Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/3433—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices
  • G09G3/344—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices based on particles moving in a fluid or in a gas, e.g. electrophoretic devices
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/166—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
  • G02F1/167—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/2003—Display of colours
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on translational movement of particles in a fluid under the influence of an applied field
  • G02F1/1675—Constructional details
  • G02F2001/1678—Constructional details characterised by the composition or particle type
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F2203/00—Function characteristic
  • G02F2203/34—Colour display without the use of colour mosaic filters
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2300/00—Aspects of the constitution of display devices
  • G09G2300/04—Structural and physical details of display devices
  • G09G2300/0439—Pixel structures
  • G09G2300/0452—Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2300/00—Aspects of the constitution of display devices
  • G09G2300/04—Structural and physical details of display devices
  • G09G2300/0469—Details of the physics of pixel operation
  • G09G2300/0473—Use of light emitting or modulating elements having two or more stable states when no power is applied
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/06—Details of flat display driving waveforms
  • G09G2310/067—Special waveforms for scanning, where no circuit details of the gate driver are given
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/06—Details of flat display driving waveforms
  • G09G2310/068—Application of pulses of alternating polarity prior to the drive pulse in electrophoretic displays

Definitions

• the present invention is directed to driving methods for a color display device in which each pixel can display four high-quality color states.
• color filters are often used.
• the most common approach is to add color filters on top of black/white sub-pixels of a pixelated display to display the red, green and blue colors.
• red color is desired
• blue color is desired
• red and blue sub-pixels are turned to the black state so that the only color displayed is blue.
• red and blue sub-pixels are turned to the black state so that the only color displayed is green.
• black state is desired, all three-sub-pixels are turned to the black state.
• the white state is desired, the three sub- pixels are turned to red, green and blue, respectively, and as a result, a white state is seen by the viewer.
• each of the sub-pixels has a reflectance of about one third of the desired white state, the white state is fairly dim.
• a fourth sub-pixel may be added which can display only the black and white states, so that the white level is doubled at the expense of the red, green or blue color level (where each sub-pixel is only one fourth of the area of the pixel).
• the white level is normally substantially less than half of that of a black and white display, rendering it an unacceptable choice for display devices, such as e-readers or displays that need well readable black-white brightness and contrast.
• a first aspect of the present invention is directed to a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non- viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• a second aspect of the present invention is directed to a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non- viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps: (i) applying a first driving voltage to a pixel in the electrophoretic display for a first period of time to drive the pixel towards the color state of the first or second type of particles at the viewing side;
• a third aspect of the present invention is directed to a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non- viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• a fourth aspect of the present invention is directed to a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non- viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• the second driving voltage has polarity opposite that of the first driving voltage and the second driving voltage has an amplitude lower than that of the first driving voltage, to drive the pixel from the color state of the first type of particles towards the color state of the fourth type of particles or from the color state of the second type of particles towards the color state of the third type of particles, at the viewing side;
• the fourth aspect of the present invention may further comprise the following steps:
• Figure 1 depicts a display layer capable of displaying four different color states.
• FIGS 2-1 to 2-3 illustrate an example of the present invention.
• Figure 3 shows a shaking waveform which may be incorporated into the driving methods.
• FIGS 4 and 5 illustrate the first driving method of the present invention.
• FIGS 6 and 9 illustrate the second driving method of the present invention.
• Figures 7, 8, 10 and 11 show driving sequences utilizing the second driving method of the present invention.
• FIGS 12 and 15 illustrate the third driving method of the present invention.
• Figures 13, 14, 16 and 17 show driving sequences utilizing the third driving method of the present invention.
• FIGS 18 and 21 illustrate the fourth driving method of the present invention.
• Figures 19, 20, 22 and 23 show driving sequences utilizing the fourth driving method of the present invention.
• FIGS 24 and 27 illustrate the fifth driving method of the present invention.
• Figures 25, 26, 28 and 29 show driving sequences utilizing the fifth driving method of the present invention.
• Figure 30 illustrates a driving method of the present invention.
• Figure 31 illustrates an alternative driving method of the present invention. Detailed Description of the Invention
• the electrophoretic fluid related to the present invention comprises two pairs of oppositely charged particles.
• the first pair consists of a first type of positive particles and a first type of negative particles and the second pair consists of a second type of positive particles and a second type of negative particles.
• the four types of particles may also be referred to as high positive particles, high negative particles, low positive particles and low negative particles.
