, the scope of the present invention is understood to broadly encompass pigment particles of any colors as long as the three types of pigment particles have distinguishable optical properties. Thus, the three types of pigment particles may also be referred to as pigment particles of the first type, pigment particles of the second type and pigment particles of the third type.

The white particles 11 may be formed from an inorganic pigment, such as _{TiO 2, ZrO 2, ZnO,} Al 2 O 3, Sb 2 O 3, BaSO 4, PbSO 4.

The black particles 12 may be CI pigment black 26 or 28 and the like (eg, manganese ferrite black spinel or copper chromite black spinel) or carbon black.

The third type of particles may be colors such as red, green, blue, magenta, cyan or yellow. Pigments for this type of particles may include, but are not limited to, CI pigments PR254, PR122, PR149, PG36, PG58, PG7, PB15: 3, PY138, PY150, PY155 or PY20. These are commonly used organic pigments described in color index handbooks, "New Pigment Application Technology" (CMC Publishing Co, Ltd, 1986) and "Printing Ink Technology" (CMC Publishing Co, Ltd, 1984). Specific examples are Clariant Hostaperm Red D3G 70-EDS, Hostaperm Pink E-EDS, PV fast red D3G, Hostaperm red D3G 70, Hostaperm Blue B2G-EDS, Hostaperm Yellow H4G-EDS, Hostaperm Green GNX, BASF Irgazine red L 3630, Cinquasia Red L 4100 HD, and Irgazine Red L 3660 HD; Sun Chemical Phthalocyanine Blue, Phthalocyanine Green, Diarylide Yellow or Diarylide AAOT Yellow.

In addition to the colors, the first, second and third types of particles may have other distinct optical properties, such as electromagnetic outside the visible range, in the case of displays intended for light transmission, reflectance, luminescence, or machine reading. It may have a pseudo-color in the sense of the change in reflectance of the wavelengths.

The liquid in which the three types of pigment particles are dispersed may be clear and colorless. It preferably has a low viscosity and a dielectric constant in the range of about 2 to about 30, preferably about 2 to about 15, for high particle mobility. Examples of suitable dielectric fluids are hydrocarbons, such as isopar, decahydronaphthalene, DECALIN, 5-ethylidene-2-norbornene, fatty oils, paraffin oils, silicon fluids, aromatic hydrocarbons, Such as toluene, xylene, phenylxylylethane, dodecylbenzene or alkylnaphthalene, halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5 Trichlorobenzotrifluoride, chloropentafluorobenzene, dichlorononane or pentachlorobenzene, and perfluorinated solvents such as 3M Company, St. FC-43, FC-70 or FC-5060 from Paul MN, low molecular weight halogen containing polymers such as poly (perfluoropropylene oxide) from TCI America, Portland, Oregon, Halocarbon Product Corp., River Edge, Poly (chlorotrifluoroethylene) such as halocarbon oil from NJ, Galden or DuPont from Ausimont, perfluoropolyalkylethers such as Krytox Oils and Greases K-Fluid series from Delaware, Dow-corning (DC- Polydimethylsiloxane-based silicone oils from US Pat.

The display layer utilizing the display fluid of the present invention has two surfaces, a first surface 16 on the viewing side and a second surface 17 on the opposite side of the layer of display fluid from the first surface 16. . The second surface is thus on the non-visible side. The term “viewing side” refers to the side from which images are viewed.

The display fluid is sandwiched between two surfaces. On the side of the first surface 16, there is a common electrode 14, which is a transparent electrode layer (eg ITO) that is spread over the entire top surface of the display layer. On the side of the second surface 17, there is an electrode layer 15 comprising a plurality of pixel electrodes 15a. However, as will be readily apparent to those skilled in the art of electrophoretic displays, other electrode arrangements may be used because the various particles 11, 12, 13 only respond to an electric field applied within a layer of display fluid. have; For example, the common electrode can be replaced by a series of strip electrodes or by a matrix of electrodes similar to the pixel electrodes 15a.

Display fluid is filled in the display cells. The display cells may or may not be aligned with the pixel electrodes. The term "display cell" refers to a micro-container filled with an electrophoretic fluid. Examples of “display cells” may include cup-shaped microcells as described in US Pat. No. 6,930,818 and microcapsules as described in US Pat. No. 5,930,026. Micro-containers may be in any shape or sizes, all of which are within the scope of the present application.

The area corresponding to the pixel electrode may be referred to as a pixel (or sub-pixel). The driving of the region corresponding to the pixel electrode is made by applying a voltage potential difference (or known as a driving voltage or an electric field) between the common electrode and the pixel electrode.

Pixel electrodes are described in US Pat. No. 7,046,228, the contents of which are incorporated herein by reference in their entirety. Note that although an active matrix driving with a thin film transistor (TFT) backplane is mentioned for the layer of pixel electrodes, the scope of the present invention encompasses other types of electrode addressing as long as the electrodes serve the desired functions.

The space between two vertical dotted lines represents a pixel (or sub-pixel). For the sake of brevity, when "pixel" is mentioned in the driving method, the term also encompasses "sub-pixels".

Two pigment particles of the three types of pigment particles have opposite charge polarities and the third type of pigment particles are lightly charged. The term “weakly charged” or “lower charge strength” is intended to refer to the charge level of the particles being less than about 50%, preferably from about 5% to about 30%, of the charge strength of the stronger charged particles. do. In one embodiment, the charge intensity may be measured in terms of zeta potential. In one embodiment, the zeta potential is determined by a Colloidal Dynamics AcoustoSizer IIM with a CSPU-100 signal processing unit, an ESA EN # Attn flow through cell (K: 127). Instrument constants such as the density of the solvent used in the sample, the dielectric constant of the solvent, the speed of sound in the solvent, and the viscosity of the solvent, all of which are input before testing at the testing temperature (25 ° C.). Pigment samples are dispersed in a solvent (usually a hydrocarbon fluid having less than 12 carbon atoms) and diluted between 5 and 10% by weight. The sample also contains a charge control agent (Solsperse 17000; "Solsperse" is a registered trademark) available from Lubrrizol Corporation, Berkshire Hathaway company, in a weight ratio of charge control agent to particles of 1:10. The mass of the diluted sample is determined and the sample is then loaded into the flow through cell for determination of the zeta potential.

For example, if the black particles are positively charged and the white particles are negatively charged, the chromic pigment particles may be weakly charged. In other words, in this example, the charges of the black and white particles are much stronger than the charge of the chromining particles.

In addition, weakly charged chromogenic particles have a charge polarity equal to the charge polarity of either of the other two types of stronger charged particles. In the following, it will be assumed that the chromic particles 13 have a charge of the same polarity as the second (black) particles 12.

Note that, among the three types of pigment particles, one type of particle with weak charge preferably has a larger size.

In addition, in the context of the present application, a high drive voltage V _H1 or V _H2 is defined as a drive voltage sufficient to drive a pixel from one extreme color state to another extreme color state. If the first and second types of pigment particles are particles with higher charge, the high driving voltage (V _H1 or V _H2 ) is from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, Or vice versa, a sufficient driving voltage to drive the pixel. For example, a high drive voltage V _H1 refers to a drive voltage sufficient to drive a pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, and V _H2 of the second type. Refers to a driving voltage sufficient to drive a pixel from the color state of the pigment particles to the color state of the pigment particles of the first type. In this scenario as described, the low drive voltage V _L is the pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the third type (which may take less charge and be larger in size). It is defined as the drive voltage which may be sufficient to drive. For example, while black and white particles are not visible from the viewing side, a low driving voltage may be sufficient to drive to the color state of the chromining particles.

Generally V _L is less than 50%, preferably less than 40% of the amplitude of V _H (eg V _H1 or V _H2 ).

The following is an embodiment illustrating a driving scheme of how different color states may be displayed by an electrophoretic fluid as described above.

Example 1

This example is demonstrated in Figs. 2A to 2C. The white pigment particles 21 are negatively charged while the black pigment particles 22 are positively charged, and both types of pigment particles are smaller than the chromogenic particles 23.

The chromic particles 23 have the same charge polarity as the black particles, but have a weak charge. As a result, the black particles move faster than the chromic particles 23 under predetermined driving voltages.

In FIG. 2A, the applied driving voltage is +15 V (ie, V _H1 , ie, the pixel electrode is at +15 V with respect to the common electrode). In this case, the negative white particles 21 move relatively close to the positive pixel electrode 25 or relatively to the positive pixel electrode 25 and the positive black particles 22 and the positive The chromic particles 23 move to be relatively close to the negative common electrode 24 or to be relatively to the negative common electrode 24. As a result, black color is seen from the viewing side. The chromic particles 23 move toward the common electrode 24 on the viewing side; However, because of their lower charge strength and larger size, they travel slower than black particles.

In FIG. 2B, when a driving voltage of −15 V (ie, V _H2 ) is applied, the negative white particles 21 are closer to the positive common electrode 24 relatively at the viewing side or Move relative to the positive common electrode 24 and move the positive black particles and the positive chromogenic particles relatively close to the negative pixel electrode 25 or relatively to the negative pixel electrode 25. . As a result, white color is seen from the viewing side.

Note that V _H1 and V _H2 have opposite polarities and have the same amplitude or different amplitudes. In the embodiment as shown in FIG. 2, V _H1 is positive (same polarity as black particles) and V _H2 is negative (same polarity as white particles).

The drive from the white color state of FIG. 2B to the color development state of FIG. 2C may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type (ie white), pigment particles of the second type (i.e. black) and pigment particles of the third type (i.e. color development), all of which are either solvents or Dispersed in a solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

The method applies pixels of the first type of electrophoretic display by applying a low driving voltage sufficient to drive the third type of pigment particles to the viewing side while leaving the first and second types of pigment particles on the non-viewing side. Driving from the color state of the pigment particles toward the color state of the third type of pigment particles and wherein the polarity of the applied low driving voltage is the same as that of the third type of pigment particles. .

In order to drive the pixel in the color state of the third type of pigment particles, i.e. red (see FIG. 2C), the method comprises the first type of pigment particles, i.e. white (see FIG. Starts in the color state.

When the color of the third type of particles is visible at the viewing side, the other two types of particles may be mixed at the non-viewing side (opposite side of the viewing side), so that it is intermediate between the colors of the first and second types of particles. It may also lead to a color state. If the particles of the first and second types are black and white and the particles of the third type are red, in Fig. 2C, when the red color is seen from the viewing side, the gray color is on the non-viewing side.

The driving method will ideally ensure both color brightness (i.e. black particles are invisible) and color purity (i.e. white particles are invisible) in the scenario of FIG. In practice, however, this desired result is difficult to achieve for a variety of reasons including particle size distribution and particle charge distribution.

One solution to this is to use a shaking waveform before driving from the color state of the first type of pigment particles (ie white) to the color state of the third type of pigment particles (ie red). The shaking waveform consists of repeating a pair of opposite drive pulses for many cycles. For example, the shaking waveform may consist of a +15 V pulse for 20 msec and a -15 V pulse for 20 msec and these pairs of pulses are repeated 50 times. The total time of this shaking waveform will be 2000 msec. The symbol "msec" means milliseconds.

The shaking waveform may be applied to the pixel regardless of the optical state (black, white or red) before the driving voltage is applied. After the shaking waveform is applied, the optical state will not be pure white, pure black or pure red. Instead, the color state will be derived from a mixture of three types of pigment particles.

In the case of the method as described above, the shaking waveform is applied before the pixel is driven to the color state of the pigment particles of the first type (ie white). Using this added shaking waveform, the white state is somewhat the same as without the shaking waveform, but the color state of the third type of pigment particles (i.e. red) is both in color brightness and color purity. This would be much better than no shaking waveforms. This is an indication of better separation of white particles from red particles as well as better separation of black particles from red particles.

Each of the drive pulses in the shaking waveform is applied for a drive time that does not exceed half of the drive time required to drive from the full black state to the full white state or vice versa. For example, if it takes 300 msec to drive a pixel from a full black state to a full white state or vice versa, the shaking waveform may consist of a positive pulse and a negative pulse applied for 150 msec or less, respectively. In practice, the shaking waveform pulses are preferably shorter.

Note that in all figures throughout the application, the shaking waveform is truncated (ie, the number of pulses is less than the actual number).

The waveform used to drive the display in the colored (red) state of FIG. 2C is shown in FIG. In this waveform, a high negative drive voltage (V _H2 , for example -15 V) is applied during the period of t2 to drive the pixel towards the white state after the shaking waveform. From the white state, the pixel may be driven toward the color development state (ie red) by applying a low positive voltage (V _L , eg, +5 V) during the period of t3 (ie, FIG. 2B). The pixel from FIG. 2 to C).

The drive period "t2" is a time period sufficient to drive a pixel to a white state when V _H2 is applied and the drive period "t3" is a time period sufficient to drive a pixel from a white state to a red state when V _L is applied. . The drive voltage is preferably applied for a period of t1 before the shaking waveform to ensure DC balance. The term “DC balance” is intended throughout this specification to mean that the driving voltages applied to the pixel when being integrated over one time period (eg, the period of the entire waveform) are substantially zero.

First drive method:

Waveforms useful in the first drive method of the present invention are illustrated in FIG. 4; This waveform may be used to replace the driving period of t3 in FIG.