• the black particles (K) and yellow particles (Y) are the first pair of oppositely charged particles, and in this pair, the black particles are the high positive particles and the yellow particles are the high negative particles.
• the red particles (R) and the white particles (W) are the second pair of oppositely charged particles, and in this pair, the red particles are the low positive particles and the white particles are the low negative particles.
• the black particles may be the high positive particles; the yellow particles may be the low positive particles; the white particles may be the low negative particles and the red particles may be the high negative particles.
• the color states of the four types of particles may be intentionally mixed.
• yellow particles and red particles may be used where both types of particles carry the same charge polarity and the yellow particles are higher charged than the red particles.
• the yellow state there will be a small amount of the red particles mixed with the greenish yellow particles to cause the yellow state to have better color purity.
• the white particles may be formed from an inorganic pigment, such as Ti0 2 , Zr0 2 , ZnO, A1 2 0 3 , Sb 2 0 3 , BaS0 4 , PbS0 4 or the like.
• the black particles may be formed from CI pigment black 26 or 28 or the like (e.g., manganese ferrite black spinel or copper chromite black spinel) or carbon black.
• Particles of non-white and non-black colors are independently of a color, such as, red, green, blue, magenta, cyan or yellow.
• the pigments for color particles may include, but are not limited to, CI pigment PR 254, PR122, PR149, PG36, PG58, PG7, PB28, PB15:3, PY83, PY138, PY150, PY155 or PY20.
• CI pigment PR 254, PR122, PR149, PG36, PG58, PG7, PB28, PB15:3, PY83, PY138, PY150, PY155 or PY20 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).
• 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,
• Novoperm Yellow HR-70-EDS Hostaperm Green GNX, BASF Irgazine red L 3630, Cinquasia Red L 4100 HD, and Irgazin Red L 3660 HD; Sun Chemical phthalocyanine blue, phthalocyanine green, diarylide yellow or diarylide AAOT yellow.
• the color particles may also be inorganic pigments, such as red, green, blue and yellow. Examples may include, but are not limited to, CI pigment blue 28, CI pigment green 50 and CI pigment yellow 227.
• the four types of particles may have other distinct optical characteristics, such as optical transmission, reflectance, luminescence or, in the case of displays intended for machine reading, pseudo-color in the sense of a change in reflectance of electromagnetic wavelengths outside the visible range.
• a display layer utilizing the display fluid of the present invention has two surfaces, a first surface (13) on the viewing side and a second surface (14) on the opposite side of the first surface (13).
• the display fluid is sandwiched between the two surfaces.
• a common electrode (11) which is a transparent electrode layer (e.g., ITO), spreading over the entire top of the display layer.
• an electrode layer (12) which comprises a plurality of pixel electrodes (12a).
• the pixel electrodes are described in US Patent No. 7,046,228, the content of which is incorporated herein by reference in its entirety. It is noted that while 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.
• TFT thin film transistor
• Each space between two dotted vertical lines in Figure 1 denotes a pixel. As shown, each pixel has a corresponding pixel electrode. An electric field is created for a pixel by the potential difference between a voltage applied to the common electrode and a voltage applied to the corresponding pixel electrode.
• the solvent in which the four types of particles are dispersed is 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.
• suitable dielectric solvent include hydrocarbons such as Isopar®, decahydronaphthalene (DECALIN), 5- ethylidene-2-norbornene, fatty oils, paraffin oil, silicon fluids, aromatic hydrocarbons such as toluene, xylene, phenylxylylethane, dodecylbenzene or alkylnaphthalene, halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5 -trichlorobenzotri fluoride, chloropentafluoro-benzene, dichlorononane or
• pentachlorobenzene, and perfluorinated solvents such as FC-43, FC-70 or FC-5060 from 3M Company, St. Paul MN, low molecular weight halogen containing polymers such as poly(perfluoropropylene oxide) from TCI America, Portland, Oregon, poly(chlorotrifluoro- ethylene) such as Halocarbon Oils from Halocarbon Product Corp., River Edge, NJ, perfluoropolyalkylether such as Galden from Ausimont or Krytox Oils and Greases K-Fluid Series from DuPont, Delaware, polydimethylsiloxane based silicone oil from Dow-corning (DC -200).
• FC-43, FC-70 or FC-5060 from 3M Company, St. Paul MN
• low molecular weight halogen containing polymers such as poly(perfluoropropylene oxide) from TCI America, Portland, Oregon, poly(chlorotrifluoro- ethylene) such as Halocarbon Oils from
• the charge carried by the "low charge” particles may be less than about 50%, preferably about 5% to about 30%, of the charge carried by the "high charge” particles. In another embodiment, the “low charge” particles may be less than about 75%, or about 15% to about 55%, of the charge carried by the "high charge” particles. In a further embodiment, the comparison of the charge levels as indicated applies to two types of particles having the same charge polarity.
• the charge intensity may be measured in terms of zeta potential.
• the zeta potential is determined by Colloidal Dynamics AcoustoSizer IIM with a CSPU-100 signal processing unit, ESA EN# Attn flow through cell (K:127).
• the instrument constants such as density of the solvent used in the sample, dielectric constant of the solvent, speed of sound in the solvent, viscosity of the solvent, all of which at the testing temperature (25°C) are entered before testing.
• Pigment samples are dispersed in the solvent (which is usually a hydrocarbon fluid having less than 12 carbon atoms), and diluted to be 5-10% by weight.
• the sample also contains a charge control agent (Solsperse 17000®, available from Lubrizol Corporation, a Berkshire Hathaway company; "Solsperse” is a Registered Trade Mark), with a weight ratio of 1 : 10 of the charge control agent to the particles.
• Solsperse 17000® available from Lubrizol Corporation, a Berkshire Hathaway company; "Solsperse” is a Registered Trade Mark
• the mass of the diluted sample is determined and the sample is then loaded into the flow-through cell for
• the amplitudes of the "high positive” particles and the "high negative” particles may be the same or different.
• the amplitudes of the "low positive” particles and the “low negative” particles may be the same or different.
• the two pairs of high- low charge particles may have different levels of charge differentials.
• the low positive charged particles may have a charge intensity which is 30% of the charge intensity of the high positive charged particles and in another pair, the low negative charged particles may have a charge intensity which is 50% of the charge intensity of the high negative charged particles.
• the following is an example illustrating a display device utilizing such a display fluid.
• the high positive particles are of a black color (K); the high negative particles are of a yellow color (Y); the low positive particles are of a red color (R); and the low negative particles are of a white color (W).
• the electric field generated by the low driving voltage is sufficient to separate the weaker charged white and red particles to cause the low positive red particles (R) to move all the way to the common electrode (21) side (i.e., the viewing side) and the low negative white particles (W) to move to the pixel electrode (22a) side.
• a red color is seen.
• weaker charged particles e.g., R
• stronger charged particles of opposite polarity e.g., Y
• these attraction forces are not as strong as the attraction force between two types of stronger charged particles (K and Y) and therefore they can be overcome by the electric field generated by the low driving voltage. In other words, weaker charged particles and the stronger charged particles of opposite polarity can be separated.
• the black particles (K) is demonstrated to carry a high positive charge
• the yellow particles (Y) to carry a high negative charge
• the red (R) particles to carry a low positive charge
• the white particles (W) to carry a low negative charge
• the particles carry a high positive charge, or a high negative charge, or a low positive charge or a low negative charge may be of any colors. All of these variations are intended to be within the scope of this application.
• the lower voltage potential difference applied to reach the color states in Figures 2(c) and 2(d) may be about 5% to about 50% of the full driving voltage potential difference required to drive the pixel from the color state of high positive particles to the color state of the high negative particles, or vice versa.
• the electrophoretic fluid as described above is filled in display cells.
• the display cells may be cup-like microcells as described in US Patent No. 6,930,818, the content of which is incorporated herein by reference in its entirety.
• the display cells may also be other types of micro-containers, such as microcapsules, microchannels or equivalents, regardless of their shapes or sizes. All of these are within the scope of the present application.
• a shaking waveform prior to driving from one color state to another color state, may be used.
• the shaking waveform consists of repeating a pair of opposite driving pulses for many cycles.
• the shaking waveform may consist of a +15 V pulse for 20 msec and a -15 V pulse for 20 msec and such a pair of pulses is repeated for 50 times.
• the total time of such a shaking waveform would be 2000 msec (see Figure 3).
• the shaking waveform may be applied regardless of the optical state (black, white, red or yellow) before a driving voltage is applied. After the shaking waveform is applied, the optical state would not be a pure white, pure black, pure yellow or pure red. Instead, the color state would be from a mixture of the four types of pigment particles.