In the initial stage, a high negative drive voltage (V _H2 , for example -15 V) is applied, followed by a positive drive voltage (+ V ') to drive the pixel towards the red state. The amplitude of + V 'is less than 50% of the amplitude of V _H (eg, V _H1 or V _H2 ).

In this drive waveform, a high negative drive voltage V _H2 is applied during the period of t4 to push the white particles toward the viewer side, and then a positive drive voltage of + V 'is applied during the period of t5. This pulls the white particles down and pushes the red particles towards the viewer side.

200 msec 일 수도 있다.In one embodiment, t4 may be in the range of 20-400 msec and t5 is

200 msec may be sufficient.

4), 바람직하게는 적어도 8 사이클들 동안 반복된다. 적색 컬러는 각각의 구동 사이클 이후에 더 강해진다.The waveform of FIG. 4 is at least 4 cycles (N

4), preferably repeated for at least 8 cycles. The red color becomes stronger after each drive cycle.

The driving method of FIG. 4 may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying said first drive voltage having the same polarity as one type of pigment particles;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage being the pigment particle of the third type to drive the pixel towards the color state of the third type of pigment particles on the viewing side. Applying the second driving voltage having the same polarity as the above; And

Repeating steps (i) and (ii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged.

In one embodiment, the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage.

As mentioned, a drive waveform as shown in FIG. 4 may be used to replace the drive period of t3 in FIG. 3, and FIG. 5 illustrates the combined waveform after this replacement. In other words, the drive sequence may be followed by: a shaking waveform, then driving towards a white state for a period of t2 and then applying the waveform of FIG. 4.

In another embodiment, driving to a white state during the period of t2 may be eliminated, in which case the shaking waveform is applied immediately before applying the waveform of FIG. 4 (see FIG. 6).

In one embodiment, the drive sequence of FIG. 5 or FIG. 6 is DC balanced.

Second drive method:

Waveforms useful in the second drive method of the present invention are illustrated in FIG. This waveform is an alternative to the drive waveform of FIG. 4 and may also be used to replace the drive period of t3 in FIG.

4) 동안 반복된다.In this alternative waveform, after the red-going pulse in period t5 and before the white-going pulse in white in period t4 and the pulse in red in period t5 are repeated. Wait time "t6" has been added. During the waiting time, no drive voltage is applied. The entire waveform of FIG. 7 also includes multiple cycles (eg, N

4) is repeated.

The waveform of FIG. 7 is designed to release charge imbalance stored in dielectric layers in an electrophoretic display device, especially when the resistance of the dielectric layers is high, for example at low temperatures.

In the context of the present application, the term "low temperature" refers to a temperature lower than about 10 ° C.

The latency probably dissipates unwanted charge stored in the dielectric layers, short pulse ("t4") to drive the pixel towards the white state and longer pulse ("t5") to drive the pixel towards the red state. Can make it more efficient. As a result, this alternative driving method will better separate low charged pigment particles from higher charged pigment particles. The wait time "t6" may be in the range of 5-5,000 msec, depending on the resistance of the dielectric layers.

This driving method of FIG. 7 may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying said first drive voltage having the same polarity as one type of pigment particles;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage being the pigment particle of the third type to drive the pixel towards the color state of the third type of pigment particles on the viewing side. Applying the second driving voltage having the same polarity as the above;

(iii) applying no driving voltage to the pixel during the third time period; And

A method of driving an electrophoretic display, comprising repeating steps (i), (ii) and (iii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged.

In one embodiment, the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage.

As mentioned, the drive waveform shown in FIG. 7 may also be used to replace the drive period of t3 in FIG. 3 (see FIG. 8). In other words, the drive sequence may be followed by: a shaking waveform, then driving towards a white state for a period of t2 and then applying the waveform of FIG. 7.

In another embodiment, driving to a white state during the period of t2 may be eliminated, in which case the shaking waveform is applied before applying the waveform of FIG. 7 (see FIG. 9).

In another embodiment, the drive sequence of FIG. 8 or 9 is DC balanced.

It should be noted that the lengths of any drive cycles mentioned in this application may be temperature dependent.

Third drive method:

FIG. 10A demonstrates the relationship between the applied drive voltage V ′ and the optical performance, based on the waveform of FIG. 3. As shown, the applied positive drive voltage V ′ may affect the red state performance of the color display device described above. The red state performance of the display device is represented as an a * value utilizing the L * a * b * color system.

The maximum a * in FIG. 10A is shown at the applied drive voltage V ′ in FIG. 3, which is about 3.8 V. FIG. However, if a change of ± 0.5 V is made to the applied drive voltage, the resulting a * value will be about 37, which is approximately 90% of the maximum a *, and will therefore still be acceptable. This tolerance is caused by, for example, a change in electronic components of the display device, a drop in battery voltage over time, a change in the batch of TFT backplanes, a change in the placement of the display devices, or temperature and humidity variations. It may be beneficial to accommodate changes in the drive voltages that are made.

Based on the data given in FIG. 10A, a study was conducted to find a range of drive voltages V ′ capable of driving in a red state beyond 90% of the maximum a * value. In other words, if any driving voltages in the above range are applied, the optical performance is not greatly affected. Thus, this range may be referred to as the "voltage-insensitive" range. The wider the "voltage desensitization" range, the better the driving method is tolerant to batch changes and environmental changes.

In Figure 4 there are three parameters, t4, t5 and N, which should be considered for this study. The effects of the three parameters on the voltage-insensitive range are mutual and non-linear.

Following the model of FIG. 10A, one can find the optimal value sets for the three parameters to achieve the widest voltage-desensitization range for the waveform of FIG. 4. The results are summarized in FIG. 10B.

When t4 is between 40-140 msec, t5 is at least 460 msec and N is at least 7, the voltage-desensitization range (i.e. 3.7 V to 6.5 V) based on FIG. 3.3 V to 4.7 V) twice the width.

The optimized parameters discussed above are also applicable to any of the driving methods of the present invention.

Thus, the third driving method may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the layer of the common electrode and the pixel electrode. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

The method has a voltage desensitization range of at least 0.7 V. A method for driving an electrophoretic display.

In this way, if a drive voltage within this range is applied, the optical quality of the color state achieved is at least 90% of the maximum allowable "a *" value.

Note also that the data shown in FIGS. 10A and 10B are collected at ambient temperature.

Fourth drive method:

Waveforms useful in the fourth drive method of the present invention are illustrated in FIG. This drive waveform may be used to replace the drive period of t3 in FIG.

In the initial stage, a high negative drive voltage (V _H2 , eg -15 V) is applied to the pixel during the period of t7 (see the corresponding pulse in period t4 of FIG. 4). This pulse is followed by a wait time of t8, during which no voltage is applied. After the waiting time, a positive driving voltage (V ', eg, less than 50% of V _H1 or V _H2 ) is applied to the pixel for a period of t9 (see the corresponding pulse in period t5 of FIG. 4). After the pulse at t9, but before the various steps of the waveform are repeated, there is a second latency of t10 where no voltage is applied. The waveform in FIG. 11 is repeated N times. The term “wait time” refers to a time period during which no drive voltage is applied, as described above.

This driving method is not only particularly effective at low temperatures, but also can provide the display device with a better tolerance of structural changes caused during the manufacture of the display device. Thus its usefulness is not limited to low temperature driving.

In the waveform of FIG. 11, the first waiting time t8 is very short while the second waiting time t10 is longer. The period of t7 is also shorter than the period of t9. For example, t7 may be in the range of 20-200 msec; t8 may be less than 100 msec; t9 may be in the range of 100-200 msec; t10 may be less than 1000 msec.

FIG. 12 shows the waveform generated by inserting the waveform of FIG. 11 instead of the period t3 of FIG. In Fig. 3, the white state is displayed for the period t2. As a general rule, the better the white state in this period, the better the red state to be displayed at the end of the waveform.

In the shaking waveform, the positive / negative pulse pair is preferably repeated 50-1500 times, and each pulse is preferably applied for 10 msec.

In one embodiment, driving to a white state during the period of t2 may be eliminated, in which case the shaking waveform is applied before applying the waveform of FIG. 11 (see FIG. 13).

The fourth driving method of FIG. 11 may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying said first drive voltage having the same polarity as one type of pigment particles;

(ii) applying no driving voltage to the pixel during the second time period;

(iii) applying a second driving voltage to the pixel for a third period of time, the second driving voltage being the pigment particle of the third type to drive the pixel towards the color state of the third type of pigment particles on the viewing side. Applying the second driving voltage having the same polarity as the above;

(iv) applying no driving voltage to the pixel during the fourth time period; And

And repeating steps (i) to (iv).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged.

In one embodiment, steps (i) to (iv) are repeated at least three times.

In one embodiment, the second drive voltage is less than 50% of the drive voltage sufficient to drive the pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, or vice versa.

In another embodiment, the drive sequence of FIG. 12 or FIG. 13 is DC balanced.

Fifth Driving Method:

As shown in Fig. 2A, since black particles and red particles have the same charge polarity, they tend to move in the same direction. Although black particles move faster than red particles under certain driving voltages because of their higher charge and possibly also smaller size, some of the red particles may still be driven to the viewer side with the black particles, thus the quality of the black state. It can also reduce the.

14 shows a typical waveform for driving a pixel toward a black state. Shaking waveforms (described above) are included to ensure color brightness and purity. As shown, a high positive drive voltage (V _H1 , eg, +15 V) is applied during the period of t12 to drive the pixel towards the black state after the shaking waveform. The drive voltage is applied for a period of t11 before the shaking waveform to ensure DC balance.

FIG. 15 illustrates a waveform that may be added to the end of the waveform of FIG. 14 to drive a pixel towards a black state. The combined waveform can further provide better separation of the black particles from the red particles, making the black state more saturated with less red tinting.

3 이다) 그리고 더 바람직하게는 적어도 5 내지 7 회 동안 인가된다.In Fig. 15, short pulse "t13" of V _H2 (negative) is applied, followed by longer pulse "t14" of V _H1 (positive) and waiting time (0 V) of t15. This sequence is performed at least once, preferably at least three times (ie, N is

3) and more preferably for at least 5 to 7 times.

Pulse "t14" is usually at least twice the length of pulse "t13".

The short pulse "t13" of V _H2 will push the black and red particles toward the pixel electrode and the longer pulse "t14" of V _H1 will push them to the common electrode side (ie the viewing side). Since the speeds of the two types of pigment particles are not the same under the same driving voltages, this asymmetrical driving sequence will be more beneficial for black particles than for red particles. As a result, the black particles can be better separated from the red particles.

The latency "t15" is optional, depending on the dielectric layers in the display device. At lower temperatures, it is true that the resistance of the dielectric layers is more pronounced, in which case a waiting time may be needed to release the charge trapped in the dielectric layers.

The fifth driving method of FIG. 15 may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying said first drive voltage having the same polarity as one type of pigment particles;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage being a pigment particle of the second type to drive the pixel towards the color state of the pigment particles of the second type on the viewing side. Applying the second driving voltage having the same polarity as the above;

(iii) optionally applying no driving voltage to the pixel for a third time period; And

If present, comprising repeating steps (i), (ii) and (iii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged.

FIG. 16 shows a composite waveform combining the waveform of FIG. 14 with the waveform of FIG. 15. However, it is also noted that depending on the particle velocity and the number of cycles N of the sequence, "t12" may be shortened. In other words, at the end of "t12", the pixel does not need to be in full black. Instead, the waveform of FIG. 15 can start in any state from black to white, including gray, if the number N of sequences is sufficient to drive the pixel to the last black state.

The method as described in FIGS. 14-16 may also be utilized to drive a pixel to a black state at low temperatures. In this case, the period t14 should be longer than t13 and the waiting time t15 should be at least 50 msec.

In one embodiment, the drive sequence of FIG. 16 is DC balanced.

Sixth drive method:

17 shows a typical waveform for driving a pixel in a white state. Shaking waveforms (described above) are included to ensure color brightness and purity. The driving voltage of V _H2 is applied for a period of t17 after the shaking waveform. The driving voltage of V _H1 is applied for a period of t16 before the shaking waveform to ensure DC balance.

18A and 18B show waveforms that may be used to replace pulse t17 of the waveform of FIG. 17.

This driving method is particularly suitable for low temperature driving, but is not limited to low temperature driving.

In Fig. 18A, a short pulse "t18" of V _H1 (positive) is applied, followed by a longer pulse "t19" of V _H2 (negative) and a waiting time (0 V) of t20. As shown in FIG. 18B, the amplitude of the negative drive voltage V ″ applied during t19 may be higher than the amplitude of V _H2 (eg, −30 V instead of −15 V).

3 이다), 그리고 더 바람직하게는 적어도 5 내지 7 회 동안 인가된다.This sequence is performed at least once, preferably at least three times (ie N in FIGS. 18A and 18B is

3), and more preferably for at least 5 to 7 times.

t19 must be longer than t18. For example, t18 may be in the range of 20-200 msec and t19 may be less than 1000 msec. The waiting time t20 should be at least 50 msec.

The sixth driving method as shown in FIGS. 18A and 18B may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel toward the color state of the pigment particles of the second type on the viewing side. Applying said first drive voltage having the same polarity as the two types of pigment particles;

(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage being a pigment particle of the first type to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying the second driving voltage having the same polarity as the above;

(iii) applying no driving voltage to the pixel during the third time period; And

Repeating steps (i) and (ii).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged.