• Each of the driving pulse in the shaking waveform is applied for not exceeding 50% (or not exceeding 30%, 10% or 5%) of the driving time required from the full black state to the full yellow state, or vice versa, in the example.
• the shaking waveform may consist of positive and negative pulses, each applied for not more thanl50 msec. In practice, it is preferred that the pulses are shorter.
• the shaking waveform as described may be used in the driving methods of the present invention.
• the shaking waveform is abbreviated (i.e., the number of pulses is fewer than the actual number).
• a high driving voltage (Vm or VH2) is defined as a driving voltage which is sufficient to drive a pixel from the color state of high positive particles to the color state of high negative particles, or vice versa (see Figures 2a and 2b).
• a low driving voltage (V or VL2) is defined as a driving voltage which may be sufficient to drive a pixel to the color state of weaker charged particles from the color state of higher charged particles (see Figures 2c and 2d).
• the amplitude of VL (e.g., Vu or VL2) is less than 50%, or preferably less than 40%, of the amplitude of Vii (e.g., Vm or Vm).
• FIG 4 illustrates a driving method to drive a pixel from a yellow color state (high negative) to a red color state (low positive).
• a high negative driving voltage VH2, e.g., -15V
• VLI low positive voltage
• the driving period t2 is a time period sufficient to drive a pixel to the yellow state when VH2 is applied and the driving period t3 is a time period sufficient to drive the pixel to the red state from the yellow state when VLI is applied.
• a driving voltage is preferably applied for a period of tl before the shaking waveform to ensure DC balance.
• the term "DC balance", throughout this application, is intended to mean that the driving voltages applied to a pixel is substantially zero when integrated over a period of time (e.g., the period of an entire waveform).
• Figure 5 illustrates a driving method to drive a pixel from a black color state (high positive) to a white color state (low negative).
• a high positive driving voltage VHI, e.g., +15V
• VL2 low negative voltage
• t6 a period of t6
• the driving period t5 is a time period sufficient to drive a pixel to the black state when VHI is applied and the driving period t6 is a time period sufficient to drive the pixel to the white state from the black state when VL2 is applied.
• a driving voltage is preferably applied for a period of t4 before the shaking waveform to ensure DC balance.
• the entire waveform of Figure 4 is DC balanced. In another embodiment, the entire waveform of Figure 5 is DC balanced.
• the first driving method may be summarized as follows:
• a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• the second driving method of the present invention is illustrated in Figure 6. It relates to a driving waveform which is used to replace the driving period of t3 in Figure 4.
• the high negative driving voltage (VH2, e.g., -15V) is applied for a period of t7 to push the yellow particles towards the viewing side, which is followed by a positive driving voltage (+V) for a period of t8, which pulls the yellow particles down and pushes the red particles towards the viewing side.
• the amplitude of +V is lower than that of VH (e.g., VHI or V ). In one
• the amplitude of the +V is less than 50% of the amplitude of VH (e.g., VHI or V H2 ).
• t8 is greater than t7.
• t7 may be in the range of 20-400 msec and t8 may be > 200 msec.
• the waveform of Figure 6 is repeated for at least 2 cycles (N> 2), preferably at least 4 cycles and more preferably at least 8 cycles.
• N> 2 cycles preferably at least 4 cycles and more preferably at least 8 cycles.
• the red color becomes more intense after each driving cycle.
• the driving waveform as shown in Figure 6 may be used to replace the driving period of t3 in Figure 4 (see Figure 7).
• the driving sequence may be: shaking waveform, followed by driving towards the yellow state for a period of t2 and then applying the waveform of Figure 6.
• the step of driving to the yellow state for a period of t2 may be eliminated and in this case, a shaking waveform is applied before applying the waveform of Figure 6 (see Figure 8).
• the entire waveform of Figure 7 is DC balanced. In another embodiment, the entire waveform of Figure 8 is DC balanced.
• Figure 9 illustrates a driving waveform which is used to replace the driving period of t6 in Figure 5.
• a high positive driving voltage (VHI, e.g., +15V) is applied, for a period of t9 to push the black particles towards the viewing side, which is followed by applying a negative driving voltage (-V) for a period of tlO, which pulls the black particles down and pushes the white particles towards the viewing side.