In one embodiment as shown in FIG. 18A, the second voltage is required to drive the pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, or vice versa. Voltage.

In another embodiment as shown in FIG. 18B, the second voltage is the drive voltage required to drive the pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, or vice versa. Has an amplitude higher than that of

19A and 19B show composite waveforms combining the waveform of FIG. 18A or 18B with the waveform of FIG. 17, respectively.

In the shaking waveform, the positive / negative pulse pair is preferably repeated 50-1500 times, and each pulse is preferably applied for 10 msec.

In one embodiment, the drive sequence of FIG. 19A or 19B is DC balanced.

7th driving method:

The seventh driving method of the present invention drives a pixel toward an intermediate color state (eg, gray).

20A and 20B illustrate the particle movements involved. As shown, the pixel in the black state (see FIG. 20A) is driven toward the gray state when a low negative drive voltage V _L (eg, -5 V) is applied. In the process, a low drive voltage pushes red particles towards the pixel electrode and a mixture of black and white particles is visible at the viewer side.

The waveform used for this driving method is shown in FIG. A high positive drive voltage (V _H1 , eg +15 V) is applied after the shaking waveform for a time period of t22 to drive the pixel towards the black state. From the black state, the pixel is driven towards the gray state by applying a low negative drive voltage (V _L , e.g. -5 V) during the period of t23, i.e. from (A) to (B) of FIG. May be driven.

The drive period t22 is a time period sufficient to drive the pixel to the black state when V _H1 is applied, and t23 is a time period sufficient to drive the pixel from the black state to the gray state when V _L is applied. Prior to the shaking waveform, the pulse of V _H1 is preferably applied for a period of t21 to ensure DC balance.

22 illustrates a drive waveform that may be used to replace pulse t23 of FIG. 21. In the initial stage, a high positive drive voltage (V _H1 , eg +15 V) is applied for a short period of t24 to push black particles towards the viewer side, but t24 drives the pixel in full black state. Not enough, then applying a low negative drive voltage (V _L , eg -5 V) for the period of t25 to drive the pixel towards the gray state. The amplitude of V _L is less than 50% of V _H (eg, V _H1 or V _H2 ).

4), 바람직하게는 적어도 8 사이클들 동안 반복된다.The waveform of FIG. 22 is at least 4 cycles (N

4), preferably repeated for at least 8 cycles.

Both at ambient temperature, time period t24 is less than about 100 msec and t25 is usually greater than 100 msec.

The seventh driving method as shown in FIG. 22 may be summarized as follows:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first time period, the first drive voltage being of the second type to drive the pixel towards the color state of the pigment particles of the second type. Applying the first driving voltage having the same polarity as the pigment particles and having a first time period not sufficient to drive a pixel in a full color state of pigment particles of a second type at the viewing side;

(ii) applying a second drive voltage to the pixel for a second period of time, the second drive voltage being at the viewer side to drive the pixel towards the mixed state of the first and second types of pigment particles; Applying said second drive voltage having the same polarity as the pigment particles of the type; And

Repeating steps (i) and (ii).

As mentioned above, the second drive voltage is about 50% of the first drive voltage in this method.

FIG. 23 shows a complex waveform combining the waveform of FIG. 21 and the waveform of FIG. 22, wherein the drive period t23 of FIG. 21 is replaced with the waveform of FIG. 22. The complex waveform consists of four phases. The first phase is a DC balance phase t21; The second phase is a shaking step; The third phase is to drive the pixel in the black state (t22). The waveform used in the third phase can be any waveform that drives the pixel to a good black state. The fourth phase consists of a high positive drive voltage for a short time period t24 followed by a low negative drive voltage for a longer time period t25. The fourth phase is repeated several times, as mentioned.

Note that in FIG. 23, t22 may be optional.

By changing the low negative voltage (V _L ), it is possible to adjust the gray state more stepped or darker. In other words, the waveform sequence and shape may remain the same; The amplitude of V _L is variable (eg, -4 V, -5 V, -6 V or -7 V), causing different gray levels to be displayed. This feature can potentially reduce the required space for look-up tables in the drive circuit, resulting in lower costs. The driving method as illustrated can produce a high quality intermediate state (of the first type of pigment particles and the second type of pigment particles) with very little color interference from the third type of pigment particles. have.

In one embodiment, the drive sequence of FIG. 23 is DC balanced.

8th driving method:

24 illustrates waveforms used in the eighth drive method of the present invention. This waveform is intended to be applied to pixels that are not in the white state (ie the color state of the pigment particles of the first type).

In the initial stage, a high negative drive voltage (V _H2 , for example -15 V) is applied for a period of t26 followed by a waiting time of t27. After the waiting time, a positive driving voltage (V ', eg, less than 50% of V _H1 or V _H2 ) is applied for a period of t28, followed by a second waiting time of t29. The waveform in FIG. 24 is repeated N times. The term “wait time” refers to a time period during which no drive voltage is applied, as described above.

This driving method is particularly effective at low temperatures and can also shorten the overall driving time to the red state.

The time period t26 is considerably short in the range of about 50% of the time required to drive from the full black state to the full white state, and thus is not sufficient to drive the pixel in the full white color state. Time period t27 may be less than 100 msec; Time period t28 may range from 100-200 msec; The time period t29 may be less than 1000 msec.

The waveform of FIG. 24 is intended to be applied to a pixel in which the waveform of FIG. 11 is in a white state (ie, the color of pigment particles of the first type) while the waveform of FIG. 24 is intended to be applied to a pixel that is not in a white state. Except that, it is similar to the waveform of FIG.

FIG. 25 is an embodiment where the waveform of FIG. 24 is applied to a pixel in a black state (ie, the color state of pigment particles of the second type).

In the shaking waveform, the positive / negative pulse pair is preferably repeated 50-1500 times, and each pulse is preferably applied for 10 msec.

The eighth driving method of FIG. 24 may be summarized as follows, as of FIG. 11:

As a driving method for an electrophoretic display, the electrophoretic display comprises a first surface on the viewing side, a second surface on the non-visible side and an electrophoretic fluid, wherein the electrophoretic fluid is sandwiched between the common electrode and the layer of pixel electrodes. And pigment particles of the first type, pigment particles of the second type and pigment particles of the third type, all of the pigment particles being dispersed in a solvent or solvent mixture,

a) the three types of pigment particles have different optical properties from each other;

b) pigment particles of the first type and pigment particles of the second type have opposite charge polarities; And

c) pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower strength,

That way:

(i) applying a first drive voltage to the pixel in the electrophoretic display for a first period of time, the first drive voltage being driven to drive the pixel towards the color state of the pigment particles of the first type on the viewing side. Applying said first drive voltage having the same polarity as one type of pigment particles;

(ii) applying no driving voltage to the pixel during the second time period;

(iii) applying a second driving voltage to the pixel for a third period of time, the second driving voltage being the pigment particle of the third type to drive the pixel towards the color state of the third type of pigment particles on the viewing side. Applying the second driving voltage having the same polarity as the above;

(iv) applying no driving voltage to the pixel during the fourth time period; And

And repeating steps (i) to (iv).