• VHI high positive driving voltage
• -V negative driving voltage
• the amplitude of the -V is lower than that of VH (e.g., VHI or V ). In one embodiment, the amplitude of -V is less than 50% of the amplitude of VH (e.g., VHI or V H2 ). In one embodiment, tlO is greater than t9. In one embodiment, t9 may be in the range of 20-400 msec and tlO may be > 200 msec.
• the waveform of Figure 9 is repeated for at least 2 cycles (N> 2), preferably at least 4 cycles and more preferably at least 8 cycles.
• the white color becomes more intense after each driving cycle.
• the driving waveform as shown in Figure 9 may be used to replace the driving period of t6 in Figure 5 (see Figure 10).
• the driving sequence may be: shaking waveform, followed by driving towards the black state for a period of t5 and then applying the waveform of Figure 9.
• the step of driving to the black state for a period of t5 may be eliminated and in this case, a shaking waveform is applied before applying the waveform of Figure 9 (see Figure 11).
• the entire waveform of Figure 10 is DC balanced. In another embodiment, the entire waveform Figure 11 is DC balanced.
• This second driving method of the present invention may be summarized as follows:
• a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• the amplitude of the second driving voltage is less than 50% of the amplitude of the first driving voltage.
• steps (i) and (ii) are repeated at least 2 times, preferably at least 4 times and more preferably at least 8 times.
• the method further comprises a shaking waveform before step (i).
• the method further comprises driving the pixel to the color state of the first or second type of particles after the shaking waveform but prior to step (i).
• the second driving method of the present invention is illustrated in Figure 12. It relates to an alternative to the driving waveform of Figure 6, which may also be used to replace the driving period of t3 in Figure 4.
• the waveform of Figure 12 there is a wait time tl3 added. During the wait time, no driving voltage is applied.
• the entire waveform of Figure 12 is also repeated at least 2 times (N >2), preferably at least 4 times and more preferably at least 8 times.
• the waveform of Figure 12 is designed to release the charge imbalance stored in the dielectric layers and/or at the interfaces between layers of different materials, in an electrophoretic display device, especially when the resistance of the dielectric layers is high, for example, at a low temperature.
• low temperature refers to a temperature below about 10°C.
• the wait time presumably can dissipate the unwanted charge stored in the dielectric layers and cause the short pulse (tl 1) for driving a pixel towards the yellow state and the longer pulse (tl2) for driving the pixel towards the red state to be more efficient.
• this alternative driving method will bring a better separation of the low charged pigment particles from the higher charged ones.
• the time periods, tl 1 and tl2, are similar to t7 and t8 in Figure 6, respectively. In other words, tl2 is greater than tl 1.
• the wait time (tl3) can be in a range of 5-5,000 msec, depending on the resistance of the dielectric layers.
• the driving waveform as shown in Figure 12 may also be used to replace the driving period of t3 in Figure 4 (see Figure 13).
• the driving sequence may be: shaking waveform, followed by driving towards the yellow state for a period of t2 and then applying the waveform of Figure 12.
• the step of driving to the yellow state for a period of t2 may be eliminated and in this case, a shaking waveform is applied before applying the waveform of Figure 12 (see Figure 14).
• the entire waveform of Figure 13 is DC balanced. In another embodiment, the entire waveform of Figure 14 is DC balanced.
• Figure 15 illustrates an alternative to the driving waveform of Figure 9, which may also be used to replace the driving period of t6 in Figure 5.
• this alternative waveform there is a wait time tl6 added. During the wait time, no driving voltage is applied.
• the entire waveform of Figure 15 is also repeated at least 2 times (N >2), preferably at least 4 times and more preferably at least 8 times.
• the waveform of Figure 15 is also designed to release the charge imbalance stored in the dielectric layers and/or at the interfaces of layers of different materials, in an electrophoretic display device.
• the wait time presumably can dissipate the unwanted charge stored in the dielectric layers and cause the short pulse (tl4) for driving a pixel towards the black state and the longer pulse (tl5) for driving the pixel towards the white state to be more efficient.
• the time periods, tl4 and tl5, are similar to t9 and tlO in Figure 9, respectively.
• tl5 is greater than tl4.
• the wait time (tl6) may also be in a range of 5-5,000 msec, depending on the resistance of the dielectric layers.
• the driving waveform as shown in Figure 15 may also be used to replace the driving period of t6 in Figure 5 (see Figure 16).
• the driving sequence may be: shaking waveform, followed by driving towards the black state for a period of t5 and then applying the waveform of Figure 15.
• the step of driving to the black state for a period of t5 may be eliminated and in this case, a shaking waveform is applied before applying the
• the entire waveform of Figure 16 is DC balanced. In another embodiment, the entire waveform of Figure 17 is DC balanced.
• the third driving method of the present invention therefore may be summarized as follows:
• a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• the amplitude of the second driving voltage is less than 50% of the amplitude of the first driving voltage.
• steps (i), (ii) and (iii) are repeated at least 2 times, preferably at least 4 times and more preferably at least 8 times.
• the method further comprises a shaking waveform before step (i).
• the method further comprises a driving step to the full color state of the first or second type of particles after the shaking waveform but prior to step (i).
• any of the driving periods referred to in this application may be temperature dependent.
• the fourth driving method of the present invention is illustrated in Figure 18. It relates to a driving waveform which may also be used to replace the driving period of t3 in Figure 4.
• a high negative driving voltage (VH2, e.g., -15V) is applied to a pixel for a period of tl7, which is followed by a wait time of tl8.
• a positive driving voltage (+V, e.g., less than 50% of Vm or V ) is applied to the pixel for a period of tl9, which is followed by a second wait time of t20.
• the waveform of Figure 18 is repeated at least 2 times, preferably at least 4 times and more preferably at least 8 times.
• wait time refers to a period of time in which no driving voltage is applied.
• the first wait time tl8 is very short while the second wait time t20 is longer.
• the period of tl7 is also shorter than the period of tl9.
• tl7 may be in the range of 20-200 msec; tl8 may be less than 100 msec; tl9 may be in the range of 100-200 msec; and t20 may be less than 1000 msec.
• Figure 19 is a combination of Figure 4 and Figure 18.
• a yellow state is displayed during the period of t2.
• the better the yellow state in this period the better the red state that will be displayed at the end.
• the step of driving to the yellow state for a period of t2 may be eliminated and in this case, a shaking waveform is applied before applying the waveform of Figure 18 (see Figure 20).
• the entire waveform of Figure 19 is DC balanced. In another embodiment, the entire waveform of Figure 20 is DC balanced.
• Figure 21 illustrates a driving waveform which may also be used to replace the driving period of t6 in Figure 5.
• a high positive driving voltage Vm, e.g., +15V
• a negative driving voltage e.g., less than 50% of Vm or Vm
• the waveform of Figure 21 may also be repeated at least 2 times, preferably at least 4 times and more preferably at least 8 times.
• the first wait time t22 is very short while the second wait time t24 is longer.
• the period of t21 is also shorter than the period of t23.
• t21 may be in the range of 20-200 msec; t22 may be less than 100 msec; t23 may be in the range of 100-200 msec; and t24 may be less than 1000 msec.
• Figure 22 is a combination of Figure 5 and Figure 21.
• a black state is displayed during the period of t5.
• the better the black state in this period the better the white state that will be displayed at the end.
• the step of driving to the black state for a period of t5 may be eliminated and in this case, a shaking waveform is applied before applying the waveform of Figure 21 (see Figure 23).
• the entire waveform of Figure 22 is DC balanced. In another embodiment, the entire waveform of Figure 23 is DC balanced.
• the fourth driving method of the invention may be summarized as follows:
• a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• the amplitude of the second driving voltage is less than 50% of the amplitude of the first driving voltage.
• steps (i)-(iv) are repeated at least 2 times, preferably at least 4 times and more preferably at least 8 times.
• the method further comprises a shaking waveform before step (i).
• the method further comprises driving the pixel to the color state of the first or second type of particles after the shaking waveform but prior to step (i).
• This driving method not only is particularly effective at a low temperature, it can also provide a display device better tolerance of structural variations caused during manufacture of the display device. Therefore its usefulness is not limited to low temperature driving.
• This driving method is particularly suitable for low temperature driving of a pixel from the yellow state (high negative) to the red state (low positive).
• a low negative driving voltage (-V) is first applied for a time period of t25, followed by a low positive driving voltage (+V") for a time period of t26. Since the sequence is repeated, there is also a wait time of t27 between the two driving voltages.
• Such a waveform may be repeated at least 2 times (N' > 2), preferably at least 4 times and more preferably at least 8 times.
• the time period of t25 is shorter than the time period of t26.
• the time period of t27 may be in the range of 0 to 200 msec.