In one embodiment, the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged.

In one embodiment, steps (i) to (iv) are repeated at least three times.

In one embodiment, the second drive voltage is less than 50% of the drive voltage sufficient to drive the pixel from the color state of the pigment particles of the first type to the color state of the pigment particles of the second type, or vice versa.

In one embodiment, the drive sequence of FIG. 25 is DC balanced.

Generation of intermediate colors:

The driving methods of the present invention are advantageous for making it possible to display intermediate colors (ie mixtures of colors of two particles) in addition to the colors of single particles. In many cases, displays in which the methods will be used will be required to display gray scale images that will require area adjustment of the display. This area adjustment increases the number of colors that can be displayed, but at the cost of reducing the resolution of the display since the number of pixels in the display is subjected to area adjustments to form one gray scale “super pixel”. Providing each pixel of the display with the ability to display intermediate colors, and increasing the number of intermediate colors each pixel can display, reduces the number of pixels that must be used in each super pixel, Thus increasing the resolution of the gray scale display.

One method for the generation of a medium gray color (ie a mixture of colors of black and white particles) has already been discussed above with reference to FIGS. 20A and 20B. The gray color is also ± 15 V to drive the pixel first in either the black or white state (A or FIG. 2B, respectively) and then toward the white or black state, respectively. It may be generated by applying a high drive voltage of, but terminating this drive voltage before reaching a white or black state to produce a gray state. However, in the three particle systems used in the present methods, it is advantageous to create a gray state using this method starting in the white state rather than in the black state, for reasons of FIGS. 26A (A) and (B). ) And (C) and (D) of FIG. 26B.

26A and 26B illustrate the creation of a gray state starting from a white state. (A) of FIG. 26A (the same material as that of FIG. 2B) drives white particles 21 toward the viewer side and black particles 22 and red particles 23 toward the pixel electrode. Illustrates the generation of a white state by the application of a high negative drive voltage (-15 V, V _H2 ). From the white state of Fig. 26A, a short driving pulse of high positive voltage (+ 15V, V _H1 ) drives white particles toward the pixel electrode and black and red particles toward the viewer side. The short drive pulse ends at the time when the white and black particles are mixed adjacent to the viewer side. Since red particles have a lower electrophoretic mobility than black particles, red particles move more slowly away from the pixel electrode, and are therefore caused by black and white particles lying between the red particles and the viewer's surface in the gray state. It is screened from the viewer. Accordingly, (B) of FIG. 26A presents a "clean" gray color consisting only of a mixture of colors of black and white particles and free from contamination by the colors of the red particles.

In contrast, FIGS. 26B (C) and (D) illustrate the generation of a gray state starting from a black state. (C) of FIG. 26B (the same material as that of FIG. 2A) shows black particles 22 and red particles 23 toward the viewer side, and white particles 21 adjacent to the pixel electrode. Illustrates the generation of a black state by the application of a high positive drive voltage (+15 V, V _H1 ). From the black state of Fig. 26B, a short drive pulse of negative voltage (-15 V, V _H2 ) drives white particles toward the viewer side and black and red particles toward the pixel electrode. The short drive pulse ends at the time when the white and black particles are mixed adjacent to the viewer side. However, since the red particles have a lower electrophoretic mobility than the black particles, the red particles move more slowly away from the viewer side and thus mix with the black and white particles in the gray state; In practice, red particles may tend to lie closer to the viewer side than black particles. Accordingly, (D) of FIG. 26B shows a "dirty" gray color in which the mixture of colors of black and white particles is significantly contaminated by the color of red particles.

As already mentioned, the gray color state of the pixel may be generated starting from either the black color state or the white color state. Similarly, a bright red color state (mixture of colors of white and red particles) may be generated starting with either a red color state or a white color state. In the former case, a high negative drive voltage (for a short period of time, which is insufficient to first drive to a full red color state (see FIG. 2C) and then reach the white color state of FIG. -15 V, V _H2 ) is applied. The high negative driving voltage causes the white particles 21 to move quickly toward the viewer side, the black particles 22 to move quickly toward the pixel electrode, and the red particles 23 toward the pixel electrode. Make it move slower. The driving voltage is terminated while the white and red particles are mixed, so that a bright red color is visible at the viewer side. Black particles are placed close to the pixel electrode and are therefore hidden from the viewer by white and red particles. In the latter case, first drive in a full white state (see FIG. 2 (B)) and then a low positive drive voltage (+5 V, V _L for an insufficient period of time to reach the red state of FIG. 2C). ) Is applied. The low negative drive voltage causes the white particles 21 to move toward the pixel electrode and the red particles to the viewer side, thus again producing a mixture of red and white particles and a display of bright red color. Instead of using a continuous low negative drive voltage, a transition from the white state to the bright red state may be achieved using a push-pull waveform as illustrated in FIG. 5, 6, 8, or 9. .

It has been found empirically that the bright red state resulting from the red state is much less uniform than that produced from the white state. Although the reasons for this uniformity difference are not fully understood, changes in the positions of the various particles in the microcapsules (if present) and in the electrophoretic mobility of the individual particles and the various parts of the electrophoretic display It is believed to be related to the changes in. Also, the low drive voltage used in the drive from the red color state appears to be more affected by changes in power supplies than the higher drive voltage.

27 illustrates the waveform used to drive the display from the white state to the bright red state. In the waveform of FIG. 27, a high negative drive voltage (V _H2 , eg -15 V) is applied during the period of t31 to drive the pixel towards the white state. From the white state, the pixel is driven towards the red state by applying a low positive voltage (V _L , for example +5 V) during the period of t32, and thus from the state of FIG. Drive the pixel in the state of C). Finally, the pixel is driven from the red state to the bright red state by applying a high negative drive voltage (V _H2 , eg -15 V) for a period t33 shorter than the period t31 and insufficient to drive the pixel in a full white state. do. The shaking waveform is preferably applied before the pulse going white at period t31, and a negative drive voltage (e.g. V _H2 , e.g. -15 V) is preferably shaken to ensure DC balance. It is applied for a period of t30 before the king waveform. Although the waveform of FIG. 27 is essentially the waveform of FIG. 3, it will be appreciated that a pulse that turns white at period t33 is added. The exact shade of bright red achieved can be varied by adjusting the duration of the period t33, which will typically be in the range of about 20-300 msec, usually 20-100 msec. The duration of period t33 will typically be about 10 to about 60% of the duration of period t31.