• the amplitudes of the driving voltages, V and V" may be 50% of the amplitude of VH (e.g., VHI or V ). It is also noted that the amplitude of V may be the same as, or different from, the amplitude of V".
• the entire waveform of Figure 25 is DC balanced. In another embodiment, the entire waveform of Figure 26 is DC balanced.
• This driving method is particularly suitable for low temperature driving of a pixel from the black state (high positive) to the white state (low negative).
• a low positive driving voltage (+V) is first applied for a time period of t28, followed by a low negative driving voltage (-V") for a time period of t29. Since this sequence is repeated, there is also a wait time of t30 between the two driving voltages.
• Such a waveform may be repeated at least 2 times (e.g., N' > 2), preferably at least 4 times and more preferably as least 8 times.
• the time period of t28 is shorter than the time period of t29.
• the time period of t30 may be in the range of 0 to 200 msec.
• the amplitudes of the driving voltages, V and V" may be 50% of the amplitude of VH (e.g., VHI or V ). It is also noted that the amplitude of V may be the same as, or different from, the amplitude of V".
• the entire waveform of Figure 28 is DC balanced. In another embodiment, the entire waveform of Figure 29 is DC balanced.
• the fifth driving method can be summarized as follows:
• a driving method for an electrophoretic display comprising a first surface on the viewing side, a second surface on the non-viewing side and an electrophoretic fluid which fluid is sandwiched between a common electrode and a layer of pixel electrodes and comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein
• the method comprises the following steps:
• the third period of time is greater than the first period of time, the second driving voltage has polarity opposite that of the first driving voltage and the second driving voltage has an amplitude lower than that of the first driving voltage;
• steps (v)-(vii) are repeated at least 2 times, preferably at least 4 times and more preferably at least 8 times.
• Figures 30 and 31 illustrate alternative driving methods of the invention.
• the methods may also be viewed as “re-set” or “pre-condition", prior to driving a pixel to a desired color state.
• the waveform in Figure 30 comprises three parts, (i) driving to a first state (yellow),
• the waveform in Figure 31 is the complimentary waveform to Figure 30 and comprises three parts, (i) driving to second state (black), (ii) applying a driving voltage (VH2, e.g., -15 V) having the same polarity as that of the second (yellow) particles for a short period of time, t 2 , which is not sufficiently long to drive from the second (black) state to the first (yellow) state, resulting in a dark yellow state, and (iii) shaking.
• VH2 driving voltage
• t 2 e.g., -15 V
• the length of ti or t 2 would depend on not only the final color state driven to (after the re-set and pre-condition waveform of Figure 30 or 31), but also the desired optical performance of the final color state (e.g., a*, AL* and Aa*). For example, there is least ghosting when ti in the waveform of Figure 30 is 40 msec and pixels are driven to the third (white) state regardless of whether they are driven from red, black, yellow, or white.
• the shaking waveform consists of repeating a pair of opposite driving pulses for many cycles.
• the shaking waveform may consist of a +15V pulse for 20 msec and a -15 V pulse for 20 msec and such a pair of pulses is repeated for 50 times.
• the total time of such a shaking waveform would be 2000 msec.
• Each of the driving pulses in the shaking waveform is applied for not exceeding half of the driving time required for driving 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 yellow state, or vice versa, the shaking waveform may consist of positive and negative pulses, each applied for not more than 150 msec. In practice, it is preferred that the pulses are shorter.
• the four types of particles should be in a mixed state in the display fluid.
• a pixel is then driven to a desired color state (e.g., black, red, yellow, or white).
• a positive pulse may be applied to drive the pixel to black; a negative pulse may be applied to drive the pixel to yellow; a negative pulse followed by a positive pulse of lower amplitude may be applied to drive the pixel to white, or a positive pulse followed by a negative pulse of lower amplitude may be applied to drive the pixel to red.
• the methods with the "re-set” or “pre-condition” of the present invention have the added advantage of shorter waveform time in achieving the same levels of optical performance (including ghosting).
• a driving method for driving a pixel of an electrophoretic display comprising a first surface on a viewing side, a second surface on a non-viewing side, and an electrophoretic fluid disposed between a first light-transmissive electrode and a second electrode, the electrophoretic fluid comprising a first type of particles, a second type of particles, a third type of particles, and a fourth type of particles, all of which are dispersed in a solvent, wherein
• the method comprises the steps of:

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• 2018
  • 2018-10-03 CN CN201880061918.3A patent/CN111149149B/zh active Active
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