Achieving a dark red color state (i.e., a mixture of colors of black and red particles) is bright because black and red particles have charges of the same polarity and therefore tend to respond to applied electric fields in similar ways. It is much more difficult than achieving a red color state. For example, first, the pixel is driven to the red state of FIG. 2C, and then a high positive driving voltage (+15 V, V _H1 ) used to drive the pixel to the black state of FIG. 2A is obtained. If an attempt is made to produce a mixture of red and black particles by application, red particles already adjacent to the front electrode as shown in FIG. 2C will still be adjacent to this front electrode and are placed sideways to accommodate the reaching black particles. Will not go to. The result is that even after a high positive driving voltage is applied for a long period, which is much longer than the period required to drive the pixel from the white state of FIG. 2B to the black state of FIG. The "dark red" state of is actually just slightly darker than the previous red state.

It has been found that two methods exist to achieve a satisfactory dark red state. The first method uses a waveform as illustrated in FIG. 28 and starts in the essentially dark gray color state. As shown in the figure, this waveform first applies a high positive drive voltage (+15 V, V _H1 ) to drive the pixel to a dark gray state (not full black state). This high positive drive voltage is followed by a low positive drive voltage (V _L , eg, +5 V) for a period of time t36, which is usually considerably longer than t35 to drive the pixel in a dark red state. For the reasons described, the high positive drive pulse at period t35 may optionally be preceded by a shaking waveform and / or a high negative drive voltage pulse (V _H2 , eg -15 V) during period t34. have. The duration of t36 may vary widely but may typically be about 300-2000 msec, more generally 500-1000 msec; The darkness of the resulting dark red color can be varied by varying the duration of t36, where longer durations tend to increase the redness of the generated color.

The second method of achieving a satisfactory dark red state uses a waveform as illustrated in FIG. 29 where the material is the same as in FIG. 5, but for the reasons discussed below, the durations of the various drive pulses shown in FIG. Will vary from those in FIG. 5. From the discussion of FIG. 5 above, the main portion of the relevant waveform is the pulses directed to the red of the low positive drive voltage (V _L , eg, +5 V), denoted as duration t39 in FIG. 29, the duration in FIG. 29. It will be recalled to include alternately with the pulses turning white at the high negative drive voltage V _H2 , eg -15 V, denoted as t40. This sequence of alternating pulses includes: (a) a pulse directed to white of a high negative drive voltage (V _H2 , eg, -15 V) of a duration t37 intended for DC balance; (b) shaking waveforms; And (c) the high negative drive voltage (V _H2 , eg -15V) of duration t38, which may or may not be different from the duration t40 of the pulses towards the later white already mentioned. Any one or more of the pulses that are directed to white may be preceded.

The waveform of FIG. 5 has been described above as generating a pure red color state. However, by adjusting the durations t39 and t40 of FIG. 29, and / or by adjusting the driving voltages V ′ and V _H2 applied during these periods, this type of waveform is not only pure red color state but also dark red and It has been found empirically that bright red color states can also be created. As the size of V 'increases, the red color darkens, while as the size of V' decreases, the red color brightens. Similarly, if the duration of t40 is increased compared to t39, a brighter red color will be produced, while if the duration of t39 is increased compared to t40, a darker red color will be produced. Clearly, combinations of changes in both drive voltage and duration may be used. the durations of t39 and t40 can vary over a wide range; For example, at 25 ° C., t40 may vary from 60 to 20 msec, while t39 may vary from 300 to 600 msec. Even wider ranges may be desirable at low temperatures such as 0 ° C .; For example, at this temperature t40 may be 60 msec and t39 may be 3000 msec.

Example 2

The electrophoretic medium as substantially described above with reference to FIG. 1 is characterized in that 30% by weight of polymer-coated titania particles (white), 8% by weight of polymer-coated mixed metal oxide particles (in isoparaffin solvent) Black) and 7% by weight of red pigment particles and prepared by adding a charge control agent (Solsperse 19000). White particles had negative charges, while both black and red particles had positive charges, while red particles had a lower charge density than black particles. The resulting electrophoretic medium was loaded into a standard test cell provided with an essentially transparent front electrode and with reference to FIGS. 2A, 2B, 2C and 26A, respectively. It was driven to its white, black, red and gray states as described above. L *, a * and b * values for all four color development states were measured using standard techniques, and the results were as follows:

The reflectance Y in the gray state was 10.3%. From these results, it will be appreciated that the experimental medium of the present invention was able to display good white, black and red states and also to display gray states.

Although the invention has been described with reference to specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a situation, materials, compositions, processes, process step, or steps to particular aspects and scope of the invention. All such modifications are intended to be within the scope of the claims appended hereto.

Claims (31)

As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on a viewing side, a second surface on a non-viewing side and an electrophoretic fluid, the electrophoretic fluid comprising pigment particles of a first type. , Pigment particles of a second type and pigment particles of a third type, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method,
(i) applying a first drive voltage to the pixel in the electrophoretic display during a first time period, the first drive voltage having a polarity for driving the pigment particles of the first type towards the first surface. Applying the first driving voltage, thereby causing the pixel to display the optical properties of the pigment particles of the first type at the first surface;
(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage having a polarity to drive the pigment particles of the third type towards the first surface, whereby the second Applying the second driving voltage to drive the pixel towards the optical properties of the third type of pigment particles at one surface; And
A method for driving an electrophoretic display, comprising repeating steps (i) and (ii). The method of claim 1,
Wherein the pigment particles of the first type are negatively charged and the pigment particles of the second type are positively charged. The method of claim 1,
Wherein the amplitude of the second drive voltage is less than 50% of the amplitude of the first drive voltage. The method of claim 1,
The steps (i) and (ii) are repeated at least four times. The method of claim 1,
A method of driving a electrophoretic display, further comprising applying a shaking waveform prior to step (i). The method of claim 5,
Driving the pixel with the full optical properties of the pigment particles of the first type after the shaking waveform but before step (i). The method of claim 1,
(iii) applying no driving voltage to the pixel for a third time period after step (ii) but before the step of repeating steps (i) and (ii); And
Further comprising repeating steps (i), (ii) and (iii). The method of claim 7, wherein
The steps (i), (ii) and (iii) are repeated at least four times. The method of claim 7, wherein
A method of driving a electrophoretic display, further comprising applying a shaking waveform prior to step (i). The method of claim 9,
Driving the pixel with the full optical properties of the pigment particles of the first type after the shaking waveform but before step (i). The method of claim 1,
The first time period is from 40 to 140 msec, the second time period is at least 460 msec and steps (i) and (ii) are repeated at least seven times. The method of claim 1,
(iii) applying no drive voltage to the pixel for a third time period after step (i) but before step (ii);
(iv) applying no driving voltage to the pixel for a fourth time period after step (ii) but before repeating the steps; And
Further comprising repeating steps (i) to (iv). The method of claim 12,
The steps (i) to (iv) are repeated at least three times. The method of claim 12,
A method of driving a electrophoretic display, further comprising applying a shaking waveform prior to step (i). The method of claim 12,
Driving the pixel with the full optical properties of the pigment particles of the first type after the shaking waveform but before step (i). As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, the electrophoretic fluid comprising a first type of pigment particles, a second type of pigment particles and a first electrophoretic fluid. Three types of pigment particles, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method,
(i) applying a first drive voltage to the pixel in the electrophoretic display during a first time period, the first drive voltage having a polarity for driving the pigment particles of the first type towards the first surface. Applying the first driving voltage, thereby causing the pixel to display the optical properties of the pigment particles of the first type at the first surface;
(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage having a polarity to drive the pigment particles of the third type towards the first surface, whereby the second Applying the second driving voltage to drive the pixel towards the optical properties of the third type of pigment particles at one surface; And
(iii) applying a third driving voltage during a third time period, wherein the third driving voltage has the same polarity as the first driving voltage, the third time period is shorter than the first time period, Thereby applying the third drive voltage to produce a mixture of the optical properties of the first type of pigment particles and the third type of pigment particles at a viewing surface. The method of claim 16,
And the duration of the third time period is about 20 to about 80% of the duration of the first time period. The method of claim 17,
And the duration of the third time period is about 20 to about 40% of the duration of the first time period. The method of claim 16,
A method of driving a electrophoretic display, further comprising applying a shaking waveform prior to step (i). The method of claim 19,
Prior to the shaking waveform, further comprising applying a driving voltage for driving the pigment particles of the first type towards the first surface. As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, the electrophoretic fluid comprising a first type of pigment particles, a second type of pigment particles and a first electrophoretic fluid. Three types of pigment particles, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method,
(i) applying a first drive voltage to the pixel in the electrophoretic display during a first period of time, the first drive voltage having a polarity driving the pigment particles of the second type towards the first surface. Applying the first driving voltage, thereby causing the pixel to display the optical properties of the pigment particles of the second type at the first surface; And
(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage having the same polarity as the first driving voltage but having a magnitude lower than the first driving voltage, thereby The second driving voltage driving the pigment particles of the third type at a first surface and producing a mixture of optical properties of the pigment particles of the second type and the pigment particles of the third type at the first surface. A method of driving a electrophoretic display, comprising the step of applying a. The method of claim 21,
And the duration of the second time period is about 100 to about 150% of the duration of the first time period. The method of claim 21,
A method of driving a electrophoretic display, further comprising applying a shaking waveform prior to step (i). The method of claim 23,
Prior to the shaking waveform, further comprising applying a driving voltage for driving the pigment particles of the first type towards the first surface. As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, wherein the electrophoretic fluid comprises a first type of pigment particles, a second type of pigment particles and a Three types of pigment particles, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method,
(i) applying a first drive voltage to the pixel in the electrophoretic fluid for a first time period, the first drive voltage having a polarity driving the pigment particles of the first type towards the first surface; Applying the first driving voltage, thereby causing the pixel to display the optical properties of the pigment particles of the first type at the first surface;
(ii) applying a second drive voltage to the pixel for a second period of time, the second drive voltage having a polarity driving the pigment particles of the third type towards the first surface; Applying a driving voltage; And
Repeating steps (i) and (ii),
The durations of steps (i) and (ii) and the magnitudes of the voltages applied in the steps are equal to one of the pigment particles of the first type and the pigment particles of the second type at the first surface. A drive method for an electrophoretic display, adapted to produce a mixture of pigment particles and optical properties of the pigment particles of the third type. The method of claim 25,
A method of driving a electrophoretic display, further comprising applying a shaking waveform prior to step (i). The method of claim 26,
Prior to the shaking waveform, further comprising applying a driving voltage for driving the pigment particles of the first type towards the first surface. As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, the electrophoretic fluid comprising a first type of pigment particles, a second type of pigment particles and a first electrophoretic fluid. Three types of pigment particles, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method has a voltage insensitive range of at least about 0.7 V, wherein the “voltage insensitive range” is a pigment particle of the first type while maintaining a * of at least about 90% of the maximum a * value achievable. A variation in the driving voltage that is acceptable in driving a pixel from the optical properties of the third type of pigment particles to the optical properties of the third type of pigment particles. As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, the electrophoretic fluid comprising a first type of pigment particles, a second type of pigment particles and a first electrophoretic fluid. Three types of pigment particles, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method,
(i) applying a first drive voltage to the pixel in the electrophoretic display during a first time period, the first drive voltage having a polarity for driving the pigment particles of the first type towards the first surface. Applying the first driving voltage, thereby causing the pixel to display the optical properties of the pigment particles of the first type at the first surface;
(ii) applying a second driving voltage to the pixel for a second period of time, the second driving voltage having a polarity to drive the pigment particles of the second type towards the first surface, whereby the second Applying the second driving voltage to drive the pixel towards the optical properties of the pigment particles of the second type at one surface; And
A method for driving an electrophoretic display, comprising repeating steps (i) and (ii). The method of claim 29,
(iv) applying no driving voltage to the pixel for a third period of time after step (ii) but before repeating steps (i) and (ii); And
Further comprising repeating steps (i), (ii) and (iii). As a driving method for an electrophoretic display,
The electrophoretic display comprises a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid, the electrophoretic fluid comprising a first type of pigment particles, a second type of pigment particles and a first electrophoretic fluid. Three types of pigment particles, all of which are dispersed in a liquid,
a) the three types of pigment particles have different optical properties from each other;
b) the pigment particles of the first type and the pigment particles of the second type have opposite charge polarities; And
c) the pigment particles of the third type have the same charge polarity as the pigment particles of the second type but have a lower zeta potential,
The method,
(i) applying a first drive voltage to the pixel in the electrophoretic display during a first period of time, the first drive voltage having a polarity driving the pigment particles of the second type towards the first surface. Wherein the first time period is not sufficient to drive the pixel with the full optical properties of the pigment particles of the second type at the first surface;
(ii) applying a second driving voltage to the pixel for a second time period, wherein the second driving voltage is mixed at the viewing side of the pigment particles of the first type and the pigment particles of the second type. Applying the second drive voltage having a polarity to drive the pigment particles of the first type to drive the pixel towards a state; And
A method for driving an electrophoretic display, comprising repeating steps (i) and (ii).

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